Ultrahigh fuel utilization in polymer electrolyte fuel cells - Part II: A modeling study

In this paper, ultrahigh fuel utilization (>98%) in polymer electrolyte fuel cells (PEFCs) is numerically studied to investigate three aspects for this operation strategy: its effect on fuel cell performance, occurance of fuel starvation, and altered water management. Simulation results reveal that the anode flow, when using pure hydrogen fuel, decelerates to nearly zero under the high fuel utlization. The anode gas flow remains high in the hydrogen concentration throughout the gas flow channel, eliminating concerns of fuel starvation and increased anode overpotential. The numerical study confirms the experimental observation that the high-fuel-utilization strategy has very little impact on cell power output in the stable operating regime. It is shown that fuel cell's water removal almost totally relies on the cathode channel flow under ultrahigh fuel utilization, which may be one cause for experimentally observed instability in fuel cell operation under low current density.