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The feasiblity of solar-powered, self-propelled data buoys Egles, David William 1987

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THE FEASIBILITY OF SOLAR-POWERED, SELF-PROPELLED DATA BUOYS by DAVID WILLIAM EGLES B . S c , The U n i v e r s i t y of V i c t o r i a , 1984. A THESIS SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE i n THE FACULTY OF GRADUATE STUDIES DEPARTMENT OF OCEANOGRAPHY We accept t h i s t h e s i s as conforming to the r e q u i r e d standard THE UNIVERSITY OF BRITISH COLUMBIA October 1987 © David W i l l i a m E g l e s , 1987 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. Department The University of British Columbia 1956 Main Mall Vancouver, Canada V6T 1Y3 DE-6(3/81) ABSTRACT The purpose o f t h i s s t u d y i s t o e x p l o r e t h e f e a s i b i l i t y o f a r e c e n t d e v e l o p m e n t i n o c e a n o g r a p h i c i n s t r u m e n t a t i o n known as an a c t i v e d r i f t e r b u o y . The a c t i v e d r i f t e r i s a s e l f - p r o p e l l e d , s o l a r -powered d a t a buoy w h i c h has t h e c a p a b i l i t y o f i n f l u e n c i n g i t s d r i f t r a t e and d i r e c t i o n w i t h t h e use o f a t h r u s t e r / r u d d e r s y s t e m . T h i s s t u d y e x a m i n e s t h e a c t i v e d r i f t e r s d e v e l o p e d t h u s f a r , and d i s c u s s e s a s e r i e s o f e x p e r i m e n t s w h i c h p r o v i d e s u f f i c i e n t i n f o r m a t i o n t o p r e d i c t t h e performance of a buoy o f f s h o r e . The a c t i v e d r i f t e r was c o n c e i v e d at the I n s t i t u t e o f Ocean S c i e n c e s a t P a t r i c i a B a y , B . C . Under the d i r e c t i o n o f E n g i n e e r G.R. S m i t h , a p r o t o t y p e was b u i l t and r e c e i v e d l i m i t e d t e s t i n g i n i n s h o r e w a t e r s . Seaboy M a r i n e S e r v i c e s L t d . , a m a n u f a c t u r e r o f d a t a b u o y s , began i t s own a c t i v e d r i f t e r program i n 1984, and i n 1985 made i t s p r o t o t y p e a v a i l a b l e t o t h e a u t h o r f o r a s e r i e s of e x p e r i m e n t s t o d e f i n e i t s c a p a b i l i t i e s and p r o v i d e d a t a f o r f u t u r e d e v e l o p m e n t . The Seaboy a c t i v e d r i f t e r was named Ranger 1 , and had a s h a l l o w , s p o o n - s h a p e d h u l l w i t h a c i r c u l a r deck t o m a x i m i z e t h e a r e a a v a i l a b l e f o r a p h o t o v o l t a i c a r r a y . The buoy was 2m i n d i a m e t e r and had a f o i l shaped k e e l lm d e e p . A 12 V DC t h r u s t e r combined w i t h a 36 cm. model a i r p l a n e p r o p e l l e r p r o p e l l e d t h e buoy at a speed o f 0 . 5 0 m/s i n calm w a t e r . The 210 peak w a t t s o l a r a r r a y c h a r g e d a bank of s i x 55 amp hour g e l l e d e l e c t r o l y t e l e a d a c i d i i b a t t e r i e s and p r o v i d e d t h e power t o o p e r a t e t h e e l e c t r o n i c s p a y l o a d and f o r p r o p u l s i o n . The Ranger t e s t i n g program i n c l u d e d a measurement o f the e f f e c t i v e power o f t h e h u l l a t t h e B . C . R e s e a r c h tow t a n k f a c i l i t i e s . Experiments i n t h e tow tank r e v e a l e d t h a t a d e s i g n speed o f 0 . 5 0 m/s r e q u i r e d 4 w a t t s of t h r u s t , and t h a t a s t a t i c a f t t r i m was r e q u i r e d t o p r e v e n t t h e buoy from submerging i n t o i t s own wake. E x t e n s i v e i n s h o r e t e s t s were performed on t h e Ranger buoy i n E l k L a k e , n e a r V i c t o r i a . These t e s t s showed t h a t t h e a c t u a l power r e q u i r e d t o p r o p e l t h e buoy a t 0 . 5 0 m/s was 32 w a t t s . Downwind d r i f t t e s t s showed t h e buoy t r a v e l l e d a t a r a t e o f 5% o f t h e lm wind s p e e d . U p w i n d , t h e combined e f f e c t s of s u r f a c e d r i f t , waves and wind d r a g r e d u c e d t h e f o r w a r d buoy speed by a f a c t o r e q u a l t o 5.4% of t h e wind s p e e d , and t h e maximum speed i n which the buoy c o u l d make f o r w a r d headway was 10 m/s. A s i m u l a t i o n b a s e d on t h e r e s u l t s o f t h e s e e x p e r i m e n t s was performed t o p r e d i c t t h e performance o f an a c t i v e d r i f t e r d e p l o y e d at Ocean S t a t i o n Papa ( 5 0 ° N , 1 4 5 ° W ) . At t h i s s i t e , the average wind speeds a r e 1 0 . 5 m/s, w i t h s u r f a c e d r i f t c u r r e n t s equal t o 3.3% of the wind s p e e d . With an average d a i l y t o t a l i n s o l a t i o n of 9 . 6 MJ/m2 ' t h e buoy would be a b l e to motor 12.7 hours a d a y . In t h e s e c o n d i t i o n s , the a c t i v e d r i f t e r c o u l d r e d u c e t h e annual d r i f t r a t e t o 43% o f a comparable u n p r o p e l l e d buoy. T h i s i s comparable to a deep-drogued s p a r buoy, i n d i c a t i n g no s i g n i f i c a n t improvement i n p e r f o r m a n c e o v e r t h e l e s s s o p h i s t i c a t e d buoys commonly i n u s e . The s i m u l a t i o n shows t h a t f o r an a c t i v e d r i f t e r buoy t o become a p r a c t i c a l a l t e r n a t i v e t o buoys now a v a i l a b l e , changes must be made i n t h e h u l l shape t o reduce d r a g and t h e e f f e c t s of winds and waves on buoy m o b i l i t y . i v TABLE OF CONTENTS PAGE A b s t r a c t i i I n t r o d u c t i o n 1 1.0 Background 4 1.1 Role o f D r i f t i n g Buoys i n Oceanography 4 1.2 F e d e r a l Government A c t i v e D r i f t e r Buoy 9 Program 1.3 Seaboy A c t i v e D r i f t e r Buoy Program 13 2.0 C l i m a t o l o g y o f the Northeastern P a c i f i c 17 2.1 C l i m a t e C o n t r o l s 18 2.2 I n s o l a t i o n 20 2.3 Wind C l i m a t e 21 2.4 Wave C l i m a t e 23 2.5 P r e v a i l i n g and Wind Driven Currents 36 2.6 A i r Temperature 40 2.7 Summary of Operating Environment 42 3.0 Pro t o t y p e A c t i v e D r i f t e r Buoy S p e c i f i c a t i o n s 43 3.1 Design Goals 43 3.2 E v o l u t i o n o f the A c t i v e D r i f t e r H u l l Shape 45 3.2.1 H u l l Design C r i t e r i a 45 3.2.2 I0S A c t i v e D r i f t e r H u l l 46 3.2.3 Seaboy A c t i v e D r i f t e r 48 3.3 D e s c r i p t i o n o f the Ranger Buoy 54 3.4 Ranger Buoy S p e c i f i c a t i o n s 62 4.0 Mechanical T e s t i n g o f the Prototype Buoy 65 4.1 Tow Tank T e s t i n g 65 4.1.1 Experimental Method 66 4.1.2 Observations 68 4.1.3 R e s u l t s 71 4.1.4 D i s c u s s i o n 71 4.2 Measurement o f Wind Induced D r i f t on Ranger I 83 4.2.1 Experimental Method 83 4.2.2 R e s u l t s 84 4.2.3 D i s c u s s i o n and C o n c l u s i o n s 84 V PAGE 5.0 Inshore Sea T r i a l s 86 5.1 Purpose o f the Experiments 86 5.2 Experiment L o c a t i o n : Elk Lake 87 5.3 Experimental Method 92 5.*+ D i s c u s s i o n o f Measurement E r r o r s 96 5.5 R e s u l t s o f the Inshore T r i a l s 100 5.5.1 F l a t Water Buoy Speed Runs 100 5.5.2 Average T h r u s t e r Power vs. Buoy 107 Speed 5.5.3 E f f e c t s o f Winds on Buoy M o b i l i t y 110 5.5.4 Downwind D r i f t T r i a l s 113 5.6 Summary o f Inshore T e s t R e s u l t s 117 6.0 O f f s h o r e Performance S i m u l a t i o n 118 6.1 D e s c r i p t i o n o f the Performance Model 119 6.2 Energy A v a i l a b i l i t y - WATSUN S i m u l a t i o n 121 6.2.1 Program D e s c r i p t i o n 121 6.2.2 S i m u l a t i o n R e s u l t s 122 6.3 Buoy M o b i l i t y a t S t a t i o n Papa 130 6.3.1 Buoy Performance i n Steady Winds 131 6.3.2 Buoy Displacement with V a r i a b l e Wind 133 D i r e c t i o n 6.3.3 D i s c u s s i o n 138 6.4 Comparison o f Design Changes to Ranger Buoys 139 6.4.1 E f f e c t o f I n c r e a s i n g Array E f f i c i e n c y 139 6.4.2 E f f e c t o f Reducing Power Requirement 141 by 10* 6.4.3 E f f e c t o f a 10£ Reduction i n Buoy 142 Operating Speed 6.4.4 U t i l i z a t i o n o f A l t e r n a t e Power Sources 143 6.4.5 C o n c l u s i o n s - Recommended Design Changes 143 6.5 D i s c u s s i o n 144 7.0 C o n c l u s i o n s 147 B i b l i o g r a p h y 150 Acknowledgments 152 Appendices 153 v i LIST OF TABLES PAGE 2. 1 Mean and standard deviat ion of da i ly 21 t o t a l radiat ion st Stn. Papa. 2. 2 Frequency of preva i l ing wind d i rec t ions 29 at Stn. Papa 2. 3 Average da i ly a i r temperature at Stn. 41 Papa. 2. 4 Summary of cl imate at Stn. Papa. 42 3. 1 Summary of IOS buoy hu l l s p e c i f i c a t i o n s . 48 3. 2 Ranger buoy technica l s p e c i f i c a t i o n s . 62 3. 3 Power budget for a production Ranger buoy. 64 4. , 1 Ranger buoy resistance tests - B.C. 72 Research data. 4. .2 F la t water speed t r i a l s data. 73 4. .3 Comparison of d r i f t rate of Ranger buoy 84 and d r i f t sheet. 5, . 1 Sample data product from a speed run. 95 5, .2 LORAN posi t ions of mooring dock. 98 5, .3 Comparison of LORAN and actual posi t ions 98 of dock. 5 .4 Data summary for Elk Lake t r i a l s . 101 5 .5 Summary of f latwater speed t r i a l s data. 102 5 .6 Thruster deduction c o e f f i c i e n t s for 105 Ranger II. 5 .7 Data used for ana lys is of wind e f fec ts on 111 buoy speed. 5 .8 Wind d r i f t data for unpowered runs. 114 6 . 1 Energy analys is summary for 210 peak Watt 124 array. 6 .2 Hours of thruster operation per day at 125 Stn. Papa. 6. . 3 Essent ia l and to ta l load analys is by 129 month. 6 .4 Simulation of buoy performance with 132 constant wind d i rec t ion 6 . 5 Simulation of buoy performance with 136 var iable wind d i r e c t i o n . 6 .6 Buoy d r i f t with proposed design changes. 140 v i i LIST OF FIGURES PAGE 1. 1 Spar buoy developed by Hermes Electronics 6 1. 2 N0AA TIROS Meteorological Drifting Buoy 6 1. 3 Example of drifting buoy tracks in North 8 Pacific 1. 4 I0S Active Drifter Buoy prototype 12 2. 1 Major pressure features and storm tracks 19 in the N.E. Pacific - January. 2. 2 Major pressure features and storm tracks 19 in the N.E. Pacific - July. 2. 3 Mean monthly insolation at Stn Papa 22 2. Seasonal average winds in the N.E. 24 Pacific - January & April. (b) Seasonal average winds in the N.E. 24 Pacific - July & October. 2. .5 Mean monthly winds at St. Papa 1970-1979. 26 2. 6(a) Wind roses for Stn. Papa, Jan-Jun. 27 (b) II II n II II Jul-Dec. 28 2. 7(a) Wind speed exceedance for Stn. Papa, 30 January to June. (b) Wind speed exceedance for Stn. Papa, 31 July to December. 2 .8 Combined wave height exceedance for 34 selected months at Stn. Papa. 2 .9 Combined wave period frequency for 35 selected months at Stn. Papa. 2 .10 Major circulation features of the N.E. 37 Pacific. 2 •11(a) Surface currents of the N. Pacific in Jan. 38 (b) H it it II II ti Aug 39 3 . 1 Institute of Ocean Sciences active 47 drifter. 3 .2 I0S active drifter during sea tr i a l s 47 3 . 3 Section Drawing of Ranger 1. 50 3 .4 Modified keel of Ranger 2. 52 3 .5 Block diagram of buoy systems. 55 3 .6 Cross sectional drawing of solar panel. 57 3 .7 Current/voltage characteristics of Ranger 58 solar modules. 3 .8 Electronics payload of buoy. 60 3 .9 Remote programming options menu. 61 v i i i PAGE 4. . 1 H u l l r e s i s t a n c e vs v e l o c i t y i n f l a t water. 74 4. .2 Buoy heave vs v e l o c i t y " " 11 75 4. .3 Buoy t r i m vs v e l o c i t y i n f l a t water. 76 4. .4 E f f e c t i v e power vs v e l o c i t y i n f l a t water. 77 4. ,5 N a t u r a l l o g o f e f f e c t i v e power and 80 v e l o c i t y . 5.1 Course and speed t r i a l s on Elk Lake. 88 5.2 Wind d i r e c t i o n frequency d u r i n g Elk Lake 90 t r i a l s . 5.3 S c a t t e r p l o t o f wind speed and d i r e c t i o n 91 a t Elk Lake 5.4 Buoy course d u r i n g Aug 11 speed run. 94 5.5 Power vs speed f o r f l a t w a t e r t r i a l s 103 5.6 F l a t w a t e r power curve f o r Ranger I I buoy. 106 5.7 T h r u s t e r power vs speed f o r a l l t r i a l s . 108 5.8 C o r r e c t e d buoy speed vs wind speed. 109 5.9 Downwind d r i f t t r a c k s , J u l y 25, 1986. 115 6.1 Charge e f f i c i e n c y vs. s t a t e o f charge 123 f o r l e a d a c i d b a t t e r i e s . 6.2 Load f r a c t i o n d e l i v e r e d a t Stn. Papa 126 (from WATSUN-PV S i m u l a t i o n ) . 6.3 Hours of motoring w i t h i n s o l a r energy 127 budget f o r a Ranger buoy a t Stn Papa. 6.4 S t r a i g h t l i n e d r i f t per month of powered 134 and unpowered Ranger buoys. 6.5 Net d r i f t o f unpowered and a c t i v e d r i f t e r 137 buoys with v a r i a b l e wind d i r e c t i o n s . i X INTRODUCTION An a c t i v e d r i f t e r i s an untethered buoy designed to c o l l e c t oceanographic and m e t e o r o l o g i c a l data f a r o f f s h o r e . I t d i f f e r s from standard d r i f t i n g spar buoys i n t h a t i t can i n f l u e n c e i t s d r i f t r a t e t o some extent with the use of a p r o p e l l e r / r u d d e r d r i v e system. In i t s c o n c e p t u a l form, the a c t i v e d r i f t e r was intended as a r o b o t i c , mobile data c o l l e c t i o n p l a t f o r m o p e r a t i n g on the ocean s u r f a c e . I t would be unique as i t c o u l d e x t r a c t the energy needed f o r p r o p u l s i o n and day to day o p e r a t i o n from the environment through the use of a p h o t o v o l t a i c a r r a y to c o n v e r t s u n l i g h t t o e l e c t r i c a l energy. I t c o u l d operate unattended f o r a year a t a time, t r a v e l a p r e s c r i b e d course or remain a t a d e s i g n a t e d s t a t i o n . T h i s concept was given support from government and p r i v a t e i n d u s t r y , and i n a l l t h r e e separate agencies had i n i t i a t e d a c t i v e d r i f t e r programs. Since 1984, over one m i l l i o n d o l l a r s has been expended on buoy developments. One p r i v a t e s e c t o r company i n v o l v e d i n the a c t i v e d r i f t e r development was Seaboy Marine S e r v i c e s Ltd., a Sidney based buoy manufacturing f i r m . Although now defunct, Seaboy c a r r i e d the a c t i v e d r i f t e r concept the f a r t h e s t , and by 1986 had produced a s o p h i s t i c a t e d and v e r s a t i l e buoy capable of motoring at speeds of 0.50 m/s, f o l l o w i n g a programmed course and t e l e m e t e r i n g data through VHF and s a t e l l i t e l i n k s . 1 T h e a u t h o r j o i n e d S e a b o y i n 1 9 8 5 w i t h t h e a s s i s t a n c e o f a B . C . S c i e n c e C o u n c i l G R E A T s c h o l a r s h i p . H i s r o l e w i t h S e a b o y w a s a s a n o c e a n o g r a p h i c c o n s u l t a n t a n d a s a s u p e r v i s o r o f t h e t e s t i n g p r o g r a m s f o r t h e b u o y h u l l a n d s y s t e m s a s d e v e l o p m e n t p r o c e e d e d . T h e i n d i v i d u a l t e s t s p e r f o r m e d b y t h e a u t h o r a n d d o c u m e n t e d i n t h i s w o r k i n c l u d e d : 1 . E x p e r i m e n t s t o m e a s u r e t h e b u o y d r i f t r a t e i n r e s p o n s e t o w i n d . 2 . T o w t a n k t e s t i n g o f b u o y h u l l a t B . C . R e s e a r c h . 3 . C o m p r e h e n s i v e t e s t i n g o f t h e p r o t o t y p e R a n g e r b u o y i n E l k L a k e . U n f o r t u n a t e l y , d e s p i t e a l m o s t t w o y e a r s o f d e v e l o p m e n t o n t h e a c t i v e d r i f t e r p r o j e c t , t h e b u o y w a s n e v e r s u f f i c i e n t l y a d v a n c e d t o b e t a k e n o f f s h o r e f o r s e a t r i a l s . T o d a t e , t h e f e a s i b i l i t y o f t h e a c t i v e d r i f t e r c o n c e p t h a s n o t b e e n p r o v e n n o r t h e p r a c t i c a l l i m i t a t i o n s o f b u o y m o b i l i t y d e f i n e d . T h i s r e p o r t s u m m a r i z e s t h e r e s u l t s o f t h e t e s t s p e r f o r m e d b y t h e a u t h o r . I t a l s o e x a m i n e s t h e o p e r a t i n g c l i m a t e f o r a n a c t i v e d r i f t e r d e p l o y e d i n t h e N o r t h P a c i f i c t o p r o v i d e a n e n g i n e e r i n g s u m m a r y o f a v e r a g e c o n d i t i o n s . T h e r e s u l t s o f t h e i n s h o r e t e s t s a r e t h e n e x t r a p o l a t e d t o o f f s h o r e c o n n d i t i o n s u s i n g a n u m e r i c a l m o d e l t o p r e d i c t t h e b u o y p e r f o r m a n c e t h r o u g h a t y p i c a l y e a r . T h e g o a l s o f t h i s w o r k a r e t o u s e t h e r e s u l t s o f t h e l i m i t e d a c t i v e d r i f t e r t e s t p r o g r a m a n d p r e d i c t i t s p e r f o r m a n c e 2 offshore. This study defines the degree of mobility a solar powered buoy would be capable of in the offshore environment. It w i l l determine i f the buoy w i l l be either a slow d r i f t e r , a buoy that can station keep, or a buoy with an appreciable amount of mobility in the wind and wave climate that prevails in the North P a c i f i c . 3 1.0 BACKGROUND 1.1 ROLE OF DRIFTING BUOYS IN OCEANOGRAPHY The s c i e n c e o f oceanography has a g o a l o f r e s o l v i n g and un d e r s t a n d i n g each o f the p h y s i c a l , c h e m i c a l and b i o l o g i c a l p r o c e s s e s t h a t o c c u r s i n the oceans and a t t h e i r b o u n d a r i e s . P r e r e q u i s i t e t o a statement o f un d e r s t a n d i n g i s an important p r o c e s s where the p r o p e r t i e s o f the ocean a r e measured, monitored, and determined. The oceanographer l o o k s f o r cause and e f f e c t , forms a t h e o r y i n h i s mind, and r e t u r n s t o h i s data t o t e s t h i s h y p o t h e s i s . Often, as s u c c e e d i n g g e n e r a t i o n s o f t h e o r i e s have passed, the oceanographer w i l l t r y t o c o l l e c t more a c c u r a t e , more d e t a i l e d and l o n g e r - t e r m data. P h y s i c a l oceanographers have always had g r e a t d i f f i c u l t y c o m p i l i n g s u f f i c i e n t data t o s a t i s f y t h e i r wants. To a c c u r a t e l y r e s o l v e phenomenon such as E l Nino or carbon d i o x i d e a b s o r p t i o n by t h e sea, an oceanographer would need a long term time s e r i e s o f a i r and water column p r o p e r t i e s f o r l o c a t i o n s c l o s e l y spaced a c r o s s the e n t i r e P a c i f i c Ocean. With l i m i t e d r e s o u r c e s , oceanographers a r e f o r c e d t o be t h r i f t y and s e t t l e f o r fewer data p o i n t s and s m a l l e r s c a l e s t u d i e s . Oceanographic d r i f t i n g buoys a r e a t e c h n o l o g i c a l example of the c l e v e r n e s s o f oceanographers a t c o l l e c t i n g data over l a r g e expanses o f ocean with l i m i t e d e x p e n d i t u r e . They a r e a c o s t -e f f e c t i v e compromise t o moored data buoys or d e d i c a t e d c r u i s e s 4 and c o l l e c t s y n o p t i c data f o r m e t e o r o l o g i c a l , c i r c u l a t i o n or a i r - s e a i n t e r a c t i o n s t u d i e s . Although they a r e l i m i t e d i n c a p a b i l i t y , they a r e used t o s i m u l t a n e o u s l y measure p r e v a i l i n g c u r r e n t s , s u r f a c e water p r o p e r t i e s and b a r o m e t r i c p r e s s u r e t r e n d s . The most common a p p l i c a t i o n o f t h e s e l o w - c o s t d r i f t i n g i n s t r u m e n t p l a t f o r m s i s t o p r o v i d e m e t e o r o l o g i c a l data f o r weather a n a l y s i s and f o r e c a s t i n g . A c c u r a t e c l i m a t e p r e d i c t i o n r e q u i r e s a f a i r d e n s i t y o f r e a l - t i m e or near r e a l - t i m e b a r o m e t r i c p r e s s u r e o b s e r v a t i o n s over a l a r g e area o f ocean. Expendable buoys a r e a more r e l i a b l e o p t i o n than s h i p s o f o p p o r t u n i t y and a f r a c t i o n o f the c o s t o f a moored m e t e o r o l o g i c a l buoy. D r i f t i n g buoys a l s o have p l a y e d a r o l e i n s c i e n t i f i c s t u d i e s such as the TOGA experiments i n the south P a c i f i c (Kozak and P a r t r i d g e , 1985). They can be used t o monitor temperature d i s t r i b u t i o n i n the mixed l a y e r , p r o v i d i n g data f o r heat budget and t r a n s p o r t s t u d i e s . As Lagrangian d r i f t e r s t h e s e buoys t r a c k s u r f a c e or near s u r f a c e c u r r e n t s and with simultaneous p r e s s u r e measurements can be used t o determine g e o s t r o p h i c wind speed and d i r e c t i o n . On o c c a s i o n buoys have been used t o t r a c k the path o f o i l s p i l l s . D r i f t i n g buoys, such as the spar buoy shown i n F i g u r e 1.1 have been i n use f o r 15 y e a r s . They were o r i g i n a l l y developed as an expendable, e a s i l y d e p l o y a b l e instrument t o p r o v i d e s e v e r a l d a i l y b a r o m e t r i c p r e s s u r e measurements i n remote ar e a s o f the ocean. They r e p o r t data u s i n g the ARGOS s a t e l l i t e l i n k a t 5 FIGURE 1.1: Spar buoy developed by Hermes E l e c t r o n i c s . FIGURE 1.2: NOAA T I R O S M e t e o r o l o g i c a l D r i f t i n g B u o y . 6 intervals between two and six hours depending on location. These buoys are manufactured in many countries including Canada by Hermes Electronics. Modern drifting buoys such as the TIROS drifting buoy developed by NOAA in the United States shown in Figure 1.2 cost in the order of $15,000 and have a deployed l i f e expectancy of 14 months. If drogued with a window shade or holey sock drogue, they can be used for Lagrangian current studies. These buoys measure surface water temperature to within 1° C, and some tow a pressure/thermistor string for measurements through the mixed layer. Barometric pressure is measured within Imbar over the deployed l i f e of the buoy. Recently, attempts have been made to include wind speeds at a height of 1m above the sea surface as one of the parameters monitored by the buoys. Present development in drifting buoy technology is aimed at reducing the size and costs of the drifting buoys and increasing the number and frequency of measurements. Buoys are designed to be air-deployable using methods similar to launching sonobuoys. This allows a large area to be seeded with buoys over the course of a few days and reduces the ship time required. Drifting buoys are of value to the meteorologist or oceanographer providing he or she is willing to accept data from wherever the buoy drifts to. In 1981, the undrogued spar buoys deployed by the Atmospheric Environment Service in the North Pacific averaged 19 km per day in a generally easterly direction (AES, 1985). Figure 1.3 illustrates the magnitude of 7 buoy movement over a one year period after deployment. For Lagrangian current studies, the close coupling between water movement and buoy displacement is desirable. In other cases, such as the calibration of satellite imagery with temperature data from a drifting buoy or for barometric pressure reports used in weather forecasting, i t is desirable to have the buoys remain within a specific region as long as possible. For these applications, a moored data buoy would be ideal, but at a cost of $250,000 each, the proliferation of such buoys is limited by budget considerations. But as a supplement to moored buoys , drifting buoys are s t i l l effective at increasing the number of pressure points available to forecasters trying to chart the development of weather systems over the ocean. Attempts have been made to increase the usefulness of drifting buoys for weather forecasting. Buoy drift rates can be slowed through the use of drogues deployed at depths of several hundreds of meters where the effects of wave and wind driven currents are minimal. An alternate strategy used is to reseed the area with waves of buoys spaced a few months apart so that when some drift out of the area of interest, others replace them. 1 . 2 FEDERAL GOVERNMENT ACTIVE DRIFTER BUOY PROGRAM Drifting buoys have partially satisfied the needs for additional data in the remote areas of the ocean without expending a large amount of money. However, the minimal capabilities of the buoys in terms of sensor and telemetry 9 o p t i o n s and a l a c k o f c o n t r o l o f p o s i t i o n have l i m i t e d the a p p l i c a t i o n s o f these buoys. With t h i s i n mind, a program was e s t a b l i s h e d i n 1982 a t the F e d e r a l Government I n s t i t u t e o f Ocean S c i e n c e s i n P a t r i c i a Bay, B.C. t o i n v e s t i g a t e t h e f e a s i b i l i t y o f c o n t r o l l i n g t h e d r i f t r a t e and d i r e c t i o n o f d r i f t i n g buoys. The m o t i v a t i o n f o r t h i s program was the o p i n i o n t h a t a " d r i f t i n g " buoy would be o f more v a l u e i f i t c o u l d o p e r a t e i n d e p e n d e n t l y o f ocean c u r r e n t s and e i t h e r remain a t a d e s i g n a t e d l o c a t i o n or t r a v e l a programmed c o u r s e . The p r o j e c t was t o examine the p o t e n t i a l f o r a s e l f - p r o p e l l e d autonomous data buoy which, i d e a l l y , c o u l d be s e l f d e p l o y i n g , i e . once i t was dropped beyond the range o f l o c a l t i d a l c u r r e n t s would motor hundreds o f m i l e s o f f s h o r e t o a d e s i g n a t e d s t a t i o n . The buoy would then remain on s t a t i o n d e s p i t e the winds and c u r r e n t s which tend t o c a r r y s t a n d a r d d r i f t i n g buoys away. Such a buoy would be a b l e t o c o l l e c t data from a s i n g l e l o c a t i o n w h i l e c o s t i n g a f r a c t i o n o f what a moored buoy would. The a c t i v e d r i f t e r concept developed from a f e a s i b i l i t y study i n i t i a t e d by Mr. G. R. Smith, a mechanical e n g i n e e r a t the I n s t i t u t e . The r e s u l t s o f Smith's p r e l i m i n a r y i n v e s t i g a t i o n a r e summarized i n (Smith, 1984). In the e a r l y s t a g e s , Smith c o n s i d e r e d the o p t i o n s o f t h e r m o e l e c t r i c power, wind and wave power and s o l a r energy. S o l a r energy was s e l e c t e d as the most p r a c t i c a l power system f o r a p r o t o t y p e buoy as the l e a s t amount o f development was r e q u i r e d . Smith began h i s experiments with a 4m s k i f f and i n s t a l l e d a 10 solar array of four 35 watt modules, an electric motor propulsion system and a commercially manufactured autopilot system. The skiff tests were designed to evaluate various components of the active drifter buoy and highlight the areas where development should be concentrated. The preliminary tests showed the importance of power conservation and careful design and matching of the electrical components to maximize the efficiency of the power utilization. Mr. Smith used the results of the skiff tests to design a prototype active drifter buoy. He concentrated his priorities on hull and onboard control system design. The hull shape selected was a shallow inverted cone 2m in diameter and 0.5m deep (see Figure 1.4). The hull was constructed of fibreglass and had a total displacement of 380 kg. A fin keel with 150 kg of lead ballast and a battery bank weighing 150 kg provided the righting moment for the buoy. The onboard system developed included a microcomputer that performed power management functions, data collection and navigation. A SATNAV system was incorporated for position fixing, and an analog compass was used for steering. Smith had the opportunity to f i e l d test the prototype buoy during the f a l l of 1984. The buoy was launched from the Institute research vessel Parizeau in the vicinity of Station Papa ( 50°N, 145° W) .1000 km offshore and tracked for a period of one week before recovery. During that period the buoy made a net progress of 95 km, against an average wind of 30 km/hr. 11 Ba I l a s t Shoe Rudder FIGURE 1.4: I n s t i t u t e of Ocean Sciences A c t i v e D r i f t e r buoy prototype. 