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Energy saving through integrated greenhouse climate control for heating, ventilation and carbon dioxide… Lee, Dal-Hoon 1993

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ENERGY SAVING THROUGH INTEGRATED GREENHOUSE CLIMATE CONTROL FOR HEATING, VENTILATION AND CARBON DIOXIDE ENRICHMENT  by Dal—Hoon Lee B.  Eng.,  M.  Eng.,  Hanyang University,  Seoul,  University of Alberta,  Korea,  Edmonton,  1971 1979  A THESIS SUBMITTED IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF APPLIED SCIENCE  in FACULTY OF GRADUATE STUDIES Department of Bio—Resource Engineering  We accept this thesis as conforming to the required standard  THE UNIVERSITY OF BRITISH COLUMBIA December 1993 ©  Dal H.  Lee,  1993  ____  In presenting this thesis  in  partial fulfilment of the requirements for an advanced degree at the University of British Columbia, I agree that the Library shall make it freely available for reference and study. I further agree that permission for extensive copying of this thesis for scholarly purposes may be granted by the head of my department or by his or her representatives. It is understood that copying or publication of this thesis for financial gain shall not be allowed without my written permission.  (Signature)  Department of  1o  I2.5oLlC5  The University of British Columbia Vancouver, Canada  Date  DE-6 (2/88)  ;(4J  -/i4--  ABSTRACT  computer  A  model  was  developed  for  predicting  heating,  ventilation and CO 2 enrichment requirements for a standard tomato greenhouse range located in the Fraser valley of British Columbia. Predicted and measured data were  compared  for typical  cases  of  outside weather conditions.  The mathematical model which is comprised of heat and mass balances  for  the  greenhouse  thermal  environment  and  crop  photosynthesis has yielded reasonably accurate simulation results compared to observed values.  Heating requirement was predicted to within 10-14% for three typical actual  cases energy  of  weather  consumption  conditions, data  under  but one  deviated  by  35%  from  situation(Case  #3).  Predicted ventilation demand also followed closely the trend of observed vent openings data, except for Case #4  .  achieved in different manners for the four cases.  11  Energy saving is  TABLE OF CONTENTS  PAGE ABSTRACT  ii  TABLE OF CONTENTS  iii  LIST OF TABLES  v  LIST OF FIGURES  vi  ACKNOWLEDGEMENT  vii  SECTION 1.  INTRODUCTION  1  1.1 General  1  1.2 Objectives  3  SECTION 2. LITERATURE REVIEW  4  2.1 Computer Modeling  4  2.2 Evironmental Factors and Plant Growth  8  2.2.1 Light or PAR  8  2.2.2 Temperature  9  2.2.3 Interaction of Temperature/Light Effect  12  2.2.4 IIu:midity  12  2.2.5 Carbon Dioxide  ) 2 (C0  SECTION 3. MATERIAL AND METHODS  13 17  3.1 Data Collection  17  3.2 Mathematical Modeling and Computer Simulations..21 3.2.1 Heat Balance  23  3.2.1.1 Heating Requirement  27  3.2.1.2 Ventilation Requirement  29  iii  3.2.2 Mass Balances  .  3.2.2.1 Mass Balance for Moisture  31  3.2.2.2 Mass Balance for Carbon Dioxide..  33  SECTION 4. RESULTS AND DISCUSSION  SECTION 5  •  39  4.1 Heating Requirement  39  4.2 Ventilation Requirement  43  4.3 Carbon Dioxide Requirement  47  4.4 Energy- Saving  49  CONCLUSION AND RECOMMENDATIONS  84  5.1 Conclusions  84  5.2 Recommendatins  85  REFERENCES APPENDIX A.  31  87 Summary Table of Heating, Ventilation and CO R 2 equirements  APPENDIX B. Monthly Energy Consumption Data  iv  94 107  LIST OF TABLES  3.1 Data Collection  19  3.2 Outside Climate Conditions Considered  20  4.1 Simulation Results for Case 1  54a  4.2 Simulation Results for Case 2  55  4.3 Simulation Results for Case 3  58  4.4 Simulation Results for Case 4  61  V  LIST OF FIGURES  3.1 Energy Flux Schematics  18a  3.2 The Dimensions of the Greenhouse  18b  4.la Outside Climate Conditions for Case 1  64  4.lb Inside Climate Conditins for Case 1  65  4. ic Heating Requirement for Case 1  66  4. id Ventilation Requirement for Case 1  67  4. le C02 Depletion and Supply for Case 1  68  4. 2a Outside Climate Conditions for Case 2  69  4.2b Inside Climate Conditins for Case 2  70  4. 2c Heating Requirement for Case 2  71  4.2d Ventilation Requirement for Case 2  72  4. 2e C02 Depletion and Supply for Case 2  73  4. 3a Outside Climate Conditions for Case 3  74  4.3b Inside Climate Conditins for Case 3  75  4. 3c Heating Requirement for Case 3  76  4.3d Ventilation Requirement for Case 3  77  4. 3e CO2 Depletion and Supply for Case 3  78  4.4a Outside Climate Conditions for Case 4  79  4.4b Inside Climate Conditins for Case 4  80  4. 4c Heating Requirement for Case 4  81  4.4d Ventilation Requirement for Case 4  82  4. 4e C02 Depletion and Supply for Case 4  83  vi  ACKNOWLEDGEMENT  The author wishes to express his gratitude to Dr. Anthony A.K. Lau for his guidance and suppervision of this study. supports,  His ideas,  suggestions and experience in the field of greenhouse  management ensured the success of this report.  The author also wishes to thank Dr. K.L. Pinder and Dr. K.V. Lo  for reviewing the  initial manuscript,  providing me with the  necessary advice and sitting on my Committee.  Also my sincere gratitude to my wife,  Hye—Kyoo Lee,  constructive criticism and inspiration during my M.A.Sc.  vii  for her  1 SECTION 1. INTRODUCTION  1.1 General  Greenhouses  are  to  means  provide  protected  cultivation  of  horticultural crops to overcome adverse climate conditions. Through proper  climate  environmental  control,  plants  are  grown  under  optimal  conditions and hence greenhouse crop products can  offer the best possible quality and consistency to local consumers. The  consistent  periods  when  quality imported  reliability of supply. continent Canada,  and  assures  a  premium  product  field  price  varies  peak  in  price  quality  in  and  Increasing exports to other parts of the  overseas  have  been  realized  recent  in  years.  In  the present farm gate value of greenhouse vegetable and  flower production amounts to some 500 million dollars.  High energy cost remains a major obstacle to a stronger growth of  the  industry,  processes  of  as  energy  heating,  related  ventilation,  expenses  in  lighting,  the  multiple  carbon  dioxide  enrichment and irrigation account for about 20 to 30 percent of the total operating cost. Concern over potential instability in fossil fuel  costs  and  their  availability  intensification of research efforts conservation early  1970’s.  particular  techniques Although,  concern  to  and at  has  resulted  energy  present,  energy  who  an  aiming at developing energy  alternate  growers  in  often  sources saving  choose  since is  to  not  the of  maximize  2 production at all costs, any longterm solution to the problem shall consider environmental protection that calls  for reduced fossil  fuel usage.  Energy conservation can be achieved in a variety of ways including better design and maintenance of greenhouse  heating &  ventilating systems and improved control of greenhouse environment using computer—based environmental controllers. Computers have the capacity to control the greenhouse environment to pre—selected set point  values.  Commercial  greenhouse  computers  have  made  steady  progress in producing the best possible aerial environment for the crop while minimizing the risk of disease and infestation. Today’s cultivation  techniques  such  as  hydroponics,  carbon  dioxide  enrichment, supplemental lighting and irrigation, as well as energy conservation by means of thermal screens have been incorporated in the control algorithms that consider some interactions among the major greenhouse environment variables  —  temperature,  humidity,  light, and carbon dioxide, also, electrical conductivity and pH of the nutrient solution. Nevertheless, the use of the physiological processes (Bailey,  of  plant growth  1985),  and  in the  hence,  control  optimal  algorithms  greenhouse  yield  is minimal cannot  be  achieved when energy saving is desired.  This thesis isolates energy and carbon dioxide as the critical factors of production, and uses the computer modelling and systems simulation  approach  for  the  analysis  of  commercial  greenhouse  3 facilities. Computer modelling and simulation provides an effective means to obtain quantitative information for system optimization purposes.  The overall goal of this research study is to develop  algorithms for optimizing energy use and crop yield.  1.2  Objectives  The specific objectives are listed as follows:  1. to predict energy consumption involved in the heating, ventilation and CO 2 enrichment processes;  2. to predict ventilation requirement;  3. to estimate CO 2 depletion due to crop photosynthesis and ventilation;  4. to verify simulated results with actual data, and  5.  to recommend an integrated climate control algorithm for energy conservation purposes.  4  SECTION 2.  2.1  LITERATURE REVIEW  Computer Modeling  Modeling and simulation of the climate control behavior of greenhouses can be regarded as the backbone in the development of control algorithms.  Mathematical  modelling  classified as steady state  of  the  thermal  environment  (static modelling)  can  be  or transient state  (dynamic modelling). Static models can be used to estimate heating and ventilation demands,  for instance,  more  accurately  appriorate  characteristics level)  for  (leaf,  while dynamic models are describing  instantaneous  cover and air temperatures,  humidity,  2 CO  of the system accurately.  The first comprehensive study to characterize the physics of the greenhouse environment was published by Businger (1963). Steady state equations are used to calculate the energy fluxes occuring in a greenhouse, whereby the storage capacity of the system is assumed negligible relative to the daily energy input,  and therefore the  greenhouse is considered to adjust immediately to changes in the external vaper  conditions.  pressure  of  Air and the  equilibrium conditions.  cover temperature,  greenhouse Subsequently,  air  are  as well  assumed  to  as be  the in  on the basis of Businger’s  5  Walker  work,  et  al. (1983)  presented  an  energy  balance  for  greenhouse air as follows:  (1.1)  q+q+qr+qf=qcd+qg+qv+qff+qt+qp  where  8 q  =  net solar input  q  =  equipment heat  q  =  heat of respiration  qf  =  furnace heat  cd qg  =  convective/conductive heat transfer  =  heat to ground  =  ventilation heat loss  q  =  heat of photosynthesis  q  *  infiltration heat loss  =  thermal radiation to sky  =  All units are in [WJ or equivalent.  Several terms represent a negligible energy flux. The heats of respiration and photosynthesis are often ignored, amounting to less than 3% of the incident solar radiation.  The heat flux down  into the ground is also very small compared to upward convective, conductive, and radiative losses  (Horiguchi,  1979). The heat from  equipment such as lights and fans will be excluded from greenhouses that use natural ventilation system and no supplemental lighting.  Modelling presented  by  of many  the  greenhouse  other  thermal  researchers  with  complexity (For example, Arinze et al.,  environment different  1984; Bot,  has  been  degrees  of  1983; Kimball,  1986) while others have attempted models relating growth of a crop  6 to the environment for interactive environmental control and van de Vooren,  Steady  state  1980, Takakura,  models  are  (Challa  1982).  adequate  for  sizing  heating  and  ventilation equipment for greenhouse operations, and to some extent provide a basic level of climate control.  Kimball  (1973)  pointed  out that it is necessary to calculate accurately the heating and cooling  requirements  in  order  to  evaluate  controlling temperature in greenhouses.  various  methods  of  A simulation model will  calculate the energy fluxes occurring in a greenhouse. The fluxes are formulated in terms of known weather and greenhouse parameters. Unknowns (temperatures and vapour pressures) can then be calculated from the solution to a set of simultaneous energy balance equations that  describe  several  components  of  the  greenhouse  thermal  environment.  Albright  et  al.(1985)  presented  a  lumped model  for  insitu  thermal calibration of unventilated greenhouse. They introduced the concept of a  “thermal mass temperature” to be incorporated in a  single equation that comprised of  four parameters,  namely,  heat  capacity, overallheat transfer coefficient, correction factor for radiative heat transfer and solar heating efficiency.  Marsh and  Albright (1991a,b) extended their method to estimate the achievable temperature inside a ventilated greenhouse  Each of these models gave reasonably accurate prediction of  7 the greenhouse environmental conditions, suggesting that the models may not be  very  sensitive to  certain parameters,  and therefore  unnecessarily complicated models are not warranted. In this regard, Van Bavel et al. (1985) made a comparison of simulation models for calculating the greenhouse climate and its energy requirements for both heating and cooling. Seven sets (days) of data that represent various weather  conditions  in Lubbock  (USA),  Tokyo  (Japan)  and  Wageningen (The Netherlands) were used for detailed computations. They concluded that although the models differ with regard to heat and mass transfer parameters between the greenhouse air and the crop, the control functions for heating and cooling, and the method of estimating transpiration, same  results  in  air  requirements. However,  the models produced essentially the  temperature,  humidity,  and  heating  significant differences were found between  the estimates of daily amounts of transpiration.  