WATER ELECTROLYSIS SYSTEM AND METHOD OF CONTROLLING THE SAME

Description

CROSS-REFERENCE TO RELATED APPLICATION

This application claims under 35 U.S.C. § 119(a) the benefit of Korean Patent Application No. 10-2024-0122533 filed in the Korean Intellectual Property Office on Sep. 9, 2024, the entire contents of which are incorporated herein by reference.

BACKGROUND

Technical Field

The present disclosure relates to a water electrolysis system and a method of controlling the same.

Background

A polymer electrolyte membrane (PEM) water electrolysis system refers to a device configured to separate water into hydrogen and oxygen using an electrochemical reaction by supplying electric power from the outside. The PEM water electrolysis system is in the limelight as a next-generation means capable of ensuring clean hydrogen because the PEM water electrolysis system has features such as a high hydrogen generation speed, a high hydrogen purity, and flexible drivability. Moreover, when electric power applied to the water electrolysis system is replaced with environmentally-friendly renewable energy (solar energy, wind power energy, and the like), hydrogen may be produced without environmental pollution, and hydrogen may be produced by using surplus electric power to maximize the utilization of the renewable energy.

In general, the PEM water electrolysis is used in the form of a stack made by stacking and assembling unit cells to achieve the amount of production of hydrogen required for PEM water electrolysis.

A membrane-electrode assembly (MEA) is positioned at an innermost side of a unit cell of a water electrolysis stack. The membrane-electrode assembly includes a perfluorinated sulfonic acid ionomer-based electrolyte membrane capable of moving hydrogen ions (protons), and a positive electrode (anode) and a negative electrode (cathode) respectively disposed on two opposite surfaces of the electrolyte membrane. Hereinafter, the water electrolysis means polymer electrolyte membrane (PEM) water electrolysis.

In addition, a porous transport layer (PTL), a gas diffusion layer (GDL), and a gasket may be stacked on each of outer portions of the MEA on which the positive electrode and the negative electrode are positioned. A separator (or bipolar plate) may be bonded to an outer side of the PTL and the GDL. The separator includes flow paths (flow fields) through which a reactant, a coolant, and a product produced by a reaction flow, or it may include a structure that may be substituted for the flow paths.

An electrochemical reaction of the water electrolysis occurs in the membrane-electrode assembly including a perfluorosulfonic acid-based ionomer electrolyte membrane, the positive electrode, and the negative electrode. Water supplied to the positive electrode is separated into oxygen, hydrogen ions (protons), and electrons. Then, the hydrogen ions move to the negative electrode, which is a reduction electrode, through the membrane, while the electrons move to the negative electrode through an external circuit and supplied electric power. The hydrogen ions and the electrons react together in the negative electrode and produce hydrogen. For the above-mentioned reaction, Ir-based and Ru-based catalysts, such as IrO₂ and RuO₂, are generally used for the positive electrode, while catalysts including Pt are mainly used for the negative electrode.

SUMMARY

Meanwhile, when the PEM water electrolysis system operates, the positive electrode and the negative electrode respectively produce oxygen and hydrogen, and a mixture of these gases generated in this manner may cause a risk of explosion. Therefore, the PEM water electrolysis system needs to be essentially equipped with a hydrogen safety facility. The PEM water electrolysis system in the related art is equipped with a control system having hydrogen concentration (oxygen concentration) sensors, which are respectively applied to the positive electrode (negative electrode) separators and configured to automatically stop the water electrolysis system when the concentration exceeds a predetermined concentration. In this case, because the hydrogen concentration (oxygen concentration) is measured on the separator, a value of the hydrogen concentration (oxygen concentration) in the water electrolysis stack may be larger than a measurement value measured on the separator. That is, it is impossible to ignore the likelihood of explosion caused by a gas mixture remaining in the water electrolysis stack.

Accordingly, the present disclosure is provided to achieve not only a function of automatically controlling and stopping the PEM water electrolysis system in the related art but also a function of ensuring safety of the system by removing the gas mixture remaining in the water electrolysis stack, which has not been appropriately removed in the related art, by injecting pure oxygen (hydrogen), which is produced by the PEM water electrolysis system, into the positive electrode (negative electrode) when the hydrogen concentration (oxygen concentration) reaches a dangerous concentration.

