JP7495802B2 - Construction method of floating water structure and temporary mooring float used therefor - Google Patents

Description

The present invention relates to a construction method for floating water structures, such as floating offshore wind turbines, that are installed on the ocean, and a temporary mooring float used therefor.

In recent years, the use of renewable energy has been promoted from the perspective of environmental impact and the effective use of natural energy, and among these, wind power generation, which has a large potential for generating electricity, has been attracting attention.

In particular, compared to onshore, the offshore environment is favorable for obtaining wind suitable for wind power generation, and as such is a suitable environment for installing wind power generation equipment, the development and installation of offshore wind power generation equipment has progressed in recent years.

Offshore wind turbines are roughly classified into fixed-bottom types, which are installed in waters shallower than 50 meters, and floating types, which are installed in waters deeper than 50 meters, with fixed-bottom types currently predominating.

However, since ocean areas 50 meters or deeper are far from land, have a lot of wind, and are well suited to securing power generation potential, it is thought that the demand for floating offshore wind turbines will increase.

A floating offshore wind turbine comprises a float that is suspended in water and a superstructure in which the nacelle and blades are supported on the top of a support tower erected on the float, with the superstructure being supported by the float.

A widely known type of floating structure is a spar-type structure that floats in the water and stands upright in the vertical direction.

Conventionally, to install this spar-type floating offshore wind power generation device, the float is laid flat and transported to the installation area by barge or towing, ballast water is injected into the float to raise it up so that its top end protrudes above the water surface, the float is moored, and then the superstructure is moved to the top end of the float by a crane ship or the like in this state, and the float and the superstructure are connected (see, for example, Patent Document 1).

JP 2014-227966 A

However, the ocean areas where floating offshore wind turbines are installed, at depths of 50 m or more, often have harsher oceanographic conditions than the ocean areas where general marine construction work is carried out, and the installation work for floating offshore wind turbines must be carried out under harsh oceanographic conditions only when the oceanographic conditions are relatively calm, which limits the timing and duration of the installation work.

When installing this floating offshore wind turbine, a series of operations must be carried out: raising the float, suspending the superstructure, and connecting and mooring the float and superstructure. Because this series of operations cannot be interrupted, it is difficult to find a time when the ocean conditions are right for operation.

In addition, the installation of floating offshore wind turbines requires harsh oceanographic conditions and delicate work using large work vessels, which creates the problem of low work availability.

In recent years, as wind turbines have become larger in order to reduce the cost of generating electricity, the floating structures that support them have also become larger. As a result, the waters in which these larger offshore wind turbines are installed are becoming deeper, which in turn makes the oceanographic conditions more severe, resulting in lower operating rates.

In view of these conventional problems, the present invention has been made with the objective of providing an installation method for a floating offshore wind turbine that reduces the amount of work required in the installation area and enables efficient installation.

The invention described in claim 1, which aims to solve the above-mentioned problems of the prior art, is characterized in that in a construction method for a floating water structure in which an upper structure is connected to a lower floating structure erected in water, the lower floating structure is erected in a specified temporary mooring area, and then the erected lower floating structure is detachably held by a temporary mooring float, and the temporary mooring float is connected to an anchor body installed on the bottom of the water with a mooring rope, so that the lower floating structure is moored in the temporary mooring area in an erected state.

The invention described in claim 2 is characterized in that, in addition to the configuration of claim 1, multiple temporary mooring floats holding the lower floating structures are connected to each other, and the multiple lower floating structures are moored in the temporary mooring area.

The invention described in claim 3 is characterized in that, in addition to the configuration of claim 1 or 2, ballast water is introduced into or discharged from the lower floating structure while the lower floating structure is held by the temporary mooring float.

The invention described in claim 4 is characterized in that, in addition to the configuration of any one of claims 1 to 3, the upper structure is connected to the lower floating structure held by the temporary mooring float in the temporary mooring area.

The feature of the invention described in claim 5 is that, in addition to the configuration of any one of claims 1 to 4, after the lower floating structure is moored in the temporary mooring area in an upright state, the mooring line is removed from the temporary mooring float and the lower floating structure is moved to the installation area while being held by the temporary mooring float.