12 T h i s t e s t was deemed s u c c e s s f u l a t demonstrating t h a t the a c t i v e d r i f t e r was c a p a b l e o f locomotion under adverse c u r r e n t s and winds. However, the t e s t s d i d not l i m i t the energy a v a i l a b l e f o r p r o p u l s i o n as the buoy was deployed with f u l l y charged b a t t e r i e s and the energy c o l l e c t e d by the s o l a r a r r a y was not measured. T h e r e f o r e w h i l e t h i s o f f s h o r e t e s t p r o v i d e d the o p p o r t u n i t y t o t e s t the p r o t o t y p e equipment, i t d i d not o f f e r a p r o o f o f concept, namely whether a buoy was c a p a b l e o f any degree o f forward movement g i v e n the r e s t r i c t e d power g e n e r a t i o n of the s o l a r a r r a y . The t e s t s d i d p r o v i d e power e s t i m a t e s f o r f u t u r e development. Subsequent o f f s h o r e t e s t s by Smith were o f l i m i t e d s u c c e s s . A r e p e a t e d deployment at the hot vents, (48° N, 127°W), was c u t s h o r t by a t h r u s t e r f a i l u r e w i t h i n 24 hours a f t e r l a u n c h i n g . L a t e r i n 1986 f u n d i n g f o r the p r o j e c t was reduced and development d i r e c t e d towards s m a l l e r systems. 1.3 SEABOY ACTIVE DRIFTER BUOY PROGRAM I t was a t t h i s p o i n t t h a t a newly formed company, Seaboy Marine S e r v i c e s L t d . was founded and began i t s involvement w i t h the A c t i v e D r i f t e r p r o j e c t . Seaboy n e g o t i a t e d a t e c h n o l o g y t r a n s f e r agreement with the I n s t i t u t e o f Ocean S c i e n c e s and with a d d i t i o n a l f u n d i n g p r o v i d e d by a F e d e r a l Government N a t i o n a l Research C o u n c i l program, began development of i t s own A c t i v e D r i f t e r buoy. 13 Seaboy's design c r i t e r i a were for a s e l f - r i g h t i n g solar powered buoy capable of a h u l l speed of 2.9 km/hr (1.6 kts). The e l e c t r o n i c s payload was to be s u f f i c i e n t l y complex to handle navigation, steering and propulsion, i n t e r n a l systems management and support a standard suite of oceanographic and meteorological sensors (Seaboy, 1985). The buoy was to be completely autonomous and operate for extended periods up to a year offshore with no s e r v i c i n g . Data telemetry options were to include VHF for inshore work and ARGOS for offshore. Seaboy experimented with a variety of h u l l shapes using scale models in a test tank, and eventually selected a parabola section fore-and-aft and a c i r c u l a r crossection. The si z e of the o r i g i n a l prototype, which was c a l l e d Ranger 1, was s i m i l a r to the IOS buoy at 2.0m across the deck and 1m deep. A f u l l length keel was used with a lead shoe at the bottom to enhance the s e l f r i g h t i n g a b i l i t y . Much of the Seaboy research was devoted to the development of the microprocessor c o n t r o l l e r to administer the buoy functions. Almost two years of dedicated time for a team of k was spent designing, building and testing several generations of e l e c t r o n i c packages for the buoy. The f i n a l version allowed the buoy to be operated manually through a VHF link or automatically with s a t e l l i t e telemetry and navigated using LORAN and a compass. In the course of the Ranger buoy development at Seaboy, the author supervised several phases of prototype testing and evaluation. These tests were documented in a series of internal 14 and term papers and i n c l u d e d downwind d r i f t t e s t s ( E g l e s , 1985a), m e c h a n i c a l and tow tank t e s t i n g o f the p r o t o t y p e Ranger h u l l , ( E g l e s , 1985d), and summary o f the i n s h o r e Ranger buoy t e s t i n g , J u l y - A u g u s t , 1985, ( E g l e s , 1986a). An overview of the Ranger buoy program was p r e s e n t e d and p u b l i s h e d a t Oceans 85 i n San Diego i n November 1985 ( E g l e s , 1985c). The Ranger buoy program proceeded a t Seaboy u n t i l August, 1986 when i t was suspended due t o f i n a n c i a l problems. At t h i s p o i n t the p r o t o t y p e buoy had been completed and had undergone e x t e n s i v e i n s h o r e t e s t i n g a t E l k Lake near V i c t o r i a , B.C. These t e s t s p r o v i d e d the o p p o r t u n i t y t o measure the buoy speed, power budget and response t o wind and waves. U n f o r t u n a t e l y , no o f f s h o r e o r extended t e s t s had been made w i t h the Ranger so the performance o f f s h o r e can o n l y be i n t e r p r e t e d from the i n s h o r e t r i a l s . A lthough Seaboy has abandoned t h e A c t i v e D r i f t e r concept, a s m a l l e r s c a l e program c o n t i n u e d a t the I n s t i t u t e o f Ocean S c i e n c e s i n c o n j u n c t i o n w i t h a p r i v a t e c o n t r a c t o r , O c e a n e t i c Measurement L t d . O c e a n e t i c has developed a s m a l l e r v e r s i o n o f the buoy t h a t i s 1m i n diameter and uses a l e s s s o p h i s t i c a t e d e l e c t r o n i c s p a y l o a d . The p r o t o t y p e s were deployed f o r a s h o r t p e r i o d i n the w i n t e r o f 1986 but s u f f e r e d t r a n s m i t t e r problems. Development c o n t i n u e d i n 1987 with r e s e a r c h i n t o the f e a s i b i l i t y o f wind powered p r o p u l s i o n . T h i s t h e s i s i s concerned with the f e a s i b i l i t y o f s o l a r powered p r o p u l s i o n a t sea, with p a r t i c u l a r a t t e n t i o n t o the 15 a p p l i c a t i o n o f a c t i v e d r i f t e r buoys. I t l o o k s a t the f a c t o r s t h a t determine t o what e x t e n t a s e l f - p r o p e l l e d buoy w i l l be a b l e t o modify i t s p o s i t i o n on the ocean. A d i s c u s s i o n has been made o f the environment the buoy i s r e q u i r e d to o p e r a t e i n , with summaries o f the wind, wave and c u r r e n t c o n d i t i o n s t h a t the buoy w i l l encounter. The r e s u l t s o f the mechanical and i n s h o r e t e s t s o f t h e Ranger buoy p r o t o t y p e developed by Seaboy w i l l be used to determine the power r e q u i r e d t o p r o p e l the buoy under g i v e n c o n d i t i o n s . F i n a l l y , t h e s e a s p e c t s w i l l be combined i n an energy budget a n a l y s i s t o determine the range of m o b i l i t y t h a t c o u l d be e xpected by an A c t i v e D r i f t e r buoy with the i n p u t o f a g i v e n amount o f s o l a r energy and the average o f f s h o r e c o n d i t i o n s the buoy would encounter. 16 2.0 CLIMATOLOGY OF THE NORTHEAST PACIFIC The A c t i v e D r i f t e r buoy i s a unique development i n ocea n o g r a p h i c i n s t r u m e n t a t i o n i n t h a t t h e energy r e q u i r e d f o r data c o l l e c t i o n , p r o c e s s i n g and t e l e m e t r y i s e x t r a c t e d from the s u r r o u n d i n g environment. T h i s type o f buoy d i f f e r s from o t h e r s o l a r powered buoys i n t h a t the r e s i d u a l power not r e q u i r e d by th e s e e s s e n t i a l l o a d s i s d i v e r t e d t o a p r o p u l s i o n system and a l l o w i n g the p l a t f o r m t o e x e r t some degree o f c o n t r o l over i t s p o s i t i o n on the ocean s u r f a c e . The degree o f m o b i l i t y t h a t such a s o l a r powered v e h i c l e w i l l be c a p a b l e o f depends on s e v e r a l f a c t o r s i n c l u d i n g the amount o f s o l a r energy a v a i l a b l e , the e f f i c i e n c y o f c o n v e r s i o n o f t h i s energy t o motion and the en v i r o n m e n t a l c o n d i t i o n s t h a t the buoy must o p e r a t e i n . S i n c e the A c t i v e D r i f t e r concept had i t s o r i g i n s on the West Coast o f Canada, p r a c t i c a l a p p l i c a t i o n s under c o n s i d e r a t i o n i n c l u d e d weather m o n i t o r i n g i n the n o r t h e a s t e r n P a c i f i c . As d e t a i l e d c l i m a t e data i s a v a i l a b l e from Ocean Weather S t a t i o n Papa (50°N, T+5°W), t h i s a r e a has been s e l e c t e d as the h y p o t h e t i c a l o p e r a t i n g environment o f an a c t i v e d r i f t e r f o r the a n a l y s i s o f the p o t e n t i a l o f s o l a r power systems i n oceanography. Environment Canada m a i n t a i n e d r o t a t i n g weather s h i p s a t t h i s l o c a t i o n from 1959 to 1980, and h i s t o r i c a l r e c o r d s o f i n s o l a t i o n , wind and observed wave h e i g h t have been used i n t h i s r e p o r t . T h i s s e c t i o n examines the c l i m a t o l o g y o f the n o r t h e a s t e r n 17 P a c i f i c , and i n p a r t i c u l a r S t a t i o n Papa, t o d e f i n e the wind, wave and c u r r e n t c o n d i t i o n s t h a t a buoy o p e r a t i n g o f f s h o r e can be expected t o encounter. A d i s c u s s i o n o f the f a c t o r s t h a t govern the weather p a t t e r n s , the a v a i l a b l e s o l a r r a d i a t i o n and a summary o f average monthly c o n d i t i o n s has been p r e s e n t e d . 2.1 CLIMATE CONTROLS In most o f f s h o r e r e g i o n s , the f a c t o r s t h a t have the l a r g e s t e f f e c t on t h e d r i f t r a t e o f a data buoy, namely winds, waves and s u r f a c e c u r r e n t s a r e the d i r e c t r e s u l t o f the p r e v a i l i n g weather c o n d i t i o n s . T i d e s and d e n s i t y d r i v e n c i r c u l a t i o n i n the upper few meters o f the ocean can be c o n s i d e r e d second o r d e r e f f e c t s i n t h e v i c i n i t y o f S t a t i o n Papa and a r e not s i g n i f i c a n t . Two l a r g e s c a l e semi-permanent p r e s s u r e systems dominate the weather i n the n o r t h e a s t e r n s e c t o r o f the P a c i f i c Ocean: the A l e u t i a n Low and the P a c i f i c High ( or the P a c i f i c A n t i c y c l o n e ). Seasonal v a r i a t i o n s i n the i n t e n s i t y and p o s i t i o n o f these p r e s s u r e c e l l s determine the p r e v a i l i n g winds. These systems a l s o a c t as a waveguide, c h a n n e l i n g s m a l l s c a l e storms on a t r a c k between the c e n t e r s o f the major p r e s s u r e f e a t u r e s . F i g u r e s 2.1 and 2.2 show the mean p o s i t i o n and f e a t u r e s o f these c e l l i n January and J u l y . ( F a l k n e r , 1975). Through the f a l l , the A l e u t i a n Low b u i l d s i n i n t e n s i t y and moves southward t o i t s w i n t e r maximum, near 50° N, 180 ° W. At the same time, the P a c i f i c High weakens. The p r e s s u r e g r a d i e n t near the c o a s t i s from southwest t o n o r t h e a s t , with s t r o n g 18 19 c y c l o n i c ( c o u n t e r c l o c k w i s e ) winds p r e v a i l i n g . The o f f s h o r e winds are p r e d o m i n a n t l y s o u t h e r l y (SE, S and SW). In w i n t e r , the f r e q u e n c y and i n t e n s i t y o f e x t r a t r o p i c a l c y c l o n e s i n c r e a s e . These b r i n g the w i n t e r g a l e s and high winds and r a i n s a s s o c i a t e d w i t h them. In summer, the combined weakening of the A l e u t i a n Low and the s t r e n g t h e n i n g o f the P a c i f i c A n t i c y c l o n e w i t h a northward d i s p l a c e m e n t o f both o f these systems change the weather i n the N o r t h e a s t P a c i f i c . The summer home o f the P a c i f i c High i s around 37 deg. N, 152 deg. W, w i t h a n t l c y c l o n i c wind c i r c u l a t i n g around the c e n t e r . The p r e v a i l i n g winds become northwest through the summer. At the same time, a low p r e s s u r e g r a d i e n t c e n t r e b u i l d s over t h e North American c o n t i n e n t , so the sea l e v e l p r e s s u r e d e c r e a s e s eastward. Storms are l e s s f r e q u e n t and t h e i r t r a c k s a r e pushed northward by the P a c i f i c High. 2.2 SOLAR INSOLATION The m o b i l i t y o f an A c t i v e D r i f t e r buoy i s a f u n c t i o n of a number o f f a c t o r s i n c l u d i n g the amount of energy a v a i l a b l e f o r p r o p u l s i o n . T h i s can be c a l c u l a t e d w i t h knowledge o f the i n t e g r a t e d s o l a r r a d i a t i o n , the c o n v e r s i o n e f f i c i e n c y o f the p h o t o v o l t a i c a r r a y and the c h a r g e / d i s c h a r g e e f f i c i e n c y o f the b a t t e r y s t o r a g e system. I n s o l a t i o n data f o r S t a t i o n Papa has been summarized i n T a b l e 2.1. T h i s t a b l e l i s t s the average t o t a l g l o b a l r a d i a t i o n ( d e s i g n a t e d R a d i a t i o n F i e l d 1 or RF1 by Environment Canada ) 20 i n c i d e n t on a f l a t p l a t e c o l l e c t o r based on the p e r i o d from 1959 t o 1980. F i g u r e 2.3 p l o t s the average monthly RF1 i n s o l a t i o n i n megajoules per square meter from 1970 t o 1979 (Monthly R a d i a t i o n Summary, 1970-1979). Mean Stc Dev JAN 2 98 MJ/m 1 . 42 FEB 5 50 1 . 29 MAR 9 09 3. 77 APR 13 70 4. 88 MAY 16 70 6. 07 JUN 15 99 5. 37 JUL 14 92 4. 67 AUG 12 78 4. 43 SEP 10 48 4. 19 OCT 6 74 " 3. 18 NOV 3 76 1 . 75 DEC 2 39 " 1 . 15 Mean 9 59 MJ/m2 3. 51 TABLE 2.1: Mean and Standard D e v i a t i o n o f d a i l y t o t a l r a d i a t i o n a t Stn Papa, 1959-1980. (Environment Canada r e c o r d s , 1987). 2 . 3 WIND CLIMATE Wind c l i m a t e i s an important determinant o f buoy m o b i l i t y as both the d i r e c t wind drag on the buoy s u p e r s t r u c t u r e and the wind g e n e r a t e d waves and s u r f a c e c u r r e n t s work to d i s p l a c e any o b j e c t on t h e sea s u r f a c e . As d i s c u s s e d i n S e c t i o n 2.1, the winds i n the n o r t h e a s t e r n P a c i f i c a r e determined t o be c y c l o n i c or a n t i c y c l o n i c depending on the r e l a t i v e p o s i t i o n s o f the A l e u t i a n Low or P a c i f i c High. The s t r e n g t h o f t h e s e winds i s d i c t a t e d by the magnitude o f the p r e s s u r e g r a d i e n t s , and a r e g r e a t e s t i n w i n t e r . Superimposed on 21 the stationary pressure systems are e x t r a t r o p i c a l storms which are also most frequent in winter. The seasonal variations in wind speed and d i r e c t i o n for the offshore regions of the northeastern P a c i f i c are shown in Figure 2.k. (Brown et a l , 1986). This diagram shows that far offshore the winds are westerly in d i r e c t i o n regardless of season. It i s these winds that drive the standing surface c i r c u l a t i o n . The figures also show that the winds are deflected as they approach the coastline, being northwesterly for part of the summer and southwesterly through the winter. The average wind speed at Station Papa has been plotted in Figure 2.5. The wind roses shown in Figure 2.6 show that the frequency of winds from the SW quadrant (W, SW and S) approximates 7Q%. Table 2.2 shows the frequency of observed p r e v a i l i n g winds at Station Papa for the eight primary compass headings. Wind speed exceedance plots by season have been included in Figure 2.7 and show that winds exceed 20 knots more than 50 # of the time in the period from October to A p r i l . These figures show that a d r i f t i n g buoy deployed in the v i c i n i t y of Station Papa can expect on the average southwesterly winds of 12.5 m/s in the winter and westerly winds of 6.0 m/s in the summer. 2.4 WAVE CLIMATE Waves w i l l impede the progress of a buoy in two ways. F i r s t , wave action contributes to surface d r i f t currents through a 23 155W • V E C T O R M E A N V E L O C I T T 1837 - 1 9 H 3 M E A N S P E E D (KNOTS) 1837 - 1985 13UW TRANSVERSE MKRCATOR :ALE AT 135W IS 1:10500000 145W 140VY 13UW GUN 35N SON 1 2 3 W GUN 33N SON H O W 1 3 3 W 1 3 U W 1 2 3 W 12uV FIGURE 2.4a: Seasonal average winds i n the N.E. P a c i f i c 24 155W GUN 35N 50N 1 4 3 W 14UW 135W 130W 1 2 5 IY 155W V E C T O R M E A N V E L O C I T T 1617 - 1903 M E A N S T E E D (KNOTS) 1B37 - 1905 T R A N S V E R S E MERCATOR S C A L E AT 135W I S 1 : 1 0 5 0 0 0 0 0 » 10 Imota \ GON ."55N 50N 130W i « w juuw IJUW iar ,w 12 ill?* FIGURE 2.4b: Seasonal average winds i n the N . E . P a c i f i c . 15 < a J F M A M J . J A S O N D Month 1970-1979 FIGURE 2.5: Mean M o n t h l y winds a t S t n . Papa 1970-1979. 26 N=7467 MARCH APRIL N=7299 MAY KU7483 N=7235 JUNE • FIGURE 2.6aftJind roses f o r Stn. Papa, Jan-June 27 28 WIND DIRECTION! Month N NE E SE S SW W NW + + h + + +. + + J AN 7 7 10 13 17 16 17 13 FEB 6 7 7 12 17 18 20 13 MAR 3 4 5 9 15 IS 23 IS APR 6 5 5 8 14 20 25 17 MAY 5 3 7 11 i a 21 22 13 JUN 5 5 5 10 15 20 25 15 JUL 5 3 5 8 14 22 27 16 AUG 6 3 3 7 13 23 28 17 SEP 6 3 4 9 18 23 22 15 •CT 5 3 4 7 16 22 27 16 NOV 8 5 5 8 15 20 24 15 DEC 7 5 6 11 15 20 20 16 AvG 6 4 6 -9 16 20 23 15 TABLE 2.2: Frequency o+ p r e v a i l i n g wind d i r e c t i o n ? per 100 o b s e r v a t i o n s at Stn. Papa. 29 JANUARY FEBRUARY WM) SPEED (MS) MARCH APRIL 10 «o 60 100 20 « ae oo MAY •*=>7*88 WTO SctED (MS> JUNE ^7235 WM) S°EED OK IS; FIGURE 2.7a: Wind speed exceedance at Stn. Papa, January June. 30 JULY 7JSI AUGUST W O SPEED (kTS) SEPTEMBER M-69SB 80 h}0 M «o io ao SPEED (kIS) OCTOBER M-7122 wrc SPEED (KTS) 40 ""So WTO SPEED C*"S) N=7O20 NOVEMBER Kb 7002 DECEMBER ~"wJo ATO SPEED i<IS) w o SPEED <ktsj FIGURE 2.7b: Wind speed exceedance at Stn. Papa, July-Dec 31 mechanism known as Stokes D r i f t . The magnitude of t h ese c u r r e n t s a r e r e l a t e d to both the amplitude, A, and wavenumber, k, of the deep water s u r f a c e g r a v i t y waves a c c o r d i n g to the f o l l o w i n g e q u a t i o n (LeBlond and Mysak, 1978): (1) U s = A 2 ( g k V / 2 where wavenumber i s r e l a t e d t o wavelength, X , by: ( 2 ) k = 2 n / X Kenyon (1969) showed t h a t the magnitude o f the s u r f a c e d r i f t c u r r e n t s i n a f u l l y developed sea c o n d i t i o n s c o u l d be e x p r e s s e d as a f u n c t i o n o f wind speed where: (3) u"s = 0.016 W W = wind speed at 10m The second mechanism t h a t works t o slow a h u l l on the ocean s u r f a c e i s the i n t e r a c t i o n between the waves and the h u l l i t s e l f i n c l u d i n g the e f f e c t s o f b r e a k i n g waves. Wave a c t i o n i n c r e a s e s the drag f o r c e s on the h u l l and i n p a r t i c u l a r the s k i n drag. B r e a k i n g waves w i l l a c c e l e r a t e the buoy f o r a few seconds and i n extreme c a s e s may c a p s i z e the buoy. A survey of the wave c l i m a t e t h a t a buoy can expect o f f s h o r e w i l l a l l o w the c a l c u l a t i o n of wave induced c u r r e n t s , but the i n t e r a c t i v e e f f e c t s can o n l y be observed i n the f i e l d . Of p a r t i c u l a r i n t e r e s t to an A c t i v e D r i f t e r buoy study are the average wave h e i g h t s , the average p e r i o d and the frequency e x p e c t a t i o n of waves s i g n i f i c a n t enough to slow or stop forward p r o g r e s s o f the buoy. 32 A t S t a t i o n P a p a , t h e w a v e c l i m a t e r e f l e c t s t h e w i n d r e g i m e d e s c r i b e d i n S e c t i o n 2 . 3 . T h e w a v e d i r e c t i o n s a r e p r e d o m i n a n t l y SW, w i t h p e a k w a v e s f r o m t h e W, SW o r S d i r e c t i o n 7 0 $ o f t h e t i m e . A s w e l l s p a w n e d b y e x t r a t r o p i c a l s t o r m s i s c o m m o n l y f o u n d p r o p a g a t i n g f r o m SW t o N E . S i g n i f i c a n t w a v e h e i g h t s a r e t h e a v e r a g e o f t h e o n e t h i r d h i g h e s t w a v e s i n a w a v e f i e l d . F o r f u l l y d e v e l o p e d s e a s s i g n i f i c a n t w a v e s h a v e b e e n r e l a t e d t o w i n d s p e e d a c c o r d i n g t o t h e f o l l o w i n g r e l a t i o n ( P i e r s o n a n d M o s k o w i t z , 1 9 6 4 ) : ( 4 ) H = 0 . 0 1 2 W 2 W = w i n d a t 10m I/O O b s e r v e d s i g n i f i c a n t w a v e h e i g h t s a t S t a t i o n P a p a v a r y w i t h s e a s o n , r a n g i n g f r o m 4 . 9 t o 5.5m b e t w e e n O c t o b e r a n d A p r i l , d e c r e a s i n g t o 1.2 t o 2 . 1 m f r o m J u n e t o A u g u s t a n d i n c r e a s i n g t o 5m i n t h e A u g u s t - S e p t e m b e r p e r i o d ( T h o m s o n , 1 9 8 1 ) . T h e c o m b i n e d w a v e h e i g h t e x c e e d a n c e s p l o t t e d i n F i g u r e 2 . 8 s h o w t h a t w a v e h e i g h t s h a v e a n 8 0 # p r o b a b i l i t y o f b e i n g g r e a t e r t h a n 2m i n w i n t e r a n d 1.2m i n s u m m e r ( B r o w n e t a l , 1 9 8 6 ) . T h e r e i s a 5 0 $ p r o b a b i l i t y t h a t w a v e h e i g h t s w i l l h i g h e r t h a n 3m i n w i n t e r a n d 1.6m i n s u m m e r . T h e f r e q u e n c y o f o b s e r v e d w a v e p e r i o d s i s s h o w n b y m o n t h i n F i g u r e 2 . 9 ( B r o w n e t a l , 1 9 8 6 ) . T h e s e p l o t s s h o w t h e p e a k w a v e p e r i o d t o b e 12 t o 1 3 s e c o n d s t h r o u g h o u t t h e y e a r , w i t h a s e c o n d a r y p e a k o f 8 - 9 s e c o n d s t h r o u g h t h e s u m m e r . T h e l o n g e r p e r i o d w a v e s a r e t h e b a c k g r o u n d s w e l l w i t h w a v e l e n g t h s i n t h e N=4223 JANUARY N=5694 JULY N=4€34 OCTOBER FIGURE 2.8: Combined wave height months at Stn. Papa. exceedance f o r s e l e c t e d or. h-H a a so pd ro vo O o 3 cr D fD a OJ < fD TS fD •"i H -O a i-t> o •-( cn fD i—1 0 n rf a PERCENT _\0T. 20* 307. PERCENT or. ic-: isy. 207: 25* 307. G o o 51 lo—ii CD s ^ Q-13 o o (/I U-17 m Q > G > 50 o I 3 O rf CO OJ rf CO rf 3 OJ T J 0J o o ro z s I m O o m o PERCENT 07j 107j 207. 307. > SO o r d e r o f 245m or g r e a t e r and i t can be assumed t h a t t h ese w i l l not a d v e r s e l y e f f e c t a buoy t r a v e l l i n g on the s u r f a c e . 2 . 5 PREVAIL ING AND WIND DRIVEN CURRENTS The s u r f a c e c u r r e n t s o f the n o r t h e a s t e r n P a c i f i c r e s u l t from the s u p e r p o s i t i o n o f the l o c a l t i d a l and s y n o p t i c s c a l e wind-d r i v e n c u r r e n t s , and the semi-permanent c i r c u l a t i o n system o f the ocean d r i v e n by t r a d e winds. The l a r g e s c a l e c i r c u l a t i o n f e a t u r e s a r e l a b e l l e d i n F i g u r e 2.10 (from Thomson, 1981). F i g u r e 2.11 c h a r t s the s u r f a c e c i r c u l a t i o n o f the n o r t h P a c i f i c i n August and January (from USSR M i n i s t r y o f Defence C u r r e n t A t l a s , 1954). I t shows a southward d i s p l a c e m e n t and i n t e n s i f i c a t i o n o f the North P a c i f i c c u r r e n t i n w i n t e r r e l a t i v e t o summer. The c h a r t s a l s o show the average s u r f a c e c u r r e n t s i n the v i c i n i t y o f S t a t i o n P t o be i n the o r d e r o f 0.5 m/s. The c u r r e n t s c h a r t s shown thus f a r r e p r e s e n t mean s u r f a c e f l o w s i n both v e l o c i t y and d i r e c t i o n . However, the d r i f t c u r r e n t s i n t h e f i r s t few meters o f the ocean a r e the r e s u l t o f s y n o p t i c s c a l e winds and a r e the sum o f : s u r f a c e d r i f t = shear c u r r e n t due to t a n g e n t i a l wind drag + wave induced c u r r e n t due t o n o n l i n e a r e f f e c t s + c o r r e c t i o n terms due to c o u p l i n g o f wind and wave e f f e c t s . Many a u t h o r s have attempted t o c a l c u l a t e the magnitude o f 3 6 >?0 Schematic diaprjm i>l pro ailing surface current* in North Pacific Ocean Double arrows are intense boundary currents speeds. rvpicallv 1-2 m s ( 2 - 4 k m . over most of region speeds arc less than 0 25 m's (0 5 kill Subarctic Boundan separates subarctic Pacific Region to north from subtropic Pacific Region to south Broken arrow s correspond to u inter Da» idson Current oil Oregon-Washington coast. FIGURE 2.10: Major c i r c u l a t i o n features of the North Pac i f i e . FIGURE 2.11a: Surface c u r r e n t s i n the N. P a c i f i c i n January. FIGURE 2.11b: Surface currents in the N. P a c i f i c in August. t h e wind d r i f t c u r r e n t s , and s u r f a c e c u r r e n t s i n t h e o r d e r of 1-5$ o f t h e 10m winds have been p r e d i c t e d (Huang, 1979). E m p i r i c a l o b s e r v a t i o n s c o m p i l e d by Huang from 1950 t o 1975 have shown an average d r i f t c u r r e n t g i v e n by: d r i f t c u r r e n t v e l o c i t y = 0.033 U U = s u r f a c e wind ( 5 ) d r i f t c u r r e n t d i r e c t i o n = 15 t o r i g h t o f wind T h e r e f o r e , f o r t h e purposes o f p r e d i c t i n g t h e motions o f a d r i f t i n g buoy d e p l o y e d o f f s h o r e , i t w i l l be assumed t h a t t h e buoy w i l l respond t o both t h e d i r e c t wind drag f o r c e s on t h e h u l l and s u r f a c e d r i f t c u r r e n t s g i v e n by e q u a t i o n ( 5 ) . I t s h o u l d be noted t h a t t h e l o c a l winds w i l l o n l y on t h e a v e r a g e be e q u a l t o t h e p r e v a i l i n g winds and does not p r e c l u d e s m a l l s c a l e v a r i a t i o n s i n s u r f a c e c u r r e n t . The example o f t h e a c t u a l t r a c k s o f d r i f t i n g buoys d e p l o y e d by Environment Canada o f F i g u r e 1.3 shows t h e s m a l l s c a l e d e v i a t i o n s from mean c u r r e n t s . The undrogued buoys had an average d r i f t r a t e o f 0.79 m/s which i n c l u d e s t h e e f f e c t s o f wind drag and s u r f a c e c u r r e n t s . 2.6 AIR TEMPERATURE The average a i r t e m p e r a t u r e a t t h e sea s u r f a c e i s o f i n t e r e s t because t h e e l e c t r i c a l power o u t p u t o f t h e s o l a r a r r a y i s i n v e r s e l y p r o p o r t i o n a l t o t e m p e r a t u r e . T h i s i s an i n h e r e n t p r o p e r t y o f the s e m i - c o n d u c t o r s i l i c o n c r y s t a l s t h a t a r e used t o c o n v e r t s u n l i g h t t o e l e c t r i c i t y . In the Ranger 1 p h o t o v o l t a i c modules, t h i s t e m p e r a t u r e response i s g i v e n by: 4 0 (6) dP = -0.42 dT where P = Peak Output (Watts) of s o l a r module T = temperature ( C e l c i u s ) Therefore, the surrounding a i r temperature i s required to p r e d i c t the s o l a r module output while deployed offshore. The average a i r temperature by month i s given i n Table 2.3. Month A i r Temperature degrees C JAN 5. .0 FEB 5. .0 MAR 4. .4 APR 5. .6 MAY 7. 2 JUN 8. ,9 JUL 11 . 1 AUG 13. 3 SEP 13. 3 OCT 10. 6 NOV 8. 3 DEC 6. 1 Mean 8. 2 TABLE 2.3: Average d a i l y temperatures by month (B.C. S a i l i n g D i r e c t i o n s , Vol 1, Anon, 1976). 41 2 . 