An embodiment of the present disclosure provides a water electrolysis system including: a water electrolysis stack configured to produce oxygen and hydrogen from reactive water, discharge the oxygen to a positive electrode, and discharge the hydrogen to a negative electrode; and an oxygen tank and a hydrogen tank connected to the water electrolysis stack and configured to respectively store oxygen and hydrogen discharged from the water electrolysis stack, in which the oxygen tank is connected to the water electrolysis stack to supply the stored oxygen back to the water electrolysis stack, and in which the hydrogen tank is connected to the water electrolysis stack to supply the stored hydrogen back to the water electrolysis stack.

According to the embodiment, the oxygen tank may be 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 higher than an allowable hydrogen concentration that is a preset concentration. In one suitable aspect, the preset hydrogen concentration suitably may be about 2%.

According to the embodiment, the hydrogen tank may be 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 higher than an allowable oxygen concentration that is a preset concentration. In one suitable aspect, the preset oxygen concentration suitably may be about 3%.

According to the embodiment, the water electrolysis system may include: a first sensor part disposed at a rear end of the positive electrode of the water electrolysis stack and configured to measure a hydrogen concentration in the fluid discharged from the positive electrode; and a second sensor part disposed at a rear end of the negative electrode of the water electrolysis stack and configured to measure an oxygen concentration in the fluid discharged from the negative electrode.

According to the embodiment, the water electrolysis system may include: a controller configured to control a supply of oxygen and hydrogen from the oxygen tank and the hydrogen tank to the water electrolysis stack; a first valve configured to adjust the amount of oxygen to be discharged from the oxygen tank; and a second valve configured to adjust the amount of hydrogen to be discharged from the hydrogen tank, in which the controller performs control to turn on or off the first valve and the second valve.

According to the embodiment, the controller may perform control to supply oxygen or hydrogen to the water electrolysis stack when a concentration value measured by the first sensor part or the second sensor part is equal to or higher than the allowable hydrogen concentration or the allowable oxygen concentration.

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

According to the embodiment, the first sensor part may be disposed at a portion where the positive electrode separator and the water electrolysis stack are connected, and the second sensor part may be disposed at a portion where the negative electrode separator and the water electrolysis stack are connected.

According to the embodiment, the water electrolysis system may include: a third valve configured to be opened or closed to adjust a movement of the fluid, which is discharged from the water electrolysis stack, to the positive electrode separator; and a fourth valve configured to be opened or closed to adjust a movement of the fluid, which is discharged from the water electrolysis stack, to the negative electrode separator.

According to the embodiment, the controller may perform control to close the third valve or the fourth valve when a concentration of hydrogen or oxygen in the fluid discharged from the water electrolysis stack is equal to or higher than the allowable hydrogen concentration or the allowable oxygen concentration.

According to the embodiment, the water electrolysis system may include: a deionization tank connected to the water electrolysis stack and configured to supply the stored reactive water to the water electrolysis stack.

According to the embodiment, the water electrolysis system may include: an ejector disposed at a connection portion between the deionization tank and the water electrolysis stack, in which the oxygen tank is connected to the ejector to supply oxygen to the water electrolysis stack by using a pressure difference of the reactive water passing through the ejector.

According to the embodiment, the ejector may include: an introduction part into which the reactive water is introduced; a confluence part into which oxygen is merged; and a discharge part from which the fluid made by mixing reactive water and oxygen is discharged.

According to the embodiment, a cross-sectional area of the introduction part may decrease in a flow direction in which the reactive water flows, and the confluence part may be configured to surround one end of the introduction part based on the flow direction.

According to the embodiment, the water electrolysis system may include: a compressor configured to maintain pressure so that pressure in the water electrolysis stack is higher than normal pressure, and pressure in the hydrogen tank is higher than the pressure in the water electrolysis stack.

Another embodiment of the present disclosure provides a method of controlling a water electrolysis system, the method including: a concentration measurement step of measuring, by a first sensor part and a second sensor part, a hydrogen concentration and an oxygen concentration in a fluid discharged from a water electrolysis stack; and a gas supply step of supplying, by a controller, oxygen stored in an oxygen tank or hydrogen stored in a hydrogen tank to the water electrolysis stack.

