Electrolyzer Operating Methods and Electrolyzer Systems

This application is a continuation-in-part of and claims priority to U.S. Utility application Ser. No. 18/943,406 filed Nov. 11, 2024, which is a divisional of and claims priority to U.S. Utility application Ser. No. 17/938,319 filed Oct. 6, 2022, which claims priority to U.S. Provisional Patent Application Ser. No. 63/252,552 filed Oct. 6, 2021, the disclosures of which are incorporated herein in their entirety by reference.

As electricity production migrates to lower carbon dioxide (CO) footprint technologies, the ability to convert electricity into low-carbon or zero-carbon transportation fuels is becoming an increasingly important challenge in mitigating global COemissions. Among the options for such fuels, hydrogen gas (H) has a unique advantage in that its oxidation product is water. Thus, hydrogen gas represents a low-carbon transportation fuel if it can be manufactured with a low-carbon footprint.

Hydrogen production through water electrolysis represents a pathway for creating this clean energy carrier. Electrolyzers operate by applying an electric current to split water molecules into hydrogen and oxygen. The rate of hydrogen production in an electrolyzer is directly related to the current density at which the system operates.

Flexible electrolyzer systems that can respond to changing conditions on the electricity input side of the operation, the hydrogen output side of the operation, or both, are needed to facilitate the growing hydrogen economy.

Various aspects of the present disclosure provide a method of operating an electrolyzer. The method includes changing a current density associated with operation of the electrolyzer based on one or more electricity input factors, or one or more hydrogen output factors, or both.

Various aspects of the present disclosure provide an electrolyzer system. The electrolyzer system includes an electrolyzer including one or more electrolyzer cells each including a first half cell with a first electrode and a second half cell with a second electrode. The electrolyzer system also includes a controller to control a current applied through the one or more electrolyzer cells. The controller is configured to dynamically set the current density based on one or more electricity input factors, or one or more hydrogen output factors, or both.

In various aspects, the one or more electricity input factors can include balancing load on an electrical grid supplying electricity to the electrolyzer; an excess or deficit of environmentally-generated electricity supplied to the electrolyzer; forecasted environmental conditions potentially causing a future excess or deficit of environmentally-generated electricity supplied to the electrolyzer; a battery charge level of one or more batteries that supply electricity to the electrolyzer; carbon intensity of electricity supplied to the electrolyzer; downstream product carbon intensity requirements; or a combination thereof.

In various aspects, the one or more hydrogen output factors can include demand for hydrogen produced by the electrolyzer; balancing hydrogen production load of the electrolyzer with hydrogen production load of one or more other electrolyzers; hydrogen pipeline demand for hydrogen produced by the electrolyzer; downstream hydrogen pipeline demand for the hydrogen produced by the electrolyzer; storage facility demand for the hydrogen produced by the electrolyzer; hydrogen compressor needs for a hydrogen compressor that compresses the hydrogen produced by the electrolyzer; price, future price, trading credit, hydrogen credit, margin gained from selling hydrogen, or a combination thereof, for the hydrogen produced by the electrolyzer; purchase agreement fulfilment for the hydrogen produced by the electrolyzer; electricity price of electricity generated from the hydrogen produced by the electrolyzer; or a combination thereof.

Various aspects of the present invention provide various advantages over other methods of operating an electrolyzer or electrolyzer systems. For example, various aspects of the method and system of the present invention provide various advantages relating to electricity input factors compared to other methods and systems, such as grid load balancing advantages, renewable energy integration advantages, forecast-based operation advantages, battery integration advantages, carbon intensity optimization advantages, downstream product carbon intensity requirement advantages, or a combination thereof.

Various aspects of the method and system of the present invention provide grid load balancing advantages such as the ability to rapidly respond to electrical grid fluctuations more quickly than traditional power plants can adjust their generation. Various aspects of the method and system of the present invention provide grid load balancing advantages such as providing grid stability by serving as a responsive load that can be quickly adjusted. Various aspects of the method and system of the present invention provide grid load balancing advantages such as accommodation for power generation that cannot be curtailed quickly including nuclear, gas, coal, and hydroelectric generation. In various aspects of the method and system of the present invention, in addition to balancing grid load, the electrolyzer system provides the advantage of rapid response to electrical grid fluctuations. Unlike traditional power plants, which may require significant time to adjust their generation levels, the electrolyzer system can quickly ramp up or down its current density to stabilize the grid. This capability can enhance grid reliability and ensure consistent operation during periods of sudden changes in electricity availability.

