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Solar heating of integrated greenhouse-animal shelter systems Ben-Abdallah, Noureddine 1983

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SOLAR HEATING OF INTEGRATED GREENHOUSE-ANIMAL SHELTER SYSTEMS BY NOUREDDINE BEN-ABDALLAH B.^Sc. Texas A & M U n i v e r s i t y , 1969 M.A.Sc. The U n i v e r s i t y of B r i t i s h Columbia, 1974 A Thesis submitted in p a r t i a l f u l f i l m e n t of the requirements f o r the degree of Doctor of Philosophy ( I n t e r d i s c i p l i n a r y ) We accept t h i s t h e s i s as conforming to the required standard THE. UNIVERSITY OF BRITISH COLUMBIA SEPTEMBER, 1983 0 N. Ben-Abdallah. 1983 In p r e s e n t i n g t h i s t h e s i s i n p a r t i a l f u l f i l m e n t o f the requirements f o r an advanced degree a t the U n i v e r s i t y o f B r i t i s h Columbia, I agree t h a t the L i b r a r y s h a l l make i t f r e e l y a v a i l a b l e f o r r e f e r e n c e and study. I f u r t h e r agree t h a t p e r m i s s i o n f o r e x t e n s i v e copying of t h i s t h e s i s f o r s c h o l a r l y purposes may be granted by the head of my department o r by h i s o r her r e p r e s e n t a t i v e s . I t i s understood t h a t c o p y i n g or p u b l i c a t i o n o f t h i s t h e s i s f o r f i n a n c i a l g a i n s h a l l not be allowed without my w r i t t e n p e r m i s s i o n . Department of The U n i v e r s i t y o f B r i t i s h Columbia 2075 Wesbrook P l a c e Vancouver, Canada V6T 1W5 Date DE-6 (2/79} ABSTRACT An analytical procedure to determine the. 2.lh<LcZL\)Q.neJ>& oh greenhouse, as 6 0lan. collectors was presented. This procedure was used to ptie.cU.ct the ciicct oh 6e.ve.KaZ COM traction parameters, on solar radiation input to greenhouses. The orientation oh the. greenhouse was hound to be. the. most e-hhe.ctive- construction parameter controlling solar radiation input to greenhouses. The ehhe.cti.ve. albedo oh the plant canopy was also hound to be a i>ignihicant hector. A new solar greenhouse design, suitable hor high latitude legion* was developed. The results showed that an internal solar collector could be incon.pon.ated at, an integral part oh the greenhouse design. The concept developed could be used as a h^ee-standing greenhouse on. in a combination with livestock building. The ehhiciency oh the solar input was investigated hor the conventional and the shed greenhouses, both at> a hn.ee-standing unit and a greenhouse-animal shelter system, using computed simulation analyses. The results indicated that the ehh-tcA-zncy oh solan, input <U> highly dependent on location) the ehh^-^ oh location on the shed type design •Id more pro hound. A typical case oh a gneenhouse-hog barn production system was investigated using computer simulation analyses. The results showed that such a hood production system achieves a sianihicant reduction in conventional h^el consumption due to both animal waste heat recovery and solar energy utilization. ABSTRACT i TABLE OF CONTENTS i i LIST OF TABLES x i LIST OF FIGURES x v i ACKNOWLEDGEMENTS XX i INTRODUCTION 1 GREENHOUSE INDUSTRY IN CANADA 2 NEED FOR ENERGY CONSERVATION 3 • PROPOSITIONS 6 OBJECTIVES OF THE STUDY 7 ASSUMPTIONS ; 8 INFERENCES 8 SCOPE OF THE STUDY 9 ORGANISATION OF THE MANUSCRIPT 10 LITERATURE REVIEW 11 GREENHOUSE THERMAL ENVIRONMENT MODELS 12 SOLAR HEATING OF GREENHOUSES 19 Non-Integral S o l a r C o l l e c t o r s 20 Excess I n t e r n a l Heat C o l l e c t i o n 26 I n t e g r a l S o l a r C o l l e c t o r s 31 GASES OF TOTAL CONFINEMENT ANIMAL HOUSING UNITS .... 36 Ammonia 36 Hydrogen S u l f i d e 37 Methane 38 Carbon D i o x i d e 38 i i CARBON DIOXIDE ENRICHMENT OF GREENHOUSES 39 GREENHOUSE-LIVESTOCK BUILDING COMBINATION 41 PART I; ANALYSIS OF THE EFFECT OF SEVERAL CONSTRUCTION  PARAMETERS ON THE SOLAR RADIATION INPUT INTO  GREENHOUSES 44 CHAPTER 1. SOLAR RADIATION TRANSMISSION FACTORS OF GREENHOUSES 45 INTRODUCTION 46 SECTION A. ESTIMATION OF THE MONTHLY AVERAGE DAILY BEAM, DIFFUSE AND TOTAL TRANSMITTANCE OF THE GREENHOUSE TRANSPARENT SURFACES 47 Assumptions 4 8 Theory F o r m u l a t i o n 49 SECTION B. ESTIMATION OF THE MONTHLY AVERAGE DAILY BEAM, DIFFUSE AND TOTAL TRANSMISSION FACTORS OF GREENHOUSE 53 D e f i n i t i o n s of Tr a n s m i s s i o n F a c t o r s 54 Beam T r a n s m i s s i o n F a c t o r (BTF) 54 D i f f u s e T r a n s m i s s i o n F a c t o r (DTF) 55 T o t a l T r a n s m i s s i o n F a c t o r (TTF) 55 D e s c r i p t i o n of the Computer Model f o r T r a n s m i s s i o n F a c t o r s 56 Sample Output: R e s u l t s and D i s c u s s i o n ... 57 SECTION C. USE OF THE TOTAL TRANSMISSION FACTOR TO COMPARE GREENHOUSES FOR THEIR SOLAR- RADIATION INPUT EFFICIENCY 66 E f f e c t of O r i e n t a t i o n on the Greenhouse TTF 67 E f f e c t of Double G l a z i n g on the Greenhouse TTF 67 E f f e c t of I n s u l a t i n g the North Wall on the TTF of an East-West Glasshouse .... 69 E f f e c t of I n s u l a t i n g the North Wall and North Roof on the TTF of an East-West Glasshouse 72 E f f e c t of L o c a t i o n on the Greenhouse TTF.. 72 Shed vs Gable Greenhouse 75 Shed vs Brace Greenhouse 75 E f f e c t of L o c a t i o n on Shed Greenhouse TTF. 77 E f f e c t of Length, Width and I n s u l a t i n g the East and West Walls on the TTF of a Shed Greenhouse 80 Con c l u s i o n s •• 8 ^ NOMENCLATURE 89 CHAPTER 2. TOTAL SOLAR RADIATION CAPTURE FACTORS OF GREENHOUSES 91 INTRODUCTION 92 SECTION A. TOTAL CAPTURE FACTORS FOR GABLE GREENHOUSES 93 Assumptions 94 Theory F o r m u l a t i o n 95 R e s u l t s and D i s c u s s i o n 97 SECTION B. CALCULATION OF CONFIGURATION FACTORS FOR DIFFUSE RADIATION IN GREENHOUSES. 101 Assumptions 102 Theory 10 2 R e s u l t s and D i s c u s s i o n 103 E f f e c t o f Greenhouse Width 105 E f f e c t of Greenhouse Length 105 E f f e c t o f Roof Slope 109 Co n c l u s i o n s I l l NOMENCLATURE 113 PART I I ; ANALYSIS OF GREENHOUSE-LIVESTOCK COMBINATION FOR POSSIBLE ENERGY CONSERVATION 114 CHAPTER 3. COMPUTER SIMULATION MODEL OF ENERGY REQUIREMENTS FOR LIVESTOCK BUILDING 115 INTRODUCTION 116 SECTION A. MATHEMATICAL MODEL DEVELOPMENT FOR THE LIVESTOCK BUILDING 118 Assumptions 119 Heat Balance About The L i v e s t o c k B u i l d i n g . 119 Tr a n s m i s s i o n Heat T r a n s f e r 120 V e n t i l a t i o n Heat T r a n s f e r 123 V e n t i l a t i o n System C o n t r o l 124 V e n t i l a t i o n Rate f o r Humidity C o n t r o l 125 V e n t i l a t i o n Rate f o r Temperature C o n t r o l 127 V e n t i l a t i o n Rate f o r Animal Comfort 128 Heat and Moi s t u r e P r o d u c t i o n by L i v e s t o c k 128 Energy Consumption by V a r i a b l e Speed Fans 130 SECTION B. COMPARISON BETWEEN SOL-AIR AND HEAT BALANCE METHODS FOR TRANSMISSION LOSS CALCULATION 131 S o l - A i r Temperature Methods 132 Heat Balance Method 135 Comparison of the R e s u l t s by the Three Methods 136 SECTION C..vGASE STUDY I: HEATING AND VENTILATION REQUIREMENTS OF A CONVENTIONAL SWINE FINISHING BARN 142 D e s c r i p t i o n and Assumptions 143 R e s u l t s and D i s c u s s i o n 146 Conc l u s i o n s 154 NOMENCLATURE 155 CHAPTER 4. COMPUTER SIMULATION MODEL OF HEATING REQUIREMENTS FOR A CONVENTIONAL GABLE GREENHOUSE 159 INTRODUCTION 160 SECTION A. MATHEMATICAL MODEL DEVELOPMENT FOR THE GABLE GREENHOUSE 161 Assumptions 162 Heat Balance About The Greenhouse 165 Tr a n s m i s s i o n Heat T r a n s f e r 165 I n f i l t r a t i o n Heat Loss 166 S o l a r Energy Captured by the Greenhouse 167 SECTION B. CASE STUDY I I : HEATING REQUIREMENTS OF A CONVENTIONAL GABLE GLASSHOUSE 171 D e s c r i p t i o n and Assumptions 172 R e s u l t s and D i s c u s s i o n 173 Con c l u s i o n s 192 NOMENCLATURE 194 CHAPTER 5. COMPUTER SIMULATION MODEL OF ENERGY REQUIREMENTS FOR A COMBINED GREENHOUSE-LIVESTOCK BUILDING 198 INTRODUCTION 199 SECTION A. MATHEMATICAL MODEL DEVELOPMENT FOR THE GREENHOUSE-LIVESTOCK COMBINATION 200 Assumptions 201 Heat Balance About The B u i l d i n g 202 Zone I: A t t i c Space 202 Zone I I : L i v e s t o c k B u i l d i n g 202 Zone I I I : Greenhouse 203 Advantages and Disadvantages of D i r e c t Use of Exhaust A i r 205 SECTION B. CASE STUDY I I I : ENERGY REQUIREMENTS OF A GABLE GLASSHOUSE-SWINE FINISHING BARN COMBINATION 209 D e s c r i p t i o n and Assumptions 210 Re s u l t s and D i s c u s s i o n 212 Con c l u s i o n s 225 NOMENCLATURE 227 PART I I I : ANALYSIS OF A SOLAR-SHED GREENHOUSE-LIVESTOCK COMBINATION 228 CHAPTER 6. COMPUTER SIMULATION MODEL OF HEATING REQUIREMENTS OF SOLAR-SHED GREENHOUSE 229 INTRODUCTION 230 SECTION A. HEAT BALANCE ABOUT THE SOLAR-SHED GREENHOUSE 231 Assumptions 232 Energy Balance 232 Thermal R a d i a t i o n Heat Loss from Greenhouse Cover 2 34 Convection Heat Loss from the Greenhouse Cover 236 C a l c u l a t i o n of the Outside Sur f a c e Temperature of the Roof and the Walls of the Greenhouse 236 Conduction Heat Loss from the Greenhouse 240 I n f i l t r a t i o n Heat Loss from the Greenhouse 240 Supplemental Heat Requirement 240 SECTION B. CALCULATION OF SOLAR RADIATION CAPTURE BY A SHED-GREENHOUSE AND SOLAR RADIATION INCIDENT ON THE COLLECTOR 24 2 Assumptions 243 E s t i m a t i o n of the T o t a l S o l a r R a d i a t i o n I n c i d e n t on the F l a t P l a t e S o l a r C o l l e c t o r i n s i d e a Shed-Type Greenhouse 24 3 E s t i m a t i o n of the T o t a l S o l a r R a d i a t i o n Captured by the P l a n t Canopy 247 E f f i c i e n c y o f S o l a r Capture by the Greenhouse P l a n t Canopy 249 U s e f u l Energy Gain of the S o l a r C o l l e c t o r 250 C a l c u l a t i o n of D i f f u s e R a d i a t i o n C o n f i g u r a t i o n F a c t o r s 253 SECTION C. CASE STUDY IV: SUPPLEMENTAL HEATING REQUIREMENTS OF A SOLAR-SHED GREENHOUSE 259 D e s c r i p t i o n and Assumptions 260 R e s u l t s and D i s c u s s i o n 261 E f f e c t of S e l e c t i v e C o a t i n g and Average Temperature of the Absorber P l a t e 273 Co n c l u s i o n s 276 NOMENCLATURE 279 CHAPTER 7. COMPUTER SIMULATION MODEL OF HEATING REQUIREMENTS OF SOLAR-SHED GREENHOUSE -LIVESTOCK COMBINATION 2 87 INTRODUCTION 2 88 SECTION A. DESCRIPTION OF THE COMPUTER MODEL FOR THE SOLAR-SHED GREENHOUSE-LIVESTOCK BUILDING COMBINATION 289 Assumptions 290 D e s c r i p t i o n o f the Computer Model 290 SECTION B. CASE STUDIES V AND V I : HEATING REQUIREMENTS OF A SOLAR-SHED GREENHOUSE-SWINE FINISHING BARN COMBINATION 29 7 CASE STUDY V 298 D e s c r i p t i o n and Assumptions 298 R e s u l t s and D i s c u s s i o n 298 Comparison of R e s u l t s w i t h P r e v i o u s Case S t u d i e s 30*8 CASE STUDY VI 310 D e s c r i p t i o n and Assumptions 310 R e s u l t s and D i s c u s s i o n 313 Co n c l u s i o n s 316 SUMMARY 318 CONCLUSIONS 319 RECOMMENDATIONS • 320 CONTRIBUTIONS • 322 REFERENCES 323 APPENDICES • 332 APPENDIX A: CALCULATION OF BEAM TRANSMITTANCE OF GREENHOUSE COVERS 33 3 APPENDIX B: SAMPLE COMPUTER OUTPUT FOR GREENHOUSE TRANSMISSION FACTORS 33.7 APPENDIX C: ESTIMATION OF HOURLY DIRECT, DIFFUSE AND TOTAL SOLAR RADIATION ON TILTED SURFACES OF ANY ORIENTATION 345 APPENDIX D: NUMERICAL CALCULATION OF PSYCHROMETRIC PROPERTIES OF MOIST AIR 356 APPENDIX E: HEAT AND MOISTURE PRODUCTION BY SWINE .. 36 2 APPENDIX F: SAMPLE COMPUTER SIMULATION OUTPUT FOR A SWINE FINISHING BARN (CASE STUDY I) .. 366 APPENDIX G: SAMPLE COMPUTER SIMULATION OUTPUT FOR A CONVENTIONAL GABLE GREENHOUSE (CASE STUDY II) 379 APPENDIX H. SAMPLE COMPUTER SIMULATION OUTPUT FOR A CONVENTIONAL GREENHOUSE-SWINE FINISHING BARN COMBINATION (CASE STUDY I I I ) 392 APPENDIX I. SAMPLE COMPUTER SIMULATION OUTPUT FOR A SOLAR-SHED GREENHOUSE (CASE STUDY I V ) . 405 APPENDIX J : SAMPLE COMPUTER SIMULATION OUTPUT FOR A SOLAR-SHED GREENHOUSE-HOG BARN COMBINATION (CASE STUDY V) 418 APPENDIX K: DERIVATION OF EQUATIONS 9 & 11 OF CHAPTER 4 4 31 APPENDIX L: CALCULATION OF THE MEAN PLATE TEMPERATURE OF THE COLLECTOR FOR THE CONSTANT FLOW CASE 439 APPENDIX M: COMPUTER PROGRAMS 457 LIST OF TABLES CHAPTER 1 1.1 Monthly average d a i l y t o t a l i n s o l a t i o n on a h o r i z o n t a l s u r f a c e , ground albedo and r a t i o of d i f f u s e to t o t a l r a d i a t i o n f o r the l o c a t i o n s s e l e c t e d f o r t h i s study 59 1.2 Sample computer output f o r an E-W s i n g l e g l a s s cover greenhouse (Vancouver; December) .... 62 1.3 3.1 Sample computer output f o r an E-W s i n g l e g l a s s cover greenhouse (Vancouver; J u l y ) CHAPTER 2 CHAPTER 3 63 2.1 R a d i a t i o n c o n f i g u r a t i o n f a c t o r s between the two s l o p e s o f r o o f and from one r o o f slope to gable ends f o r a gable greenhouse having a width of 10 metres 110 V a r i a b l e s used to c a l c u l a t e h e a t i n g v e n t i l a t i o n requirements of a c o n v e n t i o n a l swine f i n i s h i n g barn 147 CHAPTER 4 4.1 V a r i a b l e s used to c a l c u l a t e h e a t i n g demands of a c o n v e n t i o n a l gable greenhouse 175 4.2 4.3 177 Monthly average h e a t i n g l o a d , s o l a r energy i n p u t , s o l a r c o n t r i b u t i o n and supplemental heat requirements i n MJ per m^ of greenhouse f l o o r area and percent o f the h e a t i n g l o a d s u p p l i e d by s o l a r f o r the c o n v e n t i o n a l gable greenhouse of Case Study I I - Vancouver, B.C. .. Monthly average h e a t i n g l o a d , s o l a r energy i n p u t , s o l a r c o n t r i b u t i o n and supplemental heat requirements i n MJ per n\2 of greenhouse f l o o r area and percent o f the h e a t i n g l o a d s u p p l i e d by s o l a r f o r the c o n v e n t i o n a l gable greenhouse of Case Study I I - Montreal, Quebec .. 179 4.4 4.5 Monthly average h e a t i n g l o a d , s o l a r energy i n p u t , s o l a r c o n t r i b u t i o n and supplemental heat requirements i n MJ per m2 of greenhouse f l o o r area and percent of the h e a t i n g l o a d s u p p l i e d by s o l a r f o r the c o n v e n t i o n a l gable greenhouse of Case Study I I (Minimum I n s i d e Temperature = 15°C) - H a l i f a x , N.S 180 Monthly average h e a t i n g l o a d , s o l a r energy i n p u t , s o l a r c o n t r i b u t i o n and supplemental heat requirements i n MJ per m2 of greenhouse f l o o r area and percent of the h e a t i n g l o a d s u p p l i e d by s o l a r f o r the c o n v e n t i o n a l gable greenhouse of Case Study I I (Minimum I n s i d e Temperature = 10°C) - H a l i f a x , N.S 182 Monthly average h e a t i n g l o a d , s o l a r energy i n p u t , s o l a r c o n t r i b u t i o n and supplemental heat requirements i n MJ per m2 of greenhouse f l o o r area and per c e n t of the h e a t i n g l o a d s u p p l i e d by s o l a r f o r the c o n v e n t i o n a l gable greenhouse of Case Study I I (Minimum I n s i d e Temperature = 20°C) - H a l i f a x , N.S 183 4.7 E f f e c t of minimum i n s i d e greenhouse temperature on supplemental heat requirement and expected energy savings due to r e d u c i n g the minimum temperature from 20°C . 185 4.8 E f f e c t o f i n f i l t r a t i o n r a t e on supplemental heat requirement f o r a c o n v e n t i o n a l gable glasshouse kept at a minimum i n s i d e temperature of 20°C 187 4.6 CHAPTER 5 5.1 Monthly average 5.2 MJ heat l o s s , s o l a r energy i n p u t and s o l a r energy u t i l i z e d by the greenhouse i n .._ per m2 of f l o o r area f o r the atta c h e d greenhouse-swine f i n i s h i n g barn of Case Study I I I (Minimum Greenhouse Temperature = 15°C) - H a l i f a x , N.S. .. 214 Monthly average h e a t i n g l o a d , waste heat c o n t r i b u t i o n t o the greenhouse h e a t i n g l o a d from the l i v e s t o c k b u i l d i n g and supplemental heat requirement i n MJ per m2 of greenhouse f l o o r area f o r the at t a c h e d greenhouse-swine f i n i s h i n g barn of Case Study I I I (Minimum Greenhouse Temperature = 15°C) - H a l i f a x , N.S. .. 215 5.3 Monthly average heat l o s s , s o l a r energy i n p u t and s o l a r energy u t i l i z e d by the greenhouse i n MJ per m2 of f l o o r area f o r the attached greenhouse-swine f i n i s h i n g barn of Case Study I I I (Minimum Greenhouse Temperature = 10°C) - H a l i f a x , N.S. .. 218 5.4 Monthly average h e a t i n g l o a d , waste heat c o n t r i b u t i o n t o the greenhouse h e a t i n g l o a d from the l i v e s t o c k b u i l d i n g and supplemental heat requirement i n MJ per m 2 of greenhouse f l o o r area f o r the atta c h e d greenhouse - swine f i n i s h i n g barn o f Case Study I I I (Minimum Greenhouse Temperature = 10°C) - H a l i f a x , N.S. .. 219 5.5 E f f e c t o f lowering the minimum greenhouse temperature on energy savings f o r the att a c h e d greenhouse-swine f i n i s h i n g barn of Case Study I I I 222 5.6 Monthly average supplemental heat requirements f o r a c o n v e n t i o n a l and an atta c h e d greenhouse (MJ per m2 greenhouse f l o o r area) a l s o expected pe r c e n t savings as a f u n c t i o n o f the minimum greenhouse temperature 224 CHAPTER .6 6.1 V a r i a b l e s used to c a l c u l a t e h e a t i n g demands of a s o l a r - s h e d greenhouse 262 6.2 Monthly average heat l o s s , s o l a r energy i n p u t , s o l a r c o n t r i b u t i o n and h e a t i n g l o a d i n MJ per m2 of greenhouse f l o o r area and percent of the heat l o s s s u p p l i e d by s o l a r f o r the shed greenhouse of Case Study IV - Vancouver, B.C 26 3 6.3 Monthly average heat l o s s , s o l a r energy i n p u t , s o l a r c o n t r i b u t i o n and h e a t i n g l o a d i n MJ per m2 of greenhouse f l o o r area and pe r c e n t of the heat l o s s s u p p l i e d by s o l a r f o r the shed greenhouse of Case Study IV - Montreal, P.Q 266 6.4 Monthly average heat l o s s , s o l a r energy i n p u t , s o l a r c o n t r i b u t i o n and h e a t i n g l o a d i n MJ per m of greenhouse f l o o r area and pe r c e n t of the l o s s s u p p l i e d by s o l a r f o r the shed greenhouse of Case Study IV - H a l i f a x , N.S 2 heat 6.5 Monthly average h e a t i n g l o a d and s o l a r energy s u p p l i e d by the i n t e g r a l c o l l e c t o r i n MJ per m2 of f l o o r area as w e l l as the s o l a r f r a c t i o n s f o r the s o l a r - s h e d greenhouse of Case Study IV .. 270 6.6 Monthly average supplemental heat requirements f o r the c o n v e n t i o n a l gable and the s o l a r - s h e d greenhouses i n MJ per m2 of greenhouse f l o o r area and percentage energy savings as a f f e c t e d by l o c a t i o n 272 6.7 Monthly and y e a r l y f r a c t i o n of h e a t i n g l o a d s u p p l i e d by the i n t e g r a l s o l a r c o l l e c t o r as a f u n c t i o n of the average absorber p l a t e temperature and i t s o p t i c a l p r o p e r t i e s f o r the s o l a r - s h e d greenhouse of Case Study IV 275 CHAPTER 7 7.1 V a r i a b l e s used to c a l c u l a t e h e a t i n g demands of a s o l a r - s h e d greenhouse 300 7.2 V a r i a b l e s used to c a l c u l a t e v e n t i l a t i o n requirements of a t w o - l e v e l shed swine f i n i s h i n g barn 301 7.3 Summary of r e s u l t s of the s o l a r - s h e d greenhouse-hog barn combination l o c a t e d i n H a l i f a x 303 7.4 Summary of r e s u l t s of the s o l a r - s h e d greenhouse-hog barn combination l o c a t e d i n Vancouver 305 7.5 Comparison of monthly supplemental heat requirement and energy savings by the d i f f e r e n t greenhouse s t u d i e d - H a l i f a x 309 7.6 Comparison of monthly supplemental heat requirement and energy savings by the d i f f e r e n t greenhouse s t u d i e d - Vancouver 310 7.7 E f f e c t of greenhouse s i z e on the performance of a s o l a r - s h e d greenhouse-hog barn combination l o c a t e d i n H a l i f a x 314 APPENDIX L L . l E f f e c t of a i r flow r a t e through the c o l l e c t o r on the absorber and the o u t l e t temperature : the s o l a r - s h e d greenhouse of case study L.2 f o r the s o l a r - s h e d greenhouse of case study IV (Vancouver, B.C.) 450 E f f e c t of a i r flow r a t e through the c o l l e c t o r on the s o l a r energy c o l l e c t e d and s o l a r f r a c t i o n f o r the s o l a r - s h e d greenhouse of case study IV (Vancouver, B.C.) 452 CHAPTER 1 1.1 Monthly average d a i l y beam t r a n s m i t t a n c e f o r v a r i o u s s u r f a c e s o f a greenhouse wi t h s i n g l e g l a s s cover 60 1.2 Montly average d a i l y t o t a l t r a n s m i t t a n c e f o r v a r i o u s s u r f a c e s of a greenhouse wi t h s i n g l e g l a s s cover 61 1.3 Monthly average d a i l y beam, d i f f u s e and t o t a l s o l a r t r a n s m i s s i o n f a c t o r s f o r a gable greenhouse 64 1.4 E f f e c t of E-W and N-S o r i e n t a t i o n on the t o t a l t r a n s m i s s i o n f a c t o r f o r a gable greenhouse 68 1.5 E f f e c t of double g l a z i n g o f an E-W o r i e n t e d glasshouse on the t o t a l t r a n s m i s s i o n f a c t o r 70 1.6 E f f e c t o f i n s u l a t i n g the n o r t h w a l l o r n o r t h w a l l and r o o f of an E-W o r i e n t e d glasshouse on the t o t a l t r a n s m i s s i o n f a c t o r 71 1.7 E f f e c t of l o c a t i o n of an E-W o r i e n t e d glasshouse on the t o t a l t r a n s m i s s i o n f a c t o r 73 1.8 Comparison of the t o t a l t r a n s m i s s i o n f a c t o r s f o r gable, Brace and shed-type greenhouses 76 1.9 E f f e c t of l o c a t i o n on the t o t a l t r a n s m i s s i o n f a c t o r f o r a shed-type greenhouse 78 1.10 C o n t r i b u t i o n by the d i f f e r e n t s u r f a c e s o f a shed-type greenhouse f o r the beam, d i f f u s e and t o t a l s o l a r r a d i a t i o n by month 81 1.11 E f f e c t of l e n g t h and i n s u l a t i n g the e a s t and west w a l l s of a shed-type greenhouse on i t s t o t a l t r a n s m i s s i o n f a c t o r 83 1.12 C o n t r i b u t i o n o f the east and west w a l l s o f a shed-type greenhouse to the d i f f u s e and t o t a l s o l a r r a d i a t i o n i n p u t as a f u n c t i o n of greenhouse l e n g t h 84 1.13 E f f e c t of l e n g t h , width and i n s u l a t i n g e a s t and west w a l l s of an E-W shed greenhouse on i t s monthly average d a i l y t o t a l t r a n s m i s s i o n f a c t o r 85 CHAPTER 2 2.1 E f f e c t o f p l a n t albedo on the s o l a r r a d i a t i o n capture f a c t o r f o r a gable greenhouse 98 2.2 R a d i a t i o n c o n f i g u r a t i o n f a c t o r between two r e c t a n g l e s forming an a r b i t r a r y angle 104 2.3 E f f e c t o f l e n g t h and width on the r a d i a t i o n c o n f i g u r a t i o n f a c t o r s f o r gable greenhouses having a r o o f s lope of 15 degrees 106 2.4 E f f e c t of l e n g t h and width on the r a d i a t i o n c o n f i g u r a t i o n f a c t o r s f o r gable greenhouses having a ro o f s l o p e of 20 degrees 107 2.5 E f f e c t of l e n g t h and width on the r a d i a t i o n c o n f i g u r a t i o n f a c t o r s f o r gable greenhouses having a r o o f s l o p e o f 25 degrees 108 CHAPTER 3 3.1 Thermal r a d i a t i o n exchange between a w a l l and i t s environment 134 3.2 Hourly temperature and s o l a r r a d i a t i o n on a h o r i z o n t a l s u r f a c e used f o r the c a l c u l a t i o n of t r a n s m i s s i o n heat l o s s by the s o l - a i r temperature and heat balance methods 137 3.3 Comparison of h o u r l y t r a n s m i s s i o n heat l o s s as estimated u s i n g s o l - a i r temperature equations ( T h r e l k e l d , O'Callaghan) and c a l c u l a t e d by heat balance about the w a l l s of a t y p i c a l farm b u i l d i n g (a g = 0.2; e £ = 0.9) 140 3.4 Comparison of h o u r l y t r a n s m i s s i o n heat l o s s as estimated u s i n g s o l - a i r temperature equations ( T h r e l k e l d , O'Callaghan) and c a l c u l a t e d by heat balance about the w a l l s of a t y p i c a l farm b u i l d i n g (a g = 0.2; = 0.2) 141 3.5 F l o o r p l a n of the swine f i n i s h i n g barn used i n Case Study I 144 3.6 C r o s s - s e c t i o n o f the swine f i n i s h i n g barn used i n Case Study I 145 3.7 V e n t i l a t i o n r a t e requirement of the swine f i n i s h i n g barn f o r a minimum i n s i d e temperature o f 20°C and a maximum i n s i d e r e l a t i v e humidity of 85% f o r the o u t s i d e d r y - b u l b and dew-point temperatures i n d i c a t e d i n the graph (January) 149 3.8 V e n t i l a t i o n r a t e requirement of the swine f i n i s h i n g barn f o r a minimum i n s i d e temperature o f 20°C and a maximum i n s i d e r e l a t i v e humidity of 85% f o r the o u t s i d e d r y - b u l b and dew-point temperatures i n d i c a t e d i n the graph (August) 150 3.9 Nomograph f o r determining the c o s t o f energy used f o r v e n t i l a t i o n o f swine f i n i s h i n g barns ... 152 CHAPTER 4 4.1 C r o s s - s e c t i o n of the c o n v e n t i o n a l gable greenhouse used i n Case Study I I 174 4.2 Monthly average s o l a r energy u t i l i z a t i o n f a c t o r and f r a c t i o n of h e a t i n g l o a d s u p p l i e d by p a s s i v e s o l a r f o r an E-W gable greenhouse .... 189 4.3 E f f e c t of l o c a t i o n on the s o l a r energy u t i l i z a t i o n f a c t o r by month f o r an E-W gable greenhouse 191 CHAPTER 5 5.1 C r o s s - s e c t i o n a l view of the gable greenhouse-hog barn combination (Case Study I I I ) 211 CHAPTER 6 6.1 Schematic o f a s o l a r - s h e d greenhouse showing energy flows and s o l a r r a d i a t i o n i n c i d e n t on the i n t e g r a l c o l l e c t o r 233 6.2 E f f e c t of l e n g t h and width on the r a d i a t i o n c o n f i g u r a t i o n f a c t o r s f o r s o l a r - s h e d greenhouses having a r o o f slope of 20 degrees ... 256 6.3 E f f e c t of l e n g t h and width on the r a d i a t i o n c o n f i g u r a t i o n f a c t o r s f o r s o l a r - s h e d greenhouses having a r o o f slope of 30 degrees ... 257 6.4 E f f e c t o f l e n g t h and width on the r a d i a t i o n c o n f i g u r a t i o n f a c t o r s f o r s o l a r - s h e d greenhouses having a r o o f slope of 45 degrees ... 258 CHAPTER 7 7.4 7.6 of o p e r a t i o n of the s o l a r h e a t i n g system ;olar-shed g r e e n h o u s e - l i v e s t o c k b u i l d i n g 7.1 Modes  of a sc combination 293 7.2 D i r e c t h e a t i n g of a s o l a r - s h e d greenhouse-l i v e s t o c k b u i l d i n g combination by the i n t e g r a l s o l a r h e a t i n g system (Mode 1 operation) 29 4 7.3 S o l a r energy c o l l e c t i o n and storage i n a s o l a r - s h e d g r e e n h o u s e - l i v e s t o c k b u i l d i n g combination (Mode 2 op e r a t i o n ) 295 Heating of a s o l a r - s h e d g r e e n h o u s e - l i v e s t o c k b u i l d i n g combination from the thermal storage (Mode 3 operation) 296 7.5 Schematic of the c r o s s - s e c t i o n o f a s o l a r - s h e d greenhouse-hog barn combination used i n Case Study V 299 Monthly performance of the s o l a r - s h e d greenhouse-hog barn combination (Case Study V) .. 307 7.7 Schematic of the c r o s s - s e c t i o n of a s o l a r - s h e d greenhouse-hog barn combination used i n Case Study VI 312 7.8 E f f e c t o f greenhouse f l o o r area on the monthly average f r a c t i o n o f the h e a t i n g l o a d s u p p l i e d by a c t i v e s o l a r c o l l e c t i o n and barn waste heat recovery f o r s o l a r - s h e d greenhouse-hog barn combination of Case Study VI 315 APPENDIX K K . l Beam and d i f f u s e s o l a r r a d i a t i o n i n p u t from a v e r t i c a l w a l l of a greenhouse 433 K.2 D i f f u s e s o l a r r a d i a t i o n i n p u t from a gable roof of a greenhouse 436 APPENDIX L L . l Schematic of a s e c t i o n of the a i r s o l a r c o l l e c t o r l o c a t e d w i t h i n a s o l a r - s h e d greenhouse 441 The author wishes to express h i s s i n c e r e thanks and a p p r e c i a t i o n to P r o f e s s o r L.M. S t a l e y , the r e s e a r c h s u p e r v i s o r , f o r h i s guidance, encouragement and c o n s t r u c t i v e c r i t i c i s m throughout the p e r i o d of t h i s study. S i n c e r e thanks are due to Dr. M. I q b a l of the Department of Mechanical E n g i n e e r i n g f o r h e l p i n g me understand the s c i e n c e of s o l a r energy and heat t r a n s f e r . Without the background gained from h i s e x c e l l e n t graduate courses, t h i s study would not have been p o s s i b l e . Thanks are extended to Dr. T.A. Black of the Department of S o i l S c i e n c e , Dr. P.A. J o l l i f f e o f the Department of P l a n t Science and Dr. J.W. Zahradnik and Dr. N.R. B u l l e y of the Department of Bio-Resource E n g i n e e r i n g f o r t h e i r i n v a l u a b l e s u g g e s t i o n s . The author expresses h i s s i n c e r e a p p r e c i a t i o n to Mrs. D. Chong and Ms. V. E l l i s f o r t h e i r e f f i c i e n c y and c o - o p e r a t i o n i n t y p i n g and e d i t i n g some p a r t s of the t h e s i s . F i n a l l y , the f i n a n c i a l a s s i s t a n c e of B r i t i s h Columbia Hydro and Power A u t h o r i t y through the Graduate Research and E n g i n e e r i n g Technology Awards program i s g r a t e f u l l y acknowledged. INTRODUCTION GREENHOUSE INDUSTRY IN CANADA* Greenhouse p r o d u c t i o n o f f l o w e r s , nursery p l a n t s and vegetab l e crops i s a s i g n i f i c a n t component o f Canadian a g r i c u l t u r e . The 19 80 t o t a l s u r f a c e area under g l a s s and p l a s t i c was est i m a t e d a t 382.76 h e c t a r e s , w i t h the p r o v i n c e of O n t a r i o a c c o u n t i n g f o r 60 p e r c e n t o f the t o t a l , f o l l o w e d by B r i t i s h Columbia w i t h l e s s than 14 percent and Quebec w i t h s l i g h t l y over 11 p e r c e n t . The t o t a l s a l e s value o f f l o w e r s , ornamentals, bedding p l a n t s and vegetables was estimated a t over 216 m i l l i o n d o l l a r s i n 1980; wh i l e the t o t a l f u e l c o s t used by the greenhouse i n d u s t r y was over 25 m i l l i o n d o l l a r s , or 11.6 percent o f the s a l e s v a l u e . In 19 80 the annual f u e l c o s t s per u n i t area under cover 2 ranged between 5.53 S/m i n the p r o v i n c e o f Quebec to 2 9.60 $/m i n Nova S c o t i a . The n a t i o n a l average was e s t i m a t e d 2 at 6.6 3 $/m . U n i t f u e l c o s t i n O n t a r i o was c l o s e s t to the 2 n a t i o n a l average a t 7.07 $/m because o f i t s l a r g e c o n t r i b u t i o n i n s u r f a c e area under cover; w h i l e i n B r i t i s h Columbia, due to r e l a t i v e l y warm c l i m a t e , the u n i t f u e l c o s t was onl y 5.70 $/m2. The low f u e l c o s t s per u n i t area i n Quebec may be a t t r i b u t e d t o the f a c t t h a t some greenhouses i n the p r o v i n c e do not operate f o r the e n t i r e y e a r . In Nova S c o t i a , the high A l l the s t a t i s t i c a l i n f o r m a t i o n i n t h i s s e c t i o n i s d e r i v e d by the author from S t a t i s t i c s Canada, Greenhouse Industry, Catalogue 22-202, 1979-1980. * f u e l c o s t s per u n i t greenhouse area c o u l d be e x p l a i n e d by h i g h e r f u e l p r i c e s and c o l d e r c l i m a t e than i n southern O n t a r i o . NEED FOR ENERGY CONSERVATION The need f o r energy c o n s e r v a t i o n and renewable sources of energy u t i l i z a t i o n f o r greenhouse h e a t i n g was a r e s u l t o f the continuous i n c r e a s e , f o r the l a s t decade, of c o n v e n t i o n a l f u e l c o s t s . The i n c r e a s e i n energy c o s t s have focused the a t t e n t i o n of greenhouse o p e r a t o r s on c o n s e r v a t i o n methods such as i n s t a l l a t i o n o f thermal c u r t a i n s , use of double covers and more e f f i c i e n t greenhouse d e s i g n s , p l a n t i n g l a t e i n the season, or growing p l a n t s r e q u i r i n g lower temperatures. In c o n j u n c t i o n with a p p l y i n g c o n s e r v a t i o n techniques, some growers went i n t o f o s s i l f u e l s u b s t i t u t i o n programs. These i n c l u d e d waste heat u t i l i z a t i o n , combustion of wood and wood r e s i d u e s , and s o l a r energy u t i l i z a t i o n . However, much more r e s e a r c h , development and demonstration p r o j e c t s are needed to keep a v i a b l e greenhouse i n d u s t r y o p e r a t i n g i n adverse c l i m a t i c c o n d i t i o n s . O b v i o u s l y there i s no s i n g l e s o l u t i o n t o the energy dilemma f a c i n g the greenhouse i n d u s t r y today. However, the author b e l i e v e s a combination of new energy c o n s e r v i n g i d e a s and concepts, s o l a r energy u t i l i z a t i o n and waste heat recovery and re-use may a l l e v i a t e the burden of high f u e l c o s t s f o r greenhouse o p e r a t o r s . The work p r e s e n t e d i n t h i s study on i n t e r n a l s o l a r energy c o l l e c t i o n and u t i l i z a t i o n , and animal waste heat r e c o v e r y and use f o r greenhouse h e a t i n g , i s only one of the many p o s s i b l e concepts which might prove reasonably e f f i c i e n t i n r e d u c i n g the dependence of the greenhouse i n d u s t r y on non-renewable energy s o u r c e s . T h e r e f o r e , the f o l l o w i n g proposed concept should be taken as a p a r t i a l s o l u t i o n and should be a p p l i e d i n combination w i t h o t h e r energy c o n s e r v a t i o n methods f o r green-houses . In t h i s study, i t i s proposed t h a t animal heat from l i v e -stock b u i l d i n g s be used i n c o n j u n c t i o n w i t h s o l a r energy to heat a d j a c e n t greenhouses. Two s i t u a t i o n s need to be i n v e s t i -gated: r e t r o f i t o f e x i s t i n g s t r u c t u r e s and i n c o r p o r a t i o n of a new and e f f i c i e n t d e s i g n f o r expansions and new o p e r a t i o n s . The c r i t e r i a f o r the new design were: ease of c o n s t r u c t i o n and improvement of the i n t e r n a l s o l a r r a d i a t i o n c o l l e c t i o n e f f i c i e n c y of the a t t a c h e d greenhouse. O b v i o u s l y , f o r ease o f c o n s t r u c t i o n a standard gable s t r u c t u r e , w i t h the l o n g - a x i s o r i e n t e d east-west, d i v i d e d by a v e r t i c a l w a l l at the r i d g e g i v i n g two shed s e c t i o n s , was proposed. One s e c t i o n i s an animal s h e l t e r and the other a greenhouse. T h i s d e s i g n would p e r m i t t h e i n s t a l l a t i o n o f a s o l a r c o l l e c t o r i n s i d e the greenhouse, on the upper p o r t i o n of the d i v i d i n g w a l l on the s o u t h - f a c i n g s i d e . The placement of the c o l l e c t o r , i n t h i s manner, i s not expected to i n t e r f e r e with p l a n t s or normal o p e r a t i o n s w i t h i n the greenhouse. However, i t remained t o be seen i f the shed-shaped greenhouse would p e r f o r m a t l e a s t as w e l l as a c o n v e n t i o n a l gable greenhouse h a v i n g i d e n t i c a l f l o o r a r e a , o r i e n t a t i o n and c o n s t r u c t i o n m a t e r i a l s . S u r p r i s i n g l y enough, t h e o r e t i c a l a n a l y s e s i n d i c a t e d t h a t i t s performance as a s o l a r c o l l e c t o r was s i g n i f i c a n t l y b e t t e r than a g a b l e shape greenhouse under Vancouver c l i m a t i c c o n d i t i o n s . T h e r e -f o r e , i t was then d e c i d e d t h a t the shed-shaped greenhouse c o u l d a l s o be used e f f i c i e n t l y as a f r e e - s t a n d i n g s t r u c t u r e . T h i s new d e s i g n was then c a l l e d by the aut h o r as a " s o l a r - s h e d greenhouse" and was a n a l y s e d , i n t h i s s t u d y , s e p a r a t e l y and i n c o m b i n a t i o n w i t h a l i v e s t o c k b u i l d i n g . In 19 80, a s o l a r - s h e d greenhouse was c o n s t r u c t e d a t the A g r i c u l t u r e Canada Research and P l a n t Q u a r a n t i n e S t a t i o n i n S a a n i c h t o n on Vancouver I s l a n d , B r i t i s h Columbia. I t s p e r -formance i s b e i n g compared to a c o n v e n t i o n a l g a b l e g l a s s h o u s e l o c a t e d a t the same s i t e . P r e l i m i n a r y r e s u l t s were p r e s e n t e d by S t a l e y e t a l . ( 1 9 8 1 ) . i I t i s hoped t h a t the da t a c o l l e c t e d from the e x p e r i m e n t a l greenhouse a t S a a n i c h t o n would be used f o r c a l i b r a t i o n o f the mathematical model developed i n t h i s s t u d y . T h i s would make i t p o s s i b l e t o p r e d i c t i t s performance a c c u r a t e l y a t o t h e r l o c a t i o n s i n Canada and elsewhere. PROPOSITIONS The f o l l o w i n g p r o p o s i t i o n s were c o n s i d e r e d to apply to t h i s s t udy: 1. High c o s t s of energy are p l a g u i n g the producers of greenhouse crops, even though the growers are t a k i n g steps to conserve f u e l by i n s t a l l i n g n i g h t heat s a v i n g c u r t a i n s , u s i n g double l a y e r s o f p l a s t i c w i t h an a i r space between the l a y e r s , p l a n t i n g crops l a t e i n the season and growing p l a n t s which have lower temperature requirements (Baird e t a l . ( 1 9 7 7 ) ) . 2- Greenhouses waste s u b s t a n t i a l amounts o f heat by v e n t i l a t i o n d u r i n g the day w h i l e they consume l a r g e amounts of supplemental heat at n i g h t (Chandra and W i l l i t s ( 1 9 8 0 ) , B r u n d r e t t and Turkewitsch(19 79), B a i r d e t a l . ( 1 9 7 7 ) , Short e t a l . ( 1 9 7 6 ) , McCormick(19 76), L i u and Carlson(1976) , P r i c e e t a l . ( 1 9 7 6 ) , W i l l i t s e t a l . (1979), Simpkins e t a l . ( 1 9 7 9 ) ) . 3. E x t e r n a l s o l a r c o l l e c t o r s f o r greenhouses r e q u i r e a l a r g e amount of a d d i t i o n a l space, thus r e s u l t i n g i n a waste of v a l u a b l e land (Brundrett and Turkewitsch(19 79)). 4. I n t e r n a l s o l a r c o l l e c t o r s l o c a t e d i n the r i d g e area of c o n v e n t i o n a l greenhouses w i l l c a s t a shadow on the p l a n t canopy, thus reducing crop p r o d u c t i v i t y (Wiegand(1976)). 5. I n t e r n a l s o l a r c o l l e c t o r s l o c a t e d on the north w a l l of c o n v e n t i o n a l greenhouses w i l l be shaded by the p l a n t s , thus r e d u c i n g the c o l l e c t i o n e f f i c i e n c y o f the s o l a r c o l l e c t o r CWiegand (.1976) ) . 6. V e n t i l a t i o n and supplemental heat i s r e q u i r e d , even d u r i n g c o l d weather p e r i o d s , t o keep the humidity w i t h i n the l i v e s t o c k b u i l d i n g s at a c c e p t a b l e l e v e l s (Bon e t a l . ( 1 9 81), S t a u f f e r and Vaughan(1981), Sokhansanj e t a l . ( 1 9 8 1 ) , S p i l l m a n e t a l . ( 1 9 8 1 ) ) . OBJECTIVES OF THE STUDY The p r i n c i p l e aim o f t h i s study was to reduce the dependence of greenhouse o p e r a t i o n s on f o s s i l f u e l s . The f o l l o w i n g were the main o b j e c t i v e s : 1. To develop a simple, mathematical model which would p r e d i c t the s o l a r r a d i a t i o n capture of greenhouses as a f u n c t i o n of measured i n s o l a t i o n and greenhouse c o n s t r u c t i o n parameters. , 2. To develop a computer s i m u l a t i o n model f o r e s t i m a t i n g p o t e n t i a l energy savings due t o the u t i l i z a t i o n of waste animal heat from l i v e s t o c k b u i l d i n g s t o supplement greenhouse h e a t i n g demand i n a greenhouse-animal s h e l t e r combination. 3. To develop a s u i t a b l e system f o r improving i n t e r n a l s o l a r energy capture by the greenhouse i n an i n t e g r a t e d g r e e n h o u s e - l i v e s t o c k b u i l d i n g . The major assumptions u n d e r l y i n g o b j e c t i v e s 2 and 3 were as f o l l o w s : 1. L i v e s t o c k producers are w i l l i n g to operate greenhouses or v i c e v e r s a , or a c o o p e r a t i v e between a l i v e s t o c k producer and a greenhouse op e r a t o r c o u l d be o r g a n i z e d . 2. Exhaust a i r from the l i v e s t o c k b u i l d i n g does not have a d e t r i m e n t a l e f f e c t on the growth of greenhouse c r o p s . INFERENCES The major i n f e r e n c e s r e l a t e d to t h i s study were the f o l l o w i n g : 1. Daytime waste heat from a greenhouse can be s t o r e d f o r n i g h t use. 2. A s i g n i f i c a n t amount o f s u r p l u s a n i m a l waste h e a t i s a v a i l a b l e t o j u s t i f y i t s recovery f o r greenhouse usage. 3. The shape o f the greenhouse can be a l t e r e d from the c o n v e n t i o n a l i n order t o accommodate f o r an e f f i c i e n t i n t e r n a l s o l a r c o l l e c t i o n system without s e r i o u s l y a f f e c t i n g the a v a i l a b i l i t y o f l i g h t to the p l a n t canopy. 