JP7642216B2 - Construction method for spar-type offshore wind power generation equipment - Google Patents

Description

The present invention relates to a method for constructing a spar-type offshore wind power generation facility that is installed on the sea in relatively deep waters, specifically, a method for constructing a spar-type offshore wind power generation facility in a state where at least the tower and nacelle are constructed as a single unit.

For example, the following Patent Document 1 proposes an offshore wind power generation facility consisting of a float, mooring lines, a tower, and a nacelle and multiple blades installed at the top of the tower, in which the float is a spar-type floating structure consisting of a lower concrete floating structure in which concrete precast cylindrical bodies are stacked vertically in multiple tiers and each precast cylindrical body is fastened and integrated with PC steel, and an upper steel floating structure connected to the upper side of the lower concrete floating structure. Note that a spar-type refers to a floating structure with a long, slender cylindrical shape like a rod-shaped fishing float.

When installing the above-mentioned spar-type offshore wind power generation equipment at sea, it is desirable to carry out construction in a bay with calm waves. However, while the draft (part below the water surface) of the float is generally deep, at over 70 m, the water depth in a bay is generally shallower than this, making construction in a bay difficult. For this reason, when installing a spar-type offshore wind power generation facility, as shown in Patent Document 2 below, the float is floated sideways on the sea adjacent to the production yard and transported to the installation site by a towing ship, or the float is loaded onto a barge and towed to the installation site. When erecting the float, ballast water is poured in and the float is slowly erected to an upright position by gradually letting out the wire from a winch tied to the bottom of the float, and then solid ballast is poured in to ensure draft. After that, the tower, nacelle, and multiple blades are assembled and connected to the float in one go by a crane installed on a large crane ship, or the tower, nacelle, and blades are attached in that order by a crane installed on a large crane ship.

Patent No. 5274329 JP 2012-201219 A

In the construction of conventional offshore wind power generation facilities, if only the float is transported to the installation site at sea, a large amount of ballast water must be poured in to erect the float at the installation site at sea. After erecting the float, solid ballast is poured in and the ballast water is discharged at the same time. After the substation equipment is installed, the ballast water is adjusted to match the weight when the tower, nacelle, and blades are attached. However, with this conventional construction method, various tasks must be performed at the sea at the installation site, which takes a lot of time and effort, and when a large number of offshore wind power generation facilities are installed, this causes the process to become longer. Therefore, there is a strong demand for further efficiency in construction than is currently the case.

On the other hand, the reason why the float is raised with the assistance of a wire drawn from a winch is that when ballast water is poured in, the float suddenly rises upright at a certain point, and when the float reaches an upright position due to its inertial force, it generates rocking (vibration), which may cause damage to the float or its associated equipment. Therefore, raising a float at sea is a dangerous task that requires the utmost care and caution.

The first objective of the present invention is to further improve the efficiency of construction and shorten the construction period when constructing spar-type offshore wind power generation facilities.

Secondly, the objective is to provide a method for safely and efficiently erecting a spar-type offshore wind power generation facility by injecting ballast water.

In order to solve the first problem, the present invention according to claim 1 provides a construction method for a spar-type offshore wind power generation facility including a spar-type floating body, a tower erected on the floating body, a nacelle attached to a top of the tower, and a plurality of blades attached to the nacelle, the construction method comprising:
a first step of loading a predetermined amount of solid ballast into the bottom of the float, arranging a drainage pump in the area where the solid ballast was loaded and providing a ballast water drainage facility surrounded by a perforated pipe of a predetermined height, attaching a tower, a nacelle, and a predetermined number of blades as necessary to the upper part of the float to complete the construction all at once, loading the whole into a semi-submersible barge at the quay, and transporting it to the sea for installation of the spar-type offshore wind power generation facility;
A second step of injecting water into the semi-submersible barge at sea where the spar-type offshore wind power generation facility is installed, making the semi-submersible barge float on seawater, and moving the semi-submersible barge aside;
A third step of erecting the spar-type offshore wind power generation facility by injecting ballast water into the float;
The present invention provides a construction method for a spar-type offshore wind power generation facility, which is characterized by comprising a fourth step of using a large crane ship to install any remaining blades that have not yet been installed, and finally adjusting the ballast water to achieve the specified draft state.

In the invention described in claim 1, the tower, nacelle, and a predetermined number of blades, if necessary, are attached to the float to complete the installation, and then loaded onto a semi-submersible barge at the wharf and transported to the sea where the spar-type offshore wind power generation facility is to be installed. At this time, since the nacelle is a heavy object weighing tens to hundreds of tons and the blades are also heavy objects, it is necessary to significantly lower the center of gravity of the spar-type offshore wind power generation facility so that the nacelle and blades do not become submerged when floated off at the local sea. In addition, since it is difficult to inject solid ballast after the tower is attached, a predetermined amount of solid ballast is injected into the bottom of the float beforehand. The advance injection of the solid ballast contributes to lowering the center of gravity of the spar-type offshore wind power generation facility, and allows the nacelle and blades to be semi-submerged at an angle so that they do not become submerged when floated off.

