Semi-submersible floating object for offshore wind turbine and construction method of semi-submersible floating object

Abstract

The invention relates to a semi-submersible float (2-1), in particular for offshore wind turbines, comprising four struts comprising a central column (4) for receiving a wind turbine mast (6), and at least three outer columns (8) connected by branches to the central column to form a lower buoy (10). The float does not have an upper branch connecting the central column and the outer column, and the outer column and the lower pontoon are each assembled from planar panels (81-86, 101-104) and each have a polyhedral cross-section. The invention also relates to a method for constructing the floater.

Description

Technical Field

[0001] The present invention relates to the general field of semi-submersible floats for offshore wind turbines.

[0002] In particular, the present invention relates to a novel semi-submersible floating structure and a construction method thereof. Background Art

[0003] The purpose of offshore wind turbines is to generate electricity from wind energy using turbines and generators. There are two main types of offshore wind turbines: fixed wind turbines, which are embedded in the seabed (in shallow water, usually less than 50 meters); and floating wind turbines, which have the advantage of being built on land and embedded in the seabed at depths of more than 50 meters.

[0004] The floating wind turbine of the present invention includes a turbine, which generally consists of a motor having a plurality of blades rotating about a horizontal axis and a generator connected to the motor. The motor and generator are fixed to the upper end of a vertical mast (or tower). The lower end of the mast is mounted on a floating support structure (hereinafter referred to as a floater).

[0005] There are several main types of floats used for offshore wind turbines: semi-submersible floats, submerged floats with tensioned cables (or tension leg platforms, or TLP platforms), SPAR floats (single point mooring power storage devices), "barge" type semi-submersible floats and floats equipped with pendulum-type counterweights.

[0006] The present invention relates in particular to semi-submersible floats, i.e., a steel or concrete base, generally in the form of a tripod, with three (or four) cylindrical columns connected by a metal structure. The stability of this structure is ensured by a ballast system that allows it to be partially submerged. These structures are characterized by their large size and shallow draft.

[0007] For example, reference may be made to publication FR 3,064,973, which describes a semi-submersible hybrid floating structure comprising a central column and three outer columns connected to the central column by buoy-like branches.

[0008] Although the design of this hybrid float is relatively simple, it has the disadvantage that it takes a long time to assemble and can be expensive to manufacture. Summary of the Invention

[0009] The object of the present invention is to propose a semi-submersible float structure which allows for extremely short construction and delivery times at low costs.

[0010] To achieve this goal, a semi-submersible float is used, specifically for offshore wind turbines, comprising: four columns, including a central column for receiving the mast of the wind turbine, and at least three external columns connected to the central column by branches forming lower buoys, wherein, according to the invention, the float has no upper branches connecting the central column to the external columns, and the external columns and the lower buoys are both assembled from flat panels and have a polyhedral cross-section.

[0011] The floater according to the present invention is notable in that its main components (the outer columns and the lower pontoon) are assembled from multiple flat panels, which greatly facilitates the floater's manufacturing process. Due to this feature, the construction and delivery time of the floater can be significantly shortened compared to the large-diameter cylindrical columns of the prior art, due to the richer supply chain (due to the global capabilities of the shipbuilding industry).

[0012] This makes it possible to propose a robust and reliable floater that meets the operating conditions and required performance requirements of the implantation site and has a satisfactory cost-benefit ratio. In addition, due to its simple construction, the associated risks are also controlled.

[0013] Preferably, the central column is assembled from planar panels and has a polyhedral cross section. This arrangement can further reduce the construction time and cost of the float.

[0014] The end of the central column may advantageously be provided with a transition piece having a downwardly tapering truncated cone shape.

[0015] Alternatively, the central column may advantageously have a truncated cone shape tapering downwards, which is particularly advantageous for the overall design of the wind turbine.

[0016] The outer columns may be of the same height, and the center column may be of a different height than the outer columns.

