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

Abstract

The invention relates to a floating support structure (2-1) for an offshore wind turbine, the structure comprising a lower connector (4) centered on an axis (X-X) of a tower (9) of the wind turbine and comprising at least three lower receptacles (10) which are regularly distributed around the axis of the tower of the wind turbine, an upper connector (6) centered on the axis of the tower of the wind turbine and comprising, in an upper portion, means (14) for accommodating a wind turbine tower and, in a lower portion, at least three upper receptacles (12) which are regularly distributed around the axis of the tower of the wind turbine, and at least three identical tubular central columns (8) which are fitted by a lower end into one of the receptacles of the lower connector and by an opposite, upper end into one of the receptacles of the upper connector so as to form a floating support pylon in the vertical extension of the tower of the wind turbine. The invention also relates to a method for assembling such a structure.

Description

Description Title of the invention: Floating support structure with multiple central columns for an offshore wind turbine and method of assembling such a structure Technical Field

[0001] The present invention relates to the general field of offshore wind turbines, i.e. those installed off the coast, and more particularly to floating support structures for floating offshore wind turbines.

[0002] The invention also relates to a method of installing an offshore wind turbine provided with such a support structure. Prior art

[0003] 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.

[0004] The floating wind turbines to which the present invention relates comprise a turbine generally formed by a motor with several horizontal-axis rotating blades and an electric generator coupled to the motor, the motor and generator being fixed to an upper end of a vertical mast (or pylon). The lower end of the mast is mounted on a floating support structure.

[0005] There are four main families of floating support structures 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

[0006] Semi-submersible floats are the most common float design currently available. They consist of a steel or concrete foundation that generally takes the form of a tripod with three (or four) cylindrical columns connected to each other by metal structures. The stability of the structure is ensured by a ballasting system that allows part of the foundation to be submerged. This structure is characterized by its large size and reduced draft. Reference may be made to publication WO 2019 / 106283, which describes a semi-submersible float structure and a method for installing a wind turbine equipped with such a float structure.

[0007] “TLP” type platforms are floats which have the particularity of being mostly submerged, the platform being connected to the seabed by tensioned cables which oppose the rise of the float by exerting a force towards the bottom.

[0008] The "SPAR" type float is characterized by its cylindrical shape, which is an extension of the wind turbine mast. Its stability is provided by a heavy ballast that lowers the center of gravity of the assembly and is equipped with catenary anchors allowing the wind turbine to be fixed by attachment to the seabed. Reference may be made to publications WO 2005 / 021961, WO 2006 / 121337 and WO 2006 / 132539, which describe examples of the construction of a "SPAR" platform, its anchoring and its installation process at sea.

[0009] Finally, semi-submersible barge-type floats come in the form of a more compact foundation that is comparable to a rectangular barge with a hole in its center and made primarily of concrete or steel.

[0010] Most floating support structures were not designed to be part of large-scale industrialization. Indeed, these Floats usually consist of a large number of parts to assemble, which requires time and floor space. Statement of the invention

[0011] The invention therefore aims to propose a floating support structure (of the “SPAR” type, semi-submersible or “TLP” type) for an offshore wind turbine which simplifies its assembly and speeds up the assembly time while minimizing the space required on land.

[0012] According to the invention, this aim is achieved by means of a floating support structure with multiple central columns for an offshore wind turbine, comprising: - at least two identical and independent central tubular columns which are assembled together around an axis of a wind turbine mast so as to form a floating support pylon forming a vertical extension of the wind turbine mast; - a lower connector centered on the axis of the wind turbine mast and intended to ensure support and absorption of the forces of the central columns at their respective lower ends; and - an upper connector centered on the axis of the wind turbine mast and comprising, in an upper part, means for receiving the wind turbine mast and, in a lower part, at least two upper receptacles for receiving an upper end of the central columns.

[0013] The invention is remarkable in that it is based on a modular approach for the production of the floating support structure. In particular, from lower and upper connectors, the invention provides for forming the floating support pylon using a plurality of identical and independent central columns which are assembled using these connectors. The number of central columns may be 2, 3, 4, 5, 6, etc. and thus vary the design of the floating support structure depending on the conditions of the site where the structure is to be installed.

