Effects of anisotropic permeability and electrical conductivity of gas diffusion layers on the performance of proton exchange membrane fuel cells

Abstract

A 3-dimensional model for an in-house proton exchange membrane (PEM) fuel cell with serpentine channels has been developed in order to investigate the sensitivity of the fuel cell performance to the anisotropic gas permeability and electrical conductivity of gas diffusion layers (GDLs). For a realistic range of transport properties being investigated, the fuel cell performance was found to be very sensitive to the electrical conductivity but almost insensitive to the gas permeability of the GDL. For the given operating conditions, the current density was found to be a maximum in the vicinity of the edge between the flow channel and the rib of the current collector. Since the most common GDL materials present a rather significant anisotropy in the in-plane directions, the effects of such anisotropy has been evaluated. Given that the through-plane conductivity is maintained constant for all the cases investigated, for a realistic range of the in-plane electrical conductivity, the fuel cell performance was found to be almost insensitive to this parameter. Therefore such anisotropy can be practically ignored. Finally, for single phase operating conditions, the U-bend in the serpentine channel has no effect on the overall performance of the fuel cell. Hence, only a straight channel of the fuel cell may be modelled and used as a quick performance indicator.