A comprehensive investigation on performance heterogeneity of commercial-size fuel cell stacks during dynamics operation

The performance heterogeneity of commercial-size proton exchange membrane (PEM) fuel cells comprises both inter-cell consistency and intra-cell uniformity, which can lead to the generation of degrading stressors, such as harmful variations in local cell voltage and current density. However, there is a notable absence of a thorough investigation of the potential correlation between inter-cell consistency and intra-cell uniformity. To address this knowledge gap, a comprehensive experimental study was conducted via the current distribution model to assess the impact of several operating variables, including loading rate, cathode stoichiometry ratio, and cathode pressure, on the performance heterogeneity of commercial-size fuel cell stacks. The results indicate that cells situated on both end sides of the stack are more susceptible to non-equipotential phenomena owing to liquid water accumulation and the inhomogeneity of oxygen distribution, which in turn lead to the redistribution of the in-plane current as well as the deviation of the bipolar plate potential. Moreover, a significant correlation exists between inter-cell consistency and intra-cell uniformity of cells placed at both ends of the stack with a correlation coefficient > 0.85. The enhancement of fuel cell stack output performance and reduction of performance heterogeneity may be achieved by optimizing pressure and stoichiometric ratio. However, it should be noted that there exists a discrepancy in the operating conditions necessary to achieve optimal performance and minimal performance heterogeneity. Finally, the recommendations given for the implementation of cell voltage monitors (CVMs) were summarized. This study provides a comprehensive reference for analyzing complex heterogeneity issues within fuel cells, revealing significant potential in their application.