Construction method of floating body type offshore wind power generation facility

Abstract

To provide a construction method of a floating type offshore wind power generation facility which enables safe construction of a large floating type offshore wind power generation facility without using a large self-elevation barge suitable for the large wind power generation facility.SOLUTION: A self-elevation barge 20 is stopped near a floating body 2 lying on a sea bottom SB, and a crane 23 is used to provide lower portion split members 4c, 4d forming a lower part of a tower 4 on a column 2a of the floating body 2 in a standing state. Upper split members 4a, 4b forming an upper part of the tower 4 are held in a standing state by a holding part 31 of a tower holding device 30 mounted on a barge body 21. The crane 23 is used to install a nacelle hub 5 on an upper part of the upper portion split members 4a, 4b. The barge body 21 is elevated to a next step work height L2 higher than an initial step work height L1 and the holding part 31 is moved by a moving mechanism 32 of the tower holding device 30 to move an integrated object of the upper portion split members 4a, 4b and the nacelle hub 5 onto the lower portion split members 4c, 4d.SELECTED DRAWING: Figure 12

Description

[Technical Field]

[0001] The present invention relates to a construction method for a floating offshore wind power generation facility, and more specifically to a construction method for a floating offshore wind power generation facility that can safely construct a large floating offshore wind power generation facility with a float draft of 20 m or less when moored in the target sea area, without using an appropriately large self-elevating barge. [Background technology]

[0002] Floating offshore wind power generation facilities, which have a structure in which a wind turbine is erected on a float moored in a submerged or semi-submerged state in the sea area, are classified according to the structure of the float into spar-type, semi-submerged, TLP (tension leg barge) type, and barge (concrete) type. For example, a spar-type floating offshore wind power generation facility has a column-shaped spar-type float about 50 to 100 meters in height, most of which is submerged, and a wind turbine is erected on this single huge spar-type float (see, for example, Patent Document 1). When moored in the sea area where the facility is to be installed, the draft of the spar-type float is about 50 to 100 meters. On the other hand, for floating offshore wind power facilities other than the spar type, such as semi-submersible, TLP, and barge types, the floats are semi-submerged and floating on the sea surface, and when moored in the target sea area, the draft of the semi-submersible, TLP, and barge floats is each 20m or less.

[0003] One possible method for constructing floating offshore wind power generation facilities other than spar types, such as semi-submersible, TLP, and barge types, is to use a self-elevating barge (also known as an SEP vessel) to assemble an assembly of wind power generation equipment on a float. When constructing medium-sized or small floating offshore wind power generation facilities where the height from the bottom of the float to the nacelle hub (the rotation axis of the nacelle) is, for example, less than 130 m, this construction method using a self-elevating barge can safely and stably install the tower segments and nacelle hub on the float that has been placed on the seabed using a crane mounted on a medium-sized self-elevating barge with a maximum lifting load of, for example, between 600 t and 1,300 t.

[0004] However, when constructing a large floating offshore wind farm where the height from the bottom of the float to the nacelle hub (the nacelle rotation axis) is, for example, 130 m or more, the weight of the nacelle hub becomes very large, and the height at which the nacelle hub is installed becomes very high. As a result, the height may exceed the allowable height at which a crane mounted on a medium-sized self-elevating barge can safely support the load of the nacelle hub and perform lifting operations. Therefore, it may be difficult to safely and stably construct a large floating offshore wind farm using only a crane mounted on a medium-sized self-elevating barge. One possible method for constructing a large floating offshore wind farm is to use a large self-elevating barge with a crane that can lift a maximum load of, for example, 1,500 tons or more. However, such large self-elevating barges are rare in Japan, making their use difficult. Therefore, a new construction method that can safely construct large floating offshore wind farms without using a large self-elevating barge was needed. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2012-202250 Summary of the Invention [Problem to be solved by the invention]

[0006] An object of the present invention is to provide a construction method for a floating offshore wind power generation facility that can safely construct a large floating offshore wind power generation facility with a floater draft of 20 m or less when moored in the target sea area without using an appropriately large self-elevating barge. [Means for solving the problem]

[0007] In order to achieve the above object, the present invention provides a construction method for a floating offshore wind power generation facility, which includes a float moored in a target sea area for installation and a wind power generation device erected on the float, and in a state where the float is moored in the target sea area for installation and the draft from the water surface to the bottom of the float is 20m or less, the method comprising: a state where the float is anchored on the seabed of a sea area with a water depth of 8m to 20m, and a lifting leg; a barge body that can be raised and lowered relative to the lifting leg; and a wind power generation device mounted on the barge body. A self-elevating barge having a crane and a lifting leg is placed on the seabed in a jacked-up state and parked near the float, and a tower support device is mounted on the barge body, the tower support device having a support part capable of holding a tower segment that constitutes the wind power generation device and a movement mechanism that moves the support part relative to the barge body, and the barge body is fixed at a predetermined initial process working height relative to the lifting leg, and the crane is used to lift the lower segment that constitutes the lower part of the tower onto the float. a nacelle hub constituting the wind power generation system is installed on the floating body by the crane; the floating body is then raised relative to the lifting legs to a next-step working height that is higher than the initial-step working height, thereby fixing the floating body to the lifting legs; the holding part is moved by the moving mechanism to move the integrated upper section and nacelle hub onto the lower section that is installed relative to the column, thereby connecting the lower section to the upper section of the lower section; and the crane is then used to install a plurality of blades that constitute the wind power generation system on the nacelle hub, thereby manufacturing an assembly in which the wind power generation system is constructed on the floating body; and the assembly is then raised from the seabed and transported by sea to the target sea area for installation, and moored in the target sea area. [Effects of the Invention]

[0008] The present invention is a construction method for floating offshore wind power generation facilities with a floater draft of 20 meters or less while moored in the target sea area. It can be used for construction of floating offshore wind power generation facilities of other types (semisubmersible, TLP, and barge types) except for spar types. In relatively shallow waters with a water depth of 8 meters to 20 meters, the floater can be stably settled on the seabed, and a self-elevating barge can be stably moored in a jacked-up state near the floater. The work of erecting the lower section members that constitute the lower part of the tower on the column of the floater is performed at a relatively low position and with the component weight within the allowable load. Therefore, even when a medium-sized self-elevating barge is used to construct a large floating offshore wind power generation facility, the barge body can be fixed to the lifting legs of the self-elevating barge at the specified initial process working height, and the lifting work can be safely performed using the crane installed on the self-elevating barge. Next, the upper section of the tower is held in an upright position by the holding portion of the tower support device mounted on the barge body, and the nacelle hub is installed on top of the upper section using a crane, allowing for safe assembly of the integrated unit with the nacelle hub installed on the upper section. Next, the barge body is raised using the lifting legs of the self-elevating barge to a next-step working height, which is higher than the initial working height, and the integrated unit of the upper section and nacelle hub, held by the holding portion, is moved by the moving mechanism of the tower support device onto the lower section installed on the column of the float. This allows for safe and stable installation of the upper section of the tower and the nacelle hub, even when a medium-sized self-elevating barge is used to construct a large floating offshore wind power generation facility. Then, a crane mounted on the self-elevating barge is used to install multiple blades on the nacelle hub, allowing for the production of an assembly with a wind power generation system built on a float. After the assembly is manufactured, it is raised from the seabed and transported by sea to the target installation area, where construction of the floating offshore wind turbine is completed simply by mooring the assembly. Therefore, with this invention, it is possible to safely construct a large floating offshore wind turbine whose float draft is 20 m or less when moored in the target installation area without using a correspondingly large self-elevating barge. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is an explanatory diagram showing a schematic front view of a semi-submersible floating offshore wind power generation facility constructed in accordance with the present invention. [Figure 2] This is an explanatory diagram showing a schematic plan view of a pier constructed as a temporary floating structure in the sea area, and multiple wind power generation device assembly parts temporarily placed on the floating structure using a transport ship. [Figure 3] 3 is an explanatory diagram showing a schematic side view of the floating structure of FIG. 2. FIG. [Figure 4] FIG. 3 is an explanatory diagram showing a schematic plan view of the sea area in which the floating structure of FIG. 2 is constructed. [Figure 5] This is an explanatory diagram showing a schematic plan view of the state in which the self-elevating barge has been moored near the floating structure from the state shown in Figure 2, and the tower segments and nacelle hub, which are assembly parts of the wind power generation device that were temporarily placed on the floating structure, have been transferred to the self-elevating barge. [Figure 6] 6 is an explanatory diagram illustrating the state of FIG. 5 as viewed from the side. FIG. [Figure 7] This is an explanatory diagram showing a schematic plan view of the state in which the transport ship is moved from the state shown in Figure 5 to a position away from the floating structure, and the lower dividing member that constitutes the lower part of the tower is erected using a crane mounted on a self-lifting barge on the floating column placed in the first work area set up in the sea area adjacent to the floating structure. [Figure 8] 8 is an explanatory diagram illustrating the state of FIG. 7 in cross section. FIG. [Figure 9] This is an explanatory diagram that shows a schematic plan view of the state in which, from the state shown in Figures 7 and 8, the upper divided member that constitutes the upper part of the tower is held on the barge body by the holding part of the tower holding device mounted on the self-elevating barge, and the nacelle hub is installed on the upper divided member using a crane mounted on the self-elevating barge. [Figure 10] 10 is an explanatory diagram illustrating the state of FIG. 9 in cross section. FIG. [Figure 11]This is an explanatory diagram illustrating, in a plan view, the state in which the barge body is raised to the next process working height using the lifting legs of the self-lifting barge from the state in Figures 9 and 10, and then the upper divided member and nacelle hub integrated unit is installed on the lower divided member erected on the float located in the first working area using the tower support device and crane mounted on the self-lifting barge. [Figure 12] 12 is an explanatory diagram illustrating the state of FIG. 11 as seen from the side. FIG. [Figure 13] 10 is an explanatory diagram showing an enlarged plan view of the state in which the upper divided member of the tower is held on the barge body by the holding portion of the tower holding device. FIG. [Figure 14] 14 is an explanatory diagram illustrating the state of FIG. 13 as viewed from the side. FIG. [Figure 15] 15 is an explanatory diagram showing an enlarged side view of the state in which the tower segment members held by the holding parts have been moved outboard by the movement mechanism of the tower holding device from the state shown in FIGS. 13 and 14. FIG. [Figure 16] 16 is an explanatory diagram illustrating the state of FIG. 15 in a plan view. FIG. [Figure 17] FIG. 13 is an explanatory diagram showing a schematic plan view of the state in which blades are attached to a nacelle hub installed on a floating body placed in the first working area from the state shown in FIGS. 11 and 12, and the assembly is completed in the first working area. [Figure 18] This is an explanatory diagram showing a schematic plan view of the state in which the self-elevating barge has been moored near the floating structure from the state shown in Figure 17, and the tower segments and nacelle hub, which are assembly parts of the wind power generation device that were temporarily placed on the floating structure, have been transferred to the self-elevating barge. [Figure 19] 19 is an explanatory diagram showing a schematic plan view of the state in which the assembly has been completed in the second work area from the state in FIG. 18. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, a method for constructing a floating offshore wind power generation facility will be described based on the embodiment shown in the drawings.

