Building method for spar-type offshore wind power generation facility

Abstract

To efficiently build a spar-type offshore wind power generation facility by assembling a top unit structure of the facility at once in construction and to enable work to be carried out stably by suppressing oscillation especially when heavy matter is hung by a semi-sub type crane used in construction.SOLUTION: A building method for a spar-type offshore wind power generation facility 1 includes: a first step for carrying out assembly of a top unit structure 12 of an offshore wind power generation facility composed of a tower 6, a nacelle 8, and a blade 9 on a frame 13 for assembly in a sea area selected as a calm area with comparatively mild waves; a second step for lifting the top unit structure 12 assembled on the frame 13 for assembly at once by a semi-sub type crane 2 provided with a mobile type counter weight device 3 on the deck surface to transport the top unit structure to a building site for the offshore wind power generation facility 1; a third step for retaining a floating body 4 offshore in a standing state; and a fourth step for completing the offshore wind power generation facility 1 by coupling the top unit structure 12 to the top unit of the floating body 4 in a lifted state by the semi-sub type crane 2.SELECTED DRAWING: Figure 17

Description

[Technical field]

[0001] The present invention relates to a method for constructing a spar-type offshore wind power generation facility for stably and collectively constructing the superstructure (tower, nacelle, and blades) of the offshore wind power generation facility. [Background technology]

[0002] Traditionally, hydroelectric, thermal and nuclear power generation have been the main power generation methods used, but in recent years, wind power generation, which uses natural wind to generate electricity, has been attracting attention from the perspective of the environment and the effective use of natural energy. Wind power generation facilities can be installed on land or on water (mainly offshore), but in Japan, which has mountainous terrain behind its coasts, there are few plains in coastal areas where stable winds can be expected. On the other hand, Japan is surrounded by sea on all sides, and has the advantage that winds suitable for generating electricity can be easily obtained on the sea and there are fewer restrictions on installation. For this reason, many different types of offshore wind power generation facilities and floating structures have been proposed in recent years.

[0003] The floating structure can be broadly classified into a barge type float, which floats on the water surface, a semi-submersible type, in which the lower part of the float is submerged below the water surface to float in a semi-submerged state, and a spar type, which floats in an upright position like a fishing float.

[0004] With regard to the spar-type float, the applicant has proposed in Patent Document 1 listed below an offshore wind power generation facility consisting of a float, mooring lines, a tower, and a nacelle and multiple wind turbine blades installed at the top of the tower, wherein the float is an offshore wind power generation facility with a spar-type floating structure consisting of a lower concrete floating structure part (hereinafter referred to as the concrete floating structure part) in which concrete precast cylindrical bodies are stacked vertically in multiple tiers and each precast cylindrical body is fastened and integrated with PC steel members, and an upper steel floating structure part (hereinafter referred to as the steel floating structure part) connected to the upper side of this lower concrete floating structure part (hereinafter referred to as the steel floating structure part).

[0005] In the method of constructing the float of the spar-type offshore wind power generation facility, as shown in Fig. 22, the steel floating part is divided into steel rings of a predetermined weight and then the steel rings are welded together to complete the steel floating part. The steel floating part is then loaded onto a barge and transported to the on-site fabrication yard, where it is unloaded (landed) at a quay using a large crane ship of 1300t class. Meanwhile, the concrete floating part is manufactured in a concrete manufacturer's factory in a state where each ring is divided into several parts in the circumferential direction for the convenience of truck transportation, and these divided rings are transported by truck to the on-site fabrication yard where they are joined together in the circumferential direction. Then, the concrete floating part is completed by connecting each ring in the longitudinal direction using PC steel material, and finally, the steel floating part and the concrete floating part are joined together using a large crane ship of 1300t class to complete the float. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Patent No. 5274329 [Patent Document 2] JP 2012-201219 A Summary of the Invention [Problem to be solved by the invention]

[0007] When constructing a spar-type offshore wind power generation facility offshore, it is desirable to install wind turbine equipment such as the tower, nacelle, and blades with the spar-type float floating on the ocean in a bay with calm waves. However, while the draft (part below the water surface) of the spar-type float is deep, at approximately 70 m or more, the water depth in a bay is generally shallower than this, making construction in the bay difficult. As such, the installation of the wind turbine equipment has traditionally been carried out outside the bay where the water is deep, using a large crane ship 70, as shown in Figure 23 (see Patent Document 2).