Conventional climate control technology affect plant growth in an indirect manner by manipulating the aerial environment. Recent research works (Challa et al.1988; Dixon, 1987; Jones et al. 1991b) indicate that increasing efforts are being focused upon biosystem simulation,  which is essential for a better understanding of the  relationship between the physical and the biological systems, and eventually the synthesis of improved climate control strategies. Control  algorithms  responses  directly,  water potential,  that for  link  to  instance,  online leaf  measurement  temperature,  of  plant  leaf  area,  net photosynthetic rate and transpiration rate  8  were explored by Hashimoto et al. al.  (1980), Hack (1989) and  Yang et  (1990).  Environmental Factors and Plant Growth  2.2  Conventionally,  greenhouse  the  aerial  environment  is  represented by spatial average values of climate variables, namely solar  radiation  concentration,  and  which  are  light,  temperature,humidity  factors  that  affect  the  and  2 CO  physiological  processes and hence the growth and development of plants.  The principle of limiting factors stated that the rate of a process is limited by the pace of the slowest factor 1979).  In general,  temperature) growth  and  all these major growth factors  (Mastalerz,  (light,  have to be at their optimal values for maximum development.  There are  exceptions,  though,  2 and CO plant  when one  factor is at an inadequate level, other factors could be maintained at high levels to compensate for the deficiency.  Plant growth is a collection of many processes with different sensitivities to environmental factors which may interact with each other. This section reviews these factors whereas the next section concerns  computer modeling.  Knowledge  of  these  two  aspects  are  nesessary for executing the process of finding the most desirable or optimal climate control strategy.  9  2.2.1 Light or PR  Gaastra  (1959)  found  that  the  photosynthetic  rate  of  individual tomato leaves approached a maximum when light or PAR (photosynthetically Active Radiation)  reached above 120-150  . 2 W/ra  Yet, the rate of canopy photosynthesis continued to increase beyond 150  , 2 W/m  since a crop canopy consists of layers of leaves,  such  that light transmitted through the upper leaves will be absorbed by leaves lower in the canopy.  de Visser and Vesseur (1982)  as cited by Cockshull concluded  that 1% less light would reduce greenhouse cucumber yield by about 1*,  and the yield reduction was more obvious in the early part of  the year. A similar correlation was found for tomatoes.  Another important index is light integral.  It is related to  flower initiation and development. For tomatoes, light integrals of .d permitted almost all flowers on a truss to develop to 2 0.9 MJ/m anthers whereas Vancouver,  a  almost  all  tomato crop  flowers  seeded  aborted  at  0.35  in November will  .d. 2 MJ/m  In  start to bear  fruit in February when the light level is sufficient to meet this criterion.  2 • 2 • 2.  Temperature  The temperature range over which plants can photosynthesize is  10 large.  For  plants  C3  photorespiration  such  activity  as  tomatoes  increases  and  cucumbers,  temperature  with  and  counteracts the stimulating effect of temperature on growth. Thus, temperature regime is lower for C3 plants(15-25 °C) compared to C4 plants gain,  (30-45  For photosynthesis  °C).  and therefore,  dry weight  day temperature must be higher than night temperature,  so  that dark respiration rate is minimized.  The  horticultural  temperature  control,  between  (24°C  T  Controlling because grower’s  day/18°C  sensors  are  experience  Nevertheless, night)  i.e.  humidity  the  the  and  industry  RH.,  (e.g.  a  temperature  greenhouse  temperature  night)  T  a  to not  very  band 65%  and  precise  dictate  similar  a  uses  (20°C  level  accurate.  the  desired  between  RH.,  day  and  night)  is  not  band  is  maintained  day/16°C  is  more  Also  an  can  individual  80%  be  night).  difficult  humidity (e.g.  for  levels. day,  90%  created  for  humidity control.  The  proper  photosynthesis,  temperature  but  it  also  balance between vegetative (flower  and  fruit)  growth.  exerts  (leaf, At  a  only  strong  important influence  stem and shoot)  higher  the  and generative  temperatures,  assimilate demand by the growing fruits  on  for  come at the  the  strong  expense of  delayed growth of newly set fruits and even flower abortion because of low assimilate surplus. After some time, the total sink strength of the fruits becomes low and the plant can have strong vegetative  11 growth again.  Healthy flowers will then develop resulting in the  onset of a second cycle of strong fruit growth. This cyclic pattern of generative growth and vegetative growth means plants probably tend to a functional balance between the two kinds of growth; for tomatoes, intermediate temperatures of 19°C to 21°C are required for the most stable fruit growth.  Greenhouse temperature temperatures,  crops  than  respond  to  the  depending  more  to  daytime  specific  on  the  the  amplitude  of  24—hour and  nighttime  the  temperature  fluctuations and the buffering capacity of the plant. al.  average  Lacroix et  (1993) reconfirmed that greenhouse temperature regimes could be  more  flexible  than  those  traditionally  used.  As  long  as  the  temperature setting followed a sine wave that produced the same 24h—average temperature, temperature setpoints might be manipulated so as to reduce energy consumption by 3 to 15% without adversely affecting 1989).  production  (Miller  et  al.,  1985;  Aikman  and  Picken,  In other words, the setpoint can be lowered when heat loss  is higher than average due,  for example, to high wind conditions;  it can also be increased when the heat loss factor is anticipated to be relatively low.  In this way we can shift some heating to  periods when it is less costly to heat the greenhouse.  In  terms  of  biological  control  of  pests,  cooler  growing  regimes for tomato crop would make it more difficult to control infestations  of  the  greenhouse  whitefly  (Trialeurodes  12 vaporariorum),  as cool night temperatures promote colonization by  the pest but not its parasite (Encarsia formosa).  13 2.2.3. Interaction of temperature/light effect  If the greenhouse is maintained at a lower temperature, crop  can  easily  grow  too  ‘heavy’,  particularly  when  the  there  is  sufficient light. The disadvantages of a heavy crop are that they are more likely attacked by fungal diseases and they produce lower quality  Depending  fruits.  on  the  light  level,  one must  find  a  temperature setting that enables maximum assimilation.  Calvert  (1964)  studied the behavior of young tomato plants.  His data showed that the relative growth rate at 15.6 °C will fall if the daily light integral drops from 2.0 to 1.5 2 MJ/m . d but can be restored to its original level if the 24h average temperature is raised to 17.2 °C.  2.2.4 Humidity  Relative  humidity  level  transpiration to take place.  of  70-80%  allows  adequate  High humidity in excess of 90% can  increase the incidence of fungal diseases due to condensation of water vapor on the foliage whenever the leaf temperature is lower than the dewpoint temperature of the air. A more serious effect is a reduction in transpiration. Less transpiration will not only mean less  ability  for  the  plant  to  cool  itself  and  subsequent  leaf  dousage, will have implications for growth and development, fruit quality,  occurrence of physiological disorders,  and cause weaker  14 plants which become more sensitive to rapid changes in environment. For example, Calcium is less mobile in the leaves and young fruits, thus restricting cell division and ultimately the sink capacity of the fruit.  Grange and Hand  (1987)  argued that the most useful term for  describing the humidity of air inside greenhouses is not relative humidity,  but rather the vapor pressure deficit  (vpd)  which has  values usually ranging from 0 to 1 kPa. Low vpd values correspond to high relative humidity and vice versa. For tomatoes, Cockshull (1988)  found that the young leaves have smaller area when the vpd  is low (0.1—0.2 kPa).  A proper humility level is essential for pollination. Pollen is  less  likely to be  shed from the anthers under high humidity  conditions, while humidity too low will cause pollen to tend not to stick to the stigma.  Bakker weight  and  (1988) number  found that final yield in terms of both fruit of  of  fruits  tomatoes  was  reduced  by  high  nighttime humidity. Fruit quality at harvest and shelf life of the fruits were also poored.  2.2.5 Carbon Dioxide  Nighttime  ) 2 (C0  respiration  contributes  2 to CO  the  greenhouse  15 atmosphere.  At dawn,  2 concentrations often exceed the normal CO  atmospheric level of 340 ppm, but as light levels increase during the day, photosynthesis quickly consumes the excess and drives CO 2 to below 340 ppm. more severe as cease  at  In multispan greenhouses,  less  levels  of  infiltration occurs. 50—100  ppm,  2 depletion is even CO  Growth could virtually  if not compensated by  increased  light level and/or temperature.  In  time  winter  (January  and  February),  the  amount  of  2 CO  generated by the central hot water heating system is sufficient to elevate the CO 2  concentration beyond 340 ppm. As the heating demand  decreases towards spring time, increased  light  consumption,  level  2 CO  2 supply is also reduced, CO  lead to more  can  be  depleted  photosynthesis considerably  and  below  while  thus  2 CO  ambient,  production will therefore be substantially below its potential. It was estimated that 350 kg/ha of dry matter and 7000 kg/ha (11%) of loss in fruit production will occur because of CO 2 depletion while about 40000 kg/ha more fruits or 1700 kg/ha more dry matter results from enrichment to 1000 ppm.  2 CO  enrichment  productivity  and  of  quality  greenhouses of  is  greenhouse  practised crops.  The  to  improve  beneficial  effects of adding carbon dioxide to the greenhouse environment have been well documented. In short, tomato fruit size and number (more trusses and more fruit per truss) peak  is  shifted  forward.  are increased,  Earliness may be  and the harvest  increased by several  16 days.  weights  Dry  increased  up  to  30%  in  tomato  young  plants  propagated under low winter light conditions and C02 enrichment; it appears that increases in photosynthetic rate due to enhanced C02 concentration sufficient  to  gradient  even  under  sustain  early  flower  low  conditions  light  development.  Transport  are of  carbohydrates to the developing fruit are increased at higher CO 2 concentrations.  Threefold normally  2 CO  enrichment  recommended  if  (i.e.  to  enriched  practicable.  1000  1500  Above  ppm) ppm,  is the  accumulated starch can cause deformation of chloroplast structure which  may  ventilation,  limit  photosynthetic  capacity.  the  absence  of  it is customary to supply CO 2 at a flow rate of  56  In  kg/ha.h in order to attain an enrichment level of 1000 ppm in a greenhouse full of plants under moderate light and calm weather conditions. By the end of April it becomes increasingly uneconomic to maintain a constant ventilation  is  level  of  1000 ppm CO 2 in the daytime as  frequently required to  remove  excess  solar heat  under sunny and warm climatic conditions.  According  to  Hicklenton  (1988),  as  the  frequency  of  air  exchange increases due to more ventilation or when photosynthetic consumption  is  substantially, concentration.  greater, up  to  the 170  2 CO  injection  kg/ha.h,  to  rate  should  maintain  In terms of resource utilization,  the  increase desired  it required 1400  3 of natural gas to be combusted to prevent CO m 2 depletion while it  17 needs 16000 m 3 of natural gas to raise the CO 2 level to 1000 ppm. Maximum benefit will accrue if C02 enrichment is available between sunrise and sunset (Challa and Schadenponk,  1986).  Daytime greenhouse temperatures can be raised between 3 and 5°C when CO 2 is applied, so that ventilators remain closed for a longer period. Nevertheless, both processes of carbon dioxide uptake and transpiration are diffusion processes. As mass diffusivity of water vapor in air is almost twice as large as that of carbon dioxide, CO 2 supplement has to give way to ventilation if vent openings are the only means to control excessive humidity.  18 SECTION 3. MATERIALS JND METHODS  The study consists of two parts: data collection and computer simulations.  3.1 Data Collection  Actual greenhouse  data  were  (Hazelmere  collected  from  Greenhouses)  a  commercial  growing  vegetable  tomatoes  in  South  Surrey, B.C. The greenhouse is of Venlo-style, multispan type; the entire greenhouse is comprised of many smaller houses having the same dimensions. The dimensions of a greenhouse are shown in Figure 3.1. There are 27 houses and the total floor area is 25,400 m 2 for the tomates. Table 3.1 shows the different types of outside climate and inside climate data, as well as data related to the heating and ventilation systems.  All  the  Canadian Climatrol Systems, Control humidity  ‘  sensors were  installed  the representative of  in  1990  by  ‘Priva Climate  based in the Netherlands, except for the outside relative sensor  initiated.  