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Solar Collector Development
details of t h e e x p e r i m e n t a l procedure are given in Ref. (2). T h e e x p e r i m e n t a l results are p l o t t e d i n Fig. 4 as encircled dots.
Conclusion T h e theoretical analysis of solar mirror panels predicts the o p t i m u m angle, a n d t h e c o n c e n t r a t i o n a t the o p t i m u m angle closely.
Solar Abstracts I--Evaporative Processes (Distillation) E d w a r d s , D. K., N. B a y a r d de Volo, I. C a r t o n , a n d A. Leung, Dept. of E n g i n e e r i n g , U n i v e r s i t y of California, Los Angeles, "Basic H e a t T r a n s f e r Studies R e l a t e d to the Use a n d C o n t r o l of Solar E n e r g y " , F i n a l R e p o r t , N S F G20246, R e p o r t No. 64-14, M a r c h 1964, 161 pp. The report is in 5 parts. Part 1 summarizes methods for the calculation of radiant heat transfer between isothermal solids, an extension of Part 1 of Report 60-93 and Appendix A of Report 62-27. Parts 2 and 3 contain the results of investigations into the radiation characteristics of various materials for use in the collection and control of solar energy. Part 4 deals with some aspects of the problem of collecting solar energy in a porous bed, and Part 5 reports results of an investigation of the suppression of free convection heat transfer, a matter of concern in terrestrial solar collector design. Radiation characteristics and integral equations of transfer are presented for calculation of radiation transfer between solids which are polarizing and imperfectly diffusing. Approximations which reduce the integral equations to simultaneous linear algebraic equations are delineated. Engineering calculations including specular reflection with polarization according to the Fresnel relations are shown to be feasible with present knowledge. K h a m m , M. L., N a t i o n a l Physical Lab., New Delhi, "Solar W a t e r D i s t i l l a t i o n i n N o r t h I n d i a " , Journal of Scientific and Industrial Research, A-General, Sept. 1962, 5 pp., Illus. A summary of results obtained from studies conducted over the past several years on various aspects of solar distillation in northern India. The economics of installation and operation are also discussed.
II--Space
Water
Heating
and
Absorptive
Collectors H e a t h , Atwood R., Jr., a n d P r e s t o n T. Maxwell, NASA, "Solar Collector D e v e l o p m e n t " , Astronautics and Aerospace Engineering, M a y 1963, 4 pp., Illus. The variety of methods under development for conversion of thermal (solar) energy to electricity have stimulated a broad parallel interest in the development of solar collectors. Such devices must concentrate the relatively low-level solar energy (about 130 w/sq ft at the earth's orbit in space) to a usable density (temperature) for the particular energy-conversion method to be employed. The principal factors which must be weighed or considered, can be listed, not necessarily in order of importance, as follows: Operating temperature of the energy-conversion device or system. Efficiency. Weight per unit projected area. 152
REFERENCES 1. Zarem, A. M. and Erway, D. 1)., "Introduction to the Utilization of Solar Energy," McGraw-Hill Book Company, New York, 1963, p. 375. 2. D. L. Merchant, "Analysis and Evaluation of Mirror Solar Panels," M.S. Thesis, Mechanical Engineering Department, New Mexico State University, University Park, New Mexico, December, 1964. Specific power: thermal energy per unit weight at a specific temperature. Prelaunch storage volume and deployment method. Many other factors must be considered, such as structural integrity and stiffness, potential optical degradation due to thermal gradients and space-environment effects, scalability to higher power levels, requirements for masters, and magnetic properties.
