Methods for operating a fuel cell system under reduced load conditions

• US 7,846,569 B2
• Filed: 12/21/2005
• Issued: 12/07/2010
• Est. Priority Date: 07/27/1999
• Status: Active Grant

• Current Assignee: DCNS SA (Government of France)
• Original Assignee: IdaTech LLC (IdaTech Ltd.)
• Inventors: Herron, Thomas G., Edlund, David J., Holmes, Craig F.
• Primary Examiner(s): Alejandro; Raymond
• Application Number:
  US11/316,488
• Publication Number:
  US 20060134473A1
• Time in Patent Office: 1,812 Days
• Field of Search: 429/13, 429/17, 429/19, 429/22, 429/23, 429/25, 429/26, 429/34
• US Class Current: 429/423
• CPC Class Codes: H01M 16/006 of fuel cells with rechargeable batteries
• CPC Class Codes: H01M 8/04089 of gaseous reactants
• CPC Class Codes: H01M 8/04298 Processes for controlling fuel cells or fuel cell systems
• CPC Class Codes: H01M 8/04365 of other components of a fuel cell or fuel cell stacks
• CPC Class Codes: H01M 8/04552 of the individual fuel cell
• CPC Class Codes: H01M 8/04559 of fuel cell stacks
• CPC Class Codes: H01M 8/04582 of the individual fuel cell
• CPC Class Codes: H01M 8/04589 of fuel cell stacks
• CPC Class Codes: H01M 8/04619 of fuel cell stacks
• CPC Class Codes: H01M 8/04626 of auxiliary devices, e.g. batteries, capacitors
• CPC Class Codes: H01M 8/04753 of fuel cell reactants
• CPC Class Codes: H01M 8/0494 of fuel cell stacks
• CPC Class Codes: H01M 8/04947 of auxiliary devices, e.g. batteries, capacitors
• CPC Class Codes: H01M 8/0612 from carbon-containing material
• CPC Class Codes: H01M 8/0656 by electrochemical means H01M8/065 takes precedence
• CPC Class Codes: H01M 8/0662 Treatment of gaseous reactants or gaseous residues, e.g. cleaning
• CPC Class Codes: H01M 8/0687 Reactant purification by the use of membranes or filters
• CPC Class Codes: H01M 8/249 comprising two or more groupings of fuel cells, e.g. modular assemblies
• CPC Class Codes: Y02E 60/10 Energy storage using batteries
• CPC Class Codes: Y02E 60/50 Fuel cells

Abstract

Methods for operating a fuel cell system under reduced load conditions. The fuel cell system includes a control system for regulating the power produced by the fuel cell system. The fuel cell system further includes a fuel cell stack adapted to produce electrical power from a feed. In some embodiments, the fuel cell system includes a fuel processing assembly adapted to produce the feed for the fuel cell stack from one or more feedstocks. The control system regulates the power produced by the fuel cell system to prevent damage to, and/or failure of, the system. The methods include selectively diverting at least a portion of the feed from delivery to the fuel cell stack if an applied load is less than the currently available power output of the fuel cell system.

Claims

1. A method for operating a fuel cell system that is configured to receive an applied load and which comprises a fuel processing assembly configured to produce a feed stream containing hydrogen gas, and a fuel cell system having a currently available power output and configured to receive at least a portion of the feed stream and to produce electrical power therefrom, the method comprising:

producing a feed stream with the fuel processing assembly operating at a rate of production of the feed stream;

delivering at least a portion of the feed stream to a fuel cell stack;

operating the fuel cell system under conditions wherein the applied load is less than the currently available power output at least a portion of the time; and

selectively diverting, as a diverted portion, a portion of the feed stream from delivery to the fuel cell stack responsive to the applied load being less than the currently available power output, wherein the selectively diverting step does not include stopping the production of the feed stream by the fuel processing assembly.

2. The method of claim 1, wherein the selectively diverting step does not include reducing the rate of production of the feed stream by the fuel processing assembly.

3. The method of claim 1, wherein the diverted portion includes all of the feed stream.

4. The method of claim 1, wherein the diverted portion includes some, but not all, of the feed stream.

5. The method of claim 1, wherein the selectively diverting step includes delivering a subportion of the diverted portion of the feed stream to at least one hydrogen storage device.

