Scalable electrolysis cell and stack and method of manufacturing the same at high speed

Abstract

To provide a scalable electrolysis cell designed for high-speed manufacturing and an electrolyzer stack comprising multiple electrolysis cells.SOLUTION: An electrolysis cell comprises a membrane, an anode electrode, a cathode electrode, an anode flow field, a cathode flow field, and a bipolar plate assembly. The bipolar plate assembly includes multiple repeated water delivery windows arranged adjacently to the front-end portion of the anode flow field lined up in a y axis. Each water delivery window is associated with the length of window along the y axis in the anode flow field. The electrolysis cell is configured such that the number of water delivery windows, an effective diameter, or the length of window is selected so as to maintain a water flow resistance that is less than a target threshold level of an electrolyzer cell, a water temperature rise, or an oxygen volume fraction at the outlet of the cell.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] INCORPORATION BY REFERENCE OF RELATED PATENT APPLICATIONS This application claims the benefit of priority under 35 U.S.C. § 119(e) to U.S. Provisional Patent Application No. 63 / 218,446, filed July 5, 2021, and U.S. Provisional Patent Application No. 63 / 311,773, filed February 18, 2022, the entire contents of which are incorporated herein by reference in their entirety.

[0002] Field of the Invention The present disclosure relates to electrochemical cells, and more particularly, to electrochemical cells and stacks designed for scalable and rapid manufacturing. [Background technology]

[0003] An electrochemical cell is a device for using electricity to induce a chemical reaction or to generate electricity using a chemical reaction. When electricity is the output, the cell can be considered a fuel cell or expander cell, depending on the chemical product. When electricity is the input, the cell can be considered an electrolyzer cell, compressor cell, or purification cell, depending on the chemical product. For example, an electrolyzer takes in electrical energy and stores it in a fuel, such as hydrogen, by splitting water into its components. In contrast, a fuel cell can essentially be thought of as an electrolyzer working in the opposite direction, where hydrogen and oxygen are provided to the cell, which then combines these molecules to form water, releasing electrical energy in the process. The basic elements of these devices are two electrodes, an ion-conducting electrolyte, and an ion-permeable layer separating the two electrodes, although it is also possible to operate an electrolyzer or fuel cell in a membraneless configuration. Electrochemical cells can also include a separator between the electrodes to prevent the products from mixing inside the cell. In the case of solid-state electrolysis cells, the membrane and separator may be combined into an integrated, solid, ion-conducting layer. A complete electrochemical cell may also include flow fields for delivering reactants to the electrodes, seals for isolating the reactants from each other and from the environment, and one or more impermeable separator plates, also called bipolar plates, for isolating one cell from adjacent cells in the stack and, in some embodiments, for containing separate cooling fluids for thermal management of the cells.

[0004] A variety of electrolytes can be used in electrochemical cells, including proton exchange membranes, anion exchange membranes, solid oxide ceramic membranes, and liquid alkaline solutions such as potassium hydroxide and sodium hydroxide. Different electrolytes require different operating conditions, and each has its own advantages and limitations. Advantages of proton and anion exchange membrane electrolytes include relatively low operating temperatures and cells that can be constructed using unitized layer electrolytes / membranes. Electrolyzers using such membranes have distinct advantages over other electrolyzer cells that can operate using pure liquid water as a feedstock, rather than caustic solutions or water vapor, thereby greatly simplifying the balance of the system in practice. Such electrolyzers can also be operated without liquid water on the cathode, allowing for the production of hydrogen gas with low vapor phase water content.

[0005] The impact of carbon dioxide on global climate change is well documented. As society's efforts to address global climate change accelerate, the need to deeply decarbonize most or all of human energy use becomes clear and urgent. The use of hydrogen as a carbon-free energy carrier is essential to reach certain segments of human industry that are difficult or impossible to decarbonize directly with electricity. Examples of such segments include steel production, fertilizer manufacturing, construction, and heavy transportation such as trucking, maritime shipping, and air transport. In addition to these segments, hydrogen's energy density and stable storage properties make it the most promising candidate for seasonal-scale energy storage, leading to the establishment of resilience in electric grids that use only renewable electricity. This will be necessary to completely convert energy use to carbon-free sources. These and other advantages have attracted a high level of interest in the production of "green hydrogen".

[0006] Hydrogen is given the label "green" if it is produced by electrolysis from renewable electricity (wind, solar, hydro, etc.). The scale required to meet the potential demand for green hydrogen in a future global energy system is staggering. The production capacity of electrolyzers will need to increase by orders of magnitude over the next decade to meet such demand, and their cost will need to decrease by more than tenfold. Until now, the manufacture of hydrogen electrolyzers has been a niche industry, with small systems and limited deployment based on cells and stacks designed for research and development. Little consideration has been given to the production speeds required to manufacture and assemble the cells and stacks at a rate commensurate with society's ultimate needs. Summary of the Invention

[0007] Recognizing the urgent need for innovative electrolyzer technology, the inventors of the present application have developed a scalable electrolysis cell and stack, along with a scalable stack compression system, and rapid manufacturing methods. Embodiments of the present application minimize the capital costs for manufacturing a wide range of electrochemical cell stack sizes and enable rapid manufacturing of electrochemical cells, including water electrolyzers.

[0008] The basic process of water electrolysis involves feeding water to a positively charged anode and conducting ions between the anode and a negatively charged cathode. Oxygen gas is produced at the anode and hydrogen gas is produced at the cathode at room temperature at sea level. The particular ions conducted between the anode and cathode depend on the electrolyte used. In an acid cell, positively charged hydronium ions are conducted from the anode to the cathode. In an alkaline cell, negatively charged hydroxide ions are conducted from the cathode to the anode. In both systems, the overall reaction is the same: (2)H2O(l) → (2)H2(g) + O2(g). Electricity must be supplied to drive the reaction. The open circuit or thermoneutral voltage for the basic reaction of hydrogen to liquid water is 1.481, therefore a voltage higher than 1.481 must be applied to a hydrogen electrolysis cell fed with liquid water in order for the reaction to proceed (as discussed below, an overvoltage is usually required for the reaction to proceed at an acceptable rate). The size of the cell (i.e., active area) determines the rate of hydrogen / oxygen production from a single cell at a given applied voltage. The total current required for a particular applied voltage may be proportional to the size of the cell (i.e., active area). In practical systems, multiple cells can be "stacked" on top of each other to increase production capacity. This stack of cells results in the need to apply a higher voltage (an integer multiple of the number of cells) to drive the reaction. For example, 1000 cm 2 The unit cell is 500cm 2 It can generate the same hydrogen flow as two stacked cells, but at 500 cm 2 The stack requires twice the voltage and half the current. Flexibility in selecting the required voltage and current can be an important consideration in the design and cost of the total electrolysis system. For example, a power supply for high current and low voltage may be more expensive than a power supply for high voltage and low current because of the size of the conductors required and the additional materials required for their construction.

[0009] As the reaction proceeds, water is consumed and hydrogen + oxygen gas is produced, so water must be continuously fed to the cell to feed the reaction. Stoichiometry is a term related to the "balance" of a chemical reaction. In an electrochemical cell, the term "stoichiometry" or "stoich" refers to the ratio of reactants fed to the cell to the amount needed to exactly balance the total reaction. For example, an electrolysis cell operating at a water stoichiometry of 2 has as its input twice the amount of water required to produce hydrogen and oxygen exiting the cell. Conserving the mass of the system at 1 stoichiometry indicates that 1 kg of hydrogen production per hour is associated with approximately 8 kg of oxygen production per hour and approximately 9 kg of water consumption per hour. Electrolyzers can typically be operated at a minimum water stoichiometry above 1 to ensure adequate reactants everywhere in the cell. For example, when the water flow stoichiometry is 1, all of the water provided to the cell is converted to oxygen on the anode, resulting in a 100% oxygen fraction at the cell outlet (i.e., no water exits the cell). This condition may be unstable and may result in damage due to anode starvation of the cell near the outlet. It may also result in high fluid velocity and pressure loss at the outlet since everything leaving the cell is in gas phase. Thus, process conditions may be selected to maintain the oxygen vapor fraction at the cell outlet below a given threshold. For example, an outlet oxygen fraction of less than 40% may result in less than a two-fold increase in the water inlet-to-outlet flow field velocity. A water stoichiometry of 100 or more may be required to maintain an oxygen fraction of less than 40%.

[0010] The electrolysis process is not 100% efficient, and as a result, some of the input electricity is converted to heat in the cell rather than being stored as chemical energy as hydrogen. This results in a voltage greater than the thermal neutral voltage (1.481) required for a practical hydrogen output flow rate. The energy savings of this system are realized when the fraction of power delivered to the cell that heats up (voltage × current) is reduced by [1-(1.481 / V cellIt can be shown that the water stoichiometry can be equal to [1-(1.481 / 1.8)]. A practical electrolysis cell can operate at 1.8 V, with the result that [1-(1.481 / 1.8)] = ~18% of the power is delivered to the cell and converted to heat rather than hydrogen. A practical electrolysis cell therefore requires cooling during operation, and an efficient way to achieve this cooling can be to utilize the process water itself to cool the cell. Depending on the operating conditions of the cell, a relatively high flow rate of water may be required to ensure that the peak temperature of the cell is maintained below an acceptable threshold and that the temperature gradient within the cell is also acceptable. This flow rate may also represent a water stoichiometry that is much greater than 1. For example, operating at 1.8 V and releasing 18% of the input energy into heat, the water stoichiometry can be 2.7 W / cm. 2 For a cell operating at 1000 K, a water stoichiometry of approximately 160 may be required to maintain a temperature rise across the cell of less than 10° C. From the design considerations mentioned above, the flow rate of water to the cell is dictated by the need for adequate reactants or the need for adequate temperature control, whichever is higher.

[0011] Managing the water provided to the hydrogen electrolysis cell / stack can be a major consideration for the overall hydrogen generation system. Flow rate, pressure, temperature, and composition must all be adjusted to meet the requirements of the cell / stack. A typical system includes a liquid-gas separator, heat exchanger, pump, and deionization system in a loop with the anode side of the cell / stack to recirculate the water at the required flow rate. As the system produces hydrogen and oxygen, 1 "stoichiometric" water is consumed. The consumed water can be replenished by injecting 1 stoichiometric fresh water into the system loop from a source of acceptable quality (e.g., demineralized water, desalinated water, or municipal water). Given the scale of the electrolysis plant, the required water flow consumed by the cell / stack can be proportional to the plant capacity. It may be desirable to keep other process parameters (pressure, temperature, composition) constant regardless of scale, as this can greatly simplify system component selection, overall system control, and engineering, procurement, and construction (EPC) costs at the deployment site. For example, water pumps may generally be commercially available in a wide range of scales of flow rate for a given pressure capability. It may therefore be advantageous to have a basic cell / stack where the water flow resistance is independent of the size of the cell or stack. Larger systems can then be built in a modular fashion from more cells and / or more stacks without the need to change the water pump technology and basic pressure ratings for the system and plant.

[0012] The elements of a hydrogen electrolyzer stack can include a stack of repeating members and a system of non-repeating members. As the name suggests, the repeating members increase in volume with the stack height and typically include the membrane / electrolyte, anode and cathode electrodes, water and hydrogen flow fields, water and hydrogen seals, and bipolar cell separator plates. The non-repeating members typically include end units and mechanical systems to maintain stack compression. The end units can also include power terminals, electrical isolators, fluid distribution and / or drain / purge manifolds, and structural end plates. The stack compression system can include tension elements, spring elements, and adjustable elements used to transfer mechanical forces (tension) in the tension and spring elements to mechanical forces (compression) in the stack core of the repeating members. This compression of the stack core can be essential to ensure both electrical contact and fluid tightness between the individual cells and the end units. For convenience, one can define a Cartesian coordinate system with perpendicular xyz axes, where "x" is parallel to the general direction of water flow through the stack, "y" is perpendicular to x and in the same plane defined by a single cell, and "z" is generally parallel to the stacking direction of the cells. In this context, compression systems generally function to apply a compressive load along the z axis.

[0013] To function properly over the expected range of operating conditions for the electrolyzer stack, the compression system can maintain appropriate compression on the stack over a temperature range, taking into account thermal expansion and contraction. The system can also apply a compressive load high enough to prevent the cells from separating over the expected range of operating pressures in the cells. Separation as pressure increases can result in reduced performance due to loss of contact between the cells, fluid leakage, or both. The electrolysis cells and stacks can be designed for a maximum allowable working pressure (MAWP) on both the hydrogen and water sides of the cells. The MAWP, desired cell-cell contact pressure, core mechanical stiffness, overall operating temperature range, and expected changes in repeating member thicknesses can be the primary drivers for the design of the stack compression system.

[0014] A typical electrolytic cell may be generally circular or rectangular in shape, although other shapes are possible. Historically, circular cells were chosen to allow for a circular cell pressure boundary when establishing the MAWP of the cell. In recent years, rectangular cells have been introduced due to their major advantages in reducing material waste during manufacturing. Rectangular cells can maintain cell pressure boundaries that rely on friction and / or bonding between the cell frame and the bipolar plates. In both cases, a typical compression system used may include two thick end plates (one at each end of the stack core) and a number of spring-loaded tie rods extending between the plates and generally evenly distributed around the xy plane of the stack to minimize deformation of the end plates. The tie rods can act as both the tension and adjustable elements of the compression system. As the tension load increases on the adjustable rods, the end plates can act like diaphragms and flex to transfer the compression load to the stack core. Basic structural mechanics dictate that as the load increases (higher MAWP and more preload required for contact or sealing), the thickness or material stiffness of the end plates also increases to prevent excessive bending and loss of contact near the central region of the cell. Basic structural mechanics also dictate that as the area of ​​the cell increases in the xy plane, the thickness or material stiffness of the end plates also increases to prevent excessive bending and loss of contact near the central region of the cell. As the area increases, the total number of rods / springs also increases to minimize the spacing between the rods and peripheral bending and contact / sealing issues. These changes may require redesign, reassembly, and revalidation of the stack and system from the base level when larger cells are desired. As a result, manufacturing challenges may arise due to multidimensional variations in the members, changes in handling requirements, and other inconsistencies and changes in assembly procedures.

[0015] As mentioned above, the basic elements of an electrolyzer cell include two electrodes, a unitized solid ionically conductive separation membrane, flow fields for delivering reactants to the electrodes, seals for isolating the reactants from each other and the environment, and an impermeable bipolar plate. The cell design may also include features to facilitate stacking of cells and sealing between stacked cells. These may include seals for water and / or hydrogen, windows and ports at the cell periphery for distributing and collecting water, oxygen and hydrogen, and various other detailed features to ensure that loads from compression of the stack core are directed in the proper proportions to the active areas and periphery seals of the individual cells. As the cells are stacked, the windows at the cell periphery may align to form a continuous plenum through which water, oxygen and hydrogen may be directed in / out of the cells and towards the ends of the stack. In a typical electrolysis stack, due to limited available area around the xy boundary, these plenums may align with holes provided in one or both of the end plates, thereby facilitating external process fluid connections from the system to the stack. Through-hole features in the end plates may weaken their structure, requiring the end plates to be thicker or more rigid. Pipes exiting the stack along the z-axis may require additional z-height in the end units to distribute and collect fluids from plenums located around the xy-plane. This space may also be added to the thickness of the end plates. If insufficient space is allocated, poor distribution of fluids to the stack or high pressure loss through the stack may result, thereby affecting performance or durability. Pipes exiting the stack along the z-axis may also create inconvenient installation and alignment problems for plumbing connections to the system. It may be advantageous to manifold the plenums together in one or both end units and make the process connections to the stack perpendicular to z in the x and / or y directions.However, with tension elements encompassing the entire xy plane, it may be difficult for the process connection to exit the stack boundary other than along the z axis without interfering with the tension member.

[0016] Thus, an embodiment of the present disclosure provides a scalable electrolyzer cell that has substantially equal resistance to water flow, equal temperature rise, and equal outlet oxygen fraction at a given operating voltage regardless of the selected active area. In some embodiments, the cell may be substantially rectangular and characterized by a dimension along the x-axis selected according to the roll web width (w) of the membrane, electrodes, and / or flow field material used in its manufacture. In some embodiments, the desired roll web width (w) may be selected based on maintaining process parameters for the operating cell within target thresholds. For example, it may be desirable to keep the cell's water pressure drop below the pumping pressure limit of the system in which the cell may be installed. Alternatively, it may be desirable to keep the water flow temperature below the stack temperature gradient limit to ensure acceptable performance and life. Alternatively, it may be desirable to maintain the cell outlet oxygen volume fraction below a limit that ensures stable performance and life of the cell. Alternatively, the desired roll web width (w) may be selected based on available source material for constructing the cell. For example, it may be desirable to select a roll web width that minimizes scrap material in converting the rolls into parts during assembly. In this case, the desired roll web widths for the membrane, electrodes, and flow fields may be the same or different. If they are different, the selected roll web width may be selected based on the most expensive of the membranes, electrodes and flow fields, and other rolls of material may be selected with a web width (w) that matches the others, where matching means a roll web width (w) that optimizes production speed and / or overall cost.

[0017] In some embodiments, variable cell area can be achieved from scalable cells by adjusting the length of the cell along the y-axis. Water distribution windows may be placed parallel to the y-axis along the leading edge of the anode flow field, and each window may be associated with a unit length of the anode flow field. The leading edge of the anode flow field may be defined as the edge where water enters the anode flow field. The area or effective diameter (diameter of a circle having an area equal to the area of ​​the window) of each water distribution window may be selected to maintain the water velocity along the z-axis through the window below a predetermined threshold, with the water flow stoichiometry selected to maintain one or more of the temperature rise or oxygen outlet volume fraction of the cell below a target threshold. The unit length associated with each water distribution window may be selected to keep the water velocity along the x-axis at the leading edge of the anode flow field below a predetermined threshold. The number of water distribution windows can then be selected to achieve an overall target hydrogen production rate for the cell while maintaining the water flow pressure loss, water temperature rise, and oxygen outlet volume fraction below the target thresholds.

[0018] In another embodiment, a bipolar plate assembly for a scalable electrolysis cell is provided, comprising a bipolar plate, a hydrogen seal, a water seal, and a fluid distribution frame. The fluid distribution frame may be configured to position, couple, and house the cathode flow field, the cathode electrode, the membrane, the anode electrode, and the anode flow field between two adjacent bipolar plates. The fluid distribution frame may also be configured to uniformly distribute the water flow from one or more water delivery windows to the leading edge of the anode flow field. The fluid distribution frame may further be configured to uniformly collect the water and oxygen flow from the trailing edge of the anode flow field and distribute the flow to one or more oxygen collection windows. The trailing edge may be defined as the edge of the anode flow field where the water and / or oxygen exit the flow field. The non-uniform distribution or collection may be defined as less than ±50% velocity change at the leading edge and / or trailing edge of the flow field. The fluid distribution frame may further be configured such that a hydrogen seal fits between the frame and the bipolar plate adjacent to the cathode flow field. The fluid distribution frame may be further configured to receive a water seal between the frame and the bipolar plate adjacent the anode flow field. The fluid distribution frame may be further configured to allow for curing of at least one of the hydrogen or water seals by ultraviolet light, microwave, magnetic curing, thermal curing, solvent curing, two-part epoxy curing, and / or moisture curing. To accomplish this, the frame may be constructed of a UV-transparent material or a microwave-transparent material, which allows the ultraviolet light to access the hydrogen seal disposed between the frame and the bipolar plate. The advantage of ultraviolet and microwave cured seals is the possibility of very fast curing and short cycle times, which results in high speed and low cost manufacturing of the bipolar plate assemblies. Alternatively, the fluid distribution frame may be constructed of a material that functions as a seal, thereby eliminating the need for curing. For example, the frame itself may be made of silicone rubber or polyurethane, or any of a variety of other polymers that have suitable properties and geometries to deform under compression and form a hydrogen seal, a water seal, or both.For example, the frame may be manufactured by combining a two-shot injection molding process as a single integral component with a rigid base frame with overmolded elastomeric patterns for the hydrogen seal, water seal, or both. In another example, the fluid distribution frame may be constructed by screen printing the hydrogen and / or water seal on one or both sides of a plastic film in a roll-to-roll process. The fluid distribution frame may be further configured to collect hydrogen flow from one or more trailing edges of the cathode flow field and deliver the flow to one or more hydrogen collection windows. The fluid distribution frame may be further configured to fit an internal seal between the anode and cathode flow fields, the seal being applied to at least one of the membrane, the catalyst coated membrane, the electrode, the subgasket boundary of the membrane-electrode assembly, or the frame itself. The anode flow field may be further configured to be larger than the cathode flow field to facilitate application of a compressive load to the internal seal when the cell stack is compressed. The fluid distribution frame, water seals and hydrogen seals may further be positioned to minimize unsupported seal areas in a projection along the z-axis, where an unsupported seal area is defined as any area along the z-axis where compressive loads cannot be transferred between members. For example, it may be advantageous for seal performance and reliability to ensure that less than 50% of the projected seals along the z-axis remain unsupported.

