Development of a stack having an optimized flow field structure with low cross transport effects

PEM fuel cells when operated on hydrogen from renewable sources are viewed as one of the most environmentally friendly energy conversion systems due to their high electrical efficiency. However, this advantage is depending on the overall system design, which is largely determined by the allowable operating conditions of the fuel cell stack itself. Besides the active materials, design and shape of the gas distribution zone have a significant influence on stack operation. In order to optimize overall system performance, a fuel cell stack with improved flow field design and performance was developed. An investigation on channel geometries led to a serpentine flow field with a moderate degree of parallelization and ribs with variable width to reduce cross transport effects. The resulting flow field subsequently has been modified slightly to allow a high volume production process. Summarizing, power as well as the degrees of H2 and air utilization could be enhanced leading to a power density enhancement. Furthermore, weight reduction of end plates nearly by half using an improved end plate design led to an overall improved stack design.