Ocean current power generation system

Abstract

This ocean current power generation system includes a floating body that floats on the sea surface, a rope body connected to the floating body, a support column of which an end part is connected to the rope body or passes through the rope body inside a vertically extending cylinder, a power generation device connected to the support column, a first mooring rope connected to a first anchor fixed to a quay or the seabed, and a power transmission cable that is wound around the mooring rope and extends.

Description

Ocean current power generation system

[0001] The present invention relates to an ocean current power generation system.

[0002] Ocean currents are said to generate hundreds of TWh of energy per year worldwide. Because ocean currents are more stable than the fluctuations of solar and wind power, ocean current-based power generation has attracted attention as a stable power generation method. Furthermore, because ocean current power generation does not emit carbon dioxide (CO2), it is also attracting attention as a natural energy source with an extremely low environmental impact. Ocean current power generation technology involves using ocean or river currents to rotate a rotating body such as a propeller, converting the kinetic energy of the water current into electrical energy to generate electricity. In the waters near Japan, the ocean current known as the Kuroshio Current does not always flow in the same location. Typically, the Kuroshio Current flows more than tens of kilometers away from the coast. Places more than tens of kilometers away from the coast are often deep waters with depths of 1,000 meters or more, making it difficult to install anchors on the seabed. Floating a power generation device without an anchor could lead to the device drifting, potentially resulting in instability in power generation.

[0003] Conventionally, ocean current power generation systems have been developed that use a mooring line to anchor a floating power generation unit installed on the seabed. Patent Document 1 (Patent Document 1) describes a floating ocean current power generation device equipped with a turbine that rotates due to the current of seawater and a pod that supports the turbine and houses a power generation unit that generates electricity through the rotation of the turbine. The ocean current power generation device includes a fixing means (such as a sinker) that is fixed to the seabed, a mooring line connected at one end to the fixing means and at the other end to the pod, and a mooring angle detection means that detects the mooring angle, which is the inclination of the mooring line relative to the fixing means. Patent Document 2 (Patent Document 2) discloses an ocean current power generation system that can access ocean currents far from the coast. The ocean current power generation system consists of a payload (underwater sail and power generation turbine) attached to the other end of a tether, one end of which is fixed to an anchor point. The ocean current generates hydrodynamic lift on the underwater sail, exerting a force that pulls the payload in a direction transverse to the movement of the ocean current. Therefore, with this ocean current power generation system, the payload can be deployed in an area of ​​ocean currents up to 20 km from the coast.

[0004] JP 2014-214602 A JP 2018-111483 A

[0005] The invention of Patent Document 1 requires a sinker or the like to be fixed to the seabed. Fixing a structure to the seabed is only possible in waters up to a depth of several hundred meters, and it is difficult to fix a structure to the seabed in deeper waters. The invention of Patent Document 2 allows for the placement of an ocean current power generation device even in locations several tens of kilometers from the coast. However, there is a risk that the power generation turbines may deviate from the main axis of the ocean current, causing the multiple power generation turbines to move independently and become uncontrollable.

[0006] An object of the present invention is to provide an ocean current power generation system that can stably generate ocean current power even in deep sea areas far from the coast.

[0007] The invention described in claim 1 is an ocean current power generation system including a float floating on the seawater surface, a cable connected to the float, a support pole whose end is connected to the cable or whose cable passes through a vertically extending cylinder, a power generation device connected to the support pole, a first mooring line connected to a first anchor fixed to a quay or the seabed, and a power transmission cable wound around and extending from the mooring line.The invention described in claim 2 is the ocean current power generation system described in claim 1, characterized in that the float has a buoyancy adjustment device that adjusts the magnitude of buoyancy or a cable adjustment device that adjusts the length of the cable.The invention described in claim 3 is the ocean current power generation system described in claim 2, in which the cable is connected to a second anchor in contact with the seabed, and power generation by the power generation device is performed with the cable tensioned. The invention described in claim 4 is the ocean current power generation system described in claim 3, wherein the propulsion device provided on the float moves the float and the power generation device horizontally in a state in which the second anchor connected to the cable is pulled up to the position of the lower end of the strut by controlling the buoyancy adjustment device or the cable adjustment device. The invention described in claim 5 is the ocean current power generation system described in claim 1, wherein the specific gravity of the mooring cable is 1 or less. The invention described in claim 6 is the ocean current power generation system described in claim 1, wherein the strut has a rotating part and a non-rotating part, and the power generation device is connected to the rotating part. The invention described in claim 7 is an ocean current power generation system comprising: a float that floats on the seawater surface; a generator provided on the float; a support pillar having a rotating part and a non-rotating part, the end of which is connected to the float and which has a rotation transmission mechanism disposed inside a vertically extending cylinder, the support pillar having a rotating part connected to the rotating body and a non-rotating part; a first mooring line connected to a first anchor fixed to a quay or the seabed; and a transmission cable wound around the mooring line and extending.

[0008] According to the present invention, it is possible to provide an ocean current power generation system that can stably perform ocean current power generation even in deep sea areas far from the coast.

[0009] FIG. 1 is a diagram showing an ocean current power generation system to which this embodiment is applied. FIG. 2 is a plan view explaining the functions of the power generation device and fins of the ocean current power generation system to which this embodiment is applied. FIG. 3 is a diagram showing the functional configuration of a float and a power generation device of the ocean current power generation system to which this embodiment is applied. FIG. 4 is a diagram for explaining the position of the ocean current and the current position of the power generation device. FIG. 5 is a diagram showing a processing flow for moving the power generation device to an optimum position. FIG. 6 is a diagram showing rotation control of the power generation device. FIG. 7 is a diagram showing rotation control of the power generation device. FIG. 8 is a diagram showing the processing flow for rotation control of the power generation device. FIG. 9 is a diagram showing an ocean current power generation system to which this embodiment is applied. FIG. 10 is a diagram showing a state in which the rotor support column has been pulled up to directly below the float. FIG. 11 is a diagram showing an ocean current power generation system to which this embodiment is applied.

