Electrochemical cell system

Abstract

An electrochemical cell system. The electrochemical cell system comprising one or more stack of cell units arranged in an enclosure, the enclosure extending lengthwise parallel to a first axis and one or more electrical connector, configured to provide electrical power to or from said one or more stack, each said electrical connector extending between a first connection point for electrically connecting that electrical connector out of the enclosure and a second connection point for electrically connecting that electrical connector to one or more stack, said first and second connection points being separated by a distance extending parallel to the first axis. Said one or more electrical connector comprises at least one portion that extends laterally relative to said first axis, said portion being configured to deform to accommodate changes in length between said connection points caused by temperature changes within the enclosure.

Description

[0001] ELECTROCHEMICAL CELL SYSTEM

[0002] Field of the Invention

[0003] The present invention relates to an electrochemical cell system, and in particular, an electrochemical cell system, electrolyser cell units or stacks thereof in an enclosure. The electrochemical cell system comprises 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 integration of solid oxide electrolyser cell (SOEC) units within the enclosure to form the 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 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

[0008] 15059181-1 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, fluid delivery pipework, and bus bars for distribution of electrical current to the stacks or cell units therein, 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, and intermediate and high temperature electrochemical cell units in general, i.e. those that operate at temperatures above 350 °C, is that their elevated operational temperatures (relative to the surrounding environment) can lead to significant changes in the size of the system during start-up and cool-down due to the coefficient of thermal expansion of the materials used. Furthermore, in some electrochemical cell systems, for example where the electrochemical cell units are solid oxide electrolyser cell (SOEC) units, or more specifically metal- supported solid oxide electrolyser cell (MS-SOEC) units, at least some of the components may have ceramic or relatively brittle components within them. Such components can be relatively fragile, or temperamental when exposed to bending forces or unexpected (or out-of-the-ordinary) mechanical strains or stresses. The present invention seeks to reduce the likelihood of such bending forces or unexpected (or out-of-the-ordinary) mechanical strains or stresses, and to thus reduce or eliminate the opportunities for consequential failures or defects within the electrochemical cell system.

[0012] SUMMARY OF THE INVENTION

[0013] According to a first aspect of the present invention there is provided an electrochemical cell system comprising: one or more stack of cell units arranged in an enclosure, the enclosure extending lengthwise parallel to a first axis; and one or more electrical connector, configured to provide electrical power to or from said one or more stack, each said electrical connector extending between a first connection point for electrically connecting that electrical connector out of the enclosure and a second connection point for electrically connecting that electrical connector to one or more stack, said first and second connection points being separated by a distance extending parallel to the first axis; wherein said one or more electrical connector comprises at least one portion that extends laterally relative to said first axis, said portion being configured to deform to accommodate changes in length between said connection points caused by temperature changes within the enclosure.

[0014] 15059181-1 In some embodiments, said one or more electrical connector comprises at least one corner or bend to form said at least one portion that extends laterally relative to said first axis. In some embodiments, the one or more electrical connector comprises at least two corners or bends to form a first of said at least one portion that extends laterally relative to said first axis. The at least one portion is thus defined by a change in direction or a change in cross section, or some physical break or change in the form of the electrical connector, along its length to change from a predominantly axial direction of extension to a predominantly lateral direction of extension.

[0015] In some embodiments the electrochemical cell system is an electrolyser system. However, it may instead be a fuel cell system.

[0016] In some embodiments the enclosure is a pressure vessel.

[0017] In some embodiments, there is a plurality of stacks, and the plurality of stacks is arranged in one or more array of stacks.

[0018] In some embodiments there is a plurality of electrical connectors, each electrical connector configured to provide electrical power to one or more stack, or one or more array of stacks.

[0019] In some embodiments the first connection point is on an inside of a removable lid of the enclosure.

[0020] In some embodiments the at least one portion that extends laterally relative to said first axis extends substantially perpendicular to said first axis when the temperature of a common volume within the enclosure is at a normal (or mid-point) operating temperature for the cell units. In this substantially perpendicular condition, the electrical connectors can be configured to be at their minimal stress and strain condition within the enclosure. In this manner, when the common volume is instead at ambient temperatures - e.g. during assembly of the system, or just prior to start up, the electrical connector can be at a negative flex condition due to relative shrinkage of the length thereof due to the temperature being lower than the normal (or mid-point) operating temperature, whereas when the common volume is instead at a maximum operating temperature, the electrical connector can be at a positive flex condition due to relative elongation of the length thereof due to the temperature being higher than the normal (or mid-point) operating temperature. However, it is possible instead for the substantially perpendicular state to be at start up, or any other temperature, or for a perpendicular state never to be achieved - instead the portion may merely extend laterally.

