Electrolyzer cell temperature control

Abstract

The electrolytic cell system comprises a stack of one or more electrolytic cell cells, each comprising first and second half-cells comprising first and second electrodes, respectively, and a separator between the first and second half-cells, and an electric current is applied between the first and second electrodes. The system further comprises first and second electrolyte feed streams for feeding a first electrolyte solution at a first inlet temperature to the first half-cell and a second electrolyte solution at a second inlet temperature to the second half-cell, respectively, first and second electrolyte outlet streams for withdrawing the first and second electrolyte solutions from the first and second half-cells, respectively, and a temperature controller for controlling the first inlet temperature at a first defined temperature and the second inlet temperature at a second defined temperature.

Description

[Background technology]

[0001] (CROSS-REFERENCE TO RELATED APPLICATIONS) This application claims priority under 35 U.S.C. § 120 to U.S. Provisional Application No. 63 / 305,470, filed February 1, 2022, and entitled "TEMPERATURE CONTROL OF AN ELECTROLYZER CELL," and U.S. Application No. 17 / 938,319, filed October 5, 2022, and entitled "SYSTEMS AND METHODS FOR PRODUCING HYDROGEN GAS," the disclosures of which are incorporated herein by reference in their entireties.

[0002] Hydrogen production can play a key role because hydrogen gas is required for many chemical processes. As of 2019, approximately 70 million tons of hydrogen were produced annually worldwide for various uses, such as in oil refining, ammonia production (through the Haber process), methanol production (through carbon monoxide reduction), or as a fuel in transportation.

[0003] Historically, the majority of hydrogen (approximately 95%) has been produced from fossil fuels (e.g., by steam reforming of natural gas, partial oxidation of methane, or coal gasification). Other methods of hydrogen production include biomass gasification, low- or no-CO2 emission methane pyrolysis, and water electrolysis. Electrolysis uses electricity to split water molecules into hydrogen gas and oxygen gas. To date, electrolysis systems and methods have generally been more expensive than fossil fuel-based production methods. However, fossil fuel-based methods can be more environmentally damaging and generally result in increased CO2 emissions. Therefore, there is a need for cost-competitive and environmentally friendly hydrogen gas production electrolysis systems and methods. Summary of the Invention [Means for solving the problem]

[0004] The present disclosure describes an electrolyzer system comprising a stack of one or more electrolyzer cells, each comprising a first half-cell with a first electrode, a second half-cell with a second electrode, and a separator between the first and second half-cells, wherein an electric current is applied between the first and second electrodes of each of the one or more electrolyzer cells. The system also comprises a first electrolyte feed stream for feeding a first electrolyte solution at a first inlet temperature to a first half-cell of each of the one or more electrolyzer cells, a second electrolyte feed stream for feeding a second electrolyte solution at a second inlet temperature to a second half-cell of each of the one or more electrolyzer cells, a first electrolyte outlet stream for withdrawing the first electrolyte solution from the first half-cell of each of the one or more electrolyzer cells, a second electrolyte outlet stream for withdrawing the second electrolyte solution from the second half-cell of each of the one or more electrolyzer cells, and a temperature controller for controlling the first inlet temperature at a first defined temperature and the second inlet temperature at a second defined temperature.

[0005] The present disclosure also provides a method for producing electrolytic electrolysis cells comprising the steps of: feeding a first electrolyte solution at a first inlet temperature via a first electrolyte feed stream to a first half-cell of each of the one or more electrolyzer cells, each first half-cell of the one or more electrolyzer cells comprising a first electrode; and feeding a second electrolyte solution at a second inlet temperature via a second electrolyte feed stream to a second half-cell of each of the one or more electrolyzer cells, each first half-cell of the one or more electrolyzer cells comprising a first electrode. Each second half cell comprises a second electrode, and a first electrode of each of the one or more electrolytic cell is separated from the second electrode by a separator; applying a specified current between the first electrode and the second electrode of each of the one or more electrolytic cell; controlling a first inlet temperature of the first electrolyte solution at a first specified temperature; and controlling a second inlet temperature of the second electrolyte solution at a second specified temperature. The present invention provides, for example, the following items. (Item 1) 1. An electrolyzer system comprising: A stack of one or more electrolyzer cells, each electrolyzer cell comprising: a first half-cell with a first electrode; a second half-cell with a second electrode; a separator between the first half cell and the second half cell; a stack of one or more electrolyzer cells, wherein a defined current is applied between the first electrode and the second electrode of each of the one or more electrolyzer cells; a first electrolyte feed stream for delivering a first electrolyte solution at a first inlet temperature to the first half-cell of each of the one or more electrolyzer cells; a second electrolyte feed stream for delivering a second electrolyte solution at a second inlet temperature to the second half-cell of each of the one or more electrolyzer cells; a first electrolyte outlet stream for withdrawing the first electrolyte solution from the first half-cell of each of the one or more electrolyzer cells; a second electrolyte outlet stream for withdrawing the second electrolyte solution from the second half-cell of each of the one or more electrolyzer cells; a temperature control device for controlling the first inlet temperature at a first defined temperature and for controlling the second inlet temperature at a second defined temperature; An electrolytic cell system comprising: (Item 2) 2. The electrolytic cell system of claim 1, wherein the temperature controller is configured to set one or both of the first and second specified temperatures based on at least one of the specified current, a voltage measured across the first and second electrodes of at least one of the one or more electrolytic cell cells, an overall voltage measured across the stack, a flow rate of the first electrolyte solution through the first half-cell of at least one of the one or more electrolytic cell cells, a flow rate of the second electrolyte solution through the second half-cell of at least one of the one or more electrolytic cell cells, a thermophysical property of the first electrolyte solution, a thermophysical property of the second electrolyte solution, a first outlet temperature of the first electrolyte solution exiting the first half-cell of at least one of the one or more electrolytic cell cells, and a second outlet temperature of the second electrolyte solution exiting the second half-cell of at least one of the one or more electrolytic cell cells. (Item 3) 3. The electrolytic cell system of claim 1, wherein at least a first portion of the first electrolyte solution in the first electrolyte outlet stream is recycled back to the first electrolyte feed stream and at least a first portion of the second electrolyte solution in the second electrolyte outlet stream is recycled back to the second electrolyte feed stream, and wherein the temperature controller comprises at least one electrolyte heat exchanger configured to heat or cool one or both of the first portion of the first electrolyte solution and the first portion of the second electrolyte solution prior to recycling back to the first and second electrolyte feed streams. (Item 4) 4. The electrolytic cell system of claim 3, wherein the temperature control device further comprises at least one bypass line configured to bypass one or both of the second portion of the first electrolyte solution and the second portion of the second electrolyte solution without passing through the at least one electrolyte heat exchanger. (Item 5) 5. The electrolytic cell system of claim 4, wherein the electrolyte heat exchanger comprises a cooler configured to cool one or both of the first portion of the first electrolyte solution and the first portion of the second electrolyte solution, and the temperature control device further comprises an electrolyte heater configured to heat one or both of the second portion of the first electrolyte solution and the second portion of the second electrolyte solution. (Item 6) 6. The electrolytic cell system of claim 4, further comprising at least one flow control valve configured to adjust a ratio of a first flow rate of one or both of the first portion of the first electrolyte solution and the first portion of the second electrolyte solution through the at least one electrolyte heat exchanger to a second flow rate of one or both of the second portion of the first electrolyte solution and the second portion of the second electrolyte solution through the at least one bypass line. (Item 7) 7. The electrolytic cell system of any one of items 3-6, further comprising one or more electrolyte holding tanks upstream of the at least one electrolyte heat exchanger, wherein one or both of the first electrolyte solution and the second electrolyte solution flow from the first and second electrolyte outlet streams to the one or more electrolyte holding tanks. (Item 8) 8. The electrolytic cell system of any one of items 1 to 7, wherein at least a first portion of the first electrolyte solution from the first electrolyte outlet stream is recycled as at least a portion of the first electrolyte solution fed to the first half-cell of each of the one or more electrolytic cell cells via the first electrolyte feed stream, and the temperature control device comprises at least a first electrolyte heat exchanger configured to heat or cool the first portion of the first electrolyte solution from the first electrolyte outlet stream. (Item 9) 9. The electrolyzer system of claim 8, further comprising a first electrolyte bypass line configured to bypass a second portion of the first electrolyte solution from the first electrolyte outlet stream without passing through the first electrolyte heat exchanger. (Item 10) 10. The electrolytic cell system of claim 9, further comprising a first control valve configured to adjust a first ratio between a first flow rate of a first portion of the first electrolyte solution through the first electrolyte heat exchanger and a second flow rate of a second portion of the first electrolyte solution through the first electrolyte bypass line, the first ratio being selected to provide the first specified temperature. (Item 11) 11. The electrolytic cell system of any one of items 8-10, further comprising a first electrolyte holding tank upstream of the first electrolyte heat exchanger, wherein at least a first portion of the first electrolyte solution flows from the first electrolyte outlet stream to the first electrolyte holding tank and then to the first electrolyte heat exchanger. (Item 12) 12. The electrolyzer system of any one of items 1-11, wherein at least a first portion of the second electrolyte solution from the second electrolyte outlet stream is recycled as at least a portion of the second electrolyte solution fed to the second half-cell of each of the one or more electrolyzer cells via the second electrolyte feed stream, and the temperature control device comprises a second electrolyte heat exchanger configured to heat or cool at least the first portion of the second electrolyte solution from the second electrolyte outlet stream. (Item 13) 13. The electrolyzer system of claim 12, further comprising a second electrolyte bypass line configured to bypass a second portion of the second electrolyte solution from the second electrolyte outlet stream without passing through the second electrolyte cooler. (Item 14) 14. The electrolytic cell system of claim 13, further comprising a second control valve configured to adjust a second ratio between a first flow rate of a first portion of the second electrolyte solution through the second electrolyte heat exchanger and a second flow rate of a second portion of the second electrolyte solution through the second electrolyte bypass line, the second ratio selected to provide the second specified temperature. (Item 15) 15. The electrolytic cell system of any one of items 12 to 14, further comprising a second electrolyte holding tank upstream of the second electrolyte heat exchanger, wherein at least a first portion of the second electrolyte solution flows from the second electrolyte outlet stream to the second electrolyte holding tank and then to the second electrolyte heat exchanger. (Item 16) 1. A method comprising: delivering a first electrolyte solution at a first inlet temperature via a first electrolyte feed stream to a first half-cell of each of the one or more electrolyzer cells, each first half-cell of the one or more electrolyzer cells comprising a first electrode; feeding a second electrolyte solution at a second inlet temperature via a second electrolyte feed stream to a second half-cell of each of the one or more electrolyzer cells, each second half-cell comprising a second electrode, the first electrode of each of the one or more electrolyzer cells being separated from the second electrode by a separator; applying a defined current between the first electrode and the second electrode of each of the one or more electrolyzer cells; controlling the first inlet temperature of the first electrolyte solution at a first defined temperature; controlling the second inlet temperature of the second electrolyte solution at a second defined temperature; A method comprising: (Item 17) 17. The method of claim 16, further comprising setting one or both of the first and second specified temperatures based on at least one of the specified current, a voltage measured across the first and second electrodes of at least one of the one or more electrolytic cell cells, an overall voltage measured across the stack, a flow rate of the first electrolyte solution through the first half-cell of at least one of the one or more electrolytic cell cells, a flow rate of the second electrolyte solution through the second half-cell of at least one of the one or more electrolytic cell cells, a thermophysical property of the first electrolyte solution, a thermophysical property of the second electrolyte solution, a first outlet temperature of the first electrolyte solution exiting the first half-cell of at least one of the one or more electrolytic cell cells, and a second outlet temperature of the second electrolyte solution exiting the second half-cell of at least one of the one or more electrolytic cell cells. (Item 18) 18. The method of claim 16, further comprising: recycling at least a first portion of the first electrolyte solution exiting a first half-cell of the one or more electrolytic cell back to the first electrolyte feed stream; and recycling at least a first portion of the second electrolyte solution exiting a second half-cell of the one or more electrolytic cell back to the second electrolyte feed stream; wherein controlling a first inlet temperature of the first electrolyte solution and controlling a second inlet temperature of the second electrolyte solution comprises heating or cooling one or both of the first portion of the first electrolyte solution and the first portion of the second electrolyte solution prior to recycling back to the first and second electrolyte feed streams. (Item 19) 19. The method of claim 18, wherein one or both of controlling the first inlet temperature of the first electrolyte solution and controlling the second inlet temperature of the second electrolyte solution comprises bypassing heating or cooling by one or both of the second portion of the first electrolyte solution and the second portion of the second electrolyte solution. (Item 20) 18. The method of claim 16, further comprising: recycling at least a first portion of the first electrolyte solution exiting a first half-cell of the one or more electrolytic cell back to the first electrolyte feed stream; and recycling at least a first portion of the second electrolyte solution exiting a second half-cell of the one or more electrolytic cell back to the second electrolyte feed stream; wherein controlling a first inlet temperature of the first electrolyte solution and a second inlet temperature of the second electrolyte solution comprises cooling one or both of the first portion of the first electrolyte solution and the first portion of the second electrolyte solution and heating one or both of the second portion of the first electrolyte solution and the second portion of the second electrolyte solution prior to recycling back to the first electrolyte feed stream and the second electrolyte feed stream. (Item 21) 21. The method of claim 19, wherein one or both of controlling the first inlet temperature of the first electrolyte solution and controlling the second inlet temperature of the second electrolyte solution comprises adjusting a ratio of a first flow rate of one or both of the first portion of the first electrolyte solution and the first portion of the second electrolyte solution to a second flow rate of one or both of the second portion of the first electrolyte solution and the second portion of the second electrolyte solution. (Item 22) 22. The method of any one of items 16-21, further comprising recycling at least a first portion of the first electrolyte solution exiting the first half-cell of the one or more electrolyzer cells as at least a first portion of the first electrolyte solution of the first electrolyte feed stream, and wherein controlling a first inlet temperature of the first electrolyte solution comprises heating or cooling at least the first portion of the first electrolyte solution. (Item 23) 23. The method of claim 22, further comprising bypassing the heating or cooling with a second portion of the first electrolyte solution. (Item 24) 24. The method of claim 23, further comprising adjusting a first ratio of a first flow rate of a first portion of the first electrolyte solution to a second flow rate of a second portion of the first electrolyte solution. (Item 25) 25. The method of any one of items 16-24, further comprising recycling at least a first portion of the second electrolyte solution exiting the second half-cell of the one or more electrolyzer cells as at least a portion of the second electrolyte solution of the second electrolyte feed stream, and controlling a second inlet temperature of the second electrolyte feed stream comprises heating or cooling at least the first portion of the second electrolyte solution. (Item 26) 26. The method of claim 25, further comprising bypassing the heating or cooling with a second portion of the second electrolyte solution. (Item 27) 27. The method of claim 26, further comprising adjusting a second ratio of a first flow rate of a first portion of the second electrolyte solution to a second flow rate of a second portion of the second electrolyte solution. [Brief explanation of the drawings]

