Method and apparatus for controlling a combined heat and power fuel cell system

• US 6,835,483 B2
• Filed: 05/30/2002
• Issued: 12/28/2004
• Est. Priority Date: 05/31/2001
• Status: Expired due to Fees

• Current Assignee: Plug Power Inc.
• Original Assignee: Plug Power Inc.
• Inventors: Skidmore, Dustan L., Ballantine, Arne W., Parks, John W., Hallum, Ryan
• Primary Examiner(s): Ryan, Patrick
• Assistant Examiner(s): Parsons, Thomas H.
• Application Number:
  US10/159,392
• Publication Number:
  US 20020182467A1
• Time in Patent Office: 943 Days
• Field of Search: 429/24, 429/26, 429/35, 429/39
• US Class Current: 429/435
• CPC Class Codes: H01M 8/04007 related to heat exchange
• CPC Class Codes: H01M 8/04089 of gaseous reactants
• CPC Class Codes: H01M 8/0432 Temperature; Ambient temperature
• CPC Class Codes: H01M 8/04373 of auxiliary devices, e.g. reformers, compressors, burners
• CPC Class Codes: H01M 8/04559 of fuel cell stacks
• CPC Class Codes: H01M 8/04589 of fuel cell stacks
• CPC Class Codes: H01M 8/04604 Power, energy, capacity or load
• CPC Class Codes: H01M 8/04701 Temperature
• CPC Class Codes: H01M 8/04731 of other components of a fuel cell or fuel cell stacks
• CPC Class Codes: H01M 8/04738 of auxiliary devices, e.g. reformer, compressor, burner
• CPC Class Codes: H01M 8/04753 of fuel cell reactants
• CPC Class Codes: H01M 8/04768 of the coolant
• CPC Class Codes: H01M 8/04776 at auxiliary devices, e.g. reformer, compressor, burner
• CPC Class Codes: H01M 8/0612 from carbon-containing material
• CPC Class Codes: Y02E 20/14 Combined heat and power generation [CHP]
• CPC Class Codes: Y02E 60/50 Fuel cells

Abstract

A cogeneration fuel cell system and associated methods of operation are provided that accommodate a demand for heat as well as a demand for electric power. The system is operated among various modes to balance heat and power demand signals. In general, a fuel cell system is coupled to a power sink and a heat sink, and a controller is adapted to respond to data signals from the power sink and the heat sink. As examples, such data signals from the heat sink may include a temperature indication or a heat demand signal (such as from a thermostat), and such data signals from the power sink may include a voltage or current measurement, an electrical power demand signal, or an electrical load.

Claims

1. A fuel cell system, comprising:

a fuel cell stack and a first coolant circuit, wherein the first coolant circuit is adapted to circulate a first coolant through the fuel cell stack and transfer heat from the fuel cell stack to a heat sink;

a second heat source and a second coolant circuit, wherein the second coolant circuit is adapted to circulate a second coolant through the second heat source to transfer heat from the second heat source to the heat sink;

a controller connected to a first pump and adapted to vary an output of the first pump, wherein the first pump is located in the first coolant circuit; and

a second pump, wherein the controller is connected to the second pump and adapted to vary an output of the second pump, and wherein the second pump is located in the second coolant circuit,

wherein the heat sink comprises a heat exchanger that includes a first flow path adapted to receive a flow of the first coolant, a second flow path separate from the first flow path adapted to receive a flow of the second coolant and a third flow path separate from the first and second flow paths adapted to receive a flow of a third fluid.

2. The system of claim 1, wherein the second heat source is a fuel processing reactor.

3. The system of claim 1, wherein the second heat source is a system exhaust gas oxidizer.

4. The system of claim 1, wherein the heat sink is a water tank.

5. The system of claim 1, wherein the heat sink is a body of water.

6. The system of claim 1, wherein the heat sink comprises air contained in a building.

7. The system of claim 1, wherein the heat sink comprises a generator portion of an adsorption cooling system.

8. The system of claim 1, wherein at least one of the first and second coolant circuits include a radiator having a variable speed radiator fan.

9. The system of claim 8, further comprising:

a heat demand sensor connected to the controller and adapted to vary a speed of the radiator fan to maintain a temperature of the heat sink above a predetermined level.

