Electrochemical cell stack

Abstract

The invention relates to a cell stack (1) comprising a plurality of electrochemical cells (2) and two plates (3, 6) having a rectangular basic shape, namely a distributor plate (3) and an end plate (6), between which the cells (2) are clamped, wherein: the distributor plate (3) has a plurality of channels (12, 13, 22) provided for supplying media to the cells (2) or discharging it from the cells (2), said channels being straight, per se, being oriented in some cases orthogonally and in some cases parallel to one another, and opening perpendicularly at lateral surfaces (25, 26, 27, 28) of the distributor plate (3), which connect a top face (30) of the distributor plate (3) to a bottom face (29) of the distributor plate (3); there is at least one imaginary plane (ME), which is situated in parallel between the top face (30) and the bottom face (29) of the distributor plate and which intersects at least two channels (12, 13, 22) provided for conducting different media; and the end plate (6) has no distributor structures.

Description

[0001] Electrochemical cell stack

[0002] The invention relates to an electrochemical cell stack, in particular an electrolysis cell stack, which has geometrically defined structures for the distribution of media with which the cells are operated and / or temperature-controlled.

[0003] German patent DE 101 17 572 B4 relates to an electrochemical cell stack, in particular in the form of a fuel cell stack, which comprises alternately arranged membrane electrode units and separator plates. The separator plates of the device according to DE 101 17 572 B4 have channel areas for supplying and removing fluids to and from the membrane electrode units. Adjacent separator plates are rotated 180° relative to each other, with the rotation being about a surface normal to the planes in which the mutually parallel separator plates are arranged. According to the teaching of DE 101 17 572 B4, this makes it possible to transmit forces to a membrane electrode unit without bending moment.

[0004] German patent application DE 10 2011 088 992 B4 discloses a distribution block for a fuel cell stack. The distribution block is coupled to a fuel cell stack module, and the distribution block is attached to an end plate of the fuel cell stack. In addition to a gas channel, the distribution block includes a curved, electrically insulated cooling water channel. The electrical insulation is achieved using a pre-formed, tube-like insulating element.

[0005] A possible geometry for a media distributor for an electrolysis cell is detailed in DE 10 2013 216 587 B4. This design features supply channels located on two opposite sides outside a media distribution structure. These supply channels have trapezoidal cross-sections and include channels for water supply, water drainage, oxygen drainage, and hydrogen drainage. A polymer electrolyte fuel cell stack described in EP 0 981 175 B1 comprises a plurality of unit cells stacked on top of each other using conductive separators. Each unit cell has a polymer electrolyte membrane and a catalytic reaction layer. According to EP 0 981 175 B1, the fuel cell stack includes, among other things, an inlet distributor and an outlet distributor for supplying and removing media.

[0006] The invention is based on the objective of providing an electrochemical cell stack that is further developed compared to the aforementioned prior art, taking into account manufacturing aspects as well as flow engineering aspects and striving for good space utilization.

[0007] This problem is solved according to the invention by a cell stack with the features of claim 1. The cell stack can in particular be an electrolysis cell stack for producing hydrogen from water.

[0008] The cell stack according to the application comprises several electrochemical cells, in particular electrolysis cells. The cell stack further comprises two plates, each with an at least approximately rectangular plan, namely a distribution plate and an end plate. The electrochemical cells are clamped between the two aforementioned plates. The distribution plate has several channels for supplying media to the cells or for removing media from the cells. The term "media" here includes operating media as well as cooling media. The channels formed in the distribution plate, through which the media flow, have a straight shape when viewed from above and are, in some cases, orthogonal to one another and, in others, parallel to one another.The channel outlets are located on the side faces of the distributor plate, with the channels oriented perpendicular to the side faces and each side face connecting a top and bottom surface of the distributor plate. There is at least one imaginary plane, parallel to the top and bottom surfaces of the distributor plate, which intersects at least two channels designed to carry different media. In contrast to the distributor plate, the end plate does not have any distributor structures.

