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TRANSCRIPT
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- SA'DYA REPOPT SAND85- 1251 Unlimited Release UC-63 Printed January 1986
The Determination of Optimum Mounting Configurations for Flat-Plate Photovoltaic Modules Based on a Structured Field
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Experiment and Simulated Results From PVFORM, a Photovoltaic System III~IEII;I~AII~~~~~I~~~~IIII~I~~~III~~AIIIIII~IIIIIA Performance Model 8232-211063587
David F. Menicucci
Prepared by Sandia National Laboratories Albuquerque, New Mexico 87185 and Livermore, California 94550 for the United States Department of Energy under Contract DE-AC04-76DP00789
I
SAND85- 1251 Unlimited Release
Printed January 1986
Distribution Category UC - 63
The Determination of Optimum Mounting Configurations for Flat-Plate Photovoltaic
Modules Based on a Structured Field Experiment and Simulated Results From
PVFORM, a Photovoltaic System Performance Model
David F. Menicucci Sandia National Laboratories
Albuquerque, NM 87185
Abstract The performance of a photovoltaic (PV) system is affected by its mounting configuration. The optimal configuration is unclear because of lack of experience and data. Sandia National Laboratories, Albuquerque (SNLA), has conducted a controlled field experiment to compare four types of the most common module mountings. The data from the experiment were used to verify the accuracy of PVFORM, a new computer program that simulates P V performance. PVFORM was then used to simulate the performance of identical P V modules on different mounting configurations a t 10 sites throughout the L J S . This report describes the module mounting configurations, the experimental methods used, the specialized statistical techniques used in the analysis, and the final results of the effort. The module mounting configurations are rank ordered a t each site according to their annual and seasonal energy production performance, and each is briefly discussed in terms of its advantages and disadvantages in various applications.
Issued by Sandia National Laboratories, operated for the United States Department of Energy by Sandia Corporation. NOTICE This report was repared as an account of work sponsored by an agency of the United States Eovernment. Neither the United States Govern- ment nor any agency thereof, nor any of their employees, nor any of their contractors, subcontractors, or their emplo ees, makes any warranty, ex- press or implied, or assumes any legal liaxility or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, prod- uct, or process disclosed, or represents that ita use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise, does not necessarily constitute or imply ita endorsement, recommendation, or favoring by the United States Government, any agency thereof or any of their contractors or subcontractors. The views and opinions expressed here- in do not necessarily state or reflect those of the United States Government, any agency thereof or any of their contractors or subcontractors.
Printed in the United States of America Available from National Technical Information Service US. Department of Commerce 5285 Port Royal Road Springfield, VA 22161
NTIS price codes Printed copy: A03. - I”:--..-: - 1
CONTSNTS
I N T R O D U C T I O N
EXPERIMENTAL DESIGd
D A T A C O L L E C T I O N A N D ANALYSIS
DISCUSSION
CONCLUSIONS
REFERENCES
APPENDIX -- P l o t s of M o n t h l y E n e r g y P e r f o r m a n c e
F i g u r e
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2
3
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ILLUSTRATIONS
C o n f i g u r a t i o n T e s t M a t r i x
Modu le E f f i c i e n c y C o m p a r i s o n
A c t u a l a n d P r e d i c t e d d c Power ! Two-Axis T r a c k i n g
PVFORM E n e r g y P r e d i c t i o n s , A l b u q u e r q u e , N M
TABLES
T a b l e
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2
3
R e s u l t s of S t a t i s t i c a l A n a l y s i s o f M e a s u r e d a n d S i m u l a t e d ( i n P a r e n t h e s e s ) F u l l Day T o t a l E n e r g y P r o d u c t i o n
Summary of S i m u l a t e d Modu le M o u n t i n g A n n u a l P e r f o r m a n c e C o m p a r i s o n s a t 1 0 S i t e s i n t h e U.S.
Summary o f S i m u l a t e d Modu le M o u n t i n g S p r i n g P e r f o r m a n c e C o m p a r i s o n s a t 1 0 S i t e s i n t h e U . S .
P a g e
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8 10
1 3 25
2 9
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1 4
1 6
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TABLES ( C o n t i n u e d )
T a b l e P a g e
4 Summary of S i m u l a t e d Module M o u p t i n g Summer
5 Summary o f S i m u l a t e d Module M o u n t i n g F a l l
6 Summary of S i m u l a t e d Module M o u n t i n g W i n t e r
7 Summary o f S i m u l a t e d Module M o u n t i n g C o m p a r i q o n s
P e r f o r m a n c e C o m p a r i s o n s a t 10 S i t e s i n t h e U.S. 20
Performance C o m p a r i s o n s a t 10 S i t e s i n t h e U . S . 2 1
P e r f o r m a n c e C o m p a r i s o n s a t 10 S i t e s i n t h e U . S . 2 2
A n n u a l I n s o l a t i o n A v a i l a b i l i t i e s a t 10 S i t e s i n t h e U.S. - A n n u a l ( kWh/m2 ) 2 3
10
11
8 Summary o f S i m u l a t e d A v a i l a b l e I n s o l a t i o n f o r D i f f e r e n t F l a t - P l a t e T r a c k i n g C o n f i g u r a t i o n s a t 10 S i t e s i n t h e U . S . - S p r i n g (kWh/m2) 2 3
D i f f e r e n t F l a t - P l a t e T r a c k i n g C o n f i g u r a t i o n s a t 10 S i t e s i n t h e U.S. - Summer (kWh/m2) 24
D i f f e r e n t F l a t - P l a t e T r a c k i n g C o n f i g u r a t i o n s a t 10 S i t e s i n t h e U.S. - F a l l (kWh/m2) 2 4
D i f f e r e n t F l a t - P l a t e T r a c k i n g C o n f i g u r a t i o n s a t 10 S i t e s i n t h e U . S . - W i n t e r (kWh/m2)
9 Summary o f S i m u l a t e d A v a i l a b l e I n s o l a t i o n f o r
Summary o f S i m u l a t e d A v a i l a b l e I n s o l a t i o n f o r
Summary o f S i m u l a t e d A v a i l a b l e I n s o l a t i o n f o r
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THE DETERMINATION OF OPTIMUM M O U N T I N G CONFIGURATIONS FOR FLAT-PLATE PHOTOVOLTAIC MODULES
BASED ON A STRUCTURED FIELD EXPERIMENT
A PHOTOVOLTAIC SYSTEM PERFORMANCE MODEL A N D S I M U L A T E D RESULTS FROM PVFORMt
I N T R O D U C T I O N
The m o u n t i n g c o n f i g u r a t i o n o f a PV s y s t e m a f f e c t s i t s p e r f o r -
mance . E x p e r i e n c e w i t h f i e l d e d PV s y s t e m s , f o r e x a m p l e , h a s shown
t h a t t r a c k i n g f l a t - p l a t e s y s t e m s c a n p r o d u c e c o n s i d e r a b l y more e n e r g y
t h a n c a n f i x e d - t i l t a r r a y s . P a s t s t u d i e s h a v e shown t h a t i n some
s o u t h w e s t e r n l o c a t i o n s ( e . g . I A l b u q u e r q u e , N e w M e x i c o ) I a t w o - a x i s
t r a c k i n g s y s t e m may i n t e r c e p t u p t o 30% more e n e r g y t h a n a f i x e d a r r a y
t i l t e d t o w a r d t h e s o u t h a t a n a n g l e e q u a l t o t h e l a t i t u d e o f t h e
l o c a t i o n (1). The a d d i t i o n a l e n e r g y p r o d u c e d b y t h e t r a c k i n g s y s t e m
may o f f s e t t h e i n c r e a s e d cos t o f t h e two-ax i s t r a c k i n g m e c h a n i s m .
S i n c e A l b u q u e r q u e ' s c l imate i s v e r y c o n d u c i v e t o s o l a r a p p l i c a t i o n s ,
t h e s e p o s i t i v e e f f e c t s may n o t b e r e p e a t a b l e i n o t h e r r e g i o n s . A t a n y
s p e c i f i c l o c a t i o n , i t i s n o t e n t i r e l y c l e a r w h i c h c o n f i g u r a t i o n w i l l
y i e l d t h e l o w e s t c o s t / p e r f o r m a n c e r a t i o . F o r example, t w o - a x i s s y s -
t e m s c o s t more t h a n e i t h e r o n e - a x i s o r f i x e d s y s t e m s , b u t t h e y a l s o
p r o d u c e more e n e r g y . The r e l a t i o n s h i p b e t w e e n t w o - a x i s , o n e - a x i s , a n d
f i x e d - t i l t s y s t e m s i s n o t f u l l y known b e c a u s e t o o few o f t h e s e s y s t e m s
h a v e b e e n f i e l d e d t o p r o v i d e a d e q u a t e s t a t i s t i c s c o v e r i n g t h e many
c o m b i n a t i o n s o f m o u n t i n g t y p e , l o c a l w e a t h e r , a n d s y s t e m c o s t . The
l i m i t e d d a t a a v a i l a b l e f r o m o p e r a t i o n a l s y s t e m s , h o w e v e r , s u g g e s t t h a t
t r a c k i n g s y s t e m s a r e p r o d u c i n g more e n e r g y t h a n was p r e d i c t e d . Conse-
q u e n t l y , t h e most c o s t - e f f e c t i v e PV m o d u l e m o u n t i n g c o n f i g u r a t i o n f o r
a n y s p e c i f i c s i t e r e m a i n s unknown.
T h i s u n c e r t a i n t y i s a p r o b l e m f o r a l l PV s y s t e m d e s i g n e r s a n d
g r e a t l y i n c r e a s e s t h e r i s k o f f i e l d i n g a s y s t e m t h a t i s n o t c o s t
7
e f f e c t i v e . A s a c o n t r i b u t i o n t o t h e s o l u t i o n of t h i s problem, S a n d i a N a t i o n a l L a b o r a t o r i e s , A l b u q u e r q u e (SNLA) , a t i t s P h o t o v o l t a i c
Advanced S y s t e m s T e s t F a c i l i t y (PASTF) h a s c o n d u c t e d a c o n t r o l l e d
f i e l d e x p e r i m e n t t h a t compares t h e p e r f o r m a n c e of f o u r commonly u s e d
m o d u l e m o u n t i n g c o n f i g u r a t i o n s :
1. F i x e d f i x e d t i l t toward t h e s o u t h w i t h t h e t i l t a n g l e e q u a l t o t h e l a t i t u d e , a s i s common p rac t i ce i n t h e
PV communi ty 2. Two-Axis t w o - a x i s t r a c k i n g
3 . N S s i n g l e - a x i s t r a c k i n g w i t h t h e a x i s h o r i z o n t a l a n d
o r i e n t e d n o r t h t o s o u t h
4. EW s i n g l e - a x i s t r a c k i n g w i t h t h e a x i s h o r i z o n t a l a n d
o r i e n t e d e a s t t o w e s t .
