Cell stack system for a fuel cell system

Abstract

The invention relates to a cell stack system (100) for a fuel cell system, having a plurality of cell stacks (110), each cell stack (110) having an anode section (120) and a cathode section (130), a tube system (50) for supplying anode supply gas (AZG) and cathode supply gas (KZG) to the cell stacks (110) and for discharging anode exhaust gas (AAG) and cathode exhaust gas (KAG) from the cell stacks (110), a distributor system (10) per cell stack (110), each distributor system (10) connecting the anode section (120) and the cathode section (130) of the corresponding cell stack (110) to the tube system (50) for a fluidic communication, and a holding device (70) for holding the cell stack (110), wherein the cell stacks (110) can be moved relative to the holding device (70), and the holding device (70) is mechanically separate from the tube system (50) or from the distributor systems (10).

Description

[0001] Cell stack system for a fuel cell system

[0002] The present invention relates to a cell stack system for a fuel cell system and in particular to a cell stack system in which cell stacks are movable relative to a holding device.

[0003] Cell stack systems for fuel cell systems are known in the prior art. Such cell stack systems comprise multiple cell stacks. Compensation for thermal expansion in these cell stack systems is typically achieved using compensation tubes, such as bellows tubes. The bellows tubes are usually radially symmetric and used in large numbers. These compensation tubes are repeatedly inserted in sections along the entire length of the tube system. Thermal compensation is coupled via the tube system with the fluid supply via the tube system. A disadvantage of this solution is that the compensation tubes require very fragile and costly high-temperature components, which increase the complexity of the cell stack system and can pose a sealing problem due to the need for additional welds or flanges.

[0004] Against this background, one object of the present invention is to at least partially remedy the disadvantages described above. In particular, the object of the present invention is to provide a cell stack system in which the compensation of the thermal length change is separated from the fluid supply.

[0005] The above objects are achieved by a cell stack system having the features of claim 1. Further features and details of the invention emerge from the subclaims, the description and the drawings.

[0006] Accordingly, a cell stack system for a fuel cell system is provided. The cell stack system comprises a plurality of cell stacks, each cell stack having an anode section and a cathode section, a piping system for supplying anode feed gas and cathode feed gas to the cell stacks and for discharging anode exhaust gas and cathode exhaust gas from the cell stacks, a manifold system per cell stack, each manifold system fluidly connecting the anode section and the cathode section of the corresponding cell stack to the piping system, and a holding device for holding the cell stacks, the cell stacks being movable relative to the holding device, and the holding device being mechanically separated from the piping system or manifold systems.

[0007] Because the holding device is mechanically separated from the piping or distribution systems, the fluid supply can be separated from the thermal expansion compensation. Thermal expansion compensation is achieved by allowing the cell stacks to move relative to the holding devices. The piping and distribution systems only fulfill the function of fluid supply, i.e., fluid inflow and fluid outflow.

[0008] The expression "wherein the holding device is mechanically separated from the piping system or the distribution systems" means that the holding device on the one hand and the piping system and the distribution systems on the other hand are not directly mechanically connected to one another. There is therefore no direct mechanical connection between the holding device on the one hand and the piping system and the distribution systems on the other. There is contact between the holding device and the cell stacks in that the cell stacks are held by the holding device. The cell stacks are movable relative to the holding device. There is also a fluid-communicating connection between the piping system and the distribution systems and between the distribution systems and the cell stacks.

[0009] In the present application, a fuel cell system is understood to mean a system (e.g., SOFC: Solid Oxide Fuel Cell) that has fuel cells for generating electrical energy using a fuel, or a system (e.g., SOEC: Solid Oxide Electrolyzer Cell) that has electrolysis cells for generating a fuel using electrical energy. A cell stack therefore comprises multiple fuel cells or multiple electrolysis cells.

[0010] The anode section of the cell stack supplies all cells (fuel cells or electrolysis cells) with anode feed gas and removes anode exhaust gas from all cells (fuel cells or electrolysis cells). The cathode section of the cell stack supplies all cells (fuel cells or electrolysis cells) with cathode feed gas and removes cathode exhaust gas from all cells (fuel cells or electrolysis cells).

[0011] According to one embodiment of the cell stack system, the cell stack system comprises connecting elements arranged between the holding device and the cell stacks. The connecting elements establish mechanical contact between the holding device and the cell stacks. The connecting elements allow the cell stacks to move relative to the holding device. Alternatively, the connecting elements can be omitted. In this case, direct mechanical contact occurs between the holding device and the cell stacks, whereby the cell stacks are also movable relative to the holding device.

