Offshore wind power generation facilities

Abstract

We provide offshore wind power generation equipment equipped with energy storage devices that can be installed and operated in a manner suitable for offshore wind power generation. [Solution] An offshore wind power generation facility 10, wherein the energy storage device 22 includes an air tank 30 for storing compressed air, a pair of tanks 40 that can be switched to communicate with either the air tank 30 or the atmosphere and are capable of storing a mixture of water and air, an air compression means 34 that supplies water from the tank 40 communicating with the atmosphere to the other tank 40 to raise the water level and isothermally compress the air in the tank 40, and a hydroelectric power generation means 38 that supplies compressed air from the air tank 30 to the tank 40 to lower the water level, isothermally expands the compressed air in the tank 40 to pressurize the water in the tank 40, and generates hydroelectric power using the hydroelectric energy of the pressurized water, and the air tank 30 is formed inside the foundation structure 12.

Description

[Technical Field]

[0001] This invention relates to offshore wind power generation equipment. [Background technology]

[0002] Conventionally, floating offshore wind power generation facilities are known (see, for example, Patent Documents 1 and 2). A floating offshore wind power generation facility comprises a floating body used as a foundation, mooring lines for anchoring the floating body to the seabed, a tower installed on the floating body, and a wind turbine consisting of a nacelle and multiple blades installed at the top of the tower. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2014-218186 [Patent Document 2] Japanese Patent Publication No. 2014-173586 [Overview of the project] [Problems that the invention aims to solve]

[0004] In the floating offshore wind power generation facilities described above, it is desirable to integrate energy storage devices with the scale of power generation into the floating structure in order to ensure stable power transmission. However, even lithium-ion energy storage devices, which have a relatively small footprint per kW of power generation, require 100m² of secondary battery space. 2 For floating offshore wind power generation of 2MW to 3MW scale, the required energy output is 200 to 300m offshore. 2 Laying down a power storage device is difficult because it requires a large installation area. Furthermore, installing heavy objects like power storage devices on top of a floating body makes it difficult to secure the center of buoyancy and the center of gravity of the floating body. Installation in seawater is not feasible because it requires airtightness and pressure resistance, posing many challenges such as cost and the need to secure the center of gravity of the floating body. In addition, secondary batteries are not considered suitable for environments exposed to seawater.

[0005] The cost of power transmission work from floating offshore wind power generation facilities to land is generally around 15-20% of the total construction cost, although this depends on the distance from the shore. It is desirable to reduce power transmission costs by smoothing the power generation using batteries and cutting peak power. For this purpose, a method of storing the generated power on electric carrier ships equipped with a large number of batteries and transporting it from the sea to land is being considered. However, there is a problem in that batteries cannot be stored while the electric carrier ships are in operation.

[0006] The present invention has been made in view of the above, and aims to provide an offshore wind power generation facility equipped with an energy storage device that can be installed and operated in a manner suitable for offshore wind power generation. [Means for solving the problem]

[0007] To solve the above-mentioned problems and achieve the objective, the offshore wind power generation facility according to the present invention comprises a foundation structure provided in the water, a tower erected on the foundation structure, a wind turbine provided on the tower, a wind power generation means that generates wind power by the rotation of the wind turbine, and a power storage device that stores electricity in the form of compressed air, wherein the power storage device comprises an air tank for storing compressed air, a pair of tanks whose communication destination can be switched to either the air tank or the atmosphere and which can store a mixture of water and air, an air compression means that supplies water from the tank communicating with the atmosphere to the other tank to raise the water level and isothermally compress the air in the tank, and a hydropower generation means that supplies compressed air from the air tank to the tank to lower the water level, isothermally expands the compressed air in the tank to pressurize the water in the tank, and generates hydropower using the hydroelectric energy of the pressurized water, wherein the air tank is formed inside the foundation structure.

[0008] Furthermore, another offshore wind power generation facility according to the present invention is characterized in that, in the above-described invention, the foundation structure is a floating structure.

[0009] Furthermore, another offshore wind power generation facility according to the present invention is characterized in that, when the wind speed is high, the air compression means is operated using the power generated by the wind power generation means and compressed air is stored in the air tank, while when the wind speed is low, compressed air is supplied from the air tank to perform hydroelectric power generation by the hydroelectric power generation means and transmit the generated power.

[0010] Furthermore, another offshore wind power generation facility according to the present invention is characterized in that, in the invention described above, the tower or the tank is provided with intake and exhaust ports for exhausting air from inside the tank or drawing air into the tank. [Effects of the Invention]

[0011] The offshore wind power generation equipment according to the present invention comprises a foundation structure provided underwater, a tower erected on the foundation structure, a wind turbine provided on the tower, a wind power generation means that generates wind power by the rotation of the wind turbine, and a power storage device that stores electricity in the form of compressed air, wherein the power storage device comprises an air tank for storing compressed air, a pair of tanks whose communication destination can be switched to either the air tank or the atmosphere and which are capable of storing a mixture of water and air, and the other tank which is in communication with the atmosphere The system includes an air compression means that supplies water into the tank to raise the water level and isothermally compress the air in the tank, and a hydroelectric power generation means that supplies compressed air from the air tank into the tank to lower the water level, isothermally expands the compressed air in the tank to pressurize the water in the tank, and generates hydroelectric power using the hydroelectric energy of the pressurized water. Since the air tank is formed inside the foundation structure, it has the effect of providing an offshore wind power generation facility equipped with an energy storage device that can be installed and operated in a manner suitable for offshore wind power generation.

