Power control device, hydrogen production system, and hydrogen production method

Abstract

The power control device for a hydrogen production system according to one embodiment comprises: a power generation device that generates power using a renewable energy; a hydrogen production device that produces hydrogen using the power generated by the power generation device; and a connection unit that connects the power generation device and the hydrogen production device to a power system. The power control device determines, on the basis of the power generated by the power generation device and the power reversely flowed to the power system, a power command value supplied to the hydrogen production device so that hydrogen is produced in a state in which the reverse power flow to the power system always occurs.

Description

[Technical Field]

[0001] The present disclosure relates to a power control device for a hydrogen production system, a hydrogen production system, and a hydrogen production method. [Background technology]

[0002] Water electrolysis devices are used to produce hydrogen by electrolyzing water. In particular, hydrogen produced using only renewable energy without emitting carbon dioxide is called green hydrogen, and is expected to become widespread as an energy source with a low environmental impact. A power generation system described in Patent Document 1 is known as a technology for producing hydrogen using renewable energy sources. This power generation system includes solar panels, a storage battery, and a hydrogen production device that produces hydrogen using electricity generated by the solar panels, and produces hydrogen by supplying surplus electricity that cannot be reverse-flowed to the commercial grid during output restrictions to the hydrogen production device. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2017-51083 [Patent Document 2] Japanese Patent Publication No. 2022-12339 Summary of the Invention [Problem to be solved by the invention]

[0004] The device described in Patent Document 1 uses a hydrogen production device to produce hydrogen when surplus electricity occurs due to output restrictions, so the capacity utilization rate of the hydrogen production device is low and the cost of hydrogen production is high. In order to improve the capacity utilization rate of the hydrogen production device, it is desirable to use most of the electrical energy generated by renewable energy sources in the hydrogen production device.

[0005] However, because the amount of electricity generated by renewable energy sources fluctuates greatly, electricity may flow into the system from the power grid when power generation temporarily drops due to weather changes, etc. Since electricity from the power grid includes non-renewable energy, if hydrogen is produced using electricity received from the power grid, it will not be possible to prove that the hydrogen is derived from renewable energy.

[0006] Therefore, the present disclosure aims to produce hydrogen that can be proven to be derived from renewable energy sources. [Means for solving the problem]

[0007] A power control device for a hydrogen production system according to one aspect of the present disclosure includes a power generation device that generates electricity using renewable energy, a hydrogen production device that produces hydrogen using the electricity generated by the power generation device, and a connection unit that connects the power generation device and the hydrogen production device to an electric power grid. This power control device determines a power command value to be supplied to the hydrogen production device based on the electricity generated by the power generation device and the electricity that flows back into the electric power grid, so that hydrogen is produced while a backflow to the electric power grid is constantly occurring. [Effects of the Invention]

[0008] According to aspects of the present disclosure, it is possible to produce hydrogen that can be proven to be derived from renewable energy. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a diagram illustrating a schematic diagram of a hydrogen production system according to an embodiment. [Figure 2] FIG. 2 is a block diagram showing the functional configuration of the power control device. [Figure 3] FIG. 2 is a block diagram illustrating an example of the hardware configuration of a power control device. [Figure 4] 4 is a flowchart showing the flow of processing by the power control device when the water electrolysis device is in a stopped state. [Figure 5]4 is a flowchart showing the flow of processing by the power control device when the water electrolysis device is in operation. DETAILED DESCRIPTION OF THE INVENTION

[0010] A power control device for a hydrogen production system according to one aspect of the present disclosure includes a power generation device that generates electricity using renewable energy, a hydrogen production device that produces hydrogen using the electricity generated by the power generation device, and a connection unit that connects the power generation device and the hydrogen production device to an electric power grid. This power control device determines a power command value to be supplied to the hydrogen production device based on the electricity generated by the power generation device and the electricity that flows back into the electric power grid, so that hydrogen is produced while a backflow to the electric power grid is constantly occurring.

[0011] This power control device produces hydrogen while constantly providing a reverse power flow to the power grid, preventing the unintentional use of power received from the power grid to produce hydrogen, and therefore making it possible to produce hydrogen that can be proven to be derived from renewable energy.

[0012] When the power generated by the power generation device is Ppv, the standby power of the hydrogen production device is Pax, and the power flowed back to the power grid is Pex, the power control device may determine the power command value Pav based on the following equation (1): Pav = Ppv - Pax - Pex (1)

[0013] The hydrogen production system may further include a power storage device connected to the connection section, and when the hydrogen production device is stopped and the power command value is smaller than a threshold, the hydrogen production device is not operated and the power generated by the power generation device is charged to the power storage device, and when the power command value is equal to or greater than the threshold, the power command value is output to the hydrogen production device to produce hydrogen. By operating the hydrogen production device to produce hydrogen after the power command value becomes equal to or greater than the threshold, the hydrogen production device is less likely to stop due to fluctuations in the amount of power generated by the power generation device, improving the operating rate of the hydrogen production device. As a result, the hydrogen production efficiency can be increased.

[0014] When the hydrogen production device is operating and the power command value is smaller than the threshold value, the power command value may be output to the hydrogen production device to produce hydrogen, and the power storage device may be caused to discharge the shortfall in power. By discharging the shortfall in power from the power storage device, hydrogen can be continuously produced using the hydrogen production device even when the amount of power generated by the power generation device decreases. This improves the operating rate of the hydrogen production device and increases the hydrogen production efficiency.