6. The method of claim 1, wherein the selectively diverting step includes delivering a subportion of the diverted portion of the feed stream to at least one hydrogen-consuming device.

7. The method of claim 6, wherein the at least one hydrogen-consuming device includes a combustion assembly that is adapted to combust the subportion of the diverted portion of the feed stream.

8. The method of claim 7, wherein the combustion assembly includes a combustion chamber that is adapted to heat the fuel cell system.

9. The method of claim 1, wherein the fuel processing assembly includes at least one fuel processor adapted to produce the feed stream by steam reforming a feedstock comprising water and at least one of a hydrocarbon and an alcohol.

10. The method of claim 9, wherein the fuel processing assembly is adapted to produce a mixed gas stream containing hydrogen gas from the feedstock, and further wherein the fuel processing assembly includes a separation region in which the mixed gas stream is separated into the feed stream and at least one byproduct stream.

11. The method of claim 10, wherein the separation region includes a membrane module including at least one hydrogen selective membrane.

12. The method of claim 11, wherein the at least one hydrogen selective membrane is formed from at least one of palladium and a palladium alloy.

13. The method of claim 1, wherein the fuel cell system further includes a battery bank that is adapted to store at least a portion of the electrical power produced by the fuel cell stack and which includes a current level of stored power and a maximum amount of stored power, and further wherein the selectively diverting step includes selectively diverting, as the diverted portion, a portion of the feed stream from delivery to the fuel cell stack responsive to the applied load being less than the currently available power output and the current level of stored power of the battery bank being within a predetermined range of the maximum amount of stored power.

14. The method of claim 13, wherein the selectively diverting step does not include reducing the rate of production of the feed stream by the fuel processing assembly.

15. The method of claim 13, wherein the diverted portion includes all of the feed stream.

16. The method of claim 13, wherein the diverted portion includes some, but not all, of the feed stream.

17. The method of claim 13, wherein the selectively diverting step includes selectively diverting the diverted portion of the feed stream from delivery to the fuel cell stack responsive to the applied load being less than the currently available power output and the current level of stored power of the battery bank being equal to the maximum amount of stored power.

18. The method of claim 17, wherein the selectively diverting step does not include reducing the rate of production of the feed stream by the fuel processing assembly.

19. The method of claim 13, wherein the selectively diverting step includes delivering a subportion of the diverted portion of the feed stream to at least one hydrogen storage device.

20. The method of claim 13, wherein the selectively diverting step includes delivering a subportion of the diverted portion of the feed stream to at least one hydrogen-consuming device.

21. The method of claim 20, wherein the at least one hydrogen-consuming device includes a combustion assembly that is adapted to combust the subportion of the diverted portion of the feed stream.

22. The method of claim 21, wherein the combustion assembly includes a combustion chamber that is adapted to heat the fuel cell system.

23. The method of claim 13, wherein the fuel processing assembly includes at least one fuel processor adapted to produce the feed stream by steam reforming a feedstock comprising water and at least one of a hydrocarbon and an alcohol.

24. The method of claim 23, wherein the fuel processing assembly is adapted to produce a mixed gas stream containing hydrogen gas from the feedstock, and further wherein the fuel processing assembly includes a separation region in which the mixed gas stream is separated into the feed stream and at least one byproduct stream.

25. The method of claim 24, wherein the separation region includes a membrane module including at least one hydrogen selective membrane.

26. The method of claim 25, wherein the at least one hydrogen selective membrane is formed from at least one of palladium and a palladium alloy.

27. The method of claim 5, wherein the hydrogen storage device includes a hydride bed adapted to store the subportion of the diverted portion of the feed stream.

28. The method of claim 19, wherein the hydrogen storage device includes a hydride bed adapted to store the subportion of the diverted portion of the feed stream.

29. The method of claim 1, the method further comprising detecting when the applied load to the fuel cell stack is less than the currently available power output from the fuel cell stack.

30. The method of claim 13, the method further comprising detecting when the applied load to the fuel cell stack is less than the currently available power output from the fuel cell stack.