6 SUMMARY OF BUOY OPERATING ENVIRONMENT The f o l l o w i n g t a b l e p r e s e n t s a summary o f the average c o n d i t i o n s an A c t i v e D r i f t i n g buoy c o u l d be expected t o encounter o p e r a t i n g near S t a t i o n Papa i n the North P a c i f i c . MONTH INSOLATION TEMP WINDS WIND %> CURRENTS WAVE HT MJ/m C m/s 10 m/s m/s(3.3#U) >2m, % January 2.98 5.0 11.8 60 0.39 70 February 5.50 5.0 12.4 60 0.41 70 March 9.09 4.4 10.8 55 0.36 70 A p r i l 13.70 5.6 9.9 50 0.33 65 May 16.70 7.2 9.3 40 0.31 50 June 15.99 8.9 8.2 30 0.27 40 J u l y 14.97 11.1 7.8 20 0.26 30 August 12.78 13.3 8.2 30 0.27 40 September 10.48 13.3 9.3 40 0.31 58 October 6.75 10.6 11.8 60 0.39 70 November 3.76 8.3 12.9 60 0.43 70 December 2.39 6.1 13.4 70 0.44 70 Average 9.59 8.2 10.5 48 0.35 59 TABLE 2.4: Summary o f monthly c l i m a t e a t S t a t i o n Papa. 42 3.0 PROTOTYPE ACTIVE DRIFTER BUOY SPECIFICATIONS 3.1 DESIGN GOALS The a c t i v e d r i f t e r buoy programs a t the I n s t i t u t e o f Ocean S c i e n c e s and a t Seaboy Marine S e r v i c e s L t d . had the i d e n t i c a l d e s i g n g o a l s o f d e v e l o p i n g an autonomous data c o l l e c t i o n p l a t f o r m w i t h : - the a b i l i t y t o p r o p e l i t s e l f w i t h energy d e r i v e d from the environment which i s s t o r e d or used as r e q u i r e d ; - the a b i l i t y t o determine i t s p o s i t i o n onboard which a l l o w s i t t o f o l l o w a predetermined c o u r s e or remain a t a s e l e c t e d l o c a t i o n f o r long p e r i o d s o f time; - the a b i l i t y t o c o l l e c t data and r e t u r n i t a l o n g w i t h p o s i t i o n i n f o r m a t i o n v i a s a t e l l i t e or d i r e c t r a d i o l i n k ; - the a b i l i t y t o monitor or c o n t r o l a l l a s p e c t s o f i t s o p e r a t i o n . The degree t o which the buoy c o u l d modify i t s own p o s i t i o n i n the ocean environment was u n c e r t a i n d u r i n g the i n i t i a l development phases, and was t o be determined d u r i n g e x t e n s i v e f i e l d t r i a l s . However, The IOS program g o a l s would have been s a t i s f i e d i f the buoy were a " s l o w - d r i f t e r " or had the p o t e n t i a l t o s t a t i o n - k e e p once deployed o f f s h o r e (Smith, 1986, per. comm.), but the buoy would be most v a l u a b l e i f i t had " the a b i l i t y t o move a d i s t a n c e exceeding the average d a i l y d r i f t under o f f s h o r e c o n d i t i o n s " (Smith, 1984). Seaboy was more ambitious, a d v e r t i s i n g t h a t the buoy would be a b l e t o t r a v e l t o a p r e s e l e c t e d o f f s h o r e l o c a t i o n s a t a de s i g n speed o f 0.8 m/s (Seaboy, 1985 product s h e e t ) . The Seaboy 43 program was t o develop a buoy with "the a b i l i t y t o be deployed from shore and, a f t e r c o l l e c t i n g data f o r a p e r i o d o f time, r e t u r n t o shore f o r s e r v i c i n g " (Seaboy, 1985). P r a c t i c a l c o n s i d e r a t i o n s d i c t a t e d t h a t t h e buoy c o u l d be no l a r g e r than a few metres i n l e n g t h . The buoy had t o be s m a l l enough t o be e a s i l y handled by oceanographic v e s s e l s and not c o n s t i t u t e a hazard t o s h i p p i n g . Furthermore, the buoy c o u l d o n l y be c o s t - c o m p e t i t i v e w i t h spar buoys i f p r i c e d between $30-35,000 U.S. f o r a Met/Ocean sens o r equipped buoy ( I n t e r n a t i o n a l M a r k e t i n g S e r v i c e s , 1985). In t h e r o l e o f a data c o l l e c t i o n p l a t f o r m , the a c t i v e d r i f t e r was d e s i g n e d t o s u p p o r t an a r r a y o f m e t e o r o l o g i c a l and o c e a n o g r a p h i c s e n s o r s . These were t o i n c l u d e : a i r temperature b a r o m e t r i c p r e s s u r e 1m wind speed and d i r e c t i o n water temperature s a l i n i t y PH wave h e i g h t s u r f a c e c u r r e n t speed and d i r e c t i o n F i n a l l y , i n o r d e r t o be an e f f e c t i v e i nstrument, the commercial a c t i v e d r i f t e r buoy must have a s e r v i c e i n t e r v a l o f g r e a t e r than one year, must be r e l i a b l e and m e c h a n i c a l l y simple, and must be a b l e t o s u r v i v e a l l c o n d i t i o n s on the ocean i n c l u d i n g c a p s i z i n g . 44 3.2 EVOLUTION OF THE ACTIVE DRIFTER HULL 3.2.1 HULL DESIGN CRITERIA Data buoy h u l l shapes are chosen to p r o v i d e a s t a b l e , seaworthy and c o s t e f f e c t i v e p l a t f o r m f o r data c o l l e c t i o n i n s t r u m e n t s . The a c t i v e d r i f t e r buoy h u l l was a l s o r e q u i r e d to be e a s i l y p r o p e l l e d , have good d i r e c t i o n a l s t a b i l i t y , and have a low p r o f i l e above the w a t e r l i n e t o minimize wind drag. At low speeds, the buoy h u l l r e s i s t a n c e i s dominated by f r i c t i o n a l drag f o r c e s , which are r e l a t e d to the square of v e l o c i t y by: 2 (3.1) D = 2-P-Cd.A.V where p = f l u i d d e n s i t y 2 Cd = drag c o e f f i c i e n t o f h u l l A = c r o s s s e c t i o n a l a r e a to f l o w V = f l u i d v e l o c i t y The power r e q u i r e d t o p r o p e l t h e h u l l through the water, P, i s t h e p r o d u c t o f drag and v e l o c i t y , so power i s r e l a t e d t o the cube of v e l o c i t y : (3.2) P = D.V = 2-P-Cd.A.V 3 2 3 = const.V T h i s i m p l i e s t h a t the lowest p r a c t i c a l buoy v e l o c i t y s h o u l d be used. From s e c t i o n 2.5, w i t h s u r f a c e c u r r e n t s i n the o r d e r of 3.3$ of the average wind speed of 10.5 m/s, the d r i f t c u r r e n t s a t S t a t i o n Papa w i l l average 0.35 m/s. For a buoy t o s t a t i o n - k e e p 45 o r t o make any headway, the net buoy speed under o f f s h o r e c o n d i t i o n s must exceed t h i s . Smith e l e c t e d t o use a minimum des i g n speed o f 0.50 m/s f o r the IOS a c t i v e d r i f t e r , w i t h Seaboy s e l e c t i n g 0.8 m/s as t h e i r t a r g e t . The h u l l shape d e s i g n a t e d f o r the p r o t o t y p e buoy was l a r g e l y determined by the d e c i s i o n t o u t i l i z e s o l a r energy as the power s o u r c e f o r the buoy. While c u r s o r y c o n s i d e r a t i o n was g i v e n t o t h e r m o e l e c t r i c g e n e r a t o r s , and t o wind and wave energy systems, s o l a r power was s e l e c t e d as the t e c h n o l o g y was a v a i l a b l e and e a s i l y adapted (Smith, 1984). T h i s i m p l i e d a buoy shape with a l a r g e f l a t deck t o maximize the c o l l e c t i o n a r e a of the s o l a r a r r a y . 3.2.2 IOS ACTIVE DRIFTER BUOY PROGRAM The f i r s t a c t i v e d r i f t e r buoy was designed by G.R. Smith a t IOS i n 1983, and i s shown i n F i g u r e 3.1 and 3.2. I t had a c i r c u l a r deck 2m i n diameter, a shallow, c o n i c a l body with a c e n t r a l f i n k e e l 1m deep. The c o n i c a l shape was i n c o r p o r a t e d f o r ease o f f a b r i c a t i o n . T h i s c o n f i g u r a t i o n had s u f f i c i e n t deck area f o r 4 33 peak watt s o l a r modules, a payload w e l l i n the k e e l t h a t used the b a t t e r i e s as b a l l a s t and a l e a d shoe on the k e e l to improve s e l f - r i g h t i n g . I t was f a b r i c a t e d o f f i b r e g l a s s and had an aluminum e x t r u s i o n around the p e r i m e t e r to p r o t e c t a g a i n s t impact. A summary o f the h u l l s p e c i f i c a t i o n s a r e i n c l u d e d i n T a b l e 3.1. 4 6 t o t a l h e i g h t : k e e l depth: d i s p l a c e m e n t : m a t e r i a l : diameter: shape: 2.0m c i r c u l a r deck c o n i c a l h u l l 0.5m deep f i n k e e l 1.0m 0.9m 380 kg. f i b r e g l a s s TABLE 3.1: Summary of IOS buoy h u l l s p e c i f i c a t i o n s . The p r o t o t y p e IOS h u l l was b u i l t as a p l a t f o r m t o demonstrate the a c t i v e d r i f t e r concept and t o p r o v i d e a t e s t bed f o r the onboard systems b e i n g developed as p a r t o f p r o j e c t . O p t i m i z i n g t h e h u l l shape f o r the maximum e f f i c i e n c y was not c o n s i d e r e d important t o the p r o o f o f concept i n the IOS program, and t h e remainder o f the development a t the I n s t i t u t e f o c u s e d on c o n t r o l l e r and s o f t w a r e systems. 3.2.3 SEABOY'S ACTIVE DRIFTER PROGRAM Seaboy began i t s own a c t i v e d r i f t e r program i n 1985. T h e i r g o a l s were t o o p t i m i z e the performance o f the a c t i v e d r i f t e r and to c o m m e r c i a l i z e the concept. S i n c e p r o p u l s i o n was the primary l o a d i n the a c t i v e d r i f t e r , p r i o r i t y was put on r e d u c i n g the h u l l drag and improving the e f f i c i e n c y o f the p r o p u l s i o n system. Seaboy's development program i n c l u d e d s e v e r a l months o f tank t e s t i n g w i t h s c a l e models t o e v a l u a t e many p o t e n t i a l h u l l shapes. Seeking a combination o f low drag and s e l f - r i g h t i n g a b i l i t y , catamaran, swath and kayak shapes were a l l e l i m i n a t e d i n f a v o u r o f a s h a l l o w p a r a b o l o i d s e c t i o n a l o n g the k e e l l i n e and a 4 8 c i r c u l a r c r o s s s e c t i o n . Tank t e s t s w i t h t h i s shape gave some i n f o r m a t i o n on t h e s e l f - r i g h t i n g and t r a c k i n g a b i l i t i e s o f t h i s shape but were v e r y c u r s o r y i n n a t u r e . The f i r s t f u l l - s i z e Seaboy p r o t o t y p e was c a l l e d a Ranger 1 buoy, and was s i m i l a r i n s i z e and shape t o t h e IOS buoy ( s e e F i g u r e 3 . 3 ) . The Ranger h u l l was spoon s h a p e d , w i t h t h e deep bow and a s h a l l o w s t e r n . L i k e t h e IOS buoy i t was 2m a c r o s s t h e deck but u n d e r w a t e r , had a s h a l l o w e r k e e l and s m a l l e r p r o f i l e . The h u l l had an e s t i m a t e d 30$ l e s s drag than the IOS p r o t o t y p e (Ross L y l e , 1987, p e r . comm.) . Seaboy used a f l a t b l a d e k e e l w i t h two 75 k g . a i r f o i l shaped l e a d k e e l w e i g h t s b o l t e d t h r o u g h the b a s e . The t h r u s t e r motor was f a i r e d i n t o t h e k e e l and t h e r u d d e r suspended between t h e h u l l and t h e k e e l s h o e . In o r d e r t o improve s t a b i l i t y and r e d u c e the buoy h a n d l i n g w e i g h t , s e c t i o n s o f t h e h u l l were a l l o w e d t o f l o o d w i t h s e a w a t e r . The h u l l was d i v i d e d i n t o t h r e e l a t e r a l compartments s e p a r a t e d by w a t e r t i g h t b u l k h e a d s . The c e n t r a l b a t t e r y and i n s t r u m e n t w e l l was l e f t d ry w h i l e t h e o u t b o a r d compartments were f l o o d e d w i t h 200kg o f water when t h e buoy was d e p l o y e d . The Ranger 1 p r o t o t y p e was ready f o r e v a l u a t i o n i n the s p r i n g o f 1985 when the a u t h o r began h i s work w i t h Seaboy . H i s r o l e i n t h e Seaboy d e s i g n team was t o p r o v i d e e n g i n e e r i n g i n p u t d u r i n g t h e deve lopment p h a s e s , . and t o s u p e r v i s e the m e c h a n i c a l and o n - t h e - w a t e r buoy t e s t i n g program. The f i r s t e x p e r i m e n t s per fo rmed by the a u t h o r were c a l i b r a t e d tow tank t e s t s o f the Ranger 1 h u l l . The B . C . 49 TOP VIEW FIGURE 3.3:Section drawing of Ranger 1. 50 Research C o u n c i l was c o n t r a c t e d i n J u l y t o measure the f l u i d drag o f the p r o t o t y p e h u l l a t t h e tow tank f a c i l i t i e s on the campus of the U n i v e r s i t y o f B r i t i s h Columbia. The r e s u l t s o f t h e s e t e s t s a r e summarized i n Chapter 4. The author a l s o had the o p p o r t u n i t y t o measure the d r i f t r a t e o f an unpowered v e r s i o n o f the h u l l d u r i n g f i e l d experiments i n Saanich I n l e t f o r experiments performed f o r a term paper. The r e s u l t s showed the buoy d r i f t r a t e averaged 7-9$ o f t h e 1m wind speed i n l i g h t t o moderate winds ( E g l e s , 1985a) as compared t o 2-4$ f o r t h e Hermes spar buoy. F u r t h e r experiments showed t h a t the buoy was a l s o s t a b l e i n the i n v e r t e d p o s i t i o n . As both o f these f e a t u r e s were c o n s i d e r e d u n a c c e p t a b l e , the mechanical d e s i g n team a t Seaboy m o d i f i e d s e v e r a l o f the f e a t u r e s . While t h e h u l l shape was l e f t unchanged, the b l a d e k e e l was r e p l a c e d w i t h a hollow, a i r f o i l shaped s e c t i o n . The p a y l o a d w e l l was extended i n t o the k e e l , and the b a t t e r i e s p l a c e d i n t h i s w e l l t o lower t h e c e n t e r of g r a v i t y and improve s e l f -r i g h t i n g a b i l i t y . The f l o o d e d s i d e tanks were s e a l e d and a d d i t i o n a l b a l l a s t i n c l u d e d i n a k e e l shoe to compensate f o r the i n c r e a s e d buoyancy. F i g u r e 3.4 shows the m o d i f i c a t i o n s made to the k e e l shape. These changes were completed by the s p r i n g o f 1986, and the p r o t o t y p e e l e c t r o n i c s p a yload was ready f o r f i e l d t e s t i n g . I t was w i t h t h i s v e r s i o n t h a t the i n s h o r e f i e l d t r i a l s a t E l k Lake were performed by the author from June t o August, 1986. These t e s t a r e summarized i n Chapter 5. 51 52 T h i s buoy had the e s s e n t i a l f e a t u r e s o f a p r o d u c t i o n a c t i v e d r i f t e r buoy. I t was c a p a b l e o f automatic n a v i g a t i o n , and c o u l d s u c c e s s f u l l y f o l l o w a compass c o u r s e or t r a v e l t o a p r e d e s i g n a t e d l a t i t u d e and l o n g i t u d e . Communications was s u c c e s s f u l l y a c h i e v e d through VHF ( a l t h o u g h the range was l i m i t e d ) and through an ARGOS s a t e l l i t e t r a n s m i t t e r . The measurement o f t h r u s t e r v o l t a g e and c u r r e n t , motor speed and rudder c u r r e n t had been c a l i b r a t e d . Software was developed t o the p o i n t t h a t the buoy c o u l d be programmed t o f o l l o w a m u l t i p l e l e g course, c o u l d r e a c t t o a f o u l e d p r o p e l l e r and would shutdown n o n - e s s e n t i a l systems t o c o n s e r v e power when the b a t t e r i e s were deeply d i s c h a r g e d . In essence, w i t h the o c c a s i o n a l debuging o f s o f t w a r e and hardware problems the buoy was ready f o r i n s h o r e t r i a l s . However, the p r o t o t y p e buoy had not reached the s t a g e where i t was ready f o r o f f s h o r e t e s t s . Development was s t i l l n e c e s s a r y t o e n g i n e e r the buoy f o r o f f s h o r e c o n d i t i o n s w i t h p a r t i c u l a r a t t e n t i o n r e q u i r e d t o the r u d d e r / t h r u s t e r systems. Extended t e s t i n g o f the e l e c t r o n i c s payload was e s s e n t i a l to prove t h a t unattended o p e r a t i o n f o r months a t a time would be p o s s i b l e . In t h i s r e s p e c t , a t l e a s t s i x months of a d d i t i o n a l development would have been n e c e s s a r y b e f o r e deep water deployments would have been c o n s i d e r e d . The next s e c t i o n s summarize the s p e c i f i c a t i o n s and f e a t u r e s o f the Ranger a c t i v e d r i f t e r buoy as they were b e f o r e the p r o j e c t was abandoned. 53 3.3 D E S C R I P T I O N OF THE RANGER BUOY The f o l l o w i n g s e c t i o n s d e s c r i b e each o f the buoy components and systems. The t e c h n i c a l s p e c i f i c a t i o n s a r e summarized i n s e c t i o n 3.4. A b l o c k diagram o f buoy systems has been i n c l u d e d i n F i g u r e 3.5. 3.3.1 HULL The Ranger h u l l i s shown i n F i g u r e 3.3. The h u l l i s c o n s t r u c t e d o f g l a s s - r e i n f o r c e d f i b r e g l a s s . The deck i s c i r c u l a r t o maximize the area a v a i l a b l e f o r p h o t o v o l t a i c modules. The h u l l c e n t e r l i n e p r o f i l e i s spoon-shaped t o reduce h u l l drag by a t t e m p t i n g t o m a i n t a i n laminar f l o w through as much of t h e h u l l l e n g t h as p o s s i b l e . The 1m l o n g by 140 cm deep f o i l shaped k e e l w i t h a NACA 0017.5 f o i l s e c t i o n p r o v i d e s d i r e c t i o n a l s t a b i l i t y and houses the t h r u s t e r motor. A b a l l a s t shoe weighing 185 kg. i s b o l t e d t o the base o f the k e e l t o reduce p i t c h and r o l l . A s k e g l e s s rudder i s hung between the h u l l and the k e e l shoe. The h u l l i s d i v i d e d i n t o t h r e e w a t e r t i g h t compartments by l a m i n a t e d p l y w o o d / f i b r e g l a s s bulkheads. Only the c e n t e r w e l l i s a c c e s s i b l e , through two gasketed hatches. The c e n t e r compartment c o n t a i n s the b a t t e r y pack, e l e c t r o n i c s housing and rudder s e r v o assembly. The buoy p e r i m e t e r i s p r o t e c t e d by a 5cm h y d r a u l i c hose f i x e d i n s i d e an aluminum c h a n n e l . The s o l a r a r r a y i s mounted f l a t on the deck t o reduce windage and to a l l o w p e r i o d i c f l u s h i n g w i t h seawater.. The p a n e l s a r e r e t a i n e d w i t h a c e n t r a l antenna mounting p l a t e and a n o d i z e d c l i p s . The p l a t e s u p p o r t s the VHF, LORAN and Argos antenna and a s t r o b e l i g h t . 3.3.2 RUDDER SYSTEM The rudder i s a r e s i n c o a t e d wood c o r e f o i l 45 cm by 7cm wide. I t i s hung on a s t a i n l e s s rod through the q u a r t e r c o r d . The s t e e r i n g mechanism c o n s i s t s o f a DC s e r v o motor d r i v i n g a worm gear t o t r a n s l a t e r o t a r y motion of the motor t o l e f t / r i g h t rudder motion. A feedback p o t e n t i o m e t e r a t t a c h e d t o the rudder post senses rudder p o s i t i o n and a l l o w s the s o f t w a r e a u t o p i l o t t o m a i n t a i n proper rudder o r i e n t a t i o n . 54 REMOTE TERMINAL \ VHF RADIO \ MODEM ARGOS TX SENSORS LORAN-C COMPASS ONBOARD COMPUTER INTERNAL SENSORS BATTERIES POWER MANAGEMENT SOLAR ARRAY RUDDER MOTOR THRUSTER MOTOR FIGURE 3.5: Block diagram of buoy systems 55 3.3.3 THRUSTER SYSTEM The thruster i s made up of three basic components: a watertight housing, motor and propeller. The housing consists of an anodized aluminum tube and endcaps sealed with o-rings. A high e f f i c i e n c y low speed 12 V DC permanent magnet motor i s enclosed in the housing. A tef l o n bearing and shaft gland form a watertight seal around the propeller shaft. Several propellers were used including a 27 cm weedless e l e c t r i c outboard prop, and two model airplane propellers 28 and 36 cm in diameter. 3.3 .4 SOLAR ARRAY The photovoltaic arra^ mounted on the deck of the buoy provides a l l power for the buoy e l e c t r o n i c s and propulsion. The array consists of six t r i a n g u l a r panels mounted to form a hexagon and covering the buoy deck. Each panel contains 35 10 cm single c r y s t a l s i l i c o n solar c e l l s wired in ser i e s . The superstrate i s low-iron tempered solar glass, and the c e l l s are encapsulated with ethyl v i n y l acetate pottant. Figure 3.6 shows a cross section of the modules b u i l t for the Ranger. A layer of white tedlar bonded to 1.0mm 5052 aluminum forms the substrate. A medium density foam i s adhered to the underside for r i g i d i t y , with an aluminum backing. The e n t i r e module i s surrounded by an aluminum channel. The solar modules were manufactured by the author in 1984. Jhe array used on the buoy was rated at 192 watts at 100 mW/cm at 18 C. A subsequent array was manufactured but never i n s t a l l e d . However, i t was rated at 210 watts at 100 mW/cm at 18C. The current/voltage c h a r a c t e r i s t i c s for these solar panels are shown in Figure 3.7. For the simulation the higher output array has been s p e c i f i e d . Note that the development of a power regulator for the solar array was scheduled but never completed before the end of the project. 3.3 .5 POWER STORAGE The power storage system consists of a bank of six sealed lead calcium gelled e l e c t r o l y t e batteries. The battery bank stores excess amounts of solar energy when ava i l a b l e and supplies power for the elect r o n i c s and propulsion on demand. The batteries were rated at 55 amp-hrs each at the 20 hr rate. Four of the batteries were placed in the payload well in the keel to lower the center of gravity of the buoy. 56 FIGURE 3.6: Cross s e c t i o n of Ranger s o l a r panel. 57 VOLTS FIGURE 3 .7 C u r r e n t / v o l t a g e c h a r a c t e r i s t i c s of Ranger s o l a r modules. 58 3 .3 .6 ONBOARD COMPUTER The f u n c t i o n s o f the onboard computer are t o o v e r s e e a l l a s p e c t s o f buoy o p e r a t i o n i n c l u d i n g data a c q u i s i t i o n and p r o c e s s i n g , a u t o p i l o t c o n t r o l , n a v i g a t i o n , t h r u s t e r o p e r a t i o n , communications, power management and i n t e r n a l systems d i a g n o s t i c s . The computer i s i n t e r f a c e d w i t h a d i g i t a l compass, a LORAN r e c e i v e r , VHF and ARGOS t e l e m e t r y packages, s t e e r i n g and t h r u s t e r motors, and i n t e r n a l and e x t e r n a l s e n s o r s . A l l buoy e l e c t r o n i c s a r e housed i n a w a t e r t i g h t aluminum box 85 cm by 35 cm by 22 cm h i g h . The onboard computer c o n s i s t s o f a low power s i n g l e board computer c a r d a d m i n i s t e r i n g a r e l a y c a r d , f o u r i n t e r f a c e c a r d s and a power management c a r d . A b l o c k diagram o f th e payload i s g i v e n i n F i g u r e 3.8. The s i n g l e board computer uses a HD64180 enhanced Z-80 CPU w i t h 64k o f RAM/EPROM. Inpu t / o u t p u t i s through two s e r i a l RS232S p o r t s t o communicate w i t h a remote o p e r a t i n g t e r m i n a l e i t h e r d i r e c t l y or through a VHF r a d i o l i n k . The r e l a y c a r d has 14 r e l a y s t o s w i t c h power t o the buoy subsystems i n c l u d i n g : t h r u s t e r rudder motor A/D c a r d a u t o p i l o t LORAN-C Radio/Modem ARGOS Payload The i n t e r f a c e c a r d s a r e used to c o n d i t i o n the i n p u t / o u t p u t from the v a r i o u s d e v i c e s t o a CPU r e a d a b l e format. The m i c r o p r o c e s s o r developed f o r the Ranger buoy had s e v e r a l f e a t u r e s e s s e n t i a l t o the s u c c e s s f u l o p e r a t i o n f o r extended p e r i o d s . These i n c l u d e d a watchdog tim e r , s e p a r a t e m i c r o p r o c e s s o r s on each o f the r e l a y , power management and s t a t i o n management c a r d s which v e r i f y the o p e r a t i o n s o f the o t h e r c a r d s and HCMOS components f o r low power consumption. When o p e r a t i n g near shore, the buoy may be c o n t r o l l e d manually u s i n g a remote t e r m i n a l . A Tandy 100 l a p - t o p computer i n t e r f a c e d w i t h a VHF r a d i o was used. The t e r m i n a l communicates w i t h the buoy u s i n g a VHF l i n k w i t h a range of 2 km. The buoy a c c e p t s commands from the t e r m i n a l and can be reprogrammed with waypoints, compass headings or manually. The t e r m i n a l may a l s o be used t o r e t r i e v e data from the buoy i n c l u d i n g p o s i t i o n , t h r u s t e r c u r r e n t and v o l t a g e and i n t e r n a l d i a g n o s t i c s messages. F i g u r e 3.9 i l l u s t r a t e s the menu o p t i o n s a v a i l a b l e i n the remote programming s o f t w a r e . 59 o _ -J re O ^ co u : 5 t o •X w s K 1 f J FIGURE 3.8: B l o c k d i a g r a m of buoy e l e c t r o n i c s p a y l o a d 60 MAIN MENU PAYLOAD a u t o m a t i c s e t w a y p o i n t -g e t w a y p o i n t -s e t c o u r s e -s t a t i o n keep -NAVIGATION an/air s p a r e g e n e r i c RPM on/o-ff message s i eep manual s t r o b e c a r r i e r on/o-f-f d i a g n o s t i c s t a t u s c l o c k -motor a n / o f f - c e n t e r r u d d e r -motor r e v e r s e - h e a d i ng c a l i b r a t e -set-read-FIGURE 3 . 9 : Remote programming options menu. 3 . 3 SUMMARY OF RANGER BUOY SPECIFICATIONS TABLE 3 . 2 : RANGER BUOY TECHNICAL SPECIFICATIONS H u l l : Diameter: Depth below w a t e r l i n e : Height above w a t e r l i n e : Displacement: M a t e r i a l s : 2.1 m 70 cm 5 cm 510 kg g l a s s r e i n f o r c e d f i b r e g l a s s T h r u s t e r : P r o p e l l e r type: E f f i c i e n c y : P i t c h : T h r u s t e r motor type: M a n u f a c t u r e r : Max. E f f i c i e n c y : Typ. E f f i c i e n c y : Power requirement: 36 cm Master A i r s c r e w model a i r p l a n e p r o p e l l e r 70% a t 300 rpm. 15 cm 12 V DC permanent magnet I n e r t i a Motors Corp. 76.7% @ 12V DC, 2.15 A 296 rpm, torqu e = 0.64 N-m 50% @ 12.5 V, 2.6A (32 w a t t s ) 250 rpm, t o r q u e = 0.80 N-m 32 W (under l o a d ) R u d d e r : Dimensions: M a t e r i a l s : C o n t r o l : 45 cm x 18 cm f i b r e g l a s s on wood c o r e DC s e r v o motor & worm gear feedback p o t e n t i o m e t e r on shaf S o l a r A r r a y : Number o f Modules: M a n u f a c t u r e r : C o n s t r u c t i o n : Area: Peak Output ( e a c h ) : A r r a y Output: Open C i r c u i t v o l t a g e ( V o c ) : S h o r t C i r c u i t c u r r e n t ( I s c ) : Peak V o l t a g e (Vmp): Peak C u r r e n t (Imp): F i l l F a c t o r : E f f i c i e n c y : Temp. C o e f f . o f E f f i c i e n c y : S e r i e s R e s i s t a n c e : C a l i b r a t i o n C o n d i t i o n s : 6 S o l e c I n t e r n a t i o n a l Inc. Tempered g l a s s / E V A / T e d l a r 0.377 m 35.0 Watts each 207 W 19.95 V 2.55 A 15.58 V 2.21 A 68% 9.5% 0.045 % per C 1.19 Ohm 100.0 mW/cm , 18°C Battery Storage: Type: Ma n u f a c t u r e r : C a p a c i t y : Number o f b a t t e r i e s : S i z e : Weight: Lead C a l c i u m Gel C e l l s Johnson C o n t r o l s - Globe Div. 55 Ahr @ 20 Hr r a t e , 23°C 26cm x 17cm x 22cm h i g h 17.7 kg Onboard E l e c t r o n i c s : Computer: CPU Type: F e a t u r e s : Cards: HD64180 @ 6.144 MHz HCMOS components watchdog t i m e r 64K RAM/EPROM RS232S s e r i a l c h a n n e l s (2) p a r a l l e l p o r t s (2) Relay C o n t r o l Card (14 r e l a y s ) Power Management Card S t a t i o n Management Card MUX Card I n t e r f a c e Cards (4) Communications: VHF: ARGOS: Repco FSK Radio Modem (1200 Bd) 2 watts, 166.815 MHz 7 km range max. S y n e r g e t i c s I n t . Model 2101A 401.65 MHz 8 passes/day Navigation: Compass: LORAN: A u t o p i l o t : D i g i c o u r s e Mieco C-Master X Comdev Marine Model 2000 63 Power Budget: P r o d u c t i o n Ranger The power budget f o r a p r o d u c t i o n Ranger buoy i s g i v e n i n T a b l e 3.3. A p r o d u c t i o n buoy d i f f e r s from t h e Ranger 1 through s e v e r a l f e a t u r e s designed t o reduce the o v e r a l l power consumption. These were t o i n c l u d e a s o f t w a r e a u t o p i l o t o p e r a t e d by t h e CPU t o r e p l a c e the power-hungry Comdev a u t o p i l o t , and e l i m i n a t i o n o f the VHF r a d i o . UNIT POWER DUTY CYCLE TOTAL (wa t t s ) ( w a t t s ) ELECTRONICS 2.05 1 2.05 ARGOS Tx 0.08 1 0.08 LORAN 1.00 1 1.00 STROBE 0.30 0.5 0.15 THRUSTER 32.00 up t o 1.0 32.00 RUDDER 3.00 " " 1 . 