Water electrolysis system having power supply control function for protecting water electrolysis stack from instability of renewable energy power

Abstract

The present technology relates to a water electrolysis system having a power supply control function capable of protecting a water electrolysis stack from instability of renewable energy power. The water electrolysis system comprises: a renewable energy production device for producing renewable energy; a renewable energy storage device for storing the produced renewable energy; a water electrolysis device for electrolyzing water by using at least one of the renewable energy and stored energy supplied from the renewable energy storage device; a gas storage device for storing gas produced by electrolysis in the water electrolysis device; and a power supply control device which controls power supply to the water electrolysis device so as to, if a gradient of power change of the renewable energy is greater than a preset power increase reference gradient, charge the renewable energy storage device by distributing at least a portion of the renewable energy, and if the gradient of power change of the renewable energy is less than a preset power decrease reference gradient, supplement the renewable energy by distributing at least a portion of the stored energy of the renewable energy storage device.

Description

A water electrolysis system equipped with a power supply control function to protect the water electrolysis stack from the instability of renewable energy power.

[0001] The present invention relates to a water electrolysis system having a power supply control function capable of protecting electrodes of a water electrolysis stack using renewable energy power, and more particularly, to a water electrolysis system having a power supply control function capable of protecting electrodes in a water electrolysis stack by charging or discharging an added battery when a sudden or sudden decrease in power is supplied to the water electrolysis stack.

[0002] Water electrolysis is a technology that uses electrolysis to produce oxygen and hydrogen, particularly hydrogen. Recently, attention has been focused on utilizing renewable energy sources like solar and wind power to purify the electricity used for electrolysis.

[0003] The use of renewable energy as a power source has brought about many changes in the operation of electrolysis systems.

[0004] First, the difficulty of controlling operating pressure and differential pressure has increased. Unlike conventional grid power supply conditions that provided a constant power supply, renewable energy produces irregular power, which in turn leads to irregular power supply to the electrolysis system. Consequently, the gas production of the electrolysis system also becomes irregular due to the irregular power supply, increasing the difficulty of system control to maintain the corresponding differential pressure and operating pressure.

[0005] Meanwhile, to maintain high-purity hydrogen production, purification devices such as Pressure Swing Absorption (PSA) or Temperature Swing Absorption (TSA) are being installed downstream of electrolysis systems. Since these purification devices operate at a minimum pressure of 5 bar, it is desirable for the electrolysis system's operating pressure to match the pressure required by the purification devices.

[0006] In this case, when the electrolysis system operates at a high operating pressure, if the power supplied to the electrolysis system decreases, the operating pressure also drops rapidly, and the operating efficiency of the purification device also drops sharply, so the difficulty of controlling the operating pressure and differential pressure of the electrolysis system increases further.

[0007] Second, the use of renewable energy as a power source has expanded the scope of power supply that must be addressed, unlike grid power supply conditions. In particular, gas crossover, which can occur in low-power supply areas, must be prevented. If the ratio of hydrogen mixed with oxygen exceeds 4% due to gas crossover, the risk of explosion significantly increases. Therefore, the hydrogen-to-oxygen ratio is typically maintained within 2%, half the explosion threshold.

[0008] Typically, commercial membranes used in alkaline water electrolysis prevent gas mixing. However, due to the formation of microscopic physical pores, gases still mix at a minimal, constant rate. This rate is greater when a small amount of hydrogen gas produced with low power mixes with a small amount of oxygen gas, rather than when hydrogen gas produced with high power mixes with oxygen gas. Therefore, expanding the power operating range of a water electrolysis system by applying technology that prevents hydrogen gas crossover is one way to lower the cost of hydrogen production.

[0009] Third, due to the nature of renewable energy generation, power can be intermittent, which can negatively impact key materials within the electrolysis stack. Specifically, for electrodes, which have a significant impact on electrolysis performance, a sudden increase in the supplied power can cause phase changes or structural collapse in the electrode catalyst. Conversely, a sudden decrease in the supplied power or a power interruption can generate reverse current, leading to electrode deterioration. Because electrodes account for a significant portion of the overall production cost of the electrolysis system, and because electrode performance cannot be restored once degraded, technologies for preventing electrode deterioration are crucial.

