Sofc system and method which maintain a reducing anode environment

Patent metadata

Field	Value
Publication number	US-2018131018-A1
Application number	US-201615346052-A
Country	US
Kind code	A1
Filing date	Nov 8, 2016
Priority date	Nov 8, 2016
Publication date	May 10, 2018
Grant date	—

Abstract

A solid oxide fuel cell system and method including a hotbox containing a fuel cell stack, a fuel supply configured to provide a fuel to the fuel cell stack, and a hydrogen supply thermally integrated with the hotbox. The hydrogen supply is configured to produce hydrogen during or shortly after the SOFC system is shutdown using residual heat of the hot box, and to provide the hydrogen to the SOFC stack such that an anode reducing environment is maintained in the stack.

First claim

What is claimed is:

1 . A solid oxide fuel cell (SOFC) system, comprising:
a hotbox containing a SOFC stack; a fuel supply configured to provide a fuel to the fuel cell stack; and a hydrogen supply thermally integrated with the hotbox, wherein the hydrogen supply is configured to produce hydrogen during or shortly after the SOFC system shutdown using residual heat of the hot box, and to provide the hydrogen to the SOFC stack, such that an anode reducing environment is maintained in the SOFC stack.

2 . The SOFC system of claim 1 , further comprising:
a hydrogen conduit fluidly connecting the hydrogen supply to the fuel cell stack; and a first valve configured to control hydrogen flow through the hydrogen supply conduit, the first valve is powered by the SOFC stack and the first valve is a normally open valve configured to automatically open when the SOFC system is shut down.

3 . The SOFC system of claim 1 , wherein the hydrogen supply is embedded between walls of the hotbox or disposed inside of the hotbox.

4 . The SOFC system of claim 3 , wherein the hydrogen supply is embedded between upper parts of the walls of the hotbox.

5 . The SOFC system of claim 1 , wherein the hydrogen supply comprises a solid metal hydride hydrogen storage material.

6 . The SOFC system of claim 5 , further comprising:
a hydrogen separator configured to separate hydrogen from an anode exhaust conduit of the SOFC stack; and a recharge conduit configured to provide separated hydrogen from the hydrogen separator to the hydrogen supply.

7 . The SOFC system of claim 6 , wherein:
the recharge conduit is configured to provide the separated hydrogen to the hydrogen supply during steady-state operation of the SOFC system; the hydrogen supply is configured to store the hydrogen provided by the separator during steady-state operation of the SOFC system; and the hydrogen supply is configured to release the stored hydrogen during or shortly after the SOFC system shutdown using the residual heat of the hot box, and to provide the released hydrogen to the anode electrodes of the SOFC stack before the SOFC stack temperature reaches 750° C.

8 . The SOFC system of claim 1 , wherein the hydrogen supply comprises a thermochemical hydrogen generation source which produces the hydrogen from a hydrogen and oxygen containing source using the residual heat of the hot box.

9 . The SOFC system of claim 8 , wherein:
the thermochemical hydrogen generation source comprises a material selected from zinc, ceria (CeO 2 ), ceria doped with a transition metal or a rare earth, lanthanum-strontium manganite (LSM) and a combination of sodium carbonate and Mn 3 O 4 ; and the hydrogen and oxygen containing source comprises a water or potassium hydride tank or conduit.

10 . The SOFC system of claim 9 , further comprising a water separator configured to separate water from an exhaust output from the hotbox and a water tank configured to store the separated water,
wherein the water tank configured to provide the stored water to the hydrogen supply during or shortly after the shutdown of the SOFC system.

11 . A method of operating a solid oxide fuel cell (SOFC) system, comprising:
operating the SOFC system which includes a hotbox containing a SOFC stack, a fuel supply and a hydrogen supply in steady state to generate electricity using fuel provided from the fuel supply; performing a shut down the SOFC system; and providing hydrogen from the hydrogen supply during or shortly after the SOFC system shutdown using residual heat of the hot box to the SOFC stack, such that an anode reducing environment is maintained in the SOFC stack.

