Experimental evaluation of electrode conversion efficiency of alkali metal thermal to electric converter

The alkali metal thermal to electric converter (AMTEC) system which utilizes the sodium ion conductivity of a beta"-alumina solid electrolyte (BASE) is expected to have high conversion efficiency above 30% including practical heat losses. However, the achieved experimental 0efficiencies have been around 15%. In this paper, current-voltage characteristics and heat and mass transfer processes on a single cell have been examined experimentally and thermal electrode conversion efficiency has been discussed. Measured electrode conversion efficiency without thermal losses showed that it was about 40% at a power density of 0.3 W/cm². A theoretical analysis on the thermal losses has also been conducted and these losses are estimated to be 0.3 W/cm² in a practical tube type cell, so that an actual cell system efficiency of 30% is expected.