An alkaline electrolyzer apparatus

Abstract

The invention relates to an alkaline electrolyzer arrangement (10, 40, 70, 310) for producing hydrogen gas. The arrangement comprises a first alkaline electrolyzer unit (11, 41, 71, 311) and a second alkaline electrolyzer unit (21, 51, 81, 321), each of the first and second alkaline electrolyzer units comprising a first end plate (13, 23, 43, 53, 73, 83, 313, 323), a second end plate (15, 25, 45, 55, 75, 85, 315, 325), and a plurality of electrolyzer cells (19, 29, 49, 59) forming a cell stack (17, 27, 47, 57, 77, 87, 117, 317, 327) arranged between the first and second end plates. The alkaline electrolyzer arrangement further comprises a load bearing surface (30, 30', 60, 90, 330) arranged between the first and second alkaline electrolyzer units such that the second alkaline electrolyzer unit is arranged vertically above the first alkaline electrolyzer unit and is supported by the load bearing surface.

Description

TECHNICAL FIELD

[0001] The present invention relates generally to an alkaline electrolyzer arrangement for producing hydrogen gas, comprising a first alkaline electrolyzer unit and a second alkaline electrolyzer unit. BACKGROUND

[0002] With more and more countries pursuing a decarbonization strategy, hydrogen gas is likely to become more important as an energy transport means. The use of hydrogen gas is particularly relevant for industries that face challenges with direct electrification, such as steel and the manufacture of certain chemicals, long-distance transport, shipping, and the aviation industry. Preferably, the produced hydrogen gas has a low carbon footprint and is ultimately green, for example by electrolyzing water using electricity from renewable sources. In addition to regulations and market design, the cost of hydrogen production remains an obstacle.

[0003] An electrolyzer or water electrolyzer is an electrochemical device for splitting water molecules into hydrogen and oxygen gas by means of an electric current. The electrolyzer comprises an electrolyzer cell in which the electrochemical process takes place. The electrolyzer cell typically consists of two electrodes (anode and cathode) immersed in a liquid electrolyte or adjacent to a solid electrolyte and a membrane or other porous transport layer that facilitates the transport of reactants and removal of products. At the electrodes, water is split into oxygen and hydrogen gas, with ions (typically H+or OH-) passing through the liquid or solid membrane electrolyte. The membrane between the two electrodes is also responsible for keeping the produced gases (hydrogen and oxygen) separated and avoiding gas mixing.

[0004] The electrolyzer typically comprises a plurality of such electrolyzer cells arranged in a cell stack and arranged between two end plates that provide mechanical support. The cell stack can also comprise separators as an insulating material between the two opposing electrodes in the electrolyzer cell, seals, and a frame for further mechanical support. Furthermore, a plurality of electrolyzer units can be arranged in an electrolyzer system comprising appliances for cooling, processing hydrogen gas (e.g., for purification and compression), converting the power input (e.g., transformers and rectifiers), processing the water supply (e.g., deionization), and gas output (e.g., oxygen). Such an electrolyzer system can for example be comprised in a hydrogen production facility.

[0005] Electrolyzers are typically classified into different technologies based on the electrolyte and the temperature at which they are operated. For example, alkaline electrolyzers use a liquid alkaline electrolyte, while proton exchange membrane (PEM) electrolyzers use a solid polymer electrolyte, and solid oxide electrolyzers (SOEC) use a solid ceramic material as electrolyte.

[0006] All types of electrolyzers have a relatively high cost of producing hydrogen. However, in relation to the platinum group metal based catalysts typically used for PEMs, alkaline electrolyzers are typically associated with cheaper catalysts. Furthermore, alkaline electrolyzers typically have a higher durability due to the lower solubility of the exchangeable electrolyte and the anode catalyst. In addition, alkaline electrolyzers typically achieve a higher gas purity due to the lower gas diffusion rate in the alkaline electrolyte.

[0007] However, there are still challenges associated with electrolyzers and in particular for hydrogen production facilities requiring a large installation surface area. This together with the relatively less installation of large hydrogen production facilities requires making electrolyzer installations more efficient and cost effective. SUMMARY

[0008] It is an object of the present invention to overcome at least some of the above-mentioned problems and to provide an alkaline electrolyzer installation for producing hydrogen which is at least to some extent an improvement over the prior art solutions. This object and other objects are achieved with an alkaline electrolyzer installation for producing hydrogen comprising a first alkaline electrolyzer unit and a second alkaline electrolyzer unit, as will become apparent in the following.

[0009] According to a first aspect of the present invention, there is provided an alkaline electrolyzer installation for producing hydrogen. The installation comprises a first alkaline electrolyzer unit and a second alkaline electrolyzer unit, each of the first and second alkaline electrolyzer units comprising a first end plate, a second end plate and a plurality of electrolyzer cells forming a cell stack arranged between the first and second end plates, wherein the alkaline electrolyzer installation further comprises a load bearing surface arranged between the first and second alkaline electrolyzer units such that the second alkaline electrolyzer unit is arranged vertically above the first alkaline electrolyzer unit and is supported by the load bearing surface.

[0010] Hence, the surface area for installing the electrolyzer installation is used more efficiently. In other words, by using the same amount of surface area for installing the electrolyzer installation, the capacity of the electrolyzer installation is increased. Thus, by the present invention, the capacity per surface area of the electrolyzer installation is increased. The capacity can for example be defined as the hydrogen production capacity.

[0011] It will be appreciated that when it is stated that the second alkaline electrolyzer unit is arranged vertically above the first alkaline electrolyzer unit and is supported by the load bearing surface, the second alkaline electrolyzer unit is arranged on top of the first alkaline electrolyzer unit, with the load bearing surface arranged between the first alkaline electrolyzer unit and the second alkaline electrolyzer unit. Thus, the second alkaline electrolyzer unit is arranged vertically above the first alkaline electrolyzer unit, the second alkaline electrolyzer unit comprising a first end plate, a second end plate, and a plurality of electrolyzer cells forming a cell stack arranged between the first end plate and the second end plate, the first alkaline electrolyzer unit comprising a first end plate, a second end plate, and a plurality of electrolyzer cells forming a cell stack arranged between the first end plate and the second end plate, wherein the second alkaline electrolyzer unit is supported by the load bearing surface.

[0012] The first end plate and the second end plate of the first alkaline electrolyzer unit can be referred to as a first unit first end plate and a first unit second end plate, respectively. Further, the cell stack of the plurality of electrolyzer cells arranged between the first unit first end plate and the first unit second end plate can be referred to as a first unit cell stack. Correspondingly, the first end plate and the second end plate of the second alkaline electrolyzer unit can be referred to as a second unit first end plate and a second unit second end plate, respectively. Further, the cell stack of the plurality of electrolyzer cells arranged between the second unit first end plate and the second unit second end plate can be referred to as a second unit cell stack.

