Detachable structure of floating offshore wind turbine

Abstract

We provide floating offshore wind turbines that achieve high efficiency and cost reduction in construction and maintenance work. [Solution] Multiple anchors on the seabed and a float carrying a wind turbine are connected by mooring lines via float balls, so that the float is held in a fixed position above the sea surface and can be detached from the mooring lines.

Description

[Technical field]

[0001] The present invention relates to a floating body for an offshore wind turbine that is suitable for mooring and installing on the ocean at a depth of about 30 to 150 meters, relatively close to the coastline, to generate electricity. [Background technology]

[0002] Japan has declared to the international community that it will be carbon neutral by 2050, and in order to achieve this, it is necessary to promote the use of renewable energy, and increasing the amount of power generated by offshore wind turbines is seen as one effective means of achieving this goal. Because there are fewer obstacles blocking the wind offshore compared to on land, and the wind direction and speed are more stable than on land, the development and increase of offshore wind power generation facilities is an urgent issue for ensuring a stable supply of electricity in the future, as well as for realizing a decarbonized society.

[0003] Japan is surrounded by the sea on all sides, and while it is believed that there are many coasts where offshore wind turbines can be installed, many of these areas are deep compared to their distance from the coastline. For this reason, the main source of power development using offshore wind turbines is shifting from the fixed-bottom type (a method in which the base of the tower is fixed to the seabed and the wind turbine is installed on the top of the tower that protrudes above the sea surface), which has been widespread up until now, to the floating type (a method in which the entire wind turbine, including the tower, is mounted on a float and floated on the sea, and the wind turbine is moored and held in place by multiple mooring lines such as ropes or chains attached to anchors dropped on the seabed).

[0004] Currently, floating offshore wind power generation facilities in practical use include spar type, TLP type, semi-submersible type, and barge type, each of which is said to have advantages and disadvantages, as described in Non-Patent Document 1. With the exception of the barge type, most of these types have mooring lines attached to the float underwater, which makes installation time-consuming, and this is thought to be one of the factors that hinders the reduction of construction costs.

[0005] At the same time, the mooring means for floating offshore wind turbines proposed up to now have been configured to connect the float carrying the wind turbine directly to multiple anchors installed on the seabed with mooring lines. Therefore, once the float and anchors are connected and construction is completed, the float and mooring lines are not detached until the operation of the wind turbine is terminated, unless there is a special reason to do so. Therefore, when maintaining wind turbines, all inspection, repair, and other work must be done offshore where the turbines are installed.For example, in recent years, wind turbines have become more powerful, and some with blades that are nearly 100m long are being put to practical use.However, a large, dedicated work vessel (SEP vessel) must be prepared for the installation of the blades on the wind turbines during construction and for the periodic blade replacement work, which is also thought to be one of the factors that increase operating costs.

[0006] In order to increase offshore wind power generation in the future, reducing the costs of construction and maintenance is an essential issue that must be resolved. In particular, it is said that 60 to 70 percent of the construction cost of floating offshore wind turbines is the cost of manufacturing the float, setting it in a fixed position offshore, and assembling the wind turbine offshore. To reduce these costs, it is effective to assemble the float, tower, and wind turbine main body as much as possible at the nearest port that has production facilities such as large cranes and docks, and then tow the completed equipment to the installation area. At the same time, if mooring equipment for the float could be prepared in advance offshore at the installation site, and the completed combined float and wind turbine could be towed offshore and connected to the mooring equipment, it is thought that it would be possible to reduce costs and shorten construction time at the same time.

