Redox flow battery

Abstract

Redox flow battery (1), with at least one cell (2), characterized by the fact that In tanks (3, 4) for storing electrolyte liquids (5, 6), at least one lance (3-1, 4-1, 3-2, 4-2) is arranged for a supply of the electrolyte liquid (5, 6) to the at least one cell (1) and / or for a return of the electrolyte liquid (5, 6) from the at least one cell (2), wherein along one extension direction of the at least one lance (3-1, 3-2, 4-1, 4-2) within the tanks (3, 4) several holes (10) are formed in a wall of the at least one lance (3-1, 3-2, 4-1, 4-2), wherein cross-sectional areas of the holes (10) in the lances (3,4) are selected such that a volume flow guided by the lances (3,4) is divided equally among the holes (10) of the respective lance (3,4) or a respective volume flow through the holes is at least equalized to each other.

Description

[0001] The invention relates to a redox flow battery.

[0002] A redox flow battery, also known as a liquid battery, wet cell, or simply redox flow battery, is a type of accumulator. Redox flow batteries have the potential to play a significant role in storing electrical energy from renewable sources, as they can store fluctuating energy sources such as solar and / or wind power and release it as needed. A defining characteristic of redox flow batteries is that the chemical energy is stored not in a solid, as is typical, but in a liquid electrolyte. This electrolyte is usually stored in two separate tanks and can be used in a cell of the redox flow battery as required. Inside the cell are two electrodes: an anode and a cathode.A membrane, particularly one that conducts ions, separates or divides the cell into two half-cells, with an electrode located in each of the half-cells.

[0003] A commonly used type of redox flow battery is the vanadium redox flow battery, in which vanadium compounds are present in both electrolytes: the electrolyte flowing past the anode and the electrolyte flowing past the cathode. During discharge of the redox flow battery, the following oxidation occurs at the anode: V 2+ ↔HV 3+ +e - The following reduction takes place at the cathode during discharge: VO 2+ +2H + +e - ↔VO 2++H₂O. Electrons are supplied to the anode and absorbed by the cathode, causing a current to flow between the two electrodes. Due to the respective electrode reactions, a charge imbalance arises between the two half-cells, necessitating a charge exchange across the membrane. This reaction is reversible in the redox flow reaction, allowing the redox flow battery to be recharged. Typically, such a redox flow battery does not consist of just one cell, but rather several cells combined into a so-called stack, which can, for example, achieve significantly higher power output.

[0004] To achieve maximum capacity of the redox flow battery, the aim is to utilize as much of the liquid electrolyte as possible during charging and discharging.

[0005] Therefore, it is important that no dead zones can form in the tanks where electrolyte fluid is located that is not pumped through the cell and whose charge therefore cannot be changed.

[0006] From DE 10 2010 004 942 A1 a redox flow cell is known in which stirrers with stirring blades are provided in the tanks for storing the electrolyte liquids.

[0007] An electrolyte mixing device for redox flow batteries is known from KR 10 2018 0 031 998 A. The device described has a plurality of through-holes on the side wall of an inlet tube for introducing an electrolyte through the inlet tube and achieving uniform mixing of the electrolyte. The redox flow battery induces uniform mixing with the electrolyte remaining in an electrolyte storage section by uniformly introducing the electrolyte, which has undergone an oxidation and reduction reaction in the electrolyte storage section.

[0008] A redox flow battery for the uniform mixing of an electrolyte is known from KR 10 2020 0 082 458 A. The redox flow battery comprises: a battery cell with a positive electrode and a negative electrode formed therein; an electrolyte storage tank that supplies electrolyte to the positive and negative electrodes; a supply flow path that connects the electrolyte storage tank and the battery cell to supply the electrolyte from the electrolyte storage tank to the battery cell; a return flow path that connects the electrolyte storage tank and the battery cell to return the electrolyte from the battery cell to the electrolyte storage tank; a pressure supply unit that provides pressure for circulating the electrolyte between the electrolyte storage tank and the battery cell; and an electrolyte distributor with a spray hole for distributing the electrolyte supplied from the electrolyte storage tank.