[0021] In some embodiments, said at least one portion that extends laterally to said first axis has a length that is, or extends a lateral distance that is equal to or greater than 20% of the distance between the connection points along the first axis. In some embodiments, the length or lateral distance is equal to or greater than 30% or even 40 or 50% of the distance between the connection points along the first axis. In some embodiments this length is a cumulative length of the lengths of all the portions that extend laterally to said first axis. This size for the length, or the cumulative length, allows the at least one portion to have enough length or lateral distance to enable the deforming of the at least one portion - for example by way of bending or flexing - to vary a general angle thereof relative to the first axis sufficiently to absorb any length changes within the system - both of the electrical connections and the other parts of the system - which may change length at

[0022] 15059181-1 different rates - due to coefficients of thermal expansion of the various components within the common volume of the enclosure.

[0023] In some embodiments, the or each electrical connector includes one or more hinge portions that is configured to have a lower bending stiffness than adjacent regions of the electrical connector. These hinge portions may be provided along the at least one portion, or may define such a portion between two of said hinge portions. For example, two or more of said hinge portions may be provided and they define a portion that extends laterally relative to said first axis between the two said hinge portions

[0024] More than one portion that extends laterally relative to said first axis may be provided on each electrical connector, and thus there may be more than two hinge portions.

[0025] In some embodiments, on each electrical connector there is positioned along the electrical connector: a first portion that extends substantially parallel to the first axis; a second portion that extends laterally to said first axis; a third portion that extends laterally to said second portion and said first axis; a fourth portion that extends substantially parallel to the first axis; and a fifth portion that that extends laterally to said first axis.

[0026] In some embodiments, between each of the first, second, third, fourth and fifth portions there is a corner or bend in the electrical connector.

[0027] In some embodiments the corner or bend is substantially at a right-angle (for example in at least one state of flexure of the electrical connector, as the angle can vary when the laterally extending portion deforms).

[0028] In some embodiments the first portion connects directly to a removable lid of the enclosure.

[0029] In some embodiments the fifth portion connects directly to the at least one stack.

[0030] In some embodiments, there are at least two electrical connectors, each with at least one portion that extends laterally to said first axis, the at least two electrical connectors extending from a removable lid of the enclosure to a respective one of at least two stacks. To create an electrical circuit across the stacks, each of the two stacks will also be connected to a second electrical connector, but the second electrical connector may instead take a different form, and may connect the respective stack to another stack - for example forming a series or parallel circuit with the connected stacks.

[0031] In some embodiments, the at least two electrical connectors run substantially parallel to one another. However, in some embodiments they have different lengths at least when measured parallel to the first axis.

[0032] In some embodiments, where two or more electrical connectors with at least one portion that extends laterally to said first axis are provided, the electrical connector(s) of those electrical

[0033] 15059181-1 connectors with a longer length have a longer lateral extension than the electrical connector(s) of those electrical connectors with a shorter length.

[0034] In some embodiments, there is one or more hinge portion on the second portion. In some embodiments there are exactly two hinge portions on the second portion.

[0035] In some embodiments there is at least one hinge portion on the third portion.

[0036] In some embodiments there is no hinge portion on the first and fourth portions, other than if present at the corner or bend between those portions and their adjacent portions.

[0037] In some embodiments, the one or more hinge portion comprises a region of reduced cross sectional area. It thus is more flexible than the adjacent regions.

[0038] In some embodiments, the one or more electrical connector is comprised of one or more metal rod or strip or ribbon.

[0039] In some embodiments, the or each metal rod or strip or ribbon has a substantially rectangular cross section.

[0040] In some embodiments, the electrical connectors have a solid, or mono-core, structure, i.e. they are not wound or braided, or otherwise multi-cored cables.

[0041] In some embodiments, the electrical connectors are self-supporting, and configured to be spaced apart so as to be electrically isolated from one another along their lengths.

[0042] In some embodiments, the portions of the electrical connectors that extend generally longitudinally or axially, rather than laterally, are substantially rigid or resiliently deformable, and will tend to undergo minimal deformation during use of the system. This helps them maintain electrical isolation between neighbouring electrical connectors as they may not have an insulating external coating due to the temperatures within the common volume being higher than the melting point of most polymers. Although the laterally extending portions are intended to deform, i.e. flex to accommodate the length changes, they are made of a resilient or elastic material so that they are only resiliently deformed - the electrical connectors are configured to avoid plastic deformation when they deform.

