In Situ Performance Analysis of a High Temperature PEM Fuel Cell Stack at Loads

A high temperature PEM fuel cell stack, consisting of 65 planar single cells, was operated in a commercial power module with pure hydrogen and ambient air. AC impedance tests were conducted on the stack module after it reached a steady operating status. The equivalent circuit diagram with three time constants was derived to simulate the measured impedance data. The impedance measurement and simulation were performed to the stack module at different operation settings of stack temperature and load current in order to validate the derived equivalent circuit diagram. In this way, the kinetic and mass transfer processes occurring inside the stack were mechanistically discriminated and identified.