WO2011108933A1 - Method for use with maintenance of offshore wind turbines, and assembly comprising a vessel and a lift device - Google Patents

Method for use with maintenance of offshore wind turbines, and assembly comprising a vessel and a lift device Download PDF

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Publication number
WO2011108933A1
WO2011108933A1 PCT/NL2011/050155 NL2011050155W WO2011108933A1 WO 2011108933 A1 WO2011108933 A1 WO 2011108933A1 NL 2011050155 W NL2011050155 W NL 2011050155W WO 2011108933 A1 WO2011108933 A1 WO 2011108933A1
Authority
WO
WIPO (PCT)
Prior art keywords
elevator device
wind turbine
vessel
platform
lifting device
Prior art date
Application number
PCT/NL2011/050155
Other languages
French (fr)
Inventor
Adrianus Henricus Schampers
Original Assignee
Outsmart B.V.
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Outsmart B.V. filed Critical Outsmart B.V.
Publication of WO2011108933A1 publication Critical patent/WO2011108933A1/en

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Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B66—HOISTING; LIFTING; HAULING
    • B66D—CAPSTANS; WINCHES; TACKLES, e.g. PULLEY BLOCKS; HOISTS
    • B66D1/00—Rope, cable, or chain winding mechanisms; Capstans
    • B66D1/60—Rope, cable, or chain winding mechanisms; Capstans adapted for special purposes
    • B66D1/605—Rope, cable, or chain winding mechanisms; Capstans adapted for special purposes scaffolding winshes
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B63—SHIPS OR OTHER WATERBORNE VESSELS; RELATED EQUIPMENT
    • B63B—SHIPS OR OTHER WATERBORNE VESSELS; EQUIPMENT FOR SHIPPING 
    • B63B27/00—Arrangement of ship-based loading or unloading equipment for cargo or passengers
    • B63B27/16—Arrangement of ship-based loading or unloading equipment for cargo or passengers of lifts or hoists
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F03—MACHINES OR ENGINES FOR LIQUIDS; WIND, SPRING, OR WEIGHT MOTORS; PRODUCING MECHANICAL POWER OR A REACTIVE PROPULSIVE THRUST, NOT OTHERWISE PROVIDED FOR
    • F03D—WIND MOTORS
    • F03D80/00—Details, components or accessories not provided for in groups F03D1/00 - F03D17/00
    • F03D80/50—Maintenance or repair
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F05—INDEXING SCHEMES RELATING TO ENGINES OR PUMPS IN VARIOUS SUBCLASSES OF CLASSES F01-F04
    • F05B—INDEXING SCHEME RELATING TO WIND, SPRING, WEIGHT, INERTIA OR LIKE MOTORS, TO MACHINES OR ENGINES FOR LIQUIDS COVERED BY SUBCLASSES F03B, F03D AND F03G
    • F05B2230/00—Manufacture
    • F05B2230/60—Assembly methods
    • F05B2230/61—Assembly methods using auxiliary equipment for lifting or holding
    • F05B2230/6102—Assembly methods using auxiliary equipment for lifting or holding carried on a floating platform
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F05—INDEXING SCHEMES RELATING TO ENGINES OR PUMPS IN VARIOUS SUBCLASSES OF CLASSES F01-F04
    • F05B—INDEXING SCHEME RELATING TO WIND, SPRING, WEIGHT, INERTIA OR LIKE MOTORS, TO MACHINES OR ENGINES FOR LIQUIDS COVERED BY SUBCLASSES F03B, F03D AND F03G
    • F05B2240/00—Components
    • F05B2240/90—Mounting on supporting structures or systems
    • F05B2240/91—Mounting on supporting structures or systems on a stationary structure
    • F05B2240/916—Mounting on supporting structures or systems on a stationary structure with provision for hoisting onto the structure
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F05—INDEXING SCHEMES RELATING TO ENGINES OR PUMPS IN VARIOUS SUBCLASSES OF CLASSES F01-F04
    • F05B—INDEXING SCHEME RELATING TO WIND, SPRING, WEIGHT, INERTIA OR LIKE MOTORS, TO MACHINES OR ENGINES FOR LIQUIDS COVERED BY SUBCLASSES F03B, F03D AND F03G
    • F05B2240/00—Components
    • F05B2240/90—Mounting on supporting structures or systems
    • F05B2240/91—Mounting on supporting structures or systems on a stationary structure
    • F05B2240/917—Mounting on supporting structures or systems on a stationary structure attached to cables
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F05—INDEXING SCHEMES RELATING TO ENGINES OR PUMPS IN VARIOUS SUBCLASSES OF CLASSES F01-F04
    • F05B—INDEXING SCHEME RELATING TO WIND, SPRING, WEIGHT, INERTIA OR LIKE MOTORS, TO MACHINES OR ENGINES FOR LIQUIDS COVERED BY SUBCLASSES F03B, F03D AND F03G
    • F05B2240/00—Components
    • F05B2240/90—Mounting on supporting structures or systems
    • F05B2240/95—Mounting on supporting structures or systems offshore
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E10/00—Energy generation through renewable energy sources
    • Y02E10/70—Wind energy
    • Y02E10/72—Wind turbines with rotation axis in wind direction
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E10/00—Energy generation through renewable energy sources
    • Y02E10/70—Wind energy
    • Y02E10/727—Offshore wind turbines
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
    • Y02P70/50—Manufacturing or production processes characterised by the final manufactured product