[0043] In some embodiments, the or each stack, or the one or more array of stacks, is mounted within the enclosure such that it allows movement thereof along said first axis. As the stacks may be connected to the removable lid of the enclosure by one or more manifolds - for supplying fluids to and exhausting fluids from the stacks, as well as the electrical connector(s). This movement allows for expansion and contraction of those manifolds. This can occur alongside the accommodation of the changes in length between said connection points, and is caused by temperature changes within the enclosure. As the manifolds may be made of a different material than the electrical connector(s), there can be additional or less movement of the stacks versus that of the electrical connector(s), and thus the laterally extending portions can accommodate that relative motion and expansions between the removable lid and the stacks.

[0044] In some embodiments, the stacks or the at least one array of stacks are mounted within the enclosure via an articulated or sliding or rolling coupling to said enclosure.

[0045] 15059181-1 In a typical solid oxide electrolyser system, the temperature difference between the external wall of the enclosure and an internal operational temperature of the stacks are significant, and due to the coefficient of thermal expansion of the materials of the manifold and the electrical connector, their lengths will vary considerably compared to that of the enclosure, between the time of assembly (room temperature - i.e. usually between 20 and 25 °C) and the time of normal operational use (around 550 °C for an SOEC, although operational temperatures for an intermediate temperature solid oxide electrolyser cell unit is typically anything between 400 and 700 °C). For example, if the manifold is 7m long, and if made of steel, that length of steel, when increased in temperature by 525 °C, will elongate by about 48mm. With the present invention, the articulation enabled for the electrical connector (as well as for the manifold) allows the expansion relative to the enclosure as the system heats up, and the contraction again as it cools down (e.g. at shut down), to be accommodated without adding excessive stresses or strains to the cell units within the stacks, thus removing undesirable levels of stress and strain from the electrochemical cell system.

[0046] Connections may extend between the stacks and each manifold, and each manifold may comprise one or more channels or pipes. The electrical connections are configured to be routed such that they do not impact against these channels or pipes as they flex.

[0047] In some embodiments, the manifolds and connections define an inlet manifold configured to provide fluid to each of said stacks and / or a product manifold configured to exhaust off-gas or product from each of said stacks. An inlet manifold for fuel may be defined. The fluid may be a fuel, which may be a combustible fluid if the electrochemical cell system is operating in a power delivery mode, or a fluid for separation (e.g. one or more of water / steam, carbon dioxide and nitrogen dioxide) if operating instead in a regenerative mode. A second inlet manifold for sweep gas or oxidant (provided to an oxygen volume) may be provided. At least one product manifold, for offgas from a fuel or oxygen volume of the stacks may be provided, in some embodiments separate product manifolds are provided for off-gas from the fuel and oxygen volumes respectively.

[0048] In some embodiments the stacks are configured as one or more arrays of stacks. Each array may have its own manifolds, channels, pipes and electrical connections, although a manifold and an electrical connection may instead connect with multiple arrays. In some embodiments a manifold is fluidically connected with multiple arrays (preferably all arrays) via respective fluidic connections. Such fluidic connections may be of a flexible type.

[0049] In some embodiments each array is one or more pair of stacks, arranged side by side, and multiple pairs may be spaced along the length of the enclosure, e.g. in rows. For example, each row may have one or more than one pairs of stacks, and there may be multiple rows.

[0050] In some embodiments the manifolds and connections also define a plurality of electrical conductors for providing electrical current to each said array.

[0051] In some embodiments, said enclosure includes a plurality of interfaces or control circuits to provide or control fluid and electrical connections to said manifolds and electrical conductors. In some embodiments, all of said interfaces or control circuits are located on said removable lid, or on an outside of the enclosure.

[0052] 15059181-1 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.

[0053] In some embodiments the electrochemical cell units operate at a target operational temperature in excess of 400 °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.

[0054] 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. A further removable lid, a further plurality of stacks and a further manifold may be provided for the second opening. Each end of the enclosure thus may have an electrochemical cell assembly formed from a removable lid, a plurality of stacks and one or more manifold, along with appropriate connections. In some embodiments, the electrochemical cell assembly further comprises any one or more of a) the support bed and b) the sled for sitting on the support bed.

[0055] Within the or each enclosure, the stacks of that enclosure are generally preferred to be configured to be located within a common volume or space within the enclosure. They may be connected by the or each support bed and the or each manifold to a common electrochemical cell assembly that is connected to the enclosure using bolts, or the common volume or space may contain more than one electrochemical cell assembly.

[0056] The or each enclosure is preferably a sealed vessel once closed by one or more removable lid, and it is preferably a pressure vessel. References to enclosure, vessel and pressure vessel herein may each be used interchangeably.

[0057] 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.

