An Optimal Stoichiometric Ratio Based Fan Voltage Control Strategy for Maximizing Net Power Density in an Open‐Cathode PEMFC

ABSTRACT

In an open‐cathode polymer electrolyte membrane fuel cell (PEMFC), a single fan must simultaneously supply oxygen, remove product water, and dissipate reaction heat, so its parasitic power directly erodes the net power delivered by the system. Selecting the fan operating condition is therefore a trade‐off rather than a matter of supplying as much air as possible. In practice; however, the air stoichiometric ratio (SR) inside the cathode channel cannot be measured directly without an in‐channel flow sensor, and fan operation has consequently been fixed or tuned for thermal or efficiency targets rather than for net power. A fan‐voltage‐based control strategy that maximizes the net power density of an open‐cathode PEMFC is therefore proposed. The airflow into each cathode channel is estimated by coupling the computational fluid dynamics (CFD)‐derived system‐resistance curve with the fan pressure–flow rate ( P – Q ) curve, allowing the SR to be quantified without a flow sensor. The net power density at 24 V is 74.6% lower than at the optimal 8 V, because parasitic fan power rises steeply once the mass‐transfer gain saturates near 12 V. The optimal SR, distributed within 10–20, is modeled as a third‐order polynomial of current density and mapped into a continuous fan‐voltage roadmap. This roadmap raises the peak net power density to 0.300 W/cm ² in the parallel channel (5.6%) and 0.249 W/cm ² in the pin channel (4.4%) relative to fixed‐voltage operation, with up to 42.1% gain at low current. The strategy transfers across flow‐channel geometries.