Method for constructing spar-type offshore wind power generation facility

Abstract

[Problem] To provide a method for constructing a spar-type offshore wind power generation facility while simply compensating shortage of crane lift height of a SEP barge equipped with a crane. [Solution] This method comprises: a first step for assembling an upper structure body 12 on a semi-submersible spud barge 46 by using a SEP barge 14 equipped with a crane, while using the semi-submersible spud barge 46 as an assembling frame 13 in a sea area of relatively calm waves, with the semi-submersible spud barge 46 being submerged or set on the seabed; a second step for lifting the assembled upper structure body 12 all at once by a large crane ship 2 and carrying the assembled upper structure body 12 to a construction place of an offshore wind power generation facility 1, after floating the assembling frame 13; a third step for holding a floating body 4 on the ocean in a standing state; and a fourth step for completing the offshore wind power generation facility 1 by connecting the upper structure body 12 to an upper part of the floating body 4 while the upper structure body 12 is lifted by the large crane ship 2.

Description

Construction method for spar-type offshore wind power generation facilities

[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.

[0002] Traditionally, hydroelectric, thermal, and nuclear power generation have been the primary power generation methods, but in recent years, wind power generation, which utilizes natural wind to generate electricity, has been attracting attention from the perspective of environmental friendliness 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 along the coast where stable winds can be expected. On the other hand, Japan is surrounded by sea on all sides, and the sea offers the advantage of easily obtaining winds suitable for power generation and fewer restrictions on installation. For this reason, various 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 barge-type floats that float on the water surface, semi-submersible floats that float in a semi-submerged state with the lower part of the float submerged below the water surface, and spar-type floats that float 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 comprising a float, mooring lines, a tower, a nacelle and a plurality of 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 comprising a lower concrete floating structure part (hereinafter referred to as the concrete floating structure part) formed by stacking concrete precast cylindrical bodies in multiple tiers in the height direction and fastening the precast cylindrical bodies together with PC steel steel, and an upper steel floating structure part (hereinafter referred to as the steel floating structure) connected to the upper side of the lower concrete floating structure part (hereinafter referred to as the steel floating structure).

[0005] In a floater construction method for the spar-type offshore wind power generation facility, as shown in Fig. 22, the steel floating body is divided into steel rings of a predetermined weight at a shipyard, and then these steel rings are welded together to complete the steel floating body. The steel floating body is then loaded onto a barge and transported to an on-site fabrication yard, where it is unloaded (landed) at a quay using a large 1300-ton crane ship. Meanwhile, the concrete floating body is manufactured at a concrete manufacturer's factory, with each ring divided circumferentially for ease of truck transport. These divided rings are transported by truck to the on-site fabrication yard, where they are joined together circumferentially, and then the rings are joined longitudinally using PC steel to complete the concrete floating body. Finally, the steel floating body and the concrete floating body are joined together using a large 1300-ton crane ship to complete the float.

[0006] Japanese Patent No. 5274329 Japanese Patent Application Laid-Open No. 2012-201219

[0007] When constructing a spar-type offshore wind power generation facility offshore, it is desirable to install the tower, nacelle, blades, and other superstructures while the spar-type float is floating on the ocean in a bay with calm waves. However, the draft (the part below the water surface) of the spar-type float is deep, at approximately 70 m or more, while the water depth in a bay is generally shallower, making construction in the bay difficult. Therefore, when installing the wind turbine facility, it has been customary to use a large crane barge 70 outside the bay where the water is deep, as shown in Figure 23 (see Patent Document 2).

[0008] When assembling the superstructure, since the waters outside the deep bay are susceptible to the effects of wind and waves, it has been proposed to use a crane-equipped SEP barge to assemble the superstructure, including the tower, nacelle, and blades, in a sea area selected as a calm area with relatively calm waves.However, as offshore wind power generation facilities have become larger, there have been cases where the crane lifting height cannot be secured with the current crane-equipped SEP barge, and a simple method of compensating for the lack of crane lifting height has been desired.