[0010] First Embodiment An embodiment of the present invention will be described in detail below with reference to the accompanying drawings. Fig. 1 shows an ocean current power generation system 1 to which this embodiment is applied. The ocean current power generation system 1 is composed of a power generation device 20, floats 30, 32, a propulsion device 40, a positioning information receiver 50, cables 60, 61, 62, a control device 70, mooring lines 80, a cross beam 85, power transmission cables 90, 95, 97, a sinker 100, a fin 110, an anchor 200, etc.

[0011] The power generation device 20 serving as an ocean current power generation unit is composed of a rotor 21, a rotor support column 22, etc. A generator 47 (see Figure 3) is built into the rotor 21. The rotor 21 converts the energy of the ocean current into rotational energy, and the generator further converts the rotational energy into electrical energy. The electricity generated by the generator is sent to land via a power transmission cable 90 and supplied to a power grid, etc. The rotor 21 may be any mechanism capable of converting the energy of the ocean current into rotational energy, and a rotary turbine or the like is used. The depth at which the power generation device 20 floats is preferably one where the ocean current flows quickly. For example, the power generation device 20 is installed so as to float at a depth of several tens to several hundreds of meters.

[0012] The float 30 is a structure having buoyancy, and is connected to the power generation device 20 via a cable 60. The float 32 is a structure having buoyancy, and is connected to the fin support column 26 via a cable 62. Since the floats 30 and 32 must always float on the sea surface, they have a buoyancy that balances the force that tends to sink them toward the seabed due to the weight of the power generation device 20 and the sinker 100.

[0013] The float 30 may be provided with a cable adjustment device (not shown) equipped with a motor. By reeling in the cable 60, the power generation device 20 can be positioned at shallower water depths, or by lengthening the cable 60, the power generation device 20 can be positioned at deeper water depths. Similarly, the float 32 may also be provided with a cable adjustment device (not shown). By reeling in or lengthening the cable 62, the depth at which the fin 110 is located can be adjusted.

[0014] In this way, by changing the lengths of the ropes 60 and 62, it is possible to adjust the depth of the power generation device 20 and the fins 110. Even at the same location, it is possible to increase the amount of power generated by placing the power generation device 20 at a depth where there is a strong ocean current. Here, "adjusting the length of the rope" means changing the length of the rope portion that supports the load in the sea and performs the mooring function, and the length of the portion that has been reeled in and is not performing its function in the sea is not included in the length of the rope.

[0015] The float 30 is equipped with a buoyancy adjustment device that can adjust its buoyancy. The float 30 has a ballast tank (not shown) inside, and a buoyancy adjustment device that can inject and discharge ballast water. The float 30 can reduce its buoyancy by injecting surrounding seawater into the ballast tank as ballast water. The float 30 can also increase its buoyancy by discharging the ballast water in the ballast tank to the surrounding area. The buoyancy adjustment device only needs to be able to adjust the buoyancy of the float, and does not have to be able to inject and discharge ballast water.

[0016] 1 , the float 30 is connected to the power generation device 20 via the cable 60, but the float 30 may be connected directly to the rotor support column 22 without the cable 60. Similarly, the float 32 is connected to the fin 110 via the cable 62, but the float 32 may be connected directly to the fin support column 26 without the cable 62.

[0017] The propulsion device 40 serving as a propulsion unit is fixed to the floats 30 and 32, and can move the float 30 on the sea surface in any direction by, for example, rotating a propeller driven by a motor. The positioning information receiver 50 serving as a position detection unit can receive positioning radio waves from a positioning satellite such as a GPS and measure its own position. One end of the cord 60 is fixed to the float 30, and the other end is fixed to the rotor support column 22 of the power generation unit 20. One end of the cord 62 is fixed to the float 32, and the other end is fixed to the fin support column 26 that supports the fin 110. For example, the cords 60 and 62 may be metal wires. The cords 60 and 62 are preferably made of a lightweight material that has high strength and elasticity. For example, the cords 60 and 62 may be made of Izanas (registered trademark) manufactured by Toyobo Co., Ltd. In addition, the float 32 may also be equipped with a propulsion device 40, a positioning information receiver 50, and a control device 70, similar to the float 31.

[0018] The rotor support column 22 has a rotating part 23 connected to the rotor. Bearings and the like are arranged at the upper and lower ends of the rotating part 23 so that it can rotate freely. Therefore, when the direction of the ocean current changes, the rotating part 23 rotates, allowing the rotor 21 to always be located downstream of the current.

[0019] The rotor support column 22 is a columnar structure that extends vertically and has its center of gravity at its lower end. One end of the cord 60 is connected to the float 30, and the other end is connected to the rotor support column 22. The connection between the float 30 and the columnar rotor support column 22 that extends vertically and has its center of gravity at its lower end by the cord 60 ensures vertical and horizontal stability of the power generation device 20, and has the effect of keeping it in a fixed position.

[0020] In the horizontal direction, in an environment where seawater flows in a fixed direction around the vertically extending rotor support column 22, the column is subjected to the same level of flow pressure on both sides of the column, making it easy to maintain horizontal stability. Furthermore, the connection between the float 30 floating on the seawater surface, the cable 60, and the columnar rotor support column 22, which is vertically extending and has its center of gravity at its lower end, makes it possible to suppress vertical movement. For example, when subjected to a vertically downward force, an upward restoring force is applied due to the buoyancy of the float on the seawater surface. Therefore, the rotor support column 22 is easy to maintain vertical stability. Furthermore, the power generation device 20, which is rigidly connected to the rotor support column 22, also maintains vertical stability.