According to the embodiment, the method may include: a safety determination step of determining, by the controller, whether a concentration value measured in the concentration measurement step is equal to or higher than a preset allowable hydrogen concentration or a preset allowable oxygen concentration.

According to the embodiment, the gas supply step may include an oxygen supply step of supplying oxygen to the water electrolysis stack, and the oxygen supply step may be performed when the measured concentration value is equal to or higher than the allowable hydrogen concentration.

According to the embodiment, the gas supply step may include a hydrogen supply step of supplying hydrogen to the water electrolysis stack, and the hydrogen supply step may be performed when the measured concentration value is equal to or higher than the allowable oxygen concentration.

According to the embodiment, the method may include: a fluid cut-off step of blocking, by the controller, the fluid discharged from the water electrolysis stack when the measured concentration value is equal to or higher than the allowable hydrogen concentration or the allowable oxygen concentration.

As discussed, the method and system suitably include use of a controller or processer.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view illustrating a water electrolysis system in the pre-existing technology.

FIG. 2 is a schematic view illustrating a water electrolysis system according to some embodiments of the present disclosure.

FIG. 3 is a flowchart illustrating a method of controlling the water electrolysis system according to some embodiments of the present disclosure.

FIG. 4 is a flowchart illustrating the method of controlling the water electrolysis system according to some embodiments of the present disclosure.

FIG. 5 is a flowchart illustrating the method of controlling the water electrolysis system according to some embodiments of the present disclosure.

DETAILED DESCRIPTION

Hereinafter, some exemplary embodiments of the present disclosure will be described in detail with reference to the illustrative drawings. In giving reference numerals to constituent elements of the respective drawings, it should be noted that the same constituent elements will be designated by the same reference numerals, if possible, even though the constituent elements are illustrated in different drawings. Further, in the following description of the exemplary embodiments of the present disclosure, a detailed description of publicly known configurations or functions incorporated herein will be omitted when it is determined that the detailed description obscures the subject matters of the exemplary embodiments of the present disclosure.

The terms first, second, A, B, (a), and (b) may be used to describe constituent elements of the embodiments of the present disclosure. These terms are used only for the purpose of discriminating one constituent element from another constituent element, and the nature, the sequences, or the orders of the constituent elements are not limited by the terms. Further, unless otherwise defined, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by those skilled in the art to which the present disclosure pertains. The terms such as those defined in commonly used dictionaries should be interpreted as having meanings consistent with meanings in the context of related technologies and should not be interpreted as ideal or excessively formal meanings unless explicitly defined in the present application.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the disclosure. As used herein, the singular forms “a,” “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. These terms are merely intended to distinguish one component from another component, and the terms do not limit the nature, sequence or order of the constituent components. It will be further understood that the terms “comprises” and/or “comprising,” when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items. Throughout the specification, unless explicitly described to the contrary, the word “comprise” and variations such as “comprises” or “comprising” will be understood to imply the inclusion of stated elements but not the exclusion of any other elements. In addition, the terms “unit”, “-er”, “-or”, and “module” described in the specification mean units for processing at least one function and operation and can be implemented by hardware components or software components and combinations thereof.

Although exemplary embodiment is described as using a plurality of units to perform the exemplary process, it is understood that the exemplary processes may also be performed by one or plurality of modules. Additionally, it is understood that the term controller/control unit refers to a hardware device that includes a memory and a processor and is specifically programmed to execute the processes described herein. The memory is configured to store the modules, and the processor is specifically configured to execute said modules to perform one or more processes which are described further below.

Further, the control logic of the present disclosure may be embodied as non-transitory computer readable media on a computer readable medium containing executable program instructions executed by a processor, controller or the like. Examples of computer readable media include, but are not limited to, ROM, RAM, compact disc (CD)-ROMs, magnetic tapes, floppy disks, flash drives, smart cards and optical data storage devices. The computer readable medium can also be distributed in network coupled computer systems so that the computer readable media is stored and executed in a distributed fashion, e.g., by a telematics server or a Controller Area Network (CAN).

Unless specifically stated or obvious from context, as used herein, the term “about” is understood as within a range of normal tolerance in the art, for example within 2 standard deviations of the mean. “About” can be understood as within 10%, 9%, 8%, 7%, 6%, 5%, 4%, 3%, 2%, 1%, 0.5%, 0.1%, 0.05%, or 0.01% of the stated value. Unless otherwise clear from the context, all numerical values provided herein are modified by the term “about”.

