The o b j e c t i v e o f t h i s s t u d y i s t o p e r f o r m a s y n t h e s i s o f e x i s t i n g n a t i o n a l wind energy assessments t o develop an improved c o n s i s t e n t assessment o f t h e g e o g r a p h i c a l d i s t r i b u t i o n o f t h e a v a i l a b l e wind power o v e r t h e U n i t e d S t a t e s . Previous n a t i o n a l wind energy assessments have been reviewed w i t h r e s p e c t t o t e c h n i q u e s , assumptions, d a t a sets/summaries, and i n

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... e r p o l a t i o n schemes used. The o v e r a l l r e p r e s e n t a t i v e n e s s o f t h e r e s o u r c e maps produced has been e v a l u a t e d D i s c r e p a n c i es e x i s t among ' p r e v i o u s assessments w i t h r e g a r d t o geographical v a r i a t i o n s and t h e e s t i m a t e d v a l u e s o f wind power. I n f o r m a t i o n from t h e e x i s t i q g n a t i o n a l wind energy assessments and v a r i o u s o t h e r sources has been s e l e c t i v e l y used t o form a s y n t h e s i z e d n a t i o n a l assessment. As p a r t o f t h e s y n t h e s i s , a d d i t i o n a l r e s e a r c h was performed t o f u r t h e r improve t h e n a t i o n a l assessment. T h i s i n c l u d e d a more d e t a i l e d examination o f some o f t h e i n h e r e n t problems w i t h r e s p e c t t o t h e r e p r e s e n t a t i v e n e s s and r e l i ab i l i t y o f t h e s u r f a c e and rawinsonde wind data, techniques employed i n t h e v e r t i c a l e x t r a p o l a t i o n o f wind power, i n t h e e s t i m a t i o n o f wind power o v e r mountainous and o f f s h o r e areas and areas o f sparse data, and i n t h e a n a l y s i s and i n t e r p o l a t i o n o f t h e values. The r e f i n e d a n a l y s i s o f t h e mean annual wind power a t 50 m above exposed areas o v e r t h e c o n t i g u o u s U n i t e d S t a t e s i s shown i n F i g u r e 1 . Exposed areas r e f e r t o l o c a t i o n s which a r e u n o b s t r u c t e d t o t h e wind, such as h i l l t o p l o c at i o n s o v e r r e g i o n s o f g e n t l y r o l l i n g and h i l l y t e r r a i n , and capes and open s h o r e l i n e s i t e s a l o n g c o a s t a l r e g i o n s . The e s t i m a t e s a r e considered t o be l o w e r l i m i t s f o r exposed s i t e s . A few i s o l a t e d areas may have 50-100% g r e a t e r wind power t h a n t h e a n a l y s i s shows. Thus, t h e e s t i m a t e s must n o t be c o n s t r u e d as r e p r e s e n t a t i v e o f a l l s i t e s w i t h i n an area. S p e c i f i c a l l y , t h e e s t i m a t e s a r e n o t r e p r e s e n t a t i v e where t o p o g r a p h i c f e a t u r e s b l o c k o r channel a i r f l o w . I n mountainous r e g i o n s , t h e e s t i m a t e s a r e t h e l o w e r l i m i t s expected f o r t y p i c a l , well-exposed s i t e s a l o n g mountain summits, r i d g e s , and gaps. These e s t i m a t e s a r e p r i m a r i l y based on t h e c l i m a t o l o g y o f t h e winds a l o f t . However, t h e r e l a t i o n s h i p between mountain summit wind power and f r e e a i r wind power a t summit h e i g h t i s h i g h l y v a r i a b l e . Over some i s o l a t e d mountains and r i d g e s , t h e wind speeds a r e enhanced c o n s i d e r a b l y , and t h e wind power may be a f a c t o r o n s w n E 0 .z 2 of 2 o r 3 g r e a t e r t h a n t h e v a l u e s i n d i c a t e d i n t h e a n a l y s e s . The s l o p e and o r i e n t a t i o n o f a r i d g e t o t h e p r e v a i l i n g winds g r e a t l y e f f e c t t h e wind power. Thus, r e l a t i v e l y l o w i s o l a t e d r i d g e s , gaps, and s a d d l e s , may have g r e a t e r wind power t h a n h i g h e r mountain summits. A l l mountainous r e g i o n s , w i t h t h e except i o n o f some areas i n t h e Southwest, a r e e s t i m a t e d t o have c o n s i d e r a b l e w i n d 2 power p o t e n t i a l ( a t l e a s t 300 W/m ) . However, even t h e Southwest may have some w e l l exposed s i t e s (where t h e winds a r e enhanced) w i t h h i g h w i n d power p o t e n t i a l . 