T h e r e s u l t s o f t h i s e x p e r i m e n t were u s e d t o v e r i f y t h e a c c u r a c y o f
PVFORM, S N L A ' s n e w l y d e v e l o p e d c o m p u t e r s i m u l a t i o n model f o r P V per- f o r m a n c e . PVFORM w a s t h e n u s e d t o e s t ima te t h e p e r f o r m a n c e o f t h e
f o u r m o u n t i n g c o n f i g u r a t i o n s a t e i g h t d i f f e r e n t s i t e s r e p r e s e n t i n g major c l i m a t i c r e g i o n s i n t h e U.S.
EXPERIMENTAL D E S I G N
I d e a l l y r t h e p e r f o r m a n c e of a l l f o u r c o n f i g u r a t i o n s w o u l d be
m e a s u r e d c o n c u r r e n t l y . However , hardware l i m i t a t i o n s a t PASTF a l lowed
c o n c u r r e n t t e s t i n g o f o n l y two c o n f i g u r a t i o n s . S i x c o m p a r i s o n t e s t s
( a l l p o s s i b l e c o m b i n a t i o n s o f t h e f o u r c o n f i g u r a t i o n s t e s t ed t w o a t a t i m e ) were made. F i g u r e 1 o u t l i n e s t h e c o m p a r i s o n m a t r i x . I n e a c h
c o m p a r i s o n t e s t r t w o d i f f e r e n t m o u n t i n g c o n f i g u r a t i o n s w i t h i d e n t i c a l
PV m o d u l e s were tes ted c o n c u r r e n t l y s ide -by- s ide . P e r f o r m a n c e d a t a
were recorded from e a c h m o d u l e e v e r y m i n u t e b e t w e e n t h e h o u r s o f
9:30 am a n d 3 : O O pm. T e s t s were c o n d u c t e d o n c l e a r d a y s t o e l i m i n a t e
b i a s r e s u l t i n g from t h e day-to-day w e a t h e r v a r i a t i o n s . To e l i m i n a t e
b i a s i n t h e p a i r - s e l e c t i o n p r o c e s s r a r andom number t a b l e was u s e d t o d e t e r m i n e t h e o r d e r i n w h i c h each o f t h e c o m p a r i s o n t e s t s was r u n .
A f t e r o n e complete s e t of s i x c o m p a r i s o n tests w a s c o m p l e t e d , a s e c o n d
s e t w a s r u n ( a g a i n i n r andom o r d e r ) t o i n c r e a s e t h e sample s i z e a n d t o
e l i m i n a t e p o s s i b l e b i a s d u e t o s e a s o n a l w e a t h e r c h a n g e s t h a t m i g h t
o c c u r d u r i n g t h e t e s t per iod .
8
CONHGURATlON # 1 2 3 4
1
2
3
4
F i g u r e 1. C o n f i g u r a t i o n T e s t M a t r i x
The s t a t i s t i c a l model u s e d i n t h e a n a l y s i s o f t h e e x p e r i m e n t a l
d a t a w a s
x ( i r j ) = XBAR + D ( i ) + C ( J ) + E R R ( i r j )
w h e r e
x ( i I j ) is t h e mean e n e r g y p e f o r m a n c e f o r t h e i t h system i n t h e j t h c o n f i g u r a t i o n ,
XBAR i s t h e g r a n d m e a n r
D ( i ) i s t h e d a y e f f e c t f o r t h e i t h s y s t e m r
C( j ) i s t h e c o n f i g u r a t i o n e f f e c t f o r t h e j t h c o n f i g u r a t i o n r
E R R ( i r j ) is a r a n d o m e r r o r ,
i=l t o 1 2 p a i r s ( 6 p a i r s repea ted t w i c e ) ,
j=1 t o 4 c o n f i g u r a t i o n s .
A p p l i c a t i o n o f t h i s s t a t i s t i c a l model made it p o s s i b l e t o es t imate t h e
c o n f i g u r a t i o n e f f e c t s a n d t h e d a y e f f e c t s , t o r a n k t h e s e e f f e c t s r a n d
t o a s s e s s t h e s t a t i s t i c a l d i f f e r e n c e b e t w e e n them. A s a r e s u l t r e a c h c o n f i g u r a t i o n c o u l d be r a n k o r d e r e d w i t h r e s p e c t t o e n e r g y p e r f o r -
mance . F o l l o w i n g t h e s t a t i s t i c a l a n a l y s i s r t h e PVFORM c o m p u t e r s imu-
l a t i o n mode l w a s v e r i f i e d b y c o m p a r i n g i t s p r e d i c t i o n s w i t h t h e t e s t
9
r e s u l t s . PVFORM was t h e n used t o e s t ima te a n n u a l e n e r g y a t a number o f d i f f e r e n t s i t e s i n t h e U.S.
DATA C O L L E C T I O N A N D A N A L Y S I S
A t t h e h e a r t of t h i s e x p e r i m e n t w a s t h e c o m p a r i s o n of t h e pe r fo r -
mance o f t w o i n d i v i d u a l PV m o d u l e s m o u n t e d i n d i f f e r e n t c o n f i g u r a - t i o n s . Of p r i m a r y i m p o r t a n c e w a s t h e s e l e c t i o n o f two m o d u l e s whose
p e r f o r m a n c e c h a r a c t e r i s t i c s were a s s i m i l a r a s p o s s i b l e w i t h i n t h e r a n g e of e n 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 m i g h t be e n c o u n t e r e d d u r i n g t h e
c o m p a r i s o n r u n s . F o r t h i s r e a s o n r g r e a t ca re was t a k e n i n t h e se lec-
t i o n of t h e t w o m o d u l e s t o be u s e d i n t h e e x p e r i m e n t . M o d u l e s t h a t
appeared t o h a v e s i m i l a r p e r f o r m a n c e c h a r a c t e r i s t i c s were s e l e c t e d
f r o m a f i e l d e d a r r a y o n t h e b a s i s of m e a s u r e m e n t s o f s h o r t c i r c u i t
c u r r e n t a n d o p e n c i r c u i t v o l t a g e . The m o d u l e s were t h e n m o u n t e d o n
s e p a r a t e t w o - a x i s t r a c k i n g s y s t e m s a t t h e S N L A PASTFr w h e r e t h e i r
p e r f o r m a n c e c h a r a c t e r i s t i c s were m e a s u r e d . The p e r f o r m a n c e o f e a c h
m o d u l e w a s recorded e v e r y m i n u t e . P o w e r r p l a n e o f a r r a y i n s o l a t i o n r
m o d u l e t e m p e r a t u r e r a n d t h e a m b i e n t w e a t h e r c o n d i t i o n s were r e c o r d e d .
T h e s e tes ts r a n g e d f r o m 1 t o 3 d a y s a n d were c o n d u c t e d u n d e r c lear s k y
c o n d i t i o n s .
The e n e r g y e f f i c i e n c y of b o t h m o d u l e s w a s c o m p u t e d a n d t h e e f f i -
c i e n c y d i f f e r e n c e s f o r e a c h m i n u t e o f t h e t e s t were t h e n p l o t t e d i n
h i s t o g r a m form t o d e t e r m i n e i f t h e d a t a d i s t r i b u t i o n s were n o r m a l .
T h i s s t e p was i m p o r t a n t b e c a u s e t h e s u b s e q u e n t s t a t i s t i c a l t e s t s a s s u m e d t h e d i f f e r e n c e s were n o r m a l l y d i s t r i b u t e d a b o u t a z e r o mean.
I f t h e d a t a d i s t r i b u t i o n s were n o t n o r m a l r t h e s i g n i f i c a n c e l e v e l o f
t h e t e s t r e s u l t s w o u l d be unknown. I n e v e r y t e s t r t h e d a t a a p p e a r e d
t o b e n o r m a l l y d i s t r i b u t e d .
S t a n d a r d t t e s t s were a p p l i e d t o t h e s e d a t a t o t e s t t h e n u l l h y p o t h e s i s t h a t t h e p e r f o r m a n c e d i f f e r e n c e s w e r e e q u a l t o z e r o . I f
t h e s t a t i s t i c a l t e s t s r e p e a t e d l y i n d i c a t e d t h a t t h e d i f f e r e n c e s were
s i g n i f i c a n t l y d i f f e r e n t f r o m z e r o r a n o t h e r s e t of m o d u l e s was se-
l e c t e d r a n d t h e s t a t i s t i c a l t e s t s r e p e a t e d . F o u r d i f f e r e n t m o d u l e s
were t e s t ed o v e r s e v e r a l w e e k s u n t i l t w o m o d u l e s were f o u n d whose
10
p e r f o r m a n c e m e a s u r e s were s u f f i c i e n t l y c l o s e so t h a t t h e n u l l h y p o t h e -
s is c o u l d n o t be r e j ec t ed a t t h e 5% l e v e l o f s i g n i f i c a n c e . T h e s e t w o
m o d u l e s were t e s t e d f o r 2 w e e k s u n d e r v a r i o u s w e a t h e r c o n d i t i o n s t o e n s u r e t h a t t h e i r p e r f o r m a n c e i n d i f f e r i n g e n v i r o n m e n t a l c o n d i t i o n s were s i m i l a r . All o f t h e 1-day t e s t s i n d i c a t e d no s t a t i s t i c a l l y
s i g n i f i c a n t d i f f e r e n c e s b e t w e e n t h e m o d u l e s . F i g u r e 2 i s a t y p i c a l t i m e p l o t of t h e d i f f e r e n c e i n e f f i c i e n c i e s b e t w e e n t h e t w o m o d u l e s .
As c a n be s e e n , t h e a v e r a g e d i f f e r e n c e i n e f f i c i e n c y i s a b o u t e q u a l t o
z e r o l a n d t h e d a t a appear t o be n o r m a l l y d i s t r i b u t e d . The m i s s i n 9
values a r e d u e t o i n s t r u m e n t f a i l u r e s . The t v a l u e c o m p u t e d f o r t h e
s e t of d i f f e r e n c e s o n t h i s d a y i s 0.5839! w e l l b e l o w t h e t a b l e d v a l u e
of 1.96 ( 2 - t a i l e d t e s t for g r e a t e r t h a n 1 2 0 o b s e r v a t i o n s a t t h e 5% l e v e l of s i g n i f i c a n c e ) . Thus ! t h e n u l l h y p o t h e s i s t h a t t h e mean d i f -
f e r e n c e b e t w e e n t h e e f f i c i e n c i e s o f t h e two m o d u l e s is z e r o c a x n o t b e
r e j ec t ed ! a n d t h e m o d u l e s a r e a s s u m e d t o h a v e n e a r l y i d e n t i c a l p e r f o r -
c h a r a c t e r i s t i c s .
