Nuclear power plant operation method and regulated power supply equipment

Abstract

Provided is a nuclear power plant operation method wherein: a nuclear power plant (100) operates for a set output; electric power of part of the output is supplied to a hydrogen production device (16) installed in a power generation plant so that a set amount of hydrogen is normally produced; and when there is a demand for increased regulated power in an electric power system (14), hydrogen production by the hydrogen production device (16) is stopped or the produced amount of hydrogen is reduced, and increased regulated power is provided to the electric power system (14). On the basis of a predicted amount of renewable energy generation, a transaction amount in a supply / demand market, and information pertaining to a transaction price status, the nuclear power plant (100) stops the hydrogen production device (16) and provides increased regulated power upon receiving a notification when the regulated power price is high or when the generated amount of renewable energy is less than the predicted amount.

Description

Nuclear power plant operation methods and adjustment power supply facilities

[0001] The present invention relates to a nuclear power plant operation method and an adjustable power supply facility.

[0002] A nuclear power plant and its operating method that can effectively utilize and suppress fluctuations in the thermal output of a nuclear reactor while adjusting the output to the power grid according to load demands are being studied.

[0003] Patent Document 1 discloses that "when there is no surplus thermal output of the reactor relative to the load demand, the nuclear power plant performs a first operation in which the entire amount of thermal output of the reactor is introduced into the steam turbine to generate electricity and the hydrogen production system is stopped; when there is surplus thermal output of the reactor and the surplus thermal output is equal to or less than the upper limit of the hydrogen production system, the nuclear power plant performs a second operation in which the thermal output of the reactor is maintained and part of the thermal output is introduced into the steam turbine to generate electricity and the remainder is supplied to the hydrogen production system to produce hydrogen; and when the surplus thermal output of the reactor exceeds the upper limit of the hydrogen production system, the nuclear power plant performs a third operation in which the thermal output of the reactor is reduced so that the surplus thermal output is equal to or less than the upper limit of the hydrogen production system, and part of the thermal output is introduced into the steam turbine to generate electricity and the remainder is supplied to the hydrogen production system to produce hydrogen."

[0004] Japanese Patent Application Laid-Open No. 2023-076833

[0005] It is expected that renewable energy will be introduced on a large scale into future power grids. As this era of large-scale renewable energy introduction arrives, there are concerns that nuclear power will lose profits due to a decline in the amount and price of electricity sold.

[0006] On the other hand, variable renewable energy (VRE) such as solar power generation and wind power generation is, in principle, dependent on natural conditions, making it difficult to predict its power output in advance, and there are cases where the expected power output differs significantly from the actual output. In order to maintain high quality of power even when such variable power sources are added, a power source that can act as an adjuster to absorb fluctuations in power output caused by the variable power sources is required.

[0007] Another proposal is to use excess electricity from renewable energy sources to produce hydrogen, which can then be stored and used as energy. However, revenue from hydrogen production depends on the hydrogen sales price and production costs (operation rate of the hydrogen production equipment), and since operation using surplus electricity reduces the operation rate of the hydrogen production equipment, there are concerns that the economic viability will further deteriorate if hydrogen production costs rise.

[0008] As mentioned above, Patent Document 1 discloses the first, second, and third operation modes, but does not disclose whether they satisfy the objectives of ensuring profits, securing adjustable power sources, and a stable supply of hydrogen production. Therefore, there is room for improvement in the operation method of a nuclear power plant.

[0009] The present invention has been made in consideration of the above-mentioned problems, and its purpose is to stabilize power quality by enabling output adjustment while ensuring profits, and at the same time to ensure a stable supply of hydrogen.

[0010] In order to solve the above problems, the method of operating a nuclear power plant of the present invention is characterized in that the nuclear power plant is operated at a constant output, a part of the electric power output is supplied to a hydrogen production device installed in the power plant to constantly produce a constant amount of hydrogen, and when there is a demand for power adjustment capability in the power grid, hydrogen production by the hydrogen production device is stopped or the amount of hydrogen produced is reduced, thereby providing power adjustment capability to the power grid. Other aspects of the present invention will be described in the embodiments described later.

