Performance analysis of a micro CHP system based on high temperature PEM fuel cells subjected to degradation

Micro Combined Heat and Power (microCHP) systems based on High Temperature Polymer Electrolyte Membrane (HTPEM) fuel cells is a promising technology allowing to produce electricity and heat with very high efficiency and low emissions also for small power systems. Polybenzimidazole (PBI) based HTPEM fuel cells, thanks to their high CO tolerance, allow the use of fuels other than pure hydrogen by means of a simplified fuel processing unit. However, their relatively low performance and performance degradation rate are still issues to be overcome in order to allow commercialization. In this work, an energy simulation model developed by the authors in a previous research work, has been improved taking into account the degradation of the fuel cell stack in order to assess the performance of the system over long period of operation. The fuel cells performance degradation over time has been implemented on the basis of experimental data obtained by the authors and on data found in literature. The performance of the system has been studied in different configurations that include the introduction of a lithium battery storage in addition to the fuel cell stack. System parameters, such as electrical and thermal energy production, import/export of electricity and primary energy savings have been calculated and compared for different system configurations. Results show that battery integration can improve system performance and that the effect of fuel cell degradation reduces the electricity production. The effect on overall efficiency can be mitigated if heat is recovered.