0 3.00 COMPASS 0.26 " 1.0 0.26 TOTAL 38.54 TABLE 3.3 Power Budget f o r a P r o d u c t i o n Ranger buoy. 4.0 MECHANICAL TESTING OF THE PROTOTYPE BUOY In the p r o c e s s o f d e v e l o p i n g the a c t i v e d r i f t e r a t Seaboy many d e s i g n d e c i s i o n s were based on the r e s u l t s o f mechanical t e s t s performed on p r o t o t y p e s and components. T h i s s e c t i o n d e s c r i b e s t e s t s performed by the author i n the c o u r s e o f t h e A c t i v e D r i f t e r buoy p r o j e c t which have a d i r e c t b e a r i n g on the performance model i n Chapter 6. These i n c l u d e a c a l i b r a t e d measurement o f the e f f e c t i v e power cu r v e o f a p r o t o t y p e h u l l i n f l a t water, the e f f e c t o f monochromatic waves on h u l l drag and an e s t i m a t e of wind drag e f f e c t s on the buoy. 4.1 TOW TANK TESTS The Ocean E n g i n e e r i n g Department of B.C. Research o p e r a t e s a 4m by 100m by 2m deep tow tank w i t h wave making equipment i n Vancouver. With these f a c i l i t i e s , i t was p o s s i b l e t o a c c u r a t e l y measure the drag o f the a c t i v e d r i f t buoy h u l l as a f u n c t i o n o f towing speed i n both calm water and i n a s i m u l a t e d chop. T h i s i n f o r m a t i o n i s v i t a l l y important t o both h u l l d e s i g n and buoy o p e r a t i n g s t r a t e g y as i t d e f i n e s what t h r u s t i s r e q u i r e d to p r o p e l the buoy a t a g i v e n v e l o c i t y . The f o l l o w i n g measurements were performed a t the B . C . Research tow tank: ( i ) R e s i s t a n c e t e s t i n f l a t water ( i i ) E f f e c t o f buoy t r i m on h u l l drag ( i i i ) E f f e c t of s m a l l chop on h u l l drag 6 5 T h i s s e c t i o n summarizes the o b s e r v a t i o n s and data c o l l e c t e d i n t h e s e experiments, and i n c l u d e s a d i s c u s s i o n o f the s i g n i f i c a n c e o f the r e s u l t s . 4 . 1 . 1 EXPERIMENTAL METHOD The tow tank apparatus p r o v i d e d the o p p o r t u n i t y t o measure the t o t a l r e s i s t a n c e o f the buoy h u l l t o t r a v e l through the water. I t e f f e c t i v e l y measures the combined f r i c t i o n a l drag and the wave-making r e s i s t a n c e o f the h u l l a t a c o n s t a n t v e l o c i t y . With enough t r i a l s , the r e s i s t a n c e c u r v e o f the buoy can be d e f i n e d and the e f f e c t i v e power r e q u i r e d t o p r o p e l the buoy c a l c u l a t e d . To perform a r e s i s t a n c e measurement, the buoy was towed the l e n g t h o f the tank a t a d e s i g n a t e d speed. The tow apparatus was a t r o l l e y t h a t runs on t r a c k s p a r a l l e l t o the tank. The t r o l l e y c o n t a i n e d a PDP11 computer data a c q u i s i t i o n system i n t e r f a c e d w i t h heave, t i l t and r e s i s t a n c e s e n s o r s . A v i d e o camera was mounted a t the r e a r o f the t r o l l e y t o photograph the buoy wake. The buoy was a t t a c h e d t o t h e t r o l l e y by a v e r t i c a l arm t h a t b o l t s v i a a f l a n g e t o the buoy deck. The towing arm was p o s i t i o n e d t o emulate the buoy t h r u s t e r . I t p u l l e d the buoy forward w h i l e a t the same time was f r e e t o move v e r t i c a l l y to measure buoy heave. A t y p i c a l t r i a l proceeded as f o l l o w s : 1. The buoy and t r o l l e y were winched s l o w l y t o the f a r end o f the tank. 66 2. The technicians waited for a short period (typ. 1 minute) for the water to s e t t l e , then the sensor zeros were established. 3. The t r o l l e y was accelerated to a designated speed. When the measured speed on board the t r o l l e y reached within 10$ of the desired v e l o c i t y , the computer data recording system activated. 4. The resistance, heave and t i l t measurements were recorded for the remainder of the run u n t i l the t r o l l e y was decelerated. By example, at 0.5 m/s, 90 seconds of data were av a i l a b l e . 5. A computer video terminal plotted the resistance, heave and t i l t data as a function of time. The technician then observed the data for quality and manually edited the data. In t h i s way, the noise from the acceleration and deceleration phases were eliminated. The computer then averaged the good data and displayed a table of s t a t i s t i c s for that run. 6. The buoy would then be winched to the other end of the tank and the process repeated. The data product for an i n d i v i d u a l run consists of four s t a t i s t i c a l averages for the selected time period: ( i ) Speed - measured buoy speed during run; ( i i ) Resistance - as measured by s t r a i n gauges on the towing bar; ( i i i ) Heave - how much the buoy i s depressed compared to the s t a t i c l e v e l ; ( i v ) Trim - fore and a f t t i l t of the buoy. In the course of the 23 towing runs performed, three separate experiments were attempted and are described below: 1. Flat water resistance test: The purpose of t h i s experiment was to derive the e f f e c t i v e power curves for the buoy in f l a t water. The buoy was towed at speeds from 0.25 m/s to 1.00 m/s in increments of 0.125 m/s. The entire experiment was repeated a f t e r r e c a l i b r a t i o n of the sensors on the towing apparatus. A power curve defined by seven points was produced. 67 2. A l t e r n a t e t r i m t e s t : T h i s experiment t e s t e d the h y p o t h e s i s t h a t the buoy r e s i s t a n c e c o u l d be lowered by r a i s i n g the bow of the buoy under power. The buoy was trimmed w i t h a s t e r n l i s t o f 0.6 and 1.0 by r e d i s t r i b u t i o n o f the weight o f the s o l a r p a n e l s on the deck. Three runs were performed a t speeds o f 0.75 m/s and 1.0 m/s. 3. R e s i s t a n c e i n waves: T h i s t e s t attempted t o measure the change i n r e s i s t a n c e o f the buoy i n s m a l l waves. The waves were c r e a t e d by a s m a l l paddle a t t h e f a r end of the tank, and the buoy was towed i n t o them. The waves were monochromatic, w i t h a h e i g h t o f 23 cm and a wavelength o f 1m. Two t r i a l s were performed a t speeds o f 0.5 m/s and 1.25 m/s. 4.1.2 OBSERVATIONS T r i a l 1-3 - t h e s e runs were performed to t e s t equipment and t o p r o v i d e an e s t i m a t i o n o f the range of r e s i s t a n c e v a l u e s expected. - a t 0.5 m/s the buoy towed n i c e l y and evenly, but a t 0.85 m/s the buoy submerged and the run was h a l t e d f o r f e a r o f damage t o the equipment. - a t 0.75 m/s the bow tended t o depress, but the problem d i d not become c r i t i c a l . A d i s c u s s i o n w i t h B.C. Research p e r s o n n e l , G. Stensgaard and G. Novlesky l e d t o the c o n c l u s i o n t h a t the p o s i t i o n o f the towing b r a c k e t was a t f a u l t . To be most r e p r e s e n t a t i v e , the tow p o i n t s h o u l d be a t t a c h e d a l o n g the l i n e o f the p r o p e l l e r s h a f t , or near the c e n t e r o f g r a v i t y . I t was not f e l t t h a t t h i s was p r a c t i c a l f o r the buoy due to the p o s i t i o n o f the t h r u s t e r deep i n the k e e l . To compensate f o r t h i s problem and s i m u l a t e the moment induced by the p r o p e l l e r t h r u s t (which would have c o u n t e r e d the observed tendency f o r the bow to submerge), a d e c i s i o n was made 6 8 t o r e d i s t r i b u t e the weight of the s o l a r p a n e ls on the deck. A s i n g l e panel was removed and r e p l a c e d with a 9 kg mass ( t h e weight o f the s o l a r p a n e l ) t o m a i n t a i n a c o n s t a n t d i s p l a c e m e n t . A t a b l e o f p o s i t i o n s f o r the 9 kg weight on the buoy c e n t e r l i n e was c a l c u l a t e d t o p r o v i d e a p i t c h i n g moment equ a l t o t h e t h r u s t produced a t a s p e c i f i c v e l o c i t y . A s c a l e was drawn on the deck of the buoy t o mark placement o f the weight. T r i a l 4-9 - the buoy was towed f o r t h e s e s i x runs w i t h o u t mishap, and the data r e c o r d e d . - a t low speeds, the p o s i t i o n o f the 9 kg t r i m weight was v e r y c l o s e t o the c e n t e r of mass o f the removed s o l a r p a n e l s , s i m u l a t i n g the near s t a t i c buoy c o n f i g u r a t i o n . - a t low speeds t h e r e was very l i t t l e bow o r s t e r n wake. - a t h i g h e r speeds (>0.5 m/s) the bow tended t o submerge as waves were pushed forward by the bow. - some wake t u r b u l e n c e was observed. - w i t h a l l t r i a l s , the r e s i s t a n c e v a l u e s were f a i r l y c o n s i s t e n t a f t e r running up the f i r s t 25 m o f the tank, and up t o the l a s t 10m. - the heave v a l u e s ( v e r t i c a l d e p r e s s i o n o f the buoy) s l o w l y d e c r e a s e d through the f i r s t h a l f o f the run then l e v e l e d o f f . T h i s may be the r e s u l t s o f t h e buoy s i n k i n g i n t o i t s own bow wave, once e s t a b l i s h e d . - the t r i m a n g l e t y p i c a l l y i n c r e a s e d s t e a d i l y throughout the run, perhaps due t o s h i f t i n g of the water b a l l a s t . T r i a l 10 - a t an attempted run of 1.0 m/s, the buoy began t o submerge h a l f way down the tank. - the t r o l l e y was brought t o an abrupt h a l t . - data was a v a i l a b l e f o r the f i r s t h a l f o f the run but was s u s p e c t due t o the r a p i d l y changing p i t c h o f the buoy. T r i a l 11 - a t a speed o f 0.6 m/s, the r e s i s t a n c e data was meaningless, i n d i c a t i n g a m a l f u n c t i o n i n the s e n s o r s . - G. Novlesky f e l t damage was s u s t a i n e d when the t r o l l e y was stopped i n t r i a l 10, and the s e n s o r s were s u b s e q u e n t l y checked and r e c a l i b r a t e d . T r i a l 12-18 - 7 runs proceeded w i t h o u t problem, with speed from 0.25 m/s to 0.85 m/s. - the p l o t o f the data p o i n t s p r o v i d e d a smooth curve, and G. Stensgaard was c o n f i d e n t t h a t t h ese t r i a l s produced a c c u r a t e data, and the f i r s t 11 t r i a l s s h o u l d be i g n o r e d . - the t r e n d f o r the bow to submerge at h i g h e r speeds 6 9 r e m a i n e d . Based on t h e o b s e r v a t i o n s o f t h e f i r s t 18 t r i a l s , t h e upper speed l i m i t o f t h e buoy b e f o r e submergence became c r i t i c a l was 0.8 m / s , t h e d e s i g n speed o f the buoy. A second e x p e r i m e n t was p e r f o r m e d a t t h e tow tank f a c i l i t i e s t o o b s e r v e i f t h e speed l i m i t c o u l d be i n c r e a s e d by t r i m m i n g t h e buoy s t e r n down. To do t h i s t h e 9 kg we igh t was moved as f a r a f t as p o s s i b l e , 107 cm f rom t h e f o r w a r d edge o f t h e main h a t c h . T h i s gave t h e buoy a t r i m o f 0 . 6 ° t o s t e r n . A s i n g l e tow o f 0.75 m/s i n d i c a t e d l i t t l e change i n r e s i s t a n c e f rom p r e v i o u s r u n s , but the bow s t i l l t ended t o submerge. To i n c r e a s e the s t e r n t r i m , the r e m a i n i n g s o l a r p a n e l i n t h e bow was removed, and a second 9 kg w e i g h t p l a c e d on the s t e r n 96 cm f rom t h e h a t c h . T h i s c r e a t e d a n o t i c e a b l e s t e r n l i s t o f 1.0°. T r i a l 19-21 - w i t h the 18 kg o f we igh t on the s t e r n , t h e t endency f o r t h e bow t o submerge was d i m i n i s h e d , and the buoy l i s t e d t o s t e r n d u r i n g a run a t 0.75 m / s . - a t 1.0 m/s t h e buoy s t i l l d i d not submerge, but sank i n t h e bow wave. - water s l o s h e d o v e r t h e s t e r n , submerg ing i t s l i g h t l y . - r e s i s t a n c e v a l u e s d i d not change a p p r e c i a b l y . - i n t e r n a l movement o f water i n t h e s i d e t a n k s may have been r e s p o n s i b l e f o r odd t r i m a n g l e s . To measure the e f f e c t s o f waves, a few runs a t speeds o f 0 .5 m/s and 0 .75 m/s were a t t e m p t e d . Buoy t r i m was r e t u r n e d t o t h a t o f f l a t water r e s i s t a n c e t e s t s o f T r i a l s 13 and 14. The buoy was towed i n 23 +/ - 2 cm waves as measured from t r o u g h t o c r e s t w i t h a r u l e r . T r i a l 22-23 - s m a l l chop washed s t r a i g h t o v e r t h e buoy, and t h e buoy appeared on the v e r g e o f s u b m e r g i n g . - waves were o b s e r v e d t o be 23 cm h i g h , w i t h 1m w a v e l e n g t h s 70 - r e s i s t a n c e v a l u e s were 4 t i m e s f l a t wa te r v a l u e s , but G. N o v l e s k y f e l t t h e water was s p l a s h i n g e l e c t r i c a l c o n t a c t s o f t h e s e n s o r s and v a l u e s were q u e s t i o n a b l e . 4 . 1 . 3 RESULTS T a b l e 4.1 summarizes t h e d a t a r e c o r d e d d u r i n g each o f the 23 speed runs a t t h e B . C . R e s e a r c h tow t a n k . Note t h a t the u n c e r t a i n t i e s g i v e n f o r t h e r e s i s t a n c e , heave and t r i m measurements r e p r e s e n t the s e n s o r a c c u r a c y as e s t a b l i s h e d d u r i n g t h e c a l i b r a t i o n p r o c e s s . T a b l e 4 .2 i s a r e d u c e d v e r s i o n o f T a b l e 4 . 1 , l i s t i n g the d a t a f rom T r i a l s 12 t o 18 a f t e r the second s e n s o r r e c a l i b r a t i o n . I t was the o p i n i o n o f B . C . R e s e a r c h p e r s o n n e l t h a t t h e s e runs a c c u r a t e l y measured t h e h u l l r e s i s t a n c e i n f l a t w a t e r . F i g u r e 4.1 p l o t s r e s i s t a n c e as a f u n c t i o n o f v e l o c i t y f o r t h i s d a t a s e t . F i g u r e 4 . 2 and 4 . 3 p l o t t h e buoy heave and t r i m as a f u n c t i o n o f v e l o c i t y . The e f f e c t i v e power, t h e p r o d u c t o f towing r e s i s t a n c e and buoy speed i s shown i n F i g u r e 4 . 4 . 4 . 1 . 4 DISCUSSION Three e x p e r i m e n t s were per fo rmed a t the B . C . R e s e a r c h Ocean E n g i n e e r i n g C e n t e r . The f i r s t exper iment d e f i n e d the f l a t water power c u r v e f o r the buoy, and r e q u i r e d 18 runs t o c o m p l e t e . Of t h e s e , T r i a l s 12 t o 18 were c o n s i d e r e d r e l i a b l e d a t a , and have been used i n F i g u r e 4 . 1 . T h i s p l o t shows t h a t a smooth c u r v e can j o i n t h e seven da ta p o i n t s , i n d i c a t i n g the q u a l i t y o f t h e d a t a . 71 SEABOY RESISTANCE TEST DATA RUN No. to LOCATION of" 9 k g WEIGHT (cm) TARGET SF'EED U.ts) SF'EED (kts) SF'EED (m/s) RESIST (Ni HEAVE (mm) CHANGE OF TRIM <Deg> bow up — bow dn EFFECTIVE POWER (Ul) APPLIED TRIMMING MOMENT(Nm) + bow up — bow dn COMMENTS 1 1. 00 1.00 0.51 4. 88 - 2. 48 4- - 1.70 1.70 0.e6 51. 46 - _ 44. 44 _ 3 - 1.50 1.50 0. 76 19.08 - — 14.54 _ 4 -13.5 1.50 1.52 0.77 20.54 +-1. 20 -14.22 0. 09 15. 86 11.98 5 -0.S 0.50 0.50 0.25 1.51 -2.79 0.07 0.38 0.68 6 1. 00 0.99 0.50 10.69 -6.35 - 0 . 29 5. 38 2.94 7 -1 .3 0.75 0.74 o.3e 6.52 -4.32 -0.23 2. 45 1.58 e -6 .6 1.25 1.27 0.65 12.07 -9.65 - 0 . 26 7.79 5. 88 9 -45.7 1.75 1.78 0.90 25.95 -18.54 - 1 . 46 23. 47 40.67 10 -45. 7 2.00 1 . 97 1.00 40. 19 -21.08 -0.89 40. 22 40.67 i i -6 .6 1.25 - - - - - - _ 12 -6 .6 1.25 1.27 0.65 12.56 +-0 06 -10.41 -0.75 8. 10 5.88 13 -13.5 1.50 1.51 0.77 17.35 -13.46 -1.04 13.31 11. 9B 14 -3 .3 1.00 1.02 0.52 7.76 -6 . 86 -0.54 4.02 2.94 lli - l . B 0.75 0. 75 0.38 4.21 -4.57 - 0 . 3B 1.61 1.5B 16 -0 .8 0.50 0.51 0.26 1.55 -2.79 0.38 O. 40 0. 68 17 -45.7 1.75 1.78 0. 90 26. 40 -19.30 - 1 . 69 23.87 40.67 IS -7 .6 1.35 1. 34 0.68 12.91 -11.43 -0.91 8.79 6.78 19 -106.7 1.50 1.52 0. 77 16. 90 -17.27 -0.96 13.05 94.91 20 -106.7 1.50 1.53 0.78 17.52 -22.35 -0.52 13.62 167.21 21 -106.7 2.00 2.02 1.03 31.59 -35.56 - 1 . 76 32. 41 167.21 22 -12.7 1.50 1.50 0.76 46.32 -60.45 4. 13 35. 29 1 1. 98 1 T -25. 4 1.00 1.00 0.51 33. 10 -37.85 1.67 16.81 11.98 equipment setup q u e s t i o n a b l e p o i n t q u e s t i o n a b l e p o i n t q u e s t i o n a b l e p o i n t u n s t a b l e - d i v i n g submerged r e c a l i b r a t i o n , good bow up t r i m t e s t waves - wet t r a n s d u c e r s TABLE 4.1: Ranger Buoy Resistance Tests - B.C. Research. SEABOY RESISTANCE TEST DATA RUN SPEED SPEED RESIST HEAVE CHANGE OF EFFECTIVE No. (kts) (m/s) (N) (mm) TRIM (Deg) POWER + bow up (W) - bow dn 16 0.51 0.26 1. 56 -2.79 0.38 0. 40 15 0.75 0. 38 4. 23 -4.57 -0. 38 1.61 14 1.02 0.52 7. 78 -6.86 -0.54 4.03 12 1.27 0.65 12. 59 -10.41 -0.75 8. 12 18 1.34 0.68 12. 94 -11.43 -0.91 8.81 13 1.51 0.77 17. 39 -13.46 -1.04 13.34 17 1. 78 0. 90 1.00 1. lO 26. 47 -19.30 -1.69 23.94 TABLE 4.2: Flat water speed t r i a l s — reduced data. 0.5 1.0 1.5 2.0 knots Veloci ty FIGURE 4.1: H u l l r e s i s t a n c e i n f l a t water. 7 4 75 I 1 F 1 0.5 1.0 1.5 2.0 knots B u o y V e l o c i t y FIGURE 4.3: Buoy t r i m v s . v e l o c i t y . 7 6 77 The e f f e c t i v e power cu r v e o f F i g u r e 4.4 i s a p l o t of the t h r u s t r e q u i r e d t o d r i v e the buoy a t a g i v e n speed i n f l a t water. The e f f e c t i v e power i s the " t o w l l n e power", or the power needed t o overcome the r e s i s t a n c e o f the h u l l t o motion. I t d i f f e r s from the e l e c t r i c a l power d e l i v e r e d t o the motor by the p roduct o f motor e f f i c i e n c y , p r o p e l l e r e f f i c i e n c y and t h r u s t r e d u c t i o n through p r o p e l l e r / h u l l i n t e r a c t i o n . The e f f e c t i v e power has been c a l c u l a t e d from the data by: (4.1) P = R e s i s t a n c e x v e l o c i t y = R t.U where r e s i s t a n c e was measured d u r i n g the tow tank t e s t s . For a slow speed buoy l i k e the Ranger, the observed r e s i s t a n c e i s the r e s u l t of t h r e e p r o c e s s e s : - s k i n f r i c t i o n - wave making r e s i s t a n c e - eddy f o r m a t i o n The r e l a t i v e magnitudes of t h e se e f f e c t s can be compared by c a l c u l a t i n g the "speed to l e n g t h " r a t i o or T a y l o r Q u o t i e n t f o r the h u l l u s i n g ( 4 . 2 ) . (4.2) SLR = V ( m / s 2 ) 1 / 2 where L i s the w a t e r l i n e l e n g t h i n f e e t and V i s the h u l l speed i n knots. For the Ranger buoy, (4.2) y i e l d s v a l u e s of 0.4 and 0 . 6 f o r speeds o f 0.5 and 0.75 m/s. S i n c e t hese r a t i o s a r e l e s s than 78 0.8, i t can be assumed t h a t the Froude or wave-making e f f e c t s a r e s m a l l and f r i c t i o n a l f o r c e s dominate the h u l l r e s i s t a n c e (Van Dorn, 1984). Under these c i r c u m s t a n c e s , the e f f e c t i v e power can be approximated by the p o l y n o m i a l e q u a t i o n s g i v e n i n ( 4 . 3 ) , where the exponent, n, i s a c h a r a c t e r i s t i c o f the h u l l and determined e x p e r i m e n t a l l y ( P h i l l i p s - B e r t , 1957). (4.3) P = k.V n e To determine the c o e f f i c i e n t s o f the e f f e c t i v e power f u n c t i o n f o r t h e Ranger buoy, the n a t u r a l l o g a r i t h m of (4.3) was taken, where: (4.4) l n ( p e ) = In C O + n . l n ( V ) The p l o t o f l n ( P e ) and l n ( V ) shown i n F i g u r e 4.5 shows a l i n e a r r e l a t i o n s h i p , w i t h the s l o p e and i n t e r c e p t d e f i n i n g ( 4 . 5 ) , the e f f e c t i v e power f u n c t i o n : (4.5) P = 32.1 . V 3 - 2 e A r e s o l u t i o n o f the e f f e c t i v e power r e l a t i o n s h i p f o r the Ranger buoy i s v a l u a b l e because i t d e f i n e s the t h r u s t r e q u i r e d to p r o p e l the buoy a t a g i v e n speed, and a l l o w s the o p e r a t i n g speed t o be a d j u s t e d to f i t v a r i o u s power budgets. These are important elements o f the performance s i m u l a t i o n of c h a p t e r 6. For example, t h e s e experiments have shown t h a t an a c t i v e d r i f t e r c o u l d be o p e r a t e d a t the d e s i g n speed of 0.8 m/s, with 15.7 watts 79 POWER VS S P E E D RELATIONSHIP TOW TANK DATA 3.5 -1 — -1 .4 -1.2 -1 -0.8 - O . G -0.4 -0.2 In ( SPEED IN m/a ) FIGURE 4.5: Natural l og of e f f e c t i v e power and v e l o c i t y 80 o f t h r u s t e r power i n calm water. Note t h a t the e f f e c t i v e power c u r v e s d e r i v e d from the tow tank t e s t s a r e f o r f l a t water and r e p r e s e n t the optimum v a l u e s . Under n a t u r a l c o n d i t i o n s w i t h winds and waves, the power cu r v e s w i l l be d i s p l a c e d upwards and t o the l e f t . Each s e t o f wind and wave c o n d i t i o n s w i l l a f f e c t the h u l l d i f f e r e n t l y depending on the wave c h a r a c t e r i s t i c s , w a ve/hull i n t e r a c t i o n , wind drag c o e f f i c i e n t s and many o t h e r f a c t o r s . The tow tank t r i a l s r e v e a l e d an i n t e r e s t i n g f e a t u r e o f buoy h u l l b e h a v i o u r under power: the tendency t o run with a bow-down a t t i t u d e as shown i n F i g u r e 4.3. T h i s problem was s e r i o u s enough t h a t d u r i n g an attempted speed run a t 0.86 m/s, the bow sank so deeply t h a t water washed over the deck. Through t r i a l s 1 t o 3, t h i s was a t t r i b u t e d t o the l o c a t i o n o f the tow attachment p o i n t . However, d e s p i t e r e d i s t r i b u t i o n o f weights on the deck t o s i m u l a t e the moment arm of the t h r u s t e r , the buoy s t i l l t r a v e l e d w i t h a depressed bow a t h i g h e r v e l o c i t i e s . T h i s was the f a u l t o f the h u l l shape s e l e c t e d as the broad bow a t h i g h e r v e l o c i t i e s formed a deep bow wave. S i n c e the h u l l i s spoon shaped w i t h more of t h e buoyancy coming from the forward h a l f o f the buoy, the buoy tended t o s i n k i n t o the bow wave. T r i a l s 18 t o 20 showed t h a t the tendency f o r the bow to submerge c o u l d be suppressed by moving the c e n t e r o f g r a v i t y a f t . With a 1.0 degree s t a t i c s t e r n l i s t , the h u l l drag a t 0.78m/s was w i t h i n 0.2 N o f the l e v e l t r i m v a l u e , showing no s i g n i f i c a n t i n c r e a s e i n h u l l drag f o r the changes made. A second run a t 1.0 81 m/s was completed s u c c e s s f u l l y whereas the buoy had submerged a t 1.0 m/s In e a r l i e r t r i a l s . T h e r e f o r e , t h i s experiment showed t h a t the upper buoy speed c o u l d be extended beyond 0.8 m/s w i t h l i t t l e a dverse e f f e c t on drag f o r c e s by compensating the buoy t r i m . The f i n a l experiment observed the buoy response t o waves and attempted t o q u a n t i f y the e f f e c t s o f a s m a l l chop on h u l l drag. In the monochromatic waves c r e a t e d by a paddle a t the end o f the tank, the buoy encountered g r e a t d i f f i c u l t y , and the deck was f r e q u e n t l y washed by waves. Although the r e s i s t a n c e v a l u e s a r e s u s p e c t due t o the p o s s i b i l i t y o f water damage t o the s e n s o r s , they showed t h a t drag f o r c e s i n c r e a s e d from 2 t o 5 times the f l a t water v a l u e s a t a g i v e n speed. The r e s u l t s o f t h i s experiment h i g h l i g h t e d the need f o r a more comprehensive a n a l y s i s o f wave e f f e c t s d u r i n g the i n s h o r e t r i a l s . S e v e r a l p o i n t s s h o u l d be made about the experiments performed a t the f a c i l i t i e s a t B.C. Research. There i s some u n c e r t a i n t y as t o how the i n t e r n a l motions o f the water b a l l a s t a f f e c t e d h u l l drag, and as t o whether e q u i l i b r i u m had been reached d u r i n g the runs. The s t e a d i l y d e c l i n i n g bow a n g l e as the buoy t r a v e l l e d the l e n g t h o f the tank i n d i c a t e d a steady s t a t e had not been a c h i e v e d d u r i n g a run, perhaps due t o hull/wave i n t e r a c t i o n . Secondly, the tow tank experiments y i e l d e d no i n f o r m a t i o n on the d i r e c t i o n a l s t a b i l i t y o f the buoy. The towing apparatus was r i g i d l y b o l t e d t o the deck of the buoy, a l l o w i n g no yawing 8 2 m o t i o n . D i r e c t i o n a l s t a b i l i t y t e s t s were r e l e g a t e d t o the i n s h o r e t e s t p rogram. F i n a l l y , t h e tank t e s t i n g was per fo rmed on t h e Ranger buoy p r o t o t y p e h u l l w i t h a f l a t b l a d e k e e l . The buoy was s u b s e q u e n t l y r e d e s i g n e d w i t h a f o i l k e e l and t e s t e d d u r i n g t h e i n s h o r e t r i a l s . T h e r e f o r e , t h e tank r e s u l t s have o n l y l i m i t e d a p p l i c a b i l i t y t o t h e o f f s h o r e s i m u l a t i o n . A t tempts w i l l be made t o r e l a t e the e f f e c t i v e power f o r both h u l l s i n the next c h a p t e r . 4 . 2 MEASUREMENT OF WIND INDUCED DRIFT ON RANGER I An u n t e t h e r e d buoy i s s u b j e c t t o d r i f t f rom both c u r r e n t s and w i n d . In t h e s p r i n g o f 1985, a s i m p l e e x p e r i m e n t was p e r f o r m e d t o measure t h e magni tude o f t h e wind d r a g component on o b s e r v e d d r i f t r a t e s . A p r e v i o u s s t u d y by t h e a u t h o r had shown an e a r l y Ranger p r o t o t y p e t o be a f a s t d r i f t e r , w i t h speeds i n the o r d e r o f 7 -9^ o f t h e wind speed ( E g l e s , 1985a) . T h i s e x p e r i m e n t was t o q u a n t i f y the e f f e c t s o f s u b s e q u e n t d e s i g n changes t o t h e buoy s u p e r s t r u c t u r e a f t e r the o r i g i n a l t r i a l s . 4 . 2 . 1 EXPERIMENTAL METHOD To measure the buoy d r i f t r a t e , the p o s i t i o n s were measured as a f u n c t i o n o f t ime and compared t o s i m u l t a n e o u s wind v e l o c i t i e s . T h i s exper iment was per fo rmed June 25, 1985 near the s h i p p i e r s a t the I n s t i t u t e o f Ocean S c i e n c e s . Two t r i a l s were p e r f o r m e d . V i s u a l p o s i t i o n i n g methods were 8 3 used w i t h p o i n t s a l o n g the p i e r s as r e f e r e n c e s as the winds were blowing p a r a l l e l t o the docks. The buoy d r i f t was timed from the e a s t end o f the p i e r t o the west end, a d i s t a n c e o f 300 metres. At t h e same time, the d r i f t r a t e s o f a p l a s t i c t a r p on the s u r f a c e o f t h e water were measured. The d r i f t s heet was used t o d i s t i n g u i s h between c u r r e n t and d i r e c t wind p r o p u l s i o n o f the buoy. Wind measurements were made with a hand-held B e r n o u l l i type anemometer. 4.2 .2 RESULTS The data c o l l e c t e d a r e summarized i n T a b l e 4.3 below. Note t h a t the wind speeds have been averaged over the whole run. TRIAL BUOY ELAPSED DISTANCE DRIFT WIND $WIND TIME (metres) RATE (m/s) (m/s) 1 Ranger 40 min 262 m 0. 109 2. , 5 4, .4$ D r i f t Sht 40 it 192 m 0. 080 2. , 5 3, .1$ 2 Ranger 52 ti 329 m 0. ,106 3 , .0 3 .5$ D r i f t Sht 52 tt 262 m 0. ,084 3. .0 2 .8 TABLE 4.3: D r i f t r a t e data f o r Ranger I and d r i f t sheet, June 25, 1985. 4.2 .3 DISCUSSION AND CONCLUSIONS From the two t r i a l s performed, the buoy d r i f t r a t e s were observed t o be 4.3$ and 3.5$ of the wind speed. Of the t o t a l d r i f t , the s u r f a c e c u r r e n t component (assuming no t i d a l f l o w s ) was 3.1$ and 2.8$. The d i f f e r e n c e can be a t t r i b u t e d t o wind 8 4 d r a g , and r e p r e s e n t s 1.2% and 0 .7$ o f t h e p r e v a i l i n g w i n d s . The o b s e r v e d e f f e c t o f wind drag on the buoy o f l e s s than 1$ i s a c c e p t a b l e f o r a d r i f t i n g buoy, and i t would p r o b a b l y be d i f f i c u l t t o r e d u c e the windage f u r t h e r . However, t h e t o t a l d r i f t r a t e o f t h e Ranger I w i l l s t i l l be i n the o r d e r o f k% o f t h e wind speed s i n c e t h e buoy i s s h a l l o w and moves w i t h t h e top 1m l a y e r i n t h e w a t e r . 