Detachable structure of offshore wind power generator floating body

Abstract

To provide a floating offshore wind power generator capable of achieving high efficiency and cost reduction in construction and maintenance work.SOLUTION: The floating body is held at a fixed position on the sea surface by connecting a plurality of anchors on the sea bottom surface and the floating body mounted with the wind power generator by a mooring rope via a floating ball, and the floating body can be attached to and detached from the mooring rope.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a floating offshore wind turbine suitable for mooring and installation on the ocean at a depth of approximately 30m to 150m, relatively close to the coastline, to generate electricity. [Background technology]

[0002] Japan has declared to the international community that it will become 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 than on land, and 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 stable power supply in the future and for realizing a decarbonized society.

[0003] Japan is surrounded by the sea on all sides, and while it is thought that there are many coasts where offshore wind turbines could be installed, many of these areas are deep compared to their distance from the coastline.As a result, the main source of power generation using offshore wind turbines is shifting from the previously popular bottom-fixed type (a method in which the base of the tower is fixed to the seabed and the wind turbine is installed at the top of the tower that protrudes above the water surface) to the floating type (a method in which the entire wind turbine, including the tower, is mounted on a float and floats 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] As described in Non-Patent Document 1, floating offshore wind power generation facilities currently in practical use include spar, TLP, semi-submersible, and barge types, each of which is said to have advantages and disadvantages. With the exception of the barge type, most of these types have mooring lines attached to the floating structure underwater, which makes installation time-consuming and is thought to be one of the factors hindering reductions in construction costs.

[0005] At the same time, the mooring methods for floating offshore wind turbines proposed to date 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 complete, the float and mooring lines are not detached until the wind turbine's operation is terminated, unless there is a very good reason not to do so. Therefore, when maintaining wind turbines, all inspections, repairs, and other work must be carried out offshore where the turbines are installed.For example, as wind turbines have become more powerful in recent years, turbines with blades reaching nearly 100 meters in length are now being put into practical use, but the installation of blades onto wind turbines during construction and the periodic blade replacement work require the use of large, dedicated work vessels (SEP vessels), which are also thought to be one of the factors behind increased operating costs.

[0006] Reducing construction and maintenance costs is an essential issue that must be resolved in order to increase offshore wind power generation in the future. It is said that 60 to 70 percent of the construction cost of floating offshore wind turbines, in particular, is the cost of manufacturing the float, setting it in place offshore, and assembling the wind turbines offshore. To reduce these costs, an effective construction method would be to assemble the float, tower, and wind turbine itself 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 can be prepared in advance at the offshore installation site, and the completed combined float and wind turbine can be towed offshore and connected to the mooring equipment, it is thought that costs can be reduced and construction time can be shortened.

[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 a floating platform on water" [Patent Document 2] Patent Publication No. 2022-189073 "Assembly device and assembly method for floating offshore wind turbines" [Non-patent literature]

[0009] [Non-Patent Document 1] "Current Status and Outlook for Wind Power Generation," November 2020, Agency for Natural Resources and Energy [Non-patent document 2] "A Thoroughly 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 this invention aims to solve is to propose a detachable structure for the float of an offshore wind turbine, which is intended to be installed in waters 30m to 150m deep, by making the float and mooring lines detachable, thereby enabling high efficiency and cost reduction in construction and maintenance work.

[0011] The second problem that this invention aims to solve is the development of a float detachment structure that will allow for easy laying of temporary cables on the sea surface, thereby enabling the first problem of disconnecting and reconnecting the float and mooring rope to be solved without the need for a large ship.

[0012] The third problem that this invention aims to solve is the first problem of disconnecting the float from the mooring line and reconnecting it, which requires adjacent floats to be pulled together.However, this involves considering a float attachment / detachment structure that would allow 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 allow the float to be detached from its mooring lines, assembled at the nearest port and towed to the installation area, and, once set up, will prevent the wind turbine from tilting due to wind or waves on the sea surface.

[0014] The fifth problem that this invention aims to solve is the investigation of a suitable shape for the 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 rope that uses this shape. [Means for solving the problem]

[0015] To solve the first 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. The offshore wind turbine of the present invention is a floating offshore wind turbine mounted on a floating body moored and installed in the ocean at a depth of approximately 30 to 150 meters, relatively close to the coastline, and generates electricity by rotating the blades using offshore wind power.