X--Photoelectric, Photovoltaic, and Piezoelectric
Photogalvanic
Wolf, M., Heliotek, Sylmar, Calif., " D r i f t Fields i n P h o t o v o l t a i c Solar E n e r g y C o n v e r t e r Cells", Proceedings of the IEEE, M a y , 1963, 20 pgs. A theoretical investigation into the effects of electrostatic drift fields in the diffused region and in the base region of photovoltaic solar-energy converter cells has been carried out. Expressions for a single-layer and a two-layer model for each of the two regions have been evolved. These expressions have been applied to the study of the semiconductor parameters in the diffused region with and without drift field. The applicability of surface recombination velocities in the normal expected range has been established, and the introduction of a drift field in the diffused region has been found to necessitate only a decrease of the minority carrier lifetime by a factor of 4.4 compared to the field-free case. Further, a study of the effect of drift fields in the base region of solar cells upon the rate of their performance degradation due to nuclear particle irradiation has shown that drift fields in the base region can considerably reduce the radiation damage rate and increase the useful life of solar cells in the Van Allen belt enviromnents by about an order of magnitude over that of present n on p radiation resistant silicon solar cells. Various configurations of the drift fields in the base layer, including arrangement in one and two layers with drift field, were investigated in order to find the most promising layout for the achievement of the slowest degradation rates, and to lay the groundwork for future device design work. Data for the more promising configurations are given. Keller, J. W., R. D. Shelton, R. A. P o t t e r , a n d L. Lacy, Research Projects Division, George C. M a r s h a l l Space F l i g h t Center, H u n t s v i l l e , A l a b a m a , "A S t u d y of t h e Effect of G e o m a g n e t i c a l l y T r a p p e d R a d i a t i o n o n U n p r o t e c t e d Solar Cells", Proceedings of the IRE, N o v e m b e r , 1962, 8 pgs. The problem of solar cell damage by proton and electrou radiation is treated analytically from a theoretical and empirical viewpoint. The general approach is to form a damage integral, consisting of the integral over the energy spectrum, for both electrons and protons, of an integrand formed by the product of the differential energy spectrmn and a damage function, and to relate this damage integral to the deterioration of solar cells under irradiation. The damage function is considered theoretically from the microscopic viewpoint of collision theory and empirically by using available experimental data. By making several approximations and assumptions, the data from the solar cell patches on Explorer XI is compared with predictions based upon the empirical relationship developed for the damage integral.
Solar Energy
Conclusion T h e theoretical analysis of solar mirror panels predicts the o p t i m u m angle, a n d t h e c o n c e n t r a t i o n a t the o p t i m u m angle closely.
Solar Abstracts I--Evaporative Processes (Distillation) E d w a r d s , D. K., N. B a y a r d de Volo, I. C a r t o n , a n d A. Leung, Dept. of E n g i n e e r i n g , U n i v e r s i t y of California, Los Angeles, "Basic H e a t T r a n s f e r Studies R e l a t e d to the Use a n d C o n t r o l of Solar E n e r g y " , F i n a l R e p o r t , N S F G20246, R e p o r t No. 64-14, M a r c h 1964, 161 pp. The report is in 5 parts. Part 1 summarizes methods for the calculation of radiant heat transfer between isothermal solids, an extension of Part 1 of Report 60-93 and Appendix A of Report 62-27. Parts 2 and 3 contain the results of investigations into the radiation characteristics of various materials for use in the collection and control of solar energy. Part 4 deals with some aspects of the problem of collecting solar energy in a porous bed, and Part 5 reports results of an investigation of the suppression of free convection heat transfer, a matter of concern in terrestrial solar collector design. Radiation characteristics and integral equations of transfer are presented for calculation of radiation transfer between solids which are polarizing and imperfectly diffusing. Approximations which reduce the integral equations to simultaneous linear algebraic equations are delineated. Engineering calculations including specular reflection with polarization according to the Fresnel relations are shown to be feasible with present knowledge. K h a m m , M. L., N a t i o n a l Physical Lab., New Delhi, "Solar W a t e r D i s t i l l a t i o n i n N o r t h I n d i a " , Journal of Scientific and Industrial Research, A-General, Sept. 1962, 5 pp., Illus. A summary of results obtained from studies conducted over the past several years on various aspects of solar distillation in northern India. The economics of installation and operation are also discussed.
