FUEL CELL STACK

Abstract

The invention relates to a fuel cell stack having a variety of individual cells stacked up to form a stack, having at least one humidifier section integrated into the stack and arranged at one end of the individual cells as an electrochemical section. The invention is characterized in that a heat exchanger section is arranged on the side of the at least one humidifier section facing away from the electrochemical section, wherein flow plates for distributing fluids in at least three sections of the stack have the same external geometry.

Claims

1. A fuel cell stack having a variety of individual cells stacked up to form a stack, having at least one humidifier section integrated into the stack, which is arranged at one end of the individual cells as an electrochemical section, wherein on the side of the at least one humidifier section facing away from the electrochemical section, a heat exchanger section is arranged, wherein flow plates for distributing fluids in the at least three sections of the stack have the same external geometry, wherein in the heat exchanger section, thermally conductive, temperature-resistant foils are arranged between two flow plates, through which the inflowing gas and outflowing gas flow alternately.

2. The fuel cell stack as claimed in claim 1, wherein flow occurs through the flow plates of each section in parallel and flow occurs through the at least three sections in series, wherein inflowing, compressed air flows first through the heat exchanger section, then through the humidifier section, and then through a cathode side of the electrochemical section.

3. The fuel cell stack as claimed in claim 1, wherein the connection openings of the flow plates of the at least three sections have the same geometry, wherein distributor plates for the media are arranged between the sections.

4. canceled.

5. The fuel cell stack as claimed in claim 1, wherein membranes which are permeable to water vapor are arranged in the humidifier section between each two flow plates, through which the inflowing gas and outflowing gas flow alternately.

6. The fuel cell stack as claimed in claim 5, wherein two of the flow plates which each have cooling medium channels on their back are combined to form a structure, on one side of which the inflowing gas flows and on the other side of which the outflowing gas flows.

7. The fuel cell stack as claimed in claim 1, wherein the flow plates of the heat exchanger section and/or the humidifier section have flow fields, in particular similar to the flow fields in the electrochemical section, wherein the flow fields on each of the surfaces are connected to different connection openings and are alternately stacked with membranes and/or foils arranged in between.

8. The fuel cell stack as claimed in claim 1, wherein the humidifier sections and heat exchanger sections are arranged at one end of the electrochemical section.

9. The fuel cell stack as claimed in claim 1, wherein the humidifier sections and heat exchanger sections are arranged at both ends of the electrochemical section.

10. A use of a fuel cell stack as claimed in claim 1 for providing electrical power in an at least partially electrically driven vehicle.

11. The fuel cell stack as claimed in claim 2, wherein the connection openings of the flow plates of the at least three sections have the same geometry, wherein distributor plates for the media are arranged between the sections.

12. The fuel cell stack as claimed in claim 2, wherein membranes which are permeable to water vapor are arranged in the humidifier section between each two flow plates, through which the inflowing gas and outflowing gas flow alternately.

13. The fuel cell stack as claimed in claim 3, wherein membranes which are permeable to water vapor are arranged in the humidifier section between each two flow plates, through which the inflowing gas and outflowing gas flow alternately.

14. The fuel cell stack as claimed in claim 3, wherein membranes which are permeable to water vapor are arranged in the humidifier section between each two flow plates, through which the inflowing gas and outflowing gas flow alternately.

15. The fuel cell stack as claimed in claim 2, wherein the flow plates of the heat exchanger section and/or the humidifier section have flow fields, in particular similar to the flow fields in the electrochemical section, wherein the flow fields on each of the surfaces are connected to different connection openings and are alternately stacked with membranes and/or foils arranged in between.

16. The fuel cell stack as claimed in claim 3, wherein the flow plates of the heat exchanger section and/or the humidifier section have flow fields, in particular similar to the flow fields in the electrochemical section, wherein the flow fields on each of the surfaces are connected to different connection openings and are alternately stacked with membranes and/or foils arranged in between.

17. The fuel cell stack as claimed in claim 3, wherein the humidifier sections and heat exchanger sections are arranged at one end of the electrochemical section.

18. The fuel cell stack as claimed in claim 5, wherein the humidifier sections and heat exchanger sections are arranged at both ends of the electrochemical section.

19. The fuel cell stack as claimed in claim 6, wherein the humidifier sections and heat exchanger sections are arranged at both ends of the electrochemical section.

20. The fuel cell stack as claimed in claim 7, wherein the humidifier sections and heat exchanger sections are arranged at both ends of the electrochemical section.