85 5 .0 INSHORE SEA TRIALS D u r i n g t h e f i v e weeks t h a t spanned J u l y 8 t o August 11, the p r o t o t y p e Ranger buoy was d e p l o y e d on E l k Lake near V i c t o r i a as p a r t o f a program d e s i g n e d by the a u t h o r t o e v a l u a t e t h e hardware and s o f t w a r e d e v e l o p m e n t s . W h i l e some t e s t s were d e s i g n e d s p e c i f i c a l l y t o p r o v i d e e n g i n e e r i n g d a t a t o S e a b o y ' s t e c h n i c i a n s , most e x p e r i m e n t s were per fo rmed t o examine how t h e a c t i v e d r i f t e r r e a c t e d t o a range o f wind and wave c o n d i t i o n s . The f o l l o w i n g c h a p t e r summarizes the r e s u l t s o f the e x p e r i m e n t s p e r f o r m e d by t h e a u t h o r and d e r i v e s t h e buoy p e r f o r m a n c e e q u a t i o n s needed f o r t h e s i m u l a t i o n o f buoy p e r f o r m a n c e i n an o f f s h o r e r e g i o n . 5.1 . PURPOSE OF THE EXPERIMENTS In J u l y , 1986, the assembly o f the Ranger II p r o t o t y p e was c o m p l e t e d . S e v e r a l days o f t e s t i n g i n P a t r i c i a Bay were used t o debug t h e e l e c t r o n i c s and s o f t w a r e , a f t e r which t h e buoy was h a u l e d and p r e p a r e d f o r a c o m p r e h e n s i v e s e t o f i n s h o r e t r i a l s . The p u r p o s e o f t h e s e t r i a l s were t o e x e r c i s e the buoy and d e m o n s t r a t e t h a t the hardware and s o f t w a r e per fo rmed t o the d e s i g n g o a l s . These t r i a l s were a l s o used t o measure the e f f e c t s o f wind and waves on buoy s p e e d , and t h e t h r u s t e r power r e q u i r e d t o d r i v e t h e h u l l and o t h e r p a r a m e t e r s r e q u i r e d by the o f f s h o r e p e r f o r m a n c e m o d e l . The s p e c i f i c g o a l s o f the i n s h o r e t r i a l s were as f o l l o w s : 1. P r o v i d e b u r n - i n t ime f o r e l e c t r o n i c s and m e c h a n i c a l 8 6 s y s t e m s . 2 . Demonst ra te a u t o p i l o t n a v i g a t i o n t h r o u g h w a y p o i n t f o l l o w i n g and compass c o u r s e . 3. Demonst ra te s o f t w a r e r o u t i n e s f o r s t a t i o n - k e e p i n g , a u t o p i l o t s t e e r i n g , m u l t i p l e waypo in t c o u r s e f o l l o w i n g , and p r o p e l l e r deweed ing . 4 . Measure t o t a l buoy power budget and s p e c i f i c a l l y a v e r a g e t h r u s t e r power vs s p e e d . 5. C o r r e l a t e buoy speed w i t h wind s p e e d , d i r e c t i o n and wave h e i g h t . 6. De te rmine VHF r a n g e . 7. D e t e r m i n e LORAN r e l i a b i l i t y , a c c u r a c y 8 . Measure unpowered d r i f t r a t e o f buoy. 5.2 EXPERIMENT LOCATION: ELK LAKE The s i t e s e l e c t e d f o r t h e i n s h o r e t r i a l s was E l k Lake , an 186 Ha f r e s h w a t e r b a s i n l o c a t e d between S i d n e y and V i c t o r i a on S a a n i c h P e n i n s u l a . The l a k e was chosen f o r i t s s i z e , i t s p r o x i m i t y t o S i d n e y and because adequate s e c u r i t y f a c i l i t i e s were a v a i l a b l e f o r s t o r a g e o f the buoy and i t s t e n d e r . E l k Lake i s r o u g h l y t r i a n g u l a r i n s h a p e , 2 .0 km l o n g by 1.2 km wide and i s shown i n F i g u r e 5 . 1 . I t has a f l a t bot tom w i t h a mean depth o f 8 . 8 m, and a maximum depth o f 15.3m ( F i s h and W i l d l i f e S u r v e y , 1969) . The l a k e i s used p r i m a r i l y f o r r e c r e a t i o n by s a i l b o a t e r s , water s k i e r s and swimmers i n t h e summer and rowers y e a r r o u n d . The l i m n o l o g y o f E l k Lake has been summarized by N o r d i n ( 1981 ) . D u r i n g the summer, the l a k e i s u n i f o r m l y s t r a t i f i e d , w i t h 87 FIGURE 5 . 1 : C o u r s e f o r speed t r i a l s on E l k Lake. 88 a marked t h e r m o c l i n e a t a depth o f 6-9m. In August t h e l a k e r e a c h e s i t s maximum t e m p e r a t u r e o f 20 d e g r e e s C and i s a p o p u l a r b a t h i n g s p o t . However, t h e l a k e i s e u t r o p h i c and somewhat swampy a round t h e p e r i m e t e r . The volumes o f the i n f l o w and o u t f l o w a r e m i n o r , s o t h e r e a r e no p r e v a i l i n g c u r r e n t s . The wind c l i m a t e a t E l k Lake was o f i n t e r e s t d u r i n g the Ranger t r i a l s as i t was hoped t h e e x p e r i m e n t s might measure t h e e f f e c t s o f w inds on buoy p e r f o r m a n c e . The wind s p e e d s a r e l i g h t i n t h e summer months, u s u a l l y l e s s than 5m/s , due t o the absence o f s t o r m s and t h e p r e s e n c e o f s t a t i o n a r y h i g h p r e s s u r e sys tems o v e r t h e West C o a s t o f B r i t i s h C o l u m b i a . D u r i n g t h e i n s h o r e t r i a l s w inds were t h e r m a l i n n a t u r e , i n c r e a s i n g d u r i n g t h e day and d r o p p i n g o f f a t s u n s e t . At t h e t e s t s i t e t h e s u r r o u n d i n g t o p o g r a p h y p l a y s a l a r g e r o l e i n d e t e r m i n i n g the p r e v a i l i n g wind d i r e c t i o n . There a r e l a r g e h i l l s t o t h e n o r t h and southwest o f t h e l a k e , and a low r i d g e t o t h e e a s t . F i g u r e 5.2 shows t h a t t h e p r e v a i l i n g winds f o r each o f t h e 38 speed runs p e r f o r m e d were most f r e q u e n t l y f rom t h e N o r t h e a s t e r n q u a d r a n t . A s c a t t e r g r a m o f wind speed and d i r e c t i o n d u r i n g t h e t r i a l s i s shown i n F i g u r e 5 . 3 . The wave c l i m a t e o f t h i s i n l a n d l a k e was l i m i t e d t o the o c c a s i o n a l s m a l l chop d u r i n g the t r i a l p e r i o d . The l a c k o f s u s t a i n e d winds and l i m i t e d f e t c h ( 1km ) r e s t r i c t e d wave g r o w t h . The maximum wave h e i g h t d u r i n g the t r a i l s was e s t i m a t e d t o be 0. 2m. 89 FIGURE 5.2: Frequency of wind d i r e c t i o n s during Elk Lake t r i a l s . (values are number of observations) 9 0 OT "8 <u a in T3 C •H 3 8 7 6 5 4 3 2 1 SW W NW N NE SE FIGURE 5 . 3 : S c a t t e r p l o t o f wind speed and d i r e c t i o n d u r i n g E l k Lake t r i a l s . (* = s i n g l e o b s e r v a t i o n ) 91 5.3 EXPERIMENTAL METHOD To o b s e r v e t h e R a n g e r ' s c a p a b i l i t i e s i n v a r i o u s c o n d i t i o n s , a t r i a n g u l a r c o u r s e w i t h 1.2km l e g s was d e s i g n a t e d on E l k Lake as shown i n F i g u r e 5 . 1 . The w a y p o i n t s o f the c o u r s e were d e f i n e d by l a t i t u d e and l o n g i t u d e c o o r d i n a t e s programmed i n t o t h e Ranger O n - B o a r d c o m p u t e r . The c o u r s e was s e t so as t o maximize the l e n g t h o f t h e each l e g , w h i l e k e e p i n g t h e buoy f a r enough o f f s h o r e t h a t t h e wind c o n d i t i o n s were more o r l e s s s t e a d y . T y p i c a l l y the buoy was programmed t o p r o c e e d t o one o r more o f t h e w a y p o i n t s u s i n g the a u t o m a t i c n a v i g a t i o n r o u t i n e o r a p r e s e t compass c o u r s e u s i n g t h e t e s t s e t . P o s i t i o n f i x e s were o b t a i n e d by p o l l i n g t h e Ranger LORAN t h r o u g h t h e t e s t s e t as were samples o f t h e t h r u s t e r c u r r e n t and v o l t a g e , r u d d e r c u r r e n t , buoy h e a d i n g and p r o p e l l e r RPM. The buoy was o f t e n c h a s e d w i t h t h e Z o d i a c t e n d e r because the VHF range was l i m i t e d , and t o o b t a i n wind i n f o r m a t i o n c l o s e t o the buoy. Winds speeds were measured w i t h an R.M. Young Model 05103 anemometer. I t was mounted on top o f a 1m p o l e f i x e d t o the Z o d i a c , and measurements read f rom a d i g i t a l d i s p l a y m a n u f a c t u r e d by Seaboy . The wind measurements r e c o r d e d were random samples o f a ten s e c o n d a v e r a g e . Wind d i r e c t i o n s were d e t e r m i n e d by c o m p a r i n g t h e vane a n g l e o f the R.M. Young w i t h a hand h e l d compass , and were r e c o r d e d as magne t ic b e a r i n g s . A t tempts were made t o r e c o r d wind measurements w i t h i n a few hundred metres o f the buoy . 9 2 The f o l l o w i n g d e s c r i b e s t h e d u r i n g t h e c o u r s e o f the t r i a l s : i n d i v i d u a l e x p e r i m e n t s per formed 1. Speed Runs To measure t h e buoy speed i n d i f f e r e n t wind and wave c o n d i t i o n s , t h e buoy was programmed t o p r o c e e d towards one o f the s e l e c t e d w a y p o i n t s on the c o u r s e , and i t s p o s i t i o n r e c o r d e d a t i n t e r v a l s o f 3-5 m i n u t e s . F i g u r e 5 .4 i s an example o f a buoy t r a c k i n a s i n g l e t r i a l . Speed runs were r e p e a t e d i n the upwind, downwind and c r o s s w l n d d i r e c t i o n s t o p r o v i d e i n f o r m a t i o n about t h e e f f e c t s o f w inds on buoy p r o g r e s s . On s e v e r a l o c c a s i o n s speed runs were made on a c a l m l a k e t o p r o v i d e c o m p a r a t i v e d a t a t o t h e r e s u l t s o f the tank t e s t i n g a t B . C . R e s e a r c h . In some t r i a l s , t h e buoy was d i r e c t e d t o p r o c e e d on a compass c o u r s e d i r e c t l y upwind . Between each s u c c e s s i v e p o s i t i o n f i x by t h e buoy LORAN, t h e p a y l o a d was i n t e r r o g a t e d f o r t h e s t a t u s messages d e t a i l i n g the power used by t h e v a r i o u s buoy s y s t e m s . From the t h r u s t e r v o l t a g e and c u r r e n t the power c u r v e s f o r the buoy were g e n e r a t e d . A l s o r e c o r d e d a t t h i s t ime were t h e p r o p e l l e r RPM and the buoy h e a d i n g a c c o r d i n g t o t h e i n t e r n a l compass . The d a t a p r o d u c t f o r an i n d i v i d u a l speed run i s shown i n T a b l e 5 . 1 . 2. S o f t w a r e A n a l y s i s The speed runs p r o v i d e d t h e o p p o r t u n i t y t o e x e r c i s e the a u t o p i l o t and n a v i g a t i o n s o f t w a r e r o u t i n e s . The t ime s e r i e s o f p o s i t i o n measurements were p l o t t e d t o d e t e r m i n e how d i r e c t l y the buoy p r o c e e d e d t o i t s d e s t i n a t i o n , and how i t compensated f o r d r i f t . The a b i l i t y t o f i n d a w a y p o i n t , and t o p r o c e e d t o the next one was demonst ra ted d u r i n g each speed t r i a l . The s t a t i o n -k e e p i n g mode was t e s t e d by programming a s m a l l watch c i r c l e , and o b s e r v i n g the buoy as i t d r i f t e d out o f t h e s e b o u n d a r i e s i n windy c o n d i t i o n s , and then powered up t o r e t u r n t o the watch c i r c l e . 3. P r o p e l l e r E v a l u a t i o n D u r i n g the t r i a l s t h r e e p r o p e l l e r c o n f i g u r a t i o n s were t e s t e d . The f i r s t two weeks o f t e s t i n g a 26cm. w e e d l e s s Mercury e l e c t r i c o u t b o a r d prop was u s e d , and the f i n a l t h r e e week t e s t e d two s i z e s o f model a i r p l a n e p r o p s . Speed runs and c o u r s e 9 3 UPWIND S P E E D RUN AUGUST 11, 1986 48.3200 48.3199 -48.3198 -48.3197 -48.3196 -48.3195 - o • •& 48.3194 -48.3193 -48.3192 -O 48.3191 -£ 48.3190 -5 48.3189 -48.3188 -48.3187 -48.3186 -48.3185 -48.3184 -48.3183 -48.3182 -48.3181 -48.3180 H 1 1 1 1 1 1 , 1 -123.2430 -123.2410 -123.2390 -123.2370 -123.2350 FIGURE 5.4: Buoy course during August 11 upwind speed run. LONGITUDE 94 RANGER PERFORMANCE TEST RESULTS * * # * * ^ * * * * * * * # * 5?: * * * * # * * # * # :!: * # 1: AUG 11, 36 TRIAL 9: SPEED RUN' PT D TO PT C TIME LATITUDE LONGITUDE DISTANCE SPEED THRUSTER V O L T A G E POKER RUDDER 0.00 48 .3195 123.2423 START 2.57 12.7 32.G 0.21 8 .00 48.3195 123.2412 193 0.41 2 .63 12.8 O O . I 0.23 10.00 48.3195 123.2403 49 0.41 2 .60 12.9 f\ 0 1 12.00 48.3195 123.2104 49 0.41 2.63 12.9 3 3 . 9 0.21 14.00 48 .3195 123.2401 37 0.30 2 .66 12 .9 3 4 . 3 0.21 18.00 48 .3195 123.2394 85 0.36 2.54 12.7 3 2 . 3 0.27 20.00 48 .3195 123.2390 49 0.41 25.00 48 .3195 123.2382 98 O oo 2.49 12.5 31.1 0.21 2G.00 48.3195 123.2378 49 0.27 2.49 12.5 31 .1 0.2.1 30 .00 4S.319G 123.2374 52 C.43 2.51 12.6 31 .6 0.20 33.00 48.3197 123 .2363 111 0.37 2.57 12.8 3 2 . 9 0.23 37 .00 48.3197 123.2301 49 0.41 2 .60 12.8 3 3 . 3 o. £ 39.00' 48^3197 123.2353 37 0.30 2 .57 12.9 33 .2 0.29 -11.00 48.3198 123.2354 52 0.43 2.54 12.9 32 .8 0.26 43 .00 40.3190 123.2350 49 0.41 2 .60 12.9 3 3 . 5 0.2 3 4 5 . 0 0 48.3199 123.2346 52 0.43 2.CO 12.9 3 3 . 5 0.20 • 17.00 43.3199 123 ^34 49 0.4.1 NET: 1051 0.37 2 .57 12:8. 3 2 . 9 0.23 AVERAGE : : 060 0.38 TABLE 5.1: Sample data product from a speed run. f o l l o w i n g were p e r f o r m e d w i t h a l l p r o p s , and t h e t h r u s t e r power and speed r e c o r d e d . 4. Unpowered D r i f t Rate The unpowered d r i f t r a t e s were measured by f o l l o w i n g the buoy downwind and r e c o r d i n g p o s i t i o n and wind s p e e d . Wave c o n d i t i o n s were judged by e y e . 5. O t h e r E x p e r i m e n t s VHF range was measured by l o c a t i n g the t e s t s e t on t h e dock and d e t e r m i n i n g t h e p o s i t i o n o f the buoy a t which r e l i a b l e d a t a t r a n s m i s s i o n were no l o n g e r r e c e i v e d . LORAN r e p e a t a b i l i t y was d e t e r m i n e d by r e c o r d i n g t h e LORAN c o o r d i n a t e s o f the buoy when l o c a t e d a t t h e dock f o r s e v e r a l d i f f e r e n t d a y s . A b s o l u t e a c c u r a c y was compared w i t h t h e known p o s i t i o n o f t h e dock as d e t e r m i n e d f rom t o p o g r a p h i c c h a r t s . 5.4 DISCUSSION OF MEASUREMENT ERRORS B e f o r e a n a l y z i n g the r e s u l t s o f the i n s h o r e t r i a l s a d i s c u s s i o n o f the n a t u r e and a c c u r a c y o f the measurements s h o u l d be made. W h i l e o p e r a t i n g on E l k Lake , a t ime s e r i e s r e c o r d o f buoy p o s i t i o n , s p e e d , compass h e a d i n g and i n t e r n a l sys tem power r e q u i r e m e n t s was made, and t h i s d a t a s e t i s t o be i n t e r p r e t e d t o d e t e r m i n e t h e f e a s i b i l i t y o f s o l a r powered p r o p u l s i o n . The p u r p o s e o f t h i s s e c t i o n i s t o e s t a b l i s h the c o n f i d e n c e i n t e r v a l o f t h e measured d a t a so t h a t the r e s u l t s may be kept i n p e r s p e c t i v e . ( i ) LORAN p o s i t i o n s : P o s i t i o n f i x e s were used i n the c a l c u l a t i o n o f buoy speed i n both the powered and unpowered mode. The a b s o l u t e a c c u r a c y o f LORAN p o s i t i o n s va ry between 0.2 and 4 . 6 km and i s dependent on t h e p r o x i m i t y and geometry o f the b r o a d c a s t i n g s t a t i o n s i n t h e c h a i n b e i n g used ( C a n a d i a n H y d r o g r a p h i c S e r v i c e , 1983 ) . T h e r e p e a t a b i l i t y o f LORAN p o s i t i o n f i x e s i s much b e t t e r , between 15 and 100m. LORAN s i g n a l s a r e p r i m a r i l y low f r e q u e n c y ground waves and a r e s u b j e c t t o r e f r a c t i o n a t l a n d / s e a i n t e r f a c e s . For t h i s r e a s o n the a c c u r a c y o f t h e LORAN p o s i t i o n f i x e s i n E l k Lake must be examined c l o s e l y . To measure the r e l a t i v e and a b s o l u t e a c c u r a c i e s o f the Ranger LORAN two s i m p l e e x p e r i m e n t s were p e r f o r m e d . The LORAN used i n t h e Ranger buoy, a Me ico model C - M a s t e r X, has a r e s o l u t i o n o f one second o f l a t i t u d e and l o n g i t u d e . At the l a t i t u d e o f E l k Lake , t h e n : ( 5 . 1 ) 1 s e c l a t i t u d e = 18m 1 s e c l o n g i t u d e = 12m T h e r e f o r e , the measurement o f d i s t a n c e between two s u c c e s s i v e LORAN c o - o r d i n a t e s A ( y 1 , x 1 ) and B ( y 2 , x 2 ) w i l l a t b e s t have an u n c e r t a i n t y o f : e r r o r = [ ( 3 6 ) 2 + ( 2 4 ) 2 ] 1 / 2 ( 5 . 2 ) = + / - 43.3m An e x p e r i m e n t was per fo rmed t o c o n f i r m t h i s bound. The buoy p o s i t i o n r e p o r t e d w h i l e moored a t the dock was p o l l e d on t h r e e s e p a r a t e o c c a s i o n s and t h e f i x e s compared . The r e s u l t s a r e as f o l l o w s : 97 LATITUDE LONGITUDE JULY 11 48 3202 123 2429 21 48 3202 123 2435 25 48 3204 123 2430 s t a n d a r d 0001 0003 d e v i a t i o n TABLE 5 . 2 : R e p o r t e d LORAN p o s i t i o n s o f dock on E l k L a k e . At E l k L a k e , t h e s e s t a n d a r d d e v i a t i o n s a r e e q u a l t o 18m n o r t h and s o u t h and 36m i n an e a s t - w e s t d i r e c t i o n , g i v i n g a net u n c e r t a i n t y i n p o s i t i o n o f 40m. T h i s i s i n good agreement w i t h t h e c a l c u l a t e d r e s o l u t i o n . T h e r e f o r e , p o s i t i o n s a r e m e a s u r a b l e w i t h some c o n f i d e n c e t o w i t h i n 45m. The g e o g r a p h i c f i x a c c u r a c y a t E l k Lake was d e t e r m i n e d by c o m p a r i n g t h e a v e r a g e measured p o s i t i o n a c c o r d i n g t o the LORAN w i t h t h e p l o t t e d p o s i t i o n o f the dock on the t o p o g r a p h i c map: LATITUDE LONGITUDE p o s i t i o n by LORAN 48 3202 123 2431 p o s i t i o n on c h a r t 48 3195 123 2455 d i f f e r e n c e 319 m TABLE 5 . 3 : G e o g r a p h i c f i x a c c u r a c y o f LORAN p o s i t i o n s . The p u b l i s h e d LORAN a c c u r a c y i s 460m ( M e i c o C - M a s t e r X manua l , 1984) . S i n c e t h e a b s o l u t e e r r o r s a r e s t a b l e and do not a f f e c t r e p e a t a b i l i t y , t h i s v a l u e i s o f academic i n t e r e s t o n l y . ( i i ) Time Measurements: The d a t a a c q u i s i t i o n p r o c e s s began w i t h t h e s e l e c t i o n o f the a p p r o p r i a t e menu i t e m on t h e t e s t s e t , t r a n s m i s s i o n o f t h e command t o t h e buoy, e x e c u t i o n o f the command 9 8 by the on-board computer, t r a n s m i s s i o n o f the data t o the t e s t s e t and d i s p l a y o f the r e s u l t s . S i n c e most o f the measurements made d u r i n g the t r i a l s were r e c o r d e d as a time s e r i e s u s i n g t h i s p r o c e s s , i t i s important t o determine the u n c e r t a i n t y o f the a c t u a l time a s s i g n e d t o a p a r t i c u l a r v a l u e . The t y p i c a l t urnaround time from i n t e r r o g a t i o n t o data r e c e p t i o n o f a p o s i t i o n f i x v a r i e d from 10 t o 30 seconds or more, depending on r a d i o i n t e r f e r e n c e , d i s t a n c e between the t e s t s e t and buoy, antennae h e i g h t and the l o c a l c o n d i t i o n s . By l i s t e n i n g t o the VHF r a d i o , t h e time the buoy a c t u a l l y began p r o c e s s i n g a command c o u l d be measured more a c c u r a t e l y t o w i t h i n +-15 seconds. However, i n g e n e r a l the a c c u r a c y o f time measurements i s +- 30 seconds, and t h e r e f o r e the time s e r i e s measurements were r e c o r d e d t o the n e a r e s t minute, ( i i i ) Buoy Power Budget: T h r u s t e r c u r r e n t and v o l t a g e were sampled between p o s i t i o n f i x e s t o monitor the buoy power budget. The v a l u e s r e c o r d e d were i n s t a n t a n e o u s samples taken when the pay l o a d was i n t e r r o g a t e d through the t e s t s e t . The t h r u s t e r c u r r e n t and v o l t a g e measurements had been c a l i b r a t e d a t Seaboy b e f o r e the t r i a l s , and a r e a c c u r a t e t o w i t h i n 0.1 ampere and 0.1 v o l t . Rudder c u r r e n t s were averaged over a p e r i o d o f 10 seconds and the v a l u e s s t o r e d i n a b u f f e r . The sample r e c o r d e d was the l a s t v a l u e s t o r e d i n t h e b u f f e r , which was updated every 20 seconds. 99 5.5 RESULTS OF THE INSHORE TRIALS The f i v e week Ranger buoy program on E l k Lake p r o v i d e d an a s s e s s m e n t o f t h e p r o t o t y p e and h i g h l i g h t e d a r e a s f o r f u t u r e d e v e l o p m e n t . But more i m p o r t a n t l y , t h e p e r f o r m a n c e d a t a f rom the t r i a l s can be a n a l y z e d t o r e s o l v e how t h i s p a r t i c u l a r two meter v e h i c l e w i l l p e r f o r m o f f s h o r e . I n - t h e - w a t e r t e s t s a r e n e c e s s a r y t o u n d e r s t a n d how much power the buoy n e e d s , how f a s t i t can go w i t h a l i m i t e d energy budget and how i t r e s p o n d s t o i t s e n v i r o n m e n t . The f o l l o w i n g summarizes t h e r e s u l t s o f the summer E l k Lake t r i a l s . The emphas is o f t h e a n a l y s i s i s t o d e r i v e t h e i n f o r m a t i o n r e q u i r e d t o p r e d i c t the p e r f o r m a n c e o f an a c t i v e d r i f t e r i n o f f s h o r e c o n d i t i o n s r a t h e r than mere ly t o e v a l u a t e t h e Seaboy p r o d u c t . A compendium o f t h e d a t a c o l l e c t e d d u r i n g the t r i a l s i s found i n T a b l e 5.4. The v a l u e s l i s t e d a r e a v e r a g e s o f the i n d i v i d u a l o b s e r v a t i o n s o v e r each speed r u n . The d a t a c o l l e c t e d f o r t h e downwind d r i f t t e s t s a r e c o m p i l e d i n T a b l e 5.7. 5.5.1 F l a t Water Buoy Speed Runs F l a t water speed runs r e v e a l what the maximum p o s s i b l e buoy v e l o c i t y would be w i t h i n a g i v e n t h r u s t e r power b u d g e t . They a l s o p r o v i d e d c o n t r o l l e d c o n d i t i o n s t o compare the v a r i o u s p r o p e l l e r s . S i n c e the tank t e s t i n g was a l s o p e r f o r m e d i n ca lm w a t e r , the r e s u l t s o f the Ranger II t r i a l s can be compared t o the 100 RANGER PERFORMANCE TRIALS O DATE TRIAL DESCRIPTION COURSE PROP TIME DISTANCE SPEED THRUSTER VOLTAGE POWER JULY a 1 buoy t r y o u t — winds n/a ramp-->E shore MERC 49 1051 0. 36 2. 13.5 31.4 JULY 14 1 speed run - s h i f t y Pt D — > Pt B MERC 57 1252 0.37 2. 37 13.9 33 T upwind speed t r i a l Pt C _ \ Pt D MERC 40 624 0.26 2.61 14 .2 37. 1 4 crosswind speed t r i a l Pt B - > Pt D MERC 45 1093 0. 4 2.35 14 32. 9 JULY 19 1 l i g h t c rosswind run Pt D — ^ Pt B MERC 44 1268 0. 48 2.36 13. 9 32. 9 2 crosswind speed run Pt B -> Pt C MERC 22 549 0.42 2.45 14.2 34.7 3 downwind speed run Pt C Pt D MERC 2e 976 0.58 2.3 14 32 4 poor d a t a / s h o r t run downwi nd MERC 6 208 0.58 2.46 13.9 34 .2 5 poor Pt D - > Pt E MERC 17 353 0.35 2. 46 14 34. 4 JULY 21 1 f1 atwater/upwi nd Pt D — s Pt B MERC 47 1263 O. 45 2. 16 13 .2 28.4 -i l i g h t upwind t r i a l Pt B - > Pt C MERC 19 531 0. 47 2. 42 14. 1 34.2 3 l i g h t downwind Pt C - > Pt B MERC 35 1268 6.6 2. 42 14.2 34.3 JULY 22 1 f1 atwater/upwi nd Pt B -> Pt D MERC 53 1265 0. 4 1.97 12. 4 24. 4 flatwater/downwi nd Pt B _ V Pt D MERC 48 1207 0. 42 1.93 12 .2 23.5 JULY 25 1 good f l a t w a t e r Pt D - > Pt B MERC 50 1354 0. 45 1. 95 12. 2 23. 9 2 good f l a t w a t e r Pt B -> Pt D MERC 44 1208 0. 46 1.99 12.4 24. 7 i. upwind speed run upwi nd MERC 34 667 0.33 2.58 14.3 36. 8 AUG 1 1 upwind speed run Pt D - > Pt B 28/13 1287 0.58 2. 5 12. B 32 2 downwind speed run Pt B -> Pt D 2B/1B 16 4B7 0.51 2.75 13.4 36.9 2a downwind speed run dowr.k ii nd 23/18 19 600 0. 53 2. 49 12.a 31.9 AUG 5 1 upwind speed run Pt D _ s Ft B 2S/1B 43 i2ei 0.5 2. es 13.9 39. 4 2 downwi nd/crosswind Pt 3 -> Pt D 29/18 32 1121 0.58 2.99 14.1 42. 3 3 upwind speed r u n Pt C — > Pt B 36/15 37 922 0. 42 2. 36 14.1 33. 4 4 downuind but poor Ft B -> Pt D 36/15 1 4 464 0.55 2. 49 14.1 35. 1 I pec- data Pt -:> Pt B 36/15 16 365 0. 38 2. 1 1 13 27. 3 lb poor data Pt D -> Pt B 36/15 "Ttr. 899 0. 43 2. 14 13. 1 2S. 1 2 crosswind speed run Pt B -> Ft D 36/15 40 1205 0 .5 2.31 13.9 32 — •jpwind speed run Pt D - > Pt r 36/15 36 1042 0. 48 2. 96 14.2 41.9 4 dewnwind speed run Ft C -:• Pt D 36/15 ZO 1042 0. 58 2. 92 14.1 41.3 A'J3 1 1 1 gcz:d -flatwater Pt D -:• Pt B 36/15 20 682 0. 57 2. 27 12. 1 27. 5 good f l a t w a t e r Pt D -> Pt B 36/15 338 0. 43 2.31 12.2 28. 1 f1 atwatsr/downwind Pt B Pt n 36/15 45 12C5 0. 45 2. 32 12.2 28. 2 4 f i atwater/upwind Pt D -> F t B 36/15 33 1087 0. 48 2. 35 12.2 2B. 6 5 crosswind speed run Pt B Pt D 36/15 o 22e 0. 42 2. 35 i ~* 23. 7 c crosswind speed run Pt h F't D 36/15 -T r: S"^ 5 0. 46 2.34 12.2 5 '. : g-t upwind sce = d run Ft D F t if 1216 v . 4 3 2 . 7 T 12 .2 23. 9 I : z-.- acwr.«i-.d s-e«?d " j n Ft Pt r r t / is 4 1 i *•* — c 0. 4 B 2.-1 12.3 29. 7 . :3w: r,d sc = ed run Pt D Ft C 36/15 1051 0. 37 — c -j . c :2. 9 TABLE 5 . 4 : Data summary for Elk Lake t r i a l s . Ranger I tank t r i a l s t o q u a n t i f y the e f f e c t s o f t h e d e s i g n changes and e s t i m a t e t h e net e f f i c i e n c y o f the p r o p u l s i v e s y s t e m . A t o t a l o f 9 o f t h e 38 speed runs were made d u r i n g the i n s h o r e t r i a l s were on f l a t w a t e r . These runs were made i n the e a r l y m o r n i n g , b e f o r e t h e t h e r m a l winds had d e v e l o p e d . S i n c e the t r i a l s were per fo rmed e a r l y i n the day , and the sun was low on t h e h o r i z o n , t h e t h r u s t e r v o l t a g e was g e n e r a l l y low and hence the a v e r a g e power i s a l s o low. A c o m p a r i s o n o f t h e measured t h r u s t e r power and buoy speed f o r t h e 9 f l a t water t r i a l s i s shown i n F i g u r e 5 . 5 . On t h i s graph t h e d a t a i s d i s t i n g u i s h e d by t h e t y p e o f p r o p e l l e r u s e d . Note t h a t t h r u s t e r power r e f e r s t o the e l e c t r i c a l power i n p u t t o t h e t h r u s t e r motor , r a t h e r than the p r o p e l l e r t h r u s t . These r e s u l t s a r e summarized i n T a b l e 5 . 5 : RUNS PROPELLER SPEED (V) POWER (P ) P / S RATIO (m /s ) ( w a t t s ) (N) 5 M e r c u r y 26 cm. 0 .436 + / - 0 .05 25 .0 + / - 0.01 57 .3 4 T a i p a n 36 cm. 0 .483 " 28.1 " 58 .2 A v e r a g e 0.46 " 26 .4 " 57 .4 TABLE 5 . 5 : Summary o f f l a t w a t e r speed t r i a l s . Note t h a t the power t o speed r a t i o s computed i n t h i s t a b l e show t h a t t h e Mercury p r o p e l l e r i s m a r g i n a l l y more e f f i c i e n t than the model a i r p l a n e prop i n the f l a t w a t e r t r i a l s . From the f l a t w a t e r t r i a l s i t i s p o s s i b l e to e s t i m a t e the 102 FLATWATER S P E E D TRIALS • ti O CC POWER VS VELOCITY 0.2 0.3 • 26 cm MERCURY prop 0.4 SPEED (m/s) 0.5 0.6 + 36 cm MASTER prop FIGURE 5 . 5 : Power vs. speed f o r f l a t w a t e r t r i a l s . 103 power c u r v e f o r t h e Ranger buoy . S i n c e t h e t h r u s t e r power s h o u l d be a m u l t i p l e o f t h e e f f e c t i v e power by a f a c t o r e q u a l t o the net e f f i c i e n c y o f t h e p r o p u l s i o n s y s t e m , e q u a t i o n ( 4 . 3 ) can s t i l l be u s e d . S u b s t i t u t i n g the a v e r a g e speed and power f rom t h e E l k Lake d a t a i n t o ( 4 . 3 ) y i e l d s : ( 5 . 3 ) P = 303.5 . V 3 ' 2 3.2 T h i s e q u a t i o n f i t s the V dependence o b s e r v e d i n the tank t r i a l s t o t h e d a t a f rom t h e i n s h o r e t e s t s . Note t h a t the c o e f f i c i e n t i n ( 5 . 