0.6
TIME OF DAY (HOURS)
F i g u r e 2. Module E f f i c i e n c y C o m p a r i s o n
The c o n f i g u r a t i o n t e s t s b e g a n w i t h t h e r andom s e l e c t i o n o f a p a i r o f c o n f i g u r a t i o n s f o r t e s t i n g . The f i r s t t e s t i n v o l v e d a f i x e d - t i l t
s y s t e m m e a s u r e d a g a i n s t a t w o - a x i s t r a c k i n g s y s t e m . The t e s t o f t h e s e
two m o u n t i n g c o n f i g u r a t i o n s was r e p e a t e d f o r a s u f f i c i e n t number o f
d a y s t o e n s u r e t h a t s u f f i c i e n t d a t a were recorded u n d e r r e l a t i v e l y
c l e a r s k y c o n d i t i o n s . The m o d u l e s were t h e n r e m o u n t e d i n d i f f e r e n t
c o n f i g u r a t i o n s , a s o u t l i n e d i n t h e e x p e r i m e n t a l p l a n , a n d t h e d a t a
c o l l e c t i o n p r o c e s s was r e p e a t e d . A f t e r a l l 6 c o n f i g u r a t i o n c o m p a r i -
s o n s were t e s t e d , t h e e n t i r e p r o c e d u r e w a s r e p e a t e d , r e s u l t i n g i n a s e c o n d s e t o f d a t a f o r e a c h c o n f i g u r a t i o n c o m p a r i s o n a n d a t o t a l o f 1 2
sets of c o m p a r i s o n d a t a a v a i l a b l e f o r a n a l y s i s . The d a t a were s t o r e d
o n t h e S N L A m a i n f r a m e c o m p u t e r s t o r a g e s y s t e m . ( A c c i d e n t a l loss o f t w o o f t h e d a t a s e t s , d u e t o c o m p u t e r h a r d w a r e f a i l u r e , w a s c o n s i d e r e d
i n s i g n i f i c a n t a s b o t h se t s were g e n e r a t e d d u r i n g t h e r e p e a t e d p o r t i o n
o f t h e t e s t i n g . M o r e o v e r , a l l t h e c o n f i g u r a t i o n c o m p a r i s o n s were
r e p r e s e n t e d a t l e a s t o n c e , a n d f o u r o f them were r e p r e s e n t e d twice . )
D u r i n g t h e c o n f i g u r a t i o n c o m p a r i s o n t e s t s , d a t a were recorded
e a c h m i n u t e . The t o t a l e n e r g y d e r i v e d f r o m a g i v e n c o n f i g u r a t i o n was c a l c u l a t e d from t h e m i n u t e - b y - m i n u t e power m e a s u r e m e n t s t a k e n d u r i n g
t h e t e s t . A l l t e s t s were r u n f rom 9:30 a m u n t i l 3 : O O pm a n d , t h e r e -
f o r e l t h e e n e r g y t o t a l s f r o m e a c h c o n f i g u r a t i o n were d i r e c t l y compar-
a b l e a n d were u s e d t o a s s e s s o v e r a l l d a i l y p e r f o r m a n c e o f e a c h m o d u l e
m o u n t i n g c o n f i g u r a t i o n . T h e s e f u l l - d a y e n e r g y t o t a l s were i n p u t t o
t h e s t a t i s t i c a l model. From t h i s a n a l y s i s , a r a n k o r d e r i n g o f t h e
r e l a t i v e p e r f o r m a n c e o f e a c h c o n f i g u r a t i o n w a s made ( T a b l e 1 ) . I n
Table 1 t h e " l e a s t s q u a r e mean" i s a d i m e n s i o n l e s s e s t i m a t o r o f t h e
r e l a t i v e e n e r g y p e r f o r m a n c e a d j u s t e d f o r w e a t h e r d i f f e r e n c e s o n t h e
d i f f e r e n t t e s t d a y s . The "P v a l u e " i s t h e p r o b a b i l i t y o f a n e r r o r i n
j u d g e m e n t i f i t i s d e c i d e d t h a t a n y two c o n f i g u r a t i o n s d i d n o t p e r f o r m
e q u a l l y . F o r e x a m p l e , t h e P v a l u e o f 0.0145 i n t h e t a b l e i s u s e d t o compare t h e p e r f o r m a n c e o f a t w o - a x i s t r a c k i n g c o n f i g u r a t i o n w i t h a n EW c o n f i g u r a t i o n . I n t h i s c a s e , t h e p r o b a b i l i t y i s 1.45% t h a t a n
e r r o r i n j u d g e m e n t wou ld b e made i f i t i s a s s u m e d t h a t t h e t w o s y s t e m s
p r o d u c e d d i f f e r e n t a m o u n t s o f e n e r g y . The v e r y s m a l l P v a l u e s s u p p o r t
t h e a s s u m p t i o n t h a t t h e p e r f o r m a n c e l e v e l s o f t h e f o u r c o n f i g u r a t i o n s
a r e s i g n i f i c a n t l y d i f f e r e n t a t t h i s p a r t i c u l a r t i m e of t h e y e a r .
12
T a b l e 1
R e s u l t s of S t a t i s t i c a l A n a l y s i s of Measured a n d S i m u l a t e d ( i n P a r e n t h e s e s )
F u l l Day T o t a l E n e r g y P r o d u c t i o n
Rank M o u n t i n g L e a s t S q u a r e P V a l u e s O r d e r C o n f i g u r a t i o n Mean EW N S F i x e d
1 T w o - A x i s 35.38 .0145 .0007 .OOOl (35.34) ( . 0 0 7 8 ) ( . 0 0 0 7 ) ( .0001)
2 EW
3 N S
4 F i x e d
32.61 -- .0481 . O O O l (32 .26) ( . 0443) ( .0001)
-- . O O O l 30.24 -- (30.30) ( . O O O l )
22.55 (22 .82 )
The t e s t s were c o n d u c t e d i n l a t e f a l l , a time when t h e s o l a r c o n d i t i o n s a r e s i m i l a r t o t h o s e i n t h e s p r i n g . B u t b e c a u s e c o n d i t i o n s
i n l a t e f a l l a r e n o t s i m i l a r t o t h o s e i n summer o r w i n t e r r c o n c l u s i o n s a b o u t t h e r e l a t i v e p e r f o r m a n c e of e a c h m o u n t i n g c o n f i g u r a t i o n may b e
a p p l i c a b l e o n l y f o r t h e f a l l a n d s p r i n g p o r t i o n s o f t h e y e a r . F o r
r e l i a b l e c o n c l u s i o n s a b o u t t h e a n n u a l p e r f o r m a n c e o f t h e f o u r m o u n t i n g
c o n f i g u r a t i o n s , t h e e x p e r i m e n t s h o u l d be r e p e a t e d d u r i n g summer a n d
w i n t e r c o n d i t i o n s . T i m e a n d m o n e t a r y c o n s i d e r a t i o n s , h o w e v e r r make
t h i s o p t i o n imprac t i ca l . A s a r e a s o n a b l e a l t e r n a t i v e t o a d d i t i o n a l
f i e l d t e s t i n g r t h e d a t a f r o m t h i s e x p e r i m e n t were u s e d t o v e r i f y t h e
a c c u r a c y o f PVFORM, w h i c h w a s t h e n u s e d t o s i m u l a t e t h e c o m p a r i s o n
t e s t s f o r a full y e a r . PVFORM was t h e n u s e d t o s i m u l a t e t h e compari-
s o n tests i n v a r i o u s c l i m a t i c r e g i o n s t h r o u g h o u t t h e c o u n t r y . U s i n g
t h i s a p p r o a c h r c o n c l u s i o n s were d r a w n a b o u t t h e r e l a t i v e p e r f o r m a n c e
o f e a c h of t h e f o u r m o u n t i n g c o n f i g u r a t i o n s f o r w i d e s p r e a d g e o g r a p h -
i c a l r e g i o n s .
D I S C U S S ION
PVFORM ( 2 ) w a s d e v e l o p e d a t S N L A a n d r e p r e s e n t s t h e b e s t a v a i l -
a b l e a p p r o a c h e s t o m o d e l l i n g PV p e r f o r m a n c e . T h i s code i n c o r p o r a t e s
1 3
t h e u s e of t h e a n i s o t r o p i c d i f f u s e s o l a r r a d i a t i o n model d e v e l o p e d by P e r e z ( 3 ) a n d a t h e r m a l p e r f o r m a n c e model d e v e l o p e d by F u e n t e s ( 4 ) .
The P e r e z model is u s e d t o es t imate t o t a l s o l a r r a d i a t i o n o n t i l t e d
s u r f a c e s based on m e a s u r e m e n t s o f t o t a l h o r i z o n t a l a n d d i r e c t n o r m a l
r a d i a t i o n . So lar E n e r g y R e s e a r c h I n s t i t u t e t e s t ed t h e P e r e z m o d e l a t
v a r i o u s l o c a t i o n s t h r o u g h o u t t h e c o u n t r y a n d f o u n d i t t o be a c c u r a t e
t o w i t h i n a b o u t 4% ( 5 ) . The t h e r m a l modelr t e s t ed i n s e v e r a l o f
SNLA’s PV f i e l d t e s t s i t e s r i s g e n e r a l l y a c c u r a t e t o w i t h i n a b o u t 3%.
T h e s e two models p r o v i d e t h e b a s i s f o r PVFORM’s p r e d i c t i o n s r w h i c h a r e
u s u a l l y a c c u r a t e i n r a n g e s b e t w e e n 2 % a n d 5 % . F i g u r e 3 s h o w s a n
e x a m p l e of t h e a c c u r a c y of t h i s model.
26 -
20
B 0
0
.