[0010] Recently, a battery system has been added to the electrolysis system in conjunction with renewable energy, which serves as an emergency power generation system to prevent the electrolysis system from shutting down in the event of a power outage.

[0011] As an example of a water electrolysis system for this purpose, reference may be made to Patent Publication No. 10-2023-0117930 (August 10, 2023) (Title: Water electrolysis system linked to renewable energy production device) (hereinafter referred to as “prior art”).

[0012] The above-described prior art relates to a water electrolysis system linked to a renewable energy production device, which can stably control the water electrolysis device even in an emergency operation, wherein the water electrolysis system includes: a renewable energy production device that produces first electricity; an electrolysis device that uses the first electricity to decompose water vapor to produce hydrogen; a buffer tank that stores hydrogen produced by the electrolysis device; a fuel cell connected to the buffer tank; and an auxiliary device (BOP, Balance of Plant) connected to the electrolysis device to control the operation of the electrolysis device. In addition, the electrolysis system is implemented such that, during normal operation, the auxiliary device operates based on the first electricity produced by the renewable energy production device to operate the electrolysis device, and in an emergency situation, the fuel cell produces second electricity using the hydrogen stored in the buffer tank, and the auxiliary device operates based on the second electricity produced by the fuel cell to stop the operation of the electrolysis device.

[0013] According to these conventional electrolysis systems, the power supply to the electrolysis device is diversified by sharing renewable energy, uninterruptible power supplies (UPS), and fuel cells, but this is only to respond to emergency situations such as EDS.

[0014] The present invention aims to provide a water electrolysis system having a power supply control function that can stably maintain power supply by utilizing an energy storage device and further protect electrodes within a water electrolysis stack when renewable energy power is supplied rapidly or rapidly to the water electrolysis stack.

[0015] The present invention provides a water electrolysis system, comprising: a renewable energy production device that produces renewable energy; a renewable energy storage device that stores the generated renewable energy; a water electrolysis device that electrolyzes water using at least one of the renewable energy and the storage energy supplied from the renewable energy storage device; a gas storage device that stores gas produced by electrolysis in the water electrolysis device; and a power supply control device that controls the power supply to the water electrolysis device, such that (1) when a slope of a power change of the renewable energy is greater than a preset power increase reference slope, at least a portion of the renewable energy is distributed to charge the renewable energy storage device, and (2) when a slope of a power change of the renewable energy is less than a preset power decrease reference slope, at least a portion of the storage energy of the renewable energy storage device is distributed to replenish the renewable energy.

[0016] Meanwhile, the power supply control device can control the power supply to the water electrolysis device so that (3) when the pressure change slope of the gas stored in the gas storage device is greater than a preset pressure increase reference slope, at least a portion of the renewable energy is distributed to charge the renewable energy storage device, and (4) when the pressure change slope of the gas stored in the gas storage device is less than a preset pressure increase reference slope, at least a portion of the stored energy of the renewable energy storage device is distributed to supplement the renewable energy.

[0017] In addition, the power supply control device can control the power supply to the electrolyzer so as to distribute at least a portion of the renewable energy to charge the renewable energy storage device when (3') the slope of the power change of the renewable energy is greater than a preset power increase reference slope or the slope of the pressure change of the gas produced in the electrolyzer is greater than a preset pressure increase reference slope, and the energy storage amount of the renewable energy storage device is equal to or lower than a predetermined upper limit, and (4') when the slope of the power change of the renewable energy is less than a preset power decrease reference slope or the slope of the pressure change of the gas produced in the electrolyzer is less than a preset pressure decrease reference slope, and the energy storage amount of the renewable energy storage device is equal to or higher than a predetermined lower limit, and the power supply to the electrolyzer can be distributed at least a portion of the stored energy of the renewable energy storage device to replenish the renewable energy.

[0018] Additionally, the power supply control device can adjust the preset pressure rise reference slope to increase as the energy storage amount of the renewable energy storage device approaches the upper limit value.

[0019] The present invention provides the following advantages by enabling the battery system to distribute / supplement rapidly increasing or decreasing power in the form of charging / discharging when power from renewable energy is supplied to an electrolysis stack.

