Fuel cell stack assembly

Abstract

Fuel cell stack assembly (1) comprising a fuel cell stack for generating electric energy and a housing (15) for housing the fuel cell stack, wherein the fuel cell stack comprises at least a plurality of alternatively arranged bipolar plates and membrane electrode assemblies stacked in a stacking direction, which form an energy-generating cell stack body (11 ). The fuel cell stack assembly (1 ) further comprises first and second endplates (10, 12) sandwiching the cell stack body (11) in the stacking direction, and at least one clamping element (6) which is adapted to clamp the cell stack body and the first and second endplate together for forming a fuel cell stack subunit (13). The fuel cell stack subunit has open sides (5), at which the cell stack body is exposed to an environment, and two of these open sides are covered by the endplates, wherein at the remaining open sides of the cell stack body a plate element (4) is arranged which covers at least partly and / or entirely the respective open sides of the stack on which it is arranged for preventing the cell stack body (11) from being touched.

Description

[0001] Fuel Cell Stack Assembly

[0002] Description:

[0003] The present invention relates to a fuel cell stack assembly according to the preamble of claim 1 .

[0004] Usually, a fuel cell stack assembly comprises a stack body including a plurality of membrane electrode assemblies (MEAs), which are separated by so called bipolar plates (BPP). The bipolar plates usually comprise at least two electrically conducting metal plates, so-called flow field plates, which are placed on top of each other and have a flow field for the reactants at one side and a flow field for a cooling fluid on the other side. Each bipolar plate and / or membrane electrode assembly comprises a fuel, oxidant, and coolant inlet manifold, and a fuel, oxidant, and coolant outlet manifold. The flow field of each plate forms an active area in which electric energy is generated via electrochemical reaction.

[0005] Additionally, a fuel cell stack comprises a pair of terminal plates collecting the electric current produced by the cell stack body, and a pair of endplates sandwiching the terminal plates. Further, an insulation plate may be provided between each of the terminal plate and the adjacent endplate to electrically insulate them.

[0006] The electrochemical reaction in a fuel cell generates high-voltage electrical energy and heat. To ensure complete electrical insulation, protect the fuel cell stack from environmental factors such as water and dirt, and prevent the escape of reactant gases, the fuel cell stack is enclosed in a housing. However, there is a risk of accidental contact with the stack body when it needs to be removed or installed within the housing. While the endplates may offer partial protection, the other open sides of the stack body remain exposed to the environment and could be accidentally touched while handling the stack, thereby posing safety risks.

[0007] It is therefore object of the present invention, to provide an improved fuel cell stack assembly that is easy to handle while ensuring electrical safety.

[0008] This object is solved by fuel cell stack assembly according to claim 1 .

[0009] In the following a fuel cell stack assembly is disclosed which comprises a fuel cell stack for generating electric energy and a housing for housing the fuel cell stack. The housing may have a stack enclosure covering all sides of the cell stack body, a bottom and top plate that may be fastened or integrated to the stack enclosure. The fuel cell stack comprises at least a plurality of alternatively arranged bipolar plates and membrane electrode assemblies stacked in a stacking direction, which form an energy-generating cell stack body, at least two endplates sandwiching the cell stack body in the stacking direction, and at least one clamping element which is adapted to clamp the cell stack body and the first and second endplate together for forming a fuel cell stack subunit. The fuel cell stack subunit has at least one open side, at which the cell stack body is exposed to an environment, and two sides at which the cell stack body is covered by the endplates, wherein the fuel cell stack subunit is housed in the housing.

[0010] In order to provide a fuel cell stack assembly that is easy to handle, specifically during the removal and installation of the cell stack body into the housing, while ensuring electrical safety, the fuel cell stack subunit, which is housed in the housing, further has at least one plate element (4), which is arranged at at least one of the at least one open sides of the cell stack body and covers at least partly the at least one open side of the cell stack body for preventing the cell stack body from being touched. The at least one plate element remains attached to the cell stack body as a leave-on touch protection, acting as an electrically insulating layer on the respective open sides of the cell stack body. Thus, during the removal and installation of the fuel cell stack subunit into the housing, the plate element prevents direct contact with the cell stack body while ensuring electrical safety, making it easier to handle. It should be noted that the plate element, attached to the fuel cell stack subunit so as to cover at least one open side of the cell stack body, is a separate element from the housing and is configured for installation in, or removal from, the housing together with the fuel cell subunit as a unit. Thus, a distance is maintained between the plate element and the housing when the fuel cell stack subunit is inserted into the housing, thereby facilitating easy handling of the fuel cell stack subunit, preventing direct contact with the cell stack body, and ensuring electrical safety. It should be further noted that the at least one plate element remains at the fuel cell stack subunit even after the fuel cell stack subunit has been installed in the housing.

