FR3139794A1 - Floating support structure with multiple central columns for offshore wind turbine and method of assembling such a structure - Google Patents

Abstract

Floating support structure with multiple central columns for an offshore wind turbine and method of assembling such a structure The invention relates to a floating support structure (2-1) for an offshore wind turbine, comprising a lower connector (4) centered on an axis (X-X) of a mast (9) of the wind turbine and comprising at least three lower receptacles (10) regularly distributed around the axis of the mast of the wind turbine, an upper connector (6) centered on the axis of the mast of the wind turbine and comprising, in an upper part, means for receiving (14) a wind turbine mast and, in a lower part, at least three upper receptacles (12) regularly distributed around the axis of the wind turbine mast of the wind turbine, and at least three identical tubular central columns (8) which are assembled at a lower end in one of the receptacles of the lower connector and at an opposite upper end in one of the receptacles of the upper connector (from so as to form a floating support pylon fitting into the vertical extension of the wind turbine mast. The invention also relates to a method of assembling such a structure. Figure for abstract: Fig. 1.

Description

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

The present invention relates to the general field of offshore wind turbines, that is to say installed offshore, and more particularly to floating support structures for floating offshore wind turbines.

The invention also relates to a method of installing an offshore wind turbine provided with such a support structure.

An offshore wind turbine aims to use wind energy to produce 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 depth of the seabed typically exceeds 50m.

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

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

Semi-submersible floats are the most common float model currently available. It is a steel or concrete foundation which is pre -
usually in the form of a tripod with three (or four) cylindrical columns linked together by metal structures. The stability of the structure is ensured thanks to a ballast system which allows the immersion of part of the foundation. This structure is characterized by its large size and reduced draft. We can refer to the publication WO 2019/106283 which describes a semi-submersible float structure and a method of installing a wind turbine provided with such a float structure.

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

The “SPAR” type float is characterized by its cylindrical shape as an extension of the wind turbine mast. Its stability is given to it by heavy ballast which lowers the center of gravity of the assembly and which is equipped with catenary anchors allowing the wind turbine to be attached to the seabed. We can refer to the publications WO 2005/021961, WO 2006/121337 and WO 2006/132539 which describe examples of the production of a “SPAR” platform, its anchoring and its installation process at sea.

Finally, semi-submersible “barge” type floats come in the form of a more compact foundation which is comparable to a rectangular barge pierced in its center and made mainly of concrete or steel.

Most floating support structures were not designed for large-scale industrialization. Indeed, these floats generally consist of a large number of elements to assemble, which requires time and space on the ground.

The object of the invention is therefore to propose a floating support structure (of the “SPAR” type, semi-submersible or of the “TLP” type) for an offshore wind turbine which makes it possible to simplify its assembly and accelerate the assembly time while minimizing the space required on land.

• au moins deux colonnes centrales tubulaires identiques et indépendantes qui sont assemblées les unes aux autres autour d’un axe d’un mât de l’éolienne de façon à former un pylône de support flottant s’inscrivant dans le prolongement vertical du mât de l’éolienne ;
• un connecteur inférieur centré sur l’axe du mât de l’éolienne et destiné à assurer un maintien et une reprise des efforts des colonnes centrales au niveau de leur extrémité inférieure respective ; et
• un connecteur supérieur centré sur l’axe du mât de l’éolienne et comprenant, dans une partie supérieure, des moyens de réception du mât de l’éolienne et, dans une partie inférieure, au moins deux réceptacles supérieurs pour recevoir une extrémité supérieure des colonnes centrales.

In accordance with the invention, this goal is achieved thanks to a floating support structure with multiple central columns for an offshore wind turbine, comprising:

• at least two identical and independent tubular central columns which are assembled together around an axis of a mast of the wind turbine so as to form a floating support pylon fitting into the vertical extension of the mast of the wind turbine wind turbine ;
• a lower connector centered on the axis of the wind turbine mast and intended to ensure maintenance and recovery 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.

