Impacts of Pore Scale Gas Diffusion Layer Deformation on PEMFC Performance at Sub Zero Operation

Abstract

Understanding the effect of clamping pressure on the cold start performance of a polymer electrolyte membrane fuel cell (PEMFC) by considering inhomogeneous compression and intrusion of gas diffusion layers (GDLs) is crucial. In the present study, a three-dimensional model has been adopted to assess the transport phenomena of PEMFC by incorporating the deformed GDLs, which were not considered in the previous PEMFC cold start investigations. A non-linear correlation between contact resistance and clamping pressure is considered in the present unsteady PEMFC model, which would improve the accuracy and practicality of the simulation. A detailed study on the distributions of oxygen, current density, and ice accumulation at two different start-up temperatures (−20 °C and −30 °C) under various clamping pressures is carried out. The numerical findings amply indicate the impracticality of considering uncompressed GDL in cold start simulations with its factitious overestimation of the cell performance. Optimizing the clamping pressure is also essential since a larger clamping pressure would cause more ice to accumulate in the porous media, which would make the reactants at the catalyst sites unavailable. The findings in this study illustrate the relation between the clamping pressure and cold start temperature. For both −30 °C and −20 °C, the uncompressed case gives the highest performance, and with 2 MPa, the cell shuts down sooner than 0.5 MPa and 1 MPa. This study will guide the stack assembly process in practical application.