System forming an anchor point for offshore wind turbine floats and installation method

Abstract

The invention relates to a system (2) forming an anchor point for offshore wind turbine floats, comprising at least one containment enclosure (6) having an open bottom (8) and an open top (10), the containment enclosure being at least partially filled with a solid granular material (12) capable of withstanding shear with the seabed (4) on which the containment enclosure is intended to rest, the containment enclosure further comprising at least one attachment (14) for securing a mooring line (16) of the float.

Description

Description Title of the invention: System forming an anchor point for offshore wind turbine floats and installation method Technical Field

[0001] The present invention relates to the general field of floats for offshore wind turbines. It relates more specifically to anchoring systems connected to the seabed and making it possible to maintain such floats. Prior art

[0002] An offshore wind turbine uses 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] Floating wind turbines typically comprise a turbine generally formed by a motor with several rotating blades on a horizontal axis and an electric generator coupled to the motor, the motor and generator being fixed to an upper end of a vertical mast (or pylon) whose lower end of the mast is mounted on a float.

[0004] There are three main categories of floats for offshore wind turbines: the semi-submersible float, the submerged float with tensioned cables (or "TLP" platform for "Tension-Leg Platform" in English), and the "SPAR" type float (for "Single Point Anchor Reservoir").

[0005] Semi-submersible and SPAR (Single Point Anchor Reservoir) floats are the most common float designs currently available. These are steel or concrete structures that take the most often in the form of a tripod with three columns connected to each other (for the semi-submersible type float) or a single central column (for the SPAR type float). The structure of these floats includes a submerged part and anchor lines which are not tensioned but which must nevertheless resist the drift of the assembly.

[0006] Several technologies exist for making anchor lines for floats for offshore wind turbines: drag anchors (e.g. "Delta Flipper" or "Stevpris" anchors) which are particularly suitable for anchoring catenary lines in sedimentary soils (clayey, sandy to sandy-clayey), anchor piles which consist of driving a metal tube, either by driving into the seabed made up of sandy-clayey to silty-clayey soil, or by drilling into a rocky seabed; or by suction into a "soft" silty-clayey to clayey seabed, and the gravity anchor which is placed in the seabed made up of sedimentary soil (clayey, sandy to sandy-clayey) and / or rocky type and which serves as a fixed point for the anchor lines by resisting thanks to its weight.

[0007] In floating offshore wind farm development projects, the heterogeneity of seabed soil conditions where the soil type changes rapidly in nature and thickness can pose risks to the anchoring system and its installation, raising concerns among developers of these projects.

[0008] For example, outcropping or subcropping rocky soils and / or soils with thin layers of sediment over weathered rocks do not allow the installation of drag anchor systems. However, these types of soils also pose problems if drilling and grouting or pile installation is chosen.

[0009] Generally, these risks are related to the geotechnical profile of the soil and the conditions of the seabed (irregularities, singularities of the seabed such as slopes, inclinations, depressions, incisions, rock blocks, etc.) which, if encountered, raise concerns that may compromise the anchoring system and its installation. Statement of the invention

[0010] The object of the invention is to propose a system forming a gravity anchor point which is simple to manufacture and implement and which, once placed on the seabed, resists anchoring forces mainly thanks to its own weight.

[0011] According to the invention, this object is achieved by means of a system forming an anchoring point for offshore wind turbine floats, comprising at least one cellular containment enclosure having an open bottom and an open top, the containment enclosure being at least partly filled with a solid granular material capable of resisting shear with a seabed on which the containment enclosure is intended to rest, the containment enclosure further comprising at least one fastener for fixing a mooring line of the float.

[0012] The system forming an anchor point according to the invention is remarkable in that it comprises a containment enclosure having a light weight due to its structure but which is filled with a solid granular material to make it heavier when it is placed on the seabed. This results in an assembly comprising the containment enclosure and its solid granular material - called a gravity anchor point - which has a low manufacturing cost and simplified implementation, in particular compared to pile anchoring systems.

[0013] The containment vessel may have a cylindrical shape with a plurality of radial walls. In this case, the radial walls of the containment vessel may be connected to each other at an axis of symmetry of the containment vessel. Alternatively, the radial walls of the containment vessel may be connected to an internal cylinder centered on an axis of symmetry of the containment vessel.

[0014] The containment enclosure may have a polygonal shape with a plurality of radial walls. In this case, these radial walls may be connected between them at an axis of symmetry of the containment enclosure. Alternatively, the radial walls of the containment enclosure may be connected to an internal polygon centered on an axis of symmetry of the containment enclosure.

[0015] The system may include a plurality of identical containment enclosures connected to each other.

[0016] In this case, containment enclosures of the anchoring system can be stacked on top of each other and / or placed next to each other.

[0017] The containment enclosure may be composed of the assembly of a plurality of enclosure sectors assembled together.

[0018] Preferably, a lower surface of the containment vessel is corrugated or saw-tooth shaped to increase the coefficient of friction between the containment vessel and the seabed material.

[0019] More preferably, the system further comprises a solid ballast material disposed around the containment vessel.

[0020] An internal surface of the containment enclosure may be provided with roughness in order to limit the risk of the system becoming loose.