ACTUAL
TIME OF DAY (HOURS)
F i g u r e 3 . A c t u a l a n d P r e d i c t e d dc P o w e r r Two-Axis T r a c k i n g
PVFORM w a s v e r i f i e d b y u s i n g t h e i n s o l a t i o n a n d w e a t h e r d a t a r m e a s u r e d d u r i n g t h e t e s t , a s i n p u t d a t a . The m o d u l e n o m i n a l o p e r a t i n g
c e l l t e m p e r a t u r e ( N O C T ) I a m o d u l e t e m p e r a t u r e a n d a s s o c i a t e d e f f i -
c i e n c y / a n d power d e g r a d a t i o n c o e f f i c i e n t were a l s o s u p p l i e d a s i n p u t
14
parameters. The e n e r g y o u t p u t c a l c u l a t e d by PVFORM was t h e n c o m p a r e d
t o t h e o u t p u t m e a s u r e d d u r i n g t h e t e s t ! a n d t h e same s t a t i s t i c a l
a n a l y s i s w a s a p p l i e d . If t h e model i s a c c u r a t e ! t h e s i m u l a t e d e n e r g y
t o t a l s w i l l be a b o u t e q u a l t o t h e m e a s u r e d t o t a l s r a n d t h e s t a t i s t i c a l
a n a l y s i s o f t h e s i m u l a t e d d a t a w i l l y i e l d t h e same r e s u l t s a s t h e
s t a t i s t i c a l a n a l y s i s a p p l i e d t o t h e m e a s u r e d d a t a . T h i s i s a p o w e r f u l
t e s t f o r a c c u r a c y b e c a u s e i t m e a s u r e s t h e d i f f e r e n c e b e t w e e n t h e
f u n d a m e n t a l c o n c l u s i o n s d r a w n from a n a n a l y s i s o f t h e s i m u l a t e d d a t a
v e r s u s t h e c o n c l u s i o n s d r a w n from t h e m e a s u r e d d a t a . The PVFORM m o d e l
w a s u s e d t o s i m u l a t e t h e r e s u l t s o f e a c h c o n f i g u r a t i o n c o m p a r i s o n
t e s t . The a m b i e n t w e a t h e r c o n d i t i o n s r e c o r d e d d u r i n g t h e tests were
s u p p l i e d t o t h e PVFORM model a s i n p u t parameters . The mode l w a s r u n
a n d p r o d u c e d a n es t imated power f o r e a c h t i m e p e r i o d i n w h i c h p o w e r
w a s e x p e r i m e n t a l l y m e a s u r e d . The v a l u e s were t h e n u s e d t o c o m p u t e
e n e r g y t o t a l s o v e r t h e p e r i o d 9:30 am t o 3 : O O pm. A n a l y s i s o f v a r i -
a n c e w a s a p p l i e d t o t h e da t a t o t a l s , a n d t h e r e s u l t s a r e shown ( i n p a r e n t h e s e s ) i n Table 1. A s shown i n T a b l e l r t h e d i f f e r e n c e s b e t w e e n
t h e m e a s u r e d f u l l d a y e n e r g y t o t a l s a n d t h e s i m u l a t e d t o t a l s a r e v e r y
s m a l l r a n d t h e r a n k o r d e r i n g s o f t h e c o n f i g u r a t i o n s a r e i d e n t i c a l .
Based o n t h i s e v i d e n c e , t h e PVFORM model w a s c o n s i d e r e d t o be a p p l i c a -
b l e f o r s i m u l a t i n g t h e c o n f i g u r a t i o n c o m p a r i s o n e x p e r i m e n t i n d i f f e r -
e n t e n v i r o n m e n t a l c o n d i t i o n s .
T h e PVFORM model w a s u s e d t o perform a 1-year s i m u l a t i o n o f e a c h
of t h e f o u r PV m o d u l e c o n f i g u r a t i o n s i n t h e A l b u q u e r q u e a r ea . W e a t h e r
d a t a f o r t h e s i m u l a t i o n were t a k e n from t h e A l b u q u e r q u e T y p i c a l Mete-
o r o l o g i c a l Year ( T M Y ) data s e t . The m o d u l e c h a r a c t e r i s t i c s u s e d i n
t h e model v e r i f i c a t i o n t e s t ( a u t u m n d a t a o n l y ) were a l s o a p p l i e d f o r
t h e s e r u n s . P l o t t e d r e s u l t s o f t h e s i m u l a t i o n a r e shown i n F i g u r e 4.
A s e x p e c t e d ! t h e p r e d i c t e d r a n k o r d e r i n g of t h e m o u n t i n g c o n f i g u r a -
t i o n s i n m i d - O c t o b e r i s c o n s i s t e n t w i t h t h e r e s u l t s o f t h e e x p e r i -
m e n t a l m e a s u r e m e n t s performed a t S N L A a t t h e same t i m e o f y e a r . T h i s
r e s u l t l e n d s f u r t h e r c r e d e n c e t o t h e v a l i d i t y of u s i n g t h e PVFORM
model a s a tool t o s i m u l a t e th .e p e r f o r m a n c e of PV m o d u l e s i n d i f f e r e n t
m o u n t i n g c o n f i g u r a t i o n s .
I
JAN FEB MAR APR MAY JUN JUL AUG SEP o(=T NOV DEC
F i g u r e 4. PVFORM E n e r g y P r e d i c t i o n s , A l b u q u e r q u e , NM
P r e v i o u s s t u d i e s based o n i s o t r o p i c d i f f u s e i n s o l a t i o n models
h a v e shown t h a t , i n s o u t h w e s t e r n c l imates , a t w o - a x i s t r a c k i n g sys tem
w i l l i n t e r c e p t a b o u t 30% more i n s o l a t i o n t h a n a f i x e d - t i l t system (1) .
I f PV p e r f o r m a n c e i s a s s u m e d t o be d i r e c t l y p r o p o r t i o n a l t o i n s o l a t i o n
a v a i l a b i l i t y , i t c a n be c o n c l u d e d t h a t e n e r g y p r o d u c t i o n f o r a t w o -
a x i s s y s t e m w i l l be 30% g r e a t e r t h a n f o r a f i x e d - t i l t s y s t e m . How-
e v e r , f i e l d o b s e r v a t i o n s by SNLA a n d o t h e r s h a v e shown t h a t t h e a c t u a l
e n e r g y i n c r e a s e i s b e t w e e n 33% a n d 41% (5 ,6) . N o e s t ima tes o f i n -
creased e n e r g y p r o d u c t i o n from o t h e r t r a c k i n g s c h e m e s h a v e b e e n d o c u -
m e n t e d . The s i m u l a t e d a n n u a l PV p e r f o r m a n c e u s i n g t h e PVFORM model
s h o w s a n i n c r e a s e o f 37% i n a v a i l a b l e i n s o l a t i o n f o r a t w o - a x i s t r a c k - i n g s c h e m e v e r s u s a f i x e d - t i l t s y s t e m , b u t o n l y a 34% i n c r e a s e i n
e n e r g y p r o d u c t i o n . The d i f f e r e n c e b e t w e e n 3 4 % a n d 37% is d u e t o i n c r e a s e d m o d u l e o p e r a t i n g t e m p e r a t u r e o f t h e t w o - a x i s t r a c k i n g c o n -
f i g u r a t i o n i n t h e S N L A t e s t s . I n t h e s e t e s t s , a l l of t h e m o d u l e s w e r e
16
m o u n t e d a t t h e same h e i g h t above t h e g r o u n d f o r b o t h t r a c k i n g and f i x e d - t i l t c o n f i g u r a t i o n s . T h u s , t h e n a t u r a l c o o l i n g e f f e c t s o f t h e
w i n d a r o u n d t h e modules i s e q u a l l y a p p l i e d r e g a r d l e s s o f how t h e
m o d u l e is m o u n t e d . T h e r e f o r e , t h e i n c r e a s e i n t e m p e r a t u r e was d u e t i n
l a r g e p a r t , t o t h e i n c r e a s e d i n s o l a t i o n o n t h e m o d u l e s u r f a c e . T h i s
may n o t be obse rved i n f i e l d e d a r r a y s t h a t a r e o f t e n m o u n t e d on r a c k s
near t h e g r o u n d a n d c a n o p e r a t e a t a h i g h e r t s m p e r a t u r e t h a n m o d u l e s m o u n t e d o n t r a c k i n g p e d e s t a l s . The s i g n i f i c a n c e o f t h i s i s t h a t t h e
PVFORM es t ima tes of i n c r e a s e d i n s o l a t i o n a v a i l a b i l i t y o n t h e f i x e d
t i l t a n d t w o - a x i s s u r f a c e s a r e a b o u t e q u a l t o f i e l d m e a s u r e d v a l u e s , a n d t h e model c a n b e u s e d t o p r o d u c e r e a s o n a b l y a c c u r a t e PV p e r f o r -
mance s i m u l a t i o n s .
PVFORM w a s a l s o u s e d t o p e r f o r m s i m u l a t i o n s f o r n i n e o t h e r s i tes
i n t h e U.S.: B o s t o n , M A ; C h a r l e s t o n , S C ; D a l l a s , TX: E l y , N V ; F r e s n o ,
C A ; H o n o l u l u , H I ; M a d i s o n , W I ; Omaha, N E ; a n d S a n t a Maria, CA. Each
s i t e r e p r e s e n t s a d i f f e r e n t c l i m a t i c r e g i o n w i t h i n t h e U.S. T a b l e 2
s h o w s t h e a n n u a l p e r f o r m a n c e o f t h e f o u r c o n f i g u r a t i o n s a n d t h e i r r a n k
o r d e r a t e a c h s i t e . The " a n n u a l e n e r g y p r o d u c t i o n " i s t h e t o t a l
e n e r g y p r o d u c e d by a m o d u l e w i t h a n o v e r a l l e f f i c i e n c y o f 10 .6% a t a
c e l l t e m p e r a t u r e of 28°C a n d a n o m i n a l o p e r a t i n g c e l l t e m p e r a t u r e o f
46°C . The p e r c e n t d i f f e r e n c e s i n t h e r e l a t i v e p r o d u c t i o n a r e a l s o
l i s t e d i n t h e t a b l e . F o r example, t h e i n f o r m a t i o n i n t h e t a b l e i n d i -
c a t e s t h a t a t w o - a x i s t r a c k i n g PV s y s t e m i n A l b u q u e r q u e w i l l p r o d u c e
a b o u t 34.4% more e n e r g y t h a n a f i x e d f l a t - p l a t e s y s t e m t i l t e d toward
t h e s o u t h a t a n a n g l e e q u a l t o t h e l a t i t u d e . T a b l e s 3 t h r o u g h 6 con-
t a i n t h e s i m u l a t e d s e a s o n a l p e r f o r m a n c e r e s u l t s f o r e a c h c o n f i g u r a t i o n
a t e a c h of t h e 10 s i t e s . The s e a s o n s o f t h e y e a r a r e r e p r e s e n t e d by
t h e f o l l o w i n g m o n t h s : w i n t e r - - D e c , J a n , F e b ; s p r i n g - - M a r , Apr, May;
summer--Juri, J u l , Aug; f a l l - - S e p r O c t , Nov. S i m u l a t e d i n s o l a t i o n
a v a i l a b i l i t i e s f o r e a c h of t h e s i t e s a r e l i s t e d i n T a b l e s 7 t h r o u g h 11. The s e a s o n a l v a l u e s o f t o t a l e n e r g y p r o d u c t i o n a n d i n s o l a t i o n
a v a i l a b i l i t y c a n be c o n v e r t e d t o a v e r a g e d a i l y v a l u e s b y d i v i d i n g t h e
t a b l e d v a l u e s b y t h e f o l l o w i n g t o t a l number o f d a y s : w i n t e r - 90,
s p r i n g - 92, summer - 92, f a l l - 91. A p p e n d i x 1 c o n t a i n s p l o t s o f t h e
m o n t h l y e n e r g y p e r f o r m a n c e f o r e a c h m o d u l e m o u n t i n g c o n f i g u r a t i o n i n
each o f t h e 1 0 TMY t e s t s i t e s .
1 7
T a b l e 2
Summary o f S i m u l a t e d Module Mount ing Annual P e r f o r m a n c e C o m p a r i s o n s a t 1 0 S i t e s i n t h e U.S.
Site
A1 buquerque, NM
Boston, MA
Charleston, SC
Dallas, TX
Fresno, CA
Honolulu, HI
Madison, WI
Omaha, NE
Santa Maria. CA
Mount i pg Conf iu.