[0011] According to the present invention, it is possible to stabilize the quality of power by enabling output adjustment while ensuring profits, and at the same time, it is possible to ensure a stable supply of hydrogen.

[0012] Fig. 1 is a diagram showing the configuration of a nuclear power plant according to an embodiment of the present invention; Fig. 2 is a diagram showing the device configuration of a water electrolysis system as an example of a hydrogen production device; Fig. 3 is a diagram showing an operation example of a nuclear power plant; Fig. 4 is a diagram showing an example of profit calculation for each operation example; Fig. 5 is a block diagram of a computer;

[0013] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings, etc. The following description shows specific examples of the contents of the present invention, and the present invention is not limited to these descriptions. Various changes and modifications can be made by those skilled in the art within the scope of the technical ideas disclosed in this specification. Furthermore, in all drawings used to explain the present invention, parts having the same functions are designated by the same reference numerals, and repeated explanations thereof may be omitted.

[0014] 1 is a diagram showing the configuration of a nuclear power plant 100 according to this embodiment. The nuclear power plant 100 has a hydrogen production device 16 installed in a nuclear power plant 11. To facilitate understanding of the configuration, this configuration shows a schematic circuit configuration that shows only the main equipment components. A generator 12 of the nuclear power plant 11 is connected to a power grid 14 via a transformer 13 (main transformer).

[0015] The hydrogen production device 16 is connected to the in-station circuit via a semiconductor power conversion device 17 and a transformer 18. The power system 14 indicates an extra-high voltage system.

[0016] The nuclear power plant 100 operates at a constant output (operation at an output that can be considered constant), and supplies a portion of the electric power output to a hydrogen production device 16 installed within the power plant to constantly produce a constant amount of hydrogen. Note that the power plant refers to a plant including related facilities installed alongside the nuclear power plant 11.

[0017] The hydrogen production device 16 functions as a load balancing capacity for the power grid, and is configured to exchange monitoring signals and the like with the central load balancing center 19 via a dedicated line 21 as needed. A control device 20 is installed to control the semiconductor elements in the semiconductor power conversion device 17. Because the nuclear power plant 11 and the hydrogen production device 16 are installed independently, there is normally no control between them. The hydrogen production device 16 controls the semiconductor power conversion device 17 via the control device 20 in response to commands from the central load balancing center 19 in accordance with the electricity traded in the load balancing market, etc., and stops the hydrogen production device 16 when there is a demand for increased load balancing capacity in the power grid.

[0018] 2 is a diagram showing the device configuration of a water electrolysis system 200 as an example of the hydrogen production device 16. As shown in Fig. 2 , the water electrolysis system 200 mainly includes a water electrolysis stack 101, a hydrogen gas tank 102, an oxygen gas tank 103, water piping 106, hydrogen gas piping 107, oxygen gas piping 108, a water pump 109, a large cooler 110, a water flow control valve 111, a small cooler 112, a hydrogen gas tank pressure control valve 113, an oxygen gas tank pressure control valve 114, an electrolysis stack hydrogen gas pressure control valve 115, an electrolysis stack oxygen gas pressure control valve 116, an oxygen gas / water separation tank 117, an electrolysis stack water pressure control valve 118, a water tank 119, and a hydrogen gas / water separation tank 120. The water electrolysis system 200 also includes a control device 20.

[0019] The control device 20 is configured with, for example, a CPU (Central Processing Unit), RAM (Random Access Memory), ROM (Read Only Memory), etc. The control device 20 is realized by a predetermined program (control program) stored in the ROM being loaded into the RAM and executed by the CPU. The program here is for causing a computer to execute a control method. Note that control signal lines and the like between the control device 20 and each controlled device, such as the water flow adjustment valve 111, are not shown in the figure.

[0020] FIG. 5 is a block diagram of a computer 980 used as the control device 20. The control device 20 includes one or more computers 980 shown in FIG. 5. In FIG. 5, the computer 980 includes a CPU 981, a storage unit 982, a communication I / F (interface) 983, an input / output I / F 984, and a media I / F 985. Here, the storage unit 982 includes a RAM 982a, a ROM 982b, and an HDD 982c. The communication I / F 983 is connected to a communication circuit 986. The input / output I / F 984 is connected to an input / output device 987. The media I / F 985 reads and writes data from a recording medium 988.