[0015] The power control device may stop operation of the hydrogen production device when the remaining charge of the power storage device falls below a reference value due to the discharge of power from the power storage device. By stopping the hydrogen production device when the remaining charge falls below the reference value, it is possible to continue reverse power flow to the power grid using the stored power.

[0016] When the power command value is greater than the rated output of the hydrogen production device, the power control device may operate the hydrogen production device at the rated output and charge the surplus power to the power storage device. Storing the surplus power in the power storage device can improve the energy efficiency of the hydrogen production system.

[0017] The hydrogen production system of the present disclosure includes a power generation device that generates electricity using renewable energy, a hydrogen production device that produces hydrogen using the electricity generated by the power generation device, a connection unit that connects the power generation device and the hydrogen production device to an electric power grid, and a power control device that controls the operation of the hydrogen production device. The power control device determines a power command value to be supplied to the hydrogen production device based on the electricity generated by the power generation device and the electricity that flows back into the electric power grid, so that hydrogen is produced while a backflow to the electric power grid is constantly occurring.

[0018] This hydrogen production system produces hydrogen while constantly generating a reverse power flow to the power grid, preventing unintended power reception from the power grid, and therefore producing hydrogen that can be proven to be derived from renewable energy.

[0019] The hydrogen production system may further include a power storage device connected to the connection section, and the power control device may charge the power storage device with power generated by the power generation device without operating the hydrogen production device when the hydrogen production device is stopped and the power command value is smaller than a threshold value, and output the power command value to the hydrogen production device to produce hydrogen when the power command value is equal to or greater than the threshold value. By operating the hydrogen production device to produce hydrogen after the power command value becomes equal to or greater than the threshold value, the hydrogen production device is less likely to stop due to fluctuations in the amount of power generated by the power generation device, improving the availability of the hydrogen production device. As a result, the hydrogen production efficiency can be increased.

[0020] When the hydrogen production device is operating and the power command value is smaller than the threshold value, the power control device may output a power command value to the hydrogen production device to produce hydrogen and may also discharge the shortfall in power from the power storage device. By discharging the shortfall in power from the power storage device, it becomes possible to continue producing hydrogen even when the amount of power generated by the power generation device decreases. This improves the operating rate of the hydrogen production device and increases the hydrogen production efficiency.

[0021] The hydrogen production method disclosed herein includes the steps of obtaining the amount of power generated by a power generation device that generates power using renewable energy, flowing at least a portion of the power generated by the power generation device back into an electric power grid, determining a power command value to be supplied to a hydrogen production device based on the power generated by the power generation device and the power flowed back into the electric power grid, and outputting the power command value to the hydrogen production device to produce hydrogen while backflow to the electric power grid is constantly occurring.

[0022] This hydrogen production method produces hydrogen while constantly generating a reverse power flow to the power grid, preventing unintended power reception from the power grid, and therefore producing hydrogen that can be proven to be derived from renewable energy.

[0023] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. In the following description, the same or equivalent elements are denoted by the same reference numerals, and redundant description will not be repeated.

[0024] [Hydrogen production system] 1 is a diagram schematically illustrating a hydrogen production system 1 according to one embodiment. The hydrogen production system 1 produces hydrogen derived from renewable energy. As shown in FIG. 1, the hydrogen production system 1 includes a power generation device 2, a power storage device 3, a hydrogen production device 4, a power control device 5, and a connection unit 10.

[0025] The connection unit 10 electrically connects the power generation device 2, the power storage device 3, and the hydrogen production device 4 to one another. The connection unit 10 is, for example, a distribution board that distributes power to various devices. The connection unit 10 is connected to an electric power grid 50, which is an external general power transmission and distribution system, and transmits power to the electric power grid 50 or receives power from the electric power grid 50 depending on the power supply and power consumption of the hydrogen production system 1. The power supply of the hydrogen production system 1 is the sum of the power generated by the power generation device 2 and the power discharged from the power storage device 3. The power consumption of the hydrogen production system 1 is the sum of the power consumption of the hydrogen production device 4 (the sum of the power consumption of the water electrolysis device 6 and the power consumption of the auxiliary machinery 7, which will be described later) and the power charged to the power storage device 3.

[0026] For example, when the power supply of the hydrogen production system 1 is greater than the power consumption, power flows out from the hydrogen production system 1 to the power grid 50 via the connection part 10. On the other hand, when the power supply of the hydrogen production system 1 is less than the power consumption, power flows from the power grid 50 to the hydrogen production system 1 via the connection part 10. However, as will be described later, the hydrogen production system 1 produces hydrogen in a state where reverse power flow to the power grid 50 occurs all the time. Reverse power flow refers to the transmission of power exceeding 0 kW from the hydrogen production system 1 to the power grid 50. Note that when the connection part 10 is connected to the power grid 50, the frequency of the power propagating through the connection part 10 is synchronized with the frequency of the commercial power of the power grid 50.

[0027] In one embodiment, a relay device 14 may be provided between the connection unit 10 and the power grid 50. The relay device 14 monitors the power flowing from the power grid 50 to the hydrogen production system 1 and blocks the forward power flow from the power grid 50 to the hydrogen production system 1. Forward power flow refers to the flow of power flowing from the power grid 50 to the hydrogen production system 1. Preventing the inflow of power from the power grid 50 reliably prevents the use of power from the power grid 50, including non-renewable energy, for hydrogen production. Note that if the relay device 14 operates, the operation of the hydrogen production system 1 is forcibly stopped. To prevent this forced stop, the hydrogen production system 1 prevents the inflow of power from the power grid 50 to the hydrogen production system 1, regardless of the operation of the relay device 14.

