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More on the solar ice maker
and 105 ly per day respectively. The exact values may differ from the mean values for reasons stated earlier. For December at Poona, the observed average total radiat i o n , / ) , is 447 ly per day. Hence the average ch)udiness index tT[T = f t / H o = 447/650 = 0.68. Assuming that the distribution curve /(T = 0.68 in Fig. 11 is valid for Poona as well, it is observed that for about 17 percent of days in l)ecember the cloudiness is equal to or less than 0.57, while for about 40 percent days the sky is clearer than that corresponding to K T = 0.71. Hence for 43 percent of the days in December the cloudiness at Poona is between 0.57 ,rod 0.71.
Relationship Between Monthly Average Daily Diffuse and Daily Total Radiation
In December at Poona H0 = 650 ly per day. Therefore h'T = f t / H o = 447/650 = 0.677
Assuming that a mean curve (Fig. 13) is valid for solar radiation at Poona D/~? = 0.25
/~'~ = H0 - £r X H00 = 0.25 X 0.677 = 0.169 Or, the average of the daily diffuse radiation at Poona in December is /) = 0.169 X 650 = 110 ly per day This compares well with the observed average value 94.8 ly per day of diffuse radiation.
T h e m o n t h l y a v e r a g e v a l u e s of t h e d a i l y diffuse r a d i a t i o n s h o w a l i n e a r r e l a t i o n s h i p w i t h t h o s e of t h e d a i l y t o t a l r a d i a t i o n (Fig. 13). T h e o b s e r v e d p o i n t s line u p a l o n g t h e e x p e r i m e n t a l c u r v e d e r i v e d b y t h e m e t h o d of l e a s t s q u a r e s . T h e a g r e e m e n t b e t w e e n t h e experimental relationship thus derived and the curve o b t a i n e d b y L i u a n d J o r d a n is g o o d . T h e d i f f e r e n c e c a n be a s c r i b e d t o insufficient d a t a for s t a t i s t i c a l a n a l ysis a n d to t h e p r o b a b l e e x i s t e n c e of h i g h e r d u s t c o n t e n t in t h e D e l h i s k y . H e r e also a m e a n c u r v e m a y be u s e d for c o m p u t a t i o n s till f u r t h e r d a t a are a v a i l a b l e . A s a n i l l u s t r a t i o n , we will a s c e r t a i n t h e a v e r a g e d a i l y diffuse r a d i a t i o n o n a h o r i z o n t a l s u r f a c e a t P o o n a in D e c e m b e r w h e n t h e a v e r a g e of t h e m e a s u r e d t o t a l r a d i a t i o n is 447 ly p e r d a y .
Acknowledgement
L e t t e r to the E d i t o r
equipment which would be cheaper and better suited than present equipment to the needs of economically underdeveloped countries. And I think that there is reasonable possibility that a suitable research and development program could achieve worthwhile results along this line. RAYMOND W. BLISS, JR. Donovan & Bliss 5372 Bennett Valley Road Santa Rosa, California, USA
MORE
ON THE
SOLAR
ICE
MAKER
"A Case for a Solar Ice Maker", which appeared in the January 1963 issue of SOLAR E N E R G Y , is indeed a thoughtprovoking article. There is no particular problem in designing durable and reliable solar ice-making machines within the high cost figures mentioned by the author. His figures amount to stipulating an initial cost not higher than $20 U.S. per daily pound of icemaking capacity. If there really is a substantial demand for solar ice-making equipment at the high cost mentioned by the author, my firm would be happy to supply such a demand, and we could make a very pleasant profit doing so. But I believe that the author, after considering the matter further, will conclude that his stipulated cost figures are unacceptably ifigh for ready marketability. On the other hand, I am sure that the author is completely right concerning the genuine need for improved refrigeration 52
T h a n k s a r e d u e to t h e D i r e c t o r G e n e r a l O b s e r v a tories, N e w D e l h i for t h e solar r a d i a t i o n d a t a . T h e p a p e r is p u b l i s h e d w i t h t h e p e r m i s s i o n of t h e D i r e c t o r , Central Building Research Institute, Roorkee.
REFERENCES 1. Parmelee, G. V., "Irradiation of Vertical and Horizontal Surfaces by Diffuse Solar Radiation from Cloudless Skies," A S H V E Transaction, 60, 1954, pp. 341-358. 2. Liu, Y. H. AND Jordan, R. C., " T h e Interrelationship and Characteristic Distribution of Direct, Diffuse and Total Solar R a d i a t i o n , " Solar Energy, IV, 3, July 1960. 3. Moon, P., "Proposed Standard Radiation Curves for Engineering use," Franklin Institute, 9.30, 1940, pp. 583-617. 4. Threlkeld, J. L. and Jordan, R. C., " D i r e c t Solar Radiation available on Clear Days," H . P . A .C., 9.9, 12, December 1957, pp. 135-145.