4. An i n t e g r a t e d g r e e n h o u s e - l i v e s t o c k o p e r a t i o n i s more energy e f f i c i e n t than a separate greenhouse p r o d u c t i o n system. The scope of t h i s study was l i m i t e d t o i n v e s t i g a t i o n s u s i n g computer s i m u l a t i o n s . The study c o n s i s t e d of four s t a g e s . In the f i r s t stage, the e f f e c t of greenhouse c o n s t r u c t i o n parameters i n c l u d i n g shape and energy c o n s e r v a t i o n measures on the s o l a r r a d i a t i o n captured by the greenhouse were s t u d i e d t h e o r e t i c a l l y . In the second stage, mathematical models were developed f o r the d i f f e r e n t subsystems of the g r e e n h o u s e - l i v e s t o c k combination. These subsystems i n c l u d e d ; a l i v e s t o c k b u i l d i n g , a c o n v e n t i o n a l greenhouse and a s o l a r -shed greenhouse. In the t h i r d stage, a computer s i m u l a t i o n model was developed based upon the mathematical models of the second stage. .The computer model was kept as g e n e r a l as p o s s i b l e such t h a t i t c o u l d be used to analyse a s i n g l e greenhouse, a s i n g l e l i v e s t o c k b u i l d i n g , a c o n v e n t i o n a l greenhouse-animal s h e l t e r combination, and a s o l a r - s h e d greenhouse e i t h e r f r e e - s t a n d i n g or a t t a c h e d t o a l i v e s t o c k b u i l d i n g . The complete computer program was w r i t t e n i n the FORTRAN language. In the f o u r t h stage, the computer s i m u l a t i o n model was used to i n v e s t i g a g e the f e a s i b i l i t y o f a c o n v e n t i o n a l greenhouse-hog barn combination, and a s o l a r a s s i s t e d greenhouse-swine f i n i s h i n g house combination. The f e a s i b i l i t y study was based on energy savings o n l y . For the convenience and c l a r i t y of p r e s e n t a t i o n , t h i s manuscript i s presented i n three separate p a r t s . P a r t I de a l s w i t h the e f f e c t i v e n e s s o f greenhouses as s o l a r c o l l e c t o r s , where the s o l a r r a d i a t i o n i n p u t and then the s o l a r energy capture by greenhouses are covered i n Chaper 1 and Chapter 2, r e s p e c t i v e l y . P a r t I I i n v e s t i g a t e s the f e a s i b i l i t y of a r e t r o f i t s i t u a t i o n of a c o n v e n t i o n a l g r e e n h o u s e - l i v e s t o c k b u i l d i n g combination. In t h i s p a r t , Chapter 3 i s devoted t o the l i v e s t o c k subsystem, Chapter 4 t o the greenhouse subsystem, w h i l e the combination of the subsystems i s t r e a t e d i n Chapter 5. F i n a l l y , s o l a r energy u t i l i z a t i o n i n a g r e e n h o u s e - l i v e s t o c k b u i l d i n g combination i s i n v e s t i g a t e d i n P a r t I I I . This p a r t i n c l u d e s Chapter 6 where the development of the s o l a r - s h e d greenhouse concept i s g i v e n i n d e t a i l , and Chapter 7 where the combination of t h i s new greenhouse d e s i g n t o an animal s h e l t e r i s i n v e s t i g a t e d . Each of the three p a r t s c o u l d be read s e p a r a t e l y with the e x c e p t i o n of S e c t i o n B of Chapter 2, where the c a l c u l a t i o n o f d i f f u s e r a d i a t i o n c o n f i g u r a t i o n f a c t o r s f o r gable greenhouses i s needed f o r f u l l u nderstanding of the m a t e r i a l i n Chapter 4. A l s o , the mathematical model f o r a l i v e s t o c k b u i l d i n g developed i n Chapter 3 i s a requirement f o r Chapter 7. LITERATURE REVIEW GREENHOUSE THERMAL ENVIRONMENT MODELS Most of the e x i s t i n g mathematical models are based on the energy balance method. T h i s method c o n s i s t s of d i v i d i n g the greenhouse i n t o d i f f e r e n t components; cover, p l a n t canopy, ground and greenhouse a i r mass. The heat and mass f l u x e s among these components are modeled mathematically thus o b t a i n i n g an energy balance f o r each component of the greenhouse system. The r e s u l t i s the g e n e r a t i o n of a system of simultaneous a l g e b r a i c equations to y i e l d the temperatures of the components. S e v e r a l models a r e d i s c u s s e d i n t h i s s e c t i o n whose major o b j e c t i v e i s the p r e d i c t i o n of temperature and humidity i n s i d e the greenhouse. The d i f f e r e n c e s between these models are the assumptions u n d e r l y i n g t h e i r development and the boundary c o n d i t i o n s chosen t o a r r i v e a t a f i n a l s o l u t i o n . Probably the most important assumption, where d i s c r e p a n c i e s between models occur, i s the treatment o f the heat c a p a c i t y of the greenhouse. Some of the models, e i t h e r e x p l i c i t l y o r i m p l i c i t l y , t r e a t a l l components of the greenhouse system as having a n e g l i g i b l e heat c a p a c i t y ; w h ile o t h e r s , s i n g l e out the s o i l component as having a s i g n i f i c a n t heat c a p a c i t y . However, some of the authors o f these models have a l s o expressed concern about t r e a t i n g the p l a n t canopy component as having a n e g l i g i b l e heat c a p a c i t y , but none has c o n s i d e r e d i t otherwise. Ob v i o u s l y , the c h o i c e o f the assumptions with r e s p e c t to the system component's heat c a p a c i t y depends on the intended use of the model. I f the d e t e r m i n a t i o n of psychrometric p r o p e r t i e s of the a i r w i t h i n the greenhouse i s the o b j e c t i v e of the model development, then the heat c a p a c i t y of the s o i l and perhaps t h a t of the p l a n t canopy ( i . e . t a l l p l a n t s a t f u l l stage of growth) should be c o n s i d e r e d . On the other hand, i f the o b j e c t i v e of the model i s the p r e d i c t i o n of greenhouse h e a t i n g requirements, then the steady s t a t e a n a l y ses are adequate (Kindelan, 1980). Other d i s c r e p a n c i e s between the e x i s t i n g models are the s e l e c t i o n s of the boundary c o n d i t i o n s . Primary boundary c o n d i t i o n s , t h a t i s c l i m a t i c v a r i a b l e s t h a t are e a s i l y o b t a i n a b l e , would be p r e f e r r e d . For example, the use of net r a d i a t i o n i n t o the greenhouse or the ground temperature as i n p u t s t o the model i s not recommended. P r e f e r a b l y , these v a r i a b l e s should be determined by the mathematical model from primary boundary c o n d i t i o n s such as s o l a r r a d i a t i o n i n c i d e n t on a h o r i z o n t a l s u r f a c e and ambient a i r temperature. B r i e f d e s c r i p t i o n s f o l l o w o f the most r e c e n t and f r e q u e n t l y r e f e r r e d to mathematical models f o r the p r e d i c t i o n of a green-house thermal environment: Walker (1965) presented an a n a l y t i c a l procedure f o r p r e d i c t i n g temperatures w i t h i n both heated and v e n t i l a t e d greenhouses. A heat balance i n a greenhouse was expressed mathematically i n v o l v i n g s o l a r heat g a i n , c o n d u c t i o n heat l o s s , thermal r a d i a t i o n heat l o s s to atmosphere, v e n t i l a t i o n heat l o s s , e v a p o t r a n s p i r a t i o n heat l o s s , and furnace heat. Experimental t e s t s were conducted to determine the a p p l i c a b i l i t y of the a n a l y t i c a l procedure f o r the p r e d i c t i o n of greenhouse temperatures* They found a mean d i f f e r e n c e between the p r e d i c t e d and observed temperature of 1.4°C f o r p e r i o d s of high s o l a r r a d i a t i o n i n p u t when v e n t i l a t i o n was r e q u i r e d . The a n a l y t i c a l procedure was r e p o r t e d s u i t a b l e f o r p r e d i c t i n g the greenhouse heat requirement d u r i n g c o l d weather p e r i o d s but t e s t r e s u l t s were not i n c l u d e d . Selcuk (1970) used unsteady s t a t e heat and mass balance equations f o r c o n t r o l l e d - e n v i r o n m e n t greenhouses y i e l d i n g 24 simultaneous n o n - l i n e a r d i f f e r e n t i a l e q u a t i o n s . These equations were s o l v e d n u m e r i c a l l y u s i n g the f i n i t e d i f f e r e n c e method. A greenhouse a n a l y s i s which i n c l u d e d the e f f e c t s of s o i l water e v a p o r a t i o n , p l a n t t r a n s p i r a t i o n , and condensation on the cover was presented. Formulations of the heat balance on the cover, heat and mass balance on t h e . a i r s t r e a m , heat balance over the p l a n t canopy and heat balance on moist s o i l were gi v e n i n d e t a i l , greenhouse. The model was found to p r e d i c t temperatures of p l a n t , cover, s o i l s u r f a c e , and i n l e t and o u t l e t a i r w i t h i n 1.5°C. A f i v e percent d i f f e r e n c e between p r e d i c t e d and measured a i r humidity r a t i o s was r e p o r t e d . Takakura e t al.(1971) presented probably the most d e t a i l e d computer s i m u l a t i o n model a v a i l a b l e f o r p r e d i c t i n g temperature v a r i a t i o n s of the s o i l - p l a n t canopy-greenhouse system components. The a n a l y s i s i n c l u d e d s o i l water e v a p o r a t i o n , p l a n t t r a n s p i r a t i o n , condensation on the g l a s s cover, and heat storage i n the s o i l . A two-dimensional heat conduction e q u a t i o n was used to model the s o i l . The s o l u t i o n r e q u i r e s the temperature a t a c e r t a i n depth as a boundary c o n d i t i o n . Beam and d i f f u s e components of s o l a r r a d i a t i o n were c o n s i d e r e d s e p a r a t e l y . Heat balance equations were g i v e n f o r p l a n t s u r f a c e , s o i l s u r f a c e , g l a s s s u r f a c e and a i r w i t h i n the greenhouse. The model was t e s t e d f o r s p e c i f i c days and found to g i v e reasonably a c c u r a t e v a l u e s f o r temperature v a r i a t i o n s . Duncan e t a l .(1976) r e p o r t e d on the development and use of a greenhouse s i m u l a t i o n model f o r p r e d i c t i n g w i n t e r h e a t i n g loads and e v a l u a t i n g the p o t e n t i a l storage and reuse of excess s o l a r energy i n a greenhouse with a rock bed. The greenhouse energy balance model . accounted f o r s o l a r r a d i a t i o n i n p u t , thermal r a d i a t i o n heat l o s s , conduction heat l o s s , v e n t i l a t i o n heat l o s s , e v a p o t r a n s p i r a t i o n heat l o s s and heat l o s s to the ground. The thermal r a d i a t i o n 'and conduction heat l o s s e s were combined u s i n g the o v e r a l l heat t r a n s f e r c o e f f i c i e n t method. The s o l a r heat g a i n w i t h i n a greenhouse was taken as equal to s o l a r r a d i a t i o n i n c i d e n t on an o u t s i d e h o r i z o n t a l s u r f a c e m u l t i p l i e d by two c o n s t a n t s , one r e p r e s e n t i n g the t r a n s m i t t a n c e of the greenhouse c o v e r i n g m a t e r i a l and the other the a b s o r p t i v i t y of the p l a n t canopy. The a b s o r p t i v i t y of p l a n t s and o t h e r o b j e c t s i n the greenhouse to s o l a r r a d i a t i o n was taken as 0.70 to 0.85. D e t a i l e d a n a l y s i s of heat l o s s to the ground was not g i v e n , but each u n i t l e n g t h of greenhouse p e r i m e t e r was assumed to have an e q u i v a l e n t o v e r a l l heat t r a n s f e r c o e f f i c i e n t equal to t h a t o f one u n i t area o f w a l l . C a l i b r a t i o n and v a l i d a t i o n of the model was accomplished u s i n g 3-day measured data i n A p r i l w i t h i n an experimental greenhouse l o c a t e d a t L e x i n g t o n , Kentucky. They found a mean temperature d i f f e r e n c e between simulated and measured va l u e s of l e s s than 1°C. Analyses u s i n g the rock bed s i m u l a t i o n were performed f o r two 9-day win t e r h e a t i n g p e r i o d s r e p r e s e n t i n g c o l d January weather and m i l d e r March weather f o r an under-bench rock storage system. T h e i r r e s u l t s showed l i t t l e p o t e n t i a l f o r excess s o l a r energy storage i n January but p o t e n t i a l l y 11.1% r e d u c t i o n i n h e a t i n g requirement i n March. F r o e h l i c h e t al.(1979) developed a mathematical model f o r p r e d i c t i n g the s t e a d y - p e r i d d i c thermal behavior of greenhouses. The temperature of i n t e r n a l greenhouse a i r , p l a n t canopy, f l o o r s u r f a c e and c o v e r i n g s u r f a c e s were p r e d i c t e d i n c l o s e d form. The model a l s o p r e d i c t s the humidity of the greenhouse a i r . T e s t i n g of the model was found to p r e d i c t the temperatures with reasonable accuracy. But a s i g n i f i c a n t d i f f e r e n c e o c c u r r e d between the measured and p r e d i c t e d humidity r a t i o s at low v e n t i l a t i o n r a t e s . Kindelan(1980) d e s c r i b e d a model to s i m u l a t e the i n t e r n a l greenhouse environment by the energy balance method. The system was d i v i d e d i n t o f o u r components s i m i l a r to the model presented by Takakura e t a l . ( 1 9 7 1 ) . The s o i l , p l a n t , i n t e r n a l a i r and cover were modeled by heat and mass balances. For the s o i l heat flow a n a l y s i s , u n l i k e Takakura's model, the deep ground temperature was not given as a boundary c o n d i t i o n but o b t a i n e d as an a d d i t i o n a l - r e s u l t of the s i m u l a t i o n . I t was s t a t e d i n the paper t h a t t e s t i n g of the greenhouse model was c a r r i e d out by p r e d i c t i n g the ambient c o n d i t i o n s i n a s m a l l hydroponic greenhouse, but o n l y p r e d i c t e d values were r e p o r t e d . T h e r e f o r e , the p r e d i c t i o n accuracy of the model c o u l d not be e v a l u a t e d . Chandra e t al.(1981) improved on the model represented by F r o e h l i c h et al.(1979) by i n c o r p o r a t i n g a d e t a i l e d a n a l y s i s of thermal r a d i a t i o n exchange between p l a n t s and greenhouse s u r f a c e s . The s u r f a c e s were assumed gray, i s o t h e r m a l , and p e r f e c t l y d i f f u s e . 1 When the greenhouse a i r temperature and r e l a t i v e humidity are g i v e n , the model p r e d i c t s the heat and moisture balances of the greenhouse a i r . The model was t e s t e d u s i n g measured greenhouse data r e p o r t e d by F r o e h l i c h ( 1 9 7 6 ) . The data were gathered i n a 22 m x 11 m east-west o r i e n t e d s i n g l e - g l a z e d glasshouse l o c a t e d a t C o r n e l l U n i v e r s i t y . Hourly data f o r o u t s i d e a i r temperature and humidity r a t i o , greenhouse a i r temperature and humidity r a t i o , p l a n t canopy and f l o o r s u r f a c e temperatures i n the greenhouse, and the t o t a l h o u r l y s o l a r r a d i a t i o n on a h o r i z o n t a l s u r f a c e o u t s i d e the greenhouse were used as i n p u t s i n the model. F i v e t e s t days (2 i n August, 1 i n November and 2 i n December) were s e l e c t e d r e p r e s e n t i n g summer and w i n t e r c o n d i t i o n s . Comparison of model p r e d i c t i o n s and measured greenhouse data i n d i c a t e d t h a t the mathematical model can p r e d i c t the greenhouse thermal environment w i t h reasonable accuracy. B r u n d r e t t and Abbot (1981) developed a thermal model f o r p r e d i c t i n g h o u r l y or d a i l y averaged h e a t i n g or v e n t i l a t i n g loads of greenhouses. During the development of the model the f o l l o w i n g f a c t o r s were c o n s i d e r e d ; c o v e r i n g m a t e r i a l , p a s s i v e s o l a r c o n t r i b u t i o n , a i r i n f i l t r a t i o n or v e n t i l a t i o n r a t e , temperature s t r a t i f i c a t i o n w i t h i n the greenhouse and v a r i a t i o n i n the o u t s i d e a i r temperature. The model i s a l s o capable of p r e d i c t i n g h e a t i n g loads f o r greenhouses equipped w i t h thermal c u r t a i n s . The thermal model has been e x t e n s i v e l y t e s t e d u s i n g an experimental greenhouse l o c a t e d i n southern O n t a r i o . They found t h a t monthly average weather c o n d i t i o n s are s u i t a b l e f o r p r e d i c t i n g annual f u e l consumption by greenhouses. During d a y l i g h t hours when s o l a r energy i s a v a i l a b l e , the supplemental heat requirement f o r the greenhouse i s zero or s m a l l . Most of the f o s s i l f u e l f o r greenhouse h e a t i n g i s used a t n i g h t . T h e r e f o r e , heat storage i s a necessary p a r t of a s o l a r energy c o l l e c t i o n system. With r e s p e c t to s o l a r energy a p p l i c a t i o n s to greenhouse h e a t i n g , s o l a r c o l l e c t i o n systems can be d i v i d e d i n t o " i n t e g r a l " and " n o n - i n t e g r a l " c o l l e c t o r s depending on whether the c o l l e c t o r i s c o n tained i n s i d e the greenhouse, or i s a separate c o n s t r u c t i o n o u t s i d e the greenhouse. Furthermore, i n t e g r a l s o l a r c o l l e c t i o n systems can be c l a s s i f i e d as " a c t i v e " or " p a s s i v e " . A comparison of i n t e g r a l versus n o n - i n t e g r a l c o l l e c t o r s f o r greenhouses i s g i v e n i n a l i s t of advantages and disadvantages by P r i c e e t a l . (1976) . An i n t e g r a l s o l a r c o l l e c t i o n system i n a greenhouse w i l l save on the c o s t of c o l l e c t o r c o n s t r u c t i o n and on equipment t h a t would be needed to t r a n s f e r e x t e r n a l l y c o l l e c t e d heat to the greenhouse. In a d d i t i o n , heat l o s s e s i n h e r e n t i n e x t e r n a l c o l l e c t o r s would be e l i m i n a t e d or a t l e a s t reduced by i n t e g r a l c o l l e c t o r s . However, i n t e r n a l greenhouse c o l l e c t i o n systems u s u a l l y have a low e f f i c i e n c y and g i v e lower o p e r a t i n g temperatures than e x t e r n a l c o l l e c t o r s . A l s o , an e x i s t i n g greenhouse may have a poor o r i e n t a t i o n and c o n f i g u r a t i o n f o r i n s t a l l i n g i n t e r n a l s o l a r c o l l e c t o r s . E x t e r n a l c o l l e c t o r s u s u a l l y g i v e h i g h e r c o l l e c t i o n e f f i c i e n c y . They can be i n s t a l l e d a t optimum o r i e n t a t i o n and t i l t f o r s o l a r energy c o l l e c t i o n . The s i z e of i n t e g r a l s o l a r c o l l e c t o r s w i t h i n the greenhouse i s l i m i t e d by a v a i l a b i l i t y of s u i t a b l e space s i n c e care must be taken not to shade p l a n t growing areas while the s i z e of e x t e r n a l c o l l e c t o r s i s u s u a l l y o p t i m i z e d by making use of a p p r o p r i a t e economic a n a l y s e s . NON-INTEGRAL SOLAR COLLECTORS A number of r e s e a r c h e r s have developed low-cost, e x t e r n a l s o l a r c o l l e c t o r s f o r greenhouse a p p l i c a t i o n s u s i n g c l e a r p l a s t i c covers and a b l a c k p l a s t i c absorber sheet. Much of t h i s work was done at Rutgers U n i v e r s i t y , New J e r s e y . Mears and B a i r d (1976) d e s c r i b e d the development and t e s t i n g of t h i s type of c o l l e c t o r coupled w i t h a water heat storage r e s e r v o i r underneath benches i n an a d j o i n i n g greenhouse. The- c o l l e c t o r s were 1.52 m x 2.44 m and 3.96 m x 5.49 m with a d j u s t a b l e l e g s t h a t allowed f o r d i f f e r e n t s lope angles. A l l t e s t s were c a r r i e d out w i t h c o l l e c t o r s a t a 40° t i l t angle. The frames had a plywood back over which two sheets of p o l y e t h y l e n e p l a s t i c were l a i d and separated by a i r to support a b l a c k p o l y e t h y l e n e absorber sheet. At the bottom the b l a c k p o l y e t h y l e n e was p u l l e d up over the frame to p r o v i d e a r e t u r n g u t t e r f o r the heated water. Water flow over the black sheet was maintained by a 31.75 mm PVC header p i p e a t the top of the frame w i t h 0.79 mm h o l e s d r i l l e d on 152.4 mm c e n t e r s . A c l e a r p l a s t i c sheet was used as a cover. I n i t i a l l y the authors found t h a t water flow over the b l a c k p l a s t i c sheet was uneven forming r i v u l e t s . T h i s reduced the p o s s i b l e e f f i c i e n c y of the c o l l e c t o r s i n c e l a r g e areas were not behaving as a c o l l e c t o r . Water coverage was improved by adding d e t e r g e n t to the water supply and e f f i c i e n c y was improved. A f u r t h e r improvement to s h e e t i n g a c t i o n of water was o b t a i n e d by adding a second c l e a r sheet over the c o l l e c t o r and u s i n g a i r i n f l a t i o n to separate these two sheets and f o r c e one c l e a r sheet a g a i n s t the b l a c k c o l l e c t o r sheet. T h i s a l s o improved the i n s u l a t i o n of the c o l l e c t o r . L i g h t absorbed by the second p l a s t i c sheet does not c r e a t e an e f f i c i e n c y l o s s s i n c e t h i s sheet i s i n c o n t a c t w i t h the water and any heat i t c o l l e c t s i s t r a n s f e r r e d t o the water. F i n a l improvements were a d d i t i o n of i n s u l a t i o n to the back of the c o l l e c t o r s and a d d i t i o n of a p o l y p r o p y l e n e mesh shade c l o t h over the b l a c k p o l y e t h y l e n e c o l l e c t o r sheet to improve the evenness of water flow. Under t h e i r t e s t c o n d i t i o n s the authors found t h a t f o r temperature d i f f e r e n c e s up to 22°C the low c o s t p l a s t i c d e s ign compared f a v o r a b l y w i t h c o n v e n t i o n a l c o l l e c t o r s . At 33°C temperature d i f f e r e n c e the e f f i c i e n c y f e l l to about o n e - t h i r d t h a t of a c o n v e n t i o n a l c o l l e c t o r . These u n i t s can p r o v i d e l a r g e amounts of low q u a l i t y heat, but to be w e l l u t i l i z e d they should be coupled to l a r g e heat storage u n i t s w i t h high c a p a c i t y heat t r a n s f e r u n i t s . ' Roberts e t al.(1976) designed a p l a s t i c f i l m s o l a r c o l l e c t o r s i m i l a r i n many r e s p e c t to the one d e s c r i b e d by Mears and B a i r d (.1976) . T h i s c o l l e c t o r has done away wit h the plywood back and used two a i r - i n f l a t e d , c l e a r p o l y e t h y l e n e tubes w i t h a b l a c k p o l y e t h y l e n e absorber sheet sandwiched between them. A 31.75 mm header pipe w i t h h o l e s on 101.6 mm c e n t e r s d i s t r i b u t e s water from the top of the frame to flow over the absorber sheet to the r e t u r n g u t t e r a t the bottom. Detergent was added to the water supply to achieve good s h e e t i n g a c t i o n of water over the b l a c k l a y e r . A l s o , the p r e s s u r e of the c l e a r top sheet touching the b l a c k absorber helped to produce an even flow of water. These c o l l e c t o r s were c o n s t r u c t e d 3.05 m h i g h and 7.32 m long w i t h e a s i l y a d j u s t a b l e supports to vary the c o l l e c t o r t i l t a ngle. The authors r e p o r t e d these c o l l e c t o r s have withstood 96 km/h winds and snow storms without damage. These r e s e a r c h e r s a l s o p o i n t e d out t h a t e f f i c i e n c y decreased a t h i g h e r c o l l e c t i o n temperatures. At the time of w r i t i n g t h e i r paper i n i t i a l c o n s t r u c t i o n c o s t s f o r t h i s d e s i g n were 5.38 d o l l a r s per square metre. The p l a s t i c would have to be r e p l a c e d a n n u a l l y at a c o s t of 1.61 d o l l a r s per square metre. To g a i n b e n e f i t from t h i s type of low c o s t s o l a r c o l l e c t o r the greenhouse system should i n c l u d e : low-cost, l a r g e storage; heat c o n s e r v a t i o n measures; and low-cost, high c a p a c i t y heat exchangers. F u r t h e r m o d i f i c a t i o n s and improvements to t h i s c o l l e c t o r system were r e p o r t e d by Mears e t a l . ( 1 9 7 7 ) . Four p l a s t i c l a y e r s were used i n s t e a d of f i v e . The c o l l e c t o r s had a c l e a r , i n f l a t e d tube f o r the f r o n t l a y e r s and a b l a c k tube to a c t as the absorber p l a t e , support, and back i n s u l a t i o n . A l s o , i t was found t h a t an a l u m i n i z e d l a y e r i n s e r t e d between the absorber p l a t e and back i n f l a t e d cushion reduced the heat l o s s c o e f f i c i e n t by 10 percent due to r e f l e c t i v e i n s u l a t i o n . The authors c a u t i o n t h a t i n d i r e c t s u n l i g h t w i t h no water f l o w i n g the black p l a s t i c c o l l e c t o r sheet can become warm enough to permanently s t i c k to the f r o n t c l e a r sheet. The c o l l e c t o r e f f i c i e n c y ranged between 40 and 60 percent with b e s t e f f i c i e n c y on warm days. On the c o l d e s t days e f f i c i e n c y f e l l to 35 pe r c e n t . T h i s c o l l e c t o r system was c o n s t r u c t e d on a commercial s i t e i n 1978 a t the Kube Pak C o r p o r a t i o n , Allentown, New J e r s e y . Mears e t a l .(1978) r e p o r t e d on the c o n s t r u c t i o n of a 0.54 hec t a r e greenhouse w i t h thermal storage and v e r t i c a l v i n y l c u r t a i n heat exchanger coupled to 1000 square metres of the Rutgers' d e s i g n , n o n - i n t e g r a l , i n f l a t e d - p l a s t i c - f i l m s o l a r c o l l e c t o r s . F u r t h e r i n f o r m a t i o n concerning the performance of the Rutgers system f o r oth e r s o l a r h e a t i n g of greenhouse a p p l i c a t i o n s can be found i n p u b l i c a t i o n s by Mears e t al.(1979) and Simpkins e t a l . (1979). M i l b u r n e t a l . (1977) at Penns y l v a n i a S t a t e U n i v e r s i t y designed a low-cost, a i r - h e a t i n g s o l a r c o l l e c t o r with a f l a t f i b e r g l a s s g l a z i n g f o r greenhouse a p p l i c a t i o n s . C o n s t r u c t i o n was simple and the c o s t was one-half to o n e - t h i r d t h a t o f a c o n v e n t i o n a l s o l a r c o l l e c t o r . The absorber p l a t e was made of 28 gauge sheet s t e e l p a i n t e d f l a t b l a c k . The framing was wood and the s i d e s and back were i n s u l a t e d with f o i l f a c ed polyurethane board. A rock bed storage system was used. The system f o r c o l l e c t i n g and s t o r i n g heat, and h e a t i n g the greenhouse was f u l l y automated by use of d i f f e r e n t i a l thermostats t o operate the a p p r o p r i a t e fans f o r h e a t i n g or c o l l e c t i n g mode. Another type of s o l a r c o l l e c t o r which may be c l a s s i f i e d under n o n - i n t e g r a l systems i s the s o l a r pond. Researchers a t the Ohio State U n i v e r s i t y and the Ohio A g r i c u l t u r a l Research and Development Center have done experiments u s i n g 'Solar ponds' f o r greenhouse h e a t i n g . The s o l a r pond may a c t both as a s o l a r energy c o l l e c t o r and a heat s t o r a g e . Long term storage of summer heat f o r winter h e a t i n g requirements can be achieved. Short e t al.(1976) designed an experimental s o l a r pond; 3 . 6 m deep, 8.5m wide, and 18 . 3 m long. The pond was l i n e d with two 30-mil c h l o r i n a t e d - p o l y e t h y l e n e l i n e r s over a sand bottom and i n s u l a t e d s i d e w a l l s . A s a l t concen-t r a t i o n g r a d i e n t was e s t a b l i s h e d i n the pond so t h a t the bottom 1.8 m had a 20 percent s a l t s o l u t i o n c o n v e c t i v e zone. The top 1.8 m of the pond had a c o n c e n t r a t i o n g r a d i e n t o f 20 percent s a l t to zero percent s a l t a t the s u r f a c e . T h i s top l a y e r was non-convective, s i n c e the s p e c i f i c g r a v i t y i n c r e a s e s w i t h i n c r e a s i n g s a l t c o n c e n t r a t i o n i n the zone fromO - 2.8m depth. Solai r a d i a t i o n passes through the s a l t water and heats the black pond l i n e r ; t h i s heats the 20 percent s a l t c o n c e n t r a t i o n g r a d i e n t a t the bottom of the pond. The non-convective upper layer i s e s s e n t i a l l y transparent to incoming u l t r a v i o l e t and v i s i b l e r a d i a t i o n and opaque to r e r a d i a t e d thermal energy. The non-convective top l a y e r a l s o p r o v i d e s good i n s u l a t i o n a g a i n s t c o n d u c t i v e l o s s e s . S o l a r ponds of t h i s type must be l e a k - p r o o f or the hot b r i n e w i l l be l o s t , as w e l l as the i n s u l a t i o n e f f e c t i v e n e s s of dry s o i l around the pond. I n i t i a l o p e r a t i o n showed t h a t the pond had a good p o t e n t i a l t o perform as expected, but s e v e r a l o p e r a t i n g problems were observed: wind causes s u r f a c e mixing o f the s a l t g r a d i e n t ; r a i n water d i l u t e s the proper g r a d i e n t at the s u r f a c e ; and o r g a n i c d e b r i s can c o l l e c t i n the pond and o b s t r u c t incoming s o l a r r a d i a t i o n . To overcome some of the problems caused by wind, r a i n and d e b r i s and a l s o to study i n s u l a t i n g b e n e f i t s o f the cover, H u s s e i n i e t a l . (1979) c o n s t r u c t e d a p o l y e t h y l e n e cover over the s o l a r pond designed by Short e t a l . (1976). They a l s o i n s t a l l e d a r e f l e c t o r on the n o r t h w a l l w i t h a t i l t angle of 75° over the pond i n an attempt t o i n c r e a s e the s o l a r r a d i a t i o n i n p u t . T h e i r t e s t s showed t h a t the p l a s t i c cover was of q u e s t i o n a b l e b e n e f i t . The cover and s u p p o r t i n g frame decreased the r a d i a t i o n to the pond's s u r f a c e by about 10 pe r c e n t . They a l s o found t h a t the maximum b e n e f i t o f the r e f l e c t o r o c c u r r e d i n the win t e r months. The annual energy g a i n o f the pond w i t h a r e f l e c t o r was 12 percent f o r a slope o f 75°, and 14 percent f o r s lope equal t o 90°. Shah et al.(1981) added another refinement to the s o l a r pond concept by u s i n g a heat pump t h a t uses a s o l a r pond as i t s heat source f o r h e a t i n g the greenhouse. T h i s i n c r e a s e s the e f f e c t i v e n e s s o f the heat pump as w e l l as the s o l a r pond. A heat pump designed f o r a source temperature o f 5°C to 40°C i n the pond has g r e a t e r s t a b i l i t y and h i g h e r e f f i c i e n c y than a heat pump t h a t uses the ambient a i r as i t s heat source. A l s o , the energy storage and a v a i l a b i l i t y o f s t o r e d energy i s i n c r e a s e d by a heat pump. Energy can be e f f i c i e n t l y e x t r a c t e d down t o lower temperatures i n the heat source even when the s o l a r pond temperature i s below t h a t of the greenhouse. EXCESS INTERNAL HEAT COLLECTION An excess amount of heat from the c o l l e c t e d and trapped s o l a r r a d i a t i o n w i t h i n greenhouses i s u s u a l l y a v a i l a b l e around noon hours. T h i s excess heat must be e l i m i n a t e d by e i t h e r n a t u r a l or f o r c e d v e n t i l a t i o n . Many de s i g n concepts have been proposed t o c o l l e c t t h i s excess heat and s t o r e i t f o r l a t e r use (Wilson e t a l . ( 1 9 7 7 ) , B a i r d e t a l . ( 1 9 7 7 ) , Rotz and A l d r i c h ( 1 9 7 8 ) , M i l b u r n and A l d r i c h ( 1 9 7 9 ) , A l b r i g h t et al.(1979) and Chandra and W i l l i t s ( 1 9 8 0 ) ) . Wilson e t al.(1977) adopted the n o t i o n o f the greenhouse as a s o l a r c o l l e c t o r ; they attempted t o determine i t s s o l a r energy c o l l e c t i o n e f f i c i e n c y and ways t o i n c r e a s e t h i s e f f i c i e n c y . In t h e i r a n a l y s i s , they c o n s i d e r e d the greenhouse as a h o r i z o n t a l f l a t p l a t e s o l a r c o l l e c t o r o f s u r f a c e area equal t o i t s f l o o r a r e a. The greenhouse s o l a r c o l l e c t i o n e f f i c i e n c y was then c a l c u l a t e d by d i v i d i n g the s o l a r component of daytime h e a t i n g l o a d by the measured i n s o l a t i o n as given by weather data. They found t h a t f o r the greenhouse under study, l o c a t e d at C o r n e l l U n i v e r s i t y , the greenhouse s o l a r c o l l e c t i o n e f f i c i e n c y , as d e f i n e d above, was about 32 p e r c e n t . Among the methods Wilson e t a l . have proposed to improve the greenhouse s o l a r c o l l e c t i o n e f f i c i e n c y were: a d d i t i o n of a second cover, i n s u l a t i o n of the n o r t h w a l l , i n s u l a t i o n of a p o r t i o n or a l l of the n o r t h r o o f , and m o d i f y i n g the greenhouse shape t o maximize s o l a r r a d i a t i o n i n p u t . B a i r d e t a l . (1977) d e s c r i b e d the d e s i g n and o p e r a t i o n of a greenhouse s o l a r h e a t i n g system t h a t uses p a r t i a l shading i n the greenhouse a t t i c as the s o l a r c o l l e c t o r and an under-bench rock thermal s t o r a g e . The p a r t i a l shading i s accomplished by a l a y e r of p o l y p r o p y l e n e shade c l o t h and a l a y e r of c l e a r p o l y e t h y l e n e which c o n s t i t u t e the o n l y a d d i t i o n a l c o s t of the s o l a r c o l l e c t o r . The authors hope t h i s system would be s u i t a b l e f o r ornamental f o l i a g e producers, where a 50 percent r e d u c t i o n i n l i g h t w i l l probably be a c c e p t a b l e . The system has been t e s t e d i n a glasshouse l o c a t e d a t Bradenton, F l o r i d a . T h e i r r e s u l t s showed t h a t t h i s 1 s o l a r h e a t i n g system p r o v i d e s enough heat to m a i n t a i n a minimum greenhouse temperature a t l e a s t 14°C above ambient. For reason of l i g h t a v a i l a b i l i t y , the above d e s c r i b e d system o b v i o u s l y i s not a p p l i c a b l e under Canadian c o n d i t i o n s . Rotz and A l d r i c h (197 8) attempted to p r e d i c t , through computer s i m u l a t i o n s , the p o s s i b l e f u e l s a v i n g s and c o s t b e n e f i t s f o r the use of thermal i n s u l a t i o n (double g l a z i n g and/or thermal blankets) and s o l a r heat u t i l i z a t i o n ( i n t e r n a l or e x t e r n a l c o l l e c t i o n ) i n a commercial-sized greenhouse a t e i g h t l o c a t i o n s a c r o s s the Un i t e d S t a t e s . T h e i r c o n c l u s i o n s i n d i c a t e d t h a t a l l these systems were able to reduce the f u e l requirement s u b s t a n t i a l l y a t a l l l o c a t i o n s except the i n t e r n a l c o l l e c t i o n system. T h i s system o n l y performed w e l l i n the m i l d c l i m a t i c r e g i o n s ( i . e . C a l i f o r n i a , F l o r i d a ) . In c o l d c l i m a t e r e g i o n s of the U.S., i n t e r n a l s o l a r energy c o l l e c t i o n i n greenhouses was p r e d i c t e d to r e s u l t i n l e s s than 5 per c e n t f u e l s a v i n g . M i l b u r n and A l d r i c h (1979) s t u d i e d the e f f e c t i v e n e s s of c o l l e c t i n g the excess heat generated by s o l a r r a d i a t i o n i n a greenhouse by c i r c u l a t i n g the warm a i r as i t i s c o l l e c t e d under the ro o f r i d g e of the greenhouse through a rock heat storage u n i t . In p a r t i c u l a r , they compared a system using a p l a s t i c tube w i t h i n l e t h o l e s p l a c e d along the r i d g e of the greenhouse w i t h a fan and d u c t i n g to c i r c u l a t e the warm a i r from the r i d g e to the heat storage u n i t s w i t h a s i m i l a r system minus the p l a s t i c t u b i n g . in their conclusion to the study, the authors found t h a t w i t h t h i s method of c o l l e c t i o n o f excess i n t e r n a l heat i n a s i n g l e cover greenhouse, l o c a t e d i n P e n n s ylvania, 10 to 20 per c e n t of the annual h e a t i n g l o a d c o u l d be met. The performance of t h i s system was found to be dependent on ambient temperature, crop zone temperature and a i r flow r a t e . The use of the p e r f o r a t e d c o l l e c t i o n duct i n the r i d g e improved the c o l l e c t i o n e f f i c i e n c y o f the system. Chandra and W i l l i t s (1980) developed a computer s i m u l a t i o n model to p r e d i c t the thermal behavior o f a greenhouse att a c h e d to a rock bed thermal storage s i t u a t e d o u t s i d e the greenhouse. The rock storage i s charged from excess s o l a r energy c o l l e c t e d i n the greenhouse. The model as presented i n the paper was intended to p r e d i c t temperatures, r e l a t i v e h u m i d i t i e s , and heat balances f o r the greenhouse a i r and the rock bed. The model was t e s t e d u s i n g measured data from a prototype o p e r a t i n g system l o c a t e d i n R a l e i g h , North C a r o l i n a . The p r e d i c t e d v a l u e s o f temperatures and h u m i d i t i e s were reasonably c l o s e to the measured data. However, an estimate f o r the system e f f i c i e n c y , e i t h e r p r e d i c t e d o r c a l c u l a t e d from e x p e r i mental data, was not g i v e n . A l b r i g h t e t al.(1979) t e s t e d y e t another method of improving the greenhouse as a p a s s i v e s o l a r c o l l e c t o r . T h i s method c o n s i s t e d of l a y i n g f l a t wide p o l y e t h y l e n e t u b i n g , f i l l e d w i t h water, on the benches or ground between the rows of pots or p l a n t s . These tubes are u s u a l l y r e f e r r e d to as Q-mats*. The purpose of these Q-mat tubes i s t o i n c r e a s e the thermal mass w i t h i n the greenhouse. T e s t s performed with the Q-mats i n d i c a t e d t h a t approximately 55 per c e n t of the i n c i d e n t s o l a r r a d i a t i o n was absorbed when they were used w i t h the absence of p l a n t canopy. However, when the Q-mat * Trade name. tubes were p l a c e d under a t h i c k canopy (chrysanthemums i n the bud stage), o n l y 25 percent of the s o l a r r a d i a t i o n above the canopy was absorbed by the tubes. Experiments w i t h Q-mats performed by the authors at C o r n e l l U n i v e r s i t y d u r i n g the w i n t e r i n d i c a t e d a c o n t r i b u t i o n of about 10 percent t o the n i g h t h e a t i n g requirement o f a Brace I n s t i t u t e s t y l e greenhouse. Lawand e t al.(1973, 1975) proposed an u n c o n v e n t i o n a l l y shaped greenhouse f o r c o l d e r r e g i o n s . The b a s i s f o r the new design was t o maximize s o l a r r a d i a t i o n i n p u t and reduce heat l o s s e s a s s o c i a t e d w i t h c o n v e n t i o n a l greenhouse d e s i g n s . The proposed greenhouse has a l o n g - a x i s o r i e n t e d e a s t -west, the s o u t h - f a c i n g r o o f and w a l l are t r a n s p a r e n t , and the i n s u l a t e d n o r t h - f a c i n g w a l l i s i n c l i n e d toward the south and covered w i t h s o l a r r a d i a t i o n r e f l e c t i v e m a t e r i a l on the i n t e r i o r f a c e . The angle o f the t r a n s p a r e n t r o o f , and the i n c l i n e d w a l l are l o c a t i o n s p e c i f i c . These angles are chosen to o p t i m i z e both the s o l a r r a d i a t i o n t r a n s m i s s i o n by the south r o o f , and the r e f l e c t i o n of t h i s r a d i a t i o n by the r e a r w a l l on the p l a n t canopy. T h i s type of d e s i g n became to be known as the Brace I n s t i t u t e greenhouse. An experimental Brace I n s t i t u t e greenhouse having the t r a n s p a r e n t s u r f a c e s covered w i t h a double l a y e r of p o l y e t h y -lene was t e s t e d d u r i n g a c o l d w i n t e r i n Quebec C i t y . The authors claimed a r e d u c t i o n i n h e a t i n g requirements of 30 to 40 percent compared to a c o n v e n t i o n a l , double l a y e r e d p l a s t i c covered greenhouse. They a l s o r e p o r t e d an i n c r e a s e i n crop yields (tomatoes and l e t t u c e ) grown i n the new greenhouse. The improved crop p r o d u c t i o n was a t t r i b u t e d t o i n c r e a s e d l i g h t a v a i l a b i l i t y i n the Brace I n s t i t u t e green-house d u r i n g the w i n t e r p e r i o d . INTEGRAL SOLAR COLLECTORS Very l i t t l e r e s e a r c h has been done on i n t e g r a l s o l a r c o l l e c t o r s f o r greenhouses because of t h e i r l i m i t e d a p p l i c a t i o n s . I n t e g r a l s o l a r c o l l e c t o r s are l i k e l y to be l i m i t e d t o r e l a t i v e l y s m a l l greenhouses. As a g e n e r a l r u l e , the s i z e o f c o l l e c t o r r e q u i r e d f o r s o l a r h e a t i n g o f greenhouses should be approximately equal t o the f l o o r area o f the green-house. I t i s i m p o s s i b l e t o i n s t a l l a c o l l e c t o r system of t h i s s i z e w i t h i n the greenhouse without shading the p l a n t s and i n t e r f e r i n g with normal greenhouse o p e r a t i o n s . Recognizing the above l i m i t a t i o n s , r e s e a r c h e r s who attempted to apply i n t e g r a l - s o l a r c o l l e c t o r s t o greenhouse h e a t i n g have c o n c e n t r a t e d on t,he use o f the n o r t h - f a c i n g w a l l of the greenhouse. P r e v i o u s s t u d i e s showed t h a t i n s u l a t i o n of the nor t h w a l l had no e f f e c t on p l a n t y i e l d ( W i l l i t s e t a l . 1979). L i g h t l e v e l s i n i n s u l a t e d greenhouses such as the Brace d e s i g n were i n v e s t i g a t e d by Turkewitsch and Brundrett(1979) f o r Toronto and Winnipeg, u s i n g a computer s i m u l a t i o n model. Four greenhouses were chosen f o r study; a N-S o r i e n t e d gable, an E-W o r i e n t e d gable, a Brace type and a Greensol type. The l a t t e r i s a m o d i f i e d Brace d e s i g n , developed by the authors. Both the Brace and the Greensol have an i n s u l a t e d and r e f l e c t i v e n o r t h w a l l . F l o o r l e v e l r a d i a t i o n i n the f o u r greenhouses were computed. When the r e s u l t s of the two gable greenhouses were compared, the N-S r i d g e was found t o c o l l e c t more s o l a r r a d i a t i o n i n the summer months, and l e s s i n the w i n t e r months than the one w i t h an E-W r i d g e o r i e n t a t i o n . However, when the r e s u l t s of the f o u r greenhouses were compared, the authors found t h a t the Brace type has the h i g h e s t w i n t e r s o l a r r a d i a t i o n c o l l e c t i o n e f f i c i e n c y and the lowest summer c o l l e c t i o n e f f i c i e n c y of a l l the greenhouses i n both l o c a t i o n s . L i u and Carlson(1976) have proposed a greenhouse design u s i n g a f l a t p l a c e c o l l e c t o r f a c i n g south at a t i l t angle of 60°. I t would be l o c a t e d on the r o o f of an A-frame head house b u i l t i n s i d e the n o r t h w a l l of the greenhouse. The authors recommended t h a t a s i n g l e - p l a t e , c o r r u g a t e d aluminum c o l l e c t o r be used. The aluminum should be dark coated, and a copper tube m a n i f o l d , w i t h h o l e s d r i l l e d to match the v a l l e y s i n the aluminum c o r r u g a t i o n s , suspended over the top o f the c o l l e c t o r t o supply water flow. A g u t t e r at the bottom would c o l l e c t the heated water. A s e l e c t i v e r e f l e c t i n g c o l l e c t o r cover may be used t o enhance the r a d i a t i o n f o r crop growth i n the p l a n t -i n g a r ea. C a l c u l a t i o n s f o r t h i s d e s i g n are presented f o r B e l t s v i l l e , Maryland at 4 0°N l a t i t u d e f o r a greenhouse 7.32m long by 6.1m 2 wide. The i n t e g r a l s o l a r c o l l e c t o r has a s u r f a c e area o f 36m . The authors estimated t h a t the s o l a r c o l l e c t o r and storage system c o u l d account f o r 78 percent o f the greenhouse h e a t i n g l o a d . 