Theoretical Analysis for Improving the Efficiency Of HT-PEMFC through Unreacted Hydrogen Circulation

To increase the efficiency of fuel processor and HT-PEMFC (High Temperature-Proton Exchange Membrane Fuel Cell) combined system, it is essential to improve the efficiency of a fuel processor. In this research, the fuel processor was simulated by Aspen Hysys® simulator, and effect of the various operating conditions on the total efficiency was investigated. Thermal efficiency of the fuel processor increased as the temperature and S/C (Steam to carbon) ratio increased, and the efficiency was higher at the S/C ratio of 3 than at the S/C of 4 at the reformer temperature of 700 ℃ and higher. Under the selected operating conditions of the fuel processor, recycling of unreacted hydrogen from the anode off gas (AOG) of the HT-PEMFC improve the overall efficiency of the combined fuel processer and HT-PEMFC by a factor of 1.28. Operating conditions where the AOG supplied excessive heat than required for fuel processor operation were excluded. The high-efficiency operating conditions of the fuel cell system were proposed with the target of 5 kW of output as the capacity of the household HT-PEMFC.