Hoisting assembly, hoisting system and method therefor

Abstract

Hoisting assembly (27), wherein the hoisting assembly comprises: a chain (20) that is configured to be attached to a crane (8) or outrigger of a wind turbine platform (6); a motor device (26) that is operatively connected to the chain and is configured to move along the chain, wherein the motor device is provided with a hook (28) that is configured to connect to a load on a vessel (22); and a heave compensation system (130) that is operatively connected to the motor device, wherein the heave compensation system is configured to generate a heave movement signal based on the heave movement of the vessel and to transmit the heave movement signal to the motor device, wherein the motor device is configured to compensate the heave movement of the vessel by moving along the chain based on the heave movement signal received from the heave compensation system.

Description

[0001] HOISTING ASSEMBLY, HOISTING SYSTEM AND METHOD THEREFOR

[0002] The present invention relates to a hoisting assembly. The present invention further relates to a hoisting system that comprises the hoisting assembly, and a method for hoisting a load to a wind turbine platform. The hoisting assembly and hoisting systems are also configured to be used to hoist a load to a wind turbine platform.

[0003] Wind turbines are generally provided with a platform. This platform can be used as a base for personnel when performing maintenance operations on the wind turbine. Maintenance equipment needs to be transferred from a vessel, for example a cargo vessel or a crew transfer vessel, to the wind turbine platform. The wind turbine platform is normally positioned substantially higher than the sea level. Therefore, the cargo needs to be transferred upwards. To achieve this, a wind turbine crane may be positioned on the wind turbine platform. The wind turbine crane is configured to hoist cargo and / or crew, or other materials, to the wind turbine platform.

[0004] A problem of hoisting cargo from the vessel to the wind turbine platform by using the wind turbine crane is that the vessel may be subject to heave movement. This heave movement can for example be caused by waves that are present on the body of water on which the vessel floats. The heave movement can cause damage to the hoisted cargo, as the heave movement can cause the deck of the ship to bump onto the cargo during the hoisting of the cargo.

[0005] To prevent damage to the cargo during hoisting, the wind turbine crane may comprise a mechanism to compensate the heave movement of a vessel or ship. An example of such a wind turbine crane is disclosed in EP 3 653 484 Al. The wind turbine crane is provided with a hoisting mechanism that comprises hoisting cable. The wind turbine crane is provided with a ranging device that is adapted to provide data relating to a detected distance from a reference point of the wind turbine to the ship. Furthermore, a motion reference unit (MRU) may be positioned on the ship. The MRU is adapted to provide data relating to a detected motion of the ship. The hoisting cable is then moved in response to the detected motion of the ship.

[0006] A downside of the system disclosed in EP 3 653 484 Al is that the hoisting cable is always present on the wind turbine crane. This is disadvantageous as the hoisting cable is in this way continually subject to weather conditions, thereby reducing the lifetime of the system.

[0007] It is an object for the present invention to obviate or at least reduce the abovementioned problems. In particular, it is an object of the present invention to improve the lifetime of a heave compensating hoisting assembly.

[0008] This object is achieved by a hoisting assembly, wherein the hoisting assembly comprises:

[0009] a chain that is configured to be attached to a crane or outrigger of a wind turbine platform;a motor device that is operatively connected to the chain and is configured to move along the chain, wherein the motor device is provided with a hook that is configured to connect to a load on a vessel; and

[0010] a heave compensation system that is operatively connected to the motor device, wherein the heave compensation system is configured to generate a heave movement signal based on the heave movement of the vessel and to transmit the heave movement signal to the motor device,

[0011] wherein the motor device is configured to compensate the heave movement of the vessel by moving along the chain based on the heave movement signal received from the heave compensation system.

[0012] An advantage of the hoisting assembly is that the hoisting assembly can be easily attached and detached from the wind turbine platform. The chain of the assembly can be attached to and detached from the boom from a wind turbine crane that is already present on a wind turbine platform. As the motor device is configured to be coupled to and be moved along the chain, also the motor device can be in a way attached to and detached from the wind turbine crane.