2 A 46.47m greenhouse wi t h a f l a t p l a t e s o l a r c o l l e c t o r as a p a r t of the n o r t h - f a c i n g w a l l w i t h a crushed rock thermal storage l o c a t e d underneath the co n c r e t e f l o o r was designed and t e s t e d by C l i c k and P i l e ( 1 9 8 0 ) . The greenhouse was b u i l t w i t h one-quarter c i r c l e p i p e frame members t o form the south w a l l and r o o f . The n o r t h w a l l was an i n s u l a t e d wood frame c o n s t r u c t i o n The c o v e r i n g was two a i r separated l a y e r s o f p o l y e t h y l e n e s h e e t i n g 2 The 28m f l a t p l a t e c o l l e c t o r on the i n t e r i o r o f the n o r t h -f a c i n g w a l l used 26 guage, c o r r u g a t e d metal r o o f i n g p a i n t e d f l a t b l a c k , f a s t e n e d over a system o f wooden spacers t h a t formed a i r - f l o w channels behind the b l a c k metal c o l l e c t o r . A fan i n the bottom o f the w a l l p u l l e d a i r through a plenum a t the top of the w a l l and then f o r c e d the- heated a i r through the rock s t o r a g e . The c o o l e d a i r e x i t e d the rock storage at the f r o n t i n s i d e w a l l o f the greenhouse. A d i f f e r e n t i a l thermostat c o n t r o l l e d the c i r c u l a t i n g f an moving a i r through the s o l a r c o l l e c t o r . When the a i r behind the c o l l e c t o r p l a c e was 10°C hig h e r than the rock storage temperature, a i r was c i r c u l a t e d through the system. Data c o l l e c t e d d u r i n g the w i n t e r of 1979-1980 i n d i c a t e d t h a t a greenhouse of t h i s type, l o c a t e d i n C o o k e v i l l e , Tennessee, c o u l d r e a l i z e s i g n i f i c a n t energy savings up u n t i l l a t e November and b e g i n n i n g again i n l a t e February. The authors found t h a t t h i s system c o u l d reduce h e a t i n g c o s t s or extend growing seasons i n unheated greenhouses. The Boeing Company has i n t r o d u c e d an i n t e r e s t i n g approach to i n t e g r a l s o l a r c o l l e c t o r s f o r greenhouse use (Deminet, 1976). The g l a s s c o l l e c t o r s f u n c t i o n both as the greenhouse g l a z i n g and as a s o l a r c o l l e c t o r . T h i s concept would i n c r e a s e the r a t i o o f c o l l e c t o r t o greenhouse f l o o r a r e a . As s t a t e d e a r l i e r , low r a t i o s are the major c o n s t r a i n t s t o e f f i c i e n t use of i n t e g r a l s o l a r c o l l e c t o r s f o r greenhouses. The Boeing dual greenhouse c o v e r - s o l a r c o l l e c t o r system i s b a s i c a l l y a sandwich c o n s t r u c t i o n with t h r e e l a y e r s o f g l a s s forming two spaces. The top space i s empty wi t h a p a r t i a l vacuum. The bottom l a y e r i s designed to conduct the flow of c i r c u l a t i n g c o l l e c t o r f l u i d . I d e a l l y , the c o l l e c t o r f l u i d can be chosen to t r a n s m i t o n l y s e l e c t e d p o r t i o n s of the s o l a r spectrum so t h a t the most u s e f u l p o r t i o n o f i n s o l a t i o n f o r p l a n t growth ( p h o t o s y n t h e t i c a l l y a c t i v e r a d i a t i o n ) i s t r a n s m i t t e d t o the crop. The p o r t i o n of the s o l a r spectrum a t o t h e r wavelengths i s absorbed and t r a n s -formed to heat i n the c o l l e c t o r f l u i d . I t appears t h a t t h i s technology might have a p p l i c a t i o n i n warm c l i m a t e s where mid-day s c r e e n i n g of some d i r e c t i n s o l a t i o n i s necessary anyway. At the time Deminet(1976) presented h i s paper, the system was not t r i e d i n a p r a c t i c a l a p p l i c a t i o n and s u i t a b l e c o l l e c t o r f l u i d s had not been chosen. R e c e n t l y , van Bavel and Sadler(1979) a t Texas A & M U n i v e r s i t y , experimented w i t h what they have c a l l e d f l u i d -r o o f greenhouse concept. The t e s t s were performed i n a s m a l l , s p e c i a l l y designed greenhouse. No crops were grown i n the greenhouse, but the f l o o r was covered w i t h a standard S t . Augustine t u r f . The main o b j e c t i v e s of these p r e l i m i n a r y t e s t s were to f i n d s o l u t i o n s t o some c o n s t r u c t i o n e n g i n e e r i n g problems, r a t h e r than to conduct a d e t a i l e d study On p l a n t behavior i n the d i f f e r e n t environment c r e a t e d by the f l u i d -f i l t e r r o o f . Experience gained by the authors from these p r e l i m i n a r y t e s t s suggested t h a t the plumbing and c i r c u l a t i o n of the copper c h l o r i d e s o l u t i o n , used as i n f r a r e d absorbing f l u i d , p r e s e n t problems t h a t must be s o l v e d p r i o r to any p r a c t i c a l a p p l i c a t i o n . I t i s d o u b t f u l t h a t the f l u i d - r o o f greenhouse concept would be a p p l i e d i n c o l d e r regions* T h e r e f o r e , no f u r t h e r d i s c u s s i o n s of t h i s system w i l l be g i v e n d u r i n g t h i s study. The i n t e r e s t e d reader i s r e f e r r e d t o p u b l i c a t i o n s by van Bavel (1978), van Bavel and Damagnez(1978), and van Bavel et a l . ( 1 9 8 0 ) . Gaseous contaminants found i n c o n f i n e d animal b u i l d i n g s o r i g i n a t e not o n l y from manure decomposition but a l s o from the animals themselves. M e t a b o l i c processes by the housed animals c o n s t i t u t e the main source of carbon d i o x i d e i n barns, w h i l e decomposition of manure i s the c h i e f c o n t r i b u t o r to ammonia, methane and hydrogen s u l f i d e c o n c e n t r a t i o n s found i n animal barns. A p p l i c a t i o n of the g r e e n h o u s e - l i v e s t o c k b u i l d i n g combination concept r e q u i r e s the knowledge not o n l y of the gases p r e s e n t i n the v e n t i l a t e d a i r from the l i v e s t o c k b u i l d i n g but a l s o t h e i r c o n c e n t r a t i o n s . U n f o r t u n a t e l y , a c t u a l data on gas c o n c e n t r a t i o n s i n exhaust a i r from animal barns under Canadian c o n d i t i o n s are not r e a d i l y a v a i l a b l e . However, r e c e n t i n f o r m a t i o n g i v e n by McQuitty and Feddes (1982) and van D a l f s e n and B u l l e y (1982) c o u l d be used as a g u i d e l i n e to estimate the expected c o n c e n t r a t i o n s i n the exhaust a i r . AMMONIA A l i t e r a t u r e review undertaken by McQuitty and Feddes (1982) r e v e a l e d t h a t NH^ c o n c e n t r a t i o n s vary c o n s i d e r a b l y i n animal barns. In a w e l l v e n t i l a t e d b u i l d i n g , -expected c o n c e n t r a t i o n s appear to l i e i n the 5 to 30 ppm range. Values of 50 ppm however, are not uncommon d u r i n g p e r i o d s o f w i n t e r minimum v e n t i l a t i o n r a t e s . McQuitty and Feddes (1982) recorded NH^ c o n c e n t r a t i o n s i n the range of 5 to 12 ppm i n f o u r swine b u i l d i n g s ; 2 to 12 ppm i n two b r o i l e r houses; and l e s s than 2 ppm i n f o u r d a i r y barns. van D a l f s e n and B u l l e y (.1982) r e p o r t e d a range between 1 to 7 ppm i n f o u r d a i r y u n i t s with s u b f l o o r manure stora g e . During a g i t a t i o n of manure, high e r NH^ c o n c e n t r a t i o n s can be a n t i c i p a t e d , p o s s i b l y i n the range o f 100 to 200 ppm (McQuitty and Feddes, 1982). HYDROGEN SULFIDE Values of H 2S c o n c e n t r a t i o n s have been found to be u n d e t e c t a b l e to low i n many t o t a l confinement animal b u i l d i n g s . C o n c e n t r a t i o n s i n swine barns tend to be somewhat h i g h e r than i n b u i l d i n g s housing other types of animals. McQuitty and Feddes (1982) found mean H 2S c o n c e n t r a t i o n s under win t e r c o n d i t i o n s of l e s s than 10 ppb i n two b r o i l e r houses and f o u r d a i r y barns. In f o u r swine barns, the authors found mean H 2S c o n c e n t r a t i o n s of 70 ppb j u s t above the s l o t t e d -f l o o r w h i l e l e s s than 10 ppb was measured i n the exhaust a i r . van D a l f s e n and B u l l e y (1982) found t h a t H 2S was u n d e t e c t a b l e i n the f o u r d a i r y u n i t s d u r i n g normal o p e r a t i n g c o n d i t i o n s . However, when n.anure i s d i s t u r b e d , p a r t i c u l a r l y by a g i t a t i o n , an immediate r e l e a s e of the gas i n l a r g e q u a n t i t i e s w i l l occur r e s u l t i n g i n c o n s i d e r a b l e i n c r e a s e i n c o n c e n t r a t i o n s . They r e p o r t e d a c o n c e n t r a t i o n of 2.7 ppm d u r i n g a g i t a t i o n of the manure i n the four d a i r y barns. METHANE McQuitty and Feddes (1982) s t a t e d t h a t CH 4 c o n c e n t r a t i o n s l i k e l y to be encountered i n v e n t i l a t e d animal b u i l d i n g s would not be a d i r e c t h e a l t h hazard, even under w i n t e r minimum v e n t i l a t i o n r a t e s . Expected c o n c e n t r a t i o n s were not r e p o r t e d . CARBON DIOXIDE C0 2 i s normally p r e s e n t i n f r e s h a i r a t a c o n c e n t r a t i o n i n the order o f 300 ppm. C o n c e n t r a t i o n s i n the range of 500 to 3000 ppm were experienced i n v e n t i l a t e d animal b u i l d i n g s . During w i n t e r c o n d i t i o n s , McQuitty and Feddes(1982) found c o n c e n t r a t i o n s of C0 2 to be l e s s than 4000 ppm i n fou r swine b u i l d i n g s , two b r o i l e r houses and four d a i r y barns i n A l b e r t a . The e f f e c t of C O 2 enrichment on greenhouse crop p r o d u c t i o n was r e c e n t l y i n v e s t i g a t e d by W i l l i t s and Peet (1981) i n R a l e i g h , North C a r o l i n a . Greenhouse crops t e s t e d were tomatoes, cucumbers and bedding p l a n t s . Average concen-t r a t i o n s o f C 0 2 w i t h i n the greenhouse ranged between 1000 and 1050 ppm when the s e t p o i n t was e s t a b l i s h e d a t 1000 ppm. T h e i r experimental r e s u l t s i n d i c a t e d an average i n c r e a s e d y i e l d of 14.6 percent f o r tomatoes, 42 percent f o r cucumbers and 104 percent f o r bedding p l a n t s . For cucumbers, the percentage i n c r e a s e ranged between 32.2% to 60.7% depending on the c u l t i v a r w i t h V e t o m i l g i v i n g the greatest i n c r e a s e i n p r o d u c t i o n . Among the bedding p l a n t s t e s t e d , pepper p l a n t s were h e a v i e r i n the CO^ e n r i c h e d greenhouse by 135 percen t , f o l l o w e d by r e g u l a r tomatoes, then c h e r r y tomatoes which showed i n c r e a s e s i n ha r v e s t weights of 123 percent and 69 percent, r e s p e c t i v e l y . No attempt was made to "grow out" these p l a n t s to determine CO,, enrichment e f f e c t on f r u i t y i e l d s i n the f i e l d . O bviously, the i n c r e a s e d y i e l d s due to greenhouse C O 2 enrichment found by W i l l i t s and Peet (1981) c o u l d o n l y be taken as a r e p r e s e n t a t i v e case due to the complexity o f the i n t e r a c t i o n s between CO,, c o n c e n t r a t i o n s and oth e r environmental f a c t o r s i n c l u d i n g l i g h t i n t e n s i t y and temperature. In any event, the study by the above mentioned authors showed the b e n e f i c i a l e f f e c t s of C 0 2 enrichment on greenhouse crop. Since the a c t u a l C 0 2 c o n c e n t r a t i o n s i n exhaust a i r from l i v e s t o c k b u i l d i n g i s not w e l l d e f i n e d , the p o t e n t i a l i n c r e a s e i n y i e l d s of crops grown i n a greenhouse-animal s h e l t e r combination c o u l d not be determined without e x p e r i m e n t a t i o n . In a d d i t i o n , exhaust a i r from animal barns c o n t a i n s o t h e r gases than C0 2, i n c l u d i n g high c o n c e n t r a t i o n s of water vapour which may have an adverse e f f e c t on greenhouse crop p r o d u c t i v i t y . An e x t e n s i v e review of the l i t e r a t u r e , undertaken f o r t h e p r e s e n t r e s e a r c h p r o j e c t , r e v e a l e d t h a t n e i t h e r t h e o r e t i c a l nor experimental i n f o r m a t i o n on the concept of combined g r e e n h o u s e - l i v e s t o c k b u i l d i n g systems was a v a i l a b l e . However, the l i t e r a t u r e search i n d i c a t e d a s i g n i f i c a n t amount of r e s e a r c h , development and demonstration p r o j e c t s were performed on greenhouse-residence combinations by e n g i n e e r s , a r c h i t e c t s and e c o l o g i s t s . The greenhouse i s mainly used i n t h i s case as a s o l a r c o l l e c t o r p a r t i a l l y .to p r o v i d e the h e a t i n g l o a d o f the att a c h e d house. In a g r e e n h o u s e - l i v e s t o c k combination, the b a s i c approach i s t o t a l l y d i f f e r e n t than t h a t used with r e s p e c t to the greenhouse-residence combination, s i n c e the concept of the former combination i s to use animal heat to supply some of h e a t i n g requirements of the att a c h e d greenhouse. T h e r e f o r e , the i n f o r m a t i o n on greenhouse-residence combination i s somewhat i r r e l e v a n t to t h i s study and w i l l not be d i s c u s s e d f u r t h e r . The i n t e r e s t e d reader i s r e f e r r e d to the many e x c e l l e n t papers p u b l i s h e d i n the Proceedings of the annual conferences on S o l a r Energy f o r Heating Greenhouses and Greenhouse-residence combinations*. * A v a i l a b l e from N a t i o n a l T e c h n i c a l Information S e r v i c e U.S. Department of Commerce S p r i n g f i e l d , VA 22161 In 1980, r e s e a r c h e r s a t Kansas S t a t e U n i v e r s i t y p u b l i s h e d a study d e a l i n g w i t h a greenhouse-animal s h e l t e r combination (Spillman e t a l . 1980). The main o b j e c t i v e s of the r e s e a r c h underway a t Kansas S t a t e U n i v e r s i t y were to e v a l u a t e y i e l d and q u a l i t y o f greenhouse crops s u p p l i e d w i t h exhaust a i r from a hog house, and to compare the amounts of f o s s i l f u e l requirements of a c o n v e n t i o n a l greenhouse to those of a greenhouse u s i n g exhaust a i r from animal b u i l d i n g s w i t h s o l a r energy s t o r a g e . The Kansas S t a t e U n i v e r s i t y experimental f a c i l i t y u n i t . c o n s i s t e d of an experimental greenhouse a t t a c h e d t o the south-f a c i n g w a l l of a swine f i n i s h i n g barn and a c o n v e n t i o n a l greenhouse f o r c o n t r o l . Both greenhouses have the same dimensions of 6 m by 7.3 m and were covered by a i r i n f l a t e d double p o l y e t h y l e n e f i l m . The a i r flow r a t e from the hog barn was i n t r o d u c e d t o the experimental greenhouse e i t h e r a t 3 3 680 m per hour or 1200 m per hour. In a d d i t i o n the 3 experimental greenhouse had 7.25 m v e r t i c a l rock bed thermal storage f o r excess i n t e r n a l s o l a r heat c o l l e c t i o n . S p i l l m a n e t a l (1980) d e a l t e x c l u s i v e l y w i t h the e f f e c t s of s u p p l y i n g the greenhouse wi t h animal produced carbon d i o x i d e on crop p r o d u c t i o n . A i r samples taken w i t h i n the atta c h e d greenhouse i n d i c a t e d a carbon d i o x i d e c o n c e n t r a t i o n of 1500 ppm when both hoghouse and greenhouse were u n v e n t i l a t e d , and 450 ppm to 600 ppm when both were v e n t i l a t e d . In a d d i t i o n t o v e n t i l a t i o n r a t e s , CO, c o n c e n t r a t i o n s i n the greenhouse depend upon the number and weights of the animals i n the barn; 124 to 202 hogs averaging 30 to 135 kg were prese n t d u r i n g the experiments. P l a n t growth s t u d i e s were performed on tomatoes, cucumbers and b r o c c o l i . Tomato p l a n t s i n the att a c h e d green-house were s t o c k i e r w i t h darker green c o l o r e d l eaves than p l a n t s i n the c o n t r o l greenhouse d u r i n g the f i r s t t h ree months. Then a p p a r e n t l y , they developed i n t e r v e i n a l c h l o r o s i s and d r y i n g and c u r l i n g o f the lower l e a v e s . A week l a t e r , the f r u i t s were d i s c o v e r e d to have blossom end r o t . About t h r e e weeks l a t e r , these symptoms a l s o appeared i n the c o n t r o l green-house. Average p r o d u c t i o n was very low i n both greenhouses. The authors a t t r i b u t e d the d i s e a s e and e v e n t u a l l y the poor y i e l d to unbalanced f e r t i l i z a t i o n . A n a l y s i s o f the y i e l d data f o r cucumbers grown i n both greenhouses showed t h a t marketable f r u i t i n the C0 2 house was 31 percent more than from the c o n t r o l house. A l s o , the marketable f r u i t i n the experimental greenhouse weighed 4a percent p l a n t more than those grown i n the c o n t r o l house. B r o c c o l i t r a n s p l a n t s grown i n the att a c h e d greenhouse had tops weight (above ground) more than 2 1/2 times when compared t o the b r o c c o l i p l a n t s grown i n the c o n t r o l house. A s u r p r i s i n g r e s u l t was n i t r o g e n content i n the b r o c c o l i t o p s , which was over 3 times as much f o r p l a n t s grown i n the C0 2 house compared to those grown i n the c o n t r o l greenhouse. PART I ANALYSIS OF THE EFFECT OF SEVERAL CONSTRUCTION PARAMETERS ON THE SOLAR RADIATION INPUT INTO GREENHOUSES CHAPTER 1 SOLAR RADIATION TRANSMISSION FACTORS OF GREENHOUSES INTRODUCTION To compare greenhouses from a s o l a r energy standpoint, a standard or bench mark i s r e q u i r e d so that the e f f e c t of l a t i t u d e , s o l a r r a d i a t i o n a v a i l a b i l i t y , s i z e , o r i e n t a t i o n , shape and co v e r i n g m a t e r i a l can be estimated. A term which the author c a l l s "a greenhouse t r a n s m i s s i o n f a c t o r " i s d e f i n e d , then used to compare greenhouses with d i f f e r e n t c o n s t r u c t i o n parameters and at d i f f e r e n t l o c a t i o n s for t h e i r s o l a r r a d i a t i o n input e f f i c i e n c y . This chapter i s d i v i d e d i n t o three s e c t i o n s . The f i r s t d e s c r i b e s a method f o r e s t i m a t i n g the monthly average d a i l y beam, d i f f u s e and t o t a l transmittance of the greenhouse t r a n s p a r e n t s u r f a c e s . The second s e c t i o n g i v e s the mathematical e x p r e s s i o n s for the s o l a r r a d i a t i o n t r a n s m i s s i o n f a c t o r s of greenhouses. A l s o , the r e l a t i v e c o n t r i b u t i o n to beam, d i f f u s e and t o t a l s o l a r r a d i a t i o n by the d i f f e r e n t s u r f a c e s of the greenhouse are i n v e s t i g a t e d . In the l a s t s e c t i o n , the t o t a l t r a n s m i s s i o n f a c t o r concept i s used to i n v e s t i g a t e the e f f e c t of s e v e r a l energy c o n s e r v a t i o n s t r a t e g i e s on the s o l a r r a d i a t i o n input i n t o greenhouses l e a d i n g to a new design which the author c a l l s "a s o l a r - s h e d " greenhouse. SECTION A ESTIMATION OF THE MONTHLY AVERAGE DAILY BEAM, DIFFUSE AND TOTAL TRANSMITTANCE OF THE GREENHOUSE TRANSPARENT SURFACES TRANSMITTANCE OF THE GREENHOUSE TRANSPARENT SURFACES The f o l l o w i n g s e c t i o n d e s c r i b e s the method used to c a l c u l a t e the monthly average beam and t o t a l t r a n s m i t t a n c e o f the greenhouse c o v e r i n g m a t e r i a l t o s o l a r r a d i a t i o n . These average val u e s are r e q u i r e d t o estimate the beam and t o t a l greenhouse t r a n s m i s s i o n f a c t o r s as i n d i c a t e d i n S e c t i o n B of t h i s chapter by equations (13) and (15) r e s p e c t i v e l y . ASSUMPTIONS The f o l l o w i n g assumptions are made i n order t o c a l c u l a t e the weighted average d a i l y beam and t o t a l t r a n s m i t t a n c e f o r the greenhouse c o v e r i n g m a t e r i a l s . : i ) No condensation or dust accumulation on the greenhouse c o v e r i n g such t h a t the t r a n s m i t t a n c e i s f o r the c o v e r i n g m a t e r i a l o n l y . However, a b s o r p t i o n and r e f l e c t i o n l o s s e s are accounted f o r . i i ) The t r a n s m i t t a n c e o f the greenhouse c o v e r i n g m a t e r i a l to the d i f f u s e component of r a d i a t i o n i s independent of the o r i e n t a t i o n and t i l t o f the s u r f a c e . I t i s assumed t o be cons t a n t and equal t o t h a t o f the beam. THEORETICAL FORMULATION * The i n stantaneous beam s o l a r r a d i a t i o n f l u x t r a n s m i t t e d through a greenhouse t r a n s p a r e n t cover i s , then, the d a i l y energy weighted beam t r a n s m i t t a n c e o f the s u r f a c e to the d i r e c t component of s o l a r r a d i a t i o n may be c a l c u l a t e d by i n t e g r a t i n g e q u a t i o n (1) from s u n r i s e to sunset as f o l l o w s : b,day / ^ b * 3 / / / " ss V w ' (2) 10 s r S i n c e s o l a r r a d i a t i o n data are u s u a l l y a v a i l a b l e on an ho u r l y b a s i s , the d a i l y beam t r a n s m i t t a n c e of the greenhouse c o v e r i n g m a t e r i a l may be approximated by: (3) * The d e f i n i t i o n of symbols used i n t h i s s e c t i o n can be found on Pages 89 and 90. For f e a s i b i l i t y s t u d i e s of s o l a r energy a p p l i c a t i o n s t o greenhouses, i t i s more important t o be able t o estimate monthly average d a i l y beam and t o t a l t r a n s m i t t a n c e f o r each of the t r a n s p a r e n t greenhouse s u r f a c e s which are l o c a t i o n dependent. For l o c a t i o n s where both monthly average d a i l y d i f f u s e and t o t a l i n s o l a t i o n on a h o r i z o n t a l s u r f a c e are known, the monthly average h o u r l y d i f f u s e and t o t a l i n s o l a t i o n may be estimated u s i n g the L i u and Jordan method (1960). Since most w i d e l y a v a i l a b l e s o l a r r a d i a t i o n data are i n the form of monthly average t o t a l i n s o l a t i o n on a h o r i z o n t a l s u r f a c e , c o r r e l a t i o n equations must be used to separate the monthly average d a i l y t o t a l s o l a r r a d i a t i o n i n t o i t s two components. Many e m p i r i c a l equations have been proposed f o r such a purpose ( L i u and Jordan (1960) , Page (1961) , T u l l e r (1976) and I q b a l (1978). I q b a l (1978) giv e s a d e t a i l e d d i s c u s s i o n of these c o r r e l a t i o n s , i n c l u d i n g a comparison o f the r e s u l t s o b t a i n e d by each of these methods. Here, I q b a l 1 s c o r r e l a t i o n e q u a t i o n , H d/H = 0.958 - 0.982 K~T ( 4 ) i s used throughout the a n a l y s i s . When the monthly average h o u r l y d i f f u s e and t o t a l i n s o l a t i o n on a h o r i z o n t a l s u r f a c e are known, then the monthly average h o u r l y beam s o l a r r a d i a t i o n i n c i d e n t on a t i l t e d s u r face " i " of the greenhouse i s determined as f o l l o w s : I b , i = (I ~Id)Rb,i r (5) where R 5 / i = c o s 8 j / c o s e n (6) where cos6 n= cos* cos 6 cosw + sin<j> sin<5 (7) and c o s ^ i = costf^ sin<$ sin<p s i n * cos<p sintf^ COSY i + cos<S cos«p costfi COSU) + cosw cos<5 s i n ^ i c o s Y i sin<f + cos<5 s i n t f i s i n Y i sinu> . (8) A l s o , the monthly average d a i l y d i f f u s e s o l a r r a d i a t i o n on the t i l t e d s u r f a c e i s , H d , i = ( 1 / 2 ) d + c o s S i ) H d +(1/2) o ( l - costiiJH . (9) In t h i s e q u a t i o n , the s k y - d i f f u s e r a d i a t i o n H,, and the d ground r e f l e c t e d r a d i a t i o n aH are assumed i s o t r o p i c . — — < . u u j . a i - j . u i i " . i i a i c assuiuea Knowing the d i f f e r e n t components o f the r a d i a t i o n on the t i l t e d s u r f a c e , the monthly average d a i l y beam t r a n s m i t t a n c e of greenhouse s u r f a c e s may be estimated as f o l l o w s : ss _ / ss T b ' i = S T b , i 1 b , i X) X b , i ( i 0 ) sr ' s r and for the monthly average d a i l y t o t a l transmittance, T . 1 ( I D where ( 1 2 ) i s the d a i l y t o t a l s o l a r r a d i a t i o n i n c i d e n t on the greenhouse tr a n s p a r e n t s u r f a c e , i . The beam and d i f f u s e transmittance for tne g l a s s as a f u n c t i o n of the angle of i n c i d e n c e and the o p t i c a l p r o p e r t i e s of the g l a s s and i t s t h i c k n e s s are c a l c u l a t e d using the method d e s c r i b e d by D u f f i e and Beckman (1974). T h i s method takes i n t o account both r e f l e c t i o n and a b s o r p t i o n l o s s e s . For the d i f f u s e transmittance the angle of in c i d e n c e i s assumed to be constant and taken to be equal to 58°. A summary of the above method i s in c l u d e d i n Appendix A for the sake of completeness. SECTION B ESTIMATION OF THE MONTHLY AVERAGE DAILY BEAM, DIFFUSE AND TOTAL TRANSMISSION FACTORS OF GREENHOUSES SOLAR RADIATION TRANSMISSION FACTORS OF GREENHOUSES DEFINITIONS OF TRANSMISSION FACTORS * The greenhouse t r a n s m i s s i o n f a c t o r i s d e f i n e d as the r a t i o of the s o l a r energy t r a n s m i t t e d through the greenhouse co v e r i n g system to that i n c i d e n t on a h o r i z o n t a l surface area equal to the f l o o r s u r f a c e area of the greenhouse with the absence of the greenhouse c o v e r i n g . As s o l a r r a d i a t i o n i n c i d e n t of the greenhouse s u r f a c e s i s composed of beam and d i f f u s e r a d i a t i o n and the t r a n s p a r e n t covering has a d i f f e r e n t t r a n s m i t t a n c e value for each of the two components of r a d i a t i o n , then we have two d i s t i n c t t r a n s m i s s i o n f a c t o r s which could be def i n e d as f o l l o w s : BEAM TRANSMISSION FACTOR (BTF) Beam s o l a r r a d i a t i o n t r a n s m i t t e d through the t r a n s l u c e n t greenhouse cov e r i n g BTF = Outside beam s o l a r r a d i a t i o n i n c i d e n t on a h o r i z o n t a l surface equal to the f l o o r of the greenhouse n _ _ E A T H i b , i b , i i = 1 ' BTF = • (13) A H f b * The d e f i n i t i o n of symbols used i n t h i s s e c t i o n can be found on Pages 89 and 90. DIFFUSE TRANSMISSION FACTOR (DTF) D i f f u s e s o l a r r a d i a t i o n t r a n s m i t t e d through the t r a n s l u c e n t greenhouse covering DTF = Outside d i f f u s e s o l a r r a d i a t i o n i n c i d e n t on a h o r i z o n t a l s u r f a c e equal to the f l o o r of the greenhouse. n _ _ I A x H i d , i d, i i = 1 DTF = . (14) A H f d TOTAL TRANSMISSION FACTOR (TTF) Knowing the beam and d i f f u s e t r a n s m i s s i o n f a c t o r s , a t o t a l t r a n s m i s s i o n f a c t o r f o r the greenhouse may a l s o be d e f i n e d i n a s i m i l a r manner. T o t a l s o l a r r a d i a t i o n t r a n s m i t t e d through the t r a n s l u c e n t greenhouse covering TTF = . Outside t o t a l s o l a r r a d i a t i o n i n c i d e n t on a h o r i z o n t a l s urface equal to the f l o o r of the greenhouse TTF n n n £ A T H S A T H Z A i i i i b, i b, i + i=1 i=1 i=1 A H A H f f (15) DESCRIPTION OF THE COMPUTER MODEL FOR TRANSMISSION FACTORS A computer program was w r i t t e n i n FORTRAN to compute the s o l a r energy t r a n s m i t t e d through each of the s u r f a c e s of a greenhouse, t h e i r percent c o n t r i b u t i o n to s o l a r input, and the greenhouse t r a n s m i s s i o n f a c t o r s . The program was o r i g i n a l l y w r i t t e n for monthly average d a i l y v a l u e s , but with minor m o d i f i c a t i o n s i t could be used f o r s p e c i f i c days. The program w i l l a l s o handle any number of s u r f a c e s per greenhouse as long as they are f l a t , any number of covers as long as they are of the same m a t e r i a l f o r any p a r t i c u l a r s u r f a c e . D i f f e r e n t covering m a t e r i a l s for d i f f e r e n t s u r f a c e s are p e r m i t t e d . Input v a r i a b l e s ; 1. Monthly average d a i l y t o t a l i n s o l a t i o n on a h o r i z o n t a l s u r f a c e . 2. R e f l e c t i v i t y of surrounding s u r f a c e s to s o l a r r a d i a t i o n . Input parameters: 1. L o c a t i o n of the greenhouse ( l a t i t u d e ) 2. Number of s u r f a c e s which make up the greenhouse 3. O r i e n t a t i o n , t i l t and number of covers for each of the s u r f a c e s 4. O p t i c a l p r o p e r t i e s (index of r e f r a c t i o n and e x t i n c t i o n c o e f f i c i e n t ) and t h i c k n e s s of greenhouse covering m a t e r i a l f o r each of the s u r f a c e s Outputs: 1. Average d a i l y beam, d i f f u s e and t o t a l t r a n s m i t t a n c e of each of s u r f a c e s making up the greenhouse. 2. Average d a i l y beam, d i f f u s e and t o t a l s o l a r energy t r a n s m i t t e d through v a r i o u s surfaces . 3. C o n t r i b u t i o n of each surface to beam, d i f f u s e and t o t a l s o l a r energy i n p u t s . 4. D a i l y beam, d i f f u s e and t o t a l s o l a r energy t r a n s m i t t e d through the greenhouse c o v e r i n g . 5. Average d a i l y beam, d i f f u s e and t o t a l t r a n s m i s s i o n f a c t o r s f o r the greenhouse. SAMPLE OUTPUT; RESULTS AND DISCUSSION A 500 square metre gable glasshouse was used as an example. The greenhouse length and width are 50m and 10m r e s p e c t i v e l y , with a w a l l height of 2m and an 18° r o o f s l o p e . The l o n g - a x i s of the greenhouse i s east-west o r i e n t e d . The cover i s s i n g l e g l a s s with the f o l l o w i n g c h a r a c t e r i s t i c s ; E x t i n c t i o n C o e f f i c i e n t 0.161 cm 1 Index of R e f r a c t i o n 1.526 L o c a t i o n Vancouver, B.C. (49.25°N) The monthly average d a i l y t o t a l i n s o l a t i o n on a h o r i z o n t a l s u r f a c e and the monthly average ground cover r e f l e c t i v i t y f o r s o l a r r a d i a t i o n (albedo) used as i n p u t t o the program are i n d i c a t e d i n Table 1.1. The c a l c u l a t e d monthly average d a i l y d i f f u s e t r a n s m i t t a n c e f o r the s i n g l e g l a s s cover was 0.818, which i s independent of o r i e n t a t i o n and t i l t a n g l e s . The monthly average d a i l y beam t r a n s m i t t a n c e and t o t a l t r a n s m i t t a n c e f o r the v a r i o u s s u r f a c e s o f the greenhouse are shown i n F i g u r e s 1.1 and 1.2, r e s p e c t i v e l y . A sample of r e s u l t s of the other outputs of the computer model are shown f o r December and f o r J u l y i n Tables 1.2 and 1.3, r e s p e c t i v e l y . These two t a b l e s are i n c l u d e d here f o r d i s c u s s i o n purposes. Appendix B g i v e s a complete computer output f o r a greenhouse having c o n s t r u c t i o n parameters as d e s c r i b e d above. The t r a n s m i s s i o n f a c t o r s f o r the beam, d i f f u s e and t o t a l s o l a r r a d i a t i o n are shown i n F i g u r e 1.3 I t i s important t o n o t i c e t h a t the greenhouse d i f f u s e t r a n s m i s s i o n f a c t o r (DTF) remains f a i r l y constant over the MONTREAL (45.5*N) WINNIPEG (50*N) EDMONTON (53.5'N) VANOOUVER (49.25*N) TUSOON (32.5*N) H H H H Month kJ.m "2day"' a kJ.B~ "2day-1 a "H kJ.»-2day"' a IT kJ.^day - 1 a IT H" Jan 5 272 0.32 0.52 5 230 0.32 0.39 3 682 0.32 0.44 2 970 0.18 0.65 13 180 0.30 Feb 8 870 0.33 0.45 9 247 0.33 0.33 6 987 0.33 0.40 5 565 0.17 0.59 16 359 0.30 Mar 14 056 0.25 0.40 14 226 0.25 0.33 12 678 0.25 0.35 10 502 0.12 0.50 22 394 0.23 Apr lb 192 0.20 0.47 27 447 0.22 0.41 17 615 0.22 0.38 15 188 0.14 0.48 27 425 0.21 May 20 167 0.20 0.45 20 794 0.20 0.42 20 711 0.20 0.42 20 502 0.14 0.43 30 501 0.20 Jun 22 092 0.20 0.43 22 259 0.20 0.43 22 259 0.20 0.42 22 845 0.14 0.41 29 246 0.26 Jul 21 297 0.20 0.44 23 012 0.20 0.39 22 886 0.20 0.39 23 179 0.14 0.38 26 192 0.32 Aug 17 581 0.20 0.47 10 497 0.20 0.39 18 033 0.20 0.42 19 121 0.14 0.41 24 602 0.31 Sep 12 975 0.20 0.46 13 472 0.20 0.44 13 054 0.20 0.42 13 682 0.14 0.44 23 849 0.23 Oct a 954 0.20 0.50 8 494 0.20 0.46 8 075 0.20 0.42 7 280 0.14 0.54 18 493 0.26 Nov 4 268 0.23 0.64 4 644 0.23 0.51 4 100 0.23 0.47 3 766 0.15 0.61 14 895 0.25 Dec 3 891 0.28 0.59 3 766 0.28 0.47 2 678 0.28 0.49 2 385 0.18 0.67 12 761 0.27 Table 1.1 Monthly average d a i l y t o t a l i n s o l a t i o n on a h o r i z o n t a l s u r f a c e , ground albedo and r a t i o of d i f f u s e to t o t a l r a d i a t i o n f o r the l o c a t i o n s s e l e c t e d f o r t h i s study. Note: The values f o r H are taken from "World Survey of C l i m a t o l o g y " , see r e f e r e n c e Hare and Hay (19 74). - H d/H are c a l c u l a t e d . - For source of the ground albedo "a" r e f e r to the t e x t , pages 72 & 74 FIGURE 1.1 MONTHLY AVERAGE DAILY BEAM TRANSMITTANCE ( T ^ FOR VARIOUS SURFACES OF A GREENHOUSE WITH SINGLE GLASS COVER. TOO 951 UJ <J Z < 90h < -70 LLI o <65 a: 60 > < i X Z 55h O 50j i — i — i — r V a n c o u v e r , BC (49.25°N) Orientation l T i l t Angle —^ n— A - . ^ N20 t—* N90° E/W20° • a E/W90° S20° o - ^ S 9 0 ° J L I I J L _L M A M J J A S O N D MONTH FIGURE 3.. 2: MONTHLY AVERAGE DAILY TOTAL TRANSMITTANCE (T) FOR VARIOUS SURFACES OF A GREENHOUSE WITH SINGLE GLASS COVER. VANCOUVER DECEMBER Area Solar Energy Transmitted M**2 (KJ/day) Beaa Diffuse Total ContrI but i on To TotaI Beaa Diffuse Total 100. 263. 263. 28. 28. I 00. 242904. 34297 I . 0. 8962. 8962. 0. 82072. 333855. 333855. 22958. 22958. 81910. 324976. 676826. 333855. 31919. 3 19 19. 81910. 0.402 0.568 0.0 0.015 0.0 15 0.0 0.094 0.380 0.380 0.026 0.026 0.093 0.2 19 0.457 0.225 0.022 0.022 0.055 T o t a l T r a n s m i t t e d Beam D i f f u s e T o t a I 603799. 877607. 48 I 404. BTF DTF TTF 1.519 1.104 1.242 Table 1.2 Saaple Computer Output (50a x 10m x 2a) and I S I : south waI I S2: south r o o f S3: n o r t h roof for an E-H single glass cover greenhouse * Roof Slope S4: e a s t w a l l S5: west wa I I S6: n o r t h waI I BTF DTF TTF d e f i n e d Eq. I d e f i n e d Eq. 2 d e f i n e d Eq. 3 VANCOUVER JULY S Area Solar Energy Transmitted M"2 (KJ/day) Bean Diffuse Total Contri button To Total Beaa Diffuse Total 100. 263 263. 28. 28. I 00. 348908. 3233063. 26 I 3476. 165209. I 65209. 89404 . 489930. I 862202. I 862202. I 37 I 80. I 37 I 80. 489930. 838838. 5095265. 4475678. 302389. 302389. 573349 . 0.053 0.489 0.395 0.025 0.025 0.014 0.098 0.374 0.374 0.028 0.028 0.098 0.072 0.439 0.386 0.026 0.026 0.050 Beam 66 I 5268. T o t a l T r a n s m i t t e d D i f f u s e T o t a I 4978622. 1 1593892 . BTF 0.927 DTF I . I I 8 TTF I .000 Table 1.3 Saaple Computer Output for an E-W single glass cover greenhouse (50a x I OB X 2a) and 18* Roof Slope S I S2 S3 south wa I I south r o o f n o r t h roof S4 S5 S6 e a s t waI I west wa I I n o r t h waI BTF DTF TTF d e f i n e d Eq. I d e f i n e d Eq. 2 d e f i n e d Eq. 3 FIGURE 1.3: MONTHLY AVERAGE DAILY BEAM (BTF), DIFFUSE (DTF) AND TOTAL (TTF) SOLAR TRANSMISSION FACTORS FOR A GABLE GREENHOUSE. year, since the g l a s s transmittance to d i f f u s e r a d i a t i o n i s independent of the in c i d e n c e angle. However, the greenhouse beam t r a n s m i s s i o n f a c t o r (BTF) i s high during the winter months (November, December, January and February), but low dur i n g the summer months. The high (BTF) during winter months f o r an east-west o r i e n t e d greenhouse i s due to high beam tra n s m i t t a n c e of the south roof and south w a l l (Fig.1.1) and high s o l a r r a d i a t i o n i n c i d e n t on the south s u r f a c e s Table 1.2 shows that for December the c o n t r i b u t i o n of the two south s u r f a c e s to the t o t a l beam r a d i a t i o n input i s 97%. For the summer months the d a i l y beam trans m i t t a n c e of the south w a l l decreases ( F i g . 1.1) and the beam r a d i a t i o n i n c i d e n t on the south s u r f a c e s a l s o decreases (Table 1.3) which e x p l a i n s the lower (BTF) for the summer months. For the month of J u l y the c o n t r i b u t i o n of the two south s u r f a c e s to the t o t a l beam s o l a r r a d i a t i o n input i s only 54.2% as compared to 97% f o r December. T h e r e f o r e , the high greenhouse t o t a l t r a n s m i s s i o n f a c t o r (TTF) during the winter p e r i o d for an east-west o r i e n t e d greenhouse i s due to the high c o n t r i b u t i o n of the south s u r f a c e s to the beam component of s o l a r r a d i a t i o n . SECTION C USE OF THE TOTAL TRANSMISSION FACTOR TO COMPARE GREENHOUSES FOR THEIR SOLAR RADIATION INPUT EFFICIENCY USE OF THE TOTAL TRANSMISSION FACTOR The percent l o s s o r g a i n i n s o l a r r a d i a t i o n i n p u t t o a greenhouse "y" as compared t o a greenhouse "x" may be c a l c u l a t e d from t h e i r greenhouse t o t a l s o l a r r a d i a t i o n t r a n s m i s s i o n f a c t o r s (TTF) as f o l l o w s : (TTF) - (TTF) x y % LOSS/GAIN = X 100. (TTF) x EFFECT OF ORIENTATION ON THE GREENHOUSE TTF F i g u r e 1.4 shows the e f f e c t of north - s o u t h and east-west o r i e n t a t i o n on the t o t a l t r a n s m i s s i o n f a c t o r . The t o t a l s o l a r energy i n p u t i s h i g h e r i n the w i n t e r months and lower i n the summer f o r the E-W o r i e n t a t i o n than f o r the N-S o r i e n t a t i o n . During January, the s o l a r r a d i a t i o n i n p u t t o the E-W greenhouse i s (1.02-1.21/1.02)xl00 = 18.6% high e r than f o r the N-S green-house, but i t i s 6.6% lower i n June and J u l y . T h e r e f o r e , an E-W o r i e n t e d greenhouse r e q u i r e s l e s s supplemental heat d u r i n g the h e a t i n g season and l e s s v e n t i l a t i o n i n the summer i f the heat l o s s from the greenhouse i s assumed t o be independent of o r i e n t a t i o n . FIGURE 1.4: EFFECT OF E-W AND N-S ORIENTATION ON THE TOTAL TRANSMISSION FACTOR (TTF) FOR A GABLE GREENHOUSE. EFFECT OF DOUBLE GLAZING ON THE GREENHOUSE TTF The e f f e c t o f double g l a z i n g on s o l a r r a d i a t i o n i n p u t to the greenhouse i s shown i n F i g u r e 1.5. The l o s s o f s o l a r energy i n p u t due to double g l a z i n g i s o n l y 13%. However, economics must be c o n s i d e r e d such t h a t the savings i n the c o s t of energy w i l l o f f s e t the i n c r e a s e i n c a p i t a l c o s t f o r double g l a z i n g . A l s o , l o s s o f p r o d u c t i v i t y due to l i g h t r e d u c t i o n i n the double g l a z e d greenhouse must be c o n s i d e r e d . EFFECT OF OPAQUE NORTH WALL ON THE TTF OF AN EAST-WEST GLASSHOUSE The e f f e c t o f c o v e r i n g the n o r t h w a l l o f a greenhouse wit h opaque i n s u l a t i o n on the h e a t i n g l o a d was i n v e s t i g a t e d t h e o r e t i c a l l y by Chandra e t al.(1976) and e x p e r i m e n t a l l y by Wilson e t a l . ( 1 9 7 7 ) . The percent r e d u c t i o n i n h e a t i n g r e q u i r e -ments i s p r o p o r t i o n a l to the r e l a t i v e s u r f a c e area o f the nort h w a l l t o the t o t a l exposed s u r f a c e area o f the greenhouse. Wilson e t al.