which  With the  was  set  up  climate data  in  1991  when  this  storage protocol  of  study was the  PRIVA  CV—250 climate control computer system, these data were collected and stored at various time intervals, ranging from 5 minutes to two hours.  These data were obtained under a wide range of outside climate conditions. Records compiled from such measurements were analyzed  <Fig.  3.la Energy Flux Schematics>  lL2  O,8m  m  I—. — Section View  27 houses  =  172.8 ri  147  L. <Fig.  3.lb The dimensions of a greenhouse>  19 Parameters monitored and/or controlled by the Priva CV—250 Climate control computer system:  Outside Climate: —  -  —  -  Temperature Wind speed Solar radiation Relative humidity  Inside Climate: —  —  -  —  Temperature 2 Concentration CO Relative humidity Solar radiation  Heating: —  —  Heating water temperature Boiler temperature  Ventilation: —  —  Windward vent openings Leeward vent openings  Table 3.1 Data Collection  20  CASE  SOLAR  TEMPERATURE  1.  H  H  2.  H  L  3.  L  H  4.  L  L  Solar;  H :  greater than 600 W/m 2  L :  less than 300 W/m 2  Temperature; H : greater than 20 °C L :  less than 10 °C  Table 3.2 Outside Climate Conditions Considered  21 for achieving the research objectives.  3.2 Mathematical Modelling and Computer Simulations  A transient state mathematic model that is comprised of heat and mass balances, and having a time step of one hour will be used to predict energy consumption due to heating and ventilation and C02 enrichment.  For the purpose of computer modeling, hourly  data were retrieved from the Priva Computer and stored on the hard disk  of  a  P.C.  Outside  climate  data  constituted  the  boundary  conditions for the mathematical model whereas energy consumption and vent openings data were used for model verification. Table 3.2 shows  the outside conditions considered for this research.  Four  cases with different combinations of outside weather in terms of solar  radiation  (and  thus  PAR  or  light)  and  temperature  were  selected among a months of data for the simulations,in order to test the flexibility of the computer model.  Inputs for the model  are the physical characteristics of the crop, of the greenhouse and of the control system.  Three types of climate control actions were considered in the computer model; they are temperature control, humidity control and 2 CO  control.  strategies changes,  Industrial that  and  climate computers  combine  feedback  feedforward  (proportional  have  algorithms &  integral)  advanced control that  anticipate  algorithms  for  22 making adjustments.  Heat balance and psychrometric equations are  used in the feedforward control algorithms for temperature control. However,  equations  that represent plant physiological  processes  have not been applied to date, and are presented in this section.  Temperature Control  When the inside air temperature (T ) is lower than the heating 1 setpoint,  furnace  heating  is  required.  When  the  inside  air  temperature becomes higher than the ventilation setpoint, vents are opened.  Humidity Control  When  the  inside  relative  humidity  (W)  is  higher  than  the  relative humidity setpoint, vents will be opened, provided that the moisture content of outside air  ) 0 (W  is not greater than that of  inside air (Wi). In the event that the ventilation rate for humidity control exceeds that required for temperature control, temperature  could  drop  below  the  heating  inside air  setpoint,  thus  necessitating supplemental heating to restore the temperature to its setpoint value.  2 Control CO  When the greenhouse CO 2 level is lower than the ambient CO 2  23 level of  340 ppm,  vents should be opened to bring the 2 CO level  closer to the ambient level if CO 2 enrichment is not made. When high 2 is required for enhancing photosynthesis, then vent dosage of CO openings should be optimized to conserve valuable resources.  [3.2.1) Heat Balance  The heat balance equation enables us to determine the heating or  ventilation  requirement  of  the  greenhouse  for  temperature  control. The heat balance equation can be derived from equation 1.1 upon removal of insignificant terms, thus  fld  sens  —  —  qjf  (2  .  1)  In words, the net amount of heat accumulated in the greenhouse is equal to the difference between heat gains and heat losses. Heat transfered to soil underneath the greenhouse floor is assumed to be negligible; this assumption is justified for a mature crop having an  extensive  radiation. flux  from the  is  that  can  effectively  intercept  most  solar  This assumption also implies minimal nighttime energy  accumulation which  canopy  soil  is  to  the  greenhouse.  In this  study,  net heat  simulated directly in place of air temperature,  compatible with the standard way of  first  solving for  temperature in a differential equation, and then computing net heat accumulation.  In equation(2.l),  sensible heat gain is defined as  the portion of absorbed solar radiation that has not been utilized  24 in transpiration for plants to cool themselves during the daytime, and is represented by  801 a*q  =  —  (2.2)  —  where a is solar absorptivity of the plant canopy,  X is the  latent heat of vaporization(2450 kj/kg), Np is transpiration rate, mp  the  is  mass  of  ç,  plants,  is  specific  j/kg.°C) and T is plant(leaf) temperature, is  chosen to  be  one hour  in the  admitted into the greenhouse, , 801 q  =  *  ‘•  where (for  T  glass,  10  *  heat  of  plants(4200  t is the time step and  simulation runs.  Solar  energy  is given by  Af  (2.3)  is the effective transmissivity of greenhouse cover usually  0.70  to  O.75)[%),  10  is  the  outside  solar  radiation [Win ] and Af is the greenhouse floor area [m 2 ]. 2  Effective transmissivity is defined as the amount of  solar  radiation received on an inside horizontal surface (at plant canopy level) surface  as of  a  percent the  of  same  that area.  falling  on  an  effective  The  outside  horizontal  transmissivity  of  greenhouse cover is different from its transmittance at the glazing level.  The  latter  shows  mainly  properties of glazing material, incidence.  However,  the  former  the  effects  of  the  optical  sky clearness and solar angle of is  further  influenced  by  the  25 greenhouse geometric configuration and internal structures. Lau and Staley  (1989)  have made an in depth study of this parameter for  different types of greenhouse; results indicated that r varies from 0.65 to 0.75 for most climate conditions.  Transpiration provides both the motive force for water uptake by the roots and a mechanism for cooling the leaf.  Although the  transpiration rate of a greenhouse crop is governed by stomatal resistance (degree of closure of the stomata) which in turn depends on the environmental factors of light intensity, leaf temperature, ambient humidity or vapor pressure deficit, CO 2 level, leaf water potential,  as well as  stomatal opening is most sensitive to light  or solar radiation. Literature review (Morris et al., 1956; Bakker and van de Vooren,  Stanghellini et al.,  1984;  1992)  indicated a  strong correlation between solar radiation and transpiration for well—watered greenhouse crops. For instance, Morris et al., reported that the ratio of transpiration  (Mr)  (1957)  to solar radiation  ) was found to vary with plant height. At a plant height of 0 (I=r*I 0.25 m,  this ratio was 0.45 and it incresed from 0.60 at a plant  height of 0.70 m to 0.80 when the plants are 1.55 m tall. Beyond this height, the ratio became constant.  De tomato  Graaf  and  plants  in  van  den  winter,  Ende about  (1981)  observed  5%  the  of  solar  that  for  small  radiation  was  convered into latent heat via transpiration. For full—grown crops, this  percentage  was  37%.  As  solar  intensity  increased,  26 transpiration increased from 0.2 mm/day to 3-5 mm/day. tomato plants had reached a height of 1.7 a  further  increase  in  height  was  not  Once the  at the end of 2 months,  in  accompanied  by  increased  transpiration, which agrees with results obtained by Morris et al., (1957). Regression equations were obtained as follows:  lvii,  =  0.l6*0.00408*I  +  0.30  h  =  0.8  =  *Ipd 8 O 4 *O•OO 25 O•  +  0.50  h  =  1.3 in  =  O.37*O.OO4O8*I  +  0.61  h  where  Mi,  height (i.e. .d 2 J/cm  to  and  stage  expressed  in  of plant growth),  ‘pd  ‘pd  are  equivalent  factor of 0.00408. height of 1.7 Therefore,  in  the  amount  of  For instance,  latent  1.7  heat  of  (2.4)  in  [rnm/d],  and  h  is  had been converted heat  using  a  plant from  conversion  a full—grown tomato crop with a  will have a Mi, of 3.6 mm/d when latent  in  vaporization  ‘pd  is 2000 J/cm .d. 2  required to  convert  liquid water to vapor form in order for transpiration to occur can be a substantial part of the energy flux entering the greenhouse. Once daily transpiration assumed  to  is known,  be proportional  percentage of  to  hourly transpiration rate is  the hourly  solar  radiation  as  a  pd• 1  More sophisticated transpiration models have been proposed by Stanghellini  and van Meurs  measured  or  estimated  boundary  layer  (1992),  leaf  resistance  which take  temperature,  and  leaf  area  into account the  stomatal index.  resistance,  Boundary  layer  27 resistance (also called external resistance) accounts for sensible heat  transfer  resistance)  while  stomatal  resistance  (also  called  internal  represents latent heat flux due to transpiration.  3.2.1.1  Heating requirement  Whenever heat gains are less than heat losses  (eqn. 2.1),  becomes negative and an equivalent amount of heat shall be supplied to  the  greenhouse  to  maintain  the  setpoint  nighttime heating demand of a greenhouse, boiler, and is computed as  (ASAE,  1992)  q,  no  solar  transfer may  :  (2 . 5)  heat  input  be positive  U  *  *  1 (T  —  is  available.  The  conduction  heat  or negative depending on the relative  magnitudes of the inside (T ) 1  =  The  is used to size the  q  since  temperature.  and outside (T ) 0  temperatures.  ) 0 T  (2.6)  where, U: overall heat transfer coefficient [w/m .°C) 2 : 5 A  surface area of the greenhouse  T:  inside greenhouse temperature [°C)  : 0 T  outside air temperature [°C)  [1112)  28  Greenhouse heating systems are designed to maintain a given inside  temperature  at  a  given  outside  temperature.  The  former  depends on the crop grown and the latter depends on the location.  The overall heat transfer coefficient made up of three components, coefficient, outside  the  heat  is usually  the inside convective heat transfer  conductance  convective  (U—value)  of  the  transfer  glazing  material  coefficient.  Unlike  and  the  buildings  where the materials themselves contribute about 75% to 90% of the thermal  resistance,  surface/air coefficients  greenhouse  interfaces become  and  the  covers  thus  the  dominant  U—value. Most of the time, mixed  are  thin  convective  factors  for  so  that  heat  transfer  evaluating  (forced and free)  the  the  convection is  the prevailing mode on the outside of the greenhouse cover due in part to the wind effect whereas free convection dominates the heat transfer mode at the inside surface. There are wide discrepancies among research findings (Takakura et al., 1985), some of which are definitely out of range, despite the dependence of these values on the  specific  site  and  the  greenhouse  different studies. Papadakis et al of  studies  that  pertained  to  structure  (1992) this  used  in  the  have reviewed a number  aspect,  and  recommended  correlations for these coefficients.  Preliminary  calculations  demonstrated in Fig.  of  daily  energy  consumption  as  3.1 showed that the correlations recommended  29 by Papadakis et al.,  (1992) have not necessarily given rise to more  accurate predictions of daily energy use than the results obtained by adapting the standard U-values (ASAE, 1992). Hence, the standard U—values will, therefore, be used for all steady—state simulations in this study.  Infiltration is natural air movement due to leakage through cracks  other  or  small  in  openings  the  greenhouse  structure.  Therefore infiltration heat loss is always present regardless of whether or not ventilation is taking place. The following equation represents infiltration heat loss  =  0.5  *  V  *  N  *  1 (T  —  ) 0 T  (2.7)  where, V : volume of the greenhouse [xn ) 3 N : natural infiltration air exchange per hour [1/h) 1 : T  inside greenhouse temperature [°C)  0 : outside air temperature [°C) T  *  N varies from 0.75/hr for a new Venlo—structure to 3.0/hr for wooden frame or old greenhouse.  3.2.1.2. Ventilation requirement  Again,  referring to  the heat  whenever q is greater than zero,  balance  equation  (eqn.  2.1),  excess heat needs to be removed  from the greenhouse by ventilation if the outside temperature is  30 less than the desired inside temperature,  and if wind conditions  permit. The conventional control algorithm for natural ventilation of greenhouses with ridge ventilators is capable of minimizing the spatial  distribution  ventilator  of  operations  in  temperature, order  to  limiting  reduce  wear  the  frequency  and  tear  of  on the  mechanisms, and protecting ventilators from strong winds. However, no particular attention is paid to the conservation of resources such as energy and CO . 