[0019] In some embodiments, a method of manufacturing a bipolar plate assembly for a scalable electrolysis cell is described. In some embodiments, the method includes a series of manufacturing steps in a continuous production line designed for high speed assembly. First, materials for the bipolar plate, hydrogen seal, water seal and fluid distribution frame can be selected from suitable candidate materials that match the production, operation, performance and life expectancy of the electrolyzer to be manufactured. Second, the bipolar plate can be manufactured from a coil of the selected material by stamping, laser cutting, water jet cutting, or other suitable metal forming techniques. If required for performance or durability, the bipolar plate can be coated with a layer of a suitable material. For example, a thin layer of gold is required for PEM electrolyzers and a thin layer of nickel is required for AEM electrolyzers. Alternatively, no coating may be required and the produced bipolar plate only needs to be passivated and / or cleaned after formation to eliminate contamination and promote adhesion of the applied hydrogen seal. Various standard passivation and cleaning methods can be used to ensure minimal free metal and hydrophobic contamination on the bipolar plate surface. Third, the hydrogen seal may be applied to the bipolar plate in an uncured state. Methods include screen printing, rotary screen printing, stencil printing, robotic dispensing, injection molding, compression molding or stamp printing and may be selected based on factors such as, but not limited to, process speed, cycle time, material waste and machine costs. For example, screen printing may be a very fast method but may not be suitable for seals that are too thick or that are not planar by design. In another example, multiple screen printing runs may be run to build up the required thickness for the seal. Fourth, a fluid distribution frame manufactured in a separate process may be aligned with the bipolar plate and hydrogen seal in the xy plane and pressed onto the uncured hydrogen seal with an appropriate force to ensure that a non-breakable seal can be created between the cathode flow field of the cell and both the water distribution window and the outer perimeter of the cell. The fluid distribution frame may also be pressed onto the hydrogen seal to achieve a specific target thickness for the bipolar plate assembly.This method allows the final thickness of the hydrogen seal to be varied, thereby reducing tolerance stack-up and overall bipolar plate thickness variation due to variations in either the bipolar plate thickness, the fluid distribution frame thickness or both. At this point, the hydrogen seal may be cured by an appropriate process (as discussed herein) or may remain uncured. Fifth, the water seal may be applied to the fluid distribution frame in an uncured state. Methods include screen printing, rotary screen printing, stencil printing, robotic dispensing, injection molding, compression molding or stamp printing and may be selected based on factors including, but not limited to, process speed, cycle time, material waste and machine cost. Sixth, if not pre-cured, the water seal and hydrogen seal may be cured using an appropriate process such as ultraviolet curing, microwave curing, thermal curing, solvent curing, two-part epoxy curing or moisture curing based on factors including process speed, cycle time and machine cost. For example, ultraviolet curing may be a very fast method, but requires a light source with line of sight to the uncured seal material. For curing the hydrogen seal between the bipolar plate and the fluid distribution frame made of materials that are opaque to light, ultraviolet light curing may not work. If the fluid distribution frame or bipolar plate are transparent to ultraviolet light, rapid curing may be possible using this technique. An advantage of selecting a transparent material for the fluid distribution frame may be that both the hydrogen seal and the water seal can be cured simultaneously, eliminating the cost and process time associated with separate curing steps.

[0020] In another embodiment, a scalable electrolyzer stack compression system is described that is adapted to receive and compress a plurality of scalable electrolyzer cells having a substantially fixed dimension along the x-axis and a variable dimension along the y-axis. The compression system can include tension members along two opposing sides of a generally rectangular cell stack, which sides can be parallel to the y-axis such that the stressed area of ​​the tension members increases in proportion to the variable y-axis dimension (e.g., y-axis length) of the cells. The two sides adjacent to the tension members can be left open to facilitate rapid stack assembly and efficient process connections to the stack, or can optionally include additional tension members. In some embodiments, the tension members can be further characterized as being constructed from a substantially flat sheet of material that is wrapped around a frame structure that encloses the ends and two variable length sides of the stack. The wraps can be formed into a semi-cylindrical shape at each end of the stack, creating a generally elliptical racetrack shape when viewed along the y-axis. This shape can have the advantage that the wrap material can be configured such that mechanical stresses within the wrap can be substantially tensile and bending of the semi-cylindrical end units can be minimized. The wrap may be configured to allow a slip surface between the wrap and the associated semi-cylindrical end unit of the cell stack. The wrap features a generally fixed dimension along the x-axis and a scalable dimension along both the y-axis (cell area) and z-axis (number of cells), allowing the same material and thickness to be used regardless of the active area of ​​the cells or stack height. As the cell area increases with increasing length along the y-axis, the wrap depth along the y-axis may grow arbitrarily proportionally. Since the added active area may require additional compressive load for assembly, naturally the material added to increase the y-axis depth of the wrap may provide a structure that carries this load in direct proportion at the same wrap thickness. This geometric scalability may provide advantages in simplified and consistent manufacturing of wraps for different stacks, and economies of scale for raw material sourcing.In that case, the thickness of the wrap may simply be a function of the fixed x-axis dimension of the cell, the desired preload applied to the stack core during assembly, and / or the rated maximum allowable operating pressure of the electrolyzer. The thickness of the wrap may be greater than or equal to the dimension of the cathode flow field along the x-axis multiplied by the ratio of the maximum allowable operating pressure of the electrolyzer to the tensile strength of the selected wrap material.

[0021] In another embodiment, the wrap may be constructed from one piece of material connected at a single seam, or more than one piece of material connected at several seams. For example, it may be advantageous to construct the wrap from two opposing halves connected with a hinge pin-like joint on the flat side of the oval racetrack shape. This construction facilitates high speed direct stack assembly within one half of the wrap through one or both open faces of the wrap. It also allows the second half of the wrap to be used in efficiently pre-compressing the stack of cells after stacking is completed. It also allows the two wrap halves to be efficiently connected to a continuous structural interface by inserting a hinge pin along the y-axis into the aligned hinge loops formed in each wrap half. The connection method may be formed using alternative connection designs such as lap welds, lap bolts, flange welds, flange bolts, hem hooks and / or hem hooks with fasteners. The wrap may be designed to be generally continuous along the y-axis or to have strips along the flat sides. The width and length of the strips can be selected to facilitate formation of a selected connection design. The width and length of the strips can be selected to achieve a desired strength and / or a desired elasticity under load. The strips may extend partially around one or both wrap halves or may completely divide the two halves into separate bands. The strips may have a uniform y-axis dimension along the z-axis or may vary. The variation in strip shape in the yz-plane can be selected to achieve a desired strength, a desired elasticity, or both.

[0022] In another embodiment, the semi-cylindrical end units may be configured to accommodate an adjustable element of the compression system. The adjustable element may be fully accommodated within one or both of the cylindrical end units, thereby reducing the overall volume compared to a stack having an adjustable element outside the tension element boundary. The adjustable element may include screws, nuts, springs, pads, shoes, and other structural members required to transfer tensile stresses from the wrap to compressive stresses within the stack core. The members of the adjustable element may be configured to facilitate separation of two or more members aligned along the z-axis with the cell stack from within the wrap boundary, thereby stretching the wrap while the cell stack is compressed. The adjustable element may be configured with a longer adjustable length when a cell stack of more cells is compressed. The adjustable element may also include features that allow an external system to compress the cell stack during initial assembly. For example, holes and contact pads may be provided to allow the cell stack to be compressed to a desired precise load during assembly using hydraulic or pneumatic cylinders as part of a high speed manufacturing machine. An adjustable element can then be fitted to transfer the load from the manufacturing system to the wrap to achieve the desired final and precise load on the cell stack. One or many adjustable elements may be mounted within the cylindrical end unit. The number of adjustable elements may be designed to scale in proportion to the y-axis dimension of the cell stack and / or the number of fluid distribution windows selected for the scalable cells to be compressed.

[0023] In another embodiment, the wrap may include features to facilitate cell stack alignment and mating with compression fixtures. For example, the wrap may include holes or slots along one or both flat sides to allow for contact of alignment rails with one or more edges of the cells when the cells are placed on the stack during assembly. It should be understood that the holes or slots do not necessarily have to be rectangular or circular. These features can be designed to allow for establishing precise reference points along the z-axis, which can ensure that all cells in the cell stack are precisely aligned relative to each other and to the cell stack compression system. The wrap may also include features that allow for access to adjustable elements in one or both semi-cylindrical end units to facilitate compression. For example, holes can be provided in the wrap to allow for hydraulically actuated posts to compress the cell stack to a desired first load. Additional holes may be provided to allow for access to adjustable screws or nuts for the purpose of transferring load from the compressor to the wrap. It should also be understood that the holes do not necessarily have to be rectangular or circular.

[0024] In another embodiment, a scalable electrolyzer stack is described, comprising a cell stack of scalable electrolyzer cells, a scalable cell stack end unit, and a scalable cell stack compression system. The electrolyzer stack includes a number of individual cells arranged along a z-axis. When these cells are aligned in the cell stack, the water distribution window and hydrogen distribution window present in each cell are aligned along the z-axis to form water and hydrogen plenums for distributing and collecting process fluids to and from the individual cells in the cell stack.

[0025] The electrolyzer stack may also include process ports entering and / or exiting the stack compression system boundary on a plane defined by the xz plane through freely accessible sides of the compression system. The stack may include a process manifold at one end unit of the stack and a drain / purge manifold at the opposite end unit. These manifolds may be configured to fluidly connect the stack process ports with appropriate fluid plenums in the cell stack. In this way, a single water flow is delivered to the water inlet port of the stack, subdivided among multiple water inlet plenums, further subdivided and delivered to individual water distribution windows, and associated with the length of the leading edge of the anode flow field. Each associated length of the leading edge of the anode flow field may deliver water flow to the anode electrode at a mass flow rate and velocity to ensure that the pressure drop, temperature rise, and oxygen volume fraction increase are below target thresholds for each parameter over the length of the flow along the x-axis of the anode flow field. At the trailing edge of the anode flow field, the trailing edge of the associated length delivers water / oxygen flow to associated water collection windows which combine to form a water collection plenum which can deliver water and oxygen to a common manifold and ultimately to a single water outlet port for connection to an electrolysis system.

[0026] Power terminals may be provided on both end units, one at the positive pole and one at the negative pole, to supply electricity to the stack. Access to the individual cells of the cell stack may be provided on one or both freely accessible sides of the cell stack for probing individual cell voltages. In some cases, when the z-axis is substantially aligned with the gravity vector, it may be advantageous for the stack's positive pole to be at the top and the negative pole to be at the bottom. In this configuration, any gas bubbles formed on the anode side of the cells may be motivated by gravity to move away from the electrodes, thereby freeing access for water to further react and potentially improving the performance of the cell stack. In other configurations where the z-axis is not substantially aligned with the gravity vector, it may still be advantageous for the stack's positive pole to be elevated relative to the negative pole for similar reasons.

[0027] In some cases, it may be advantageous for the process connections, such as water inflow, water / oxygen outflow, and hydrogen outflow, to be in the upper end unit. In this configuration, oxygen bubbles will tend to rise due to gravity in the water outlet plenum, since they make up a significant volume percent of the outlet fluid at the anode side. If there is a process manifold at the top end, the rising oxygen bubbles can flow in the desired general direction, which can help prevent liquid slugging, gas phase lock, and / or other flow instabilities potentially caused by flowing bubbles against gravity. In some cases, it is advantageous for the drain / purge manifold to be in the lower end unit. During start-up and service of the electrolyzer stack, it may be necessary to drain stationary water from the electrolyzer stack before connecting or disconnecting the stack from the system. During operation or commissioning, it may be necessary to purge the hydrogen collection plenum of condensate water. A drain / purge manifold located at the lowest point relative to gravity can most easily facilitate complete drainage of water from the stack. During use, it may also be necessary to purge the cathode with an inert gas, such as nitrogen, before hydrogen is first produced on the cathode. The drain / purge manifold may also be configured to accept a process connection for an inert gas purge of the cathode side of the stack.

[0028] In another embodiment, a method of manufacturing a scalable electrolyzer stack is described that includes a stack assembly station located at the end of a cell assembly line. The stack station may be configured to allow multiple operators to perform operations simultaneously, thereby accelerating the throughput of the completed stack and allowing high speed manufacturing of both cells and stacks. For example, a full-scale stack may include 300 cells, and a manufacturing facility configured to manufacture 1,000 megawatts of electrolyzer stacks per year may need to process up to 1,000 such stacks and 300,000 corresponding cells annually. For one production shift running 1,750 man-hours per year, this production capacity requires a tack time of about 20 seconds per cell. With 300 cells per stack, each stack station may require up to 1.8 hours. In some embodiments, the stations may include 1) preparation and loading of non-repetitive stack members in an assembly fixture, 2) placement and alignment of cells, 3) compression, leak checking and locking of the cell stack, and 4) finishing and unloading of the stack. These stations may be conveniently located on a rotary table at the end of the cell manufacturing line. These stations may be at 90 degree angles to each other, whereby the non-repetitive station may be first, the cell placement station may be second, the cell stack compression and leak station may be third, and the stack finishing and unloading station may be last. Each station may include specific tools, fixtures, and equipment to facilitate the task. For example, the cell placement and alignment station may include one or more cell alignment rails on which individual cells may be positioned to ensure straight and precise alignment along the z-axis. The function of this rail may be facilitated by features such as holes and / or slots in the stack compression wrap. The table may be controlled to rotate 90 degrees every 1.8 hours after the final cell in the stack has been placed and aligned at the second station.Some stations require more working hours than others, and a single worker may perform duties at more than one station.

[0029] The system can facilitate the assembly of scalable cells and stacks based on a fixed roll web width (w) along the x-axis as described above. The cell assembly line can transport the members in a direction generally along the y-axis. Such a conveyor can flexibly handle cells of various fields, since there are varying cell dimensions for larger or smaller cells in the conveying direction, and wider cell assembly belts, machines and handling devices are not required. At the end of the cell assembly line, a rotating stack assembly station can be located so that the stack compression system configured for cells of different sizes can accept the cells. A scalable compression system also based on the same fixed roll web width (w) makes it possible to handle the assembly of stacks of cells of different areas, changing only the distance along the y-axis for the pick-and-place operation.

[0030] The system also allows production rates of over 1,000 stacks per year. For example, a rotary table operator may only need 30 minutes to complete the job. This could increase cell production rates by a factor of four, resulting in tack times of about 5 seconds per cell. Fast curing technologies, such as UV curing, can expedite such cycle times, thereby enabling a single stack manufacturing line to produce up to 4,000 megawatt-class stacks per year in a single shift. Flexibility in scalable cell, stack and manufacturing process design can protect investments in such lines from premature obsolescence as technology improves and different size stacks may be required by sales.

[0031] The described manufacturing system can also be flexible in terms of electrolysis technology. The system can produce PEM electrolyzers as long as PEM components and materials are used in the cell assembly line. The system can produce AEM electrolyzers as long as AEM components and materials are used in the cell assembly line.

[0032] In another embodiment, a rapid manufacturing method of internal seals for scalable electrolysis cells is described. A desired roll web width of membrane or catalyst coated membrane along the x-axis can be selected. The material from the roll can be directed through a seal applicator along the y-axis, and the uncured internal seal can be applied to one side of the material using one of screen printing, rotary screen printing, stencil printing, or robotic dispensing methods. The method selection can be based on the required production speed (i.e., process cycle and / or tack time), and multiple application cycles can be used to build up the thickness required to function on the seal. The applied internal seal can be cured using a rapid curing system such as ultraviolet curing, microwave curing, thermal curing, solvent curing, two-part epoxy curing, or moisture curing. The membrane-gasket assembly or catalyst coated membrane-gasket assembly roll can then be cut into individual component pieces using a flat knife die, rolling knife die, laser, or any other common cutting method. The resulting individual component pieces can be transported to a cell assembly machine for integration into a complete scalable electrolysis cell.

[0033] In another embodiment, a method of manufacturing a unitized electrode flow field for a scalable electrolysis cell is described. The electrode substrate of the desired roll web width along the x-axis can be selected from one of foam, felt, woven screen, expanded metal, or sintered metal frit. The flow field substrate of the desired roll web width along the x-axis can be selected from one of foam, felt, woven screen, expanded metal, or sintered metal frit. The electrode substrate material from the roll can be directed along the y-axis through a calender roller configured to achieve the desired thickness and surface properties of each edge of the electrode substrate. For example, the rolling rollers positioned on either edge of the substrate web can be of the same or different diameters and of the same or different materials. It may be advantageous to use harder and / or smaller rolls on the edges of the electrode substrate to be converted into active electrodes to achieve a denser and / or smoother surface for conversion. It may also be advantageous to use softer and / or larger rolls on the edges of the electrode substrate to be laminated to the flow field substrate to maintain a more porous and / or rougher surface for lamination.

[0034] The electrode substrate may be converted into an active electrode by suitable processing. For example, the electrode material may be spray coated, screen printed, rotary screen printed, doctor blade coated, slot die coated, curtain coated, squeegee coated, or laminated onto a suitable surface of the electrode substrate using heat and / or pressure. The electrode conversion process may also include a post-coating step. For example, the coating may be dried, heat treated, annealed, or physically or chemically treated to promote bonding to the substrate and / or functional performance of the cell. The flow field substrate material from the roll may be oriented along the y-axis and placed adjacent to the active electrode web, and the electrode and flow field web may be bonded together through a lamination process. The lamination process may include roller rolling, where the mating surfaces of the electrode web and flow field web are mechanically compressed to entangle and lock the solid fibers and / or interlayers of the substrate together. The laminated electrode flow field roll may then be cut into separate pieces, which are transported to a cell assembler for integration into a complete scalable electrolysis cell.

[0035] It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the present disclosure as claimed. Further objects, features and advantages of the present application will become apparent from the following detailed description of the preferred embodiments when considered in conjunction with the drawings. [Brief description of the drawings]

[0036] The accompanying drawings are incorporated in and constitute a part of this specification. The drawings illustrate only certain embodiments of the present disclosure and, together with the foregoing and following descriptions, serve to explain the principles of the disclosure. Wherever possible, the same identification numbers are used throughout the different drawings to refer to common or similar components.

