Investigation on the performance heterogeneity within a fuel cell stack considering non-isopotential of bipolar plates

The isopotential assumption of bipolar plate was widely employed to study the heterogeneity within a fuel cell stack, not only for numerical modelling purposes, but also for the deployment of cell voltage monitors (CVMs). Although this assumption is questionable according to previous studies, few comprehensive investigations have been conducted on the possible coupling phenomenon between the non-isopotential within one cell and stack's heterogeneity between cells. Taking a U-type commercial stack as an example, we conducted orthogonal tests and discovered: (a) when air stoichiometry is low, the air supply is insufficient for the cell farthest from the manifold's air inlet, making the local voltage near the cell's air outlet lower than the others. (b) Under the wet condition, liquid water accumulates at the manifold's air outlet and impedes the air flow of the nearest cell, leading to lower local voltage at cell's air outlet. (c) Under the dry condition, for the cell closest to the manifold's air inlet, the local voltage of cell's air inlet is counterintuitively higher than the others, possibly due to the self-humidification effect. Finally, the suggestions were given to the deployment of CVMs and typical working conditions were summarized.