Water electrolysis system and method for operating water electrolysis system

Abstract

Provided are: a water electrolysis system capable of providing an adjustment force solely by the water electrolysis system; and a method for operating the water electrolysis system. This water electrolysis system generates hydrogen gas and oxygen gas as generated gases from water by applying grid power to a plurality of water electrolysis stacks through a rectifier, and adjusts power consumption in accordance with an instruction to provide adjustment force, and is characterized in that, when the instruction to provide the adjustment force is received within a contract time zone in which provision of the adjustment force is contracted, the amount of water supplied to the water electrolysis stacks, the temperature of the water electrolysis stacks, and pressure can be controlled according to the amount of power obtained by adding, to the amount of power consumption of the water electrolysis stacks, the amount of power of the adjustment force to be provided.

Description

Water electrolysis system and water electrolysis system operation method

[0001] The present invention relates to a water electrolysis system that changes power consumption in response to demands in an electricity supply and demand adjustment market, and a method for operating the water electrolysis system.

[0002] Unlike fossil fuels, hydrogen is a clean energy source that does not emit carbon dioxide when burned. For this reason, hydrogen has attracted attention as one of the clean energy sources for combating global warming, and technological developments related to the production, transportation, and use of hydrogen are underway. Water electrolysis systems are known as one method for producing hydrogen. In this context, the present application relates to an apparatus for producing hydrogen on a large scale by electrolyzing water using renewable energy, etc., and a control method for the apparatus.

[0003] CO ２ Free hydrogen needs to be produced from energy sources such as renewable energy and nuclear power. Renewable energy sources such as wind and solar power have large fluctuations in output over time, and as their power generation capacity increases, adjustment capabilities are needed to balance power supply and demand. Meanwhile, water electrolysis systems that produce hydrogen are consumers, but their power consumption can be adjusted, and the amount of power they consume is large. For this reason, it has been proposed to adjust the power consumption of water electrolysis systems and use this as adjustment capabilities.

[0004] Patent Document 1 states that in the event of demand response, optimal operation of the hydrogen production equipment and the storage battery / hydrogen storage equipment can level out fluctuations in the supply and demand balance caused by fluctuations in renewable energy output and provide adjustment power to the power grid.

[0005] Patent Document 2 states that by combining the production and storage of hydrogen, the charging of storage batteries, and the power generation of fuel cells, if an error occurs between the predicted value of surplus power used as the basis for formulating the power transmission plan and the actual value, the error can be easily reduced.

[0006] Therefore, Patent Documents 1 and 2 state that fluctuations in the supply and demand balance due to fluctuations in the output of renewable energy can be leveled out by changing the output of the hydrogen production device and charging and discharging the storage battery, thereby providing adjustment power to the power grid.

[0007] JP 2019-170097 A JP 2020-54085 A

[0008] In Patent Documents 1 and 2, the response of the output control of the hydrogen production device is slower than that of a storage battery, making it difficult to operate stably, and therefore there is a problem in that a large proportion of the adjustment power control must be handled by the storage battery.

[0009] Therefore, the present invention aims to provide a water electrolysis system and a method for operating a water electrolysis system that can provide adjustment power solely by the water electrolysis system, by controlling the water supply amount and the water electrolysis stack temperature and pressure to an amount that corresponds to the hydrogen production amount necessary for providing the agreed-upon adjustment power, rather than controlling the water supply amount and the water electrolysis stack temperature and pressure to an amount that is optimally suited to the hydrogen production amount, during the time period when adjustment power agreed upon in the adjustment power market is provided, and by quickly responding to a request for the provision of adjustment power by changing the output of the water electrolysis device.

