Electrolyser with an insulator disposed between cell sub-stacks

Abstract

The invention relates to an electrolyzer (1, 17) with a cell stack comprising a first cell sub-stack (5) and a second cell sub-stack (6), wherein opposite ends of the cell stack are electrically connected to each other via a current conductor (12). The cell sub-stacks (5, 6) are connected in parallel or in series with each other, and an insulator (14) is arranged between the cell sub-stacks (5, 6), wherein the arrangement of cell sub-stacks (5, 6) and insulator (14) is clamped by a common clamping device.

Description

[0001] The invention relates to an electrolyzer.

[0002] Electrolyzers, also known as electrolysis devices, are used to carry out electrochemical electrolysis. During electrolysis, electrical energy is used to force a redox reaction in order to produce substances that are difficult or expensive to produce in large quantities using purely chemical processes.

[0003] As the energy transition progresses, water electrolysis for hydrogen production is gaining increasing importance. To be economically viable compared to hydrogen production from fossil sources, water electrolysis is being optimized, particularly with regard to production and plant costs.

[0004] An electrolyzer typically has several electrolysis cells, each comprising an anode and a cathode, arranged in a cell stack. Depending on the design, the cells can be connected electrically in series or in parallel. It is also common to connect several cells in series, one after the other, to form a cell sub-stack. These cell sub-stacks can, for example, be mounted separately and then assembled into the complete cell stack.

[0005] DE 1006401 B relates to an electrolyzer for the electrolytic decomposition of water to produce hydrogen and oxygen under a pressure of more than 5 atm. The electrolyzer is of the filter press type, in which electrically connected decomposition cells are arranged in series in a column-shaped assembly, clamped between solid end plates, and held together by solid tie rods. The assembly is equipped with a central power supply point to which one pole of the power source is connected, while the other pole is connected to the two end plates.

[0006] US Patent 3,623,967 A relates to an electrolyzer for the production of an alkali metal chlorate. The electrolyzer comprises two electrolysis cells connected in series. Each cell has its own housing, and the connection between the cells is grounded.

[0007] Based on this, the object of the invention is to provide an electrolyzer for water electrolysis that is inexpensive to produce and flexible to operate and maintain.

[0008] This problem is solved by an electrolyzer having the features of claim 1. Advantageous embodiments are described in the dependent claims and the description.

[0009] The electrolyzer according to the invention comprises a cell stack formed from at least two cell sub-stacks and at least one insulator. The insulator is arranged between the cell sub-stacks such that the inner ends of the cell sub-stacks, which are in contact with the insulator, are electrically insulated from one another. The cell sub-stacks are electrically connected in parallel and / or in series, wherein the inner ends of the cell sub-stacks are electrically connectable to the poles of a power supply, and the opposite ends of the cell stack are electrically connectable to one another via a current conductor, which may be grounded.

[0010] By dividing the cell stacks into individual stacks that can be manufactured, assembled, tested, stored, and transported, even larger cell stacks can be easily manufactured and maintained. The electrolyzer according to the invention also allows for greater flexibility in electrical connections and wiring, and thus also in electrolysis operation. A further advantage is that the arrangement of cell stacks and insulator, because the cell stacks and insulator are arranged as a stack—that is, in a row within the cell stack—can be clamped to the cell stack by a single clamping device. This saves space and simplifies the control and regulation of the mechanical clamping.

[0011] The cell stacks of the electrolyzer can comprise one or more electrolysis cells. If there are multiple electrolysis cells, these can be arranged in series in contact with each other within the cell stack and are preferably connected electrically in series. End plates can be provided at the ends of the cell stacks. These are electrically connected to the pole of the electrolysis cell at the respective end of the cell stack and, if present, each form one end of the cell stack. That is, the end plates are at the same potential as the pole of the electrolysis cell at the respective end of the cell stack and thus themselves form a pole. In the present application, those ends of cell stacks that are in contact with an insulator are referred to as inner ends of cell stacks. The ends of cell stacks that are connected to the ends of the cell stack, i.e.,The cell substacks and insulator(s) located at the ends of the entire stack are referred to as the outer ends of the cell substacks. Therefore, the outer ends of the cell substacks are located at the two opposite ends of the cell stack.

[0012] In one design, the cell stacks can be subdivided into substacks, which can also be called blocks. The substacks can also have end plates at their ends, with these end plates serving as the end plates of the cell stack itself, located at the inner and outer ends. The substacks are arranged sequentially within the cell stack and electrically connected in series. Two end plates of opposite polarity touch each other. This subdivision into substacks simplifies the manufacturing, transport, and assembly of the electrolyzer. Furthermore, the additional end plates, together with the insulator, provide mechanical stability to the cell stack.

[0013] In one embodiment, the cell sub-stacks are connected in parallel to each other in a circuit between the poles of a power supply. For this purpose, the ends of the cell sub-stacks located at the insulator, i.e., the inner ends of the cell sub-stacks, are each electrically connected to a first pole of the power supply. The outer ends of the cell stack or cell sub-stacks are electrically connected to a second pole of the power supply via the current conductor.

[0014] In another embodiment, the cell stacks are connected in series in a circuit between the poles of a power supply, or can be connected / switched. For this purpose, an inner end of a first cell stack, located at the insulator, is electrically connected to a first pole of the power supply, and an inner end of a second cell stack, also located at the insulator, is electrically connected to a second pole of the power supply. The circuit between the poles of the power supply can be closed via the current flow between the outer ends of the cell stacks or the cell stack itself.

[0015] The power supply can be a three-phase mains connection equipped with a rectifier to provide direct current for electrolysis. Alternatively, operation is possible with a power supply that directly provides direct current, such as a renewable energy source like a photovoltaic system. The power supply can provide a corresponding voltage depending on the desired power and current; however, the voltage can also be regulated instead of the current. The voltage is applied between the first and second terminals of the power supply. The first terminal can be the negative terminal and the second terminal the positive terminal, or vice versa.

[0016] The cell stack comprises the cell sub-stacks connected to the power supply and the insulator, as well as the necessary components for electrical contact. Each electrolysis cell within the cell sub-stack can have an anode and cathode, as well as an electrolyte supply and gas discharge. If a cell sub-stack contains multiple electrolysis cells, these cells can be connected in series such that the total voltage across the cell sub-stack is determined by the sum of the individual voltages of the electrolysis cells. The electrolysis cells and the cell sub-stacks each have a negative and a positive terminal. The cells can be arranged so that the negative terminal of one cell touches the positive terminal of another, thus electrically coupling the negative and positive terminals.

