Evaporation front position control in alkali metal thermal electric

Abstract

The present invention provides an alkali metal thermal to electric conversion (AMTEC) cell of the type employing an alkali metal flowing between a high-pressure zone and low-pressure zone in the cell through a solid electrolyte structure. According to the invention, the cell preferably includes a condenser communicating with the low-pressure zone for condensing alkali metal vapor migrating through the low-pressure zone from the solid electrolyte structure. A return channel is coupled to the condenser for directing condensed alkali metal from the condenser toward a hot end of the cell. An evaporator is coupled to the return channel for evaporating the condensed alkali metal and communicates with the high-pressure zone. The evaporator includes means for controlling an evaporation front position of the alkali metal in response to variations in the temperature gradient within the cell as caused by load changes on the cell. Such means for controlling the evaporation front position preferably includes a wick having an alkali metal evaporation surface spanning the temperature gradient. For instance, a conically shaped surface diverging toward the hot end of the cell may be employed.