[0058] References to heating the stacks may be replaced with references to heating the enclosure or vessel and vice versa.

[0059] 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.

[0060] 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.

[0061] 15059181-1 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.

[0062] 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.

[0063] 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.

[0064] 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.

[0065] 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.

[0066] 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.

[0067] 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.

[0068] 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.

[0069] 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

[0070] 15059181-1 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 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.

[0071] In some embodiments, the electrolyser system comprises a controller configured to perform the balancing process.

[0072] 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).

[0073] The removable lid(s) may be similarly insulated.

[0074] 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.

[0075] 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.

[0076] Brief Description of the Drawings

[0077] 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:

[0078] Figs. 1 and 2 are simplified schematic views of an electrolyser system;

[0079] Fig. 3 is a simplified control device for controlling an electrolyser system;

[0080] Figs. 4 and 5 are side elevation and top plan, cut-away schematic views of an electrochemical cell system;

[0081] Fig. 6 is a perspective schematic view of an electrochemical cell assembly;

[0082] Fig. 7 is a perspective schematic view of an enclosure over the electrochemical cell assembly of Fig. 6, forming an electrochemical cell system;

[0083] 15059181-1 Fig. 8 is a side elevation, cut-away schematic view of the electrochemical cell system of Fig. 7;

[0084] Fig. 9 is a front elevation, schematic view of a frame for holding one or more manifolds within a common volume within the enclosure of the electrochemical cell system of Fig. 8;

[0085] Fig. 10 is a side elevation, cut-away, schematic view of an electrochemical cell system, featuring an elongated enclosure and an electrochemical cell assembly inserted at each end of the enclosure;

[0086] Fig. 11 is a perspective schematic view showing electrical connectors between the lid and the stacks;

[0087] Fig. 12 is a side view showing one electrical connector between the lid and a stack;

[0088] Fig. 13 side view of the electrical connector of Fig. 12 when elevated to a higher temperature, showing expansion of the electrical connector being absorbed by a laterally extending portion;

[0089] Fig. 14 is a perspective schematic of an electrical connector showing hinge portions on a laterally extending portion; and

[0090] Figs. 15 and 16 are side views, similar to Figs. 12 and 13, but showing relative flex of the lateral extending portion due to the presence of two laterally spaced hinge portions.

[0091] Detailed Description

[0092] In the following figures and description, like reference numerals will be used for like elements in different figures.

[0093] 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.

[0094] 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.

[0095] 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.

[0096] Each stack 10 comprises a stack of electrolyser cell units. A typical stack may have 100 to 500 electrolyser cell units.

[0097] 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

[0098] 15059181-1 fluid volumes are fluidically separated from one another such that the first and second fluids therein cannot mix.

[0099] 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.

[0100] 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.

[0101] 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 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.

[0102] 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.

[0103] 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 off-gas 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.

[0104] 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.

[0105] 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.

[0106] 15059181-1 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, 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 from a common volume supply 165.

[0107] 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.

[0108] 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.

[0109] 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.

[0110] 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.

[0111] 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.

[0112] 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.

[0113] 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.

[0114] 15059181-1 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.

[0115] 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).

[0116] 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 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.

[0117] 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 offgas 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.

[0118] 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.

[0119] 15059181-1 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.

[0120] 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.

[0121] 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.

[0122] 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.

[0123] 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.

[0124] 15059181-1 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.

[0125] 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.

[0126] 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), 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.

[0127] 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).

[0128] 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.

[0129] 15059181-1 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 Figures 4 to 10 as appended hereto.

[0130] 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.

[0131] 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.

[0132] 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.

[0133] 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.

[0134] As shown in figure 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.

[0135] 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, as shown in figures 6, 8 and 9, a pivoted support frame 34 can be

[0136] 15059181-1 provided. As shown in figure 8, this pivoted support frame 34 provides hinged connections 42 between the manifold 32 (in this case formed of three separate manifolds 44, 46, 48, each designating a different fluid manifold) 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. Three manifolds 44, 46, 48 are shown in figure 6 and related figures. The manifolds are provided between the enclosure (inner face of the insulation) and the stacks 10. In this example, one set of three manifolds 44, 46, 48 is fluidically coupled to the stacks along one side of the central axis and a second set of three manifolds is fluidically coupled to the stacks along the other side of the central axis, but it need not be the case that there are multiple sets of manifolds - there may be only one set along one side of the central axis or indeed the set(s) may be along the central axis, inbetween rows of stacks. It will be understood that each set of 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 figure 6). It will also be understood that three manifolds are exemplary, other numbers of manifolds (e.g., 1, 2, 3, or 4, preferably at least 3) may be provided depending upon the level of internal manifolding required (as discussed with reference to figures 1 and 2).