After transporting the spar-type offshore wind power generation equipment to the sea where it will be installed, the semi-submersible barge is filled with water to put it in a semi-submerged state, and the spar-type offshore wind power generation equipment is floated on the seawater while the semi-submersible barge is moved aside (second step).

Then, ballast water is injected into the float to erect the spar-type offshore wind power generation equipment (step 3). After that, if there are any blades that have not yet been installed, they are installed using a large crane ship, and finally, the ballast water is adjusted to achieve the specified draft state (step 4).

In this invention, not only the floating body is constructed, but also the tower, nacelle, and, if necessary, a certain number of blades are attached to it, and the floating body is transported, erected, and the remaining blades are installed. This makes it possible to further improve the efficiency of construction compared to the current situation and shorten the construction period.

In addition, because solid ballast is placed inside the float beforehand, all that is required at sea during installation is the injection and discharge of ballast water, which also makes construction more efficient and helps to shorten the construction period.

In the present invention, a drainage pump is disposed in advance in the solid ballast injection area, and a ballast water discharge facility is provided with the drainage pump surrounded by a perforated pipe of a predetermined height. In the present invention, at least a tower, a nacelle, and a predetermined number of blades as necessary are attached to form a one-piece construction state, and measures must be taken to prevent the lower end of the float from sinking and the nacelle and blades from being submerged when floating on the sea. For this reason, solid ballast is injected in advance, but since the nacelle, blades, and blades are quite heavy, it is expected that the amount of solid ballast will need to be increased. Even in such cases, it is possible to reduce the minimum amount of ballast water by making it possible to remove the water from the solid ballast area as well.

In order to solve the second problem, the present invention relates to a second aspect, in which, in erecting the spar-type offshore wind power generation facility in the third step,
There is provided a construction method for a spar-type offshore wind power generation facility as described in claim 1, in which the center of gravity of the float or tower of the spar-type offshore wind power generation facility is offset in advance by a center of gravity offsetting means, and ballast water is continuously injected to erect the spar-type offshore wind power generation facility upright.

In the invention described in claim 2 , when the spar-type offshore wind power generation facility is erected, the center of gravity of the float or tower of the spar-type offshore wind power generation facility is offset in advance by a center of gravity offsetting means. As shown in the embodiment described later, by offsetting the center of gravity, when the facility transitions from a floating state sideways due to the injection of ballast water to an erection operation, this erection operation becomes slower and the rocking that occurs after the facility approaches an upright state can be suppressed.

Here, "eccentricity of the center of gravity position" does not mean eccentricity only in the direction along the longitudinal central axis of the float, but refers to movement of the center of gravity position including eccentricity in a plane perpendicular to the longitudinal central axis of the float.

This makes it possible to safely and efficiently erect spar-type offshore wind power generation equipment by injecting ballast water.

In order to solve the second problem, the present invention relates to a third aspect, in which, in erecting the spar-type offshore wind power generation facility in the third step,
There is provided a construction method for a spar-type offshore wind power generation facility as described in claim 1, in which the center of gravity of the float or tower of the spar-type offshore wind power generation facility is offset in advance by a center of gravity decentering means, ballast water is injected, and after the spar-type offshore wind power generation facility starts to be raised upright, the injection of ballast water is stopped at a predetermined amount to temporarily stop the spar-type offshore wind power generation facility in an oblique state before being raised upright, and then ballast water is gradually injected again to raise the spar-type offshore wind power generation facility upright.

The invention described in claim 3 is a second invention method for erecting a spar-type offshore wind power generation facility. Specifically, when erecting a spar-type offshore wind power generation facility, the center of gravity of the float or tower of the spar-type offshore wind power generation facility is made eccentric in advance by a center of gravity eccentricity means. By making the center of gravity eccentric, when the facility transitions from a floating state sideways due to the injection of ballast water to an erection operation, this erection operation can be slowed down.

Next, ballast water is injected, and after the float for the spar-type offshore wind power generation facility starts to raise up, the injection of ballast water is stopped at a predetermined amount, so that the spar-type offshore wind power generation facility is stopped in the tilted state before it is raised upright. By shifting the position of the center of gravity of the float, the raising action can be slowed down, and by stopping the injection of ballast water at a predetermined amount, it becomes easy to stop the float in the tilted state before it is raised upright.

Finally, the spar-type offshore wind turbine is raised upright by gradually injecting more ballast water. When raising the spar-type offshore wind turbine from an angled, stopped position, only a small amount of inertial force acts, so it is possible to almost completely eliminate rocking immediately after raising the turbine.

