Cell stack with a large number of electrochemical cells stacked on top of each other

Abstract

The invention relates to a cell stack (12) comprising a plurality of electrochemical cells (10) stacked one above the other. At least one inlet channel (30) and at least one outlet channel (32) for supplying and discharging a medium to the cells (10) are formed in the cell stack (12). The inlet channel (30) and the outlet channel (32) are formed by respective recesses in the cells (10). The inlet channel (30) and the outlet channel (32) each have an open end (52) and a closed end (50) with respect to the cell stack (12). Both the open end (52) of the inlet channel (30) and the open end (52) of the outlet channel (32) are arranged on a common first side (48) of the cell stack (12). A tube (60) is arranged in the inlet channel (30), the tube (60) extending from the open end (52) to nearly the closed end (50) of the inlet channel (30). The tube (60) has at least one opening (62, 63) near the closed end (50).

Description

Technical field

[0001] The invention relates to a cell stack comprising a plurality of electrochemical cells stacked one above the other. State of the art

[0002] Electrochemical cells are electrochemical energy converters and are known in the form of fuel cells or electrolysis cells.

[0003] A fuel cell converts chemical reaction energy into electrical energy. In conventional fuel cells, hydrogen (H2) and oxygen (O2) are converted into water (H2O), electrical energy, and heat.

[0004] In contrast to a fuel cell, an electrolysis cell is an energy converter which, when electrical voltage is applied, preferentially splits water into hydrogen and oxygen.

[0005] DE102022205235 discloses a cell stack comprising a plurality of electrochemical cells stacked one above the other. At least one inlet channel and at least one outlet channel are formed in the cell stack for supplying and discharging a medium (e.g., water, oxygen, or hydrogen) to and from the cells. The inlet channel and the outlet channel are formed by respective recesses or ports in the cells, as shown, for example, in DE102020215024 A1 using bipolar plates. The inlet channel and the outlet channel each have an open end and a closed end with respect to the cell stack. Both the open end of the inlet channel and the open end of the outlet channel are arranged on a common first side of the cell stack; this can also be referred to as a U-flow.Furthermore, a cell stack is also known which has the open end of the inlet channel and the open end of the outlet channel on opposite sides of the cell stack; this can also be referred to as a Z-flow.

[0006] The object of the present invention is to combine the advantages of these two fundamental alternatives. Disclosure of the invention

[0007] For this purpose, the cell stack with a plurality of electrochemical cells stacked one above the other has at least one inlet channel and at least one outlet channel for supplying and discharging a medium to the cells. The inlet channel and the outlet channel are formed by respective recesses in the cells. The inlet channel and the outlet channel each have an open end and a closed end with respect to the cell stack. Both the open end of the inlet channel and the open end of the outlet channel are arranged on a common first side of the cell stack. A tube is arranged in the inlet channel, wherein the tube projects from the open end almost to the closed end of the inlet channel. The tube has at least one opening near the closed end.

[0008] The medium can be, for example, water, hydrogen, air or a cooling medium, which is supplied to the individual electrochemical cells via the inlet channel.

[0009] By arranging the tube in the inlet channel, a virtually advantageous Z-shaped flow through the cell stack is achieved in terms of flow technology. At the same time, both connections for the inlet channel and outlet channel are positioned on one side of the cell stack to save space, similar to the connections in a U-shaped flow pattern. With the Z-shaped flow pattern, the sum of the inlet and outlet paths is constant for each cell. Due to the quasi-Z-shaped flow through the cell stack, a more uniform flow pattern can be achieved across all cells; in particular, a uniform temperature distribution can be achieved within the cell stack.

[0010] In advantageous designs, the opening is a front opening of the tube. The medium thus flows through the tube with virtually no loss in a first direction to a second side of the cell stack, which is opposite the first side and essentially marks the other end of the cell stack. For this purpose, the tube must not be flush with the closed end of the inlet channel, but must be spaced apart by a distance of, for example, 1 cm.