Various aspects of the method and system of the present invention provide renewable energy integration advantages such as increasing or maximizing utilization of intermittent renewable energy by increasing production during high generation periods. Various aspects of the method and system of the present invention provide renewable energy integration advantages such as the ability to reduce electrolyzer load when renewable generation is low, allowing critical infrastructure to receive available power, or increase electrolyzer load when renewable generation is high. Various aspects of the method and system of the present invention provide renewable energy integration advantages such as promoting overall renewable energy adoption by creating flexible demand. Various aspects of the method and system of the present invention can promote renewable energy adoption by creating flexible demand. By dynamically adjusting its load, the system can support the integration of intermittent renewable energy sources, such as wind and solar, into the energy grid, thereby reducing reliance on fossil fuels and encouraging the transition to cleaner energy systems.

Various aspects of the method and system of the present invention provide forecast-based operation advantages such as pre-emptive adjustment of production based on forecasted environmental conditions. Various aspects of the method and system of the present invention provide forecast-based operation advantages such as time-shifting of electrolyzer product needs and electricity consumption for economic benefits. For example, the system can preemptively increase hydrogen production during off-peak hours when electricity costs are lower, or during periods of high renewable energy generation, to optimize operational efficiency and reduce costs. Various aspects of the method and system of the present invention provide forecast-based operation advantages such as anticipatory response to weather forecasts including wind and cloud cover to increase, decrease, or optimize production rates.

Various aspects of the method and system of the present invention provide battery integration advantages such as extended operation during periods of low battery charge by reducing current density. Various aspects of the method and system of the present invention provide battery integration advantages such as utilization of excess generation when batteries do not require charging. Various aspects of the method and system of the present invention provide battery integration advantages such as support for battery management objectives through controlled load adjustment. Various aspects of the method and system of the present invention provide battery integration advantages such as complementary operation with battery storage systems in integrated energy networks. In various aspects, by dynamically adjusting its current density, the system can utilize excess electricity when batteries are fully charged or reduce its load during periods of low battery charge, ensuring efficient energy management across the network.

Various aspects of the method and system of the present invention provide carbon intensity optimization advantages such as operation at optimal times to maintain carbon intensity below threshold levels for subsidy eligibility. Various aspects of the method and system of the present invention provide carbon intensity optimization advantages such as increasing or maximizing carbon credits and subsidies by timing production during low carbon intensity periods. Various aspects of the method and system of the present invention provide carbon intensity optimization advantages such as an ability to target tiered subsidy levels through strategic operation. Various aspects of the method and system of the present invention provide carbon intensity optimization advantages such as real-time response to grid carbon intensity fluctuations throughout the day. Various aspects of the method and system of the present invention provide carbon intensity optimization advantages such as receipt of increased or maximized subsidies including full credits for lifecycle emissions below a predetermined COe/kg H.

Various aspects of the method and system of the present invention provide downstream product carbon intensity requirement advantages such as production of hydrogen with carbon intensity levels tailored for specific downstream applications. Various aspects of the method and system of the present invention provide downstream product carbon intensity requirement advantages such as support for decarbonization requirements in ammonia, fertilizer, or sustainable aviation fuel production, or for heating in steel or concrete production. Various aspects of the method and system of the present invention provide downstream product carbon intensity requirement advantages such as meeting regulatory carbon requirements for end products that use hydrogen as an input. Various aspects of the method and system of the present invention provide downstream product carbon intensity requirement advantages such as enhanced marketability of hydrogen for carbon-sensitive applications.

Various aspects of the method and system of the present invention provide various advantages relating to hydrogen output factors compared to other methods and systems, such as multiple electrolyzer management advantages, demand-responsive production advantages, pipeline integration advantages, storage facility optimization advantages, compressor integration advantages, economic optimization advantages, microgrid and industrial park integration advantages, electricity generation advantages, modeling and forecasting advantages, or a combination thereof.