[0017] The electrolysis cells can, in principle, have any shape and, according to a preferred embodiment, are polygonal or round in cross-section. The electrolysis cells are specifically designed for water electrolysis, preferably for acidic or alkaline water electrolysis, and particularly preferably for alkaline water electrolysis under pressure, also known as pressure alkaline electrolysis. Accordingly, the electrolyzer is also designed for alkaline water electrolysis, especially pressure alkaline electrolysis.

[0018] The electrolyzer according to the invention has an insulator between the two cell stacks. The insulator prevents the two cell stacks from being electrically connected to each other by contact at their respective ends or poles. Furthermore, the insulator ensures a certain spatial distance. An insulator can be understood to be, in particular, an electrical insulator having an electrical conductivity of at most 10⁻⁸ < S / m, preferably at most 10⁻¹⁰ < S / m, and most preferably at most 10⁻¹⁶ < S / m.

[0019] In embodiments, the arrangement of cell stacks and the insulator arranged between them is clamped by a clamping device. This clamping device can preferably be the only clamping device by which the arrangement is clamped to the cell stack. The clamping device is designed to compress the cell stack along its longitudinal axis, so that the relative position of the cell stacks, the insulator, and any other components arranged between them is secured or fixed. For pressure electrolysis, the compressive force for compressing the cell stack and the electrolysis cells arranged therein can be so high that the cells are sealed from the environment during electrolysis operation, in which the pressure inside the cells is higher than the ambient pressure.

[0020] The connection from the inner ends of the cell stacks to the power supply pole to which the respective inner end is electrically connectable or connected, and / or the connection from the current conductor to the respective power supply pole to which the outer ends are electrically connected, can be made via electrical conductors. These conductors can be any type of electrical conductor, such as wired cables or busbars.

[0021] If the inner ends of the cell stacks, i.e., the ends or poles of the cell stacks arranged on the insulator, are each connected or connectable to a first pole of a power supply, and the outer ends are electrically connected or connectable to the second pole of the power supply via the current conductor, then the first and second cell stacks are electrically connected or switchable in parallel. The current conductor connects like poles at the outer ends of the cell stacks. If, on the other hand, the inner end of the first cell stack is electrically connected or connectable to the first pole, e.g., the negative pole, of the power supply, and the inner end of the second cell stack is connected or connectable to the second pole, e.g., the positive pole, of the power supply, or vice versa, and the outer ends are connected to each other via the current conductor, then the first and second cell stacks are electrically connected or switchable in series.The current flow connects opposite poles of the cell stacks at their outer ends.

[0022] By connecting the cell stacks in series, the current flow can be halved compared to a parallel connection while maintaining the same power output. This ensures that the power electronics, which control the electrolyzer and, in particular, the power supply, and which can be part of the electrolyzer, achieve a longer lifespan and are more cost-effective to manufacture. Furthermore, the series connection allows for material savings in the electrical conductors, especially between the current conductor and the terminal of the power supply to which the current conductor is connected during operation of the respective cell stack.

[0023] Simultaneously, the insulator allows the cell stacks to be clamped together by the clamping device, both in parallel and series connections. For this purpose, the insulator is arranged in contact with the cell stacks between them. The electrolyzer according to the invention is therefore characterized by a very compact design, which results in corresponding material savings and simplified assembly, enabling more economical and faster production of the electrolyzer. Furthermore, the insulator ensures that the clamping force is distributed more evenly across the cross-sectional area of ​​the electrolysis cells, thus preventing cell bulging.Bulging can occur particularly when an increasing number of electrolysis cells are braced together via tension rods whose anchor points are arranged perpendicular to the force flow direction outside the cell circumference, or when the temperature profile of the cells during electrolysis operation is inhomogeneous with increasing cell diameter.

[0024] Furthermore, the insulator allows at least one cell stack to be deactivated or disabled with minor modifications to the electrolyzer. This is achieved by interrupting the connection between the inner end of the first and / or second cell stack and the respective power supply terminal to which the inner end of the cell stack is electrically connected. If the cell stacks are connected in series, the respective terminal is connected to the power supply. Operating only one cell stack allows the electrolyzer to operate at a correspondingly reduced power output. This can be particularly advantageous with fluctuating power supplies, which are typical for renewable energy systems. Additionally, deactivating one cell stack allows for easy maintenance of that unused stack while the other cell stack continues to operate. If necessary, e.g.,For certain maintenance tasks, both cell sub-stacks can also be deactivated.

[0025] According to one embodiment, the electrolyzer is characterized in that a switch is provided which has an initial state and a first switching state, wherein when switching to the first switching state the connection between the inner end of the first cell stack and the first pole of the power supply, with which the inner end of the first cell stack is electrically connected, is interrupted or is interrupted and, if the cell stacks are connected in series, a connection between the first pole and the current conductor is established or is established.

[0026] In its initial state, all electrical components of the electrolyzer are connected as previously described. As soon as the switch is moved to its first switching state, for example by an operator or a control device, the connection between the inner end of the first cell stack and the respective terminal of the power supply to which the inner end of the first cell stack is electrically connected is interrupted. For this purpose, the connection between the power supply and the first cell stack has a corresponding switching element. This switching element could be, for example, a relay, a switchable diode, or a thyristor. The switching element can be activated by the switch.

[0027] Furthermore, when the first switching state is activated, if the cell stacks are electrically connected in series, a connection is also established between the power supply terminal to which the inner end of the first cell stack was connected and the power supply line connected to the outer end of the second cell stack. In some configurations, a switchable conductor, electrically connected to the power supply line, may be used for this purpose. The switchable conductor could be, for example, a cable, a busbar, or another type of power line. A switching element, such as a diode or a relay, is integrated into the switchable conductor.This switching element allows the connection between the respective pole to which the first cell stack was connected in the initial state and the current conductor to be established when the first switching state is activated, so that the circuit from the outer end of the second cell stack via the switchable conductor and the switching element of the switchable conductor to the power supply is closed.

[0028] When the first switching state is activated, the first cell sub-stack is therefore no longer part of the circuit, i.e., no longer connected to the power supply, and instead only the second cell sub-stack is connected to the power supply.

[0029] The advantage of including the switch is that the electrolyzer can be operated at half power as needed. This makes the electrolyzer more versatile. Furthermore, the first cell stack can be easily serviced when disconnected from the power supply, thus improving both usability and user-friendliness.

[0030] According to one embodiment, the electrolyzer is characterized in that the switch has a second switching state, wherein when switching to the second switching state the connection between the inner end of the second cell stack and the pole of the power supply with which the inner end of the second cell stack is connected in the initial state is interrupted and, if the cell stacks are connected in series, an electrical connection is established between the outer end of the first cell stack and the current conductor.

