Construction method of floating type offshore wind power generation facility

Abstract

To provide a method capable of effectively constructing a floating type offshore wind power generation facility with the float draft of 20 m or less in a mooring state in an installing target sea area without maintaining a facility installation base of the floating type offshore wind power generation facility on a quay.SOLUTION: A construction method constructs a temporary on-water structure 10 in a sea area with a water depth of 8 m or more and 20 m or less, transports assembly components of a nacelle hub 5, a blade 6, and a tower 4 to form a wind power generation device 3 to the on-water structure 10, and temporarily puts the assembly components on the on-water structure 10. A float 2 is transported by sea to the vicinity of the on-water structure 10 and is landed on a sea bottom SB. The assembly components of the wind power generation device 3 are installed in sequence on the float 2 using a crane 23 of a self-elevating platform 20 stopped in the vicinity of the on-water structure 10, and an assembly 9 that the wind power generation device 3 is erected on the float 2 is manufactured. After that, the assembly 9 is transported by sea to an installation target sea area, and the assembly 9 is moored in the installation target sea area.SELECTED DRAWING: Figure 6

Description

[Technical field]

[0001] The present invention relates to a construction method for a floating offshore wind power facility, and more specifically, to a construction method for a floating offshore wind power facility that can efficiently construct a floating offshore wind power facility with a float draft of 20 m or less when moored in the target sea area, without the need to prepare a mounting base (base port) for the floating offshore wind power facility on a quay. [Background technology]

[0002] Floating offshore wind power generation facilities, which have a structure in which a wind power generation device is erected on a float moored in a submerged or semi-submerged state in the sea area, are classified into spar type, semi-submerged type, TLP (tension leg platform) type, and barge (concrete) type according to the structure of the float. For example, in a spar type floating offshore wind power generation facility, a column-shaped spar type float with a height of about 50 m to 100 m is mostly submerged, and a wind power generation device is erected on the huge spar type float (for example, see Patent Document 1). The draft of the spar type float when moored in the sea area to be installed is about 50 m to 100 m. On the other hand, in the semi-submerged, TLP, and barge type floating offshore wind power generation facilities other than the spar type, the float is floated on the sea in a semi-submerged state, and the draft of the semi-submerged float, the TLP float, and the barge float when moored in the sea area to be installed is 20 m or less. Specifically, for example, in a semi-submersible floating offshore wind power facility, a semi-submersible float having multiple columns about 20m to 40m in height and connectors (so-called footing members, etc.) that connect the columns together is floated on the sea in a semi-submerged state, and a wind power generation device is erected on one of the columns of the float.

[0003] In a typical construction method for a spar-type floating offshore wind turbine, the spar-type float and the tower that constitute the wind turbine are connected in a tilted state on land such as a quay, and the combined spar-type float and tower are loaded onto a semi-submersible barge in the tilted state and transported to an ocean area with a water depth of 100 m or more. Then, the combined spar-type float and tower are launched in an ocean area with a water depth of 100 m or more, and the ballast water of the spar-type float is adjusted to make the combined unit that was tilted sideways stand upright. The upright combined unit is then towed to the target ocean area for installation, and moored in the target ocean area with a water depth of 100 m or more. Next, a fixed crane barge is used to install a nacelle hub on the top of the tower, and blades are installed on the nacelle hub, completing the construction of the spar-type floating offshore wind turbine.

[0004] The invention described in Patent Document 1 differs from general construction methods in that a bent section is provided midway through the tower and the wind turbine (nacelle hub and blades) is installed on the tower on land; however, even in the invention described in Patent Document 1, the integrated spar-type floating body (foundation) and the wind power generation tower are assembled on land.

[0005] The float and the wind power generating device that constitute the floating offshore wind power generation facility are very large in size and very heavy. Therefore, it is difficult to transport the float and the tower as a unit over a long distance on land. Therefore, when manufacturing the float and the tower as a unit on land, as in the general construction method and the invention described in Patent Document 1, it is necessary to secure a space on land such as a quay to mount the assembly parts of the float and the wind power generating device and a space to manufacture the unit. However, in many cases, the ground of a general quay does not have the strength to withstand the load of the unit. Therefore, in order to prepare a mounting base (base port) for the floating offshore wind power generation facility on a quay, large-scale construction such as ground improvement work to improve the bearing capacity of the quay and apron is required, which requires a relatively large amount of cost, labor, and time. Furthermore, it may be difficult to secure a large space on a quay as a mounting base for the floating offshore wind power generation facility.

