Semi-submersible float for offshore wind turbine

Abstract

Semi-submersible Float for Offshore Wind Turbine The invention relates to a semi-submersible float (2) for an offshore wind turbine, comprising at least three vertical columns (4, 6), one of which is intended to receive a wind turbine mast, the vertical columns being connected to each other by pontoons (8) each formed by a plurality of flat panels (81 to 84) which are assembled together at edges (10) extending longitudinally between two columns, the edges of the pontoons being rounded and connected at each of their longitudinal ends to a column by means of a transition piece (12). Figure for the abstract: Fig. 1.

Description

Title of the invention: Semi-submersible float for offshore wind turbine. Technical field

[0001] The present invention relates to the general field of semi-submersible floats used for offshore wind turbines. More specifically, it relates to a new semi-submersible float architecture. Previous technique

[0002] An offshore wind turbine aims to harness wind energy to generate electricity using a turbine and an electric generator. There are two main types of offshore wind turbines: fixed wind turbines, which are installed on the seabed (at shallow depths typically less than 50m), and floating wind turbines, which offer the advantage of being able to be built on land and installed in areas where the seabed depth typically exceeds 50m.

[0003] The floating wind turbines covered by the present invention comprise a turbine generally formed by a motor with several rotating horizontal-axis blades and an electric generator coupled to the motor, the motor and generator being fixed to the upper end of a vertical mast (or pylon). The lower end of the mast is mounted on a floating support structure (hereinafter referred to as the float).

[0004] There are several main families of floats for offshore wind turbines: semi-submersible floats, submerged floats with tensioned cables (or "TLP" platforms for "Tension-Leg Platform" in English), "SPAR" type floats (for "Single Point Anchor Reservoir"), semi-submersible "barge" type floats, and floats with a pendulum counterweight.

[0005] The invention relates more specifically to semi-submersible floats, that is to say, steel or concrete foundations generally in the form of a tripod with three (or four) cylindrical columns connected by metal structures. The stability of the structure is ensured by a ballast system that allows part of the foundation to be submerged. This structure is characterized by its large size and shallow draft.

[0006] Reference may be made, for example, to publication FR 3,064,973 which describes a semi-submersible hybrid float structure comprising a central column and three outer columns connected to the central column by pontoon-shaped branches.

[0007] This type of hybrid float has the advantage of a simple design. However, such a construction has a significant weight that is strongly influenced by fatigue. Description of the invention

[0008] There is therefore a need to be able to have a semi-submersible float whose weight is optimized while respecting fatigue criteria.

[0009] This goal is achieved by means of a semi-submersible float for offshore wind turbine, comprising at least three vertical columns, one of which is intended to receive a wind turbine mast, the vertical columns being connected to each other by pontoons, each formed by a plurality of flat panels which are assembled together at the level of edges extending longitudinally between two columns, and in which, according to the invention, the edges of the pontoons are rounded and are connected at each of their longitudinal ends to a column by means of a transition piece.

[0010] The float according to the invention is remarkable in that the edges of the pontoons are not sharp (i.e., at right angles) but are rounded, which limits stress concentrations and thus significantly improves the fatigue behavior of these areas. Compared to right angles, this feature allows the float to meet fatigue criteria while reducing its weight. As for the transition piece, it limits stresses in the area of ​​the connection between the pontoons and the float columns.

[0011] Furthermore, the invention improves the manufacturability of pontoons by eliminating the continuity of the transverse stiffeners from one face of the pontoon to another. The invention also improves the hydrodynamic behavior of the float by eliminating the undesirable effects associated with the sharp edges of the prior art.

[0012] Preferably, the rounded edges of the pontoons have a quarter-circle geometry with a radius between 100 and 1500mm.

[0013] Preferably also, the rounded edges of the pontoons have the same thickness as the adjacent flat panels.

[0014] The transition piece may have one end which is rounded to connect to the longitudinal end of a rounded edge and an opposite end which forms a right angle.

[0015] The transition piece can be a piece obtained by one of the following techniques: forging, molding, forming by press bending, and additive manufacturing going from a triangular shape on one side, to a rounded shape on its opposite side.

[0016] Preferably, each flat panel is provided on one inner face with two or three main longitudinal stiffeners and a plurality of secondary stiffeners transverse. This feature reduces the weight of the float and makes it easier to manufacture.

[0017] In this case, the main stiffeners of each flat panel are preferably regularly spaced from each other by means of vertical partitions delimiting ballasting areas.

[0018] According to one embodiment, the float comprises four vertical columns, including a central column (4) which is intended to receive the wind turbine mast, and three outer columns are connected to the central column by lower pontoons.

[0019] In this embodiment, the outer columns can each be formed by an assembly of flat panels. Alternatively, the outer columns can each have a substantially cylindrical shape.

[0020] In this embodiment, the float may further comprise at least one walkway between an upper end of an outer column and the central column. Such a walkway facilitates access to the float (by helicopter, for example) or provides a second access point for a maintenance vessel.

[0021] Still in this embodiment, the central column may have a truncated conical shape or a cylindrical shape.

[0022] According to an advantageous arrangement of the invention, the float includes inside each pontoon and / or each outer column a ballast zone that can be adjusted to correct the trim of the float and improve the hydrodynamic behavior of the float. Brief description of the drawings

[0023] [Fig-1] Fig. 1 represents in perspective a semi-submersible float according to the invention.

[0024] [Fig.2] The [Fig.2] is a cross-sectional view along II-II of the [Fig.1].

[0025] [Fig.3] Fig.3 shows the stiffeners inside a pontoon of the float of the [Fig.l]. Description of the implementation methods

[0026] Fig. 1 represents in perspective a semi-submersible float 2 for offshore wind turbine according to a first embodiment of the invention.