[0013] It will be appreciated that the electrolyzer cells in the cell stack in each of the first alkaline electrolyzer unit and the second alkaline electrolyzer unit typically comprise two electrodes (an anode and a cathode) separated by a membrane and operate in a liquid alkaline electrolyte solution (in short: alkaline electrolyte) to achieve water electrolysis. In use, oxygen (and water) is generated at the anode by means of OH anions and hydrogen (and OH anions) is generated at the cathode by means of supplied electrons. Alkaline electrolyte and / or water can be continuously supplied to the alkaline electrolyzer unit. OH anions are transported from the cathode to the anode via the membrane. Each cell stack in the first alkaline electrolyzer unit and the second alkaline electrolyzer unit comprises a plurality of such electrolyzer cells.

[0014] According to at least one example embodiment, the surface area of the electrodes in the electrolyzer cells in the cell stack in each of the first alkaline electrolyzer unit and the second alkaline electrolyzer unit is between 0.5 and 3 m2.

[0015] It will be appreciated that the first alkaline electrolyzer unit is a separate unit from the second alkaline electrolyzer unit. Thus, the electrolyzer cells in the cell stack of the first alkaline electrolyzer unit are separate from the electrolyzer cells in the cell stack of the second alkaline electrolyzer unit and are operated independently. For example, the electrolyzer cells in the cell stack of the first alkaline electrolyzer unit are arranged between the first and second end plates of the first alkaline electrolyzer unit, whereas the electrolyzer cells in the cell stack of the second alkaline electrolyzer unit are not arranged between the first and second end plates of the first alkaline electrolyzer unit (as they are arranged between the first and second end plates of the second alkaline electrolyzer unit). However, the first and second electrolyzer units can be configured to provide the generated gases (hydrogen and / or oxygen) to a common conduit, even though the electrolyzer cells in the cell stack of the first alkaline electrolyzer unit are separate from the electrolyzer cells in the cell stack of the second alkaline electrolyzer unit and are operated independently.

[0016] According to at least one example embodiment, the first and second end plates are base plates or load carrier plates. Thus, the first and second end plates form the main carrier structure of the cell stack of the associated electrolyzer unit. Typically, the first and second end plates are different from any electrodes of the cell stack.

[0017] It will be appreciated that when stating that the second alkaline electrolyzer unit is arranged vertically above the first alkaline electrolyzer unit and is supported by the load support surface, the alkaline electrolyzer device is described with respect to a three-dimensional space. For example, in a Cartesian coordinate system (an xyz system defined by an x-axis, a y-axis, and a z-axis), a horizontal plane is defined by the x-axis and the y-axis (i.e., the xy-plane), and the z-axis is a vertical axis that passes through the horizontal plane. In other words, the z-axis or vertical axis is parallel to the axis followed by gravity. Thus, the position of the second alkaline electrolyzer unit relative to the z-axis is higher compared to the position of the first alkaline electrolyzer unit. According to at least one example embodiment, the lowest z-coordinate of the second alkaline electrolyzer unit is higher than the highest z-coordinate of the first alkaline electrolyzer unit.

[0018] It will be appreciated that the second alkaline electrolyzer unit is typically arranged on top of the first alkaline electrolyzer unit. For example, the second alkaline electrolyzer unit is arranged in the same position relative to the x-axis and the y-axis (i.e., in the horizontal plane) as the first alkaline electrolyzer unit. According to at least one example embodiment, the position relative to the x-axis and the y-axis of the second alkaline electrolyzer unit at least partially overlaps the position relative to the x-axis and the y-axis of the first alkaline electrolyzer unit. Thus, the second alkaline electrolyzer unit can be aligned with the first alkaline electrolyzer unit in the horizontal plane (the xy-plane) or slightly offset.

[0019] According to at least one example embodiment, the load support surface is comprised in one of the first and second alkaline electrolyzer units.

[0020] Hence, no separate assembly step is required to arrange the load support surface such that the second alkaline electrolyzer cell unit is arranged vertically above the first alkaline electrolyzer cell unit and is supported by the load support surface. In other words, the load support surface is integrated in one of the first alkaline electrolyzer cell unit and the second alkaline electrolyzer cell unit. Hence, the load support surface is simply arranged by arranging the second alkaline electrolyzer cell unit vertically above the first alkaline electrolyzer cell unit such that the second alkaline electrolyzer cell unit is arranged vertically above the first alkaline electrolyzer cell unit and is supported by the load support surface.

[0021] According to at least one example embodiment, the load support surface is comprised in the first alkaline electrolyzer cell unit. Preferably, the load support surface of the first alkaline electrolyzer cell unit is a top surface of the first alkaline electrolyzer cell unit. Hence, during assembly of the alkaline electrolyzer device, the first alkaline electrolyzer cell unit can be placed in its correct position, after which the second alkaline electrolyzer cell unit is arranged on top of the first alkaline electrolyzer cell unit, on which top it is supported by the load support surface of the first alkaline electrolyzer cell unit. Hence, assembly of the alkaline electrolyzer device is improved.

[0022] According to at least one example embodiment, the load support surface is comprised in at least one of the first end plate and the second end plate of the first alkaline electrolyzer cell unit.

[0023] Hence, the load support surface is integrated into already existing components of the first alkaline electrolyzer cell unit. Therefore, a separate load support structure arranged between the first alkaline electrolyzer cell unit comprising the load support surface and the second alkaline electrolyzer cell unit can be omitted. Moreover, since the first end plate and the second end plate are typically load carrier plates, the load support surface is integrated into the main carrier structure of the cell stack of the first alkaline electrolyzer cell unit. The load support surface can be comprised in or integrated in the first end plate and / or the second end plate of the first alkaline electrolyzer cell unit.

[0024] According to at least one example embodiment, the electrolyzer cells in the respective cell stacks of the first alkaline electrolyzer cell unit and the second alkaline electrolyzer cell unit are stacked vertically.

[0025] Hence, the capacity per unit surface area can also be increased. Hence, the electrolyser cells are sandwiched in a vertical direction, or along the z-axis, as described in relation to the previously described Cartesian coordinate system. Hence, the first end plate, the stack of cells, and the second end plate are arranged sequentially in the vertical direction. In other words, the central axis of the first and second alkaline electrolyser units is a vertical axis. Typically, each electrolyser cell in such a vertical stack arrangement comprises electrodes and membranes sandwiched in the vertical direction or along the z-axis. According to at least one example embodiment, the electrodes and / or membranes are tilted or canted with respect to the xy-plane to avoid gas traps.

[0026] For example, the first end plate of the first alkaline electrolyser unit is arranged on a ground surface of an electrolyser site for the alkaline electrolyser arrangement. The second end plate of the first alkaline electrolyser unit is aligned with the first end plate and arranged above the first end plate, such that the vertically arranged stack of cells of the first alkaline electrolyser unit is arranged between the first end plate and the second end plate. The second end plate comprises a load support surface on which the second alkaline electrolyser unit is supported. Hence, the first end plate of the second alkaline electrolyser unit is arranged on the second end plate of the first alkaline electrolyser unit. The second end plate of the second alkaline electrolyser unit is aligned with the first end plate and arranged above the first end plate, such that the vertically arranged stack of cells of the second alkaline electrolyser unit is arranged between the first end plate and the second end plate and vertically above the first alkaline electrolyser unit.

