ELECTROLYZER OPERATING METHODS AND ELECTROLYZER SYSTEMS

A method of operating an electrolyzer 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.

BACKGROUND

As electricity production migrates to lower carbon dioxide (CO2) footprint technologies, the ability to convert electricity into low-carbon or zero-carbon transportation fuels is becoming an increasingly important challenge in mitigating global CO2 emissions. Among the options for such fuels, hydrogen gas (H2) 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.

SUMMARY OF THE INVENTION

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 CO2e/kg H2.

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.

DETAILED DESCRIPTION OF THE INVENTION

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.

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 “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 (CO2e), produced per unit of energy, activity, or product.

As used herein, hydrogen's CO2e (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 (H2) can be formed electrochemically by a water-splitting reaction where water is split into oxygen gas (O2) and H2 gas 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 H2 generation 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 H2 gas.

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.

FIG. 1 is a schematic diagram of a generic water electrolyzer cell 100 that converts water into hydrogen and oxygen with electrical power is illustrated in FIG. 1. In an example, the electrolyzer cell 100 comprises two half cells: a first half cell 111 and a second half cell 121. In an example, the first and second half cells 111, 121 are separated by a separator 131, such as a membrane 131. In an example, the separator 131 comprises a porous or an ion-exchange membrane 131. In examples wherein the separator 131 comprises 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 separator 131 is 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 separator 131 can be selected so that it can function in an acidic and/or an alkaline electrolytic solution, as appropriate. Other properties for the separator 131 that 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 separator 131 is 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 cell 111 comprises a first electrode 112, which can be placed proximate to the separator 131, and the second half cell 121 comprises a second electrode 122, which can be placed proximate to the separator 131, for example on an opposite side of the separator 131 from the first electrode 112. In an example, the first electrode 112 is the anode for the electrolyzer cell 100 and the second electrode 122 is the cathode for the electrolyzer cell 100, such that for the remainder of the present disclosure the first half cell 111 may also be referred to as the anode half cell 111, the first electrode 112 may also be referred to as the anode 112, the second half cell 121 may also be referred to as the cathode half cell 121, and the second electrode 122 may also be referred to as the cathode 122. Each of the electrodes 112, 122 can be coated with one or more electrocatalysts to speed the reaction toward the hydrogen gas (H2 gas) and/or the oxygen gas (O2 gas). 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 (RuO2), or a high-surface area nickel.

The ohmic resistance of the separator 131 can affect the voltage drop across the anode 112 and the cathode 122. For example, as the ohmic resistance of the separator 131 increases, the voltage across the anode 112 and the cathode 122 may increase, and vice versa. In an example, the separator 131 has a relatively low ohmic resistance and a relatively high ionic mobility. In an example, the separator 131 has a relatively high hydration characteristics that increase with temperature, and thus decreases the ohmic resistance. By selecting a separator 131 with lower ohmic resistance known in the art, the voltage drop across the anode 112 and the cathode 122 at a specified temperature can be lowered.

In an example, the anode 112 is electrically connected to an external positive conductor 116 and the cathode 122 is electrically connected to an external negative conductor 126. When the separator 131 is wet and is in electrolytic contact with the electrodes 112 and 122, and an appropriate voltage is applied across the conductors 116 and 126, O2 gas is liberated at the anode 112 and H2 gas is liberated at the cathode 122. In certain configurations, an electrolyte, e.g., one comprising of a solution of KOH in water, is fed into the half cells 111, 121. For example, the electrolyte can flow into the anode half cell 111 through a first electrolyte inlet 114 and into the cathode half cell 121 through a second electrolyte inlet 124. In an example, the flow of the electrolyte through the anode half cell 111 picks up the produced O2 gas as bubbles 113, which exits the anode half cell 111 through a first outlet 115. Similarly, the flow of the electrolyte through the cathode half-cell 121 can pick up the produced H2 gas as bubbles 123, which can exit the cathode half cell 121 through a second outlet 125. The gases can be separated from the electrolyte downstream of the electrolyzer cell 100 with one or more appropriate separators. In an example, the produced H2 gas is dried and harvested into high pressure canisters or fed into further process elements. The O2 gas 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 111, 121 as needed.

In an example, a controller 128 can be included to control the current applied through the electrolyzer cell 100 (for example by controlling a voltage that is applied across the conductors 116 and 126). In an example, the controller 128 can be configured to control an operating current density for the cell 100 (e.g., by applying a current that corresponds to a desired current density based on the area of the cell 100) so that the current density for the cell 100 can 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 cell 100 is from about 1.5 volts (V) to about 3.0 V. In an example, an operating current density for the electrolyzer cell 100 is from about 0.1 A/cm2 to about 3 A/cm2. Each cell 100 has a size that is sufficiently large to produce a sizeable amount of H2 gas when operating at these current densities. In an example, a cross-sectional area of each cell 100 (e.g., a width multiplied by a height for a rectangular cell) is from about 0.25 square meters (m2) to about 15 m2, such as from about 1 m2 to about 5 m2, for example from about 2 m2 to about 4 m2, such as from about 2.25 m2 to about 3 m2, such as from about 2.5 m2 to about 2.9 m2. 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 (m3) to about 2 m3, such as from about 0.15 m3 to about 1.5 m3, for example from about 0.2 m3 to about 1 m3, such as from about 0.25 m3 to about 0.5 m3, for example from about 0.275 m3 to about 0.3 m3. 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 m3 to about 200 m3, such as from about 2 m3 to about 100 m3, for example from about 2.5 m3 to about 50 m3.

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 cells 100 are assembled and electrically connected in series into an electrolyzer stack. Each of the plurality of cells 100 can operate at a lower higher voltage and at the same current density as a single electrolyzer cell 100, which makes the system far more efficient. In an example, an electrolyzer stack can comprise from about five (5) electrolyzer cells 100 to about 500 electrolyzer cells 100, for example eighty (80) electrolyzer cells 100 or more connected in series to provide an electrolyzer stack.

FIG. 2 shows a schematic diagram of a portion of such an electrolyzer stack 130 of electrolyzer cells 132A-132N (collectively referred to as “electrolyzer cells 132” or “electrolyzer cell 132”). Each cell 132 in the stack 130 can have any one of the structures described above with respect to the example electrolyzer cell 100 of FIG. 1, e.g., with one or both of the anode half cell 111 and the cathode half cell 121. In addition, each cell 132 can 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 H2 production described herein.

In an example, the electrolyzer cells 132 are connected electrically in series with conductors 304. In an example, the stack 130 comprises a large number of electrolyzer cells 132 connected in series, e.g., fifty (50) or more electrolyzer cells 132, sixty (60) or more electrolyzer cells 132, seventy (70) or more electrolyzer cells 132, eighty (80) or more electrolyzer cells 132, ninety (90) or more electrolyzer cells 132, one hundred (100) or more electrolyzer cells 132, one hundred fifty (150) or more electrolyzer cells 132, two hundred (200) or more electrolyzer cells 132, three hundred (300) or more electrolyzer cells 132, and so on. The individual electrolyzer cells 132 in the example electrolyzer stack 130 are labeled with reference numbers 132A through 132N, with only the first electrolyzer cell 132A, the second electrolyzer cell 132B, and the last electrolyzer cell 132N being shown in FIG. 2. In an example, the electrical positive conductor (e.g., the positive conductor 116 in FIG. 1) of one cell 132A is electrically connected to the electrical negative conductor of the subsequent cell 132B (e.g., the negative conductor 126 in FIG. 1) with a connecting conductor 134, with the following exceptions: (a) the positive conductor of the final cell 132N at the highest voltage is connected to a power supply 136; and (b) the negative conductor of the first cell 132A at the lowest voltage is connected to a ground 138 of the electrical circuit. In an example, the power supply 136 is a constant-current voltage-limited rectifier that converts grid AC power to a suitable DC power level. In an example, the power supply 136 can be controlled by a controller that is configured to control the current density of the electrolyzer cells 132 in the stack 130 (similar to the controller 128 described above with respect to FIG. 1), 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 cell 100 can be any physical structure configured to allow for the liberation of oxygen gas at the anode 112 and for the liberation of hydrogen gas at the cathode 122. In an example, the electrolyzer cell 100 can comprise components that can dynamically operate at high current densities (e.g., at 2 A/cm2 or higher). By providing for operation at high current densities, the electrolyzer cells 100 can allow operators to meet their targeted production rate with fewer cells, thereby reducing capital expenses. In addition, by allowing the electrolyzer cells 100 to dynamically operate over a wide range of operational current densities, the electrolyzer cells 100 can provide operators with a large turndown ratio, which can enable the operators to increase or reduce production.

The operation of electrolyzer cells at high current densities can result in significant challenges, such as, but not limited to, large gas volumes produced at high current densities, significant temperature and pressure fluctuations, membrane erosion or fatigue, large amount of heat generated in the cell, and/or high flow rates of electrolyte. Therefore, in an example, each electrolyzer cell 100 can include a configuration of an anode pan assembly and/or a cathode pan assembly that can overcome one or more of these challenges, such as, but not limited to, reducing or minimizing large temperature variations of the electrolyte along the height of the cell; reducing or minimizing masking of the nominal active area with gas; reducing or minimizing formation of a stagnant gas pocket that can result in localized drying out of the membrane; and/or reducing or minimizing significant pressure fluctuations due to slug or plug flow at the cell outlets.

Due to large gas volumes, static gas pockets can form on the electrode or at the top of the cell. Providing high electrolyte flow rates and utilizing features that cause gas lift to create high local shear rates may help to minimize static gas pocket formation on the electrode. However, a high electrolyte flow rate coupled with large production of gas and large amounts of electrolyte solution entering and exiting the cell presents significant challenges associated with slug and plug flow. This type of flow can be reduced or minimized by using a specified manifold and the outlet tube configuration, described in more detail below.

In some examples, a pan assembly can be used on the anode or the cathode side of the electrolyzer cell 100. The pan assembly can include an effective collection system at the top of the cell to minimize and in some cases prevent the formation of large stagnant gas pockets at the top of the cell. In an example, the collection system comprises a manifold and an outlet tube with large cross-sectional area that effectively provides space for gas to collect as well as electrolyte to flow while also reducing or minimizing the likelihood of masking of the membrane and/or slug or plug flow. The pan assembly can provide for two phase (gas/liquid) flow that is effectively directed out of the cell.

The pan assembly, manifold, and outlet tube are designed to ensure that flow is uniform or substantially uniform across the width of the cell, and that pressure fluctuations within the cell is minimal. The flow uniformity drives the need to ensure that the back pressure associated with the flow's entry into the manifold is significantly greater than the pressure drop along the length of the manifold and so that the pressure within the manifold is greater than the pressure drop exiting the manifold. Maintaining an essentially constant internal pressure distribution drives the requirement to avoid slug or plug flow through the manifold and the outlet tubing. Therefore, the pan assembly comprising the manifold and the outlet tube can provide for reliable cell operation across a high range of electrolyte flows and high current densities.

As the current density is increased in the cell, power dissipation can also rise dramatically. Large spatial and/or temporal temperature fluctuations can damage the membrane. The contribution of internal power dissipation to the cell's internal temperature distribution can be reduced or minimized through operating conditions such as the maintaining temperature, flow rate of the inflowing electrolyte, and/or re-circulation of the inflowing electrolyte. High electrolyte flow rates can provide for a high amount of convective heat transfer within the cell, thereby helping to reduce or minimize the heat buildup and concomitant temperature rise within the cell that may otherwise result from an increase in current density. In an example, the pan assembly of the electrolyzer cell includes a baffle plate configuration inside the pan assembly that can reduce or minimize the impact of fluctuating power dissipation on the internal temperature of the cell by helping to ensure that the electrolyte remains isothermal or substantially isothermal along the height of the cell and so that thermal equilibrium is achieved rapidly after the operating current density is changed.

In the generic electrolyzer cell 100 described above with respect to FIG. 1, the anode half cell 111 can comprise an anode pan assembly that includes the anode 112 and the anode electrolyte (also referred to as “anolyte”). Similarly, the cathode half cell 121 can comprise a cathode pan assembly that includes the cathode 122 and the cathode electrolyte (also referred to as “catholyte”). The anode pan assembly and the cathode pan assembly can be separated by the separator 131 (e.g., a diaphragm, a membrane electrode assembly (MEA), one or more ion exchange membranes (IEM), or another type of membrane or separator). The anode pan assembly and/or the cathode pan assembly can include components, such as a collection system that collects the gas and the electrolyte for flow out of the cell 100. A separator assembly can include one or more of an anion exchange membrane (AEM), a cation exchange membrane (CEM), or another separator depending on the desired reactions at the anode 112 and the cathode 122. In between these components, various additional separator components can be provided, e.g., to separate the membrane 131 from the anode 112, to separate the membrane 131 from the cathode 122, as well as provide mechanical integrity to the membranes or other separator structures. In addition to these components, individual gaskets or gasket tape may be provided in between and along the outer perimeter of the components to seal the compartments from fluid leakage.

In an example, all of the components described above are aligned parallel or substantially parallel to each other and optional peripheral bolting may be provided to stack them together in the electrochemical cell 100. In a filter press configuration, no peripheral bolting may be required. In a stack of electrochemical cells, the anode 112 of one electrochemical cell 100 can be electrically connected with the cathode 122 of an adjacent electrochemical cell. The current passes through the stack of electrochemical cells during operation.

FIGS. 3-8 show several views of an example pan assembly 140 that can be used as the anode pan assembly for the anode half cell 111 or as the cathode pan assembly for the cathode half cell 121 in the electrolyzer cell 100 shown in FIG. 1 or in one of the individual electrolyzer cells 132 in the stack 130 of FIG. 2. FIG. 3 is a front view of the pan assembly 140 and FIG. 4 is a cross sectional view of the pan assembly 140. It is to be understood that in the electrochemical cell 100 or 132, the pan assembly 140 can be used as the anode pan assembly or as the cathode pan assembly, or both, depending on the need and the reaction at the anode 112 and the cathode 122. The next component of the cell such as the anode 112 or the cathode 122 can be placed on top of the pan assembly 140 shown the front view of FIG. 3.

As illustrated in FIGS. 3 and 4, the pan assembly 140 includes a pan 142. Inside the depth of the pan 142 and at the top of the pan 142 is housed a manifold 144 (shown in FIG. 4). The manifold 144 can be connected to one or more outlet tubes 146 depending on the requirements for the electrolyzer cell 100. For example, the design can incorporate 2, 3, 4, or more outlet tubes 146 on each pan assembly 140, on the same or either side of the pan 142 in order to minimize the cell thickness, and maximize the number of cells 100 that can fit in an electrolyzer frame of a particular size. FIGS. 5 and 6 show close-up details of the manifold 144 and the outlet tube 146.

In an example, a depth DManifold of the manifold 144 and/or the cross sectional area of the manifold 144 and/or a size of the outlet tube 146 is selected so that the pan assembly 140 provides a relatively large cross sectional area of the manifold 144 in order to reduce or minimize the occurrence of slug and plug flow of the two phase system, but also to provide enough space between a wall of the manifold 144 and the electrode placed on top of the pan 142 (e.g., the anode or the cathode depending on whether the pan assembly 140 forms an anode pan or a cathode pan) for the gas and electrolyte to have an unimpeded flow and for the membrane to stay wetted. The depth DManifold of the manifold 144 and/or the cross sectional area of the manifold 144 and/or a size of the outlet tube 146 can also dictate the overall thickness of the cell 100.

In an example of the pan assembly 140, the manifold 144 has a depth DManifold (shown in FIGS. 5 and 6) that is from about 0.25 (25%) to about 0.75 (75%) of a depth DPan of the pan 142, for example from about 0.25 (25%) to about 0.6 (60%) of the depth DPan, such as from about 0.25 (25%) to about 0.5 (50%) of the depth DPan of the pan 142, for example from about 0.25 (25%) to about 0.4 (40%) of the depth DPan of the pan 142, such as from about 0.25 (25%) to about 0.3 (30%) of the depth DPan of the pan 142, for example from about 0.3 (30%) to about 0.75 (75%) of the depth DPan of the pan 142, such as from about 0.3 (30%) to about 0.6 (60%) of the depth DPan of the pan 142, for example from about 0.3 (30%) to about 0.5 (50%) of the depth DPan of the pan 142, such as from about 0.3 (30%) to about 0.4 (40%) of the depth DPan of the pan 142, for example from about 0.4 (40%) to about 0.75 (75%) of the depth DPan of the pan 142, such as from about 0.4 (40%) to about 0.6 (60%) of the depth DPan of the pan 142, for example from about 0.4 (40%) to about 0.5 (50%) of the depth DPan of the pan 142, such as from about 0.5 (50%) to about 0.75 (75%) of the depth DPan of the pan 142, for example from about 0.5 (50%) to about 0.6 (60%) of the depth DPan of the pan 142, such as from about 0.6 (60%) to about 0.75 (75%) of the depth DPan of the pan 142.

In an example, the manifold 144 has an upward taper at the top (best seen in FIG. 6). The upward taper creates an internal volume or zone above the upper edge of the membrane 131 positioned next to the electrode, providing a small region for a gas-rich mixture to form without resulting in the drying out of the membrane 131.

An example flow path for the gas and electrolyte mixture through the pan assembly 140 is shown by the dotted line 148 in FIGS. 7 and 8. As can be seen in FIGS. 7 and 8, in an example, the flow path 148 of the two phases of the gas and the electrolyte passes upwards from the main part of the pan 142 to the top of the manifold 144 and then down into the manifold 144 through a set of notches 150 at the top of the manifold 144. The gas and the electrolyte can then flow out through the outlet tube 146.

In order to accommodate a large amount of the gas and the electrolyte solution flowing though the manifold 144 and the outlet tube 146, e.g., due to high current densities and high flow rates, and to reduce or minimize the occurrence of slug and plug flow, in an example, the cross sectional area of the manifold 144 and the outlet tube 146 is large enough to maintain the superficial liquid velocity of the electrolyte to be about 0.35 m/s or less, for example about 0.25 m/s or less, such as about 0.2 m/s or less, for example about 0.15 m/s or less, such as about 0.1 m/s or less, for example about 0.08 m/s or less, such as about 0.05 m/s or less, for example about 0.01 m/s or less. The cross sectional area of the manifold 144 and the outlet tube 146 is large enough to maintain a superficial gas velocity (e.g., O2 gas from an anode pan or H2 gas produced from the cathode pan) to be about 5 m/s or less, for example about 4.5 m/s or less, such as about 4 m/s or less, for example about 3.5 m/s or less, such as about 3 m/s or less, for example about 2.5 m/s or less, such as about 2 m/s or less, for example about 1.5 m/s or less, such as about 1 m/s or less.

