Electrolysis system and method for providing an electrolysis system

Abstract

The invention relates to an electrolysis plant (100) for converting water in the context of proton exchange membrane electrolysis or anion exchange membrane electrolysis, wherein the electrolysis plant (100) has one or more stacks (110a, 110b, 110c, 110d), wherein one or each of the several stacks has several electrolysis cells (120) with a membrane (122), wherein the electrolysis plant (100) further comprises a pressure vessel (150) which is filled with nitrogen (h) or is configured to be filled with nitrogen, and wherein the one or the several stacks (110a, 110b, 110c, 110d) are arranged in the pressure vessel (150).

Description

[0001] The invention relates to an electrolysis plant for converting water in the context of proton exchange membrane (PEM) electrolysis or anion exchange membrane (AEM) electrolysis, and a method for providing such an electrolysis plant. State of the art

[0002] Hydrogen can be produced using electrolysis, a process in which water is split into oxygen and hydrogen using electrical energy. This is also known as water electrolysis. One example of this is proton exchange membrane (PEM) electrolysis. These systems are also referred to as PEM electrolysis plants or PEM electrolyzers. Typically, such an electrolysis plant has one or more PEM stacks; each PEM stack contains several electrolysis cells, each with a proton exchange membrane. Anion exchange membrane (AEM) electrolysis is another type of electrolysis.

[0003] In PEM electrolysis, for example, a large portion of the water typically remains on the oxygen side (anode) of the membrane. While the hydrogen is produced and removed on the other side of the membrane (cathode), the oxygen initially remains in the water in bubble form and is then typically separated from the water as a continuous phase in a container. The pressure at the cathode (hydrogen side, i.e., hydrogen production) is typically above 20 barg or even above 30 barg, sometimes reaching up to 100 barg. At the anode (oxygen side, i.e., water splitting), the pressure of the oxygen product is lower than the pressure on the cathode side, e.g., slightly above atmospheric pressure. This allows for the avoidance or at least reduction of oxygen contamination of the hydrogen. The oxygen-side section of the electrolysis system can, in principle, also be designed for lower pressures.This is also referred to as a differential pressure design of the electrolysis system.

[0004] During operation of the electrolysis plant, it is unavoidable that some hydrogen will diffuse back to the oxygen side or otherwise enter the system, for example, due to defects or tears in the membrane. As has been shown, even fiber-reinforced membranes are not completely tear-resistant. This can lead to the formation of an explosive gas mixture, which may ignite and, in the resulting explosion, damage the electrolysis plant. Consequently, at least some parts of the plant located near components such as the PEM stacks, particularly piping and similar components, must be designed for high pressures due to the risk of explosion or detonation. Therefore, despite the low operating pressure on the oxygen side, no costs can be saved by designing corresponding parts of the plant for this lower operating pressure.

[0005] Furthermore, the flexibility of the system is significantly reduced, as the design for very high operating pressures means that the design for a specific number or geometric arrangement of stacks is in turn designed with a specific number of electrolysis cells, or must be designed with this in turn.

[0006] Against this background, the task arises to specify a better option for an electrolysis plant or its provision, in particular to make the electrolysis plant more variable and / or economical. Disclosure of the invention

[0007] This problem is solved by an electrolysis plant and a method for providing an electrolysis plant with the features of the independent claims. Embodiments are the subject of the dependent claims and the following description. Advantages of the invention

[0008] The invention relates to water electrolysis and electrolysis plants, their operation, and their provision, i.e., the installation of electrolysis plants. The method and the plant will be described in detail below.

[0009] Such electrolysis plants typically serve to produce or obtain hydrogen by means of electrolysis. In so-called water electrolysis, water is converted (split) into hydrogen and oxygen; that is, in addition to hydrogen, oxygen is always also obtained or produced simultaneously. There are various types of electrolysis in water electrolysis, with the present invention relating to so-called proton exchange membrane electrolysis (PEM electrolysis). The fundamentals of this are known, e.g., from "Bessarabov et al.: PEM electrolysis for Hydrogen production. CRC Press." However, the proposed invention is also applicable to so-called anion exchange membrane (AEM) electrolysis, which functions similarly.

