An electrolysis cell stack, a method for detecting a leak and use of an electrolysis cell stack

Abstract

Disclosed is an electrolysis cell stack (10) comprising a plurality of support structures (2) each including an inner aperture (3). The electrolysis cell stack (10) further comprises a plurality of cathodes (17), a plurality of anodes (18), a plurality of bipolar plates (4), a plurality of gas impermeable membranes (19), and pressing means 5 (20) arranged for pressing neighbouring support structures (2) of the plurality of support structures (2) against each other. Further, the electrolysis cell stack (10) comprises a liquid conduit (13) arranged between neighbouring support structures (2) of the plurality of support structures (2), wherein the liquid conduit (13) is arranged outside an outer periphery (40) of the inner aperture (3), deionized water (41) arranged 10 in the liquid conduit (13), and conductivity monitoring means (42) arranged for monitoring a conductivity of the deionized water (41). [0111] A method for detecting a leak in an electrolysis cell stack (10) and use of an electrolysis cell stack (10) is also disclosed.

Description

AN ELECTROLYSIS CELL STACK, A METHOD FOR DETECTING A LEAK ANDUSE OF AN ELECTROLYSIS CELL STACKField of the invention

[0001] The invention relates to the invention relates to an electrolysis cell stack comprising a plurality of support structures each including an inner aperture. The electrolysis cell stack further comprises a plurality of cathodes, a plurality of anodes, a plurality of bipolar plates, a plurality of gas impermeable membranes, and pressing means arranged for pressing neighbouring support structures of the plurality of support structures against each other. Furthermore, the invention relates to a method for detecting a leak in an electrolysis cell stack and use of an electrolysis cell stack.Background of the invention

[0002] In electrolysis cells and electrolysis cell stacks oxygen (02) and hydrogen (H2) is produced by electrodes - in the form of cathodes and anodes - operating in an electrolyte e.g., a liquid alkaline solution. The electrodes are separated by a diaphragm - also called a membrane -, separating the product gases and transporting hydroxide ions (OH-) from one electrode to the other. At least in electrolysis cell stacks, bipolar plates are arranged to ensure electrical connection between the cathodes and anodes of neighbouring cells, and it is known to provide a seal between stack element to prevent leakage of electrolyte or gasses to the surroundings.

[0003] A small electrolyte leakage from a cell stack will often result in formation of crystals on the cell stack outer surface around the leak spot and a large leakage will discharge electrolyte and / or gasses to the surroundings. Thus, by means of periodical visual inspection leaks of the cell stack can be monitored and the cell stack can be taken out of commission and repaired.

[0004] However, such a monitoring system is labour intensive and costly and from US patent application US 2017 / 0107633 Al it is known to provide three independent seals within each other to reduce the risk of leakage and to enable that leakage may be detected by monitoring the pressure in the intermediate zones between seals. However,such an arrangement is costly and space consuming and will only work in a pressurized electrolysis system.

[0005] An object of the invention is therefore to provide for a more advantageous technique for detecting leaks in an electrolysis cell stack.Summary of the invention

[0006] In an aspect, the invention relates to an electrolysis cell stack comprising a plurality of support structures each including an inner aperture. The electrolysis cell stack further comprises a plurality of cathodes, a plurality of anodes, a plurality of bipolar plates, a plurality of gas impermeable membranes, and pressing means arranged for pressing neighbouring support structures of the plurality of support structures against each other. Further, the electrolysis cell stack comprises a liquid conduit arranged between neighbouring support structures of the plurality of support structures, wherein the liquid conduit is arranged outside an outer periphery of the inner aperture, deionized water arranged in the liquid conduit, and conductivity monitoring means arranged for monitoring a conductivity of the deionized water.

[0007] Providing deionized water arranged in the liquid conduit arranged between neighbouring support structures is advantageous in that any leak of the electrolyte arranged inside the cell stack when the cell stack is used for producing hydrogen and oxygen will easily and very fast be detected by the conductivity monitoring means arranged for monitoring a conductivity of the deionized water because deionized water does not conduct electricity whereas the electrolyte by nature is a good conductor of electricity. Furthermore, any leakage of the deionized water into the electrolyte arranged in contact with the anodes and cathodes will substantially not affect the operation of the electrolysis cell stack.

[0008] In this context the term “pressing means” should be understood as any form of press suited for pressing neighbouring electrolysis cell elements against each other in an electrolysis cell stack. I.e., the term includes any kind of hydraulic press, pneumatic press, tie rod, bolts, braces, clamping arrangement or other.

[0009] In this context the term “conductivity monitoring means” should be understood as any form of conductivity monitor suited for monitoring a conductivity of deionized water. I.e., the term includes any kind of monitor using two or more electrodes where an alternating current is applied to one electrode and the potential between the electrodes is measure so that the conductivity of the intermediate fluid can be determined using the distance between the electrodes and their surface area using Ohm's law. The term also includes conductivity probes using e.g., two inductively coupled coils where one is the driving coil producing a magnetic field and it is supplied with accurately known voltage and the other forms a secondary coil of a transformer. The fluid passing through a channel in the sensor forms one turn in the secondary winding of the transformer and the induced current is the output of the conductivity monitor. The term further includes any kind conductivity meter, conductivity sensor, conductivity gauge or other of the above-described type or using other technology e.g., combined with temperature sensor to measure the temperature and achieve automatic temperature compensation or other technologies known to the skilled person.

[0010] Furthermore, in this context the term “gas impermeable” should be understood as the membrane being substantially impermeable to gas during normal use in an electrolysis cell stack. However, in certain other circumstances - e.g., if the gas impermeable membrane is not submerged in electrolyte (i.e., if the gas impermeable membrane is dry) - the membrane could - in these “unnormal” situations - be at least partly permeable to gas.

[0011] In an exemplary embodiment of the invention, the electrolysis cell stack further comprises deionized water pump means arranged for circulating the deionized water in the liquid conduit.

[0012] Circulating the deionized water in the liquid conduit is advantageous in that it hereby is possible to detect a leak using only one or a few conductivity monitoring means in that the electrolyte mixed with the deionized water hereby will be transported to the conductivity monitoring means as opposed to providing the liquid conduit with a plurality of liquid conduit or wait until the leaked electrolyte reached the conductivitymonitoring means through diffusion. Hereby is achieved a faster and more inexpensive detection of leaks.

[0013] In this context the term “pump means” should be understood as any kind of pump suited for establishing a flow of a fluid. I.e., the term includes any kind of rotary or reciprocating positive-displacement pump, any kind of injector, any kind of driven propeller, or other.

[0014] In an exemplary embodiment of the invention, the electrolysis cell stack further comprises pressurizing means arranged for raising the pressure of the deionized water in the liquid conduit.

[0015] Providing the electrolysis cell stack with pressurizing means enabling that the pressure of the deionized water in the liquid conduit can be raised is advantageous in that this provides an additional method for detecting leaks in that by pressure testing the deionized water in the liquid conduit also leaks between the outside of the electrolysis cell stack and the liquid conduit can be detected and / or such a pressure test can be used as a backup system to monitoring that the conductivity monitoring means are operating correctly.