[0028] The power generation device 2 is a renewable energy power generation device that generates power using renewable energy. For example, the power generation device 2 is a solar power generation facility that includes solar panels that convert sunlight (Photovoltaic: PV) into electricity. The type of power generation device 2 is not limited to solar power generation as long as it uses renewable energy. For example, the power generation device 2 may be a device that generates power using wind power, geothermal power, or biomass power.

[0029] The power generation capacity Ppv of a power generation device 2 that uses renewable energy fluctuates over time. For example, the power generation capacity of solar power generation fluctuates greatly depending on the amount of solar radiation and temperature. The power generation capacity of wind power generation fluctuates greatly depending on wind speed. Similarly, in biomass power generation, the properties of the raw material biomass may not be constant, and in such cases, the output is unstable. In one embodiment, when the power generation capacity Ppv of the power generation device 2 fluctuates, the hydrogen production system 1 adjusts the loads on the power storage device 3 and the hydrogen production device 4 (power consumption of the hydrogen production system 1) to constantly generate reverse power flow to the power grid 50.

[0030] A power conversion device 11 is provided between the power generation device 2 and the connection unit 10. The power conversion device 11 is, for example, a power conditioning system (PCS) that converts DC power generated by the power generation device 2 into AC power.

[0031] The power storage device 3 includes a storage battery that stores the power generated by the power generation device 2. The storage battery included in the power storage device 3 is, for example, a secondary battery such as a lithium-ion battery, a lead-acid battery, or a redox flow battery. The power storage device 3 may also be an energy storage device other than a secondary battery, such as a flywheel, a compressed air energy storage (CAES) facility, or a large-capacity capacitor, as long as it can convert power into some kind of energy and store it. The power storage device 3 may further include a monitoring device that monitors the remaining capacity of the storage battery (remaining stored power amount), and a controller that controls charging and discharging of the storage battery.

[0032] A power conversion device 12 is provided between the power storage device 3 and the connection unit 10. The power conversion device 12 is a power conditioner that converts DC power and AC power into each other. For example, when power is charged to the power storage device 3, the power conversion device 12 converts the AC power supplied from the connection unit 10 into DC power. On the other hand, when power is discharged from the power storage device 3, the power conversion device 12 converts the DC power discharged from the power storage device 3 into AC power. In the following description, the power charged and discharged from the power storage device 3 is referred to as Pgr. Positive power Pgr means power supplied (discharged) from the power storage device 3, and negative power Pgr means power consumed (charged) by the power storage device 3.

[0033] The hydrogen production device 4 produces hydrogen using the power generated by the power generation device 2. The hydrogen production device 4 includes a water electrolysis device 6 that produces hydrogen by electrolyzing water, and auxiliary equipment 7 for operating the water electrolysis device 6. The amount of hydrogen produced by the water electrolysis device 6 depends on the power consumption of the water electrolysis device 6. Specifically, as the power consumption Pel of the water electrolysis device 6 increases, the amount of hydrogen produced increases. The power consumption Pel of the water electrolysis device 6 is adjusted in accordance with the power command value Pav received from the power control device 5. The hydrogen production device 4 may also include a storage device for storing the produced hydrogen.

[0034] The auxiliary equipment 7 is an accessory device that operates the water electrolysis device 6. Examples of the auxiliary equipment 7 include a cooling water pump that circulates cooling water, an electrolyte pump that circulates electrolyte, an antifreeze heater, a chiller, etc. To facilitate the start and stop of the water electrolysis device 6, the auxiliary equipment 7 operates not only while the water electrolysis device 6 is in operation, but also while the water electrolysis device 6 is stopped. Therefore, the power consumption Pax of the auxiliary equipment 7 is approximately constant regardless of the operating state of the water electrolysis device 6. In other words, the power consumption Pax of the auxiliary equipment 7 can be said to be the standby power of the hydrogen production device 4.

[0035] A rectifier 13 is provided between the water electrolysis device 6 and the connection unit 10. The rectifier 13 converts AC power from the connection unit 10 into DC power and supplies it to the water electrolysis device 6. The water electrolysis device 6 produces hydrogen using the DC power supplied from the rectifier 13. Note that if the water electrolysis device 6 operates on AC power, the rectifier 13 does not need to be provided.

[0036] [Power control device] The power control device 5 is a computer such as a PLC (Programmable Logic Controller) equipped with a processor, a storage device, an input device, a display device, a communication device, etc., and controls the overall operation of the hydrogen production system 1. The power control device 5, for example, loads a program stored in the storage device and executes the loaded program on the processor, thereby realizing various functions described below. In the power control device 5, an operator can use the input device to input commands and perform other operations to manage the hydrogen production system 1, and the operating status of the hydrogen production system 1 can be visualized and displayed on the display device.

[0037] The power control device 5 is communicatively connected to the power generation device 2, the power storage device 3, the water electrolysis device 6, and the auxiliary devices 7. The power control device 5 sends control signals to the power storage device 3, the water electrolysis device 6, and the auxiliary devices 7 to control their operation. More specifically, the power control device 5 controls the power consumption Pel of the water electrolysis device 6 and the power Pgr charged and discharged from the power storage device 3 so that hydrogen is produced with a constant reverse flow to the power grid 50. In other words, the power supply and power consumption of the hydrogen production system 1 are adjusted based on the power generation amount Ppv of the power generation device 2 so that a constant amount of reverse flow power Pex always flows from the connection part 10 to the power grid 50. By producing hydrogen with a constant reverse flow, hydrogen that can be proven to have been produced using only renewable energy (green hydrogen) is produced.