[0010] The electrolysis system, and in particular its next smaller component, the "electrolysis module," comprises one or more stacks; depending on the type of electrolysis system, these are either PEM stacks or AEM stacks. Each stack contains several electrolysis cells, each with a membrane; depending on the type of electrolysis system, this membrane is either a proton exchange membrane or an anion exchange membrane. The individual electrolysis cells with their membranes are typically planar, and several of them are stacked on top of each other to form a stack. Bipolar plates can be positioned between two adjacent membranes.

[0011] In electrolysis (this applies particularly to PEM and AEM electrolysis), water, especially demineralized water, is supplied to the electrolysis cells as the feed medium, where the water is converted (split) into hydrogen and oxygen. Unlike PEM stacks, AEM stacks preferably use 0.01 to 3 molar sodium or potassium hydroxide solutions as the electrolyte and coolant, the concentration of which is kept at least approximately constant by the addition of water.

[0012] As mentioned, most of the water typically remains on the oxygen side of the membrane during electrolysis. While the hydrogen is produced and removed on the other side of the membrane, the oxygen initially remains in bubble form in the water and is then typically fed, as an oxygen-containing fluid stream, into a container called an oxygen separator. There, the gaseous oxygen is separated from the water as a continuous phase, yielding an oxygen product stream that is typically released into the atmosphere and / or can be used for other purposes.

[0013] A fluid stream consisting mainly of water is then fed back to the electrolysis cells from the oxygen separator. This is therefore a closed loop, at least with regard to the water. A hydrogen-containing fluid stream is fed from one side of the electrolysis cells to a hydrogen separator. Unlike the oxygen-containing fluid stream, the proportion of water in the hydrogen-containing fluid stream is typically significantly lower; however, it may still contain water that was transported through the membrane along with the hydrogen.

[0014] The hydrogen separator separates the hydrogen from the water, producing a so-called hydrogen product stream which is typically intended for further use and is therefore first purified and / or stored.

[0015] Furthermore, the electrolysis system according to the invention comprises a pressure vessel that is filled with nitrogen – and in particular gaseous nitrogen – or that is designed to be filled with nitrogen. In any case, during operation of the electrolysis system, the pressure vessel is filled with nitrogen. The one or more stacks – and thus the sometimes very large number of cells – are arranged in the pressure vessel.

[0016] The individual stacks therefore only need to be mechanically designed to withstand a low external pressure, as any problems caused by explosions or detonations are prevented by the nitrogen present – ​​at least during operation. This allows for the use of significantly more efficient electrolysis cells, especially those with very thin membranes. For example, the membrane can be thinner than 100 µm or even thinner than 55 µm. Furthermore, a large number of stacks can be connected to a process water module with a cooling function. This makes it particularly easy to connect more than 300, possibly more than 500, or even up to 800 or more cells in series. Depending on the type, this could involve, for example, two to 20 stacks electrically connected in series and arranged together in a pressure vessel.The significantly lower resulting cell voltage thus overcomes the higher cell degradation that conventionally occurs with increased oxygen product pressure.

[0017] In one embodiment, the electrolysis cells in each stack are arranged horizontally, meaning that the individual, planar electrolysis cells extend at least substantially in a horizontal plane (relative to gravity). It is also conceivable that the electrolysis cells in each stack are arranged vertically, meaning that the individual, planar electrolysis cells extend at least substantially in a vertical plane (relative to gravity). A combination of horizontally and vertically oriented stacks is also conceivable.

[0018] In one embodiment, the one or more stacks are pre-assembled on a rack, in particular a separate rack, and can thus be inserted into the pressure vessel. The rack(s) can then be easily slid into the pressure vessel, resulting in simple installation of the electrolysis system.

