The impact of flow field plate misalignment on the gas diffusion layer intrusion and performance of a high-temperature polymer electrolyte fuel cell

Abstract

Tolerances in the production process of flow field plates for polymer electrolyte fuel cells (PEFCs) and the assembly of single cells and stacks can lead to a misalignment among the flow field plates. Due to clamping and misalignment, shear stresses can be forced on the membrane electrode assembly (MEA). Furthermore, the gas diffusion layer (GDL) intrudes into the channel. In this study, five different degrees of misalignment (0 to 1000μm) are applied to a fuel cell model consisting of two flow field plates with five adjacent channels each (1 mm width) and an MEA in between them. For each degree, the MEA is compressed by about 30% and 3D images (tomograms) are recorded using an X-ray computer tomograph (CT). Analyzing the cross-section of the channels, the maximum intrusion depth varies for each channel. Furthermore, the shape of the membrane becomes ever more wavelike, with increasing misalignment and the position of the maximum intrusion depth shifts sideways from the center of the channel. Additionally, high-temperature polymer electrolyte fuel cell (HT-PEFC) single cell experiments are carried out. Two degrees of misalignment are set (normal assembly and 1000μm). The performances of both degrees of misalignment are within 5% at a power density of 0.24 W.cm−2.