WATER ELECTROLYSIS DEVICE AND METHOD FOR 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. 10-2024-0184233, filed in the Korean Intellectual Property Office on Dec. 11, 2024, the entire contents of which are incorporated herein by reference.

BACKGROUND

Technical Field

The present disclosure relates to a water electrolysis device, and a method for controlling the same.

Background

A water electrolysis device using a polymer electrolyte membrane (PEM) (hereinafter, “an inner electrolyte membrane”) separates water into hydrogen and oxygen through an electrochemical reaction and is regarded as a next-generation technology for producing clean hydrogen due to its advantages, such as fast hydrogen production rate, a high purity of the produced hydrogen, and a flexible operability.

Moreover, when the electric power supplied for electrochemical reactions to the water electrolysis device is replaced with eco-friendly regenerative energy, surplus electricity can be converted into hydrogen without emitting environmental pollutants.

In general, an inner electrolyte membrane includes a water electrolysis stack assembled by stacking a plurality of unit cells to achieve the desired hydrogen-production capacity.

The electrochemical reaction of the water electrolysis device occurs in a membrane-electrode assembly including perfluorinated sulfonic acid ionomer-based electrolyte membrane and anode/cathode electrodes, and after the water supplied to the anode is separated into oxygen, hydrogen ions, and electrons, hydrogen ions move through the inner electrolyte membrane toward the cathode that is a reduction electrode, and electrons move to the cathode through external circuits and supply sources so that hydrogen ions and electrons react with each other in the cathode to generate hydrogen.

Meanwhile, the purity of the feed water may be important for stable production of hydrogen in the water electrolysis device. This is because when the purity of the feed water is introduced into the water electrolysis stack while the purity of the feed water is lowered, the hydrogen production generated in the water electrolysis stack may decrease and the lifespan of the water electrolysis device may be shortened. The impurities that affect the purity of the feed water may be classified into cations, anions, and organic substances, and when the impurities flow into the water electrolysis stack, the electrodes and the inner electrolyte membrane deteriorate, so that there is an increasing need for the water electrolysis device that may manage the purity of the feed water.

SUMMARY

The present disclosure has been made to solve the above-mentioned problems occurring in the prior art while advantages achieved by the prior art are maintained intact.

Some embodiments of the present disclosure provides a water electrolysis device that may manage a purity of feed water.

The technical problems to be solved by the present disclosure are not limited to the aforementioned problems, and any other technical problems not mentioned herein will be clearly understood from the following description by those skilled in the art to which the present disclosure pertains.

According to some embodiments of the present disclosure, a water electrolysis device includes a water electrolysis stack, a supply pipeline configured to deliver feed water to the water electrolysis stack, and a transport layer provided on an upstream side of the water electrolysis stack on the supply pipeline. In aspects, the transport layer suitably may be porous as disclosed herein.

The water electrolysis device may further include an electric power supply unit configured to supply electric power to the water electrolysis stack, and a processor operatively coupled to the electric power supply unit, and the processor may control the electric power supply unit such that the electric power supply unit stops supply of electric power to the water electrolysis stack when a concentration of impurities precipitated by the transport layer is equal to or more than a reference concentration.

The water electrolysis device may further include a first pressure gauge disposed upstream of the transport layer on the supply pipeline, and a second pressure gauge provided between the transport layer and the water electrolysis stack on the supply pipeline, and the processor may determine that the concentration of the impurities has reached the reference concentration when a difference between a first pressure sensed by the first pressure gauge and a second pressure sensed by the second pressure gauge is greater than or equal toa reference pressure difference.

The water electrolysis device may further include a circulation pump configured to pump the feed water flowing through the supply pipeline, and operatively coupled to the processor, and the processor may stop the circulation pump when the difference between the first pressure and the second pressure is greater than or equal to the reference pressure difference.

The reference pressure difference may be about 1.1 times an initial differential pressure between the first pressure gauge and the second pressure gauge.

The water electrolysis device may further include an ion conductivity sensor positioned between the transport layer and the water electrolysis stack and configured to sense an ion conductivity of the feed water.

The processor may be operatively coupled to the ion conductivity sensor and controls the electric power supply unit when a value of the ion conductivity sensed by the ion conductivity sensor is less than or equal toa first reference ion conductivity.

A value of the first reference ion conductivity may be about 0.95 times an initial value of the ion conductivity.

The ion conductivity sensor may include an electrolyte membrane in contact with the feed water, a current source configured to apply a current to the electrolyte membrane, and a voltage sensor connected to two points of the electrolyte membrane to sense a voltage therebetween.

The current source may apply an alternating current to the electrolyte membrane, and the ion conductivity sensed by the ion conductivity sensor may be calculated as a value

( L R ⁢ A )

of a distance (L) between the two points, for a product of a converted resistance value (R) corresponding to a real number part of a value converted by Nyquist Plot in an AC resistance value by the alternating current applied to the electrolyte membrane, and an area (A) of the electrolyte membrane, which is defined by two directions crossing one direction connecting the two points.