[0037] [Figure 1] FIG. 1 shows an isometric view of a preferred embodiment of a scalable electrolyzer stack, including its main components and a defined Cartesian coordinate system.

[0038] [Figure 2ab] 2a and 2b show an exemplary prior art electrolyzer stack including major components and features that may limit the scalability of its design.

[0039] [Diagram 3] FIG. 3 shows a cross section of electrolysis cell components in the active area of ​​a typical cell showing ion, electron and fluid flows for proton and anion exchange membrane electrolysis technology.

[0040] [Figure 4] FIG. 4 illustrates an isometric view of the electrolytic cell element of FIG. 3, showing an exemplary cross-flow orientation of the process fluids and the repetition of the cell element along the z-axis to form a stack of cells.

[0041] [Figure 5a] FIG. 5a shows an isometric view of an anode flow field member illustrating the tradeoffs that exist in scaling the cell active area.

[0042] [Figure 5b] FIG. 5b shows the mathematical model output for pressure drop versus velocity through an exemplary flow field of water and hydrogen flows and an exemplary pressure drop target threshold.

[0043] [Figure 5c] FIG. 5c shows the mathematical model output of water temperature rise versus water stoichiometric value for two example cell operating voltage values ​​and example water temperature rise threshold values.

[0044] [Figure 5d] FIG. 5d shows the mathematical model output of oxygen volume fraction at the outlet versus water stoichiometric value for an exemplary cell operating pressure and an exemplary oxygen volume fraction threshold value.

[0045] [Figure 5e]FIG. 5e shows test results for water flow resistance for various candidate flow fields, confirming the model results of FIG. 5b for water flow pressure loss, and showing alternative exemplary pressure loss target thresholds.

[0046] [Figure 6] FIG. 6 shows a plan view of an example cell showing features including water delivery and collection windows, the ability to scale the cell active area by replicating the water windows, and the associated anode flow field length along the y axis, which is fixed along the x axis based on the desired roll web width (w).

[0047] [Figure 7a] FIG. 7a shows an exploded view of exemplary components of a bipolar plate assembly designed to enable rapid manufacturing.

[0048] [Figure 7b] FIG. 7b shows a cross-sectional view of the bipolar plate assembly of FIG. 7a illustrating the arrangement and internal sealing features for the membranes, electrodes and flow field members that, when added to the bipolar plate assembly, comprise a scalable electrolysis cell according to a preferred embodiment of the present invention.

[0049] [Figure 7c] FIG. 7c shows a cross-sectional view of FIG. 7b in which the cathode flow field is formed as an integral three-dimensional structure with the bipolar plate, rather than as a separate member.

[0050] [Figure 8] FIG. 8 shows a top view of the bipolar plate assembly of FIG. 7a looking down along the z-axis, illustrating the projected alignment of exemplary water and hydrogen seals.

[0051] [Figure 9] FIG. 9 shows an isometric view of a typical water distribution window, illustrating the distribution and sealing features that may be included in the frame to provide uniform water flow over the relevant length of the anode flow field.

[0052] [Figure 10] FIG. 10 shows a top view of the bipolar plate assembly of FIG. 7a looking upward along the z-axis and illustrates the projected alignment of exemplary water and hydrogen seals.

[0053] [Figure 11] FIG. 11 shows an isometric view of a typical hydrogen collection window and illustrates distribution and sealing features that may be included in the frame to uniformly collect hydrogen produced by the cell and deliver it to one or more collection windows.

[0054] [Figure 12] FIG. 12 illustrates the basic steps that may be included in a rapid manufacturing process for a bipolar plate assembly.

[0055] [Figure 13] FIG. 13 shows the basic steps that may be included in a rapid manufacturing process for applying a cell internal seal to a membrane or catalyst coated membrane.

[0056] [Figure 14a] FIG. 14a illustrates the basic steps that may be included in a rapid manufacturing process for making an integrated electrode flow field member.

[0057] [Figure 14b] FIG. 14b shows some illustrative examples of embossing or patterning the surfaces of the electrodes and / or flow field substrates to promote bonding during lamination.

[0058] [Figure 15] FIG. 15 illustrates the basic steps that may be included in a rapid manufacturing process for assembling a unitized electrolysis cell.

[0059] [Figure 16]FIG. 16 shows a y-axis view of an exemplary stack compression system illustrating a tensile wrap surrounding the core cell stack and end units, whereby mechanical tension in the wrap is balanced by mechanical compression in the cell stack.

[0060] [Figure 17a] FIG. 17a shows a cross-sectional view of the stack of FIG. 1, illustrating the relationship of the compression system wrap and the scalability of the cells along the y-axis.

[0061] [Figure 17b] FIG. 17b shows a cross section of FIG. 17a, illustrating the involvement of stack alignment fixtures through gaps provided in the wraps, and of movable cell positioning actuators along opposite sides of the cells.

[0062] [Figure 18a] FIG. 18a shows the y-axis view of an exemplary stack compression system at the final three stages during the compression process, with the electrolyzer stack fully compressed and locked.

[0063] [Figure 18b] FIG. 18b illustrates an exemplary connection for connecting the lower and upper portions of the wrap depicted in FIG. 18a.

[0064] [Figure 19] FIG. 19 shows an example configuration of the adjustable elements of the compression system packaged within the lower semi-cylindrical end unit, illustrating the internal separation force created by locking the system, resulting in compression of the cell stack and tension within the wraps.

[0065] [Figure 20] FIG. 20 shows the basic steps that may be included in a rapid manufacturing process for placing individual electrolysis cells in a cell stack through freely accessible faces provided by the target stack compression system and aligned as shown in FIG. 17b.

[0066] [Figure 21] FIG. 21 shows a rotary table stack assembly station that may be included at the end of the high speed line of FIG.

[0067] [Figure 22] FIG. 22 shows an integrated diagram of an exemplary rapid manufacturing process combining the above-mentioned processes for a bipolar plate assembly, a membrane gasket assembly, a cathode electrode flow field assembly, an anode electrode flow field assembly, a scalable electrolysis cell assembly, and a scalable electrolyzer stack assembly.

[0068] [Figure 23a-d] Figures 24a, 24b, 24c, and 24d show alternative embodiments of the compression system.

[0069] [Figure 24] FIG. 25 shows strength measurement data for samples of candidate flow field materials, showing permanent changes in thickness as a function of exposed mechanical stress.

[0070] [Diagram 25] FIG. 26 shows an embodiment of a complete megawatt class electrolysis stack including elements disclosed herein. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0071] A detailed description of some preferred embodiments will now be given with reference to the accompanying drawings, in which: although the specification relates to electrolysis, it will be understood by those skilled in the art that the features, components and methods described are applicable and adaptable to other electrochemical technologies, including hydrogen compressors and hydrogen purifiers.

[0072] Figure 1 shows an isometric view of an embodiment of a scalable electrolyzer stack (101) including its main components: bottom wrap (103), top wrap (104), cell stack (105), bottom end unit (106), top end unit (107), and a defined Cartesian coordinate system (102). The stack (101) can be characterized as having variable dimensions along the y-axis and z-axis, and a relatively fixed dimension along the x-axis of Figure 1. A change in the active area of ​​the cells in the cell stack (105) can increase or decrease the dimension of the stack along the y-axis. A change in the number of cells used in the cell stack can increase or decrease the dimension of the cell stack along the z-axis. For convenience of manufacturing (more on this below), the compression system of the stack assembly may comprise two pieces, namely a lower wrap (103) and an upper wrap (104), connected at a joint (109) to form a continuous tension boundary around the cell stack (105) and the end units (106) and (107) when viewed along the y-axis. This wrap configuration may also provide free access to two opposing sides of the stack aligned with respect to the xz-plane (102). The lower wrap (103) and / or the upper wrap (104) may also comprise holes, slots or other gap features (108) to facilitate rapid stack assembly, as described in process (1801) below. The lower end unit (106) and the upper end unit (107) may each comprise several components including end blocks, gaskets, manifolds, electrical insulation and / or power terminals. Additionally, one or both end units may be configured to include adjustable elements for compressing the cell stack.

[0073] 2a and 2b show an exemplary prior art electrolyzer stack including key components and features that may limit the scalability of its design, as well as a reference coordinate system (202). In prior art electrolyzer stacks, the cell shape can be circular (201a) or rectangular (201b). Both shapes can embody common elements including end plates (203a / b) and (204a / b), tension elements-tie rods (206), adjustable elements-screws, nuts, springs (205), cell stacks (208a / b), and ports (207a / b) for carrying process fluids in and out of the stack. An essential element of the electrolysis stack can be maintaining a compressive load on the cell stacks (208a / b). As shown, this has historically been achieved by connecting the structural plates (203a / b) and (204a / b) at either end of the cell stack with tie rods (206). The tie rods may be threaded to allow adjustment to vary the height of the cell stack and to generate tension in the rods used as a source of compression for the cell stack core. The overall compression load may be a function of the pressure required by the cell active area, the pressure required by the seals between each cell, and the operating pressure in the process fluid of the cells acting to separate the cells from each other. As the active area of ​​the cell stack becomes larger (e.g., for higher capacity systems), the total pressure required by the entire cell may remain fixed, thereby increasing the total force required for the compression system in proportion to its area. Thus, as the cells in the stack (201a / b) grow in the xy plane, the end plates (203a / b) and (204a / b) may become very heavy and thick. Also, the number of tie rods (206) may be increased to minimize structural bending of the end plates. Because the tie rods (206) can surround the entire periphery of the cell stacks (208a / b), the only space available for connecting the process fluid ports (207a / b) can be through the end plates (203a / b) and / or (204a / b).The overall variation in size, weight, and tensile element mass of conventional electrolyzer cell stacks can limit the ability to scale designs and manufacturing systems for such designed cells and stacks.

[0074] FIG. 3 shows a cross-section of an embodiment of an exemplary core electrolysis cell member (301) in the active area of ​​the cell, showing typical ion, electron, and fluid flows for proton (312) and anion (313) exchange membrane electrolysis technology. Here, (308) is an impermeable separator, i.e., bipolar plate, (305) is the cathode flow field, (307) is the cathode electrode, (304) is the ion conducting membrane, (306) is the anode electrode, and (303) is the anode flow field. When a power source is attached to the cell, which has a negative electrode (309) at the bottom and a positive electrode (310) at the top, electrons (311) can flow upward through the cell. If the cell is acidic, proton conducting (312), positively charged hydronium ions can be directed by the resulting electric field to migrate downward through the membrane (304). If the cell is of alkaline hydroxide conduction type (313), negatively charged hydroxide ions may be directed by the resulting electric field to migrate upward through the membrane (304). In both types, hydrogen may be formed on the cathode (307) and flow into the cathode flow field (305), while oxygen may be formed on the anode (306) and flow into the anode flow field (303). In dry cathode systems, water may be provided only to the anode flow field (303) as a reactant to form hydrogen and oxygen. Stoichiometry is a term relating to the "balance" of a chemical reaction. In electrochemical cells, the term "stoichiometry" or "stoichiometry" refers to the ratio of reactants provided to the cell to the amount needed to exactly balance the total reaction. As previously described herein, the water stoichiometry provided to the anode flow field (303) may be much higher than unity. Also, because the fluid in the anode flow field (303) may be mostly liquid, this section may represent a significant flow resistance compared to the cathode flow field. The thickness of the cathode flow field (314) and the anode flow field (315) may affect the flow rate, temperature distribution, and pressure loss within the cell. The overall cell pitch (316) of the cell may be determined by the thickness of each of the components (303)-(308) that make up the complete cell.A small cell pitch (316) may be desirable to produce an electrolyzer stack with high power density and small size for a given hydrogen production rate [kg / hr]. Thus, optimizing the geometry of the anode flow field, its length in the water flow direction along the x-axis, its width along the y-axis, and its thickness along the z-axis, may be an important design goal for an electrolyzer. For example, the anode flow field (303) and / or the cathode flow field (305) may be configured with thicknesses of 0.1-5.0 mm, 0.2-3.0 mm, 0.3-2 mm, 0.5-2 mm, or 0.6-2 mm. Although they are shown in FIG. 3 as having relatively equal thicknesses, the flow fields (303) and (305) may be selected with the same or different thicknesses based on factors to optimize cell process conditions, performance, and manufacturing.

[0075] FIG. 4 shows an isometric view (401) of an embodiment of a stack core (301), further illustrating exemplary cross-flow orientations (408) and (409) of process fluids, as well as the repetition of cell members (410) along the z-axis to produce a stack of cells. Here, a bipolar plate (308) can be seen separating one cell of thickness (316) from an adjacent cell 410 (below). The bipolar plate (308) of another adjacent cell can be seen above the cell (401). Water and oxygen (408) can flow along the x-axis within a composite anode electrode flow field (403) of thickness (404). Hydrogen (409) can flow along the y-axis within a composite cathode electrode flow field (405) of thickness (406). Assuming the cell is oriented with the gravity vector pointing downward and parallel to the z-axis, placing the anode above the membrane as shown can advantageously allow buoyancy forces to assist in the movement of oxygen bubbles formed on the anode electrode into the water flowing through the anode flow field above the anode electrode.

[0076] FIG. 5a shows an isometric view (501) of an embodiment of an anode flow field member (506) illustrating the tradeoffs that may exist in scaling the cell area. The anode flow field base unit may have a width "w" (505) along the x-axis, a length "l" (504) along the y-axis, and a thickness "t" (503) along the z-axis. The width "w" (505) of the base unit along the x-axis may be 5-1000 cm, 5-500 cm, 5-100 cm, or 10-50 cm. The length "l" (504) of the base unit along the y-axis may be 0.5-100 cm, 1-50 cm, 2-25 cm, or 2-10 cm. The area (507) of the base unit may be determined by multiplying the width "w" (505) by the length "l" (504). The water flow area at the leading edge (508) of this base unit can be determined by multiplying the thickness "t" (503) by the length "l" (504). The water flow for a fixed stoichiometry and efficiency (509) into this water flow area (508) can be determined by the area (507). To achieve higher hydrogen production [kg / hr] at a constant efficiency and water stoichiometry, additional area "dA" (511a) and / or (511b) can be required. If "dw" (510b) is added to "w" (505) to create "dA" (511b), additional water (513b) can be required to enter the fixed leading edge flow area (508). The added water flow can thereby increase the water flow velocity through the cell, which can result in an increased pressure drop (514). When "dl" (510a) is added to "l" (504) to make "dA" (511a), the additional water (513a) can provide a proportional increase in the fixed leading edge flow area (512a). The additional water can flow through the incremental proportional flow area (512a) without increasing the pressure drop (514). Thus, the expanded area along the y-axis allows all process conditions (pressure, temperature, and oxygen volume fraction) within the cell to remain constant. The total water flow rate may necessarily be proportional to the hydrogen / oxygen production rate, while other system parameters may be unchanged by the expansion of the cell along the y-axis only.This can greatly simplify the resulting electrolyzer systems made from cells and cell stacks designed in this way. For example, electrolyzer production plant specifications, including pressure ratings, temperature ratings and / or fluid composition ratings, can be consistent for plants of different water flows and hydrogen / oxygen capacities. This in turn can simplify engineering procurement and construction activities, expand the available supply of system components, and reduce overall hydrogen production costs.

[0077] FIG. 5b shows mathematical model results (531) for pressure loss per unit flow length (514) [mbar / cm] as a function of flow velocity (509) [cm / s] for hydrogen gas (532) and liquid water (533) through a typical porous medium that may be used for the anode and / or cathode flow fields. Also shown is an exemplary target pressure loss threshold (534) that may be selected based on the overall electrolyzer stack and system design. The threshold (534) represents an upper limit for water pressure loss, thereby defining a target threshold for water velocity in the anode flow field (535). As is evident from the results (531), the pressure loss per unit length for hydrogen can be several times smaller than the pressure loss for water at a given velocity. Thus, when increasing the cell area, it may be advantageous to prioritize cell expansion based on water velocity and flow length. For example, a water pump for supplying water to an electrolysis cell may have a pressure capability of up to 10 bar. The anode flow field (501) may be advantageously configured such that the water velocity (509) remains within the capabilities of commonly available and / or economically useful system water pumps, such as less than 100 cm / s, less than 50 cm / s, less than 20 cm / s, less than 10 cm / s, or less than 5 cm / s.

[0078] FIG. 5c shows the mathematical model results (541) for the water temperature rise (515) [°C] as a function of the stoichiometric value of the supplied water. The heat released during electrolyzer operation may be a function of the efficiency, which in turn may be a function of operating cell voltage. Saving energy for the cell may result in an equation for the water temperature rise as specified in equation 5c-1 below: where V is the operating cell voltage, V0 is the thermoneutral cell voltage [1.481 V], HHV is the higher heating value of hydrogen [141.79 MJ / kg], c p is the specific heat capacity of water [4.182 kJ / kg°C], and St is the stoichiometry of water delivered to the cell. Plots (542) and (543) show the results of this model at two possible operating voltages, representing exemplary values ​​for the beginning of life [BoL] and end of life [EoL] of the electrolysis cell. Also shown are exemplary water temperature rise target thresholds (544), above which the electrolysis cell cannot operate stably or durable, or above which the electrolysis system cannot operate efficiently. The temperature rise thresholds can be used in conjunction with the EoL voltage limit to define a lower threshold for the water stoichiometry (545). To maintain stable and durable operation of the electrolysis cell, it can be advantageous to select a water stoichiometry that maintains the water temperature rise at the end of life below 100°C, below 50°C, below 25°C, below 15°C, or below 10°C.

[0079]

number

[0080] FIG. 5d shows the mathematical model results (551) for the oxygen volume fraction at the anode flow field outlet (552) as a function of the stoichiometric value of the delivered water. The process of electrolysis splits water into hydrogen on the cathode side and oxygen on the anode side. Once oxygen is formed on the anode, it can mix as a gas with the delivered liquid water resulting in a two-phase flow in the anode flow field. The volume fraction of oxygen at the anode outlet can be indicative of the operational stability, performance, and / or durability of the electrolysis cell, and a target threshold for this parameter can be set by the designer. Conserving mass for the cell can result in an equation for the oxygen outlet volume fraction as specified in Equation 5d-1, where r O2 is the density of oxygen gas at the anode outlet, and r H2O is the density of the liquid water at the anode outlet, and St is the stoichiometry of the water delivered to the cell. Plot (552) shows the results of this model at a pressure of 10 bara at the anode of the electrolysis cell, along with an exemplary oxygen volume fraction threshold (554) above which the cell may not operate stably or durable or above which the electrolysis system may not operate efficiently. The oxygen volume fraction threshold may be used to specify a lower threshold water stoichiometry (555). To maintain stable and durable operation of the electrolysis cell, it may be advantageous to select a water stoichiometry that maintains the oxygen volume fraction below 80%, below 60%, below 50%, below 40%, or below 30%.

[0081]

number

[0082] Figure 5e shows test results (561) for pressure drop per unit flow length (514) [mbar / cm] as a function of liquid water flow velocity (509) [cm / s] through several potential porous media that may be used for the anode and / or cathode flow fields. The mathematical model results from Figure 5b (533) are again referenced for an exemplary target pressure drop threshold (534) that may be selected based on the overall electrolyzer stack and system design. The threshold (534) may represent an upper limit for water pressure drop, thereby defining a target threshold for water velocity in the anode flow field (535) for these actual potential flow field candidates (Samples 1-8).