The term “water electrolysis stack” used herein refers to an arrangement of electrodes, membranes, and associated components that collectively perform water electrolysis to produce hydrogen and oxygen.

The term “reactive water” used herein refers to water introduced into the electrolysis stack as the feedstock for generating hydrogen and oxygen.

The term “positive electrode separator” used herein refers to a device or assembly configured to separate oxygen from water in the fluid discharged from the positive electrode part.

The term “negative electrode separator” used herein refers to a device or assembly configured to separate oxygen from water in the fluid discharged from the negative electrode part.

In addition, the term ‘rear end’ disclosed in the present disclosure means a relatively downstream side based on a direction in which a fluid flows.

Hereinafter, embodiments of the present disclosure will be specifically described with reference to FIGS. 1 to 4.

FIG. 1 is a schematic view illustrating a water electrolysis system 1′ in the related art.

With reference to FIG. 1, in the water electrolysis system 1′ in the related art, reactive water is supplied to a water electrolysis stack 10′ from a deionization tank 40′. The water electrolysis stack 10′ produces oxygen and hydrogen from the reactive water by using an electrochemical reaction. In this case, oxygen is produced from a positive electrode 12′, hydrogen is produced from a negative electrode 13′, and the oxygen and the hydrogen may be discharged through different routes. However, in this case, oxygen and hydrogen may be mixed because of various reasons, such as a fracture of an electrolyte membrane, operating pressure, and electric current, in the water electrolysis stack 10′, and this phenomenon may be referred to as a cross-over phenomenon.

In the case of the system in the related art, sensors may be installed on a positive electrode separator and a negative electrode separator to measure an oxygen concentration or a hydrogen concentration in a fluid discharged from the water electrolysis stack 10′. In this case, because the oxygen concentration or the hydrogen concentration is measured in the separator, a value of the oxygen concentration or the hydrogen concentration in the water electrolysis stack 10′ may be larger than a measurement value measured on each of the separators.

FIG. 2 is a schematic view illustrating a water electrolysis system 1 of the present disclosure.

With reference to FIG. 2, the water electrolysis system 1 of the present disclosure may include a water electrolysis stack 10, an oxygen tank (O₂ tank) 26, and a hydrogen tank (H₂ tank) 38.

The water electrolysis stack 10 may receive reactive water and produce oxygen and hydrogen from the reactive water. In this case, oxygen may be discharged through a positive electrode (anode) 12, and hydrogen may be discharged through a negative electrode (cathode) 13. However, as described above, the cross-over phenomenon may occur because of various reasons. Therefore, hydrogen, together with oxygen, may be discharged through the positive electrode 12, and oxygen, together with hydrogen, may be discharged through the negative electrode 13. In this case, water (H₂O), which is the reactive water, may also be discharged.

The oxygen tank 26 and the hydrogen tank 38 may be configured to respectively store oxygen and hydrogen discharged from the water electrolysis stack 10. In this case, the oxygen tank 26 and the hydrogen tank 38 may be connected to the water electrolysis stack 10 to respectively store oxygen and hydrogen.

For example, the oxygen tank 26 may be connected to the positive electrode 12 of the water electrolysis stack 10 through a pipe, and the hydrogen tank 38 may be connected to the negative electrode 13 of the water electrolysis stack 10 through a pipe. In this case, a separator, a valve, or the like, which will be described below, may be positioned in the pipe.

In addition, the oxygen tank 26 may reuse the stored oxygen. For example, the oxygen tank 26 may supply the stored oxygen back to the water electrolysis stack 10, and the oxygen tank 26 may be connected to the water electrolysis stack 10 through a pipe. In this case, the oxygen tank 26 and the water electrolysis stack 10 may be connected by a pipe different from a pipe through which the fluid is discharged from the water electrolysis stack 10.

Likewise, the hydrogen tank 38 may reuse the stored hydrogen. For example, the hydrogen tank 38 may supply the stored hydrogen back to the water electrolysis stack 10, and the hydrogen tank 38 may be connected to the water electrolysis stack 10 through a pipe. In this case, the hydrogen tank 38 and the water electrolysis stack 10 may be connected by a pipe different from the pipe through which the fluid is discharged from the water electrolysis stack 10.