[0012] Furthermore, according to other offshore wind power generation equipment of the present invention, since the foundation structure is a floating structure, it has the effect of being able to utilize the floating structure as an air tank.

[0013] According to another offshore wind power generation facility of the present invention, when the wind speed is high, the air compression means is operated using the generated power by the wind power generation means, and compressed air is stored in the air tank. On the other hand, when the wind speed is low, compressed air is supplied from the air tank to perform hydroelectric power generation by the hydroelectric power generation means, and the generated power is transmitted. Therefore, it has the effect of smoothing the wind power generation output by storing electricity at the peak of wind power generation and transmitting power at low wind speeds or when there is no wind.

[0014] According to another offshore wind power generation facility of the present invention, the tower or the tank is provided with an air intake / exhaust port for exhausting air from the tank or sucking air into the tank. Therefore, it has the effect of avoiding the suction of seawater droplets.

Brief Description of the Drawings

[0015] [Figure 1] Fig. 1(1) is a side view showing an embodiment of the offshore wind power generation facility according to the present invention, and (2) is a configuration diagram of the power storage device. [Figure 2] Fig. 2 is a diagram showing the compression charging process according to this embodiment. [Figure 3] Fig. 3 is a diagram showing the expansion power generation process according to this embodiment. [Figure 4] Fig. 4 is a diagram showing the process of smoothing and storing the generated power according to this embodiment. [Figure 5] Fig. 5(1) is a diagram showing an example of monthly output fluctuations of the offshore wind power generation facility, and (2) is a diagram showing an example of daily output fluctuations in summer.

Embodiments for Carrying Out the Invention

[0016] Hereinafter, an embodiment of the offshore wind power generation facility according to the present invention will be described in detail based on the drawings. Note that the present invention is not limited by this embodiment.

[0017] (Offshore Wind Power Generation Facility) As shown in Figure 1(1), the offshore wind power generation facility 10 according to an embodiment of the present invention comprises a floating body 12, a tower 14 erected on the upper surface of the floating body 12, a wind turbine 20 consisting of a nacelle 16 and a plurality of blades 18 installed at the top of the tower 14, and an energy storage device 22. The nacelle 16 has a generator (wind power generation means) that generates wind power by the rotation of the wind turbine 20. The floating body 12 is moored to the seabed G via a plurality of mooring ropes 24. Power transmission cables 26 for transmitting the power generated by the offshore wind power generation facility 10 to land (not shown) are laid on the seabed G.

[0018] The floating body 12 is a spar-type floating body consisting of a vertically elongated, substantially cylindrical floating body structure (foundation structure) with a hollow interior. The lower part of the floating body 12 is submerged below the seawater surface WL, and the upper part of the floating body 12 is slightly above the seawater surface WL. The floating body 12 can be made of concrete or steel. In the example shown in the figure, the floating body 12 is made of a precast concrete lower part and a steel upper part, but the entire length of the floating body may be made of steel pipe. Inside the floating body 12, the lowest part is used as a ballast tank 28, and the upper part is used as an air tank for the energy storage device 22. The ballast tank 28 has a fixed ballast section 28A at the bottom and a ballast water section 28B at the top. Water can be added to or discharged from the ballast water section 28B, allowing the buoyancy (draft) of the floating body 12 to be adjusted. Note that the foundation structure of the present invention is not limited to a spar-type floating body, but may also be a semi-submersible type or a barge type floating body. Furthermore, the foundation structure is not limited to a floating structure; it may also be a foundation structure installed in a fixed state on the seabed G (a fixed-bottom offshore wind power generation facility).

[0019] (Energy storage device) As shown in Figure 1(2), the energy storage device 22 comprises an air tank 30, a pair of tank units A and B, a discharge / intake switching unit 32, a water pump 34, a circulating water pump 36, and a power generation turbine 38, and stores electricity in the form of compressed air. The energy storage device 22 is installed on a frame 12A placed on the upper surface of the floating body 12, excluding the air tank 30. In this embodiment, charging and discharging are performed by isothermal compression and isothermal expansion of air using only air and water, without generating CO2 from the combustion of fossil fuels.

[0020] The energy storage device 22 utilizes CAES (Compressed Air Energy Storage) technology to store electrical energy as compressed air. The floating body 12 is used as a pressure storage body for compressed air, enabling the storage of electricity generated by wind power and the smoothing of fluctuating power generation. When using the massive, pressure-resistant, airtight floating body 12 as a pressure storage body, the optimal energy storage device 22 is a switchable pressurized expansion CAES system that takes in air from the top of a tall tower 14, which is less affected by waves from the sea surface WL, and where the air temperature for storage is ambient temperature. This energy storage device 22 requires only air and water for ambient temperature operation. Note that so-called insulated CAES energy storage devices are unsuitable because they require a separate heat storage volume for a high-temperature heat transfer medium in addition to the compressed air storage volume.