21. A use of a fuel cell stack as claimed in claim 2, for providing electrical power in an at least partially electrically driven vehicle.

Description

IN THE FIGURES

[0017] FIG. 1 shows a schematic representation of a first possible embodiment of a fuel cell stack according to the invention;

[0018] FIG. 2 shows an alternative possible embodiment of a fuel cell stack according to the invention in a representation similar to that in FIG. 1;

[0019] FIG. 3 shows a top view of a flow plate as can be used, for example, in the area of the section used as a charge air cooler or humidifier;

[0020] FIG. 4 shows a schematic sectional view through a section of flow plates in the section used as a charge air cooler and/or humidifier having flow plates according to FIG. 3;

[0021] FIG. 5 shows a flow plate similar to that in FIG. 3 in an alternative embodiment; and

[0022] FIG. 6 shows a structure similar to that in FIG. 4 having flow plates according to the structure shown in FIG. 5.

[0023] In the representation of FIG. 1, a possible structure of a fuel cell stack 1 is shown in an embodiment according to the invention. There are three sections between two end plates designated by 2. An electrochemical section 3, which is provided with a variety of individual cells for providing the electrical power. This section 3 consists of stacked individual cells in PEM technology and essentially corresponds to a conventional fuel cell stack or fuel cell stack, respectively. A humidifier section 4 is located adjacent, followed by a heat exchanger section 5. The humidifier section 4 is used to humidify the supply air flowing into the electrochemical section 3 in which moisture from the exhaust air of the electrochemical section 3 is used for humidification. The structure is a plate humidifier having membranes 22 permeable to water vapor, which are shown later.

[0024] The heat exchanger section 5 is used as an charge air cooler in order to correspondingly cool the supply air, which is typically hot and dry after its compression, for example from temperatures of 200 to 250° C., which are typical after compression, to a temperature level of approximately 100° C., for example 80 to 120° C. The flow path is now shown by the arrows. The supply air flows into the heat exchanger section 5 on one side thereof at the point designated by 6 and flows through it. It is then deflected by a distribution plate (not shown here) after it has flowed through the flow plates of the heat exchanger section 5 in parallel. Now it flows in series through the humidifier section 4, within which it also flows through the individual flow plates in parallel to one another. The supply air flow cooled and humidified in this way then arrives in the area of a further distribution plate and at the point designated here as 7 in the electrochemical section 3 and flows through its individual cells in parallel. The moist exhaust air from the electrochemical section 3 then returns to the humidifier section 4 at the point designated 8 and releases the moisture contained therein to the supply air. The exhaust air then flows into the heat exchanger section 5 and absorbs heat from the supply air flow before it flows out of the fuel cell stack 1 again at point 9.

[0025] In the exemplary embodiment shown here, this entire structure is provided at one end of the electrochemical section 3 and is integrated between the end plates 2 of the structure. Alternatively, thereto, the structure could also be designed as indicated in FIG. 2. In this case, the structure is correspondingly integrated at both ends of the electrochemical section 3, without the flow being explicitly drawn again here, which makes additional connecting lines necessary. In addition, the two end plates 2 are arranged in a conventional manner directly adjacent to the electrochemical section 3, while the humidifier sections 4 and the heat exchanger sections 5 are provided as charge air coolers outside the end plates 2 on both sides. Both structures according to FIGS. 1 and 2 can be combined with one another as desired, so the structure could also be provided on both sides of the electrochemical section 3 inside the end plates 2, for example, or only on one side, similarly to the representation in FIG. 1 but outside of the end plate 2, as indicated in FIG. 2.

[0026] The individual sections 3, 4, 5 now comprise flow plates 10, 10′. These flow plates 10, 10′, which are often designed as bipolar plates, are fundamentally known to the person skilled in the art from the field of the electrochemical section and here of the individual cells. This type of flow plates can now also be used largely identically in the other sections 4, 5, wherein it is also possible in particular here to switch to more cost-effective materials and manufacturing processes for the flow plates, but without changing the geometry thereof, and this relates in particular to the external geometry and the geometry of connection openings. The entire structure can then be stacked in the manner known from the electrochemical section 3 and sealed via seals between the individual flow plates 10, 10′ easily, reliably, and in the manner known per se.

