Water electrolysis control system and water electrolysis control method
The water electrolysis control system addresses the challenge of maintaining high operating rates and extending the lifespan of electrolytic stacks by dynamically adjusting temperature and voltage in response to grid fluctuations, enhancing efficiency and reducing costs.
Patent Information
- Authority / Receiving Office
- WO · WO
- Patent Type
- Applications
- Current Assignee / Owner
- HITACHI LTD
- Filing Date
- 2025-11-07
- Publication Date
- 2026-06-25
AI Technical Summary
Water electrolysis systems producing green hydrogen face challenges in maintaining high operating rates and extending the lifespan of electrolytic stacks due to fluctuations in renewable energy supply, which require grid stabilization capabilities, leading to decreased efficiency and increased equipment replacement costs.
A water electrolysis control system and method that incorporates voltage, current, and temperature measuring units, along with a control unit to manage water flow rate and cooling, adjusting the electrolytic stack's temperature and voltage in response to grid power changes, thereby minimizing current fluctuations and maintaining high operating rates.
The system effectively contributes to grid stabilization while maximizing hydrogen production efficiency and reducing equipment degradation, thus lowering operational costs and extending the lifespan of the electrolytic stack.
Smart Images
Figure JP2025039026_25062026_PF_FP_ABST
Abstract
Description
Water electrolysis control system and water electrolysis control method
[0001] The present invention relates to a water electrolysis control system and a water electrolysis control method.
[0002] In order to realize a low-carbon society, power generation using renewable energy (renewable energy) such as sunlight and wind power is becoming active instead of thermal power generation using fossil fuels. However, since the electric power generated by renewable energy fluctuates greatly due to natural phenomena, it cannot be used as a substitute for conventional grid power as it is, and it also becomes a factor that destabilizes the grid. Therefore, green hydrogen has been proposed, which uses the electric power generated by renewable energy to electrolyze water, generate hydrogen, store it, and use it as fuel (including for power generation purposes).
[0003] The electrolysis of water is performed by a water electrolysis system including a minimum structural unit called an electrolytic cell, an electrolytic stack in which a plurality of cells are electrically stacked in series, a power supply device that supplies and controls power to the electrolytic stack, a pump that supplies water to the electrolytic stack, and auxiliary devices such as a hydrogen compressor. The renewable energy power required for the production of green hydrogen may be supplied directly from renewable energy facilities or via the grid. When attempting to produce green hydrogen on a certain scale (in the MW level), the latter supply method is often selected.
[0004] The method of producing green hydrogen using an electrolysis system is more costly compared to gray hydrogen produced from conventional fossil fuels. Therefore, cost reduction is important for the market expansion of green hydrogen. The costs include the operating cost, which is the electricity cost for converting water into hydrogen, and the equipment cost of the water electrolysis system itself. The operating cost becomes a dominant factor when the system is operating for a long time. A water electrolysis system that can produce the same amount of hydrogen with less electric power is advantageous. On the other hand, the equipment cost is the introduction cost of the electrolytic stack, the power supply device, and the auxiliary devices.
[0005] By increasing the operating rate, which is the ratio of power input to the installed capacity of the electrolytic cell, the amount of hydrogen produced relative to the equipment cost can be increased. Also, since the electrolytic stack has a shorter lifespan compared to other components, the number of replacements multiplied by the unit cost during a certain operating period becomes dominant. To reduce the number of replacements, it is desirable to suppress its degradation and extend its lifespan. Systems that incorporate this degradation suppression are also a differentiating factor. For this reason, conventional technologies have disclosed technologies to increase electrolysis efficiency and technologies to reduce lifespan.
[0006] Japanese Patent Publication No. 2005-290557
[0007] Because renewable energy will be transmitted through the grid for green hydrogen production, the grid is expected to remain unstable in the short term. Therefore, water electrolysis systems that produce green hydrogen are expected to possess not only the ability to produce hydrogen but also the ability to contribute to grid stabilization (referred to here as adjustment capability). Specifically, this involves adjusting the power supplied to the electrolysis stack (electrolysis power) in response to any surplus or shortage of power in the grid.