[0012] According to a further embodiment of the cell stack system, the connecting elements are designed as sliding elements. The sliding elements slide on the holding device. The sliding elements can be mechanically firmly connected to the cell stacks.

[0013] According to a further embodiment of the cell stack system, the cell stack system has a plurality of sliding element fixing elements, wherein each sliding element is mechanically fixedly connected to a distribution system by means of a sliding element fixing element. Advantageously, the forces acting during the thermally induced movement of a cell stack are then not transmitted via the seal between the cell stack and the distribution system. The force for the movement is essentially transmitted between the cell stack and the distribution system via one or more sliding elements, in particular two sliding elements. Furthermore, the sliding element fixing elements can also consist of several parts, e.g., if the distribution system also has several sections.

[0014] According to a further embodiment of the cell stack system, the holding device is designed as a rail system, wherein the rail system has rails, and wherein the sliding elements are designed to slide on the rails. The rail system can provide a technologically simple and less error-prone system. In particular, the rail system can have two rails. According to a further embodiment of the cell stack system, the connecting elements are designed as rolling elements. The friction during rolling is generally lower than during sliding. Therefore, the rolling elements can reduce the friction compared to sliding elements. The cell stacks can therefore be moved particularly easily relative to the holding device.

[0015] According to another embodiment of the cell stacking system, the rolling elements are designed as balls. Advantageously, balls are particularly stable due to their shape, can bear high loads, and are easy to manufacture.

[0016] According to another embodiment of the cell stack system, the rolling elements are designed as cylinders. In particular, the cylinders can be circular cylinders. Circular-cylindrical rolling elements are also easy to manufacture.

[0017] According to a further embodiment of the cell stack system, each connecting element has a plurality of elastic elements. Due to the elastic elements, the cell stacks are movable relative to the holding device. In particular, the connecting element has between 2 and 5, between 2 and 8, between 2 and 10, or between 2 and 20 elastic elements. The elastic elements can be, for example, thin plates. The thin plates can comprise metal. Such plates can bend by a few millimeters. This allows a displacement of the cell stacks relative to the holding device by a few millimeters. In particular, this allows a displacement of the cell stacks relative to the holding device of 1 mm to 3 mm, 1 mm to 5 mm, 1 mm to 7 mm, or 1 mm to 10 mm.

[0018] According to a further embodiment of the cell stack system, the pipe system extends in a longitudinal direction. "The pipe system extends in a longitudinal direction" means that the pipe system preferably extends along a straight line. Alternatively, the longitudinal direction can also have one or more bends. With a pipe system extending in the longitudinal direction, the number of cell stacks can be increased particularly easily.

[0019] According to a further embodiment of the cell stack system, a single section of the pipe system is configured as a bellows tube at a fluid inlet of the pipe system. If the pipe system comprises multiple pipes, all pipes of the pipe system can have a single section configured as a bellows tube. The term "at a fluid inlet" means in the region of the fluid inlet. A bellows tube is a pipe whose pipe wall has a wave-like structure that can expand and contract in the pipe direction.

[0020] According to a further embodiment of the cell stack system, the pipe system comprises at least one anode supply pipe, at least one cathode supply pipe, at least one anode discharge pipe, and at least one cathode discharge pipe. Each distribution system comprises an anode supply section for supplying anode supply gas from the anode supply pipe to the anode section, an anode discharge section for discharging anode exhaust gas from the anode section to the anode discharge pipe, a cathode supply section for supplying cathode supply gas from the cathode supply pipe to the cathode section, and a cathode discharge section for discharging cathode exhaust gas from the cathode section to the cathode discharge pipe.

[0021] Accordingly, the pipe system comprises four or more pipes. The pipe system can also be fluidly connected to cell stacks arranged in two rows. In this case, the pipe system can, in particular, comprise two anode feed pipes or two cathode feed pipes.

[0022] According to a further embodiment of the cell stack system, the cell stack system has a holding device fixing element, wherein the pipe system is mechanically firmly connected to the holding device at a pipe system fixing point by means of the holding device fixing element. Because the pipe system is firmly connected to the holding device at the fixing point, the fixing point represents the reference point for the thermally induced linear expansion of the cell stack system. The cell stacks are movable relative to the holding device, as described above and below in the text. In particular, the cell stacks are movable in the longitudinal direction relative to the fixing point.Even the piping system, which is mechanically firmly connected to the holding device at the fastening point, can expand longitudinally with the holding device fastening point as a fixed point in the longitudinal direction, relative to this fixed point, due to thermal expansion. At the fluid inlet, the bellows tube facilitates the thermally induced length change of the piping system. The piping system end can be provided without a fluid connection. The fluid outlet can be on the side of the fluid inlet. In this case, a thermally induced length change does not impose any restrictions on the side of the piping system that has the piping system end.