[0038] Fig. 2 is a block diagram showing the functional configuration of the power control device 5. As shown in Fig. 2, the power control device 5 includes, as its functional configuration, a power generation amount acquiring unit 21, a control information acquiring unit 22, a power consumption acquiring unit 23, a remaining power storage amount acquiring unit 24, a command value generating unit 25, a control unit 26, and a storage unit 27.

[0039] The power generation amount acquiring unit 21 acquires the power generation amount Ppv of the power generation device 2. For example, the power generation amount Ppv of the power generation device 2 is measured using a wattmeter provided in the power conversion device 11. The power generation amount acquiring unit 21 periodically acquires the measured value of the power generation amount Ppv of the power generation device 2.

[0040] The control information acquisition unit 22 acquires various information used to control the hydrogen production system 1. For example, the control information acquisition unit 22 acquires the power consumption Pax of the auxiliary equipment 7 and the minimum reverse flow power, which is the minimum value of power that can be reverse-flowed from the hydrogen production system 1 to the power grid 50. The power consumption Pax of the auxiliary equipment 7 is a set value determined by the specifications of the auxiliary equipment 7. The minimum reverse flow power is a design value determined by the designer of the hydrogen production system 1. The minimum reverse flow power is determined with a certain margin in mind so that power does not unintentionally flow in from the power grid 50 when the power generation amount Ppv of the power generation device 2 fluctuates.

[0041] The power consumption acquisition unit 23 periodically acquires the power consumption Pel of the water electrolysis device 6 of the hydrogen production device 4. The remaining power storage amount acquisition unit 24 periodically acquires the remaining power storage amount Egr of the power storage device 3 (the amount of power stored in the power storage device 3). The remaining power storage amount Egr of the power storage device 3 is measured, for example, by a monitoring device for the power storage device 3. The power consumption acquisition unit 23 and the remaining power storage amount acquisition unit 24 store the acquired power consumption Pel and remaining power storage amount Egr in the memory unit 27 in chronological order.

[0042] The command value generator 25 generates a power command value Pav to be output to the water electrolysis device 6 based on the power generation amount Ppv of the power generation device 2, the power consumption Pax of the auxiliary device 7, and the reverse flow power Pex. The power command value Pav generated by the command value generator 25 is a target value for the power consumption Pel of the water electrolysis device 6. For example, the command value generator 25 determines the power command value Pav based on the following equation (1):

[0043] Pav = Ppv - Pax - Pex (1)

[0044] In equation (1), the backward flow power Pex is set to the minimum backward flow power. That is, the power command value Pav is the surplus power remaining after allocating the power generation amount Ppv of the power generation device 2 to the power consumption Pax of the auxiliary device 7 and the backward flow power Pex. In other words, by determining the power command value Pav based on equation (1), it is possible to allocate power for producing hydrogen to the water electrolysis device 6 while always ensuring power for backward flow to the power grid 50.

[0045] The control unit 26 controls the water electrolysis device 6 to control the amount of hydrogen produced. For example, the control unit 26 sends a control signal to the water electrolysis device 6 to switch between operating and stopping the operation of the water electrolysis device 6. When operating the water electrolysis device 6, the control unit 26 outputs a power command value Pav to the water electrolysis device 6 to produce hydrogen according to the power command value Pav. Upon receiving the power command value Pav from the control unit 26, the water electrolysis device 6 adjusts the amount of hydrogen produced so that the power consumption Pel of the water electrolysis device 6 approaches the power command value Pav. In other words, as the power command value Pav output from the control unit 26 to the water electrolysis device 6 increases, the amount of hydrogen produced by the water electrolysis device 6 increases.

[0046] The control unit 26 also controls the charging and discharging of the power storage device 3. For example, when a charge command value is transmitted from the control unit 26 to the power storage device 3, the power storage device 3 receives part of the power generated by the power generation device 2 via the connection unit 10 and charges the storage battery. On the other hand, when a discharge command value is transmitted from the control unit 26 to the power storage device 3, the power storage device 3 discharges the power stored in the storage battery toward the connection unit 10. The power Pgr discharged from the power storage device 3 is allocated to at least one of the power consumption Pel of the water electrolysis device 6, the power consumption Pax of the auxiliary machinery 7, and the reverse flow power Pex to the power grid 50.

[0047] The storage unit 27 stores time-series data of various information such as the power generation amount Ppv of the power generation device 2, the power Pgr charged to and discharged from the power storage device 3, the remaining power storage amount Egr of the power storage device 3, the power command value Pav, and the power consumption Pel of the water electrolysis device 6. The storage unit 27 may also store the power consumption Pax of the auxiliary device 7 and the minimum reverse flow power.

[0048] [Hardware configuration] Next, the hardware configuration of the power control device 5 will be described. Fig. 3 is a block diagram showing an example of the hardware configuration of the power control device 5. As shown in Fig. 3, the power control device 5 includes one or more computers 100. The computer 100 includes a processor 101, a main memory unit 102, an auxiliary memory unit 103, a communication control unit 104, an input device 105, and an output device 106. The power control device 5 is configured by one or more computers 100 configured by this hardware and software such as a program.