[0011] As illustrated in FIG. 1 , a floating offshore wind power facility 1 includes a float 2 moored in the target sea area for installation and a wind turbine 3 erected on the float 2. In the target sea area for installation, the float 2 is moored to the seabed SB using mooring lines 8, anchors 9, or the like. This construction method for the floating offshore wind power facility 1 is a method for constructing a floating offshore wind power facility 1 with a draft DF from the water surface to the bottom of the float 2 of 20 m or less while the float 2 is moored in the target sea area for installation. In other words, this construction method can be adopted for constructing floating offshore wind power facilities 1 of other types (semi-submersible, TLP, barge) except for the spar type. This construction method is particularly suitable for constructing semi-submersible floating offshore wind power facilities 1. In the following description, the combined body of the float 2 and the wind power generation device 3 before mooring in the target sea area for installation will be referred to as assembly 7, and the assembly 7 in the moored state in the target sea area for installation will be referred to as floating offshore wind power generation facility 1.

[0012] This embodiment illustrates the construction of a semi-submersible floating offshore wind power generation facility 1. As illustrated in Fig. 1, a semi-submersible floater 2 is submerged in the sea to a predetermined draft DF and moored in a semi-submerged state. The wind turbine 3 has a nacelle hub 5 (a nacelle and hub integrated unit) installed on top of a tower 4 that extends vertically, and multiple blades 6 arranged radially on the nacelle hub 5. Electrical equipment such as a generator, brake equipment, and gearbox are built into the nacelle hub 5, and a power cable connected to the generator is arranged inside the tower 4.

[0013] This embodiment illustrates a wind turbine generator 3 having three blades 6 and a tower 4 composed of four segments 4a to 4d. The number of blades 6 provided in the wind turbine generator 3, the structure of the blades 6, and the number of segments (4a to 4d) constituting the tower 4 are not limited to this embodiment. For example, the blades 6 may be structured by connecting multiple members, or the tower 4 may be composed of two, three, five or more segments. In this embodiment, an engagement portion 4e that protrudes outward from the outer peripheral surface of the second-highest segment 4b constituting the tower 4 is provided at the bottom. The reason for providing the engagement portion 4e on the segment 4b will be explained later.

[0014] This construction method is particularly suitable for constructing a large floating offshore wind power facility 1 in which the height from the bottom of the floating body 2 to the nacelle hub 5 (rotational axis of the nacelle) is, for example, 130 m or more. The longitudinal length (height) of the tower 4 constituting the large floating offshore wind power facility 1 is approximately 80 m to 150 m, and the width (thickness) of the tower 4 is approximately 5 m to 15 m. The weight of the tower 4 is approximately 1,000 t to 2,000 t. The longitudinal length (height) of each of the segment members 4 a to 4 d is approximately 25 m to 50 m, and the weight of each of the segment members 4 a to 4 d is approximately 200 t to 700 t. The height of the nacelle hub 5 is approximately 8 m to 15 m, the longitudinal length is approximately 15 m to 25 m, and the width is approximately 7 m to 15 m. The weight of the nacelle hub 5 is approximately 600 t to 1,200 t. The length of one blade 6 in the longitudinal direction is about 80 m to 150 m, and the weight of one blade 6 is about 50 t to 100 t.

[0015] The semi-submersible float 2 has multiple pillar-shaped columns 2a extending in the vertical direction and connectors 2b (so-called footing members) that connect the columns 2a to each other. In this embodiment, the connectors 2b have a structure including a cross-shaped connector in a plan view and polygonal support sections in a plan view that are provided at each of the four ends of the connector. A column 2a is erected on each of the four support sections. The lower end of a tower 4 is fixed to one of the columns 2a that constitutes the semi-submersible float 2, so that the wind turbine generator 3 is erected on one column 2a. The upper end of the column 2a and the lower end of the tower 4 (divided member 4d) are joined by, for example, bolting or welding.

[0016] The float 2 is configured to be able to store (fill) ballast water inside, and the draft (DF) and attitude of the float 2 can be adjusted by adjusting the amount of stored ballast water. The semi-submersible float 2 has a length and width of approximately 60 m to 100 m in plan view, and the height of the column 2a of the semi-submersible float 2 is approximately 15 m to 50 m. Note that the structure of the float 2, specifically, in the case of a semi-submersible float 2, the shape and structure of the column 2a, the shape and structure of the connecting body 2b, the number and arrangement of the columns 2a erected on the connecting body 2b, and the position of the column 2a on which the wind turbine generator 3 is erected, are not limited to the configuration of this embodiment, and floats 2 with various other configurations can also be used. For example, when constructing a TLP-type floating offshore wind power generation facility 1, a known TLP-type float 2 is used, and when constructing a barge-type floating offshore wind power generation facility 1, a known barge-type float 2 is used.

[0017] The procedure for this construction method is explained below.

[0018] As illustrated in FIGS. 2 and 3 , in this construction method, assembly work for the assembly 7 is performed in an ocean area with a water depth DW (depth from the sea surface position WL to the seabed SB) of 8 m to 20 m. In this embodiment, a temporary floating structure 10 is constructed in an ocean area with a water depth DW of 8 m to 20 m to temporarily store assembly components for the wind turbine generator 3 (separate members 4a to 4d of the tower 4, the nacelle hub 5, and the blades 6), and assembly work for the assembly 7 is performed near the floating structure 10. In this embodiment, a pier is constructed in an ocean area as the temporary floating structure 10, but a floating structure, for example, can also be constructed in an ocean area as the temporary floating structure 10. In this construction method, for example, if there is an already-developed base port (quay) facing an ocean area with a water depth DW of 8 m to 20 m, the assembly components for the wind turbine generator 3 can be temporarily stored at the base port without constructing the temporary floating structure 10.

[0019] In this embodiment, an example of an offshore structure 10 having a rectangular shape in a plan view is shown. The offshore structure 10 is large enough to temporarily store the divided members 4a to 4d of the tower 4, the nacelle hub 5, and the blades 6, which are the assembly parts that make up the wind turbine generator 3, and is constructed to withstand the weight of the assembly parts that are temporarily stored. The offshore structure 10 is constructed in the sea area by a known method.

[0020] As shown in Fig. 2, in this construction method, work areas A (A1, A2) where assembly work of the assembly body 7 and subsequent additional work are performed are provided in a sea area adjacent to a temporary storage location (floating structure 10 or base port) where assembly parts of the wind turbine generator 3 are temporarily stored. In this embodiment, two work areas A1, A2 are provided in the sea area adjacent to the floating structure 10, and the floating structure 10 is configured to be able to temporarily store two sets of assembly parts of the wind turbine generator 3. The number of work areas A to be provided in the sea area adjacent to the temporary storage location where assembly parts of the wind turbine generator 3 are temporarily stored can be determined appropriately depending on the number of floating offshore wind power generation facilities 1 to be constructed; for example, a configuration in which one work area A is provided, or a configuration in which three or more work areas A are provided, can also be used. It is preferable that the temporary storage location for the assembly parts of the wind power generation device 3 be configured so that multiple sets of assembly parts of the wind power generation device 3 can be temporarily stored, but it can also be configured so that only one set of assembly parts of the wind power generation device 3 can be temporarily stored at a time.

