Floating intervention vessels, associated intervention assemblies and facilities intended to temporarily moor themselves on offshore wind turbine platforms

Abstract

The present invention relates to a floating intervention vessel, an associated intervention assembly, and a facility intended for temporarily mooring itself on an offshore wind turbine platform. The vessel comprises a float (80) and a wind turbine intervention assembly carried by the float (80). The float (80) comprises a buoyant body (86) and a fastening base plate (88) protruding from the buoyant body (86) along a fastening axis (A-A') on the underside of the offshore wind turbine platform. The buoyant body (86) defines a ballast receiving volume. The vessel comprises a ballast controller configured to control the amount of ballast received in the ballast receiving volume to raise an upper contact surface (94) of the base plate (88) and place the upper contact surface (94) in contact with the underside of the offshore wind turbine platform. The float (80) is monohulled.

Description

[Technical Field]

[0001] The present invention relates to an offshore floating intervention vessel, which is intended to be temporarily moored on an offshore wind turbine platform to carry out installation and / or maintenance interventions on the wind turbine, the floating vessel comprising: a float intended to be at least partially submerged in a body of water; - an offshore floating intervention vessel comprising a wind turbine intervention assembly held by floats, the wind turbine intervention assembly including at least one lifting device configured to lift wind turbine equipment. [Background technology]

[0002] Such vessels are intended to carry out installation, removal and / or maintenance interventions on offshore wind turbines installed on floating platforms.

[0003] Such intervention vessels are particularly suitable for carrying out installation and / or maintenance work on offshore wind farms located in waters deeper than 60 m.

[0004] Wind turbine installation and maintenance may be carried out using an offshore platform such as the fixed base platform disclosed in EP 2275340. Such a platform is particularly suitable for shallow waters where the wind turbine is attached to the bottom of the body of water using a mast support permanently installed on the bottom of the body of water.

[0005] However, the majority of offshore wind turbine resources are found in water depths greater than 60 m, where traditional seabed anchoring is not economically or practically feasible. To exploit this potential, floating wind turbine platforms are used.

[0006] In such a platform, the mast of the wind turbine is held by a floating base that is anchored at the bottom of the body of water by anchor lines.

[0007] An example of a floating wind turbine platform comprises a floating base comprising several floating struts connected to each other by pontoons and / or lattices, and a mast may extend from the top of one of the struts, for example.

[0008] Floating wind platforms create more difficult operation and maintenance ("O&M") conditions for wind turbines, which requires new operation and maintenance strategies and techniques.

[0009] This is especially true considering that the installed power of floating wind platforms is increasing year by year, reaching 8 MW, 12 MW, 15 MW, and now even 20 MW, which increases the mat height (over 100 m) and blade length (over 80 m).

[0010] Offshore wind turbines may require recurring and extensive maintenance operations given their expected long lifespan (over 25 years).

[0011] When these wind turbines are supported by a floating base, maintenance operations may require the platform to be disconnected from its moorings and towed by a tall harbor crane to port for maintenance. These operations are time-consuming, very expensive, and cause significant disruption to power generation.

[0012] Solutions for offshore lifting at significant depths (e.g., 60m-120m) exist but are not entirely satisfactory.

[0013] For example, jack-up maintenance platforms may be used, however, these jack-up platforms are fixed to the seabed while the wind turbines are located on floating bases, making the lifting operations very complicated to carry out, given the relative displacement between the jack-up platform and the floating base due to the movement of the water body.

[0014] Semi-submersible installation and maintenance units also exist. These units are either moored to the floating wind turbine platform or can be dynamically positioned and placed relative to the floating wind turbine platform ("dynamic positioning"). However, these units have their own roll, pitch, yaw, and heave motions, which also make lifting difficult.

[0015] Yet another solution is to place a crane on the floating base of the wind turbine. The crane moves together with the floating base, which greatly simplifies the lifting operation. However, given the required size of the crane, its transfer, its installation on the floating base, and its disassembly are heavy tasks requiring specialized, rare, and expensive vessels. Summary of the Invention

[0016] It is therefore an object of the present invention to provide an offshore intervention vessel that is suitable for operations on offshore wind turbines that require a high degree of positioning accuracy, and that is simple and inexpensive to operate.

[0017] To this end, the invention relates to an intervention vessel of the type described above, characterized in that the float comprises a buoyant body and a fastening base plate protruding relative to the buoyant body along a fastening axis on the underside of the offshore wind turbine platform, the buoyant body defining a ballast receiving volume, the floating vessel comprising a ballast controller configured to control the amount of ballast received in the ballast receiving volume to raise an upper contact surface of the base plate and place it in contact with the underside of the offshore wind turbine platform, and the float is monohulled.