[0019] In one embodiment, the pressure in the pressure vessel is variably adjustable. This allows, in particular, the nitrogen pressure in the pressure vessel to be set as precisely as possible to a minimum pressure for the hydrogen produced. That is, the nitrogen pressure can be set to a value that is at most a predetermined value higher than the pressure on the hydrogen side, but especially still (slightly) higher than the pressure on the hydrogen side. This predetermined value can be, for example, 10, 100, or 500 mbar, or even more. Put another way, the hydrogen pressure (on the hydrogen side of the electrolysis cells; the hydrogen product pressure) can be set to a value with only a small negative offset (relative to the nitrogen pressure), and in particular, this can be adjusted variably. The (absolute) pressure can, for example, be set to a value between 5 bar and 100 bar.This eliminates the need for downstream product gas compression, throttling, or expansion, meaning the stacks are only subjected to the necessary mechanical stress.

[0020] The nitrogen pressure can be increased or decreased as needed, even after a certain operating time of the electrolysis plant, to adjust the clamping forces if necessary. Generating back pressure with nitrogen against the hydrogen and oxygen product pressures allows for a significantly simpler and lighter clamping structure for the cells into stacks. In particular, this structure does not need to compensate for the entire pressure range from atmospheric to operating or design pressure. This pressure vessel concept achieves a high degree of integration between the tasks of gas production / separation and sealing under pressure.

[0021] In one embodiment, water flows through both the anode side (oxygen side) and the cathode side (hydrogen side), as this minimizes the local pressure difference within the individual electrolysis cell (in the direction of flow) due to the high degree of symmetry. This flow reduces the risk of dead water zones, where the ion concentration increases and thus allows harmful stray currents to occur.

[0022] The outermost electrolysis cells of a stack, which are more susceptible to wear and tear (e.g., the three, five, or ten outermost cells), are, in one embodiment, thicker, for example, by up to 30% or up to 50%, than the other electrolysis cells. This also applies to the membrane, meaning the membrane is thicker. This makes these electrolysis cells more stable. These outer electrolysis cells can also be equipped with larger openings, allowing for a larger water flow for cooling.

[0023] In one embodiment, strain gauges are attached to one or each of the multiple stacks. This can serve, for example, to detect mechanical stresses in a plane of critical electrolysis cell plates or the end plates, thus enabling countermeasures such as reducing the temperature difference of the water between the inlet and outlet of a stack (increasing water circulation or reducing the resulting stack operating voltage) if necessary.

[0024] In one embodiment, a water polisher (i.e., a water purification or treatment system) is arranged on the cathode or hydrogen side. The higher partial pressure of oxygen results in a greater oxygen concentration at the hydrogen-producing cathode. This increases both the probability of peroxide formation according to the law of mass action and also leads to increased fluoride release. To minimize subsequent reactions with piping and equipment, the water flow on the cathode side is preferably suitable for direct treatment, i.e., in particular, per module.

[0025] In one embodiment, a heater is provided in a nitrogen purge circuit; this can be used as a measure to adjust the heat profile in the pressure vessel and thus enable, for example, a faster start-up (i.e., ramp-up).

[0026] In one embodiment, a nitrogen supply line, i.e., a supply line for the nitrogen to the pressure vessel, is arranged such that it is located in the coldest area of ​​one or at least one of the several stacks (i.e., at the water inlet) and / or in a flat guide in order to keep the temperature difference between the surface and the nitrogen temperature as small as possible.

[0027] In one embodiment, one or each of the multiple stacks exhibits a pressure differential, ideally a small pressure differential of max. 500 mbar, between the anode and cathode compartments. This allows the bipolar plate and, in particular, the membrane to be designed with thinner walls, which increases the internal electrical conductivity and also the thermal conductivity. Consequently, the membrane core temperature is lower than with thicker membranes located at a greater distance from the cooling process water.