[0009] The arrangement of various channels for operating and cooling media, some parallel and some perpendicular to each other, in the distribution plate, which is also commonly referred to as a manifold, combined with the absence of channels in the end plate, represents a rationally implementable manufacturing concept. This allows for the transmission of significant forces in the stacking direction, i.e., orthogonal to the planes in which the plates lie, during subsequent operation of the cell stack. The end plate can be considerably thinner than the distribution plate.

[0010] From the channels running through the distribution plate, the various media are supplied to the individual electrochemical cells via so-called main channels, which are oriented perpendicular to the planes defined by the plates, i.e., running in the stacking direction. The same applies to the discharge of media from the electrochemical cells. For the supply and discharge of media via the distribution plate, for example, two opposing sides of the distribution plate can be used. Likewise, three or all four sides can be used for this purpose. In extreme cases, a single side of the distribution plate is sufficient for the inlet and outlet of media. In all these cases, the top surface of the distribution plate facing away from the electrochemical cells can be free of any fluid connections.

[0011] In cases where exactly two surfaces of the distributor plate are used for the inlet and outlet of media, a first medium, i.e., a fluid, can be supplied at one end and discharged at the opposite end. A second medium, flowing simultaneously through the distributor plate, can be guided either in co-current or counter-current flow. This means that either one specific surface is exclusively for the media supply and the opposite surface exclusively for the media discharge, or—in the case of counter-current flow—there is at least one inlet and at least one outlet for a flowing medium on both sides. A heat exchanger function can be utilized, particularly in the case of opposing flows.

[0012] If all four side surfaces of the distribution plate are used for the supply and discharge of media, then, for example, two of these narrow surfaces, which connect the top and bottom of the plate, can be used exclusively for media supply, and the other two side surfaces exclusively for media discharge, with each media supply always opposite its corresponding media discharge. Alternatively, in cases where connections are located on all four narrow side surfaces of the distribution plate, one or more of these surfaces, in particular all side surfaces, can be used for both the supply and discharge of operating and / or cooling media. The term "cooling medium" does not preclude the possibility that the corresponding medium is used to heat the cell stack in certain operating conditions, for example, during the start-up phase at low ambient temperatures.

[0013] Regardless of the function of the various media passing through the distribution plate, two pairs of parallel channels can, for example, run alongside each long side of the rectangular (non-square) distribution plate. Each of these pairs could, for instance, consist of a cooling water channel and a process water channel. The cooling water channel can be positioned closer to the long side than the process water channel, with the process water channel opening onto a shorter, narrow side of the distribution plate compared to the long side. Unlike the cooling water channel, the process water channel in this configuration can be connected to the long side via a duct stub and closed at the narrow side by a blanking plug.

[0014] In addition to the channels running parallel to the long sides of the rectangular distribution plate, a media channel can also run parallel to each short side of the distribution plate. The media channels can terminate on one of the long sides of the distribution plate. Alternatively, connections for the media channels can be located on the short sides of the distribution plate.

[0015] The various channels located in the distribution plate can be arranged – viewed from above – in a point-symmetrical manner with respect to the center of the distribution plate. A first group of channels, consisting of a pair of channels on one of the long sides of the distribution plate and a single channel on one of the short sides, can form an L-shape. Similarly, a second such group of three channels also forms an L-shape. The first L-shaped group of channels can be transformed into the second L-shaped group by an imaginary rotation of 180°.

[0016] The channels for operating or cooling media, which in some cases are parallel to each other and in others orthogonal to each other, run through the distribution plate and are generally arranged between two parallel planes that lie within the distribution plate parallel to its top and bottom surfaces. The use of the terms "top" and "bottom" here does not imply the orientation of the distribution plate in space. In any case, each of the two planes is tangent to at least one channel. The distance between the two planes can be half the thickness of the distribution plate or more. This means that most of the thickness of the distribution plate, defined as the distance between the top and bottom surfaces, is used as space for the passage of an operating medium and / or a cooling medium.Optionally, between the two mutually parallel planes, each of which is tangent to at least one channel, there exists a layer in which, viewed in the normal direction of the planes, there is an overlap between at least two channels, the thickness of which corresponds to at least 5% of the distance between the two planes.