[0016] The floating offshore wind turbine of the present invention has a float mounted on a wind turbine generator and floating on the sea surface, with multiple floats floating on the sea surface at concentric positions on the sea surface, and the float and floats are connected by multiple float mooring lines attached radially to the float.

[0017] Next, multiple float mooring lines, each consisting of a rope or chain with 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 it, the weight of the float mooring lines, and the tension acting on each mooring line. In the above configuration, each floater mooring line is pulled toward the floater with equal force, applying tension to the floater mooring line and the floater bead mooring line. As a result, the floater is constantly pulled horizontally outward with equal force by the multiple floater mooring lines. This action moored the floater 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 in each mooring line fluctuates accordingly. Even if the tension in each mooring line fluctuates, 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 changes in the tension of each mooring line, and the floating body also moves horizontally on the sea surface accordingly. Due to this action, the floating body does not move significantly and is moored stably, even with changes in the tide level and waves that occur on the sea surface.

[0019] To achieve the first objective of this invention, which is a structure for attaching and detaching a float to a float mooring line, each float must remain in the same position even when the float and the float mooring line are detached. As mentioned above, each float is connected to an anchor on the seabed and is constantly pulled outward. Therefore, if the float mooring line is detached from the float, the float will immediately move away from its original position. As a result, it is 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 temporary cables 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 after the float is separated from the mooring line.

[0020] When actually removing the float, a procedure is required to prepare a temporary float to replace the float, or a spare float to replace the float after the float and offshore wind turbine are assembled, and float it near the original offshore wind turbine before connecting the floats with temporary cables. Applying this procedure makes it possible to efficiently remove, reinstall, and restore the float with the offshore wind turbine mounted while maintaining the mooring position of the float ball, etc., thereby solving the first problem of the present invention.

[0021] Regarding the second problem that the present invention aims to solve, a specific structure for solving the problem is shown below. When a configuration with a detachable float and float mooring rope structure like the one described above is applied to offshore wind turbines, which are expected to become larger in the future, the distance between adjacent floats is expected to become longer, which would make it difficult to route the temporary cable connecting the floats. Even if a long temporary cable is pulled from one float to the next using a work boat, there is a concern that the temporary cable itself will sink in the water and a small work boat with little propulsion power will not be able to reach the next float. While it is possible to reach the next float using a large ship with high propulsion power, preparing a large ship increases costs. To enable long temporary cables to be pulled even by a work vessel with a small propulsion force, the temporary cable is laid on the temporary cable subsidence prevention buoys at a constant pitch while being pulled, so that the wire does not sink into the sea.

[0022] To address the third problem this invention aims to solve, after the temporary cable has been stretched close to the adjacent float, one end of the towing vessel is connected to the adjacent float with an auxiliary cable, and the temporary cable is pulled using a powerful winch mounted on the towing vessel. This procedure makes it possible for even a vessel with little propulsion power to pull adjacent floats together with great force, so even if the float and floater mooring line are detached, the float can be held in a fixed position, and at the same time, the float and floater mooring line can be easily reconnected.

[0023] 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 it from the installation area to the nearest port and return it for maintenance. However, some floating offshore wind turbines, like spar-type turbines, have a center of gravity positioned as deep below the water surface as possible, which reduces tilting when the wind hits the turbine or suppresses rocking caused by waves on the sea surface.

[0024] A wind power generator of this type is difficult to assemble on a quay even in port facilities with deep quays, and the effects of the present invention cannot be expected. To address this issue, the float of the present invention is a semi-submersible or barge-type float assembled in a port, with a weight suspended from the float's underside using a rope, allowing the weight to be raised and lowered. The float and wind turbine are assembled in the port and towed to the installation area, where the weight is lowered toward the seabed. By placing the weight as deep as possible, but not deep enough to reach 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 its restoring force. This effect is expected to suppress tilting of the wind turbine when it catches wind, and to suppress 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 a large restoring force, thereby resolving the fourth problem.

[0025] The fifth problem that the present invention aims to solve is as follows: To further facilitate the attachment and detachment of the float, an articulated float is floated around the float outside the float, in a position 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 allows the connecting line to be shortened, making it easier to attach and detach the float. [Effects of the Invention]

[0026] The detachable structure of the offshore wind turbine float according to the present invention allows the float on which the wind turbine is mounted to be removed and reinstalled while maintaining the mooring equipment of the floating offshore wind turbine once it has been set in a designated position, which is thought to be effective in reducing costs during construction and maintenance.

