Thermal Managing End Plate For Fuel Cell Stack Assembly

Abstract

Fuel cell stack assemblies having a positive end plate and a negative end plate. The end plates can be formed from a central structural element with an insulating end plate cover and an insulating end plate manifold. A plurality of cathode plates and a plurality of fuel cell assemblies can be arranged in a stack having an alternating pattern of cathode plates and fuel cell assemblies, with the positive end plate and the negative end plate provided on either end of the stack of cathode plates and fuel cell assemblies.

Claims

1. An asymmetrical fuel cell stack assembly comprising: a fuel cell stack assembly having a positive end plate and a negative end plates formed from structural elements which have different structural features; an end plate manifold formed from electrically insulating materials, such as plastic; at least one structural element configured with voids from a top face to a bottom face; wherein the voids reduces the thermal flux transfer pathways from the environment outside the assembly; and, wherein the heat loss at least one end plate manifold is reduced.

2. The asymmetrical fuel cell stack assembly of claim 1 wherein at least one end plate is configured to engage an end plate cover.

3. The asymmetrical fuel cell stack assembly of claim 1 further comprising at least one end plate cover.

4. The asymmetrical fuel cell stack assembly of claim 1 wherein the negative end plate manifold has-sinusoidal-wave-shaped air flow channels from a first side edge to an opposing side edge.

5. The asymmetrical fuel cell stack assembly of claim 1 further comprising the positive end plate manifold has air flow formed as straight-walls from the first side edge to the opposing side edge.

6. The asymmetrical fuel cell stack assembly of claim 1 further comprising: a plurality of fuel cell assemblies; and, wherein the structural elements are configured to apply a compressive mechanical force to at least the fuel cell assemblies between them.

7. The asymmetrical fuel cell stack assembly of claim 1 wherein the heat loss at the negative end plate manifold is reduce at least 20%.

8. The asymmetrical fuel cell stack assembly of claim 1 wherein the heat loss at the negative end plate manifold is reduce at least 25%.

9. The asymmetrical fuel cell stack assembly of claim 1 wherein the heat loss at the negative end plate manifold is reduce about 30%.

10. The asymmetrical fuel cell stack assembly of claim 1 wherein the heat loss at the at the positive end plate manifold is reduce at least 20%

11. The asymmetrical fuel cell stack assembly of claim 1 wherein the heat loss at the at the positive end plate manifold is reduce at least 25%.

12. The asymmetrical fuel cell stack assembly of claim 1 wherein the heat loss at the positive end plate manifold is reduce about 28%.

13. A method of balancing heat removal from an operational fuel cell stack to increase the operating temperature window, the method comprising: forming an asymmetrical fuel cell stack assembly having a positive end plate and a negative end plate which have different structural features; wherein the negative end plate manifold (330) has-sinusoidal-wave-shaped air flow channels from a first side edge (331) to an opposing side edge (332); wherein the positive end plate manifold has air flow formed as straight-walls from the first side edge (231) to the opposing side edge (232); and, wherein heat loss from at least one end plate manifold is reduced.

14. The method of balancing heat removal from an operational fuel cell stack of claim 13 wherein in the heat loss at the negative end plate manifold is reduce at least 20%.

15. The method of balancing heat removal from an operational fuel cell stack of claim 13 wherein in the heat loss at the negative end plate manifold is reduce at least 25%.

16. The method of balancing heat removal from an operational fuel cell stack of claim 13 wherein in the heat loss at the negative end plate manifold is reduce about 30%.

17. The method of balancing heat removal from an operational fuel cell stack of claim 13 wherein in the heat loss at the positive end plate manifold is reduce at least 20%

18. The method of balancing heat removal from an operational fuel cell stack of claim 13 wherein in the heat loss at the positive end plate manifold is reduce at least 25%.

19. The method of balancing heat removal from an operational fuel cell stack of claim 13 wherein in the heat loss at the positive end plate manifold is reduce about 28%.

Description

DRAWINGS

[0013] The summary, as well as the following detailed description, is further understood when read in conjunction with the appended drawings. For the purpose of illustrating the disclosure, there are shown in the drawings exemplary implementations of the disclosure; however, the disclosure is not limited to the specific methods, compositions, and devices disclosed. In the figures, like reference numerals designate corresponding parts throughout the different views. All callouts and annotations are hereby incorporated by this reference as if fully set forth herein. In addition, the drawings are not necessarily drawn to scale. In the drawings:

[0014] FIG. 1 illustrates aspects of an exploded side view of components of a fuel cell stack assembly of the present disclosure;

[0015] FIG. 2 illustrates aspects of an exploded side view of components of a positive end plate of the present disclosure; and

[0016] FIG. 3 illustrates aspects of an exploded side view of components of a negative end plate of the present disclosure.