[0008] To incorporate this capability into the water electrolysis system, a situation arises that contradicts the differentiating technology described in the background. In other words, in order to contribute electricity (in this case, to reduce the amount of electricity that should be input to electrolysis), the electrolysis power will decrease further. Also, in order to prepare for the absorption of electricity, a margin must always be maintained in the electrolysis stack. This means that the operating rate cannot be raised to 100% in order to ensure adjustment capacity in the hydrogen production facility. Due to these factors, the operating rate will decrease significantly.
[0009] The object of the present invention is to provide a water electrolysis control system and a water electrolysis control method that have the ability to contribute power adjustment capabilities to the power grid and suppress a decrease in the operating rate of the electrolysis stack in a water electrolysis system for producing green hydrogen.
[0010] The present invention relates to a water electrolysis control system for an electrolysis system having an electrolysis stack connected to a power grid and producing hydrogen, and is characterized in that it comprises a voltage measuring unit, a current measuring unit and a temperature measuring unit installed on the electrolysis stack, a power supply device that receives power commands from a higher-level control, and a control unit that controls at least one of the water flow rate and cooling amount to the electrolysis stack, and the control unit controls the temperature of the electrolysis stack based on changes in the power commands from the power grid.
[0011] Furthermore, the present invention relates to a water electrolysis control method for an electrolysis system having an electrolysis stack connected to a power grid and producing hydrogen, a voltage measuring unit, a current measuring unit and a temperature measuring unit installed on the electrolysis stack, a power supply device that receives power commands from a higher-level control, and a control unit that controls at least one of the water flow rate and cooling amount to the electrolysis stack, characterized in that the control unit controls the temperature of the electrolysis stack based on changes in the power commands from the power grid.
[0012] According to the present invention, a water electrolysis control system and a water electrolysis control method can be provided that have the ability to contribute power adjustment capacity to the power grid and suppress a decrease in the operating rate of the electrolysis stack in a water electrolysis system for producing green hydrogen.
[0013] This is a schematic diagram showing the water electrolysis system of Example 1. This is a schematic diagram showing the water electrolysis system using an electrolytic stack as a comparative example. This is a diagram illustrating the typical current-voltage characteristics of an electrolytic stack. This is a diagram showing the change in power on the grid side when the grid requests power from the electrolysis system. This is a diagram showing the change in power on the electrolysis side when the grid requests power from the electrolysis system. This is a diagram showing the change in power on the grid side when the grid requests power absorption from the electrolysis system. This is a diagram showing the change in power on the electrolysis side when the grid requests power absorption from the electrolysis system. This is a diagram showing the change in current on the electrolysis side when the grid requests power from the electrolysis system described in Example 1. This is a diagram showing the change in voltage on the electrolysis side when the grid requests power from the electrolysis system described in Example 1. This is a diagram showing the change in current on the electrolysis side when the grid requests power absorption from the electrolysis system described in Example 1. This is a diagram showing the change in voltage on the electrolysis side when the grid requests power absorption from the electrolysis system described in Example 1. This is a flowchart diagram showing the control of the electrolysis system described in Example 1. This is a flowchart diagram showing the control of the electrolysis system described in Example 1. A diagram of the user interface of the electrolysis system described in Example 1. A diagram of the user interface of the electrolysis system described in Example 1. A schematic configuration diagram showing the water electrolysis system described in Example 2. A schematic configuration diagram showing the water electrolysis system described in Example 3. A time series diagram showing the discharge command to the battery system for the water electrolysis system described in Example 3. A time series diagram showing the charge command to the battery system for the water electrolysis system described in Example 3.
[0014] First, the problems of the present invention will be specifically described with reference to the drawings. Figure 2 is a schematic diagram showing a water electrolysis system using an electrolytic stack as a comparative example. It shows a hydrogen production system including an electrolytic stack having a proton exchange membrane (PEM). In this figure, the four electrolytic stacks 102 (102a, 102b, 102c, 102d) are electrically connected in series, and both ends are connected to a power supply 101. The power supply has the function of converting the AC of the system 120 to DC and simultaneously adjusting the current flowing to the electrolytic stack to a current command value. The water involved in electrolysis is supplied in parallel to the oxygen electrode (anode side) of the electrolytic stack by a pump 106.
