POWER TRANSMISSION SYSTEM

Abstract

A power transmission system enables the electrical contacting of a stack with a power line or with an adjacent stack. The stack is made up of a plurality of planar electrochemical modules and is closed off at each of the end faces by a stack-side power transmission plate. The power line to be contacted ends with a line-side power transmission plate. The power transmission system comprises at least one porous, metallic body which is arranged between the stack-side power transmission plate of the stack to be contacted and the line-side power transmission plate of the power line or the stack-side power transmission plate of the adjacent stack and is electrically connected to these power transmission plates. In addition, the porous, metallic body is sealed in a gastight manner by a closed circumferential seal.

Claims

1-15. (canceled)

16. A power transmission system for electrically contacting a stack with a power line or with an adjacent stack, wherein the power line to be contacted ends with a line-side power transmission plate and a stack to be contacted is in each case made up of a stack of at least one planar electrochemical module that is closed at each end face thereof by a stack-side power transmission plate; the power transmission system comprising: at least one porous, metallic body arranged between the stack-side power transmission plate of the stack to be contacted and the line-side power transmission plate of the power line or the stack-side power transmission plate of the adjacent stack and said porous, metallic body being electrically connected to the power transmission plates; and a closed circumferential seal disposed to form a gastight seal around said porous, metallic body.

17. The power transmission system according to claim 16, further comprising at least one spacer disposed to keep the power transmission plates to be contacted at a distance from one another.

18. The power transmission system according to claim 16, wherein said porous, metallic body is configured as a separate component.

19. The power transmission system according to claim 16, wherein said at least one porous, metallic body is clamped between the power transmission plates to be contacted.

20. The power transmission system according to claim 16, wherein said circumferential seal extends circumferentially around said porous, metallic body between the power transmission plates to be contacted.

21. The power transmission system according to claim 16, wherein said porous metallic body is powder-metallurgically produced component having a percolating structure in respect of an electrical conductivity thereof.

22. The power transmission system according to claim 16, wherein the porous metallic body has a mesh structure, a nonwoven structure, or a sponge structure.

23. The power transmission system according to claim 16, wherein a plurality of porous, metallic bodies are stacked on top of one another in an electrical connection direction between the power transmission plates to be electrically contacted.

24. The power transmission system according to claim 16, wherein a plurality of porous, metallic bodies are arranged between the two power transmission plates to be electrically contacted and are spatially separated from one another and in each case sealed in a gastight manner by a closed circumferential seal.

25. The power transmission system according to claim 16, wherein the porous, metallic body is formed from a metal selected from the group consisting of nickel, copper, chromium, iron, molybdenum, tungsten, vanadium, manganese, niobium, tantalum, titanium, cobalt, and an alloy containing at least one of these metals.

26. The power transmission system according to claim 16, wherein the closed circumferential seal is made of glass solder, mica, or a high-temperature adhesive.

27. The power transmission system according to claim 16, wherein material of said porous, metallic body has a coefficient of thermal expansion that is higher than a coefficient of thermal expansion of a material of said seal.

28. The power transmission system according to claim 27, wherein the coefficient of thermal expansion of the material of said seal and the coefficient of thermal expansion of the material of said porous, metallic body differ from each other by not more than 10*10.sup.6 K.sup.1.

29. The power transmission system according to claim 16, wherein the stack-side power transmission plates of the stack and/or the line-side power transmission plate of the power line is formed with through-openings for an introduction or discharge of process gases.

30. The power transmission system according to claim 16, wherein a through-opening is formed in the stack-side power transmission plate to be contacted of the stack within a region enclosed by said seal so as to allow gas exchange with a sealed process gas space operated in a reducing atmosphere in the electrochemical module.

Description

[0022] Further advantages of the invention may be derived from the following description of working examples with reference to the accompanying figures, in which the size ratios are not always shown true to scale for purposes of illustrating the present invention. In the various figures, the same reference numerals are used for corresponding components.

[0023] The figures show:

[0024] FIG. 1a: a schematic perspective view of a power transmission system as per a first embodiment of the invention;

[0025] FIG. 1b: an exploded view of the power transmission system of FIG. 1a;

[0026] FIG. 1c: a schematic cross-sectional view of the power transmission system of FIG. 1a along the line I-II;

[0027] FIG. 2: a schematic cross-sectional view of a power transmission system as per a second embodiment of the invention;

[0028] FIG. 3a: a schematic perspective view of a power transmission system as per a third embodiment of the invention;

[0029] FIG. 3b: an exploded view of the power transmission system of FIG. 3a;

[0030] FIG. 3c: a schematic cross-sectional view of the power transmission system of FIG. 3a along the line I-II.