[0018] The intervention vessel according to the invention may comprise one or more of the following features, taken alone or according to any technically possible combination: - the upper contact surface of the base plate comprises an anchor assembly configured to eliminate relative movement between the upper contact surface of the base plate and the underside of the offshore wind turbine platform, the anchor assembly specifically comprising at least one suction anchor pad, and / or magnetic anchor pad, and / or friction anchor pad; the float has at least one docking fender located on the base plate, the docking fender optionally protruding relative to the buoyant body along a fastening axis; the float has an L-shaped cross section when viewed in a vertical plane containing the fastening axis, or the float has a C-shaped cross section when viewed in a vertical plane containing the fastening axis, the docking fender and the base plate defining an intermediate space therebetween for receiving a structure of the offshore wind turbine platform; the lifting device comprises at least one lifting and / or handling unit selected from an intervention crane, a forklift, a wind turbine blade gripper, and / or a motion compensation device; - the lifting device comprises a fixed mast formed from a lattice of beams assembled together, the mast projecting vertically above the buoyant body; the mast has a height greater than the height of the float, the mast advantageously having a centre of gravity located at a height less than half the height of the mast; - the cross-sectional dimensions and / or thickness of the lattice beams decrease along the mast from bottom to top; the lifting device comprises a telescoping mast, the telescoping mast being deployable between a retracted configuration in which its free end is located in the vicinity of the float and an upward deployed configuration; the telescoping mast axis is tiltable between a vertical configuration, a first configuration tilted in a first direction at a non-zero angle relative to the vertical, and a second configuration tilted in a second direction opposite the first direction at a non-zero angle relative to the vertical; - the float comprises at least one propeller thruster arranged below the buoyancy body and / or below the base plate; each horizontal section of the buoyant body has a maximum axial dimension measured along the fastening axis that is less than 0.75 times the maximum transverse dimension of the horizontal section, preferably less than 0.50 times the maximum transverse dimension of the horizontal surface, the maximum transverse dimension being measured perpendicular to the fastening axis;

[0019] The invention also relates to an offshore intervention assembly comprising a vessel having a hull defining at least one space for storing wind turbine equipment and a floating vessel as defined above, The floating vessel is movable relative to the ship between a transport position of the floating vessel to the offshore wind turbine platform, where the base plate of the float is held fixed against the underside of the hull, and an intervention position, where the floating vessel is disposed away from the ship for intervention on the offshore wind turbine platform.

[0020] An interventional assembly according to the present invention may include the following features. The vessel comprises at least one rack for storing wind turbine equipment, and optionally at least one handling assembly having a handling member movable between a position for gripping the wind turbine equipment in the storage rack and an intervention position outside the vessel's hull.

[0021] The present invention also relates to an offshore installation comprising an offshore intervention assembly as defined above and an offshore wind turbine platform, wherein the floating vessel is movable through a body of water from its transport position to an intervention position in which the base plate rests below the underside of the offshore wind turbine platform, and wherein the maximum axial dimension of each horizontal section of the buoyancy body, measured along a fastening axis, is less than 90% of the maximum dimension of the offshore wind turbine platform, measured parallel to the same fastening axis.

[0022] A facility according to the invention may include the following features: - an offshore wind turbine platform comprising a floating foundation having at least three floating struts and lower pontoons connecting the at least three floating struts two by two, the lower pontoons defining at least a portion of the underside of the floating wind turbine platform, an upper contact surface of a base plate engaged below the underside of the lower pontoons between two adjacent floating struts, and a maximum transverse dimension of each horizontal section of the buoyant body being less than the distance horizontally separating two adjacent floating struts, or comprising a floating foundation formed from a barge with or without a central hole. [Brief explanation of the drawings]

[0023] The invention will be better understood on reading the following description, given purely by way of example and made with reference to the accompanying drawings, in which: [Figure 1] FIG. 1 is a front view of a floating wind turbine platform where intervention has to be performed using an intervention assembly according to the present invention. [Figure 2] FIG. 2 illustrates a top view of a floating wind turbine platform and an intervention assembly positioned adjacent the floating wind turbine platform. [Figure 3] 1(a)(b) are side views of a floating intervention vessel of an intervention assembly according to the invention; [Figure 4] FIG. 4 is a three-quarter perspective view of a fastening base plate of the floating vessel of FIG. 3 on a floating wind turbine platform, the base plate including fastening pads. [Figure 5] FIG. 1 illustrates a floating vessel with a fixed mast moored on an offshore wind turbine platform during an intervention on a wind turbine blade. [Figure 6] 6 is a view similar to FIG. 5 during an intervention on the nacelle of the wind turbine. [Figure 7] 6 is a view similar to FIG. 5, but with the floating vessel equipped with a telescoping mast. [Figure 8] 1A-1C are side views sequentially illustrating the approach and mooring of a floating vessel to an offshore wind platform. [Figure 9] 1A-1C are side views sequentially illustrating the approach and mooring of a floating vessel to an offshore wind platform. [Figure 10] 1A-1C are side views sequentially illustrating the approach and mooring of a floating vessel to an offshore wind platform. [Figure 11] FIG. 3 is a top view similar to FIG. 2 showing the transfer of the blade from the floating vessel to the transport vessel. DETAILED DESCRIPTION OF THE INVENTION

[0024] A first floating offshore intervention assembly 10 according to the present invention is shown in particular in Figures 2 to 6 and 8 to 11 .

[0025] The intervention assembly 10 floats on a body of water 12. It is intended to perform installation and / or maintenance interventions on at least one floating offshore wind turbine platform 14 shown in Figure 1 .

[0026] An offshore wind turbine platform 14 is located on the surface of a body of water 12, for example, at an offshore wind farm.