[0006] The drawings illustrate generally, by way of example, but not by way of limitation, various embodiments discussed in the present document.

[0007] [Figure 1] FIG. 1 is a schematic diagram of an exemplary electrolyzer system for the electrolysis of water to produce hydrogen gas, including a temperature controller for controlling the inlet temperature of the electrolyte solution being fed to the electrolyzer cells of the system.

[0008] [Figure 2] FIG. 2 is a schematic diagram of another exemplary electrolyzer system for the electrolysis of water to produce hydrogen, with an alternative temperature control device for controlling the inlet temperature of the electrolyte solution being fed to the electrolyzer cells of the system.

[0009] [Figure 3] FIG. 3 is a graph of data for an experiment in which a temperature control device was implemented to control the inlet temperature of the electrolyte solution into the electrolytic cell. DETAILED DESCRIPTION OF THE INVENTION

[0010] Detailed Description The following detailed description includes references to the accompanying drawings, which form a part of the detailed description. The drawings show, by way of illustration, specific embodiments in which the invention may be practiced. These embodiments, also referred to herein as "examples," are described in sufficient detail to enable those skilled in the art to practice the invention. Exemplary embodiments may be combined, other embodiments may be utilized, or structural and logical changes may be made without departing from the scope of the present invention. While the disclosed subject matter will be described in conjunction with the recited claims, it is understood that the exemplified subject matter is not intended to limit the claims to the disclosed subject matter. The following detailed description, therefore, is not to be taken in a limiting sense, and the scope of the present invention is defined by the appended claims and their equivalents.

[0011] References herein to "one embodiment," "an embodiment," "an example embodiment," etc. indicate that the described embodiment may include a particular feature, structure, or characteristic, but not all embodiments necessarily include that particular feature, structure, or characteristic. Also, such phrases do not necessarily refer to the same embodiment. Furthermore, when a particular feature, structure, or characteristic is described in connection with one embodiment, it is understood that this is within the knowledge of one of ordinary skill in the art to affect such feature, structure, or characteristic in connection with other embodiments, whether or not explicitly described.

[0012] Values ​​expressed in range format should be interpreted in a flexible manner to include not only the numerical values ​​explicitly recited as limits of that range, but also all individual numerical values ​​or subranges contained within that range, as if each numerical value and subrange were explicitly recited. For example, a recited range of values ​​"about 0.1 to about 5" should be interpreted to include not only the explicitly recited values ​​of about 0.1 and about 5, but also all individual concentrations within the recited range of values ​​(e.g., 1, 1.23, 2, 2.85, 3, 3.529, and 4) and subranges falling within the recited range (e.g., about 0.1% to 0.5%, about 1.21% to 2.36%, about 3.3% to 4.9%, or about 1.2% to 4.7%, to name just a few). The phrase "about X to Y" has the same meaning as "about X to about Y," unless otherwise indicated. Similarly, the statement "about X, Y, or about Z" has the same meaning as "about X, about Y, or about Z," unless otherwise indicated.

[0013] As used herein, the terms "a," "an," or "the" are used to include "one or more than one" unless the context clearly dictates otherwise. The term "or" is used to refer to a non-exclusive "or" unless otherwise indicated. Unless otherwise indicated, the phrase "at least one of," when referring to a listed group, is used to mean any combination of one or two or more of the group members. For example, the statement "at least one of A, B, and C" can have the same meaning as "A; B; C; A and B; A and C; B and C; or A, B, and C," or the statement "at least one of D, E, F, and G" can have the same meaning as "D; E; F; G; D and E; D and F; D and G; E and F; E and G; F and G; D, E, and F; D, E, and G; D, F, and G; E, F, and G; or D, E, F, and G." Commas can be used to the left or right of the decimal point symbol as a separator or digit grouping symbol; for example, "0.000,1" is equivalent to "0.0001."

[0014] In the methods described herein, steps can be performed in any order without departing from the principles of the invention, except when a time or sequence of operations is explicitly recited. Furthermore, defined steps can be performed in parallel unless explicit language recites them to be performed separately. For example, the recited act of doing X and the recited act of doing Y can be performed simultaneously in a single operation, and the resulting process would fall within the literal scope of the process. Recitation in a claim to the effect that a first step is performed, then several other steps are subsequently performed, shall be taken to mean that the first step is performed before any of the other steps, but that the other steps can be performed in any suitable sequence, unless a sequence is further recited within the other steps. For example, a claim element reciting "step A, step B, step C, step D, and step E" shall be interpreted to mean that step A is performed first and step E is performed last, and that steps B, C, and D may be performed in any sequence between steps A and E (including one or more steps being performed in parallel with step A or step E) and the sequence still falls within the literal scope of the claimed process. A given step or subset of steps may also be repeated.

