Patent Application
20250011948
The present disclosure relates generally to electrolyzers, and more particularly, relates to electrolyzer stacks including a cell block and a bladder for applying force to the cell block, electrolysis systems including such electrolyzer stacks, and methods for operating such electrolysis systems.
An electrolyzer is an electrochemical device that converts water into hydrogen and oxygen using the process of electrolysis. Electrolyzers are commonly used to produce hydrogen. Hydrogen is used in many industrial applications, such as, for example ammonia production. Electrolyzers may be used for localized hydrogen production, for example as fuel for vehicles equipped with hydrogen fuel cells. Electrolyzers may also be used to store energy from dynamic electrical sources, such as wind turbines and solar cells.
An electrolyzer stack for an electrolysis system is provided. The electrolyzer stack includes a cell block and a bladder. The cell block includes a plurality of cells configured to receive and convert water to form a hydrogen product stream. The bladder is configured for fluid communication with the hydrogen product stream and operatively disposed to apply a force to the cell block when pressurized by a portion of the hydrogen product stream.
In some embodiments, the electrolyzer stack further includes a side stream line providing fluid communication between the hydrogen product stream and the bladder to advance the portion of the hydrogen product stream to bladder.
In some embodiments, the electrolyzer stack further includes a compression plate disposed between the bladder and the cell block, wherein the bladder when pressurized applies the force to the compression plate that transfers to the cell block.
In some embodiments, the electrolyzer stack further includes a first end plate disposed adjacent to the bladder opposite compression plate.
In some embodiments, the electrolyzer stack of claim 4, further comprising a second end plate disposed adjacent to the cell block on a side opposite the compression plate, wherein the first and second end plates are linked together to constrain expansion of the electrolyzer stack including constraining expansion of the bladder in a direction away from the cell block.
In some embodiments, the electrolyzer stack further includes a tension rod that extends between and at least partially links the first and second end plates together.
In some embodiments, the electrolyzer stack further includes a spring that is coupled to and cooperates with the tension rod to link the first and second end plates together.
In some embodiments, the plurality of cells correspondingly includes a plurality of seals that are disposed between the compression plate and the second end plate and that overlie each other to define a perimeter region that is disposed about an active zone of the cell block.
In some embodiments, the bladder overlies the active zone of the cell block.
In some embodiments, the bladder has an outer perimeter that interfaces with the compression plate and that is substantially superposed with the perimeter region defined by the plurality of seals.
In some embodiments, the electrolyzer further includes a pair of terminal plates including a first terminal plate disposed between the cell block and the compression plate and a second terminal plate that is disposed between the cell block and the second end plate, wherein the bladder overlies the first terminal plate.
In some embodiments, the pair of terminal plates are configured to communicate electricity to the cell block to drive electrolysis of water to form the hydrogen product stream.
According to an alternative embodiment, an electrolysis system includes a water source, a power source, and an electrolyzer stack. The electrolyzer stack includes a cell block and a bladder. The cell block includes a plurality of cells in fluid communication with the water source to receive water and in communication with the power source to electrolyze water to form a hydrogen product stream. The bladder is configured for fluid communication with the hydrogen product stream and operatively disposed to apply a force to the cell block when pressurized by a portion of the hydrogen product stream.
In some embodiments, the electrolysis system further includes power electronics in communication with the electrolyzer stack and is configured to control operation of the cell block to produce the hydrogen product stream.
In some embodiments, the electrolysis system further includes a recycle stream line that is in fluid communication with the electrolyzer stack and the water source to recycle a remaining portion of water from the electrolyzer stack to the water source.
According to an alternative embodiment, a method for operating an electrolysis system is provided. The method includes introducing water to an electrolyzer stack comprising a cell block, electrolyzing water in the cell block to form a hydrogen product stream, and pressurizing a bladder with a portion of the hydrogen product stream to apply a force to the cell block.
In some embodiments, the electrolyzer stack further includes a side stream line that is in fluid communication with the hydrogen product stream and the bladder, and wherein pressurizing includes advancing the portion of the hydrogen product stream along the side stream line to the bladder.
