Stack assembly

Abstract

A support system for supporting an electrochemical cell stack 107, the support system 100 comprising: a plurality of frames 101, each frame comprising a cutout 102 portion configured to surround at l

Description

BACKGROUND TO THE INVENTION Electrochemical cell stacks are devices that use electrochemical reactions to produce electrical energy, chemical products, or both. In conventional examples, each cell in an electrochemical cell stack comprises a membrane electrode assembly sandwiched between bipolar plates. It is necessary that the different elements of the cell are held together in the stack under pressure. For this reason, the cells in a electrochemical cell stack may be arranged along a common axis, and pressure applied to the distal ends of the stack along the axis. This allows pressure to be applied to many cells at once. One of the most common applications of electrochemical cell stacks is water electrolysis, which is the process of applying an electrical current to water, separating it into hydrogen and oxygen. The hydrogen can then be captured for use as a fuel source. To release the energy, the hydrogen is recombined with oxygen either by combustion or in a fuel cell, producing only water as a by-product. Fuel cells can also be comprised of electrochemical cell stacks, which are operated in reverse to convert chemically stored energy into an electrical current. There is an increasing demand for electrochemical cell stacks in many industries. For example, the hydrogen industry is experiencing rapid growth as demand for zero-carbon renewable fuels increases. Electrochemical cell stacks for electrolysis can be powered by renewable electricity sources such as wind power, to generate hydrogen fuel with minimal greenhouse gas emissions. However, existing electrochemical cell systems are complex and expensive, leading to high assembly, installation and maintenance costs. To be cost effective, electrochemical cell stacks must be able to operate for long periods without failure, and without compromising the safety of the system. Accordingly, there is a need for electrochemical cell systems which are lower-cost to assembly and maintain, but which do not compromise reliability or safety. SUMMARY OF THE INVENTION According to a first example, there comprises a support system for supporting an electrochemical cell stack, the support system comprising: a plurality of frames, each frame comprising a cutout portion configured to surround at least part of the electrochemical cell stack; and a spacer assembly arranged to maintain a spacing between at least two adjacent frames of the plurality of frames; wherein each of the plurality of frames are arranged parallel to a compression axis of the electrochemical cell stack. The plurality of frames protect the cell stack from damage, support the weight of the cell stack, and contain the resultant forces arising from the pressure loading of the cell stack. Spacing the frame assemblies apart using spacer assemblies increases the internal volume of the support system, allowing a larger cell stack to be contained. In addition, the bending and torsional stiffness of the support system is increased. The open design of the support system allows easier access to the cell stack, for attaching other equipment or feed lines, or to perform inspection and maintenance. Optionally, the number of frames in the plurality of frames is between 2 and 6. Optionally, the spacer assembly comprises at least one spacer block and at least one tie rod. The tie rod may be tensioned so as to cause the frames to be pressed together. This increases the rigidity of the support system. Optionally, the at least one tie rod in the spacer assembly runs though the at least one spacer block to connect the adjacent frames together. This arrangement protects the tie rods from damage and corrosion, and allows the tie rods to be arranged perpendicular to the plane of the frames. Optionally, the spacer assembly comprises a plurality of spacer blocks. This allows lateral forces to be transferred between a pair of frames at several places, or through several successive frames. Optionally, the at least one tie rods extends through the plurality of spacer blocks. This simplifies assembly and improves lateral load transfer. The tie rods may extend all the way through the support system from one end to another. Optionally, the cutouts of the plurality of frames are arranged along a common axis. This simplifies insertion and removal of the cell stack. Optionally, the electrochemical cell stack is elongate in a direction perpendicular to the compression axis, and wherein the support system is configured to support an electrochemical cell stack such that the common axis of the cutouts is oriented parallel to the elongate direction of the electrochemical cell stack. This means that smaller cutouts are required, which allows the frames to be smaller. Optionally, the support system further comprises an explosion-resistant compliant cabinet configurable to contain the electrochemical cell stack and plurality of frames. Optionally, the support system further comprises a bolster plate configurable to support the electrochemical cell stack. The