[0049] When the power control device 5 is configured by multiple computers 100, the multiple computers 100 may be connected locally or via a communication network such as the Internet or an intranet. This connection logically constructs a single power control device 5.

[0050] The processor 101 executes an operating system, application programs, etc. The main memory 102 is composed of a ROM (Read Only Memory) and a RAM (Random Access Memory). The auxiliary memory 103 is a storage medium composed of a hard disk, flash memory, etc. The auxiliary memory 103 generally stores a larger amount of data than the main memory 102. The communication control unit 104 is composed of a network card or a wireless communication module. At least a part of the communication function with other devices in the power control device 5 may be realized by the communication control unit 104. The input device 105 is composed of a keyboard, a mouse, a touch panel, a microphone for voice input, etc. The output device 106 is composed of a display, a printer, etc.

[0051] The auxiliary storage unit 103 stores the program 110 and data necessary for processing. The program 110 causes the computer 100 to execute each functional element of the power control device 5. The program 110, for example, realizes the functions of the power control device 5 in the computer 100. For example, the program 110 is read by the processor 101 or the main storage unit 102, and causes at least one of the processor 101, the main storage unit 102, the auxiliary storage unit 103, the communication control unit 104, the input device 105, and the output device 106 to operate. For example, the program 110 reads and writes data from and to the main storage unit 102 and the auxiliary storage unit 103.

[0052] The program 110 may be provided in the form of being recorded on a tangible storage medium such as a CD-ROM, a DVD-ROM, a semiconductor memory, etc. The program 110 may also be provided as a data signal via a communication network.

[0053] [Hydrogen production method] Next, a hydrogen production method according to one embodiment will be described with reference to Figures 4 and 5. This hydrogen production method is executed by a power control device 5. More specifically, to ensure that the hydrogen is derived from renewable energy, the power control device 5 adjusts the load (power consumption) of the power storage device 3 and the hydrogen production device 4, thereby producing hydrogen in a state where it is constantly flowed backward to the power grid 50.

[0054] The operation of the power control device 5 differs depending on the operating state of the water electrolysis device 6. Therefore, in the following explanation, the operation of the power control device 5 will be described separately for when the water electrolysis device 6 is stopped and when it is operating.

[0055] 4 is a flowchart showing the processing flow of the power control device 5 when the water electrolysis device 6 is stopped. The steps shown in FIG. 4 are repeatedly executed at predetermined intervals. As shown in FIG. 4, in a hydrogen production method according to one embodiment, first, the power generation amount acquisition unit 21, the control information acquisition unit 22, the power consumption acquisition unit 23, and the remaining power storage amount acquisition unit 24 of the power control device 5 acquire various data (step ST1). For example, the various data acquired include the power generation amount Ppv of the power generation device 2, the power consumption Pax of the auxiliary equipment 7, the minimum reverse flow power, and the remaining power storage amount Egr of the power storage device 3. The acquired various data are stored in the storage unit 27.

[0056] Next, power is flowed backward to the power grid 50 at the minimum backward flow power (step ST2). That is, the backward flow power Pex is set to the minimum backward flow power. The backward flow power Pex is allocated from the power generated by the power generation device 2 or the power discharged from the power storage device 3. Next, the command value generating unit 25 of the power control device 5 generates a power command value Pav (step ST3). The power command value Pav is determined based on the above-mentioned equation (1).

[0057] Next, it is determined whether the power generation amount Ppv of the power generation device 2 is greater than the sum of the power consumption Pax of the auxiliary device 7 and the reverse flow power Pex (step ST4). If Ppv > Pax + Pex is not established, the power generation amount Ppv of the power generation device 2 cannot cover the power consumption Pax and the reverse flow power Pex of the auxiliary device 7, so the control unit 26 controls the power storage device 3 to discharge the shortfall in power from the power storage device 3 (step ST6). At this time, the power Pgr discharged from the power storage device 3 is expressed by the following equation (2). The power Pgr discharged from the power storage device 3 continues the reverse flow from the hydrogen production system 1 to the power grid 50.

[0058] Pgr = Pax + Pex - Ppv (2)

[0059] On the other hand, if Ppv > Pax + Pex is established, it is determined whether the power command value Pav is greater than a threshold value Pperm (step ST5). The threshold value Pperm is a value obtained by adding a certain margin to the sum of the minimum output of the water electrolysis device 6 and the power consumption Pax of the auxiliary device 7. The margin is set to a somewhat large value so that operation of the water electrolysis device 6 can be continued even if the power generation amount Ppv of the power generator 2 decreases due to changes in weather, etc. after operation of the water electrolysis device 6 has started.

[0060] If the power command value Pav is equal to or less than the threshold value Pperm, the control unit 26 charges the power storage device 3 with surplus power without operating the water electrolysis device 6 (step ST7). If operation of the water electrolysis device 6 is started when there is insufficient surplus power, it will be necessary to stop operation of the water electrolysis device 6 when the amount of power generated by the power generator 2 subsequently decreases Ppv, which is likely to result in a decrease in the availability of the water electrolysis device 6. In step ST7, the power Pgr to be charged to the power storage device 3 is set to the power command value Pav.

[0061] On the other hand, if the power command value Pav is greater than the threshold value Pperm, the operation of the water electrolysis device 6 is started (step ST8). The operation of the water electrolysis device 6 starts the production of hydrogen. Even in this case, part of the power generation amount Ppv of the power generation device 2 is allocated to the reverse flow power Pex, and the reverse flow to the power grid 50 continues.