In order to accommodate the high current densities and the high flow rates as noted herein, in some examples, the cross sectional area of the manifold 144 (e.g. comprising the depth DManifold of the manifold 144 of from about 0.25 (25%) to about 0.75 (75%) of the depth DPan of the pan 142) is from about 520 square millimeters (mm2) to about 6200 mm2, for example from about 520 mm2 to about 6000 mm2, such as from about 520 mm2 to about 5000 mm2, for example from about 520 mm2 to about 4000 mm2, such as from about 520 mm2 to about 3000 mm2, for example from about 520 mm2 to about 2000 mm2, such as from about 520 mm2 to about 1000 mm2, for example from about 600 mm2 to about 6200 mm2, such as from about 600 mm2 to about 6000 mm2, for example from about 600 mm2 to about 5000 mm2, such as from about 600 mm2 to about 4000 mm2, for example from about 600 mm2 to about 3000 mm2, such as from about 600 mm2 to about 2000 mm2, for example from about 600 mm2 to about 1000 mm2, such as from about 800 mm2 to about 6200 mm2, for example from about 800 mm2 to about 6000 mm2, such as from about 800 mm2 to about 5000 mm2, for example from about 800 mm2 to about 4000 mm2, such as from about 800 mm2 to about 3000 mm2, for example from about 800 mm2 to about 2000 mm2, such as from about 800 mm2 to about 1000 mm2, for example from about 1000 mm2 to about 6200 mm2, such as from about 1000 mm2 to about 6000 mm2, for example from about 1000 mm2 to about 5000 mm2, such as from about 1000 mm2 to about 4000 mm2, for example from about 1000 mm2 to about 3000 mm2, such as from about 1000 mm2 to about 2000 mm2, for example from about 2000 mm2 to about 6200 mm2, such as from about 2000 mm2 to about 6000 mm2, for example from about 2000 mm2 to about 5000 mm2, such as from about 2000 mm2 to about 4000 mm2, for example from about 2000 mm2 to about 3000 mm2, such as from about 3000 mm2 to about 6200 mm2, for example from about 3000 mm2 to about 6000 mm2, such as from about 3000 mm2 to about 5000 mm2, for example from about 3000 mm2 to about 4000 mm2, such as from about 4000 mm2 to about 62000 mm2, for example from about 4000 mm2 to about 6000 mm2, such as from about 4000 mm2 to about 5000 mm2, for example from about 5000 mm2 to about 6200 mm2, such as from about 5000 mm2 to about 6000 mm2.

In some examples wherein the cross-sectional area of the manifold 144 is as recited above, the outlet tube 146 fluidly connected to the manifold 144 can have an equivalent diameter EDoutlet (shown in FIG. 5) is from about 26 millimeters (mm) to about 89 mm, for example from about 26 mm to about 80 mm, such as from about 26 mm to about 75 mm, for example from about 26 mm to about 70 mm, such as from about 26 mm to about 60 mm, for example from about 26 mm to about 50 mm, such as from about 26 mm to about 40 mm, for example from about 26 mm to about 30 mm, such as from about 30 mm to about 89 mm, for example from about 30 mm to about 80 mm, such as from about 30 mm to about 75 mm, for example from about 30 mm to about 70 mm, such as from about 30 mm to about 60 mm, for example from about 30 mm to about 50 mm, such as from about 30 mm to about 40 mm, for example from about 40 mm to about 89 mm, such as from about 40 mm to about 80 mm, for example from about 40 mm to about 75 mm, such as from about 40 mm to about 70 mm, for example from about 40 mm to about 60 mm, such as from about 40 mm to about 50 mm, for example from about 50 mm to about 89 mm, such as from about 50 mm to about 80 mm, for example from about 50 mm to about 75 mm, such as from about 50 mm to about 70 mm, for example from about 50 mm to about 60 mm, such as from about 60 mm to about 89 mm, for example from about 60 mm to about 80 mm, such as from about 60 mm to about 75 mm, for example from about 70 mm to about 89 mm, such as from about 70 mm to about 80 mm, for example from about 70 mm to about 75 mm.

Those having skill in the art will appreciate that what may be considered a “high electrolyte flow rate” may be in comparison to the size of the electrochemical cell 100. For example, a “high flow rate” for a relatively narrow cell, e.g., from about 300 mm to about 600 mm wide, may correspond to a flow rate of about 200 kg/h, while a “high flow rate” for a large commercial size cell, e.g., from about 2 meters (m) to about 3 m wide, may correspond to a flow rate of about 800 kg/h or more, for example about 1000 kg/h or more, such as about 1350 kg/h or more, for example about 1500 kg/h or more, such as about 1750 kg/h or more, for example about 2000 kg/h or more, such as about 2250 kg/h or more, for example about 2500 kg/h or more, such as about 2700 kg/h or more. The cross sectional area of the manifold 144, the cross sectional area of the outlet tube 146, and/or the baffle assembly can accommodate high electrolyte flow rates and high gas flow rates associated with operation at high current densities as described herein and provide for a superficial liquid velocity that is about 0.2 m/s or less and a gas flow rate that is about 3 m/s or less so that slug and plug flow are unlikely to develop.

In some examples, the pan assembly can include a baffle assembly inside the pan assembly, wherein the baffle assembly can reduce or minimize the impact of high current density and/or fluctuating power dissipation on the internal temperature profile along the height of the electrolyzer cell. The baffle assembly can be suspended in the pan assembly, for example between a back pan wall and the electrode. In an example, the baffle assembly includes one or more ribs inside the pan. The one or more ribs can include one or more notches. A baffle plate comprising one or more slots can be included and configured to fit onto the one or more ribs such that a corresponding structure of the baffle plate can fit into the one or more notches of the one or more ribs.

FIGS. 9-15 show several views of a pan assembly 160 that includes an example baffle assembly 162. Similar to the pan assembly 140 described above with respect to FIGS. 3-8, the pan assembly 160 can be used as the structure for one or both of the anode half cell 111 and the cathode half cell 121 in the electrolyzer cell 100 of FIG. 1. For example, if the pan assembly 160 is used to form part of the anode half cell 111, then the pan assembly 160 can be an anode pan assembly. Similarly, if the pan assembly 160 is used to form part of the cathode half cell 121, then the pan assembly 160 can be a cathode pan assembly. Like the pan assembly 140, the pan assembly 160 includes a pan 164 (e.g., an anode pan and/or a cathode pan) and an outlet tube 166. The pan assembly 160 can also include a manifold 168 through which electrolyte and produced gas can flow before exiting the pan assembly 160 through the outlet tube 166, which can be similar or identical to the manifold 144 described above with respect to the pan assembly 140. In other words, the pan assembly that forms either the anode assembly or the cathode assembly, or both, can include features of both the pan assembly 140 described above with respect to FIGS. 3-8 and of the pan assembly 160 described below.

In an example, the baffle assembly 162 of the pan assembly 160 includes a baffle plate 170 that is fitted within the pan 162. In an example, the baffle plate 170 comprises one or more slots 172 (best seen in FIG. 10). Each slot 172 can interact with a corresponding rib 174 (shown in FIGS. 9, 11, and 12), wherein the one or more ribs 174 and the baffle plate 170 form the baffle assembly 162. The baffle plate 170 can have any number of slots 172 depending on the number of ribs 174 in the baffle assembly 162. The number of slots can be e.g., from 1 to about 200 in the baffle plate 170. The baffle plate 170 can be fitted over the ribs 174 in the pan 164. In an example, the one or more ribs 174 are perpendicular or substantially perpendicular to the baffle plate 170 and to the overall orientation of the pan 164. In other words, in an example, the baffle plate 170 is parallel or substantially parallel to a major surface of the pan 164, such as a back wall 178 of the pan 164. The electrode 176 associated with the pan assembly 160 (e.g., the anode 112 if the pan assembly 160 is an anode pan assembly or the cathode 122 if the pan assembly 160 is a cathode pan assembly) can be attached to the top of the pan assembly 160, e.g., on a side of the baffle assembly 162 that is opposite the back wall 178 of the pan 164.

In an example, each of the one or more ribs 174 can include one or more structures to position the baffle plate 170 relative to the pan 164 and/or relative to the electrode 176. In an example, these structures include one or more notches on each rib 174, wherein each notch slidably engages with a corresponding slot 172 on the baffle plate 170 in order to position the baffle plate 170 relative to the pan 164, e.g., so that the baffle plate 170 is suspended at a specified location relative to the electrode 176 and/or relative to the back wall 178 of the pan 164, as can be seen in FIGS. 9, 11, and 12. The notches in the ribs 174 are not visible in the Figures because the notches have been filled with the baffle plate 170. The distance of the baffle plate 170 from the electrode 176 and from the back wall 178 of the pan 164 can be changed by modifying the depth of the notches along the ribs 174.

The positioning of the slots 172 in the baffle plate 170, the length of the slots 172, and/or the distance between the slots 172 can affect the fitting of the baffle plate 170 onto the one or more ribs 174. In an example, the baffle plate 170 is a solid plate with the slots 172 formed therein, as best seen in FIG. 10. In other examples, the baffle plate can be an expanded metal plate or a mesh. In an example, the baffle plate 170 is made from a conductive metal, such as, but not limited to, nickel, stainless steel, and the like. In another example, the baffle plate 170 is made from a polymeric material. In either case, the baffle plate 170 can be configured to snap into place using features on the ribs 174.

As described earlier, the contribution of internal power dissipation to the internal temperature distribution within the electrolyzer cell 100 can be reduced or minimized through operating conditions such as the temperature and flow rate of the electrolyte flowing through the half cells 111, 121 (e.g., through the pan assemblies 160 that form the half cells 111, 121). High electrolyte flow rates can increase and in some examples maximize the convective heat transfer within the electrolyzer cell 100, thereby helping to reduce or minimize heat buildup and the corresponding concomitant temperature rise within the cell 100 that could otherwise result from the high current densities described herein. As discussed above, operating at high electrolyte flow rates and high current densities can lead to slugging or plug flow at the cell outlet, which can result in pressure fluctuations that can shorten the lifetime of the membrane 131. The pan assemblies 140, 160 described herein with the manifold 144 and outlet configurations and/or the baffle assembly 162 are designed to reduce or minimize slug and plug flow. In particular, the baffle assembly 162 can provide for mixing of the electrolyte as it flows through the pan assembly 160 to enhance convective heat transfer within the electrolyte during electrolysis.

In some examples, the baffle assembly 162 is designed and positioned in such a way that the gas produced at the electrode 176 can mix with the electrolyte on the side of the baffle plate 170 closest to the electrode 176, resulting in a relatively low density column and defining a riser section. The low density mixture can rise relatively quickly through the riser section. Once above the top of the baffle plate 170, the gas can disengage and flow into the manifold 168 and then into the outlet tube 166. A fraction of the electrolyte may then drop back down the side of the baffle plate 170 closer to the back wall 178 (i.e., the side opposite to the electrode 176) of the pan 164 into a down-comer region, thereby creating a circulation loop. This circulation loop (with a riser section 180 on the side of the baffle plate 170 closer to the electrode 176 and a down-comer section 182 on the side of the baffle plate 170 opposite the electrode 176) that is formed in the pan assembly 160 is illustrated conceptually in FIG. 13, where it is compared to a comparative pan assembly 184 that does not include a baffle assembly, such as one with a baffle plate like the baffle plate 170, such that there is no resulting formation of a circulation pattern. FIG. 14 shows vector plots of a simulated flow distribution of electrolyte in the pan assembly 160 with the baffle plate 170 included (left side of FIG. 14) and a comparative pan assembly 184 without a baffle assembly (right side of FIG. 14). As can be seen in FIG. 14, without a baffle plate, the electrolyte solution rises slowly up though the comparative pan assembly 184. The gas evolved at the electrode 176 impacts the flow of the electrolyte, dragging some of the electrolyte up, and buffeting some of the electrolyte laterally. Gas lift is evident along the upper left wall (adjacent to the electrode 176) in the comparative pan assembly 184. While the comparative pan assembly 184 without the baffle plate does result in the formation of a weak circulation of electrolyte, the pan assembly 160 that includes the baffle plate 170 creates a strong circulation within the pan assembly 160. As is evident from FIG. 14, the flow in the riser section 180, e.g., the side of the baffle plate 170 closest to the electrode 176, is strongly oriented upward due to gas lift, and the flow on the down-comer section 182, e.g., the side of the baffle plate 170 closest to the back wall 178 of the pan assembly 160, is strongly oriented downward. The relatively high velocities and shear rates in the riser section 180 help sweep gas from the electrode 176, provide efficient top to bottom mixing within the pan assembly 160, and drive increased convective cooling.

The baffle assembly 162 can be used to create rapidly flowing circulation loops so that the electrolyte remains substantially isothermal as it flows through the pan assembly 160. Due to the high degree of top-bottom mixing and circulation, rapid thermal equilibration of the electrolyte can be achieved as it flows into and through the pan assembly 160. Another advantage is that relatively cold electrolyte can be introduced into the pan assembly 160 which can equilibrate with warm circulating electrolyte fluid. The circulation rate (or laps of the recirculation loop during electrolyte transit through the pan assembly 160) can be anywhere from 1 to 200. The high circulation rate can also drive larger shear rates adjacent to the membrane 131, helping to sweep gas away from the membrane 131 and/or enhance or maximize heat transfer from the membrane 131 to the electrode 176.

The positioning of the baffle plate 170 with respect to the electrode 176 as well as to the back wall 178 of the pan 164 and/or the width WBaffle and length LBaffle of the baffle plate 170 (shown in FIG. 15), can affect the velocity of the electrolyte through the riser section 180 as well as the down-comer section 182, thereby affecting the circulation rate of the electrolyte within the pan assembly 160. It has been found that if the baffle plate 170 is located farther than a specified critical distance from the electrode 176 then the circulation pattern of the riser section 180 and the down-comer section 182 may not be formed. Specifically, it has been found that when the gap between the baffle plate 170 and the electrode 176 is too large, free convection of the relatively light, gas-rich zone adjacent to the electrode 176 rises relatively rapidly compared to the slowly rising electrolyte farther away from the electrode 176. The resultant shear forces may drag up some of the electrolyte, which can then fall back down on the side of the baffle plate 170 closer to the electrode 176 as the gas disengages into the manifold 168 at the top of the pan assembly 160, resulting in a weak circulation forming on the side of the baffle plate 170 closest to the electrode 176. In such a configuration, the baffle plate 170 may not divide between a riser section and a down-comer section, and a strong circulation current may not form. If, on the other hand, the baffle plate 170 is too close to the electrode 176, then the space between the electrode 176 and the baffle plate 170 may fill with gas as the gas is formed at the electrode 176, choking off electrolyte flow in the space between the baffle plate 170 and the electrode 176. A high volume fraction of gas in the space between the baffle plate 170 and the electrode 176 can result in the membrane and/or the electrode 176 masking, and poor electrical and thermal transport.

The depth DPan of the pan 164, the relative depth DBaffle of the baffle plate 170 relative to the electrode 176, the height HBaffle of the baffle plate 170 relative to the total height HPan of the pan 164, and/or the vertical location of the baffle plate 170 within the pan 164 (e.g., as dictated by the vertical distance HTop from a top edge of the baffle plate 170 to a top wall of the pan 164 and the corresponding vertical distance HBot from a bottom edge of the baffle plate 170 to a bottom wall of the pan 164), as illustrated in FIG. 13, can impact the circulation pattern of the electrolyte within the pan 164.

In an example, the distance of the baffle plate 170 from the electrode 176 (i.e., the relative depth DBaffle of the baffle as illustrated in FIG. 13) is from about 5 mm to about 25 mm, for example from about 5 mm to about 15 mm, such as from about 5 mm to about 12 mm, for example from about 5 mm to about 10 mm, such as from about 5 mm to about 8 mm, for example from about 5 mm to about 6 mm, for example from about 6 mm to about 25 mm, such as from about 6 mm to about 15 mm, for example from about 6 mm to about 12 mm, such as from about 6 mm to about 10 mm, for example from about 6 mm to about 8 mm, for example from about 8 mm to about 25 mm, such as from about 8 mm to about 15 mm, for example from about 8 mm to about 12 mm, for example from about 8 mm to about 10 mm, for example from about 10 mm to about 25 mm, such as from about 10 mm to about 15 mm, for example from about 10 mm to about 12 mm, such as from about 12 mm to about 25 mm, for example from about 12 mm to about 15 mm. In some examples, the distance DBaffle of the baffle plate 170 from the electrode 176 is equivalent to the depth of the notches on the ribs 174.

In an example, the distance DBaffle from the baffle plate 170 to the electrode 176 is at from about 0.25 (25%) to about 0.5 (50%) of the total depth DPan of the pan 164, for example from about 0.25 (25%) to about 0.4 (40%) of the total depth DPan of the pan 164, such as from about 0.25 (25%) to about 0.3 (30%) of the total depth DPan of the pan 164, for example from about 0.3 (30%) to about 0.5 (50%) of the total depth DPan of the pan 164, such as from about 0.4 (40%) to about 0.5 (50%) of the total depth DPan of pan 164.

In an example, the height HBaffle and the positioning of the baffle plate 170 is such that it leaves space at the top (HTop in FIG. 13) and/or a space at the bottom (HBot in FIG. 13) of the pan 164 for gas and liquid flow. In some examples where the manifold 168 and the baffle plate 170 both are present in the pan assembly 160, depending on the depth of the manifold 168 and the placement of the baffle plate 170 with respect to the depth DPan of the pan 164, the baffle plate 170 may run behind the manifold 168 (e.g., between the manifold 168 and the electrode 176) towards the top of the pan 164 or the baffle plate 170 may end below the manifold 168. In either case, there can be a space between the baffle plate 170 and the top and/or bottom of the pan 164 for gas and liquid flow.

In an example, the space HBot between a bottom edge of the baffle plate 170 and the bottom wall of the pan 164 is from about 6 mm to about 75 mm, for example from about 6 mm to about 65 mm, such as from about 6 mm to about 50 mm, for example from about 6 mm to about 40 mm, such as from about 6 mm to about 30 mm, for example from about 6 mm to about 20 mm, such as from about 6 mm to about 10 mm, for example from about 10 mm to about 75 mm, such as from about 10 mm to about 65 mm, for example from about 10 mm to about 50 mm, such as from about 10 mm to about 40 mm, for example from about 10 mm to about 30 mm, such as from about 10 mm to about 20 mm, for example from about 10 mm to about 15 mm, such as from about 20 mm to about 75 mm, for example from about 20 mm to about 65 mm, such as from about 20 mm to about 50 mm, for example from about 20 mm to about 40 mm, such as from about 20 mm to about 30 mm, for example from about 30 mm to about 75 mm, such as from about 30 mm to about 65 mm, for example from about 30 mm to about 50 mm, such as from about 30 mm to about 40 mm, for example from about 40 mm to about 75 mm, such as from about 40 mm to about 65 mm, for example from about 50 mm to about 75 mm, such as from about 50 mm to about 65 mm, for example from about 60 mm to about 75 mm.

In some embodiments, the anode and/or the cathode pan assembly provided herein, with the aforementioned manifold and the outlet tube and/or the baffle assembly provide several advantages such as, but not limited to, accommodating the aforementioned high flow rate of anolyte or catholyte and/or reducing or minimizing the incidence of slug or plug flow; reducing or minimizing large spatial and/or temporal temperature fluctuations; reducing or minimizing pressure fluctuations due to multiphase flow in the cell, e.g., to less than 0.5 psi; and/or reducing or minimizing membrane erosion and/or fatigue.