bolster plate ensures that loads transfers loads evenly across the cell stack and frames. Optionally, the support system can be configured to reposition the electrochemical cell stack such that the electrochemical cell stack is at least partially positioned externally to the plurality of frames. This facilitates maintenance, inspection and removal / insertion of the cell stack. Optionally, the support system comprises a slidably movable platform configurable to reposition the electrochemical cell stack between a first position and a second position. In some examples, the cell stack may be positionable at an intermediate position between the first and second positions. In other examples, the slidably moveable platform can only be locked in place at the first and second positions. Optionally, the support system further comprises a detection device positioned externally to the plurality of frames, and wherein the detection device is configurable to detect faults in the electrochemical cell stack or support system. The open design of the support system allows the detection device access to the cell stack (either physically or as a line of sight) between adjacent frames. Optionally, the support system further comprises a power supply conduit for connection to the electrochemical cell stack, wherein the power supply conduit is positioned in the spacing distance between the adjacent frames. Optionally, the support system further comprises means for applying pressure to an electrochemical cell stack. Optionally, the plurality of frames are arranged parallel to each other. This further simplifies assembly and manufacturing. In other examples, the frames may be positioned at other angles relative to each other. BRIEF DESCRIPTION OF THE DRAWINGS Figures l(a)-(d) show views of an exemplary support system. Figure 1(a) shows an isometric view. Figure 1(b) shows a cross-section through the mid-plane of the support system. Figures 1(c) and 1(d) respectively show isometric views of a frame and a spacer block used in the support system. Figures 2(a)-(b) show portions of isometric views of an exemplary support system and slidably moveable platform. Figure 2(a) shows an exemplary electrochemical cell stack supported by the support system, while Figure 2(b) omits the electrochemical cell stack for the purposes of clarity. Figures 3(a)-(b) show isometric views of an exemplary support system and slidably moveable platform, including a power supply system. Figure 4 shows an isometric view of an electrochemical cell system comprising a plurality of cell stacks and respective support systems. Figures 5(a)-(c) each show simplified plan views of exemplary support structures, each sub-figure using a different frame layout. DETAILED DESCRIPTION An exemplary support system will now be described with reference to Figure 1. Figure 1(a) shows a support system 100. The support system 100 supports an electrochemical cell stack 107 (also referred herein to as a "cell stack" or simply "the stack"), the exterior dimensions of which are shown in dotted lines. Each cell in the cell stack 107 comprises two electrodes, a cathode and an anode. When a voltage is applied across the electrodes, the anode becomes positively charged and the cathode becomes negatively charged. This causes the ions in the electrolyte solution to move towards the electrodes, where they can participate in the electrochemical reaction. At the anode, oxidation occurs, which involves the loss of electrons from the electrode. This produces positively charged ions that are released into the electrolyte solution. At the cathode, reduction occurs, which involves the gain of electrons by the electrode. This produces negatively charged ions that are also released into the electrolyte solution. Pressure is applied to the upper and lower ends of the cell stack 107 to compress the components of the cell stack 107 together. The compression forces applied to the cell stack 107 can be considered to substantially act through the compression axis 107a. In some examples, the cells in the cell stack are also arranged along the compression axis 107a. The compression axis 107a may be the geometrical central axis of the stack 107. In other examples, the compression axis 107a is offset from the geometrical central axis of the stack 107. Applying a compressive force to the cell stack 107 generates equal and opposite resultant forces (hereinafter simply referred to as "the resultant forces") through the frame assembly 100. The resultant forces are also substantially in the direction of the compression axis 107a. The magnitude of the resultant forces may be dependent on factors such as the cell active area and / or the sealing method used to seal the cell stack 107. In some examples, the resultant forces are between 100-150 tonnes in normal operation, or in further examples between 120-140 tonnes. In some embodiments, other forces may also be applied to the cell stack 107. These forces will also generate resultant forces. However, in general, the largest forces applied to the cell stack 107 will be applied along the compression axis 107a. The support system 100 is configured to carry the weight of the electrochemical cell stack 107 and withstand