[0027] The body of water 12 near the offshore wind turbine platform 14 has a depth of more than 50 metres, typically between 60m and 1000m.

[0028] The body of water 12 may be, for example, an ocean, a sea, a lake, and / or a river.

[0029] Referring to FIG. 1 , the wind turbine platform 14 comprises a floating foundation 16, for example, with columns or of the barge type, with or without a central hole, an anchor assembly 17 that anchors the floating foundation 16 to the bottom 18 of the body of water 12, and a wind turbine 20 supported by the floating foundation 16.

[0030] In the example shown in the figures, the floating foundation 16 is a semi-submersible platform. In this example, it comprises at least three floating columns 22, structural elements 24 connecting the floating columns 22, and an optional bridge (not shown). Alternatively, as indicated above, the floating foundation 16 may be formed by a prismatic barge, with or without a central hole.

[0031] In the illustrated embodiment, the structural elements 24 here comprise lower pontoons 26A connecting each pair of adjacent floating columns 22 to the bottom of the floating columns 22, and upper pontoons 26B connecting each pair of adjacent floating columns 22 to the top of the floating columns 22. Alternatively (not shown), the lower and / or upper pontoons may radially connect each column to a central point of the foundation 16 and / or to the central floating column.

[0032] The floating struts 22 extend vertically. Inside, they present a buoyant volume that is at least partially filled with gas, providing buoyancy to the floating foundation 16. The buoyancy is adapted so that the floating foundation 16 is partially immersed in the body of water 12.

[0033] The anchor assembly 17 comprises a plurality of anchor lines 30 connecting each support pole 22 to the bottom 18 of the body of water 12. In the example of Figure 1, each floating support pole 22 is connected to at least one anchor line 30, preferably two to four anchor lines 30.

[0034] Thus, the wind turbine platform 14 is maintained in a horizontal position within the body of water 12 .

[0035] The wind turbine 20 conventionally comprises a mast 32, a nacelle 34 rotatably mounted on top of the mast 32, and a rotor 36 rotatably mounted relative to the nacelle 34, preferably about a horizontal axis.

[0036] The rotor 36 includes a central hub 38 and blades 40 that project radially from the central hub 38 and are removably attached to the hub 38 .

[0037] The mast 32 is attached to the top of the floating struts 22, in this example coaxially with the axis of one of the floating struts 22. Alternatively, the mast 32 is fixed non-coaxially to the floating struts 22.

[0038] The floating support 22 and advantageously the lower pontoon 26A define an underside 42 of the wind turbine platform 14. The underside 42 has at least one flat area intended for mooring a floating vessel 50 of the intervention assembly 10, as will be shown below.

[0039] The intervention assembly 10 is configured to be moved to the surface of a body of water 12 to access an offshore wind turbine platform 14 and perform an intervention.

[0040] The intervention may be, for example, installation of the wind turbine equipment, maintenance of the wind turbine equipment, and / or decommissioning of the wind turbine equipment. In particular, the wind turbine equipment may be a blade 40, and the intervention may be installation of the blade 40, maintenance of the blade 40, or replacement of the blade 40.

[0041] As shown in Figures 2 and 11, the intervention assembly 10 comprises a floating intervention vessel 50 and a transport vessel 52 intended to transport the floating vessel 50 and wind turbine equipment for their installation or replacement on the wind turbine 20 of the offshore wind turbine platform 14.

[0042] The transport vessel 52 comprises a hull 54 defining a spacer 56 and a bridge 58. The transport vessel 52 comprises at least one rack 60 for storing wind turbine equipment and a handling assembly 62.

[0043] The support racks 60 are, for example, located on the bridge 58 and / or within the spacers 56. The support racks 60 hold wind turbine equipment, for example, blades 40 or mechanical or electrical equipment of the nacelle 34.

[0044] The hull 54 has sidewalls 64, also called "skin", and a bottom 66, also called "keel", which defines a lower surface 68 with which the floating vessel 50 is intended to engage, and the floating vessel 50 is supported on the sidewalls 64, as will be shown below.

[0045] The handling assembly 62 includes, for example, a crane and / or a lifting arm. The handling assembly 62 includes at least one handling member 63 that can grasp the equipment on the rack 60 and move the equipment over the hull 54 to bring it to the floating vessel 50 when the floating vessel 50 moves away from the hull 54, as shown in Figure 11 .

[0046] Preferably, the handling assembly 62 is of standard capacity in the offshore area. For example, the handling assembly 62 has a lifting capacity of less than 1500 tons. Its achievable height is generally less than 40 meters. Therefore, the vessel 52 has standard dimensions and is therefore readily available.

[0047] 3, the floating vessel 50 comprises a mono-hull float 80 defining an interior volume 81 for receiving ballast, and a ballast controller 82 configured to control the volume of ballast received within the interior ballast receiving volume 81. The interior volume 81 is advantageously compartmentalized to ensure stability in the event of an accidental leak.

[0048] The floating vessel 50 further comprises an intervention assembly 84 mounted on the float 80, the intervention assembly 84 protruding upward from the upper surface of the float 80.

[0049] A monohull float consists of a single floating hull, with or without a keel, in contrast to multihulls such as catamarans, outrigger canoes, trimarans, and quadrimarans. Monohull floats specifically lack any above-water or above-water superstructure connecting several separate shells.