In some embodiments, the electrolyzer stack further includes a compression plate disposed between the bladder and the cell block, and wherein pressurizing includes pressurizing the bladder to apply the force to the compression plate that transfers to the cell block.
In some embodiments, the electrolyzer stack further includes an end plate that is disposed adjacent to the bladder opposite the compression plate, and wherein pressurizing includes constraining expansion of the bladder in a direction away from the cell block with the end plate.
In some embodiments, the electrolysis system is incorporated into a vehicle, and the method further includes operating the electrolysis system in the vehicle.
The above features and advantages and other features and advantages of the present disclosure are readily apparent from the following detailed description of the best modes for carrying out the disclosure when taken in connection with the accompanying drawings.
The appended drawings are not necessarily to scale and may present a somewhat simplified representation of various preferred features of the present disclosure as disclosed herein, including, for example, specific dimensions, orientations, locations, and shapes. Details associated with such features will be determined in part by the particular intended application and use environment.
As required, detailed embodiments of the present disclosure are disclosed herein; however, it is to be understood that the disclosed embodiments are merely exemplary of the disclosure that may be embodied in various and alternative forms. The figures are not necessarily to scale; some features may be exaggerated or minimized to show details of particular components. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a representative basis for teaching one skilled in the art to variously employ the present disclosure.
Unless specifically stated from context, as used herein, the term “about” is understood as within a range of normal tolerance in the art, for example within 2 standard deviations of the mean. “About” can be understood as within 10%, 5%, 1%, 0.5%, 0.1%, 0.05%, or 0.01% of the stated value. “About” can alternatively be understood as implying the exact value stated. Unless otherwise clear from the context, the numerical values provided herein are modified by the term “about.”
Electrolyzers are categorized into three main types: alkaline electrolyzers, solid oxide electrolyzers, and proton exchange membrane (PEM) electrolyzers. Alkaline electrolyzers use an alkaline solution as an electrolyte, such as potassium hydroxide (KOH) or sodium hydroxide (NaOH). Solid oxide uses a solid ceramic material as an electrolyte, which conducts oxygen ions at high temperatures (typically around 800° C. to 1000° C.). In one example, PEM electrolyzers include a cell block formed of a plurality of stacked cells (e.g., in series) in which each cell includes various components including various membrane electrode assembly (MEA) components. The MEA components include a solid polymer membrane (i.e., proton exchange membrane or PEM) that is disposed between an anode and a cathode. The MEA components that make up the cathode include a catalyst layer disposed adjacent to a gas diffusion layer (GDL). Likewise, the MEA components that make up the anode include a catalyst layer disposed adjacent to a porous transport layer (PTL). The PEM selectively allows positively charged hydrogen ions to pass through the membrane between the anode and the cathode as part of the electrolysis process to convert water into hydrogen and oxygen.
PEM electrolyzers may be designed to apply a force (e.g., a compressive force) to the cell block during operation to counter increase pressure(s) that is produced from converting liquid water to hydrogen gas to operate more efficiently. The force helps prevent hydrogen leakage and reduces contact resistance along the cell block by countering dimensional changes (e.g., expansion or contraction) of the PEM electrolyzer's stack length (e.g., stack height). The change in the PEM electrolyzer's stack length may be caused, for example, by swelling, thermal expansion, and/or creep of the various components, such as, for example, the seal gasket(s) that seals the cells of the cell block, and/or one or more of the various MEA components within the cell block. Some of the current designs are ineffective due to swelling, thermal expansion, creep, and/or high pressures.
In high pressure electrolyzers, for example where up to 30 bars (3 MPa) or more of hydrogen pressure may be produced, issues or concerns of hydrogen leakage and/or reduction in electrolysis effectiveness may be further increased. In such electrolyzers, the increased pressures also increase the hardware used to apply a force to counter dimensional changes of the electrolyzer's stack length. The additional hardware increases an electrolyzer's stack volume, weight, and design complexity.
Accordingly, it is desirable to provide electrolyzer stacks that address one or more of the foregoing issues, electrolysis systems including such electrolyzer stacks, and methods for operating such electrolysis systems. Furthermore, other desirable features and characteristics of the various embodiments described herein will become apparent from the subsequent detailed description and the appended claims, taken in conjunction with the accompanying drawings and this background.