[0014] The fact that the central columns are all identical greatly simplifies the assembly of the floating support structure. These central columns, as well as the lower and upper connectors, can be prefabricated in series from the same model and quickly assembled on site. This simplifies assembly and saves time.

[0015] The floating support pylon can be devoid of a crosspiece so as to form a SPAR type float.

[0016] Alternatively, each central column may be connected to at least one tubular crosspiece, one end of which opposite the central column constitutes a flotation node radially spaced from the floating support pylon so as to form a semi-submersible type float.

[0017] In a variant, each central column is connected, on the one hand at 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 crosspiece and the diagonal crosspiece being connected to each other at the level of the flotation node so as to form a floating unitary assembly of triangular shape.

[0018] In another variant, each central column is connected, on the one hand at its lower end to at least one first radial crosspiece, and on the other hand above its lower end to at least one second radial crosspiece, the radial crosspieces being connected to each other at the level of the flotation node so as to form a floating unitary assembly of rectangular shape.

[0019] Advantageously, each floating unit assembly comprises at least one flotation module positioned at its flotation node.

[0020] Each of these flotation modules may comprise a central rod extending parallel to the axis of the wind turbine mast and on which are fitted at least one steel ring and / or at least one ring made of non-metallic material.

[0021] The axis of the wind turbine mast can be aligned with a center of symmetry of the float. Alternatively, the axis of the mast can be offset from a center of symmetry of the float.

[0022] Preferably, the respective flotation nodes of the floating unit assemblies are connected to each other by at least one cable, the flotation nodes comprising cable tensioning devices.

[0023] The structure may further comprise at least one flotation element positioned around the cable.

[0024] Preferably, each floating unit assembly comprises a ballast piping network housed within at least one of the cross members and the central column.

[0025] The floating support pylon and / or at least one of the radial cross members may comprise at least one central flotation unit.

[0026] In one embodiment, the lower connector is an independent part of the central columns and includes at least two lower receptacles for each receiving a lower end of the central columns.

[0027] In another variation, the lower connector is a clamp clamping the respective lower ends of the central columns.

[0028] The invention also relates to a method of assembling a floating support structure as defined above, comprising a step of dry assembly of the lower end of each central column on the lower connector, followed by a step of dry assembly of the upper connector on the upper end of each central column.

[0029] The invention also relates to a method of assembling a floating support structure as defined above, successively comprising: - a step of assembling the floating unit elements on the lower connector by lifting each unit element and pivoting it to rest the flotation node on a support previously positioned on land to ensure the correct lateral positioning of the floating unit element; - a step of assembling the upper connector on the upper end of the central column of each floating unit element; and - a step of connecting the central columns of the floating unit elements to the lower and upper connectors by welding, gluing or mechanical assembly.

[0030] The assembly steps can be carried out on a submersible platform allowing the floating support structure to be launched in a calm area protected from the swell.

[0031] In this case, the submersible platform is advantageously equipped with a lifting gantry allowing the wind turbine mast to be assembled on the upper part of the upper connector of the floating support structure. Brief description of the drawings

[0032] [Fig. 1] Figure 1 is a perspective view of a semi-submersible type floating support structure with four floating unit assemblies according to a first embodiment of the invention.

[0033] [Fig. 2] Figure 2 is a side view of the floating support structure of Figure 1.

[0034] [Fig. 3] Figure 3 is an exploded view of the floating support structure of Figures 1 and 2.

[0035] [Fig. 4A] Figure 4A is a perspective view of a SPAR-type floating support structure according to a second embodiment of the invention.

[0036] [Fig. 4B] Figure 4B is an exploded view of a variant of the SPAR-type floating support structure according to this second embodiment.

[0037] [Fig. 5] Figure 5 is a perspective view of a semi-submersible type floating support structure with three floating unit assemblies according to a third embodiment of the invention.

[0038] [Fig. 6] Figure 6 is a perspective view of a semi-submersible type floating support structure with five floating unit assemblies according to a fourth embodiment of the invention.

