Thermal energy recovery of molten carbonate fuel cells by thermally regenerative electrochemical cycles

Abstract

Molten carbonate fuel cell (MCFC) is combined with the thermally regenerative electrochemical cycle (TREC) to form a novel hybrid system. TREC is considered for harvesting the waste heat of the MCFC and converting it into electricity. The hybrid system performance analyzed in terms of energetic and exergetic, and optimum criteria for critical parameters, like the current density, power output, and efficiency, are specified. Moreover, the effects of the MCFC and TREC critical design parameters on the system performance are discussed. It was obtained that a higher operating temperature of the MCFC increases the power output and efficiency of the hybrid system while decreases exergy destruction. Higher temperature coefficient and regeneration efficiency and lower internal resistance for the TREC lead to higher power output. Multi-objective optimization was applied, and for choosing the final optimal solution, Fuzzy, TOPSIS, and LINMAP decision-making techniques are employed. It was revealed that the maximum power output density and exergy efficiency for the hybrid system was about 6.4%–26.5% and 7.5%–26.4% higher than a standalone MCFC, respectively. Furthermore, the MCFC-TRECs system is evaluated against other MCFC-based hybrid systems, and it was found that TREC could be considered a favorable option for waste heat recovery of the MCFC. The outcomes of the present paper are useful for the design and optimization of the MCFC hybrid system and improving the thermal performance.