Analyses of the fuel cell stack assembly pressure

Abstract

A proper stacking design and cell assembly are important to the performance of fuel cells. The cell assembly will affect the contact behavior of the bipolar plates with the membrane electrode assembly (MEA). Not enough assembly pressure may lead to leakage of fuels, high contact resistance and malfunctioning of the cells. Too much pressure, on the other hand, may result in damage to the gas diffusion layer and/or MEA. The stacking design may affect the pressure distribution within the fuel cell stack and thus the interfacial contact resistance. Uneven distribution of the contact pressure will result in hot spots which may have a detrimental effect on fuel cell life. In this study, finite element analysis (FEA) procedures were established for a PEM single cell with point stack assembly method. The mechanical properties and geometrical dimensions of all the fuel cell components, such as bipolar plates, membrane, gas diffusion layer and end plates were collected for accurate simulation. From the FEAs, the compliance as well as the pressure distribution of the single cell was calculated. In order to verify the results of the analysis, experimental tests, with a pressure film inserted between the bipolar plates and the MEA, were conducted to establish the actual pressure distribution. Color variations of the pressure film could be calibrated to obtain pressure distribution. Compliance of the gas diffusion layer was also measured. The analysis procedures for the fuel cell stacking assembly were established by comparing the simulation results with those of the experimental data at various levels of assembly pressures. They can help determine the proper stacking parameters such as stacking design, bipolar plate thickness, sealing size and assembly pressure, and are important in obtaining a consistent fuel cell performance.