Cathode exhaust Gas Recirculation for Polymer Electrolyte Fuel Cell Stack

Abstract

To ensure the required reliability and efficiency of a Polymer Electrolyte Fuel Cell (PEFC) system, an emergency situation in which the supply of ambient air has to be sealed off, is considered. In this case oxygen from a separate gas tank is fed to the fuel cell system. To prevent the loss of oxygen by the exhaust, the cathode gas can be fed back by cathode gas recirculation while oxygen is injected. Thereby the opportunity to feed back the humidity of the exhaust air for additional fuel cell humidification becomes available. The humidification of a PEFC is essential to ensure high protonic conductivity and reduce voltage losses. However, the water content of the inlet gas has to be regulated to prevent the electrodes from flooding. To control the humidity of the system the gas flow rate, the temperature of the fuel cell and the cathode gas can be adjusted. In addition, the enhanced water content in the system allows increasing the operating temperatures. This work focuses on an experimental study of a 12 kW PEFC-System with cathode gas recirculation and a phenomenological model to optimize the fuel cell humidification depending on the operating parameters.