[0031] The switch therefore has a second switching state, which is similar to the first in that, instead of the first cell stack, the second cell stack is disconnected or deactivated from the power supply when switching to this state. The connection between the power supply and the second cell stack also includes a switching element for disconnecting the power supply from the second cell stack. This switching element can also be switched by the switch. A second switchable conductor, such as a cable, busbar, or other power line, can be provided for the connection between the terminal of the power supply to which the second cell stack was connected in the initial state and the power supply line. A switchable switching element, such as a diode or a relay, can be integrated into this second switchable conductor.This switchable switching element allows the connection between the respective pole, to which the inner end of the second cell stack was connected in the initial state, and the current conductor to be established when the second switching state is activated, so that the circuit for the power supply is closed.

[0032] The switch can have only the initial state, only the first switching state, or only the second switching state. However, in some versions, the switch can also have both the first and second switching states.

[0033] By providing the first and second switching states, the flexibility of the electrolysis operation is further increased because it allows for easy selection of whether both cell stacks, only the first cell stack, only the second cell stack, or neither cell stack should be used. In particular, this makes it possible to ensure an even load on both cell stacks during operation where only one cell stack is active at a time.

[0034] The connection between the current conductor and the respective terminal of the power supply to which the first or second cell sub-stack is connected in the initial state (i.e., before switching to the first or second switching state) can be established, at least partially, via a common switchable conductor, i.e., a single switchable conductor connected to the current conductor. This switchable conductor can integrate both the switching element for the connection to the terminal of the power supply to which the first cell sub-stack is connected in the initial state and the switching element for the connection to the terminal of the power supply to which the second cell sub-stack is connected in the initial state.

[0035] The switching elements can be any suitable electronic component. By using a single switchable conductor for the two cell stacks, material can be saved compared to using two separate switchable conductors, resulting in lower production costs.

[0036] According to one embodiment, the electrolyzer is characterized in that the clamping device comprises two end plates, each bearing against opposite ends of the cell stack, and several tie rods, which can also be referred to as tension rods or tie rods. The tie rods are each attached to the end plates in such a way that the cell stacks arranged between the end plates, as well as the insulator, are subjected to a compressive force that compresses the cell stack along its longitudinal axis to clamp it.

[0037] The end plates of the clamping device are made of an electrically conductive material, in particular metal, and are located at opposite ends of the cell stack, i.e., at the outer ends of the cell sub-stacks. Accordingly, they rest against the sides of the cell sub-stacks facing away from the insulator. The end plates are connected to the cell sub-stacks in such a way that an electrical connection can exist between the ends of the cell sub-stacks and the end plates. In such a case, the respective end plates exhibit essentially the same potential as the outer ends of the cell sub-stacks.

[0038] The tension rods of the clamping device can be made of metal or a composite material. They are typically cylindrical with a circular cross-section, although other cross-sectional shapes are also possible. The tension rods are attached to the end plates in such a way that they exert a compressive force along the longitudinal direction of the cell stack on the arrangement of cell sections and insulator located between the end plates. For this purpose, the end plates can be provided with corresponding threads into which matching threads on the tension rods engage. It is also possible to apply tension using nuts that fit threads on the tension rods. Hydraulic tensioning is also possible. Alternatively, a tension rod can be positively or rigidly connected to one of the end plates, thus applying the tensile stress that compresses the components between the end plates.The tensioning is done via a nut on the other head plate.

[0039] Multiple tie rods can be electrically insulated or conductively connected to the end plates. Insulation can be achieved, for example, using insulating washers and non-conductive separating paste.

[0040] The tie rods can be evenly distributed around the circumference of the head plates to ensure the most uniform force possible is applied to the electrolyzer components located between them. Typically, more than four tie rods, preferably between six and nine, can be provided for this purpose.

[0041] According to one embodiment, the electrolyzer is characterized in that at least one of the drawbars is electrically connected to the end plates and forms the current path between the opposite ends of the cell stack and thus also the outer ends of the cell sub-stacks. In this embodiment, the cell sub-stacks are electrically connected to the end plates at opposite ends of the cell stack and electrically contacted by the drawbars, which in turn are electrically connected to the end plates. A single drawbar can be electrically connected to both end plates, but it is also possible for several drawbars, in particular all drawbars, to be electrically connected to the end plates. The connection can be established by direct contact of the drawbar(s) with the end plates and / or by additional electrical conductors.

[0042] The drawbar(s) electrically connected to the end plates are at least partially electrically conductive, so that they can conduct current between the end plates and thus also between the ends of the cell stack, and thus also between the outer ends of the cell sub-stacks.

[0043] Due to the advantageous interconnection of the cell stacks, the current flow between the opposite ends of the cell stack, at least in series connections with two cell stacks, exhibits only a low electrical potential. This has the advantage that even conventional tie rods, typically made of a solid body, for example, steel, can serve as current conductors. More complex designs, in which tie rods are formed as hollow bodies or hollow cylinders with electrical conductors, such as power cables, arranged within these cavities, or tie rods with a sheath made of a highly electrically conductive material, such as copper or aluminum, are possible, but not necessary.

[0044] In a preferred embodiment, the at least one tie rod is designed as a solid body, i.e., without axial openings for electrical conductors, and in particular as a monolithic solid body. This solid body design ensures higher tensile strength. The solid body can consist of only a single material, preferably a steel, such as a heat-treatable steel, in particular a heat-treatable steel with material suitability according to DIN EN 13445-2. Such tie rods are easy to manufacture and test, and due to the elimination of additional conductors, such as copper or aluminum cables, they are particularly material-efficient and easily recyclable.

[0045] Optionally, the pull rods can be coated with an alkali-resistant and / or electrically non-conductive protective layer, so that they are corrosion-protected and / or at least touch-safe when cold.

[0046] Using the tie rods as conductors between the ends of the cell stack saves components and material that would otherwise be needed for additional conductors. This results in significant savings in production costs. Furthermore, the electrolyzer is characterized by a particularly compact design because a separate conductor outside the clamping device is no longer required.

[0047] According to one embodiment, the electrolyzer is characterized in that the switchable conductor is electrically connected to the at least one pull rod and / or at least one of the end plates.

[0048] The switchable conductor can be connected to at least one of the drawbars electrically connected to the end plates to provide a connection to the electrolyzer circuit. For this purpose, the switchable conductor can be contacted via a terminal or any other suitable connection for establishing an electrical connection, such as a weld. Terminals or welds have the advantage that they do not need to penetrate the cross-section of the drawbar and therefore do not impair its tensile strength.

