Abstract: A fuel cell stack comprising a fuel inlet and an oxidant inlet for allowing the supply of a fuel and an oxidant to the fuel cell stack, respectively, and a fuel outlet and an oxidant outlet for allowing the removal of an anode exhaust and a cathode exhaust from the fuel cell stack, respectively, wherein the fuel outlet is fluidly connected to a high frequency purge valve.

Abstract: An electrochemical fuel cell stack with integrated anode exhaust valves is disclosed, comprising a plurality of fuel cells, each fuel cell having an anode and at least one anode flow field channel, an anode exhaust manifold fluidly connected to the at least one anode flow field channel of each fuel cell, and a means for minimizing fluid backflow from the anode exhaust manifold into the anode flow field channels of the fuel cells. Methods for purging, and reducing fuel cell voltage variations within, the electrochemical fuel cell stack are also disclosed.

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: A fuel cell stack comprising a fuel inlet and an oxidant inlet for allowing the supply of a fuel and an oxidant to the fuel cell stack, respectively, and a fuel outlet and an oxidant outlet for allowing the removal of an anode exhaust and a cathode exhaust from the fuel cell stack, respectively, wherein the fuel outlet is fluidly connected to a high frequency purge valve.

Abstract: Liquid cooled systems having coolant circulation loops must often operate in below freezing conditions. For instance, in various applications certain fuel cell systems must be able to tolerate repeated shutdown and storage in below freezing conditions. Conventional glycol-based coolants typically used for internal combustion engines are generally unsuitable for use in the associated fuel cell cooling subsystems due to the presence of additives and/or inhibitors which are normally included to deal with problems relating to decomposition of the glycol. With additives or inhibitors present, the coolant conductivity can be sufficiently high as to result in electrical shorting or corrosion problems. However, provided the purity of the coolant is maintained, a pure glycol and water coolant mixture may be used as a fuel cell system coolant to obtain suitable antifreeze protection. Adequate purity can be maintained by including an ion exchange resin unit in the cooling subsystem.

Abstract: In a hydrogen gas line where the composition of the gas is primarily hydrogen, impurities present in the gas line will typically reduce the speed of sound. Accordingly, an acoustic sensor can be used in such a hydrogen gas line to indicate when impurities have accumulated in the gas line. In particular, the hydrogen gas line may be in a fuel line for an electrochemical fuel cell system. The sensor may comprise transducers, more particularly piezoelectric transducers, as both sound detectors and/or sound generators. Further, the sensor can measure either the speed or frequency of sound to determine the hydrogen concentration. If the fuel is recirculated back to the anode inlet, such a hydrogen sensor in the anode exhaust may be used to determine when it is beneficial to purge the anode exhaust to the external atmosphere.

Abstract: Liquid cooled systems having coolant circulation loops must often operate in below freezing conditions. For instance, in various applications certain fuel cell systems must be able to tolerate repeated shutdown and storage in below freezing conditions. Conventional glycol-based coolants typically used for internal combustion engines are generally unsuitable for use in the associated fuel cell cooling subsystems due to the presence of additives and/or inhibitors which are normally included to deal with problems relating to decomposition of the glycol. With additives or inhibitors present, the coolant conductivity can be sufficiently high as to result in electrical shorting or corrosion problems. However, provided the purity of the coolant is maintained, a pure glycol and water coolant mixture may be used as a fuel cell system coolant to obtain suitable antifreeze protection. Adequate purity can be maintained by including an ion exchange resin unit in the cooling subsystem.

Abstract: Fragile, porous carbonaceous parts can be impregnated with a methacrylate polymer by curing the impregnated methacrylate in a curing atmosphere above atmospheric pressure. Preferably, the curing atmosphere is substantially free of oxygen. Thin carbonaceous components of flexible graphite for use in solid polymer fuel cells can be suitably impregnated in this way.

Abstract: Fragile, porous carbonaceous parts can be impregnated with a methacrylate polymer by curing the impregnated methacrylate in a curing atmosphere above atmospheric pressure. Preferably, the curing atmosphere is substantially free of oxygen. Thin carbonaceous components of flexible graphite for use in solid polymer fuel cells can be suitably impregnated in this way.