[0039] [Fig. 7] Figure 7 is a perspective view of a semi-submersible type floating support structure with six floating unit assemblies according to a fifth embodiment of the invention.

[0040] [Fig. 8] Figure 8 is a perspective view of a floating support structure according to an alternative embodiment of the first embodiment of the invention.

[0041] [Fig. 9] Figure 9 is a perspective view of the floating support structure according to another alternative embodiment of the first embodiment of the invention.

[0042] [Fig. 10] to [Fig. 17] Figures 10 to 17 are views showing an example of the different steps of an assembly method according to the invention of a floating support structure of Figure 1.

[0043] [Fig. 18] Figure 18 shows an example of maintenance on an offshore wind turbine mounted on the floating support structure of Figure 1.

[0044] [Fig. 19] Figure 19 is a perspective view of the floating support structure according to yet another alternative embodiment of the first embodiment of the invention with a central flotation unit between the central columns.

[0045] [Fig. 20] Figure 20 is a perspective view of an alternative embodiment of the floating support structure according to the third embodiment of the invention.

[0046] [Fig. 21] Figure 21 is a perspective view of a semi-submersible and eccentric floating support structure with two floating unit assemblies according to a sixth embodiment of the invention.

[0047] [Fig. 22A] Figure 22A shows an alternative embodiment of the floating support structure according to the third embodiment.

[0048] [Fig. 22B] Figure 22B shows another alternative embodiment of the floating support structure according to the third embodiment.

[0049] [Fig. 23] Figure 23 shows an example of the embodiment of a ballast pipe network within a floating support structure according to the invention. Description of the embodiments

[0050] Figures 1 to 3 represent a floating support structure 2-1 of the semi-submersible type according to a first embodiment of the invention and intended to receive an offshore wind turbine mast (not shown).

[0051] According to the 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 four in number in the first embodiment of figures 1 to 3) tubular central columns 8 which are all identical and independent of each other so as to form a pylon forming a vertical extension of the mast 9 of the wind turbine.

[0052] The 8 central columns typically have a diameter between 2 and 4 meters. They may or may not be internally reinforced. They are typically made using various assembly technologies and are easy to manufacture without significant investment.

[0053] As shown in Figure 3, the lower connector 4 is, in this embodiment, a part independent of the central columns which is centered on a vertical axis XX of the wind turbine mast and which comprises at least two (four in number in this exemplary embodiment) lower receptacles 10 regularly distributed around the vertical axis XX, open upwards and each intended to receive by fitting together complementary shapes the lower end of a central column 8.

[0054] Likewise, the upper connector 6 is a part independent of the central columns which is centered on a vertical axis XX of the mast 9 of the wind turbine and which comprises, in a lower part, at least two (four in number on this example of embodiment) upper receptacles 12 regularly distributed around the vertical axis XX, open downwards and each intended to receive by fitting together complementary shapes the upper end of a central column 8.

[0055] The upper connector 6 further comprises, in an upper part, means for receiving the mast 9 of the wind turbine. Typically, these receiving means are in the form of a ring 14 inside which the lower end of the mast of the wind turbine is fitted before being fixed (by welding for example).

[0056] Of course, it is possible to consider other ways of receiving the wind turbine mast. Similarly, it is possible to consider that the upper connector is a single piece with at least part of the wind turbine mast.

[0057] As for the central columns 8, they are all identical, independent of one another, and each has the form of a cylinder which extends vertically and the lower end of which is fitted and then assembled inside one of the receptacles 10 of the lower connector 4, and the upper end is fitted and then assembled inside one of the receptacles 12 of the upper connector 6.

[0058] Preferably, as shown in Figure 4B, the receptacles 10 of the lower connector and / or the receptacles 12 of the upper connector each comprise a centering guide 16 intended to facilitate the assembly of a corresponding end of the central column.

[0059] For example, in the embodiment of Figure 4B, these centering guides 16 are in the form of two plates 16a, 16b positioned in a cross and beveled in their respective end portion to form a point. Of course, the centering guides can take other forms.