10. The system of claim 1, wherein the controller is adapted to maintain a temperature of the fuel cell stack above a predetermined level.

11. The system of claim 1, wherein the controller is adapted to maintain a temperature of the second heat source above a predetermined level.

12. The system of claim 1, further comprising a third heat source and a third coolant circuit, wherein the third coolant circuit is adapted to circulate a third coolant through the third heat source to transfer heat from the third heat source to the heat sink;

and

a third pump, wherein the controller is connected to the third pump and adapted to vary an output of the third pump, and wherein the third pump is located in the third coolant circuit.

13. The system of claim 12, wherein the second heat source is a fuel processing reactor, and wherein the third heat source is a system exhaust gas oxidizer.

14. A method of operating a fuel cell system, comprising:

transferring heat from a fuel cell to a first coolant circuit;

transferring heat from a second system heat source to a second coolant circuit;

transferring heat from each of the first and second coolant circuits using a heat sink that includes a first flow path for a first coolant of the first coolant circuit, a second coolant flow path, separate from the first coolant flow path for a second coolant for the second coolant circuit and a third flow path separate from the first and second flow paths for a third fluid;

varying a first coolant flow through the first coolant circuit to maintain a temperature of the fuel cell below a predetermined level; and

varying a second coolant flow through the second coolant circuit to maintain the second system heat source below a predetermined level.

15. The method of claim 14, wherein the second system heat source is a fuel processing reactor.

16. The method of claim 14, wherein the second system heat source is a system exhaust gas oxidizer.

17. The method of claim 14, wherein the heat sink is a water tank.

18. The method of claim 14, wherein the heat sink is a body of water.

19. The method of claim 14, wherein the heat sink comprises air contained in a building.

20. The method of claim 14, wherein the heat sink comprises a generator portion of an adsorption cooling system.

21. The method of claim 14, further comprising:

selectively flowing at least one of the first coolant and second coolant through a radiator; and

operating a fan to blow air across the radiator to remove heat from the radiator.

22. A fuel cell system, comprising:

a first heat source and a first coolant circuit, wherein the first coolant circuit is adapted to circulate a first coolant through the fuel cell stack and remove heat from the first heat source;

a second heat source and a second coolant circuit, wherein the second coolant circuit is adapted to circulate a second coolant through the second heat source to remove heat from the second heat source;

a first heat exchanger comprising a first coolant flow path and a second coolant flow path, wherein the heat exchanger is adapted to transfer heat from the first coolant to the second coolant when a first temperature of the first coolant is greater than a second temperature of the second coolant;

a second heat exchanger located along the second coolant circuit downstream from the first heat exchanger, the second heat exchanger being adapted to transfer heat from the second coolant circuit to a heat sink fluid when the second coolant in the second heat exchanger has a higher temperature than the heat sink fluid;

a radiator system comprising a radiator and a fan, the radiator system being located along the second coolant circuit between the first heat exchanger and the second heat exchanger, the radiator being adapted to remove heat from the second coolant circuit;

a controller connected to a first pump and adapted to vary an output of the first pump, wherein the first pump is located in the first coolant circuit;

a second pump, wherein the controller is connected to the second pump and adapted to vary an output of the second pump, and wherein the second pump is located in the second coolant circuit.

23. The system of claim 22, wherein the controller is adapted to vary a speed of the radiator to maintain the heat sink fluid above a predetermined temperature.

24. The system of claim 23, wherein the first heat source is a fuel processing reactor and the second heat source is a fuel cell stack.

25. The system of claim 22, wherein the controller is adapted to vary a speed of the second pump to maintain the heat sink fluid above a predetermined temperature.

26. The system of claim 22, wherein the first heat source is a fuel cell stack and the second heat source is a fuel processing reactor.

27. The system of claim 22, wherein the first heat source is a fuel cell stack and the second heat source is a system exhaust gas oxidizer.

28. The system of claim 22, wherein the first heat source is a system exhaust gas oxidizer.

29. The system of claim 22, wherein the heat sink is a water tank.

30. The system of claim 22, wherein the heat sink comprises air contained in a building.

31. The system of claim 22, wherein the heat sink comprises a generator portion of an adsorption cooling system.