Patent Application
20240279819
The present invention relates generally to electrolyzer systems, and more particularly to novel end plate assemblies for one or more electrolyzer stacks of an electrolyzer system.
The drive for renewable energy solutions has resulted in substantial investments into water electrolysis or electrolyzer technologies. It is estimated that the electrolyzer market could increase to 300 GW over the next few decades, and power-to-gas is poised to become a multi-billion dollar market for on-site electrolyzer systems. Electrolyzers use DC electricity to split water into hydrogen and oxygen. As one example, a proton electron membrane (PEM) electrolysis cell is a device which produces hydrogen and oxygen gas using DC electricity to electrochemically split water. A PEM cell contains an active area in which the presence of catalyst permits the reactions to take place. In the electrolysis cell, water enters the anode and is split into protons, electrons, and oxygen gas. The protons are conducted through the membrane, while the electrons pass through the electrical circuit. At the cathode, the protons and electrons recombine to form hydrogen gas.
Often, a number of electrolysis cells are assembled together in order to meet production requirements. One common type of assembly is a stack which includes a plurality of stacked electrolysis cells that are electrically connected in-series, such as in a bipolar configuration.
Certain shortcomings of the prior art are overcome, and additional advantages are provided herein through the provision of an electrolyzer system which includes a stack of at least one electrolyzer cell, for instance, for generating hydrogen from water. The stack includes a current collector of the at least one electrolyzer cell, an end plate assembly, and an isolation plate. The isolation plate is positioned between the end plate assembly and the current collector to electrically isolate the current collector from the end plate assembly. The end plate assembly includes at least one fluid channel to allow fluid to pass through the end plate assembly, where the at least one fluid channel is in fluid communication with at least one fluid channel through the current collector and the isolation plate. The end plate assembly includes an end plate and a fluid-isolating insert residing, at least in part, within a pocket in the end plate. The fluid-isolating insert includes at least one electrically-isolating fluid channel that defines, at least in part, the at least one fluid channel of the end plate assembly, where the fluid-isolating insert increases an effective length of a fluid conduction path between the current collector and the end plate through the at least one fluid channel of the end plate assembly.
In one embodiment, the pocket in the end plate extends into the end plate from a surface of the end plate closest to the isolation plate. Further, in one or more implementations, a seal is disposed, in part, within a groove in one of the isolation plate or the fluid-isolating insert at an interface of the isolation plate and fluid-isolating insert within the stack.
In one or more embodiments, a gap exists in the pocket between the fluid-isolating insert and the end plate, and the fluid fills the gap between the fluid-isolating insert and the end plate, which facilitates pressure-balancing opposite sides of the seal.
In one or more other embodiments, a pressure-containment seal is disposed between the fluid-isolating insert and the end plate of the end plate assembly.
In one or more further embodiments, a conductive insert is disposed between the fluid-isolating insert and the end plate within the pocket, where the conductive insert defines, in part, the at least one fluid channel of the end plate assembly. In one implementation, the conductive insert includes a platinum material which causes a localized electrolysis reaction at the conductive insert within the at least one channel of the end plate assembly.
In a further embodiment, the end plate assembly includes a plurality of fluid channels and a manifold to allow the fluid to pass through the end plate assembly via the manifold of the end plate assembly. The plurality of fluid channels of the end plate assembly are in fluid communication with a plurality of fluid channels through the current collector and the isolation plate. The fluid-isolating insert includes a plurality of electrically-isolating fluid channels that define, at least in part, the plurality of fluid channels of the end plate assembly. The fluid-isolating insert increases effective length of fluid conduction paths between the current collector and the end plate through the plurality of fluid channels of the end plate assembly.
In one embodiment, the end plate facilitates supplying a clamping force to the electrolyzer stack, and the fluid-isolating insert satisfies pressure-containment restrictions within the electrolyzer stack.
