Fuel Cell Assembly

Abstract

Disclosed herein is a fuel cell assembly including a fuel cell stack including one or more fuel cells stacked in a stacking direction. The fuel cell assembly further includes a first and second clamping plate for clamping the fuel cell stack between the first clamping plate and the second clamping plate in the stacking direction. The fuel cell assembly further includes at least one clamping element for interconnecting the first and second clamping plate. The clamping element is made of a creep-resistant material.

Claims

1. A fuel cell assembly comprising a fuel cell stack comprising one or more fuel cells stacked in a stacking direction; a first and second clamping plate for clamping the fuel cell stack between the first clamping plate and the second clamping plate in the stacking direction; and at least one clamping element for interconnecting the first and second clamping plate, wherein the clamping element is made of a creep-resistant material.

2. The fuel cell assembly according to claim 1, wherein the first clamping plate, the second clamping plate and the fuel cell stack have an overall thermal expansion coefficient in the stacking direction that is within 30%, preferably within 10%, more preferably within 5%, of the thermal expansion coefficient, in the stacking direction, of the clamping element.

3. The fuel cell assembly according to claim 1, wherein the first clamping plate and/or the second clamping plate and/or the clamping element are made of a material having a similar thermal expansion coefficient, wherein the thermal expansion coefficient is preferably within 30%, preferably within 10%, more preferably within 5%, of the thermal expansion coefficient of the fuel cell stack in the stacking direction.

4. The fuel cell assembly according to claim 3, wherein the material of the first clamping plate and/or the material of the second clamping plate and/or the material of the clamping element is a ceramic material.

5. The fuel cell assembly according to claim 4, wherein the ceramic material is a ceramic matrix composite, which preferably includes a matrix of aluminum oxide, zirconium oxide, yttrium oxide-stabilized zirconium dioxide, or silicon carbide.

6. The fuel cell assembly according to claim 1, the first clamping plate and/or the second clamping plate and/or the clamping element are made of a material having a thermal expansion coefficient in the range from 1?10.sup.?6/K to 20?10.sup.?6/K, particularly from 5?10.sup.?6/K to 13?10.sup.?6/K.

7. The fuel cell assembly according to claim 1, wherein the fuel cell assembly further comprises a first force transmission plate arranged between the fuel cell stack and the first clamping plate and/or a second force transmission plate arranged between the fuel cell stack and the second clamping plate.

8. The fuel cell assembly according to claim 3, wherein the first force transmission plate has the same thermal expansion coefficient as the first clamping plate and/or the second force transmission plate has the same thermal expansion coefficient as the second clamping plate.

9. The fuel cell assembly according to claim 7, wherein the first clamping plate is in direct contact with the first force transmission plate and/or the second clamping plate is in direct contact with the second force transmission plate.

10. The fuel cell assembly according to claim 7, wherein the first force transmission plate has an inner surface facing an upper surface of the fuel cell stack and the second force transmission plate has an inner surface facing a lower surface of the fuel cell stack, wherein the inner surface of the first force transmission plate, the inner surface of the second force transmission plate, the upper surface of the fuel cell stack and the lower surface of the fuel cell stack are essentially parallel to each other.

11. The fuel cell assembly according to claim 7, wherein the first force transmission plate is in direct contact with the fuel cell stack and/or the second force transmission plate is in direct contact with the fuel cell stack.

12. The fuel cell assembly according to claim 7, wherein the fuel cell assembly further comprises a first intermediate layer and/or a second intermediate layer, wherein the first intermediate layer is arranged between the first force transmission plate and the fuel cell stack and the second intermediate layer is arranged between the second force transmission plate the fuel cell stack, wherein the first intermediate layer and the second intermediate layer each comprise a mica sheet.

13. The fuel cell assembly according to claim 12, wherein the fuel cell assembly further comprises at least one thermal expansion adjustment plate configured to maintain a designated clamping force on the fuel cell stack, wherein the at least one thermal expansion adjustment plate is arranged between the clamping element and the first clamping plate; arranged between the clamping element and the second clamping plate; comprised in the first intermediate layer; and/or comprised in the second intermediate layer.