[0021] Furthermore, even if the power generation device 20 moves to a position shifted from directly below the floating body 30, even if the cable 60 tilts, the rotor support column 22 remains stable in the vertical direction without tilting because it is columnar with its center of gravity at its lower end. This reinforces the above-mentioned stability. Therefore, the ocean current power generation system 1 is less likely to be swept away by ocean currents, and has the effect of remaining stable in a fixed position.

[0022] The ropes 61 connect the floats 33a, 33b, and 33c to the mooring lines 80. The farther the ocean current flows from land, the longer the mooring lines 80 extending from the anchors 200 need to be. This increases the weight of the mooring lines 80, which can lead to instability and damage to the mooring lines 80. Therefore, by connecting the floats 33a, 33b, and 33c to the mooring lines 80 using the ropes 61 as described above, the weight of the mooring lines 80 can be distributed and the mooring lines 80 can be stably positioned. One end of the rope 61 is fixed to the floats 33a, 33b, or 33c, and the other end is fixed to the mooring lines 80. For example, by placing the ropes 61 every 500 m, the load on the mooring lines 80 due to their own weight can be reduced. The length of the ropes 61 can be adjusted as needed. For example, in areas where the mooring lines 80 cross a waterway, the mooring lines 80 need to be installed at a location deeper than the diving depth of the ship, and therefore the lines 61 need to be extended deeper than the diving depth so that the mooring lines 80 are installed at a depth that does not affect the ship. Note that the floats 33a, 33b, and 33c may also be equipped with a propulsion device 40, a positioning information receiver 50, and a control device 70, similar to the float 30.

[0023] The control device 70 determines whether the float 30 is in the appropriate location based on the position information from the positioning information receiver 50. If it determines that the float 30 has deviated from the appropriate location, it drives the propulsion device 40 to move the float 30 to the appropriate location. The float 30 is always towing the power generation device 20 with the cable 60, so the power generation device 20 can remain in the appropriate location. An information receiver (not shown) is installed on the float 30, and by receiving information on weather and sea conditions, it constantly monitors the center position of the Kuroshio Current.

[0024] The mooring line 80 is made of a high-strength wire that connects the power generation unit 20 and the anchor 200. The mooring line 80 may be a high-strength metal wire that has been treated with anti-rust technology. Since the mooring line 80 is used over long distances, it is required to be not only strong but also lightweight. For example, it is preferable to use a fibrous material that has high strength and elastic modulus, but also a specific gravity of 1 or less, so that it floats on water. For example, Izanas (registered trademark) manufactured by Toyobo Co., Ltd. may be used.

[0025] The power transmission cable 90 is a cable for transmitting electricity generated by the generator of the power generation device 20. Because the power transmission cable 90 is weaker than the mooring rope 80, it is wound around the mooring rope 80 to prevent mechanical stress, such as tension, from being placed on the power transmission cable 90. The mooring rope 80 is fixed to an anchor 200 fixed to the seabed. The power transmission cable 90 extends from the anchor 200, crawling along the seabed and reaching land. The mooring rope 80 and the rope bodies 60, 61, 62 are made of, for example, Izanas (registered trademark) manufactured by Toyobo. When the mooring rope 80 is extended long distances underwater, it may break under its own weight, so a lightweight yet strong material is desirable. In particular, a rope that has buoyancy underwater can reduce the weight burden.

[0026] One end of the cross beam 85 is fixed to the rotor support column 22, and the other end is fixed to the fin support column 26. In the example shown in Fig. 1, two cross beams 85 connect the rotor support column 22 and the fin support column 26. The cross beams 85 are preferably made of metal or resin.

[0027] The power transmission cable 95 transmits electricity generated by the power generation device 20 to the battery 12 (not shown) of the float 30. The power transmission cable 95 is arranged along the rope body 60. A portion of the electricity generated by the generator is sent to a battery (not shown) in the float 30 by the power transmission cable 95 and stored therein. A portion of the electricity generated by the generator is sent to a battery (not shown) in the float 32 via a power transmission cable (not shown) inside the cross beam 85 and a power transmission cable 97 and stored therein.

[0028] The weight 100 is connected to the lower end of the rotor support column 22 that constitutes the power generation device 20. The weight 100 has the effect of stabilizing the attitude and position of the power generation device 20. If there is more weight at the lower end of the rotor support column 22 than at the upper end, the stability required to keep the rotor support column 22 vertical is increased. Furthermore, the increased mass due to the presence of the weight 100 acts to suppress the power generation device 20 from being swept away by ocean currents, thereby stabilizing the position of the power generation device 20. When the seabed S1 is shallow, the weight 100 can be fixed to the seabed S1. When the seabed S1 is deep, the weight 100 will float in the seawater S2.

[0029] The weight 102 is connected to the lower end of the fin support column 26 that supports the fin 110. The weight 102 has the effect of stabilizing the attitude and position of the fin 110. If there is more weight at the lower end of the fin support column 26 than at the upper end, the stability required to keep the fin support column 26 vertical increases.

[0030] The fins 110 are supported by the fin support columns 26. The fins 110 function to generate lift when subjected to the flow of ocean currents. The fins 110 generate lift in a direction perpendicular to the flow of ocean currents. The generated lift acts to pull the power generation device 20 in a direction perpendicular to the rotation axis of the rotor 21.

[0031] The anchor 200 is installed on the seabed S1 at a depth of several tens to several hundred meters. If the seabed S1 is covered with sediments, the anchor 200 is fixed by embedding it in the sediments. If the seabed S1 is bedrock with little sediment, the anchor 200 is fixed by driving piles, bolts, etc. into the seabed S1. This type of work of fixing the anchor 200 is difficult in deep sea areas. In sea areas where the Kuroshio Current flows quickly, there are many areas with a depth of 1,000 meters or more, making it difficult to fix the anchor 200 to the seabed. For these reasons, the anchor 200 is installed on the seabed S1 at a depth of up to several hundred meters, which is the depth at which installation is possible.