The water electrolysis stack may include an inner electrolyte membrane provided as an interior thereof, and a thickness of the electrolyte membrane may be smaller than a thickness of the inner electrolyte membrane.

The water electrolysis stack may include a stack transport layer provided as an interior thereof, and configured to precipitate impurities included in the feed water introduced into the water electrolysis stack, and i) a size of pores of the transport layer may be less than or equal to a size of pores of the stack transport layer, ii) a porosity of the transport layer may be less than or equal to a porosity of the stack transport layer, or iii) the transport layer may be provided such that a transport layer corresponding to the stack transport layer has two layers.

The water electrolysis device may further include a supply tank connected to a point between the ion conductivity sensor and the water electrolysis stack on the supply pipeline, and accommodating carbon dioxide to be supplied to the feed water, an ejector provided on the supply pipeline and configured to pump carbon dioxide to the water electrolysis stack together with the feed water, and an opening/closing valve provided between the ejector and the supply tank.

The opening/closing valve may be operatively coupled to the processor, and the processor may control the opening/closing valve such that the carbon dioxide is supplied from the supply tank to the feed water when a value of the ion conductivity sensed by the ion conductivity sensor is greater than or equal to a second reference ion conductivity.

A value of the second reference ion conductivity may be greater than a value of the first reference ion conductivity.

According to some embodiments of the present disclosure, a method for controlling a water electrolysis device includes supplying feed water to a water electrolysis stack such that the feed water passes through a transport layer provided on an upstream side of the water electrolysis stack, calculating a pressure difference between a first pressure of the feed water sensed by a first pressure gauge provided on an upstream side of the transport layer and a second pressure of the feed water sensed by a second pressure gauge provided between the transport layer and the water electrolysis stack, and stopping supply of electric power to the water electrolysis stack or stopping supply of the feed water to the water electrolysis stack when the pressure difference is greater than or equal to a reference pressure difference.

The method may further include sensing an ion conductivity of the feed water by using an ion conductivity sensor provided between the second pressure gauge and the water electrolysis stack and stopping the supply of the electric power to the water electrolysis stack or stopping the supply of the feed water to the water electrolysis stack when the sensed ion conductivity is equal to or less than a first ion conductivity.

The method may further include informing a user to replace the transport layer when the pressure difference is greater than or equal to the reference pressure difference, and informing the user to replace an electrolyte membrane included in the ion conductivity sensor when the ion conductivity sensed in the sensing of the ion conductivity is equal to or less than the first ion conductivity.

The method may further include supplying carbon dioxide to the feed water when the sensed ion conductivity in the sensing of the ion conductivity is equal to or less than a specific second ion conductivity.

The method may further include informing a user to fill the carbon dioxide when a pressure of the carbon dioxide supplied to the feed water in the supplying of the carbon dioxide is less than a pressure of the feed water.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objects, features and advantages of the present disclosure will be more apparent from the following detailed description taken in conjunction with the accompanying drawings:

FIG. 1 is a schematic view of a water electrolysis device according to some embodiments of the present disclosure;

FIG. 2 is a schematic view of an ion conductivity sensor according to some embodiments of the present disclosure;

FIG. 3 is a schematic view of a supply tank, an ejector, an opening/closing valve, and a water electrolysis stack according to some embodiments of the present disclosure;

FIG. 4 is a schematic view of a water electrolysis device according to some embodiments of the present disclosure;

FIG. 5 is a flowchart illustrating a control method that compares upstream and downstream pressures, then evaluates ion conductivity to selectively stop power or feed water flow to the electrolysis stack and issue alerts for transport layer or electrolyte membrane replacement, according to some embodiments of the present disclosure; and

FIG. 6 is flowchart illustrating subsequent steps in which carbon dioxide is injected into the feed water when ion conductivity falls below a secondary threshold, and a refill notice is generated when the CO₂ supply pressure drops beneath the fee water pressure. according to some embodiments of the present disclosure.

DETAILED DESCRIPTION

Hereinafter, some embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. In adding reference numerals to the components of the drawings, it should be noted that the same components have the same numerals as possible even when they are illustrated on different drawings. Furthermore, in describing the embodiments of the present disclosure, detailed descriptions associated with well-known functions or configurations will be omitted if they may make subject matters of the present disclosure unnecessarily obscure.

In describing components of embodiments of the present disclosure, the terms first, second, A, B, (a), (b), and the like may be used herein. These terms are only used to distinguish one element from another element, but do not limit the corresponding elements irrespective of the nature, order, or priority of the corresponding elements. Furthermore, unless otherwise defined, all terms including technical and scientific terms used herein are to be interpreted as is customary in the art to which the present disclosure belongs. Such terms as those defined in a generally used dictionary are to be interpreted as having meanings equal to the contextual meanings in the relevant field of art and are not to be interpreted as having ideal or excessively formal meanings unless clearly defined as having such in the present application.