As noted above, operation of the electrolyzer cell at high current densities can result in significant challenges, such as, but not limited to, large amount of heat generated in the cell. In an electrolyzer cell producing a large amount of gas at high current densities, the gas/electrolyte mixture can have a lower specific heat, a lower density, and/or a lower thermal conductivity than the electrolyte alone. Therefore, the heat removal efficiency of the electrolyte can be reduced as the gas hold up increases. Local temperatures can then rise quickly if a gas pocket masks a region of the electrode. If a significant region of the electrode is masked, the unmasked region will have to work harder, increasing the local Joule heating. Local hot spots thus developed can damage the membrane. As the current density is increased in the cell, power dissipation can also rise dramatically. Large spatial and/or temporal temperature fluctuations can damage the membrane.

FIGS. 16-19 and 20A-20C show an illustrative example of a pan assembly 190 that can be used as the anode pan assembly for the anode half cell 111 or as the cathode pan assembly for the cathode half cell 121, or both, in the electrolyzer cell 100 shown in FIG. 1. The pan assembly 190 includes a plurality of ribs 194 with specified geometry and/or spacing, and/or via the use of one or more welds 196 that couple an electrode 198 of the pan assembly 190 to the ribs 194, wherein the welds 196 have a specified weld density and cross-sectional configuration to reduce or minimize power dissipation in order to improve temperature distribution during operation of the cell. The pan assembly 190 can also include features of the pan assembly 140 described above with respect to FIGS. 3-8 (e.g., a manifold and outlet tube through which electrolyte and produced gas can flow before exiting the pan assembly 190, which can be similar or identical to the manifold 144 and outlet tube 146 described above with respect to the pan assembly 140) and/or features of the pan assembly 160 described above with respect to FIGS. 9-15 (e.g., a baffle assembly, which can be similar or identical to the baffle assembly 162 described above with respect to the pan assembly 160). In other words, the pan assembly that forms either the anode assembly or the cathode assembly, or both, can include features of the pan assembly 140 described above with respect to FIGS. 3-8 and/or of the pan assembly 160 described above with respect to FIGS. 9-15 in addition to features of the pan assembly 190 described below.

The rib geometry, rib spacing, and/or weld density and cross-sectional configurations in the pan assembly 190 can reduce or minimize the effect of one or more of these challenges, such as, but not limited to, by more effectively distributing current across the pan assembly 190 to reduce the chance of hot spot formation, reduce or avoid large spatial and/or temporal temperature fluctuations of the electrolyte along the height of the pan assembly 190, and/or reduce or minimize membrane damage due to hot spots.

The design of the pan assembly 190 comprising the one or more ribs 194 and the welds 196, as described below, can provide for efficient current distribution across the active area of the cell when operating at high current densities. The cross-sectional area of the ribs 194 and the welds 196 can also allow the cells to be more effective for operational and economical purposes.

Similar to the pan assemblies 140 and 160 described above with respect to FIGS. 3-15, the pan assembly 190 can be used as the structure for one or both of the anode half cell 111 and the cathode half cell 121 in the electrolyzer cell 100 of FIG. 1, i.e., the pan assembly 190 can form the anode half cell 111 such that the pan assembly 190 is an anode pan assembly and/or the pan assembly 190 can form the cathode half cell 121 such that the pan assembly 190 is a cathode pan assembly. The pan 192 can include an interior for receiving an electrolyte (i.e., an anolyte if the pan assembly 190 is an anode pan assembly and a catholyte if the pan assembly 190 is a cathode pan assembly) and an electrode 198 (i.e., the anode 112 in an anode pan assembly 190 or the cathode 122 is a cathode pan assembly 190). The anode pan assembly and the cathode pan assembly can be separated by a separator (i.e., the membrane 131), which can be, for example, one or more of a diaphragm, a membrane electrode assembly (MEA), or an ion exchange membrane (IEM). The pan assembly 190 can further comprise components, such as a collection system (e.g., a manifold such as the manifold 144 or 168 described above) that collects the gas and the electrolyte for flow out of the pan assembly 190. Various additional separator components can be provided, e.g., to separate the one or more membranes from the anode, to separate the one or more membranes from the cathode, to separate one membrane from another membrane (e.g., to separate an anion exchange membrane (AEM) from a cation exchange membrane (CEM)), and/or to provide mechanical integrity to the one or more membranes. In addition to these components, individual gaskets or gasket tape may be provided in between and along the outer perimeter of the components to seal the compartments from fluid leakage.

In an example, the pan assembly 190 includes a pan 192, one or more ribs 194 positioned vertically inside the pan 192, an electrode 198 coupled to the one or more ribs 194, and one or more welds 196 that weld the electrode 198 to the one or more ribs 194. FIG. 16 is a front view of an illustrative example of the pan assembly 190, FIG. 17 is a side cross-sectional view of the pan assembly 190, and FIG. 18 is an enlarged view of the cross-section taken along line 18 in FIG. 17. The Figures show the one or more structures that can form the one or more ribs 194. As can be seen particularly in the view of FIG. 18, in an example, the one or more ribs 194 can be perpendicular or substantially perpendicular to a major dimension of the pan 192. For example, each of the one or more ribs 194 can be perpendicular or substantially perpendicular to one or more major faces of the pan 192, such as the electrode 198 or a back pan wall 200.

On top of the pan 192 and on top of the one or more ribs 194 can be placed the electrode 198. As can be seen, in an example, the electrode 198 can be welded to the one or more ribs 194 with one or more welds 196. In an example, each of the one or more ribs 194 is coupled to the back wall 200 of the pan 192 by one or more tabs 202 that are coupled to the back wall 200 with one or more tab welds 204.

In an example, the electrode 198 can be electrically coupled to the supplied electrical current via the one or more welds 196. During operation of a cell that uses the pan assembly 190 to form the cathode half cell, current flows into the cathode (e.g., the electrode 198 of the cathode pan assembly 190) through the welds 196 of the cathode pan assembly 190. Then, the current flows from the cathode 198 to the one or more ribs 194 of the cathode pan assembly 190. The current then flows through the one or more ribs 194 of the cathode pan assembly 190 through the tabs 202 and finally into a conductor contacting the pan 192 of the cathode pan assembly 190 (e.g., to the anode half cell of an adjacent cell or to a contact plate). During operation of a cell that uses the pan assembly 190 to form the anode half cell, current flows from a conductor contacting the pan 192 of the anode pan assembly 190 (e.g., from the cathode half cell of an adjacent cell or from a contact plate) to the ribs 194 of the anode pan assembly 190 through the tabs 202, then to the anode (e.g., the electrode 198 of the anode pan assembly 190), and then into a conductor that is electrically connected to one or more of the welds 196 of the anode pan assembly 190. As noted above, the one or more ribs 194 can be welded to the back wall 200 of the pan 192 via the tabs 202 and the tab welds 204. In an example, the tabs 202 set the spacing of the tab welds 204 between the bottom of the ribs 194 and the back wall 200 of the pan 192. Since the current flows between the back wall 200 of the pan 192 and the electrode 198 through the ribs 194, the tabs 202 can provide adequate weld cross-section between the ribs 194 and the pan 192. The tabs 202 can facilitate better current distribution across the active area and provide electrical contact between the ribs 194 and the pan 192. However, in other examples, the ribs 194 can be directly welded to the back wall 200 of the pan 192 and may not be connected through tabs.

The geometry and spacing of the one or more ribs 194 can dictate current flow through the pan assembly 190. The geometry of the ribs 194 can include, but not limited to, the number of the ribs 194, the height HRib of the ribs 194, the physical design of the ribs 194, the pitch PRibs between adjacent ribs 194, and/or the thickness TRib of the ribs 194 (as shown in FIG. 19). As the current flows in through the welds 196, the geometry, spacing or density, and/or cross-sectional area of the welds 196 can also impact current flow through the pan assembly 190. As increasingly high currents flow through the cell, the density and the cross sectional area of the welds 196 can significantly impact the local Joule heating and avoid membrane damage from local hot spots. Provided herein are a unique geometry, spacing, and cross-sectional area of the ribs 194 as well as the welds 196 that can facilitate efficient operation of the electrochemical cell made up of one or two of the pan assemblies 190 at high current densities.

The physical configuration, i.e., the overall shape, of the one or more ribs 194 can be selected for one or more purposes. For example, one or more of the ribs 194 can be solid plates, such as solid plates of conductive metal, such as the example ribs 194A shown in FIG. 20A. In another example, the one or more ribs 194 can include one or more holes or openings that allow the electrolyte to move laterally within the pan 192, such as the one or more ribs 194B having holes 206 as shown in FIG. 20B. In an example, the one or more ribs 194 include one or more notches for receiving one or more other structures, such as the ribs 194C shown in FIG. 20C that include one or more notches 208 for receiving portions of a baffle plate 210 (which is described in more detail below). In an example, the one or more ribs 194 can include both holes 206 and notches 208, as with the ribs 194C shown in FIG. 20C, or can include only the holes 206 or only the notches 208.

The number of ribs 194 inside the pan 192 can impact the current distribution and the power dissipation within the pan assembly 190. In an example, the number of ribs 194 inside the pan 192 is from 1 to 75 of the ribs 194, such as from 1 to 60 of the ribs 194, for example from 1 to 50 of the ribs 194, such as from 1 to 40 of the ribs 194, for example from 1 to 30 of the ribs 194, such as from 1 to 20 of the ribs 194, such as from 1 to 10 of the ribs 194, for example from 1 to 5 of the ribs 194, such as from 5 to 75 of the ribs 194, for example from 5 to 60 of the ribs 194, such as from 5 to 50 of the ribs 194, for example from 5 to 40 of the ribs 194, such as from 5 to 30 of the ribs 194, for example from 5 to 20 of the ribs 194, such as from 5 to 10 of the ribs 194, for example from 10 to 75 of the ribs 194, such as from 10 to 60 of the ribs 194, for example from 10 to 50 of the ribs 194, such as from 10 to 40 of the ribs 194, for example from 10 to 30 of the ribs 194, such as from 10 to 20 of the ribs 194, for example from 20 to 75 of the ribs 194, such as from 20 to 60 of the ribs 194, for example from 20 to 50 of the ribs 194, such as from 20 to 40 of the ribs 194, for example from 20 to 30 of the ribs 194, such as from 30 to 75 of the ribs 194, for example from 30 to 60 of the ribs 194, such as from 30 to 50 of the ribs 194, for example from 30 to 40 of the ribs 194, such as from 40 to 75 of the ribs 194, for example from 40 to 60 of the ribs 194, such as from 40 to 50 of the ribs 194, for example from 50 to 75 of the ribs 194, such as from 50 to 60 of the ribs 194, for example from 60 to 75 of the ribs 194. For example, the pan assemblies 190 shown in FIGS. 16-19 and 20A-20C show the pan 192 containing five (5) ribs 194.

A cross-sectional perspective view of the exemplary pan assembly 190 is shown in FIG. 19. The electrode 198 and the welds 196 are not shown in FIG. 19. As described above, the pan assembly 190 includes one or more ribs 194 positioned vertically in the pan 192, e.g., the ribs 194 are coupled to the back wall 200 of the pan 192, such as with the tabs 202, and the ribs 194 extend from the back wall 200 toward the electrode. In FIG. 19, the pitch, or the distance between, two adjacent ribs 194 is labeled as PRibs, the height of the one or more ribs 194 is labeled as HRib, and the thickness of the one or more ribs 194 is labeled as TRib. The ribs 194 are shown in FIG. 19 as comprising holes 206 for the movement of the electrolyte as well as notches 208. The notches 208 facilitate fitting of specified sections of a baffle plate 210 into the space formed by the notches 208 in order to secure the baffle plate 210 to the one or more ribs 194. The baffle plate 210 can be similar or identical to the baffle plate 170 described above with respect to the pan assembly 160 of FIGS. 9-15. In an example, the one or more ribs 194 are made of a conductive metal, such as, but not limited to, nickel, stainless steel, and the like.

It is to be understood that the holes 206 and the notches 208 may not be present, e.g., the ribs 194 can each be formed from a solid plate, such as the ribs 194A of FIG. 20A, or the ribs 194 can have notches 208 but not have holes 206, or the ribs 194 can have the holes 206 and not the notches 208. The holes 206, if present, need not be of any specific shape or size. For example, the holes 206 can be circular openings, slits, perforations, or a mesh.

In an example, the length LRib of the one or more ribs 194 (FIG. 16) is from about 0.25 meters (m) to about 1.5 m, for example from about 0.25 m to about 1.2 m, such as from about 0.25 m to about 1 m, for example from about 0.25 m to about 0.8 m, such as from about 0.25 m to about 0.6 m, for example from about 0.25 m to about 0.5 m, such as from about 0.25 m to about 0.4 m, for example from about 0.25 m to about 0.3 m, such as from about 0.5 m to about 1.5 m, for example from about 0.5 m to about 1.2 m, such as from about 0.5 m to about 1 m, for example from about 0.5 m to about 0.8 m, such as from about 0.5 m to about 0.6 m, for example from about 0.6 m to about 1.5 m, such as from about 0.6 m to about 1.2 m, for example from about 0.6 m to about 1 m, such as from about 0.6 m to about 0.8 m, for example from about 0.7 m to about 1.5 m, such as from about 0.7 m to about 1.2 m, for example from about 0.7 m to about 1 m, such as from about 0.7 m to about 0.8 m, for example from about 0.8 m to about 1.5 m, such as from about 0.8 m to about 1.2 m, for example from about 0.8 m to about 1 m.

In an example, the length of the notch 208 in each of the one or more ribs 194 is from about 5 millimeters (mm) to about 100 mm, for example from about 5 mm to about 80 mm, such as from about 5 mm to about 60 mm, for example from about 5 mm to about 50 mm, such as from about 5 mm to about 40 mm, for example from about 5 mm to about 30 mm, such as from about 5 mm to about 20 mm, for example from about 5 mm to about 10 mm, such as from about 10 mm to about 100 mm, for example from about 10 mm to about 50 mm, such as from about 10 mm to about 40 mm, for example from about 10 mm to about 30 mm, such as from about 10 mm to about 20 mm, for example from about 20 mm to about 100 mm, such as from about 20 mm to about 50 mm, for example from about 20 mm to about 40 mm, such as from about 20 mm to about 30 mm, for example from about 30 mm to about 100 mm, such as from about 30 mm to about 50 mm, for example from about 30 mm to about 40 mm, such as from about 40 mm to about 100 mm, for example from about 40 mm to about 50 mm, such as from about 50 mm to about 100 mm, for example from about 75 mm to about 100 mm.

In an example, the thickness TRib of the one or more ribs 194 is from about 1 mm to about 3 mm, for example from about 1 mm to about 2.5 mm, such as from about 1 mm to about 2 mm, for example from about 1 mm to about 1.5 mm, such as from about 2 mm to about 3 mm, for example from about 2 mm to about 2.5 mm, such as from about 2.5 mm to about 3 mm.

In an example, the height HRib of the one or more ribs 194 is from about 10 mm to about 110 mm, for example from about 10 mm to about 100 mm, such as from about 10 mm to about 75 mm, for example from about 10 mm to about 70 mm, such as from about 10 mm to about 60 mm, for example from about 10 mm to about 50 mm, such as from about 10 mm to about 40 mm, for example from about 10 mm to about 30 mm, such as from about 20 mm to about 110 mm, for example from about 20 mm to about 75 mm, such as from about 20 mm to about 70 mm, for example from about 20 mm to about 60 mm, such as from about 20 mm to about 50 mm, for example from about 20 mm to about 40 mm, such as from about 20 mm to about 30 mm, for example from about 30 mm to about 110 mm, such as from about 30 mm to about 75 mm, for example from about 30 mm to about 70 mm, such as from about 30 mm to about 60 mm, for example from about 30 mm to about 50 mm, such as from about 30 mm to about 40 mm, for example from about 40 mm to about 110 mm, such as from about 40 mm to about 75 mm, for example from about 40 mm to about 70 mm, such as from about 40 mm to about 60 mm, for example from about 40 mm to about 50 mm, such as from about 50 mm to about 110 mm, for example from about 50 mm to about 75 mm, such as from about 50 mm to about 70 mm, for example from about 50 mm to about 60 mm, such as from about 60 mm to about 110 mm, for example from about 60 mm to about 75 mm, such as from about 70 mm to about 110 mm, for example from about 70 mm to about 80 mm.

In an example, the pitch PRibs between two adjacent ribs 194 is from about 40 mm to about 200 mm, for example from about 40 mm to about 150 mm, such as from about 40 mm to about 140 mm, for example from about 40 mm to about 130 mm, such as from about 40 mm to about 120 mm, for example from about 40 mm to about 110 mm, such as from about 40 mm to about 100 mm, for example from about 40 mm to about 80 mm, such as from about 40 mm to about 70 mm, for example from about 60 mm to about 200 mm, such as from about 60 mm to about 150 mm, for example from about 60 mm to about 140 mm, such as from about 60 mm to about 130 mm, for example from about 60 mm to about 120 mm, such as from about 60 mm to about 110 mm, for example from about 60 mm to about 100 mm, such as from about 60 mm to about 80 mm, for example from about 80 mm to about 200 mm, such as from about 80 mm to about 150 mm, for example from about 80 mm to about 100 mm, such as from about 100 mm to about 200 mm, for example from about 100 mm to about 150 mm, such as from about 100 mm to about 140 mm, for example from about 100 mm to about 130 mm, such as from about 100 mm to about 120 mm, for example from about 125 mm to about 200 mm, such as from about 125 mm to about 150 mm, for example from about 125 mm to about 140 mm, such as from about 130 mm to about 150 mm, for example from about 75 mm to about 120 mm.

As shown in FIGS. 18 and 20A-20C, the electrode 198 can be welded to the top of the one or more ribs 194 with a plurality of welds 196. In an example, the electrode 198 is a planar electrode or an expanded metal or a mesh. In examples where the electrode 198 is an expanded metal or a mesh, the thickness of each strand that forms the mesh can be from about 0.5 mm to about 3 mm, for example from about 0.5 mm to about 2.5 mm, such as from about 0.5 mm to about 2 mm, for example from about 0.5 mm to about 1.5 mm, such as from about 0.5 mm to about 1 mm, for example from about 1 mm to about 3 mm, such as from about 1 mm to about 2.5 mm, for example from about 1 mm to about 2 mm, such as from about 1 mm to about 1.5 mm, for example from about 1.5 mm to about 3 mm, such as from about 1.5 mm to about 2.5 mm, for example from about 1.5 mm to about 2 mm, such as from about 2 mm to about 3 mm, for example from about 2.5 mm to about 3 mm.

