INSTALLATION OF A WIND TURBINE ON A FLOATING FOUNDATION

Abstract

A vessel for use in installation of a wind turbine on a floating foundation is provided, where both the vessel and the floating foundation are in floating condition and subject to sea-state induced motions. The vessel includes a floating hull; a crane including a hoisting system to suspend the wind turbine; a mast alignment system provided to engage on the wind turbine mast of the suspended wind turbine, and bring and maintain the wind turbine mast in alignment with the mounting axis of the floating foundation in order to compensate for sea-state induced motions; and a restraining system arranged to restrain the floating foundation only in a horizontal plane relative to the floating hull of the vessel and to allow for both sea-state induced heave motion and sea-state induced tilt motions in one or more vertical planes of the mast mounting structure relative to the hull of the vessel.

Claims

1. A vessel for use in installation of a wind turbine on a floating foundation, wherein both the vessel and the floating foundation are in floating condition and subject to sea-state induced motions, wherein the wind turbine to be installed comprises at least a part of a wind turbine mast having a lower end portion, and comprises a rotor assembly with rotor blades, the rotor assembly being mounted on the wind turbine mast, wherein the floating foundation comprises a mast mounting structure configured to mount the wind turbine mast thereon and having an upwardly directed mounting axis, wherein the vessel comprises: a floating hull; a crane arranged on the hull, wherein the crane is provided with a hoisting system adapted to suspend the wind turbine from the crane, the hoisting system is adapted to raise and lower the wind turbine in a controllable manner, and wherein the crane comprises a heave compensation device adapted to compensate for sea-state induced heave motion of the wind turbine mast relative to the mast mounting structure of the floating foundation; a mast alignment system configured toin useengage on the wind turbine mast of a suspended wind turbine, and configured to bring and maintain the wind turbine mast in alignment with the mounting axis of the floating foundation in order to compensate for sea-state induced motions, at least including tilt motions in one or more vertical planes, of the wind turbine mast relative to the mounting axis of the floating foundation; and a restraining system configured to restrain the floating foundation only in a horizontal plane relative to the floating hull of the vessel and to allow for both said sea-state induced heave motion and said sea-state induced tilt motions in one or more vertical planes of the mast mounting structure relative to the hull of the vessel, wherein the vessel is provided with one or more sensors configured for monitoring both said sea-state induced heave motion and said sea-state induced tilt motions in one or more vertical planes of the mast mounting structure relative to the hull of the vessel, and wherein said one or more sensors are linked to a controller which is configured to cause automated operation of the heave compensation device and of the mast alignment system.

2. The vessel according to claim 1, wherein the restraining system comprises a vessel mounted gripper device, the gripper device having an engagement member configured to engage on the mast mounting structure of the floating foundation, and having an active controlled motion mechanism configured to provide a controlled motion of the engagement member relative to the hull of the vessel and thereby a controlled restraining of the engaged floating foundation relative to the hull of the vessel in the horizontal plane, whilst allowing for both said sea-state induced heave motion and for sea-state induced tilt motions in one or more vertical planes of the mast mounting structure relative to the hull of the vessel.

3. The vessel according to claim 1, wherein the mast alignment system comprises at least one mast engaging device having a mast engagement member as well as an actively controlled motion mechanism that is configured and operated to provide a controlled motion of the mast engagement member in the horizontal plane so as to bring and maintain the wind turbine mast of the suspended wind turbine in alignment with the mounting axis of the floating foundation.

4. The vessel according to claim 1, wherein the mast alignment system comprises an upper mast engaging device as well as a lower mast engaging device, each of the upper mast engaging device and lower mast engaging device having a mast engagement member as well as an actively controlled motion mechanism that is configured to provide a controlled motion of the mast engagement member in a horizontal plane, and wherein the active controlled motion mechanisms are configured to bring and maintain the wind turbine mast of the suspended wind turbine in alignment with the mounting axis of the floating foundation.

5. The vessel according to claim 3, wherein each actively controlled motion mechanism comprises a first set of one or more horizontal tracks extending in a first horizontal direction, said first set of one or more horizontal tracks supporting at least one first carrier, and said at least one first carrier supporting a second set of one or more horizontal tracks extending in a second horizontal direction different from the first direction, the second set of one or more horizontal tracks supporting one or more further second carriers supporting said mast engagement device.

