CYCLE ANALYSES OF THERMOELECTRIC-POWER GENERATION AND HEAT-PUMPS USING THE BETA''-ALUMINA ELECTROLYTE

Cycle analyses of the alkali-metal thermoelectric conversion (AMTEC) a nd the high-temperature heat pump using the beta''-alumina electrolyte was performed. It is shown that the isothermal expansion or compressi on of the sodium ion flow through the electrolyte coincides with the e xpansion or compression process in the Ericsson cycle, respectively, w hen the internal losses by thin electrolyte and electrodes are small. The isothermal compression approximation in the heat-pump cycle is mor e consistent with the isothermal expansion in the AMTEC cycle than the adiabatic compression discussed in an earlier report. Typical voltage -current characteristics and thermal efficiencies for both the AMTEC a nd the heat pump are presented including not only the saturated liquid case, hut also the superheated vapour case of sodium at the high temp erature side. The operation in superheated vapour shows a decrease in the power-generation efficiency for the AMTEC and an increase in the c oefficient of performance for the heat pump.