SORFC system and method with an exothermic net electrolysis reaction

• US 20040191595A1
• Filed: 06/20/2003
• Published: 09/30/2004
• Est. Priority Date: 03/24/2003
• Status: Active Grant

• Current Assignee: Bloom Energy Corporation
• Original Assignee: Bloom Energy Corporation
• Inventors: Finn, John E., McElroy, James Frederick
• Granted Patent: US 7,201,979 B2
• Time in Patent Office: Days
• US Class Current: 429/418
• CPC Class Codes: C25B 1/00 Electrolytic production of inorganic compounds or non-metals
• CPC Class Codes: C25B 1/04 by electrolysis of water
• CPC Class Codes: C25B 9/73 of the filter-press type
• CPC Class Codes: H01M 8/04014 Heat exchange using gaseous fluids; Heat exchange by combustion of reactants
• CPC Class Codes: H01M 8/04119 with simultaneous supply or evacuation of electrolyte; Humidifying or dehumidifying
• CPC Class Codes: H01M 8/04231 Purging of the reactants
• CPC Class Codes: H01M 8/0625 in a modular combined reactor/fuel cell structure
• CPC Class Codes: H01M 8/0656 by electrochemical means H01M8/065 takes precedence
• CPC Class Codes: H01M 8/1231 with both reactants being gaseous or vaporised
• CPC Class Codes: H01M 8/186 by electrolytic decomposition of the electrolytic solution or the formed water product
• CPC Class Codes: Y02E 60/36 Hydrogen production from non-carbon containing sources, e.g. by water electrolysis
• CPC Class Codes: Y02E 60/50 Fuel cells
• CPC Class Codes: Y02P 20/129 Energy recovery, e.g. by cogeneration, H2recovery or pressure recovery turbines
• CPC Class Codes: Y02P 20/133 Renewable energy sources, e.g. sunlight

Abstract

A solid oxide regenerative fuel cell system is used to supply power in a fuel cell mode and to generate a hydrocarbon fuel in an electrolysis mode. The system includes a solid oxide regenerative fuel cell and a reactor adapted to convert an exhaust emitted from the solid oxide regenerative fuel cell to a hydrocarbon gas when the solid oxide regenerative fuel cell operates in an electrolysis mode.

Claims

1. A terrestrial solid oxide regenerative fuel cell system, comprising:

a solid oxide regenerative fuel cell; and

a reactor adapted to convert an exhaust emitted from the solid oxide regenerative fuel cell to a hydrocarbon gas when the solid oxide regenerative fuel cell operates in an electrolysis mode.

2. The system of claim 1, wherein:

the exhaust comprises hydrogen and carbon monoxide;

the hydrocarbon gas comprises methane; and

the reactor comprises a Sabatier reactor.

3. The system of claim 1, wherein:

the exhaust comprises hydrogen and carbon monoxide;

the hydrocarbon gas comprises methanol; and

the reactor comprises a methanol synthesis reactor.

4. The system of claim 1, wherein the exhaust comprises hydrogen and carbon monoxide and the hydrocarbon gas comprises at least one gas selected from the group consisting of ethane, propane, octane, formic acid and formaldehyde.

5. The system of claim 1, further comprising:

an inlet conduit which is adapted to provide an inlet gas stream into the solid oxide regenerative fuel cell;

an outlet conduit which is adapted to provide the exhaust gas stream from the solid oxide regenerative fuel cell into the reactor; and

a heat exchanger which is adapted to transfer heat from an exothermic reaction in the reactor to the inlet stream of the solid oxide regenerative fuel cell operating in the electrolysis mode.

6. The system of claim 1, further comprising a hydrocarbon fuel storage vessel adapted to store the hydrocarbon fuel generated when the solid oxide regenerative fuel cell operates in the electrolysis mode and to provide the hydrocarbon fuel into the solid oxide regenerative fuel cell when the solid oxide regenerative fuel cell operates in the fuel cell mode.

7. A terrestrial solid oxide regenerative fuel cell system, comprising:

a solid oxide regenerative fuel cell; and

a means for converting an exhaust emitted from the solid oxide regenerative fuel cell to a hydrocarbon gas when the solid oxide regenerative fuel cell operates in an electrolysis mode.

8. The system of claim 7, wherein:

the exhaust comprises hydrogen and carbon monoxide; and

the hydrocarbon gas comprises methane.

9. The system of claim 7, wherein:

the exhaust comprises hydrogen and carbon monoxide; and

the hydrocarbon gas is converted to methanol.

