Patent attributes
A PEM fuel cell power plant includes fuel cells, each of which has a cathode reactant flow field plate which is substantially impermeable to fluids, a coolant source, and a fluid permeable anode reactant flow field plate adjacent to said coolant source. The anode reactant flow field plates pass coolant from the coolant sources into the cells where the coolant is evaporated to cool the cells. The cathode flow field plates prevent reactant crossover between adjacent cells. By providing a single permeable plate for each cell in the power plant the amount of coolant present in the power plant at shut down is limited to a degree which does not require adjunct coolant purging components to remove coolant from the plates when the power plant is shut down during freezing ambient conditions. Thus the amount of residual frozen coolant in the power plant that forms in the plates during shut down in such freezing conditions will be limited. The power plant can thus be restarted and brought up to full operating power levels quickly due to the reduced amount of frozen coolant that must be melted during startup. Pressure in the coolant source is preferably greater than ambient pressure, and pressure in the anode reactant flow field is greater than the pressure in the coolant source so as to prevent the coolant from flooding the cells. The power plant is well suited for use in powering vehicles.