The water electrolysis system 1 may include a positive electrode separator (anode separator) 20, a deionization tank (deionized tank) 40, and a negative electrode separator (cathode separator) 30.

The positive electrode separator 20 may be configured to separate oxygen and water. The positive electrode separator 20 may separate oxygen and water from the fluid discharged from the positive electrode 12. The positive electrode separator 20 may be connected to the water electrolysis stack 10 and the oxygen tank 26.

Specifically, the positive electrode separator 20 may be connected to the positive electrode 12 of the water electrolysis stack 10 through a first oxygen pipe 200. In addition, a rear end of the positive electrode separator 20 may be connected to the oxygen tank 26 through a second oxygen pipe 210. Therefore, oxygen, which is separated from water by the positive electrode separator 20, may move to the oxygen tank 26 along the second oxygen pipe 210.

A positive electrode drain pipe 240 may be connected to the positive electrode separator 20, and the separated water may be recovered to the deionization tank 40 through the positive electrode drain pipe 240 or discharged to the outside. In this case, the positive electrode drain pipe 240 may be connected to the positive electrode separator 20 and the deionization tank 40, and the positive electrode drain pipe 240 may branch off from an intermediate portion between the positive electrode separator 20 and the deionization tank 40 and be directed toward the outside.

The deionization tank 40 may be configured to supply the stored reactive water to the water electrolysis stack 10. The deionization tank 40 may be connected to the water electrolysis stack 10 through a reactive water supply pipe 230. A pump 41 may be disposed in the reactive water supply pipe 230, and the reactive water may be moved to the water electrolysis stack 10 by pressure generated by the pump 41.

The negative electrode separator 30 may be configured to separate hydrogen and water. The negative electrode separator 30 may separate hydrogen and water from the fluid discharged from the negative electrode 13. The negative electrode separator 30 may be connected to the water electrolysis stack 10 and the hydrogen tank 38.

Specifically, the negative electrode separator 30 may be connected to the negative electrode 13 of the water electrolysis stack 10 through a first hydrogen pipe 300. In addition, a rear end of the negative electrode separator 30 may be connected to the hydrogen tank 38 through a second hydrogen pipe 310. Therefore, hydrogen, which is separated from water by the negative electrode separator 30, may move to the hydrogen tank 38 along the second hydrogen pipe 310.

A negative electrode drain pipe 330 may be connected to the negative electrode separator 30, and the separated water may be discharged to the outside through the negative electrode drain pipe 330.

The oxygen tank 26 and the hydrogen tank 38 may supply the stored oxygen or hydrogen back to the water electrolysis stack 10. In this case, there may be a particular condition.

For example, the oxygen tank 26 may be configured to supply the stored oxygen to the water electrolysis stack 10 in case that a hydrogen concentration in the fluid discharged from the positive electrode 12 is equal to or higher than an allowable hydrogen concentration that is a preset concentration. In this case, the fluid discharged from the positive electrode 12 may be a fluid in which oxygen, hydrogen, and water are mixed.

Likewise, the hydrogen tank 38 may be configured to supply the stored hydrogen to the water electrolysis stack 10 in case that an oxygen concentration in the fluid discharged from the negative electrode 13 is equal to or higher than an allowable oxygen concentration that is a preset concentration.

The allowable hydrogen concentration and the allowable oxygen concentration may be concentrations for ensuring the safety of the water electrolysis system 1. For example, in case that pure oxygen and hydrogen are mixed by the cross-over phenomenon, a risk of explosion caused by a chemical reaction between the two gases may be increased. The risk of explosion may vary depending on a ratio between oxygen and hydrogen. In case that the concentrations of oxygen and hydrogen exceed the concentration for ensuring the safety, it is necessary to shut down the water electrolysis system 1. For example, in case that a proportion of hydrogen in the fluid discharged to the positive electrode 12 is 4 to 94%, the proportion of hydrogen may be in an explosion range. International standards, such as ISO 22734, related to water electrolysis products require safety control systems to shut down the water electrolysis systems when the concentration exceeds 50% of a lower explosion limit (4%) and an upper explosion limit (94%). That is, the water electrolysis system 1 may be shut down in case that a proportion of hydrogen in the fluid discharged from the positive electrode 12 reaches 2% or a proportion of oxygen in the fluid discharged from the positive electrode 12 reaches 3%. However, the numerical values are not necessarily limited to the above-mentioned numerical values because the numerical values may be changed in accordance with an environment and an application field of the system.

