Solar Power Satellite Life-Cycle Energy Recovery Consideration S. WEINGARTNER *, J. BLUMENBERG ** Summary: The construction, in-orbit installation and maintenance of a solar power satellite (SPS) will demand large amounts of energy. As a minimum requirement for an energy effective power satellite it is asked that this amount of energy be recovered. The energy effectiveness in this sense resulting in a positive net energy balance is a prerequisite for a cost-effective power satellite. This paper concentrates on life-cycle energy recovery instead of monetary aspects. The trade-offs between various power generation systems (different types of solar cells, solar dynamic), various construction and installation strategies (using terrestrial or extra-terrestrial resources) and the expected/required lifetime of the SPS are reviewed. The presented work is based on a 2-year study performed at the Technical University of Munich. The study showed that the main energy which is needed to make a solar power satellite a reality is required for the production of the solar power plant components (up to 65 %), especially for the solar cell production. Whereas transport into orbit accounts in the order of 20 % and the receiving station on earth (rectenna) requires about 15 % of the total energy investment. The energetic amortization time, i.e. the time the SPS has to be operational to give back the amount of energy which was needed for its production, installation and operation, is about two years. Introduction The solar power satellite (SPS) concept as proposed by P. Glaser [1] considers an Earth-orbiting solar-electric power plant which beams its generated power to a receiving station on Earth. The provided electrical power on the order of a few GW on Earth and is supposed to be a considerable contribution to terrestrial power needs. Once installed and operational such a SPS could deliver energy with little negative effects on the Earth's environment - no emissions, no contribution to the greenhouse effect, no nuclear waste. The only critical factor with regard to the environment is the energy transmission from orbit down to Earth. Figure .1 shows the conceptual design of the NASA/DoE reference system. Two main options are considered for transferring the energy from the satellite to the receiving station: a microwave transmission or a laser beam. According to several NASA studies, e.g. [2], [3], the impact of both options on the atmosphere is considered * Deutsche Aerospace AG, Munich, Germany, Space Transportation and Propulsion Systems ** Technical University of Munich, Munich, Germany Institute C for Thermodynamics
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