(1977) found no change i n l i g h t l e v e l s i n the greenhouse w i t h an opaque n o r t h w a l l . The Tra n s m i s s i o n F a c t o r s method (Figure 1.6) p r e d i c t s a 5.6% l o s s o f t o t a l s o l a r r a d i a t i o n i n p u t due to the opaque i n s u l a t i o n o f the nort h w a l l of an East-West o r i e n t e d greenhouse. V i r t u a l l y a l l t h i s l o s s i s d i f f u s e r a d i a t i o n . T h e r e f o r e , i t s e f f e c t i s r e s t r i c t e d t o a narrow band near the n o r t h w a l l . FIGURE 1.5: EFFECT OF DOUBLE GLAZING OF AN E-W ORIENTED GLASSHOUSE ON THE TOTAL TRANSMISSION FACTOR (TTF). FIGURE 1.6: EFFECT OF INSULATING THE NORTH WALL OR NORTH WALL AND.ROOF OF AN E-W ORIENTED GLASSHOUSE ON THE TOTAL TRANSMISSION FACTOR (TTF). EFFECT OF OPAQUE NORTH WALL AND NORTH ROOF ON THE TTF OF AN EAST-WEST GLASSHOUSE  I n s u l a t i n g the no r t h w a l l and the no r t h r o o f t o t a l l y o r p a r t i a l l y with an opaque m a t e r i a l was proposed by Wilson e t a l . (1977). F i g u r e 1.6 shows t h a t a c o n s i d e r a b l e l o s s i n s o l a r energy i n p u t may be experienced w i t h t h i s system o f i n s u l a t i o n . From F i g u r e 1.6, the average l o s s e s may be c a l c u l a t e d to be i n the order o f 25% f o r January and i n c r e a s i n g to about 5 0% i n June f o r a greenhouse l o c a t e d at Vancouver, B.C. (49.25°N) w i t h a l l the no r t h w a l l and ro o f being i n t r a n s p a r e n t . In a d d i t i o n , one expects a shading problem d u r i n g most times of the year, depending on the l a t i t u d e o f the greenhouse. A movable o r a d j u s t a b l e opaque i n s u l a t i o n system might a l l e v i a t e the shading problem. EFFECT OF LOCATION ON THE GREENHOUSE TTF An east-west o r i e n t e d greenhouse (100m x 10m x 2m) was analyzed f o r four d i f f e r e n t l o c a t i o n s i n Canada, t o determine the e f f e c t o f l a t i t u d e and s o l a r r a d i a t i o n a v a i l a b i l i t y on the s o l a r energy i n p u t t o a greenhouse. The r e s u l t s expressed i n terms of d a i l y t o t a l t r a n s m i s s i o n f a c t o r s are i n c l u d e d i n F i g u r e 1.7. The monthly average d a i l y t o t a l s o l a r r a d i a t i o n on a h o r i z o n t a l s u r f a c e and the ground albedo used as i n p u t v a r i a b l e s t o the computer model are i n c l u d e d i n Table 1.1. The v a l u e s f o r the ground albedo f o r Montreal FIGURE 1.7: EFFECT OF LOCATION OF AN E-W ORIENTED GLASSHOUSE ON THE TOTAL TRANSMISSION FACTOR (TTF). were taken from Hay (1976) and those of Winnipeg and Edmonton were were assumed to be the same as those of Montreal w h i l e those o f Vancouver were from Hare & Hay (1974). The e f f e c t s of e r r o r s i n the e s t i m a t i o n of the ground albedo on the s o l a r energy input to a greenhouse i s expected to be small since the c o n t r i b u t i o n of the r e f l e c t e d component to t o t a l s o l a r r a d i a t i o n i n c i d e n t on the v a r i o u s s u r f a c e s of the greenhouse i s s m a l l , e s p e c i a l l y on the roof where the c o n f i g u r a t i o n f a c t o r between the roof and ground i s only 0.03 for a 20° s l o p e . F i g u r e 1.7 shows that the same greenhouse l o c a t e d at a d i f f e r e n t l o c a t i o n w i l l have d i f f e r e n t s o l a r r a d i a t i o n t r a n s m i s s i o n f a c t o r s , e s p e c i a l l y d u r i n g the winter p e r i o d . Among the four l o c a t i o n s s t u d i e d , the greenhouse loca t e d at Edmonton has the highest (TTF), while Montreal and Vancouver the lowest (TTF). For example, for the month of January, the t r a n s m i s s i o n f a c t o r f o r the greenhouse used i n t h i s a n a l y s i s i s 1% higher for Montreal than for Vancouver, 16% for Winnipeg and 25% f o r Edmonton. The greenhouse t o t a l t r a n s m i s s i o n f a c t o r i s not only a f f e c t e d by the l a t i t u d e of i t s l o c a t i o n as shown by the d i f f e r e n c e i n (TTF) between Winnipeg and Vancouver which are l o c a t e d at approximately the same l a t i t u d e , but a l s o by weather f a c t o r s ( i . e . c l o u d , smog e t c . ) . The e f f e c t of weather f a c t o r s on s o l a r r a d i a t i o n may be estimated by the r a t i o of d i f f u s e to t o t a l i n s o l a t i o n Hd/H. The c a l c u l a t e d v a l u e s of these r a t i o s are i n c l u d e d i n Table 1.1. These v a l u e s suggest a c o r r e l a t i o n between t o t a l s o l a r r a d i a t i o n t r a n s m i s s i o n and capture and H^/H w i t h lower r a t i o s f a v o u r i n g the t r a n s m i s s i o n f a c t o r . SHED VS. GABLE GREENHOUSE Changing the shape of a greenhouse from a c o n v e n t i o n a l gable to a shed type c o n s t r u c t i o n i n c r e a s e s the south f a c i n g s u r f a c e area, thus improving the s o l a r r a d i a t i o n i n p u t to the greenhouse d u r i n g the w i n t e r months, as shown i n F i g u r e 1.8 f o r M o ntreal. However, d u r i n g the summer months, the s o l a r r a d i a t i o n i n p u t to the shed greenhouse i s i n the same order of magnitude as t h a t f o r the gable greenhouse. The expected average i n c r e a s e i n s o l a r energy i n p u t to the shed greenhouse d u r i n g the w i n t e r months over.the gable greenhouse i s about 20% (Figure 1.8). Another advantage of the shed d e s i g n i s the f a c i l i t y by which a s o l a r c o l l e c t o r may be i n t e g r a t e d w i t h i n the greenhouse at the upper p o r t i o n o f the opaque n o r t h w a l l . SHED VS. BRACE GREENHOUSE The Brace greenhouse was developed by T.A. Lawand e t a l . (1975) at the Brace Research I n s t i t u t e . The d e s i g n was s p e c i f i c a l l y c onceived f o r c o l d c l i m a t e r e g i o n s . A diagram o f the Brace greenhouse i s shown i n F i g u r e 1.8 (Shape B). The greenhouse must be east-west o r i e n t e d w i t h the n o r t h w a l l i n s u l a t e d and sloped at an angle equal t o the sun's z e n i t h . MONTH FIGURE 1.8: COMPARISON OF THE TOTAL TRANSMISSION FACTORS (TTF) FOR GABLE, BRACE AND SHED-TYPE GREENHOUSES. * % S o l a r R a d i a t i o n Input Gain/Loss f o r Shed vs Gable angle d u r i n g the summer s o l s t i c e . The i n n e r s u r f a c e o f the n o r t h w a l l i s covered with a s o l a r r a d i a t i o n r e f l e c t i o n m a t e r i a l ( i . e . aluminum f o i l ) to d i r e c t r a d i a t i o n on to the p l a n t canopy. The t r a n s m i s s i o n f a c t o r method i s used here to compare the Brace and the shed greenhouse f o r t h e i r s o l a r r a d i a t i o n i n p u t e f f i c i e n c y as a f u n c t i o n of the time of the year. The r e s u l t s f o r Montreal are shown i n F i g u r e 1.8. When the t o t a l t r a n s m i s s i o n f a c t o r s f o r Brace and shed are compared to t h a t o f a c o n v e n t i o n a l gable greenhouse, i t can be seen from F i g u r e 1.8 t h a t d u r i n g the c o l d months (October to March i n c l u s i v e ) , the Brace i s e q u i v a l e n t to the gable greenhouse w h i l e the shed admits more s o l a r r a d i a t i o n d u r i n g t h a t same p e r i o d o f the y e a r . During the warm months (May to August i n c l u s i v e ) , the shed becomes e q u i v a l e n t t o the gable green-house w h i l e the Brace captures l e s s s o l a r r a d i a t i o n . Thus, the Brace greenhouse i s more e f f i c i e n t than the gable or shed greenhouse due to i t s lower energy requirement f o r v e n t i l a t i o n . EFFECT OF LOCATION ON SHED GREENHOUSE TTF The monthly average t o t a l t r a n s m i s s i o n f a c t o r s (TTF) were c a l c u l a t e d f o r f i v e l o c a t i o n s having l a t i t u d e s r a n g i n g from 32.5°N (Tuscon, AZ.) to 53.5°N (Edmonton, A l t a . ) . The r e s u l t s f o r a shed greenhouse having a roof s l o p e o f 20 degrees and o n l y the n o r t h w a l l i n s u l a t e d are shown i n F i g u r e 1.9. These r e s u l t s are based on data f o r H and a as given i n Table 1.1. The ground albedo f o r Tuscon was assumed to be N D J MONTH FIGURE 1.9: EFFECT OF LOCATION ON THE TOTAL TRANSMISSION FACTOR (TTF) FOR A SHED-TYPE GREENHOUSE. constant over the year and equal to 0.20. A simultaneous examination of Table 1.1 and Fig u r e 1.9 i n d i c a t e s c l e a r l y the e f f e c t of l a t i t u d e and c l o u d i n e s s index Krp on the t o t a l t r a n s m i s s i o n f a c t o r . As expected, the e f -f e c t of l a t i t u d e and K t on (TTF) i s small i n the summer, g i v i n g a t o t a l t r a n s m i s s i o n f a c t o r c l o s e to u n i t y for a l l the f i v e l o c a t i o n s s t u d i e d . However, during the winter months, the i n f l u e n c e of K-p and l a t i t u d e on (TTF) becomes more pronounced. I t i s i n t e r e s t i n g to n o t i c e the low (TTF) f o r Montreal f o r the month of November which can be exp l a i n e d by the r e l a t i v e l y high c l o u d i n e s s index ( K ^ = 0.64) f o r that month. The e f f e c t of the c l o u d i n e s s index on (TTF) can a l s o be seen by comparing the r e s u l t s f o r Vancouver with those of Winnipeg. Even though these two c i t i e s are l o c a t e d at app-r o x i m a t e l y the same l a t i t u d e , the t o t a l t r a n s m i s s i o n f a c t o r s f o r Winnipeg during the winter months are s i g n i f i c a n t l y h i g h -er than those f o r Vancouver. Examination of Table 1.1 i n d i c a t e s that Winnipeg has lower c l o u d i n e s s i n d i c e s during the c o r r e s -ponding months. The i n f l u e n c e of l a t i t u d e (TTF) can e a s i l y be seen i f the r e s u l t s of Tuscon, Winnipeg and Edmonton are examined si m u l t a n e o u s l y (Figure 1.9 and Table 1.1). For the month of December, the average t o t a l t r a n s m i s s i o n f a c t o r f o r the shed greenhouse i s p r a c t i c a l l y the same for Montreal, Vancouver and Tuscon (Figure 1.9). However (TTF) f o r Winnipeg and Edmonton, when compared to that of Montreal, are 23% and 37% higher r e s p e c t i v e l y . EFFECT OF LENGTH, WIDTH AND OPAQUE EAST AND WEST  WALLS ON THE TTF OF A SHED GREENHOUSE The c o n t r i b u t i o n of the south w a l l , east and west walls and the south roof of a shed-type greenhouse to the beam, d i f f u s e and t o t a l s o l a r r a d i a t i o n input i n t o the s t r u c t u r e as i t v a r i e s with time of the year i s d e p i c t e d i n F i g u r e 1.10. The shed greenhouse used i n t h i s example i s 100 metres long by 10 metres wide with a south roof slope of 20 degrees from the h o r i z o n t a l . The height of the t r a n s p a r e n t s e c t i o n of the south w a l l i s assumed to be 2 metres. Fig u r e 1.10 shows that the c o n t r i b u t i o n of the south w a l l to the d i r e c t component of s o l a r r a d i a t i o n input i n t o the greenhouse i s i n the order of 20 percent during the winter months and decreased to a lowvalue of only 3 percent during the summer p e r i o d . T h i s decrease in the beam r a d i a t i o n c o n t r i b u t i o n can be a t t r i b u t e d to the high i n c i d e n c e angle causing a r e d u c t i o n i n the beam transmittance of the south cover. On the other hand, the c o n t r i b u t i o n of the same w a l l to the d i f f u s e component of s o l a r r a d i a t i o n input remained f a i r l y constant throughout the year at an approximate value of 12 p e r c e n t . T h i s i s a d i r e c t r e s u l t of the assumed constant d i f f u s e transmittance of the covering m a t e r i a l . The c o n t r i b u t i o n of the east and west w a l l s combined to beam s o l a r r a d i a t i o n input to the shed greenhouse i s L U CD I — ZD PQ Q£ I — o <c o CO FIGURE 1.10: CONTRIBUTION BY THE DIFFERENT SURFACES OF A SHED-TYPE GREENHOUSE FOR THE BEAM (a) , DIFFUSE (b) AND TOTAL (c) SOLAR RADIATION BY MONTH. ( L o c a t i o n : Montreal, Quebec). 00 I—' very s m a l l throughout the year as i s c l e a r l y i n d i c a t e d by F i g u r e 1.10(a). The c o n t r i b u t i o n of these w a l l s to the d i f f u s e component i s s l i g h t l y h i g h e r than t h a t f o r the d i r e c t component, but s t i l l r e l a t i v e l y low as can be d e p i c t e d i n F i g u r e 1.10(b). T h e r e f o r e , f o r t h i s s i z e of greenhouse, the east and west w a l l s c o u l d be made opaque without a s i g n i f i c a n t l o s s of t o t a l s o l a r r a d i a t i o n i n p u t , as can be seen from F i g u r e 1.10(c). The e f f e c t of l e n g t h on the t o t a l s o l a r r a d i a t i o n t r a n s m i s s i o n f a c t o r (TTF) of a 10 metre wide and 20 degree r o o f s l o p e shed-type greenhouse i s shown i n F i g u r e 1.11. The r e s u l t s i n d i c a t e d i n the above mentioned f i g u r e are f o r a greenhouse l o c a t e d i n the Montreal r e g i o n . I t i s c l e a r from F i g u r e 1.11 t h a t i n c r e a s i n g the l e n g t h of the shed greenhouse wi t h t r a n s p a r e n t e a s t and west w a l l decreases the t o t a l t r a n s -m i s s i o n f a c t o r s i g n i f i c a n t l y . The decrease i n the d a i l y TTF i s more pronounced f o r the r e l a t i v e l y s h o r t e r greenhouses. T h i s i s due to the l a r g e c o n t r i b u t i o n of d i f f u s e s o l a r r a d i a t i o n t r a n s m i t t e d through the east and west w a l l s when compared to the t o t a l r a d i a t i o n i n p u t t o the greenhouse. I f the east and west w a l l s of the shed greenhouse were i n s u l a t e d w i t h an opaque m a t e r i a l , then the monthly d a i l y average t o t a l t r a n s -m i s s i o n f a c t o r s become the same f o r any greenhouse l e n g t h . O b v i o u s l y , t h i s i m p l i e s t h a t i n s u l a t i n g the e a s t and west w a l l s of a s h o r t shed greenhouse r e s u l t s i n a significant decrease i n solar 2.2 en o I— (_> CO co CO I— CD L U CD UJ 0-8 F M A M J J A S O N MONTH F i g u r e 1.11: EFFECT OF LENGTH AND INSULATING THE EAST AND WEST WALLS OF A SHED-TYPE GREENHOUSE ON ITS TOTAL TRANSMISSION FACTOR. ( L o c a t i o n : M o n t r e a l , Quebec) FIGURE 1.12: CONTRIBUTION OF THE EAST AND WEST WALLS OF A SHED-TYPE GREENHOUSE TO THE DIFFUSE AND TOTAL SOLAR RADIATION INPUT AS A FUNCTION OF GREENHOUSE LENGTH. (L o c a t i o n : M o n t r e a l , Quebec). MONTH FIGURE 1.13: EFFECT OF LENGTH, WIDTH AND INSULATING EAST AND WEST WALLS OF AN E-W SHED GREENHOUSE ON ITS MONTHLY AVERAGE DAILY TOTAL TRANSMISSION FACTOR (TTF). Curves A & B North W a l l I n s u l a t e d Curves C & D N, E & W Walls I n s u l a t e d Other C o n s t r u c t i o n Parameters: Roof Slope: 20° South Wall Height: 2 m Covering M a t e r i a l : S i n g l e Layer G l a s s L o c a t i o n : Montreal, Quebec. energy input to i t ( F i g . 1.11). The above f a c t can b e t t e r be seen by examination of F i g u r e 1.12, which i n d i c a t e s the e f f e c t of the length on the percent c o n t r i b u t i o n of the east and west w a l l s of the shed greenhouse to the d i f f u s e and t o t a l s o l a r r a d i a t i o n input. A c c o r d i n g to the above f i g u r e , i n s u l a t i n g the east and west w a l l s of a shed greenhouse having a length of 50 metres or more r e s u l t s i n only a small l o s s ( l e s s than 5 percent) i n s o l a r r a d i a t i o n input. The e f f e c t of the width of a shed-type greenhouse on the t o t a l s o l a r r a d i a t i o n t r a n s m i s s i o n f a c t o r i s shown i n Figure 1.13. Doubling the width from 10 metres to 20 metres has r e s u l t e d in a maximum decrease of the greenhouse TTF of only 9 p e r c e n t . T h i s decrease i s due to the lower percent c o n t r i b u t i o n of s o l a r r a d i a t i o n input through the south w a l l r e l a t i v e to the south roof for the case of the wider greenhouse. CONCLUSIONS Using the t o t a l t r a n s m i s s i o n f a c t o r as a c r i t e r i o n , the f o l l o w i n g c o n c l u s i o n s were drawn for s i n g l e span glasshouses as fa r as t h e i r s o l a r r a d i a t i o n input e f f i c i e n c y was concerned. 1. An east-west o r i e n t e d greenhouse captures more s o l a r r a d i a t i o n during the winter than a north-south o r i e n t e d greenhouse. 2. Double g l a z i n g (glass) r e s u l t s i n 13% l o s s o f s o l a r energy i n p u t t o an east-west o r i e n t e d greenhouse as compared to s i n g l e g l a s s cover. 3. Opaque i n s u l a t i o n o f the n o r t h w a l l o f an east-west o r i e n t e d gable greenhouse causes l e s s than 6% l o s s i n the t o t a l s o l a r r a d i a t i o n i n p u t . V i r t u a l l y a l l t h i s l o s s i s d i f f u s e r a d i a t i o n , and i t s e f f e c t i s r e s t r i c t e d to a narrow r e g i o n near the n o r t h w a l l . 4. Opaque i n s u l a t i o n o f the n o r t h w a l l and r o o f of an e a s t -west o r i e n t e d gable greenhouse r e s u l t s i n a c o n s i d e r a b l e l o s s i n s o l a r energy i n p u t . For the greenhouse s t u d i e d , the l o s s was from 29% i n January to 50% i n June. 5. On a per u n i t f l o o r area b a s i s , the s o l a r energy i n p u t to a shed type greenhouse i s h i g h e r d u r i n g the h e a t i n g season p e r i o d than t h a t t o a gable greenhouse. 6. In g e n e r a l , an i n c r e a s e i n the l e n g t h of a shed-type greenhouse r e s u l t s i n a decrease i n the t o t a l s o l a r r a d i a t i o n t r a n s m i s s i o n f a c t o r (TTF). T h i s r a t e of decrease i n TTF i s found to be i n the order of 1%, 0.25% and 0.05% per metre f o r the greenhouse l e n g t h ranges of 10 to 20m, 20 to 50m and 50 to 100m, r e s p e c t i v e l y (Figure 1.11). 7. Doubling the width from 10 to 20m of a 100m long shed-type greenhouse has decreased the TTF by l e s s than 9%. 8. Opaque i n s u l a t i o n of the e a s t and west w a l l s of a shed-type greenhouse r e s u l t s i n o n l y a s l i g h t decrease i n t o t a l s o l a r r a d i a t i o n i n p u t (<5%) p r o v i d e d i t s l e n g t h i s kept above 50 metres. 9. The greenhouse t o t a l t r a n s m i s s i o n f a c t o r was found to be a f u n c t i o n of l a t i t u d e and the r a t i o of d i f f u s e to t o t a l s o l a r r a d i a t i o n on a h o r i z o n t a l s u r f a c e . NOMENCLATURE Symbol D e f i n i t i o n U n i t s 2 A^ - area of greenhouse f l o o r -m A. - area o f a s p e c i f i c s u r f a c e " i " o f the /-r v* /~\ <r\ T-\ V-\ /~\ n n / ~ i <\ »-\ <<~» 1 s-\ •» •» greenhouse e n c l o s u r e m 2 H b ' H d ' H ~ m o n t n l y average d a i l y beam, d i f f u s e and t o t a l r a d i a t i o n i n c i d e n t on a h o r i z o n t a l s u r f a c e o u t s i d e the greenhouse, r e s p e c t i v e l y kJ-m~ H b i ' H d i ' H i ~ m o n t n l - y average beam, d i f f u s e and ' ' t o t a l r a d i a t i o n i n c i d e n t on a s p e c i f i c s u r f a c e " i " o f the greenhouse e n c l o s u r e , r e s p e c t i v e l y kJ.m monthly average d a i l y e x t r a t e r r e s t r i a l / s o l a r r a d i a t i o n on a h o r i z o n t a l s u r f a c e k j / -2 H q -  I b ~ instantaneous beam r a d i a t i o n i n c i d e n t on a s p e c i f i c s u r f a c e I b > t ~ i n s t a n t a n e o u s beam r a d i a t i o n t r a n s m i t t e d through the s p e c i f i c s u r f a c e - h o u r l y beam r a d i a t i o n i n c i d e n t on a s u r f a c e monthly average h o u r l y beam r a d i a t i o n i n c i d e n t on a s p e c i f i c s u r f a c e " i " of the greenhouse e n c l o s u r e Id - monthly average h o u r l y d i f f u s e r a d i a t i o n i n c i d e n t on a h o r i z o n t a l s u r f a c e o u t s i d e the greenhouse monthly average h o u r l y t o t a l r a d i a t i o n i n c i d e n t on a h o r i z o n t a l s u r f a c e o u t s i d e the greenhouse kJ KT - c l o u d i n e s s index (K T = H/Ho) R b , i ~ r a t i ° o f beam r a d i a t i o n on a t i s u r f a c e " i " t o t h a t on a hor i z c t i l t e d  h o r i z o n t a l s u r f a c e , r e s p e c t i v e l y :b' *b' Tb,day ~ i n s t a n t a n e o u s , average h o u r l y and average d a i l y t r a n s m i t t a n c e o f a t r a n s p a r e n t s u r f a c e to beam s o l a r r a d i a t i o n r e s p e c t i v e l y b , i d , i i e h 0. 1 monthly average d a i l y t r a n s m i t t a n c e of a s p e c i f i c s u r f a c e " i " to beam, d i f f u s e and t o t a l s o l a r r a d i a t i o n r e s p e c t i v e l y s o l a r r a d i a t i o n i n c i d e n c e angle f o r a h o r i z o n t a l s u r f a c e s o l a r r a d i a t i o n i n c i d e n c e angle w i t h r e s p e c t to a s p e c i f i c s u r f a c e " i " of the greenhouse e n c l o s u r e l a t i t u d e angle ( l o c a t i o n of the greenhouse) sun's d e c l i n a t i o n angle hour angle t i l t angle of a s p e c i f i c s u r f a c e " i " o f the greenhouse e n c l o s u r e ( v e r t i c a l , e = 90°) r a d i a n s r a d i a n s r a d i a n s r a d i a n s r a d i a n s r a d i a n s 4> 1 Y• - o r i e n t a t i o n angle of a s p e c i f i c s u r f a c e " i " o f the greenhouse e n c l o s u r e (south, y = 0°) r a d i a n s UJ , a) - s u n r i s e and sunset hour angles r e s p e c t i v e l y r a d i a n s a - ground albedo near the greenhouse CHAPTER 2 TOTAL SOLAR RADIATION CAPTURE FACTORS OF GREENHOUSES INTRODUCTION T h i s chapter d i s c u s s e s the d i f f u s e s o l a r r a d i a t i o n l o s s e s from greenhouses. The f i r s t s e c t i o n o f the chapter i s devoted t o the s p e c i a l case of a gable greenhouse where two sources o f d i f f u s e l o s s e s are i d e n t i f i e d : d i r e c t l o s s from the gable r o o f and i n d i r e c t l o s s o f d i f f u s e r a d i a t i o n due to the e f f e c t i v e albedo of the p l a n t canopy and the uncovered greenhouse f l o o r . Taking these two l o s s e s i n t o account, the t o t a l s o l a r r a d i a t i o n t r a n s m i s s i o n f a c t o r p r e v i o u s l y d e f i n e d i n chapter 1 i s m o d i f i e d to gi v e what the author c a l l s "a greenhouse t o t a l capture f a c t o r " . A mathematical e x p r e s s i o n f o r the s o l a r r a d i a t i o n t o t a l capture f a c t o r i s a l s o g i v e n f o r the case of a gable greenhouse. The second s e c t i o n of t h i s chapter i n t r o d u c e s a method of c a l c u l a t i n g the r a d i a t i o n c o n f i g u r a t i o n f a c t o r s f o r green-house a p p l i c a t i o n s . Numerical va l u e s o f the c o n f i g u r a t i o n f a c t o r s are r e q u i r e d f o r the e s t i m a t i o n o f the greenhouse capture f a c t o r s . SECTION A TOTAL CAPTURE FACTORS FOR GABLE GREENHOUSES TOTAL CAPTURE FACTORS FOR GABLE GREENHOUSES The greenhouse t o t a l t r a n s m i s s i o n f a c t o r as def i n e d p r e v i o u s l y does not take i n t o account the d i f f u s e r a d i a t i o n l o s s e s through the roof and the r e f l e c t i o n l o s s e s from the p l a n t canopy. These two sources of s o l a r r a d i a t i o n l o s s w i l l be considered i n the f o l l o w i n g chapter for the case of a gable greenhouse. ASSUMPTIONS With res p e c t to the d e r i v a t i o n of the greenhouse s o l a r r a d i a t i o n capture f a c t o r , the f o l l o w i n g assumptions are made: i ) Only the ab s o r p t i o n and r e f l e c t i o n l o s s e s of the g l a s s cover are accounted f o r . i i ) No condensation or dust accumulation on the glass cover. i i i ) The e f f e c t of the s t r u c t u r a l frame i s neg l e c t e d . iv) A l l the beam r a d i a t i o n t r a n s m i t t e d through the g l a s s cover i s i n c i d e n t on p l a n t canopy ( i . e . t a l l p l a n t s and low roof s l o p e ) . v) Plant r e f l e c t i o n for s o l a r r a d i a t i o n i s p e r f e c t l y d i f f u s e d . v i i ) M u l t i p l e r e f l e c t i o n s between the p l a n t canopy and the greenhouse cover are neglected (only the f i r s t r e f l e c t i o n i s c o n s i d e r e d ) . THEORETICAL FORMULATION* Assumption ( i v ) s t a t e s that a l l the beam r a d i a t i o n t r a n s m i t t e d through any greenhouse s u r f a c e i reaches the p l a n t s . Then the beam r a d i a t i o n from surface i t h a t i s i n c i d e n t on the p l a n t canopy i s simply, A. T. .5, . . (1) l b, l b, l But, only a f r a c t i o n of the d i f f u s e r a d i a t i o n t r a n s m i t t e d through the sur f a c e i i s reaching the p l a n t s . T h e r e f o r e , the d i f f u s e r a d i a t i o n from surface i which i s i n c i d e n t on the p l a n t canopy may be represented by A i 7 d # i H d / i ( l - x d f i F ) . (2) The above ex p r e s s i o n i s v a l i d only i f the two r o o f s l o p e s are made of the same m a t e r i a l such that the d i f f u s e t r a n s m i t -tance can be considered equal for both s l o p e s . Furthermore, i n the case of t a l l p l a n t canopies, such as tomatoes and ro s e s , the f a c t o r F i s clo s e to zero for the v e r t i c a l s u r -faces of the greenhouse, which i m p l i e s that a l l the d i f f u s e r a d i a t i o n t r a n s m i t t e d through the v e r t i c a l w a l l s of the greenhouse reaches the p l a n t canopy. However, i n the case of the greenhouse roof, a f r a c t i o n of the d i f f u s e r a d i a t i o n coming from one side of the roof i s t r a n s m i t t e d and l o s t to the o u t s i d e through the other side of the roof. The d i f f u s e r a d i a t i o n l o s s through the greenhouse roof i s represented i n * The d e f i n i t i o n of symbols used i n t h i s s e c t i o n can be found on Page 113. equation (2) by the term which i s p r o p o r t i o n a l to T , . F, Q , I where F i s the r a d i a t i o n c o n f i g u r a t i o n f a c t o r between the two s l o p e s of the greenhouse r o o f . The f a c t o r F may be c a l c u l a t e d u s i n g the method d e s c r i b e d by F e i n g o l d (1966). A summary of the method and i t s a p p l i c a t i o n to greenhouse c o n f i g u r a t i o n f a c t o r s i s d i s c u s s e d i n a l a t e r s e c t i o n of t h i s chapter. The t o t a l s o l a r r a d i a t i o n from any s u r f a c e i of the greenhouse which i s i n c i d e n t on the p l a n t canopy i s then c a l c u l a t e d u s i n g equations 1 and 2 as f o l l o w s : A. H. = A. Ex. . H. . + T . .H. . (1 - T , - F ) ] . (3) i i l b , i b , i d , i d , i d , i The t o t a l s o l a r r a d i a t i o n coming from any s u r f a c e i of the greenhouse t h a t i s absorbed by the p l a n t can be c a l c u l a t e d by m u l t i p l y i n g e q u a t i o n 3 by a c o r r e c t i o n f a c t o r f o r r e f l e c t i o n l o s s e s due to the p l a n t albedo, to g i v e , A i 5 i ( 1 - p T d , i } ' ( 4 ) In e q u a t i o n 4 o n l y the f i r s t r e f l e c t i o n i s c o n s i d e r e d as shown i n the sketch below. A l s o , the r e f l e c t e d r a d i a t i o n by the p l a n t canopy i s assumed to be d i f f u s e d r e g a r d l e s s of the o r i g i n a l i n c i d e n t r a d i a t i o n . PT, .A.H ' d, l I i c o ver ( d i f f u s e t r a n s m i t t a n c e , d, i p l a n t canopy ( e f f e c t i v e albedo, p ) Now, a " t o t a l s o l a r r a d i a t i o n capture f a c t o r " f o r the greenhouse may be d e f i n e d as the r a t i o o f the s o l a r energy captured by the p l a n t canopy to t h a t i n c i d e n t on a h o r i z o n t a l o u t s i d e s u r f a c e whose area i s equal t o the greenhouse ground area. The greenhouse t o t a l capture f a c t o r (TCF) may be c a l c u l a t e d as f o l l o w s : n E A i [ T b / i H b f i + T d f i H d i ( l - T D i F ) ] ( l - P T D i ) 1 = 1 TCF= - . (5) Af H The t o t a l s o l a r r a d i a t i o n capture f a c t o r for a greenhouse i s u s e f u l for comparing greenhouses at d i f f e r e n t l o c a t i o n s and with v a r i o u s greenhouse c o n s t r u c t i o n parameters ( i . e . i n s u l a t i o n , r oof s l o p e , e t c . ) f o r t h e i r e f f e c t i v e n e s s as pas s i v e s o l a r energy c o l l e c t o r s . RESULTS AND DISCUSSION The e f f e c t of s o l a r r a d i a t i o n l o s s through the greenhouse roof and the r a d i a t i o n l o s s due to the e f f e c t i v e albedo of the p l a n t canopy are shown i n Figure 2.1. The curves represented i n the f i g u r e are for a gable greenhouse l o c a t e d i n the Vancouver, B.C. area and having the c o n s t r u c t i o n parameters as i n d i c a t e d on the diagram i n Figu r e 2.1. The d i r e c t l o s s of s o l a r r a d i a t i o n through the roof can be seen from F i g u r e 2.1 by comparing the t o t a l t r a n s m i s s i o n f a c t o r (TTF) curve to the curve for an e f f e c t i v e p l a n t canopy albedo of zero. The word d i r e c t l o s s i s used here to d i s t i n g u i s h i t from that due to the MONTH FIGURE 2.1: EFFECT OF PLANT ALBEDO ON THE SOLAR RADIATION CAPTURE FACTOR FOR A GABLE GREENHOUSE. Dimensions: 100 m x 10 m O r i e n t a t i o n : E-W l o n g - a x i s Cover: S i n g l e Layer 3 mm Glass L o c a t i o n : Vancouver, B.C. (49.25°N) r e f l e c t i o n of s o l a r r a d i a t i o n by the p l a n t canopy. The d i r e c t l o s s c o n s t i t u t e s the s o l a r r a d i a t i o n t r a n s m i t t e d through the roof but has never reached the p l a n t s or any other o b j e c t i n s i d e the greenhouse. As can be seen from F i g u r e 2.1, t h i s l o s s i s small provided the roof slope i s kept low. For the example c i t e d here, t h i s l o s s was found to be in the order of f i v e percent of the t o t a l s o l a r r a d i a t i o n e n t e r i n g the greenhouse. On the other hand, the s o l a r r a d i a t i o n l o s s due to r e f l e c t i o n by the p l a n t canopy and o b j e c t s i n s i d e the greenhouse are found to be r e l a t i v e l y more s i g n i f i c a n t than the d i r e c t l o s s through the r o o f . Obviously , r e f l e c t i o n l o s s e s are d i r e c t l y dependent on the e f f e c t i v e albedo of the p l a n t canopy i n c l u d i n g f l o o r and other o b j e c t s . Experimental values of the e f f e c t i v e albedo w i t h i n greenhouses are not r e a d i l y a v a i l a b l e ; however, two h y p o t h e t i c a l values of 0.1 and 0.3 were used for i l l u s t r a t i o n purposes. The s o l a r r a d i a t i o n l o s s e s due to p l a n t canopy r e f l e c t i o n as expressed i n terms of the greenhouse t o t a l capture f a c t o r are shown i n F i g u r e 2.1. These l o s s e s were found to be 8 and 24 percent for e f f e c t i v e albedos of 0.1 and 0.3 r e s p e c t i v e l y when compared to an albedo of zero. In t h i s a n a l y s i s , the e f f e c t i v e albedo i s taken as a constant throughout the year. In r e a l i t y , i t s value i s c l o s e l y r e l a t e d to the type of crop grown and i t s stage of development. The e f f e c t i v e albedo could a l s o be a r t i f i c a l l y m o d i f i e d to improve the greenhouse s o l a r r a d i a t i o n capture f a c t o r . T h i s indeed has been done with the use of Q-mats* f o r s o l a r energy c o l l e c t i o n and storage. One e f f e c t of the Q-mats i s a r e d u c t i o n i n the e f f e c t i v e greenhouse albedo. Q -mats i s a trade name for a s o l a r c o l l e c t o r developed i n France s p e c i f i c a l l y for greenhouse a p p l i c a t i o n s , i t c o n s i s t s of black p l a s t i c mats which are layed f l a t on the greenhouse f l o o r and/or under the p l a n t s , then f i l l e d with water to t r a n s p o r t the energy c o l l e c t e d to a thermal storage tank. Q-mats are a l s o used as a heat d i s t r i b u t i o n system i n waste energy recovery a p p l i c a t i o n s to greenhouses. SECTION B CALCULATION OF CONFIGURATION FACTORS FOR DIFFUSE RADIATION IN GREENHOUSES CALCULATION OF  CONFIGURATION FACTORS In the f i r s t s e c t i o n of t h i s chapter, i t was found that the s o l a r r a d i a t i o n capture f a c t o r f o r gable greenhouses i s dependent on the d i f f u s e r a d i a t i o n c o n f i g u r a t i o n f a c t o r s between the two slopes of the r o o f . T h i s s e c t i o n c o n c e n t r a t e s on an a n a l y t i c a l method to c a l c u l a t e these c o n f i g u r a t i o n f a c t o r s to be used with res p e c t to gable greenhouses. ASSUMPTIONS The f o l l o w i n g assumptions are made with respect to the d e r i v a t i o n of the r a d i a n t - i n t e r c h a n g e c o n f i g u r a t i o n f a c t o r s f o r greenhouse a p p l i c a t i o n s : i ) The r a d i a t i o n from any sur f a c e i i s p e r f e c t l y d i f f u s e . i i ) The su r f a c e i s i s o t h e r m a l . THEORY* The r a d i a t i o n c o n f i g u r a t i o n f a c t o r F-|_2 i s d e f i n e d as the f r a c t i o n of the r a d i a t i o n l e a v i n g an isothermal w a l l of sur f a c e area A-^  that i s i n c i d e n t upon another w a l l of area A geometric shape commonly present with respect to * The d e f i n i t i o n o f symbols used i n t h i s s e c t i o n can be found on Page 113. greenhouses can be t r e a t e d as two r e c t a n g l e s having a common edge. The s p e c i a l case o f such r e c t a n g l e s forming a r i g h t angle leads to a simple formula found i n most heat t r a n s f e r textbooks. The g e n e r a l case o f two r e c t a n g l e s forming an a r b i t r a r y angle has been f i r s t t r e a t e d by Hamilton and Morgan (1952) who ob t a i n e d the e x p r e s s i o n shown i n F i g u r e 2.2. Numerical va l u e s o f the c o n f i g u r a t i o n f a c t o r s as c a l c u l a t e d u s i n g Hamilton and Morgan's eq u a t i o n are gi v e n by F e i n g o l d (1966) f o r c e r t a i n angles and dimensions. U n f o r t u n a t e l y , the t a b u l a t e d v a l u e s do not cover the range o f dimensions u s e f u l f o r greenhouse a p p l i c a t i o n s . I t i s the o b j e c t o f t h i s s e c t i o n to o b t a i n v a l u e s f o r c o n f i g u r a t i o n f a c t o r s to be used f o r d i f f u s e r a d i a t i o n a n a l y s i s i n gable greenhouses. For a d e t a i l e d a n a l y s i s and more comprehensive r e s u l t s o f c o n f i g u r a t i o n f a c t o r s f o r t r i a n g u l a r and c i r c u l a r r o o f green-houses, the reader i s r e f e r r e d t o McAdam e t a l . ( 1 9 7 1 ) . RESULTS AND DISCUSSION The e x p r e s s i o n shown i n F i g u r e 2.2 i s used to determine the c o n f i g u r a t i o n f a c t o r F between the two r o o f s l o p e s o f a gable greenhouse, and the c o n f i g u r a t i o n f a c t o r from one ro o f slope t o the p l a n t canopy, F'. Then, the r a d i a t i o n c o n f i g u r a t i o n f a c t o r from one r o o f s l o p e to the two gable ends F" i s c a l c u l a t e d as f o l l o w s : F" = 1 - F - F' (6) The r a d i a t i o n c o n f i g u r a t i o n f a c t o r s are determined f o r greenhouse le n g t h s from 10 t o 100 metres and having a width from 5 to 15 metres w i t h roof s l o p e s chosen to cover the L = cjb; N = a/b. i •• Wb\ l\ - (1+N2)V+L*) 1«»*.-o»*+cot»» r L 2(l + AT2 + £2_-2ATLcos_<P) 1 L 2) + it,in n ( [ i + ; v 2 + Z 2 _ 2 ^ j L ( . o s ^ J [(l + L*f(N* + L*-ML cos / , cos8 + J A 2 sin- <D In J (-Y2 +i 2 _ 2 i V L -os ,h) ( t + Nz + £•> J j A TZ cos"*) + .V tan-1 j - V(A'2 + X2 - 2ATZ, cos 0 ) cot"1 y/(N2 + X2 - 2 ATZ, cos «D) + J A7 sin <D sin 2<J> ^ ( 1 + iVs sin2 + Ltan-1j + cos * J * i / A* cos* \ ,/ £-ATcos<t>Y] 0 ) [ t a n (,7^A' 2siOT)) + t a n _ 1 ( v T l T A^n^ J d) f % ( l + s W O ) f t a n - i ( d z l Jo L \.V(l+22sms<I>)/ \ >/(l + 2 2sin*0)/J J| FIGURE 2.2: RADIATION CONFIGURATION FACTOR BETWEEN TWO RECTANGLES FORMING AN ARBITRARY ANGLE.* * Source: F e i n g o l d , A. (1966) range commonly used by the greenhouse i n d u s t r y . Three r o o f s l o p e s were s e l e c t e d , namely 15°, 20° and 25° f o r which the r e s u l t s are shown i n F i g u r e s 2.3, 2.4 and 2.5, r e s p e c t i v e l y . For each roof s l o p e , the v a l u e s of F and F" are p l o t t e d as a f u n c t i o n of greenhouse l e n g t h and width. The e f f e c t o f roof slope on the r a d i a t i o n c o n f i g u r a t i o n f a c t o r s can be seen i n Table 2.1. EFFECT OF GREENHOUSE WIDTH For any r o o f s l o p e , i n c r e a s i n g the width decreases the c o n f i g u r a t i o n f a c t o r . T h i s e f f e c t i s s i g n i f i c a n t o n l y f o r r e l a t i v e l y s h o r t greenhouse. For example, f o r a r o o f slope of 20° (Figure 2.4) and a greenhouse l e n g t h of 20 metres, an i n c r e a s e i n the greenhouse width from 5 to 10 metres r e s u l t s i n a decrease f o r the va l u e o f the f a c t o r F from 0.05657 to 0.05298. However, f o r the same r o o f s l o p e but f o r a greenhouse l e n g t h of 70 metres, the v a l u e s of F become 0.0592 and 0.0582 f o r a 5 and 10 metres greenhouse width r e s p e c t i v e l y . EFFECT OF GREENHOUSE LENGTH For r o o f s l o p e s and widths i n v e s t i g a t e d , the c o n f i g u r a t i o n f a c t o r F i s found to i n c r e a s e w i t h i n c r e a s i n g greenhouse l e n g t h . The r a t e of i n c r e a s e of F wi t h l e n g t h i s l a r g e r f o r s h o r t e r greenhouses. For long greenhouses, the e f f e c t o f l e n g t h on the v a l u e of F becomes s m a l l . T h i s i s due to the e f f e c t o f the gable ends which becomes very s m a l l f o r the long H O a M M U) O ROOF td > to do W n O RE OF CO M 3 fi a W o 3 G CD cn >-3 M PC m cn > m — PC 2! > a o < M S! c r CO z H m o a i — cn > PC m o CD o 2 —1 o TH , , M o> o > m w DI CA OF > OF TT m —i i—1 O Ul 2! ES O n W o *3 CD H W w (O 9QT > 00 3 O O cn f O W O O M O c! W w M o JO O tr1 o a G cn w cn < H 25 o > 25 D a o >-3 a w ss o H > H O 25 a o M o a 25 M H M O cn a •-3 H O 25 > O i-3 O cn *j O TO CD CO CD m 3> m co LOT > H o G 8 f M W O •-3 O » O M hi i-3 JO o o a o o H > t-3 o 80T greenhouses as d e p i c t e d i n F i g u r e s 2.3 to 2.5 by the s m a l l v a l u e s o f the c o n f i g u r a t i o n f a c t o r s between the r o o f slope and the gable ends F". For the purpose of i l l u s t r a t i o n , take f o r example a greenhouse having a r o o f slope of 20 degrees and a width of 10 metres; then by F i g u r e 2.4 i t can be seen t h a t the value o f F i n c r e a s e s from 0.0466 to 0.0573 f o r an i n c r e a s e i n l e n g t h from 10 to 50 metres. However, i f the greenhouse l e n g t h i s i n c r e a s e d from 60 to 100 metres, the valu e s of F has i n c r e a s e d o n l y from 0.0578 to 0.0588. EFFECT OF ROOF SLOPE The greenhouse r o o f slope has more e f f e c t on the value of the c o n f i g u r a t i o n f a c t o r F than the l e n g t h and width of the greenhouse. Table 2.1 g i v e s the valu e s of. F and F" as a f u n c t i o n o f greenhouse l e n g t h f o r three r o o f s l o p e s and a cons t a n t width of 10 metres. I t i s important t o n o t i c e t h a t the valu e s of F" are much high e r than those of F f o r s h o r t greenhouse r e g a r d l e s s of the r o o f s l o p e . T h i s i m p l i e s t h a t the r a d i a t i o n l o s s from the gable, ends must be c o n s i d e r e d when d e a l i n g w i t h s h o r t greenhouses d u r i n g the c a l c u l a t i o n o f the t o t a l capture f a c t o r s (TCF) d e f i n e d i n the p r e v i o u s s e c t i o n . In long greenhouses (say > 50 metres) the end e f f e c t s may be n e g l e c t e d s i n c e the f r a c t i o n of r a d i a t i o n t r a n s m i t t e d through one roof slope t h a t i s l o s t through the gable ends i s expected to be l e s s than 2%. T h e r e f o r e , equation 5 f o r the c a l c u l a t i o n of TABLE 2.1 RADIATION CONFIGURATION FACTORS BETWEEN THE TWO SLOPES OF ROOF (F)  AND FROM ONE ROOF SLOPE TO GABLE ENDS (F") FOR A GABLE GREENHOUSE HAVING A WIDTH OF 10 METRES Greenhouse Roof Slope Length 1 5 ° 2 0 ° 25° (m) F F" F F" F F" 10 0.0264 0.0674 0.0466 0.0902 0.0722 0.1130 20 0.0300 0.0342 0.0530 0.0461 0.0822 0.0581 30 0.0313 0.0229 0.0553 0.0309 0.0859 0.0390 40 0.0320 0.0172 0.0566 0.0232 0.0878 0.0293 50 0.0324 0.0138 0.0573 0.0181 0.0890 0.0235 60 0.0327 0.0115 0.0578 0.0155 0.0898 0.0196 70 0.0329 0.0098 0.0582 0.0133 0.0903 0.0168 80 0.0330 0.0086 0.0584 0.0116 0.0907 0.0147 90 0.0331 0.0077 0.0586 0.0103 0.0911 0.0130 100 0.0332 0.0069 0.0588 0.0093 0.0913 0.0117 the greenhouse t o t a l capture f a c t o r (TCF) as d e r i v e d i n s e c t i o n A of t h i s chapter i s v a l i d f o r long greenhouses o n l y , s i n c e d u r i n g the d e r i v a t i o n , the r a d i a t i o n l o s s by the gable ends has been n e g l e c t e d . For the case of the greenhouse shown i n F i g u r e 2.1, having the dimensions of 100 m x 10 m wit h 18° r o o f s l o p e , the f a c t o r F has a va l u e of 0.0477 wh i l e t h a t o f F" i s o n l y 0. 00 8. T h e r e f o r e , the e f f e c t of F" on the r a d i a t i o n l o s s from the greenhouse was not c o n s i d e r e d d u r i n g the a n a l y s i s , thus the r e s u l t s g i v e n i n F i g u r e 2.1. CONCLUSIONS Based upon the c a l c u l a t e d greenhouse c o n f i g u r a t i o n f a c t o r s the f o l l o w i n g c o n c l u s i o n s may be made w i t h r e s p e c t to d i f f u s e r a d i a t i o n l o s s : 1. For a giv e n r o o f s l o p e , i n c r e a s i n g the width r e s u l t s i n a decreased d i r e c t d i f f u s e r a d i a t i o n l o s s through the greenhouse r o o f . T h i s e f f e c t i s more s i g n i f i c a n t f o r r e l a t i v e l y s h o r t greenhouses. 2. For roof s l o p e s and widths commonly used by the greenhouse c o n s t r u c t i o n i n d u s t r y , i n c r e a s i n g the l e n g t h tends to i n c r e a s e the d i r e c t d i f f u s e r a d i a t i o n l o s s through the greenhouse r o o f . T h i s e f f e c t i s found t o be more s i g n i f i c a n t f o r r e l a t i v e l y s h o r t greenhouses. 3. The extent of d i r e c t d i f f u s e r a d i a t i o n l o s s through the greenhouse r o o f i s more dependent on i t s r o o f slope than i t s l e n g t h or width. of l e n g t h and width on the d i r e c t l o s s of d i f f u s e r a d i a t i o n be n e g l e c t e d . 5. During the c a l c u l a t i o n of the t o t a l s o l a r r a d i a t i o n capture f a c t o r s of greenhouses, the gable ends e f f e c t may be n e g l e c t e d when d e a l i n g w i t h long greenhouses (> 50 m) having low r o o f s l o p e s (< 20°). 