[0011] In an alternative or complementary variant, the tube has a plurality of openings in its outer surface. This allows a portion of the flowing medium to be diverted from the inside of the tube to the outside into the actual inlet channel for supplying the cells even before the second end of the cell stack. Thus, the supply to the cells does not begin at the last cell (on the second side), but is evened out along the inlet channel.

[0012] If the pipe has openings in its outer surface, its end can also be flush with the closed end of the inlet channel.

[0013] In an advantageous refinement, the frequency and / or cross-section of the openings increases toward the closed end. This allows the flow in the actual inlet channel to be optimized to supply the individual cells. Short description of the drawings

[0014] Embodiments of the invention are explained in more detail with reference to the drawings and the following description.

[0015] They show: Fig. 1 a perspective view of a cell stack known from the prior art, comprising several electrochemical cells arranged one above the other, wherein only the essential areas are shown. Fig. 2 a schematic view of the cell stack with a known circulation variant for a medium. Fig. 3 a schematic view of the cell stack with another known circulation variant for a medium. Fig. 4 in a perspective view a tube for insertion into an inlet channel of the cell stack. Fig. 5 a schematic view of the cell stack with a circulation for a medium according to the invention. Embodiments of the invention

[0016] In the following description of the embodiments of the invention, identical or similar elements are designated by the same reference numerals, whereby a repeated description of these elements is omitted in individual cases. The figures only schematically illustrate the subject matter of the invention.

[0017] Fig. 1 shows a perspective view of a cell stack 12 known from DE102022205235, which comprises a number of electrochemical cells 10 arranged one above the other. The cell stack 12 of Fig. 1 is designed as an electrolysis cell stack and has an inlet channel 30 (for water) and two outlet channels 32 (for water and hydrogen). On the top side of the cell stack 12 there is an upper end plate 16 with the connections for the channels 30, 32 arranged thereon. The cell stack 12 has a lower end plate 18 on its underside. An insulation plate 20 is assigned to the end plates 16, 18 on their side facing the cell stack 12. A first current collector 22 and a second current collector 24 are shown on the side of the cell stack 12. The individual electrochemical cells 10 have bipolar plates and membrane electrode assemblies, as are known from the prior art. Several hundred electrochemical cells 10 can be located within a cell stack 12, which, when stacked, have a height h 12 of the cell stack 12.

[0018] Fig. Figure 2 shows a schematic view of the cell stack 12, a circulation variant for the media flowing through the cell stack 12, which can also be referred to as U-flow or C-flow. The circulation 54 according to the schematic representation according to Fig. 2 is done clockwise.

[0019] In this selected variant, the circulating reactant 38 flows into the at least one inlet channel 30 via an open end 52 on an underside - the first side 48 - of the cell stack 12. Opposite the open end 52, the at least one inlet channel 30 has a closed end 50 in the region of its upper side - the second side 46. The electrochemical cells 10, which are arranged one above the other in the cell stack 12, extend laterally from the at least one inlet channel 30 and are stacked vertically. The circulation 54 of the circulating reactant 38 flows evenly through them in a clockwise direction. The circulating reactant 38 flows out again via the at least one outlet channel 32, which runs parallel to the at least one inlet channel 30, in the region of its underside 48 at the open end 52.

[0020] Such a circulation variant is known for both fuel cells and electrolysis cells. By designing the cell stack 12 with such a U-flow, the cell stack 12 can be easily coupled to the other components by simply flange-mounting it. The disadvantage of this design is that the electrochemical cell 10, which is furthest from the open end 52, is located the greatest distance from both the open end 52 of the inlet channel 30 and the open end 52 of the outlet channel 32, and is thus at a maximum disadvantage with regard to the supply of the medium or reactants 38.

