Improved water management by alternating air flow directions in a proton exchange membrane fuel cell stack

Abstract

This work presents the water management improvement of a water-cooled proton exchange membrane fuel cell stack with alternating air flow directions. This method only needs to add two three-way solenoid valves and several pipelines to the original system. The effects of different alternating modes, different alternating intervals and different hydrogen purge periods on the stack performance are experimentally studied. The advantages and disadvantages of the scheme have also been discussed in detail. Experimental results confirm that the method can significantly increase the stack voltage. When the operating temperature is 65 °C and the current density is 0.8 A/cm2, the stack voltage can be improved by 19.46%. Alternating air flow directions causes a redistribution of the water inside the stack. This can make the water distribution more uniform and achieve self-humidification. The proposed solution can also increase air pressure. However, alternating air flow directions will make the stack voltage fluctuate significantly. The alternating interval should be a trade-off between the fluctuation amplitude and the fluctuation frequency. The amplitude of the stack voltage fluctuation cannot be reduced by adjusting the purge period. This research provides a new reference for the water management improvement.