[0006] Furthermore, in a typical construction method for a spar-type floating offshore wind power facility, work is required to raise the integral spar-type float and tower that have been laid down sideways in waters with a depth of 100 m or more. The construction method described in Patent Document 1 also requires the hinge opening and closing means to change the rear part of the tower hinge and the spar-type float (foundation) from a laid-down state to an upright state. Therefore, the construction methods proposed in the past also have the problem of requiring advanced and complicated work on the sea. As such, the construction methods proposed in the past have various problems and there is room for improvement. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] JP 2012-202250 A Summary of the Invention [Problem to be solved by the invention]

[0008] The object of the present invention is to provide a construction method for a floating offshore wind power facility that can efficiently construct a floating offshore wind power facility with a float draft of 20 m or less when moored in the target sea area, without the need to prepare a mounting base (base port) for the floating offshore wind power facility on a quay. [Means for solving the problem]

[0009] In order to achieve the above object, the present invention provides a construction method for a floating offshore wind power facility, which includes a float moored in a target sea area and a wind power generation device erected on the float, and in which the draft from the water surface to the bottom end of the float is 20 m or less while the float is moored in the target sea area, the construction method includes constructing a temporary floating structure in a sea area with a water depth of 8 m to 20 m, and attaching the assembly parts of the nacelle hub, blades and tower that constitute the wind power generation device to the floating structure. the assembly parts are transported by sea, the assembly parts are temporarily placed on the floating structure, the float is transported by sea to the vicinity of the floating structure and set down on the seabed, the assembly parts are sequentially installed on the float using a crane of a self-elevating barge parked near the floating structure, an assembly in which the wind power generation device is constructed on the float is manufactured, and then the assembly is floated up 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. Effect of the Invention

[0010] The present invention is a construction method for a floating offshore wind power generation facility with a float having a draft of 20m or less when moored in the sea area to be installed, and can be adopted for construction of floating offshore wind power generation facilities of other types (semi-submersible, TLP, barge type) except for the spar type. According to the present invention, a temporary floating structure is constructed in a relatively shallow sea area with a water depth of 8m to 20m, so the cost, labor, and time required for constructing the floating structure are relatively small. Since the assembly parts of the wind power generation device are temporarily placed on the floating structure, there is no need to prepare a mounting base for the floating offshore wind power generation facility where the assembly parts are temporarily placed together on a quay. In addition, by constructing the floating structure in a sea area with a water depth of 8m to 20m, it is possible to moor a self-elevating barge near the floating structure, and the floating body can be easily landed on the seabed near the floating structure. By using a crane on a self-raising barge that is not affected by waves and further by anchoring the float to the seabed, the assembly parts of the wind power generation device are sequentially installed on the float to manufacture an assembly in which the wind power generation device is constructed on the float, and this can be done very stably and efficiently. After the assembly is manufactured, the assembly is raised from the seabed and transported by sea to the target sea area, and construction of the floating offshore wind power facility is completed simply by mooring the assembly in the target sea area. Therefore, in the present invention, even if there is no need to prepare an installation base for the floating offshore wind power facility on a quay, a floating offshore wind power facility (other types of floating offshore wind power facility excluding spar type) with a float with a draft of 20 m or less when moored in the target sea area can be efficiently constructed. [Brief description of the drawings]

[0011] [Figure 1] FIG. 1 is an explanatory diagram showing a schematic front view of a semi-submersible floating offshore wind power facility constructed according to the present invention. [Diagram 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 assembly parts of a wind power generation device transported by sea by a carrier ship being temporarily placed on the floating structure. [Diagram 3] 3 is an explanatory diagram illustrating a schematic side view of the abovewater structure of FIG. 2. [Figure 4]3 is an explanatory diagram illustrating a schematic plan view of the sea area in which the above-water structure of FIG. 2 is constructed. [Diagram 5] 3 is an explanatory diagram showing a schematic plan view of the self-elevating barge parked near the waterborne structure from the state shown in FIG. 2. FIG. [Figure 6] 1 is an explanatory diagram showing a schematic side view of a state in which some of the assembly parts of a wind turbine generator that were temporarily placed on an above-water structure have been transferred to a self-elevating barge. FIG. [Figure 7] This is an explanatory diagram showing a schematic plan view of the state in which the mooring position of the self-elevating barge relative to the waterfront structure has been changed from the state shown in Figure 6, and the semi-submersible float transported by sea has been landed on the seabed near the pier. [Figure 8] FIG. 8 is an explanatory diagram showing a schematic side view of the state in which the tower segments and the nacelle hub, which have been transferred to the self-elevating barge from the state shown in FIG. 7, are installed on the floating body. [Figure 9] 9 is an explanatory diagram illustrating a schematic plan view of a state in which blades are attached to a nacelle hub following the state shown in FIG. 8; FIG. [Figure 10] This is an explanatory diagram showing a schematic plan view of an assembly in which a tower, nacelle hub, and blades are installed on a floating body, and the assembly components of a wind power generation device that has been temporarily placed on a floating structure are moved from the assembly area and transferred to a self-elevating barge. [Figure 11] This is an explanatory diagram showing a schematic plan view of the state in which the mooring position of the self-elevating barge relative to the floating structure has been changed from the state shown in Figure 10, and the newly transported floating body has been landed on the seabed near the floating structure. [Figure 12] 12 is an explanatory diagram illustrating a schematic plan view of the state in which the manufacture of three assemblies has been completed from the state in FIG. 11. FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] Hereinafter, a construction method for a floating offshore wind power facility of the present invention will be described based on an embodiment shown in the drawings.

