4-1. Solar Dynamic Power for Space Station Freedom THOMAS L. LABUS, RICHARD R. SECUNDE & RONALD G. LOVELY Summary The Space Station Freedom Program is presently planned to consist of two phases, the baseline phase and the growth, or evolutionary, phase. At the completion of the baseline phase, Freedom's manned base will consist of a transverse boom with attached manned modules and 75 kW of available electric power supplied by photovoltaic (PV) power sources. In the initial growth phase, electric power available to the manned base will be increased to 125 kW by the addition of two solar dynamic (SD) power modules, one at each end of the transverse boom. Power for manned base growth to 300 kW will be supplied by additional SD equipment. Studies have shown that SD power for the growth eras will result in life cycle cost savings of $3 to $4 billion when compared to PV-supplied power. Summary of SD Power Module In the SD power module, a concentrator collects and focuses solar energy into a heat receiver with integral thermal energy storage. A power conversion unit removes thermal energy from the receiver and converts that energy to electrical energy. The concentrator is an offset paraboloid with a reflecting surface made up of triangular mirrored facets mounted in hexagonal frames. The overall concentrator will be pointed to within 0.1 degree of the true sunline. The receiver accepts solar energy and transfers it as thermal energy to the gaseous working fluid of the heat engine by means of integral heat exchanging passages. Using the heat of fusion of a mixture of salts, it also stores a portion of the solar energy as heat for use during the eclipse portion of the orbit. The power conversion unit (PCU) uses a heat engine based on the closed Brayton thermodynamic cycle in which the working fluid is a mixture of He and Xe gases. Temperatures of state points in the cycle are selected so that refractory materials are not necessary for long life. Since the closed Brayton cycle (CBC) is a single phase gas cycle, the conversion hardware (heat exchangers, turbine, compressor, etc.) can be designed for operation in low earth orbit, and tested with confidence in test facilities on earth before launch into space. For mechanical-to-electrical power conversion, the PCU includes a solid rotor, Lundell type, three phase alternator located on the turbine/compressor shaft. The alternator electrical output is converted to distribution quality power by power management and distribution equipment located within the SD Thomas L. Labus and Richard R. Secunde, NASA-Lewis Research Center, Cleveland, OH 44135, USA; Dr Ronald G. Lovely, Rocketdyne Div., Rocketdyne International, Canoga Park, CA 91303, USA. Paper number IAF-ICOSP89-4-1.
RkJQdWJsaXNoZXIy MTU5NjU0Mg==