0191-9067/85 $3.00 + .00 Copyright e 1985 SUNSAT Energy Council A CONCEPTUAL DESIGN OF A SOLAR-RAY SUPPLY SYSTEM IN THE SPACE STATION NOBUHIRO TANATSUGU, MASAMICHI YAMASHITA Institute of Space and Astronautical Science Komaba, Meguro-ku Tokyo 153, Japan KEI MORI Faculty of Science and Technology Department of Administrative Engineering Keio University, Hiyoshi, Kohhoku-ku Yokohama 223, Japan Abstract — Some of the activities planned for the space station, e.g., the cultivation experiment of plants, the room illumination of modules and sunbathing for the crew, etc., will require a lot of energy in the original form of the solar rays. In order to meet this requirement, a solar ray supply system (SRSS) presented here has been proposed. The solar rays are collected and concentrated by means of the solar ray collector made of lenses or mirrors and transmitted anywhere it is needed by means of the light conducting fiber cable and radiated from the emitters well suited for each purpose. The present system has two primary advantages in comparison with an electricity-light conversion system: (1) the light provided is suitable for photosynthesis in plants because its spectrum is nearly consistent with natural sunlight accepted on the ground, (2) the very high system efficiency (higher than 50%) can be expected because of direct utilization of solar ray without any conversion. The spectrum of solar ray provided in the present system is limited between 350 and 850 nm in order to avoid the harmful effects on human beings and plants, but the system is also able to supply a solar ray with the wider spectral range necessary for a solar pumped laser and photochemical plants. The present solar-ray supply system shall be proposed to the U.S. Space Station project as one of the seven International Study Task being performed in Japan. INTRODUCTION We can accept the mean solar energy of 1353 W/m2 (called solar constant) on Earth orbit without an atmosphere, which is decomposed into the spectral irradiance as shown in Fig. 1 (1). The visible part of the solar radiation energy lies in the band from 400 to 700 nm which includes 55.4% of total solar power and is of interest to life science experiments. When we treat the visible part of the solar ray, the light intensity is usually evaluated using illuminance in unit of lx. We can get a solar light intensity of 126,760 lx on the Earth orbit. The present SRSS is planned to utilize directly the solar ray without any transformations. It provides the solar ray necessary for various activities in the space station, for instance, cultivation experiments on plants and algae, sunbathing for the crew and room illumination. This system can also be applied to various other experiments using the solar ray such as the solar- pumped laser and the photochemical plants. In this case, it is necessary to adjust the band of the solar spectral irradiance to be collected so as to be suitable for each purpose.
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