Floating support structure with multiple central columns for an offshore wind turbine and method of assembling such a structure

Abstract

The present invention relates to a floating support structure (2-1) for an offshore wind turbine, comprising: a lower connector (4) centered on the axis (XX) of a wind turbine mast (9) and including at least three lower receptacles (10) evenly distributed around the axis of the wind turbine mast; an upper connector (6) centered on the axis of the wind turbine mast and including at least three upper receptacles (12) at its upper part, with receiving means (14) for the wind turbine mast, and at least three identical tubular central struts (8), the lower end of which is assembled in one of the receptacles of the lower connector and the upper end of which is assembled in one of the receptacles of the upper connector (so as to form a floating support pylon that fits onto the vertical extension of the wind turbine mast). The present invention also relates to a method for assembling such a structure.

Description

[Technical Field]

[0001] The present invention relates to the general field of offshore wind turbines installed offshore, and more particularly to floating support structures for floating offshore wind turbines. The invention also relates to a method for installing an offshore wind turbine with such a support structure. [Background technology]

[0002] The purpose of an offshore wind turbine is to harness wind energy to generate electricity through a turbine and generator. There are two main types of offshore wind turbines: bottom-fixed wind turbines, which are installed on the seabed (typically at a minimum depth of less than 50 m), and floating wind turbines, which are constructed on land and offer the advantage of being installed in areas where the seabed depth is typically greater than 50 m.

[0003] The floating wind turbine that is the subject of the present invention comprises a turbine generally formed by a motor having several rotating blades with a horizontal axis and a generator coupled to the motor, the motor and the generator being fixed at the upper end of a vertical mast (or pylon), the lower end of which is itself attached to a floating support structure.

[0004] There are four main groups of floating support structures for offshore wind turbines: semi-submersible floaters, submersible floaters with tension cables ("tension leg platforms" (TLPs)), "single point anchor reservoir" (SPAR) type floaters, "barge" type semi-submersible floaters, and floaters with pendulum counterweights.

[0005] Semi-submersible floats constitute the most widely used model of floats today. They generally comprise a steel or concrete base in the form of a tripod with three (or four) cylindrical columns connected to each other by a metal structure. The stability of the structure is ensured by a ballast system that allows part of the base to be submerged. This structure is characterized by its large size and shallow draft. Reference is made to US Pat. No. 5,623,499, which describes a semi-submersible floating structure and a method for installing a wind turbine with such a floating structure.

[0006] A "TLP" type platform is a floating structure characterized by being largely submerged. The platform is connected to the seabed by tension cables that exert a downward force, preventing the floating structure from rising.

[0007] The "SPAR" type floater features a cylindrical shape that fits over the extension of the wind turbine's mast. Stability is provided to the floater by heavy ballast, which lowers the unit's center of gravity and is equipped with suspension anchors for securing the wind turbine by hooking it to the seabed. See U.S. Pat. Nos. 5,623,997, 5,793,522 and 5,793,537, which describe embodiments of the "SPAR" platform, its mooring and its installation process at sea.

[0008] Finally, the "barge" type semi-submersible floater has a more compact foundation configuration corresponding to a rectangular barge with a through-hole and constructed primarily of concrete or steel. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] International Publication No. 2019 / 106283 [Patent Document 2] International Publication No. 2005 / 021961 [Patent Document 3] International Publication No. 2006 / 121337 [Patent Document 4] International Publication No. 2006 / 132539 Summary of the Invention [Problem to be solved by the invention]

[0010] Most floating support structures were not designed to accommodate the scope of large-scale industrialization, and indeed, these floaters typically require a large number of components to be assembled, as well as time and ground space.

[0011] The object of the present invention is to propose a floating support structure (of the "SPAR" type, semi-submersible or "TLP" type) for offshore wind turbines, which simplifies its assembly, accelerates the assembly time and minimizes the ground space required. [Means for solving the problem]

[0012] According to the invention, this object is achieved by a floating support structure for an offshore wind turbine having a plurality of central columns, the floating support structure comprising: at least two identical and independent tubular central columns assembled together around the axis of the wind turbine mast to form a floating support pylon that fits into a vertical extension of the wind turbine mast; a lower connector centered on the axis of the wind turbine mast to ensure that the force of the central column is supported and absorbed at each lower end; and an upper connector centered on the axis of the wind turbine mast, having at its upper part receiving means for the wind turbine mast, and at its lower part having at least two upper receptacles for receiving the upper end of the central column.