[0021] Fig. 3 shows a schematic view of the cell stack 12 of another circulation variant for the media flowing through the cell stack 12, which can also be referred to as Z-flow. In the illustration according to Fig. 3, the flow through the individual electrochemical cells 10 of the cell stack 12 arranged one above the other takes place via a Z-flow 58. This means that the circulating reactant 38 enters at an open end 52 on the underside 48 of the at least one inlet channel 30, the opposite end of which is designed as a closed end 50.

[0022] After flowing through the cells 10, the circulating reactant 38 flows through the outlet channel 32 in an unchanged flow direction 76. The circulating reactant 38 thus flows out again via the at least one outlet channel 32 at its open end 52 in the region of its upper side 46. The flow of the circulating reactant 38 through the at least one inlet channel 30 and the at least one outlet channel 32 is highly uniform across all cells 10, resulting in a uniform media distribution and also a uniform temperature distribution in the individual electrochemical cells 10 of the cell stack 12. The more uniform the temperature distribution, the lower the probability of local temperature hotspots occurring within the cell stack 12.

[0023] From the representation according to Fig. 3 further shows that a flow path length 82 extends from the open end 52 of the at least one inlet channel 30 to the open end 52 of the at least one outlet channel 32. This flow path length 82 is substantially identical with respect to all electrochemical cells 10 arranged one above the other in the cell stack 12, which also contributes to the uniformity of the temperature distribution and the flow characteristics through the cell stack 12.

[0024] A cell close to the first side 48 has a greater distance to the open end 52 of the outlet channel 32 (disadvantage). Since the (total) pressure generally drops in the direction of flow, a cell close to the first side 48 is supplied with a higher (static) pressure level, but would also have a higher exhaust backpressure level. A cell further away from the first side 48 would, complementarily, have a lower supply pressure level, but also a lower exhaust backpressure. Purely qualitatively, one would therefore expect that when comparing the cell supply to the cells 10 in a cell stack 12, the uniform distribution of the Z-flow would be more similar to the uniform distribution of the U-flow.

[0025] According to the invention, the advantages of U-flow and Z-flow are combined; thus, despite the space-saving U-shaped flow through the cell stack 12, the benefit of a Z-flow is achieved by suitable flow guidance in the inlet channel 30, namely in particular the homogenization of the flow across all cells 10. The "U-shape" direction of action is, so to speak, inverted to a "Z-shape" in the inlet channel 30.

[0026] This shows Fig. 4, a tube 60, which is inserted into the inlet channel 30 of the cell stack 12. The tube 60 has an open end 61 at one end, which corresponds to the open end 52 of the inlet channel 30. The inlet channel 30 is formed by corresponding recesses in the individual cells 10, more precisely by corresponding recesses in the bipolar plates and membrane electrode assemblies. The tube 60 has a partial length h 12which corresponds approximately to the height of the cell stack 12. If the tube 60 is arranged in the inlet channel 30, it thus projects through all cells 10, or at least through the largest part of the cells 10. The tube 60 has at least one opening 62, 63 opposite its open end 61. In the embodiment of the Fig. 4, the tube 60 has both an end opening 62 and a plurality of small openings 63 formed in its outer surface.

[0027] Fig. Figure 5 shows a schematic view of the cell stack 12, the circulation variant according to the invention for a medium flowing through the cell stack 12. The cell stack 12 has on its first side 48 the open ends 52 of the inlet channel 30 and the outlet channel 32, as shown in Fig. 2. On its second side 46, the cell stack 12 has the closed ends 50 of the inlet channel 30 and the outlet channel 32.

[0028] The tube 60 is inserted into the inlet channel 30 of the cell stack 12, specifically such that its open end 61 coincides with the open end 52 of the inlet channel 30. The opening 62 of the tube 60 opposite the open end 61 is arranged on the upper side 46 of the cell stack 12, but of course not in a sealing manner, but rather such that the medium can escape from the interior of the tube 60 via the opening 62 to the exterior of the tube 60.

