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EP-4739615-A1 - INSTALLATION OF A WIND TURBINE ON A FLOATING FOUNDATION

EP4739615A1EP 4739615 A1EP4739615 A1EP 4739615A1EP-4739615-A1

Abstract

Installation of a wind turbine on a floating, wherein use is made of a vessel with a crane and a motion suppressor device mounted to the hull of the vessel. Engagement with the motion suppressor device counters the rise of the floating foundation caused by the step of increase of buoyancy, thereby the motion suppressor device suppressing at least Z-axis motion of the floating foundation relative to the hull of the vessel. Use is made of an installation tool comprising a lower coupler configured to couple to the mast mounting structure, an upper coupler configured to couple to the mast foot, and a multi-degrees of freedom, preferably six-degrees of freedom, connector assembly having a controllable stiffness, which connector assembly interconnects the lower coupler and the upper coupler, wherein the connector assembly is configured to controllable vary the stiffness of the interconnection.

Inventors

  • WIJNING, DIEDERICK BERNARDUS
  • VAN BOVEN, Robin

Assignees

  • Itrec B.V.

Dates

Publication Date
20260513
Application Date
20240704

Claims (20)

  1. 1 . Method for installation of a wind turbine (100) on a floating foundation (200) that is in floating condition and subject to sea-state induced motions, e.g. at the site of an offshore windfarm, wherein the wind turbine to be installed comprises at least a wind turbine mast (101) having a mast foot (102) and a mast top (103), preferably also comprises a nacelle (110) mounted on the mast top, preferably without any rotor blades, wherein the floating foundation comprises a mast mounting structure (210) configured to mount the mast of the wind turbine thereon and secure the mast foot to the mast mounting structure, e.g. wherein the mast mounting structure and the mast foot are each provided with an annular flange structure, which flange structures are to be fastened to one another by multiple fasteners, wherein the mast mounting structure has an upwardly directed mounting axis, wherein use is made of a vessel (1) which is in floating condition and comprises: - a floating hull (10), -a crane (50) arranged on the hull, wherein the crane is provided with a hoisting system comprising winch driven hoist cables (61-64), which hoisting system is adapted to support the weight of the wind turbine and suspend the wind turbine from the hoist cables, which hoisting system is adapted to raise and lower the wind turbine in a controllable manner, - a motion suppressor device (70) mounted to the hull of the vessel, wherein the vessel is arranged in vicinity of the floating foundation allowing the crane to position the wind turbine above the mast mounting structure, wherein sea-state induces relative motion between the floating foundation and the hull of the vessel in horizontal X- axis and Y- axis directions, in vertical Z-as axis direction, and in rotational directions about the horizontal X- axis and Y- axis and about the vertical Z-axis, wherein the method comprises: engaging the motion suppressor device (70) with the floating foundation, increasing buoyancy of the floating foundation (200), e.g. by de-ballasting the floating foundation, e.g. by pumping ballast water from the floating foundation into one or more ballast tanks of the vessel (1), wherein the engagement with the motion suppressor device counters the rise of the floating foundation caused by the increase of buoyancy, thereby the motion suppressor device suppressing at least Z-axis motion of the floating foundation relative to the hull of the vessel, preferably, the buoyant force of the floating foundation suppressed by the motion suppressor device being at least 50%, e.g. at least 75%, of the weight of the wind turbine, wherein use is made of an installation tool (300) comprising: a lower coupler (310) configured to couple to the mast mounting structure (210), an upper coupler (320) configured to couple to the mast foot (102), a multi-degrees of freedom, preferably six-degrees of freedom, connector assembly (350) having a controllable stiffness, which connector assembly interconnects the lower coupler and the upper coupler, wherein the connector assembly is configured to controllable vary the stiffness of the interconnection, wherein the method further comprises: arranging the installation tool (300) at the mast mounting structure (210) and locking the lower coupler (310) to the mast mounting structure, suspending the wind turbine (100) from the hoisting system of the crane (50) and moving the suspended wind turbine above the installation tool, setting the stiffness of the connector assembly (350) at a low stiffness, mating the upper coupler (320) with the mast foot (102) whilst the connector assembly is set at said low stiffness, locking the upper coupler (320) to the mast foot (102), gradually increasing stiffness of the connector assembly to a high stiffness so as to cause the suspended wind turbine to be brought in motion synchronized with the mast mounting structure of the floating foundation due to forces transmitted via the connector assembly, landing the wind turbine (100) onto the mast mounting structure (210) whilst maintaining the high stiffness of the connector assembly such that the wind turbine is provisionally secured to the floating foundation by means of the installation tool, fastening the mast foot of the wind turbine (102) permanently to the mast mounting structure (210), e.g. by multiple fasteners, releasing the installation tool (300) from the mast foot and the mast mounting structure.
  2. 2. Method according to claim 1, wherein the increased buoyancy initially causes an upward load exerted by the floating foundation (200) on the motion suppressor device (70) of at least 1000 tonnes.
  3. 3. Method according to claim 1 or 2, wherein the weight of the wind turbine (100) that is landed on the mast mounting structure (210) is more than 1000 tonnes, e.g. more than 2000 tonnes.
  4. 4. Method according to any one or more of claims 1 - 3, wherein the suppressor device (70) is arranged on the longitudinal axis of the hull of the vessel (1), e.g. at the stern of the vessel, e.g. wherein the crane (50) is also mounted at the stern of the vessel.