[0027] According to at least one example embodiment, the first alkaline electrolyser unit further comprises a planar structure extending from the first end plate to the second end plate, and wherein the planar structure comprises the load support surface.

[0028] Hence, the first alkaline electrolyser unit comprises a planar structure which is a load support structure independent of the first and second end plates and which comprises the load support surface. Such a planar structure provides an advantageous support for the second alkaline electrolyser unit.

[0029] According to at least one example embodiment, the planar structure comprises an inwardly facing surface arranged to face the stack of cells of the first alkaline electrolyser unit and an outwardly facing surface arranged to face the second alkaline electrolyser unit, wherein the outwardly facing surface is the load support surface.

[0030] Hence, the top surface of the first alkaline electrolyser unit mentioned in the foregoing is preferably the outwardly facing surface of the planar structure and serves as the load support surface. Hence, the arrangement of the second alkaline electrolyser unit on top of the first alkaline electrolyser unit is improved.

[0031] According to at least one example embodiment, the load bearing structure extends from a first end plate to a second end plate of at least one of the first alkaline electrolyzer cell unit and the second alkaline electrolyzer cell unit. Thus, the load bearing structure can increase the robustness of the corresponding alkaline electrolyzer cell unit. For example, the load bearing structure can be configured to compress the electrolyzer cells in the cell stack. Thus, connecting rods can be omitted, or at least reduced.

[0032] The load bearing structure may, for example, be attached to a top portion or top surface of the first end plate of the first alkaline electrolyzer cell unit and to a top portion or top surface of the second end plate of the first alkaline electrolyzer cell unit and thereby extend from the top portion or top surface of the first end plate to the top portion or top surface of the second end plate. The top portion or top surface of the end plate here refers to the portion or surface of the end plate facing the second alkaline electrolyzer cell unit. As an alternative, the load bearing structure may be attached to a bottom portion or bottom surface of the first end plate of the second alkaline electrolyzer cell unit and to a bottom portion or bottom surface of the second end plate of the second alkaline electrolyzer cell unit and thereby extend from the bottom portion or bottom surface of the first end plate to the bottom portion or bottom surface of the second end plate. The bottom portion or bottom surface of the end plate here refers to the portion or surface of the end plate facing the first alkaline electrolyzer cell unit.

[0033] According to at least one example embodiment, the load bearing surface is integrated in the load bearing structure (or planar structure) of the first alkaline electrolyzer cell unit or the second alkaline electrolyzer cell unit, or in at least one of the first end plate and the second end plate of the first alkaline electrolyzer cell unit, which is in contact with the electrolyte of the corresponding alkaline electrolyzer cell unit. Thus, by having the structure comprising the load bearing surface in contact with the electrolyte of the first alkaline electrolyzer cell unit, the load bearing surface can be integrated in the first alkaline electrolyzer cell unit. Alternatively, by having the structure comprising the load bearing surface in contact with the electrolyte of the second alkaline electrolyzer cell unit, the load bearing surface can be integrated in the second alkaline electrolyzer cell unit. For example, in embodiments where the load bearing surface is comprised in at least one of the first end plate and the second end plate of the first alkaline electrolyzer cell unit, the first end plate and the second end plate are in contact with the electrolyte of the first alkaline electrolyzer cell unit. Furthermore, in embodiments where the load bearing surface is comprised in the load bearing structure or planar structure extending from the first end plate to the second end plate of at least one of the first alkaline electrolyzer cell unit and the second alkaline electrolyzer cell unit, the load bearing structure or planar structure can be arranged such that it is in contact with the electrolyte of the corresponding alkaline electrolyzer cell unit.

[0034] According to at least one example embodiment, the electrolyzer cells in the respective cell stack of the first alkaline electrolyzer cell unit and the second alkaline electrolyzer cell unit are stacked horizontally.

[0035] Thus, a conventional cell stack arrangement can be used for the alkaline electrolyzer arrangement. Thus, the electrolyzer cells are clamped in a horizontal direction, or along the x-axis or the y-axis, as described in relation to the previously described Cartesian coordinate system. Thus, the first end plate, the cell stack, and the second end plate are arranged sequentially in the horizontal direction (along the x-axis or the y-axis). In other words, the central axis of the first and second alkaline electrolyzer units is a horizontal axis. Typically, each electrolyzer cell in such a horizontal stack arrangement comprises electrodes and membranes clamped in a horizontal direction or along the x-axis or the y-axis.

[0036] For example, the first and second end plates of the first alkaline electrolyzer unit are arranged on a ground surface of an electrolyzer site for the alkaline electrolyzer arrangement. The first and second end plates of the first alkaline electrolyzer unit are typically aligned in the horizontal direction and are arranged side by side such that the horizontally arranged cell stack of the first alkaline electrolyzer unit is arranged between the first and second end plates. According to at least one example embodiment, wherein a load bearing surface is comprised in the first and second end plates of the first alkaline electrolyzer unit, the load bearing surface is typically split between a top surface of the first end plate and a top surface of the second end plate on which respective first and second end plates of the second alkaline electrolyzer unit are supported. Thus, the first end plate of the second alkaline electrolyzer unit is arranged on top of the first end plate of the first alkaline electrolyzer unit and the second end plate of the second alkaline electrolyzer unit is arranged on top of the second end plate of the first alkaline electrolyzer unit. Thus, the first and second end plates of the second alkaline electrolyzer unit and the horizontally arranged cell stack arranged therebetween are arranged vertically above the first alkaline electrolyzer unit.

[0037] According to at least one example embodiment, the load bearing surface is a grid or a lattice.

[0038] Thus, a load bearing surface is provided which is robust but relatively light in weight. For example, the load bearing structure comprising the load bearing surface is arranged as a grid or a lattice. Alternatively, for embodiments wherein the load bearing surface is comprised in the first and / or second end plate of the first alkaline electrolyzer unit, the corresponding first and / or second end plate(s) is / are arranged as a grid or a lattice. For example, the grid or lattice is 3D printed or otherwise manufactured to provide a structure configured to withstand a high vertical load, i.e. at least corresponding to the weight of the second alkaline electrolyzer unit. By having the grid or lattice as the load bearing surface, transport of gas or liquid to and / or from the first and second alkaline electrolyzer units is facilitated as such transport can be achieved via openings in the grid or lattice.

[0039] According to at least one example embodiment, the alkaline electrolyzer arrangement further comprises an intermediate load support plate arranged between the first end plate and the second end plate of the first alkaline electrolyzer cell unit, wherein the second alkaline electrolyzer cell unit is at least partially supported by the intermediate load support plate.

[0040] Such an intermediate load support plate is typically arranged to enclose a portion of the cell stack or comprises a central structure forming a portion of the cell stack. Such a central structure may, for example, comprise a grid or mesh that is capable of letting the alkaline electrolyte flow through. The central structure is, for example, arranged between two electrodes and can form a virtual cell (i.e. a cell of the cell stack that does not produce hydrogen gas or oxygen gas as no electric potential is applied between the electrodes of the virtual cell). The intermediate load support plate is typically arranged distanced from the first end plate and the second end plate, typically equidistantly arranged from the first end plate and the second end plate. The alkaline electrolyzer arrangement can comprise more than one intermediate load support plate. For such an embodiment, the plurality of intermediate load support plates is arranged along a distance from the first end plate to the second end plate. The intermediate load support plate can be referred to as an intermediate load support structure.