[0013] The present invention is notable for being based on a modular approach to constructing floating support structures. In particular, the present invention provides floating support pylons formed from upper and lower connectors by using a plurality of identical, independent central columns assembled for these connectors. The number of central columns can be 2, 3, 4, 5, 6, etc., thus varying the design of the floating support structure depending on the conditions at the site where the structure is to be installed.

[0014] The fact that the central struts are all identical greatly simplifies the assembly of the floating support structure: in fact, they can be prefabricated in succession using the same model, as can the upper and lower connectors, and quickly assembled on site. The floating support pylon may lack a crosspiece, forming a SPAR type floater. Each central strut may be connected to at least one tubular crosspiece, the ends of the tubular crosspieces opposite the central strut constituting float nodes radially spaced from the floating support pylon to form a semi-submersible float.

[0015] In one variant, the central strut is connected, on the one hand, in the region of its lower end to at least one radial crosspiece and, on the other hand, above its lower end to at least one diagonal crosspiece, the radial and diagonal crosspieces being joined to one another in the region of the floating nodes so as to form a triangular floating unit assembly.

[0016] In another variant, each central strut is connected on the one hand to at least one first radial crosspiece in the region of its lower end and on the other hand to at least one second radial crosspiece above its lower end, the radial crosspieces being connected to one another in the region of the body nodes to form a rectangular-shaped body unit assembly.

[0017] Advantageously, each floating unit assembly comprises at least one floating body module arranged in the region of a floating body node. Each floating module may comprise a central rod extending parallel to the axis of the wind turbine mast, on which at least one steel ring and / or at least one non-metallic ring is attached.

[0018] The axis of the wind turbine mast may be aligned on the centre of symmetry of the floating body, or alternatively the axis of the mast may be offset relative to the centre of symmetry of the floating body. Preferably, each floating node of the floating unit assembly is connected to one another by at least one cable, the floating node comprising a cable tensioning device.

[0019] The structure may also include at least one buoyant element disposed around the cable. Preferably, each floating unit assembly comprises a network of ballast pipes housed within at least one of the crosspiece and the central strut.

[0020] At least one of the floating support pylons and / or radial crosspieces may comprise at least one central floating unit. In one variation, the lower connector is a separate piece from the central post and includes at least two lower receptacles, each of which receives a lower end of the central post.

[0021] In another variation, the lower connectors are for clamping the lower ends of each of the central posts. Another object of the invention is a method for assembling a floating support structure as defined above, comprising the steps of dry assembling the lower end of each central strut onto a lower connector, followed by dry assembling an upper connector onto the upper end of each central strut.

[0022] Yet another object of the present invention is a method for assembling a floating support structure as defined above, comprising the steps of: - assembling the floating unit elements onto the lower connectors by lifting each unit element and pivoting it to rest the floating node on supports previously positioned on the ground to ensure proper lateral positioning of the floating unit elements; assembling an upper connector to the upper end of the central strut of each floating unit element; connecting the central strut of the floating unit element to the upper and lower connectors by welding, adhesive or mechanical assembly.

[0023] The assembly step may be carried out on a submersible platform that allows the floating support structure to be launched in a calm area protected from waves. In this case, the submersible platform is provided with a lifting gantry for assembling the mast of the wind turbine on top of the upper connector of the floating support structure. [Brief explanation of the drawings]