[0032] With the above-described configuration, the ocean current power generation system 1 can extend the mooring rope 80 and the power transmission cable 90 to an area deeper than the point where the anchor 200 is laid, making it possible to float the power generation device 20 in the underwater world S2, a deep area where the Kuroshio Current flows. Since the distance between the anchor 200 and the power generation device 20 can range from several kilometers to several hundred kilometers, there is a risk that the power transmission cable 90 will break under its own weight. For this reason, it is desirable to entangle the power transmission cable 90 with the mooring rope 80, which is made of a wire stronger than the power transmission cable 90.

[0033] Furthermore, gravity tends to cause the power generation device 20 to sink in the underwater space S2, but against this, the buoyancy of the float 30 on the sea surface S3 acts on the float 30, causing the rope 60 connected to the float 30 to pull the power generation device 20 upward. Therefore, the float 30 needs to have a mechanism with sufficient buoyancy so that it can be maintained on the sea surface S3. As described above, the power generation device 20 is supported by the buoyancy of the float 30 and the mooring rope 80, and therefore can maintain a stable floating state in the underwater space S2.

[0034] Under normal operating conditions, the power generation device 20 connected to the mooring lines 80 remains stable in a substantially fixed position. In other words, the tension from the mooring lines 80, its own weight, the buoyancy from the float 30, and the force the power generation device 20 receives from the ocean current are all in balance. The position of the power generation device 20 may shift due to changes in the speed of the ocean current, for example. In this case, the control device 70 detects a deviation from the center of the Kuroshio Current from the position information of the positioning information receiver 50, and drives the propulsion device 40 to move to an appropriate location. As described above, the ocean current power generation system 1 can stably generate ocean current power even in deep sea areas.

[0035] FIG. 2 is a plan view illustrating the functions of the power generation device and fins of an ocean current power generation system to which this embodiment is applied. However, the floating bodies 30, 32 and the ropes 60, 62 are omitted from the drawing. The mooring rope 80 is connected to the rotor support column 22. The rotor support column 22 is connected to the rotor 21 via a member 87. One end of the cross beam 85 is connected to the rotor support column 22, and the cross beam 85 and the member 87 are fixed at a constant angle α. The angle α is preferably 90°. The other end of the cross beam 85 is fixed to the fin support column 26. The fin support column 26 supports the fin 110. In a stable state, the angle β between the fin 110 and the cross beam 85 is also preferably approximately 90°.

[0036] In Fig. 2, when an ocean current 250 is flowing in the direction of the arrow, the flow around the shape of the fin 110 generates a lift force 300. The lift force 300 is a force that acts in a direction perpendicular to the flow direction of the ocean current 250. In the situation shown in Fig. 2, the tension of the mooring line 80 and the lift force 300 are balanced and stable. In this situation, the rotation axis of the rotor 21 is aligned with the flow direction of the ocean current 250, resulting in optimal efficiency in converting the energy of the ocean current 250 into rotational energy.

[0037] The fins 110 rotate around the fin support columns 26 so that the angle β is variable. Therefore, when the direction of the ocean current 250 changes, the fins 110 can be controlled to adjust the angle β so that the rotating body 21 can capture the energy of the ocean current 250 at an optimal angle.

[0038] 3 is a diagram showing the functional configuration of a float 30 and a power generation device 20 of an ocean current power generation system 1 to which this embodiment is applied. The float 30 includes a propulsion device 40, a battery 12, a positioning information receiver 50, a communication device 14, an AHRS 16, a control device 70, an acoustic communication device 24, an acoustic positioning device 25, etc. The power generation device 20 includes a rotor 21, a rotor support column 22, a control device 41, an inertial navigation system 42, an acoustic communication device 43, a transponder 44, a generator 47, a current meter 48, a depth meter 49, etc.

[0039] The battery 12 receives electricity generated by the power generation device 20 via a power transmission cable 95 (see FIG. 1 ). The battery 12 supplies electricity to a motor that drives the propulsion device 40. The propulsion device 40 is fixed to the float 30, and can move the float 30 on the sea surface in any direction by, for example, rotating a propeller driven by the motor. The positioning information receiver 50 acquires absolute position information of the float 30. The positioning information receiver 50 functions as a receiver that receives positioning information via radio waves from a positioning satellite such as GPS. The positioning information receiver 50 acquires three-dimensional position information (latitude, longitude, and altitude) of the float 30. The positioning information receiver 50 outputs the acquired absolute position information of the float 30 to the control device 70.

[0040] The communication device 14 transmits and receives information via radio waves from land or via communication satellites. The information received by the communication device 14 as an acquisition unit includes meteorological and sea state information. Weather information includes weather, weather charts, wind speed distribution, precipitation distribution, typhoon information, and temperature distribution. Sea state information includes current, estimated, or forecast information such as ocean current direction and current speed distribution. For example, the sea state information may be information published by the Japan Meteorological Agency, such as 50-meter deep ocean currents, daily ocean current analysis charts, and ocean current forecast charts, and information published by the Japan Coast Guard, such as ocean current charts, ocean current prediction charts, Kuroshio Current axis, Kuroshio Current axis direction, distance to the Kuroshio Current axis, and strong current observation information. The communication device 14 acquires (receives) sea state information via radio waves from land or communication satellites and outputs the acquired information to the control device 70. The communication device 14 may also receive radio waves from communication relay devices (not shown) installed on the floating bodies 33a, 33b, 33c, etc.