[0049] Connecting the switchable conductor to the at least one pull rod, which is electrically connected to the end plates, allows for a simple implementation of the switch. This eliminates the need to run additional conductors to the respective poles of the cell stacks. Instead, the circuit with the switchable conductor can simply be closed via the pull rod, which is also conductively connected in the initial state.

[0050] According to another embodiment, the electrolyzer is characterized in that the drawbars are electrically insulated from the end plates and the opposite ends of the cell stack are connected by an electrical conductor located outside the clamping device, i.e., not part of the clamping device. The electrical conductor can be a cable, a busbar, or another type of conductor. It forms the current path between the opposite ends of the cell stack. Busbars are either a single or multi-part rigid sheet or another type of rigid conductor. Optionally, this electrical conductor can be surrounded by an alkali-resistant and / or electrically non-conductive protective layer, thus protecting it from corrosion and / or at least making it touch-safe when cold.

[0051] According to this design, the tie rods have no electrical connection to the end plates. They are separated from the end plates, for example, by appropriate insulating elements. Instead, the electrical connection between the ends of the cell stack is made by the electrical conductor, which acts as a current conductor and is connected to the corresponding poles of the electrolysis cells or end plates at the outer ends of the cell stack. One or more electrical conductors, particularly busbars, can be used.

[0052] The electrical conductor that carries the current can be electrically connected to the cell stacks via specially designed contact elements. These can be, in particular, adapter plates that are connected to the poles of the cell stacks, for example, screwed to the cell frame of the electrolysis cell. Using a busbar as a current conductor makes it particularly easy to connect the cell stacks electrically because busbars can be easily mounted from the outside, especially by screwing them in place, without additional supports, thus reducing assembly effort and production costs.

[0053] According to one embodiment, the electrolyzer is characterized in that the electrical conductor, which forms the current flow between the opposite ends of the cell stack, is attached to the end plates.

[0054] The electrical conductor can be electrically connected to the end plates via appropriate adapters or fasteners. The circuit is then closed by the fact that the outer ends or poles of the cell stacks are electrically connected at opposite ends of the cell stack to the end plates on which they are located, and the end plates are electrically connected to the electrical conductor that carries the current.

[0055] This design is particularly advantageous because the current conductor can be assembled and disassembled without releasing the tension of the cell stack, and requires only a few components and materials. This reduces assembly and maintenance effort and saves on material and production costs.

[0056] According to one embodiment, the electrolyzer is characterized in that the cell stacks each have end plates arranged at opposite ends. The end plates are typically made of an electrically conductive material, in particular metal, or a composite material. They can be electrically connected to the pole of the respective electrolysis cell to which they abut at the end of the cell stack. As a result, the end plates essentially have the same electrical potential as the respective electrical pole of the electrolysis cell at the end of the cell stack and thus each constitute a pole of the cell stack. In electrolysis cells connected in series, one end or end plate of the cell stack forms a positive pole, and the other, opposite end or the inserted end plate of the cell stack forms a negative pole.

[0057] The electrical connection between the outer ends of the cell stacks, which are located at opposite ends of the cell stack, can be achieved by connecting the end plates at the outer ends of the cell stacks to each other via the current conductor, instead of connecting the poles of the electrolysis cells. The electrical connection between the inner ends of the cell stacks, which are located at the insulator, and the pole(s) of the power supply can be achieved via electrical conductors that are electrically connected to the end plates at the inner ends of the cell stacks.

[0058] The end plates can be designed in such a way that they can be connected to a busbar as an electrical conductor or current carrier without an additional adapter or other components. Therefore, the provision of end plates also simplifies assembly and reduces production costs.

[0059] In some designs, the end plates can be located at the outer ends of the cell stack, i.e., at the opposite ends of the cell stack, and replace the end plates. This also allows for material savings.

[0060] According to one embodiment, the electrolyzer is characterized in that the switchable conductor is electrically connected to the electrical conductor that forms the current flow between the opposite ends of the cell stack.

[0061] Analogous to the design where an electrically conductive pull rod is connected to the switchable conductor, an electrical conductor can also be electrically connected to the switchable conductor when a separate current conductor is provided outside the tensioning device. As previously described, this connection can be made using a variety of suitable connection methods. This also eliminates the need for additional components, thus reducing production effort and costs.

[0062] According to one embodiment, the electrolyzer is characterized in that the insulator is a continuous disk or a disk with openings, particularly openings in the axial direction. The openings can, for example, divide the insulator into segments or subsegments. The shape of its cross-section can be similar to the shape of the electrolysis cells or end plates; that is, in the case of circular electrolysis cells or end plates, the insulator can be a disk with a circular outer contour, e.g., a circular disk or at least an annular disk, or a combination thereof. In the case of rectangular electrolysis cells or end plates, the insulator can be a disk with a correspondingly rectangular outer contour.

[0063] The insulator can have a small thickness or height relative to its maximum cross-section, thus resembling a disc. The insulator can be designed with continuous contact surfaces on its end faces, or surfaces with at least one recess, which contact the inner ends of the cell stacks. The primary requirement is that the insulator is designed to spatially separate the cell stacks in such a way that no voltage flashovers or leakage currents occur between the inner ends of the cell stacks to which it rests during electrolysis. For this purpose, the thickness of the insulator can be equal to or greater than a minimum creepage distance.If such a minimum thickness is maintained, any shaped recesses, openings, spaces or gaps, such as those that occur in segmented insulators, can be provided on the insulator without endangering electrical safety in electrolysis operation through creepage flashovers.

[0064] The minimum creepage distance is the shortest path along a surface of the insulator where no leakage current exceeding 0.5 A, preferably 0.3 A, and particularly preferably 0.1 A, occurs between potentials at the end and beginning of the path, where the voltage difference between the potentials corresponds to a maximum voltage difference between the electrolysis cells or end plates to which the insulator is connected. The minimum creepage distance depends on the degree of contamination of the insulator surface and the tracking resistance of the material(s) from which the insulator is made. It can be determined as described in DIN EN 606641 201901.

[0065] For electrolysis operation up to 2000 m above sea level, with a tracking resistance of the insulator material below 400 V and voltage differences between the inner ends or poles of the cell stacks of up to 1.25 kV DC, the minimum creepage distance for 0.5 A is, for example, 20 mm; for a voltage difference of up to 1.5 kV DC, it is 24 mm. Accordingly, the thickness of the insulator can be 20 mm or more for voltage differences between the inner ends or poles of the cell stacks of up to 1.25 kV DC; for a voltage difference of up to 1.5 kV DC, it can be 24 mm or more.