[0007] Currently, maintenance work on wind turbines is generally carried out offshore, where they are installed. However, this work is carried out at high altitudes offshore, where the turbines are rocked by waves, and requires the preparation of the aforementioned large dedicated work vessels (SEP vessels) or the mobilization of inspectors and workers with special skills. This is also thought to be one of the obstacles to reducing operating costs. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Patent 7432975 "Floating platform, anchor vessel body, float, and installation method for installing floating platform on water" [Patent Document 2] Patent Publication 2022-189073 "Assembly device and assembly method for floating offshore wind power generation equipment" [Non-patent literature]

[0009] [Non-Patent Document 1] "Current situation and outlook for wind power generation" November 2020, Agency for Natural Resources and Energy [Non-Patent Document 2] "The Easy Book on Wind Power Generation" B&T Books, Nikkan Kogyo Shimbun Summary of the Invention [Problem to be solved by the invention]

[0010] The first problem that the present invention aims to solve is to propose a detachable structure for an offshore wind turbine float, which enables high efficiency and cost reduction in construction and maintenance work by making the float and mooring lines detachable for a floating offshore wind turbine to be installed in sea areas with a water depth of 30m to 150m.

[0011] The second problem that this invention aims to solve is the consideration of a detachable structure for the float that would enable easy routing of temporary cables above the sea surface, thereby making it possible to accomplish the first problem of disconnecting and reconnecting the float and mooring lines without using a large ship.

[0012] The third problem that this invention aims to solve is the first problem of disconnecting and reconnecting the float from the mooring line, which requires adjacent floats to be pulled together.The third problem that this invention aims to solve is the consideration of a float attachment and detachment structure that would enable even a small work boat to pull the temporary cable with great force.

[0013] The fourth problem that this invention aims to solve is the study of a detachable structure for connecting an offshore wind turbine float to its mooring lines, which will be capable of being detached from its mooring lines, assembled at the nearest port and towed to the installation area, and, once setup is complete, will prevent the wind turbine from tilting due to the wind or from tilting due to waves on the sea surface.

[0014] The fifth problem that this invention aims to solve is the investigation of a suitable shape of float to make it easier to attach and detach the float, and the investigation of the attachment and detachment structure of the offshore wind turbine float and mooring line using this shape. [Means for solving the problem]

[0015] In order to solve the first problem that the present invention aims to solve, the floating body of an offshore wind turbine according to the present invention is configured as follows. The offshore wind turbine of the present invention is intended as a floating offshore wind turbine that is mounted on a float that is moored and installed on the ocean at a depth of about 30 to 150 meters, relatively close to the coastline, and generates electricity by rotating the blades using the wind power at sea.

[0016] The floating offshore wind turbine of the present invention has a float mounted on the sea surface and a number of floats arranged in concentric circles around the center of the float, and connects the float and the floats with a number of float mooring lines attached radially to the float.

[0017] Next, multiple float mooring lines, each consisting of a rope or chain having its own weight, are connected to each float, and the other end of each float mooring line is connected to an anchor installed concentrically around a position directly below the main float on the seabed. Each float has sufficient buoyancy to maintain a floating state on the sea surface against the weight of the float mooring lines connected to each float, the weight of the float mooring lines, and the tension acting on each mooring line. In the above configuration, each floating body mooring line is pulled toward the floating body with equal force, and tension is applied to the floating body mooring line and the float bead mooring line. As a result, the floating body is always pulled horizontally outward with equal force by the multiple floating body mooring lines. This action moored the floating body in a fixed position near the center surrounded by multiple floats installed on the sea surface.

[0018] Furthermore, the position of the floating body and each float changes up and down and left and right due to changes in the tide level and ocean waves, and the tension of each mooring line changes accordingly. Even if the tension of each mooring line changes, each float connected to an anchor on the seabed moves horizontally on the sea surface in the direction that balances the tension in response to the change in tension of each mooring line, and the floating body also moves horizontally on the sea surface accordingly. Due to this action, the floating body is moored stably without moving significantly even with changes in the tide level and waves that occur on the sea surface.

[0019] In order to realize the first objective of the present invention, which is a structure for attaching and detaching a float and a float mooring line, each float needs to remain in the same position even if the float and the float mooring line are separated. As mentioned above, each float is connected to an anchor on the seabed and is constantly pulled outward, so if the float mooring line is separated from the float, the float moves away from its original position to the outside immediately afterwards. As a result, it becomes difficult to reattach the float mooring line to the float. In the first embodiment of the present invention, adjacent floats are connected to each other with a temporary cable before the float is separated from the mooring line. This configuration makes it possible to keep each float in the same position on the sea surface even if the float is separated from the mooring line.