Various aspects of the method and system of the present invention provide multiple electrolyzer management advantages such as balanced production across groups of electrolyzers for system optimization. Various aspects of the method and system of the present invention provide multiple electrolyzer management advantages such as compensation capability when other units are offline for maintenance. Various aspects of the method and system of the present invention provide multiple electrolyzer management advantages such as prioritization of the most efficient electrolyzers at higher current densities. Various aspects of the method and system of the present invention provide multiple electrolyzer management advantages such as maintenance of consistent total output despite individual unit variability. Various aspects of the method and system of the present invention provide multiple electrolyzer management advantages such as ability to quickly respond to safety conditions by load balancing.

Various aspects of the method and system of the present invention provide demand-responsive production advantages such as matching production to varying downstream demand requirements. Various aspects of the method and system of the present invention provide demand-responsive production advantages such as support for industrial processes with fluctuating hydrogen needs including production of fertilizer, one or more hydrocarbons for sustainable aviation fuel, or for heating during steel or cement production. Various aspects of the method and system of the present invention provide demand-responsive production advantages such as accommodation for batch processes that periodically need high hydrogen volumes. Various aspects of the method and system of the present invention provide demand-responsive production advantages such as dynamic production adjustment based on real-time or forecasted demand.

Various aspects of the method and system of the present invention provide pipeline integration advantages such as responsiveness to downstream pipeline demand fluctuations. Various aspects of the method and system of the present invention provide pipeline integration advantages such as support for various end-use applications including fueling, transportation, and chemical production. Various aspects of the method and system of the present invention provide pipeline integration advantages such as optimal pipeline pressure and flow management. Various aspects of the method and system of the present invention provide pipeline integration advantages such as balanced input to match variable withdrawal rates from the pipeline.

Various aspects of the method and system of the present invention provide storage facility optimization advantages such as prevention of hydrogen storage facility overflow by reducing production when storage is near capacity. Various aspects of the method and system of the present invention provide storage facility optimization advantages such as efficient replenishment of storage when levels are low. Various aspects of the method and system of the present invention provide storage facility optimization advantages such as integration with forecasted hydrogen demand to optimize storage levels. Various aspects of the method and system of the present invention provide storage facility optimization advantages such as reduced need for excessive storage capacity through dynamic production.

Various aspects of the method and system of the present invention provide compressor integration advantages such as operational coordination with hydrogen compressors. Various aspects of the method and system of the present invention provide compressor integration advantages such as adaptability when compressor units are offline for maintenance. Various aspects of the method and system of the present invention provide compressor integration advantages such as pressure management for optimal compressor efficiency. Various aspects of the method and system of the present invention provide compressor integration advantages such as ability to adjust inlet pressure through controlled production rates.

Various aspects of the method and system of the present invention provide economic optimization advantages such as response to hydrogen price, futures, trading credits, hydrogen credits, or margin gained by selling hydrogen. Various aspects of the method and system of the present invention provide economic optimization advantages such as optimization of production timing independent of electricity price. Various aspects of the method and system of the present invention provide economic optimization advantages such as increased or maximized producer revenue while fulfilling purchase agreements. Various aspects of the method and system of the present invention provide economic optimization advantages such as strategic production increases during high-value periods in hydrogen purchase agreements.

Various aspects of the method and system of the present invention provide microgrid and industrial park integration advantages such as support for integrated energy systems. Various aspects of the method and system of the present invention provide microgrid and industrial park integration advantages such as enhanced functionality for data centers using renewable energy with hydrogen backup. Various aspects of the method and system of the present invention provide microgrid and industrial park integration advantages such as capability for arbitrage between electricity and hydrogen markets. Various aspects of the method and system of the present invention provide microgrid and industrial park integration advantages such as flexible resource allocation between hydrogen production and direct electricity use. Various aspects of the method and system of the present invention provide microgrid and industrial park integration advantages such as support for fueling stations for various vehicles including trucks, cars, forklifts, or drones.