[0060] Once fitted inside the receptacles 10, 12 of the lower and upper connectors, the central columns 8 are fixed to the connectors by welding, gluing or mechanical assembly.

[0061] The first embodiment of the invention illustrated by figures 1 to 3 concerns a “semi-submersible” type float with four floating unit assemblies.

[0062] By "floating unitary assembly" is meant that, for each central column, at least one radial tubular crosspiece and at least one diagonal tubular crosspiece are provided which are connected, on the one hand to the central column, and on the other hand to a flotation node spaced radially from the floating support pylon.

[0063] In the various embodiments described below (with the exception of that described in connection with FIGS. 4A, 4B, 22A and 22B), the floating unit assemblies have a triangular shape.

[0064] More specifically for these embodiments, for each central column 8, a radial tubular crosspiece 20 is connected to a lower end of the column forming an angle of between 75° and 90° with the latter, and a diagonal tubular crosspiece 22 is connected, on the one hand to the column above the lower end thereof, and on the other hand to a free end of the radial crosspiece forming therewith a flotation node 24 spaced radially from the vertical axis XX so as to form a floating unitary assembly 18 having a triangular shape.

[0065] These floating unitary elements 18 of triangular shape are preferably all identical to each other, which facilitates, on the one hand, their manufacture, and on the other hand, their assembly on the lower and upper connectors.

[0066] In this first embodiment, the floating support structure 2-1 has four identical triangular-shaped floating unit assemblies 18 which are regularly spaced from each other (i.e. at the same angle of 90°).

[0067] Of course, floating unit assemblies can have other shapes than a triangular shape depending on the number and arrangement of radial and diagonal cross members. Similarly, they are not necessarily all identical to each other.

[0068] Furthermore, each floating unitary assembly 18 comprises a flotation module 26 which is positioned at its flotation node 24, that is to say at the free end of the radial 20 and diagonal 22 crosspieces opposite the vertical axis XX of the mast.

[0069] Each flotation module 26 consists of a central rod 28 which extends parallel to the vertical axis XX of the mast and on which are fitted at least one steel ring 30 forming a ballast tank and / or at least one ring made of non-metallic material 32.

[0070] In the exemplary embodiment of figures 1 and 2, each flotation module 26 thus comprises a steel ring 30 surmounted by three rings of non-metallic material 32, two other rings of non-metallic material 32 being mounted under the steel ring 30.

[0071] Advantageously, the non-metallic rings 32 are standardized and all identical to each other (in terms of dimensions and material), which makes it possible to adjust their number at each flotation node 24 depending on the installation conditions of the wind turbine.

[0072] These non-metallic rings 32 are made of non-metallic materials, either solid, foam or syntactic foam in order to act as flotation. The non-metallic materials may be thermosets, thermoplastics or elastomers. These non-metallic rings are held on the central rod 28 by any means (for example by circlips).

[0073] In addition, the steel rings 30 forming ballast tanks are connected to a network of ballast piping (described in connection with figure 23) which is housed inside at least one of the crosspieces 20, 22 and the central column in order to open out at a control zone (not shown in the figures) located above the upper connector 6.

[0074] The respective flotation nodes 24 of the floating unit assemblies 18 are connected to each other by at least one cable 36, at least some of the flotation nodes being equipped with a cable tensioning device. The one or more cables 36 are thus prestressed and make it possible to reduce the overall weight of the floating support structure and to reduce its assembly time.

[0075] As shown in FIG. 1 relating to the first embodiment, it may be a plurality of metal cables 36 connecting two by two the flotation nodes of the floating unit assemblies 18.

[0076] In this case, the tensioning of the cables 36 can be ensured by a screw-nut system, or a hydraulic cylinder (operating in traction) making it possible to pull the end of the cable towards one of the flotation nodes, while the other end of the cable is connected to the neighboring flotation node. In this configuration, there are as many cable tensioning devices as there are floating unit elements 18. These tensioning devices can be removable in the case of hydraulic cylinders.