[0015] Furthermore, defined steps can be performed in parallel unless express claim language recites them as being performed separately. For example, a claimed step of performing X and a claimed step of performing Y can be performed simultaneously in a single operation, and the resulting process would fall within the literal scope of the claimed process.

[0016] The term "about" as used herein can allow for a degree of variation within a value or range, e.g., within 10%, 5%, 1%, 0.5%, 0.1%, 0.05%, 0.01%, 0.005%, or 0.001% of a stated value, or of a stated limit of a range, and includes the strictly stated value or range.

[0017] The term "substantially" as used herein refers to a "majority of" or "mostly," such as 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%.

[0018] Additionally, phraseology or terminology employed herein and not otherwise defined should be understood to be for purposes of description only and not of limitation. Furthermore, all publications, patents, and patent documents referred to herein are incorporated herein by reference in their entirety, as if individually incorporated by reference. In the event of inconsistent usage between this document and those documents so incorporated by reference, the usage in the incorporated references should be considered supporting that of this document, and in the event of irreconcilable inconsistencies, the usage in this document will control.

[0019] Hydrogen gas (H) can be formed electrochemically through a water splitting reaction in which water is split into oxygen gas (O) and H gas at the anode and cathode of an electrochemical cell, respectively. Examples of such electrochemical processes include, but are not limited to, proton-electrolyte membrane (PEM) electrolysis and alkaline water electrolysis (AWE). In such electrochemical reactions, the operating energy required 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 anode may be separated by a separator, such as a membrane, which can reduce ionic species migration. While a separator can improve the overall efficiency of the cell, this may come at the cost of additional resistive losses within the cell, which in turn increases the operating voltage. Other inefficiencies in water electrolysis may include solution resistive losses, electrical conduction inefficiencies, and / or electrode overpotentials, among others.

[0020] 1 is a schematic diagram of a system 100 for electrolytically converting water (HO) to hydrogen gas (H) and (optionally) oxygen gas (O) using electrical power. The exemplary system 100 includes an electrolyzer cell 102. The electrolyzer cell 102 comprises two half-cells: a first half-cell 111 and a second half-cell 121. In some embodiments, the first and second half-cells 111, 121 are separated by a separator 131, such as a membrane 131. In some embodiments, the separator 131 comprises a porous membrane (e.g., a microporous membrane or a nanoporous membrane), an ion exchange membrane, or an ion solvation membrane. In embodiments where the separator 131 comprises an ion exchange membrane, the membrane can be of different types, such as an anion exchange membrane (AEM), a cation exchange membrane (CEM), a proton exchange membrane (PEM), or a bipolar ion exchange membrane (BEM).

[0021] In embodiments where separator 131 is a cation exchange membrane, the cation exchange membrane can be a conventional membrane such as those available from Asahi Kasei Corp. (Tokyo, Japan), Membrane International Inc. (Glen Rock, NJ, USA), or Chemours Company (Wilmington, DE, USA). Examples of cation exchange membranes include, but are not limited to, the membrane sold by Chemours Company under the trade name N2030WX and the membrane sold by Asahi Kasei Corp. under the trade names F8020 / F8080 or F6801. Examples of materials that can be used to form the cation exchange membrane include, but are not limited to, perfluoropolymers containing anionic groups, such as sulfonic acid groups and / or carboxylic acid groups. However, it should be understood that in some embodiments, cation exchange membranes that are more restrictive, thus allowing migration of one species of cation while restricting migration of another species of cation, can be used, depending on the need to restrict or allow migration of specific cation or anionic species between electrolytes. Similarly, in some embodiments, anion exchange membranes may be used that are more restrictive, thus allowing the migration of one species of anion while restricting the migration of another species of anion, depending on the need to restrict or allow the migration of particular anion species between electrolytes. Such restrictive cation and anion exchange membranes are commercially available and can be selected by one skilled in the art.

[0022] In some embodiments, separator 131 can be selected so that it can function in acidic and / or alkaline electrolyte solutions, as appropriate. Other properties for separator 131 that may be desirable include, but are not limited to, high ionic selectivity, low ionic resistance, high burst strength, and high stability in electrolyte solutions within a temperature range of room temperature up to 150° C. or higher.

[0023] In one embodiment, the separator 131 is stable within a temperature range of about 0°C to about 150°C, such as about 0°C to about 100°C, about 0°C to about 90°C, etc., such as about 0°C to about 80°C, about 0°C to about 70°C, etc., such as about 0°C to about 60°C, about 0°C to about 50°C, etc., such as about 0°C to about 40°C, or about 0°C to about 30°C, etc.

[0024] To achieve a desired product or products in the electrolyte solution, it may be useful to use ion-specific ion exchange membranes that allow migration of one type of ion (e.g., cations for CEMs and anions for AEMs) but not another, or that allow migration of one type of ion and another.

[0025] In some embodiments, the first half-cell 111 includes a first electrode 112 that may be located adjacent to a separator 131, and the second half-cell 121 includes a second electrode 122 that may be located adjacent to the separator 131, for example, on the opposite side of the separator 131 from the first electrode 112. In some embodiments, the first electrode 112 is an anode for the electrolyzer cell 102, and the second electrode 122 is a cathode for the electrolyzer cell 102; therefore, later in this 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 accelerate the reaction toward hydrogen gas (H gas) and / or oxygen gas (O 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 combinations thereof such as platinum-rhodium, platinum-ruthenium, nickel mesh coated with ruthenium oxide (RuO), or high surface area nickel.

[0026] 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 can increase, and vice versa. In some embodiments, the separator 131 has a relatively low ohmic resistance and a relatively high ion mobility. In some embodiments, the separator 131 has a relatively high hydration characteristic that increases with temperature, thus decreasing the ohmic resistance. By selecting a separator 131 with a lower ohmic resistance, as known in the art, the voltage drop across the anode 112 and the cathode 122 at a specified temperature can be reduced.

[0027] In one embodiment, the anode 112 is electrically connected to an external positive conductor 116 (also referred to as the "anode conductor 116"), and the cathode 122 is electrically connected to an external negative conductor 126 (also referred to as the "cathode conductor 126"). When a separator 131 is wetted and in electrolytic contact with the electrodes 112 and 122, and an appropriate voltage is applied across the conductors 116 and 126, O gas is liberated at the anode 112 and H gas is liberated at the cathode 122. In one configuration, an electrolyte, for example, consisting of a solution of KOH in water, is pumped 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 one embodiment, the flow of electrolyte through the anode half-cell 111 traps the produced O gas as bubbles 113, which exit the anode half-cell 111 through a first outlet 115. Similarly, the flow of electrolyte through the cathode half-cell 121 can trap the produced H gas as bubbles 123, which can exit the cathode half-cell 121 through a second outlet 125. Gases can be separated from the electrolyte downstream of the electrolyzer cell 102 using one or more suitable separators. In one embodiment, the produced H gas is dried and collected in a high-pressure canister or pumped into further process elements. The O gas can simply be allowed to vent to the atmosphere or can be stored for other uses. In one embodiment, the electrolyte is recycled back into the half-cells 111, 121 as needed.

[0028] As described in further detail below, at least a portion of the electrolyte exiting each half-cell 111, 121 via electrolyte outlet 115, 125 can be recycled back to the electrolyte inlet 114, 124 (e.g., anolyte withdrawn from the anode half-cell 111 via anolyte outlet 115 can be recycled back to the anolyte inlet 114, and catholyte withdrawn from the cathode half-cell 121 via catholyte outlet 125 can be recycled back to the catholyte inlet 124). Because the electrolyte outlet temperature may vary over time due to fluctuations in current density and other factors in the operation of the cell 102, in certain embodiments, the outlet electrolyte for one or both of the recirculation loops can be pumped into a holding tank so that the temperature of the recirculating electrolyte is more stable and less subject to temperature fluctuations. In the embodiment shown in FIG. 1, a first holding tank 132 receives anolyte from anolyte outlet 115 (also referred to as "anolyte holding tank 132"), and a second holding tank 134 receives catholyte from catholyte outlet 125 (also referred to as "catholyte holding tank 134").

[0029] In one embodiment, a typical voltage across the electrolyzer cell 102 (e.g., the voltage difference between the anode conductor 116 and the cathode conductor 126) is between about 1.5 volts (V) and about 3.0 V. In one embodiment, the operating current density for the electrolyzer cell 102 is about 0.1 A / cm 2 ~About 3A / cm 2 Each cell 102 has a size large enough to produce very large amounts of H gas when operated at these current densities. In one embodiment, the cross-sectional area of ​​each cell 102 (e.g., width x height for a rectangular cell) is about 0.25 square meters (m 2 ) ~ approx. 15m 2 , about 1 m 2 ~about 5m 2 etc., for example, about 2 m 2 ~about 4m 2 , about 2.25m 2 ~about 3m 2 etc., approximately 2.5m 2 ~approx. 2.9m 2In one embodiment, the total volume (e.g., width x height x depth) of each cell is approximately 0.1 cubic meters (m 3 ) ~ approx. 2m 3 , about 0.15m 3 ~about 1.5m 3 etc., for example, about 0.2 m 3 ~approx. 1m 3 , approx. .25m 3 ~about 0.5m 3 etc., for example, about 0.275 m 3 ~about 0.3m 3 In one embodiment, the total volume of the entire electrolyzer system (e.g., the combined volume of all cells in all stacks in a plant) is about 1 m 3 ~about 200m 3 , about 2m 3 ~approx. 100m 3 etc., for example, about 2.5 m 3 ~approx. 50m 3 is.