[0011] Furthermore, the number of open sides of the fuel cell stack subunit may vary depending on its shape. The subunit may have different shapes, such as cylindrical, triangular, rectangular, or any other shape, each with a different number of open sides. For example, a rectangular-shaped subunit may have four open sides, whereas a triangle-shaped subunit may have three open sides. Here, the open sides are the sides of the cell stack body with which the fuel cell stack body is exposed to the environment. Usually, the endplates cover two sides of the cell stack body. Thus, in a vertical fuel cell stack the endplates would cover the top and bottom sides.

[0012] According to an embodiment, at all open sides of the cell stack body a plate element is arranged, which covers at least partly the respective open side of the cell stack body. For instance, the open sides of the cell stack body can be partially covered by at least one plate element, which may be in the form of a stripe. Thus, the plate element doesn’t need to fully enclose all open sides to prevent the stack from being touched. This has the advantage that the plate element can provide a touch protection without significantly increasing the overall weight and thickness of the cell stack body. Additionally, since the plate element partially covers the cell stack body, there is sufficient aeration for the stack, preventing build-up of condensed water vapor on the stack.

[0013] In an alternative embodiment, at least one plate element covers at least one entire open side of the cell stack body. For instance, at least one plate element may be in the form of a continuous flat panel, entirely covering at least one open side on which it is arranged. This provides protection against accidental contact with the cell stack body, even if the cell stack body is incautiously handled.

[0014] Preferably, the plate element may be arranged on all sides of the cell stack body, partially and / or entirely covering the respective open side from being touched. Thereby, it is also possible that one open side of the cell stack body may be partially covered by at least one plate element, while another open side is entirely covered by another plate element. This arrangement of the plate elements protects against accidental contact with the cell stack body while also ensuring proper ventilation for the stack, preventing condensation of water vapor.

[0015] According to a further embodiment, at one open side of the cell stack body, two or more plate elements may be arranged. With other words, at one open side of the cell stack body, two plate elements may be arranged next to each other or overlapping each other to partially and / or entirely covering the respective open side of the cell stack body. Thus, two or more plate elements can be arranged in the required orientation based on the shape and requirements of the fuel cell stack subunit, thereby preventing contact with the cell stack body.

[0016] According to a further preferred embodiment, at least two plate elements are connected at their edges to each other and form plate element assembly. Preferably the plate elements of the plate element assembly are arranged in an angle to each other. Thereby it is further preferred that the angel between the plate elements is similar to the angel defined by two adjacent open sides of the cell stack body. For example, a rectangular shaped stack has a 90°angel between two adjacent open sides. Thus, the plate assembly may also have two plates which are arranged in a 90° angle. Further, the plate elements themselves may cover the respective open side entirely or only partially. This design simplifies the process of installing the plate element, as it can cover at least two open sides simultaneously with a single plate element assembly. Furthermore, in case the plate elements of a single plate assembly are not covering the entire open side, a further plate element or plate element assembly can be arranged at the stack, in such a way that at least two plate elements abut against each other or overlapped with each other to fully cover the respective open sides of the stack.

[0017] According to a preferred embodiment, at least one plate element extends from the first endplate to the second endplate of the cell stack body in the stacking direction. Thus, the plate elements can be directly secured or fastened to the first and second endplates of the cell stack body, without requiring additional clamping elements, thereby providing a leave-on touch protection and forming a complete full cell stack subunit adapted to be enclosed within the housing. This ensures long-lasting touch protection to the full cell stack subunit, particularly when removing or installing it into the housing.

[0018] Preferably, at least one plate element extends over a width of at least one open side of the cell stack body. For instance, the plate element may extend horizontally to cover the width of the cell stack body, making it suitable for mounting them on the cell stack body in all directions regardless of its stacking direction. According to a further embodiment it is also possible to combine a vertical extending plate element and a horizontally extending plate element at one open side, thereby covering almost the entirety of the open side.