[0021] The air tank 30 stores compressed air and is installed inside the floating body 12. In order to install the giant wind turbine 20 offshore, it is necessary to install a huge airtight, pressure-resistant floating body 12 deep in the seawater to suppress oscillations caused by waves and to ensure the correct position of the floating center of gravity. This ensures buoyancy from the internal air and lowers the floating center of gravity below the center of buoyancy to suppress fluctuations of the wind turbine 20 caused by waves. The pressure resistance of the floating body 12 is required to be 1 MPaG at a water depth of 100 m. The density of seawater is 1020-1030 kg / m³. 3 The density of the atmosphere is 1 kg / m³ 3 The density of air at a pressure of 1 MPaG is 10 kg / m³. 3 Therefore, even if compressed air is stored in the air tank 30 inside the floating body 12, it does not affect the securing of buoyancy.

[0022] The internal volume of the floating body 12 that defines the storage capacity of the energy storage device 22 is 3,000 m³, even considering the ballast water inside the floating body that adjusts the center of gravity, for a spar-type floating body with a diameter of 8 m installed at a water depth of 100 m or more. 3 A certain volume can be expected. The energy storage capacity based on the floating volume is expected to be around 1-2 MWh if the internal storage pressure is 1.5 MPaG.

[0023] Tank units A and B are composed of a pair of identical pressurized tanks 40 capable of storing a mixture of water and air. The pressurized tank 40 can be, for example, a roughly cylindrical tank with a lid and bottom. Each tank unit A and B may consist of one pressurized tank or two or more pressurized tanks. The top of the pressurized tank 40 is provided with a water inlet 42 and an air communication port 44, and the bottom of the pressurized tank 40 is provided with a water inlet / outlet port 46. Tank units A and B can switch the communication port 44 (communication destination) to either the air tank 30 or the atmosphere via a discharge / intake switching unit 32. Since tank units A and B also oscillate due to the rocking of the floating body 12 caused by waves (for example, an inclination angle of about ±6°), it is desirable to have a structure that makes it easy to bring the discharge port (communication port 44) and the seawater surface close together during the discharge stroke after pressurization of the pressurized tank 40 is complete. For such a pressurized tank 40, it is desirable to use, for example, a vertically elongated tank.

[0024] The discharge / intake switching unit 32 includes a pipe 48 connected to the air tank 30, two branch pipes 50 branching from the pipe 48, pressure regulating valves 52A and 52B provided on each branch pipe 50, and piping units A1 and B1 connected to the ends of each branch pipe 50, respectively. Piping units A1 and B1 each have a pipe 54 communicating with the branch pipe 50, an exhaust silencer 58 provided on one side of the pipe 54 via a solenoid valve 56, and an intake check valve 62 and an intake filter 64 provided on the other side of the pipe 54 via a solenoid valve 60. The exhaust silencer 58 is provided on the exhaust port side, and the intake filter 64 is provided on the intake port side. The exhaust port is a vent for exhausting air from inside the pressurized tank 40, and the intake port is a vent for drawing air into the pressurized tank 40. These intake and exhaust ports 58A, which form the ventilation openings, are located at the top of the tower 14 to avoid the suction of seawater spray, as shown in Figure 1(2). However, the location of the intake and exhaust ports 58A is not limited to the top of the tower 14. For example, the intake and exhaust ports 58A may be located at the bottom of the tower 14, near the support frame 12A, or in tank units A, B, etc. A pipe 66 that communicates with the communication port 44 at the top of the pressurized tank 40 is connected to the piping 54 between the solenoid valve 60 and the intake check valve 62. A water level sensor 68 for detecting the water level in the pressurized tank 40 and the piping 66 is provided between the solenoid valve 60 and the intake check valve 62. A pressure sensor (not shown) for detecting pressure is provided between the solenoid valves 56 and 60 of the piping 54.

[0025] The switching of the flow path by the discharge / intake switching unit 32 is performed automatically by a control device (not shown) that controls the pressure regulating valves 52A, 52B and solenoid valves 56, 60 based on the water level detection signal from the water level sensor 68. For example, during the compression stroke in tank unit A, the solenoid valves 56, 60 of piping units A1 and B1 are closed to perform compression. At this time, tank unit B is in communication with the atmosphere. Subsequently, the compression stroke is terminated when the pressure sensor detects a signal indicating that the discharge pressure has been reached. Alternatively, the compression stroke may be terminated when the water level sensor 68 detects a signal indicating that the water level in the pressurized tank 40 has reached a predetermined set water level. Subsequently, the solenoid valve 60 and pressure regulating valve 52A on the piping unit A1 side are opened to connect tank unit A and the air tank 30, and the discharge of compressed air to the air tank 30 is started. Subsequently, when the water level in the piping 66 on the piping unit A1 side rises and reaches a predetermined set water level, the water level sensor 68 outputs a water level detection signal corresponding to that set water level. Based on this output, the solenoid valve 60 on the piping unit A1 side is closed, ending the discharge process.

