Study of Parabolic Solar Concentrators SUMIO KATO, HIROSHI ODA, YASUHIRO TAKESHITA, YOSHINORI SAKAI, TATSUSABURO NAKAMURA & OSAMU MURAGISHI Summary A conceptual design study of solar concentrators teas carried out and mirror segment models were fabricated and tested. Three kinds of configurations (1.5 kWe, 10 kWe, 15 kWe) were studied. Analyses of the collector efficiencies, standard errors and the optical system were performed. Based on this, we formulated system specifications and design parameters to minimize optical errors. Introduction Power supply requirements for space systems will increase with the steadily growing size and complexity of such systems. After the space station is constructed, large space projects such as free-flying platforms and space factories are likely to be built. Such ambitious projects will require far more than the 10-100 kWe power supply now available. Photovoltaic power systems, which have been in use up to now, are impractical at the power levels desired due to the extremely large solar arrays which would be required. Such arrays would be very massive, substantially increase the drag on the spacecraft (especially in low Earth orbit) and be much more difficult to maneuver. Solar dynamic power systems are more efficient and are about half the size of their photovoltaic counterparts. Parabolic solar concentrators have been studied by many groups [1-4]. We carried out a conceptual investigation of such systems, designed and built examples of mirror segment models, and tested them for their efficiency. This paper describes our design study and presents results of the mirror tests. Conceptual Design of Parabolic Solar Concentrators Basic Assumptions and Requirements Our work was based on three different sets of power supply specifications: 1.5 kWe, lOkWe and 15 kWe output power levels in the same orbit as the space station. The energy conversion system was assumed to use a closed Brayton cycle (CBC) with worst-case efficiencies of either 11% (1.5 kWe case) or 13% (10 and 15 kWe cases). Sumio Kato, Hiroshi Oda, Yasuhiro Takeshita, Yoshinori Sakai, Aircraft Engineering Division, Kawasaki Heavy Industries, LTD., 1 Kawaskai-cho, Kakamigahara-shi, Gifu-ken, 504, Japan; Tatsusaburo Nakamura and Osamu Muragishi, Technical Institute, Kawasaki Heavy Industries, LTD., 1-1 Kawasaki-cho, Akashi- shi, Hyogo-ken, 673 Japan.
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