[0031] FIG. 1a to FIG. 3c each show a perspective view or a corresponding cross-sectional view of a first, second and third embodiment of the power transmission system of the invention. FIG. 1a, FIG. 1b, FIG. 1c and FIG. 2 schematically show a stack comprising a power transmission system by means of which a power cable is contacted (the power cable is not shown and can be electrically contacted via the hole 21 with the line-side power transmission plate 15), while FIGS. 3a, 3b and 3c show a power transmission system in which directly adjacent stacks are electrically connected directly to one another. The stacks 11, 11 shown each consist of electrochemical modules 12, for example SOFCs, which are stacked on top of one another and electrically connected in series and the stacks are closed off at each of the two end faces by a stack-side power transmission plate (base or covering plate) 13,13,13,13. The stack-side power transmission plates have been powder-metallurgically produced from a powder batch composed of 95% by weight of elemental chromium powder and 5% by weight of a prealloy powder composed of iron with 0.8% by weight of yttrium.

[0032] To establish contact with the cable-like power line, the end of the power line (not shown) is pushed into the hole 21 of the line-side power transmission plate 15 and electrically connected thereto. The line-side power transmission plate 15 consists of a high-temperature-resistant, melt-metallurgically produced steel such as X1CrWNbTiLa22-2 (obtainable under the tradename Crofer 22 H) or X1 CrTiLa22 (obtainable as Crofer 22 APU) and is therefore likewise electrically conductive. The line-side power transmission plate 15 is electrically connected to the stack-side power transmission plate 13 via a nickel gauze, the porous metallic body 16, located inbetween. To produce reliable and low-ohm contacting over the entire contact area of the metallic gauze 16 with the power transmission plates 13; 15, the metallic gauze 16 is laid between the two power transmission plates 13, 15 to be contacted, gently pressed together and the line-side power transmission plate 15 which has been placed on top is loaded with a weight during the joining process. Instead of a single gauze, it is also possible to stack a plurality of gauzes on top of one another. The power-conducting element 16 does not necessarily have to be configured as gauze, but instead it is also possible to use inserts composed of a metallic mesh, woven fabric, formed-loop knit, drawn-loop knit, nonwoven, sponge or the like or a powder-metallurgically produced porous component. The metallic gauze 16 or a stack of a plurality of gauzes placed on top of one another is sealed in a gastight manner from the surroundings by a closed circumferential seal 17. As material for the seal 17, use was made of glass solder which is applied in viscous form by means of a dispenser to the surface of one of the two power transmission plates or to the surface of both power transmission plates. The glass solder hardens after joining of the two power transmission plates 13, 15 to be contacted and by material-to-material bonding also establishes a mechanical connection between the two power transmission plates 13, 15 to be contacted. The coefficient of thermal expansion .sub.(20-950) of the glass solder used is about 8.Math.10.sup.6 K.sup.1 and is thus slightly lower than the coefficient of thermal expansion of nickel (at 20 C.: 13.4.Math.10.sup.6 K.sup.1). Owing to the seal 17, the power-conducting element 16 does not have to be made of expensive noble metals or otherwise particularly corrosion-resistant or oxidation-resistant materials and recourse can be made to inexpensive materials such as nickel. Optional spacers 18 ensure parallel orientation of the joined power transmission plates 13, 15. Ceramic or metallic plates, pins, felts or the like have been found to be useful as spacers 18. The power transmission system realized in this way saves space and can also be realized very inexpensively since, firstly, inexpensive materials can be used and, in addition, manufacture makes do with only a few working steps. It is naturally also conceivable to use a plurality of power transmission units which are electrically connected in parallel instead of one power transmission unit for further conduction of the power from or to the power transmission plate. This creates redundancy for the event of individual power transmission units acquiring a higher ohmic resistance or failing.

[0033] The embodiment shown in FIG. 2 is slightly modified compared to the first embodiment: the sealed interior space with the gauze 16 is opened by means of the hole 20 through the stack-side power transmission plate 13 to the fuel gas space of the neighboring electrochemical module, so that gas exchange with the reducing atmosphere of the fuel gas space is made possible. This has the advantage that residual oxygen which has remained in the sealed interior space on joining of the two power transmission plates 13, 15 is displaced during the course of first operation.

[0034] FIG. 3a, FIG. 3b and FIG. 3c show a power transmission system in which a stack 11 is contacted not with a power cable but directly with a directly adjacent stack 11. The sheet-like porous metallic body 16 is clamped between the two stack-side power transmission plates 13, 13 of the adjacent stack. In FIG. 3a, it is also possible to see gas passage openings 19 in the stack-side power transmission plate 13, through which openings process gases (fuel gas or offgas) are conveyed from one stack 11 into the adjacent stack 11. These gas passage openings 19 are likewise sealed from the environment by means of glass solder. Adjacent stacks 11, 11 can naturally also be contacted indirectly by means of a power cable located inbetween in a manner analogous to working example 1.