[0015] The decomposed oxygen and the water that was not decomposed are both discharged from the electrolytic stack and separated into oxygen gas and water in the gas-liquid separator 104. The water is cooled in the cooler 105 and then returned to the pump. Although not shown in this figure, water is replenished as needed before and after cooling.
[0016] From the hydrogen electrode (cathode side) of the electrolytic stack, decomposed hydrogen is discharged along with some associated water, which is also separated into hydrogen gas and water by the gas-liquid separator 103. When electrolysis occurs in the electrolytic stack, about 20-30% of the input electricity is converted into heat. Therefore, by supplying low-temperature water to the electrolytic stack, the heat accumulated in the electrolytic stack is discharged along with the water. The high-temperature water after gas-liquid separation is cooled and then supplied back to the electrolytic stack.
[0017] Figure 3 illustrates the typical current-voltage characteristics of an electrolytic stack. It is a schematic diagram of the typical current-voltage characteristics of a PEM electrolytic stack. When a voltage above a certain level is applied to the electrolytic stack, a current begins to flow and then increases almost linearly. This current reflects the amount of hydrogen produced. As the temperature of the electrolytic stack rises, this voltage-current curve shifts toward the direction of lower voltage and a gentler slope (lower resistance).
[0018] Therefore, from the perspective of hydrogen production efficiency, that is, the ratio of hydrogen produced to input power, the electrolytic stack temperature is raised as much as possible to lower the voltage required to pass the same current. On the other hand, rising the temperature of the electrolytic stack accelerates its deterioration. To reduce the temperature rise of the electrolytic stack, the water flow rate is increased by operating the pump and the circulating water is cooled by operating the cooler.
[0019] In the control unit 210 shown in Figure 2, temperature information from the temperature sensor 107 attached to the electrolytic stack is processed as statistical information in the aggregation unit 112. Only when the temperature exceeds the temperature threshold related to the deterioration of the electrolytic stack is a temperature reduction command issued from the threshold comparison unit 113 to the auxiliary equipment control unit 216, causing the auxiliary equipment (coolers such as pumps and compressors) to be driven more powerfully.
[0020] In summary, the hydrogen production system supplies power from the power grid to the electrolytic stack, and monitors the temperature of the electrolytic stack while operating the pumps and coolers. The system then raises the temperature as much as possible without causing degradation, increasing the efficiency of hydrogen production relative to the amount of electricity used, and accepting the maximum amount of power to carry out hydrogen production in order to increase the operating rate of the equipment.
[0021] If we attempt to give this hydrogen production system the power adjustment capability to the grid, it will become impossible to operate it with the high efficiency and high operating rate described above. We will now explain the problems associated with this.
[0022] Let's consider the case where a hydrogen production system contributes power to the grid. Figure 4A shows the change in power on the grid side when the grid requests power from the electrolysis system. Figure 4B shows the change in power on the electrolysis side when the grid requests power from the electrolysis system. When the higher-level control system managing the grid commands the water electrolysis system to contribute ΔP of power, the power supply attempts to reduce the power to the electrolysis stack by ΔP. In reality, it attempts to respond to this power reduction by reducing the current. This current phenomenon directly leads to a decrease in the amount of hydrogen produced. This decrease in hydrogen is undesirable from the perspective of the system's objective of hydrogen production.
[0023] On the other hand, let's consider the case where the hydrogen production system absorbs power from the grid. Figure 5A shows the change in power on the grid side when the grid requests power absorption from the electrolysis system. Figure 5B shows the change in power on the electrolysis side when the grid requests power absorption from the electrolysis system. When the higher-level control that manages the grid issues a command to the water electrolysis system to contribute ΔP of power, the power supply attempts to increase the power to the electrolysis stack by ΔP. In reality, it attempts to respond to this power increase by increasing the current. An increase in current directly leads to an increase in the amount of hydrogen produced. This increase is desirable from the perspective of hydrogen production. However, conversely, it is necessary to constantly reduce the power by that amount and keep the system on standby, which is undesirable in the long term.