[0021] The invention also relates to a method of installing a system as defined above, comprising transporting the system forming an anchoring point on a barge to an installation area and then placing it on the seabed.

[0022] Alternatively, the method of installing a system as defined above may comprise towing at sea to an installation area of ​​the system forming an anchor point, the latter being equipped with temporary flotation devices, then placing the system on the seabed by deflating and / or filling the flotation devices with seawater. Brief description of the drawings

[0023] [Fig. 1] Figure 1 is a sectional and in-situ view of an anchor point system according to the invention.

[0024] [Fig. 2] Figure 2 represents the system of Figure 1 in perspective.

[0025] [Fig. 3A] and [Fig. 3B] Figure 3A and Figure 3B represent a system in perspective according to an alternative embodiment of the invention.

[0026] [Fig. 4A] and [Fig. 4B] Figure 4A and Figure 4B represent polygonal-shaped systems according to other alternative embodiments of the invention.

[0027] [Fig. 5A] and [Fig. 5B] Figure 5A and Figure 5B represent polygonal-shaped systems according to still other alternative embodiments of the invention.

[0028] [Fig. 6A] and [Fig. 6B] Figure 6A and Figure 6B represent cylindrical-shaped systems according to still other alternative embodiments of the invention.

[0029] [Fig. 7A] and [Fig. 7B] Figure 7A and Figure 7B represent a system according to still other alternative embodiments of the invention.

[0030] [Fig. 8A] and [Fig. 8B] Figure 8A and Figure 8B represent a system according to still other alternative embodiments of the invention.

[0031] [Fig. 9] Figure 9 is a sectional and in-situ view of a system according to the invention surrounded by solid granular material.

[0032] [Fig. 10] Figure 10 is a sectional and situational view of a system according to yet another alternative embodiment of the invention. Description of the embodiments

[0033] The invention relates to a system forming a gravity anchor point which has the function of retaining offshore wind turbine floats (for example semi-submersible or SPAR type floats) thanks to its heavy mass which remains placed on the seabed and / or thanks to the friction generated on the seabed.

[0034] Figure 1 represents an example of such a system 2 forming a gravity anchor point in situation, that is to say placed on a seabed 4.

[0035] According to the invention, this system 2 comprises at least one cellular confinement enclosure 6 having a bottom 8 which is open and a top 10 which is also open. The confinement enclosure 6 may be made of concrete and / or prestressed or non-prestressed steel.

[0036] Furthermore, this containment enclosure 6 is at least partly filled with a solid granular material 12 which is capable of resisting shear with the seabed 4 on which the containment enclosure is intended to rest. The solid granular material 12 may consist of a large rocky granular material.

[0037] The containment enclosure 6 further comprises at least one attachment 14 (or “pad-eye” in English) intended to allow the attachment of a mooring line 16 of the float.

[0038] The system 2 according to the invention thus consists of a mooring resistance by shear and by abutment of the combined system of the confinement enclosure 6 with the volume of solid granular material 12.

[0039] It should be noted that the volume of the selected solid granular material 12 (surface area and height) is defined according to the required anchoring resistance.

[0040] It will also be noted that the volume of the solid granular material 12 used by the system according to the invention is located inside, outside and under the containment enclosure 6.

[0041] It should also be noted that the containment enclosure of the system according to the invention can take different forms.

[0042] Thus, in the embodiment of Figure 2, the containment enclosure 6-1 of the system has a cylinder shape with a plurality of radial walls 18 which are connected to each other at an axis of symmetry XX of the containment enclosure.

[0043] More specifically, in the embodiment of Figure 2, the radial walls 18 are six in number and are angularly regularly spaced from each other.

[0044] In the embodiment of Figures 3A and 3B, the containment enclosure 6-2 of the system has a cylinder shape with a plurality of radial walls 18 which are connected to an internal cylinder 20 centered on an axis of symmetry XX of the containment enclosure.

[0045] In the embodiment of Figures 4A and 4B, the containment enclosures 6-3 and 6-4 of the anchor point system each have a polygon shape (here a hexagon) with a plurality of radial walls 22.

[0046] In the embodiment of Figure 4A, these radial walls 22 are connected to an internal polygon (here a hexagon) centered on an axis of symmetry XX of the confinement enclosure 6-3.

[0047] In the embodiment of Figure 4B, these radial walls 22 are connected to each other at an axis of symmetry XX of the confinement enclosure 6-4.

[0048] Furthermore, whatever the geometric shape of the containment enclosure, the system according to the invention may comprise several identical containment enclosures connected to each other.

[0049] Thus, in the embodiment of Figure 5A, the system 2a comprises two containment enclosures 6-3 as described in connection with Figure 4A, the two containment enclosures being stacked on top of each other along their axis of symmetry XX.

[0050] Similarly, in the embodiment of Figure 5B, the system 2b comprises six containment enclosures 6-3 as described in connection with Figure 4A. In addition, the containment enclosures are stacked two by two along their axis of symmetry XX, and the three pairs of containment enclosures thus formed are joined to each other.