[0013] As illustrated in FIG. 1, a floating offshore wind power facility 1 includes a float 2 moored in a target sea area and a wind power generation device 3 erected on the float 2. In the target sea area, the float 2 is moored to the seabed SB using mooring lines 7, anchors 8, etc. As illustrated in FIG. 1, the present invention is a construction method for a floating offshore wind power facility 1 in which the draft DF from the water surface to the bottom of the float 2 is 20 m or less when the float 2 is moored in the target sea area. In other words, the present invention can be adopted in the construction of floating offshore wind power facilities 1 of other types (semi-submersible type, TLP type, barge type) except for the spar type. The present invention is particularly suitable for the construction of a semi-submersible type floating offshore wind power facility 1.

[0014] In this embodiment, a semi-submersible floating offshore wind power generation facility 1 is constructed as an example. As illustrated in Fig. 1, a semi-submersible float 2 is sunk to a predetermined draft DF in the sea area and moored in a semi-submerged state. The wind power generation device 3 has a nacelle hub (an integrated nacelle and hub) 5 installed on the top of a tower 4 extending in the vertical direction, and a plurality of blades 6 are radially arranged on the nacelle hub 5. A generator, a brake device, a gearbox, etc. are built into the nacelle hub 5, and a power cable connected to the generator is arranged inside the tower 4.

[0015] In this embodiment, a wind power generation device 3 having three blades 6 and a tower 4 composed of three divided members 4a is exemplified. The number of blades 6 provided in the wind power generation device 3, the structure of the blades 6, the number of divided members 4a constituting the tower 4, and the like are not limited to this embodiment. For example, the blades 6 may have a structure in which a plurality of members are connected, and the tower 4 may be composed of a single long member.

[0016] The tower 4 has a longitudinal length (height) of about 80m to 150m, and a width (thickness) of about 5m to 15m. The tower 4 weighs about 1000t to 2000t. The longitudinal length (height) of each divided member 4a is about 25m to 50m, and a weight of each divided member 4a is about 300t to 700t. The nacelle hub 5 has a height of about 8m to 15m, a longitudinal length of about 15m to 25m, and a width of about 7m to 15m. The nacelle hub 5 weighs about 600t to 1000t. The longitudinal length of one blade 6 is about 80m to 150m, and a weight of one blade 6 is about 50t to 90t.

[0017] The semi-submersible float 2 has a plurality of 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 connector section that is cross-shaped in a plan view, and support sections that are polygonal in a plan view and are provided at four ends of the connector section, respectively, and the columns 2a are erected on each of the four support sections. Each column 2a constituting the semi-submersible float 2 is provided with an engagement hole into which the lower part of the tower 4 can be inserted, and the wind power generation device 3 is erected on one of the columns 2a.

[0018] The float 2 is structured to be capable of storing ballast water therein, and the magnitude of buoyancy acting on 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 about 60 m to 100 m in plan view, and the height of the column 2a of the semi-submersible float 2 is about 25 m to 50 m. Note that the structure of the float 2, specifically, in the case of the 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 where the wind power generation device 3 is erected, are not limited to the configuration of this embodiment, and floats 2 of various other configurations can be adopted. In this embodiment, a semi-submersible float 2 is exemplified, but when a TLP-type floating offshore wind power generation facility 1 is constructed, a known TLP-type float 2 is used, and when a barge-type floating offshore wind power generation facility 1 is constructed, a known barge-type float 2 is used.

[0019] The procedure of the construction method for the floating offshore wind power facility 1 of the present invention will be described below.

[0020] As illustrated in Figs. 2 and 3, in the present invention, a temporary floating structure 10 is constructed in an ocean area with a water depth DW (depth from sea surface position WL to seabed SB) of 8 m to 20 m. In this embodiment, a pier is constructed in an ocean area as the temporary floating structure 10. In the present invention, a floating structure (float) can also be constructed in an ocean area as the temporary floating structure 10. In the present invention, a carrier ship 40 (specifically, for example, a LOLO ship) equipped with a crane is then used to transport the assembly parts of the nacelle hub 5, blades 6, and tower 4 that constitute the wind turbine 3 to the floating structure 10, and the assembly parts are temporarily placed on the floating structure 10 using a crane or the like of the carrier ship 40. It is preferable to transport the assembly parts of the wind power generation device 3 by sea to the floating structure 10, but when the floating structure 10 is constructed in an ocean area close to a quay, for example, the assembly parts can be transported (loaded and unloaded) from the quay to the floating structure 10 using a crane 30 arranged on the floating structure 10 or a crane arranged on the quay. Also, for example, the assembly parts may be transported to the floating structure 10 using an air vehicle such as a helicopter or a large drone. In this embodiment, a mobile crane 30 is transported by sea together with the assembly parts of the wind power generation device 3 by a carrier ship 40, and the crane 30 is arranged on the floating structure 10.

