On electric resistance effects of non-homogeneous GDL deformation in a PEM fuel cell

The electric resistance is very important for the performance of a proton exchange membrane (PEM) fuel cell. However, the performance analysis is more complex as the cell operates under assembly conditions. At such conditions, the mass transfer is deteriorated but the electric conductivity is favored. In this paper, the electric resistance of a cell is evaluated by application of a recently developed method in the through-plane direction of the electrodes, together with consideration of the contact resistance between the gas diffusion layer (GDL) and bi-polar plates (BPP) for various assembly pressures. The predicted electric resistance and deformed GDL were implemented in an existing CFD code for evaluation of the PEM fuel cell performance. It is found that the electric current is distributed in a narrow area in the GDL under the shoulders and then redistributed into the BPP above the channels for all cases. The channel/rib structure promotes a non-homogeneous electric conductivity along the cell in the in-plane direction and a concentrated area of the current flow around the corner of the BPP close to the channels as the cell is subject to an assembly pressure. Additional contact areas are created between the GDL and BPP at the vertical interface when the cell operates at an assembly pressure above 2 MPa. Therefore, both the corner of a BPP close to the channel and the GDL region become the dominating zones, where the electric current under the middle of the channel must cross over a longer distance due to the intrusion of the GDL into the BPP. In addition, the optimized cell performance is obtained as the cell is operating below 1 MPa assembly pressure. The findings are useful for proper design of PEM fuel cells.