[0009] The invention is based on the objective of improving a redox flow battery with regard to the mixing of the electrolyte fluids in the tanks and the avoidance of dead zones in the tanks.

[0010] The problem is solved according to the invention by a redox flow battery with the features of claim 1. Advantageous embodiments of the invention are set forth in the dependent claims.

[0011] In particular, a redox flow battery is created, with at least one cell, wherein at least one lance for a supply of the electrolyte liquid to the at least one cell and / or for a return of the electrolyte liquid from the at least one cell is arranged in tanks for storing electrolyte liquids, wherein along one extension direction of the at least one lance within the tanks several holes are formed in a wall of the at least lance.

[0012] The redox flow battery allows the electrolyte fluid to be drawn from the tank (supply from tank to cell) and / or returned (return from cell to tank) in such a way that turbulent flow is created within the tank, resulting in thorough mixing of the electrolyte fluid throughout. This effectively prevents the formation of dead zones within the tank, ensuring that the entire electrolyte fluid is available for charging and discharging. This is achieved by providing each tank of the redox flow battery with at least one lance for a supply and / or return flow, through which the electrolyte fluid is drawn from or returned. The at least one lance is, in particular, elongated and hollow inside.The at least one lance is designed as a hollow body and has several holes arranged in its wall along one direction of extension. During the feed phase, the electrolyte fluid enters the lance from the tank (also called the feed lance), and during the return phase, the electrolyte fluid exits the tank from the inside of the return lance (also called the return lance). Each tank of the redox flow battery has at least one such lance for a feed phase and / or a return phase. In particular, each tank has at least one such lance for the return phase (return lance). The multiple holes in the wall of the at least one lance generate turbulent flow within the tanks, resulting in efficient mixing of the respective electrolyte fluids. This turbulent flow is caused in particular by the respective exit and / or exit of the lance.The entry of the electrolyte fluid through the holes creates turbulence in the area of ​​the individual holes due to the volume flows occurring, which propagate into the interior of the tank and thus lead to turbulent flow and effective mixing throughout the entire tank.

[0013] One advantage of the disclosed redox flow battery is that no moving parts are required within the tanks to generate mixing and, in particular, turbulent flow. Furthermore, the lances are easy to manufacture and can be easily arranged and attached to the tanks. For example, the lances can be inserted into the tanks and bolted to them. Alternatively, the lances can be welded to the tanks (subsequently) or integrated into the tanks during their manufacture.

[0014] A redox flow battery has at least one cell. However, it can also be configured to combine several cells into a stack. A stack then comprises several cells and two tanks containing the electrolyte fluids. Each of the two tanks contains at least one lance.

[0015] The holes in the walls of the lances are, for example, arranged at regular or irregular intervals along the longitudinal direction of the lances.

[0016] The lances are made of, or comprise, a suitable plastic. For example, polyethylene (PE) or polypropylene (PP) can be used. However, due to their resistance to various media, polyvinyl chloride (PVC-U, PVC-C), polycarbonate (PC), polymethyl methacrylate (PMMA), polyvinylidene fluoride (PVDF), and ethylene tetrafluoroethylene copolymer (ETFE) are also suitable. The lances may include additional elements for mechanical fixation and / or interface elements for connecting to a pump circuit and for sealing, such as screw caps, inserts, gaskets, union nuts, etc. It is also possible that such components are welded together, or are welded to be welded, or are integrated and permanently attached to the respective tank during its manufacture.

[0017] The cross-sectional areas of the holes in the lances are designed such that the volume flow from each lance is distributed evenly across the holes, or at least that the volume flow through each hole is equalized. This ensures that the same, or at least an equal, volume flow is generated through the holes during the supply and / or return flow along the entire length of a lance. This promotes uniform mixing and the development of turbulent flow throughout the entire tank, particularly across its entire height. Fluid dynamics principles, particularly those of hydrodynamics, are used to select the cross-sectional areas of the holes in order to achieve equal volume flow rates at each hole. Empirical tests and / or simulations can be employed to determine the optimal number of holes and / or optimal cross-sectional areas.For example, it may be possible to specify a starting value for the diameter or cross-sectional area of ​​a hole at one end of a lance and to determine the diameters or cross-sectional areas of the remaining holes based on empirical tests and / or simulations.