On the Cover Dr. Zoltan J. Kiss, scientist of the Radio Corporation of America Laboratories, Princeton, N. J., focuses experimental optical maser that recently successfully converted natural sunlight for the first time into a continuous beam of coherent infrared radiation. The apparatus used consisted of a 12-inch hemispherical mirror for focusing the sunlight, a solid state optical maser using a calcium-fluoride crystal, and a spectrometer for detecting the maser output. Solar Energy
Relationship Between Monthly Average Daily Diffuse and Daily Total Radiation
In December at Poona H0 = 650 ly per day. Therefore h'T = f t / H o = 447/650 = 0.677
Assuming that a mean curve (Fig. 13) is valid for solar radiation at Poona D/~? = 0.25
/~'~ = H0 - £r X H00 = 0.25 X 0.677 = 0.169 Or, the average of the daily diffuse radiation at Poona in December is /) = 0.169 X 650 = 110 ly per day This compares well with the observed average value 94.8 ly per day of diffuse radiation.
T h e m o n t h l y a v e r a g e v a l u e s of t h e d a i l y diffuse r a d i a t i o n s h o w a l i n e a r r e l a t i o n s h i p w i t h t h o s e of t h e d a i l y t o t a l r a d i a t i o n (Fig. 13). T h e o b s e r v e d p o i n t s line u p a l o n g t h e e x p e r i m e n t a l c u r v e d e r i v e d b y t h e m e t h o d of l e a s t s q u a r e s . T h e a g r e e m e n t b e t w e e n t h e experimental relationship thus derived and the curve o b t a i n e d b y L i u a n d J o r d a n is g o o d . T h e d i f f e r e n c e c a n be a s c r i b e d t o insufficient d a t a for s t a t i s t i c a l a n a l ysis a n d to t h e p r o b a b l e e x i s t e n c e of h i g h e r d u s t c o n t e n t in t h e D e l h i s k y . H e r e also a m e a n c u r v e m a y be u s e d for c o m p u t a t i o n s till f u r t h e r d a t a are a v a i l a b l e . A s a n i l l u s t r a t i o n , we will a s c e r t a i n t h e a v e r a g e d a i l y diffuse r a d i a t i o n o n a h o r i z o n t a l s u r f a c e a t P o o n a in D e c e m b e r w h e n t h e a v e r a g e of t h e m e a s u r e d t o t a l r a d i a t i o n is 447 ly p e r d a y .
Acknowledgement
L e t t e r to the E d i t o r
equipment which would be cheaper and better suited than present equipment to the needs of economically underdeveloped countries. And I think that there is reasonable possibility that a suitable research and development program could achieve worthwhile results along this line. RAYMOND W. BLISS, JR. Donovan & Bliss 5372 Bennett Valley Road Santa Rosa, California, USA
MORE
ON THE
SOLAR
ICE
MAKER
"A Case for a Solar Ice Maker", which appeared in the January 1963 issue of SOLAR E N E R G Y , is indeed a thoughtprovoking article. There is no particular problem in designing durable and reliable solar ice-making machines within the high cost figures mentioned by the author. His figures amount to stipulating an initial cost not higher than $20 U.S. per daily pound of icemaking capacity. If there really is a substantial demand for solar ice-making equipment at the high cost mentioned by the author, my firm would be happy to supply such a demand, and we could make a very pleasant profit doing so. But I believe that the author, after considering the matter further, will conclude that his stipulated cost figures are unacceptably ifigh for ready marketability. On the other hand, I am sure that the author is completely right concerning the genuine need for improved refrigeration 52
T h a n k s a r e d u e to t h e D i r e c t o r G e n e r a l O b s e r v a tories, N e w D e l h i for t h e solar r a d i a t i o n d a t a . T h e p a p e r is p u b l i s h e d w i t h t h e p e r m i s s i o n of t h e D i r e c t o r , Central Building Research Institute, Roorkee.
REFERENCES 1. Parmelee, G. V., "Irradiation of Vertical and Horizontal Surfaces by Diffuse Solar Radiation from Cloudless Skies," A S H V E Transaction, 60, 1954, pp. 341-358. 2. Liu, Y. H. AND Jordan, R. C., " T h e Interrelationship and Characteristic Distribution of Direct, Diffuse and Total Solar R a d i a t i o n , " Solar Energy, IV, 3, July 1960. 3. Moon, P., "Proposed Standard Radiation Curves for Engineering use," Franklin Institute, 9.30, 1940, pp. 583-617. 4. Threlkeld, J. L. and Jordan, R. C., " D i r e c t Solar Radiation available on Clear Days," H . P . A .C., 9.9, 12, December 1957, pp. 135-145.
On the Cover Dr. Zoltan J. Kiss, scientist of the Radio Corporation of America Laboratories, Princeton, N. J., focuses experimental optical maser that recently successfully converted natural sunlight for the first time into a continuous beam of coherent infrared radiation. The apparatus used consisted of a 12-inch hemispherical mirror for focusing the sunlight, a solid state optical maser using a calcium-fluoride crystal, and a spectrometer for detecting the maser output. Solar Energy