6. The vessel according to claim 4, wherein each actively controlled motion mechanism comprises a first set of one or more horizontal tracks extending in a first horizontal direction, said first set of one or more horizontal tracks supporting at least one first carrier, and said at least one first carrier supporting a second set of one or more horizontal tracks extending in a second horizontal direction different from the first direction, the second set of one or more horizontal tracks supporting one or more further second carriers supporting said mast engagement device.

7. The vessel according to claim 3, wherein the mast engaging device comprises a trolley that is vertically guided along one or more vertical guide rails, the trolley supporting the mast engaging member with interposition of the actively controlled motion mechanism between the trolley and the mast engaging member to provide a controlled motion of the mast engagement member in the horizontal plane.

8. The vessel according to claim 3, wherein the crane is provided with first and second upper sheave blocks that are horizontally spaced apart, wherein the mast engaging member is provided with first and second lower sheave blocks that are horizontally spaced apart, and wherein a first multiple fall cable arrangement extends between the first upper and lower sheave blocks and a second multiple fall cable arrangement extends between the second upper and lower sheave blocks.

9. The vessel according to claim 1, wherein the crane has a vertical crane structure erected on the hull of the vessel, the vertical crane structure having a lower section fixed on the hull and a slewable top section, and wherein the hoisting device comprises one or more winch drive cables depending from one or more sheave blocks arranged on the slewable top section.

10. The vessel according to claim 9, wherein the mast alignment system is mounted on the vertical crane structure of the crane, wherein the alignment system comprises one or more mast engaging devices mounted on the vertical crane structure, and wherein the slewable top section of the vertical crane structure is provided with an upper mast engaging device and the fixed lower section of the vertical crane structure is provided with a lower mast engaging device.

11. The vessel according to claim 1, wherein the vessel is a semi-submersible vessel, wherein the hull has a pair of substantially parallel, laterally spaced buoyant pontoons, a row of multiple columns supported by and extending upwardly from each of the pair of substantially parallel, laterally spaced buoyant pontoon, and a deck structure supported by upper ends of said row of multiple columns, and wherein the crane is mounted on the deck structure of the hull.

12. The vessel according to claim 4, wherein the upper and lower mast engaging devices are at least 20 meters apart in vertical direction.

13. The vessel according to claim 3, wherein the actively controlled motion mechanism comprises rack and pinion drives.

14. The vessel according to claim 1, wherein the vessel comprises one or more quick fill water ballast tanks configured for holding ballast water below a water line, the quick fill ballast tanks comprising ballast water fill doors located below the water line for dumping sea water into the quick fill ballast tanks in order to compensate for weight transfer from the vessel to the floating foundation caused by landing of the wind turbine on the floating foundation.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0116] In the drawings:

[0117] FIG. 1 illustrates the installation of a wind turbine on a floating foundation according to the invention,

[0118] FIG. 2 illustrates the installation in a view from above,

[0119] FIG. 3 illustrates the installation in a front view with the wind turbine suspended from the crane of the vessel in a plumb line orientation,

[0120] FIG. 4 illustrates the installation of FIG. 3 in a side view,

[0121] FIG. 5 is an enlargement of a portion of FIG. 4 illustrating the upper mast engaging device and the suspension of the wind turbine,

[0122] FIG. 6 shows the portion of FIG. 5 in a front view,

[0123] FIG. 7 is an enlargement of a portion of FIG. 4 illustrating the lower mast engaging device and the restraining system that acts on a stabilizing column of the floating foundation,

[0124] FIG. 8 illustrates the operation of the alignment system of the invention in a front view,

[0125] FIG. 9 illustrates the operation of the alignment system of the invention in a side view,

[0126] FIG. 10 is an enlargement of a portion of FIG. 8 illustrating the upper mast engaging device,

[0127] FIG. 11 is an enlargement of a portion of FIG. 9 illustrating the lower mast engaging device and the restraining system that acts on a stabilizing column of the floating foundation,

[0128] FIG. 12 shows the portion of FIG. 11 in front view,

[0129] FIGS. 13a,b,c illustrate the upper mast engaging device of the alignment system,

[0130] FIGS. 14a-e illustrate the crane and the upper mast engaging device of the alignment system,

[0131] FIG. 15 illustrates the installation of a pre-assembly of an upper mast part, nacelle, and rotor blades on a floating foundation already provided with a lower mast part,

[0132] FIGS. 16a, b illustrate the operation of the alignment system in the method of FIG. 15.

