Enclosure for an electrochemical cell system

Abstract

An enclosure for housing at least one stack of electrochemical cell units. The enclosure comprising a vessel, thermal insulation and an inner skin. The thermal insulation being disposed between an outer face of the inner skin and an inner face of the vessel. The inner skin forming at least part of a common volume in the enclosure within which said at least one stack of electrochemical cell units is located. The enclosure comprising an adjustment mechanism to mechanically alter a shape of the inner skin, such that the inner skin is configured to be reshaped to urge an outermost face of the thermal insulation towards the inner face of the vessel.

Description

[0001] ELECTROCHEMICAL CELL SYSTEM

[0002] Field of the Invention

[0003] The present invention relates to an enclosure for housing at least one stack of electrochemical cell units, and in particular an electrochemical cell system comprising an enclosure for housing at least one stack of electrochemical cell units. The electrochemical cell system may be an electrolyser system or a fuel cell system. The present invention also provides a method of assembling the enclosure. The electrochemical cell system may comprise at least one stack of electrochemical cell units - typically electrolyser cell units, which may include cell units of solid oxide or molten carbonate electrolyser cells. The present invention more specifically relates to the assembly of an enclosure for receiving solid oxide electrolyser cell (SOEC) units within the enclosure to form an insulated, pressurisable, electrochemical cell system. The solid oxide electrolyser cell (SOEC) units may include metal-supported solid oxide electrolyser cell (MS-SOEC) units.

[0004] Background to the Invention

[0005] Electrochemical cell units are commonly referred to as fuel cell units or electrolyser cell units, and in some instances their names are interchangeable as some fuel cell units can work as electrolyser cell units and some electrolyser cell units can operate as fuel cell units, each either as a producer of electricity or in a regenerative mode - electrolyzing a fluid to electrochemically split it into two or more component parts. For example, some fuel cell units can produce electricity by using an electrochemical conversion process that oxidises fuel to produce electricity. Some fuel cell units can also, or instead, operate as regenerative fuel cells (or reverse fuel cells) units, often known as electrolyser cell units, for example to separate hydrogen and oxygen from water, carbon monoxide and oxygen from carbon dioxide, or nitrogen monoxide and oxygen from nitrogen dioxide.

[0006] Electrochemical cell units may be tubular or planar in configuration. Planar cell units may be arranged overlying one another in a stack arrangement, for example 100-400 cell units in a stack, with the individual fuel cell units arranged, for example, electrically in series. Tubular cell units may be arranged in groups, stacks or coils thereof.

[0007] A solid oxide fuel cell (SOFC) unit that produces electricity is based upon a solid oxide electrolyte that conducts negative oxygen ions from an oxygen electrode to a fuel electrode located on opposite sides of the electrolyte. For this, a fuel, or reformed fuel, contacts the fuel electrode and an oxidant, such as air or an oxygen rich fluid, contacts the air electrode. A solid oxide electrolyser cell (SOEC) may have the same structure as an SOFC but is essentially that SOFC operating in reverse, or in its regenerative mode, to achieve the electrolysis of fuel, for example water and / or carbon dioxide, by input of electrical energy and using the solid oxide electrolyte to produce hydrogen gas and / or carbon monoxide and oxygen. Conventional ceramic-supported (e.g. fuel electrode-supported) SOFCs and SOECs have low mechanical strength and are vulnerable to fracture. Hence, metal-supported SOFCs and SOECs have been developed which have the active cell component layer supported on a metal substrate. In these cells, the ceramic layers can be

[0008] 15059730-1 very thin since they only perform an electrochemical function: that is to say, the ceramic layers are not self-supporting but rather are thin coatings / films laid down on and supported by the metal substrate. Such metal-supported SOEC stacks are more robust, lower cost, have better thermal properties than ceramic-supported SOECs and can be manufactured using conventional metal welding techniques.

[0009] Electrolyser cell stacks commonly operate at elevated temperatures. For example, intermediate or high temperature electrolysers (such as SOEC and alkaline electrolyte cells) have operational temperatures in excess of 400 °C, typically 450 °C to 700 °C for an intermediate temperature electrolyser such as one based on an MS-SOEC, and above 700 °C for high temperature electrolysers.

[0010] Electrolyser cell stack(s) can be assembled within a housing, and can be combined with heat exchangers and fluid delivery pipework, amongst other equipment, to form an electrolyser system, and the electrolyser system will be configured to supply input gas to and exhaust off-gas from the electrolyser cell stack(s) at the required operational temperatures.

[0011] An issue with these electrolyser systems can arise due to their elevated operational temperatures (relative to the surrounding environment). It would be desirable to provide an enclosure for these systems that protects personnel from these elevated temperatures, and a method for assembling such an enclosure.

[0012] SUMMARY OF THE INVENTION

[0013] According to a first aspect of the present invention there is provided an enclosure for housing at least one stack of electrochemical cell units, comprising a vessel, thermal insulation and an inner skin, the thermal insulation being disposed between an outer face of the inner skin and an inner face of the vessel, and the inner skin forming at least part of a common volume in the enclosure within which said at least one stack of electrochemical cell units is located, the enclosure comprising an adjustment mechanism to mechanically alter a shape of the inner skin, such that the inner skin is configured to be reshaped to urge an outermost face of the thermal insulation towards the inner face of the vessel.

[0014] The enclosure of the present invention, by the presence of the thermal insulation, provides an insulated electrochemical cell system once the at least one stack and other infrastructure of the electrochemical cell system has been housed within the enclosure. As the enclosure is thermally insulated, the enclosure protects personnel from internal temperatures of the enclosure during operation of the system and reduces thermal losses from the system thereby improving efficiency of the system.

[0015] The present invention also provides a simple solution for installing thermal insulation securely within the outer skin: by reshaping (mechanically expanding, or increasing the radius of) the inner skin after inserting it and the thermal insulation into the enclosure, it is possible to urge the thermal insulation against or towards the outer skin, thus closing a working gap between the

[0016] 15059730-1 thermal insulation and the vessel that allowed the thermal insulation and the inner skin to be fitted into the vessel (e.g. through an opening at one end thereof).

[0017] In some embodiments, an external shape of the inner skin is adjustable for urging an outermost face of the thermal insulation towards the inner face of the vessel.

[0018] In some embodiments, an outer skin is provided on an outside of the thermal insulation (i.e., between the insulation and the vessel). The outer skin may be made of metal. In some embodiments, upon reshaping (mechanically expanding, or increasing the radius of) of the inner skin, an outermost face of the thermal insulation, which is covered by the outer skin, expands (increases the radius of) the outer skin towards and into contact with the inner face of the vessel. The outer skin may form a protective layer around the thermal insulation.

[0019] In some embodiments, the thermal insulation or the outer skin is clamped by the reshaping (mechanically expanding, or increasing the radius) to be urged (or biased) against the inner face of the vessel. In other embodiments, it may remain loose fitting, but retained, against the inner face of the vessel (e.g., with one or more gaps between the thermal insulation or outer skin and the inner face of the vessel).

[0020] In some embodiments, the inner skin is a metallic inner skin. For example, it may comprise one or more metal layers.

[0021] In some embodiments, the thermal insulation comprises at least one layer of thermal insulation.

[0022] In some embodiments the thermal insulation is formed of a multilayer insulation (i.e., layers of respective thermal insulation materials).

[0023] The vessel may form the outside of the enclosure - for example, a perimeter, an outer wall or an external boundary of the enclosure. In other embodiments there may be additional wraps or the like around the vessel.