[0077] In a multi-cable variant (not shown), a single cable tensioning device may be provided. By tensioning this cable, the other cables are also tensioned because, in this variant, the floating unit elements have a degree of rotation possible around the vertical axis XX at their anchoring in the lower and upper connectors.

[0078] In an alternative embodiment not shown, it may be a single metal cable or chain that connects all the flotation nodes of the floating unit assemblies. In this alternative, the single cable passes from the grooves provided at each flotation node, these grooves being provided with blockers (cable clamps) making it possible to fix the position of the cable once the tension has been obtained. Thus, the path of the cable corresponds to the circumference of the floating support structure defined by the floating unit assemblies 18. The tension of the cable or chain is achieved by a device such as a jack or a screw-nut system fixed to the two ends of the cable (or chain).

[0079] Finally, a possible alternative to cables is to use horizontal steel struts connecting the flotation nodes of the floating unit elements. Quick mechanical connectors then ensure the connection. between the spacers and the flotation nodes in order to reduce assembly time as much as possible.

[0080] Figure 4A and Figure 4B represent two variants of a floating support structure 2-2, 2-2' according to a second embodiment of the invention, respectively in perspective and exploded view.

[0081] The floating support structures 2-2, 2-2' according to the second embodiment of the invention form “SPAR” type floats (for “Single Point Anchor Reservoir”), i.e. cylindrical floats forming an extension of the wind turbine mast.

[0082] More specifically, the floating support structure 2-2 according to the variant of figure 4A comprises four central tubular columns 8 which are all identical to each other and independent of each other so as to form a pylon forming the vertical extension of the wind turbine mast.

[0083] Similarly, the floating support structure 2-2' according to the variant of figure 4B comprises three central tubular columns 8 which are all identical to each other so as to form a pylon.

[0084] Furthermore, unlike the first embodiment, the central columns 8 forming the pylon of these two floating support structures 2-2, 2-2' are all devoid of crosspieces (both radial and diagonal).

[0085] Figure 5 is a perspective view of a floating support structure 2-3 according to a third embodiment of the invention.

[0086] In this embodiment, the floating support structure 2-3 forms a semi-submersible float with three floating unit assemblies 18 which are angularly spaced from each other by the same angle of 120°. In this configuration, the cables 36 form a triangle.

[0087] The other features of this floating support structure are similar to those described in connection with the first embodiment.

[0088] Figure 6 is a perspective view of a floating support structure 2-4 according to a fourth embodiment of the invention.

[0089] In this embodiment, the floating support structure 2-4 forms a semi-submersible float with five floating unit assemblies 18 which are angularly spaced from each other by the same angle of 72°. In this configuration, the cables 36 form a pentagon.

[0090] The other features of this floating support structure are similar to those described in connection with the first embodiment.

[0091] Figure 7 is a perspective view of a floating support structure 2-5 according to a fifth embodiment of the invention.

[0092] In this embodiment, the floating support structure 2-5 forms a semi-submersible float with six floating unit assemblies 18 which are angularly spaced from each other by the same angle of 60°. In this configuration, the cables 36 form a hexagon.

[0093] The other features of this floating support structure are similar to those described in connection with the first embodiment.

[0094] Figure 8 is a perspective view of a floating support structure 2-1' according to an alternative embodiment of the first embodiment of the invention, i.e. a floating support structure forming a semi-submersible float with four floating unit assemblies 18 which are angularly spaced from each other by the same angle of 90°.

[0095] This embodiment variant has the particularity that flotation elements 38 are positioned around each cable 36. For example, these flotation elements 38 are in the form of foam cylinders mounted around the cables.

[0096] These flotation elements 38 complement the flotation modules 26 positioned at the level of the flotation nodes of the floating unit assemblies 18.

[0097] The other features of this floating support structure are similar to those described in connection with the first embodiment.

[0098] Figure 9 is a perspective view of a floating support structure 2-1" according to another alternative embodiment of the first embodiment of the invention, i.e. a floating support structure forming a semi-submersible float with four floating unit assemblies 18 which are angularly spaced from each other by the same angle of 90°.

