System for determining a gas composition within a shut down fuel cell power plant and method of operation

• US 7,147,945 B2
• Filed: 09/16/2002
• Issued: 12/12/2006
• Est. Priority Date: 09/16/2002
• Status: Active Grant

• Current Assignee: Audi AG (Volkswagen AG)
• Original Assignee: UTC Fuel Cells, LLC
• Inventors: Reiser, Carl A., Balliet, Ryan J.
• Primary Examiner(s): Sines, Brian J.
• Application Number:
  US10/244,495
• Publication Number:
  US 20040053089A1
• Time in Patent Office: 1,548 Days
• Field of Search: 429/12, 429/13, 429/22, 429/50, 429/61, 429/64, 422/83, 422/98, 73/10.1, 73/10.2, 73/232
• US Class Current: 429/429
• CPC Class Codes: H01M 8/0258 characterised by the configuration of channels, e.g. by the flow field of the reactant or coolant
• CPC Class Codes: H01M 8/0267 having heating or cooling means, e.g. heaters or coolant flow channels
• CPC Class Codes: H01M 8/04228 during shut-down
• CPC Class Codes: H01M 8/04303 applied during shut-down
• CPC Class Codes: H01M 8/241 with solid or matrix-supported electrolytes
• CPC Class Codes: H01M 8/2457 with both reactants being gaseous or vaporised
• CPC Class Codes: H01M 8/2465 Details of groupings of fuel cells
• CPC Class Codes: Y02E 60/50 Fuel cells

Abstract

The invention is a system (10) and method for determining a gas composition within a fuel cell (12) of a shut down fuel cell power plant. The system (10) includes at least one fuel cell (12), a sensor circuit (86) secured in electrical connection with the fuel cell (12), wherein the circuit (86) includes a power source (88), a voltage-measuring device (90), and a sensor circuit switch (92). The circuit (86) is secured so that the power source (88) may selectively deliver a pre-determined sensing current to the fuel cell (12) for a pre-determined sensing duration. The system (10) selectively admits the reducing fluid into an anode flow field (28) of the cell (12) whenever the sensor circuit (86) senses that a shut down monitoring voltage of the fuel cell (12) is the same as or exceeds a calibrated sensor voltage limit of the fuel cell (12).

Claims

1. A system for determining a gas composition within a fuel cell 12 of a shut down fuel cell power plant, the system comprising;

a. at least one fuel cell 12 for generating electrical current from hydrogen containing reducing fluid and process oxidant reactant streams, wherein the fuel cell includes an anode electrode 14 and a cathode electrode 16 on opposed sides of an electrolyte 18, an anode flow field 28 adjacent the anode electrode 14 for directing the reducing fluid stream to flow adjacent to the anode electrode 14, a cathode flow field 30 adjacent the cathode electrode 16 for directing the process oxidant stream to flow adjacent the cathode electrode 16, and an anode inlet valve 62 secured in fluid communication with the anode flow field 28 for selectively admitting the reducing fluid into the anode flow field 28; and

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b. a sensor circuit 86 secured in electrical connection with the fuel cell 12, wherein the circuit 86 includes a power source 88, a voltage-measuring device 90, and a sensor circuit switch 92, the sensor circuit 86 being secured to the fuel cell 12 so that the power source 88 may selectively deliver a pre-determined sensing current to the fuel cell 12 for a pre-determined sensing duration.

2. The system for determining a gas composition within a fuel cell 12 of a shut down fuel cell power plant of claim 1, further comprising a hydrogen admitting controller means secured in electrical communication with the sensor circuit 86 and the anode inlet valve 62 for selectively admitting the hydrogen containing reducing fluid into the anode flow field 28 whenever the sensor circuit 86 senses that a shut down monitoring voltage of the fuel cell 12 is about the same as or exceeds a sensor voltage limit of the fuel cell 12 power plant.

3. The system for determining a gas composition within a fuel cell 12 of a shut down fuel cell power plant of claim 2, further comprising an anode recycle line 66 secured in fluid communication between an anode outlet 42 and an anode inlet 40, and an anode recycle blower 68 secured to the anode recycle line 66 for directing at least a portion of an anode exhaust stream from the anode outlet 42 to the anode inlet 40.