6. The t o t a l s o l a r r a d i a t i o n capture f a c t o r s (TCF) of greenhouses are h i g h l y dependent on the e f f e c t i v e albedo of the p l a n t canopy w i t h i n the greenhouse. A h i g h albedo r e s u l t s i n l a r g e d i f f u s e r a d i a t i o n l o s s , thus a low t o t a l s o l a r r a d i a t i o n capture f a c t o r . NOMENCLATURE Symbol A f A. l F F' F" b , i ' H d , i D e f i n i t i o n f l o o r area o f a greenhouse area o f a s p e c i f i c s u r f a c e " i " o f the greenhouse e n c l o s u r e r a d i a t i o n c o n f i g u r a t i o n f a c t o r between the two ro o f s l o p e s o f the greenhouse r a d i a t i o n c o n f i g u r a t i o n f a c t o r from one ro o f slope t o the p l a n t canopy r a d i a t i o n c o n f i g u r a t i o n f a c t o r from one ro o f slope t o the two gable ends monthly average d a i l y i n s o l a t i o n monthly average d a i l y beam and d i f f u s e r a d i a t i o n i n c i d e n t on a s p e c i f i c s u r f a c e " i " of the greenhouse e n c l o s u r e , r e s p e c t i v e l y U n i t s as d e f i n e d by equ a t i o n (3) T . , T, monthly average d a i l y t r a n s m i t t a n c e b , i d , i a S p e c i f i c s u r f a c e " i " t o beam and d i f f u s e s o l a r r a d i a t i o n , r e s p e c t i v e l y of 2 m m . _ -2 kJ .m kJ .m -2 kJ .m -2 P e f f e c t i v e p l a n t canopy albedo PART II ANALYSIS OF GREENHOUSE-LIVESTOCK COMBINATION FOR POSSIBLE ENERGY CONSERVATION CHAPTER 3 COMPUTER SIMULATION MODEL OF ENERGY REQUIREMENTS FOR LIVESTOCK BUILDINGS INTRODUCTION The f i r s t c hapter of t h i s study i s mainly intended to examine the energy requirements of c o n v e n t i o n a l l i v e s t o c k b u i l d i n g s . I t i s d i v i d e d i n t o two s e c t i o n s . The f i r s t s e c t i o n deals p r i m a r i l y w i t h the development of the mathematical model f o r the l i v e s t o c k b u i l d i n g . The purpose o f the model i s to p r e d i c t the thermal and e l e c t r i c a l energy r e q u i r e d to p r o v i d e a c o n t r o l l e d atmospheric environment w i t h i n the l i v e s t o c k f a c i l i t y . F a c t o r s c o n s i d e r e d i n the computer model development are v e n t i l a t i o n , animal s e n s i b l e and l a t e n t heat p r o d u c t i o n , heat t r a n s m i s s i o n through the b u i l d i n g envelope, and s o l a r r a d i a t i o n e f f e c t s on heat l o s s or g a i n from the s t r u c t u r e . The computer model i n i t s p r e s e n t form i s designed to perform energy a n a l y s e s on l i v e s t o c k b u i l d i n g s . I t i s not intended to p r e d i c t the environmental c o n d i t i o n s w i t h i n the b u i l d i n g . However, with simple m o d i f i c a t i o n s to some of the s u b r o u t i n e s , the computer model c o u l d p r e d i c t the i n s i d e temperature and r e l a t i v e humidity o f a l i v e s t o c k f a c i l i t y . The model c o u l d be used to examine the e f f e c t o f v a r y i n g the o r i e n t a t i o n and the l e v e l o f i n s u l a t i o n of the b u i l d i n g , and the e f f e c t of v a r y i n g the minimum winter and the maximum summer v e n t i l a t i o n r a t e s on the t o t a l energy consumption by the l i v e s t o c k b u i l d i n g . The second s e c t i o n g i v e s a d e t a i l e d d i s c u s s i o n of the s o l - a i r methods a v a i l a b l e f o r c a l c u l a t i n g the t r a n s m i s s i o n heat t r a n s f e r from b u i l d i n g s . A comparison between the r e s u l t s o b t a i n e d by two s o l - a i r methods to those r e s u l t i n g from a d e t a i l e d heat balance about the b u i l d i n g w a l l s i s i n c l u d e d . The l a s t s e c t i o n o f t h i s chapter d e s c r i b e s the a p p l i c a t i o n of the computer model through a case study. The model was used to determine the h e a t i n g and v e n t i l a t i o n requirements of a c o n v e n t i o n a l swine f i n i s h i n g barn. A l s o , the r e s u l t s are analyzed to examine i f excess heat i s a v a i l a b l e f o r the purpose of s u p p l y i n g p a r t i a l l y the h e a t i n g l o a d of an adjacent greenhouse. SECTION A MATHEMATICAL MODEL DEVELOPMENT FOR THE LIVESTOCK BUILDING MODEL DEVELOPMENT ASSUMPTIONS In d e v e l o p i n g the model, s e v e r a l assumptions were made: i ) E f f e c t of heat storage i n the w a l l s and the f l o o r i s n e g l e c t e d . i i ) Heat t r a n s f e r through the f l o o r i s accounted f o r d u r i n g the heat t r a n s f e r c a l c u l a t i o n s through the peri m e t e r o f the b u i l d i n g . i i i ) Complete mixing o f the a i r i n the b u i l d i n g . iv) Constant heat and moisture p r o d u c t i o n by the animals housed w i t h i n the b u i l d i n g . HEAT BALANCE ABOUT THE LIVESTOCK BUILDING When the above assumptions are taken i n t o c o n s i d e r a t i o n , the g e n e r a l heat balance about the b u i l d i n g can be represented as: ANIMAL SENSIBLE HEAT PRODUCTION + SUPPLEMENTAL HEAT = HEAT FOR VENTILATION + HEAT TRANSMISSION ; or i n equation form: QSENS + QSUP = QVENT + QTRAN ^ D e t a i l s o f each o f the terms of the energy balance equation are r e p r e s e n t e d i n t h i s chapter. The t r a n s m i s s i o n heat t r a n s f e r i n c l u d e s the c o n d u c t i v e , c o n v e c t i v e and r a d i a t i v e heat exchange between the b u i l d i n g and i t s environment. The e f f e c t of s o l a r r a d i a t i o n on the t r a n s m i s s i o n heat t r a n s f e r a l s o needs to be c o n s i d e r e d . Two methods are a v a i l a b l e to e s t imate the e f f e c t of the s o l a r energy absorbed by the w a l l s o f the b u i l d i n g on the t r a n s m i s s i o n heat t r a n s f e r . The s o l - a i r temperature method i s w i d e l y used and i s w e l l d e s c r i b e d by T h r e l k e l d (.1970) and O'Callaghan (1978) and the ASHRAE Handbook of Fundamentals (1977). The s o l a r r a d i a t i o n absorbed by a w a l l has the same e f f e c t as a r i s e i n the o u t s i d e temperature. The r i s e i n the o u t s i d e temperature i s d i r e c t l y p r o p o r t i o n a l t o the a b s o r p t i v i t y o f a s u r f a c e t o s o l a r r a d i a t i o n anfl' t o the s o l a r r a d i a t i o n i n c i d e n t on t h a t s u r f a c e , and i n v e r s e l y p r o p o r t i o n a l to the c o n v e c t i v e heat t r a n s f e r c o e f f i c i e n t due to wind. The o u t s i d e temperature c o r r e c t e d f o r s o l a r r a d i a t i o n e f f e c t i s termed s o l - a i r temperature and may be d e f i n e d i n i t s s i m p l e s t form ( T h r e l k e l d , 1970). by the f o l l o w i n g e x p r e s s i o n : T . = Tn + a. I ./h . (2) s a , i 0 l s , i ' w,i v ' O'Callaghan (1978) m o d i f i e d the above e x p r e s s i o n to take i n t o account the e f f e c t of the emission of long-wave r a d i a t i o n by the s u r f a c e . H i s m o d i f i e d e x p r e s s i o n f o r s o l - a i r t e n p e r a t u r e . i s : T . = ? + Ca. I . - e.I„)/h . (3) s a , i 0 l s , i l I ' w,i where 1^ i s the i n t e n s i t y of long-wave r a d i a t i o n from a b l a c k body at the temperature of the ambient a i r . T.£ i s taken as zero f o r a v e r t i c a l w a l l because i t i s assumed t h a t thermal r a d i a t i o n from the ground balances r a d i a t i o n l o s t to the sky. S o l - a i r methods are d i s c u s s e d f u r t h e r i n S e c t i o n B. A second method based on a d e t a i l e d heat balance about the outer s u r f a c e of each of the w a l l s making up the envelope of the b u i l d i n g can be used to determine the e f f e c t of s o l a r and thermal r a d i a t i o n on the t r a n s m i s s i o n heat t r a n s f e r . T h i s method i s s u i t a b l e f o r d i g i t a l computer c a l c u l a t i o n s . For the purpose of t h i s a n a l y s i s , the second method i s used i n order to take i n t o c o n s i d e r a t i o n the e f f e c t of sky and ground r a d i a n t heat exchange to the e x t e r i o r s u r f a c e s of the b u i l d i n g . The f o l l o w i n g g e n e r a l heat balance equation about each of the outer s u r f a c e s of the b u i l d i n g envelope i s used to c a l c u l a t e the s u r f a c e temperatures: e.o [T 4 . - 0.5 (1 + cos 3.) T 4. - 0.5 (1 - cos 0.) T 4 ] l s , i l sky l g + h • (T . - T_) - U. (T. - T .) - a. I . = 0 w,i s , i 0 l b s , i l s , i (4) where h , the wind heat t r a n s f e r c o e f f i c i e n t i s estimated w u s i n g McAdams (1954) r e l a t i o n s h i p h = 20.52 + 13.68 W . (5) w equal to the ambient a i r temperature. The t o t a l s o l a r r a d i a t i o n i n c i d e n t on a s u r f a c e o f any t i l t and o r i e n t a t i o n I . i s c a l c u l a t e d i n Appendix C. The e f f e c t i v e sky s, 1 temperature i s a f u n c t i o n o f many m e t e o r o l o g i c a l v a r i a b l e s such as water vapour content and a i r temperature. S e v e r a l c o r r e l a t i o n equations between the e f f e c t i v e sky temperature and the m e t e o r o l o g i c a l v a r i a b l e s have been proposed (Brunt (1932 ), B l i s s (1961) , Swinbank (1963 ) , W h i l l i e r (1967 ), Morse and Read (1968)>. In t h i s a n a l y s i s , Swinbank's c o r r e l a t i o n T s k y = ° ' 0 5 5 2 T u * 5 C 6 ) r e l a t i n g the sky temperature t o the l o c a l environmental temperature i s employed. S o l u t i o n o f equation (A) i s r e q u i r e d f o r each exposed s u r f a c e " i " o f the b u i l d i n g t o determine i t s o u t e r surface temperature, T g ^. For a b u i l d i n g w i t h an u n v e n t i l a t e d a t t i c space, the a t t i c temperature can be estimated whence the outer s u r f a c e temperature of the r o o f s u r f a c e s are known using the f o l l o w i n g r e l a t i o n s h i p : m m T = (U A T, + 7 U.A.T .)/(U A + > U.A.) . (7) a c c b j 3 s , : ) ' / v c c D 3 j = l j = l where U^A^ are f o r the exposed s u r f a c e s of the a t t i c space. The o v e r a l l heat t r a n s f e r c o e f f i c i e n t s U.'s exclude the o u t s i d e f i l m c o e f f i c i e n t s . The t o t a l heat t r a n s m i s s i o n between the b u i l d i n g and i t s environment may then be c a l c u l a t e d u s i n g the f o l l o w i n g e q u a t i o n : where U.'s are the o v e r a l l heat t r a n s f e r c o e f f i c i e n t s f o r the w a l l s e x c l u d i n g the o u t s i d e f i l m c o e f f i c i e n t s . The terms on the r i g h t hand s i d e o f the above e q u a t i o n r e p r e s e n t the heat l o s s or g a i n by the f o u n d a t i o n , the perim e t e r , the c e i l i n g and. the w a l l s o f the b u i l d i n g , r e s p e c t i v e l y . VENTILATION HEAT TRANSFER V e n t i l a t i o n system d e s i g n f o r l i v e s t o c k housing i n v o l v e s d e t e r m i n i n g the optimum a i r flow r a t e and p r o v i d i n g an even a i r d i s t r i b u t i o n w i t h i n the b u i l d i n g . In t h i s study, o n l y the v e n t i l a t i o n r a t e i s determined and i t i s assumed t h a t the v e n t i l a t i o n system i s p r o p e r l y designed f o r good a i r d i s t r i b u t i o n . V e n t i l a t i o n o f a l i v e s t o c k b u i l d i n g c o n s i s t s o f three stages depending on the o u t s i d e c l i m a t i c c o n d i t i o n s . For low o u t s i d e temperature, v e n t i l a t i o n i s used f o r moisture c o n t r o l w i t h i n the b u i l d i n g . At i n t e r m e d i a t e o u t s i d e temperatures, the i n s i d e temperature i s m a i n t a i n e d at i t s QTRAN = U f A f ( V T 0 ) + . U p P ( W n_ (8) i = l optimum l e v e l by i n c r e a s i n g the v e n t i l a t i o n r a t e . When the o u t s i d e temperature approaches or exceeds the optimum i n s i d e temperature, animal comfort determines the r e q u i r e d v e n t i l a t i o n r a t e ( C h r i s t i a n s o n a n d - H e l l i c k s o n , 1977) . The MWPS* handbook C1980) and the Canadian Farm B u i l d i n g Code (1977) recommend t y p i c a l v e n t i l a t i o n r a t e s f o r animal comfort based on animal type and s i z e . VENTILATION SYSTEM CONTROL I d e a l l y , the v e n t i l a t i o n system should keep the i n s i d e temperature and r e l a t i v e humidity at t h e i r optimum l e v e l s f o r any o u t s i d e c l i m a t i c c o n d i t i o n s . T h i s i s o b v i o u s l y not p o s s i b l e without the i n s t a l l a t i o n o f a c o o l i n g system. S e v e r a l c o n t r o l systems have been used f o r l i v e s t o c k b u i l d i n g v e n t i l a t i o n c o n t r o l . The most commonly used c o n t r o l system i s a cons t a n t low flow r a t e f o r winter v e n t i l a t i o n and a constant h i g h flow r a t e f o r summer v e n t i l a t i o n . T h i s type of system c o n t r o l can be ac h i e v e d by e i t h e r a two-speed fan and a thermostat or two - s i n g l e speed fans with the low speed fan o p e r a t i n g c o n t i n u o u s l y . The Midwest Plan S e r v i c e (19 80) d e s c r i b e s some v e n t i l a t i o n c o n t r o l systems and g i v e s t h e i r w i r i n g diagrams. For the purpose o f t h i s s i m u l a t i o n , two s e t s o f v a r i a b l e speed fans are s e l e c t e d . The v a r i a b l e low speed fans are used f o r moisture c o n t r o l d u r i n g c o l d p e r i o d s . These fans are c o n t r o l l e d by a hu m i d i s t a t . For summer v e n t i l a t i o n , * MWPS: Midwest Plan S e r v i c e t h e r m o s t a t i c a l l y c o n t r o l l e d v a r i a b l e high-speed fans are used to c o n t r o l the i n s i d e temperature near an optimum l e v e l . The low a i r flow r a t e i s determined a c c o r d i n g t o the mass balance e q u a t i o n when the h u m i d i s t a t i s s e t a t the maximum r e l a t i v e humidity a l l o w a b l e . For t h a t r e l a t i v e humidity an a i r flow r a t e i s determined u s i n g a moisture balance d e f i n e d below; then, the supplementalsheat r e q u i r e d t o keep the i n s i d e temperature at an optimum l e v e l i s c a l c u l a t e d from the energy balance equation. T h i s procedure i s c o n t i n u e d u n t i l the heat balance p r e d i c t s c o o l i n g requirements then the h i g h flow r a t e fans a re a c t i v a t e d and the a i r flow r a t e i n c r e a s e d to maintain the i n s i d e temperature a t the d e s i r e d l e v e l , r e s u l t i n g i n a lower r e l a t i v e h umidity w i t h i n the b u i l d i n g . The a i r flow rate w i l l i n c r e a s e w i t h i n c r e a s i n g o u t s i d e a i r temperature to a maximum r a t e recommended by l o c a l b u i l d i n g codes f o r animal comfort. At t h i s p o i n t , the r e s u l t i n g i n s i d e temperature i s d i c t a t e d by the o u t s i d e c l i m a t i c c o n d i t i o n s . VENTILATION RATE FOR HUMIDITY CONTROL The v e n t i l a t i o n r a t e f o r humidity c o n t r o l i s determined by performing a moisture balance about the l i v e s t o c k b u i l d i n g . Under normal o p e r a t i n g c o n d i t i o n s , there are two sources o f water vapour p r o d u c t i o n w i t h i n the l i v e s t o c k b u i l d i n g : a) The water vapour r e l e a s e d by the animals through r e s p i r a t i o n f o r non-sweating farm animals. b) The water vapour evaporated from wetted s u r f a c e s w i t h i n the b u i l d i n g , i n c l u d i n g f e c e s and u r i n e . The two sources o f water vapour p r o d u c t i o n are u s u a l l y combined and r e f e r r e d t o as the t o t a l b u i l d i n g l a t e n t heat. I f we l e t m w be the t o t a l m o i s t u r e produced, then the t o t a l b u i l d i n g l a t e n t heat may be c a l c u l a t e d u s i n g the l a t e n t heat o f v a p o r i z a t i o n o f water as f o l l o w s : Q = m h_ ... e w f g (9) where the formula f o r i s g i v e n by Cooper (1969) as h, = 2504.44 - 2.4 (T, - 273.16). (10) r g b When the r a t e o f m o i s t u r e p r o d u c t i o n w i t h i n the b u i l d i n g i s known, t h e mass b a l a n c e about the open system w i l l take the form *a W b - m a W 0 + mw ' U 1 ) T h e r e f o r e , the a i r mass f l o w r a t e r e q u i r e d t o remove the m o i s t u r e produced i s (12) m a Then, the s e n s i b l e h e a t l o s t due to the i n t r o d u c t i o n of f r e s h a i r i n t o the b u i l d i n g can be c a l c u l a t e d from the mass flow r a t e o f v e n t i l a t i n g a i r and the e n t h a l p y change o f the a i r as f o l l o w s : where the enthalpy of the a i r in the building, h£, i s taken at the barn dry-bulb temperature and a t the dew-point temperature of the o u t s i d e a i r . The v e n t i l a t i o n r a t e , f o r an exhaust fan system, may then be c a l c u l a t e d u s i n g the s p e c i f i c volume o f the a i r at the i n s i d e c o n d i t i o n , thus: V = v m /3600 . C14) Whence, the v e n t i l a t i o n r a t e r e q u i r e d t o remove the moisture produced i s known, the supplemental heat necessary t o maintain the d e s i r e d i n s i d e temperature may be estimated from the f o l l o w i n g heat balance e q u a t i o n about the b u i l d i n g QSUP = QSENS " QTRAN " QVENT * ( 1 5 ) VENTILATION RATE FOR TEMPERATURE CONTROL The v e n t i l a t i o n r a t e r e q u i r e d f o r temperature c o n t r o l i s determined by performing a heat balance about the b u i l d i n g . In t h i s case, no supplemental heat i s needed, but the v e n t i l a t i o n r a t e must be i n c r e a s e d t o keep the i n s i d e temperature at i t s optimum l e v e l . The heat balance f o r the i n s i d e temperature c o n t r o l can be w r i t t e n as QVENT = QSENS " QTRAN * ( " 1 6 ) Then, the a i r mass flow r a t e r e q u i r e d f o r temperature c o n t r o l can be c a l c u l a t e d from Qy^jjrp and the enthalpy change of the incoming f r e s h a i r as f o l l o w s : m a - Q V E N T / ( h b - h O ) ' ( 1 7 ) The r e s u l t i n g r e l a t i v e humidity i n s i d e the b u i l d i n g i s then determined from the s o l u t i o n o f the mass balance equation. D e t a i l s o f the method used here f o r the c a l c u l a t i o n of the ps y c h r o m e t r i c p r o p e r t i e s o f moist a i r are i n c l u d e d i n Appendix D. VENTILATION RATE FOR ANIMAL COMFORT The v e n t i l a t i o n r a t e r e q u i r e d f o r animal comfort du r i n g periods o f hot weather i s d i c t a t e d by the type and age of the animal, l o c a t i o n and c o n s t r u c t i o n parameters o f the b u i l d i n g and the a i r d i s t r i b u t i o n system. For t h i s s i m u l a t i o n model the maximum v e n t i l a t i o n r a t e i s l e f t as a parameter to be s e l e c t e d by the user depending on the p a r t i c u l a r a p p l i c a t i o n o f the model. HEAT AND MOISTURE PRODUCTION BY LIVESTOCK The use of the mathematical model r e q u i r e s accurate i n f o r m a t i o n on the heat and moisture r e l e a s e d w i t h i n the l i v e s t o c k confinement s t r u c t u r e f o r the type o f animals housed. The heat and moisture p r o d u c t i o n r a t e i s dependent upon the breed and s i z e o f the animals housed, the temperature and the r e l a t i v e humidity w i t h i n the b u i l d i n g and upon the management p r a c t i c e s used i n o p e r a t i n g the l i v e s t o c k f a c i l i t y . E x t e n s i v e data are a v a i l a b l e f o r p r e d i c t i n g the amounts of heat and water vapour generated by v a r i o u s types o f l i v e s t o c k . The b a s a l heat p r o d u c t i o n of many types o f animals i s r e a d i l y a v a i l a b l e i n many p u b l i c a t i o n s r e l a t e d to farm animal environmental p h y s i o l o g y . The b a s a l heat p r o d u c t i o n f o r most homeothermes may a l s o be c a l c u l a t e d using the equation developed by Brody (1945) . Data on the s e n s i b l e and l a t e n t heat p r o d u c t i o n by i n d i v i d u a l animals are a l s o w i d e l y a v a i l a b l e f o r most domestic animals (Bond e t al.(1952, 1959, 1963, 1965), Hazen and Mangold (1960), K e l l y e t a l . ( 1 9 4 8 ) , Longhouse et al.<1960>, Ota e t a l . (1953), Restrepo e t al.(1977) and Riskowski e t a l . (1977)). However, data o b t a i n e d through t e s t s on s i n g l e animals i s not s u i t a b l e f o r the design of h e a t i n g , v e n t i l a t i n g and a i r c o n d i t i o n i n g systems f o r l i v e s t o c k housing s i n c e t h i s type of data does not r e p r e s e n t the a c t u a l o p e r a t i n g c o n d i t i o n s of l i v e s t o c k f a c i l i t i e s . Care must be taken when u s i n g p u b l i s h e d r e s e a r c h data on heat and moisture p r o d u c t i o n r a t e o f domestic animals since the c o n d i t i o n s under which the experiments were conducted and the methods o f measurements used i n f l u e n c e the r e s u l t s o b t a i n e d , thus, t h e i r range of a p p l i c a b i l i t y . For example, when e s t i m a t i n g the moisture produced, i t i s necessary t o d i s t i n g u i s h between animal moisture p r o d u c t i o n and room moisture p r o d u c t i o n . The l a t t e r i n c l u d e s both water vapour r e l e a s e d by the animals and the moisture evaporated from the wetted s u r f a c e s w i t h i n the b u i l d i n g and from waste products (feces and u r i n e ) . The room moisture production i s more u s e f u l f o r h e a t i n g and v e n t i l a t i n g systems d e s i g n than animal moisture g e n e r a t i o n alone provided the management techniques to be adopted i n the a c t u a l b u i l d i n g are s i m i l a r to those used to o b t a i n the experimental data. ENERGY CONSUMPTION BY VARIABLE SPEED FANS Fan power requirements f o r v a r i a b l e a i r volume systems using v a r i a b l e speed fans as a means of volume c o n t r o l can be estimated from the r a t i o of the a i r flow d e l i v e r e d to the design a i r c a p a c i t y f o r the f a n . H i t t l e (1979) g i v e s the f o l l o w i n g r e g r e s s i o n equation to c a l c u l a t e the f r a c t i o n of f u l l - l o a d power: P f = 0.00153 + 0.005208 L f + 1.1086 L^ - 0.11635563 L 3 . (18) In the above e q u a t i o n , L f i s the p a r t - l o a d r a t i o d e f i n e d as the d e l i v e r e d a i r flow i n any p e r i o d of one hour d i v i d e d by the design a i r flow r a t e f o r the f a n . I t i s recommended that L j be kept above 0.4. SECTION B COMPARISON BETWEEN SOL-AIR AND HEAT BALANCE METHODS FOR TRANSMISSION LOSS CALCULATION BUILDING TRANSMISSION LOSS: SOL-AIR TEMPERATURE  METHODS VS HEAT BALANCE METHOD In S e c t i o n A of t h i s c hapter, i t has been s t a t e d t h a t two s o l - a i r temperature methods are a v a i l a b l e f o r e s t i m a t i n g the t r a n s m i s s i o n heat t r a n s f e r from b u i l d i n g s : Threlkeld,'s e q u a t i o n and 0'Callaghan's e q u a t i o n . T h i s s e c t i o n i s devoted to a d i s c u s s i o n o f the two s o l - a i r temperature equations i n c l u d i n g a comparison of r e s u l t s o b t a i n e d by the two equations to those c a l c u l a t e d u s i n g a d e t a i l e d heat balance about the w a l l s o f a t y p i c a l farm b u i l d i n g . SOL-AIR TEMPERATURE METHODS 1. T h r e l k e l d ' s Equation: T h r e l k e l d ' s s o l - a i r temperature method as r e p r e s e n t e d by e q u a t i o n 2 of t h i s chapter does not take i n t o account the thermal r a d i a t i o n l o s s e s from the b u i l d i n g outer s u r f a c e s to the ground and sky. T h e r e f o r e , the t r a n s m i s s i o n heat as determined through the use of equation 2 i s expected t o be under-estimated. The un d e r - e s t i m a t i o n of the heat l o s s w i l l be more pronounced i f the b u i l d i n g m a t e r i a l making up the oute r s u r f a c e o f w a l l s has a high e m i s s i v i t y f o r i n f r a - r e d r a d i a t i o n . 2. Q'Callaghan's Equation: Equation 3 of t h i s chapter estimates the s o l - a i r temperature as g i v e n by O'Callaghan (1978). When compared wit h T h r e l k e l d ' s e q u a t i o n , 0*Callaghan's e x p r e s s i o n i n c l u d e s the thermal r a d i a t i o n heat l o s s from the o u t e r s u r f a c e of the w a l l s t o the s u r r o u n d i n g s . T h i s l o s s i s r e p r e s e n t e d i n e q u a t i o n 3 by the i n c l u s i o n of the term E l ^ . During the a p p l i c a t i o n of 0 ' C a l l a g h a n 1 s e q u a t i o n the f o l l o w i n g two assumptions are made: 1. For v e r t i c a l s u r f a c e s , I £ becomes zero. T h i s i s based upon the argument t h a t the thermal r a d i a t i o n l o s s from the w a l l to the sky i s o f f s e t by the r a d i a t i v e . g a i n from the ground. 2. For n o n - v e r t i c a l w a l l s , r e g a r d l e s s of t i l t a n g l e s , the net r a d i a t i v e l o s s by the surface i s p r o p o r t i o n a l to the a b s o l u t e temperature of the ambient a i r r a i s e d t o the f o u r t h power, or i n equation form, (19) The net r a d i a t i v e energy l o s s from a v e r t i c a l w a l l t o the ground and the sky i s i l l u s t r a t e d i n F i g u r e 3.1(a)-. The net r a d i a t i v e l o s s i n t h i s case i s p r o p o r t i o n a l t o : < - 0 ^ < k y - 0.5 T< . (20) In o r d e r f o r the f i r s t assumption t o h o l d , the above e x p r e s s i o n must be i d e n t i c a l to zero. In a s i m i l a r manner, an examination of F i g u r e 3.1(b) f o r a n o n - v e r t i c a l w a l l a :VERTICAL W A L L btTILTED W A L L FIGURE. 3.1: THERMAL RADIATION EXCHANGE BETWEEN A WALL AND ITS ENVIRONMENT. r e v e a l s t h a t the net r a d i a t i v e l o s s from the s u r f a c e to the sky and ground i s p r o p o r t i o n a l t o : T 4 - 0.5 (1 + cos3)T 4, - 0.5 (1 - c o s p ) T 4 . (21) s sky 9 T h e r e f o r e the second assumption i s v a l i d o n l y i f the above e x p r e s s i o n i s equal to T 4 . I t i s i n t e r e s t i n g t o note t h a t f o r the s p e c i a l case of a h o r i z o n t a l s u r f a c e , the second assumption becomes v a l i d when, 4 4 4 T - T , = T . (22) s sky o HEAT BALANCE METHOD From the above d i s c u s s i o n o f the s o l - a i r temperature methods f o r e s t i m a t i n g t r a n s m i s s i o n heat l o s s from b u i l d i n g s , i t i s c l e a r t h a t the assumptions u n d e r l y i n g these methods are not always a p p l i c a b l e . T h e r e f o r e , a d e t a i l e d heat balance about the o u t e r s u r f a c e of the w a l l s i s p r e f e r r e d i f a d i g i t a l computer i s used. D e t a i l s o f the heat balance method i s i n c l u d e d i n S e c t i o n A of t h i s chapter, e q u a t i o n 4 to equation 8. T h i s method e l i m i n a t e s the two assumptions a s s o c i a t e d with 0 ' C a l l a g h a n 1 s e q u a t i o n . However, i n equation 4 f o r c a l c u l a t i n g the s u r f a c e temperature of the w a l l the ground temperature (T ) appears as an unknown. Si n c e , t h i s temperature i s seldom measured, i t must be c a l c u l a t e d or assumed. With the e x c e p t i o n of s p e c i a l cases ( i . e . a s p h a l t s u r f a c e exposed t o s u n l i g h t ) , the ground temperature may be c o n s i d e r e d equal to the a i r temperature. T h i s assumption i s not expected t o s i g n i f i c a n t l y a f f e c t the r e s u l t s c o n s i d e r i n g the a p p l i c a t i o n s of the an a l y s e s are p r i m a r i l y intended f o r r u r a l grass covered areas. COMPARISON OF THE RESULTS BY THE THREE METHODS The t r a n s m i s s i o n heat l o s s from a t y p i c a l swine b u i l d i n g i s c a l c u l a t e d u s i n g T h r e l k e l d ' s e q u a t i o n , 0 * C a l l a g h a n 1 s equation and by a heat balance about the o u t e r s u r f a c e s of b u i l d i n g w a l l s . The h o u r l y heat l o s s from the s e l e c t e d b u i l d i n g i s c a l c u l a t e d f o r the environmental temperature and s o l a r r a d i a t i o n shown i n F i g u r e 3.2. The valu e s i n t h i s f i g u r e r e p r e s e n t an average day f o r the month of December i n the H a l i f a x area. The cor r e s p o n d i n g h o u r l y heat t r a n s m i s s i o n l o s s e s are g i v e n i n F i g u r e s 3.3 and 3.4 f o r a constant indoor temperature of 18°C. Two types of s u r f a c e c o a t i n g are i n v e s t i g a t e d , because of the e f f e c t o f r a d i a t i o n p r o p e r t i e s of the s u r f a c e on the r a d i a t i v e exchange. In F i g u r e 3.3, the a b s o r p t i v i t y f o r s o l a r r a d i a t i o n of the s u r f a c e o f the w a l l s i s taken as 20 per c e n t while i t s e m i s s i v i t y to i n f r a - r e d r a d i a t i o n i s 90 pe r c e n t . T h i s s u r f a c e c o n d i t i o n i s r e p r e s e n t a t i v e of white p a i n t e d w a l l s . F i g u r e 3.4 i s f o r the case where both the a b s o r p t i v i t y and the e m i s s i v i t y are equal to 20 pe r c e n t . T h i s s u r f a c e c o n d i t i o n u s u a l l y r e p r e s e n t s a b u i l d i n g w i t h aluminum s i d i n g f i n i s h . 1 6 12 18 24 FIGURE 3.2: HOURLY TEMPERATURE AND SOLAR RADIATION ON A HORIZONTAL SURFACE USED FOR THE CALCULATION OF TRANSMISSION HEAT LOSS BY THE SOL-AIR M U) TEMPERATURE AND HEAT BALANCE METHODS. ^ An examination of F i g u r e 3.3 i n d i c a t e s t h a t T h r e l k e l d ' s equation, as expected, under-estimates the t r a n s m i s s i o n heat l o s s because i t does not c o n s i d e r the thermal r a d i a t i o n heat l o s s from the s u r f a c e . On the o t h e r hand, 0'Callaghan's s o l - a i r temperature e q u a t i o n g i v e s heat t r a n s m i s s i o n v a l u e s h i g h e r than those p r e d i c t e d by the d e t a i l e d heat balance method. T h i s i n d i c a t e s t h a t the r o o f r a d i a t i v e heat l o s s i s o v e r - e s t i m a t e d , s i n c e the r a d i a t i v e l o s s from the v e r t i c a l w a l l s i s taken as zero w i t h t h i s method of t r a n s m i s s i o n heat l o s s c a l c u l a t i o n . I t i s i n t e r e s t i n g to note when the s u r f a c e e m i s s i v i t y i s reduced from 0.9 ( F i g . 3.3) to 0.2 ( F i g . 3.4), the d i s c r e p a n c i e s between the r e s u l t s f o r t r a n s m i s s i o n heat l o s s by the three methods become s m a l l . T h i s f u r t h e r i n d i c a t e s t h a t the d i f f e r e n c e between the three methods i s due to the manner by which the r a d i a t i v e l o s s i s t r e a t e d . T h e r e f o r e , i t can be concluded t h a t f o r w a l l s with an o u t s i d e s u r f a c e having a low e m i s s i v i t y f o r long-wave r a d i a t i o n , the r a d i a t i v e heat l o s s becomes l e s s s i g n i f i c a n t ; thus, the simpl e r s o l - a i r temperature methods c o u l d be used to c a l c u l a t e t r a n s m i s s i o n l o s s from b u i l d i n g s i n s t e a d o f the more complex heat balance method without i n t r o d u c i n g s i g n i f i c a n t e r r o r s i n the f i n a l r e s u l t s . The s o l - a i r temperature methods have a l s o been compared to the heat balance method f o r the month of June. A s i m i l a r t r e n d i n the comparative r e s u l t s to those obtained f o r December was found i n d i c a t i n g t h a t the above c o n c l u s i o n s c o u l d be a p p l i e d t o oth e r months of the year as w e l l . * ff CD n K; II a o M • > to > > •= O II M o > W <a O - v - G 3^ t-3 a f t-1 en O hj t-3 K *o M o > f to G H f a H 3 o cn O I > H 50 i-3 W 3 •d M t-3 G 50 M W O G > t-3 H O 25 cn H o G 50 M U) n o s > to H cn O 3 o a o G 50 t-< K HOURLY T R A N S M I S S I O N HEAT LOSS PER UNIT FLOOR AREA ( K J . M - 2 ) t-3 a w M t-t o t-t > a > 3 > a cn 3 H cn cn H O 2 a w > t-3 t-t o cn cn > cn M cn t-3 H t-3 M O G cn n 3 > o t-t o G t-t > t-3. W O 1 Ol >-3 s: f t-i rtiG o £ 3 tr <+ o> 0) 0) •• tr H - I—' I—1 O cr OfrT 65 CO /- N oo CD 1 1 h- — > <C UJ ~r~ <c 1 1 1 CD 1 1, J <c CO CO ai O sz CD CO 1 i i — >-I or :=) LU CD rn 45 351— "1 1 1 1 1 P T 1 1 1 1 1 r H a l i f a x , N . S . December 1 1 1 1 1 1 1 r T b =18°C , 2 Length: 100m Width: 11m Thermal R e s i s t a n c e s (m".K/W) - w a l l s : 2.12 - c e i l i n g : 3.16 HOUR J I L J L J I L J I I I L 1 6 12 18 24 FIGURE 3.4: COMPARISON OF HOURLY TRANSMISSION HEAT LOSS AS ESTIMATED USING SOL-AIR TEMPERATURE EQUATIONS (THRELKELD , 0*CALLAGHAN) AND CALCULATED BY HEAT BALANCE ABOUT THE WALLS OF A TYPICAL FARM BUILDING. {a g = 0.2; E £ = 0.2} SECTION C CASE STUDY I HEATING AND VENTILATION REQUIREMENTS OF A CONVENTIONAL SWINE FINISHING BARN DESCRIPTION AND ASSUMPTIONS The computer s i m u l a t i o n model developed i n S e c t i o n A of t h i s chapter was used t o p r e d i c t the supplemental heat requirement as w e l l as the necessary v e n t i l a t i o n r a t e f o r a swine f i n i s h i n g barn. For the purpose o f the case study, the f o l l o w i n g assumptions are made: i) The p i g s e n t e r the b u i l d i n g at an average weight of 50 kg t o be f i n i s h e d t o a market weight o f 90 kg. i i ) The s i z e d i s t r i b u t i o n o f the animals i n the barn i s u n i f o r m l y d i s t r i b u t e d between s t a r t and f i n i s h weight such t h a t the average hog weight may be taken as 70 kg. i i i ) The optimum d r y - b u l b temperature f o r maximum d a i l y weight g a i n and maximum feed c o n v e r s i o n e f f i c i e n c y i s taken as 20°C (T u r n b u l l and B i r d , 1979). iv) The maximum a l l o w a b l e r e l a t i v e humidity i n the barn d u r i n g c o l d weather p e r i o d s i s taken as 85 percent. v) The maximum summer v e n t i l a t i o n r a t e f o r animal comfort i s chosen as 0.05 m 3/s per p i g (MWSP-1, 1980),. 2 v i ) A net f l o o r space requirement o f 0.6 m per p i g i s used. Figures 3.5and 3.6 show the f l o o r p l a n and the c r o s s - s e c t i o n a l view of the f i n i s h i n g hog barn, r e s p e c t i v e l y . The b u i l d i n g used i n the case study i s 100 m long by 11 m wide. A storage «"» \ Handling A l l e y Storage & Isolat ion 48 32 Pens 4 ,8x1 ,5 Area \ / Handl ing A l l e y 32 Pens 4,8x1,5 4,8 100m 4,8 JL FIGURE 3.5: FLOOR PLAN OF THE SWINE FINISHING BARN USED IN CASE STUDY I FIGURE 3.6: CROSS-SECTION OF THE SWINE FINISHING BARN USED IN CASE STUDY I . <_n and i s o l a t i o n area having a width o f 4 m d i v i d e s the barn i n t o two equal s e c t i o n s of 64 pens each. A l l the pens are of equal s i z e and have the dimensions of 4.8 m x 1.5 m. Each pen houses on the average 12 p i g s ; t h e r e f o r e , the t o t a l number of animals i n the b u i l d i n g a t any i n s t a n t would be around 1536 hogs i f the barn i s f u l l y o c c u p i e d . Assuming an average o f ten weeks per f i n i s h i n g p e r i o d , then the expected annual p r o d u c t i o n would be 7 980 hogs.7~ The t o t a l confinement swine b u i l d i n g chosen f o r the case study has a s o l i d concrete f l o o r and i s w e l l i n s u l a t e d . The 2 r e s i s t a n c e s t o heat conduction are 5.88 and 4.0m K/W f o r the c e i l i n g and f o r the w a l l s , r e s p e c t i v e l y . More i n f o r m a t i o n concerning the c o n s t r u c t i o n parameters o f the b u i l d i n g as w e l l as the management p r a c t i c e s used are i n c l u d e d i n Table 3.1. The t o t a l heat and room l a t e n t heat produced by the hogs i s estimated u s i n g the work done by Bond e t a l (1959) and Carson (1972). D e t a i l e d c a l c u l a t i o n s f o r heat and moisture p r o d u c t i o n w i t h i n the hog barn are i n c l u d e d i n Appendix E. RESULTS AND DISCUSSION Hourly computer s i m u l a t i o n r e s u l t s f o r a t y p i c a l day of each month o f the year are i n c l u d e d i n Appendix F. Tables F . l to F.12 show the h o u r l y and d a i l y heat l o s s e s due to t r a n s m i s s i o n through the b u i l d i n g envelope and those due to v e n t i l a t i o n f o r the o u t s i d e d r y - b u l b and dew-point temperatures are i n d i c a t e d i n the t a b l e s . The h o u r l y supplemental heat and TABLE 3.1 VARIABLES USED TO CALCULATE HEATING VENTILATION  REQUIREMENTS OF A CONVENTIONAL SWINE FINISHING BARN C o n s t r u c t i o n Parameters Length: Width: Height; Roof Slope: O r i e n t a t i o n : 100 m 11 m 2.5 m 26.57° East-West Long A x i s C o n s t r u c t i o n M a t e r i a l s P r o p e r t i e s B u i l d i n g Area RSI U Component , 2 , ^ -*1 ^ (m ) SI (m 2 K/W) (kJ m" 2h" 1K" 1 South Roof North Roof South Wall North W a l l E a s t Wall West Wall Gable E a s t End Wall Gable West End Wall C e i l i n g Foundation (Insulated) 615 615 200 200 22 22 15 15 1100 111 0.19 0.19 4.00 4.00 4. 00 4.00 0.24 0.24 5.88 1.49 18.61 18.61 0.90 0.90 0.90 0.90 15.19 15.19 0.61 2.41 0.2 0.2 0.2 0.2 0.2 0.2 0.2 0.2 0.22 0.22 0.22 0.22 0.22 0.22 0.22 0.22 Pe r i m e t e r 222 (Insu l a t e d ) (m) 1.45 (m.K/W) 2.48 (kJ.m-lh-lK.-l) Management Parameters L o c a t i o n : Number o f hogs: Average weight: Minimum i n s i d e temperature: Maximum i n s i d e r e l a t i v e h u m i d i t y : Maximum v e n t i l a t i o n r a t e : V e n t i l a t i o n system type: Vancouver, B.C. Mo n t r e a l , Quebec H a l i f a x , N.S. 1536 70 kg 20°C 85% 50 l i t r e s per second per hog V a r i a b l e speed fans (12 kW peak load) a s v e n t i l a t i o n r a t e requirements as w e l l as the e l e c t r i c a l energy consumed by the fans are i n c l u d e d i n the Tables of Appendix F. As expected, the s i m u l a t i o n r e s u l t s i n d i c a t e t h a t supplemental heat i s not needed f o r the swine f i n i s h i n g barn with the c o n s t r u c t i o n parameters and the i n s i d e environmental c o n d i t i o n s p r e v i o u s l y d e s c r i b e d i n Table 3.1. The hogs produced enough s e n s i b l e heat to compensate f o r the t r a n s m i s s i o n heat l o s s and the energy needed to heat the amount o f v e n t i l a t i o n a i r t h a t i s r e q u i r e d t o keep the i n s i d e r e l a t i v e humidity below 85 percent. I t i s i n t e r e s t i n g t o note t h a t the recommended v e n t i l a t i o n r a t e f o r animal comfort o f 50 l i t r e s per second per hog i s adequate, s i n c e the i n s i d e temperature remained at the design l e v e l o f 2 0°C u n t i l the o u t s i d e temperature has r i s e n above 18°C. The i n c r e a s e o f the i n s i d e temperature above the optimum l e v e l o c c u r r e d i n the day time d u r i n g the warm months of June, J u l y , August and September. Winter and summer h o u r l y v e n t i l a t i o n r a t e s as p r e d i c t e d by the s i m u l a t i o n model are shown i n F i g u r e s 3.7 and 3.8, r e s p e c t i v e l y . The curve f o r h o u r l y v e n t i l a t i o n r a t e s f o r a t y p i c a l day d u r i n g the month o f January CFig. 3.7) f o l l o w s very c l o s e l y the o u t s i d e d r y - b u l b temperature curve which i n d i c a t e s t h a t the v e n t i l a t i o n a i r i s used f o r temperature c o n t r o l . F i g u r e 3.8 shows the h o u r l y v e n t i l a t i o n r a t e s f o r a t y p i c a l day i n August. I t can be seen t h a t the v e n t i l a t i o n 1 6 12 18 24 HOUR FIGURE 3.7: VENTILATION RATE REQUIREMENT OF THE SWINE FINISHING BARN FOR A MINIMUM INSIDE TEMPERATURE OF 20°C AND A MAXIMUM INSIDE RELATIVE HUMIDITY OF 85% FOR THE OUTSIDE DRY-BULB AND DEW-POINT TEMPERATURES INDICATED IN THE GRAPH. M FIGURE 3.8: VENTILATION RATE REQUIREMENT OF THE SWINE FINISHING BARN FOR A MINIMUM INSIDE TEMPERATURE OF 2 0°C AND A MAXIMUM INSIDE RELATIVE HUMIDITY OF 85% M FOR THE OUTSIDE DRY-BULB AND DEW-POINT TEMPERATURES INDICATED IN THE GRAPH. ° r a t e i s a t i t s maximum value f o r most of the day time hours i n d i c a t i n g t h a t the i n s i d e temperature i s above the set p o i n t of 20°C. Appendix F a l s o g i v e s the e l e c t r i c a l power i n p u t to the fans from which the monthly, then the y e a r l y e l e c t r i c a l energy consumption by the v e n t i l a t i o n system may be e s t i m a t e d . By Tables F. 1 to F.12, i t can be c a l c u l a t e d t h a t a t o t a l annual e l e c t r i c a l energy of 16869 kWh was used to v e n t i l a t e the t y p i c a l swine f i n i s h i n g barn. The expected annual hog p r o d u c t i o n f o r the barn under study i s i n the order of 7980 hogs which r e s u l t s i n a v e n t i l a t i o n energy requirement per hog produced o f about 2.11 kWh. F i g u r e 3.9 i s a nomograph which can be used to determine the r e l a t i v e c o s t of energy to the market value of the product as a f u n c t i o n of the u n i t c o s t o f e l e c t r i c i t y and the market value of the f i n i s h e d hog. By F i g u r e 3.9, i t can be seen t h a t a t the p r e s e n t c o s t of e l e c t r i c i t y a t s i x cents per kWh and f o r s a l e s v a l u e of $100 per hog, the cost of e l e c t r i c a l energy used f o r v e n t i l a t i o n r e p r e s e n t s only 0.1 p e r c e n t o f the market v a l u e . T h e r e f o r e , f o r a hog f i n i s h i n g e n t e r p r i s e , an i n c r e a s e i n the c o s t o f energy i s not expected to a f f e c t s i g n i f i c a n t l y the o p e r a t i n g c o s t i n a d i r e c t manner; but, i n d i r e c t l y through the i n f l u e n c e of the c o s t of energy on feed p r i c e s . Due to the sma l l f r a c t i o n of the o p e r a t i n g c o s t of a hog f i n i s h i n g e n t e r p r i s e t h a t can Percent cost of energy of the market value Energy requirement (kWh per hog produced) FIGURE 3.9: NOMOGRAPH FOR DETERMINING THE COST OF ENERGY USED FOR VENTILATION OF SWINE FINISHING BARNS. I—' t o be a t t r i b u t e d to energy c o s t , i t i s u n l i k e l y t h a t a combined g r e e n h o u s e - l i v e s t o c k b u i l d i n g , designed s t r i c t l y f o r the purpose of energy c o n s e r v a t i o n , w i l l be b e n e f i c i a l to the hog producer. The amount of s e n s i b l e heat a v a i l a b l e i n the v e n t i l a t i o n a i r f o r p o t e n t i a l use i n greenhouse h e a t i n g may be es t i m a t e d using the t o t a l v e n t i l a t i o n r a t e from Tables F . l t o F.12 of Appendix F as f o l l o w s : = 3600 PV C p . (23) The v e n t i l a t i o n r a t e V v a r i e d from a win t e r low o f 3.66 m3/s 3 to a maximum of 76.80 m /s d u r i n g the summer months. As a f i r s t approximation, assume t h a t the exhaust a i r from the swine b u i l d i n g i s at 20°C and standard atmospheric pressure, ~ r— —— i 3 1.204 kg/m and the than the d e n s i t y "p" may be taken as 1.204 kg/n s p e c i f i c heat "C p" at constant p r e s s u r e a t 1.012 kJ/kg. °C. Th e r e f o r e , the amount of heat a v a i l a b l e i n the exhaust a i r "q/AT" i s i n the range of 16 MJ/°C to 337 MJ/°C w i t h the a c t u a l v a l u e depending on the o u t s i d e temperature. The p o t e n t i a l a v a i l a b l e energy i n the upper s c a l e o f the range w i l l not be u s e f u l s i n c e i t corresponds to p e r i o d s o f high o u t s i d e temperature when the greenhouse does not r e q u i r e heat. I t i s expected t h a t most o f the energy g a i n from the l i v e s t o c k b u i l d i n g w i l l be f o r moderate o u t s i d e temperatures d u r i n g the s p r i n g and f a l l p e r i o d s . Note t h a t d i r e c t waste heat r e c o v e r y from the swine b u i l d i n g v e n t i l a t i o n system i s u s e f u l o n l y when the greenhouse temperature i s below 2 0°C. CONCLUSIONS The f o l l o w i n g c o n c l u s i o n s can be drawn from the r e s u l t s of the s i m u l a t i o n of h e a t i n g and v e n t i l a t i o n requirements of the hog f i n i s h i n g barn d e s c r i b e d i n t h i s s e c t i o n : 1. For a w e l l i n s u l a t e d b u i l d i n g , no supplemental heat i s r e q u i r e d f o r an i n s i d e temperature o f 20°C and a r e l a t i v e humidity below 85 percent. 2. For a v a r i a b l e speed fan system, i t i s found t h a t about 2.1 kWh of e l e c t r i c a l energy i s r e q u i r e d to f i n i s h a hog from 50 kg to market weight. 3. The c o s t of energy f o r v e n t i l a t i o n i s a small f r a c t i o n o f the o p e r a t i n g c o s t and re p r e s e n t s o n l y 0.1 percent of the hog market v a l u e . The above estimated value i s based upon $0.06/kWh f o r e l e c t r i c a l power and $100 hog market value. 4. The amount of s e n s i b l e heat a v a i l a b l e i n the exhaust a i r from the swine barn i s found to be between 16 and 337 MJ/°C. The a c t u a l v a l u e depends on the o u t s i d e temperature. 