[0020] First, by distributing renewable energy power at a certain rate so that the batteries are charged when the renewable energy power surges, the power produced from renewable energy can be charged to the batteries without being wasted, which can have the effect of preventing a decrease in system efficiency.

[0021] Second, when the power of renewable energy is rapidly reduced, by discharging the battery and replenishing the power of renewable energy at a certain rate, it can serve as a kind of buffer that prevents the operating pressure of the high-pressure electrolysis system from rapidly decreasing, and can have the effect of preventing the hydrogen purification efficiency of the hydrogen purification equipment from deteriorating due to a rapid decrease in the operating pressure.

[0022] Third, by mitigating the rapid fluctuations in the power supplied to the electrolysis system, the phenomenon of the pressure of the hydrogen produced rising or falling rapidly is resolved, and the difficulty of controlling the operating pressure and differential pressure of the electrolysis system is also reduced.

[0023] FIG. 1 is a block diagram briefly showing the overall structure of a water electrolysis system having a power supply function capable of protecting a water electrolysis stack from the instability of renewable energy power according to one embodiment of the present invention.

[0024] FIG. 2 is a graph showing power supply control when the power of renewable energy increases rapidly, according to one embodiment of the present invention.

[0025] FIG. 3 is a graph showing power supply control when the power of renewable energy drops sharply, according to one embodiment of the present invention.

[0026] FIG. 4 is a flowchart showing a method for controlling electrolysis power supply by a electrolysis system having a power supply control function according to one embodiment of the present invention.

[0027] Hereinafter, a water electrolysis system having a power supply control function capable of protecting a water electrolysis stack from instability of renewable energy power according to embodiments of the present invention will be described in detail with reference to the attached drawings.

[0028] In the drawings below, the same reference numerals denote the same components. The sizes of each component in the drawings may be exaggerated for clarity and understanding of the description. In addition, the embodiments described below are merely exemplary, and various additional modifications are possible. In the description of each component in this specification, unless there is a description that clearly designates the order of arrangement with respect to each other, each component may be arranged in any suitable order. Similarly, in the description of steps for performing a specific function in this specification, unless there is a description that clearly designates the order, each step may be performed in any suitable order. In addition, the singular expression may include the plural expression unless the context clearly indicates otherwise, and the referent terms "above" and similar referent terms may apply to both the singular and the plural. In addition, terms such as "part," "member," "module," "means," "apparatus," and "device" described in the specification mean a unit that processes at least one function or operation, which may be implemented with only hardware, only software, or a combination of hardware and software. Lines connecting components or related elements illustrated in the drawings are merely representative of functional, physical, and / or circuit connections, and actual implementations may include various functional, physical, and / or circuit means that may be replaced or added. The use of all examples or exemplary terms is for the sole purpose of describing the technical idea of ​​the invention, and the scope of the invention should not be limited by such examples or exemplary terms, unless otherwise defined by the claims.

[0029] First, referring to FIG. 1, a water electrolysis system including a power supply function capable of protecting a water electrolysis stack from the instability of renewable energy power according to one embodiment of the present invention is briefly described.

[0030] Referring to the drawings, a water electrolysis system according to an embodiment of the present invention may include a renewable energy production device (10), a renewable energy storage device (30), a rectifier (20), a water electrolysis device (or a water electrolysis stack) (50), a pure water supply device (62), an electrolyte circulation device (64), a gas purification device (70), a gas storage device (80), and a power supply control device (40).

[0031] A renewable energy production device (10) generates electric energy from various energy sources such as solar power, wind power, hydropower, and nuclear power.

[0032] The renewable energy storage device (30) can be understood as an ESS and can store electric energy generated by a renewable energy production device (10). The renewable energy storage device (30) can be referred to as a battery. In addition, the renewable energy storage device (30) can supply stored power to a connected device, for example, under the control of a power supply control device (40).

[0033] The rectifier (20) is configured to convert electric energy produced by the renewable energy production device (10) into a direct current voltage of a specific voltage. The rectifier (20) may include a voltage / current measurement function capable of measuring the voltage and / or current of the electric energy being input or output.