[0017] Preferably, the central column includes an access door to the tower supporting the wind turbine's turbine, located below the interface with the tower and the additional internal reinforcement structure of the interface with the tower. This access door allows operators to enter the structure, thereby accessing equipment located inside the tower. Compared to the prior art (in which access doors are typically located several meters above the interface with the tower), the access door is preferably located several meters lower, away from the area of ​​the internal reinforcement structure of the interface with the tower.

[0018] It is also preferred that the planar panels forming the outer column are assembled together by at least one circular rod to improve its fluid dynamics and reduce stress concentrations.

[0019] Preferably, the planar panels forming the outer columns and the lower pontoon may be reinforced by longitudinal internal reinforcements and / or transverse internal reinforcements.

[0020] The planar panels forming the outer columns and the lower pontoons may also be reinforced by longitudinal and / or transverse external reinforcements. External reinforcements have the advantage over internal reinforcements that the welding operations necessary to install such reinforcements are facilitated.

[0021] More preferably, the outer columns are connected to each other by prestressed cables. The advantage of the prestressed cables is that they absorb part of the out-of-plane forces, thereby reducing the load on the structure and thus its mass.

[0022] The float further comprises components, each component extending between the central column and one of the lower buoys to partially transfer the in-plane load on the central column to the lower buoy. The components are in a tubular or polyhedral shape.

[0023] The lower buoys may be arranged at an angle of 120° to form a star-shaped structure.

[0024] The present invention also relates to a method for modularly constructing a floating object as described above, comprising: - assembling planar panels to form, on the one hand, the lower pontoon and, on the other hand, the central column, - Assemble the lower pontoons to the central branch structure supporting the central column, - Assembling the outer columns on the lower branches, and - Assemble the central column on the central branch structure.

[0025] The lower pontoon can be assembled on the central branch structure by welding. In this case, advantageously, the welding for assembling the lower pontoon on the central branch structure is external, using external reinforcements connected by welding to facilitate its installation.

[0026] Alternatively, the lower buoys may be assembled to the central branch structure by mechanical connections.

[0027] Furthermore, at sea, the lower pontoons of the floating barge can be assembled on the central branch structure.

[0028] Alternatively, at sea, the lower buoys may be mounted floatingly on the central branch structure. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] [ Figure 1 ] Figure 1 is a perspective view of a float according to a first embodiment of the present invention.

[0030] [ Figure 2 ] Figure 2is a perspective view of a float according to a second embodiment of the present invention.

[0031] [ Figure 3 ] Figure 3 is a perspective view of a float according to a third embodiment of the present invention.

[0032] [ Figure 4 ] Figure 4 is a perspective view of a float according to a fourth embodiment of the present invention.

[0033] [ Figure 5 ] Figure 5 is a perspective view of a float according to a fifth embodiment of the present invention.

[0034] [ Figure 6 ] Figure 6 is a perspective view of a float according to a sixth embodiment of the present invention.

[0035] [ Figure 7 ] Figure 7 is a perspective view of a float according to a seventh embodiment of the present invention.

[0036] [ Figure 8 ] Figure 8 is a perspective view of a float according to an eighth embodiment of the present invention.

[0037] [ Figure 9 ] Figure 9 It is the arrangement of the outer columns of the mounting float and the inner reinforcement of the lower pontoon according to the present invention.

[0038] [ Figure 10 ] Figure 10 It is the arrangement of the outer reinforcement of the lower pontoon of the mounted float according to the present invention.

[0039] [ Figure 11 ]to[ Figure 13 ] Figure 11 、 Figure 12 and Figure 13 are different variants of the method for building a floating object according to the invention. DETAILED DESCRIPTION

[0040] Figure 1 FIG. 2 is a perspective view of a semi-submersible floating object 2 - 1 for an offshore wind turbine according to a first embodiment of the present invention.

[0041] The floating object 2 - 1 comprises four pillars, including a central pillar 4 and three outer pillars 8 . The central pillar 4 is used to receive the mast 6 of the wind turbine. The three outer pillars 8 are connected to the central pillar 4 through branches forming a lower buoy 10 .

