Fuel cell hibernation mode method and apparatus
First Claim
1. A method of operating a power system comprising at least a first power source and a second power source, wherein the first power source and the second power source are electrically coupled in parallel to one another via a direct current (DC) power bus, wherein the first power source is a first fuel cell stack, and wherein a cathode of the first fuel cell stack is coupled to a positive DC voltage portion of the DC power bus via a first diode, the method comprising:
- halting a flow of an oxidant to the first fuel cell stack in response to at least one of a power demand of the power system or a load supplied to a power system being less than a threshold, wherein the first amount of power decreases as a residual amount of oxidant in the first fuel cell stack is reacted;
operating a fuel recirculation system to recirculate a flow of a fuel to the first fuel cell stack at least during at least a portion of a period while the flow of the oxidant to the first fuel cell stack is halted; and
replacing the decreased first amount of power with a corresponding second amount of power from the second power source.
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Abstract
A system and method for operating a power system with a fuel cell stack and a power source are disclosed. Briefly described, one embodiment is a method that halts a flow of an oxidant to the first fuel cell stack in response to at least one of a power demand of the power system or a load supplied to a power system being less than a threshold, wherein the first amount of power decreases as a residual amount of oxidant in the first fuel cell stack is reacted; operates a fuel recirculation system to recirculate a flow of a fuel to the first fuel cell stack at least during at least a portion of a period while the flow of the oxidant to the first fuel cell stack is halted; and replaces the decreased first amount of power with a corresponding second amount of power from the second power source.
60 Citations
26 Claims
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1. A method of operating a power system comprising at least a first power source and a second power source, wherein the first power source and the second power source are electrically coupled in parallel to one another via a direct current (DC) power bus, wherein the first power source is a first fuel cell stack, and wherein a cathode of the first fuel cell stack is coupled to a positive DC voltage portion of the DC power bus via a first diode, the method comprising:
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halting a flow of an oxidant to the first fuel cell stack in response to at least one of a power demand of the power system or a load supplied to a power system being less than a threshold, wherein the first amount of power decreases as a residual amount of oxidant in the first fuel cell stack is reacted; operating a fuel recirculation system to recirculate a flow of a fuel to the first fuel cell stack at least during at least a portion of a period while the flow of the oxidant to the first fuel cell stack is halted; and replacing the decreased first amount of power with a corresponding second amount of power from the second power source. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15)
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16. A power system, comprising:
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a direct current (DC) bus with a positive DC voltage rail; a first power source comprising; a first fuel cell stack electrically coupled to the DC bus and operable to output a first amount of power to a load; a first diode electrically coupled between a cathode of the first fuel cell stack and the positive DC voltage rail of the DC bus, and operable to conduct current such that an output voltage of the first fuel cell stack is substantially equal to a voltage of the DC bus; an oxidant supply system fluidly coupled to the first fuel cell stack via at least an oxidant supply valve and operable to selectively supply a flow of an oxidant to the first fuel cell stack; and a fuel recirculation system fluidly coupled to the first fuel cell stack via at least a fuel recirculation valve and operable to supply a flow of a fuel to the first fuel cell stack; a second power source electrically coupled to the DC bus and operable to output a second amount of power to the load; and a controller controllably coupled to the oxidant supply valve and the fuel recirculation valve, and operable to close the oxidant supply valve to halt the flow of the oxidant to the first fuel cell stack in response to the load being less than a threshold so that the first amount of power decreases as a residual amount of oxidant in the first fuel cell stack is reacted, wherein the fuel recirculation system maintains the flow of the fuel to the first fuel cell stack while at least a portion of the residual amount of oxidant in the first fuel cell stack is reacted. - View Dependent Claims (17, 18, 19, 20, 21, 22, 23, 24)
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25. A power system, comprising:
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a fuel cell stack electrically coupled to a DC bus and operable to output a first amount of power to a load; a power source electrically coupled to the DC bus and operable to output a second amount of power to the load; means for maintaining an output voltage of the fuel cell stack at least equal to a DC voltage of the DC bus when the fuel cell stack is operating; means for halting a flow of an oxidant to the fuel cell stack in response to the load being less than a threshold so that the first amount of power decreases as a residual amount of oxidant in the first fuel cell stack is reacted; means for recirculating a flow of a fuel to the first fuel cell stack while at least a portion of the residual amount of oxidant in the first fuel cell stack is reacted; and means for replacing the decreasing first amount of power from the fuel cell stack by increasing the second amount of power from the power source. - View Dependent Claims (26)
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Specification