Water electrolysis system and control method thereof

Abstract

The system of the present disclosure utilizes a water electrolysis stack to decompose water into hydrogen and oxygen. Hydrogen is discharged from the negative electrode and stored in the hydrogen tank, and oxygen is discharged from the positive electrode and stored in the oxygen tank. The stored gas may be recycled into the electrolysis stack as needed. The sensing portion measures the hydrogen concentration and oxygen concentration in the exhaust fluid, and the controller compares these readings to safety limits. If the concentration is too high, the valve automatically adjusts to control the flow of the stored gas. Other components, such as injectors and pressure controls, assist in ensuring effective operation and preventing unsafe gas build-up.

Description

[0001] Cross-references to related applications

[0002] This application claims the benefit of Korean Patent Application No. 10-2024-0122533, filed with the Korean Intellectual Property Office on September 9, 2024, the entire contents of which are incorporated herein by reference. Technical Field

[0003] This disclosure relates to a water electrolysis system and its control method. Background Technology

[0004] Polymer electrolyte membrane (PEM) water electrolysis systems are devices configured to separate water into hydrogen and oxygen through an electrochemical reaction using externally supplied electricity. Due to their high hydrogen production rate, high hydrogen purity, and flexible operation, PEM water electrolysis systems are attracting significant attention as a next-generation means of ensuring clean hydrogen production. Furthermore, when the electricity used in the water electrolysis system is replaced by environmentally friendly renewable energy sources (solar, wind, etc.), hydrogen can be produced without polluting the environment, and excess electricity can be used to produce hydrogen, maximizing the utilization of renewable energy.

[0005] Generally, PEM water electrolysis is used in the form of stacks made by stacking and assembling cell units to achieve the required hydrogen production for PEM water electrolysis.

[0006] The membrane electrode assembly (MEA) is located at the innermost part of the unit cell in the water electrolyzer stack. The MEA includes a perfluorosulfonic acid ionomer-based electrolyte membrane capable of transporting hydrogen ions (protons), and a positive electrode (anode) and a negative electrode (cathode) respectively disposed on two opposite surfaces of the electrolyte membrane. In the following text, water electrolysis refers to polymer electrolyte membrane (PEM) water electrolysis.

[0007] Furthermore, the porous transport layer (PTL), gas diffusion layer (GDL), and gaskets can be stacked sequentially on the outer portions of the MEA where the positive and negative electrodes are located. Separators (or bipolar plates) can be attached to the outer sides of the PTL and GDL. The separator includes a flow path (flow field) through which reactants, coolant, and products generated by the reaction flow, or it can include structures that can incorporate alternative flow paths.

[0008] An electrochemical reaction of water electrolysis occurs in a membrane electrode assembly comprising a perfluorosulfonic acid-based ionomer electrolyte membrane, a positive electrode, and a negative electrode. Water supplied to the positive electrode is separated into oxygen, hydrogen ions (protons), and electrons. The hydrogen ions then move through the membrane to the negative electrode, which serves as a reduction electrode, while the electrons move to the negative electrode via an external circuit and supplied electricity. The hydrogen ions and electrons react together at the negative electrode to produce hydrogen gas. For the above reaction, Ir-based and Ru-based catalysts, such as IrO2 and RuO2, are typically used at the positive electrode, while Pt-based catalysts are primarily used at the negative electrode. Summary of the Invention

[0009] Meanwhile, when a PEM water electrolysis system is operating, oxygen and hydrogen are generated at the positive and negative electrodes, respectively. The mixture of these gases produced in this way may pose an explosion risk. Therefore, PEM water electrolysis systems essentially require hydrogen safety facilities. Related technologies have PEM water electrolysis systems equipped with control systems featuring hydrogen (oxygen) concentration sensors applied to both the positive and negative electrode separators and configured to automatically shut down the electrolysis system when the concentration exceeds a predetermined level. In this case, since the hydrogen (oxygen) concentration is measured at the separator, the actual hydrogen (oxygen) concentration in the water electrolysis reactor may be higher than the value measured at the separator. In other words, the possibility of an explosion caused by the gas mixture remaining in the water electrolysis reactor cannot be ignored.

[0010] Therefore, this disclosure is not only for realizing the function of automatically controlling and stopping the PEM water electrolysis system in the related art, but also for realizing the function of ensuring system safety by injecting pure oxygen (hydrogen) generated by the PEM water electrolysis system into the positive electrode (negative electrode) to remove the gas mixture remaining in the water electrolysis stack that has not been properly removed in the related art when the hydrogen concentration (oxygen concentration) reaches a dangerous concentration.

[0011] Embodiments of this disclosure provide a water electrolysis system, comprising: a water electrolysis reactor configured to generate oxygen and hydrogen from reacting water, discharging oxygen to a positive electrode and discharging hydrogen to a negative electrode; and an oxygen tank and a hydrogen tank connected to the water electrolysis reactor and configured to store oxygen and hydrogen discharged from the water electrolysis reactor, respectively, wherein the oxygen tank is connected to the water electrolysis reactor to supply the stored oxygen back to the water electrolysis reactor, and wherein the hydrogen tank is connected to the water electrolysis reactor to supply the stored hydrogen back to the water electrolysis reactor.