[0050] 4, the mono-hull float 80 comprises a buoyant body 86 and a base plate 88 that is not permanently attached to the offshore wind turbine platform 14 and / or the vessel 52 and that projects relative to the buoyant body 86 along a horizontal fastening axis A-A'. The float 80 advantageously comprises a docking fender 90 and at least one thruster 92.

[0051] The float 80 is preferably of small thickness. For example, each horizontal section of the buoyant body 86, particularly the horizontal segment of the buoyant body 86 having the largest area, has a maximum axial dimension DA along the fastening axis A-A' that is less than 0.75 times the maximum transverse dimension DT of the buoyant body 86, measured perpendicular to the fastening axis A-A'. Preferably, the maximum axial dimension DA is less than 0.50 times its maximum transverse dimension DT, and preferably less than 0.40 times its maximum transverse dimension DT.

[0052] The buoyant body 86 advantageously has a height HF which exceeds its other dimensions, in particular its maximum axial dimension DA and its maximum transverse dimension DT.

[0053] Similarly, the height HF of the buoyant body 86 is preferably greater than 2.0 times the maximum axial dimension DA, and in particular greater than 3.0 times the maximum axial dimension DA. The height of the float 80 is also advantageously greater than 1.2 times the maximum transverse dimension DT.

[0054] Furthermore, the maximum axial dimension DA of the buoyant body 86 is less than 0.75 times, in particular less than 0.50 times, and advantageously less than 0.20 times the maximum axial dimension DP of the floating wind turbine platform 14 (seen in Figure 11), measured parallel to the fastening axis A-A'.

[0055] Also, if the floating wind turbine platform 14 comprises multiple columns 22, the maximum transverse dimension DT is preferably less than the distance DF (seen in FIG. 5) horizontally separating the floating columns 22.

[0056] This allows the floating platform 14 to remain a safe distance from the anchor lines 30 .

[0057] 4, the buoyancy body 86 of the monohull float 80 defines a central through-hole that opens parallel to the fastening axis A-A'. The float 80 therefore has a continuous lower buoyancy region, two upright portions protruding on either side of the lower buoyancy region, and an upper region that defines the upper surface of the float 80.

[0058] The base plate 88 projects from the buoyant body 86, preferably from the lower end of the buoyant body 86, along the fastening axis A-A'.

[0059] The maximum axial dimension DAS of the base plate 88, measured from the buoyant body 86 along the fastening axis A-A', is preferably greater than 0.5 times the maximum axial dimension DA of the buoyant body 86, and in particular greater than 0.8 times the maximum axial dimension DA of the buoyant body 86.

[0060] The base plate 88 defines an upper contact surface 94 with the underside 42 of the offshore wind turbine platform and / or the underside 68 of the hull 54 .

[0061] The area of ​​the contact surface 94 is, for example, at least 50% greater than the area of ​​the horizontal section of the buoyant body 86 having the largest area.

[0062] In the example shown, the maximum axial dimension DAS of the base plate 88 is greater than 50% of the width, measured along the fastening axis A-A', of the lower surface 42 of the pontoon 26A against which the base plate 88 abuts.

[0063] As shown in FIG. 4, the contact surface 94 preferably includes at least one anchor element 95 that allows for fastening to the lower surface 42,68.

[0064] The anchor assembly 95 comprises, for example, at least one anchor pad, preferably a plurality of anchor pads, for the lower surface 42, 68. The or each anchor pad is in particular a suction anchor pad for a volume of fluid arranged between the contact surface 94 and the lower surface 42, 68. Advantageously, the suction anchor pad then comprises a peripheral seal, which is held by the contact surface 94 and intended to press in a sealing manner against the lower surface 42, 68. The volume of fluid present inside the peripheral seal between the contact surface 94 and the lower surface 42, 68 is then intended to be suctioned to activate the anchor, which results in particular from the pressure of the surrounding water exerting a connecting force.

[0065] Alternatively or additionally, the at least one anchor pad is a friction anchor pad and / or a magnetic anchor pad.

[0066] In the embodiment shown, the base plate 88 is fixed relative to and permanently protrudes from the buoyant body 86. In one variation (not shown), the base plate 88 is retractable from a deployed configuration relative to the buoyant body 86 to a stowed position inside the buoyant body 86.

[0067] In this example, given the geometry of the floating foundation 16, the or each docking fender 90 projects from the buoyant body 86 along a fixed axis A-A' above and vertically offset from the base plate 88. Here, the docking fender 90 extends from the upper end of the buoyant body 86. Alternatively, for other floating foundations 16, the or each docking fender 90 is flush with the buoyant body 86.

[0068] The docking fender 90 comprises, for example, an elastomeric block that can contact the upper pontoon 26B.

[0069] The base plate 88 and the docking fender 90 therefore define a gap 96 therebetween that can allow for insertion of the lower pontoon 26A of the platform 14. Advantageously, another elastomeric block is present in this gap to dampen the docking of the lower pontoon 26A.

[0070] In the particular example shown in FIG. 3, the float 80 advantageously has a C-shaped profile in side view.

