Energetic, exergetic and ecological analyses of a high-temperature proton exchange membrane fuel cell based on a phosphoric-acid-doped polybenzimidazole membrane

According to the first and second laws of thermodynamics, energetic, exergetic and ecological performances of a high-temperature proton exchange membrane fuel cell (HT-PEMFC) using the polybenzimidazole membrane doped with phosphoric acid molecules as electrolyte are investigated in this study. Mathematical expressions for the energy efficiency, power output, exergy destruction rate, exergy efficiency, entropy production rate and ecological coefficient of performance of the HT-PEMFC are derived. Model validation shows that the adopted HT-PEMFC model is valid and reliable. Generic performance characteristics for the HT-PEMFC are revealed. Optimum operating regions for various performance parameters are given based on the optimization criterion of maximum power density. Furthermore, effects of some main operating conditions and designing parameters on the HT-PEMFC system performance are discussed in detail. The results indicate that a higher operating temperature and a greater doping level are significant to the HT-PEMFC system performance improvement, while the operating pressure and relative humidity have less impacts on the HT-PEMFC performance. This work considers both the energy benefit and loss from the point of view of preservation of natural resources and the results may provide some theoretical support for designing higher performance HT-PEMFC systems.