[0010] In light of the above, the present invention provides a "water electrolysis system that supplies grid power to a plurality of water electrolysis stacks via a rectifier to produce hydrogen gas and oxygen gas as product gases from water, and adjusts power consumption in response to a command to provide adjustment power, wherein, when the command to provide adjustment power is received within an agreed time slot for the provision of adjustment power, the water electrolysis system is capable of controlling the amount of water supplied to the water electrolysis stacks, the temperature and the pressure of the water electrolysis stacks in response to an amount of electric power obtained by adding the amount of electric power of the adjustment power to be provided to the amount of electric power consumed by the water electrolysis stacks."

[0011] The present invention provides a "water electrolysis system operation method that supplies grid power to a plurality of water electrolysis stacks via a rectifier to generate hydrogen gas and oxygen gas as product gases from water, and adjusts power consumption in response to a command to provide adjustment power, wherein when a command to provide adjustment power is received within an agreement time slot for which the provision of adjustment power has been agreed upon, the method controls the amount of water supplied to the water electrolysis stacks, the temperature and the pressure of the water electrolysis stacks in accordance with the amount of power obtained by adding the amount of power consumed by the water electrolysis stacks to the amount of adjustment power to be provided, and sets the amount of adjustment power that can be provided so that the sum of the adjustment power bid price and the hydrogen sales price after the adjustment power is provided when the adjustment power is provided is greater than the hydrogen sales price when the adjustment power is not provided."

[0012] According to the present invention, the temperature and pressure of the water electrolysis stack can be stably controlled in response to the provision of adjustment power, which is one method of stabilizing the grid.

[0013] Fig. 1 is a diagram showing an example of the configuration of a water electrolysis system according to an embodiment of the present invention. Fig. 2 is a diagram showing an example of the internal block configuration of a system control unit of a water electrolysis system according to an embodiment of the present invention. Fig. 3 is an explanatory diagram of operation control for providing upward adjustment capacity. Fig. 4 is an explanatory diagram of operation control for providing downward adjustment capacity. Fig. 5 is an explanatory diagram of operation control for providing upward adjustment capacity.

[0014] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Note that each drawing is merely a schematic illustration to allow a sufficient understanding of the present invention. Therefore, the present invention is not limited to the illustrated examples. Furthermore, in each drawing, common or similar components are designated by the same reference numerals, and redundant explanations thereof will be omitted.

[0015] Before describing the embodiments of the present invention, the prerequisites for the water electrolysis system will be summarized below.

[0016] First, the water electrolysis stacks used in water electrolysis systems include alkaline, solid polymer, and anion exchange membrane types. The present invention is applicable to any type of electrolytic cell, but a solid polymer type with excellent output response will be shown as an example.

[0017] In a typical water electrolysis stack, the energy conversion efficiency from electricity to hydrogen is approximately 70-90%. The remaining energy is converted into heat, heating the components of the water electrolysis stack and the water flowing inside. As a result, the temperature increases from upstream to downstream along the water flow path, resulting in temperature variations within the water electrolysis stack. While the resistance of the electrolysis cell decreases as the temperature increases, exceeding its heat-resistant temperature can lead to deterioration of the electrolyte membrane and electrode catalysts that make up the electrolysis cell, resulting in increased resistance, thinning of the electrolyte membrane that separates hydrogen and oxygen, increasing the permeability of hydrogen and oxygen, developing holes in the electrolyte membrane, or electrical short circuits. Furthermore, when the volume ratio of generated gas to water, the raw material, is high in the electrolysis cell flow path, an insufficient water supply to the electrodes increases resistance, causing current concentration in regions with a low gas volume ratio. Such current concentration can lead to localized temperature increases, leading to degradation and failure. Therefore, it is important to suppress temperature differences and the occurrence of high-gas volume ratio regions within the electrolysis cell.

[0018] Much of the heat generated in the water electrolysis stack is carried out of the stack by the supplied water, and the temperature difference generated along the water flow path inside the water electrolysis stack is proportional to the amount of heat generated in the electrolytic cell and inversely proportional to the water flow rate. Furthermore, the amount of gas generated is proportional to the current, and the higher the current value, the higher the gas volume ratio at the flow path outlet. Therefore, to prevent temperature differences and high gas volume ratio regions within the electrolysis cell, it is important to supply sufficient water in accordance with the current and output of the water electrolysis stack while maintaining a temperature appropriate for hydrogen production.