[0008] However, at present, there are only a few large crane ships in Japan that are capable of constructing offshore wind power generation facilities, and the daily usage fee (charter fee) is expensive, which poses the problem of huge charter costs.In response to this, in recent years, semi-submersible cranes equipped with cranes on semi-submersible floats have been manufactured for the construction of offshore wind power generation facilities, but since semi-submersible floats have a lighter weight than large crane ships, they are more susceptible to the effects of waves and lack stability, and when heavy objects such as towers and nacelles are hoisted, the entire float will shake and become unstable, which can cause problems during the assembly work of the wind power generation facilities.

[0009] Therefore, the main object of the present invention is to provide a method for constructing a spar-type offshore wind power generation facility, which improves the efficiency of construction by assembling the upper structure of the spar-type offshore wind power generation facility in a single construction project, and which enables the semi-submersible crane used for construction to carry out work stably by suppressing swaying, especially when suspending heavy loads. [Means for solving the problem]

[0010] In order to solve the above problems, the present invention according to claim 1 provides a method for constructing a spar-type offshore wind power generation facility, comprising the steps of: A first step is to assemble the upper structure of the offshore wind power generation equipment, which consists of a tower, a nacelle, and blades, on an assembly stand in a sea area selected as a calm area with relatively calm waves; A second step of lifting the upper structure assembled on the assembly stand together by a semi-submersible crane equipped with a mobile counterweight device on the deck surface and transporting it to a construction site of the offshore wind power generation facility; After assembling the entire float on the quay, the completed float is transported by a semi-submersible spud barge to the construction site of the offshore wind power generation facility, and the float is floated off into the ocean. The third step is to attach mooring lines to hold the float in an upright position. A method for constructing a spar-type offshore wind power generation facility is provided, comprising a fourth step of connecting the upper structure to the top of the float while it is hoisted by the semi-submersible crane to complete the offshore wind power generation facility.

[0011] In the invention described in claim 1, the superstructure of the offshore wind power generation facility, which is composed of the tower, nacelle, and blades, is assembled on an assembly platform in a sea area selected as a calm area with relatively calm waves (first step). Next, the superstructure assembled on the assembly platform is lifted together by a semi-submersible crane equipped with a mobile counterweight device on the deck surface and transported to the construction site of the offshore wind power generation facility (second step).

[0012] On the other hand, after the entire float is assembled on the quay, the completed float is transported to the construction site of the offshore wind power generation facility by a semi-submersible spud barge, and once the float is floated off into the ocean, mooring lines are attached to hold the float in an upright position (third step). This third step is a separate process from the first and second steps, and may be performed before or after the first and second steps. It may also be performed simultaneously.

[0013] The upper structure is quite heavy, but since the semi-submersible crane is designed with a mobile counterweight device installed on the deck surface, when the upper structure is lifted by the crane, the weight of the mobile counterweight device is moved to a position where rocking due to the lifting load can be suppressed, thereby suppressing the rocking of the hull and achieving stabilization.

[0014] Finally, the superstructure is connected to the top of the float while still hoisted by the semisubmersible crane to complete the offshore wind power generation facility (fourth step). In this invention, the superstructure of the spar-type offshore wind power generation facility is assembled in one go using a semisubmersible crane, which makes construction more efficient. In addition, the semisubmersible crane is equipped with a mobile counterweight device, which makes it possible to perform work stably by suppressing shaking, especially when a heavy load is suspended.