[0023] According to a further embodiment of the cell stack system, the pipe system has a pipe system start, a pipe system end, and a pipe system length. The pipe system attachment point is at least 30% of the pipe system length, at least 35% of the pipe system length, at least 40% of the pipe system length, or at least 45% of the pipe system length away from the pipe system start and from the pipe system end. In particular, the pipe system attachment point is arranged substantially in the center of the pipe system. Because the pipe system attachment point and the holding device attachment point, which represents the reference point for thermal expansion, are firmly connected to one another, and the pipe system attachment point is arranged as centrally as possible in the pipe system, the difference in the thermally induced length change of the pipe system in both directions of the pipe system is not too great.

[0024] Further advantages, features, and details of the invention will become apparent from the following description, in which embodiments are described in detail with reference to the drawings. They show:

[0025] Fig. 1 is a schematic view of a cell stack system in a first embodiment;

[0026] Fig. 2 is a sectional view of the cell stack system of Fig. 1 along the line Illi;

[0027] Fig. 3 is a schematic detailed representation of a distribution system and a piping system;

[0028] Fig. 4 is a schematic view of a cell stack system in another embodiment; and Fig. 5 is a schematic view of a cell stack system in another embodiment.

[0029] Fig. 1 shows a schematic view of a cell stack system 100 in a first embodiment. The cell stack system 100 can be used as part of a fuel cell system. The cell stack system 100 comprises a plurality of cell stacks 110, a piping system 50, a distribution system 10 per cell stack 110, and a holding device 70. Each cell stack comprises an anode section 120 and a cathode section 130. The piping system 50 serves to supply anode feed gas AZG and cathode feed gas KZG to the cell stacks 110 and to discharge anode exhaust gas AAG and cathode exhaust gas KAG from the cell stacks 110. Each distribution system 10 connects the anode section 120 and the cathode section 130 of the corresponding cell stack 110 in fluid communication with the piping system 50.

[0030] The holding device 70 serves to hold the cell stacks 110. The cell stacks 110 are movable relative to the holding device 70. Furthermore, the holding device 70 is arranged mechanically separated from the pipe system 50 or the distribution systems 10, i.e., there is no direct mechanical connection between the holding device 70 on the one hand and the pipe system 50 and the distribution systems 10 on the other.

[0031] By mechanically separating the holding device 70 on the one hand and the pipe system 50 and the distribution systems 10 on the other, the fluid supply to the cell stack system 100 can be separated from the compensation for the thermal length change of the cell stack system 100. The compensation for the thermal length change of the cell stack system 100 is achieved by the relative mobility of the cell stacks 110 with respect to the holding device 70. In contrast, the pipe system 50 and the distribution systems 10 fulfill the function of supplying the anode feed gas AZG and the cathode feed gas KZG and the function of discharging the anode exhaust gas AAG and the cathode exhaust gas KAG.

[0032] Furthermore, Fig. 1 shows connecting elements 20, which are designed as sliding elements 22. The sliding elements 22 are arranged between the holding device 70 and the cell stacks 110. The sliding elements 22 are mechanically firmly connected to the cell stacks 110. The sliding elements 22 can slide on the holding device 70 to ensure the relative mobility of the cell stacks 110 to the holding device 70. Alternatively, there is no fixed connection between the sliding elements 22 and the cell stacks 110.

[0033] The holding device 70 can be designed as a rail system 80. The rail system 80 comprises a plurality of rails, in particular two rails. The sliding elements 22 are designed to slide on the rails.

[0034] As can be seen in Fig. 1, the distribution systems 10 establish a fluid-communicating connection between the pipe system 50 and the cell stacks 110. The distribution systems 10 are guided through recesses 12 of the holding device 70. Furthermore, the pipe system 50 extends in a longitudinal direction 52. With such a routing of the pipe system 50, the number of cell stacks 110 of the cell stack system 100 can be easily increased without having to make major changes to the cell stack system 100.

[0035] The cell stack system 100 can have a holding device fixing element 40. The holding device fixing element 40 establishes a mechanically fixed connection from a pipe system fixing point 42 of the pipe system 50 to a holding device fixing point 44 of the holding device 70. Thus, the holding device fixing point 44 of the holding device 70 represents a reference point for the thermally induced length change of the cell stack system 100. The cell stacks 110 are displaceable in the longitudinal direction 52 in both directions relative to the holding device fixing point 44 by means of the sliding elements 22. The pipe system 50 can also realize a thermally induced change in length in the longitudinal direction 52 in both directions relative to the holding device fastening point 44, since the pipe system is connected to the holding device 70 at the holding device fastening point 44 of the holding device 70.