[0099] This embodiment variant has the particularity that flotation units 40 are positioned around the radial crosspieces 20 of each floating unit assembly 18. For example, these flotation units 40 are in the form of foam cylinders mounted around the radial crosspieces.

[0100] Here, these flotation units 40 replace the flotation modules positioned at the level of the flotation nodes 24 of the floating unit assemblies 18.

[0101] The other features of this floating support structure are similar to those described in connection with the first embodiment.

[0102] In connection with Figures 10 to 17, an example of assembly and installation of a floating support structure according to the invention will now be described, in particular the floating support structure 2-5 according to the fifth embodiment of the invention.

[0103] Of course, the assembly method applied to the other embodiments of the invention follows obviously from that described below.

[0104] Assembly can be carried out at the quayside or on an offshore assembly platform (catamaran type) which can be submersible. Using a submersible catamaran allows for greater autonomy, not being dependent on the assembly site and, above all, on the availability of lifting equipment on site.

[0105] Prior to starting assembly, the lower and upper connectors, as well as the floating unit assemblies, can be built in series.

[0106] In a first step, a cylindrical counterweight 42 is placed on the ground at the assembly site, this counterweight being intended to be secured by tendons 50 to the flotation nodes 24 of the floating unit assemblies 18 in order to ensure gravity anchoring of the floating support structure (see the situation illustrated in figure 18).

[0107] In the embodiment shown in Figure 10, this counterweight 42 has a central recess 44 intended to receive the lower connector of the floating support structure.

[0108] In the next step illustrated by Figure 11, the lower connector 4 of the floating support structure is moved (e.g. using a crane or a lifting gantry) to be positioned in the recess 44 of the counterweight 40. In the absence of such a recess, the lower connector is placed directly on the counterweight.

[0109] During the next step (figure 12), positioning supports 46 are advantageously arranged on the assembly site around the counterweight 42 at the precise locations where the flotation modules of the floating unit assemblies will have to rest.

[0110] These 46 positioning supports will allow for quick and precise positioning of the floating unit elements as well as perfect adjustment of the verticality of the central columns when installing the upper connector. Of course, they will be reusable.

[0111] As shown in Figure 13, the floating unit elements 18 are assembled one after the other on the lower connector 4. For this purpose, each floating unit element 18 is lifted (using the crane or the lifting gantry) to vertically introduce the lower end of its central column 8 into one of the receptacles 10 of the lower connector. The floating unit element is also pivoted around its central column to rest its flotation module 26 on one of the positioning supports 46.

[0112] Figure 14 shows the progress of the process with the assembly of a second floating unit element 18 on the lower connector 4.

[0113] Figure 15 represents the structure once all the floating unit elements 18 are assembled on the lower connector 4.

[0114] Once all the floating unit elements 18 have been assembled and then fixed (by welding, by gluing or by mechanical assembly) on the lower connector 4, the next step shown in figure 16 consists of assembling (using the crane or the assembly gantry) the upper connector 6 on the upper end of the central columns, then ensuring a fixing of these parts together (by welding, by gluing or by mechanical assembly).

[0115] A control platform 48 can then be mounted around the upper end of the upper connector 6.

[0116] In a final step of assembling the floating support structure 2-5 (Figure 17), the cables 36 are attached to the respective flotation nodes 24 of the floating unit assemblies 18 and then tensioned. The wind turbine mast and turbine can then be installed using the crane or lifting gantry.

[0117] As shown in Figure 18, maintenance of the offshore wind turbine mounted on a floating support structure according to the invention (here the structure 2-1 with four floating unit assemblies of Figure 1) is possible in particular to allow the replacement of the components of the turbine 52 or the blades 54.

[0118] For this purpose, the diagonal cross members 22 of at least some of the floating unit assemblies 18 of the floating support structure 2-1 are equipped with pins 56 (see also Figure 1) in order to allow the installation of a temporary platform 58 in order to install a telescopic structure 60.

[0119] It should be noted that the 56 spindles can also accommodate other maintenance structures associated with climbing crane options.