[0012] According to an embodiment, the oxygen tank can be configured to supply the stored oxygen to the water electrolysis reactor when the hydrogen concentration in the fluid discharged from the positive electrode is equal to or greater than a permissible hydrogen concentration as a preset concentration. In a suitable aspect, the preset hydrogen concentration can be suitably about 2%.

[0013] According to an embodiment, the hydrogen tank can be configured to supply the stored hydrogen to the water electrolysis reactor when the oxygen concentration in the fluid discharged from the negative electrode is equal to or greater than a preset allowable oxygen concentration. In a suitable aspect, the preset oxygen concentration can be suitably about 3%.

[0014] According to an embodiment, the water electrolysis system may include: a first sensing unit disposed at the rear end of the positive electrode of the water electrolysis reactor and configured to measure the hydrogen concentration in the fluid discharged from the positive electrode; and a second sensing unit disposed at the rear end of the negative electrode of the water electrolysis reactor and configured to measure the oxygen concentration in the fluid discharged from the negative electrode.

[0015] According to an embodiment, the water electrolysis system may include: a controller configured to control the supply of oxygen and hydrogen from an oxygen tank and a hydrogen tank to the water electrolysis reactor; a first valve configured to regulate the amount of oxygen discharged from the oxygen tank; and a second valve configured to regulate the amount of hydrogen discharged from the hydrogen tank, wherein the controller performs control to open or close the first valve and the second valve.

[0016] According to the embodiment, when the concentration value measured by the first sensing unit is equal to or greater than the permissible hydrogen concentration, the controller performs control to supply oxygen to the water electrolysis reactor, and / or when the concentration value measured by the second sensing unit is equal to or greater than the permissible oxygen concentration, the controller performs control to supply hydrogen to the water electrolysis reactor.

[0017] According to an embodiment, the water electrolysis system may include: a positive electrode separator connected to the water electrolysis reactor and an oxygen tank, configured to separate oxygen and water from the fluid discharged from the positive electrode; and a negative electrode separator connected to the water electrolysis reactor and a hydrogen tank, configured to separate hydrogen and water from the fluid discharged from the negative electrode.

[0018] According to the implementation method, the first sensing unit can be disposed at the connection between the positive electrode separator and the water electrolysis reactor, and the second sensing unit can be disposed at the connection between the negative electrode separator and the water electrolysis reactor.

[0019] According to an embodiment, the water electrolysis system may include: a third valve configured to be opened or closed to regulate the movement of fluid discharged from the water electrolysis reactor to the positive electrode separator; and a fourth valve configured to be opened or closed to regulate the movement of fluid discharged from the water electrolysis reactor to the negative electrode separator.

[0020] According to the implementation method, when the concentration of hydrogen or oxygen in the fluid discharged from the water electrolysis reactor is equal to or greater than the permissible hydrogen concentration or permissible oxygen concentration, the controller can perform control to close the third valve or the fourth valve.

[0021] According to an embodiment, the water electrolysis system may include a deionization tank connected to the water electrolysis reactor and configured to supply stored reaction water to the water electrolysis reactor.

[0022] According to an embodiment, the water electrolysis system may include an ejector disposed at the connection between the deionization tank and the water electrolysis reactor, wherein an oxygen tank is connected to the ejector to supply oxygen to the water electrolysis reactor using the pressure difference of the reacting water passing through the ejector.

[0023] According to an embodiment, the injector may include: an inlet where reactive water is introduced; a confluence where oxygen is drawn in; and an outlet where the fluid obtained by mixing reactive water and oxygen is discharged.

[0024] According to the embodiment, the cross-sectional area of ​​the inlet can be reduced along the flow direction of the reaction water, and the confluence can be configured to surround one end of the inlet based on the flow direction.

[0025] According to an implementation, the water electrolysis system may include: a compressor configured to maintain pressure such that the pressure in the water electrolysis reactor is greater than the normal pressure, and the pressure in the hydrogen tank is greater than the pressure in the water electrolysis reactor.

[0026] Another embodiment of this disclosure provides a method for controlling a water electrolysis system, the method comprising: a concentration measurement step, wherein a first sensing unit and a second sensing unit measure the hydrogen concentration and oxygen concentration in a fluid discharged from a water electrolysis reactor; and a gas supply step, wherein a controller supplies oxygen stored in an oxygen tank or hydrogen stored in a hydrogen tank to the water electrolysis reactor.

[0027] According to an implementation, the method may include: a safety judgment step, in which the controller determines whether the hydrogen concentration value measured in the concentration measurement step is equal to or greater than a preset permissible hydrogen concentration, and / or whether the oxygen concentration value measured in the concentration measurement step is equal to or greater than a preset permissible oxygen concentration.

[0028] According to the implementation, the gas supply step may include an oxygen supply step that supplies oxygen to the water electrolysis reactor, and the oxygen supply step may be performed when the measured hydrogen concentration value is equal to or greater than the permissible hydrogen concentration.

[0029] According to the implementation, the gas supply step may include a hydrogen supply step of supplying hydrogen to the water electrolysis reactor, and the hydrogen supply step may be performed when the measured oxygen concentration value is equal to or greater than the allowable oxygen concentration.

[0030] According to an implementation, the method may include a fluid cut-off step, wherein when the measured concentration value is equal to or greater than the permissible hydrogen concentration, or when the measured concentration value is equal to or greater than the permissible oxygen concentration, the controller blocks the fluid discharged from the water electrolysis reactor.

