Current distribution mapping in polymer electrolyte fuel cells—A finite element analysis of measurement uncertainty imposed by lateral currents

Abstract

Using the finite element method, lateral currents in two different configurations for current distribution mapping in polymer electrolyte fuel cells (PEFCs) were simulated and the impact on the accuracy of measurement was analysed. The measurement techniques were of a conventional and a newly developed type, based on a segmented bipolar plate (BPP), respectively, a non-segmented bipolar plate combined with a printed circuit board (PCB). In both cases, neither the membrane electrode assemblies (MEAs) nor the gas diffusion layers (GDLs) were segmented and local currents were detected passively. The resistance of the measurement circuit and the current density gradient between neighbouring segments were found to be the major parameters causing current spreading. As expected, a significantly higher uncertainty of measurement could be observed and experimentally verified for the non-segmented bipolar plate. However, the accuracy is increasing with increasing homogeneity of the current density distribution. Achieving a uniform utilisation of the active area is a major task in fuel cell development and approaching this objective also improves the quality of measurement. Consequently, the application of non-segmented bipolar plates as highly flexible and practical measurement technique is a suitable option for current distribution mapping in technically relevant single cells and fuel cell stacks.