Stack, in particular a fuel cell stack or an electrolysis stack

Abstract

The invention relates to a stack (1), comprising a housing (2) and a cell stack (3) accommodated in the housing (2) and consisting of a plurality of electrochemical cells (4) that have a substantially rectangular basic shape with two longitudinal sides (4.1) and two transverse sides (4.2) and are each aligned perpendicularly with respect to a base (2.1) of the housing (2), so that the stacking direction (8) runs parallel to the base (2.1). According to the invention, the cell stack (3) is connected to at least one sliding element (5), via which the cell stack (3) is mounted on a sliding surface (6) on the housing side, so that the cell stack (3) is movable relative to the housing (2) in the stacking direction (8).

Description

[0001] Description

[0002] Stack, especially or

[0003] The invention relates to a stack having the features of the preamble of claim 1. The stack may, in particular, be a fuel cell stack or an electrolysis stack.

[0004] Preferred areas of application of the invention are fuel cell systems and electrolysis systems, in particular for the production of hydrogen.

[0005] State of the art

[0006] A stack comprises a plurality of electrochemical cells in a stacked arrangement. This cell stack is enclosed in a housing, and the cell stack can be housed in the housing either vertically or horizontally. This means that the electrochemical cells can be stacked either vertically or horizontally.

[0007] If the stacking direction is horizontal, forces act on the cell stack, in particular a gravitational force resulting from the cell stack's own weight, as well as other forces resulting from external influences such as vibrations. These forces cause the individual electrochemical cells in the cell stack to shift against each other, causing the cell stack to bend or sag in the middle. This reduces the stability of the cell stack. In addition, there is an inhomogeneous force and load distribution in the area of ​​the active surfaces of the individual electrochemical cells, which impairs the stack performance. Furthermore, contact between the electrochemical cells and the housing can occur, leading to a short circuit or stack failure.US 2008 / 0305368 A1 discloses a fuel cell stack with a cell stack housed in a housing, the stacking direction of which runs horizontally. To prevent the electrochemical cells from shifting against each other under the influence of force, the individual cells are each supported on the housing by an element arranged at the edge, specifically in the area of ​​projections on the housing side against which the elements rest. Under the influence of force, the projections then absorb the forces.

[0008] US 2015 / 0380762 A1 discloses a fuel cell stack with a cell stack housed in a housing, the stacking direction of which also runs horizontally. To limit displacement of the individual fuel cells relative to one another, a limitedly flexible intermediate layer is arranged between the underside of the cell stack and the housing.

[0009] Based on the prior art described above, the object of the present invention is to further increase the mechanical stability of a cell stack accommodated in a housing, the stacking direction of which runs horizontally.

[0010] To achieve this objective, the stack having the features of claim 1 is proposed. Advantageous developments of the invention are set forth in the subclaims.

[0011] Disclosure of the invention

[0012] The proposed stack comprises a housing and a cell stack accommodated in the housing, consisting of a plurality of electrochemical cells. The cells essentially have a rectangular basic shape with two long sides and two transverse sides, and are each aligned perpendicularly with respect to a base of the housing, so that the stacking direction runs parallel to the base. According to the invention, the cell stack is connected to at least one sliding element, via which the cell stack is mounted on a sliding surface on the housing side, so that the cell stack is movable in the stacking direction relative to the housing.

[0013] The movable mounting of the cell stack provides support and thus promotes a homogeneous force and load distribution in the area of ​​the active surfaces of the electrochemical cells. This means that there is no, or only a significantly reduced, impairment of stack performance due to inhomogeneous force and load distribution. Furthermore, the movable mounting of the cell stack allows for thermally induced length changes, thus preventing stresses in the cell stack. As a result, the mechanical stability of the cell stack and thus the stack as a whole can be improved.

[0014] The at least one sliding element also enables low-wear movement of the cell stack relative to the housing. At the same time, it protects the outer edges of the electrochemical cells from deformation. The housing-side sliding surface, which interacts with the at least one sliding element, absorbs the forces acting on the cell stack and / or caused by the cell stack's own weight. At the same time, the sliding surface ensures the sliding function of the at least one sliding element.

[0015] Preferably, the electrochemical cells are arranged in the housing such that their longitudinal sides run essentially parallel and their transverse sides essentially perpendicular to the bottom of the housing. The cell stack is thus arranged horizontally in the housing. In this arrangement, the risk of the cell stack bending due to the application of force is particularly high, so the advantages of the invention are particularly evident here.

[0016] In a further development of the invention, it is proposed that the at least one sliding element be connected to the cell stack via an adhesive. The adhesive ensures a secure connection between the sliding element and the cell stack. Furthermore, it is proposed that the adhesive surrounds a longitudinal side of at least one electrochemical cell in a U-shape, at least in some areas. The adhesive is thus also arranged in some areas between the electrochemical cells, so that the adhesive can be used both as a spacer and as an insulator.