The invention is remarkable in that it is based on a modular approach for producing the floating support structure. In particular, from lower and upper connectors, the invention plans to form the floating support pylon using a plurality of identical and independent central columns which are assembled using these connectors. The number of central columns could 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 installed.

Because the central columns are all identical, this greatly simplifies the assembly of the floating support structure. In fact, these central columns, but also the lower and upper connectors, can be prefabricated in series on the same model and quickly assembled on site. This results in a simplification of assembly and a saving of time.

The floating support pylon may be devoid of a crosspiece so as to form a SPAR type float.

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

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 unitary floating assembly of triangular shape.

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 unitary floating assembly of rectangular shape.

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

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

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 eccentric in relation to a center of symmetry of the float.

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

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

Preferably, each floating unit assembly comprises a ballast piping network housed inside at least one of the crosspieces and the central column.

The floating support pylon and/or at least one of the radial crosspieces may comprise at least one central flotation unit.

In a variant, the lower connector is an independent part of the central columns and comprises at least two lower receptacles to each receive a lower end of the central columns.

In another variant, the lower connector is a clamp clamping the respective lower ends of the central columns.

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 dry assembly of the upper connector on the upper end of each central column.

• une étape d’assemblage des éléments unitaires flottant sur le connecteur inférieur en soulevant chaque élément unitaire et en le pivotant pour faire reposer le nœud de flottaison sur un support préalablement positionné à terre pour garantir le bon positionnement latéral de l’élément unitaire flottant ;
• une étape d’assemblage du connecteur supérieur sur l’extrémité supérieure de la colonne centrale de chaque élément unitaire flottant ; et
• une étape de connexion des colonnes centrales des éléments unitaires flottant aux connecteurs inférieur et supérieur par soudage, par collage ou par assemblage mécanique.

The invention also relates to a method of assembling a floating support structure as defined above, successively comprising:

• a step of assembling the unitary elements floating on the lower connector by lifting each unitary element and pivoting it to rest the flotation node on a support previously positioned on the ground to guarantee the correct lateral positioning of the floating unitary 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, by gluing or by mechanical assembly.

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

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.

There 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.

There is a side view of the floating support structure of the .

There is an exploded view of the floating support structure of Figures 1 and 2.

There is a perspective view of a SPAR type floating support structure according to a second embodiment of the invention.

There is an exploded view of a variant of the SPAR type floating support structure according to this second embodiment.

There 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.

There 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.

There 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.

There is a perspective view of a floating support structure according to an alternative embodiment of the first embodiment of the invention.

There is a perspective view of the floating support structure according to another alternative embodiment of the first embodiment of the invention.

has Figures 10 to 17 are views showing an example of the different stages of an assembly process according to the invention of a floating support structure of the .

There shows an example of maintenance on an offshore wind turbine mounted on the floating support structure of the .

There 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.

There is a perspective view of a variant embodiment of the floating support structure according to the third embodiment of the invention.

There is a perspective view of a floating support structure of the semi-submersible and eccentric type with two floating unit assemblies according to a sixth embodiment of the invention.

There shows an alternative embodiment of the floating support structure according to the third embodiment.

There shows another alternative embodiment of the floating support structure according to the third embodiment.

There shows an example of production of a ballast piping network within a floating support structure according to the invention.

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).

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 (that is to say at least two, and four in number on 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 fitting into the vertical extension of the mast 9 of the wind turbine.

The central columns 8 generally have a diameter of between 2 and 4 meters. They may or may not be reinforced inside. They are typically made using different assembly technologies and are easy to manufacture without significant investment.

As shown on the , 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 embodiment) lower receptacles 10 regularly distributed around the vertical axis XX, open upwards and each intended to receive by interlocking complementary shapes the lower end of a central column 8.

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

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 wind turbine mast is fitted before being fixed (by welding for example).

Of course, it is possible to consider other means of receiving the wind turbine mast. Likewise, it is possible to envisage that the upper connector forms a single piece with at least part of the wind turbine mast.

