Performance investigation of an updated alkali metal thermoelectric converter-thermally regenerative electrochemical cycles-thermoelectric generator hybrid system

Abstract

For further recovery of waste heat, alkali metal thermoelectric converter (AMTEC), thermally regenerative electrochemical cycles (TRECS), and two-stage thermoelectric generator (TTEG) are incorporated into a novel thermoelectric coupling system. The waste heat from AMTEC is split into TRECS and TTEG simultaneously. A general mathematical model including the main irreversible losses inside the system and the external heat leakage is built. With the optimization of the current density of AMTEC, the electrolyte thickness, and the fraction of heat dumped into each subsystem, the maximum modeling efficiency and power output are about twice as much as the single AMTEC system. They are 11% and 14% higher than the efficiency and power output obtained if the heat provided to the TRECS and TTEG are equal. Proper distribution of waste heat is necessary. The parametric selection criteria for the optimum states of the hybrid system operation are achieved. Furthermore, the effects of a set of critical factors relevant to TRECS and TTEG are also evaluated. The optimal dimensionless current of TTEG can maximize the power output of the hybrid system, while the internal resistance of TRECS decreases the power output. The conclusions obtained here are general and involve several special cases.