The geometry, spacing, density, and/or cross-sectional area of the welds 196 can impact current flow through the pan assembly 190. As the operational current density is increased and more current flows through the cell, the density of the welds 196 (e.g., the cross-sectional area of the welds 196 and the spacing between welds 196) can impact the local Joule heating. The density of the welds 196 can be selected to reduce the or minimize the chances of membrane damage due to the formation local hot spots. The example welds 196 in FIGS. 20A-20C are illustrated as spots. However, the welds 196 can be in form of lines, spots, patterns, or any other shape, or combinations thereof. For example, a spot welder can form the welds 196 as spots, while a laser welder can produce the welds 196 as lines and/or spots and/or patterns. Patterns that the welds 196 can be formed as include, but are not limited to, a combination of dots, an array of dots, dashes, spots, lines, and line segments, which can be arranged in the pattern of any geometrically regular shape, such as a generally rectangular geometry, a generally circular geometry, or a generally hexagonal geometry, or can be arranged in an irregular shape.

Examples of welding techniques that can be used to form the welds 196 include, but are not limited to: laser welding, TiG welding, and spot welding, for example resistance spot welding. Laser welding may enable a single linear weld 196 along a substantial portion of the length LRib of one of the ribs 194 up to and including the entire length LRib of the rib 194 in order to weld the rib 194 to the electrode 198. For example, when the one or more ribs 194 are a solid plate (e.g., ribs 194A of FIG. 20A) or a plate with holes that does not include notches 208 (e.g., the ribs 194B of FIG. 20B), there may be a single linear weld 196 along the whole length LRib of the rib 194 in order to join the rib 194 to the electrode 198. Laser welding or TiG welding may also be used to create welds 196 in the form of line segments. For example, when the one or more of the ribs 194 include notches 208 (e.g., the ribs 194C of FIG. 20C), there may be segments of weld lines over the portions of the ribs 194 that come into contact with the electrode 198, but not over the notches 208. Laser welding can also produce weld patterns comprising dots, an array of dots, dashes, spots, line segments, long lines, and any specified geometry, such as an oval geometry, rectangular geometry, circular geometry, hexagonal geometry, or combinations thereof. The weld geometries may be dictated by the shape of the welding tip and anvil, such as when the welds are created with resistance welding. TiG welds may be created manually, and can be in arbitrary form.

In an example, the geometry of the welds 196 includes the number of welds in the pan 192. The number of the welds 196 coupling the electrode 198 to the ribs 194 can impact the current distribution and the power dissipation within the pan assembly 190. In an example, the number of welds 196 per rib 194 that are in the form of the spots (such as the example spot welds 196 shown in FIGS. 18 and 20A-20C) is from 10 to 50 of the welds 196 per rib 194, for example from 10 to 40 of the welds 196 per rib 194, such as from 10 to 30 of the welds 196 per rib 194, for example from 10 to 20 of the welds 196 per rib 194, such as from 20 to 50 of the welds 196 per rib 194, for example from 20 to 40 of the welds 196 per rib 194, such as from 20 to 30 of the welds 196 per rib 194, for example from 30 to 40 of the welds 196 per rib 194, such as from 35 to 40 of the welds 196 per rib 194, for example from 40 to 50 of the welds 196 per rib 194.

In an example, the distance between the welds 196 when in the form of spot welds is from about 25 mm to about 200 mm, for example from about 25 mm to about 150 mm, such as from about 25 mm to about 100 mm, for example from about 25 mm to about 75 mm, such as from about 25 mm to about 50 mm, for example from about 50 mm to about 200 mm, such as from about 50 mm to about 150 mm, for example from about 50 mm to about 100 mm, such as from about 50 mm to about 75 mm, for example from about 75 mm to about 200 mm, such as from about 75 mm to about 150 mm, for example from about 75 mm to about 100 mm, such as from about 100 mm to about 200 mm, for example from about 100 mm to about 150 mm, independently in x- and y-directions.

In an example, the number of the welds 196 per rib 194 that are in the form of line welds or line segment welds is between 1 to 75 of the welds 196 per rib 194, for example from 1 to 70 of the welds 196 per rib 194, such as from 1 to 60 of the welds 196 per rib 194, for example from 1 to 50 of the welds 196 per rib 194, such as from 1 to 40 of the welds 196 per rib 194, for example from 1 to 30 of the welds 196 per rib 194, such as from 1 to 20 of the welds 196 per rib 194, for example from 1 to 10 of the welds 196 per rib 194, such as from 2 to 75 of the welds 196 per rib 194, for example from 2 to 70 of the welds 196 per rib 194, such as from 2 to 60 of the welds 196 per rib 194, for example from 2 to 50 of the welds 196 per rib 194, such as from 2 to 40 of the welds 196 per rib 194, for example from 2 to 30 of the welds 196 per rib 194, such as from 2 to 20 of the welds 196 per rib 194, for example from 2 to 10 of the welds 196 per rib 194, such as from 10 to 75 of the welds 196 per rib 194, for example from 10 to 70 of the welds 196 per rib 194, such as from 10 to 60 of the welds 196 per rib 194, for example from 10 to 50 of the welds 196 per rib 194, such as from 10 to 40 of the welds 196 per rib 194, for example from 10 to 30 of the welds 196 per rib 194, such as from 10 to 20 of the welds 196 per rib 194, for example from 25 to 75 of the welds 196 per rib 194, such as from 25 to 50 of the welds 196 per rib 194, for example from 50 to 75 of the welds 196 per rib 194, such as from 60 to 75 of the welds 196 per rib 194.

In an example, the distance between the welds 196 when in the form of the line welds or line segment welds is from about 40 mm to about 200 mm, for example from about 40 mm to about 150 mm, such as from about 40 mm to about 100 mm, for example from about 40 mm to about 75 mm, such as from about 75 mm to about 200 mm, for example from about 75 mm to about 150 mm, such as from about 75 mm to about 100 mm, for example from about 100 mm to about 200 mm, such as from about 100 mm to about 150 mm, for example from about 150 mm to about 200 mm, independently in x- and y-directions.

In an example, when the one or more ribs 194 comprise the one or more notches 208 and the welds 196 comprise one or more line segments that weld the electrode 198 to the ridges of the ribs 194 formed between notches 208, the line segment of a particular weld 196 can run along the entire length of a ridge between notches 208 or along only a partial length of a ridge between notches 208. In an example, the length of a line segment weld 196 is the length of the ridge between notches 208 or the length of the line segment weld 196 is from about 0.25 m to about 1 m, for example from about 0.25 m to about 0.8 m, such as from about 0.25 m to about 0.6 m, for example from about 0.25 m to about 0.5 m, such as from about 0.25 m to about 0.4 m, for example from about 0.25 m to about 0.3 m, such as from about 0.5 m to about 1 m, for example from about 0.5 m to about 0.8 m, such as from about 0.5 m to about 0.6 m, for example from about 0.6 m to about 1 m, such as from about 0.6 m to about 0.8 m, for example from about 0.7 m to about 1 m, such as from about 0.7 m to about 0.8 m, for example from about 0.8 m to about 1 m.

In an example, the distance between two adjacent line segment welds 196 is from about 5 mm to about 100 mm, for example from about 5 mm to about 80 mm, such as from about 5 mm to about 60 mm, for example from about 5 mm to about 50 mm, such as from about 5 mm to about 40 mm, for example from about 5 mm to about 30 mm, such as from about 5 mm to about 20 mm, for example from about 5 mm to about 10 mm, such as from about 10 mm to about 100 mm, for example from about 10 mm to about 50 mm, such as from about 10 mm to about 40 mm, for example from about 10 mm to about 30 mm, such as from about 10 mm to about 20 mm, for example from about 20 mm to about 100 mm, such as from about 20 mm to about 50 mm, for example from about 20 mm to about 40 mm, such as from about 20 mm to about 30 mm, for example from about 30 mm to about 100 mm, such as from about 30 mm to about 50 mm, for example from about 30 mm to about 40 mm, such as from about 40 mm to about 100 mm, for example from about 40 mm to about 50 mm, such as from about 50 mm to about 100 mm, for example from about 75 mm to about 100 mm.

In example, the cross-sectional area of each weld 196 is from about 6 square millimeters (mm2) to about 3300 mm2, for example from about 6 mm2 to about 3000 mm2, such as from about 6 mm2 to about 2000 mm2, for example from about 6 mm2 to about 1000 mm2, such as from about 6 mm2 to about 500 mm2, for example from about 6 mm2 to about 300 mm2, such as from about 6 mm2 to about 100 mm2, for example from about 50 mm2 to about 3300 mm2, such as from about 50 mm2 to about 3000 mm2, for example from about 50 mm2 to about 2000 mm2, such as from about 50 mm2 to about 1000 mm2, for example from about 50 mm2 to about 500 mm2, such as from about 50 mm2 to about 300 mm2, for example from about 50 mm2 to about 100 mm2, such as from about 100 mm2 to about 3300 mm2, for example from about 100 mm2 to about 3000 mm2, such as from about 100 mm2 to about 2000 mm2, for example from about 100 mm2 to about 1000 mm2, such as from about 100 mm2 to about 500 mm2, for example from about 100 mm2 to about 300 mm2, such as from about 500 mm2 to about 3300 mm2, for example from about 500 mm2 to about 3000 mm2, such as from about 500 mm2 to about 2000 mm2, for example from about 500 mm2 to about 1000 mm2, such as from about 1000 mm2 to about 3300 mm2, for example from about 1000 mm2 to about 3000 mm2, such as from about 1000 mm2 to about 2000 mm2, for example from about 2000 mm2 to about 3000 mm2, such as from about 2500 mm2 to about 3000 mm2.

In an example, the geometry, spacing or density, and/or cross-sectional area of the welds 196 is such that a ratio of the cross-sectional area of the electrode 198 relative to the total cross-sectional area of the welds 196 is from about 15:1 to about 2000:1, for example from about 15:1 to about 1000:1, such as from about 15:1 to about 500:1.

In an example, the geometry, spacing or density, and/or cross-sectional area of the welds 196 is such that the current density through each weld 196 when the cell 190 is operating at its maximum current density is about 20 amps per square millimeter (A/mm2) or less, for example about 19 A/mm2 or less, such as 18 A/mm2 or less, for example about 17 A/mm2 or less, such as about 16 A/mm2 or less, for example about 15 A/mm2 or less, such as about 14 A/mm2 or less, for example about 13 A/mm2 or less, such as about 12.5 A/mm2 or less, for example about 12 A/mm2 or less, such as about 11 A/mm2 or less, for example about 10 A/mm2 or less, such as about 9 A/mm2 or less, for example about 8 A/mm2 or less, or from about 5 A/mm2 to about 20 A/mm2, such as from about 7.5 A/mm2 to about 15 A/mm2, for example from about 7.5 A/mm2 to about 10 A/mm2.

In one specific and non-limiting example, the welds 196 are in the form of spot welds and there are from 10 to 50 of the welds 196 per rib 194, the distance between adjacent spot welds 196 is from about 25 mm to about 200 mm (independently in the x- and y-directions), the cross-sectional area of each spot weld 196 is from about 6 mm2 to about 3300 mm2, and the current density through each spot weld 196 is 6 A/mm2 or less, for example 4 A/mm2 or less. In another specific and non-limiting example, the welds 196 are in the form of line welds and there from 1 to 75 of the welds 196 per rib 194, the distance between adjacent line welds 196 is from about 40 mm to about 200 mm (independently in the x- and y-directions), the cross-sectional area of each line weld 196 is from about 6 mm2 to about 3300 mm2, and the current density through each line weld 196 is 6 A/mm2 or less, for example 4 A/mm2 or less.

In an example, a pan assembly comprising one or any combination of the structures described above for the pan assemblies 140, 160, 190 can provide for a superficial liquid velocity of the electrolyte through the pan assembly 140, 160, 190 of 0.1 m/s or less, for example 0.08 m/s or less, such as 0.05 m/s or less, for example 0.01 m/s or less.

Control of the temperature within the electrochemical cell can be important for operation of the cell. In operation, the current density through the cell can be varied often, for example in response to one or more electricity input factors and/or one or more hydrogen output factors. To maximize performance and the lifetime of the separator, it is generally preferred to maintain the separator within a small range of temperatures. If the temperatures of the electrolyte inlets into the electrochemical cell is held constant or substantially constant while the current density is changed significantly, the temperature at the separator will vary significantly.

The inventors have discovered that the flow rates of electrolyte through the anode half cell and the cathode half cell of the electrochemical cell 100 can be set so that the resulting temperature of the electrolyte outlet streams can be maintained within a specified range at the highest expected operational current density using convenient temperatures for the inlet streams. FIG. 21 shows an example electrochemical cell 300 that is configured for temperature control to maintain a temperature of a separator 331 within the cell 300. The cell 300 is similar to the example cell 100 described above with respect to FIG. 1. For example, like the cell 100, the electrochemical cell 300 comprises two half cells: a first half cell 311 and a second half cell 321. In an example, the first and second half cells 311, 321 are separated by a separator 331, such as a membrane 331.

The first half cell 311 can comprise a first electrode 312, which can be placed proximate to the separator 331, and the second half cell 321 can comprise a second electrode 322, which can be placed proximate to the separator 331, for example on an opposite side of the separator 331 from the first electrode 312. In an example, the first electrode 312 is the anode for the cell 300 and the second electrode 322 is the cathode for the cell 300, such that the first half cell 311 may also be referred to as the anode half cell 311, the first electrode 312 may also be referred to as the anode 312, the second half cell 321 may also be referred to as the cathode half cell 321, and the second electrode 322 may also be referred to as the cathode 322. Each of the electrodes 312, 322 can be coated with one or more electrocatalysts to speed the reaction toward the hydrogen gas (H2 gas) and/or the oxygen gas (02 gas), such as, 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, or nickel mesh coated with ruthenium oxide (RuO2).

The anode 312 can be electrically connected to an external positive conductor 316 and the cathode 322 can be electrically connected to an external negative conductor 326. When the separator 331 is wet and is in electrolytic contact with the electrodes 312 and 322, and an appropriate voltage is applied across the conductors 316 and 326, O2 gas is liberated at the anode 312 or H2 gas is liberated at the cathode 322, or both. In certain configurations, an electrolyte, e.g., one comprising of a solution of KOH in water, is fed into the half cells 311, 321. For example, the electrolyte can flow into the anode half cell 311 through a first electrolyte inlet 314 and into the cathode half cell 321 through a second electrolyte inlet 324. In an example, the flow of the electrolyte through the anode half cell 311 can pick up produced O2 gas as bubbles 313, which exit the anode half cell 311 through a first outlet 315. Similarly, the flow of the electrolyte through the cathode half cell 321 can pick up produced H2 gas as bubbles 323, which can exit the cathode half cell 321 through a second outlet 325.

By referring to a lookup table an operator can set the temperatures of the inlet streams 314, 324 as a function of the current density at which the cell 300 is currently being run such that the resulting temperatures of the outlet streams 315, 325 does not fluctuate significantly, e.g., so that the temperatures of the outlet streams 315, 325 are within a specified temperature variance of a target temperature. In another example, the temperature of the inlet streams 314, 324 can be varied in order to maintain a temperature of the separator 331 at a constant or substantially constant set point (which can be determined by measuring the temperatures of one or both of the outlet streams 325, 315 and calculating the temperature of the separator 331 based on one or more of the temperature of the outlet stream(s) 315, 325 and the operating current density). In an example, the inlet temperature control is automated through one or more controllers 340, 342 (e.g., a first controller 340 configured for temperature control of the first inlet stream 314 and a second controller 342 configured for temperature control of the second outlet stream 324 based on temperature of the second outlet stream 325), such as a programmable logic controller (“PLC”). The temperature control can be linked to one or more of: the current density setting (e.g., the current across the electrolyzer cell 300 per area of the electrodes 312, 322), the voltage across the electrolyzer cell 300, and the temperature of the corresponding outlet stream 315, 325. In some examples, the temperature control can be automated using a proportional-integral-derivative (“PID”) controller, or a feed-forward control scheme, or both. In an example, the inlet temperature control is controlled via a feed-forward control based on a current density setpoint and the observed voltage across the electrolyzer cell 300. In another example, in addition to the feed-forward control by current density, the temperature of the corresponding electrolyte outlet 315, 325 can also be used to control the temperature of the inlet 314, 324 via a PID controller tuned for slow response, which can allow the temperature of the outlet 315, 325 to fine tune the temperature of the inlet 314, 324, after a fast response from the feed-forward controller.

In an example, shown in FIG. 21, control of the temperatures of the inlet stream 314, 324 is effectively accomplished using a mixing scheme with a cooling heat exchanger 344, 346 that can cool at least a portion of the hot electrolyte return as it flows from the electrolyte outlet 315, 325 to the corresponding electrolyte inlet 314, 315. In the example of FIG. 21, a first cooling heat exchanger 344 is configured for cooling electrolyte of the first outlet stream 315 exiting the anode half cell 311 before it is recycled to the first inlet stream 314. A similar second cooling heat exchanger 346 is configured for cooling electrolyte of the second outlet stream 325 exiting the cathode half cell 321 before it is recycled to the second inlet stream 324. In an example, the electrolyte recycling configuration can include a bypass line 350, 352 that is configured to allow some or all of the recycling electrolyte to bypass the cooling heat exchanger 344, 346 (e.g., a first bypass line 350 to bypass the first cooling heat exchanger 344 and a second bypass line 352 to bypass the second cooling heat exchanger 346) so that the bypassing portion of the electrolyte is not cooled and remains at or near the hot temperature at the electrolyte outlet 315, 325. A corresponding bypass control valve 354, 356 can be included to modulate the proportion of recycling electrolyte that flows through the cooling heat exchanger 344, 346 and the proportion that will flow through the bypass line 350, 352 (e.g., a first control valve 354 to modulate flow through the first cooling heat exchanger 344 and the first bypass line 350 and a second control valve 356 to modulate flow through the second cooling heat exchanger 346 and the second bypass line 352). In the example shown in FIG. 21, the bypass control valves 354, 356 are situation on the bypass lines 350, 352. However, those having skill in the art will appreciate that the control valve(s) can be positioned at the inlet line feeding into the cooling heat exchangers 344, 346 or at the outlet line exiting the cooling heat exchangers 344, 346, which would still achieve the same effect of modulating the proportion of the electrolyte that flows through the heat exchangers 344, 346 and the bypass lines 350, 352.

The streams flowing through the cooling heat exchanger 344, 346 and the bypass line 350, 352 are then mixed to achieve a specified set-point temperature. For example, if it is desired that the temperature of the electrolyte fed to the cell 300 via the inlet 314, 324 be higher than its current temperature, then the control valve 354, 356 can be controlled so that a lower proportion of the electrolyte flows through the cooling heat exchanger 344, 346 relative to the proportion of the electrolyte that flows through the bypass line 350, 352 so that a relatively smaller amount of the electrolyte is cooled by the cooling heat exchanger 344, 346, and thus so that the temperature of the electrolyte after mixing the two streams is higher. Similarly, if it is desired that the temperature of the electrolyte fed to the cell 300 be lower than its current temperature, then the control valve 354, 356 can be controlled so that a higher proportion of the electrolyte flows through the cooling heat exchanger 344, 346 relative to the proportion that flows through the bypass line 350, 352 so that a relatively higher amount of the electrolyte is cooled by the cooling heat exchanger 344, 346, and thus so that the temperature of the electrolyte after mixing the two streams is lower.