The present disclosure relates generally to electrolyzers, and more particularly, relates to electrolyzer stacks including a cell block and a bladder for applying force to the cell block, electrolysis systems including such electrolyzer stacks, and methods for operating such electrolysis systems.
In one of more embodiments of the disclosure, the electrolyzer stack includes a cell block that includes a plurality of cells configured to receive and convert water to form a hydrogen product stream. A bladder is configured for fluid communication with the hydrogen product stream and is operatively disposed to apply a force to the cell block when pressurized by a portion of the hydrogen product stream.
In one or more embodiments of the disclosure, the electrolyzer stack is part of an electrolysis system. The electrolysis system further includes a water source and a power source that are in communication with the electrolyzer stack. During operation of the electrolysis system, liquid water is fluidly communicated from the water source to the electrolyzer stack and electricity is communicated from the power source to the electrolyzer stack. The electrolyzer stack converts the liquid water feedstock using electricity to produce the hydrogen product stream via electrolysis. A portion of the hydrogen product stream is fluidly communicated to the bladder, thereby pressurizing the bladder and applying a force (e.g., compressive force) to the cell block to counter the increase in pressure in the cell block that is produced from converting the liquid water feedstock to hydrogen gas. The force helps prevent hydrogen leakage and reduces electrical contact resistance along the cell block by countering dimensional changes (e.g., expansion or contraction) of the electrolyzer's stack length (e.g., stack height). The change in the electrolyzer's stack length may be caused, for example, by swelling, thermal expansion, and/or creep of the various components, such as, for example, the seal gasket(s) that seals the cells of the cell block, and/or one or more of the various membrane electrode assembly (MEA) components within the cell block.
In higher pressure hydrogen production applications, for example, where up to 30 bars (3 MPa) or more of hydrogen pressure may be produced in the cell block, the resulting hydrogen product stream will correspondingly also be at a higher pressure. In one or more embodiments of the disclosure, the portion of the higher pressure-hydrogen product stream fluidly communicated to the bladder further increases the pressure within the bladder including the resulting force applied to the cell block. This helps to further counter the increased pressure within the cell block.
In one or more embodiments of the disclosure, the bladder may be used in combination with one or more stack springs to apply a resulting force to the cell block via the compression plate. In such embodiments, the stack spring(s) apply a stack force to the cell block to mitigate the stack compression force fluctuation and the effects of dimension change. Examples of dimensional changes are the reduction of sealing pressure and the increase in electrical contact resistance, resulting from an increase in the distance between repeating cells (i.e., cell-to-cell pitch).
When swelling, thermal expansion, and/or creep occurs, the stack springs may compensate for dimensional changes by automatically adjusting the stack springs' length with a minimal amount of change in spring force. Thus, the stack can maintain a nominally stable stack force and hence, sealing pressure and contact resistance.
In an exemplary embodiment, advantageously hydrogen leakage is reduced, minimized, or prevented, and the electrolysis effectiveness is improved in the cell block as a result of the higher force(s) being applied by the bladder to counter any dimensional changes to the cell block and/or electrolyzer stack.
As illustrated, the electrolyzer stack 40 receives electricity (i.e., an electrical current) from the power source 30 via line 32 and water from the water source 20 via line 22. The electrolyzer stack 40 convert water from the water source 20 into hydrogen and oxygen via electrolysis using electricity supplied by the power source 30. Hydrogen gas is output from the electrolyzer stack 40 as a hydrogen product stream 122 (shown
During operation of the electrolysis system 10, the power source 30 supplies direct current to the electrolyzer stack 40. Examples of power sources include, but are not limited to, batteries, solar cells, DC generators, wind turbines, hydropower plants, and/or the like.
The power electronics 50 are in communication with the electrolyzer stack 40 and are configured to control the operation of the electrolyzer stack 40. For example, the power electronics 50 may control the amount of voltage and current supplied to the electrolyzer stack 40 from the power source 30.
The plurality of cells 72 includes a plurality of seals 74 and a plurality of separator plates 210. The cells in the plurality of cells 72 are stacked in the cell block 70 and are electrically connected in series. Each cell in the plurality of cells 72 includes various components, including membrane electrode assembly (MEA), a pair of separator plates, and a pair of seals.