the resultant forces. In some embodiments, the compression axis 107a is aligned vertically, such that the weight of the cell stack 107 is also applied to the support system 100 along the compression axis 107a. In other examples, the support system 100 has a different orientation in use. For example, the cell stack 107 may be arranged such that the compression axis 107a is horizontal. The support system 100 includes a frame assembly 100a comprising a plurality of frames 101. The frames 101 are each substantially flat plates with a length L, width W and thickness T. In other examples, the frames 101 may be curved in one or more planes, rather than flat. This may improve the stiffness of the frames 101 by increasing the second moment of area of the frames 101, and / or provide improved access to the cell stack 107. The frames 101 are thin, that is T <<L and W. In some examples, the frames have an increased thickness, such that the thickness T is an appreciable fraction of at least the width W if not the length L. This increases the torsional and bending stiffness of the frames 101, but makes them more difficult to manufacture as well as heavier. The two L x W faces can be defined as the primary faces of the frame 101. Each frame comprises a cutout portion 102, which is a volume of empty space extending through the frame 101 from one primary face to the other. The centroid of the cutout 102 may be collocated with the centroid of the frame 101, as shown. That is, the cutout 102 may be located in the centre of the frame 101. In other examples, the cutout 102 may not be aligned with the centre of the frame 101. The cutout 102 may be located closer to the top of the frame 101, for example, allowing more room for equipment to be located beneath a vertically-mounted electrochemical cell stack. In some examples, the cutout 102 is configured to surround the electrochemical cell stack 107. In other words, the cutout 102 may be shaped and sized such that the electrochemical cell stack 107 can fit within the cutout 102. In other examples, the cutout 102 may be shaped and sized such that the electrochemical cell stack 107 can pass through the cutout 102. When the electrochemical cell stack 107 is positioned within the cutout of a frame 101, the frame 101 surrounds the cell stack 107 on four sides within the plane of the frame 101. By sizing the cutouts 102 larger than the electrochemical cell stack 107, the cell stack 107 can be installed into, or removed out of, the support system through the cutouts 102, without having to disassemble the frame assembly 100a. The frame assembly 100a may be configured to have a front side lOOf which is accessible for maintenance / access, and a rear side lOOr which does not need to be accessed. The parts of the support system which need to be inspected or accessed may be positioned towards the front side lOOf, or to open towards the front side lOOf, while those parts of the support system lOOr which do not need to be regularly accessed are positioned towards the rear side lOOr. This allows the support system to be positioned such that only the front side lOOf is accessible, while the rear side is e.g. positioned against a wall or connected to other systems. The cutout 102 defines the walls 101b of the frames 101. Each wall has a width V. The frames 101 are arranged substantially parallel to each other, in the sense that that the frames 101 are all orientated in the same direction. In other words, the primary faces of the frames are all parallel. In other examples, the plurality of frames 101 are not substantially parallel, as discussed further in relation to Figure 5. In the embodiment shown, the frame assembly 100a is comprised of a plurality of identical frames 101, that is, frames 101 with substantially identical dimensions and material characteristics. This reduces manufacturing costs, as the frames 101 can be mass-produced. In other examples, the plurality of frames 101 may include different frame types, such that the frames 101 are not all identical. For example, the outermost frames 101 of the frame assembly 100a may comprise protrusions or additional mounting points, to allow components of the support system 100 to be mounted at the distal ends of the frame assembly 100a. In other examples, the dimensions of the cutout 102 may vary between frames 101. For example, the frames 101 towards the front side lOOf of the frame assembly 100a may have cutouts 102 sized significantly larger than exterior dimensions of the cell stack 107, while the frames 101 towards the rear side lOOr of the frame assembly 100a have smaller sized cutouts 102 which are not so much larger than the exterior dimensions of the cell stack 107. This reduces material stresses in the second side of the frame assembly 100a, while providing clearance for the cell stack 107 to be accessed or inserted from the first side of the frame assembly 100a, In the example shown, the cutout portions 102 of the frames 101 are aligned along a common central axis 109. That is, a common axis 109 can be defined which passes through the centroid of each cutout 102. This ensures that a consistent hollow crosssection is maintained from one end of the frame assembly 100a to the