[0016] In this context the term “pressurizing means” should be understood as any form of pressurizer suited for raising the pressure of the deionized water in the liquid conduit. I.e., the term includes any kind of pump, injector, or any kind of spring, pneumatic, hydraulic or actuator operated piston or membrane arrangement, or other.

[0017] In an exemplary embodiment of the invention, the conductivity monitoring means, the deionized water pump means and / or the pressurizing means is arranged external to a space formed by the outermost periphery of the plurality of support structures, the plurality of cathodes, the plurality of anodes, the plurality of bipolar plates and the plurality of gas impermeable membranes.

[0018] Arranging the conductivity monitoring means, the deionized water pump means and / or the pressurizing means outside the stack element is advantageous in thatconductivity monitoring means, the deionized water pump means and / or the pressurizing means hereby are more easily accessible during service or repair.

[0019] In an exemplary embodiment of the invention, the plurality of bipolar plates or the plurality of gas impermeable membranes are arranged inside the inner aperture of the plurality of support structures.

[0020] Arranging a bipolar plate or a gas impermeable membrane inside the inner aperture of the support structure is advantageous in that this reduces material use regarding this bipolar plate or gas impermeable membrane and it provides a more compact electrolysis cell stack.

[0021] In an exemplary embodiment of the invention, the plurality of bipolar plates or the plurality of gas impermeable membranes are suspended by the plurality of support structures inside the inner aperture of the plurality of support structures.

[0022] Suspending a bipolar plate or a gas impermeable membrane inside the inner aperture of a support structure by is advantageous in that the bipolar plate or gas impermeable membrane hereby is securely fixed, and it that provides a more compact electrolysis cell stack.

[0023] In an exemplary embodiment of the invention, the plurality of support structures comprises a structure core and a coating, wherein the coating includes a thermoplastic material or elastomer material at least partly enclosing the structure core and wherein the plurality of bipolar plates or the plurality of gas impermeable membranes are suspended by the plurality of support structures inside the inner aperture of the plurality of support structures by means of the coating.

[0024] Coating the structure core by means of a thermoplastic material or elastomer material is advantageous in that thermoplastic material and elastomer material are easy to mould and excellent at retaining its shape after moulding whereby is it possible to mould functional features into the coating during the moulding process or form functional features - such as complex ducts, seals, pins, depressions, flow inhibiter, turbulators or other - by means of the coating - i.e., provide the support structure withcomplex functional features in a simple and inexpensive way. Thus, by coating the structure core in a thermoplastic material or elastomer material it is possible to suspend the bipolar plate or the gas impermeable membrane in the inner aperture of the support structure in a simple and efficient way and since another advantage of the thermoplastic material and elastomer material is that they are excellent electrical insulators that coating will also ensure that the bipolar plate is electrically insulated from the structure core thus reducing the risk of getting an electric shock when touching an electrolysis cell stack containing such electrolysis cell elements. Furthermore, thermoplastic material is typically more resistant to deteriorated by exposure to oxygen - particularly in a pressurized electrolysis cell system. Even further, it is advantageous to coat the structure core in a thermoplastic material in that it hereby is relatively easy to provide the support structure with the necessary production tolerances without having to machine the structure core extensively - thereby reducing production cost of the support structure. However, elastomer material is often easier to handle and mould and often provides better sealing properties and it is therefore often advantageous to use elastomer material as coating in an unpressurized electrolysis cell system.

[0025] In an exemplary embodiment of the invention, the liquid conduit is formed between outer sealing means and inner sealing means arranged between the neighbouring support structures of the plurality of support structures.

[0026] Forming seal on both sides of the liquid conduit between the neighbouring support structures is advantageous in that the seals makes the electrolysis cell stack hereby is more leak-proof and in that this is a simple and effective way of forming the liquid conduit.

[0027] In this context the term “sealing means” should be understood as any form of seal suited for sealing an enclosure formed by the sealing means when the side of the electrolysis cell element comprising the seal is pressed against a neighbouring electrolysis cell element in an electrolysis cell stack. I.e., the term includes any kind of gasket, O-ring, protrusion, ridge, sealant or other.

[0028] In an exemplary embodiment of the invention, the outer sealing means is extending continuously along an outer periphery of the neighbouring support structures of the plurality of support structures.

[0029] Making the outer sealing means extend continuously along the outer periphery of the support structure is advantageous in that this enables better utilisation of the entire support structure to enable a more compact design.

[0030] In an exemplary embodiment of the invention, the inner sealing means is extending continuously outside an outer periphery of the inner aperture of the neighbouring support structures of the plurality of support structures.

[0031] Making the inner sealing means is extending continuously outside an outer periphery of the inner aperture is advantageous in that this enables better utilisation of the entire support structure to enable a more compact design.

[0032] In an exemplary embodiment of the invention, the plurality of support structures comprises a structure core and a coating, wherein the coating includes a thermoplastic material or elastomer material at least partly enclosing the structure core and wherein the outer sealing means and / or the inner sealing means are formed integrally with the coating.

[0033] Forming the outer sealing means and / or the inner sealing means as an integrated part of the coating is advantageous in that this is a simple, efficient and inexpensive way of forming the sealing means.

[0034] In an exemplary embodiment of the invention, a first cathode of the plurality of cathodes is arranged between a first bipolar plate of the plurality of bipolar plates and a first gas impermeable membrane of the plurality of gas impermeable membranes, wherein the electrolysis cell stack further comprises a first electrolyte conduit arranged between the first bipolar plate and the first gas impermeable membrane, wherein a first anode of the plurality of anodes is arranged in the other side of the first gas impermeable membrane in relation to the first cathode, wherein the first anode is arranged between the first gas impermeable membrane and a second bipolar plate ofthe plurality of bipolar plates, and wherein the electrolysis cell stack further comprises a second electrolyte conduit arranged between the first gas impermeable membrane and the second bipolar plate. Building the electrolysis cell stack in this way ensures a compact and efficient electrolysis cell stack.

[0035] In an exemplary embodiment of the invention, the electrolysis cell stack further comprises electrolyte arranged in the first electrolyte conduit and the second electrolyte conduit. Hereby is achieved an advantageous embodiment of the invention.

[0036] In an exemplary embodiment of the invention, the electrolysis cell stack further comprises electrolyte pump means arranged for generating a flow of the electrolyte through the first electrolyte conduit and / or the second electrolyte conduit.

[0037] Providing the electrolysis cell stack with electrolyte pump means to generating a flow of the electrolyte through the first electrolyte conduit and / or the second electrolyte conduit is advantageous in that it provides for a more efficient electrolysis cell stack.

[0038] In an exemplary embodiment of the invention, the pressure of the deionized water in the liquid conduit is lower that the pressure of the electrolyte in the first electrolyte conduit and the second electrolyte conduit.

[0039] Arranging the electrolysis cell stack so that the pressure of the deionized water in the liquid conduit is lower that the pressure of the electrolyte in the first electrolyte conduit and the second electrolyte conduit is advantageous in that it hereby is ensured that the electrolyte always leaks into the liquid conduit if a leak occurs so that the leak can be detected quickly by means of the conductivity monitoring means.