The pair of separator plates (from the plurality of separator plates 210) contains flow channels that interface with the MEA and that allow the flow of fluids (e.g., water, hydrogen gas, and oxygen gas) to or from the MEA. Each separator plate is electrically conductive and facilitates the transport of electrons to assist in establishing electrical circuit of the electrolysis process.
The MEA includes a solid polymer membrane (i.e., proton exchange member or PEM), an anode (i.e., anode-catalyst layer), and a cathode (i.e., cathode-catalyst layer). The PEM is disposed between the anode-catalyst layer and the cathode-catalyst layer. The cathode-catalyst layer is disposed adjacent to a gas diffusion layer (GDL). Likewise, the anode-catalyst layer disposed adjacent to a porous transport layer (PTL). The PEM contains an active zone where the electrochemical reaction for the conversion of water to hydrogen via electrolysis occurs. The PEM selectively allows positively charged hydrogen ions to pass through the membrane between the anode and the cathode as part of the electrolysis process to convert water into hydrogen and oxygen.
Each cell is structured such that the MEA is disposed between the pair of separator plates. The pair of seals (from the plurality of seals 74) prevent leakage of fluids (e.g., water, hydrogen gas, and oxygen gas) from the interface between the MEA and the pair of separator plates. The pair of seals defines an MEA perimeter 79 (shown in
The MEA perimeter 79 is related to a perimeter region 76. The perimeter region 76 is a region defined by the plurality of seals 74 and the MEA perimeter 79 of each seal in the plurality of seals 74. In other words, the MEA perimeter 79 is related to a cell and the perimeter region 76 is related to the plurality of cells 72.
As illustrated, the electrolyzer stack 40 receives water from the water source 20 via line 22 line and an electrical current from the power source 30 via line 32. The electrolyzer stack 40 may receive the electrical current through a wiring, a bus, and/or an electrical connector (not shown), where for example, the electrical connector is electrically coupled to a terminal plate 160 (e.g., first terminal plate).
Water is advanced into and through the cell block 70 via a water inlet 180 that feeds the plurality of cells 72 via the plurality of separator plates 210. The terminal plates 160 and 170, the plurality of separator plates 210, each MEA in the plurality of cells 72 create an electrical circuit that drives the electrolysis process when electrical current is applied to the cell block 70. When electrical current is passed through the plurality of cells 72 between the terminal plates 160 and 170, water advancing in the cell 72 is converted into hydrogen and oxygen via an electrolysis process.
As illustrated, oxygen gas and any unused, remaining and/or by-product water is removed from the cells 72 via a water-and-oxygen outlet 200. The water-and-oxygen outlet 200 advances the removed water to the recycle stream line 44, which passes the water back to the water source 20.
The hydrogen gas produced in the cells 72 is advanced to the hydrogen header 190. From the hydrogen header 190, the hydrogen gas exits the electrolyzer stack 40 to form the hydrogen product stream 122. The hydrogen product stream 122 advances through the hydrogen product line 120, which is in fluid communication with line 42 (shown
As illustrated, a portion or side stream 132 of the hydrogen product stream 122 is fluidly communicated to the bladder 80 via a side stream line 130. In one or more embodiments of the disclosure, the portion of the hydrogen product stream 84 is introduced to and pressurizes the bladder 80. In an exemplary embodiment, the bladder 80 is pressurized at the same or substantially the same pressure as the hydrogen product stream 122. For example, the fluid circuit section including lines 120 and 130 between the cell block 70 and the bladder 80 may be free of any flow restrictive valving or device, or alternatively, if any valving or other flow restrictive devices are included in lines 120 and 130, valving or device(s) are opened at substantially maximum flow during operation of the electrolysis system 10.
While the bladder 80 is pressurized, the bladder 80 applies a force (e.g., a compressive force or a force in the direction of the cell block 70) directly or indirectly to a compression plate 90 (e.g., moveable compression plate, for example, up or down in the illustrated orientation) that facilitates evenly distributing and transferring the force to the cell block 70. As illustrated, the compression plate 90 is disposed adjacent to and between the bladder 80 and the cell block 70, and for example, can move towards the cell block 70 in response to the force applied by the bladder 80 to transfer the force to the cell block 70.