[0020] When actually removing the float, it is necessary to prepare a temporary float to replace the float, or a spare float to replace the float after assembling the float and the offshore wind turbine, and float it near the original offshore wind turbine before connecting the floats with the temporary cable. By applying this procedure, it becomes possible to efficiently remove the float with the offshore wind turbine mounted on it, reinstall it, and restore it while maintaining the mooring position of the float, etc., and the first problem of the present invention can be solved.

[0021] Regarding the second problem that the present invention aims to solve, a specific structure for solving the problem is shown below. In the case of applying a configuration with a detachable structure for the float and the float mooring rope as described above to offshore wind turbines, which are expected to become larger in the future, it is expected that the distance between adjacent floats will be long, and in that case, it is considered that it will be difficult to lay the temporary cable connecting the floats. Even if a long temporary cable is laid from one float to the next float using a work boat, there is a concern that the temporary cable itself will sink in the water and a small work boat with a small propulsion force will not be able to reach the next float. It is possible to reach the next float using a large ship with a large propulsion force, but preparing a large ship is a factor that increases costs. In order to enable a long temporary cable to be pulled even by a work vessel with a small propulsive force, the temporary cable is placed on the temporary cable subsidence prevention buoy at a constant pitch while being pulled. This will prevent the wire from sinking in the sea.

[0022] For the third problem that this invention aims to solve, after the temporary cable is stretched close to the adjacent float, one end of the towing work vessel is connected to the adjacent float by an auxiliary cable, and the temporary cable is pulled using a powerful winch mounted on the towing work vessel. This procedure makes it possible for adjacent floats to be pulled together with strong force even by a vessel with small propulsion power, so that even if the float and the float mooring line are separated, the float can be held in a fixed position, and at the same time, the work of reconnecting the float and the float mooring line can be easily carried out.

[0023] In order to solve the fourth problem that the present invention aims to solve, the floating body of the offshore wind turbine according to the present invention is configured as follows. By solving the first to third problems of the present invention described above, it becomes possible to assemble a floating offshore wind turbine at the nearest port and tow it to the installation area, or to tow the floating offshore wind turbine from the installation area back to the nearest port for maintenance. However, some floating offshore wind turbines, like the spar type, have their center of gravity positioned as deep below the water surface as possible, thereby suppressing the wind turbine's tilt when it catches the wind and suppressing the swaying caused by waves on the sea surface.

[0024] A wind turbine generator of this type is difficult to assemble on a quay, even in a port facility having a deep quay, and the effects of the present invention cannot be expected. In response to this problem, the float of the present invention is constructed such that a semi-submersible or barge-type float is assembled in a port, a weight is hung from the underside of the float using a rope, and the weight can be raised and lowered. The float and wind turbine are assembled and completed in the port, and then towed to the installation area, where the weight is lowered to the seabed. By setting the weight as deep as possible, but not to the seabed, the center of gravity of the entire structure including the wind turbine, float, and weight is lower than the float on the sea surface, increasing the restoring force. This effect is expected to suppress the inclination of the wind turbine when it catches the wind, or to suppress the swaying caused by waves on the sea surface. The above configuration makes it possible to realize a floating offshore wind turbine with a detachable floating structure and large restoring force, thereby resolving the fourth problem.

[0025] The fifth problem that the present invention aims to solve is as follows. To make it easier to attach and detach the float, an articulated float is floated around the float in a position outside the float that does not come into contact with the float, and the articulated float is connected to anchors arranged concentrically on the seabed with a float mooring line. The float and the articulated float are further connected with a connecting line. This configuration makes it possible to shorten the connecting line, making it easier to attach and detach the float. Effect of the Invention

[0026] The attachment and detachment structure of the offshore wind turbine float of the present invention makes it possible to remove and reattach the float equipped with the wind turbine while maintaining the mooring equipment of the floating offshore wind turbine once set in a designated position, which is considered to be effective in reducing costs during construction and maintenance.