Various aspects of the method and system of the present invention provide electricity generation advantages such as optimization of hydrogen production for subsequent electricity generation. Various aspects of the method and system of the present invention provide electricity generation advantages such as strategic timing of electricity sales to the grid for increased or maximized profitability. Various aspects of the method and system of the present invention provide electricity generation advantages such as balancing direct grid electricity sales versus hydrogen-to-electricity conversion. Various aspects of the method and system of the present invention provide electricity generation advantages such as enhanced profitability of renewable electricity generation facilities.

Various aspects of the method and system of the present invention provide modeling and forecasting advantages such as site-specific optimization models for each electrolyzer installation. Various aspects of the method and system of the present invention provide modeling and forecasting advantages such as integration of forecasted electricity and hydrogen prices into operational decisions. Various aspects of the method and system of the present invention provide modeling and forecasting advantages such as computer modeling to determine optimal current density setpoints. Various aspects of the method and system of the present invention provide modeling and forecasting advantages such as dynamic response to changing market conditions.

Reference will now be made in detail to certain aspects of the disclosed subject matter. While the disclosed subject matter will be described in conjunction with the enumerated claims, it will be understood that the exemplified subject matter is not intended to limit the claims to the disclosed subject matter.

Throughout this document, values expressed in a range format should be interpreted in a flexible manner to include not only the numerical values explicitly recited as the limits of the range, but also to include all the individual numerical values or sub-ranges encompassed within that range as if each numerical value and sub-range is explicitly recited. For example, a range of “about 0.1% to about 5%” or “about 0.1% to 5%” should be interpreted to include not just about 0.1% to about 5%, but also the individual values (e.g., 1%, 2%, 3%, and 4%) and the sub-ranges (e.g., 0.1% to 0.5%, 1.1% to 2.2%, 3.3% to 4.4%) within the indicated range. The statement “about X to Y” has the same meaning as “about X to about Y,” unless indicated otherwise. Likewise, the statement “about X, Y, or about Z” has the same meaning as “about X, about Y, or about Z,” unless indicated otherwise.

In this document, the terms “a,” “an,” or “the” are used to include one or more than one unless the context clearly dictates otherwise. The term “or” is used to refer to a nonexclusive “or” unless otherwise indicated. The statement “at least one of A and B” or “at least one of A or B” has the same meaning as “A, B, or A and B.” In addition, it is to be understood that the phraseology or terminology employed herein, and not otherwise defined, is for the purpose of description only and not of limitation. Any use of section headings is intended to aid reading of the document and is not to be interpreted as limiting; information that is relevant to a section heading may occur within or outside of that particular section.

In the methods described herein, the acts can be carried out in a specific order as recited herein. Alternatively, in any aspect(s) disclosed herein, specific acts may be carried out in any order without departing from the principles of the invention, except when a temporal or operational sequence is explicitly recited. Furthermore, specified acts can be carried out concurrently unless explicit claim language recites that they be carried out separately or the plain meaning of the claims would require it. For example, a claimed act of doing X and a claimed act of doing Y can be conducted simultaneously within a single operation, and the resulting process will fall within the literal scope of the claimed process.

The term “about” as used herein can allow for a degree of variability in a value or range, for example, within 10%, within 5%, or within 1% of a stated value or of a stated limit of a range, and includes the exact stated value or range.

The term “substantially” as used herein refers to a majority of, or mostly, as in at least about 50%, 60%, 70%, 80%, 90%, 95%, 96%, 97%, 98%, 99%, 99.5%, 99.9%, 99.99%, or at least about 99.999% or more, or 100%. The term “substantially free of” as used herein can mean having none or having a trivial amount of, such that the amount of material present does not affect the material properties of the composition including the material, such that about 0 wt % to about 5 wt % of the composition is the material, or about 0 wt % to about 1 wt %, or about 5 wt % or less, or less than, equal to, or greater than about 4.5 wt %, 4, 3.5, 3, 2.5, 2, 1.5, 1, 0.9, 0.8, 0.7, 0.6, 0.5, 0.4, 0.3, 0.2, 0.1, 0.01, or about 0.001 wt % or less, or about 0 wt %.

As used herein, “carbon intensity” is a measurement of the amount of carbon dioxide emissions, or equivalent (COe), produced per unit of energy, activity, or product.

