Methods for the installation and maintenance of floating wind turbines

Abstract

The present invention relates to a method for the maintenance and installation of an offshore wind turbine, comprising the steps of: - positioning a floating service vessel (8) having a crane (10) above a semi-submerged substructure (2) of a floating wind turbine (1), wherein the substructure (2) comprises several mainly vertical pontoons or columns (3, 4, 5) interconnected by tubular beams (6); - bringing the tubular beams (6) into contact with a connecting structure (14) of the service vessel; and - lifting the service vessel (8) above the waterline.

Description

Technical Field

[0001] The present invention relates to a method for the installation and maintenance of a floating wind turbine. More particularly, the present invention relates to the installation and maintenance of a wind turbine in an offshore environment where the wind turbine is disposed on a semi-submersible foundation floating in a body of water.

Background Art

[0002] A wind turbine for use offshore includes a tower that forms a support portion of the wind turbine. This tower can be disposed on the seabed when the water depth is not so deep, or can be disposed on a floating substructure when the water depth is deep. The installation and maintenance of a wind turbine are most often carried out using a floating service vessel having a crane in order to perform the necessary installation or maintenance work. One significant problem with this solution is that due to the relative movement between the service vessel and the wind turbine, such work can only be carried out in relatively calm seas. Further, using a large floating vessel for the installation and maintenance of an offshore wind turbine is a costly operation. One alternative solution is to tow a floating wind turbine to shore and perform the installation at a quay, but this is also a costly and time-consuming operation.

[0003] One known solution for avoiding this problem can be found in Norwegian Patent NO346593. This invention reduces this problem by using a portable crane lifted onto a floating substructure supporting a wind turbine by means of an on-board crane disposed on a service vessel.

[0004] U.S. Patent Application Publication No. 20110017659(A1) teaches an apparatus and method for the assembly and maintenance of a wind turbine, in which the wind turbine tower is supported by the seabed and a jack-up offshore platform having a crane for the assembly and maintenance of the wind turbine. The legs of the jack-up platform are also supported by the seabed. This solution can only be used in relatively shallow waters.

[0005] U.S. Patent No. 8701579(B2) describes an offshore wind turbine installation vessel in which the turbine is installed on a foundation that has been laid on the seabed. The crane used for the installation work is mounted on the installation vessel. This solution does not take into account the relative movement between the foundation and the installation vessel due to the effects of waves.

[0006] U.S. Patent No. 10302068(B2) describes the use of a jack-up platform with a crane for the installation and maintenance of offshore wind turbines. This platform is an offshore platform previously used for hydrocarbon production. This solution can only be used in shallow water and does not take into account the relative movement due to wave action when the substructure of the wind turbine is floating on the water surface.

[0007] U.S. Patent No. 11168666(A1) describes a jacking platform for facilitating the installation of an offshore wind turbine, the jacking platform having a receiving space and comprising a central positioning system configured to position the received floating barge in the center of the receiving space.

[0008] WO2017204656A1 describes a method for providing a vessel having a broad submerged hull and a narrow tower extending upward from the submerged hull. The submerged portion of the vessel is comprised of attachable utility units.

[0009] U.S. Patent Application Publication No. 2012183359(A1) describes a method for installing a submersible platform. The method includes the step of lowering the platform into the water from a vessel positioned above the platform, with a spud connecting the vessel to the platform stabilizing the platform during the lowering. The assembly of the vessel and the platform, and the vessel used to connect to the platform, are also disclosed.

[0010] WO2022045896A1 discloses a ship for offshore structures, such as wind turbines. The ship has a cargo deck and two longitudinally extending upper edges of hull sidewalls configured to be located above the waterline.

[0011] DE19741988 shows a wind turbine with a crane temporarily attached to its tower. The crane is movable up and down along the tower.

[0012] DE19647515 shows a similar crane that allows for the installation of additional tower sections on top of the tower section to which the crane is mounted.

[0013] U.S. Patent Application Publication No. 20180282134 also describes a crane mounted on the tower of a wind turbine, which is movable up and down along the tower. This crane is configured to replace the blades of the wind turbine.

[0014] DE102012002720A1 also describes a crane attached to the tower structure of a wind turbine.

[0015] U.S. Patent No. 9,120,652 describes a wind turbine with a small service crane located inside the nacelle. When the service crane is needed, a hatch can be opened and the crane can be removed from there. GB2558242A indicates a larger service crane located at the top of the nacelle.

[0016] In all these known solutions, the crane is fixed to the tower of the wind turbine or to the semi-submersible substructure of the wind turbine, or is positioned to be removable. [Overview of the project] [Problems that the invention aims to solve]

[0017] [Means for solving the problem]

[0018] The present invention relates to a method for the maintenance and installation of offshore wind turbines, - A step for positioning a floating service vessel with a crane above the semi-submerged substructure of a floating wind turbine, wherein the substructure comprises several mainly vertical pontoons or columns interconnected by tubular beams, - The step of bringing the tubular beam into contact with the connecting structure of the service vessel, - Steps to lift the service vessel above the waterline and This includes methods.

[0019] The connecting structure is preferably a leg that protrudes from the service vessel, and each leg is provided with a connecting structure to contact a tubular beam.

[0020] In one preferred embodiment, the legs are of the jack-up type and can be moved up and down.

[0021] In another preferred embodiment, the legs cannot be moved.

[0022] Preferably, a floating service vessel i) Steps to extend the legs and lift the service vessel out of the water, ii) discharging ballast from the semi-submerged lower structure and raising the lower structure until the service vessel is above the sea surface It is raised above the sea surface by either of the following.

[0023] In a preferred embodiment, the legs are pedestals or gantries.