[0021] The floating structure 10 is preferably constructed in a calm water area where the influence of waves is small. As illustrated in Fig. 4, the floating structure 10 is preferably constructed in an ocean area inside a breakwater 50 installed in a bay or the like. The ocean area inside the breakwater 50 here refers to an ocean area where the influence of waves is reduced by the breakwater 50. The floating structure 10 is preferably constructed in an ocean area where the floating offshore wind power generation facility 1 is to be installed, or in an ocean area close to a quay 60 where assembly parts of the wind power generation device 3 are loaded onto a carrier ship 40.

[0022] As shown in Fig. 3, when constructing a pier 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, shaped steel such as H-shaped steel or steel pipe piles are used for the support piles 11. For example, shaped steel such as H-shaped steel is used for the girders 12 and the braces 14. For example, covering plate is used for the deck material 13.

[0023] When constructing a floating structure in an ocean area as the floating structure 10, mooring equipment that serves as the base of the floating structure is installed in the ocean area. The floating structure is then constructed by fixing a float that constitutes the top plate of the floating structure on top of the mooring equipment that is moored to the seabed SB. The members used to construct the floating structure 10 are transported to the target area for constructing the floating structure 10 using a vessel such as a carrier ship 40. The method of constructing the floating structure 10 in an ocean area is not particularly limited, and it may be constructed by a known method.

[0024] The floating structure 10 has a size large enough to temporarily store the assembly parts constituting at least one wind power generation device 3, and has a structure that allows a carrier ship 40 or a self-elevating barge 20 (hereinafter referred to as SEP vessel 20) to be docked, which will be described later. As illustrated in FIG. 2, the floating structure 10 may have a size large enough to allow some of the blades 6 constituting the wind power generation device 3 to protrude from the floating structure 10. The floating structure 10 has a structure that can withstand the weight of the assembly parts of at least one wind power generation device 3. As illustrated in FIG. 3, the height H from the sea level WL to the upper surface of the floating structure 10 may be set to, for example, 1 m or more and 10 m or less. In this embodiment, the floating structure 10 is illustrated as a rectangular structure in a plan view, but the floating structure 10 may have a structure or shape different from that of this embodiment as long as it satisfies the above-mentioned conditions.

[0025] The longitudinal length of the floating structure 10 in plan view may be set to, for example, 50 m to 250 m, and the width may be set to, for example, 40 m to 60 m. The load capacity of the floating structure 10 may be set to, for example, 1 t / m 2 More than 15t / m2 It is advisable to set the load capacity as follows. The entire surface structure 10 may be set to the same load capacity, but different load capacities can also be set for the areas where the assembly parts of the wind turbine generator 3 are placed and the areas where they are not. 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 surface structure 10, the load capacity of the area where the nacelle hub 5 is placed is, for example, 8 t / m 2 More than 12t / m 2 Hereinafter, the load capacity of the area on which the divided member 4a of the tower 4 is placed is, for example, 3t / m 2 More than 8t / m 2 Hereinafter, the load capacity of the area on which the blade 6 is placed is, for example, 1 t / m 2 More than 5t / m 2 It is recommended to set it as follows.

[0026] As shown in Fig. 2, in this embodiment, a temporary mooring facility 15 and a temporary protection facility 16 are provided near the floating structure 10 as facilities used for mooring the carrier ship 40 to the floating structure 10. Note that the mooring facility 15 and the protection facility 16 are omitted and not shown in the drawings other than Fig. 2 and Fig. 4.

[0027] As illustrated in FIG. 2 and FIG. 3, in this embodiment, a frame supporting the nacelle hub 5 is provided on the floating structure 10, and the nacelle hub 5 is placed on the frame. In addition, a frame supporting each of the divided members 4a constituting the tower 4 is provided on the floating structure 10, and the divided members 4a are placed on the frame in a horizontally laid state. In this embodiment, the three divided members 4a are arranged side by side. Furthermore, a frame structured to mount the three blades 6 in a vertically spaced state is provided on the floating structure 10, and the three blades 6 are arranged vertically. Each blade 6 is arranged in a horizontally laid state, and a part of the blade 6 protrudes from the floating structure 10. Since the nacelle hub 5 and the divided members 4a are relatively heavy, it is preferable to arrange them without stacking them vertically. Since the blade 6 is large in size and relatively light, it is preferable to arrange a plurality of blades 6 vertically.

[0028] After the assembly parts of the wind turbine 3 have been temporarily placed on the floating structure 10, the carrier ship 40 is moved away from the floating structure 10. Thereafter, as illustrated in Fig. 5, the SEP vessel 20 is stopped near the floating structure 10. Then, as illustrated in Fig. 6, some or all of the assembly parts of the wind turbine 3 that were temporarily placed on the floating structure 10 are transferred to the SEP vessel 20 using a crane 23 mounted on the SEP vessel 20.