[0030] Temperature control Control of the temperature within the electrolyzer cell 102 can be important for the operation of the cell 102 and for the overall efficiency of the system 100. During operation, the current density through the cell 102 can often fluctuate, for example, due to fluctuations in electricity prices. To maximize the performance and life of the separator 131, it is generally preferable to maintain the separator 131 within a small temperature range. However, even if the temperature of the electrolyte being fed to the cell 102 at the inlets 114, 124 is held constant or substantially constant, the temperature in the separator 131 will fluctuate significantly if the current density changes significantly.

[0031] The inventors have discovered that the electrolyte flow rates through the anode half-cell 111 and cathode half-cell 121 of the electrochemical cell 100 can be set so that the resulting temperatures of the electrolyte outlet streams 115, 125 can be maintained within specified ranges at the highest specified operating current by controlling the electrolyte temperature in the inlet streams 114, 124.

[0032] By referencing a lookup table or some other criteria, an operator can set the temperature of the inlet streams 114, 124 as a function of the current at which the cell 102 is currently operating so that the resulting temperature of the outlet streams 115, 125 does not significantly increase or decrease, e.g., the temperature of the outlet streams 115, 125 is within a temperature spread of the target temperature. As used herein, the term "prescribed current" refers to a planned, predefined current at which the cell 102 should be operated, either currently or at some future time. Thus, in some embodiments, the setpoint temperature for the inlet streams 114, 124 will be selected based on the current at which the cell 102 is currently operated. In other embodiments, the setpoint temperature for the inlet streams 114, 124 may be selected based on the current at which the cell 102 will be operated at some future time, e.g., so that the temperature of the inlet streams 114, 124 can begin to change to compensate for expected changes in temperature that will result when the operating current is changed. In some embodiments, the temperatures of the inlet streams 114, 124 can be varied to maintain the temperature of the electrolyte in the separator 131 at a constant or substantially constant set point. In some embodiments, the temperature of the electrolyte in the separator 131 can be determined by measuring the temperature of one or both of the outlet streams 115, 125 and calculating the temperature of the separator 131 based on one or more of the temperatures of the outlet streams 115, 125 and the operating current. In some embodiments, the inlet temperature control is automated through one or more controllers 140, 142, such as programmable logic controllers (“PLCs”). In the embodiment shown in FIG. 1 , the system 100 can include a first controller 140 (also referred to as “anolyte controller 140”) configured to control the temperature of the anolyte inlet 114 and a second controller 142 (also referred to as “catholyte controller 142”) configured to control the temperature of the catholyte inlet 124.In another embodiment (not shown), a single controller can be used to control the temperature of both the anolyte inlet 114 and the catholyte inlet 124 (e.g., by controlling one or more control valves in both the anolyte recirculation loop and the catholyte recirculation loop, as described below).

[0033] As described in more detail below, temperature control can be coupled to one or more of the current setting (e.g., the current across the electrolyzer cell 102 divided by the active area of ​​the electrodes 112, 122), the voltage across the electrolyzer cell 102, and the temperature of the corresponding outlet streams 115, 125. In some embodiments, temperature control can be automated using a proportional-integral-derivative ("PID") controller, or a feedforward control scheme, or both. In one embodiment, the inlet temperature is controlled via feedforward control based on one or more of the current set point, the flow rate of electrolyte through the cell 102, and the observed voltage across the electrolyzer cell 102. In another embodiment, in addition to feedforward control by current, the temperature of the corresponding electrolyte outlet 115, 125 can also be used to control the temperature of the inlet 114, 124 via a PID controller tuned for slow response, which can allow the temperature of the outlet 115, 125 to fine-tune the temperature of the inlet 114, 124 after a fast response from the feedforward controller.

[0034] The combination of fast linear temperature control of one or both of the electrolyte inlets 114, 124 and a feedforward controller that sets the inlet temperature setpoint based on one or more of the current, electrolyte flow rate, and observed voltage across the cell 102 can provide stable temperature control for the outlet streams 115, 125 when changing the current (e.g., when changing the current applied across the cell 102 to change the H production rate). Such fast temperature management can compensate for rapid changes in current while minimizing thermal effects on the separator 131, electrodes 112, 122, and other components of the cell 102.

[0035] 1 , control of the temperature of the inlet streams 114, 124 is effectively accomplished using a mixing scheme with electrolyte coolers 144, 146 that can cool at least a portion of the hot electrolyte reflux from the electrolyte outlets 115, 125 (or from the corresponding holding tanks 132, 134, if the system 100 includes outlet holding tanks 132, 134) as it recirculates to the corresponding electrolyte inlets 114, 115. In the example of FIG. 1 , the first electrolyte cooler 144 is configured to cool the anolyte from the anolyte outlet 115 exiting the anode half cell 111 before it is recirculated back to the anolyte inlet 114 (so that the first electrolyte cooler 144 will also be referred to as the “anolyte cooler 144”). A similar second electrolyte cooler 146 is configured to cool the catholyte from the catholyte outlet 125 exiting the cathode half cell 121 before being recycled to the catholyte inlet 124 (so that the second electrolyte cooler 146 will also be referred to as "catholyte cooler 146"). Each of the electrolyte coolers 144, 146 can comprise any type of cooling device operable to cool the electrolyte streams in one or both of the recirculation loops, including, but not limited to, a heat exchanger (such as a shell and tube heat exchanger or other type of heat exchanger, and using any operable cooling medium such as cooling water, cooling air, or a different cooled stream) or an electrical cooler.

[0036] In certain embodiments, the electrolyte recirculation configuration may include bypass lines 150, 152 configured to allow some or all of the recirculating electrolyte to bypass its corresponding electrolyte cooler 144, 146. For example, a first bypass line 150 may bypass the anolyte cooler 144 (and may be referred to as the “anolyte bypass line 150”), and a second bypass line 152 may bypass the catholyte cooler 146 (and may be referred to as the “catholyte bypass line 152”). The bypassed portions of the electrolyte in the bypass lines 150, 152 are not cooled by their corresponding electrolyte coolers 144, 146, such that the bypassed portions remain at or near the elevated temperature they had when they exited the cells 102 in the electrolyte outlets 115, 125.

[0037] One or more control valves may be included for each electrolyte recirculation line to regulate the proportion of recirculating electrolyte that flows through the electrolyte coolers 144, 146 and the proportion that will flow through the bypass lines 150, 152. In one example, the control valves may be on the bypass lines 150, 152 themselves, such as a first bypass line control valve 154 (also referred to as the “anolyte bypass control valve 154”) for controlling the flow rate through the anolyte bypass line 150 and / or a second bypass line control valve 156 (also referred to as the “catholyte bypass control valve 156”) for controlling the flow rate of catholyte through the catholyte bypass line 152. By using the control valves 154, 156 to control the flow rate of electrolyte through the bypass lines 150, 152, the control valves 154, 156 also act to regulate the flow rate through the corresponding electrolyte coolers 144, 146. For example, the total recirculation flow rate of anolyte recirculating from anolyte outlet 115 to anolyte inlet 114 is set, so that if anolyte bypass control valve 154 reduces the flow rate of anolyte through anolyte bypass line 150, this will necessarily increase the relative flow rate of anolyte through anolyte cooler 144.

[0038] 1 , this may include a first heat exchanger inlet control valve 158 (also referred to as “anolyte inlet control valve 158”) for controlling the flow rate of anolyte into the anolyte cooler 144 and / or a second heat exchanger inlet control valve 160 (also referred to as “catholyte inlet control valve 160”) for controlling the flow rate of catholyte into the catholyte cooler 146. In another example, the control scheme may include a control valve for controlling the flow rate at the outlet out of the electrolyte coolers 144, 146 in addition to or instead of the bypass control valves 154, 156 or one or both of the heat exchanger inlet control valves 158, 160. In the embodiment shown in FIG. 1, this may include a first heat exchanger outlet control valve 162 (also referred to as "anolyte outlet control valve 162") for controlling the flow rate of anolyte exiting the anolyte cooler 144 and / or a second heat exchanger outlet control valve 164 (also referred to as "catholyte outlet control valve 164") for controlling the flow rate of catholyte exiting the catholyte cooler 146.

[0039] Those skilled in the art will understand that any one of the control valves 154, 158, 162 on the anolyte recirculation side can be used to adjust the flow rate of anolyte through the anolyte cooler 144 and the anolyte bypass line 150, and that the control valve or valves 154, 158, 162 used is a matter of design choice. For example, temperature control of the recirculating anolyte may be achieved through use of only the anolyte bypass control valve 154, only the anolyte inlet control valve 158, only the anolyte outlet control valve 162, the combination of the anolyte bypass control valve 154 and the anolyte inlet control valve 158, or the combination of the anolyte bypass control valve 154 and the anolyte outlet control valve 162. Similarly, those skilled in the art will understand that any one of the control valves 156, 160, 164 on the catholyte recirculation side can be used to adjust the flow rate of catholyte through the catholyte cooler 146 and the catholyte bypass line 152, and is a matter of design choice. For example, temperature control of the recirculating catholyte may be accomplished through use of only the catholyte bypass control valve 156, only the catholyte inlet control valve 160, only the catholyte outlet control valve 164, a combination of the catholyte bypass control valve 156 and the catholyte inlet control valve 160, or a combination of the catholyte bypass control valve 156 and the catholyte outlet control valve 164.

[0040] Depending on the ambient temperature and the volume of electrolyte being used, in some embodiments, system 100 may also include one or more electrolyte heaters on one or both recirculation sides of system 100 to achieve a defined electrolyte inlet temperature for one or both of anolyte inlet 114 and catholyte inlet 115. In one embodiment, one or both of electrolyte coolers 144, 146 can be replaced with an electrolyte heater. In another embodiment, an electrolyte heater can be included on one or both bypass lines 150, 152 to heat the electrolyte flowing through the bypass lines 150, 152 (similar to the scheme shown for temperature control subsystem 210 in example system 200 of FIG. 2 ). In yet another embodiment, a heater can be included on one or both of electrolyte holding tanks 132, 134 to heat the electrolyte solution in the holding tanks 132, 134 before flowing to the recirculation and cooling loop.