[0027] In addition, the detachment structure of the offshore wind power generator float of the present invention can maintain the position of each float even after the float is removed from the float mooring line. Furthermore, it becomes easy to lay the temporary cable to maintain the position of the float. If the wind power generator is removed from the mooring equipment and transported to the nearest port equipped with production facilities, the amount of work on the sea can be reduced, which is effective in reducing costs.

[0028] In addition, the attachment and detachment structure of the offshore wind turbine float according to the present invention allows the floating wind turbine to be assembled using the nearest port facilities and then towed to the installation area. By sinking the weight suspended from the underside of the main float deep into the sea, the restoring force of the main float is increased, which is expected to have the effect of increasing the restoring force against the tilt of the wind turbine when it catches the wind and against waves on the sea surface.

[0029] In addition, by applying the detachable structure of the offshore wind power generator float of the present invention, it will be possible to use the mooring equipment to install floats of different structures and different types of wind power generators. It is expected that the development of larger wind power generators, which is expected to progress in the future, and the trial operation of prototype offshore wind power generators will be efficiently promoted, and cost reductions can also be expected. [Brief description of the drawings]

[0030] [Figure 1] FIG. 1 is a bird's-eye view showing an offshore wind turbine generator according to a first embodiment of the present invention, installed on the ocean. [Diagram 2] FIG. 2 is a bird's-eye view showing the configuration of the offshore wind turbine generator according to the first embodiment of the present invention when it is replaced with a temporary floating body on the sea. [Diagram 3] FIG. 3 is a bird's-eye view showing the configuration of the offshore wind turbine generator according to the first embodiment of the present invention after replacement with a temporary floating body on the ocean. [Figure 4]FIG. 4 is a bird's-eye view showing an example of a configuration in which a temporary cable is laid out before the offshore wind turbine generator according to the second embodiment of the present invention is replaced with a temporary floating body on the sea. [Diagram 5] FIG. 5 is a bird's-eye view showing an example of a configuration for applying tension to a temporary cable of an offshore wind turbine according to a third embodiment of the present invention before replacement with a temporary floating body on the sea. [Figure 6] FIG. 6 is a bird's-eye view showing an example of a configuration in which an offshore wind turbine according to a fourth embodiment of the present invention is assembled in a nearest port or harbor, towed to an installation area, and the weight is lowered downward after setup. [Figure 7] FIG. 7 is a bird's-eye view showing an example in which embodiments 1 to 4 are applied and different types of floating offshore wind turbines are attached by utilizing the already installed mooring configuration. [Figure 8] FIG. 8 is a bird's-eye view showing the configuration of an offshore wind turbine generator according to a fifth embodiment of the present invention, which illustrates an example of a configuration in which articulated floats make it even easier to attach and detach the float. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS EXAMPLES

[0031] The floating offshore wind turbine of the present invention is configured to hold a float equipped with a wind turbine at a fixed position on the sea surface by connecting the float to multiple anchors on the seabed with multiple mooring lines in an ocean area with a depth of 30 m to 150 m. The difference between the present invention and conventional floating offshore wind turbines is that the present invention has a structure that allows the float to be detached from the mooring lines. If the float and mooring lines, once set up, could be detached as needed and then reconnected to restore them, it would be possible to increase the efficiency of construction and maintenance work and reduce costs. Furthermore, it could also be used for other types of wind turbines, which is thought to be useful for the larger size of floating offshore wind turbines that will be developed in the future, and for the trial operation of floating offshore wind turbines of different structures and types. A first embodiment of the present invention will be described below with reference to FIGS.

[0032] FIG. 1 shows an overall bird's-eye view of the wind turbine generator body, float, and mooring ropes of the first embodiment. A float 1 in the first embodiment of the present invention is equipped with a wind power generator 2 on its upper surface, and a hollow portion is submerged below the sea surface, generating buoyancy in the float 1, causing it to float on the sea surface. A plurality of float mooring hooks 3 are attached to the outer surface of the float 1 facing outward, and float mooring lines 4 are attached radially to the float mooring hooks 3. Next, a plurality of floats 5 are floated concentrically on the sea surface with the float 1 at the center, and the ends of each float mooring rope 4 are tied to each float 5.