[0017] According to a possible further development, the cell stack comprises a clamping unit, wherein the stacked arrangement, which includes the electrochemical cells, the distribution plate, and the end plate, is sandwiched between components of the clamping unit. The clamping unit can be designed for hydraulic clamping, and may also include a control mechanism for the preload applied to the electrochemical cells.

[0018] Regarding the materials used to manufacture the clamping unit, a wide variety of materials commonly used in mechanical and plant engineering can be employed. These include metallic materials, such as corrosion-resistant steel, as well as non-metallic materials, particularly plastics.

[0019] An embodiment of the invention is explained in more detail below with reference to a drawing. The drawing shows, in a simplified form:

[0020] Fig. 1 shows a stack of electrochemical cells, namely electrolysis cells, in side view.

[0021] Fig. 2 shows several components, including a distributor plate, arranged according to Fig. 1.

[0022] Fig. 3 shows the distributor plate in a partially cutaway top view.

[0023] Fig. 4 shows another view of the distributor plate.

[0024] A cell stack, designated by reference numeral 1, is configured as a stack of numerous cells 2, namely electrolysis cells, for hydrogen production from water. Regarding the basic structure and function of the stack 1, i.e., the electrolysis stack, reference is made to the prior art mentioned at the outset. Within the stack 1, above the stacked cells 2, is a distributor plate 3, also referred to as a manifold. This plate acts as a fluid distributor, supplying and discharging 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 is an end plate 6, designed as a solid plate, which is capable of absorbing forces but does not have a fluid-related function in this case. The end plate 6 is significantly thinner than the distributor plate 3.

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

[0026] Above the distributor 3 is a hydraulic compression device 7, also part of the stack 1, whose plan view corresponds at least approximately to that of the end plate 6. The hydraulic compression device 7 is also commonly referred to as the clamping unit and, like the end plate 6, extends laterally beyond the cells 2 in all directions. The end plate 6 and the compression device 7 are held together by rods 8, which are arranged laterally next to the cells 2 as tie rods. Screws screwed onto the rods 8 are designated 9, and washers inserted between the screws 9 and the end plate 6 or the compression device 7 are designated 10.

[0027] The compression device 7 is supplied with hydraulic oil via a hydraulic connection 11. The compression device 7 comprises several pistons 18, which are arranged in a matrix configuration in the top view and exert a force on the distributor 3 and thus also on the cells 2. The pistons 18 are guided in a housing 17 of the compression device 7 and contact a housing 35 of the manifold 3. The housing 35 rests on the stacked cells 2 and already loads them with its own weight. Below the arrangement of the cells 2 and the end plate 6, a lower plate 31 is visible in Fig. 1, which can actually be considerably thinner than shown in Fig. 1. Like the end plate 6, the lower plate 31, which by definition belongs to the clamping unit 7, is not permeated by any fluid unless it serves to accommodate optional hydraulic components.

[0028] The distributor plate 3, like the compression device 7, has a rectangular, not square, plan. Long sides of the distributor plate 3 are designated 25, 26, and short sides 27, 28. In general, the long sides 25, 26 and short sides 27, 28, in a three-dimensional view, form lateral surfaces 25, 26, 27, 28, which connect a bottom surface 29 with a top surface 30 of the distributor plate 3. The bottom surface 29 and the top surface 30 lie in parallel, in this case horizontal, planes.

[0029] The distributor plate 3 is traversed by several channels 12, 13, 22 for different media. Here, 12 denotes a cooling water channel, 13 a process water channel, and 22 a hydrogen channel. An arrangement of a cooling water channel 12 and a process water channel 13 constitutes a channel pair, which is arranged parallel to the longitudinal side 25, 26. Within each channel pair 12, 13, the cooling water channel 12 is located closer to the nearest longitudinal side 25, 26 than the process water channel 13. The parallel channels 12, 13 are formed as blind bores extending from a narrow side 27, 28.