The oxygen tank 26 and the hydrogen tank 38 may be connected to the water electrolysis stack 10 through pipes to supply the stored oxygen and the stored hydrogen to the water electrolysis stack 10. For example, the oxygen tank 26 may be connected to the water electrolysis stack 10 through an oxygen resupply pipe 220, and the hydrogen tank 38 may be connected to the water electrolysis stack 10 through a hydrogen resupply pipe 320.

The water electrolysis system 1 of the present disclosure may include first and second sensor parts 21 and 31 configured to measure a concentration of oxygen or hydrogen in the fluid discharged from the water electrolysis stack 10.

The first sensor part 21 may be disposed at a rear end of the positive electrode 12 of the water electrolysis stack 10 and configured to measure a hydrogen concentration in the fluid discharged from the positive electrode 12. For example, the first sensor part 21 may be disposed at a portion where the positive electrode separator 20 and the water electrolysis stack 10 are connected. More specifically, the first sensor part 21 may be disposed in the first oxygen pipe 200. A position of the first sensor part 21 may be appropriately adjusted. The first sensor part 21 may be disposed to be close to the positive electrode 12. Alternatively, the first sensor part 21 may be positioned on the positive electrode 12. As described above, the position of the first sensor part 21 may be changed to a position suitable for measuring a hydrogen concentration in the fluid discharged from the positive electrode 12.

The second sensor part 31 may be disposed at a rear end of the negative electrode 13 of the water electrolysis stack 10 and configured to measure an oxygen concentration in the fluid discharged from the negative electrode 13. For example, the second sensor part 31 may be disposed at a portion where the negative electrode separator 30 and the water electrolysis stack 10 are connected. More specifically, the second sensor part 31 may be disposed in the first hydrogen pipe 300. A position of the second sensor part 31 may be appropriately adjusted. The second sensor part 31 may be disposed to be close to the negative electrode 13. Alternatively, the second sensor part 31 may be positioned on the negative electrode 13. As described above, the position of the second sensor part 31 may be changed to a position suitable for measuring an oxygen concentration in the fluid discharged from the negative electrode 13.

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

The first valve 27 may adjust the amount of oxygen to be discharged from the oxygen tank 26. For example, the first valve 27 may be disposed in the oxygen resupply pipe 220. The first valve 27 may be opened or closed to adjust the amount of oxygen to be moved from the oxygen tank 26 to the water electrolysis stack 10.

The second valve 39 may adjust the amount of hydrogen to be discharged from the hydrogen tank 38. For example, the second valve 39 may be disposed in the hydrogen resupply pipe 320. The second valve 39 may be opened or closed to adjust the amount of hydrogen to be moved from the hydrogen tank 38 to the water electrolysis stack 10.

The controller 60 may control a supply of oxygen and hydrogen from the oxygen tank 26 and the hydrogen tank 38 to the water electrolysis stack 10. For example, the controller 60 may perform control to turn on or off the first valve 27 and the second valve 39. The controller 60 may determine whether to supply oxygen or hydrogen to the water electrolysis stack 10 on the basis of an oxygen concentration or a hydrogen concentration in the fluid discharged to the water electrolysis stack 10. Specifically, in case that a concentration value measured by the first sensor part 21 or the second sensor part 31 is equal to or higher than the allowable hydrogen concentration or the allowable oxygen concentration, the controller 60 may perform control to supply oxygen or hydrogen to the water electrolysis stack 10. The first sensor part 21 and the second sensor part 31 may be connected to the controller 60 and transmit or receive electrical signals to or from the controller 60. The information on the hydrogen concentration and the oxygen concentration measured by the first sensor part 21 and the second sensor part 31 may be transferred to the controller 60.

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

The third valve 22 may be opened or closed to adjust the movement of the fluid, which is discharged from the water electrolysis stack 10, to the positive electrode separator 20. For example, the third valve 22 may be closed to block the fluid discharged from the positive electrode 12 of the water electrolysis stack 10.