3 ) d i f f e r s f rom t h e e f f e c t i v e power e q u a t i o n ( 4 . 9 ) d e t e r m i n e d f rom t h e tow tank t e s t s : ( 4 . 9 ) P = 32.1 . V 3 " 2 e by a f a c t o r o f 10. Put a n o t h e r way, t h i s d i f f e r e n c e s t a t e s t h a t o n l y 10$ o f t h e e l e c t r i c a l power i s a c t u a l l y c o n v e r t e d t o f o r w a r d m o t i o n . The rema inder i s d i s s i p a t e d as heat i n the motor and s h a f t s e a l s o r i n e d d i e s and waves c r e a t e d by the h u l l and p r o p e l l e r . Note t h a t t h i s c o m p a r i s o n assumes t h a t t h e e f f e c t i v e power o f t h e Ranger II h u l l i s t h e same as t h a t measured o f the Ranger I. S i n c e t h e r e were minor d e s i g n changes i n t h e k e e l i t s e l f , m a r g i n a l l y i n c r e a s i n g the buoy d i s p l a c e m e n t and w e t t e d a r e a , t h e r e may be s l i g h t d i f f e r e n e c e s i n t h e e f f e c t i v e power c u r v e s f o r t h e two b u o y s . However, s i n c e the o f f s h o r e p e r f o r m a n c e model c o n s i d e r s o n l y the Ranger II r e s u l t s , t h e d i f f e r e n c e s a r e not c r i t i c a l . 104 E q u a t i o n ( 5 . 3 ) i s p l o t t e d w i t h the d a t a i n F i g u r e 5 .6 t o p r e d i c t t h e t h r u s t e r power budget t o d r i v e t h e h u l l a t a g i v e n speed i n f l a t w a t e r . Note t h a t t h i s i s d i f f e r e n t f rom t h e e f f e c t i v e power c u r v e f o r the buoy due t o m e c h a n i c a l i n e f f i e n c i e s o f t h e t h r u s t e r motor and p r o p e l l e r . I t i s o f i n t e r e s t t o compare the measured p r o p u l s i v e e f f i c i e n c y w i t h t h e r e s u l t s d i s c u s s e d i n S e c t i o n 4 . 2 . I f t h e e f f e c t i v e power d i f f e r s f rom the power used t o d r i v e t h e buoy by t h e t h r u s t e r and p r o p e l l e r e f f i c i e n c y and by a t h r u s t d e d u c t i o n c o e f f i c i e n t due t o p r o p e l l e r / h u l l i n t e r a c t i o n , then t h e e f f e c t i v e power can be e x p r e s s e d a s : ( 5 . 4 ) P = P ^ . n ^ . n .n,_ e t t p h where P = E f f e c t i v e Power P^ = T h r u s t e r Power n^ = E f f i c i e n c y o f motor and s e a l s n " " p r o p e l l e r n^ = P r o p e l l e r / h u l l e f f e c t s The motor and p r o p e l l e r e f f i c i e n c y c o e f f i c i e n t s were measured i n t h e m e c h a n i c a l t e s t s summarized i n s e c t i o n 4 . 2 , and a r e i n c l u d e d i n T a b l e 5 . 6 . A c o n s e r v a t i v e e s t i m a t e o f the magni tude o f t h e p r o p e l l e r / h u l l i n t e r a c t i o n e f f e c t s has been used based on a d i s c u s s i o n by P h i l l i p s - B i r t , 1957. SYSTEM EFFICIENCY SOURCE t h r u s t e r n^ = 0.50 e m p i r i c a l p r o p e l l e r n = 0 .70 " i n t e r a c t i o n n^ = 0 .80 e s t i m a t e d h net 0 .28 TABLE 5 . 6 : T h r u s t d e d u c t i o n c o e f f i c i e n t s f o r Ranger II buoy. 105 FLATWATER SPEED TRIALS POWER VS VELOCrTY, ELK LAKE DATA 1 0 0 - i _ _ _ _ 1.0 SPEED (m/s) FIGURE 5.6: F l a t w a t e r power c u r v e f o r Ranger buoy. 106 By example, i f the average calm water t h r u s t e r power o f 26.4 watts a t 0.46 m/s i s s c a l e d w i t h the h y p o t h e t i c a l p r o p u l s i v e e f f i c i e n c y o f 28$, then the e f f e c t i v e power o f the Ranger II would be 7.4 watts a t t h a t speed. T h i s i s much l a r g e r than the 2.7 watt p r e d i c t e d by ( 4 . 9 ) . However, t h e r e a r e many d i f f e r e n c e s between the c o n t r o l l e d c o n d i t i o n s i n a tow tank and the l a k e t r i a l s t h a t c o u l d account f o r t h e s e d i f f e r e n c e s . For example, the observed buoy speed was determined from the time taken t o t r a v e l between two p o i n t s , and d i d not c o n s i d e r the path taken t o get t h e r e . F o u l i n g o f the h u l l by weeds and a l g a e may a l s o have i n c r e a s e d the drag. The important r e s u l t o f the f l a t w a t e r t r i a l s was t o d e f i n e the t h r u s t e r power budget, and the maximum speed the Ranger II buoy can make w i t h i n the energy budget. T h i s i s summarized by (5 . 3 ) : (5.3) P = 303.5 . V 3 - 2 5.5.2 Average Thruster Power vs Buoy Speed A s c a t t e r p l o t o f the average t h r u s t e r power versus speed made good i s shown i n F i g u r e 5.7 f o r the data i n T a b l e 5.4. Aver a g i n g a l l t r i a l s w i l l determine a " t y p i c a l " o p e r a t i n g power budget f o r the t h r u s t e r system i n s t a l l e d as opposed t o the f l a t w a t e r average which was b i a s e d towards lower power by e a r l y morning runs. 107 o CO n O C pa m ui o s; (D i-l < cn Tl fD ro a i-h o rr 01 CO -50 - . £ - 4 0 5 r. -30 o :CL: OS -20 J — CO D; -10 R A N G E R . E L K LAKE _PER FOR MAN CE TRIALS :o:r;z ~o;2 BUOY 0.3 I .0.4 . ; ; ; SPEED ;(ms:,:): 0:5 :o.6: BUOY SPEED vs. WIND VELOCITY ELK LAKE TRIALS 0.7 — i — WIND SPEED (m/» ) FIGURE 5.8: Corrected buoy speed vs. wind speed. 109 As shown i n F i g u r e 5.7, the mean t h r u s t e r power budget o f 32 watts y i e l d s a net buoy speed o f 0.47 m/s. For calm c o n d i t i o n s , e q u a t i o n (5.3) y i e l d s a speed o f 0.50 m/s. For the model d i s c u s s e d i n c h a p t e r 6, the t h r u s t e r power w i l l be f i x e d a t t h i s v a l u e o f 32 watts g i v i n g a calm water speed o f 0.50 m/s. 5.5.3 E f f e c t s of Winds on Buoy M o b i l i t y As d i s c u s s e d i n Chapter 2, a buoy o p e r a t i n g i n a s t a t i o n -keeping mode o r deployed o f f s h o r e on the West Coast, w i l l spend a l a r g e p a r t o f i t s time motoring a g a i n s t the p r e v a i l i n g winds. One important parameter r e q u i r e d t o p r e d i c t the net p r o g r e s s o f the buoy under t h e s e c o n d i t i o n s i s the e f f e c t o f winds on buoy m o b i l i t y and t h e t h r e s h o l d wind speed a t which a Ranger can no l o n g e r make forward headway. Dur i n g the p e r i o d i n which the Ranger buoy was made a v a i l a b l e f o r e x p e r i m e n t a t i o n , wind v e l o c i t i e s d i d not exceed 10 m/s, and sea c o n d i t i o n s were o n l y d e v e l o p i n g , not f u l l y d eveloped. However, the data s e t summarized i n T a b l e 5.4 can p r o v i d e some i n f o r m a t i o n on the r e l a t i v e e f f e c t s of winds and from t h e s e r e s u l t s the t h r e s h o l d wind v e l o c i t y w i l l be p r e d i c t e d . During the E l k Lake t r i a l s , 9 o f the 38 runs were made d i r e c t l y upwind. The data f o r these t r i a l s a r e summarized i n T a b l e 5.7. During these runs the wind ranged from 1.3 to 5.0 m/s. A p l o t o f buoy speed as a f u n c t i o n o f wind speed s h o u l d then r e v e a l some i n f o r m a t i o n about how the wind r e t a r d s buoy 110 UPWIND SPEED TRIALS ******************* DA IE I RIAL 1 I ME SPEED THRUS1ER BATTERY PUWER WIND (mi ns) (m/s) CURRENT VOL fAGE (watts) (m/s) (amps) JUL 14 3 40. OO O. 26 2.61 14. 20 3 7. 10 5. 00 21 •y 19. OO O. 4/ 2. 42 1 4. 10 31. 20 2. 60 A- O 6 34. tX) O. 33 2. 58 1 4. 30 36. SO 2.50 AUG 1 1 32. OO O. 52 2. SO 12. BO 31. 90 2. 30 AUG 5 1 43. OO 0. SO 2. 85 13.90 39. 4O 2. 40 3 37. OO O. 42 2. 36 14. 10 3 3 . l u 1 . 30 / 36. OO O. 48 2. 96 14. 20 41 . 90 3.40 1 1 7 42. OO O. 4B 2. 3 7 12. 20 28. 90 1 . 40 9 47. OO 0.37 2.57 12.80 32. 90 3. 60 1 ABLE 5 . /: Data used -for analysis o+ wind e f i e c t s on buoy speed. 111 p r o g r e s s . However, s i n c e buoy speed i s a l s o a f u n c t i o n o f t h r u s t e r power, which a l s o v a r i e d between runs, i t i s n e c e s s a r y to e l i m i n a t e one o f t h e se v a r i a b l e s . T h i s was done by a s s i g n i n g an a r b i t r a r y power budget of 35 watts and c o r r e c t i n g the measured buoy v e l o c i t y to t h a t v a l u e . 35 watts was s e l e c t e d as i t was the average t h r u s t e r power f o r the 9 upwind t r i a l s . Buoy v e l o c i t y was c o r r e c t e d u s i n g the r a t i o o f measured power to s t a n d a r d power, from (5.3) where: (5.5) [V(55 w ) ] 5 2 = fV ( o b s ) ] 5 ' 2 35 watts P (obs) F i g u r e 5.8 p l o t s the c o r r e c t e d buoy speed as a f u n c t i o n of wind speed f o r the upwind t r i a l s . The r e s u l t s o f a l i n e a r r e g r e s s i o n a r e a l s o p l o t t e d . T h i s l i n e has the e q u a t i o n : (5.6) V = -0.06U + 0.57 m/s showing t h a t from the data c o l l e c t e d , the forward buoy motion i s r e t a r d e d by an amount ro u g h l y e q u a l t o 5# o f the wind speed. Using (5.6) we can a l s o see t h a t wind speeds i n the o r d e r o f 10  m/s w i l l be s u f f i c i e n t t o stop the buoy c o m p l e t e l y . A comparison to the r e s u l t s of the f l a t water t r a i l s and e q u a t i o n (5.6) show t h a t the i n t e r c e p t , c o r r e s p o n d i n g to calm winds o v e r s t a t e s the buoy speed. With a t h r u s t e r power of 35 watts (5.3) p r e d i c t s a f l a t water speed o f 5.1 m/s as compared to 5.7 m/s from ( 5 . 6 ) . T h i s d i f f e r e n c e i n d i c a t e s t h a t a s t r a i g h t l i n e r e l a t i o n s h i p summarizing the data i n F i g u r e 5.8 may be 112 i n a p p r o p r i a t e , and a c u r v e may be more a p p l i c a b l e . I n t u i t i v e l y t h i s may be more c o r r e c t as the e f f e c t s o f l a r g e r seas w i t h b r e a k i n g waves would have r e l a t i v e l y g r e a t e r damping e f f e c t on buoy p r o g r e s s . Note t h a t e q u a t i o n s ( 5 . 3 ) and ( 5 . 6 ) were d e t e r m i n e d f rom t h e d a t a a v a i l a b l e , and have been e x t r a p o l a t e d t o wind speeds beyond t h e 5.0 m/s measured . Because t h e e f f e c t s o f d e v e l o p e d s e a s and b r e a k i n g waves would work f u r t h e r t o impede buoy p r o g r e s s , the e f f e c t s a t h i g h e r wind s p e e d s would be e x p e c t e d t o be l a r g e r . T h e r e f o r e , i t can be assumed t h a t t h e s e e s t i m a t e s a r e c o n s e r v a t i v e , and a c t u a l buoy p r o g r e s s may be l e s s under o f f s h o r e c o n d i t i o n s . However, as a f i r s t a p p r o x i m a t i o n f o r the s i m u l a t i o n , t h e s e e q u a t i o n s w i l l be u s e d . 5.5.4 Downwind D r i f t T r i a l s T h r e e t r i a l s were per fo rmed t o o b s e r v e the downwind d r i f t r a t e o f t h e unpowered buoy as a f u n c t i o n o f the 1m wind s p e e d s . The d r i f t r a t e i s o f i n t e r e s t t o p r e d i c t the net buoy d i s p l a c e m e n t when i n s u f f i c i e n t power i s a v a i l a b l e to o p e r a t e the t h r u s t e r , and as a c o m p a r i s o n t o c o n v e n t i o n a l d r i f t i n g b u o y s . The o b s e r v e d wind d r i f t i s the sum o f wind i n d u c e d c u r r e n t s and d i r e c t wind drag on the buoy s u p e r s t r u c t u r e , where: ( 5 . 7 ) Wind Drag = 1.p . . C d . A . l ) 2 — a i r where U i s the wind speed and Cd i s the drag c o e f f i c i e n t o f the 113 48.3220 48.3218 48.3216 48.3214 48.3212 48.3210 48.3208 48.3206 H 48.3204 48.3202 -48.3200 -48.3198 -48.3196 48.3194 48.3192 -\ 48.3190 123 2440 DOWNWIND DRIFT TRIAL JULY 25, 1986 OS B9 7 — i 123.2420 1 123.2400 123.231 LONGITUDE F I G U R E 5.9: Downwind d r i f t t r a c k s , J u l y 25, 1 9 8 6 . 115 From T a b l e 5.8, i t can be seen t h a t the wind-induced d r i f t averaged 3$ o f the 1m wind speed. T h i s d e f i n e s the d r i f t r a t e a t the lower end o f the wind range as experiments were o n l y performed i n winds from 3.9 t o 5.8 m/s. T h i s v a l u e may be l a r g e r i n h i g h e r winds due t o sea s t a t e and wind d r i v e n c u r r e n t s , and i n o f f s h o r e c o n d i t i o n s when f e t c h and d u r a t i o n a r e g r e a t e r . S i n c e simultaneous measurements of s u r f a c e d r i f t c u r r e n t s were not made, i t was i m p o s s i b l e t o d i s t i n g u i s h between the wind drag and s u r f a c e d r i f t components o f buoy motion i n t h i s experiment. As d e s c r i b e d i n S e c t i o n k.2. s t u d i e s o f the Ranger I buoy i n 1985 showed t h a t wind d r i f t was r e s p o n s i b l e f o r 25$ of the net buoy d r i f t o r d r i f t r a t e s c l o s e t o 1$ o f the wind speed. S i n c e m o d i f i c a t i o n s were s u b s e q u e n t l y made to the s u p e r s t r u c t u r e , i n c l u d i n g the i n s t a l l a t i o n o f a ARGOS antennae housing which i n c r e a s e d the p r o j e c t e d area by 25$, i t i s expected the wind d r i f t c o n t r i b u t i o n w i l l be s l i g h t l y h i g h e r . For the purposes of the s i m u l a t i o n i n Chapter 6, a nominal v a l u e o f 2$ o f the wind speed w i l l be used as the wind drag e f f e c t o f buoy motion. A second p o i n t o f i n t e r e s t i s the t h e o r e t i c a l t h r e s h o l d wind speed, which was c a l c u l a t e d t o be 10 m/s i n S e c t i o n 5.5.3. T h i s v a l u e may a l s o be e s t i m a t e d from the d r i f t t e s t data. We have seen so f a r t h a t : (5.8) Wind D r i f t = S u r f a c e d r i f t c u r r e n t + d i r e c t wind e f f e c t s = 0.033 U + 0.02 U = 0.053 U Then f o r a f l a t w a t e r buoy speed of 0.50 m/s and a downwind d r i f t 1 1 6 r a t e o f 5# o f the wind speed, a headwind o f 9.4 m/s would be s u f f i c i e n t t o stop the Ranger buoy from making any forward p r o g r e s s . T h i s i s o n l y an e s t i m a t i o n , and i t i s u n f o r t u n a t e t h a t i t c o u l d not be c o n f i r m e d e m p i r i c a l l y . However, s i n c e t h e r e i s c l o s e agreement between t h i s v a l u e and t h a t determined i n 5.5.3, a nominal v a l u e o f 10.0 m/s w i l l be used i n the o f f s h o r e performance model. In summary, the wind d r i f t experiments show the expected buoy d r i f t r a t e t o be i n the o r d e r o f 3 # o f the 1m winds, and the maximum wind the buoy w i l l s t a t i o n - k e e p i n w i l l be 10 m/s. 5 . 6 SUMMARY OF INSHORE TEST RESULTS The f o l l o w i n g e q u a t i o n s p a r a m e t e r i z e the Ranger a c t i v e d r i f t e r buoy performance i n the i n s h o r e t r i a l s : 1. F l a t water power e q u a t i o n (5.3) P = 303.5 V 3 ' 2 watts 2. Average T h r u s t e r budget P = 32 watts 3. E f f e c t o f Wind on speed (5.6) V = -0.054 U + 0.57 m/s 4. Unpowered d r i f t r a t e (5.8) V = 0.05 U m/s 117 6.0 SIMULATION OF ACTIVE DRIFTER PERFORMANCE OFFSHORE The purpose o f t h i s study i s t o determine i f an a c t i v e d r i f t e r buoy has the a b i l i t y t o s i g n i f i c a n t l y modify i t s d r i f t r a t e and d i r e c t i o n , and whether the degree o f buoy m o b i l i t y on the ocean s u r f a c e can j u s t i f y the use o f a c t i v e d r i f t e r s f o r oc e a n o g r a p h i c measurements. D e s p i t e the investment o f over one m i l l i o n d o l l a r s i n a c t i v e d r i f t e r buoy development, none of the c o o p e r a t i n g a g e n c i e s have had the o p p o r t u n i t y t o prove t h a t t h ese buoys can make p o s i t i v e headway under o f f s h o r e c o n d i t i o n s . The tow tank and i n s h o r e t e s t i n g d e s c r i b e d i n the p r e v i o u s s e c t i o n s a r e by f a r the most comprehensive a n a l y s i s o f buoy performance, and t h i s data w i l l be used t o assemble a model of buoy c a p a b i l i t i e s d u r i n g a deployment o f f the B r i t i s h Columbia c o a s t . The s i m u l a t i o n developed f o r t h i s a n a l y s i s models the buoy m o b i l i t y a t Ocean S t a t i o n Papa (50N, 145W). The e s s e n t i a l s o f t h i s model a r e an u n d e r s t a n d i n g o f the s o l a r power a v a i l a b l e to the buoy, the d i s t a n c e i t can t r a v e l w i t h i n the l i m i t e d power budget and how the buoy r e a c t s t o the ocean environment. These t h r e e f a c t o r s have been d i s c u s s e d i n d i v i d u a l l y i n t h i s work, and i n t h i s c h a p t e r w i l l be combined t o g i v e an o v e r a l l view o f the p o t e n t i a l o f a s e l f p r o p e l l e d buoy. The a c t i v e d r i f t e r buoy performance i s a d i s c u s s i o n o f the a b i l i t y o f the buoy to change i t s p o s i t i o n . In the m a j o r i t y o f 118 a p p l i c a t i o n s the a c t i v e d r i f t e r buoy would be programmed to s t a t i o n keep, and the s i m u l a t i o n w i l l endeavour t o measure the s u c c e s s o f the buoy a t remaining a t a d e s i g n a t e d l o c a t i o n a g a i n s t the wind induced d r i f t . Where s t a t i o n keeping i s not p o s s i b l e , then t h e s i m u l a t i o n w i l l p r e d i c t the d r i f t r a t e o f a powered buoy as compared t o an unpowered d r i f t i n g buoy deployed a t S t a t i o n Papa. 6.1 DESCRIPTION OF THE PERFORMANCE MODEL The purpose of t h e p r e d i c t i o n model i s t o p r o v i d e a f i r s t e s t i m a t e o f how the Ranger buoy would perform o f f s h o r e . The model i s based on e q u a t i o n s d e r i v e d i n p r e v i o u s s e c t i o n s and uses a s i m p l i f i e d d e s c r i p t i o n o f i t s o p e r a t i n g environment from c h a p t e r 2. The model was i n t e n t i o n a l l y l e f t u n s o p h i s t i c a t e d , and the q u a l i t a t i v e r e s u l t s a r e more a p p l i c a b l e than the v a l u e s themselves. The s i m u l a t i o n model assumes the net buoy m o b i l i t y can be determined i f t h e s e parameters a r e known: buoy m o b i l i t y = fn{ energy produced by the s o l a r a r r a y , power requirements o f the buoy, e f f e c t s o f ocean environment } where: 1. Energy P r o d u c t i o n : i s a f u n c t i o n o f i n s o l a t i o n , c o n v e r s i o n e f f i c i e n c y o f the s o l a r a r r a y , and a b i l i t y t o use the energy d i r e c t l y or s t o r e i t f o r f u t u r e use. The Ranger energy budget w i l l be determined from the i n s o l a t i o n data g i v e n i n s e c t i o n 2.2, and through the use o f a computer program developed 119 a t t h e U n i v e r s i t y o f W a t e r l o o t o model s t a n d - a l o n e s y s t e m s . The energy p r o d u c t i o n p r e d i c t e d by t h i s d e t a i l e d i n t h e next s e c t i o n . p h o t o v o l t a i c program i s 2 . Buoy Power R e q u i r e m e n t s : The buoy p a y l o a d and t h r u s t e r power b u d g e t s d e f i n e d i n s e c t i o n s 3 .3 and 5 . 5 . 2 . a r e : e l e c t r o n i c s & t e l e m e t r y 3 .3 w a t t s c o n t . t h r u s t e r 32.0 " r u d d e r 3.0 " " compass 0 . 3 " " The maximum speed t h e buoy was c a p a b l e o f w i t h i n t h i s power budget was 0.51 m / s . F o r t h e p u r p o s e s o f t h i s m o d e l , the buoy sys tems have been d e s i g n a t e d as e s s e n t i a l and s e c o n d a r y l o a d s , where: E s s e n t i a l Load 3.3 w a t t s c o n t i n u o u s Secondary " 35 .3 The e s s e n t i a l l o a d s a r e t h e buoy e l e c t r o n i c s , p o s i t i o n i n g equipment and t e l e m e t r y s y s t e m . The s e c o n d a r y l o a d s a r e the p r o p u l s i o n s y s t e m : t h e t h r u s t e r , r u d d e r and compass . I f the b a t t e r y s t a t e o f c h a r g e d r o p s below a p r e s e t t h r e s h o l d , t h e s e c o n d a r y l o a d s w i l l be s a c r i f i c e d i n f a v o r o f the buoy p a y l o a d . In t h i s way, when i n s u f f i c i e n t power i s a v a i l a b l e f o r p r o p u l s i o n , t h e buoy can s t i l l a c t as a d r i f t i n g buoy and t r a n s m i t d a t a . T h i s was a f e a t u r e programmed i n t o t h e Ranger s o f t w a r e as p a r t o f a power management r o u t i n e . 3. E f f e c t s o f O p e r a t i n g C o n d i t i o n s : The e f f e c t s o f w i n d s , and waves on t h e buoy were o b s e r v e d d u r i n g the i n s h o r e t r i a l s . The net e f f e c t on buoy speed has been s i m p l i f i e d and was e x p r e s s e d as a f u n c t i o n o f wind s p e e d , U, where: ( 5 . 6 ) buoy speed = 0 .57 - 0 .054 U m/s when powered ( 5 . 8 ) = - 0 . 0 5 U " unpowered A p o s i t i v e buoy speed i n d i c a t e s a net d i s p l a c e m e n t i n an upwind d i r e c t i o n . As d i s c u s s e d b e f o r e , t h e s e l i n e a r i z e d e q u a t i o n s a r e a p p r o x i m a t i o n s and a r e based on e x p e r i m e n t s per fo rmed i n 10 m/s winds o r l e s s . 120 6.2 ENERGY AVAILABILITY - WATSUN SIMULATION 6.2.1 PROGRAM DESCRIPTION The energy a v a i l a b l e t o t h e Ranger buoy f o r p r o p u l s i o n , t e l e m e t r y and data a c q u i s i t i o n i s l i m i t e d by the area o f the s o l a r a r r a y , and by th e s e t h r e e f a c t o r s : * s o l a r a v a i l a b i l i t y * c o n v e r s i o n e f f i c i e n c y o f s o l a r a r r a y * s t o r a g e c a p a c i t y In o r d e r t o p r e d i c t the energy budget with which the Ranger can o p e r a t e , a computer program developed by the U n i v e r s i t y o f Waterloo WATSUN S i m u l a t i o n L a b o r a t o r y was used (WATSUN, 1987). The WATSUN-PV r o u t i n e was designed t o model b a t t e r y backed s t a n d -a l o n e p h o t o v o l t a i c power systems. The s i m u l a t i o n uses an h o u r l y time st e p , and c a l c u l a t e s e l e c t r i c a l power g e n e r a t i o n , energy u t i l i z a t i o n and l o s s o f l o a d p r o b a b i l i t i e s f o r a g i v e n l o a d p r o f i l e . One important f e a t u r e of t h i s program i s t h a t the e f f e c t s of temperature on a r r a y output a r e c a r e f u l l y c a l c u l a t e d u s i n g h o u r l y ambient temperatures i n c l u d e d i n the i n p u t weather data f i l e . The major elements o f the program are d e s c r i b e d below: 1. Weather data: A WATSUN L a b o r a t o r i e s computer r o u t i n e s y n t h e s i z e d a weather data f i l e o f h o u r l y samples from the h i s t o r i c a l monthly averages o f i n s o l a t i o n , a i r temperature and wind speeds f o r S t a t i o n Papa found i n c h a p t e r 2 to c r e a t e a " t y p i c a l m e t e o r o l o g i c a l y e a r " i n p u t data s e t . 2. Thermodynamic bala n c e : In the WATSUN model, the power output 1 2 1 o f a p h o t o v o l t a i c module i s e s t i m a t e d u s i n g a thermodynamic b a l a n c e w i t h i n the PV module i t s e l f . The panel output i s c a l c u l a t e d from the i r r a d i a n c e l e v e l , and c o r r e c t e d by the temperature c o e f f i c i e n t o f c e l l c o n v e r s i o n e f f i c i e n c y . The model c a l c u l a t e s c e l l temperature as a f u n c t i o n o f i r r a d i a n c e and e s t i m a t e s c o n v e c t i v e heat l o s s e s t o the s u r r o u n d i n g a i r by c o n s i d e r i n g ambient temperature, wind speed and r e l a t i v e h u m i d i t y . 3. B a t t e r y Model: The program i n c l u d e s b a t t e r y s t o r a g e and monit o r s s t a t e o f charge as a f u n c t i o n o f time. The charge e f f i c i e n c y i s modelled w i t h a t h r e e s t e p f u n c t i o n o f S t a t e o f Charge (SOC) as shown i n F i g u r e 6.1. At low s t a t e s o f charge, e f f i c i e n c y i s low due t o the energy r e q u i r e d t o i n i t i a t e the fo r m a t i o n o f l e a d o x i d e and the i n c r e a s e i n i n t e r n a l r e s i s t a n c e i n t h e b a t t e r y . Through most o f the range (SOC = 0.2 t o 0.9), charge e f f i c i e n c y i s 80$, but f o r SOC ap p r o a c h i n g 1.0, the e f f i c i e n c y drops t o 70$. T h i s emulates a two ste p charge r e g u l a t o r , where the r e g u l a t o r s w i t c h e s t o a p u l s e or f l o a t charge when the b a t t e r i e s near the 100£ SOC l e v e l . Note t h a t the model does not account f o r the v a r i a t i o n o f b a t t e r y c a p a c i t y w i t h temperature. In p r a c t i c e , l e a d a c i d c e l l a r e r a t e d a t 23 C, and a t the average temperature a t Stn. Papa o f 8.2 C, c a p a c i t y w i l l be reduced t o 80% of the r a t e d c a p a c i t y ( C o i a and Szymborski, 1987). Rather than add the c o m p l i c a t i o n o f temperature e f f e c t s , i t w i l l be assumed t h a t the u s a b l e c a p a c i t y i s 330 Ah or 1.98 kWh a t the minimum temperature. k. Load Model: The Ranger was b u i l t w i t h a power management r o u t i n e which f u n c t i o n e d as a l o a d c o n t r o l l e r . Sensors measured b a t t e r y v o l t a g e and when the b a t t e r y s t a t e o f charge reached a lower t h r e s h o l d o f 70% d i s c h a r g e d , the t h u s t e r use was r e s t r i c t e d . T h i s would p r e s e r v e the remaining c a p a c i t y f o r the payl o a d . The WATSUN program models t h i s f e a t u r e by d i v i d i n g the lo a d s i n t o e s s e n t i a l and secondary l o a d s . 5. R e g u l a t o r Model: S o l a r power r e g u l a t o r s a r e r a r e l y more than 98$ e f f i c i e n t . In the model, the r e g u l a t o r i s t r e a t e d as a v a r i a b l e r e s i s t a n c e , d i s s i p a t i n g 2% of the incoming power. A s i m i l a r c o e f f i c i e n t o f 2% i s used t o account f o r l i n e l o s s e s . 6.2.2 SIMULATION RESULTS WATSUN-PV was used t o c a l c u l a t e the amount of energy a v a i l a b l e t o the a c t i v e d r i f t e r . I t p r e d i c t s when the e s s e n t i a l l o a d s can be s a t i s f i e d , and the p e r i o d s when secondary l o a d s can 122 1.0->* <£ 0 .5-w i—i CJ I—I Cu Pu Maximum Charge Ef f i c i e n c y D E f f i c i e n c y @ SOC = 1.0 —I 1 1 1 1 0.2 0 .4 0 .6 0 .8 1.0 STATE OF CHARGE FIGURE 6 . 1 : Charge e f f i c i e n c y v s . S t a t e of Charge f o r l e a d a c i d b a t t e r i e s . 123 ENERGY ANALYSIS SUMMARY MUNIH INCIDENT RADIAI ION <kWh> AVAILABLE ARRAY OU I PUI ( kWh) NE I ENERGY USED ( k W h ) 1 U TAL LUAD ( k W h ) ESSENTIAL LOAD ( k W h ) TOTAL FRACTION DELIVERED ESSENTIAL FRACTION DELIVERED + J AN 49 5 cr _ i 28. 67 2.44 0. 204 0. 546 FEB 113 1 1 11 25.9 2. 20 0.326 0. 670 MAR 24V 25 24 28.67 2. 44 O. 642 0.828 APR 218 21 27. 74 2. 36 0. 597 O. 854 MAY 371 3 7 35 28. 67 2.44 0. 913 0.977 JUN 338 30 2/. 74 2.36 0.879 0.979 JUL 328 32 31 28. 67 2. 44 U.843 0. 960 AUG 312 30 29 28. 67 2. 44 0. 801 0. 954 SEP 226 T > 21 27. 74 2. 36 0.592 0. B65 OC i 121 12 11 28. 67 2. 44 0. 311J 0. 653 NOV 67 7 6 27. 74 2. 36 0. 169 0.532 DEC 40 4 4 28. 67 2. 44 0. OB 1 0. 489 + ±40 228 28. /2 O. + i30 O. 776 I ABLE 6.1: Energy analysis summary far 210 peak watt solar array at Stn. Papa be u s e d . From t h i s , t h e number o f o p e r a t i n g h o u r s per day f o r t h e t h r u s t e r sys tem can be c a l c u l a t e d . T a b l e 6.1 p r e s e n t s the energy a n a l y s i s summary f o r a Ranger buoy d e p l o y e d a t S t a t i o n Papa . I t shows f i r s t t h a t t h e s o l a r a r r a y w i l l o u t p u t on t h e a v e r a g e 241 kWhr p e r y e a r w h i l e 2433 kWhr o f energy were i n c i d e n t on t h e a r r a y . The i n t e r v a l s o v e r which the e s s e n t i a l and s e c o n d a r y l o a d s c o u l d be s a t i s f i e d a r e shown i n F i g u r e 6 . 