[0009] On the other hand, with regard to the work of connecting the superstructure to a floating body floating on the ocean using a large crane barge 70 outside a deep bay, there are currently only a few large crane barges in Japan that are capable of constructing offshore wind power generation facilities, and the daily usage fee (charter fee) is high, resulting in enormous charter costs. Therefore, in recent years, semi-submersible cranes equipped with cranes on semi-submersible floaters have been manufactured for the construction of offshore wind power generation facilities, but because semi-submersible floaters have a lighter weight than large crane barges, they are more susceptible to the effects of waves and lack stability. In addition, when heavy objects such as a tower or nacelle are hoisted, the entire floater will rock and become unstable, which could cause problems during the assembly work of the wind power generation facility.

[0010] Therefore, the first object of the present invention is to provide a method for constructing a spar-type offshore wind power generation facility in a sea area selected as a calm area with relatively calm waves, using a crane-equipped SEP barge to assemble superstructures such as a tower, nacelle, and blades, while easily compensating for the lack of crane lifting height of the crane-equipped SEP barge.

[0011] The second challenge is to ensure stable operation by suppressing the shaking that occurs when a heavy object is suspended when connecting the upper structure of a spar-type offshore wind power generation facility to a floating body in a single operation using a semi-submersible crane.

[0012] In order to solve the first problem, the present invention according to claim 1 provides a method for constructing a spar-type offshore wind power generation facility, comprising: a first step of using a semi-submersible spud barge as an assembly platform in a sea area selected as a calm area with relatively calm waves, and assembling the superstructure of the offshore wind power generation facility, consisting of a tower, nacelle, and blades, on the semi-submersible spud barge using a SEP barge with a crane while the semi-submersible spud barge is submerged or anchored on the seabed; a second step of floating the semi-submersible spud barge, and then using a large crane ship to lift the superstructure assembled on the assembly platform all at once and transporting it to the construction site of the offshore wind power generation facility; and a third step of assembling the entire floater on the quay, transporting the completed floater to the construction site of the offshore wind power generation facility by the semi-submersible spud barge, and once the floater has floated off into the sea, attaching mooring lines to hold the floater in an upright position. and a fourth step of connecting the upper structure to the top of the floating body while it is still lifted by the large crane ship, thereby completing the offshore wind power generation facility.

[0013] In the invention described in claim 1, a semi-submersible spud barge is used as an assembly platform in a sea area selected as a calm area with relatively calm waves, and while the semi-submersible spud barge is submerged or resting on the seabed, a crane-equipped SEP barge is used to assemble the superstructure of the offshore wind power generation facility, consisting of the tower, nacelle, and blades, on the semi-submersible spud barge (first step). By using a semi-submersible spud barge as the assembly platform and completing the superstructure with the semi-submersible spud barge submerged or resting on the seabed, it is possible to secure an additional lifting height for the crane used for assembly by the height of the submerged or resting spud barge, thereby eliminating the need for a crane lifting height when assembling an ultra-large offshore wind power generation facility.

[0014] Next, once the assembly of the superstructure is completed on the assembly platform (a submerged or bottom-mounted semi-submersible spud barge), the submerged or bottom-mounted semi-submersible spud barge is raised to the surface and then lifted all together using a large crane barge equipped with a mobile counterweight device on its deck, and transported to the construction site of the offshore wind power generation facility (second step).

[0015] On the other hand, after the entire floater is assembled at the quay, the completed floater is transported to the construction site of the offshore wind power generation facility by a semi-submersible spud barge, and once the floater is floated offshore, mooring lines are attached to hold the floater 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 in parallel.

[0016] The upper structure is quite heavy, but the semi-submersible crane is designed with a mobile counterweight device on the deck surface, so when the upper structure is lifted by the crane, the weight of the mobile counterweight device is moved to a position where the rocking caused by the lifting load can be suppressed, thereby suppressing the rocking of the hull and achieving stability.

[0017] Finally, the superstructure is lifted by the large crane ship and connected to the top of the floating body to complete the offshore wind power generation facility (fourth step).

[0018] As a second aspect of the present invention, there is provided a method for constructing a spar-type offshore wind power generation facility as set forth in claim 1, wherein 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 together with prestressing steel members, and a steel floating body section connected to the upper side of this concrete floating body section, or a spar-type float consisting of a concrete float formed by stacking concrete rings in a plurality of tiers and fastening each concrete ring together with prestressing steel members.

