Investigation of Waste-heat Recovery for Ground Site of Space Solar Power Systems

Abstract

Space Solar Power Systems (SSPSs) are renewable-energy systems that provide a continuous power supply. However, the efficiency of electric-power generation of SSPSs in the research phase needs to be improved. We investigated waste-heat recovery for a ground site of SSPSs to improve this efficiency. One type of SSPSs collects solar energy and converts it into electromagnetic wave in space then transmits it to a ground site on Earth. Most proposed ground sites for SSPSs are spread over several kilometers and receive 1–2 GW. The transmission frequency from space has been considered to be 2.45, 5.8, and 10 GHz, and the size of the ground site differs for each. The conversion efficiency of receiving power at the ground site is assumed to be approximately 70–90%. Therefore, the rest of the energy becomes waste heat. We investigated the wasteheat recovery for a ground site in terms of the frequencies and size of the transmitting antenna and ground site. The cooling system for the ground site is an air-cooling system, and the usable energy of waste heat as a heat source was estimated to be up to 48%.