This makes it possible to safely and efficiently erect spar-type offshore wind power generation equipment by injecting ballast water.

As a fourth aspect of the present invention, there is provided a construction method for a spar-type offshore wind power generation facility as described in either of claims 2 or 3 , in which the center of gravity decentering means is a weight detachably attached to the outer surface of the float for the spar-type offshore wind power generation facility.

The invention described in claim 4 shows a first embodiment of the center of gravity eccentric means. Specifically, the center of gravity eccentric means is a weight detachably attached to the outer surface of the spar-type offshore wind power generation facility float.

According to a fifth aspect of the present invention, there is provided a method for erecting a float for a spar-type offshore wind power generation facility as set forth in the fourth aspect, in which the weight is attached to a position above the sea surface when erected.

According to the invention described in claim 5 , the weight is attached to a position above the sea surface when the float is erected. After the float is erected, the weight that is no longer needed can be easily removed.

According to a sixth aspect of the present invention, there is provided a construction method for a spar-type offshore wind power generation facility as set forth in either of the second or third aspect, wherein the center of gravity offsetting means is solid ballast placed inside the floating body.

The invention described in claim 6 shows a second embodiment of the center of gravity eccentric means. Specifically, the center of gravity eccentric means uses solid ballast poured into the float for the spar-type offshore wind power generation facility. Solid ballast is usually poured into the float after it is erected, but unlike water, solid ballast does not move up to the inclination angle of the angle of repose (the angle of the slope at which the float can be stable without collapsing) and maintains the eccentric state, so it can be used as a means for eccentricating the center of gravity. In addition, the moving speed of solid ballast is slower than that of water after passing the angle of repose, and the eccentric state is maintained while the amount of eccentricity gradually decreases until just before the float is erected, so it can be used as a center of gravity eccentric means.

As explained above in detail, according to the present invention, it is possible to further improve the efficiency of construction and shorten the construction period when constructing spar-type offshore wind power generation facilities.

It will also be possible to safely and efficiently erect spar-type offshore wind power generation equipment by injecting ballast water.

FIG. 1 is an overall side view of a spar-type offshore wind power generation facility 1. FIG. Showing a precast cylindrical body 15, (A) is a longitudinal cross-sectional view, (B) is a plan view (viewed along line B-B), and (C) is a bottom view (viewed along line C-C). 1A and 1B are diagrams showing how precast cylindrical bodies 15 are fastened together. A vertical cross-sectional view showing the boundary between the lower concrete floating structure section 4A and the upper steel floating structure section 4B. 1A and 1B are a longitudinal cross-sectional view and a transverse cross-sectional view, respectively, showing the state in which solid ballast has been poured into the float and the state in which a drainage system 29 has been installed. This shows the construction procedure (part 1) of a spar-type offshore wind power generation facility 1. This shows the construction procedure (part 2) of the spar-type offshore wind power generation facility 1. This shows the construction procedure (part 3) of the spar-type offshore wind power generation facility 1. This is the construction procedure (part 4) of the spar-type offshore wind power generation facility 1. This is the construction procedure (part 5) of the spar-type offshore wind power generation facility 1. This is the construction procedure (part 6) of the spar-type offshore wind power generation facility 1. This is the construction procedure (part 7) of the spar-type offshore wind power generation facility 1. FIG. 13 is a diagram showing a modified construction example of the spar-type offshore wind power generation facility 1. 13 is a procedure (part 1) for erecting the float 4 showing the second embodiment of the gravity center decentering means. This is the procedure for setting it up (part 2). This is the procedure for setting it up (part 3). This is the procedure for standing it up (part 4). This is the procedure for standing it up (part 5). FIG. 13 is a graph showing a comparison between experimental values and analytical results. 13 is a graph showing the effect of the eccentricity of the float's center of gravity on the response (raising action).

Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.
[Spar-type offshore wind power generation facility 1]
Before describing the "construction method for a spar-type offshore wind power generation facility" according to the present invention, a structural example of the spar-type offshore wind power generation facility 1 will be described in detail with reference to Figs. 1 to 5.

As shown in FIG. 1, the spar-type offshore wind power generation facility 1 is composed of a cylindrical spar-type float 4, a mooring line 5 connected to the float 4, a tower 6, and a wind turbine 7 consisting of a nacelle 8 and multiple blades 9, 9... that are installed on the top of the tower 6.

As shown in FIG. 2, the float 4 is made up of a lower concrete floating structure 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 structure, and an upper steel floating structure 4B connected to the upper side of the lower concrete floating structure 4A.

