Flooding Characteristics and Countermeasures in a PEM Fuel Cell System

Abstract

PEM fuel cell systems in automotive applications must provide a low minimum power compared to their maximum power. Especially systems without external humidification require a rather low stoichiometry and elevated pressure at the cathode to avoid dry-out at low load operation. Targeted experiments show that this may cause flooding, as the gas velocity becomes too low for sufficient liquid water drainage. An increase of the gas velocity would cause a membrane dry-out, negatively impacting the cells performance and lifetime. One solution for this issue is proposed in this work: a dynamic operation of the air system, which is periodically switched between one set point for membrane humidification and another one for liquid water drainage. A sophisticated experimental fuel cell system is used to test the proposed solution on a 100kW stack.