Definitions

  • the invention relates to a method for use with maintenance of an offshore wind farm comprising a plurality of offshore wind turbines.
  • the invention also relates to an assembly comprising a vessel and an elevator device, in particular for use with maintenance of an offshore wind farm comprising a plurality of offshore wind turbines.
  • DE10013442 discloses an offshore wind turbine provided with a tower which is installed in a sea having a water surface, a nacelle which is arranged at the upper end of the tower, and also a rotor which is connected to the nacelle.
  • the nacelle can be rotated about a vertical axis, whereas the rotor can be rotated about a horizontal axis.
  • the tower has a vessel mooring platform.
  • the nacelle is provided with a helicopter landing platform.
  • a number of electrical components are provided in a container which is mounted in a detachable manner adjacent to the nacelle. In case of failure of the electrical components being provided in the container, the container can be lowered to a vessel floating in the sea by a hoisting cable driven by a winch.
  • the winch can be installed at the helicopter landing platform, the nacelle or the vessel mooring platform of the tower. Thus, the entire container can be replaced.
  • An offshore wind farm comprises a large number of offshore wind turbines. It is costly to install a winch at each offshore wind turbine in the wind farm and to replace an entire container having electrical components for maintenance and/or repair. Furthermore, each offshore wind turbine in the wind farm requires additional maintenance, for example changing oil in the gear box of the electrical generator, and also additional repair and attendance for other reasons. It is rather hazardous and expensive to deliver or receive personnel and/or goods using a helicopter. Alternatively, personnel and/or equipment can be delivered to the vessel mooring platforms of the towers of the wind turbines using crew transfer vessels. This can be unsafe as well depending on weather and sea conditions.
  • the platforms of the wind turbines of a wind farm are located at a height above the water surface, for example approximately 20 m.
  • Service engineers have to step from the crew transfer vessel onto a ladder at a lower end of the tower and then have to climb up to the platform.
  • the interior of the tower is accessible from the platform through an entrance door. It is thus rather cumbersome for service engineers to take components and relatively heavy tools to the tower.
  • each wind turbine is provided with a tower, which is installed in a sea having a water surface, a support structure, which is attached to the tower above the water surface, and which support structure is provided with a platform, in which the support structure is provided with at least one fixing point, and in which the method comprises:
  • the elevator device is provided with a driving unit and at least one hoisting member.
  • the driving unit comprises a winch
  • the hoisting member may be a hoisting cable which is winded up the winch.
  • the elevator device is self-hoisting and can be elevated to the level of the platform autonomously after connecting the hoisting member to the fixing point.
  • the platform of the support structure is attached to the tower above the water surface, whereas the support structure may comprise a boom which is attached to the tower above the platform and which is provided with the fixing point.
  • the elevator device can be lowered autonomously from the level of the landing structure to the vessel floating in the sea below the fixing point.
  • the vessel may then move to another offshore wind turbine in the wind farm, after which the elevator device can be elevated to the level of the landing structure autonomously again for maintenance and/or repair.
  • the elevator device can be used for maintenance and/or repair of a number of offshore wind turbines in the wind farm without major modifications to the wind turbines, for example it is not necessary that the wind turbines are each provided with a winch or other hoisting device. This allows for flexible maintenance and/or repair activities in the wind farm and substantially reduces the costs involved.
  • WO2006/005705 discloses an offshore wind turbine having a fixing point.
  • a vessel floating in the sea has a winch and a cable which can be connected to the fixing point.
  • the vessel can be lifted from the sea by means of the winch.
  • this vessel does not have a self-hoisting elevator device which can be elevated while the vessel remains floating in the sea.
  • US4739721 discloses a boat which is designed as a self-hoisting unit for the vertical and horizontal transfer of persons and/or equipment from a ship to an offshore platform and vice versa. However, this document does not relate to maintenance of offshore wind turbines.
  • the assembly according to the invention comprises a second elevator device for personnel and/or goods, which second elevator device is provided with a driving unit and at least one hoisting member, which can be driven by the driving unit, and in which the vessel floating in the sea is moved to a third wind turbine and below the fixing point of the support structure of the third wind turbine, and in which the hoisting member of the second elevator device is connected to the fixing point of the support structure of the third wind turbine, and in which the hoisting member is driven by the driving unit of the second elevator device for suspending the second elevator device from the fixing point and elevating the second elevator device from the vessel to the platform of the third wind turbine for allowing transfer of personnel and/or goods between the elevator device and the platform of the third wind turbine.
  • the vessel can be used for delivering a plurality of elevator devices to offshore wind turbines of the offshore wind farm, respectively.
  • the hoisting member can be driven by the driving unit of the elevator device for suspending the second elevator device from the fixing point and lowering the second elevator device from the platform to the vessel.
  • the vessel may also pick up a plurality of elevator devices from respective offshore wind turbines in an offshore wind farm after maintenance and/or repair have been completed.
  • the or each elevator device has a lower end, in which the assembly comprises a lifting device which is situated between the vessel and the lower end of the elevator device, in which the lifting device can be displaced between an extended position and a retracted position, in which the lifting device comprises an actuating member for urging the lifting device from the retracted position to the extended position, and in which the lifting device in its extended position can have a stationary state, in which the lifting device is maintained in its extended position, and a released state, in which the lifting device is released from its extended position for allowing displacement of the lifting device between the extended position and the retracted position, and in which the lower end of the elevator device is lifted from the vessel by actuating the actuating member for urging the lifting device from the retracted position to the extended position, and in which the lifting device in its extended position is kept in its stationary state before the hoisting member is driven by the driving unit of the elevator device, and in which the lifting device in its extended position is released to its released state after the hoisting member has been driven by the driving
  • the actuating member is first actuated for urging the lifting device to the extended position and lifting the elevator device up from the vessel.
  • the elevator device is lifted to an initial height of 0.5 m above the deck of the vessel.
  • the lifting device being in its extended position is held in its stationary state, so that the motion of the elevator device and the motion of the vessel are linked.
  • the hoisting member is connected to the fixing point and subsequently the hoisting member is driven by the driving unit of the elevator device.
  • the hoisting member has been pulled taut, the elevator device is just becoming suspended from the fixing point. Then, at the top of a heave motion of the vessel, the lifting device still being in its extended position is released to its released state.
  • the lifting device can be displaced between the extended position and the retracted position and the elevator device becomes fully suspended from the fixing point.