In another embodiment, an end plate assembly for an electrolyzer stack is provided. The end plate assembly includes an end plate to facilitate supplying a clamping force the electrolyzer stack, and a fluid-isolating insert residing, at least in part, within a pocket in the end plate. The fluid-isolating insert includes at least one electrically-isolating fluid channel that defines, at least in part, at least one fluid channel of the end plate assembly, and the fluid-isolating insert increases an effective length of a fluid conduction path within the end plate assembly.
In a further embodiment, an end plate assembly for an electrolyzer stack is provided, which includes an end plate to facilitate supplying a clamping force to the electrolyzer stack, an anode-fluid-isolating insert, and a cathode-fluid-isolating insert. The anode-fluid-isolating insert resides, at least in part, within a pocket in the end plate, and includes at least one electrically-isolating anode fluid channel that defines, at least in part, at least one anode fluid channel of the end plate assembly, where the anode-fluid-isolating insert increases an effective length of an anode fluid conduction path within the end plate assembly. The cathode-fluid-isolating insert resides, at least in part, within another pocket in the end plate, and includes at least one electrically-isolating cathode fluid channel that defines, at least in part, at least one cathode fluid channel of the end plate assembly, where the cathode-fluid-isolating insert increases an effective length of a cathode fluid conduction path within the end plate assembly.
Additional features and advantages are realized through the techniques described herein. Other embodiments and aspects are described in detail herein and are considered a part of the claimed aspects.
One or more aspects are particularly pointed out and distinctly claimed as examples in the claims at the conclusion of the specification. The foregoing and objects, features, and advantages of one or more aspects are apparent from the following detailed description taken in conjunction with the accompanying drawings in which:
The accompanying figures, which are incorporated in and form a part of this specification, further illustrate the present invention and, together with this detailed description of the invention, serve to explain aspects of the present invention. Note in this regard that descriptions of well-known systems, devices, processing techniques, etc., are omitted so as to not unnecessarily obscure the invention in detail. It should be understood, however, that the detailed description and this specific example(s), while indicating aspects of the invention, are given by way of illustration only, and not limitation. Various substitutions, modifications, additions, and/or other arrangements, within the spirit or scope of the underlying inventive concepts will be apparent to those skilled in the art from this disclosure. Note further that numerous inventive aspects or features are disclosed herein, and unless inconsistent, each disclosed aspect or feature is combinable with any other disclosed aspect or feature as desired for a particular application of the concepts disclosed.
As discussed, the push for renewable energy sources and systems has driven substantial investments in water-electrolysis, or electrolyzer technologies. Electrolyzers use DC electricity to split water into hydrogen and oxygen. As an example, a proton electron membrane (PEM) electrolysis cell is a device which produces hydrogen and oxygen using DC electricity to electrochemically split water. A PEM cell contains an active area in which the presence of a catalyst permits the reactions to take place. In the electrolysis cell, water enters the anode and is split into protons, electrons, and oxygen gas. The protons are conducted through the membrane, while the electrons pass through the electrical circuit. At the cathode, the protons and electrons recombine to form hydrogen gas.
Depending on the implementations, a number of electrolysis cells can be assembled together in order to meet hydrogen or oxygen production requirements. One common type of assembly is a stack which includes a plurality of stacked electrolysis cells that are electrically connected in-series, for instance, in a bipolar configuration. The cells of an electrolysis stack are typically compressed between spring-loaded, upper and lower rigid end plates. In order to ensure optimal conversion of water to hydrogen and oxygen by each electrolysis cell in the stack, uniform current distribution across the active areas of the electrodes of each cell is desired. This uniform current distribution requires uniform contact pressure over the active areas of the electrode, which is facilitated by providing the spring-loaded compression between the upper and lower end plates of the stack.