[0019] According to a further preferred embodiment, at least one plate element is arranged between the cell stack body and the at least one clamping element. The clamping element retains pressure to the stack to keep the cell stack body together with the endplates, resulting in a compact stack. Additionally, by placing the plate element between the clamping element and the stack, the plate element may be held in place along the open side of the fuel cell stack. Thereby, further fastening elements for fastening the plate element to the stack may not be required and may be omitted.

[0020] However, for an improved fastening of the plate element to the stack, fasting elements may be provided which fasten the plate element to the stack and / or to the clamping bands. For example, at least one plate element may be fastened to at least one clamping element on one open side of the stack, thus securing the two or more plate elements easily with the stack. According to a further embodiment, the plate element can be securely arranged on at least one open side of the cell stack body using a fastening interface, which is used to secure the plate element to the cell stack body. The fastening interface could be a groove, a clamping element, a latch, a snap tag, a lug, and / or a hole in the plate element. This hole in turn could be a threaded-through hole, a threaded blind hole, or a through hole through which a fastening element can be passed.

[0021] According to a further embodiment, at least one plate element has a plurality of openings. Usually, the cell stack body becomes humid during or after operation. If the plate element fully covers the stacked body, the humidity may condense on the plate element and trickle onto the stacked body, or accumulate at the bottom, which in turn might result in a short circuit. To prevent this condensation issues, the plate element is provided with a plurality of openings, which ensures sufficient aeration of the stack and still provides touch protection of the stack at all times.

[0022] Preferably, the plurality of openings is evenly distributed throughout the surface of the plate element. This ensures that the fuel cell stack is sufficiently aired in all places.

[0023] Alternatively, the plurality of openings may be unevenly scattered throughout the surface of the plate element or arranged in any order on the plate element to prevent the accumulation of condensed water on the cell stack body. Thereby, these parts of the stack can be aired where the most condensation is expected.

[0024] According to a preferred embodiment, the plurality of openings is arranged in a series of sequential rows, wherein the openings of one row are offset from the openings of an adjacent row. When condensation occurs on the plate element, the offset arrangement of the openings helps the condensed water to evaporate before it drips onto the cell stack body. The openings guide the condensed water to flow down around them, and the heat from the cell stack body helps to evaporate the condensed water as it travels across the surface of the plate element, preventing it from dripping directly onto the bottom plate of the housing and accumulating there. By guiding the flow of condensed water, this pattern of arrangement of plurality of opening facilitates evaporation, preventing accumulation of the condensed water on the cell stack body, and thereby prevents any short circuit which might be caused by accumulated water.

[0025] Preferably, the at least one of the openings has a flange which protrudes towards the cell stack body. This flange formed at the sides of the opening, helps to enhance the direction of flow of condensed water vapor around the openings, making it easier for the water vapor to evaporate before it has a chance to accumulate at the bottom of the stack.

[0026] According to further preferred embodiments, at least one plate element is made from an electrically isolating material, such as a plastic material or a rubber material or a thermoplastic material. This provides additional insulation to the cell stack body and prevents any short circuit when removing or installing the cell stack body into the housing.

[0027] In an alternative embodiment, at least one plate element is made from a non-electrically isolating material, such as metal, and has at least one surface which is coated with an electrically insulating material. This has the advantage that the plate element made of metal can be durable and easy to shape. In addition, coating the metal plate with electrically insulating material provides electrical insulation while still benefiting from the structural integrity and conductivity of the metal material.

[0028] Further preferred embodiments are defined in the dependent claims as well as in the description and the figures. Thereby, elements described or shown in combination with other elements may be present alone or in combination with other elements without departing from the scope of protection.

[0029] In the following, preferred embodiments of the invention are described in relation to the drawings, wherein the drawings are exemplarily only, and are not intended to limit the scope of protection. The scope of protection is defined by the accompanied claims, only.

