Abstract: A fuel cell system is disclosed that employs an expander for recovering mechanical energy from a cathode exhaust fluid produced by the fuel cell system to generate torque. The expander is coupled to a shaft of a compressor with a freewheel mechanism, wherein the freewheel mechanism transfers the torque from the expander to the compressor when a rate of rotation of a driveshaft of the expander is greater than the rate of rotation of the shaft of the compressor, and selectively militates against the expander acting as a restrictor to the shaft of the compressor when a rate of rotation of the driveshaft of the expander is substantially equal to or less than a rate of rotation of the shaft of the compressor.

Abstract: A method for reducing the probability of an air/hydrogen front in a fuel cell stack is disclosed that includes closing anode valves for an anode side of the fuel cell stack to permit a desired quantity of hydrogen to be left in the anode side upon shutdown and determining a schedule to inject hydrogen during the time the fuel cell stack is shutdown. The pressure on an anode input line is determined and a discrete amount of hydrogen is injected into the anode side of the stack according to the determined schedule by opening anode input line valves based on the determined pressure along the anode input line so as to inject the hydrogen into the anode side of the stack.

Abstract: A method for creating an oxygen depleted gas in a fuel cell system, including operating a fuel cell stack at a desired cathode stoichiometry at fuel cell system shutdown to displace a cathode exhaust gas with an oxygen depleted gas. The method further includes closing a cathode flow valve and turning off a compressor to stop the flow of cathode air.

Abstract: A fuel cell stack assembly is disclosed that includes a porous member disposed within a flow path for a reactant. A fluid collection member is provided within the flow path adjacent to and in fluid communication with the porous member. The porous member and the fluid collection member cooperate to collect liquid water from the reactant flowing in the flow path, wherein the collected liquid water may be drained from the fluid collection member.

Abstract: A bipolar plate for a fuel cell is disclosed including a first unipolar plate having an active surface with a plurality of flowfield channels formed therein. The first unipolar plate further includes an inlet header disposed at a first end of the unipolar plate that is in communication with the active surface, and an outlet header disposed at a second end of the unipolar plate having an exhaust opening formed therethrough. A peripheral edge of the exhaust opening is chamfered and is also in communication with the active surface. The chamfered exhaust opening forms a water removal channel in the bipolar plate. A fuel cell stack including the bipolar plate is also disclosed.

Abstract: A fuel cell stack is disclosed that utilizes a porous material internally disposed in the fuel cell outlet manifolds, wherein the porous material facilitates the transport of liquid water from the plate outlets thereby minimizing the accumulation of liquid water in the fuel cell stack.

Abstract: A fuel cell stack that includes an actuating device or devices for selectively providing interdigitated reactant gas flow and straight reactant gas flow through reactant gas flow channels to reduce water accumulation in the diffusing media layers of the stack. In one embodiment, the fuel cell stack employs internal actuators that selectively close the inlet end of every other flow channel and the outlet end of every other opposite flow channel to provide the interdigitated flow. In another embodiment, the interdigitated flow is provided by external actuation where two inlet manifolds and two outlet manifolds are provided. One input manifold is closed to close the input ends of every other flow channel and one outlet manifold is closed to close the output ends of every other opposite flow channel.

Abstract: A bipolar plate for a fuel cell is provided that includes a flowfield having an active surface with an inlet region and an outlet region. The active surface of the flowfield is in communication with the inlet region and the outlet region and has at least one flow channel formed therein. The at least one flow channel further has a cross-sectional area at the outlet region that is less than a cross-sectional area at the inlet region. In particular embodiments, the at least one flow channel is bifurcated. A fuel cell stack including a fuel cell and the bipolar plate is also provided.

Abstract: A technique for determining whether a cooling fluid pump used for pumping a cooling fluid through a fuel cell stack has failed. The technique includes measuring the temperature of the cooling fluid at the output from the stack and/or measuring the cathode exhaust gas temperature as close as possible to the cathode outlet of the stack. The measured temperature is compared to a temperature that would be expected under the current operating conditions of the fuel cell system in a controller. If the difference between the measuring temperature and the expected temperature is large enough, then the controller provides a warning signal of pump failure, and also possibly reduces the stack outlet power.

Abstract: A method for refueling hydrogen fuel cell powered vehicles is disclosed, that is capable of automatically disabling the vehicle systems, resetting the vehicle systems to allow for normal vehicle operation after the refueling event is complete, and determining if a faulty refueling event has been detected and allows normal vehicle operation.