[0051] In the embodiment of Figure 6A, the system 2c comprises three containment enclosures 6-2 as described in connection with Figure 3A, the three containment enclosures being stacked on top of each other along their axis of symmetry XX.

[0052] In the embodiment of Figure 6B, the system 2d comprises nine containment enclosures each formed of a containment enclosure 6-2 as described in connection with Figure 3A. Here, the containment enclosures are stacked three by three along their axis of symmetry XX, and the three trios of containment enclosures thus formed are attached to each other.

[0053] In the embodiment of Figures 7A and 7B, the containment enclosure is composed of the assembly of a plurality of containment enclosure sectors assembled to each other.

[0054] Thus, in the example of Figure 7A, the containment enclosure 6-5 has a cylindrical shape and is composed of the assembly of five identical angular sectors 26. In the example of Figure 7B, the containment enclosure 6-6 has a star shape and is composed of the assembly of four identical angular sectors 28.

[0055] According to an advantageous arrangement illustrated in particular in FIG. 8A, the lower surface 30 of the containment enclosure 6-7 of the system forming an anchoring point has saw teeth in order to increase the coefficient of friction between the containment enclosure and the material of the seabed.

[0056] Also in order to increase the coefficient of friction between the containment vessel and the seabed material, the lower surface 32 of the containment vessel 6-8 of the system may alternatively be corrugated (see Figure 8B).

[0057] According to another advantageous arrangement illustrated by FIG. 9, the system forming an anchor point further comprises a solid granular material 38 which is arranged around the containment enclosure 6. This solid granular material 38 may be the same as that used to fill (at least partially) the containment enclosure of the system.

[0058] The presence of the solid granular material 38 around the containment enclosure has the advantage of increasing the lateral resistance of the vertical alveolar structure to sub-horizontal traction.

[0059] According to yet another advantageous arrangement illustrated by figure 10, the confinement enclosure 6 of the system forming an anchoring point comprises, at the level of its internal surface 40, roughnesses making it possible to limit the risk of the system becoming loose relative to the solid granular material 12.

[0060] A method of installing a system forming an anchor point as defined above may be as follows. The initial step is to transport the system on a barge to an installation area. Then, the system is placed on the seabed.

[0061] Another method of installing a system forming an anchor point as defined above can be as follows. The initial step is to tow the system out to sea to its installation area. For this purpose, the system will be equipped with temporary flotation devices, such as buoys for example.

[0062] Once arrived at the installation area, the system, and more specifically its containment vessel, is placed on the seabed by deflating and / or filling the flotation devices with seawater, then the solid granular material is deposited to at least partially fill the interior of the containment vessel.

Claims

Claims 1. System (2) forming an anchor point for offshore wind turbine floats, comprising at least one cellular containment enclosure (6; 6-1 to 6-9) having an open bottom (8) and an open top (10), the containment enclosure being at least partly filled with a solid granular material (12) capable of resisting shear with a seabed (4) on which the containment enclosure is intended to rest, the containment enclosure further comprising at least one fastener (14) for fixing a mooring line (16) of the float.

2. System according to claim 1, in which the containment enclosure (6-1, 6-2) has a cylinder shape with a plurality of radial walls (18).

3. System according to claim 2, in which the radial walls (18) of the containment enclosure are connected to each other at an axis of symmetry (XX) of the containment enclosure (6-1).

4. System according to claim 2, in which the radial walls (18) of the containment enclosure are connected to an internal cylinder (20) centered on an axis of symmetry (XX) of the containment enclosure (6-2).

5. System according to claim 1, in which the containment enclosure (6-3, 6-4) has a polygon shape with a plurality of radial walls (22).

6. System according to claim 5, in which the radial walls (12) of the containment enclosure are connected to each other at an axis of symmetry (XX) of the containment enclosure (6-4).

7. System according to claim 5, in which the radial walls (22) of the containment enclosure are connected to an internal polygon centered on an axis of symmetry (XX) of the containment enclosure (6-3).

8. System according to any one of claims 1 to 7, comprising a plurality of identical containment enclosures connected to each other.

9. The system of claim 8, wherein containment enclosures are stacked on top of each other.

10. System according to one of claims 8 and 9, containment enclosures are placed next to each other.

11. System according to any one of claims 1 to 10, in which the containment enclosure (6-5) is composed of the assembly of a plurality of enclosure sectors (26) assembled to each other.

12. A system according to any one of claims 1 to 11, wherein a lower surface (30, 32) of the containment enclosure (6-7, 6-8) is corrugated or saw-tooth shaped.

13. A system according to any one of claims 1 to 12, further comprising a granular solid material (38) disposed around the containment enclosure (6).

14. System according to any one of claims 1 to 13, in which an internal surface (40) of the containment enclosure is provided with roughness in order to limit the risk of the system becoming loose.

15. A method of installing a system according to any one of claims 1 to 14, comprising transporting the anchor point system on a barge to an installation area and then placing it on the seabed.

16. A method of installing a system according to any one of claims 1 to 14, comprising towing at sea to an installation area of the system forming an anchor point, the latter being equipped with temporary flotation devices, then placing the system on the seabed by deflating and / or filling the flotation devices with seawater.

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