Thermal Characteristics of Multi-Heat Source Recovery in a Fuel Cell Combined Heat and Power System

Fuel cell-based combined heat and power (CHP) systems enable cascade conversion of hydrogen chemical energy into electricity and heat, providing an effective pathway to enhance overall energy utilization efficiency. In this study, a system-level simulation model for a proton exchange membrane fuel cell CHP waste heat recovery system is developed, incorporating stack waste heat, auxiliary component heat dissipation, catalytic combustion heat, and air-source heat pump upgrading. The multi-source coupling characteristics and the effects of key operating parameters on system performance are quantitatively investigated. The results show that within the current density range of 0.2–1.2 A/cm 2 , the fuel cell stack is the dominant heat source, with heat generation increasing linearly with current density. The catalytic combustion unit acts as a marginal heat source, contributing less than 2% of total heat. The performance of the heat pump system is primarily influenced by ambient temperature and compressor speed. The system energy distribution exhibits significant load dependence: as current density increases, the stack heat contribution rises from 35% to 78%, and the primary source of auxiliary power consumption shifts from the heat pump compressor to the stack air compressor. Although the heat pump COP continues to decline, the system COP first increases and then stabilizes. Sensitivity analysis indicates that ambient temperature improves CHP efficiency by 18% while increasing compressor speed enhances thermal efficiency by 51.7%, but reduces electrical efficiency by 25.2%, resulting in an overall CHP efficiency improvement of 11.0%. In contrast, cathode inlet pressure has a nearly neutral impact on system performance (<0.7% fluctuation).