SORFC system and method with an exothermic net electrolysis reaction

• US 7,201,979 B2
• Filed: 06/20/2003
• Issued: 04/10/2007
• 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
• Primary Examiner(s): Alejandro; Raymond
• Application Number:
  US10/465,636
• Publication Number:
  US 20040191595A1
• Time in Patent Office: 1,390 Days
• Field of Search: 429/17, 429/13, 429/21, 429/26, 429/30, 429/19, 205/343, 205/412
• 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 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;

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 the solid oxide regenerative fuel cell and generating the oxygen and the hydrocarbon fuel;

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;

the hydrocarbon fuel comprises methane; and

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.

2. The method of claim 1, 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.

3. The method of claim 1, 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.

4. The method of claim 1, further comprises removing the hydrocarbon fuel generated in the electrolysis mode from a solid oxide regenerative fuel cell system.

5. The method of claim 1, further comprising:

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

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

converting the exhaust gas stream 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.

6. 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 stream emitted from the solid oxide regenerative fuel cell to a hydrocarbon gas in an exothermic reaction;

transferring heat from an exothermic reaction to the inlet gas stream; and

further comprising operating the solid oxide regenerative fuel cell in a fuel cell mode to generate power;

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;

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;

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.

7. The method of claim 6, 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.

8. The method of claim 7, 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 excess heat in the Sabatier reactor.

9. The method of claim 6, 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.

10. The method of claim 6, further comprises removing the hydrocarbon gas generated in the electrolysis mode from a solid oxide regenerative fuel cell system.

11. The method of claim 6 wherein a complete electrolysis reaction resulting in a formation of the hydrocarbon gas is a net exothermic electrolysis reaction.

12. The method of claim 11, 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.

13. The method of claim 12, wherein no external heat is provided to the solid oxide regenerative fuel cell operating in the electrolysis mode.