[0036] At a fluid inlet 54 of the pipe system 50, a single section of the pipe system 50 can be configured as a bellows tube 56. The bellows tube 56 allows a thermally induced change in length of the pipe system 50 in the longitudinal direction 52 without causing problems with additional connections at the fluid inlet 54.

[0037] As shown in Fig. 1, the pipe system 50 has a pipe system start 46, a pipe system end 48, and a pipe system length L. The pipe system fastening point 42 is preferably arranged substantially in the center of the pipe system. In any case, the pipe system fastening point 42 is at least 30% of the pipe system length L, at least 35% of the pipe system length L, at least 40% of the pipe system length L, or at least 45% of the pipe system length L from the pipe system start 46 and the pipe system end 48. This ensures that the two sides of the pipe system 50 to the right and left of the pipe system fastening point 42 do not have excessively different thermally induced length changes in the longitudinal direction 52.

[0038] Fig. 2 shows a schematic sectional view of the cell stack system 100 of Fig. 1 along the line II-II. Shown are the cell stack 110, the distribution system 10, the pipe system 50, two connecting elements 20, which are designed as sliding elements 22, the holding device 70, which can be designed as a rail system 80, and two sliding element fixing elements 30. The two sliding elements 22 are mechanically firmly connected to the distribution system 10 by means of the two sliding element fixing elements 30. Due to the two sliding element fixing elements 30, the force caused by the thermally induced change in length of the cell stack system 100, which acts between the cell stack 110 and the distribution system 10, does not need to be transmitted via the seal between the cell stack 110 and the distribution system 10. Instead, the force can be transmitted via the sliding elements 22 between the cell stack 110 and the distribution system 10.

[0039] If the distribution system 10 has multiple sections, then the two sliding element fixing elements 30 may have multiple elements to mechanically connect the multiple sections to the two sliding elements 22.

[0040] The pipe system 50 shown in Fig. 2 can have several pipes and the distribution system shown in Fig. 2 can have several sections, as shown for example in Fig. 3.

[0041] Fig. 3 shows a schematic detailed representation of a distribution system 10 with several sections 122, 124, 132, 134 and a pipe system 50 with several pipes 62, 64, 66, 68. The pipe system 50 has an anode feed pipe 62, a cathode feed pipe 64, an anode discharge pipe 66 and a cathode discharge pipe 68. The distribution system 10 has an anode supply section 122 for supplying anode supply gas AZG from the anode supply pipe 62 to the anode section 120, an anode discharge section 124 for discharging anode exhaust gas AAG from the anode section 120 to the anode discharge pipe 66, a cathode supply section 132 for supplying cathode supply gas KZG from the cathode supply pipe 64 to the cathode section 130 and a cathode discharge section 134 for discharging cathode exhaust gas KAG from the cathode section 130 to the cathode discharge pipe 68.

[0042] Fig. 4 shows a schematic view of a cell stack system 100 in a further embodiment. Only the differences from the cell stack system 100 shown in Fig. 1 will be discussed. As shown in Fig. 4, the connecting elements 20 are designed as rolling elements 24. By means of the rolling elements 24, the cell stacks 110 can be movably mounted relative to the holding device 70. In particular, the rolling elements 24 can be designed as cylinders 28. The cylinders 28 are preferably circular cylinders. Alternatively, the rolling elements 24 can be designed as balls 26.

[0043] Fig. 5 shows a schematic view of a cell stack system 100 in a further embodiment. Only the differences from the cell stack system 100 shown in Fig. 1 will be discussed. As shown in Fig. 5, the connecting elements 20 have a plurality of elastic elements 36. By means of the elastic elements 36, the cell stacks 110 can be movably mounted relative to the holding device 70. The elastic elements can, in particular, comprise thin metal plates.