Two -Axis NS EW Fixed
Two - Ax i s NS EW Fixed
Two- Axi s NS EW Fixed
Two- Axi s NS EW Fixed
Two-Axis NS EW Fixed
Two-Axis NS EW Fixed
Two-Ax i s NS EW Fixed
Two- Axis NS EW Fixed
Two-Axis NS EW Fixed
Two-Axi s NS EW Fixed
Energy Production % Difference (kWh/ml) NS EW Fixed
346.2 306.9 275.6 257.6
207.5 180 .8 169 .9 160.7
226.3 202.6 1 9 0 . 1 180.9
262.8 236.4 2 1 3 . 1 200.4
338.5 295.7 266.4 249.9
306 .5 276.9 242.5 2 2 7 . 1
263.9 246.7 217.7 205.2
225.9 195 .3 185.6 176.4
262.5 227.5 211.4 198 .4
287 .2 256.3 2 3 6 . 1 223.0
12.8
14.8
11 .7
11.2
14.5
10.7
6.9
15.7
15.4
1 2 . 0
25 .6 11.4
2 2 . 1 6.4
1 9 . 0 6 .6
23.3 10.9
2 7 . 1 11.0
26.4 14.2
21.2 13.4
21 .7 5.2
24.2 7.6
21 .6 8 . 6
34.4 1 9 . 2
7 .0
2 9 . 1 12.5
5.7
2 5 . 1 1 2 . 0
5 . 1
31.2 1 8 . 0
6.4
35.4 18 .3
6 . 6
35.0 21.9
6 .8
28.6 20.2
6 . 1
28 .0 10.7
5.2
32.4 14.7
6 .6
28.8 1 4 . 9
5.9
18
T a b l e 3
Summary o f S i m u l a t e d Module Moun t ing S p r i n g P e r f o r m a n c e C o m p a r i s o n s a t 1 0 S i t e s i n t h e U.S.
Rank Order
1 2 3 4
Mounting Conf iq.
Two- Axis NS EW Fixed
% Difference NS EW Fixed
6.0 30.5 35.6 23.1 27.9
3.9
Energy Produc- tion (kWh/ma)
97.4
74.6 91.8
71.8
- Site
Albuquerque, NM
Boston, MA Two- Ax i s NS EW Fixed
Two-Axis NS EW Fixed
Two-Axis NS EW Fixed
Two- Ax i s NS EW Fixed
Two -Ax i s NS EW Fixed
Two -Axis NS EW Fixed
Two-Axi s NS EW Fixed
Two-Axis NS EW Fixed
58.7 54.2 46.9 45.4
8.4 25.1 29.4 15.4 19.4
3.4
Charleston, SC 66.5 63.1 54.2 52.9
5.3 22.7 25.6 16.5 19.3
2.4
Dallas, TX 68.1 64.4 54.2 52.7
5.7 25.6 29.3 18.9 22.3
2.9
Ely. NV 94.9 88.3 71.1 68.3
7.5 33.5 39.0 24.2 29.3
4.1
Fresno, CA 89.8 84.8 68.7 65.9
6.0 30.8 36.3 23.5 28.6
4.2
Honolulu, HI 68.4 66.8 55.7 54.1
2.3 22.6 26.3 19.9 23.5
3.0
Madison, WI 66.7 60.6 52.9 51.4
10.0 25.8 29.8 14.4 18.0
3.2
Omaha, NE 71.2 65.6 55.8 53.7
8.4 27.5 32.5 17.6 22.1
3.9
Santa Maria. CA Two-Axis NS EW Fixed
77.8 73.4
6.0 24.9 28.2 17.9 21.0
2.6 62.3 60.7
1 9
T a b l e 4
Summary of S i m u l a t e d Module Mounting Summer Performance Comparisons a t 10 S i t e s i n t h e U . S .
Site Albuquerque, NU
Boston. MA
Charleston, SC
Dallas, TX
Ely. NV
Fresno, CA
Honolulu, HI
Mad i son, W I
Omaha, NE
Santa Maria. CA
Mounting Conf ia.
TWO- AXi S NS EW F i x e d
Two-Axis NS EW F i x e d
Two-Axis NS EW F i x e d
n o - Axi s NS EW F i x e d
~ w o -Ax i s NS EW F i x e d
Two- Axi s NS EW F i x e d
Two- Axi s NS EW F i x e d
Two- Axi s NS EW F i x e d
Two -Ax i s NS EW F i x e d
Two -Axis NS EW F i x e d
Rank Order
1 2 3 4
1 2 3 4
1 2 3 4
1 2 3 4
1 2 3 4
1 2 3 4
1 2 3 4
1 2 3 4
1 2 3 4
1 2 3 4
Energy Produc- a Difference tion (kWh/mZ) NS EW Fixed
96.1 93.8 74.2 67.1
67.9 65.6 53.8 49.6
61.2 60.1 50.4 47.4
82.0 80.5 64.0 58.5
98.6 95.7 75.4 68.8
102.3 99.7 77.3 69.2
75.6 74.6 60.7 56.0
73.1 70.3 58.0 53.9
83.1 80.4 63.9 58.2
90.9 88.8 72.3 66.6
2 . 4 2 9 . 4 2 6 . 4
3.6 26.4 21.9
1.7 21.3 19.2
1.9 28.1 25.7
3.0 30.8 27.0
2.5 32.3 29.1
1.3 24.5 22.9
4.0 25.9 21.1
3.4 30.1 25.8
2.3 25.7 22.8
43.1 39.9 10.6
37.1 32.3 8.5
29.2 26.9 6.5
40.2 37.6 9.4
43.4 39.2 9.6
47.9 44.2 11.7
34.9 33.2 8.4
35.4 30.2 7.6
42.8 38.2 9.8
36.4 33.3 8.5
20
T a b l e 5
Summary of S i m u l a t e d Module Mount ing F a l l P e r f o r m a n c e C o m p a r i s o n s a t 1 0 S i t e s i n t h e U.S.
- Site
Albuquerque, NM
Boston, MA
Charleston, SC
Dallas, TX
Ely. W
Fresno, CA
Honolulu, HI
Madison, WI
Omaha, NE
Santa Maria, CA
Mounting Conf ia.
TWO- Axis NS EW Fixed
Two-Axis NS EW Fixed
Two- Axi s NS EW Fixed
Two -Ax i s NS EW Fixed
Two- Axi s NS EW Fixed
Two- Axi s NS EW F i x e d
Two -Ax i s NS EW Fixed
Two- Axis NS EW F i x e d
Two-Axis NS EW Fixed
Two-Axis NS EW Fixed
Rank order
1 2 3 4
1 3 2 4
1 3 2 4
1 2 3 4
1 2 3 4
1 2 3 4
1 2 3 4
1 4 2 3
1 3 2 4
1 2 3 4
Energy Produc- a Difference tion (kWh/mz) NS EW Fixed
81.8 68.7 66.1 63.6
47.0 38.0 38.9 37.8
54.7 46.1 46.6 44.8
63.3 54.1 51.8 49.8
81.7 67.1 65.0 62.7
72.7 61.0 59.5 57.6
64.3 58.6 52.9 50.9
47.9 38.5 40.4 39.2
57.6 46.3 47.4 45.7
65.8 55.2 55.2 53.2
19.1
23.7
18.6
17.0
21.8
19.2
9.7
24.6
24.5
19.4
23.7 3.9
20.7 2.5
17.5 0.9
22.3 4.5
25.7 3.2
22.3 2.6
21.5 10.8
18.9 4.8
21.6 2.4
19.4 0.0
28.7 8.0 4.0
24.3 0.4 2.9
22.2 3.0 4.0
27.1 8.6 3.9
30.5 7.1 3.8
26.3 5.9 3.2
26.3 15.2 4.0
22.3 1.9 2.9
26.1 1.3 3.6
23.8 3.7 3.7
Tab le 6
Summary of S i m u l a t e d Module Mount ing W i n t e r P e r f o r m a n c e C o m p a r i s o n s a t 1 0 S i t e s i n the U . S .
Site Albuquerque, NM
Boston, MA
Charleston, SC
Dallas, TX
Ely. NV
Fresno, CA
Honolulu, HI
Madison, WI
Omaha, NE
Santa Maria, CA
Mounting Conf ig . Two-Axis NS EW Fixed
Two-Axis NS EW Fixed
Two -Axis NS EW Fixed
Two- Axi s NS EW Fixed
Two -Axis NS EW Fixed
Two -Ax i s NS EW Fixed
Two -Ax i s NS EW Fixed
Two-Axis NS EW Fixed
Two-Axi s NS EW Fixed
Two-Axi 6 NS EW Fixed
Rank Order
1 4 2 3
1 4 2 3
1 4
3
1 4 2 3
1 4 2 3
1 4 2 3
1 3 2 4
1 4 2 3
1 4 2 3
1 4 2 3
2 ,
Energy Produc- % Difference t ion ( kWh/m2 1 NS EW Fixed
70.9 52.6 60.6 55.1
33.8 23.0 30.2 27.9
43.9 33.2 38.9 35.8
49.4 37.5 43.2 39.5
63.3 44.6 54.9 50.3
41.6 31.3 37.0 34.3
55.6 46.7 48.3 44.2
38.2 25.9 34.3 31.8
50.6 35.1 44.3 40.7
52.6 38.9 46.3 42.5
34.9
46.9
32.2
32.1
41.9
32.9
19.2
47.3
44.0
35.2
17.0 15.3
11.9 31.2
12.8 17.2
14.5 15.3
15.3 23.1
12.5 18.2
15.1 3.5
11.4 32.3
14.3 26.0
13.5 19.1
28.6 4.9 9.9
21.3 21.1 8.3
22.6 7.8 8.7
25.4 5.3 9.5
25.8 12.8 9.1
21.3 9.6 7.8
25.9 5.7 9.4
19.8 23.0 7.6
24 ..3 15.9 8.8
23.8 9.2 9.1
22
T a b l e 7
Summary o f S i m u l a t e d Module M o u n t i n g C o m p a r i s o n s A n n u a l I n s o l a t i o n A v a i l a b i l i t i e s a t 1 0 S i t e s i n t h e
A n n u a l (kWh/rn2)
SITE
Albuquerque, NM
Boston, MA
Charleston, SC
Dallas, TX
Ely. NV
Fresno. CA
Honolulu, HI
Madison, WI
Omaha, NE
Santa Maria, CA
TOT. HOR
2 1 1 2 . 7
1 2 6 2 . 0
1 5 4 1 . 0
1 7 0 4 . 9
1 9 1 5 . 8
1 9 8 3 . 5
1 8 8 7 . 9
1 3 6 5 . 0
1 5 3 5 . 7
1 8 3 3 . 9
- 2A
3 4 5 7 . 2
1 9 3 9 . 9
2 2 1 0 . 6
2 5 9 1 . 5
3 2 6 0 . 7
3 1 3 9 . 1
2 6 0 2 . 5
2 1 2 3 . 1
2 5 1 2 . 2
2 7 9 2 . 8
NS
3 0 3 1 . 3
1 6 8 6 . 4
1 9 6 7 . 2
2 3 1 9 . 5
2 8 1 9 . 3
2 8 1 0 . 9
2 4 2 3 . 6
1 8 2 8 . 0
2 1 6 9 . 1
2 4 6 6 . 6
EW - 2 7 1 5 . 3
1 5 7 5 . 5
1 8 4 2 . 7
2 0 7 9 . 9
2 5 3 2 . 9
2 4 4 4 . 1
2 1 3 2 . 4
1 7 2 7 . 6
1 9 9 7 . 9
2 2 7 4 . 7
TILT
2 5 3 1 . 2
1 4 8 8 . 8
1 7 4 9 . 8
1 9 5 1 . 7
2 3 7 2 . 1
2 2 8 3 . 9
2 0 0 6 . 4
1 6 3 9 . 2
1 8 7 1 . 9
2 1 4 3 . 1
u. s.