[0018] In one embodiment, each tank is equipped with at least one lance for supplying electrolyte fluid to the at least one cell and at least one lance for returning electrolyte fluid from the at least one cell. This further enhances the generation of turbulent flow within the tanks and the mixing of the respective electrolyte fluids, as both the supply and return lances contribute to this process. The lances are arranged, in particular, on opposite sides of each tank. This allows for the generation of turbulent flow throughout the entire tank volume. For tanks with a rectangular or square cross-section, the lances can also be arranged in opposite corners (or along the corners).

[0019] In one embodiment, the lances are cylindrical. In particular, the lances comprise a hollow cylinder. This allows standard components, especially (standard) tubes, to be used to form the lances. To manufacture a lance, a tube is, for example, provided with bores to form the holes. The holes are formed, in particular, in a lateral surface of the hollow cylinder.

[0020] In one embodiment, the lances are sealed at the end that terminates inside the tank. This ensures that the electrolyte fluid passes exclusively through the holes arranged in the lances.

[0021] In one embodiment, the lances are arranged vertically within the tank and extend over at least a large portion of the tank's height. This allows the electrolyte fluid to be drawn off (supply) or returned (return) over the entire height or length of the tank. In particular, this enables the formation of turbulent flow throughout the entire tank volume.

[0022] In one embodiment, the holes are formed on opposite sides of the lance walls. This allows the electrolyte fluid to enter and exit the lances on both (longitudinal) sides. This further improves the formation of turbulent flow.

[0023] In one embodiment, the flow directions through the holes of the respective lances for the supply and return of the tanks are arranged parallel to each other. This allows for particularly effective generation of turbulent flow. In other words, the holes of the supply and return lances of a tank are, in this embodiment, arranged essentially facing each other.

[0024] In one embodiment, the flow directions of at least some of the holes in the respective lances of the tanks are directed towards a tank center axis or surface running parallel to the lances and are perpendicular to it. This further improves the generation of turbulent flow and mixing. In particular, it can be provided that a volume flow is directed towards the tank center axis or tank center surfaces (and, in the case of holes on opposite sides, additionally towards an end wall of the tanks) or "drawn off" from this direction. This ensures that the largest possible number of liquid particles in the tank are moved and mixed. Mixing can be improved in this way, especially when the tanks are enlarged along one longitudinal side to increase storage capacity.The tank's central surface, in particular, divides one side, which is longer in relation to the tank's dimensions, into two equal parts.

[0025] In one embodiment, it is provided that the cross-sectional areas of the holes in the lances are different, at least in groups or sections.

[0026] In a further embodiment, the cross-sectional area of ​​the holes in the lances for the supply flow increases at least in groups or sections towards an end terminating inside the tank, and the cross-sectional area of ​​the holes in the lances for the return flow decreases at least in groups or sections towards an end terminating inside the tank. In normal operation, this means, in particular, that the cross-sectional area of ​​the holes in the supply lance increases at least in groups or sections with increasing immersion depth in the electrolyte, and the cross-sectional area of ​​the holes in the return lances decreases at least in groups or sections with increasing immersion depth in the electrolyte. This ensures that the flow rate is constant or at least can be equalized along the entire length of the lance.

[0027] In one embodiment, the holes have a circular cross-section, with the diameters of the circular holes in the feed lances having a ratio of 5:9:13, at least in groups or sections, and the diameters of the circular holes in the return lances having a ratio of 13:9:6, at least in groups or sections. For cylindrical lances with an inner diameter of 20 mm, the circular holes in the feed lances can, for example, have the following diameters: 5 mm, 9 mm, 13 mm. Similarly, the circular holes in the return lance can have the following diameters: 13 mm, 9 mm, 6 mm. In principle, other ratios can also be chosen, provided that this allows for a balanced volume flow through the individual holes of a lance.