[0013] It is noted that the present invention is not limited to be applied to an existing crane on a wind turbine platform. The invention can for example also be applied on an outrigger with a hoisting eye that is positioned on the wind turbine platform.

[0014] As the chain, and particularly the motor device, are the most expensive part of a hoisting system, it is advantageous that the chain and the motor device can be stored safely in another location. For example, the chain and / or motor device can be stored in the vessel which brings the cargo the wind turbine platform. Alternatively, the chain and / or motor device can also be stored inside the wind turbine, for example in the tower thereof. In this way, the chain and motor device are only exposed to weather conditions when actually being used for hoisting. In this way, the wear on the hoisting assembly is effectively reduced. As a consequence, the operation costs of the hoisting assembly are also reduced.

[0015] A further advantage of the hoisting assembly is that, due to the ability to store the hoisting assembly in other locations than attached to the wind turbine crane, maintenance on the hoisting assembly is easier. Maintenance can for example be performed in the safe and sheltered conditions on the vessel or inside the (tower of the) wind turbine which brings the cargo to the wind turbine platform. Alternatively, or additionally, the hoisting assembly can be easily brought to a specialised workshop.

[0016] An even further advantage is that, because a hoisting assembly is only attached to the wind turbine crane when it needs to be used, less units of the hoisting assembly are necessary. In contrast to the hoisting systems of the prior art, which are always present on the wind turbine crane and thus every wind turbine crane on every wind turbine needs to be provided with a hoistingsystem. This further reduces the operation costs of the hoisting assembly according to the invention.

[0017] A further advantage compared to the hoisting systems of the prior art which use a cable, is that the hoisting assembly of the present invention does not necessitate the use of a winch. This simplifies the hoisting assembly.

[0018] An advantage of the heave compensation system is that the motion of the vessel of which cargo is transported towards the wind turbine platform can be compensated. The compensation of the heave movement, which can be described as the vertical movement of the vessel, prevents any damage to the vessel, particularly the deck of the vessel, and / or the cargo itself. The heave compensation system generates a heave movement signal which indicates if and to what extent the vessel is subject to a heave movement. Based on the heave movement signal, the motor device can move itself along the chain to compensate the heave movement. In this way, the relative distance between the motor device and the vessel can be kept constant. As the cargo is hoisted with the motor device, also the relative distance between the cargo and the vessel is constant. Therefore, any collision between the cargo and the vessel during hoisting is prevented.

[0019] A further advantage is that due to the heave compensation of the heave compensation system the personnel working on the vessel can work more safely. In particular, the chance of collision of the personnel with the cargo is reduced. Furthermore, the chance of personnel getting stuck between the cargo and the vessel is also reduced.

[0020] The heave compensation system is operatively coupled to the motor device. The operative coupling may be wireless or mechanical. Generally, part of the heave compensation system will be configured to be positioned on the vessel in order to determine the heave movement of the vessel.

[0021] The motor device compensates the heave movement of the vessel by moving along the chain in a synchronized manner with respect to the heave movement of the vessel.

[0022] In an embodiment the heave compensation system is configured to be attached to the vessel.

[0023] By attaching the heave compensation system to the vessel there is a direct connection between the heave compensation system and the vessel, which provides the possibility to provide a direct measurement of the heave movement of the vessel. In this way, the relative movement between the motor device and the vessel can be determined.

[0024] In an embodiment the heave compensation system comprises a lever that is connected to the motor device with a rotation axis and is configured to be attached to the vessel such that the heave movement of the vessel causes a rotational movement of the lever around the rotation axis, and wherein the rotational movement generates the heave movement signal.The rotational movement can generate a heave movement signal in different ways. For example, the heave movement signal may be based on the rotational force, rotational offset, or rotational torque of the lever.