5. A greenhouse-swine b u i l d i n g combination i s not b e n e f i c i a l t o the hog producer i f o n l y energy i s c o n s i d e r e d . NOMENCLATURE D e f i n i t i o n A c A, A. 1 A. 3 C P h b h 0 w, 1 h f g h I S , l L f Surface area o f the c e i l i n g Surface area o f the founda t i o n Surface area o f any w a l l " i " S u rface area o f any exposed s u r f a c e " j " of the a t t i c space S p e c i f i c heat of a i r at constant pressure S p e c i f i c enthalpy o f moist a i r a t the i n s i d e d r y - b u l b temperature and at the dew-point temperature o f the ou t s i d e a i r S p e c i f i c enthalpy of moist a i r a t the ou t s i d e c o n d i t i o n s Average c o n v e c t i v e heat t r a n s f e r c o e f f i c i e n t due to the wind f o r the ou t s i d e s u r f a c e o f any w a l l " i " L a t e n t heat o f v a p o r i z a t i o n of water Black body r a d i a t i o n a t the o u t s i d e 4 dry-bulb temperature (1^ = OTQ) T o t a l s o l a r r a d i a t i o n i n c i d e n t on any w a l l " i " P a r t - l o a d r a t i o o f the fan d e f i n e d as the d e l i v e r e d a i r flow i n any one hour d i v i d e d by the de s i g n a i r flow r a t e f o r the fan m m m m k J . k g - 1 . K - 1 ^a k J . k g - 1 ^a kJ.kg ~^ ^a kJ.h 1.m"2.K 1 kJ.kg ^ 3w « _  , -1 -2 k J . h . m , _ , -1 -2 kJ.h .m dimensionless m Mass flow r a t e o f the v e n t i l a t i o n a i r kg .h 1 a a m w T o t a l moisture produced w i t h i n the k9 w'h ^ l i v e s t o c k b u i l d i n g P B u i l d i n g parameter m P j F r a c t i o n o f f u l l - l o a d power f o r a dimensionless v a r i a b l e speed fan Q S e n s i b l e heat a v a i l a b l e i n v e n t i l a t i o n kJ.h 1 a i r Q e T o t a l b u i l d i n g l a t e n t heat kJ.h ^  Q S E N S T o t a l s e n s i b l e heat p r o d u c t i o n w i t h i n kJ.h 1 the b u i l d i n g Q s u p Supplemental heat requirement f o r the kJ.h ^  l i v e s t o c k b u i l d i n g Q T R A N Heat l o s s o r gai n through the b u i l d i n g kJ.h * envelope Q V E N T Heat l o s s or gain due to v e n t i l a t i o n kJ.h ^  T A t t i c temperature K T^ I n s i d e d r y - b u l b temperature K T Q Outside d r y - b u l b temperature K T s k y E f f e c t i v e temperature o f the sky K T S o l - a i r temperature f o r s u r f a c e " i " K S c l / X T Outside s u r f a c e temperature of any K s / 1 w a l l " i " T Outside s u r f a c e temperature o f any K s i 3 exposed s u r f a c e " j " of the a t t i c space T Temperature o f the ground at the s u r f a c e K g U U. U. 3 U V v W W b w o O v e r a l l heat t r a n s f e r c o e f f i c i e n t o f the c e i l i n g O v e r a l l heat t r a n s f e r c o e f f i c i e n t o f the f o u n d a t i o n Heat t r a n s f e r c o e f f i c i e n t o f any w a l l " i " e x c l u d i n g the o u t s i d e f i l m c o e f f i c i e n t Heat t r a n s f e r c o e f f i c i e n t o f any exposed s u r f a c e " j " o f the a t t i c e space e x c l u d i n g the o u t s i d e f i l m c o e f f i c i e n t E f f e c t i v e heat t r a n s f e r c o e f f i c i e n t f o r the perimeter V e n t i l a t i o n r a t e S p e c i f i c volume of i n s i d e a i r (exhaust v e n t i l a t i o n system) Wind speed Humidity r a t i o of i n s i d e a i r Humidity r a t i o of o u t s i d e a i r Slope of s u r f a c e " i " from the -1 -2 -1 kJ.h .m .K -1 k J . h ~ 1 . i r f 2 . K ~ 1 kJ.h - 1.m 2 . K _ 1 -1 -2 -1 kJ.h x.m .K x , T , -1 -1 v - l kJ.h .m .K 3 -1 m . s 3 v. -1 m . k g a m. s -1 kg .kg" 1 rw 3 a kg . kg w^ a r a d i a n s -1 a r f a c e " i " t o s o l a r h o r i z o n t a l A b s o r p t i v i t y of su r a d i a t i o n E m i s s i v i t y of su r f a c e " i " t o l o n g -wave r a d i a t i o n -1 -2 -4 Stefan-Boltzmann constant kJ.h .m .K (a = 20.411 x 10" 8) p D e n s i t y o f a i r kg.m AT Operating temperature d i f f e r e n c e K between the l i v e s t o c k b u i l d i n g and the greenhouse CHAPTER i\ COMPUTER SIMULATION MODEL OF HEATING REQUIREMENTS FOR A CONVENTIONAL GABLE GREENHOUSE INTRODUCTION T h i s chapter i s devoted t o an a n a l y s i s of energy flows with r e s p e c t to a c o n v e n t i o n a l greenhouse. I t c o n s i s t s of two separate s e c t i o n s . The f i r s t s e c t i o n d e a l s w i t h the development of a mathematical model u s i n g energy balances about the d i f f e r e n t components of the greenhouse. A l s o s t a t e d i n t h i s s e c t i o n , are the assumptions made d u r i n g the greenhouse mathematical model development. In the second s e c t i o n , s i m u l a t i o n r e s u l t s of a case study are g i v e n f o r a c o n v e n t i o n a l gable glasshouse. The computer s i m u l a t i o n analyses c o n c e n t r a t e on the e f f e c t s o f i n s i d e greenhouse temperature and i n f i l t r a t i o n on the h e a t i n g l o a d s . A l s o , the p a s s i v e s o l a r c o n t r i b u t i o n s to the green-house h e a t i n g requirements f o r d i f f e r e n t minimum indoor temperatures are i n v e s t i g a t e d i n d e t a i l . SECTION A MATHEMATICAL MODEL DEVELOPMENT FOR THE GABLE GREENHOUSE "ASSUMPTIONS In developing the model, the f o l l o w i n g assumptions were made: i ) E f f e c t o f heat storage i n the greenhouse f l o o r i s neg l e c t e d . i i ) E f f e c t o f shading by the s t r u c t u r a l frame i s negl e c t e d . i i i ) No condensation or dust accumulation on the greenhouse c o v e r i n g such t h a t the tra n s m i t t a n c e f o r s o l a r r a d i a t i o n i s f o r the c o v e r i n g m a t e r i a l only. i v ) The greenhouse c o v e r i n g m a t e r i a l i s assumed to be opaque to long wave r a d i a t i o n . v) The tran s m i t t a n c e of the greenhouse c o v e r i n g m a t e r i a l to d i f f u s e r a d i a t i o n i s assumed to be constant and equal to t h a t o f the beam transmittance f o r an angle of i n c i d e n c e o f 1.0123 r a d i a n s . v i ) The p l a n t canopy r e f l e c t s d i f f u s e l y r e g a r d l e s s of whether the o r i g i n a l i n c i d e n t r a d i a t i o n i s beam or d i f f u s e i n nature. v i i ) M u l t i p l e r e f l e c t i o n between the p l a n t canopy and the greenhouse cover i s n e g l e c t e d . v i i i ) Energy consumption by p h o t o s y n t h e s i s and e v a p o t r a n s p i r a t i o n i s assumed t o be n e g l i g i b l e . The f i r s t assumption i m p l i e s t h a t the heat storage c a p a c i t y of the s o i l i s n e g l i g i b l e r e l a t i v e to the d a i l y energy i n p u t to the greenhouse. T h i s assumption i s adequate i f the purpose o f the s i m u l a t i o n model i s to compute he a t i n g requirements r a t h e r than i n s i d e environmental c o n d i t i o n s , response times or time c o n s t a n t s of d i f f e r e n t h e a t i n g elements (Kindelan, 1980) . The second assumption may be j u s t i f i e d f o r s t e e l and aluminum greenhouse s t r u c t u r e s , s i n c e the percentage s u r f a c e occupied by s t r u c t u r a l members i s very s m a l l compared to the t o t a l area of the t r a n s p a r e n t cover. For wood c o n s t r u c t i o n t h i s percentage u s u a l l y does not exceed 5 p e r c e n t . The t h i r d assumption i m p l i e s t h a t the greenhouse cover must be c l e a n from dust which i s u s u a l l y the case s i n c e greenhouse o p e r a t o r s p e r i o d i c a l l y wash the g l a s s . As f a r as condensation i s concerned, i t u s u a l l y does not occur i n a s i g n i f i c a n t amount to a f f e c t s o l a r r a d i a t i o n i n p u t . I t s e f f e c t i s mainly on the n i g h t heat l o s s from p l a s t i c covered greenhouses. I t s e f f e c t on heat l o s s from glasshouses was found to be n e g l i g i b l e due to the low t r a n s m i s s i v i t y of g l a s s to long wave r a d i a t i o n compared to t h a t of some p l a s t i c s (Walker and Walton, 1971). The f o u r t h assumption i s v a l i d f o r greenhouse covered w i t h g l a s s and probably polycarbonate and f i b e r g l a s s . The t r a n s m i s s i v i t y of the above greenhouse c o v e r i n g m a t e r i a l s to long wave r a d i a t i o n as measured by Godbey e t a l . (1977) are 0.03. 0.06 and f o r g l a s s , p o l y c a r b o n a t e and c o r r u g a t e d f i b e r g l a s s , r e s p e c t i v e l y . For p o l y e t h y l e n e covered greenhouses, the theory formulated i n t h i s study should be m o d i f i e d a c c o r d i n g l y to take i n t o account the t r a n s m i s s i v i t y o f the p l a s t i c f i l m to long wave r a d i a t i o n . The f i f t h assumption was used by D u f f i e and Beckman (1974) f o r g l a s s covered s o l a r c o l l e c t o r a n a l y s e s . I t i s assumed to e q u a l l y h o l d f o r glasshouse a n a l y s e s . Assumption (vi) o f p e r f e c t d i f f u s e r e f l e c t i o n may not be i n s e r i o u s e r r o r p r o v i d e d the whole p l a n t canopy i s c o n s i d e r e d . The seventh assumption i m p l i e s t h a t o n l y the f i r s t r e f l e c t i o n i s c o n s i d e r e d . That i s , s o l a r r a d i a t i o n exchange a s s o c i a t e d w i t h m u l t i p l e r e f l e c t i o n s compared t o the f i r s t r e f l e c t i o n i s n e g l i g i b l e , because of the hig h a b s o r p t i o n of the p l a n t canopy and the hig h t r a n s m i t t a n c e of the cover to s o l a r r a d i a t i o n . I t has been proven by many r e s e a r c h e r s ( F r o e h l i c h e t a l . (1979), Walker (1965))that s o l a r r a d i a t i o n used by p l a n t s f o r p h o t o s y n t h e s i s , and energy r e l e a s e d d u r i n g the r e s p i r a t i o n p r ocess are n e g l i g i b l e r e l a t i v e t o other energy i n p u t s to the greenhouse. T h i s j u s t i f i e s the f i r s t p a r t o f the e i g h t h assumption. On the oth e r hand, e v a p o t r a n s p i r a t i o n may be s i g -n i f i c a n t d u r i n g p e r i o d s , the greenhouse u s u a l l y does not r e q u i r e supplemental h e a t i n g . T h e r e f o r e , the e f f e c t o f evapotrans-p i r a t i o n on e s t i m a t i n g d a i l y h e a t i n g loads i s n e g l i g i b l e . HEAT BALANCE ABOUT THE GREENHOUSE When a l l the above assumptions are taken i n t o c o n s i d e r a t i o n , the heat balance about the greenhouse may be s t a t e d as f o l l o w s : SUPPLEMENTAL HEAT + SOLAR RADIATION INPUT - INFILTRATION - HEAT TRANSMISSION = 0 or i n equation form: QSOL + QSUP " QINF " QTRAN = ° TRANSMISSION HEAT TRANSFER B a s i c a l l y the same method employed w i t h r e s p e c t t o the l i v e s t o c k b u i l d i n g i s used t o estimate the heat t r a n s f e r by conduction, c o n v e c t i o n and r a d i a t i o n between the greenhouse and i t s environment. T h i s method i s v a l i d s i n c e the greenhouse g l a s s cover i s assumed t o be opaque to thermal r a d i a t i o n . The o u t s i d e s u r f a c e temperature of the g l a s s cover f o r each o f the w a l l s o f the greenhouse i s c a l c u l a t e d using equation (4) of Chapter 3. Then, the t r a n s m i s s i o n heat t r a n s f e r between the greenhouse and i t s environment i s c a l c u l a t e d as f o l l o w s : Qm_... = U_A£ (T -T ) + U P (T -T ) + > U.A. (T -T .) (2) TRAN f f g o p g o / J I I g s , i , „ „ ^) T=l The heat t r a n s f e r c o e f f i c i e n t U^ i n c l u d e s the i n s i d e f i l m c o e f f i c i e n t and the r e s i s t a n c e o f the c o v e r i n g m a t e r i a l of any s u r f a c e i of the greenhouse. where R. = + R . (4) 1 h. . The f i r s t term on the r i g h t hand sid e of e q u a t i o n (2) represents the heat l o s s or gain through the f o u n d a t i o n , the second term r e p r e s e n t s t h a t of the greenhouse p e r i m e t e r , and the t h i r d term r e p r e s e n t s the heat l o s s or g a i n through the w a l l s and the r o o f of the greenhouse. INFILTRATION HEAT LOSS The s e n s i b l e heat l o s s or gain due to a i r i n f i l t r a t i o n / e x f i l t r a t i o n from the greenhouse i s c a l c u l a t e d u s i n g the air-exchange method. Q I N F = PCpVa (V To> ( 5 ) I f the a i r i s assumed at standard pressure and temperature of 20°C, then C p = 1.012 kJ.kg~ 1.K~ 1 and p = 1.204 kg.m - 3 , and equation (5) becomes, Q I N F - 1 ' 2 1 8 V g N a CV To } ( 6 ) The number of a i r changes f o r any greenhouse w i l l depend on the s t r u c t u r e , c o v e r i n g m a t e r i a l , maintenance, the extent of wind p r o t e c t i o n and the indoor-outdoor temperature d i f f e r e n t i a l . R e p r e s e n t a t i v e values of a i r i n f i l t r a t i o n r a t e s t h a t can be expected i n v a r i o u s types of greenhouse are g i v e n i n a p u b l i c a t i o n by the On t a r i o M i n i s t r y of A g r i c u l t u r e and Food*. For newly c o n s t r u c t e d glasshouses the estimated a i r i n f i l t r a t i o n r a t e i s between 0.75 and 1.5 a i r changes per hour. For o l d glasshouses, the i n f i l t r a t i o n r a t e ranges between 1.0 and 2.0 a i r changes per hour, depending on the q u a l i t y o f the maintenance, to the greenhouse g l a z i n g . For p l a s t i c - c o v e r e d greenhouses, the i n f i l t r a t i o n and e x f i l t r a t i o n r a t e s range from 0.2 to 1.0 a i r changes per hour. SOLAR ENERGY CAPTURED BY THE GREENHOUSE The t o t a l s o l a r r a d i a t i o n e n t e r i n g the greenhouse i s the sum of the s o l a r energy t r a n s m i t t e d through each of the t r a n s p a r e n t s u r f a c e s making up the greenhouse envelope. Since the t r a n s m i s s i o n of the c o v e r i n g m a t e r i a l t o s o l a r r a d i a t i o n i s dependent on the form of the o r i g i n a l r a d i a t i o n i n c i d e n t on the s u r f a c e , the s o l a r r a d i a t i o n t r a n s m i t t e d through each s u r f a c e i s t r e a t e d s e p a r a t e l y f o r the beam and d i f f u s e components of the t o t a l i n s o l a t i o n . For the v e r t i c a l w a l l s o f the greenhouse, the d i r e c t r a d i a t i o n t r a n s m i t t e d through any s u r f a c e " i " i s B . = B T, . A. . (7) w,i v,y b , i l * Energy C o n s e r v a t i o n i n O n t a r i o Greenhouses. P u b l i c a t i o n 65. M i n i s t r y of A g r i c u l t u r e and Food, O n t a r i o . And, f o r the d i f f u s e component, the d i f f u s e s o l a r r a d i a t i o n t r a n s m i t t e d through s u r f a c e " i " may be w r i t t e n as: D . = D T , . A. , (8) w,i v,y d , 1 1 where " Y " i s the o r i e n t a t i o n of the v e r t i c a l w a l l . I f the p l a n t s i n the greenhouse are t a l l , then a l l the s o l a r r a d i a t i o n t r a n s m i t t e d through the v e r t i c a l w a l l s of the greenhouse i s i n t e r c e p t e d by the p l a n t canopy. The s o l a r r a d i a t i o n t r a n s m i t t e d through s u r f a c e " i " o f the greenhouse t h a t i s captured by the p l a n t canopy can be e s timated by I . = (B + D .) ( 1 - C ) [1 + G ( 1 - T , .-a.)] (9)* w,i w,x w,i a , 1 1 where "c" i s the albedo of the p l a n t canopy and "a^" i s the a b s o r p t i v i t y of the c o v e r i n g m a t e r i a l to s o l a r r a d i a t i o n . Two assumptions are made wit h r e s p e c t to the above equation. F i r s t , the r a d i a t i o n r e f l e c t e d by the p l a n t canopy i s d i f f u s e r e g a r d l e s s of the form of the o r i g i n a l r a d i a t i o n i n c i d e n t on the p l a n t s . The second assumption i s t h a t the t r a n s m i s s i v i t y of the c o v e r i n g m a t e r i a l to > d i f f u s e s o l a r r a d i a t i o n i s high and t h a t the albedo of the p l a n t s i s low such t h a t the c o n t r i b u t i o n of m u l t i p l e r e f l e c t i o n s i s n e g l i g i b l e . Equation (9) takes i n t o account onl y the f i r s t r e f l e c t i o n . The t o t a l s o l a r r a d i a t i o n t r a n s m i t t e d through the v e r t i c a l w a l l s of the greenhouse and captured by the p l a n t canopy i s simply. * D e r i v a t i o n of equation (9) i s g i v e n i n Appendix K. n Jw = Z ( B w , i + Dw,i> [ 1 ^ ( 1 - T d , i - a i ) ] ' ( 1 0 ) i = l The c o n t r i b u t i o n o f the gable r o o f to the s o l a r energy i n p u t to the greenhouse may be estimated i n a s i m i l a r manner. F i r s t the s o l a r r a d i a t i o n i n c i d e n t on each slope of the r o o f i s d i v i d e d i n t o i t s d i r e c t and d i f f u s e components. Then, the s o l a r r a d i a t i o n t r a n s m i t t e d through slope " j " of the ro o f and i n t e r c e p t e d by the p l a n t canopy i s c a l c u l a t e d as f o l l o w s : I . = B x, A . + D . T , . A r , D r,j b,j r,j r,j d,j r,j [(1-F ) + F ( 1 - T , . * - a . J F ] (11)* r->r r-*-r d , j * j * r-*p Equation (11) assumes t h a t a l l the beam r a d i a t i o n t r a n s m i t t e d through the ro o f o f the greenhouse i s i n t e r c e p t e d by the p l a n t canopy. T h i s assumption i s v a l i d f o r r e l a t i v e l y low roof s l o p e s . A l s o , o n l y the f i r s t r e f l e c t i o n i s c o n s i d e r e d i n the above a n a l y s i s . The " j * " i n equation (11) i n d i c a t e s t h a t the r a d i a t i o n p r o p e r t i e s o f the o p p o s i t e slope are used i f the two slopes of the gable r o o f are not of the same m a t e r i a l . The t o t a l s o l a r r a d i a t i o n o r i g i n a t i n g from the gable r o o f o f the greenhouse and i n t e r c e p t e d by the p l a n t canopy i s c a l c u l a t e d from equation (11) through a simple summation to g i v e , 2 I' = ^ B . x, . A . + D . T , . A . [(1-F ) r Z-/ r,j b,D r,3 r,j &,i r,j r-*r j = l + F ( 1 - T , - * - a . J F ] (12) r-»-r d , ] * j* r+p * D e r i v a t i o n of the d i f f u s e component of equation (11) i s g i v e n i n Appendix K. The r a d i a t i o n c o n f i g u r a t i o n f a c t o r s F and F i n r->r r+p equations (11) and (12) can be c a l c u l a t e d u s i n g the method d e s c r i b e d i n S e c t i o n B of Chapter 2. The c a l c u l a t i o n o f the t r a n s m i t t a n c e o f the greenhouse c o v e r i n g m a t e r i a l s f o r beam and d i f f u s e s o l a r r a d i a t i o n i s d e s c r i b e d i n d e t a i l i n Appendix A. The amount of t o t a l s o l a r r a d i a t i o n o r i g i n a t i n g from the r o o f s l o p e s and captured by the greenhouse i s dependent on the albedo of the p l a n t canopy and the r a d i a t i o n p r o p e r t i e s o f the r o o f - c o v e r i n g m a t e r i a l . Again, i f o n l y the f i r s t r e f l e c t i o n i s c o n s i d e r e d then the s o l a r energy captured by the top of the p l a n t canopy may be estimated by I r = I'r ( 1 - s ) [1 + ? d - r d f r - a r ) 1 (13) Equation (13) i s v a l i d when the two sl o p e s o f the gable r o o f have approximately the same va l u e s f o r the t r a n s m i t t a n c e and absorptance to s o l a r r a d i a t i o n . The t o t a l s o l a r energy captured by the greenhouse i s the sum of the s o l a r r a d i a t i o n from the v e r t i c a l w a l l s and roo f of the greenhouse. Thus, Q C_ T = 1 + 1 (14) SOL w r S E C T I O N B CASE STUDY I I HEATING REQUIREMENTS OF A CONVENTIONAL GABLE GLASSHOUSE DESCRIPTION AND ASSUMPTIONS The computer s i m u l a t i o n model developed i n S e c t i o n A of t h i s chapter was used to p r e d i c t hourly values of the t r a n s m i s s i o n heat l o s s from the greenhouse envelope, the heat l o s s due to i n f i l t r a t i o n , and the s o l a r energy captured by the greenhouse. Then, the supplemental heat requirement as w e l l as the f r a c t i o n of the t o t a l heat load s u p p l i e d through n a t u r a l s o l a r r a d i a t i o n capture by the greenhouse were c a l c u l a t e d using the p r e d i c t e d hourly heat l o s s and s o l a r energy i n p u t s . The f o l l o w i n g a d d i t i o n a l assumptions are made with r e s p e c t to the c o n v e n t i o n a l greenhouse case study. i ) Only the minimum greenhouse temperature i s s p e c i f i e d and assumed constant throughout the time of the s i m u l a t i o n (This assumption i s adequate i f the main o b j e c t i v e i s the determination of heating l o a d s ) . i i ) I n f i l t r a t i o n r a t e i s assumed to be constant. i i i ) The albedo of the p l a n t canopy w i t h i n the greenhouse i s constant and assumed equal to ten percent. The gable greenhouse used i n the case study has a length of 100m and a width of 10m. The long a x i s of the greenhouse i s east-west o r i e n t e d . The f o o t i n g and the perimeter of the greenhouse are i n s u l a t e d to minimize heat l o s s to the ground. The greenhouse i s covered with a s i n g l e l a y e r of g l a s s . Other p e r t i n e n t c o n s t r u c t i o n parameters, the p r o p e r t i e s of the c o n s t r u c t i o n m a t e r i a l s as w e l l as the greenhouse management parameters are given i n Table 4.1. To complete the d e s c r i p t i o n of the f a c i l i t y a c r o s s - s e c t i o n a l view of the greenhouse i s shown i n Figure 4.1. RESULTS AND DISCUSSION A sample computer s i m u l a t i o n output for a con v e n t i o n a l gable greenhouse l o c a t e d i n Vancouver, B.C. i s inc l u d e d i n Appendix G (Tables G.l to G.12). These t a b l e s give the hourly and d a i l y r e s u l t s f o r a t y p i c a l day of each month of the year. The r e s u l t s apply to the greenhouse d e s c r i b e d i n Table 4 J. and operated at a minimum temperature ( i . e . n i g h t temperature) of 15°C. The in f o r m a t i o n i n the t a b l e s i n c l u d e the s o l a r r a d i a t i o n p a s s i v e l y captured by the greenhouse, t r a n s m i s s i o n and i n f i l t r a t i o n heat l o s s e s as w e l l as the p r e d i c t e d supplemental heat requirement and the f r a c t i o n of the t o t a l heat l o s s that i s s u p p l i e d by s o l a r due to n a t u r a l s o l a r energy c o l l e c t i o n by the greenhouse. A summary of the r e s u l t s of Appendix G i s shown, on a monthly b a s i s , i n Table 4.2. ( 0 , 1 h a ) i ^_ 1 0 m FIGURE 4.1: CROSS-SECTION OF THE CONVENTIONAL GABLE GREENHOUSE USED IN CASE STUDY I I . -J INSULATED J V PERIMETER' 3 VARIABLES USED TO CALCULATE HEATING DEMANDS  OF A CONVENTIONAL GABLE GREENHOUSE C o n s t r u c t i o n Parameters Length: Width: 100 m 10 m Height: 2 m Roof Slope: 18° O r i e n t a t i o n : East-West Long A x i s C o n s t r u c t i o n M a t e r i a l s P r o p e r t i e s S u r f a c e M a t e r i a l Area (m2) U (Wm^K"1) South Roof North Roof South Wall North Wall East Wall West Wall F o o t i n g S i n g l e Glass S i n g l e G l a s s S i n g l e Glass S i n g l e Glass S i n g l e Glass S i n g l e Glass I n s u l a t e d Concrete 526 526 200 200 28 28 110 8.83 8.83 8. 03 8.03 8.03 8.03 0.67 0, 0, 0. 0. 0. 0. 08 08 08 08 08 08 0.94 0.94 0.94 0.94 0.94 0.94 Perimeter ^Insulated 220 (m) 0.67 (Wm_1K Gla s s P r o p e r t i e s Thickness: E x t i n c t i o n C o e f f i c i e n t : R e f r a c t i o n Index: A b s o r p t i v i t y to S o l a r R a d i a t i o n : E m i s s i v i t y f o r Thermal R a d i a t i o n : 0.3 cm 0.252 cm" 1 1.526 0.08 0.94 Management Parameters L o c a t i o n : Minimum Greenhouse 1 I n f i l t r a t i o n Rate: P l a n t Canopy Albedo remperature: Vancouver, B.C. Montr e a l , Quebec H a l i f a x , N.S. 10°C, 15°C, or 20°C 1.5 A i r changes per hour 0.1 A c l o s e examination of Table 4.2 r e v e a l s the f o l l o w i n g p o i n t s w i t h r e s p e c t to a s i n g l e g l a z e d gable greenhouse o p e r a t i o n a t a minimum i n s i d e temperature of 15°C and l o c a t e d i n the Vancouver, B.C. area, i) The h e a t i n g season extends over the twelve months of the year. T h i s i s due to c o o l summer n i g h t s which are c h a r a c t e r i s t i c o f the r e g i o n , i i ) The n a t u r a l c o n t r i b u t i o n of s o l a r r a d i a t i o n to the greenhouse h e a t i n g l o a d can be as low as 15 percent i n the summer months and i n c r e a s i n g to 37 per c e n t i n the s p r i n g p e r i o d . The annual average i s found to be o n l y 28 percent even though the annual s o l a r energy captured by the greenhouse w e l l exceeds the annual h e a t i n g l o a d requirement. For t h i s t y p i c a l case, the r a t i o of annual s o l a r energy i n p u t t o annual heat l o s s i s i n the order of 1.5. T h e r e f o r e , i f an adequate seasonal thermal storage i s i n c o r p o r a t e d ; t h e o r e t i c a l l y , the greenhouse c o u l d be heated s o l e l y by the n a t u r a l s o l a r energy capture of the greenhouse. F u r t h e r computer analyses were performed on an i d e n t i c a l greenhouse to t h a t used i n the Vancouver case. The purpose of the a d d i t i o n a l analyses i s to i n v e s t i g a t e the e f f e c t o f c l i m a t i c c o n d i t i o n s on the greenhouse performance. MONTHLY AVERAGE HEATING LOAD, SOLAR ENERGY INPUT, SOLAR CONTRIBUTION AND SUPPLEMENTAL HEAT REQUIREMENTS 2 IN MJ PER m OF GREENHOUSE FLOOR AREA AND PERCENT  OF THE HEATING LOAD SUPPLIED BY SOLAR FOR THE  CONVENTIONAL GABLE GREENHOUSE OF CASE STUDY I I  (MINIMUM INSIDE TEMPERATURE = 15°C) VANCOUVER, B.C. Month Heat Loss S o l a r Input S o l a r C o n t r i b u t i o n Supplemental Heat Percent S o l a r January 462 187 112 350 24 February 365 225 106 259 29 March 383 360 130 253 34 A p r i l 262 394 97 165 37 May 15 3 465 53 100 35 June 77 528 24 53 31 J u l y 43 512 10 33 21 August 32 487 6 26 17 September 80 372 13 67 15 October 232 276 66 166 28 November 340 160 84 256 25 December 449 138 101 348 22 Year 2878 4104 802 2076 28 Summaries of the r e s u l t s f o r the two a d d i t i o n a l l o c a t i o n s in Canada are i n c l u d e d i n Tables 4.3 and 4.4 f o r Montreal, P.Q. and H a l i f a x , N.S. r e s p e c t i v e l y . When the values i n Tables 4.3 and 4.4 are compared to those i n Table 4.2 f o r Vancouver, i t can be seen that the extent of the greenhouse h e a t i n g season i n H a l i f a x i s s i m i l a r to that f o r Vancouver; however, the heating season f o r Montreal i s three months s h o r t e r . T h i s may be a t t r i b u t e d to the warmer summer nights i n the Montreal region as compared to the Vancouver or H a l i f a x r e g i o n s . I t i s a l s o i n t e r e s t i n g to n o t i c e that the annual s o l a r energy c o n t r i b u t i o n to the heating load i s s l i g h t l y lower f o r H a l i f a x and Montreal than the value of 28 percent p r e v i o u s l y found f o r Vancouver even though the s o l a r r a d i a t i o n input to the greenhouse i s higher i n the former c i t i e s than i n the l a t e r . O bviously, the e f f e c t of the i n c r e a s e d s o l a r input was c a n c e l l e d by the higher greenhouse heating loads f o r H a l i f a x and Montreal when compared to Vancouver. The annual supplemental heat requirements i n megajoules per square metre of f l o o r area were found to be 2076, 2718 and 3262 f o r a greenhouse operated at a minimum temperature of 15°C and l o c a t e d i n Vancouver, ( H a l i f a x and Montreal r e s p e c t i v e l y . Thus, a greenhouse l o c a t e d i n the Vancouver area w i l l r e q u i r e 31 MONTHLY AVERAGE HEATING LOAD, SOLAR ENERGY INPUT, SOLAR CONTRIBUTION AND SUPPLEMENTAL HEAT REQUIREMENTS 2 IN MJ PER m OF GREENHOUSE FLOOR AREA AND PERCENT  OF THE HEATING LOAD SUPPLIED BY SOLAR FOR THE  CONVENTIONAL GABLE GREENHOUSE OF CASE STUDY I I (MINIMUM INSIDE TEMPERATURE = 15°C) MONTREAL, QUEBEC Month Heat Loss S o l a r Input S o l a r C o n t r i b u t i o n Supplemental Heat Percent S o l a r January 908 170 170 738 19 February 750 218 191 559 26 March 609 367 200 409 33 A p r i l 340 392 125 215 37 May 85 465 17 68 20 June 4 525 0 4 0 J u l y 0 510 0 0 0 August 0 485 0 0 0 September 47 370 5 42 11 October 257 270 67 190 26 November 465 150 115 350 25 December 810 123 123 687 15 Year 4275 4045 1013 3262 24 MONTHLY AVERAGE HEATING LOAD, SOLAR ENERGY INPUT, SOLAR CONTRIBUTION AND SUPPLEMENTAL HEAT REQUIREMENTS 2 IN MJ PER m OF GREENHOUSE FLOOR AREA AND PERCENT  OF THE HEATING LOAD SUPPLIED BY SOLAR FOR THE  CONVENTIONAL GABLE GREENHOUSE OF CASE STUDY I I  (MINIMUM INSIDE TEMPERATURE = 15 °C) HALIFAX, N.S. Month Heat Loss S o l a r Input S o l a r C o n t r i b u t i o n Supplemental Heat Percent S o l a r January 640 167 143 497 22 February 586 217 158 428 27 March 533 356 176 357 33 A p r i l 366 392 134 232 37 May 216 464 75 141 35 June 93 525 24 69 26 J u l y 31 509 4 27 13 August 25 485 4 21 13 September 70 370 9 61 13 October 209 269 49 160 23 November 357 149 85 272 24 December 567 121 114 453 20 Year 3693 4024 975 2718 26 percent and 57 percent l e s s energy when compared to greenhouses l o c a t e d i n H a l i f a x and Montreal r e s p e c t i v e l y . Furthermore, when the r a t i o s of annual s o l a r r a d i a t i o n captured by the greenhouse to the annual heat l o s s e s are compared, again, i t i s found that Vancouver area holds the advantage. These r a t i o s are 0.95, 1.09 and 1.42 f o r Montreal, H a l i f a x and Vancouver r e s p e c t i v e l y . T h e r e f o r e , long term thermal storages are l i k e l y to be more adaptable to the Vancouver area than the H a l i f a x or Montreal areas. A new area of r e s e a r c h f o r energy c o n s e r v a t i o n i n greenhouse p r o d u c t i o n i s the development of low temperature hybrids of greenhouse crops. T h e r e f o r e , the computer s i m u l a t i o n model was used here, to i n v e s t i g a t e the e f f e c t of minimum greenhouse temperature on supplemental heat requirement and f r a c t i o n of the heating load s u p p l i e d by p a s s i v e s o l a r . The t y p i c a l greenhouse with the c o n s t r u c t i o n parameters as s p e c i f i e d i n Table 4 . l i s again used i n t h i s a n a l y s i s . For the purpose of t h i s study, the greenhouse i s assumed to be l o c a t e d i n the H a l i f a x area. Analyses were performed f o r minimum greenhouse temperatures of 10°C, 15°C and 20°. Summaries of these analyses are shown i n Tables 4.4 to 4 . 6 . MONTHLY AVERAGE HEATING LOAD, SOLAR ENERGY INPUT,  SOLAR CONTRIBUTION AND SUPPLEMENTAL HEAT REQUIREMENTS  IN MJ PER m2 OF GREENHOUSE FLOOR AREA AND PERCENT  OF THE HEATING LOAD SUPPLIED BY SOLAR FOR THE  CONVENTIONAL GABLE GREENHOUSE OF CASE STUDY I I (MINIMUM INSIDE TEMPERATURE = 10°C) HALIFAX, N.S. Month Heat Loss S o l a r Input S o l a r C o n t r i b u t i o n Supplemental Heat Percent S o l a r January 482 167 112 370 23 February 444 217 123 321 28 March 377 356 123 254 33 A p r i l 215 392 69 146 32 May 87 464 18 69 21 June 19 525 2 17 14 J u l y - 509 - - -August - 485 - - -September - 370 - - -October 75 269 7 68 9 November 206 149 44 162 21 December 409 121 87 322 21 Year 2321 4024 585 1736 25 MONTHLY AVERAGE HEATING LOAD, SOLAR ENERGY INPUT, SOLAR CONTRIBUTION AND SUPPLEMENTAL HEAT REQUIREMENTS 2 IN MJ PER m OF GREENHOUSE FLOOR AREA AND PERCENT  OF THE HEATING LOAD SUPPLIED BY SOLAR FOR THE  CONVENTIONAL GABLE GREENHOUSE OF CASE STUDY I I (MINIMUM INSIDE TEMPERATURE = 20°C) HALIFAX, N.S. Month Heat Loss S o l a r Input S o l a r C o n t r i b u t i o n Supplemental Heat P e r c e n t S o l a r January 796 167 164 632 20 February 729 217 189 540 26 March 689 356 225 464 33 A p r i l 518 392 193 325 37 May 370 464 148 222 40 June 220 525 85 135 39 J u l y 115 509 28 87 25 August 107 485 23 84 21 September 192 370 52 140 27 October 363 269 102 261 28 November 507 149 120 387 24 December 725 121 121 603 17 Year 5331 4024 1451 3880 27 Table 4.7 g i v e s the p r e d i c t e d monthly supplemental heat requirements f o r the s e l e c t e d three minimum greenhouse temperatures as w e l l as the expected p o t e n t i a l energy savings due to r e d u c i n g the minimum greenhouse temperature from 20°C t o 15°C and to 10°C r e s p e c t i v e l y . The annual p o t e n t i a l energy s a v i n g due to r e d u c i n g the minimum greenhouse temperature from 20°C t o 15°C i s about 30 percent. An a d d i t i o n a l 25 percent can be expected i f the minimum temperature i s f u r t h e r decreased to 10°C or around 5 percent s a v i n g per degree r e d u c t i o n i n temperature. O b v i o u s l y , the above approximation i s only v a l i d f o r a l l year around greenhouse o p e r a t i o n as can c l e a r l y be seen i n Table 4.7. The c o n t r i b u t i o n of s o l a r r a d i a t i o n to the annual h e a t i n g l o a d i s not s i g n i f i c a n t l y a f f e c t e d by lowering the greenhouse temperature as can be d e p i c t e d i n Tables 4.4 to 4.6. Reducing the greenhouse indoor temperature tends to i n c r e a s e the monthly f r a c t i o n o f the h e a t i n g l o a d s u p p l i e d by s o l a r d u r i n g the w i n t e r months but i t has an o p p o s i t e e f f e c t d u r i n g the other months of the year, thus r e s u l t i n g i n a n e g l i g i b l e o v e r a l l e f f e c t when the e n t i r e year i s c o n s i d e r e d (Tables 4.4 to 4.6). As expected, lowering of the minimum i n s i d e temperature of the greenhouse i n c r e a s e d s i g n i f i c a n t l y the r a t i o o f s o l a r r a d i a t i o n capture to heat l o s s . From Tables 4.4 to 4.6, t h i s r a t i o on an annual b a s i s , can be c a l c u a t e d as 0.75, 1.09 TABLE 4.7 EFFECT OF MINIMUM INSIDE GREENHOUSE TEMPERATURE  ON SUPPLEMENTAL HEAT REQUIREMENT AND EXPECTED  ENERGY SAVINGS DUE TO REDUCING THE MINIMUM TEMPERATURE FROM 20°C HALIFAX, N.S. Supple. Supple. ^ Supple. Month Heat* Heat* Percent x^t* Percent T =20°C T =15°C S a v i n 9 S T = 1 0 o c Savings 2 9 g January 632 497 21 370 41 February 540 428 21 321 41 March 464 357 23 254 45 A p r i l 325 232 29 146 55 May 222 141 36 69 69 June 135 69 49 17 87 J u l y 87 27 69 - 100 August 84 21 75 - 100 September 140 61 56 7 95 October 261 160 39 68 74 November 387 272 30 162 58 December 603 4 53 25 322 47 Year 3880 2718 30 1736 55 2 In MJ per m greenhouse f l o o r area per month and 1.73 f o r minimum i n s i d e temperatures of 20°C, 15°C and 10°C r e s p e c t i v e l y . Another method of c o n s e r v i n g energy i n greenhouses i s r e d u c i n g i n f i l t r a t i o n / e x f i l t r a t i o n l o s s e s ( i . e . p l a s t i c cover over a g l a s s h o u s e ) . However, the economics of any r e t r o f i t to minimize i n f i l t r a t i o n heat l o s s depends on the net energy s a v i n g s . The mathematical model developed i n S e c t i o n A of t h i s chapter i s u t i l i z e d here to p r e d i c t the p o t e n t i a l annual savings due to e l i m i n a t i o n of a i r i n f i l t r a t i o n i n t o the greenhouse. A summary of the s i m u l a t i o n r e s u l t s i s i n c l u d e d i n Table 4.8. The r e s u l t s are f o r an east-west gable greenhouse wi t h s i n g l e g l a s s cover and operated a t a minimum i n s i d e temperature of 20°C, o t h e r s p e c i f i c a t i o n f o r the greenhouse are i n c l u d e d i n Table 4.1. The weather data used here are t y p i c a l of the H a l i f a x r e g i o n . Table 4.8 shows t h a t the monthly average heat l o s s due to i n f i l t r a t i o n ranged between 7 to 13 percent r e s u l t i n g i n an annual average of 12 percent. The energy savings as c a l c u l a t e d from Table 4.8 are gross v a l u e s ; t h e r e f o r e , net savings are expected to be r e l a t i v e l y s m a l l e r . Thus, i t can be concluded t h a t w i t h the e x c e p t i o n of o l d and badly maintained glasshouses, r e d u c i n g i n f i l t r a t i o n i s not c o n s i d e r e d to be a s i g n i f i c a n t f a c t o r i n energy c o n s e r v a t i o n f o r greenhouse. EFFECT OF INFILTRATION RATE ON SITPPT.PMPM-PKT KEPT AT A MINIMUM INSIDE TEMPERATURE OF 20°C HALIFAX, N.S. Supplemental (MJ/m2 F l o o r Area Heat per Month) Month 1.5 A i r Changes Zero Per Hour I n f i l t r a t i o n Percent Due to I n f i l t r a t i o n January 632 552 13 February 540 473 12 March 464 407 12 A p r i l 325 286 12 May 222 197 11 June 135 121 10 J u l y 87 79 9 August 84 78 7 September 140 127 9 October 261 233 11 November 387 343 11 December 603 524 13 Year 3880 3420 12 Conventional greenhouses are b a s i c a l l y passive s o l a r h eating systems. T h e i r e f f i c i e n c i e s when expressed as a f r a c t i o n of the greenhouse heating load that i s s u p p l i e d by the sun were p r e v i o u s l y found to be i n the order of 25 p e r c e n t . The e f f i c i e n c y can be improved by making the greenhouse as an a c t i v e system and p r o v i d i n g f o r s o l a r energy storage. The p o t e n t i a l of a c t i v e s o l a r energy c o l l e c t i o n and storage can be determined using the s o l a r energy u t i l i z a t i o n f a c t o r (S.E.U.) concept (Ben A b d a l l a h , 1978 and 1979). T h i s f a c t o r i s d e f i n e d as the r a t i o of the s o l a r energy c o n t r i b u t i o n (to the heating load) to the s o l a r r a d i a t i o n captured by the greenhouse. By d e f i n i t i o n , a s o l a r energy u t i l i z a t i o n f a c t o r of u n i t y i m p l i e s that a l l s o l a r r a d i a t i o n captured by the greenhouse i s u t i l i z e d , t h e r e f o r e , no excess energy i s a v a i l a b l e f o r storage. The monthly average s o l a r energy u t i l i z a t i o n f a c t o r f o r an e a s t -west gable greenhouse covered w i t h s i n g l e l a y e r of g l a s s are p l o t t e d i n F i g u r e 4.2. For the sake of comparison the monthly average f r a c t i o n s of the greenhouse h e a t i n g l o a d t h a t i s s u p p l i e d by s o l a r are a l s o shown. The r e s u l t s are f o r two i d e n t i c a l greenhouses one l o c a t e d i n Vancouver and the other i n Montreal. MONTH FIGURE 4.2: MONTHLY AVERAGE SOLAR ENERGY UTILIZATION FACTOR AND FRACTION OF HEATING LOAD SUPPLIED BY PASSIVE SOLAR FOR AN E-W GABLE GREENHOUSE (SINGLE GLASS COVER, MINIMUM INSIDE TEMPERATURE 15°C). The i n f o r m a t i o n presented i n the graph of F i g u r e 4.2 can be i n t e r p r e t e d as f o l l o w s : f o r example, the month of January, i t i s seen t h a t , f o r Vancouver, 60 p e r c e n t of the s o l a r r a d i a t i o n captured by the greenhouse i s p a s s i v e l y u t i l i z e d to supply 24 percent of the h e a t i n g l o a d while i n the case of Montreal, a l l the s o l a r energy i s u t i l i z e d to supply o n l y 19 p e r c e n t of the greenhouse h e a t i n g l o a d . For the summer months,the greenhouse h e a t i n g l o a d i n Montreal i s zero, thus, the s o l a r energy u t i l i z a t i o n f a c t o r i s zero f o r t h a t p e r i o d , while f o r Vancouver 1 to 5 p e r c e n t of s o l a r energy captured i s u t i l i z e d to supply 17 to 31 percent of the h e a t i n g l o a d . S o l a r energy storage may c o n t r i b u t e s i g n i f i c a n t l y to energy savings d u r i n g the s p r i n g and f a l l . As can be seen from F i g u r e 4.2 f o r example, i n A p r i l , 25 percent f o r Vancouver, and 32 percent f o r Montreal of the s o l a r energy captured by the greenhouse are u t i l i z e d to supply 37 percent of the h e a t i n g l o a d . The s o l a r energy u t i l i z a t i o n f a c t o r i s c l o s e l y r e l a t e d to the environmental temperature and to the a v a i l a b i l i t y o f s o l a r r a d i a t i o n . T h e r e f o r e , i t i s expected to be l o c a t i o n dependent. The e f f e c t of l o c a t i o n on the CD \— >-i o M A M J J A S O N D MONTH FIGURE 4.3: EFFECT OF LOCATION ON THE SOLAR ENERGY UTILIZATION FACTOR (S.E.U.) BY MONTH FOR AN E-W GABLE GREENHOUSE (SINGLE GLASS COVER, MINIMUM INSIDE TEMPERATURE OF 15°C). s o l a r energy u t i l i z a t i o n f a c t o r i s de p i c t e d i n Figure 4.3. The f i g u r e i n d i c a t e s that among the three l o c a t i o n s analysed, Vancouver i s more s u i t a b l e f o r improvement to the s o l a r energy u t i l i z a t i o n by the i n c o r p o r a t i o n of a thermal s t o r a g e . A l s o shown on Figure 4.3, the annual s o l a r energy u t i l i z a t i o n f a c t o r s f o r the three l o c a t i o n s which have the values of 0.20, 0.24 and 0.25 f o r Vancouver, H a l i f a x and Montreal r e s p e c t i v e l y . The corresponding annual f r a c t i o n s of the heating loads which are s u p p l i e d by s o l a r are 0.28, 0. 26 and 0.24 f o r Vancouver, H a l i f a x and Montreal r e s p e c t i v e l y . O b v i o u s l y , the annual s o l a r energy u t i l i z a t i o n f a c t o r s are of value only when long-term thermal storages are a n t i c i p a t e d . CONCLUSIONS The f o l l o w i n g c o n c l u s i o n s can be drawn from the r e s u l t s of the s i m u l a t i o n of heating requirements and s o l a r energy u t i l i z a t i o n of the co n v e n t i o n a l gable greenhouse d e s c r i b e d i n t h i s s e c t i o n : 1. The annual s o l a r energy c o n t r i b u t i o n to the greenhouse heating load was found to be about 25 percent. T h i s percentage i s found to be only s l i g h t l y a f f e c t e d by l o c a t i o n and minimum greenhouse temperature s e t t i n g . 2. The r a t i o of s o l a r r a d i a t i o n capture by the greenhouse to the annual heating load was found to be i n the range o f 0.75 to 1.75 depending on the l o c a t i o n of the greenhouse and i t s minimum temperature s e t t i n g . T h e r e f o r e , t h e o r e t i c a l l y a greenhouse with a seasonal thermal storage could be made s e l f s u f f i c i e n t i n energy f o r most cases. 3. Lowering of the greenhouse minimum temperature r e s u l t s i n s i g n i f i c a n t energy s a v i n g s . A f i v e percent energy saving f o r each degree K e l v i n r e d u c t i o n i n temperature could be expected. 4. For a we l l c o n s t r u c t e d and maintained greenhouse, minimizing i n f i l t r a t i o n was found to be an i n s i g n i f i c a n t f a c t o r i n energy c o n s e r v a t i o n . Net savings of l e s s than ten percent could be expected. 5. The s o l a r energy u t i l i z a t i o n f a c t o r could be improved s i g n i f i c a n t l y during the s p r i n g and f a l l p e r i o d s by s t o r i n g daytime excess heat f o r nighttime use. T h i s would i n c r e a s e the annual s o l a r energy u t i l i z a t i o n f a c t o r from i t s low value o f about 0.20 f o r c o n v e n t i o n a l greenhouses. NOMENCLATURE Symbol A f A. l A B B v, Y B w, 1 C P D w,i F F r->-r F m h. . i , i De f i n i t i o n Surface area of the foundation Surface a r e a of any v e r t i c a l w a l l " i " S u rface area s l o p e d roof " j " Beam s o l a r r a d i a t i o n i n c i d e n t on sloped r o o f " j " Beam s o l a r r a d i a t i o n i n c i d e n t on a v e r t i c a l w a l l o f o r i e n t a t i o n y Beam s o l a r r a d i a t i o n t r a n s m i t t e d through any v e r t i c a l w a l l " i " S p e c i f i c heat o f a i r at constant pressure D i f f u s e s o l a r r a d i a t i o n i n c i d e n t on sloped r o o f " j " D i f f u s e s o l a r r a d i a t i o n i n c i d e n t on a v e r t i c a l w a l l of o r i e n t a t i o n y D i f f u s e s o l a r r a d i a t i o n t r a n s m i t t e d through any v e r t i c a l w a l l " i " R a d i a t i o n c o n f i g u r a t i o n f a c t o r between the roof and the p l a n t canopy Ra d i a t i o n c o n f i g u r a t i o n f a c t o r between the two sl o p e s o f the greenhouse roof Monthly average f r a c t i o n o f the greenhouse h e a t i n g load s u p p l i e d by p a s s i v e s o l a r A v e r a g e c o n v e c t i v e h e a t t r a n s f e r c o e f f i c i e n t f o r t h e i n s i d e s u r f a c e o f t h e g r e e n h o u s e c o v e r U n i t s m m m 2 kJ.h -"-.m-2 kJ.h .m kJ.h -1 kJ.ka 1.K~ 1 "a -1 2 kJ.h .m kJ.h .m kJ.h" -1 . T .