Experimental and Systems Studies of the Alkali Metal Thermoelectric Converter for Aerospace Power

The alkali metal thermoelectric converter (AMTEC) is a thermally regenerative electrochemical device for the direct conversion of heat to electrical energy. It is characterized by high potential efficiencies and no moving parts, which makes it a candidate for space power applications. This paper presents a review of AMTEC operating principles and characteristics showing that device conversion efficiencies of 15-40% may be achievable. Experimental voltage vs current curves are presented where power densities of 0.7 W/cm are observed. Measured electrode efficiencies of up to 40% that confirm the high potential efficiencies of the AMTEC are presented. Also shown are the results of preliminary radiation heat-transfer measurements, data that can be utilized to study methods for reducing parasitic radiation losses in the AMTEC. Finally, the results of a preliminary design study are presented showing that by incorporating the AMTEC into existing space power system designs, conversion efficiencies of 15-20% may be achieved at specific powers of 14-17 We/kg in a small power system (800 W). Similar performance is also predicted for a much larger («360 kW) nuclear electric system.