[0066] If the contamination of the insulator surfaces is reduced and the tracking resistance of the insulator material is increased, the minimum creepage distance is smaller and the thickness of the insulator can be correspondingly reduced. For electrolysis operation up to 2000 m above sea level with little or no contamination, a tracking resistance of the insulator material of at least 400 V, preferably at least 600 V, and a maximum voltage difference between the inner ends or poles of the cell stacks of up to 1.25 kV DC, the thickness of the insulator can be, for example, 4.2 mm or more for the minimum creepage distance, and 5.5 mm or more for a voltage difference of up to 1.5 kV DC. These specifications refer to the thickness during electrolysis operation, in which the cell stack is clamped with the clamping device.

[0067] In some embodiments, the thickness of the insulator can also be reduced by ensuring that the path lengths along the insulator's surfaces between the inner ends of the cell stacks exceed the minimum creepage distance, thus preventing leakage currents along these paths. This can be achieved, for example, by a circumferential overhang on the insulator's outer circumference and / or by providing projections and / or recesses, such as grooves, stepped designs, or chamfers on the outer circumference and in axial openings to extend the path length beyond the minimum creepage distance.

[0068] The minimum thickness of the insulator can then be reduced by up to the amount by which the length of the shortest path is longer than the minimum creepage distance. Reducing the thickness of the insulator has the advantage of saving material and simplifying handling during insulator assembly and cell stack installation.

[0069] According to one embodiment, the electrolyzer is characterized by the fact that the insulator consists of an electrically insulating, pressure-resistant material, such that the insulator does not deform substantially when subjected to the compressive force used to clamp the cell stack. The insulator can, for example, be made of a composite material. This composite material can be a fiber-reinforced composite, in particular a laminated material according to DIN EN 60893. It can, for example, be a glass-fiber-reinforced epoxy resin. Such composite materials are characterized by easy processing, which is also due to their light weight, and by favorable electrical insulation properties. In addition to high mechanical strength, they can also exhibit high temperature resistance.

[0070] Sufficient mechanical strength of the insulator can be achieved, for example, with a compressive strength of the material of at least 200 N / mm², preferably at least 350 N / mm², under uniaxial pressure according to DIN ISO 604, and a flexural strength of at least 300 N / mm² according to DIN ISO 178. High compressive and flexural strength of the insulator prevents warping of the electrolysis cells and allows for an increase in the number of electrolysis cells in the cell stack.

[0071] According to one embodiment, the electrolyzer is characterized in that the insulator has a contact surface on each of its opposing sides, with which it abuts an end face at the inner end of a cell stack. The surface of the contact surface can be shaped complementarily to the surface of the respective end face of the electrolysis cell or end plate against which the insulator abuts, or it can have an excess of material, i.e., an increased thickness, with respect to the complementary shape in order to counteract unwanted bulging of the end face. The circumference of the contact surface on one or preferably both sides of the insulator can be larger than the circumference of the end face such that at least a portion of the respective contact surface remains free.

[0072] In one embodiment, the end faces at the inner ends of the cell stacks are flat, and the contact surfaces of the insulator are also flat. This ensures the most uniform possible force transmission due to the clamping action between the cell stack and the insulator. Particularly if the insulator has axial openings, the area bounded by the circumference of the contact surface can be larger than the actual contact area on one or, preferably, both sides of the insulator.

[0073] Leaving at least part of the installation area clear allows the cell stack to be moved relative to the insulator during assembly without protruding beyond the insulator. This enables greater tolerances in positioning and thus simpler production, while still ensuring uniform force transmission.

[0074] In a preferred embodiment, on one or, preferably, both sides of the insulator, the area bounded by the circumference of the contact surface is larger than the actual contact surface along the entire outer circumference of the insulator. The respective contact surface thus has a circumferential overhang. This overhang prevents contaminants from penetrating between the inner ends of the cell stacks. As a result, the insulator can have a thickness that minimizes or eliminates contamination. Furthermore, it increases the path length along the surface of the insulator at the outer circumference between the inner ends of the cell stacks.

[0075] The previously described configurations concern electrolyzer configurations with only two cell stacks. According to this configuration, it is also possible to provide additional cell stacks and insulators. In a series connection, at least one further insulator (e.g., a second one) and at least one further cell stack (e.g., a third one) can be arranged between the first or second cell stack and the end of the cell stack where the respective cell stack is located. The further insulator is arranged between the first or second cell stack and the further cell stack. The further cell stack and the first or second cell stack, between which the further insulator is located, are connected in parallel or can be connected in parallel. For this purpose, the end of the further cell stack that is located at the further insulator, i.e.,The inner end of the next cell stack must be electrically connected to the same terminal of the power supply as the cell stack to which it is electrically connected in parallel. The other, outer end of the next cell stack and the end of the first or second cell stack located at the next insulator are each electrically connected to the power supply. "Electrically connected to the end of a cell stack" can mean: electrically connected to the terminal of the outermost electrolysis cell or, if end plates are provided, to the respective end plate. The arrangement of cell stacks and insulators is, in turn, clamped to the cell stack via the clamping device.

[0076] In a preferred embodiment, at least one further cell sub-stack and at least one further insulator are arranged at each of the two opposite ends of the cell stack, such that the same number of cell sub-stacks are connected in parallel or switchable to each pole of the power supply. The cell sub-stacks and insulators are clamped together with the first and second cell sub-stacks and their insulators to form the cell stack by the clamping device. The cell sub-stacks can be of identical design. They can contain the same number and type of electrolysis cells. The cell stack thus has two halves or groups of cell sub-stacks connected in series, each comprising cell sub-stacks connected in parallel or switchable to each other. The electrolyzer can then be operated particularly simply in a process in which one group is deactivated at a time.is and in the other group one or more cell sub-stacks are activated or deactivated, or both groups are activated and the same number of cell sub-stacks are activated or deactivated in each group. "Activated" means that the group or cell sub-stack is part of the power supply circuit.

[0077] By using multiple cell stacks, higher power outputs can be achieved. Furthermore, during production and operation in multiple sub-units, it is possible to increase the total number of electrolysis cells in the cell stack while simultaneously enabling easy transport and flexible electrolysis operation, e.g., dependent on hydrogen demand or electricity availability.

[0078] According to another embodiment, the electrolyzer is characterized in that the switch has a third switching state, wherein, when switching to the third switching state, the connection between the additional cell stack and the respective pole of the power supply to which the additional cell stack is connected in the initial state is interrupted. The additional cell stack is thus no longer part of the circuit between the poles of the power supply. Accordingly, the previously described embodiment, in which several additional cell stacks are provided alongside the first two cell stacks, can also be combined with the embodiment in which a switch is provided. Through the switch and a corresponding circuit, any combination of cell stacks can be operated, while the correspondingly different cell stacks are not operated.By providing the switch, it is possible, as previously explained in relation to the corresponding design type, to use the electrolyzer as flexibly as possible.

