Bipolar plate
The bipolar plate design optimizes fluid flow and spatial utilization in electrochemical systems by aligning ports with the active field, reducing pressure loss and material usage, thus enhancing power density and efficiency.
Patent Information
- Authority / Receiving Office
- JP · JP
- Patent Type
- Applications
- Current Assignee / Owner
- SCHAEFFLER TECHNOLOGIES AG & CO KG
- Filing Date
- 2024-05-02
- Publication Date
- 2026-04-21
AI Technical Summary
Existing bipolar plates in electrochemical systems face challenges in optimizing fluid flow and spatial utilization, particularly in fuel cell systems, where competing objectives such as minimizing flow resistance and maximizing space efficiency are not adequately addressed.
A bipolar plate design with a rectangular shape featuring three ports, where the cooling water port is positioned between two operating means ports, and the ports have elongated, non-rectangular cross-sections, with specific ratios of their dimensions to optimize fluid flow and minimize pressure loss.
The design achieves low pressure loss and efficient space utilization by aligning ports with the active field, allowing for uniform fluid distribution and reduced material usage, enhancing power density and flow efficiency.
Smart Images
Figure 2026512904000001_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to a bipolar plate which, according to the preamble of claim 1, is intended for use in an electrochemical system and through which a refrigerant can flow.
Background Art
[0002] Bipolar plates are known, for example, from WO 2022 / 253384. A known bipolar plate consists of two rectangular half sheets, on the short sides of which three ports are arranged in contact with each other. These are two ports intended to allow a working medium to pass through and one port arranged between said ports and intended to allow a refrigerant to pass through.
[0003] WO 2006 / 054399 describes another bipolar plate having a rectangular basic shape, on each of the short sides of which three ports for different fluids are arranged. In this case, as in the case of WO 2022 / 253384, the centre of the three adjacent ports is rectangular and the two outer ports have a pentagonal cross-sectional shape.
[0004] A bipolar plate which is intended for use in a fuel cell system and has a port with a triangular cross-sectional shape through which it passes is known, for example, from DE 10 2018 128 593 A1 and WO 2014 / 102534.
[0005] Disclosed in German Patent Application Publication No. 102008056900, a bipolar plate which is also a component of a fuel cell, has an arrangement of three ports, which are sometimes triangular in shape, sometimes deformed rectangular in shape, and sometimes pentagonal in shape. The ports are not arranged in a line touching each other. Rather, the arrangement of the three ports forms an L-shape, with two ports located touching the short side of the bipolar plate, while a third port, separated from the short side by one of the first two ports, is located touching the long side of the bipolar plate.
[0006] Various configuration options for bipolar plates forming ports with circular cross-sections are described in detail, for example, in German Patent Application Publication No. 102021212053 and German Patent Application Publication No. 102021207304. [Overview of the Initiative] [Problems that the invention aims to solve]
[0007] The present invention aims to define fuel cells for use in electrochemical systems, and more particularly, fuel cell systems that are further developed with respect to the fluid mode and spatial utilization compared to the cited prior art. [Means for solving the problem]
[0008] This objective is achieved, according to the present invention, by a bipolar plate having the features of claim 1. The bipolar plate has a rectangular basic shape in a well-known basic concept, with three ports, namely two operating means ports and one cooling water port, arranged adjacent to each other on its short side. The cooling water port is located between the two operating means ports. The cooling water port has a port long side oriented parallel to the short side of the plate, while each operating means port has a port long side oriented parallel to the long side of the plate. A rectangular active field is arranged between the three ports on one short side of the plate and the three ports on the opposite short side of the plate, and the active field has two active field long sides arranged parallel to the long side of the plate. The active field has linear channels for directing the flow of the operating means and the flow of the coolant parallel to the active field long sides.