other. Alternatively, the cutout portions 102 may not be aligned along a common axis. For example, as previously discussed the cutouts 102 of frames 101 towards one side of the frame assembly 101 may be larger than cutouts 102 of frames 101 towards the other side of the frame assembly. This may result in the centroids of the cutouts 102 towards the first side not being aligned with the centroids of the cutouts 102 towards the second side. The frames 101 are arranged with their length L substantially parallel to the compression axis 107a. This means that the frames 101 and the tension force carried by the frame assembly 100 are aligned. As will be discussed in relation to Figure 5 below, in other examples the frames 101 are not arranged substantially parallel to the compression axis 107a. Since the cell stack is positioned within the cutout 102 of the frames 101, the resultant forces are entirely self-contained within the frames 101. Thus, the resultant force can be carried entirely by the frames 101 themselves. The maximum stress caused by the resultant forces (i.e. the resultant stress) occurs at the region of minimum cross-sectional area. In some examples, the minimum cross-sectional area of the frame assembly 100a may be found in the mid-plane 108, and is given by the formula: N x T x 27 Where N is the number of frames. The value of these parameters is chosen to ensure that the resultant stress is well below acceptable levels throughout each frame. The acceptable level of stress may be determined by failure conditions such as the buckling stress of the frame 101, or by a maximum allowable strain or distortion in the frame 101. For a given resultant force, the maximum resultant stress can be reduced by increasing the thickness T or wall width W of the frames, or by increasing the number of frames N. In the embodiment shown, there are 5 frames. In other embodiments, the number of frames may be between 2 and 6. Each frame 101 is connected to an adjacent frame 101 by a spacer assembly 104. The spacer assemblies 104 maintain a fixed separation distance between each pair of frames 101. Spacing the frames apart increases the second moment of area of the frame assembly 100a without increasing the total volume of material required for the frames 101, increasing the bending stiffness of the frame assembly 100a. In addition, spacing the frames 101 apart means that the frame assembly 100a can support the distal ends of the electrochemical cell stack 107, minimising bending stresses within the cell stack 107. In some embodiments, the frames 101 are manufactured by waterjet or lasercutting the shape of the frames 101 from a sheet of material. Alternatively, the frames may be manufactured in other ways, such as casting. Despite their name, it will be understood the cutouts 102 do not necessarily need to be formed by cutting out material from a preformed frame, and could instead be formed e.g. by a mould during a casting process. In some embodiments, the frames 101 are comprised of multiple components joined together, rather than a single piece of material. For example, a frame 101 may consist of two upright walls joined together at their distal ends by horizontal beams. In the embodiment shown, the spacer blocks 103 connect to the frames 101 at the corners of the frame, with an additional pair of spacer blocks 103 connected along the mid-plane 108 of the frames 101. Using multiple spacer blocks 103 ensures that loads can be transferred between frames 101 without causing local overstressing or deformation of the frames 101 or spacer blocks 103. The spacer assembly 104 creates a fixed spacing distance between each pair of frames 101. Referring in particular to Figure 1(b), each spacer assembly 104 comprises at least one rigid spacer block 103 and at least one tie rod 105. The tie rods 105 provide a tensile force which compress the frames 101 against the spacer blocks. This keeps the frame assembly rigid. The tie rod 105 is secured at both distal ends by a nut and spacer assembly 105a. Tension can be applied to the tie rod by pre-tensioning, or by tightening one of the nuts. In the embodiment shown, the spacer assemblies 104 and frames 101 are arranged such that a single tie rod can be inserted through a plurality of frames 101 and spacer blocks 103. That is, the tie rod 105 passes through one frame 101, through a spacer block 103, then through another frame 101 and another spacer block 103. In the embodiment shown, the spacer blocks 103 comprise bores 103a for the tie rods 105 to pass through. The bores 103a protect the tie rods 105 from damage or corrosion. In addition, by passing directly through the spacer blocks 103, the tie rods 105 apply a compression force directly orthogonal to the contact plane between the spacer blocks 103 and frames 101. Each spacer assembly 104 comprises a tie rod in the sense that each spacer assembly 104 is compressed between a pair of frames 101 by a tie rod. Thus, a spacer assembly 104 can be considered to comprise a tie rod 105 even if that tie rod does not make physical contact with the spacer blocks 103 in that spacer assembly 104, and the forces from the tie rod 105 are transferred indirectly into the spacer blocks 103. As shown by