[0028] The individual stacks are thus based on electrolysis cells that operate particularly efficiently, significantly more so than conventional electrolysis systems without the use of a nitrogen pressure vessel. This allows the specific minimum recirculating water volume to be reduced while maintaining the same, proven inlet and outlet temperatures compared to conventional electrolysis systems. The significantly thinner membrane also eliminates the disadvantages of conductivity at lower inlet temperatures (at constant temperature).

[0029] The outlet or control temperature is of little consequence. Therefore, a larger number of stacks can be connected to a process water module that has a fixed maximum water circulation rate. The increased oxygen pressure compensates for the higher oxygen flow.

[0030] For the selection of different operating pressures, the proposed electrolysis plant does not require costly redesign or redevelopment of the stacks or essential components such as seals and clamping systems; only the product lines and instrumentation need to be modified, which is relatively simple. The adaptation is therefore limited to the peripheral components, which are standard parts.

[0031] Adjusting the size of the individual stacks, in particular the number of electrolysis cells per stack, is possible through the clamping mechanism (which serves to clamp the electrolysis cells) designed for lower forces, in order to match them, for example, to the levels of an existing DC voltage source.

[0032] The pressure vessel reliably protects the sensitive stacks from atmospheric influences and is particularly suitable for maritime operating conditions such as nearshore, nearshore floating and offshore, or dusty locations.

[0033] In one embodiment, a feed and / or cooling water stream is supplied serially to at least some of the multiple stacks. The feed or cooling water is therefore not supplied to all stacks in parallel, but rather to at least some stacks connected in series for process engineering purposes, which simplifies the even distribution of the water. This is possible because the pressure vessel reduces atmospheric temperature influences, resulting in more homogeneous mechanical stress and thus making larger temperature differences compared to the outlet temperatures acceptable.

[0034] Flowfield components, such as a structured bipolar plate and / or flow guide vanes, which are conductively connected to the gas diffusion layer of each cell, can be designed heterogeneously in the plane to achieve higher heat and mass transfer over the flow path. This can be achieved, for example, by varying the flow channels in terms of width, spacing, and / or depth within the bipolar plate. The flowfield components can also be surface-coated to promote advantageous bubble detachment. The coatings can be provided with local gradients, e.g., corresponding to simulated and / or measured local conditions such as pH, temperature, and bubble concentration.

[0035] Wear-resistant coatings can also be applied to the Flowfield components of the stacks with deliberately varying thicknesses, depending on, for example, assumed and / or measured wear under operating conditions. Additionally or alternatively, the stacks can be rotatably mounted, allowing the inlet and outlet sides to be easily interchanged in a symmetrical design, thus ensuring uniform wear. The stacks can therefore be rotatably mounted by 180°; the orientation of the axis of rotation depends on the arrangement of the inlet and outlet sides, which are intended to be interchangeable. Stainless steel, such as SS316L, preferably with a coating, e.g., niobium, is a particularly suitable material for the Flowfield components.

[0036] In idle mode (i.e., at rest or idle), one or more of the stacks can be operated at very low currents, e.g., less than 1%, less than 0.5%, or even less than 0.1% of the nominal current, to maintain a stable oxidation state of a mixed-precious-metal catalyst on the anode side. Nitrogen is added to the water-oxygen side as needed to maintain a sufficient margin from the lower explosive limit of the hydrogen-oxygen mixture, which would otherwise be achieved through gas crossover over time. The hydrogen side is considered less critical because its upper explosive limit is farther from the pure gas (94%, compared to 4% for the lower limit); furthermore, oxygen diffuses more slowly into hydrogen than vice versa, due in part to the effective molecular diameter. However, a nitrogen purge line is also optionally provided here.However, both sides can also relax during longer periods of rest, which delays and reduces nitrogen dosing.

[0037] The cell blocks of the stacks are bonded together with a gas-tight adhesive instead of conventional clamping (in the area of ​​the sealing surfaces of the cell plates); the individual cells can also be encapsulated with polymer and / or cured to form a block. This allows for more cost-effective manufacturing.