[0009] According to claim 1, the product of the length of the port long side of the refrigerant port and the length of the port long side of one of the two operating means ports is at least six times, and in particular at least eight times, the product of the length of the port short side of the refrigerant port and the length of the port short side of the operating means port. The referred port short side of the operating means port is oriented parallel to the port long side of the refrigerant port. In each case, the port long side of one of the two operating means ports is aligned and positioned to align with the active field long side.
[0010] This invention is based on the consideration that partially competing objectives must be considered when configuring the fluid conduction contour in a fuel cell system stack or other electrochemical cell stack. Therefore, a fluid-favorable configuration may require a lot of space. For example, if only flow resistance within the channel is considered, a circular channel cross-section is considered best.
[0011] However, not only the flow of gaseous or liquid fluid within the channel, but also the transport of fluid flowing out of the channel must be considered, for example, when this fluid is distributed as uniformly as possible over a flat region, such as in the form of an active field in an electrochemical cell, such as a fuel cell. The same applies when fluid located in a flat region is to be recovered and supplied to the channel. Furthermore, whether the fluid is in the form of a liquid and / or gas may be important.
[0012] With respect to the flow of refrigerant through an activated field or a linear channel within an activated field, it is advantageous if the port is exactly the same width as the activated field. However, in such embodiments, the operating means port must be positioned 100% lateral to the activated field. In this case, space can be saved by approximating the cross-section of the operating means port to a circle, which provides the maximum area for a given size.
[0013] An activated field through which the operating mechanism and refrigerant flow linearly is highly advantageous in that it generates particularly low pressure loss. The flow paths of the operating mechanism and refrigerant are divided at as few points as possible to further minimize pressure loss.
[0014] Due to the very different properties of liquid media, particularly refrigerants, and gaseous media such as hydrogen and air or oxygen, when constructing fluid conduction components, the media-specific properties must also be considered. This relates, for example, to the configuration of a distributor field positioned between an array of various ports and an active field. In the distributor field, various media must be distributed transversely across the bipolar plate, i.e., perpendicular to the main flow direction of the media. Since transverse distribution of gaseous working media is easier than transverse distribution of liquid refrigerants, the longitudinal orientation of the working means ports relative to the longitudinal direction of the bipolar plate, which coincides with the main flow direction of the working media, seems in principle wise when combined with the transverse orientation of the refrigerant ports. In principle, this method is known from the prior art, including the aforementioned references WO2022 / 253384A1 and WO2006 / 054399A1.
[0015] The solution according to the present invention surpasses this approach by providing a more extreme cross-sectional shape of the port that deviates more from a compact, for example, substantially rectangular or circular shape. Increased flow resistance is considered in the port and in the channel that is formed from a whole of similar ports and extends through a cell stack comprising a number of bipolar plates.
[0016] A fraction having a numerator given by the product of the length of the port's long side of the refrigerant port and the length of the port's long side of one of the two operating means ports, and a denominator corresponding to the product of the port's short side of the refrigerant port and the port's short side of the operating means port, is in the range of 6 to 30, particularly 8 to 18, according to various possible embodiments.
[0017] According to various possible configurations, the length of the port length of the refrigerant port parallel to the short side of the bipolar plate, where the length of the short side of the plate is measured in the transverse direction of the rectangular non-square bipolar plate, corresponds to at least 40%, and in particular at least half, of the width of the bipolar plate. At the same time, the aforementioned port length extends over, for example, less than 80% of the length of the short side of the bipolar plate.
[0018] The refrigerant port can be positioned in the center between the two long sides of the bipolar plate. Alternatively, an eccentric arrangement of the refrigerant ports can be considered, especially when two adjacent operating means ports are of unequal size.
[0019] Compared to conventional solutions, the remarkably elongated, not strictly rectangular, cross-sectional shape of the refrigerant port can be described, in particular, by the fact that the long side of the refrigerant port oriented transversely to the bipolar plate is perpendicular to the long side of the port and is longer than the long side of the operating means port oriented parallel to the long side of the bipolar plate.