The precast cylindrical bodies 15 constituting the lower concrete floating structure section 4A are circular cylindrical precast members with the same cross section in the axial direction as shown in FIG. 3, and each is manufactured using the same formwork, or hollow precast members manufactured by centrifugal molding are used.

In addition to the reinforcing bars 20, sheaths 21, 21... are embedded in the wall at appropriate intervals in the circumferential direction for inserting the PC steel bars 19. 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 anchor plates for fixing. In addition, multiple hanging fittings 23 are provided on the top surface.

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 rods 19, 19... extending upward from the lower precast cylindrical body 15 through the sheaths 21, 21..., and then fitting the anchor plate 24 into the box-out section 22, and introducing tension into the PC steel rods 19 with the nut member 25 to integrate them. In addition, grout material is injected into the sheaths 21 through the grout injection hole 27 (see Figure 4(B)). 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.

Next, as shown in Figure 4(B), a coupler 26 is screwed onto the protruding portion of the PC steel rod 19 to connect the upper PC steel rods 19, 19..., and the PC steel rods 19, 19... are then inserted into the sheaths 21, 21... of the upper precast cylindrical body 15 while stacking them, and the procedure of fixing the PC steel rods 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 cylindrical body 15 and the upper precast cylindrical body 15 to ensure watertightness and to bond the mating surfaces.

As shown in FIG. 2, the upper steel floating structure 4B is composed of a steel tubular body 17 located relatively on the lower side and a steel tubular body 18 located relatively on the upper side. The lower steel tubular body 17 has a lower portion with the same outer diameter as the precast tubular body 15, and is connected to the precast tubular body 15. The upper portion of the steel tubular body 17 has a truncated cone shape with a gradually narrowing diameter.

The upper steel cylindrical body 18 is a cylindrical body whose outer diameter 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 (bolt fastening is used in the illustrated example).

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. In the illustrated example, a ladder 13 is provided at the top of the upper steel cylindrical body 18, and a walkway scaffolding 14 is provided circumferentially at approximately the boundary between the tower 6 and the upper steel cylindrical body 18.

As shown in Figure 1, the mooring point K of the mooring line 5 to the float 4 is set below sea level and at a position higher than the center of gravity G of the float 4. This makes it possible to prevent ships from coming into contact with the mooring line 5. In addition, a resistance moment is generated at the mooring point about the center of gravity G of the float 4 to prevent the float 4 from tipping over too much, making it possible to properly maintain the tilted attitude of the tower 6. The other end of the mooring line 5 is connected to an anchor sunk in the seabed.

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 other components. This nacelle 8 is quite heavy, weighing anywhere from tens to hundreds of tons. Incidentally, the nacelle weight of a 5 MW wind turbine exceeds 200 tons.

In recent years, the blades 9 are mainly made of highly rigid carbon fiber composite materials. The number of blades is about 3 to 5, but the most common structure is a three-blade structure.

[Construction method for spar-type offshore wind power generation equipment]
Next, a construction method for the above-mentioned spar-type offshore wind power generation facility 1 will be described in detail.

The present invention relates to a construction method for a spar-type offshore wind power generation facility 1 including a spar-type floating body 4, a tower 6 erected on the floating body 4, a nacelle 8 attached to the top of the tower 6, and a plurality of blades 9 attached to the nacelle 8,
a first step of loading a predetermined amount of solid ballast 32 into the bottom of the float 4, attaching a tower 6, a nacelle 8, and a predetermined number of blades 9 as necessary to the top of the float 4 to complete the construction all at once, loading the float 4 onto a semi-submersible barge 33 at a quay, and transporting the float 4 to the sea where the spar-type offshore wind power generation facility 1 will be installed;
A second step of pouring water into the semi-submersible barge 33 to put it in a semi-submerged state at the sea where the offshore wind power generation facility 1 is to be installed, floating the spar-type offshore wind power generation facility 1 on seawater, and moving the semi-submersible barge 33 aside;
A third step of erecting the spar-type offshore wind power generation facility 1 by injecting ballast water into the float 4;
If there are any blades 9 that have not yet been installed, they are installed using a large crane ship, and the fourth step is to adjust the ballast water to a predetermined draft state. This will be described in detail below with reference to Figures 6 to 14.

<First Step>
Once the float 4 has been manufactured in a specified wharf area, a specified amount of solid ballast 32 is loaded onto the bottom of the float 4, as shown in Fig. 6. A drainage pump 30 for discharging ballast water is installed within the area where the solid ballast 32 is loaded, and a ballast water discharge facility 29 is provided such that the pump is surrounded by a perforated pipe 31 of a specified height.