[0024] [Figure 1] 1 is a perspective view of a semi-submersible floating support structure having four floating unit assemblies in accordance with a first embodiment of the present invention; FIG. [Figure 2] FIG. 2 is a side view of the floating support structure of FIG. 1. [Figure 3] FIG. 3 is an exploded view of the floating support structure of FIGS. 1 and 2. [Figure 4A] FIG. 2 is a perspective view of a floating support structure of the SPAR type according to a second embodiment of the present invention. [Figure 4B] FIG. 10 is an exploded view of a variant of a floating support structure of the SPAR type according to the second embodiment. [Figure 5] FIG. 10 is a perspective view of a semi-submersible floating support structure having three floating unit assemblies according to a third embodiment of the present invention. [Figure 6] FIG. 10 is a perspective view of a semi-submersible floating support structure having five floating unit assemblies in accordance with a fourth embodiment of the present invention. [Figure 7] FIG. 10 is a perspective view of a semi-submersible floating support structure having six floating unit assemblies in accordance with a fifth embodiment of the present invention. [Figure 8] FIG. 2 is a perspective view of a floating support structure according to a variant of the first embodiment of the present invention. [Figure 9] FIG. 10 is a perspective view of a floating support structure according to another variant of the first embodiment of the present invention. [Figure 10] 2A-2C show an example of the various steps in the assembly process according to the invention of the floating support structure of FIG. 1; [Figure 11] 2A-2C show an example of the various steps in the assembly process according to the invention of the floating support structure of FIG. 1; [Figure 12] 2A-2C show an example of the various steps in the assembly process according to the invention of the floating support structure of FIG. 1; [Figure 13] 2A-2C show an example of the various steps in the assembly process according to the invention of the floating support structure of FIG. 1; [Figure 14] 2A-2C show an example of the various steps in the assembly process according to the invention of the floating support structure of FIG. 1; [Figure 15] 2A-2C show an example of the various steps in the assembly process according to the invention of the floating support structure of FIG. 1; [Figure 16] 2A-2C show an example of the various steps in the assembly process according to the invention of the floating support structure of FIG. 1; [Figure 17] 2A-2C show an example of the various steps in the assembly process according to the invention of the floating support structure of FIG. 1; [Figure 18] 2 is a diagram showing an example of maintenance of an offshore wind turbine mounted on the floating support structure of FIG. 1. FIG. [Figure 19] FIG. 10 is a perspective view of a floating support structure having a central floating unit between central struts according to yet another variation of the first embodiment of the present invention. [Figure 20] FIG. 10 is a perspective view of a modified floating support structure according to the third embodiment of the present invention. [Figure 21] FIG. 10 is a perspective view of a semi-submersible floating support structure offset relative to two floating unit assemblies in accordance with a sixth embodiment of the present invention. [Figure 22A] FIG. 10 is a diagram showing a modified example of the floating support structure according to the third embodiment. [Figure 22B] 10 shows another variant of the floating support structure according to the third embodiment. [Figure 23] 1 illustrates an embodiment of a ballast pipe network within a floating support structure according to the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0025] 1 to 3 show a semi-submersible floating support structure 2-1 according to a first embodiment of the present invention. The floating support structure 2-1 is intended to receive an offshore wind turbine mast (not shown).

[0026] According to the present invention, the floating support structure 2-1 comprises an assembly between a lower connector 4, an upper connector 6 and a plurality (i.e. at least two, and in the first embodiment of Figures 1 to 3 four) of tubular central struts 8, which are all identical and independent of each other so as to form a pylon that fits into the vertical extension of the mast 9 of a wind turbine.

[0027] The central columns 8 generally have a diameter of 2 to 4 meters. They may or may not be internally reinforced. They are typically manufactured by a variety of assembly techniques and are easily manufactured without substantial investment.

[0028] As shown in FIG. 3, in this embodiment the lower connector 4 is a separate part from the central pillar, centred on the vertical axis XX of the wind turbine mast and comprising at least two (four in this embodiment) lower receptacles 10 evenly distributed around the vertical axis XX, opening towards the top and each intended to receive the lower end of the central pillar 8 by nesting of a complementary shape.

[0029] Similarly, the upper connector 6 is a separate part from the central pillar, centered on the vertical axis XX of the wind turbine mast 9, and comprising at its lower part at least two (four in this embodiment) upper receptacles 12 evenly distributed around the vertical axis XX, opening towards the bottom and each intended to receive the upper end of the central pillar 8 by nesting of complementary shapes.

[0030] At the top, the upper connector 6 also comprises receiving means for the wind turbine mast 9. Typically, these receiving means are in the form of a ring 14, inside which the lower end of the wind turbine mast is fitted before being fixed (for example by welding).