  • the elevator device is subsequently hoisted up by driving the hoisting member. This may be slow relative to the heave motions of the vessel. If a relatively high heave motion occurs shortly after release of the lifting device, a hard impact between the vessel and the elevator device will normally be prevented because of the initial height formed by the lifting device in the extended position. The impact will be experienced by the lifting device only. As the lifting device is in its released state, the lifting device may displace from the extended position to the retracted position. Thus, the lifting device reduces the risk of damage to the vessel and/or the elevator device caused by heave motions of the vessel.
  • the lifting device may comprise a cushioning device for cushioning the displacement of the lifting device from the extended position to the retracted position.
  • a cushioning device for cushioning the displacement of the lifting device from the extended position to the retracted position.
  • the lifting device may be biased to the extended position by the cushioning device. As a result, the lifting device is in its extended position when the lifting device is released.
  • the lifting device may be integrated with the elevator device.
  • the lifting device is arranged at the lower end of the elevator device.
  • the lifting device will protrude downwardly from the lower end of the elevator device.
  • the lifting device is released which allows the lifting device to be displaced to its extended position. After the lifting device in its extended position has contacted the vessel and abuts against it, the lifting device can be fixed in its stationary state.
  • the lifting device can be constructed in various ways.
  • the lifting device can also be attached to the deck of the vessel.
  • the elevator device then has to be lowered accurately above the lifting device on the deck of the vessel.
  • the lifting device comprises a plurality of support legs, in which each support leg can be displaced in a sliding manner between the extended position and the retracted position.
  • Each support leg may be provided with a hydraulic cylinder for actuating the support leg from the retracted position to the extended position.
  • the cushioning device may be integrated with the hydraulic cylinders.
  • the undersides of the support legs which abut against the vessel may be provided with cushioning elements.
  • the or each elevator device may comprises a motion compensator device for compensating the motion of the elevator device being suspended by the hoisting member from the fixing point relative to the motion of the vessel floating in the sea.
  • the motion compensator device can have a stationary state and an active state.
  • the motion compensator device is a rigid structure in its stationary state. In the active state, the motion compensator device guarantees that the hoisting member is kept taut when the elevator device is resting on the vessel.
  • the motion compensator device can be constructed in various ways.
  • the driving unit comprises a winch, in which the hoisting member comprises a hoisting cable which is winded up on the winch, and in which the motion compensator device comprises an arm which is pivotably connected to the elevator device, and a resilient member which is connected between the arm and the elevator device, and in which the arm is provided with a pulley, and in which the hoisting cable is guided from the winch via the pulley to the fixing point.
  • each wind turbine is provided with at least two fixing points, which are distanced with respect to each other, and in which the or each elevator device comprises at least two hoisting members, and in which the hoisting members of the elevator device are connected to the respective fixing points of the support structure of the first wind turbine and second wind turbine.
  • the use of two or more hoisting members prevents rotation of the elevator device in a horizontal plane during hoisting of the elevator device.
  • the elevator device may comprise a support frame, and in which the support frame carries a container which is connected to the support frame in a releasable manner.
  • the container consists of a standard ISO container having corner castings.
  • the corner castings of the container may be connected to the support frame using twist locks.
  • the support frame comprises the driving unit and the hoisting member, and in which, when the support frame carrying the container has been elevated to the platform, the container is disconnected from the support frame and connected to the support structure of the wind turbine, and in which the hoisting member is driven by the driving unit of the support frame for suspending the support frame from the fixing point and lowering the support frame from the platform to the vessel while the container remains connected to the support structure of the wind turbine.
  • the support frame that has been lowered onto the vessel can be connected subsequently to another container.
  • a single support frame can be used for delivering a plurality of containers to a number of wind turbines.
  • the support structure of the wind turbine is provided with guide members for guiding the elevator device to a predefined position when the elevator device is elevated to the platform.
  • the elevator device may be locked by locking members with respect to the support structure when the elevator device has been elevated to the platform. In that case, the elevator device is suspended from the support structure by means of the locking members and the driving unit for driving the hoisting member can be shut off.
  • the or each driving unit comprises an electromotor and electrical accumulators for feeding the electromotor.
  • the or each elevator device may be driven in a fully autonomous manner, i.e. it is not necessary to supply energy from an external energy source.
  • the invention also relates to an assembly comprising a vessel and an elevator device for personnel and/or goods, which elevator device is provided with a driving unit and at least one hoisting member, which can be driven by the driving unit.
  • the assembly according to the invention may be constructed as described above.
  • the assembly may also be used for gaining access to other offshore structures than offshore wind turbines.
  • the elevator device has a lower end, in which the assembly comprises a lifting device which is situated between the vessel and the lower end of the elevator device, in which the lifting device can be displaced between an extended position and a retracted position, in which the lifting device comprises an actuating member for urging the lifting device from the retracted position to the extended position, and in which the lifting device in its extended position can have a stationary state, in which the lifting device is maintained in its extended position, and a released state, in which the lifting device is released from its extended position for allowing displacement of the lifting device between the extended position and the retracted position.
  • the assembly comprises a lifting device which is situated between the vessel and the lower end of the elevator device, in which the lifting device can be displaced between an extended position and a retracted position, in which the lifting device comprises an actuating member for urging the lifting device from the retracted position to the extended position, and in which the lifting device in its extended position can have a stationary state, in which the lifting device is maintained in its extended position, and a released state
  • the lifting device of the assembly may comprise a cushioning device for cushioning the displacement of the lifting device from the extended position to the retracted position.
  • the lifting device may be integrated with the elevator device.
  • the lifting device comprises a plurality of support legs, in which each support leg can be displaced in a sliding manner between the extended position and the retracted position.
  • Each support leg may be provided with a hydraulic cylinder for actuating the support leg from the retracted position to the extended position.
  • the cushioning device may be integrated with the hydraulic cylinders.
  • the undersides of the support legs which abut against the vessel may be provided with cushioning elements.
  • the elevator device of the assembly may comprises a motion compensator device for compensating the motion of the elevator device when it is being suspended by the hoisting member relative to the motion of the vessel floating in the sea.
  • the motion compensator device can have a stationary state and an active state.
  • the motion compensator device is a rigid structure in its stationary state. In the active state, the motion compensator device guarantees that the hoisting member is kept taut when the elevator device is resting on the vessel.