[0029] In this embodiment, the SEP vessel 20 is stopped with its side aligned along the side of the floating structure 10, and the crane 23 of the SEP vessel 20 is used to transfer the three separate members 4a and the nacelle hub 5 that were temporarily placed on the floating structure 10 to the SEP vessel 20. The SEP vessel 20 is provided with a platform on which each separate member 4a is mounted in an upright position, and when the separate members 4a are transferred from the floating structure 10 to the SEP vessel 20, the crane 23 causes the separate members 4a, which had been laid sideways, to be placed in an upright position and mounted on the SEP vessel 20.

[0030] 5 and 6, 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 vertically relative to the barge body 21, and a large 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 is not equipped with a propulsion device and is moved by towing.

[0031] As shown in Fig. 6, when the SEP vessel 20 is stopped, the lifting legs 22 are moved downward relative to the barge body 21 floating in the sea area, so that the lower ends of the lifting legs 22 are placed on the seabed SB. From that state, the barge body 21 is moved upward relative to the lifting legs 22, so that the barge body 21 is moved to a position higher than the sea surface, and the barge body 21 is supported in midair by the lifting legs 22. By raising the barge body 21 to a height where waves cannot reach it, the barge body 21 is no longer affected by waves.

[0032] The water depth at which the SEP vessel 20 can be stopped by the lifting legs 22 is approximately 40 m or less. In the present invention, the floating 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 stopped in a stable state near the floating structure 10. If the ground of the seabed SB near the floating structure 10 does not have sufficient strength to stably stop the SEP vessel 20, simple ground improvement work, etc., may be carried out in advance to increase the strength of the seabed SB near the floating structure 10.

[0033] After some or all of the assembly parts of the wind power generation device 3 temporarily placed on the floating structure 10 are transferred to the SEP vessel 20, the lifting legs 22 of the SEP vessel 20 are moved away from the seabed SB to make the SEP vessel 20 movable on the sea. Then, as illustrated in FIG. 7, the SEP vessel 20 is moved so that the bow or stern side of the SEP vessel 20 runs along the side of the floating structure 10, and the SEP vessel 20 is stopped again near the floating structure 10. Then, as illustrated in FIG. 7 and FIG. 8, the floating body 2 is transported by sea to the vicinity of the floating structure 10 and is set in a state where it is landed on the seabed SB. It is preferable that the floating body 2 is arranged in such a direction that the columns 2a on which the wind power generation device 3 is erected are located on the floating structure 10 side and the SEP vessel 20 side.

[0034] During marine transportation, the floating body 2 is floated on the sea with a relatively small amount of ballast water stored therein, and is towed to the vicinity of the floating structure 10 using a tugboat or the like. After the floating body 2 is moved to the vicinity of the floating structure 10, ballast water is poured into the floating body 2 to gradually sink the floating body 2, and the bottom of the floating body 2 is set to a state where it is set to the seabed SB. If the ground of the seabed SB where the floating body 2 is to be set to the bottom is not flat, it is preferable to level or cure the ground of the seabed SB to a flat state before placing the floating body 2 in the vicinity of the floating structure 10. Preferably, as illustrated in FIG. 8, sandbags or the like are placed on the seabed SB where the floating body 2 is to be set to the bottom, forming a flat mound on which the floating body 2 is to be set to the bottom, and the floating body 2 is set to the bottom on the mound.

[0035] In the present invention, the floating structure 10 is constructed in a sea area with a water depth DW of 8 m or more and 20 m or less, so that the semi-submersible floating body 2, the TLP floating body 2, and the barge floating body 2 can be towed to the vicinity of the floating structure 10. In addition, the assembly work of the wind power generation device 3 on the floating body 2 can be performed with each type of floating body 2 landed on the seabed SB. In other words, in a sea area with a water depth DW of less than 8 m, the water depth DW is too shallow, so it is difficult to tow the floating body 2 to the vicinity of the floating structure 10. In a sea area with a water depth DW of more than 20 m, the water depth DW is too deep, so it is difficult to assemble the wind power generation device 3 on the floating body 2 with the floating body 2 landed on the seabed SB.

[0036] Then, as illustrated in Figures 8 and 9, using the crane 23 of the SEP vessel 20 parked near the floating structure 10, assembly components of the wind power generation device 3 are sequentially installed on the float 2 to manufacture an assembly 9 in which the wind power generation device 3 is constructed on the float 2.

[0037] More specifically, the crane 23 of the SEP vessel 20 is used to insert the divided member 4a constituting the base part of the tower 4 transferred to the SEP vessel 20 into an engagement hole of one column 2a of the floating body 2. Next, the crane 23 is used to connect the divided member 4a constituting the middle part of the tower 4 transferred to the SEP vessel 20 onto the divided member 4a constituting the root part, and the divided member 4a constituting the upper end part of the tower 4 is connected onto the divided member 4a constituting the middle part, thereby constructing the tower 4 on the column 2a. Next, the crane 23 is used to install the nacelle hub 5 transferred to the SEP vessel 20 on the top of the tower 4. After that, the crane 23 is used to attach each blade 6 to the nacelle hub 5, thereby manufacturing an assembly 9 in which the wind turbine generator 3 is erected on the floating body 2.