[0026] Meanwhile, during the expansion stroke in tank unit A, on the piping unit A1 side, solenoid valve 60 and pressure regulating valve 52A are opened and solenoid valve 56 is closed, and on the piping unit B1 side, pressure regulating valve 52B is closed and solenoid valves 56 and 60 are opened to start intake. Subsequently, when the water level in the pressurized tank 40 of tank unit A reaches a predetermined set water level, the water level sensor 68 outputs a water level detection signal corresponding to that set water level. Based on this output, the pressure regulating valve 52A on the piping unit A1 side is closed. Subsequently, when the water level in the pressurized tank 40 of tank unit A drops and reaches a predetermined set water level, the water level sensor 68 outputs a water level detection signal corresponding to that set water level. Based on this output, the expansion stroke in tank unit A is terminated. After that, the expansion stroke in tank unit B begins. In this case, solenoid valve 56 on the piping unit A1 side is opened, solenoid valve 56 on the piping unit B1 side is closed, and pressure regulating valve 52B on the piping unit B1 side is opened. At this time, tank unit B and air tank 30 are in communication, and tank unit A is in communication with the atmosphere.

[0027] The water level sensor 68 detects the water level in the pressurized tank 40 and the water level in the piping 66. It is preferable to use a detection method such as a laser type that can detect variable water levels for the water level sensor 68. Based on the detected water level, the amount of residual compressed air at the end of compression and discharge, and the end of the discharge stroke can be detected. It is preferable to install the water level sensor 68 above the piping 66 so that it can detect the water level rising through the piping 66 after filling the pressurized tank 40. The compression stroke is terminated when a signal indicating that the discharge pressure has been reached is detected by the pressure sensor, and then the discharge stroke begins, discharging as much compressed air as possible into the air tank 30. The end of the discharge stroke is detected by the water level detection signal from the water level sensor 68. For example, the end of the discharge stroke is detected when the detected water level reaches a set detection level set above the piping 66. Alternatively, the end of the compression stroke may be detected when the detected water level reaches a set detection level set in the pressurized tank 40.

[0028] Here, the amount of air remaining between the solenoid valve 60 in the discharge / intake switching unit 32 and the water surface in the piping 66 is compressed air that is not discharged to the air tank 40, so minimizing this amount is necessary to improve the performance of the air compressor. For this reason, it is desirable to set the position of the water surface in the piping 66 detected by the water level sensor 68 at the end of the discharge stroke as close to the solenoid valve 60 as possible. Furthermore, it is desirable to make the space between the water surface in the piping 66 and the solenoid valve 60 as small as possible. In this way, the amount of compressed air remaining between the solenoid valve 60 and the water surface in the piping 66 at the end of the discharge stroke can be reduced.

[0029] Furthermore, as water is discharged from the pressurized tank 40, the residual compressed air expands, and when it falls below atmospheric pressure, air is drawn into the pressurized tank 40 via the intake check valve 62, and the pressurized tank 40 is filled with air. The end of air filling may be timed to coincide with the detection of the water level by the water level sensor 68 in the pressurized tank 40 on the compression stroke side. In order to prevent water from remaining in the pressurized tank 40 during the intake stroke, the switching timing of tank units A and B may be adjusted according to the water level detected by the water level sensor 68 to prevent water from remaining in the pressurized tank 40 during the air filling stroke.

[0030] The water pump 34 supplies water from one tank unit B (or A) to the other tank unit A (or B), which is connected to the atmosphere. The water pump 34 is an air compression means that raises the water level in the pressurized tank 40 with the supplied water (water piston), and isothermally compresses the air in the pressurized tank 40. In this embodiment, by raising and lowering the water level in tank units A and B with the water supply from the water pump 34, isothermally compresses air when the water level rises and performs atmospheric intake due to pressure drop when the water level falls. The motor that drives the water pump 34 is powered by electricity generated by wind power generation. It is desirable that this motor be a rotation speed control type, a number control type, or a combination of both, which can increase or decrease the pump drive power according to the fluctuating input power. The suction side of the water pump 34 is connected to a pipe 74 that communicates with the water inlet / outlet 46 at the bottom of the pressurized tank 40 via pipes 70 and 72, and the discharge side is connected to a pipe 78 that communicates with the water inlet 42 at the top of the pressurized tank 40 via a check valve 76. Solenoid valves 80A and 80B are provided in pipe 72, solenoid valves 82A and 82B are provided in pipe 74, and solenoid valves 84A and 84B are provided in pipe 78. Pipe 70 is connected to pipe 72 between solenoid valves 80A and 80B. The check valve 76 on the discharge side is connected to pipe 78 between solenoid valves 84A and 84B. Pipe 72 is connected to pipe 74 via solenoid valves 80A and 80B.

[0031] Switching of the water supply path from the water pump 34 is performed automatically by a control device (not shown) that controls solenoid valves 80A-84A, 80B-84B, etc., based on the water level detection signal from the water level sensor 68. For example, when supplying water from tank unit A (pressurized tank 40), which is in communication with the atmosphere, to tank unit B (pressurized tank 40), solenoid valves 80A and 84B are opened, and the other solenoid valves are closed, and water is supplied from the water inlet / outlet port 46 of tank unit A (pressurized tank 40) to the water inlet port 42 of tank unit B (pressurized tank 40) via the water pump 34. The supplied water raises the water level in tank unit B (pressurized tank 40), and the air inside tank unit B (pressurized tank 40) is isothermally compressed. The compressed air, compressed to the target pressure, is discharged to the air tank 30. When the discharge of compressed air to the air tank 30 is complete, solenoid valves 80B and 84A are opened, and the other solenoid valves are closed. This switches the water flow from the water pump 34 from flowing from tank unit A to tank unit B to flowing from tank unit B to tank unit A. This makes it possible for tank units A and B to continuously draw in and compress the atmosphere.