DNI
2 6 0 9 . 7
1 1 6 5 . 9
1 3 5 5 . 7
1 7 5 5 . 4
2 4 1 3 . 5
2 2 5 7 . 8
1 2 7 4 . 4
1 3 1 1 . 8
1 6 7 4 . 3
1 9 5 8 . 8
T a b l e 8
Summary o f S i m u l a t e d A v a i l a b l e I n s o l a t i o n f o r D i f f e r e n t F l a t - P l a t e T r a c k i n g C o n f i g u r a t i o n s a t 1 0 S i t e s i n t h e
SITE
Albuquerque, NM
Boston, MA
Charleston, SC
Dallas, tX
Ely, NV
Fresno, CA
Honolulu, HI
Mad i s on, W I
Omaha, NE
Santa Maria, CA
TOT. HOR
6 3 5 . 0
3 7 5 . 8
4 7 6 . 5
4 6 8 . 1
5 5 9 . 4
5 9 5 . 5
5 2 4 . 1
4 1 0 . 6
4 5 5 . 7
5 2 8 . 4
S p r i n g
2A
9 5 9 . 8
5 4 0 . 9
6 4 5 . 5
6 5 8 . 6
8 9 8 . 9
9 0 5 . 5
6 7 2 . 7
6 1 6 . 2
6 7 8 . 5
7 5 0 . 4
-
( kWh/m2)
NS
8 9 9 . 8
4 9 7 . 2
6 1 0 . 6
6 2 1 . 1
8 3 0 . 3
8 4 8 . 1
6 5 6 . 5
5 5 7 . 1
6 2 3 . 1
7 0 4 . 2
- - EW
7 2 5 . 6
4 2 9 . 5
522 .3
5 1 9 . 4
6 6 4 . 8
6 8 2 . 3
5 4 4 . 6
4 8 5 . 6
5 2 5 . 9
5 9 3 . 9
TIT,T
6 9 7 . 5
4 1 4 . 9
5 0 9 . 7
5 0 4 . 2
6 3 8 . 1
6 5 4 . 7
5 2 8 . 3
4 7 0 . 3
5 0 5 . 6
5 7 8 . 3
U . S .
- DN I
7 0 3 . 5
3 0 5 . 6
375 .3
423 .4
6 2 5 . 7
6 3 1 . 0
3 0 6 . 6
3 7 0 . 5
4 3 5 . 9
498 .4
Table 9
Summary o f Simulated Ava i lab le I n s o l a t i o n f o r D i f f e r e n t F l a t - P l a t e Tracking Conf igurat ions a t 10 S i t e s i n t h e U.S.
Summer (kWh/m2)
SITE
Albuquerque, NM
Boston, MA
Charleston. gC Dalld6. TX
Ely. NV
Fresno, CA
Honolulu, HI
Madison, WI
Omaha, NE
Santa Maria, CA
TOT. HOR
717.11
498.4
496.1
620.9
700.3
757.3
578.8
537.1
585.9
665.6
29 1001. a
663.7
616.3
843.5
987.8
1094.1
745.7
724.1
835.5
887.4
M 975.7
638.9
604.8
826.1
955.8
1062.9
735.9
693.7
805.6
865.5
- EW
764.1
521.0
503.5
651.3
744.5
812.3
595.1
568.9
634.6
698.0
TILT 690.2
479.9
471.8
594.4
678.6
726.4
548.3
528.4
577.5
642.3
DNI 741.5
400.4
355.7
563.8
742.3
834.0
301.4
451.6
543.9
648.7
T a b l e 1 0
Summary o f S i m u l a t e d A v a i l a b l e I n s o l a t i o n f o r D i f f e r e n t F l a t - P l a t e T r a c k i n g C o n f i g u r a t i o n s a t 10 S i t e s i n t h e U.S.
F a l l ( kWh/m2 )
-- SITE
Albuquerque, NM
Boston, MA
Charleston, SC
Dallas, TX
Ely, NV
Fresno, CA
Honolulu, HI
Madison, WI
Omaha, NE
Santa Maria, CA
TOT. HOR
455.0
249.1
339.6
380.5
408.7
423.6
442.2
263.4
300.4
387.1
2A - 824.5
440.4
535.8
626.9
798.6
744.7
638.7
451.9
551.2
645.1
NS
675.6
352.4
446.4
529.2
640.6
611.1
578.9
357.9
437.0
531.3
- EW - 657.5
362.6
452.7
507.9
628.4
601.1
521.9
377.2
448.6
536.2
TILT
630.4
352.2
434.8
488.2
604.3
581.3
501.3
366.6
432.6
515.9
DN I
641.4
275.5
343.1
455.2
616.4
558.4
334.7
289.2
390.0
454.8
-
2 4
Table 11
Summary o f S i m u l a t e d A v a i l a b l e I n s o l a t i o n f o r D i f f e r e n t F l a t - P l a t e T r a c k i n g C o n f i g u r a t i o n s a t 1 0 S i t e s i n t h e U.S.
W i n t e r ( kWh/m2 )
SITE TOT. HOR - 2A NS EW TILT DNI Albuquerque, N?4 305.6 670.9 480.0 568.2 513.1 523.1
B o s t o n , MA 138.7 294.8 197.9 262.5 241.8 184.4
C h a r l e s t o n , SC
D a l l a s , TX
E l y , NV
F r e s n o , CA
Honolu lu , H I
Madison, WI
Omaha, NE
Santa Maria , CA
228.8
235.3
247.5
207.2
342.8
153.9
193.6
252.8
413.1 305.5 364.2
462.5 343.1 401.3
572.3 392.6 495.2
394.7 288.7 348.4
545.3 452.3 470.7
330.9 219.2 295.9
447.0 303.3 388.8
510.1 365.6 446.5
333.4
364.8
451.1
321.5
428.6
273.9
356.1
406.6
281.4
313.1
429.2
234.4
331.8
200.4
304.5
356.8
C O N C L U S I O N S
The s t u d y s u p p o r t s t h e f o l l o w i n g c o n c l u s i o n s :
1, T h e r e a r e s t a t i s t i c a l l y s i g n i f i c a n t d i f f e r e n c e s b e t w e e n t h e
p e r f o r m a n c e s o f i d e n t i c a l PV m o d u l e s m o u n t e d i n e a c h of t h e
f o u r c o n f i g u r a t i o n s t e s t e d a t S N L A . A r a n k o r d e r i n g o f t h e
m o u n t i n g c o n f i g u r a t i o n s r based o n t h e d i f f e r e n c e s , c a n be
made f o r t h e A l b u q u e r q u e a rea f o r t h e p e r i o d o f m i d - O c t o b e r . I n t h i s p a r t o f t h e y e a r , t h e t w o - a x i s t r a c k i n g s y s t e m p r o -
d u c e s t h e g r e a t e s t t o t a l a m o u n t o f d a i l y e n e r g y , a n d t h e
f i x e d t i l t p r o d u c e s t h e l e a s t . T h i s i s a n e x p e c t e d t r e n d i n
October , b u t does n o t r e p r e s e n t t h e r e m a i n d e r o f t h e y e a r .
T h e p r i m a r y u s e o f t h e m e a s u r e d t e s t r e s u l t s w a s t o v e r i f y
t h e a c c u r a c y o f t h e PVFORM c o m p u t e r m o d e l . The model w a s
shown t o r e p r o d u c e p r e c i s e l y t h e S N L A c o n f i g u r a t i o n c o m p a r i -
s o n t e s t r e s u l t s . F u r t h e r ! t h e m o d e l h a s p r o d u c e d m e a s u r e s
o f PV m o d u l e p e r f o r m a n c e f o r d i f f e r e n t c o n f i g u r a t i o n s t h a t
2 5
2.
are r e a s o n a b l y c o n s i s t e n t w i t h l i m i t e d m e a s u r e d d a t a . T h e r e - f o r e r i t i s c o n c l u d e d t h a t t h e PVFORM model i s a n a p p r o p r i a t e
t o o l f o r s i m u l a t i n g t h e a n n u a l p e r f o r m a n c e o f a m o d u l e
m o u n t e d i n t h e f o u r c o n f i g u r a t i o n s .
The r e l a t i v e p e r f o r m a n c e o f t h e f o u r m o d u l e m o u n t i n g c o n f i g u -
r a t i o n s v a r i e s t h r o u g h o u t t h e y e a r , a n d t h i s v a r i a n c e i s masked i n t h e c o m p u t a t i o n of a n a n n u a l p e r f o r m a n c e v a l u e . I n
A l b u q u e r q u e d u r i n g J u n e , f o r e x a m p l e , t h e p e r f o r m a n c e o f t h e
n o r t h - s o u t h a x i s t r a c k i n g s y s t e m is a b o u t t h e same a s a
t w o - a x i s t r a c k i n g s y s t e m . I n J a n u a r y , h o w e v e r , a n o r t h - s o u t h
a x i s t r a c k i n g s y s t e m p r o d u c e s t h e l e a s t e n e r g y among t h e f o u r
c o n f i g u r a t i o n s . The r e l a t i v e l y p o o r p e r f o r m a n c e of t h e
n o r t h - s o u t h a x i s t r a c k i n g s y s t e m i n t h e l o w - i n s o l a t i o n m o n t h s
i s s u f f i c i e n t l y o f f s e t b y g o o d p e r f o r m a n c e d u r i n g t h e h i g h -
i n s o l a t i o n m o n t h s s o t h a t i t s a n n u a l p e r f o r m a n c e is s e c o n d
o n l y t o a t w o - a x i s t r a c k i n g s y s t e m . T h e r e f o r e , i f t h e l o a d demand on a P V s y s t e m is s e a s o n a l , a n a n a l y s i s o f t h e r e l a -
t i v e p e r f o r m a n c e o f e a c h m o u n t i n g c o n f i g u r a t i o n i n t h a t
s p e c i f i c s e a s o n may be n e c e s s a r y t o e n s u r e t h a t t h e o p t i m a l
system i s d e s i g n e d .