The term “feed water” herein refers to the purified or pre-treated water stream introduced into the water-electrolysis stack for electrochemical splitting of H₂O into hydrogen and oxygen.

The term “transport layer” herein refers to a gas- and liquid-permeable, electrically conductive substrate positioned in the supply pipeline. The term “transport layer” may be formed porous. The term “transport layer” may also be understood as a porous transport layer positioned in the supply pipe.

The term “stack transport layer” herein refers to a porous transport layer that is structurally integrated within the water-electrolysis stack. Here, the term “stack transport layer” refers to a porous transport layer used in the water electrolysis stack, which can be assembled within the water electrolysis stack.

Hereinafter, various embodiments of the present disclosure will be described in detail with reference to FIGS. 1 to 6.

FIG. 1 is a schematic view of a water electrolysis device according to some embodiments of the present disclosure. FIG. 2 is a schematic view of an ion conductivity sensor according to some embodiments of the present disclosure. FIG. 3 is a schematic view of a supply tank, an ejector, an opening/closing valve, and a water electrolysis stack according to some embodiments of the present disclosure.

Referring to FIGS. 1 to 3, a water electrolysis device 100 may be a device that separates water into hydrogen and oxygen through an electrochemical reaction using a polymer electrolyte membrane (PEM) (hereinafter, an ‘inner electrolyte membrane’).

The water electrolysis device 100 may include a water electrolysis stack 110 that is assembled by stacking a plurality of unit cells by using an inner electrolyte membrane, and a supply pipeline 101 for introducing feed water into the water electrolysis stack 110. Furthermore, the water electrolysis device 100 may include an electric power supply unit 120 for supplying electric power to the water electrolysis stack 110.

The water electrolysis stack 110 may include a membrane-electrode assembly (MEA), an inner electrolyte membrane for movement of hydrogen ions to the membrane-electrode assembly (MEA), and an anode and a cathode that are provided on opposite side surfaces of the inner electrolyte membrane, respectively.

A stack transport layer (not illustrated) that is provided separately from the transport layer 420 positioned in the supply pipe 101 and provided as a porous transport layer (PTL) within the water electrolysis stack 110, a gas diffusion layer (GDL), and a gasket may be stacked on an outer area of the membrane-electrode assembly, in which the anode and the cathode are located, and a passage or a separator, through which a product generated through a reaction between a reactant and cooling water may be combined with an outer area of the stack transport layer and the gas diffusion layer.

When the feed water is supplied to water electrolysis cells of the water electrolysis stack 110, the feed water supplied to the anode may be separated into oxygen, hydrogen ions, and electrons, and then the hydrogen ions and the electrons may move to the cathode. Accordingly, the hydrogen ions and the electrons may react with each other in the cathode to produce hydrogen. For this reaction, an iridium (Ir)-based catalyst or a ruthenium (Ru)-based catalyst may be used in the anode, and a catalyst containing platinum (Pt) may be used in the cathode. However, the type of the catalyst is not limited thereto.

According to the above-described principle, the feed water that flows through the supply pipeline 101 is introduced into the water electrolysis stack 110 and is generated while hydrogen and oxygen are separated. To this end, the water electrolysis device 100 may include a (1-1)-th discharge pipeline 201 and a (2-1)-th discharge pipeline 301 that are connected to the water electrolysis stack 110, respectively.

The water electrolysis device 100 may include a water tank 200 that is connected to the (1-1)-th discharge pipeline 201, and a (1-2)-th discharge pipeline 202 and a supply pipeline 101 that are connected to the water tank 200, respectively.

A discharge sensor 210 may be provided on the (1-1)-th discharge pipeline 201. The discharge sensor 210 may be a component for determining whether ionic impurities are generated in the water electrolysis stack 110 by measuring the ion conductivity of the discharged water that flows through the (1-1)-th discharge pipeline 201.

The discharge water that flows through the (1-1)-th discharge pipeline 201 and the feed water that is introduced through a water supply pump 250 may be accommodated in the water tank 200. A tank sensor 220 may be provided in the water tank 200. The tank sensor 220 may be a component for measuring ion conductivities of the discharged water and the feed water accommodated in the water tank 200.

The (1-2)-th discharge pipeline 202 may be connected to the water tank 200 to allow oxygen accommodated in the water tank 200 to flow. A first discharge filter 230 and a first discharge valve 240 may be provided on the (1-2)-th discharge pipeline 202, and the oxygen that flows through the (1-2)-th discharge pipeline 202 may be filtered by the first discharge filter 230 and then be discharged to the outside when the first discharge valve 240 opens the (1-2)-th discharge pipeline 202.