[0019] The invention of claim 2 specifically defines the structure of the float. Specifically, the float structure can be a spar-type float consisting of a concrete floating section made of concrete rings stacked in multiple stages and fastened together with prestressing steel bars, and a steel floating section connected to the upper side of the concrete floating section, or a spar-type float consisting of a concrete float made of concrete rings stacked in multiple stages and fastened together with prestressing steel bars.

[0020] 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 waterproof bulkhead is installed around the tower in the semi-submersible spud barge used as the assembly platform to prevent water from entering the tower.

[0021] The invention described in claim 3 is characterized in that a waterproof bulkhead is installed around the tower to prevent water from entering the tower. Since various electrical equipment may be installed inside the tower, a waterproof bulkhead is installed around the equipment to prevent water from entering the tower.

[0022] In order to solve the second problem, the present invention provides, as claim 4, a method for constructing a spar-type offshore wind power generation facility as described in claim 1, in which a semi-submersible crane ship equipped with a mobile counterweight device on its deck surface is used as the large crane ship.

[0023] In the invention described in claim 4, a semi-submersible crane ship equipped with a mobile counterweight device on the deck surface is used as the large crane ship. Because the semi-submersible crane is equipped with a mobile counterweight device, it is possible to suppress shaking, especially when suspending heavy loads, and work can be carried out stably.

[0024] As a fifth aspect of the present invention, there is provided a method for constructing a spar-type offshore wind power generation facility as set forth in claim 4, in which the mobile counterweight device is made movable in any direction by providing a running part on the underside of the weight, and winches are placed at the four or three corners, or at the front and rear of the weight, and a wire drawn out from the winch is connected to the weight, and the weight is controlled to move to a predetermined position by operating the winch.

[0025] The invention described in claim 5 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 predetermined position by operating the winch.

[0026] As explained above in detail, according to the present invention, when assembling superstructures such as a tower, nacelle, and blades using a crane-equipped SEP barge in a sea area selected as a calm area with relatively calm waves, it becomes possible to construct a spar-type offshore wind power generation facility while simply compensating for the lack of crane lifting height of the crane-equipped SEP barge.

[0027] In addition, when connecting the upper structure of a spar-type offshore wind power generation facility to the floating body in a single operation using a semi-submersible crane, it becomes possible to carry out work stably by suppressing the shaking that occurs when a heavy object is suspended.

[0028] 1 is an overall view of a spar-type offshore wind power generation facility 1. It is a longitudinal cross-sectional view of a floating body 4. It shows a precast cylindrical body 15, where (A) is a longitudinal cross-sectional view, (B) is a plan view (viewed in the direction of the arrows along line BB), and (C) is a bottom view (viewed in the direction of the arrows along line CC). It is (A) and (B) diagrams showing how the precast cylindrical bodies 15 are fastened together. It is an enlarged longitudinal cross-sectional view showing the boundary between the concrete floating body section 4A and the steel floating body section 4B. It shows a semi-submersible crane 2 according to the present invention, where (A) is a side view and (B) is its plan view. It is a plan view showing another example of a mobile counterweight device 3. It is a plan view showing yet another example of a mobile counterweight device 3. It shows a construction procedure (part 1) of a spar-type offshore wind power generation facility 1 according to the present invention. It is a construction procedure (part 2) of a spar-type offshore wind power generation facility 1 according to the present invention. It is a construction procedure (part 3) of a spar-type offshore wind power generation facility 1 according to the present invention. FIG. 4 is a construction procedure (part 4) of the spar-type offshore wind power generation facility 1 according to the present invention. FIG. 5 is a construction procedure (part 6) of the spar-type offshore wind power generation facility 1 according to the present invention. FIG. 7 is a construction procedure (part 8) of the spar-type offshore wind power generation facility 1 according to the present invention. FIG. 9 is a construction procedure (part 10) of the spar-type offshore wind power generation facility 1 according to the present invention. FIG. 11 is a construction procedure (part 12) of the spar-type offshore wind power generation facility 1 according to the present invention. FIG. 5 is an assembly procedure diagram of the upper structure 12 showing a modified example of the assembly frame 13. FIG. 6 is a flow chart showing a conventional floating body construction method. FIG. 7 is a construction procedure diagram of the collective construction using a large crane ship 70 in Patent Document 2.