[0041] The electrolytes flowing through the electrolyte coolers 144, 146 and bypass lines 150, 152 are then mixed to provide cooled electrolyte at a temperature lower than the temperature upstream of the electrolyte coolers 144, 146, which is pumped back into its corresponding half-cell 111, 121 via the electrolyte inlets 114, 124. The relative flow rates of electrolyte passing through the electrolyte coolers 144, 146 versus the bypass lines 150, 152 are selected to achieve a defined setpoint temperature for the electrolyte inlets 114, 124. For example, if a higher temperature of anolyte to be pumped into the anode half-cell 111 via inlet 114 is desired than its current temperature, one or more control valves 154, 158, 162 on the anolyte recirculation side can be controlled to allow a lower proportion of anolyte to flow through the anolyte cooler 144 relative to the proportion of anolyte flowing through the anolyte bypass line 150. This results in a relatively smaller amount of anolyte being cooled by the anolyte cooler 144, and therefore the temperature of the anolyte after mixing the two streams will be higher. Similarly, if a lower temperature of the catholyte to be pumped into the cathode half-cell 121 is desired than its current temperature, one or more control valves 156, 160, 154 on the catholyte recirculation side can be controlled so that a higher proportion of catholyte flows through the catholyte cooler 146 relative to the proportion that flows through the catholyte bypass line 152. This arrangement results in a relatively larger amount of catholyte being cooled by the catholyte cooler 146, and therefore the temperature of the catholyte after mixing the two streams will be lower.

[0042] In certain embodiments, system 100 also includes flow control valves 166, 168 located downstream of the mixing point where cooled electrolyte exiting electrolyte coolers 144, 146 mixes with uncooled electrolyte from bypass lines 150, 152. In certain embodiments, system 100 includes a first flow control valve 166 for controlling the flow rate of anolyte recycled to anolyte inlet 114 and a second flow control valve 168 for controlling the flow rate of catholyte recycled to catholyte inlet 124. System 100 also includes make-up lines for each recirculation loop, such as an anode-side make-up line 170 for introducing make-up water or make-up anolyte into anolyte inlet 114, and a cathode-side make-up line 172 for introducing make-up water or make-up catholyte into catholyte inlet 124, to introduce additional water or electrolyte to compensate for water consumed as part of the electrolysis reactions that generate H gas at cathode 122 and (optionally) O gas at anode 112.

[0043] In one embodiment, one or both of the electrolyte coolers 144, 146 are oversized at least slightly in terms of the flow rates that the electrolyte coolers 144, 146 can accommodate or the heat exchange capacity of the electrolyte coolers 144, 146 so that the combination of the electrolyte coolers 144, 146 and the bypass lines 150, 152 can provide adequate temperature and flow control. The inventors have found that this type of temperature control for the electrolyte inlet streams 114, 124 can provide fast and linear or near-linear inlet temperature control compared to controlling the temperature of the inlet streams 114, 124 by varying the amount of cooling water being pumped to the electrolyte coolers 144, 146.

[0044] The system 100 may include one or more temperature sensors to measure the temperature of the electrolyte outlets 115, 125 for one or both of the recirculation loops in the system 100. The temperature of the electrolyte outlets 115, 125 may be used as an approximation of the temperature of the separator 131 in the cell 102 at that particular time. In other embodiments, the temperature at the separator 131 may be assumed to be a specified number of degrees higher (based on historical experimental data) than the temperature measured by the temperature sensors on the electrolyte outlets 115, 125. In still other embodiments, other parameters of the cell 102 may be used to estimate the temperature at the separator 131 instead of, or in addition to, the temperature of the electrolyte outlets 115, 125. For example, the voltage across the cell 102 (or each cell, if the cell 102 is part of a larger electrolyzer stack) may be measured, and the measured voltage across the cell may be used to determine an estimated temperature at the separator 131 of the cell 102 (or of each cell in the stack, if the cell 102 is part of a larger electrolyzer stack). In one embodiment, a first outlet temperature sensor 174 is positioned on the anolyte outlet 115 and measures the outlet temperature of the anolyte exiting the anode half-cell 111 (also referred to as "anolyte outlet temperature sensor 174"), and a second outlet temperature sensor 176 is positioned on the catholyte outlet 125 and measures the outlet temperature of the catholyte exiting the cathode half-cell 121 (also referred to as "catholyte outlet temperature sensor 176"). In operation, one or both of the controllers 140, 142 can be configured to receive outlet temperature signals from one or both of the electrolyte outlet temperature sensors 174, 176 corresponding to one or both of the electrolyte outlets 115, 125. In an embodiment in which system 100 includes separate anolyte controller 140 and catholyte controller 142, anolyte controller 140 can be configured to receive a first outlet temperature signal from anolyte outlet temperature sensor 174, and catholyte controller 142 can be configured to receive a second outlet temperature signal from catholyte outlet temperature sensor 176.

[0045] The one or more controllers 140, 142 use temperature signals received from outlet temperature sensors 174, 176 to control one or more control valves 154, 156, 158, 160, 162, 164 included within the system 100 to achieve a desired temperature set point for the corresponding electrolyte inlet 114, 124, and to control the electrolyte flow rate through the electrolyte coolers 144, 146 and bypass lines 150, 152. For example, the anolyte controller 140 may receive a temperature signal from the anolyte outlet temperature sensor 174 corresponding to the temperature of the anolyte outlet 115. The anolyte controller 140 uses the anolyte outlet temperature signal to control the one or more control valves 154, 158, 162, which in turn control the flow rate of recirculating anolyte through the anolyte cooler 144 and anolyte bypass line 150 at a rate that will achieve a specified temperature set point for the anolyte inlet 114. The anolyte controller 140 can also be configured to control the flow control valve 166 to control the overall flow rate of anolyte recirculated to the anolyte inlet 114, which may also be varied to achieve a defined anolyte inlet temperature set point.

[0046] Similarly, the catholyte controller 142 can receive a temperature signal from a catholyte outlet temperature sensor 176 corresponding to the temperature of the catholyte outlet 125. The catholyte controller 142 uses the catholyte outlet temperature signal to control one or more control valves 156, 160, 164 to control the flow rate of recirculating catholyte through the catholyte cooler 146 and the catholyte bypass line 152 at a rate that will achieve a specified temperature setpoint for the catholyte inlet 124. The catholyte controller 142 can also be configured to control a flow control valve 168 to control the overall flow rate of catholyte recirculated to the catholyte inlet 124, which may also be varied to achieve a specified catholyte inlet temperature setpoint.

[0047] As described above, the defined temperature setpoints for one or both of the electrolyte inlets 114, 124 can be set based on the current currently being applied across the electrolyzer cell 102 or the current planned to be applied across the electrolyzer cell 102 at a future time. As will be understood by those skilled in the art, it is known that the temperature in the separator within the electrolyzer cell can depend on the current being applied across the cell, with lower current densities tending to result in less heating due to resistive losses and lower temperatures in the separator, and higher current densities tending to result in more heat due to resistive losses and higher temperatures in the separator. Accordingly, in certain embodiments, the system 100 can include an ammeter 178 configured to measure the current through the electrolyzer cell 102. In one embodiment shown in FIG. 1, the ammeter 178 can measure the current passing through one or both of the anode conductor 116 and the cathode conductor 126. In another example, the current passing through the cell 102 can be determined by measuring or otherwise determining the current being provided by a power supply. For example, if current is supplied to the cell 102 from a rectifier that rectifies alternating current from an AC source into direct current that is supplied to the cell 102, the current provided by the rectifier can be used by one or more controllers 140, 142 as the current for the cell 102, which can be used in conjunction with the temperature in the separator 131 (e.g., determined in relation to the outlet temperature measured by one or both outlet temperature sensors 174, 176). In other examples, the temperature control scheme can be configured to control the electrolyte temperature for a stack of multiple electrolyzer cells. In such examples, an ammeter or other device for determining the current through a cell can be configured to determine or provide the current through one of the cells in the stack, through multiple cells in the stack, or through the entire stack.

[0048] In another embodiment, the system 100 can include a voltmeter 180 to measure the voltage across the cell 102, for example, measuring the potential difference between the anode conductor 116 and the cathode conductor 126. The voltmeter 180 can be included instead of, or in addition to, the ammeter 178. One or both of the controllers 140, 142 can receive a voltage signal from the voltmeter 180. In certain embodiments, the current can be determined by one or more of the controllers 140, 142 by dividing the measured voltage by the resistance through the electrolyzer cell 102, which can be known from previous experimentation. In some embodiments, the voltmeter 180, in conjunction with the current through the cell 102, can be used by one or more controllers to determine the power dissipated in the cell 102, which can be related to the temperature of the separator 131.

[0049] The current determined by one or both of the controllers 140, 142 can be used to control one or both of the recirculation loops to achieve a specified anolyte inlet temperature, or a specified catholyte inlet temperature, or both. For example, one or both controllers 140, 142 can use a look-up table of expected temperatures at the separator 131 at a particular anolyte inlet temperature and / or catholyte inlet temperature and when the electrolyzer cell 102 is operating at a particular current. One or both controllers 140, 142 can then use the look-up table, the determined current, and the specified target temperature for the separator 131 to determine the desired specified inlet temperature or temperatures for the anolyte inlet 114 and the catholyte inlet 124. One or both controllers 140, 142 can then control one or more control valves 154, 156, 158, 160, 162, 164 on each recirculation loop so that the relative proportion of electrolyte flowing through each electrolyte cooler 144, 146 to the electrolyte flowing through its corresponding bypass line 150, 152 will achieve a specified electrolyte inlet temperature determined based on the current and a specified target temperature for the separator 131.