In an example, a flow control valve 360, 362 located downstream of the mixing point can ensure that a feed flow rate of the electrolyte to the inlet 314, 324 remains constant or substantially constant (e.g., a first flow control valve 360 to control the flow rate of electrolyte to the first inlet 314 and a second flow control valve 362 to control the flow rate of electrolyte to the second inlet 324). In another example (not shown), a temperature control valve (similar to the control valve 354, 356 in FIG. 21) can control the flow rate through the cooling heat exchanger 344, 346 and a flow control valve can control the flow rate through the heat exchanger bypass line 350, 352. In an example, the cooling heat exchanger 344, 346 is at least slightly oversized (in terms of the flow rate that the heat exchanger 344, 346 can accommodate or the heat exchange capacity of the heat exchanger 344, 346), so that the combination of the cooling heat exchanger 344, 346 and the bypass line 350, 352 can provide for adequate temperature control and flow control. The inventors have found that this type of temperature control for the electrolyte inlet stream 314, 324 can provide for fast and linear or substantially linear inlet temperature control, compared to controlling the temperature of the inlet stream 314, 324 by changing the amount of cooling water being fed to the cooling heat exchanger 344, 346.

The combination of a fast linear temperature control of the inlet 314, 324 with a feed-forward controller setting the inlet temperature set point based on current density or observed voltage across the cell 300, or both, can provide for stable temperature control for the outlet stream 315, 325 when changing the current density (e.g., when changing the current density being applied across the cell 300 in order to change the H2 production rate based on one or more electricity input factors and/or one or more hydrogen output factors). Rapid temperature management in this way can compensate for quick changes of current density while minimizing thermal shock to the separator 331, the electrodes 312, 322, and other components of the cell 300.

Method of Operating an Electrolyzer.

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. In various aspects, the one or more electricity input factors and one or more hydrogen output factors do not include a regional price of electricity supplied to the electrolyzer or a regional demand for electricity supplied to the electrolyzer. In various aspects, the changing of the current density associated with the operation of the electrolyzer is not based on a regional price of electricity supplied to the electrolyzer or a regional demand for electricity supplied to the electrolyzer. In other aspects, the one or more electricity input factors do include a price of electricity supplied to the electrolyzer and/or a demand for electricity supplied to the electrolyzer, and the changing of the current density associated with the operation of the electrolyzer can be based on a price of electricity supplied to the electrolyzer and/or a demand for electricity supplied to the electrolyzer. The changing of the current density associated with the operation of the electrolyzer can be based on the one or more electricity input factors. The changing of the current density associated with the operation of the electrolyzer can be based on the one or more hydrogen output factors. The changing of the current density associated with the operation of the electrolyzer can be based on the one or more electricity input factors and the one or more hydrogen output factors.

The electrolyzer can be any suitable electrolyzer as described herein with respect to the electrolyzer system. The electrolyzer can include one or more electrolyzer cells each include a first half cell with a first electrode and a second half cell with a second electrode. The electrolyzer can include at least two of the electrolyzer cells. The electrolyzer can have a total size of 1 m3 to 90 m3, or 1 m3 to 45 m3, or 1 m3 to 20 m3. The electrolyzer can have a total size of at least about 2.5 m3.

The first half cell can include a pan, one or more ribs inside the pan, and a baffle plate coupled to the one or more ribs. The baffle plate can partition a volume in the pan to provide a riser region on a first side of the pan proximate to the first electrode and a down-comer region on a second side of the baffle plate opposite the first side. The riser region can facilitate gas formed at the first electrode to rise and avoid formation of gas pockets, and wherein the down-comer region can facilitate downward flow of an electrolyte solution. The rise of the gas and the downward flow of the electrolyte solution can cause circulation in the pan that facilitates thermal equilibrium and reduced temperature variation in the electrolyte. The first half cell can include a pan, a manifold positioned inside the pan, and an outlet tube exiting the manifold for electrolyte to exit the pan. A cross-sectional area of the manifold can be configured so that an electrolyte flow rate and a gas flow rate through the manifold are low enough to avoid slug flow or plug flow. The first half cell can include a pan, one or more ribs positioned vertically inside the pan, and a plurality of welds that weld the first electrode to the one or more ribs, wherein the plurality of welds can form a distributed array of welds across the electrode that distribute current across the electrode during operation of the electrochemical cell. Each electrolyzer cell can further include a separator between the first half cell and the second half cell, wherein a number, size, and positions of the plurality of welds can be such that an impact of power dissipation on a temperature of the separator is reduced to reduce damage due to high local temperature.

The various structural aspects of the electrolyzer cells and other supporting apparatus described herein—i.e., the manifold 144 and outlet tube 146 configuration of the example pan assembly 140 to accommodate a high gas production rate and a high electrolyte flow rate (as described herein with respect to FIGS. 3-8); the baffle plate assembly 162 of the example pan assembly 160 to further accommodate the high gas production rate and high electrolyte flow rate and to assist in temperature distribution within the electrolyte flowing through the pan assembly (as described herein with respect to FIGS. 9-15); the ribs 194 and welds 196 for coupling the electrode 198 to the ribs 194 for power and current distribution and improved temperature distribution (as described herein with respect to FIGS. 16-19 and 20A-20C); and the temperature control subsystem for maintaining the electrolyte temperature during operation of the cell in response to changes in current density (as described herein with respect to FIG. 21)—allow the overall water electrolysis H2 gas generation system to be flexible and dynamically accommodate a wide range of operational parameters. Specifically, the structural and systematic aspects described herein can allow the electrolyzer cells to operate over a wide range of current densities while still being able to accommodate a wide disparity in heat generation, temperature fluctuation, and gas production rate. For example, electrolyzer cells comprising one or more of these features can operate at a current density over a dynamic range of from as low as 0.05 A/cm2 to as high as 10.0 A/cm2, or from as low as about 150 milliamps per square centimeter (mA/cm2) to as high as about 3000 mA/cm2, such as from about 250 mA/cm2 to about 2750 mA/cm2, for example from about 500 mA/cm2 to about 2500 mA/cm2, such as from about 750 mA/cm2 to about 2250 mA/cm2, for example from about 1000 mA/cm2 to about 2000 mA/cm2. This large dynamic range of operating current densities can allow an operator with considerable flexibility to choose a threshold at which to start the transition from a load gaining current density to a load shedding current density and a threshold at which to operate a load shedding current density or to shut of the electrolyzer cells completely, and to include one or more additional intermediate price thresholds at which to set one or more intermediate operating current densities. The structural and systematic aspects described herein also allow the electrolyzer cells to accommodate a wide range electrolyte flow rates and gas production rates while still reducing or minimizing slug or plug flow of the electrolyte or the produced gas through the electrolyzer cells and/or exiting the electrolyzer cells.

These structural and systematic aspects can allow the electrolyzer cells to be operated at a current density that is higher than a specified current density and/or at a H2 gas production rate that is higher than a specified gas production rate (i.e., the “nominal” current density and/or the “nominal” H2 gas production rate for the electrolyzer cell or for the plant as a whole), which can be referred to as “load gaining.” Likewise, the electrolyzer cells are configured to be operated at a current density that is lower than a specified current density and/or at a H2 gas production rate that is lower than a specified gas production rate (i.e., the “nominal” current density and/or the “nominal” H2 gas production rate for the electrolyzer cell or for the plant as a whole), which can be referred to as “load shedding.”

The electrolyzer cells described herein can also be manufactured at relatively low capital expenditures (“CapEx”) compared to conventional water-splitting electrolysis cells. As used herein, the terms “capital expenditures” and “CapEx” refers to capital expenses incurred to engineer, design, procure, and construct the electrolyzer cells and supporting equipment (e.g., piping, deionized water generation, pumps for electrolyte and water circulation, gas processing and storage, electricity rectifiers, electricity transformers, and electricity bussing).

The relatively low CapEx cost required to design and construct the electrolyzer cells of the present disclosure can allow the electrolyzer cells to be designed to be capable of accommodating a maximum current density that is higher than the “nominal” current density, e.g., the current density associated with an optimum current density for which the electrolyzer cells are being designed (which corresponds to a nominal desired H2 gas production rate for which the overall plant is being designed). In other words, if the total plant is designed for an average H2 gas production capacity (corresponding to a particular cell size and nominal current density), then the cells can be designed with one or more of the structure features described herein that allow the electrolyzer cell to achieve a higher current density (and thus a higher H2 gas production rate) without making the design of the cells uneconomical. For example, the designed H2 gas production rate for the entire plant may translate to a nominal operating current density of about 1 A/cm2. But in accordance with the present disclosure, the electrolyzer cells can be designed so that they can handle a substantially larger current density, such as a current density of about 1.5 A/cm2 or higher, for example about 1.6 A/cm2 or higher, such as about 1.7 A/cm2 or higher, for example about 1.75 A/cm2 or higher, such as about 1.8 A/cm2 or higher, for example about 1.9 A/cm2 or higher, such as about 2 A/cm2 or higher, for example about 2.1 A/cm2 or higher, such as about 2.2 A/cm2 or higher, for example about 2.25 A/cm2 or higher, such as about 2.3 A/cm2 or higher, for example about 2.4 A/cm2 or higher, such as about 2.5 A/cm2 or higher, for example about 2.6 A/cm2 or higher, such as about 2.7 A/cm2 or higher, for example about 2.75 A/cm2 or higher, such as about 2.8 A/cm2 or higher, for example about 2.9 A/cm2 or higher, such as about 3 A/cm2 or higher, for example about 3.1 A/cm2 or higher, such as about 3.2 A/cm2 or higher, for example about 3.25 A/cm2 or higher, such as about 3.3 A/cm2 or higher, for example about 3.4 A/cm2 or higher, such as about 3.5 A/cm2 or higher. Similarly, the supporting equipment for the cells (e.g., piping, deionized water generation, pumps for electrolyte and water circulation, gas processing and storage, electricity rectifiers, electricity transformers, and electricity bussing) may be “oversized” relative to what would be required for the nominal H2 gas production rate and nominal current density.

The relatively low CapEx of the electrolyzer cells described herein and their supporting equipment are such that it can still be economical, from a capital investment perspective, to operate the electrolyzer cells of the present disclosure at a current density that is lower than a specified current density and/or at a H2 gas production rate that is lower than a specified gas production rate (which can be the same or different from the specified current density or the specified H2 gas production rate associated with a load gaining situation, for example the specified current density can be certain percentage of the nominal current density and/or the specified H2 gas production rate can be a certain percentage of the nominal H2 gas production rate) when carrying out load shedding in order to reduce the overall operating expenditures (“OpEx”). As used herein, the terms “operating expenditures” and “OpEx” refer to the ongoing cost of generating hydrogen gas with the electrolyzer cells and other supporting equipment, which can include, but is not limited to, electricity costs, operations labor, regular ongoing maintenance, insurance, engineering and supervision operations, short-term consumables, and sales and administration expenses. In contrast, typical electrolyzer cells having higher CapEx costs cannot economically produce hydrogen in a load shedding situation, even though it reduces the OpEx, because the CapEx of the typical electrolyzer cells are so high.

The electrolyzer cells and overall system of the present disclosure allow for dynamic control over the current density at which the electrolyzer cells are capable of effectively and efficiently load shedding and load gaining compared to existing electrolyzer cells. As described in more detail below, the ability of the electrolyzer cells to operate over a wide range of current densities and gas production rates allows the systems and methods described herein to provide for strategic and dynamic operation of the electrolyzer cells for H2 gas production so that the average cost for H2 gas production is reduced and in some instances minimized over the course of long-range operation of the system. In an example, the electrolyzer cells can be designed to be operated at a maximum current density (which results in a corresponding maximum H2 gas production rate) that is 1 amp per square centimeter (A/cm2) or more, for example a maximum achievable current density of about 1.5 A/cm2, for example a maximum achievable current density of about 2.0 A/cm2, for example about 2.5 A/cm2, for example a maximum achievable current density of about 3 A/cm2 for example a maximum achievable current density of about 3.5 A/cm2. In addition, the electrolyzer cells and overall system of the present disclosure can allow for economic operation at a minimum economically-viable current density (which results in a corresponding minimum H2 gas production rate) of about 750 milliamps per square centimeter (mA/cm2) or less, for example a minimum economically-viable current density of about 600 mA/cm2, for example a minimum economically-viable current density of about 500 mA/cm2, for example a minimum economically-viable current density of about 400 mA/cm2, such as a minimum economically-viable current density of about 300 mA/cm2, for example a minimum economically-viable current density of about 250 mA/cm2, for example a minimum economically-viable current density of about 200 mA/cm2, for example a minimum economically-viable current density of about 150 mA/cm2. Therefore, in an example where the maximum achievable current density for the electrolyzer cells is about 3 A/cm2 (or about 3000 mA/cm2) and a minimum economically-viable current density of about 150 mA/cm2, then the electrolyzer cell is able to operate as low as about 5% of the maximum achievable current density (i.e., 150 mA/cm2 being 5% of 3000 mA/cm2), which means that the electrolyzer cells have a load shedding and load gaining operating range of 95% (i.e., from 5% to 100% of the maximum achievable current density).

The electrolyzer cells can be designed to achieve a maximum capacity. As used herein, the term “maximum capacity,” when referring to the electrolyzer cells, refers to the maximum current density that the electrolyzer cell can reliably achieve (taking into account the ability of the electrolyzer cell to dissipate generated heat in order to avoid or minimize damage to the cell's separator and/or to remove gas being produced within the cell without slug or plug flow of the gas or the electrolyte). In an example, the maximum capacity current density is 1.5 A/cm2 or more, for example 1.6 A/cm2 or more, 1.7 A/cm2 or more, 1.75 A/cm2 or more, 1.8 A/cm2 or more, 1.9 A/cm2 or more, 2 A/cm2 or more, 2.1 A/cm2 or more, 2.2 A/cm2 or more, 2.25 A/cm2 or more, 2.3 A/cm2 or more, 2.4 A/cm2 or more, 2.5 A/cm2 or more, 2.6 A/cm2 or more, 2.7 A/cm2 or more, 2.75 A/cm2 or more, 2.8 A/cm2 or more, 2.9 A/cm2 or more, 3 A/cm2 or more, 3.1 A/cm2 or more, 3.2 A/cm2 or more, 3.25 A/cm2 or more, 3.3 A/cm2 or more, 3.4 A/cm2 or more, or 2.5 A/cm2.

In an example, “load shedding” (i.e., situations where the operating current density of the electrolyzer cells is reduced) includes reducing the operating current density of the electrolyzer cell to 30% or less of the maximum capacity, for example 29% or less of the maximum capacity, 28% or less of the maximum capacity, 27% or less of the maximum capacity, 26% or less of the maximum capacity, 25% or less of the maximum capacity, 24% or less of the maximum capacity, 23% or less of the maximum capacity, 22% or less of the maximum capacity, 21% or less of the maximum capacity, 20% or less of the maximum capacity, 19% or less of the maximum capacity, 18% or less of the maximum capacity, 17.5% or less of the maximum capacity, 17% or less of the maximum capacity, 16% or less of the maximum capacity, 15% or less of the maximum capacity, 14% or less of the maximum capacity, 13% or less of the maximum capacity, 12.5% or less of the maximum capacity, 12% or less of the maximum capacity, 11% or less of the maximum capacity, 10% or less of the maximum capacity, 9% or less of the maximum capacity, 8% or less of the maximum capacity, 7.5% or less of the maximum capacity, 7% or less of the maximum capacity, 6% or less of the maximum capacity, or 5% or less of the maximum capacity.

In an example, “load gaining” (i.e., situations where the operating current density of the electrolyzer cells is increased) includes increasing the operating current density to 70% or more of the maximum capacity, 75% or more of the maximum capacity, 76% or more of the maximum capacity, 77% or more of the maximum capacity, 77.5% or more of the maximum capacity, 78% or more of the maximum capacity, 79% or more of the maximum capacity, 80% or more of the maximum capacity, 81% or more of the maximum capacity, 82% or more of the maximum capacity, 82.5% or more of the maximum capacity, 83% or more of the maximum capacity, 84% or more of the maximum capacity, 85% or more of the maximum capacity, 86% or more of the maximum capacity, 87% or more of the maximum capacity, 87.5% or more of the maximum capacity, 88% or more of the maximum capacity, 89% or more of the maximum capacity, 90% or more of the maximum capacity, 91% or more of the maximum capacity, 92% or more of the maximum capacity, 92.5% or more of the maximum capacity, 93% or more of the maximum capacity, 94% or more of the maximum capacity, 95% or more of the maximum capacity, 96% or more of the maximum capacity, 97% or more of the maximum capacity, 97.5% or more of the maximum capacity, 98% or more of the maximum capacity, 98.5% or more of the maximum capacity, 99% or more of the maximum capacity, 99.5% or more of the maximum capacity, 99.9% or more of the maximum capacity, or to the maximum capacity (i.e., to 100% of the maximum capacity).

In an example, the electrolyzer system (i.e., comprising all of the electrolyzer cells in the plant) can generate at least about 1 kilogram of H2 gas per hour (kg H2/hr), such as at least about 1.5 kg H2/hr, at least about 5 kg H2/hr, at least about 10 kg H2/hr, at least about 25 kg H2/hr, at least about 50 kg H2/hr, at least about 100 kg H2/hr, at least about 500 kg H2/hr, at least about 1000 kg H2/hr, at least about 1500 kg H2/hr, at least about 2000 kg H2/hr, at least about 2500 kg H2/hr, at least about 3000 kg H2/hr, at least about 3500 kg H2/hr, at least about 4000 kg H2/hr, at least about 4500 kg H2/hr, or at least about 5000 kg H2/hr. In an example, the electrolyzer system can generate up to about 30000 kg H2/hr, for example up to about 25000 kg H2/hr, up to about 20000 kg H2/hr, up to 15000 kg H2/hr, or up to 10000 kg H2/hr. As will be appreciated by a person of skill in the art, the actual mass of H2 gas produced by the electrolyzer system will depend on many factors including the area of each electrolyzer cell, the number of electrolyzer cells in the electrolyzer system, and the current density at which the electrolyzer cells are being operated. In an example, the mass of H2 gas that can theoretically generated per ampere of current supplied to the electrolyzer cells is about 3.761×10−5 kg H2/hr. Therefore, the theoretical mass of H2 gas that the electrolyzer system can generate is equal to the total amps supplied for electrolysis, which in turn is equal to the current density being applied to the electrolyzer cells multiplied by the total area of the electrolyzer cells (or the area per electrolyzer cell times the number of cells times the current density).

The changing of the current density associated with the operation of the electrolyzer can include increasing the current density associated with the operation of the electrolyzer, decreasing the current density associated with the operation of the electrolyzer, or a combination thereof. The changing of the current density associated with the operation of the electrolyzer can includes increasing the current density associated with the operation of the electrolyzer at least one time during a 24-hour period, decreasing the current density associated with the operation of the electrolyzer at least one time during a 24-hour period, or a combination thereof. The changing of the current density associated with the operation of the electrolyzer can include increasing the current density associated with the operation of the electrolyzer such that the current density is within a range of values of about 0.05 A/cm2 to 10.0 A/cm2, decreasing the current density associated with the operation of the electrolyzer such that the current density is within a range of values of about 0.05 A/cm2 to 10.0 A/cm2, or a combination thereof. The changing of the current density associated with the operation of the electrolyzer can include increasing the current density associated with the operation of the electrolyzer such that the current density is within a range of values of about 0.15 A/cm2 to 3.0 A/cm2, decreasing the current density associated with the operation of the electrolyzer such that the current density is within a range of values of about 0.15 A/cm2 to 3.0 A/cm2, or a combination thereof.