[0032] The water supply to the pressurized tank 40 has two functions. First, it supplies water to the pressurized tank 40 and compresses the air inside by raising the water level. Second, it uses the water supplied to the pressurized tank 40 to absorb the heat of air compression through heat exchange. Therefore, the water supply to the pressurized tank 40 ensures a compression cycle time that allows for heat exchange, so that the heat generated by isothermal compression can be transferred to the water in each cycle, enabling isothermal compression within the pressurized tank 40. In addition, a cooling area for heat exchange is ensured as the water surface area. Furthermore, water with a constant flow rate is mixed with the compressed air to maintain the heat transfer coefficient required during heat exchange. By using isothermal compression, a heat exchanger to recover the heat of compression is unnecessary, and a heat transfer medium tank for heat storage is also unnecessary.

[0033] The air tank 30 supplies compressed air into the pressurized tank 40, lowering the water level in the pressurized tank 40, and pressurizes the water in the pressurized tank 40 by isothermal expansion of the compressed air in the pressurized tank 40. The air supplied from the air tank 30 to the pressurized tank 40 is supplied with an expansion cycle time that allows for heat exchange, so that the heat generated by isothermal expansion can be transferred to the water in each cycle, enabling isothermal expansion within the pressurized tank 40. In addition, a heating area for heat exchange is ensured as the water surface area. Furthermore, it is preferable to mix water with a constant flow velocity into the compressed air so that the heat transfer coefficient required during heat exchange can be maintained.

[0034] The circulating water pump 36 is installed in parallel with the water pump 34 in the piping 86 that connects the pipes 72 and 78.

[0035] The hydroelectric turbine 38 functions as a hydroelectric power generation means that generates hydroelectric power using the hydroelectric energy of pressurized water pressurized in the pressurizing tank 40 by air supply from the air tank 30. The hydroelectric energy of the pressurized water is the potential energy (head) corresponding to the pressure of the pressurized water. In the example in Figure 1(2), the hydroelectric turbine 38 is shown installed downstream of pipes 88A~C that branch off from pipe 72 between solenoid valves 80A and 80B. The downstream side of the hydroelectric turbine 38 is connected to pipe 74 between solenoid valves 82A and 82B. In this configuration, for example, when generating hydroelectric power using the hydroelectric energy of pressurized water pressurized in tank unit A (pressurizing tank 40), solenoid valves 80A, 82B, and 84A are opened, and the other solenoid valves are closed, and pressurized water is supplied to the hydroelectric turbine 38 from the inlet / outlet port 44 of tank unit A (pressurizing tank 40) via pipes 72 and 88A~C. The hydroelectric turbine 38 rotates with the supplied pressurized water, causing a generator (not shown) to generate electricity. The water used to rotate the hydroelectric turbine 38 (the water used for hydroelectric power generation) is recovered into tank unit B (pressurized tank 40) via piping 74.

[0036] Next, an example of the operation and function of the energy storage device 22 during the compression charging process and expansion power generation process will be described. <Compression charging process> As shown in Figure 2(1), when compressing with tank unit B, at the start of compression, tank unit B is connected to air tank 30 and tank unit A is connected to the atmosphere. Pressure regulating valves 52A and 52B on the air tank 30 side are closed. Assume that tank unit B is filled with pressurized air and tank unit A is filled with water. Solenoid valves 80A and 84B are opened, and all other solenoid valves are closed.

[0037] As shown in Figures 2(2) and (3), when water from tank unit A is supplied to the water inlet 42 at the top of tank unit B by the water pump 34, the air inside tank unit B is isothermally compressed by the rising water level (water piston action). Meanwhile, air is drawn into tank unit A. To avoid drawing in seawater spray, the air is drawn in from a high position at the top of tower 14.

[0038] As shown in Figure 2(4), when the compressed air pressure in tank unit B reaches the target pressure, the solenoid valve 60 and pressure regulating valve 52B of piping unit B1 are opened, and the discharge of compressed air from tank unit B to air tank 30 begins, and the air is pressurized. When tank unit B is filled with water, the discharge ends. After the discharge is complete, the discharge / intake switching unit 32 switches the connection between tank units A and B to the air tank 30 and the atmosphere. Thereafter, water is supplied from tank unit B to tank unit A using the same procedure as above to perform compression in tank unit A, and these steps are repeated to continuously pressurize compressed air in air tank 30, thereby storing the input power of the drive motor of the water pump 34 in the form of air pressure exergy.

[0039] <Expansion power generation process> As shown in Figure 3(1), when tank unit A is to expand, at the start of expansion, tank unit A is connected to the air tank 30 and tank unit B is connected to the atmosphere. The pressure regulating valve 52B on the air tank 30 side is closed. It is assumed that tank unit A is filled with water and tank unit B is filled with air. The solenoid valve 56 and solenoid valves 84B, 80B, and 82A of piping unit A1 are closed, and the other solenoid valves are opened. The water inlet and outlet 46 at the bottom of tank unit A and the water inlet and outlet 46 at the bottom of tank unit B are connected by pipes 74 and 72 to enable water supply to the hydroelectric turbine 38. The pressure regulating valve 52A on the air tank 30 side is opened, and compressed air from the air tank 30 is supplied to tank unit A.