-1 -2 -1 kJ.h .m .K I' r w I w,i N a P QINF QSOL QSUP TRAN T o t a l s o l a r r a d i a t i o n t r a n s m i t t e d through the r o o f t h a t i s captured by the p l a n t canopy T o t a l s o l a r r a d i a t i o n t r a n s m i t t e d through the greenhouse roof and i n t e r c e p t e d by the p l a n t canopy T o t a l s o l a r r a d i a t i o n t r a n s m i t t e d through r o o f s l o p e " j " t h a t i s i n t e r c e p t e d by the p l a n t canopy T o t a l s o l a r r a d i a t i o n t r a n s m i t t e d through the v e r t i c a l w a l l s of the greenhouse t h a t i s captured by the p l a n t canopy T o t a l s o l a r r a d i a t i o n t r a n s m i t t e d through w a l l " i " o f the greenhouse t h a t i s captured by the p l a n t canopy Greenhouse i n f i l t r a t i o n r a t e ( a i r changes) Greenhouse perimeter Heat l o s s due to i n f i l t r a t i o n S o l a r energy i n p u t t o the greenhouse Supplemental heat requirement f o r the greenhouse Heat l o s s o r g a i n through the greenhouse envelope Thermal r e s i t a n c e o f the greenhouse cover f o r any s u r f a c e " i " e x c l u d i n g the o u t s i d e s u r f a c e wind c o e f f i c i e n t k J.h" 1 kJ.h -1 k J . h " 1 k J . h " 1 k J . h " 1 h m -1 kJ.h kJ.h k J . h " 1 kJ.h -1 h.m 2.K.kJ - 1 I 1 R c , 1 S.E.U, S , l U i u w T b , i T b , j T d , i T d , j a • 1 2 — 1 Thermal r e s i s t a n c e of the greenhouse h.m .K.kJ cover m a t e r i a l o f any s u r f a c e " i " Monthly average s o l a r energy u t i l i z a t i o n f a c t o r I n s i d e greenhouse temperature K Outside environmental temperature K Outside s u r f a c e temperature of any K w a l l " i " -1 -2 -1 O v e r a l l heat t r a n s f e r c o e f f i c i e n t o f kJ.h .m K the f o u n d a t i o n Heat t r a n s f e r c o e f f i c i e n t o f any s u r f a c e " i " e x c l u d i n g the o u t s i d e f i l m c o e f f i c i e n t E f f e c t i v e heat t r a n s f e r c o e f f i c i e n t f o r the per i m e t e r Volume of the greenhouse Wind speed Transmittance o f w a l l " i " t o beam s o l a r -r a d i a t i o n T r ansmittance o f r o o f slope " j " to beam s o l a r r a d i a t i o n T ransmittance o f w a l l " i " to d i f f u s e s o l a r r a d i a t i o n T r ansmittance of r o o f slope " j " to d i f f u s e s o l a r r a d i a t i o n Absorptance of w a l l " i " t o s o l a r r a d i a t i o n Absorptance of the greenhouse roof to s o l a r r a d i a t i o n , -1 -2 -1 kJ.h .m .K k J . h ^ . m . K ^ m km. h -1 O r i e n t a t i o n of the s u r f a c e from due r a d i a n s south -3 Density of a i r Kg.m Albedo o f the p l a n t canopy CHAPTER 5 COMPUTER S I M U L A T I O N MODEL OF ENERGY REQUIREMENTS FOR A COMBINED GREENHOUSE-LIVESTOCK B U I L D I N G INTRODUCTION The mathematical model developed i n Chapter 3 f o r the a n a l y s i s of v e n t i l a t i o n requirements of animal s h e l t e r s , and th a t developed i n Chapter 4 to p r e d i c t the h e a t i n g loads of c o n v e n t i o n a l greenhouses are combined i n t h i s chapter to determine the p o t e n t i a l energy savings which c o u l d be r e a l i z e d by a combined g r e e n h o u s e - l i v e s t o c k b u i l d i n g o p e r a t i o n . The chapter c o n s i s t s of two s e c t i o n s . In the f i r s t s e c t i o n , the combined model i s d e s c r i b e d ; a l s o a b r i e f d i s c u s s i o n on the e f f e c t s of p o l l u t a n t s p r e s e n t i n the exhaust a i r from the animal s h e l t e r on p l a n t growth i s presented. The second s e c t i o n i s devoted to a computer s i m u l a t i o n a n a l y s i s of a t y p i c a l r e t r o f i t case o f a gable g l a s s h o u s e -hog barn combination. In t h i s case study, emphasis was on the c o n t r i b u t i o n o f animal waste heat recovery to the greenhouse h e a t i n g requirements. F i n a l l y , a comparison of heat demands by a f r e e - s t a n d i n g and an attached greenhouse i s a l s o g i v e n . S E C T I O N A MATHEMATICAL MODEL DEVELOPMENT OF GREENHOUSE-LIVESTOCK COMBINATION MODEL DEVELOPMENT ASSUMPTIONS A l l the assumptions s t a t e d with res p e c t to the l i v e s t o c k model development i n Chapter 3 and those made during the development of the co n v e n t i o n a l greenhouse mathematical model i n Chapter 4 apply to the combined g r e e n h o u s e - l i v e s t o c k case. In a d d i t i o n , the f o l l o w i n g assumptions were c o n s i d e r e d : i ) The v e n t i l a t i o n a i r f o r temperature or moisture c o n t r o l of the l i v e s t o c k b u i l d i n g i s taken as 100 percent o u t s i d e a i r . i i ) The v e n t i l a t i o n a i r from the l i v e s t o c k b u i l d i n g i s exhausted d i r e c t l y i n t o the greenhouse to be u l t i m a t e l y l o s t by e x f i l t r a t i o n through the greenhouse vents. i i i ) The w a l l s e p a r a t i n g the l i v e s t o c k space from that o f the greenhouse i s assumed to be a d i a b a t i c s i n c e conduction heat t r a n s f e r between the two b u i l d i n g s i s r e l a t i v e l y small compared to the t o t a l heat exchange between the b u i l d i n g s and t h e i r environments. iv) Only the s e n s i b l e p o r t i o n o f the waste heat from the l i v e s t o c k b u i l d i n g i s recovered, thus the p r e d i c t e d energy savings by t h i s model are c o n s e r v a t i v e . HEAT BALANCE ABOUT THE BUILDING For the purpose of heating load c a l c u l a t i o n s , the g r e e n h o u s e - l i v e s t o c k combination system can be taken as a s i n g l e s t r u c t u r e composed of the f o l l o w i n g three zones: i ) The a t t i c zone i i ) The l i v e s t o c k zone i i i ) The greenhouse zone ZONE I: ATTIC SPACE The temperature i n the a t t i c space i s estimated as i n d i c a t e d with re s p e c t to the c o n v e n t i o n a l l i v e s t o c k u n i t i n Chapter 3: equations (7), (2) and ( 3 ) . The a t t i c temperature i s assumed to be a f u n c t i o n of the barn temperature, the o u t s i d e a i r temperature, the s o l a r r a d i a t i o n absorbed by the roof, and the r e s p e c t i v e thermal r e s i s t a n c e s of the roof and the c e i l i n g of the l i v e s t o c k b u i l d i n g . ZONE I I : LIVESTOCK BUILDING The supplemental heat r e q u i r e d by the l i v e s t o c k b u i l d i n g may be c a l c u l a t e d whence the a t t i c temperature i s determined. The general heat balance equation about the l i v e s t o c k zone may be w r i t t e n as f o l l o w s : QSUP,L QSENS ~ QVENT ~ ^TRAN , (1) where the plus s i g n (+) i n d i c a t e s that only the p o s i t i v e values are co n s i d e r e d . The s e n s i b l e heat r e l e a s e d by the animal, the v e n t i l a t i o n r a t e and v e n t i l a t i o n heat l o s s and t r a n s m i s s i o n heat l o s s are c a l c u l a t e d using the method presented i n Chapter 3 with r e s p e c t to the c o n v e n t i o n a l l i v e s t o c k b u i l d i n g . ZONE I I I : GREENHOUSE The general heat balance equation about the attached greenhouse may be s t a t e d as f o l l o w s : SUPPLEMENTAL HEAT + SOLAR ENERGY INPUT + HEAT RECOVERED FROM LIVESTOCK BUILDING - HEAT TRANSMISSION = 0, or i n equation form: QSUP,G = QSOL + QHRL ~ QTRAN , ( 2 ) where the plus sign (+) i n d i c a t e s that only the p o s i t i v e values are co n s i d e r e d . The above equation i s s i m i l a r to equation ( 1 ) of Chapter 4 with the ex c e p t i o n that the i n f i l t r a t i o n heat l o s s term i s re p l a c e d by the heat recovery from v e n t i l a t i o n a i r of the l i v e s t o c k zone. The t r a n s m i s s i o n heat l o s s through the greenhouse envelope i s c a l c u l a t e d using the same method which was developed e a r l i e r i n Chapter 4 with respect to the co n v e n t i o n a l gable greenhouse. The s o l a r energy input to the greenhouse i s estimated using the same methodology developed i n Chapter 4 , to determine the s o l a r r a d i a t i o n captured by co n v e n t i o n a l gable greenhouse. The only a d d i t i o n a l subroutine r e q u i r e d f o r the case of a combined l i v e s t o c k - g r e e n h o u s e system i s an al g o r i t h m to determine the heat input from the l i v e s t o c k b u i l d i n g that i s used to p a r t i a l l y supply the heating load of the greenhouse. S i n c e , i t i s assumed that only the s e n s i b l e p o r t i o n of the l i v e s t o c k b u i l d i n g heat i s to be recove r e d , then the s e n s i b l e heat a v a i l a b l e may be c a l c u l a t e d as f o l l o w s : QHRL = • ™ C p ( T b " V • (3) The above equation c l e a r l y shows that the a v a i l a b i l i t y of s e n s i b l e heat i s d i r e c t l y p r o p o r t i o n a l to the l i v e s t o c k v e n t i l a t i o n r a t e i n u n i t mass of a i r per un i t time and to the temperature d i f f e r e n c e between that of the l i v e s t o c k b u i l d i n g and of the greenhouse. In c a l c u l a t i n g the c o n t r i b u t i o n of the heat recovered to the greenhouse heating l o a d , the s e n s i b l e heat a v a i l a b l e from the l i v e s t o c k b u i l d i n g i s considered only during time p e r i o d s when the attached greenhouse r e q u i r e d supplemental heat. Thus, i n most cases, the c o n t r i b u t i o n of waste heat to the greenhouse heating load i s zero around noon hours, because p a s s i v e s o l a r energy alone can supply the t o t a l greenhouse heat demand. ADVANTAGES AND DISADVANTAGES OF DIRECT USE OF EXHAUST AIR The i n t r o d u c t i o n of exhaust a i r from the l i v e s t o c k b u i l d i n g d i r e c t l y i n t o the greenhouse has many advantages as w e l l as disadvantages. An obvious advantage of the d i r e c t exchange system i s i t s low c o s t . The e x i s t i n g exhaust fans used with c o n v e n t i o n a l barns could e a s i l y be adapted f o r the combined g r e e n h o u s e - l i v e s t o c k system without the a d d i t i o n of e x t r a equipment, such as heat exchangers. Another advantage of the d i r e c t use of the exhaust a i r i s i t s b e n e f i c i a l e f f e c t of i n c r e a s i n g the a i r pressure w i t h i n the greenhouse, thus reducing i n f i l t r a t i o n of o u t s i d e a i r to a minimum l e v e l . A t h i r d advantage i s the n a t u r a l carbon d i o x i d e enrichment of the greenhouse environment which could r e s u l t i n an in c r e a s e i n the y i e l d of the crop. Some of the disadvantages of the d i r e c t a i r exchange system between the l i v e s t o c k b u i l d i n g and the greenhouse are r e l a t e d to dust and ammonia accumulation. Dust i n the exhaust a i r from the l i v e s t o c k b u i l d i n g may accumulate on the greenhouse c o v e r i n g m a t e r i a l and on the leaves of the p l a n t s thus p o s s i b l y causing a r e d u c t i o n i n the s o l a r r a d i a t i o n a v a i l a b i l i t y f o r p h o t o s y n t h e s i s as w e l l as f o r p a s s i v e s o l a r energy c o l l e c t i o n . T h i s problem of dust accumulation c o u l d be a l l e v i a t e d by i n s t a l l i n g a i r f i l t e r s a t the entrances of the exhaust f a n s . Ammonia when pr e s e n t i n hig h c o n c e n t r a t i o n s might be a s e r i o u s problem wi t h r e s p e c t to u n d e s i r a b l e odor and p o s s i b l y damage to the p l a n t s . A very l i m i t e d amount of r e s e a r c h work has been done on the e f f e c t s o f ammonia on p l a n t s . Only a few s p e c i e s has been t e s t e d f o r acute i n j u r y by t h i s gas but too l i t t l e i s known on p l a n t responses to l o w - l e v e l , l o n g -term exposure to c o n s i d e r c h r o n i c e f f e c t s . I t has been r e p o r t e d i n a U.S. Environmental P r o t e c t i o n Agency (EPA) r e p o r t (1978) and i n the experimental work on tomato p l a n t s by Thornton and S e t t e r s t r o m (1940) t h a t i n t e r n a l pH i n c r e a s e s i n the l e a f t i s s u e and changes i n pigmentation of the l e a f c o u l d be c o n s i d e r e d c h r o n i c responses t o NH^. The EPA r e p o r t s t a t e s t h a t c o n c e n t r a t i o n s o f 55 ppm r e q u i r e one hour to i n j u r e tomato p l a n t s . The other gas which may be presen t i n the exhaust a i r from l i v e s t o c k b u i l d i n g s i s hydrogen s u l f i d e . Thornton and S e t t e r s t r o m (.1940) found t h a t H 2S was o n l y m i l d l y t o x i c to p l a n t t i s s u e as compared with other gases. With r e s p e c t to tomato p l a n t s , they gave the f o l l o w i n g order of t o x i c i t y of the gases: C l 2 > S 0 2 > NH 3 > HCH > H 2S . Ammonia and hydrogen s u l f i d e c o n c e n t r a t i o n s i n l i v e s t o c k b u i l d i n g s depend on many f a c t o r s i n c l u d i n g type and d e n s i t y of c o n f i n e d animals, type of manure h a n d l i n g system and the r a t e of v e n t i l a t i o n . van D a l f s e n and B u l l e y (1982) measured NH^ and H 2S c o n c e n t r a t i o n s w i t h i n f o u r d a i r y barns having s u b f l o o r manure s t o r a g e s . T h e i r r e s u l t s i n d i c a t e d a range of ammonia c o n c e n t r a t i o n s i n the b u i l d i n g s between 2.5 to 6.5 ppm d u r i n g normal c o n d i t i o n s , while H 2S was found i n measurable q u a n t i t i e s only d u r i n g the a g i t a t i o n of manure. Even then hydrogen s u l f i d e c o n c e n t r a t i o n s were l e s s than 3 ppm. Consequently, H 2S i s not expected to be a l i m i t i n g f a c t o r f o r l i v e s t o c k -greenhouse combination systems because of i t s low c o n c e n t r a t i o n and i t s r e l a t i v e l y low l e v e l of t o x i c i t y to p l a n t s . C e r t a i n l y acute i n j u r y t o p l a n t s w i l l not occur a t the low l e v e l of ammonia c o n c e n t r a t i o n s r e p o r t e d by van D a l f s e n and B u l l e y (1982) i n animal b u i l d i n g s . However, r e s e a r c h work i s needed to determine the c h r o n i c e f f e c t of l o w - l e v e l c o n c e n t r a t i o n s of ammonia on the p r o d u c t i v i t y of greenhouse p l a n t s . A l s o , one must c o n s i d e r the f a c t t h a t s p e c i e s of p l a n t s have shown d i f f e r e n t l e v e l s of t o l e r a n c e to gaseous p o l l u t i o n . There a l s o may be c o n s i d e r a b l e v a r i a t i o n i n p o l l u t a n t . s e n s i t i v i t y between c u l t i v a r s w i t h i n a s p e c i e s (Howe and Woltz, 1982). Environmental f a c t o r s such as temperature, humidity, l i g h t i n t e n s i t y , CC^ c o n c e n t r a t i o n , water supply and n u t r i e n t a v a i l a b i l i t y may be s i g n i f i c a n t i n a s c e r n i n g the p l a n t s u s c e p t i b i l i t y to gaseous p o l l u t a n t s (Ormrod and Blom, 1978). S E C T I O N B CASE STUDY 111 ENERGY REQUIREMENTS OF A GABLE GLASSHOUSE-SWINE F I N I S H I N G BARN COMBINATION SWINE FINISHING BARN-GREENHOUSE COMBINATION - A CASE STUDY DESCRIPTION AND ASSUMPTIONS A schematic of the attached greenhouse to a hog f i n i s h i n g barn i s shown i n Figure 5.1. As can be seen i n the f i g u r e , the two b u i l d i n g s have a common w a l l ; o b v i o u s l y , t h i s c o n f i g u r a t i o n w i l l be i m p r a c t i c a l i n regions where snow accumulation i s a f a c t o r without p r o v i s i o n f o r snow removal from the south roof of the l i v e s t o c k b u i l d i n g or some other means of p r o t e c t i n g the north roof of the greenhouse from snow loads. Otherwise, a space between the two s t r u c t u r e s should be l e f t c l e a r where snow s l i d i n g from the south roof of the l i v e s t o c k b u i l d i n g can accumulate without damage to the greenhouse. The north w a l l of the greenhouse should s t i l l be i n s u l a t e d . With the exce p t i o n of the common w a l l , other j c o n s t r u c t i o n parameters such as l e v e l of i n s u l a t i o n , dimensions, and o p t i c a l p r o p e r t i e s of the greenhouse g l a s s cover; and management p r a c t i c e s such as number of hogs, s i z e s , minimum and maximum v e n t i l a t i o n r a t e s e t c . . . a r e i d e n t i c a l to those used with res p e c t to case s t u d i e s I and I I . T h e r e f o r e , the reader i s r e f e r r e d to s e c t i o n B of each of Chapters 3 and 4 f o r d e t a i l e d i n f o r m a t i o n on b u i l d i n g FIGURE 5.1: CROSS-SECTIONAL VIEW OF THE GABLE GREENHOUSE-HOG BARN COMBINATION (CASE STUDY I I I ) . s p e c i f i c a t i o n s , o p e r a t i n g parameters and assumptions u n d e r l y i n g case study I I I . A d d i t i o n a l assumptions which apply s p e c i f i c a l l y to t h i s case study are as f o l l o w s : i ) The v e n t i l a t i o n a i r from the hog barn i s drawn d i r e c t l y i n t o the greenhouse f o l l o w i n g a dust removal process. i i ) No attempt i s made i n t h i s study f o r barn l a t e n t heat recovery; t h e r e f o r e only the s e n s i b l e p o r t i o n i s assumed r e c o v e r a b l e . T h i s i m p l i e s that the p r e d i c t e d energy savings are r a t h e r c o n s e r v a t i v e estimates of the p o t e n t i a l s a v i n g s . i i i ) The r a t i o of number of animals to un i t area of greenhouse i s assumed con s t a n t throughout t h i s a n a l y s i s ; a c t u a l l y , i t i s dependent on the number o f hogs i n the barn a t any time t o the de s i g n v a l u e . RESULTS AND DISCUSSION A sample output of the computer s i m u l a t i o n model f o r an attached greenhouse to a f i n i s h i n g hog barn i s i n c l u d e d i n Appendix H. Tables H.l to H.12 show the hourly energy flows between the attached greenhouse, the l i v e s t o c k b u i l d i n g and the outdoor environment f o r a t y p i c a l day of each month of the year. Among the values shown i n the t a b l e s are the h o u r l y energy inputs to the greenhouse which include the s o l a r r a d i a t i o n captured by the p l a n t canopy and the s e n s i b l e heat contained i n the v e n t i l a t i o n a i r from the l i v e s t o c k b u i l d i n g that i s p o t e n t i a l l y a v a i l a b l e f o r recovery and use by the attached greenhouse. The t a b l e s i n Appendix H, a l s o show the hourly heat l o s s e s from the greenhouse from which the hourly heating load when the energy input from v e n t i l a t i o n a i r i s neglected as w e l l as the a c t u a l hourly heating load when the l i v e s t o c k s e n s i b l e heat i s recovered are c a l c u l a t e d . The l a s t two columns i n Tables H.l to H.12 are r e s p e c t i v e l y , the hourly f r a c t i o n of the greenhouse heat l o s s that i s s u p p l i e d by p a s s i v e s o l a r and the hourly f r a c t i o n of the heating load ( a f t e r the pa s s i v e c o n t r i b u t i o n of s o l a r r a d i a t i o n ) that i s s u p p l i e d by s e n s i b l e heat recovery from the swine b u i l d i n g v e n t i l a t i o n a i r . For the purpose of d i s c u s s i o n , the in f o r m a t i o n contained i n Appendix H i s summarized i n Tables 5.1 and 5.2. Table 5.1 concentrates on the pa s s i v e s o l a r c o n t r i b u t i o n to the attached greenhouse heating load while Table 5.2 give s the c o n t r i b u t i o n of s e n s i b l e heat recovery from the hog b u i l d i n g v e n t i l a t i o n a i r to the greenhouse heating l o a d . MONTHLY AVERAGE HEAT LOSS, SOLAR ENERGY INPUT AND SOLAR ENERGY UTILIZED BY THE GREENHOUSE IN MJ PER m  OF FLOOR AREA FOR THE ATTACHED GREENHOUSE-SWINE  FINISHING BARN OF CASE STUDY I I I  (MINIMUM GREENHOUSE TEMPERATURE = 15°C) HALIFAX, N.S. Month S o l a r Energy Heat ^°S,S2 Captured MJ/m ,MT/_2I _x. Used U t i l i . (MJ/m ) (MJ/m2) F a c t o r P e r cent S u p p l i e d by S o l a r January 481 156 116 0.74 24 February 441 202 128 0.63 29 March 405 335 144 0.43 36 A p r i l 280 369 111 0.30 40 May 166 436 65 0.15 39 June 69 493 18 0.04 25 J u l y 24 479 3 <0.01 13 August 18 458 3 <0.01 16 September 50 350 10 0.03 19 October 159 255 44 0.17 28 November 265 140 69 0.49 26 December 424 114 93 0.82 22 Year 2782 3787 804 0.21 29 MONTHLY AVERAGE HEATING LOAD, WASTE HEAT CONTRIBUTION  TO THE GREENHOUSE HEATING LOAD FROM THE LIVESTOCK  BUILDING AND SUPPLEMENTAL HEAT REQUIREMENT IN MJ PER m2  OF GREENHOUSE FLOOR AREA FOR THE ATTACHED GREENHOUSE- SWINE FINISHING BARN OF CASE STUDY I I I (MINIMUM GREENHOUSE TEMPERATURE = 15°C) HALIFAX, N.S. Month Heating Load (MJ/m2) Waste Heat C o n t r i b u t i o n (MJ/m2) Supplemental Heat Requirement (MJ/m2) Percent S u p p l i e d by Waste Heat January 365 54 311 15 February 313 46 267 15 March 261 52 209 20 A p r i l 169 55 114 32 May 101 61 40 61 June 51 51 0 100 J u l y 21 21 0 100 August 15 15 0 100 September 40 40 0 100 October 115 82 33 71 November 196 75 121 39 December 331 64 267 19 Year 1978 616 1362 31 The c o n s t r u c t i o n parameters and management p r a c t i c e s of the greenhouse analyzed here are i d e n t i c a l to the con v e n t i o n a l gable greenhouse d e s c r i b e d i n Chapter 4 , with the e x c e p t i o n of the presence of a common w a l l with the l i v e s t o c k b u i l d i n g . T h e r e f o r e , the r e s u l t s of Table 5.1 of t h i s chapter are d i r e c t l y comparable to r e s u l t s obtained i n Chapter 4 and summarized i n Table 4.4 o f t h a t chapter. Comparison of the r e s u l t s i n d i c a t e that the annual heat l o s s from the attached greenhouse i s 2782 megajoules per square meter of f l o o r area (MJ/m2) as compared to 3693 MJ/m2 f o r the fre e standing greenhouse. T h i s represents a r e d u c t i o n of 25 percent which i s due to i n s u l a t i o n of the north w a l l of the greenhouse and the e l i m i n a t i o n of i n f i l t r a t i o n heat l o s s . On the othe r hand, the s o l a r r a d i a t i o n captured by the attached greenhouse i s lower than that captured by the free standing greenhouse. The corresponding values are 3787 and 4024 megajoules per square metre of f l o o r area a n n u a l l y . The s i x percent r e d u c t i o n i n energy capture i s a t t r i b u t e d to the i n s u l a t e d north w a l l of the attached greenhouse. Even though, the s o l a r c o n t r i b u t i o n to the greenhouse heat l o s s was reduced from 975 to 804 megajoules per square meter of f l o o r area; the net r e d u c t i o n i n greenhouse heating load i s 740 MJ/m2 or 27 percent i n favor of the attached greenhouse. The annual s o l a r energy u t i l i z a t i o n f a c t o r was reduced from 0.24 f o r the f r e e s t anding greenhouse ( F i g . 4.3, Chapter 4) to 0.21 f o r the a t t a c h e d greenhouse (Table 5.1, Chapter 5 ) . The lowering o f the s o l a r energy u t i l i z a t i o n f a c t o r i s due to the reduced heat l o s s from the atta c h e d greenhouse. Table 5.2 g i v e s the p r e d i c t e d monthly and annual c o n t r i b u t i o n to the greenhouse h e a t i n g l o a d o f s e n s i b l e waste heat recovery from v e n t i l a t i o n a i r of the l i v e s t o c k b u i l d i n g . The monthly percentage of greenhouse h e a t i n g l o a d s u p p l i e d by waste heat from the hog barn ranged from 15 percent i n January to 100 percent d u r i n g the summer months g i v i n g an annual p r e d i c t e d average i n the order of 30 p e r c e n t . In t h i s case study, the expected annual savings i n energy from waste heat are about 600 megajoules per square metre of greenhouse area. The p r e d i c t e d annual supplemental heat requirement f o r 2 the attached greenhouse t o the hog barn i s 1362 MJ/m as 2 compared to 2718 MJ/m f o r a f r e e s t a n d i n g c o n v e n t i o n a l greenhouse. In Chapter 4, i t was concluded from the a n a l y s i s of a c o n v e n t i o n a l greenhouse t h a t lowering the greenhouse minimum i n s i d e temperature by one degree K e l v i n has r e s u l t e d i n a f i v e p ercent r e d u c t i o n i n the annual supplemental heat requirement. Tables 5.3 and 5.4 of t h i s chapter g i v e a summary of the r e s u l t s of an a n a l y s i s which i s performed p r i m a r i l y t o determine the e f f e c t o f lowering the greenhouse minimum MONTHLY AVERAGE HEAT LOSS, SOLAR ENERGY INPUT AND  SOLAR ENERGY UTILIZED BY THE GREENHOUSE IN MJ PER m 2  OF FLOOR AREA FOR THE ATTACHED GREENHOUSE-SWINE  FINISHING BARN OF CASE STUDY I I I  (MINIMUM GREENHOUSE TEMPERATURE = 10°C) HALIFAX, N.S. S o l a r Energy ~ , _ ,. , Heat _ Percent S u p p l i e d Month Los s - „ , , r T i. •, . by S o l a r , 2 Captured Used U t i l i . J M J / m (MJ/m ) (MJ/m2) F a c t o r January 364 156 88 0.56 24 February 334 202 100 0.50 30 March 289 335 103 0.31 36 A p r i l 166 369 61 0.17 37 May 62 436 14 0.03 23 June 14 493 2 <0.01 14 J u l y - 479 - 0.00 -August - 458 - 0.00 -September - 350 - 0.00 -October 52 255 6 0.02 12 November 153 140 37 0.26 24 December 306 114 69 0.61 23 Year 1740 3787 480 0.^ 13 28 MONTHLY AVERAGE HEATING LOAD, WASTE HEAT CONTRIBUTION  TO THE GREENHOUSE HEATING LOAD FROM THE LIVESTOCK 2 BUILDING AND SUPPLEMENTAL HEAT REQUIREMENT IN MJ PER m  OF GREENHOUSE FLOOR AREA FOR THE ATTACHED GREENHOUSE-SWINE FINISHING BARN OF CASE STUDY I I I (MINIMUM GREENHOUSE TEMPERATURE = 10°C) HALIFAX, N.S. Month H e a t i n g Load (MJ/m2) Waste Heat C o n t r i b u t i o n (MJ/m2) Supplemental Heat Requirement (MJ/m2) Percent S u p p l i e d by Waste Heat January 276 ^ 102 174 37 February 234 83 151 36 March 186 94 92 50 A p r i l 105 87 18 83 May 48 48 0 100 June 12 12 0 100 J u l y - - - -August - - - -September - - - -October 46 46 0 100 November 116 108 8 93 December 237 115 122 49 Year 1260 695 565 55 temperature on the supplemental heat requirement of an attached greenhouse to a swine f i n i s h i n g barn. For t h i s a n a l y s i s the greenhouse minimum temperature was reduced from 150C to 10°C. A comparison of Table 5.1 to Table 5.3 i n d i c a t e s t h a t the annual heat l o s s from the greenhouse was reduced from 2782 to 1740 megajoules per square metre of f l o o r area when the minimum temperature s e t t i n g was dropped from 15°C to 10°C. Obviously the s o l a r r a d i a t i o n captured by the greenhouse remained the same, but, as expected the s o l a r energy u t i l i z a t i o n f a c t o r has been reduced s i g n i f i c a n t l y . The decrease i n the s o l a r energy u t i l i z a t i o n f a c t o r from a value of 0.21 to 0.13 i s due to the lower greenhouse o p e r a t i n g temperature. The monthly and y e a r l y c o n t r i b u t i o n of s e n s i b l e waste heat recovery from the hog barn to the attached greenhouse heating load i s shown . i n Table 5.4 for a minimum greenhouse temperature s e t t i n g of 10°C. Comparing the values i n Tab l e 5.2(15°C) to those i n Table 5.4 (10°C) i n d i c a t e f i r s t l y that the heating season was reduced from 12 months to 9 months and the annual heating l o a d , n e g l e c t i n g the c o n t r i b u t i o n of waste heat, was reduced from 1978 to 1260 megajoules per square metre of f l o o r area. Secondly, the waste heat c o n t r i b u t i o n to the greenhouse h e a t i n g l o a d was i n c r e a s e d d u r i n g the wint e r months. The annual c o n t r i b u t i o n of waste heat r e c o v e r y from the hog barn to the greenhouse h e a t i n g l o a d has i n c r e a s e d from 31 pe r c e n t f o r a minimum greenhouse temperature o f 15°C to 55 perc e n t f o r a minimum temperature of 10°C. T h i r d l y , the annual supplemental heat requirement based upon greenhouse u n i t f l o o r area has decreased from 1362 MJ/m2 to 565 MJ/m2 f o r minimum temperatures of 15°C and 10°C r e s p e c t i v e l y . T h i s r e p r e s e n t s about 60 perc e n t i n energy savings which i n d i c a t e s t h a t greenhouse o p e r a t i n g temperature i s a s i g n i f i c a n t f a c t o r f o r a g r e e n h o u s e - l i v e s t o c k combination. The s i g n i f i c a n c e of lowering the minimum greenhouse o p e r a t i n g temperature on energy savings f o r an attach e d greenhouse-swine f i n i s h i n g barn i s e v i d e n t from Table 5.5. The greenhouse minimum o p e r a t i n g temperatures used i n the analyses r e p r e s e n t e d i n Table 5.5 are 20°C, 15°C and 10°C r e s p e c t i v e l y . The perc e n t energy savings shown i n the t a b l e are based upon the 20°C case. The p r e d i c t e d annual energy savings due to lowering the greenhouse minimum temperature from 20°C to 15°C and 10°C are 52 and 80 percent r e s p e c t i v e l y . As p r e v i o u s l y s t a t e d , the main purpose o f P a r t I I of t h i s study i s to determine the p o t e n t i a l energy savings by r e c o v e r i n g the waste heat from a l i v e s t o c k o p e r a t i o n and usin g i t t o p a r t i a l l y supply the h e a t i n g demand of an EFFECT OF LOWERING THE MINIMUM GREENHOUSE TEMPERATURE ON ENERGY SAVINGS FOR THE ATTACHED OF CASE STUDY I I I HALIFAX, N.S. Month Supplemental Heat (MJ per m2 Greenhouse F l o o r Area) Percent Savings T =20°C T =15°C 9 g T =10°C g T =15°C g T =10°C g January- 462 311 174 33 62 February 395 267 151 32 62 March 339 209 92 38 73 A p r i l 235 114 18 51 92 May 159 40 0 75 100 June 100 0 0 100 100 J u l y 64 0 0 100 100 August 59 0 0 100 100 September 99 0 0 100 100 October 189 33 0 82 100 November 280 121 8 57 97 December 433 267 122 38 72 Year 2814 1362 565 52 80 adjacent greenhouse. The promising case of a swine f i n i s h i n g barn i s used as an example t o demonstrate i f s i g n i f i c a n t energy savings c o u l d be achieved through the o p e r a t i o n of a g r e e n h o u s e - l i v e s t o c k combination. The r e s u l t s of a combination system operated i n the H a l i f a x area are given i n Table 5.6. The p o t e n t i a l energy savings are h i g h l y dependent on the minimum greenhouse temperature s e t t i n g as can c l e a r l y be seen i n the t a b l e . For t h i s case study, the p r e d i c t e d annual energy savings were i n the order of 27, 50 and 67 per c e n t f o r minimum greenhouse temperatures of 20°C, 15°C and 10°C r e s p e c t i v e l y . The above percentage energy savings are c a l c u l a t e d u s i n g a c o n v e n t i o n a l f r e e s t a n d i n g gable greenhouse as a base f o r comparison. In many i n s t a n c e s , the greenhouse o p e r a t o r s choose t o grow low temperature crops d u r i n g the w i n t e r season and a r e l a t i v e l y h i g h e r temperature crop d u r i n g the ot h e r seasons of the. year. For such a case, the expected annual energy savings would be somewhat d i f f e r e n t from the valu e s g i v e n above. L e t us take f o r example, a greenhouse operated at a low temperature of 10°C d u r i n g the months of November through February and a t 15°C d u r i n g the ot h e r months of the year; then from Table 5.6 , the p r e d i c t e d annual supplemental h e a t i n g requirements can be c a l c u l a t e d as 2243 megajoules per square metre of f l o o r area f o r the c o n v e n t i o n a l 2 greenhouse and 851 MJ/m f o r the attached greenhouse r e s u l t i n g i n an expected annual energy savings i n the order of 62 p e r c e n t . TABLE 5.6 MONTHLY AVERAGE SUPPLEMENTAL HEAT REQUIREMENTS  FOR A CONVENTIONAL AND AN ATTACHED GREENHOUSE* (MJ PER m2 GREENHOUSE FLOOR AREA)  ALSO EXPECTED PERCENT SAVINGS AS A FUNCTION OF THE MINIMUM GREENHOUSE TEMPERATURE T = 20°C g T = 15°C g T g = 10°C Month Supplemental Heat Percent Savings Supplemental Heat Percent Savings Supplemental Heat Percent Savings Con. A t t . Con. A t t . Con. A t t . January 632 462 27 497 311 37 370 174 53 February 540 395 27 428 267 38 321 151 53 March 464 339 27 357 209 41 254 92 64 A p r i l 325 235 28 232 114 51 146 18 88 May 222 159 28 141 40 72 69 0 100 June 135 100 26 69 0 100 17 0 100 J u l y 87 64 26 27 0 100 - - -August 84 59 30 21 0 100 - -September 140 99 29 61 0 100 7 0 100 October 261 189 28 160 33 79 68 0 100 November 387 280 28 272 121 56 162 8 95 December 603 433 28 453 267 41 322 122 62 Year 3880 2814 27 2718 1362 50 1736 565 67 * L o c a t i o n : H a l i f a x , N.S. f O to The above savings i n energy can be a t t r i b u t e d t o the e l i m i n a t i o n of the heat l o s s from the n o r t h w a l l of the greenhouse, the m i n i m i z a t i o n o f o u t s i d e a i r i n f i l t r a t i o n i n t o the greenhouse and the u t i l i z a t i o n o f a f r a c t i o n of the s e n s i b l e heat produced by the animals. These savings c o u l d be f u r t h e r improved i f an e f f i c i e n t l a t e n t heat recovery system c o u l d be designed and u t i l i z e d to recover some of the l a t e n t heat produced by the animals. CONCLUSIONS From the i n f o r m a t i o n a v a i l a b l e on l e v e l s o f ammonia and hydrogen s u l f i d e c o n c e n t r a t i o n s encountered i n the exhaust a i r from animal s h e l t e r s under normal o p e r a t i n g c o n d i t i o n s , and on the t o l e r a n c e of p l a n t s to these gases, i t may be concluded t h a t : I n t r o d u c i n g the a i r from the animal s h e l t e r d i r e c t l y i n t o the at t a c h e d greenhouse i s not expected to have d e t r i m e n t a l e f f e c t s on the growth of a t l e a s t some greenhouse c r o p s . 2 Computer s i m u l a t i o n analyses o f a 1000 m gable greenhouse at t a c h e d to a c o n v e n t i o n a l swine f i n i s h i n g barn housing 1536 hogs, and l o c a t e d i n the H a l i f a x , N.S. area, r e v e a l e d the f o l l o w i n g r e s u l t s : 1. The y e a r l y percentage o f the h e a t i n g requirements t h a t c o u l d be s u p p l i e d by animal waste heat r e c o v e r y i s i n the order of 30 perce n t , w h i l e the greenhouse minimum o p e r a t i n g temperature was s e t at 15°C. When t h i s temperature was reduced to 10°C, the above percentage i n c r e a s e d t o 55 p e r c e n t . 2. The minimum greenhouse o p e r a t i n g temperature i s a s i g n i f i c a n t f a c t o r i n a c c e s s i n g the r e a l i z a b l e energy savings from g r e e n h o u s e - l i v e s t o c k combination systems. 3. The p r e d i c t e d annual energy savings o f the a t t a c h e d greenhouse t o the hog barn compared to a f r e e - s t a n d i n g gable greenhouse having the same c o n s t r u c t i o n and management parameters are: 27, 50 and 67 per c e n t f o r minimum greenhouse temperatures of 20°C, 15°C and 10°C, r e s p e c t i v e l y . Symbol C P HRL QSENS QSOL QSUP,G QSUP,L QTRAN QVENT D e f i n i t i o n U n i t s S p e c i f i c heat of barn exhaust a i r Mass flow r a t e o f barn exhaust a i r S e n s i b l e heat recovered from kJ.h l i v e s t o c k b u i l d i n g S e n s i b l e heat produced by the animals S o l a r energy captured by the greenhouse Supplemental heat requirement o f the greenhouse Supplemental heat requirement of the l i v e s t o c k b u i l d i n g T r a n s m i s s i o n heat l o s s from - l i v e s t o c k b u i l d i n g (equation 1) - greenhouse (equation 2) V e n t i l a t i o n heat l o s s from kJ.h l i v e s t o c k b u i l d i n g Dry-bulb temperature of the barn K Dry-bulb temperature of the K greenhouse kJ.kg~ 1.K~ 1 k g . h - 1 -1 k J . h - 1 k J . h " 1 k J . h " 1 k J . h " 1 k J . h " 1 -1 PART I I I ANALYSIS OF A SOLAR-SHED GREENHOUSE-LIVESTOCK COMBIMATI ON CHAPTER 6 COMPUTER SIMULATION MODEL OF HEATING REQUIREMENTS OF SOLAR-SHED GREENHOUSE INTRODUCTION T h i s chapter g i v e s a d e t a i l e d a n a l y s i s o f a new s o l a r greenhouse s p e c i f i c a l l y designed f o r hig h l a t i t u d e r e g i o n s . The greenhouse has a shed shape from which the name " S o l a r -Shed" was adopted by the author. The l o n g - a x i s o f the s o l a r - s h e d greenhouse must be east-west o r i e n t e d . The no r t h w a l l i s i n s u l a t e d and a s o l a r c o l l e c t o r i s i n s t a l l e d at the upper p a r t of i t s i n n e r s u r f a c e . The s o l a r energy c o l l e c t e d c o u l d be s t o r e d e i t h e r i n a rock storage under the benches or i n wet e a r t h underneath the greenhouse f l o o r . The chapter i s d i v i d e d i n t o t hree s e c t i o n s . The f i r s t g i v e s the energy balance equations used w i t h the computer s i m u l a t i o n model to determine the heat l o s s from the greenhouse. The second s e c t i o n goes i n t o a d e t a i l e d t h e o r e t i c a l a n a l y s i s of s o l a r r a d i a t i o n capture by the p l a n t canopy, as w e l l as, an a n a l y t i c a l technique of e s t i m a t i n g the u s e f u l heat g a i n by the i n t e g r a l s o l a r c o l l e c t o r . The theory developed i n the f i r s t two s e c t i o n s i s then a p p l i e d t o a case study i n o r d e r to i n v e s t i g a t e the performance of the s o l a r - s h e d greenhouse. The case study i s the s u b j e c t o f the f i n a l s e c t i o n of t h i s chapter where the e f f e c t o f l o c a t i o n , mean p l a t e temperature and type o f absorber p l a t e on the monthly and y e a r l y average s o l a r f r a c t i o n s i s s t u d i e d . The energy savings r e a l i z e d by the s o l a r - s h e d over a c o n v e n t i o n a l gable greenhouse are estimated f o r three l o c a t i o n s i n Canada. SECTION A HEAT BALANCE ABOUT THE SOLAR-SHED GREENHOUSE The p h y s i c a l model of the s o l a r - s h e d greenhouse chosen f o r t h i s study i s shown s c h e m a t i c a l l y i n F i g u r e 6.1. ASSUMPTIONS The f o l l o w i n g assumptions were made i n determining the heat balance o f the greenhouse: i ) Thermal storage i n the greenhouse s t r u c t u r e , ground bed, benches and p l a n t canopy i s n e g l e c t e d t o a l l o w steady s t a t e heat t r a n s f e r c a l c u l a t i o n s . i i ) E v a p o r a t i o n from the s o i l s u r f a c e i n the greenhouse i s n e g l i g i b l e . i i i ) P l a n t s t r a n s p i r a t i o n , p h o t o s y n t h e s i s and r e s p i r a t i o n are n e g l e c t e d . iv) There i s no i n t e r n a l energy g e n e r a t i o n i n s i d e the greenhouse. v) There i s no condensation on the i n s i d e s u r f a c e of the g l a s s cover, o r dust accumulation, t h e r e f o r e the t r a n s m i t t a n c e o f the c o v e r i n g i s taken as t h a t o f the g l a s s l a y e r o n l y . ENERGY BALANCE When a l l the above assumptions were taken i n t o account, the steady s t a t e heat balance equation f o r the p h y s i c a l model of F i g u r e 6.1 i s giv e n by SOLAR-SHED GREENHOUSE FIGURE 6 . 1 : SCHEMATIC OF A SOLAR-SHED GREENHOUSE SHOWING ENERGY FLOWS AND SOLAR RADIATION INCIDENT ON THE INTEGRAL COLLECTOR. Q s u p " Q s o l " Q r a d ~ Q c o n " Q i n f " Q c o n d (1) From F i g u r e 6.1 and equ a t i o n ( 1 ) i t can be seen t h a t the energy i n p u t t o the greenhouse i n c l u d e s the s o l a r r a d i a t i o n absorbed by the p l a n t canopy and o b j e c t s i n the greenhouse p l u s t h a t absorbed by the c o v e r i n g m a t e r i a l . For a completely c l o s e d system the heat i s l o s t by c o n v e c t i o n and by r a d i a t i o n from the greenhouse cover. Since i n f i l t r a t i o n and e x f i l t r a t i o n always occur i n greenhouses, an a d d i t i o n a l term i s i n c l u d e d i n equation ( 1 ) to account f o r the heat l o s s due to i n f i l t r a t i o n . I f the r i g h t hand s i d e of equation ( 1 ) i s n e g a t i v e , supplemental heat i s r e q u i r e d . The supplemental heat can be p r o v i d e d by the s o l a r h e a t i n g system and/or by the furnace. THERMAL RADIATION HEAT LOSS FROM GREENHOUSE COVER Thermal r a d i a t i o n l o s s from the greenhouse i s a f u n c t i o n of the greenhouse w a l l s temperature, sky temperature and ground temperature. The thermal r a d i a t i o n l o s s from the r o o f o f the greenhouse can be w r i t t e n as Q c = A F .. e a ( T 4 - T 4 , ) + A F a (T^-T 4) . (2) v r a d , r o o f r r+sky r v r sky' r r+g r r g In g e n e r a l , the thermal r a d i a t i o n l o s s from any of the greenhouse w a l l s may be c a l c u l a t e d u s i n g the f o l l o w i n g e q u a t i o n : Q , . = A. e. o[F ^ r a d , i I l i->-sky For v e r t i c a l w a l l s , we have F. . = F. = 0.5 l+sky 1-KJ T h e r e f o r e equation ( 3) reduces t o : Q r a d , i [A, e.a/2] [2T«-T* k y-T<] For the greenhouse r o o f , we have (5) F 1 + COS r->-sky and, cos 6 r+g (6) (7) I n s e r t i n g equations ( 6) and ( 7) i n t o (.2) and s i m p l i f y i n g we o b t a i n , Q c = A e o [ r a d , r o o f r r (8) E v a l u a t i o n of equations ( 5) and ( 8 ) r e q u i r e s the knowledge of the sky and ground temperatures. The e f f e c t i v e sky temperature i s a f u n c t i o n of many m e t e r o l o g i c a l v a r i a b l e s such as water vapour content and a i r temperature. S e v e r a l c o r r e l a t i o n equations between the e f f e c t i v e sky temperature and the m e t e o r o l o g i c a l v a r i a b l e s have been proposed (Brunt (1932), B l i s s (1961)/ Swinbank ( 1963), W h i l l i e r . (1967 ), Morse and Read (1968)).. 1 In t h i s a n a l y s i s Swinbank's c o r r e l a t i o n r e l a t i n g the sky temperature t o the l o c a l environmental temperature i s used, T . = 0.0552 T 1 * 5 ( 9 ) sky a The ground s u r f a c e temperature may be d i f f e r e n t from the l o c a l a i r temperature e s p e c i a l l y d u r i n g low wind speed p e r i o d s . Due to the complexity of p r e d i c t i n g the l o c a l ground s u r f a c e temperature a c c u r a t e l y , i t i s assumed to be equal t o the l o c a l a i r temperature i n t h i s study. CONVECTION HEAT LOSS FROM THE GREENHOUSE COVER The c o n v e c t i v e heat exchange between any s u r f a c e i of the greenhouse and the surroundings i s given by Q . = h .A. (T.