2 . T a b l e 6.1 and t h i s p l o t show t h a t w h i l e the p r o p u l s i o n sys tem can o p e r a t e f o r o n l y a f r a c t i o n o f t h e t i m e , a v e r a g i n g 53$, t h e buoy d a t a p r o c e s s i n g , p o s i t i o n i n g and t e l e m e t r y sys tem w i l l be a b l e t o f u n c t i o n an a v e r a g e o f 78$ o f the t ime th rough t h e y e a r . The number o f hours per day o f t h r u s t e r o p e r a t i o n has been shown i n F i g u r e 6 . 3 . On the a v e r a g e , 12 .7 hours o f p r o p u l s i o n a r e a v a i l a b l e , w h i l e i n t h r o u g h the w i n t e r o n l y 4 . 9 hours were p o s s i b l e . At no t ime c o u l d the buoy motor 24 hours per day . MONTH HOURS/DAY JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC 4 . 9 7 .8 15.4 14.3 21 .9 21 . 1 20 .2 19.2 14.2 7 .4 4. 1 1 . 9 AVG 12.7 hours TABLE 6 . 2 : Hours o f t h r u s t e r o p e r a t i o n per day . 125 LOAD FRACTION DELIVERED STATION PAPA 1 —i o -\ 1 1 1 1 1 1 1 1— 1 1 1 JAN FED MAR APR MAY JUN JUL AUG SEP OCT NOV DEC MONTH FIGURE 6.2: Load f r a c t i o n d e l i v e r e d at S t n . Papa (from WATSUN-PV s i m u l a t i o n ) , 126 HOURS OF MOTORING RANOER 1 AT STATION PAPA 2 2 H 20 1 8 1 6 1 4 1 2 1 0 8 -JAN V / • / / / / ' A A •'/-• / / , A / / / • / / —r-rco SA / / , A A A A •' A A Vs / /-' / A V A • / / / / ' / A v / \ / / A A ' s, / / / / / / ' /; v// / / A A V / >• / /. / / / / ' y A / A, / / / / ' / / T A A A / ' / A A. A A V / / A AA1 ' A A A A A A • / / V/. '/, A A V A • / A V VA A / / / /A Y A A I • / / •' / s V/ \VA / A, A / A / A • A / ' / / / / . / / VA i ^ , /A ' / s / / AY A V / A A A. A / • / y / / / /. / / v / JUL \A\ ' A , V AA y A / V/ A A ' A A V/ A / \ A / / / . / / . / / \AA TA~A ' s, A A A / AUG A v / Vs ' A / / / , A / / / ' / / / / V A : / / A A \ A GCP / / . / / / / • / / ' / , ' / ,. / / • / / / / / / •' / / 1 MAR APR MAY JUN MONIH O C T N O V FIGURE 6 . 3 : Hours of motoring wit h i n s o l a r energy budgets f o r a Ranger at Stn. Papa. 127 T a b l e 6 .3 g i v e s a d e t a i l e d month by month a n a l y s i s o f t h e p e r i o d s f o r which the e l e c t r o n i c s and t h r u s t e r had i n s u f f i c i e n t power t o o p e r a t e . I t a l s o shows t h a t o n l y 2 kWh o f energy were wasted when, i n t h e summer more energy was a v a i l a b l e f rom the s o l a r a r r a y than r e q u i r e d t o f u l l y c h a r g e t h e b a t t e r i e s and o p e r a t e t h e t h r u s t e r . T h i s i m p l i e s an energy u t i l i z a t i o n o f g r e a t e r than 99%. The buoy power s y s t e m , w i t h 3.96 kWh o f b a t t e r y s t o r a g e , has a s m a l l b a t t e r y pack r e l a t i v e t o the a r r a y s i z e f o r s t a n d - a l o n e PV power s y s t e m s . T h i s i s t h e r e s u l t o f l i m i t e d s p a c e w i t h i n the buoy . A second t e s t was per fo rmed t o gauge the e f f e c t o f i n c r e a s i n g t h e b a t t e r y bank by k5% t o 5 .76 kWh by r e p l a c i n g the 55 AHr c e l l s w i t h 80 AHr g e l c e l l s . W h i l e the amount o f energy wasted d e c r e a s e d from 2 kWh per annum t o near 0, t h e changes i n t h e f r a c t i o n a l l o a d d e l i v e r y were n e g l i g i b l e . The e s s e n t i a l l o a d d e l i v e r e d i n c r e a s e d f rom 77.6% t o 78.2%, and t h r u s t e r o p e r a t i o n i n c r e a s e d by an a v e r a g e o f o n l y 12 m i n u t e s per day . L a r g e i n c r e a s e s i n b a t t e r y c a p a c i t y t o 20 kWh would be n e c e s s a r y t o improve t h e w i n t e r p e r f o r m a n c e by a s i g n i f i c a n t amount, but a r e i m p r a c t i c a l w i t h the p r e s e n t h u l l c o n f i g u r a t i o n . In summary, the i m p o r t a n t r e s u l t o f the WATSUIM-PV s i m u l a t i o n i s t o d e f i n e t h e number o f hours o f o p e r a t i o n o f the t h r u s t e r a v a i l a b l e w i t h i n the s o l a r energy b u d g e t . 1 2 8 -+ +-TIME TOTAL LOAD NOT MET ( h o u r s ) -+ +-ENERGY WASTED ABOVE ESSEN!. (MWh) M O N T H TIME ESSENI. LOAD NOT MET ( h o u r s ) ESSENT LOAD ENERGY SHORT (MWh) TOTAL LOAD ENERGY SHORT (MWh) ENERGY WASTED ABOVE IOI AL (MWh) ENERGY DELIV-ERED (MWh) JAN OOO 0. OOl 592. OOO 0. 018 0. OOO o. 000 0. 007 FEB OOO 0. OOO 453. 000 0. 013 0. 000 0. ooo o. 009 MAR 128. OOO 0. OOO 266. OOO 0. 0O8 0. 000 o. 000 0. 019 APR 105. 000 o. 000 290. OOO 0. 008 0. 000 0. ooo 0. 017 MAY 17. OOO 0. ooo 65. OOO 0. O02 0. ooo o. 000 o. 026 JUN 15. 000 0. 000 87. 000 0. 002 0. ooo o. 002 0. 025 JUL 30. OOO o. 000 117. OOO 0. 0O3 0. 000 0. ooo 0. 024 AUG 34. 000 0. ooo 148. 000 0. 004 0. ooo 0. ooo 0. 023 SEP 97. 000 0. 000 294. OOO 0. 0O7 0. ooo 0. ooo 0. 017 OCF 258. ooo 0. 000 513. 000 0. 015 O. 000 0. 000 0. OlO NOV 337. 000 0. 001 598. ooo 0. 018 O. 000 0. ooo o. 006 DEG 379. ooo o. OOl 683. ooo o. 021 O. ooo o. ooo o. 003 - H 4106.OOO TO I 1960.OOO 0. 003 O. 118 O. OOO O. 0O3 O. 1B6 TABLE 6.3: E s s e n t i a l and t o t a l load a n a l y s i s by month. 129 6 .3 BUOY MOBILITY AT STATION PAPA The n u m e r i c a l model developed f o r t h i s study a s s i m i l a t e s the e q u a t i o n s d e r i v e d i n the i n s h o r e t e s t s d e s c r i b i n g the Ranger a c t i v e d r i f t e r and p r e d i c t s how the buoy would perform under t y p i c a l o f f s h o r e c o n d i t i o n s . As n e i t h e r of the a c t i v e d r i f t e r buoy development programs were s u f f i c i e n t l y advanced t o conduct e x t e n s i v e o f f s h o r e t e s t s , the s i m u l a t i o n can o n l y e s t i m a t e the a c t u a l buoy p r o g r e s s and the r e s u l t s a r e d i f f i c u l t t o v e r i f y . For t h i s reason the model i s i n t e n t i o n a l l y l e f t as s i m p l e as p o s s i b l e . The s i m u l a t i o n i s d i v i d e d i n t o two p a r t s : a one d i m e n s i o n a l model o f buoy d r i f t w i t h and w i t h o u t power, and a second model t h a t adds v a r i a b l e wind d i r e c t i o n s t o determine net d i s p l a c e m e n t as opposed t o i n t e g r a t e d path l e n g t h of Ranger d r i f t . Attempts were not made t o add v a r i a b l e speeds to the model, or t o e s t i m a t e the e f f e c t s o f l a r g e developed sea as t h e se were not c o n s i d e r e d e s s e n t i a l t o the g o a l o f p r o v i d i n g a f i r s t a p p r o x i m a t i o n of buoy p r o g r e s s o f f s h o r e . Note t h a t both models assume t h a t the buoy motors d i r e c t l y i n t o the wind when s u f f i c i e n t energy i s a v a i l a b l e f o r p r o p u l s i o n . Although a more s o p h i s t i c a t e d buoy may always motor towards a d e s i g n a t e d waypoint, the a c t i v e d r i f t e r modeled i n t h i s s i m u l a t i o n i s i n t e n d e d to be a slow d r i f t e r and works a g a i n s t p r e v a i l i n g d r i f t . 130 6 .3 .1 BUOY PERFORMANCE IN STEADY WINDS 6 . 3 . 1 . 1 S i m u l a t i o n D e s c r i p t i o n The steady wind s i m u l a t i o n makes the assumption t h a t the buoy i s o p e r a t e d i n one dimension w i t h c o n s t a n t wind speeds e q u a l t o the average wind speed f o r t h a t month. The buoy d r i f t s d i r e c t l y downwind and motors a g a i n s t the d r i f t . T h i s s i n g l e dimension model d e f i n e s the Ranger's a b i l i t y t o compete w i t h t h e wind drag and d r i f t c u r r e n t s working t o d i s p l a c e i t . The s i m u l a t i o n i s a d i r e c t a p p l i c a t i o n o f the e q u a t i o n ( 5 . 6 ) , the wind e f f e c t s on buoy speed, and (5.8), the downwind d r i f t r a t e o f the buoy, where the net d r i f t r a t e f o r the buoy was the sum o f t h e powered and unpowered l e g s , p r o p o r t i o n e d by t h e number o f t h r u s t e r hours a v a i l a b l e , h ,: (6.1) Net D r i f t = h x (0.57 - 5.4#U) + (24 - h ) x 5%U (m/s) Rate where U i s the average wind speed i n m/s. To put the r e s u l t s i n p e r s p e c t i v e , the net d r i f t per day and month were c a l c u l a t e d . 6 . 3 . 1 . 2 R e s u l t s A comparison of the d r i f t d i s t a n c e s f o r a powered and unpowered Ranger buoy deployed i n the c o n d i t i o n s p r e v a i l i n g a t S t a t i o n Papa i s shown i n Ta b l e 6.4. I t shows the annual d i s p l a c e m e n t o f a d r i f t i n g buoy i n the shape o f a Ranger buoy would be 16,500 km., a t a r a t e e q u i v a l e n t to f i v e p e r c e n t o f the average wind speed. T h i s i s a very f a s t d r i f t r a t e when compared 1 3 1 BUOY PERFORMANCE SUMMARY MONTH DAYS TOTAL THRUSTER USE PER DAY AVERAGE BUOY DRIFT DRIFT DIST. DRIFT DIST. WIND SPEED RATE per 24 Hrs. per month DISTANCE TRAVELLED DISTANCE TRAVELLED NET DIFFERENCE with power with power (hours) (m/s) (m/s) (km) (km) (km/day) (km/month) (km/month) JAN 31 4.9 11.a 0.59 50.98 1580 41.8 1295 286 FEB 28 7.a 12.4 0.62 53.57 1500 38.9 10B9 410 MAR 31 15.4 10.a 0.54 46.66 1446 17.4 540 906 APR 30 14.3 9.9 0.50 42.77 1283 15.4 462 821 MAY 31 21.9 9.3 0.47 40. 18 1245 -1.9 -57 1303 JUN 30 21. 1 B.2 0.41 35.42 1063 -5.4 -161 1224 JUL 31 20.2 7.8 0.39 33.70 1045 -5.5 -172 1217 AUG 31 19.2 8.2 0.41 35.42 1098 -1.8 -54 1153 SEP 30 14.2 9.3 0.47 40. 18 1205 12.9 3BS 818 OCT 31 7.4 11.8 0.59 50.98 1580 37.0 1146 434 NOV 30 4. 1 12.9 0.65 55.73 1672 48.2 1445 227 DEC 31 1.9 13. 4 0.67 57.89 1795 54.3 1682 112 AVERAGE 12.7 10.5 0.52 45.29 1376 — — — 1 t 20.943 , 742 16512 7603.OOO 8909 TABLE 6.4: Simulation of buoy performance with constant wind di r e c t i o n . t o s par buoys, which i n p r a c t i c e have averaged 19km. per day or 7,000 km. per year (AES, 1985). An a c t i v e d r i f t e r buoy motoring f o r a p o r t i o n o f the day d e f i n e d by T a b l e 6.2 would reduce the d r i f t r a t e by g r e a t e r than h a l f t o 7,600 km. L i k e a l l s o l a r power systems, the power a v a i l a b i l i t y i n the summer f a r exceeds the w i n t e r . For the Ranger buoy, the w i n t e r d r i f t r a t e (from Nov. t o Jan.) i s slowed o n l y by ~\2% over the expected d r i f t o f an unpowered buoy. In the summer months from May t o September, the buoy makes s u f f i c i e n t headway t o s t a t i o n -keep a g a i n s t the p r e v a i l i n g winds and wind d r i v e n c u r r e n t s . T h i s i s d i s p l a y e d g r a p h i c a l l y i n F i g u r e 6.4. These r e s u l t s a r e o n l y v a l i d f o r a s i n g l e d i m e n s i o n a l p i c t u r e . The enormous d r i f t r a t e s i n the o r d e r o f 0.6 m/s may be p o s s i b l e w i t h the l a r g e wind drag c o e f f i c i e n t f o r the buoy, but i n p r a c t i c e , d i s p l a c e m e n t s o f t h i s magnitude would be reduced by s h i f t s i n wind d i r e c t i o n s . D r i f t under v a r i a b l e d i r e c t i o n s w i l l be e x p l o r e d i n the next s e c t i o n . 6 . 3 . 2 BUOY DISPLACEMENT WITH VARIABLE WIND DIRECTION 6 . 3 . 2 . 1 Simulation Description The second s i m u l a t i o n added the v a r i a b l e o f wind d i r e c t i o n t o t h e model. I t c o n s i d e r s the wind speed t o be c o n s t a n t throughout the month, but a p p o r t i o n s the d r i f t d i r e c t i o n with a frequency o f observed wind d i r e c t i o n s , taken from the Ta b l e 2.3. 133 RANGER DOWNWIND DRIFT Simulation at Ocean Station Papa 2 - i JAN FED MAR APR MAY JUN JUL AUG SEP OCT NOV DEC • UNPOWERED BUOY + ACTIVE DRIFTER BUOY FIGURE 6.4: S t r a i g h t l i n e d r i f t per month of unpowered and a c t i v e d r i f t e r buoys. 134 The net buoy displacement over a given period was the sum of the i n d i v i d u a l legs with directions limited to the eight primary compass headings. The length of time spent on each heading corresponded to the observed frequency of winds from that d i r e c t i o n . The speed made good during that leg was calculated from (6.1) as the sum of the powered and unpowered components. In a l l cases the buoy motored in a d i r e c t i o n to reduce the wind d r i f t . 6 .3 .2 .2 R e s u l t s The net d r i f t rate in variable wind conditions i s shown by month in Table 6.5. As expected, i t presents a more r e a l i s t i c prediction of d r i f t rates as wind directions are constantly s h i f t i n g and occasionally the buoy w i l l be blown back to i t s s t a r t i n g point. With a variable regime, the net buoy displacement averages 6,100 km per year as a d r i f t e r and 2,600 km with some power ava i l a b l e . The proportional difference in d r i f t between the active and unpowered buoys i s 43$. While the d r i f t distances are smaller than those predicted in the previous simulation, the r e l a t i v e differences between the active d r i f t e r and the version without propulsion are the same; the d r i f t rates are reduced by more than half. Table 6.5 shows that station keeping i s possible k months of the year. Figure 6.5 compares the r e l a t i v e d r i f t of the active and unpowered buoys at Station Papa by month. In the f a l l 135 1 1 UNPOWERED BUOY 1 1 RANGER ACTIVE DRIFTER 1 1 * . MONTH " NORTH EAST NET DRIFT ! NORTH EAST NET DRIFT ! COMPONENT COMPONENT DRIFT DIRECTION ! COMPONENT COMPONENT DRIFT DIRECTION ! of DRIFT of DRIFT (km/ (km/ (true ! ai DRIFT ai DRIFT (km/ (km/ (true 1 (km) (km) day) month) degrees) ! (km) (km) day) month) degrees) i JAN B.3 6.8 10.8 334 39.2 6.8 5.6 B.8 274 39.2 FEB 9.7 11.5 15.O 421 49.9 7.0 8.4 10.9 306 49.9 MAR 4.9 16.0 16.7 518 72.9 1.8 6.0 6.2 194 72.9 APR 5.2 15.8 16. 7 500 71.7 1.9 5.7 6.0 180 71.7 MAY 9.a 11.7 15.2 473 50.2 -0.5 -0.5 -0.7 -22 50.2 JUN 6.0 12. 1 13.5 406 63. 4 -0.9 -1.8 -2. 1 -62 63.4 JUL 5.7 13.8 15.0 464 67.8 -0.9 -2.3 -2.5 -76 67.8 AUG 5.0 16.4 17. 1 530 73. 1 -0.2 -0.8 -o.a -26 73. 1 SEP 8.8 14.6 17. 1 512 59.0 2.8 4.7 5.5 165 59.0 OCT 9.2 21.8 23.7 734 67. 1 6.7 15.8 17.2 532 67. 1 NOV 7. 1 19.3 20.5 615 69.9 6. 1 16.6 17.7 532 69.9 DEC 8. 7 16. 3 18.5 573 61.8 8.2 15.3 17.3 537 61.8 + — — — — — — — — AVERAGE 16.6 507 63.4 7.0 211 62. 1 k. TOTAL 6079 2533 TABLE 6 . 5 : S i m u l a t i o n o f buoy pe r fo rmance w i t h v a r i a b l e w ind d i r e c t i o n . RANGER DOWNWIND DRIFT Simulation at Ocean Station Papa 800 s € a (rt ct kJ 2 O 700 -GOO 500 -400 -ZOO 200 -100 --too -'/ f A 'A A< n / A 'A. VA. / , / A A A A A A A A VA A . A A / V L A T n / s VA A A A A ' / V A V A A A V. A A / VA V. \ Vi A A / / V A A ' / A A A A / A V, A A A A \ A Y V A i 71 / '/ v/ A h A A \ A\ YA A A\ A\ vAi CA \ A\ JAN —I rco i 1— MAR APR —\ MAY I JUN T JUL AUG SEP -1 OCT NOV I— DEC UNPOWERED BUOY | \ \ | ACTIVE DRIFTER BUOY F I G U R E 6 . 5 : Net d r i f t of unpowered and a c t i v e d r i f t i n g buoys with v a r i a b l e wind d i r e c t i o n s . 137 months, the wind d i r e c t i o n s a r e predominantly s o u t h w e s t e r l y , and the net d r i f t r a t e s a r e much h i g h e r than the r e s t o f the year. In January and February the wind d i r e c t i o n s a r e more v a r i a b l e and the buoy d i s p l a c e m e n t s a r e much l e s s . From March to September the a v a i l a b i l i t y o f s o l a r energy f o r p r o p u l s i o n a l l o w s much o f the d r i f t t o be r e c o v e r e d . For t h i s p e r i o d , the model p r e d i c t s the buoy c o u l d remain w i t h i n 350 km of a d e s i g n a t e d l o c a t i o n . 6.3.3 DISCUSSION The s i m u l a t i o n s performed have shown t h a t an a c t i v e d r i f t e r buoy can reduce the net d r i f t by more than h a l f o f a comparable unpowered buoy. The a c t i v e d r i f t e r can a l s o remain with 350 km o f a d e s i g n a t e d l o c a t i o n f o r 6 months a year, and can s t a t i o n -keep d u r i n g the summer months. The q u e s t i o n a r i s e s as t o how t h i s compares to the s t a n d a r d d r i f t i n g buoys p r e s e n t l y i n use. Undrogued spar buoys have been observed t o d r i f t a t a r a t e of 2% to 5# of the wind speed ( S t a r k and Campbell, 1978) and "iX to 2% w i t h a deep drogue ( G a r r e t t , 1978). In the North P a c i f i c , Hermes spar buoys deployed by Environment Canada were observed t o d r i f t a t a r a t e of 5.5 t o 6.4 km per day drogued and 17.4 t o 21.0 km per day undrogued ( B e a l , 1985). From T a b l e 6.5, the annual average d r i f t r a t e o f an a c t i v e d r i f t e r i s 7.2 km per day, w i t h the f a l l performance not much d i f f e r e n t than spar buoys t r a v e l l i n g 17.4 km. per day. T h i s shows t h a t a w e l l drogued spar buoy i s as e f f e c t i v e a t s l o w i n g 138 t h e d r i f t r a t e as a s o l a r powered a c t i v e d r i f t e r . On ly d u r i n g the s i x months f rom March t o September does t h e a c t i v e d r i f t e r have s u p e r i o r p e r f o r m a n c e t o s t a n d a r d s p a r b u o y s . In t h e f a l l , w i t h s t r o n g and c o n s i s t e n t w i n d s , and low i n s o l a t i o n l e v e l s , the buoy d r i f t r a t e exceeds t h a t o f the r e m a i n i n g t h r e e s e a s o n s . Based on t h e s e r e s u l t s , i f t h e a c t i v e d r i f t e r c o n c e p t i s t o become f e a s i b l e , c o n t i n u e d deve lopment i s r e q u i r e d t o improve t h e p e r f o r m a n c e . The f o l l o w i n g s e c t i o n compares t h e r e l a t i v e e f f e c t s on buoy m o b i l i t y o f s m a l l changes i n s e v e r a l o f the buoy c h a r a c t e r i s t i c s t o h i g h l i g h t where p o t e n t i a l deve lopment s h o u l d be f o c u s s e d . 6.4 COMPARISON OF DESIGN CHANGES TO RANGER BUOYS The s i m u l a t i o n model d e s c r i b e d i n s e c t i o n 6 . 3 . 2 was used t o c o n t r a s t t h e buoy p e r f o r m a n c e w i t h minor e n g i n e e r i n g c h a n g e s . These i n c l u d e d an i n c r e a s e i n s o l a r a r r a y e f f i c i e n c y by 4$, a r e d u c t i o n i n power budget by 10$, and a d o p t i n g a s l o w e r d e s i g n speed t o 0 . 45 m / s . The r e s u l t s o f t h e s e changes a r e e x p l o r e d i n d i v i d u a l l y i n the f o l l o w i n g s e c t i o n s and a s s e m b l e d i n T a b l e 6 . 6 . The s i m u l a t i o n o u t p u t has been i n c l u d e d i n the a p p e n d i c e s . 6.4.1 EFFECT OF INCREASING ARRAY EFFICIENCY The s o l a r a r r a y used on the Ranger buoy i s r a t e d a t 210 w a t t s , and has a net module e f f i c i e n c y o f 9 . 3 $ . Commerc ia l s i n g l e c r y s t a l modules have an e f f i c i e n c y o f 11 .7$ , and w i t h c a r e f u l c e l l ma tch ing t h i s can be i n c r e a s e d t o 13$. 139 COMPARISON OF DESIGN CHANGES RANGER AS TESTED w i t h 294 pW ARRAY w i t h 10% LESS POWER REDUCE SPEED t o 0 . 4 5 n/s w i t h UNLIMITED POWER T h r u s t e r Net D r i f t T h r u s t e r Net D r i f t T h r u s t e r Net D r i f t T h r u s t e r Net D r i f t T h r u s t e r Nat D r i f t ( h r s / d a y ) (kra/oth) ( h r s / d a y ) (kn/mth) ( h r s / d a y ) ( k a / n t h ) ( h r s / d a y ) (kn /mth ) ( h r s / d a y ) (km/a th ) JAN 4 . 9 274 6 . 3 257 5 . 4 26B 6 . 5 262 24 38 FEB 7 .a 306 10 .9 261 B . 4 297 9 . 9 290 24 68 MAR 15 .4 194 1 9 . 9 9B 16 .4 173 ia.a 160 24 13 APR 1 4 . 3 180 2 0 . 6 39 15 .5 153 18 .2 132 24 - 3 6 MAY 2 1 . 9 - 2 2 2 3 . 6 -61 2 2 . 5 - 3 5 2 3 . 5 - 7 24 - 6 9 JUN 2 1 . 1 - 6 2 2 4 . 0 - 1 2 6 2 2 . 3 - B 8 2 4 . 0 - 7 6 24 - 1 2 6 JUL 2 0 . 2 - 7 6 2 4 . 0 - 1 7 7 2 1 . 9 - 1 2 2 2 4 . 0 - 1 1 7 24 - 1 7 7 AUG 19. 2 - 2 5 2 3 . 0 - 1 3 5 20 . 7 - 7 0 2 3 . 0 - 7 3 24 - 1 6 3 SEP 14 .2 165 2 0 . 9 0 15 .5 132 2 0 . 2 65 24 - 7 5 • C T 7 .4 532 10. 4 451 B .O 518 9 . 5 502 24 84 NOV 4 . 1 532 5 . 9 494 4 . 4 525 5 . 4 514 24 121 DEC 1.9 537 3. 1 516 2 . 1 534 2 . 7 527 24 131 SVG 12. 7 16. 1 13 .6 15 .5 24 TOT 2535 1617 22B5 2179 - 1 9 3 " - - — « U - « I f a high q u a l i t y module c o u l d be manufactured f o r the Ranger buoy having an o v e r a l l e f f i c i e n c y o f 13#, the module would have an output o f 49 watts as opposed t o 35 watts f o r the modules used. The a r r a y s i z e would then be 294 watts, an i n c r e a s e i n power o u t p u t o f 40#. The WATSUN-PV program c a l c u l a t e d t h a t f o r the l a r g e r a r r a y output, t h e use o f the p r o p u l s i o n system would i n c r e a s e from 12.7 t o 16.1 hours per day on average. I n s e r t i n g the r e v i s e d t h r u s t e r i n t o the buoy performance s i m u l a t i o n , the average d r i f t d e c r e a s e d t o 1,600 km per year, a improvement o f 36 p e r c e n t . The model p r e d i c t s t h a t s t a t i o n keeping would be p o s s i b l e 5 months a yea r . These a r e s i g n i f i c a n t improvements made w i t h o n l y minor changes t o the buoy. 6.4.2 EFFECT OF REDUCING POWER REQUIREMENT BY 10* I t i s c o n c e i v a b l e t h a t the power r e q u i r e d t o p r o p e l the buoy at a d e s i g n speed o f 0.5 m/s c o u l d be reduced by f a i r i n g the h u l l , r e d u c i n g form drag or i n c r e a s i n g the e f f i c i e n c y o f the p r o p u l s i o n system. The r e s u l t s o f a 10# decrease i n t h r u s t e r power requirement, f o r what ever the cause, a r e e x p l o r e d i n t h i s s e c t i o n . A 10$ decre a s e i n power would reduce the secondary l o a d t o 32 watts. Through the energy model, the t h r u s t e r o p e r a t i o n i s i n c r e a s e d t o 13.6 hours per day, and the average annual d r i f t would be reduced by 13 p e r c e n t t o 2285 km. per year. The d r i f t r a t e i n the f a l l months changes very l i t t l e as i t i s i n t h i s 141 p e r i o d t h a t the s o l a r a v a i l a b i l i t y i s a t i t s lowest. 6.4.3 EFFECT OF A 10$ REDUCTION IN BUOY OPERATING SPEED S i n c e i t was shown t h a t the e f f e c t i v e power o f the h u l l v a r i e s r o u g h l y as a cube o f v e l o c i t y , a d e c r e a s e i n o p e r a t i n g speed may be o f f s e t by t h e i n c r e a s e i n t h r u s t e r hours a s s o c i a t e d w i t h the d e c r e a s e i n e l e c t r i c a l power. T h i s combination c o u l d r e s u l t i n a net i n c r e a s e i n buoy p r o g r e s s . To e s t i m a t e the e f f e c t s o f t h i s change, an o p e r a t i n g speed o f 0.45 m/s, 10$ l e s s than the d e s i g n a t e d speed o f 0.50 m/s, was chosen. From (5 . 3 ) , the power t o d r i v e the h u l l a t t h i s speed i n f l a t water was c a l c u l a t e d t o be 23.55 watts. T h i s i s a net d e c r e a s e o f 36$ over the t h r u s t e r budget of 32 watts f o r 0.50 m/s. The buoy speed made good i n winds was e s t i m a t e d from ( 6 . 2 ) , which i s e q u a t i o n (5.6) m o d i f i e d f o r the lower speed. (6.2) V = 0.52 - 0.54 U m/s The r e s u l t s a r e i n c l u d e d i n T a b l e 6.6. The number o f t h r u s t e r hours w i t h t h e lower power consumption i n c r e a s e s to 15.5. T h i s i s o f f s e t by the lower speeds, but net d r i f t s t i l l d e c r e a s e s 14$ t o 2,200 km per year over the buoy t r a v e l l i n g a t 0.50 m/s. T h i s shows the buoy o p e r a t i n g s t r a t e g y s h o u l d be c o n s i d e r e d c a r e f u l l y and the buoy speed s e l e c t e d t o o p t i m i z e the net p r o g r e s s . 142 6 . 4 . 4 UTILIZATION OF ALTERNATE POWER SOURCE The f i n a l t e s t t h a t was per fo rmed c o n s i d e r e d t h e buoy c a p a b i l i t i e s i f s u f f i c i e n t power were a v a i l a b l e t o o p e r a t e t h e t h r u s t e r 24 hours a day y e a r r o u n d . P r a c t i c a l l y , t h i s i s beyond t h e c a p a b i l i t i e s f o r a s o l a r power sys tem f o r t h e Ranger buoy, and an a l t e r n a t e power s o u r c e would have t o be c o n s i d e r e d . H y p o t h e t i c a l l y , a t h e r m o e l e c t r i c g e n e r a t o r o r a p r i m a r y b a t t e r y / s o l a r h y b r i d a r e s e v e r a l o p t i o n s t h a t might be c o n s i d e r e d . However, i t i s o f i n t e r e s t t o l o o k a t t h e buoy p e r f o r m a n c e w i t h an expanded power s o u r c e as t h i s d e f i n e s t h e l i m i t a t i o n s o f t h e p r e s e n t h u l l d e s i g n . T a b l e 6 .6 shows t h a t a Ranger c a p a b l e o f m o t o r i n g 24 hours p e r day would be a b l e t o s t a t i o n keep t h r o u g h o u t the y e a r w i t h i n a s e v e r a l hundred k i l o m e t e r watch c i r c l e . The p o s i t i v e headway p o s s i b l e i n t h e summer would be i n t h e o r d e r o f 500km, and t h i s would be l o s t t h r o u g h the w i n t e r . T h i s shows t h a t the p r e s e n t Ranger h u l l can o n l y s t a t i o n keep, and under no c i r c u m s t a n c e s would i t be a b l e t o motor g r e a t d i s t a n c e s i n t o the w i n d . 6 . 4 . 5 CONCLUSION - RECOMMENDED DESIGN CHANGES T h i s a n a l y s i s has shown t h a t s e v e r a l r e l a t i v e l y minor changes can be made t o improve the p e r f o r m a n c e o f an a c t i v e d r i f t e r buoy . C e r t a i n l y , t h e e a s i e s t change t o make i s i n the 143 o p e r a t i n g speed, which sho u l d be a d j u s t e d t o o p t i m i z e the buoy headway w i t h i n the power budget l i m i t a t i o n s . The s e l e c t i o n o f t h i s speed s h o u l d be made with a more d e t a i l e d knowledge of the buoy response t o winds. The second f a c t o r t h a t can e a s i l y be changed i n v o l v e s an expansion o f the power a v a i l a b l e from the s o l a r a r r a y . T h i s c o u l d be accomplished by m a nufacturing a module with c o n s i s t e n t l y h igh q u a l i t y c e l l s . The o t h e r d e s i g n changes recommended i n c l u d e a h u l l r e d e s i g n t o reduce t h e h u l l r e s i s t a n c e and decrease t h e e f f e c t s o f wave and wind drag. 6.5 D I S C U S S I O N The purpose of t h i s examination was t o combine the e q u a t i o n s d e r i v e d t o d e s c r i b e the Ranger buoy i n a n u m e r i c a l model to p r e d i c t how the buoy would o p e r a t e o f f s h o r e . Attempts t o summarize the Ranger's response t o wind, waves and c u r r e n t s with elementary l i n e a r e q u a t i o n s a l l o w e d the model t o remain simple, and i t i s i n t e n d e d as o n l y a f i r s t a p p r o x i m a t i o n . The r e s u l t s o f the s i m u l a t i o n s show the Ranger buoy i s o n l y c a p a b l e o f s t a t i o n keeping, and w i l l not be a b l e to motor g r e a t d i s t a n c e s i n t o the wind. In the North P a c i f i c , w i t h p r e v a i l i n g winds c a r r y i n g the buoy on a n o r t h e a s t e r l y t r a c k , the buoy would at b e s t be a b l e t o remain w i t h i n s e v e r a l thousand k i l o m e t e r s of a d e s i g n a t e d s t a t i o n over the c o u r s e of a year. 144 The a n a l y s i s o f the e f f e c t s o f minor d e s i g n changes h i g h l i g h t t h e n a t u r e o f t h e R a n g e r ' s i n a b i l i t y t o meet t h e d e s i g n g o a l s f o r m o b i l i t y beyond the a v e r a g e d a i l y d r i f t . The upper l i m i t o f Ranger p e r f o r m a n c e i s r e s t r i c t e d t o s t a t i o n k e e p i n g as shown by t h e s i m u l a t i o n o f a Ranger buoy m o t o r i n g 24 h o u r s a day . T h i s i s t h e r e s u l t o f t h e h u l l shape used and i t s r e s p o n s e t o w i n d s . From e q u a t i o n ( 5 . 