[0017] The following procedure can be used to connect the at least one sliding element to the cell stack. In a first step, the adhesive is partially applied to one side of the cell stack using a dispensing process. The adhesive also flows between the electrochemical cells, so that they are enclosed by the adhesive in a U-shape. This is particularly advantageous when the outer edges of the electrochemical cells are each formed by a sharp-edged bipolar plate. In a second step, the sliding element is then bonded on.

[0018] The housing-side sliding surface can be formed by the housing, preferably by the bottom of the housing, or can be attached to the housing, preferably to the bottom of the housing. In the former case, the production of the sliding surface may require an additional work step during housing manufacture, which may include, for example, machining the housing.

[0019] Advantageously, the sliding surface has a greater extent in the stacking direction than the at least one sliding element. This ensures that the sliding element is always in contact with the sliding surface, even when the cell stack moves in the stacking direction relative to the housing. The extent of the sliding surface in the stacking direction is preferably at least two-thirds, preferably at least three-quarters, of the stack height of the cell stack. The stack height corresponds to the extent of the cell stack in the stacking direction; when the cell stack is arranged horizontally, the stack height therefore corresponds to a longitudinal extent of the cell stack. Furthermore, the sliding surface is preferably arranged substantially centrally with respect to the stack height of the cell stack. The cell stack is therefore supported in particular centrally, i.e. in the region in which the deflection of the cell stack is greatest if no support is provided.

[0020] Furthermore, it is proposed that the sliding surface be divided transversely to the stacking direction into several sliding surfaces that are spaced apart from one another. The overall size of the sliding surface can be reduced in this way without losing the associated advantages. For example, two parallel sliding surfaces arranged at a distance from one another can be provided, which provide optimal support for the cell stack.

[0021] Preferably, at least two sliding surfaces are provided, which are formed or arranged on opposite sides of the housing. For example, a sliding surface on the bottom can be opposite a sliding surface on the top. This is particularly advantageous when there is little air between the cell stack and the housing, so that contact between the cell stack and a top of the housing cannot be ruled out. The sliding surface then enables low-wear contact, in particular in the event of a thermally induced change in length of the cell stack, i.e. when the cell stack moves relative to the housing. Ideally, the contact between the cell stack and a sliding surface formed or arranged on the top side of the housing is established via at least one further sliding element connected to the cell stack.

[0022] In a further development of the invention, it is therefore proposed that each sliding surface is assigned at least one sliding element connected to the cell stack.

[0023] According to a preferred embodiment of the invention, the housing is constructed in multiple parts, particularly two parts. The multi-part design of the housing facilitates the formation or arrangement of the sliding surface(s) on the housing side. The housing can, for example, comprise a U-shaped part and a flat part, or two L-shaped parts.

[0024] The invention and its advantages are explained in more detail below with reference to the accompanying drawings. These show:

[0025] Fig. 1 is a schematic longitudinal section through a first stack according to the invention,

[0026] Fig. 2 shows a schematic cross section through the stack of Figure 1,

[0027] Fig. 3 shows a schematic longitudinal section through a second stack according to the invention,

[0028] Fig. 4 is a schematic cross-section through the stack of Figure 3,

[0029] Fig. 5 is a schematic representation of a sliding element and a sliding surface of a stack according to the invention and

[0030] Fig. 6 shows a further schematic representation of a sliding element and a sliding surface of a stack according to the invention.

[0031] Detailed Description of the Drawings Figures 1 and 2 show a first stack 1 according to the invention, which comprises a housing 2 and a cell stack 3 comprising a plurality of electrochemical cells 4 accommodated in the housing 2. The electrochemical cells 4 each have a rectangular basic shape, so that each cell 4 has two long sides 4.1 and two transverse sides 4.2 (see Figure 2). The stacking direction 8 of the cells 4 runs horizontally and is indicated in Figure 1 by an arrow. The extension of the cell stack 3 in the stacking direction 8 corresponds to the stack height h.

[0032] The housing 2, in which the cell stack 3 is accommodated, has a base 2.1 and a ceiling 2.2. In the region of the base 2.1, the housing 2 forms a sliding surface 6 which has an extension Li in the stacking direction 8 that corresponds approximately three-quarters of the stack height h. The sliding surface 6 interacts with a sliding element 5 which is connected to the cell stack 3. The connection is established via an adhesive 7 that surrounds the longitudinal edge 4.1 of at least one electrochemical cell 4 in a U-shape, at least in some regions (not shown in Figure 1). The sliding element 5 has an extension L2 in the stacking direction 8 that corresponds approximately two-thirds of the stack height h.