DETAILED DESCRIPTION OF EMBODIMENTS

[0133] In the drawings the figures illustrate the installation of a wind turbine 1 on a floating foundation 100 that is in floating condition and subject to sea-state induced motions, e.g. at the site of an offshore windfarm.

[0134] The wind turbine 1 to be installed comprises at least a part of a wind turbine mast 2 having a lower end portion, and comprises a rotor assembly, here embodied with a nacelle 3 having a hub and with rotor blades 4, which rotor assembly has been mounted on the wind turbine mast 2.

[0135] The floating foundation 50 is, by way of example, shown as being of the design discussed in WO2009/131826. One of the stabilizing columns 51 thereof at a corner of the foundation, is provided with a mast mounting structure 52 that is configured to mount the mast 2 of the wind turbine 1 thereon. This structure 52 has an upwardly directed mounting axis 53 which is the main axis along which the landing of the mast 2 onto the foundation 50 takes place.

[0136] Use is made of a vessel 200, here a semi-submersible vessel, which comprises: [0137] a floating hull 201, [0138] a crane 250 that is arranged on the hull.

[0139] The crane 250 is provided with a hoisting system 275 that is adapted to support the weight of the wind turbine 1 and suspend the wind turbine 1 from the crane 250, which hoisting system is adapted to raise and lower the wind turbine in a controllable manner.

[0140] The crane 250 and/or the hoisting system 275 thereof comprises a heave compensation device 300 that is adapted to compensate for sea-state induced heave motion of the wind turbine mast 2 relative to the mast mounting structure 52 of the floating foundation 50.

[0141] For example, the heave compensation device comprises one or more motion sensors for monitoring the actual heave motion(s).

[0142] Use is made of a mast alignment system 400 that is configured to engage on the suspended wind turbine, here on the mast 2 of the suspended wind turbine 1, and to bring and maintain the mast 2 of the wind turbine in alignment with the mounting axis 53 of the floating foundation in order to compensate for sea-state induced motions, at least including tilt motions in one or more vertical planes, of the wind turbine mast 2 relative to the mounting axis of the floating foundation 50.

[0143] Generally, the installation method compriseswith the hull of the vessel 200 in floating condition and the floating foundation 50 in floating conditionthe steps of: [0144] suspending the wind turbine 1 from the crane 250 by means of the hoisting system 275, [0145] positioning the lower end of the mast 2 of the suspended wind turbine 1 above the mast mounting structure 52 of the floating foundation 50, [0146] operating the heave compensation device 300 so as to compensate for sea-state induced heave motion of the wind turbine mast 2 relative to the mast mounting structure 52 of the floating foundation 50, [0147] operating the mast alignment system 400 so as to bring and maintain the mast 2 of the wind turbine 1 in alignment with the mounting axis 53 of the floating foundation 50 in order to compensate for sea-state induced tilt motions of the wind turbine mast 2 relative to the mounting axis 53 of the floating foundation, [0148] whilst the heave compensation device 300 and the mast alignment system 400 are in operation, operating the hoisting system 275 and thereby lowering the suspended wind turbine 1 with the lower end portion of the mast 2 onto the mast mounting structure 52 of the floating foundation 50, [0149] fastening the mast 2 with the lower end portion thereof to the mast mounting structure 52 of the floating foundation.

[0150] It is preferred, that at least the mast alignment system 400 remains in operation during a part or all of the fastening step, e.g. the system 400 serving or assisting in stabilizing of the wind turbine relative to the foundation during this step.