[0041] The control device 70 as a control unit is primarily configured with a computer including, for example, a CPU, ROM, RAM, auxiliary storage device, etc. Processing programs that realize predetermined functions may be stored in the ROM or auxiliary storage device. Various functions are realized by running the stored programs under the control of the CPU. The control device 70 also acquires self-position information from the positioning information receiver 50. The control device 70 compares ocean current information, such as ocean current speed and direction, with the self-position information to determine whether the self-position is located within an area with strong ocean currents. If the self-position is outside of the strong ocean currents, it issues a command to drive the propulsion device 40 to move to a location with strong ocean currents. The control device 70 can also use prediction information to determine a movement position in advance and control movement.

[0042] The AHRS 16 measures the heading and pitch angles of the power plant 20 based on information from sensors such as a gyro and an accelerometer.

[0043] The acoustic communication device 24 and the acoustic positioning device 25 are provided at the bottom of the float 30. The acoustic communication device 24 includes, for example, a transceiver including a transmitter that transmits acoustic waves as position detection waves into the water and a receiver that receives acoustic waves (reflected waves) as position detection waves. The acoustic communication device 24 has the function of transmitting and receiving information to and from the acoustic communication device 43 of the power generation plant 20, which will be described later, using acoustic communication. As described above, the acoustic communication device 24 and the acoustic positioning device 25 are fixed to the float and constitute a receiving unit that transmits and receives position detection waves. The acoustic positioning device 25, which serves as a position calculation unit, calculates the position of the power generation plant 20 based on the position detection waves received by the receiving unit.

[0044] The acoustic positioning device 25 measures the relative position of the power generation plant 20 with respect to the float 30 based on a response from a transponder 44 of the power generation plant 20, which will be described later. As the acoustic positioning device 25, for example, a super short base line (SSBL) positioning system may be used. In the SSBL positioning system, pulsed sounds are periodically emitted into the water, and response echoes to the pulsed sounds are received by at least three sensors, and the linear distance to the power generation plant 20, as well as the azimuth angle and pitch angle, are calculated. Then, the position of the power generation plant 20 is measured in a three-dimensional relative coordinate system with the float 30 as the reference.

[0045] The rotor 21 is a turbine that converts the energy of ocean currents into rotational energy. The rotor 21 houses a generator 47, a control device 41, an inertial navigation system 42, and the like. The generator 47 further converts the rotational energy into electrical energy. The electricity generated by the generator 47 is sent to land via a power transmission cable 90 (see FIG. 1) and supplied to a power grid, etc. The rotor 21 is connected to the rotor support column 22 via a member 87 (see FIG. 2).

[0046] The rotor support column 22 has a function of supporting the rotor 21, and can also support a plurality of rotors. The rotor support column 22 is preferably in the form of a column having a weight at the bottom end.

[0047] The control device 41 is configured to be able to control the power generation device 20. The control device 41 controls various devices of the power generation device 20 (for example, the inertial navigation system 42, the acoustic communication device 43, the transponder 44, and the fin 110 (see FIG. 1 )). The control device 41 is configured mainly by a computer including, for example, a CPU, a ROM, a RAM, and an auxiliary storage device. A computer program that realizes predetermined functions is stored in the ROM or the like. Then, the computer program is loaded into the CPU or RAM and operated under the control of the CPU to realize various functions. Each function of the control device 41 may be realized by an integrated circuit.

[0048] The inertial navigation system 42 measures the travel distance, travel direction, speed, etc. of the power generation plant 20 from its starting point based on information from sensors such as a gyroscope and an accelerometer.

[0049] The acoustic communication device 43 is configured to enable transmission and reception of information to and from the acoustic communication device 24 of the floating body 30 using acoustic communication. The acoustic communication device 43 has a configuration similar to that of the acoustic communication device 24. When the transponder 44 receives a sound transmitted from the acoustic positioning device 25 of the floating body 30, it instantaneously transmits a response sound to the acoustic positioning device 25. As described above, the acoustic communication device 43 and the transponder 44 are fixed to the power generation device 20 and constitute a transmitting unit that receives and returns position detection waves.

[0050] The power generation device 20 further includes a current meter 48 that measures the direction and speed of ocean currents, and a depth meter 49 that measures the depth of the power generation device 20. The current meter 48 and the depth meter 49 may be installed somewhere, such as on a part of the non-rotating part of the rotor 21, on the member 87, or on the rotor support column 22. By measuring the measurement data of the current meter 48 and the depth meter 49 continuously or periodically, it is possible to understand time-series changes in ocean currents at a specific depth.

[0051] As described above, the acoustic positioning device 25 serving as a position calculation unit can grasp the relative position of the power generation unit 20 from the float 30. Furthermore, the position calculation unit can also calculate the absolute position of the power generation unit 20 based on the absolute position of the float 30 determined by the position detection unit receiving positioning radio waves from a positioning satellite such as a GPS. When moving the float 30 using the propulsion unit 40, the control unit 70 grasps the positions of the float 30 and the power generation unit 20, the positions of the float 30 and the float 32, and, if there are multiple power generation units 20, the positions of the power generation units 20 themselves, and controls the power generation units 20 to prevent them from colliding with each other.

[0052] FIG. 4 is a diagram illustrating the position of ocean currents and the current position of the power generation device. The floating body 30 can acquire daily weather and sea condition information via the communication device 14, receiving radio waves from land and communication satellites. The control device 70 can create an ocean current velocity distribution map as shown in FIG. 4 from the acquired sea condition information. The control device 70 acquires the position information of the floating body 30 received by the positioning information receiver 50 and the relative position information of the power generation device 20 from the acoustic positioning device 25, and calculates the absolute position information of the power generation device 20. The control device 70 then identifies the current position P1 of the power generation device 20 on the current velocity distribution map. Next, the control device 70 determines that a position P2 on the current velocity distribution map, where there is a stronger ocean current than the current position P1 of the power generation device 20, is more suitable for ocean current power generation. In this case, the control device 70 drives the propulsion device 40 to move the power generation device 20 from the current position P1 to position P2.