[0024] In some embodiments, the vessel is a pressure vessel. This allows the system to also operate at elevated pressures (above environmental pressures), which can improve the efficiency of an electrolyser and in particular the downstream off-gas delivery system. Typically, the environmental pressure surrounding the enclosure is around 1 bar. However, off-gases from an electrolyser system, such as hydrogen and oxygen, typically need to be collected and stored at a higher than ambient pressure. Therefore, by having the electrolyser system operating at a pressure higher than ambient (i.e. higher than that of the environment surrounding the enclosure), the off-gas will also be at that higher pressure. This in turn means that downstream equipment will have less work to do to recondition the off-gas to storage pressures. In this configuration, the system is an insulated, pressurised, electrochemical cell system.

[0025] The shape of the inner skin may be configured to be mechanically altered through outward radial displacement to cause an outer face of the inner skin to bear against an innermost face of the thermal insulation, and thus to urge the outermost face of the thermal insulation towards the

[0026] 15059730-1 inner face of the vessel. For example, the inner skin may be flexible such that its shape can be mechanically altered without fracture of said inner skin.

[0027] In some embodiments, the inner skin provides a structural support for the thermal insulation within the enclosure both during installation and use of the enclosure. In prior art enclosures, any thermal insulation is more typically supported by many anchors extending from the outer skin, with the anchors providing the support for the thermal insulation, rather than an inner skin. As such, in the prior art, any inner skin provides minimal support for the insulation during the assembly process. The present invention thus provides a more robust assembly for inserting into the vessel prior to reshaping (mechanically expanding, or increasing the radius of) of the inner skin.

[0028] In some embodiments, during assembly, the innermost face of the thermal insulation is pre-fitted to the inner skin prior to installing them as an assembly into the vessel.

[0029] In some embodiments, during assembly, the inner skin is pre-fitted to the innermost face of the thermal insulation prior to installing them as an assembly into the vessel.

[0030] In some embodiments, during assembly, the outer skin is pre-fitted to the outermost face of the thermal insulation prior to installing them as an assembly into the vessel. In some embodiments, both the inner skin and the outer skin are pre-fitted to the thermal insulation prior to installing them as an assembly into the vessel. Thus, during assembly, the outer skin is pre-fitted to the outermost face of the thermal insulation prior to installing the inner skin, the thermal insulation and the outer skin as an assembly into the vessel.

[0031] Such pre-fitting above may comprise affixing one material to the other, for example by chemical or mechanical means.

[0032] In some embodiments, the assembly has an initial size that is smaller than an initial size of the inner face of the vessel (and smaller than an opening at one end of the vessel and enclosure), such that the assembly can be easily inserted through the opening into the vessel, prior to reshaping (mechanically expanding, or increasing the radius of) the inner skin.

[0033] In some embodiments, there are more than one such assembly, each shorter than the vessel, for installing in a linear sequence within the vessel. For example there may be 2, 3, 4, or 5, or at most 6 such assemblies.

[0034] In such an embodiment, it is preferred that a collective length of the more than one assembly extends substantially a full length of a cylindrical part of the vessel. For example the vessel may comprise a central cylindrical part between open end part (having a removable lid closed over it) and a closed end part, and the assemblies are arranged in an array along a longitudinal axis of that cylindrical part.

[0035] 15059730-1 In some embodiments, a removable lid is fitted to the enclosure to close the opening. In some embodiments, the at least one stack and at least one manifold for the at least one stack is mounted to the removable lid.

[0036] In some embodiments, the thermal insulation and the inner skin, or the one or more assembly thereof, are initially retained, held or suspended within the vessel, prior to reshaping of the inner skin, by one or more locator pin that extends inwardly from the inner face of the vessel.

[0037] In some embodiments, one or more upper locator pin extending from a top of the vessel, may extend through the outer skin (if provided), the thermal insulation and the inner skin. In some embodiments, two or more such locator pins are provided for each assembly.

[0038] In some embodiments, additional locator pins are provided. For example, one or more of the upper locator pins may extend through the thermal insulation and the inner skin from the top part of the vessel, and a further one or more lower locator pin may be located, for each assembly if more than one such assembly is provided, at a respective one of two spaced ends of either or both of the thermal insulation and the inner skin, or the assembly or assemblies thereof.

[0039] In some embodiments, the locator pins are installed into the vessel once the thermal insulation and the inner skin, or the assembly or assemblies thereof, have been inserted into the vessel, for correctly locating the thermal insulation and the inner skin, or the assembly or assemblies thereof, within the vessel prior to and during reshaping of the inner skin. The locator pins then do not obstruct the insertion of the thermal insulation and the inner skin, or the assembly or assemblies thereof, into the vessel. In other embodiments, however, the pins are fitted first, and then the assemblies are fitted into the vessel, prior to having the shape of the inner skin mechanically altered with the adjustment mechanism.

[0040] In some embodiments, the adjustment mechanism may be operable during manufacture of the enclosure. The adjustment mechanism may comprise a camming component or a threaded component to mechanically alter a shape of the inner skin. In some embodiments, the movement of the gripper is by moving or rotating the camming component or the threaded component - for example by rotating it, or by rotating a nut or actuator thereon. Such adjustment mechanisms do not rely on thermal expansion and / or sliding of surfaces over one another to mechanically alter a shape of the inner skin. This improves reliability and insulative properties of the insulation. Nonetheless, it will be understood that any differential thermal expansion between components may alter contact and relative shapes therebetween.

[0041] In some embodiments, the inner skin is adjustable (i.e., in manufacture is adjusted) using the adjustment mechanism by the adjustment mechanism being configured to push against an end of the inner skin. The adjustment mechanism may be mounted on a lower locator pin. There may be a set (i.e. a plurality) of adjustment mechanisms mounted on a corresponding set (i.e., plurality) of lower locator pins along an axial length of the enclosure.

[0042] In some embodiments, the inner skin is adjusted (reshaped) using either or both of two adjustment mechanisms, one fitted at each of two spaced ends of the inner skin, for example one

[0043] 15059730-1 on each lower locator pin. These two adjustment mechanisms can each be configured to adjustably push against the respective ends of the inner skin. In some embodiments, the inner skin is adjusted (reshaped) using either or both of two sets of adjustment mechanisms, one set fitted at each of two spaced ends of the inner skin, for example one set of adjustment mechanisms on each set of lower locator pins.

[0044] In some embodiments, the or each adjustment mechanism comprises a gripper to grip the respective end of the inner skin. In some embodiments, the or each adjustment mechanism comprises an adjuster for moving the gripper. The adjuster may comprise a camming component or a threaded component. In some embodiments, the movement of the gripper is by moving or rotating the camming component or the threaded component - for example by rotating it, or by rotating a nut or actuator thereon.

[0045] In some embodiments, the outer skin (when provided), the thermal insulation and the inner skin, or the one or more assemblies comprised thereof, have generally rounded or arcuate forms. Once installed they can be concentric with the cylindrical part of the vessel.

[0046] In some embodiments, there are two or more assemblies of thermal insulation and inner skin (and optionally outer skin) fitted within the vessel, each fitted linearly along the length of the cylindrical part of the vessel, each positioned to bear against the next along the cylindrical part of the outer skin.

[0047] In some embodiments, the assemblies have a cross-sectional shape approximating a horseshoe shape - defining an arcuate shape with two spaced ends. In some embodiments, the arcuate shape extends at least 200 degrees and at most 310 degrees around the inside of the vessel, optionally between 250 degrees and 290 degrees around the inside of the vessel.

[0048] In some embodiments, the enclosure comprises an insulation infill for installing between spaced ends of the thermal insulation after installation of the inner skin. In some embodiments, the insulation infill is formed with an arcuate shape and size such that it substantially completes a circular form for the thermal insulation within the vessel, albeit disrupted by the one or more locator pin.

[0049] In some embodiments, the enclosure comprises an inner skin infill for installing between spaced ends of the inner skin after reshaping of the inner skin (i.e., after mechanically altering a shape of the inner skin). In some embodiments, the inner skin infill is formed with an arcuate shape and size such that it substantially completes a circular form for the inner skin within the inner vessel, albeit disrupted by the one or more locator pin and the adjustment mechanism.