The fourth valve 32 may be opened or closed to adjust the movement of the fluid, which is discharged from the water electrolysis stack 10, to the negative electrode separator 30. For example, the fourth valve 32 may be closed to block the fluid discharged from the negative electrode 13 of the water electrolysis stack 10.

The controller 60 may perform control to open or close the third valve 22 and the fourth valve 32. For example, the controller 60 may perform control to close the third valve 22 or the fourth valve 32 in case that a concentration of hydrogen or oxygen in the fluid discharged from the water electrolysis stack 10 is equal to or higher than the allowable hydrogen concentration or the allowable oxygen concentration. For example, in case that the oxygen concentration in the fluid discharged from the negative electrode 13 is equal to or higher than the allowable oxygen concentration, the water electrolysis system 1 may be exposed to a risk of explosion. In this case, the controller 60 may close the fourth valve 32 and block the pipe to prevent the fluid discharged from the negative electrode 13 from being introduced into the negative electrode separator 30 or the hydrogen tank 38.

The positions at which the third valve 22 and the fourth valve 32 are disposed may be appropriately adjusted. For example, the third valve 22 may be disposed in the first oxygen pipe 200, and the fourth valve 32 may be disposed in the first hydrogen pipe 300. However, this configuration does not exclude a case in which the third valve 22 and the fourth valve 32 are respectively disposed in the second oxygen pipe 210 and the second hydrogen pipe 310. The positions of the third and fourth valves 22 and 32 may be changed within a range for achieving the object of the present disclosure.

The water electrolysis system 1 may include an ejector 50.

The ejector 50 may be disposed at a connection portion between the deionization tank 40 and the water electrolysis stack 10. For example, the ejector 50 may be disposed in the reactive water supply pipe 230.

The reactive water and the oxygen may simultaneously pass through the ejector 50. For example, the oxygen tank 26 may be connected to the ejector 50 to supply oxygen to the water electrolysis stack 10 by using a pressure difference of the reactive water passing through the ejector 50.

Specifically, the ejector 50 may include an introduction part 51, a confluence part 52, and a discharge part 53. The introduction part 51 may be a component into which the reactive water is introduced. The confluence part 52 may be a component into which oxygen is merged. The discharge part 53 may be a component from which a fluid made by mixing the reactive water and the oxygen is discharged.

Specifically, a cross-sectional area of the introduction part 51 may decrease in a flow direction in which the reactive water flows. For example, the introduction part 51 may be configured to be similar to a nozzle. The confluence part 52 may be connected to the oxygen tank 26 through the oxygen resupply pipe 220. The confluence part 52 may be configured to surround one end of the introduction part 51 based on the flow direction. The reactive water may be introduced into the introduction part 51 of the ejector 50 by pressure generated by the pump 41. Therefore, in case that the reactive water flows through the introduction part 51, the pressure of the reactive water decreases, such that oxygen may be introduced into the ejector 50 through the confluence part 52. The reactive water and the oxygen, which are mixed in the ejector 50, may pass through the discharge part 53 and be supplied to the electrolyte stack. That is, oxygen may be resupplied to the water electrolysis stack 10 by using the pressure generated by the existing pump 41 and adding the configuration of the ejector 50 without separate power.

The water electrolysis system 1 may include a compressor 37.

The compressor 37 may maintain high pressure in the hydrogen tank 38. For example, the compressor 37 may maintain the pressure in the hydrogen tank 38 so that the pressure in the hydrogen tank 38 is higher than pressure in the water electrolysis stack 10. In this case, the pressure in the water electrolysis stack 10 may be higher than the normal pressure.

The compressor 37 may be positioned at a front end of the hydrogen tank 38. For example, the compressor 37 may be positioned in the second hydrogen pipe 310. However, this configuration does not exclude a case in which the compressor 37 is positioned in the first hydrogen pipe 300.

Because the pressure in the hydrogen tank 38 is maintained to be higher than the pressure in the water electrolysis stack 10, the stored hydrogen may be resupplied to the water electrolysis stack 10 from the hydrogen tank 38 only by adjusting the second valve 39 without providing separate additional power.

A third sensor part 23 configured to measure a hydrogen concentration may be installed on the positive electrode separator 20, and a fourth sensor part 33 configured to measure an oxygen concentration may be installed on the negative electrode separator 30.