3 ) , t h e h u l l r e s p o n s e t o winds i s such t h a t 10 m/s winds w i l l be s u f f i c i e n t t o p r e v e n t t h e p r e s e n t d e s i g n f rom making headway t h r o u g h 6 months a y e a r r e g a r d l e s s , o f power a v a i l a b i l i t y . I t must be c o n c l u d e d t h a t f o r an a c t i v e d r i f t e r buoy t o be s u c c e s s f u l , a d i f f e r e n t h u l l shape s h o u l d be c o n s i d e r e d , and one t h a t i s c a p a b l e o f f o r w a r d mot ion i n g r e a t e r wind c o n d i t i o n s than t h e Ranger buoy. The next q u e s t i o n i s whether i n i t s p r e s e n t c o n f i g u r a t i o n , o r w i t h minor d e s i g n changes the Ranger buoy has any a d v a n t a g e s o v e r t h e d r i f t i n g s p a r buoys a v a i l a b l e . The a c t i v e d r i f t e r buoy c o n c e p t was g i v e n s u p p o r t as t h e r e was an o p i n i o n i n t h e s c i e n t i f i c community t h a t t h e r e was v a l u e i n a buoy t h a t c o u l d e x e r t some c o n t r o l o v e r i t s p o s i t i o n . The Ranger 2 was t h e most e f f i c i e n t , l o w e s t powered a c t i v e d r i f t e r d e v e l o p e d , and t h e s i m u l a t i o n has shown t h a t t h e a v e r a g e d r i f t r a t e can be as low as 7 km per day . With a 40$ i n c r e a s e i n a r r a y o u t p u t , a r e d u c t i o n i n power r e q u i r e d t o d r i v e the buoy and perhaps a r e d u c t i o n i n o p e r a t i n g s p e e d , the d r i f t r a t e c o u l d be r e d u c e d t o a few k i l o m e t e r s a day . By c o m p a r i s o n s t a n d a r d d r i f t i n g buoys w i t h a deep drogue 145 d r i f t a t a r a t e o f 6 km p e r day i n t h e Nor th P a c i f i c . T h e r e f o r e , i n i t s p r e s e n t f o r m , t h e a c t i v e d r i f t e r a c t u a l l y d r i f t s f a s t e r than t h e buoys i t was d e s i g n e d t o r e p l a c e . With c h a n g e s , t h e d r i f t r a t e might be o n l y m a r g i n a l l y s l o w e r than s p a r b u o y s , i n d i c a t i n g t h a t i n i t p r e s e n t f o r m , t h e a c t i v e d r i f t e r c o n c e p t i s not f e a s i b l e . A c o m p l e t e h u l l r e d e s i g n must be c o n s i d e r e d i f t h e buoy i s t o s u b s t a n t i a l l y i n c r e a s e i t s m o b i l i t y i n t h e ocean e n v i r o n m e n t . On ly w i t h t h e a b i l i t y t o c o n t r o l i s p o s i t i o n beyond s t a t i o n k e e p i n g w i l l t h e added expense and c o m p l e x i t y o f an a c t i v e d r i f t e r j u s t i f y i t s u s e . 146 7.0 CONCLUSION The p u r p o s e o f t h i s s t u d y was t o d e t e r m i n e t h e c a p a b i l i t i e s o f an a c t i v e d r i f t e r buoy i n an o f f s h o r e o p e r a t i n g e n v i r o n m e n t f rom t h e i n f o r m a t i o n g a t h e r e d d u r i n g c a l i b r a t e d tow tank t e s t i n g and e x t e n s i v e t r i a l s i n E l k L a k e . C h a p t e r s i x has endeavoured t o a s s e m b l e a s y n o p s i s o f the buoy p e r f o r m a n c e under t y p i c a l Nor th P a c i f i c c o n d i t i o n s d e r i v e d f rom t h e s i m u l a t i o n model d e v e l o p e d . The r e s u l t s d e f i n e the l i m i t s o f the Seaboy a c t i v e d r i f t e r , and f rom t h i s a d e c i s i o n can be made as t o whether such a buoy i s a f e a s i b l e t o o l f o r o c e a n o g r a p h e r s and m e t e o r o l o g i s t s . The s t u d y has shown t h a t i n i t s p r e s e n t c o n f i g u r a t i o n , the Ranger a c t i v e d r i f t e r o f f e r s o n l y m a r g i n a l l y s l o w e r d r i f t r a t e s than t h e s p a r buoys commonly i n u s e . At t h r e e t i m e s t h e c o s t o f a s p a r buoy, i t i s d i f f i c u l t t o see t h a t t h e added c o m p l e x i t y i s j u s t i f i a b l e . In i t s p r e s e n t f o r m , t h e o n l y advan tage o f the Ranger i s t h e l a r g e power base a v a i l a b l e , where , a t t h e s a c r i f i c e o f t h e p r o p u l s i o n s y s t e m , up t o 240 kwh o f power a r e a v a i l a b l e . For s p e c i a l a p p l i c a t i o n s , the Ranger c o u l d s u p p o r t a v a r i e t y o f s e n s o r and t e l e m e t r y sys tems n o r m a l l y not c o n s i d e r e d because o f power l i m i t a t i o n s . For t h e use o f a c t i v e d r i f t e r s t o become j u s t i f i a b l e , then the p e r f o r m a n c e must a t l e a s t approach the o r i g i n a l d e s i g n g o a l s . The buoy would have t o be c a p a b l e o f speeds i n t h e o r d e r o f 1.0 m / s , and have the p o t e n t i a l t o make p o s i t i v e headway i n average deep ocean c o n d i t i o n s . T h i s s t u d y has shown t h a t the l i m i t s o f 147 the p r e s e n t h u l l a r e as a s low d r i f t e r , o r pe rhaps t o s t a t i o n keep . To improve t h e a c t i v e d r i f t e r p e r f o r m a n c e t o any a p p r e c i a b l e d e g r e e , t h e h u l l form would have t o be r a d i c a l l y changed w i t h emphas is on r e d u c e d wind d r a g , lower h u l l r e s i s t a n c e and a nar rower p r o f i l e t o a l l o w t h e buoy t o make p r o g r e s s i n waves. A l t e r n a t i v e power s o u r c e s must a l s o be c o n s i d e r e d , as a s t a t i o n k e e p i n g buoy needs t h e most power i n t h e f a l l when s o l a r a v a i l a b i l i t y i s a t i t s l o w e s t . These a r e s e v e r a l o f t h e changes r e q u i r e d t o make the a c t i v e d r i f t e r buoy t e c h n i c a l l y f e a s i b l e . To make the buoy a p r a c t i c a l a l t e r n a t i v e t o s p a r b u o y s , s e v e r a l o t h e r f a c t o r s , i n c l u d i n g the c o s t - e f f e c t i v e n e s s o f an a c t i v e d r i f t e r , must be be c o n s i d e r e d . The a c t i v e d r i f t e r was g i v e n s u p p o r t as t h e r e was a c o n c e n s u s i n government and i n d u s t r y t h a t an i n d e p e n d e n t l y m o b i l e d a t a buoy c o u l d s a t i s f y a v a s t market f o r l o w - c o s t d a t a c o l l e c t i o n a t s e l e c t e d l o c a t i o n s . A Ranger buoy as a s e n s o r p l a t f o r m had a p r o j e c t e d c o s t i n the o r d e r o f f o r t y thousand d o l l a r s w i t h o u t s e n s o r s . Wi th t h e p r e s e n t f i s c a l r e s t r a i n t i n both government and t h e o i l i n d u s t r y , the market p o t e n t i a l f o r a c t i v e d r i f t e r buoys i s l i m i t e d . Even w i t h t h e c a p a b i l i t y t o s t a t i o n k e e p i n g or b e t t e r , t h e market would be d u b i o u s . F u r t h e r m o r e , the degree o f i n v e s t m e n t r e q u i r e d t o c o m p l e t e the deve lopment makes t h e a c t i v e d r i f t e r c o n c e p t an u n l i k e l y c o m m e r c i a l v e n t u r e i n a p r o f i t o r i e n t e d i n d u s t r y . W h i l e t h e c o n c e p t o f a s o l a r powered s e l f - p r o p e l l e d buoy may 148 be i m p r a c t i c a l , s o l a r power has a p l a c e i n o c e a n o g r a p h i c da ta b u o y s . The Canad ian government has r e c e n t l y d e p l o y e d two t e t h e r e d NOMAD s t y l e deep s e a weather buoys 600 km o f f t h e B r i t i s h C o l u m b i a c o a s t . At p r e s e n t t h e s e buoys a r e not s o l a r powered, but the r e s u l t s o f t h e energy a n a l y s i s p e r f o r m e d f o r t h e Ranger s o l a r p a n e l s would be a p p l i c a b l e t o t h e s e buoys i f p h o t o v o l t a i c s were t o be i n c o r p o r a t e d i n t h e f u t u r e . 149 BIBLIOGRAPHY A n o n . , ( 1976 ) , B r i t i s h C o l u m b i a S a i l i n g D i r e c t i o n s , V o l . 1. B e a l , B . , ( 1985 ) , p e r s o n a l c o m m u n i c a t i o n , A t m o s p h e r i c E n v i r o n m e n t S e r v i c e , M a r i n e F o r e c a s t i n g C e n t r e . Brown, R . D . e t a l , ( 1986) , M a r i n e C l i m a t e A t l a s - C a n a d i a n West C o a s t . , U n p u b l i s h e d m a n u s c r i p t , C a n a d i a n C l i m a t e C e n t r e P u b l i c a t i o n Repor t 8 6 - 1 0 . C a n a d i a n H y d r o g r a p h i c S e r v i c e , ( 1983 ) , Notes on t h e use o f LORAN-C c h a r t s , second e d i t i o n . Ocean S c i e n c e and S u r v e y s , Dept . o f F i s h e r i e s and Oceans p u b l i c a t i o n . C o i a , R . P . and J . S z y m b o r s k i , ( 1987 ) , C o l d t e m p e r a t u r e p e r f o r m a n c e o f GNB's A b s o l y t e s e a l e d l e a d a c i d c e l l s . U n p u b l i s h e d T e c h . Rpt # GNB R&D 12 /86 . 21pp. E g l e s , D .W. , ( 1985a ) , Compar ison o f buoy d r i f t r a t e t o wind s p e e d , OCGY 405 Term P a p e r , F e b . 1985. ( 1985b) , The r e l a t i o n s h i p between s u r f a c e c u r r e n t and w i n d . , OCGY 514 Term P a p e r , Mar. 1985. ( 1 9 8 5 c ) , M e c h a n i c a l t e s t i n g o f the Ranger buoy p r o t o t y p e , U n p u b l i s h e d m a n u s c r i p t , Seaboy M a r i n e S e r v i c e L t d . , Aug 1985. (1985d) , Ranger 1: A s e l f p r o p e l l e d d a t a buoy. P r o c . IEEE Oceans 85 , San D i e g o , C A . , Nov. 1985. pp . 5 6 - 6 1 . ( 1986 ) , Summary o f t h e Ranger 1 i n s h o r e t e s t i n g p r o g r a m . , U n p u b l i s h e d m a n u s c r i p t , Seaboy M a r i n e S e r v i c e s L t d . , S e p t . 1986. E n v i r o n m e n t Canada , ( 1987 ) , Ocean S t a t i o n Papa r a d i a t i o n summary. A t m o s p h e r i c Env i ronment S e r v i c e r e c o r d s , T a b l e 206, F1107 .00065 . ( 1970 -1979 ) , Month ly r a d i a t i o n summary. , A t m o s p h e r i c Env i ronment S e r v i c e , V o l s 11 -20 . F a l k n e r , D . A . , (1975) , M e t e o r o l o g y o f the Nor th P a c i f i c . U n p u b l i s h e d m a n u s c r i p t , I n s t i t u t e o f Ocean S c i e n c e s , P a t r i c i a Bay , B . C . G a r r e t t , J o h n . , (1978) , D r i f t i n g buoys f o r ocean da ta c o l l e c t i o n . , P r o c . IEEE Oceans '78 pp 155-159. Huang, N . E . , (1979) , On s u r f a c e d r i f t c u r r e n t s i n the o c e a n . , J . 150 F l u i d M e c h a n i c s , jn, pp 191-208. Kenyon , K . E . , ( 1969 ) , S t o k e s d r i f t f o r random g r a v i t y w a v e s . , J. G e o p h y s i c a l R e s e a r c h 74 , No. 28, D e c . 20, 1 9 6 9 . , pp 6691-6699. Kozak , R . P . , and R.M. P a r t r i d g e , ( 1985 ) , The r o l e o f d r i f t i n g buoys i n t h e T r o p i c a l Ocean G l o b a l Atmosphere (TOGA) P r o g r a m . , P r o c . IEEE Oceans ' 8 5 . , San D i e g o , C A . , Nov. 1985. pp . 1317-1325. L e B l o n d , P . H . , and L . A . M y s a k . , (1978) , Waves i n the o c e a n . E l s e v i e r S c i e n t i f i c P u b l i s h i n g C o . , Amsterdam. 602 p. N o r d i n , R . N . , ( 1981 ) , P r e l i m i n a r y r e p o r t on the use o f E l k Lake as a b a l a n c i n g r e s e r v o i r f o r i r r i g a t i o n : P o s s i b l e e f f e c t s on l i m n o l o g y , water q u a l i t y and f i s h e r i e s . U n p u b l i s h e d m a n u s c r i p t , Dep t . o f Env i ronment Repor t 1981 -08 -20 . P i e r s o n , W . J . , and M o s k o w l t z , L . , 1964. A p r o p o s e d s p e c t r a l form f o r f u l l y d e v e l o p e d wind s e a s based on t h e s i m i l a r i t y t h e o r y o f S . A . K i t a i g o r o d s k i i . J . Geophys . R e s . 69 :5181 -5190 . P h i l l p i s - B r i t , D . , (1957) The manual f o r n a v a l a r c h i t e c t u r e o f s m a l l c r a f t , H u t c h i s o n * C o . , pp 351, see p g . 193. S m i t h , G . R . , ( 1984 ) , The A c t i v e D r i f t e r : An autonomous d a t a b u o y . , P r o c e e d i n g s o f t h e P a c i f i c C o g r e s s on M a r i n e T e c h n o l o g y (PACON) 1985. OST 8 / 5 - 1 1 . Seaboy M a r i n e S e r v i c e s L t d . , ( 1985 ) , P r e l i m i n a r y s p e c i f i c a t i o n s o f t h e Ranger 1 A c t i v e D r i f t e r . , U n p u b l i s h e d m a n u s c r i p t . , ( 1985b) , Development o f r o b o t buoys f o r o c e a n o g r a p h i c r e s e a r c h , U n p u b l i s h e d m a n u s c r i p t , PILP P r o p o s a l #674. S t a r k , R . G . and A . H . C a m p b e l l , ( 1979) , The Hudson Bay m e t e o r o l o g i c a l d r i f t i n g buoy e x p e r i e m e n t , P r o c . o f the 13 Annua l Cong . o f C a n . M e t e o r o l o g i c a l and O c e a n o g r a p h i c S o c i e t y , May 3 0 -J un 1, 1979. Thomson, R . E . , (1981) , Oceanography o f the B . C . c o a s t , C a n . S p e c . P u b l . F i s h . A q u a t . S c i . 56. 291 pp . USSR M i n i s t r y o f D e f e n c e , (1976) , A t l a s o f the oceans - P a c i f i c Ocean , Pergamon P r e s s , 302 pp . Van D o r n , W. G . , (1974) , Oceanography and seamansh ip , Dodd, Mead and C o . , New Y o r k , 481 pp . WATSUN S i m u l a t i o n L a b o r a t o r y , (1987) , PV u s e r s manual and program d o c u m e n t a t i o n , WATSUN-PV s o f t w a r e . 151 ACKNOWLEDGEMENTS The a u t h o r w ishes t o e x p r e s s h i s s i n c e r e g r a t i t u d e to the p a r t i e s t h a t made t h i s work p o s s i b l e . In p a r t i c u l a r , he wishes t o thank the s t a f f o f Seaboy Mar ine S e r v i c e s L t d . f o r t h e i r h e l p and s u p p o r t d u r i n g the r e s e a r c h phase o f t h i s p r o j e c t , and t o Mr. P a t r i c k F i s h e r , P r e s i d e n t o f Seaboy, f o r the o p p o r t u n i t y t o p a r t i c i p a t e i n h i s companies and f o r h i s s u p p o r t th roughout the p r o j e c t and a f t e r . Mr. E g l e s would a l s o l i k e to thank the r e v i e w i n g commit tee , and i n p a r t i c u l a r Dr . P . H . L e B l o n d , Head o f the Department o f Oceanography, f o r h i s f a i t h and e n d u r i n g s u p p o r t from a c c e p t a n c e i n t o the M a s t e r s program to c o m p l e t i o n o f t h i s t h e s i s . 152 APPENDICES 153 APPENDIX A: WATSUN-PV PRINTOUT 154 * # * W A T S U N - P V I . O * * * * *• * U N I V E R S I T Y ' OF ' W A T E R L O O * * J U N E 1 9 8 7 * * * D E V E L O P E D B Y : T H E S Y S I E M S D E S I G N E N E R G Y G R O U P D E P A R I M E N I O F S Y S T E M S D E S I G N E N G I N E E R I N G A R R A Y D A T A F I L E N A M E : E G G L E S B A T T E R Y D A I A P I L E N A M E : E U B A I L O A D D A I A P I L E N A M E : E G L U A D N U M B E R O h A R R A Y S : 1 N U M B E R O P B A I F E R 1 E S : t . 155 SABB I MY STNPAPA, PAU WAT SUN—PV 1.0 1987 09 24 12:23:lO B a t t e r y D a t a 1 B a t t e r y C a p a c i t y 55.0000 2 B a t t e r y V o l t a g e 12.0000 J I n i t i a l S t a t e o f C h a r g e 100.000 4 Minimum S t a t e of C h a r g e '.. 20.0000 5 Maximum D i s c h a r g e Ef f i c i e n c y . . . . 80.0000 6 Maximum C h a r g e E f f i c i e n c y 8 0 . 0 0 0 0 7 C h a r g e E f f i c i e n c y a t S t a t e of C h a r g e = 1007. .. /O.OOOO amp V 7. '/. X -hrs Load Oat; 1 Load V o l t a g e ( n o m i n a l ) 12.0000 V 2 E s s e n t i a l L o a d D e l i v e r y ? ( l = y e s , O=no) l.OOOOO 3 Number of Days i n "weekdays" 7.00000 d a y s 4 Number of Days i n "week" 7.00000 d a y s 5 Maximum E s s e n t i a l L o a d f o r "weekdays" 3.28000 W 6 Maximum E s s e n t i a l Load f o r "weekends" O.00000 W 7 Maximum l o t a l L o a d f o r "weekdays" 3B.5400 W 8 Maximum T o t a l L o a d f o r "weekends" 0.00000 W 9 PROFILE: E s s e n t i a l L o a d F r a c t i o n - "weekdays", f r a c t i o n 1. (J0 1. OO 1. OO 1. OO 1. OO 1. OO 1. OO 1.00 1. OU 1. OO 1 . OO 1.00 1.OO 1.00 1.OO 1.00 1.OO 1.00 1.OO 1.OO 1.OO 1.OO 10 PROf-lLE: E s s e n t i a l L o a d F r a c t i o n - "weekend"., f r a c t i o n O. 30 0.30 0.30 0.30 0.30 0.30 0.6O 0.90 0.60 0.60 O. 4b 0. 45 0.45 0.45 0.45 0.60 0.90 0.90 0.90 0.6O 0.30 0.30 11 PROFILE: l o t a l L o a d F r a c t i o n - "weekdays" f r a c t i o n 1.OO 1.OO 1.OO 1.OO 1.00 1.OO 1.OO 1.OO 1.OO 1.OO 1.OO 1. UO 1.OO 1.OO 1.OO 1.OO 1.OO 1.UO 1.OO 1.OO 1.OO 1.oo 12 PROFILE: l o t a l L o a d F r a c t i o n - "weekends" f r a c t i o n O.30 0.3U 0.30 0.30 0.30 U.30 O.faO O.VU O.feu O.tu O.4b 0.45 0.45 0.45 0.45 O. 6U O.VU 0.90 U.VO 0.60 O.30 O.SO 13 PROFILE: M o n t h l y l o a d s c a l e f a c t o r s 1.OO 1.OO 1.OO 1.OO 1.OO 1.OO 1.OO 1.OO 1.OO 1.OO 1.OO 1.00 1.0O 1 .OO 0.45 0. 30 l.OO 1. OO O. l b O. 30 S e l e c t ? 156 SABB TMY STNPAPA, PAC WATSUN-PV I.O 19B7 09 24 12:23:10 S i m u l a t i o n D a t a 1 O.OOOOO y e a r ~> d a y s 3 S t a r t Day Number (Jan 1=1, Feb 1 = 32, e t c . ) . . 1.OOOOO day 4 D e t a i l e d P r i n t I n t e r v a l (No=0, l = h a u r , e t c ) . . . . O.OOOOO h r 5 S t a r t i n g Hour of D e t a i l e d P r i n t (No=0, 1-24).. 0.OOOOO hr 6 O.OOOOO day J O.OOOOO day - A r r a y D a t a 1 Number of Modul e s fc.UUOUU 2 A r e a p e r Module 0.3/7UU m\d 3 A r r a y A z i m u t h (O=south, +=west) U.OOOOCJ d e g r e e s 4 A r r a y S l o p e . . . . . Msttegrees 5 R e f e r e n c e A r r a y O p e r a t i n g T e m p e r a t u r e . . . 1B.OUOO C A R e f e r e n c e I n s o l a t i o n L e v e l lOOO.OU WVm2 / R e f e r e n c e Module Output Power 35.U0U0 W B Nominal O p e r a t i n g C e l l l e m p e r a t u r e 20.<JO<_>0 C 9 Temperature C o e f f i c i e n t o f E f f i c i e n c y O.450UOE-O2 7./C 10 F r o n t P a n e l S o l a r A b s o r p t a n c e U. lOUOU 11 E m i s s i v i t y 0.95000 12 I r a n s m i t t a n c e ( v i s i b l e ) U.95UOO 13 I r a n s m i t t a n c e ( i n f r a r e d ) 0.90000 14 Back P a n e l E m i s s i v i t y U.9OO0O R e g u l a t o r D a t a 1 R e g u l a t o r E f f i c i e n c y 9 8 . U O 0 U 7. 2 R e g u l a t o r V o l t a g e 12-OUUO V 3 L i n e ( w i r i n g ) l o s s e s 2 .0UOUO 7. 157 I ABLE OF CONSECUTIVE HOURS SYSTEM IS "DOWN" I PERIUD LEN6IH ! FAILURE TO MEET LOAD C h r s J 1 C n u m b e r o-f o c c u r r e n c e s J 1 ESSENTIAL ! FULL i : 20 ! 58 2 : 13 ! 25 3 ! 7 ! 9 4 1 10 : 3 5 I lO i 6 6 1 14 : a 7 ! 12 : 6 S t IB 1 7 9 ! 24 ! 7 10 1 2 2 1 9 11 : 12 : B 12 1 17 1 12 13 : S : 8 14 12 ! 13 15 ! 14 ! 17 16 i 7 1 14 17 ! 4 1 13 IB 1 1 : 14 19 1 1 : 16 20 1 1 ! 15 2 1 : 0 ! lO 2 2 1 0 1 7 23 ! O 3 • 25 ! O l i 3 26 1 0 1 2 39 : O 1 1 42 1 0 ! 2 43 ! O 44 1 o ! 5 46 : 0 : i 65 I o 1 1 67 i o i 2 69 1 u • 2 /O i u 1 115 ! o : l 10 I AL ! I960 i ! 4107 1 TU1AL HUURS OK LOAD DEMAND ! (HIS SIMULATION PERIOD 1 1 ESSEN 1 IAL FULL t I 8/60 8760 LLTSS-OF-LOAO ! PR0BAB1LIIY ! 0.2237 0.4688 158 SABB 1 MY SINPAPA, PAC WATSUN-PV I.O 19B7 09 24 12:23:10 CHARGE PERIDD I N I T I A L STATE-OF—CHARGE HISTOGRAM ( V e r t i c a l A x i s i s P e r c e n t a g e o-f Time =3033.hrs.) IU0. -90. 80. 70. + I 6 G . 50. + 40.+ 30. + 20. 10. + I «* ** ** ## #» »» ** #* #* • * #* *• *«• »* *» ** ** »* #* ** *• ** ** »* ** ** ** *» ** *# *# ** *# *« •« ** ** »* *» •* *« «* * * ** ** * * *# #* ## # # u. +—+• O 5 ( O) ( IO 15 20 25 30 35 40 45 50 55 60 65 70 75 HO 85 90 95 lOO BATTERY S TA TE—OF CHARGE ("/.) ( 0) ( 62) < B) < 3) ( 1) C 2) ( 1) ( 1) ( 1) 0) ( 0) ( 10) < 4) ( 2) ( 1) ( 1) ( 1) < 1) ( 1) 159 S A B B T M Y S T N P A P A , P A C W A T S U N - P V 1 . 0 1 9 B 7 0 9 2 4 1 2 : 2 3 : 1 0 B A T T E R Y S T A T E — O F — C H A R G E H I S T O G R A M , ( V e r t i c a l A x i s i s P e r c e n t a g e o f T i m e = 8 7 6 0 . h r s . ) 1 0 0 . + # I I I 9 0 . + I 8 0 . + ! 7 0 . + I I I i * * I * * ! #* 6 0 . + * * : ** ! * * i * • : ** 5 0 . + * » I * # i * * * # ! *» @ 4 0 . + * * ! «• : *» *• I * * 3 0 . + » « » « * * * * : * * 2 0 . + # » I # * : *• ! »» : * • i o . + * * i * » # * i ! ** ** *# • ! •# #* ** »* i # * * « » # * » * » • * ## * * » * • * » # O . + — + — + — + — + — + — + — + — + — + — + — + — + — + — > — + — + — + — + — + — + 0 5 1 0 1 5 2 0 2 5 3 0 3 5 4 0 4 5 5 0 5 5 6 0 6 5 7 0 7 5 8 0 8 5 9 0 9 5 1 U O B A T T E R Y S T A I E - O F C H A R G E (%> ( O ) ( 0 ) ( 6 7 ) ( 7 ) < 2 ) ( 1 ) ( 1 ) ( 1 ) ( 1 ) ( 1 ) ( O) < O ) < 9 ) ( 4 ) < 2 ) < 1 ) ( 1 ) ( 1 ) ( 1 ) ( 1 ) 160 SABB TMY SINPAPA, PAC WATSUN-PV I.O 1987 09 24 12:23s ##»»#****»•#*«#»####»*•«>*•*•*» * ENERGY ANALYSIS SUMMARY * #»**#*****••»*» #*#*••-*»*#•»#»# M INCIDENT AVAIL- NET TOTAL ESSENT. TOTAL ESSENT. • RADIA- ABLE ENERGY LOAD LOAD FRACTION FRACTION N TION ARRAY USED DELIV- DELIV-T OUTPUT ERED ERED H (MWh) (MWh) (MWh) (MWh) (MWh) JAN 0.049 0.005 0.005 0.029 0.002 0.204 O. 546 FEB 0. 1 13 0.011 O . O l l 0.026 0.002 0.326 O. 670 MAR 0.249 0.025 0. 024 0.029 O.U02 0.642 0.B28 APR 0.218 O.U22 0.021 0.02B 0.002 0.597 0.B54 MAY 0.371 0.0 57 0.035 0.029 0.002 0.913 0.977 JUN O. 338 O. 033 0.030 0.028 O. 002 0. 879 O. V/9 JUL 0.328 0.032 0.031 0.029 0.002 0.843 0. 960 AUG 0.312 0.030 U.029 0.029 0.002 0. 801 0. 954 SEP 0.226 0.022 0.021 0.O28 0.002 0.592 0.B65 UCI 0. 121 0. 012 O . O l l 0.029 0.0O2 0.310 0.653 NUV O.U67 0.007 0. 006 O.U2B 0.002 O. 169 0. 532 DEC 0.040 0.004 0.004 0.029 0.002 O. OBI O. 4B9 1UI 2. 433 0.241 0.229 0.33B 0.029 O. 531 O. 776 M r i ME ESSENT. TIME TOTAL ENERGY ENERGY ENERGY O ESSEN 1. LOAD T UT AL LOAD WASTED WASTED DELIV-N LOAD ENERGY LOAD ENERGY ABOVE ABUVE ERED r NUT MET SHUR 1 NUT MET SHURT ESSEN r. 1 UT AL H ( h o u r s ) (MWh) ( h o u r s ) (MWh) (MWh) (MWh) (MWh) JAN 338.OOO O.OOl 592.OOO O.OIB O.OOO 0. OOO O. 007 FEB 222.OOO O. OOO 453.OOO O. U13 O. OOO O.OOO O. OOV MAR 128.OOO O.OOO 2&6.00O O.OOB 0. OOO O. OOO 0. 019 APR 105.OOO 0. 000 290.OOO O.OOB . O.OOO 0. OOO 0.017 MAY 17.OOO O.OOO 65.OOO O. 002 O.OOO O. OOO O. 026 JUN 15.OOO O. OOO B7.000 0.002 O. OOO 0. 002 0. 025 JUL 30.OOO O. OOO 117.OOO 0.003 O.OOO 0. OOO 0.024 AUG 34.OOO O.OOO 14B.OOO O. 004 O. OOO O. OOO 0. 023 SEP 9 7.OOO 0. OOO 294.OOO O. 007 O. OOO O. OOO 0.017 OCT 258.OOO O. OOO 513.OOO 0.015 O.OOO O. OOO 0. 010 NUV 337.OOO 0. OOl 598.OOO o.oia 0. OOO 0. OOO O . 006 DEC 379.OOO O. OOl 683.OOO O. 021 O. OOO 0. OOO O. O03 1011960.000 0. 003 4106.000 O. 118 O.OOO O. 003 O. 186 161 APPENDIX B: BUOY PERFORMANCE MODEL WITH SELECTED DESIGN CHANGES 162 UNPOWERED BUOY ! RANGER ACTIVE DRIFTER cn co MTJN I H NOR TH EAST NET DRIFT ! NOR IH EAST NET DRIFT CDMPONEN T CQMPONEN1 DRIFT DIRECTION ! CUMPONEN T COMPONENT DRIFT DIRECTION of DRIFT of DRIFT (km/ (km/ ( t r u e ! of DRIFT of DRIFT (km/ (km/ ( t r u e (km) (km) day) month) d e g r e e s ) ! (km) (km) day) month) d e g r e e s ) JAN 8.3 6. 8 10.8 334 39.2 6. 8 5.6 8.8 274 39.2 FEB 9. 7 11.5 15.0 421 49.9 7.U 8. 4 10.9 306 49.9 MAR 4.9 16. O 16. 7 518 72. 9 1.8 6. 0 6.2 194 72.9 APR 5.2 15.8 16.7 500 71.7 1.9 5. 7 6.0 180 71.7 MAY 9.8 11.7 15.2 473 50.2 - 0 . 5 - 0 . 5 - 0 . 7 — T 7 50.2 JUN 6.0 12. 1 13.5 406 63.4 - 0 . 9 - 1 . 8 - 2 . 1 -62 63.4 JUL 5. 7 13. 8 15. 0 464 67.8 - 0 . 9 —2. 3 —2. 5 -76 67.8 AUG 5.0 16. 4 17. 1 530 73. 1 - 0 . 2 - 0 . 8 - 0 . 8 -26 73. 1 SEP 8. 8 14.6 17. 1 512 59. 0 2.8 4.7 5 .5 165 59.0' UCI 9.2 21.8 23. 7 734 67. 1 6. 7 15.8 17.2 532 1 6<1 NOV 7. 1 19. J 2'J. 5 615 69.9 6. 1 16.6 17.7 532 69.9 DEC 8.7 16.3 18.5 573 61. a 8.2 15. 3 1?.3 537 61.8 AVERAGE 16.6 507 63. 4 7.0 211 62. 1 1 Q 1 AL 6079 2533 MODEL 1: S t a n d a r d Ranger Buoy. UNPOWERED BUOY RANGER ACTIVE DRIFTER MQN'I H NORTH COMPONENT of DRIFT (km) EAST COMPONENT of DRIFT (km) NET DRIFT (km/ (km/ day) month) DRIFT DIRECTION ( t r u e NORTH COMPONENT of DRIFT (km) EAST COMPONENT of DRIFT (km) NET DRIFT (km/ (km/ day) month) DRIFT ! DIRECTION ! ( t r u e ! d e g r e e s ) I JAN B.3 6.8 10. 8 334 39. 2 6.4 5.2 8.3 257 39.2 FEB 9. 7 11.5 15.0 421 49.9 6. O 7. 1 9.3 261 49. 9 MAR 4.9 16.0 16. 7 518 72.9 0.9 3.0 3.2 98 72.9 APR 5.2 15. 8 16.7 500 71.7 0.4 1.2 1.3 39 71.7 MAY 9.B 11.7 15.2 473 50.2 -1.3 -1.5 -2.0 -61 50.2 JUN 6.0 12. 1 13.5 406 63.4 -1.9 -3.8 -4.2 -126 63.4 JUL 5. 7 13.8 15.O 464 67.8 —2.2 -5. 3 -5. 7 -177 67.8 AUG 5.0 16. 4 17. 1 530 73. 1 -1.3 -4.2 -4.4 -135 73. 1 SEP B.8 14.6 17. 1 512 59. U 0. 0 0. 0 O. 0 0 59. O OCT 9.2 21.8 23.7 734 67. 1 5.7 13.4 14.6 451 67. 1 NOV 7. 1 19. 3 20.5 615 69.9 5. 7 15. 5 16.5 494 69. 9 DEC 8.7 16. 3 18.5 573 61 .8 7.9 14.7 16. 7 516 61.8 :+• AVERAGE 16.6 507 63.4 4.5 135 62.1 TOTAL 6079 161B MODEL 2: Increase array size to 294 pW. ! UNPOWERED BUOY : RANGER ACTIVE DRIF1ER MUN TH NORTH EAST NET DRIFI : NORTH EAST NET DRIFT COMPONENT COMPONENT DRIFT DIRECTION ! COMPONENT COMPONENT DRIFT DIRECTION ai DRIFT of DRIFT (km/ (km/ ( t r u e ! of DRIFT ai DRIFT (km/ (km/ ( t r u e (km) (km) day) month) d e g r e e s ) ! (km) (km) day) month) d e g r e e s ) JAN B.3 6.8 10.B 334 39.2 1.0 O.B 1.2 3B 39.2 FEB 9.7 11.5 15.0 421 4 9 . 9 1.6 I.B 2. 4 68 49.9 MAR 4.9 16.0 16.7 518 72.9 0. 1 0.4 O. 4 13 72.9 APR 5. 2 15.8 16. 7 500 71.7 -0.4 -1. 1 -1. 2 -36 71.7 MAY 9.8 11.7 15.2 473 50. 2 -1.4 -1.7 —2.2 -69 50.2 JUN 6.0 12. 1 13.5 406 63. 4 -1.9 -3.8 -4.2 -126 63. 4 JUL 5. 7 13.-8 15.0 464 &7.B -2.2 -5.3 -5. 7 -177 67.8 AUG 5. 0 16. 4 17. 1 530 73. 1 -1.5 -5. 1 -5.3 -165 73. 1 SEP 8.8 14.6 17. 1 512 59.0 -1. 3 -2. 1 -2.5 -75 59.0 OCT 9.2 21.8 23. 7 734 67. 1 l.O 2.5 2.7 84 67. 1 NOV 7. 1 19.3 20.5 615 69. 9 1.4 3.8 4.0 121 69.9 DEC 8.7 16.3 18.5 573 61.8 2. O 3.7 4.2 131 61. B AVERAGE 16. 6 507 63.4 -0.5 -16 62. 1 1 QT AL 6079 -193 MODEL 3: P r o p u l s i o n a v a i l a b l e 24 h o u r s a d a y . UNPOWERED BUOY i RANGER ACTIVE DRIFTER CJNTH NORTH EAST NET DRIFT ! NORTH EAST NET DRIFT COMPONENT " COMPONENT DRIFT DIRECTION ! COMPONENT COMPONENT DRIFT DIRECTION of DRIFT of DRIFT (km/ (km/ ( t r u e ! of DRIFT of DRIFT (km/ (km/ ( t r u e (km) (km) day) month) d e g r e e s ) ! (km) (km) day) month) d e g r e e s ) JAN B. 3 6. 8 10.8 334 39.2 6.7 5.5 8.6 268 39.2 FEB 9.7 11.5 15.0 421 49.9 6.8 8. 1 10.6 297 49.9 MAR 4.9 16. 0 16.7 518 72. 9 1.6 5.3 5.6 173 72.9 APR 5.2 15.8 16.7 500 71.7 1.6 4.B 5. 1 153 71. 7 MAY 9.a 11.7 15.2 473 50.2 -0.7 -0.9 -1. 1 -35 50.2 JUN 6.0 12. 1 13.5 406 63. 4 -1.3 -2.6 -2.9 -BB 63. 4 JUL 5. 7 13. 8 15.O 464 67.8 -1.5 —3.6 -3.9 _ j 2 2 67. B AUG 5.0 16. 4 17. 1 530 73. 1 -0. 7 -2.2 -2.3 -70 73. 1 SEP B.8 14.6 17. 1 512 59.0 2.3 3.B 4.4 132 59.0 •CI 9.2 21.8 23. 7 734 67. 1 6.5 15.4 16.7 51B 67. 1 NOV 7. 1 19. 3 20.5 615 69. 9 6.0 16. 4 17.5 525 69.9 DEC 8. 7 16.3 18.5 573 61.8 B. 1 15.2 17.2 534 61.8 AVERAGE 16. 6 507 63. 4 6.3 190 62. 1 OIAL 6079 2285 MODEL 4: Power r e q u i r e d to p r o p e l l h u l l reduced 10%. i UNPOWERED BUOY RANGER ACTIVE DRIFTER MON IH NORTH EAST NET DRIFT ! NOR IH EAST NET DRIFT COMPONENT COMPONENT DRIFT DIRECTION ! COMPONENT COMPONENT DRIFT DIRECTION of DRIFT of DRIFT (km/ (km/ ( t r u e ! of DRIFT o f DRIFT (km/ (km/ ( t r u e (km) (km) day) month) d e q r e e s ) ! (km) (km) day) month) d e g r e e s ) JAN B.3 6.8 10. B 334 39.2 6.5 5.3 8.4 262 39.2 FEB 9. 7 11.5 15.0 421 49.9 6. 7 7.9 10.3 290 49.9 MAR 4.9 16.0 16. 7 51B 72.9 1.5 4.9 5. 1 160 ,72.'?, APR 5.2 15.8 16. 7 500 71.7 1.4 4.2 4.4 132 71."7 MAY 9.B 11.7 15.2 473 SO.2 -0.2 -0.2 -0.2 -7 50.2 JUN 6. O 12. 1 13.5 406 63. 4 -1. 1 -2.3 -2.5 -76 63.4 JUL 5.7 13.8 15.O 464 67.a -1.4 -3.5 -3.8 -117 67:8 AUG 5.0 16.4 17. 1 530 73. 1 -O. 7 -2.2 -2.3 -73 73. 1 SEP a . a 14.6 17. 1 512 59.0 1. 1 1.9 2.2 65 59.0 OCT 9. 2 21.8 23. 7 734 67. 1 6.3 14.9 16.2 502 67. 1 NOV 7. 1 19. 3 20.5 615 69.9 5.9 16. 1 17. 1 514 69.9 DEC 8. 7 16. 3 IB. 5 573 61. a B. O 15.0 17.0 527 61.8 AVERAGE 16.6 507 63. 4 6.0 182 62. 1 TOTAL 6079 2178 MODEL 5: Reduce h u l l speed by 10% 

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