Interaction phenomena of electrically coupled cells under local reactant starvation in automotive PEMFC stacks

The local current density distribution of polymer electrolyte membrane fuel cells (PEMFCs) can be distorted by various error states. Differences in current density distributions (CDDs) of adjacent cells in a stack are equilibrized by in-plane currents within the sandwiched bipolar plates. Degradation stressors such as detrimental differences in local cell voltage and current density maxima can thus be generated. A novel method was therefore developed to intentionally manipulate CDD profiles by integrating local artificial starvation into only one fuel cell in an assembly. This technique is applied to automotive-sized PEMFCs single cells as well as in 20 cell short-stack to analyze such voltage and current redistribution phenomena. A drastic distortion of local cell voltage is only observed for stacks, which is explained by a supplementary simulation. The local voltage distribution of an electrically coupled fuel cell is therefore calculated by combining CDD measurements with a spatially resolved polarization curve model. The capabilities and limits of a multipoint cell voltage monitoring measurement device are discussed on this basis. The inspected correlation between these two independent online measurement techniques allows to localize such error states with considerable accuracy during operation of automotive sized PEMFC stacks.