Method for improving the cold starting capability of an electrochemical fuel cell
AssigneeBallard Power Systems Inc.
InventorsJoy A. Roberts, Jean St-Pierre, Marian E. van der Geest, Abderrahmane Atbi, Nicholas J. Fletcher
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Abstract
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.
Claims14
A method of ceasing operation of an electric power generation system comprising a fuel cell stack connectable to an external electrical circuit for supplying electric current to said external circuit, said stack comprising at least one fuel cell comprising a membrane electrode assembly comprising an anode, a cathode, and an ion exchange membrane interposed between said anode and said cathode, said at least one fuel cell further comprising a fuel stream passage for directing a fuel stream to said anode and an oxidant stream passage for directing an oxidant stream to said cathode, each of said streams being flowable to said fuel cell stack, said method comprising the sequential steps of:
- (a) interrupting the supply of electric current from said fuel cell stack to said external circuit;
- (b) purging water from at least one of said passages by directing a fluid stream through said at least one of said passages;
- wherein at least one of said fuel and oxidant streams is a humidified reactant stream, and said system further comprises a reactant stream humidifier for producing said humidified reactant stream from an incoming reactant stream by directing said incoming reactant stream therethrough, and step (b) comprises flowing said reactant stream to said fuel cell stack to purge said at least one passage, such that said humidifier is bypassed.
A method of ceasing operation of an electric power generation system comprising a fuel cell stack connectable to an external electrical circuit for supplying electric current to said external circuit, said stack comprising at least one fuel cell comprising a membrane electrode assembly comprising an anode, a cathode, and an ion exchange membrane interposed between said anode and said cathode, said at least one fuel cell further comprising a fuel stream passage for directing a fuel stream to said anode and an oxidant stream passage for directing an oxidant stream to said cathode, each of said streams being flowable to said fuel cell stack, said method comprising the sequential steps of:
- (a) interrupting the supply of electric current from said fuel cell stack to said external circuit;
- (b) purging water from at least one of said passages by directing a fluid stream through said at least one of said passages;
- and
- (c) reducing the temperature of at least a portion of said membrane electrode assembly to below the freezing temperature of water.
A method of ceasing operation of an electric power generation system comprising a fuel cell stack connectable to an external electrical circuit for supplying electric current to said external circuit, said stack comprising at least one fuel cell comprising a membrane electrode assembly comprising an anode, a cathode, and an ion exchange membrane interposed between said anode and said cathode, said at least one fuel cell further comprising a fuel stream passage for directing a fuel stream to said anode and an oxidant stream passage for directing an oxidant stream to said cathode, said method comprising the sequential steps of:
- (a) interrupting the supply of electric current from said fuel cell stack to said external circuit;
- (b) reducing the temperature of said at least one fuel cell to below the normal stack operating temperature;
- (c) purging water from at least one of said passages.
Dependencies are inferred from the claim text.