[0020] The rectangular or deformed rectangular shape of the refrigerant port can be combined with the pentagonal cross-sectional shape of the operating means port in the bipolar plate. In particular, both operating means ports in the same triple port array may be pentagonal. Optionally, two operating means ports positioned adjacent to a refrigerant port are configured to be mirror-symmetric with respect to each other. The length of the port's long side in the aforementioned quotient ranges from 6 to 30 and is measured on the side of the operating means port that has the shortest distance from the nearest long side of the bipolar plate.
[0021] For refrigerant ports, particularly cooling water ports, with at least a nearly rectangular cross-section, the ratio between the length of the port's long side and the length of the port's short side is greater than 3 and may be in the range of 4 to 10.
[0022] Two port arrays, each with three ports, can be formed mirror images of a plane located midway between the two short sides of a bipolar plate.
[0023] In a preferred embodiment, the long sides of the two operating means ports are aligned with each other and aligned with one of the long sides of the active field. This has the advantage of optimally utilizing the bottom area of the bipolar plate, which, due to the arrangement of the active field and ports on the plate, leads to material savings and a high power density per plate.
[0024] It was found to be advantageous for the distributor field to be positioned between the port array and the active field, with multiple parallel channel sections oriented in the flow direction ST extending along the long side of the plate positioned between each cooling water port and the adjacent distributor field. Preferably, each distributor field spreads out in a fan shape from its respective channel section toward the active field.
[0025] Preferably, the operating means ports are arranged on adjacent sides (in this case, inclined sides) of each distributor field so as to extend parallel to the path of the distributor field.
[0026] Instead, the configuration of the port arrays located on both sides of the plane may be different from each other. For example, in the flow direction ST, that is, the cooling water ports initially arranged on the inflow side have a length / width ratio that is at least 50% larger than the cooling water ports subsequently arranged on the outflow side in the flow direction ST. The higher pressure of the cooling water on the inflow side enables the use of particularly narrow and elongated ports to supply cooling water to the active field. Only a small transverse component of the cooling water flow ensures uniform cooling across the entire width of the active field. At the outflow end of the refrigerant channels extending through the bipolar plate, the refrigerant ports having a non-extreme length / width ratio ensure that the refrigerant is discharged with low flow resistance.
[0027] The bipolar plate can be composed of two half plates, in particular half sheets, using manufacturing techniques known in principle. In these cases, the refrigerant channels are formed between the half plates. An electrochemical system comprising a plurality of bipolar plates of the type according to the invention is, for example, a stationary or mobile fuel cell system, a redox flow battery, or an electrolyzer for hydrogen production.
[0028] Exemplary embodiments of the invention and comparative examples not claimed are explained in more detail below with reference to the drawings.
Brief Description of the Drawings
[0029] [Figure 1] Shows a bipolar plate for use in an electrochemical system, i.e., a fuel cell system. [Figure 2] Comparative examples not claimed are shown in figures similar to Figure 1.
Modes for Carrying Out the Invention
[0030] In the following text, where applicable, the same reference numerals are used for both the exemplary embodiment according to Figure 1 and the comparative example according to Figure 2, which is only for the purpose of explanation.
[0031] A bipolar plate, denoted collectively by reference numeral 1, is used in an electrochemical cell, i.e., a fuel cell stack, to define the half-cell of one electrochemical cell from the half-cell of another electrochemical cell. For the basic function of an electrochemical system comprising multiple bipolar plates 1 arranged in a stack, please refer to the prior art cited at the beginning.
[0032] The bipolar plate 1 is constructed in a manner known in principle from two half-plates through which a coolant flows. In this case, the half-plates are made of sheet metal, i.e., constructed as half-sheets. Alternatively, the half-plates can be manufactured from a conductive composite material containing graphite and bonded by polymers.
[0033] The working medium flows over the outer surface of the bipolar plate 1 within the cell stack, also abbreviated as a stack. The rectangular active field, denoted by 10, where the desired electrochemical reaction occurs, occupies most of the area of the bipolar plate 1.