[0041] According to at least one example embodiment, the second alkaline electrolyzer cell unit is at least partially supported by the intermediate load support plate is achieved by a load support surface being comprised in the intermediate load support plate as well as the first end plate and the second end plate of the first alkaline electrolyzer cell unit. The load support surface is typically divided between a top surface of the first end plate, a top surface of the second end plate and a top surface of the intermediate load support plate on which the respective first end plate, second end plate and intermediate plate of the second alkaline electrolyzer cell unit is supported. Thus, for such an embodiment, the second alkaline electrolyzer cell unit comprises an intermediate plate arranged between the first end plate and the second end plate of the second alkaline electrolyzer cell unit corresponding to the intermediate load support plate of the first electrolyzer cell unit. As an alternative, the second alkaline electrolyzer cell unit is at least partially supported by the intermediate load support plate is achieved by a load support structure supported by the first end plate and the second end plate as well as the intermediate load support plate, wherein the load support structure comprises a load support surface as previously described.

[0042] According to at least one example embodiment, the alkaline electrolyzer arrangement comprises one or more sensors configured to measure temperature, pressure and / or electrical conductivity, wherein the one or more sensors are integrated in the intermediate load support plate. Such an integration is advantageous as the sensor(s) can be easily arranged in a middle section of the cell stack due to the arrangement of the intermediate load support plate.

[0043] According to at least one example embodiment, at least the first alkaline electrolyzer cell unit further comprises at least one connection rod arranged to extend from the first end plate to the second end plate and configured to compress the electrolyzer cells in the cell stack, wherein the load support surface is distanced from the at least one connection rod.

[0044] Thus, the electrolyser cells in the cell stack of the first alkaline electrolyser unit are compressed and held tightly within the first and second end plates by the at least one connecting rod. When it is stated that the load bearing surface is distanced from the at least one connecting rod, it is to be understood that the load bearing surface is different from the at least one connecting rod. In other words, according to at least one example embodiment, the load bearing surface is not comprised in the at least one connecting rod, or in any connecting rod arranged to extend from the first end plate to the second end plate and configured to compress the electrolyser cells in the cell stack. However, according to at least one alternative example embodiment, for the above-mentioned vertically arranged cell stack of the first and second alkaline electrolyser units, the first alkaline electrolyser unit can comprise at least two connecting rods, wherein the respective end surfaces of the at least two connecting rods facing the second alkaline electrolyser unit comprise the load bearing surface. Thus, the first end plate of the second alkaline electrolyser unit can be supported by the end surfaces of the at least two connecting rods of the first alkaline electrolyser unit.

[0045] Generally, the second alkaline electrolyser unit further comprises at least one connecting rod arranged to extend from the first end plate to the second end plate of the second alkaline electrolyser unit, the connecting rod being configured to compress the electrolyser cells in the cell stack. Thus, the load bearing surface is distanced from, or different from, the at least one connecting rod.

[0046] According to at least one example embodiment, the alkaline electrolyser arrangement further comprises a conduit configured to transport the generated gases from the electrolyser cells of the cell stack, wherein the conduit is arranged vertically between the first and second alkaline electrolyser units.

[0047] Thus, an efficient way of arranging the conduit is provided. For example, the first and second alkaline electrolyser units can be configured to provide the generated gases to the same conduit. For example, the conduit comprises a first conduit system for handling the generated hydrogen gas and a second conduit system for handling the generated oxygen gas, the second conduit system being separate and different from the first conduit system.

[0048] According to at least one example embodiment, the conduit is further configured to transport alkaline electrolyte (or its corresponding solution) and / or water to and from the first and second alkaline electrolyser units. Thus, the conduit can comprise a third conduit system for handling the alkaline electrolyte and / or water. Generally, the alkaline electrolyte and / or water is recirculated into and out of the cell stack.

[0049] According to at least one example embodiment, the conduit is at least partly comprised in a load bearing structure comprising the aforementioned load bearing surface. The load bearing structure can further comprise a sensor or a metering appliance for measuring the flow of gas or liquid.

[0050] According to at least one example embodiment, the load bearing surface is arranged horizontally.

[0051] Hence, an advantageous support is provided for the second alkaline electrolyzer unit. Namely, the load bearing surface is typically a horizontal surface extending in the xy-plane.

[0052] According to at least one example embodiment, the alkaline electrolyzer arrangement further comprises an enclosure housing the first alkaline electrolyzer unit and the second alkaline electrolyzer unit.

[0053] Hence, any leaked gas from the first alkaline electrolyzer unit and the second alkaline electrolyzer unit can be trapped inside the enclosure.

[0054] According to at least one example embodiment, the alkaline electrolyzer arrangement further comprises a gas sensor configured to detect any leaked gas from the first alkaline electrolyzer unit and the second alkaline electrolyzer unit, wherein the gas sensor is arranged inside the enclosure vertically above the second alkaline electrolyzer unit.

[0055] Hence, an effective arrangement for detecting leaked gas is provided. The gas sensor is typically configured to detect hydrogen and / or oxygen.

[0056] According to at least one example embodiment, the enclosure comprises a guiding surface arranged in a top portion of the enclosure, wherein the guiding surface is configured to guide any leaked gas to the gas sensor.

[0057] Hence, the detection of leaked gas is improved. Hence, the gas sensor is typically arranged in a top portion of the enclosure.

[0058] According to at least one example embodiment, the first alkaline electrolyzer unit and the second alkaline electrolyzer unit are connected in series or in parallel.

[0059] Namely, the first alkaline electrolyzer unit and the second alkaline electrolyzer unit can be electrically connected in series or in parallel.

[0060] According to at least one example embodiment, the first alkaline electrolyzer unit and the second alkaline electrolyzer unit are arranged to operate as redundant units. Alternatively, they are arranged to operate independently of each other (or jointly) to provide hydrogen.

[0061] According to at least one example embodiment, the operating temperature of each of the first and second electrolyzer cell units is between 70°C and 90°C. Such an operating temperature can be referred to as a normal operating temperature. The operating pressure of each of the first and second electrolyzer cell units can for example be between 1 bar and 30 bar.

[0062] According to at least one example embodiment, the alkaline electrolyte is potassium hydroxide KOH or sodium hydroxide NaOH. For KOH, the concentration can for example be 57 M (Molar).