[0040] As shown in Figure 3(2), the water in tank unit A is pressurized by the isothermal expansion of compressed air within tank unit A. A portion of the pressurized water is continuously supplied to the hydroelectric turbine 38 via pipes 74 and 72, and hydroelectric power generation is performed. After power generation starts, the pressure regulating valve 52A on the air tank 30 side is closed. The water used for hydroelectric power generation is drained into tank unit B via pipe 74. The air in tank unit B is released into the atmosphere due to the rising water level. Meanwhile, another portion of the pressurized water is supplied from pipe 78 to the water inlet 42 at the top of tank unit A via pipe 72 and the circulating water pump 36.

[0041] As shown in Figure 3(3), once water is filled into tank unit B, power generation using pressurized water supplied from tank unit A is terminated.

[0042] As shown in Figure 3(4), the discharge / intake switching unit 32 switches the connection between the air tank 30 and tank units A and B to the atmosphere. Subsequently, power generation is performed by tank unit B using the same procedure as above, and these steps are repeated to continuously generate hydroelectric power with the hydroelectric turbine 38, thereby converting the compressed air in the air tank 30 into a pressure head equivalent to the head of the hydroelectric power plant and discharging the generated power.

[0043] According to this embodiment, at low wind speeds, the power generated by wind power can be smoothed by controlling the rotation speed or number of the power-generating turbines 38 of the energy storage device 22, or a combination of both. Furthermore, in calm conditions, stable power transmission can be performed up to the maximum power generated by the energy storage device 22.

[0044] Incidentally, during the compression process described above, the ambient temperature air filled in the pressurized tank 40 will rise in temperature by the amount of compression power unless it is cooled after each expansion cycle. Isothermal compression is achieved by minimizing this temperature rise. Therefore, in order to minimize the temperature difference ΔTc between the temperature of the water used as the cooling medium in the pressurized tank 40 and the temperature of the air that has risen due to compression, it is necessary to maximize the amount of heat exchange Qc (heat exchange amount Qc = Uc × Ac × ΔTc) between the water and air in the pressurized tank 40. Ac is the heat exchange area and Uc is the heat transfer coefficient. The amount of heat exchange Qc is determined from the design specifications of the energy storage device 22, and the temperature difference ΔTc is determined from the target expansion polytropic index. A heat exchange mechanism within the pressurized tank 40 is required that satisfies a cooling capacity Uc × Ac = Qc / ΔTc suitable for the structure of the pressurized tank 40.

[0045] Since the absolute value of the difference in compression power between adiabatic compression and isothermal compression does not change significantly from low pressure to high pressure, the power that can be reduced by isothermal compression also does not change significantly. To prevent the cooling capacity Uc × Ac from changing significantly even when the pressure rises due to changes in the water level in the pressurized tank 40, it is desirable to have a structure in which the heat exchange area Ac and the heat transfer coefficient Uc change with the water level. Examples of such a structure include a structure in which a laminated core is built into the pressurized tank 40, and a structure in which sprayed water is supplied to the pressurized tank 40.

[0046] The amount of water Qwc injected into the pressurized tank 40 is set to equal the target isothermal compression cycle time tc seconds. The amount of water Qwc injected is Qwc(m 3 / s)=Vc(m 3 It can be calculated using ) / tc(s). Vc is the capacity of the pressurized tank 40.

[0047] Furthermore, during the expansion process described above, when compressed air from the air tank 30 is supplied to the pressurized tank 40, the water in the pressurized tank 40 is pressurized by the pressure of the air and supplied to the hydroelectric turbine 38. The temperature of the supplied air, which is at the temperature inside the air tank 30, decreases by the amount of expansion power with each expansion cycle. Isothermal expansion is achieved by minimizing this temperature drop. Therefore, in order to minimize the temperature difference ΔTe between the temperature of the water, which acts as the heating medium in the pressurized tank 40, and the temperature of the air that has decreased due to expansion, it is necessary to maximize the amount of heat exchange Qe (heat exchange amount Qe = Ue × Ae × ΔTe) between the water and air in the pressurized tank 40. Ae is the heat exchange area, and Ue is the heat transfer coefficient. The amount of heat exchange Qe is determined from the design specifications of the energy storage device 22, and the temperature difference ΔTe is determined from the target expansion polytropic index. A heat exchange mechanism within the pressurized tank 40 is required that satisfies the heating capacity Ue × Ae = Qe / ΔTe, which is suitable for the structure of the pressurized tank 40.

[0048] The difference in expansion power between adiabatic expansion and isothermal expansion becomes overwhelmingly larger as the expansion stroke becomes lower pressure. Therefore, it is desirable to have a structure with a heat exchange area Ae and a heat transfer coefficient Ue that can ensure a heat exchange amount Qe from heating by injected water, especially in the latter half of the expansion stroke when the amount of water in the pressurized tank 40 decreases. Examples of such structures include a structure in which a laminated core is built into the pressurized tank 40, and a structure in which injected water is supplied to the pressurized tank 40.