FURTHER DISCLOSURE

[0017] The present disclosure may be understood more readily by reference to the following detailed description taken in connection with the accompanying figures and examples, which form a part of this disclosure. It is to be understood that this disclosure is not limited to the specific devices, methods, applications, conditions or parameters described and/or shown herein, and that the terminology used herein is for the purpose of describing particular exemplars by way of example only and is not intended to be limiting of the claimed disclosure. Also, as used in the specification including the appended claims, the singular forms “a,” “an,” and “the” include the plural, and reference to a particular numerical value includes at least that particular value, unless the context clearly dictates otherwise. The term “plurality”, as used herein, means more than one. When a range of values is expressed, another exemplar includes from the one particular value and/or to the other particular value. Similarly, when values are expressed as approximations, by use of the antecedent “about,” it will be understood that the particular value forms another exemplar. All ranges are inclusive and combinable.

[0018] It is to be appreciated that certain features of the disclosure which are, for clarity, described herein in the context of separate exemplar, may also be provided in combination in a single exemplary implementation. Conversely, various features of the disclosure that are, for brevity, described in the context of a single exemplary implementation, may also be provided separately or in any subcombination. Further, reference to values stated in ranges include each and every value within that range.

[0019] FIG. 1 shows a schematic side view of an exploded assembly of a fuel cell stack assembly of the present disclosure. A positive end plate 200 and a negative end plate 300 are provided on either end of the fuel cell stack assembly 100. When assembled, compressive force is applied between the positive end plate 200 and negative end plate 300 to compress the internal layers together with sufficient force for optimal electrical performance. The internal layers include a plurality of cathode plates 150.sub.1 to 150.sub.n and fuel cell assemblies 250.sub.1 to 250.sub.n, provided in alternating layers of cathode plates and fuel cell assemblies. Cathode plate 150.sub.n is adjacent to the positive end plate 200, while the negative end plate 300 is adjacent to the first fuel cell assembly 250.sub.1. Current collection can be achieved directly from the end cells, 250.sub.1 and 250.sub.n, or via current collector plates (not shown) that are disposed between each of the end cells and adjacent end plates 200, 300. The use of current collector plates can avoid ohmic losses and improve performance.

[0020] It has been observed that with conventional end plates, a fuel cell stack assembly cannot be operated in low environmental temperatures without cathode air recirculation to maintain an adequate temperature on the top and bottom fuel cells (the fuel cells within the first and n-th fuel cell assemblies 250.sub.1 and 250.sub.n). The temperature problems with the top and bottom fuel cells were determined to result from overcooling or overheating due to a lack of thermal insulation provided by the end plates from the surrounding environmental temperatures. Conventional end plates are formed from cast or machined metallic materials which are overmoulded with suitable polymeric compounds to provide suitable electrical isolation. Alternatively, conventional end plates can be formed as molded polymeric reinforced laminates. Such known endplates can provide an excess of thermal flux outward from the adjacent fuel cells. In particular, the top fuel cell can experience overcooling, due to being surrounded on both sides with cathode plates 150.sub.n and 150.sub.n-1, with only cathode plate 150.sub.n-1 experiencing heating from another adjacent fuel cell assembly 250.sub.n-1. Cathode plate 150.sub.n can provide overcooling as it is not heated by another adjacent fuel cell and is instead thermally contacting the positive end plate 200. Accordingly, the top fuel cell can be overcooled when a conventional positive end plate is utilized in a fuel cell stack. Conversely, the bottom fuel cell 250.sub.1 can be overheated in certain operational environments as it is only adjacent to one cathode plate and receives some limited cooling effects from the negative end plate 300.

[0021] In one aspect, the present disclosure provides improved designs for the positive end plates 200 and negative end plates 300 for use in the fuel cell stack assemblies as shown in FIG. 1. It has been discovered through experimentation that a more even temperature profile across the fuel cell assemblies 250.sub.1 and 250.sub.n can be achieved by utilizing end plates formed from a plurality of components, rather than an overmolded metallic piece.