[0015] As the present invention according to claim 2, there is provided a method of constructing a spar-type offshore wind power generation facility as set forth in claim 1, in which the float is a spar-type float consisting of a concrete floating body section formed by stacking concrete rings in a plurality of tiers and fastening each concrete ring with prestressing steel members to form an integrated unit, and a steel floating body section connected to the upper side of the concrete floating body section, or a spar-type float consisting of a concrete float consisting of stacking concrete rings in a plurality of tiers and fastening each concrete ring with prestressing steel members to form an integrated unit.

[0016] The invention described in claim 2 specifically defines the structure of the float. Specifically, the float structure may be a spar-type float consisting of a concrete float section in which concrete rings are stacked in a number of stages and each concrete ring is fastened and integrated with prestressing steel members, and a steel float section connected to the upper side of the concrete float section, or a spar-type float consisting of a concrete float in which concrete rings are stacked in a number of stages and each concrete ring is fastened and integrated with prestressing steel members.

[0017] The present invention according to claim 3 provides a method for constructing a spar-type offshore wind power generation facility according to claim 1, in which a SEP barge, a monopile foundation, a jacket foundation or a caisson foundation is used as the assembly frame.

[0018] The invention described in claim 3 above shows a specific example of an assembly platform. Specifically, the assembly platform can be a SEP barge, a monopile foundation, a jacket foundation, or a caisson foundation.

[0019] As the present invention related to claim 4, there is provided a method of constructing a spar-type offshore wind power generation facility as described in claim 1, in which the mobile counterweight device is made movable in any direction by providing a running part on the underside of the weight, a winch is placed at the four or three corners, or at the front and rear of the weight, a wire is paid out from the winch and connected to the weight, and the weight is moved and controlled to a predetermined position by operating the winch.

[0020] The invention described in claim 4 specifically defines the structure of a mobile counterweight device. Specifically, a suitable example is a device in which a running part is provided on the underside of the weight to allow it to move in any direction, a winch is placed in an appropriate position, and the weight is controlled to move to a specified position by operating the winch. Effect of the Invention

[0021] As explained above in detail, according to the present invention, the superstructure of a spar-type offshore wind power generation facility can be assembled in a single operation, thereby improving the efficiency of construction, and the semi-submersible crane used in construction can perform work stably by reducing swaying, especially when suspending heavy loads. [Brief description of the drawings]

[0022] [Figure 1] FIG. 1 is an overall view of a spar-type offshore wind power generation facility 1. [Diagram 2] FIG. [Diagram 3] 1 shows a precast cylindrical body 15, in which (A) is a longitudinal cross-sectional view, (B) is a plan view (viewed in the direction of the arrow BB), and (C) is a bottom view (viewed in the direction of the arrow CC). [Figure 4] 1A and 1B are diagrams showing how precast cylindrical bodies 15 are fastened together. [Diagram 5] 1 is an enlarged vertical cross-sectional view showing the boundary between a concrete floating body portion 4A and a steel floating body portion 4B. [Figure 6] 1A and 1B show a semi-submersible crane 2 according to the present invention, in which (A) is a side view and (B) is a plan view thereof. [Figure 7] FIG. 2 is a plan view showing another example of the movable counterweight device 3. [Figure 8] FIG. 2 is a plan view showing yet another example of the movable counterweight device 3. [Figure 9] 1 shows a construction procedure (part 1) for the spar-type offshore wind power generation facility 1 according to the present invention. [Figure 10] 2 shows a construction procedure (part 2) for the spar-type offshore wind power generation facility 1 according to the present invention. [Figure 11] 3 shows the construction procedure (part 3) of the spar-type offshore wind power generation facility 1 according to the present invention. [Figure 12] 4 shows the construction procedure (part 4) of the spar-type offshore wind power generation facility 1 according to the present invention. [Figure 13] 5 shows the construction procedure (part 5) of the spar-type offshore wind power generation facility 1 according to the present invention. [Figure 14] 6 shows the construction procedure (part 6) of the spar-type offshore wind power generation facility 1 according to the present invention. [Figure 15] 7 shows the construction procedure (part 7) of the spar-type offshore wind power generation facility 1 according to the present invention. [Figure 16] 8 shows the construction procedure (part 8) of the spar-type offshore wind power generation facility 1 according to the present invention. [Figure 17] 9 shows the construction procedure (part 9) of the spar-type offshore wind power generation facility 1 according to the present invention. [Figure 18] This shows the construction procedure (part 10) of the spar-type offshore wind power generation facility 1 according to the present invention. [Figure 19] FIG. 11 is an assembly procedure diagram of an upper structure showing another example of the assembly stand 13. [Figure 20] FIG. 11 is an assembly procedure diagram of an upper structure showing another example of the assembly stand 13. [Figure 21] FIG. 11 is an assembly procedure diagram of an upper structure showing another example of the assembly stand 13. [Figure 22] FIG. 1 is a flow chart showing a conventional floating body construction method. [Figure 23] FIG. 1 is a diagram showing a procedure for integrated construction using a large crane ship 70 in Patent Document 2. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0023] Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.