The drainage pump 30 is surrounded by a perforated pipe 31 to prevent solid ballast 32 from entering. If the hole diameter of the perforated pipe 31 is larger than the particle size of the solid ballast, it is recommended to cover the perforated pipe 31 with a permeable sheet such as a perforated or non-perforated nonwoven fabric or fibrous sheet. The height of the perforated pipe 31 should be at least higher than the height of the solid ballast 32. In the embodiment shown in Figure 6, the upper surface of the solid ballast 32 is covered with a perforated plate 33, and the solid ballast 32 is restrained so that it cannot move.

In the present invention, at least the tower 6, nacelle 8, and, if necessary, a predetermined number of blades 9 are attached to form a unitary construction state. Therefore, measures are required to prevent the nacelle 8 and blades 9 from being submerged when the vessel is floated on the sea, and solid ballast 32 is introduced in advance to move the center of gravity to the lower end. However, since the tower 6, nacelle 8, and blades 9 are quite heavy, it is expected that the amount of solid ballast 32 will need to be increased. Even in such cases, it is possible to reduce the minimum amount of ballast water by making it possible to remove the water from within the solid ballast 32 area.

The solid ballast 32 is preferably a powdered or granular material with a higher specific gravity than water, specifically, one or more of the following: minerals including sand, gravel, and barite; and metals including metal powders and metal particles such as iron and lead. By adjusting the material of the solid ballast 32, it is possible to deposit ballast material with an appropriate specific gravity.

Next, a tower 6 is connected to the top of the float 4, a nacelle 8 is attached, and if necessary, a predetermined number of blades 9 are attached to complete the overall construction state (this state is also called the spar-type offshore wind power generation facility 1). In this embodiment, the blades 9 are not attached in the overall construction state, but are attached separately later.

As shown in FIG. 7, the spar-type offshore wind power generation facility 1 is transported using a semi-submersible barge 33. The semi-submersible barge 33 is loaded while adjusting the ballast water of the semi-submersible barge 33. At this time, a weight 2 for offsetting the center of gravity with respect to the float 4 or tower 6 is detachably attached. The weight 2 constitutes the "center of gravity offsetting means" of the present invention. For ease of removal, it is desirable to attach the weight 2 to the outer surface of the float 4 or tower 6 at a position that will be above sea level when erected. The advantages of attaching the weight 2 will be described later.

Here, eccentricity of the center of gravity does not mean eccentricity only in the direction (Z-axis) along the longitudinal central axis of the spar-type offshore wind power generation facility 1, but means movement of the center of gravity including eccentricity in the planar directions (X- and Y-axis planes) perpendicular to the longitudinal central axis of the spar-type offshore wind power generation facility 1. Therefore, the weight 2 may be provided at one location on the outer surface of the spar-type offshore wind power generation facility 1, and it is not desirable to provide the weight 2 at an even number of locations (for example, 180° or 90° positions) so as to be symmetrical on the outer surface of the spar-type offshore wind power generation facility 1.

Then, as shown in FIG. 7, the equipment is transported by a towing vessel 34 to the sea where it will be installed.

<Second Step>
To float off the spar-type offshore wind power generation facility 1, as shown in Fig. 8, the semi-submersible barge 33 is filled with water to make it semi-submerged, the spar-type offshore wind power generation facility 1 is floated on seawater, and the semi-submersible barge 33 is evacuated. When the spar-type offshore wind power generation facility 1 is floating on seawater, the center of gravity of the spar-type offshore wind power generation facility 1 is moved to the lower end side by the prior injection of solid ballast 32 into the float 4, so that the spar-type offshore wind power generation facility 1 floats in an inclined state and the nacelle 8 is separated upward from the sea surface, as shown in Fig. 9.

<Third Step>
Next, as shown in Figure 9, a ballast barge 35 equipped with ballast pump equipment is brought close to the floated-off spar-type offshore wind power generation facility 1 so that water can be injected, and a ballast hose 36 is inserted into the inside of the float 4 to enable the supply of ballast water.

When ballast water is injected and a predetermined amount of ballast water is continuously injected into the spar-type offshore wind power generation facility 1 at a constant rate, the pitch angle of the float (the inclination angle θ between the longitudinal central axis of the float 4 and the water surface) increases, albeit slowly at first. Then, after a certain point, the float 4 begins to suddenly start to rise, as shown in Figure 10. Then, as shown in Figure 11, the spar-type offshore wind power generation facility 1 rises almost vertically.

By attaching the waist 2 to the float 4 or tower 6 and offsetting the center of gravity, as shown in the embodiment described below, when the float moves from a sideways floating state to an upright state by injecting ballast water, this upright movement becomes slower and the rocking that occurs after the float moves closer to an upright state can be suppressed. This makes it possible to safely and efficiently upright the spar-type offshore wind power generation facility 1 by injecting ballast water.

Once the spar-type offshore wind power generation facility 1 has been erected, the weight 2 is removed as shown in FIG. 12.

