Increasing thermal dissipation of fuel cell stacks under partial electrical load

• US 20060257696A1
• Filed: 05/10/2005
• Published: 11/16/2006
• Est. Priority Date: 05/10/2005
• Status: Active Grant

• Current Assignee: Bloom Energy Corporation
• Original Assignee: Bloom Energy Corporation
• Inventors: Gottmann, Matthias, Russell, Ian, Sridhar, K.R.
• Granted Patent: US 7,700,210 B2
• Time in Patent Office: Days
• US Class Current: 429/430
• CPC Class Codes: H01M 2008/1293 Fuel cells with solid oxide electrolytes
• CPC Class Codes: H01M 2008/147 Fuel cells with molten carbonates
• CPC Class Codes: H01M 8/04007 related to heat exchange
• CPC Class Codes: H01M 8/04619 of fuel cell stacks
• CPC Class Codes: H01M 8/04753 of fuel cell reactants
• CPC Class Codes: H01M 8/0625 in a modular combined reactor/fuel cell structure
• CPC Class Codes: H01M 8/184 Regeneration by electrochemical means
• CPC Class Codes: H01M 8/2425 High-temperature cells with solid electrolytes
• CPC Class Codes: H01M 8/2432 Grouping of unit cells of planar configuration
• CPC Class Codes: H01M 8/244 with matrix-supported molten electrolyte
• CPC Class Codes: H01M 8/249 comprising two or more groupings of fuel cells, e.g. modular assemblies
• CPC Class Codes: Y02E 60/50 Fuel cells

Abstract

A method of operating a high temperature fuel cell system containing a plurality of fuel cell stacks includes operating one or more of the plurality of fuel cell stacks at a first output power while operating another one or more of the plurality of the fuel cell stacks at a second output power different from the first output power.

Claims

1. A method of operating a high temperature fuel cell system comprising a plurality of fuel cell stacks, the method comprising operating one or more of the plurality of fuel cell stacks at a first output power while operating another one or more of the plurality of the fuel cell stacks at a second output power different from the first output power.

2. The method of claim 1, wherein a sum of output powers from the plurality of the stacks equals to a total desired or required output power.

3. The method of claim 2, wherein a combined thermal dissipation of the plurality of the stacks is higher compared to operation of the plurality of the stacks at a same output power.

4. The method of claim 3, wherein each one of the plurality of stacks is thermally integrated with one or more other stacks, such that each one of the plurality of stacks provides dissipated heat to one or more other stacks or absorbs heat from one or more other stacks.

5. The method of claim 1, further comprising separately controlling an amount of fuel provided to each of the plurality of fuel cell stacks, such that more fuel is provided to the one or more stacks operating at the first output power than to the one or more stacks operating at the second output power which is lower than the first output power.

6. The method of claim 1, wherein:

the plurality of fuel cell stacks comprise a first set of fuel cell stacks containing one or more first stacks and a second set of fuel cell stacks containing one or more second stacks;

a same amount of fuel is provided to each of the one or more first fuel cell stacks and to each of the one or more second fuel cell stacks; and

a load on the first and the second sets of stacks is repeatedly varied such that the output power of the first set of stacks is alternately higher or lower than the output power of second sets of stacks.

7. The method of claim 6, wherein the load variation frequency on the first and the second sets of stacks is 1 kHz or higher.

8. The method of claim 6, wherein the load on the first and on the second sets of stacks is varied by reversing a polarity of current provided to the stacks.

9. The method of claim 1, wherein each of the plurality of fuel cell stacks is separately electrically connected to at least one of a power conditioning subsystem and a power control subsystem.

10. The method of claim 1, wherein the plurality of fuel cell stacks comprise a plurality of solid oxide fuel cell stacks.

11. The method of claim 1, further comprising operating three or more sets of fuel cell stacks of the plurality of fuel cell stacks at different output powers.