[0120] Whatever the embodiment of the invention, it will be noted that it is possible, during the assembly of the floating support structure, to insert at least one central flotation unit 62 between the central columns 8 forming the pylon (see figure 19 with a floating support structure 2-1 with four floating unit assemblies 18 and figure 21 with a structure of floating support 2-6 with two floating unit sets). This central flotation unit 62 makes it possible to increase the flotation of the floating support structure.

[0121] Thus, in the example illustrated in Figure 19, this central flotation unit 62 (for example a foam cylinder) is inserted vertically along the axis XX between the central columns before the step of placing the upper connector on the upper end of the central columns.

[0122] In an alternative not shown in the figures, such a central flotation unit may be pre-installed on the first central column which is assembled during assembly of the floating support structure.

[0123] Figure 20 is a perspective view of an alternative embodiment of the floating support structure 2-3' according to the third embodiment of the invention.

[0124] This embodiment variant differs from that described in connection with Figure 5 in that the lower connector of the structure does not include lower receptacles for receiving the lower ends of the columns. Here, it is a simple 4' clamping collar which clamps the respective lower ends of the central columns.

[0125] In this embodiment, to facilitate the assembly of the central columns of the floating support structure 2-3', a lower connector of the type described in connection with Figure 5 can be temporarily installed on the ground.

[0126] All of the embodiments of the floating support structure according to the invention which have been described so far relate to structures in which the axis XX of the wind turbine mast is aligned with a center of symmetry of the float (the floating support pylon is aligned with the center of symmetry of the structure).

[0127] In contrast, Figure 21 is a perspective view of a semi-submersible type floating support structure according to a sixth embodiment of the invention which is off-center.

[0128] In this sixth embodiment, the floating support structure 2-6 comprises only two floating unit assemblies 18 which form between them a angle which is different from 180°. Also, the X'-X' axis of the wind turbine mast 9 is eccentric relative to the center of symmetry of the structure.

[0129] Furthermore, in this sixth embodiment, each of the two floating unit assemblies 18 comprises two flotation modules 26 which are positioned at their respective flotation node 24. Of course, the presence of two flotation modules per floating unit assembly can be applied to the flotation support structures of the other embodiments.

[0130] Still in this sixth embodiment, the cable connecting the respective flotation nodes 24 of the two floating unit assemblies 18 is replaced by a bracing element 36'.

[0131] Furthermore, this sixth embodiment provides for positioning a central flotation unit 62 between the central columns 8 forming the pylon.

[0132] Figure 22A and Figure 22B show two alternative embodiments of the 2-3" floating support structure of the semi-submersible type with three rectangular floating unit assemblies according to the third embodiment.

[0133] In these two embodiments, each floating unit assembly 18' has a rectangular shape with a central column 8, as well as two radial crosspieces 20a, 20b (namely a high radial crosspiece 20a and a low radial crosspiece 20b spaced from each other along the axis XX of the mast 9) and a diagonal crosspiece 22.

[0134] Furthermore, in the embodiment variant of figure 22A, the flotation modules 26' are in the form of vertical columns of polygonal cross-section (here hexagonal) which can be produced by assembling flat panels.

[0135] In the embodiment variant of figure 22B, the flotation modules 26" are in the form of vertical columns of cylindrical shape.

[0136] Figure 23 shows an exemplary embodiment of a ballast pipe network within a floating support structure according to the invention (partially shown in the figure), and more particularly within a floating unitary assembly 18 of triangular shape.

[0137] This ballast piping network thus comprises pipes 64 which are housed inside the radial 20 and diagonal 22 crosspieces of the floating unit assembly. These pipes 64 open at the level of the flotation modules inside ballast compartments 66 and open into the same central conduit 68 housed inside the central column 8 of the floating unit assembly.

[0138] At its upper end, the central pipe 68 is advantageously provided with 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 assembly which facilitates the assembly and operation of the floating support structure.