[0040] In an exemplary embodiment of the invention, the electrolysis cell stack comprises a plurality of liquid conduits, wherein each liquid conduit of the plurality of liquid conduits is arranged between neighbouring support structures of the plurality of support structures and wherein the plurality of liquid conduits is fluidly connected in series to form a continuous liquid conduit.

[0041] Connecting the liquid conduits in series to form a continuous liquid conduit is advantageous in that a single conductivity monitoring mean hereby can be used for monitoring the conductivity of the deionized water throughout the entire electrolysis cell stack and in that a single deionized water pump can be used for establishing flow of the deionized water throughout the entire electrolysis cell stack.

[0042] In an exemplary embodiment of the invention, the electrolysis cell stack comprises a plurality of liquid conduits, wherein each liquid conduit of the plurality of liquid conduits is arranged between neighbouring support structures of the plurality of support structures and wherein every other liquid conduit of the plurality of liquid conduits are fluidly connect in series to form a first continuous liquid conduit and wherein the remaining liquid conduits of the plurality of liquid conduits are fluidly connect in series to form a second continuous liquid conduit.

[0043] Forming alternately a first continuous liquid conduit and a second continuous liquid conduit throughout the electrolysis cell stack is advantageous in that the e.g., the first continuous liquid conduit hereby can be used for monitoring leaks in all the anode compartments in the electrolysis cell stack and the second continuous liquid conduit hereby can be used for monitoring leaks in all the cathode compartments in the electrolysis cell stack. Thereby a faster and more precise position of the leak can be established.

[0044] In an exemplary embodiment of the invention, the coating is electrically insulating.

[0045] Forming the coating of an electrically insulating material is advantageous in that the bipolar plate - which is used as an electrical conductor during use - is electrically insulated from the structure core whereby the risk of getting an electric shock when touching the support structure is reduced or eliminated.

[0046] In an exemplary embodiment of the invention, the structure core is made of metal, such as steel.

[0047] Forming the structure core from metal is advantageous in that metal is a strong, durable and relatively inexpensive material that relatively easily can be moulded or machined into the desired shape.

[0048] In an exemplary embodiment of the invention, the structure core is formed monolithic.

[0049] Forming the structure core monolithic - i.e., from a single piece of material - is advantageous in that a structure core without joints can be formed stronger and / or lighter thereby reducing costs and / or weight.

[0050] In an exemplary embodiment of the invention, the thermoplastic material is selected from a group consisting of: Polypropylene (PP), Polyethylene (PE), Polyphenylene sulphide (PPS), Polysulfone (PSU) and Polyphenyl sulfone (PPSU).

[0051] A common quality of PP, PE, PPS, PSU and PPSU is that these thermoplastic materials are all excellent electrical insulators that are easy to mould and thereby particularly suited for suspending a bipolar plated inside the centre aperture of a support structure. Furthermore, a common quality is that these thermoplastic materials are very resistant to deterioration due to the oxygen exposure the material is exposed to in an operating electrolysis cell stack comprising several electrolysis cell elements.

[0052] In an exemplary embodiment of the invention, the coating is enclosing between 50% and 100%, preferably between 65 and 99%, and most preferred between 80% and 99% of the structure core.

[0053] Coating a majority of the surface area of the structure core by means of the coating is advantageous in that this reduces the risk of the structure core getting in electrical contact with electrically conducting parts of the electrolysis cell stack during use and it provides better protection of structure core from harmful fluids during use in an operating electrolysis cell stack. Thus, the present coating ranges are advantageous in relation to functionality and durability.

[0054] In a further aspect, the invention relates to a method for detecting a leak in an electrolysis cell stack according to any of the previously discussed electrolysis cell stacks, wherein the method comprises the steps of: monitoring a conductivity of the deionized water by means of the conductivity monitoring means, and generating an output by means of the conductivity monitoring means if a conductivity of the deionized water is above a predefined level, wherein the output is indicative of a leak in the electrolysis cell stack.

[0055] Detecting leaks in an electrolysis cell stack by monitoring the conductivity of the deionized water surrounding the stack core is advantageous in that it hereby is possible to quickly detect a leak in the electrolysis cell stack in a simple and relatively inexpensive manner. It should be noted that the predefined level could e.g., be zero, almost zero conductivity, or a predefined value some margin above zero depending on the purity of the deionized water.

[0056] Furthermore, by means of the present invention both monitoring and containment of eventual leaks has been achieved in that if conductivity in the deionized water is detected it only means that the barrier between the liquid conduit and the stack core is leaking - i.e., the leak is still contained within the stack and production may continue in that the barrier between the outside and the liquid conduit in most case still will be intact in that a leak to the outside can be detected by a visual inspection.

[0057] In an exemplary embodiment of the invention, the method further comprises isolating the deionized water in the liquid conduit if the conductivity monitoring means detect a conductivity of the deionized water above a predefined level.

[0058] Isolating the deionized water in the liquid conduit by sealing of any circulation of deionized water exchange, if the conductivity monitoring means detect a conductivity of the deionized water above a predefined level, is advantageous in that if the leakage results in pressure build up in the liquid conduit this is contained inside the liquid conduit whereby the risk of further leaks is reduced.

[0059] In another aspect, the invention relates to use of an electrolysis cell stack according to any of the previously discussed electrolysis cell stacks in a pressurized electrolysis system which is configured to produce hydrogen and / or oxygen.

[0060] Using the electrolysis cell stack in a pressurized electrolysis system is particularly advantageous in that the leaking electrolyte hereby will be forced into the liquid conduit so that a leak may easily and fast be detected.The drawings

[0061] For a more complete understanding of this disclosure, reference is now made to the following brief description, taken in connection with the accompanying drawings and detailed description, wherein like reference numerals represent like parts. The drawings illustrate embodiment of the invention and elements of different drawings can be combined within the scope of the invention:Fig. 1 illustrate elements of a part of an electrolysis cell stack in a perspective view according to an embodiment of the invention,Fig. 2 illustrates an electrolysis system according to an embodiment of the invention,Fig. 3 illustrates a front view of an electrolysis cell element according to an embodiment of the invention,Fig 4 illustrates a side view of a cross section down the middle of the electrolysis cell element disclosed in fig. 3, andFig. 5 illustrates a an enlarges cutout of the electrolysis cell element disclosed in fig. 4.Detailed description

[0062] The present invention is described in view of exemplary embodiments only intended to illustrate the principles and implementation of the present invention. The skilled person will be able to provide several embodiments within the scope of the claims.

[0063] Fig. 1 illustrates an example of a part of an electrolysis cell stack 10 of an electrolysis system 21 according to an embodiment of the invention. In this embodiment the electrolysis cell stack 10 comprises a plurality of similar adjacent electrolysis cells that are forced together by pressing means 20 e.g., in the form of hydraulics, bolts and nuts, spindles or similar arrangements (see fig. 2).

[0064] In this embodiment electrolysis cell stack 10 comprises a plurality of bipolar plates 4 suspended inside an inner aperture 3 of a support structure 2. The bipolar plate 4 may be a metal or plastic plate that is forming a gas and liquid tight barrier separating flow of gas and electrolyte on the two sides of an electrolysis cell element 1. Thus, the bipolar plate 4 fully prevents fluid flow across the electrolysis cell element 1. However, in another embodiment a gas impermeable membrane 19 would instead be suspended inside the inner aperture 3 of the support structure 2.