[0019] Hereinafter, with reference to FIG. 1, a configuration example of a water electrolysis system 100 according to an embodiment of the present invention will be described.

[0020] As shown in FIG. 1 , a water electrolysis system 100 according to an embodiment of the present invention includes a water tank 13, a plurality of water electrolysis units 20 (20 a...20 n), a hydrogen gas tank 61, an oxygen gas tank 62, a system control unit 80, and a data communication unit 90.

[0021] The water electrolysis system 100 performs hydrogen production operation by adjusting the voltage from a grid power 73, using an isolation transformer 71 that insulates the water electrolysis unit 20 from the grid side, a rectifier 70 that converts AC power to DC power, and supplying DC power from the rectifier 70 to the water electrolysis stack 23 via a DC cable 72. In the example shown in Fig. 1 , the power supply line from the rectifier 70 is connected to the water electrolysis unit 20a and the water electrolysis unit 20n, but the multiple water electrolysis units 20 are connected in series and parallel so that a general large-scale DC power supply can be used. There is no particular limitation on the number of series-parallel connections.

[0022] Details will be described later, but the main functions of each part in Figure 1 are as follows. First, the water tank 13 is a storage unit for water to be supplied to the water electrolysis unit 20. The water electrolysis unit 20 is a component that electrolyzes water to produce hydrogen gas and oxygen gas. The hydrogen gas tank 61 is a storage unit for hydrogen gas produced by the water electrolysis unit 20. The oxygen gas tank 62 is a storage unit for oxygen gas produced by the water electrolysis unit 20. The system control unit 80 is a component that controls the operation of each part of the system. The data communication unit 90 is a component that transmits and receives data to and from the outside. The functions of each part will be described in detail below.

[0023] A water tank 13, which stores water to be supplied to the water electrolysis units 20, is connected to each water electrolysis unit 20 via water piping 10. In the water electrolysis system 100, water in the water tank 13 is pressurized by a water pump 11, cooled by a large cooler 12, and then taken into the oxygen electrode side of the water electrolysis unit 20. In the example shown in Fig. 1 , the water electrolysis system 100 is configured to supply water only to the oxygen electrode side. However, the water electrolysis system 100 may be configured to supply water to both the hydrogen electrode side and the oxygen electrode side.

[0024] 1 , the water electrolysis unit 20 includes a water flow rate control valve 21 and a small cooler 22. The water electrolysis unit 20 also includes a water electrolysis stack 23 that electrolyzes water to generate hydrogen gas and oxygen gas.

[0025] The water electrolysis unit 20, which electrolyzes water to produce hydrogen gas and oxygen gas, is composed of components on the hydrogen system 30 side related to hydrogen and components on the oxygen system 40 side related to oxygen. Of these, the components on the hydrogen system 30 side include a separation tank 31, a pressure adjustment valve 32, and a water discharge valve 33.

[0026] The separation tank 31 is a component that separates water and hydrogen gas. The pressure regulating valve 32 is a valve for sending hydrogen gas from the water electrolysis unit 20 to the hydrogen gas tank 61 via the hydrogen gas pipe 51 by adjusting its opening. The pressure regulating valve 32 has a function of adjusting the internal pressure of the water electrolysis stack 23 to a predetermined pressure by adjusting its opening. The water discharge valve 33 is a valve that discharges water separated in the separation tank 31 to the outside. The water discharge valve 33 has a function of adjusting the internal pressure of the water electrolysis stack 23 to a predetermined pressure by adjusting its opening.