[0031] Naturally, other receiving means for the mast of the wind turbine may be envisaged, as may the upper connector forming one and the same part with at least a part of the mast of the wind turbine.

[0032] Regarding the central columns 8, the central columns 8 are all identical and independent of one another, and each is in the form of a vertically extending cylinder. The lower end of each central column 8 is nested into one of the receptacles 10 of the lower connector 4, and then assembled. The upper end of each central column 8 is nested into one of the receptacles 12 of the upper connector 6, and then assembled.

[0033] Preferably, as shown in FIG. 4B, the lower connector receptacle 10 and / or the upper connector receptacle 12 each include a centering guide 16 intended to make assembly of the corresponding end of the central post 8 easier.

[0034] For example, in the embodiment of Figure 4B, these centering guides 16 are in the form of two plates 16a, 16b arranged in a cross shape and chamfered at their respective ends to form points. Of course, the centering guides may have other forms.

[0035] Once the central post 8 is fitted inside the receptacles 10, 12 of the upper and lower connectors, it is secured to the connectors by welding, adhesive, or mechanical assembly. The first embodiment of the present invention shown in Figures 1 to 3 relates to a "semi-submersible" floating body having four floating unit assemblies.

[0036] "Floating unit assembly" means that for each central strut there is provided at least one radial tubular crosspiece and at least one diagonal tubular crosspiece, which are connected to the central strut on the one hand and to floating nodes radially spaced from the floating support pylon on the other hand.

[0037] In the various embodiments described below (except for the embodiments described in connection with Figures 4A, 4B, 22A and 22B), the floating unit assembly has a triangular shape. More precisely, in these embodiments, for each central strut 8, a radial tubular crosspiece 20 is connected to the lower end of the strut by forming an angle between 75° and 90° with the lower end of the strut, and an oblique tubular crosspiece 22 is connected to the strut above its lower end, on the one hand, and to its free end by forming a float node 24 radially spaced from the vertical axis XX, so as to form a floating unit assembly 18 having a triangular shape.

[0038] These triangular shaped floating unit elements 18 are preferably all identical to one another, which on the one hand makes it easier to manufacture the floating unit elements 18 and on the other hand makes it easier to assemble the floating unit elements 18 onto the upper and lower connectors.

[0039] In this first embodiment, the floating support structure 2-1 has four identical triangular floating unit assemblies 18 spaced evenly from one another (ie, by equal angles of 90°).

[0040] Of course, the floating unit assemblies may have shapes other than triangular, depending on the number and arrangement of radial and diagonal crosspieces. Similarly, the floating unit assemblies do not necessarily all have to be identical to one another.

[0041] Each floating unit assembly 18 also comprises a floating module 26 arranged in the region of its floating node 24, i.e. at the free ends of the radial crosspieces 20 and diagonal crosspieces 22 opposite the vertical axis XX of the mast.

[0042] Each floating body module 26 comprises a central rod 28 extending parallel to the vertical axis XX of the mast, to which is attached at least one steel ring 30 and / or at least one ring 32 made of a non-metallic material forming a ballast tank.

[0043] Thus, in the embodiment of Figures 1 and 2, each floatation module 26 comprises a steel ring 30 on which three rings of non-metallic material 32 rest, with two other rings of non-metallic material 32 attached below the steel ring 30.

[0044] Advantageously, the non-metallic rings 32 are standardized and are all identical to one another (in terms of dimensions and material), which helps to adjust the number of non-metallic rings 32 for each floating body node 24 depending on the conditions of the wind turbine installation.

[0045] These non-metallic rings 32 are made of a non-metallic material, either solid or syntactic foam, to act as floating bodies. The non-metallic material may be thermoset, thermoplastic, or elastomeric. These non-metallic rings are retained on the central rod 28 by any means, such as a circlip.

[0046] In addition, the steel ring 30 forming the ballast tank is connected to a ballast pipe network (described in relation to Figure 23) housed inside at least one of the crosspieces 20, 22 and the central column, so as to terminate in the area of ​​a control zone (not shown) located above the upper connector 6.