[0024] The following describes a method for solving the above-mentioned problems based on an embodiment of the present invention.
[0025] Figure 1 is a diagram showing the configuration of the water electrolysis system in Embodiment 1. The arrangement and connection of the power supply unit 101, the electrolysis stack 102, and other auxiliary equipment 100 (pump and hydrogen compressor) are the same as in Figure 2. The control unit 110 is also the same, and is equipped with an auxiliary equipment control unit that monitors the temperature of each electrolysis stack with sensors, collects statistical data, and instructs the auxiliary equipment to cool the stack based on the temperature upper limit and threshold.
[0026] The electrolysis system is connected to a power grid and has an electrolysis stack that produces hydrogen. The water electrolysis control system includes a voltage measuring unit, a current measuring unit, and a temperature measuring unit installed on the electrolysis stack, a power supply unit that receives power commands from a higher-level control unit, and a control unit that controls at least one of the water flow rate and cooling amount to the electrolysis stack.
[0027] As a characteristic of the water electrolysis control method, the additional parts of the control unit 110, which is a control device characterized in this example, will be described. It consists of a higher-level control unit 1115 that receives a power command from the system control that sends a power command to the electrolysis system for the purpose of maintaining the stability of the system and generates a power command and control commands to auxiliary equipment, a voltage division unit 114 that divides the stack voltage value from the power command value from the control unit, and an auxiliary equipment control unit 116 that controls the received auxiliary equipment with the auxiliary equipment command value.
[0028] The control unit 110 has the ability to contribute power adjustment power to the power system by controlling the temperature of the electrolytic stack based on changes in power commands from the power system, thereby suppressing a decrease in the operating rate of the electrolytic stack. In summary, in response to changes in power commands from the system, the stack voltage is changed by evaluating the temperature of the stack and changing the water flow rate and cooling amount to control the temperature, thereby minimizing the range of change in the current command. By changing the stack voltage and controlling it to minimize the range of change in the current command, the range of change in the current command can be reduced.
[0029] This will be explained in more detail below. Figure 6A shows the change in current on the electrolysis side when the power grid requests power from the electrolysis system described in Example 1. Figure 6B shows the change in voltage on the electrolysis side when the power grid requests power from the electrolysis system described in Example 1. This shows the changes in current and voltage on the electrolysis side when the power grid requests power from the electrolysis system. Because the power drawn from the grid is required to be reduced, the electrolysis power of the electrolysis stack moves in the direction of decreasing. From the perspective of hydrogen production, we do not want to reduce the electrolysis current, which is directly related to the amount of hydrogen produced, so we control the auxiliary equipment to reduce the voltage instead of the current.
[0030] In other words, by slowing down the operation of auxiliary equipment (flow rate for pumps, cooling capacity for coolers) and raising the temperature of the electrolytic cell, the voltage drop becomes greater than the current drop. As a result, the current drop is minimized while still meeting the power supply from the grid.
[0031] Figure 6C shows the change in current on the electrolysis side when the electrolysis system described in Example 1 is required to absorb power from the power system. Figure 6D shows the change in voltage on the electrolysis side when the electrolysis system described in Example 1 is required to absorb power from the power system. It shows the changes in current and voltage on the electrolysis side when the electrolysis system is required to absorb power from the power system.
[0032] Because there is a demand for increased power drawn from the grid, the electrolytic power of the electrolytic stack is increased. From the perspective of hydrogen production, an increase in electrolytic current, which is directly related to the amount of hydrogen produced, is desirable. However, due to the demand from the grid, it is necessary to keep this increase in current available at all times, and it is preferable to suppress this increase as much as possible.