[0049] In the expansion stroke, the heat exchange area is only the water surface in the pressure tank 40, which is not sufficient unlike during compression. Therefore, it is desirable to provide a means for enhancing the heat exchange capacity. Thus, in the present embodiment, in order to expand the heat exchange area Ae that can contribute to heating the expanded air, a circulating water pump 36 for circulating the water drained from the bottom of the pressure tank 40 is installed, and the drained water is sprayed in a spray form from the upper part of the pressure tank 40. The water intake of the circulating water pump 36 branches from a pipe 72 connected to the water supply and drainage port 46 at the bottom of the pressure tank 40, and the discharge of the circulating water pump 36 is to a pipe 78 connected to the water supply port 42 at the upper part of the pressure tank 40. Thereby, without hindering the drainage for expansion, the expansion air space during expansion is filled with the sprayed water (sprayed water) to secure the heat exchange area Ae and enable isothermal expansion. The circulating water pump 36 desirably has the minimum amount of water necessary to enable isothermal expansion with the minimum pump power consumption, and the differential pressure between the water intake and discharge of the circulating water pump 36 is minimized. Note that during the repetition of the expansion cycle, the temperature of the circulating sprayed water decreases by the amount of the heat exchange.

[0050] The compressed air from the air tank 30 to the pressure tank 40 is supplied at the same time as the switching timing by an electromagnetic valve or the like of the pair of pressure tanks 40. The supply start pressure Pe1 (MPaG) corresponding to Ge1 (kg) equivalent to the same amount as the calculated air mass Ge2 (kg) at the target expansion stop pressure Pe2 (MPaG) and the tank capacity V (m 3 ) and the supply air volume Ve1 (m 3 ) are supplied.

[0051] The circulating water pump 36 starts spraying the sprayed water into the pressure tank 40 at the same time as the compressed air is supplied from the air tank 30 into the pressure tank 40, and expands by (V - Ve1) (m 3 ) from the supply pressure Pe1 (MPaG) and stops when it reaches the pressure Pe2 (MPaG).

[0052] To reduce the polytropic index of expansion, a heat exchanger for heating the circulating water may be inserted into the piping path of the circulating water pump 36. The circulating water may be heated with high-temperature water from sources such as air conditioning hot water, industrial waste heat, or solar heat, thereby increasing the temperature difference between the expanding air and the injected water during expansion and increasing the amount of heat required for heating.

[0053] Compressed air from air tank 30 is supplied to pressurized tank 40 at an air volume of Ve1(m³). 3 Pressurized water is generated by the inflow of a certain amount, and this pressurized water is supplied to the hydroelectric turbine 38. In the case of constant-pressure constant-head power generation, it is desirable to use a hydroelectric turbine 38 that is appropriate for the head and water supply amount, as the head difference (m) held by this pressurized water is constant pressure.

[0054] As water is supplied to the hydroelectric turbine 38, the suction pressure Pe1 (MPaG) decreases, and the head of water at the hydroelectric turbine 38 decreases. Therefore, the type of turbine may be changed and selected according to the magnitude and volume of the changing head, or multiple hydroelectric turbines 38 may be connected in series or parallel to generate electricity.

[0055] (Process of smoothing and storing generated power) Figure 4 shows an example of the process of smoothing and storing wind power generation electricity according to this embodiment. As shown in Figure 4(1), when the wind speed is high, the water pump 34 of the energy storage device 22 is operated using power generated by a wind turbine (not shown) to start charging. As a result, as shown in Figure 4(2), air is drawn in at the top of the tower 14, compressed on the upper surface of the floating body 12, and the compressed air is stored in the air tank 30 of the floating body 12. The air pressure in the air tank 30 at the start of charging is assumed to be 0 MPaG, and the air pressure in the air tank 30 at the end of charging (when the storage is complete) is assumed to be about 0.8 MPaG.

[0056] On the other hand, when the wind speed is low, compressed air is supplied from the air tank 30 of the floating body 12 to generate hydroelectric power using the hydroelectric turbine 38 of the energy storage device 22, and this generated power is transmitted to the power transmission cable 26. The air pressure in the air tank 30 is assumed to be about 0.8 MPaG at the start of power generation, and the air pressure in the air tank 30 is assumed to be about 0 MPaG at the end of power generation (when the air supply is complete).

[0057] Figure 5(1) shows an example of monthly output fluctuations for an offshore wind power generation facility, and (2) shows an example of daily output fluctuations during the summer. As shown in these figures, the output of an offshore wind power generation facility is affected by wind conditions and fluctuates greatly from month to day. The energy storage device 22 of this embodiment is installed on this offshore wind power generation facility, and the energy storage device 22 is operated according to the wind conditions. For example, when the wind speed is high, the energy storage device 22 isothermally compresses the atmosphere according to the fluctuating power generated by wind power generation, and stores the compressed air in the air tank 30 in the form of pressure exergy. This reduces the power transmitted from the wind power generation by the amount of stored energy. On the other hand, when the wind speed is low, the energy storage device 22 supplies pressurized water from the compressed air in the air tank 30 to the hydroelectric turbine 38 to perform hydroelectric power generation, and this generated power is transmitted to the power transmission cable 26. In this way, the power generated, which fluctuates depending on wind conditions, can be stored in the energy storage device 22, smoothed out, and transmitted, thereby stabilizing the transmitted power from wind power generation.

