Semi-submersible floating vessel for offshore wind turbines

Abstract

The present invention relates to a semi-submersible floating body (2) for an offshore wind turbine, the floating body comprising four vertical supports, including at least three central supports (4,6), one of which is intended to receive a wind turbine mast, and a vertical support (6) connected together by a pontoon (8), the lower pontoon (8) being formed by a plurality of planar panels (81-84) assembled together at a longitudinally extending edge (10) between two supports, the edges of the pontoons being rounded and connected to the supports via a transition section (12) at each of their longitudinal ends.

Description

Technical Field

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[0001] The present invention relates to the general field of semi-submersible floating bodies used in offshore wind turbines. More specifically, the present invention relates to the structure of a novel semi-submersible floating body.

Background Art

[0002] The purpose of an offshore wind turbine is to utilize the energy of the wind to generate electricity by means of a turbine and a generator. Offshore wind turbines include two main types: fixed-bottom wind turbines installed on the seabed (typically in shallow depths less than 50 m), and floating wind turbines that can be constructed on land and installed in areas where the seabed depth typically exceeds 50 m.

[0003] The floating wind turbine targeted by the present invention generally includes a turbine formed by a motor having several rotating blades on a horizontal axis and a generator coupled to the motor. The motor and the generator are fixed to the upper end of a vertical mast (or pylon). The lower end of the mast is attached to a floating support structure (hereinafter referred to as "floating body").

[0004] There are several main groups of floating bodies for offshore wind turbines, including semi-submersible floating bodies, submersible floating bodies with tension legs (tension leg platforms (TLPs)), SPAR (single point anchor reservoir) type floating bodies, barge type semi-submersible floating bodies, and floating bodies with pendulum type counterweights.

Prior Art Documents

Patent Documents

[0006] More specifically, this invention relates to a semi-submersible floating structure, i.e., a steel or concrete foundation forming a tripod-like structure with approximately three (or four) cylinders connected by a metal structure. The stability of the structure is ensured by a ballast system that allows a portion of the foundation to be submerged in water. A characteristic feature of this structure is its large size and shallow draft.

[0007] For example, one can refer to Patent Document 1, which describes a semi-submersible hybrid floating structure including a central support and three outer support columns connected to the central support by pontoon-shaped branching sections.

[0008] This type of hybrid float has the advantage of a simple design. However, such a structure has considerable weight and is highly susceptible to fatigue. Therefore, a semi-submersible floating vehicle with optimized weight while meeting fatigue criteria is required. [Means for solving the problem]

[0009] This objective is achieved by a semi-submersible floating structure for offshore wind turbines, the floating structure comprising at least three vertical supports, one of which is intended to receive a wind turbine mast, the vertical supports being connected together by pontoons, each formed by a plurality of planar panels assembled together at longitudinally extending edges between two of the supports. According to the present invention, the edges of the pontoons are rounded and connected to the supports via transitions at each of their longitudinal ends.

[0010] The floating body according to the present invention is noteworthy in that the edges of the pontoon are not sharp (i.e., not right angles) but rounded, which allows for limiting stress concentration and thus substantially improving the fatigue properties in these areas. Compared to right angles, this feature allows the floating body to meet fatigue criteria while reducing its weight. With respect to the transition, this allows for limiting stress in the connection area between the pontoon and the floating body's supports.

[0011] In addition, the present invention makes it possible to improve the manufacturability of pontoons by eliminating the continuity of lateral reinforcement from one side of the pontoon to the other. The present invention also makes it possible to improve the hydrodynamic behavior of floating bodies by eliminating the side effects associated with the sharp edges of the prior art.

[0012] Preferably, the rounded edge of the pontoon has a quadrant shape with a radius of 100 to 1,500 mm. Preferably, the rounded edges of the pontoon have the same thickness as the adjacent planar panel.