[0031] As discussed, the method and system appropriately include the use of a controller or processor. Attached Figure Description

[0032] Figure 1 This is a schematic diagram illustrating a water electrolysis system in the prior art.

[0033] Figure 2 This is a schematic diagram illustrating a water electrolysis system according to some embodiments of the present disclosure.

[0034] Figure 3 This is a flowchart illustrating a method for controlling a water electrolysis system according to some embodiments of the present disclosure.

[0035] Figure 4 This is a flowchart illustrating a method for controlling a water electrolysis system according to some embodiments of the present disclosure.

[0036] Figure 5 This is a flowchart illustrating a method for controlling a water electrolysis system according to some embodiments of the present disclosure. Detailed Implementation

[0037] In the following description, some exemplary embodiments of the present disclosure will be described in detail with reference to the illustrative accompanying drawings. When assigning reference numerals to the constituent elements of the various drawings, it should be noted that, where possible, the same constituent elements will be represented by the same reference numerals even if they are shown in different drawings. Furthermore, in the following description of exemplary embodiments of the present disclosure, detailed descriptions will be omitted where it is determined that a detailed description of a well-known configuration or function involved herein would obscure the subject matter of the exemplary embodiments of the present disclosure.

[0038] The terms first, second, A, B, (a), and (b) are used to describe the constituent elements of embodiments of this disclosure. These terms are used only to distinguish one constituent element from another, and the nature, order, or sequence of the constituent elements is not limited by these terms. Furthermore, unless otherwise defined, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure pertains. Terms such as those defined in common dictionaries should be interpreted as having a meaning consistent with the relevant technical context and should not be construed as having an ideal or overly formal meaning unless explicitly defined in this application.

[0039] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit this disclosure. Unless the context clearly indicates otherwise, the singular forms (“a,” “an,” and “the”) used herein also include the plural forms. These terms are intended only to distinguish one component from another, and they do not limit the nature, order, or sequence of the constituent components. It should be further understood that when the terms “comprise” and / or “include” are used in this specification, the presence of the stated feature, integer, step, operation, element, and / or component is specified, but the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof is not excluded. As used herein, the term “and / or” includes any and all combinations of one or more of the associated listed items. Throughout this specification, unless explicitly stated otherwise, the word “comprise” and variations such as “comprises” or “comprising” are to be understood as implying inclusion of the stated elements, but not excluding any other elements. Furthermore, the terms “unit,” “device,” “section,” and “module” described in the specification refer to a unit for performing at least one function and operation, and can be implemented by hardware components or software components and combinations thereof.

[0040] While exemplary embodiments are described as using multiple units to perform exemplary processes, it should be understood that exemplary processes can also be performed by one or more modules. Furthermore, it should be understood that the term controller / control unit refers to a hardware device including a storage unit and a processor, specifically programmed to perform the processes described herein. The storage unit is configured to store modules, and the processor is specifically configured to execute said modules to perform one or more processes further described below.

[0041] Furthermore, the control logic of this disclosure can be embodied in a non-transient computer-readable medium containing executable program instructions that are executed by a processor, controller, etc. Examples of computer-readable media include, but are not limited to, ROM, RAM, optical disc (CD)-ROM, magnetic tape, floppy disk, flash drive, smart card, and optical data storage device. The computer-readable medium can also be distributed across a network-coupled computer system, enabling the computer-readable medium to be stored and executed in a distributed manner, for example, via a telematics server or a controller area network (CAN).

[0042] Unless otherwise specified or obvious from the context, as used herein, the term “about” is understood to mean within the normal tolerance range in the field, such as within 2 standard deviations of the mean. “About” can be understood as within 10%, 9%, 8%, 7%, 6%, 5%, 4%, 3%, 2%, 1%, 0.5%, 0.1%, 0.05%, or 0.01% of the specified value. All numerical values ​​provided herein are modified by the term “about” unless the context clearly specifies otherwise.

[0043] As used in this article, the term "water electrolyzer" refers to the arrangement of electrodes, membranes, and related components that work together to perform water electrolysis to produce hydrogen and oxygen.

[0044] The term "reaction water" as used in this article refers to water introduced into the electrolytic reactor as a feedstock for the production of hydrogen and oxygen.

[0045] The term "positive electrode separator" as used in this article refers to a device or component configured to separate oxygen from water in a fluid discharged from the positive electrode.

[0046] The term "negative electrode separator" as used in this article refers to a device or component configured to separate oxygen from water in a fluid discharged from the negative electrode.

[0047] Furthermore, the term "rear end" disclosed in this disclosure refers to the relatively downstream side based on the direction of fluid flow.

[0048] In the following text, reference will be made to Figures 1 to 4 The embodiments of this disclosure are described in detail.

[0049] Figure 1 This is a schematic diagram showing a water electrolysis system 1' in the related art.

[0050] refer to Figure 1 In the existing water electrolysis system 1', reaction water is supplied from deionization tank 40' to water electrolysis reactor 10'. Water electrolysis reactor 10' uses an electrochemical reaction to generate oxygen and hydrogen from the reaction water. In this case, oxygen is produced by the positive electrode 12' and hydrogen by the negative electrode 13', and the oxygen and hydrogen can be discharged through different pathways. However, in this case, within water electrolysis reactor 10', due to various reasons such as electrolyte membrane rupture, operating pressure, and current, oxygen and hydrogen may mix; this phenomenon is known as cross-over.

