Performance analysis of a direct carbon fuel cell with molten carbonate electrolyte

The model of a packed bed anode DCFC (direct carbon fuel cell) with molten carbonate as an electrolyte and graphite as a fuel is established to globally evaluate its performance. Thermodynamic-electrochemical analyses on the performance of the DCFC are implemented, in which the activation overpotential, ohmic overpotential, and concentration overpotential are taken as the main sources of voltage losses. The analytical expressions for the cell voltage, power output, efficiency, and entropy production rate are derived, from which the general performance characteristics are discussed in detail. At the anode, the ohmic overpotential in each slab resulting from the carbon phase is found to be about three orders of magnitude larger than that resulting from the electrolyte phase. The radius of the real contact area between two neighboring graphite particles decreases at an accelerating rate as one goes up in the bed, and the corresponding constriction resistance will increase at an accelerating rate. The decrease in the operating current density and anode dimension and the increase in the operating temperature will lessen the overall ohmic overpotential. The effects of the operating current density, operating temperature and anode dimension on the performance are discussed, and the optimum criteria for some important performance parameters are determined.