[0083] FIG. 6 shows a plan view of an embodiment of an exemplary cell (601) illustrating features including water delivery windows (603) and water collection windows (604), the ability to scale the cell active area by replicating the water windows, and an associated unit anode flow field length (608) along the y axis that is generally fixed along the x axis based on a desired roll web width (w) (609). The area or effective diameter (diameter of a circle having an area equal to the area of ​​the window) of each water distribution window (603) may be selected to maintain water velocity along the z axis through the window below a predetermined threshold, with water flow stoichiometry selected to maintain one or more of the cell's temperature rise or oxygen outlet volume fraction below a target threshold. For example, to minimize pressure loss, the water velocity along the z axis through each window (603) may be maintained below 10 m / s, below 4 m / s, or below 2 m / s. By selecting the unit length (504) associated with each water distribution window, the water flow area (508) (shown in FIG. 5a) at the leading edge of the anode flow field can be shaped such that the water velocity along the x-axis at the leading edge (509) is kept below a predetermined threshold. The number of water distribution windows can then be selected to achieve an overall target hydrogen production rate for the cell while maintaining the water flow pressure drop (514) (shown in FIG. 5a), water temperature rise (515) (shown in FIG. 5a), and oxygen outlet volume fraction below the target threshold. The cell (601) can comprise an active area (611) and a contoured area (610). The contoured area can define several fluid flow windows for water delivery (603), water and oxygen collection (604), and hydrogen collection (606). As will be explained, the number of water windows (603) can be scaled to fit the active area, while the number of hydrogen windows (606) cannot be scaled, resulting in cells having more water windows than hydrogen windows for any single configuration of a cell. The water delivery and / or collection windows may be circular, rectangular or another shape that allows for low-cost and fast manufacturing of the cell (601). For window shapes other than circular, the "effective diameter" can be found by determining the diameter of a circular hole of equivalent area to the window.Each water window (603) may be associated with a unit length along the y-axis of the anode flow field (504). The effective diameter of the window (603) may be configured to be 1%-110% of the unit length (504), 5%-75% of the unit length, 10%-50% of the unit length, or 25%-50% of the unit length. Water flow may proceed along a path (605) from the delivery window (603) across the associated section of the active area (611) to the collection window (604). In operating the cell, hydrogen may be produced on the cathode side along the path (605), which may flow along flow lines (607) to one or more hydrogen collection windows (606). These collection windows (606) may be at one or both ends of the cell and may consist of one or more windows (606) at each end. As additional hydrogen / oxygen capacity is required, incremental water windows and associated flow field lengths (608) can be added along the y-axis to increase hydrogen / oxygen production while maintaining constant operating conditions - pressure, temperature and fluid composition - within the cell. The total number of windows selected for a particular cell (601) can determine the active area of ​​the entire cell and can be a number between 1 and 100, 2 and 50, 2 and 25 or 2 and 20. An increase in the length of the cell along the y-axis can result in an increase in the flow length of the streamlines (607) for hydrogen collection, but the flow resistance to hydrogen gas in the cathode flow field (as shown in FIG. 5b) is much less than that of liquid water in the anode flow field, thereby making the effect on cell, stack or system conditions and performance negligible. Thus, additional hydrogen windows are not required as the size of the cell is expanded. The cell can also include features (612) at one or more locations along the contour area (610) to facilitate instrumentation connections for measuring and / or controlling cell performance.The scalable electrolysis cell may include a membrane, an anode electrode, a cathode electrode, an anode flow field, a cathode flow field, and a bipolar plate assembly, the bipolar plate assembly may define one or more water delivery windows disposed along one edge of the anode flow field aligned with the y-axis, each water delivery window may be associated with a length along the y-axis of the anode flow field, and the number, effective diameter and / or associated length of the anode flow field of the water delivery windows may be selected to maintain water flow resistance or water temperature rise or cell outlet oxygen volume fraction below a target threshold value for the electrolyzer cell. The combined number of water delivery windows and oxygen collection windows may be equal to or greater than the number of hydrogen collection windows of the electrolysis cell. The effective diameter of each water delivery window may be 5% to 110% of the associated length along the y-axis of the anode flow field of the electrolysis cell. The dimension of the anode flow field along the x-axis may be the same as each water delivery window of the electrolysis cell. The length along the y-axis associated with each water delivery window may be selected based on the thickness of the anode flow field to keep the average water velocity at the leading edge of the anode flow field below 100 cm / s for the electrolysis cell. The water stoichiometry may be selected to keep the cell temperature rise at end of life below 50° C. or to keep the oxygen volume fraction at the trailing edge of the anode flow field below 80% in the electrolysis cell. The hydrogen flow velocity vector in the cathode flow field may be generally parallel to the y-axis of the electrolysis cell.As discussed herein, in some embodiments, the scalable electrolyzer stack can comprise a number of scalable electrolysis cells aligned along the z-axis in a stacked configuration, each cell can comprise a membrane, an anode electrode, a cathode electrode, an anode flow field, a cathode flow field and a bipolar plate assembly, the stacked bipolar plate assembly can define one or more water delivery plenums disposed along one edge of the anode flow field, each water delivery plenum can be sized to maintain a water velocity through the plenum along the z-axis below a target threshold, each water delivery plenum can be associated with a length along the y-axis of the anode flow field, and the number and / or size of the water delivery plenums can be selected to maintain one of water flow resistance or water temperature rise or cell outlet oxygen volume fraction below a target threshold for the electrolyzer stack. The combined number of water delivery plenums and oxygen collection plenums can be equal to or greater than the number of hydrogen collection plenums. The stack may further comprise end units at either end of the cell stack, a scalable structural wrap compression system, and at least one fluid manifold included in one end unit, the manifold facilitating delivery of water to the stack through a freely accessible face of the compression system along the y-axis. The fluid manifold may be disposed at an upper end of the stack relative to a gravity vector along the z-axis. The stack may further comprise a drain manifold and / or a purge manifold disposed at a lower end of the stack relative to a gravity vector along the z-axis. The sizes of the water flow ports and manifolds connecting the individual cell stack plenums may be selected to provide flow distribution to the individual plenums that varies by less than ±25%.

[0084] FIG. 7a shows an exploded view (701) of an embodiment of an exemplary member of a bipolar plate assembly (BPA) designed to enable rapid manufacturing. The BPA (701) comprises a bipolar plate (308), a hydrogen seal (705), a fluid distribution frame (704), and a water seal (703). The bipolar plate (308) can be constructed of a substrate suitable for the environment of the electrolysis cell. For example, if the cell is of an acidic proton conducting type, (308) may comprise an alloy of titanium, stainless steel, Inconel, nickel-chromium, or a combination thereof. Such bipolar plates for acidic cells may also be coated with a suitable corrosion resistant coating, such as platinum, gold, tin, carbon, titanium nitride, or a combination thereof. If the cell is of an alkaline hydroxide conducting type, (308) may comprise an alloy of iron, steel, stainless steel, nickel, nickel-chromium, Inconel, Fecralloy, or a combination thereof. Such bipolar plates for alkaline cells may also be covered with suitable coatings such as platinum, gold, tin, nickel, carbon, or combinations thereof. The hydrogen seal (705) may be configured to be applied to the bipolar plate (308) using a rapid manufacturing process. Suitable rapid methods include screen printing, rotary screen printing, stencil printing, robotic dispensing, compression molding, injection molding, stamp printing, or by die cutting and lamination of hot melt adhesive films made from polyester, urethane, nylon, ethylene or other chemically and mechanically suitable polymeric compounds. The thickness of the seal (705) may be manufactured in one or more application steps. It may be advantageous to apply the gasket (705) in an uncured state to facilitate bonding between the frame (704) and the plate (308). It may also be advantageous for the seal (705) to be curable by a rapid curing method such as ultraviolet curing, microwave curing, heat curing, solvent curing, two-part epoxy curing or moisture curing, or a combination of these methods. If the seal (705) is made in multiple application steps, curing may or may not be required between the steps.The seal (705) may comprise a compatible elastomeric or polymeric material such as silicone, polyurethane, polyolefin, urethane, acrylate, vinyl, butyl, EPDM, nitrile, SBR, SEBS, SIBS or EVA. The seal (705) may be constructed with a reinforcing material embedded in the seal, such as wire mesh, open cell foam, expanded metal, or sintered metal frit. This reinforcement can provide a functional advantage in sealing high pressure fluids by strengthening the polymer / elastomeric seal material. It can also provide an assembly advantage in setting the correct thickness of the BPA by providing a hard stop when assembling, compressing, and curing the plate (308) / seal (705) / frame (704). The hardness or durometer of the cured seal material may be relatively soft or medium durometer. For example, it may be advantageous for the seal (705) to exhibit a relatively compressible modulus of elasticity compared to the bipolar plate (308) and / or frame (704) to provide elasticity to the cell contour area (610) when the cell stack is compressed. For example, the hardened hydrogen seal (705) may be configured with a modulus of elasticity ranging from 0.01 MPa to 100 MPa, 0.1 to 50 MPa, 1.0 to 25 MPa, or 5 to 20 MPa. Alternatively, the geometry of the seal (705) may be adjusted to achieve the desired elasticity. The thickness of the seal (705) may be increased or decreased. For example, the thickness of the seal (705) may range from 10 to 500, 20 to 250, 25 to 250, or 25 to 100 μm. The width of the seal (705) may also be increased or decreased. For example, the width of the seal (705) may range from 0.5 to 15 mm, 1 to 10 mm, or 2 to 5 mm. The materials and properties selected for the seals (705) may be different for acid or alkaline cell designs. The fluid distribution frame (704) may be constructed from a relatively rigid plastic material.For example, it can be made by injection molding, compression molding, extrusion, casting or slip casting of polycarbonate, urethane, polysulfone, polyamide, polyamideimide, acrylonitrile-butadiene-styrene, high density polyethylene, polyphenylene sulfide, polyetherimide, silicone, polyurethane, polyolefin, urethane, acrylic, polyvinyl chloride, polystyrene, polypropylene, polyetheretherketone, polyimide or acrylate or another suitable mechanical, electrical, chemical and thermal properties polymer or elastomer. The frame (704) is made from a continuous film of material, which is then shaped by a die, knife die, rotary die, laser or water jet cutting. The frame (704) can be constructed with a modulus of elasticity ranging from 1.0 MPa to 100,000 MPa, 10 to 50,000 MPa, 100 to 10,000 MPa, or 1,000 to 10,000 MPa. Advantageously, the frame (704) can be fabricated from a visible, UV or microwave transparent material to facilitate UV or microwave curing of the hydrogen seal (705) after it is bonded to the bipolar plate 308 using the hydrogen seal as an adhesive. The frame (704) can include specific geometric features for positioning the cell flow fields, electrodes, and membranes. The frame (704) can also include the geometry required for uniformly distributing and collecting process fluids from the cells, as well as features for mating and compressing the internal seal between the anode and cathode flow fields of the cells. The frame (704) may also include features (612) (shown in FIG. 6) intended to facilitate cell voltage measurement after assembly into a cell stack. The water seal (703) can be configured to be applied to the fluid distribution frame (704) using a rapid manufacturing process. Suitable rapid methods include screen printing, rotary screen printing, stencil printing, robotic dispensing, compression molding, injection molding, stamp printing, or by die cutting and lamination. The thickness of the seal (703) can be manufactured in one or more application steps.The seal (703) may also be advantageously curable by a fast curing method such as UV curing, microwave curing, heat curing, solvent curing, two-part epoxy curing or moisture curing or a combination of these methods. If the seal (703) is made in multiple application steps, curing may or may not be required between the steps. The seal (703) may include an elastomeric or polymeric material such as silicone, polyurethane, polyolefin, urethane, acrylate, vinyl, butyl, EPDM, nitrile, SBR, SEBS, SIBS or EVA. The hardness or durometer of the cured seal material may be relatively soft or medium durometer. For example, it may be advantageous for the seal (703) to exhibit a relatively compressible modulus of elasticity compared to the bipolar plate (308) and / or frame (704) to provide resilience to the cell contour area (610) when the cell stack is compressed. For example, the hardened water seal (703) can be configured with a modulus of elasticity ranging from 0.01 MPa to 100 MPa, 0.1 to 50 MPa, 1.0 to 25 MPa, or 5 to 20 MPa. Alternatively, the geometry of the seal (703) can be adjusted to achieve the desired elasticity. The thickness of the seal (703) can be increased or decreased. For example, the thickness of the seal (703) can range from 10 to 500, 20 to 250, 25 to 250, or 25 to 100 μm. The width of the seal (703) can also be increased or decreased. For example, the width of the seal (703) can range from 0.5 to 15 mm, 1 to 10 mm, or 2 to 5 mm. The materials and properties selected for the seal (703) may be different for acidic or alkaline cell designs. Seal (703) may also be incorporated into the geometry of frame (704) by appropriate selection of materials and geometries, thereby eliminating the need to apply seal (703) in a separate step. For example, frame (704) can be configured to have the geometry of seal (703) and manufactured from a material of appropriate elastic modulus to provide the water sealing function in a single member.Alternatively, the frame (704) may be manufactured in a two-step process, whereby the seal (703) may be injection or compression molded directly onto a previously injection molded rigid plastic substrate. In another example, the seal (703) may be applied to the fluid distribution frame (704) by screen printing onto one side of a plastic film in a roll-to-roll process. The bipolar plate (308) is shown as a flat plate, but features may be formed in the central region (706) that are intended to serve as flow fields for the cathode and anode or sides of the cell. These features may comprise channels, dimples, or other geometric shapes that protrude along the z-axis, giving the bipolar plate (308) a three-dimensional shape, creating structural support for the flow fields, electrodes and / or membranes, while also creating flow-directing paths for the hydrogen, water / oxygen, or both fluids.

[0085] FIG. 7b shows a cross-sectional view (711) of an embodiment of the bipolar plate assembly (701) of FIG. 7a, illustrating the locations and internal seal features for the membrane (304), electrodes / and flow field members (403) and (405), which, when added to the bipolar plate assembly, constitute a scalable electrolysis cell (601) according to a preferred embodiment of the present invention. The cross-section of the frame (704) can be arranged to have a step (714) into which an internal seal (713) can fit to separate the anode electrode flow field (403) from the cathode electrode flow field (405). The step (714) can be configured to surround the cathode electrode flow field (405) and fully support the outer edges of the anode electrode flow field (403) and membrane (304). In this way, the anode flow field (403) can be larger than the cathode flow field (405) in the xy-plane (712). Upon compression, the electrode flow fields (403) and (405) can be configured to deform, allowing the internal seal (713) to compress between the membrane (304) and the step (714) of the frame (704). The cathode electrode flow field (405) can advantageously be elastic so as to contact the membrane (304) over the range of thermal expansion, internal gas pressure and component thickness variations expected in the manufacturing cell (601). Similarly, the thickness, width and elastic modulus of the seals (703), (705) and (713) can be tailored to achieve the requisite elasticity to provide a sealing function over the range of thermal expansion, internal gas pressure and component thickness variations expected in the manufacturing and operation of the cell (601).

[0086] FIG. 7c shows a cross-sectional view and embodiment of FIG. 7b illustrating an alternative geometry of the bipolar plate (308) whereby the cathode electrode flow field (405) can be replaced with features (723) formed directly in the plate (308). These features (723) can comprise channels, dimples or other geometric shapes that protrude along the z-axis, giving the bipolar plate (308) a three-dimensional shape and creating structural support for the flow fields, electrodes and / or membranes while also creating flow-guiding paths for the hydrogen, water / oxygen or both fluids. These features can be created by mechanical stamping, machining, hydroforming or other suitable manufacturing methods. The anode and / or cathode flow fields can be selected and formed from one or more of foam, felt, woven screen, expanded metal, or sintered metal frit. The anode and / or cathode flow fields can be formed in the bipolar plate by stamping or hydroforming processes.

[0087] Figure 7d shows an isometric view of an alternative embodiment in which the bipolar plate assembly includes a porous sheet (732) into which the hydrogen seal (705) can be embedded using screen printing, liquid dispensing, injection or compression molding or other suitable processes. In this configuration, the porous sheet (732) can provide the function of the cathode electrode flow field (405) from Figure 7b, providing both mechanical reinforcement for the hydrogen seal (705) and open space for hydrogen gas flow from the active area of ​​the cell to the hydrogen gas window (606). The porous sheet (732) can also provide precise thickness control of the bipolar plate assembly during pressing and curing of the hydrogen seal (705) and frame (704).

[0088] FIG. 7e illustrates an embodiment of the cross-sectional view of FIG. 7d with the addition of a cathode electrode (722), membrane (304), anode electrode flow field (403) and internal seal (714). After assembly and curing, the hydrogen seal (705) can be fully embedded within the porous structure of the porous sheet (732) to form a gas-tight seal for hydrogen gas within the cathode while simultaneously physically bonding the bipolar plate (308) to the porous sheet (732) and frame (704). The porous sheet (732) can be selected from one or more of foam, felt, woven screen, expanded metal, or sintered metal frit. The porous sheet can include alloys of iron, steel, stainless steel, nickel, nickel-chromium, inconel, fecralloy, or combinations thereof, and can be coated with a suitable coating, such as platinum, gold, tin, nickel, carbon, or combinations thereof.

[0089] FIG. 8 shows a top view of an embodiment of the bipolar plate assembly (701) of FIG. 7a looking down along the z-axis (802), showing the projected alignment of the water seal (703) and hydrogen seal (705). It may be important that the water seal (703) is uniformly supported by the frame (704) and hydrogen seal (705) to minimize local bending of the fluid distribution frame and potential loss of the seal. Any gap in the total material thickness for the frame (704) and / or hydrogen seal (705) may result in bending of the frame when the water seal (703) is compressed by adjacent cells in the cell stack. Excessive bending may in turn result in inadequate compression of the water seal (703) and subsequent leakage. For example, a gap of more than twice the thickness of the frame in one section may result in excessive bending. Uniform support can be determined by evaluating the percentage of the total projected area of ​​the water seal (703) that is not supported by the full thickness sections of the frame (704) and hydrogen seal (705). To provide adequate support, the percentage of the projected area that is not supported may be less than 10%, less than 20%, less than 30% or less than 50%. Also shown is a step (714) in the frame (704), which completely surrounds and bounds the open active area (611) of the cell (601). The step (714) can be configured to have a width that allows the internal seal (713) to drop out of the cathode flow field (405) while providing a pocket in which the anode flow field (403) can be placed. Also shown is a reference dimension "w" (609) that represents the desired roll web width as described above according to the scalability of the cell (601). A detailed view (803) is described in FIG. 9.

[0090] FIG. 9 shows an isometric view of an exemplary water distribution window (803) embodiment, illustrating the distribution (905) and seal (713) features included in the frame (704) to provide a uniform water flow (908) over the relevant length of the anode electrode flow field (403). A portion of one water delivery window (603) is shown, with the water velocity vector (907) entering the window (603) generally along the z-axis and turning and spreading in the xy-plane toward the leading edge of the anode flow field (403). The delivery window (603) can be configured with one or more distribution features (905) to facilitate spreading of the flow (907) in the xy-plane, as shown by vector (908), to enter the leading edge of (403) in a uniform manner along the y-axis. The distribution features (905) can be integrated into the frame (704) or formed as part of the geometric features of the water seal (703) (shown in FIGS. 7a-e and 8). The frame may also be configured with mechanical support features (906) to ensure sufficient compressive load is transferred to the hydrogen seal (705) between the frame (704) and the bipolar plate (308), as shown in FIG. 7b. The mechanical support features (906) may also be formed as part of the geometric features of the water seal (703). The cathode electrode flow field (405) is shown positioned inside the step (714) of the frame (704) with the membrane (304) separating the cathode flow field (405) and the anode flow field (403) flow fields. The internal seal (713) is shown between the membrane (304) and the step (714) of the frame (704), with the overlap with the anode electrode flow field (403) visible. In this configuration, the anode electrode flow field (403) may be larger than the cathode electrode flow field such that it overlaps the seal step (714) around the entire perimeter of the active area. The step (714) can act to ensure that the cathode electrode flow field (405) and the anode electrode flow field (403) remain properly positioned and that the internal seal (713) is properly positioned on the step (714). Ensuring these features can be essential for reliable and rapid assembly of cells and stacks.