2  The ventilation rate will be determined by the temperature control and the humidity control. Ventilation rate for temperature control  Q  where,  (Q)  is given by  /(p  =  *  cp  *  (T  —  )) 0 T  (2.8)  : net heat accumulation [W) p c, :  :  air density [kg/m ] 3 specific heat capacity [J/kg. °C)  1 : greenhouse air (ventilation setpoint) T  temperature  1°C) 0 : outside air temperature [°C) T /s) 3 Q : ventilation rate for temperature control [m  The number of air changes per hour, N, will then be calculated from :  31 =  Q  *  3600/V  .  (2.9)  where V is greenhouse volume [m ]. 3  This computed value of N will be compared to the nuiiber of air changes involved in ventilation for humidity control.  [3.2.2) Mass Balance  The  mass  balance  enables  us  to  determine  the  ventilation  requirement for humidity control and to determine the amount of CO 2 needed to enrich the greenhouse atmosphere to desirable level.  [3.2.2.1] Mass Balance for Moisture  Ventilation for humidity control necessitates a mass balance to be written about the moisture regime of the greenhouse. Equating the net moisture accumulation rate to ventilation rate will lead to the following equation:  Mfld =N  —  (2 . 10)  Md  where M is net moisture accumulation before ventilation [kg/s), is transpiration rate  [kg/s),  and M is moisture condensation  rate [kg/s]. Similar to the heat balance, moisture accumulation is  32 simulated directly in place of air moisture content,  as used in  standard transient—state equations.  In words, moisture accumulation before ventilation is the net  result  of  condensation  moisture  on  the  production  glass  cover  via or  transpiration  crop  Good  leaves.  and  greenhouse  management will maintain an appropriate humidity level so as to avoid  condensation  assumes  that  the  on  the  glass  leaves.  cover  and  Also, the  the  steady—state model  greenhouse  air  are  at  equilibrium, so that condensation on the cover is ignored. In this study,  computed values of crop transpiration rate  (Mr)  is used in  place of M in the moisture balance.  Ventilation rate for humidity control is expressed as  Qh  =  !%/(  p  *  1 (W  —  W ) 0 )  (2.11)  where, M is transpiration rate [kg/s], W 1 is inside greenhouse air moisture content or humidity ratio  [kg water/kg dry air),  outside air moisture content or humidity ratio [kg/kg),  and  0 is W Qh  is  ventilatin rate for humidity control 3 [m / s).  Similar to the case of ventilation for temperature control, the number of air changes per hour, Nh,  Nb  Qb  is calculated as  *  3  6  0  0  /  V  w  34 [3.2.2.2) Mass Balance for Carbon Dioxide.  The mass balance for CO 2 involves CO 2 input(gain), 2 over time(one hour). and change of CO depletion  due  to  photosynthetic  (including infiltration)  2 losses CO  2 losses arise from its CO  consumption  loss. In general,  and  ventilation  filtered flue gases of  the central hot water heating system are used for CO 2 enrichment and therefore CO 2 supply is directly linked to energy supply (van Berkel, 1986). This is also the method used at the Hazelmere Greenhouses. Equating  the  depletion)  rate  of  change  of  with  2 CO  net  accumulation(or  of CO , we have the following equation: 2  p *3*C./t  Cd  5 is where C  =  =  C  —  (2.13)  Cd  C ±  (2.14)  2 supply(kg/ha.h), CO  ventilation and infiltration  2 loss(or gain) C is CO  (kg/ha.h),  due to net photosynthsis(kg/ha.h), greenhouse voluine(m ) 3  First,  due to  and C is CO 2 consumption  is CO 2 3 density(kg/m ) ,  p  V is  and C 1 is greenhouse CO 2 concentration(ppm).  let us look at CO 2 demand.  For CO 2 consumption due to  photosynthesis, the classic model presented by Acock et al. and modified by Jones et al.  (1991a)  (1978)  to account for the influence  of temperature is used, as it applies to the tomato crop during all stages of growth. Thus  35  Cpn=(PgR)  *  .  (2.15)  where,  .f(T)*r*C. z*K*I+(1—m)*r*C.*f(T) 1 *ln 1 K *K*I*eKL+(1-m)*t*C * 1 f(T)  (2.16) where, Pg : gross photosyntheric rate [mg/m .sJ 2 R : Respiration rate [mg/m .s) 2 r  :  1 : C  leaf conductance to CO 2 transfer [mis) inside CO 2 concentration [mg/rn ) 3  K : canopy extinction coefficient [dimensionless) a :  leaf light utilization efficiency [mg C0 /j) 2  *O.45) 0 I : PAR at top of canopy(= r*1  ] 2 [w/m  in :  leaf transmission coefficient(usually 0.10)  L :  leaf area index  f(T)=1_(  2 [in  2 floor area) leaves/rn  TmajT T  (2.17)  36 is The temperature at which Pg is maximum,  ,  i. e  when f(T)=1.O and T is The temperature below which f(T) and thus photosynthesis is zero. Respiration is assumed to be 10% of gross photosynthesis.  Two  scenarios  are  considered  for  the  C  term,  which  is  expressed as = N *p*V* (C 8  where C 0 is  —  ) 0 C  / Af  (2. 18)  ambient CO 2 concentration and N 8 is ventilation  supply rate.  The  first  scenario  outside (ambient)  340  applies  ppm  level  when  2 CO  is  depleted  and  is  to  be  below  the  replenished  ventilation to let inside air mix with outside air content.  by  Thus  C becomes negative and is effectively added to the CO 2 supply.  The  minimum  number  of  air  changes  per  hour  for  2 CO  replenishment will be computed as  *  3600/V  (2.19)  where P*A ‘  — 0 (C ) 1 *p C  (2.20)  37 calculated value of  This  the ventilation rate  can then be  compared with ventilation rates estimated by equations (2.12)  (2.9)  and  in order to arrive at a ventilation rate that satisfied all  the requirements for temperature control, humidity control and CO 2 control.  All the computed N-values shall be verified with the actual (supply) ventilation rate due to roof vent openings,  as given  by  a regression equation that related wind speed and vent openings to ventilation rate (Bot,1983),  8 Q  =  a  Af  *  (7+1) V exp (—8.42*1O  *  (‘j+I))  *  (2.21)  where opening  is  Q  [%),  I  the  is  ventilation  rate  [m / 3 s),  is  ventilator  infiltration expressed in equivalent units of  ventilator opening [%],  and v,, is the wind speed [m/s).  Number of air changes per hour due to ventilation supply is given by  8 N  =  8 Q  *  3600/V (2.22)  The  second  scenario  pertains  to  2 CO  enrichment  beyond  the  38 ambient  ppm  340  level.  Ventilation  for  temperature  control  or  humidity control will become a sink component of the mass balance for CO . Hence C becomes positive and is added to photosynthetic 2 consumption as CO 2 demand.  Finally, we consider CO 2 supply. For carbon dioxide enrichment using flue gases,  2 supply rate may be estimated from the heat CO  supply rate.  Heat supply,  qf[w),  is computed from heat transfer equations  for convection and radiation, thus  qf = (h +  where  h,  hCf  hcf + hr)*Apw*(Tpw  and  natural convection, . 2 [W/m  °C),  A,  is  hr  are  heat  —  T)  (2.23)  transfer  coefficents  due  to  forced convection and radiation, respectively total  temperature[°C), correlations (Holman,  pipe  and 1991),  hCf  surface are  ) 2 area[m obtained  emissivity  of  the  and from pipe  is  pipe  empirical material  is  0.95.  2 supply in [kg/ha.hJ CO  is calculated from the stoichiometric  relation between natural gas(CH ) combustion and CO 4 2 release, thus,  (2.24)  39 —___________  CS  *Iif 3 * 6 1 8  It should be noted that heat supply to the greenhouse did not necessarily come directly from the boiler; residual pipe heat may be used for heating over a continuous period. Supply of CO 2 can only be realized if heat is released from the boiler at a particular hour.  Preliminary inspection of pipe temperature data  indicated  that heat release from the boiler was highly correlated to the rise of pipe temperature over the previous  period.  On the computer  simulations, the quantity of CO 2 supply will be calculated if this condition is satisfied. In the summer heat requirement is minimal 2 demand can be substantial, the hot water from the boiler while CO can be diverted to a water storage tank for subsequent nighttime use.  The more expensive way of CO 2 supplementation via liquid CO 2  supply is not considered in this thesis.  40 SECTION 4. RESULTS AND DISCUSSION  Four days of varied outside climate conditions as depicted in Figs. 4.la to 4.4a were selected from the 1991 data and used in the simulation  runs.  The  climate  factors  considered  were  solar  intensity and temperature. Measured inside climate conditions are illustrated  in  Figs.  4.lb  to  4.4b.  Results  are  presented with  regard to heating requirement, ventilation requirement, as well as 2 enrichment. The general behavior of the mathematical model will CO be verified against the actual data.  4.1.  Heating Requirement  Figs.  4.lc to Fig4.4c show the heating requirements of the  four cases.  Case 1  (high solar radiation and high outside temperature):  Diurnal outdoor temperatures varied from 8°C at night to 21°C during the daytime, while solar radiation follows a smooth pattern, peaking at 900 W/m 2 on this summer day. The trend and magnitude of the inside temperature indicated that daytime temperature setpoints are  light-dependent.  As  the  heating  setpoint  temperature  was  changed from the nighttime value of 19°C to its daytime value of 22°C between 5 a.m. and 8 a.m., the rate of increase in temperature was 1.5°C/h, which fell within the recommended range of 1.0 to 1.5°C  41 per hour  in order to allow the plant to adjust  gradually  to  condensation temperature  the on  greenhouse  the  leaves  temperature  and  fruits.  its temperature  thereby  avoiding  Ventilation  setpoint  increased from 22°C to 27°C when solar intensity was  raised from 240 W/m 2 to 900 W/m . This phenomenon also conformed to 2 conventional greenhouse climate control strategy.  Comparison is made between the calculated values of q with other researchers’ findings. With reference to egn.  (2.2), g is  a function of solar energy entering the greenhouse as well as crop transpiration.  Discounting the  amount  of  solar  energy used  for  transpiration and stored by the plant thermal mass, the remaining fraction of solar radiation that contributes to sensible heating of the greenhouse  (computed as 1 /q, 8 q )  was found to be 0.38±0.02 as  compared to values of 0.25 reported by Bailey and Seginer and 0.40 reported by Critten admitted  solar  energy  was  (1991). retained  In other words, as  sensible  (1988)  only 40% of heat  in  the  greenhouse. Heating demand, q difference  between  ,  was calculated on an hourly basis as the  sensible  heat  gain  and  sensible  heat  loss,  nevertheless, the predicted q can only be verified with an actual energy  consumption  record  on  a  daily  basis.  The  greenhouse  management record indicated that total daily energy consumption amounted to 146 GJ for both the tomato greenhouse range (2.54 ha) and the pepper greenhouse range (1.83 ha). Since the two greenhouse  42 ranges are identical in construction, the actual energy consumption for  the  tomato  simulation  greenhouse will  model  temperature  predicted  control,  and  a  a  be  85  GJ  heating  heating  of  (58% demand  supply  of  146  of  95  95  GJ  GJ);  the  GJ  for  based  on  convective and radiative heat transfer from the hot water pipes to the greenhouse air. Simulation results therefore differed from the actual  data  temperature humidity  12%.  by  control  control,  On  consistently  hence  during the daytime.  day,  this  no  the  ventilation  exceeded  supplemental  that  heating  rate  for  required  for  was  necessary  Energy consumption was therefore attributed  largely to nighttime heating requirements,  as  is also evidenced  from the measured pipe water temperature of less than 45°C during the daytime.  Case 2  This  (high solar radiation and low outside temperature)  day  is  characterized  by  more  diffuse  sunlight  when  compared to Case #1, although solar radiation climbed to a similar maximum value of 850 W/m2 in the early afternoon. The greenhouse required  heating  some  temperature  was  in  below  the  45  °C  morning during  hours. the  day.  Again, The  pipe water outside  air  temperature was 3 to 6 °C less than that encountered in Case #1, causing greater heat loss to the surroundings;  the percentage of  admitted  heat  solar  (qsens/qsol  =  energy  0.22—0.30)  retained  as  accordingly.  sensible  was  smaller  There was a 14% difference  between the calculated heating demand of 96 GJ versus the actual  43 energy consumption of 112 GJ on this day, while a prediction of 116 GJ based on heating supply equations was more accurate.  Case 3  (low solar radiation and high outside temperature)  The diurnal outside temperature fluctuated by less than 20%, whereas the inside air temperature followed a typical pattern of 23°C day/16°C  night temperature  solar energy input, negative  values,  For this  settings.  day with  low  the sensible heat gain by air was reduced to  the  heat  balance  of  the  greenhouse  is  thus  governed by the greater thermal gradient between daytime indoor and outdoor  temperature,  eventually  leading  to  a  higher  heating  requirement of the greenhouse during the daytime hours than during the nighttime.  The simulated and actual energy consumption data differ by 35%. The predicted value derived from the demand—side equations or supply-side equations alike was about 110 GJ, while actual daily energy consumption was 167 GJ. The large discrepancy is likely due to the excessive heat loss to the outside through wide ventilator openings  (more than 60% leeward-side)  at night, as shown in Table  4.3, which is not accounted for in the heat demand equations. The high outdoor temperature together with low wind speed means the temperature of the glass is also relatively high, moisture can condense out. continued to  transpire  so that little  The plants are now fully matured and  at night,  delivering  some  10-20%  of the  44 daily total transpiration capacity. As moisture accumulated in the greenhouse necessary  and  could  have  to  not  be  adequate  removed  by  ventilation  relative humidity level below ±90%,  condensation,  to  maintain  it  the  was  inside  resulting in additional heat  loss.  