Experimental investigation on performance and water transfer in passive type PEFC

Abstract

A fuel cell with a simple structure and operating at nearly ambient temperature and pressure is suitable for low cost small-sized generator sets ranging from several to tens Watts for home, outdoor and emergency use. This kind of fuel cell is called passive or self-breathing PEFC. Water management is very important and sometimes crucial for a long term stable operation in the passive type PEFC because control of gas temperature and humidity is inherently not easy for the PEFC. In this paper, various performance characteristics regarding the passive type PEFC were experimentally investigated using a rated 55 W fuel cell module with 20 cells laid out in plane. The properties, such as the output voltage of each cell, the temperature, pressure and humidity of hydrogen and air, were measured with time in the dead-end system and the recirculation system for hydrogen supply. The water balance in the fuel cell module was then calculated and the behavior of generated water, which should cause output power breakdown and voltage fluctuation in certain conditions, was also discussed. Results showed that a sudden power breakdown in a long time continuous operation with dead-end hydrogen supply system was caused by flooding in the anode and that this shortcoming was overcome by introducing a simple hydrogen recirculation system with valves and a water trap. Results also showed that 95% of produced water by the reaction was discharged from the cathode to the atmosphere in the form of vapor and that 5% trapped in the form of liquid in the hydrogen recirculation system.