THERMIONIC AMTEC CASCADE CONVERTER CONCEPT FOR HIGH-EFFICIENCY SPACE POWER/

This paper presents trade studies that address the use of the thermion ic/AMTEC cell - a cascaded, high efficiency, static power conversion c oncept that appears well-suited to space power applications, Both the thermionic and AMTEC power conversion approaches have been shown to be promising candidates for space power, Thermionics offers system compa ctness via modest efficiency at high heat rejection temperatures, and AMTEC offers high efficiency at modest heat rejection temperature, Fro m a thermal viewpoint, the two are ideally suited for cascaded power c onversion: thermionic heat rejection and AMTEC heat source temperature s are essentially the same. In addition to realizing conversion effici encies potentially as high as 35 - 40% such a cascade offers the follo wing perceived benefits: Survivability - capable of operation in the V an Alien belts; Simplicity - static conversion, no moving parts; Long lifetime - no inherent life-limiting mechanisms identified; Technology readiness - Large thermionic database; AMTEC efficiencies of 18% curr ently being demonstrated, with more growth potential available; and Te chnology, growth - applicable to both solar thermal and reactor-based nuclear space power systems. Mechanical approaches and thermal/electri c matching criteria for integrating thermionics and AMTEC into a singl e conversion device are described. Focusing primarily on solar thermal space power applications, parametric trends are presented to show the performance and cost potential that should be achievable with present -day technology in cascaded thermionic/AMTEC systems.