12. The method of claim 1, wherein the plurality of the stacks are operated at different output powers during a partial system load which is lower than a designed system operating load.

14. The method of claim 12, wherein:

the at least one stack comprises a plurality of solid oxide fuel cell stacks;

the output power of each of the plurality of solid oxide fuel cell stacks is periodically cycled above and below an average desired or required output power at the same time; and

a combined thermal dissipation of the plurality of the stacks is higher compared to a thermal dissipation of the plurality of the stacks operated at a constant output power over the period of time.

13. A method of operating a high temperature fuel cell system comprising at least one fuel cell stack, the method comprising:

periodically cycling an output power of the at least one fuel cell stack above and below an average desired or required output power, such that the output power substantially equals the average desired or required output power over a period of time;

storing electrical energy when the output power is above the average total desired or required output power; and

releasing the stored electrical energy when the output power is below the average total desired or required output power.

15. A fuel cell system, comprising:

a plurality of fuel cell stacks; and

a power system comprising at least one of a power conditioning subsystem and a power control subsystem;

wherein the fuel cell stacks are separately electrically connected to the power system.

16. The system of claim 15, wherein:

the power system comprises both the power conditioning subsystem and the power control subsystem; and

the power system is adapted to operate one or more of the plurality of fuel cell stacks at a first output power while operating another one or more of the plurality of the fuel cell stacks at a second output power different from the first output power, such that a sum of output powers from the plurality of the stacks equals to a total desired or required output power.

17. The system of claim 15, further comprising:

a fuel supply conduit or vessel;

a plurality of fuel inlet conduits, each one of the plurality of fuel inlet conduits separately connecting at least one of the plurality of the fuel cell stacks to the fuel supply conduit or vessel; and

a plurality of fuel flow control devices;

wherein;

each one of the plurality of fuel flow control devices is located on each one of the plurality of fuel inlet conduits; and

each one of the plurality of fuel flow control devices is adapted to independently control an amount of fuel being provided through each one of the plurality of fuel inlet conduits.

18. The system of claim 15, wherein the plurality of fuel cell stacks comprise a plurality of thermally integrated solid oxide fuel cell stacks.

19. A fuel cell system, comprising:

a plurality of fuel cell stacks; and

a first means for operating one or more of the plurality of fuel cell stacks at a first output power while operating another one or more of the plurality of the fuel cell stacks at a second output power different from the first output power.

20. The system of claim 19, wherein:

a sum of output powers from the plurality of the stacks equals to a total desired or required output power;

a combined thermal dissipation of the plurality of the stacks is higher compared to operation of the plurality of the stacks at a same output power;

each one of the plurality of stacks is thermally integrated with one or more other stacks, such that each one of the plurality of stacks provides dissipated heat to one or more other stacks or absorbs heat from one or more other stacks; and

the plurality of the stacks are operated at different output powers during a partial system load which is lower than a designed system operating load.

21. The system of claim 19, further comprising:

a fuel supply conduit or vessel;

a plurality of fuel inlet conduits, each one of the plurality of fuel inlet conduits separately connecting at least one of the plurality of the fuel cell stacks to the fuel supply conduit or vessel; and

second means for independently controlling an amount of fuel being provided through each one of the plurality of fuel inlet conduits.

22. The system of claim 19, wherein:

the plurality of fuel cell stacks comprise a first set of fuel cell stacks containing one or more first stacks and a second set of fuel cell stacks containing one or more second stacks; and

the first means repeatedly varies a load on the first and the second sets of stacks such that the output power of the first set of stacks is alternately higher or lower than the output power of second sets of stacks, while a same amount of fuel is provided to each of the one or more first fuel cell stacks and to each of the one or more second fuel cell stacks.

23. The system of claim 19, wherein:

each of the plurality of fuel cell stacks is separately electrically connected to the first means; and

the plurality of fuel cell stacks comprise a plurality of solid oxide fuel cell stacks.