[0028] The invention is explained in more detail below with reference to preferred embodiments and the figures. These show: Fig. 1 a schematic representation of an embodiment of the redox flow battery; Fig. 2 a schematic representation of a tank and lances arranged therein in an embodiment of the redox flow battery (side view); Fig. 3 a schematic representation of the tank and lances arranged therein in the embodiment of the redox flow battery (top view); Fig. 4a, b schematic representations of an embodiment of the pre-lead lance in a side view and in a perspective view; Fig. 5a, b schematic representations of an embodiment of the return lance in a side view and in a perspective view.

[0029] The Fig. Figure 1 shows a schematic representation of an embodiment of the redox flow battery 1. The redox flow battery 1 comprises a cell 2 and two tanks 3, 4, each containing an electrolyte fluid 5, 6. Only one cell 2 is shown here; however, the redox flow battery 1 can, in principle, also comprise several cells 2, which are combined to form a (cell) stack. The electrolyte fluids 5, 6 are supplied to the cell 2 by means of pumps 7, 8 in two separate circuits 30, 40 and subsequently returned to the tanks 3, 4. Inside the cell 2 are two electrodes, an anode (-) and a cathode (+). A membrane 9, in particular an ion-conducting membrane, separates or divides the cell 2 into two half-cells 2-1, 2-2, with one electrode (+) and one electrode (-) being arranged in each of the half-cells 2-1, 2-2. Each half-cell 2-1, 2-2 is assigned to one of the tanks 3, 4 or one of the circuits 30, 40.For charging and discharging, the redox flow battery 1 is operated in a manner known per se, in particular in the manner described in the introduction to the description, so that it will not be discussed in more detail here.

[0030] In the example shown, both electrolyte liquids contain 5, 6 vanadium compounds, which can each exist in different charge states. However, other suitable electrolytes can also be used.

[0031] In tanks 3 and 4 for storing the electrolyte fluids 5 and 6, a supply lance 3-1 and 4-1 are each arranged for supplying the electrolyte fluid 5 and 6 to cell 2, and a return lance 3-2 and 4-2 are arranged for returning the electrolyte fluid 5 and 6 from cell 2 to tank 3 and 4. Along one direction of extension of the lances 3-1 and 4-2 within tanks 3 and 4, several holes 10 are formed in one wall of the lances 3-1 and 4-2.

[0032] This is schematically shown in the Fig. Figure 2 shows only a tank 3 and a circuit 30. The holes 10 are arranged at regular intervals on the lances 3-1 and 3-2. The supply lance 3-1 is connected to the pump 7, for example, by screwing it to a standard interface. The pump 7 extends partially into the tank 3, so that the supply lance 3-1 is slightly shorter than the return lance 3-2, which is connected, in particular by screwing it, to an interface on a top surface 3-3 of the tank 3.

[0033] In the illustrated embodiment of the redox flow battery 1, two lances 3-1, 3-2, 4-1, 4-2 are provided for each tank 3, 4. However, the use of only one lance 3-1, 3-2, 4-1, 4-2 or additional lances per tank 3, 4 is also possible. In particular, a return lance 3-2, 4-2 can be provided as the only lance per tank 3, 4.

[0034] It is specifically intended that the lances 3-1, 3-2 are cylindrical in shape. In particular, the lances 3-1, 3-2 each form a hollow cylinder or are shaped like a hollow cylinder. The lances 3-1, 3-2 can, for example, include as an essential component a (plastic) tube into which, for example, bores are made to form the holes 10.

[0035] It is specifically intended that the lances 3-1, 3-2 are sealed at an end 11 terminating inside the tank. For example, a suitable (plastic) plug can be used for this purpose.

[0036] It is specifically provided that the lances 3-1, 3-2 are arranged vertically in the tank 3 and extend at least over a large part of a height 3-4 of the tank 3.

[0037] In the example shown, the supply lance 3-1 has, in particular, eight holes 10. The return lance 3-2 has, in particular, ten holes. Depending on the size of the tank 3 and / or the requirements for a flow rate and / or the available pumping capacity of the pump 7, more or fewer holes 10 may be provided.

