Performance assessment of an integrated molten carbonate fuel cell-thermoelectric devices hybrid system for combined power and cooling purposes

In order to recover the waste heat produced in molten carbonate fuel cells (MCFCs), a new hybrid system mainly consisting of an MCFC, a thermoelectric generator, and a thermoelectric cooler is integrated for performance enhancement. The irreversible losses in each subsystem are fully considered. The relationship between the dimensionless electric current of the thermoelectric element and the electric current density of the MCFC is discussed in detail. Based on non-equilibrium thermodynamics, the analytical formulas for power density and efficiency of the hybrid system are specified under different operation conditions. The general performance characteristics of the hybrid system are revealed and the optimum regions for several parameters are given. Numerical calculations show that the power density and efficiency of the hybrid system are 3.4% and 4.0% larger than that of the stand-alone MCFC, respectively. The effects of some main operating and design parameters on the performance of the proposed system are discussed through parametric analyses. Abundant numerical calculation examples are provided to show how to improve the system performance. The results obtained may provide some theoretical bases for the MCFC performance improvement through heat management method.