3 . I n t h e 10 l o c a t i o n s s t u d i e d , t h e r e l a t i v e r a n k i n g of t h e
a n n u a l p e r f o r m a n c e of t h e d i f f e r e n t m o u n t i n g c o n f i g u r a t i o n s
d i d n o t c h a n g e . T h a t i s , o n a n a n n u a l b a s i s , t w o - a x i s t r a c k - i n g p r o d u c e d t h e most e n e r g y ! a n d f i x e d t i l t p r o d u c e d t h e
l e a s t . However r t h e c l e a r - s k y c o n d i t i o n s , w h i c h a r e p r e v a -
l e n t i n a r i d a n d s e m i a r i d r e g i o n s , h a v e t w o i m p o r t a n t e f f e c t s
o n m o d u l e p e r f o r m a n c e . F i r s t , a l l m o d u l e m o u n t i n g c o n f i g u r a -
t i o n s perform r e l a t i v e l y w e l l i n t h e s e d r y a r eas . F o r
e x a m p l e , a f i x e d - t i l t s y s t e m o p e r a t i n g i n A l b u q u e r q u e , NM, p r o d u c e s a b o u t a s much e n e r g y a s a t w o - a x i s t r a c k i n g s y s t e m
o p e r a t i n g i n M a d i s o n r W I . S e c o n d , t h e d i f f e r e n c e s b e t w e e n
t h e r e l a t i v e p e r f o r m a n c e of t h e v a r i o u s m o u n t i n g c o n f i g u r a -
t i o n s i s l a r g e s t i n a r i d o r s e m i a r i d l o c a t i o n s . For e x a m p l e ,
a t w o - a x i s s y s t e m i n A l b u q u e r q u e r N M ; E l y , N V ; o r F r e s n o , C A
w i l l p r o d u c e a b o u t 35% more e n e r g y t h a n f i x e d - t i l t systems.
2 6
The p e r c e n t a g e i n c r e a s e f o r t h e same s y s t e m s a t t h e o t h e r
s i t e s i n t h i s s t u d y a v e r a g e d a b o u t 2 7 % .
4. I n c o m p a r i n g t h e a n n u a l p e r f o r m a n c e o f t h e t w o - a x i s t r a c k i n g
s y s t e m w i t h t h e n o r t h - s o u t h a x i s t r a c k i n g s y s t e m , i t w a s
f o u n d t h a t t h e a d v a n t a g e of t h e t w o - a x i s s y s t e m r a n g e d
b e t w e e n 6% a n d 15%. T h e r e f o r e , d e p e n d i n g o n t h e c o s t o f
t r a c k i n g d e v i c e s , t h e r e may be o c c a s i o n s w h e r e t h e s i n g l e -
a x i s s y s t e m may be t h e most c o s t - e f f e c t i v e o p t i o n . T h i s i s
e s p e c i a l l y t r u e i n l o w - l a t i t u d e l o c a t i o n s l i k e H o n o l u l u , H I .
I n t h e s e a r e a s , t h e s u n a l t i t u d e a n g l e s a r e l a r g e a l l y e a r .
T h i s t e n d s t o i n c r e a s e t h e r e l a t i v e p e r f o r m a n c e o f t h e h o r i -
z o n t a l s i n g l e - a x i s t r a c k i n g s y s t e m s .
5. The a d v a n t a g e s o f t h e EW a x i s t r a c k i n g s y s t e m o v e r a f i x e d -
t i l t o r i e n t a t i o n r a n g e d b e t w e e n 5% a n d 8%. I n most a p p l i c a -
t i o n s , t h e small p o t e n t i a l i n c r e a s e i n e n e r g y p r o d u c t i o n from
a n east-west a x i s t r a c k i n g s y s t e m w i l l n o t p a y f o r t h e
i n c r e a s e d c o s t s o f t h e t r a c k i n g m e c h a n i s m . I f a t r a c k i n g
s y s t e m i s b e i n g s t u d i e d a s a n a l t e r n a t i v e t o o n e i n a f i x e d -
t i l t c o n f i g u r a t i o n , t h e t w o - a x i s o r n o r t h - s o u t h a x i s c o n f i g u -
r a t i o n s s h o u l d be t h e o n l y c o n s i d e r a t i o n s .
6. The e n e r g y p r e d i c t i o n s a n d s u b s e q u e n t c o m p a r i s o n s p r e s e n t e d
i n t h i s paper a r e based o n a new a n d more a c c u r a t e s o l a r
r a d i a t i o n model t h a t i s n o t i n g e n e r a l u s e t o d a y . T h e s e
e n e r g y p e r f o r m a n c e e s t ima tes a r e n o t r e p r o d u c i b l e when t h e
a n a l y s i s i s based o n t h e more common r a d i a t i o n m o d e l s . S i n c e
a v a i l a b l e t a b l e s o f s o l a r r a d i a t i o n a v a i l a b i l i t y a n d m o d u l e
e n e r g y p e r f o r m a n c e a r e b a s e d o n t h e s e o l d e r m o d e l s , t h e
r e s u l t s p r e s e n t e d h e r e c a n n o t be a c c u r a t e l y r a t i o e d o r cor- r e l a t e d t o e x i s t i n g t a b u l a t e d d a t a . The o n l y n o t i c e a b l e
t r e n d i s t h a t t h e new e s t i m a t e s o f e n e r g y p e r f o r m a n c e a n d
i n s o l a t i o n a v a i l a b i l i t i e s a r e g e n e r a l l y 7% t o 18% h i g h e r t h a n
e x i s t i n g p u b l i s h e d v a l u e s a n d a r e r e a s o n a b l y c o n s i s t e n t w i t h
t h e m e a s u r e d d a t a t h a t a r e a v a i l a b l e . S N L A i s i n t h e p r o c e s s
of u s i n g PVFORM t o g e n e r a t e new e s t ima tes o f s o l a r a v a i l a -
b i l i t i e s a n d t h e c o r r e s p o n d i n g e n e r g y p e r f o r m a n c e o f m o d u l e s
mounted i n va r ious t r ack ing and f ixed o r i e n t a t i o n s f o r many l o c a t i o n s i n t he Typical Meteorological Year network.
7 . T h i s s tudy concent ra ted on the comparison of the four most popular t r ack ing conf igu ra t ions . Howeverr t h e r e a r e two o t h e r t r ack ing schemes t h a t should be considered whenever t r ack ing is a module mounting opt ion . These inc lude ( a ) a module mounted to r o t a t e about a v e r t i c a l a x i s w i t h the s u r f a c e t i l t e d upward equal t o t h e l a t i t u d e and ( b ) a module mounted t o r o t a t e about a s i n g l e a x i s w i t h t h e a x i s p a r a l l e l t o t h e po la r a x i s . SNLA is i n t h e p rocess of t e s t i n g t h e s e two c o n f i g u r a t i o n s so t h a t t h e i r t o t a l energy product ion can be s imulated and compared w i t h t h e fou r c o n f i g u r a t i o n s descr ibed i n t h i s paper.
28
REF ERE NC ES
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2.
3.
4.
5.
6.
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M e n i c u c c i , D. F. I PVFORM, A P h o t o v o l t a i c S y s t e m A n a l y s i s P r o g r a m : Users M a n u a l , SAND85-0376, ( S a n d i a N a t i o n a l Labora to r i e s , A l b u q u e r q u e I N M r 1985) .
P e r e z , R., An A n i s o t r o p i c Model of D i f f u s e S o l a r R a d i a t i o n W i t h A p p l i c a t i o n s t o a n O p t i m i z a t i o n of Compound P a r a b o l i c C o n c e n t r a - - t o r s , USDOE, #DEFG0577ET20182, A t m o s p h e r i c S c i e n c e s R e s e a r c h C e n t e r , S t a t e U n i v e r s i t y of New York a t A l b a n y r 1 9 8 4 .
F u e n t e s , M. K . , A S i m p l i f i e d T h e r m a l Model of P h o t o v o l t a i c M o d u l e s , S A N D 8 5 - 0 3 3 0 , ( S a n d i a N a t i o n a l L a b o r a t o r i e s r A l b u q u e r q u e I N M , 1 9 8 5 ) .
H u l s t r o m , R. L. I B r a n c h C h i e f I R e n e w a b l e R e s o u r c e A s s e s s m e n t a n d I n s t r u m e n t a t i o n r S o l a r E l e c t r i c R e s e a r c h D i v i s i o n , S o l a r E n e r g y R e s e a r c h I n s t i t u t e : P e r s o n a l c o m m u n i c a t i o n s .
S h u s h n a r , G. J . # e t a l l " B a l a n c e of S y s t e m Cos ts €o r a 5 M W P h o t o - v o l t a i c G e n e r a t i n g S y s t e m , ' ' A R C 0 S o l a r , I n c l p r e s e n t e d a t t h e IEEE/PES 1985 W i n t e r M e e t i n q , New York , N e w Y o r k r F e b 3-8, 1985.
APPEN D I X
P l o t s of M o n t h l y E n e r g y P e r f o r m a n c e
3 1 , 3 2
LEGEND 0 FD(EDllLT
0 TWO-AXISTkACKlNG
--A. 0 -. .&gm..sm&&.- -W
/. 72-.:,.\ ......
..............................................................................
5 JAN fXB MAR APR MAY x#r( .NJL AUG SEP Ocrr NOV DEC
F i g u r e A l . PVFORM E n e r g y P r e d i c t i o n s , A l b u q u e r q u e , NM
-1 LEGEND FIXEDTILT
........................................ 0 EAST-WEST AXIS A NORTH-SOUTH AXIS - 0 TWO-AXIS - - - - TRACKING - - -
JAN FEB MAR AFT? MAY JUN JUL AUG S P OCT NOV DEC
F i g u r e A2. PVFORM E n e r g y P r e d i c t i o n s , B o s t o n , MA
F i g u r e A 3 . PVFORM E n e r g y P r e d i c t i o n s , C h a r l e s t o n , S C
LEGEND
I
JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC
F i g u r e A 4 . PVFORM E n e r g y P r e d i c t i o n s , D a l l a s - F t . W o r t h , TX
3 4
F i g u r e A 5 . PVFORM E n e r g y P r e d i c t i o n s , E l y , N V
LEGEND 45
5 JAN FEE MAR APR MAY XIN JJL AUG SEP OCT NOV DEC
F i g u r e A6. PVFORM E n e r g y P r e d i c t i o n s , F r e s n o , C A
3 5
45. LEGEND
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al' 5 ~ - JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC
....
JAN FEB MAR APR MAY XIN Juc AUG SEP OCT NOV DEC
Figure A 8 . PVFORM Energy Predictionsr Madisonr WI
3 6
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-------- 0 TWO-AXIS TRACKING ...,...,........ .......... .. ............... .. ..... ............. )..... .. ...