[0027] The water electrolysis unit 20 also includes a separation tank 41, a pressure regulating valve 42, and a water discharge valve 43 as components on the oxygen system 40 side related to oxygen. The separation tank 41 is a component that separates water and oxygen gas. The pressure regulating valve 42 is a valve for sending water from the water electrolysis unit 20 to the oxygen gas tank 62 via the oxygen gas pipe 52 by adjusting its aperture. The pressure regulating valve 42 has a function of adjusting the internal pressure of the water electrolysis stack 23 to a predetermined pressure by adjusting its aperture. The water discharge valve 43 is a valve that discharges water separated in the separation tank 41 to the outside of the water electrolysis stack 23. The water discharge valve 43 has a function of adjusting the internal pressure of the water electrolysis stack 23 to a predetermined pressure by adjusting its aperture.

[0028] In the water electrolysis system 100, the water separated in the separation tank 31 and the separation tank 41 is adjusted to a predetermined pressure by the water discharge valve 33 and the water discharge valve 43, recovered in the water tank 13, and then supplied again to the water electrolysis stack 23 via the water pump 11.

[0029] The water electrolysis system 100 then supplies the hydrogen gas G1 stored in the hydrogen gas tank 61 to the outside by opening the pressure adjustment valve 63. At this time, the water electrolysis system 100 adjusts the pressure of the hydrogen gas G1 to a predetermined pressure by adjusting the aperture of the pressure adjustment valve 63 to a predetermined aperture.

[0030] The water electrolysis system 100 also supplies the oxygen gas G2 stored in the oxygen gas tank 62 to the outside by opening the pressure regulating valve 64. At this time, the water electrolysis system 100 adjusts the pressure of the oxygen gas G2 to a predetermined pressure by adjusting the aperture of the pressure regulating valve 64 to a predetermined aperture.

[0031] 2 is an internal block diagram of the system control unit 80. The configuration of the system control unit 80 will be described below with reference to FIG.

[0032] 2, a system control unit 80 configured using a computer includes a calculation unit 81 and a storage unit 82. The calculation unit 81 includes an operation control unit 81a, a value setting unit 81b, and a regulation capability determination unit 81c.

[0033] The operation control unit 81a is a component that controls the hydrogen production operation of the water electrolysis system 100. The value setting unit 81b is a component that sets various parameters. The adjustment capacity determination unit 81c is a component that determines the amount of power to be provided as adjustment capacity.

[0034] The storage unit 82 also stores reference information 82a and a control program Pr. The reference information 82a is information that is referenced when performing hydrogen production operation or when setting various parameters. The control program Pr is a program that causes the calculation unit 81 to function as an operation control unit 81a, a value setting unit 81b, and an adjustment power determination unit 81c. The control program Pr is stored in a storage medium 99, and is installed directly or indirectly from the storage medium 85 into the system control unit 80.

[0035] Data measured in the water electrolysis system 100, such as the water electrolysis stack voltage, the water electrolysis cell voltage, and the temperature, pressure, flow rate, and current of each part of the apparatus, are managed by the system control unit 80. The system control unit 80 controls the DC power using the rectifier 70 based on the operation command, and calculates the operation variables required for stable operation of the water electrolysis stack 23 based on the data and reference information 82a ( FIG. 2 ) pre-registered in a storage unit 82 ( FIG. 2 ). The system control unit 80 then transmits control signals to each device in the water electrolysis system 100, such as the valves, pumps, and coolers, to control each device.

[0036] Next, we will explain the control method of the water electrolysis system when supplying control reserve, but before that, we will explain the underlying concept of supplying control reserve. First, in the electricity supply and demand adjustment market, trading of control reserve is agreed upon through advance bidding. For example, in the case of tertiary control reserve, the amount of control reserve that can be supplied is sometimes agreed upon through bidding the day before the actual supply and demand cross section, or the ΔkW that can be used for adjustment in the target week (Saturday to Friday) is sometimes agreed upon through bidding the week before the target week. In either case, the response time (the time from when a command is issued to when it is supplied), duration, supplyable amount, and increase / decrease category for trading control reserve are determined before the actual supply and demand cross section.