Figure 1(b) and 1(c), in some embodiments the spacer blocks 103 comprise alignment pins 103c, which mate with corresponding holes 101c in the frames 101c. This arrangement allows the frame assembly 100a to be assembled more easily, as the frames 101 and spacer blocks 103 can be aligned before the tie rod 105 is inserted. The spacer assemblies only need to carry lateral forces perpendicular to the width of the frames and the compression axis, which are substantially lower than the resultant forces parallel to the compression axis 107. This means that the size and strength of the spacer assembly 103 can be reduced, saving weight and cost. The frames 101 and spacer blocks 103 may be made of any suitable material for bearing the required maximum stress levels. In some examples, construction-grade steel may be used, such as S460ML steel. Higher or lower grade steels may also be used, depending on their cost and availability, and factors such as the weight and size of the cell stack 107. The selection of material may determine the physical parameters of the frames 101 and / or spacer blocks 103, such as the thickness T of each frame 101. The electrochemical cell stack 107 can be positioned between the upper 106a and lower 106b bolster plates. In this position, the cell stack is positioned within the cutout portions 102 of the frames 101, such that each frame 101 surrounds the cell stack above, below and to the left and right side (up, down, left, and right being defined in relation to Figure 1(a)). In some examples, the support system 100 further comprises one or more support members positioned at a distal end of the support system 100, i.e. towards the outside of the frame assembly 100a. The support members are attached to the frame assembly 100a and / or bolster plates 106, and are configured to carry a portion of the resultant forces, thereby reducing stresses in the frames 101. The support members may take the form of a beam or plate which connects the upper bolster plate 106a to the lower bolster plate 106, or which connects an upper portion of a frame 101 to a lower portion. The support member may be spaced from adjacent frames 101 of the frame assembly 100a using a spacer assembly, as previously described. The support member may not be configured to surround the cell stack 107 in use, meaning that support member does not require a large cutout. Accordingly, the support member may take the form of an additional frame 101 which lacks a cutout portion 102 (or having a smaller cutout portion 102). Such a support member can be joined to the frame assembly 100a at the rear side lOOr of the support structure. The cell stack 107 would remain accessible through the front side lOOf of the support structure 100. Alternatively or additionally, a front support member may be joined to the front side lOOf of the support structure 100. The front support member may be joined to the frame assembly using a quick-release mechanism, such that the front support member can be easily removed to allow access to the cell stack 107 or interior of the frame assembly 100a. Figure 2 shows a support system 200 configured to support an electrochemical cell stack 207. The support system 200 comprises a compression system for applying compression forces along the axis 207a of the cell stack. In some embodiments, the compression system is a piston located underneath the lower bolster plate 206b, configured to actuate the lower bolster plate 206b relative to the upper bolster plate 206a along the compression axis 207a. The electrochemical cell stack 207 has a rectangular cross-section. The cell stack 207 may have different cross-sections in other embodiments, for example a circular or elliptical cross-section. The cell stack 207 is elongate along the axis 207b, that is, its length X along the axis 207b is greater than its length Y perpendicular to the axis 207b. The cell stack 207 is oriented in the support system 200 such that the elongate direction 207b is parallel to along which the frames 201 are arranged. This allows the cutouts 202 and frames 201 to be narrower, simplifying manufacturing. In addition, the bending moments generated in the upper and lower horizontal portions of the frames 201 are reduced. The support system 200 can be configured to position the electrochemical cell stack 207 in two different positions. In a first position, the cell stack 207 is positioned within the frame assembly 200a, and aligned with the pressure application system. That is, the cell stack 207 can be fully installed and activated in the first position. In the second position, the cell stack 207 is supported at least partially externally to the frame assembly 200a. In the second position, the cell stack 207 is more easily accessible, facilitating easier installation, removal, maintenance, and inspection of the cell stack 207. In other words, the first position is the internal, installed position, and the second position is the external, maintenance / installation position. Figure 2(b) shows a cell stack 207 positioned in the second position, i.e. positioned externally of the frame assembly 200a. The support system 200 comprises a slidably moveable platform 209, consisting of a drawer 209a connected to