The invention described in claim 6 is characterized in that the temporary mooring float used in the construction method of a floating water structure described in any one of claims 1 to 5 is provided with a pair of holding floats connected to each other in a state that allows them to be opened and closed horizontally, and the lower floating structure is held upright between the holding floats so that it can be held from both sides.

The invention described in claim 7 is characterized in that, in addition to the configuration of claim 6, the holding float has a concave holding portion formed on the opposing sides into which the lower floating structure fits.

The invention described in claim 8 is characterized in that, in addition to the configuration of claim 7, the holding float is provided with a cushioning member made of an elastic material on the inner circumferential surface of the holding part.

The feature of the invention described in claim 9 is that, in addition to the configuration of any one of claims 6 to 8, the pair of grasping floats are connected to each other at one end by a hinge portion so that they can rotate horizontally, and are provided with a connecting portion which is removably connected to the other end.

The invention described in claim 10 is characterized in that, in addition to the configuration of any one of claims 6 to 9, the entire structure is formed in a rectangular shape, and can be joined to other temporary mooring floats.

The construction method for a floating water structure according to the present invention, by incorporating the configuration of claim 1, allows the floating body to be temporarily moored in an upright state in calm waters, reducing the amount of work required in installation areas with severe oceanographic phenomena and enabling efficient construction.

In addition, in the present invention, by adopting the configuration of claim 2, multiple lower floating structures can support each other and be temporarily moored stably.

In addition, by providing the configuration of claim 3 in the present invention, the draft of the lower floating structure during mooring can be adjusted, allowing for temporary mooring in a more stable state.

Furthermore, by providing the configuration of claim 4 in the present invention, the upper structure connection work can be performed in a stable state in calm sea areas.

Furthermore, in the present invention, by providing the configuration of claim 5, the lower floating structure or the floating water structure can be moved in a stable state to the installation area.

In addition, by being provided with the configuration of claim 6, the temporary mooring float of the present invention can accurately grasp the lower floating structure and temporarily moor it in a stable state.

Furthermore, in the present invention, by providing the configuration of claim 7, the temporary mooring float can be securely held.

Furthermore, in the present invention, by adopting the configuration of claim 8, damage to the lower floating structure can be prevented.

In addition, by providing the configuration of claim 9 in the present invention, the task of grasping the lower floating structure can be carried out smoothly.

Furthermore, in the present invention, by providing the configuration of claim 10, the temporary mooring floats support each other, so that multiple upright lower floating structures can be temporarily moored in a stable state.

FIG. 1 is a front view showing an example of a floating water structure according to the present invention. FIG. 1 is a cross-sectional view showing the procedure of the construction method for a floating water structure according to the present invention, illustrating the state of the erection work of the lower floating structure in the temporary mooring area. A cross-sectional view showing the installation work state of the above temporary mooring float. FIG. 4A is a perspective view showing an example of the temporarily moored float in FIG. 3, and FIG. 4B is a perspective view showing another example of the temporarily moored float. FIG. 4 is a cross-sectional view showing the state of the ballast adjustment work of the above. FIG. 2 is a cross-sectional view showing the state when the above is temporarily moored. FIG. FIG. 2 is an oblique view showing the state in which multiple lower floating structures of the same are temporarily moored. This is a cross-sectional view showing the connecting work between the lower floating structure and the upper structure and the temporary mooring state in the temporary mooring area. FIG. 2 is a side view showing the state of towing operation of the floating water structure.

Next, the construction method for a floating structure on water and an embodiment of a temporary mooring float used therein according to the present invention will be described based on the examples shown in Figures 1 to 10.

This embodiment will be described using a floating offshore wind power generation device as an example of a floating water structure 1, and the reference numeral in the figure indicates the floating water structure 1.

As shown in FIG. 1, the floating water structure 1 comprises a lower floating structure 2 that stands in the water and an upper structure 3 that is connected to the lower floating structure 2, and is designed to be installed in a specified installation area 4 with the upper structure 3 supported by the lower floating structure 2.

Installation area 4 is an area with a water depth of 50 m or more, a high wind volume, and is expected to have a large potential for generating electricity from wind power.