[0037] The increase category is a category in which adjustment capacity is provided to deal with the occurrence of a shortage imbalance in the power supply area. The decrease category is a category in which adjustment capacity is provided to deal with the occurrence of a surplus imbalance in the power supply area.

[0038] Although a water electrolysis system is typically operated under conditions that optimize the hydrogen production cost and efficiency, it is necessary to vary the power consumption of the water electrolysis system 100 within the response time in order to provide adjustment power within the contracted response time. At this time, the temperature change caused by the change in the heat generation amount of the water electrolysis stack 23 resulting from changing the power consumption of the water electrolysis system 100 within the response time is difficult to control due to its slow time response.

[0039] A control method for stably operating the water electrolysis system 100 when adjusting capacity is provided will be described below with reference to Figures 3 to 5. In Figures 3 to 5, the horizontal axis represents the actual supply and demand cross section for 24 hours on the day, and the vertical axis represents the relationship between the power consumption and the equipment operation amount, which are changed in accordance with the supply command given during the contract time period.

[0040] 3 is an explanatory diagram of operational control for providing upward adjustment power in the 20 MW water electrolysis system 100. If the system control unit 80 receives a command to provide upward adjustment power from the adjustment power market operator while the water electrolysis stack 23 is producing hydrogen with a power consumption of 20 MW during a time period when the agreed-upon adjustment power of 5 MW is provided, the system control unit 80 changes the output (equipment operation amount) of the rectifier 70 from 20 MW to 15 MW, sets the power consumption of the water electrolysis stack 23 to 15 MW, and provides the agreed-upon upward adjustment power of 5 MW.

[0041] Thereafter, the system control unit 80 calculates the operation variables required for stable operation of the water electrolysis stack 23 based on the reference information 82 a registered in advance in the storage unit 82, and transmits control signals to each device of the water electrolysis system 100, such as the valves, pumps, and coolers, to control each device.

[0042] Furthermore, after the time period for providing the agreed-upon 5 MW adjustment power ends, the system control unit 80 calculates the output of the rectifier 70 using a value setting unit 81 b based on the hydrogen demand and the stored amount so that the hydrogen demand can be met, and calculates the operation amount required for stable operation of the water electrolysis stack 23 based on reference information 82 a registered in advance in the storage unit 82. The system control unit 80 then transmits control signals to each device, such as the valves, pumps, and coolers, of the water electrolysis system 100 to control each device.

[0043] The idea behind Figure 3 is that the equipment is operated only after a supply command is issued during the contract time slot, and the contracted 5 MW of upward adjustment power is supplied, while the stable operation of the water electrolysis stack 23 under the new operating conditions is sought and dealt with. This idea can be said to be a reactive process for the long-term contract time slot.

[0044] Figure 4 is also an explanatory diagram of operational control for providing downward adjustment capacity in the 20 MW water electrolysis system 100. This example is for a long-term contract time slot, as in Figure 3, but the idea is to transition to stable operation of the water electrolysis stack 23 in a new operating state before the contract time slot begins (i.e., before a supply command is issued).

[0045] Specifically, in FIG. 4 , before the time period when the agreed-upon adjustment power of 5 MW is provided, when the water electrolysis stack 23 is producing hydrogen at a power consumption of 20 MW, the system control unit 80 changes the output of the rectifier 70 from 20 MW to 15 MW, and controls each device of the water electrolysis system 100, such as the valves, pumps, and coolers, under the condition that the water electrolysis stack 23 is producing hydrogen at a power consumption of 20 MW.

[0046] When the system control unit 80 receives a command to provide adjustment power from the adjustment power market operator, the system control unit 80 changes the output of the rectifier 70 from 15 MW to 20 MW, sets the power consumption of the water electrolysis stack 23 to 20 MW, and provides the agreed downward adjustment power of 5 MW.