[0021] The hydrogen production process of the water electrolysis system 200 is as follows: Water is supplied from a water tank 119 to the oxygen electrode side of each water electrolysis stack 101 by a water pump 109. A predetermined voltage is applied to the water electrolysis stack 101 to electrolyze water, generating hydrogen and oxygen. The generated hydrogen is adjusted to a predetermined pressure by the electrolysis stack hydrogen gas pressure regulating valve 115, passes through the hydrogen gas piping 107, and is collected in the hydrogen gas tank 102. The pressure is adjusted to a predetermined pressure by the hydrogen gas tank pressure regulating valve 113, and the hydrogen gas 104 is supplied to the outside. The generated oxygen is discharged from the water electrolysis stack 101 together with water that was not electrolyzed, separated in the oxygen gas / water separation tank 117, adjusted to a predetermined pressure by the electrolysis stack oxygen gas pressure regulating valve 116, passes through the oxygen gas piping 108, and is collected in the oxygen gas tank 103. The pressure is adjusted to a predetermined pressure by the oxygen gas tank pressure regulating valve 114, and the oxygen gas 105 is supplied to the outside. The water separated in the oxygen gas / water separation tank 117 is adjusted to a predetermined pressure by an electrolysis stack water pressure regulating valve 118, collected in a water tank 119, and supplied again via a water pump to the water electrolysis stack 101. Although a power supply line is not shown in Figure 2, the water electrolysis stack 101 is connected to a general large-scale DC power supply and supplies power required for water electrolysis.

[0022] The water electrolysis system 200 in FIG. 2 is assumed to be a system in which water is supplied to both the oxygen electrode side and the hydrogen electrode side, but in a proton permeation type solid polymer water electrolysis stack, water may be supplied only to the oxygen electrode side.

[0023] Water electrolysis systems other than the proton permeation type have two water supply systems, and water is also supplied to the hydrogen electrode side, as shown in water electrolysis system 200 in Fig. 2. The generated hydrogen is separated in hydrogen gas / water separation tank 120, adjusted to a predetermined pressure by electrolysis stack hydrogen gas pressure regulating valve 115, passed through hydrogen gas piping 107, and collected in hydrogen gas tank 102. The water separated in the hydrogen gas / water separation tank 120 is adjusted to a predetermined pressure by electrolysis stack water pressure regulating valve 118, collected in water tank 119, and supplied again to the water electrolysis stack 101 via the water pump.

[0024] The electrolysis stack hydrogen gas pressure regulating valve 115 and the electrolysis stack oxygen gas pressure regulating valve 116 are equipment specific to the water electrolysis system 200. A typical water electrolysis stack 101 has variations in characteristics and variations in electrolysis voltage due to deterioration, so even if the same current is passed through it, differences in resistance values ​​result in differences in electrolysis efficiency.

[0025] In the water electrolysis system 200, the electrolysis voltage of each water electrolysis stack is measured, and the pressure of the water electrolysis stack with a high electrolysis voltage is reduced by adjusting the electrolysis stack hydrogen gas pressure regulating valve 115 and the electrolysis stack oxygen gas pressure regulating valve 116. This reduces the reaction resistance, thereby lowering the voltage of the electrolysis stack with a high voltage and reducing the voltage difference with the other electrolysis stacks, enabling operation with increased electrolysis efficiency.

[0026] The opening and closing degrees of the electrolysis stack hydrogen gas pressure adjustment valve 115 and the electrolysis stack oxygen gas pressure adjustment valve 116 are constantly monitored to prevent backflow due to pressure differences with other electrolysis stacks, and a control algorithm is provided to control the pressures of both gas tanks by controlling the hydrogen gas tank pressure adjustment valve 113 and the oxygen gas tank pressure adjustment valve 114 according to the situation.

[0027] Fig. 3 is a diagram showing examples of operation of the nuclear power plant 100. Fig. 3 shows an operation example 3A under base conditions (100% output), an operation example 3B when an increase in the adjustable power capacity is required at a constant nuclear power output, and an operation example 3C when an increase in the adjustable power capacity is required during variable nuclear power output operation. Fig. 1 will be referred to as appropriate.