[0034] The bipolar plate 1 has an elongated rectangular shape, with long sides denoted as 2 and 3 and short sides denoted as 4 and 5. The length of the bipolar plate 1 is denoted as L1, and the much smaller width of the bipolar plate is denoted as B1. Adjacent to the first short side 4 is the first port array 6, and adjacent to the second short side 5 is the second port array 7. The first port array 6, located on the left side of the array shown in Figures 1 and 2, comprises three ports 11, 12, and 13 arranged in contact with each other, namely two operating means ports 11 and 13 for passing operating means of an electrochemical system, and a cooling water port 12, commonly referred to as a refrigerant port, for supplying cooling water to the bipolar plate 1.
[0035] The cooling water flows through the bipolar plate 1 in the flow direction ST, that is, substantially along the longitudinal direction of the bipolar plate 1, from left to right in the illustrated case. This does not imply any explanation of the actual orientation of the bipolar plate 1. In particular, the bipolar plate 1 can be oriented vertically within the cell stack.
[0036] On the second short side 5 are three further ports 14, 15, and 16 belonging to the second port array 7. In this case, the working fluid, in particular hydrogen and atmospheric oxygen, is conducted through the two outer ports 14 and 16, i.e., ports arranged adjacent to the two long sides 2 and 3, while the cooling water is discharged from the bipolar plate 1 through the central port 15. All ports 11, 12, 13, 14, 15, and 16 extend through the fuel cell stack in the stacking direction.
[0037] The rectangular activated field 10 is positioned between three ports 11, 12, and 13 on the short side 4 of the plate and three ports 14, 15, and 16 on the opposite short side 5 of the plate, and the activated field 10 has two activated field long sides 22 and 22', which in the embodiment shown herein are positioned parallel to the plate long sides 2 and 3. The activated field 10 has linear channels 10a for directing the flow of the working medium, i.e., hydrogen and oxygen, and the flow of the refrigerant, i.e., cooling water, parallel to the activated field long sides 22 and 22'.
[0038] In particular, in an embodiment of the bipolar plate 1 made of two interconnected, three-dimensionally embossed thin half-sheets, the linear channels 10a in the active field 10 are formed through each half-sheet, thereby existing in a positive form on one side of the half-sheet and in an inverse negative form on the other side of the half-sheet.
[0039] Between port arrays 6 and 7 and the active field 10 are distributor fields 8 and 9. Based on the plan views in Figures 1 and 2, the flows of different materials intersect, while the different materials remain separated from each other. Between the cooling water ports 12 and 15 and the distributor fields 8 and 9, it can be seen that multiple channel sections 17 are parallel to each other and oriented in the flow direction ST.
[0040] The extent of the flat region where the short channel portion 17 is located already shows a clear difference between the exemplary embodiment in Figure 1 and the comparative example in Figure 2.
[0041] As shown in Figure 1, the cooling water supplied to the distributor field 8 through the channel portion 17 flows mostly linearly, i.e., along the longitudinal direction of the bipolar plate 1, through the distributor field 8 to the activated field 10. Only in the relatively narrow edge region of the distributor field 8 does the cooling water flow need to spread out in a large fan shape to reach the activated field 10 across its entire width. Similar conditions exist in the region of the second distributor field 7 and the second port array 7, i.e., on the cooling water outlet side, in which case the cooling water flow is integrated.
[0042] In relation to the exemplary embodiment shown in Figure 1, the unclaimed comparative example shown in Figure 2 exhibits a much more pronounced fan-shaped spread of the cooling water flow in the first distributor field 7, and furthermore, a much more pronounced constriction of the cooling water flow in the second distributor field 8. This results in significantly higher flow resistance in the case of Figure 2. Continuous, linear flow through the bipolar plate 1 occurs only in a very narrow central region, as ideally shown in Figure 2 by a single long arrow oriented in the flow direction ST.