  • the driving unit of the elevator device of the assembly may comprise a winch, in which the hoisting member comprises a hoisting cable which is winded up on the winch, and in which the motion compensator device comprises an arm which is pivotably connected to the lifting device, and a resilient member which is connected between the arm and the lifting device, and in which the arm is provided with a pulley, and in which the hoisting cable is guided from the winch around the pulley.
  • the elevator device of the assembly may comprise at least two hoisting members, for example two hoisting cables. It is also possible for the elevator device of the assembly to comprise a support frame and a container which is connected to the support frame in a releasable manner.
  • the container consists of a standard ISO container having corner castings. The corner castings of the container may be connected to the support frame using twist locks.
  • the driving unit may comprise an electromotor and electrical accumulators for supplying energy to the electromotor.
  • Figure 1 shows an assembly of a vessel and an elevator device according to a first embodiment of the invention.
  • Figure 2a-2d show an elevator device according to a second embodiment of the invention.
  • Figures 3a-3f show schematic side views of an elevator device being hoisted up to a platform of an offshore wind turbine.
  • An offshore wind farm comprises a number of offshore wind turbines.
  • Figure 1 shows one offshore wind turbine 1 of the offshore wind farm.
  • the other wind turbines in the wind farm may be constructed in a corresponding or identical manner.
  • the wind turbine 1 comprises a tower 2 which is installed in a sea 3 having a water surface 4.
  • a support structure having a boom 10 and a platform 6 is attached to the tower 2.
  • the tower 2 has bumper bars 7 and a ladder 8 which leads to the platform 6.
  • the platform 6 is used for delivering personnel and heavy equipment to the tower.
  • the boom 10 is provided with two fixing points 1 1 and guide members 32.
  • An assembly comprising a vessel 14 and an elevator device 18 is brought below the fixing points 1 1 of the boom 10.
  • the elevator device 18 is mounted on the deck 15 of the vessel 14.
  • the elevator device 18 constitutes a container having a bottom, four side walls extending from the bottom, and a roof 19.
  • the container 18 may be provided with a workshop and residence means, such as a bed, kitchen, and/or toilet (not shown).
  • the container 18 also has corner castings 33 which can be locked with respect to the boom 10.
  • the corner castings are defined by standard ISO dimensions, for example.
  • a driving unit 20 is mounted on the roof 19 of the container 18.
  • the driving unit is constructed as a winch 20. Two hoisting cables 21 can be wound and unwound by the winch 20.
  • the container 18 comprises a motion compensator device 26 for keeping the hoisting cables 21 taut during heave motions of the vessel 14.
  • the motion compensator device 26 has two arms 27 which can be pivoted with respect to respective pivot axes 28. Both arms 27 are connected to the roof 19 of the container 18 by means of respective resilient members 29.
  • the hoisting cables 21 are guided from the winch 20 over a number of pulleys 30, including a pulley 30 which is attached to the arms 27.
  • the point of application of the hoisting forces is defined by the pulleys 31 .
  • the arms 27 may pivot about the pivot axes 28 (as shown in dotted lines in figure 1 ), which varies the length of the portion of hoisting cable 21 between the winch 20 and the pulley 31 .
  • the motion compensator device 26 may compensate for heave motions of the vessel 14.
  • the container 18 comprises a lifting device for lifting the container 18 with respect to the deck 15 of the vessel 14.
  • the lifting device comprises four support legs 23, which can be displaced in a sliding manner between an extended position and a retracted position.
  • the support legs 23 can be actuated from the retracted position to the extended position by means of hydraulic cylinders or other actuating members 24.
  • the hydraulic cylinders 24 may be adapted for cushioning the displacement of the support legs 23 between the extended position and the retracted position.
  • the supporting legs 23 also have shock damping elements arranged at their undersides.
  • FIGS. 2a-2c show a second embodiment of the elevator device according to the invention.
  • the same reference numerals are used for designating the same or
  • the elevator device 18 as shown in figures 2a-2c comprises a support frame 40 and a container 41.
  • the container 41 constitutes a standard ISO container having corner castings 42 which can be connected to the support frame 40, for example by means of twist locks.
  • the support frame 40 is provided with two side supports 46 and a top frame 47 which connects the side supports 46.
  • the support legs 23 are integrated with the side supports 46.
  • the top frame 47 has four corner castings 33 for locking with the boom 10 of the tower 2 of the wind turbine 1 .
  • the winch 20, the motion compensation device 26 and the hoisting cables 21 are mounted on the top frame 47.
  • the winch 20 can be driven by an electrical motor 48.
  • the energy for the electrical motor 48 is supplied by electrical accumulators 43.
  • the hydraulic cylinders 24 for actuating the support legs 23 are supplied with hydraulic fluid using hydraulic accumulators 44.
  • the hydraulic cylinders 24 of support legs 23 are actuated for urging the support legs 23 to the extended position.
  • the elevator device 18 is lifted from the deck 15 of the vessel 14, for example to a height of 0.5 m above the deck 15.
  • the hydraulic cylinders 24 of the support legs 23 maintain the support legs 23 in the extended position.
  • the support legs 23 of the elevator device 18 rest on the deck 15.
  • the motion of the vessel 14 and the motion of the elevator device 18 are linked to each other.
  • the stern 16 of the vessel 14 is stabilised against the bumper bars 7 of the tower 2 using the thrust of the propulsion system of the vessel 14.
  • a person steps from the vessel 14 onto the ladder 7 and climbs up to the platform 6.
  • An auxiliary line 49 is lowered to the vessel 14 floating below the fixing points 1 1 of the boom 10 (figure 3a).
  • the auxiliary line 49 is connected to the hoisting cables 21 which are subsequently pulled up and fitted to the fixing points 1 1 .
  • the hoisting cables 21 are pulled taut such that the motion compensator device 26 can compensate for both a lengthening and a shortening of the hoisting cables 21 .
  • the hydraulic cylinders 24 of the support legs 23 are released and the winch 23 is driven to haul in the hoisting cables 21 .
  • the elevator device 18 becomes suspended from the hoisting cables 21 attached to the fixing points 1 1 . If the elevator device 18 has been hoisted up over a relatively small distance only, a heave motion of the vessel 14 which is higher than expected may cause a collision between the deck 15 and the support legs 23 of the elevator device 18. As a result of the release of the support legs 23, they can be slid inwards from the extended position to the retracted position without causing damage to the lower side of the elevator device 18.
  • the elevator device 18 is elevated further by the hoisting cables 21 until the elevator device 18 is received by the guide members 32.
  • the hoisting cables 21 pull the elevator device 18 against the boom 10, after which the corner castings 33 of the elevator device 18 can be locked to the boom 10, for example using twist locks.
  • the elevator device 18 can be used for delivering personnel and/or equipment to the platform 6 of the wind turbine 1 .
  • the elevator device 18 can be lowered to a vessel floating below the fixing points 1 1 . This can be achieved by carrying out the steps described above in the reverse order.
  • the vessel 14 carrying the elevator device 18 can then be brought to another offshore wind turbine in the offshore wind farm.
  • the vessel 14 can also be provided with a plurality of elevator devices 18.
  • the vessel 14 can then deliver a plurality of elevator devices 18 to various offshore wind turbines in the offshore wind farm. This results in very efficient and flexible maintenance of the offshore wind farm.
  • the hoisting members may also be constructed as wires or chains.
  • the invention is not limited to use with maintenance of offshore wind turbines.
  • the method as described above and/or as claimed in the appended claims may also be used for transferring personnel and/or goods from the vessel to an offshore platform or any other stationary structure at sea.