[0050] In some embodiments, the thermal insulation is sized to be loose fitting inside the vessel during initial assembly, and upon reshaping of the inner skin (i.e., after mechanically altering a shape of the inner skin), the thermal insulation becomes tight fitting inside the outer skin. In some embodiments, however, the thermal insulation, or the assembly or assemblies comprising it, remains loose fitting (for example with one or more gaps between the thermal insulation or outer skin and the inner face of the vessel), albeit retained with minimal gapping, within the vessel after

[0051] 15059730-1 reshaping of the inner skin (i.e., after mechanically altering a shape of the inner skin). This allows for relative expansion of parts of the thermal insulation during normal operation of the electrochemical cell system. In some embodiments, the temperature within the common volume in the enclosure during normal use will be in excess of 400eC, and thus some parts will want to expand as the system heats up to that temperature due to their coefficient of thermal expansion.

[0052] In some embodiments, the inner skin has a longitudinal edge facing the removable lid (or end insulation of the enclosure - i.e. fitted to the removable lid or the closed end). There may be a space between the longitudinal edge and the removable lid, or the insulation may be compressible. This allows for expansion of the inner skin (i.e. the assemblies incorporating the inner skin) as it heats up to normal operating temperatures of the electrochemical cell system.

[0053] In some embodiments, the assemblies distributed longitudinally along the length of the enclosure have neighbouring edges, and they may be touching one another or they may be spaced from each other. In some embodiments, the separate assemblies (arcuate members) are not joined to one another. In some embodiments there are three such arcuate members, and they are not welded together.

[0054] In some embodiments, the outer skin is thinner walled than the inner skin - in other words the outer skin has a thickness which is less than a thickness of the inner skin.

[0055] In some embodiments, the inner skin is made of stainless steel. In some embodiments it is 1.5 mm to 3 mm thick, optionally 1.5 mm to 2.5 mm thick.

[0056] In some embodiments the outer skin is formed of stainless steel. In some embodiments it is a foil. In some embodiments it is 0.1 mm to 0.5 mm thick, optionally 0.15 mm to 0.3 mm thick. It may then be a lining for a pressure vessel.

[0057] In some embodiments, the removable lid is also insulated. An opposite end of the enclosure may also be insulated.

[0058] In some embodiments, inner skin infill and insulation infill are fitted at a bottom of the enclosure, inside the vessel, once the inner skin has been installed and reshaped (mechanically expanded, or increased the radius of). These infills may be formed of one or more arcuate member - for example two - one either side of and / or surrounding at least one support leg for supporting the at least one stack.

[0059] The present invention also provides a method of manufacturing an electrochemical cell system within an enclosure, the enclosure comprising a vessel, the method comprising installing thermal insulation and an inner skin in the vessel such that the thermal insulation is disposed between an outer face of the inner skin and an inner face of the vessel, and adjusting a shape of the inner skin with an adjustment mechanism to urge an outermost face of the thermal insulation towards the inner face of the vessel. In some embodiments, the method further comprises positioning at least one stack of electrochemical cell units within the enclosure (e.g., disposed within an insulated space inside the inner face of the inner skin).

[0060] 15059730-1 The present invention also provides a method of manufacturing an enclosure for an electrochemical cell system, the enclosure comprising a vessel, the method comprising installing thermal insulation and an inner skin in the vessel such that the thermal insulation is disposed between an outer face of the inner skin and an inner face of the vessel, and adjusting a shape of the inner skin with an adjustment mechanism to urge an outermost face of the thermal insulation towards the inner face of the vessel. The enclosure may be for use in an electrochemical cell system. In some embodiments, the method further comprises positioning at least one stack of electrochemical cell units within the enclosure (e.g., disposed within an insulated space inside the inner face of the inner skin).

[0061] In some embodiments of the method, the enclosure is as defined above.

[0062] In some embodiments, the method comprises positioning the inner skin and the thermal insulation within the vessel skin using one or more locator pins extending inwardly from the inner face of the vessel to the inner skin prior to adjusting the shape of the inner skin. The locator pin may initially suspend or support the inner skin and the thermal insulation (i.e., weight thereof), or simply may locate it in a central position (e.g. parallel to a longitudinal axis of the vessel).

[0063] In some embodiments, one or more upper locator pin is used to centralise the thermal insulation and inner skin within the vessel. As previously noted, in prior art enclosures, the thermal insulation is more typically supported by many anchors extending from / to an outer skin, with the anchors providing the support for the thermal insulation, rather than the inner skin providing that support.

[0064] In some embodiments, the upper locator pin(s) are centred, or angularly equidistant from, legs or adjustment mechanisms or lower locator pins in a lower part of the enclosure.

[0065] In some embodiments, the inner skin is thicker than the outer skin such that it (the inner skin) provides structural support for the thermal insulation, whereas the outer skin may simply provide a protective coating for the thermal insulation.

[0066] In use, an inner part of the thermal insulation will be hotter than, and thus will expand more than, an outer part of the thermal insulation.

[0067] In some embodiments, the one or more arcuate members or assemblies will expand axially as the internal temperature of the enclosure increases to operational temperatures of the electrochemical cell system. The one or more arcuate members are thus typically installed loosely in the axial / longitudinal direction to allow them to expand within the enclosure, perhaps into a touching configuration.

[0068] In some embodiments, any insulation provided for the removable lid(s) and any end wall(s) of the enclosure will be flexible so that thermal expansion of the inner skin, the thermal insulation and the outer skin (if provided) can be accommodated by that flexibility without damaging the end walls or lids.

[0069] 15059730-1 The electrochemical cell units may be electrolyser cell units, and they may be based on a solid oxide electrolyte and so are solid oxide electrolyser cells (SOEC). The electrolyser cell units may be metal-supported electrolyser cells (e.g., MS-SOEC), which aids stability of said cell units.

[0070] In some embodiments the electrochemical cell units operate at a target operational temperature in excess of 400 °C (e.g., 400-800 °C, optionally 450-700 °C). The temperatures referred to may be a temperature of the stack(s) - for example, the temperature of the product or off-gas (from the fuel or oxygen volumes of the stack(s)) may be used as the temperature of the stack(s) or the temperature of the stack(s) derived therefrom.

[0071] In some embodiments the enclosure has a second opening at a second end of the enclosure. The second end is typically opposite the first end. Installation of the thermal insulation and the inner skin may occur at either end, or at both ends if more than one assembly thereof is to be installed.

[0072] A further removable lid and a further plurality of stacks may be provided for the second opening. Each end of the enclosure thus may have an electrochemical cell assembly installed therethough, formed from a removable lid, a plurality of stacks and one or more manifold, along with appropriate connections.

[0073] The enclosure is preferably a sealed vessel once closed by the or each removable lid, and it is preferably a pressure vessel. References to enclosure, vessel and pressure vessel herein may each be used interchangeably.

[0074] To achieve the desired operation temperatures, it may be necessary to heat the stacks. This process may also comprise heating the enclosure or vessel. It may be assumed that the temperature within the volume or space within the enclosure or vessel is substantially the same as that of the stacks and the temperature of either may be measured.

[0075] References to heating the stacks may be replaced with references to heating the enclosure or vessel and vice versa.

[0076] References to supply of a fluid or gas to the stacks may involve providing said fluid or gas to one or both of a fuel volume and an oxygen volume of the cell units within the stacks (i.e. to anode and / or cathode sides of the cell units), unless otherwise specified.

[0077] In some embodiments, for each electrochemical cell assembly, the plurality of stacks are arranged in the enclosure in sets of at least 6 stacks, optionally at least 10 stacks, and optionally at least 20 stacks. For example, if supplied in pairs that are arranged side by side, the stacks may be arranged in an array of stacks that is two wide and in 3, 5 or 10 rows. In some embodiments they may instead be four wide. For example an array may feature a four wide, six row, set of stacks, and thus totalling 24 stacks. Instead there may be 2, 3, 4, 5 or 7 (or more) rows.