[0047] Each floating node 24 of the floating unit assembly 18 is connected to one another by at least one cable 36, and at least some of the floating nodes are provided with a device for tensioning the cable. The cables 36 are therefore prestressed, effectively reducing the overall weight of the floating support structure and shortening the assembly time of the floating support structure.

[0048] With respect to the first embodiment, as shown in FIG. 1, the cables 36 may be a plurality of metal cables 36 connecting the float nodes of pairs of floating unit assemblies 18 . In this case, the tension of the cables 36 can be ensured by a screw-nut system or by hydraulic jacks (operated by traction) for pulling the other end of the cable towards the adjacent floating node, while the other end of the cable is connected to one of the floating nodes. In this configuration, there are as many cable tensioning devices as there are floating unit elements 18. These tensioning devices are removable in the case of hydraulic jacks.

[0049] In a variant with multiple cables (not shown), a single device may be provided for tensioning the cables. When a cable is tensioned, the other cables are also tensioned, since in this variant the floating unit element has a degree of rotation possible about the vertical axis XX in the fixing areas in the upper and lower connectors.

[0050] In a variant not shown, the cable may be the same and only cable or metal chain connecting all floating nodes of the floating unit assembly. In this variant, a single cable passes over grooves formed in each floating node, and blockers (cable clamps) are attached to these grooves to fix the position of the cable when tension is generated. In this way, the trajectory of the cable corresponds to the circumference of the floating support structure defined by the floating unit assemblies 18. The tension in the cable or chain is generated by devices such as jacks or screw-nut systems fixed to the two ends of the cable (or chain).

[0051] Finally, a possible alternative to cables is to rely on horizontal steel spacers that join the floating nodes of the floating unit elements together. Rapid mechanical connectors then ensure the connection between the spacers and the floating nodes, minimizing installation time.

[0052] 4A and 4B show, in perspective and exploded views, respectively, two variants of the floating support structure 2-2, 2-2' according to the second embodiment of the present invention. The floating support structure 2-2, 2-2' according to the second embodiment of the invention forms a "SPAR" ("Single Point Anchor Reservoir") type float, i.e. a cylindrical float nested in the extension of the mast of a wind turbine.

[0053] More precisely, the floating support structure 2-2 according to the variant of FIG. 4A comprises four tubular central columns 8, all identical to one another and independent of one another, so as to form a pylon that fits into the vertical extension of the mast of a wind turbine.

[0054] Similarly, the floating support structure 2-2' according to the variant of FIG. 4B comprises three tubular central struts 8, all identical to one another so as to form a pylon. Also, in contrast to the first embodiment, all of the central struts 8 forming the pylons of these two floating support structures 2-2, 2-2' are devoid of cross-pieces (both radial and diagonal).

[0055] FIG. 5 is a perspective view of a floating support structure 2-3 according to a third embodiment of the present invention. In this embodiment, the floating support structure 2-3 forms a semi-submersible float having three floating unit assemblies 18 equiangularly spaced apart by 120°. In this configuration, the cables 36 form a triangle.

[0056] Other features of this floating support structure are similar to those described in relation to the first embodiment. FIG. 6 is a perspective view of a floating support structure 2-4 according to a fourth embodiment of the present invention.

[0057] In this embodiment, the floating support structures 2-4 form a semi-submersible float having five floating unit assemblies 18 spaced apart at equal angles of 72°. In this configuration, the cables 36 form a pentagon.

[0058] Other features of this floating support structure are similar to those described in relation to the first embodiment. FIG. 7 is a perspective view of a floating support structure 2-5 according to a fifth embodiment of the present invention.

[0059] In this embodiment, the floating support structure 2-5 forms a semi-submersible float having six floating unit assemblies 18 spaced apart at equal angles of 60°. In this configuration, the cables 36 form a hexagon.

[0060] Other features of this floating support structure are similar to those described in relation to the first embodiment. Figure 8 is a perspective view of a floating support structure 2-1' according to a variant of the first embodiment of the present invention, i.e., a floating support structure forming a semi-submersible float having four floating unit assemblies 18 spaced apart from each other at equal angles of 90°.