Abstract

Maintenance of an offshore wind farm comprising a plurality of offshore wind turbines is carried out. Each wind turbine is provided with a tower, which is installed in a sea and a support structure, which is attached to the tower and which comprises a platform with a fixing point.A vessel is moved to a first wind turbine and below the fixing point of the first wind turbine. A hoisting member of an elevator device mounted on the vessel is connected to the fixing point of the first wind turbine. The hoisting member is driven by a driving unit of the elevator device for suspending the elevator device from the fixing point and elevating the elevator device from the vessel to the platform of the first wind turbine. This allows transfer of personnel and/or goods between the elevator device and the platform of the first wind turbine. Subsequently the elevator device is lowered from the platform to the vessel and the hoisting member of the elevator device is disconnected from the fixing point of the first wind turbine. The vessel is then moved to a second wind turbine and below the fixing point of the second wind turbine. Using the hoisting member the elevator device is elevated from the vessel to the platform of the second wind turbine for allowing transfer of personnel and/or goods between the elevator device and the platform of the second wind turbine.

Description

Title: Method for use with maintenance of offshore wind turbines, and assembly comprising a vessel and a lift device.
The invention relates to a method for use with maintenance of an offshore wind farm comprising a plurality of offshore wind turbines. The invention also relates to an assembly comprising a vessel and an elevator device, in particular for use with maintenance of an offshore wind farm comprising a plurality of offshore wind turbines.
DE10013442 discloses an offshore wind turbine provided with a tower which is installed in a sea having a water surface, a nacelle which is arranged at the upper end of the tower, and also a rotor which is connected to the nacelle. The nacelle can be rotated about a vertical axis, whereas the rotor can be rotated about a horizontal axis. The tower has a vessel mooring platform. The nacelle is provided with a helicopter landing platform. A number of electrical components are provided in a container which is mounted in a detachable manner adjacent to the nacelle. In case of failure of the electrical components being provided in the container, the container can be lowered to a vessel floating in the sea by a hoisting cable driven by a winch. The winch can be installed at the helicopter landing platform, the nacelle or the vessel mooring platform of the tower. Thus, the entire container can be replaced.
An offshore wind farm comprises a large number of offshore wind turbines. It is costly to install a winch at each offshore wind turbine in the wind farm and to replace an entire container having electrical components for maintenance and/or repair. Furthermore, each offshore wind turbine in the wind farm requires additional maintenance, for example changing oil in the gear box of the electrical generator, and also additional repair and attendance for other reasons. It is rather hazardous and expensive to deliver or receive personnel and/or goods using a helicopter. Alternatively, personnel and/or equipment can be delivered to the vessel mooring platforms of the towers of the wind turbines using crew transfer vessels. This can be unsafe as well depending on weather and sea conditions.
In practice, the platforms of the wind turbines of a wind farm are located at a height above the water surface, for example approximately 20 m. Service engineers have to step from the crew transfer vessel onto a ladder at a lower end of the tower and then have to climb up to the platform. The interior of the tower is accessible from the platform through an entrance door. It is thus rather cumbersome for service engineers to take components and relatively heavy tools to the tower.
It is an object of the invention to provide an improved method for use with
maintenance of an offshore wind farm comprising a plurality of wind turbines. This object is achieved according to the invention by a method for use with maintenance of an offshore wind farm comprising a plurality of offshore wind turbines, in which each wind turbine is provided with a tower, which is installed in a sea having a water surface, a support structure, which is attached to the tower above the water surface, and which support structure is provided with a platform, in which the support structure is provided with at least one fixing point, and in which the method comprises:
- providing an assembly comprising a vessel and an elevator device for personnel and/or goods, which elevator device is provided with a driving unit and at least one hoisting member, which can be driven by the driving unit,
- moving the vessel floating in the sea to a first wind turbine and below the fixing point of the support structure of the first wind turbine,
- connecting the hoisting member of the elevator device to the fixing point of the support structure of the first wind turbine,
- driving the hoisting member by the driving unit of the elevator device for suspending the elevator device from the fixing point and elevating the elevator device from the vessel to the platform of the first wind turbine for allowing transfer of personnel and/or goods between the elevator device and the platform of the first wind turbine,
- when the elevator device has been elevated to the platform, driving the hoisting member by the driving unit of the elevator device for suspending the elevator device from the fixing point and lowering the elevator device from the platform to the vessel,
- disconnecting the hoisting member of the elevator device from the fixing point of the support structure of the first wind turbine,
- moving the vessel floating in the sea to a second wind turbine and below the fixing point of the support structure of the second wind turbine,
- connecting the hoisting member of the elevator device to the fixing point of the support structure of the second wind turbine,
- driving the hoisting member by the driving unit of the elevator device for suspending the elevator device from the fixing point and elevating the elevator device from the vessel to the platform of the second wind turbine for allowing transfer of personnel and/or goods between the elevator device and the platform of the second wind turbine.
According to the invention, the elevator device is provided with a driving unit and at least one hoisting member. For example, the driving unit comprises a winch, and the hoisting member may be a hoisting cable which is winded up the winch. The elevator device is self-hoisting and can be elevated to the level of the platform autonomously after connecting the hoisting member to the fixing point. The platform of the support structure is attached to the tower above the water surface, whereas the support structure may comprise a boom which is attached to the tower above the platform and which is provided with the fixing point. When maintenance and/or repair has been completed, the elevator device can be lowered autonomously from the level of the landing structure to the vessel floating in the sea below the fixing point. The vessel may then move to another offshore wind turbine in the wind farm, after which the elevator device can be elevated to the level of the landing structure autonomously again for maintenance and/or repair. Thus, the elevator device can be used for maintenance and/or repair of a number of offshore wind turbines in the wind farm without major modifications to the wind turbines, for example it is not necessary that the wind turbines are each provided with a winch or other hoisting device. This allows for flexible maintenance and/or repair activities in the wind farm and substantially reduces the costs involved.
It is also noted that WO2006/005705 discloses an offshore wind turbine having a fixing point. A vessel floating in the sea has a winch and a cable which can be connected to the fixing point. The vessel can be lifted from the sea by means of the winch. However, this vessel does not have a self-hoisting elevator device which can be elevated while the vessel remains floating in the sea.
It is also noted that US4739721 discloses a boat which is designed as a self-hoisting unit for the vertical and horizontal transfer of persons and/or equipment from a ship to an offshore platform and vice versa. However, this document does not relate to maintenance of offshore wind turbines.
It is possible that the assembly according to the invention comprises a second elevator device for personnel and/or goods, which second elevator device is provided with a driving unit and at least one hoisting member, which can be driven by the driving unit, and in which the vessel floating in the sea is moved to a third wind turbine and below the fixing point of the support structure of the third wind turbine, and in which the hoisting member of the second elevator device is connected to the fixing point of the support structure of the third wind turbine, and in which the hoisting member is driven by the driving unit of the second elevator device for suspending the second elevator device from the fixing point and elevating the second elevator device from the vessel to the platform of the third wind turbine for allowing transfer of personnel and/or goods between the elevator device and the platform of the third wind turbine.