[0078] In some embodiments, the common volume is in fluidic communication with one or more of a fuel volume and an oxygen volume of each of the one or more stacks during operational use of the system. For example, the common volume may be fluidically connected with one of fuel and oxygen volumes at an outlet of each stack, and optionally also at an inlet of each stack.

[0079] 15059730-1 In some embodiments, the common volume is in fluidic communication with the oxygen volume of each of the stacks. In other words, the oxygen volume of the plurality of stacks is open manifolded (i.e., not manifolded to separate it from the common volume), and thus the oxygen outlet of each stack exhausts fluid from the oxygen volume into the common volume.

[0080] In some embodiments, the fuel and oxygen volumes of each stack are fully manifolded and so neither volume is in fluidic communication with the common volume. In such cases, a vessel fluid is supplied to the common volume within the enclosure. The vessel fluid may comprise a purge gas. The vessel fluid may comprise or consist of nitrogen or air.

[0081] The enclosure may be provided with a common volume inlet and a common volume exhaust for supply to and exhaust from the common volume. The vessel fluid may supply heat to the common volume and the stacks during a start-up cycle for the system.

[0082] In some embodiments, the fuel volume of each of the stacks is manifolded. Preferably, the manifolding is configured such that fuel flows through the plurality of stacks in parallel. The stacks themselves are also typically configured such that the fuel flows through the plurality of cell units in parallel.

[0083] Preferably, the enclosure is a pressure vessel configured to withstand a pressure difference between the inside of the pressure vessel and an ambient pressure surrounding the enclosure.

[0084] In some embodiments, a control system is provided that is configured to regulate (e.g. using back pressure regulation) the pressure of at least one or both of the fuel volume and the oxygen volume of the stacks, and optionally also to regulate pressure in the common volume, for example independently or via fluidic communication between the common volume and one of the fuel and oxygen volumes, at a pressure greater than ambient pressure.

[0085] In some embodiments, the pressure of at least one or both of the fuel volume and the oxygen volume (and optionally the common volume) is at least 0.5barg, optionally at least lbarg, optionally at least 1.5barg, optionally between 1.5barg and 3barg, optionally at most 10 barg, optionally at most 5barg. 1 barg is 1 bar above ambient, i.e. typically around 2 bar. When pressurised to a pressure higher than ambient pressure, this elevated pressure can be used to balance fluid pressure within the fuel and oxygen volumes of the stacks, thus reducing the stresses within the internal walls of the cell units / stacks. This is beneficial in particular since electrochemically active materials within the cell units of the stacks can be relatively brittle compared to the metal / steel support layer in the case of a MS-SOEC, and the balanced pressures between the stack and the common volume can additionally de-stress the exterior walls of the stacks.

[0086] In some embodiments, the regulating of the pressures comprises regulating the pressure of the fuel volume and the oxygen volume to balance pressure between the fuel volume and the oxygen volume, and optionally also the common volume, either directly because the common volume is not in fluid communication with the fuel or oxygen volume or indirectly via fluidic communication between the common volume and one of the fuel and oxygen volume. The pressure may be balanced such that a difference in pressure between neighbouring volumes is at most 0.5 bar, optionally at most 0.2 bar, optionally at most 0.1 bar, or optionally at most 0.05 bar. Balancing

[0087] 15059730-1 the pressure comprises controlling any pressure imbalance, i.e. to reduce or eliminate a pressure difference, across the cell units or stacks by supplying one or more of fluid to the fuel or oxygen volume - or regulating the exhaust from said volumes.

[0088] In some embodiments, the electrolyser system comprises a controller configured to perform the balancing process.

[0089] Due to the elevated temperature of the common volume, and / or the stacks, during normal operation of the electrochemical cell system, the enclosure can be internally and / or externally lined with one or more thermal insulation layer. In some embodiments, the enclosure only has internal thermal insulation. Ideally the insulation is effective to maintain the external temperature of an external wall of the enclosure at no more than 50 °C, and preferably at no more than 30 °C, or no more than 10 °C higher than the ambient temperature surrounding the enclosure (if higher).

[0090] The removable lid may be similarly insulated.

[0091] Particular and preferred aspects of the invention are set out in the accompanying independent claims. Combinations of features from the dependent claims may be combined with features of the independent claims as desired and appropriate and not merely as explicitly set out in the claims. The term "comprising" as used herein to specify the inclusion of components also includes examples in which no further components are present.

[0092] An enabling disclosure of the present invention, to one of ordinary skill in the art, is provided herein. Reference now will be made in detail to examples of the invention, one or more examples of which are set forth below. Each example is provided by way of explanation of the invention, and not limitation of the invention.

[0093] Brief Description of the Drawings

[0094] Features of the present invention will now be described in further detail, by way of various embodiments, and just by way of example, with reference to the accompanying drawings (which drawings are not to scale), in which:

[0095] Figs. 1 and 2 are simplified schematic views of an electrolyser system;

[0096] Fig. 3 is a simplified control device for controlling an electrolyser system;

[0097] Figs. 4 and 5 are side elevation and top plan, cut-away schematic views of an electrochemical cell system;

[0098] Fig. 6 is a schematic section through an enclosure of the present invention housing a single stack, or a single line of stacks;

[0099] Fig. 7 is an enlarged schematic view of the region in a dashed circle shown in Fig. 6; and

[0100] 15059730-1 Fig. 8 schematically illustrates in perspective view an example of the thermal insulation and inner and outer skins in three parts that distribute along a longitudinal axis of the enclosure.

[0101] Detailed Description

[0102] In the following figures and description, like reference numerals will be used for like elements in different figures.

[0103] In the following description, the electrochemical cell systems will be described as if they are electrolyser systems (which could be a reversible fuel cell operating in a regenerative mode), for ease of reference. However, it is to be appreciated that the electrochemical cell systems could also be configured as a fuel cell system operating in a power delivery mode.

[0104] Fig. 1 is a simplified schematic of an electrolyser system 100 including a plurality of electrolyser stacks 10 in an enclosure 105. The enclosure 105 may be a pressure vessel 105 configured to withstand a pressure difference between its interior and exterior.

[0105] An array 110 of four stacks 10 is shown in Fig. 1, but it will be understood that any number of stacks 10 may be present, including fewer and greater than four, for example 1, 2, 10, 12 and so forth.

[0106] Each stack 10 comprises a stack of electrolyser cell units. A typical stack may have 100 to 500 electrolyser cell units.

[0107] The electrolyser cell units each comprise a first fluid volume (for a first fluid - typically fuel for the electrolysis process - e.g. at least one of steam, carbon dioxide and nitrogen dioxide) and a second fluid volume (for a second fluid - typically oxygen as a product of the electrolysis process), which fluid volumes are fluidically separated from one another such that the first and second fluids therein cannot mix.

[0108] Each stack 10 has a first fluid inlet 115 and a first fluid outlet 116, each of which is in fluidic communication with the first fluid volumes of each electrolyser cell unit 10. Supply of the first fluid to the first fluid volume is via the first fluid inlet 115 and exhaust from the first fluid volume is by the first fluid outlet 116. The first fluid is provided to the first fluid volume of the stacks 10 from a first fluid source 143 via the respective first fluid inlets 115 of the stacks 10.

[0109] In the example of Fig. 1, the first fluid is fully manifolded within the system. That is, there is a manifold enclosing the fluid within the system and providing fluidic communication between the first fluid source 143, external to the enclosure 105, and the first fluid inlets 115 of the stacks 10. Likewise, there is a manifold providing fluidic communication between the first fluid outlets 116 of the stacks 10 and a first fluid volume off-gas collection 163, external to the enclosure 105.

