Bipolar plate and method for manufacturing bipolar plate
Patent Information
- Application Number
- JP2024504537
- Authority / Receiving Office
- JP · JP
- Patent Type
- Patents
- Current Assignee / Owner
- Priority Date
- 2021-08-18
- Filing Date
- 2022-07-11
- Publication Date
- 2025-06-02
- Estimated Expiration
- 2042-07-11
AI Technical Summary
Existing bipolar plates for fuel cells face challenges in optimizing fluid and flow distribution, as well as manufacturing efficiency, which affect the uniformity and efficiency of medium flow within the fuel cell.
The bipolar plate is composed of two embossed half-plates with varying embossing depths and channel heights, featuring coolant and media ports, distribution fields, and active fields, with non-uniform embossing structures to enhance flow cross-sections and directionality, allowing for uniform medium flow and optimized supply to the active field.
This design achieves a uniform and efficient flow of gases like oxygen-containing air and hydrogen across the fuel cell, enhancing power generation by ensuring uniform medium distribution and reducing resistance, particularly in edge regions.
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Abstract
Description
[Technical field]
[0001] The present invention relates to a bipolar plate consisting of two embossed half plates for a fuel cell. Furthermore, the present invention relates to a method for manufacturing the bipolar plate. [Background technology]
[0002] Various bipolar plates for fuel cells are known, for example, from DE 102017130489 A1 and WO 2018 / 141319 A1. The known bipolar plates comprise a first corrugated plate with a hole pattern and a second plate arranged sealingly on the corrugated plate. The hole pattern of the first plate is provided for passing gases substantially transversely to the corrugations. The bipolar plates thus provided are optimized in particular with regard to flow distribution.
[0003] Further bipolar plates for electrochemical systems are known, for example, from DE 202016107302. The known bipolar plate consists of half plates, called separator plates. The separator plates have through holes for the passage of a medium. The distribution or collection area of the separator plate is provided with a plurality of webs in which channels are formed in fluid communication with the through holes. Furthermore, a flow field is formed by the separator plate, which is in fluid communication with the through openings via the distribution or collection area and has guiding structures for guiding the medium through the flow field. In addition, there is a continuous lowered transition area arranged between the distribution or collection area and the flow field. In the device according to DE 202016107302, the flow guiding structures in the transition area have a height that is lower than the height of the structures in the flow field, the height being in each case to be measured perpendicular to the flat surface of the separator plate.
[0004] A method for manufacturing separator plates for fuel cells is known from EP 3529842. As part of this method, a material mixture is used which contains carbon powder as the main component and, in addition, various plastic components are used.
[0005] DE 10 2017 118 319 A1 discloses a coating for bipolar plates that can be used in fuel cells or electrolysers. The proposed coating is a homogeneous or heterogeneous solid metal solution containing precious metals and non-metallic chemical elements. Summary of the Invention [Problem to be solved by the invention]
[0006] The object of the present invention is to further develop a bipolar plate for fuel cells with respect to fluid or flow technical and production technical aspects in comparison with the above-mentioned prior art. [Means for solving the problem]
[0007] This problem is solved according to the invention by a bipolar plate having the features of claim 1. Likewise, the problem is also solved by a method for manufacturing a bipolar plate according to claim 7. The embodiments and advantages of the invention described below in relation to the manufacturing method also apply mutatis mutandis to the device, i.e. the bipolar plate, and vice versa.
[0008] The bipolar plate consists of two embossed half plates, which overlap each other and have a rectangular elongated basic shape, by which the coolant ports and the medium ports located on the longitudinal sides of the half plates are formed. Next to the ports, there are also distribution fields formed by the half plates and provided for coolant distribution and medium distribution, as well as active fields arranged on both sides of the bipolar plate.
[0009] In the distribution field, embossments of the half plates are formed in such a way that an increase in the free flow cross section is provided for the medium flowing in the direction of the port, which is located on the opposite longitudinal side of the bipolar plate from the respective port and is intended for the passage of another medium of the fuel cell. The targeted widening of the flow cross section thus achieved makes it possible to achieve a particularly uniform flow of the medium through the fuel cell, i.e. the oxygen-containing gas, in particular air, and the further gas containing hydrogen.
[0010] The increase in the flow cross section is implemented in particular by reducing the height of the coolant channels formed between the half plates in the transverse direction of the half plates. Additionally or alternatively, the diversity of the flow cross section can be achieved by different surface areas of the flow-guiding embossing elements. If different embossing depths are provided, the height of the edge channel that is fluidly connected to a media port and is the furthest away is, for example, at least 15% greater than the height of the nearest media channel located in the distribution field and supplied by the same port.
