Thermodynamic analysis of a novel combined heating and power system based on low temperature solid oxide fuel cell (LT-SOFC) and high temperature proton exchange membrane fuel cell (HT-PEMFC)

Low-temperature solid oxide fuel cell (LT-SOFC) and high temperature proton exchange membrane fuel cell (HT-PEMFC) have attracted significant attention due to outstanding advantages over traditional fuel cells. To increase the energy utilization ratio of LT-SOFC and solve the fuel supply problem of HT-PEMFC, a new combined heating and power (CHP) system mainly composed of a LT-SOFC unit, gas processing unit, HT-PEMFC unit and waste heat recovery (WHR) unit is proposed. For the CHP system, LT-SOFC can not only be used as power generation system, but also as fuel source of HT-PEMFC and heat source of WHR unit. Moreover, the influences of the recirculation percentage, fuel utilization and operating temperature of LT-SOFC on the system performance are revealed. Under typical conditions, the net electric power and total output power of the CHP system are 1002.7 kW and 1388.6 kW, and the net electric efficiency and the total energy efficiency are 62.5% and 86.5%, respectively. The superior performance of CHP system compared with other relevant systems proves its feasibility, and the analysis results also provide theoretic foundation for LT-SOFC based cogeneration systems.