[0110] Each stack 10 may have a second fluid inlet 122 and a second fluid outlet 123, which, where present, is in fluidic communication with the second fluid volume of each cell unit 10. Exhaust from the second fluid volume is by the second fluid outlet 123, and an optional supply of a second

[0111] 15059730-1 fluid to the second fluid volume is via the optional second fluid inlet 122. The optional second fluid is provided, in this example, as a sweep flow gas to the second fluid volume of the stacks 10 from a second fluid source 144 via respective second fluid inlets 122 to assist in sweeping product (e.g. oxygen) from the cell units.

[0112] In the example of Fig. 1, the second fluid is open manifolded within the system. That is, there is a vessel inlet 120 to the enclosure 105 for delivery of the second fluid to the interior of the enclosure 105 from the second fluid source 144, but there is no branched manifold to deliver the second fluid to respective second fluid inlets 122 of each stack 110.

[0113] Exhaust from the second fluid volume of the stacks 110 is also open manifolded. That is, there is a vessel exhaust 121 from the enclosure 105 for exhaust of second fluid volume off-gas from the interior of the enclosure 105 to the second fluid off-gas collection 164 - in this example the offgas or product, mixed with the second fluid, but there is no branched manifold between the respective second fluid outlets 123 of each stack 110 and the vessel exhaust 121.

[0114] In some cases the second fluid may be partially manifolded within the enclosure - i.e. there may exist a manifold between the vessel inlet 120 and the respective second fluid inlets 122 of the stacks 110, or there may exist a manifold between the respective second fluid outlets 123 of the stacks 110 and the vessel exhaust 121.

[0115] In some cases both the inlet and exhaust of the second fluid may be manifolded, as depicted in Fig. 2, to ensure that any second fluid (herein in this example a sweep gas) that is supplied to the second fluid volume is effective at sweeping through the cell units, such that the product / off-gas released into the second fluid volume can then be removed therefrom. This will occur particularly during start up, shut down and standby modes.

[0116] In Fig. 2 the electrolyser system 101, which is otherwise similar to the electrolyser system 100 of Fig. 1, includes inlet and exhaust manifolds for the second fluid which communicate with the second fluid source 144 and second fluid collection 164, respectively. Further, the electrolyser system 101 has a vessel inlet 120 and a vessel exhaust 121 for a vessel fluid supplied to a common volume of the enclosure 105 that contains the stacks 10, from a common volume supply 165.

[0117] Optionally the vessel fluid can be supplied via a heater 152. Heaters may optionally also be provided for the first and second fluids supplied from the first and second fluid sources 143, 144.

[0118] The vessel fluid may thereafter be exhausted from the common volume to a common volume collection 166 through the vessel exhaust 121. As such, in this embodiment the common volume of the enclosure 105 is in fluid communication with neither the first nor the second fluid volumes.

[0119] When the stacks are operated at elevated pressures, the vessel fluid in the common volume may be regulated to balance the pressure in the common volume with the pressure in the first and / or second fluid volumes. Similarly, the pressures may be balanced between the first and second fluid volumes.

[0120] 15059730-1 The vessel fluid may be a relatively inert gas to avoid corrosion of the components within the enclosure, and to minimized the possibility of a reaction between the vessel fluid and any leakage of product (e.g. hydrogen, carbon monoxide, nitrogen or oxygen) or first and second fluids from the manifolded passages elsewhere within the enclosure. For example, the vessel fluid may be air or nitrogen.

[0121] It will be appreciated that it is sometimes preferable for the second fluid to be open manifolded, as in Fig. 1, or partially manifolded as discussed above, such that there exists fluidic communication between the second fluid volume of the stacks and the interior of the enclosure 105 for pressure equalisation therebetween - in turn simplifying control strategies and pipework required for the respective fluids.

[0122] It will be understood that similar partial or fully manifolded arrangements to those shown schematically in Figs. 1 and 2 are known in the art, albeit not with the stacks being provided in an enclosure.

[0123] In the examples of Figs. 1 and 2, the first fluid volume is typically a fuel volume and, during steady operation, is for fuel - usually steam and / or carbon dioxide, but possibly other compounds for electrolysing, such as nitrogen dioxide. In cases where the electrolyser cell units in the stacks 10 comprise an oxygen ion conducting electrolyte (e.g., solid oxide electrolyte cell units), the first fluid volume off-gas exhausted to the first fluid off-gas collection 163 comprises hydrogen and / or carbon monoxide and / or nitrogen monoxide (dependent on the fuel used). This off-gas is generated in the electrolysis reaction, and is mixed with unspent fuel in the off-gas. The second fluid volume off-gas exhausted to the second fluid off-gas collection 164 instead comprises oxygen that is generated in the electrolysis reaction. The second fluid off-gas may be pure oxygen or oxygen enriched sweep gas if mixed with a sweep gas.

[0124] The second fluid volume off-gas is preferably controlled through selective use of a sweep gas such that it may comprise at least 50% by weight of oxygen generated by the cell units. In some embodiments, the second fluid volume off-gas 164 may be substantially pure oxygen, if purely the product of the electrolysis process, although it might more normally be oxygen enriched air or nitrogen if a sweep gas (air or nitrogen) is also being used. Ideally, however, the oxygen is at least 90% (by weight) pure oxygen when the system 20 is operating at a steady state operation, as the present invention is ideally operated without an externally sourced sweep gas. In such a configuration the stacks are just supplied the first fluid, i.e. one fluid to the first fluid input 115 for each stack 10.

[0125] Other than the fluid inlet(s) and outlets, the stack / electrolyser / vessel will have inputs (terminals, not shown) for power (for applying a current across the electrolyser cell units in the stacks 110).

[0126] Operationally, a stack will usually want to avoid large pressure differentials across the cell units, so a threshold pressure differential between the first and second fluid volumes can be set appropriately, or the first fluid volume's pressure (on a first side of each cell unit) can be controlled to balance the pressures across the cell units. In one example, the pressure differential can be controlled (and is kept as small as possible) by use of a common regulator system across or

[0127] 15059730-1 between the two sides of the cell units (the anode side and the cathode side). However, in operation it is sometimes advantageous to control the pressure differential to be positive on the second fluid volume's side to ensure that any oxygen leaks leak into the fuel side, rather than the other way around, which could instead be hydrogen leaking to the oxygen side. This is better for the stack's operational lifetime as there will be less degradation of the electrochemically active layers of the cell units, and less opportunity for an abrupt failure of the cell unit due to combustion of the hydrogen with the oxygen.

[0128] The electrolyser system 100 typically operates at an elevated temperature, for example 400-700 °C for cell units based on a solid oxide electrolyte. It will be appreciated that heat in the first fluid off-gas and the second fluid off-gas will typically be exchanged with (transferred to) the first fluid and, if present, second fluid prior to their delivery to the stacks 10, typically prior to their entry into the enclosure 205 using one or more heat exchangers (but typically two or more heat exchangers such that heat is recovered from the first fluid volume off-gas and the second fluid volume off-gas). In steady state operation said heat exchange may be sufficient to maintain an operating temperature of the electrolyser system 100 when practiced alongside electrical temperature control by varying a power level applied to the electrolyser cell units. Heaters 150 and / or 151 (e.g., an electric heater and / or a trim heater) may be provided in an input stream of the first and / or second fluid, respectively, to provide additional heat to said fluids and for providing additional heat control flexibility within the system. Said heaters may be sized for steady state requirements only, or may also be used for other operational modes, e.g. warm-up or standby.

[0129] In steady state operation, the first and second fluid volume off-gases will usually be at a similar temperature to the operational temperature of the electrolyser cell units. However, a specific delta from the input temperature will depend upon the amount of electrical power supplied to the electrolyser system / stacks / cell units, and the internal resistance of the cell units.