[0011] According to various possible embodiments, a fluid connection is provided between the edge channel and a bypass that runs parallel to the active field. The bypass does not contribute to the generation of power. Nevertheless, the flow through the bypass, which is facilitated by the widening of the cross section of the edge channel, is accepted, since a low resistance supply of the flow medium to the edge channel in particular is considered to be advantageous with regard to the uniform utilization of the active field.
[0012] The distribution field does not necessarily have a uniform structure over its entire surface. For example, the distribution field may comprise a transverse distribution area adjacent to the ports and a longitudinal distribution area located between this area and the active field. The terms "transverse distribution area" and "longitudinal distribution area" are intended to indicate that the medium, i.e. typically a gas, is distributed to a region primarily related to the transverse or longitudinal directions, respectively, of the entire elongated bipolar plate.
[0013] The transverse distribution area can be configured, for example, as a dimpled area, which can be characterized by a particularly good mixing effect. In addition, the dimpled area can be configured in such a way that it can flow in the transverse direction of the half plate and thus with a particularly low resistance through the entire bipolar plate. The transverse direction can thus represent the preferred direction of at least a section of the distribution field. On the other hand, the longitudinal distribution area can present, for example, a groove structure with substantially straight grooves extending in the longitudinal direction of the bipolar plate and optionally widening towards the active field, through which the individual channels are formed.
[0014] The bipolar plate can be manufactured by embossing two half-plates in such a way that each half-plate has a non-uniform embossing depth over its entire width and by joining the two half-plates overlapping each other to form a bipolar plate with coolant channels of non-uniform height between the half-plates. In this regard, the main flow direction of the coolant corresponds to the longitudinal direction of the half-plates during operation of the bipolar plate, and the two outer faces of the half-plates facing away from the coolant channels define media channels, which likewise have a non-uniform height corresponding to the non-uniform embossing depth of the half-plates and are configured to guide the media in both the main flow direction and the transverse direction. Here, the media flow cross-section extends continuously or discontinuously in the transverse direction starting from the ports formed by the openings made in the half-plates.
[0015] In the context of a possible embodiment of the manufacturing method, the two half-plates, which are typically not completely mirror symmetrical with respect to each other, are placed one on top of the other in such a way that a flow channel for a first medium flowing with a first transverse flow component, i.e. a displacement component, is formed on the outer surface of the first half-plate, and at the same time a flow channel for a second medium flowing with an opposite transverse flow component, in particular in a mainstream direction, is formed on the opposite outer surface of the second half-plate, the flow channels extending in opposite directions having a height that increases in the direction in which the respective other flow channel begins.
[0016] In the following, some exemplary embodiments of the invention are explained in more detail with the aid of drawings. [Brief description of the drawings]
[0017] [Figure 1] 1 shows a cross section of a bipolar plate of a fuel cell in plan view. [Diagram 2] 2 shows details of a bipolar plate and other fuel cell components according to FIG. 1 in a cross-sectional view. [Diagram 3] Further details of the bipolar plate are shown in a schematic diagram. [Figure 4] Further details of the bipolar plate are shown in a schematic diagram. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0018] Unless otherwise stated, the following description relates to all exemplary embodiments, in all figures, parts which correspond to each other or have essentially the same effect are provided with the same reference signs.
[0019] The bipolar plate, generally designated by reference number 1, is part of a fuel cell stack 10, also simply called a stack, which comprises a number of similar fuel cells 11. In this respect, each bipolar plate 1 can be characterized as comprising two fuel cells 11. With regard to the main features of the fuel cell stack 10, reference is made to the prior art cited at the beginning.
[0020] The bipolar plate 1 consists of two half plates 2, 3, each of which has an embossed structure 4. Overall, the bipolar plate 1 has the shape of an elongated rectangle, whose longitudinal direction is indicated by LR and whose transverse direction is indicated by QR. The central plane in which the two half plates 2, 3 overlap each other is indicated by ME. In a typical application, the bipolar plate 1 is vertically aligned.
[0021] In a basic concept known per se, the bipolar plate 1 has various ports 5, 6, 7, namely the coolant port 5 and the medium ports 6, 7. In this example, the coolant port 5 is adjacent to the short side of the bipolar plate 1, while the medium ports 6, 7, located adjacent to the coolant port 5 and through which the substances necessary for operating the stack 10, i.e. to generate electrical energy, are adjacent to the longitudinal side of the bipolar plate 1. The ports 5, 6, 7 visible in FIG. 1 are used to introduce cooling water or medium. In addition, there are three further ports for discharging the cooling water or medium. In this example, a gaseous medium is referred to, even if a liquid substance flows through the ports 6, 7.