As shown in FIG. 12, a ladder 13 is attached to the top of the float 4, and a walkway scaffolding 14 is provided. Furthermore, one end of a mooring rope 5 is tethered to the float 4, and the other end is tethered to an anchor sunk in the seabed to stabilize the float 4.

<Fourth Step>
Next, if there are any blades 9, 9 ... that have not yet been installed, they are installed to the nacelle 8 while being suspended by a crane provided on a large crane ship 37, as shown in Figure 13. The blades 9 may be installed all at once, or one by one.

Once all components have been installed, the ballast water is adjusted to achieve the specified draft condition and construction is complete.

When installing the blades 9 and other components, it is necessary to discharge an amount of ballast water commensurate with their weight. However, the ballast water discharge equipment 29 installed within the solid ballast 32 makes it possible to discharge the ballast water from the solid ballast 32, making it easy to reduce the minimum amount of ballast water. In addition, since the ballast water from the solid ballast 32 can be discharged even when the blades 9 are removed, it is easy to ensure an inclination that allows float-on.

[Another example of a method for erecting a spar-type offshore wind power generation facility 1]
Next, a second embodiment of the method for erecting the spar-type offshore wind power generation facility 1 will be described in detail.

In this second embodiment, the weight 2 is still attached beforehand, but by changing the method of injecting ballast water, it can be done more safely and efficiently.

In this second embodiment, after ballast water is injected and the spar-type offshore wind power generation equipment 1 starts to raise up, the injection of ballast water is stopped at a predetermined amount to temporarily stop the spar-type offshore wind power generation equipment 1 in the tilted position before it is raised upright, and then ballast water is gradually injected again to raise the spar-type offshore wind power generation equipment 1 upright.

Compared to the first embodiment in which water is injected continuously, this embodiment differs in that the injection of ballast water is stopped midway when the spar-type offshore wind power generation equipment 1 begins a sudden upward movement, thereby stopping the spar-type offshore wind power generation equipment 1 in the tilted position before it was raised upright.

By attaching the weight 2 that decenters the center of gravity, the uprighting movement becomes slower, making it possible to stop the spar-type offshore wind power generation equipment 1 in an inclined state before it is upright. After the spar-type offshore wind power generation equipment 1 is stopped in an inclined state, water is gradually poured in to make the spar-type offshore wind power generation equipment 1 stand upright. This makes it possible to carry out the operation more safely and efficiently, as the shaking caused by the inertial force that occurs when the spar-type offshore wind power generation equipment 1 is upright is only slight.

When using the solid ballast 34 described below as the center of gravity decentering means, it is desirable that the tilt angle θ at which the spar-type offshore wind power generation facility 1 is stopped in an inclined state before being erected upright is an angle equal to or less than the angle of repose of the solid ballast 32.

[Second embodiment of gravity center decentering means]
In the above embodiment, an example in which the weight 2 is used as the center of gravity eccentric means has been shown, but an example in which solid ballast 32 is used as the center of gravity eccentric means will be described in detail with reference to Figures 15 to 19. Note that the ballast water discharge equipment 29 is omitted in these figures.

As shown in FIG. 15, once the spar-type offshore wind power generation facility 1 is manufactured in a specified quay area, it is loaded onto a semi-submersible barge 33 while adjusting the ballast. With the spar-type offshore wind power generation facility 1 loaded, solid ballast 32 is poured into the float 4. Note that the solid ballast 32 can also be poured before loading onto the semi-submersible barge 33. The solid ballast 32 is allowed to flow without being restrained by any means. Therefore, since the spar-type offshore wind power generation facility 1 is loaded onto the semi-submersible barge 33 in a horizontal position, the solid ballast 32 is spread out horizontally. In other words, when the spar-type offshore wind power generation facility 1 is in a horizontal position, the center of gravity of the float 4 is offset by the solid ballast 32.

As shown in FIG. 17, once the spar-type offshore wind power generation equipment 1 is transported by a towing vessel 34 to the sea where it is to be installed, it is floated on the sea. To float off the spar-type offshore wind power generation equipment 1, as shown in FIG. 16, water is poured into the semi-submersible barge 33 to put it in a semi-submerged state, the spar-type offshore wind power generation equipment 1 is floated on seawater, and then the semi-submersible barge 33 is separated from the spar-type offshore wind power generation equipment 1.

Next, as shown in FIG. 17, a ballast barge 35 carrying ballast water pump equipment is brought close to the floated-off float 4 so that water can be injected, and a ballast hose 33 is inserted into the inside of the spar-type offshore wind power generation facility 1 to enable the supply of ballast water.