[0038] In installing the blades 6, similar to the installation work of the tower partition members 4a and the nacelle hub 5, the crane 23 of the SEP vessel 20 may be used to transfer each blade 6 from the surface structure 10 to the SEP vessel 20, and then each blade 6 may be installed on the nacelle hub 5, or the blades 6 that have been temporarily placed on the surface structure 10 may be installed directly on the nacelle hub 5 using the crane 23 without performing the transfer work.

[0039] Thereafter, the crane 30 or the like arranged on the floating structure 10 is used to set up the electrical equipment and electrical wiring of the wind power generation device 3 (so-called pre-assembly). Then, testing of the electrical equipment of the wind power generation device 3 (so-called pre-commissioning) is performed. If multiple assemblies 9 are not manufactured in parallel on the floating structure 10, the pre-assembly and pre-commissioning are performed directly in the assembly area where the float 2 is first landed on the bottom.

[0040] Then, after confirming that there are no abnormalities in the wind turbine 3, the amount of stored ballast water in the float 2 is reduced, and the assembly 9 is raised from the seabed SB. Then, while the assembly 9 is floating on the sea, it is towed by a tugboat or the like to the target sea area for installation. Thereafter, as illustrated in FIG. 1, the assembly 9 (float 2) is moored to the seabed SB using mooring lines 7, anchors 8, or the like in the target sea area for installation. After that, a submarine cable is connected to the wind turbine 3, and a final operation check (so-called final commissioning) of the floating offshore wind power generation facility 1 is performed. With the above, the construction of the floating offshore wind power generation facility 1 is completed.

[0041] As illustrated in Fig. 10, when a plurality of assemblies 9 are manufactured in parallel for the surface structure 10, the assembly 9 is manufactured by performing the installation work of the blades 6 in the assembly area where the float 2 is first landed on the bottom. The assembly 9 is then raised from the seabed SB, and while the assembly 9 is floating on the sea, a tugboat or the like is used to move the assembly 9 to the sea area on the other side of the surface structure 10 away from the assembly area where the float 2 was first landed on the bottom. The moved assembly 9 is then landed on the seabed SB near the surface structure 10, and the above-mentioned pre-assembly and pre-commissioning are performed on the assembly 9 using a crane 30 or the like arranged on the surface structure 10.

[0042] As illustrated in Fig. 10, while the assembly 9 is being moved and pre-assembly and pre-commissioning are being performed on the assembly 9, assembled parts of the wind turbine generator 3 constituting the assembly 9 to be manufactured next are transported by sea using a carrier ship 40, and the assembled parts are temporarily placed on the floating structure 10. Then, as illustrated in Fig. 11, in the same work procedure as described above, the second assembly 9 is manufactured by performing the work of transferring some or all of the assembled parts temporarily placed on the floating structure 10 to the SEP vessel 20, the work of transporting the float 2 constituting the assembly 9 to be manufactured next by sea to the vicinity of the floating structure 10 and landing it on the seabed SB, and the work of sequentially installing the assembled parts of the wind turbine generator 3 on the float 2 using the crane 23 of the SEP vessel 20.

[0043] As shown in Fig. 12, the manufactured assemblies 9 are successively moved from the area where the float 2 was initially landed to the sea area on the other side of the floating structure 10 away from the area, and pre-assembly and pre-commissioning are successively performed, so that a plurality of assemblies 9 are manufactured in parallel on the floating structure 10. The assemblies 9 that have been pre-commissioned are successively transported to the sea area where they are to be installed and moored.

[0044] After the use of the floating structure 10 as a manufacturing base is completed, the floating structure 10 is removed from the sea area. If a pier was constructed as the floating structure 10, the holes in the seabed SB where the support piles 11 were inserted are backfilled to restore the state of the seabed SB to the state before the floating structure 10 was constructed.

[0045] As described above, the present invention is a construction method for a floating offshore wind power facility in which the draft of the float 2 is 20 m or less when moored in the sea area to be installed, and can be adopted for construction of floating offshore wind power facilities 1 of other types (semi-submersible type, TLP type, barge type) except for the spar type. In the present invention, a temporary floating structure 10 is constructed in a relatively shallow sea area with a water depth DW of 8 m or more and 20 m or less, so the cost, labor, and time required for constructing the floating structure 10 are relatively small. When a pier is constructed as the floating structure 10 as in this embodiment, the length of the support piles 11 driven into the seabed SB is relatively short because the sea area is relatively shallow, and the cost, labor, and time required for constructing the pier are relatively small. When a floating structure is constructed as the floating structure 10, the sea area is relatively shallow, so the work of mooring the mooring equipment constituting the floating structure to the seabed SB can be performed relatively easily, and the cost, labor, and time required for constructing the floating structure are relatively small.

