Abstract: A plurality of flow field plate assemblies forms a fuel cell stack. Each flow field plate assembly has a first flow field plate positionable on an anode side of a membrane electrode assembly (MEA) of a first fuel cell, a second flow field plate positionable on a cathode side of an MEA of a second fuel cell, adjacent the first fuel cell. At least one back-feed channel is interposed between the first and second flow field plates. At least a portion of the back-feed channel or a reactant manifold opening formed by the first and second flow field plates has a geometry that forms regions of high and low capillary forces, promoting liquid migration toward regions substantially isolated from a flow of reactants, to prevent water collection and ice formation. The migrated liquid is purged during a purge of the fuel cell stack after operation.

Abstract: Improved water distribution can be obtained within the cells of a fuel cell series stack by maintaining a suitable temperature difference between the cathode and anode sides of each cell in the stack during shutdown. This can be accomplished by thermally insulating the “hot” end and sides of the stack and by providing a thermal mass adjacent to the “hot” end.

Abstract: Improved water distribution can be obtained within the cells of a fuel cell series stack by maintaining a suitable temperature difference between the cathode and anode sides of each cell in the stack during shutdown. A method of shutting down a fuel cell stack having at least two fuel cells stacked in series, each fuel cell having a cathode side and an anode side, the method comprising: stopped the generation of electricity from the stack; allowing the stack to cool over a cooldown period; and maintaining a temperature difference between the cathode side and the anode side of each fuel cell during the cooldown period, wherein the direction of the temperature difference in each fuel cell is the same. The fuel cell stack may comprise coolant channels, Peltier devices and anode and cathode reactant flow fields.

Abstract: Improved water distribution can be obtained within the cells of a fuel cell series stack by maintaining a suitable temperature difference between the cathode and anode sides of each cell in the stack during shutdown. This can be accomplished by thermally insulating the “hot” end and sides of the stack and by providing a thermal mass adjacent to the “hot” end.

Abstract: A fuel cell system comprising a fuel cell stack and at least one hydration sensor apparatus for measuring membrane hydration in the fuel cell stack is disclosed. The hydration sensor apparatus comprises (1) an electrically insulated sensor comprising a polymer electrolyte membrane, (2) a power supply, and (3) a load resistor. The sensor, the power supply and the load resistor of the hydration sensor apparatus are electrically connected and the sensor of the hydration sensor apparatus is fluidly connected to the fuel cell stack such that, during operation of the fuel cell system, the polymer electrolyte membrane of the hydration sensor apparatus is exposed to a fuel fluid stream of the fuel cell stack.

Abstract: A plurality of flow field plate assemblies forms a fuel cell stack. Each flow field plate assembly has a first flow field plate positionable on an anode side of a membrane electrode assembly (MEA) of a first fuel cell, a second flow field plate positionable on a cathode side of an MEA of a second fuel cell, adjacent the first fuel cell. At least one back-feed channel is interposed between the first and second flow field plates. At least a portion of the back-feed channel or a reactant manifold opening formed by the first and second flow field plates has a geometry that forms regions of high and low capillary forces, promoting liquid migration toward regions substantially isolated from a flow of reactants, to prevent water collection and ice formation. The migrated liquid being is purged during a purge of the fuel cell stack after operation.

Abstract: A flow field plate assembly for use in a fuel cell, a plurality of which can form a fuel cell stack, comprises first and second flow field plates and a body comprising a porous medium interposed between the first and second flow field plates, the porous medium being operable to allow passage of a fuel and an oxygen-containing gas therethrough, and block from passage therethrough, a flow of liquids to prevent water collection and ice formation, which may block passages formed on at least a portion of the first and/or second flow field plates.

Abstract: A fuel cell system is operated with the fuel supply pressure greater than the oxidant supply pressure to the fuel cell. This gives improved performance particularly when the fuel cell system is closed on the fuel side. The magnitude of fuel overpressure may be varied in accordance with variations in the fuel cell operating parameters.

Abstract: Apparatus and methods of ceasing operation of an electric power generating system improve the cold starting capability of the system. The system comprises a fuel cell stack connectable to an external circuit for supplying power to the external circuit. The stack comprises at least one solid polymer fuel cell, and the system further comprises a fuel passage for directing a fuel stream through the stack and an oxidant passage for directing an oxidant stream through the stack, a sensor assembly connected to the stack for monitoring a parameter indicative of stack performance, a controller for controlling at least one stack operating parameter, and a control system communicative with the sensor assembly and stack operating parameter controller.

Abstract: A fuel cell system is operated with the fuel supply pressure greater than the oxidant supply pressure to the fuel cell. This gives improved performance particularly when the fuel cell system is closed on the fuel side. The magnitude of fuel overpressure may be varied in accordance with variations in the fuel cell operating parameters.

Abstract: Apparatus and methods of ceasing operation of an electric power generating system improve the cold starting capability of the system. The system comprises a fuel cell stack connectable to an external circuit for supplying power to the external circuit. The stack comprises at least one solid polymer fuel cell, and the system further comprises a fuel passage for directing a fuel stream through the stack and an oxidant passage for directing an oxidant stream through the stack, a sensor assembly connected to the stack for monitoring a parameter indicative of stack performance, a controller for controlling at least one stack operating parameter, and a control system communicative with the sensor assembly and stack operating parameter controller.