Case 4  The  (low solar radiation and low outside temperature)  simulated  heating  demand  is  236  GJ,  and  is  in  good  agreemnent (within 10%) with the actual energy consumption record of 215 GJ, although the predicted heating supply of 173 GJ is of f by 20%. large  This day as characterized by low solar energy input and  daytime  energy  heat  loss  consumption  investigated;  the  the  to  ambient  would  be  the  results  of  the  naturally  greatest  of  mathematical  implied  the  four  model  that cases  accurately  reflected this point.  4.2  Ventilation Requirement  The  ventilation  requirement  of  each  of  the  four  cases  is  illustrated in Figs. 4.ld to 4.4d. Simulation results are presented in terms  of  ventilation  the number for  of  air  temperature  changes per hour,  control,  humidity  as  related to  control  and  2 CO  replenishment.  The ventilation rates were computed from the heat and mass  45 balance equations, on the basis of the necessity to remove excess heat  solar  (net  heat  accumulation)  or  excess  moisture  in  the  greenhouse. Minimum ventilation rate required to restore the CO 2 level back to 340 ppm is also calculated when CO 2 is depleted below this ambient level. The actual or supply ventilation rate was next computed and all ventilation rates were converted to the number of air changes per hour for comparison purposes.  Case 1  (high solar radiation and high outside temperature):  It was suggested that if a sunny day with high temperature is expected,  vents should be opened wide early in the morning,  the  greenhouse temperature will then tend not to rise so much during the mid—day. Since a cooler plant transpires less than a warm one, a larger vent opening therefore would not necessarily lead to an increase in transpiration. The additional venting is warranted even 2 level cannot be maintained at an optimum level for if it means CO photosynthesis,  as  excessive  plant  temperatures  are  more  detrimental to plant growth than a temporary somewhat lower CO 2 level.  Examination of the greenhouse climate conditions on this day revealed that the leeward vents were opened 20—30% in the morning. Carbon dioxide enrichment beyond 340 ppm was not apparent except for  the  early  morning  hours  when  the  boiler  was  activated  to  elevate the temperature from the nighttime setpoint to the daytime  46 If the vents were opened wider, more CO 2 would have been  setpoint.  lost through ventilation.  In the middle portion of the day,  CO  level was depleted considerably below 340 ppm; at one point, it was near the lower limit of 50-100 ppm, the CO 2 compensation point. This is the moment when 2 CO enrichment is most beneficial,  thus,  the  boiler should be turned on in order to utilize the CO 2 from the flue gases.  Although the temperature data  needed during the day,  showed that  no heating  is  the hot water can be diverted to a water  storage tank for later use.  Ventilation rate for temperature control steadily increased from  to  4.3/h  27.9/h  between  0900  and  1700  hours,  whereas  ventilation rate for humidity control ranged from 6.5/h to 9.7/h during the same time period.  These ventilation rates fall within  the range of values for average—sized greenhouses, 0.04  2 / 3 m . s m  Whittle  or  0.3  to  Lawrence,  and  ventilation supply rate,  40  air  1960).  changes Upon  per hour  checking  of 0.00036 to  (Critten, with  the  1991; actual  it is seen that the ventilation strategy  had been governed by humidity control. Since vents were not opened adequately  for  temperature  control,  roof  sprinklers  have  been  effectively used on this hot summer day  Case 2  (high solar radiation and low outside temperature)  The number of air changes per hour as plotted in Fig. indicate  that  the  computed  ventilation  rates  for  4.2d  temperature  47 control  and humidity control  are  in good agreement with actual  ventilation rate. In the morning, ventilators are opened to remove excessive moisture, resulting in humidity levels below 80%. In the afternoon, control,  ventilation  is  directed  more  towards  temperature  as humidity is allowed to build up somewhat. Ventilation  requirement for this day is not high, as all N—values are found to be below 10 air changes per hour.  Case 3  (low solar radiation and high outside temperature)  Solar energy is the primary driving force behind temperature rise. On this day with low solar intensity, ventilation demand for temperature control is nil,  rather,  the greenhouse needs heating  for the entire 24—hour period. However, ventilators were opened for humidity control.  In the mathematical model, transpiration occurs  only during the day, This  assumption  considerable daytime  is  resulting in no vent openings at nighttime. in  nighttime  ventilation  contradiction vent  rate  to  openings.  agrees  actual  data  which  Nevertheless,  reasonably  well  show  predicted  with  actual  ventilation rate, except for 1500 hour when predicted Nh of 18.7/h is more than doubles the actual N 8 of 8.0/h.  Case 4  (low solar radiation and low outside temperature)  Vents were opened on this day for the sole purpose of humidity control.  The  predicted  ventilation  rate  for  humidity  control  48 consistently  exceeds  the  actual  ventilation  supply  rate;  large  discrepancies exist during the daytime hours. These findings tend to  reflect  another  shortcoming  of  the  mathematical  model  for  transpiration, in that transpiration is correlated only with solar radiation, while other factors such as vapor pressure deficit and 2 CO  concentration  are  ignored.  On  this  day,  carbon  dioxide  enrichment is well executed, and it is possible that stomates are closed somewhat under high ambient CO 2 concentration, thus reducing transpiration.  49 4.3  As central  Carbon Dioxide Requirement  carbon hot  dioxide  water  is  heating  supplied system,  from the it  can  flue  be  gases  expected  of that  the 2 CO  enrichment is possible only when the burner is switched on to meet the heating demand of the greenhouse. Measured CO 2 levels in each of the four cases will be inspected to verify this criteria. loss  2 CO  (photosynthetic consumption and/or ventilation loss) will be  presented along with CO 2 gain (CO 2 supply via burner flue gases) in Figs.  4.le to 4.4e for the four cases.  Case 1  This  (high solar radiation and high outside temperature):  day  with  abundant  solar  radiation  resulted  in  zero  heating demand during the day hours. The burner was therefore off under these circumstances although the pipes were maintained at a temperature of ±40°C for humidity control most of the time. As a result,  2 CO  levels were depleted below  340  ppm for  an  extended  period. Even though vents were opened to 50%, the amount of ambient 2 introduced into the greenhouse apparently cannot satisfy the CO high photosynthetic consumption. As seen from Fig. 4.le, CO 2 supply was consistent with the trend of CO 2 concentration. The maximum CO 2 level of 1100 ppm observed at dawn 2 supply rate of 180 kg/ha.h. peak CO  (0600 hour)  coincided with a  50  Case 2  (high solar radiation and low outside temperature)  As mentioned earlier,  the greenhouse requires  some heating  during the morning hours, but no more heating is needed when solar energy is seen to increase into the day. CO 2 concentration was only raised to 830 ppm at 0600 hour, subsequently, it continued to fall below 340 ppm as the small amount of heating requirement is met by residual heat in the pipes. Similar to case #1 then, as the burner was not on, no supply of CO 2 should be realized. Yet, the computed 2 CO  supply  values  contradictory  to  (Fig. the  4.2e)  measured  were 2 CO  irregular  and  concentration  were  obvious  profile.  This  abnormality is likely due to the imposed logical condition on CO 2 supply which is  linked with a rise in pipe temperature.  Between  0800 and 1800 hours, the pipe temperature profile was seen to have some  minor  fluctuations  of  1  to  criterion ill-conditioned. Again,  2  °C,  thus  making  the  logical  the extent of vent openings of  less than 30% could not sustain the CO 2 level at 340 ppm during the daytime  hours  when  the  greenhouse  environment  called  for  ventilation.  Case 3  (low solar radiation and high outside temperature)  2 levels never reached beyond 400 ppm on this day even though CO the greenhouse required heating most of the time.  For instance,  heating demand was estimated at 10.4 GJ/h at 0700 hour, level was only at 294 ppm at this hour.  but CO 2  Heat and thus CO 2 supply  51 could not be predicted on the basis of the the measured pipe water temperatures which were probably erratic.  However,  inspection of  the vent opening data could provide a hint of why CO 2 levels were this low. On this day, vents were opened quite wide  (usually more  than 60%), leading to a ventilation air exchange rate of 6 to 12/h; the loss of CO 2 through ventilators could be greater if the wind speed  high  were  on  this  day.  Photosynthetic  consumption  was  relatively small due to low light levels. The possibility that flue gases were dumped rather than used for CO 2 enrichment cannot be eliminated for this case.  Case 4  (low solar radiation and low outside temperature)  The greenhouse consumed 215 GJ of energy as compared to 167 GJ for  case  #3.  Simulated  2 CO  supply  rate  is  consistent  with  the  observed CO 2 concentrations. In contrast to case #3, CO 2 enrichment was very effective; evidently, the CO 2 regime of the greenhouse was high  during  this  day,  except  for  the  noon  hour.  A  major  contributing factor is the small vent openings of less than 15% during  the  daytime  so  that  loss  of  the  enriched  2 CO  through  ventilators was kept to a minimum.  4.4  Energy Saving  The actual energy consumption record for the four cases (85, 112,  167  and  215  GJ,  respectively)  did  demonstrate  a  trend  of  52 increased  energy  use  as  the  outside  weather  conditions  became  increasingly severe. This section presents the implications of the climate control actions on energy saving aspects.  Case 1  This  (high solar radiation and high outside temperature):  day  is  characterized  by  excess  solar  input  to  the  greenhouse even after ventilation demand for humidity control. This excess amount of solar energy was found to be 63 GJ and could be stored for nighttime use. were  allowed to deplete  During the daytime,  2 concentrations CO  substantially below the normal  340 ppm  level, in order to save energy but at the expense of photosynthesis and  thus  crop  yield.  It  was  estimated  using  the  mass  balance  equation for CO 2 that 60 GJ of heat would have been required to enrich the greenhouse environment to 800 ppm.  Case 2  As  (high solar radiation and low outside temperature)  discussed  previously  under  the  section  ‘Ventilation  Requirement’, the ventilation rate for humidity control was greater than  the  ventilation  rate  for  temperature  control,  thereby  necessitating supplemental heat of 16.8 GJ to maintain the heating setpoint temperature. excessive,  as  The ventilation rate should be considered  humidity  was  consistently  driven  below  85%.  A  tolerance of humidity level at 90% meant that vent openings could be reduced,  so that less supplemental heat is required and energy  53 saving of 10.2 GJ (9% of the daily energy use) could be realized.  Carbon dioxide levels on this day were lower than in case #1, even though there were hours with supplemental heating.  Further  simulations suggested that 71 GJ of heat will be required to bring about a 800 ppm CO 2 level in the greenhouse. Again the energy thus saved has to be weighed against potential reduction in crop yield.  Case 3  (low solar radiation and high outside temperature)  The daytime relative humidity profile (Fig. 4.3b) showed that humidity levels were around 85% as a result of wide vent openings, ranging from 60% at 0900 hour to 80% at 1400 hour.  At the same  time, the greenhouse space required continuous heating throughout the day.  Yet,  2 levels were never boosted to beyond 400 ppm due CO  to these large vent openings.  Computations indicated that 28.5 GJ  of heat could be saved while CO 2 concentrations would have been raised to 650 ppm or more if vent openings had been restricted to 20% or below.  Case 4  (low solar radiation and low outside temperature)  In contrast to case #3, this was a relatively calm day with a lower wind speed. As the end of the growing season was approaching, a lot of leaves in the bottom layers had been removed;  the crop  transpired less and thus the greenhouse required less ventilation  54 for humidity control. smaller vent  openings  The two factors combined to result in much than case  #3.  Energy  saving was  realized  through avoiding excessive supply of heat and thus CO 2 from the burner to offset the loss of CO 2 associated with ventilation.  lout W/rn2  0.0 0.0 0.0 0.0 0.0 21.0 117.0 244.0 368.0 541.0 715.0 825.0 887.0 891.0 856.0 806.0 661.0 100.0 46.0 56.0 26.0 1.0 0.0 0.0  1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24  Solar Temp.  