[0091] FIG. 10 shows a top view of the embodiment of the bipolar plate assembly (701) of FIG. 7a looking upward along the z-axis (1002), showing the projected alignment of the water seal (703) and hydrogen seal (705). The bottom view more clearly shows how elements of the hydrogen seal (705) are included for the purpose of supporting the water seal (703). For example, the seal (705) may include features such as those shown in (1004) to match the corresponding geometry of the water seal (703). The seal (705) may also include features such as those shown in (1005) to support the step (714) (shown in FIGS. 7b, 7c, 7e, 8, and 9) along the hydrogen trailing edge of the cathode electrode flow field. To allow hydrogen gas to exit into the collection window (606), bridge mechanisms (1105) and (1106) can be included within the frame (705) as detailed in diagram (1003) of FIG.

[0092] FIG. 11 shows an isometric view of one embodiment of a typical hydrogen collection window (606), showing bridge (1105) and (1106) and internal seal (713) features contained within a frame to uniformly collect hydrogen (1108) produced by the cell and deliver it (1107) to one or more collection windows (606). A section of one hydrogen collection window (606) is shown with the hydrogen velocity vector (1107) exiting the window (606) generally along the z-axis, rotating out of the xy-plane where it exits the trailing edge of the cathode electrode flow field (405). The collection window (606) may be configured with one or more bridge features (1105) and (1106) to facilitate uniform collection of the flow (1108) from the xy-plane, as well as to provide mechanical support for both the internal seal (713) and the water seal (705). The bridge features (1105, 1106) may be integrated into the frame (704) or may be formed as part of the geometric features of the hydrogen seal (705) (shown in Figures 7a-e, 8, 10). As part of the hydrogen seal (705) geometry, the bridge features can be made using a porous reinforcing material such as wire mesh, open cell foam, expanded metal, or sintered metal frit. This porous reinforcing material can be formed as a full or partial extension of the cathode electrode flow field (405), a porous sheet (732), as shown in Figures 7d and 7e. The cathode electrode flow field (405) is shown positioned inside a step (714) of the frame (704) with a membrane (304) separating the cathode flow field (405) and anode flow field (403) flow fields. An internal seal (713) is shown between the membrane (304) and a step (714) of the frame (704) showing overlap with the anode flow field (403). The bipolar plate assembly can include a fluid distribution frame configured to position and house at least one of a cathode flow field, a cathode electrode, a membrane, an internal seal, an anode electrode, or an anode flow field between two adjacent bipolar plates.The fluid distribution frame can be configured to allow diffusion of water flow in the xy plane from one or more water delivery windows to the leading edge of the anode flow field to provide a leading edge velocity distribution within plus or minus 50% of the average velocity of the flow field. The fluid distribution frame can be configured to collect water and oxygen flow from the trailing edge of the anode flow field and impose a change in the trailing edge velocity distribution within plus or minus 50%. A hydrogen seal can be disposed between the frame and the bipolar plate adjacent the cathode flow field, while a water seal can be disposed between the frame and the bipolar plate adjacent the anode flow field. The fluid distribution frame can include a visible light transparent material or an ultraviolet light transparent material or a microwave transparent material. The bipolar plate assembly can be configured to collect hydrogen flow from one or more trailing edges of the cathode flow field and deliver the flow to one or more hydrogen collection windows. The fluid distribution frame can be configured to mate with an internal seal between the anode flow field and the cathode flow field, the seal being applied to at least one of the membrane, the catalyst coated membrane, the electrode, the subgasket boundary of the membrane-electrode assembly, or the frame itself. The fluid distribution frame, water seal, and hydrogen seal can be arranged such that the unsupported seal area is less than 50% in a projected view along the z-axis. The anode flow field can be larger than the cathode flow field in the fluid distribution frame, and the anode flow field can facilitate the application of a compressive load to the internal seal. The bipolar plate assembly can include a bipolar plate material selected from one or more of stainless steel, titanium, nickel, carbon, chromium, iron, or alloys thereof. The bipolar plate assembly can include a bipolar plate that can be coated with one or more of platinum, gold, tin, palladium, rhodium, titanium nitride, nickel, carbon, or chromium. An electrolysis cell using the described fluid distribution frame can have a compressed cell pitch of 2.5 mm or less.

[0093] FIG. 12 shows an embodiment of basic steps in a rapid manufacturing process (1201) for a bipolar plate assembly. A bipolar plate (308) can be loaded onto an assembly line. A hydrogen seal (705) can then be applied to the bipolar plate (308) in an uncured state (1203) using a suitable rapid application method such as screen printing, rotary screen printing, stencil printing, or robotic dispensing. A fluid distribution frame (704) can then be positioned against the bipolar plate (308) and pressed onto the seal (705) (1204). For a bipolar plate (308) with formed flow field features (723), it may be advantageous to apply the seal (705) to the frame (704) rather than the bipolar plate prior to process step (1204). For example, a screen or stencil printing process (1203) may perform better on flat members. Thus, if the bipolar plate (308) is not flat, applying the seal (705) to the frame (704) and then pressing it together with the bipolar plate (308) may be a preferred sequence of operations. The material properties, geometry, and thickness of the uncured seal (705) may be selected to ensure proper adhesion to both the bipolar plate (308) and the frame (704). The thickness and geometry may further be selected to ensure that the resulting uncured seal forms a continuous gasket between the bipolar plate (308) and the frame (704) after pressing (1204). The pressing step (1204) may include assembling the members at a fixed compressive load using a mechanical, pneumatic, or hydraulic press and flat tool, or by utilizing a vacuum system to apply a uniform vacuum pressure to the assembly through a sealed bag or membrane. The pressing step (1204) may include assembling the members to achieve a constant thickness in the uncured state. After pressing, the hydrogen seal (705) can be cured using a suitable fast cure method such as UV cure, microwave cure, heat cure, solvent cure, two-part epoxy cure or moisture cure, or the hydrogen seal can be left uncured at this stage.The water seal (703) can then be applied in an uncured state (1205) to the top of the frame (704) using a suitable high speed application method such as screen printing, rotary screen printing, stencil printing, or robotic dispensing. The material properties, geometry, and thickness of the uncured seal (703) can be selected to ensure proper adhesion to the frame (704). As discussed with respect to FIG. 7a, the thickness and geometry of the seal (703) can be further selected to ensure proper elastic compliance to form a reliable water seal over the range of expected thickness tolerances of the cell members in high speed manufacturing. For example, a thicker water seal (703) can provide a wider range of seals and accommodate larger thickness tolerances for the electrode flow fields. A narrower water seal (703) can provide a lower overall load in the contoured area (610) for a given compression, thereby minimizing the percentage of stack compression load taken up by the seal and ensuring proper contact pressure in the active portion of the cell. The final step (1206) may be to cure the seal(s) (703) and (705), if not previously cured, using one or more of UV cure, microwave cure, heat cure, solvent cure, two-part epoxy cure, or moisture cure. In certain embodiments, it may be advantageous to apply a water seal (703) to the frame (704) prior to pressing step (1204) in either an uncured or cured state, or to design the frame (704) with an integrated water seal (703) during its manufacture. The final bipolar plate assembly (1207) may be tested to ensure quality after the curing step (1206). For example, following the curing step (1206), fixtures and machines for pressure testing and for verifying that the cured seals are leak-tight may be used in line with the manufacture of the bipolar plate assembly.A method of manufacturing a bipolar plate assembly for a scalable electrolysis cell can include selecting materials for the bipolar plate, hydrogen seal, water seal, and fluid distribution frame, applying a hydrogen seal to one of the bipolar plate or fluid distribution frame in an uncured state, aligning the fluid distribution frame to the bipolar plate, compressing to fit the uncured hydrogen seal between the plate and the frame, and applying a water seal to the fluid distribution frame. At least one of the hydrogen seal or water seal can be cured using an ultraviolet curing method, a microwave curing method, a thermal curing method, a solvent curing method, a two-part epoxy curing method, or a moisture curing method. The hydrogen seal and the water seal can be cured simultaneously. The water seal can be formed during the manufacture of the fluid distribution frame prior to mating with the uncured hydrogen seal. The fluid distribution frame can be pressed together with the bipolar plate with sufficient force to ensure that a continuous, unbroken seal is formed between the bipolar plate and the fluid distribution frame, and / or achieve a target thickness of the bipolar plate assembly that varies by no more than ±25%. The hydrogen and / or water seal can be applied using a screen or stencil printing process. Either the hydrogen seal or the water seal or both may be applied in the uncured state with a thickness of 10-1000 μm and a width of 0.5-15 mm.

[0094] FIG. 13 shows an embodiment of a basic step (1301) in a rapid manufacturing process for applying a cell internal seal (713) to a membrane (1305). A membrane or catalyst coated membrane "CCM" (1304) is selected from the desired roll web width (w) (609). The membrane may be acidic, proton conducting or alkaline, hydroxide conducting. The membrane may be bare or have an electrocatalyst applied to one or both sides. The catalyst coating on one or both sides may be continuous or coated in patches with bare membrane exposed at the edge of each patch. A roll of web width (w) (609) may be loaded onto an unwind station designed to hold the web (1305) flat under known surface tension and allow it to move along the y-axis (1302). The internal seal (713) may then be applied directly to the membrane or CCM using a suitable rapid application method (1307), such as screen printing, rotary screen printing, stencil printing, or robotic dispensing. The internal seal (713) can then be cured (1307) using one or more of UV cure, microwave cure, heat cure, solvent cure, two-part epoxy cure or moisture cure. The web can then be advanced where discrete membrane-gasket assembly pieces (1309) can be cut from the roll (1308) using a suitable method such as die cutting, rotor cutting or laser cutting and provided to a separate cell assembly process (1501) (shown in FIG. 15). Waste from the membrane or CCM roll may be collected at the end of the line (1310) for regeneration and / or recycling.A method for manufacturing an internal seal for a scalable electrolysis cell can include selecting one of the membranes or catalyst-coated membranes of a desired roll web width along the x-axis, directing the web of the roll through a seal applicator along the y-axis, applying an uncured internal seal to one side of the web using one of screen printing, stencil printing or robotic dispensing methods, curing the applied internal seal using one of UV curing, microwave curing, heat curing, solvent curing, two-part epoxy curing or moisture curing, cutting the roll of membrane gasket assembly or catalyst-coated membrane gasket assembly into separate pieces, and transporting the resulting individual pieces to a cell assembly machine. The membrane material can be acidic, proton-conducting or alkaline, hydroxide-conducting, and can be uncoated, continuously coated or patch coated as a CCM on one or both sides. The internal seal can be applied to the anode and / or cathode side of the web.

[0095] FIG. 14a illustrates an embodiment of basic steps in a rapid manufacturing process (1401) for making an integrated electrode flow field member (1413). One or more rolls of porous substrate (1403a) can be selected based on the desired roll web width (w) (609), as described above. The substrate can include foam, felt, woven screen, expanded metal, sintered frit, or fiber cloth or paper. The substrate selected can have a porosity of up to 98%, where porosity is defined as the volume percent of the substrate available for fluid flow therethrough. For example, the porosity can be 98%-40%, 95%-50%, 90%-60%, or 95%-80%. The composition of the substrate can include iron, nickel, chromium, steel, stainless steel, Inconel, aluminum, titanium, carbon, or combinations thereof. The substrate can be plated or coated with other materials, such as platinum, gold, tin, carbon, titanium nitride or PTFE, or another corrosion-inhibiting layer including an engineered layer of polymeric or oxide material with conductive metal or carbon pathways. The roll (1403a) may be loaded onto an unwinding station designed to hold the web flat under known surface tension and allow it to move along the y-axis (1402). The roll (1403a) can be calendered through a set of rollers (1404) and (1405) to laminate two or more layers together, reduce the porosity of the web, reduce or increase its thickness, increase its strength, increase its stiffness, and / or create desired surface properties on one or both sides of the web (1406). For example, the substrate may be advantageously relatively smooth on one side and rough on the other side to facilitate later steps in the process. It may also be advantageous to achieve a porosity gradient through the thickness of the substrate. For example, it may be beneficial for downstream processes for one side of the calendered substrate (1406) to have a relatively low porosity to accommodate conversion to an electrode, while the opposite side of (1406) has a relatively high porosity to facilitate bonding with a second substrate.To achieve different properties on each side of the web (1406), the rollers (1404) and (1405) may be of the same or different diameters, and / or may be made of the same or different materials, and / or may be constructed with different surface finishes or coatings, and / or may be provided with specific surface patterns that may be embossed on one or both sides of the rolled web (1403a). The calendered substrate (1406) may then be converted into an electrode (1408) in step (1407). For example, the electrode material may be coated by spray coating, screen printing, rotary screen printing, doctor blade coating, slot die coating, curtain coating, squeegee coating, or laminated as a film, transfer paper, or solid layer using heat and / or pressure onto the appropriate surface of the electrode substrate (1406). The electrode applied in step (1407) may include suitable catalyst materials, conductive support materials, ionically conductive binder materials, and inert binder materials, along with suitable solvents to facilitate electrode application. The selection of multiple binder materials, such as primary, secondary, tertiary, etc., for the ink can ensure proper adhesion of the electrode to the substrate (1406) and proper structural integrity of the final electrode layer itself to prevent delamination and / or washing away of the electrode during operation of the electrolytic cell. The binder used can consist of ion-conducting polymers alone or a combination of both ion-conducting and non-conducting polymers to optimize the adhesion and ion-conducting functionality of the electrode. The ion-conducting binder can be selected from ionomers completely dissolved in a suitable solvent (liquid ionomer solutions) or from dispersions of non-soluble ionomers in a suitable fluid carrier (ionomer dispersions). In a preferred embodiment, it can be advantageous to use liquid ionomer solutions as electrode binders to allow the formation of a continuous ion-conducting membrane within the structure of the final electrode after application and during operation of the electrolytic cell.In another preferred embodiment, it may be advantageous to use a primary inert binder in combination with a secondary ionically conductive binder to achieve optimal resistance to washout and low ionic resistance. In another preferred embodiment, it may be advantageous to combine both a liquid ionomer solution and an ionomer dispersion in the electrode to achieve optimal resistance to washout and low ionic resistance. The electrode conversion step (1407) may also include post-coating steps. For example, the coating may be dried, heat treated, annealed, and / or physically or chemically treated to promote bonding to the substrate and / or enhance the electrochemical performance of the cell. The conversion step (1407) may also include a chemical or physical vapor deposition process for conversion to an active electrode (1408). The conversion step (1407) may also include plasma or flame spray methods for depositing electrode material on the substrate (1406) or for chemically reacting and / or converting the substrate (1406) into an active electrode. Following step (1407), the electrode web (1408) may be placed adjacent to a second roll of porous substrate (1403b). This substrate may be the same as (1403a) or different, and may be selected based on a similar range of possible materials and properties as (1403a), but may be selected to meet the functional requirements for the fluid flow field, rather than the electrode. For example, making (1403b) the same as (1403a) may result in the highest purchase volume and lowest supply costs. Selecting (1403b) from a substrate different from (1403a) may be advantageous for cell performance (electrical resistance, flow resistance, thermal conductivity, mechanical elasticity or mechanical strength). In process step (1410), the electrode web (1408) may be laminated to the flow field web (1409) by a suitable lamination process. The lamination step (1410) may include mechanical rolling or calendaring through rollers similar to (1404) and (1405) to promote simultaneous infiltration of solid fibers, membranes or wires from web (1408) into web (1409).To achieve this mechanical bond, the similar rollers (1404) and (1405) may be of the same or different diameters, and / or may be made of the same or different materials, and / or may be configured with different surface finishes or coatings, and / or may be equipped with specific surface patterns. It may be advantageous to select (1403a) and (1403b) from the same supply of material, but to perform a pre-calender (1403b) shortly before the lamination step (1410). The pre-calendering step may include embossing a pattern on the side (1409) that is to be co-infiltrated with (1408) to promote mechanical bonding. The lamination step (1410) may include other steps, including heat treatment or application of a bonding promoter, such as an adhesive, a polymer suspension, a liquid ionomer solution or an ionomer dispersion, to one or more of the webs (1408) and (1409). The order of steps (1407) and (1410) may be reversed so that conversion of the web (1406) to electrodes (1408) can be performed after lamination to the web (1409). Certain electrode materials and / or methods may be advantageously formed only after calendaring and lamination to ensure sufficient adhesion is maintained in the final web (1411). In some cases, the electrodes may be coated onto a membrane, in which case the converting step (1407) may be omitted in the process (1401). Following the lamination step (1410), the unitized electrode flow field web (1411) may be processed (1412) to create individual pieces (1413) of appropriate size for integration into the electrolysis cell (601). For example, the web (1411) may be processed in step (1412) by punching with a knife or other cutting die to ensure accurate sizing of the pieces. The exact size of component (1413) may depend on whether an anodic or cathodic electrode flow field is being generated, and the size may also depend on the design tolerances required for reliable, high speed integration with the bipolar plate assembly (1201).The overall process (1401) may be adapted to produce either anodic or cathodic flow fields as desired, and the specific materials, coatings, steps and setup of the lines may be the same or different for each. In production, two independent lines may be used to simultaneously produce one anodic and one cathodic flow field to allow for rapid production of a complete electrolysis cell. A method of manufacturing an integrated electrode flow field for a scalable electrolysis cell can include: selecting an electrode substrate of a desired roll web width along the x-axis from one of foam, felt, woven screening, expanded metal, or sintered metal frit; selecting a flow field substrate of a desired roll web width along the x-axis from one of foam, felt, woven screening, expanded metal, or sintered metal frit; directing the electrode substrate web along the y-axis through a calendaring roller configured to achieve a desired thickness and surface properties on each side of the electrode substrate; converting the electrode substrate to an active electrode; directing the flow field substrate web adjacent to the electrode substrate web along the y-axis while passing through a lamination process to bond the electrodes and flow fields together; cutting the laminated electrode flow field roll into individual pieces; and conveying the resulting individual pieces to a cell assembler. The electrode and flow field substrate materials can include at least one of carbon, nickel, titanium, iron, chromium, stainless steel, or Inconel. One or more of the electrode web and flow field web can be provided with a roughened, patterned, or embossed surface to facilitate lamination. The lamination process may include a bond promoter selected from one of an adhesive, a polymer dispersion, a liquid ionomer solution or an ionomer dispersion. The electrode flow field web may comprise a foam electrode and a woven screen flow field after lamination. The conversion of the electrodes may be performed before or after lamination.

[0096] Figure 14b shows some exemplary embodiments of patterning or embossing of the electrodes and / or flow field substrates to promote enhanced bonding during the lamination process (1410). The patterns can be linear along the y-axis as shown at (1421) and (1422), along the x-axis (not shown), or along both the x-axis and y-axis in a cross-hatch style (1423) and (1424). The depth and spacing of the contour shapes (triangles (1421), rectangles (1422) or other shapes (not shown)) can be optimized based on the materials and other properties of the substrates being laminated.