[0079] The description and claims refer to an assembled state of the electrolyzer with the clamping device attached.

[0080] The invention will be explained in more detail below with reference to the accompanying drawings and the exemplary embodiments shown in the drawings. The drawings show: Fig. 1 a side sectional view of an electrolyzer with series connection and separate current conduction; Fig. 2 a side sectional view of an electrolyzer with series connection and at least one conductive pull rod as current conduction; Fig. 3 a side electrolyzer made of Fig. 1 in a first switching state; Fig. 3 bden electrolyzer from Fig. 1 in a second switching state; Fig. 4 a side sectional view of an electrolyzer with parallel connection and separate current conduction; Fig. 5 a side sectional view of an electrolyzer with parallel connection and at least one conductive pull rod as current conduction; Fig. 6 a side sectional view of an electrolyzer with a further cell stack and a further insulator; and Fig. 7 a side sectional view of an electrolyzer with several further cell stacks and insulators.

[0081] Fig. 1 Figure 1 shows a schematic, side sectional view of electrolyzer 1. Electrolyzer 1 can be supplied with direct current for electrolysis operation via a power supply 2, which is fed by three-phase current and includes a rectifier. However, other direct current sources are also possible as the power supply 2. The power supply 2 has a positive terminal 3 and a negative terminal 4. The positive terminal 3 is electrically connected to, or can be connected to, the cell stack 5. The negative terminal 4 is electrically connected to, or can be connected to, the cell stack 6. The cell stacks 5 and 6 together form the cell stack. The cell stack, and thus the cell stacks 5 and 6, are formed from individual electrolysis cells 7. The cell stacks 5 and 6 can each have an end plate at their ends (in Fig. 1 (indicated by hatching), which is electrically connected to the pole of the electrolysis cell at the respective end of the cell substack 5, 6. They can also be subdivided into substacks (not shown) which are electrically connected in series within the respective cell substack 5, 6. The substacks can also each have an end plate at their ends, with the end plates at the inner and outer ends of the cell substack 5, 6 being the end plates of the respective cell substack 5, 6. The end plates of the substacks are electrically connected to the poles of the electrolysis cell at the respective end of the substack and thus each form a pole of the substack. Accordingly, in a cell substack 5, 6, the substacks connected in series touch each other with their oppositely polarized end plates.

[0082] The cell stack has a head plate 8, 9 at each of its opposite ends. The head plates 8, 9 are connected to each other via tie rods 10, 11. The tie rods 10, 11 are connected to the head plates 8, 9 in such a way that the cell sub-stacks 5, 6 arranged between them are subjected to a compressive force. The cell sub-stacks 5, 6 are electrically connected to their respective head plates 8, 9 at their outer ends. However, instead of separate end plates at the outer ends of the cell sub-stacks 5, 6, it is also possible for the end plates at the outer ends of the cell sub-stacks 5, 6 to be designed as the head plates 8, 9 and replace them, or to be integrated into the head plates 8, 9. The head plates 8, 9 and / or the outer ends of the cell sub-stacks 5, 6 are each connected to each other by the electrical conductor 12.This means that the opposite ends of the cell stack are also electrically connected to each other via the conductor 12, which forms a current conductor 12. The connection of the electrical conductor 12 to the outer ends of the cell sub-stacks 5, 6 can be made at the poles of the electrolysis cells, which are arranged at the outer ends of the cell sub-stacks 5, 6, at the poles of the end plates, or at the end plates 8, 9.

[0083] The tie rods 10, 11 are electrically insulated from the end plates 8, 9. The conductor 12 is preferably a busbar. However, other electrical conductors, such as power cables, can also be used as the busbar 12. The busbar 12 and / or the end plates 8, 9 can be grounded. In the example of the Fig. 1 The busbar is connected to an earthing point 13 via a switchable switching element S7. The busbar 12 is preferably arranged outside a clamping device comprising the end plates 8, 9 and tie rods 10, 11. The busbar 12 is not part of the clamping device. It closes the circuit between the positive terminal 3 of the power supply 2, the first cell stack 5, the second cell stack 6, and the negative terminal 4 of the power supply 2.

[0084] The insulator 14 is also arranged between the cell stacks 5 and 6. Due to its position between the cell stacks 5 and 6, the insulator 14 is also subjected to the compressive force applied by the tie rods 10 and 11 and the end plates 8 and 9 of the clamping device. The insulator 14 ensures that the positive terminal of cell stack 5 at its inner end does not make electrical contact with the negative terminal of the inner end of cell stack 6. The insulator 14 ensures that the circuit is closed only via the opposite ends of the cell stack and the current conductor 12, so that cell stacks 5 and 6 are electrically connected in series.

[0085] The insulator 14 consists of an electrically insulating, pressure-resistant material, so that it essentially does not deform when subjected to a compressive force to clamp the cell stack. It can, for example, be made of a composite material, such as a fiber-reinforced composite. The shape of the insulator 14 is typically adapted to the shape of the electrolysis cells. The insulator 14 can be a solid disk or a disk with cutouts, particularly with openings in the axial direction, for example, a circular disk or annular disk, which can be segmented into segments and subsegments.

[0086] Furthermore, the electrolyzer 1 has the switch 15 and the switchable conductor 16 (The switchable conductor 16 is in the Fig. 1 (as also shown in the other figures, the insulator is arranged perspectively behind the insulator 14 and is typically not connected to the insulator 14). The switchable conductor 16 is electrically connected to the busbar 12. The switching elements S1, S2, S3, and S4 are actuated by the switch 15. The switching element S7 can optionally also be actuated by the switch 15. The switching element S1 is arranged between the inner end of the cell stack 5 and the positive terminal 3 of the power supply 2. It can be used to open or close the electrical connection between the inner end of the cell stack 5, or its terminal, and the positive terminal 3 of the power supply 2. The switching element S3 is arranged between the switching element S1 and the positive terminal 3 of the power supply 2. It can be used to open or close the electrical connection between the positive terminal 3 of the power supply 2 and the switchable conductor 16.Switching elements S2 and S4 are arranged on cell stack 6 and negative terminal 4 of the power supply 2 analogously to S1 and S3. In the shown state, which represents the initial state, switching elements S3 and S4 are open, whereas switching elements S1 and S2 are closed. In the initial state, both cell stacks 5 and 6 are part of the power supply circuit, and electrolysis can be carried out in both cell stacks 5 and 6 of the electrolyzer 1. The switchable conductor 16 is not part of the electrolyzer 1 circuit in the initial state.