[0033] Therefore, the auxiliary equipment is controlled to increase the voltage instead of the current by this increase. In other words, the operation of the auxiliary equipment (flow rate for a pump, cooling capacity for a cooler) is accelerated to lower the temperature of the electrolytic cell, thereby making the increase in voltage greater than the increase in current.
[0034] As a result, it is possible to respond to power contributions from the grid while minimizing the increase in current. The control unit 110 has the ability to contribute power adjustment power to the power grid by controlling at least one of the water flow rate and cooling amount to the electrolytic stack so that the range of change in the current command to the electrolytic stack becomes small in response to changes in the power command from the power grid, and the range of change in the voltage of the electrolytic stack becomes large while evaluating the temperature of the electrolytic stack, thereby suppressing a decrease in the operating rate of the electrolytic stack.
[0035] The flow of the higher-level control unit and auxiliary equipment control unit to achieve the above operations will be explained. Figure 7A is a flowchart for controlling the electrolysis system described in Example 1. Figure 7B is also a flowchart for controlling the electrolysis system described in Example 1. The flow of the higher-level control unit shown in Figure 7A will be explained. First, the auxiliary equipment operating temperature monitoring task, which is essential for the operation of the hydrogen production system, is started (step 701). Next, it is decided whether to provide power commands from the grid, i.e., adjustment power, for the operation of the water electrolysis system (step 702). This decision takes into account the cost-effectiveness of providing adjustment power and the costs related to hydrogen production, which are determined by the price of renewable energy electricity purchased from the grid and the equipment price, but this is complex so it will not be specified here. Under normal operation, the maximum power command value determined from the perspective of hydrogen production is received (step 703), and this is continuously commanded to the power source as the normal power command value.
[0036] On the other hand, when providing adjustment power, a command value is issued to the power supply as the power command for standby before activating the adjustment power, which is the maximum power determined from the perspective of hydrogen production minus the amount set aside for the adjustment power contribution (704). The adjustment power command is received in the next step (step 705). The direction of the adjustment power is determined (step 706), and if the command is to provide power to the grid as adjustment power (a decrease in power for the electrolytic stack), a temperature rise command is issued to the auxiliary equipment operation control (step 707). Conversely, if the command is to absorb power from the grid as adjustment power (an increase in power for the electrolytic stack), a temperature drop command is issued to the auxiliary equipment operation control (step 708).
[0037] Next, the operation flow of the auxiliary equipment control unit shown in Figure 7B will be explained. When the auxiliary equipment control is started, it first operates at its initial values (step 721). Temperature information of the electrolytic stack is obtained from temperature monitoring (step 722), and it is compared to whether it is the upper limit temperature set by the system (step 723). If so, it commands the auxiliary equipment (pump and cooler) to increase power and speed to operate more efficiently (step 725). The increment value is set separately. Otherwise, it continues to operate at its initial values.
[0038] Next, the system checks for the presence and type of commands from higher-level control (step 724). If a temperature rise command is received, the system instructs the auxiliary equipment (pumps and coolers) to reduce their power and speed so that they operate more slowly (step 726). The reduction value is set separately. On the other hand, if a temperature drop command is received, the system instructs the auxiliary equipment (pumps and coolers) to increase their power and speed so that they operate more efficiently (step 725).
[0039] The thresholds and power increase / decrease values for auxiliary equipment that appear in these flowcharts are set separately in the user interface. Figure 8A is a diagram of the user interface of the electrolytic system described in Example 1. Figure 8B is a diagram of the user interface of the electrolytic system described in Example 1. Figure 8A is an example of a parameter setting table for the behavior of higher-level control and a display table showing the effects of this embodiment, and Figure 8B is an example of a parameter setting table for the behavior of auxiliary equipment control.
[0040] By using the higher-level control and auxiliary equipment control described above, it is possible to meet power adjustment requests from the grid while maximizing the operating rate of the hydrogen production system.
[0041] When the electrolytic power is reduced by a power command from the power grid, the power of auxiliary equipment is contributed to the power grid. When the electrolytic power is increased by a power command from the power grid, the power of auxiliary equipment is absorbed from the power grid, thereby meeting the power adjustment request from the grid.