[0021] The longitudinal length of the floating structure 10 in plan view is, for example, 100 m to 500 m, and the width is, for example, 50 m to 200 m. The area of ​​the floating structure 10 is, for example, 5,000 m. 2 More than 100,000m 2 As shown in FIG. 3, the height h from the sea surface WL to the top surface of the floating structure 10 may be set to, for example, 2 m or more and 7 m or less. The load capacity of the floating structure 10 may be set to, for example, 1 t / m 2 More than 30t / m 2 The load capacity is set as follows. The entire area of ​​the floating structure 10 may be set to the same load capacity, but different load capacities can also be set for the area where the assembly parts of the wind turbine generator 3 are placed and the area where they are not placed. Also, different load capacities can be set for each temporary placement area for each assembly part of the wind turbine generator 3. Specifically, in the floating structure 10, the load capacity of the area where the nacelle hub 5 is placed is, for example, 5 t / m 2 More than 30t / m 2 Hereinafter, the load capacity of the area where the divided members 4a to 4d of the tower 4 are placed is, for example, 5 t / m 2 More than 30t / m 2 Hereinafter, the load capacity of the area where the blade 6 is placed is, for example, 2 t / m 2More than 15t / m 2 It is recommended to set it as follows.

[0022] As shown in Fig. 3, when a pier is constructed as an above-water structure 10, the pier is constructed using, for example, a plurality of support piles 11 driven into the seabed SB, a plurality of girders 12 spanning between the support piles 11, a plurality of deck materials 13 forming the top plate of the upper part of the pier, and a plurality of braces 14 reinforcing the connections between the support piles 11. For example, H-shaped steel or steel pipe piles are used for the support piles 11. For example, H-shaped steel or other steel is used for the girders 12 and the braces 14. For example, a covering plate or the like is used for the deck material 13.

[0023] The shape and structure of the floating structure 10 are not limited to the configuration exemplified in this embodiment, as long as it can be constructed in an ocean area with a water depth DW of 8 m or more and 20 m or less and is configured to allow temporary placement of assembly components for the wind turbine generator 3. For example, the floating structure 10 can also be constructed in other planar shapes, such as an L-shape or a cross-shape when viewed from above.

[0024] As illustrated in FIG. 2, in this embodiment, a first work area A1 is provided on one longitudinal side of the floating structure 10, and a second work area A2 is provided on the other longitudinal side of the floating structure 10. The size of each work area A is large enough to accommodate the placement of a floating body 2. In FIG. 2, the imaginary outer frame of each work area A is indicated by a dashed line. The work area A is preferably provided adjacent to the floating structure 10, but can also be provided at a distance from the floating structure 10. Preferably, a buoy or the like is provided in the sea area to visualize the extent of each work area A. Note that it is sufficient for the workers and managers involved in the construction to be aware of the extent and boundaries of each work area A, and it is not necessary to visualize the extent of each work area A in the sea area.

[0025] As illustrated in FIG. 4, the offshore structure 10 is preferably constructed in a calm sea area where the impact of waves is minimal. Preferably, the offshore structure 10 is constructed in a sea area behind a breakwater 70 installed in a bay or the like. The "sea area behind the breakwater 70" here refers to a sea area where the impact of waves is reduced by the breakwater 70. By utilizing idle waters other than the shipping route and avoiding anchorages as much as possible, port activities using existing quays are not affected and coexistence with previous users is possible. Alternatively, the offshore structure 10 may be constructed in the target sea area where the floating offshore wind power generation facility 1 will be installed, or in a sea area close to a quay 80 where assembly components for the wind turbine 3 will be loaded onto a carrier ship. In this embodiment, the offshore structure 10 is constructed in a sea area away from the quay 80. However, for example, the offshore structure 10 could also be constructed adjacent to the quay 80, so that it is continuous with the quay 80.

[0026] When constructing the floating structure 10 in an area of ​​the sea away from a quay 80, as in this embodiment, the floating structure 10 is designed to allow a carrier ship 60 that transports assembly parts for the wind turbine generator 3 to dock. As equipment used to moor the carrier ship 60 to the floating structure 10, temporary mooring equipment and temporary protection equipment should be provided near the floating structure 10. Note that the mooring equipment and protection equipment are omitted from the drawings.

[0027] When constructing a floating structure in the sea area as the floating structure 10, mooring equipment that serves as the base of the floating structure is installed in the sea area using piles or the like. After that, a float (barge) that forms the upper part of the floating structure is fixed to the mooring equipment that is fixed to the seabed SB, thereby constructing the floating structure as the floating structure 10. Note that the method for constructing the floating structure 10 in the sea area is not particularly limited, and it may be constructed using any known method.

[0028] In the case where the assembly parts of the wind turbine generator 3 are temporarily stored at a prepared base port (quay 80) without constructing a temporary offshore structure 10, a work area A is provided in the sea area adjacent to the base port where the assembly work of the assembly 7 and subsequent additional work will be carried out. The base port can be prepared by carrying out ground improvement work to improve the bearing capacity of the quay 80. The load-bearing capacity of the base port should be set to satisfy the same conditions as when constructing the above-mentioned offshore structure 10.

[0029] As illustrated in FIG. 2 , after a temporary storage location (floor structure 10) for the assembly parts of the wind turbine generator 3 is constructed, the assembly parts (segment members 4a to 4d of the tower 4, the nacelle hub 5, and the blades 6) that make up the wind turbine generator 3 are temporarily placed on the temporary storage location (floor structure 10). In this embodiment, two sets of assembly parts of the wind turbine generator 3 are temporarily placed on thefloor structure 10. When thefloor structure 10 is constructed in an ocean area away from a quay 80, the assembly parts of the wind turbine generator 3 are transported over the sea by a carrier 60 (specifically, for example, a LOLO vessel) equipped with a crane, and when the carrier 60 is docked at the floating structure 10, the assembly parts loaded on the carrier 60 are unloaded onto the floating structure 10 using the crane mounted on the carrier 60. It is preferable to transport the assembly parts of the wind turbine generator 3 by sea to the floating structure 10, but if the floating structure 10 is constructed in an ocean area close to or adjacent to the quay 80, it is also possible to transport the assembly parts of the wind turbine generator 3 by land to the quay 80, and then use a crane or the like installed on the quay 80 to move the assembly parts from the quay 80 onto the floating structure 10 and store them temporarily. When the assembly parts of the wind turbine generator 3 are to be temporarily stored at the base port (quay 80), the assembly parts of the wind turbine generator 3 may be transported by land to the base port, or the assembly parts of the wind turbine generator 3 may be transported by sea to the base port.

[0030] In this embodiment, with a carrier ship 60 docked in the sea area on one side of the underwater structure 10 in the width direction, the divided members 4a to 4d of the tower 4 and the nacelle hub 5 are loaded and unloaded in an area on one side of the underwater structure 10 in the width direction, and with the carrier ship 60 docked in the sea area on the other side of the underwater structure 10 in the width direction, the blades 6 are unloaded in an area on the other side of the underwater structure 10 in the width direction. The position and direction in which the carrier ship 60 is docked relative to the underwater structure 10, and the number of carrier ships 60 that are docked relative to the underwater structure 10 are not particularly limited. For example, multiple carrier ships 60 can be docked relative to the underwater structure 10 to load and unload assembly parts.

[0031] In this embodiment, the assembly parts of the wind turbine generator 3 are temporarily stored together by type, but the arrangement of each assembly part temporarily stored on the floating structure 10 is not particularly limited. In this embodiment, a horizontal placement frame supporting the segments 4a to 4d of the tower 4 is placed on the floating structure 10, and the segments 4a to 4d are placed sideways on the horizontal placement frame. In addition, a frame supporting the blades 6 is provided on the floating structure 10, and the blades 6 are placed sideways on the frame. In this embodiment, the blades 6 temporarily stored on the floating structure 10 do not protrude from the floating structure 10, but it is also possible for some of the temporarily stored blades 6 to protrude from the floating structure 10, for example. In other words, the floating structure 10 may be large enough that some of the blades 6 protrude. In this embodiment, in addition to the assembly parts of the wind turbine generator 3, a mobile crane 50 and a work platform 52 (SPMT: multi-axle platform) equipped with an erection device 51 are placed on the floating structure 10.

[0032] After the assembly parts for the wind turbine generator 3 have been temporarily placed on the floating structure 10, the carrier ship 60 is moved away from the floating structure 10. Then, as illustrated in Figures 5 and 6, a self-elevating barge 20 (hereinafter referred to as the SEP vessel 20) is parked near the floating structure 10 in a jacked-up state (hereinafter referred to as the jacked-up state) with its lifting legs 22 seated on the seabed. In this construction method, a medium-sized SEP vessel 20 with a maximum lifting load of its onboard crane 23 of, for example, 600 tons or more and 1,300 tons or less is used. The SEP vessel 20 is preferably parked in a jacked-up state so that the side on which the crane 23 is mounted is aligned with the side of the floating structure 10.

[0033] The SEP vessel 20 comprises a barge body (platform) 21 that can move on the water, a plurality of lifting legs 22 that can move up and down relative to the barge body 21, and a crane 23 mounted on the barge body 21. It is preferable to use a self-propelled SEP vessel 20 in which the barge body 21 is equipped with a propulsion device, but it is also possible to use a non-self-propelled SEP vessel 20 that does not have a propulsion device and is moved by towing.

[0034] As shown in Figure 6, when the SEP vessel 20 is stopped in a jacked-up state, the lifting legs 22 are moved downward relative to the barge main body 21 floating in the sea area, so that the lower ends of the lifting legs 22 are placed on the seabed SB. From this state, the barge main body 21 is moved upward relative to the lifting legs 22, so that the barge main body 21 is moved to a position higher than the sea surface level WL, and the barge main body 21 is supported in midair by the lifting legs 22. By raising the barge main body 21 to a height out of the reach of waves, the barge main body 21 is no longer affected by waves.