a rail 209b. In other examples, the slidably moveable platform 209 actuatable using a piston arrangement, or other mechanism. The drawer 209a is configured to support the cell stack 207. The rail 209b is connected to the frame assembly 101 via the lower bolster plate 206b. The slidably moveable platform 209 allows the cell stack to be installed on the drawer in the second position 209b as shown. The drawer 209a and cell stack 207 are then slid into the frame assembly 200a, whereupon the components of the support system 200 such as the pressure application system can be connected to the cell stack 207. The rail 209b is telescopic, allowing it to actuate the drawer 209a over a greater distance. The drawer 209a supports the cell stack 207 from the sides, leaving the central underside and topside of the cell stack 207 accessible for the pressure application system. In some embodiments, the electrochemical cell stack 207 may supported directly by the frame assembly 200a or pressure application system when in the first position, rather than by the slidably moveable platform 209. This means that the slidably moveable platform 209 can be removed from the frame assembly 200a when not being used to install or remove the cell stack 207. In some embodiments, a single slidably moveable platform 209 is used for multiple support systems 200. For example, the slidably moveable platform 209 is attached to a first support system 200, and used to install a first cell stack 207 in the first support system 200. Once the cell stack 207 is installed and supported by the first support system 200, the slidably moveable platform 209 is removed from the first support system 200 and connected to a second support system 200, whereupon it is used to install a second cell stack 207 in the second support system 200. Figure 3 shows an isometric view of a support system 300 supporting an electrochemical cell stack 307. The cell stack 307 is shown in the first position, i.e. positioned entirely within the frame assembly 300a. The open design of the frame assembly 300a facilitates access to and monitoring of the electrochemical cell stack 307. The frame assembly 300a has an open design in the sense that it comprises a plurality of thin frames 301 separated by mostly empty space. In other words, the separation distance between adjacent frames 301 is greater than the thickness of the frames 301. The support system 300 comprises a power supply system for supplying electrical power to the cell stack 307. The electrical power may be used to perform electrolysis. The power supply system consists of a pair of busbars 311 extending over the top of the frame assembly 300a. In other embodiments, the busbars 311 extend around the sides of the frame assembly 100a, or underneath the frame assembly 100a. The busbars 311 act as electrical conduits for supplying high-voltage electrical current to the cell stack 307. The busbars 312 are in electrical connection with the cell stack 307 by means of sub-conduits 312 connected between the busbars 311 and cell stack 307. In some embodiments, a first busbar 311 is held at a first voltage, and a second busbar 311 is held at a second voltage. The first busbar 311 is connected via a first set of sub-conduits to the anodes of the cell stack 307, and the second busbar 311 is connected via a second set of sub-conduits to the cathodes of the cell stack 307. Thus, a potential difference for performing electrolysis can be generated between the anodes and cathodes of the cells in the cell stack 307. The open design of the frame assembly 300a allows the sub-conduits 312 to be positioned in the spacing distances between frames 301. Thanks to the open design of the frame assembly 300a, the power supply system can becomparatively simple, consisting primarily of straight busbars 311 and sub-conduits 312. By contrast, a closed-design support system requires convoluted wiring layouts, in order to route electrical power around the components of the support system and connect the cell stack 307. The support system 300 comprises a detection device 313 positioned beneath the frame assembly 300a. The detection device 313 is configured to detect faults in the electrochemical cell stack 307 and / or support system 300. As previously discussed, electrochemical cell stacks can be used for water electrolysis to generate hydrogen and oxygen. A leak from the from the electrochemical cell stack 307 can cause highly combustible hydrogen and oxygen gas to build up within or around the cell stack 307, so it is advantageous to quickly detect leaks and immediately shut down the cell stack 307 pending inspection. This reduces the risk of fire or explosion. In some embodiments, the detection device 313 comprises a detection tray positioned underneath the frame assembly 300a, which is configured to detect fluids leaking from the electrochemical cell stack 307. The open design of the frame assembly 300a means that fluid escaping from the cell stack 307 can leak through the frame assembly 300a and collect in the detection tray. A weight scale or other sensor detects fluid pooling in the detection tray. If the volume or rate of fluid leakage exceeds a threshold amount, the cell stack 307 is shut down