[0065] In a compartment 24 on one side of the bipolar plate 4 an anode 18 is arranged and this compartment 24 is therefore referred to as an anode compartment 24. In the compartment 25 on the other side of the bipolar plate 4 a cathode 17 is arranged and this compartment 25 is therefore referred to as an anode compartment 25. Thus, in this embodiment a bipolar plate 4 forms an end wall of an anode compartments 24 and another bipolar plate 4 forms an end wall of a cathode compartments 25. The other end wall of each of these compartments 24, 25 is in this embodiment formed by a gas impermeable membrane 19.

[0066] In this embodiment the anodes 18 and cathodes 17 are electrically connected by means of the bipolar plate 4. In fig. 1, the bipolar plates 4 are illustrated with a plurality of circles which is intended to illustrate the part of the bipolar plate 4 that is electrically connected to the electrodes - i.e., the anodes 18 and cathodes 17. Thus, in this embodiment the electrolysis cell stack 10 will alternately comprise a number of anode compartments 24 and cathode compartments 25. In this embodiment the electrical connection between electrodes 17, 18 and bipolar plates 4 is formed by means of spot welding, but in another embodiment the electrical connection could be established by means of regular welding, soldering, mechanical connections (screws,bolts, rivets etc.), wires or other e.g., depending on how the bipolar plate 4 was made and from which material it was made.

[0067] In this embodiment two electrolysis cell elements 1 of the electrolysis cell stack 10 is shown, wherein each of the electrolysis cell elements 1 in this embodiment comprise an anode compartment inlet 22 and anode compartment outlet 23 being in fluid communication with the anode compartment 24 formed inside the stack 10 so that a second electrolyte conduit 46 hereby is formed, and wherein a cathode compartment inlet 28 and cathode compartment outlet 29 being in fluid communication with the cathode compartment 25 also formed inside the stack 10 so that a first electrolyte conduit 45 hereby is formed. The inlets 22, 28 are in this embodiment located towards the bottom part of the electrolysis cell element 1 and is supplying the compartments 24, 25 with electrolyte (also referred to as lye). The compartments 24, 25 is where the electrolysis process happens i.e., the production of the gaseous hydrogen or oxygen. The produced hydrogen and oxygen are leaving the compartments 24, 25 via the outlets 23, 29 located towards the top part of the electrolysis cell element 1.

[0068] The anode compartment outlet 23 from one anode compartment 24 will in this embodiment together with anode compartment outlets 23 of other electrolysis cell elements 1 form an anode / oxygen manifold 26. In the same way, the cathode compartment outlet 23 from a cathode compartment 25 will in this embodiment together with cathode compartments outlets 29 of other electrolysis cell elements 1 form a cathode / hydrogen manifold 27.

[0069] Accordingly, a bipolar plate 4 of one electrolysis cell element 1 is on one side electrically connected to an anode 18 and on the other side electrically connected to the cathode 17, thus the bipolar plate 4 facilitates an electric connection between an anode 18 of a first cell and a cathode 17 of a second cell. As illustrated in fig. 1 the bipolar plate 4 of the left most electrolysis cell element 1 is on its left side connected to an anode 18 forming part of an adjacent cell and on its right side connected to the cathode 17 forming part of the illustrated cell. Similarly, the bipolar plate 4 of the right most electrolysis cell element 1 on fig. 1 is on its left side connected to the anode 18forming part of the illustrated cell and on its right side connected to a cathode forming part of an adjacent cell.

[0070] In the electrolysis cell stack 10 the electrolysis cell elements 1 are forced together, e.g., via threaded rods and bolts (see fig. 2), with a gas impermeable membrane 19 therebetween. The gas impermeable membranes 19 is impermeable to gases such as hydrogen and oxygen (non-polar components) but allow passage of water and polar components (ions). Accordingly, the electrolysis cell element 1 is facilitating structural support for the compartments 24, 25. The compartments 24, 25 being defined by the bipolar plate 4 and the gas impermeable membranes 19 and establishes a fluid flow path from the compartment inlets 22, 28, through each of the compartments 24, 25 to the compartment outlets 23, 29.

[0071] In this embodiment the inlets 22, 28 to respective the compartments 24, 25 are designed to establish an even distribution of electrolyte in the compartments 24, 25 to ensure optimal gas production and optimal cooling of the compartments 24, 25. The outlets 23, 29 from the respective compartments 24, 25 should be designed to effectively evacuated gas from the compartments 24, 25 and thereby ensure that no gas pocket occurs in the compartments 24, 25. This is not desired because it will reduce efficiency of the cell stack 10 and there will be a risk of gas migrating or passing the gas impermeable membrane 19.

[0072] The gas production starts when a current is allowed to flow through the electrolysis cell stack 10. More specific, when a negative potential of a direct current power supply is applied to a cathode 17 in one end of an electrolysis cell stack 10 and a positive potential of the direct current power supply is applied to an anode 18 in the other end of the electrolysis cell stack 10.

[0073] In an embodiment, the electrolyte is an alkaline electrolyte established by adding a strong base to demineralized water such as potassium hydroxide (KOH) producing K+ cations and OH- anions when the DC power is applied. The alkaline electrolyte facilitates transport of negatively charged ions OH- through the gasimpermeable membranes 19 and thus hydrogen and oxygen are produced at the electrodes according to the general principle of electrolysis (see eql and eq2 below).

[0074] Water molecules are dissociated at the cathode into H+ and OH-. Further, due to the presence of electrons e- from the direct current power source, a recombination of H+ into gaseous H2 is facilitated according to eql (1 = liquid, g = gas, ag = aqueous).

[0075] The gaseous hydrogen H2, travels upwards in the cathode compartment 25 and leaves - typically together with some electrolyte 32 - the cathode compartment 25 via the cathode compartment outlet 29.

[0076] The OH- ions in the electrolyte 32 are attracted towards the anode 18 by the electric field and is allowed to pass through the gas impermeable membranes 19. As mentioned, the gas impermeable membranes 19 ensures that no hydrogen or oxygen can pass, but the OH- ions can travel from the cathode compartment 25 to the anode compartment 24. At the anode 18, OH- anions are oxidised and producing oxygen while releasing electrons e- (seen eq2).EQ2: 2 OH- (aq)102 (g) + H2O (I) + 2 e-

[0077] The gaseous oxygen 02 travels upwards in the anode compartment 24 and leaves - typically together with some electrolyte 32 - the anode compartment 24 via the anode compartment outlet 23.

[0078] It should be mentioned that the electrolysis cell stack part and its components illustrated in fig. 1 is only one example of an electrolysis cell stack 10 of the present invention. Other geometric shapes may be suitable. Alternative locations of the anodes 18, cathodes 17 and gas impermeable membranes 19 may be relevant. Further it should be mentioned that an electrolysis cell element 1 according to the invention may be used for both gapped and zero-gap electrolysis cell stacks 10.