[0034] The electrolysis device (50) electrolyzes water using applied electrical energy (or, power) to produce hydrogen and oxygen. The electrolysis device (50) according to the present invention can be configured to operate basically using power produced by a renewable energy production device (10), and, if necessary, can additionally operate by receiving power from a renewable energy storage device (30), for example, under the control of a power supply control device (40).

[0035] The pure water supply unit (62) and the electrolyte circulation unit (64) may be referred to as a BOP (Balance of Plant). The BOP may also include various equipment and instruments for the smooth operation of the electrolysis stack (50). The electrolyte may be pure water or water diluted with potassium hydroxide / sodium hydroxide. The pure water and / or electrolyte may be referred to as feed.

[0036] The BOP may include a pump for circulating pure water and / or electrolyte, a heat exchanger for managing the temperature of the feed, a filter for filtering impurities from the feed, a measuring device for measuring the circulation flow rate, temperature, impurity concentration, etc. of the feed, and a controller for controlling the above equipment.

[0037] The gas purification device (70) purifies oxygen and / or hydrogen generated in the electrolysis device (50). In the present invention, the generation of hydrogen gas is described as an example, and therefore, the gas purification device (70) may refer to a hydrogen purification device. The gas purification device (70) may include a pressure measurement function capable of measuring the pressure of the input hydrogen gas or the pressure of the hydrogen gas output after purification.

[0038] The gas storage device (80) stores oxygen and / or hydrogen gas that has been purified after being generated in the electrolysis device (50).

[0039] The power supply control device (40) is a key element that implements the function of protecting the electrolysis stack (50) from the instability of renewable energy power by the electrolysis system according to the present invention, and functions as follows.

[0040] (1) Basically, the power produced by the renewable energy production device (10) is supplied to the electrolysis device (50). Thus, in normal times, the electrolysis device (50) operates by the renewable energy being produced in real time.

[0041] (2) When the slope of the power change of renewable energy is detected to change more than the preset power increase reference slope, i.e., when the power produced increases rapidly, the power supply control device (40) distributes at least a portion of the power produced by the renewable energy production device (10) and supplied to the electrolysis device (50) and supplies it to the renewable energy storage device (30), thereby charging the renewable energy storage device (30).

[0042] (3) Meanwhile, when the slope of the power change of renewable energy becomes smaller than the preset power decline reference slope, i.e., when the power produced decreases rapidly, the power supply control device distributes at least a portion of the stored power (or stored energy) by discharging the renewable energy storage device (30), so that the power produced by the renewable energy production device (10) and the power discharged from the renewable energy storage device (30) are simultaneously supplied to the electrolysis device (50).

[0043] The gas purification device (70) may include a DEOXO system for removing oxygen from hydrogen, or a PSA (Pressure Swing Absorption) or TSA (Temparature Swing Absorption) system for removing moisture.

[0044] The gas purification device (70) may include a gas-liquid separator for physically separating the feed and product (oxygen gas and / or hydrogen gas), a heat exchanger and condenser for condensing moisture contained in the produced gas, a demi-filter for removing fine moisture in the gas, a measuring device for measuring the pressure, circulation flow rate, temperature, moisture content, etc. of the product, and a controller for controlling the above equipment.

[0045] A differential pressure gauge is a device that measures pressure differences. It can measure the pressure difference between the oxygen-side gas-liquid separator and the hydrogen-side gas-liquid separator. A pressure gauge is a device that measures pressure. It can measure pressure within a water electrolysis system, including a gas-liquid separator. A level gauge or differential pressure gauge can be used as a measuring means for the pressure-raising process up to the set pressure and for all differential pressure control. A control valve is a device that regulates pressure. Control valves can include flow control valves, on / off valves, etc.

[0046] The method for controlling the operation of the control valve can be programmed and executed by PID or a preset operation method. The control method includes, for example, in a water electrolysis system operating under preset operating pressure and differential pressure conditions, when additional power is supplied to the water electrolysis stack (50), the amount of gas produced increases and the gas pressure simultaneously increases, thereby controlling the opening rate of the pressure control valve to increase, and conversely, when the power supplied to the water electrolysis stack (50) decreases, the amount of gas produced decreases and the gas pressure simultaneously decreases, thereby controlling the opening rate of the pressure control valve to decrease.