[0047] Thereafter, the system control unit 80 calculates the operation variables required for stable operation of the water electrolysis stack 23 based on the reference information 82 a registered in advance in the storage unit 82, and transmits control signals to each device of the water electrolysis system 100, such as the valves, pumps, and coolers, to control each device.

[0048] Furthermore, after the time period for providing the agreed-upon 5 MW adjustment power ends, the system control unit 80 calculates the output of the rectifier 70 using a value setting unit 81 b based on the hydrogen demand and the stored amount so that the hydrogen demand can be met, and calculates the operation amount required for stable operation of the water electrolysis stack 23 based on reference information 82 a registered in advance in the storage unit 82. The system control unit 80 then transmits control signals to each device, such as the valves, pumps, and coolers, of the water electrolysis system 100 to control each device.

[0049] In contrast, Figure 5 assumes a case where the settlement time period is short, and shows an example in which, in such a state, rather than searching for a new stable state in accordance with a supply command (rather than performing equipment operations for the search), it is more efficient and stable to maintain the previous state in the event of a crisis.

[0050] Specifically, in FIG. 5 , as another operational control for providing upward adjustment power in the 20 MW water electrolysis system 100, if the system control unit 80 receives a command to provide adjustment power from the adjustment power market operator while the water electrolysis stack 23 is producing hydrogen with a power consumption of 20 MW during a time period when the agreed-upon adjustment power of 5 MW is to be provided, the system control unit 80 changes the output of the rectifier 70 from 20 MW to 15 MW, sets the power consumption of the water electrolysis stack 23 to 15 MW, and provides the agreed-upon upward adjustment power of 5 MW.

[0051] When the time period for providing the agreed adjustment power is within two hours, the system control unit 80 calculates the operation amount required for stable operation of the water electrolysis stack 23, such as the valves, pumps, and coolers, of the water electrolysis system 100, based on information when the water electrolysis stack 23 was producing hydrogen with a power consumption of 20 MW, and the system control unit 80 transmits control signals to the valves, pumps, coolers, and other devices of the water electrolysis system 100 to control each device.

[0052] Furthermore, after the time period for providing the agreed-upon 5 MW adjustment power ends, the system control unit 80 calculates the output of the rectifier 70 using a value setting unit 81 b based on the hydrogen demand and the stored amount so that the hydrogen demand can be met, and calculates the operation amount required for stable operation of the water electrolysis stack 23 based on reference information 82 a registered in advance in the storage unit 82. The system control unit 80 then transmits control signals to each device, such as the valves, pumps, and coolers, of the water electrolysis system 100 to control each device.

[0053] As described above, the water electrolysis system 100 according to this embodiment can reduce changes in the temperature and pressure of the water electrolysis stack 23 caused by providing adjustment power to the adjustment power market, and can stably control the water electrolysis system 100.

[0054] The present invention is not limited to the above-described embodiment, and includes various modifications. For example, the above-described embodiment has been described in detail to clearly explain the present invention, and is not necessarily limited to a configuration including all of the described configurations. Furthermore, it is possible to replace part of the configuration of the embodiment with another configuration, and it is also possible to add another configuration to the configuration of the embodiment. Furthermore, it is possible to add, delete, or replace part of each configuration with another configuration.

