0191 -9067/81 /010043-10$02.00/0 Copyright ' 1981 SUNSAT Energy Council ASSESSMENT OF SPS PHOTOVOLTAIC SOLAR ARRAY REQUIREMENTS J. RATH AEG-TELEFUNKEN, Space and New Technologies Wedel, Federal Republic of Germany Abstract — System studies for the solar power satellite (SPS) have identified a series of requirements for the solar array which shall be met in order to make the concept technically feasible and economically attractive. The paper gives a discussion and assessment of the most relevant requirements from a state-of-the-art point of view. These requirements are solar cell efficiency, radiation resistance, kV operation of solar array, mass production, and cost aspects. It is shown that intensified R&D effort is necessary to meet the solar array requirements within the SPS time schedule. INTRODUCTION The idea of a solar power satellite (SPS) was bom in 1968. This concept, destined to convert solar energy into electrical energy and to transmit the electrical energy to Earth, has been the subject of various system studies, especially in the U.S. The main outcome of these studies is a reference system which shall serve as a baseline for further detailed studies and to comparative assessment with alternative options to satisfy the terrestrial energy demand. The power generating element of this SPS reference system is a large solar array of approximately 50 km2, which converts the incident sunlight to 10 GW electrical power in geosynchronous orbit. The solar array d.c.-power is then converted to rf-power and formed into an earth oriented focused beam by means of a 1 km diameter microwave antenna. On Earth, the microwave power beam will be collected by a receiving antenna (rectenna) of about 150 km2 and fed into the terrestrial power grid networks. As regards the solar array, two alternative options have been studied: The first option (studied by Boeing and the Johnson Space Centre) is based on singlecrystalline silicon solar cells with no sunlight concentration while the second option (Rockwell/Marshall Space Flight Centre) uses GaAs solar cells which are illuminated with a concentration ratio of 2. The following discussion will concentrate on the silicon solar cell array, however several aspects will also be relevant for the concentrating array. SOLAR ARRAY REQUIREMENTS The system studies performed so far have identified a series of requirements and characteristics which must be met in order to make the concept technically feasible
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