10. The system of claim 7, further comprising:

a means for providing an inlet gas stream into the solid oxide regenerative fuel cell;

a means for providing the exhaust gas stream from the solid oxide regenerative fuel cell into the means for converting; and

a means for transferring heat from an exothermic reaction in the means for converting to the inlet stream.

11. The system of claim 7, further comprising a means for storing the hydrocarbon fuel generated when the solid oxide regenerative fuel cell operates in the electrolysis mode and for providing the hydrocarbon fuel into the solid oxide regenerative fuel cell when the solid oxide regenerative fuel cell operates in the fuel cell mode.

12. A terrestrial solid oxide regenerative fuel cell system, comprising:

a solid oxide regenerative fuel cell; and

a Sabatier reactor adapted to convert hydrogen and carbon monoxide emitted from the solid oxide regenerative fuel cell to methane and water vapor when the solid oxide regenerative fuel cell operates in an electrolysis mode.

13. The system of claim 12, further comprising:

a methane fuel source connected to the solid oxide regenerative fuel cell fuel inlet; and

an oxidizer inlet in the solid oxide regenerative fuel cell.

14. The system of claim 13, wherein:

the solid oxide regenerative fuel cell is adapted to generate power in a fuel cell mode from oxygen or air supplied from the oxidizer inlet and from methane fuel supplied from the methane fuel source; and

the solid oxide regenerative fuel cell and the Sabatier reactor are adapted to generate and provide the methane fuel to the methane fuel source when the solid oxide regenerative fuel cell operates in the electrolysis mode.

15. The system of claim 12, further comprising:

an inlet conduit which is adapted to provide an inlet gas stream into the solid oxide regenerative fuel cell;

an outlet conduit which is adapted to provide the exhaust gas stream from the solid oxide regenerative fuel cell into the Sabatier reactor; and

a heat exchanger which is adapted to transfer heat from an exothermic reaction in the Sabatier reactor to the inlet stream.

16. The system of claim 15, further comprising:

a water vapor recovery unit adapted to recover water vapor from the solid oxide regenerative fuel cell exhaust stream and to provide the water vapor into the solid oxide regenerative fuel cell fuel inlet stream when the solid oxide regenerative fuel cell operates in a fuel cell mode; and

a hydrogen recovery unit adapted to recover hydrogen from the solid oxide regenerative fuel cell exhaust stream and to provide the hydrogen into the solid oxide regenerative fuel cell fuel inlet stream when the solid oxide regenerative fuel cell operates in a fuel cell mode.

17. The system of claim 12, further comprising a methane storage vessel adapted to store the methane generated when the solid oxide regenerative fuel cell operates in the electrolysis mode and to provide the methane into the solid oxide regenerative fuel cell when the solid oxide regenerative fuel cell operates in the fuel cell mode.

18. A method of operating a terrestrial solid oxide regenerative fuel cell system, comprising:

operating the solid oxide regenerative fuel cell system in a fuel cell mode to generate power; and

operating the solid oxide regenerative fuel cell system in an electrolysis mode to generate oxygen and a hydrocarbon fuel.

19. The method of claim 18, wherein:

the step of operating the solid oxide regenerative fuel cell system in the electrolysis mode comprises providing power, carbon dioxide and water vapor to a solid oxide regenerative fuel cell and generating the oxygen and the hydrocarbon fuel; and

the step of operating the solid oxide regenerative fuel cell system in the fuel cell mode comprises providing oxidizer and the hydrocarbon fuel to the solid oxide regenerative fuel cell and releasing carbon dioxide and water vapor from the solid oxide regenerative fuel cell.

20. The method of claim 19, wherein the hydrocarbon fuel comprises methane.

21. The method of claim 20, wherein the step of generating the oxygen and the hydrocarbon fuel comprises:

providing hydrogen and carbon monoxide emitted from the solid oxide regenerative fuel cell into a Sabatier reactor; and

converting the hydrogen and carbon monoxide to methane and water vapor in the Sabatier reactor.

22. The method of claim 21, wherein the step of converting the hydrogen and carbon monoxide to methane and water vapor in the Sabatier reactor produces a quantity of waste heat that is substantially equivalent to a heat deficiency resulting from a methane reforming reaction in the solid oxide regenerative fuel cell during the fuel cell mode.

23. The method of claim 19, further comprising:

storing the hydrocarbon fuel generated in the electrolysis mode; and

providing the stored hydrocarbon fuel into the solid oxide regenerative fuel cell when the solid oxide regenerative fuel cell operates in the fuel cell mode.