[0030] In the case of the cooling water channel 12, the blind hole on the narrow side 27, 28 is closed by a blanking plug 14. To allow cooling water to be introduced into or discharged from the cooling water channel 12, another, comparatively short blind hole is drilled into the nearest longitudinal side 25, 26, which intersects the cooling water channel 12 at a right angle. This latter blind hole forms a channel stub 16 within the completed manifold 3. A connection element 19 for cooling water is located on the outside of the channel stub 16, i.e., on the longitudinal side 25, 26. The diameter of the channel stub 16 is designated d16 and is larger than the diameter of the cooling water channel 12 designated d12. In the exemplary embodiment, the diameter d12 of the cooling water channel 12 deviates at most slightly from the diameter of the process water channel 13 designated d13.A connection element for process water, designated 15, is located at the end of the process water channel 13, that is, on the narrow side 27, 28.

[0031] Channels 12 and 13 are aligned parallel to the planes in which the electrochemical cells 2 are located. As shown in Figure 3, three channel transitions 20 extend from each cooling water channel 12. The channel transitions 20 connect to main channels that run through the stacked cells 2 in the stacking direction. The overall cooling water flow through the cell stack 1 is illustrated in Figure 2, where one fluid flow is designated FS. As shown in Figure 2, the fluid flow FS does not penetrate the end plate 6. Main channels for cooling water that run through the cell stack 1 in the stacking direction are designated 33. Plate elements 34 are associated with the cells 2.

[0032] In the case of process water separated from cooling water, i.e., water from which hydrogen and oxygen are obtained by electrolysis, there are four channel transitions 21 per process water channel 13, which are connected to channels that traverse the stack 1 in the stack direction.

[0033] Two hydrogen channels 22 are provided for conveying hydrogen in the manifold 3, aligned parallel to the narrow sides 27, 28. Each hydrogen channel 22 has a width d22 that is less than the width d13 of the process water channel 13. A connection element 23 for hydrogen is located at the hydrogen connection 4, i.e., at the end of the hydrogen channel 22. At several channel transitions 24 of the hydrogen channel 22, the flow is deflected by 90°, as in the case of the cooling water and the process water described above, to provide access to the individual cells 2. Thus, all passages located on the underside 29 of the manifold 3 are accessible via connection elements 15, 19, 23 on the side surfaces 25, 26, 27, 28. The top surface 30 of the manifold plate 3, however, is free of any openings.As can be seen in Figure 3, the hydrogen channel 22, located on the left in this representation, together with the two channels 12 and 13 located below in the same figure, describes an L-shape. Similarly, the two channels 12 and 13 located above, together with the hydrogen channel 22 on the right, are arranged in an L-shape. Thus, there are two L-shaped channel arrangements that can be transformed into one another by point reflection or by rotation by 180°, where the axis of rotation is a surface normal passing through the center of the distributor plate 3.

[0034] The planes defined by the top surface 30 and the bottom surface 29 of the distributor plate 3 are separated by a distance D3. Between the top surface 30 and the bottom surface 29, also parallel to each other, lie two planes E1 and E2. The distance between planes E1 and E2, denoted DE, is less than the thickness D3 of the distributor plate 3. EM denotes a median plane located midway between the top surface 30 and the bottom surface 29. In this case, plane EM intersects several of the channels 12, 13, and 22. A plane parallel to the median plane EM could also have this property.

