0191-9067/85 $3.00 + .00 Copyright ® 1985 SUN SAT Energy Council CRYOGENIC POWER DISTRIBUTION ON A SPACE POWER STATION N. HIGUCHI, I. ISHII, 1. KUDO and Y. KIMURA Electrotechnical Laboratory 1-1-4 Umezono. Sakura, Niihari Ibaraki, 305 Japan Abstract — A power distribution system on a 5 GW space power station (SPS) is proposed, utilizing a low voltage DC superconducting (SC) cable system. The electric power generated at the solar cells is collected up to 4 kV 10 kA by means of aluminum bus bars, and fed to the converting system through the SC cable system. The maximum current of the bus bars is determined by minimizing the summation of the Joule losses and the refrigerating load. The superconductor is aluminum stabilized NbTi, and the negative and positive conductors are laid coaxially to suppress the magnetic field outside the cable. The cable is designed to be compact for easy transportation by the space shuttle. The dimensions of the cable are varied depending on the rating. The largest diameter is 130 mm (5.1 in.) at the rating of 4 kV 250 kA. Its thermal insulation, consisting of blankets of multilayer insulation and a proper radiating system, needs no vacuum vessels in the space environment. The power for refrigerators is estimated as up to 19 MW, and its total weight is 7x IO5 kg (1.5x 106 lbs), but improvement can be expected. It is concluded that the proposed SC cable system provides a better efficiency and lower lift-off weight to the station, in comparison with the values of systems of normal conductors. INTRODUCTION A space power station is one of the most attractive solutions to the energy problem because it provides huge and absolutely clean power. It seems difficult to realize a practical SPS in this century, however, we have to continue to make efforts to improve its subsystems. The authors tried to investigate the application of a SC cable system to the reference model by NASA/DOE, rating 5 GW at the ground. According to an estimation, it is necessary to generate 10 GW on a SPS to obtain 5 GW at the ground. It is of great importance to design highly efficient subsystems. However, no improvement can be expected in the power dissipation of the aerial system, which accounts for the major portion of the loss. Therefore, it is essential to obtain lower losses in the power distribution and conversion subsystems. A superconducting cable system is quite effective in this situation. DESIGN OF CABLE SYSTEM Direct current is chosen for the distribution system, and a relatively low voltage of 4 kV is selected as the rating, which makes the insulation simple at bus bars and minimizes the allowable bending radius of the cable. Consequently, the maximum
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