[0071] Preferably, the float 80 also comprises a mooring assembly (not shown) comprising at least one mooring line configured to be deployed towards the offshore wind turbine platform 14 or on the transport vessel 52 and to ensure a robust attachment to the offshore wind turbine platform 14. This, in particular, reinforces and secures the watertight connection at the top of the platform 14.

[0072] Each thruster 92 is mounted below the buoyant body 86 and / or below the base plate 88. The thrusters 92 comprise, for example, at least one rotating propeller mounted within a tubular casing.

[0073] Each thruster 92 is preferably mounted to rotate about a vertical axis with an angular stroke of, for example, 360°.

[0074] The thrusters 92 are configured to move the vessel 50 horizontally within the body of water 12, in particular between a transport position moored on the vessel 52, as shown in FIG. 2, and an intervention position in which the floating vessel is moored below the offshore wind turbine platform 14, as shown in FIG. 11.

[0075] The ballast receiving volume 81 is defined, for example, within the buoyant body 86 and / or within the mounting base plate 88. The ballast receiving volume 81 is advantageously filled with a fixed volume of ballast, preferably located in the keel, to improve autonomous navigation stability between the transport vessel 52 and the floating platform 14.

[0076] At rest, the ballast receiving volume 81 is at least partially filled with a gas, such as air, where the ballast is formed from water coming from the body of water 12.

[0077] The ballast controller 82 includes at least one pump configured to pump ballast into the ballast receiving volume 81, thereby reducing the buoyancy of the floating vessel 50, or to pump out ballast present in the ballast receiving volume 81, thereby increasing the buoyancy of the floating vessel 50.

[0078] The ballast controller 82 is therefore configured to stabilize the float 80 and control the draft of the float 80 between a lower configuration in which the base plate 88 can pass below the lower surfaces 42, 68, and an upper configuration in which the contact surface 94 of the mooring base plate 88 can abut below the lower surfaces 42, 68 and advantageously apply an upward force to the lower surfaces 42, 68.

[0079] In the example shown in Figures 3 to 6, the intervention assembly 84 comprises a device 100 for lifting the wind turbine equipment held by the float 80 and, optionally, a storage section 102 for the wind turbine equipment present on the float 80.

[0080] In the example shown in this figure, the lifting device 100 comprises a fixed mast 104 and at least one lifting and / or handling unit 106 carried by the mast 104 .

[0081] Here, the mast 104 is formed from a lattice of beams 108. Preferably, the thickness of the beams 108 forming the mast 104 decreases along the mast 104 from the bottom to the top.

[0082] This allows the structure of the mast 104 to be lighter towards its tip, lowering the center of gravity of the intervention vessel 50. Preferably, the center of gravity of the mast 104 is lowered to at least half the height of the mast 104, for example four-tenths of the height of the mast 104.

[0083] The lifting and / or handling unit 106 includes, for example, a forklift 110 movably mounted along the mast 104 and / or an intervention crane 112 movably mounted along the mast 104, preferably within the forklift 110.

[0084] The forklift 110 is movable between a lower position located on the opposite side of the storage section 102 and an upper position for intervention relative to the wind turbine 20, as can be seen, for example, in FIG.

[0085] An intervention crane 112 is operable from the mast 104 for intervention at, for example, the nacelle 34 .

[0086] The forklift 110 ensures vertical movement and is preferably equipped with a blade gripper 111.

[0087] Advantageously, the forklift 110 and / or the intervention crane 112 are equipped with a three-dimensional motion compensation table 113 to compensate for any misalignment between the forklift 110 and the wind turbine 20, in particular in translation in the horizontal plane, preferably along six axes. Compensation in the vertical direction can advantageously be performed by the forklift 110.

[0088] A method of intervention on an offshore wind turbine platform 14 using the intervention assembly 10 will now be described.

[0089] The method is described, for example, for replacing a blade 40 of the wind turbine 20. Alternatively, the intervention relates to other equipment of the wind turbine 20, for example equipment of the nacelle 34 and / or the mast 32.

[0090] First, the equipment intended for the wind turbine 20 is loaded onto the ship 52 and placed, for example, in spacers 56 or in racks 60 present on the bridge 58 .

[0091] The intervention vessel 50 is then attached to the hull 54 of the vessel 52. To do this, the ballast controller 82 is actuated to introduce ballast into the ballast receiving volume 81 and move the contact surface 94 to an elevation below the elevation of the underside 68 of the vessel 52.

[0092] The thrusters 92 are then actuated to move the base plate 88, causing it to move below the lower surface 68 of the hull 54. The ballast controller 82 is then controlled to extract ballast from the ballast receiving volume 81.

[0093] Under the effect of de-ballasting, contact surface 94 rises and strikes lower surface 68, exerting an upward force on lower surface 68. Furthermore, anchor assemblies 95 of contact surface 94 on lower surface 68 are actuated, for example, by attraction between these surfaces at anchor pads 95 or by actuating pads by friction or magnetic pads.

[0094] The docking fenders 90 abut laterally against the sidewalls 64 of the hull 54. The mooring assemblies are then put into position to complete the holding of the floating vessel 50 in place on the ship's hull 54.

[0095] The floating vessel 50 has a float 80 with the maximum axial and transverse dimensions specified above, and the float 80 has a small footprint in the body of water 12 relative to the vessel 52, so that it can be easily secured to the hull 54 of the vessel 52 and enable its easy transport to the vicinity of the offshore wind turbine platform 14, even over long distances.

