Solid oxide regenerative fuel cell

• US 20040081859A1
• Filed: 08/07/2003
• Published: 04/29/2004
• Est. Priority Date: 10/23/2002
• Status: Active Grant

• Current Assignee: Bloom Energy Corporation
• Original Assignee: iON America LLC (iON Worldwide LLC)
• Inventors: Gottmann, Matthias, Finn, John, McElroy, James, Mitlitsky, Fred
• Granted Patent: US 6,821,663 B2
• Time in Patent Office: Days
• US Class Current: 429/1
• CPC Class Codes: H01M 2008/1293 Fuel cells with solid oxide electrolytes
• CPC Class Codes: H01M 8/04067 Heat exchange or temperature measuring elements, thermal insulation, e.g. heat pipes, heat pumps, fins
• CPC Class Codes: H01M 8/182 Regeneration by thermal means
• CPC Class Codes: H01M 8/184 Regeneration by electrochemical means
• CPC Class Codes: Y02E 60/50 Fuel cells

Abstract

A Solid Oxide Regenerative Fuel Cell (SORFC) system stores waste heat from the fuel cell in a heat storage material during the discharge mode. The heat is then used to heat water to be electrolyzed during the charge mode.

Claims

1. A fuel cell system, comprising:

a regenerative fuel cell; and

a heat storage material which is adapted to store waste heat from the fuel cell during discharge mode and which is adapted to heat water provided into the fuel cell for electrolyzation during charge mode, wherein the heat storage material melts to store heat or desorbs a gas to store heat.

2. The system of claim 1, wherein the fuel cell comprises a SORFC and the material is adapted to vaporize liquid water during the charge mode.

3. The system of claim 2, wherein the material comprises a gas adsorption material which releases heat upon adsorption of the gas.

4. The system of claim 3, wherein the material comprises a zeolite bed and the gas comprises pressurized CO₂ stored in a tank connected to the zeolite bed.

5. The system of claim 2, wherein the material comprises a hydrogen storage material which is adapted to absorb hydrogen fuel and release heat during the charge mode.

6. The system of claim 5, wherein the material is adapted to desorb hydrogen fuel towards the fuel cell upon application of waste heat from the fuel cell during the discharge mode.

7. The system of claim 6, wherein the material comprises a metal hydride.

8. The system of claim 7, wherein the material comprises magnesium hydride.

9. The system of claim 2, wherein the material comprises a first high heat of fusion material which melts in discharge mode to store heat and which solidifies during charge mode to release heat.

10. The system of claim 9, wherein the material comprises aluminum chloride or sodium chlorate.

11. The system of claim 9, further comprising a second high heat of fusion material which melts in discharge mode to store heat and which solidifies during charge mode to release heat, wherein the second high heat of fusion material phase change temperature is lower than the fuel cell operating temperature by about 100°

C. or less.

12. The system of claim 11, wherein:

the second high heat of fusion material has a higher phase change temperature than the first high heat of fusion material; and

second high heat of fusion material is adapted to heat water vaporized by the first high heat of fusion material to within about 100°

C. of the fuel cell operating temperature.

13. The system of claim 12, wherein the first material comprises LiH or LiOH and the second material comprises LiF.

14. The system of claim 12, further comprising a third high heat of fusion material which melts in discharge mode to store heat and which solidifies during charge mode to release heat, wherein the third high heat of fusion material phase change temperature is lower than the phase change temperature of the second high heat of fusion material but higher than the phase change temperature of the first high heat of fusion material.

15. The system of claim 2, further comprising a carbon dioxide source which is adapted to provide carbon dioxide to the fuel cell during the charge mode.

16. The system of claim 1, further comprising a conduit which connects oxidizer outflow from the fuel cell operating in the discharge mode to the heat storage material such that the oxidizer outflow of the fuel cell operating in the discharge mode is adapted to heat the heat storage material.

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

providing a fuel and an oxidizer into a fuel cell during discharge mode;

storing waste heat generated by the fuel cell during the discharge mode in a heat storage material which melts to store heat or desorbs a gas to store heat;

heating water using the stored waste heat during charge mode; and

electrolyzing the heated water in the fuel cell during the charge mode.

18. The method of claim 17, wherein:

the fuel cell comprises a SORFC; and

heating water comprises vaporizing liquid water using the stored heat.

19. The method of claim 18, wherein the material comprises a gas adsorption material which releases heat upon adsorption of a gas.

20. The method of claim 19, wherein the material comprises a zeolite bed and the gas comprises pressurized CO₂ stored in a tank connected to the zeolite bed.

21. The method of claim 18, wherein the material comprises a hydrogen storage material which absorbs hydrogen fuel from the fuel cell and releases heat during charge mode.

22. The method of claim 21, wherein the material desorbs hydrogen fuel towards the fuel cell upon application of waste heat from the fuel cell during discharge mode.

23. The method of claim 22, wherein the material comprises a metal hydride located in a hydrogen fuel storage tank.

24. The method of claim 23, wherein the material comprises magnesium hydride.

25. The method of claim 18, wherein the material comprises a first high heat of fusion material which melts in discharge mode to store heat and which solidifies during charge mode to release heat.

26. The method of claim 25, wherein the first material comprises aluminum chloride or sodium chlorate.

27. The method claim 25, further comprising:

storing waste heat generated by the fuel cell during the discharge mode in a second high heat of fusion material which melts in discharge mode to store heat and which solidifies during charge mode to release heat; and

heating water vaporized by the first high heat of fusion material using the second high heat of fusion material.