4. A method for determining a gas composition of a fuel cell 12 of a shut down fuel cell power plant, the fuel cell power plant including at least one fuel cell 12 for generating electrical current train hydrogen containing reducing fluid and process oxidant reactant streams, wherein the fuel cell 12 includes an anode electrode 14 and a cathode electrode 16 on opposed sides of an electrolyte 18, an anode flow field 28 adjacent the anode electrode 14 tar directing the reducing fluid stream, to flow adjacent to the anode electrode 14, a cathode flow field 30 adjacent the cathode electrode 16 for directing the process oxidant stream to flow adjacent the cathode electrode 16, the method comprising the steps of:

a. securing a sensor circuit 86 having a power source 88 and a voltage measuring device 90 in electrical communication with the fuel cell 12 so that the power source may selectively deliver a predetermined sensing current to the fuel cell 12 for a predetermined sensing duration;

b. calibrating the sensor circuit 86 to determine a sensor voltage limit of the shut down fuel cell 12 power plant by the steps of;

i. determining open circuit hydrogen voltages of the fuel cell 12 when the anode electrode 14 is exposed to hydrogen gas, and determining monitoring voltages of the cell 12 when the predetermined sensing current of the sensor circuit 86 is applied to the fuel cell 12 for a predetermined sensing duration for a first reactant concentration and for a second reactant concentration within the fuel cell 12; and

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ii. calculating the sensor voltage limit from the open circuit hydrogen voltages and the monitoring voltages for the first and second reactant concentrations within the fuel cell 12.

5. The method for determining a gas composition of a shut down fuel cell 12 power plant of claim 4, comprising the further step of intermittently applying the predetermined sensing current to the fuel cell 12 for the predetermined sensing duration, and then admitting hydrogen into the fuel cell flow fields 28, 30 whenever a shut down monitoring voltage is about the same as or exceeds the sensor voltage limit.

6. The method for determining a gas composition of a shut down fuel cell 12 power plant of claim 5 comprising the further step of admitting the hydrogen through an anode inlet valve 62 secured in fluid communication between a storage source 44 of the hydrogen reducing fluid and an anode inlet 40 of the fuel cell 12.

7. The method for determining a gas composition of a shut down fuel cell 12 power plant of claim 6, comprising the further step of operating an anode recycling blower 68 secured to an anode recycling line 66 whenever hydrogen is admitted to the fuel cell 12 to uniformly distribute the admitted hydrogen throughout the anode flow field 28.

8. A method for determining a gas composition of a shut down fuel cell 12 power plant, the fuel cell power plant including at least one fuel cell 12 for generating electrical current from hydrogen containing reducing fluid and process oxidant reactant streams, wherein the fuel cell 12 includes an anode electrode 14 and a cathode electrode 16 on opposed sides of an electrolyte 18, an anode flow field 28 adjacent the anode electrode 14 for directing the reducing fluid stream to flow adjacent to the anode electrode 14, a cathode flow field 30 adjacent the cathode electrode 16 for directing the process oxidant stream to flow adjacent the cathode electrode 16, the method comprising the steps of:

a. securing a sensor circuit 86 having a power source 88 and a voltage measuring device 90 in electrical communication with the fuel cell 12 so that the power source 88 may selectively deliver a predetermined sensing current to the fuel cell 12 for a predetermined sensing duration;

b. calibrating the sensor circuit 86 to determine a sensor voltage limit of the shut down fuel cell power plant by the steps of;

i. determining a first monitoring voltage and a first open circuit hydrogen voltage across the fuel cell 12 for a first reactant concentration within the fuel cell 12 by connecting the sensor circuit 86 power source 88 to the electrodes 14, 16 to deliver to the electrodes 14, 16 the pre-determined sensing current for the pre-determined sensing duration, then measuring with the voltage-measuring device 90 the first monitoring voltage across the electrodes 14, 16 immediately prior to expiration of the sensor duration, then admitting hydrogen into the anode flow field 28 and then measuring with the voltage-measuring device 90 the first open circuit hydrogen voltage across the electrodes 14, 16;

ii. determining a second monitoring voltage and a second open circuit hydrogen voltage across the fuel cell 12 for a second reactant concentration within the fuel cell, which second reactant concentration is different than the first reactant concentration, by connecting the sensor circuit 86 power source 88 to the electrodes 14, 16 to deliver to the electrodes 14, 16 the pre-deterinined sensing current for the pre-determined sensing duration, then measuring with the voltage-measuring device 90 the second monitoring voltage across the electrodes 14, 16 immediately prior to expiration of the sensor duration, then admitting hydrogen into the anode flow field 28 and then measuring with the voltage-measuring device 90 the second open circuit hydrogen voltage across the electrodes 14, 16; and

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iii. then correlating the first monitoring voltage and the first open circuit hydrogen voltage with the second monitoring voltage and the second open circuit hydrogen voltage to determine the sensor voltage limit of the shut down fuel cell power plant.

9. The method for determining a gas composition of a shut down fuel cell power plant of claim 8, comprising the further step of intermittently applying the predetermined sensing current to the fuel cell 12 for the predetermined sensing duration, and then admitting hydrogen into the fuel cell 12 flow fields 28, 30 whenever a shut down monitoring voltage detected by the sensor circuit 86 is about the same as or exceeds the sensor voltage limit.

10. The method for determining a gas composition of a shut down fuel cell power plant of claim 9 comprising the further step of admitting the hydrogen through an anode inlet valve 62 secured in fluid communication between a storage source 44 of the hydrogen reducing fluid and an anode inlet 40 of the fuel cell.