[0096] As shown in FIG. 2, when the vessel 52 arrives close to the offshore wind turbine platform 14, for example, at a distance of less than 500 m, particularly 40 m to 300 m, from the offshore wind turbine platform 14, the mooring assembly is disconnected and the anchor assembly 95 is disabled.

[0097] The ballast controller 82 is again controlled to introduce ballast into the ballast receiving volume 81 .

[0098] Under the influence of the introduction of ballast, the float 80 separates from the hull 54 of the vessel 52 .

[0099] The thrusters 92 are then actuated to move the floating vessel 50 towards the offshore wind turbine platform 14. The thrusters 92 are also actuated to orient the base plate 88 with its mounting axis A-A' perpendicular to the axis of the lower pontoon 26A, as shown in FIG.

[0100] If necessary, the ballast is adjusted using the ballast controller 82 so that the contact surface 94 of the base plate 88 is located at an elevation lower than the elevation of the underside 42 of the floating wind turbine platform 14, and in particular lower than the elevation of the underside of the pontoon 26A.

[0101] Referring to Figure 9, the base plate 88 then passes under the lower pontoon 26A until the docking fender 90 contacts the upper pontoon 26B.

[0102] The lower pontoon 26A is received in a gap 96 between a contact surface 94 of the base plate 88 and the docking fender 90.

[0103] The float 80 is positioned between the struts 22 on opposite sides of the pontoons 26A, 26B.

[0104] The ballast controller 82 is then restarted to extract ballast from the ballast receiving volume 81. This raises the contact surface 94 that rests beneath the lower surface 42, as shown in Figure 10, and similarly exerts an upward force on this surface 42. This force is generally at least 80% of, and preferably more than, the weight of the wind turbine equipment that is intended to be raised, and in particular exceeds the weight of the wind turbine blades 40.

[0105] The anchor assembly 95 is then actuated as described above. Once this is done, the mooring assembly is advantageously connected to the offshore wind turbine platform 14 at the upper pontoon 26B.

[0106] The floating vessel 10 is therefore fixed to a floating foundation 16 of an offshore wind turbine platform 14 .

[0107] Given the dimensions of the float 80 as explained above, the float 80 is secured to the movement of the floating foundation 16 and moves with the floating foundation 16 without heaving or lifting.

[0108] The lifting device 100 then projects against the float 80 directly opposite the mast 32 of the wind turbine 20 .

[0109] When blade 40 is replaced, forklift 110 is placed in the upper position seen in Figure 5 to grasp blade 40. Blade 40 is optionally angled to orient itself with the axis of blade 40 and moved laterally to approach the blade's 40 bolting plate on the rotor hub.

[0110] Alternatively, the carriage 110 is positioned at the center of gravity of the blade 40. The nacelle 34 is oriented in azimuth to present the blade 40 in the same alignment as the grippers of the forklift 110.

[0111] Optionally, if a three-dimensional compensation device is used, it absorbs relative movements due in particular to residual flexibility of the connection between the floating foundation 16 and the float 80, and flexibility between the mast 32 of the wind turbine 20 and the mast 104 of the lifting device 100.

[0112] The blade 40 is then separated from the central hub 38 so as to be positioned on the forklift 110, which is then lowered back to its lower position.

[0113] Referring to FIG. 11 , the vessel 52 then approaches the floating vessel 50 and the handling assembly 62 of the vessel 52 is controlled to grasp the blade 40 that has been removed from the wind turbine 20 and place it in a spacer 56 or in a rack 60 located on the bridge 58.

[0114] The replacement blade 40 is then grasped by the handling assembly 62 and then loaded onto the forklift 110 in its lower position. The forklift 110 then rises to the level of the central hub 38 of the wind turbine 20 to allow the replacement blade 40 to be replaced.

[0115] Alternatively, as shown in FIG. 6, an intervention crane 112 may be actuated to move vertically (e.g., on a forklift 110 instead of the gripper 111) and positioned on the opposite side of the nacelle 34 to intervene on another piece of equipment in the nacelle.

[0116] In the intervention described here, a float 80 is attached to the lower pontoon 26A between two floating struts 22, and its maximum transverse dimension DT is less than the distance DF separating the floating struts 22 horizontally (see Figure 5). As indicated above, this limits the risk of interference with the anchor lines 30.

[0117] Thus, the lifting device 100 can be placed in a suitable position relative to the wind turbine 20 while maintaining a very effective anchoring of the float 80 on the floating foundation 16 of the wind turbine 20. The suitable position is as close as possible to the mast 32 when using an intervention crane 112. For the replacement of a blade 40, the suitable position is a distance of the mast 32 adapted so that the mast 104 is aligned with the position of the center of gravity of the blade 40.

[0118] This limits undesirable interference between the lifting and / or handling unit 106 and the wind turbine 20 .

[0119] The floating vessel 50 according to the invention therefore makes it possible to carry out complex maintenance operations, in particular replacement of blades 40 or heavy nacelle equipment 34 of wind turbines 20 on offshore wind turbine platforms 14 which hold high-power wind turbines mounted very high, for example 100 m above the surface of the body of water 12.