[0022] FIG. 2 shows aspects of a schematic of an exploded side view of a positive end plate 200 of the present disclosure. A positive end plate 200 can be formed from a central structural element 220, which is covered on a top face 221 by a positive end plate cover 210, and covered on a bottom face 222 by a positive end plate manifold 230. Positive end plate manifold 230 is adjacent to the n-th cathode plate 150.sub.n in the assembled fuel cell stack assembly. Central structural element 220 is formed from a sufficiently rigid material in order to provide structural strength to withstand the overall compression forces on the assembled fuel cell stack. In certain implementations, the structural element 220 can be formed from a lightweight metal such as aluminum. In other implementations, rigid materials such as a para-aramid synthetic fiber or carbon fiber composites can be used, provided that strength/weight performance is adequate to provide desired power/mass density for the overall fuel cell stack assembly. The positive end plate cover 210 and positive end plate manifold 230 are formed from electrically insulating materials, such as plastic. In certain implementations, the positive end plate cover 210 and positive end plate manifold 230 are releasably engageable to each other through a portion of the central structural element 220 via a plurality of snap clips. This engagement can aid in the assembly process, such that the positive end plate 200 can hold itself together while the fuel cell stack assembly components are layered together prior to application of the desired compression force.

[0023] In some implementations, positive end plate cover 210 and positive end plate manifold 230 are formed from plastic or polymeric resin materials. Suitable materials can withstand operational temperatures within the fuel cell stack assembly, are compatible with hydrogen gas, and can be PC-ABS blends, PET, glass-filled PET, PA6, glass-filled PA6, PBT, PEI, or mixtures thereof. In certain implementations, one or both of the positive end plate cover 210 and positive end plate manifold 230 can be formed from glass-filled PET, including RYNITE® sold by DuPont USA Performance Polymers.

[0024] In certain implementations, the thermal insulation is increased by reducing the contact area between the structural element 220 and the positive end plate cover 210, and reducing the contact area between the structural element 220 and positive end plate manifold 230. The contact areas can be reduced by removing as much of the hulk material within the structural element 220 by creating a rib-and-core or honeycombed structure in the structural element 220, with voids formed extending from the top face 221 to the bottom face 222. The inclusion of voids in the structural element 220 reduces the thermal flux transfer pathways from the outside environment of the fuel cell stack assembly and the top-most fuel cell assembly 250.sub.n.

[0025] The positive end plate manifold 230 can be provided with a ribbed structure to provide for fluid flow channels as well as a reduced contact area between the positive end plate manifold 230 and the structural element 220. Air flow is provided from one side edge 231 to an opposing side edge 232 of the positive end plate manifold 230. In some implementations, in order to reduce heat removal and avoid overcooling of the top-most fuel cell assembly 250.sub.n, straight-walled airflow channels can be provided to allow for the fastest airflow through past the positive end plate manifold 230 and adjacent cathode plate 150.sub.n and avoid excessive heat removal.

[0026] FIG. 3 shows aspects of a schematic of an exploded side view of a negative end plate 300 of the present disclosure. A negative end plate 300 can be formed from a central structural element 320, which is covered on a top face 322 by a negative end plate cover 310, and covered on a bottom face 321 by a negative end plate manifold 330. Negative end plate manifold 330 is adjacent to the first fuel cell assembly 250.sub.1 in the assembled fuel cell stack assembly. Central structural element 320 is formed from a sufficiently rigid material in order to provide structural strength to withstand the overall compression forces on the assembled fuel cell stack. In certain implementations, the structural element 320 can be formed from a lightweight metal such as aluminum. In other implementations, rigid materials such as a para-aramid synthetic fiber or carbon fiber composites can be used, provided that strength/weight performance is adequate to provide desired power/mass density for the overall fuel cell stack assembly. The negative end plate cover 310 and negative end plate manifold 330 are formed from electrically insulating materials, such as plastic. In certain implementations, the negative end plate cover 310 and negative end plate manifold 330 are releasably engageable to each other through a portion of the central structural element 320 via a plurality of snap clips. This engagement can aid in the assembly process, such that the negative end plate 300 can hold itself together while the fuel cell stack assembly components are layered together prior to application of the desired compression force.

[0027] In some implementations, negative end plate cover 310 and negative end plate manifold 330 are formed from plastic or polymeric resin materials. Suitable materials can withstand operational temperatures within the fuel cell stack assembly, are compatible with hydrogen gas, and can be PC-ABS blends, PET, glass-filled PET, PA6, glass-filled PA6, PBT, PET, or mixtures thereof. In certain implementations, one or both of the negative end plate cover 310 and negative end plate manifold 330 can be formed from glass-filled PET, including RYNITE® sold by DuPont USA Performance Polymers.