[0097] FIG. 15 illustrates an embodiment of a basic step (1501) in a rapid manufacturing process for assembling a unitized electrolysis cell (601). A bipolar plate assembly (1207) can be loaded onto an assembly line moving along a y-axis (1502). A cathode electrode flow field (1413a) can be placed into a cavity of the bipolar plate assembly (1207) using a suitable handling method (1503). The resulting subassembly can be advanced along the y-axis using a suitable handling method (1504) where the membrane gasket assembly (1309) can be placed into the cavity of the bipolar plate (1207). The resulting subassembly can be advanced along the y-axis using a suitable handling method (1505) where the anode electrode flow field (1413b) can be placed into the cavity of the bipolar plate (1207). For example, suitable handling methods (1503), (1504), and (1505) may include a robotic handler and / or automated linear motion machine, and may include a vision or other measurement system to ensure accuracy of positioning members. Design features of bipolar plate assembly (1207) may aid in accurate placement of members (1413a), (1309), and (1413b). For example, stepped pockets (714) in frame (704) may assist self-positioning members (1413a), (1309), and (1413b). The resulting unitized cell assembly (601) may be further processed to ensure members (1413a), (1309), and (1413b) are properly positioned within bipolar plate assembly (1206). For example, a pressing process may be performed after step (1505), whereby a generally flat platen may be used to apply a generally uniform pressure to part (1413b) along the z-axis. The pressure applied in this manner may act to flatten members (1413a), (1309), and (1413b) and ensure that they are securely positioned and seated within bipolar plate assembly (1207).Such a pressing process may be integrated into the handling method 1505 and performed simultaneously with the positioning step 1505. The pressing step may also include a leak check to ensure that members 1413a, 1309, and 1413b are properly positioned and sealed within bipolar plate 1207.

[0098] FIG. 16 shows a y-axis view of an exemplary embodiment of a stack compression system (1601), illustrating a tensile wrap (1603) surrounding a core cell stack (1604) and end units (1605) and (1606), whereby mechanical tension in the wrap (1609) may be balanced by mechanical compression in the cell stack (1607) and (1608). Also shown is a slip surface (1610) between the wrap (1603) and the end units (1605) and (1606). The slip surface (1610) may ensure that stresses in the wrap (1609) may be maintained primarily as tensile stresses, while loads from the wrap (1603) to the end units (1605) and (1606) may generally be directed perpendicular to the slip surface and radially inward through the end units. This force placement can ensure minimal bending in the end units and uniform application of pressure to the cell stack (1604) by the end units (1605) and (1606). The semi-cylindrical cross-sectional shape of the end units can aid in this force placement. The wrap (1603) may be constructed of a material of sufficient strength and elasticity to adequately maintain the compressive load on the core cell stack. For example, the wrap may be made from various alloys of steel, stainless steel, aluminum or titanium, or may include suitably strong plastics or reinforced plastics, or composite materials such as carbon, glass and aramid fibers. The thickness of the wrap "h" (1705) can be selected to ensure that the stress (1609) is below a failure threshold based on the material selected for the wrap (1603) and the maximum tension (1609) to which the wrap (1603) can be exposed. The thickness "h" (1705) may also be selected to achieve a desired expansion, contraction or spring constant of the wrap during assembly and / or use of the compression system (1601). For example, the wrap (1603) may advantageously have a lower spring constant [N / m] than the spring constant [N / m] of the cell stack (1604) to accommodate thermal expansion and contraction of the stack without substantially changing the load applied to the cell stack (1604).For example, the wrap spring constant can be selected between 0.1%-25%, 0.5%-10%, 1%-5%, or 2%-5% of the cell stack spring constant.

[0099] FIG. 17a shows an exemplary xy-plane cross-sectional view (1701) of an embodiment of the stack (101) of FIG. 1, illustrating the association of the scalability of the compression system wrap (1603) to the cell (601) along the y-axis (1702). The strips (1703) can be features of the wrap (1603) as shown in FIG. 1 (103) and (104), and these strips (1703) can collectively carry the tension (1609) of the compression system (1601). The total compressive force (1607) and (1608) in the cell stack (1604) can be equal to the total maximum tensile force (1609) in the wrap (1603) or can be divided among the multiple strips (1703) that make up the complete wrap (1603). The tensile stress in any one strip can be equal to the tensile force in the strip divided by the cross-sectional area of ​​the strip. As the cell (601) expands in the active area, a water window and associated anode flow field length (608) are added, increasing the cell (601) dimension along the y-axis. This increase in the cell's y-axis dimension may be accompanied by a proportional increase in the wrap (1603) dimension along the y-axis. New strips (1704) may be added and / or the strip length "m" (1706) may be adjusted to ensure proportionality between the increased cell (601) length and the wrap (1603) length along the y-axis. In this way, the added total compressive force required by the incremental cell area (608) can be transferred with the same tensile stress in the added strips (1704) without requiring a change in the wrap thickness "h" (1705). It may be advantageous to keep the thickness "h" (1705) the same for wraps constructed for different sized cells. For example, manufacturing methods developed to manufacture wraps for relatively large cells may be directly used to manufacture wraps for smaller cells, and vice versa. It can also be shown that the required thickness "h" (1705) of the wrap is only a function of the stack compression requirements and not the active area of ​​the cell (601). It can be shown that the thickness "h" (1705) can be selected to ensure that the tensile stress in the wrap does not exceed a predetermined fracture threshold "Su" (1707) of the wrap material.This threshold may be the yield strength or tensile strength of the material from which the strip (1703) is made. In some embodiments, the thickness "h" (1705) and / or the material of the wrap may be selected to ensure that the tensile stress in the wrap does not exceed 10%, 20%, 30%, 50%, 75%, 80% or 90% of the yield strength or tensile strength. It may also be shown that to ensure that the tensile stress in the wrap does not exceed "Su" (1707), the dimension "h" (1705) may be equal to or greater than the ratio of a selected maximum allowable operating pressure "MAWP" (1709) for hydrogen gas in the cathode flow field of the cell to the failure threshold "Su" (1707) of the wrap material, multiplied by the dimension "wc" (1708) of the cathode flow field along the x-axis, as described by Equation 17a-1 below.

[0100]

number

[0101] FIG. 17b shows an exemplary xy-plane cross-section (1710) of an embodiment of the stack (101) of FIG. 1, showing the involvement of stack alignment fixtures (1713) and (1715) through gaps provided in the wrap (108) configured for this purpose, as well as fixtures (1712) on one freely accessible face of the stack. Also shown is the involvement of movable cell positioning actuators (1716) and (1717) along both sides of the cells. Precise alignment of the cells relative to each other and to the stack compression system during stacking and compression can be important for reliable sealing, performance and durability of the electrolyzer stack. Strict mechanical constraint is an assembly process in which the six fundamental degrees of freedom of the cells (3 translations and 3 rotations) are constrained by a system of positioning reference points. In practice, this involves placing the cell (601) on a flat surface (i.e., a previously stacked cell or end unit) and abutting two adjacent edges of the cell against three fixed points, i.e., two on one side (1713) and (1715) and one on the adjacent side (1712). This positioning method fully constrains the cell without over-constraining it. The wrap (1603) extends along two opposing sides of the cell (601). To facilitate a tightly constrained assembly process, gaps (108) can be provided through the wrap walls to allow the alignment fixtures (1713) and (1715) to pass through the wrap and establish the aforementioned positioning datum. A third datum (1712) can be established on a freely accessible face of the stack without being obstructed by the wrap structure. To ensure that the cell (601) contacts the three established reference points (1712), (1713) and (1714), the cell (601) can be contacted with the reference points by a cell handling system used to move the cell from the manufacturing line into the wrap. For example, a robotic arm can be used to ensure contact when placing the cell on the stack.Alternatively, during placement of the cell (601), separate movable actuators (1716) and (1717) may be provided which act to push the cell (601) long in the x and y axes after placement on the stack, thereby ensuring that the cell (601) contacts the designated reference points (1712), (1713) and (1714). The wrap (1603) may further be configured with features to allow the necessary movable actuators (1716) to pass through the wrap and push the cell into place.

[0102] FIG. 18a shows a y-axis view of an exemplary stack compression system embodiment at three stages during the compression process (1801), ending with a fully compressed and locked electrolyzer stack (1820). In stage 1 (leftmost view), the cell stack (1504) is uncompressed, with a free height along the z-axis that may be determined by the weight of the cells and top unit, as shown by dimension (1809). The lower wrap element (1803) may include a lower end unit consisting of a half cylinder (1505) and a block (1807). The block (1807) may include drain manifolds, gaskets, spacers, electrical insulation and power terminal elements. The upper wrap element (1804) may include an upper end unit consisting of a half cylinder (1506) and a block (1808). The block (1808) may include process manifolds, gaskets, spacers, electrical insulation and power terminal elements. Block (1808) may be further configured to fit over top wrap (1805) to hold the top end unit members from separating from top wrap (1804) by gravity along the z-axis. The bottom (1803) and top (1804) wrap sections may further comprise connecting elements (1805) and (1806) that may allow the bottom and top wrap sections to be connected when aligned. In stage 2 (middle), top wrap (1804) and end unit assemblies (1506) and (1808) are lowered along the z-axis (1810) to compress cell stack (1504) to a pre-compressed height indicated by dimension (1811). This movement may be accomplished using a press powered by the force of hydraulics, pneumatics, mechanical screws or any other means capable of compressing the cell stack to dimension (1811). The upper wrap and end unit can be lowered to the point where the connection elements (1805) and (1806) are aligned to allow a fixed connection (1812) to be completed between the wrap sections. At this stage, the wrap can act as a continuous, integral structure capable of sustaining the designed tensile load.In stage 3 (far right), adjustable elements (1815), (1816) and (1817) can be mated to compress the cell stack (1504) to the final dimensions (1814). This final stage can be accomplished in multiple sub-steps. The adjustable element (1816) can be driven upward along the z-axis by temporary use of a hydraulic, pneumatic or other mechanical system to achieve the desired cell stack load. This temporary load can be advantageous to apply a precise load by incorporating load or pressure measurement equipment into the temporary system. The temporary system can also be advantageous in allowing a fixed or variable load profile to be applied during compression. For example, the cell stack may be compressed beyond the final load planned for the wrap to minimize contact resistance between the cells and the cell members. The load in the cell stack can then be lowered to the final load planned for the wrap, thereby minimizing the structural requirements for the compression system. The temporary load may cycle up and down and / or oscillate several times as the cell stack is compressed in stage 3 to ensure that all components are in intimate contact and / or seals are well fitted. After the temporary load profile is completed, the adjustable elements (1815) and (1817) may be engaged to transfer the reaction load of the cell stack (1504) from the temporary system to the integral wrap (1603). For example, the screw (1817) may be rotated to separate the pad (1816) from the shoe (1815) in the lower half cylinder (1505) and further stretch (1818) the integral wrap (1603). As the screw (1817) is rotated, the reaction load carried by the temporary system may decrease while the tensile load in the wrap (1818) may increase as the wrap (1603) stretches. When the load in the temporary system drops to zero, the stack assembly may be in its final compressed state. Leak and other quality control tests of the compression stack (1820) may be incorporated into the process (1801).For example, a leak test of the anode, cathode or both sides of the stack against the appropriate pressure can be performed during application of the temporary load before engaging the screw (1817) to ensure that the stack quality is acceptable before engaging the screw (1817). The leak test can be performed after the screw (1817) is engaged, or it can be performed before or after the screw (1817) is engaged. Other measures can be introduced, such as dimensional measurements of the compressed stack height (1814), pre-compressed height (1811), free stack height (1809), or all of these heights. The stretch (1818) of the wrap (1803) can be measured before, during and / or after the third stage to ensure proper engagement of the adjustable elements (1815), (1816) and (1817). For example, the stretch (1818) can be measured using a linear variable displacement transducer or a displacement dial indicator or a strain gauge attached to the wrap (1803). These measurements can be used to determine the final load on the cell stack (1504) by converting the extension (1818) to a force by determining the spring constant of the wraps (1803) and (1804) using Housing's law.

[0103] FIG. 18b shows various embodiments of potential connections (1812) for connecting the lower and upper sections of the wraps. Hinge pin A, as shown, comprises a lower wrap (1803) and an upper wrap (1804) configured as a series of alternating strips, formed such that when the strips are aligned, the pin (1820) can pass through a common hole formed along the y-axis (1802). The centerlines of the thicknesses of the lower and upper wraps (1821) can be configured by the hinge geometry to be aligned along the z-axis with one another and along the centerline of the pin (1820). This configuration can be advantageous to minimize bending and localized stresses of the strips around the pin when the integrated wraps are tensioned. The bent flanges of each strip (1803) and (1804) may be welded or otherwise joined at points (1822) or elsewhere to increase connection strength. The pins can be made of any suitable material of suitable strength, such as iron, steel, aluminum, titanium, plastic, reinforced plastic, or combinations or alloys of these materials. Hinge pin B is an alternative geometry to hinge pin A and may be advantageous in minimizing material thickness of the top and bottom laps. The radius of the bend in the strips (1803) and (1805) for hinge pin B may be larger, thereby reducing local stresses around the connection. The hem hook comprises interlocking opposing hem bends formed in the bottom lap (1803) and top lap (1804). This style of connection may be useful for connecting bottom and top laps configured as a continuous sheet along the y-axis, rather than a series of alternating strips. The clasped hem hook comprises a modified hem hook connection that may encapsulate the connection to counteract the natural tendency of the connection to rotate under load due to moments that may be caused by misalignment of the centerlines of the laps (1803) and (1804). The encapsulation may be incorporated into the design of the end block (1808).

[0104] FIG. 19 shows an embodiment of an exemplary configuration of adjustable elements of the compression system (1901) packaged in the lower semi-cylindrical end unit (1505), showing the internal separation forces (1909) and (1910) that are generated by locking the system, resulting in compression in the cell stack and tension in the wrap. The cell stack (105) can be abutted by a power terminal plate (1905), which can be set in a drain manifold (1904) having a drain port (1906). The compression plate (1903) can be below the drain manifold (1904) and can be located on one or more compression pads (1816), which can be distributed along the y-axis (1902) in proportion to the number of water windows provided in the cell. The compression pads (1816) can act along the z-axis (1902) to exert an upward force on the plate (1903). The shoe (1815) may be set within the lower semi-cylinder (1505) and configured to apply a generally radial distribution of force (1910) to the semi-cylinder when loaded. A screw (1817) may be threaded through the shoe (1815) and the abutment pad (1816). When the screw (1817) is turned, it acts to separate the pad (1816) from the shoe (1815), increasing the forces (1909) and (1910). The lower wrap (1803) may include the lower semi-cylinder (1505) and be placed in tension by the action of an adjustable element as described above. Also shown is a through hole (1907), which may enable the stack assembly mechanism to directly compress the pad (1816) to achieve the pre-compression means described above. The pre-compression force (1908) may be achieved using a post or rod connected to a hydraulic or other type of mechanical loader to achieve the third stage of the process (1801). The compression plate (1903), pad (1816) and shoe (1815) may be constructed from any suitable material of construction based on the design loads and resulting stresses of the system.For example, the plates, pads and / or shoes can each be selected from iron, steel, aluminum and stainless steel alloys, plastics (in various structural grades), fiber or bead reinforced plastics or composite materials (e.g., carbon fiber, fiberglass or aramid fiber). The lower half cylinder 1505 can be made from any of the aforementioned materials, as well as some typically lower strength plastics, such as polycarbonate, high density polyethylene, acrylonitrile-butadiene-styrene, polyamide, polyethylene terephthalate, polypropylene, ultra-high molecular weight polyethylene, or similar materials in terms of the relatively uniform stress expected in the member. The half cylinder (1505) can be selected from a material that promotes low friction between it and the wrap (1803) at the interface (1610). The half cylinder (1505) may be coated on the outside to further promote low friction at the interface (1610). A thin layer of polytetrafluoroethylene, etc., can be placed between the wrap (1803) and the half cylinder (1505) to promote low friction. The wrap (1803) may include holes or other features to facilitate the pre-compression means (1907) and (1908) and the screw (1817). All or most of the adjustable elements of the compression system (1901) may be packaged within the lower end unit (106), thereby saving space and providing tamper resistance for the installation of the electrolyzer stack (101). A scalable compression system for an electrolyzer stack may include a structural wrap configured to include a cell stack, an end unit, and one or more adjustable elements, the wrap may be configured to allow free access to two opposing sides of the cell stack, the wrap may be configured to function as a tensile element of the compression system, the wrap may be formed from a generally flat sheet of material having a generally uniform thickness, and the thickness of the wrap may be determined by the x-axis dimension of the cell stack and the maximum allowable operating pressure of the electrolyzer stack. The wrap thickness may be equal to or greater than the dimension of the cathode flow field along the x-axis multiplied by the ratio of the maximum allowable operating pressure of the electrolyzer to the tensile strength of the wrap material.The wrap may have a generally elliptical racetrack shape when viewed along the y-axis and may be configured to interface with the semi-cylindrical cell stack end units. The wrap and semi-cylindrical end units may be configured to slide relative to one another when the compression system is loaded. The diameter of the semi-cylindrical end units may be a dimension that is 100%-150% of the electrolysis cell dimension along the x-axis. The adjustable element of the compression system may be at least partially contained within one or both of the semi-cylindrical end units. The adjustable element may be configured to achieve a final dimension of the cell stack along the z-axis within ±25%. The wrap and semi-cylindrical end units may be configured to enable direct compression of the cell stack by a temporary stack assembly system mechanically parallel to the adjustable element. The wrap and semi-cylindrical end units may be configured to enable access to and manipulation of the adjustable element. The adjustable element may comprise one or more of a screw, a nut, a spring, a hydraulic cylinder, a pneumatic cylinder, a pressure pad, or a pressure shoe. The total amount of adjustable elements in the stack may be proportional to the number of water delivery windows provided in the cells that make up the cell stack. The wrap may be comprised of two parts connected as one of a hinge pin connection, a hem hook connection, or a hem hook connection with a fastener on each of the two flat sides of the wrap. The connection may be configured to allow the two wrap parts to be mated along the z-axis while pre-compressing the cell stack to complete the assembly of the wrap connection in the pre-compressed cell stack. The wrap may be configured to allow one or more cell stack alignment fixtures to penetrate the wrap boundary and contact one or more edges of the cell stack during assembly. The wrap may be configured to stretch along the z-axis by no more than 2% of the final length of the cell stack at the final cell stack compression load. The wrap may be configured to provide a spring constant along the z-axis of 0.1% to 25% of the spring constant of the cell stack at the target cell stack compression load.

[0105] FIG. 20 illustrates an embodiment of a basic step in a rapid manufacturing process (2001) for placing individual electrolysis cells (601) on a cell stack (1801) through freely accessible faces provided by the subject stack compression systems (2008) and (2009) and aligned as shown in the process (1701). The unitized electrolysis cell assembly (601) can be transported along the y-axis from the cell assembly process (1501). The cells (601) can be picked up by a robot and placed at position (2007) of the lower stack wrap assembly (2008) at the end of the belt (2005). Alternatively, the cells (601) can be moved directly to position (2007) along the y-axis by the conveyor belt (2005) without the need to pick and place each cell. It may be advantageous to align the z-axis of the stack wrap assembly (2008) at an angle to the gravity vector to allow gravity to assist the cell (601) in contacting the positioning reference points described in process (1701) throughout the stacking process. It may be advantageous to move the stack wrap assembly (2008) downward along the z-axis to facilitate either robotic or conveyor placement of the cell (601) from a fixed z-axis height of the belt (2005) to a position (2007). The stack conveyor and assembly system (2001) may be flexible to accommodate scalable cells in the active area as described herein, such that the belt (2005) does not need to change width (1303) to accommodate such different sized cells.