14. The fuel cell assembly according to claim 1, wherein the first clamping plate and/or the second clamping plate are planar, convex or concave with respect to the fuel cell stack.

15. The fuel cell assembly according to claim 1, wherein the fuel cells include one or more of the following: solid oxide fuel cell, molten carbonate fuel cell, phosphoric acid fuel cell, proton-exchange membrane fuel cell and alkaline fuel cell, preferably solid oxide fuel cell.

16. The fuel cell assembly according to claim 1, wherein the fuel cell stack, the first clamping plate, the second clamping plate and the at least one clamping element are arranged inside an insulation housing for thermally insulating the fuel cell stack.

17. The fuel cell assembly according to claim 16, wherein the insulation housing has a density of less than 400 kg/m.sup.3.

18. The fuel cell assembly according to claim 16, wherein the insulation housing has a density of less than 300 kg/m.sup.3.

19. The fuel cell assembly according to claim 16, wherein the insulation housing has a density of less than 275 kg/m.sup.3.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0061] The disclosure described herein will be more fully understood from the detailed description given herein below and the accompanying drawings which should not be considered limiting to the invention described in the appended claims. The drawings are showing:

[0062] FIG. 1 shows an embodiment of the fuel cell assembly disclosed herein having concave clamping plates;

[0063] FIG. 2 shows an embodiment of the fuel cell assembly disclosed herein having convex clamping plates;

[0064] FIG. 3 shows an embodiment of the fuel cell assembly disclosed herein having planar clamping plates and intermediate layers;

[0065] FIG. 4 shows an embodiment of the fuel cell assembly disclosed herein having a thermal expansion adjustment plate.

DETAILED DESCRIPTION

[0066] Reference will now be made in detail to certain embodiments, examples of which are illustrated in the accompanying drawings, in which some, but not all features are shown. Indeed, embodiments disclosed herein may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will satisfy applicable legal requirements. Whenever possible, like reference numbers will be used to refer to like components or parts.

[0067] FIG. 1-4 show different embodiments of a fuel cell assembly 1. The fuel cell assemblies 1 each comprise a fuel cell stack 2 of fuel cells. In the illustrated embodiments, the fuel cells are high-temperature solid oxide fuel cells. The solid oxide fuel cell stack 2 is clamped between a first clamping plate 3 and a second clamping plate 4, and optionally between a first force transmission plate 6 and a second force transmission plate 7. The first and second force transmission plates 6 and 7 are both arranged between the first and second clamping plates 3 and 4. The clamping force which acts on the fuel cell stack 2 is exerted by clamping elements 5. The illustrated embodiments comprise four different clamping elements 5. However other amounts are also possible. Each clamping element 5 comprises a means for clamping and maintaining a tightness. In the illustrated embodiment, each clamping element 5 comprises a screw and a nut.

[0068] In the illustrated embodiments, the clamping elements 5, the first and second force transmission plates 6 and 7 and the first and second clamping plates 3 and 4 are made of a ceramic material.

[0069] The fuel cell assembly 1 of the different illustrated embodiments further comprise a fuel supply pipe 9, an oxygen supply pipe 10 and an exhaust pipe 11.

[0070] The illustrated fuel cell assemblies 1 furthermore comprise an insulation housing 8 for thermal insulation. The first and second clamping plates 3 and 4, the first and second force transmission plates 6 and 7, the clamping element 5 and the fuel cell stack 2 are all arranged inside the insulation housing 8. In other words, the insulation housing 8 full encompasses the first and second clamping plates 3 and 4, the first and second force transmission plates 6 and 7, the clamping element 5 and the fuel cell stack 2. In still other words, no clamping forces acting on the fuel cell stack 2 are transmitted through the insulation housing 8.

[0071] Having a fuel cell stack 2 entirely inside the insulation housing 8 without the need of screws passing through nor of putting pressure through the insulation housing 8 to clamp the fuel cell stack 2 allows to use highly performant, light and brittle insulation and remove the limitation to hard, less performant and heavier insulations. This new housing allows also to electrically insulate the stack from the outside.