[0137] Because of the thermal insulation layers 16, 20, an outer wall of the enclosure 14 is maintained at a lower temperature than an inside volume of the enclosure 14 (i.e. the common volume 24) during operational use of the electrolyser system 100. During that operational use, the stacks 10, and thus the common volume 24, may be operating at a temperature of around 550 °C, whereas the outer wall of the enclosure 14 may be at a temperature only slightly elevated above ambient temperatures - for example at a temperature below 60 °C. Given these temperature differences, and the coefficient of thermal expansion of the various materials used in the system 10, there can be a significant relative movement between the end of the manifold 32 (distal from the lid 18) and the second location in the enclosure (and / or the end of the support bed 22 at the second location). As one end of each of the support bed 22 and the manifold 32 is fixed - to the enclosure 14 or the removable lid 18, the other ends thereof expand away from that fixed end. However, as the enclosure's external wall is not changing temperature to the same extent as the common volume 24 (including the manifolds 32 and the support bed 22), the enclosure 14 does not expand to the same extent as the manifold 32 and the support bed 22. Likewise, during use the manifolds and support bed may experience different temperatures, for example during warm up or shut down when fluids transported through the manifolds may be used to raise or lower the temperature of the system. As a result, the manifolds and support be expand by different amounts. The articulated connections for each of the manifold 32 and the support bed 22 thus permit the relative movements to be accommodated within the enclosure 14.

[0138] Referring next to Figure 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.

[0139] 15059181-1 Each stack 10 is connected by a link 36 to a manifold 32. In this embodiment there are manifolds down both sides of the array. Referring next to Figure 6, there are multiple manifolds 44, 46, 48 down both sides of the array, each manifold 44, 46, 48 being similar to manifolds 32. For example, there can be a fluid input manifold 44 for feeding fuel to the (fuel volume of the) stacks 10, an oxygen volume off-gas line 46 for removing oxygen volume off-gas from the oxygen volume of each of the stacks and a fuel volume off-gas manifold 48 for removing fuel volume off-gas from the fuel volume of each of the stacks. Multiple stacks can be connected to the same manifold, or separate manifolds for each stack can be provided, although it is simpler to have one manifold connecting with multiple stacks.

[0140] Still referring to Figure 6, the support bed 22 in this example is shown as two rails. A sled 23 is provided between the rails. The sled may be fixed to the lid directly or its movement relative to the lid may be constrained by the support bed 22 (in the latter case, such movement between the sled and support be being constrained in the main axis only at or adjacent to the first end of the enclosure).

[0141] In some embodiments the stacks are mounted directly onto the support bed. In other embodiments the or each stack is mounted onto the support bed by a sled. For example, the stacks 10 may be fixed to and supported by the sled 23 on the support bed. The sled can be configured to sit on the support bed, or one of the support beds if more than one is provided. In some embodiments the sled is configured to be movable relative to the or each support bed - for example it may slide or glide relative thereto. In some embodiments the sled or support bed comprises a plurality of rollers configured to allow lateral movement of at least part of said sled, and the stacks thereon, within said enclosure. This is to allow relative movement between the sled (and the stacks thereon) and the or each support bed, for example in a direction between the first end and the second end of the enclosure.

[0142] Referring next to Figure 7, the assembly 12 of Figure 6 (comprising the stacks, the manifolds and the removable lid, and in this example the support frame and the sled) along with the support bed(s), is shown enclosed within an enclosure 14, similar to that described with reference to Figs. 1, 2, 4 and 5.

[0143] Referring next to Figure 8, a side view of the assembly 12 shown in Figure 6 is now shown within the enclosure 14. This schematic view shows the hinged connections 42 between the support frame 34 and the manifolds 44, 46, 48, plus also the hinged connection 42 to the sled, to which the support frame 34 is mounted in this embodiment. In other embodiments it may be mounted directly to the support bed. It also shows that the support frame is itself flexibly assembled such that it too can flex about the hinged connections' axes. Due to the hinged connections (i.e., articulation within itself), different relative expansions and contractions of the support bed, the sled, and the various manifolds, due to differences in thermal expansion, or localised differences in temperatures, can be accommodated.

[0144] Figure 9 shows the support frame in more detail, albeit still only schematically. As can be seen, the frame comprises a top part 52, a middle part 54 and a bottom part 56, each of which can pivot about one of the hinged connections 42 (connected at each end thereof), and the frame 34 is

[0145] 15059181-1 bifurcated so that there is a side for the first set of manifolds 44, 46, 48 and another side for the second set of manifolds 44, 46, 48. Figure 9 also shows the hinged connection 42 for the frame 34 to the sled 23 which may equally be to support bed 22.