[0027] Furthermore, the detachable structure for the offshore wind turbine float according to the present invention makes it possible to maintain the position of each float even after the float is detached from the float mooring line. Furthermore, it becomes easy to lay temporary cables to maintain the position of the float. Removing the wind turbine from the mooring equipment and transporting it to the nearest port with production facilities reduces the amount of work required offshore, which is effective in reducing costs.

[0028] In addition, the detachable structure of the offshore wind turbine float of the present invention allows the floating wind turbine to be assembled using the nearest port facilities and then towed to the installation area, and the weight suspended from the underside of the main float is submerged deep in the sea, thereby increasing the restoring force of the main float, which is expected to have the effect of increasing the restoring force against tilting when the wind hits the wind and against waves on the sea surface.

[0029] Furthermore, by applying the detachable structure of the offshore wind turbine float according to the present invention, it will be possible to use the same mooring equipment to install floats of different structures and different types of wind turbines. This will enable the efficient development of larger wind turbines, which are expected to be developed in the future, and the trial operation of prototype offshore wind turbines, and is expected to reduce costs. [Brief explanation of the drawings]

[0030] [Figure 1] FIG. 1 is a bird's-eye view showing an offshore installation of an offshore wind turbine generator according to a first embodiment of the present invention. [Figure 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. [Figure 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 being replaced 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 routed 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. [Figure 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 generator according to a third embodiment of the present invention before the generator is replaced 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 generator according to a fourth embodiment of the present invention is assembled at the nearest port or the like, towed to an installation area, and after setup, the weight is lowered downward. [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 reusing the mooring configuration that has already been installed. [Figure 8] FIG. 8 shows the configuration of an offshore wind turbine generator according to a fifth embodiment of the present invention, and is a bird's-eye view showing an example of a configuration in which articulated floats make it even easier to attach and detach the float. DETAILED DESCRIPTION OF THE INVENTION [Example]

[0031] The floating offshore wind turbine of the present invention is configured to hold the float, which carries the wind turbine, in a fixed position on the sea surface by connecting it to multiple anchors on the seabed with multiple mooring lines in an ocean area with a depth of 30m to 150m.What makes this invention different from conventional floating offshore wind turbines is that it has a structure that allows the float to be detached from the mooring lines. If the float and mooring lines can be detached and reattached as needed to restore the float, it will be possible to improve the efficiency of construction and maintenance work and reduce costs. Furthermore, this method can be adapted to other types of wind turbines, which is likely to be useful in the future for larger floating offshore wind turbines and for the trial operation of floating offshore wind turbines with different structures and models. A first embodiment of the present invention will be described below with reference to FIGS.

[0032] FIG. 1 shows a bird's-eye view of the entire structure including the wind power 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 turbine 2 on its upper surface, and a hollow portion is submerged below the sea surface, generating buoyancy in the float 1, allowing 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 the float mooring ropes 4 are connected to the floats 5 .

[0033] Furthermore, a plurality of float mooring lines 6, each made of a rope or chain with 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 center 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 float mooring lines 6, or the tension acting on each mooring line. After the above is set up, 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 bead 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 moores the floater 1 at a fixed position on the sea surface near the center surrounded by the multiple buoys 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 bead mooring lines 6 are pulled.

[0034] Furthermore, the positions of the float 1 and each float ball 5 change up and down and left and right due to the rise and fall of the sea surface caused by fluctuations in the tide level and waves on the sea surface, and the tension of the float mooring lines 4 also changes accordingly, but because each float ball 5 is connected to an anchor 7 on the seabed by a float ball 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 ball mooring line 6. Due to this action, the float 1 does not move significantly and is stably moored even when the tide level changes or waves occur on the sea surface.

[0035] 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 floater 1 detachable. Detailed view A in Figure 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, it is also possible to attach a floater mooring line connector 4b midway along the floater mooring line 4 to connect the mooring lines together, and to configure the floater mooring lines 4 to be detached via this. In the configuration described above, 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 detached from the float mooring hook 3, the float 5 is immediately pulled outward and separated. As a result, it becomes extremely difficult to reattach the float mooring line 4 to the float 1. Figure 2 shows an embodiment for solving this problem.