[0046] In the present invention, the assembly parts of the wind power generation device 3 are transported to the floating structure 10 and temporarily placed on the floating structure 10, so there is no need to prepare an installation base for the floating offshore wind power facility 1, where the assembly parts are temporarily placed together on a quay. In other words, to prepare an installation base for the floating offshore wind power facility 1 on land, large-scale construction such as ground improvement work to improve the bearing capacity of the quay is required, which requires relatively high costs, labor, and time, but in the present invention, such large-scale construction of the quay is not required, and there is no need to secure a large space behind the quay. Since the water depth DW is a relatively shallow sea area, there is also the advantage that it is easy to secure an installation site for the floating structure 10 within the port area.

[0047] Furthermore, in the present invention, by constructing the floating structure 10 in an ocean area with a water depth DW of 8 m or more and 20 m or less, it is possible to moor the SEP vessel 20 near the floating structure 10, and the floating body 2 can be easily landed on the seabed SB near the floating structure 10. By using the crane 23 of the SEP vessel 20, which is not affected by waves, and further by landing the floating body 2 on the seabed SB, the assembly parts of the wind power generation device 3 can be sequentially installed on the floating body 2, and the work of manufacturing the assembly 9 in which the wind power generation device 3 is constructed on the floating body 2 can be performed efficiently in a very stable state.

[0048] After manufacturing the assembly 9, the assembly 9 is transported by sea to the target sea area, and the construction of the floating offshore wind power facility 1 is completed simply by mooring the float 2 in the target sea area. In other words, the present invention does not require complicated and advanced work to be performed in the target sea area.

[0049] Therefore, in the present invention, a floating offshore wind power facility 1 (other types of floating offshore wind power facility 1 excluding the spar type) with a float 2 having a draft of 20 m or less when moored in the target sea area can be efficiently constructed without preparing a mounting base for the floating offshore wind power facility 1 on a quay. Also, in the present invention, a temporary floating structure 10 is constructed in a relatively shallow sea area, so that the floating structure 10 can be relatively easily removed after the use of the floating structure 10 as a manufacturing base has ended. Also, the work of restoring the state of the seabed SB to the state before the floating structure 10 was constructed can be relatively easily performed.

[0050] In addition, in the present invention, by providing the floating structure 10 on which the assembly parts of the wind power generation device 3 are temporarily placed, the work of transporting the assembly parts of the wind power generation device 3 to the sea area where the assembly 9 is manufactured can be performed by the carrier ship 40 other than the self-elevating barge 23. Therefore, even when manufacturing a plurality of assemblies 9, it is not necessary to transport the assembly parts of the wind power generation device 3 by sea using the self-elevating barge 23, and the self-elevating barge 23 can be efficiently used for the assembly work of the wind power generation device 3. Since the self-elevating barge 23 is a special ship and there are only a few of them in Japan, it is very advantageous for those skilled in the art that the self-elevating barge 23 can be efficiently used for the assembly work of the wind power generation device 3 to efficiently construct a floating offshore wind power generation facility. In addition, by providing the floating structure 10, the carrier ship 40 can quickly move on to the next transportation after temporarily placing the assembly parts of the wind power generation device 3 on the floating structure 10. Therefore, by providing the floating structure 10, the operating rate of the carrier ship 40 can also be improved.

[0051] If the floating structure 10 is constructed in the sea area inside the breakwater 50, the floating structure 10 can be constructed in a sea area less affected by waves, which is advantageous in reducing the labor required for constructing the floating structure 10. In addition, the risk of water pressure due to waves acting on the floating body 2 in a state where it is landed on the seabed SB and the tower 4 installed on the floating body 2 is reduced, which is advantageous in reducing the load on the floating body 2 and the tower 4. Note that in the present invention, the floating structure 10 can also be constructed in a calm water area less affected by waves, for example, in a sea area outside the breakwater 50 or in a sea area where the breakwater 50 is not provided. In this embodiment, a case where a pier is constructed as the floating structure 10 is exemplified, but the same effect as that of constructing a pier can be achieved when a floating structure is constructed in the sea area as the floating structure 10.

[0052] Each of the assembled parts of the wind power generation device 3 is large in size and weight, and the divided members 4a, nacelle hub 5, and blades 6 that constitute the upper part of the tower 4 are installed at a relatively high position. Therefore, depending on the relative positions of the crane 30 of the SEP vessel 20, the floating structure 10, and the float 2, and the size of the crane 30 of the SEP vessel 20, it may be difficult to directly move the assembled parts temporarily placed on the floating structure 10 to the installation positions on the float 2 using the crane 30, or if the assembled parts temporarily placed on the floating structure 10 are directly moved to the installation positions on the float 2, the balance of the crane 23 may become unstable and a large load may be placed on the crane 23.

[0053] In such a case, as in this embodiment, by using the crane 23 of the SEP vessel 20 to transfer at least some of the assembly parts that were temporarily placed on the floating structure 10 to the SEP vessel 20 and then installing the transferred assembly parts on the floating body 2, the assembly work of the wind power generation equipment 3 can be carried out more stably and smoothly by the crane 23 of the SEP vessel 20.