[0050] While it is contemplated that the defined target electrolyte inlet temperature for one or both of the electrolyte inlets 114, 124 may be controlled by measuring the temperature of only one or both of the electrolyte outlets 115, 125, in certain embodiments, the system 100 may also include one or more temperature sensors to measure the temperature of the electrolyte inlets 114, 124 for one or both of the recirculation loops in the system 100. In certain embodiments, a first inlet temperature sensor 184 is positioned on the anolyte inlet 114 and measures the inlet temperature of the anolyte entering the anode half-cell 111 (also referred to as the "anolyte inlet temperature sensor 184"), and a second inlet temperature sensor 186 is positioned on the catholyte inlet 124 and measures the inlet temperature of the catholyte entering the cathode half-cell 121 (also referred to as the "catholyte inlet temperature sensor 186"). In operation, one or both of the controllers 140, 142 can be configured to receive an inlet temperature signal from one or both of the electrolyte inlet temperature sensors 184, 186, corresponding to one or both of the electrolyte inlets 114, 124. In embodiments in which the system 100 includes separate anolyte controller 140 and catholyte controller 142, the anolyte controller 140 can be configured to receive a first inlet temperature signal from the anolyte inlet temperature sensor 184, and the catholyte controller 142 can be configured to receive a second inlet temperature signal from the catholyte inlet temperature sensor 186. One or both of the controllers 140, 142 can use the inlet temperature signals from the inlet temperature sensors 184, 186 to check the effectiveness of the specific percentages of electrolyte flowing through the electrolyte coolers 144, 146 and bypass lines 150, 152 for one or both of the recirculation loops, which one or both controllers 140, 142 can use to modify the flow rate of electrolyte through the electrolyte coolers 144, 146 and their corresponding bypass lines 150, 152, as needed, to achieve the desired, defined electrolyte inlet temperature.

[0051] In one embodiment, the defined electrolyte inlet temperature can be determined based on the expected temperature change for the electrolyte as it passes through the cells 102, for example, based on the expected temperature increase for the anolyte as it passes through the anode half-cell 111 and the expected temperature increase for the catholyte as it passes through the cathode half-cell 121. For the anolyte, the expected temperature change ΔT A is defined by equation [1]. [ka] In the formula, T A, In is the inlet temperature of the anolyte, for example at the anolyte inlet 114, and T A, Out is the outlet temperature of the anolyte, for example at the anolyte outlet 115, [ka] is the mass flow rate of anolyte through the anode half cell 111, and C pA is the specific heat capacity of the anolyte, and Q A is the power dissipated as heat on the anode side of the cell 102. A is defined by equation [2]. [ka] where I is the current through the cell 102 and V LA is the dropout voltage on the anode side of cell 102. Equations [1] and [2] are combined to calculate the inlet temperature T A, In which results in equation [3]. [ka]

[0052] The dropout voltage across the cell, V L is the dropout voltage V on the anode side of cell 102, as shown in equation [4]. LA and the dropout voltage V on the cathode side of cell 102 LCIt is the sum of. [ka] In the formula, V Cell is the total voltage across the cell 102, and V TN is the thermoneutral voltage (e.g., about 1.48 V) for the electrolysis reaction in cell 102. In some embodiments, data from experiments on cell 102 or from other sources indicates the dropout voltage V on the anode side during typical operation of the cell. LA is the overall loss voltage for the entire cell, V L For example, for a particular configuration of cells, it can be shown that the anode loss voltage V LA is typically the overall loss voltage V L Approximately 80% of (e.g., V LA =0.8V L ) in which case the cathode loss voltage V LC is the overall loss voltage V L Approximately 20% of (e.g., V LC =0.2V L ) would be

[0053] In practice, one or both of the controllers 140, 142 may set the desired temperature of the separator 131 to T A, Out can be used as a setpoint for I, and the current signal value received from ammeter 178 (or from another current source through the cell) can be used, and / or the voltage signal value received from voltmeter 180 can be used as a value for I to calculate the current, and the anode side dropout voltage V LA (For example, V Cell the voltage across the cell 102 as measured by the voltmeter 180 as the overall loss voltage V calculated by equation [4] L (which can be determined experimentally on the anode side of the cell) and calculate the resulting T from equation [3]. A, In As discussed above, one or both of the controllers 140, 142 can then calculate the anolyte inlet temperature T A, InThe flow rate of anolyte through the anolyte cooler 144 and the anolyte bypass line 150 that can achieve this can be determined and one or more control valves 154, 158, 162 can be controlled accordingly.

[0054] The same analysis can be applied to the cathode side of the cell 102 to determine the specified catholyte inlet temperature. Specifically, the change in temperature for the catholyte, ΔT, based on the power dissipated as heat on the cathode side can be calculated as C The step of calculating can be calculated according to equation [5]. [ka] In the formula, T C, In is the inlet temperature of the catholyte at the catholyte inlet 124, and T C, Out is the catholyte outlet temperature at catholyte outlet 125; [ka] is the mass flow rate of catholyte through the cathode half cell 121, and C pC is the specific heat capacity of the catholyte, and Q C is the power dissipated as heat on the cathode side of the cell 102. C is defined by equation [6]. [ka] where I is the current through the cell 102 and V LC is the dropout voltage on the cathode side of cell 102. Equations [5] and [6] are combined to find the inlet temperature T C, In which results in equation [7]. [ka]

[0055] As explained above with respect to equation [4], the dropout voltage on the cathode side, V LCis the loss voltage on the anode side, V LA Combined with this, the overall dropout voltage V L Similar to the process described above, one or both of the controllers 140, 142 may adjust the desired temperature of the separator 131 to T C, Out The measured current can be used as the setting value for I, and the cathode dropout voltage V LC Determine (e.g., V Cell the voltage across the cell 102 as measured by the voltmeter 180 as the overall loss voltage V calculated by equation [4] L In conjunction with the temperature (e.g., based on experiments on the cathode side of the cell), the defined catholyte inlet temperature is calculated from equation [7] to obtain the resulting T C, In One or both of the controllers 140, 142 can then calculate the catholyte inlet temperature T C, In The flow rate of catholyte through the catholyte cooler 146 and the catholyte bypass line 152 that can achieve this can be determined and one or more control valves 156, 160, 164 can be controlled accordingly.

[0056] In the example shown in FIG. 1 , the anolyte recirculation loop (e.g., anolyte outlet 115, optional anolyte holding tank 132, anolyte cooler 144, anolyte bypass line 150, and anolyte inlet 114) is separate from the catholyte recirculation loop (e.g., catholyte outlet 125, catholyte holding tank 134, catholyte cooler 146, catholyte bypass line 152, and catholyte inlet 124). For example, the anolyte and catholyte may comprise different compositions (e.g., different chemical compounds or different concentrations of the same chemical compound or compounds). However, in some examples, the same electrolyte solution is used for both the anolyte passed through the anode half-cell and the catholyte passed through the cathode half-cell. For example, in many electrolyzer systems, potassium hydroxide (KOH) is used as both the anolyte and catholyte in the electrolyzer cells. In such an embodiment, the overall system may include a common temperature control device, and at least a portion of the recirculation loop may generally be used by both the anolyte and catholyte. Figure 2 shows an exemplary system 200 with a common temperature control scheme. Portions of system 200 that are identical to those in system 100 of Figure 1 are given the same reference numbers.

[0057] As can be seen in Figure 2, system 200 includes an electrolyzer cell 102. Many of the specific details of cell 102 are not shown in Figure 2, but one skilled in the art will understand that the electrolyzer cell 102 in system 200 can be similar to or the same as the electrolyzer cell 102 described above with respect to system 100, for example, the anode half cell 111 and the cathode half cell 121 are separated by a separator 131. The anode half cell 111 can include an anode on one side of the separator 131, and the cathode half cell 121 can include a cathode on the opposing side of the separator 131. Conductors can be electrically connected to the anode and cathode such that a voltage can be applied across the cell to generate H gas from the cathode.

[0058] Electrolyte solution is pumped into both the anode half cell 111 and the cathode half cell 121, such as anolyte into the anode half cell 111 via anolyte inlet 202 and catholyte into the cathode half cell 121 via catholyte inlet 204. Electrolyte is also withdrawn from the half cells 111, 121; for example, anolyte can be withdrawn from the anode half cell 111 via anolyte outlet 206 and catholyte can be withdrawn from the cathode half cell 121 via catholyte outlet 208. System 200 can also include one or more holding tanks for the electrolyte, such as anolyte holding tank 132, which can receive and hold anolyte from anolyte outlet 206, and catholyte holding tank 134, which can receive and hold catholyte from catholyte outlet 208.

[0059] Instead of having separate temperature control subsystems for both the anolyte and catholyte, as in system 100, system 200 includes a common temperature control subsystem 210 that can act to control the temperature for both the anolyte, which will be fed into the anode half-cell 111 via anolyte inlet 202, and the catholyte, which will be fed into the cathode half-cell 121 via catholyte inlet 204. For example, anolyte withdrawal line 212 can withdraw anolyte from anolyte holding tank 132, and catholyte withdrawal line 214 can withdraw catholyte from catholyte holding tank 134. The two withdrawal lines 212 and 214 can be combined such that the recirculating anolyte and recirculating catholyte mix together in a common recirculation line 216 that is fed into temperature control subsystem 210. The temperature control subsystem 210 is configured to control the temperature of the recirculating electrolyte to achieve a defined electrolyte inlet temperature for both the anolyte inlet 202 and the catholyte inlet 204 .

[0060] In one embodiment, temperature control subsystem 210 includes an electrolyte cooler 220 and an optional electrolyte heater 222. Common recirculation line 216 splits into a cooled recirculation branch 224 that feeds into electrolyte cooler 220 and a heated recirculation branch 226 that feeds into electrolyte heater 222. Electrolyte cooler 220 is configured to cool the electrolyte in cooled recirculation branch 224 to a lower temperature, providing cooled stream 228, while electrolyte heater 222 is configured to heat the electrolyte in heated recirculation branch 226 to a higher temperature, providing heated stream 230.