[0042] Specifically, the lower buoy 10 and the outer column 8 are arranged at an angle of 120° from each other to form a star-shaped structure.

[0043] The float 2-1 according to the present invention is characterized in that there is no upper branch connecting the central column 4 and the outer column 8. In addition, the outer column 8 and the lower buoy 10 are both assembled from flat panels and have a polyhedral cross section.

[0044] Therefore, in Figure 1 In the first embodiment shown, each outer column 8 is assembled from six planar panels 81 to 86 forming a right prism with a hexagonal base, and each lower pontoon 10 is assembled from four planar panels 101 to 104 forming a rectangular parallelepiped ( Figure 1 Only planar panels 101 and 104 are visible).

[0045] Of course, the polyhedron formed by assembling the planar panels of the external columns and the lower pontoon can be different: a rectangular parallelepiped, a right prism with a pentagonal base, etc.

[0046] Furthermore, according to a preferred arrangement of the present invention, the central column 4 is also assembled from planar panels and thus has a polyhedral cross section.

[0047] Furthermore, in the first embodiment, the lower buoy 10 of each float is on the same side of the outer column 8 (i.e., on the Figure 1 The lower buoy 10 is connected to the outer column 8 at the level of the flat panel 83 in the center column 4. Similarly, the lower buoy 10 is also connected to the same side of the center column 4.

[0048] Figure 2 2 is a perspective view of a semi-submersible floating object 2 - 2 for an offshore wind turbine according to a second embodiment of the present invention.

[0049] Compared with the first embodiment, the difference of the floating object 2-2 is that the lower buoy 10 of each floating object 2-2 is located on two adjacent sides of the outer column 8 (i.e., on the outer column 8). Figure 1 The flat panel 83 in the middle is connected to the outer column 8) at the horizontal plane.

[0050] In contrast, for the first embodiment, the lower buoy 10 is also connected to the same face of the central column 4 .

[0051] Figure 3 is a perspective view of a semi-submersible floating object 2 - 3 for an offshore wind turbine according to a third embodiment of the present invention.

[0052] Compared to the second embodiment, the float 2 - 3 differs in that the planar panels 81 to 86 forming the outer column 8 are assembled together by circular rods 12 to improve its hydrodynamic performance and reduce stress concentration.

[0053] In addition, it should be noted that in Figures 1 to 3 In each embodiment, the distal end (upper end) of the central column 4 is provided with a transition piece 14 together with the wind turbine mast 6 having a cylindrical shape.

[0054] Other shapes are also contemplated.

[0055] Therefore, in Figure 4 In the fourth embodiment shown, the semi-submersible float 2-4 differs from that in the second embodiment in that the transition piece 14' between the central column 4 and the wind turbine mast 6 has a truncated cone shape that tapers downward to limit the height of the transition area between the central column and the wind turbine mast.

[0056] exist Figure 5 In the fifth embodiment shown, the central column 4 of the semi-submersible float 2-5 has a truncated cone shape that tapers downward.

[0057] exist Figure 6 In the sixth embodiment shown, the central column 4 of the semi-submersible float 2-6 is cylindrical.

[0058] Figure 7 is a perspective view of a semi-submersible floating object 2 - 7 for an offshore wind turbine according to a seventh embodiment of the present invention.

[0059] Compared to the second embodiment, the float 2-7 is different in that it further comprises components 16, each of which extends between the central column 4 and one of the lower buoys 10 to partially transfer the in-plane load on the central column to the lower buoy.

[0060] The presence of these assemblies 16 therefore allows the height of the lower pontoon 10 to be reduced. Furthermore, the draft of the float in operation can be reduced, which allows reducing the reinforcement structures required to resist the pressure of flooding.

[0061] like Figure 7 As shown, these members 16 can be tubular. Alternatively, they can also be polyhedral.

[0062] Figure 8 is a perspective view of a semi-submersible floating object 2 - 8 for an offshore wind turbine according to an eighth embodiment of the present invention.

