Ripple Current Effects on PEMFC Aging Test by Experimental and Modeling

Abstract

Polymer electrolyte membrane fuel cells’ (PEMFCs) systems usually require power conditioning by a dc-dc boost converter to increase the output fuel cell voltage, especially for automotive applications and stationary applications. The output fuel cell current is then submitted to the high frequency switching leading to a current ripple. The ripple current effects on fuel cell are studied by experimental ripple current aging test on a five cell stack (membrane electrode assembly (MEA) surface of 220 cm2) and compared with a reference aging test. The stack is run in nominal conditions but an ac component is added to the dc load. The ac component is a 5 kHz triangle, amplitude of which is ±20% of the dc component, in order to simulate a boost waveform. Fuel cell characterizations (polarization curves, impedance spectra, and voltammetry) provide information on the PEMFC aging and the performance evolution. Local conditions are computed through a dynamic stack model. The model takes into account transport phenomena, heat transfer, and semi-empirical electrochemical reactions and includes a meshing to calculate local conditions on the MEA surface (gas reactant pressures, local temperature, gas molar fractions, water activity, and local electronic current density). The consequences about performance and aging during high frequency ripple current are explained.