[0029] By inserting the tube 60 into the inlet channel 30, an internal flow 71 in a first direction 75 from the first side 48 to the second side 46 is created inside the tube 60. At the end of the tube or at its opening 62, the flow is deflected so that downstream of the internal flow 71 along the exterior of the tube 60 - i.e. in the actual inlet channel 30 - an external flow 72 is created in a second direction 76, which is opposite to the first direction 75.

[0030] The supply of the individual electrochemical cells 10 with the medium from the inlet channel 30 therefore does not occur via the inner flow 71, but via the outer flow 72. Accordingly, the flow direction supplying the cells 10 is the second direction 76. The flow direction disposing of the cells 10 in the outlet channel 32 is also the second direction 76. With regard to the supply and disposal of the cells 10, the cell stack 12 according to the invention can therefore be referred to as a Z-flow. However, with regard to the media connections of the inlet channel 30 and outlet channel 32 on the underside 48 of the cell stack 12, a U-flow could also be referred to.

[0031] Through the pipe 60, the flow in the inlet channel 30 is thus directed—by means of the inner flow 71—essentially to the last cell of the cell stack 12, i.e., to the cell adjacent to the second side 46. There, the flow is redirected to the outer flow 72 supplying the cells 10.

[0032] Due to the presence of dynamic pressure (total pressure minus static pressure) at the last cell on the top side 46, this pressure can be recovered into static pressure, so that the supply to the cells 10 of the cell stack 12 now begins, so to speak, at the last cell. In a conventional U-configuration, however, the medium would no longer have any velocity, kinetic energy, or dynamic pressure at the last cell due to the "suffered" branches, which could be used to model the static pressure curve in the inlet channel 30.

[0033] The tube 60 is characterized in that it guides the medium entering the inlet channel 30 at the anode inlet, cathode inlet, or coolant inlet into the region of the last cells—i.e., the cells that are the greatest distance from the open end 52 of the inlet channel 30. This can be achieved by a tube 60 that stops shortly before the closed end 50 of the inlet channel 30—for example, 1 cm before. An alternative or supplementary variant is a tube 60 that is more perforated as its length increases—i.e., along the first direction 75—because the pressure recovery (conversion from dynamic to static pressure) should be shifted toward the last cells 10, i.e., those adjacent to the closed end 50. Instead of a tube 60 ending shortly before the closed end 50, it would also be conceivable for recesses in the tube wall, namely the openings 63 in the shell surface, to gradually become more frequent or larger.In this case, the pipe 60 could also rest against the closed end 50 of the inlet channel 30. QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] DE 102022205235 [0005, 0017] DE 102020215024 A1

[0005]

Claims

[1] Cell stack (12) with a plurality of electrochemical cells (10) stacked one above the other, wherein at least one inlet channel (30) and at least one outlet channel (32) for supplying and discharging a medium to the cells (10) are formed in the cell stack (12), wherein the inlet channel (30) and the outlet channel (32) are formed by respective recesses in the cells (10), wherein the inlet channel (30) and the outlet channel (32) each have an open end (52) and a closed end (50) with respect to the cell stack (12), wherein both the open end (52) of the inlet channel (30) and the open end (52) of the outlet channel (32) are arranged on a common first side (48) of the cell stack (12), characterized bythat a tube (60) is arranged in the inlet channel (30), the tube (60) projecting from the open end (52) to almost the closed end (50) of the inlet channel (30), the tube (60) having at least one opening (62, 63) near the closed end (50). [2] Cell stack (12) Claim 1 characterized by that the opening (62) is a front opening of the tube (60). [3] Cell stack (12) Claim 1 or 2 characterized by that the tube (60) has a plurality of openings (63) in its outer surface. [4] Cell stack (12) Claim 3 characterized by that the frequency of the openings (63) increases towards the closed end (50). [5] Cell stack (12) claim 3 or characterized by that the cross-section of the openings (63) increases towards the closed end (50).

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