[0061] The electrolyte cooler 220 can be similar to the electrolyte coolers 144, 146 in the system 100. For example, the electrolyte cooler 220 can be a shell-and-tube heat exchanger, an electric cooler, or any other device capable of cooling the electrolyte solution to a lower temperature. The electrolyte heater 222 can be an electric heater or other device capable of raising the temperature of a portion of the recirculating electrolyte. In some embodiments, the electrolyte heater 222 can be deactivated so as not to heat the portion of the electrolyte flowing through the heated recirculation branch 226, in which case the heated recirculation branch 226 essentially functions the same as the bypass lines 150, 152 in the system 100 of FIG. 1 .

[0062] Cooled stream 228 and heated stream 230 can be recombined such that the resulting temperature of the combined cooled and heated portions will be at or near the desired defined electrolyte inlet temperature. Specifically, cooled stream 228 can be split into cooled anolyte stream 232 and cooled catholyte stream 234, and heated stream 230 can be split into heated anolyte stream 236 and heated catholyte stream 238. Cooled anolyte stream 232 and heated anolyte stream 236 can be combined, for example, at anolyte mixing point 240 to form anolyte inlet 202. Similarly, cooled catholyte stream 234 and heated catholyte stream 238 can be combined, for example, at catholyte mixing point 242 to form catholyte inlet 204.

[0063] The temperature control subsystem 210 may also include flow valves for controlling the flow rates of one or more of the cooled anolyte stream 232, the cooled catholyte stream 234, the heated anolyte stream 236, and the heated catholyte stream 238. For example, the anolyte side of the recirculation scheme may include a first anolyte control valve 244 (also referred to as the “anolyte temperature control valve 244”) configured to control the flow rate of the cooled anolyte stream 232 and a second anolyte control valve 246 (also referred to as the “anolyte flow control valve 246”) configured to control the flow rate of the heated anolyte stream 236. The catholyte side of the recirculation scheme may include a first catholyte control valve 248 (also referred to as "catholyte temperature control valve 248") configured to control the flow rate of cooled catholyte stream 234 and a second catholyte control valve 250 (also referred to as "catholyte flow control valve 250") configured to control the flow rate of heated catholyte stream 238.

[0064] In one embodiment, the temperature control valves 244, 248 on the cooled streams 232, 234 are controlled to adjust the proportion of cooled electrolyte that will make up the electrolyte inlets 202, 204 to achieve a specified electrolyte inlet temperature; for example, the anolyte temperature control valve 244 will control the flow rate of the cooled anolyte stream 232 such that the desired specified anolyte inlet temperature for the anolyte inlet 202 will be achieved, and the catholyte temperature control valve 246 will control the flow rate of the cooled catholyte stream 236 such that the desired specified catholyte inlet temperature for the catholyte inlet 204 will be achieved. In one embodiment, the flow control valves 246, 250 are controlled to regulate the amount of heated electrolyte that will comprise the electrolyte inlets 202, 204 to ensure that a desired overall flow rate of electrolyte into the half cells 111, 121 is achieved; for example, the anolyte flow control valve 246 will control the flow rate of the heated anolyte stream 236 so that a desired overall flow rate for the anolyte inlet 202 is achieved, and the catholyte flow control valve 250 will control the flow rate of the heated catholyte stream 238 so that a desired overall flow rate for the catholyte inlet 204 is achieved.

[0065] System 200 also includes a make-up line 252 to introduce make-up water or make-up electrolyte to replace water consumed via the electrolysis reaction to generate H gas and (optionally) O gas. In the example shown in Figure 2, make-up line 252 mixes with common recirculation line 216 before splitting into cooling recirculation branch 224 and heating recirculation branch 226.

[0066] The system 200 can include one or more temperature sensors to measure the temperature of one or more of the electrolyte inlets 202, 204 and / or electrolyte outlets 206, 208. In one embodiment, an anolyte outlet temperature sensor 274 is positioned on the anolyte outlet 206 to measure the outlet temperature of the anolyte exiting the anode half-cell 111, and a catholyte outlet temperature sensor 276 is positioned on the catholyte outlet 125 to measure the outlet temperature of the catholyte exiting the cathode half-cell 121. System 200 may also include one or more controllers (not shown, but similar to controllers 140, 142 of system 100 of FIG. 1 ) that may be configured to receive outlet temperature signals from one or both of electrolyte outlet temperature sensors 274, 276, corresponding to one or both of the electrolyte outlets 206, 208, which may be used to control control valves 244, 246, 248, 250 to achieve a desired defined electrolyte inlet temperature and / or a desired overall electrolyte flow rate into each half cell 111, 121, similar to the operations described above with respect to controlling control valves 154, 156, 158, 160, 162, 164 in system 100 of FIG. 1 .

[0067] In certain embodiments, the system 200 also includes one or more temperature sensors to measure the temperature of the electrolyte inlets 202, 204 for one or both of the anode and cathode sides of the temperature control subsystem 210. For example, an anolyte inlet temperature sensor 284 may be positioned on the anolyte inlet 202 to measure the inlet temperature of the anolyte entering the anode half-cell 111, and a catholyte inlet temperature sensor 286 may be positioned on the catholyte inlet 204 to measure the inlet temperature of the catholyte entering the cathode half-cell 121. One or more controllers can be configured to receive an inlet temperature signal from one or both of the electrolyte inlet temperature sensors 284, 286, corresponding to one or both of the electrolyte inlets 202, 204, which can be used to control the control valves 244, 246, 248, 250 to achieve a desired defined electrolyte inlet temperature and / or a desired overall electrolyte flow rate into each half cell 111, 121, similar to the operations described above with respect to the control of the control valves 154, 156, 158, 160, 162, 164 in the system 100 of FIG. 1.

[0068] 1 and 2 are shown with only a single electrolyzer cell 102. However, the exemplary temperature control schemes can also be used for temperature control of the electrolyte inlet feed into a multi-cell electrolyzer stack. For example, the system 100 of FIG. 1 can include substantially the same recirculation loop with holding tanks 132, 134, electrolyte coolers 144, 146, and bypass lines 150, 152, but instead of electrolyte outlets 115, 125 exiting individual half-cells 111, 121 of each individual cell 102, each electrolyte outlet line 115, 125 can receive an outlet stream from a corresponding half-cell for each cell in the multi-cell stack. For example, in a system including a plurality of cells 102, each including an anode half cell 111 and a cathode half cell 121 (e.g., each cell 102 is the same or substantially the same as the cell 102 shown in FIG. 1 ), the anolyte outlet 115 can be configured to receive anolyte flowing out from all of the anode half cells 111 in the stack. Similarly, the catholyte outlet 125 can be configured to receive catholyte flowing out from all of the cathode half cells 121 in the stack. Similarly, in a system including a stack of cells 102, instead of electrolyte inlets 114, 124 feeding individual half cells 111, 121 of each individual cell 102, each electrolyte inlet line 114, 124 can be a common feed line that splits to feed the half cells for each cell in the multi-cell stack. For example, the anolyte inlet 114 can be configured as a common feed line that is split to feed all of the anode half cells 111 in the multi-cell stack, and the catholyte inlet 124 can be configured as a common feed line that is split to feed all of the cathode half cells 121 in the multi-cell stack. The system 200 of Figure 2 can likewise be configured to accommodate temperature control of multiple cells in a multi-cell stack, instead of just the individual cells 102 shown in Figure 2.

[0069] Simulations were performed to estimate the temperature rise and distribution of the electrolyte as it flows through the half cells 111, 121 of the electrolyzer cell 102. It was found that when the electrolyte is introduced as a cold fluid, it warms up quickly (e.g., within the first few centimeters of the height of the half cells 111, 121) and then becomes a constant or substantially constant temperature along the height of the cell 102. This uniformity or substantial uniformity of fluid temperature can provide for the avoidance of temperature gradients across the separator 131, which in turn can enable the temperature control scheme of the present disclosure.

[0070] A demonstration study was conducted in which the inlet stream temperature was varied to maintain a prescribed outlet stream temperature, and the results were in close agreement with the simulation results.

[0071] Figure 3 is a graph of data from an initial demonstration cell experiment. The temperature data is very noisy, but shows a 3 A / cm 2 It can be seen that at 1000 kJ / s (corresponding to a cell voltage of about 2.8 V), the anode inlet and outlet temperatures were about 48°C and about 78°C, respectively, and the cathode inlet and outlet temperatures were about 52°C and about 69°C, respectively. Averaging the two, the temperature rise through the cell was roughly 28°C, consistent with what the simulation predicted for those conditions. The data in Figure 3 also shows the temperature dependence of cell voltage: when operating with a higher outlet temperature, the voltage is lower (and correspondingly, the efficiency is higher). Care should be taken to ensure that the separator is warm enough to start but not overheated to the point of thermal degradation.

[0072] The above detailed description includes references to the accompanying drawings, which form a part of the detailed description. The drawings show, by way of illustration, specific embodiments in which the invention may be practiced. These embodiments are also referred to herein as "examples." Such examples may include elements in addition to those shown or described. However, the inventors also contemplate examples in which only those elements shown or described are provided. The inventors also contemplate examples using any combination or permutation of those elements shown or described (or one or more aspects thereof), either with respect to a particular example (or one or more aspects thereof) or with respect to other examples (or one or more aspects thereof) shown or described herein.

[0073] In the event of a conflicting usage between this document and any document so incorporated by reference, the usage in this document shall control.

[0074] The terms "a" or "an" are used herein, as is common in patent documents, to include "one or more than one," independently of any other instance or usage of "at least one" or "one or more." The term "or" is used herein to refer to a non-exclusive "or," unless otherwise indicated, such that "A or B" includes "A but not B," "B but not A," and "A and B." The terms "including" and "in which" are used herein as the plain-English equivalents of the respective terms "comprising" and "wherein." Also, in the following claims, the terms "including" and "comprising" are open-ended, i.e., systems, devices, articles, compositions, formulations, or processes that include elements in addition to those listed after such terms in a claim are still considered to be within the scope of that claim. Also, in the following claims, the terms "first," "second," "third," etc. are used merely as labels and are not intended to impose numerical requirements on their objects.