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

Preferably, as shown in the , the receptacles 10 of the lower connector and/or the receptacles 12 of the upper connector each include a centering guide 16 intended to facilitate the assembly of a corresponding end of the central column.

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

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

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

By “floating unitary assembly”, it is meant that, for each central column, there is provided at least one radial tubular crosspiece and at least one diagonal tubular crosspiece 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.

In the different embodiments described below (with the exception of that described in connection with Figures 4A, 4B, 22A and 22B), the floating unit assemblies have a triangular shape.

More precisely for these embodiments, for each central column 8, a radial tubular crosspiece 20 is connected to a lower end of the column at an angle of between 75° and 90° therewith, 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 by forming with the latter a flotation node 24 spaced radially from the vertical axis X-X so as to form a floating unitary assembly 18 having a triangular shape.

These floating unit 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.

In this first embodiment, the floating support structure 2-1 has four floating unit assemblies 18 of identical triangular shape which are regularly spaced from each other (that is to say at the same angle of 90°) .

Of course, the floating unitary assemblies can have shapes other than a triangular shape depending on the number and arrangement of the radial and diagonal crosspieces. Likewise, they are not necessarily all identical to each other.

Furthermore, each floating unit 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 axis vertical X-X of the mast.

Each flotation module 26 consists of a central rod 28 which extends parallel to the vertical axis X-X 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.

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 .

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 conditions of installation of the wind turbine.

These non-metallic rings 32 are made of non-metallic materials, either solid, or foam or syntactic foam in order to play a flotation role. Non-metallic materials can be thermosets, thermoplastics or elastomers. These non-metallic rings are held on the central rod 28 by any means (for example by circlips).

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

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 device for tensioning the cable. The cable(s) 36 are thus pre-stressed and make it possible to reduce the overall weight of the floating support structure and to reduce its assembly time.

As shown on the relating to the first embodiment, it may be a plurality of metal cables 36 connecting in pairs the flotation nodes of the floating unit assemblies 18.

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 The other end of the cable is connected to the neighboring flotation node. In this configuration, there are as many cable tensioning devices as floating unit elements 18. These tensioning devices can be removable in the case of hydraulic cylinders.

In a variant with several cables (not shown), a single cable tensioning device can be provided. By tensioning this one, the other cables are also tensioned because, in this variant, the floating unit elements have a possible degree of rotation around the vertical axis X-X at the level of their anchoring in the lower and upper connectors.

In a variant embodiment not shown, it may be the same and single cable or metal chain which connects all the flotation nodes of the floating unit assemblies. In this variant, the single cable passes through the grooves provided at each flotation node, these grooves being provided with blockers (cable clamps) allowing the position of the cable to be fixed 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 the chain is carried out by a device such as a jack or a screw-nut system fixed to the both ends of the cable (or chain).

Finally, a possible alternative to cables is to use horizontal steel spacers connecting the flotation nodes of the floating unit elements together. Quick mechanical connectors then ensure the connection between the spacers and the flotation nodes in order to minimize assembly time.

There and the 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.

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"), that is to say floats cylindrical in shape as an extension of the wind turbine mast.

More precisely, the floating support structure 2-2 according to the variant of the comprises four tubular central columns 8 which are all identical to each other and independent of each other so as to form a pylon fitting into the vertical extension of the wind turbine mast.

Likewise, the floating support structure 2-2' depending on the variant of the comprises three tubular central columns 8 which are all identical to each other so as to form a pylon.

Furthermore, unlike the first embodiment, the central columns 8 forming the pylon of these two floating support structures 2-2, 2-2' all have no crosspiece (both radial and diagonal).

There is a perspective view of a floating support structure 2-3 according to a third embodiment of the invention.

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 at the same angle of 120°. In this configuration, the cables 36 form a triangle.

The other characteristics of this floating support structure are similar to those described in connection with the first embodiment.