[0120] These interventions 20 can be carried out without returning to a coastal port, which reduces production time and downtime and therefore costs.

[0121] Considering the small relative offset between the offshore wind turbine platform 14 and the floating vessel 50, the lifting device 100 is fixed directly to the offshore wind turbine platform 14 using the floating vessel 50 as if it had been installed directly on the offshore wind turbine platform 14.

[0122] Therefore, there is no need to install / remove a large intervention crane on the offshore wind turbine platform 14 present on the floating vessel 50. Therefore, the use of a specific vessel and / or large capacity crane is not useful since the lifting device 100 is already present on the floating vessel 50.

[0123] The floating vessel 50 according to the present invention therefore makes it possible to easily bring a high-capacity lifting device 100 to the offshore wind turbine platform 14 while maintaining the advantage of continuing to move integrally with the offshore wind turbine platform 14, in particular the wind turbine 20.

[0124] The floating vessel 50 may move autonomously towards the offshore wind turbine platform 14 thanks to its thrusters 92 from a vessel 52 transporting the floating vessel 50 in the vicinity of the platform 14 .

[0125] Furthermore, when secured to the offshore wind turbine platform 14, the floating vessel 50 has a float 80 of reduced dimensions and therefore low inertia, but benefits from the inherent stability of the floating foundation 16 of the offshore wind turbine platform 14. The latter is sized to withstand severe storms, which ensures the stability of the floating wind turbine platform 14 even when the floating vessel 50 is moored to the floating wind turbine platform 14.

[0126] Therefore, transportation of the floating vessel 50 can be carried out with relatively fast transportation times using currently used simple ships 52. Furthermore, the dimensions of the float 80 avoid the need to modify the design of the mast 32 of the wind turbine 20, as the floating vessel 50 can be moored to the floating foundation 16 in a position adapted for the intervention.

[0127] Mooring of the float 80 to the floating foundation 16 is also very simple, particularly when the floating foundation 16 is equipped with pontoons 26A, 26B, the C-shape of the float 80 in side view allows the docking fender 90 to accommodate the lower pontoon 26A when it hits the upper pontoon 26B.

[0128] 7, the lifting device 100 does not include a fixed mast 104. The lifting device 100 includes a telescoping mast 104 that can be moved between a stowed position in which the free end of the mast 104 is adjacent the top end of the float 80 and a deployed position in which the free end of the mast 104 projects upwardly relative to the top end of the float 80.

[0129] The telescopic mast 104 is provided at its free end with one or each lifting and / or handling unit 106 , for example a gripper 111 or an intervention crane 112 , and advantageously with a motion compensation device 113 .

[0130] As shown in FIG. 7, for assembly or blade change 40, the telescoping mast 104 is deployed vertically so that the gripper 111 in the deployed position receives the blade 40.

[0131] The mast 104 is tilted away from the mast 32 of the wind turbine 20, for example at an angle of 1° to 15° from the vertical. This moves the gripper 111 away from the mast 32, so that the gripper is naturally positioned near the center of gravity of the blade 40.

[0132] Preferably, the vertical position is not used during lifting of the mass, as the tilt allows to compensate for the mechanical play of the telescoping mast 104 and stabilizes the position of the top.

[0133] Alternatively, for example, on the nacelle 34, the telescoping mast 104 may be tilted at an angle of, for example, 1° to 15° relative to the vertical to allow the intervention crane 112 to approach the nacelle 34.

[0134] This allows access to the top of the telescoping mast 104 of the nacelle 34 without having to move the floating vessel 50 close to the mast 32 .

[0135] In other words, the initial adjustment of the angle of the telescoping mast 104, followed by the deployment of the telescoping length, alternatively allows the top of the mast 104 to be moved away from the mast 32 of the wind turbine 20 in order to be at the center of gravity of the blades 40, or conversely, to be moved closer to the mast 32 of the wind turbine 32 in order to be closest to the nacelle 34 in order to perform lifting of the components of the nacelle 34.

[0136] The use of the telescoping mast 104 lowers the center of gravity of the floating vessel 50 when the telescoping mast 104 is in its stowed position, which is particularly useful during transportation of the floating vessel 50 on the ship 52 and during its autonomous movement through the body of water 12 from the hull 54 of the ship 52 to the offshore wind turbine platform 14.

Claims

1. an offshore intervention floating vessel (50), itself intended to be temporarily moored on an offshore wind turbine platform (14) to carry out installation and / or maintenance interventions on a wind turbine (20), said floating vessel (50) comprising: a float (80) intended to be at least partially submerged in a body of water (12); a wind turbine (20) intervention assembly (84) held by said float (80), said wind turbine (20) intervention assembly (84) comprising at least one lifting device (100) configured to lift wind turbine equipment, 1. The offshore intervention floating vessel (50) according to claim 1, wherein the float (80) comprises a buoyant body (86) and a fastening base plate (88) protruding relative to the buoyant body (86) along a fastening axis (A-A') on the underside (42) of the offshore wind turbine platform (14), the buoyant body (86) defining a ballast receiving volume (81), the floating vessel (50) comprising a ballast controller (82) configured to control the amount of ballast received in the ballast receiving volume (81) and to move an upper contact surface (94) of the base plate (88) upward to place the upper contact surface (94) in contact with the underside (42) of the offshore wind turbine platform (14), and the float (80) is mono-hulled.