[0035] The water depth at which the SEP vessel 20 can be moored in a jacked-up state is generally 40 m or less. With this construction method, the offshore structure 10 is constructed in an ocean area with a water depth DW of 8 m or more and 20 m or less, so the SEP vessel 20 can be moored in a stable state near the offshore structure 10. If the ground of the seabed SB does not have sufficient strength to stably moor the SEP vessel 20 in a jacked-up state, it is advisable to carry out simple ground improvement work in advance to increase the strength of the seabed SB.

[0036] As shown in FIG. 5, the barge main body 21 of the SEP vessel 20 is loaded with tower lift hoists 24 used for loading and unloading the divided members 4a to 4d. Two or more vertical mounting platforms 25 for supporting the divided members 4a to 4d of the tower 4 in an upright position are mounted on the barge main body 21. In this embodiment, two vertical mounting platforms 25 are mounted on the barge main body 21. Furthermore, in this construction method, a tower support device 30 is mounted on the barge main body 21. In this embodiment, the tower support device 30 and the crane 23 are arranged side by side in the longitudinal direction of the ship, but the arrangement of the tower support device 30 and the crane 23 on the barge main body 21 is not particularly limited. For example, the tower support device 30 and the crane 23 may also be arranged side by side in the width direction of the ship. Details of the tower support device 30 will be described later.

[0037] After the SEP vessel 20 is stopped in a jacked-up state near the floating structure 10, the crane 23 of the SEP vessel 20 is used to transfer a set of segment members 4a to 4d and the nacelle hub 5 that constitute the tower 4, which have been temporarily placed on the floating structure 10, onto the barge main body 21. Specifically, since the segment member 4d is temporarily placed on the floating structure 10 in a laid-on-its-side position, when transferring the segment member 4d temporarily placed on the floating structure 10 to the SEP vessel 20, a tower lift hoisting device 24 is used as a hoisting device for the crane 23 mounted on the SEP vessel 20, and the tower lift hoisting device 24 is connected to the upper end of the segment member 4d. Then, a work platform 52 equipped with an erection device 51 that is placed on the floating structure 10 is moved to the vicinity of the lower end of the segment member 4d that has been laid-on its side, and the lower part of the segment member 4d is held by the holding portion of the erection device 51. The work platform 52 may be operated by a human operator on board, or may be remotely controlled by a remote controller.

[0038] Next, the crane 23 lifts the upper end of the divided member 4d above the erection device 51 via the tower lift hoist 24, and rotates the lower end of the divided member 4d using the erection device 51 as a guide, thereby erecting the divided member 4d. After the erection device 51 and the lower end of the divided member 4d are released from connection, the crane 23 moves the erected divided member 4d above the vertical installation stand 25 provided on the barge main body 21. The divided member 4d is then inserted in an erect state into an insertion hole provided in the vertical installation stand 25.

[0039] Next, using a similar method, the third separate member 4c from the top of the tower 4 is erected on the floating structure 10, and the crane 23 is used to move the separate member 4c onto separate member 4d that is standing on the vertical installation stand 25 on the barge main body 21. Then, the upper end of the fourth separate member 4d from the top of the tower 4 is connected to the lower end of the third separate member 4c from the top, thereby assembling the lower separate members 4c, 4d that form the lower part of the tower 4. The lower separate members 4c, 4d are left standing on the vertical installation stand 25.

[0040] Using a similar method, the second divided member 4b from the top of the tower 4 is erected on the floating structure 10, and the crane 23 is used to insert the divided member 4b in an upright state into the insertion hole provided in the vertical installation frame 25. Thereafter, using a similar method, the first divided member 4a from the top of the tower 4 is erected on the floating structure 10, and the crane 23 is used to move the divided member 4a onto the divided member 4b that is erected on the vertical installation frame 25 on the barge main body 21. Then, the upper end of the second divided member 4b from the top of the tower 4 is connected to the lower end of the first divided member 4a from the top, thereby assembling the upper divided members 4a and 4b that form the upper part of the tower 4. The upper divided members 4a and 4b are left in an upright state on the vertical installation frame 25. The nacelle hub 5, which was temporarily placed on the floating structure 10, is also transferred onto the barge main body 21 using the crane 23.

[0041] In this embodiment, when the divided parts 4a to 4d of the tower 4 that have been temporarily placed on the floating structure 10 are transferred to the barge main body 21, the lower divided parts 4c and 4d that constitute the lower part of the tower 4 and the upper divided parts 4a and 4b that constitute the upper part of the tower 4 are respectively assembled. However, for example, the divided parts 4a to 4d of the tower 4 can also be transferred to the barge main body 21 in their respective separated states.

[0042] As illustrated in FIG. 5 , the floating body 2 is transported by sea and set ashore on the seabed SB of each work area A (A1, A2) established in the sea area adjacent to the temporary storage location (floating structure 10). During sea transportation, the floating body 2 is set afloat on the sea with a relatively small amount of ballast water stored therein, and is towed to the work area A using a tugboat or the like. Ballast water is then poured into the floating body 2, gradually sinking it until its bottom is set ashore on the seabed SB. If the ground of the seabed SB where the floating body 2 is to be set ashore is not flat, it is advisable to level or cure the ground of the seabed SB before placing the floating body 2 in the work area A. Preferably, sandbags, filter units, or the like are placed on the seabed SB where the floating body 2 is to be set ashore to form a flat mound on which the floating body 2 is to be set ashore, and the floating body 2 is set ashore on the mound.

[0043] For example, when the carrier ship 60 or the SEP ship 20 is to be docked at a position that does not interfere with the work area A, the work of transporting the float 2 by sea to the work area A and settling it on the seabed SB can be carried out in parallel with the work of using the carrier ship 60 to temporarily place the assembly parts of the wind power generation device 3 on the floating structure 10, and the work of using the crane 23 of the SEP ship 20 to transfer the assembly parts of the wind power generation device 3 from the floating structure 10 onto the barge main body 21.

[0044] In this construction method, the temporary storage location (floating structure 10) is constructed in a sea area with a water depth DW of 8 m or more and 20 m or less, allowing the semi-submersible floater 2, TLP floater 2, and barge floater 2 to be towed to a work area A near the temporary storage location. Furthermore, because the water depth DW is 8 m or more and 20 m or less, each type of floater 2 can be easily anchored to the seabed SB, allowing assembly components for the wind turbine generator 3 to be installed on the floater 2 once it has anchored to the seabed SB. In other words, in sea areas with a water depth DW of less than 8 m, the water depth DW is too shallow, making it difficult to tow the floater 2 to the vicinity of the temporary storage location. In sea areas with a water depth DW of more than 20 m, the water depth DW is too deep, making it difficult to install assembly components for the wind turbine generator 3 on the floater 2 once it has anchored to the seabed SB. Furthermore, in waters where the water depth DW exceeds 20 m, it is difficult to construct and position the floating structure 10.

[0045] After the floater 2 has been landed on the seabed SB in the work area A, the SEP vessel 20 is moved to the vicinity of the floater 2 placed in the first work area A1 and is stopped in a jacked-up state, as shown in Figures 7 and 8. The SEP vessel 20 is stopped with the side of the vessel carrying the tower support device 30 and crane 23 close to the column 2a of the floater 2 on which the wind turbine generator 3 will be erected.

[0046] 8, with the barge body 21 fixed to the lifting legs 22 at a predetermined initial process working height L1, the crane 23 of the SEP vessel 20 is used to erect the lower separate members 4c and 4d that form the lower part of the tower 4 on the column 2a of the floating body 2. The initial process working height L1 relative to the seabed SB (height H1 from the seabed SB to the top (upper deck) of the barge body 21) is set to, for example, 20 m or more and 70 m or less.

[0047] Specifically, the lower sections 4c and 4d are mounted in an upright position on a vertical installation platform 25 arranged on the barge main body 21. Tower lift hoists 24 are connected to the upper ends of the upright lower sections 4c and 4d as hoists for the crane 23, and the lower sections 4c and 4d are lifted above the vertical installation platform 25. The crane 23 then moves the upright lower sections 4c and 4d above one of the columns 2a of the floating body 2, placing their lower ends on the column 2a. The lower ends of the lower sections 4c and 4d are then fixed to the upper end of the column 2a of the floating body 2 by bolting, welding, or the like. The tower lift hoists 24 are then released from their connection to the upper ends of the lower sections 4c and 4d.

[0048] The allowable height (allowable height from the seabed SB to the lifting position of the crane 23) at which the crane 23 mounted on the medium-sized SEP vessel 20 can support the load of the lower separate members 4c, 4d and safely perform the lifting operation is, for example, approximately 130 m or less, but the height from the seabed SB to the upper ends of the lower separate members 4c, 4d (height of the lifting position) when the lower separate members 4c, 4d are installed on the column 2a of the floater 2 is, for example, approximately 60 m to 120 m from the seabed SB. Therefore, the work of installing the lower separate members 4c, 4d on the column 2a using the crane 23 of the SEP vessel 20 can be safely performed without exceeding the allowable height at which the crane 23 can support the load of the lower separate members 4c, 4d and safely perform the lifting operation, with the barge main body 21 fixed to the lifting legs 22 at the relatively low initial process working height L1.