[0063] According to at least one example embodiment, the material for the membrane used in the cell stack is ZrO or NiO. The membrane can be stabilized with a mesh, for example a polyphenylene sulfide (PPS) mesh. The membrane can for example be constituted by a thin porous foil. The thickness of such a foil can for example be between 0.05 mm and 0.5 mm. However, to avoid gas mixing, a thickness of at least 0.25 mm is preferred. It will be appreciated that the membrane is not conductive to electrons, thus avoiding electrical short-circuiting between the anode and the cathode of the electrolyzer cell, while allowing a small distance between the electrodes. The membrane is configured to conduct OH anions, since the alkaline electrolyte can penetrate into the pores of the membrane. Furthermore, the membrane separates the gases (oxygen and hydrogen) produced on the membrane separation side. It will be noted that the membrane can be referred to as a separator or a separator.

[0064] According to at least one example embodiment, the anode, i.e. the electrode (and catalyst) used in the cell stack for the oxygen side, is a nickel-plated steel electrode, for example a nickel-plated perforated stainless steel electrode.

[0065] According to at least one example embodiment, the cathode, i.e. the electrode (and catalyst) used in the cell stack for the hydrogen side, is a nickel-plated steel electrode, for example a nickel-plated perforated stainless steel electrode.

[0066] Thus, the electrodes (and catalysts) used in the cell stack for the oxygen side and the hydrogen side can be of the same type. In other words, the anode and the cathode can be made of the same material.

[0067] According to at least one example embodiment, each of the first and second electrolyzer cell units comprises a porous transport layer at the anode or the cathode. Such a transport layer can be constituted by a nickel mesh.

[0068] As known to the person skilled in the art, the device can further comprise gas separator means for the oxygen and hydrogen produced respectively, a dryer means for drying the hydrogen produced, pumps or other transport means for the alkaline solution and water and associated electrical means necessary for the operation of the device.

[0069] According to a second aspect of the application, there is provided a hydrogen production facility. The hydrogen production facility comprises a plurality of the alkaline electrolyser unit according to the first aspect of the application. Thus, the alkaline electrolyser unit can be referred to as a hydrogen-producing alkaline electrolyser unit.

[0070] For example, a single alkaline electrolyser unit can have a capacity corresponding to a few MW of power demand, typically 4-5 kWh of energy input per Nm3 H2 (normal cubic meter) produced. For example, the hydrogen production facility can comprise 50 to 150 alkaline electrolyser units, corresponding to 1 GW of power demand.

[0071] The effects and features of the second aspect of the application are largely analogous to those described above in connection with the first aspect of the application. The embodiments mentioned in relation to the first aspect of the application are largely compatible with the second aspect of the application, some of which are exemplified below.

[0072] Other advantages and features of the present application are disclosed and discussed in the following description and in the drawings. BRIEF DESCRIPTION OF DRAWINGS

[0073] These and other aspects of the present application will now be described in more detail, with reference to the appended drawings showing example embodiments of the application, wherein:

[0074] Figure 1 is a perspective view of an alkaline electrolyser unit used in accordance with example embodiments of the application,

[0075] Figure 2 is a schematic view of an electrolyser cell used in an alkaline electrolyser unit according to example embodiments of the application,

[0076] Figure 3 schematically illustrates an alkaline electrolyser arrangement according to at least one example embodiment of the application, the arrangement comprising a first electrolyser unit and a second alkaline electrolyser unit,

[0077] Figure 4A schematically illustrates a load support structure comprising a load support surface used in accordance with at least one example embodiment of the application,

[0078] Figure 4B schematically illustrates another load support structure comprising a load support surface used in accordance with at least one example embodiment of the application,

[0079] Figure 4C is a front view of an intermediate plate of an alkaline electrolyser arrangement according to at least one example embodiment of the application, e.g. Figure 3

[0080] Figure 5 ​is a schematic perspective view of an alkaline electrolyzer apparatus according to at least one example embodiment of the present invention, the apparatus comprising a first alkaline electrolyzer unit and a second alkaline electrolyzer unit,

[0081] Figure 6 is another schematic perspective view of an alkaline electrolyzer apparatus according to at least one example embodiment of the present invention, the apparatus comprising a first alkaline electrolyzer unit and a second alkaline electrolyzer unit, and

[0082] Figure 7 is schematically illustrated a further alkaline electrolyzer apparatus according to at least one example embodiment of the present invention, the apparatus comprising a first alkaline electrolyzer unit and a second alkaline electrolyzer unit. DETAILED DESCRIPTION

[0083] In the following description, for purposes of explanation and not limitation, specific details are set forth such as particular components, interfaces, techniques, etc. in order to provide a thorough understanding of the present invention. However, it will be apparent to those skilled in the art that the present invention can be practiced in other embodiments that depart from these specific details. In other instances, detailed descriptions of well-known units, devices or systems, electrolyzers and methods are omitted so as not to obscure the description of the present invention with unnecessary detail.

[0084] Figure 1 An alkaline electrolyzer unit 101 for producing hydrogen gas is schematically illustrated. The alkaline electrolyzer unit 101 can be used as a first alkaline electrolyzer unit and / or a second alkaline electrolyzer unit of an alkaline electrolyzer apparatus, as described below. Therefore, the alkaline electrolyzer unit 101 is first generally described, and then various embodiments of alkaline electrolyzer apparatuses comprising a first alkaline electrolyzer unit and a second alkaline electrolyzer unit are described.

[0085] The alkaline electrolyzer unit 101 comprises a first end plate 103, a second end plate 105, and a cell stack 107 arranged between the first end plate 103 and the second end plate 105. The cell stack 107 is formed by a plurality of electrolyzer cells 109, Figure 1 Only three of the electrolyzer cells are schematically illustrated in the cell stack 107. However, the cell stack 107 typically comprises more electrolyzer cells, for example between 50 and 700 electrolyzer cells, typically between 150 and 500 electrolyzer cells. A typical electrolyzer cell is described below with reference to Figure 2 The alkaline electrolyzer unit 101 further comprises two connection rods 111a, 111b arranged to extend from the first end plate 103 to the second end plate 105 to compress the electrolyzer cells 109 in the cell stack 107. Figure 1The two connecting rods 111a, 111b are shown as partially dashed lines as they extend through the cell stack 107. The connecting rods 111a, 111b can be attached to each of the first and second end plates 103, 107, e.g. by means of a nut or screw nut (not shown).

[0086] Figure 1 The cell stack 107 of the intermediate alkaline electrolyzer cell unit 101 is connected to a pipe 113 for transporting generated gas from the cell stack 107, and / or for transporting alkaline electrolyte to and / or from the cell stack 107, which will be described in more detail below.

[0087] Figure 2 An electrolyzer cell 209 is schematically illustrated. Figure 2 The electrolyzer cell 209 can be used in each of the plurality of electrolyzer cells 109 of the cell stack 107. Figure 1 The electrolyzer cell 209 comprises a first electrode 201 as an anode 201 and a second electrode 203 as a cathode 203. The anode 201 and the cathode 203 are separated by a membrane 205. The anode 201 and the cathode 203 operate in a liquid alkaline electrolyte solution 207 (hereinafter simply referred to as alkaline electrolyte 207) to enable water electrolysis. In use, oxygen and water are generated at the anode 201 by means of OH anions, and hydrogen and OH anions are generated at the cathode 203 by means of supplied electrons. The electrons are transferred from the anode side to the cathode side by means of an electron transfer bridge 211. The OH anions are transported from the cathode 203 to the anode 201 via the membrane 205. Figure 1 The cell stack 107 of the intermediate alkaline electrolyzer cell unit 101 typically comprises a plurality of such electrolyzer cells 209.