As used herein, hydrogen's COe (carbon dioxide equivalent) refers to the total amount of greenhouse gas emissions, measured in terms of carbon dioxide or equivalent, released during the production of the hydrogen.

Hydrogen gas (H) can be formed electrochemically by a water-splitting reaction where water is split into oxygen gas (O) and Hgas at an anode and a cathode of an electrochemical cell, respectively. Examples of such electrochemical processes include, without limitation, proton electrolyte membrane (PEM) electrolysis and alkaline water electrolysis (AWE). In such electrochemical reactions, the operating energy necessary to drive the water-splitting electrolysis reaction is high due to additional energy costs as a result of various energy inefficiencies. For example, to reduce unwanted migration of ionic species between the electrodes, the cathode and the anode may be separated by a separator, such as a membrane, which can reduce migration of the ionic species. Although the separator can improve the overall efficiency of the cell, it can come at a cost of additional resistive losses in the cell, which in turn increases the operating voltage. Other inefficiencies in water electrolysis can include solution resistance losses, electric conduction inefficiencies, and/or electrode over-potentials, among others. These various inefficiencies and the capital costs associated with minimizing them can play a role in the economic viability of Hgeneration via water splitting electrolysis.

The methods and systems provided herein relate to unique electrochemical processes that result in efficient, low cost, and low energy production of Hgas.

Various aspects of the present disclosure provide an electrolyzer system. The electrolyzer system can be any suitable electrolyzer system that can perform the method of the present disclosure. The electrolyzer system can include an electrolyzer including one or more electrolyzer cells each including a first half cell with a first electrode and a second half cell with a second electrode. The electrolyzer system can include a controller to control a current applied through the one or more electrolyzer cells. The controller can be configured to dynamically set the current density based on one or more electricity input factors, or one or more hydrogen output factors, or both. The one or more electricity input factors, and the one or more hydrogen output factors, can be the same as described herein with respect to the method of the present disclosure.

is a schematic diagram of a generic water electrolyzer cellthat converts water into hydrogen and oxygen with electrical power is illustrated in. In an example, the electrolyzer cellcomprises two half cells: a first half celland a second half cell. In an example, the first and second half cells,are separated by a separator, such as a membrane. In an example, the separatorcomprises a porous or an ion-exchange membrane. In examples wherein the separatorcomprises an ion-exchange membrane, the ion-exchange membrane can be of different types, such as an anion exchange membrane (AEM), a cation exchange membrane (CEM), a proton exchange membrane (PEM), a bipolar ion exchange membrane (BEM), an ion solvating membrane (ISM), or a microporous or nanoporous membrane.

In examples where the separatoris a cation exchange membrane, the cation exchange membrane can be a conventional membrane such as those available from, for example, Asahi Kasei Corp. of Tokyo, Japan, or from Membrane International Inc. of Glen Rock, NJ, USA, or from The Chemours Company of Wilmington, DE, USA. Examples of cation exchange membranes include, but are not limited to, the membrane sold under the N2030WX trade name by The Chemours Company and the membrane sold under the F8020/F8080 or F6801 trade names by the Asahi Kasei Corp. Examples of materials that can be used to form a cationic exchange membrane include, but are not limited to, cationic membranes comprising a perfluorinated polymer containing anionic groups, for example sulphonic and/or carboxylic groups. It may be appreciated, however, that in some examples, depending on the need to restrict or allow migration of a specific cation or an anion species between the electrolytes, a cation exchange membrane that is more restrictive and thus allows migration of one species of cations while restricting the migration of another species of cations may be used. Similarly, in some embodiments, depending on the need to restrict or allow migration of a specific anion species between the electrolytes, an anion exchange membrane that is more restrictive and thus allows migration of one species of anions while restricting the migration of another species of anions may be used. Such restrictive cation exchange membranes and anion exchange membranes are commercially available and can be selected by one ordinarily skilled in the art.

In some examples, the separatorcan be selected so that it can function in an acidic and/or an alkaline electrolytic solution, as appropriate. Other properties for the separatorthat may be desirable include, but are not limited to, high ion selectivity, low ionic resistance, high burst strength, and high stability in electrolytic solution in a temperature range of room temperature to 150° C. or higher.