When ballast water is injected and a predetermined amount of ballast water is injected inside the spar-type offshore wind power generation equipment 1, the pitch angle (the angle θ between the longitudinal line of the float and the water surface) of the spar-type offshore wind power generation equipment 1 increases, albeit slowly at first. Then, after a certain point, as shown in Figure 18, the spar-type offshore wind power generation equipment 1 suddenly begins to rise up. Then, as shown in Figure 19, the spar-type offshore wind power generation equipment 1 rises up almost vertically.

When the spar-type offshore wind power generation equipment 1 is in a horizontal position, the center of gravity of the float 4 is in an eccentric state due to the solid ballast 32 poured inside, and the pitch angle θ of the spar-type offshore wind power generation equipment 1 gradually increases due to the injection of ballast water. Even if the spar-type offshore wind power generation equipment 1 tilts, the solid ballast 32 maintains its eccentric state without moving to the inclination angle θ of the angle of repose (the angle of the slope at which stability can be maintained without collapsing). Then, the solid ballast 32 starts to move after the inclination angle θ of the spar-type offshore wind power generation equipment 1 exceeds the angle of repose, but since the moving speed is slower than that of water, the solid ballast 32 flows over time until it stands up, and finally fills the bottom of the float 4, eliminating the eccentricity of the center of gravity. However, until just before it stands upright, the eccentric state is maintained while the amount of eccentricity gradually decreases, so the rising action of the spar-type offshore wind power generation equipment 1 becomes slow and the shaking after it approaches the upright state can be suppressed to a small extent. This makes it possible to safely and efficiently raise the float 4 by injecting ballast water.

[Other examples]
(1) In the above embodiment, the spar-type offshore wind power generation facility 1 in an all-in-one construction state is configured with a float 4, a tower 6, and a nacelle 8, but as shown in Fig. 14, the spar-type offshore wind power generation facility 1 in an all-in-one construction state can also be configured with a float 4, a tower 6, a nacelle 8, and three blades 9, 9.... Note that the number of blades 9 may be all attached, or it is also possible to attach one or more of the total number.

(2) Two examples of the center of gravity decentering means have been described: a case in which a weight 2 is attached to the outer surface of the spar-type offshore wind power generation facility 1 is used, and a case in which solid ballast 32 is placed inside the float 4. However, these can also be used in combination.

Next, we will provide a detailed description of the experiments and analyses conducted to verify the effect of offsetting the center of gravity of the float 4 or tower 6 using a center of gravity offsetting means (weight 2 or solid ballast 32) in the present invention.

1.Aquarium Experiment
1.1 Model Specifications Figure 20 and Table 1 show the outline and dimensions of the floating body model 40. It is a scale of 1/36.11 of the assumed actual machine (2MW machine). It was mainly made of polyvinyl chloride pipes, and the weight and center of gravity height were adjusted by attaching steel plates to the top and bottom of the float. In addition, as shown in Figure 20, markers 41 and 42 used for motion measurement are attached to two points, 65 mm and 418 mm from the top end of the float.

1.2 Measurement method The water tank experiment was carried out in a test water tank (width: 24.4 m, length: 38.8 m, water depth during the experiment: 1.824 m).

The floating model 40 was moored in the center of the tank. The upper part of the float was moored from the tank's auxiliary cart, and the lower part was moored from the tank's shore. Adjustments were made in advance so that the mooring force would not interfere with the behavior of the floating model 40.

To measure the attitude of the floating model 40, a motion capture system (Qualysis) was used to capture the movements of the markers 41 and 42 in real time. The movements of the two markers 41 and 42 attached to the floating model 40 were captured by a total of four cameras (Qualysis 5+; 4 MP, 2048x2048 pixels, 180fps) installed on the sides of the tank, and the movements were output as spatial coordinate values every 0.02 seconds (50 Hz). Based on the converted coordinate values, the inclination angle between the float's central axis and the water surface was calculated, and this was taken as the pitch angle.

1.3 Injection of ballast water Ballast water was injected through a hose from the top of the float. The pump used was a Takumina Smoothflow pump (maximum discharge volume: 1.08 L/min, maximum discharge pressure: 1 MPa). The flow rate during the experiment was 0.73 L/min (equivalent to 5.7 m3/min in actual equipment).

2.Analysis method The analysis was performed by considering six forces - gravity acting on the float itself, gravity acting on the internal ballast water, gravity acting on the eccentricity weight, buoyancy acting on the float, and the added mass force and drag that the moving float receives from the external fluid - when any amount of ballast water is inside the float, and using a program (ADAMS: mechanism analysis software) to determine the float's posture from the dynamic balance conditions between these forces and the inertial forces associated with the float's movement.

3. Experimental and analytical results
3.1 Comparison of experimental values and analytical results (when erecting)
The experimental results during erection are shown in Figure 21, in comparison with the simulation analysis results by ADAMS. Here, the center of gravity of the float itself without internal ballast water is specified as (Xg, Yg, Zg) = (0.0022m, 0.0m, 0.788m) in the float-fixed coordinate system. Note that the float-fixed coordinate system has its origin at the bottom of the float, the Z axis points upward along the center axis of the float, and the X and Y axes perpendicular to this.