[0027] A top view of a possible structure of two such flow plates 10, 10′ can be seen in the representation of FIG. 3. They comprise three connection openings on each side. These connection openings are designated by reference numerals 11, 12, and 13 on one side and 14, 15, 16 on the other side. In the case of the flow plate 10 shown here on the left, the connections 11 and 16 on the side facing the viewer are now to be connected to one another via a flow field 17, which is indicated accordingly by the corresponding areas between the flow field 17 and the respective connection openings 11 and 16, the so-called manifolds 18. A flow channel designated by 20 is thus formed. The two cooling water connections 12, 15 are then connected to one another on the opposite side of the flow plate 10, which is not visible here. A cooling medium channel designated by 19 is thus formed. On the next flow plate 10′, which is shown here on the right, the cooling water connections 12 and 15 are in turn connected to one another on one side, while the connections 13 and 14 are connected to one another on the visible side. A flow channel designated by 21 is thus formed. As is known from the area of the flow plates 10, 10′ in the electrochemical section 3, these flow plates 10, 10′ are now positioned with their backs against one another, so that the channel 19 for the cooling medium is created between the flow plates 10, 10′. If these structures 100 made up of flow plates 10, 10′ connected to one another are stacked in mirror image to one another, the channels 20 through which one medium flows and the channels 21 through which the other medium flows always lie opposite to one another between the individual structures 100 made up of flow plates 10, 10′. This can be seen in the schematic sectional illustration of FIG. 4 through a small section of the respective section 4, 5. Between the individual plates 10, 10′ of the structure 100, the channel for the cooling medium, designated by 19 here, results on one side of the structure, for example on the surface of the flow plate 10, the channel designated by 20 for one medium results on the opposite side on the surface of the other flow plate 10′ in a channel for the other medium. This is designated by 21. A membrane or foil 22 is now arranged between the channels 20, 21 for the one and the other medium, and it can thus be seen in the illustration of FIG. 4. In the area of the humidifier section 4, this membrane or foil 22 can be a membrane permeable to water vapor, which thus enables an exchange of water vapor between the media flowing in the channel 20 and 21. Therefore, the dry supply air and the moist exhaust air are conducted in the respective channels 20, 21 in order to be able to humidify the dry supply air in the humidifier section 4 by way of the moist exhaust air. In the area of the heat exchanger section 5, such membranes are typically unsuitable because they do not withstand the relatively high temperatures of the compressed, dry, and hot supply air, or do not do so in the long term. For this reason, metal foils and graphite foils can be used as a membrane or foil 22 or the like, which are correspondingly temperature-resistant and enable good heat exchange between the hot supply air and the much cooler exhaust air. In addition, temperature control can also be achieved in both cases via the cooling medium flowing in the cooling channel 19, similarly to the structure of the individual cells in the electrochemical area 3.

[0028] As an alternative to this structure described in FIGS. 3 and 4, however, a variant is also conceivable which is of correspondingly simpler design and dispenses with the additional through-flow of cooling medium and the cooling channel 19 required for this. Only a single flow plate 10 is then necessary for this purpose, as indicated accordingly in the representation of FIG. 5. This flow plate 10 corresponds in its geometry to the previously shown flow plate 10. On the back, which cannot be seen here, it is not the openings 12 and 15 that are connected to one another, but the openings 13 and 14, so that a structure is created, so to speak which has on one side the one side of the above-described flow plate 10 and on the other side the one side of the above-described flow plate 10′. These flow plates 10 can now be stacked directly alternately mirrored to one another with the membranes or foils 22, as is indicated in the illustration in FIG. 6 similarly to the illustration in FIG. 4. This structure can be implemented even more simply and compactly and can, in particular, manage without active cooling of the sections 4 and 5. It would of course also be conceivable to actively cool only one of the sections, i.e., to design the structure according to FIGS. 3 and 4 and not the other of the sections, and to carry out the structure there according to FIGS. 5 and 6.

[0029] It is the case that the typical geometry of the connection openings 11 to 16 can also be used here in order to keep the geometry of the stack the same over all sections 3, 4, 5, in particular in the case of an integrated arrangement between the end plates. The openings 12 and 15 typically provided for the cooling water can then, for example, not be used or can also be combined with other openings. For example, the openings 11 and 12 can be used as a common inflow opening for one medium and accordingly the openings 15 and 16 can be used as common outflow openings. This can be done, for example, by connecting the individual openings in the top and bottom areas to one another, or the openings can each be connected to the flow field 17 with their own manifolds 18. In principle, it is also conceivable to provide separate sections for one and the other flow within the flow field 17. All variants are conceivable and possible here, in particular according to the design of the humidifier section 4 or heat exchanger section 5 and the volume flows and flow cross sections required according to this design in the respective sections 4, 5.