[0036] Figure 2 shows a configuration in which adjacent floats 5 are connected together with temporary cables 13 before the float mooring lines 4 are removed from the float 1. With this configuration, even if the float 1 and the float mooring lines 4 are separated, each float 5 can remain in the same position on the sea surface without separating. As shown in Figures 1 and 2, a temporary float mooring hook 9 is attached to the temporary float 8, and a towing rope 11 is connected to a towing work vessel 10 and the temporary float 8 is transported to the offshore wind turbine installation site.The float balls 5 are then connected to each other with the temporary cable 13, and the temporary float 8 and the main float 1 are then swapped, allowing the float 1 including the wind turbine 2 to be removed while maintaining the position of the float ball 5. In Figure 2, the direction of tension acting when installing the temporary cable 13 is indicated by arrow 14. Figure 2 also shows an example in which a floater mooring line sinking prevention buoy 12 is attached to one end of the floater mooring line 4 to prevent the floater from sinking into the sea even when the floater mooring line 4 is removed.

[0037] Figure 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 floating offshore wind turbines. [Example]

[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 turbines, which are expected to become larger in the future, the distance between the floats 5 is also expected to become longer, and therefore, 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 little propulsion power to pull one end of the temporary cable to reach the adjacent float. This is possible if a large ship with great propulsion power is used, but preparing a large ship increases costs. Detailed view C in Figure 4 shows an embodiment that enables a long temporary cable 13 to be pulled even by a pulling work vessel 16 with a small propulsion force. 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 is long, it will not sink in the sea, and even if the pulling work vessel 16 is small, it can easily transport the temporary cable 13 to the vicinity of an adjacent floating ball. [Example]

[0039] FIG. 5 shows a bird's-eye view of the floating offshore wind turbine and mooring rope configuration of the third embodiment. Even if one end of the temporary cable 13 can be brought to the vicinity of the adjacent float 5 by the second embodiment, the temporary cable 13 needs to be pulled with a sufficient load to keep the float 5 in the same position. However, if the pulling work vessel 16 is small, there is a concern that sufficient pulling force may not be obtained. As shown in Figure 5, after the temporary cable 13 is stretched to the vicinity of the adjacent float 5, first an auxiliary cable 18 attached to the towing work vessel is connected to the 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 vessel 16. With this configuration, even a small vessel with little propulsion power can pull adjacent floats together with great force. In detailed view D of Figure 5, arrows 21 indicate the tension acting on the temporary cable and auxiliary cable when the winch is being wound up. With this configuration, even if the propulsion power of the towing work vessel 16 is small, the floats 5 can be pulled together with great force, making it possible to hold each float in a fixed position. [Example]

[0040] Next, FIG. 6 shows a bird's-eye view of the floating offshore wind turbine and mooring rope configuration of the fourth embodiment. According to Examples 1 to 3 of the present invention, it is possible to assemble the floating offshore wind turbine in a port near the installation area and tow it from the port to the installation area, or to 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, like the spar type, have a center of gravity positioned as deep below the water surface as possible, which prevents the wind turbine from tilting when exposed to wind and also reduces rocking caused by waves on the sea surface.

[0041] A wind power generator of this type is difficult to assemble on the quay of a port, even if the port has deep quays, and the effective effects of the present invention cannot be expected. To address this issue, the float of the present invention is constructed so 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 reeled in. The float 1 with the weight 22 suspended from its bottom and the wind turbine 2 are assembled in the port, and then towed to the installation area, where the weight 22 is lowered toward the seabed. If the weight is set at a depth that does not reach the seabed, but is as far away from the float 1 as possible, the center of gravity of the entire structure floating on the sea will be lowered, increasing its restoring force. With the above configuration, it is possible to realize a floating body with a large restoring force on the ocean, even for the floating offshore wind turbines that reflect the configurations of Examples 1 to 3 of the present invention.

[0042] Next, FIG. 7 shows an application example in which Examples 1 to 4 are applied to a floating body having a different structure from that of Example 1, or to an offshore wind power generator of a different type from that of Example 1. The mooring method for floating offshore wind turbines currently in practical use, with the exception of 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.With these floating offshore wind turbines, once the float is connected to multiple anchors installed on the seabed with mooring lines, basically no consideration is given to separating the mooring lines from the float until the operation of the offshore wind turbine has ended.