[0079] The gas impermeable membrane 19 is as mentioned impermeable to gases but must be selectively permeable to ions. Therefore, it may be of a hydrophilic materialthat attracts water or other polar components, like OH-, but repels non-polar components like H2 or 02. As a non-limiting example, the gas impermeable membrane 19 may be made of an open mesh polyphenylene sulphide fabric, which is coated with a mixture of polysulfone and of zirconium oxide. The gas impermeable membrane 19 may have a thickness between 0.2mm and 0.9mm such as 0.5 mm, a porosity of 55%, the same density as water and an operating temperature between 75 °C and 110°C such as 80°C.

[0080] The electrodes 17, 18 may be made of a corrosion-resistant metal. The oxygen-producing anode 18 may be made of e.g., nickel, a nickel coating on a steel core or of a nickel-iron alloy coated on a simple steel or nickel plate. The hydrogenproducing cathode 17 may generally be made of a steel core with some catalytic coating. Such coatings may include plain unactivated nickel, activated nickel alloys (NiMo, NiSn, NiS) or even platinum group metals. The electrodes 17, 18 may be either solid or use thin, porous or perforated plates. For example, a thin 0.3mm pure nickel plate with 50% perforation can be used for the anode 18, while a similarly thin 0.3mm perforated nickel plate coated with NiS can be used for the cathode 17.

[0081] In this embodiment the support structures 2 comprise outer sealing means 9 and inner sealing means 12 so that a liquid conduit 13 is formed outside the outer periphery 40 of the inner aperture 3 between neighbouring support structures 2 in the electrolysis cell stack 10 is formed the support structures 2 are pressed against each other. In this embodiment deionized water 41 is arranged in this liquid conduit 13 so that leaks of electrolyte 32 from inside the anode compartment 24 or the cathode compartment 25 into the liquid conduit 13 can be detected by monitoring the conductivity of the deionized water 41 in the liquid conduit 13 by means of conductivity monitoring means 42 (see fig. 2) - as will be discussed in more details in relation to the following figures.

[0082] In this embodiment support structures 2 of the electrolysis cell stack 10 comprises a deionized water flow arranged similarly to the electrolyte flow system in that in this embodiment each support structures 2 comprise a first deionized water inlet 49 and first deionized water outlet 51 establishing a flow through the liquid conduit 13on the anode side (i.e., first support structure side 7 (see fig. 4)) of all the support structure 2 so that a first continuous liquid conduit 47 is formed, in that in this embodiment each support structures 2 comprise a second deionized water inlet 50 and second deionized water outlet 552 establishing a flow through the liquid conduit 13 on other side (i.e., the cathode side or second support structure side 8 (see fig. 4)) of each of all the support structures 2 so that a second continuous liquid conduit 48 is formed. In this way it is possible to detect if an anode compartment 24 or a cathode compartment 25 is leaking by monitoring the deionized water 41 in the first continuous liquid conduit 47 and in the second continuous liquid conduit 48 by separate conductivity monitoring means 42 (see fig. 2).

[0083] Fig. 2 illustrates an electrolysis system 21 according to an embodiment of the invention which in this embodiment comprises an electrolysis cell stack 10 formed by a plurality of electrolysis cell elements 1, a plurality of cathodes 17, a plurality of anodes 18, and a plurality of gas impermeable membranes 19 held and forced together by pressing means 20 which in this embodiment comprises threaded rods 30 and nuts 31 forcing two endplates of the stack 10 against each other to press neighbouring electrolysis cell elements 1 against each other.

[0084] As mentioned, the gas leaves the stack 10 via the upper manifolds 26, 27. The gas from each manifold 26, 27 is separated from the electrolyte 32 which is subsequently recirculated. In this embodiment the electrolysis system 21 also comprises an oxygen storage 36 to which the produced oxygen is led and a hydrogen storage 37 to which the produced hydrogen is led. As the gas separation is not essential for the invention, this is not described in further details.

[0085] In this embodiment the electrolysis system 21 comprises a vessel 33 to which the recirculated electrolyte 32 is led and in this embodiment demineralized water 34 and a base 35 - in this case potassium hydroxide - is mixed in the vessel 33 to form an electrolyte 32 which is led into the electrolysis cell stack 10 to enter the compartments 24, 25 through the compartment inlets 22, 28. In this embodiment the electrolysis cell stack 10 also comprise electrolyte pump means 38 - in this case in the form of a pump - arranged for controlling the flow speed of the electrolyte 32 and inanother embodiment the electrolysis cell stack 10 could also comprise a heat exchanger for temperature regulation of the electrolyte 32 for increasing or decreasing the temperature of the electrolyte 32 before it is guided into the electrolysis cell stack 10. In another embodiment the electrolyte pump means 38 could be provided elsewhere in the circuit or the circulation could be driven by the gas production in the electrolysis cell stack 10.

[0086] The flow speed of gas vs electrolyte fraction is advantageous to control in that in this way it is possible to control the volume of electrolyte 32 in the outlet manifolds 26, 27. Thus, the gas / electrolyte fraction can be controlled in various ways requiring a process system (not illustrated) which comprises a controller, pumps, sensors, valves, meters, etc.

[0087] Non-limiting examples of control of gas vs electrolyte fraction can be by controlling the power supply. This is because there is a relationship between gas production and power consumption. Alternatively, or in addition, the gas vs electrolyte fraction can be controlled by controlling the pressure in the electrolysis cell stack 10 or the flow of quantity of electrolyte 32 per unit time into the electrolysis cell stack 10.

[0088] An electrolysis system 21 is typically designed to operate at a given pressure and temperature based on a trade-off between output and cost. In this embodiment the electrolysis system 21 is designed to operate at a pressure at around 15-20 Bar but in another embodiment the electrolysis system 21 could be designed to operate at a lower pressure - such as 9-15 Bar, 5-8 Bar, 2-4 Bar or even unpressurized - or the electrolysis system 21 could be designed to operate at a higher pressure - such as 25-35 Bar, 30- 70 Bar, 80-150 Bar or even higher. As a general rule the higher operation pressure, the more expensive electrolysis system 21 but at high pressure the gas is compressed in the stack 10 and thus higher gas production can be expected and less cost to compress the gas subsequently can be expected.

[0089] In this embodiment electrolysis cell stack 10 further comprises deionized water pump means 43 arranged for circulating the deionized water 41 through all the liquid conduits 13 formed between neighbouring support structures 2 inside theelectrolysis cell stack 10 and in this embodiment the electrolysis cell stack 10 further comprises pressurizing means 44 arranged for raising the pressure of the deionized water 41 in the single continuous liquid conduit 13. In this embodiment the pressurizing means 44 is the same as deionized water pump means 43 but in another embodiment the pressurizing means 44 could also or instead comprise a separate pump, a pressure regulator, a valve arrangement or other.