  5. 5. Method according to any one or more of claims 1 - 4, wherein the installation tool (300) is mounted to the motion suppressor device (70), preferably such that the installation tool establishes the engagement between the motion suppressor device and the floating foundation (200), preferably the lower coupler (310) being connected to the motion suppressor device, e.g. gimballing about X-axis and Y-axis, e.g. freely gimballing about said axes.
  6. 6. Method according to claim 5, wherein the lower coupler (310) is displaceable in Z-axis direction relative to the motion suppressor device (70), e.g. by one or more Z-axis motion actuators (342, 343), e.g. in a controllable manner, e.g. the one or more Z-axis motion actuators being configured to vary stiffness and/or damping thereof, and/or the one or more Z-axis motion actuators being configured to provide for control of vertical position of the lower coupler relative to the motion suppressor device.
  7. 7. Method according to any one or more of claims 1 - 6, wherein the motion suppressor device (70) is rigid in Z-axis direction relative to the hull of the vessel (10).
  8. 8. Method according to any one or more of claims 1 - 7, wherein the motion suppressor device (70) is movable in a horizontal plane, preferably only in the horizontal plane, relative to the hull of the vessel (10).
  9. 9. Method according to claim 8, wherein the motion suppressor device (70) is configured to control motion of the mast mounting structure (210) in the X-axis direction and in the Y- axis direction, whilst suppressing motion in the Z-axis direction, wherein, for example, the motion suppressor device is configured and operated to dampen motion of the mast mounting structure in the X-axis direction and in the Y-axis direction.
  10. 10. Method according to any one or more of claims 1 - 9, wherein the floating foundation (200) is anchored via anchoring lines, e.g. catenary anchoring lines, and the vessel is held in position by means of a dynamic positioning system (DP system) of the vessel.
  11. 11. Method according to claim 8, wherein the motion suppressor device (70) comprises motion actuators (80) configured for causing movement of the motion suppressor device relative to the hull in a horizontal plane, preferably only in the horizontal plane relative to the hull of the vessel, wherein, for example, X-axis motion actuators as well as Y-axis motion actuators are present to control motion in said direction relative to the hull.
  12. 12. Method according to claim 11 , wherein the motion suppressor device (70) comprises a motion control unit controlling the motion actuators (80) thereof, wherein, for example, the motion control unit is configured to provide a damping mode in which the motion actuators dampen motion of the motion suppressor device relative to the hull (10), e.g. in a horizontal plane, preferably only in the horizontal plane relative to the hull of the vessel.
  13. 13. Method according to any one or more of claims 1 - 12, wherein a monitoring system is provided which is configured and operated to monitor position and/or motion of a portion of the floating foundation (200) on which motion suppressor device engages (70), e.g. the mast mounting structure (210), e.g. via the lower coupler of the installation tool (310), wherein, for example, the monitoring system is linked to the motion control unit of the motion actuators of the motion suppressor device.
  14. 14. Method according to claim 5, wherein, the installation tool (300), for example the lower coupler (310) thereof, is mounted to the motion suppressor device (70) via a Z-axis motion mechanism (340) that is configured and operated to control motion of the installation tool relative to the motion suppressor device, wherein, for example, the Z-axis motion mechanism is configured and operated to provide for controlled variation of vertical stiffness of the Z-axis motion mechanism.
  15. 15. Method according to any one or more of claims 1 - 14, wherein the suppressor device (70) comprises a cantilevered arm (75), e.g. a pair of cantilevered arms (75), wherein an inner end of each cantilevered arm is connected to the hull (10), and wherein the cantilevered arm(s) each project outward from the hull of the vessel, and wherein the cantilevered arm(s) absorb the upward force exerted by the increased buoyancy of the floating foundation (200) so as to suppress relative Z-axis motion.
  16. 16. Method according to any one or more of claims 1 - 15, wherein the installation tool (300) is mounted between a pair of cantilevered arms of the motion suppressor device (70), e.g. the lower coupler (310) being connected to outer ends of the cantilevered arms (75).
  17. 17. Method according to any one or more of claims 1 - 16, wherein the connector assembly (350) of the installation tool comprises multiple hydraulic cylinders (360) arranged to allow for setting of stiffness of the connector assembly in said multi-degrees of freedom, e.g. said six degrees of freedom, e.g. the cylinders being arranged as in a Stewart platform.
  18. 18. Method according to claim 17, wherein setting of the stiffness of the connector assembly (350) is done by setting of the pressure in the multiple hydraulic cylinders (360), wherein, for example, the installation tool has multiple pressurized gas tanks connectable via an associated control valve to a medium-separator having a gas filled chamber separated by a piston from a hydraulic liquid filled chamber, the latter being connected to one or more of the hydraulic cylinders.
  19. 19. Method according to any one or more of claims 1 - 18, wherein the connector assembly (350) of the installation tool (300) comprises multiple double sided hydraulic cylinders, each having a cylinder body and having a piston rod extending through opposed axial ends of the cylinder body, wherein a piston on the piston rod delimits equal crosssection chambers in the cylinder body, wherein, preferably, a controllable throttle bypass is provided between the chambers of each cylinder and wherein, preferably, the method comprises adjusting the throttle so as to set damping of the connector assembly.
  20. 20. Method according to any one or more of claims 1 - 19, wherein each of the lower coupler (310) and the upper coupler (320) comprises a C-shaped main body and a pivotal door member (315) configured to move between an opened and closed position thereof, so that in the closed position the coupler forms an annulus, and the opened position allowing removal of the installation tool after completion of the wind turbine installation.