[0013] The transition section has one rounded end that connects to the longitudinal end of the rounded edge, and the opposite end that forms a right angle. This transition section may be a part obtained by one of the following techniques: forging, casting, press bending, and additive manufacturing, which transforms the triangular shape on one side into a rounded shape on the opposite side.

[0014] Preferably, each planar panel is provided with two or three main longitudinal reinforcements and a plurality of secondary transverse reinforcements on its inner surface. This feature allows for a reduction in the weight of the floating body and facilitates its manufacture.

[0015] In this case, the main reinforcing members of each planar panel are preferably spaced evenly apart from one another by vertical partitions that define the ballast area. According to one embodiment, the floating body comprises a vertical column including a central column (4) intended to receive a wind turbine mast, and three outer columns are connected to the central column by a lower pontoon.

[0016] In this embodiment, each of the outer columns may be formed by assembling flat panels. Alternatively, each of the outer columns may have a substantially cylindrical shape. Furthermore, in this embodiment, at least one gangway may be further provided between the upper end of the outer column and the central column. Such a gangway facilitates access to the floating body (e.g., by helicopter) or enables having a second access point for a maintenance vessel.

[0017] Furthermore, in this embodiment, the central column may have a frustum shape or a cylindrical shape. According to one advantageous configuration of the present invention, the floating body comprises ballast areas that can be adjusted inside each pontoon and / or inside each outer column to correct the attitude of the floating body and improve the hydrodynamic behavior of the floating body.

Brief Description of the Drawings

[0018] [Figure 1] It is a perspective view of a semi-submersible floating body according to the present invention. [Figure 2] It is a cross-sectional view taken along II-II of FIG. 1. [Figure 3] It shows a reinforcing material inside the pontoon of the floating body in FIG. 1.

Modes for Carrying Out the Invention

[0019] FIG. 1 shows a perspective view of a semi-submersible floating body 2 for an offshore wind turbine according to a first embodiment of the present invention. In this embodiment, the floating body 2 comprises four vertical columns including a central column 4 intended to receive a wind turbine mast (not shown in FIG. 1) and three outer columns 6 connected to the central column 4 by a branch portion forming a lower pontoon 8.

[0020] More specifically, the lower pontoon 8 and the outer strut 6 are spaced apart from each other at an angle of 120° to form a star-shaped structure. Of course, it is possible to assume that the vertical struts of the floating body are connected together by the upper pontoon and / or the lower pontoon.

[0021] Furthermore, at least the pontoons are formed by a plurality of flat panels assembled together. More specifically, in the embodiment of FIG. 1, each lower pontoon 8 is constituted by the assembly of four flat panels 81 to 84 forming a rectangular parallelepiped (in FIG. 1, only the flat panels 81 and 84 are visible).

[0022] Of course, it is possible to assume that the number of flat panels forming each pontoon is different (for example, five, six, etc.). According to the present invention, the flat panels of each pontoon extend longitudinally between two struts and are assembled together with rounded edges 10, and the edges 10 are connected to the struts via transition portions 12 at each of their longitudinal ends.

[0023] More specifically, as shown in FIG. 2, the edge 10 of the pontoon has a quarter-circular shape with a radius of 100 to 1,500 mm. The rounded edges 10 of the pontoons are each connected to the vertical struts of the floating body by the transition portions 12 at their two longitudinal ends, enabling a change from a quarter-circular shape to a right-angled shape.

[0024] For this purpose, as shown in the magnifying glass in FIG. 1, the transition portion 12 has a rounded end 12a connected to the longitudinal end of the rounded edge 10 and an opposite end 12b forming a right angle.

[0025] This transition portion 12 is a component that can be obtained by one of the techniques of forging, casting, forming by press bending, and additive manufacturing that changes from a triangular shape on one side to a rounded shape on the opposite side.

[0026] Furthermore, the rounded edges 10 of the pontoon 8 may have the same or different thickness as the adjacent planar panel. According to one advantageous configuration shown in Figure 3, each planar panel 81-84 constituting the pontoon 8 is provided on its inner surface with two or three main longitudinal reinforcements 14 and a plurality of secondary transverse reinforcements 16.