[0090] In this embodiment the pressure of the deionized water 41 in the liquid conduits 13 is raised by the pressurizing means 44 to a pressure above atmospheric pressure so that the deionized water 41 will leak out of the electrolysis cell stack 10 enabling that a leakage in the outer sealing means 9 can be visually detected or can be detected by monitoring the pressure of the deionized water 41. However, in this embodiment the pressure of the deionized water 41 is maintained below the pressure of the electrolyte 32 in the first and second electrolyte conduit 45, 46 to ensure that if the inner sealing means fails the electrolyte 32 will flow into the liquid conduit 13 where the leak may be detected by the conductivity monitoring means 42. However, in another embodiment the electrolysis cell stack 10 would not comprise pressurizing means 44 and the deionized water 41 in the liquid conduits 13 would be unpressurized or the electrolysis cell stack 10 could comprise pressure reducing means (not shown) to reduce the pressure of the deionized water 41 in the liquid conduits 13 to a pressure below atmospheric pressure e.g., if electrolysis system 21 was unpressurized.

[0091] In this embodiment the conductivity monitoring means 42, the deionized water pump means 43 and the pressurizing means 44 are all arranged external to a space formed by the outermost periphery of the support structures 2 but in another embodiment conductivity monitoring means 42, the deionized water pump means 43 and / or the pressurizing means 44 could be provided inside the stack 10 at each liquid conduit 13 e.g., to better and / or faster determine the exact location of a leak.

[0092] In this embodiment leaks in the electrolysis cell stack 10 is detected by monitoring a conductivity of the deionized water 41 at the conductivity monitoring means 42 by means of the conductivity monitoring means 42. In this case the deionized water 41 is constantly circulated past the conductivity monitoring means 42 but, inanother embodiment, the leaking electrolyte 32 could reach one or more conductivity monitoring means 42 through simple diffusion. If the conductivity monitoring means 42 detects that the conductivity of the deionized water 41 is above a predefined level, the conductivity monitoring means 42 will generate an output which is indicative of a leak in the electrolysis cell stack 10. This output could then trigger an audial and / or visual alarm, it could trigger a shutdown of the electrolysis system 21 (e.g., depending on the size of the conductivity), it could be transferred to the control system of the electrolysis system 21 or other.

[0093] If the conductivity monitoring means 42 detect that the conductivity of the deionized water 41 is above a predefined level the deionized water 41 is in this embodiment isolated in the liquid conduit 13 so that the circulation of the deionized water 41 is cut off to ensure that any pressure build up in the liquid conduit 13 due to the leak is primarily restricted inside the electrolysis cell stack 10. In this embodiment the deionized water 41 is isolated in the liquid conduit 13 by means of two valves 53 located immediately outside the stack 10 so that any flow of deionized water 41 in and out of the electrolysis cell stack 10 is blocked. However, in another embodiment the valves 53 could be located inside the stack 10, each liquid conduit 13 between all the neighbouring support structures 2 could be provided with one or more valves 53, or the valves 53 could be arranged differently.

[0094] Fig. 3 illustrates a front view of an electrolysis cell element 1 according to an embodiment of the invention. In this embodiment the electrolysis cell element 1 comprises a support structure 2 formed with an inner aperture 3 in which a bipolar plate 4 is suspended so that the bipolar plate 4 forms an impermeable wall in the aperture 3. As better seen in figs. 4 and 5 the support structure 2 is in this embodiment formed by a structure core 5 provided with a coating 6 arranged so that the bipolar plate 4 is suspended in the inner aperture 3 by means of this coating 6. However, in another embodiment a gas impermeable membrane 19 could instead be suspended in the inner aperture 3 or neither a bipolar plate 4 nor a gas impermeable membrane 19 would be suspended in the inner aperture 3 and the bipolar plate 4 and the gas impermeable membrane 19 would be suspended inside the electrolysis cell stack 10by other means - e.g., by being sandwiched between the support structures 2, by being suspended by dedicated suspensions, by being attached to the support structures 2 outside the inner aperture 3 or other.

[0095] In this embodiment the visible first support structure side 7 of the support structure 2 comprises outer sealing means 9 and inner sealing means 12 where in between the liquid conduit 13 is formed when the first support structure side 7 is pressed against the neighbouring electrolysis cell element 1 in an electrolysis cell stack 10. However, in another embodiment the liquid conduit 13 could be formed as an indentation or groove in the support structure 2 and / or in another embodiment the support structure 2 could comprise further sealing means 9, 12 arranged inside the inner sealing means 12 and / or outside the outer sealing means 9 and / or the support structure 2 could comprise further liquid conduit 13 arranged inside the inner sealing means 12 and / or outside the outer sealing means 9 e.g., for additional protection against leaks, for cooling purposes or other.

[0096] In this embodiment outer sealing means 9 is extending continuously along an outer periphery 11 of the support structure 2 and in this embodiment the inner sealing means 12 is extending continuously outside the outer periphery 40 of the inner aperture 3 of the support structures 2 but in another embodiment the outer sealing means 9 and / or the inner sealing means 12 could be arranged elsewhere on the support structure 2 - such as closer to each other, further away from each other, they could be waving e.g., to pass obstacles or other.

[0097] As a non-limiting example, the outer diameter of the electrolysis cell element 1 is in this embodiment around 950 mm. However, in another embodiment the outer diameter of the electrolysis cell element 1 could be bigger - such as 1,200 mm, 1,800 mm, 2,300 mm or even bigger - or smaller such as 820 mm, 690 mm, 510 mm or even smaller, e.g., depending on the electrolysis cell stack 10 capacity, manufacturing options, available space or other.

[0098] Fig 4 illustrates a side view of a cross section down the middle of the electrolysis cell element 1 disclosed in fig. 3. In this embodiment the support structure2 comprises a first support structure side 7 and a second support structure side 8 opposite the first support structure side 7 and in this embodiment the outer sealing means 9 and the inner sealing means 12 (seen more clearly in fig. 5) is only arranged on the first support structure side 7. However, in another embodiment the outer sealing means 9 and / or the inner sealing means 12 could also or instead be arranged on the second support structure side 8, e.g., to form the previously discussed separate first continuous liquid conduit 47 and second continuous liquid conduit 48.

[0099] In this embodiment the width of one electrolysis cell element 1 is around 16 mm. However, in another embodiment the width of the electrolysis cell element 1 could be bigger - such as 20 mm, 25 mm, 30 mm or even bigger - or smaller such as 14 mm, 12 mm, 10 mm or even smaller, e.g., depending on the electrolysis cell stack 10 capacity, manufacturing options, available space or other. An electrolysis cell stack 10 may comprise from two electrolysis cell element 1 to several hundred electrolysis cell element 1 such as from up to 100, 150, 200, 230, . . .500 or even more electrolysis cell element 1. Hence, the length of an electrolysis cell stack 10 may be from around 40 mm to e.g., 10 meters. Several stacks 10 may be connected in series or in parallel. The design of an electrolysis cell stack 10 may be determined by voltage and thus requirements to the power supply of the electrolysis system 21. Further stack design parameters may be depending on available space, required capacity, etc.