Thus, the vessel can be used for delivering a plurality of elevator devices to offshore wind turbines of the offshore wind farm, respectively. When the second elevator device has been elevated to the platform, the hoisting member can be driven by the driving unit of the elevator device for suspending the second elevator device from the fixing point and lowering the second elevator device from the platform to the vessel. The vessel may also pick up a plurality of elevator devices from respective offshore wind turbines in an offshore wind farm after maintenance and/or repair have been completed. It is possible that the or each elevator device has a lower end, in which the assembly comprises a lifting device which is situated between the vessel and the lower end of the elevator device, in which the lifting device can be displaced between an extended position and a retracted position, in which the lifting device comprises an actuating member for urging the lifting device from the retracted position to the extended position, and in which the lifting device in its extended position can have a stationary state, in which the lifting device is maintained in its extended position, and a released state, in which the lifting device is released from its extended position for allowing displacement of the lifting device between the extended position and the retracted position, and in which the lower end of the elevator device is lifted from the vessel by actuating the actuating member for urging the lifting device from the retracted position to the extended position, and in which the lifting device in its extended position is kept in its stationary state before the hoisting member is driven by the driving unit of the elevator device, and in which the lifting device in its extended position is released to its released state after the hoisting member has been driven by the driving unit of the elevator device and the elevator device has just been suspended from the fixing point.
In this case, the actuating member is first actuated for urging the lifting device to the extended position and lifting the elevator device up from the vessel. For example, the elevator device is lifted to an initial height of 0.5 m above the deck of the vessel. The lifting device being in its extended position is held in its stationary state, so that the motion of the elevator device and the motion of the vessel are linked. The hoisting member is connected to the fixing point and subsequently the hoisting member is driven by the driving unit of the elevator device. When the hoisting member has been pulled taut, the elevator device is just becoming suspended from the fixing point. Then, at the top of a heave motion of the vessel, the lifting device still being in its extended position is released to its released state. As a result, the lifting device can be displaced between the extended position and the retracted position and the elevator device becomes fully suspended from the fixing point. The elevator device is subsequently hoisted up by driving the hoisting member. This may be slow relative to the heave motions of the vessel. If a relatively high heave motion occurs shortly after release of the lifting device, a hard impact between the vessel and the elevator device will normally be prevented because of the initial height formed by the lifting device in the extended position. The impact will be experienced by the lifting device only. As the lifting device is in its released state, the lifting device may displace from the extended position to the retracted position. Thus, the lifting device reduces the risk of damage to the vessel and/or the elevator device caused by heave motions of the vessel.
The lifting device may comprise a cushioning device for cushioning the displacement of the lifting device from the extended position to the retracted position. When a heave motion of the vessel causes an impact to the lifting device, the impact is absorbed by the cushioning device. The lifting device may be biased to the extended position by the cushioning device. As a result, the lifting device is in its extended position when the lifting device is released.
The lifting device may be integrated with the elevator device. For example, the lifting device is arranged at the lower end of the elevator device. When the lifting device is in its extended position, the lifting device will protrude downwardly from the lower end of the elevator device. When lowering the elevator device onto the vessel, the lifting device is released which allows the lifting device to be displaced to its extended position. After the lifting device in its extended position has contacted the vessel and abuts against it, the lifting device can be fixed in its stationary state.
It is noted that the lifting device can be constructed in various ways. For example, the lifting device can also be attached to the deck of the vessel. The elevator device then has to be lowered accurately above the lifting device on the deck of the vessel.
It is possible that the lifting device comprises a plurality of support legs, in which each support leg can be displaced in a sliding manner between the extended position and the retracted position. Each support leg may be provided with a hydraulic cylinder for actuating the support leg from the retracted position to the extended position. The cushioning device may be integrated with the hydraulic cylinders. Furthermore, the undersides of the support legs which abut against the vessel may be provided with cushioning elements.
In addition to the lifting device, the or each elevator device may comprises a motion compensator device for compensating the motion of the elevator device being suspended by the hoisting member from the fixing point relative to the motion of the vessel floating in the sea. The motion compensator device can have a stationary state and an active state. The motion compensator device is a rigid structure in its stationary state. In the active state, the motion compensator device guarantees that the hoisting member is kept taut when the elevator device is resting on the vessel.
The motion compensator device can be constructed in various ways. For example, the driving unit comprises a winch, in which the hoisting member comprises a hoisting cable which is winded up on the winch, and in which the motion compensator device comprises an arm which is pivotably connected to the elevator device, and a resilient member which is connected between the arm and the elevator device, and in which the arm is provided with a pulley, and in which the hoisting cable is guided from the winch via the pulley to the fixing point.
It is possible that the support structure of each wind turbine is provided with at least two fixing points, which are distanced with respect to each other, and in which the or each elevator device comprises at least two hoisting members, and in which the hoisting members of the elevator device are connected to the respective fixing points of the support structure of the first wind turbine and second wind turbine. The use of two or more hoisting members prevents rotation of the elevator device in a horizontal plane during hoisting of the elevator device.
The elevator device may comprise a support frame, and in which the support frame carries a container which is connected to the support frame in a releasable manner. For example, the container consists of a standard ISO container having corner castings. The corner castings of the container may be connected to the support frame using twist locks.
It is possible that the support frame comprises the driving unit and the hoisting member, and in which, when the support frame carrying the container has been elevated to the platform, the container is disconnected from the support frame and connected to the support structure of the wind turbine, and in which the hoisting member is driven by the driving unit of the support frame for suspending the support frame from the fixing point and lowering the support frame from the platform to the vessel while the container remains connected to the support structure of the wind turbine. The support frame that has been lowered onto the vessel can be connected subsequently to another container. As a result, a single support frame can be used for delivering a plurality of containers to a number of wind turbines.
It is possible that the support structure of the wind turbine is provided with guide members for guiding the elevator device to a predefined position when the elevator device is elevated to the platform. The elevator device may be locked by locking members with respect to the support structure when the elevator device has been elevated to the platform. In that case, the elevator device is suspended from the support structure by means of the locking members and the driving unit for driving the hoisting member can be shut off.
It is possible that the or each driving unit comprises an electromotor and electrical accumulators for feeding the electromotor. The or each elevator device may be driven in a fully autonomous manner, i.e. it is not necessary to supply energy from an external energy source.
The invention also relates to an assembly comprising a vessel and an elevator device for personnel and/or goods, which elevator device is provided with a driving unit and at least one hoisting member, which can be driven by the driving unit. The assembly according to the invention may be constructed as described above. The assembly may also be used for gaining access to other offshore structures than offshore wind turbines.
For example, the elevator device has a lower end, in which the assembly comprises a lifting device which is situated between the vessel and the lower end of the elevator device, in which the lifting device can be displaced between an extended position and a retracted position, in which the lifting device comprises an actuating member for urging the lifting device from the retracted position to the extended position, and in which the lifting device in its extended position can have a stationary state, in which the lifting device is maintained in its extended position, and a released state, in which the lifting device is released from its extended position for allowing displacement of the lifting device between the extended position and the retracted position.
The lifting device of the assembly may comprise a cushioning device for cushioning the displacement of the lifting device from the extended position to the retracted position. The lifting device may be integrated with the elevator device. For example, the lifting device comprises a plurality of support legs, in which each support leg can be displaced in a sliding manner between the extended position and the retracted position. Each support leg may be provided with a hydraulic cylinder for actuating the support leg from the retracted position to the extended position. The cushioning device may be integrated with the hydraulic cylinders. Furthermore, the undersides of the support legs which abut against the vessel may be provided with cushioning elements.