[0024] [Hybrid spar-type offshore wind power generation facility 1] First, a spar-type offshore wind power generation facility 1 to which the present invention is applied will be described in detail with reference to Figs. 1 to 5.

[0025] As shown in detail in Figure 1, the spar-type offshore wind power generation facility 1 is composed of a spar-type cylindrical floating body 4, mooring lines 10, a tower 6, and a wind turbine 7 consisting of a nacelle 8 installed on the top of the tower 6 and a number of blades 9, 9...

[0026] As shown in FIG. 2, the float 4 comprises a concrete floating section 4A in which concrete precast cylindrical bodies 15, 15... are stacked vertically in multiple tiers and each precast cylindrical body 15, 15... is fastened together with PC steel members 19 to form an integrated body, and a steel floating section 4B connected to the upper side of the concrete floating section 4A.

[0027] Ballast materials such as water, gravel, fine aggregate, coarse aggregate, and metal particles can be charged or discharged into or from the hollow portion of the floating body 4, making the buoyancy (draft) adjustable. The charging / discharging of ballast materials is possible by employing the fluid transport method previously proposed by the applicant in JP 2012-201217 A.

[0028] The concrete floating section 4A is composed of concrete precast cylindrical bodies 15, 15.... As shown in Fig. 3, the precast cylindrical bodies 15 are circular cylindrical precast members having the same cross section in the axial direction, and each is manufactured using the same formwork, or a hollow precast member manufactured by centrifugal molding is used.

[0029] In addition to the reinforcing bars 20, sheaths 21, 21... for inserting the PC steel bars 19 are embedded in the wall surface at appropriate intervals in the circumferential direction. The lower ends of these sheaths 21, 21... are formed with sheath enlarged diameter sections 21a so that couplers for connecting the PC steel bars 19 can be inserted, and the upper sections are formed with box-opening sections 22 for fitting in anchor plates for fixing. In addition, a plurality of hanging fittings 23 are provided on the upper surface.

[0030] As shown in Fig. 4(A), the precast cylindrical bodies 15 are fastened together by stacking the precast cylindrical bodies 12, 12 while inserting the PC steel members 19, 19... extending upward from the lower precast cylindrical body 15 into the sheaths 21, 21..., and then fitting the anchor plate 24 into the box-out portion 22 and introducing tension into the PC steel members 19 with the nut member 25 to integrate them. Furthermore, grout material is injected into the sheath 21 from the grout injection hole 27. The hole 24a formed in the anchor plate 24 is a grout injection confirmation hole, and the filling of the grout material is completed when the grout material is discharged from the confirmation hole.

[0031] 4(B), couplers 26 are screwed onto the protruding parts of the prestressing steel 19 to connect the upper prestressing steel members 19, 19..., and then the prestressing steel members 19, 19... are stacked while being inserted into the sheaths 21, 21... of the upper precast tubular body 15, and the procedure of fixing the prestressing steel members 19 in place in the above manner is repeated in order to stack them up in the height direction. At this time, an adhesive 28 such as an epoxy resin-based adhesive or sealant is applied to the joint surfaces between the lower precast tubular body 15 and the upper precast tubular body 15 to ensure watertightness and to bond the mating surfaces.