2 I n nonmountainous r e g i o n s , t h e mean annual w i n d power i s h i g h (>400 -W/m ) over t h e c e n t r a l and s o u t h e r n G r e a t P l a i n s ; o f f s h o r e and exposed c o a s t a l s i t e s i n t h e N o r t h e a s t and Northwest; and i n p a r t s o f Wyoming, Montana, and t h e 2 s o u t h Texas c o a s t . H i g h wind power (>400 W/m ) a l s o e x i s t s a l o n g t h e exposed c o a s t a l and o f f s h o r e areas o f Alaska, w i t h t h e g r e a t e s t amounts a p p e a r i n g a l o n g t h e A l e u t i a n P e n i n s u l a and I s l a n d s . M o d e r a t e l y h i g h w i n d power 2 (300-400 W/m ) can be expected o v e r t h e n o r t h e r n G r e a t P l a i n s and exposed s i t e s a l o n g t h e G r e a t Lakes and i n Hawaii. Seasonal p a t t e r n s o f w i n d power a r e s i m i l a r t o t h e annual p a t t e r n s . The season(s) o f maximum w i n d power i s shown i n F i g u r e 2 and t h e a n a l y s e s f o r each season a r e shown i n F i g u r e s 3 t h r o u g h 6. Over t h e e a s t e r n o n e -t h i r d o f t h e n a t i o n , maximum wind power o c c u r s d u r i n g t h e w i n t e r and e a r l y s p r i n g . A s p r i n g maximum o c c u r s o v e r t h e G r e a t P l a i n s , t h e N o r t h -C e n t r a l s t a t e s , t h e Texas c o a s t , most nonmountainous areas i n t h e West (e.g., t h e b a s i n s and broad v a l l e y s ) , and o f f s h o r e areas o f c e n t r a l and s o u t h e r n C a l i f o r n i a . W i n t e r maxima o c c u r o v e r a l l mountainous r e g i o n s , e x c e p t f o r some areas i n t h e l o w e r Southwest where t h e s p r i n g w i n d power i s about e q u a l l y as l a r g e . A more comp l e t e d e s c r i p t i o n o f t h e r e f i n e d w i n d power a n a l y s e s i s g i v e n i n S e c t i o n 6 o f t h i s r e p o r t . The " l a r g e s c a l e " r e g i o n s o f h i g h and l o w w i n d power a r e s i m i l a r t o t h o s e i d e n t i f i e d i n p r e v i o u s assessments. However, many s i g n i f i c a n t d i f f e r e n c e s i n t h e wind power e s t i m a t e s and g e o g r a p h i c a l d i s t r i b u t i o n s between t h i s s y n t h e s i s and t h e p r e v i o u s n a t i o n a l assessments a r e e v i d e n t ( s e e S e c t i o n 5 ) . F u r t h e r a n a l y s e s o f t h e d a t a s e t s used i n t h e s e assessments a r e n o t l i k e l y t o r e s u l t i n an improved n a t i o n a l assessment. I n t h e f u t u r e , emphasis s h o u l d be p l a c e d on s e p a r a t e r e g i o n a l a n a l y s e s u s i n g d a t a f r o m a l l a v a i l a b l e sources f o r each r e g i o n . FIGURE 2. Season(s) o f Maximum Wind Power. Over mountainous regions (shaded areas), t h e season(s) indicated i s f o r exposed mountain s i t e s . Seasons a r e abbreviated, where necessary, as follows: W = w i n t e r , SP = spring. 2 FIGURE -3. Winter -Average Wind Power (W/m ) Estimated a t 50 m Above Exposed Areas. Over mountainous regions (shaded areas), t h e estimates a r e lower l i m i t s expected f o r exposed mountain tops and r i d g e s . 2 FIGURE 4. Spring -Average Wind Power (W/m ) Estimated a t 50 m Above Exposed Areas. Over mountainous regions (shaded areas), t h e estimates a r e lower 1 i m i t s expected f o r exposed mountain tops and r i d g e s . CONTENTS