Y W
: €s'. " 'A x lo:
- - JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC
F i g u r e A 9 . PVFORM E n e r g y P r e d i c t i o n s ! Omaha, NE
- JAN FFB MAR APR MAY XM XIL AUG SEP OCT NOV DEC
F i g u r e A 1 0 . PVFORM E n e r g y P r e d i c t i o n s , S a n t a Maria, C A
37
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38
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, *
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E d DeMao
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G e o r g e C o k k i n i d e s S id Firs tman
GILA RIVER PRODUCTS C h a n d l e r , A2 85224 A t t n : W i l l i a m R. B e l l
HEERY ENERGY CONSULTANTS 880 West Peachtree S t ree t A t l a n t a , GA 30367 A t t n : G l e n n Jardine
HELIONETICS 1 7 3 1 2 E a s t m a n S t ree t I r v i n e , CA 9 2 7 1 4 A t t n : Larry Suelz le
HEMLOCK SEMICONDUCTOR COMPANY ( 2 ) 1 2 3 3 4 G e d d e s R o a d H e m l o c k , M I 48628 A t t n : A r v i d A r v i d s o n
J a m e s R. M c C o r m i c k
HUGHES AIRCRAFT P. 0. B o x 9399 B u i l d i n g A1 M / S 40843 Long B e a c h , CA 9 0 8 1 0 A t t n : G e o r g e N a f f
I E E 345 E . 47th Stree t New York, NY 1 0 0 1 7 A t t n : R o b e r t K l e i n
INTERSOL POWER CORPORATION ( 2 ) 1 1 9 0 1 W. C e d a r A v e . L a k e w o o d , CO 80228 A t t n : John Sanders
D i c k S t e g e m a n
4 0
J . C . SCHUMACHER ( 2 ) 580 Airport Road Oceanride, CA 92054 Attn : Stephen M. Lord
Joeeph C. Schumacher
J E T PROPULSION LABORATORY ( 8 ) 4800 Oak Grove Drive Pasadena, CA 91109 A t t n : Bud Powell
Gerald Praver Russ Sugimura Anthony Pearson Kent Volkmer Len Re i t e r W. T. Callaghan Ron Ross
KELLAM, BIRD, JOHNSON, INC. 612 North Park S t r e e t Columbus, OH 43215 Attn: John Ayres
KYOCERA (3) 8611 Balboa Avenue San Diego, CA 92123-1580 Attn: W i l l i a m E v e r i t t
R. Alan Panton Luis Alvarez
LOS ANGELES DEPT. OF WATER & POWER ( 2 ) 1 1 1 North Hope S t r e e t Los Angeles, CA 90051 Attn: W i l l i a m W. Engels
Kevin G. McAvoy
MARTIN MARIETTA (3) P. 0. Box 179 Denver, CO 80201 At tn : H. Wroton
Bob Hein Matt Imamura
MC DONNELL DOUGLAS ASTRONAUTICS CO. 5301 Bolsa Avenue, M/S 431, 10-3 Huntington Beach, CA 92647 At tn : Lloyd E. Sanchez
MERIDAN CORP. ( 2 ) 5113 Leesburg Pike S u i t e 700 F a l l s Church, VA 22041 Attn: Brad M a C l e e r
Judy Hogan
METAL IRON CO.
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P, 0. BOX 4590
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Ed Kern Daniel Bergman
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Cather ine M. Joyce J u r i s P. Kalejs F r i t z V. Wald
MONO SOLAR , 8635 Aviat ion Blvd. Inglewood, CA 90301 At tn : Bulent M. Basol
I NC .
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COMPANY ( 2 )
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Glen Rumbold
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Harry Zwibel
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Stephen I. K a p l a n
ONTARIO MINISTRY OF ENERGY 56 Wellesley Street West T o r o n t o , C a n a d a M7A 237 A t t n : I a n L e w i s
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R o b e r t B. S t rass le r
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K a y F i r o r K e e n e M. Matsuda
POLY DYNE 1 2 3 0 Sharon Park D r i v e S u i t e 6 1 Menlo P a r k , CA 94025 A t t n : Pe te r B o s
POLYTECHNIC INSTITUTE OF NEW YORK 333 Jay S t ree t B r o o k l y n , NY 1 1 2 0 1 A t t n : A n n - C h r i s t i n e A l b e r t s o n
PROA 4 0 1 9 E d i t h B l v d . NE B u i l d i n g 2 B A l b u q u e r q u e , NM 87 1 0 7 A t t n : C o n r a d Seagroves
PUBLIC SERVICE ELECTRIC & GAS CO.
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D o n Martinez
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R o b e r t V e s t
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4 2
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RICHWAY ENTERPRISES 6752 R o c k g l e n A v e . San Diego, CA 9 2 1 1 1 A t t n : R i c h a r d L. Q u i n c e y
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SALT RIVER PROJECT P. 0. B o x 1 9 8 0 Phoenix, AZ 8 5 0 0 1 A t t n : Steve C h a l m e r s
SAN DIEGO GAS ELECTRIC CO. 1 1 0 W. A Street B o x 1 8 3 1 San D i e g o , CA 9 2 1 1 2 A t t n : Wes G o o d w i n
SAN DIEGO STATE UNIVERSITY Dept. of Physics San Diego, CA 9 2 1 8 2 A t t n : A l a n R. S w e e d l e r
S C I E N T I F I C ANALYSIS , INC. 4249 L o m a c S t ree t S u i t e C M o n t g o m e r y , AL 3 6 1 06 A t t n : A l l e n G u n n
S E R I ( 4 ) 1 6 1 7 C o l e B l v d . G o l d e n , CO 8 0 4 0 1 A t t n : R i c h a r d D e B l a s i o
L. K a z m e r s k i T. Surek E. W i t t
SOH10 ( 2 ) 3092 B r o a d w a y C l e v e l a n d , OH 4 4 1 1 5 A t t n : L. T r a n
R. C u l l
SOLAR ELECTRIC CO. OF NM 2700 E s p a n o l a NE A l b u q u e r q u e , NM 8 7 1 1 0 A t t n : Steve V e r c h i n s k i
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SOLAR INVERTER 8480 C l i f f r i d g e L a n e L a J o l l a , CA 92037 A t t n : J a m e s R o s s
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SOLAREX CORPORATION ( 2 ) 1 3 3 5 Piccard D r i v e R o c k v i l l e , MD 20850 A t t n : Daniel Bumb
H a l M a c o m b e r
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SOLLOS, INC. 1 5 1 9 C o m s t o c k A v e n u e Los A n g e l e s , CA 90024 A t t n : Mi lo Macha
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SPECIALTY CONCEPTS, INC. 9025 E t o n A v e , S t e D C a n o g a Park, CA 9 1 3 0 4 A t t n : Tom B. P h i l p
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SPECTROEAB, INC. 12500 G l a d s t o n e A v e n u e Sylmar, CA 91342 A t t n : A l e x G a r c i a
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R o g e r G. L i t t l e Mark B. Sp i tzer
SPRINGBORN LABORATORIES, I N C 10 Springborn C e n t e r E n f i e l d , CT 06082 A t t n : B e r n a r d Baum
Paul B. W i l l i s
STANDARD O I L COMPANY (Ohio) 1608 Midland B l d g . C l e v e l a n d , OH 44115 A t t n : T o b y K. A l f r e d
STANDARD O I L COMPANY (Ohio) 4440 Warrensville C e n t e r Rd . C l e v e l a n d , OH 44128 A t t n : R o n a l d C. C u l l
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Fred N o b i l e R o b e r t A. Shade, Jr.
SUPERWAVE TECHNOLOGY 2895 N o r t h w e s t e r n Pky. Santa C l a r a , CA 95125 A t t n : B r u c e Minaee
SYSTEMS DEL SOL 10933 L o s A l a m i t o s B l v d . L o s A l a m i t o s , CA 90720 A t t n : Cra ig P. B o y d
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TEXAS INSTRUMENTS INC s P.O. Box 225936, M/S 147 Dallas, TX 75265 A t t n : Jules D. L e v i n e
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E d w a r d A. Sequeira
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UNION CARBIDE CORPORATION O l d R i d g e b u r n R o a d D a n b u r y , CT 06817 A t t n : James L. Young
UNION CARBIDE CORPORATION ( 2 ) 3333 Index S t r e e t Washougal, WA 98671 A t t n : S r idha r K. Iya
Hiroshi Morihara
UNIVERSITY OF CALIFORNIA, LOS ANGELES ( 2 )
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P a t r i c i a D. Sparks
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UNIVERSITY OF ILLINOIS-CHICAGO C i v i l E n g i n e e r i n g Mechanical and Metallurgy D e p t . C h i c a g o , I L 60680 A t t n : Steven D a n y l u k
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UNIVERSITY OF SOUTHERN CALIFORNIA Univers i ty Park LOB Angeles, CA 90089-1 11 2 A t t n : Randell T. S w i m
UNIVERSITY OF TEXAS AT ARLINGTON E l e c t r i c a l Engr. Dept. Ar l ing ton , TX 76019 A t t n : Jack F i t z e r
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USAF P.O. Box 5400 Albuquerque, NM 87115 Attn : John Hanson
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WESTINGHOUSE 5301 Cent ra l NE Albuquerque, NM 87108 Attn: B. Weidle
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E. Ray
WEDTECH CORPORATION 4226 N. Shadydale Covina, CA 91722 Attn: Emilio Font
WES CONSULTING, INC. 20380 town Center Lane, Su i t e 170 Cupert ino, CA 95014 Attn: Wayne E. Shannon
WINDWORKS ( 2 ) R t . 2 Box 44A Mukwonago, W I 53149 Attn: Donald Thomas
Hans Meyer
Max F i n d e l l 836 Rio Arrlba Ave. SE Albuquerque, NM 87123
Dale Haskins P.O. Box 6 Ti jeras , NM 87059
George Warfield Consul t a n t RD 2 Box 264 Vergennes, VT 05491
Melvin E i sens t ad t Attorney a t Law 3225 Candelaria NE S u i t e A Albuquerque, NM 87107
1251 2363 2364 2364 2525 2525 363 2 3661 6000 6200 6220 622 1 622 1 622 1 622 1 622 1 6221 622 1 6223 6223 6223 6223 6224 6224 6224 6224 622 7 8024 3141 31 51
W. Boyer H. Barne t t W. Bower B. Brumley R. Clark J. Freese T. Baca J. Campbell E. Beckner V. Dugan D. Schueler E. Burgess J. Cannon R. Lundgren D. Menicucci ( 2 5 ) B. Pe t t e r son M. Thomas E. Boes G. Jones T. Key H. Post J. Stevens D. Arvizu L. Beavis A. Maish C. S t i l l w e l l J. A. Leonard M. A. Pound C. M. Ostrander ( 5 ) W. L. Garner ( 3 )
3154-3 C. H. Dalin ( 2 8 ) f o r DOE/TIC (Unlimited r e l e a s e )