[0055] 10: Water piping 11: Water supply pump 12: Large cooler 13: Water tank 20, 23a, 23n: Water electrolysis unit 21: Water flow rate adjustment valve 22: Small cooler 23: Water electrolysis stack 30: Hydrogen system 31: Separation tank 32: Pressure adjustment valve 33: Water discharge valve 40: Oxygen system 41: Separation tank 42: Pressure adjustment valve 43: Water discharge valve 51: Hydrogen gas piping 52: Oxygen gas piping 61: Hydrogen gas tank 62: Oxygen gas tank 63: Pressure adjustment valve 64: Pressure adjustment valve 70: Rectifier 71: Isolation transformer 72: DC cable 73: System power 80: System control unit 81: Calculation unit 81a: Operation control unit 81b: Value setting unit 81c: Adjustment power determination unit 82: Memory unit 82a: Reference information 85: Storage medium 90: Data communication unit 100: Water electrolysis system G1: Hydrogen gas G2: Oxygen gas W1: Water Pr: Control program

Claims

1. A water electrolysis system that supplies grid power to multiple water electrolysis stacks via a rectifier to generate hydrogen gas and oxygen gas as product gases from water, and adjusts power consumption in response to a command to provide adjustment power, characterized in that when a command to provide adjustment power is received within an agreed time period for the provision of adjustment power, the system is capable of controlling the amount of water supplied to the water electrolysis stacks, the temperature and pressure of the water electrolysis stacks in accordance with the amount of power obtained by adding the amount of power of the adjustment power to be provided to the amount of power consumed by the water electrolysis stacks.

2. A water electrolysis system as claimed in claim 1, characterized in that during a period when no command to supply adjustment power has been received, the amount of water supplied to the water electrolysis stack, the temperature of the water electrolysis stack, and the pressure are controlled in accordance with the optimal power consumption of the water electrolysis stack.

3. A water electrolysis system as claimed in claim 1, characterized in that, before the contract time period in which the supply of adjustment power is contracted, the amount of water supplied to the water electrolysis stack, the temperature and pressure of the water electrolysis stack are controlled in accordance with the amount of power consumed by the water electrolysis stack plus the amount of power of the adjustment power to be supplied, and when a command to supply adjustment power is subsequently received, the amount of power consumed by the water electrolysis stack is increased by an amount equal to the contracted amount of power to be supplied.

4. A water electrolysis system as claimed in claim 1, characterized in that, when a command to provide adjustment power is received during a period in which an agreed-upon upward adjustment power is provided, the amount of power consumed by the water electrolysis stack is reduced by an amount equal to the agreed-upon amount of power to be provided, and, if the period in which adjustment power is provided is short, the amount of water supplied to the water electrolysis stack, the temperature of the water electrolysis stack and the pressure are controlled in accordance with the amount of power consumed before the power consumption of the water electrolysis stack was changed.

5. A water electrolysis system as claimed in claim 4, characterized in that, when a command to provide adjustment power is received during a time period in which the agreed upon upward adjustment power is provided, the amount of power consumed by the water electrolysis stack is reduced by an amount equal to the agreed upon amount of power to be provided, and, if the time period in which the adjustment power is provided is within two hours, the amount of water supplied to the water electrolysis stack, the temperature of the water electrolysis stack and the pressure are controlled in accordance with the amount of power consumed before the power consumption of the water electrolysis stack was changed.

6. A method for operating a water electrolysis system which provides grid power to a plurality of water electrolysis stacks via a rectifier to generate hydrogen gas and oxygen gas from water as product gases, and adjusts power consumption in response to a command to provide adjustment power, characterized in that when a command to provide adjustment power is received within an agreement time period in which the provision of adjustment power is agreed upon, the method is capable of controlling the amount of water supplied to the water electrolysis stacks, the temperature and pressure of the water electrolysis stacks in accordance with the amount of power obtained by adding the amount of power of the adjustment power to be provided to the amount of power consumed by the water electrolysis stacks, and setting the amount of adjustment power that can be provided so that the bidding price for adjustment power when adjustment power is provided plus the hydrogen sales price after the adjustment power is provided is greater than the hydrogen sales price when adjustment power is not provided.

7. A method for operating a water electrolysis system according to claim 6, comprising the steps of: monitoring a hydrogen storage amount and setting a supplyable amount of adjustment power so that the hydrogen supply amount of the water electrolysis system can meet the hydrogen demand.

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