Description

INSTALLATION OF A WIND TURBINE ON A FLOATING FOUNDATION The present invention relates to the installation of a wind turbine on a floating foundation. In the field of offshore windfarms it is known to install a fixed foundation on the seabed, e.g. a jacket or a monopile, and to then install the wind turbine on top of the fixed foundation. The latter of commonly done in a step-by-step approach, e.g. wherein first the mast is installed on the pre-installed foundation, then the nacelle is mounted on the top of the mast, and then the rotor blades are fitted to the hub of the nacelle. Other approaches, e.g. wherein a nacelle already fitted with two (of the three) rotor blades is supplied in the so-called bunny ears configuration, are also known. It is also known to install the mast together with the nacelle, often called the “tower nacelle assembly” or “TNA” in the industry on the fixed foundation, and then later mounted the rotor blades. Fixed foundation offshore wind turbines are effective in relatively shallow waters. In deeper waters it is envisaged that floating foundation wind turbines will be most effective, e.g. economical. For example, the document WO2009/131826 discloses several designs of floating foundations for wind turbines. In the field of floating foundation wind turbines it is at present the common understanding that assembly of the entire floating foundation wind turbine, so the combination of the floating foundation and of the wind turbine, is done remote from the actual windfarm. For example, assembly is done at a port-based yard. The entire floating foundation wind turbine is then towed from the assembly location to the remote offshore windfarm location. For example, Hywind Scotland is a wind farm using floating foundation wind turbines. These wind turbines have a 120 meters tall mast mounted on a spar- type floating foundation. The mounting of the wind turbines on the spar-type floating foundation was done in a fjord in Norway using the Saipem 7000 floating crane. The assemblies were then towed across the North Sea to the coast of Scotland near Peterhead. In the windfarm, three suction anchors anchor each floating foundation to the seabed. At the site of the offshore windfarm, in contrast to a (shielded) shore-based, e.g. quayside, installation location, the wave conditions are likely to be (over the year) more prominent, so that the floating foundation as well as any crane vessel that is used for installation of the wind turbine will be subject to relevant sea-state induced motions, generally each with its own dynamic behaviour. In WO2022/084344 an alternative approach for assembly floating foundation wind turbines and/or for creating a windfarm with one or more floating foundation wind turbines is presented. Generally, the floating foundation comprises a mast mounting structure configured to mount the mast of the wind turbine thereon and having an upwardly directed mounting axis. In this known approach, use is made of a vessel with a floating hull, a crane arranged on the hull, wherein the crane is provided with a hoisting system that is adapted to support the weight of the wind turbine and suspend the wind turbine from the crane. The hoisting system is adapted to raise and lower the wind turbine in a controllable manner. The crane and/or the hoisting system thereof comprises a heave compensation device that is adapted to compensate for sea-state induced heave motion of the wind turbine mast relative to the mast mounting structure of the floating foundation. Use is made of a mast alignment system that is configured to engage on the suspended wind turbine, e.g. on the mast of the suspended wind turbine, and to bring and maintain the mast of the wind turbine 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. The known method comprises - with the hull of the vessel in floating condition and the floating foundation in floating condition - the steps of: - suspending the wind turbine from the crane by means of the hoisting system, - positioning the lower end of the mast of the suspended wind turbine above the mast mounting structure of the floating foundation, - operating the heave compensation device so as to compensate for sea-state induced heave motion of the wind turbine mast relative to the mast mounting structure of the floating foundation, - operating the mast alignment system so as to bring and maintain the mast of the wind turbine in alignment with the mounting axis of the floating foundation in order to compensate for sea-state induced tilt motions of the wind turbine mast relative to the mounting axis of the floating foundation, - whilst the heave compensation device and the mast alignment system are in operation, operating the hoisting system and thereby lowering the suspe