AN APPLICATION OF THE AVAILABLE ENERGY CONCEPT TO THE ECONOMIC EVALUATION OF SPS* M. NAKAGAWA Hitotsubashi University 2-1 Naka Kunitachi-shi Tokyo 186, Japan From the viewpoint of macroengineering with the objective of making a comprehensive strategy for the preservation and improvement of the Earth’s environment through the creation of space civilization foundation, the solar power satellite (SPS) program has the importance of strategic highlands. In the initial phase of creative activities in space, the necessary energy will be self-supplied by means of solar power generation within each individual system. As the size of the activities expands, demands will increase for electric power supply by means of microwave or laser from an independent power center. The system for energy self-supply within space (System a) and the system for energy supply from space to the Earth (System /J) will require different criteria for measurement of economic value. It is assumed that the criteria for the evaluation of economic activities on Earth dictates higher priority of industrialization to a project with better cost benefit as indicated by cost-benefit analysis. Therefore satellite utilization projects which yield more public benefit, such as communication satellite, broadcasting satellite and Earth observation satellite are preferred, and in their industrial applications, the size which meets the principle of profit maximization according to the classic law of cost is selected. The industrial applications of the Space Shuttle for new medicines and new materials are already evaluated to be capable of achieving benefits exceeding break-even points. If we now divide the process of building SPS strategic highlands into phases, Phase A would be achieving the technical and economic viability of the solar power center. That is to say, to set up Central SPS (abbreviated as CSPS) in the center of System a for the supply of electric power to the satellites and the station in the system. (In case surplus power in the system is stored for making CSPS, this may be called Prephase A.) CSPS is operated and managed so as to maintain some reserve after a certain period of time, having met all the demands for System a. Then the phase moves to B for building System ft. CSPS starts transmitting electricity directly to the Earth. It must be noted, however, that System is still at this stage (a subsystem of System a), and is not yet independent. In other words, the total revenue of System a is included in the captial account, and System becomes a special corporation like Electric Power Development Company of Japan. It is a kind *Presented at the Fourth ISAS Space Energy Symposium, at ISAS, Tokyo, 1 March 1985.
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