Optimal design and performance evaluation of a cogeneration system based on a molten carbonate fuel cell and a two-stage thermoelectric generator

Abstract

ABSTRACT Integrating a two-stage thermoelectric generator (TTEG) with a molten carbonate fuel cell (MCFC), a new hybrid system is put forward to harvest the waste heat from the MCFC for performance improvement. Both thermodynamic and electrochemical irreversible losses in each subsystem are fully taken into account. The thermoelectric element (TEM) number ratio between hot stage and cold stage is optimally designed using power output as objective function. The mathematical relationship between MCFC operating current density and the optimised TTEG dimensionless electric current is obtained, from which the MCFC operating current density interval that allows TTEG to function is determined. The analytical expressions for equivalent power output and efficiency to evaluate the hybrid system performance are obtained. The proposed hybrid system is demonstrated to be superior to either stand-alone MCFC or MCFC/single-stage TEG hybrid system. Effects of some crucial design and operation parameters on the system performance are revealed by parametric studies.