[0054] In particular, as in this embodiment, if the divided parts 4a of the tower 4 that were temporarily placed on the floating structure 10 are transferred in an upright position to the SEP vessel 20, the swaying of the divided parts 4a when the divided parts 4a mounted on the SEP vessel 20 are lifted by the crane 23 and moved to the floating body 2 can be reduced, which is advantageous for smooth installation work of the divided parts 4a.

[0055] In addition, by transferring at least some of the assembly parts temporarily stored on the floating structure 10 to the SEP vessel 20, it is possible to quickly secure space on the floating structure 10 for temporarily storing the assembly parts of the wind power generation device 3 that constitute the next assembly 9 to be manufactured. This is therefore extremely effective when manufacturing multiple assemblies 9 in parallel.

[0056] In the present invention, when possible, the assembly parts of the wind turbine generator 3 temporarily placed on the floating structure 10 may be directly installed on the floating body 2 using the crane 23 of the SEP vessel 20.

[0057] As described above, the present invention, which uses a temporary floating structure 10 and an SEP vessel 20 installed in a sea area with a water depth of 8 m or more and 20 m or less, is a method suitable for constructing other types of floating offshore wind power facilities 1 except for the spar type, and is a method that is significantly different in concept from the construction of a spar type floating offshore wind power facility.

[0058] The reason for this is that, for example, when manufacturing a spar-type floating offshore wind turbine on land, as in the general construction method and the invention described in Patent Document 1, it is necessary to prepare a manufacturing base for the floating offshore wind turbine on land, such as a quay.

[0059] Also, for example, when an assembly of a spar-type float and a wind power generation device of a general structure is manufactured in an ocean area, it is necessary to place a spar-type float with a height of about 50 m to 100 m in an upright state in the water, and the spar-type float is placed in a deep ocean area with a water depth of about 100 m to 200 m. In a deep ocean area with a water depth of about 100 m to 200 m, the lifting legs 22 of the SEP vessel 20 cannot be landed on the seabed SB. Therefore, the SEP vessel 20 cannot be effectively used in the construction of a spar-type floating offshore wind power generation facility. In addition, it takes a lot of cost, effort, and time to build a temporary floating structure in a deep ocean area with a water depth of about 100 m to 200 m, and a large crane such as that mounted on the SEP vessel 20 must be installed on the floating structure. In addition, in a deep ocean area, the work of removing the floating structure and the work of restoring the state of the seabed SB also require a lot of cost and effort.

[0060] As described above, the present invention is a construction method discovered in consideration of the characteristics of other types of floating offshore wind power facilities 1 except for the spar type, and the technical concept is significantly different from the construction of a spar type floating offshore wind power facility. Note that, although the construction of a semi-submersible type floating offshore wind power facility 1 has been exemplified above, the same construction method can achieve the same effects when constructing a TLP type floating offshore wind power facility or a barge type floating offshore wind power facility. [Explanation of symbols]

[0061] 1. Floating offshore wind power generation facilities 2. Floating Body 2a Column 2b Concatenation 3. Wind power generation equipment 4. Tower 4a Partition 5 Nacelle hub 6 Blades 7 Mooring line 8. Anchor 9 Assembly 10 Floating structures 11 Support pile 12 Girder material 13 Deck materials 14 Braces 15 Mooring Facilities 16 Anti-shock equipment 20 Self-elevating platform vessel (SEP vessel) 21 Barge body 22 Lifting legs 23 Crane (mounted on a self-elevating barge) 30 Crane (located on the pier) 40 Carrier 50 Breakwater 60 Quay SB Undersea WL sea level position

Claims

1. A construction method for a floating offshore wind power generation facility, comprising a float moored in a target sea area and a wind power generation device erected on the float, in which the draft from the water surface to the bottom end of the float is 20 m or less when the float is moored in the target sea area, comprising: Construct a temporary floating structure in an area of ​​the ocean with a depth of 8m to 20m. an assembly of a nacelle hub, blades and tower constituting the wind turbine generator is transported to the floating structure, the assembly is temporarily placed on the floating structure, the float is transported by sea to the vicinity of the floating structure and is set down on the seabed; using a crane of a self-elevating barge parked near the floating structure, the assembly components are sequentially installed on the floating body to manufacture an assembly in which the wind 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 floated from the seabed and transported over sea to the target sea area for installation, and the assembly is moored in the target sea area for installation.

2. The construction method for a floating offshore wind power facility according to claim 1 , wherein a pier or a floating structure is constructed in the sea area as the above-water structure.

3. 3. A construction method for a floating offshore wind power facility as described in claim 1 or 2, wherein, when using the self-elevating barge to sequentially install the assembly parts on the floating body, at least some of the assembly parts that have been temporarily placed on the water structure are transferred to the self-elevating barge, and the transferred assembly parts are installed on the floating body.

4. 3. The construction method for a floating offshore wind power facility according to claim 1 or 2, wherein the above-water structure is constructed in a sea area inside a breakwater.

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