THERMOELECTRIC POWER GENERATION ARPA-E Small Engines Workshop, May 2014 Scope: Historical perspective Technology basics – Materials – Devices Today’s applications Commercialization potential Dmitri Kossakovski, Advanced R&D, Gentherm, Inc. [email protected] SUMMARY – THERMOELECTRIC GENERATORS Highlights Concerns • High reliability due to • Material level efficiency in 6- minimum of moving parts 10% range in WHR applications • Field-proven in space and terrestrial apps • System level efficiency in 1- 3% range • Well-suited for autonomous applications • Usage of scarce elements • Industry push to low cost • Low production volumes materials, devices and production methods • Slow progress in material improvement 2 HISTORICAL PERSPECTIVE THERMOELECTRICS – AN OLD KID ON THE BLOCK • Late XIX century – electroplating needs electricity! • Heat source: gas or coke • Material system: ZnSb/Fe 192 Watts, at 54 Volts and 3.5 Amps Top view of electrical circuit http://www.douglas-self.com/MUSEUM/POWER/thermoelectric/thermoelectric.htm 4 RELIABLE AUTONOMOUS POWER 5 TODAY’S APPLICATIONS Curiosity Mars lander, ~120 W TEG (all spacecraft flying beyond Mars uses a TEG) Gas-powered TEG for remote generation of electricity along pipelines, up to 500 W per unit Water heater or gas furnace pilot light control 750 mV, ~50 mW 30 mV, ~10 mW 6 TECHNOLOGY BASICS CONVERSION OF HEAT TO POWER • solid state effect • compound semiconductors are most efficient • materials judged by figure of merit, Z, preferring: - Low thermal conductivity - High electrical conductivity - High thermo EMF (Seebeck) Construction of a typical commercial device 8 TYPICAL THERMOELECTRIC SEMICONDUCTORS • No material covers wide temperature range • Average ZT is not far from 1 • Dependence on low abundance materials 9 MATERIAL LEVEL EFFICIENCY 10