[0044] List of reference symbols

[0045] 10 distribution system

[0046] 12 Recess

[0047] 20 connecting element

[0048] 22 Sliding element

[0049] 24 rolling element

[0050] 26 balls

[0051] 28 cylinders

[0052] 30 Sliding element fixing element

[0053] 36 elastic elements

[0054] 40 Holding device-fixing element

[0055] 42 Pipe system fastening point

[0056] 44 Holding device - fastening point

[0057] 46 Pipe system start

[0058] 48 Pipe system end

[0059] 50 pipe system

[0060] 52 Longitudinal direction

[0061] 54 Fluid inlet

[0062] 56 bellows tube

[0063] 62 Anode feed pipe

[0064] 64 Cathode feed tube

[0065] 66 Anode discharge pipe

[0066] 68 Cathode discharge tube

[0067] 70 Holding device

[0068] 80 rail system

[0069] 100 cell stack system

[0070] 110 cell stacks

[0071] 120 anode section

[0072] 122 Anode feed section

[0073] 124 Anode discharge section

[0074] 130 Cathode section

[0075] 132 Cathode feed section

[0076] 134 Cathode discharge section AZG Anode feed gas

[0077] AAG anode exhaust gas

[0078] KZG cathode feed gas

[0079] KAG cathode exhaust gas

[0080] L Pipe system length

Claims

Patent claims 1. Cell stack system (100) for a fuel cell system, comprising a plurality of cell stacks (110), each cell stack (110) having an anode section (120) and a cathode section (130), a pipe system (50) for supplying anode feed gas (AZG) and cathode feed gas (KZG) to the cell stacks (110) and for discharging anode exhaust gas (AAG) and cathode exhaust gas (KAG) from the cell stacks (110), a distribution system (10) per cell stack (110), each distribution system (10) fluidly connecting the anode section (120) and the cathode section (130) of the corresponding cell stack (110) to the pipe system (50), characterized by a holding device (70) for holding the cell stacks (110), the cell stacks (110) being arranged relative to the holding device (70) are movable, and wherein the holding device (70) is mechanically separated from the pipe system (50) or the distribution systems (10).

2. Cell stack system (100) according to claim 1, characterized in that the cell stack system (100) has connecting elements (20) which are arranged between the holding device (70) and the cell stacks (110).

3. Cell stack system (100) according to claim 2, characterized in that the connecting elements (20) are designed as sliding elements (22).

4. Cell stack system (100) according to claim 3, characterized in that the cell stack system (100) has a plurality of sliding element fixing elements (30), wherein each sliding element (22) is mechanically fixedly connected to a distribution system (10) by means of a sliding element fixing element (30).

5. Cell stack system (100) according to claim 3 or 4, characterized in that the holding device (70) is designed as a rail system (80), wherein the rail system (80) has rails, and wherein the sliding elements (22) are designed to slide on the rails.

6. Cell stack system (100) according to claim 2, characterized in that the connecting elements (20) are designed as rolling elements (24).

7. Cell stack system (100) according to claim 6, characterized in that the rolling elements (24) are designed as balls (26).

8. Cell stack system (100) according to claim 6, characterized in that the rolling elements (24) are designed as cylinders (28).

9. Cell stack system (100) according to claim 2, characterized in that each connecting element (20) has a plurality of elastic elements (36).

10. Cell stack system (100) according to one of the preceding claims, characterized in that the pipe system (50) extends in a longitudinal direction (52).

11. Cell stack system (100) according to one of the preceding claims, characterized in that a single section of the pipe system (50) at a fluid inlet (54) of the pipe system (50) is designed as a bellows tube (56).

12. Cell stack system (100) according to one of the preceding claims, characterized in that the pipe system (50) has at least one anode feed pipe (62), at least one cathode feed pipe (64), at least one anode discharge pipe (66) and at least one cathode discharge pipe (68), wherein each distribution system (10) has an anode feed section (122) for feeding anode feed gas (AZG) from the anode feed pipe (62) to the anode section (120), an anode discharge section (124) for discharging anode exhaust gas (AAG) from the anode section (120) to the anode discharge pipe (66), a cathode feed section (132) for feeding cathode feed gas (KZG) from the cathode feed pipe (64) to the cathode section (130) and a cathode discharge section (134) for discharging cathode exhaust gas (KAG) from the cathode section (130) to the cathode discharge pipe (68).

13. Cell stack system (100) according to one of the preceding claims, characterized in that the cell stack system (100) has a holding device fixing element (40), wherein the pipe system (50) is mechanically firmly connected to the holding device (70) at a holding device fixing point (44) at a pipe system fixing point (42) by means of the holding device fixing element (40).

14. Cell stack system (100) according to claim 13, characterized in that the pipe system (50) has a pipe system start (46), a pipe system end (48) and a pipe system length (L), and the pipe system fastening point (42) is at least 30% of the pipe system length (L), at least 35% of the pipe system length (L), at least 40% of the pipe system length (L) or at least 45% of the pipe system length (L) away from the pipe system start (46) and the pipe system end (48).

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