[0029] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

[0030] [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. FIG.

[0031] 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 and a plurality of blades 9, 9... installed on the top of the tower 6.

[0032] As shown in Figure 2, the float 4 comprises a concrete floating section 4A in which concrete precast cylindrical bodies 15, 15... are stacked in multiple layers in the vertical direction 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 this concrete floating section 4A.

[0033] Ballast material such as water, gravel, fine or coarse aggregate, or metal particles can be introduced into or discharged from the hollow portion of the floating body 4, thereby making it possible to adjust the buoyancy (draft). The introduction / discharge of ballast material is possible by employing the fluid transport method previously proposed by the present applicant in JP 2012-201217 A.

[0034] 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 with the same cross section in the axial direction, and are each manufactured using the same formwork, or hollow precast members manufactured by centrifugal molding are used.

[0035] In addition to the reinforcing bars 20, sheaths 21, 21... for inserting the PC steel members 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 members 19 can be inserted, and the upper parts are formed with box-out sections 22 for fitting anchor plates for fixing. In addition, a plurality of hanging fittings 23 are provided on the upper surface.

[0036] As shown in Figure 4(A), the precast cylindrical bodies 15 are fastened together by stacking the precast cylindrical bodies 15, 15 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 plates 24 into the box cutout portions 22, and applying tension to the PC steel members 19 with the nut members 25 to unite them. Grout material is then injected into the sheaths 21 through the grout injection holes 27. The holes 24a formed in the anchor plates 24 are grout injection confirmation holes, and the filling of the grout material is completed when the grout material is dispensed from the confirmation hole.

[0037] Next, as shown in Figure 4(B), couplers 26 are screwed onto the protruding portions of the PC steel members 19 to connect the upper PC steel members 19, 19..., and then the PC steel members 19, 19... are stacked while being inserted into the sheaths 21, 21... of the upper precast cylindrical body 15, and the PC steel members 19 are fixed in place in the same manner as above. This procedure is repeated in order to stack the precast cylindrical body 15 in the height direction. At this time, an adhesive 28 such as an epoxy resin or a sealant is applied to the joint surfaces between the lower precast cylindrical body 15 and the upper precast cylindrical body 15 to ensure watertightness and to bond the mating surfaces.

[0038] 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 lower steel cylindrical body 17 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 in the illustrated example). The upper part of the steel cylindrical body 17 has a truncated conical shape with a gradually narrowing diameter.

[0039] The upper steel cylindrical body 18 is a cylindrical body with an outer diameter dimension that is continuous with the outer diameter of the upper part of the lower steel cylindrical body 17, and is connected to the lower steel cylindrical body 17 by bolts or welding (bolt fastening is used in the illustrated example). These steel cylindrical bodies 17, 18 are made up of steel rings divided into predetermined weights, and the steel rings are integrated by welding them circumferentially.

[0040] 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 approximately the same, and the outer shape is continuous in the vertical direction without any steps or the like.

[0041] As shown in Figure 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 prevents the ship from coming into contact with the mooring line 10. In addition, a resistance moment is generated around the center of gravity G of the float 4 at the mooring point P to prevent the float 4 from tipping over too much, so that the tilting posture of the tower 6 can be maintained appropriately.

[0042] 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.

[0043] [Regarding the 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.

[0044] As shown in Figure 6, the semi-submersible crane 2 is provided with a crane 5 on the deck surface of a semi-submersible floating body 11 which is composed of a plurality of columns 31, 31... serving as buoyant bodies and connecting members 33, 33... which connect these.

[0045] The semi-submersible float 11 comprises the plurality of columns 31, three in the illustrated example, which serve as buoyancy 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 at the vertices of a polygon in plan view, for example, and then connecting these columns 31 with connecting members 33.