[0053] The data of the ocean current velocity distribution map can be transmitted to a server at a power generation system management center on land via the communication device 14. The manager of the power generation system can check the current position P1 of the power generation device 20 and the optimal position P2 for ocean current power generation on the ocean current distribution map.

[0054] 5 is a diagram showing a process flow for moving a power generation device to an optimal location. The positioning information receiver 50 of the float 30 acquires absolute position information of the float 30 by acquiring positioning information from GPS satellites (S100). Next, the acoustic positioning device 25 acquires relative position information of the power generation device 20 by transmitting and receiving position detection waves (sound waves) from the acoustic communication device 24 (S110). The control device 70 calculates absolute position information of the power generation device 20 from the absolute position information of the float 30 and the relative position information of the power generation device 20 (S120). The communication device 14 acquires (receives) oceanographic information such as the direction and speed of ocean currents, and outputs this information to the control device 70 (S130). The control device 70 compares the position of the power generation device 20 with the position of the ocean current and determines whether the power generation device 20 should be moved to a location with a stronger current (S140). If it is determined that movement is necessary (YES in S140), the control device 70 determines the position to which the power generation device 20 should be moved (S150). A towing (movement) plan for the power generation device 20 is created using the propulsive force of the float 30 (S160). The ocean current power generation system includes the float 30, the float 32, the power generation device 20, the fin 110, etc., and it is necessary to move to the destination while avoiding collisions between these. The control device 70 creates a plan for how to control the movement. Thereafter, the float 30 and the propulsion devices 40 of the float 32 are operated in accordance with the movement plan to control the movement (S170).

[0055] In addition to the macroscopic movement control described above, the ocean current power generation system also performs microscopic movement control by adjusting the power generation device 20 and fins 110 at optimal positions. For example, if the lift force of the fins 110 acts in a direction perpendicular to the direction of the ocean current as shown in Figure 2 and is well balanced, microscopic movement control is not necessary. However, the direction of the ocean current is not always constant.

[0056] The direction of the ocean current 250 is measured by a current meter 48. The inertial navigation system 42 monitors the direction of the power generation device 20. Therefore, when the control device 70 determines that the direction of the ocean current 250 and the direction of the power generation device 20 have deviated significantly by more than a certain angle, it executes microscopic movement control.

[0057] 6 to 8 are diagrams illustrating rotation control of the power generation device. However, when the direction of the ocean current 250 changes as shown in FIG. 6, it is desirable from the perspective of power generation efficiency to align the direction of the rotation axis of the rotor 21 with the direction of the ocean current 250. In the case of FIG. 6, the control device 41 changes the angle at which the lift force acts by increasing the angle β of the fin 110 as shown in FIG. 7. By doing so, the power generation device 20 moves so that the mooring line 80 rotates clockwise on the drawing of FIG. 6. When the power generation device 20 moves so that the direction of the ocean current 250 and the direction of the rotation axis of the rotor 21 are aligned, the mooring line 80 is balanced again at this position. That is, as shown in FIG. 8, the angle β of the fin 110 is set to 90°, maintaining a state in which the tension of the mooring line 80 and the lift force 300 are balanced.

[0058] FIG. 9 is a diagram showing a process flow for controlling the rotation of the power generation device. The control device 70 acquires measurement data obtained by measuring the direction and velocity of the ocean current using the current meter 48 (S700). The control device 70 determines whether the direction of the ocean current 250 and the direction of the axis of the rotor 21 deviate by an angle equal to or greater than a threshold value (S710). If the angular deviation is not equal to or greater than the threshold value (NO in S710), the process returns to S700. If the angular deviation is equal to or greater than the threshold value (YES in S710), the control device 70 controls the fins so that the direction of the rotation axis of the rotor 21 coincides with the direction of the ocean current 250 (S720). The control device 70 then controls the rotor 21 so that lift is generated perpendicular to the direction of the ocean current 250 (S730). Specifically, the control device 70 fine-tunes the fins 110 so that the angular deviation between the direction of the ocean current 250 and the direction of the rotation axis of the rotor 21 is less than the threshold value.

[0059] If the water directly below the power generation device 20 is deep, the power generation device 20 will be floating at a point far away from the anchor 200. This can cause the power generation device 20 to move far away from the optimal location for power generation or to deviate from the optimal direction. The ocean current power generation system of the present invention allows the power generation device 20 to autonomously move to the optimal location or move in the optimal direction. In other words, the above-described embodiment can provide an ocean current power generation system that can stably generate ocean current power.

[0060] As described above, the ocean current power generation system of the present invention can control the position of the power generation device to move horizontally to an appropriate sea area and to rotate within a predetermined sea area in response to changes in ocean current conditions. Therefore, the present invention can provide an ocean current power generation system that can stably and efficiently generate ocean current power even in deep sea areas far from the shore.

[0061] Second Embodiment Figure 10 is a diagram showing an ocean current power generation system 2 to which this embodiment is applied. The ocean current power generation system 2 is configured by connecting a floating body 30, four anchors 210a to 210d (hereinafter sometimes collectively referred to as "anchors 210"), and vertically extending ropes 60a to 60d (hereinafter sometimes collectively referred to as "rods 60"). The ropes 60 are in a taut, moored state due to tension, and the floating body 30 is partially submerged below the sea surface compared to when it is not connected to the ropes 60.

[0062] The float 30 is equipped with a buoyancy adjustment device 74 that can adjust its buoyancy. The float 30 has a ballast tank (not shown) inside, and is equipped with a buoyancy adjustment device 74 that can inject and discharge ballast water. The float 30 can reduce its buoyancy by injecting surrounding seawater into the ballast tank as ballast water. The float 30 can also increase its buoyancy by discharging the ballast water in the ballast tank to the surrounding area. The buoyancy adjustment device 74 only needs to be able to adjust the buoyancy of the float, and does not have to inject or discharge ballast water.