[0033] Furthermore, a plurality of float mooring lines 6, each made of a rope or chain having its own weight, are connected to each float 5, and the other end of each float mooring line 6 is connected to a plurality of anchors 7 installed concentrically around a point directly below the float 1 on the seabed. Each float 5 has sufficient buoyancy to maintain a floating state on the sea surface against the weight of the float mooring lines 4 and the float mooring lines 6, or the tension acting on each mooring line. After the above is set, each floater mooring line 4 is pulled toward the floater 1 with equal force, applying tension to the floater mooring lines 4 and the buoy mooring lines 6. As a result, the floater 1 is pulled horizontally outward with equal force by the multiple floater mooring lines 4. This action moors the float 1 at a fixed position on the sea surface near the center surrounded by the multiple floats 5. Arrow 4a in Figure 1 indicates the direction in which the floater mooring lines 4 are pulled, and arrow 6a indicates the direction in which the buoy mooring lines 6 are pulled.

[0034] The positions of the float 1 and each float 5 change up and down and left and right due to the rise and fall of the sea level caused by tide changes and waves on the sea surface, and the tension of the float mooring line 4 also changes from time to time in response to these changes, but since each float 5 is connected to an anchor 7 on the seabed by a float mooring line 6, the float 1 moves horizontally on the sea surface in a direction that balances the tension of the main float mooring line 4 and the float mooring line 6. Due to this action, the float 1 does not move significantly and is stably moored even if the tide changes or waves occur on the sea surface.

[0035] In order to solve the first problem of the present invention, it is necessary to make the part that connects the floater mooring line 4 to the float 1 detachable. Detailed view A in Fig. 1 shows an example of a structure that allows the floater mooring line 4 to be detached from the floater mooring hook 3. Alternatively, as shown in detailed view B, a floater mooring line connecting fitting 4b that connects the mooring lines to each other can be attached to the middle of the floater mooring line 4, and the floater mooring lines 4 can be detached from each other via this. In the above-mentioned configuration, each float 5 is connected to an anchor 7 on the seabed and is constantly pulled outward, so if the float mooring line 4 is removed from the float mooring hook 3, the float 5 is immediately pulled outward and separated. As a result, the task of reattaching the float mooring line 4 to the float 1 becomes extremely difficult. An embodiment for solving this problem is shown in Figure 2.

[0036] Figure 2 shows a configuration in which adjacent floats 5 are connected together with a temporary cable 13 before the float mooring line 4 is removed from the float 1. With this configuration, even if the float 1 and the float mooring line 4 are separated, each float 5 can be kept in the same position on the sea surface without being separated. As shown in Figures 1 and 2, a temporary float mooring hook 9 is attached to a temporary float 8, and a towing rope 11 is connected to a towing work boat 10 and the temporary float 8 is transported to the installation site of the offshore wind turbine. After connecting the floats 5 to each other with the temporary cable 13, the temporary float 8 and the main float 1 are swapped, and the float 1 including the wind turbine 2 can be removed while maintaining the position of the float 5. In Fig. 2, the direction of tension acting when the temporary cable 13 is attached is indicated by an arrow 14. Also shown in Fig. 2 is an example in which a floater mooring line sinking prevention buoy 12 is attached to one end of the floater mooring line 4 so that the floater does not sink into the sea even when the floater mooring line 4 is removed.