[0106] FIG. 21 shows an embodiment of a rotary table stack assembly station (2104) showing its placement at the end of a high speed line (2001). The stack station (2104) can be configured to allow multiple operators to perform operations simultaneously, thereby accelerating the throughput of finished stacks and allowing high speed manufacturing of both cells and stacks. For example, a full scale stack can contain 300 or more cells, and a manufacturing facility configured to manufacture 1,000 megawatts of electrolyzer stacks per year may need to process up to 1,000 or more such stacks and 300,000 or more corresponding cells annually. For one production shift running 1750 working hours per year, this production capacity requires a tack time of about 20 seconds per cell, which may define the required conveying speed of the cells (601) on the belt (2005). With 300 cells per stack, each stack station 1-4 on the rotary table 2104 may require up to 1.8 hours to complete its task. Stations 1-4 of the rotary table (2104) may include: 1) preparing and loading non-repeating stack members such as bottom lap and end units (1803 / 1505 / 1807) and top lap and end units (1804 / 1506 / 1808) in an assembly fixture provided on the table (2104); 2) cell placement and alignment as specified in the stack process (2001); 3) cell stack compression, leak check, and locking as specified in the process (1801 / 1901); and 4) stack finishing and unloading from the table (2104). These stations may be conveniently located on the rotary table at the end of the cell manufacturing line. These stations may be at 90 degree angles to each other, whereby the non-repeating station may be the first, the cell placement station may be the second, the cell stack compression and leak station may be the third, and the stack finishing and unloading station may be the last. Each station may include specific tools, fixtures, and equipment to facilitate the task.For example, the cell placement and alignment station may include one or more cell alignment rails along which individual cells may be positioned to ensure straight and accurate alignment along the z-axis, as identified in process (1710). The function of the rails may be facilitated by features such as holes and / or slots in the stack compression wrap (1603). The table may be controlled to rotate 90 degrees each time the last cell in the stack is placed and aligned at the second station. Some stations may require more labor hours than others, a single worker may perform duties at more than one station, or stations may be combined. For example, depending on the duration required for stations 1 and 4, these activities may be performed in series, reducing the number of stations to three at 120 degrees on the rotating table (2104) instead of four stations at 90 degrees. The cell assembly line (2001) may transport the cells (601) in a direction generally along the y-axis (2103). Such a conveyor can flexibly handle cells of various fields, since there are varying cell dimensions in the conveying direction (y-axis) for larger or smaller cells, and wider cell assembly belts, machines and handling devices are not required. At the end of the cell assembly line (2001), the rotating stack assembly station (2104) may be arranged to allow the stack compression system configured for different size cells to accept different quantities of cells, so that the system can manufacture electrolyzer stacks of variable active areas and variable cell numbers on the same line. The scalable compression system (1801), also based on a fixed roll web width "w" (1303), makes it possible to handle the assembly of stacks of cells of different areas, varying only the distance along the y-axis for the pick-and-place operation in step 2 on the table (2104). This system (2101) also allows production rates of more than 1,000 stacks per year. For example, an operator of the rotating table (2104) may need only 30 minutes to complete a task at stations 1-4.This could result in a four-fold increase in cell production rate, resulting in a tack time of approximately 5 seconds per cell and a corresponding increase in the speed along the y-axis of the belt (2005). Fast curing techniques such as UV curing could expedite such cycle times in manufacturing the bipolar plate assemblies (1206) and membrane gasket assemblies (1309), thereby enabling a single stack manufacturing line to manufacture up to 4,000 megawatt class stacks per year in a single shift. The integrated design and flexibility of the scalable cells, stacks and manufacturing process could protect the investment in such a line from premature obsolescence as technology improves and different size stacks may be required by sales. The manufacturing system described is also flexible with respect to electrolysis technology and can be configured to manufacture PEM or AEM type cells and stacks. A method for manufacturing a scalable electrolytic cell stack can include placing a lower wrap element and an end unit assembly in a stack fixture, placing an upper wrap element and an end unit assembly in a stack fixture, aligning a freely accessible surface of the lower wrap in the direction of piece flow in a manufacturing line for manufacturing scalable electrolytic cells, placing individual cells on the lower wrap through the freely accessible surface, lowering the upper wrap and the end unit assembly along the z-axis to pre-compress the cell stack, engaging connecting elements of a wrap-style compression system to connect the lower wrap and the upper wrap into a unitary structure, further compressing the cell stack according to a desired compression profile, and locking the stack under a compressive load using adjustable elements of the compression system. The stack assembly can be accomplished using a rotary table at the end of the cell manufacturing line. The rotary table can include stations for loading non-repetitive members, placing and aligning cells, compressing the assembly, quality checking, and unloading the final stack. Cell alignment fixtures can be provided on at least two adjacent edges of the cell stack.The cells can be automatically moved from the end of the cell manufacturing line to the inside of the bottom wrap using one of a robotic placement, a linear motion actuator, or gravity. The cells can be moved directly through the freely accessible surface of the bottom wrap by the cell manufacturing line's conveyor system. The bottom wrap and end unit assembly can be moved downward along the z-axis after each cell is moved into position. The z-axis of the stack assembly can be angled with respect to the gravity vector such that cells placed within the bottom wrap are oriented by gravity toward cell alignment fixtures on one or more edges of the cell stack. Movable cell alignment actuators can be engaged on one or more edges of the cell stack such that cells placed within the bottom wrap are oriented toward cell alignment fixtures on one or more opposing edges of the cell stack.

[0107] FIG. 22 shows an embodiment of a rapid manufacturing system that combines the above-mentioned processes for the bipolar plate assembly (1201), membrane gasket assembly (1301), cathode electrode flow field assembly (1401h), anode electrode flow field assembly (1401x), scalable electrolysis cell assembly (1501), and scalable electrolysis cell stack assembly (1801). The system can be configured to synchronize the rate of each process to achieve a continuous flow of cells (601) to the process (2104). The rate-limiting step anywhere in the system may dictate the maximum rate at which the cells (601) and stack (1801) can be produced. For example, the curing of the hydrogen seal (705) and water seal (703) in the process (1201) may be the longest cycle time in the system (2201), taking 30 seconds. With this cycle time, only 210,000 cells can be produced per year in one production shift operating at 1750 labor hours per year. Alternatively, a curing method that reduces the cycle time to 5 seconds would allow over 1.2 million cells to be manufactured in the same single shift, assuming that the seal cure remains the rate limiting process in the system (2201). For example, simultaneous UV curing of both the hydrogen (705) and water (703) seals as shown in step (1206) of process (1201) can comprise cycle times of 30 seconds, 20 seconds, 10 seconds, 5 seconds or less. If process (1201) comprises a 30 second cycle time instead of a 5 second cycle time, six parallel lines of process (1201) may be required to achieve the same single shift capacity, which would require six times the cost for equipment and production space and may significantly impact the cost of the electrolyzer stack (101). This system (2201) can manufacture PEM electrolyzers as long as the PEM components and materials are put into processes (1201), (1301) and (1401). This system is capable of manufacturing AEM electrolyzers as long as the AEM components and materials are put into the process (1201), (1301) and (1401).

[0108] Figures 24a, 24b, 24c, and 24d show an alternative embodiment of a compression system 1901. The compression system (2401) comprises one semi-cylindrical end unit (2404) and one end block (2405), and may connect wrap elements (2403) using cross pins (2409) passing through holes (2408), as shown in detailed figure 24d. Multiple sets of holes (2408) may be provided in the wrap (2403) to facilitate compression of stacks of different heights or different numbers of cells using the same compression hardware. Slots (2406) and (2407) may be provided in the wrap (2403) to facilitate alignment of the internal stack members during assembly and compression using shoulder bolts (2406) or similar means (either temporary or permanent). Internal members similar to those shown in Figure 19 are labeled with the same identification numbers on Figure 24b for clarity. As shown in FIG. 24c, the wrap (2403) may comprise one or more independent layers of material wrapped around a semi-cylindrical end unit (2404). These layers may be formed by plastically bending the layers prior to assembly or by elastically bending the layers during assembly. Elastic bending of the layers during assembly may have the manufacturing advantage that each layer of the wrap (2403) may be manufactured from a single two-dimensional cut pattern without considering bending tolerances, thereby simplifying construction and reducing costs. Additionally, plastically deformed materials may exhibit different stress / strain relationships compared to elastically deformed materials, which may affect the forces applied to the cell stack. For larger active area cell stacks (105), the wrap (2403) may be expanded along the y-axis without the need to change thickness or number of layers. Similarly, the end units (2404) may be expanded along the y-axis to accommodate large area cells according to the scalable cells described herein. The end units (2405) may be expanded along the y-axis or may be made from modular units whose amounts vary along the y-axis to accommodate larger area cells.Other design and fabrication features of the wrap (2403), end unit (2404) and end unit (2405) remain unchanged for such large area cells, thereby simplifying design and manufacturing and reducing costs by reusing parts for multiple stack products.

[0109] FIG. 25 shows measured strength data (2561) for several samples of candidate flow field materials, showing the permanent change in thickness (2509) as a function of mechanical exposure stress (2514). Representative samples were exposed to various levels of mechanical stress and the unloaded thickness was measured after each level, resulting in the curve shown in FIG. 25. This curve then represents the material yield strength as a function of the calendared thickness. During assembly of the electrolysis stack, a compressive load is applied to the active area to maintain good contact and low contact resistance between layers in the cells and between individual cells in the stack. The compressive load applied during assembly can be greater than the expected internal fluid pressure of the stack to ensure that the cells or cell members do not separate during operation. To ensure that this contact is maintained, it is desirable to maintain the elastic behavior of the cells and cell members during assembly and operation. As indicated by limits (2534) and (2535), it may then be advantageous to calendar the flow field material to a value less than X% of its initial thickness during fabrication of the flow field (e.g., during calendaring and / or lamination) to ensure that the material remains elastic during stack assembly and operation. For the candidate materials tested, x=40%, however, the specific value for any candidate flow field material may be greater or less than 40% based on the specific characteristics and material properties of the candidate, including porosity, basis weight (defined as mass per unit area in the xy plane), material of construction, and porous shape (e.g., foam, mesh, expanded metal, felt, or other).

[0110] FIG. 26 shows a preferred embodiment of a complete megawatt-class electrolysis stack (2601) including the inventive elements disclosed herein. The stack of scalable cells (105) including scalable membranes, electrodes, flow fields, seals, frames and bipolar plates are designed and fabricated as previously disclosed and are housed and compressed within the wraps (2403) and end blocks (2605a and 2605b) using cross pins (2409) to hold the wraps and end blocks together. In the illustrated megawatt-class stack, up to 400 such cells with 8 water flow windows may be preferred to achieve a water flow velocity of less than 20 cm / s and a cell pitch of 1.6 mm with a pressure drop of less than 2 bard and a temperature rise of less than 20° C., as shown. It may be preferred to construct the cathode flow field from stainless steel wire mesh and the anode flow field from multiple (2 or 3) nickel foam layers laminated and calendered to thickness. It may be preferred to reinforce the electrodes with calendared nickel foam. The stack may include one or more end blocks (2605b) depending on the selected cell length along the y-axis. In the illustrated megawatt class stack, two end blocks (2605a) and four end blocks (2605b) may be preferred. Each end block (2605b) may include an adjustable element as described in Figs. 19 and 24 to apply final compression to the stack unit after assembly as described in process (1801) of Fig. 18a. The wrap (2403) may be constructed of one or more layers, with more layers being preferred as the width of the selected cell along the x-axis increases as described for Figs. 17a (variable "h") and 24. For the illustrated megawatt class stack, the total number of layers may be three or four depending on the strength of the material used for each layer, the x-axis dimension of the cell stack, and the maximum allowable operating pressure of the electrolyzer stack.For the illustrated megawatt class stack operating with hydrogen MAWP up to 30 barg, three layers of fully hard 304 stainless steel with a yield strength of 140 ksi and a thickness of 0.5 mm for each layer may be preferred, which can meet the requirement that the total thickness "h" is equal to or greater than the x-axis dimension of the cathode flow field of the cell multiplied by the ratio of the MAWP to the yield strength of the wrap material. The total number of cross pins (2409) may be proportional to the total number of end blocks (2605a and 2605b). Slots (2406 and 2407) are shown to facilitate alignment, guiding and attachment of the manifolds (1904 and 2604) during assembly. Slots (2407) also facilitate accurate restraint assembly and can serve the function of the "gap (108)" described in FIG. 17b. Also shown is an exemplary lifting system (2603) integrated into the wrap (2403) and crown (2404) to facilitate lifting and movement of the stack after final assembly. This system may consist of a crossbar located at the top of the crown (2404) in the wrap (2403) with a threaded hole to accept a standard lifting eye or swivel (2603) as shown. Two such swivels may be preferred for the megawatt class stack shown in FIG.

[0111] Further embodiments:

[0112] A-1. an electrolysis cell comprising a membrane, an anode electrode, a cathode electrode, an anode flow field, a cathode flow field, and a bipolar plate assembly; where the bipolar plate assembly comprises a plurality of repeating water delivery windows disposed adjacent a leading edge of the anode flow field aligned with a y-axis, each water delivery window being associated with a window length along the y-axis of the anode flow field; and where the electrolysis cell is configured such that the number of water delivery windows, effective diameter or window length are selected to maintain water flow resistance, water temperature rise, or cell outlet oxygen volume fraction below target thresholds for the electrolysis cell.

[0113] A-2. The electrolytic cell of A-1, wherein the bipolar plate assembly includes one or more oxygen collecting windows and hydrogen collecting windows, and the total number of water delivery windows and oxygen collecting windows is equal to or greater than the number of hydrogen collecting windows.

[0114] A-3. The electrolytic cell of A-1, wherein the effective diameter of each water delivery window is between 5% and 110% of its associated window length.

[0115] A-4. An electrolysis cell as described in A-1, wherein the dimension of the anode flow field along the x-axis perpendicular to the leading edge of the anode flow field is the same for each water delivery window.

[0116] A-5. An electrolysis cell as described in A-1, wherein the window length associated with each water delivery window is selected based on the thickness of the anode flow field to (a) maintain an average water velocity at the leading edge of the anode flow field of less than 100 cm / s at rated hydrogen production power, or (b) maintain a water pressure drop of less than 5 bar difference at rated hydrogen production power.

[0117] A-6. The electrolysis cell of A-1, wherein the electrolysis cell is configured to use a water stoichiometry selected to maintain a cell temperature rise at the end of life below 50° C. or to maintain an oxygen volume fraction at the trailing edge of the anode flow field below 95%.

[0118] A-7. The electrolysis cell of A-1, wherein the cathode flow field is oriented such that the hydrogen flow velocity vector within the cathode flow field is generally parallel to the leading edge of the anode flow field.

[0119] A-8. The electrolysis cell of A-1, wherein the bipolar plate assembly comprises a bipolar plate and a fluid distribution frame, and a central region of the bipolar plate assembly is at least partially bounded by the fluid distribution frame and the two bipolar plates and includes at least one of a cathode flow field, a cathode electrode, the membrane, an anode electrode or an anode flow field.

[0120] A-9. The electrolysis cell of A-8, further comprising a water seal disposed between the frame and the bipolar plate adjacent the anode flow field.

[0121] A-10. The electrolysis cell of A-9, wherein at least one of the fluid distribution frame or the water seal is configured to allow spreading of water flow in the xy plane from one or more water delivery windows to the leading edge of the anode flow field, thereby providing a leading edge water velocity distribution within ±50% of the average velocity of the anode flow field.

[0122] A-11. The electrolysis cell of A-9, wherein at least one of the fluid distribution frame or the water seal is configured to collect water and oxygen flows from the trailing edge of the anode flow field and imposes no more than ±50% variation in the trailing edge velocity distribution for the anode flow field.

[0123] A-12. The electrolysis cell of A-8, further comprising a hydrogen seal disposed between the fluid distribution frame and the bipolar plate adjacent the cathode flow field.

[0124] A-13. An electrolytic cell as described in A-8, wherein the fluid distribution frame comprises a visible light transmissive material or an ultraviolet light transmissive material.

[0125] A-14. The electrolysis cell of A-8, wherein the bipolar plate assembly is configured to collect hydrogen flow from one or more trailing edges of the cathode flow field and deliver said flow to one or more hydrogen collection windows.

[0126] A-15. The electrolysis cell of A-8, wherein the fluid distribution frame is configured to mate with an internal seal between the anode flow field and the cathode flow field, and the internal seal is applied to at least one of the membrane, the catalyst coated membrane, the electrode, a subgasket boundary of the membrane-electrode assembly, or the fluid distribution frame itself.

[0127] A-16. a water seal disposed between the frame and the bipolar plate adjacent the anode flow field; a hydrogen seal disposed between the fluid distribution frame and the bipolar plate adjacent the cathode flow field; An electrolysis cell as described in A-8, wherein the fluid distribution frame, water seal and hydrogen seal are positioned such that, in a projected view along the z-axis, the unsupported seal area is less than 50%.

[0128] A-17. The electrolytic cell of A-1, wherein the anode flow field is greater than the cathode flow field, the anode flow field facilitating application of a compressive load to the internal seal.

[0129] A-18. The electrolytic cell of A-1, wherein the bipolar plate assembly includes a bipolar plate, the bipolar plate comprising a material selected from the group consisting of stainless steel, titanium, nickel, carbon, chromium, iron and alloys thereof.

[0130] A-19. The electrolytic cell of A-5, having a compressed cell pitch of 5.0 mm or less, 3.0 mm or less, or 2.0 mm or less.

[0131] A-20. The electrolytic cell of A-1, wherein at least one of the anode flow field or the cathode flow field comprises at least one of a foam, a felt, a woven screen, an expanded metal, or a sintered metal frit.

[0132] A-21. An electrolytic cell as described in A-1, wherein the cathode flow field comprises geometric features that protrude into the bipolar plate along a z-axis perpendicular to the y-axis and x-axis.

[0133] B-1. 1. A method of manufacturing a bipolar plate assembly for an electrolysis cell, comprising the steps of: Selecting materials for the bipolar plates, hydrogen seals, water seals, and fluid distribution frame; Applying a hydrogen seal to a bipolar plate or fluid distribution frame; aligning the fluid distribution frame against the bipolar plate and compressing the fluid distribution frame to fit a hydrogen seal therebetween; applying a water seal to the fluid distribution frame; and curing at least one of the hydrogen seal or the water seal using an ultraviolet cure method, a microwave cure method, a thermal cure method, a solvent cure method, a two-part epoxy cure method, or a moisture cure method; A method of manufacturing a semiconductor device, comprising: The bipolar plates, hydrogen seals, water seals and fluid distribution frames contain two-dimensional patterns suitable for manufacturing using stamping, laser cutting, water jet cutting, robotic dispensing and / or screen printing methods.

[0134] B-2. The method according to B-1, wherein both the hydrogen seal and the water seal are cured simultaneously.

[0135] B-3. The method of claim B-1, wherein the water seal is formed during manufacture of the fluid distribution frame and prior to mating with the hydrogen seal.

[0136] B-4. The method of B-1, wherein the fluid distribution frame is pressed together with the bipolar plate with sufficient force to ensure that a continuous, unbreakable seal is formed between the bipolar plate and the fluid distribution frame.

[0137] B-5. The method of B-1, wherein the fluid distribution frame is pressed together with the bipolar plates to achieve a target thickness of the bipolar plate assembly that varies by no more than ±25%.

[0138] B-6. The method of B-5, wherein the hydrogen seal is reinforced with one of a wire mesh, an open cell foam, an expanded metal sheet, or a sintered metal frit.