[0072] The fuel cell stack 2, the first and second clamping plates 3 and 4 and the first and second force transmission plates 6 and 7 are placed in a thermal insulation 8 with only electrical connection and fuel inlet 9, air inlet 10 and exhaust 11 passing through the insulation.

[0073] All the parts are therefore at high operating temperature, typically between 600? C. and 1000? C. and the system is maintaining itself compressed with ceramic materials.

[0074] Typically the solid oxide fuel cell (SOFC) stack 2 comprises interconnects with a thickness between 0.5 mm to 3 mm and cells with a surface between 40?40 to 150?150 mm, compressed between two ceramic plates. The stack 2 contains typically between 1 to 100 cells. The ceramic plates are compressed by ceramic screws and nuts around and act as a spring to transfer the force from the screws to the stack.

[0075] The rigid ceramic plates transfer and even the force from the ceramic plates to the stack 2. The stack 2 is therefore exposed to an even and constant pressure on its surface. Ceramic plate 6 can contain two pipes connections 9 and 10 sealed typically with glass materials. It is possible to extend the number of pipes connection and add some mixing microfluidic in that plate to pre-mix gases before the stack or the reforming chamber.

[0076] Ceramic plates 3 and 4 can be either flat, convex or concave with a thickness between 2 mm to 20 mm. Typically with a thermal expansion coefficient (CTE) between 5e?6 to 13e?6/K and a Young modulus between 100 to 400 GPa.

[0077] Ceramic plates 6 and 7 may have a flatness under 200 um and a thickness between 0.5 to 10 mm. Typically with a CTE between 5e?6 to 13e?6/K and a Young modulus between 100 to 400 GPa.

[0078] The screws and nuts are ceramic based. Typically with a CTE between 5e?6 to 13e?6/K and a Young modulus between 100 to 400 GPa.

[0079] Having no compression needed through insulation allows to use brittle with low compression strength insulation. Typically an insulation for SOFC would have a resistance to compression higher than 1 MPa, a conductivity higher than 0.1 W/m*K and a density higher than 350 kg/m3. By allowing brittle insulation, we can use an insulation with a resistance to compression lower than 0.3 MPa, a thermal conductivity typically lower than 0.03 W/m*K and a density lower than 275 kg/m3. Therefore, a factor of 3 in size is gained and a factor of 4 in weight is gained.

[0080] In the fuel cell assembly 1 shown in FIG. 1, the first and second clamping plate 3 and 4 each have a concave shape (bend towards from the fuel cell stack). By contrast, in the fuel cell assembly shown in FIG. 2, the first and second clamping plate 3 and 4 each have a convex shape (bend away from the fuel cell stack).

[0081] In the fuel cell assembly 1 shown in FIG. 3, the first and second clamping plate 3 and 4 are each planar. The fuel cell assembly 1 shown in FIG. 3 furthermore comprise a first intermediate layer 13 and a second intermediate layer 14. The first intermediate layer 13 is arranged between the first force transmission plate 6 and the fuel cell stack 2. The second intermediate layer 14 is arranged between the second force transmission plate 7 and the fuel cell stack 2. The illustrated embodiments also comprises two further intermediate layers, which are arranged between the first force transmission plate 6 and the first clamping plate 3, as well as between the second force transmission plate 7 and the second clamping plate 4.

[0082] The fuel cell assembly 1 shown in FIG. 4 comprises a thermal expansion adjustment plate 15 which is arranged on top of the fuel cell stack 2.

LIST OF DESIGNATIONS

[0083] 1 fuel cell assembly [0084] 2 fuel cell stack [0085] 3 first clamping plate [0086] 4 second clamping plate [0087] 5 clamping element [0088] 6 first force transmission plate [0089] 7 second force transmission plate [0090] 8 insulation housing [0091] 9 fuel supply pipe [0092] 10 oxygen supply pipe [0093] 11 exhaust pipe [0094] 12 interconnector [0095] 13 first intermediate layer [0096] 14 second intermediate layer [0097] 15 thermal expansion adjustment plate