[0049] Similarly, when the separate segments 4c, 4d are mounted on the barge main body 21 in their separate states, the barge main body 21 is fixed to the initial process working height L1 relative to the lifting legs 22, and the crane 23 of the SEP vessel 20 is used to move the upright segment 4d above one of the columns 2a of the float 2 so that the lower end of the segment 4d is placed on the column 2a. The lower end of the segment 4d is then fixed to the upper end of the one of the columns 2a of the float 2 by bolting, welding, or the like. Thereafter, the crane 23 is used to move the upright segment 4c above the segment 4d standing on the column 2a, and the upper end of the segment 4d is connected to the lower end of the segment 4c to assemble the lower segment 4c, 4d.

[0050] Next, the upper sections 4a and 4b and the nacelle hub 5 are installed on top of the lower sections 4c and 4d, which are erected on the column 2a. With the upper sections 4a and 4b and the nacelle hub 5 installed on the lower sections 4c and 4d, the height from the seabed SB to the nacelle hub 5 (the rotation axis of the nacelle) is, for example, approximately 130 to 200 meters. By raising the barge main body 21 relative to the lifting legs 22, it is possible to set the lifting position of the crane 23 of the medium-sized SEP vessel 20 to a height that allows it to reach the installation position of the nacelle hub 5; however, if the barge main body 21 is positioned too high relative to the lifting legs 22, the stability of the lifting operation by the crane 23 will be reduced. Therefore, the allowable height (allowable height from the seabed SB to the lifting position of the crane 23) at which the crane 23 of the medium-sized SEP vessel 20 can safely support the load of the nacelle hub 5 that constitutes the large floating offshore wind power generation facility 1 and perform lifting work is approximately 130 m or less, and it is difficult for the crane 23 of the medium-sized SEP vessel 20 to support the load of the nacelle hub 5 that constitutes the large floating offshore wind power generation facility 1 and perform installation work of the nacelle hub 5.

[0051] 9 to 12, in this construction method, the upper divided members 4a, 4b and the nacelle hub 5 are installed on the lower divided members 4c, 4d that are erected on the column 2a using a tower support device 30. First, the configuration of the tower support device 30 will be described with reference to FIGS. 13 to 16.

[0052] 13 and 14, the tower holding device 30 includes a holding unit 31 capable of holding the divided member 4b of the tower 4, and a moving mechanism 32 that moves the holding unit 31 relative to the barge main body 21. The holding unit 31 in this embodiment includes a holding unit 31a that holds the outer peripheral surface of the divided member 4b, a switching mechanism 31b that switches between a state in which the holding unit 31a holds the divided member 4b and a released state (a state in which the holding unit 31a does not hold the divided member 4b), and a support arm 31c that supports the load of the divided member 4b.

[0053] In this embodiment, the front side of the gripper 31a is configured to be openable and closable by a hinge mechanism that constitutes the switching mechanism 31b. As illustrated in Fig. 13, when the split member 4b is placed inside the gripper 31a and the front side of the gripper 31a is brought into contact with the split member 4b, the outer circumferential surface of the split member 4b is held by the gripper 31a. As illustrated in Fig. 16, when the front side of the gripper 31a is opened by the switching mechanism 31b and moved away from the split member 4b, the split member 4b is released.

[0054] As shown in FIG. 14, the support arm 31c is rotatably connected to the lower part of the gripping part 31a. The support arm 31c is configured to engage with an engaging part 4e that protrudes from the lower part of the outer circumferential surface of the divided member 4b. In this embodiment, a hook-shaped support arm 31c is provided, and by hooking the support arm 31c onto the engaging part 4e, the weight of the divided member 4b is supported by the support arm 31c. When the support arm 31c is rotated relative to the gripping part 31a and the engagement of the support arm 31c with the engaging part 4e is released, the divided member 4b is released. The configuration of the holding part 31 is not limited to that of this embodiment, and various other configurations are possible as long as it is capable of holding the divided member 4b.

[0055] The movement mechanism 32 is configured to be able to move the holding unit 31 from on board the SEP vessel 20 (on the barge main body 21) to outside the vessel (outside the barge main body 21). As illustrated in Figures 13 and 14, the movement mechanism 32 of this embodiment is configured to have a first movement mechanism 33 and a second movement mechanism 39. The first movement mechanism 33 is configured to have a base 34, an arm 35, a first connecting unit 36, an actuator 37, and a second connecting unit 38. The actuator 37 is configured, for example, by a hydraulic cylinder or a pneumatic cylinder in which a rod 37b is extendable and retractable (movable forward and backward) relative to a cylinder 37a.

[0056] A rod-shaped first connecting part 36 extending in the longitudinal direction of the SEP vessel 20 (hereinafter referred to as the longitudinal direction) is joined to the side surface of the holding part 31 (gripping part 31a) in the longitudinal direction, and the tip end of an arm 35 extending in the width direction of the SEP vessel 20 (hereinafter referred to as the width direction) is rotatably connected to the first connecting part 36. The rear end of the arm 35 is rotatably connected to the base 34. The first connecting part 36 and the arm 35 are provided on each side surface of the holding part 31 (gripping part 31a) on both sides in the longitudinal direction.

[0057] Additionally, a rod-shaped second connecting part 38 extending in the longitudinal direction of the ship is joined to the side surface of the holding part 31 (gripping part 31a) in the longitudinal direction of the ship, and the tip end (tip end of rod 37b) of the actuator 37 extending in the width direction of the ship is rotatably connected to the second connecting part 38. The rear end part (rear end part of cylinder 37a) of the actuator 37 is rotatably connected to the base 34. The second connecting part 38 and the actuator 37 are provided on each of the side surfaces on both sides in the longitudinal direction of the holding part 31 (gripping part 31a).

[0058] 13 and 14, when the projection length of the rod 37b relative to the cylinder 37a of the actuator 37 is shortened, the holding unit 31 is positioned near the side of the barge main body 21 above the SEP vessel 20. As shown in FIGS. 15 and 16, when the rod 37b is extended relative to the cylinder 37a of the actuator 37 to lengthen the projection length of the rod 37b relative to the cylinder 37a, the arm 35 and actuator 37 rotate relative to the base 34, and the holding unit 31 moves diagonally downward toward the outside in the beam direction of the barge main body 21. The first moving mechanism 33 moves the holding unit 31 while maintaining its verticality with the divided member 4b upright.

[0059] The second movement mechanism 39 is used to fine-tune the horizontal position of the holding part 31. As illustrated in Figures 15 and 16, the second movement mechanism 39 in this embodiment is composed of a pair of rails 40 for movement in the ship's longitudinal direction. A pair of rails 40 for movement in the ship's longitudinal direction, extending in the ship's longitudinal direction, are laid on the barge main body 21, spaced apart in the ship's breadth direction. The base 34 is configured to be able to move in the ship's longitudinal direction on the rails 40 for movement in the ship's longitudinal direction. The position of the holding part 31 in the ship's longitudinal direction can be adjusted by moving the base 34 in the ship's longitudinal direction relative to the rails 40 for movement in the ship's longitudinal direction.

[0060] The moving mechanism 32 is not limited to the configuration of this embodiment and can have various other configurations as long as it is configured to move the holding unit 31 from on board the SEP vessel 20 to a desired position outside the vessel. For example, the second moving mechanism 39 can be configured to adjust the position of the holding unit 31 in the vessel length direction and the vessel width direction.

[0061] 9 and 10, in the work of installing the upper separate members 4a, 4b and the nacelle hub 5 on the lower separate members 4c, 4d that are erected on the column 2a of the floating body 2, first, the top of the barge main body 21 is fixed to the lifting legs 22 at the initial process working height L1, and the holding part 31 of the tower support device 30 is placed on the barge main body 21. Then, using the crane 23 of the SEP vessel 20, the upper separate members 4a, 4b that are erected on the vertical installation stand 25 are lifted above the vertical installation stand 25.

[0062] Next, the crane 23 is used to move the upright upper sections 4a, 4b above the holding parts 31, so that the lower parts of the upper sections 4a, 4b are held by the holding parts 31. In this embodiment, the support arms 31c of the holding parts 31 are engaged with the engaging parts 4e provided on the lower parts of the upper sections 4a, 4b (sections 4b), so that the weight of the upper sections 4a, 4b is supported by the holding parts 31 (support arms 31c). Next, the crane 23 is used to install the nacelle hub 5, which has been placed on the barge main body 21, above the upper sections 4a, 4b that are held by the holding parts 31.

[0063] Similarly, when the separate segments 4a, 4b are mounted on the barge main body 21, the top of the barge main body 21 is fixed to the lifting legs 22 at the predetermined initial process working height L1. Then, the crane 23 of the SEP vessel 20 is used to move the upright segment 4b above the holder 31, with the lower part of the segment 4b held by the holder 31. Next, the crane 23 is used to move the upright segment 4a above the segment 4b held by the holder 31, and the upper end of the segment 4b is connected to the lower end of the segment 4a to assemble the upper segments 4a, 4b. The nacelle hub 5 is then installed using the crane 23 on top of the upper segments 4a, 4b held by the holder 31.

[0064] The upper segments 4a, 4b are held by the holding portion 31 of the tower support device 30 described above, and the work of assembling the integrated unit with the nacelle hub 5 installed on the upper segments 4a, 4b is carried out with the barge body 21 fixed to the lifting legs 22 at a relatively low initial process working height L1. This means that the crane 23 of the medium-sized SEP vessel 20 can support the load of the upper segments 4a, 4b and the nacelle hub 5 and perform the lifting work safely and stably without exceeding the allowable height.

[0065] After the nacelle hub 5 is installed on the upper divided members 4a, 4b, the lifting device that was connected (slinged) to the nacelle hub 5 is removed from the nacelle hub 5, and the crane 23 is stored in the SEP vessel 20 (the crane 23 is lowered).