Abstract: An electrochemical fuel cell stack assembly having a variable active area. The fuel cell stack uses a blocking member to selectively block the flow of reactants through channels of the flow fields of the anode and/or cathode flow paths. Blocking portions of the flow paths allows the fuel cell stack to maintain reactant flow velocities in a desired predetermined range. This enables the control and variation of the active area of the fuel cell, enhancing water management of the fuel cell stack.

Abstract: One embodiment of the invention includes a first fuel cell component comprising a first face, a first hydrophilic coating overlying at least a first portion of the first face, and a second less hydrophilic coating overlying at least a second portion of the first face.

Abstract: An electric insulator for a fuel cell stack with a plurality of fuel cell plates is provided. The electric insulator includes an insulation layer having a water management feature adapted to militate against liquid water contacting the fuel cell plates. Fuel cell stacks having the water management feature are also described.

Abstract: A bipolar plate includes angled facets oriented to form V-shaped projections on the plate edge. Liquid leaving the reactant channels is drawn back into the V-shaped grooves of the projections, leaving no liquid to obstruct the channel exit openings. The bipolar plate includes one portion of the bipolar plate offset from another portion of the bipolar plate so as to expose the reactant channels. The liquid is drawn toward the end portions of the reactant channels by capillary forces, while the gas flows can exit near the beginning of the offset portion. A fuel cell stack includes angled facets that are rotated to lie in the plane of the bipolar plate edges. The edges are chamfered so the channel exit openings of the reactant channels are at the tip portions thereof, thus allowing the liquid to flow away from the channel exit openings and the gas to exit freely.

Abstract: A fuel cell assembly is disclosed that utilizes a water transport structure extending from fuel cell plates of the assembly into fuel cell assembly manifolds, wherein the water transport structure facilitates the transport of liquid water from the fuel cell plates thereby minimizing the accumulation of liquid water and ice in the fuel cell stack.

Abstract: A plate for a fuel cell is disclosed, wherein an inlet aperture is disposed at a first end of the plate and an outlet aperture is disposed at a second end of the plate. The plate includes a first side and a second side. The first side of the plate has a flow field formed therein between the inlet aperture and the outlet aperture, the flow field having a plurality of flow channels formed therein, the plurality of flow channels in communication with a plurality of outlet ports formed in the plate. The second side of the plate has a plurality of drainage channels formed therein adjacent the outlet aperture, the plurality of drainage channels in fluid communication with the outlet ports and the outlet aperture, wherein a cross-sectional area occupied by each of the plurality of flow channels is substantially equal to a cross-sectional area occupied by each of the plurality of drainage channels.

Abstract: A device and method to extract water from a moisture-rich fuel cell flowpath. A water transport unit is integrated into the fuel cell so that liquid water stagnation within flow channels and manifolds is reduced. In one embodiment, the device includes numerous flowpaths that include an active region and an inactive region. The water transport unit includes a hydrophilic member such that upon passage of a fluid with the excess water through the inactive region of the device flowpath and into the presence of the hydrophilic member, it absorbs excess water from the fluid.

Abstract: A bipolar plate for a fuel cell is provided that includes a flowfield having an active surface with an inlet region and an outlet region. The active surface of the flowfield is in communication with the inlet region and the outlet region and has at least one flow channel formed therein. The at least one flow channel further has a cross-sectional area at the outlet region that is less than a cross-sectional area at the inlet region. In particular embodiments, the at least one flow channel is bifurcated. A fuel cell stack including a fuel cell and the bipolar plate is also provided.

Abstract: A method for refueling hydrogen fuel cell powered vehicles is disclosed, that is capable of automatically disabling the vehicle systems, resetting the vehicle systems to allow for normal vehicle operation after the refueling event is complete, and determining if a faulty refueling event has been detected and allows normal vehicle operation.

Abstract: A bipolar plate for a fuel cell is disclosed including a first unipolar plate having an active surface with a plurality of flowfield channels formed therein. The first unipolar plate further includes an inlet header disposed at a first end of the unipolar plate that is in communication with the active surface, and an outlet header disposed at a second end of the unipolar plate having an exhaust opening formed therethrough. A peripheral edge of the exhaust opening is chamfered and is also in communication with the active surface. The chamfered exhaust opening forms a water removal channel in the bipolar plate. A fuel cell stack including the bipolar plate is also disclosed.