[0051] In existing systems, sensors can be installed on both the positive and negative electrode separators to measure the oxygen or hydrogen concentration in the fluid discharged from the water electrolysis reactor 10'. In this case, since the oxygen or hydrogen concentration is measured in the separators, the value of the oxygen or hydrogen concentration in the water electrolysis reactor 10' may be greater than the value measured on each separator.

[0052] Figure 2 This is a schematic diagram showing the water electrolysis system 1 of this disclosure.

[0053] refer to Figure 2 The water electrolysis system 1 disclosed herein may include a water electrolysis reactor 10, an oxygen tank (O2 tank) 26, and a hydrogen tank (H2 tank) 38.

[0054] The water electrolysis reactor 10 can receive reactive water and generate oxygen and hydrogen from it. In this case, oxygen can be discharged through the positive electrode (anode) 12, and hydrogen can be discharged through the negative electrode (cathode) 13. However, as mentioned above, cross-permeation may occur for various reasons. Therefore, hydrogen may be discharged through the positive electrode 12 together with oxygen, and oxygen may be discharged through the negative electrode 13 together with hydrogen. In this case, water (H2O) (which is reactive water) may also be discharged.

[0055] Oxygen tank 26 and hydrogen tank 38 can be configured to store oxygen and hydrogen discharged from water electrolyzer 10, respectively. In this case, oxygen tank 26 and hydrogen tank 38 can be connected to water electrolyzer 10 to store oxygen and hydrogen, respectively.

[0056] For example, oxygen tank 26 can be connected to the positive electrode 12 of water electrolysis reactor 10 via a pipeline, and hydrogen tank 38 can be connected to the negative electrode 13 of water electrolysis reactor 10 via a pipeline. In this case, separators, valves, etc., which will be described below, can be located in the pipeline.

[0057] Furthermore, oxygen tank 26 can reuse the stored oxygen. For example, oxygen tank 26 can supply the stored oxygen back to water electrolyzer 10, and oxygen tank 26 can be connected to water electrolyzer 10 via a pipeline. In this case, oxygen tank 26 and water electrolyzer 10 can be connected via a pipeline different from the pipeline from which fluid is discharged from water electrolyzer 10.

[0058] Similarly, the hydrogen tank 38 can reuse the stored hydrogen. For example, the hydrogen tank 38 can supply the stored hydrogen back to the water electrolyzer 10, and the hydrogen tank 38 can be connected to the water electrolyzer 10 via a pipeline. In this case, the hydrogen tank 38 and the water electrolyzer 10 can be connected via a pipeline different from the pipeline from which the fluid is discharged from the water electrolyzer 10.

[0059] The water electrolysis system 1 may include a positive electrode separator (anode separator) 20, a deionizer (deionizer) 40 and a negative electrode separator (cathode separator) 30.

[0060] The positive electrode separator 20 can be configured to separate oxygen and water. The positive electrode separator 20 can separate oxygen and water from the fluid discharged from the positive electrode 12. The positive electrode separator 20 can be connected to the water electrolysis reactor 10 and the oxygen tank 26.

[0061] Specifically, the positive electrode separator 20 can be connected to the positive electrode 12 of the water electrolysis reactor 10 via a first oxygen pipeline 200. Furthermore, the rear end of the positive electrode separator 20 can be connected to the oxygen tank 26 via a second oxygen pipeline 210. Therefore, oxygen separated from water by the positive electrode separator 20 can move along the second oxygen pipeline 210 to the oxygen tank 26.

[0062] The positive electrode drain line 240 can be connected to the positive electrode separator 20, and the separated water can be recycled back to the deionization tank 40 or discharged to the outside through the positive electrode drain line 240. In this case, the positive electrode drain line 240 can be connected to both the positive electrode separator 20 and the deionization tank 40, and the positive electrode drain line 240 can branch off from the middle section between the positive electrode separator 20 and the deionization tank 40 and point to the outside.

[0063] The deionization tank 40 can be configured to supply the stored reaction water to the water electrolysis reactor 10. The deionization tank 40 can be connected to the water electrolysis reactor 10 via the reaction water supply line 230. A pump 41 can be provided on the reaction water supply line 230, and the reaction water can be moved to the water electrolysis reactor 10 by the pressure generated by the pump 41.

[0064] The negative electrode separator 30 can be configured to separate hydrogen and water. The negative electrode separator 30 can separate hydrogen and water from the fluid discharged from the negative electrode 13. The negative electrode separator 30 can be connected to the water electrolysis reactor 10 and the hydrogen tank 38.

[0065] Specifically, the negative electrode separator 30 can be connected to the negative electrode 13 of the water electrolyzer 10 via a first hydrogen pipeline 300. Furthermore, the rear end of the negative electrode separator 30 can be connected to a hydrogen tank 38 via a second hydrogen pipeline 310. Therefore, the hydrogen separated from the water by the negative electrode separator 30 can move along the second hydrogen pipeline 310 to the hydrogen tank 38.

[0066] The negative electrode drain pipe 330 can be connected to the negative electrode separator 30, and the separated water can be discharged to the outside through the negative electrode drain pipe 330.

[0067] Oxygen tank 26 and hydrogen tank 38 can supply the stored oxygen or hydrogen back to the water electrolyzer 10. In this case, specific situations may arise.