[0063] Compared to the second embodiment, the floats 2-8 differ in that the outer columns 8 are connected to each other by prestressed cables 18. More specifically, these prestressed cables 18 are fixed to the planar panels of the outer columns. The presence of these cables allows the width of the lower buoy 10 to be reduced due to the out-of-plane moment loads transmitted to the cables.

[0064] This results in a reduction in the weight of the float. At the same time, wave sensitivity and the resulting loads are reduced, allowing for a reduction in structural reinforcement. Furthermore, the installation time of the float is shortened due to the reduced dimensions of the lower buoy connection.

[0065] The prestressing load of the cables is arranged to ensure that the cables remain in tension throughout the use of the float.

[0066] Of course, it is also possible to imagine that the floating object also has Figure 7 The components shown and Figure 8 Prestressed cables shown.

[0067] according to Figure 9 In an advantageous configuration particularly shown in FIG, the outer columns 8 of the float according to the invention may be reinforced by longitudinal inner reinforcements 20a and / or transverse inner reinforcements 20b.

[0068] Likewise, the lower pontoon 10 of the float may be reinforced by longitudinal internal reinforcements 22a and / or transverse internal reinforcements 22b.

[0069] Alternatively or additionally, the outer columns 8 of the float according to the invention may be reinforced by longitudinal outer reinforcements and / or transverse outer reinforcements.

[0070] Similarly, if Figure 10 As shown, the lower pontoon 10 of the float may be reinforced by longitudinal external reinforcements 24a and / or transverse external reinforcements 24b.

[0071] Preferably, if Figures 1 to 8 As shown, the outer columns 8 of the float have the same height, while the central column 4 has a different height than the outer columns.

[0072] Preferably, if Figure 1 As shown, the central column 4 of the floater according to the invention includes an access door 28 to the tower supporting the turbine of the wind turbine, located below the interface with the tower and the internal additional reinforcement structure at the interface with the tower. This new position of the door lowers the external platform and shortens the access for maintenance personnel from the support vessel to the maintenance position.

[0073] about Figures 11 to 13 , next, the modular construction method of a floating object according to the present invention will be introduced.

[0074] Generally speaking, the method involves assembling planar panels to form, on the one hand, the lower pontoon and, on the other hand, the outer columns. The lower pontoon thus formed is then assembled to a central branch structure supporting the central column. Similarly, the outer columns thus formed are assembled to the lower branches. Finally, the central column can be assembled to the central branch structure.

[0075] There can be different variations.

[0076] For example, in Figure 11 In the variant shown, four blocks, namely three identical outer blocks B and one central block C, are assembled together, each outer block B being assembled from an outer column 8 located on a lower buoy 10, and the central block C being assembled from a central column 4 located on a central branch structure 30 supporting the central column.

[0077] The three outer blocks B are then assembled by welding on the central block C. This variant avoids welding in fatigue-sensitive areas.

[0078] In order to limit fatigue stresses associated with welding, the central branch structure 30 is designed to space the weld areas of the central column.

[0079] exist Figure 12 In the variant shown, three blocks are assembled together, namely two identical outer blocks B and a main module D, each outer block B being assembled from an outer column 8 located on a lower buoy 10, and the main module D being assembled from a central column 4 located on a central branch structure 32 including the lower buoy and the outer columns.

[0080] The two external blocks B are then assembled to the main module D by welding. Compared to the previous solution, this variant reduces the number of connections and thus shortens the time of the final assembly phase. It also avoids welding in fatigue-sensitive areas.

[0081] exist Figure 13 In the variant shown, only two blocks are assembled together, namely an external block B and a main module D', the external block B being assembled from external columns 8 located on lower pontoons 10, and the main module D' being assembled from central columns 4 on a central branch structure 34, which includes two lower pontoons, each of which is equipped with an external column.

[0082] The outer block B is assembled to the main module D' by welding. Compared to the previous solution, this variant further reduces the number of connections. It also avoids welding in fatigue-sensitive areas.