[0066] 11 and 12, the barge body 21 is then raised relative to the lifting legs 22 to a next process working height L2 that is higher than the initial process working height L1, and the barge body 21 is fixed relative to the lifting legs 22. The next process working height L2 relative to the seabed SB (height H2 from the seabed SB to the top (upper deck) of the barge body 21) is set to, for example, 50 m or more and 100 m or less.

[0067] Next, the lifting gear of the crane 23 is connected (slinged) to the nacelle hub 5. The load of the integrated upper sections 4a, 4b and nacelle hub 5 is supported by the holding parts 31 (mainly the support arms 31c), and the wire rope of the crane 23 is kept taut, but the crane 23 is placed in a state where the load of the integrated assembly is hardly applied.

[0068] Next, the moving mechanism 32 of the tower support device 30 moves the support unit 31, which holds the integral assembly of the upper segments 4a, 4b and the nacelle hub 5, onto the lower segments 4c, 4d erected on the column 2a of the float 2. In this embodiment, the actuator 37 constituting the first moving mechanism 33 is operated to move the support unit 31 diagonally downward toward the outside of the barge main body 21 in the ship's width direction, thereby adjusting the height of the lower parts of the upper segments 4a, 4b and the upper parts of the lower segments 4c, 4d held by the support unit 31. The second moving mechanism 39 also horizontally aligns the lower parts of the upper segments 4a, 4b and the upper parts of the lower segments 4c, 4d held by the support unit 31. At this time, the hoisting gear of the crane 23 remains connected to the nacelle hub 5, and the wire rope of the crane 23 is kept taut, so that the tip of the boom of the crane 23 follows the movement of the support unit 31. The crane 23 is maintained in a state where the load of the integral upper divided members 4a, 4b and nacelle hub 5 is hardly applied thereto.

[0069] As described above, in this construction method, the load of the integrated unit consisting of the upper sections 4a, 4b and the nacelle hub 5 is not supported by the crane 23. Instead, the load of the integrated unit is supported by the tower support device 30, and the crane 23 is used as an auxiliary device to suppress swaying of the integrated unit when the support part 31 and the integrated unit are moved. Therefore, even when the barge body 21 is fixed to the lifting legs 22 at a relatively high next-process working height L2, the crane 23 does not become unstable, and the integrated unit consisting of the upper sections 4a, 4b and the nacelle hub 5 can be safely and stably moved onto the lower sections 4c, 4d using the tower support device 30. Note that, as described above, using the crane 23 as an auxiliary device is advantageous in suppressing swaying of the integrated unit when the tower support device 30 is used to move the integrated unit consisting of the upper sections 4a, 4b and the nacelle hub 5. However, the work of moving the integrated unit can also be performed using only the tower support device 30 without using the crane 23.

[0070] Next, with the holding unit 31 holding the integral upper divided members 4a, 4b and the nacelle hub 5, the lower parts of the upper divided members 4a, 4b are connected to the upper parts of the lower divided members 4c, 4d. After that, the support arm 31c is rotated relative to the gripping unit 31a of the holding unit 31 to disengage the engagement between the engagement unit 4e provided on the lower part of the upper divided members 4a, 4b (divided member 4b) and the support arm 31c. Then, the switching mechanism 31b opens the front of the gripping unit 31a, releasing the holding (gripping) state of the upper divided members 4a, 4b by the holding unit 31 (gripping unit 31a). Then, the movement mechanism 32 (first movement mechanism 33) moves the holding unit 31 toward the barge main body 21, and the holding unit 31 is placed on the barge main body 21. Through the above operations, the tower 4 and nacelle hub 5 are installed on the column 2a of the floating body 2.

[0071] Next, with the crane 23 stored, the SEP vessel 20 lowers the barge main body 21 relative to the lifting legs 22 to the sea surface position WL, so that the barge main body 21 is floating on the sea surface, and moves the lower ends of the lifting legs 22 above the seabed SB. Then, the SEP vessel 20 moves toward the surface structure 10 and stops the SEP vessel 20 in a jacked-up state near the area where the blades 6 of the surface structure 10 are temporarily stored. Thereafter, the crane 23 of the SEP vessel 20 is used to transfer the blades 6 that were temporarily stored on the surface structure 10 onto the barge main body 21.

[0072] Thereafter, the SEP vessel 20 loaded with the blades 6 is moved to the vicinity of the floating body 2 placed in the first work area A1, and the SEP vessel 20 is stopped in a jacked-up state. Then, as shown in FIG. 17, the barge body 21 is raised to a predetermined height relative to the lifting legs 22, and the barge body 21 is fixed to the lifting legs 22. The crane 23 of the SEP vessel 20 is then used to install (attach) the blades 6 loaded on the barge body 21 to the nacelle hub 5, thereby manufacturing the assembly 7 in which the wind turbine generator 3 is constructed on the floating body 2. By performing the above operations, the assembly work of the assembly 7 is completed in the first work area A1, as shown in FIG. 17.

[0073] Since the weight of the blades 6 is relatively light compared to the nacelle hub 5, even when the barge body 21 is fixed at a relatively high position (for example, at about the next process working height L2) relative to the seabed SB, the work of installing the blades 6 on the nacelle hub 5 can be carried out safely and stably using the crane 23 of the SEP vessel 20.

[0074] 18, additional work, including adjustment work, is performed on the assembly 7 in the first work area A1 where the assembly work has been completed. The SEP vessel 20 is moved from the vicinity of the first work area A1 toward the surface structure 10 and stopped near the surface structure 10 in a jacked-up state. After that, the crane 23 of the SEP vessel 20 is used to transfer the set (four) separate members 4a to 4d and the nacelle hub 5 that constitute the tower 4, which had been temporarily placed on the surface structure 10, onto the barge main body 21. At this time, the lower separate members 4c and 4d, which are formed by connecting the upper end of the fourth separate member 4d from the top of the tower 4 with the lower end of the third separate member 4c from the top, are placed upright on a vertical installation frame 25, and the upper separate members 4a and 4b, which are formed by connecting the upper end of the second separate member 4b from the top of the tower 4 with the lower end of the first separate member 4a from the top, are placed upright on another vertical installation frame 25.

[0075] 19, the SEP vessel 20 is then moved to the vicinity of the floating body 2 placed in the second working area A2, and the SEP vessel 20 is stopped in a jacked-up state. Thereafter, the assembly 7 is fabricated in the second working area A2 for the floating body 2 that has been anchored to the seabed SB in the second working area A2 using a work procedure similar to the assembly work of the assembly 7 described above in the first working area A1. While the SEP vessel 20 is performing assembly work on the floating body 2 in the second working area A2, additional work can be performed on the assembly 7 in the first working area A1, where assembly work has already been completed.

[0076] The additional work is preparatory work performed on the assembly 7 before it is transported to the sea area where it will be installed, and specifically includes pre-commissioning work. Pre-commissioning work involves setting up, testing, adjusting, and the like of the electrical equipment of the assembly 7. In this embodiment, the additional work is performed on the assembly 7 after assembly work has been completed in the first work area A1, where assembly work has already been completed. The additional work on the assembly 7 after assembly work may be performed, for example, by moving the assembly 7 outside work area A and performing it in waters outside work area A.

[0077] After the pre-commissioning work has confirmed that there are no abnormalities in the wind turbine generator 3, the assembly 7 is gradually raised from the seabed SB by reducing the amount of ballast water stored in the floating body 2. Then, while the assembly 7 is floating on the sea, it is transported by sea to the target sea area for installation using a tugboat or the like.

[0078] As shown in Figure 1, the assembly 7 moved to the target sea area for installation is moored to the seabed SB using mooring lines 8, anchors 9, etc. After that, a submarine cable is connected to the wind turbine 3, and a final operational check (so-called final commissioning) of the floating offshore wind power facility 1 is carried out. This completes the construction of the floating offshore wind power facility 1.

[0079] 19, when continuing the assembly work of the assembly 7, the assembly 7 is moved from the first work area A1, and then a new float 2 is placed in the first work area A1. Furthermore, new assembly parts for the wind turbine generator 3 are transported by sea using a carrier 60 or the like, and when the carrier 60 is docked at the floating structure 10, the assembly parts loaded on the carrier 60 are unloaded onto the floating structure 10 using a crane mounted on the carrier 60, and the new assembly parts are temporarily placed on the floating structure 10.

[0080] Thereafter, in the same work procedure, additional work including adjustment work is performed on the assembly 7 in the second work area A2 after the assembly work has been completed, and similar assembly work of the assembly 7 is performed on the floater 2 that has been anchored to the seabed SB in the first work area A1. Then, the assembly 7 that has completed the additional work in the second work area A2 is floated from the seabed SB, transported by sea to the target sea area for installation, and the assembly 7 is moored in the target sea area for installation.

[0081] In this way, by simultaneously carrying out the work of temporarily placing the assembly parts of the wind power generation device 3 on the floating structure 10, the work of assembling the assemblies 7 in each work area A, the addition work, and the work of transporting the assemblies 7 after the addition work has been completed by sea to the sea area where they will be installed and mooring them, multiple floating offshore wind power generation facilities 1 can be constructed in parallel.