[0061] A notable feature of this variant is that buoyant elements 38 are arranged around each cable 36. For example, these buoyant elements 38 are in the form of foam cylinders attached around the cables.

[0062] These body elements 38 form a complement to the body modules 26 arranged in the region of the body nodes of the floating unit assemblies 18 . Other features of this floating support structure are similar to those described in relation to the first embodiment.

[0063] FIG. 9 is a perspective view of a floating support structure 2-1″ according to another variant of the first embodiment of the present invention, i.e., a floating support structure forming a semi-submersible float having four floating unit assemblies 18 spaced apart from each other at equal angles of 90°.

[0064] A notable feature of this variant is that the floating units 40 are arranged around the radial crosspieces 20 of each floating unit assembly 18. For example, these floating units 40 are in the form of foam cylinders mounted around the radial crosspieces.

[0065] Here, these floating units 40 act as substitutes for the floating modules located in the region of the floating nodes 24 of the floating unit assemblies 18 . Other features of this floating support structure are similar to those described in relation to the first embodiment.

[0066] In relation to Figures 10 to 17, these illustrate examples of the assembly and installation of floating support structures according to the invention, in particular floating support structures 2 to 5 according to the fifth embodiment of the invention. Of course, assembly processes applicable to other embodiments of the invention will be apparent from those described below.

[0067] Assembly can take place at the quayside or on a submersible (catamaran) offshore assembly platform. The use of an underwater catamaran provides greater autonomy and independence from the installation location, particularly the availability of lifting means at that location.

[0068] Prior to launching the assembly, the upper and lower connectors and the floating unit assembly may be produced in series. In a first step, a cylindrical counterweight 42 is placed on the ground at the assembly site. This counterweight is intended to be secured by ties 50 to the floating nodes 24 of the floating unit assemblies 18 to ensure gravity anchoring of the floating support structure (see arrangement shown in Figure 18).

[0069] In the embodiment shown in Figure 10, the counterweight 42 has a central recess 44 for receiving the lower connector of the floating support structure. 11, the lower connector 4 of the floating support structure is moved (e.g., by a crane or lifting gantry) so that it is positioned within the recess 44 of the counterweight 40. If no such recess exists, the lower connector is positioned directly on the counterweight.

[0070] During the next step (FIG. 12), positioning supports 46 are advantageously placed in the assembly location around the counterweight 42 at the exact location where the floatation module of the floatation unit assembly will rest.

[0071] These positioning supports 46 allow for fast and accurate positioning of the floating unit elements and also allow for full adjustment of the verticality of the central column during placement of the upper connector. Naturally, the positioning supports 46 are reusable.

[0072] As shown in Figure 13, the floating unit elements 18 are successively assembled onto the lower connector 4. For this purpose, each floating unit element 18 is lifted (by a crane or lifting gantry) to introduce the lower end of its central column 8 vertically into one of the receptacles 10 of the lower connector, and the floating unit element is pivoted about its central column so that its float module 26 rests on one of the positioning supports 46.

[0073] FIG. 14 shows the progression of the process of assembling the second floating unit element 18 onto the lower connector 4. FIG. 15 shows the structure after all floating unit elements 18 have been assembled onto the lower connector 4.

[0074] Once all the floating unit elements 18 have been assembled and then secured (by welding, gluing or mechanical assembly) to the lower connector 4, the next step shown in Figure 16 consists of assembling (by a crane or assembly gantry) the upper connector 6 to the upper end of the central column and then securely fastening these parts together (by welding, gluing or mechanical assembly).

[0075] A control platform 48 may then be attached around the top end of the upper connector 6 . In the final assembly step of the floating support structure 2-5 (Figure 17), the cables 36 are secured to each floating node 24 of the floating unit assembly 18 and then tensioned. The wind turbine mast and turbine may then be installed by crane or lifting gantry.

[0076] As shown in Figure 18, maintenance of an offshore wind turbine mounted on a floating support structure according to the present invention (here, structure 2-1 having four floating unit assemblies of Figure 1) may allow for the replacement of components of the turbine 52 or blades 54 in particular.

[0077] For this purpose, at least some of the diagonal crosspieces 22 of the floating unit assemblies 18 of the floating support structure 2-1 are equipped with spindles 56 (see also Figure 1) to allow the installation of a temporary platform 58 for installing the expansion structure 60.