2. 2. The floating vessel (50) of claim 1, wherein the upper contact surface (94) of the base plate (88) comprises an anchor assembly (95) configured to eliminate relative movement between the upper contact surface (94) of the base plate (88) and the underside (42) of the offshore wind turbine platform (14), the anchor assembly (95) specifically comprising at least one suction anchor pad, and / or magnetic anchor pad, and / or friction anchor pad.

3. 3. The floating vessel (50) according to claim 1 or 2, wherein the float (80) has at least one docking fender (90) positioned on the base plate (88), and the docking fender (90) optionally protrudes relative to the buoyant body (86) along the fastening axis (A-A').

4. 4. The floating vessel (50) according to claim 3, wherein the float (80) has an L-shaped cross section when viewed in a vertical plane including the fastening axis (A-A'), or the float (80) has a C-shaped cross section when viewed in a vertical plane including the fastening axis (A-A'), and the docking fender (90) and the base plate (88) define an intermediate space (96) therebetween for receiving a structure of the offshore wind turbine platform (14).

5. 5. The floating vessel (50) according to any one of claims 1 to 4, wherein the lifting device (100) comprises at least one lifting and / or handling unit (104) selected from an intervention crane (112), a forklift (110), a wind turbine blade gripper (111), and / or a motion compensation device (113).

6. 6. The floating vessel (50) according to any one of claims 1 to 5, wherein the lifting device (100) comprises a fixed mast (104) formed from a lattice of beams (108) assembled together, the mast (104) projecting vertically above the buoyant body (86).

7. 7. The floating vessel (50) according to claim 6, wherein the mast (104) has a height greater than the height of the float (80), and the mast (104) advantageously has a center of gravity located at a height less than half the height of the mast (104).

8. 8. The floating vessel (50) of claim 6 or 7, wherein the transverse dimensions and / or thicknesses of the beams (108) of the lattice decrease from bottom to top along the mast (104).

9. The floating vessel (50) according to any one of claims 1 to 5, wherein the lifting device (100) comprises a telescopic mast (104), the telescopic mast (104) being deployable between a retracted configuration in which a free end thereof is disposed in the vicinity of the float (80) and an upward deployed configuration.

10. 10. The floating vessel (50) of claim 9, wherein the axis of the telescoping mast (104) is tiltable between a vertical configuration, a first configuration tilted in a first direction at a non-zero angle relative to the vertical, and a second configuration tilted in a second direction opposite the first direction at a non-zero angle relative to the vertical.

11. The floating vessel (50) according to any one of claims 1 to 10, wherein the float (80) comprises at least one propeller thruster (92) arranged below the buoyant body (86) and / or below the base plate (88).

12. 12. The floating vessel (50) according to any one of claims 1 to 11, wherein each horizontal section of the buoyant body (86) has a maximum axial dimension measured along the fastening axis (A-A') that is less than 0.75 times the maximum transverse dimension of the horizontal section, preferably less than 0.50 times the maximum transverse dimension of a horizontal surface, the maximum transverse dimension being measured perpendicular to the fastening axis (A-A').

13. An offshore intervention assembly (10) comprising a vessel (52) having a hull (54) defining at least one storage space for wind turbine equipment, and a floating vessel (50) according to any one of claims 1 to 12, The floating vessel (50) is movable relative to the vessel (52) between a transport position of the floating vessel (50) to an offshore wind turbine platform (14), in which the base plate (88) of the float (80) is fixedly held against the underside (68) of the hull (54), and an intervention position in which the floating vessel is disposed away from the vessel (52) for intervention on the offshore wind turbine platform (14).

14. 14. An offshore intervention assembly (10) according to claim 13, wherein the vessel (52) comprises at least one rack (60) for storing wind turbine equipment and optionally at least one handling assembly (62) having handling members (63) movable between a position for gripping wind turbine equipment in the storage rack (60) and an intervention position outside the hull (54).

15. 15. An offshore installation comprising an offshore intervention assembly (10) according to claim 13 or 14 and an offshore wind turbine platform (14), wherein the floating vessel (50) is movable through the body of water (12) from a transport position to an intervention position in which the base plate (88) abuts below an underside (42) of the offshore wind turbine platform (14), and wherein a maximum axial dimension of each horizontal section of the buoyant body (86), measured along the fastening axis (A-A'), is less than 90% of a maximum dimension of the offshore wind turbine platform (14), measured parallel to the same fastening axis (A-A').

16. 16. The offshore facility of claim 15, wherein the offshore wind turbine platform (14) comprises a floating foundation (16) having at least three floating struts (22) and lower pontoons (26A) connecting the at least three floating struts (22) two by two, the lower pontoons (26A) defining at least a portion of the lower surface (42) of the floating wind turbine platform (14), the upper contact surface (94) of the base plate (88) being engaged below the lower surface of the lower pontoons (26A) between two adjacent floating struts (22), and the maximum transverse dimension of each horizontal section of the buoyant body (86) being less than a distance horizontally separating the two adjacent floating struts (22) or comprising a floating foundation formed from a barge with or without a central hole.

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