[0046] A deck main body 38 is provided on the upper surface of the floating body base 30, and a cantilevered deck section 37 is provided on one end of the deck main body 38. A movable counterweight deck section 39 is provided on the opposite side of the overhanging deck section 37, straddling the deck main body 38. A cantilevered frame structure 34 is disposed on the underside of the overhanging deck section 37 for structural reinforcement. Similarly, cantilevered frame structures 35 and 36 are disposed on the underside of the movable counterweight deck section 39 for structural reinforcement. The width of the deck main body 38 gradually decreases toward the left side of the drawing, and the overhanging deck section 37 protrudes like a bar from the leading edge of the deck main body 38, forming the bow side. The movable counterweight deck section 39 is a space provided to ensure a range of movement for the counterweight, and is located on the stern side. The deck main body 38 and the deck portion 39 for the movable counterweight have a stepped structure due to the deck overlap, but they may be flush.

[0047] 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 transmitted directly to the column 31. A fixed type crane is preferable as the crane 5, but in some cases a mobile crane can be mounted on the deck main body 38. In either case, it is necessary for the crane to have the lifting capacity and lifting height necessary to erect the tower 6, nacelle 8, and blades 9 of the offshore wind power generation facility. Furthermore, if a tower crane is used, the self-elevating structure makes it easy to ensure the desired lifting height.

[0048] A tower gripping device 40 is provided at the tip of the extending deck portion 37 to integrally fix 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.

[0049] A mobile counterweight device 3 is provided on the upper surface of the mobile counterweight deck 39. As shown in FIG. 6B, the mobile counterweight device 3 is configured such that a running section is provided on the underside of a weight 42, allowing it to move in any direction. Winches 41A-41D are provided at each corner, and wires 43a-43d extending from the winches 41A-41D are connected to the corners of the weight 42, respectively. The weight 42 is controlled and moved 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 desirable to coordinate the control of each winch 41A-41D using a computer (not shown).

[0050] As shown in the figure, the weight 42 has a box-shaped structure and can be adjusted by adding ballast material such as slag aggregate inside, or by adding a combination of steel material or the like if the weight is insufficient.

[0051] As shown in Figure 7, the winches 41 may be arranged at three corners of a substantially equilateral triangle, with wires 43a to 43c being reeled out from the winches 41A to 41C connected to a weight 42, and the weight 42 may be controlled to move to a predetermined position by operating the winches 41A to 41C. Alternatively, as shown in Figure 8, more simply, winches 41A and 41B may be arranged at the front and rear of the weight 42, with wires 43a and 43b being reeled out from the winches 41A and 41B connected to the weight 42, and the weight 42 may be controlled to move to a predetermined position in the Y direction by operating the winches 41A and 41B. In this case, it is desirable to provide movement guides 44 on both sides of the weight 42 so that the weight 42 can only move in the Y direction.

[0052] As shown in FIG. 6, it is desirable to provide fin stabilizers 32, 32 in the submersible portion of the semi-submersible float 11 to enhance stability against waves.

[0053] [Method of Constructing Spar-Type Offshore Wind Power Generation Facility 1] Next, a method of 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. 9 to 21. FIG.

[0054] <First Step> As shown in Figure 9, once the crane-equipped SEP barge 14 has been docked at the quay in the quay yard, the towers 6, 6..., nacelle 8, and blades 9, 9... are loaded onto the SEP barge 14 using a crane 45. The crane-equipped SEP barge 14 has vertically extending piers (hereinafter also referred to as "lifting legs") that can be raised and lowered at three or four locations on the barge, and is equipped with a hydraulic jack system that drives the lifting legs to move up and down, so that the lifting legs can be lowered downward to support their lower ends on the seabed, and can be further lowered to lift the barge portion above sea level, and the crane 45 is integrally provided on the barge, so that cargo can be loaded and unloaded onto the barge.

[0055] Next, as shown in Figure 10, an assembly platform 13 is set up in a sea area selected as a calm area with relatively calm waves. This assembly platform 13 is a platform for assembling the upper structure 12 of the offshore wind power generation facility 1, which is made up of the tower 6, nacelle 8, and blades 9. A semi-submersible spud barge 46 is used as the assembly platform 13. 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 which is equipped with three or four vertically extending piers (lift legs) that can be raised and lowered. As shown in Figure 10, this semi-submersible spud barge 46 can be stably supported by anchoring the lift legs to the seabed.