In one or more embodiments of the disclosure, the force applied by the bladder 80 is represented by the following equation:
where FB is the force the bladder 80 applies on the compression plate 90, PB is the pressure of hydrogen gas contained within the bladder 80, and AB is the area of the bladder 80 that is in physical contact with the compression plate 90. AB is defined by the area created by the outer perimeter 82 (as discussed further below) of the bladder 80 that is substantially superposed with the perimeter region 76 defined by the plurality of seals 74. AB is the same, or essentially the same, as AH2 as discussed below.
In one or more embodiments of the disclosure, during operation of the electrolyzer stack 40, pressure builds up internally within the cell block 70 from the production of hydrogen gas, resulting in a force(s) being exerted in an outwardly direction(s) by the cell block. The force is described by the following equation:
where FH2 represents the total force from the hydrogen pressure, FH2 represents the total hydrogen pressure, and AH2 is an area defined by the perimeter region 76. AH2 is the same since all electrolyzer cells in the plurality of electrolyzer cells are equivalent and stacked in an aligned configuration as shown in
In some embodiments, the electrolyzer stack 40 may expand (i.e., increase in height) when the electrolyzer cells 72 experience a force(s) caused by an increase of hydrogen pressure, if an opposing or counter force is not otherwise being applied to the electrolyzer stack 40.
The bladder force FB counters the total force FH2 by applying an opposing force that is equivalent to the FH2. Because AB equals AH2 and because the bladder pressure equals the internal pressure of the electrolyzer stack 40, the compression plate 90 remains stationary. Thus, the length of electrolyzer stack 40 does not change, thereby remaining substantially dimensionally stable.
In some embodiments, the electrolyzer stack 40 includes the cell block 70, a compression plate 90, the bladder 80, an end plate 100 (e.g., first end plate), an end plate 110 (e.g., second end plate), the hydrogen product line 120, the side stream line 130, a tension rod 140, a spring 150, the terminal plate 160, the terminal plate 170, the plurality of cells 72, and a plurality of seals 74.
As briefly discussed above, the cells 72 corresponding include the seals 74 that overlie each other to define the perimeter region 76 that is disposed about an active zone 78 of the cell block 70. As used herein, the phase “active zone” is understood to mean the zone or region where the electrochemical reaction for the conversion of water to hydrogen via electrolysis occurs. As illustrated, the bladder 80 overlies the active zone 78 of the cell block 70. As used herein, the term “overlies” is understood to mean that in one or more orientations of the cell block 70, the bladder 80 is over the cell block 70, while in other orientations, although the bladder 80 may not be over the cell block 70, the bladder 80 is either directly or indirectly adjacent to the cell block 70. The bladder 80 has an outer perimeter 82 that is substantially superposed with the perimeter region 76 defined by the plurality of seals 74. The outer perimeter 82 is equivalent (e.g., aligned and matched) or substantially equivalent to the MEA perimeter 79.
As illustrated, the cell block 70 is disposed adjacent to and between the terminal plates 160 and 170. On the side opposite the cell block 70 of the terminal plate 160, the compression plate 90 is disposed adjacent to and between the terminal plate 160 and the bladder 80. Further and as illustrated, the bladder 80 is disposed adjacent to and between the compression plate 90 and the end plate 100.
As discussed above, the bladder 80, when pressurized, applies the force to the compression plate 90 that transfers to the cell block 70. In one or more embodiments of the disclosure, the bladder 80 applies the force over the area of the bladder 80 that is in physical contact with the compression plate 90. This area (i.e., bladder area) is the portion of the bladder 80, within the perimeter region 76, that is in physical contact with the compression plate 90. That is, the bladder area is substantially aligned and matches the area of the perimeter region 76.
In an exemplary embodiment, the bladder 80 is formed of or otherwise includes an elastic material that can be expanded and contracted without significant plastic deformation. Further, in an exemplary embodiment, the elastic material is substantially inert to hydrogen so that the bladder can be exposed to hydrogen for extended periods of time with any substantial degradation in its physical and mechanical properties including elongation and elastic properties and substantial non-permeability to hydrogen gas. Non-limiting examples of the elastic material suitable for forming the bladder 80 include polymer material such as rubbers and fiber reinforced thermoplastic polymers or metals such as stainless steel and aluminum.