24. The method of claim 18, further comprises removing the hydrocarbon fuel generated in the electrolysis mode from a solid oxide regenerative fuel cell system for use or sale outside the solid oxide regenerative fuel cell system.

25. The method of claim 18, wherein the hydrocarbon fuel is selected from a group consisting of methane, ethane, propane, octane, methanol, formic acid and formaldehyde.

26. The method of claim 25, wherein the hydrocarbon fuel comprises methane.

27. The method of claim 18, wherein the hydrocarbon fuel comprises methanol.

28. The method of claim 18, further comprising:

providing an inlet gas stream into the solid oxide regenerative fuel cell;

providing the exhaust gas stream from the solid oxide regenerative fuel cell into a reactor;

converting the exhaust gas emitted from the solid oxide regenerative fuel cell to a hydrocarbon gas in an exothermic reaction; and

transferring heat from an exotherrnic reaction to the inlet gas stream.

29. A method of operating a terrestrial solid oxide regenerative fuel cell system, comprising:

providing an inlet gas stream into a solid oxide regenerative fuel cell operating in an electrolysis mode;

providing an exhaust gas stream from the solid oxide regenerative fuel cell into a reactor;

converting the exhaust gas emitted from the solid oxide regenerative fuel cell to a hydrocarbon gas in an exothermic reaction; and

transferring heat from an exothermic reaction to the inlet gas stream.

30. The method of claim 29, wherein a complete electrolysis reaction resulting in a formation of the hydrocarbon gas is a net exothermic electrolysis reaction.

31. The method of claim 30, wherein no heat storage material is used to provide heat recovered during a fuel cell mode to the solid oxide regenerative fuel cell operating in the electrolysis mode.

32. The method of claim 31, wherein no external heat is provided to the solid oxide regenerative fuel cell operating in the electrolysis mode.

33. The method of claim 29, further comprising operating the solid oxide regenerative fuel cell in a fuel cell mode to generate power.

34. The method of claim 33, wherein:

the step of operating the solid oxide regenerative fuel cell in the electrolysis mode comprises providing power, carbon dioxide and water vapor to the solid oxide regenerative fuel cell and generating the oxygen and the hydrocarbon gas in the reactor; and

the step of operating the solid oxide regenerative fuel cell in the fuel cell mode comprises providing oxidizer and a hydrocarbon fuel to the fuel cell and releasing carbon dioxide and water vapor from the solid oxide regenerative fuel cell.

35. The method of claim 34, wherein:

the hydrocarbon fuel comprises methane;

the step of providing the exhaust gas stream from the solid oxide regenerative fuel cell into a reactor comprises providing hydrogen and carbon monoxide emitted from the solid oxide regenerative fuel cell into a Sabatier reactor;

the step of converting the exhaust gas emitted from the solid oxide regenerative fuel cell to a hydrocarbon gas in an exothermic reaction comprises converting the hydrogen and carbon monoxide to methane and water vapor in the Sabatier reactor; and

the step of transferring heat from an exothermic reaction to the inlet gas stream comprises passing the inlet gas stream through a heat exchanger located in a Sabatier reactor subsystem.

36. The method of claim 35, wherein the step of converting the hydrogen and carbon monoxide to methane and water vapor in the Sabatier reactor produces a quantity of waste heat that is substantially equivalent to a heat deficiency resulting from a methane reforming reaction in the solid oxide regenerative fuel cell during the fuel cell mode.

37. The method of claim 36, wherein the solid oxide regenerative fuel cell and the Sabatier reactor are operated to sustain the solid oxide regenerative fuel cell at a desired operating temperature by heat transfer from the Sabatier reactor to the solid oxide regenerative fuel cell without generating substantial excess heat in the Sabatier reactor.

38. The method of claim 34, further comprising:

storing the hydrocarbon gas generated in the electrolysis mode; and

providing the stored hydrocarbon gas as a fuel into the solid oxide regenerative fuel cell when the solid oxide regenerative fuel cell operates in the fuel cell mode.

39. The method of claim 34, further comprises removing the hydrocarbon gas generated in the electrolysis mode from a solid oxide regenerative fuel cell system for use or sale outside the solid oxide regenerative fuel cell system.

40. The method of claim 29, wherein the hydrocarbon gas is selected from a group consisting of methane, ethane, propane, octane, methanol, formic acid and formaldehyde.

41. The method of claim 40, wherein the hydrocarbon gas comprises methane.

42. The method of claim 40, wherein the hydrocarbon gas comprises methanol.