[0146] Referring next to Figure 10, a variant of the electrolysis system 200 is shown in which the enclosure 14 is elongated and configured with removable lids at both ends for accommodating an electrolyser assembly at each end thereof. In this case, each electrolyser assembly is supported by and fixed to a respective first location at a respective end of the enclosure, and articulation of the manifolds and / or support leg is distal from respective lids, located at or adjacent to a central region of the enclosure.

[0147] 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.

[0148] Referring next to Figure 11, an embodiment of the present invention is shown, in which a electrochemical cell system 100 (in this example an electrolyser system) comprises six stacks 10 of cell units, arranged in an array - 2 by 3, for mounting within an enclosure, the enclosure, as per the previous examples, extending lengthwise parallel to a first axis 58. In this figure, the removable lid 18 is shown, but the rest of the enclosure 14 is hidden so that the arrangement of three electrical connectors 60, 62, 64 between the removable lid 18 and the stacks 10 can be seen.

[0149] In this embodiment, three electrical connectors 60, 62, 64 are provided, although other embodiments may have one or more than one.

[0150] Each electrical connector 60, 62, 64 may provide a single polarity for a stack 10, or it may be a dual polarity connector assembly, with positive and negative connectors extending along it, and electrically isolated from one another, thus allowing both positive and negative poles to extend along the same electrical connector 60, 62, 64.

[0151] The stacks 10 may be separately connected with additional connectors (not shown) to one or more other stacks 10 to put the stacks in series or parallel connection, as desired by the system design specification.

[0152] Each electrical connector 60, 62, 64 is configured to provide electrical power to at least one of the stacks 10 from a power input / output 86 (see Figures 12, 13, 15 and 16), so that the stacks 10 can perform electrolysis on the supplied fuel (e.g. water, carbon dioxide) from the appropriate manifold (see earlier drawings). However, in the case of the electrochemical cell units instead being fuel cell units for operating in a power delivery mode, each said electrical connector 60, 62, 64 may instead take electrical power from the stacks 10 for delivery outside of the enclosure via the power input / output 86.

[0153] There is a separate connection point at each end of each electrical connector. The electrical connectors 60, 62, 64 thus each extends between a first connection point 66a, 66b, 66c and a second connection point 68a, 68b, 68c. The first connection points 66a, 66b, 66c are provided on

[0154] 15059181-1 the removable lid 18 (or connected elsewhere on the enclosure if preferred) for electrically connecting that electrical connector out of the enclosure - in this embodiment via the power input / output 86. The second connection points 68a, 68b, 68c are instead for electrically connecting the respective electrical connector to one or more stack 10. In this embodiment the connection points 68a, 68b, 68c are provided on the respective stacks 10 to which they connect. However, in some embodiments they may be at a separate connector that connects to each stack in an array.

[0155] The electrical connectors 60, 62, 64 extend generally along the length of the enclosure and thus the first and second connection points of each electrical connector are separated by a distance 70 extending parallel to the first axis 58 (see Figures 12, 13 and 16. As the second connection points are each at a different stack 10, and since those stacks 10 can likewise be spaced along the length of the enclosure 14, the distance 70 for each electrical connector 60, 62, 64 can be different.

[0156] Each electrical connector 60, 62, 64 comprises at least one portion that extends laterally relative to said first axis 58. In this example, each electrical connector 60, 62, 64 comprises five portion, each separated by a bend or fold, along the length of the respective electrical connector 60, 62, 64, the second portions 74a, 74b, 74c, the third portions 76a, 76b, 76c and fifth portions 80a, 80b, 80c being the ones that extend laterally relative to said first axis 58. In this embodiment the first portions 72a, 72b, 72c and the fourth portions 78a, 78b, 78c instead extend generally parallel to the said first axis 58.

[0157] The electrical connectors may be supported by an electrically insulating cradle (not shown) that allows the electrical connectors to slide (due to thermal expansion) parallel to said first axis 58, for example the cradle may support the fourth portions 78a, 78b, 78c of the electrical connectors. The cradle may be fixed to the support bed 22 or enclosure 14. The cradle may support the weight of the electrical connectors, improving reliability of the system.

[0158] The fifth portions 80a, 80b, 80c, which are electrically connected to the one or more stack 10 at the second connection points 68a, 68b, 68c, may additionally be supported by a top plate of the stack to which a given portion connects. The support is an insulative support between the top plate and the fifth portion. The support may be fixed to the fifth portion. The support may rest on the top plate. Preferably, the support is located on the top plate, for example by insertion in a blind hole or by fitting over a protrusion. The hole or protrusion may be a lifting hole or lifting eye for lifting the stack, repurposed for locating the support.