Time h  High High  0 0 0 0 0 7 37 77 116 170 225 260 279 281 270 254 208 32 14 18 8 0 0 0  PARin W/m2  Case 1. Date:91252(Jun.18,91)  0 0 0 0 0 5 29 61 93 136 180 208 224 225 216 203 167 25 12 14 7 0 0 0  inside I J/cm2.h  8.8 8.4 8.0 7.6 7.3 7.3 9.7 12.7 15.6 17.5 18.0 18.5 18.8 19.5 20.3 21.1 22.1 13.4 13.2 13.1 13.1 12.9 12.6 12.7  Tout C  87 90 91 93 93 82 77 77 82 82 77 72 77 68 64 64 64 64 72 82 85 82 84 86 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.2 0.4 1.1 2.0 2.7 2.9 3.0 2.8 2.2 2.0 2.0 1.3 0.4 0.2 0.2 0.4  rn/s  vw  16.0 15.8 16.3 17.5 18.8 19.8 20.8 21.1 22.6 24.6 25.4 26.7 26.7 27.4 27.2 27.5 26.7 20.9 21.0 18.7 16.7 16.2 16.1 16.0  Tin C  86.2 87.4 88.4 87.8 87.1 84.7 81.2 83.7 84.5 86.5 85.1 85.2 86.0 81.8 76.2 73.8 72.6 86.2 87.9 83.8 81.4 87.6 85.3 87.8  RHin %  Simulation Results for Case 1  RHout %  TABLE 4.1  0.0062 0.0064 0.0060 0.0060 0.0059 0.0052 0.0057 0.0070 0.0091 0.0102 0.0099 0.0096 0.0104 0.0096 0.0095 0.0100 0.0106 0.0059 0.0067 0.0076 0.0080 0.0078 0.0076 0.0077  Wo kg/kg  0.0096 0.0100 0.0104 0.0110 0.0120 0.0125 0.0126 0.0132 0.0143 0.0172 0.0174 0.0188 0.0190 0.0188 0.0172 0.0171 0.0163 0.0133 0.0138 0.0114 0.0096 0.0102 0.0096 0.0101  Wi kg/kg  49.3 57.3 64.7 69.6 73.1 78.4 70.0 65.6 56.9 48.5 45.0 39.5 35.0 35.0 35.0 30.4 0.0 33.1 45.8 20.3 20.0 24.6 27.0 28.3  Twater C  373.5 377.8 391.5 398.5 547.0 1084.6 762.4 493.1 330.5 184.4 161.9 130.2 108.5 102.3 111.0 88.3 67.9 241.4 712.8 407.4 182.0 204.4 228.5 220.7  C02 ppm  1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 2.8 1.3 9.0 6.9 9.0 7.4 10.0 6.3 1.0 1.0 20.3 14.6 4.3 2.1 1.4  5.5 3.7 3.5 1.4 1.2 7.6 20.1 32.0 37.2 40.0 40.0 45.6 50.0 50.0 50.0 50.0 50.0 9.8 7.4 51.7 34.6 22.9 20.2 16.5  vent openings windward leeward %  0 0 0 0 0 2.1 li.7 24.4 36.8 54.1 71.5 82.5 88.7 89.1 85.6 80.6 66.1 10 4.6 5.6 2.6 0.1 0 0  Tout/lU  0.0 0.0 0.0 0.0 0.0 -1.6 1.0 6.0 6.8 10.4 17.7 19.7 24.1 22.7 23.3 21.3 18.0 2.7 1.0 1.5 0.7 0.0 0.0 0.0  qsens 03/h  0.0 0.0 0.0 0.0 0.0 1.4 8.0 16.7 25.2 37.1 49.0 56.6 60.8 61.1 58.7 55.3 45.3 6.9 3.2 3.8 1.8 0.1 0.0 0.1  qsol 03/h  0.0 0.0 0.0 0.0 0.0 2.1 2.1 0.6 3.2 4.3 1.7 2.8 0.0 1.5 -0.4 0.6 -1.7 -12.4 0.2 -4.9 -4.3 0.0 0.0 0.0  qaccp 03/h  Simulation Results heat and mass balances  5.0 5.1 5.8 6.9 8.0 8.7 7.7 5.8 4.9 4.9 5.1 5.7 5.5 5.5 4.8 4.4 3.2 5.2 5.4 3.9 2.5 2.3 2.4 2.3  qcd 03/h  1.9 2.0 2.2 2.6 3.1 3.3 3.0 2.2 1.9 1.9 2.0 2.2 2.1 2.1 1.8 1.7 1.2 2.0 2.1 1.5 1.0 0.9 0.9 0.9  qif GJ/h  0.00 0.00 0.00 0.00 0.00 0.06 0.32 0.67 1.01 1.49 1.97 2.27 2.44 2.45 2.35 2.22 1.82 0.27 0.13 0.15 0.07 0.00 0.00 0.00  Mp kg/s  0.000 0.000 0.000 0.000 0.000 0.008 0.046 0.095 0.143 0.211 0.279 0.321 0.346 0.347 0.333 0.314 0.257 0.039 0.018 0.022 0.010 0.000 0.000 0.000  mm/hr  6.9 7.1 8.0 9.5 11.1 13.6 9.6 2.1 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 4.5 6.5 3.9 2.8 3.1 3.4 3.2  heating demand qnet<0 03/h  6.8 8.7 10.4 11.3 11.9 13.1 10.7 9.6 7.2 4.8 3.9 2.5 1.5 1.4 1.4 0.5 1.0 2.3 5.0 0.3 0.6 1.5 2.0 2.3  qf GJfh  0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.1 3.6 10.6 11.8 16.5 15.1 17.1 15.1 15.3 7.9 0.0 1.0 1.5 0.0 0.0 0.0  ventilation demand qnet>0 GJ/h  0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.1 4.3 12.1 12.1 17.6 16.1 20.8 19.9 27.9 8.8 0.0 1.6 3.5 0.0 0.0 0.0  Nt 1/h  0.0 0.0 0.0 0.0 0.0 0.2 1.4 3.3 5.8 6.5 7.9 7.4 8.6 8.1 9.3 9.4 9.7 1.1 0.5 1.2 1.4 0.0 0.0 0.0  Nh 1/h  Ns 1/h  0.0 0.0 0.0 0.0 0.0 0.0 0.1 0.1 0.3 0.7 2.0 4.7 6.6 7.4 7.4 7.2 5.3 1.1 0.9 4.0 0.9 0.2 0.2 0.3  Nc lIh  0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.7 2.6 2.5 2.0 1.7 1.6 1.7 1.3 0.9 1.3 0.0 0.0 0.2 0.0 0.0 0.0 2.4 2.7 3.7 4.2 14.8 54.6 32.5 12.3 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 49.2 23.7 0.0 0.0 0.0 0.0  Cvent kgfha.h  0.0 0.0 0.0 0.0 0.0 2.2 11.5 21.3 27.1 28.4 30.9 29.3 26.9 26.0 27.0 22.8 17.8 9.0 4.7 5.5 2.5 0.1 0.0 0.0  Pn kg/ha.h  0.0 0.0 0.0 0.0 0.0 6.7 1.5 1.0 1.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.5 6.1 0.5 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 6.2 2.6 3.6 4.5 4.7 5.5 5.3 5.2 5.2 5.4 4.9 4.6 4.9 6.1 2.3 2.5 3.5 0.0 0.0 0.0 0.0 0.0 0.0 0.0 185.4 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 69.5 35.1 68.5 0.0 0.0 21.5 0.0 0.0  C02 qco2 qco2= 800 supply GJ/h GJ/h kg/ha.h  PARin: inside photosynthetically active radiation [W lin: inside solar intensity [J/cm2.h] lout: Outside solar intensity [W/m2} RH1n: Inside humidity [%J RHout: Outside humidity [%] Tin: Inside temperature [C] Tout: outside temperature [C] Tw: pipe temperature [C] Vw: Wind speed [mis] Win: Inside moisture content [kg/kg dry air] Wout: outside moisture content [kg/kg dry air] Ccons: total C02 consumption rate [kg/ha.h] Cvent: C02 loss due to ventilation [ppm/h] Pn: Net photosysnthetic rate [ppm/h] qsens: sensible heat gain by air [GJ/h] qsol: solar heat admitted into greenhouse [GJ/h] qcd: conduction heat loss [GJ/h} qif: infiltration heat loss [GJ/hJ qaccp: heat accumulated by plants [G3/h] qnet: heating or ventilation demand [GJ/hJ N: Number of air changes [1/h] Ns: Actual Ventilation Supply Rate [1/hJ Nt Ventilation Rate for Temperature control [1/h]  Notation:  Solar Temp. lout W/m2  0 0 0 0 0 15 63 154 316 317 414 539 773 844 771 596 533 443 362 97 31 2 0 0  High Low  Time h  1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 0.0 0.0 0.0 0.0 0.0 5.1 21.3 52.0 106.7 107.0 139.7 181.9 260.9 284.9 260.2 201.2 179.9 149.5 122.2 32.7 10.5 0.7 0.0 0.0  PARin W/m2  0 0 0 0 0 4.05 17.01 41.58 85.32 85.59 111.78 145.53 208.71 227.88 208.17 160.92 143.91 119.61 97.74 26.19 8.37 0.54 0 0  inside I J/cm2.h  Case 2. Date: 91243 (Jun 12, 91)  9.8 9.5 9.7 9.8 9.5 8.8 10 10.9 12.3 13 13.7 14.6 15.5 15.6 15.5 15.1 15.1 15.4 15.2 12.9 12.1 11.4 10.7 10.2  Tout C  85 88 89 87 87 76 67 67 56 59 63 63 67 72 59 72 72 72 82 87 80 83 86 88 0.6 0.1 0.2 0.4 0.5 0.4 0.6 1.8 2.1 2.4 3.2 3.1 3.9 4.6 4.5 4.5 4.2 3.2 3.1 2 0.6 0.3 0.5 0.3  vw rn/s  16 15.9 16.3 17.5 18.5 19.8 19.7 19.7 20.4 20.5 23.1 24.3 24.7 24.9 24.8 24.1 24.1 23.1 22.1 18.4 17.2 16.5 15.8 16.2  Tin C  85.1 86 87.6 86.1 83.8 78.7 76.7 75.9 79.9 83.9 87.3 88.6 85 83.6 83.4 85.9 84.2 84.6 82.9 77.1 78.6 83.9 87.1 84.2  RHin %  Simulation Results for Case 2.  RHout %  TABLE 4.2  0.0066 0.0067 0.0068 0.0065 0.0064 0.0053 0.0051 0.0054 0.0050 0.0055 0.0058 0.0063 0.0073 0.0079 0.0064 0.0077 0.0077 0.0078 0.0088 0.0081 0.007 0.0069 0.0071 0.0068  Wo kg/kg  0.01 0.0095 0.0098 0.0106 0.0116 0.0113 0.0116 0.0117 0.0136 0.0165 0.018 0.0196 0.0186 0.0197 0.0192 0.0198 0.0185 0.0134 0.013 0.0122 0.0094 0.0096 0.01 0.0095  Wi kg/kg  36.4 37.8 50.5 62.3 72.1 70.9 60.0 59.6 50.1 50.3 41.9 36.3 35.4 37.2 36.8 38.5 35.3 32.9 49.6 56.8 60.3 61.6 62.9 61.8  Twater C  240.3 296.3 300 342.9 456.1 829.8 505.7 348.6 227.3 225 171 92.3 92.9 74.3 96.3 74.7 97 94.3 114.2 183.6 198.3 225.9 261.8 300  C02 ppm  0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0  3.0 2.1 2.1 0.8 0.5 3.0 32.8 36.5 28.6 31.8 18.2 21.8 29.0 31.2 27.4 17.8 17.4 19.8 23.4 45.3 25.4 22.8 3.2 4.3  vent openings windward leeward % %  0 0 0 0 0 1.5 6.3 15.4 31.6 31.7 41.4 53.9 77.3 84.4 77.1 59.6 53.3 44.3 36.2 9.7 3.1 0.2 0 0  lout/lO  0.0 0.0 0.0 0.0 0.0 -2.5 1.3 3.1 4.8 6.1 2.7 8.2 14.6 16.5 15.4 11.9 10.7 8.9 7.2 1.9 0.6 0.0 0.0 0.0  qsens 03/h  0.0 0.0 0.0 0.0 0.0 1.0 4.3 10.6 21.7 21.7 28.4 37.0 53.0 57.9 52.9 40.9 36.6 30.4 24.8 6.7 2.1 0.1 0.0 0.1  qsol 03/h  0.0 0.0 0.0 0.0 0.0 2.8 -0.2 0.0 1.5 0.2 5.5 2.6 0.9 0.4 -0.2 -1.5 0.0 -2.1 -2.1 -7.9 -2.6 -1.5 0.0 0.0  qaccp 03/h  Simulation Results heat and mass balances  4.3 4.4 4.6 5.4 6.3 7.6 6.7 6.1 5.6 5.2 6.5 6.7 6.4 6.5 6.5 6.3 6.3 5.4 4.8 3.8 3.5 3.5 3.5 4.2  qcd GJ/h  1.7 1.7 1.8 2.1 2.4 2.9 2.6 2.4 2.2 2.0 2.5 2.6 2.5 2.5 2.5 2.4 2.4 2.1 1.8 1.5 1.4 1.4 1.4 1.6  qif GJ/h  0.00 0.00 0.00 0.00 0.00 0.05 0.22 0.55 1.13 1.13 1.47 1.92 2.75 3.01 2.75 2.12 1.90 1.58 1.29 0.35 0.11 0.01 0.00 0.00  Mp kg/s  0.000 0.000 0.000 0.000 0.000 0.008 0.032 0.078 0.160 0.160 0.209 0.272 0.390 0.426 0.389 0.301 0.269 0.224 0.183 0.049 0.016 0.001 0.000 0.000  mm/h  6.0 6.2 6.4 7.4 8.7 13.1 8.1 5.4 3.0 1.1 .3 1.1 0.0 0.0 0.0 0.0 0.0 0.0 0.0 3.4 4.3 4.9 4.9 5.8  heating demand qnet<0 03/h  3.0 3.3 5.5 7.5 9.4 8.9 6.7 6.6 4.7 4.8 2.8 1.7 1.5 1.8 1.7 2.1 1.6 1.4 4.4 6.3 7.2 7.6 8.0 7.7  qf GJJh  0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 5.8 7.5 6.5 3.3 2.0 1.5 0.6 0.0 0.0 0.0 0.0 0.0  venting demand qnet>.0 GJ/h  0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 5.3 6.8 5.9 3.1 1.9 1.6 0.7 0.0 0.0 0.0 0.0 0.0  Nt 1/h  0.0 0.0 0.0 0.0 0.0 0.3 1.0 2.6 3.9 3.1 3.7 4.4 7.4 7.7 6.5 5.3 5.3 8.6 9.3 2.5 1.4 0.1 0.0 0.0  Nh 1/h  C—  Ns 1/h  0.1 0.0 0.0 0.1 0.1 0.1 0.9 2.9 2.7 3.4 2.7 3.1 5.1 6.4 5.5 3.7 3.4 2.9 3.3 3.9 0.7 0.3 0.1 0.1  Nc 1/h  0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 2.9 2.8 2.1 1.2 1.4 1.2 1.5 1.0 1.3 1.1 1.2 0.8 0.3 0.0 0.0 0.0 0 0 0 0 15 67 39 4 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0  Cvent kgfha.h  0.0 0.0 0.0 0.0 0.0 1.7 6.8 14.7 23.0 23.0 25.1 21.2 24.5 21.7 25.1 19.3 21.6 19.4 19.2 8.9 3.3 0.2 0.0 0.0  Pn kg/ha.h  0.0 0.0 0.0 0.0 0.0 4.6 0.4 0.4 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0  qco2 03/h  0.0 0.0 0.0 0.0 0.0 5.4 2.3 3.7 4.4 5.0 4.9 4.5 5.1 4.9. 5.3 4.7 5.1 4.8 4.9 4.4 3.7 3.6 0.0 0.0  qco2= 800 03/h  0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 99.5 0.0 0.0 0.0 97.9 0.0 76.3 0.0 0.0 106.3 136.1 131.5 135.8 0.0 0.0  C02 Suppy kg/ha.h  PARin: inside photosynthetically active radiation [W un: inside solar intensity [Jicm2.h] lout: Outside solar intensity [W/m2} RHin: Inside humidity [%] RHout: Outside humidity [%] Tin: Inside temperature [C] Tout: outside temperature [C] Tw: pipe temperature [C] Vw: Wind speed [mis] Win: Inside moisture content [kg/kg dry air] Wout: outside moisture content [kg/kg dry air] Ccons: total CO2 consumption rate [kg/ha.h] Cvent: C02 loss due to ventilation [ppm/h] Pn: Net photosysnthetic rate [ppm/h] qsens: sensible heat gain by air [GJ/h] qsol: solar heat admitted into greenhouse [03/h] qcd: conduction heat loss [03/h] qif: infiltration heat loss [03/h] qaccp: heat accumulated by plants [03/h] qnet: heating or ventilation demand [03/h] N: Number of air changes [1/h] Ns: Actual Ventilation Supply Rate [1/h] Nt: Ventilation Rate for Temperature control [1/h]  Notation:  Solar Temp. lout W/m2  0 0 0 0 0 0 1 8 27 89 106 105 108 166 156 71 50 36 23 5 0 0 0 0  Low High  Time h  1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 0.0 0.0 0.0 0.0 0.0 0.0 0.3 2.7 9.1 30.0 35.8 35.4 36.5 56.0 52.7 24.0 16.9 12.2 7,8 1.7 0.0 0.0 0.0 0.0  PARin W/m2  Case 3. Date:91355(Aug.30,91)  0 0 0 0 0 0 0.27 2.16 7.29 24.03 28.62 28.35 29.16 44.82 42.12 19.17 13.5 9.72 6.21 1.35 0 0 0 0  inside I J/cm2.h  16.8 16.5 16.6 16.6 16.5 16.4 16.4 16.4 16.3 16.9 17.3 18.0 17.7 18.0 18.5 18.0 17.7 17.4 16.9 15.9 15.3 15.0 14.9 14.7  Tout C  94 94 94 94 94 94 94 94 88 88 94 94 88 88 88 88 88 82 82 88 88 80 94 94  RHout %  TABLE 4.3  1.9 0.4 0.8 1.2 0.5 0.8 1.4 1.3 1.7 1.0 2.0 2.1 2.3 2.5 2.0 2.9 2.5 1.2 2.0 3.1 1.7 2.0 1.9 1.4  vw ni/s  18.2 18.0 17.7 17.4 17.8 19.8 22.1 22.4 22.1 22.2 23.0 24.0 23.5 23.1 22.2 22.7 21.3 20.8 20.9 19.1 17.2 17.0 16.6 16.9  Tin C  89.3 91.5 91.8 92.9 93.5 87.1 78.2 77.8 81.0 83.3 84.8 84.9 84.4 83.3 82.3 82.3 84.1 87.3 85.3 84.6 86.9 87.0 89.9 90.7  RHin %  0.0115 0.0112 0.0113 0.0113 0.0112 0.011 0.0110 0.0110 0.0102 0.0106 0.0116 0.0121 0.0111 0.0114 0.0117 0.0114 0.0111 0.0102 0.0099 0.0099 0.0098 0.0085 0.01 0.0098  0.0117 0.0117 0.0117 0.0116 0.0122 0.0126 0.013 0.0132 0.0134 0.0138 0.015 0.016 0.0154 0.0146 0.0136 0.0143 0.0134 0.0135 0.0132 0.0117 0.0106 0.0105 0.0106 0.0109  Wo Wi kg/kgkglkg  Simulation Results for Case 3.  20.0 20.0 20.0 20.0 28.6 75.0 75.0 75.0 75.0 75.0 75.0 75.0 75.0 75.0 75.0 46.6 35.8 42.5 47.5 27.5 20.4 20.7 22.8 20.0  Twater C  177.9 185.6 194.3 185.9 195.3 203.2 293.6 390.0 387.0 338.8 317.3 319.8 328.0 292.7 261.8 315.2 321.3 377.3 424.2 244.8 176.7 176.4 180.8 193.5  C02 ppm  13.5 25.6 24.4 32.4 3.9 5.0 4.9 1.3 1.5 11.3 9.5 10.0 10.0 24.8 16.6 8.0 1.7 0.0 0.0 20.9 18.3 0.9 0.0 4.0  64.8 79.4 79.3 92.3 49.4 51.1 58.3 60.9 59.4 73.5 64.1 60.0 60.0 80.0 77.7 60.0 42.0 27.9 26.5 71.9 78.4 58.2 55.0 59.2  vent openings windward leeward % %  0 0 0 0 0 0 0.1 0.8 2.7 8.9 10.6 10.5 10.8 16.6 15.6 7.1 5 3.6 2.3 0.5 0 0 0 0  0.0 0.0 0.0 0.0 0.0 0.0 -4.9 -0.8 -0.4 -1.4 -3.2 -3.6 -1.5 -2.3 -2.2 -2.0 -0.7 -0.5 -0.5 -0.1 0.0 0.0 0.0 ‘0.0  qsens GJ/h  0.0 0.0 0.0 0.0 0.0 0.0 0.1 0.5 1.9 6.1 7.3 7.2 7.4 11.4 10.7 4.9 3.4 2.5 1.6 0.3 0.0 0.0 0.0 0.0  qsol 03/h  0.0 0.0 0.0 0.0 0.0 0.0 4.9 0.6 -0.6 0.2 1.7 2.1 -1.1 -0.9 -1.9 1.1 -3.0 -1.1 0.2 -3.8 0.0 0.0 0.0 0.0  qaccp 03/h  Simulation Results heat and mass balances  1.0 1.0 0.8 0.6 0.9 2.4 4.0 4.2 4.0 3.7 4.0 4.2 4.0 3.5 2.6 3.3 2.5 2.4 2.8 2.2 1.3 1.4 1.2 1.5  qcd 03/h  0.7 1.3 0.8 0.5 0.8 2.1 3.1 3.4 2.9 3.4 2.7 2.8 2.6 2.1 1.7 1.9 1.5 1.6 1.7 1.2 1.0 0.9 0.8 1.2  qif GJ/h  1.23 1.15 0.53 0.37 0.27 0.17 0.04 0.00 0.00 0.00 0.00  0.00 0.00 0.00 0.00 0.00 0.00 0.01 0.06 0.20 0.66 0.78 0.78 0.80  Mp kg/s  0.000 0.000 0.000 0.000 0.000 0.000 0.001 0.008 0.028 0.093 0.111 0.110 0.113 0.174 0.164 0.074 0.052 0.038 0.024 0.005 0.000 0.000 0.000 0.000  1.3 1.4 1.1 0.8 1.3 3.3 10.4 6.5 6.0 6.5 8.7 9.4 7.1 7.2 5.7 6.6 4.2 3.8 4.4 3.1 1.8 1.9 1.6 2.1  heating demand qnet<0 GJ/h mm/hr  0.2 0.2 0.3 0.3 1.5 9.7 9.3 9.3 9.3 9.3 9.2 9.0 9.1 9.2 9.3 3.7 2.1 3.3 4.2 1.2 0.4 0.5 0.8 0.4  qf 03/h  0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0  venting demand qnet>0 GJIh  0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0  Nt 1/h  0.0 0.0 0.0 0.0 0.0 0.0 0.1 0,8 1.9 6.2 7.0 6.1 5.7 11.5 18.7 5.4 5.0 2.4 1.5 0.6 0.0 0.0 0.0 0.0  Nh 1/h  1/h  6.4 1.8 3.5 6.3 1.2 1.9 3.8 3.5 4.5 3.6 6.3 6.3 6.9 11.1 8.0 8.5 4.8 1.5 2.4 12.2 7.0 5.1 4.5 3.8  0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 7.0 7.8 13.5 4.9 2.7 4.5 4.3 0.0 0.0 0.1 0.0 0.0 0.0 0.0  Ns  Nc 1/h  0.0 0.0 0.0 0.0 0.0 0.0 0.0 15.7 18.