[0151] It is preferred, that at least the heave compensation device 300 remains in operation during a part or all of the fastening step, e.g. the device 300 serving or assisting in supporting at least part of the weight of the wind turbine relative to the foundation also during this step, e.g. serving or assisting in the gradual transfer of the weight of the wind turbine onto the foundation, e.g. whilst ballasting the vessel to compensate for this transfer.

[0152] As can be seen, the floating foundation is restrained by a restraining system 350 at least, or solely, in the horizontal plane relative to the vessel 200 during the wind turbine installation process.

[0153] As an example, the restraining system for the foundation involves the use of a vessel mounted gripper device 351, which gripper device has an engagement member 352 that engages on the floating foundation, here on the mast mounting structure 52 of the floating foundation. The gripper device 351 has an actively controlled motion mechanism 353, e.g. similar of design to those of the mast engaging devices 420, 440, that is configured and operated to provide a controlled motion of the engagement member 352 relative to the hull of the vessel 200 and thereby effects a controlled restraining of the engaged floating foundation 50 relative to the hull of the vessel.

[0154] As can be seen in FIGS. 1 and 2, it is envisaged in this example, that the assembly of the wind turbine 1 to be installed is done onboard the vessel 200. The vessel sails to the windfarm where the floating foundations are already present, e.g. anchored, with multiple wind turbines 1 in yet to be assembled state stored on the vessel.

[0155] For example, the main components of at least 5 wind turbines are stored separately on board, here upper mast parts 2a and lower mast parts 2b, nacelles 3, and rotor blades 4.

[0156] As preferred, multiple floating foundations 50 are already anchored at their final location in an offshore windfarm, all without wind turbine 1, and the vessel 200 sails to the windfarm and successively the wind turbines are assembled on board and then installed on the floating foundations 50.

[0157] As preferred, the landing of the mast 2 onto the mast mounting structure 52 causes, or is followed by, a preliminary fastening between the mast and the foundation being established, so that the wind turbine is stable relative to the foundation, e.g. allowing for ceasing the operation of the alignment system 400, e.g. allowing for disengaging the alignment system.

[0158] The alignment system 400 shown by way of example, comprises an upper mast engaging device 420 as well as a lower mast engaging device 440, each having a mast engagement member 421, 441 as well as an actively controlled motion mechanism 422, 442 that is configured and operated to provide a controlled motion of the mast engagement member in a horizontal plane.

[0159] The mast engaging devices 420, 440 act on the mast 2 at different heights, e.g. the lower one below the centre of gravity G of the wind turbine 1 to be installed and the upper one above said centre of gravity G.

[0160] The actively controlled motion mechanisms 422, 442 are configured and operated to bring and maintain the mast 2 of the suspended wind turbine 1 in alignment with the mounting axis 53 of the floating foundation 50 during the relevant moments of the installation process.

[0161] It is illustrated, e.g. in FIGS. 13a-c, that each actively controlled horizontal motion mechanism 422, 442 comprises a first set of one or more horizontal tracks 422a extending in a first horizontal direction, said first set supporting at least one first carrier 422b1, 422b2, and said one or more first carriers supporting a second set of one or more horizontal tracks 422c1, 422c2 extending in a second horizontal direction different from the first direction, e.g. the first and second direction being orthogonal directions, the second set of one or more horizontal tracks supporting one or more further second carriers 422d1, 422d2 supporting the mast engagement device 421, 441.

[0162] It is illustrated that each mast engaging device 420, 440 of the alignment system 400 comprises a trolley 425, 445 that is vertically guided along one or more vertical guide rails 426, 446 here mounted to the crane structure of the crane 250. Each trolley supports the mast engaging member with interposition of the actively controlled motion mechanism between the trolley and the mast engaging member to provide a controlled motion of the mast engagement member in a horizontal plane, e.g. in two orthogonal horizontal directions.

[0163] The mast engaging member 421 is suspended from the crane 250 by means of the hoisting device upper and the wind turbine 1 is suspended from this mast engaging member 421.

[0164] The crane has a vertical crane structure 260 that is erected on the hull of the vessel. Here the vertical crane structure has a lower section 261 of the crane structure fixed on the hull and a slewable top section 262 on slew bearing 262a.