[0075] The method embodiments described herein can be implemented, at least in part, by a machine or computer. Some embodiments may include a computer-readable or machine-readable medium encoded with instructions operable to configure an electronic device to perform a method as described in the above embodiments. Such method implementations may include code such as microcode, assembly language code, higher-level language code, or the like. Such code may include computer-readable instructions for performing various methods. The code may form part of a computer program product. Furthermore, in some embodiments, the code may be tangibly stored on one or more volatile, non-transitory, or non-volatile tangible computer-readable media, such as during execution or at other times. Examples of these tangible computer-readable media include, but are not limited to, hard disks, removable magnetic disks, removable optical disks (e.g., compact disks and digital video disks), magnetic cassettes, memory cards or sticks, random access memory (RAM), read-only memory (ROM), and the like.

[0076] The above description is intended to be illustrative, not restrictive. For example, the above-described examples (or one or more aspects thereof) can be used in combination with each other. Other embodiments may also be utilized by those of ordinary skill in the art upon review of the above description. The Abstract is provided to comply with 37 C.F.R. §1.72(b) to enable the reader to quickly ascertain the nature of the present technical disclosure. It should be considered with the understanding that it will not be used to interpret or limit the scope or meaning of the claims. Also, in the above Detailed Description, various features may be grouped together for the purpose of concisely simplifying the disclosure. This should not be construed as intending that any unclaimed disclosed feature is essential to any claim. Rather, inventive subject matter may lie in less than all features of a particular disclosed embodiment. Thus, the following claims are herein incorporated into the Detailed Description as examples or embodiments, with each claim standing on its own as a separate embodiment, and it is contemplated that such embodiments can be combined with each other in various combinations or permutations. The scope of the invention should be determined with reference to the appended claims, along with the full scope of equivalents to which such claims are entitled.

Claims

1. 1. An electrolyzer system comprising: one or more electrolyzer cells, each electrolyzer cell comprising: a first half cell with a first electrode; a second half-cell with a second electrode; a separator between the first half cell and the second half cell; one or more electrolyzer cells, wherein an electric current is applied between the first electrode and the second electrode of each of the one or more electrolyzer cells; a first electrolyte feed stream for delivering a first electrolyte solution at a first inlet temperature to the first half-cell of each of the one or more electrolyzer cells; a second electrolyte feed stream for delivering a second electrolyte solution at a second inlet temperature to the second half-cell of each of the one or more electrolyzer cells; a first electrolyte outlet stream for withdrawing the first electrolyte solution from the first half-cell of each of the one or more electrolyzer cells; a second electrolyte outlet stream for withdrawing the second electrolyte solution from the second half-cell of each of the one or more electrolyzer cells; 1. A temperature control device, the temperature control device comprising one or more controllers, the one or more controllers: a current between the first electrode and the second electrode of at least one of the one or more electrolyzer cells; a voltage measured across the first and second electrodes of at least one of the one or more electrolyzer cells; and a temperature controller configured for feedforward control of the temperature in the separator of at least one of the one or more electrolyzer cells by adjusting one or both of a first inlet temperature and a second inlet temperature of at least one of the one or more electrolyzer cells based on one or both of: An electrolytic cell system comprising:

2. 2. The electrolyzer system of claim 1, wherein the one or more controllers are also configured for feedforward control of the temperature at the separator of at least one of the one or more electrolyzer cells by adjusting one or both of a first inlet temperature and a second inlet temperature of at least one of the one or more electrolyzer cells based on at least one of an overall voltage measured across the one or more electrolyzer cells, a flow rate of the first electrolyte solution through the first half-cell of at least one of the one or more electrolyzer cells, and a flow rate of the second electrolyte solution through the second half-cell of at least one of the one or more electrolyzer cells.

3. 3. The electrolyzer system of claim 1 or claim 2, wherein at least a first portion of the first electrolyte solution in the first electrolyte outlet stream is recycled back to the first electrolyte feed stream and at least a first portion of the second electrolyte solution in the second electrolyte outlet stream is recycled back to the second electrolyte feed stream, and the temperature control device comprises at least one electrolyte heat exchanger configured to heat or cool one or both of the first portion of the first electrolyte solution and the first portion of the second electrolyte solution prior to recycling back to the first and second electrolyte feed streams.

4. 4. The electrolyzer system of claim 3, wherein the temperature control device further comprises at least one bypass line configured to bypass one or both of the second portion of the first electrolyte solution and the second portion of the second electrolyte solution without passing through the at least one electrolyte heat exchanger.

5. 5. The electrolyzer system of claim 4, wherein the at least one electrolyte heat exchanger comprises a cooler configured to cool one or both of the first portion of the first electrolyte solution and the first portion of the second electrolyte solution, and the at least one electrolyte heat exchanger further comprises an electrolyte heater configured to heat one or both of the second portion of the first electrolyte solution and the second portion of the second electrolyte solution.

6. 5. The electrolytic cell system of claim 4, further comprising at least one flow control valve configured to adjust a ratio of a first flow rate of one or both of the first portion of the first electrolyte solution and the first portion of the second electrolyte solution through the at least one electrolyte heat exchanger to a second flow rate of one or both of the second portion of the first electrolyte solution and the second portion of the second electrolyte solution through the at least one bypass line.

7. 2. The electrolyzer system of claim 1, wherein at least a first portion of the first electrolyte solution from the first electrolyte outlet stream is recycled as at least a portion of the first electrolyte solution fed to the first half-cell of each of the one or more electrolyzer cells via the first electrolyte feed stream, and wherein the temperature control device comprises an electrolyte heat exchanger configured to heat or cool at least the first portion of the first electrolyte solution from the first electrolyte outlet stream.

8. 8. The electrolyzer system of claim 7, further comprising an electrolyte bypass line configured to bypass a second portion of the first electrolyte solution from the first electrolyte outlet stream without passing through the electrolyte heat exchanger.

9. 9. The electrolyzer system of claim 8, further comprising a control valve configured to adjust a ratio of a first flow rate of a first portion of the first electrolyte solution through the electrolyte heat exchanger and a second flow rate of a second portion of the first electrolyte solution through the electrolyte bypass line, the ratio selected to provide a defined temperature relative to the first inlet temperature of the first electrolyte feed stream.

10. 1. A method comprising: delivering a first electrolyte solution at a first inlet temperature via a first electrolyte feed stream to a first half-cell of each of the one or more electrolyzer cells, each first half-cell of the one or more electrolyzer cells comprising a first electrode; feeding a second electrolyte solution at a second inlet temperature via a second electrolyte feed stream to a second half-cell of each of the one or more electrolyzer cells, each second half-cell comprising a second electrode, the first electrode of each of the one or more electrolyzer cells being separated from the second electrode by a separator; applying an electric current between the first electrode and the second electrode of each of the one or more electrolyzer cells; controlling the temperature in the separator of at least one of the one or more electrolyzer cells; Including, Controlling the temperature in the separator of at least one of the one or more electrolyzer cells comprises: a current between the first electrode and the second electrode of at least one of the one or more electrolyzer cells; a voltage measured across the first and second electrodes of at least one of the one or more electrolyzer cells; and a first inlet temperature and a second inlet temperature of at least one of the one or more electrolyzer cells based on one or both of:

11. 11. The method of claim 10, wherein adjusting one or both of the first inlet temperature and the second inlet temperature of at least one of the one or more electrolyzer cells for the feedforward control is also based on at least one of an overall voltage measured across the one or more electrolyzer cells, a flow rate of the first electrolyte solution through the first half-cell of at least one of the one or more electrolyzer cells, and a flow rate of the second electrolyte solution through the second half-cell of at least one of the one or more electrolyzer cells.

12. 12. The method of claim 10 or claim 11, further comprising: recycling at least a first portion of the first electrolyte solution exiting a first half-cell of the one or more electrolyzer cells back to the first electrolyte feed stream; and recycling at least a first portion of the second electrolyte solution exiting a second half-cell of the one or more electrolyzer cells back to the second electrolyte feed stream, wherein one or both of controlling the first inlet temperature of the first electrolyte solution and controlling the second inlet temperature of the second electrolyte solution comprises heating or cooling one or both of the first portion of the first electrolyte solution and the first portion of the second electrolyte solution prior to recycling back to the first electrolyte feed stream and the second electrolyte feed stream.

13. 13. The method of claim 12, wherein one or both of adjusting the first inlet temperature and adjusting the second inlet temperature comprises bypassing heating or cooling by one or both of the second portion of the first electrolyte solution and the second portion of the second electrolyte solution.

14. 12. The method of claim 10 or claim 11, further comprising: recycling at least a first portion of the first electrolyte solution exiting a first half-cell of the one or more electrolyzer cells back to the first electrolyte feed stream; and recycling at least a first portion of the second electrolyte solution exiting a second half-cell of the one or more electrolyzer cells back to the second electrolyte feed stream, wherein one or both of adjusting the first inlet temperature and adjusting the second inlet temperature comprises cooling one or both of the first portion of the first electrolyte solution and the first portion of the second electrolyte solution and heating one or both of the second portion of the first electrolyte solution and the second portion of the second electrolyte solution prior to recycling back to the first electrolyte feed stream and the second electrolyte feed stream.

15. 14. The method of claim 13, wherein one or both of adjusting the first inlet temperature and adjusting the second inlet temperature comprises adjusting a ratio of a first flow rate of one or both of the first portion of the first electrolyte solution and the first portion of the second electrolyte solution to a second flow rate of one or both of the second portion of the first electrolyte solution and the second portion of the second electrolyte solution.

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