[0078] It is clear that the spindle 56 may employ other maintenance structures related to climbing crane options. Regardless of the embodiment of the present invention, it is clear that during assembly of the floating support structure, at least one central floating unit 62 may be inserted between the central struts 8 forming the pylon (see Figure 19 with the floating support structure 2-1 having four floating unit assemblies 18, and Figure 21 with the floating support structure 2-6 having two floating unit assemblies). This central floating unit 62 facilitates the floating of the floating support structure.

[0079] Thus, in the example shown in Figure 19, this central floating unit 62 (e.g., a foam cylinder) is inserted vertically between the central posts along axis XX prior to placing the upper connectors at the upper ends of the central posts.

[0080] In an alternative not shown, such a central floating unit may be pre-installed on a first central column that is assembled during installation of the floating support structure. FIG. 20 is a perspective view of a modified floating support structure 2-3' according to a third embodiment of the present invention.

[0081] This variant differs from that described in relation to Figure 5 in that the lower connector of the structure does not have a lower receptacle for receiving the lower ends of the struts. Here, the lower connector is a simple cable clamp 4' for clamping the lower end of each of the central struts.

[0082] In this variant, a lower connector of the type described in connection with Figure 5 may be temporarily installed on the ground to make assembly of the central column of the floating support structure 2-3' easier. All embodiments of the floating support structure according to the invention described so far relate to a structure in which the axis XX of the wind turbine mast is aligned over the centre of symmetry of the float (the floating support pylon is aligned over the centre of symmetry of the structure).

[0083] In contrast, Figure 21 is a perspective view of an offset semi-submersible floating support structure according to a sixth embodiment of the present invention. In this sixth embodiment, the floating support structure 2-6 comprises only two floating unit assemblies 18. These floating unit assemblies 18 together form angles that differ by 180°, and the axis X'-X' of the wind turbine mast 9 is offset relative to the center of symmetry of the structure.

[0084] Also in this sixth embodiment, each of the two floating unit assemblies 18 comprises two floating body modules 26 arranged in the region of the respective floating body node 24. Naturally, the presence of two floating body modules per floating unit assembly can also be applied to the floating support structure of the other embodiments.

[0085] Furthermore, in this sixth embodiment, the cables connecting the float nodes 24 of each of the two floatable unit assemblies 18 are replaced by bracing elements 36'.

[0086] This sixth embodiment also provides for the placement of a central floating unit 62 between the central columns 8 forming a pylon. 22A and 22B show two variants of a semi-submersible floating support structure 2-3'' having three rectangular shaped floating unit assemblies according to the third embodiment.

[0087] In these two variants, each floating unit assembly 18' has a rectangular shape having a central strut 8, two radial crosspieces 20a, 20b (specifically, an upper radial crosspiece 20a and a bottom radial crosspiece 20b spaced apart according to the axis XX of the mast 9), and a diagonal crosspiece 22.

[0088] Also, in the variant of FIG. 22A, the floating body modules 26' are in the form of vertical struts of polygonal cross section (here hexagonal), which can be made by assembly of flat panels.

[0089] In the variation of FIG. 22B, the floating body module 26'' is in the form of a cylindrical vertical strut. FIG. 23 shows an embodiment of a ballast pipe network within a floating support structure according to the present invention (partially shown in the figure), and more particularly within a triangular shaped floating unit assembly 18.

[0090] The ballast pipe network comprises pipes 64 housed inside the radial crosspieces 20 and diagonal crosspieces 22 of the floating unit assembly. These pipes 64 terminate in the area of ​​the floatation modules in a ballast compartment 66 and open into the same central conduit 68 housed in the central strut 8 of the floating unit assembly.

[0091] In the region of its upper end, the central conduit 68 advantageously comprises a connection system 70 capable of cooperating with a complementary use system 72 housed in the upper connector 6 of the floating support structure. In other words, these systems 70, 72 form a "plug and play" type unit that makes the assembly and start-up of the floating support structure easier.

