A photovoltaic 12/1 concentrating solar power system with a unique launch stowing configuration
Recent advancements in photovoltaic solar cells made from gallium arsenide (GaAs) have shown that with concentration ratios greater than one solar constant, overall efficiencies up to 23% can be achieved. A second issue applicable to solar power systems for spacecraft is the cost driver, which requires that the efficiency/weight ratio be improved so that solar panels with high output, weighing less, will reduce payload weights, which, in turn, reduces launch costs. This has resulted in a Figure of Merit being introduced to grade the characteristics of solar panels for spacecraft. This Figure of Merit defines a ratio of watts/kilogram for a solar panel. Typical flat plate panels on current spacecraft, fabricated with silicon solar cells without concentration, provide Figures of Merit of 25 to 30 watts/Kg. This paper describes a new design of a 12/1 solar concentrator in which conservative calculations show improvements on this Figure of Merit by a major factor. An ultra-lightweight cylindrical solar concentrator is coiled up around a spacecraft in the launch mode, using the same principle as is used in Lufkin type metal measuring tapes. This provides a high volumetric efficiency launch folded mode as compared to the current method of accordion pleats of flat solar panels. The deployment means of this coiled launch mode configuration is much simpler and inherently more reliable than the current unfolding of accordion pleats, and is self powered by the spring action of the coiled cylindrical aluminum mirror. A special triangular heat pipe transfers the heat absorbed by the solar array to the cylindrical mirror, which also acts as the heat dissipator. Through the use of flexible bellows in the heat pipe assembly the assembly collapses to a cylindrical shape having a radial thickness of less than 1 inch, so that only two coils of this concentrating collector around a 10 ft diameter spacecraft results in a 2 ft. wide, x 66 ft. long deployed collector module capable of generating 2.8 Kwatts of net electrical power with GaAs solar cells having efficiencies of 20%. For a typical 10 ft. diameter spacecraft in a geosynchronous orbit, four such two ft. wide modules would generate at total power of 11.2 Kwatts, and add less than 4 inches to the launch diameter to the spacecraft. Detail weight and ANSYS thermal computer calculations presented in the paper conclude that the maximum temperature of the solar cells in this configuration is less than 70 C and the collector Figure of Merit is between 80 and 100 watts/Kg., depending upon the weight of the heat pipes. The detail design of the heat pipes is continuing and updated calculations are presented in the paper. The cost of this solar power system in production is estimated to be less than $250/watt, because of the 12/1 reduction in the cost of the solar cells as compared to current solar panels.
- Research Organization:
- Optical Energy Technologies Inc., Stamford, CT (US)
- OSTI ID:
- 20000301
- Resource Relation:
- Conference: 33rd Intersociety Energy Conversion Engineering Conference, Colorado Springs, CO (US), 08/02/1998--08/06/1998; Other Information: 1 CD-ROM. Operating system required: Windows 3.x; Windows95/NT; Macintosh; UNIX. All systems need 2X CD-ROM drive., PBD: 1998; Related Information: In: Proceedings of the 33. intersociety energy conversion engineering conference, by Anghaie, S. [ed.], [2800] pages.
- Country of Publication:
- United States
- Language:
- English
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