[0043] 7 (Application example A) shows an example in which the embodiments 1 to 3 are applied to a floating body 25 of a spar-type offshore wind power generator. By attaching a mooring hook 26 to the floating body 25 of the spar-type offshore wind power generator, the mooring equipment of embodiments 1 to 3 can be used to install the spar-type offshore wind power generator. Figure 7 (Application Example A) shows an example in which Examples 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 system, a rotating ring 29 is attached, and multiple mooring hooks 30 are attached to the outer surface of the rotating ring. By attaching weights 31 and weight hanging ropes 32 to this cylindrical barge-type floating body 28 as well, it is possible to increase the restoring force after installation at sea. Furthermore, (application example C) in FIG. 7 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, even after a floating offshore wind turbine is operated for a certain period of time and then decommissioned, the mooring equipment, including anchors and floats, can be left behind and reused to moor new offshore wind turbines. This is expected to reduce the cost of building new wind turbines and the cost of developing prototypes. [Example]

[0045] Next, Fig. 8 shows a bird's-eye view of the floating offshore wind turbine and mooring rope configuration of the fifth embodiment. In Figure 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 Figure 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 partially open shape, so that a float equipped with a wind turbine generator can be placed inside the articulated float through this open part. According to the sixth embodiment, the floater connecting cable 36 can be shortened, so that the cylindrical barge-type floater 2 can be expected to be attached and detached more easily. [Industrial Applicability]

[0046] This application is applicable to floating offshore wind turbines, which are expected to become larger in size and new product development will be promoted in the future, and proposes a configuration that enables the reuse of mooring equipment. This technology is expected to 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 to have potential for 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 rope 4a Arrow indicating the direction in which the floating mooring line is pulled 4b Floating mooring rope connecting fittings 5 Floats 6 Float mooring rope 6a Arrow indicating the direction in which the buoy mooring line is pulled 7. Anchor 8 Temporary Floating Structure 9 Temporary floating mooring hook 10 Towing Work Boat 11 Tow rope 12 Floating mooring rope sink 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 indicating the direction of travel of the towing work vessel 18 Auxiliary Cable 19 Auxiliary cable mounting hook 20 winch 21 Arrows showing tension acting on the temporary cable and auxiliary cable when the winch is hoisted 22 weight 23 Weight hanging rope 24 Arrow indicating the situation of lowering the weight 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 of 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 Example of application of vertical axis offshore wind turbines 34 Articulated float 35 Articulating Hook 36 Floating body connecting rope

Claims

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 a plurality of anchors installed on the seabed with ropes, chains, or other lines to moor the wind turbine at a fixed position on the seawater surface. In this detachable structure, 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 seawater surface from the float as the center, and the float mooring lines are connected to a plurality of floats installed concentrically on the seawater surface from the float as the center, and further the plurality of floats are connected to a plurality of anchors installed concentrically on the seabed directly below the float with a plurality of float mooring lines, so that the float is moored at an approximately fixed position on the seawater surface near the center surrounded by the plurality of floats, and adjacent floats are connected to each other with detachable temporary cables.

2. A detachable structure for an offshore wind turbine float, characterized in that in the temporary cable described in claim 1 that connects adjacent floats described in claim 1, temporary cable subsidence prevention buoys are attached at regular intervals to the temporary cable extended above the sea surface between the adjacent floats 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 either claim 1 or claim 2 is connected to one of the adjacent floats described in either 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 either claim 1 or claim 2, and the temporary cable is then 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 the temporary cable is then wound up with the winch, thereby attracting the adjacent floats to each other by the temporary cable.

4. 10. A detachable structure for an offshore wind turbine float, comprising: a plurality of weight suspending ropes that can be extended and wound up toward the underside of the float according to claim 1; weights attached to the lower ends of the plurality of suspending ropes and suspended from the float; and the plurality of weight suspending ropes are extended offshore to lower the weights toward the seabed and stop and hold them at a position just before they reach the seabed.

5. 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 a plurality of anchors installed on the seabed with ropes or chains or the like to moor the wind turbine at a fixed position on the seawater surface, is characterized in that a plurality of floater connecting lines are detachably attached to the outer periphery of the float on which the offshore wind turbine is mounted, the plurality of floater connecting lines are connected to an articulated float that surrounds the outside of the float without contacting it and is positioned on the sea surface with a portion of it loose, with a plurality of anchors installed concentrically on the seabed with a center directly below the float connected to the articulated float with a plurality of floater mooring lines.

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