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

Abstract

The local current density distribution of polymer electrolyte membrane fuel cells can be distorted by various error states. Differences in current density distributions of adjacent cells in a stack are equilibrized by in-plane currents within the sandwiched bipolar plates. Degradation stressors like detrimental differences of local cell voltage and current density maxima can thus be generated. A novel method was therefore developed to intentionally manipulate current density distribution profiles by integrating local artificial starvation to only one fuel cell in an assembly. This technique is applied in automotive-sized PEMFC single cell as well as in 20 cells 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 current density distribution 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.