[0068] For example, oxygen tank 26 can be configured to supply stored oxygen to water electrolysis reactor 10 when the hydrogen concentration in the fluid discharged from positive electrode 12 is equal to or greater than the permissible hydrogen concentration (which is a preset concentration). In this case, the fluid discharged from positive electrode 12 can be a fluid in which oxygen, hydrogen and water are mixed.

[0069] Similarly, the hydrogen tank 38 can be configured to supply the stored hydrogen to the water electrolyzer 10 when the oxygen concentration in the fluid discharged from the negative electrode 13 is equal to or greater than the permissible oxygen concentration (which is a preset concentration).

[0070] The permissible hydrogen and oxygen concentrations can be used to ensure the safety of the water electrolysis system 1. For example, in the case where pure oxygen and hydrogen are mixed through cross-permeation, the risk of explosion caused by the chemical reaction between the two gases increases. The explosion risk varies depending on the ratio of oxygen to hydrogen. If the concentrations of oxygen and hydrogen exceed the concentrations required to ensure safety, it is necessary to shut down the water electrolysis system 1. For example, if the hydrogen content in the fluid discharged to the positive electrode 12 is between 4% and 94%, the hydrogen content may be within the explosive range. International standards related to water electrolysis products, such as ISO 22734, require that the safety control system shut down the water electrolysis system when the concentration exceeds 50% of the lower explosive limit (4%) and upper explosive limit (94%). That is, the water electrolysis system 1 can be shut down when the hydrogen content in the fluid discharged from the positive electrode 12 reaches 2% or the oxygen content in the fluid discharged from the positive electrode 12 reaches 3%. However, the values ​​are not limited to the above values, as they can vary depending on the system's environment and application.

[0071] Oxygen tank 26 and hydrogen tank 38 can be connected to water electrolyzer 10 via pipelines to supply the stored oxygen and hydrogen to water electrolyzer 10. For example, oxygen tank 26 can be connected to water electrolyzer 10 via oxygen resupply pipeline 220, and hydrogen tank 38 can be connected to water electrolyzer 10 via hydrogen resupply pipeline 320.

[0072] The water electrolysis system 1 disclosed herein may include a first sensing unit 21 and a second sensing unit 31, configured to measure the concentration of oxygen or hydrogen in a fluid discharged from the water electrolysis reactor 10.

[0073] The first sensing unit 21 can be disposed at the rear end of the positive electrode 12 of the water electrolysis reactor 10 and configured to measure the hydrogen concentration in the fluid discharged from the positive electrode 12. For example, the first sensing unit 21 can be disposed at the connection between the positive electrode separator 20 and the water electrolysis reactor 10. More specifically, the first sensing unit 21 can be disposed in the first oxygen line 200. The position of the first sensing unit 21 can be adjusted appropriately. The first sensing unit 21 can be disposed close to the positive electrode 12. Alternatively, the first sensing unit 21 can be located on the positive electrode 12. As described above, the position of the first sensing unit 21 can be changed to a position suitable for measuring the hydrogen concentration in the fluid discharged from the positive electrode 12.

[0074] The second sensing unit 31 can be disposed at the rear end of the negative electrode 13 of the water electrolysis reactor 10 and configured to measure the oxygen concentration in the fluid discharged from the negative electrode 13. For example, the second sensing unit 31 can be disposed at the connection between the negative electrode separator 30 and the water electrolysis reactor 10. More specifically, the second sensing unit 31 can be disposed in the first hydrogen pipeline 300. The position of the second sensing unit 31 can be adjusted appropriately. The second sensing unit 31 can be disposed close to the negative electrode 13. Alternatively, the second sensing unit 31 can be located on the negative electrode 13. As described above, the position of the second sensing unit 31 can be changed to a position suitable for measuring the oxygen concentration in the fluid discharged from the negative electrode 13.

[0075] The water electrolysis system 1 may include a first valve 27, a second valve 39, and a controller 60.

[0076] The first valve 27 can regulate the amount of oxygen discharged from the oxygen tank 26. For example, the first valve 27 can be located in the oxygen resupply line 220. The first valve 27 can be opened or closed to regulate the amount of oxygen moving from the oxygen tank 26 to the water electrolysis reactor 10.

[0077] The second valve 39 can regulate the amount of hydrogen discharged from the hydrogen tank 38. For example, the second valve 39 can be installed in the hydrogen resupply line 320. The second valve 39 can be opened or closed to regulate the amount of hydrogen moving from the hydrogen tank 38 to the water electrolyzer 10.

[0078] The controller 60 can control the supply of oxygen and hydrogen from oxygen tank 26 and hydrogen tank 38 to the water electrolyzer 10. For example, the controller 60 can perform control to turn on or off the first valve 27 and the second valve 39. The controller 60 can determine whether to supply oxygen or hydrogen to the water electrolyzer 10 based on the oxygen or hydrogen concentration in the fluid discharged into the water electrolyzer 10. Specifically, if the concentration value measured by the first sensing unit 21 or the second sensing unit 31 is equal to or greater than the permissible hydrogen concentration or permissible oxygen concentration, the controller 60 can perform control to supply oxygen or hydrogen to the water electrolyzer 10. The first sensing unit 21 and the second sensing unit 31 can be connected to the controller 60 and send or receive electrical signals from the controller 60. Information about the hydrogen and oxygen concentrations measured by the first sensing unit 21 and the second sensing unit 31 can be transmitted to the controller 60.

