The impact of operating parameters and system architecture on the water management of a multifunctional PEMFC system

Abstract

The focus of this paper is on multifunctional PEMFC application considering the products electric power and oxygen depleted air (ODA) to be used in aviation. Presented are operation and architecture analyses of a PEMFC system (HyPM XR 12) based on process simulations as well as experimental investigations. The effects of the stack temperature (20–90 °C), the operating pressure (0.2–2.0 bar) and the cathode stoichiometric ratio (1.0–5.0) on the resulting average relative humidity of the cathode exhaust gas and consequently on the efficiency and stability are evaluated for a single and a highly innovative twin system (serial cathode including an interim condensation process). The results achieved are used to identify operation and architecture improvements for an appropriate water management, a key aspect to optimize efficiency and stability of PEMFC systems [1]. Based on the process simulation and experimental investigations can be summarized: In single and twin system operation the stack temperature and the cathode stoichiometric ratio have to be decreased at reduced operating pressure to avoid membrane dehydration. An additional feed gas humidification could be appropriate, especially at low pressure operation. The twin system architecture is relevant to minimize fuel cell flooding at high operating pressure and low stoichiometric ratios required to achieve ODA specifications.