[0043] The generally straight, low-resistance flow through the bipolar plate 1 shown in Figure 1 is mainly achieved by the configuration of port arrays 6 and 7. The cooling water ports 12 and 15 each have an elongated rectangular shape, and the long side 18 of the associated ports 12 and 15 is parallel to and tangent to the nearest short side 4 and 5 of the plate. The short side of the cooling water ports 12 and 15 is denoted by reference numeral 19. The long side 18 of each cooling water port 12 and 15 has a length L18 that is more than three times the length of the short side 19 of the same cooling water port 12 and 15, denoted by L19.
[0044] Unlike the cooling water ports 12 and 15, the operating means ports 11, 13, 14, 15, and 16 each have a pentagonal cross-sectional shape. In this case, the longest sides 20 and 20' of the five sides of the operating means ports 11, 13, 14, and 16 are closest to the long sides 2 and 3 of the bipolar plate 1 adjacent to the relevant operating means ports 11, 13, 14, and 16. As a result, the long sides 20 and 20' of all the operating means ports 11, 13, 14, and 16 are oriented perpendicular to the long side 18 of the cooling water ports 12 and 15.
[0045] Parallel to the long sides 18 of the cooling water ports 11 and 15 are the short sides of the operating means ports 11, 13, 14, and 16, denoted by reference numeral 21. The short side 21 is the side of the operating means ports 11, 13, 14, and 16 that is the shortest distance from the adjacent short sides 4 and 5 of the bipolar plate 1. The length of the port short side 21 is denoted by L21.
[0046] The following relationships exist between different ports 11, 12, 13, 14, 15, and 16 with different lengths L18, L19, L20, and L21. 6 < (L18 × L20) / (L19 × L21) < 30
[0047] The fraction given by this relationship, namely the quotient of the product of the lengths of the two longer sides 18, 20, and 20' (L18, L20) as the numerator and the product of the lengths of the two shorter sides 19, 21 (L19, L21) as the denominator, is a dimensionless value, and therefore the validity of this relationship does not depend on the chosen units. [Explanation of Symbols]
[0048] 1 bipolar plate 2. Long side of the bipolar plate, long side of the plate 3. Long side of the bipolar plate, long side of the plate 4. Short side of bipolar plate, short side of plate 5. Short side of bipolar plate, short side of plate 6-port configuration, cooling water inlet side 7-port arrangement, cooling water outlet side 8 Distribution station 9 Distributor field 10 Active field 10a Linear Channel 11 Operating means port 12 Cooling water ports 13 Operating means port 14 Operating means port 15 Cooling water ports 16 Operating means port 17 Channel Section 18 Long side of the cooling water port, port length 19 Cooling water port short side, port short side 20, 20' Operating means port long side, port long side 21 Operating means Short side of port, short side of port 22, 22' Long side of the active field B1 Bipolar plate width L1 Bipolar Plate Length L18 Cooling water port length L19 Cooling water port length (short side of port) L20 Operating means port length of the port's long side L21 Operating means port port length ST flow direction
Claims
1. A bipolar plate for an electrochemical system having a rectangular basic shape, wherein three ports (11, 12, 13, 14, 15, 16), namely two operating means ports (11, 13, 14, 16) and one refrigerant port (12, 15), are arranged in contact with each other on the short sides (4, 5) of the bipolar plate, and the refrigerant port (12, 15) is positioned between the operating means ports (11, 13, 14, 16). The rectangular active field (10) is positioned and has a port long side (18) oriented parallel to the short sides (4, 5) of the plate, while each operating means port (11, 13, 14, 16) has a port long side (20) oriented parallel to the long sides (2, 3) of the plate, and the rectangular active field (10) is positioned between the three ports (11, 12, 13) on the short side (4) of the plate and the three ports (14, 15, 16) on the opposite short side (5) of the plate. The activated field (10) has two activated field long sides (22, 22'), and the two activated field long sides (22, 22') are each arranged parallel to the plate long sides (2, 3), and the activated field (10) has a straight channel (10a) for directing the flow of the operating means and the flow of the refrigerant parallel to the activated field long sides (22, 22'), and the length of the port long side (18) of the refrigerant ports (12, 15) A bipolar plate characterized in that the product of the length (L18) and the length (L20) of the long side (20) of one of the two operating means ports (11, 13, 14, 16) adjacent to the refrigerant ports (12, 15) is at least six times the product of the length (L19) of the short side (19) of the refrigerant ports (12, 15) and the length (L21) of the short side (21) of the operating means ports (11, 13, 14, 16).