pending inspection and maintenance. In other examples, the detection device 313 may comprise infra-red sensors, moisture sensors, chemical detectors or other sensors. Figure 4 shows an electrochemical cell system consisting of a plurality of support systems 400. Each support system comprises a frame assembly 400a configured to support an electrochemical cell stack 407. Each support system 400 comprises an explosion-resistant cabinet 414, which surrounds a frame assembly 400a and cell stack 407. In other embodiments, a plurality of support systems 400 and cell stacks 407 are contained within a single explosion-resistant cabinet 414. The explosion-resistant cabinet 414 comprises a sealable panel or door (not shown) which can be opened to allow access to the frame assembly 400a and cell stack 407. When sealed, the explosion-resistant cabinet contains fires and explosions resulting from a faulty cell stack 407 or support system 400. The cell stacks 407 may pose a particularly high explosion or fire risk compared to the rest of the electrochemical cell system, because the cell stack 407 may generate combustible gases such as hydrogen or oxygen. By containing the cell stack 407 within an explosion-resistant cabinet, the rest of the electrochemical cell system can be designed to meet less stringent explosion and fire resistance requirements. Containing each cell stack 407 within a separate explosionresistant cabinets 414 prevents damage to neighbouring cell stacks 407 and support systems 400 in the electrochemical cell system, which could otherwise result in a chainreaction of further explosions and / or fires in the neighbouring cell stacks 407. In some embodiments, the explosion-resistant cabinets 414 are constructed in accordance with ATEX directive, ensuring robust protection against, and containment of, fires and explosions. In some embodiments, the explosion-resistant cabinets 414 are sealable such that gas interchange cannot take place between the interior and exterior. This ensures that combustible gases (such as hydrogen or oxygen) leaking from a faulty cell stack 407 are contained within the cabinet 414, rather than being dispersed around the wider electrochemical cell system. From there, the gases can be safely extracted from the cabinet through the gas exchange conduits 415. Figure 5 shows simplified views of different configurations of a support system 500 for supporting a cell stack 507 (the exterior dimensions of which are shown by dashed lines). The views are plan views, such that the compression axis of the cell stack is normal to the plane of the image. The cell stack 507 has an elongate direction 507b. The support system 500 comprises a plurality of frames 501, wherein adjacent frames are separated by spacer assemblies 503. The frames 501 are parallel to the compression axis, meaning that the length of the frames is aligned perpendicular to the plane of the image. In Figure 5(a), the frames 501 are arranged parallel to each other. The frames 501 are also aligned so that their widths are perpendicular to the elongate direction of the cell stack 507. As previously discussed, this arrangement minimises the size of the cutouts in the frames 501, reducing material costs and bending stresses. In addition, aligning the frames 501 parallel to each other along a common axis simplifies the design requirements for the spacer assembly 503. In Figure 5(b), the frames 501 are still arranged parallel to the compression axis, but the frames 501 are not parallel to each other. Instead, the frames 501 are oriented in a herringbone pattern, such that adjacent frames 501 are closer together on one side of the elongate axis 507b than the other. This frame assembly allows fewer frames 501 to cover the same length along the elongate direction 507b. This means that fewer frames 107 can be used to surround a cell stack of a given elongate length. However, the angular offsets between adjacent frames 501 mean that a more complex spacer assembly design is required. Alternatively or additionally, the frames 501 may be oriented in a herringbone pattern relative to the compression axis, rather than the elongate axis 507b as shown. This means that the frames 501 would not all be parallel to the compression axis. In the example shown, the spacer assemblies 503 join together all of the frames 501 on each side. In other examples, spacer assemblies 503 may connect together adjacent frames only at points where the separation distance is low. In Figure 5(c), the frames 501 are arranged parallel to the compression axis. However, the frames 501 are not flat plates. Instead, the frames are each curved around an axis parallel to the compression axis. This increases the second moment of area of each frame 501 and thereby their stiffness in bending along the elongate direction 507b, without increasing the weight of the frames 501. This support structure 500 therefore provides increased stiffness. However, a more complex spacer assembly design may be required for flat frames 501 compared to curved frames 501. The frames 501 are not all arranged in parallel, since some of the frames 501 are arranged anti-parallel (that is, facing 180 degrees in the opposite direction) to each other.