[0087] If both cell stacks 5 and 6 are to be operated continuously, continuous electrical conductors (i.e., conductors without switches or switching elements) can be used instead of switch 15, and the switchable conductor 16 can be omitted. However, switch 15 and the switchable conductor 16 allow for more flexible electrolysis operation. Further details regarding the switching states are described below. Fig. 3 a und Fig. 3 b described.

[0088] Fig. 2 Figure 1 shows a schematic, side sectional view of electrolyzer 17. Its construction is largely identical to that of electrolyzer 1. However, unlike electrolyzer 1, electrolyzer 17 does not have separate electrical conductors for current flow. Instead, the drawbars 22, 23 are electrically connected to the end plates 20, 21, forming the current flow 12. For the purpose of better illustration, the electrical connection of the drawbars 22, 23 to the end plates 20, 21 is shown in the figure. Figur 2 shown with the electrical connections 18 and 19. However, the electrical connection can also be made in other ways; for example, in the case of pull rods that are fastened or tightened via a screw connection, it can be made simply via conductive washers between the end plate 20, 21 and the nut or tightening aid. In this way, the pull rods 22, 23 replace the busbar 12 in Figur 1 and form the current conductor 12 between the ends of the cell stack or the outer ends of the cell sub-stacks, thereby closing the circuit of the electrolyzer 17 to the power supply 2. The switchable conductor 25 is electrically connected to at least one of the drawbars 22, 23 and / or end plates 8, 9. Furthermore, at least one of the drawbars 22, 23 or end plates 8, 9 can be connected to an earthing point 24 via the switching element S7. In a clamping device with several drawbars, one, several, or all of the drawbars can form the current conductor 12.

[0089] Fig 3 Figure a again shows electrolyzer 1. In this illustration, however, electrolyzer 1 is not shown in its initial state, but in the first switching state of switch 15. In this first switching state, switching elements S1 and S4 are open, so that the cell stack 5, originally connected to the positive terminal 3 of the power supply 2, is no longer part of the electrolyzer 1 circuit. Instead, the positive terminal 3 is connected to the cell stack 6. For this purpose, switching element S3 is closed, so that the switchable conductor 16, together with the busbar 12, closes the circuit to the outer end of the cell stack 6. A connection between the negative terminal 4 and the inner end of the cell stack 6 still exists via the closed switch S2. In this switching state, only the cell stack 6 is connected, so the operating power is halved. Switching element S7 is open.

[0090] Fig. 3 b shows the first switching state Fig. 3 a corresponding second switching state of switch 15. In this state, switching elements S1 and S4 are closed, and S2 and S3 are open. This disconnects the cell stack 6 from the negative terminal 4 of the power supply 2. The circuit is thus closed between the positive terminal 3, the negative terminal 4, and the cell stack 5 by the closed switching elements S1 and S4 and the switchable conductor 16, which is electrically connected to the current conductor 12. Switching element S7 is open. The operating power is also halved in this operating mode.

[0091] In Fig. 4 Figure 1 shows electrolyzer 1 with cell stacks 5 and 6 connected in parallel. Each cell stack 5 and 6 comprises two substacks arranged in series, which touch each other at their electrically conductive end plates and are connected in series. The inner ends, or positive terminals, of the first and second cell stacks 5 and 6, which are located on the insulator 14, are each connected, or connectable, to the positive terminal 3 of the power supply 2. The outer ends of the cell stacks 5 and 6 are electrically connected to each other via a current conductor 12. The current conductor 12 is also connected to the negative terminal 4 of the power supply 2. The current conductor 12 is, as shown in Figure 1, connected to the positive terminal 4 of the power supply 2. Fig. 1 A separate current conductor, e.g., a busbar, is not part of the clamping device with end plates 8, 9, and tie rods 10, 11. The tie rods 10, 11 are electrically insulated from the end plates 8, 9 and thus also from the outer ends of the cell sub-stacks 5, 6. The switch 15 is configured such that, in the initial state, with switching elements S1 and S2 closed, both cell sub-stacks 5, 6 can be operated in the circuit. In the first or second switching state, i.e., when S1 or S2 opens, the first cell sub-stack 5 or the second cell sub-stack 6 is disconnected from the circuit and deactivated, respectively. The switching element S7 of the grounding 13 is open.

[0092] Fig. 5 shows the electrolyzer Fig. 4 however, with at least one drawbar 10, 11 as a current conductor 12. The drawbars 10, 11, which form the current conductor 12, are each electrically connected to the end plates 8, 9 at the outer ends of the cell stacks of the electrolyzer 17 and can be grounded via the switching element S7. The end plates 8, 9 are each electrically connected to the opposite ends of the cell stack or to the poles of the electrolysis cells or the end plates at the outer ends of the cell stacks 5, 6. The switch 15 is in Fig. 4 The first switching state is shown, in which the first cell sub-stack 5 is deactivated by opening the switching element S1. Similarly, the second cell sub-stack 6 can be deactivated by opening the second switching element S2.

[0093] In Fig. 6 is the electrolyzer from Fig. 2 The diagram shows a further cell stack 26, connected in parallel to the first cell stack 5, and a further insulator 28. The further cell stack 26 and the further insulator 28 are arranged between the outer end of the first cell stack 5 and the end plate 8 at that end. The further insulator 28 is positioned between the further cell stack 26 and the previously outer end of the cell stack 5, which is now an inner end within the cell stack. The first cell stack 5 and the further cell stack 26 are electrically connected in parallel. The outer end of the further cell stack 26 and the inner end of the cell stack 5 that rests against the further insulator 28 are each connected to the current conductor 12, which is formed by the tie rods 10, 11.At the outer end of the further cell stack 26, the electrical connection to the current conductor 12 is made via the head plate 8, which is electrically conductive and is electrically connected to the drawbars 10, 11.

[0094] Switch 15 of electrolyzer 17 in Fig. 6 It has a third switching state with which the further cell sub-stack 26 can be deactivated, for example by opening a switching element S5, which is arranged between positive terminal 3 of the power supply 2 and the inner end of the further cell sub-stack 26. In the electrolyzer 17 shown, the current is supplied 12 via the pull rods 10, 11, i.e., the pull rods are part of the circuit between terminals 3, 4 of the power supply 2. However, it can instead be, as in Fig. 7 As shown, a separate current conductor 12, which is not a tie rod 10, 11 and not part of the tensioning device, e.g. a busbar, may also be provided. Instead of just one further cell stack 26 and further insulator 28, several cell stacks can also be connected in parallel to the first or the second cell stack and each be electronically isolated from the adjacent or neighboring cell stack by an insulator.

