Development of segmented thermoelectric multicouple converter technology

The Jet Propulsion Laboratory (JPL), Pratt & Whitney Rocketdyne, and Teledyne Energy Systems, Inc., have teamed together under JPL leadership to develop the next generation of advanced thermoelectric space reactor power conversion systems. The program goals are to develop the technologies needed to achieve a space nuclear power system specific mass goal of less than 30 kg/kW at the 100 kW power level with a greater than 15 year lifetime. The technologies required for such a power system include liquid metal cooled reactors with outlet temperatures ranging from 1125 K up to 1325 K, segmented thermoelectric multicouple converter (STMC) arrays which can achieve greater than 8 percent system efficiency and carbon-carbon heat pipe radiator panels to reduce the radiator subsystem areal density to a goal of 5 kg/m². The STMC Program's development efforts focused on a highly compact conductively coupled modular thermoelectric converter assembly (TCA) design. STMC design efforts were based on a multicouple design similar to the SP-100 Program's design but using segmented thermoelectric (TE) legs rather than the single alloy silicon-germanium legs. Efforts have addressed in parallel the selection and optimization of the most promising high temperature thermoelectric materials, the development of the various STMC components and sub-assemblies, design, analysis, fabrication and assembly of subscale STMC devices as well as scale-up plans to the 100 kW-class power level. The performance of the selected high temperature TE materials and initial thermal, electrical and mechanical test results on several STMC demonstration devices are reported.