The upper structure 3 has a nacelle 6 and blades 7 supported on the top of the support tower 5, and the lower end of the support tower 5 is connected to the upper end of the lower floating structure 2.

The lower floating structure 2 is a spar-type (hanging float) float, and is equipped with a vertically long cylindrical floating body 8 with an internal cavity, and an upper structure connecting part 9 protruding from the upper surface of the floating body 8, and the upper structure 3 is connected to the upper structure connecting part 9.

The upper structure connecting part 9 is formed with a smaller diameter than the floating body 8, and a step part 10 is formed at the joint between the upper structure connecting part 9 and the floating body 8.

The floating body 8 can adjust its buoyancy and move its center of gravity by injecting and discharging ballast water 11 into the hollow space, and can stand upright in the water stably by pouring ballast material 12 into the inner bottom of the hollow space.

The ballast material 12 is made of gravel, iron ore, slag, concrete, and other materials with a higher specific gravity than water.

To construct such a floating water structure 1, first, the lower floating structure 2 is fabricated in a fabrication yard on land. The fabrication yard only needs to be located on the coast, and may be located away from the installation area 4 and temporary mooring area 13 described below.

After fabrication is complete, the lower floating structure 2 is temporarily stored in a lying position in the fabrication yard or a nearby temporary storage area.

Then, when a time is chosen that allows for easy transportation, the lower floating structure 2 is floated on the water from the coast using a semi-submersible barge or a crane, etc., while still lying flat, and towed in that state to the designated temporary mooring area 13.

The temporary mooring area 13 is set in a relatively shallow, calm sea area that is less affected by oceanographic conditions, while still ensuring sufficient water depth to erect the lower floating structure 2.

Then, as shown in FIG. 2, ballast water 11 is injected into the hollow space inside the floating body 8 in a specified temporary mooring area 13, the center of gravity is shifted to the lower end side of the lower floating structure 2, and the lower floating structure 2 is erected (erecting process).

Next, as shown in FIG. 3, the raised lower floating structure 2 is detachably held by the temporary mooring float 14 and moved to a predetermined mooring position (holding process).

As shown in Figure 4 (a), the temporary mooring float 14 has a pair of holding floats 15, 15 connected to each other in a state that allows them to be opened and closed. By connecting the pair of holding floats 15, 15 to each other, the lower floating structure 2 is held in an upright position between the holding floats 15, 15.

In addition, the temporary mooring float 14 is formed so that the overall shape is rectangular when the pair of holding floats 15, 15 are connected, and it can be joined to other temporary mooring floats 14 by butting their sides together.

The joined temporary mooring floats 14 may be connected to each other by a connecting rope (not shown), or may be connected by bridging a steel member or the like between the two temporary mooring floats 14, 14 and fixing both ends of the member to the temporary mooring float 14 by welding or the like.

Each holding float 15, 15 is formed as a hollow rectangular parallelepiped with a cavity inside, and has concave holding sections 16 on opposing sides, so that the holding sections 16 can be connected together with their sides facing each other.

The means for connecting a pair of holding floats 15, 15 is not particularly limited, and for example, they may be connected to each other with a connecting rope, or they may be connected by bridging a steel material or the like between the holding floats 15, 15 and fixing both ends of the material to the holding floats 15, 15 by welding or the like.

In addition, each holding float 15, 15 can adjust its buoyancy and draft by filling and discharging water into the hollow space.

The holding portion 16 is formed to match the outer shape of the part of the lower floating structure 2 to be grasped, which in this embodiment is the outer diameter of the upper structure connecting portion 9, and when a pair of grasping floats 15, 15 are joined to each other, a circular hole is formed by both holding portions 16, 16.

The hole formed by both retaining parts 16 has a diameter that is approximately the same as or slightly larger than the diameter of the upper structure connecting part 9.

In addition, an arc-shaped cushioning member 17 made of an elastic material such as rubber may be fixed to the inside of each holding portion 16, and a pair of holding floats 15, 15 may be joined so that the holding portion 16 grips the upper structure connection portion 9 of the lower floating structure 2 via the cushioning member 17.

