Gassler, Carter D. and Durka, Michael J. and Barry, Matthew M.
(2025)
A Mixed Methods Approach to Modeling Performance Losses In Thermoelectric Generators Due to Material Sublimation.
Proceedings of Nuclear and Emerging Technologies for Space (2025).
pp. 295-302.
Abstract
Thermoelectric generators (TEGs) serve as critical components in remote power systems, particularly in radioisotope thermoelectric generators (RTGs) used for deep-space missions. These devices leverage the Seebeck effect to convert heat into electrical energy. However, the long-term performance of TEGs, especially those based on silicon-germanium (SiGe) alloys, can degrade due to sublimation of the thermoelectric materials under high-temperature conditions. This sublimation leads to a non-uniform reduction in the cross-sectional area of the thermoelectric legs, affecting their electrical and thermal conductivities and ultimately impacting overall power output. This study introduces a mixed-methods model that combines finite differencing and an analytic unicouple-level model to assess the sublimation effects on SiGe-based unicouples over time. The model discretizes thermoelectric legs into axial slices, enabling the modeling of temperature-dependent sublimation rates axially along the unicouple. Experimental correlations from NASA JPL are used to model mass loss as a function of temperature, which is subsequently translated into reductions in cross-sectional leg area. The proposed model provides a robust framework for evaluating the end-of-life performance of RTGs, offering insights into the mitigation of sublimation effects through advanced materials and coatings.
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