The one or more electricity input factors can be factors involving the electricity input to the electrolyzer. 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 electricity input factors can include a price of electricity supplied to the electrolyzer (e.g., a regional price, or a contract price) and/or a demand for electricity supplied to the electrolyzer. In other aspects, the one or more electricity input factors are free of a price of electricity supplied to the electrolyzer or a demand for electricity supplied to the electrolyzer. The changing of the current density associated with the operation of the electrolyzer can be based on one and not more than one of the electricity input factors. The changing of the current density associated with the operation of the electrolyzer can be based on more than one of the electricity input factors.

The changing of the current density associated with the operation of the electrolyzer can be based on an electricity input factor of balancing load on an electrical grid supplying electricity to the electrolyzer. The changing of the current density associated with the operation of the electrolyzer can include decreasing the current density in response to a decreased amount of electricity available on the electrical grid. The changing of the current density associated with the operation of the electrolyzer can include increasing the current density in response to an increased amount of electricity available on the electrical grid. An electrolyzer load could be ramped up or down more quickly than the electrical supply station or an electrical grid. If there is a rapid change in the amount of electricity on the grid, in either direction, one response might be to use an electrolyzer to stabilize the overall load on the grid. The price of electricity may or may not change during these periods, but using an electrolyzer to balance the grid could still provide economic benefits in areas other than electrolysis or hydrogen or oxygen generation. Some power generation cannot be curtailed, or turned off, in a timely manner, and would need a load to use the excess power being generated. This could be a case with gas, coal, nuclear, or hydroelectric power plants. Alternatively, when there is too much load on the grid, the current density of the electrolyzer could be decreased. The current density of the electrolyzer can be ramped up or down to balance the load on the electrical grid.

The changing of the current density associated with the operation of the electrolyzer can be based on an electricity input factor of an excess or deficit of environmentally-generated electricity supplied to the electrolyzer. The environmentally-generated electricity can include electricity generated by solar cells, wind electricity generation, or a combination thereof. The changing of the current density associated with the operation of the electrolyzer can include decreasing the current density in response to a decreased amount of the environmentally-generated electricity. The changing of the current density associated with the operation of the electrolyzer can include increasing the current density in response to an increased amount of the environmentally-generated electricity. In an abundance of available environmentally-generated electricity, such as if the wind or solar power generation is strong, the electrolyzer current density can be turned up. The electrolyzer current can be turned up to immediately take advantage of the abundance of environmentally-generated electricity (e.g., the timing of electricity generation can match the timing of hydrogen production), or to consume the excess environmentally-generated electricity over a specific period of time such as 1 min to 2 h, or 15 min to 60 min, or less than or equal to 2 h and greater than or equal to 1 min and less than, equal to, or greater than 2 min, 5 min, 10 min, 15 min, 20 min, 30 min, 45 min, 1 h, or 1.5 h. Alternatively, if there is less environmentally-generated electricity, the electrolyzer current density can be lowered so what power is available could be used for other needs or industries.

The changing of the current density associated with the operation of the electrolyzer can be based on an electricity input factor of forecasted environmental conditions potentially causing a future excess or deficit of environmentally-generated electricity supplied to the electrolyzer. The forecasted environmental conditions can include wind conditions, sunlight conditions, or a combination thereof. The changing of the current density associated with the operation of the electrolyzer can include decreasing the current density in response to a forecasted decreased amount of the environmentally-generated electricity. The changing of the current density associated with the operation of the electrolyzer can include increasing the current density in response to a forecasted increased amount of the environmentally-generated electricity. The electrolyzer can be pre-emptively adjusted due to forecasted environmental conditions. The need for the electrolyzer product (e.g., hydrogen and/or oxygen) or the need to consume electricity can be time-shifted to provide economic benefits, such as based on a future price of electricity, a future need to balance the grid, a future use of the electrolyzer product(s), or for any of the other reasons disclosed herein. One example of this would be to produce more product(s) during the day, if powered by a solar power generator, owing to the forecasted sunset and night. Similarly, wind forecasting, cloud forecasting, and the like, could be a basis for a change in electrolyzer load.

The changing of the current density associated with the operation of the electrolyzer can be based on an electricity input factor of a battery charge level of one or more batteries that supply electricity to the electrolyzer. The changing of the current density associated with the operation of the electrolyzer can include decreasing the current density in response to a low charge level of the one or more batteries. The changing of the current density associated with the operation of the electrolyzer can include increasing the current density in response to a high charge level of the one or more batteries. A battery can be used to power the electrolyzer alone or in combination with an electricity generation facility, and the electrolyzer current density can be changed in response to operating conditions of the battery. For example, if the battery is at a low state of charge, the electrolyzer could be turned down to maintain operation for a longer period of time. Alternatively, if the battery does not need to be charged, the electrolyzer could take the excess load from the electrical generation facility that would have been used to charge the battery, or the electrolyzer can be operated at a higher current density so to more rapidly drain the battery energy storage. The changing of the current density associated with the operation of the electrolyzer can include lowering the current density during the day to allow the battery to charge, so that the battery can be sufficiently charged to power electrolyzer operation during the night.

The changing of the current density associated with the operation of the electrolyzer can be based on an electricity input factor of carbon intensity of electricity supplied to the electrolyzer. The carbon intensity of electricity supplied to the electrolyzer can be the amount of carbon dioxide produced per unit of energy of the electricity supplied to the electrolyzer. The changing of the current density associated with the operation of the electrolyzer can include decreasing the current density in response to increased carbon intensity of the electricity supplied to the electrolyzer, or in response to predicted increased carbon intensity of the electricity supplied to the electrolyzer. The changing of the current density associated with the operation of the electrolyzer can include decreasing the current density during a period of increased carbon intensity to receive a carbon credit or offset credit. The changing of the current density associated with the operation of the electrolyzer can include decreasing the current density during a period of increased carbon intensity to avoid a fee or tax, to stay within cap-and-trade guidelines or limits for hydrogen produced by the electrolyzer, to receive a CO2e credit, to stay under CO2e limits, or a combination thereof. The changing of the current density associated with the operation of the electrolyzer can include increasing the current density in response to decreased carbon intensity of the electricity supplied to the electrolyzer, or in response to predicted decreased carbon intensity of the electricity supplied to the electrolyzer. The changing of the current density associated with the operation of the electrolyzer can include increasing the current density to obtain more carbon credit, offset credit, CO2e credit, or a combination thereof, for hydrogen produced by the electrolyzer more quickly. For example, current density can be increased to obtain more credit for hydrogen more quickly when the carbon intensity of the electricity used to power the electrolyzer is lower. If an electrolyzer needs to operate below a threshold carbon intensity, for example to benefit from subsidies or operate within regulations, its current density can be raised or lowered based on the carbon intensity of the available power. The carbon intensity of electricity can be the amount of carbon dioxide or equivalent produced per unit of energy. The carbon intensity of generated electricity can fluctuate throughout the day. The greater the proportion of the total energy product that comes from environmentally-generated power, the less CO2 is produced per unit of energy. However, during peak energy usage times, environmentally-generated power is sometimes not sufficient to satisfy all power needs, and power generation must be supplemented with conventional non-environmentally-generated power. By determining the amount of CO2 produced per hour and the amount of power produced per hour, the amount of carbon dioxide produced per unit of energy can be determined, such as in terms of CO2/MW/hr. The method can include operating the electrolyzer in such a way that optimizes the operation time within the desired carbon intensity region with the amount of hydrogen produced. Each electrolyzer may have different efficiencies for operation, in which case, their operational current densities can be adjusted to maximize subsidies, such as by having the lowest carbon intensity while maintaining desired hydrogen production, or having tiered levels of carbon intensity if subsidies are tiered, either stepwise or progressively, based on carbon intensity. The operational current densities of the electrolyzers can be the same or they can each be unique, depending on the properties (e.g., efficiency) of each electrolyzer. This is a distinctly different approach than the on/off approach that could be used for less capable products such as filter press in which 25% output from four electrolyzers could be achieved by running two electrolyzers at 50% and having the other two off. In various aspects of the present disclosure, all four of the electrolyzers can be run at 25%, or some combination of operational current densities can be used to reach 25%, which can be more efficient overall than running two electrolyzers at 50%.

While the carbon intensity of the hydrogen may be important to meet regulations around hydrogen, it can alternatively or additionally implicate downstream processing. For example, if a product uses hydrogen and that product has carbon intensity requirements, the electrolyzer can be operated in response to parameters around that product. The changing of the current density associated with the operation of the electrolyzer can be based on an electricity input factor of downstream product carbon intensity requirements. The changing of the current density associated with the operation of the electrolyzer can include decreasing the current density to satisfy carbon intensity requirements of a product made from the hydrogen produced by the electrolyzer. The product can include ammonia for fertilizer or one or more hydrocarbons for sustainable aviation fuel, or the hydrogen can be used for heating in a manufacturing process of steel and/or concrete. For example, if ammonia for fertilizer or hydrocarbons for sustainable aviation fuel needs to decarbonize fully or partially, or if steel or concrete needs to be produced via a manufacturing process that uses less carbon for heating, hydrogen produced with lower carbon intensity could be used.

The one or more hydrogen output factors can be factors involving the hydrogen output from the electrolyzer. 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. The changing of the current density associated with the operation of the electrolyzer can be based on one and not more than one of the hydrogen output factors. The changing of the current density associated with the operation of the electrolyzer can be based on more than one of the hydrogen output factors.

The changing of the current density associated with the operation of the electrolyzer can be based on a hydrogen output factor of demand for hydrogen produced by the electrolyzer. The changing of the current density associated with the operation of the electrolyzer can include decreasing the current density in response to decreasing demand for the hydrogen produced by the electrolyzer, or in response to predicted decreased demand for the hydrogen produced by the electrolyzer. The changing of the current density associated with the operation of the electrolyzer can include increasing the current density in response to increasing demand for the hydrogen produced by the electrolyzer, or in response to predicted increased demand for the hydrogen produced by the electrolyzer. If the demand for the product (hydrogen and/or oxygen) changes, then the production rate of the electrolyzer can be changed to accommodate this. For example, if a steel, cement, or fertilizer production facility changes its production rate based on other factors, runs batch reactors that periodically need high volumes of hydrogen, or needs variable amounts depending on the part of the process that is running, then the electrolyzer could increase or decrease current density to meet the demand.

The changing of the current density associated with the operation of the electrolyzer can be based on a hydrogen output factor of balancing hydrogen production load of the electrolyzer with hydrogen production load of one or more other electrolyzers. The balancing can be equalizing, or the balancing can be reproportioning the hydrogen production load between the electrolyzers in unequal amounts. The changing of the current density associated with the operation of the electrolyzer can include decreasing the current density in response to an increased hydrogen production load of one or more other electrolyzers. The changing of the current density associated with the operation of the electrolyzer can include increasing the current density in response to a decreased hydrogen production load of one or more other electrolyzers. If an electrolyzer is part of a group of electrolyzers, then if one electrolyzer is turned off for a reason (planned or unplanned) then the others could be run at a higher current density to maintain the same overall output of product. Alternatively, an electrolyzer load could be lowered and the others can be run at a higher current density. A need to balance the production load across a series of electrolyzers, resulting in a need to run one or more electrolyzers at higher load and other electrolyzers at zero or lower load, can be caused by various reasons. Some planned examples can include running system tests, maintenance on components that impact efficiency, purging out impurities in the liquid or gas stream, distribution of additives within the system, maintaining safe operating conditions for an electrolyzer such as keeping gas mixtures within safe limits, and the like. Another example is a desire to operate the most efficient electrolyzers at a higher current density and the least efficient electrolyzers at a lower current density. Efficiency can be total voltage across the stack, voltage of individual cells, impurities in the gas products from the electrolyzer, energy efficiency of the balance of plant around the electrolyzer (e.g., pumps, heaters, instruments), and the like, or a combination thereof. An electrolyzer could be run at a higher or lower current density if the concentration and/or temperature of electrolyte is out of balance in order to bring it into balance more quickly and/or to avoid less efficient operation while it is being brought into balance. The electrolyzer system can be capable of accommodating batch processes that periodically require high hydrogen volumes. By dynamically adjusting its production rate, the system can meet the fluctuating hydrogen needs of industrial processes, such as fertilizer production or steel manufacturing, ensuring consistent supply during peak demand periods.

The changing of the current density associated with the operation of the electrolyzer can be based on a hydrogen output factor of hydrogen pipeline demand for hydrogen produced by the electrolyzer. In various aspects, this can be equivalent to a hydrogen load balancing of the pipeline. In various aspects, the electrolyzer system can balance its hydrogen input to match variable withdrawal rates from pipelines. This capability can ensure optimal pipeline pressure and flow management, allowing the system to respond to fluctuations in downstream demand and maintain consistent operation. The changing of the current density associated with the operation of the electrolyzer can include decreasing the current density in response to a decreased hydrogen pipeline demand for the hydrogen produced by the electrolyzer. The changing of the current density associated with the operation of the electrolyzer can include increasing the current density in response to an increased hydrogen pipeline demand for the hydrogen produced by the electrolyzer. The changing of the current density associated with the operation of the electrolyzer can be based on a hydrogen output factor of downstream hydrogen pipeline demand for hydrogen produced by the electrolyzer. The changing of the current density associated with the operation of the electrolyzer can include decreasing the current density in response to a decreased downstream hydrogen pipeline demand for the hydrogen produced by the electrolyzer. The changing of the current density associated with the operation of the electrolyzer can include increasing the current density in response to an increased downstream hydrogen pipeline demand for the hydrogen produced by the electrolyzer. Varying downstream production totals can be a basis for adjusting the current density of the electrolyzer upward or downward. The demand for hydrogen at the consumption end of a pipeline can impact how much hydrogen should be added into the pipeline. This could be the case for fueling, loading onto vehicles for transportation, or consumption of a variety of ways such as chemical production via chemical reaction, electrical production in fuel cells or turbines, burning for heat energy for industrial or residential purposes, and the like.

The changing of the current density associated with the operation of the electrolyzer can be based on a hydrogen output factor of storage facility demand for hydrogen produced by the electrolyzer. Increased storage facility demand can be increased storage space for the hydrogen at the storage facility. Decreased storage facility demand can be decreased storage space for the hydrogen at the storage facility. The system can integrate forecasted hydrogen demand to optimize storage levels. By predicting future consumption needs, the electrolyzer can dynamically adjust its production rate to prevent storage overflow and ensure efficient replenishment of hydrogen inventory. The changing of the current density associated with the operation of the electrolyzer can include decreasing the current density in response to decreased storage facility demand for the hydrogen produced by the electrolyzer. The changing of the current density associated with the operation of the electrolyzer can include increasing the current density in response to increased storage facility demand for the hydrogen produced by the electrolyzer. If the generated hydrogen product is being sent to a storage facility, electrolyzer current density can be increased or decreased based on the status of facility. Similarly to the levels of a battery on the supply side of the electrolyzer, the hydrogen storage facility could be close to full, in which case the method can include running the electrolyzer at a lower current density. Alternatively, if the storage facility is nearly empty, the method can include running the electrolyzer at a higher current density to replenish the storage. The method can include incorporating storage facility status into forecasts for hydrogen demand when accounting for what production rate an electrolyzer or electrolyzers should be run at.

The changing of the current density associated with the operation of the electrolyzer can be based on a hydrogen output factor of hydrogen compressor needs for a hydrogen compressor that compresses hydrogen produced by the electrolyzer. The electrolyzer system can includes pressure management capabilities to optimize compressor efficiency. By adjusting its hydrogen production rate, the system can maintain consistent inlet pressure to the compressor, ensuring reliable operation and reducing wear on compressor components. The hydrogen produced by the electrolyzer can be combined with hydrogen produced by one or more other electrolyzers prior to being fed to the hydrogen compressor. The changing of the current density associated with the operation of the electrolyzer can include decreasing the current density to decrease an inlet pressure of the hydrogen to the hydrogen compressor. The changing of the current density associated with the operation of the electrolyzer can include increasing the current density to increase an inlet pressure of the hydrogen to the hydrogen compressor. Hydrogen from an electrolyzer may exit it at or near atmospheric pressure or up to 30-50 bar. Compressors are commonly used to move, store, or use the hydrogen in another application. Compressors have their own operating parameters and efficiencies. Increasing or decreasing the electrolyzer production can be in response to needing to increase or decrease operational settings around compressor or a group of compressors. For example, if multiple compressors receive hydrogen from multiple electrolyzers, and one compressor needs maintenance, the multiple electrolyzers could ramp down to provide a constant flow of hydrogen to the one remaining operational compressor. Alternatively, when more compressors are brought online or otherwise have an increased capacity, the electrolyzer(s) can be ramped up to increase production. An electrolyzer system can include one or more other operation units, such as a demister, between the electrolyzer and the compressor. The compressor can run in response to the inlet pressure thereof. A plant can include multiple compressors with inlets connected to the same hydrogen feed pipe. If one of the compressors is turned off or is running less efficiently, the current density of the electrolyzer can be lowered to maintain the inlet pressure of the compressors. If additional compressors are added, or one or more of the compressors run at increased efficiency, the current density of the electrolyzer can be raised to maintain the inlet pressure of the compressors. The method can include using a feed forward control, wherein a higher inlet pressure of the compressors or of the hydrogen feed pipe the connects to the compressor inlets is a basis for lowering the current density of the electrolyzer, and a lower inlet pressure of the compressors or of the hydrogen feed pipe is a basis for raising the current density of the electrolyzer.

The changing of the current density associated with the operation of the electrolyzer can be based on a hydrogen output factor of price, future price, trading credit, hydrogen credit, margin gained from selling hydrogen, or a combination thereof, for hydrogen produced by the electrolyzer. The electrolyzer system can strategically increase hydrogen production during high-value periods, such as when market prices for hydrogen are elevated or when fulfilling purchase agreements with premium pricing terms. This capability can increase or maximize revenue while ensuring compliance with contractual obligations. The changing of the current density associated with the operation of the electrolyzer can include decreasing the current density in response to decreasing price, future price, trading credit, hydrogen credit, margin gained from selling hydrogen, or a combination thereof, for hydrogen produced by the electrolyzer. The changing of the current density associated with the operation of the electrolyzer can include increasing the current density in response to increasing price, future price, trading credit, hydrogen credit, margin gained from selling hydrogen, or a combination thereof, for hydrogen produced by the electrolyzer. Electrolyzer current density can be changed in response to price, future price, trading credit, hydrogen credit, margin gained from selling hydrogen, or a combination thereof, for hydrogen produced by the electrolyzer. As the hydrogen product prices change, more or less hydrogen can be produced to sell. This can be independent of electricity price changes. The margin gained from selling hydrogen accounts for the cost of making the hydrogen in the first place. In one example, the current density can be adjusted based on the efficiency (e.g. voltage) of the system. If the process is more efficient, then more hydrogen can be produced per unit of power (i.e., more efficient is fewer kWh/kg H2). In more detail, if an electrolyzer is less efficient such as from getting older, it would make sense to lower the current density to still produce hydrogen at a profit (albeit less quantity of product). Another example involves changing plant conditions. If the electrolyzer is colder, it is less efficient and costs more kWh/kg H2 produced. As the process warms up (e.g., from running higher voltage), the efficiency increases. The method can include raising or lowering the current density based on the external price of hydrogen in combination with the incoming price of electricity with respect to the present state of operation of the plant (e.g., electrolyzer efficiency).