[0028] Operation example 3A is an example of base load operation of a nuclear power plant, in which 100% of the power generation output is transmitted to the grid.

[0029] Operation example 3B is an example of baseload operation of a nuclear power plant, just like operation example 3A, except that when there is no request for adjustable load capacity, the adjustable load range of power is used for hydrogen production, and when there is a request for adjustable load capacity, the adjustable load range is used as the adjustable load range. In operation example 3B, the nuclear power plant 100 operates at a constant output, and the control device 20 supplies a portion of the output power to the hydrogen production device 16 installed in the power plant to constantly produce a constant amount of hydrogen, and when there is a request for adjustable load capacity from the power grid 14, the control device 20 stops hydrogen production by the hydrogen production device 16 and provides adjustable load capacity to the power grid 14. When the period for which adjustable load capacity is requested has elapsed, the control device 20 supplies power to the hydrogen production device 16 installed in the power plant to resume constantly producing a constant amount of hydrogen.

[0030] Operation example 3C is an example of variable output operation of a nuclear power plant, in which when there is no request for adjustable power, power within the adjustable range is used for hydrogen production, and when there is a request for adjustable power, power within the adjustable range is used as adjustable power. In operation example 3C, the nuclear power plant 100 operates in an adjustable output mode, and the control device 20 supplies a portion of the output power to the hydrogen production device 16 installed in the power plant to constantly produce a fixed amount of hydrogen, and when there is a request for adjustable power from the power grid 14, it stops hydrogen production by the hydrogen production device 16 and provides adjustable power to the power grid 14. When the period required for adjustable power has elapsed, the control device 20 supplies power to the hydrogen production device 16 installed in the power plant to resume constantly producing a fixed amount of hydrogen.

[0031] Although it depends on the power grid to which it is connected, in areas where there is little constant demand and high demand for adjustment capacity, if nuclear power is operated constantly, there will be an oversupply, and power plants will be required to reduce their output. However, in areas with high demand for adjustment capacity, there is also a high demand in the supply and demand market, so in this embodiment, by reducing constant power using hydrogen, additional revenues are secured by selling electricity, producing and selling hydrogen, and supplying adjustment capacity (which is possible with this configuration).

[0032] The above-mentioned adjustment range serves as a power source that can adjust to compensate for sudden drops in power output caused by variable power sources, even when variable power sources such as solar power generation and wind power generation are added to the power grid. Here, the economic viability of nuclear power plants was examined in Figure 4, with the adjustment range set to 0.3%, 3%, and 30% of the rated output of the nuclear power plant.

[0033] Figure 4 shows an example of revenue calculation for each operation example. Figure 4 shows the revenue for operation examples 3B and 3C in Figure 3 when the revenue for operation example 3A in Figure 3 is set to "1". The adjustment ranges are set to 0.3%, 3%, and 30% of the rated output of the nuclear power plant. Hydrogen sales revenue was calculated at 100 yen / Nm3, which is the selling price taking into account the current price of imported hydrogen and transportation costs. Note that Nm3 is normal lube.

[0034] In the case of operation example 3C, when variable output operation is used, the revenue from selling electricity will decrease significantly by the amount of output adjustment, and the revenue from selling hydrogen and the revenue from the power adjustment capacity will be added. When the adjustment range is 30%, the revenue will be greater than 1, and an improvement in the economic efficiency of the nuclear power plant can be expected.

[0035] In the case of Operation Example 3B, like Operation Example 3A, this is an example of baseload operation for a nuclear power plant, so when the adjustment range is small at 0.3%, the profit is almost 1, and as the adjustment range increases, the overall profit increases. When the adjustment range is 30%, the profit is even greater than in Operation Example 3C, and further improvements in the economic efficiency of the nuclear power plant can be expected.

[0036] It should be noted that the profit calculation in Fig. 3 takes into account the income from selling hydrogen produced by the hydrogen production device 16, but in the water electrolysis system 200 in Fig. 2 , oxygen is also produced and stored in the oxygen gas tank 103. Therefore, if the income from selling oxygen is also taken into account, further improvement in economic efficiency can be expected.