Various sizes of electrolyzer stacks can be produced. For instance, in one embodiment, an electrolyzer stack can include up to 100 or more electrolysis cells arranged in-series in a bipolar configuration. Further, in one or more implementations, voltage across the electrolyzer stack can vary in operation between 200-300 volts, in one example. An electrolyzer system can be provided by connecting in-series multiple electrolyzer stacks and providing a common set of fluid supply and return manifolds to the stacks. For instance, with an electrolyzer system having 5 electrolyzer stacks connected in-series, the voltage across the individual stacks can range from 0 volts at starting to 1500 volts in operation, that is, in the noted 300 volt stack example. Further, depending on the implementation, the electrolyzer system can include one or more sets of series-connected electrolyzer stacks to generate a desired amount of hydrogen and/or oxygen. With such high-voltage electrolyzer systems, shunt-to-ground fluid currents through the anode and cathode ports of an electrolyzer stack within the system can potentially cause performance issues, as well as result in localized corrosion of stack components over time.
For instance, shunt currents through the anode and/or cathode ports can cause electrolyzer system performance and safety issues, as well as result in localized corrosion of electrolyzer stack components. Shunt current can be dependent on, for instance, water quality, port size, insulator plate thickness, and/or secondary fluid contaminants. The end plates are typically formed as rigid metal plate structures, such as stainless steel plates, which perform well when applying compressive pressure to the electrolyzer stack. One approach to reducing shunt currents through the anode and/or cathode ports of an electrolyzer stack is to increase thickness of the primary isolation plates or layers positioned adjacent to the upper and lower end plates. However, aside from increasing the overall height of the stack, this approach has inherent limits due to costs, material availability, and pressure-containment restrictions.
Disclosed herein, in one or more embodiments, are assemblies which significantly increase the effective isolation distance between, for instance, a collector plate and end plate in an electrolyzer stack, in order to increase effective length of a fluid-supported, electrical conduction path between the current collector and the end plate material (e.g., conductive material), and thereby, decrease shunt currents within the electrolyzer stack. These assemblies are especially significant for electrolyzer stacks placed in-series and operated at high voltage, such as in the case of the 1500 volt DC example noted.
In one or more embodiments, disclosed herein is an end plate assembly for an electrolyzer stack of an electrolyzer system to, for instance, generate hydrogen from water. The end plate assembly includes an end plate configured to facilitate supplying a clamping force to the electrolyzer stack, and a fluid-isolating insert residing, at least in part, within a pocket formed in the end plate. The fluid-isolating insert includes at least one electrically-isolating fluid channel that defines, at least in part, at least one fluid channel of the end plate assembly. The fluid-isolating insert is configured to increase an effective length of a fluid conduction path (i.e., a fluid-supported electrical conduction path) between, for instance, a current collector of the electrolyzer stack and the end plate. Advantageously, using one or more fluid-isolating inserts in association with the end plate to form an end plate assembly such as disclosed herein can increase the effective isolation length of fluid conduction paths within the end plate assembly by factors of, for instance, 4 to 8 times, or more, without high material costs or loss of pressure integrity.
By way of example,
In the depicted embodiment, end plate assembly 110 includes an end plate 120 and an anode-fluid-isolating insert 130 (or, more generally, a fluid-isolating insert). End plate 120 is formed of a metal (or metal alloy or other conductive material) and is configured with sufficient size and rigidity to facilitate applying and sustaining the desired clamping force to the electrolyzer stack, which as illustrated, can include a plurality of electrolyzer cells 101, with the number of electrolyzer cells being dependent on the desired electrolyzer stack output.