In addition, the configuration of the temporary mooring float 14 is not limited to the above-mentioned embodiment, and may be, for example, as shown in Figure 4 (b), a pair of grasping floats 15, 15 having a hinge portion 18 on one end side, connected to each other by the hinge portion 18 so as to be rotatable in the horizontal direction, and connected at the other end side so as to be detachably connected.

Also, an existing work barge or the like may be used as the holding floats 15, 15 that make up the temporary mooring float 14, and the lower floating structure 2 may be clamped and held by the work barge.

Meanwhile, before the gripping process by the temporary mooring float 14 begins, an anchor body 20 is installed on the bottom 13a of the temporary mooring area 13, one end of a mooring line 19 is connected to the anchor body 20, and a buoy or the like is attached to the other end of the mooring line 19 as a marker and floated on the sea.

When the temporary mooring float 14 is to be moored to the anchor body 20, a buoy or the like is pulled up and the mooring lines 19 are detachably connected to predetermined locations (the four corners in this embodiment) of the temporary mooring float 14, so that the temporary mooring body 14 is moored (catenary moored) to the anchor body 20 with the mooring lines 19, 19... hanging slack.

The anchor body 20 may be installed on the water bottom 13a with the temporary mooring float 14 and the anchor body 20 connected by a mooring line 19.

The anchor body 20 is not particularly limited, but may be a sinker, pile, drag anchor, suction pile, etc.

Next, as shown in FIG. 5, a material carrier vessel 21 such as a gut ship or gut barge is pulled up alongside the temporary mooring float 14, and with the lower floating structure 2 held by the temporary mooring float 14, ballast material 12 is poured into the float body 8 (ballast adjustment work).

At that time, a generator and an underwater pump are installed on the temporary mooring float 14, and the work is carried out while keeping the draft of the lower floating structure 2 constant by injecting and discharging ballast water 11 inside the float body 8.

Then, as shown in Figures 6 and 7, ballast water 11 is discharged from inside the float body 8, and the step portion 10 is brought into contact with the lower edges of the peripheral portions of both retaining portions 16, i.e., the bottom surface of the temporary mooring float 14, and the lower floating structure 2 is moored in the temporary mooring area 13 in an upright state.

When mooring multiple lower floating structures 2 in the temporary mooring area 13, the series of operations shown in Figures 2 to 6 are repeated for each lower floating structure 2, and then, as shown in Figure 8, the temporary mooring floats 14 are joined together and temporarily moored in that state.

As shown in Figure 8, when a new lower floating structure 2 is temporarily moored, the mooring lines 19, 19... connected to the temporary mooring float 14 that holds the existing lower floating structure 2 may be removed and replaced with the temporary mooring float 14 that holds the new lower floating structure 2.

Then, as shown in FIG. 9, if necessary, the lower floating structure 2 and the upper structure 3 are connected while temporarily moored in the temporary mooring area 13.

The upper structure 3 is assembled in a production yard near the coast of the temporary mooring area 13 or near the temporary mooring area 13. The assembled upper structure 3 is then lifted by a crane ship or the like and moved onto the temporarily moored lower floating structure 2, and once aligned, it is lowered to connect the lower end of the support tower section 5 to the upper structure connecting section 9.

The floating water structure 1, in which the upper structure 3 and the lower floating structure 2 are connected, is temporarily moored while being held by the temporary mooring float 14 in the temporary mooring area 13 or another temporary mooring area.

Then, when the sea conditions in the installation area 4 are favorable and installation is possible, as shown in FIG. 10, the temporary mooring float 14 is removed, and the floating water structure 1, with the upper structure 3 and the lower floating structure 2 connected, is towed in an upright state from the temporary mooring area 13 to the installation area 4.

In addition, towing may be performed by removing only the mooring lines 19, 19... from the temporary mooring float 14, with the floating water structure 1 still held by the temporary mooring float 14.

Next, in the installation area 4, as shown in FIG. 1, the mooring ropes 23, 23... each having one end connected to an anchor member 22 on the bottom of the water, are connected to the floating structure 1 at a predetermined position, and the construction is completed by mooring it (full mooring).