Claims

1. A support system for supporting an electrochemical cell stack, the support system comprising:a plurality of frames, each frame comprising a cutout portion configured to surround at least part of the electrochemical cell stack; anda spacer assembly arranged to maintain a spacing between at least two adjacent frames of the plurality of frames;wherein each of the plurality of frames are arranged parallel to a compression axis of the electrochemical cell stack.

2. The support system of claim 1, wherein the number of frames in the plurality of frames is between 2 and 6.

3. The support system of claims 1 or 2, wherein the spacer assembly comprises at least one spacer block and at least one tie rod.

4. The support system of any preceding claim, wherein the at least one tie rod in the spacer assembly runs though the at least one spacer block to connect the adjacent frames together.

5. The support system of any preceding claim, wherein the spacer assembly comprises a plurality of spacer blocks.

6. The support system of claim 5, wherein the at least one tie rods extends through the plurality of spacer blocks.

7. The support system of any preceding claim, wherein the cutouts of the plurality of frames are arranged along a common axis.

8. The support system of claim 7, wherein the electrochemical cell stack is elongate in a direction perpendicular to the compression axis, and wherein the support system is configured to support an electrochemical cell stack such that the common axis of the cutouts is oriented parallel to the elongate direction of the electrochemical cell stack.

9. The support system of any preceding claim, further comprising an explosionresistant compliant cabinet configurable to contain the electrochemical cell stack and plurality of frames.

10. The support system of any preceding claim, further comprising a bolster plate configurable to support the electrochemical cell stack.

11. The support system of any preceding claim, wherein the support system can be configured to reposition the electrochemical cell stack such that the electrochemical cell stack is at least partially positioned externally to the plurality of frames.

12. The support system of claim 11, wherein the support system comprises a slidably movable platform configurable to reposition the electrochemical cell stack between a first position and a second position.

13. The support system of any preceding claim, further comprising a detection device positioned externally to the plurality of frames, and wherein the detection device is configurable to detect faults in the electrochemical cell stack or support system.

14. The support system of any preceding claim, further comprising a power supply conduit for connection to the electrochemical cell stack, wherein the power supply conduit is positioned in the spacing distance between the adjacent frames.

15. The support system of any preceding claim, further comprising means for applying pressure to an electrochemical cell stack.

16. The support system of any preceding claim, wherein the plurality of frames are arranged parallel to each other.

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