[0165] The hoisting device comprises one or more winch drive cables 276, 277 depending from sheave blocks 278, 279 arranged on the slewable top section, here on a forked pivotal jib 265 of the slewable top section.

[0166] The slewing of the top section 262 may be used to pick-up an assembled wind turbine 1 from the deck of the vessel 200 by means of the hoisting device and to bring the wind turbine with its mast above the mast mounting structure of the floating foundation 50.

[0167] It is shown that the slewable top section 262 of the vertical crane structure is provided with the upper mast engaging device 420 and that the fixed lower section 261 of the vertical crane structure is provided with a lower mast engaging device 440.

[0168] With reference to FIGS. 15, 16a, 16b, now the installation of a wind turbine on a floating foundation 50 will be discussed. As shown, the lower mast part 2b has already be mounted on the foundation 50, e.g. during production of the foundation 50 or at sea, e.g. using the vessel 200 used for completion of the wind turbine or another offshore vessel, e.g. equipped with a general-purpose heavy lift crane.

[0169] The FIGS. 15, 16a, 16b illustrate that a pre-assembled assembly of the upper mast part 2a, nacelle 3, and rotor blades 4 is handled as a subassembly or a unit by the crane 250 of the vessel 200 for placing this unit on top of the lower mast 2b. It is shown, as an option, that the crane structure of the crane 250 is configured to handle two of such assemblies at the same time. Here the left-hand assembly in FIG. 15 is supported in an operation position above a lower mast part 2b already mounted on the floating foundation 50 and the right-hand one is supported in a transport position, at a lower level than the operative position for reasons of vessel stability.

[0170] For example, using the vessel 200 a method for installation of the wind turbine can be performed which comprises, with the hull of the vessel 200 as well as the foundation 50 in floating condition, the steps of: [0171] transporting the wind turbine assembly (or assemblies) in the lower transport position (right-hand in FIG. 15) from a pre-assembly location to the installation location where the foundation 50 is present, e.g. at the wind farm, [0172] moving the vessel 200 into position relative to the foundation 50 and keeping the vessel in such relative position, preferably involving the use of a restraining device 350, 351 as described herein. [0173] lifting the wind turbine assembly from the lower transport position into the raised operation position (left-hand FIG. 15) and positioning the wind turbine assembly above the lower mast part 2b already mounted on the foundation 50, e.g. involving moving the vessel 200 relative to the (moored) foundation 50.

[0174] The method further comprisesas follows from FIGS. 16a, bthat due to operation of the two active horizontal motion devices 420, 440 engaging on the subassembly that is to be installed, the upper mast part 2a is brought and kept in alignment with the lower mast part 2a (at some distance above the top end of the lower mast part) so as to compensate for sea-state induced motions, e.g. including tilt motions of the foundation and/or vessel due to sea state as illustrated. It is submitted that the subassembly is preferably engaged by the two devices 420, 440 as balancing only this assembly is effectively more difficult than balancing a wind turbine comprising a full-length mast. For example, there is a vertical spacing between the devices 420, 440 engaging on the subassembly of at least 20 meters.

[0175] The crane 250, preferably, is also equipped with a heave compensation device associated so as to compensate for sea-state induced vertical motion of the lower end of the upper mast part 2a relative to the lower mast part 2b that is mounted on the floating foundation.

[0176] FIG. 16b illustrates that the two active horizontal motion devices 420, 440 are operated to maintain alignment of the mast parts, ahead and also during (the first phase at least) the lowering of the assembly onto the top of the lower mast part 2b.

[0177] In a preferred embodiment, the vessel 200 is stabilized by suitable operation of one or more damping devices, e.g. roll and/or pitch motion damping devices. For example, the vessel 200 is equipped with a roll damping device that comprises one or more mobile solid ballast bodies guided on a track on the hull, and an associated displacement drive and displacement drive control, said drive control being adapted to cause motion of said one or more solid ballast bodies so as to compensate for sea-state induced vessel roll motion. For example, the vessel further comprises at least one pitch damping device comprising one or more mobile solid ballast bodies guided on a track and an associated displacement drive and displacement drive control, said drive control being adapted to cause motion of said one or more solid ballast bodies so as to compensate for sea-state induced vessel pitch motion.