[0083] It is noted that the welds used to assemble the lower buoys of the external blocks on these different central branch structures can be external by using external reinforcements.

[0084] It should also be noted that, as an alternative to welding, the lower buoys of the outer blocks can be assembled on these different central branch structures by mechanical connections.

[0085] Likewise, these assemblies can be performed on floating barges or afloat at sea.

Claims

1. A semi-submersible floating object (2-1 to 2-8) particularly for offshore wind turbines, comprising: Four pillars, comprising a central pillar (4) for receiving a mast (6) of a wind turbine, and at least three outer pillars (8), wherein the at least three outer pillars (8) are connected to the central pillar (4) by branches forming a lower buoy (10), the floating object has no upper branches connecting the central pillar (4) and the outer pillars (8), and the outer pillars (8) and the lower buoy (10) are both assembled from plane panels (81 to 86, 101 to 104) and have a polyhedral cross-section, characterized in that the plane panels (81 to 86) forming the outer pillars (8) are assembled together by at least one circular rod (12) to improve their fluid dynamic performance and reduce stress concentration.

2. The floating object according to claim 1, characterized in that: The central column (4) has a truncated cone shape that tapers downward.

3. The floating object (2-4) according to claim 1 or 2, characterized in that: A transition piece (14') having a downwardly tapered truncated cone shape is provided at the end of the central column (4).

4. The floating object according to claim 1, characterized in that: The central column (4) has a truncated cone shape that tapers downward.

5. The floating object according to any one of claims 1 to 4, characterized in that: The outer columns (8) have the same height, and the central column (4) has a height different from that of the outer columns.

6. The floating object according to any one of claims 1 to 5, characterized in that: The central column (4) includes an access door (28) to a tower supporting the turbine of the wind generator, the access door (28) being located below the interface with the tower and an internal additional reinforcement structure of the interface with the tower.

7. The floating object according to any one of claims 1 to 6, characterized in that The planar panels forming the outer columns (8) and the lower pontoons (10) are reinforced by longitudinal internal reinforcements (20a, 22a) and / or transverse internal reinforcements (20b, 22b).

8. The floating object according to any one of claims 1 to 7, characterized in that: The planar panels forming the outer columns (8) and the lower pontoons (10) are reinforced by longitudinal external reinforcements (24a) and / or transverse external reinforcements (24b).

9. The floating object (2-6) according to any one of claims 1 to 8, characterized in that The outer columns (8) are connected to each other by prestressed cables (18).

10. The float (2-5) according to any one of claims 1 to 9, further comprising: Assemblies (16), each assembly (16) extending between the central column (4) and one of the lower buoys (10) to partially transfer in-plane loads on the central column to the lower buoy.

11. The floating object according to claim 10, characterized in that: The component (16) is in the shape of a tube or a polyhedron.

12. The floating object according to any one of claims 1 to 11, characterized in that The lower buoys (10) are arranged at an angle of 120° to form a star-shaped structure.

13. A method for modular construction of a floating object according to any one of claims 1 to 12, characterized in that: include: - assembling said planar panels to form, on the one hand, the lower buoy (10) and, on the other hand, said outer columns (4), - Assembling the lower buoy to the central branch structure (30-34) supporting the central column, - assembling the outer column on the lower buoy, and - Assembling the central column (4) on the central branch structure.

14. The method according to claim 13, characterized in that The lower buoy is assembled on the central branch structure by welding.

15. The method according to claim 14, characterized in that By using external reinforcements connected by welding, the welds used to assemble the lower pontoon to the central branch structure are external.

16. The method according to claim 13, characterized in that The lower buoy is assembled on the central branch structure through mechanical connectors.

17. The method according to any one of claims 13 to 15, characterized in that The lower buoy is mounted on the central branch structure in an offshore floating barge.

18. The method according to any one of claims 13 to 15, characterized in that The lower buoy is floated and assembled on the central branch structure at sea.

Images