[0033] As can be seen from Figure 2, the sliding surface 6 is divided into two parallel sliding surfaces 6 that are spaced apart from one another. Each sliding surface 6 is assigned a sliding element 5 connected to the cell stack 3. The cell stack 3 is supported on the sliding surfaces 6 of the housing 2 via the sliding elements 5, so that forces acting on the cell stack 3 as well as the dead weight of the cell stack 3 are dissipated via the housing 2. The support also counteracts any displacement of the electrochemical cells 4 relative to one another, so that the cell stack 3 does not bend. Furthermore, the interaction of sliding elements 5 and sliding surfaces 6 allows thermal changes in the length of the cell stack 3, so that internal stresses are avoided.

[0034] Figures 3 and 4 show a further preferred embodiment of a stack 1 according to the invention. This differs from that of Figures 1 and 2 in that the housing 2 forms two further sliding surfaces 6 in the region of its cover 2.2, which interact with sliding elements 5 that are connected to the cell stack 3 via the adhesive 7. The cell stack 3 is movably mounted on these, also relative to the cover 2.2 of the housing 2. At the same time, the sliding elements 5 ensure that the cell stack 3 does not come into direct contact with the housing 2, thus reducing the risk of a short circuit. The sliding elements 5 therefore serve simultaneously as spacers and insulators.

[0035] Figure 5 shows, by way of example, a sliding element 5 connected to a cell stack 3, via which the cell stack 3 is movably mounted on a sliding surface 6 of a housing 2. The sliding element 5 in combination with the sliding surface 6 thus enables particularly low-wear movement of the cell stack 3 relative to the housing 2. At the same time, the cell stack 3 is supported on the sliding surface 6 via the sliding element 5, so that a force F acting on the cell stack 3 is introduced into the housing 2 via the sliding element 5. This support prevents deflection of the cell stack 3.

[0036] The sliding element 5 is connected to the cell stack 3 by means of the adhesive 7 in such a way that the longitudinal sides 4.1 of several electrochemical cells 4 are at least partially embedded in the adhesive 7. This means that the adhesive 7 surrounds the longitudinal edges 4.1 in a U-shape. In this way, the longitudinal edges 4.1 are protected from deformation.

[0037] Figure 6 shows, by way of example, a housing 2 having a projection 9 in the area of ​​the base 2.1. In this case, the projection 9 is formed by a bead. Alternatively, the projection 9 can also be formed by a material reinforcement. In both cases, the projection 9 stiffens the base 2.1 of the housing 2, making it more capable of absorbing forces without causing deformation of the housing 2. The projection 9 therefore simultaneously forms the sliding surface 6, on which the cell stack 3 is movably mounted via the sliding element 5.

Claims

Claims 1 . Stack (1), comprising a housing (2) and a cell stack (3) accommodated in the housing (2) and consisting of a plurality of electrochemical cells (4), which essentially have a rectangular basic shape with two long sides (4.1) and two transverse sides (4.2) and are each aligned perpendicularly with respect to a base (2.1) of the housing (2), so that the stacking direction (8) runs parallel to the base (2.1), characterized in that the cell stack (3) is connected to at least one sliding element (5), via which the cell stack (3) is mounted on a housing-side sliding surface (6), so that the cell stack (3) is movable in the stacking direction (8) relative to the housing (2).

2. Stack (1) according to claim 1, characterized in that the electrochemical cells (4) are arranged in the housing (2) such that their longitudinal sides (4.1) run substantially parallel and their transverse sides (4.2) run substantially perpendicular to the bottom (2.1) of the housing (2).

3. Stack (1) according to claim 1 or 2, characterized in that the at least one sliding element (5) is connected to the cell stack (3) via an adhesive (7), wherein preferably the adhesive (7) surrounds a longitudinal side (4.1) of at least one electrochemical cell (4) at least partially in a U-shape.

4. Stack (1) according to one of the preceding claims, characterized in that the housing-side sliding surface (6) is formed by the housing (2), preferably by the bottom (2.1) of the housing (2), or is attached to the housing (2), preferably to the bottom (2.1) of the housing (2).

5. Stack (1) according to one of the preceding claims, characterized in that the sliding surface (6) in the stacking direction (8) has a greater extent (Li) than the at least one sliding element (5), wherein preferably the extent (Li) of the sliding surface (6) in the stacking direction (8) is at least two-thirds, preferably at least three-quarters, of the stack height (h) of the cell stack (3), wherein furthermore preferably the sliding surface (6) is arranged substantially centrally with respect to the stack height (h).

6. Stack (1) according to one of the preceding claims, characterized in that the sliding surface (6) is divided transversely to the stacking direction (8) into several sliding surfaces (6) which are spaced apart from one another.

7. Stack (1) according to one of the preceding claims, characterized in that at least two sliding surfaces (6) are provided, which are formed or arranged on opposite sides of the housing (2).

8. Stack (1) according to one of the preceding claims, characterized in that each sliding surface (6) is assigned at least one sliding element (5) connected to the cell stack (3).

9. Stack (1) according to one of the preceding claims, characterized in that the housing (2) is designed in several parts, in particular in two parts, wherein the housing (2) preferably comprises a U-shaped part and a flat part or two L-shaped parts.

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