[0030] The figures show: Fig. 1 : A schematic perspective view of a fuel cell stack assembly according to a preferred embodiment;

[0031] Fig. 2: An illustrated view of plate elements assembly according to a preferred embodiment;

[0032] Fig. 3: A schematic perspective view of fuel cell stack subunit according to a preferred embodiment;

[0033] Fig. 4: An illustrated view of fuel cell stack subunit with horizontally extended plate element according to a preferred embodiment;

[0034] Fig. 5: An illustrated view of fuel cell stack subunit according to a further preferred embodiment;

[0035] Fig. 6: A front perspective view of a plate element assembly according to a preferred embodiment; and

[0036] Fig. 7: A schematic perspective view of plate element according to a preferred embodiment.

[0037] In the following same or similar functioning elements are indicated with the same reference numerals.

[0038] Fig.1 schematically illustrates a fuel cell stack assembly 1 comprises a fuel cell stack that has at least a plurality of alternatively arranged bipolar plates and membrane electrode assemblies stacked in a stacking direction, which form an energy-generating cell stack body 11 . A first endplate 10 and second endplate 12 sandwich the cell stack body 11 in the stacking direction, and a clamping element 6 clamps the cell stack body 11 and the first endplate 10 and second endplate 12 together, forming a fuel cell stack subunit 13. At two sides, the fuel cell stack subunit 13 is covered by the endplates 10 and 12, but the remaining sides 5 are open to an environment.

[0039] As shown in Fig.1 , the fuel cell stack subunit 13 is usually enclosed within a housing 15 to protect the fuel cell stack subunit 13 from the environment and to ensure safety from the heat and high electric energy generated by the cell stack body 11 during and after operation. However, when removing or installing the fuel cell stack subunit 13 into the housing 15, there is a risk of touching the open sides 5 of the cell stack body 11 , which poses a safety hazard. Therefore, to prevent direct contact with the open side 5 of the cell stack body 11 , at least one plate element 4, as shown in Fig.1 , is arranged on at least one of the open sides 5 of the cell stack body 11 to serve as leave-on touch protection, preventing the cell stack body 11 from being touched, even after it has been installed into the housing 15.

[0040] Additionally, as shown in Fig. 1 , the fuel cell stack subunit 13 together with plate element 4 is installed within the housing 15 such that a distance 20 is formed between the plate element 4 and the housing 15. Thus, the fuel cell stack subunit 13 with plate element 4 is a distinct unit separate from housing 15, thereby facilitating easier handling of the fuel cell stack subunit 13, while providing electrical safety.

[0041] The plate element 4 can be a single plate element, as illustrated in Fig. 1 , but it is also possible to combine two plate elements for forming a plate element assembly 3 as is illustrated in Fig. 2. In the illustrated embodiment, two plate element assemblies 3-1 , 3- 2 are provided, each of which comprises three plate elements 4-1, 4-2, 4-3, and 4-4, 4-5, 4-6 which are arranged in a 90° to each other. This design simplifies the process of installing the plate elements 4, as each plate element assembly 3 already covers three sides of the cell stack body 11 .

[0042] As can be further seen in Fig. 2, the plate elements 4-4, 4-6, 4-3 do not cover the entire wide sides of the cell stack body 11 but only two thirds of the sides. Therefore, the two plate element assemblies, 3-1 and 3-2, are arranged overlapping each other to provide leave-on touch protection for cell stack body 11, enclosing all open sides of cell stack body 11 .

[0043] As mentioned above, each plate element assembly 3 illustrated in Fig. 2 is formed by connecting three individual plate elements at their edges, covering at least three open sides of the cell stack body 11. Thereby, assembly 3-1 is formed by connecting three plate elements 4-1 , 4-2, and 4-3 at their edges, and assembly 3-2 is formed by joining plate elements 4-4, 4-5, and 4-6. In this configuration, plate elements 4-1 and 4-3 of assembly 3-1 , and plate elements 4-4 and 4-6 of assembly 3-2, are arranged partly overlapping each other, and thereby enclosing all the open sides 5 of the cell stack body 11 . It goes without saying that the cell stack body 11 could also be covered by four individual plate elements arranged separately on the open sides 5 of the cell stack body 11 , each fully covering the respective open sides 5. Additionally, it is possible to jointly arrange at least one plate element assembly 3 and at least one individual plate element 4 on the open sides 5 to cover the entire cell stack body 11 .