Meanwhile, the water electrolysis device 100 may include a separator 300 that is connected to the (2-1)-th discharge pipeline 301, a (2-2)-th discharge pipeline 302 and a (2-3)-th discharge pipeline 303 that are connected to the separator 300, respectively.

The separator 300 may be a device for separating solids contained in the hydrogen gas generated by the water electrolysis stack 110. The (2-2)-th discharge pipeline 302 may be connected to the separator 300 to allow the hydrogen gas separated by the separator 300 to flow. A second discharge filter 310 and the second discharge valve 320 may be provided on the (2-2)-th discharge pipeline 302, and the hydrogen that flows through the (2-2)-th discharge pipeline 302 may be discharged to the outside when the second discharge valve 320 opens the (2-2)-th discharge filter 302 after being filtered by the second discharge filter 310.

The (2-3)-th discharge pipeline 303 connected to the separator 300 may discharge the solids generated in the separator 300 together with the discharged water. Furthermore, the discharge water discharged from the separator 300 may be recovered to the water tank 200.

Meanwhile, the discharge water and the feed water accommodated in the water tank 200 may flow through the supply pipeline 101 to be supplied to the water electrolysis stack 110 again. To maintain the temperatures of the discharge water and the feed water circulated through the supply pipeline 101, a cooler 260 may be provided on the supply pipeline 101. Hereinafter, the discharge water and the feed water that flow through the supply pipeline 101 may be referred to as feed water. The feed water that has passed through the cooler 260 may be adjusted to a temperature for being supplied to the water electrolysis stack 110.

The supply pipeline 101 may supply the feed water to a circulation pump 400. In this way, the water electrolysis device 100 may include a circulation pump 400 that is configured to pump the feed water that flows through the supply pipeline 101 to the water electrolysis stack 110, and a supply pipeline 101 that is formed to supply the feed water to the water electrolysis stack 110.

The water electrolysis device 100 may include a transport layer 420 that is provided between the circulation pump 400 and the water electrolysis stack 110. The water electrolysis device 100 may include an ion filter 440, an ion conductivity sensor 460, a supply tank 470, and a controller 500.

The ion filter 440 may be a component for removing ionic impurities contained in the feed water. A supply sensor 450 may be provided on a downstream side of the ion filter 440. The supply sensor 450 may be a component for determining whether the feed water may be supplied to the water electrolysis stack 110 by measuring the ion conductivity of the feed water that has passed through the ion filter 440.

The transport layer 420 may be provided between the ion filter 440 and the circulation pump 400 on the supply pipeline 101. Unlike the ion filter 440, the transport layer 420 may be formed of a metal of titanium (Ti). More specifically, the transport layer 420 may be provided in the form of titanium fiber felt or titanium particles. When the ion filter 440 is a component for removing ionic impurities of the feed water, the transport layer 420 may be a component for precipitating impurities or organic impurities in the form of particles of the feed water.

The transport layer 420 may be provided on an upstream side of the water electrolysis stack 110 on the supply pipeline 101. The transport layer 420 may be provided as a porous transport layer (PTL). For an improved sensitivity of the transport layer 420 compared to the stack transport layer (not illustrated) provided in an interior of the water electrolysis stack 110, i) a size of pores of the transport layer 420 may be equal to or less than a size of pores of the stack transport layer, ii) a porosity of the transport layer 420 may be equal to or less than a porosity of the stack transport layer, or iii) the transport layer 420 may be provided such that a transport layer corresponding to the stack transport layer has two layers.

The stack transport layer included as a PTL may be also provided in the interior of the water electrolysis stack 110 to precipitate the impurities contained in the feed water introduced into the water electrolysis stack 110, the transport layer 420 may be a component for filtering the impurities of the feed water supplied to the water electrolysis stack 110 in advance as it has a porosity that is smaller than the porosity of the stack transport layer, has a size of pores that is the size of the pores of the stack transport layer or less, or is provided in two or more layers corresponding to the stack transport layer.

With this configuration, the stability of the water electrolysis device 100 may be improved because the ionic impurities in the feed water supplied to the water electrolysis stack 110 may be filtered by the ion filter 440, and particle impurities or organic impurities may be filtered by the transport layer 420.

Meanwhile, when a specific amount or more of impurities are precipitated in the transport layer 420, it is necessary to stop supply of the feed water to the water electrolysis stack 110 for the stability of the water electrolysis stack 110.

To this end, the water electrolysis device 100 may include first and second pressure gauges 410 and 430 to estimate the amount of impurities precipitated on the transport layer 420. The first pressure gauge 410 may be provided on an upstream side of the transport layer 420 on the supply pipeline 101. The second pressure gauge 430 may be provided on a downstream side of the transport layer 420 on the supply pipeline 101.

More specifically, the first pressure gauge 410 may be provided between the circulation pump 400 and the transport layer 420, and the second pressure gauge 430 may be provided between the transport layer 420 and the ion filter 440.