The elevator device of the assembly may comprises a motion compensator device for compensating the motion of the elevator device when it is being suspended by the hoisting member relative to the motion of the vessel floating in the sea. The motion compensator device can have a stationary state and an active state. The motion compensator device is a rigid structure in its stationary state. In the active state, the motion compensator device guarantees that the hoisting member is kept taut when the elevator device is resting on the vessel.
The driving unit of the elevator device of the assembly may comprise a winch, in which the hoisting member comprises a hoisting cable which is winded up on the winch, and in which the motion compensator device comprises an arm which is pivotably connected to the lifting device, and a resilient member which is connected between the arm and the lifting device, and in which the arm is provided with a pulley, and in which the hoisting cable is guided from the winch around the pulley.
The elevator device of the assembly may comprise at least two hoisting members, for example two hoisting cables. It is also possible for the elevator device of the assembly to comprise a support frame and a container which is connected to the support frame in a releasable manner. For example, the container consists of a standard ISO container having corner castings. The corner castings of the container may be connected to the support frame using twist locks. The driving unit may comprise an electromotor and electrical accumulators for supplying energy to the electromotor.
The invention also relates to an elevator device for an assembly as described above. The invention will now be described in more detail by way of example with reference to the accompanying figures. Figure 1 shows an assembly of a vessel and an elevator device according to a first embodiment of the invention.
Figure 2a-2d show an elevator device according to a second embodiment of the invention.
Figures 3a-3f show schematic side views of an elevator device being hoisted up to a platform of an offshore wind turbine.
An offshore wind farm comprises a number of offshore wind turbines. Figure 1 shows one offshore wind turbine 1 of the offshore wind farm. The other wind turbines in the wind farm may be constructed in a corresponding or identical manner. The wind turbine 1 comprises a tower 2 which is installed in a sea 3 having a water surface 4. A support structure having a boom 10 and a platform 6 is attached to the tower 2. The tower 2 has bumper bars 7 and a ladder 8 which leads to the platform 6. The platform 6 is used for delivering personnel and heavy equipment to the tower. The boom 10 is provided with two fixing points 1 1 and guide members 32.
An assembly comprising a vessel 14 and an elevator device 18 is brought below the fixing points 1 1 of the boom 10. The elevator device 18 is mounted on the deck 15 of the vessel 14. In the exemplary embodiment shown in figure 1 , the elevator device 18 constitutes a container having a bottom, four side walls extending from the bottom, and a roof 19. The container 18 may be provided with a workshop and residence means, such as a bed, kitchen, and/or toilet (not shown). The container 18 also has corner castings 33 which can be locked with respect to the boom 10. The corner castings are defined by standard ISO dimensions, for example. A driving unit 20 is mounted on the roof 19 of the container 18. The driving unit is constructed as a winch 20. Two hoisting cables 21 can be wound and unwound by the winch 20.
The container 18 comprises a motion compensator device 26 for keeping the hoisting cables 21 taut during heave motions of the vessel 14. The motion compensator device 26 has two arms 27 which can be pivoted with respect to respective pivot axes 28. Both arms 27 are connected to the roof 19 of the container 18 by means of respective resilient members 29. The hoisting cables 21 are guided from the winch 20 over a number of pulleys 30, including a pulley 30 which is attached to the arms 27. The point of application of the hoisting forces is defined by the pulleys 31 . The arms 27 may pivot about the pivot axes 28 (as shown in dotted lines in figure 1 ), which varies the length of the portion of hoisting cable 21 between the winch 20 and the pulley 31 . Thus, the motion compensator device 26 may compensate for heave motions of the vessel 14.
The container 18 comprises a lifting device for lifting the container 18 with respect to the deck 15 of the vessel 14. In this exemplary embodiment, the lifting device comprises four support legs 23, which can be displaced in a sliding manner between an extended position and a retracted position. The support legs 23 can be actuated from the retracted position to the extended position by means of hydraulic cylinders or other actuating members 24. The hydraulic cylinders 24 may be adapted for cushioning the displacement of the support legs 23 between the extended position and the retracted position. The supporting legs 23 also have shock damping elements arranged at their undersides.
Figures 2a-2c show a second embodiment of the elevator device according to the invention. The same reference numerals are used for designating the same or
corresponding features. The elevator device 18 as shown in figures 2a-2c comprises a support frame 40 and a container 41. The container 41 constitutes a standard ISO container having corner castings 42 which can be connected to the support frame 40, for example by means of twist locks. The support frame 40 is provided with two side supports 46 and a top frame 47 which connects the side supports 46. The support legs 23 are integrated with the side supports 46. The top frame 47 has four corner castings 33 for locking with the boom 10 of the tower 2 of the wind turbine 1 . The winch 20, the motion compensation device 26 and the hoisting cables 21 are mounted on the top frame 47. The winch 20 can be driven by an electrical motor 48. The energy for the electrical motor 48 is supplied by electrical accumulators 43. The hydraulic cylinders 24 for actuating the support legs 23 are supplied with hydraulic fluid using hydraulic accumulators 44.
The operation for delivering an elevator device to the wind turbine 1 will now be described with reference to figures 3a-3f. The operation of the elevator device 18 and its components may be remotely controlled.
The hydraulic cylinders 24 of support legs 23 are actuated for urging the support legs 23 to the extended position. As a result, the elevator device 18 is lifted from the deck 15 of the vessel 14, for example to a height of 0.5 m above the deck 15. The hydraulic cylinders 24 of the support legs 23 maintain the support legs 23 in the extended position. The support legs 23 of the elevator device 18 rest on the deck 15. The motion of the vessel 14 and the motion of the elevator device 18 are linked to each other. The stern 16 of the vessel 14 is stabilised against the bumper bars 7 of the tower 2 using the thrust of the propulsion system of the vessel 14. A person steps from the vessel 14 onto the ladder 7 and climbs up to the platform 6. An auxiliary line 49 is lowered to the vessel 14 floating below the fixing points 1 1 of the boom 10 (figure 3a). The auxiliary line 49 is connected to the hoisting cables 21 which are subsequently pulled up and fitted to the fixing points 1 1 .
The hoisting cables 21 are pulled taut such that the motion compensator device 26 can compensate for both a lengthening and a shortening of the hoisting cables 21 . Then, at the top of a heave motion of the vessel 14 (see dotted lines in figure 3d), the hydraulic cylinders 24 of the support legs 23 are released and the winch 23 is driven to haul in the hoisting cables 21 . Thus, the elevator device 18 becomes suspended from the hoisting cables 21 attached to the fixing points 1 1 . If the elevator device 18 has been hoisted up over a relatively small distance only, a heave motion of the vessel 14 which is higher than expected may cause a collision between the deck 15 and the support legs 23 of the elevator device 18. As a result of the release of the support legs 23, they can be slid inwards from the extended position to the retracted position without causing damage to the lower side of the elevator device 18.
The elevator device 18 is elevated further by the hoisting cables 21 until the elevator device 18 is received by the guide members 32. The hoisting cables 21 pull the elevator device 18 against the boom 10, after which the corner castings 33 of the elevator device 18 can be locked to the boom 10, for example using twist locks. The elevator device 18 can be used for delivering personnel and/or equipment to the platform 6 of the wind turbine 1 .
The elevator device 18 can be lowered to a vessel floating below the fixing points 1 1 . This can be achieved by carrying out the steps described above in the reverse order. The vessel 14 carrying the elevator device 18 can then be brought to another offshore wind turbine in the offshore wind farm. The vessel 14 can also be provided with a plurality of elevator devices 18. The vessel 14 can then deliver a plurality of elevator devices 18 to various offshore wind turbines in the offshore wind farm. This results in very efficient and flexible maintenance of the offshore wind farm.
The invention is not limited to the exemplary embodiments shown in the figures. The skilled person may apply various modifications which are within the scope of the invention. For example, the hoisting members may also be constructed as wires or chains. In addition, the invention is not limited to use with maintenance of offshore wind turbines. The method as described above and/or as claimed in the appended claims may also be used for transferring personnel and/or goods from the vessel to an offshore platform or any other stationary structure at sea.