[0139] B-7. The method of claim B-1, wherein the hydrogen seal or water seal is applied using a screen or stencil printing process, and at least one of the hydrogen seal or water seal is applied in an uncured state having a thickness of 10 to 1000 μm and a width of 0.5 to 15 mm.

[0140] C-1. 1. A compression system for an electrolyzer cell stack, comprising: a structural wrap including one or more wrap layers circumferentially surrounding at least a portion of an electrolyzer cell stack including a plurality of cells; end units at opposite ends of the electrolyzer cell stack; one or more adjustable elements proximate to one or more end units; A compression system comprising: The structural wrap allows free access to opposite sides of the cell stack; The structural wrap acts as the tension element in the compression system, The one or more wrap layers are substantially flat sheets of material having an essentially uniform thickness; The total thickness of the one or more wrap layers is determined by the x-axis dimension of the cell stack and the maximum allowable operating pressure of the electrolyzer cell stack.

[0141] C-2. A compression system as described in C-1, wherein the total wrap thickness is greater than or equal to the dimension along the x-axis of the cathode flow field of the cells in the cell stack multiplied by the ratio of the maximum allowable operating pressure of the electrolytic cell to the tensile strength of the wrap material.

[0142] C-3. A compression system as described in C-1, wherein the wrap has a generally elliptical racetrack shape when viewed along the y-axis and is configured to connect with the end units, and one or more of the end units have a semi-cylindrical shape when viewed along the y-axis.

[0143] C-4. The compression system of C-3, wherein the wrap is configured to slide against the one or more semi-cylindrical end units when the compression system is loaded.

[0144] C-5. The compression system of C-3, wherein a diameter of the one or more semi-cylindrical end units is between 100% and 150% of a dimension of the electrolytic cell along the x-axis.

[0145] C-6. A compression system as described in C-3, wherein the adjustable element of the compression system is at least partially contained within one or both of the end units.

[0146] C-7. The compression system of C-6, wherein the adjustable element is configured to achieve a final dimension of the cell stack along the z-axis within ±25%.

[0147] C-8. The compression system of C-6, wherein at least one of the wrap and end units is configured to enable direct compression of the cell stack by a temporary stack assembly system mechanically parallel to the adjustable element.

[0148] C-9. The compression system of C-6, wherein at least one of the wrap and the end unit is configured to allow access to and operation of the adjustable element.

[0149] C-10. The compression system of C-6, wherein the adjustable element comprises one or more of a screw, a nut, a spring, a hydraulic cylinder, a pneumatic cylinder, a pressure pad, or a pressure shoe.

[0150] C-11. A compression system as described in C-3, wherein the total amount of adjustable elements in the stack is proportional to the number of water delivery windows provided in the cells that make up the cell stack.

[0151] C-12. the wrap comprises one or more components connected to continuously enclose the cell stack on each of two flat sides of the wrap using one or more of a cross pin connection, a hinge pin connection, a hem hook connection, or a fastener-equipped hem hook connection; or the wrap is comprised of one or more layers of flexible sheet material that includes one semi-cylindrical end unit and is configured to mate and connect with a second end unit with one or more cross pins; or A compression system as described in C-1, wherein one or more layers of the wrap are constructed from a material of sufficient yield strength and thickness to remain elastic when encasing one or more end units.

[0152] C-13. A compression system as described in C-12, wherein the connection is configured to allow the wraps to be fitted along the z-axis while pre-compressing the cell stack to complete assembly of the wrap connections in the pre-compressed cell stack.

[0153] C-14a. A compression system as described in C-1, wherein the cell stack comprises cells having a hexagonal shape that allows for fully constrained alignment fixation from the open end of the wrap.

[0154] C-14b. A compression system as described in C-1, wherein the wrap is configured to allow one or more cell stack alignment fixtures to penetrate the wrap boundary and contact one or more edges of the cell stack during assembly.

[0155] C-15. The compression system of C-1, wherein the wrap is configured to stretch along the z-axis no more than 2% of the final length of the cell stack at the final cell stack compression load.

[0156] C-16. The compression system of C-1, wherein the wrap is configured to provide a spring constant along the z-axis that is between 0.1% and 25% of the spring constant of the cell stack at the target cell stack compression load.

[0157] D-1. An electrolyzer stack comprising a plurality of electrolysis cells aligned along the z-axis in a stacked configuration, where: Each cell includes a membrane, an anode electrode, a cathode electrode, an anode flow field, a cathode flow field, and a bipolar plate assembly; adjacent bipolar plate assemblies at least partially bound one or more water delivery plenums disposed along edges of the anode flow field; Each water delivery plenum is sized to maintain a water velocity through the plenum along the z-axis below a target threshold; Each water delivery plenum is associated with a length along the y-axis of the anode flow field; The number or size of the water delivery plenums is configured to maintain one of the water flow resistance or water temperature rise or cell outlet oxygen volume fraction below a target threshold for the electrolyzer stack.

[0158] D-2. The stack of D-1, further comprising an oxygen delivery plenum and a hydrogen collection plenum, the total number of water delivery plenums and oxygen collection plenums being greater than or equal to the number of hydrogen collection plenums.

[0159] D-3. The stack of D-2 further comprises end units at opposing ends of the stacked configuration of the electrolytic cell, a scalable structural wrap compression system, and at least one fluid manifold included in one of the end units, the fluid manifold facilitating delivery of water to the stack along the y-axis through a freely accessible face of the compression system.

[0160] D-4. A stack as described in D-3, wherein the fluid manifold is positioned at the top end of the stacked configuration of electrolytic cells with respect to a gravity vector along the z-axis.

[0161] D-5. The stack of D-3 further comprises a drain manifold or purge manifold disposed at a lower end of the stack of electrolytic cells relative to a gravity vector along the z-axis.

[0162] D-6. A stack as described in D-3, wherein the sizes of the water flow ports and manifolds connecting the individual cell stack plenums are selected to provide flow distribution to the individual plenums that varies by less than ±25%.

[0163] E-1. placing the lower wrap element and end unit assembly into a stack fixture; placing the upper wrap element and end unit assembly into a stack fixture; aligning the freely accessible surface of the lower lap in a direction of piece flow in a production line for producing the scalable electrolysis cell; placing individual cells in the lower lap through a freely accessible surface; lowering the upper wrap and end unit assembly along the z-axis to pre-compress the cell stack; mating connecting elements of a wrap-style compression system to connect the lower wrap and the upper wrap to a unitary structure; further compressing the cell stack according to a desired compression profile; and locking the stack under compressive load using an adjustable element of the compression system; A method for manufacturing an electrolyzer stack comprising:

[0164] E-2. The method according to E-1, wherein stack assembly is accomplished using a rotary table at the end of the cell manufacturing line.

[0165] E-3. The method of E-2, wherein the rotary table includes stations for loading non-repeating members, placing and aligning cells, compressing the assembly, quality checking, and unloading the final stack.

[0166] E-4. The method of claim E-1, wherein cell alignment fixtures are provided on at least two adjacent edges of the cell stack.

[0167] E-5. The method of claim E-1, wherein the cells are automatically moved from the end of the cell production line to the inside of the lower wrap using one of a robotic placement, a linear motion actuator, or gravity.

[0168] E-6. The method according to E-1, wherein the cells are moved directly through the freely accessible surface of the lower wrap by a conveyor system of the cell production line.

[0169] E-7. The method of claim E-1, wherein the lower wrap and end unit assembly is moved downward along the z-axis after each cell is moved into position.

[0170] E-8. The method described in E-1, wherein the z-axis of the stack assembly is angled with respect to the gravity vector such that cells positioned in the lower wrap are oriented by gravity toward cell alignment fixtures on one or more edges of the cell stack.

[0171] E-9. The method described in E-1, wherein a movable cell alignment actuator is engaged on one or more edges of the cell stack such that cells disposed within the lower wrap are oriented toward cell alignment fixtures on one or more opposing edges of the cell stack.

[0172] F-1. selecting a roll of material of a desired roll web width along the x-axis for use as a membrane or catalyst coating membrane; directing the web of the roll through a seal applicator along a y axis; applying an uncured interior seal to one side of the web using one of a screen printing method, a stencil printing method or a robotic dispensing method; curing the applied internal seal using either UV cure, microwave cure, heat cure, solvent cure, two-part epoxy cure or moisture cure; Cutting the roll of membrane gasket assemblies or catalyst coated membrane gasket assemblies into separate pieces; and conveying the resulting individual piece to a cell assembly machine; 23. A method for making an internal seal for an electrolysis cell, comprising:

[0173] F-2. The method according to F-1, wherein the web material is an acidic proton conducting membrane.

[0174] F-3. The method according to F-1, wherein the web material is an alkaline hydroxide conductive type membrane.

[0175] F-4. The method of F-1, wherein the web material is selected from one of a one-side continuous coated CCM or a one-side patch coated CCM.

[0176] F-5. The method of F-4, wherein an internal seal is applied to the cathode side of the web.

[0177] G-1. selecting an electrode substrate of a desired roll web width along the x-axis from one of foam, felt, woven screening, expanded metal, or sintered metal frit; selecting one or more flow field substrates of a desired roll web width along the x-axis from one of foam, felt, woven screening, expanded metal, or sintered metal frit; directing the electrode substrate web along a y-axis through a calendering roller configured to achieve a desired thickness and surface characteristics on each side of the electrode substrate; Converting the electrode substrate into an active electrode; orienting one or more flow field substrate webs adjacent to the electrode substrate web along the y-axis through the lamination process to bond the electrodes and flow fields together; cutting the laminated electrode flow field roll into individual pieces; and conveying the resulting individual piece to a cell assembly machine; A method for making an integrated electrode flow field for an electrolysis cell, comprising:

[0178] G-2. The method of G-1, wherein the electrode substrate and the flow field substrate each independently comprise at least one of carbon, nickel, titanium, iron, chromium, stainless steel or Inconel, or mixtures or alloys thereof.

[0179] G-3. The method of G-1, wherein one or more of the electrode web and the flow field web are provided with a roughened, patterned, or embossed surface to facilitate lamination.

[0180] G-4. The method of claim G-1, wherein the lamination step includes a bond promoter selected from one of an adhesive, a polymer dispersion, a liquid ionomer solution, or an ionomer dispersion.

[0181] G-5. The method of G-1, wherein the electrode flow field web comprises a foam electrode and a woven screen flow field after lamination.

[0182] G-6. The method according to G-1, wherein the electrode conversion is performed before lamination.

[0183] G-7. The method according to G-1, wherein the electrode conversion is performed after lamination.

[0184] G-8. The method of G-1, wherein the flow field porosity, basis weight, number of layers and final laminate thickness are selected to prevent yielding during assembly, compression and operation of the cell.

[0185] G-9. The method of G-1, wherein the active electrode comprises one or more binders selected from a liquid ionomer solution, an ionomer dispersion, and an inert polymer. [Explanation of symbols]

[0186] 101 Electrolyzer Stack 103 Lower Wrap 104 Top Wrap 105 Cell Stack 107 Upper end unit 106 Lower end unit 109 Joint 301 Core electrolysis cell components 303 Anode flow field 304 Ion Conductive Membrane 305 Cathode Flow Field 306 Anode Electrode 307 Cathode Electrode 308 Bipolar Plate 403 Anode flow field 405 Cathode Flow Field 601 Cell 603 Water Delivery Window 604 Water Collection Window 606 Hydrogen Collection Window 610 Contour Area 611 Active region 701 Bipolar Plate Assembly 703 Water Seal 704 Fluid Distribution Frame 705 Hydrogen Seal 713 Internal Seal 714 Steps 732 Porous Sheet

Claims

1. An electrolysis cell including a membrane, an anode electrode, a cathode electrode, an anode flow field, a cathode flow field, and a bipolar plate assembly: wherein the bipolar plate assembly comprises a plurality of repeating water delivery windows disposed adjacent a leading edge of the anode flow field aligned with the y-axis; Each water delivery window is associated with a window length along the y-axis of the anode flow field; The electrolysis cell is configured such that the number of water delivery windows, effective diameter or window length are selected to maintain water flow resistance, water temperature rise, or cell outlet oxygen volume fraction below target thresholds for the electrolysis cell.

2. the bipolar plate assembly includes one or more oxygen and hydrogen collecting windows; 10. The electrolysis cell of claim 1, wherein the total number of water delivery windows and oxygen collection windows is equal to or greater than the number of hydrogen collection windows.

3. 10. The electrolysis cell of claim 1, wherein the effective diameter of each water delivery window is between 5% and 110% of its associated window length.

4. 2. The electrolysis cell of claim 1, wherein a dimension of the anode flow field along an x-axis perpendicular to a leading edge of the anode flow field is the same for each water delivery window.

5. 2. The electrolysis cell of claim 1, wherein the window length associated with each water delivery window is selected based on the thickness of the anode flow field to (a) maintain an average water velocity at the leading edge of the anode flow field of less than 100 cm / s at rated hydrogen production power, or (b) maintain a water pressure drop of less than 5 bar differential at rated hydrogen production power.

6. 2. The electrolysis cell of claim 1, wherein the electrolysis cell is configured to use a water stoichiometry selected to maintain an end of life cell temperature rise below 50° C. or to maintain an oxygen volume fraction at the trailing edge of the anode flow field below 95%.

7. 10. The electrolysis cell of claim 1, wherein the cathode flow field is oriented such that the hydrogen flow velocity vector within the cathode flow field is generally parallel to the leading edge of the anode flow field.

8. a bipolar plate assembly comprising a bipolar plate and a fluid distribution frame; 2. The electrolysis cell of claim 1, wherein a central region of the bipolar plate assembly is at least partially bounded by the fluid distribution frame and the two bipolar plates and contains at least one of a cathode flow field, a cathode electrode, the membrane, an anode electrode or an anode flow field.

9. 10. The electrolysis cell of claim 8 further comprising a water seal disposed between the frame and the bipolar plate adjacent the anode flow field.

10. 10. The electrolysis cell of claim 9, wherein at least one of the fluid distribution frame or the water seal is configured to permit spreading of water flow in the x-y plane from the one or more water delivery windows to the leading edge of the anode flow field, thereby providing a leading edge water velocity distribution within ±50% of the average velocity of the anode flow field.

11. 10. The electrolysis cell of claim 9, wherein at least one of the fluid distribution frame or the water seal is configured to collect water and oxygen flows from the trailing edge of the anode flow field and imposes no more than ±50% variation in the trailing edge velocity distribution for the anode flow field.

12. 10. The electrolysis cell of claim 8 further comprising a hydrogen seal disposed between the fluid distribution frame and the bipolar plate adjacent the cathode flow field.

13. 10. The electrolysis cell of claim 8, wherein the fluid distribution frame comprises a visible light transmissive material or an ultraviolet light transmissive material.

14. 10. The electrolysis cell of claim 8, wherein the bipolar plate assembly is configured to collect hydrogen flow from one or more trailing edges of the cathode flow field and deliver said flow to one or more hydrogen collection windows.

15. a fluid distribution frame configured to mate with an internal seal between the anode and cathode flow fields; 9. The electrolysis cell of claim 8, wherein the internal seal is applied to at least one of the membrane, the catalyst coated membrane, the electrodes, the subgasket interface of the membrane-electrode assembly, or the fluid distribution frame itself.

16. a water seal disposed between the frame and the bipolar plate adjacent the anode flow field; a hydrogen seal disposed between the fluid distribution frame and the bipolar plate adjacent the cathode flow field; 9. The electrolysis cell of claim 8, wherein the fluid distribution frame, water seal and hydrogen seal are positioned such that, in a projected view along the z-axis, less than 50% of the seal area is unsupported.

17. 10. The electrolysis cell of claim 1, wherein the anode flow field is greater than the cathode flow field, the anode flow field facilitating application of a compressive load to the internal seal.

18. 10. The electrolysis cell of claim 1, wherein the bipolar plate assembly comprises a bipolar plate, the bipolar plate comprising a material selected from the group consisting of stainless steel, titanium, nickel, carbon, chromium, iron and alloys thereof.

19. 6. The electrolysis cell of claim 5 having a compressed cell pitch of 5.0 mm or less, 3.0 mm or less, or 2.0 mm or less.

20. 10. The electrolysis cell of claim 1, wherein at least one of the anode flow field or the cathode flow field comprises at least one of a foam, a felt, a woven screen, an expanded metal, or a sintered metal frit.

21. 10. The electrolysis cell of claim 1, wherein the cathode flow field comprises geometric features that protrude into the bipolar plate along a z-axis perpendicular to the y-axis and x-axis.

22. 1. A method of manufacturing a bipolar plate assembly for an electrolysis cell, comprising the steps of: Selecting materials for the bipolar plates, hydrogen seals, water seals, and fluid distribution frame; Applying a hydrogen seal to a bipolar plate or fluid distribution frame; aligning the fluid distribution frame against the bipolar plate and compressing the fluid distribution frame to fit a hydrogen seal therebetween; applying a water seal to the fluid distribution frame; and curing at least one of the hydrogen seal or the water seal using an ultraviolet cure method, a microwave cure method, a thermal cure method, a solvent cure method, a two-part epoxy cure method, or a moisture cure method; A method of making a compound comprising: The bipolar plates, hydrogen seals, water seals and fluid distribution frames contain two-dimensional patterns suitable for manufacturing using stamping, laser cutting, water jet cutting, robotic dispensing, and / or screen printing methods.

23. 23. The method of claim 22, wherein both the hydrogen seal and the water seal are cured simultaneously.

24. The method of claim 22 , wherein the water seal is formed during manufacture of the fluid distribution frame and prior to mating with the hydrogen seal.

25. 23. The method of claim 22, wherein the fluid distribution frame is pressed together with the bipolar plate with sufficient force to ensure that a continuous, unbroken seal is formed between the bipolar plate and the fluid distribution frame.

26. 23. The method of claim 22, wherein the fluid distribution frame is pressed together with the bipolar plates to achieve a target thickness for the bipolar plate assembly that varies by no more than ±25%.

27. 27. The method of claim 26, wherein the hydrogen seal is reinforced with one of a wire mesh, an open cell foam, an expanded metal sheet, or a sintered metal frit.

28. 23. The method of claim 22, wherein the hydrogen seal or water seal is applied using a robotic dispensing or a screen or stencil printing process, and at least one of the hydrogen seal or water seal is applied in an uncured state having a thickness of 10-1000 μm and a width of 0.5-15 mm.

29. 1. A compression system for an electrolyzer cell stack, comprising: a structural wrap including one or more wrap layers circumferentially surrounding at least a portion of an electrolyzer cell stack including a plurality of cells; end units at opposite ends of the electrolyzer cell stack; one or more adjustable elements proximate to one or more end units; A compression system comprising: The structural wrap allows free access to opposite sides of the cell stack; The structural wrap acts as the tension element in the compression system, The one or more wrap layers are substantially flat sheets of material having an essentially uniform thickness; The total thickness of the one or more wrap layers is determined by the x-axis dimension of the cell stack and the maximum allowable operating pressure of the electrolyzer cell stack.

30. An electrolyser stack comprising a plurality of electrolysis cells aligned along the z-axis in a stacked configuration, Each cell includes a membrane, an anode electrode, a cathode electrode, an anode flow field, a cathode flow field, and a bipolar plate assembly; adjacent bipolar plate assemblies at least partially bound one or more water delivery plenums disposed along edges of the anode flow field; Each water delivery plenum is sized to maintain a water velocity through the plenum along the z-axis below a target threshold; Each water delivery plenum is associated with a length along the y-axis of the anode flow field; The number or size of the water delivery plenums is configured to maintain one of the water flow resistance or water temperature rise or cell outlet oxygen volume fraction below a target threshold for the electrolyzer stack.

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