[0082] After the use of the offshore structure 10 as a manufacturing base has ended, the offshore structure 10 may be removed from the sea area, or the offshore structure 10 may be left in the sea area as a base for performing maintenance on the floating offshore wind power facility 1 (assembly 7). When the offshore structure 10 is left as a base for performing maintenance, the assembly 7 to be maintained is transported to the offshore structure 10 and the assembly 7 is landed on the seabed SB in the work area A. Then, maintenance of the assembly 7 is performed using the crane 23 of the SEP vessel 20 or the crane 50 arranged on the offshore structure 10.

[0083] When removing the offshore structure 10 from the sea area, the pier that constitutes the offshore structure 10 is dismantled and removed. After that, the holes in the seabed SB where the support piles 11 that constituted the pier were inserted are backfilled, and the state of the seabed SB is restored to the state it was in before the construction of the offshore structure 10. In this way, the offshore structure 10 that can be installed and removed in a temporary form can be moved to a different location and reinstalled and removed many times in a relatively short period of time.

[0084] As described above, this construction method can be used to construct floating offshore wind power facilities 1 of other types (semi-submersible, TLP, barge) excluding spar types, where the draft DF of the float 2 when moored in the target sea area is 20 m or less. This construction method is performed in relatively shallow sea areas with a water depth DW of 8 m or more and 20 m or less, so the float 2 can be stably settled on the seabed SB, and the SEP vessel 20 can be stably moored in a jacked-up state near the float 2. The work of erecting the lower segment members 4c, 4d that make up the lower part of the tower 4 on the column 2a of the float 2 is done at a relatively low position and with the weight of the members being the allowable load. Therefore, even when a medium-sized SEP vessel 20 is used to construct a large floating offshore wind power generation facility 1, the lifting work can be carried out safely using the crane 23 mounted on the SEP vessel 20, with the barge main body 21 fixed to the lifting legs 22 of the SEP vessel 20 at a relatively low, predetermined initial process working height L1.

[0085] In the construction of a large-scale floating offshore wind power facility 1, the subsequent work of installing the upper separate members 4a, 4b and the nacelle hub 5 on top of the lower separate members 4c, 4d is performed at a relatively high position, and because the nacelle hub 5 is heavy, it has conventionally been thought that the height exceeds the allowable height at which the nacelle hub 5 can be safely lifted by a crane 23 mounted on a medium-sized SEP vessel 20, making it difficult to safely construct a large-scale floating offshore wind power facility 1 on a medium-sized SEP vessel 20. In contrast, with this construction method, the upper separate members 4a, 4b that make up the tower 4 are held upright by the holding portion 31 of the tower support device 30 mounted on the barge main body 21 of the SEP vessel 20, and the nacelle hub 5 is installed on top of the upper separate members 4a, 4b using the crane 23 of the SEP vessel 20, allowing the upper separate members 4a, 4b and the nacelle hub 5 to be assembled as a unit safely and stably on the SEP vessel 20.

[0086] Next, the barge body 21 is raised relative to the lifting legs 22 of the SEP vessel 20 to a next-step working height L2, which is higher than the initial-step working height L1. The integrated unit of the upper segments 4a, 4b and the nacelle hub 5, held by the holding parts 31, is then moved by the moving mechanism 32 of the tower support device 30 onto the lower segments 4c, 4d erected on the column 2a of the floater 2, thereby enabling the installation of the upper segments 4a, 4b and the nacelle hub 5 that make up the tower 4 to be carried out safely and stably. Then, a crane 23 mounted on the SEP vessel 20 is used to install multiple blades 6 on the nacelle hub 5, thereby producing an assembly 7 in which the wind turbine generator 3 is constructed on the floater 2. In this construction method, the assembly 7 is assembled using the crane 23 mounted on the SEP vessel 20 and the tower support device 30 mounted on the SEP vessel 20. This allows the assembly of the assembly 7 to be carried out efficiently and in a very stable manner, without being affected by waves.

[0087] After manufacturing the assembly 7, the assembly 7 is raised from the seabed SB and transported by sea to the target installation area, and construction of the floating offshore wind turbine 1 is completed simply by mooring the assembly 7 in the target installation area. Therefore, with this construction method, it is possible to safely construct a large floating offshore wind turbine 1, in which the draft DF of the floater 2 when moored in the target installation area is 20 m or less, using a medium-sized SEP vessel 20, without using an appropriately large SEP vessel 20.

[0088] Even when a temporary floating structure 10 is constructed as a temporary storage location for assembly components of the wind turbine generator 3 in the sea area where the float 2 is to be landed, as in this embodiment, the floating structure 10 is constructed in a relatively shallow sea area with a water depth DW of 8 m to 20 m, so the cost, labor, and time required to construct the floating structure 10 are relatively low. When a pier is constructed as the floating structure 10, the length of the support piles 11 driven into the seabed SB is relatively short because of the relatively shallow sea area, and the cost, labor, and time required to construct the pier are relatively low. When a floating structure is constructed as the floating structure 10, the work of fixing the mooring equipment constituting the floating structure to the seabed SB can be relatively easily performed because of the relatively shallow sea area, and the cost, labor, and time required to construct the floating structure are relatively low. Another advantage is that the floating structure 10 is constructed in a sea area with a relatively shallow water depth DW, making it easy to secure an installation location for the floating structure 10 within the port area.

[0089] As in this embodiment, by setting up multiple work areas A in the sea area adjacent to the temporary storage location (floor structure 10), and performing additional work including adjustment work on the assembly body 7 in the work area A where assembly work has been completed, and performing assembly work on the floating body 2 that has been anchored to the seabed SB in that work area A in a different work area A from the work area A where assembly work has been completed, assembly work and additional work can be performed in parallel in different locations.

[0090] Typically, additional work takes several weeks. For example, if additional work on an assembly 7 that has already been assembled is to be performed in a location other than the work area A, a location for the assembly 7 must be secured, and the work of floating the assembly 7 and moving it to another location also requires time and effort. In contrast, as in this embodiment, if additional work on an assembly 7 that has already been assembled is continued in a work area A near the temporary storage location (floating structure 10) while assembly work on another assembly 7 is performed in another work area A in parallel, multiple floating offshore wind power generation facilities 1 can be constructed very efficiently. When multiple work areas A are provided for the temporary storage location (floating structure 10), a configuration in which multiple sets of assembly components for wind turbine power generation devices can be temporarily stored on the floating structure 10 is advantageous for efficiently constructing multiple floating offshore wind power generation facilities 1.

[0091] If the assembly 7 is transported by sea to the target sea area and a new floater 2 is landed on the seabed SB of the work area A, multiple assemblies 7 can be assembled in one work area A, making it possible to construct a large number of floating offshore wind power facilities 1 very efficiently. In particular, if assembly parts are replenished on the temporary storage location (floating structure 10) before assembly work is performed on the newly landed floater 2, this is advantageous for efficiently constructing a large number of floating offshore wind power facilities 1.

[0092] When assembling the assembly 7 in each work area A, the orientation of the wind turbine generator 3 relative to the float 2 can be set to the correct orientation when moored in the target sea area for installation. However, if the wind turbine generator 3 is assembled in the correct orientation, the crane 23 of the SEP vessel 20 and the attachment position of the blades 6 relative to the nacelle hub 5 may be far apart. In such cases, the orientation of the tower 4 relative to the float 2 or the orientation of the nacelle hub 5 relative to the tower 4 can be set to an orientation that is deviated from the correct orientation. In that case, it is advisable to correct the orientation of the tower 4 relative to the float 2 or the orientation of the nacelle hub 5 relative to the tower 4 to the correct orientation after moving the assembly 7 out of the work area A or after moving the assembly 7 to the target sea area for installation.

[0093] Because the sea area where the floating offshore wind turbines 1 are to be installed is a windy area, the period in the sea area where the work environment is calm and suitable for construction is limited to a relatively short period of several months. Therefore, if the construction of the floating offshore wind turbines 1 is not completed during a period when the work environment is relatively calm, construction will be halted until a suitable period for construction the following year. Therefore, in order to construct a large number of floating offshore wind turbines 1 within this limited short period, it is important to efficiently perform the assembly work and addition work of the assemblies 7 in a short period of time. In this regard, this construction method can significantly shorten the cycle time for sequentially constructing a large number of floating offshore wind turbines 1, making it extremely advantageous for efficiently constructing a large number of floating offshore wind turbines 1 in a short period of time.

[0094] When a temporary floating structure 10 is constructed as in this embodiment, after the floating structure 10 has finished being used as a manufacturing base, it can be left in the sea area as a base for performing maintenance on the floating offshore wind power generation facility 1 (assembly 7), which is very useful for those skilled in the art. When removing the floating structure 10, it can be done relatively easily because the sea area is relatively shallow. It is also relatively easy to restore the state of the seabed SB to the state before the floating structure 10 was constructed.

[0095] Constructing the floating structure 10 in an ocean area inside the breakwater 70 allows the floating structure 10 to be constructed in an ocean area less affected by waves, which is advantageous for reducing the labor required to construct the floating structure 10. Furthermore, this reduces the risk of water pressure due to waves acting on the floating body 2 while it is attached to the seabed SB or the tower 4 installed on the floating body 2, which is advantageous for reducing the load on the floating body 2 and the tower 4. Note that with this construction method, the floating structure 10 can also be constructed in calm ocean areas less affected by waves, for example, in an ocean area outside the breakwater 70 or in an ocean area where no breakwater 70 is installed.