A fifth sensor part 25 configured to measure a hydrogen concentration and a first demister 24 configured to remove moisture in the fluid may be disposed between the positive electrode separator 20 and the oxygen tank 26. For example, the fifth sensor part 25 and the demister may be disposed in the second oxygen pipe 210.

A sixth sensor part 36 configured to measure an oxygen concentration, a second demister 35, and a deoxidizer 34 configured to remove hydrogen in the fluid may be disposed between the negative electrode separator 30 and the hydrogen tank 38. For example, the sixth sensor part 36, the second demister 35, and the deoxidizer 34 may be disposed in the second hydrogen pipe 310.

However, because the positions of the above-mentioned sensor parts, demisters, deoxidizers, and the like may be appropriately changed, the above-mentioned configuration does not exclude a configuration in which the sensor parts, the demisters, the deoxidizers, and the like are disposed at other positions.

FIGS. 3 to 5 are flowcharts illustrating a method of controlling the water electrolysis system 1 of the present disclosure. FIGS. 4 and 5 are views illustrating that the order of some steps of the method of controlling the water electrolysis system 1 in FIG. 3 is changed.

With reference to FIGS. 3 to 5, the method of controlling the water electrolysis system 1 of the present disclosure may include a concentration measurement step S100, a safety determination step S200, a gas cut-off step, and a gas supply step S400.

The concentration measurement step S100 may be a step of measuring, by the first sensor part 21 and the second sensor part 31, a hydrogen concentration and an oxygen concentration in the fluid discharged from the water electrolysis stack 10. For example, the first sensor part 21 may measure a hydrogen concentration in the fluid discharged from the positive electrode 12, and the second sensor part 31 may measure an oxygen concentration in the fluid discharged from the negative electrode 13. The concentration measurement step S100 may be performed repeatedly and continuously. For example, in case that a concentration value measured is not equal to or higher than the allowable oxygen concentration or the allowable hydrogen concentration in the safety determination step S200 to be described below, the concentration measurement step S100 may be performed continuously again. However, this method does not exclude a case in which the concentration measurement step S100 is performed again even though the measured concentration value is equal to or higher than the allowable oxygen concentration or the hydrogen allowable.

The safety determination step S200 may be a step of determining, by the controller 60, whether the concentration value measured in the concentration measurement step S100 is equal to or higher than the allowable hydrogen concentration or the allowable oxygen concentration. In this case, whether to determine the hydrogen concentration first or whether to determine the oxygen concentration first is not limited. Therefore, the hydrogen concentration and the oxygen concentration may be simultaneously determined.

A fluid cut-off step S300 may be a step of blocking, by the controller 60, the fluid discharged from the water electrolysis stack 10 in case that the measured concentration value is equal to or higher than the allowable hydrogen concentration or the allowable oxygen concentration. For example, in case that the measured value of the hydrogen concentration in the fluid discharged from the positive electrode 12 is equal to or higher than the allowable hydrogen concentration, the controller 60 may close the third valve 22. The same process may be performed even in case that the value of the oxygen concentration in the fluid discharged from the negative electrode 13 is equal to or higher than the allowable oxygen concentration.

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

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

According to the embodiment of the present disclosure, in case that oxygen and hydrogen are mixed in the system, oxygen or hydrogen, which is produced by the operation of the water electrolysis system, is reused to avoid the gas mixture from a dangerous concentration.

According to the embodiment of the present disclosure, oxygen or hydrogen, which is produced by the operation of the water electrolysis system, may be reused without an additional power source.

According to the embodiment of the present disclosure, the system of the present disclosure may be used by adding only simple components, such as the oxygen tank, the ejector, and the valve, to a system in the related art.

The above description is simply given to illustratively describe the technical spirit of the present disclosure, and those skilled in the art to which the present disclosure pertains will appreciate that various changes and modifications are possible without departing from the essential characteristic of the present disclosure.

Therefore, the embodiments disclosed in the present disclosure are provided for illustrative purposes only but not intended to limit the technical concept of the present disclosure. The scope of the technical spirit of the present disclosure is not limited thereby. The protective scope of the present disclosure should be construed based on the following claims, and all the technical spirit in the equivalent scope thereto should be construed as falling within the scope of the present disclosure.