Enhanced Water Management with Electroosmotic Pumps for PEM Fuel Cells
S. Litster, C.R. Buie, T. Fabian, J.K. Eaton and J.G. Santiago
Stanford University, US
PEM fuel cell, flooding, water management, electroosmotic pump
Proper water management is critical for high performance with polymer electrolyte membrane (PEM) fuel cells. Without adequate hydration, losses due to the electrolyte resistance become excessive. Humidification of reactant gases ensures proper humidification of the membrane. Consequently, much of the water produced is in liquid form and flooding limits power density. Flooding is commonly addressed by removing water with excessive reactant flow rates and elevated gas pressures. This solution makes air delivery the largest parasitic load on fuel cells; air delivery can easily consume more than 20% of the fuel cell power. We are developing scalable and robust active water management technology for PEM fuel cells using electroosmotic (EO) pumps in concert with integrated capillary structures (i.e., wicks). These devices offer unique advantages to fuel cell operation as they decouple air delivery from water management. Integrated wicking structures and EO pumps increase fuel cell power density by ensuring complete membrane hydration and eliminating flooding. This system enables low reactant flow rates, and near ambient pressures for high system efficiency. Our results demonstrate two-fold increases in maximum power density when EO pumping. The EO pump is a negligible parasitic load; it consumes less than 0.5% of the fuel cell power.
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