2. The bipolar plate according to claim 1, characterized in that the long sides (20, 20') of the two operating means ports (11, 14; 13, 16) are aligned and arranged, and are aligned with one of the long sides (22, 22') of the active field.
3. The bipolar plate according to claim 1 or 2, characterized in that the product of the length (L18) of the long side (18) of the refrigerant port (12, 15) and the length (L20) of the long side (20) of one of the two operating means ports (11, 13, 14, 16) is 30 times or less the product of the length (L19) of the short side (19) of the refrigerant port (12, 15) and the length (L21) of the short side (21) of the operating means port (11, 13, 14, 16).
4. The bipolar plate according to claim 3, characterized in that the relationships specified in claims 1 to 3 apply to both operating means ports (11, 13, 14, 16) adjacent to the refrigerant ports (12, 15).
5. The bipolar plate according to any one of claims 1 to 4, characterized in that the length (L18) of the long side (18) of the refrigerant port (12, 15) corresponds to at least half of the width (B1) of the bipolar plate (1).
6. A bipolar plate according to any one of claims 1 to 5, characterized in that the long side (18) of the refrigerant ports (12, 15) is longer than the long side (20, 20') of the operating means ports (11, 13, 14, 16) which are oriented perpendicular to the long side (18).
7. A bipolar plate according to any one of claims 1 to 6, characterized in that at least one of the operating means ports (11, 13, 14, 16) has a pentagonal cross-sectional shape.
8. The bipolar plate according to claim 7, characterized in that each operating means port (11, 13, 14, 16) has a pentagonal cross-sectional shape.
9. A bipolar plate according to any one of claims 1 to 8, characterized in that the ratio of the length (L18) of the long side (18) of the refrigerant port (12, 15) to the length (L19) of the short side (19) of the refrigerant port (12, 15) is at least 3.
10. The bipolar plate according to any one of claims 1 to 9, characterized in that a port array (6, 7) having three ports each (11, 12, 13; 14, 15, 16) is formed in a mirror image with respect to a plane located in the center between the two short sides (4, 5) of the bipolar plate.
11. A bipolar plate according to any one of claims 1 to 10, characterized in that a first port array (6) having three ports (11, 12, 13) arranged in contact with each other and adjacent to the first short side (4) of the plate differs from a second port array (7), and the second port array (7) also has three ports (14, 15, 16) arranged in contact with each other and located on the second short side (5) of the plate.
12. The bipolar plate according to claim 10 or 11, characterized in that a distribution field (8, 9) is disposed between each of the port arrangements (6, 7) and the active field (10), a plurality of channel portions (17) are disposed between each refrigerant port (12, 15) and adjacent distribution fields (8, 9), the channel portions are parallel to each other and oriented in the flow direction (ST) extending along the long sides (2, 3) of the plate.
13. The bipolar plate according to claim 12, characterized in that each distributor field (8, 9) spreads out in a fan shape from its respective channel portion (17) towards the active field (10).
14. The bipolar plate according to claim 13, characterized in that the operating means ports (11, 13, 14, 16) are arranged on sides adjacent to each of the distributor fields (8, 9) so as to extend parallel to the paths of the distributor fields (8, 9).
15. The bipolar plate according to any one of claims 12 to 14, characterized in that the refrigerant port (12) initially arranged in the flow direction (ST) has a length / width ratio that is at least 50% greater than that of the refrigerant port (15) subsequently arranged in the flow direction (ST).