Ballard Power Systems Corporation

Daimler-Benz Ag

Her Majesty the Queen in Right of Canada, as Represented by the Minister

Bdf IP Holdings Ltd.

Nicholas J Fletcher

Eric G Pow

David P Wilkinson

Henry H Voss

Joy A Roberts

Jean St-Pierre

Boguslaw M Wozniczka

Peter Robert Gibb

Marian E Van Der Geest

Gustav A Boehm

Abderrahmane Atbi

Mark Christian Johnson

Shanna Denine Knights

Gordon J Lamont

Gerald Hornburg

Clarence Y Chow

Vesna Basura

Reinhold Schamm

Boguslav M Wozniczka

Wolfgang Schlosser

An electric power generation system has elements that improve the cold start capability and freeze tolerance of a constituent fuel cell stack cooperate to reduce the amount of water remaining within the passages of the stack. The system includes a purge system that is connectable to the oxidant supply, fuel supply and/or coolant passages upstream of the stack. When the stack is shut down, the stack is disconnected from an external circuit, and purge fluid is transmitted by the purge system through the stack before the stack falls below the freezing point of water. In systems where fuel and/or oxidant streams are humidified prior to entry into the stack, a humidifier bypass system may be provided in place of the purge system. The humidifier bypass system transmits reactant fluid to the stack in fluid isolation from the humidifier, so that the inlet reactant streams are unhumidified.

Apparatus for improving the cold starting capability of an electrochemical fuel cell

A method of ceasing operation of an electric power generation system improves the cold start capability and freeze tolerance of a fuel cell stack by reducing the amount of water remaining within the passages of the stack. The method involves purging one or more of the fuel cell stack oxidant and fuel passages at shutdown prior to allowing the fuel cell stack to drop to temperatures below the freezing point of water. Preferably purging at shutdown is conducted at a temperature below the stack operating temperature.

Method for improving the cold starting capability of an electrochemical fuel cell

The present invention relates to improving the overall efficiency of a fuel cell system by reducing parasitic power consumption. A controller is programmed to decrease oxidant stoichiometry until oxidant starvation is detected or until oxidant stoichiometry is about one. When oxidant starvation is detected, the oxidant stoichiometry is increased until oxidant starvation is no longer detected. The fuel cell system employs a sensor for detecting an operational characteristic such as voltage output, or oxygen or hydrogen concentration in the cathode exhaust stream. The controller uses the operational characteristic to calculate oxidant stoichiometry or to determine when there is oxidant starvation at the cathode.

Method and apparatus for operating a fuel cell

An electrochemical fuel cell stack includes a plurality of fuel cell assemblies interposed between a pair of end plate assemblies. The mechanism for securing the stack in its compressed, assembled state includes at least one compression band which circumscribes the end plate assemblies and interposed fuel cell assemblies of the stack. At least one of the end plate assemblies is sufficiently thin so as to deflect under the compressive force if the at least one end plate assembly is supported only at a peripheral edge portion thereof. Preferably, at least one of the end plate assemblies comprises a resilient member which cooperates with each compression band to urge the first end plate assembly toward the second end plate assembly, thereby applying compressive force to the fuel cell assemblies to promote sealing and electrical contact between the layers forming the fuel cell stack.

Electrochemical fuel cell stack with compression bands

A method and apparatus are provided for starting and operating an electric power generation system comprising an electrochemical fuel cell stack for supplying electric current to an external electrical circuit. The stack comprises at least one fuel cell comprising a membrane electrode assembly comprising an anode, a cathode, and a water permeable ion exchange membrane interposed between the anode and the cathode. A fuel stream and an oxidant stream are each flowable to the fuel cell. At least a portion of the membrane electrode assembly has a temperature below the freezing temperature of water. The supply of electric current to the external circuit from the fuel cell stack is commenced such that the temperature of the membrane electrode assembly exceeds the freezing temperature of water.

Method and apparatus for commencing operation of a fuel cell electric

An electrochemical fuel cell stack includes a plurality of fuel cell assemblies interposed between a pair of end plate assemblies. The mechanism for securing the stack in its compressed, assembled state includes at least one compression band which circumscribes the end plate assemblies and interposed fuel cell assemblies of the stack. Preferably, at least one of the end plate assemblies comprises a resilient member which cooperates with each compression band to urge the first end plate assembly toward the second end plate assembly, thereby applying compressive force to the fuel cell assemblies to promote sealing and electrical contact between the layers forming the fuel cell stack.

A fuel cell assembly within an electrochemical fuel cell stack has an anode layer and a cathode layer. A cooling layer is disposed adjacent the fuel cell assembly. Each layer comprises channels for directing a fluid stream from an inlet to a an outlet. The coolant stream channels extend such that, in operation, the coolest region of the cooling layer coincides with the region of the cathode layer having the highest concentration of oxygen (and/or the lowest water content), and the warmest region of the cooling layer coincides with the region of the cathode layer having the lowest concentration of oxygen (and/or the highest water content). The fuel stream channels extend such that, in operation, the fuel stream is directed to a region of the anode layer which coincides with the region of the cathode layer in which the oxidant stream has the lowest concentration of oxygen (and/or the highest water content) and is subsequently directed to a region of the anode layer which coincides with the region of the cathode layer in which the oxidant stream has the highest concentration of oxygen (and/or the lowest water content).

Electrochemical fuel cell stack with concurrent flow of coolant and

A fuel cell assembly within an electrochemical fuel cell stack has a cooling jacket disposed adjacent the cathode layer. The cooling layer comprises a coolant stream inlet, a coolant stream outlet, and at least one channel for directing a coolant stream from the coolant stream inlet to the coolant stream outlet. The coolant stream channels extend such that the coolest region of the cooling layer substantially coincides with the region of the adjacent cathode layer having the highest concentration of oxygen (and also the lowest water content), and the warmest region of the cooling layer substantially coincides with the region of the adjacent cathode layer having the lowest concentration of oxygen (and also the highest water content).

Electrochemical fuel cell stack with concurrently flowing coolant and

An electrochemical fuel cell assembly includes a membrane electrode assembly which comprises an anode, a cathode having a surface thereof exposed to ambient air, and an ion exchange membrane interposed between the anode and the cathode. A seal forms a gas-impermeable barrier around the anode to which a gaseous fuel stream is supplied. The assembly further includes a thermally conductive plate having a plurality of thermally conductive members or fins extending from a major surface of the plate. The thermally conductive members contact portions of the exposed cathode surface. Adjacent thermally conductive members cooperate with the plate and the exposed cathode surface to form air conducting channels. Heat generated exothermically in the membrane electrode assembly is dissipated to the atmosphere through the thermally conductive members.

Electrochemical fuel cell employing ambient air as the oxidant and

A load-following vaporizer converts an inlet liquid reactant stream to an outlet vapor reactant stream. The vaporizer comprises a containment shell, a nozzle and a fin block. The fin block has a base in thermal contact a heat source, preferably a thermal fluid stream. The base has a plurality of evaporative heat transfer structures that are spaced from and generally radiate from the nozzle outlet. Each of the evaporative heat transfer structures has two principal surfaces oriented such that the extension of each of the surfaces intersects the nozzle outlet. Upon contacting the evaporative heat transfer structures, the atomized liquid reactant dispersion is vaporized to produce a vaporized reactant stream. The vaporizer rapidly responds to changes in the inlet liquid reactant flow rate to produce a corresponding change in the output vapor flow rate by minimizes the liquid inventory within the heated environment. The load-following vaporizer is compact, lightweight and compatible with other components of an integrated fuel processing system.

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Vancouver, Canada

Nicholas J Fletcher