Arrangement of electrochemical cells and method for operating a stack of electrochemical cells

Abstract

An arrangement (1) of electrochemical cells (2), in particular electrolysis cells, comprises a hydraulic compression device (7) having a plurality of pistons (18), each guided in a cylinder (15, 16), which is designed to exert a compressive force on the stacked cells (2). The cylinders (15, 16) are interconnected by at least one transverse connection (12, 13) provided for pressure equalization.

Description

[0001] The invention relates to an arrangement of electrochemical cells designed according to the preamble of claim 1, which comprises a hydraulic compression device. Furthermore, the invention relates to a method for operating a stack of electrochemical cells, in particular electrolysis cells.

[0002] A cell arrangement of this type is known, for example, from DE 42 17 892 C2. The known arrangement of electrochemical cells is designed as a solid electrolyte fuel cell arrangement and comprises a plurality of pneumatically or hydraulically actuated clamping cylinders, each of which applies a force to a stack of electrochemical cells. A fuel gas feed distributor of the device according to DE 42 17 892 C2 extends through a plurality of individual cells. According to the teaching of DE 42 17 892 C2, a series or parallel connection of cell stacks is generally considered.

[0003] EP 3 951 019 A1 relates to an electrolyzer whose cells can be subjected to a pressure force by means of a hydraulic actuator. A safety device in the device according to EP 3 951 019 A1 is intended to ensure that the specified pressure is maintained. A possible minimum pressure load of 10 kg per cm 2 specified.

[0004] Another cell stack assembly, in particular for an electrolyzer, comprising a hydraulically actuated device for generating a contact force is disclosed in WO 2021 / 155919 A1. In this case, it is provided that the hydraulic device for generating a contact force is hydraulically actuated before and / or during commissioning of the cell stack assembly. Subsequently, a pressurized hydraulic line is to be shut off, and the cell stack assembly is to be put into normal operation.

[0005] WO 03 / 105 266 A1 also deals with the compression of a stack of electrochemical cells. In addition to purely mechanical variants, an embodiment is described in which a hydraulic cylinder is combined with a traction device. Here, the hydraulic cylinder is arranged outside the cell stack, while the traction device pulls through the cell stack.

[0006] WO 2021 / 121781 A1 discloses a fuel cell with an adjustment device for compensating the settling behavior within a stack structure. The adjustment device comprises a chemically activated clamping element or a pressure chamber that can be pressurized with a pressure medium.

[0007] The invention is based on the object of providing possibilities for compressing stacks of electrochemical cells which are more advanced than the prior art and which are as independent as possible of the operating conditions.

[0008] This object is achieved according to the invention by an arrangement of electrochemical cells constructed according to claim 1. The object is also achieved by a method for operating a stack of electrochemical cells according to claim 9. The embodiments and advantages of the invention explained below in connection with the operating method also apply mutatis mutandis to the device according to the application, i.e., cell arrangement, and vice versa.

[0009] The cell arrangement, in a known basic design, comprises a hydraulic compression device comprising several pistons, each guided in a cylinder. The hydraulic compression device is designed to exert a compressive force on the stacked cells of the cell arrangement.

[0010] According to claim 1, the cylinders of the hydraulic compression device are connected to one another by at least one cross connection provided for pressure equalization. In particular, all cross connections are arranged entirely within the hydraulic compression device.

[0011] Due to the cross-connection between the cylinders, force equalization is achieved within the hydraulic compression device, also known as the bracing unit. This is particularly advantageous in cases where the cell arrangement is in the form of a single cell stack. In this case, the compression device can be designed as a plate-shaped device, in which the cross-connections are located, and which projects over the stacked electrochemical cells on several sides.

[0012] In all cases, the hydraulic compression device is suitable, among other things, for performing a compensating function in the event of temperature fluctuations and different settling behavior of various components within the cell stack. This also includes tolerance compensation and compensation in the event of misalignment of individual components of the electrochemical system, in particular the electrolysis system for producing hydrogen from water. The compensating function realized by the clamping unit also contributes to ensuring that the seals present in the cell assembly fully perform their intended function across a wide range of different operating conditions.

[0013] There are no fundamental restrictions regarding the cross-sectional shape of the cylinders and pistons. In particular, circular cylinders and pistons are suitable, with conventional components being used to seal the pressure chamber containing the hydraulic oil. Cross-sectional shapes for the cylinders and pistons other than circular are also conceivable, such as oval. Other shapes, such as polygonal shapes, for the cylinders and pistons are not generally excluded.

[0014] The individual cylinders and accordingly also the pistons can be arranged in the hydraulic compression device in particular in a matrix shape, for example in a 2 x 2 pattern or in a 2 x 3 pattern.