[0025] An advantage of the lever is that a simple design can be used to measure the relative vertical movement between the motor device and the vessel. As the design is simple, production costs thereof are also relatively low.

[0026] In an embodiment the heave compensation system further comprises a rod that is arranged between the lever and the vessel for attachment of the heave compensation system to the vessel.

[0027] An advantage of the rod is that the lever can be effectively attached to the vessel. When the vessel moves vertically, the rod will move vertically which will rotate the lever around its rotation axis. Based on this movement, the heave movement signal can be generated.

[0028] The rod can be coupled to the vessel either directly or indirectly. For example, the rod may be coupled to the vessel via a mechanical connection. Alternatively, the rod may be (indirectly) coupled to the vessel by an operator that is standing on the vessel which holds the rod in his hands.

[0029] In an embodiment the lever extends in a lever direction that is angled with respect to a chain direction in which the chain extends.

[0030] The lever extends in the lever direction in a state of rest, i.e. a state without a force acting on the lever due to the heave movement of the vessel. In a preferred embodiment, the lever angle is in the range of 20-150 degrees, more preferably in the range of 40-130 degrees, and most preferably is in the range of 60-110, degrees, for example 90 degrees.

[0031] The chain will normally extend in the direction of the force of gravity. The vertical movement of the vessel will also be directed in the direction of the force of gravity. Due to the angle of the lever with the chain direction, a torque will be exerted on the lever, thereby causing it to rotate around its rotation axis.

[0032] In an embodiment the heave compensation system further comprises a chain measurement device or cable measurement device, wherein the chain measurement device is configured to generate a heave movement signal based on movement of the chain or a power cable with respect to the vessel.

[0033] The chain measurement device or the cable measurement device is preferably positioned at a fixed position above the deck of the vessel.

[0034] The chain is attached to the crane which is positioned on the wind turbine platform, thus the chain has no relative movement with respect to the wind turbine platform or wind turbine. Therefore, the relative movement of the chain with respect to the vessel can be used to determine the heave movement of the vessel.

[0035] The motor device comprises a power cable which supplies power to motor device. The power cable is attached to the motor device. The motor device may have a relative movement withrespect to the chain. The movement of the motor device along the chain is known, for example by a controller of the motor device which controls the drive of the motor device. Therefore, the relative movement of the power cable with respect to the vessel can be determined when the movement of the motor device with respect to the chain is taken into account.

[0036] An advantage of the chain measurement device or cable measurement device is that a simple design can be used to measure the relative vertical movement between the motor device and the vessel. As the design is simple, production costs thereof are also relatively low.

[0037] In an embodiment the chain measurement device or cable measurement device comprises a spring-loaded or constant torque motor actuated wheel, wherein the chain or cable is positioned on the spring -loaded or constant torque motor actuated wheel.

[0038] In the embodiment that the chain is used, a spring-loaded or constant torque motor actuated chain wheel is used as a chain measurement device.

[0039] The spring-loaded or constant torque motor actuated wheel is biased or tensioned such that the chain or cable will be tight. The wheel may use the amount of rotation in combination with the circumference of the wheel to determine the amount of chain or cable that has passed the chain measurement device or cable measurement device. Based on this, the heave movement signal may be generated and transmitted to the motor device.

[0040] In an embodiment the chain measurement device or cable measurement device comprises a reel, wherein the chain or power cable is attached to the reel and configured to wind be winded on the reel, and wherein the reel is biased to wind up the chain or power cable.

[0041] The reel may use the amount of rotation in combination with the circumference of the wheel to determine the amount of chain or cable that has passed the chain measurement device or cable measurement device. Based on this, the heave movement signal may be generated and transmitted to the motor device.

[0042] In an embodiment the chain measurement device comprises a sensor that measures the number of shackles of the chain that passes the sensor.

[0043] The sensor that measures the number of shackles could be a light sensor or a camera. The sensor could also be cooperating with detection units that are positioned on the chain.

[0044] Based on the number of shackles that have passed the chain measurement device, the heave movement signal may be generated and transmitted to the motor device.