Figure 21 shows that the simulation analysis results using ADAMS reproduce the experimental results (Experminent No. 1) well.

3.2 Effect of eccentricity of floating center of gravity on response (when standing upright)
As seen in 3.1, the ADAMS simulation can accurately predict the response of the floating body when it is raised, so next we will investigate the effect of the eccentricity of the float's center of gravity on the response by simulation. We conducted a simulation of the floating body response when it is raised for a total of three cases, changing the value of Xg to Xg=0.0 (no eccentricity), Xg=0.0022m (same as the experimental conditions), and Xg=0.0044m (when the eccentricity of the center of gravity is twice as much) by attaching weights. The results are shown in Figure 22.

Figure 22 shows that when there is no eccentricity (Xg = 0.0m), the standing up becomes steeper and there is a large amount of swaying once the person is upright. On the other hand, when the eccentricity of the center of gravity is Xg = 0.0022m, and when it is twice as large, the standing up becomes slower and there is only a small amount of swaying even when the person is close to being upright. Comparing the case where the eccentricity of the center of gravity is Xg = 0.0022m with the case where the eccentricity of the center of gravity is Xg = 0.0044m, it was found that increasing the eccentricity makes the standing up movement slower and reduces the swaying once the person is upright.

From the above, it was found that when raising a floating body by pouring water in, the raising speed can be slowed down by shifting the position of the center of gravity, and the rocking after the body is raised can be kept to a minimum.

1...Spar-type offshore wind power generation equipment, 4...Float, 4A...Lower concrete floating structure, 4B...Upper steel floating structure, 5...Mooring line, 6...Tower, 7/(7')...Wind turbine, 8...Nacelle, 9...Blade, 15...Precast tubular body, 17/18...Steel tubular body, 19...PC steel rod, 29...Ballast water drainage equipment, 30...Drainage pump, 31...Perforated pipe, 32...Solid ballast, 33...Semi-submersible barge, 34...Tow ship, 35...Ballast barge, 36...Ballast hose, 37...Large crane ship, 40...Float model, 41/42...Marker

Claims (6)

A construction method for a spar-type offshore wind power generation facility including a spar-type floating body, a tower erected on the floating body, a nacelle attached to a top of the tower, and a plurality of blades attached to the nacelle, comprising the steps of:
a first step of loading a predetermined amount of solid ballast into the bottom of the float, arranging a drainage pump in the area where the solid ballast was loaded and providing a ballast water drainage facility surrounded by a perforated pipe of a predetermined height, attaching a tower, a nacelle, and a predetermined number of blades as necessary to the upper part of the float to complete the construction all at once, loading the whole into a semi-submersible barge at the quay, and transporting it to the sea for installation of the spar-type offshore wind power generation facility;
A second step of injecting water into the semi-submersible barge at sea where the spar-type offshore wind power generation facility is installed, making the semi-submersible barge float on seawater, and moving the semi-submersible barge aside;
A third step of erecting the spar-type offshore wind power generation facility by injecting ballast water into the float;
This construction method for a spar-type offshore wind power generation facility is characterized by comprising a fourth step of installing any remaining blades using a large crane ship, and finally adjusting the ballast water to achieve the specified draft state. When erecting the spar-type offshore wind power generation facility in the third step,
2. A construction method for a spar-type offshore wind power generation facility as described in claim 1, in which the center of gravity of the float or tower of the spar-type offshore wind power generation facility is offset in advance using a center of gravity offsetting means, and ballast water is continuously injected to erect the spar-type offshore wind power generation facility upright. When erecting the spar-type offshore wind power generation facility in the third step,
2. A construction method for a spar-type offshore wind power generation facility as described in claim 1, in which the center of gravity of the float or tower of the spar-type offshore wind power generation facility is offset in advance by a center of gravity offsetting means, ballast water is injected, and after the spar-type offshore wind power generation facility starts to stand up, the injection of ballast water is stopped at a predetermined amount to temporarily stop the spar-type offshore wind power generation facility in the tilted state before it is stood upright, and then ballast water is gradually injected again to stand the spar-type offshore wind power generation facility upright. 4. The construction method for a spar-type offshore wind power generation facility according to claim 2 , wherein the center of gravity decentering means is a weight detachably attached to the outer surface of the float for the spar-type offshore wind power generation facility. The construction method for a spar-type offshore wind power generation facility according to claim 4 , wherein the weight is attached at a position above sea level when erected. 4. The construction method for a spar-type offshore wind power generation facility according to claim 2 , wherein the gravity center offsetting means is a solid ballast placed inside the floating body.

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