[0130] The electrical power is generally supplied to the stacks with a constant current. The stack is thus operated in galvanostatic conditions. The electrical resistance of the stack thus controls the voltage applied across the stack, and there is thus a variable power draw from each stack and cell unit as the resistance changes. Alternatively the power supplied to the stacks is controlled potentiostatically.

[0131] Operational efficiency can be best improved by reducing the amount of external heat supplied to the system via its fluid temperature control system - i.e. via the heaters. Where that external heat is provided for free - for example as a waste product of another industrial process, then that external heat can be usefully used without cost - i.e. it provides added financial efficiencies. However, if that external heat has an associated cost, then operational efficiencies would be better improved instead by reducing the need for such external heating. At steady state this is achieved by using both galvanostatic conditions within the stacks, i.e. a constant electrical current (constant amps), and by adopting thermoneutral voltages across the stack to avoid heat wastage in the stacks, as at a thermoneutral condition the electrolyser is in an adiabatic state, i.e. it is balanced energetically, which effectively means no heat is consumed or released.

[0132] 15059730-1 In the prior art, it is known to use either constant voltages or constant currents on a stack, and then to control the current or the voltage, respectively, to maintain the stack at a substantially thermoneutral condition. This then allows the stack to avoid overcooling or overheating, as when at under-voltage (for a galvanostatic stack - i.e. constant current), the stack shows endothermic characteristics, and it thus cools the fluid (and likewise the operational temperature of the stack), whereby the fluid output temperature is lower than the fluid input temperature, whereas when at over-voltage (for a galvanostatic stack - i.e. constant current), the stack shows exothermic characteristics, and it thus heats the fluid (and likewise the operational temperature of the stack), whereby the fluid output temperature is higher than the fluid input temperature.

[0133] At steady state, the present invention may use a galvanostatic condition for the stack, but fluctuates as necessary between thermoneutral conditions, over-voltage conditions and undervoltage conditions, in response to input fluid temperature control that aims to maintain a fluid input temperature equal to a fluid output temperature. This is done since the present inventors realised that it is relatively straightforward to measure temperature at an inlet and an outlet of the stack and thus to instead control the thermoneutral voltage automatically. In other words, at steady state the temperature delta between the fluid output temperature from the stack and the fluid input temperature for the stack is minimised, aiming for a zero delta. This then allows extended use of a galvanostatic condition for the stack, alongside a thermoneutral voltage condition, even while the stack, or one or more of the cell units therein, degrades.

[0134] Galvanostatic and thermoneutral (and galvanostatic thermoneutral) conditions such as those discussed above apply in steady state when the electrolyser system is at an operational temperature. Other steady state conditions or operating strategies, such as potentiostatic, endothermic or exothermic may also be used depending upon characteristics of the cell units and / or of input and exhaust fluids available or desired, respectively.

[0135] Other strategies are required in order to raise the electrolyser system to the operational temperature. Further, in cases where the heaters 150 and / or 151 are present, they may only have the capacity for a provision of trim heating at operational temperatures, e.g. to raise the heat of the input stream by 10-40 °C. Such heaters are unable to provide sufficient heat to the electrolyser system to warm the same from ambient to operational temperatures in a reasonable timeframe. However, provision of larger capacity heaters for the two heaters 150 and / or 151, to provide warm up heat, would result in oversized heaters for steady state operation, and thus unnecessary capex costs. Nonetheless, in each of the examples subsequently discussed, the heaters 150 and / or 151 - if in the form of trim heaters - may be used to assist warm up of the system when efficient to do so.

[0136] The abovementioned steady state operation is one mode of operation of an electrolyser system. Other modes of operation, including warm up, standby, and shutdown may be used with transitions therebetween. The electrolyser system may transition to a standby mode from a steady state (also referred to as a product-generating mode) or a warm up mode. As used herein, reference to supply / supplying or provide / providing to a volume also involves exhaust from that volume unless the context requires otherwise.

[0137] 15059730-1 Referring next to Fig. 3, there is shown a control device 400 for controlling an electrolyser cell stack of an electrolyser in an electrolyser system. The control device 400 comprises an input device 402 for receiving input from sensors 404 so as to determine at least one of: a stack operating voltage across the electrolyser stack(s), an inlet temperature at a fluid inlet, an outlet temperature at a fluid outlet and a common volume temperature. The control device 400 thus comprises a voltage monitoring system 406 for determining a stack operating voltage across the electrolyser stack(s), a current monitoring system for determining a stack operating voltage through the electrolyser stack(s); an inlet temperature monitoring and / or control system 408 for determining an inlet temperature at the fluid inlet and an outlet temperature monitoring and / or control system 410 for determining an outlet temperature at the at least one fluid outlet of the electrolyser stack(s). These systems may utilize sensors and data transmission devices or wiring. The control device receives sensor data relating to each of these measurements. The control device may control the system by controlling valves for supply to and exhaust from each fluid volume and power supplies for non-fluid heating. A suitably programmed processor 412 and associated memory 414 is provided for processing such inputs.

[0138] The control device's inlet temperature monitoring and / or control system 408 may comprise an output device for controlling the identity and temperature of a fluid entering the electrolyser stack(s) at a fluid inlet. A current control system 416 is also provided for controlling a current supply to (and in some cases from) the electrolyser stack. As mentioned above, during normal operation this is adapted to provide a constant current to the electrolyser cell stack, but the current / voltage may be reduced or turned off to automatically shut down the stack or increased to warm-up the electrolyser stack(s).

[0139] The controller may also control non-fluid heat sources (heaters and such like described above), recirculation loops, and temporary warm up configurations as described above.

[0140] In such a way, the controller 400 is adapted to control an electrolyser stack(s) and the electrolyser system 100 - for example that shown in any of Figs. 1, 2, and 4-8 as appended hereto.

[0141] Referring next to Figs. 4 and 5, an example of an electrochemical cell system in the form of an electrolyser system 200 is shown. In this embodiment, the electrolyser system 200 comprises an electrolyser assembly 12 within an enclosure 14, which enclosure 14 has an inner thermal insulation layer 16 on its inside wall. The thermal insulation layer 16 covers an inner sidewall and inner end wall of the enclosure 14.

[0142] The enclosure 14 has an opening at its end that opposes the inner end wall, which opening is closed by a removable lid 18. The removable lid 18 is also thermally insulated by an insulation layer 20.

[0143] The thermal insulation layer 16, in so far as it substantially defines a cylindrical section extending along the length of the enclosure 14, may be as described below with reference to Figures 6 to 8.

[0144] An end wall opposite to the removable lid may be separately insulated.

[0145] 15059730-1 The electrolyser system 200 comprises a plurality of stacks 10 of electrolyser cell units mounted on a support bed 22 within a common volume 24 inside the enclosure 14. The support bed 22 has a first support leg 26 and a second support leg 28. The first support leg 26 supports and fixes the support bed 22 to the enclosure 14 at a first position. The second support leg 28 supports the support bed 22 within the enclosure at a second position, spaced along a length of the enclosure 14 from the first position, in a manner such that the support bed 22, via its second support leg 28, can articulate relative to the enclosure 14. This second support leg 28 is thus not a fixed mounting. Instead, it has hinges 50 or pivoting / flexible connections for permitting movement of the support bed 22 relative to the enclosure 14. In this example, the second support leg 28 has a pivot arm 30 mounted between two parallel hinge axes 50, which hinge axes extend perpendicular to a longitudinal length of the enclosure, such that the pivot arm 30 can rotate relative to both the enclosure 14 and the support bed 22, thus allowing the articulation of the support bed 22 relative to the enclosure 14. Other forms of articulating joint can also instead be used.

[0146] Connecting between stacks 10, there is also provided a manifold 32 for providing fluidic connection to the stacks 10, via the removable lid 18, to the outside of the enclosure 14. In this example, the manifold 32 is shown to connect to the removable lid 18. Connections beyond that connection to external fluid subsystems can be as known in the art.