[0038] The embodiments of the method described above and below also apply accordingly to the plant, for which any necessary components or units must be provided, and vice versa.

[0039] The invention is explained in more detail below with reference to the accompanying drawing, which shows a system according to a preferred embodiment of the present invention. Brief description of the drawing

[0040] Figure 1 schematically shows an electrolysis plant in one embodiment. Figure 2 schematically shows a stack of the electrolysis plant according to Figure 1 . Detailed description of the drawing

[0041] In Figure 1Figure 100 schematically depicts an electrolysis plant 100 in an embodiment that can also be provided within the framework of a method according to the invention. This is an electrolysis plant for water electrolysis, for example, using PEM. As already mentioned, it could also be water electrolysis using AEM. Therefore, the following will only refer to stacks and membranes, which will then be PEM or AEM stacks or PEM or AEM membranes, respectively. In particular, the electrolysis plant shown here, and generally described within the scope of the invention, is an industrial-scale electrolysis plant for, for example, producing hydrogen on an industrial scale. A typical power output of such an electrolysis plant is, for example, more than 1 MW or even more than 20 MW.

[0042] The electrolysis system 100 features, by way of example, four stacks 110a, 110b, 110c, 110d of electrolysis units or stacks 110a, 110b. Each of these stacks features, by way of example, several electrolysis cells, each containing a membrane.

[0043] Furthermore, the electrolysis plant 100 has a pressure vessel 150 in which the stacks 110a, 110b, 110c, 110d are arranged.

[0044] Stack 110a is an example. Figure 1 enlarged in Figure 2 Figure 120 shows an electrolysis cell comprising a membrane 112 situated between two bipolar plates 124 and 126. The bipolar plates, with the possible exception of the outermost ones, can each be used for two adjacent electrolysis cells. The Figure 2 Stack 110a shown has six electrolysis cells as an example.

[0045] The membrane 122 separates the electrolysis cells into an oxygen side 114 and a hydrogen side 116; this is shown in Figure 2 Only schematically indicated. The oxygen sides 114 and the hydrogen sides 116 can each be considered together as the oxygen side and hydrogen side, respectively, of a stack or of the entire electrolysis system.

[0046] In Figure 2 The diagram also shows example Cartesian coordinate axes x and z, where the z-axis is vertical and thus aligned with the direction of gravity. The y-axis (not shown) is perpendicular to the plane of the drawing. The individual electrolysis cells are therefore horizontally aligned, i.e., parallel to the xy-plane.

[0047] The outermost one or two electrolysis cells, i.e., those at the very top and bottom (viewed in the z-direction), may be slightly thicker than the other electrolysis cells.

[0048] Stacks 110a, 110b, 110c, and 110d can all be constructed identically, i.e., like stack 110a, and further stacks of this type can also be provided. In general, an electrolysis system can have several stacks, e.g., two, four, six, eight, ten, twelve, or more, up to 50 stacks; each stack, in turn, can have several electrolysis cells, e.g., four, ten, 20, 50, or even 100 or more electrolysis cells. The stacks can be supplied with energy in a suitable manner. For example, between four and twelve electrolysis cells can each form a cell block, so that a stack can have several cell blocks.

[0049] The electrolysis plant 100 further comprises a vessel 130, which serves as an oxygen separator or oxygen-water separator. The oxygen separator 130 is connected to the stacks, or rather to each of the electrolysis cells, via a fluid connection that passes through a wall of the pressure vessel 150. This allows a fluid flow "b" to be pumped from the oxygen separator 130 to the electrolysis cells, e.g., by means of a pump 134, via a suitable fluid connection 132, e.g., pipes. Depending on the type of electrolysis plant and, for example, the number of electrolysis cells and / or stacks, several fluid connections (i.e., separate lines) located outside the stacks may also be provided. For example, one fluid connection may be provided for two stacks.

