Modeling, heat transfer, and system integration for a 4kW regenerative PEM fuel cell system

Fuel cells generate approximately as much heat as useful electricity, while electrolyzers convert approximately half the electrical energy input to heat. This study focuses on the rejection of the heat generated from electrolyzer and fuel cell stacks in a hydrogen and oxygen energy storage/conversion system aimed at battery replacement, with the objective of keeping temperatures near optimum of approximately 80 C.; An overall heat balance is performed, with the stack as a control volume, and heat transfers due to the water and gas flows are estimated. Modular, scaleable, finite difference thermal models are created. Data from actual experiments are used to help parameterize the thermal models. For the prototype fuel cell stack, the objective is met by enhancing heat convection to the surrounding air by substituting graphite fins for steel with triple the area, while for the prototype electrolyzer increasing the water flow rate and then cooling the bypass water are found to be most effective.