[0047] In sections where the power supply is constant, the pressure control valve that controls the flow of oxygen and hydrogen can also maintain a constant opening rate, but if the power supply fluctuates, the pressure control valve's opening rate also fluctuates.

[0048] For example, when the power supply increases, the amount of gas produced increases, which increases the operating pressure, and therefore the pressure regulating valve is adjusted to open the maintained opening value. When the power supply decreases, the amount of gas produced decreases, which reduces the operating pressure, and therefore the pressure regulating valve is adjusted to decrease the maintained opening value.

[0049] In particular, in the case of a water electrolysis system that uses renewable energy such as solar and wind power, the power supplied to the water electrolysis stack (50) may fluctuate rapidly.

[0050] If a sudden power drop occurs, as mentioned above, the pressure regulating valve will adjust the valve opening rate in the closing direction to maintain the pressure within the gas purification device (70). As a result, the decreasing operating pressure will rise again, allowing the set operating pressure to be maintained.

[0051] Control performed by the power supply control device (40) during a sudden power surge can be understood with reference to the graph of FIG. 2 and steps (S23) to (S27) of FIG. 4.

[0052] The slope value (S) derived from the power change value over time RE ) is the user-preset reference slope value (S SET ) is greater than, a buffer function can be implemented for power surges by charging the battery (i.e., a renewable energy storage device). At this time, the set slope value (S SET ) can be changed depending on the condition of the user's electrolysis stack (50) or system.

[0053] The rapid increase in power generation from renewable energy can be detected not only by the slope derived from the power values ​​over time, but also by the increase in pressure of the gas produced.

[0054] After determining whether a power surge has occurred through a power gradient or pressure increase, etc., it is possible to check whether the battery (30) has sufficient spare capacity to receive power in order to store a portion of the increased power in the battery (30). For example, if the battery (30) is below a predetermined upper limit, it can be determined that it has sufficient spare capacity to receive power. The upper limit may be 90%.

[0055] If the battery (30) has sufficient spare capacity to receive the rapidly increasing power, the battery (30) can be charged by the power distributed at a certain rate. On the other hand, if the battery (30) does not have sufficient spare capacity, the battery may already be sufficiently charged, and thus battery charging may be stopped to protect the battery (30).

[0056] For example, when the charge level of the battery (30) is less than 90%, it can be charged by distributing renewable energy. In addition, the battery (30) can absorb rapidly increasing renewable energy until the charge level reaches 90%.

[0057] The power distributed to the battery (30) can be calculated as follows.

[0058] P CH = |P Re - P Re-n | / S SET

[0059] Here, P CH is the power charged to the battery (30), and P RE is the electricity generated from renewable energy, and P RE-n is the power of renewable energy produced n seconds ago, and S SET is the reference slope value of the power increase change preset by the user.

[0060] Whether the battery is charged or stopped can be determined based on whether the battery's (30) charge level is within a preset range. For example, if the battery's (30) charge level is within a range of 10% to 90%, the battery (30) can be used to buffer a sudden increase or decrease in renewable energy.

[0061] In this way, by controlling the battery charging time and charging timing, the power fluctuation of the renewable energy that rapidly increases in the electrolysis stack (50) can be smoothly controlled, thereby protecting the core components within the electrolysis stack (50).

[0062] Meanwhile, in the case of charging the battery (30) due to a rapid increase in renewable energy, the degree of distributed power may change depending on the battery state of charge (SoC). For example, if the SoC is sufficiently low, power of an arbitrary standard degree may be distributed, but if the SoC is charged near a preset upper limit, a preset standard slope value (S) of the power increase change may be distributed to protect the battery. SET ) can be adjusted to increase the size.

[0063] Meanwhile, the control performed by the power supply control device (40) in the event of a sudden power drop can be understood with reference to the graph of FIG. 3 and steps (S31) to (S35) of FIG. 4.

[0064] Figure 3 corresponds to a case where the production of renewable energy rapidly decreases, the power supplied to the electrolysis stack (50) rapidly decreases, and the production of gas rapidly decreases, resulting in a decrease in operating pressure.