[0062] Next, the operation of the power control device 5 after the water electrolysis device 6 starts operating will be described. Figure 5 is a flowchart showing the processing flow of the power control device 5 when the water electrolysis device 6 is operating. Each step shown in Figure 5 is repeatedly executed at a predetermined cycle.

[0063] 5 , in a hydrogen production method according to one embodiment, first, various data to be used for power control are acquired by the power control device 5 (step ST11). For example, the various data acquired include the power generation amount Ppv of the power generation device 2, the power consumption Pax of the auxiliary device 7, the minimum reverse flow power, and the remaining power storage amount Egr of the power storage device 3. The acquired various data are stored in the storage unit 27.

[0064] Next, power is flowed backward to the power grid 50 at the minimum backward flow power (step ST12). That is, the backward flow power Pex is set to the minimum backward flow power. The backward flow power Pex is allocated from the power generated by the power generation device 2 or the power discharged from the power storage device 3. Next, the command value generating unit 25 of the power control device 5 generates a power command value Pav (step ST13). The power command value Pav is determined based on the above-mentioned equation (1).

[0065] Next, it is determined whether the power command value Pav is greater than a threshold value Pstop (step ST14). For example, the threshold value Pstop is a power threshold value at which the hydrogen production efficiency of the water electrolysis device 6 drops significantly, and is a value smaller than the threshold value Pperm.

[0066] If the power command value Pav is equal to or less than the threshold value Pstop, the operation of the water electrolysis device 6 is stopped (step ST15). This is because, when the power command value Pav is smaller than the threshold value Pstop, stopping the water electrolysis device 6 increases the total amount of hydrogen produced, rather than continuing operation with the output of the water electrolysis device 6 reduced. Next, to cover the power consumption Pax of the auxiliary device 7 and the reverse flow power Pex, the power storage device 3 discharges the shortfall in power (step ST16). At this time, the power Pgr discharged from the power storage device 3 is expressed by the above-mentioned equation (2). The power Pgr discharged from the power storage device 3 continues the reverse flow from the hydrogen production system 1 to the power grid 50.

[0067] On the other hand, if the power command value Pav is greater than the threshold value Pstop, it is determined whether the power command value Pav is greater than the threshold value Pperm (step ST17). If the power command value Pav is equal to or less than the threshold value Pperm, the control unit 26 outputs the power command value Pav to the water electrolysis device 6 (step ST18). As a result, the water electrolysis device 6 is operated at power consumption Pel corresponding to the power command value Pav to produce hydrogen.

[0068] Here, when the power command value Pav is equal to or less than the threshold value Pperm, the power generation amount Ppv of the power generation device 2 may not be enough to cover the power consumption Pel of the water electrolysis device 6, the power consumption Pax of the auxiliary equipment 7, and the reverse flow power Pex. In this case, the control unit 26 causes the power storage device 3 to discharge the shortfall in power (step ST19). At this time, the power Pgr discharged from the power storage device 3 is expressed by the following equation (2). That is, the power generation amount Ppv of the power generation device 2 and the power Pgr discharged from the power storage device 3 are allocated to the power consumption Pel of the water electrolysis device 6, the power consumption Pax of the auxiliary equipment 7, and the reverse flow power Pex.

[0069] Pgr = Pel + Pax + Pex - Ppv (3)

[0070] Next, it is determined whether the remaining amount of stored power Egr is smaller than a reference value Egrmin (step ST20). The reference value Egrmin is the amount of power that can cover the power consumption Pax and reverse flow power Pex of the auxiliary equipment 7 until the start of power generation by the power generation device 2 on the next day. The reference value Egrmin is determined based on, for example, the power consumption Pax, the minimum reverse flow power, and the current time. The reference value Egrmin may also be adjusted by reducing the power consumption Pel of the water electrolysis device 6.

[0071] If the remaining amount of stored power Egr is equal to or greater than the reference value Egrmin, discharge from the power storage device 3 continues (step ST19), and operation of the water electrolysis device 6 continues. On the other hand, if the remaining amount of stored power Egr is smaller than the reference value Egrmin, operation of the water electrolysis device 6 is stopped (step ST21). This is because if the remaining amount of stored power Egr becomes smaller than the reference value Egrmin, reverse power flow to the power grid 50 cannot be continued until the power generation device 2 starts generating power the next day. After operation of the water electrolysis device 6 is stopped, the power storage device 3 discharges the shortfall in power (step ST22). At this time, the power Pgr discharged from the power storage device 3 is expressed by the above-mentioned equation (2). The power Pgr discharged from the power storage device 3 continues reverse power flow from the hydrogen production system 1 to the power grid 50.

[0072] On the other hand, if it is determined in step ST17 that the power command value Pav is greater than the threshold value Pperm, then it is determined whether the power command value Pav is greater than the rated output Pelmax of the water electrolysis device 6 (step ST23). The rated output Pelmax is the maximum output of the water electrolysis device 6. If the power command value Pav is equal to or less than the rated output Pelmax of the water electrolysis device 6, the power command value Pav is output to the water electrolysis device 6 (step ST24). As a result, the water electrolysis device 6 produces hydrogen at an output corresponding to the power command value Pav.