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 6.5 20.0 0.0 0.0 0.0 0.0 0.0  Cvent kg/ha.h  0.0 0.0 0.0 0.0 0.0 0.0 0.1 0.9 3.1 9.6 11.2 11.1 11.4 16.2 15.1 7.8 5.6 4.1 2.7 0.6 0.0 0.0 0.0 0.0  Pn kg/ha.h  0.0 0.0 0.0 0.0 0.0 0.0 0.0 1.7 1.5 0.4 0.0 0.1 0.4 0.0 0.0 0.0 0.0 1.0 1.8 0.0 0.0 0.0 0.0 0.0  qco2 GJ/h  0.0 0.0 0.0 0.0 0.0 0.0 3.9 4.0 3.6 3.9 4.1 4.2 4.3 4.4 4.3 4.2 3.8 4.0 3.8 2.6 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 58.8 74.1 0.0 0.0 0.0 0.0 0.0  C02 qco2=800 Supply GJIh kg/ha.h  PARin: inside photosynthetically active radiation [W lin: inside solar intensity [J!cm2.hJ lout: Outside solar intensity [W/m2] RHin: Inside humidity [%] RHout: Outside humidity [%] Tin: Inside temperature [C] Tout: outside temperature [C] Tw: pipe temperature [C] Vw: Wind speed [rn/si Win: Inside moisture content [kg/kg dry air] Wout: outside moisture content [kg/kg dry air] Ccons: total C02 consumption rate [kg/ha.h] Cvent: C02 loss due to ventilation [ppm/h] Pn: Net photosysnthetic rate [ppm/h] qsens: sensible heat gain by air [GJ/hJ qsol: solar heat admitted into greenhouse [GJ/h] qcd: conduction heat loss [GJ/h] qif: infiltration heat loss [GJ/h] qaccp: heat accumulated by plants [GJ/h] qnet: heating or ventilation demand [GJ/h] N: Number of air changes [1/h] Ns: Actual Ventilation Supply Rate [1/h] Nt: Ventilation Rate for Temperature control [1/hi  Notation:  Tempt. Solar lout W/m2  0 0 0 0 0 0 0 3 26 36 104 99 40 39 41 12 2 2 2 1 0 0 0 0  Low Low  Time h  1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24  0.0 0.0 0.0 0.0 0.0 0.0 0.0 1.0 8.8 12.2 35.1 33.4 13.5 13.2 13.8 4.1 0.7 0.7 0.7 0.3 0.0 0.0 0.0 0.0  PARin W/m2  Dase 4. Date:91456(Nov.9,91)  0 0 0 0 0 0 0 0.81 7.02 9.72 28.08 26.73 10.8 10.53 11.07 3.24 0.54 0.54 0.54 0.27 0 0 0 0  inside I J/cm2.h  8.7 8.8 9.2 9.8 9.7 9.4 8.7 9.2 9.7 10.5 12.2 12.7 12.5 11.4 11.6 11.6 11.6 11.7 11.9 12.1 11.4 10.8 10.9 10.7  Tout C  84 86 88 88 90 95 100 93 93 94 94 87 100 100 94 94 93 90 86 83 82 83 83 80  RHout %  TPLE 4.4  0.1 0.1 0.1 0.2 0.1 0.1 0.1 0.1 0.1 0.2 1.5 1.7 3.6 3.4 2.6 1.5 2.3 3.3 4.9 5.7 4.7 3 2.6 3.7  vw rn/s  17.7 17.4 17.5 17.3 18.0 18.9 20.6 21.4 21.2 21.3 21.6 21.5 21.3 21.2 21.0 20.2 20.8 21.0 20.6 19.0 17.7 17.4 17.4 17.4  Tin C  84.0 85.5 87.6 87.9 86.6 85.1 81.1 78.9 80.3 80.5 77.4 77.4 78.1 79.5 82.0 86.0 81.3 79.5 79.2 81.1 82.1 82.5 82.9 80.3  RHin Wo kg/kg  0.0058 0.006 0.0064 0.0065 0.0068 0.0071 0.0070 0.0067 0.0070 0.0074 0.0083 0.0079 0.0090 0.0084 0.0080 0.0080 0.0078 0.0076 0.0075 0.0073 0.0072 0.0068 0.0069 0.0064  Simulation Results for Case 4.  0.0107 0.0105 0.011 0.0109 0.0113 0.0117 0.0125 0.0126 0.0125 0.0126 0.0126 0.0126 0.0123 0.0125 0.0128 0.0125 0.0125 0.0124 0.0121 0.0113 0.0104 0.0103 0.0104 0.0098  Wi kg/kg  36.3 43.1 43.5 48.2 47.2 65.5 75.0 68.7 70.2 66.0 65.0 65.0 65.0 65.0 47.3 52.9 56.6 53.3 43.7 39.3 38.3 40.7 47.1 53.5  Twater C  484 494 496 500 507 527 537 888 1042 686 392 297 409 1268 1632 1336 1256 1143 994 965 838 766 734 705  C02 ppm  0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0  5.8 5.4 8.5 7.8 8.5 4.1 6.2 14.5 11.1 16.2 11.8 13.0 6.7 7.0 10.0 5.0 5.0 5.0 5.0 5.4 5.8 5.0 5.0 5.0  ‘ent openings windward leeward %  0.0 0.0 0.0 0.0 0.0 0.0 0.0 -1.9 -1.7 -2.6 -7.6 -6.7 -2.7 -2.6 -2.8 -0.8 -1.4 -0.6 -0.1 -0.1 0.0 0.0 0.0 0.0  qsens 03/h  0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.2 1.8 2.5 7.1 6.8 2.7 2.7 2.8 0.8 0.1 0.1 0.1 0.1 0.0 0.0 0.0 0.0  qsol 03/h  0.0 0.0 0.0 0.0 0.0 0.0 0.0 1.7 -0.4 0.2 0.6 -0.2 -0.4 -0.2 -0.4 -1.7 1.3 0.4 -0.9 -3.4 0.0 0.0 0.0 0.0  qaccp GJ/h  Simulation Results heat and mass balances  6.3 6.0 5.8 5.2 5.8 6.6 8.3 8.5 8.0 7.5 6.5 6.1 6.1 6.8 6.5 6.0 6.4 6.5 6.0 4.8 4.4 4.6 4.5 4.7  qcd 03/h  2.4 2.3 2.2 2.0 2.2 2.5 3.2 3.3 3.1 2.9 2.5 2.4 2.4 2.6 2.5 2.3 2.5 2.5 2.3 1.8 1.7 1.8 1.7 1.8  qif OJ/h  0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.04 0.35 0.48 1.40 1.33 0.54 0.52 0.55 0.16 0.03 0.03 0.03 0.01 0.00 0.00 0.00 0.00  Mp kg/s  0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.006 0.050 0.069 0.198 0.189 0.076 0.074 0.078 0.023 0.004 0.004 0.004 0.002 0.000 0.000 0.000 0.000  mm/hr  8.7 8.3 8.0 7.2 8.0 9.1 11.5 13.6 12.8 13.0 16.7 15.1 11.2 12.1 11.8 9.1 10.3 9.5 8.5 6.7 6.1 6.4 6.3 6.4  Heating Demand qnet<0 03/h  3.6 5.1 5.2 6.3 5.9 10.0 12.0 10.3 10.7 9.6 9.3 9.3 9.4 9.4 5.3 6.7 7.5 6.7 4.6 4.0 4.0 4.6 6.0 7.5  qf 03/h  0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0  Venting Demand qnet>0 GJJh  0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0  Nt 1/h  0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.2 1.9 2.8 9.9 8.7 5.0 3.9 3.5 1.1 0.2 0.2 0.2 0.1 0.0 0.0 0.0 0.0  Nh 1/h  Ns 1/h  0.0 0.0 0.0 0.1 0.0 0.0 0.0 0.1 0.1 0.2 0.9 1.1 1.3 1.3 1.3 0.4 0.7 1.0 1.5 1.8 1.6 0.9 0.8 1.1  Nc 1/h  0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 10.5 11.2 11.5 12.2 12.2 13.4 14.3 41.1 52.0 28.0 6.9 0.0 11.3 149.8 210.2 101.3 108.6 112.1 113.3 122.8 89.6 56.7 49.2 54.0  Cvent kg/ha.h  0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.3 3.0 4.0 10.7 9.9 4.4 4.4 4.7 1.4 0.2 0.2 0.2 0.1 0.0 0.0 0.0 0.0  Pn kgfha.h  0.0 0.0 0.0 0.0 0.0 0.0 0.0 4.7 4.6 0.5 0.0 0.0 1.7 15.1 17.0 5.8 7.3 7.4 7.3 8.5 0.0 0.0 0.0 0.0  qco2 GJ/h  0.0 0.0 0.0 0.0 0.0 0.0 0.0 5.2 4.4 1.9 2.7 3.6 4.3 8.0 5.5 2.0 3.0 2.9 2.7 3.3 0.0 0.0 0.0 0.0  qco2=800 G3/h  0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 189.0 0.0 0.0 0.0 0.0 0.0 177.0 0.0 133.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0  C02 Supply kgfha.h  PAR1n: inside photosynthetically active radiation [W un: inside solar intensity [Jlcm2.h] lout: Outside solar intensity [W1m2J RHin: Inside humidity [%j RHout: Outside humidity [%J Tin: Inside temperature [C] Tout: outside temperature [C] Tw: pipe temperature [C] Vw: Wind speed [mis] Win: Inside moisture content [kg/kg dry air] Wout: outside moisture content [kg/kg dry air] Ccons: total CO2 consumption rate [kg/ha.h] Cvent: C02 loss due to ventilation [ppm/h] Pn: Net photosysnthetic rate [ppm/h] qsens: sensible heat gain by air [GJ/h] qsol: solar heat admitted into greenhouse [GJ/h] qcd: conduction heat loss [GJ/h} qif: infiltration heat loss [GJIhJ qacep: heat accumulated by plants [GJ/h] qnet: heating or ventilation demand [GJ/hJ N: Number of air changes [1/h] Ns: Actual Ventilation Supply Rate [1/h] Nt: Ventilation Rate for Temperature control [1/h]  Notation:  I  V C  1  Solar/i 0, w/m2 —a— Windspeed,m/s —--  Temperature, C —>E--- Moisture Cont.kg/kg —I-—  Time, h —*—  Relative Humity,%  Fig. 4.la <Case 1: Outside Condition>  C)  o .s  0.0025  o.005  0.0075  p.01  4-,  ci  0.0125 S C  0.015  0.0175  .02  ±  S C) F-  a  0  E D I  0  I  I-  CtS  C  Cl)  a  C  1  —B—  —.—  Pipe Temp. C Moisture Cont.kg/kg  —)E--  —I-—  Inside Temp. C Transpiration, kg/s  Time, h  —*--  Inside R.F-L, %  Fig. 4.lb <Case 1: Inside Condition>  a)  4-i  D Cl) 0  0 a) I  C 0  4-i  C  .  C)  C) .‘  -,  a) I  C  (‘3  q(sol), GJ/h —a-- Ventilation Demand ——  ——  —H---  q(sens), GJ/h Heating Supply  Time, h  —IE--  Heating Demand  Fig. 4.lc <Case 1: Heating Requirement>  ‘4  cJ  ——  I  -c C-)  C  C)  ci)  Cl)  -c  Temp. Control  —I-—  Humidity Control  —*--  C02 Replenishm’t  Time, h  —B--  Fig. 41d <Case 1: Ventilat’n Req’ment>  Act’l Vent’n Supply S  C  0  C  -I-s  C)  Cl)  ——  4  SI  —H-—  Pn, kg/ha.h  8  iI  C02 Conc., ppm  00  20-  40-  80-  100-  120-  140-  160  180-  200  —1E—  Time, h  12  Cvent, kg/ha.h  16  S  —6—  20  Fig. 4.1 e <Case 1: 002 Requirement>  \ 24  Cs, kg/ha.h  /  -400  600  -800  -1000  -1200  .9  U)  a)  o  C’]  0  0  C  C 12)  1  0  I  C  1  —B—  ——  Solar/i 0, w/m2 Windspeed, rn/s  ——  —I-—  Outside Temp. C Moisture Cont,kg/kg  Time, h  —fE--  Outside R.H, %  Fig. 4.2a <Case 2: Outside Condition>  D)  0  Cl)  C-) ci) D  0  C  a)  C  -  -  ci)  S I—  a  0  S D I  0  I  C  U)  0  C 0  Pipe Temp. C —a— Moisture Cont.kg/kg ——  —>E—  —H-—  Inside Temp. C Transpiration, kg/s  Time, h  12  —*--  Inside R.H. %  Fig. 4.2b <Case 2: Inside Condition>  0.0075  25  5c  75  I  ci)  0)  0  q(sol), GJ/h —a-- Vent’n Demand,GJ/h  —.--  —>E—  —H—-  q(sens), GJ/h Heating Supply,GJ/h  Time, h  —E--  Heating Demand,GJ/h  Fig. 4.2c <Case 2: Heating Requirement>  —.—  a) >  C  C 0  r  Temp. Control, 1/h  1  —I--—  Humid. Control, 1/h  —*—  C02 Replenishm’t  Time, h  —El—  Fig. 4.2d <Case 2: Vent’n Requirement>  Act’l Vent’n Supply -x  100•  ci  L.  C)  >  4-,  0  ——  4  8  C02 Conc. ppm —±— Pn, kg/ha.h  0  20-  40-  60-  80  C)  -c  -  120  140-  ---*---  Time, h  12  16  I  —B--  20  a a  2  J1300  cj 0  Cs, kg/ha.h  24  -100  C’)  .9  0  C)  -400  a)  C  4-,  500  600  0 C 0  -  -700 0  800  900  1000  -200  Cvent, kg/ha.h  —  I  Fig. 4.2e <Case 2: C02 Requirement>  I  C  -C  1’  —a— Solar/i 0, w/m2 —B-- Windspeed, rn/s  —?<--  —I-—  Outside Temp. C Moisture Cont.kg/kg  Time, h —-?iE—  Outside R.H., %  Fig. 4.3a <Case 3: Outside Condition>  C) -  0.0075  ‘3)  C)  C ‘3) C C  Q4J  nr  75  t  —a  ci E F-  ——  Pipe Temp. C Moisture cont.kg/kg  —I---  —8—  —>E—  Inside Temp. C Transpiration, kg/s  —fE--  Inside R.H., %  0  C’)  C) :3  0  0  I.  C C) C 0  4-’  Time, h  0) -  E I  0  F  C (ts I-  U)  0  0  1  Fig. 4.3b <Case 3: Inside Condition>  -  ci) I  c3) C  0  -C  —9—  —.--  q(sol), GJ/h Ventilation Demand  ——  —I-—-  q(sens), GJ/h Heating Supply  Time, h  —*—  Heat’g Demand, GJ/h  Fig.4.3c <Case 3: Heating Requirement>  —  ——  I  0  -C  C  a) r)  -c  Temp. Control, 1/h  —±--  Humid. Control, 1/h  —*--  C02 replenishment  Time, h —6—  Fig. 4.3d <Case 3: Vent’n Requirement>  Act’I vent’n Supply  -  c!  —.—  -----i  I  -  300  a)  8  0 C  C  1  0  -400 Ea a  0  .,r O 2 Oc’.  _________  C02 Conc., ppm  4  —±--  Pn., kg/ha.h  8  —E---  12 Time, h  Cvent, kg/ha.h  16  I,I  —B—  20  /\  ij  L  24  Cs, kg/ha.h  11J  100  C’)  _____\jwoci)  0  0-  10-  30-  40C ci)  C-)  6O-  70-  80-  Fig. 4.3e <Case 3: C02 Requirement>  _  0 Co  Ct  1  0  S ci) I  a  0  S D I  t3  0  I  0 C  1  11  Solar Radiat’n,w/m2 —a— Windspeed, mis ——  —>E—  —I—  Outside Temp., C Moisture Cont.kgikg  Time, h  12  -*--  Outside R.H., %  Fig. 4.4a <Case 4: Outside Condition>  0  C’)  I  0) D 4-.  C)  0  4-  ci) C  C  4-.  C)  C)  -S  -$  1! D 0 C D  -‘—I  Temp. or Humidity or Transpiration  -n  (p  cr A  C) C,) CD  H  3  CD  DCD  D C’)  0  C) CD  C) 0  0  Li  0 :3  V  a) I  4-’  0) C  (!3  -c  —e— q(sol), GJ/h —8--- Vent’n Demand, GJ/h  —?E—  —±—  q(sens), GJ/h Heating Suppty,GJ/h  Time, h  —*—  Heating Demand,GJ/h  Fig.4.4c <Case 4: Heating Requirement>  Cl)  ——  C-)  C Ct5 .C  a)  o  — -  4  Temp. Control, 1/h  O  •  1O  —I-—  12  i  Humidity Cont’l,l/h  —IE—  —  16  i  —Eb-  —  Act’l Vent’n Supply  I I—i r— 20  C02 Replenishm’t  Time, h  H-R —  8  H—-i  -•--  Fig.4.4d <Case 4: Vent’n Requirement>  140-  160-  c  0  G)  ——  0  J  4  -H--—  /  --*--  Time, h  12  ‘.  Pn. kg/ha.h  8  rnmmcImJmL  —.m  C02 Conc., ppm  0-  20-  40-  60  80-  • 100-  I-.  o 120-  -c ct  160-  200-  220-  ______ _________  __  H  /  Cvent, kg/ha.h  I  / \  1\\  —B---  2  c  m  a a  24  -200  400  600  1000  -1200  C,)  C)  0  C.)  a)  C  0  -1400 E  -1600  -1800  Cs, kg/ha.h  m  ________  Fig. 4.4e <Case 4: C02 Requirement>  ______  _______ _____  84 SECTION 5. CONCLUSIONS ND RECOMMENDATIONS  5.1 Conclusions  The balances  mathematical for  the  model  which  greenhouse  comprised  thermal  of  heat  and  environment  and  mass crop  photosynthesis has yielded reasonably accurate simulation results when compared to observed values.  This model could be adopted as  guidelines for an integrated climate control algorithm for energy conservation purposes.  Heating requirement was predicted to within 10—14% for three typical actual  cases energy  of  weather  conditions,  consumption  data  under  but  deviated  one  situation  by  35%  from  (case  #3).  Predicted ventilation demand also followed closely the trend of observed vent  openings data,  overpredicted  ventilation  except for case #4 when the model  rates  for  humidity  control.  Possible  causes for the discrepancies between simulated and measured data were  explored,  improvement  in  and  the  climate  analyses control  have  actions.  provided The  guidelines  model  was  able  for to  predict carbon dioxide input from heating supply computations; in general, the predicted supply of CO 2 is compatible with the measured 2 CO  concentration  circumstances  of  profiles,  case  #2  compared to actual data.  though  weather  predictions  conditions  were  under  not  the  realistic  85 Energy saving is achieved in different manners for the four In  cases.  case  #1,  excess  solar  energy  is  available  after  ventilation and can be stored for nighttime use, thus saving fossil Ventilation  fuels.  requirements  for  temperature  control  humidity control are about the same for case #2 conditions,  and and  energy saving is realized if supplemental heat can be minimized by adopting a higher tolerance  level  for humidity.  needs heating throughout the daytime hours,  The greenhouse  yet CO 2 depletion is  severe due to excessive ventilation; simulation results indicated that energy saving is possible if vent openings were restricted to 20%  or  below.  For  case  #4,  the  heating,  ventilation  and  2 CO  enrichment processes are well integrated; the model predicted no additional energy saving.  5 • 2 Recommendations  The following recommendations are made for further investigations, with an aim to finetune and validate the computer model before it can be adopted in climate control computers for improved climate control actions.  