[0147] As shown in Fig. 5, the manifold 32 also connects to the stacks 10 via links 36. Such links 36 can be any form of fluidic and / or electrical connection as well known in the art. The links are typically flexible connections to allow relative movement to occur between the manifolds and the stacks, as may occur due to the variable temperatures within the system 200, and the different materials used within the system 200.

[0148] The connection of the manifold 32 to the removable lid 18 provides support for the manifold 32 relative to the removable lid 18 such that the manifold is 32 fixed to the removable lid 18 in a first location - at a first end 38 of the enclosure 14. The other end 40 of the manifold 32 is instead supported, and articulated relative to the enclosure at a second location within the enclosure, distal from the first end of the enclosure, by a support frame 34. As with the support bed 22, this articulated connection allows relative movement between the manifold 32 and the enclosure 14 - and between the manifold 32 and the support bed 22. This can be via a pivotable or flexible connection. For example, a pivoted support frame 34 can be provided. This pivoted support frame 34 provides hinged connections between the manifold 32 and the support frame 34 and between the support frame 34 and the support bed 22. In other embodiments, a flexible frame may be provided, whereby the frame itself can flex. In other embodiments, the frame may connect directly to the enclosure 14 (and be articulated thereto), rather than to the support bed 22.

[0149] It will be understood manifolds may communicate with more than one stack, if, for example, there are four stacks provided across the width of the enclosure (e.g., a 4 by 4 arrangement, rather than the 2 by 4 arrangement shown in figures 4 and 5).

[0150] 15059730-1 Referring to Fig. 5, it can be seen that the stacks 10 are arranged in pairs and in lines along the inside of the enclosure 14. This forms an array - 2 by 4 - of stacks within the common volume 24. Other embodiments may have fewer or more rows and columns of stacks.

[0151] Each stack 10 is connected by a link 36 to a manifold 32.

[0152] In these embodiments the enclosure is shown in a horizontal configuration so that the opening is to a side of the enclosure and the electrolyser assembly is inserted in and out of the enclosure 14 in a horizontal direction. It is possible, however, for the enclosure and the electrolyser assembly to be instead configured for vertical insertion of the electrolyser assembly in and out of the enclosure.

[0153] Referring next to Fig. 6, a schematic section through an enclosure of the present invention is shown. It houses a single stack 10, or a single line of stacks 10, although it can be scaled as appropriate to fit an array of stacks like the previous embodiments.

[0154] The stack 10, as in the previous embodiments, is mounted on a support bed 22, which is itself supported by support legs 26, 28 at a bottom of a vessel that defines a cylindrical part of the enclosure 14.

[0155] The enclosure 14, as per the previous embodiments, has a generally cylindrical form, with an opening at one end for insertion of the various components, such as the support legs 26, 28, the support bed 22, the stack(s) 10 and any manifolds 32 and links 36, along with the insulation layer 16 - which in this embodiment is formed of multiple components as discussed below. The opening (at the one end) can be closable by a lid. The other end can be closed and insulated, or open for insertion of other components. Openings at one or both ends can then be closed with a removable lid 18 at one or each end, which may be insulated.

[0156] In this embodiment, the enclosure 14 is fitted with an (at least initially) loose fitting insulation layer 16 that comprises three concentric components that extend around a majority of the enclosure's angular circumference (i.e., around a wall of a cylinder formed therein). These are an outer skin 62, thermal insulation 60 inside the outer skin 62, and an inner skin 64 inside the thermal insulation 60. These layers extend at least 200 degrees and at most 310 degrees around the inside of the vessel, optionally between 250 degrees and 290 degrees around the inside of the vessel, and in this example extend approximately 270 degrees around the vessel. The inner skin 64 provides support for the thermal insulation 60 and the outer skin 62, such that these layers can be handled as an assembly. The thermal insulation 60 is depicted as a homogenous section, however it may be formed of a multilayer insulation - layers of respective materials or porosity adapted for differing temperatures provided in layers from the inner skin outwards (i.e., in the radial direction). At least two and at most 8 layers may be used.

[0157] An upper locator pin 58 is provided which descends from a top of the vessel / enclosure 14, which upper locator pin 58 is secured to the vessel (for example by being bolted thereto). It is for centralising the assembly formed of the thermal insulation and the outer and inner skins within

[0158] 15059730-1 the vessel. Additionally or alternatively, the upper locator pin 58 at least partially supports (the weight of) the inner skin and insulation (and outer skin, where present).

[0159] Inside the cavity formed by the inner skin is a common volume 24 of the enclosure 14 for accommodating the at least one stack 10 of electrochemical cell units.

[0160] The thermal insulation 60 has two bottom ends, as does the inner skin 62, forming a horseshoe shape (or incomplete circle, for example at least 270 degrees and at most 330 degrees) in cross section. These bottom ends locate next to or against two lower locator pins 68 provided in the bottom half of the enclosure 14. These lower locator pins 68 again are connected to the vessel - for example by being bolted thereto, and they each support respective adjustment mechanisms 74 (one shown in Figure 7) that can be used to reshape (mechanically expand, or increase) the diameter of the inner skin 62 to urge an outermost face of the thermal insulation 60 towards an inner face 66 of the vessel 14. This adjustment mechanism 74 will be discussed in further detail with reference to figure 7, which shows detail in the dashed circular area indicated in figure 6.

[0161] Figure 6 is a cross section at an axial (length) direction of the enclosure and shows locator pins 58, 68 at that location. The locator pins 58, 68 may be spaced along an axial length of the enclosure. Such spacing of upper locator pins is described with reference to figure 8. There may be two sets (i.e., a plurality in each set, e.g., up to 30 in each set) of lower locator pins spaced along the axial length of the enclosure, one set at each of the angular locations depicted in figure 6 (i.e., one set fitted at each of two spaced ends of the inner skin). In such cases, a set (i.e. a plurality) of adjustment mechanisms is mounted on a corresponding set (i.e., plurality) of lower locator pins along an axial length of the enclosure. The inner skin is adjusted (reshaped) using either or both of these adjustment mechanisms. One set is fitted at each of two spaced ends of the inner skin, for example one set of adjustment mechanisms on each set of lower locator pins.

[0162] As the thermal insulation and the inner skin are incomplete circles in cross section (i.e. incomplete cylinders) - by virtue of them having spaced bottom ends - to complete those circles (i.e. the cylindrical form of that section), there is also provided one or more inner skin infill 70 and one or more insulation infill 76. These bridge the gap between the bottom ends - between the lower locator pins 78, and either side of the support legs 26, 28. There can also be one or more outer skin infill 88, as shown in Figures 6 and 7. The completed circles / cylinders complete the insulation layer 16.

[0163] The upper locator pin 58 may extend through the thermal insulation and the inner skin (and the outer skin if provided) and it can then be used to retain the inner skin 64 in an angular (i.e., rotational) direction. The upper locator pin 58 may also retain the inner skin (and thereby insulation) radially (vertically) to at least partially support the weight of the insulation. This may be by the use of a nut and washer, or such like, on its inner end. The locator pin 58 can have a threaded end for that purpose to receive such a nut and the washer.

[0164] In some embodiments, more than one such upper locator pin 58 may be used along the length of the vessel 14. For example, as shown schematically in figure 8, there can be three assemblies arranged along the length of the vessel 14, each formed by an arcuate section of the inner and

[0165] 15059730-1 outer skins and the thermal insulator, and these three assemblies 80, 82, 84 can be either butted against one another along the length of the enclosure 14, or spaced slightly apart to allow for later thermal expansion. Each of those assemblies 80, 82, 84 may comprise an outer skin 62, thermal insulation 60 and an inner skin 64, all attached together as a single assembly, and retained at the top of the enclosure / vessel 14 through the outer skin 62, the thermal insulation and the inner skin 64 by one or more upper locator pin 58 via holes 90 provided therefor.

