Ballard Power Systems Corporation

Bdf IP Holdings Ltd.

Marian E Van Der Geest

Jean St-Pierre

Joy A Roberts

David P Wilkinson

Abderrahmane Atbi

Nicholas J Fletcher

Alvin Lee

Stephanie Moroz

Kevin M Colbow

Herwig Haas

Jiujun Zhang

Peter Urban

Cindy J Longley

Jens M&uuml;ller

Regina Wezel

NengYou Jia

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

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. The method comprises adjusting at least one stack operating parameter to cause the stack to operate under a drying condition that causes a net outflux of water from the stack, operating the stack under the drying condition until the water content in the stack has been reduced, and interrupting supply of power from the stack to the external circuit.

Methods and apparatus for improving the cold starting capability of a fuel cell

A method and apparatus increase the temperature of a fuel cell via reactant starvation at one or both electrodes. Reactant starvation at an electrode results in increased internal heat generation under load. Starvation conditions can be prolonged or intermittent and can be obtained, for example, by suitably reducing the supply rate of a reactant or by operating the fuel cell at sufficiently high current density so as to consume reactant faster than it is supplied. The method can allow for some generation of useful power by the fuel cell during start-up. The method is particularly suitable for starting up a solid polymer electrolyte fuel cell from temperatures below 0&deg; C.

Method and apparatus for increasing the temperature of a 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

An electrochemical fuel cell is operated with periodic reactant starvation at either or both electrodes. Periodic reactant starvation conditions cause a change in the potential of the starved electrode and may result in the removal of electrocatalyst poisons and in improved fuel cell performance. This technique may have other beneficial effects at the electrodes, including performance improvements due to water management effects or localized heating effects at the starved electrode. In a preferred method, while successive localized portions of a fuel cell electrode are periodically reactant starved, the remainder of the fuel cell electrode remains electrochemically active and saturated with reactant such that the fuel cell is able to continue to generate power.

Method and apparatus for operating an electrochemical fuel cell with periodic reactant starvation

A method and apparatus increase the temperature of a fuel cell via reactant starvation at one or both electrodes. Reactant starvation at an electrode results in an increased overvoltage at the electrode and hence increased internal heat generation under load. Starvation conditions can be prolonged or intermittent and can be obtained, for example, by suitably reducing the supply rate of a reactant or by operating the fuel cell at sufficiently high current density so as to consume reactant faster than it is supplied. The method can allow for some generation of useful power by the fuel cell during start-up. The method is particularly suitable for starting up a solid polymer electrolyte fuel cell from temperatures below 0&deg; C.

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Vancouver, Canada

Marian E Van Der Geest