When 3:30 PM - 5:00 PM Oct 02, 2009
Where 1670 CSE
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Fan the Flame with Water: Operation of PEM Fuel Cells with Dry Feeds


Jay Benzinger, Princeton University

Water management is a major technological problem with Polymer Electrolyte Membrane (PEM) Fuel Cells.  Bad performance is seen with membranes operating at low relative humidity or with liquid water flooding the fuel cell.  Employing model fuel cell reactors that elucidate the basic physics of Polymer Electrolyte Membrane (PEM) fuel cell reactors we have been able to demonstrate that the water produced at the cathode can auto-humidify the fuel cell and operate with dry feeds to 130°C.  PEM fuel cells reactors are shown to be conceptually identical to exothermic reactions, e.g. flames!  Current ignition in PEM fuel cells is analogous to thermal ignition in flames.  Current density fronts propagate in fuel cells resulting from a balance between convection and diffusion, this is analogous to flame fronts that propagate resulting from a balance between convection and heat conduction. Our model fuel cells have been employed to elucidate the mechanism of liquid water motion through the PEM fuel cell.  These experiments have illustrated the importance of gravity of PEM fuel cell operation.  We have also exploited gravity to facilitate liquid water removal in the channel-less self-draining PEM fuel cell, which operates with operates with current densities > 1 A/cm2 with dry feeds and  T >120ºC and high current densities.  This design has facilitated control and fuel utilization; we have been able to directly control power output to fixed load impedance with 100% fuel utilization with a system that requires no temperature control.  In this talk we shall review the use of reaction engineering principles to arrive at improved PEM fuel cell design.   

 

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