[0056] During assembly, as shown in FIG. 10 , first, multiple levels of the tower 6 are assembled from the bottom up on the assembly platform 13 (the semi-submersible spud platform 46) using a crane-equipped SEP platform 14. The number of levels is set so that the tower height is equal to or greater than the water depth. Once the desired number of levels (two levels in the illustration) of towers 6 have been assembled, the platform portion of the assembly platform 13 (the semi-submersible spud platform 46) is lowered and submerged or rests on the seabed. In the illustrated example ( FIG. 11 ), the platform portion is resting on the seabed. In this state, the tops of the assembled two levels of tower 6 are positioned above the water surface. Thereafter, the remaining levels of the tower 6 are assembled, and the nacelle 8 and blades 9 are assembled in that order to complete the superstructure 12.

[0057] The reason for completing the superstructure 12 with the assembly platform 13 (semi-submersible spud barge 46) submerged or landed on the seabed is to overcome the lack of crane lifting height of the crane-equipped SEP barge 14. In the future, a 20 MW class offshore wind power generation facility is planned, and as a countermeasure in case there is concern about the lack of crane lifting height of the crane-equipped SEP barge 14, it will be possible to ensure an additional lifting height for the crane used for assembly by the height at which the assembly platform 13 (semi-submersible spud barge 46) is submerged or landed on the seabed, thereby overcoming the lack of crane lifting height when assembling an ultra-large offshore wind power generation facility.

[0058] <Second Step> In the next second step, as shown in Figure 13, the assembly platform 13 (semi-submersible spud barge 46) is raised to expose the entire upper structure 12 in the air. The semi-submersible crane 2 is then pulled alongside the assembly platform 13 (semi-submersible spud barge 46), and the assembled upper structure 12 is hoisted by the crane 5. At this time, the lower end of the tower 6 is held by the tower holding device 40 to minimize swaying of the upper structure 12. Furthermore, because the upper structure 12 is quite heavy, the weight 42 of the mobile counterweight device 3 is moved rearward to stabilize the hull, which has swayed forward due to the hoisting load.

[0059] 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. 14 .

[0060] <Third Step> This third step is an operation performed separately from the first and second steps, and may be performed before or after the first and second steps. Alternatively, it may be performed simultaneously in parallel.

[0061] The third step is a work process in which, after the entire float 4 has 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 floated offshore, mooring lines are attached to hold the float 4 in an upright position.

[0062] Specifically, the float 4 is first completed in a quay yard. As a method for constructing the float, the method disclosed in Japanese Patent Application Laid-Open No. 2018-173011 proposed by the present applicant can be suitably adopted.

[0063] In the floating structure construction method, as shown in FIG. 15, a steel ring connection yard A, a concrete ring fabrication yard B, and a concrete ring connection yard C are defined in a quay yard.

[0064] The steel ring connecting yard A is equipped with a first bridge crane 50 that can travel in a fixed direction, with rotating platforms 52, 52... installed at appropriate intervals in the direction of travel of the first bridge crane, and with a mobile tent 56 that can move in the direction of travel of the first bridge crane. The concrete ring manufacturing yard B is equipped with a mobile tent 57 and a complete set of concrete ring manufacturing equipment. The concrete ring connecting yard C is equipped with a second bridge crane 55 that can travel in a fixed direction, and with a mobile tent 58 that can move in the direction of travel of the second bridge crane.

[0065] and a second step of connecting the steel rings 51, 51... to the concrete ring connecting yard C after the steel rings 51, 51... are moved to the concrete ring connecting yard C and installed in a predetermined position. The second step of connecting the concrete rings 54 fabricated in the concrete ring fabrication yard B is then carried to the concrete ring connecting yard C, and the concrete rings 54 are connected to the steel floating body sections 53B using the second bridge crane 55, and the concrete rings 54 are fastened to the steel floating body sections 53B with the second bridge crane 55 and secured together with PC steel members to complete the float 53.

