Radioisotope thermoelectric generators with novel/high performance thermoelectric modules for lunar and deep space exploration

Kurzfassung

Planetary and deep space exploration requires a continuous supply of electrical power, independent of solar irradiation, which can be provided by Radioisotope Thermoelectric Generators (RTGs). RTGs employ decay heat from a nuclear fuel and thermoelectric modules for power generation. The power output of an RTG depends on the employed kind and amount of fuel, environmental temperature, various geometrical parameters of the RTG components, and, most importantly, on the design of the thermoelectric modules. Current designs for a European RTG are based on bismuth telluride-based thermoelectric modules, which suƯer from low conversion eƯiciency and limited maximum operation temperature. Isabellenhütte thermoelectric modules based on Half-Heusler alloys and the proprietary ISA-Plan® technology are directly addressing the aforesaid disadvantages of currently available BiTe thermoelectric modules by accepting much higher operating temperature differences resulting in significantly increased conversion efficiency. However, the application of novel high temperature thermoelectric modules requires a modification of the RTG design for optimized performance, which is a complex multi-parameter optimization. To address this challenge, we have coupled a thermoelectric network model to a genetic algorithm which can be used to optimize the design with respect to various targets, e.g. maximizing gravimetric power density. Validation with full 3D finite element analysis yields diƯerence in the performance parameters of less than2% at calculation times reduced by a factor of 1000 and requiring substantially lower computational resources of the network model compared to FEA. Comparison of the optimized designs for state-of-the-art technology to Isabellenhütte modules yields substantially increased harvestable temperature differences across the thermoelectric modules, substantial design modification like reduced heat exchanger masses and significantly increased performance.