[0088] Figure 3 An alkaline electrolyzer apparatus 10 for generating hydrogen gas is schematically illustrated. The alkaline electrolyzer apparatus 10 comprises two alkaline electrolyzer cell units 11, 21, however more than two alkaline electrolyzer cell units can be comprised in the alkaline electrolyzer apparatus 10. Each of the two alkaline electrolyzer cell units 11, 21 is preferably configurable to Figure 1 The alkaline electrolyzer cell unit 101. I.e. the first alkaline electrolyzer cell unit 11 comprises a first end plate 13, a second end plate 15 and a plurality of electrolyzer cells 19 (only three of which are shown) forming a cell stack 17 arranged between the first and second end plates 13, 15. Correspondingly, the second alkaline electrolyzer cell unit 21 comprises a first end plate 23, a second end plate 25 and a plurality of electrolyzer cells 29 (only three of which are shown) forming a cell stack 27 arranged between the first and second end plates 23, 25. As will be described in more detail below, the first and second alkaline electrolyzer cell units 11, 21 are configured to be connected to each other by means of a connecting rod 111a, 111b. Figure 3As shown, the first alkaline electrolyzer unit 11 can optionally comprise an intermediate load support plate 14 (shown with dashed lines) which is arranged between the first end plate 13 and the second end plate 15. Such intermediate load support plate 14 is typically arranged to enclose a portion of the cell stack 17 or comprises a central structure forming a portion of the cell stack 17 (as further shown in Figure 4C For the sake of brevity, Figure 1 Any pipes and connecting rods shown in

[0089] The alkaline electrolyzer arrangement 10 further comprises a load support surface 30 which is arranged between the first alkaline electrolyzer unit 11 and the second alkaline electrolyzer unit 21 such that the second alkaline electrolyzer unit 21 is arranged vertically above the first alkaline electrolyzer unit 11 and is supported by the load support surface 30. In Figure 3 In embodiments of the first alkaline electrolyzer unit 11, the load support surface 30 is comprised in the first alkaline electrolyzer unit 11 by being integrated into a load support structure 31 which is a planar structure 31 extending from the first end plate 13 to the second end plate 15. In Figure 3 In this case, the load support properties can be improved by the optional intermediate load support plate 14. Thus, the load support structure 31 is supported by the first end plate 13 and the second end plate 15 as well as the intermediate load support plate 14. Thus, the second alkaline electrolyzer unit 21 is at least partially supported by the intermediate load support plate 14.

[0090] As an alternative, however, the load support surface 30 can be comprised or integrated in the second alkaline electrolyzer unit 21.

[0091] The planar structure 31 comprises an inwardly facing surface 31a which is arranged to face the cell stack 17 of the first alkaline electrolyzer unit 11 and an outwardly facing surface 31b which is arranged to face the second alkaline electrolyzer unit 21. Thus, the outwardly facing surface 31b comprises or forms the load support surface 30. The load support structure 31 as a planar structure 31 is typically formed as a cuboid, as Figure 4A individually shown in the perspective view of Figure 4B According to at least one example embodiment, the load support structure comprising the load support surface 30’ is formed as a grid or lattice 31’ as shown in

[0092] As shown in Figure 1 and Figure 3 The electrolyzer cells 109, 19, 29 in the respective cell stacks 107, 17, 27 of the alkaline electrolyzer units 101, 11, 21 are horizontally stacked, as shown in Figure 1 the perspective view of Figure 3The horizontal plane is defined by the x-axis and the y-axis (i.e. the xy-plane), and the z-axis is a vertical axis through the horizontal plane. In other words, the z-axis or vertical axis is parallel to the axis followed by gravity. Thus, for a horizontal cell stack 107, 17, 27, the cell tank cells 109, 19, 29 are in the horizontal direction or along the x-axis or y-axis. Figure 3 The x-axis as shown is sandwiched in between. Thus, the first end plate 103, 13, 23, the cell stack 107, 17, 27, and the second end plate 105, 15, 25 are sequentially arranged in the horizontal direction (along the x-axis or y-axis). In other words, the central axis of the first and second alkaline tank cell units 101, 11, 21 is a horizontal axis. Typically, each cell tank cell 109, 19, 29 in such a horizontal stack arrangement comprises electrodes 201, 203 and a membrane 205 sandwiched in the horizontal direction or along the x-axis or y-axis.

[0093] However, according to at least one example embodiment as Figure 5 shown, the cell tank cells in the respective cell stacks of the first and second alkaline tank cell units are vertically stacked. Figure 5 A perspective view of an alkaline tank device 40 for producing hydrogen gas is schematically shown, which is similar in principle to the alkaline tank device 10 of Figure 3 , but with certain structural differences as described below. Figure 5 The alkaline tank device 40 comprises two alkaline tank units, a first alkaline tank unit 41 and a second alkaline tank unit 51, although more than two alkaline tank units can be comprised in the alkaline tank device 40. Each of the two alkaline tank units 41, 51 can preferably be configured as Figure 1 the alkaline tank unit 101 of, but with a vertical stack arrangement instead of a horizontal stack arrangement. I.e. the first alkaline tank unit 41 comprises a first end plate 43, a second end plate 45, and a plurality of cell tank cells 49 (only three of which are shown), which form a cell stack 47 arranged between the first end plate 43 and the second end plate 45, and wherein the cell tank cells 49 in the cell stack 47 are vertically stacked. Correspondingly, the second alkaline tank unit 51 comprises a first end plate 53, a second end plate 55, and a plurality of cell tank cells 59 (only three of which are shown), which form a cell stack 57 arranged between the first end plate 53 and the second end plate 55, and wherein the cell tank cells 59 in the cell stack 57 are vertically stacked. Thus, the capacity per unit surface area can also be increased.

[0094] In more detail, the first end plate 43 of the first alkaline electrolyzer cell 41 is arranged on the ground surface 600 of the electrolyzer site of the alkaline electrolyzer installation 40. The second end plate 45 of the first alkaline electrolyzer cell 41 is aligned with the first end plate 43 and arranged above the first end plate 43 such that the vertically arranged cell stacks 47 of the first alkaline electrolyzer cell 41 are arranged between the first end plate 43 and the second end plate 45 with respect to the vertical direction. The second end plate 45 or rather the outwardly facing surface of the second end plate 45 comprises a load bearing surface 60 on which the second alkaline electrolyzer cell 51 is supported. Thus, the first end plate 53 of the second alkaline electrolyzer cell 51 is arranged on the second end plate 45 of the first alkaline electrolyzer cell 41. The second end plate 55 of the second alkaline electrolyzer cell 51 is aligned with the first end plate 53 and arranged above the first end plate 53 such that the vertically arranged cell stacks 57 of the second alkaline electrolyzer cell 51 are arranged between the first end plate 53 and the second end plate 55 with respect to the vertical direction and are arranged vertically above the first alkaline electrolyzer cell 41. Thus, the second alkaline electrolyzer cell 51 is arranged on top of the first alkaline electrolyzer cell 41 by means of the second end plate 45 of the first alkaline electrolyzer cell 41 and the load bearing surface 60 comprised therein.