[0079] The water electrolysis system 1 may include a third valve 22 and a fourth valve 32.

[0080] The third valve 22 can be opened or closed to regulate the movement of fluid discharged from the water electrolyzer 10 to the positive electrode separator 20. For example, the third valve 22 can be closed to block the fluid discharged from the positive electrode 12 of the water electrolyzer 10.

[0081] The fourth valve 32 can be opened or closed to regulate the movement of fluid discharged from the water electrolyzer 10 to the negative electrode separator 30. For example, the fourth valve 32 can be closed to block the fluid discharged from the negative electrode 13 of the water electrolyzer 10.

[0082] The controller 60 can perform control to open or close the third valve 22 and the fourth valve 32. For example, if the hydrogen or oxygen concentration in the fluid discharged from the water electrolysis reactor 10 is equal to or greater than the permissible hydrogen or oxygen concentration, the controller 60 can perform control to close the third valve 22 or the fourth valve 32. For example, if the oxygen concentration in the fluid discharged from the negative electrode 13 is equal to or greater than the permissible oxygen concentration, the water electrolysis system 1 may face an explosion risk. In this case, the controller 60 can close the fourth valve 32 and block the pipeline to prevent the fluid discharged from the negative electrode 13 from flowing into the negative electrode separator 30 or the hydrogen tank 38.

[0083] The positions of the third valve 22 and the fourth valve 32 can be adjusted appropriately. For example, the third valve 22 can be located in the first oxygen line 200, and the fourth valve 32 can be located in the first hydrogen line 300. However, this configuration does not preclude the possibility that the third valve 22 and the fourth valve 32 are located in the second oxygen line 210 and the second hydrogen line 310, respectively. The positions of the third valve 22 and the fourth valve 32 can be changed within the scope required to achieve the objectives of this disclosure.

[0084] The water electrolysis system 1 may include an injector 50.

[0085] The ejector 50 can be located at the connection between the deionizer 40 and the water electrolysis reactor 10. For example, the ejector 50 can be located in the reaction water supply line 230.

[0086] Reaction water and oxygen can pass through ejector 50 simultaneously. For example, oxygen tank 26 can be connected to ejector 50 to supply oxygen to water electrolysis reactor 10 using the pressure difference of reaction water passing through ejector 50.

[0087] Specifically, the injector 50 may include an inlet 51, a manifold 52, and an outlet 53. The inlet 51 may be a component for introducing reactive water. The manifold 52 may be a component for collecting oxygen therein. The outlet 53 may be a component for discharging the fluid obtained by mixing reactive water and oxygen.

[0088] Specifically, the cross-sectional area of ​​the inlet 51 can be reduced along the flow direction of the reactant water. For example, the inlet 51 can be configured to resemble a nozzle. The manifold 52 can be connected to the oxygen tank 26 via the oxygen resupply line 220. The manifold 52 can be configured to surround one end of the inlet 51 with respect to the flow direction. The reactant water can be introduced into the inlet 51 of the ejector 50 by the pressure generated by the pump 41. Therefore, when the reactant water flows through the inlet 51, the pressure of the reactant water decreases, allowing oxygen to be introduced into the ejector 50 through the manifold 52. The reactant water and oxygen mixed in the ejector 50 can be discharged through the outlet 53 and supplied to the electrolytic reactor. In other words, by utilizing the pressure generated by the existing pump 41 and adding the configuration of the ejector 50, oxygen can be resupplyed to the water electrolytic reactor 10 without a separate power source.

[0089] The water electrolysis system 1 may include a compressor 37.

[0090] Compressor 37 can maintain high pressure in hydrogen tank 38. For example, compressor 37 can maintain the pressure in hydrogen tank 38 such that the pressure inside hydrogen tank 38 is greater than the pressure inside water electrolyzer 10. In this case, the pressure in water electrolyzer 10 may be greater than the normal pressure.

[0091] The compressor 37 can be located upstream of the hydrogen tank 38. For example, the compressor 37 can be located in the second hydrogen line 310. However, this configuration does not preclude the possibility that the compressor 37 is located in the first hydrogen line 300.

[0092] Since the pressure in hydrogen tank 38 is maintained at a higher level than that in water electrolyzer 10, the stored hydrogen can be resupplyed from hydrogen tank 38 to water electrolyzer 10 simply by adjusting the second valve 39, without the need for separate additional power.

[0093] A third sensing unit 23 configured to measure hydrogen concentration can be installed on the positive electrode separator 20, and a fourth sensing unit 33 configured to measure oxygen concentration can be installed on the negative electrode separator 30.

[0094] A fifth sensor 25 configured to measure hydrogen concentration and a first demister 24 configured to remove moisture from the fluid can be disposed between the positive electrode separator 20 and the oxygen tank 26. For example, the fifth sensor 25 and the demister can be disposed in the second oxygen line 210.

[0095] A sixth sensing unit 36 ​​configured to measure oxygen concentration, a second demister 35, and a deoxygenator 34 configured to remove oxygen from the fluid can be disposed between the negative electrode separator 30 and the hydrogen tank 38. For example, the sixth sensing unit 36, the second demister 35, and the deoxygenator 34 can be disposed in the second hydrogen pipeline 310.