[0038] The respective holes 10 of the two lances 3-1, 3-2 are arranged on opposite sides of the lances 3-1, 3-2. In particular, the directions of passage through the holes 10 of lance 3-1 for the forward flow and lance 3-2 for the return flow are arranged parallel to each other. Specifically, some of the holes 10 in lances 3-1, 3-2 point towards the nearest end wall 3-5 of the tank 3, and other parts of the holes 10 point towards a tank medial surface 3-7 running parallel to lances 3-1, 3-2, which divides the longitudinal extent (length) of the tank 3 into two equal parts. The directions of passage of the holes 10 are shown schematically in the Fig. Figure 3 illustrates this, showing a schematic top view of tank 3. The directions of the holes are perpendicular to the end wall 3-5 and / or the tank's central surface 3-7. The directions of the volume flows caused by suction and inflow through the holes 10 are schematically indicated by arrows. The other tank 4 ( Fig. 1) and the other lances 4-1, 4-2 are constructed in the same way.

[0039] It is planned that the cross-sectional areas of the holes 10 in the lances 3-1, 3-2 (and the lances 4-1, 4-2 of the other tank 4, Fig. 1) are selected such that a volume flow delivered by each of the lances 3-1, 3-2 is distributed evenly among the holes 10 of the respective lance 3-1, 3-2 or that a respective volume flow through the holes 10 is at least equalized to each other.

[0040] In particular, it may be provided that the cross-sectional areas of the holes 10 in the lances 3-1, 3-2 are different at least in groups or sections.

[0041] The Fig. 4a, Fig. 4b, Fig. 5a and Fig. Figure 5b shows schematic representations of embodiments of the feed lances 3-1, 4-1 and the return lances 3-2, 4-2, each in a side view and a perspective view. In these embodiments, the lances 3-1, 3-2, 4-1, 4-2 essentially comprise a (plastic) tube. The tube is closed at one end 11, which terminates inside the tank, for example by means of a (plastic) plug. Interface elements 3-6, 4-6 are arranged at the other end 12 to connect the lances 3-1, 3-2, 4-1, 4-2 to the respective circuits and to fix them to the tank.

[0042] In order to generate a uniform volume flow through all holes 10, this embodiment provides that the cross-sectional area of ​​the holes 10 of the feed lances 3-1, 4-1 increases at least in groups or sections towards an end 11 terminating inside the tank (cf. Fig. 4a) and a cross-sectional area of ​​the holes 10 of the return lances 3-2, 4-2 decreases at least in groups or sections in the direction of an end 11 terminating inside the tank (cf. Fig. 5a).

[0043] In this embodiment, the holes 10 are provided to have a circular cross-section, wherein the diameters of the circular holes 10 of the feed lances 3-1, 4-1 have a ratio of 5:9:13 to each other, at least in groups or sections, and the diameters of the circular holes 10 of the return lances 3-2, 4-2 have a ratio of 13:9:6 to each other, at least in groups or sections. However, other suitable ratios may also be provided.

[0044] With an inner diameter of 20 mm for the feed lances 3-1, 4-1, the following numbers and diameters of circular holes 10 can be provided in the direction of the end 11 terminating inside the tank: four holes 10 spaced 135 mm apart with a diameter of 5 mm, two holes 10 spaced equally with a diameter of 9 mm, and two holes 10 spaced equally with a diameter of 13 mm. The feed lances 3-1, 4-1 then have a total length of approximately 950 mm between the interface elements 3-6, 4-6 at the ends 12 and the ends 11. In principle, the holes 10 can also have other shapes with the same cross-sectional area; however, circular holes 10 offer advantages in manufacturing, as they can be produced by drilling.

[0045] With an inner diameter of 20 mm for the return lances 3-2, 4-2, the following numbers and diameters of circular holes 10 can be provided in the direction of the end 11 terminating inside the tank: three holes 10 spaced 135 mm apart with a diameter of 13 mm, three holes 10 spaced equally with a diameter of 9 mm, and four holes 10 spaced equally with a diameter of 13 mm. The return lances 3-2, 4-2 then have a total length of approximately 1300 mm between the interface elements 3-6, 4-6 and the ends 11. In principle, the holes 10 can also have other shapes with the same cross-sectional area; however, circular holes 10 offer advantages in manufacturing, as they can be produced by drilling.