The changing of the current density associated with the operation of the electrolyzer can be based on a hydrogen output factor of purchase agreement fulfilment for hydrogen produced by the electrolyzer. The changing of the current density associated with the operation of the electrolyzer can include decreasing the current density to avoid the hydrogen produced by the electrolyzer exceeding an amount of hydrogen specified by the purchase agreement for fulfillment of the purchase agreement, or to decrease an amount by which the hydrogen produced by the electrolyzer exceeds the amount of hydrogen specified by the purchase agreement for fulfillment of the purchase agreement. The changing of the current density associated with the operation of the electrolyzer can include increasing the current density to avoid the hydrogen produced by the electrolyzer being less than an amount of hydrogen specified by the purchase agreement for fulfillment of the purchase agreement, or to decrease an amount by which the hydrogen produced by the electrolyzer is less than the amount of hydrogen specified by the purchase agreement for fulfillment of the purchase agreement. If the hydrogen produced by an electrolyzer is sold and the producer is subject to a hydrogen purchase agreement, the electrolyzer can be operated at conditions that maximize the revenue for the producer while fulfilling the contract. This can be separate from the price of electricity and can be on a case-by-case basis for the project and contract terms. If, according to the terms, hydrogen is a higher price, then the electrolyzer can be operated at a higher current density to produce more hydrogen, and likewise if, according to the terms, hydrogen is a lower price, then the electrolyzer can be operated at a lower current density to produce less hydrogen. The electrolyzer current density can be changed to meet the terms (production amount, production price, and the like) in the contract.

The changing of the current density associated with the operation of the electrolyzer can be based on a hydrogen output factor of electricity price of electricity generated from hydrogen produced by the electrolyzer. The changing of the current density associated with the operation of the electrolyzer can include increasing the current density in response to a higher electricity price of electricity generated from the hydrogen produced by the electrolyzer, or a predicted higher electricity price of electricity generated from the hydrogen produced by the electrolyzer. The changing of the current density associated with the operation of the electrolyzer can include decreasing the current density in response to a lower electricity price of electricity generated from the hydrogen produced by the electrolyzer, or a predicted lower electricity price of electricity generated from the hydrogen produced by the electrolyzer. A facility that encompasses renewable electricity generation and hydrogen generation and electricity generation from hydrogen could operate an electrolyzer in a way that is most profitable to sell electricity to the larger power grid. In this case, the electrolyzer would not be ramped up or down in response to the cost of electricity to the electrolyzer, but it would be changed in response to the value of the hydrogen to be used for electricity generation and sold to the larger power grid and the value of the renewable electricity to be sold to the larger power grid directly. In one case, if the power generated could be directed to the grid or the electrolyzer, it would be sent to the electrolyzer if the electricity price on the grid was low, or sent to the grid if the price was high. The electrolyzer would change in response to the available power rather than the price of electricity on the grid.

The electrolyzer can be a part of a microgrid or industrial park, where electricity production, hydrogen production, and electricity and hydrogen consumption are all combined. One such case would be for a data center that wants to utilize renewable energy, such as solar and wind, battery energy storage, electrolyzer, hydrogen storage, and a electricity turbine that burns hydrogen or a fuel cell array that makes electricity from hydrogen, and fueling station for vehicles (trucks, cars, forklifts, boats, flying drones, flying vehicles, and the like). All of these processes would have an impact on the current density of the electrolyzer, but would work together to maintain a functional microgrid such as one around a datacenter. The electrolyzer could produce more hydrogen to fill the hydrogen storage, or lower state of charge on the battery more quickly, or because there is excess electricity being produced. The electrolyzer could produce less hydrogen because the amount of hydrogen for the turbine, state of charge of the battery, and available renewable electricity are needed to maintain the overall microgrid energy load. This may be a form of arbitrage with various prices/markets for input electricity and various prices/markets for output hydrogen. The system can enable arbitrage between electricity and hydrogen markets, allowing operators to dynamically allocate resources based on fluctuating input and output prices. For example, the electrolyzer can prioritize hydrogen production during periods of low electricity prices or shift to direct electricity sales during periods of high grid demand, optimizing profitability across interconnected energy systems.

Models for each electrolyzer site could be developed based on the specific assets, resources, and operational requirements of the site, as well as the intended uses for the generated hydrogen and other products. Site-specific optimization models can be developed for each electrolyzer installation, taking into account local energy resources, market conditions, and operational constraints. These models can enable tailored operation of the electrolyzer system, ensuring maximum production rate and profitability at each site. These models can incorporate a wide range of variables, including the forecasted prices of electricity and hydrogen, the availability of renewable energy sources, the carbon intensity of the electricity supply, and the demand for hydrogen from downstream applications. In various aspects, a computer model can be used to optimize the operation of the electrolyzer system by dynamically determining the best current density setpoints for the electrolyzer(s) at a given time. The computer model can leverage real-time data inputs, such as electricity prices, grid load conditions, weather forecasts, and hydrogen demand, to make informed decisions about the operating parameters of the electrolyzer system. For example, the model can analyze fluctuations in electricity prices over a 24-hour period and adjust the current density to maximize hydrogen production during periods of low electricity costs while minimizing operation during high-cost periods. Similarly, the model can account for forecasted environmental conditions, such as expected solar or wind generation, to preemptively adjust the electrolyzer load in anticipation of changes in renewable energy availability. The computer model can also integrate historical data and predictive analytics to identify trends and patterns, enabling the electrolyzer system to operate more efficiently and economically over the long term. In addition, the model can incorporate constraints and objectives specific to the site, such as meeting regulatory requirements for carbon intensity, fulfilling purchase agreements for hydrogen delivery, or optimizing the use of storage facilities and compressors. By simulating various operational scenarios, the model can identify the most cost-effective and energy-efficient strategies for operating the electrolyzer system. Advanced optimization techniques, such as machine learning algorithms or feed-forward control systems, can further enhance the model's ability to adapt to changing conditions and improve decision-making accuracy. The use of a computer model can allow operators to dynamically adjust the electrolyzer system's current density in response to real-time and forecasted conditions, ensuring that the system operates at peak efficiency while meeting economic, environmental, and operational goals. This approach not only reduces operating costs but also enhances the flexibility and scalability of the electrolyzer system, making it better suited to the evolving demands of the hydrogen economy. In various aspects, the model can leverage historical data and predictive analytics to identify trends and patterns in electricity prices, hydrogen demand, and renewable energy availability. By incorporating these insights, the electrolyzer system can optimize its operation over the long term, adapting to changing market conditions and improving decision-making accuracy.

In various aspects, the changing of the current density associated with the operation of the electrolyzer can be based on, alternatively or in addition to the one or more electricity input factors and/or the one or more hydrogen output factors, a price of electricity supplied to the electrolyzer and/or a demand for electricity supplied to the electrolyzer. The demand can refer to the regional demand for electricity in the region where the electrolyzer is located. The price of electricity can refer to the regional price of electricity in the region wherein the electrolyzer is located, or can refer to a contact price of electricity to the electrolyzer which may differ from the regional price of electrolyzer in the region. In various aspects, the price of electricity supplied to the electrolyzer can be fixed (power purchase agreement) while the price to the grid is higher, giving rise to a situation where it can make more sense to sell electricity to the grid.

The method can include dynamically adjusting the current density of the electrolyzer to respond to electricity prices and/or electricity demand and load gain when electricity prices and/or demand are low and/or are decreasing and load shed when electricity prices and/or demand are high and/or are increasing. For example, if the demand for electricity increases over a period of time, then the OpEx for the electrolyzer cell can increase by a corresponding amount over the same period of time due to an increase in the price of electricity unless the operating current density of the electrolyzer cell is dynamically decreased. Thus, in a load shedding situation, the dynamic lowering of the current density has the effect of dynamically reducing the OpEx to counteract the expected rise in OpEx associated with the increase in demand.

In other words, the operating current density of the electrolyzer cells can be changed in response to a period of time when the demand for electricity and/or the price of electricity is fluctuating. Fluctuation in demand can include increases in demand (e.g., wherein demand during a first period of time is lower than during a subsequent second period of time) or decreases in demand (e.g., wherein demand during a first period of time is higher than during a subsequent second period of time). Similarly, fluctuation in price can include increases in price (e.g., wherein the price of electricity during a first period of time is lower than during a subsequent second period of time) or decreases in price (e.g., wherein the price of electricity during a first period of time is higher than during a subsequent second period of time). The dynamic operation of the electrolyzer cells can be particular useful during periods of time where the demand for electricity and/or the price of electricity is known to fluctuate (i.e., is known to increase or decrease), such as during a time period spanning from the nighttime to mid-to-late afternoon.

The ability to dynamically load gain and load shed can result in the overall average cost of H2 gas production per kilogram ($/kg) to be lower than is possible with conventional electrolyzer cells operated in a steady-state manner. In some examples, the dynamic load gaining and load shedding of the present disclosure can allow for a reduction of from about 20% to about 40% or more (e.g., even as much as 50% or more) in the cost of electricity required to produce the same amount of H2 gas.

FIG. 22 is a graph illustrating typical prices of electricity over a twenty-four hour period (e.g., from midnight to midnight of the following day), according to data collected by the Electric Reliability Council of Texas (“ERCOT”). Data line 400 represents the average price of electricity, in United States dollars per megawatt hour ($/MWh), at a particular time in the day. Data lines 402 and 404 represents one standard deviation above and one standard deviation below the average price at each particular time in the day, respectively. As can be seen by FIG. 22, the price of electricity tends to remain relatively steady from hour 1 (i.e., midnight) until about hour 10 (i.e., 9 AM), at which point the average price goes up rather steeply to above $60/MWh and with a large variation. The high average price and high variability remains until about hour 19 or hour 20 (e.g., 6-7 PM), at which point the average price begins to drop back down toward the more stable price experienced at the beginning of the day. In other words, the price of electricity tends to be low and has little variance during nighttime and early morning hours and then tends to go up and have large variability during mid-day and afternoon hours. The ability to dynamically operate the electrolyzer cells by load shedding and load gaining in response to electricity price/demand can allow the operator to, for example, operate the electrolyzer cells at high load (i.e., high current density, e.g., above a specified current density, such as above 1 A/cm2) during periods of low electricity pricing (i.e., during the night time such as from hours 1-10 and after about hour 22 in the graph of FIG. 22) and operate the electrolyzer cells at low load (i.e., low current density, e.g., below the specified current density) during periods of high electricity pricing (i.e., during the day time from hours 10-22 in the graph of FIG. 22) thereby achieving an overall electricity cost that is less than what would be incurred by conventional, steady-state operation.

FIG. 23 shows an example scenario involving changes in electricity pricing and how various aspects of the disclosed method can include dynamic operation in load gaining and load shedding manners in order to reduce the overall average price of H2 gas production compared to conventional operation of electrolyzer cells at a constant or substantially constant current density and H2 gas production rate that does not take into account the current price of electricity. Data line 406 corresponds to the fluctuating price of electricity over the course of two full days of operation. Line 408 is a data series of the operating current density of the electrolyzer cells according to the present disclosure at various times over the course of the same two days when the electrolyzer cells are being operated to load gain during periods when the electricity price is below a specified lower price threshold (e.g., about $25 per MWh in the example of FIG. 23), where the current density is ramped down when the price of electricity goes above the specified lower price threshold, and where the electrolyzer cells are shut off (i.e., operated at a current density of 0 A/cm2) when the price of electricity goes above a specified upper price threshold (e.g., about $40 per MWh in the example of FIG. 23). Data line 410 corresponds to the “nominal” current density at which the electrolyzer cells are designed to be operated (e.g., about 1 A/cm2 for the example of FIG. 23). In other words, data line 410 represents “conventional” operation of the electrolyzer cells at the capacity for which they were designed. As can be seen in FIG. 23, if the electrolyzer cells were continually operated at the nominal current density, then the average price of electricity over the two days represented by the data of FIG. 23 would be $28 per MWh.

In the example of FIG. 23, the electrolyzer cells are operated at a load gaining current density (e.g., about 2 A/cm2) when the electricity price is below the specified lower price threshold (e.g., when the price is ≤$25 per MWh in the example of FIG. 23), at a variable load shedding current density when the price of electricity is between the specified lower price threshold and the specified upper price threshold (e.g., when the price is between $25/MWh and $40/MWh in the example of FIG. 23, the current density is set somewhere between 0 and 2 A/cm2 depending on the electricity price), and are shut down if the price is above the specified upper price threshold (e.g., a current density of 0 A/cm2 when the price is greater than $40/MWh in the example of FIG. 23). In the example scenario shown in FIG. 23, the average current density over the course of the two days was about 1.6 A/cm2 (as represented by data line 412), which is about 60% higher than the nominal current density of 1 A/cm2 during conventional operation of the electrolyzer cells (e.g., above the current density associated with data line 410). Moreover, the average cost of the electricity consumed over the course of the two days of operation was about $22 per MWh (represented by data line 414), which corresponds to about a 20% reduction in the cost of electricity during the load gaining and load shedding operation of the present disclosure. In other words, in the example scenario shown in FIG. 23, not only was the electricity cost substantially lower than conventional operation of the electrolyzer cells (i.e., about $22/MWh versus about $28/MWh, or 20% less electricity cost over the same period of time), the same electrolyzer cells were able to achieve a substantially higher average current density (i.e., about 1.6 A/cm2 on average versus 1 A/cm2, or about 60% higher). As will be appreciated by those having skill in the art, this means that the same electrolyzer cells were also able to produce substantially more H2 gas (because the production rate of H2 gas is proportional to the current density) at a substantially lower operating cost.

The example scenario and the threshold electricity prices of FIG. 23 are provided for illustrative purposes only and are not intended to limit the scope of the present disclosure. Those having skill in the art will appreciate that the operating current densities of the electrolyzer cells and the threshold electricity prices that trigger adjustment of the operating current density can be varied and will still be encompassed by various aspects of the present disclosure. As noted herein, the electrolyzer cells that can be incorporated into the load gaining and load shedding systems and methods of the present disclosure can operate over a wide range of current densities, for example from a lower limit of about 0.05 A/cm2 to an upper limit of about 10.0 A/cm2, or a lower limit of about 0.15 A/cm2 up to an upper limit of 3 A/cm2 or more.

Those having skill in the art may also appreciate that the specific operating current density for a price threshold can be selected based on aspects of the specific electrolyzer cells, including, but not limited to: an optimal current density for the particular electrolyzer cell (e.g., the current density that is most efficient at producing H2 gas on the basis of the mass of H2 gas produced per MW of electricity consumed, which itself can depend on the price of electricity), a maximum current density that the electrolyzer cell can achieve (e.g., depending on the electrolyzer cell's ability to remove the gas produced and/or dissipate the heat generated), or the cost per kilogram of H2 gas produced for the electrolyzer cells at various current densities and at various electricity prices per MWh. FIGS. 24 and 25 show examples of these considerations for a particular electrolyzer cell. FIG. 24 shows a cost curve (represented by line 416) for a particular example electrolyzer cell. The cost curve 416 corresponds to the total levelized cost per kilogram of H2 gas produced at different operating current densities when the price of electricity is $26.6/MWh. For this example, electrolyzer cell, the cost curve 416 has a minimum point 418 at a current density of about 1.12 A/cm2, corresponding to a production cost of about $1.91 per kg of H2 gas produced. The cost curve 416 in FIG. 24 corresponds to the cost if the electrolyzer cell was operated at a constant current density rather than the cost if the load gaining and load shedding methods of the present disclosure are being practiced. In other words, the cost curve 416 corresponds to the example electrolyzer cell being operated in the conventional manner, similar to the line 410 of FIG. 23. If, however, various aspects of the load gaining and load shedding method of the present disclosure are practiced (e.g., similar to the example described herein with respect to FIG. 23), then the effective optimum current density for the same example electrolyzer cell (at data point 420) rises to about 1.66 A/cm2 (an increase of about 40% over the 1.19 A/cm2 for the minimum point 418 on the conventional cost curve 416) and the average cost per kilogram of H2 is reduced to about $1.69/kg H2 (a reduction of about 11.5% compared to the $1.91/kg H2 for the minimum point 418 on the conventional cost curve 416).

FIG. 25 shows a graph of the optimum current density (represented by data line 422) for a particular example electrolyzer cell as a function of the price of electricity. As used herein, the term “optimum current density” refers to the current density that achieves the minimum cost per kilogram of H2 produced at a particular electricity price. In an example, the optimum current density for each electricity price can be determined in much the same way as was performed in FIG. 24, e.g., by finding a minimum point on the cost curve associated with each electricity price. In the example of FIG. 25, when the price is below about $35/MWh (or $0.035/kWh), the optimum current density is at or above the maximum current density for which the example electrolyzer cell can operate, so that when the price is below $35/MWh, the electrolyzer cell can be run at its maximum current density of about 2 A/cm2 (e.g., the electrolyzer cell can be operated in a full load gaining manner). At a price of about $35/MWh, the optimum current density begins to go down as the price rises such that, in an example, the operating current density for the electrolyzer cell can be ramped down as the electricity price rises above $35/MWh. In other words, in the example of FIG. 25, $35/MWh is the specified lower price threshold corresponding to the start of the transition between load gaining and load shedding (as described herein with respect to FIG. 23) for an aspect of the presently disclosed method that only uses electricity price/demand as the basis for increasing or decreasing current load. As shown in FIG. 25, when the price of electricity reaches about $50/MWh, the optimum current density for the example electrolyzer cell reaches zero (0) (ignoring other considerations such as the costs of shutdown and startup labor, wear on the plant equipment, and the like). Therefore, when the price is higher than $50/MWh, the example electrolyzer cell can be shut down. In other words, in the example of FIG. 25, $50/MWh is the specified upper price threshold (as described herein with respect to FIG. 23). Those having skill in the art will appreciate that the exact price point for the specified upper price threshold can be varied from the actual price point where the optimum current density reaches zero, and the amount of variance can depend on one or more factors including, but not limited to, the capital expenditure for the example electrolyzer cells and other supporting equipment (e.g., the CapEx), the overall size of the electrolyzer cells in the plant (e.g., the size of the cell stack), the current price at which the produced H2 gas can be sold, and other operating expenses (such as the cost of labor to run the plant or to shut down and startup the plant or the price of water, or the cost of regular maintenance for the electrolyzer cells and the supporting equipment). In fact, the “optimum” current density at any point along the optimum current density curve 422 can be varied from the theoretical or calculated optimum current density based on one or more of these same factors.