[0095] For the sake of brevity, Figure 1 Any pipes and connecting rods shown in the alkaline electrolyzer cell 101 of

[0096] As Figure 5 shown, the electrolyzer cells 49, 59 of the respective cell stacks 47, 57 are tilted or canted with respect to the horizontal plane (xy-plane). Thus, the electrodes 201, 203 and / or the membranes 205 of the electrolyzer cells 49, 59 are tilted or canted with respect to the horizontal plane in order to avoid gas traps. The angle of inclination with respect to the horizontal plane can for example be between 5° and 45°.

[0097] Figure 6 A perspective view of an alkaline electrolyzer installation 70 for generating hydrogen gas is schematically shown, which installation is similar in principle to the alkaline electrolyzer installation 10 of Figure 3 , but has certain structural differences described below. Figure 6The alkaline electrolytic cell device 70 includes two alkaline electrolytic cell units, a first alkaline electrolytic cell unit 71 and a second alkaline electrolytic cell unit 81. However, the alkaline electrolytic cell device 70 may include more than two alkaline electrolytic cell units. Each of the two alkaline electrolytic cell units 71 and 81 may preferably be configured as Figure 1 1 and 2. The first alkaline electrolyzer unit 71 includes a first end plate 73, a second end plate 75, and a plurality of electrolyzer cells (not shown separately) that form a cell stack 77 disposed between the first and second end plates 73, 75. Correspondingly, the second alkaline electrolyzer unit 81 includes a first end plate 83, a second end plate 85, and a plurality of electrolyzer cells (not shown separately) that form a cell stack 87 disposed between the first and second end plates 83, 85.

[0098] Optionally, the first alkaline electrolyzer unit 71 includes a Figure 3 The intermediate load bearing plate 74 shown. For example, the intermediate load bearing plate 74 is as shown in FIG. Figure 4C Thus, the intermediate load-bearing plate 74 is arranged between the first end plate 73 and the second end plate 75 of the first alkaline electrolysis cell unit 71. Correspondingly, the second alkaline electrolysis cell unit 81 may include an intermediate plate 84 arranged between the first end plate 83 and the second end plate 85 of the second alkaline electrolysis cell unit 81. The intermediate plate 84 of the second alkaline electrolysis cell unit 81 may be as described with reference to Figure 4C Arranged as described.

[0099] and Figure 3 Compared with the alkaline electrolyzer device 10, Figure 3 In the alkaline electrolyzer apparatus 70 of the present invention, there is no separate load-bearing structure, but rather the load-bearing surface 90 is included in the first end plate 73 and the second end plate 75 of the first alkaline electrolyzer unit 71, and optionally in the intermediate load-bearing plate 74. Thus, the load-bearing surface 90 is integrated into the already existing components of the first alkaline electrolyzer unit 71. Therefore, a separate load-bearing structure including the load-bearing surface is not required.

[0100] like Figure 6As shown, the load support surface 90 is generally divided between the top surface 73a of the first end plate 73 and the top surface 75a of the second end plate 75 on which the respective first end plate 83 and second end plate 85 of the second alkaline electrolyzer cell 81 are supported. For embodiments including the intermediate load support plate 74 of the first alkaline electrolyzer cell 71 and the intermediate plate 84 of the second alkaline electrolyzer cell 81, the load support surface 90 is also included in the top surface 74a of the intermediate load support plate 74 on which the intermediate plate 84 of the second alkaline electrolyzer cell 81 is supported. Thus, the load support surface 90 includes at least two separate load support surface portions 73a, 75a, and optionally the top surface portion 74a. Thus, the first end plate 83 of the second alkaline electrolyzer cell 81 is arranged on top of the first end plate 73 of the first alkaline electrolyzer cell 71, and the second end plate 85 of the second alkaline electrolyzer cell 81 is arranged on top of the second end plate 75 of the first alkaline electrolyzer cell 71, and optionally, the intermediate plate 84 of the second alkaline electrolyzer cell 81 is arranged on top of the intermediate load support plate 74 of the first alkaline electrolyzer cell 71. Thus, the first end plate 83 and the second end plate 85 of the second alkaline electrolyzer cell 81, with the horizontally arranged cell stack 87 arranged therebetween, are arranged vertically above the first alkaline electrolyzer cell 71. Furthermore, since the first end plate 73 and the second end plate 75 of the first alkaline electrolyzer cell 71, and optionally the intermediate load support plate 74, are generally load carrier plates, the load support surface 90 is integrated into the main carrier structure of the first alkaline electrolyzer cell 71. Furthermore, as Figure 6 As clearly shown in the middle, any connecting bars 78, 88 of the first alkaline electrolyzer cell 71 and the second alkaline electrolyzer cell 81 are remote from and distinct from the load support surface 90.

[0101] Figure 4C A front view of an example intermediate plate 174 to be arranged between a first end plate and a second end plate of an alkaline electrolyzer cell is schematically shown. The intermediate plate 174 can for example be an intermediate load support plate of a first alkaline electrolyzer cell, for example Figure 3 the intermediate load support plate 14 of the embodiment of Figure 6 the intermediate load support plate 74 of the embodiment of Figure 6 the intermediate plate 84 of the embodiment of

[0102] The intermediate plate 174 is generally arranged to include a central structure 174a forming a part of a cell stack 117 (for example, Figure 3 and Figure 6Such central structure 174a can for example comprise a grid or mesh 174b, enabling the alkaline electrolyte to flow therethrough. For example, the central structure 174a is arranged between two electrodes (not shown) and can form a virtual cell. A virtual cell is a cell in the cell stack 117 that does not produce hydrogen gas or oxygen gas, as no electric potential is applied between the electrodes of the virtual cell. As an alternative, the intermediate plate 174 can simply comprise a frame that encloses a portion of the cell stack 117.

[0103] One or more sensors 174c configured to measure temperature, pressure and / or electrical conductivity can be integrated in the intermediate plate 174. Such integration is advantageous, as the sensor(s) 174c can be easily arranged in the middle section of the cell stack due to the arrangement of the intermediate plate 174.

[0104] Figure 7 A perspective view of an alkaline electrolyzer device 310 for producing hydrogen gas is schematically shown, which device is in principle similar to the alkaline electrolyzer device 10 of Figure 3 , but with certain structural differences as described below. Figure 7 The alkaline electrolyzer device 310 of comprises two alkaline electrolyzer units, a first alkaline electrolyzer unit 311 and a second alkaline electrolyzer unit 321, although more than two alkaline electrolyzer units can be comprised in the alkaline electrolyzer device 310. Each of the two alkaline electrolyzer units 311, 321 can preferably be configured as the alkaline electrolyzer unit 101 of Figure 1 , i.e. with horizontal cell stacks. I.e., the first alkaline electrolyzer unit 311 comprises a first end plate 313, a second end plate 315 and a plurality of electrolyzer cells (not shown individually) forming a cell stack 317 arranged between the first end plate 313 and the second end plate 315. Correspondingly, the second alkaline electrolyzer unit 321 comprises a first end plate 323, a second end plate 325 and a plurality of electrolyzer cells (not shown individually) forming a cell stack 327 arranged between the first end plate 323 and the second end plate 325.