There is a perspective view of a floating support structure 2-4 according to a fourth embodiment of the invention.

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 at the same angle of 72°. In this configuration, the cables 36 form a pentagon.

The other characteristics of this floating support structure are similar to those described in connection with the first embodiment.

There is a perspective view of a floating support structure 2-5 according to a fifth embodiment of the invention.

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 at the same angle of 60°. In this configuration, the cables 36 form a hexagon.

The other characteristics of this floating support structure are similar to those described in connection with the first embodiment.

There is a perspective view of a floating support structure 2-1' according to a variant embodiment of the first embodiment of the invention, that is to say a floating support structure forming a semi-submersible float with four floating unitary assemblies 18 which are angularly spaced from each other at the same angle of 90°.

This alternative embodiment 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.

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

The other characteristics of this floating support structure are similar to those described in connection with the first embodiment.

There is a perspective view of a 2-1'' floating support structure according to another alternative embodiment of the first embodiment of the invention, that is to say a floating support structure forming a semi-float submersible with four floating unit assemblies 18 which are angularly spaced from each other at the same angle of 90°.

This alternative embodiment 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.

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

The other characteristics of this floating support structure are similar to those described in connection with the first embodiment.

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

Of course, the assembly process applied to the other embodiments of the invention follows obviously from that described below.

Assembly can be carried out at the dock or on an offshore assembly platform (catamaran type) which can be submersible. The use of a submersible catamaran allows you to gain autonomy, not to be dependent on the assembly site and above all on the availability of lifting means on the site.

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

In a first step, a counterweight 42 of cylindrical shape is placed on the ground on 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 scenario illustrated in ).

In the embodiment shown on the , this counterweight 42 has a central recess 44 intended to receive the lower connector of the floating support structure.

In the next step illustrated by the , the lower connector 4 of the floating support structure is moved (for example using a crane or a lifting gantry) to be positioned in the recess 44 of the counterweight 40. In the absence of such Obviously, the lower connector is placed directly on the counterweight.

During the next step ( ), 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.

These positioning supports 46 will allow rapid 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.

As shown on the , 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 end lower part of its central column 8 in one of the receptacles 10 of the lower connector. The floating unitary element is also pivoted around its central column to rest its flotation module 26 on one of the positioning supports 46.

There represents the progress of the process with the assembly of a second floating unit element 18 on the lower connector 4.

There represents the structure once all the floating unit elements 18 have been assembled on the lower connector 4.

Once all of 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 following step shown in consists of assembling (using the crane or the assembly gantry) the upper connector 6 on the upper end of the central columns, then ensuring that these parts are fixed together (by welding, by gluing or by mechanical assembly).

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

In a final assembly step of the floating support structure 2-5 ( ), the cables 36 are fixed to the respective flotation nodes 24 of the floating unitary assemblies 18 then are put under tension. The wind turbine mast and turbine can then be installed using the crane or lifting gantry.

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

For this purpose, the diagonal crosspieces 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 the ) in order to allow the installation of a temporary platform 58 in order to install a telescopic structure 60.

Note that the pins 56 can also accommodate other maintenance structures associated with climbing crane options.

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 with a floating support structure 2-1 with four floating unit sets 18 and the with a floating support structure 2-6 with two floating unit sets). This central flotation unit 62 makes it possible to increase the flotation of the floating support structure.

Thus, in the example illustrated on the , 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.

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

There is a perspective view of a variant embodiment of the floating support structure 2-3' according to the third embodiment of the invention.

This alternative embodiment differs from that described in connection with the 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' clamp clamping the respective lower ends of the central columns.

In this alternative 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 the can be temporarily installed on the ground.

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

In contrast, the is a perspective view of a semi-submersible type floating support structure according to a sixth embodiment of the invention which is eccentric.

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

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 floating support structures of other embodiments.

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'.

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

There and the show two alternative embodiments of the 2-3'' floating support structure of the semi-submersible type with three floating unit assemblies of rectangular shape according to the third embodiment.