Claims

Claims

1. A floating support structure (2-1 to 2-6) with multiple central columns for an offshore wind turbine, comprising: - at least two identical and independent central tubular columns (8) which are assembled to each other around an axis (XX; X'-X') of a mast (9) of the wind turbine so as to form a floating support pylon forming a vertical extension of the mast of the wind turbine; - a lower connector (4) centered on the axis (XX) of the mast (9) of the wind turbine and intended to ensure maintenance and absorption of the forces of the central columns at their respective lower ends; and - an upper connector (6) centered on the axis of the wind turbine mast and comprising, in an upper part, means (14) for receiving the wind turbine mast and, in a lower part, at least two upper receptacles (12) for receiving an upper end of the central columns, - each central column being connected to at least one tubular crosspiece (20, 22) of which one end opposite the central column constitutes a flotation node (24) spaced radially from the floating support pylon so as to form a semi-submersible type float.

2. Structure according to claim 1, in which each central column (8) is connected, on the one hand at its lower end to at least one radial crosspiece (20; 20a, 20b), and on the other hand above its lower end to at least one diagonal crosspiece (22), the radial crosspiece and the diagonal crosspiece being connected to each other at the level of the flotation node (24) so ​​as to form a floating unitary assembly (18) of triangular shape.

3. Structure according to claim 1, in which each central column (8) is connected, on the one hand at its lower end to at least one first radial crosspiece (20a), and on the other hand to above its lower end to at least one second radial crosspiece (20b), the radial crosspieces being connected to each other at the level of the flotation node (24) so ​​as to form a floating unitary assembly (18) of rectangular shape.

4. Structure according to one of claims 2 and 3, in which each floating unitary assembly (18) comprises at least one flotation module (26; 26'; 26") positioned at its flotation node (24).

5. Structure according to claim 4, in which each flotation module (26) comprises a central rod (28) extending parallel to the axis (XX) of the wind turbine mast and on which are fitted at least one steel ring (30) and / or at least one ring of non-metallic material (32).

6. Structure according to any one of claims 1 to 5, in which the axis (XX) of the mast (9) of the wind turbine is aligned with a center of symmetry of the float.

7. Structure according to any one of claims 1 to 5, in which the axis (X'-X') of the mast (9) of the wind turbine is eccentric relative to a center of symmetry of the float.

8. A structure according to any one of claims 1 to 7, the respective flotation nodes (24) of the floating unit assemblies are connected to each other by at least one cable (36), the flotation nodes comprising cable tensioning devices.

9. The structure of claim 8, further comprising at least one flotation element (38) positioned around the cable (36).

10. Structure according to any one of claims 1 to 10. 9, wherein each floating unit assembly (18) comprises a network of ballast piping housed inside at least one of the cross members (20, 22) and the central column (8).

11. Structure according to any one of claims 1 to 12. 10, wherein the floating support pylon and / or at least one of the radial cross members comprises at least one central flotation unit (62).

12. Structure according to any one of claims 1 to 11, in which the lower connector (4) is an independent part of the central columns and comprises at least two lower receptacles (12) for each receiving a lower end of the central columns.

13. A structure according to any one of claims 1 to 11, wherein the lower connector is a clamping collar (4Q) clamping the respective lower ends of the central columns.

14. A method of assembling a floating support structure according to any one of claims 1 to 13, comprising a step of dry assembling the lower end of each central column (8) to the lower connector (4), followed by a step of dry assembling the upper connector (6) to the upper end of each central column.

15. Method of assembling a floating support structure according to one of claims 2 and 3, successively comprising: - a step of assembling the floating unit elements (18) on the lower connector (4) by lifting each unit element and pivoting it to rest the flotation node (24) on a support (46) previously positioned on the ground to guarantee the correct lateral positioning of the floating unit element; - a step of assembling the upper connector (6) on the upper end of the central column (8) of each floating unit element (18); and - a step of connecting the central columns of the floating unit elements to the lower and upper connectors by welding, gluing or mechanical assembly.

16. The method of claim 15, wherein the assembly steps are carried out on a submersible platform allowing the floating support structure to be launched into the water in a calm area protected from the swell.

17. The method of claim 16, wherein the submersible platform is equipped with a lifting gantry allowing to assemble the wind turbine mast on the upper part of the upper connector of the floating support structure.

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