28. The method of claim 27, wherein:

the second high heat of fusion material phase change temperature is lower than the fuel cell operating temperature by about 100°

C. or less;

the second high heat of fusion material has a higher phase change temperature than the first high heat of fusion material; and

the second high heat of fusion material heats water vaporized by the first high heat of fusion material to within about 100°

C. of the fuel cell operating temperature.

29. The method of claim 28, wherein the first material comprises LiH or LiOH and the second material comprises LiF.

30. The method of claim 28, further comprising:

storing waste heat generated by the fuel cell during the discharge mode in a third high heat of fusion material which melts in discharge mode to store heat and which solidifies during charge mode to release heat; and

heating water vaporized by the first high heat of fusion material using the third high heat of fusion material.

31. The method of claim 17, further comprising providing carbon dioxide to the fuel cell during the charge mode.

32. The method of claim 17, wherein the step of storing waste heat comprises heating the heat storage material using oxidizer outflow from the fuel cell operating in the discharge mode.

33. A fuel cell system, comprising:

a SORFC; and

a first means for storing waste heat from the SORFC during discharge mode and for heating water provided into the SORFC for electrolyzation during charge mode.

34. The system of claim 33, further comprises a second means for storing waste heat from the SORFC during discharge mode and for vaporizing water provided into the SORFC for electrolyzation during charge mode.

35. A fuel cell system, comprising:

a regenerative fuel cell;

a first heat storage material which is adapted to store waste heat from the fuel cell during discharge mode and which is adapted to vaporize water provided into the fuel cell for electrolyzation during charge mode; and

a second heat storage material which is adapted to store waste heat from the fuel cell during discharge mode and which is adapted to heat the vaporized water provided into the fuel cell for electrolyzation during the charge mode.

36. The system of claim 35, wherein:

the fuel cell comprises a SORFC;

the first heat storage material comprises a first high heat of fusion material which melts in discharge mode to store heat and which solidifies during charge mode to release heat;

the second heat storage material comprises a second high heat of fusion material which melts in discharge mode to store heat and which solidifies during charge mode to release heat; and

a phase change temperature of the first high heat of fusion material is lower than a phase change temperature of the second high heat of fusion material.

37. The system of claim 36, wherein:

the second high heat of fusion material phase change temperature is lower than the fuel cell operating temperature by about 100°

C. or less;

second high heat of fusion material is adapted to heat water vaporized by the first high heat of fusion material to within about 100°

C. of the fuel cell operating temperature;

the first high heat of fusion material comprises LiH or LiOH; and

the second high heat of fusion material comprises LiF.

38. The system of claim 36, further comprising a third high heat of fusion material which melts in discharge mode to store heat and which solidifies during charge mode to release heat, wherein the third high heat of fusion material phase change temperature is lower than the phase change temperature of the second high heat of fusion material but higher than the phase change temperature of the first high heat of fusion material.

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

providing a fuel and an oxidizer into a fuel cell during discharge mode;

storing waste heat generated by the fuel cell during the discharge mode in a first and in a second heat storage materials;

vaporizing water using the waste heat stored in the first heat storage material;

heating the vaporized water using the waste heat stored in the second heat storage material; and

electrolyzing the heated water in the fuel cell during a charge mode.

40. The method of claim 39, wherein the first and the second heat storage materials comprise a high heat of fusion materials which melt in discharge mode to store heat and which solidify during charge mode to release heat.

41. The method of claim 40, wherein:

the second high heat of fusion material phase change temperature is lower than the fuel cell operating temperature by about 100 °

C or less;

the second high heat of fusion material has a higher phase change temperature than the first high heat of fusion material;

the second high heat of fusion material heats water vaporized by the first high heat of fusion material to within about 100°

C. of the fuel cell operating temperature;

the first high heat of fusion material comprises LiH or LiOH; and

the second high heat of fusion material comprises LiF.

42. The method of claim 40, further comprising:

storing waste heat generated by the fuel cell during the discharge mode in a third high heat of fusion material which melts in discharge mode to store heat and which solidifies during charge mode to release heat; and

heating water vaporized by the first high heat of fusion material using the third high heat of fusion material.

43. A fuel cell system, comprising:

a regenerative fuel cell;

a heat storage material which is adapted to store waste heat from the fuel cell during discharge mode and which is adapted to heat water provided into the fuel cell for electrolyzation during charge mode; and

a conduit which connects oxidizer outflow from the fuel cell operating in the discharge mode to the heat storage material such that the oxidizer outflow of the fuel cell operating in the discharge mode is adapted to heat the heat storage material.

44. The system of claim 43, wherein the heat storage desorbs a gas to store heat.

45. The system of claim 43, wherein the heat storage material comprises a high heat of fusion material which melts in discharge mode to store heat and which solidifies during charge mode to release heat.

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

providing a fuel and an oxidizer into a fuel cell during discharge mode;

heating a heat storage material using oxidizer outflow from the fuel cell operating in the discharge mode to store waste heat generated by the fuel cell during the discharge mode;

heating water using the stored waste heat during charge mode; and

electrolyzing the heated water in the fuel cell during the charge mode.

47. The method of claim 46, wherein the heat storage material desorbs a gas to store heat.

48. The method of claim 46, wherein the heat storage material comprises a high heat of fusion material which melts in discharge mode to store heat and which solidifies during charge mode to release heat.