An Along-the-Channel Pseudo-2D Approach for Spatially Resolved PEM Fuel Cell Dynamics

The longevity of proton-exchange membrane fuel cells is influenced by degradation processes whose rates depend on local operating conditions such as temperature, humidity, liquid-water saturation, and reactant availability. Along-the-channel gradients imposed by the flow field can therefore be relevant when interpreting operating behaviour and when formulating models intended to support control and system studies. The AlphaPEM framework provides a dynamic through-plane description, but, in its baseline form, does not explicitly resolve axial non-uniformities in the MEA. This paper presents a pseudo-2D extension of AlphaPEM that couples an along-the-channel gas-channel model to a segment-wise MEA submodel. The original model already implements a plug-flow model discretized into multiple axial control volumes to capture the evolution of species and water vapour along the flow direction. This contribution adds a MEA model derived from the original through-plane formulation with local boundary conditions obtained from the channel (e.g., reactant and vapour concentrations) being evaluated for each axial segment. The segment model retains the key dynamic states required to represent electrochemical response and water management effects in the base framework, including cathode overpotential and membrane/catalyst-layer water variables. Electrical coupling between segments is treated explicitly. Under an equipotential bipolar-plate assumption, a common cell voltage is determined such that the sum of segment currents matches a prescribed operating point. For analysis in the frequency domain, the same structure permits aggregation via segment impedances. The contribution focuses on model formulation as well as coupling strategy and illustrates how axial gradients in operating conditions can be represented within a model that provides efficient simulation of control-relevant PEM fuel cell behaviour.