[0096] However, since the positions of the sensors, demisters, deaerators, etc. mentioned above can be appropriately changed, the above configuration does not exclude the possibility of the sensors, demisters, deaerators, etc. being placed in other positions.

[0097] Figures 3 to 5 This is a flowchart illustrating a method for controlling the water electrolysis system 1 of this disclosure. Figure 4 and Figure 5 It is shown Figure 3 A view showing that the order of some steps in the method for controlling the water electrolysis system 1 has been changed.

[0098] refer to Figures 3 to 5 The method for controlling the water electrolysis system 1 disclosed herein may include a concentration measurement step S100, a safety judgment step S200, a fluid cut-off step, and a gas supply step S400.

[0099] The concentration measurement step S100 can be a step of measuring the hydrogen and oxygen concentrations in the fluid discharged from the water electrolysis reactor 10 using the first sensing unit 21 and the second sensing unit 31. For example, the first sensing unit 21 can measure the hydrogen concentration in the fluid discharged from the positive electrode 12, and the second sensing unit 31 can measure the oxygen concentration in the fluid discharged from the negative electrode 13. The concentration measurement step S100 can be performed repeatedly and continuously. For example, in the safety judgment step S200 described below, if the measured concentration value does not meet the requirement of being equal to or greater than the permissible oxygen concentration or permissible hydrogen concentration, the concentration measurement step S100 can be performed again continuously. However, this method does not exclude the possibility of performing the concentration measurement step S100 again even if the measured concentration value is equal to or greater than the permissible oxygen concentration or permissible hydrogen concentration.

[0100] The safety judgment step S200 can be a step in which the controller 60 determines whether the concentration value measured in the concentration measurement step S100 is equal to or greater than the allowable hydrogen concentration or the allowable oxygen concentration. In this case, it is not limited to whether the hydrogen concentration or the oxygen concentration is judged first. Therefore, both the hydrogen concentration and the oxygen concentration can be judged simultaneously.

[0101] The fluid cutoff step S300 can be a step in which the controller 60 blocks the flow of fluid discharged from the water electrolysis reactor 10 when the measured concentration value is equal to or greater than the permissible hydrogen concentration or permissible oxygen concentration. For example, if the measured hydrogen concentration in the fluid discharged from the positive electrode 12 is equal to or greater than the permissible hydrogen concentration, the controller 60 can close the third valve 22. The same process can be performed if the oxygen concentration in the fluid discharged from the negative electrode 13 is equal to or greater than the permissible oxygen concentration.

[0102] The gas supply step S400 may be a step of supplying oxygen stored in oxygen tank 26 or hydrogen stored in hydrogen tank 38 to the water electrolyzer 10 via controller 60. The gas supply step S400 may include an oxygen supply step S410 and a hydrogen supply step S420. Oxygen supply step S410 may be a step of supplying oxygen to the water electrolyzer 10, and hydrogen supply step S420 may be a step of supplying hydrogen to the water electrolyzer 10. For example, controller 60 may supply stored oxygen to the water electrolyzer 10 by opening a first valve 27 located at the rear end of oxygen tank 26.

[0103] The order of the gas supply step S400 and the fluid cut-off step S300 can be changed, or the gas supply step S400 and the fluid cut-off step S300 can be performed simultaneously.

[0104] According to embodiments of this disclosure, when oxygen and hydrogen are mixed in the system, the oxygen or hydrogen produced by operating the water electrolysis system is reused to prevent the gas mixture from reaching dangerous concentrations.

[0105] According to embodiments of this disclosure, oxygen or hydrogen produced by operating a water electrolysis system can be reused without additional power.

[0106] According to embodiments of this disclosure, the system of this disclosure can be used by simply adding simple components (e.g., oxygen tanks, injectors, and valves) to a system of the related art.

[0107] The above description is merely illustrative of the technical spirit of this disclosure. Those skilled in the art will understand that various changes and modifications can be made without departing from the essential characteristics of this disclosure.

[0108] Therefore, the embodiments disclosed herein are for illustrative purposes only and are not intended to limit the technical concept of this disclosure. The scope of the technical spirit of this disclosure is not limited thereto. The scope of protection of this disclosure should be interpreted based on the following claims, and all technical spirit within the equivalent scope of the claims should be interpreted as falling within the scope of this disclosure.

Claims

1. A water electrolysis system comprising: a water electrolysis stack configured to generate oxygen and hydrogen from reaction water, to discharge the oxygen to a positive electrode, and to discharge the hydrogen to a negative electrode; and an oxygen tank and a hydrogen tank connected to the water electrolysis stack and configured to store the oxygen and the hydrogen discharged from the water electrolysis stack, respectively, wherein the oxygen tank is connected to the water electrolysis stack to supply the stored oxygen back to the water electrolysis stack, and wherein the hydrogen tank is connected to the water electrolysis stack to supply the stored hydrogen back to the water electrolysis stack. the oxygen tank is configured to supply the stored oxygen to the water electrolysis stack when a hydrogen concentration in a fluid discharged from the positive electrode is equal to or greater than an allowable hydrogen concentration, wherein the allowable hydrogen concentration is a preset hydrogen concentration.

