Solar collector development

Solar Abstracts M i l t o n D. L o w e n s t e i n Director, Technical Research Service Center, Association for Applied Solar Energy, Arizona State University, Tempe, Arizon,~ All d o c u m e n t s in t h e T e c h n i c a l R e s e a r c h S e r v i c e C e n t e r L i b r a r y are classified a c c o r d i n g to t h e c a t e gories l i s t e d b e l o w . R e p r o d u c t i o n s of t h e d o c u m e n t s , e x c e p t b o o k s , are a v a i l a b l e a t 25¢ p e r p a g e (10¢ p e r p a g e for A F A S E m e m b e r s ) .

I l I - - C o o l i n g Processes: Refrigeration and Heat Rejection S y s t e m s Duffle, J. A., R . C h u n g , a n d G. O. G. LOf, S o l a r E n e r g y Laboratory, U n i v e r s i t y of W i s c o n s i n , M a d i s o n , W i s c o n s i n , "A S t u d y of a S o l a r A i r C o n d i t i o n e r " , Mechanical Engineering, 85, N o . 8, A u g u s t , 1963, 4 p. After reviewing the principles of several solar-operated air conditioners, the paper discusses the experimental investigation which utilizes a heat supply from a fiat-plate solar colle,ctor in combination with a source of conventionally generated steam. The steam was used not as auxiliary energy supply, but to amplify the solar collector area: i.e., a solar heat exchanger equivalent to one nmch larger than the existing flat-plate collector was simulated. Solar cooling experiments were ct~rried out on 13 days during the summer of 1962. The most significant of several variable factors was that concerned with solar r,sdiation. A cooling rate of one ton can be obtained with a collector of 200 square feet with radiation at 5.5 Btu per square foot per minute. If a high degree of reliability is required of a cooling system, in most climates it will be necessary to provide an auxiliary source of energy.

IV--Heat Collectors and Solar Cookers lIeath, Atwood R., Jr., NASA Langley Research Center, and Preston T. Maxwell, NASA Headquarters, "Solar Collector Development", Aslronautics and Aerospace Engineering, l , N o . 4, M a y , 1963, 5 p. Examples of six fabricated solar collectors are listed and described, with some details of materials and methods of fabrication. All are paraboloids, except for a fresnel. It has four hinged panels, the surface consisting of electroforming nickel on a steel master that has been machined and polished. The fresnel electroform is then bonded to an electroformed stiffening structure. The others are as follows : (a) an inflatable pressurized collector formed of an aluminized mylar paraboloid and a clear mylar cover; (b) an inflatable-rigidized collector consisting of an aluminized plastic paraboloid; (c) a one-piece collector can made by electroforming a thin dish of nickel on an appropriate master; (d) a petal collector of a hub with attached petals; (e) an umbrella collector consisting of an aluminized mylar skin stretched over metal ribs and with an operational pneumatic erecting mechanism. The characteristics of the collectors are discussed under the following categories: (1) collector efficiency; (2) combined collector-absorber efficiency; (3) collector unit weight; (4) collector specific power; (5) collector packaged volume. Close, D . . l . , " F l a t P l a t e S o l a r A b s o r b e r s : T h e P r o d u c t i o n a n d T e s t i n g of a S e l e c t i v e S u r f a c e for C o p p e r Absorher Plates", Commonwealth Scientific and

Vol. 8, No. 1, 1964

I n d u s t r i a l R e s e a r c h O r g a n i z a t i o n , E n g i n e e r i n g Sect i o n , M e l b o u r n e , A u s t r a l i a , R e p o r t E . D . 7, J u n e , 1962, 19 p. A selective absorbing-emitting surface for flat-plate solar collectors has been developed. It is suitable for copper absorber plates that are used in current Australian solar water heaters. An absorber with a selective surface and one cover sheet was compared with a commercial unit with a black painted plate and two cover sheets, and was shown to collect 10 percent more heat. A method for producing absorber plates with this surface is described, and a procedure for testing the solution used for their manufacture is presented.

V--Thermoelectric C h a d d a , M . M . , arid A. P. B. S i n h a , N a t i o n a l C h e m i c a l L a b o r a t o r y , P o o n a , I n d i a , " T h e o r y of T h e r m o e l e c t r i c P o w e r in L o w - m o b i l i t y S e m i c o n d u c t o r s " , Indian Journal of Pure & Applied Physics, l , N o . 5, M a y , 1963, 3 p. The thermoelectric properties of low-mobility semicondnctors, in which the charge carriers are localized and the electrical conduction takes place through their hopping motion, have been investigated. The heat of transport (Q) and the energy lowering (¢) due to the polarization of lattice have been shown related by the expression Q = Ch - ¢~ where Ch and ¢~ are respectively the components due to polarizations associated with the ions in the hot and cold parts of the semiconductor. It has been shown that the contribution of Q to the thermoelectric power can be appreciable in some cases. The values nf Q/ch have been theoretically evaluated for a face-centred cubic crystal for certain select directions of temperature gr,idient. Linhardt, Hails D., Aeronutronic Division, Ford Motor Company, Newport Beach, California, "Coinparison of S o l a r - T h e r m a l and Solar-ElectricalT h e r m a l P r o p u l s i o n M e t h o d s " , A I A A Journal, 1, N o . 7, J u l y , 1 9 6 3 . 8 p. Solar propulsion concepts based on the simplicity of proposed designs and the availability of free solar energy are discussed. From experience in direct solar propulsion systems and solar power-conversion methods, a preliminary analysis is presented which demonstrates the advantages of either system. The performance of solar-thermal (direct) and solar-electricthermal (indirect) propulsion systems is analyzed and coinpared on the basis of payload and transfer time when applied to satellite transfer missions from 400-mile initial orbit to any high-altitude earth orbit, including escape. Consistent with present booster capabilities, initial low-orbit masses ranging from 200 to 20,000 lb are considered for the performance calculations. Hydrogen is used as propellant for both thermal jets; the perforinance is presented as a function of the frozen flow efficiency. Based on present technology of lightweight solar collectors, the direct system appears to be limited to 900 sec specific impulse, whereas the indirect system has a pogential of about 2000 sec specific impulse with arc jets and about 3000 sec with arc-jet-MHI) accelerators. The optimum specific impulse of the indirect system depends on the mission parameters and the frozen flow efficiency. For fast missions (thrust to initial weight T~,/mo = 10 3) and for propulsion purposes only, the 43