The first pressure gauge 410 and the second pressure gauge 430 may be operatively coupled to the controller 500, and the controller 500 may include a memory (not illustrated) and a processor (not illustrated).

The memory may include a volatile memory of a static random access memory (S-RAM) and a dynamic random access (D-RAM) for temporarily storing data while electric power is being supplied, and a nonvolatile memory, such as a read only memory (ROM) and an erasable programmable read only memory (EPROM) for storing data even when the supply of the electric power is cut off.

The processor may include various logic circuits and operation circuits and may process data according to a program provided from the memory and generate a control signal according to a processing result.

The first pressure gauge 410 and the second pressure gauge 430 may be operatively coupled to the processor of the controller 500. That is, the first pressure gauge 410 may sense a first pressure of the feed water that flows between the circulation pump 400 and the transport layer 420 and transmit the first pressure to the processor, and the second pressure gauge 430 may sense a second pressure of the feed water that flows between the transport layer 420 and the ion filter 440 and transmit the second pressure to the processor.

The processor may calculate a difference between the first pressure and the second pressure, and when the difference between the first pressure and the second pressure is equal to or more than a specific reference pressure difference, may determine that the concentration of impurities precipitated by the transport layer 420 is equal to or more than a reference concentration. Here, the reference pressure difference may be a value of about 1.1 times the difference between a first initial value of the first pressure and a second initial value of the second pressure sensed by the first and second pressure gauges 410 and 430 at the beginning of the operation of the water electrolysis device 100, respectively.

In other words, when the difference between the first pressure and the second pressure during the operation of the water electrolysis device 100 increases to about 1.1 times or more than the difference between the first initial value of the first pressure and the second initial value of the second pressure, which is calculated at the beginning, the processor may determine that the impurities of a specific concentration or a specific amount or more are included in the feed water in the transport layer 420. Here, the beginning may be defined as a time point, at which the water electrolysis device 100 starts to be operated.

When the processor determines that a specific concentration or more of impurities are contained in the feed water, the processor may control the circulation pump 400 to stop the operation of the circulation pump 400, and the electric power supply unit 120 may control the electric power supply unit 120 to stop the supply of electric power to the water electrolysis stack 110. To this end, both the electric power supply unit 120 and the circulation pump 400 may be operatively coupled to the processor.

Furthermore, when the processor determines that the feed water contains a specific concentration or more of impurities, the processor may inform the user to replace the transport layer 420.

Meanwhile, the above-described first and second pressure gauges 410 and 430 may be components for detecting the pressures of the feed water in respective positions, but the present disclosure is not limited thereto, and they may be components for detecting flow rates in the respective positions, and the processor may estimate the amount or concentration of the impurities precipitated in the transport layer 420 through this difference between the flow rates.

Furthermore, the water electrolysis device 100 may include an ion conductivity sensor 460 that is provided between the transport layer 420 and the water electrolysis stack 110 to detect the ion conductivity of the feed water.

The ion conductivity sensor 460 may be provided between the ion filter 440 and the water electrolysis stack 110. The ion conductivity sensor 460 may have a higher sensitivity to positive and negative ion impurities than the supply sensor 450, the discharge sensor 210, and the tank sensor 220.

The general supply sensor 450, discharge sensor 210, and tank sensor 220 for measuring ion conductivities may be sensors that are provided with a positive electrode and a negative electrode to measure the ion conductivity of the feed water as the feed water flows through a pair of plates spaced apart from each other.

Unlike this, as illustrated in FIG. 2, the ion conductivity sensor 460 may include an electrolyte membrane 461 for contact as the feed water flows, a current source 462 that applies an alternating current to the electrolyte membrane 461, and a voltage sensor 463 that is connected to the electrolyte membrane 461 and is configured to sense a voltage between two points 463a and 463b, respectively.

In this case, fixing plates (not illustrated) for fixing the electrolyte membrane 461 may be provided on opposite sides of the electrolyte membrane 461 in an upward/downward direction, and a through-hole may be formed in any one of the fixing plates so that a portion of the feed water may contact the electrolyte membrane 461 through the through-hole. Preferably, the feed water flows on an upper side of the fixing plate located on an upper side of the electrolyte membrane 461, and a portion of the flowing feed water may contact the electrolyte membrane 461 through the through-hole.

An alternating current may be applied to the two points 462a and 462b of the current source 462 through the current source 462, in the electrolyte membrane 461 which the feed water contacts, and then, a potential difference between the two points 463a and 463b may be detected through the two points 463a and 463b of the voltage sensor 463.

In this case, a conversion resistance value “R” corresponding to the real number part of a value converted by the Nyquist Plot may be calculated from an AC resistance value by the alternating current applied to the electrolyte membrane 461. Nyquist Plot is a representation of a frequency function response of a linear system in a polar diagram.