[0027] In this embodiment, the float 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 which are connected to the central column 4 by branches forming lower pontoons 8.

[0028] More specifically, the lower pontoons 8 and the outer columns 6 are spaced angularly apart from each other by 120° to form a star-shaped structure.

[0029] Of course, it is possible to consider that the vertical columns of the float are connected to each other by upper pontoons and / or lower pontoons.

[0030] Furthermore, at least the pontoons formed by a plurality of flat panels which are assembled together. More precisely, in the embodiment of [Fig. 1], each lower pontoon 8 is made up of the assembly of four flat panels 81 to 84 forming a rectangular parallelepiped (only the flat panels 81 and 84 are visible in [Fig. 1]).

[0031] Of course, it is possible to consider that the number of flat panels forming each pontoon is different (for example, five, six, etc.).

[0032] According to the invention, the flat panels of each pontoon are assembled together at the level of edges 10 which extend longitudinally between two columns and which are rounded by connecting at each of their longitudinal ends to a column by means of a transition piece 12.

[0033] More specifically, as shown in [Fig.2], the edges 10 of the pontoons have a quarter-circle geometry with a radius between 100 and 1500mm.

[0034] The rounded edges 10 of the pontoons connect at each of their two longitudinal ends to a vertical column of the float by means of a transition piece 12 allowing to go from a quarter circle shape to a right angle shape.

[0035] For this purpose, as shown on the magnifier in [Fig.1], the transition piece 12 has an end 12a which is rounded to connect to the longitudinal end of a rounded edge 10 and an opposite end 12b which forms a right angle.

[0036] This transition piece 12 is a piece that can be obtained by one of the following techniques: forging, molding, forming by press bending, and additive manufacturing going from a triangular shape on one side, to a rounded shape on its opposite side.

[0037] In addition, the rounded edges 10 of the pontoons 8 may have a thickness that is identical or different from that of the adjacent flat panels.

[0038] According to an advantageous arrangement shown in [Fig.3], each flat panel 81 to 84 constituting the pontoons 8 is provided, on an inner face, with two or three main longitudinal stiffeners 14 and a plurality of secondary transverse stiffeners 16.

[0039] Thus, in the embodiment of [Fig.3], each flat panel 81 to 84 is provided with three main longitudinal stiffeners 14 regularly spaced from each other and a plurality of secondary transverse stiffeners 16.

[0040] In addition, the main stiffeners 14 of each flat panel are advantageously spaced apart from each other by means of vertical partitions 18 delimiting ballasting areas.

[0041] Thus, inside each pontoon and / or each outer column, there is provided at least one ballast zone which can be adjusted to correct the trim of the float and improve its hydrodynamic behavior.

[0042] It should be noted that in the embodiment of [Fig. 1], the outer columns 6 of the float 2 each have a substantially cylindrical shape. Of course, the invention also applies to floats whose outer columns are each formed by an assembly of flat panels in order to present a polyhedral shape (reference may be made to patent application FR 23 01328 filed on February 13, 2023 by the Applicant).

[0043] It should also be noted that in the embodiment of [Fig. 1], the central column 4 of the float 2 receiving the wind turbine mast has a truncated cone shape that flares downwards. Of course, the invention also applies to floats whose central column has a cylindrical shape.

[0044] It should also be noted that the float may advantageously include at least one gangway (not forming part of the primary structure of the float and not shown in the figures) between an upper end of an outer column and the central column in order to facilitate access to the float (by helicopter for example) or to have a second access point for a maintenance vessel.

Claims

Demands

1. Semi-submersible offshore wind turbine float (2), comprising four vertical columns, including a central column (4) intended to receive the wind turbine mast, and three outer columns (6) connected to the central column by lower pontoons (8), each formed by a plurality of flat panels (8i to 84) assembled together at edges (10) extending longitudinally between two columns, characterized in that the edges (10) of the pontoons are rounded, connected at each of their longitudinal ends to a column by means of a transition piece (12), and have a thickness identical to that of the adjacent flat panels.

2. Float according to claim 1, characterized in that the rounded edges (10) of the pontoons (8) have a quarter-circle geometry with a radius between 100 and 1500mm.

3. Float according to any one of claims 1 and 2, characterized in that the transition piece (12) has an end (12a) which is rounded to connect to the longitudinal end of a rounded edge (10) and an opposite end (12b) which forms a right angle.

4. Float according to claim 3, characterized in that the transition piece (12) is a piece obtained by one of the following techniques: forging, molding, forming by press bending, and additive manufacturing going from a triangular shape on one side, to a rounded shape on its opposite side.

5. Float according to any one of claims 1 to 4, characterized in that each flat panel (8i to 84) of the pontoons (8) is provided on an inner face with two or three main longitudinal stiffeners (14) and a plurality of secondary transverse stiffeners (16).

6. Float according to claim 5, characterized in that the main stiffeners (14) of each flat panel are regularly spaced from each other by means of vertical partitions (18) delimiting ballasting areas.

7. Float according to claim 6, characterized in that the outer columns (6) are each formed by an assembly of flat panels.

8. Float according to claim 6, characterized in that the outer columns (6) each have a substantially cylindrical shape.

9. Float according to any one of claims 6 to 8, characterized in that it further comprises at least one walkway between an upper end of an outer column (6) and the central column (4).

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

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

12. Float according to any one of claims 6 to 11, characterized in that it comprises within each pontoon (8) and / or each outer column (6) a ballast zone that can be adjusted to correct the trim of the float and improve the hydrodynamic behavior of the float.

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