2. The water electrolysis system of claim 1, wherein, the hydrogen tank is configured to supply the stored hydrogen to the water electrolysis stack when an oxygen concentration in a fluid discharged from the negative electrode is equal to or greater than an allowable oxygen concentration, wherein the allowable oxygen concentration is a preset oxygen concentration.

3. The water electrolysis system of claim 2, wherein, 4.The water electrolysis system of claim 3, comprising: a first sensing portion provided at a rear end of a positive electrode of the water electrolysis stack and configured to measure a hydrogen concentration in a fluid discharged from the positive electrode; and a second sensing portion provided at a rear end of a negative electrode of the water electrolysis stack and configured to measure an oxygen concentration in a fluid discharged from the negative electrode. 5.The water electrolysis system of claim 4, comprising: a controller configured to control supply of oxygen and hydrogen from the oxygen tank and the hydrogen tank to the water electrolysis stack; a first valve configured to adjust an amount of oxygen discharged from the oxygen tank; and a second valve configured to adjust an amount of hydrogen discharged from the hydrogen tank, wherein the controller performs control to open or close the first valve and the second valve. the controller performs control to supply oxygen to the water electrolysis stack when a concentration value measured by the first sensing portion is equal to or greater than the allowable hydrogen concentration, and / or the controller performs control to supply hydrogen to the water electrolysis stack when a concentration value measured by the second sensing portion is equal to or greater than the allowable oxygen concentration. the preset hydrogen concentration is about 2%, and wherein the preset oxygen concentration is about 3%. 8.The water electrolysis system of claim 5, comprising:

6. The water electrolysis system of claim 5, wherein, a positive electrode separator connected to the water electrolysis stack and the oxygen tank and configured to separate oxygen and water from a fluid discharged from the positive electrode; and 7. The water electrolysis system of claim 3, wherein, a negative electrode separator connected to the water electrolysis stack and the hydrogen tank and configured to separate hydrogen and water from a fluid discharged from the negative electrode. the first sensing portion is provided at a connection of the positive electrode separator and the water electrolysis stack, and the second sensing portion is provided at a connection of the negative electrode separator and the water electrolysis stack. 10.The water electrolysis system of claim 8, comprising: a third valve configured to be opened or closed to adjust movement of a fluid discharged from the water electrolysis stack to the positive electrode separator; and a fourth valve configured to be opened or closed to adjust movement of a fluid discharged from the water electrolysis stack to the negative electrode separator.

9. The water electrolysis system of claim 8, wherein, ​ ​ ​ ​ ​ 11. The water electrolysis system of claim 10, wherein, When the hydrogen concentration in the fluid discharged from the water electrolysis stack is equal to or greater than the allowable hydrogen concentration, the controller performs control to close the third valve, and / or when the oxygen concentration in the fluid discharged from the water electrolysis stack is equal to or greater than the allowable oxygen concentration, the controller performs control to close the fourth valve.

12. The water electrolysis system according to claim 1, comprising: a deionization tank connected to the water electrolysis stack and configured to supply the stored reaction water to the water electrolysis stack.

13. The water electrolysis system according to claim 12, comprising: an ejector provided at a connection between the deionization tank and the water electrolysis stack, wherein the oxygen tank is connected to the ejector to supply oxygen gas to the water electrolysis stack.

14. The water electrolysis system of claim 13, wherein, the ejector includes: an introduction portion into which reaction water is introduced; a converging portion into which oxygen gas is converged; and an exhaust portion from which a fluid obtained by mixing the reaction water and the oxygen gas is exhausted.

15. The water electrolysis system of claim 14, wherein, a cross-sectional area of the introduction portion decreases along a flow direction in which the reaction water flows, and the converging portion is configured to surround one end of the introduction portion with reference to the flow direction.

16. The water electrolysis system according to claim 12, comprising: a compressor configured to maintain a pressure such that the pressure in the water electrolysis stack is greater than a normal pressure and the pressure in the hydrogen tank is greater than the pressure in the water electrolysis stack.

17. A method of controlling a water electrolysis system, the method comprising the steps of: a concentration measurement step in which a hydrogen concentration and an oxygen concentration in a fluid discharged from a water electrolysis stack are measured by first and second sensing portions; and a gas supply step in which oxygen gas stored in an oxygen tank or hydrogen gas stored in a hydrogen tank is supplied to the water electrolysis stack by a controller.

18. The method according to claim 17, comprising the steps of: a safety judgment step in which the controller judges whether a measured hydrogen concentration value in the concentration measurement step is equal to or greater than a preset allowable hydrogen concentration, and / or whether a measured oxygen concentration value in the concentration measurement step is equal to or greater than a preset allowable oxygen concentration.

19. The method of claim 18, wherein, the gas supply step includes an oxygen gas supply step of supplying oxygen gas to the water electrolysis stack, wherein the oxygen gas supply step is performed when the measured hydrogen concentration value is equal to or greater than the allowable hydrogen concentration, wherein the gas supply step includes a hydrogen gas supply step of supplying hydrogen gas to the water electrolysis stack, and wherein the hydrogen gas supply step is performed when the measured oxygen concentration value is equal to or greater than the allowable oxygen concentration.

20. The method according to claim 18, comprising the steps of: a fluid cutoff step in which the controller blocks a fluid discharged from the water electrolysis stack when the measured hydrogen concentration value is equal to or greater than the allowable hydrogen concentration, or when the measured oxygen concentration value is equal to or greater than the allowable oxygen concentration.

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