Optimization study of purge cycle in proton exchange membrane fuel cell system

• An advanced PEMFC system test bench for anode side studies was built.
• Anode purge gas volume and composition were measured accurately and reproducibly.
• Effect of cathode inlet gas humidification on system performance was studied.
• Mass transport resistance in GDL was found to cause significant voltage polarization.

In PEMFC (proton exchange membrane fuel cell) systems operating in dead-end mode, hydrogen purges are needed to remove accumulated inert gases and liquid water from the anode side of the fuel cell stack. Hydrogen purges were studied using different humidity levels, purge times, and purge triggering criteria. The purged gas volume and composition were accurately measured with fast data acquisition and an advanced experimental set-up. The experiments were done with constant current density with aim of keeping the anode gas recirculation rate constant. Fuel utilization per pass varied as the hydrogen content on the anode side changed. This study demonstrates how the optimized purge strategy changes with a changing humidity level. It also shows that high fuel efficiency (>99%) is easily reached and that with optimized purge strategy a very high fuel efficiency (99.9%) can be reached. It was also shown that concentration polarization due to accumulation of inert gases on the anode side is two times higher than values obtained by theoretical calculations. This result is significant for purge strategy and system design.