[0058] For example, as shown in Figure 5(1), the rated output may be set to 100%, the smoothing target to an average output of approximately 30%, and the wind power generation output of 30% or more may be set to the charging range, and less than 30% to the power generation range. When the wind power generation output is in the charging range, the energy storage device 22 isothermally compresses the atmosphere and stores the pressure in the air tank 30. On the other hand, when the wind power generation output is in the power generation range, the energy storage device 22 performs hydroelectric power generation, and this generated power is transmitted to the power transmission cable 26. By smoothing the average power generated by offshore wind power generation to a peak ratio of approximately 30%, it becomes possible to reduce the cost of power transmission equipment. For example, it becomes possible to reduce construction costs by reducing the diameter of the power transmission cable 26.

[0059] Thus, according to this embodiment, planned wind power generation becomes possible, rather than so-called wind-dependent wind power generation. Power output can be smoothed by storing energy during peak wind power generation, and power can be transmitted during low wind speeds and calm periods. Furthermore, it is possible to maintain stable smoothing and energy storage functions for constantly fluctuating power generation.

[0060] As described above, the offshore wind power generation equipment according to the present invention comprises a foundation structure provided in the water, a tower erected on the foundation structure, a wind turbine provided on the tower, a wind power generation means that generates wind power by the rotation of the wind turbine, and a power storage device that stores electricity in the form of compressed air, wherein the power storage device comprises an air tank for storing compressed air, a pair of tanks whose communication destination can be switched to either the air tank or the atmosphere and which are capable of storing a mixture of water and air, and a tank that communicates with the atmosphere The system includes an air compression means that supplies water to the other tank to raise the water level and isothermally compress the air in the tank, and a hydroelectric power generation means that supplies compressed air from the air tank to the tank to lower the water level, isothermally expands the compressed air in the tank to pressurize the water in the tank, and uses the hydroelectric energy of the pressurized water to generate hydroelectric power. Since the air tank is formed inside the foundation structure, it is possible to provide an offshore wind power generation facility equipped with an energy storage device that can be installed and operated in a manner suitable for offshore wind power generation.

[0061] Furthermore, according to other offshore wind power generation equipment of the present invention, the foundation structure is a floating structure, and therefore the floating structure can be used as an air tank.

[0062] Furthermore, according to other offshore wind power generation equipment of the present invention, when the wind speed is high, the power generated by the wind power generation means is used to operate the air compression means and compressed air is stored in the air tank, while when the wind speed is low, compressed air is supplied from the air tank to perform hydroelectric power generation by the hydroelectric power generation means and the generated power is transmitted. This makes it possible to smooth the wind power output by storing power during peak wind power generation and to transmit power during low wind speeds or when there is no wind.

[0063] Furthermore, according to other offshore wind power generation equipment of the present invention, the tower or the tank is provided with intake and exhaust ports for exhausting air from inside the tank or drawing air into the tank, so that the suction of seawater spray can be avoided. [Industrial applicability]

[0064] As described above, the offshore wind power generation equipment according to the present invention is useful for floating and fixed-bottom offshore wind power generation, and is particularly suitable for storing wind power and smoothing out fluctuating power generation. [Explanation of symbols]

[0065] 10 Offshore wind power generation facilities 12. Floating structures (foundation structures, floating structures) 12A mounting base 14 Towers 16. Nacelle (wind turbine) 18 blades 20 windmill 22 Energy storage devices 24 Mooring line 26 Power transmission cables 28 ballast tanks 28A Ballast section 28B Ballast Water Section 30 air tanks 32 Discharge / Intake Switching Section 34 Water pumps 36 Circulating water pump 38. Hydroelectric turbine (means of hydroelectric power generation) 40 pressurized tanks 42 Water inlet 44 connecting ports 46 Inlet and outlet Piping 48, 54, 66, 70, 72, 74, 78, 86, 88A~C 50 branch pipes 52A, 52B Pressure Regulating Valve 56, 60, 80A, 80B, 82A, 82B, 84A, 84B Solenoid valves 58 Exhaust Silencer 62 Intake check valve 64 Intake filter 68 Water level sensor 76 Check valve A, B Tank Unit A1, B1 Piping Unit G Undersea WL sea level

Claims

1. An offshore wind power generation facility comprising a foundation structure installed underwater, a tower erected on the foundation structure, a wind turbine installed on the tower, a wind power generation means that generates wind power by the rotation of the wind turbine, and an energy storage device that stores electricity in the form of compressed air, The offshore wind power generation facility comprises an air tank for storing compressed air, a pair of tanks whose communication destination can be switched to either the air tank or the atmosphere and which are capable of storing a mixture of water and air, an air compression means for supplying water from the tank communicating with the atmosphere to the other tank to raise the water level and isothermally compressing the air in the tank, and a hydroelectric power generation means for supplying compressed air from the air tank to the tank to lower the water level, isothermally expanding the compressed air in the tank to pressurize the water in the tank, and generating hydroelectric power using the hydroelectric energy of the pressurized water, wherein the air tank is formed inside the foundation structure.

2. The offshore wind power generation facility according to claim 1, characterized in that the foundation structure is a floating structure.

3. The offshore wind power generation facility according to claim 1 or 2, characterized in that when the wind speed is high, the air compression means is operated using the power generated by the wind power generation means and compressed air is stored in the air tank, while when the wind speed is low, compressed air is supplied from the air tank to perform hydroelectric power generation by the hydroelectric power generation means and transmit the generated power.

4. The offshore wind power generation facility according to claim 1 or 2, characterized in that the tower or the tank is provided with an intake and exhaust port for exhausting air from inside the tank or drawing air into the tank.

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