Brief Description of the Drawings

[0024] [Figure 1] It is a diagram of the first step of the method according to the present invention for arranging a floating crane vessel on the semi-submersible lower structure of a wind turbine. [Figure 2] It is a diagram of the second step of the method where the legs of the floating crane vessel are in contact with the lower structure. [Figure 3] It is a diagram of the final step of the method where the legs of the floating crane vessel are extended to lift the crane vessel above the sea surface. [Figure 4] It is a diagram of a situation where the floating vessel is supported by a truss structure and the crane is being raised for work. [Figure 5] It is a diagram of the first step of the method according to the second embodiment of the present invention where the crane vessel is arranged above the lower structure. [Figure 6] It is a diagram of the final step of the method according to FIG. 5 where ballast is discharged from the semi-submersible lower structure, thereby raising the crane vessel above the water surface.

Mode for Carrying Out the Invention

[0025] Figure 1 illustrates the first step of the method according to the present invention. Figure 1 also shows an exemplary semi-submersible substructure (2) for an offshore wind turbine unit (1). The substructure (2) is partially submerged, with the tops of the tubular beams (6) about 10 meters below sea level. The substructure (2) comprises several pontoons or columns (3, 4, 5) oriented substantially vertically, connected to one another by the tubular beams (6). The cross-sections of the pontoons or columns (3, 4, 5) can be circular, square, rectangular, or polygonal. The pontoons or columns (3, 4, 5) and / or tubular beams (6) are hollow and provide the buoyancy required for the substructure. The substructure in Figure 1 is shown in a triangular design with three pontoons or columns (3, 4, 5), but the design can also be a square, rectangular, or polygonal design. Furthermore, the substructure (2) is connected to one or more upward-extending towers (7) that support and hold the nacelles of the wind turbines. During normal operation, the substructure (2) is submerged below sea level. The substructure (2) has a ballast system to raise or lower the substructure (2) relative to the water level by pumping water into or out of the pontoons (3, 4, 5) and / or tubular beams (6).

[0026] Furthermore, Figure 1 shows a first step in positioning the service vessel (8) above the substructure. This vessel may be a barge towed by, for example, a tugboat (9), or the service vessel (8) may have an engine to move the vessel. The service vessel (8) is equipped with a crane (10) and several legs (13). In one preferred embodiment, the legs (13) may be of the jack-up type and may be moved up and down. In a second preferred embodiment, the legs (13) are of a fixed length and cannot be extended or retracted. This second embodiment is further described with reference to Figures 5 and 6. Furthermore, the service vessel (8) may be equipped with support structures such as a frame (11) to support wind turbine blades (12) to be installed or replaced.

[0027] Figure 2 shows the service vessel (8) positioned floating above the substructure (2). The legs (13) are partially extended so that the lower part of the legs (13) is in contact with the tubular beam (6). The lower part of each leg (13) has a support structure or connecting structure (14) having a shape complementary to the outer portion of the tubular beam (6).

[0028] Figure 3 shows the service vessel (8) with its legs (13) fully extended, raising it above the sea surface. In this position, the service vessel (8) is unaffected by waves, there is no relative movement between the service vessel (8) and the substructure (2), and as a result, the crane (10) can be operated even when the waves are relatively high.

[0029] When the leg (13) is fully extended, the length of the upper part of the leg (13) is such that the upper part of the leg (13) protruding upward from the deck of the service vessel (8) does not obstruct the operation of the crane (10).

[0030] Figure 4 shows the situation in Figure 3 with the legs (13) fully extended and the service vessel (8) raised above the sea surface. The crane (10) on the service vessel (8) is raised and ready for work.

[0031] Figure 5 shows a second preferred embodiment of the present invention, in which the service vessel (8) is positioned above the substructure (2). In this embodiment, the legs (13) of the service vessel (8) are not lowered; instead, ballast is discharged from the substructure (2) until the lower part of the legs (13) contacts the tubular beam (8). Instead of the legs (13), the service vessel (8) may have other types of substructure (2). Further ballast is then discharged from the substructure (2), and the substructure (2) then lifts the service vessel (8) above the waterline. Instead of the legs (13) shown in Figures 5 and 6, other types of connecting structures, such as pedestals or supports that can be connected to the tubular beam (6), may be present. [Explanation of symbols]

[0032] 1. Floating Wind Turbine Unit 2 Floating semi-submersible substructure 3, 4, 5 Pontoons / pillars 6 tubular beam 7 Wind Turbine Towers 8 Crane ship 9 tugboat 10 Cranes 11. Support structure / frame 12 turbine blades 13 Jacking up legs 14 Connecting Components

Claims

1. A method for the maintenance and installation of offshore wind turbines, - A step of positioning a floating service vessel (8) having a crane (10) above a semi-submerged substructure (2) of a floating wind turbine (1), wherein the substructure (2) comprises several mainly vertical pontoons or columns (3, 4, 5) interconnected by tubular beams (6), - A step of bringing the tubular beam (6) and the connecting structure (14) of the service vessel into contact, - A step of lifting the service vessel (8) above the water surface Methods that include...

2. The method according to claim 1, wherein the connecting structure is a leg portion (13) protruding from the service vessel (8), and each of the leg portions (13) is provided with a connecting structure (14) to contact the tubular beam (6).

3. The method according to claim 1 or 2, wherein the leg portion (13) is of the jack-up type and can be moved up and down.

4. The method according to claim 1 or 2, wherein the leg portion (13) cannot be moved.

5. The floating service vessel (8) i) The step of extending the legs (13) to raise the service vessel out of the water, ii) Discharging ballast from the semi-submerged substructure (2) and raising the substructure (2) until the service vessel (8) is above sea level. The method according to any one of claims 1 to 4, wherein the sea surface is raised by any of the following means.

6. The method according to claim 4, wherein the leg portion (13) is a base or a stand.

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