[0073] On the other hand, if the power command value Pav is greater than the rated output Pelmax of the water electrolysis device 6, the water electrolysis device 6 is operated at the rated output Pelmax (step ST25). In this case, surplus power is generated even when the water electrolysis device 6 is operated at the rated output Pelmax, and the power storage device 3 is charged with the surplus power (step ST26). At this time, the power Pgr charged to the power storage device 3 is expressed by the following equation (4):

[0074] Pgr=Pelmax+Pax+Pex-Ppv (4)

[0075] Charging of the power storage device 3 continues until the remaining power storage amount Egr reaches the maximum remaining power storage amount Egrmax (step ST27). When the remaining power storage amount Egr reaches the maximum remaining power storage amount Egrmax, charging of the power storage device 3 is stopped to protect the power storage device 3 (step ST28). If surplus power still occurs after charging of the power storage device 3 is stopped, the reverse flow power Pex is increased and the surplus power is caused to flow reversely to the power grid 50.

[0076] As described above, the power control device 5 adjusts the power Pgr charged / discharged from the power storage device 3 and the power consumption Pel of the water electrolysis device 6 in accordance with the power generation amount Ppv of the power generation device 2 so that a constant reverse power flow occurs from the hydrogen production system 1 to the power grid 50. In this way, by producing hydrogen with a constant reverse power flow to the power grid 50, hydrogen can be produced by the water electrolysis device 6 without receiving power from the power grid 50. The hydrogen produced in this way is green hydrogen that can be proven to be derived from renewable energy.

[0077] The above describes a power control device, a hydrogen production system, and a hydrogen production method according to various embodiments, but the invention is not limited to the above-described embodiments and various modifications can be made without changing the gist of the invention.

[0078] For example, as long as renewable energy is used, the power generation device 2 may be a renewable energy power generation facility other than a solar power generation device. The power generation device 2 may also be configured by combining multiple units and multiple types of renewable energy power generation facilities. Even in this case, hydrogen that can be proven to be derived from renewable energy can be produced by adjusting the load on the electricity storage device 3 and the hydrogen production device 4 according to the amount of power generated by the power generation device 2.

[0079] Furthermore, in the above embodiment, the hydrogen production system 1 includes the power storage device 3, but the power storage device 3 is not an essential component. The power consumption Pel of the water electrolysis device 6 may be adjusted according to the amount of power generated by the power generation device 2, and hydrogen may be produced in a state where reverse power flow to the power grid 50 occurs at all times.

[0080] Furthermore, in the above embodiment, reverse power flow is caused to flow to the electric power grid 50 even when the operation of the water electrolysis device 6 is stopped. However, it is sufficient if reverse power flow is constantly generated in the electric power grid 50 at least while the water electrolysis device 6 is in operation. If reverse power flow is constantly generated while the water electrolysis device 6 is in operation, electricity from the electric power grid 50 is prevented from being used to produce hydrogen, making it possible to produce hydrogen that is provably derived from renewable energy.

[0081] The auxiliary machinery 7 of the hydrogen production device 4 may be stopped while the water electrolysis device 6 is stopped. In this case, the power command value Pav is determined based on the power generation amount Ppv of the power generation device 2 and the reverse flow power Pex.

[0082] [Note] This disclosure contributes to the widespread adoption of renewable energy by resolving grid connection issues caused by unstable renewable energy generation. As such, this disclosure also contributes to the following targets of the United Nations-led Sustainable Development Goals (SDGs): Target 7.2: "By 2030, substantially increase the share of renewable energy in the global energy mix." Target 9.3: "By 2030, upgrade infrastructure and retrofit industry to make them sustainable, with increased resource-use efficiency and greater adoption of clean and environmentally friendly technologies and industrial processes. All countries will take action in accordance with their national capabilities."

[0083] The present disclosure will be described with reference to the following clauses: It should be noted that the present disclosure may include the following clauses in any combination without specific recitation:

[0084] 1. A power control device for a hydrogen production system comprising a power generation device that generates electricity using renewable energy, a hydrogen production device that produces hydrogen using the electricity generated by the power generation device, and a connection unit that connects the power generation device and the hydrogen production device to an electric power grid, a power control device that determines a power command value to be supplied to the hydrogen production device based on the power generated by the power generation device and the power that is reversely flowed to the power grid, so that hydrogen is produced in a state where reverse flow to the power grid occurs at all times.

[0085] 2. A power control device according to clause 1, which determines the power command value Pav based on the following equation (1), where Ppv is the power generated by the power generation device, Pax is the standby power of the hydrogen production device, and Pex is the power flowed back to the power grid. Pav = Ppv - Pax - Pex (1)

[0086] 3. The hydrogen production system further includes a power storage device connected to the connection part, When the hydrogen production device is stopped and the power command value is smaller than a threshold value, the hydrogen production device is not operated and the power generated by the power generation device is charged into the power storage device; 3. The power control device according to claim 1 or 2, wherein, when the power command value is equal to or greater than a threshold value, the power command value is output to the hydrogen production device to cause hydrogen to be produced.

[0087] 4. A power control device as described in clause 3, which, when the hydrogen production device is in operation and the power command value is smaller than a threshold value, outputs the power command value to the hydrogen production device to produce hydrogen and discharges the shortfall in power from the power storage device.

[0088] 5. The power control device according to clause 3 or 4, which stops operation of the hydrogen production device when the remaining charge of the power storage device falls below a reference value due to the discharge of power from the power storage device.