[0022] The various ports 5, 6, 7 are adjacent to a distribution field 8 which transitions in the flow direction SR of the medium to an active field 9 where the desired electrochemical reactions take place. For this purpose, a membrane arrangement, generally indicated at 12, comprising a catalyst coated membrane 13 (CCM) and a gas diffusion layer 14 is located in the active field 9. The membrane arrangement 12 further comprises a frame 15, also referred to as a subgasket. The seals sealing the frame 15 to the bipolar plate 1 are indicated with the reference number 16.
[0023] The embossed structures 4 of the half plates 2, 3 are constructed to be largely mirror images of each other and have a typical embossing depth T n embossing element 19 with reduced embossing depth T r With embossing elements 18 and increased embossing depth T hThe half-plates 2, 3 comprise an embossing element 17, 18, 19 of the first half-plate 2 and an embossing element 19 of the second half-plate 3. Between the embossing elements 17, 18, 19 of the first half-plate 2 and the embossing elements 17, 18, 19 of the second half-plate 3, a coolant channel 21 is formed. At the same time, flow channels 22, 23 for the flow of various media, in particular oxygen and hydrogen, are formed on the outside of the half-plates 2, 3, i.e. on the surface of the half-plates 2, 3 facing away from the coolant channel 21. The different embossing depths T r , T n , T h is the channel height K of the medium channels 22, 23 n , K h has a direct effect on K n represents the normal channel height, and K h represents the comparatively increased channel height.
[0024] The channel height K that can be used during operation of the fuel cell 11 n , K h D further depends on the geometry of the membrane configuration 12, and in FIG. 2, the minimum thickness of the membrane configuration 12 is D min The maximum thickness of the film structure 12 is D max As shown in the figure.
[0025] As shown in Fig. 1, the distribution field 8 consists of two differently structured regions 25, 26, namely a transverse distribution region 25 and a longitudinal distribution region 26. The gas flow, generally indicated by GS, has a substantial or predominant component of movement in the transverse direction QR in the transverse distribution region 25, whereas in the longitudinal distribution region 26 the gas flows substantially in the longitudinal direction LR. In the example outlined in Fig. 1, the embossing structure 4 in the transverse distribution region 25 is configured as a dimpled embossing 20. In the longitudinal distribution region 26 the embossing structure 4 has a groove shape, the grooves formed by the embossing structure 4 fan out in the direction of the active field 9.
[0026] In all exemplary embodiments, the embossed structure 4 in the distribution field 8 is configured in such a way that the gas flow GS from one media port 6, 7 to the opposite media port 7, 6, i.e. mainly in the transverse direction QR, is promoted in a targeted manner compared to conventional structured plates in electrochemical instruments. In both examples of Fig. 2 and Fig. 3, the gas flows mainly from left to right. As shown in Fig. 2, the channel height K n , K h increases significantly from left to right, i.e. in the flow direction SR, until approaching the seal 16. In this way, edge channels 27 are formed, which run closely along the media port 6 and thus are particularly far from the media port 7, through which the flow medium is introduced. From the edge channels 27 there is an open connection to the bypass 24, which bypasses the active field 9. The gas flowing through the bypass 24 does not contribute to the generation of electrical energy. This is permissible in all examples of the invention. The main advantage of the facilitated gas flow through the edge channels 27 is the optimized media supply in the edge region of the active field 9.
[0027] As far as the improvement of the media supply in the edge region of the active field 9 is concerned, reference is also made to FIG. 3, which shows a schematic representation of the distribution of the gas flow GS in the distribution field 8. Here, the thin arrows indicate the gas flow GS with a high flow resistance, and the thick arrows indicate the gas flow GS with a low flow resistance. As shown in FIG. 3, the further the distance from the media port 7 to the active field 9, the easier the gas flows. The enlarged flow cross-section of the edge channel 27, located in the region of the thickest arrow in FIG. 3, i.e. in the distribution field 8 in the right-hand region, contributes significantly to this. As a result, the gas flow through the active field 9 becomes uniform over its entire width.
[0028] This also applies to the variant shown in Fig. 4, in which, in contrast to Fig. 3, the gas flows from right to left, i.e. is first introduced into the right-hand media port 6. In the case of Fig. 4, there are various subfields 28, 29, 30, 31 in the distribution field 8, which differ from one another in terms of flow properties, i.e. the pressure drop occurring during operation of the fuel cell 11. Here, a low pressure drop is provided in the subfield 28, which extends over almost the entire width of the distribution field 8 and is especially configured for a transverse QR flow.