[0050] The stacks, or electrolysis cells, are connected to the oxygen separator 120 via a fluid connection 136, e.g., pipes, which in turn connects to a wall of the pressure vessel 150. A fluid flow "c" can be pumped from the electrolysis cells, specifically from the oxygen side 114 of each electrolysis cell, to the oxygen separator 120 via the fluid connection 126; the pump 134 may also be sufficient for this purpose. Depending on the type of electrolysis system and, for example, the number of electrolysis cells, several fluid connections (i.e., separate lines) may be provided. For example, one fluid connection may be provided for two stacks.

[0051] Furthermore, the electrolysis system 100 includes an additional container 140, which serves as a hydrogen separator or hydrogen-water separator. The stacks or electrolysis cells are connected to the hydrogen separator 140 via a fluid connection 142, e.g., pipes, through a wall of the pressure vessel. A fluid flow "e" from the electrolysis cells, specifically the hydrogen side 116 of each electrolysis cell, can be conveyed to the hydrogen separator 140 via the fluid connection 142. Depending on the type of electrolysis system and, for example, the number of electrolysis cells, several fluid connections (i.e., separate lines) may be provided. For instance, one fluid connection may be provided for two stacks. Multiple hydrogen separators are also conceivable.

[0052] During operation of the electrolysis plant 100, the fluid stream "b", which contains water, is pumped from the oxygen separator 130 to the stacks or their electrolysis cells. There, the water is converted into oxygen and hydrogen. For this purpose, an electrical voltage is applied to the electrolysis cells. The hydrogen is electrochemically transported through the membrane 112 to the hydrogen side 116 and can then be fed, possibly mixed with water vapor and a liquid water phase, as stream "e" – a hydrogen-containing fluid stream – to the hydrogen separator 140. There, the hydrogen can be separated and, for example, discharged or stored as stream "f" for further use. Water separated in the hydrogen separator 140 can, for example, be treated (not shown here) and then returned to the main water circuit as fluid stream "g".

[0053] The oxygen remains on the oxygen side 114 along with most of the water. The resulting fluid stream "c" therefore contains water and oxygen – it is an oxygen-containing fluid stream. As mentioned, the fluid stream "c" is fed to the oxygen separator 130.

[0054] It should be noted that fluid stream "c" may also contain a small amount of hydrogen. Similarly, fluid stream "e" may also contain a small amount of oxygen.

[0055] Since water is converted into oxygen and hydrogen in the electrolysis cells and the oxygen and hydrogen are removed, the amount of water decreases and therefore - in order to maintain continuous operation - new water (so-called make-up water, start-up current) can be supplied externally as current "a".

[0056] This water "a" can be pre-treated, for example (not shown here), which is not relevant to the present invention. Water separated in the hydrogen separator 140, i.e., the fluid stream "g" already mentioned, can be fed to stream a and then back to the oxygen separator 130, possibly also after prior treatment.

[0057] As mentioned, oxygen is separated from the water in the oxygen separator 130; the oxygen separated or separated in this process can be carried away as an oxygen stream "d" for further use and possibly stored.

[0058] Furthermore, the electrolysis plant 100 includes, for example, a control unit 160, which can be used to control and, if necessary, monitor the stacks or their electrolysis units or their power supply. The control unit 160 can also be configured, for example, to control or regulate (not shown here) controllable or adjustable valves.

[0059] For the operation of the electrolysis plant 100, the pressure vessel 150 is filled with nitrogen. This nitrogen is represented as a flow h. A supply line 152 for the nitrogen is located in the area of ​​a water inlet (inlet side) of a stack. The pressure is variable, for example, adjustable to a value between 5 bar and 100 bar. It is particularly advantageous if the nitrogen pressure is set to a value slightly higher than the pressure of the hydrogen obtained during electrolysis. For example, in Figure 1A valve 154 is shown, which is intended to illustrate that the pressure in the nitrogen container can be set or regulated to a predetermined value.