Further, in an exemplary embodiment, the bladder 80 contains accordion-fold (e.g., pleated or foldable wall sections) walls. The accordion-fold walls overlay each other forming one or more “V” or folded shapes when the bladder 80 is unpressurized or in a collapsed position. When the bladder 80 is pressurized, the accordion-fold walls expand, for example, the foldable wall sections (e.g., the “V’ folded shape(s)) unfold to increase the length of the wall.
On a side of the cell block 70 opposite the bladder 80, the terminal plate 170 is disposed adjacent to and between the cell block 70 and the end plate 110. The terminal plates 160 and 170 (i.e., pair of terminal plates) are electrically conductive to allow electricity to be passed through to the cell block 70 to drive the electrolysis of water to form the hydrogen product stream 122.
As illustrated, the hydrogen product stream 122 is passed through an opening or conduit in the end plate 110. The hydrogen product stream 122 is formed of the hydrogen produced by the electrolysis of water. Further and as illustrated, the side stream line 130 is in fluid communication with the hydrogen product line 120 and the bladder 80. In an exemplary embodiment, the side stream line 130 is coupled to the hydrogen product line 120 and the bladder 80 to pass along the portion of the hydrogen product stream 84 to the bladder 80 as discussed above.
In an exemplary embodiment, the tension rod 140 and spring 150 (i.e., stack spring) are coupled and cooperate to compress the cell block 70 by linking together the end plates 100 and 110. The end plates 100 and 110 are linked together to constrain expansion of the electrolyzer stack 40 including constraining expansion of the bladder 80 in a direction away from the cell block 70. In an exemplary embodiment, this helps ensure that the bladder 80, when pressurized, directs the force towards the cell block 70.
In an exemplary embodiment, the tension rod 140 and spring 150 further help provide an additional force to the cell stack 70 to ensure that some level of force is always being applied to the seals 74 and the active zone 78 despite any fluctuations in pressure and/or dimensional changes to the cell block 70 that could occur during operation and/or start-up of the electrolysis system 10.
The method 400 continues by electrolyzing (STEP 420) water in the cell block to form a hydrogen product stream. In an exemplary embodiment, a bladder 80 is pressurized (STEP 430) with a portion of the hydrogen product stream 84 to apply a force to the cell block.
In an exemplary embodiment, the electrolysis system 10 is incorporated or otherwise used in a vehicle, for example, a motor vehicle. As used herein a “vehicle” is understood to mean a device configured for transporting people, things, objects, or the like. Non-limiting examples of motor vehicles (e.g., internal combustion engine (ICE) vehicles, electric motor vehicles including electric battery and fuel cell vehicle or the like) include land vehicles (e.g., cars, trucks, motorcycles, electric bike, buses, trains or the like), aerial vehicles (e.g., airplanes, helicopters, unmanned aerial vehicles or the like), water vehicles (e.g., boats, watercrafts, or the like) and amphibious vehicles (e.g., hovercrafts or the like).
While the best modes for carrying out the disclosure have been described in detail, those familiar with the art to which this disclosure relates will recognize various alternative designs and embodiments for practicing the disclosure within the scope of the appended claims.
Any of the dimensions, configurations, etc. discussed herein may be varied as needed or desired to be different than any value or characteristic specifically mentioned herein or shown in the drawings for any of the embodiments.
It will be apparent to those skilled in the art that various modifications and variations can be made to the embodiments of the apparatus and methods of assembly as discussed herein without departing from the scope or spirit of the disclosure(s). Other embodiments of this disclosure will be apparent to those skilled in the art from consideration of the specification and practice of the various embodiments disclosed herein. For example, some of the equipment may be constructed and function differently than what has been described herein and certain steps of any method may be omitted, performed in an order that is different than what has been specifically mentioned or in some cases performed simultaneously or in sub-steps. Furthermore, variations or modifications to certain aspects or features of various embodiments may be made to create further embodiments and features and aspects of various embodiments may be added to or substituted for other features or aspects of other embodiments to provide still further embodiments.