In an example, the separatoris stable in a temperature range of from about 0° C. to about 150° C., for example from about 0° C. to about 100° C., such as from about 0° C. to about 90° C., for example from about 0° C. to about 80° C., such as from about 0° C. to about 70° C., for example from about 0° C. to about 60° C., such as from about 0° C., to about 50° C., for example from about 0° C. to about 40° C., or such as from about 0° C. to about 30° C.

It may be useful to use an ion-specific ion exchange membrane that allows migration of one type of ion (e.g., cation for a CEM and anion for an AEM) but not another, or migration of one type of ion and not another, to achieve a desired product or products in the electrolyte solution.

In an example, the first half cellcomprises a first electrode, which can be placed proximate to the separator, and the second half cellcomprises a second electrode, which can be placed proximate to the separator, for example on an opposite side of the separatorfrom the first electrode. In an example, the first electrodeis the anode for the electrolyzer celland the second electrodeis the cathode for the electrolyzer cell, such that for the remainder of the present disclosure the first half cellmay also be referred to as the anode half cell, the first electrodemay also be referred to as the anode, the second half cellmay also be referred to as the cathode half cell, and the second electrodemay also be referred to as the cathode. Each of the electrodes,can be coated with one or more electrocatalysts to speed the reaction toward the hydrogen gas (Hgas) and/or the oxygen gas (Ogas). Examples of electrocatalysts include, but are not limited to, highly dispersed metals or alloys of platinum group metals, such as platinum, palladium, ruthenium, rhodium, iridium, or their combinations such as platinum-rhodium, platinum-ruthenium, a nickel mesh coated with ruthenium oxide (RuO), or a high-surface area nickel.

The ohmic resistance of the separatorcan affect the voltage drop across the anodeand the cathode. For example, as the ohmic resistance of the separatorincreases, the voltage across the anodeand the cathodemay increase, and vice versa. In an example, the separatorhas a relatively low ohmic resistance and a relatively high ionic mobility. In an example, the separatorhas a relatively high hydration characteristics that increase with temperature, and thus decreases the ohmic resistance. By selecting a separatorwith lower ohmic resistance known in the art, the voltage drop across the anodeand the cathodeat a specified temperature can be lowered.

In an example, the anodeis electrically connected to an external positive conductorand the cathodeis electrically connected to an external negative conductor. When the separatoris wet and is in electrolytic contact with the electrodesand, and an appropriate voltage is applied across the conductorsand, Ogas is liberated at the anodeand Hgas is liberated at the cathode. In certain configurations, an electrolyte, e.g., one comprising of a solution of KOH in water, is fed into the half cells,. For example, the electrolyte can flow into the anode half cellthrough a first electrolyte inletand into the cathode half cellthrough a second electrolyte inlet. In an example, the flow of the electrolyte through the anode half cellpicks up the produced Ogas as bubbles, which exits the anode half cellthrough a first outlet. Similarly, the flow of the electrolyte through the cathode half-cellcan pick up the produced Hgas as bubbles, which can exit the cathode half cellthrough a second outlet. The gases can be separated from the electrolyte downstream of the electrolyzer cellwith one or more appropriate separators. In an example, the produced Hgas is dried and harvested into high pressure canisters or fed into further process elements. The Ogas can be allowed to simply vent into the atmosphere or can be stored for other uses. In an example, the electrolyte is recycled back into the half cells,as needed.

In an example, a controllercan be included to control the current applied through the electrolyzer cell(for example by controlling a voltage that is applied across the conductorsand). In an example, the controllercan be configured to control an operating current density for the cell(e.g., by applying a current that corresponds to a desired current density based on the area of the cell) so that the current density for the cellcan be controlled (e.g., for load gaining or load shedding as described in more detail herein).