[0032] The steel floating body section 4B is composed of a steel cylindrical body 17 located relatively on the lower side, and a steel cylindrical body 18 located relatively on the upper side. The lower part of the steel cylindrical body 17 on the lower side has the same outer diameter as the precast cylindrical body 15, and as shown in Figure 5, it is connected to the precast cylindrical body 15 by bolts or welding (bolt fastening is shown in the illustrated example). The upper part of the steel cylindrical body 17 forms a truncated cone shape with a gradually narrowing diameter.

[0033] The upper steel cylindrical body 18 is a cylindrical body with an outer diameter dimension that is continuous with the upper outer diameter of the lower steel cylindrical body 17, and is connected to the lower steel cylindrical body 17 by bolts or welding or the like (bolt fastening is shown in the illustrated example). These steel cylindrical bodies 17, 18 are composed of steel rings divided for each predetermined weight, and the steel rings are integrated by welding in the circumferential direction.

[0034] On the other hand, the tower 6 is made of steel, concrete or PRC (prestressed reinforced concrete), but it is preferable to use one made of steel so that the total weight is small. The outer diameter of the tower 6 and the outer diameter of the upper steel cylindrical body 18 are almost the same, and the outer shape is continuous in the vertical direction without any steps.

[0035] As shown in Fig. 1, the mooring point P of the mooring line 10 to the float 4 is set below the sea surface and at a position higher than the center of gravity G of the float 4. This makes it possible to prevent a ship from coming into contact with the mooring line 10. Also, since a resistance moment is generated around the center of gravity G of the float 4 at the mooring point P so as to prevent the float 4 from tipping over too much, the tilting attitude of the tower 6 can be appropriately maintained.

[0036] On the other hand, the nacelle 8 is a device equipped with a generator that converts the rotation of the wind turbine 7 into electricity, a controller that can automatically change the angle of the blades 9, and the like.

[0037] [About Semi-submersible Crane 2] Before describing in detail the method for constructing the spar-type offshore wind power generation facility 1, the semi-submersible crane 2 used in this construction method will be described in detail with reference to Figs. 6 to 8.

[0038] As shown in Figure 6, the semi-submersible crane 2 is provided with a crane 5 on the deck surface of a semi-submersible float 11 which is composed of a number of columns 31, 31... serving as buoyant bodies and connecting members 33, 33... which connect these columns.

[0039] The semi-submersible float 11 comprises the multiple columns 31, three in the illustrated example, which serve as buoyant bodies. These columns 31 are cylindrical hollow structures, and the float base 30 of the semi-submersible float 11 is formed by arranging these columns 31, for example at the vertices of a polygon in a plan view, and then connecting these columns 1031, 31 with connecting members 33.

[0040] A deck body 38 is provided on the upper surface of the floating base 30, and a cantilever-shaped overhanging deck section 37 is provided on one end of the deck body 38. A movable counterweight deck section 39 is provided on the opposite side of the overhanging deck section 37, straddling the deck body 38. A frame structure 34 is arranged in a cantilever shape on the underside of the overhanging deck section 37 to provide structural reinforcement. Similarly, the movable counterweight deck section 39 is also structurally reinforced by frame structures 35, 36 arranged in a cantilever shape on the underside of the deck. The deck body 38 is gradually narrowed in width toward the left side of the drawing, and the overhanging deck section 37 is shaped like a bar overhanging from the tip edge of the deck body 38 and is located on the bow side. The movable counterweight deck section 39 is a space provided to ensure the movement range of the weight, and is located on the stern side. In addition, the deck main body 38 and the movable counterweight deck portion 39 have a step due to the deck overlap, but they may be flush.