[0159] A material for the abovementioned insulative cradle and / or insulative support may comprise mica or alumina.

[0160] During start-up, for example, of the electrochemical cell system, there will be a significant change of temperature within the enclosure 14, as previously discussed. This change of temperature will cause movement of the stacks 10 within the enclosure 14 as the manifolds 32 and the support bed 22 will all expand in size. Similarly the electrical connectors will expand in length.

[0161] In some embodiments, the electrical connectors will be made of a different material than the manifolds or support bed, although in some embodiments they may be made of the same or similar materials. For example, in some embodiments the electrical connectors may be made of copper or a copper alloy, rather than steel, or of a different grade of steel, whereby there will be a differential

[0162] 15059181-1 of expansion between these components due to the different coefficients of thermal expansion of the various materials.

[0163] In some embodiments, the electrical connectors will be made of a composite. In some embodiments the electrical connectors will be made of a copper core with a steel shell (i.e., a steel sheath or surround which surrounds the copper core) or a copper core with a nickel shell. Such composite conductors may allow a reduced cross-sectional area for a given current, resistance and temperature, reducing space occupied by the connectors in the enclosure and at connections at each end thereof. Further, the shell aides robustness and provides corrosion resistance and some conductivity.

[0164] In addition, each component connects to different parts of the assembly within the system, whereby there will be different lengths between respective electrical connectors, and between respective manifolds, and between all of them and the support bed, and hence the stacks. Thus the distance between components will typically change, as the temperature of the system changes, due to differences in where and how each component is mounted, and also the degree and arrangement of any insulation. For example, because the external wall of the enclosure is insulated in some embodiments, its expansion is relatively limited compared to elements inside the enclosure. Hence the axial positions of the support legs are relatively unchanged by thermal variance, compared to the variance experienced by, for example, the support bed and the electrical connectors. Thus the amount each component lengthens as it heats up can vary even when the materials are the same, as a longer component will lengthen further than a short component, even if made of the same material.

[0165] In some embodiments, all these components may be made of stainless steel - the electrical connectors, the manifolds and the support bed, and with their various lengths and support arrangements they may all expand different amounts.

[0166] Furthermore, due to the placement of the ends of the components, some components may have different lateral widths in addition to, or instead of, different longitudinal lengths, whereby they can elongate laterally different amounts as they expand, whether due to different coefficients of thermal expansion or different initial lengths or widths.

[0167] Yet further, there can be differentials in these expansions due to the side of the stack (or the array thereof) to which it may be attached, as if attached on the left, they will tend to expand to the left, whereas if attached to the right they will tend to expand to the right.

[0168] They may also have different fixed points from which they expand, as some components are affixed to the removable lid, whereas the support bed may be affixed to the side of the enclosure, and the points at which they attach to the same component (i.e. the lid) will also be different for each component. There can thus be a wide variation in the amount of expansion of the various components.

[0169] For accommodating these various expansion differentials, the laterally extending portions can flex or bend forward and backward relative to the first axis 58, unlike the portions that extend along the axis 58, which can (or tend to) only move forward and backward along the axis 58 as a singular unit. The electrical connectors 60, 62, 64, due to their laterally extending portions, can thus

[0170] 15059181-1 accommodate any such expansion or relative length changes without excessively loading forces upon the connection points 66, 68 (as could occur if there was no allowance to accommodate the expansion differentials - particularly if the electrical connections expand less or more than the rest of the components (which would tend to pull or push the electrical connections out of the removable lid).

[0171] This flexing or bending of the portions of the electrical connectors that extend laterally relative to the first axis 58 is shown in Figures 12 and 13, where in Figure 12, there is no flex of the second and third portions 74, 76, whereas in Figure 13 at least the second portion 74 has flexed to accommodate an expansion of the first and fourth portions 72, 78.

[0172] It is to be noted that these figures are not drawn to scale.

[0173] It is preferred that the fifth portion 80 is provided as a relatively short portion compared to the second portion 74, and that it is less prone to flexing than the second portion 74. This is to allow the second portion, and optionally the third portion 76, to accommodate the majority of the expansion differential.

[0174] To encourage the flexing of the second portion, as shown in Figure 14, the second portion can be provided with hinge portions 82. These hinge portions can be a pivoting connection or a reduced thickness or a more flexible portion on the electrical connection, and can ensure that the second portion flexes more than the other portions. This is shown in Figures 15 and 16, where the hinge portions 82 act as bending locations for the second portion 74. This further reduces the stresses and strains experienced at the connection points 66, 68. The present invention has therefore been described above by way of example. However, 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.

