Performance of a PEM fuel cell with oscillating air flow velocity: A modeling study based on cell impedance

TL;DR

This modeling study shows that oscillating air flow velocity in PEM fuel cells can significantly reduce oxygen transport resistance, explaining experimental performance improvements observed under such conditions.

Contribution

The paper introduces a PEM fuel cell impedance model that accounts for harmonic air flow perturbations, revealing how velocity oscillations can lower transport resistance.

Findings

Oscillating air flow reduces oxygen transport resistance.

Complete compensation of resistance occurs at equal oscillation amplitudes.

Model explains experimental performance enhancements under flow oscillations.

Abstract

A model of PEM fuel cell impedance is developed taking into account imposed harmonic perturbation of the air flow velocity in the cathode channel. The flow velocity modulation with the amplitude proportional to AC amplitude of the cell potential lowers the resistivity $R_h$ due to oxygen transport in channel. When relative amplitudes of velocity and potential oscillations are equal, a complete compensation of $R_h$ occurs. This effect explains experimental findings of Kim et al. (doi:10.1016/j.jpowsour.2008.06.069) and Hwang et al.(doi:10.1016/j.ijhydene.2010.01.064), who demonstrated significant improvement of PEM fuel cell performance under oscillating air flow velocity.