[0037] Fig. 3 shows a configuration in which, after swapping the temporary float 8 with the float 1, the position of the float 5 is maintained by connecting the float mooring line 4 to the temporary float mooring hook 9 attached to the outer periphery of the temporary float 8. The detached float 1, with the wind turbine 2 mounted on it, is transported by a towing work vessel 10 to the nearest port. The first embodiment of the present invention described above is expected to have the effect of reducing the construction and maintenance costs of the floating offshore wind turbine. EXAMPLES

[0038] Next, FIG. 4 shows a bird's-eye view of the configuration of the floating offshore wind turbine and mooring lines of the second embodiment. FIG. 4 shows an example of a configuration in which adjacent floats 5 described in the first embodiment are connected to each other by a temporary cable 13. When applying Example 1 to offshore wind power generators, which are expected to become larger in the future, the distance between the floats 5 is also expected to become longer, so the routing of the temporary cable 13 connecting the floats 5 becomes an issue. Even if a long temporary cable 13 is routed from one float to the next using a boat, there is a concern that the temporary cable itself will sink in the water, making it difficult for a small pulling work boat 16 with a small propulsive force to pull one end of the temporary cable to reach the adjacent float. This is possible if a large ship with a large propulsive force is used, but preparing a large ship increases costs. Detailed view C in Fig. 4 shows an embodiment that enables even a towing work vessel 16 with a small propulsive force to pull a long temporary cable 13. As the temporary cable 13 is pulled, it is placed on a temporary cable subsidence prevention buoy 15 at a constant pitch. With this configuration, even if the temporary cable 13 becomes long, it will not sink in the sea, and even if the towing work vessel 16 is small, it becomes possible to easily transport the temporary cable 13 to the vicinity of an adjacent float. EXAMPLES

[0039] FIG. 5 shows a bird's-eye view of the configuration of the floating offshore wind turbine and mooring lines of the third embodiment. Even if one end of the temporary cable 13 can be brought close to the adjacent float 5 by the second embodiment, the temporary cable 13 needs to be pulled with a sufficient load in order to keep the float 5 in the same position. However, if the pulling work vessel 16 is small, there is a concern that a sufficient pulling force cannot be obtained. As shown in FIG. 5, after the temporary cable 13 is stretched close to the adjacent float 5, first, an auxiliary cable 18 attached to the towing work boat is connected to an auxiliary cable attachment hook 19 of the adjacent float 5, and then the temporary cable 13 is pulled using a powerful winch (hoisting machine) 20 mounted on the towing work boat 16. With the above configuration, even a small boat with a small propulsive force can pull adjacent floats together with a strong force. In the detailed view D of FIG. 5, the tension acting on the temporary cable and the auxiliary cable when the winch is wound up is indicated by an arrow 21. With the above configuration, even if the propulsive force of the towing work boat 16 is small, the floats 5 can be pulled together with a strong force, making it possible to hold each float in a fixed position. EXAMPLES

[0040] Next, FIG. 6 shows a bird's-eye view of the configuration of the floating offshore wind turbine and mooring lines of the fourth embodiment. According to the first to third embodiments of the present invention, it is possible to assemble the floating offshore wind turbine in a port near the installation area and to tow it from the port to the installation area, or tow the floating offshore wind turbine back to the nearest port for maintenance, which is expected to reduce costs. However, some floating offshore wind turbines are designed to have their center of gravity positioned as deep as possible below the water surface, like a spar type, which reduces the wind turbine's tilt when it catches the wind and also reduces the swaying caused by waves on the sea surface.

[0041] It is difficult to assemble a wind turbine generator of this type on the quay of a port, even if the port has deep quays, and the effective effects of the present invention cannot be expected. In order to address this issue, the float of the present invention is constructed such that a semi-submersible or barge-type float is assembled in a port, and a weight 22 is suspended from the bottom of the float using a weight suspending rope 23. The weight suspending rope 23 is also capable of being extended and wound up. The float 1 with the weight 22 suspended from the bottom and the wind turbine 2 are assembled in the port, and towed to the installation area, where the weight 22 is lowered toward the seabed. If the weight is set at a deep position as far away from the float 1 as possible, but not deep enough to reach the seabed, the center of gravity of the entire structure floating on the sea will be lowered, increasing the restoring force. With the above configuration, it is possible to realize a floating body with a large restoring force on the ocean for the floating offshore wind turbines reflecting the configurations of the first to third embodiments of the present invention.