[0027] Therefore, in the embodiment shown in Figure 3, each planar panel 81 to 84 is provided with three main longitudinal reinforcing members 14 and a plurality of secondary transverse reinforcing members 16 that are evenly spaced apart from each other. Furthermore, the main reinforcing members 14 of each planar panel are advantageously separated from each other by vertical partitions 18 that define the ballast area.

[0028] Therefore, each pontoon and / or each outer support is provided with at least one ballast region that can be adjusted to correct the attitude of the floating body and improve its hydrodynamic behavior.

[0029] It should be noted that in the embodiment shown in Figure 1, each of the outer support columns 6 of the floating body 2 has a substantially cylindrical shape. Of course, the present invention also applies to floating bodies in which the outer support columns are each formed by the assembly of planar panels to have a polyhedral shape (see French Patent Application No. 2301328, filed by the applicant on February 13, 2023).

[0030] Furthermore, it should be noted that in the embodiment shown in Figure 1, the central support 4 of the floating body 2 that receives the wind turbine mast has a frustoconical shape that widens downwards. Of course, the present invention is also applicable to floating bodies in which the central support has a cylindrical shape.

[0031] It should also be noted that the floating body may, advantageously, further include at least one gangway (not forming part of the primary structure of the floating body and not shown) between the upper end of the outer support and the central support to facilitate access to the floating body (e.g., by helicopter) or to have a second access point for a maintenance vessel.

Claims

1. A semi-submersible floating body (2) for offshore wind turbines, comprising four vertical supports including a central support (4) intended to receive a wind turbine mast, and three outer supports (6) connected to the central support by a lower pontoon (8), the lower pontoon (8) comprising a plurality of planar panels (8) assembled together at a longitudinally extending edge (10) between two supports. １ ~8 ４ A floating body characterized in that each is formed by a pontoon, the edge (10) of the pontoon is rounded, and at each of its longitudinal ends it is connected to a support via a transition portion (12), and has the same thickness as the adjacent planar panel.

2. The floating body according to claim 1, characterized in that the rounded edge (10) of the pontoon (8) has a quadrant shape with a radius of 100 to 1,500 mm.

3. The floating body according to claim 1 or 2, characterized in that the transition portion (12) has one rounded end (12a) that connects to the longitudinal end of the rounded edge portion (10), and the opposite end (12b) that forms a right angle.

4. The floating body according to claim 3, characterized in that the transition portion (12) is a part obtained by one of the following technologies: forging, casting, press bending, and additive manufacturing, which changes from a triangular shape on one side to a rounded shape on the opposite side.

5. Each of the planar panels (8) of the pontoon (8) １ ~8 ４ The floating body according to any one of claims 1 to 4, characterized in that two or three main longitudinal reinforcing members (14) and a plurality of secondary transverse reinforcing members (16) are provided on the inner surface of the )

6. The floating body according to claim 5, characterized in that the main reinforcing members (14) of each planar panel are evenly spaced apart from one another by vertical partitions (18) that define the ballast area.

7. The floating body according to claim 6, characterized in that each of the outer support columns (6) is formed by assembling planar panels.

8. The floating body according to claim 6, characterized in that each of the outer support columns (6) has a substantially cylindrical shape.

9. The floating body according to any one of claims 6 to 8, further comprising at least one gangway between the upper end of the outer support (6) and the central support (4).

10. The floating body according to any one of claims 6 to 9, characterized in that the central support column (4) has a frustoconical shape.

11. The floating body according to any one of claims 6 to 9, characterized in that the central support column (4) has a cylindrical shape.

12. The floating body according to any one of claims 6 to 11, characterized in that each pontoon (8) and / or each outer support (6) is provided with a ballast region which can be adjusted to correct the attitude of the floating body and improve the hydrodynamic behavior of the floating body.

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