[0044] Further, as depicted in Fig 3, it is possible that the plate elements 4 do not cover the entire open sides 5 of the cell stack body 11 but only parts thereof. For example, plate element 4-8 extends in length L from the first end plate 10 to second end plate 12, covering the whole length of the stack from end plate 10 to end plate 12 but not covering an entire width W and thereby the entire respective open side 5 of the cell stack body 11 .

[0045] Additionally, as shown in Fig. 4, the plate element 4 can extend horizontally over the entire width W of the cell stack body 11 but does not extend in length from the endplate 10 to endplate 12. Here, the plate element 4 covers the entire width W of the cell stack body 11 but not its entire length.

[0046] Further, one or more plate elements 4 may be fixed at different directions on the open sides 5 of the cell stack body 11 to cover partially and / or entirely the respective open sides based on their shape. This will prevent the cell stack body 11 from being touched while partially covering the open sides 5 ensures adequate ventilation for the stack.

[0047] As shown in Figs 3 to 5, at least one clamping element 6 clamps the cell stack body 11 with the endplates 10 and 12 in the stacking direction, in which the plate element 4 is placed between the clamping element 6 and cell stack body 11 , whereby the plate element is held at the cell stack body 11. For example, in Fig. 3, plate element 4-8 is placed between clamping element 6-1 and cell stack body 11 on one open side, while plate element 4-7 is between clamping element 6-2 and cell stack body 11 on other open side. Thus, one or more plate elements 4 can be easily clamped by one or more clamping elements 6 and held in place along the open sides 5 of the fuel cell stack 11 without any further requirement of the fastening elements. However, it is also possible to fix the plate elements by additionally fixing elements to the clamping bands or directly to other components of the stack such as the endplates to ensure that the leave-on touch protection remains in place under all circumstances.

[0048] Figs. 2, 5 and 6 illustrate that at least one of the plate elements 4 may have a plurality of openings 2 arranged throughout its surface. As shown in Fig. 5, a space 14 between the plate element assembly 3, and cell stack body 11 is quite narrow and might become humid because of the moisture from cell stack body 11 . That in turn might cause water vapor to condense on the surface of plate element assembly 3. This condensed water 16 may trickle onto the stacked body or accumulate at the bottom plate of the housing 15, which in turn might result in a short circuit. To prevent this condensation issue, plate element 4 is provided with a plurality of openings 2 throughout their surface, ensuring sufficient aeration for the stack while providing touch protection for the stack.

[0049] The plurality of opening 2 is evenly distributed throughout the surface of plate element 4, as illustrated in Figs. 5 and 6, to provide sufficient aeration for the stack in all the places. Additionally, this plurality of opening 2 is arranged in a series of sequential rows 8, where the openings of one row 9 are offset from the openings of an adjacent row 7. This offset arrangement of openings 2 helps the condensed water vapor to evaporate before it drips onto the cell stack body 11 .

[0050] As shown in Fig. 7, the offset arrangement of the plurality of openings 2 guides the condensed water 16 to flow down around them, as indicated by arrow 18, thereby prolonging the flow path for the water. This in turn allows the heat from the cell stack body 11 to evaporate the condensed water 16 as it travels across the surface of the plate element 4, indicated by arrow 18, before the water has reach the bottom plate. This prevents the condensed water vapor 16 from dripping directly onto the bottom plate of the housing 15 and accumulating there, thereby preventing any short circuits that might be caused by accumulated water. Preferably, plate element 4 is made from an electrically isolating material, providing additional insulation to the cell stack body 11 and preventing any short circuit when removing or installing the fuel cell stack subunit 13 into the housing 15.

[0051] Alternatively, plate element 4 is made of non-electrically isolating material, such as metal, wherein the metal surface of plate element 4 is coated with an electrically insulating material. Thus, the plate element 4 acts as an electrical insulation to the cell stack body 11 while still benefiting from the structural integrity and conductivity of the metal material.

[0052] In summary, the fuel cell stack subunit 13, when mounted with one or more plate elements 4 with a plurality of openings on all its open sides 5. The exposed side of the cell stack body 11 is fully or partially covered and prevented from being touched, particularly when removing or installing the fuel cell stack subunit 13 into the housing 15. Further, the plurality of openings ensures sufficient aeration for the cell stack body 11 , preventing condensation of water vapor to avoid short circuit problems while also providing touch protection to the cell stack body 11 .