[0042] Next, FIG. 7 shows an application example in which the first to fourth embodiments are applied to a floating body having a structure different from that of the floating body shown in the first embodiment, or to an offshore wind turbine of a different type from that of the first embodiment. The mooring method for floating offshore wind turbines currently in practical use, other than the TLP type, is a structure in which the float is connected to multiple anchors installed radially on the seabed in concentric circles around the float's position with heavy mooring lines, and the float is held in a fixed position on the sea surface by applying approximately equal tension to each mooring line. After the float is connected to multiple anchors installed on the seabed with mooring lines, these floating offshore wind turbines do not generally take into consideration the need to separate the mooring lines from the float until the operation of the offshore wind turbine is terminated.

[0043] 7 (Application Example A) shows an example in which the embodiments 1 to 3 are applied to a float 25 of a spar-type offshore wind power generator. By attaching a mooring hook 26 to the float 25 of the spar-type offshore wind power generator, the mooring equipment of the embodiments 1 to 3 can be used to install the spar-type offshore wind power generator. Fig. 7 (Application Example A) shows an embodiment in which the embodiments 1 to 3 are applied to a cylindrical barge-type floating body 28 equipped with a passive yaw type offshore wind turbine 29. To realize the passive yaw type, a rotating ring 29 is attached, and a plurality of mooring hooks 30 are attached to the outer surface of the rotating ring. By attaching a weight 31 and a weight suspending rope 32 to this cylindrical barge-type floating body 28 as well, it is possible to increase the restoring force after setting up on the sea. Further, FIG. 7 (Application Example C) shows an example in which a vertical axis offshore wind power generator 33 is mounted on the floating body 1 according to any one of the first to third embodiments.

[0044] As described above, after a floating offshore wind turbine is operated for a certain period of time, the mooring equipment such as anchors and floats can be left behind and reused for mooring new offshore wind turbines after it is decommissioned. This is expected to reduce the cost of constructing new wind turbines and the cost of developing prototypes. EXAMPLES

[0045] Next, FIG. 8 shows a bird's-eye view of the configuration of the floating offshore wind turbine and mooring lines of the fifth embodiment. In Fig. 8, multiple floats are connected in an arc shape to form an articulated float 34, which is placed in a position surrounding the cylindrical barge-type float 28 shown in Fig. 7, and this articulated float 34 is connected to an anchor 7 installed on the seabed using a float mooring line 6. Furthermore, using connecting hooks 35 attached to both the articulated float 34 and the cylindrical barge-type float 28, the cylindrical barge-type float 28 and the articulated float 34 are connected with a float connecting line 36. Note that the articulated float is not doughnut-shaped, but has a shape with a part open, so that a float equipped with a wind turbine generator can be inserted inside the articulated float through the open part. According to the sixth embodiment, the floater connecting cable 36 can be shortened, so that the attachment and detachment of the cylindrical barge-type floater 2 can be expected to become easier. [Industrial Applicability]

[0046] This application is applicable to floating offshore wind turbines, which are expected to become larger and new products will be developed in the future, and proposes a configuration that enables the reuse of mooring equipment. It is expected that this technology will reduce the cost of mooring equipment, which is said to account for a large portion of the construction costs of floating offshore wind turbines, as well as maintenance costs and new product development costs.It is also expected that this technology will lead to collaboration and application not only in wind power-related fields, but also in shipbuilding, transportation, fishing, and other industries. [Explanation of symbols]