[0035] Each plane E1, E2 is tangent to at least one of the channels 12, 13, 22, with the hydrogen channel 22 generally being referred to as the media channel. As can be seen from Figure 4, there are overlaps between channels 12, 13, 22 when viewed in the stacking direction, i.e., in the normal direction to the planes E1, E2. These overlaps generally lie in a layer located between the bottom surface 29 and the top surface 30, the thickness of which corresponds to at least 5% of the distance DE between the planes E1, E2. In the exemplary embodiment, the distance DE corresponds to more than 50% of the thickness D3 of the distributor plate 3. (List of reference symbols)

[0036] Cell stack, electrochemical cell manifold, hydrogen connection, coolant connection, end plate

[0037] Compression device, tensioning unit rod, tie rod screw

[0038] Washer, hydraulic connection, cooling water channel, process water channel, blanking plug

[0039] Connection element for process water channel nozzle housing piston

[0040] Connection element for cooling water, channel transition for cooling water, channel transition for process water, hydrogen channel, media channel, connection element for hydrogen, channel transition for hydrogen, long side, long side, narrow side, narrow side, bottom, top, bottom plate, 32 process water connection

[0041] 33 Main channel for cooling water

[0042] 34 plate elements

[0043] 35 Distribution plate

[0044] D3 Thickness of the distributor

[0045] DE Distance between planes E1 and E2 d12, d13, d16, d22 Channel diameter

[0046] E1, E2, EM levels

[0047] FS Fluid Flow

Claims

Patent claims 1. Cell stack (1) comprising several electrochemical cells (2) and two plates (3, 6) with a rectangular base shape, namely a distribution plate (3) and an end plate (6) between which the cells (2) are clamped, wherein the distribution plate (3) has several channels (12, 13, 22) for supplying or supplying media to or from the cells (2), which are straight and partly orthogonal, partly parallel to each other and open perpendicularly to side surfaces (25, 26, 27, 28) of the distribution plate (3) which connect a top surface (30) of the distribution plate (3) with a bottom surface (29) of the distribution plate (3), wherein at least one imaginary plane (ME) lying parallel between the top surface (30) and the bottom surface (29) of the distribution plate exists, which intersects at least two channels (12, 13, 22) provided for guiding different media, and wherein the end plate (6) is free of distribution structures.

2. Cell stack (1 ) according to claim 1 , characterized in that two pairs of parallel channels (12, 13) run alongside each longitudinal side (25, 26) of the distributor plate (3).

3. Cell stack (1 ) according to claim 2, characterized in that each pair arrangement (12, 13) is formed from a cooling water channel (12) and a process water channel (13).

4. Cell stack (1 ) according to claim 3, characterized in that the cooling water channel (12) is spaced less from the longitudinal side (25, 26) than the process water channel (13), wherein the process water channel (13) opens at a narrow side (27, 28) of the distributor plate (13).

5. Cell stack (1 ) according to claim 4, characterized in that the process water channel (12) is connected to the longitudinal side (25, 26) via a channel nozzle (16) and is closed at the narrow side (27, 28) by a blind plug (14).

6. Cell stack (1 ) according to one of claims 1 to 5, characterized in that a media channel (22) is arranged parallel to a narrow side (27, 28) of the distributor plate (3).

7. Cell stack (1 ) according to one of claims 1 to 6, characterized in that the channels (12, 13, 22) located in the distributor plate (3) are arranged in a point-symmetrical manner in a top view of the distributor plate (3).

8. Cell stack (1 ) according to one of claims 1 to 7, characterized in that two mutually parallel planes (E1 , E2) exist, between which all channels (12, 13, 22) - with contact of at least one channel (12, 13, 22) by each plane (E1 , E2) - are enclosed, wherein the distance (DE) between these planes (E1 , E2) corresponds to at least half the thickness (D3) of the distributor plate (3).

9. Cell stack (1 ) according to claim 8, characterized in that a layer exists between the two planes (E1 , E2) in which there is an overlap between at least two channels (12, 13, 22), wherein the thickness of this layer corresponds to at least 5% of the distance (DE) between the two planes (E1 , E2).

10. Cell stack (1 ) according to one of claims 1 to 9, characterized in that it additionally has a clamping unit (7), wherein the stacked arrangement comprising the electrochemical cells (2) as well as the distributor plate (3) and the end plate (6) is sandwiched between components of the clamping unit (7).

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