High current density and low stoichiometry operation of a proton exchange membrane fuel cell with microchannels

The operation of proton exchange membrane fuel cells (PEMFC) at current densities in the order of 10 A cm −2 is investigated. Such high current densities are conceivable when the fuel cell employs cathode flow microchannels with dimensions in the order of 150– 200 μ m to obtain a high pressure drop in conjunction with the perforated metal transport layers to enhance waste heat removal. Employing a state-of-the-art computational fluid dynamics model that is based on the Eulerian multiphase approach, high current density fuel cell operation is studied, and the interplay between the operational pressure, temperature and stoichiometric flow ratio is investigated in detail. The results suggest that a combination of a current density in the order of 8-10 A cm −2 together with a low stoichiometric flow ratio around ξ =1.2-1.5 is feasible, while the air only needs to be minimally humidified because the high pressure at the cathode inlet leads to immediate self-humidification of the membrane. If indeed practical, this mode of operation can lead to unprecedented high power densities. Finally, the molar ratio of the inlet water to the product water Θ is calculated, and its importance for the sizing of the humidifier is highlighted. • Fuel cell operation at high currents and low stoichiometries is investigated. • Perforated metal plates are used as gas diffusion layers. • A 1D model is used to identify fuel cell operating conditions. • A 3D model is used to investigate PEMFC operation at high current densities. • The ratio between the incoming water and the product water is calculated.