-T ) , (10) c o n , i w,i I I a where the average c o n v e c t i v e heat t r a n s f e r c o e f f i c i e n t , h i s r e l a t e d to the wind speed, w McAdams (1954) suggests the f o l l o w i n g r e l a t i o n s h i p f o r the c o n v e c t i v e heat t r a n s f e r c o e f f i c i e n t : h = 20.52 + 13.68 V . (11) w CALCULATION OF THE OUTSIDE SURFACE TEMPERATURE OF THE  ROOF AND THE WALLS OF THE GREENHOUSE The o u t s i d e s u r f a c e temperature of the greenhouse c o v e r i n g m a t e r i a l i s dependent upon the o u t s i d e ambient temperature, the i n s i d e o p e r a t i n g temperature of the greenhouse and r e s i s t a n c e to heat flow o f the cover i t s e l f . T h e r e f o r e , t o determine the o u t s i d e s u r f a c e temperature o f any w a l l , a heat balance about the w a l l i s r e q u i r e d . I f the net r a d i a n t heat exchange between the greenhouse w a l l s and the p l a n t canopy i s n e g l e c t e d and the a b s o r p t i v i t y o f the t r a n s p a r e n t cover to s o l a r r a d i a t i o n i s assumed to be c o n s t a n t and equal to a, then the s o l a r energy absorbed by any s u r f a c e i i s : Q s a , i = a i X s , i ' <12> Then, u s i n g equations ( 8 ) , (10) and (12), the heat balance equation f o r the r o o f becomes, ( A r / R r ) ( T g - T r ) = A r cra [ T 4 - 0.5 (1 + COS 8) T^ k - 0.5 (1 - cos B) T 4 ] + h W / r A r ( T r - T a ) " A r a r X s , r ( 1 3 ) and f o r the w a l l s , from equations ( 5 ), (10) and (12) we get (A./R.)(T -T.) = 0.5 A. e.a (2T 4 - T 4 - T 4) i l g l i i l sky g' + h . A.(T.-T ) - A. a. I . (14) w,i l I a i i s , i Equations (13) and (14) may be w r i t t e n i n terms of the known m e t e o r o l o g i c a l v a r i a b l e s , namely l o c a l a i r temperature and wind speed. Furthermore, the o u t s i d e c o n v e c t i v e heat t r a n s f e r c o e f f i c i e n t s f o r the r o o f and a l l " the other greenhouse w a l l s are assumed to be the same. In r e a l i t y , they depend on the wind d i r e c t i o n w i t h r e s p e c t to the s u r f a c e . Equation (11) assumes the flow i s p a r a l l e l to the f l a t s u r f a c e . In a c t u a l s i t u a t i o n s the wind may approach a s u r f a c e a t any angle. Iqbal and Khatry (1977) s t u d i e d the e f f e c t o f non-uniform flow on the e x t e r n a l heat t r a n s f e r c o e f f i c i e n t u s i n g model greenhouses i n the wind t u n n e l ; t h e i r r e s u l t s i n d i c a t e wind c o e f f i c i e n t v a l u e s h i g h e r than those o b t a i n e d by assuming flow p a r a l l e l t o the f l a t s u r f a c e . Since wind d i r e c t i o n s are seldom known, equation (11) f o r the wind c o e f f i c i e n t i s used f o r the purpose of d e v e l o p i n g the prese n t greenhouse model. I n s e r t i n g equations ( 9) and (11) i n t o (13) and (14) to o b t a i n : _ i (T - t ) = e a [T 4 - 0.5 (1 + cos 6)(0.0552 T 1 ' 5 ) R g r r r a r 0.5 (1 - cos 6) T 4 ] - a I a r s,r + (20.52 + 13.68 V)(T -T ) (15) IT Si and R j ( V T i ) = ~T~ [ 2 T i " ( 0 - 0 5 5 2 T a ' 5 ) 4 ~ T a ] " a i J s , i + (20.52 + 13.68 V) (T.-T ) (16) l a In equations (15) and (16) the ground s u r f a c e temperature i s taken to be equal t o the l o c a l a i r temperature. The o v e r a l l r e s i s t a n c e s t o heat flow R r and may be estimated u s i n g the f o l l o w i n g standard e q u a t i o n s : R^ = (1/f. ) + R (17) r 1 , r c and R i = { 1 / f i , i ] + R c ( 1 8> The i n s i d e s u r f a c e f i l m c o e f f i c i e n t s , f ^ , f o r n o n - r e f l e c t i v e s u r f a c e s are given i n ASHRAE Handbook (1977). The cover r e s i s t a n c e R c depends whether the cover i s s i n g l e or double g l a z e d . Equation (15) with equation (17) and equation (16) with equation (18) may now be s o l v e d f o r the e x t e r n a l s u r f a c e temperatures f o r the greenhouse r o o f and w a l l s . Then the t o t a l heat l o s s from the r o o f i s : Qr = <Ar/Rr) (Tg-V ' ( 1 9 ) and the t o t a l heat l o s s from any w a l l i , i s Q ± = (A ±/R i) (T -T r) . (2,0) The t o t a l ( c o n v e c t i v e p l u s r a d i a t i v e ) heat l o s s from the greenhouse can then be c a l c u l a t e d as f o l l o w s : Q = ^  ( A r / Rr ) (Tg~V + ( A i / R i } (Tg"Ti) ' ( 2 1 ) r=l i=l where m is the number of roof slopes making up the greenhouse roof and n the number of vertical walls for the greenhouse under consideration. CONDUCTION HEAT LOSS FROM THE GREENHOUSE The conduction heat l o s s i n c l u d e s heat t r a n s f e r through the greenhouse perimeter and through the fou n d a t i o n . Here i t i s assumed t h a t the heat l o s s to the greenhouse f l o o r i s i n c l u d e d i n the perimeter heat l o s s . The c o n d u c t i v e heat t r a n s m i s s i o n i s then c a l c u l a t e d as f o l l o w s : Q , = U- A,. (T -T ) + U P (T -T ) . (22) cond f f g a p g a INFILTRATION HEAT LOSS FROM THE GREENHOUSE The air-exchange method used w i t h r e s p e c t t o the gable greenhouse i s employed here. T h e r e f o r e the s e n s i b l e heat l o s s due to i n f i l t r a t i o n / e x f i l t r a t i o n may be estimated u s i n g the f o l l o w i n g e q u a t i o n : The supplemental heat requirement f o r the greenhouse may be c a l c u l a t e d by the use of equation (1) Q. , = (1/v) C V N (T -T ) i n f ' p g a g a (23) SUPPLEMENTAL HEAT REQUIREMENT sup = Q - , - Q - Q . . c - 0 w s o l * v m f ^cond (24) where Q = Q , + Q rad con as d e f i n e d by equation (21). F i n a l l y , the d a i l y h e a t i n g l o a d f o r the greenhouse i s simply: Q , = > Q (26) sup, day / J sup 24 z -hour=l The minus s i g n i n d i c a t e s t h a t o n l y negative v a l u e s are c o n s i d e r e d d u r i n g the summation p r o c e s s . The s o l a r r a d i a t i o n i n p u t to the greenhouse re p r e s e n t e d by Q , i n e q u a t i o n (24) i s t r e a t e d i n the next s e c t i o n of 2 s o l ^ t h i s chapter where an e x p r e s s i o n f o r e s t i m a t i n g the t o t a l s o l a r energy captured by the p l a n t canopy i n s i d e the greenhouse i s d e r i v e d . T h i s e x p r e s s i o n i n i t s s i m p l e s t form may be w r i t t e n as, Q . = I = 1 + 1 . (27) s o l g p w In e q u a t i o n (27), the term I r e p r e s e n t s the t o t a l amount of s o l a r r a d i a t i o n absorbed by the p l a n t canopy. The terms I and I i n d i c a t e t h a t the r a d i a t i o n i s o r i g i n a t i n g from p w the r o o f and the v e r t i c a l w a l l s of the greenhouse r e s p e c t i v e l y . D e t a i l e d e x p r e s s i o n s f o r I and I are g i v e n c p w by equations (49) and (47) r e s p e c t i v e l y . SECTION B CALCULATION OF SOLAR RADIATION CAPTURE BY A SHED-GREENHOUSE AND SOLAR RADIATION INCIDENT ON THE COLLECTOR CALCULATION OF SOLAR RADIATION CAPTURE BY A SHED-GREENHOUSE AND SOLAR RADIATION INCIDENT ON THE COLLECTOR ASSUMPTIONS For t h i s a n a l y s i s the f o l l o w i n g assumptions were made: i . The p l a n t canopy r e f l e c t s d i f f u s e l y r e g a r d l e s s o f whether the o r i g i n a l i n c i d e n t r a d i a t i o n i s beam or d i f f u s e i n nature. i i . M u l t i p l e r e f l e c t i o n between the p l a n t canopy and the greenhouse cover i s n e g l e c t e d . i i i . The r e f l e c t a n c e o f the c o l l e c t o r to the s o l a r r a d i a t i o n i s s m a l l . i v . The c o n t r i b u t i o n o f the east and west end w a l l s o f the greenhouse i s n e g l e c t e d . (L >> W) ESTIMATION OF THE TOTAL SOLAR RADIATION INCIDENT ON THE FLAT  PLATE SOLAR COLLECTOR INSIDE A SHED-TYPE GREENHOUSE The t o t a l s o l a r r a d i a t i o n i n c i d e n t on the c o l l e c t o r i s the sum of the t o t a l s o l a r r a d i a t i o n from the r o o f o f the greenhouse, a f r a c t i o n o f the d i f f u s e r a d i a t i o n r e f l e c t e d by the top of the p l a n t canopy and a f r a c t i o n o f the d i f f u s e r a d i a t i o n from the p l a n t s t h a t i s r e f l e c t e d by the i n n e r s u r f a c e o f the r o o f . Or mathematically, I = I u + I , + 1 + 1 (28) c b,c d,c r,p r , r v z ' where the f i r s t term i n the summation r e p r e s e n t s the beam s o l a r r a d i a t i o n t r a n s m i t t e d through the greenhouse r o o f t h a t i s i n c i d e n t on the s o l a r c o l l e c t o r . T h i s beam r a d i a t i o n may be e stimated by: I, = I, T, A . (2 9) b,c b,v b , r c The second term i s the d i f f u s e s o l a r r a d i a t i o n t r a n s m i t t e d through the greenhouse r o o f t h a t i s i n c i d e n t on the c o l l e c t o r . T h i s d i f f u s e r a d i a t i o n can be estimated from the d i f f u s e s o l a r r a d i a t i o n t r a n s m i t t e d through the r o o f and the c o n f i g u r a t i o n f a c t o r between the r o o f and the c o l l e c t o r , or i n equation form, I , = I , T , A F (30) d,c d,r d,r r r-*c Then the t o t a l s o l a r r a d i a t i o n i n c i d e n t on the c o l l e c t o r n e g l e c t i n g the r e f l e c t e d components i s : I' = I,_ T u A + I , T , A F . (31) c b , v b , r c d , r d , r r r+c ' The l a s t two terms i n equation (28) r e p r e s e n t the f r a c t i o n o f the r e f l e c t e d s o l a r r a d i a t i o n from the top of the p l a n t canopy t h a t i s r e a c h i n g the v e r t i c a l s o l a r c o l l e c t o r . The t h i r d term i n the equation i s the d i f f u s e r a d i a t i o n r e f l e c t e d by the top of the p l a n t canopy t h a t i s d i r e c t l y i n c i d e n t on the c o l l e c t o r . T h i s p o r t i o n o f the d i f f u s e r a d i a t i o n may be expressed as: V.p - e ^  Vc = ?I'p,i aP FP-= ( 3 2 ) F i n a l l y , the f o u r t h term i n equation (28) r e p r e s e n t s the d i f f u s e s o l a r r a d i a t i o n r e f l e c t e d by the top o f the p l a n t canopy and r e a c h i n g the s o l a r c o l l e c t o r i n d i r e c t l y v i a the process of r e f l e c t i o n of the i n n e r s u r f a c e of the greenhouse r o o f . In e quation form, t h i s p o r t i o n of the d i f f u s e r a d i a t i o n may be w r i t t e n as: X r , r = P J p Vr ( 1 " T d , r " a r ) F r + c ' ( 3 3> T h e r e f o r e , the t o t a l s o l a r r a d i a t i o n i n c i d e n t on the c o l l e c t o r with the r e f l e c t e d components i n c l u d e d may be estimated by: I = I' + p I' F + p I' F (1 - x, „ - a ) F _ ^ . (34) c c p p-*c p p->r d,r r r-»-c But, F = (A /A ) F , (35) p+r r' p r-»-p t h e r e f o r e equation (34) becomes: Jc = Zc + p J P [Vc + (VAp) ( 1 - T d , r " V Fr+p Fr->c ] (36) where the second term on the r i g h t hand s i d e of e quation (36) r e p r e s e n t s the t o t a l r e f l e c t e d r a d i a t i o n by the top of the p l a n t canopy t h a t i s r e a c h i n g the s o l a r c o l l e c t o r . The s o l u t i o n of e quation (36) r e q u i r e s the knowledge of the t o t a l s o l a r r a d i a t i o n i n c i d e n t on the top of the p l a n t canopy. T h i s amount of r a d i a t i o n may be e s t imated from the beam and d i f f u s e components o f s o l a r r a d i a t i o n t r a n s m i t t e d through the r o o f of the greenhouse as f o l l o w s : i . Beam r a d i a t i o n i n c i d e n t on t h e t o p o f t h e p l a n t c a n o p y : b, p b, n b, r p i i . D i f f u s e r a d i a t i o n i n c i d e n t on t h e t o p o f t h e p l a n t c a n o p y : I = I j T j A F . (38) d,p d , r d, r r r->-p Then t h e t o t a l s o l a r r a d i a t i o n i n c i d e n t on t h e t o p o f t h e p l a n t c a n o p y i s : I' = I, , T W A + I , T , A F . (39) p b,h b , r p d , r d , r r r->-p C o m b i n i n g e q u a t i o n s (31), (36) and (39) t o g e t t h e t o t a l s o l a r r a d i a t i o n r e a c h i n g t h e c o l l e c t o r 1 = 1 , T, A + I , T , A F + p [I, , T, „ A c b , v b , r c d , r d , r r r+c K b,h b , r p + I , T , A F ] [F + (A /A ) (1 - T , - a ) d , r d , r r r+p p+c r ' p d , r r F F ] (40) r-*p r->-c F o r c o m p a r i n g g r e e n h o u s e s o f d i f f e r e n t r o o f s l o p e s and l o c a t i o n s , t h e s o l a r r a d i a t i o n i n c i d e n t on a u n i t c o l l e c t o r a r e a i s n e e d e d . T h e r e f o r e , e q u a t i o n (40) may be r e w r i t t e n a s a f u n c t i o n o f t h e r o o f s l o p e as f o l l o w s : ^ , 1 = J b , v T b , r + J d , r T d , r F r + c c o s e c B + P [ I b , h T b , r c o t B + X d , r T d , r F r + P c o s e c B ] [ F P + c + d " ^ d , r "  ar ] F F s e c 81 • ( 4 1 ) r+p r-+c ESTIMATION OF THE TOTAL SOLAR RADIATION CAPTURED BY THE  PLANT CANOPY For a long east-west o r i e n t e d shed-type greenhouse, the c o n t r i b u t i o n of the e a s t and west w a l l to s o l a r r a d i a t i o n i n p u t may be n e g l e c t e d . T h e r e f o r e , the t o t a l s o l a r energy in p u t to the greenhouse i s through the t r a n s p a r e n t s u r f a c e s of the south r o o f and the v e r t i c a l south f a c i n g w a l l . The s o l a r energy capture of the greenhouse depends upon the p l a n t albedo and the type of the greenhouse c o v e r i n g m a t e r i a l . The t o t a l s o l a r r a d i a t i o n captured by the top of the p l a n t canopy may be estimated from equation (39) as f o l l o w s : I p = I- (1 - p) + p I' F p ^ r (1 - x d / r - a r) F ^ p (1 - p ) . (42) Then u s i n g equation (35) f o r F ^ i n t o equation (42) we get: I p = I' (1 - p) t l + p ( l - x ^ r - a r) (A r/A p) F ^ p ] . (43) The c o n t r i b u t i o n of the v e r t i c a l t r a n s p a r e n t south w a l l to the t o t a l s o l a r energy capture of the greenhouse may be c a l c u l a t e d from the beam and d i f f u s e s o l a r r a d i a t i o n i n c i d e n t on the w a l l as f o l l o w s : For the beam component of r a d i a t i o n we have: I. =1, T. A , (44) b,w b,v b,w w and f o r the d i f f u s e component, we have: I , = I , T , A . (45) d,w d,v d,w w j T h e r e f o r e , the t o t a l s o l a r r a d i a t i o n t r a n s m i t t e d through the south w a l l t h a t i s captured by the p l a n t canopy i s : Xw = ( Ib,w + Id,w ) ( 1 - P> [ 1 + P ( 1 - Td,w " *w)] • ( 4 6 ) o r , I = (I. T. + 1 , T , ) A (1 - p) [1 + p ( l - x, „ - « ) ] w b,v b,w d,v d,w w K p d,w w^ (47) T h e r e f o r e , the t o t a l s o l a r energy captured by the p l a n t canopy i n s i d e the greenhouse may be e s t i m a t e d from equations (43) and (4.7) . 1 = 1 + 1 (48) g p w Due to the albedo of the p l a n t canopy, a p o r t i o n of the i n c i d e n t r a d i a t i o n i s r e f l e c t e d , then l o s t through the greenhouse r o o f . Equations (39) and (4 3) may be combined to g i v e the t o t a l s o l a r energy captured by the top of a p l a n t canopy having a s u r f a c e area A and an albedo p. I = ( I , , T j A + I , T , A F ) (1 - p) p b,h d,r p d,r d,r r r-vp H [1 + p ( l - T . - a ) (A /A ) F 2 ] . (49) L y d,r r r p r^-p When expressed per u n i t p l a n t f l o o r area, we get: I , = (1^ , x, + I , i j F sec g) (1 - p) p , l v b,h b,r d,r d,r r^-p M w [1 + p ( l - T , - a ) F 2 sec 6] . (50) d,r r r^-p Equation (39) gi v e s the t o t a l s o l a r r a d i a t i o n i n c i d e n t on the top of the whole p l a n t canopy. L i k e w i s e , t h i s i n c i d e n t s o l a r energy may be expressed i n terms o f u n i t greenhouse f l o o r a rea, as: I' = I, , x, + I, T , F sec B • (51) p , l b,h b,r d,r L d , r r+p The c o n t r i b u t i o n o f the south w a l l may a l s o be expressed i n terms o f u n i t area of p l a n t canopy by s u b s t i t u t i n g (H/W) f o r i n equation (47). Thus, X w , l = ( I b , v Tb,w + *d,v T d , w ) ( H / W ) ( 1 - p ) [1 + p ( l - x d / W - a j ] . (52) EFFICIENCY OF SOLAR CAPTURE BY THE GREENHOUSE PLANT CANOPY The p l a n t canopy w i t h i n a greenhouse may be t r e a t e d as a pa s s i v e s o l a r c o l l e c t i o n system. The e f f i c i e n c y o f s o l a r c o l l e c t i o n i s the r a t i o o f the t o t a l s o l a r energy captured t o the t o t a l s o l a r r a d i a t i o n i n c i d e n t on a h o r i z o n t a l s u r f a c e o u t s i d e the greenhouse. T h i s e f f i c i e n c y can be estimated from equations (50) and (52) as: E = (I , + I n ) / ( I K > + I , u> ( 5 3> p , l w,l b,h d,n or E = <1/Ih> [ ( I b , h T b , r + X d , r T d , r Fr+p + I , T , F sec B) (1 - P) r d . r d . r r+D (1 + p ( l - T d f r - ar> F ^ p sec B) + d b / V T F A F + Jd,v Td,w) ( H / W ) ( 1 " p ) U + p ( 1 " Td,w " aw ) } ] ( 5 4 ) T, , T , , x, , T , , a and a are o p t i c a l p r o p e r t i e s of b , r ' d , r' b,w' d,w' r w c the t r a n s p a r e n t c o v e r i n g m a t e r i a l . p i s an o p t i c a l p r o p e r t y of the p l a n t canopy, and H, W, F and 6 are greenhouse c o n s t r u c t i o n parameters. IT p The l e n g t h o f the greenhouse does not appear e x p l i c i t l y i n the equations but i t s e f f e c t i s i n c l u d e d i n the de t e r m i n a t i o n of the c o n f i g u r a t i o n f a c t o r s as shown i n Appendix D. USEFUL ENERGY GAIN OF THE SOLAR COLLECTOR The e f f e c t s of the type and e f f i c i e n c y of the s o l a r c o l l e c t o r and the thermal energy storage upon the o v e r a l l greenhouse system i s o u t s i d e the scope of t h i s study, s i n c e the p r e s e n t work i s intended o n l y as a f e a s i b i l i t y study to i n v e s t i g a t e the e f f e c t of changing the shape of the greenhouse on i t s heat l o s s and i t s s o l a r energy i n p u t . Only the s o l a r r a d i a t i o n i n c i d e n t on the i n t e g r a l c o l l e c t o r and the estimated p o r t i o n t h a t i s a v a i l a b l e f o r immediate use or storage i s p r e d i c t e d . The t o t a l s o l a r r a d i a t i o n i n c i d e n t on a f l a t p l a t e c o l l e c t o r l o c a t e d a t the upper p o r t i o n of the i n n e r s i d e of the nor t h w a l l of the shed-type greenhouse i s d e r i v e d p r e v i o u s l y , and the f i n a l r e s u l t of the d e r i v a t i o n i s giv e n by equation (40). The remainder of t h i s s e c t i o n w i l l be devoted to f i n d i n g an approximate method f o r determining the amount of s o l a r energy a v a i l a b l e from the i n t e g r a l c o l l e c t o r . The maximum s o l a r energy c o l l e c t a b l e may be approximated by the f o l l o w i n g e x p r e s s i o n : Q , = Q , - Q. (55) c o l abs w l o s s Since the s o l a r c o l l e c t o r i s l o c a t e d i n s i d e the greenhouse and a i r i s f o r c e d on both s i d e s o f the absorber p l a t e , the heat l o s s from the c o l l e c t o r i s t h e r e f o r e c o n s i d e r e d mainly by thermal r a d i a t i o n to the greenhouse cover. Thus, equation (55) may be w r i t t e n as: Q , = A a I - { a (T 4 - T 4 ) / C ( l - £ )/£ A + (1/A F ) v c o l c c c c r'/ * c ' c c ' r r+c + (1 - e )/£ A J" } . (56) r r r where the two e x p r e s s i o n s on the r i g h t hand s i d e of equation (56) r e p r e s e n t the s o l a r r a d i a t i o n absorbed by the c o l l e c t o r and the thermal r a d i a t i o n heat l o s s . The r o o f temperature of the greenhouse, T , can be determined by the use of equations (15) and (17). The s o l a r r a d i a t i o n i n c i d e n t on the c o l l e c t o r , I c , can be c a l c u l a t e d u s i n g e q u a t i o n (41). The constants a c and £ c are the a b s o r p t i v i t y f o r s o l a r r a d i a t i o n and the e m i s s i v i t y f o r i n f r a - r e d r a d i a t i o n of the absorber p l a t e , r e s p e c t i v e l y ; and, e i s the e m i s s i v i t y of the greenhouse roof m a t e r i a l t o thermal r a d i a t i o n . The s o l u t i o n of equation (56) r e q u i r e s the knowledge of the average p l a t e temperature, T . As a f i r s t approximation, i t may be taken as a c o n s t a n t . Thus, l e t T = T + AT , (57) c g,mm where T i s a s e l e c t e d minimum greenhouse temperature, g ,mm u s u a l l y taken as the d e s i r e d n i g h t time i n s i d e a i r temperature and AT i s some s e l e c t e d temperature d i f f e r e n c e between the o p e r a t i n g c o l l e c t o r p l a t e temperature and the d e s i r e d minimum a l l o w a b l e greenhouse temperature. In order to minimize the heat l o s s from the c o l l e c t o r AT should be kept as sma l l as p o s s i b l e , s i n c e as can be seen i n equation (56) the thermal r a d i a t i o n heat exchange between the c o l l e c t o r p l a t e and the greenhouse r o o f i s a f u n c t i o n of the average p l a t e temperature r a i s e d to the f o u r t h power. The s e l e c t i o n of AT i s dependent upon the minimum u s e f u l temperature of the energy s t o r e d , and upon the energy consumed by the fans f o r s o l a r energy c o l l e c t i o n and s t o r a g e . A c o n s t a n t absorber p l a t e temperature i m p l i e s a v a r i a b l e mass flow r a t e of the t r a n s p o r t f l u i d i n the c o l l e c t o r . For the case of a constant mass flow r a t e system, a complete energy balance about the c o l l e c t o r i s r e q u i r e d to determine the p l a t e temperature.* T h e r e f o r e , equation (56) i s v a l i d o n l y f o r the case of constant p l a t e temperature. I f i t i s d e s i r e d to determine the e f f e c t of the type of the c o l l e c t o r and/or the type and s i z e o f the thermal energy storage; then mathematical models of these s p e c i f i c components must be i n c o r p o r a t e d w i t h i n the system as needed. In most a p p l i c a t i o n s , d a i l y v a l u e s of energy * The reader i s r e f e r r e d t o Appendix L f o r the d e t a i l e d a n a l y s i s of t h i s case. flows are d e s i r e d , then the d a i l y maximum s o l a r energy c o l l e c t a b l e i s simply: u ss Q n , = >^ Q + . . (58) w c o l , d a y / j w c o l s r The p l u s s i g n i n the above e q u a t i o n i n d i c a t e s t h a t o n l y p o s i t i v e v a l u e s of Q c o^ are c o n s i d e r e d d u r i n g the summation p r o c e s s . CALCULATION OF DIFFUSE RADIATION CONFIGURATION FACTORS C o n f i g u r a t i o n f a c t o r s f o r d i f f u s e r a d i a t i o n between the r o o f and s o l a r c o l l e c t o r , the p l a n t canopy and the c o l l e c t o r and the r o o f and p l a n t canopy are r e q u i r e d f o r e s t i m a t i n g the t o t a l s o l a r r a d i a t i o n i n c i d e n t on the i n t e g r a l c o l l e c t o r of a s o l a r - s h e d greenhouse as i n d i c a t e d by equation (40). Furthermore, the above c o n f i g u r a t i o n f a c t o r s are a l s o needed f o r determining the t o t a l s o l a r r a d i a t i o n i n c i d e n t on the p l a n t canopy w i t h i n the greenhouse as r e p r e s e n t e d by equation (49), as w e l l as, f o r c a l c u l a t i n g the r a d i a t i v e heat l o s s by the i n t e g r a l s o l a r c o l l e c t o r as g i v e n by e q u a t i o n (56). These f a c t o r s were c a l c u l a t e d u s i n g F e i n g o l d ' s equation g i v e n i n F i g u r e 2.2. The r e s u l t s are r e p r e s e n t e d i n g r a p h i c a l form, i n F i g u r e 6.2 to F i g u r e 6.4 f o r a s o l a r - s h e d greenhouse with a range of l e n g t h s from 10 to 100 metres and f o r widths 5, 7.5 and 10 metres. The r e q u i r e d three c o n f i g u r a t i o n f a c t o r s as a f u n c t i o n of l e n g t h and width o f a s o l a r - s h e d greenhouse having a r o o f slope of 20 degrees are shown i n F i g u r e 6.2. The roof slope i s the angle measured from the h o r i z o n t a l a t the south v e r t i c a l w a l l of the greenhouse as i n d i c a t e d i n F i g u r e 6.1. C o n f i g u r a t i o n f a c t o r s f o r s o l a r - s h e d greenhouses having roof s l o p e s of 30° and 45° are shown i n F i g u r e s 6.3 and 6.4, r e s p e c t i v e l y . I t i s c l e a r l y seen from the curves f o r c o n f i g u r a t i o n f a c t o r s versus l e n g t h t h a t f o r long s o l a r - s h e d greenhouses (> 70 m), the e f f e c t s of both l e n g t h and width on the r a d i a t i o n c o n f i g u r a t i o n f a c t o r s become n e g l i g i b l e . T h i s i s due t o the f a c t t h a t a t l a r g e greenhouse l e n g t h s , the edge e f f e c t s (end w a l l s ) become smal l r e l a t i v e to t o t a l r a d i a t i o n exchange among oth e r s u r f a c e s of the greenhouse. Thus, i n such a case, the c o n f i g u r a t i o n f a c t o r s may be taken as con s t a n t s without s i g n i f i c a n t s a c r i f i c e i n the accuracy of the analyses f i n a l r e s u l t s . Examination of F i g u r e s 6.2, 6.3 and 6.4 r e v e a l s the importance of the r o o f s l o p e on the d i f f u s e r a d i a t i o n exchange between p l a n t canopy, i n t e g r a l c o l l e c t o r and greenhouse r o o f . An i n c r e a s e i n the roof slope of a s o l a r - s h e d greenhouse decreases the amount of d i f f u s e r a d i a t i o n o r i g i n a t i n g from the r o o f t h a t would be i n t e r c e p t e d by the p l a n t canopy. For example, the value of F r _ p i s 0.19 f o r a greenhouse having dimensions of 100 m by 7.5 m and 20° roof s l o p e . T h i s value i s reduced to 0.675 and 0.49 when the ro o f slope i s i n c r e a s e d to 30° and 45°, r e s p e c t i v e l y . On the other hand, the amount o f d i f f u s e r a d i a t i o n i n c i d e n t on the i n t e g r a l c o l l e c t o r i s i n c r e a s e d f o r steeper r o o f s l o p e s ; so does, the r a d i a t i v e heat l o s s by the c o l l e c t o r to the r o o f , s i n c e t h i s l o s s i s d i r e c t l y p r o p o r t i o n a l to the value o f F wh i l e i n t u r n t h i s value i s r e l a t e d to t h a t of c - r F r _ c by the f o l l o w i n g r e l a t i o n , A F = A F . (59) r r - c c c - r o Tl cn o f > 50 i cn EC w D o 50 w M EC o C cn w cn EC > < M Z o cn f O M O O W 50 W M cn G M M O •3 O *d tr1 M Z H3 EC s: M D EC •-3 EC M O M > i-3 H O z •-3 M o z > n H3 o 50 cn AND PLANT CANOPY AND COLLECTOR ( F p r - c X p - c 00 1Q2); 102) X ^ 50 M Z * EC O G cn w z o »-3 EC M Z O) a w o w 50 w cn CONFIGURATION FACTORS BETWEEN ROOF AND PLANT CANOPY ( F r _ D x 102) 9SZ COLLECTOR ( F p _ c x 102) O 50 CO o > 50 I w a M o a 50 M w a a o G W cn a > H a 50 o o Tl F o w o u> o O W 50 w M H CI G 50 W CTl W *1 *d W n >-3 o F M a o a o •a a o a a w > M o a o o a *j H o G O a > n ••3 o M Z a o G a F W a o •-3 a H a a M o M •3 50 W CONFIGURATION FACTORS BETWEEN ROOF AND PLANT CANOPY ( F r _ p x 102) BETWEEf\ CONFIGURATION FACTORS PLANT CANOPY AND COLLECTOR (F„_ D-C 102) *1 w o •n so w cn n O > o so 1 z cn f EC w M z so O o M •-3 M O EC z SO EC W > o M Z G Z o cn EC w O C H f cn o M M Z cn EC Q t-3 EC O EC > z < M H Z Z EC a W D W > (?• o so > o AM o H W o > i-3 *i •-3 so M M cn O cn f Z o 13 o M o z o M o G D ?» ••3 tn M o o » z w M cn > • o cn CONFIGURATION FACTORS BETWEEN ROOF AND PLANT CANOPY ( F r _ p x 102); AND ROOF AND COLLECTOR ( F r _ c x 102) SECTION C CASE STUDY IV SUPPLEMENTAL HEATING REQUIREMENTS OF A SOLAR-SHED GREENHOUSE CASE STUDY IV: SUPPLEMENTAL HEATING REQUIREMENTS  OF A SOLAR-SHED GREENHOUSE DESCRIPTION AND ASSUMPTIONS The mathematical model developed i n s e c t i o n s A and B of t h i s chapter was s o l v e d u s i n g a d i g i t a l computer to determine the h o u r l y t r a n s m i s s i o n l o s s , i n f i l t r a t i o n l o s s and the p a s s i v e s o l a r energy capture by the shed-type greenhouse. Then, the h o u r l y supplemental heat requirement as w e l l as the h o u r l y and d a i l y s o l a r energy c o l l e c t a b l e by a s o l a r c o l l e c t o r p l a c e d on the n o r t h w a l l i n s i d e the greenhouse were c a l c u l a t e d . F i n a l l y the monthly average d a i l y f r a c t i o n s of the supplemental heat requirement of the greenhouse t h a t c o u l d be s u p p l i e d by the i n t e g r a l s o l a r c o l l e c t o r were esti m a t e d . Throughout the time of the s i m u l a t i o n the f o l l o w i n g are assumed t o remain c o n s t a n t : i ) the minimum greenhouse temperature, i i ) the i n f i l t r a t i o n / e x f i l t r a t i o n r a t e , and i i i ) the albedo of the p l a n t canopy w i t h i n the greenhouse. The s o l a r - s h e d greenhouse used i n t h i s case study has a l e n g t h o f 100 metres and a width of 10 metres. The long a x i s of the greenhouse i s east-west o r i e n t e d . The r o o f i s f a c i n g south and t i l t e d a t an angle of 30 degrees from the h o r i z o n t a l . An i n t e g r a l s o l a r c o l l e c t o r , having a s u r f a c e area of 577 square metres, i s i n s t a l l e d on the i n n e r s u r f a c e of the v e r t i c a l n o r t h w a l l of the shed greenhouse. The nor t h w a l l , the f o o t i n g and the perimeter of the greenhouse are i n s u l a t e d . The greenhouse i s covered with a s i n g l e l a y e r of g l a s s having a t h i c k n e s s of 3 m i l l i m e t r e s . Other p r o p e r t i e s o f the c o n s t r u c t i o n m a t e r i a l s as w e l l as the other p e r t i n e n t c o n s t r u c t i o n and management parameters are d e t a i l e d i n Table 6.1. RESULTS AND DISCUSSION A sample computer s i m u l a t i o n output f o r the s o l a r - s h e d greenhouse d e s c r i b e d above and l o c a t e d i n the Vancouver, B.C. area i s i n c l u d e d i n Appendix I (Tables 1.1 to 1.12). The h o u r l y and d a i l y v a l u e s shown i n these t a b l e s are f o r a t y p i c a l day of each month of the year. The i n f o r m a t i o n i n the t a b l e s i n c l u d e s the p a s s i v e s o l a r r a d i a t i o n capture by the p l a n t canopy, the i n f i l t r a t i o n heat l o s s , the t r a n s m i s s i o n ( c o n v e c t i o n , c o n d u c t i o n and r a d i a t i o n ) heat l o s s , the supplemental heat requirement ( e x c l u d i n g the a c t i v e s o l a r energy c o n t r i b u t i o n ) and the s o l a r energy c o l l e c t a b l e by the i n t e g r a l c o l l e c t o r . A summary of the r e s u l t s of Appendix I i s shown, on a monthly b a s i s , i n Table 6.2. I t i s important to n o t i c e t h a t the s o l a r i n p u t and s o l a r c o n t r i b u t i o n as i n d i c a t e d i n t h i s t a b l e are due to p a s s i v e s o l a r r a d i a t i o n c o l l e c t i o n o n l y ; t h a t i s , the s o l a r energy captured by the p l a n t canopy. T h e r e f o r e , the valu e s i n Table 6.2 f o r the shed-type greenhouse are d i r e c t l y comparable to those i n Table 4.2 f o r the gable greenhouse (Case Study I I ) . By comparison between the r e s u l t s i n these t a b l e s , i t can be VARIABLES USED TO CALCULATE HEATING DEMANDS  OF A SOLAR-SHED GREENHOUSE C o n s t r u c t i o n Parameters Length: Width: 100 m 10 m Height: 2 m Roof Slope: 30° O r i e n t a t i o n : East-West Long A x i s C o n s t r u c t i o n M a t e r i a l s P r o p e r t i e s Surface M a t e r i a l Area U (m2) (Wm~2K-1) South Roof South Wall North Wall East Wall West Wall F o o t i n g S i n g l e G l a s s S i n g l e G l a s s I n s u l a t e d S i n g l e G l a s s S i n g l e G l a s s I n s u l a t e d 1155 200 777 49 49 110 8.83 8.03 0.25 8. 03 8.03 0.67 0.08 0.08 0.20 0.08 0.08 0.94 0.94 0.94 0.94 0.94 Perimeter I n s u l a t e d 220 (m) 0.67 (Wm-lK - 1) — — 0.3 cm 0.252 cm" 1 i r o n G l a s s P r o p e r t i e s T h i c k n e s s : E x t r a c t i o n C o e f f i c i e n t : R e f r a c t i o n Index: A b s o r p t i v i t y t o S o l a r R a d i a t i o n : E m i s s i v i t y f o r Thermal R a d i a t i o n : Management Parameters L o c a t i o n : Minimum Greenhouse Temperature: I n f i l t r a t i o n Rate: P l a n t Canopy Albedo: 1.5260.08 0.94 Vancouver, B.C. Mon t r e a l , P.Q. H a l i f a x , N. S. 15°C 1.5 A i r changes per hour 0.1 s MONTHLY AVERAGE HEAT LOSS, SOLAR ENERGY INPUT, SOLAR  CONTRIBUTION AND HEATING LOAD IN MJ PER m 2 OF  GREENHOUSE FLOOR AREA AND PERCENT OF THE HEAT LOSS  SUPPLIED BY SOLAR FOR THE SHED GREENHOUSE OF  CASE STUDY IV (MINIMUM INSIDE TEMPERATURE = 15°C) VANCOUVER, B.C. Month Heat S o l a r S o l a r Heating Percent Loss Input* C o n t r i b u t i o n * * Load S o l a r * * January 492 172 116 376 24 February 387 210 108 279 28 March 407 334 134 273 33 A p r i l 277 345 97 180 35 May 161 393 52 109 32 June 81 442 23 58 28 J u l y 44- 432 8 36 18 August 33 429 5 28 15 September 83 340 11 72 13 October 244 261 66 178 27 November 361 146 85 276 24 December 477 122 99 378 21 YEAR 3047 3626 804 2243 26 * S o l a r input i s the s o l a r r a d i a t i o n captured by the plant canopy only and does not i n c l u d e s o l a r r a d i a t i o n i n c i d e n t on the i n t e g r a l c o l l e c t o r . seen t h a t the monthly average heat l o s s from the shed greenhouse i s h i g h e r than t h a t from the gable greenhouse, due to the l a r g e r o v e r a l l heat t r a n s f e r c o e f f i c i e n t of the shed s t r u c t u r e as compared to the gable type. On an annual b a s i s , the heat l o s s from the gable greenhouse i s 2818 megajoules per square metre of f l o o r area w h i l e f o r the shed-type the annual heat l o s s i s estimated a t 3047 megajoules per square metre; or, an i n c r e a s e i n annual heat l o s s of s i x p e r c e n t . Coupled with the i n c r e a s e i n the heat l o s s , the s o l a r r a d i a t i o n captured by the p l a n t canopy i n the shed-type greenhouse i s a l s o reduced from an annual v a l u e of 4104 megajoules per square metre to 3626 megajoules per square metre, r e p r e s e n t i n g a r e d u c t i o n i n the order of twelve p e r c e n t . However, the s o l a r c o n t r i b u t i o n or the s o l a r energy p a s s i v e l y u t i l i z e d t o compensate f o r the heat l o s s remained v i r t u a l l y the same at about 800 megajoules per square metre per year. The reason t h a t the s o l a r c o n t r i b u t i o n remained unchanged i s t h a t more s o l a r r a d i a t i o n i s i n c i d e n t upon and captured by the p l a n t canopy i n the gable greenhouse than i n the shed-type d u r i n g the warm p e r i o d s o f the year w h i l e i t i s not needed f o r h e a t i n g purposes. T h e r e f o r e , i t can be concluded t h a t the shed-type r e q u i r e s l e s s v e n t i l a t i o n than the gable-type greenhouse p r o v i d e d the s o l a r c o l l e c t o r i s covered or r e p l a c e d by a r e f l e c t i v e m a t e r i a l d u r i n g the summer months to a l l o w some of the s o l a r r a d i a t i o n i n c i d e n t upon the i n n e r s u r f a c e of the n o r t h w a l l t o escape through the south r o o f of the greenhouse. S i n c e , the p a s s i v e s o l a r c o n t r i b u t i o n has not been improved i n the shed-type greenhouse w h i l e i t s heat l o s s has i n c r e a s e d , then i t s h e a t i n g l o a d requirement i s i n c r e a s e d over the gable greenhouse. From Tables 6.2 and 4.2, t h i s i n c r e a s e can be c a l c u l a t e d as 167 megajoules per square metre a n n u a l l y or about e i g h t p e r c e n t . T h e r e f o r e , i t remains to be seen i f the i n t e g r a l s o l a r c o l l e c t o r within, the shed greenhouse can p r o v i d e enough heat to o f f s e t the i n c r e a s e d heat l o s s and r e s u l t i n a s i g n i f i c a n t net energy s a v i n g . The c o n t r i b u t i o n of the i n t e g r a l s o l a r c o l l e c t o r w i l l be i n v e s t i g a t e d l a t e r i n t h i s s e c t i o n . The e f f e c t of c l i m a t i c c o n d i t i o n s on the h e a t i n g l o a d of the shed-type greenhouse i s examined by performing analyses on an i d e n t i c a l greenhouse u s i n g Montreal then H a l i f a x weather data. Summaries of the r e s u l t s f o r the two a d d i t i o n a l l o c a t i o n s i n Canada are shown i n Tables 6.3 and 6.4 f o r Montreal and H a l i f a x , r e s p e c t i v e l y . Again, these t a b l e s are d i r e c t l y comparable to those o b t a i n e d f o r the gable greenhouse case (Tables 4.3 and 4.4). Comparison of Table 6.3 to Table 4.3 f o r Montreal r e v e a l s the f o l l o w i n g p o i n t s : i ) The annual average heat l o s s f o r the shed-type i s found to be 4550 megajoules per square metre as compared to 4275 megajoules per square metre f o r the gable-type greenhouse or approximately s i x percent i n c r e a s e . MONTHLY AVERAGE HEAT LOSS, SOLAR ENERGY INPUT, SOLAR CONTRIBUTION AND HEATING LOAD IN MJ PER m 2 OF GREENHOUSE FLOOR AREA AND PERCENT OF THE HEAT LOSS SUPPLIED BY SOLAR FOR THE SHED GREENHOUSE OF CASE STUDY IV (MINIMUM INSIDE TEMPERATURE = 15°C) MONTREAL, P.Q. Month Heat Loss S o l a r Input* S o l a r C o n t r i b u t i o n * * Heating Load Percent S o l a r * * January 968 153 153 815 16 February 799 198 189 610 24 March 648 323 204 444 32 A p r i l 361 339 126 235 35 May 89 391 16 73 18 June 5 440 1 4 20 J u l y 0 429 0 0 0 August 0 424 0 0 0 September 49 332 5 44 10 October 272 247 67 205 25 November 495 134 114 381 23 December 864 108 108 756 13 YEAR 4550 3518 983 3567 22 S o l a r input t i s the le s o l a r r a d i a t i o n captured by the p l a n t canopy only and does not i n c l u d e s o l a r r a d i a t i o n i n c i d e n t on the i n t e g r a l c o l l e c t o r . i i ) The p l a n t canopy i n the shed-type greenhouse has captured 3518 megajoules per square metre per year on the average compared to 4045 megajoules per square metre f o r the p l a n t canopy i n the gable-type. T h i s r e p r e s e n t s an annual r e d u c t i o n i n s o l a r r a d i a t i o n capture by the p l a n t canopy i n the order of t h i r t e e n p e r c e n t . i i i ) The p a s s i v e s o l a r c o n t r i b u t i o n t o the heat l o s s i s three p e r c e n t lower f o r the shed-type when compared to the gable-type greenhouse, i v ) When the energy c o n t r i b u t i o n from the i n t e g r a l s o l a r c o l l e c t o r i s n e g l e c t e d , the shed-type greenhouse r e q u i r e s nine percent more heat than the gable-type on an annual b a s i s . Comparison of H a l i f a x r e s u l t s f o r the shed-type greenhouse (Table 6.4) and the gable-type greenhouse (Table 4.4) leads t o s i m i l a r c o n c l u s i o n s as those o b t a i n e d w i t h Montreal and Vancouver weather data when the valu e s are expressed on a percentage b a s i s . The performance of the i n t e g r a l s o l a r c o l l e c t o r expressed as the monthly average f r a c t i o n of the greenhouse h e a t i n g l o a d s u p p l i e d by s o l a r i s shown i n Table 6.5 f o r the three l o c a t i o n s under study. The c o n s t r u c t i o n as w e l l as the management parameters of the s o l a r - s h e d greenhouse are i d e n t i c a l f o r the three l o c a t i o n s . The i n t e g r a l s o l a r c o l l e c t o r , having a s u r f a c e MONTHLY AVERAGE HEAT LOSS, SOLAR ENERGY INPUT, SOLAR CONTRIBUTION AND HEATING LOAD IN MJ PER m 2 OF GREENHOUSE FLOOR AREA AND PERCENT OF THE HEAT LOSS SUPPLIED BY SOLAR FOR THE SHED GREENHOUSE OF CASE STUDY IV (MINIMUM INSIDE TEMPERATURE = 15°C) HALIFAX, N.S. Month Heat Loss S o l a r Input* S o l a r C o n t r i b u t i o n Heating ** Load Percent S o l a r * * January 684 150 140 544 21 February 627 195 159 468 25 March 572 321 181 391 32 A p r i l 390 338 135 255 35 May 228 390 71 157 31 June 97 439 21 76 22 J u l y 32 428 4 28 13 August 25 423 3 22 11 September 72 330 8 64 11 October 218 245 48 170 22 November 37 9 132 85 294 22 December 606 106 106 500 17 YEAR 3930 3497 961 2969 25 * S o l a r input i s the s o l a r r a d i a t i o n captured by the p l a n t canopy only and does not i n c l u d e s o l a r r a d i a t i o n i n c i d e n t on the i n t e g r a l c o l l e c t o r . area of 577 square metres, i s i n s t a l l e d on the i n n e r s u r f a c e o f the v e r t i c a l n o r t h w a l l o f a s o l a r shed greenhouse having 1000 square metres of f l o o r a r ea. A i r i s f o r c e d over both s i d e s o f the absorber p l a t e a t a flow r a t e t o keep i t s average temperature a t 35°C. The o p t i c a l p r o p e r t i e s o f the absorber p l a t e are assumed to have equal a b s o r p t i v i t y t o s o l a r r a d i a t i o n and e m i s s i v i t y f o r i n f r a - r e d r a d i a t i o n o f 0.9. Examination of the r e s u l t s i n Table 6.5 i n d i c a t e s t h a t d u r i n g the w i n t e r months the s o l a r c o l l e c t o r c o n t r i b u t i o n i s s i g n i f i c a n t l y h i g h e r f o r Vancouver than f o r Montreal or H a l i f a x . For example, i n January f o r Vancouver, the s o l a r c o l l e c t o r c o n t r i b u t i o n i s 97 megajoules per square metre o f greenhouse f l o o r area w h i l e f o r Montreal and H a l i f a x , i t i s o n l y 50 megajoules per square metre. The h i g h c o n t r i b u t i o n f o r Vancouver co u l d be a t t r i b u t e d to the f a c t t h a t v e r t i c a l c o l l e c t o r s r e c e i v e more r a d i a t i o n a t hi g h e r l a t i t u d e s d u r i n g the w i n t e r p e r i o d . The low s o l a r energy c o l l e c t i o n by the i n t e g r a l c o l l e c t o r f o r Montreal and H a l i f a x , coupled w i t h r e l a t i v e l y h i g h greenhouse h e a t i n g loads d u r i n g the c o l d p e r i o d o f the year, r e s u l t e d i n a very s m a l l s o l a r f r a c t i o n f o r the months from November to F e b r u a r y ^ i n c l u s i v e . These f r a c t i o n s ranged from as low as 4 per c e n t i n Montreal f o r December to 14 perc e n t i n H a l i f a x f o r November compared to Vancouver which shows a low of 17 per c e n t f o r December to 32 per c e n t i n MONTHLY AVERAGE HEATING LOAD AND SOLAR ENERGY SUPPLIED BY THE INTEGRAL COLLECTOR IN MJ PER m FLOOR AREA AS WELL AS THE SOLAR FRACTIONS FOR THE SOLAR-SHED GREENHOUSE OF CASE STUDY IV L o c a t i o n Vancouver, B.C. M o n t r e a l , Quebec H a l i f a x , N.S. Month Heating Load S o l a r C o n t r . S o l a r F r a c t i o n Heating Load S o l a r Contr. S o l a r F r a c t i o n Heating Load S o l a r C o n t r . S o l a r F r a c t i o n January 376 97 0.26 815 50 0.06 544 51 0.09 February 279 89 0. 32 610 54 0 .09 468 55 0.12 March 273 108 0.39 444 82 0.19 391 82 0.21 A p r i l 180 72 0.40 235 62 0.26 255 59 0.23 May 109 64 0.59 74 64 0.87 157 55 0.35 June 58 58 1.00 4 4 1.00 76 61 0.80 J u l y 36 36 1.00 0 - - 28 28 1.00 August 28 28 1.00 0 - - 22 22 1.00 September 72 72 1.00 44 44 1.00 64 64 1.00 October 178 112 0.63 205 88 0.43 170 85 0.50 November 276 69 0.25 381 42 0.11 294 42 0.14 December 378 65 0.17 756 27 0.04 500 29 0.06 Year 2243 870 0.39 3567 517 0.14 2969 633 0.21 minimum greenhouse temperature 15°C. average c o l l e c t o r temperature 35°C. a b s o r p t i v i t y o f c o l l e c t o r 0.9 e m i s s i v i t y o f c o l l e c t o r 0.9 February. The r e l a t i v e l y high s o l a r f r a c t i o n s f o