[0015] A possible refinement provides that, in addition to the cylinders arranged in a matrix, there is at least one additional hydraulic cylinder pressurized with the same pressure. The additional hydraulic cylinder can have a different diameter than the other hydraulic cylinders, in particular a smaller diameter. In particular, the at least one additional hydraulic cylinder can be positioned centrally between the cylinders arranged in a matrix.

[0016] In any cylinder arrangement, a clearance of more than 0.1 mm, particularly more than 0.2 mm, between the pistons in the cylinders can be provided. For example, each piston is guided in the cylinder with a clearance of 0.5 mm. This allows for the compensation of even moderate misalignments.

[0017] Regardless of the number and arrangement of the hydraulic cylinders, several of the cross-connections that ensure the desired pressure equalization within the hydraulic system can, for example, be aligned orthogonally to each other. In this case, the cross-connections, which also applies to cases with other angular relationships between individual cross-connections, can span a plane that is aligned parallel to the planes in which the stacked electrochemical cells, in particular electrolysis cells, are located.

[0018] In addition to the hydraulic compression device, the stacked cell arrangement can comprise a fluid distributor located between the plate-shaped compression device and the stacked electrochemical cells, which has a plurality of lateral fluid connections. The fluid connections can be provided for the supply or discharge of operating and cooling media. In this case, a separation between process water and cooling water can be provided.

[0019] The method according to the application for operating a stack of electrochemical cells generally involves pressurizing stacked cells using several hydraulic cylinders, between which pressure is equalized. The cells can, in particular, be PEM (polymer electrolyte membrane) or proton exchange membrane (PEM) electrolysis cells. The method can also be applied to fuel cell stacks or other stacks of electrochemical cells.

[0020] Within the operating procedure, the pressure prevailing in the cylinders connected to each other via the cross connections can be regulated. Oil or water can generally be considered as the hydraulic medium. The use of water eliminates chemical reactions that would be conceivable in oil hydraulics between oil and other substances, such as hydrogen or oxygen.

[0021] In the following, several embodiments of the invention as well as a comparative example ( Fig. 6) is explained in more detail using a drawing. It shows, partly simplified: Fig. 1 a first embodiment of an arrangement of electrochemical cells, namely electrolysis cells, in side view, Fig. 2 and 3 side views of a hydraulic compression device of the arrangement according to Fig. 1, Fig. 4 a housing of the hydraulic compression device according to Fig. 2 and Fig. 3 in plan view, Fig. 5 a compared to the embodiment according to the Fig. 1 to 4 modified form of a housing of a hydraulic compression device in a view similar Fig. 4, Fig. 6 a non-claimed comparative example in a representation analogous Fig. 5, Fig. 7 - 9 further variants of housings of hydraulic compression devices in representations analogous Fig. 5.

[0022] The following explanations refer, as far as applicable and not otherwise stated, to all embodiments as well as to the unclaimed comparative example according to Fig. 6. Parts corresponding to one another or having essentially the same function are identified by the same reference numerals in all figures.

[0023] An arrangement of electrochemical cells, designated overall by 1, i.e., a cell arrangement, is designed in the exemplary embodiments as a stack of numerous cells 2, namely electrolysis cells for producing hydrogen from water. Regarding the basic structure and function of the cell arrangement 1, reference is made to the prior art mentioned above.

[0024] Within the stack 1, above the stacked cells 2, there is a distributor 3, also known as a manifold. This distributor functions as a fluid distributor, supplying operating and cooling media to and from the cells 2. A hydrogen connection is designated 4, and a coolant connection 5. Below the stacked cells 2 there is a solid plate 6, which is suitable for absorbing forces but has no fluid-technical function in this case. Alternatively, instead of the solid plate 6, another component can be located below the cells 2, which—comparable to the manifold 3—has distributor and / or collector functions for operating and / or cooling media.

[0025] Where terms such as "above" or "below" are used in this text, these statements refer only to the figures and do not imply any statement about the actual spatial orientation of the cell arrangement 1 and its individual components. In particular, designs of the stack 1 are feasible in which its plate-shaped components are aligned vertically.

[0026] Above the distributor 3 is a hydraulic compression device 7, also belonging to the stack 1, whose layout at least approximately corresponds to the layout of the plate 6. The hydraulic compression device 7 is also generally referred to as a bracing unit and, like the plate 6, projects laterally beyond the cells 2 in all directions. The plate 6 and the compression device 7 are held together by rods 8, which are arranged as tie rods laterally next to the cells 2. Nuts screwed onto the rods 8 are designated 9, and washers 10.