In an example, a typical voltage across the electrolyzer cellis from about 1.5 volts (V) to about 3.0 V. In an example, an operating current density for the electrolyzer cellis from about 0.1 A/cmto about 3 A/cm. Each cellhas a size that is sufficiently large to produce a sizeable amount of Hgas when operating at these current densities. In an example, a cross-sectional area of each cell(e.g., a width multiplied by a height for a rectangular cell) is from about 0.25 square meters (m) to about 15 m, such as from about 1 mto about 5 m, for example from about 2 mto about 4 m, such as from about 2.25 mto about 3 m, such as from about 2.5 mto about 2.9 m. In an example, the total volume of each cell (e.g., a width multiplied by a height multiplied by a depth) is from about 0.1 cubic meter (m) to about 2 m, such as from about 0.15 mto about 1.5 m, for example from about 0.2 mto about 1 m, such as from about 0.25 mto about 0.5 m, for example from about 0.275 mto about 0.3 m. In an example, the total volume of the entire electrolyzer system (e.g., the combined volume of all the cells in all the stacks in the plant) is from about 1 mto about 200 m, such as from about 2 mto about 100 m, for example from about 2.5 mto about 50 m.

As will be appreciated by those having skill in the art, operating an electrical power bus at such a low voltage and high current density can be highly inefficient. Therefore, typically a plurality of the electrolyzer cellsare assembled and electrically connected in series into an electrolyzer stack. Each of the plurality of cellscan operate at a lower higher voltage and at the same current density as a single electrolyzer cell, which makes the system far more efficient. In an example, an electrolyzer stack can comprise from about five (5) electrolyzer cellsto aboutelectrolyzer cells, for example eighty (80) electrolyzer cellsor more connected in series to provide an electrolyzer stack.

shows a schematic diagram of a portion of such an electrolyzer stackof electrolyzer cellsA-N (collectively referred to as “electrolyzer cells” or “electrolyzer cell”). Each cellin the stackcan have any one of the structures described above with respect to the example electrolyzer cellof, e.g., with one or both of the anode half celland the cathode half cell. In addition, each cellcan include one or more structures of the cell assemblies (e.g., comprising one or more structures of the pan assemblies described below). As will be appreciated by those having skill in the art, the structures of the cell assemblies (i.e., for individual pan assemblies) can provide for the overall lower cost Hproduction described herein.

In an example, the electrolyzer cellsare connected electrically in series with conductors. In an example, the stackcomprises a large number of electrolyzer cellsconnected in series, e.g., fifty (50) or more electrolyzer cells, sixty (60) or more electrolyzer cells, seventy (70) or more electrolyzer cells, eighty (80) or more electrolyzer cells, ninety (90) or more electrolyzer cells, one hundred (100) or more electrolyzer cells, one hundred fifty (150) or more electrolyzer cells, two hundred (200) or more electrolyzer cells, three hundred (300) or more electrolyzer cells, and so on. The individual electrolyzer cellsin the example electrolyzer stackare labeled with reference numbersA throughN, with only the first electrolyzer cellA, the second electrolyzer cellB, and the last electrolyzer cellN being shown in. In an example, the electrical positive conductor (e.g., the positive conductorin) of one cellA is electrically connected to the electrical negative conductor of the subsequent cellB (e.g., the negative conductorin) with a connecting conductor, with the following exceptions: (a) the positive conductor of the final cellN at the highest voltage is connected to a power supply; and (b) the negative conductor of the first cellA at the lowest voltage is connected to a groundof the electrical circuit. In an example, the power supplyis a constant-current voltage-limited rectifier that converts grid AC power to a suitable DC power level. In an example, the power supplycan be controlled by a controller that is configured to control the current density of the electrolyzer cellsin the stack(similar to the controllerdescribed above with respect to), for example to allow the stack to be dynamically operated for load gaining or load shedding in response to one or more electricity input factors or one or more hydrogen output factors, as described herein.

The physical configuration of the electrolyzer cellcan be any physical structure configured to allow for the liberation of oxygen gas at the anodeand for the liberation of hydrogen gas at the cathode. In an example, the electrolyzer cellcan comprise components that can dynamically operate at high current densities (e.g., at 2 A/cmor higher). By providing for operation at high current densities, the electrolyzer cellscan allow operators to meet their targeted production rate with fewer cells, thereby reducing capital expenses. In addition, by allowing the electrolyzer cellsto dynamically operate over a wide range of operational current densities, the electrolyzer cellscan provide operators with a large turndown ratio, which can enable the operators to increase or reduce production.