[0063] The floating body 30 may have a rope adjusting device 75 that adjusts the length of the rope 60 by winding up the rope 60 or releasing the wound rope by rotating a motor. The rope adjusting device 75 can increase the tension of the rope 60 by winding up the rope 60 fixed to the anchor 210. Here, "adjusting the length of the rope" means changing the length of the rope portion that is performing the role of supporting the load in the sea or the mooring function, and the length of the wound-up portion that is not performing its function in the sea is not included in the length of the rope.

[0064] The maximum buoyancy that can be adjusted by the buoyancy adjustment device 74 is desirably greater than the total load of the float 30, the power generation device 20 connected to the float 30, and the anchors 210a to 210d. If the maximum buoyancy is greater than the downward gravity acting on the float 30, the anchors 210a to 210d can be pulled up in a state of maximum buoyancy. The rope adjustment device 75 may pull up the rope 60, thereby pulling up the anchors 210a to 210d. The rope 62 connected below the rotor support column 22 may be the same rope (continuous rope) as the rope 60, or may be provided as a separate rope.

[0065] When the ropes 62 and 60 are continuous, the rope adjustment device 75 reels up the rope 60, thereby pulling up the anchors 210a-210d to the lower ends of the rotor support columns 22. Furthermore, the rope adjustment device 75 reels up the rope 60, bringing the rotor support columns 22 closer to the float 30. FIG. 11 shows the rotor support columns 22 reeled up to just below the float 30. As shown in FIG. 11, reeling up the rope 60 (see FIG. 10) brings the power generation unit 20 close to the seawater surface, facilitating maintenance work. Furthermore, the float 30 may be equipped with a positioning information receiver and a propulsion device (not shown). When the rotor support columns 22 are reeled up just below the float 30, the propulsion device allows the float 30 and the power generation unit 20 to be moved to a desired location with reduced rocking.

[0066] The procedure for constructing the above-described ocean current power generation system will now be described. First, ballast water is poured into the float 30 to increase its vertical depth and draft, and then the float 30 is connected to the tether 60. Next, when the ballast water is discharged, the buoyancy of the float 30 increases, and the float 30 rises to a position where the buoyancy and gravity are balanced. At this time, the tension in the tether 60 increases, and the float 30 enters a taut state. In other words, the buoyancy of the float 30 is adjusted by pouring in and discharging ballast water, thereby adjusting the tension in the tether 60. The float 30 is maintained in a taut state due to the tension generated in the tether 60 by the buoyancy of the float 30. As a result, the float 30 and the power generation device 20 can remain stably in place with little horizontal or vertical rocking.

[0067] Near the water depth where the power generation device 20 is located, a rope 60 passes through the inside of a cylindrical rotor support column 22. The rotor support column 22 can be positioned at a predetermined water depth because one end is connected to the rope 60, which is connected to the float 30 at the other end. The rotor support column 22 has a rotating part 23 connected to the rotor. Bearings and the like are arranged at the upper and lower ends of the rotating part 23 so that it can rotate freely. Therefore, when the direction of the ocean current changes, the rotating part 23 rotates, allowing the rotor 21 to always be positioned downstream of the current.

[0068] A generator 47 (see FIG. 3) is built into the rotating body 21. Electricity generated by the generator is stored in a battery 72 on the floating body 30 via a power transmission cable 95 (see FIG. 10) and then transmitted to a substation facility on land via a power transmission cable 90. The power transmission cable 90 extends around the mooring line 80. By extending the power transmission cable 90 around the mooring line 80, it is possible to prevent the power transmission cable 90 from being cut by its own weight.

[0069] The mooring line 80 connecting the float 30 to the land has floats 33a and 33b along the way. Because the floats 33a and 33b have a predetermined buoyancy, the load due to the weight of the mooring line 80 is reduced, and it is possible to prevent damage such as the breakage of the mooring line 80. The floats 33a and 33b may be placed above the seawater surface. In this case, the floats 33a and 33b may not be directly connected to the mooring line 80, but may be connected by a cable.

[0070] The cross beams 86 are members that connect the rotor support columns 22 to each other. The cross beams 86 connect the four rotor support columns 22 near their upper and lower ends, so the system is made up of a total of eight members. The cross beams 86 are preferably made of a rigid material, but may also be made of a material such as wire. By providing the cross beams 86, it is possible to reduce vibrations of the ocean current power generation system 2 compared to when the cross beams 86 are not provided.

[0071] The above-described ocean current power generation system 2 can be installed even in places where the water depth exceeds 1000 m, and therefore can provide a stable floating body even in places where the Kuroshio Current flows.

[0072] Third Embodiment Figure 12 is a diagram showing an ocean current power generation system 3 to which this embodiment is applied. The ocean current power generation system 3 is configured by connecting a float 30, four anchors 210a to 210d, and vertically extending ropes 60a to 60d. The ropes 62 are in a taut mooring state due to tension. The ocean current power generation system 3 differs from the ocean current power generation system 2 in that the rotor support columns 22 are directly connected to the float 30, and the ropes 62 are connected to the bottom ends of the rotor support columns 22 and anchors 210 on the seabed.

[0073] The rotor support column 22 is hollow cylindrical and has a rotation transmission mechanism inside. The rotation of the rotor 21 is transmitted to a generator on the float 30 via gears or the like, and the generator converts the rotational energy into electrical energy. This eliminates the need to provide a generator inside the rotor 21. Compared to accommodating a generator inside the rotor 21, not accommodating a generator inside the rotor 21 makes the inside of the rotor 21 hollow, which can reduce pressure resistance. However, if a generator is not accommodated inside the rotor 21, the above-mentioned rotational energy needs to be transmitted to the generator provided on the float 30 at sea via a transmission mechanism such as gears.