[0027] The compression device 7 can be supplied with hydraulic oil or another hydraulic medium, in particular water, via a hydraulic connection 11. Cross connections 12, 13 located within the compression device 7 are connected to the hydraulic connection 11. Blind plugs, with which individual cross connections 12, 13 are closed, are designated by 14. Via the cross connections 12, 13, the hydraulic oil or other hydraulic medium is supplied to cylinders 15, 16, which are formed within a housing of the compression device 7, designated overall by 17. Pistons guided in the cylinders 15, 16 are uniformly designated by 18. Piston rings 19 are provided to seal the pistons 18 in the cylinders 15, 16.

[0028] The pistons 18 apply a uniform pressure to the stacked cells 2. In the embodiments according to the Fig. 1 to 5 and according to the Fig. 7 to 9 each have several pistons 18. The Fig. 6 shows a comparative example not claimed, in which only a single cylinder 15 is present.

[0029] The Fig. 1 to 5 and the Fig. 7 illustrate embodiments in which a matrix arrangement, namely a 6-arrangement or a 4-arrangement ( Fig. 7) the cylinder 15 is given. In the variant according to Fig. 8, there are only two cylinders 15, which is to be understood as a minimal solution. The variant according to Fig. 9 is based on the variant according to Fig. 7, whereby in the case of Fig.9, in addition to the four-cylinder arrangement of cylinders 15, there is an additional, central, relatively small cylinder 16. In this case, too, a uniform pressure prevails in all cylinders 15, 16. Due to the pressure equalization achieved by means of the cross connections 12, 13, this also applies in cases where the pistons 18 are extended to different distances from the cylinders 15, 16, for example, due to an inclined position of components of the cells 2.

[0030] In a manner not shown, the hydraulic connection 11 can be connected to a pressure accumulator. Stack 1 can be operated, for example, as a core component of the electrolysis system while the connection between hydraulic connection 11 and the pressure accumulator is shut off, i.e., the oil is enclosed in stack 1. In more advanced process variants, oil pressure regulation is provided. Monitoring devices (not shown) can also be present, which, for example, respond in the event of an impermissible drop in oil pressure or the pressure of the other hydraulic medium. List of reference symbols 1 arrangement / stack of electrochemical cells, stack 2 electrochemical cell 3 distributors, manifold 4 Hydrogen connection 5 Coolant connection 6 plates 7 Compression device 8 rod, tension rod 9 Mother 10 Washer 11 Hydraulic connection 12 Cross connection 13 Cross connection 14 blind plugs 15 cylinders 16 cylinders 17 housings 18 pistons 19 Piston ring QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] DE 42 17 892 C2

[0002] EP 3 951 019 A1

[0003]

Claims

[1] Arrangement (1) of electrochemical cells (2), comprising a hydraulic compression device (7) having a plurality of pistons (18) each guided in a cylinder (15, 16), which is designed to exert a compressive force on the stacked cells (2), characterized by that the cylinders (15, 16) are connected to one another by at least one transverse connection (12, 13) provided for pressure equalization. [2] Cell arrangement (1) according to claim 1, characterized by that it is in the form of a single cell stack (1), wherein the compression device (7) is designed as an overall plate-shaped device which projects over the stacked electrochemical cells (2) on several sides. [3] Cell arrangement (1) according to claim 1 or 2, characterized by that several cylinders (15) are arranged in matrix form. [4] Cell arrangement (1) according to claim 3, characterized bythat in addition to the cylinders (15) arranged in matrix form, there is at least one further hydraulic cylinder (16) subjected to the same pressure. [5] Cell arrangement (1) according to claim 4, characterized by that the at least one further hydraulic cylinder (16) has a smaller diameter than the cylinders (15) arranged in matrix form and is placed centrally between the cylinders (15) arranged in matrix form. [6] Cell arrangement (1) according to one of claims 3 to 5, characterized by that several cross-connections (12, 13) are aligned orthogonally to one another, spanning a plane which is parallel to the planes in which the stacked electrochemical cells (2) lie. [7] Cell arrangement (1) according to one of claims 2 to 6, characterized bya fluid distributor (3) located between the plate-shaped compression device (7) and the stacked electrochemical cells (2), which has a plurality of lateral fluid connections (4, 5). [8] Cell arrangement (1) according to one of claims 1 to 7, characterized by that the pistons (18) are guided in the cylinders (15, 16) with a clearance of more than 0.1 mm. [9] Method for operating a stack (1) of electrochemical cells (2), wherein cells (2) stacked on top of one another are pressurized by means of several hydraulic cylinders (15, 16) between which a pressure equalization exists. [10] Method according to claim 9, characterized by that the uniform pressure in the hydraulic cylinders (15, 16) is regulated and water is used as the hydraulic medium.

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