[0100] Fig. 5 illustrates a an enlarges cutout of the electrolysis cell element 1 disclosed in fig. 4. In this embodiment the outer sealing means 9 and the inner sealing means 12 are formed integrally with the coating 6 in that the sealing means 9, 12 are formed as sealing protrusions 14 protruding from the first support structure side 7, wherein these sealing protrusions 14 are formed during the process (e.g., moulding process) by which the coating 6 is applied to the structure core 5. However, in another embodiment the sealing means 9, 12 could be formed integrally with the coating 6 though a subsequent machining process, the sealing means 9, 12 could be moulded into the coating 5, the sealing means 9, 12 could be connected to the coating 5, the sealing means 9, 12 could be resting against the coating 5 and / or the sealing means 9, 12 could be formed by the entire surface of the coating 5 being forced against aneighbouring electrolysis cell element 1 in a electrolysis cell stack 10. Or in another embodiment the support structure 2 would not comprise a coating 5 and the sealing means 9, 12 could formed during the process (e.g., moulding process) by which the structure core 5 is made - i.e., sealing means 9, 12 could be formed integrally with the structure core 5, the sealing means 9, 12 could be formed in the support structure 2 though a subsequent machining process, and / or the sealing means 9, 12 could O-rings, gaskets or other connected to the support structure 2.

[0101] In this embodiment the support structure 2 further comprises two alignment protrusions 15 and two alignment apertures 16 arranged so that when the first support structure side 7 of the electrolysis cell element 1 is forced against a second support structure side 8 of a neighbouring electrolysis cell element 1 in a electrolysis cell stack 10 the alignment protrusions 15 will engage the corresponding alignment apertures 16 in the neighbouring electrolysis cell element 1 so that the electrolysis cell elements 1 are fully aligned. However, in another embodiment the electrolysis cell element 1 could comprise another number of alignment protrusions 15 and alignment apertures 16 - such as one, three, five eight or even more.

[0102] In this embodiment the alignment protrusions 15 are formed integrally with the coating 6 in that the alignment protrusions 15 are formed during the process (e.g., moulding process) by which the coating 6 is applied to the structure core 5. However, in another embodiment the alignment protrusions 15 could be formed integrally with the coating 6 though a subsequent machining process, the alignment protrusions 15 could be connected to the coating 5, the alignment protrusions 15 could be formed by the structure core 5 and / or the alignment protrusions 15 could be enabled in another way.

[0103] In this embodiment the upper alignment protrusion 15 and alignment aperture 16 also serves as the deionized water outlet 51, 52 and the bottom alignment protrusion 15 and alignment aperture 16 (shown in fig. 5) also serves as the deionized water inlet 49, 50 so that in this embodiment all the liquid conduits 13 are fluidly connected in series to form a single continuous liquid conduit 13 - as also illustrated in fig. 2. This design is advantageous in that this design is space saving and reduces cost. However,in another embodiment the deionized water inlet 49, 50 and / or the deionized water outlet 51, 52 could be formed as separate other openings, ducts, channels or other in the support structure 2 and / or the support structure 2 could be provided with more deionized water inlet 49, 50 and / or deionized water outlet 51, 52 - such as two, three, five eight or even more.

[0104] In this embodiment the structure core 5 is made of steel but in another embodiment the structure core 5 could also or instead be made of another metal - such as aluminium, stainless steel, brass and / or other - and / or the structure core 5 could comprise another material - such as a composite material, plastic, ceramic, glass and / or other.

[0105] In this embodiment the structure core 5 is formed monolithic - i.e., in this embodiment the structure core 5 is formed from a single piece of material - but in another embodiment the structure core 5 could be formed by several parts e.g., connected by means of mutually engaging geometry, screws, bolt, rivets, adhesive or other.

[0106] In this embodiment the electrolysis cell element 1 is to be used in a pressurized electrolysis cell system 21 so in this embodiment the coating 6 is made of a thermoplastic material in the form of Polypropylene (PP) in that his material is more resistant to oxygen deterioration. However, in another embodiment the thermoplastic material could be Polyethylene (PE), Polyphenylene sulphide (PPS), Polyphenyl sulfone (PPSU), Poly sulfone (PSU) or another polymeric thermoplastic material, e.g., depending on the specific use, the specific moulding technique, the operating pressure of the electrolysis cell stack 10 or other. However, if the electrolysis cell system 21 was adapted to operate un-pressurized - i.e., substantially at atmospheric pressure - the coating 6 could also or instead be made from an elastomeric material such as natural or synthetic rubber, polyurethane, polybutadiene, neoprene and silicone or another.

[0107] In this embodiment the coating 6 is electrically insulating and in this embodiment the bipolar plate 4 is suspended in the inner aperture 3 exclusively bymeans of the coating 6 so that in this embodiment the bipolar plate 4 is fully electrically insulated from the structure core 5. In this embodiment the bipolar plate 4 is connected to the structure core 5 by means of the coating 6 during the process (e.g., moulding process) by which the coating 6 is applied to the structure core 5. However, in another embodiment the bipolar plate 4 could be connected to the structure core 5 by means of the coating 6 though a subsequent assembly process.

[0108] In this embodiment the coating 6 in this embodiment is enclosing around 98% of the surface of the structure core 5 the coating 6, and the only part of the structure core 5 not being enclosed by the coating is in this embodiment the small taps 39 arranged along the outer periphery of the structure core 5, in that these taps 39 are used for fixating the structure core 5 during the process of applying the coating 6 to the structure core 5. However, in another embodiment the structure core 5 could be fully enclosed by the coating 6 or the coating 6 would enclose less of the structure core 5 - such as only 92%, 74%, 56% or even less.

[0109] The invention has been exemplified above with reference to specific embodiments. Details of specific embodiment have been provided in order to understand the aim of the invention and can be combined where appropriate. Please note, that detailed descriptions of well-known systems, devices, circuits, and methods have been omitted so as to not obscure the description of the invention with unnecessary details.List1. Electrolysis cell element2. Support structure3. Inner aperture4. Bipolar plate5. Structure core6. Coating7. First support structure side8. Second support structure side9. Outer sealing means10. Electrolysis cell stack11. Outer periphery of support structure12. Inner sealing means13. Intermediate enclosure14. Sealing protrusion15. Alignment protrusion16. Alignment aperture17. Cathode18. Anode19. Gas impermeable membrane20. Pressing means21. El ectroly si s sy stem22. Anode compartment inlet23. Anode compartment outlet24. Anode compartment25. Cathode compartment26. Anode / oxygen manifold27. Cathode / oxygen manifold28. Cathode compartment inlet29. Cathode compartment outlet30. Rod31. Nut32. Electrolyte33. Vessel34. Water35. Base36. Oxygen storage37. Hydrogen storage38. Electrolyte pump means39. Tap40. Outer periphery of inner aperture41. Deionized water42. Conductivity monitoring means43. Deionized water pump means44. Pressurizing means45. First electrolyte conduit46. Second electrolyte conduit47. First continuous liquid conduit48. Second continuous liquid conduit49. First deionized water inlet50. Second deionized water inlet51. First deionized water outlet52. Second deionized water outlet53. Valve

Claims

Claims1. An electrolysis cell stack (10) comprising, a plurality of support structures (2) each including an inner aperture (3), a plurality of cathodes (17), a plurality of anodes (18), a plurality of bipolar plates (4), a plurality of gas impermeable membranes (19), and pressing means (20) arranged for pressing neighbouring support structures (2) of said plurality of support structures (2) against each other, a liquid conduit (13) arranged between neighbouring support structures (2) of said plurality of support structures (2), wherein said liquid conduit (13) is arranged outside an outer periphery (40) of said inner aperture (3), deionized water (41) arranged in said liquid conduit (13), and conductivity monitoring means (42) arranged for monitoring a conductivity of said deionized water (41).