[0037] The example in Figure 4 is a calculation example in which upward adjustment capacity is provided when there is a request for upward adjustment capacity in the power grid. However, based on information on the predicted amount of renewable energy power generation, trading volume in the supply and demand market, and trading price status, if a notification is received that the amount of renewable energy power generation is smaller than the predicted amount or the adjustment capacity price is high, the hydrogen production device may be stopped and upward adjustment capacity may be provided.

[0038] (Effects) The effects of this embodiment can be summarized as follows. (1) Because the power plant does not adjust its output, thermal fluctuations do not fluctuate for a predetermined period of time. Furthermore, there is no need to operate valves or the like related to output adjustment. Therefore, there is no impact on the lifespan of the nuclear power plant. (2) A stable supply of low-cost hydrogen is possible. Costs can be reduced by improving the availability of the hydrogen production device 16 and reducing power generation costs. While electricity is generally procured from the market, producing hydrogen on-site means that electricity bills are based on power generation costs, making it low cost. Furthermore, hydrogen can be produced even when transmission lines are unavailable, eliminating the need for wheeling charges. (3) The stability of the power system is good. This is because adjustment capacity can be supplied and power flow in transmission lines can be reduced. In this embodiment, as shown in FIG. 1, the hydrogen production device 16 is installed next to the nuclear power plant 11, and electricity generated by the nuclear power plant is used to produce hydrogen. (4) Profit compensation can be achieved. If the above-mentioned power generation volume is reduced, revenue from selling electricity will decrease accordingly, but by adding to this the profits from hydrogen sales and the supply and demand adjustment market, it is possible to ensure a profit level comparable to that during base load.

[0039] The nuclear power plant operating method of this embodiment has the following features: (1) In the nuclear power plant operating method, the nuclear power plant 100 operates at a constant output, and supplies a portion of the power output to a hydrogen production device 16 installed in the power plant to constantly produce a constant amount of hydrogen. When an increase in power adjustment capability is required from the power grid, hydrogen production by the hydrogen production device 16 is stopped, and increase in power adjustment capability is provided to the power grid (see operation example 3B in FIG. 3 ). This makes it possible to stabilize power quality by enabling output adjustment while ensuring profits, and at the same time ensure a stable supply of hydrogen.

[0040] (2) As an operation method for the nuclear power plant, the nuclear power plant 100 operates in an adjustable output mode, and supplies a portion of the power output to the hydrogen production unit 16 installed in the power plant to constantly produce a fixed amount of hydrogen. When the power grid requests an increase in adjustable capacity, the hydrogen production by the hydrogen production unit is stopped, and the increase in adjustable capacity is provided to the power grid (see operation example 3C in Figure 3). This allows for output adjustment while ensuring profits, thereby stabilizing the quality of power and ensuring a stable supply of hydrogen.

[0041] (3) In the method of operating a nuclear power plant according to (1) or (2), when a notification is received that the amount of renewable energy power generation is less than the forecast amount or that the price of power regulation is high, based on information on the forecast amount of renewable energy power generation, the trading volume in the supply and demand market, and the trading price situation, the hydrogen production device is stopped and an upward power regulation is provided. This makes it possible to stabilize the quality of electricity by enabling output regulation while further securing profits, and at the same time ensure a stable supply of hydrogen.

[0042] (4) A method for operating a nuclear power plant according to (1) or (2), comprising a power conversion device (semiconductor power conversion device 17) connected to an on-site circuit within the nuclear power plant and converting AC power into DC power, a hydrogen production device 16 connected to the power conversion device, and a control device 20 for controlling the power conversion device and the hydrogen production device 16.

[0043] (5) The adjustable power supply facility is connected to the in-plant circuit within the nuclear power plant and includes a power conversion device that converts AC power to DC power, a hydrogen production device 16 connected to the power conversion device, and a control device 20 that controls the power conversion device and the hydrogen production device 16. The control device 20 operates the nuclear power plant at a constant output, supplies a portion of the output power to the hydrogen production device 16 to constantly produce a constant amount of hydrogen, and when there is a request for adjustable power up to the power grid, stops hydrogen production by the hydrogen production device 16 and supplies adjustable power up to the power grid via the nuclear power plant's main circuit. This makes it possible to stabilize power quality by making output adjustments possible while ensuring profits, and at the same time ensure a stable supply of hydrogen.