[0046] The specified dimensions of the lances 3-1, 3-2, 4-1, 4-2 and holes 10, as well as the number of holes 10, are only examples and may be designed differently in other embodiments, in particular with other sizes and / or shapes of the tanks. Reference symbol list 1 Redox flow battery 2 cells 2-1 half-cell 2-2 half-cell 3 Tank 3-1 Pre-flight lance 3-2 Return lance 3-3 Top (of the tank) 3-4 Height (of the tank) 3-5 Front wall (of the tank) 3-6 Interface element 3-7 Tank center area 4 Tank 4-1 Pre-flight lance 4-2 Return lance 4-6 Interface element 5 Electrolyte fluid 6 Electrolyte fluid 7 Pump 8 pump 9 Membran 10 holes 11 End (inside the tank) 12 End 30 Circulation 40 Circulation + electrode electrode

Claims

[1] Redox flow battery (1), with at least one cell (2), characterized by , that In tanks (3, 4) for storing electrolyte liquids (5, 6), at least one lance (3-1, 4-1, 3-2, 4-2) is arranged for a supply of the electrolyte liquid (5, 6) to the at least one cell (1) and / or for a return of the electrolyte liquid (5, 6) from the at least one cell (2), wherein along one extension direction of the at least one lance (3-1, 3-2, 4-1, 4-2) within the tanks (3, 4) several holes (10) are formed in a wall of the at least one lance (3-1, 3-2, 4-1, 4-2), wherein cross-sectional areas of the holes (10) in the lances (3,4) are selected such that a volume flow guided by the lances (3,4) is divided equally among the holes (10) of the respective lance (3,4) or a respective volume flow through the holes is at least equalized to each other. [2] Redox flow battery (1) according to claim 1, characterized by , that in the tanks (3,4) at least one lance (3-1,4-1) is arranged for a supply of the electrolyte fluid (5,6) to the at least one cell (1) and at least one lance (3-2,4-2) is arranged for a return of the electrolyte fluid (5,6) from the at least one cell (2). [3] Redox flow battery (1) according to claim 1 or 2, characterized by , that the lances (3-1,3-2,4-1,4-2) are cylindrical in shape. [4] Redox flow battery (1) according to any one of the preceding claims, characterized by , that the lances (3-1,3-2,4-1,4-2) are closed at an end (11) that terminates inside the tank. [5] Redox flow battery (1) according to any one of the preceding claims, characterized by , that the lances (3-1,3-2,4-1,4-2) are arranged vertically in the tank (3,4) and extend at least over a large part of the height (3-4) of the tanks (3,4). [6] Redox flow battery (1) according to any one of the preceding claims, characterized by , that the holes (10) are formed on opposite sides of the wall of the lances (3-1,3-2,4-1,4-2). [7] Redox flow battery (1) according to any one of the preceding claims, characterized by , that the directions of passage through the holes (10) of the respective lances (3-1,4-1) for the forward flow and lances (3-2,4-2) for the return flow of the tanks (3,4) are arranged parallel to each other. [8] Redox flow battery (1) according to any one of the preceding claims, characterized by , that the directions of passage of at least part of the holes (10) of respective lances (3-1,3-2,4-1,4-2) of the tanks (3,4) point in the direction of a tank center axis or tank center surface running parallel to the lances (3-1,3-2,4-1,4-2) and are perpendicular to it. [9] Redox flow battery (1) according to any one of the preceding claims, characterized by, that the cross-sectional areas of the holes (10) in the lances (3-1,3-2,4-1,4-2) differ at least in groups or sections. [10] Redox flow battery (1) according to any one of the preceding claims, characterized by , that a cross-sectional area of ​​the holes (10) of the lances (3-1,4-1) for the forward flow towards an end (11) ending inside the tank increases at least in groups or sections and a cross-sectional area of ​​the holes (10) of the running lances (3-2,4-2) for the return flow towards an end (11) ending inside the tank decreases at least in groups or sections.

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