[0042] According to this embodiment, while maximizing the operating rate as a hydrogen production system, it is possible to respond to the power adjustment contribution from the power grid. When reducing the electrolysis power by a power command, the auxiliary devices such as pumps and coolers are operated to slow down the circulation of the auxiliary devices in the direction of increasing the temperature of the electrolysis stack, increasing the temperature of the electrolysis stack, and making the decrease in voltage larger, so that the decrease range of the current can be reduced. When increasing the electrolysis power, the auxiliary devices are operated to strengthen the circulation of the auxiliary devices in the direction of decreasing the temperature of the electrolysis stack, decreasing the temperature of the electrolysis stack, and making the increase in voltage larger (increasing the voltage change), so that the increase range of the current can be reduced. By suppressing the increase and decrease of the current due to the adjustment power contribution from the power grid, the current during standby (when normally producing hydrogen) can be set high, that is, the operating rate can be set high.
[0043] FIG. 9 is a schematic configuration diagram showing the water electrolysis system described in Example 2. The arrangement and connection relationship of the power source, electrolysis stack, and other auxiliary devices are the same as those in FIG. 1. The control unit is also configured by adding upper-level control and auxiliary device control as shown in Example 1. The difference from Example 1 is that the power of the auxiliary devices (pumps and coolers) is also supplied from the same system as the electrolysis stack. Without changing the control method from Example 1, by sharing the power supplied to the auxiliary devices with that of the electrolysis stack, the effects of the present invention can be more effectively exerted.
[0044] When obtaining power from the electrolysis stack as an adjustment force from the system, in order to suppress the decrease in the electrolysis current as in Example 1, a policy of reducing the voltage of the electrolysis stack is adopted. In this case, the operations of the pumps and coolers are controlled to be slow. That is, since it acts in the direction of reducing the power consumption of the auxiliary devices, by sharing the power of the electrolysis stack and the power of the auxiliary devices, a part of the decrease in the power of the electrolysis stack can be transferred to the decrease in the power of the auxiliary devices.
[0045] When power is absorbed from the system as an adjustment force to the electrolytic stack, in order to suppress an increase in the electrolytic current as in Example 1, a policy of lowering the voltage of the electrolytic stack is adopted. In this case, the operations of the pump and cooler are controlled to become rapid. That is, since it acts in the direction of increasing the power consumption of the auxiliary device, by sharing the power of the electrolytic stack and the auxiliary device, a part of the increase in the power of the electrolytic stack can be transferred to the increase in the power of the auxiliary device.
[0046] From the above, by sharing the electrolytic power and the power of the auxiliary device with respect to the system, a part of the increase or decrease in the current to the electrolytic stack due to the provision of the adjustment force to the system can be transferred as an increase or decrease in the power of the auxiliary device, and the increase or decrease in the current of the electrolytic stack can be further suppressed.
[0047] FIG. 10 is a schematic configuration diagram showing the water electrolysis system described in Example 3. The arrangement and connection relationship of the power source, electrolytic stack, and other auxiliary devices are the same as those in FIG. 1. The control unit is also configured by adding upper-level control and auxiliary device control as shown in Example 1. The difference from Example 1 is that a storage battery 1002 and a power supply device 1001 for controlling it are connected to the same system 120.
[0048] The control of the rise and fall of the electrolytic voltage accompanying the provision of the adjustment force described in Examples 1 and 2 so far is due to the rise and fall of the temperature of the electrolytic stack accompanying the slow and rapid control of the operation of the auxiliary device. Depending on the scale of the electrolysis system, it becomes much slower than the variation rate of the power command (time vs. power variation amount). In that case, it means that the situation where the performance of the electrolytic stack cannot be fully utilized continues until the appropriate electrolytic voltage, that is, the temperature of the electrolytic stack, is reached with respect to the provision of the adjustment force from the system.