[0041] The crane 5 is provided on the upper surface of the deck main body 38 of the semi-submersible floating body 11, near the overhanging deck portion 37. The crane 5 is installed directly above the column 31, so that the load from the crane 5 is directly transmitted to the column 31. A fixed type is preferable as the crane 5, but a mobile crane may be mounted on the deck main body 38 in some cases. In any case, it is necessary for the crane to have a lifting capacity and lifting height capable of erecting the tower 6, nacelle 8, and blades 9 of the offshore wind power generation facility. Furthermore, when a tower crane is used, the self-elevating structure makes it easy to ensure the desired lifting height.

[0042] A tower gripping device 40 is provided at the tip of the extending deck portion 37 for integrally fixing the tower of the offshore wind power generation facility to the semi-submersible crane 2. The tower gripping device 40 is a gripper mechanism that can be opened and closed.

[0043] A mobile counterweight device 3 is provided on the upper surface of the mobile counterweight deck 39. As shown in FIG. 6(B), the mobile counterweight device 3 is configured to be movable in any direction by providing a running part on the underside of a weight 42, and has winches 41A-41D at the four corners, with wires 43a-43d unwound from the winches 41A-41D connected to the corners of the weight 42, respectively, and the weight 42 is controlled to move to a predetermined position by operating the winches 41A-41D. In the mobile counterweight device 3, the weight 42 can be moved to any position within the X and Y planes in a plan view. It is preferable to control the winches 41A-41D by coordinated control using a computer (not shown).

[0044] As shown in the figure, the weight 42 has a box-shaped structure and the weight can be adjusted by putting ballast material such as slag aggregate inside, or by putting in a combination of steel material or the like if the weight is insufficient.

[0045] As shown in Fig. 7, the winches 41A to 41C may be arranged at three corners of the apex of a substantially equilateral triangle, and the wires 43a to 43c that are paid out from the winches 41A to 41C may be connected to the weight 42, respectively, and the weight 42 may be moved and controlled to a predetermined position by operating the winches 41A to 41C. Alternatively, as shown in Fig. 8, the winches 41A and 41B may be arranged at the front and rear parts straddling the weight 42, and the wires 43a and 43b that are paid out from the winches 41A and 41B may be connected to the weight 42, and the weight 42 may be moved and controlled to a predetermined position in the Y direction by operating the winches 41A and 41B. In this case, it is preferable to provide movement guides 44, 44 on both sides of the weight 42 so that the weight 42 can only move in the Y direction.

[0046] It is desirable to provide fin stabilizers 32, 32 in the submersible portion of the semi-submersible float 11, as shown in FIG. 6, to enhance stability against waves.

[0047] [Construction method for spar-type offshore wind power generation facility 1] Next, a method for constructing the spar-type offshore wind power generation facility 1 using the semi-submersible crane 2 will be described in detail with reference to Figs.

[0048] <First step> As shown in Fig. 9, once the SEP barge 11 with crane is docked at the quay at the quay yard, the tower 6, nacelle 8 and blades 9, 9 ... are loaded onto the SEP barge 11 using a crane 50. The SEP barge 11 with crane is provided with vertically extending columns (hereinafter also referred to as "lifting legs") at three or four points on the barge that can be raised and lowered, and is equipped with a hydraulic jack system that drives the lifting legs up and down, so that the lifting legs can be lowered downward to support their lower ends on the seabed, and the barge portion can be raised above the sea surface by continuing to lower the lifting legs, and a crane 45 is integrally provided on the barge to allow loading and unloading of cargo onto and from the barge.

[0049] Next, as shown in FIG. 10, an assembly platform 13 is provided in a sea area selected as a calm area with relatively calm waves. This assembly platform 13 is a platform for assembling the superstructure 12 of the offshore wind power generation facility 1, which is composed of the tower 6, the nacelle 8, and the blades 9. In the illustrated example, an SEP barge 46 is used as the assembly platform 13. The SEP barge 46 is a barge equipped with vertically extending piers (lifting legs) at three or four points on the barge, and as shown in FIG. 10, the barge can be stably supported by landing the lifting legs on the seabed. In the illustrated example, a semi-submersible spud barge 46 (with lifting legs), which will be described later, is used as the SEP barge.