The reason for calculating the conversion resistance value “R” corresponding to the real number part may be to calculate the ion conductivity of the feed water that contacts the electrolyte membrane 461 by using some embodiments that the resistance of the real number part in the high frequency area increases when generally the ionic impurities are introduced into the electrolyte membrane 461 formed of a PFSAO-based material.

(o) In this case, the ion conductivity “o” sensed by the ion conductivity sensor 460 may be defined as Equation 1.

σ = L RA [ Equation ⁢ 1 ]

In relation to Equation 1 described above, “L” may be a distance between the two points 463a and 463b of the voltage sensor 463, “R” may be a conversion resistance value corresponding to a real number part of a value converted by Nyquist Plot from an AC resistance value by the alternating current applied to the electrolyte membrane 461, and “A” may be an area “A” of the electrolyte membrane 461, which is defined in two directions that are perpendicular to one direction that connects the two points 463a and 463b of the voltage sensor 463.

That is, the ion conductivity detected by the ion conductivity sensor 460 may be calculated as the distance “L” between the two points 463a and 463b of the voltage sensor 463 for a product of the conversion resistance value “R” corresponding to the real number part of the value converted by the Nyquist Plot from the AC resistance value by the alternating current applied to the electric membrane 461 and an area “A” of the electrolyte membrane 461, which is defined by two directions that cross one direction that connects the two points 463a and 463b of the voltage sensor 463.

The electrolyte membrane 461 of the ion conductivity sensor 460 may be provided to be thinner than the inner electrolyte membrane (not illustrated) provided in an interior of the water electrolysis stack 110. This may be to relatively increase the sensitivity of the ion conductivity sensor 460.

The ion conductivity sensor 460 may be operatively coupled to the processor of the controller 500, as illustrated in FIG. 1. When the value of the ion conductivity sensed by the ion conductivity sensor 460 is equal to or less than a specific first reference conductivity, the processor may control the circulation pump 400 to stop the operation of the circulation pump 400 and may control the electric power supply unit 120 so that the electric power supply unit 120 stops supplying electric power to the water electrolysis stack 110.

Here, the value of the first reference conductivity may mean a value about 0.95 times the initial value of the ion conductivity. In other words, the processor may perform a control to stop the operations of the circulation pump 400 and the electric power supply unit 120 when the value of the ion conductivity sensed by the ion conductivity sensor 460 during the operation of the water electrolysis device 100 decreases about 0.95 times or less than the value of the ion conductivity initially sensed by the ion conductivity sensor 460 at the beginning. Here, the beginning may be defined as a time point, at which the water electrolysis device 100 starts to be operated.

Furthermore, when the value of the ion conductivity sensed by the ion conductivity sensor 460 during the operation of the water electrolysis device 100 decreases about 0.95 times or less than the value of the ion conductivity sensed by the ion conductivity sensor 460 at the beginning, the processor may inform the user to replace the electrolyte membrane 461.

Meanwhile, the water electrolysis device 100 may include a supply tank 470 that is connected to a point between the ion conductivity sensor 460 and the water electrolysis stack 110 therebetween on the supply pipeline 101 to accommodate carbon dioxide that is to be supplied to the feed water.

As illustrated in FIG. 3, the supply tank 470 may be connected to the supply pipeline 101 through the gas supply pipeline 472. The gas supply pipeline 472 may be a pipeline for supplying carbon dioxide contained in the supply tank 470 to the feed water supplied to the water electrolysis stack 110.

The water electrolysis device 100 (see FIG. 1) may be provided with an ejector 490 that is provided on the supply pipeline 101 to pump carbon dioxide together with feed water to the water electrolysis stack 110, and an opening/closing valve 480 that is disposed on the gas supply pipeline 472 and is provided between the ejector 490 and the supply pipeline 101.

The opening/closing valve 480 may be provided on the gas supply pipeline 472 to open and close a passage of the gas supply pipeline 472. The opening/closing valve 480 may be operatively coupled to a processor, and the processor may control the opening/closing valve 480 so that carbon dioxide is supplied from the supply tank 470 to the feed water when the value of the ion conductivity sensed by the ion conductivity sensor 460 is equal to or less than a specific second reference conductivity.

In this case, the value of the second reference conductivity may be provided to be greater than the value of the first reference conductivity described above. In other words, when the ion conductivity sensed by the ion conductivity sensor 460 is smaller than the value of the second ion conductivity, carbon dioxide may be supplied to the feed water. As an example, the value of the second reference conductivity may be about 0.97 times the initial value of the ion conductivity.

the feed water “w” is to help recover the performance of the water electrolysis stack 110 because H+, HCO3−, and CO2 may be generated when carbon dioxide is supplied to the feed water, and H+ may exchange ions with the electrode of the water electrolysis stack 110 or the ionic impurities in the inner electrolyte membrane so that the ionic impurities may be discharged to the outside of the water electrolysis stack 110 while not being accommodated in the water electrolysis stack 110.