[0060] In the Figure 2 The fluid flows "b", "c", and "e" are also shown, here for the individual stack 110a. It can be seen that one inlet side of stack 110a (viewed in the direction of gravity) is at the bottom, while one outlet side is at the top. Stack 110a can now be rotatable, for example, possibly within a rack, so that the inlet and outlet sides can be interchanged. For this purpose, one axis of rotation could be parallel to the x-axis, y-axis, or the xy-plane. It should be noted that the specific design of the stack's inlet and outlet is not shown here.

Claims

1. Electrolysis plant (100) for converting water in the context of proton exchange membrane electrolysis or anion exchange membrane electrolysis, wherein the electrolysis plant (100) comprises one or more stacks (110a, 110b, 110c, 110d), wherein one or each of the multiple stacks comprises multiple electrolysis cells (120) with a membrane (122), wherein the electrolysis plant (100) further comprises a pressure vessel (150) which is filled with nitrogen (h) or is equipped to be filled with nitrogen, and wherein the one or more stacks (110a, 110b, 110c, 110d) are arranged in the pressure vessel (150).

2. Electrolysis system (100) according to claim 1, wherein the one or more stacks (110a, 110b, 110c, 110d) are pre-assembled on a rack and can thus be placed in the pressure vessel (150).

3. Electrolysis system (100) according to claim 1 or 2, which is designed such that the pressure of the nitrogen in the pressure vessel (150) is variably adjustable, in particular to a value between 5 bar and 100 bar, whereby the pressure of the nitrogen in the pressure vessel is adjustable to a value which is greater, but at most by a predetermined value greater than, a pressure of the hydrogen arising on a hydrogen side of the electrolysis cells.

4. Electrolysis system (100) according to one of the preceding claims, wherein one or at least one of the several stacks is horizontally oriented.

5. Electrolysis system (100) according to one of the preceding claims, wherein one or at least one of the several stacks is rotatably mounted, in particular such that the inlet and outlet sides are interchangeable.

6. Electrolysis system (100) according to one of the preceding claims, wherein an anode side and a cathode side of the stacks are designed to be water-flowing.

7. Electrolysis system (100) according to one of the preceding claims, wherein one or more outer electrolysis cells of one or each of the multiple stacks are thicker and / or have a larger opening.

8. Electrolysis system (100) according to one of the preceding claims, further comprising a water polisher arranged on a hydrogen side of the stacks.

9. Electrolysis system (100) according to one of the preceding claims, further comprising a nitrogen purging circuit with a heater.

10. Electrolysis system (100) according to one of the preceding claims, further comprising a supply line for the nitrogen to the pressure vessel, which is arranged in the coldest area of ​​one or at least one of the several stacks.

11. Electrolysis system (100) according to one of the preceding claims, which is designed such that the pressure difference between the anode and cathode compartment of one or each of the several proton exchange membrane stacks is at most 500 mbar.

12. Electrolysis system (100) according to one of the preceding claims, which is designed such that a feed and / or cooling water stream is supplied serially to at least some of the several stacks.

13. Method for providing an electrolysis plant (100) for the conversion of water in the context of proton exchange membrane electrolysis or anion exchange membrane electrolysis, wherein the electrolysis plant (100) comprises one or more stacks, wherein one or each of the multiple stacks comprises multiple electrolysis cells (120) with a membrane (122), wherein the one or the multiple stacks are arranged in a pressure vessel (150), and wherein the pressure vessel (150) is filled with nitrogen (h).

14. Method according to claim 13, wherein the pressure of the nitrogen in the pressure vessel is set to a value which is greater than the pressure of the hydrogen arising on a hydrogen side of the electrolysis cells by at most a predetermined value, in particular at most 500 mbar.

15. Method according to claim 13 or 14, for providing the electrolysis system (100) according to any one of claims 1 to 12

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