[0050] During assembly, the SEP barge 11 with crane is pulled up alongside the assembly stand 13 and the lifting legs are lowered to position the barge portion above sea level, and the tower 6, nacelle 8, and blades 9 are assembled in that order on the assembly stand 13 to complete the upper structure 12.

[0051] <Second process> In the next second step, as shown in Figure 11, the semisubmersible crane 2 is pulled alongside the crane-equipped SEP barge 11, and the assembled superstructure 12 is suspended by the crane 5. At this time, the lower end of the tower 6 is held by the tower holding device 40 to prevent the superstructure 12 from swinging as much as possible. In addition, since the superstructure 12 is quite heavy at this time, the weight 42 of the mobile counterweight device 3 is moved rearward to stabilize the hull, which has swayed forward due to the suspended load, horizontally.

[0052] Once the upper structure 12 has been suspended by the semi-submersible crane 2, the semi-submersible crane 2 is transported by a towing vessel 47 to the construction site of the spar-type offshore wind power generation facility 1, as shown in FIG. 12.

[0053] <Third step> The third step is a process carried out separately from the first and second steps, and may be carried out before or after the first and second steps. Also, the third step may be carried out simultaneously in parallel.

[0054] The third step is a work process in which, after all the parts of the float 4 have been assembled at the quay, the completed float 4 is transported by a semi-submersible spud barge 46 to the construction site of the spar-type offshore wind power generation facility 1, and once the float 4 has been floated offshore, mooring lines are attached to hold the float 4 in an upright position.

[0055] Specifically, first, the float 4 is completed in a quay yard. As a method for constructing the float, the method proposed by the present applicant in JP 2018-173011 A can be suitably adopted.

[0056] The floating structure construction method is as shown in FIG. 13, in which a steel ring connection yard A, a concrete ring fabrication yard B, and a concrete ring connection yard C are defined in a wharf yard.

[0057] In the steel ring connecting yard A, a first bridge crane 50 is installed so that it can travel in a fixed direction, rotating platforms 52, 52... are installed at appropriate intervals in the direction of travel of the first bridge crane, and a mobile tent 56 is also provided that can move in the direction of travel of the first bridge crane. In the concrete ring production yard B, a mobile tent 57 is installed, and a complete set of concrete ring manufacturing equipment is also installed. In the concrete ring connecting yard C, a second bridge crane 55 is installed so that it can travel in a fixed direction, and a mobile tent 58 is also provided that can move in the direction of travel of the second bridge crane.

[0058] The method for constructing a floating body for a spar-type offshore wind power generation facility includes a first step of installing the steel rings 51, 51... on the rotating frames 52, 52... in that order using the first bridge crane 50, and covering them with a mobile tent 56 if necessary, and connecting the steel rings 51, 51... by welding them circumferentially while rotating them about their axis, thereby completing the steel floating body section 53B; and a second step of moving the steel floating body section 53B to the concrete ring connecting yard C and installing it in a predetermined position, and then transporting the concrete rings 54 fabricated in the concrete ring fabrication yard B in that order to the concrete ring connecting yard C, and covering them with a mobile tent 58 if necessary, and connecting the concrete rings 54 to the steel floating body section 53B using the second bridge crane 55, and fastening them together with PC steel to complete the float 53. Once the float 4 has been completed in this manner, it is moved sideways to a semi-submersible spud barge 46 at the quay for loading (roll-on), as shown in Fig. 14. This semi-submersible spud barge 46 is a barge whose draft can be adjusted to a semi-submerged state by adjusting the ballast water, and after the cargo is rolled on (loaded) onto the barge while adjusting the ballast water, the cargo can be floated offshore by adjusting the ballast water to make it semi-submerged. Therefore, once the float 4 is transported to the construction site, it can be floated and launched on the sea in a semi-submerged state without a crane.

[0059] Once the semi-submersible spud barge 46 has been towed by the towing vessel 47 and transported to the construction site of the spar-type offshore wind power generation facility 1, the semi-submersible spud barge 46 is semi-submerged to launch and float the floater 4 on the sea (roll off), as shown in Fig. 15. Then, ballast water is poured into the floater 4 to raise it upright and place it in a vertical position.