2. An electrolysis cell stack (10) according to claim 1, wherein said electrolysis cell stack (10) further comprises deionized water pump means (43) arranged for circulating said deionized water (41) in said liquid conduit (13).

3. An electrolysis cell stack (10) according to any of the preceding claims, wherein said electrolysis cell stack (10) further comprises pressurizing means (44) arranged for raising the pressure of said deionized water (41) in said liquid conduit (13).

4. An electrolysis cell stack (10) according to any of the preceding claims, wherein said conductivity monitoring means (42), said deionized water pump means (43) and / or said pressurizing means (44) is arranged external to a space formed by theoutermost periphery of said plurality of support structures (2), said plurality of cathodes (17), said plurality of anodes (18), said plurality of bipolar plates (4) and said plurality of gas impermeable membranes (19).

5. An electrolysis cell stack (10) according to any of the preceding claims, wherein said plurality of bipolar plates (4) or said plurality of gas impermeable membranes (19) are arranged inside said inner aperture (3) of said plurality of support structures (2).

6. An electrolysis cell stack (10) according to any of the preceding claims, wherein said plurality of bipolar plates (4) or said plurality of gas impermeable membranes (19) are suspended by said plurality of support structures (2) inside said inner aperture (3) of said plurality of support structures (2).

7. An electrolysis cell stack (10) according to claim 6, wherein said plurality of support structures (2) comprises a structure core (5) and a coating (6), wherein said coating (6) includes a thermoplastic material or elastomer material at least partly enclosing said structure core (5) and wherein said plurality of bipolar plates (4) or said plurality of gas impermeable membranes (19) are suspended by said plurality of support structures (2) inside said inner aperture (3) of said plurality of support structures (2) by means of said coating (6).

8. An electrolysis cell stack (10) according to any of the preceding claims, wherein said liquid conduit (13) is formed between outer sealing means (9) and inner sealing means (12) arranged between said neighbouring support structures (2) of said plurality of support structures (2).

9. An electrolysis cell stack (10) according to claim 8, wherein said outer sealing means (9) is extending continuously along an outer periphery (11) of said neighbouring support structures (2) of said plurality of support structures (2).

10. An electrolysis cell stack (10) according to claim 8 or 9, wherein said inner sealing means (12) is extending continuously outside an outer periphery (40) of said inner aperture (3) of said neighbouring support structures (2) of said plurality of support structures (2).

11. An electrolysis cell stack (10) according to any of claims 8-10, wherein said plurality of support structures (2) comprises a structure core (5) and a coating (6), wherein said coating (6) includes a thermoplastic material or elastomer material at least partly enclosing said structure core (5) and wherein said outer sealing means (9) and / or said inner sealing means (12) are formed integrally with said coating (6).

12. An electrolysis cell stack (10) according to any of the preceding claims, wherein a first cathode (17) of said plurality of cathodes (17) is arranged between a first bipolar plate (4) of said plurality of bipolar plates (4) and a first gas impermeable membrane (19) of said plurality of gas impermeable membranes (19), wherein said electrolysis cell stack (10) further comprises a first electrolyte conduit (45) arranged between said first bipolar plate (4) and said first gas impermeable membrane (19), wherein a first anode (18) of said plurality of anodes (18) is arranged in the other side of said first gas impermeable membrane (19) in relation to said first cathode (17), wherein said first anode (18) is arranged between said first gas impermeable membrane (19) and a second bipolar plate (4) of said plurality of bipolar plates (4), and wherein said electrolysis cell stack (10) further comprises a second electrolyte conduit (46) arranged between said first gas impermeable membrane (19) and said second bipolar plate (4).

13. An electrolysis cell stack (10) according to claim 12, wherein said electrolysis cell stack (10) further comprises electrolyte (32) arranged in said first electrolyte conduit(45) and said second electrolyte conduit (46).

14. An electrolysis cell stack (10) according to claim 13, wherein said electrolysis cell stack (10) further comprises electrolyte pump means (38) arranged for generating a flow of said electrolyte (32) through said first electrolyte conduit (45) and / or said second electrolyte conduit (46).

15. An electrolysis cell stack (10) according to claim 13 or 14, wherein the pressure of said deionized water (41) in said liquid conduit (13) is lower that the pressure of said electrolyte (32) in said first electrolyte conduit (45) and said second electrolyte conduit(46).

16. An electrolysis cell stack (10) according to any of the preceding claims, wherein said electrolysis cell stack (10) comprises a plurality of liquid conduits (13), wherein each liquid conduit (13) of said plurality of liquid conduits (13) is arranged between neighbouring support structures (2) of said plurality of support structures (2) and wherein said plurality of liquid conduits (13) is fluidly connected in series to form a continuous liquid conduit (13).

17. An electrolysis cell stack (10) according to any of the preceding claims, wherein said electrolysis cell stack (10) comprises a plurality of liquid conduits (13), wherein each liquid conduit (13) of said plurality of liquid conduits (13) is arranged between neighbouring support structures (2) of said plurality of support structures (2) and wherein every other liquid conduit (13) of said plurality of liquid conduits (13) are fluidly connect in series to form a first continuous liquid conduit (47) and wherein the remaining liquid conduits (13) of said plurality of liquid conduits (13) are fluidly connect in series to form a second continuous liquid conduit (48).

18. An electrolysis cell stack (10) according to any of the preceding claims, wherein said coating (6) is electrically insulating.

19. An electrolysis cell stack (10) according to any of the preceding claims, wherein said structure core (5) is made of metal, such as steel.

20. An electrolysis cell stack (10) according to any of the preceding claims, wherein said structure core (5) is formed monolithic.

21. An electrolysis cell stack (10) according to any of the preceding claims, wherein said thermoplastic material is selected from a group consisting of: Polypropylene (PP), Polyethylene (PE), Polyphenylene sulphide (PPS), Polysulfone (PSU) and Polyphenyl sulfone (PPSU).

22. An electrolysis cell stack (10) according to any of the preceding claims, wherein said coating (6) is enclosing between 50% and 100%, preferably between 65 and 99%, and most preferred between 80% and 99% of said structure core (5).

23. A method for detecting a leak in an electrolysis cell stack (10) according to any of the preceding claims, wherein said method comprises the steps of• monitoring a conductivity of said deionized water (41) by means of said conductivity monitoring means (42), and • generating an output by means of said conductivity monitoring means (42) if a conductivity of said deionized water (41) is above a predefined level, wherein said output is indicative of a leak in said electrolysis cell stack (10).

24. A method according to claim 23, wherein said method further comprises isolating said deionized water (41) in said liquid conduit (13) if said conductivity monitoring means (42) detect a conductivity of said deionized water (41) above said predefined level.

25. Use of an electrolysis cell stack (10) according to any of claims 1-22 in a pressurized electrolysis system (21) which is configured to produce hydrogen and / or oxygen.

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