In the construction method for the floating water structure 1 configured in this manner, the lower floating structure 2 is erected in the calm temporary mooring area 13 and left temporarily moored in the erected state, thereby eliminating the need to erect the lower floating structure 2 in the installation area 4, which has severe sea conditions.

As a result, in the present invention, each process of raising the lower floating structure 2, installing the upper structure 3, and connecting the lower floating structure 2 and the upper structure 3, which were previously carried out as a series of operations, can be carried out in stages, making it possible to appropriately select whether to carry out or stop work depending on the oceanographic conditions in the installation area 4, and to carry out work safely.

In addition, by temporarily mooring multiple lower floating structures 2 in an upright position in the temporary mooring area 13, work to connect multiple upper structures 3 can be carried out all at once during periods of favorable oceanographic conditions.

In addition, by temporarily mooring multiple floating water structures 1 held by temporary mooring floats 14 in the temporary mooring area 13, the process from moving to installation can be easily carried out according to the oceanographic conditions in the installation area 4.

In the above embodiment, the upper structure 3 is connected to the lower floating structure 2 in the temporary mooring area 13, but the lower floating structure 2 alone may be towed in an upright state to the installation area 4, and the work of connecting the upper structure 3 and the lower floating structure 2 may be performed in the installation area 4.

In addition, in the above-mentioned embodiment, a floating wind turbine was used as an example of the floating structure 1, but the floating structure 1 is not limited to this.

Reference Signs List 1 Floating water structure 2 Lower floating structure 3 Upper structure 4 Installation sea area 5 Support tower section 6 Nacelle 7 Blade 8 Floating body main body 9 Upper structure connection section 10 Step section 11 Ballast water 12 Ballast material 13 Temporary mooring sea area 14 Temporary mooring float 15 Gripping float 16 Holding section 17 Buffer member 18 Hinge section 19 Mooring line 20 Anchor body 21 Material carrier 22 Anchor member 23 Mooring line

Claims (10)

A construction method for a floating water structure in which an upper structure is connected to a lower floating structure erected in water, comprising:
A construction method for a floating water structure, characterized in that after the lower floating structure is raised in a specified temporary mooring area, the raised lower floating structure is detachably held by a temporary mooring float, and the temporary mooring float is connected to an anchor body installed on the water bottom with a mooring line, so that the lower floating structure is moored in the temporary mooring area in an upright state. The construction method for a floating structure on water described in claim 1, in which a plurality of temporary mooring floats holding the lower floating structures are connected to each other, and the plurality of lower floating structures are moored in the temporary mooring area. The construction method for a floating structure on water described in claim 1 or 2, in which ballast water is charged into or discharged from the lower floating structure while the lower floating structure is held by the temporary mooring float. The construction method for a floating water structure according to any one of claims 1 to 3, in which the upper structure is connected to the lower floating structure held by the temporary mooring float in the temporary mooring area. A construction method for a floating water structure as described in any one of claims 1 to 4, wherein the lower floating structure is moored in the temporary mooring area in an upright state, and then the mooring line is removed from the temporary mooring float, and the lower floating structure is moved to the installation area while being held by the temporary mooring float. A temporary mooring float used in the construction method for a floating water structure according to any one of claims 1 to 5,
A temporary mooring float comprising a pair of holding floats connected to each other in a manner that allows them to be opened and closed horizontally, and characterized in that the lower floating structure is held upright between the holding floats so that it can be grasped from both sides. The temporarily moored float according to claim 6, wherein the holding float has a concave holding portion formed on opposing sides into which the lower floating structure fits. The temporarily moored float according to claim 7, wherein the holding float is provided with a cushioning member made of an elastic material on the inner circumferential surface of the holding portion. A temporary mooring float as described in any one of claims 6 to 8, wherein the pair of holding floats are connected to each other at one end by a hinge portion so that they can rotate horizontally, and the other end has a connecting portion which is detachably connected to the other end. 10. A temporary mooring float as claimed in any one of claims 6 to 9, which is formed in a rectangular shape as a whole and is capable of being joined to other temporary mooring floats.

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