Claims

Claims
1 . A method for use with maintenance of an offshore wind farm comprising a plurality of offshore wind turbines (1 ), in which each wind turbine (1 ) is provided with a tower (2), which is installed in a sea (3) having a water surface (4), a support structure, which is attached to the tower (2) above the water surface (4), and which support structure is provided with a platform (6), in which the support structure is provided with at least one fixing point (1 1 ), and in which the method comprises:
- providing an assembly comprising a vessel (14) and an elevator device (18) for personnel and/or goods, which elevator device (18) is provided with a driving unit (20) and at least one hoisting member (21 ), which can be driven by the driving unit (20),
- moving the vessel (14) floating in the sea (3) to a first wind turbine (1 ) and below the fixing point (1 1 ) of the support structure of the first wind turbine (1 ),
- connecting the hoisting member (21 ) of the elevator device (18) to the fixing point (1 1 ) of the support structure of the first wind turbine (1 ),
- driving the hoisting member (21 ) by the driving unit (20) of the elevator device (18) for suspending the elevator device (18) from the fixing point (1 1 ) and elevating the elevator device (18) from the vessel (14) to the platform (6) of the first wind turbine (1 ) for allowing transfer of personnel and/or goods between the elevator device (18) and the platform (6) of the first wind turbine (1 ),
- when the elevator device (18) has been elevated to the platform (6), driving the hoisting member (21 ) by the driving unit (20) of the elevator device (18) for suspending the elevator device (18) from the fixing point (1 1 ) and lowering the elevator device (18) from the platform (6) to the vessel (14),
- disconnecting the hoisting member (21 ) of the elevator device (18) from the fixing point (1 1 ) of the support structure of the first wind turbine (1 ),
- moving the vessel (14) floating in the sea to a second wind turbine (1 ) and below the fixing point (1 1 ) of the support structure of the second wind turbine (1 ),
- connecting the hoisting member (21 ) of the elevator device (20) to the fixing point (1 1 ) of the support structure of the second wind turbine (1 ),
- driving the hoisting member (21 ) by the driving unit (20) of the elevator device (18) for suspending the elevator device (18) from the fixing point (1 1 ) and elevating the elevator device (18) from the vessel (14) to the platform (6) of the second wind turbine (1 ) for allowing transfer of personnel and/or goods between the elevator device (18) and the platform (6) of the second wind turbine (1 ).
2. A method as claimed in claim 1 , in which the assembly comprises a second elevator device (18) for personnel and/or goods, which second elevator device (18) is provided with a driving unit (20) and at least one hoisting member (21 ), which can be driven by the driving unit (20), and in which the vessel (14) floating in the sea (3) is moved to a third wind turbine (1 ) and below the fixing point (1 1 ) of the support structure of the third wind turbine (1 ), and in which the hoisting member (21 ) of the second elevator device (18) is connected to the fixing point (1 1 ) of the support structure of the third wind turbine (1 ), and in which the hoisting member (21 ) is driven by the driving unit (20) of the second elevator device (18) for suspending the second elevator device (18) from the fixing point (1 1 ) and elevating the second elevator device (18) from the vessel (14) to the platform (6) of the third wind turbine (1 ) for allowing transfer of personnel and/or goods between the elevator device (18) and the platform (6) of the third wind turbine (1 ).
3. A method as claimed in claim 1 or 2, in which the or each elevator device (18) has a lower end, and in which the assembly comprises a lifting device (23) which is situated between the vessel (14) and the lower end of the elevator device (18), in which the lifting device (23) can be displaced between an extended position and a retracted position, in which the lifting device (23) comprises an actuating member (24) for urging the lifting device (23) from the retracted position to the extended position, and in which the lifting device (23) in its extended position can have a stationary state, in which the lifting device (23) is maintained in its extended position, and a released state, in which the lifting device (23) is released from its extended position for allowing displacement of the lifting device (23) between the extended position and the retracted position, and in which the lower end of the elevator device (18) is lifted from the vessel (14) by actuating the actuating member (24) for urging the lifting device (23) from the retracted position to the extended position, and in which the lifting device (23) in its extended position is kept in its stationary state before the hoisting member (21 ) is driven by the driving unit (20) of the elevator device (18), and in which the lifting device (23) in its extended position is released to its released state after the hoisting member (21 ) has been driven by the driving unit (20) of the elevator device (18) and the elevator device (18) has been suspended from the fixing point (1 1 ).
4. A method as claimed in claim 3, in which the lifting device (23) comprises a cushioning device for cushioning the displacement of the lifting device (23) from the extended position to the retracted position.
5. A method as claimed in claim 3 or 4, in which the lifting device (23) is integrated with the elevator device (18).
6. A method as claimed in claim 4 or 5, in which the lifting device comprises a plurality of support legs (23), in which each support leg (23) can be displaced in a sliding manner between the extended position and the retracted position.
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7. A method as claimed in any of claims 3-6, in which the or each elevator device (18) comprises a motion compensator device (26) for compensating the motion of the elevator device (18) being suspended by the hoisting member (21 ) from the fixing point (1 1 ) relative to the motion of the vessel (14) floating in the sea (3).
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8. A method as claimed in claim 7, in which the driving unit comprises a winch (20), and in which the hoisting member comprises a hoisting cable (21 ) which is winded up on the winch (20), and in which the motion compensator device (26) comprises an arm (27) which is pivotably connected to the elevator device (18), and a resilient member (29) which is
15 connected between the arm and the elevator device (18), and in which the arm (27) is
provided with a pulley (30), and in which the hoisting cable (21 ) is guided from the winch (20) via the pulley (30) to the fixing point (1 1 ).
9. A method as claimed in any of the preceding claims, in which the support structure of 20 each wind turbine (1 ) is provided with at least two fixing points (1 1 ), which are distanced with respect to each other, and in which the or each elevator device (18) comprises at least two hoisting members (21 ), and in which the hoisting members (21 ) of the elevator device (18) are connected to the respective fixing points (1 1 ) of the support structure of the first and second wind turbine (1 ).
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10. A method as claimed in one of the preceding claims, in which the elevator device (18) comprises a support frame (40), and in which the support frame (40) carries a container (41 ) which is connected to the support frame (40) in a releasable manner.
30 1 1 . A method as claimed in claim 10, in which the support frame (40) comprises the
driving unit (21 ) and the hoisting member (21 ), and in which, when the support frame (40) carrying the container (41 ) has been elevated to the platform (6), the container (41 ) is released from the support frame (40) and connected to the support structure of the wind turbine (1 ), and in which the hoisting member (21 ) is driven by the driving unit (20) of the
35 support frame (40) for suspending the support frame (40) from the fixing point (1 1 ) and
lowering the support frame (40) from the platform (6) to the vessel (14) while the container (41 ) remains connected to the support structure of the wind turbine (1 ).
12. A method as claimed in one of the preceding claims, in which the support structure of the first and second wind turbine (1 ) is provided with guide members (32) for guiding the elevator device (18) to a predefined position when the elevator device (18) is elevated to the platform (6).
13. A method as claimed in one of the preceding claims, in which the or each driving unit (20) comprises an electromotor (48) and electrical accumulators (43) for supplying electrical energy to the electromotor (48).
14. A method as claimed in one of the preceding claims, in which personnel and/or goods are transferred from the elevator device (18) to the platform (6) of the first wind turbine (1 ) after the elevator device (18) has been elevated to the platform (6), and in which maintenance activities are carried out at the first wind turbine (1 ) by said personnel and/or using said goods.
15. An assembly comprising a vessel (14) and an elevator device (18) for personnel and/or goods, which elevator device (18) is provided with a driving unit (20) and at least one hoisting member (21 ), which can be driven by the driving unit (20).
16. An assembly as claimed in claim 14, in which the elevator device (18) has a lower end, and in which the assembly comprises a lifting device (23) which is situated between the vessel (14) and the lower end of the elevator device (18), in which the lifting device (23) can be displaced between an extended position and a retracted position, in which the lifting device (23) comprises an actuating member (24) for urging the lifting device (23) from the retracted position to the extended position, and in which the lifting device (23) in its extended position can have a stationary state, in which the lifting device (23) is maintained in its extended position, and a released state, in which the lifting device (23) is released from its extended position for allowing displacement of the lifting device (23) between the extended position and the retracted position.
17. An elevator device for an assembly according to claim 15 or 16.
PCT/NL2011/050155 2010-03-04 2011-03-04 Method for use with maintenance of offshore wind turbines, and assembly comprising a vessel and a lift device WO2011108933A1 (en)

Applications Claiming Priority (2)

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NL2004337A NL2004337C2 (en) 2010-03-04 2010-03-04 Method for use with maintenance of offshore wind turbines, and assembly comprising a vessel and a lift device.
NL2004337 2010-03-04

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WO2019001659A1 (en) * 2017-06-30 2019-01-03 Vestas Wind Systems A/S A method for servicing a wind turbine
EP3450749A1 (en) * 2017-08-31 2019-03-06 General Electric Company Hoistable induction and cooling unit for wind turbine maintenance
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EP4102063A1 (en) * 2021-06-10 2022-12-14 Vattenfall AB Offshore wind turbine comprising a platform with attached equipment container
EP4102064A1 (en) * 2021-06-10 2022-12-14 Vattenfall AB Offshore wind turbine comprising a service platform and a crane arrangement

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EP4102063A1 (en) * 2021-06-10 2022-12-14 Vattenfall AB Offshore wind turbine comprising a platform with attached equipment container
EP4102064A1 (en) * 2021-06-10 2022-12-14 Vattenfall AB Offshore wind turbine comprising a service platform and a crane arrangement

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