Claims

1. A floating support structure (2-1 to 2-6) having multiple central supports for an offshore wind turbine, At least two identical and independent tubular central support columns (8) are assembled together around the axis (X-X; X'-X') of the mast (9) of the wind turbine to form a floating support pylon that fits into the vertical extension of the mast of the wind turbine, A lower connector (4) is provided to ensure that the force of the central support column is held and received at each lower end, with the axis (X-X) of the mast (9) of the wind turbine as the center, The upper connector (6) is centered on the axis of the mast of the wind turbine, and has a receiving means (14) for the mast of the wind turbine at its upper part, and has at least two upper receptacles (12) for receiving the upper end of the central support column at its lower part, A floating support structure in which each central support is connected to at least one tubular cross piece (20, 22), and the end of the tubular cross piece opposite to the central support constitutes a floating node (24) radially spaced from the floating support pylon to form a semi-submersible floating body.

2. The structure according to claim 1, wherein each central support (8) is connected on one side to at least one radial cross piece (20; 20a, 20b) in the region of its lower end, and on the other side to at least one oblique cross piece (22) above its lower end, and the radial cross piece and the oblique cross piece are joined to each other in the region of the floating node (24) to form a triangular floating unit assembly (18).

3. The structure according to claim 1, wherein each central support (8) is connected on one side to at least one first radial cross piece (20a) in the region of its lower end and on the other side to at least one second radial cross piece (20b) above the lower end, and the radial cross pieces are connected to each other in the region of the floating node (24) to form a rectangular floating unit assembly (18).

4. The structure according to claim 2 or 3, wherein each floating unit assembly (18) comprises at least one floating module (26; 26'; 26'') located in the area of ​​the floating node (24).

5. The structure according to claim 4, wherein each floating module (26) comprises a central rod (28) extending parallel to the axis (X-X) of the mast of the wind turbine, and at least one steel ring (30) and / or at least one non-metallic ring (32) is attached to the central rod (28).

6. The structure according to claim 1, wherein the axis (X-X) of the mast (9) of the wind turbine is aligned on the center of symmetry of the floating body.

7. The structure according to claim 1, wherein the axis (X'-X') of the mast (9) of the wind turbine is offset with respect to the center of symmetry of the floating body.

8. The structure according to claim 2 or 3, wherein each of the floating nodes (24) of the floating unit assembly is connected to one another by at least one cable (36), and the floating nodes are equipped with a cable tensioning device.

9. The structure according to claim 8, further comprising at least one floating element (38) disposed around the cable (36).

10. The structure according to claim 2 or 3, wherein each floating unit assembly (18) comprises a network of ballast pipes housed inside at least one of the cross pieces (20, 22) and the central support (8).

11. The structure according to claim 1, wherein at least one of the floating support pylons and / or radial cross pieces comprises at least one central floating unit (62).

12. The structure according to claim 1, wherein the lower connector (4) is a component independent of the central support column and comprises at least two lower receptacles (12), each receiving the lower end of the central support column.

13. The structure according to claim 1, wherein the lower connector is a cable clamp (4') for clamping the lower ends of each of the central support columns.

14. A method for assembling a floating support structure according to any one of claims 1 to 3, 6, 7, 11 to 13, comprising the steps of: dry-fitting the lower end of each central support column (8) onto the lower connector (4); and subsequently dry-fitting the upper connector (6) onto the upper end of each central support column.

15. A method for assembling the floating support structure according to claim 2 or 3, To ensure proper lateral positioning of the floating unit assembly, the floating unit assembly (18) is assembled onto the lower connector (4) by lifting each unit assembly and pivoting it so that the floating node (24) is placed on a support (46) that is pre-positioned on the ground, The steps include: attaching the upper connector (6) to the upper end of the central support column (8) of each floating unit assembly (18); A method comprising the step of connecting the central support of the floating unit assembly to the upper connector and the lower connector by welding, bonding, or mechanical assembly.

16. The method according to claim 15, wherein the assembly step is performed on an underwater platform that allows the floating support structure to be launched in a calm area protected from waves.

17. The method according to claim 16, wherein the underwater platform is provided with a lifting gantry for assembling the mast of the wind turbine on the upper part of the upper connector of the floating support structure.

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