Exemplary Aspects

The following exemplary aspects are provided, the numbering of which is not to be construed as designating levels of importance:

Aspect 1 provides a method of operating an electrolyzer, the method comprising:

Aspect 2 provides the method of Aspect 1, wherein the one or more input factors comprise

Aspect 3 provides the method of any one of Aspects 1-2, wherein the one or more hydrogen output factors comprise

Aspect 4 provides the method of any one of Aspects 1-3, wherein the one or more electricity input factors and one or more hydrogen output factors do not comprise a regional price of electricity supplied to the electrolyzer or a regional demand for electricity supplied to the electrolyzer.

Aspect 5 provides the method of any one of Aspects 1-4, wherein the changing of the current density associated with the operation of the electrolyzer is not based on a regional price of electricity supplied to the electrolyzer or a regional demand for electricity supplied to the electrolyzer

Aspect 6 provides the method of any one of Aspects 1-4, wherein the changing of the current density associated with the operation of the electrolyzer is further based on a price of electricity supplied to the electrolyzer and/or a demand for electricity supplied to the electrolyzer.

Aspect 7 provides the method of any one of Aspects 1-6, wherein the changing of the current density associated with the operation of the electrolyzer comprises increasing the current density associated with the operation of the electrolyzer, decreasing the current density associated with the operation of the electrolyzer, or a combination thereof.

Aspect 8 provides the method of any one of Aspects 1-7, wherein the changing of the current density associated with the operation of the electrolyzer comprises increasing the current density associated with the operation of the electrolyzer at least one time during a 24-hour period, decreasing the current density associated with the operation of the electrolyzer at least one time during a 24-hour period, or a combination thereof.

Aspect 9 provides the method of any one of Aspects 1-8, wherein the changing of the current density associated with the operation of the electrolyzer comprises increasing the current density associated with the operation of the electrolyzer such that the current density is within a range of values of about 0.05 A/cm2 to 10.0 A/cm2, decreasing the current density associated with the operation of the electrolyzer such that the current density is within a range of values of about 0.05 A/cm2 to 10.0 A/cm2, or a combination thereof.

Aspect 10 provides the method of any one of Aspects 1-9, wherein the changing of the current density associated with the operation of the electrolyzer comprises increasing the current density associated with the operation of the electrolyzer such that the current density is within a range of values of about 0.15 A/cm2 to 3.0 A/cm2, decreasing the current density associated with the operation of the electrolyzer such that the current density is within a range of values of about 0.15 A/cm2 to 3.0 A/cm2, or a combination thereof.

Aspect 11 provides the method of any one of Aspects 1-10, wherein the changing of the current density associated with the operation of the electrolyzer is based on the one or more electricity input factors.

Aspect 12 provides the method of any one of Aspects 1-11, wherein the changing of the current density associated with the operation of the electrolyzer is based on the one or more hydrogen output factors.

Aspect 13 provides the method of any one of Aspects 1-12, wherein the changing of the current density associated with the operation of the electrolyzer is based on the one or more electricity input factors and the one or more hydrogen output factors.

Aspect 14 provides the method of any one of Aspects 1-13, wherein the changing of the current density associated with the operation of the electrolyzer is based on one and not more than one of the electricity input factors.

Aspect 15 provides the method of any one of Aspects 1-14, wherein the changing of the current density associated with the operation of the electrolyzer is based on at least two of the electricity input factors.

Aspect 16 provides the method of any one of Aspects 1-15, wherein the changing of the current density associated with the operation of the electrolyzer is based on the one or more electricity input factors comprising balancing load on an electrical grid supplying electricity to the electrolyzer.

Aspect 17 provides the method of Aspect 16, wherein the changing of the current density associated with the operation of the electrolyzer comprises decreasing the current density in response to a decreased amount of electricity available on the electrical grid.

Aspect 18 provides the method of any one of Aspects 16-17, wherein the changing of the current density associated with the operation of the electrolyzer comprises increasing the current density in response to an increased amount of electricity available on the electrical grid.

Aspect 19 provides the method of any one of Aspects 1-18, wherein the changing of the current density associated with the operation of the electrolyzer is based on the one or more electricity input factors comprising an excess or deficit of environmentally-generated electricity supplied to the electrolyzer.

Aspect 20 provides the method of Aspect 19, wherein the environmentally-generated electricity comprises electricity generated by solar cells, wind electricity generation, or a combination thereof.

Aspect 21 provides the method of any one of Aspects 19-20, wherein the changing of the current density associated with the operation of the electrolyzer comprises decreasing the current density in response to a decreased amount of the environmentally-generated electricity.

Aspect 22 provides the method of any one of Aspects 19-21, wherein the changing of the current density associated with the operation of the electrolyzer comprises increasing the current density in response to an increased amount of the environmentally-generated electricity.

Aspect 23 provides the method of any one of Aspects 1-22, wherein the changing of the current density associated with the operation of the electrolyzer is based on the one or more electricity input factors comprising forecasted environmental conditions potentially causing a future excess or deficit of environmentally-generated electricity supplied to the electrolyzer.

Aspect 24 provides the method of Aspect 23, wherein the forecasted environmental conditions comprise wind conditions, sunlight conditions, or a combination thereof.

Aspect 25 provides the method of any one of Aspects 23-24, wherein the changing of the current density associated with the operation of the electrolyzer comprises decreasing the current density in response to a forecasted decreased amount of the environmentally-generated electricity.

Aspect 26 provides the method of any one of Aspects 23-25, wherein the changing of the current density associated with the operation of the electrolyzer comprises increasing the current density in response to a forecasted increased amount of the environmentally-generated electricity.

Aspect 27 provides the method of any one of Aspects 1-26, wherein the changing of the current density associated with the operation of the electrolyzer is based on the one or more electricity input factors comprising a battery charge level of one or more batteries that supply electricity to the electrolyzer.

Aspect 28 provides the method of Aspect 27, wherein the changing of the current density associated with the operation of the electrolyzer comprises decreasing the current density in response to a low charge level of the one or more batteries.

Aspect 29 provides the method of any one of Aspects 27-28, wherein the changing of the current density associated with the operation of the electrolyzer comprises increasing the current density in response to a high charge level of the one or more batteries.

Aspect 30 provides the method of any one of Aspects 1-29, wherein the changing of the current density associated with the operation of the electrolyzer is based on the one or more electricity input factors comprising carbon intensity of electricity supplied to the electrolyzer.

Aspect 31 provides the method of Aspect 30, wherein the carbon intensity of electricity supplied to the electrolyzer is the amount of carbon dioxide produced per unit of energy of the electricity supplied to the electrolyzer.

Aspect 32 provides the method of any one of Aspects 30-31, wherein the changing of the current density associated with the operation of the electrolyzer comprises decreasing the current density in response to increased carbon intensity of the electricity supplied to the electrolyzer, or in response to predicted increased carbon intensity of the electricity supplied to the electrolyzer.

Aspect 33 provides the method of any one of Aspects 30-32, wherein the changing of the current density associated with the operation of the electrolyzer comprises decreasing the current density during a period of increased carbon intensity to receive a carbon credit or offset credit.

Aspect 34 provides the method of any one of Aspects 30-33, wherein the changing of the current density associated with the operation of the electrolyzer comprises decreasing the current density during a period of increased carbon intensity to avoid a fee or tax, to stay within cap-and-trade guidelines or limits for hydrogen produced by the electrolyzer, to receive a CO2e credit, to stay under CO2e limits, or a combination thereof.

Aspect 35 provides the method of any one of Aspects 30-34, wherein the changing of the current density associated with the operation of the electrolyzer comprises increasing the current density in response to decreased carbon intensity of the electricity supplied to the electrolyzer, or in response to predicted decreased carbon intensity of the electricity supplied to the electrolyzer.

Aspect 36 provides the method of any one of Aspects 30-35, wherein the changing of the current density associated with the operation of the electrolyzer comprises increasing the current density to obtain more carbon credit, offset credit, CO2e credit, or a combination thereof, for hydrogen produced by the electrolyzer more quickly.

Aspect 37 provides the method of any one of Aspects 1-36, wherein the changing of the current density associated with the operation of the electrolyzer is based on the one or more electricity input factors comprising downstream product carbon intensity requirements.

Aspect 38 provides the method of Aspect 37, wherein the changing of the current density associated with the operation of the electrolyzer comprises decreasing the current density to satisfy carbon intensity requirements of a product made from the hydrogen produced by the electrolyzer.

Aspect 39 provides the method of any one of Aspects 37-38, wherein the product comprises ammonia for fertilizer, one or more hydrocarbons for sustainable aviation fuel, steel production, concrete production, or a combination thereof.

Aspect 40 provides the method of any one of Aspects 1-39, wherein the changing of the current density associated with the operation of the electrolyzer is based on one and not more than one of the hydrogen output factors.

Aspect 41 provides the method of any one of Aspects 1-40, wherein the changing of the current density associated with the operation of the electrolyzer is based on at least two of the hydrogen output factors.

Aspect 42 provides the method of any one of Aspects 1-41, wherein the changing of the current density associated with the operation of the electrolyzer is based on a hydrogen output factor of demand for hydrogen produced by the electrolyzer.

Aspect 43 provides the method of Aspect 42, wherein the changing of the current density associated with the operation of the electrolyzer comprises decreasing the current density in response to decreasing demand for the hydrogen produced by the electrolyzer, or in response to predicted decreased demand for the hydrogen produced by the electrolyzer.

Aspect 44 provides the method of any one of Aspects 42-43, wherein the changing of the current density associated with the operation of the electrolyzer comprises increasing the current density in response to increasing demand for the hydrogen produced by the electrolyzer, or in response to predicted increased demand for the hydrogen produced by the electrolyzer.

Aspect 45 provides the method of any one of Aspects 1-44, wherein the changing of the current density associated with the operation of the electrolyzer is based on the one or more hydrogen output factors comprising balancing hydrogen production load of the electrolyzer with hydrogen production load of one or more other electrolyzers.

Aspect 46 provides the method of Aspect 45, wherein the changing of the current density associated with the operation of the electrolyzer comprises decreasing the current density in response to an increased hydrogen production load of one or more other electrolyzers.

Aspect 47 provides the method of any one of Aspects 45-46, wherein the changing of the current density associated with the operation of the electrolyzer comprises increasing the current density in response to a decreased hydrogen production load of one or more other electrolyzers.

Aspect 48 provides the method of any one of Aspects 1-47, wherein the changing of the current density associated with the operation of the electrolyzer is based on the one or more hydrogen output factors comprising hydrogen pipeline demand for hydrogen produced by the electrolyzer.

Aspect 49 provides the method of Aspect 48, wherein the changing of the current density associated with the operation of the electrolyzer comprises decreasing the current density in response to a decreased hydrogen pipeline demand for the hydrogen produced by the electrolyzer.

Aspect 50 provides the method of any one of Aspects 48-49, wherein the changing of the current density associated with the operation of the electrolyzer comprises increasing the current density in response to an increased hydrogen pipeline demand for the hydrogen produced by the electrolyzer.

Aspect 51 provides the method of any one of Aspects 1-50, wherein the changing of the current density associated with the operation of the electrolyzer is based on the one or more hydrogen output factors comprising downstream hydrogen pipeline demand for hydrogen produced by the electrolyzer.

Aspect 52 provides the method of Aspect 51, wherein the changing of the current density associated with the operation of the electrolyzer comprises decreasing the current density in response to a decreased downstream hydrogen pipeline demand for the hydrogen produced by the electrolyzer.

Aspect 53 provides the method of any one of Aspects 51-52, wherein the changing of the current density associated with the operation of the electrolyzer comprises increasing the current density in response to an increased downstream hydrogen pipeline demand for the hydrogen produced by the electrolyzer.

Aspect 54 provides the method of any one of Aspects 1-53, wherein the changing of the current density associated with the operation of the electrolyzer is based on the one or more hydrogen output factors comprising storage facility demand for hydrogen produced by the electrolyzer.

Aspect 55 provides the method of Aspect 54, wherein increased storage facility demand is increased storage space for the hydrogen at the storage facility, and decreased storage facility demand is decreased storage space for the hydrogen at the storage facility.

Aspect 56 provides the method of any one of Aspects 54-55, wherein the changing of the current density associated with the operation of the electrolyzer comprises decreasing the current density in response to decreased storage facility demand for the hydrogen produced by the electrolyzer.

Aspect 57 provides the method of any one of Aspects 54-56, wherein the changing of the current density associated with the operation of the electrolyzer comprises increasing the current density in response to increase storage facility demand for the hydrogen produced by the electrolyzer.

Aspect 58 provides the method of any one of Aspects 1-57, wherein the changing of the current density associated with the operation of the electrolyzer is based on the one or more hydrogen output factors comprising hydrogen compressor needs for a hydrogen compressor that compresses hydrogen produced by the electrolyzer.

Aspect 59 provides the method of Aspect 58, wherein the hydrogen produced by the electrolyzer is combined with hydrogen produced by one or more other electrolyzers prior to being fed to the hydrogen compressor.

Aspect 60 provides the method of any one of Aspects 58-59, wherein the changing of the current density associated with the operation of the electrolyzer comprises decreasing the current density to decrease an inlet pressure of the hydrogen to the hydrogen compressor.

Aspect 61 provides the method of any one of Aspects 58-60, wherein the changing of the current density associated with the operation of the electrolyzer comprises increasing the current density to increase an inlet pressure of the hydrogen to the hydrogen compressor.

Aspect 62 provides the method of any one of Aspects 1-61, wherein the changing of the current density associated with the operation of the electrolyzer is based on the one or more hydrogen output factors comprising price, future price, trading credit, hydrogen credit, margin gained from selling hydrogen, or a combination thereof, for hydrogen produced by the electrolyzer.

Aspect 63 provides the method of Aspect 62, wherein the changing of the current density associated with the operation of the electrolyzer comprises decreasing the current density in response to decreasing price, future price, trading credit, hydrogen credit, margin gained from selling hydrogen, or a combination thereof, for hydrogen produced by the electrolyzer.

Aspect 64 provides the method of any one of Aspects 62-63, wherein the changing of the current density associated with the operation of the electrolyzer comprises increasing the current density in response to increasing price, future price, trading credit, hydrogen credit, margin gained from selling hydrogen, or a combination thereof, for hydrogen produced by the electrolyzer.

Aspect 65 provides the method of any one of Aspects 1-64, wherein the changing of the current density associated with the operation of the electrolyzer is based on the one or more hydrogen output factors comprising purchase agreement fulfilment for hydrogen produced by the electrolyzer.

Aspect 66 provides the method of Aspect 65, wherein the changing of the current density associated with the operation of the electrolyzer comprises decreasing the current density to avoid the hydrogen produced by the electrolyzer exceeding an amount of hydrogen specified by the purchase agreement for fulfillment of the purchase agreement, or to decrease an amount by which the hydrogen produced by the electrolyzer exceeds the amount of hydrogen specified by the purchase agreement for fulfillment of the purchase agreement.

Aspect 67 provides the method of any one of Aspects 65-66, wherein the changing of the current density associated with the operation of the electrolyzer comprises increasing the current density to avoid the hydrogen produced by the electrolyzer being less than an amount of hydrogen specified by the purchase agreement for fulfillment of the purchase agreement, or to decrease an amount by which the hydrogen produced by the electrolyzer is less than the amount of hydrogen specified by the purchase agreement for fulfillment of the purchase agreement.

Aspect 68 provides the method of any one of Aspects 1-67, wherein the changing of the current density associated with the operation of the electrolyzer is based on the one or more hydrogen output factors comprising electricity price of electricity generated from hydrogen produced by the electrolyzer.

Aspect 69 provides the method of Aspect 68, wherein the changing of the current density associated with the operation of the electrolyzer comprises increasing the current density in response to a higher electricity price of electricity generated from the hydrogen produced by the electrolyzer, or a predicted higher electricity price of electricity generated from the hydrogen produced by the electrolyzer.

Aspect 70 provides the method of any one of Aspects 68-69, wherein the changing of the current density associated with the operation of the electrolyzer comprises decreasing the current density in response to a lower electricity price of electricity generated from the hydrogen produced by the electrolyzer, or a predicted lower electricity price of electricity generated from the hydrogen produced by the electrolyzer.

Aspect 71 provides the method of any one of Aspects 1-70, wherein the electrolyzer comprises one or more electrolyzer cells each comprising a first half cell with a first electrode and a second half cell with a second electrode.

Aspect 72 provides the method of any one of Aspects 1-71, wherein the electrolyzer comprises at least two of the electrolyzer cells.

Aspect 73 provides the method of any one of Aspects 1-72, wherein the electrolyzer has a total size of 1 m3 to 90 m3.

Aspect 74 provides the method of any one of Aspects 1-73, wherein the electrolyzer has a total size of at least about 2.5 m3.

Aspect 75 provides the method of any one of Aspects 71-74, wherein the first half cell comprises a pan, one or more ribs inside the pan, and a baffle plate coupled to the one or more ribs, wherein the baffle plate partitions a volume in the pan to provide a riser region on a first side of the pan proximate to the first electrode and a down-comer region on a second side of the baffle plate opposite the first side.

Aspect 76 provides the method of Aspect 75, wherein the riser region facilitates gas formed at the first electrode to rise and avoid formation of gas pockets, and wherein the down-comer region facilitates downward flow of an electrolyte solution, wherein the rise of the gas and the downward flow of the electrolyte solution causes circulation in the pan that facilitates thermal equilibrium and reduced temperature variation in the electrolyte.

Aspect 77 provides the method of any one of Aspects 71-76, wherein the first half cell comprises a pan, a manifold positioned inside the pan, and an outlet tube exiting the manifold for electrolyte to exit the pan, wherein a cross-sectional area of the manifold is configured so that an electrolyte flow rate and a gas flow rate through the manifold are low enough to avoid slug flow or plug flow.

Aspect 78 provides the method of any one of Aspects 71-77, wherein the first half cell comprises a pan, one or more ribs positioned vertically inside the pan, and a plurality of welds that weld the first electrode to the one or more ribs, wherein the plurality of welds form a distributed array of welds across the electrode that distribute current across the electrode during operation of the electrochemical cell.

Aspect 79 provides the method of any one of Aspects 71-78, wherein each electrolyzer cell further comprises a separator between the first half cell and the second half cell, wherein a number, size, and positions of the plurality of welds are such that an impact of power dissipation on a temperature of the separator is reduced to reduce damage due to high local temperature.

Aspect 80 provides a method of operating an electrolyzer, the method comprising:

Aspect 81 provides an electrolyzer system comprising:

Aspect 82 provides the electrolyzer system of Aspect 81, wherein the one or more input factors comprise

Aspect 83 provides the electrolyzer system of any one of Aspects 81-82, wherein the one or more hydrogen output factors comprise

Aspect 84 provides the method or system of any one or any combination of Aspects 1-83 optionally configured such that all elements or options recited are available to use or select from.