[0095] In Fig. 7 Is electrolyzer 1 off? Fig. 1 with further cell sub-stacks 26, 27 connected or switchable in parallel to the first and second cell sub-stacks 5, 6, as well as further insulators 28, 29. The two halves of the cell stack are each constructed identically and connected in series, with the cell sub-stacks of the first half being connected in Figur 7 the first and third cell sub-stacks 5, 26, and the cell sub-stacks of the second half, in Figur 7The second and fourth cell sub-stacks 6, 27 are connected or switchable in parallel to each other. Each of the two halves of the cell stack can also have more than two cell sub-stacks that can be connected or switched in parallel, each separated from the other by insulators and clamped to the cell stack by the common clamping device. The clamping device is a single clamping device that clamps all cell sub-stacks and insulators of the electrolyzer 1 to the cell stack. For particularly simple operation of the electrolyzer 1, in one method for operating the electrolyzer 1, one half can be deactivated and one or more cell sub-stacks in the other half can be activated or deactivated, or both halves (5, 26; 6, 27) can be activated or deactivated, with the same number of cell sub-stacks in each half being activated or deactivated. Reference sign

[0096] 1 Electrolyzer 2 Power supply 3 Positive terminal 4 Negative terminal 5 Cell stack 6 Cell stack 7 Electrolysis cell 8 End plate 9 End plate 10 Pull rod 11 Pull rod 12 Busbar 13 Grounding 14 Insulator 15 Switch 16 Switchable conductor 17 Electrolyzer 18 Conductor 19 Conductor 20 End plate 21 End plate 22 Pull rod 23 Pull rod 24 Grounding 25 Switchable conductor 26 Another cell stack 27 Another cell stack 28 Another insulator 29 Another insulator

Claims

1. Electrolyzer (1, 17) comprising a cell stack having a first cell sub-stack (5) and a second cell sub-stack (6), wherein opposite ends of the cell stack are electrically connected to each other via a current conductor (12), characterized by the fact that - an insulator (14) is arranged between the cell stacks (5, 6), and - the cell stacks (5, 6) are connected in parallel and / or in series to each other, and - the arrangement of cell stacks (5, 6) and insulator (14) is clamped by a clamping device.

2. Electrolyzer (1, 17) according to claim 1, characterized by the fact that the cell substacks (5, 6) are divided into substacks, with the substacks in the cell substack (5, 6) being connected in series to each other.

3. Electrolyzer according to claim 1 or 2, characterized by the fact thatThe cell stacks (5,6) are connected in parallel to each other by connecting the ends of the cell stacks (5, 6) which are arranged on the insulator (14) to a first pole (3) of a power supply (2) and connecting the current conductor (12) to a second pole (4) of the power supply (2).

4. Electrolyzer according to claim 1 or 2, characterized by the fact that The cell stacks (5, 6) are connected in series with each other by connecting one end of the first cell stack (5), which is arranged on the insulator (14), to a first pole (3) of a power supply (2) and connecting one end of the second cell stack (6), which is arranged on the insulator (14), to a second pole (4) of the power supply (2).

5. Electrolyzer (1, 17) according to claim 3 or 4, characterized by the fact that- a switch (15) is provided which has an initial state and a first switching state, - wherein the switch (15) is configured, when switching to the first switching state, to interrupt the connection between the first cell substack (5) and the pole (3) to which the first cell substack (5) is connected, and, if the cell substacks (5, 6) are connected in series, to establish an electrical connection between the first pole (3) and the current conductor (12).

6. Electrolyzer (1, 17) according to claim 5, characterized by the fact that - the switch (15) has a second switching state, - wherein the switch (15) is configured, when switching to the second switching state, to interrupt the connection between the second cell sub-stack (6) and the pole (4) to which the second cell sub-stack (6) is connected, and, if the cell sub-stacks (5, 6) are connected in series, to establish an electrical connection between the pole (4) and the current conductor (12).

7. Electrolyzer according to one of claims 5 or 6, characterized by the fact that the connection between the current conductor (12) and the pole (3, 4) to which the cell stack (5, 6) is connected in the initial state is established via a switchable conductor (16, 25).

8. Electrolyzer (1, 17) according to one of the preceding claims, characterized by the fact that the clamping device comprises two end plates (8, 9, 20, 21) which are each located at opposite ends of the cell stack, and several tie rods (10, 11, 22, 23) which are each attached to the end plates (8, 9, 20, 21) in such a way that the cell sub-stacks (5, 6; 26; 27) arranged between the end plates (8, 9, 20, 21) and the insulator (14, 28, 29) are subjected to a compressive force.

9. Electrolyzer (1, 17) according to the preceding claim, characterized by the fact thatat least one of the pull rods (10, 11; 22, 23) is electrically connected to the head plates (8, 9, 20, 21), and at least one of the pull rods (10, 11; 22, 23) is the current conductor (12).

10. Electrolyzer (1, 17) according to one of claims 8 or 9, characterized by the fact that the switchable conductor (16, 25) is electrically connected to at least one pull rod (10, 11, 22, 23) or head plate (8, 9, 20, 21).

11. Electrolyzer (1, 17) according to claim 8, characterized by the fact that the tie rods (10, 11, 22, 23) are electrically insulated from the end plates (8, 9, 20, 21) and the opposite ends of the cell stack are connected by an electrical conductor (12) outside the tensioning device, in particular a busbar, and the electrical conductor is the current guide (12).

12. Electrolyzer (1, 17) according to the preceding claim, characterized by the fact that the electrical conductor (12) is attached to the end plates (8, 9, 20, 21).

13. Electrolyzer (1, 17) according to claim 11, characterized by the fact that the cell stacks (5, 6) and / or substacks each have an end plate at the ends and the end plates are connected to the electrical conductor (12) at the opposite ends of the cell stack.

14. Electrolyzer (1, 17) according to one of claims 11 to 13, characterized by the fact that the switchable conductor (16, 25) is connected to the electrical conductor (12), a head plate (8, 9, 20, 21) or an end plate at the opposite ends of the cell stack.

15. Electrolyzer (1, 17) according to one of the preceding claims, characterized by the fact that the insulator (14) is a continuous disk or a disk with cutouts.

16. Electrolyzer (1, 17) according to any one of claims 4 to 15, characterized by the fact thatbetween a cell substack (5; 6) and an end of the cell stack at which the cell substack (5; 6) is arranged, at least one further insulator (28; 29) and at least one further cell substack (26; 27) are arranged, wherein the further cell substack (28; 29) is connected in parallel or can be connected in parallel to the cell substack (5; 6) and the further insulator (28; 29) is arranged between the cell substack (5; 6) and the further cell substack (28; 29).

Images