[0089] 6. A power control device described in any one of clauses 3 to 5, wherein when the power command value is greater than the rated output of the hydrogen production device, the hydrogen production device is operated at the rated output and surplus power is charged to the storage device.

[0090] 7. A power generation device that generates electricity using renewable energy; a hydrogen production device that produces hydrogen using the electric power generated by the power generation device; a connection part for connecting the power generation device and the hydrogen production device to an electric power grid; a power control device for controlling the operation of the hydrogen production device; Equipped with The power control device determines a power command value to be supplied to the hydrogen production device based on the power generated by the power generation device and the power that is reversely flowed to the power grid, so that hydrogen is produced in a state where reverse flow to the power grid occurs at all times.

[0091] 8. Further comprising a power storage device connected to the connection part; The power control device A hydrogen production system as described in clause 7, wherein, when the hydrogen production device is stopped and the power command value is smaller than a threshold value, the hydrogen production device is not operated and the power generated by the power generation device is charged to the power storage device, and when the power command value is equal to or greater than a threshold value, the power command value is output to the hydrogen production device to produce hydrogen.

[0092] 9. A hydrogen production system as described in clause 8, wherein, when the hydrogen production device is in operation and the power command value is smaller than a threshold value, the power control device outputs the power command value to the hydrogen production device to produce hydrogen and discharges the shortfall in power from the power storage device.

[0093] 10. A step of acquiring the amount of power generated by a power generation device that generates power using renewable energy; a step of causing at least a portion of the electric power generated by the power generation device to flow backward to an electric power grid; determining a power command value to be supplied to the hydrogen production device based on the power generated by the power generation device and the power flowed back to the power grid; a step of outputting the power command value to the hydrogen production device to produce hydrogen while a reverse power flow to the power grid is constantly occurring; A method for producing hydrogen, comprising: [Explanation of symbols]

[0094] 1. Hydrogen production system 2. Power generating equipment 3. Energy storage device 4. Hydrogen production equipment 5 Power control device 10 Connection 50 Power system Egr remaining battery capacity Pperm threshold Egrmin reference value Pav Power command value Pelmax Rated Output Pgr Charged and discharged power PPV power generation

Claims

1. A power control device for a hydrogen production system, comprising: a power generation device that generates power using renewable energy; a hydrogen production device that produces hydrogen using the power generated by the power generation device; a connection unit that connects the power generation device and the hydrogen production device to an electric power grid; and a power storage device connected to the connection unit, determining a power command value to be supplied to the hydrogen production device based on the power generated by the power generation device and the power to be reversely flowed to the power grid so that hydrogen is produced in a state where reverse power flow to the power grid occurs at all times; When the hydrogen production device is stopped and the power command value is smaller than a threshold value, the hydrogen production device is not operated and the power generated by the power generation device is charged into the power storage device; When the power command value is equal to or greater than a threshold value, the power control device outputs the power command value to the hydrogen production device to cause hydrogen to be produced.

2. 2. The power control device according to claim 1, wherein the power command value Pav is determined based on the following equation (1): Pav=Ppv-Pax-Pex...(1)

3. 2. The power control device according to claim 1, wherein, when the hydrogen production device is in operation and the power command value is smaller than a threshold value, the power command value is output to the hydrogen production device to produce hydrogen and the power storage device is caused to discharge the shortfall in power.

4. The power control device according to claim 3, wherein the operation of the hydrogen production device is stopped when the remaining charge of the power storage device becomes equal to or less than a reference value due to the discharge of power from the power storage device.

5. 2. The power control device according to claim 1, wherein when the power command value is greater than a rated output of the hydrogen production device, the hydrogen production device is operated at the rated output and surplus power is charged into the power storage device.

6. A power generation device that generates electricity using renewable energy; a hydrogen production device that produces hydrogen using the electric power generated by the power generation device; a connection part for connecting the power generation device and the hydrogen production device to an electric power grid; a power storage device connected to the connection portion; a power control device for controlling the operation of the hydrogen production device; Equipped with The power control device includes: determining a power command value to be supplied to the hydrogen production device based on the power generated by the power generation device and the power to be reversely flowed to the power grid so that hydrogen is produced in a state where reverse power flow to the power grid occurs at all times; A hydrogen production system in which, when the hydrogen production device is stopped and the power command value is smaller than a threshold value, the hydrogen production device is not operated and the power generated by the power generation device is charged to the power storage device, and when the power command value is equal to or greater than the threshold value, the power command value is output to the hydrogen production device to produce hydrogen.

7. 7. The hydrogen production system according to claim 6, wherein, when the hydrogen production device is in operation and the power command value is smaller than a threshold value, the power control device outputs the power command value to the hydrogen production device to produce hydrogen and discharges the shortfall in power from the power storage device.

8. acquiring the amount of power generated by a power generation device that generates power using renewable energy; a step of causing at least a portion of the electric power generated by the power generation device to flow backward to an electric power grid; determining a power command value to be supplied to the hydrogen production device based on the power generated by the power generation device and the power flowed back to the power grid; a step of outputting the power command value to the hydrogen production device to produce hydrogen while a reverse power flow to the power grid is constantly occurring; Including, The step of producing hydrogen includes: When the hydrogen production device is stopped and the power command value is smaller than a threshold value, charging the power generated by the power generation device to a power storage device without operating the hydrogen production device; When the power command value is equal to or greater than a threshold value, outputting the power command value to the hydrogen production device to produce hydrogen; A method for producing hydrogen, comprising:

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