[0096] For example, the assembly parts that make up the wind power generation device 3 are transported to a quay 80 (a developed base port) facing the sea, and the assembly parts are temporarily placed on the quay 80. Then, with the SEP vessel 20 moored near the quay 80, the crane 23 is used to transfer at least some of the assembly parts that were temporarily placed on the quay 80 onto the barge main body 21, and the transferred assembly parts are sequentially installed on the float 2 to manufacture the assembly 7. This also allows for efficient construction of the floating offshore wind power generation facility 1.

[0097] As in this embodiment, by providing a vertical installation platform 25 for holding the upper separate members 4a and 4b that constitute the upper part of the tower 4 in an upright position and a vertical installation platform 25 for holding the lower separate members 4c and 4d that constitute the lower part of the tower 4 in an upright position on the barge body 21 of the SEP vessel 20, the work of assembling the upper separate members 4a and 4b and the lower separate members 4c and 4d can be carried out stably and efficiently using the crane 23 of the SEP vessel 20. In addition, by using a work platform 52 equipped with an erection device 51 and a tower lift hoist 24, the work of raising each of the separate members 4a to 4d from a laid-down position to an upright position can be carried out very stably and efficiently.

[0098] In this embodiment, when the upper divided members 4a, 4b (divided member 4b) are provided with the engaging portions 4e and the holding portion 31 of the tower support device 30 is configured to have the gripping portions 31a and the support arms 31c, the load of the integrated upper divided members 4a, 4b and the nacelle hub 5 can be stably supported by engaging the support arms 31c with the engaging portions 4e, and the integrated member can be stably supported in an upright position by gripping the outer circumferential surfaces of the upper divided members 4a, 4b with the gripping portions 31a. This is advantageous for stably assembling the upper divided members 4a, 4b and the nacelle hub 5 and installing them on the lower divided members 4c, 4d.

[0099] The movement mechanism 32 of the tower support device 30, like the first movement mechanism 33 exemplified in this embodiment, only needs to have a mechanism for moving at least the support unit 31 from on the barge main body 21 to the outside of the barge main body 21. However, if a second movement mechanism 39 capable of adjusting the horizontal position of the support unit 31 is provided, as in this embodiment, it becomes possible to more easily and accurately align the upper separate members 4a, 4b with the lower separate members 4c, 4d when they are erected on the column 2a of the float 2. In other words, if the movement mechanism 32 does not have a second movement mechanism 39 capable of adjusting the horizontal position of the support unit 31, it is necessary to accurately adjust the mooring position of the SEP vessel 20 with respect to the column 2a of the float 2, or the bottom landing position of the float 2 with respect to the SEP vessel 20. However, if the movement mechanism 32 has a second movement mechanism 39 capable of adjusting the horizontal position of the support unit 31, the precision with which the SEP vessel 20 and the float 2 are positioned can be relaxed.

[0100] When the floating structure 10 is constructed as a floating structure, for example, the assembly parts of the wind turbine generator 3 are placed in advance on a float that forms the top plate of the floating structure, and the float with the assembly parts placed on it is towed to the construction area where the floating structure 10 is to be constructed. The float with the assembly parts of the wind turbine generator 3 temporarily placed on it can then be fixed on mooring equipment that is fixed to the seabed SB in the construction area. This eliminates the need to transport the assembly parts of the wind turbine generator 3 by a carrier ship 60 or the like after the floating structure 10 is constructed, allowing the floating offshore wind power facility 1 to be constructed very efficiently. Note that when the floating structure 10 is constructed as a floating structure, the assembly parts of the wind turbine generator 3 can be transported by a carrier ship 60 or the like after the floating structure is constructed in the sea area, and the assembly parts can be temporarily placed on the floating structure, just as when the floating structure 10 is constructed as a pier.

[0101] The above example illustrates the construction of a semi-submersible floating offshore wind power facility 1, but the same construction method and effects can be achieved when constructing a TLP-type floating offshore wind power facility 1 or a barge-type floating offshore wind power facility 1. This construction method can also be used when constructing multiple types of floating offshore wind power facilities 1 in parallel.

[0102] In the above example, the number of partitions constituting the upper partition of the tower 4 and the number of partitions constituting the lower partition are two, but the number of partitions constituting each of the upper and lower partitions of the tower 4 is not particularly limited, and the upper partition or the lower partition can be composed of one or three or more partitions. For example, if the upper partition is composed of only the first partition 4a from the top of the tower 4, the partition 4a can be held by the holding part 31. For example, if the upper partition is composed of the top three partitions 4a, 4b, and 4c from the tower 4, the partition 4c can be held by the holding part 31.

[0103] This construction method can also be used to construct a medium-sized floating offshore wind power facility 1 in which the height from the bottom end of the float 2 to the nacelle hub 5 (rotation axis of the nacelle) is, for example, 130 m or less. This construction method can also be used to construct an even larger floating offshore wind power facility 1 using a large SEP vessel 20. [Explanation of symbols]

[0104] 1. Floating offshore wind power generation facilities 2 Floating body 2a Column 2b Concatenation 3. Wind power generation equipment 4. Tower 4a~4d Split parts 4e Engagement part 5 Nacelle hub 6 blades 7 Assembly 8 Mooring line 9. Anchor 10 Floating structures 11 Support pile 12 Girder material 13 Floor slab material 14 braces 20 Self-elevating platform (SEP) 21 Barge body 22 Lifting legs 23 Crane (mounted on a self-lifting barge) 24 Tower lift sling 25 Vertical stand 30 Tower Support Device 31 Holding part 31a Grip part 31b Switching mechanism 31c Support arm 32 Moving mechanism 33 1st movement mechanism 34 Foundation 35 Arm 36 1st connection part 37 Actuator 37a Cylinder 37b Rod 38 2nd connection part 39 Second movement mechanism 40 Rail for moving in the captain's direction 50 Cranes (placed on floating structures) 51 Standing device 52 Work Cart 60 Carrier 70 Breakwater 80 Quay A, A1, A2 (1st and 2nd) work areas SB Undersea WL sea level position L1 Initial process working height L2 Next process working height

Claims

1. A construction method for a floating offshore wind power generation facility having a float moored in a target sea area for installation and a wind power generation device erected on the float, wherein the draft from the water surface to the bottom of the float is 20 m or less when the float is moored in the target sea area, The float is placed on the seabed in a sea area with a water depth of 8 m to 20 m, and a self-elevating barge having lifting legs, a barge body that can be raised and lowered relative to the lifting legs, and a crane mounted on the barge body is parked near the float in a jacked-up state with the lifting legs placed on the seabed, a tower support device including a support part capable of supporting a divided member of a tower constituting the wind power generation device and a movement mechanism for moving the support part relative to the barge body is mounted on the barge body; With the barge body fixed at a predetermined initial process working height relative to the lifting legs, the crane is used to erect a lower divided member constituting the lower part of the tower on the column of the float; an upper divided member constituting an upper portion of the tower is held in an upright position by the holding section, and a nacelle hub constituting the wind turbine generator is installed on the upper portion of the upper divided member using the crane; Thereafter, the barge body is raised relative to the lifting legs to a next process working height that is higher than the initial process working height, thereby fixing the barge body relative to the lifting legs, and the holding part is moved by the movement mechanism to move the integrated unit of the upper divided member and the nacelle hub onto the lower divided member that is erected on the column, thereby connecting the lower part of the upper divided member to the upper part of the lower divided member; Then, a plurality of blades constituting the wind turbine power generation device are installed on the nacelle hub using the crane, thereby manufacturing an assembly in which the wind turbine power generation device is constructed on the floating body; The method for constructing a floating offshore wind power facility is characterized in that the assembly is then raised from the seabed and transported by sea to the target sea area for installation, and the assembly is moored in the target sea area for installation.

2. A temporary floating structure is constructed in the sea area where the floating body is to be landed, transporting the tower segments, the nacelle hub, and the blades, which are assembly components that constitute the wind turbine generator, to the floating structure, and temporarily placing the assembly components on the floating structure; 2. A construction method for a floating offshore wind power facility as described in claim 1, wherein the self-elevating barge is parked in the jacked-up state near the floating structure, and the crane is used to transfer at least some of the assembly parts that were temporarily placed on the floating structure onto the barge body, and the transferred assembly parts are sequentially installed on the floating body to manufacture the assembly.

3. a plurality of work areas for landing the floating body on the bottom are provided in a sea area adjacent to the floating structure, and a plurality of sets of the assembly parts are temporarily placed on the floating structure; Using the self-elevating barge parked in the jacked-up state near any of the work areas, an assembly work is performed to install a set of assembly parts that have been temporarily placed on the floating structure onto the floating body that has been landed on the seabed in the work area, and to assemble the assembly; The self-elevating barge is moved sequentially from one work area where the assembly work has been completed to another work area, and the assembly work is performed on the floating body that has been set down on the seabed in that work area, and in parallel with this, additional work including adjustment work is performed on the assembly that has already been completed; The construction method for a floating offshore wind power facility according to claim 2 , wherein the assemblies after the additional work are completed are transported by sea to the target sea area for installation.

4. The construction method for a floating offshore wind power facility according to claim 2 or 3, wherein a pier or a floating structure is constructed in the sea area as the above-water structure.

5. transporting the tower segments, the nacelle hub, and the blades, which are assembly components that configure the wind turbine generator, to a quay facing the sea area, and temporarily placing the assembly components on the quay; 2. A construction method for a floating offshore wind power facility according to claim 1, wherein, with the self-elevating barge parked in the jacked-up state near the quay, the crane is used to transfer at least some of the assembly parts that were temporarily placed on the quay onto the barge body, and the transferred assembly parts are sequentially installed on the floating body to manufacture the assembly.

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