Thereafter, the pressure of carbon dioxide supplied to the feed water is sensed by a gas supply sensor 471, and when the pressure of carbon dioxide is lower than the pressure of the feed water, the processor may notify the user of filling of carbon dioxide.

According to the above-described structure, because the amount of impurities in the water may be efficiently reduced due to the transport layer 420 before the feed water is supplied to the water electrolysis stack 110, the durability and performance of the water electrolysis stack 110 may be improved.

Furthermore, the durability and performance of the water electrolysis stack 110 may be improved by estimating the amount or concentration of impurities precipitated in the transport layer 420 through the first and second pressure gauges 410 and 430 to cut off the electric power supplied to the water electrolysis stack 110 or preventing the feed water from being introduced into the water electrolysis stack 110.

Furthermore, by more accurately measuring the ion conductivity in the feed water by using the ion conductivity sensor 460, the durability and performance of the water electrolysis stack may be improved by cutting off the electric power supplied to the water electrolysis stack 110 or preventing the feed water from being introduced into the water electrolysis stack 110.

FIG. 4 is a schematic view of a water electrolysis device according to some embodiments of the present disclosure.

Referring to FIG. 4, the transport layer 420, the ion filter 440, and the ion conductivity sensor 460 may be provided in parallel with the supply pipeline 101, respectively, rather than a structure, in which the transport layer 420, the ion filter 440, and the ion conductivity sensor 460 are connected in series to each other on the supply pipeline 101 as in the water electrolysis device 100 of FIG. 1.

According to this structure, the transport layer 420 and the ion filter 440 may be used only when it is necessary according to the conditions of the feed water that flows through the supply pipeline 101. Accordingly, compared to the transport layer 420 and the ion filter 440 of the water electrolysis device 100 illustrated in FIG. 1, the lifespan of each of the transport layer 420 and the ion filter 440 may be improved.

For configurations other than those of the transport layer 420, the ion filter 440, and the ion conductivity sensor 460 of FIG. 4, the description of FIG. 1 will be used.

FIGS. 5 and 6 are flowcharts illustrating a method of controlling a water electrolysis device according to some embodiments of the present disclosure.

Referring to FIGS. 5 and 6, when the operation of the water electrolysis device 100 (see FIG. 1) starts (S10), a method for controlling the water electrolysis device 100 may include a preparation operation (S20), a supply operation (S30), and a pressure calculating operation (S40).

The preparation operation (S20) may be an operation of preparing the transport layer 420 on an upstream side of the water electrolysis stack 110 with respect to a flow direction of the feed water. The supply operation (S30) may be an operation of supplying the feed water to the water electrolysis stack 110 so that the feed water passes through the transport layer 420 provided on an upstream side of the water electrolysis stack 110. The supply operation (S30) may be an operation of filtering out impurities contained in the feed water through the transport layer 420.

The pressure calculating operation (S40) may be an operation of calculating the first pressure of the feed water sensed by the first pressure gauge 410 provided on the upstream side of the transport layer 420 and the second pressure of the feed water sensed by the second pressure gauge 410 provided between the transport layer 420 and the water electrolysis stack 110 to estimate the amount of the impurities filtered out by the transport layer 420.

The method for controlling the water electrolysis device 100 may include a pressure comparing operation (S50) for determining whether the pressure difference between the first pressure and the second pressure calculated in the pressure calculating operation (S40) is equal to or more than a specific reference pressure. Here, the reference pressure may be a pressure value of about 1.1 times the difference between the first initial value of the first pressure and the second initial value of the second pressure.

When the pressure difference between the first pressure and the second pressure in the pressure comparing operation (S50) is equal to or more than the reference pressure (the example of S50), according to the method for controlling the water electrolysis device 100, a first stop operation (S60) of stopping electric power to the water electrolysis stack 110 or stopping the supply of the feed water to the water electrolysis stack 110 may be performed.

Furthermore, when the difference between the first pressure and the second pressure in the pressure comparing operation (S50) is equal to or more than the reference pressure (Yes of S50), a filter notification operation (S70) of informing the user of the need to replace the transport layer 420 may be performed.

The filter notifying operation (S70) may be performed after the first stop operation (S60), but the filter notifying operation (S70) may be performed before the first stop operation (S60), and the first stop operation (S60) and the filter notifying operation (S70) may be performed simultaneously.

When the pressure difference between the first pressure and the second pressure in the pressure comparing operation (S50) is less than the reference pressure difference (No in S50), a sensing operation (S80) may be performed in the method for controlling the water electrolysis device 100.

The sensing operation (S80) may be an operation of sensing the ion conductivity of the feed water by using the ion conductivity sensor 460 provided between the second pressure gauge 430 and the water electrolysis stack 110.