[0049] Therefore, a part that cannot respond quickly enough by the slow and rapid operation of the auxiliary device with respect to the provision of the adjustment force is compensated by the charge and discharge of the storage battery. When power is provided from the electrolytic stack as an adjustment force from the system, in order to suppress a decrease in the electrolytic current as in Example 1, a policy of lowering the voltage of the electrolytic stack is adopted. In this case, the operations of the pump and cooler are controlled to become slow. However, when the scale of the electrolytic stack is large and the temperature does not rise immediately, until the rise ends, a part of the power provided from the electrolytic stack is covered by the discharge power from the storage battery.
[0050] When power is absorbed from the grid to the electrolytic stack as a regulating force, the same approach as in Example 1 is taken to suppress the increase in electrolytic current by lowering the voltage of the electrolytic stack. In this case, the operation of the pump and cooler is controlled to be rapid. However, if the electrolytic stack is large and the temperature does not drop immediately, a portion of the power absorption from the grid that the electrolytic stack takes on is covered by the power being charged to the storage battery until the temperature drops.
[0051] In practice, the charge / discharge control device receives a power command based on a response profile that reflects the time-dependent temperature rise and fall of the electrolytic stack, obtained by subtracting the adjustment force command from the electrolytic power command.
[0052] Figure 11A is a time-series diagram showing the discharge command to the battery system for the water electrolysis system described in Example 3. Figure 11B is a time-series diagram showing the charge command to the battery system for the water electrolysis system described in Example 3. When the water electrolysis system supplies power by ΔP, the electrolysis power is adjusted according to a pre-set power response profile of the electrolysis system (a gently sloping ramp-down in the diagram), and the difference with the adjustment power is covered by discharge from the battery.
[0053] Conversely, when ΔP of power is absorbed by the water electrolysis system, the electrolysis power is adjusted according to a pre-set power response profile of the electrolysis system (shown as a gently sloping ramp-up in the diagram), and the difference with the adjustment power is covered by discharge to the storage battery.
[0054] As described above, the control unit generates charge / discharge commands that reflect the difference between the time variation of the power command and the temperature change of the electrolytic stack due to the control of auxiliary equipment. If the control of auxiliary equipment cannot keep up with sudden changes in power, the system contributes power through charging and discharging from the storage battery, thereby preventing performance degradation due to differences between the required speed of power contribution and the temperature response of the electrolytic stack.
[0055] Furthermore, if the auxiliary equipment operation of the electrolytic stack in the water electrolysis system, and the resulting temperature rise and fall of the electrolytic stack, cannot keep up with the response speed required to provide adjustment power, a battery-based charge / discharge system is connected to the same system as the electrolytic stack, and the issue is addressed by transferring power from the charge / discharge system. In this way, performance degradation due to differences between the required speed for providing adjustment power and the temperature response of the electrolytic stack can be prevented.
[0056] This example describes variations of the charge / discharge system shown in Example 3. The charge / discharge system shown in Example 3 can be replaced with other energy devices. For example, solar power generation can be used as a renewable energy device, and a diesel generator as a power generation device. On the other hand, an electric double-layer capacitor, flywheel, etc., may be connected as a charging device. It goes without saying that the control profiles shown in Example 3 are applied to the control units of each device.
[0057] 100...Auxiliary equipment, 101...Power supply unit, 102...Electrolytic stack, 103...Hydrogen-side gas-liquid separator, 104...Oxygen-side gas-liquid separator, 105...Cooler, 106...Pump, 107...Temperature sensor, 110...Control unit, 111...Voltage measurement unit, 112...Temperature measurement unit, 113...Temperature information statistics unit, 114...Current command generation unit, 115...Higher-level control unit, 116...Auxiliary equipment control unit, 120...System, 210...Conventional control unit, 216...Auxiliary equipment control unit, 1001...Power supply unit for storage battery, 1002...Storage battery.
Claims
1. A water electrolysis control system for an electrolytic system having an electrolytic stack connected to a power grid and producing hydrogen, comprising: a voltage measuring unit, a current measuring unit and a temperature measuring unit installed on the electrolytic stack; a power supply device that receives power commands from a higher-level control; and a control unit that controls at least one of the water flow rate and cooling amount to the electrolytic stack, wherein the control unit controls the temperature of the electrolytic stack based on changes in the power commands from the power grid.