[0065] When a sudden power drop occurs from renewable energy, this is detected by the power supply control device (40), and the stored power in the battery (30) is discharged at a certain rate to supply additional power to the electrolysis stack (50). This alleviates the phenomenon of a sudden drop in power supply from the electrolysis stack (50).

[0066] That is, the slope value (S) derived by the power change value over time RE ) is the user-preset reference slope value (S SET ) is smaller than, a buffer function is implemented for a sudden power drop by discharging the battery (30).

[0067] At this time, the user presets the reference slope value (S SET ) can be changed depending on the condition of the user's electrolysis stack (50) or system.

[0068] The rapid decline in power output from renewable energy can be detected not only by the slope derived from power values ​​over time, but also by a decrease in pressure values ​​measured in gas purification units.

[0069] After determining whether there is a sudden drop in power through a power gradient or pressure drop, the current charge level of the battery (30) can be checked to supplement the suddenly dropped power.

[0070] If the capacity of the battery (30) is maintained above the lower limit and thus has sufficient power to compensate for the rapidly decreasing power, the battery (30) may discharge at a certain rate. On the other hand, if the capacity of the battery (30) is lower than the lower limit, battery discharge may be stopped to protect the battery (30). The lower limit of the battery capacity may be 10%.

[0071] The discharge rate of the battery can be calculated as follows:

[0072] P DIS = |P Re - P Re-n | / S SET

[0073] Here, P DIS is the power discharged from the battery (30) and distributed to the electrolysis stack (50), and P RE is the electricity generated from renewable energy, and P RE-n is the power of renewable energy produced n seconds ago, and S SET is the reference slope value of the power reduction change preset by the user.

[0074] Discharging of the battery (30) can continue until the charge level of the battery (30) reaches the lower limit.

[0075] Meanwhile, according to the present invention, power supply can be controlled based on a value measured by the pressure of the gas (e.g., hydrogen gas) produced, as well as a sudden increase or decrease in the amount of power produced by renewable energy.

[0076] For example, if the pressure of the gas being produced increases above the reference pressure or the slope of the pressure increase is greater than the preset pressure increase reference slope, it can be determined that the power of the renewable energy being produced and supplied has increased rapidly, and at this time, as described above, at least a portion of the renewable energy can be distributed to charge the renewable energy storage device (30).

[0077] Conversely, if the pressure of the gas produced is lower than the reference pressure or the pressure change slope of the gas is smaller than the preset pressure drop reference slope, it can be determined that the production of the renewable energy has decreased rapidly, and in this case, as described above, the renewable energy storage device (30) can be discharged to distribute at least a portion of the stored energy and supply it to the electrolysis stack.

[0078] The method for determining charge / discharge of a battery in a water electrolysis system according to the present invention can utilize the difference between the current (real-time) differential pressure value and the differential pressure value measured several seconds or tens of seconds ago. The difference between the two values ​​can be expressed as a quadratic function in the form of y=ax, where the value of y is the real-time differential pressure value minus the differential pressure value measured several seconds or tens of seconds ago, and x represents time. At this time, the degree to which the power of renewable energy suddenly rises or falls can be compared through the calculated slope value (a), and thereby it can be determined whether to charge or discharge the battery.

[0079] Figure 4 is a flowchart illustrating a method for controlling the supply of electrolysis power by a electrolysis system equipped with a power supply control function according to one embodiment of the present invention. Referring to this flowchart, the control operation of a electrolysis system equipped with a power supply control function capable of protecting a electrolysis stack (50) from the instability of renewable energy power according to the present invention will be described.

[0080] The electrolysis system is activated, and at the same time, the power supply control device (40) according to the present invention begins operation (S10). The following steps correspond to the algorithm processed by the power supply control device (40).

[0081] It is determined whether the charge amount (SoC) of the current renewable energy storage device (30) is lower than the charge reference value (e.g., 20%) (S21), and if it is lower than the charge reference value ('No' in S21), the produced renewable energy can be used to charge the storage device (30).

