Thermoelectric (TE) power sources have consistently demonstrated their extraordinary reliability and longevity for deep space missions as well as for some unique terrestrial applications where unattended operation in remote locations is required. They are static devices with a high degree of redundancy, no electromagnetic interferences, with well-documented “graceful degradation” characteristics and a high level of modularity and scalability. They are also tolerant of extreme environments (temperature, pressure, shock and radiation). The development of new, more efficient materials and devices is the key to improving existing space power technology and expanding into efficient, cost-effective systems using high-grade heat sources, generated through fossil fuel combustion or from waste exhaust streams in transportation, industrial and military applications.
The Thermoelectric Technology Development Project, one of two technology development projects of NASA’s Radioisotope Power Systems Program, has established a roadmap for the advancement and maturation of higher performance TE materials and devices. This roadmap starts with collaborative research efforts to identify advanced bulk thermoelectric materials, capable of quadrupling current state-of-practice average ZT values over the available operating temperature range of 1275 K to 475 K, through the exploration of structurally complex compounds. The roadmap continues with device-level experimental performance validation followed by advancing high temperature couple and multi-couple module technologies in order to establish their long term performance characteristics. We describe how some of these technologies might be infused into next generation space power systems with significantly higher conversion efficiencies and specific power, and could facilitate the development of modular system architectures thanks to highly versatile common device building blocks. We also discuss how these technology investments have helped renew interest in potential terrestrial waste heat recovery and energy harvesting applications using high grade heat sources (above 800 K), and we highlight some recent efforts, near term opportunities, and the unique challenges in terrestrial applications whose solutions can further benefit and promote NASA’s technology goals.