[0047] 1 Floating Body 2. Wind turbines 3 Floating Mooring Hook 4 Floating Mooring Lines 4a Arrow showing the direction in which the floating mooring rope is pulled 4b Floating mooring line connection fitting 5. Floats 6 Float Mooring Line 6a Arrow showing the direction in which the buoy mooring line is pulled 7. Anchor 8 Temporary Floating Structure 9 Temporary floating mooring hook 10 Towing workboat 11 Tow rope 12. Floating mooring rope sinking prevention buoy 13 Temporary Cable 14 Arrows showing tension acting on temporary cables 15 Temporary cable subsidence prevention buoy 16 Towing work boat 17 Arrow showing the direction of travel of the towing workboat 18 Auxiliary Cable 19 Auxiliary cable mounting hook 20 Winch 21 Arrows showing tension acting on the temporary cable and auxiliary cable when winching 22 Weight 23 Weight hanging rope 24 Arrows showing the situation of lowering weights in the installation area 25 Floating body and weight of spar-type offshore wind turbine 26 Floating mooring hook for spar-type offshore wind turbine 27 Example of application of a multi-stage fixed pitch passive yaw type offshore wind turbine 28 Cylindrical Barge Type Floating Body 29 Rotating Ring 30 Mooring hook for a cylindrical barge-type floating structure equipped with a passive yaw type offshore wind turbine 31 Weight of cylindrical barge type floating body 32 Weight suspension rope for cylindrical barge type float 33 Application example of vertical axis offshore wind turbine 34 Articulated float 35 Connecting Hooks 36 Floating body connecting rope

Claims

1. 1. A detachable structure for an offshore wind turbine floater in which a wind turbine is mounted on a float floating on the seawater surface and the float is connected to multiple anchors installed on the seabed with lines such as ropes or chains to moor the wind turbine at a fixed position on the seawater surface. A plurality of float mooring lines are detachably attached to the outer periphery of the float on which the offshore wind turbine is mounted, the float mooring lines extending radially above the sea surface from the float as the center, and the float mooring lines are connected to a plurality of floats installed concentrically on the sea surface from the float as the center, and further the plurality of float mooring lines are connected to a plurality of anchors installed concentrically on the seabed with a position directly below the float on the seabed as the center, so that the float is moored at an approximately fixed position on the sea surface near the center surrounded by the plurality of floats, and further adjacent floats among the floats are connected to each other with a detachable temporary cable.

2. A detachable structure for an offshore wind turbine float, comprising: a temporary cable as described in claim 1 for connecting adjacent floats as described in claim 1; and a temporary cable extending above the sea surface between the adjacent floats as described in claim 1, wherein temporary cable subsidence prevention buoys are attached at regular intervals to the temporary cable extending above the sea surface between the adjacent floats as described in claim 1, so that the temporary cable floats on the sea surface.

3. A detachable structure for an offshore wind turbine float, characterized in that one end of a temporary cable described in claim 1 or claim 2 is connected to one of the adjacent floats described in claim 1 or claim 2, and at the same time, one end of an auxiliary cable is connected to the other of the adjacent floats described in claim 1 or claim 2, and the temporary cable is further wound around a winch mounted on a pulling work vessel on the sea surface, and the auxiliary cable is also connected to the pulling work vessel, and then the temporary cable is wound up with the winch, thereby causing the adjacent floats to be pulled together by the temporary cable.

4. 2. A detachable structure for an offshore wind turbine float, comprising: a float as described in claim 1; a plurality of weight suspension ropes that can be extended and wound up toward the underside of the float; weights attached to the lower ends of the plurality of suspension ropes and suspended from the float; and the weights are lowered toward the seabed by extending the plurality of weight suspension ropes at sea, and are stopped and held at a position just before reaching the seabed surface.

5. In a floating offshore wind power generator, a wind power generator is mounted on a floating body floating on the sea surface, and the floating body and a number of anchors installed on the seabed are connected with lines such as ropes or chains to moor the wind power generator at a fixed position on the sea surface. A number of float connecting lines are attached in a detachable configuration to the outer periphery of the float on which the offshore wind power generator is mounted, and a number of floats are floated concentrically around the float on the sea surface at a position away from the float without contacting the float, and This is a detachable structure for an offshore wind turbine float, characterized in that the floats are connected to each other and integrated to form an articulated float that surrounds the floating body, and at the same time, the articulated float has a gap that allows the float to move from the inside to the outside of the articulated float while floating on the sea surface, the multiple float connecting lines are connected to the articulated float, and further, the articulated float is connected to a number of anchors installed concentrically on the seabed with a position directly below the float on the seabed as its center by a number of float mooring lines.

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