[0029] Compared to the subfield 28, the flow resistance in the edge channel 27 adjacent to the subfield 28 and at the same time running parallel to the edge of the media port 7 is reduced again. In this way, the gas moves with a low pressure drop from the media port 6 to the edge of the active field 9 which is furthest from the media port 6. The subfields 29, 30, 31 are structured by the embossed structure 4 in the described order, i.e. from the subfield 29 to the subfield 31, in such a way that an increase in flow resistance is provided. A continuous transition between the subfields 29, 30, 31 is also possible. In any case, the maximum pressure drop is present over the flow length in the region of the subfield 31. This ensures that the gas does not reach in excessive quantities from the media port 6 to the nearest region of the active field 9. Also, in the example of Figures 3 and 4, the distribution field 8 has a structure of various embossed elements 17, 18, 19, which are not shown in detail here. [Explanation of symbols]
[0030] 1 Bipolar Plate 2 Half Plates 3 Half Plate 4 Embossed structure 5 Coolant Ports 6 Media Ports 7 Media Ports 8 Distribution area 9 Active field 10 Fuel cell stack, stack 11 Fuel Cell 12 Membrane composition 13 CCM, Catalyst Coated Membrane 14 Gas diffusion layer 15 Frame, subgasket 16 Sealing part 17 Normal Depth Embossing Elements 18 Reduced depth embossing elements 19 Increased depth embossing elements 20 Dimpled embossed area 21 Coolant Channel 22 Media channel, flow channel 23 Media channel, flow channel 24 Bypass 25 Transverse distribution area 26 Longitudinal distribution area 27 Edge Channel 28 Subfields 29 Subfields 30 Subfields 31 Subfields D max Maximum thickness of film structure D min Minimum thickness of the film structure D S Subgasket Thickness GS Gas Flow K n Normal channel height of the media channel K h Increased channel height of the media channel LR Longitudinal ME center plane QR Transverse SR Flow direction T h Increased embossing depth T n Normal embossing depth T r Reduced embossing depth
Claims
1. A bipolar plate (1) having two embossed half-plates (2, 3) overlapping each other and having a rectangular elongated basic shape, in which the half-plates (2, 3) form coolant ports (5) and medium ports (6, 7) located on the longitudinal sides of the half-plates (2, 3), distribution fields (8) arranged next to the ports (5, 6, 7) and provided for coolant distribution and medium distribution, and an active field (9), in which an embossed structure (4) is formed in the distribution field (8) in such a way that an increase in the free flow cross section is provided for the medium flowing from each of the ports (6, 7) in the direction of the ports (7, 6) arranged on the opposite longitudinal side.
2. 2. The bipolar plate (1) according to claim 1, characterized in that the increase in the flow cross section is implemented by reducing the height of the coolant channels (21) formed between the half-plates (2, 3) in the transverse direction of the half-plates (2, 3).
3. 3. A bipolar plate (1) according to claim 2, characterized in that the height of the edge channel (27) furthest from the associated port (6, 7) is at least 15% higher than the height of the adjacent media channel (22, 23) located within the distribution field and supplied by the same port (6, 7).
4. 4. The bipolar plate (1) according to claim 3, characterized in that the edge channels (27) transition into bypasses (24) flanking the active field (9).
5. 5. The bipolar plate (1) according to claim 1, characterized in that the distribution field (8) comprises a transverse distribution area (25) adjacent to the ports (5, 6, 7) and a longitudinal distribution area (26) arranged between this transverse distribution area (25) and the active field (9).
6. 6. Bipolar plate (1) according to claim 5, characterized in that the transverse distribution areas (25) are configured as dimpled areas.
7. A method for manufacturing a bipolar plate (1), in which two half-plates (2, 3) are embossed in such a way that each half-plate (2, 3) has a non-uniform embossing depth over its width, and the two half-plates (2, 3) are joined together on top of each other to form a bipolar plate (1) having coolant channels (21) of non-uniform height between the half-plates (2, 3), the main direction of the coolant flow corresponding to the longitudinal direction of the half-plates (2, 3). and wherein the outer surfaces of the half-plates (2, 3) facing away from the coolant channels (21) define media channels (22, 23), which likewise have a non-uniform height corresponding to the non-uniform embossing depth of the half-plates (2, 3) and are configured to guide media in both the main direction and in the transverse direction, a media flow cross-section extending in the transverse direction starting from ports (6, 7) formed by openings made in the half-plates (2, 3).
8. 8. The method according to claim 7, characterized in that the half-plates (2, 3) are arranged one on top of the other in such a way that a flow channel (22) for a first medium flowing with the first transverse flow component is formed on an outer surface of the first half-plate (2) and, at the same time, a flow channel (23) for a second medium flowing with the opposite transverse flow component is formed on the opposite outer surface of the second half-plate (3), and the flow channels (22, 23) extending in opposite directions have a height that increases in the direction in which the respective other flow channel (23, 22) begins.