[0074] The rope 62 is connected to the lower end of the rotor support column 22 and to an anchor 210 on the seabed. As with the ocean current power generation system 2, the ocean current power generation system 3 adjusts its buoyancy by injecting and discharging ballast water from a ballast tank attached to the float 30. Therefore, discharging the ballast water increases the buoyancy and the tension of the rope 62. In this embodiment, the rope 62 is connected to the lower end of the rotor support column 22 and to the anchor 210 on the seabed, but in another embodiment, the rope 62 may pass through the hollow of the rotor support column 22 and be connected to the float 30.

[0075] The cross beams 86 are members that connect the rotor support columns 22 to each other. The cross beams 86 connect the four rotor support columns 22 near their upper and lower ends, so the system is made up of a total of eight members. The cross beams 86 are preferably made of a rigid material, but may also be made of a material such as wire. By providing the cross beams 86, it is possible to reduce vibrations of the ocean current power generation system 2 compared to when the cross beams 86 are not provided.

[0076] The float 30 is equipped with a buoyancy adjustment device 74 that can adjust its buoyancy. The float 30 has a ballast tank (not shown) inside, and is equipped with a buoyancy adjustment device 74 that can inject and discharge ballast water. The float 30 can reduce its buoyancy by injecting surrounding seawater into the ballast tank as ballast water. The float 30 can also increase its buoyancy by discharging the ballast water in the ballast tank to the surrounding area. The buoyancy adjustment device 74 only needs to be able to adjust the buoyancy of the float, and does not have to inject or discharge ballast water.

[0077] The buoyancy of the float 30 can be increased by discharging ballast water from the ballast tanks provided on the float 30. In this embodiment, when the float 30 has discharged a predetermined amount of ballast water from the ballast tanks, the buoyancy can exceed the total weight of all loads connected to the bottom of the float 30. Therefore, the anchor 210 can be lifted from the seabed to move the float 30. In this case, it is preferable to provide a hoisting device for shortening the length of the rope 62 on the float 30 or the rotor support column 22. The rope adjustment device 75 hoists the rope 62, thereby pulling the anchors 210a to 210d up to near the lower ends of the rotor support columns 22. When moving horizontally, shortening the length of the rope 62 reduces the swaying of the anchor 210 floating in the water.

[0078] The number of anchors 210 may be one anchor rather than multiple anchors. When multiple anchors 210 are present, a rope 62 connected to each anchor 210 is required. When multiple ropes 62 are present, a connecting member 88 connecting the ropes 62 to each other is preferably provided between the rotor support column 22 and the anchor 210. Multiple connecting members 88 may be provided, and the lowest connecting member 88 is preferably located directly above the anchor 210. The connecting member 88 prevents the multiple anchors 210 from colliding with each other due to horizontal swinging when the multiple anchors 210 are moved in a floating manner. The connecting member 88 may be a rigid member or a rope-like cord.

[0079] As described above, to increase the buoyancy so as to float the anchor 210 on the seabed, the float 30 needs to have a float adjustment capability that allows the maximum buoyancy to be greater than the total weight of the load below the float 30. Furthermore, when moving, the float 30 and the power generation device 20 can be moved by the propulsion device to a location optimal for power generation based on the positioning information received by the positioning information receiver 50. The ocean current power generation system 3 of this embodiment is an ocean current power generation system in a tension mooring state, but is also capable of moving the location of the power generation device 20.

[0080] 1...Ocean current power generation system, 20...Power generation device, 21...Rotor, 22...Rotor support column, 26...Fin support column, 30, 32, 33a, 33b, 33c...Floating body, 40...Propulsion device, 47...Generator, 50...Positioning information receiver, 60, 61, 62...Rope body, 65...Power transmission line, 70...Control device, 72...Battery, 74...Buoyancy adjustment device, 75...Rope body adjustment device, 80...Mooring line, 85, 86...Cross beam, 88...Connecting member, 90, 95, 97...Power transmission cable, 100, 102...Sinker, 110...Fin, 200, 210...Anchor, 250...Ocean current, 300...Lift, S1...Seabed, S2...Underwater, S3...Sea surface, P1...Current position, P2...Position, α, β...Angle

Claims

1. An ocean current power generation system comprising: a float that floats on the seawater surface; a cable connected to said float; a support pole whose end is connected to said cable or whose cable passes through the inside of a vertically extending cylinder; a power generation device connected to said support pole; a first mooring cable connected to a first anchor fixed to a quay or the seabed; and a power transmission cable wound around and extending from said mooring cable.

2. The ocean current power generation system according to claim 1, characterized in that the floating body has a buoyancy adjustment device that adjusts the magnitude of buoyancy, or a rope adjustment device that adjusts the length of the rope.

3. An ocean current power generation system as described in claim 2, wherein the cable is connected to a second anchor in contact with the seabed, and power generation by the power generation device is carried out with the cable under tension.

4. An ocean current power generation system as described in claim 3, wherein the propulsion device provided on the float moves the float and the power generation device horizontally while pulling up the second anchor connected to the rope to the position of the lower end of the support by controlling the buoyancy adjustment device or the rope adjustment device.

5. The ocean current power generation system according to claim 1, wherein the specific gravity of the mooring rope is 1 or less.

6. An ocean current power generation system according to claim 1, wherein the support has a rotating part and a non-rotating part, and the power generation device is connected to the rotating part.

7. An ocean current power generation system comprising: a float that floats on the seawater surface; a generator provided on said float; a support column having a rotating part and a non-rotating part, the end of which is connected to said float and a vertically extending cylinder with a rotation transmission mechanism disposed inside, and the rotating part being connected to the rotating body; a first mooring line connected to a first anchor fixed to a quay or the seabed; and a power transmission cable wound around and extending from said mooring line.

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