After the sensing operation (S80), in the method for controlling the water electrolysis device 100, a first ion conductivity determining operation (S90) of determining whether the ion conductivity sensed by the sensing operation (S80) is equal to or less than a specific first ion conductivity may be performed. Here, the first ion conductivity may be a value of about 0.95 times the initial value of the ion conductivity sensed by the ion conductivity sensor 460.

When the ion conductivity sensed in the sensing operation (S80) is equal to or less than the first ion conductivity (Yes of S90), a second stop operation (S100) of stopping electric power to the water electrolysis stack 110 or stopping supplying the feed water to the water electrolysis stack 110 may be performed in the method for controlling the water electrolysis device 100.

Furthermore, when the ion conductivity sensed by the sensing operation (S80) is equal to or less than the first ion conductivity (Yes of S90), in the method for controlling the water electrolysis device 100, an electrolyte membrane notification operation (S110) of informing the user to replace the electrolyte membrane 461 included in the ion conductivity sensor 460 may be performed.

The electrolyte membrane notifying operation (S110) may be performed after the second stop operation (S100), but the electrolyte membrane notifying operation (S110) may be performed before the second stop operation (S100), and the second stop operation (S100) and the electrolyte membrane notifying operation (S110) may be performed simultaneously.

If the ion conductivity sensed in the sensing operation (S80) is greater than the first ion conductivity (No in S90), in the method for controlling the water electrolysis device 100, the second ion conductivity determining operation (S120) may be performed.

The ion conductivity determining operation (S120) may be an operation of determining whether the ion conductivity sensed in the sensing operation (S80) is equal to or less than a specific second ion conductivity. Here, the second ion conductivity may be a value that is provided to be larger than the value of the first ion conductivity. As an example, when a value of the first ion conductivity is about 0.95 times the value of the initial ion conductivity, a value of the second ion conductivity may be about 0.97 times the value of the initial ion conductivity.

When the ion conductivity sensed by the sensing operation (S80) is equal to or less than the second ion conductivity (Yes of S120), a gas supply operation (S130) may be performed in the method for controlling the water electrolysis device 100.

The gas supply operation (S130) may be an operation of supplying carbon dioxide to the feed water from the supply tank 470 connected to a point between the ion conductivity sensor 460 and the water electrolysis stack 110. The reason for supplying carbon dioxide to the feed water may be to remove impurities in the interior of the water electrolysis stack 110 as described above.

In the method for controlling the water electrolysis device 100, the gas pressure comparing operation (S140) may be performed after the gas supply operation (S130). The gas pressure comparing operation (S140) may be an operation of comparing the pressure of carbon dioxide supplied from the gas supply operation (S130) and the pressure of feed water.

In the method of controlling the water electrolysis device 100, when the pressure of carbon dioxide in the gas pressure comparing operation (S140) is lower than the pressure of feed water (Yes of S140), the filling notification operation (S150) may be performed.

The filling notifying operation (S150) may be an operation of notifying the user to fill the carbon dioxide when the pressure of the carbon dioxide supplied from the gas supply operation (S130) is lower than the pressure of the feed water (Yes of S140).

The method for controlling the water electrolysis device 100 may be ended (S160) after the filling notification operation (S150) or when it corresponds to No of the second ion conductivity determining operation (S120), or No of the gas pressure comparing operation (S140).

The effects according to the method for controlling the water electrolysis device 100 will be replaced by the above description.

According to the present technology, when the amount of impurities in the feed water that flows into the water electrolysis stack is equal to or more than a specific amount due to the transport layer located on an upstream side of the water electrolysis stack, the electric power of the water electrolysis stack may be cut off or the circulation of the feed water is stopped, so that the stability of the water electrolysis stack may be improved.

In addition, according to the present technology, usability may be improved because an exchange timing of the transport layer may be recognized by using the first and second pressure gauges located on the upstream and downstream sides of the transport layer.

In addition, due to the ion conductivity sensor having an improved sensitivity, the safety of the water electrolysis device may be improved.

In addition, according to the present technology, because an exchange timing of the electrolyte membrane included in the ion conductivity sensor may be recognized by using the ion conductivity sensor, the usage may be improved.

In addition, according to the present technology, because carbon dioxide may be supplied to the feed water by using the ion conductivity sensor, the safety of the water electrolysis device may be improved.

In addition, according to the present technology, because an exchange timing of carbon dioxide may be recognized when the pressure of the carbon dioxide is lower than the pressure of the feed water, the usage may be improved.

Besides, a variety of effects directly or indirectly understood through the present disclosure may be provided.

The above description is merely an example of the technical idea of the present disclosure, and various modifications and variations may be made by one skilled in the art without departing from the essential characteristic of the present disclosure.

Accordingly, embodiments of the present disclosure are intended not to limit but to explain the technical idea of the present disclosure, and the scope and spirit of the present disclosure is not limited by the above embodiments. The scope of protection of the present disclosure should be construed by the attached claims, and all equivalents thereof should be construed as being included within the scope of the present disclosure.