Optimising the thicknesses of porous transport layers of a PEM fuel cell

This work presents a three-dimensional numerical study on the impact of geometrical parameters of the porous transport layers of a proton exchange membrane fuel cell (PEMFC) on its overall performance using ANSYS Fluent, with the overall current density as the key performance indicator under typical operating voltages of an automotive PEMFC, meanwhile maintaining proper two-phase water transport throughout the transport layers on both electrodes. The coupled charge, mass, momentum, species and energy conservation equations with source terms due to electrochemical reactions and phase change among different phases of water were solved to obtain a steady-state solution, typically using over 1.5 million meshes for the fuel cell, with each transport layer "resolved" in the height direction measuring the layer thickness. The modelling approach is validated against the measured polarisation profile of a PEMFC. Optimising the thicknesses h's of the porous transport layers is the focus of this study. Without changing other characteristics of these porous media, it would naturally be the first step to optimise the configuration of a fuel cell, which requires the least monetary and knowledge investment but potentially leads to substantial performance improvement, especially if the volume of the fuel cell can be reduced, which is important for automotive applications. Although past numerical studies that usually focused on one transport layer have offered valuable insights into optimising a fuel cell's configutration to achieve optimal performance, it will be necessary to investigate a fuel cell as an integrated entity when performance optimisation is the objective, since realistic boundary conditions for all porous transport layers are determined in real time rather than assumed. Via an iterative approach, the present study has attempted to optimise the thicknesses of all porous transport layers of a single fuel cell. Optimal performance of the PEMFC was achieved with a reduction of its volume by 5.1%.