II--Space
Water
Heating
and
Absorptive
Collectors H e a t h , Atwood R., Jr., a n d P r e s t o n T. Maxwell, NASA, "Solar Collector D e v e l o p m e n t " , Astronautics and Aerospace Engineering, M a y 1963, 4 pp., Illus. The variety of methods under development for conversion of thermal (solar) energy to electricity have stimulated a broad parallel interest in the development of solar collectors. Such devices must concentrate the relatively low-level solar energy (about 130 w/sq ft at the earth's orbit in space) to a usable density (temperature) for the particular energy-conversion method to be employed. The principal factors which must be weighed or considered, can be listed, not necessarily in order of importance, as follows: Operating temperature of the energy-conversion device or system. Efficiency. Weight per unit projected area. 152
REFERENCES 1. Zarem, A. M. and Erway, D. 1)., "Introduction to the Utilization of Solar Energy," McGraw-Hill Book Company, New York, 1963, p. 375. 2. D. L. Merchant, "Analysis and Evaluation of Mirror Solar Panels," M.S. Thesis, Mechanical Engineering Department, New Mexico State University, University Park, New Mexico, December, 1964. Specific power: thermal energy per unit weight at a specific temperature. Prelaunch storage volume and deployment method. Many other factors must be considered, such as structural integrity and stiffness, potential optical degradation due to thermal gradients and space-environment effects, scalability to higher power levels, requirements for masters, and magnetic properties.
X--Photoelectric, Photovoltaic, and Piezoelectric
Photogalvanic
Wolf, M., Heliotek, Sylmar, Calif., " D r i f t Fields i n P h o t o v o l t a i c Solar E n e r g y C o n v e r t e r Cells", Proceedings of the IEEE, M a y , 1963, 20 pgs. A theoretical investigation into the effects of electrostatic drift fields in the diffused region and in the base region of photovoltaic solar-energy converter cells has been carried out. Expressions for a single-layer and a two-layer model for each of the two regions have been evolved. These expressions have been applied to the study of the semiconductor parameters in the diffused region with and without drift field. The applicability of surface recombination velocities in the normal expected range has been established, and the introduction of a drift field in the diffused region has been found to necessitate only a decrease of the minority carrier lifetime by a factor of 4.4 compared to the field-free case. Further, a study of the effect of drift fields in the base region of solar cells upon the rate of their performance degradation due to nuclear particle irradiation has shown that drift fields in the base region can considerably reduce the radiation damage rate and increase the useful life of solar cells in the Van Allen belt enviromnents by about an order of magnitude over that of present n on p radiation resistant silicon solar cells. Various configurations of the drift fields in the base layer, including arrangement in one and two layers with drift field, were investigated in order to find the most promising layout for the achievement of the slowest degradation rates, and to lay the groundwork for future device design work. Data for the more promising configurations are given. Keller, J. W., R. D. Shelton, R. A. P o t t e r , a n d L. Lacy, Research Projects Division, George C. M a r s h a l l Space F l i g h t Center, H u n t s v i l l e , A l a b a m a , "A S t u d y of t h e Effect of G e o m a g n e t i c a l l y T r a p p e d R a d i a t i o n o n U n p r o t e c t e d Solar Cells", Proceedings of the IRE, N o v e m b e r , 1962, 8 pgs. The problem of solar cell damage by proton and electrou radiation is treated analytically from a theoretical and empirical viewpoint. The general approach is to form a damage integral, consisting of the integral over the energy spectrum, for both electrons and protons, of an integrand formed by the product of the differential energy spectrmn and a damage function, and to relate this damage integral to the deterioration of solar cells under irradiation. The damage function is considered theoretically from the microscopic viewpoint of collision theory and empirically by using available experimental data. By making several approximations and assumptions, the data from the solar cell patches on Explorer XI is compared with predictions based upon the empirical relationship developed for the damage integral.
Solar Energy