[0053] Although a single embodiment of the invention has been illustrated in the accompanying drawings and described in the above detailed description, it will be understood that the invention is not limited to the embodiment developed herein, but is capable of numerous rearrangements, modifications, substitutions of parts and elements without departing from the spirit and scope of the invention.

[0054] Reference numerals

[0055] 1 fuel cell stack assembly

[0056] 2 plurality of openings

[0057] 3 plate element assembly

[0058] 4 plate elements

[0059] 5 open sides of the stack body

[0060] 6 clamping band

[0061] 7 plurality of openings in adjacent row

[0062] 8 plurality of openings in sequential rows

[0063] 9 plurality of openings in row offset from the adjacent row

[0064] 10 first endplate

[0065] 11 cell stack body

[0066] 12 second endplate

[0067] 13 fuel cell stack subunit

[0068] 14 spaces between stack body and plate element assembly

[0069] 15 housing

[0070] 16 condensed water vapors

[0071] 18 directions of flow of condensed water vapor

[0072] 20 distance between housing and plate element

[0073] W width of the stack body

[0074] L Length

[0075] D direction of the stacking

Claims

Fuel Cell Stack AssemblyClaims:

1. Fuel cell stack assembly (1) comprising a fuel cell stack for generating electric energy and a housing (15) for housing the fuel cell stack, wherein the fuel cell stack comprises at least a plurality of alternatively arranged bipolar plates and membrane electrode assemblies stacked in a stacking direction (D), which form an energygenerating cell stack body (11), at least two endplates (10, 12) sandwiching the cell stack body (11) in the stacking direction (D), and at least one clamping element (6) which is adapted to clamp the cell stack body (11) and the first and second endplate (10, 12) together for forming a fuel cell stack subunit (13) which has at least one open sides (5), at which the cell stack body (11) is exposed to an environment, and two sides at which the cell stack body (11) is covered by the endplates (10, 12), wherein the fuel cell stack subunit (13) is housed in the housing (15), characterized in that the fuel cell stack subunit (13), which is housed in the housing (15), further has at least one plate element (4), which is arranged at at least one of the at least one open side (5) of the cell stack body (11) and covers at least partly the at least one open side (5) of the cell stack body (11) for preventing the cell stack body (11) from being touched.

2. Fuel cell stack assembly (1) according to claim 1 , wherein at all open sides (5) of the cell stack body (11) a plate element (4) is arranged, which covers at least partly the respective open side (5) of the cell stack body (11).

3. Fuel cell stack assembly (1 ) according to claim 1 or 2, wherein at least one plate element (4) extends in length (L) from the first endplate (10) to the second endplate4. Fuel cell stack assembly (1) according to any one of the preceding claims, wherein at least one plate element (4) extends over a width of the at least one open side of the cell stack body.

5. Fuel cell stack assembly (1) according to any one of the preceding claims, wherein at least one plate element (4) covers the entire respective open side (5) of the cell stack body (11).

6. Fuel cell stack assembly (1) according to any one of the preceding claims, wherein at least one plate element (4) has a plurality of openings (2).

7. Fuel cell stack assembly (1) according to claim 6, wherein the plurality of openings (2) is evenly distributed throughout the surface of the plate element (4).

8. Fuel cell stack assembly (1) according to any one of claims 6 to 7, wherein the plurality of opening (2) is arranged in a series of sequential rows (8), wherein the openings (2) of one row are arranged offset to the openings of an adjacent row (7).

9. Fuel cell stack assembly (1) according to any one of the preceding claims, wherein at least two plate elements (4) are combined for forming a plate element assembly (3).

10. Fuel cell stack assembly (1) according to any one of the preceding claims, wherein at least one plate element (4) is arranged between the cell stack body (11) and the at least one clamping element (6).

11. Fuel cell stack assembly (1 ) according to any one of the claims 6 to 10, wherein at least one of the openings (2) has a flange which protrudes towards the cell stack body (11).

12. Fuel cell stack assembly (1) according to any one of the preceding claims, wherein at least one plate element (4) is made from an electrically isolating material, such as a plastic material or a rubber material or a thermoplastic material.

13. Fuel cell stack assembly (1) according to any one of the preceding claims, wherein at least one plate element (4) is made from a non-electrically isolating material, such as a metal, and has at least one surface which is coated with an electrically insulating material.

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