[0028] In certain implementations, the thermal insulation is increased by reducing the contact area between the structural element 320 and the negative end plate cover 310, and reducing the contact area between the structural element 320 and negative end plate manifold 330. The contact areas can be reduced by removing as much of the bulk material within the structural element 320 by creating a rib-and-core or honeycombed structure in the structural element 320, with voids formed extending from the top face 322 to the bottom face 321. The inclusion of voids in the structural element 320 reduces the thermal flux transfer pathways from the outside environment of the fuel cell stack assembly and the first fuel cell assembly 250.sub.1.

[0029] The negative end plate manifold 330 can be provided with a ribbed structure to provide for fluid flow channels as well as a reduced contact area between the negative end plate manifold 330 and the structural element 320. Air flow is provided from one side edge 331 to an opposing side edge 332 of the negative end plate manifold 330. In some implementations, in order to increase heat removal and avoid overheating of the first fuel cell assembly 250.sub.1, sinusoidal-wave-shaped airflow channels can be provided to slow the airflow through past the negative end plate manifold 330 and adjacent fuel cell assembly 250.sub.1 and avoid excessive heat buildup. Further description of suitable sinusoidal wave-shaped airflow channels is provided in co-pending UK patent application entitled “COOLING PLATES FOR FUEL CELLS” filed on the same day as this application, the contents of which are hereby incorporated by reference in their entirety.

[0030] In some aspects, the present disclosure provides for an asymmetrical fuel cell stack assembly having a positive end plate and a negative end plate which have different structural features in order to have different thermal transfer properties. As described above, the negative end plate can utilize a negative end plate manifold having air flow channels designed for greater heat removal from an adjacent component as compared to the positive end plate manifold, which has air flow channels designed for less heat removal from an adjacent component. Such an implementation was found to provide the optimal balance of heat removal from an operational fuel cell stack assembly and thermal insulation from a surrounding environmental condition. Accordingly, the potential operating temperature window can be increased.

Example 1

[0031] A negative end plate 300 of the present disclosure as depicted in FIG. 3 was modeled for 3D FEA thermal analysis. The negative end plate 300, was modeled from an aluminum central structural element 320, which is covered on a top face 322 by a negative end plate cover 310, and covered on a bottom face 321 by a negative end plate manifold 230. The negative end plate cover 310 and the negative end plate manifold 230 were modeled as glass-filled PA6 nylon. A conventional end plate, formed from cast, then machined, aluminum overmolded with glass-filled PA6 nylon was modeled for 3D FEA thermal analysis for comparison. Heat loss was reduced from 25.27 W to 17.6 W.

Example 2

[0032] A positive end plate 200 of the present disclosure as depicted in FIG. 3 was modeled for 3D FEA thermal analysis. The positive end plate 200, was modeled from an aluminum central structural element 220, which is covered on a top face 221 by a positive end plate cover 210, and covered on a bottom face 222 by a positive end plate manifold 230. The positive end plate cover 210 and the positive end plate manifold 230 were modeled as glass-filled PA6 nylon. A conventional end plate, formed from cast, then machined, aluminum overmolded with glass-filled PA6 nylon was modeled for 3D FEA thermal analysis for comparison. Heat loss was reduced from 28.78 W to 20.85 W.

[0033] Those of ordinary skill in the art will appreciate that a variety of materials can be used in the manufacturing of the components in the devices and systems disclosed herein. Any suitable structure and/or material can be used for the various features described herein, and a skilled artisan will be able to select an appropriate structures and materials based on various considerations, including the intended use of the systems disclosed herein, the intended arena within which they will be used, and the equipment and/or accessories with which they are intended to be used, among other considerations. Conventional polymeric, metal-polymer composites, ceramics, and metal materials are suitable for use in the various components. Materials hereinafter discovered and/or developed that are determined to be suitable for use in the features and elements described herein would also be considered acceptable.

[0034] When ranges are used herein for physical properties, such as molecular weight, or chemical properties, such as chemical formulae, all combinations, and subcombinations of ranges for specific exemplar therein are intended to be included.

[0035] The disclosures of each patent, patent application, and publication cited or described in this document are hereby incorporated herein by reference, in its entirety.

[0036] Those of ordinary skill in the art will appreciate that numerous changes and modifications can be made to the exemplars of the disclosure and that such changes and modifications can be made without departing from the spirit of the disclosure. It is, therefore, intended that the appended claims cover all such equivalent variations as fall within the true scope of the disclosure as defined in the appended claims.