[0060] It is desirable to attach mooring ropes 10, 10 . . . to the floating body 4 in the vertical position as shown in FIG. <Fourth step> In the fourth step, as shown in Figures 17 and 18, the upper structure 12 is lifted by the semi-submersible crane 2 and connected to the top of the floating body 4 to complete the spar-type offshore wind power generation facility 1.

[0061] [Other examples] (1) In the above embodiment, a SEP barge (semi-submersible spud barge) 46 is used as the assembly base 13, but as shown in Fig. 19, a monopile foundation 48 may be used as the assembly base 13, or as shown in Fig. 20, a jacket foundation 49 may be used as the assembly base 13. Furthermore, as shown in Fig. 21, a caisson foundation 59 may be used as the assembly base 13.

[0062] (2) The above embodiment is directed to a spar-type float in which the float 4 is made up of a concrete floating section 4A and a steel floating section 4B connected to the upper side of the concrete floating section 4A, but it is also possible to construct a spar-type float in which the float 4 is made up of only the concrete floating section 4A in which the concrete rings 15, 15... are stacked in multiple tiers and each concrete ring 15, 15... is fastened and integrated with PC steel members 19 in a similar manner. Of course, the same can be said for other floating structures.

[0063] (3) In the above example, a semi-submersible crane 2 was used as a crane ship for constructing the upper structure 12 of the spar-type offshore wind power generation facility 1 in one go, but it is also possible to use a crane ship equipped with a mobile counterweight device 3 as a crane ship. [Explanation of symbols]

[0064] 1...Spar-type offshore wind power generation equipment, 2...Semi-submersible crane, 3...Mobile counterweight device, 4...Floating body, 4A...Concrete floating body section, 4B...Steel floating body section, 5·45...Crane, 6...Tower, 7...Wind turbine, 8...Nacelle, 9...Blade, 10...Mooring line, 11...SEP barge with crane, 12...Superstructure, 13...Assembly stand, 15·16...Precast cylindrical body (concrete ring), 19...PC steel, 46...Semi-submersible spud barge, 48...Monopile foundation, 49...Jacket foundation, 59...Caisson foundation

Claims

1. A method for constructing a spar-type offshore wind power generation facility, comprising the steps of: A first step of assembling an upper structure of an offshore wind power generation facility, which includes a tower, a nacelle, and blades, on an assembly stand in a sea area selected as a calm area with relatively calm waves; A second step of lifting the upper structure assembled on the assembly stand together by a semi-submersible crane equipped with a mobile counterweight device on the deck surface and transporting it to a construction site of the offshore wind power generation facility; After assembling the entire float on the quay, the completed float is transported to the construction site of the offshore wind power generation facility by a semi-submersible spud barge, and once the float is floated off into the ocean, mooring lines are attached to hold the float in an upright position; and and a fourth step of connecting the upper structure to the top of the float while it is hoisted by the semi-submersible crane to complete the offshore wind power generation facility.

2. 2. The method for constructing a spar-type offshore wind power generation facility according to claim 1, wherein the float is a spar-type float consisting of a concrete float section formed by stacking concrete rings in a plurality of stages and fastening each concrete ring with PC steel to form an integrated unit, and a steel float section connected to the upper side of the concrete float section, or a spar-type float consisting of a concrete float formed by stacking concrete rings in a plurality of stages and fastening each concrete ring with PC steel to form an integrated unit.

3. 2. The method for constructing a spar-type offshore wind power generation facility according to claim 1, wherein a SEP barge, a monopile foundation, a jacket foundation or a caisson foundation is used as the assembly frame.

4. The method for constructing a spar-type offshore wind power generation facility as described in claim 1, wherein the movable counterweight device is capable of moving in any direction by providing a running part on the underside of the weight, and a winch is placed at the four or three corners, or at the front and rear of the weight, and a wire pulled out from the winch is connected to the weight, and the weight is moved and controlled to a predetermined position by operating the winch.

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