2. A water electrolysis control system according to claim 1, wherein the control unit controls at least one of the water flow rate and cooling amount to the electrolysis stack so that the range of change of the current command to the electrolysis stack becomes small in response to a change in the power command from the power system, and so that the range of change of the voltage of the electrolysis stack becomes large while evaluating the temperature of the electrolysis stack.
3. A water electrolysis control system according to claim 1, comprising an auxiliary device including at least one of a pump for supplying water to the electrolysis stack and a hydrogen compressor, wherein the control unit controls the auxiliary device to increase the temperature of the electrolysis stack when the power command reduces the electrolysis power, thereby reducing the voltage change and decreasing the current decrease, and controls the auxiliary device to increase the temperature of the electrolysis stack when the power command increases the electrolysis power, thereby increasing the voltage change and decreasing the current increase.
4. A water electrolysis control system according to claim 3, characterized in that when the electrolysis power is reduced by the power command from the power system, the power of the auxiliary equipment is supplied to the power system, and when the electrolysis power is increased by the power command from the power system, the power of the auxiliary equipment is used to absorb power from the power system.
5. A water electrolysis control system according to claim 1, comprising: an auxiliary device including at least one of a pump and a hydrogen compressor for supplying water to the electrolysis stack; and a storage battery connected to the same power system as the electrolysis system, wherein the control unit generates a charge / discharge command that reflects the difference between the time change of the power command and the temperature change of the electrolysis stack due to the control of the auxiliary device, and if the control of the auxiliary device cannot keep up with the sudden change in power, it contributes power by charging and discharging from the storage battery.
6. A water electrolysis control system according to claim 1, wherein the control unit changes the stack voltage and controls it to minimize the range of change of the current command.
7. A water electrolysis control method for an electrolysis system having an electrolysis stack connected to a power grid and producing hydrogen, a voltage measuring unit, a current measuring unit and a temperature measuring unit installed on the electrolysis stack, a power supply device that receives power commands from a higher-level control, and a control unit that controls at least one of the water flow rate and cooling amount to the electrolysis stack, characterized in that the control unit controls the temperature of the electrolysis stack based on changes in the power commands from the power grid.
8. A water electrolysis control method according to claim 7, characterized in that the control unit controls at least one of the water flow rate and cooling amount to the electrolysis stack so that the range of change of the current command to the electrolysis stack becomes small in response to a change in the power command from the power system, and so that the range of change of the voltage of the electrolysis stack becomes large while evaluating the temperature of the electrolysis stack.
9. A water electrolysis control method according to claim 7, wherein the electrolysis system includes an auxiliary device comprising at least one of a pump for supplying water to the electrolysis stack and a hydrogen compressor, and the control unit controls the auxiliary device to increase the temperature of the electrolysis stack and reduce the voltage change and decrease in current when the power command reduces the electrolysis power, and controls the auxiliary device to increase the temperature of the electrolysis stack and increase the voltage change and decrease in current when the power command increases the electrolysis power.
10. A water electrolysis control method according to claim 9, characterized in that when the electrolysis power is reduced by the power command from the power system, the power of the auxiliary equipment is supplied to the power system, and when the electrolysis power is increased by the power command from the power system, the power of the auxiliary equipment is absorbed from the power system.
11. A water electrolysis control method according to claim 7, wherein the electrolysis system comprises an auxiliary device including at least one of a pump for supplying water to the electrolysis stack and a hydrogen compressor, and a storage battery connected to the same power system as the electrolysis system, and the control unit generates a charge / discharge command that reflects the difference between the time change of the power command and the temperature change of the electrolysis stack due to the control of the auxiliary device, and if the control of the auxiliary device cannot keep up with the sudden change in power, the power is supplied by charging and discharging from the storage battery.
12. A water electrolysis control method according to claim 7, characterized in that the control unit changes the stack voltage and controls it to minimize the range of change of the current command.