12 . The method of claim 11 , further comprising automatically opening a normally open first valve during the SOFC system shutdown to provide the hydrogen from the hydrogen supply to the SOFC stack.

13 . The method of claim 11 , wherein the hydrogen supply is embedded between walls of the hotbox or disposed inside of the hotbox.

14 . The method of claim 13 , wherein the hydrogen supply is embedded between upper parts of the walls of the hotbox.

15 . The method of claim 11 , wherein the hydrogen supply comprises a solid metal hydride hydrogen storage material.

16 . The method of claim 15 , further comprising:
separating hydrogen from an anode exhaust of the SOFC stack; and providing the separated hydrogen to the hydrogen supply.

17 . The method of claim 16 , wherein:
the separated hydrogen is provided to the hydrogen supply and stored in the hydrogen supply during steady-state operation of the SOFC system at a temperature above 750° C.; and the stored hydrogen is released during or shortly after the SOFC system shutdown using the residual heat of the hot box, and provided to the anode electrodes of the SOFC stack before the SOFC stack temperature reaches 750° C.

18 . The method of claim 11 , wherein the hydrogen supply comprises a thermochemical hydrogen generation source which produces the hydrogen from a hydrogen and oxygen containing source using the residual heat of the hot box.

19 . The method of claim 18 , wherein:
the thermochemical hydrogen generation source comprises a material selected from zinc, ceria (CeO 2 ), ceria doped with a transition metal or a rare earth, lanthanum-strontium manganite (LSM) and a combination of sodium carbonate and Mn 3 O 4 ; and the hydrogen and oxygen containing source comprises water or potassium hydride which is provided to the thermochemical hydrogen generation source during or shortly after the shutdown of the SOFC system.

20 . The method of claim 19 , further comprising:
separating water from an exhaust output from the hotbox; storing the separated water; and providing the stored water to the hydrogen supply during or shortly after the shutdown of the SOFC system.

21 . The method of claim 11 , wherein:
during the steady-state operation, the hydrogen supply is cooled by an air inlet stream supplied to the SOFC stack; and during or shortly after shut down of the SOFC system, the air inlet stream is turned off.

22 . The method of claim 21 , wherein:
during the steady-state operation, the hydrogen supply has a temperature above hydrogen filling temperature and below hydrogen release or desorption temperature due to cooling by the air inlet stream; and during or shortly after the SOFC system shutdown, the hydrogen supply temperature is increased to or above hydrogen release or desorption temperature after the air inlet stream is turned off.

23 . The method of claim 22 , wherein:
the hydrogen supply comprises a solid metal hydride hydrogen storage material; during the steady-state operation, the hydrogen supply has a temperature ranging from about 150° C. to about 300° C.; and during the shutdown operation, the hydrogen supply reaches a temperature ranging from about 400° C. to about 650° C.

24 . A solid oxide fuel cell (SOFC) system, comprising:
a hotbox containing a SOFC stack; a fuel supply configured to provide a fuel to the fuel cell stack; an electrolyzer fluidly connected to the fuel inlet conduit of the hotbox; a water source; and a power source electrically connected to the hydrogen supply, wherein the electrolyzer is configured to use power provided by the power source during or shortly after system shutdown to electrolyze water from the water source to produce hydrogen and to provide the hydrogen to the SOFC stack such that

Assignees

• Bloom Energy Corp

Inventors

• Perry Martin
• Ballantine Arne
• Gasda Michael
• Karuppaiah Chockkalingam

Classifications

• H01M8/04708

  of fuel cell reactants · CPC title

• H01M8/2425

  High-temperature cells with solid electrolytes · CPC title

• H01M8/04097 Primary

  with recycling of the reactants (H01M8/04119, H01M8/04104 take precedence) · CPC title

• H02J3/387

  Electricity · mapped topic

• H01M8/0656

  by electrochemical means (H01M8/065 takes precedence) · CPC title