[0105] Similar to the alkaline electrolyzer device 10 of Figure 3 , the first alkaline electrolyzer unit 311 comprises a load support structure 331 extending from the first end plate 313 to the second end plate 315. The load support structure 331 comprises a load support surface 330 as previously described, and in the embodiment shown in Figure 7 is arranged as a mesh or grid (e.g. as shown in Figure 4BThe load support structure 331 and the load support surface 330 are arranged between the first alkaline electrolyzer cell unit 311 and the second alkaline electrolyzer cell unit 321 such that the second alkaline electrolyzer cell unit 321 is arranged vertically above the first alkaline electrolyzer cell unit 311 and is supported by the load support surface 330. Due to the grid or lattice of the load support structure 331, the ducts 314 can advantageously extend from the cell stacks 317 of the first alkaline electrolyzer cell unit 311 through the load support structure 331 and interact with the duct portions above the load support structure 331.

[0106] As Figure 7 is shown, Figure 7 The alkaline electrolyzer arrangement 310 comprises ducts 314 configured to transport produced gas from the electrolyzer cells of the cell stacks 317, 327. The ducts 314 are arranged vertically between the first alkaline electrolyzer cell unit 311 and the second alkaline electrolyzer cell unit 321. In more detail, the ducts 314 comprise a first duct system 314a for handling produced hydrogen gas and a second duct system 314b for handling produced oxygen gas. As Figure 7 is shown in embodiments, the first duct system 314a and the second duct system 314b are separated from each other. The first alkaline electrolyzer cell unit 311 and the second alkaline electrolyzer cell unit 321 are arranged in Figure 7 to jointly provide produced gas to the first duct system 314a and the second duct system 314b. However, the first alkaline electrolyzer cell unit 311 and the second alkaline electrolyzer cell unit 321 can also be arranged to provide produced gas to separate duct systems.

[0107] Figure 7 The alkaline electrolyzer arrangement 310 comprises an enclosure 400 that houses the first alkaline electrolyzer cell unit 311 and the second alkaline electrolyzer cell unit 321. Thus, any leaked gas from the first alkaline electrolyzer cell unit 311 and the second alkaline electrolyzer cell unit 321 can be trapped inside the enclosure 400. As Figure 7 is also shown, the alkaline electrolyzer arrangement 310 comprises a first gas sensor 410 and a second gas sensor 420, both configured to detect any leaked gas from the first alkaline electrolyzer cell unit 311 and the second alkaline electrolyzer cell unit 321. The first gas sensor and the second gas sensor are arranged within the enclosure 400 vertically above the second alkaline electrolyzer cell unit 321. Thus, an effective arrangement for detecting leaked gas is provided, since any leaked gas generally moves upwards in the enclosure 400. The first gas sensor and the second gas sensor are generally configured to detect hydrogen gas and / or oxygen gas.

[0108] According to at least one example embodiment, the enclosure 400 comprises guiding surfaces 403, 405 arranged in the top portion 401 of the enclosure 400, which are configured to guide any leaked gas to the respective first and second gas sensors 410, 420. That is, the first guiding surface 403 is configured to guide any leaked gas to the first gas sensor 410, typically tilted towards the first gas sensor 410. Correspondingly, the second guiding surface 405 is configured to guide any leaked gas to the second gas sensor 420, typically tilted towards the second gas sensor 420. Thus, the detection of leaked gas is improved.

[0109] While the application has been described in connection with what is presently considered to be the most practical and preferred embodiments, it is to be understood that the application is not to be limited to the disclosed embodiments, but on the contrary, is intended to cover various modifications and equivalent arrangements. Furthermore, there is no intention that the scope of the application be limited to the exact construction described above. It is therefore apparent that various modifications and changes can be made in the implementation without departing from the scope of the application in its broader aspects. In the claims, the word "comprising" does not exclude other elements or steps, and the indefinite article "a" or "an" does not exclude a plurality. The mere fact that different features are recited in mutually different dependent claims does not indicate that a combination of these features cannot be used to advantage.

Claims

1. An alkaline electrolyzer apparatus for producing hydrogen gas, the apparatus comprising a first alkaline electrolyzer unit and a second alkaline electrolyzer unit, each of the first alkaline electrolyzer unit and the second alkaline electrolyzer unit comprising a first end plate, a second end plate, and a plurality of electrolyzer cells forming a cell stack arranged between the first end plate and the second end plate, wherein the alkaline electrolyzer apparatus further comprises a load bearing surface arranged between the first alkaline electrolyzer unit and the second alkaline electrolyzer unit such that the second alkaline electrolyzer unit is arranged vertically above the first alkaline electrolyzer unit and is supported by the load bearing surface, and wherein the load bearing surface is integrated in at least one of the first end plate and the second end plate of the first alkaline electrolyzer unit.

2. The apparatus of claim 1, wherein the electrolyzer cells in the respective cell stacks of the first alkaline electrolyzer unit and the second alkaline electrolyzer unit are stacked vertically.

3. The apparatus of claim 1, wherein the electrolyzer cells in the respective cell stacks of the first alkaline electrolyzer unit and the second alkaline electrolyzer unit are stacked horizontally.

4. The apparatus of claim 3, further comprising an intermediate load bearing plate arranged between the first end plate and the second end plate of the first alkaline electrolyzer unit, wherein the second alkaline electrolyzer unit is at least partially supported by the intermediate load bearing plate.

5. The apparatus of any one of the preceding claims, wherein at least the first alkaline electrolyzer unit further comprises at least one connecting rod arranged to extend from the first end plate to the second end plate and configured to compress the electrolyzer cells in the cell stack, wherein the load bearing surface is distanced from the at least one connecting rod.

6. The apparatus of any one of claims 1-4, further comprising a duct configured to transport produced gas from the electrolyzer cells of the cell stack, wherein the duct is arranged vertically between the first alkaline electrolyzer unit and the second alkaline electrolyzer unit.

7. The apparatus of any one of claims 1-4, wherein the load bearing surface is arranged horizontally.

8. The apparatus of any one of claims 1-4, further comprising an encapsulation cover housing the first alkaline electrolyzer unit and the second alkaline electrolyzer unit.

9. The apparatus of claim 8, further comprising a gas sensor configured to detect any leaked gas from the first alkaline electrolyzer unit and the second alkaline electrolyzer unit, wherein the gas sensor is arranged within the encapsulation cover vertically above the second alkaline electrolyzer unit.

10. The device of claim 9, wherein the enclosure comprises a guiding surface arranged in a top portion of the enclosure, wherein the guiding surface is configured to guide any leaking gas to the gas sensor.

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