Measurements of Air Velocities in Polymer Electrolyte Membrane Fuel Cell Channels Using Electrochemical Impedance Spectroscopy

In this work, air velocities in the channels of an operating polymer electrolyte membrane fuel cell are measured using electrochemical impedance spectroscopy (EIS). From the equations of the oxygen transport in fuel cell channels, we derive an analytical expression of the channel impedance at low frequencies which is a function of the operating conditions, the channel geometry and air velocity only. Air velocities are computed using a nonlinear curve fitting of the analytical channel impedance to the single cell impedance measured at current densities ranging from 0.16 to 0.5 A/cm 2 under various air stoichiometries. Our results show less than 13% of relative error between the theoretical air velocities given by the mass flow controller and those measured from the fuel cell impedance for current densities lower than 0.42 A/cm 2 . A direct application of this work is the real-time diagnostic of fuel cell channel clogging in stack configuration.