[0166] In the embodiment of figure 8, two holes 90 are provided for receiving two upper locator pins 58 in the first assembly 80 - ready to attach the first assembly 80 to the inside wall of the vessel 14. In the second assembly 82 holes 90 for three locator pins 58 are shown - ready to attach the second assembly 82 to the inside wall of the vessel 14. In some embodiments there may be just two such holes - for two locator pins 58. In the third assembly 84, there are two holes 90 for receiving two more upper locator pins 58 - ready to attach the third assembly 84 to the inside wall of the vessel 14. In other embodiments, it may be one, two or three, or more than three upper locator pins per assembly. The number can depend upon the overall length of each assembly.

[0167] Referring back to figure 7, an example of an adjustment mechanism 74 is disclosed. This figure is merely schematic and is to help with understanding a possible adjustment mechanism 74, and as such is not to scale with regard to figure 6. Nevertheless, it shows a possible form for the area shown in the dashed circle of figure 6.

[0168] As shown in figure 7, the adjustment mechanism 74 comprises a threaded member 86 that can be rotated to drive a gripper 72 in a forward and backward direction as illustrated by the arrow. That gripper 72 engages against a bottom end of the inner skin 64 so as to drive that end circumferentially within the enclosure. As the other bottom end of the inner skin 64 will be secured by a corresponding adjustment mechanism 74 at that other bottom end, or by that other bottom end resting against one of the lower locator pins 68, the movement of the first bottom end due to adjustment of the adjustment mechanism 74 will cause an increase of the radius of the inner skin 64, thus causing it to urge the thermal insulation 60 outwardly - i.e. towards the inner face of the vessel 14. That in turn will cause to the outermost face of the thermal insulation 60 (and / or the outer skin when provided) to be urged towards and potentially into engagement with an inner face 66 of the vessel 14 - usually to touch or bear there against. It can even be adjusted to clamp that outermost face against an inner face 66 of the vessel 14 if desired. However, it is preferred to not be a tight fit to allow for thermal expansion as the system heats up for operation of the electrochemical cell system.

[0169] The adjustment and reshaping (mechanically expanding, or increasing the radius) of the inner skin can thus cause the previously loose-fitting (for insertion) assembly to be tightened within the vessel 14, whereupon its position within the vessel becomes secured. As a result the locator pins 58, 68 may merely serve to locate the assembly, rather than to also carry the weight of the assembly once fully installed.

[0170] The enclosure described with reference to the preceding figures may be for an electrochemical cell system. The enclosure comprising a vessel. The enclosure may be manufactured by installing

[0171] 15059730-1 the thermal insulation and the inner skin in the vessel such that the thermal insulation is disposed between an outer face of the inner skin and an inner face of the vessel. The insulation and inner skin (and outer skin, where present) form an assembly. In positioning the assembly within the enclosure, at least one upper locator pin may be passed through the assembly to angularly locate and / or support the assembly. Subsequently, the shape of the inner skin is adjusted with the adjustment mechanism to urge an outermost face of the thermal insulation towards the inner face of the vessel. The insulation (or outer skin, where present) contacts the inner face of the vessel. The adjustment mechanism (e.g., via the lower locating pin) and the internal face of the vessel support the assembly. Where multiple assemblies are used, they are sequentially installed. Such multiple assemblies may be supported and adjusted by the same or respective adjustment mechanisms.

[0172] It will be appreciated that the present invention is not limited to only the above examples. Other examples will be readily apparent to one of ordinary skill in the art without departing from the scope of the appended claims. These and other features of the present invention have been described above purely by way of example. Modifications in detail may be made to the invention within the scope of the claims.

[0173] 15059730-1

Claims

CLAIMS1. An enclosure for housing at least one stack of electrochemical cell units, comprising a vessel, thermal insulation and an inner skin, the thermal insulation being disposed between an outer face of the inner skin and an inner face of the vessel, and the inner skin forming at least part of a common volume in the enclosure within which said at least one stack of electrochemical cell units is located, the enclosure comprising an adjustment mechanism to mechanically alter a shape of the inner skin, such that the inner skin is configured to be reshaped to urge an outermost face of the thermal insulation towards the inner face of the vessel.

2. The enclosure of claim 1, wherein the inner skin is a metallic inner skin.

3. The enclosure of claim 1 or claim 2, wherein the thermal insulation comprises at least one layer of thermal insulation.

4. The enclosure of any one of the preceding claims, wherein the thermal insulation is formed of a multilayer insulation.

5. The enclosure of any one of the preceding claims, wherein the vessel is a pressure vessel.

6. The enclosure of any one of the preceding claims, wherein the shape of the inner skin is configured to be mechanically altered through outward radial displacement to cause an outer face of the inner skin to bear against an innermost face of the thermal insulation, and thus to urge the outermost face of the thermal insulation towards the inner face of the vessel.

7. The enclosure of any one of the preceding claims, wherein the inner skin provides a structural support for the thermal insulation within the enclosure both during installation and use of the enclosure.

8. The enclosure of any one of the preceding claims, wherein, during assembly, the innermost face of the thermal insulation is pre-fitted to the inner skin prior to installing them as an assembly into the vessel.

9. The enclosure of any one of the preceding claims, wherein an outer skin is provided on an outside of the thermal insulation.

10. The enclosure of claim 8 or claim 9, wherein, during assembly, the outer skin is pre-fitted to the outermost face of the thermal insulation prior to installing the inner skin, the thermal insulation and the outer skin as an assembly into the vessel.

11. The enclosure of any one of the preceding claims, when dependent upon either claim 8 or claim 10, wherein there is more than one such assembly, each shorter than the vessel, for installing in a linear sequence within the vessel.15059730-112. The enclosure of claim 11, wherein each assembly is positioned to bear against the next along the linear sequence.

13. The enclosure of any one of the preceding claims, wherein one or more upper locator pin extending from a top of the vessel is configured to extend through the thermal insulation and the inner skin.

14. The enclosure of claim 13, wherein one or more lower locator pin is provided, located at a respective one of two spaced ends of either or both of the thermal insulation and the inner skin.

15. The enclosure of any one of the preceding claims, wherein the adjustment mechanism is configured to push against an end of the inner skin.

16. The enclosure of claim 15, wherein the adjustment mechanism is mounted on a lower locator pin.

17. The enclosure of claim 15 or claim 16, wherein the inner skin is adjustable using either or both of two adjustment mechanisms, one fitted at each of two spaced ends of the inner skin.

18. The enclosure of any one of the preceding claims, wherein the or each adjustment mechanism comprises a gripper to grip a respective end of the inner skin.

19. The enclosure of any one of the preceding claims, wherein the enclosure comprises an insulation infill for installing between spaced ends of the thermal insulation after reshaping of the inner skin.

20. The enclosure of any one of the preceding claims, wherein the enclosure comprises an inner skin infill for installing between spaced ends of the inner skin after reshaping of the inner skin.

21. The enclosure of any one of the preceding claims, wherein the thermal insulation remains loose fitting within the vessel upon reshaping the inner skin.

22. A method of manufacturing an enclosure for an electrochemical cell system, the enclosure comprising a vessel, the method comprising installing thermal insulation and an inner skin in the vessel such that the thermal insulation is disposed between an outer face of the inner skin and an inner face of the vessel, and adjusting a shape of the inner skin with an adjustment mechanism to urge an outermost face of the thermal insulation towards the inner face of the vessel.

23. The method of claim 22, wherein the enclosure is in accordance with any one of claims 1 to 21.15059730-124. The method of claim 22 or claim 23, wherein the method comprises positioning the inner skin and the thermal insulation within the vessel skin using one or more locator pins extending inwardly from the inner face of the vessel to the inner skin prior to adjusting the shape of the inner skin.

25. The method of any one of claims 22 to 24, wherein one or more upper locator pin is used to centralise the thermal insulation and inner skin within the vessel.15059730-1

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