[0066] Once the float 4 has been completed in this manner, it is moved sideways to a semi-submersible spud barge 46 at the quay, as shown in Figure 16, for loading (roll-on). 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, allowing the cargo to float off (surface and launch). Therefore, once the float 4 is transported to the construction site, it can be semi-submerged and launched onto the sea without a crane.

[0067] Once the semi-submersible spud barge 46 is towed by the towing vessel 47 and transported to the construction site of the spar-type offshore wind power generation facility 1, the floater 4 is launched and floated onto the sea (rolled off) by semi-submerging the semi-submersible spud barge 46 as shown in Fig. 17. Then, ballast water is poured into the floater 4 to raise it upright and place it in a vertical position.

[0068] It is desirable to attach mooring lines 10, 10 . . . to the float 4 in the vertical position as shown in FIG. 18 to ensure the stability of the float 4.

[0069] <Fourth Step> In the fourth step, as shown in Figures 19 and 20 , the upper structure 12 is connected to the top of the floating body 4 while being lifted by the semi-submersible crane 2, thereby completing the spar-type offshore wind power generation facility 1.

[0070] [Other Examples] (1) In the first step, the lower end portion of the tower 6 will be submerged in the sea. However, various electrical equipment may be installed in the lower end portion of the tower 6 in advance. In such a case, as shown in Figure 21, it is possible to provide a waterproof bulkhead 48 surrounding the lower end of the tower 6 to prevent flooding.

[0071] (2) The above embodiment is directed to a spar-type float in which the float 4 is composed of a concrete floating section 4A and a steel floating section 4B connected to the upper side of the concrete floating section 4A, but the same procedure can also be used to construct a spar-type float in which the float 4 is composed only of a concrete floating section 4A in which concrete rings 15, 15... are stacked in multiple tiers and each concrete ring 15, 15... is fastened and integrated with PC steel members 19. Of course, the same applies to other floating structures.

[0072] (3) In the above example, a semi-submersible crane 2 was used as a large crane ship for constructing the upper structure 12 of the spar-type offshore wind power generation facility 1 all at once, but it is also possible to use a normal large crane ship or a large crane ship equipped with a mobile counterweight device 3.

[0073] 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, 12...Superstructure, 13...Assembly stand (semi-submersible spud barge 46), 14...SEP barge with crane, 15.16...Precast cylindrical body (concrete ring), 19...PC steel, 46...Semi-submersible spud barge, 48...Waterproof bulkhead

Claims

1. A method for constructing a spar-type offshore wind power generation facility, comprising: a first step in which, in a sea area selected as a calm area with relatively calm waves, a semi-submersible spud barge is used as an assembly platform, and while the semi-submersible spud barge is submerged or anchored on the seabed, a SEP barge with a crane is used to assemble the superstructure of the offshore wind power generation facility, consisting of a tower, nacelle, and blades, on the semi-submersible spud barge; a second step in which, after the semi-submersible spud barge is raised, the superstructure assembled on the assembly platform is lifted all at once by a large crane ship and transported to the construction site of the offshore wind power generation facility; and a third step in which, after assembling the entire floater on the quay, the semi-submersible spud barge is used to transport the completed floater to the construction site of the offshore wind power generation facility, and once the floater has floated off into the sea, mooring lines are attached to hold the floater in an upright position. and a fourth step of connecting the upper structure to the top of the floating body while it is lifted by the large crane ship to complete the offshore wind power generation facility.

2. A method for constructing a spar-type offshore wind power generation facility as described in claim 1, wherein the float is a spar-type float consisting of a concrete floating body section formed by stacking concrete rings in multiple stages and fastening each concrete ring together with prestressing steel members, and a steel floating body section connected to the upper side of this concrete floating body section, or a spar-type float consisting of a concrete float formed by stacking concrete rings in multiple stages and fastening each concrete ring together with prestressing steel members.

3. A method for constructing a spar-type offshore wind power generation facility as described in claim 1, wherein a waterproof bulkhead is installed around the tower in the semi-submersible spud barge used as the assembly platform to prevent water from entering the tower.

4. A method for constructing a spar-type offshore wind power generation facility according to claim 1, wherein the large crane vessel is a semi-submersible crane vessel equipped with a mobile counterweight device on its deck surface.

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

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