In these two alternative embodiments, each floating unitary 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 one from the other along the axis X-X of the mast 9) and a diagonal crosspiece 22.

Furthermore, in the alternative embodiment of the , the flotation modules 26' are in the form of vertical columns of polygonal straight section (here hexagonal) which can be produced by assembling flat panels.

In the alternative embodiment of the , the 26'' flotation modules are in the form of vertical columns of cylindrical shape.

There shows an example of production of a ballast piping 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.

This ballast piping network thus includes 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 pipe 68 housed inside the central column 8 of the floating unit assembly.

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 (19)

Floating support structure (2-1 to 2-6) with multiple central columns for offshore wind turbine, comprising:

• at least two identical and independent tubular central columns (8) which are assembled together around an axis (XX; X'-X') of a mast (9) of the wind turbine so as to form a pylon floating support forming part of the vertical extension of the wind turbine mast;
• a lower connector (4) centered on the axis (XX) of the mast (9) of the wind turbine and intended to ensure maintenance and recovery 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 for receiving (14) the wind turbine mast and, in a lower part, at least two upper receptacles (12) to receive an upper end of the central columns.

Structure according to claim 1, in which the floating support pylon does not have a crosspiece so as to form a float (2-2) of the SPAR type. Structure according to claim 1, in which each central column (8) is connected to at least one tubular crosspiece (20, 22) whose 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. Structure according to claim 3, 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 has at least one diagonal crosspiece (22), the radial crosspiece and the diagonal crosspiece being connected to one another at the level of the flotation node (24) so as to form a unitary floating assembly (18) of triangular shape. Structure according to claim 3, 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 above its lower end to at least one second radial crosspiece (20b), the radial crosspieces being connected to one another at the flotation node (24) so as to form a unitary floating assembly (18) of rectangular shape. Structure according to one of claims 4 and 5, in which each floating unit assembly (18) comprises at least one flotation module (26; 26'; 26'') positioned at its flotation node (24). Structure according to claim 6, in which each flotation module (26) comprises a central rod (28) extending parallel to the axis (X-X) of the wind turbine mast and on which at least one steel ring is fitted (30) and/or at least one ring made of non-metallic material (32). Structure according to any one of claims 3 to 7, in which the axis (X-X) of the mast (9) of the wind turbine is aligned with a center of symmetry of the float. Structure according to any one of claims 3 to 7, in which the axis (X'-X') of the mast (9) of the wind turbine is eccentric with respect to a center of symmetry of the float. Structure according to any one of claims 3 to 9, 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 tensioning devices of the cable. Structure according to claim 10, further comprising at least one flotation element (38) positioned around the cable (36). Structure according to any one of claims 3 to 11, in which each floating unitary assembly (18) comprises a ballast piping network housed inside at least one of the crosspieces (20, 22) and the central column (8). Structure according to any one of claims 3 to 12, in which the floating support pylon and/or at least one of the radial crosspieces comprises at least one central flotation unit (62). Structure according to any one of claims 1 to 13, in which the lower connector (4) is an independent part of the central columns and comprises at least two lower receptacles (12) to each receive a lower end of the central columns. Structure according to any one of claims 1 to 13, in which the lower connector is a clamp (4') tightening the respective lower ends of the central columns. Method of assembling a floating support structure according to any one of claims 1 to 15, comprising a step of dry assembly of the lower end of each central column (8) on the lower connector (4), followed by a dry assembly step of the upper connector (6) on the upper end of each central column. Method of assembling a floating support structure according to one of claims 4 and 5, comprising successively:

• 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, by gluing or by mechanical assembly.

Method according to claim 17, in which the assembly steps are carried out on a submersible platform making it possible to launch the floating support structure in a calm area protected from swell. Method according to claim 18, in which the submersible platform is equipped with a lifting gantry allowing the mast of the wind turbine to be assembled on the upper part of the upper connector of the floating support structure.