[0044] The semiconductor power converter 17 and the transformer 18 may be present as part of the configuration of the hydrogen production device 16. The hydrogen production device 16 does not have to be located on-site at the power plant, but may be located nearby or in the surrounding area. It is preferable that the power used by the hydrogen production device 16 is not procured from the market, but is supplied (directly) from the nuclear plant, for example, by connecting a power converter to the on-site circuit.

[0045] Although an example has been described in which hydrogen production is stopped to provide power grid adjustment capability, it is also possible to provide power grid adjustment capability by appropriately reducing the production volume, such as by halving the production volume, without stopping hydrogen production. One possible way to reduce the production volume of hydrogen is to reduce the number of water electrolysis stacks 101 in operation, for example.

[0046] REFERENCE SIGNS LIST 11 Nuclear power plant (power plant) 12 Generator 13 Transformer (main transformer) 14 Power system (extra-high voltage system) 16 Hydrogen production equipment 17 Semiconductor power conversion equipment (power conversion equipment) 18 Transformer (for connecting internal circuits) 19 Central power dispatching center 20 Control device 21 Dedicated line 100 Nuclear power plant 101 Water electrolysis stack 102 Hydrogen gas tank (first tank) 103 Oxygen gas tank (second tank) 104 Hydrogen gas 105 Oxygen gas 106 Water piping 107 Hydrogen gas piping 108 Oxygen gas piping 109 Water pump 110 Large cooler 111 Water flow rate adjustment valve 112 Small cooler 113 Hydrogen gas tank pressure adjustment valve (first hydrogen pressure adjustment valve) 114 Oxygen gas tank pressure adjustment valve (first oxygen pressure adjustment valve) 115 Electrolysis stack hydrogen gas pressure regulating valve (second hydrogen pressure regulating valve) 116 Electrolysis stack oxygen gas pressure regulating valve (second oxygen pressure regulating valve) 117 Oxygen gas / water separation tank 118 Electrolysis stack water pressure regulating valve 119 Water tank 120 Hydrogen gas / water separation tank 200 Water electrolysis system

Claims

1. A method of operating a nuclear power plant, characterized in that the nuclear power plant is operated at a constant output, a portion of the electricity output is supplied to a hydrogen production unit installed within the power plant to constantly produce a constant amount of hydrogen, and when there is a demand for upregulation capability in the power grid, hydrogen production by the hydrogen production unit is stopped or the amount of hydrogen produced is reduced, thereby providing upregulation capability to the power grid.

2. A method of operating a nuclear power plant, characterized in that the nuclear power plant operates with its output adjusted, and supplies a portion of the electricity output to a hydrogen production unit installed within the power plant to constantly produce a fixed amount of hydrogen, and when there is a demand for increased power adjustment capacity in the power grid, stops hydrogen production by the hydrogen production unit or reduces the amount of hydrogen produced, thereby providing increased power adjustment capacity to the power grid.

3. A method for operating a nuclear plant according to claim 1 or claim 2, characterized in that, based on information on the forecasted amount of renewable energy power generation, trading volume in the supply and demand market, and trading price status, when a notification is received that the amount of renewable energy power generation is smaller than the forecasted amount or the price of adjustment power is high, the hydrogen production device is stopped or the amount of hydrogen produced is reduced, thereby providing increased adjustment power.

4. The method of operating a nuclear plant according to claim 1 or 2, characterized in that the nuclear plant comprises: a power conversion device connected to an in-plant circuit within the nuclear power plant and converting AC power into DC power; a hydrogen production device connected to the power conversion device; and a control device that controls the power conversion device and the hydrogen production device.

5. An adjustment power supply facility comprising: a power conversion device connected to an internal circuit within a nuclear power plant and converting AC power into DC power; a hydrogen production device connected to said power conversion device; and a control device that controls said power conversion device and said hydrogen production device, wherein said control device operates said nuclear power plant at a constant output, supplies a portion of the power output to said hydrogen production device to constantly produce a constant amount of hydrogen, and when there is a request for adjustment power to the power grid, stops hydrogen production by said hydrogen production device or reduces the amount of hydrogen produced, and supplies adjustment power to the power grid via the main circuit of said nuclear power plant.

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