[0082] Meanwhile, if the charge amount of the storage device (30) is greater than the reference value ('Yes' in S21), the power supply control function for the subsequent electrolysis stack (50) is performed.

[0083] The real-time power fluctuation slope (SRE) of renewable energy over time and the power increase reference slope (SSET) preset by the user can be compared (S23), and if the real-time power fluctuation slope (SRE) is greater than the reference slope (SSET) ('Yes' in S23), it is determined that renewable energy is rapidly increasing, and it is determined whether to distribute renewable energy to charge the storage device (30).

[0084] If the current charge amount (SoC) of the storage device (30) is below the upper limit ('Yes' in S24), a portion of the rapidly increasing power of renewable energy is distributed and charged to the storage device (30) (S26). On the other hand, if the current charge amount (SoC) of the storage device (30) is higher than the upper limit, charging of the storage device (30) is stopped (S25).

[0085] Meanwhile, the distribution of power to the storage device (30) can continue as long as it conforms to the following formula (S27).

[0086]

[0087] Meanwhile, if the slope of the power fluctuation amount (SRE) of renewable energy over time is less than the power rising reference slope (SSET) preset by the user ('No' in S23), the real-time fluctuation amount slope is less than the preset power falling reference slope ('-S SET ' or 'S SET If it is less than ('Yes' of S31), it is determined that the renewable energy is rapidly decreasing, and it is determined whether to distribute the energy stored in the storage device (30) to the electrolysis stack (50).

[0088] If the current charge of the storage device (30) is greater than the lower limit ('Yes' in S32), the storage device (30) is discharged and supplied to the electrolysis stack (50) (S33).

[0089] Power discharge by the storage device (30) can continue while conforming to the following formula (S35).

[0090]

[0091] Meanwhile, if the current charge of the storage device (30) is lower than the lower limit ('No' of S32), the discharge of the storage device (30) is stopped.

Claims

1. A renewable energy production device that produces renewable energy; A renewable energy storage device that stores the generated renewable energy; A water electrolysis device that electrolyzes water using at least one of the renewable energy and the storage energy supplied from the renewable energy storage device; A gas storage device for storing gas produced by electrolysis in the above electrolysis device; and A water electrolysis system, comprising: a power supply control device that controls the power supply to the water electrolysis device so as to supply the renewable energy to the water electrolysis device, wherein (1) when the slope of the power change of the renewable energy is greater than a preset power increase reference slope, at least a portion of the renewable energy is distributed to charge the renewable energy storage device, and (2) when the slope of the power change of the renewable energy is less than a preset power decrease reference slope, at least a portion of the stored energy of the renewable energy storage device is distributed to replenish the renewable energy.

2. In paragraph 1, The above power supply control device, (3) If the pressure change gradient of the gas stored in the gas storage device is greater than the preset pressure increase reference gradient, at least a portion of the renewable energy is distributed to charge the renewable energy storage device, and (4) A water electrolysis system characterized in that when the pressure change gradient of the gas stored in the gas storage device is smaller than a preset pressure increase reference gradient, the power supply to the water electrolysis device is controlled so as to supplement the regenerative energy by distributing at least a portion of the stored energy of the regenerative energy storage device.

3. In paragraph 2, The above power supply control device, (3') If the slope of the power change of the renewable energy is greater than the preset power increase standard slope or the slope of the pressure change of the gas produced in the electrolysis device is greater than the preset pressure increase standard slope, and if the energy storage capacity of the renewable energy storage device is below a predetermined upper limit value, at least a portion of the renewable energy is distributed to charge the renewable energy storage device, and (4') A water electrolysis system characterized in that when the slope of the power change of the renewable energy is less than a preset power drop reference slope or the slope of the pressure change of the gas produced in the water electrolysis device is less than a preset pressure drop reference slope, and when the energy storage amount of the renewable energy storage device is equal to or greater than a predetermined lower limit, the power supply to the water electrolysis device is controlled to supplement the renewable energy by distributing at least a portion of the stored energy of the renewable energy storage device.

4. In paragraph 3, The above power supply control device, A water electrolysis system characterized in that the closer the energy storage amount of the renewable energy storage device gets to the upper limit, the greater the preset pressure increase reference slope is adjusted.

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