[0175] 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.

[0176] 15059181-1

Claims

CLAIMS1. An electrochemical cell system comprising: one or more stack of cell units arranged in an enclosure, the enclosure extending lengthwise parallel to a first axis; and one or more electrical connector, configured to provide electrical power to or from said one or more stack, each said electrical connector extending between a first connection point for electrically connecting that electrical connector out of the enclosure and a second connection point for electrically connecting that electrical connector to one or more stack, said first and second connection points being separated by a distance extending parallel to the first axis; wherein said one or more electrical connector comprises at least one portion that extends laterally relative to said first axis, said portion being configured to deform to accommodate changes in length between said connection points caused by temperature changes within the enclosure.

2. The electrochemical cell system of claim 1, wherein the electrochemical cell system is an electrolyser system, and optionally comprising metal supported solid oxide electrolyser cells.

3. The electrochemical cell system of claim 1 or claim 2, wherein the enclosure is a pressure vessel.

4. The electrochemical cell system of any one of the preceding claims, wherein there is a plurality of stacks, and the plurality of stacks is arranged in one or more array of stacks.

5. The electrochemical cell system of any one of the preceding claims, wherein there is a plurality of electrical connectors, each electrical connector configured to provide or receive electrical power to or from one or more stack.

6. The electrochemical cell system of any one of the preceding claims, wherein the first connection point is on an inside of a removable lid of the enclosure.

7. The electrochemical cell system of any one of the preceding claims, wherein the at least one portion that extends laterally relative to said first axis extends substantially perpendicular to said first axis when the temperature of a common volume within the enclosure is at a normal or mid-point operating temperature for the cell units.

8. The electrochemical cell system of any one of the preceding claims, wherein said at least one portion that extends laterally to said first axis has a length that is equal to or greater than 20% of the distance between the connection points along the first axis.

9. The electrochemical cell system of any one of the preceding claims, wherein the or each electrical connector includes one or more hinge portions that is configured to have a lower bending stiffness than adjacent regions of the electrical connector.15059181-110. The electrochemical cell system of claim 9, wherein the one or more hinge portion is provided along the at least one portion.

11. The electrochemical cell system of claim 9 or claim 10, wherein two or more of said hinge portions are provided and they define a portion that extends laterally relative to said first axis between the two said hinge portions.

12. The electrochemical cell system of claim 9, claim 10 or claim 11, wherein the one or more hinge portion comprises a region of reduced cross sectional area.

13. The electrochemical cell system of any one of the preceding claims, wherein more than one portion that extends laterally relative to said first axis is provided on each electrical connector.

14. The electrochemical cell system of any one of the preceding claims, wherein on each electrical connector there is positioned along the electrical connector: a first portion that extends substantially parallel to the first axis; a second portion that extends laterally to said first axis; a third portion that extends laterally to said second portion and said first axis; a fourth portion that extends substantially parallel to the first axis; and a fifth portion that that extends laterally to said first axis.

15. The electrochemical cell system of claim 14, wherein between each of the first, second, third, fourth and fifth portions there is a corner or bend in the electrical connector.

16. The electrochemical cell system of claim 15, wherein the corner or bend is substantially at a right-angle.

17. The electrochemical cell system of claim 14, claim 15 or claim 16, wherein the first portion connects directly to a removable lid of the enclosure.

18. The electrochemical cell system of any one of claims 14 to 17, wherein the fifth portion connects directly to the at least one stack.

19. The electrochemical cell system of any one of the preceding claims, wherein there are at least two electrical connectors, each with at least one portion that extends laterally to said first axis, the at least two electrical connectors extending from a removable lid of the enclosure to a respective one of at least two stacks.

20. The electrochemical cell system of claim 19, wherein the at least two electrical connectors run substantially parallel to one another.

21. The electrochemical cell system of claim 19 or claim 20, wherein the at least two electrical connectors have different lengths at least when measured parallel to the first axis.15059181-122. The electrochemical cell system of claim 19, claim 20 or claim 21, wherein the electrical connector with a longer length has a longer lateral extension than the electrical connector with a shorter length.

23. The electrochemical cell system of any one of the preceding claims, wherein the one or more electrical connector is comprised of one or more metal rod or strip or ribbon.

24. The electrochemical cell system of any one of the preceding claims, wherein the or each stack is mounted within the enclosure such that it allows movement thereof along said first axis.

25. The electrochemical cell system of claim 24, wherein the or each stack is mounted within the enclosure via an articulated or sliding or rolling coupling to said enclosure.15059181-1

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