In accordance with one or more aspects of the present invention, anode-fluid-isolating insert 130 is provided with one or more electrically-isolating anode fluid channels 132 (i.e., anode fluid channels) that define, at least in part, the one or more fluid channels 122 of end plate assembly 110. As illustrated, in one embodiment, a pocket or recess is provided in end plate 120 from a surface of the end plate closest to the plurality of electrolyzer cells 101 so that anode-fluid-isolating insert 130 resides (in one or more embodiments) fully within the end plate boundaries and does not increase the overall height of electrolyzer stack 100. In one embodiment, the pocket within end plate 120 is formed to extend into the end plate over the one or more fluid channels through the end plate. In the embodiment of
Referring to
Various approaches to seal anode-fluid-isolating insert 130 to end plate 120 are possible, with
In one embodiment, an additional pressure seal 321 can be provided between isolation plate 301 and end plate 120. From a tolerance stack-up viewpoint, however, this is a two-way path seal, rather than a three-way path seal, such as between the anode-fluid-isolating insert, isolation plate, and end plate. This also facilitates manufacturing tolerances on the anode-fluid-isolating insert and enables use of lower cost production techniques, such as injection or compression-molding. Thus, there are two-different types of seals in this embodiment. One seal 320 provides ionic isolation, with relatively little pressure differential across the seal, and the other provides full pressure differential rating between the end plate and isolation plate. The tolerance stack-up for the ionic isolation is more forgiving than the tolerance stack-up for the pressure isolation. In the embodiment illustrated, anode-fluid-isolating insert 130 further includes a groove or notch 325 in the outer side surface of the insert that is in opposing relation to the inner surface of end plate 120 within the formed pocket. This groove 325 can be a circumferential groove configured to accommodate a further seal or gasket designed to establish a friction-fit of anode-fluid-isolating insert 130 within end plate 120 during assembly, which in turn facilitates movement and placement of the assembly over the other components in the electrolyzer stack during stack-up. Note that the seals described herein can be O-ring seals, flat gaskets, form-in-place gaskets (RTV), soft plastic molded seals, etc. For instance, in one embodiment of the pressure-balancing insert approach, the seal could be directly molded as part of the insert.
As noted,
An example of a cathode-fluid-isolating insert 400, in accordance with one or more aspects of the present invention, is depicted in
By way of example,
Referring to
As noted, in one or more embodiments, cathode-fluid-isolating insert 400 includes one or more electrically-isolating cathode fluid channels 401 (i.e., cathode fluid channels) that define, at least in part, one or more fluid channels of end plate assembly 110. Cathode-fluid-isolating insert 400 can be formed by machining, molding, or printing a non-conductive material to form, in one embodiment, a single monolithic, fluid-isolating insert, or isolator, with (for instance) a plurality of electrically-isolating cathode fluid channels 401 that extend, in one embodiment, from the outer surface of end plate 120 to cathode manifold 126 within the end plate. Note that the number and placement of electrically-isolating cathode fluid channels 401 can be dependent on the number and placement of the respective fluid channels through current collector 300 and isolation plate 301 with which the cathode fluid channels are designed to be in fluid communication.
Similar to the embodiments of
In one embodiment, an additional pressure seal 621 can be provided between isolation plate 301 and end plate 120. From a tolerance stack-up viewpoint, however, this is a two-way path seal similar to pressure seal 321 in the embodiments of
Note that, although illustrated in association with the pressure-balanced, cathode-fluid-isolating insert approach of
The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprise” (and any form of comprise, such as “comprises” and “comprising”), “have” (and any form of have, such as “has” and “having”), “include” (and any form of include, such as “includes” and “including”), and “contain” (and any form contain, such as “contains” and “containing”) are open-ended linking verbs. As a result, a method or device that “comprises”, “has”, “includes” or “contains” one or more steps or elements possesses those one or more steps or elements, but is not limited to possessing only those one or more steps or elements. Likewise, a step of a method or an element of a device that “comprises”, “has”, “includes” or “contains” one or more features possesses those one or more features, but is not limited to possessing only those one or more features. Furthermore, a device or structure that is configured in a certain way is configured in at least that way, but may also be configured in ways that are not listed.
The corresponding structures, materials, acts, and equivalents of all means or step plus function elements in the claims below, if any, are intended to include any structure, material, or act for performing the function in combination with other claimed elements as specifically claimed. The description of one or more embodiments has been presented for purposes of illustration and description but is not intended to be exhaustive or limited to in the form disclosed. Many modifications and variations will be apparent to those of ordinary skill in the art. The embodiment was chosen and described in order to best explain various aspects and the practical application, and to enable others of ordinary skill in the art to understand various embodiments with various modifications as are suited to the particular use contemplated.