Plant tissue temperatures should be routinely measured along with  greenhouse  temperature  so  as  to  generate  more  precise  predictions for sensible heat gain and hence ventilation rate for temperature control. The plant temperature can also be used in the  86 temperature function of the photosynthesis submodel.  Transpiration rate should be measured, and used to calibrate an  improved  transpiration  submodel,  which  would  account  for  environmental factors other than solar radiation alone. This will improve predictions of ventilation rate for humidity control.  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ASAE 33(5): 1701—1709.  94  APPENDIX A  95 <Case 1: Heating Requirement>  Time h  1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24  Tin C  16.0 15.8 16.3 17.5 18.8 19.8 20.8 21.1 22.6 24.6 25.4 26.7 26.7 27.4 27.2 27.5 26.7 20.9 21.0 18.7 16.7 16.2 16.1 16.0  qsens GJ/h  qsol GJ/h  qnet<0 GJ/h  qf GJ/h  0.0 0.0 0.0 0.0 0.0 —1.6 1.0 6.0 6.8 10.4 17.7 19.7 24.1 22.7 23.3 21.3 18.0 2.7 1.0 1.5 0.7 0.0 0.0 0.0  0.0 0.0 0.0 0.0 0.0 1.4 8.0 16.7 25.2 37.1 49.0 56.6 60.8 61.1 58.7 55.3 45.3 6.9 3.2 3.8 1.8 0.1 0.0 0.1  6.9 7.1 8.0 9.5 11.1 13.6 9.6 2.1 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 4.5 6.5 3.9 2.8 3.1 3.4 3.2  6.8 8.7 10.4 11.3 11.9 13.1 10.7 9.6 7.2 4.8 3.9 2.5 1.5 1.4 1.4 0.5 1.0 2.3 5.0 0.3 0.6 1.5 2.0 2.3  175.5  491.2  95.2  120.7  Notation; Tin qsens qsol qnet<0 qf  :  inside temperature [oC) sensible heat gain by air [GJ/h) : solar heat admitted into greenhouse[GJ/h) : heating demand [GJ/h) : actual(furnace) heat supply [GJ/h]  96 <Case 1: Ventilation Requirement>  Time h  1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24  Tin C  RHin  qnet>0 GJ/h  16.0 15.8 16.3 17.5 18.8 19.8 20.8 21.1 22.6 24.6 25.4 26.7 26.7 27.4 27.2 27.5 26.7 20.9 21.0 18.7 16.7 16.2 16.1 16.0  86.2 87.4 88.4 87.8 87.1 84 . 7 81.2 83.7 84.5 86.5 85. 1 85.2 86.0 81.8 76.2 73.8 72.6 86.2 87.9 83.8 81.4 87.6 85.3 87.8  0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.1 3.6 10.6 11.8 16.5 15.1 17.1 15.1 15.3 7.9 0.0 1.0 1.5 0.0 0.0 0.0  Nt 1/h  Nh 1/h  Nc 1/h  Ns 1/h  0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.1 4.3 12.1 12.1 17.6 16.1 20.8 19.9 27.9 8.8 0.0 1.6 3.5 0.0 0.0 0.0  0.0 0.0 0.0 0.0 0.0 0.2 1.4 3.3 5.8 6.5 7.9 7.4 8.6 8.1 9.3 9.4 9.7 1.1 0.5 1.2 1.4 0.0 0.0 0.0  0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.7 2.6 2.5 2.0 1.7 1.6 1.7 1.3 0.9 1.3 0.0 0.0 0.2 0.0 0.0 0.0  0.0 0.0 0.0 0.0 0.0 0.0 0.1 0.1 0.3 0.7 2.0 4.7 6.6 7.4 7.4 7.2 5.3 1.1 0.9 4.0 0.9 0.2 0.2 0.3  Notation; Tin RHin qnet>0 Nt Nh NC Ns  : : : : : : :  inside temperature [oC) inside humidity [%) ventilation demand IGJ/h) ventilation rate for temp. control [1/h) ventilation rate for humidity control [1/h) ventilation demand for C02 [1/h) actual ventilation supply rate [1/h)  97  <Case 1: C02 Requirement>  Time h  1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24  C02 ppm  Cvent kg/ha.h  373.5 377.8 391.5 398.5 547.0 1084.6 762.4 493.1 330.5 184.4 161.9 130.2 108.5 102.3 111.0 88.3 67.9 241.4 712.8 407.4 182.0 204.4 228.5 220.7  2.4 2.7 3.7 4.2 14.8 54.6 32.5 12.3 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 49.2 23.7 0.0 0.0 0.0 0.0  Pn supply )cg/ha.hkg/ha.h  0.0 0.0 0.0 0.0 0.0 2.2 11.5 21.3 27.1 28.4 30.9 29.3 26.9 26.0 27.0 22.8 17.8 9.0 4.7 5.5 2.5 0.1 0.0 0.0  0.0 0.0 0.0 0.0 0.0 185.4 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 69.5 35.1 68.5 0.0 0.0 21.5 0.0 0.0 380.0  Notation; C02 Cvent Pn Supply  : : : :  carbon dioxide concentration [ppm] C02 loss due to ventilation [kg/ha.h] net photosynthetic rate [kg/ha.h] C02 supply [kg/ha.h)  98  <Case 2: Heating Requirement>  Time h  1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24  Tin C  16 15.9 16.3 17.5 18.5 19.8 19.7 19.7 20.4 20.5 23.1 24.3 24.7 24.9 24.8 24.1 24.1 23.1 22.1 18.4 17.2 16.5 15.8 16.2  qsens GJ/h  qsol GJ/h  qnet<0 GJ/h  0.0 0.0 0.0 0.0 0.0 —2.5 1.3 3.1 4.8 6.1 2.7 8.2 14.6 16.5 15.4 11.9 10.7 8.9 7.2 1.9 0.6 0.0 0.0 0.0  0.0 0.0 0.0 0.0 0.0 1.0 4.3 10.6 21.7 21.7 28.4 37.0 53.0 57.9 52.9 40.9 36.6 30.4 24.8 6.7 2.1 0.1 0.0 0.1  6.0 6.2 6.4 7.4 8.7 13.1 8.1 5.4 3.0 1.1 6.3 1.1 0.0 0.0 0.0 0.0 0.0 0.0 0.0 3.4 4.3 4.9 4.9 5.8  3.0 3.3 5.5 7.5 9.4 8.9 6.7 6.6 4.7 4.8 2.8 1.7 1.5 1.8 1.7 2.1 1.6 1.4 4.4 6.3 7.2 7.6 8.0 7.7  430.1  95.7  116.4  111.6  qf GJ/h  Notation; Tin inside temperature [oC) qsens sensible heat gain by air [GJ/hJ qsol solar heat admitted into greenhouse[GJ/h] qnet<0 heating demand [GJ/h) qf : actual(furnace) heat supply [GJ/h)  99  <Case 2: Ventilation Requirement>  Time h  1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24  Tin C  Ruin  16 15.9 16.3 17.5 18.5 19.8 19.7 19.7 20.4 20.5 23.1 24.3 24.7 24.9 24.8 24.1 24.1 23.1 22.1 18.4 17.2 16.5 15.8 16.2  85.1 86 87.6 86.1 83.8 78.7 76.7 75.9 79.9 83.9 87.3 88.6 85 83.6 83.4 85.9 84.2 84.6 82.9 77.1 78.6 83.9 87.1 84.2  qnet>0 GJ/h  0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 5.8 7.5 6.5 3.3 2.0 1.5 0.6 0.0 0.0 0.0 0.0 0.0  Nt 1/h  Nh 1/h  0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 5.3 6.8 5.9 3.1 1.9 1.6 0.7 0.0 0.0 0.0 0.0 0.0  0.0 0.0 0.0 0.0 0.0 0.3 1.0 2.6 3.9 3.1 3.7 4.4 7.4 7.7 6.5 5.3 5.3 8.6 9.3 2.5 1.4 0.1 0.0 0.0  NC 1/h  0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 2.9 2.8 2.1 1.2 1.4 1.2 1.5 1.0 1.3 1.1 1.2 0.8 0.3 0.0 0.0 0.0  Ns 1/h  0.1 0.0 0.0 0.1 0.1 0.1 0.9 2.9 2.7 3.4 2.7 3.1 5.1 6.4 5.5 3.7 3.4 2.9 3.3 3.9 0.7 0.3 0.1 0.1  Notation; Tin RUin qnet>O Nt Nh NC Ns  : : : : : : :  inside temperature [CC) inside humidity [%) ventilation demand [GJ/h] ventilation rate for temp. control [1/h) ventilation rate for humidity control [1/h) ventilation demand for C02 [1/h] actual ventilation supply rate [1/h)  100  <Case 2:  C02 Requirement>  Time h  C02 ppm  1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24  240.3 296.3 300 342.9 456.1 829.8 505.7 348.6 227.3 225 171 92.3 92.9 74.3 96.3 74.7 97 94.3 114.2 183.6 198.3 225.9 261.8 300  Cvent Pn kg/ha.hkg/ha.h  0 0 0 0 15 67 39 4 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0  0.0 0.0 0.0 0.0 0.0 1.7 6.8 14.7 23.0 23.0 25.1 21.2 24.5 21.7 25.1 19.3 21.6 19.4 19.2 8.9 3.3 0.2 0.0 0.0  Suppy kg/ha.h  0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 99.5 0.0 0.0 0.0 97.9 0.0 76.3 0.0 0.0 106.3 136.1 131.5 135.8 0.0 0.0 783.4  Notation; C02 carbon dioxide concentration [ppm] Cvent : C02 loss due to ventilation [kg/ha.h) Pn : net photosynthetic rate [kg/ha.h) Supply : C02 supply [kg/ha.h]  101 <Case 3: Heating Requirement>  Time h  1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24  Tin C  18.2 18.0 17.7 17.4 17.8 19.8 22.1 22.4 22.1 22.2 23.0 24.0 23.5 23.1 22.2 22.7 21.3 20.8 20.9 19.1 17.2 17.0 16.6 16.9  qsens GJ/h  qsol GJ/h  qnet<O GJ/h  0.0 0.0 0.0 0.0 0.0 0.0 —4.9 —0.8 —0.4 —1.4 —3.2 —3.6 —1.5 —2.3 —2.2 —2.0 —0.7 —0.5 —0.5 —0.1 0.0 0.0 0.0 0.0  0.0 0.0 0.0 0.0 0.0 0.0 0.1 0.5 1.9 6.1 7.3 7.2 7.4 11.4 10.7 4.9 3.4 2.5 1.6 0.3 0.0 0.0 0.0 0.0  1.3 1.4 1.1 0.8 1.3 3.3 10.4 6.5 6.0 6.5 8.7 9.4 7.1 7.2 5.7 6.6 4.2 3.8 4.4 3.1 1.8 1.9 1.6 2.1  0.2 0.2 0.3 0.3 1.5 9.7 9.3 9.3 9.3 9.3 9.2 9.0 9.1 9.2 9.3 3.7 2.1 3.3 4.2 1.2 0.4 0.5 0.8 0.4  —24.0  65.2  106.1  111.9  qf GJ/h  Notation; Tin : inside temperature [oC) qsens : sensible heat gain by air [GJ/h) qsol : solar heat admitted into greenhouse[GJ/hJ qnet<0 heating demand [GJ/h) qf actual(furnace) heat supply [GJ/h)  102 <Case 3: Ventilation Requirement>  Time h  1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24  Tin C  REin  18.2 18.0 17.7 17.4 17.8 19.8 22.1 22.4 22.1 22.2 23.0 24.0 23.5 23.1 22.2 22.7 21.3 20.8 20.9 19.1 17.2 17.0 16.6 16.9  89.3 91.5 91.8 92.9 93.5 87.1 78.2 77.8 81.0 83.3 84.8 84.9 84.4 83.3 82.3 82.3 84.1 87.3 85.3 84.6 86.9 87.0 89.9 90.7  qnet>0 GJ/h  0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0  Nt 1/h  Nh 1/h  NC 1/h  Ns 1/h  0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0  0.0 0.0 0.0 0.0 0.0 0.0 0.1 0.8 1.9 6.2 7.0 6.1 5.7 11.5 18.7 5.4 5.0 2.4 1.5 0.6 0.0 0.0 0.0 0.0  0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 7.0 7.8 13.5 4.9 2.7 4.5 4.3 0.0 0.0 0.1 0.0 0.0 0.0 0.0  6.4 1.8 3.5 6.3 1.2 1.9 3.8 3.5 4.5 3.6 6.3 6.3 6.9 11.1 8.0 8.5 4.8 1.5 2.4 12.2 7.0 5.1 4.5 3.8  Notation Tin: RHin qnet>0 Nt: Nh: NC: Ns:  inside temperature [oC) inside humidity [%) ventilation demand [GJ/h) ventilation rate for temp. control [1/h) ventilation rate for humidity control [1/h) ventilation demand for C02 (1/h) actual ventilation supply rate [1/h)  103 <Case 3: C02 Requirement>  Time h  C02 ppm  1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24  177.9 185.6 194.3 185.9 195.3 203.2 293.6 390.0 387.0 338.8 317.3 319.8 328.0 292.7 261.8 315.2 321.3 377.3 424.2 244.8 176.7 176.4 180.8 193.5  Cvent Pn kg/ha.hkg/ha.h  0.0 0.0 0.0 0.0 0.0 0.0 0.0 15.7 18.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 6.5 20.0 0.0 0.0 0.0 0.0 0.0  0.0 0.0 0.0 0.0 0.0 0.0 0.1 0.9 3.1 9.6 11.2 11.1 11.4 16.2 15.1 7.8 5.6 4.1 2.7 0.6 0.0 0.0 0.0 0.0  Supply kg/ha.h  0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 58.8 74.1 0.0 0.0 0.0 0.0 0.0  Notation; C02 Cvent Pn Supply  : carbon dioxide concentration [ppm) : C02 loss due to ventilation [kg/ha.h] : net photosynthetic rate [kgfha.h) : C02 supply [kg! ha.h)  104 <Case 4: Heating Requirement>  Time h  1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24  Tin C  17.7 17.4 17.5 17.3 18.0 18.9 20.6 21.4 21.2 21.3 21.6 21.5 21.3 21.2 21.0 20.2 20.8 21.0 20.6 19.0 17.7 17.4 17.4 17.4  qsens GJ/h  0.0 0.0 0.0 0.0 0.0 0.0 0.0 —1.9 —1.7 —2.6 —7.6 —6.7 —2.7 —2.6 —2.8 —0.8 —1.4 —0.6 —0.1 —0.1 0.0 0.0 0.0 0.0 —31.6  qsol GJ/h  qnet<0 GJ/h  qf GJ/h  0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.2 1.8 2.5 7.1 6.8 2.7 2.7 2.8 0.8 0.1 0.1 0.1 0.1 0.0 0.0 0.0 0.0  8.7 8.3 8.0 7.2 8.0 9.1 11.5 13.6 12.8 13.0 16.7 15.1 11.2 12.1 11.8 9.1 10.3 9.5 8.5 6.7 6.1 6.4 6.3 6.4  3.6 5.1 5.2 6.3 5.9 10.0 12.0 10.3 10.7 9.6 9.3 9.3 9.4 9.4 5.3 6.7 7.5 6.7 4.6 4.0 4.0 4.6 6.0 7.5  27.9  236.2  173.0  Notation; Tin qsens qsol qnet<0 qf  : inside temperature [oC] : sensible heat gain by air [GJ/h) : solar heat admitted into greenhouse[GJ/h) : heating demand [GJ/h) : actual(furnace) heat supply [GJ/h]  105 <Case 4: Ventilation Requirement>  Time h  1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24  Tin C  RHin  17.7 17.4 17.5 17.3 18.0 18.9 20.6 21.4 21.2 21.3 21.6 21.5 21.3 21.2 21.0 20.2 20.8 21.0 20.6 19. 0 17.7 17.4 17.4 17.4  84. 0 85.5 87. 6 87.9 86.6 85.1 81.1 78.9 80.3 80.5 77.4 77.4 78. 1 79.5 82. 0 86.0 81.3 79.5 79.2 81.1 82 . 1 82.5 82.9 80.3  qnet>0 GJ/h  0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0  Mt 1/h  0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0  Nh 1/h  0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.2 1.9 2.8 9.9 8.7 5.0 3.9 3.5 1.1 0.2 0.2 0.2 0.1 0.0 0.0 0.0 0.0  Mc 1/h  Ms 1/h  0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0  0.0 0.0 0.0 0.1 0.0 0.0 0.0 0.1 0.1 0.2 0.9 1.1 1.3 1.3 1.3 0.4 0.7 1.0 1.5 1.8 1.6 0.9 0.8 1.1  Notation; Tin Rim qnet>0 Nt Nh Nc Ms  : : : : : : :  inside temperature [oC) inside humidity [%) ventilation demand [GJ/h] ventilation rate for temp. control [1/h) ventilation rate for humidity control [1/h) ventilation demand for C02 [1/h) actual ventilation supply rate [1/h)  106  <Case Time h  1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24  4:  C02 Requirement>  C02 ppm  484 494 496 500 507 527 537 888 1042 686 392 297 409 1268 1632 1336 1256 1143 994 965 838 766 734 705  Cvent Pn kg/ha.hkg/ha.h  10.5 11.2 11.5 12.2 12.2 13.4 14.3 41.1 52.0 28.0 6.9 0.0 11.3 149.8 210.2 101.3 108.6 112.1 113.3 122.8 89.6 56.7 49.2 54.0  0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.3 3.0 4.0 10.7 9.9 4.4 4.4 4.7 1.4 0.2 0.2 0.2 0.1 0.0 0.0 0.0 0.0  Supply kg/ha.h  0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 189.0 0.0 0.0 0.0 0.0 0.0 177.0 0.0 133.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 499.2  Notation; C02 carbon dioxide concentration [ppm] Cvent : C02 loss due to ventilation [kg/ha.hJ Pn : net photosynthetic rate [kg/ha.hJ Supply C02 supply [kg/ha.h]  a XTGNIdcTV  LOT  TOTAL  15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30  14  12 13  11  4 5 6 7 8 9 10  3  160.8  3.5 5.3 4.8 6.5 3.6 5.5 6.6 5.6 5.2 7.3 5.8 5.0 5.9 6.3 6.2 5.7 8.7 3.8 2.9 7.1 6.0 5.2 4.6 3.7 6.9 5.6 3.9 2.7 6.3 4.6  1  2  VOLUME m 3 10  DAY  JUN, 1991  6,208.0  138.0 207.0 187.0 252.0 139.0 210.0 254.0 215.0 201.0 281.0 224.0 193.0 228.0 243.0 239.0 218.0 333.0 146.0 110.0 273.0 234.0 202.0 177.0 143.0 267.0 217.0 151.0 105.0 243.0 178.0  ENERGY (G.3)  MA XNTERRtJT’TIBLE STATEMENT  158.9  3.7 3.5 3.3 2.1 5.5 3.5 5.3 5.5 6.2 7.2 5.5 7.5 4.3 3.7 3.5 3.1 3.2 3.7 4.1 3.9 3.6 3.1 5.1 5.6 5.3 8.2 8.4 8.8 7.4 7.5 7.6  VOLUME m 3 10  6,053.0  144.0 135.0 128.0 82.0 215.0 136.0 204.0 212.0 239.0 276.0 208.0 283.0 162.0 139.0 132.0 116.0 120.0 139.0 154.0 147.0 136.0 117.0 192.0 211.0 200.0 309.0 317.0 333.0 284.0 288.0 295.0  ENERGY (GJ)  <Monthly Energy Consumptio n Data>  TOTAL  10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31  1 2 3 4 5 6 7 8  DAY  MA INTERRUPTIBLE STAENT )UG, 1991 STATEMENT DATE: 1991-09-05  TOTAL  1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30  DAY  313.1  12.5 10.4 12.1 10.3 10.7 10.4 8.1 8.7 9.6 9.2 9.3 10.7 11.6 13.1 10.1 11.3 10.8 9.3 12.2 12.0 11.2 10.2 11.2 10.3 7.0 8.8 7.8 12.3 11.3 10.6  io33  VOLUME  12,071.0  485.0 402.0 467.0 398.0 413.0 400.0 312.0 336.0 370.0/ 354.0 359.0 411.0 447.0 503.0 388.0 436.0 416.0 258.0 470.0 463.0 432.0 394.0 432.0 396.0 270.0 339.0 300.0 473.0 436.0 409.0  (cs)  ENERGY  MA INTEREJJPTIELE STATEMENT NOV, 1991 SmTEMEN’r DATE: 1991-12-03  

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