[0045] In an embodiment the heave compensation system comprises a motion reference unit (MRU) that is configured to be located on the vessel, wherein the MRU is configured to generate a heave movement signal based on the heave movement of the vessel and to transmit the heave movement signal to the motor device.

[0046] The MRU may be connected to a MRU-controller that is configured to send the heave movement signal to the motor device, for example the controller of the motor device.Motion reference units may also be denoted as inertial measurement unit (IMU). The MRU may use one or more of accelerometers, gyroscopes, and / or magnetometers to measure the specific position, or change of position, of an object. The MRU may determine the relative position of an object to a reference location for example by measuring the acceleration and integrating the acceleration twice to acquire its position.

[0047] In an embodiment the heave compensation system comprises an extendable elongated element that extends between a first and a second end, the first end being attached to the vessel and the second end being attached to the fixed world, such as the wind turbine crane or chain, wherein the extension or contraction of the extendable elongated element is configured to generate the heave movement signal.

[0048] The extendable elongated element may be a rope-like element. The extendable elongated element may comprise an elastic and / or spring-like part. The extension of the extendable elongated element can be used to generate the heave movement signal. For example, at rest the length of the extendable elongated element from the first end to the second end may be X meters. During the heave movement of the vessel, the length from the first end to the second end may become (X + Y) meters. Based on the Y meters extension (or contraction) of the extendable elongated element, the heave movement signal can be determined.

[0049] In an embodiment the motor device comprises a drive and a chain wheel, wherein the drive is configured to rotate the chain wheel to move the motor device along the chain.

[0050] The drive may be operatively coupled to a controller of the motor device. The rotation of the chain wheel causes the motor device to be moved along the chain. The chain wheel can also be denoted as sprocket wheel or toothed wheel. The sprockets or tooths of the chain wheel are configured to grip onto or into the shackles such that the rotation of the chain wheel moves the motor device along the chain.

[0051] In an embodiment the chain is configured to be detachable from the wind turbine crane. Due to the chain being detachable the advantages as mentioned for the hoisting assembly can be achieved, in particular the lower operation costs, longer lifetime and easier maintenance.

[0052] In an embodiment the motor device is detachable from the chain.

[0053] Due to the motor device being detachable from the chain the advantages as mentioned for the hoisting assembly can be achieved, in particular the lower operation costs, longer lifetime and easier maintenance.

[0054] The invention further relates to a hoisting system, wherein the hoisting system comprises:

[0055] a hoisting assembly according to the invention; and

[0056] a wind turbine crane that is located on a wind turbine platform,

[0057] wherein the chain of the hoisting assembly is attached to the wind turbine crane.The hoisting system has similar effects and advantages as described for the hoisting assembly. All features as described for the hoisting assembly can be combined, either individually or together, with the hoisting system.

[0058] It is noted that all embodiments described for the hoisting assembly and which use terminology such as configured to be attached to a wind turbine crane, can be rephrased to attached to a wind turbine crane.

[0059] In an embodiment the hoisting system further comprises:

[0060] a vessel,

[0061] wherein the at least part of the heave compensation system is located on or attached to the vessel.

[0062] The invention further relates to a method for hoisting a load to a wind turbine platform, wherein the method comprises:

[0063] providing a hoisting system according to the invention;

[0064] connecting the chain to the wind turbine crane;

[0065] connecting the motor device to the chain;

[0066] connecting the load that is positioned on the vessel to the hook of the motor device; and

[0067] moving the motor device upwards along the chain towards the wind turbine platform. The method has similar effects and advantages as described for the hoisting assembly and the hoisting system. All features as described for the hoisting assembly and hoisting system can be combined, either individually or together, with the method.

[0068] In an embodiment the method further comprises:

[0069] generating, with the heave compensation system, the heave movement signal based on the heave movement of the vessel;

[0070] transmitting the heave movement signal to the motor device; and

[0071] compensating the heave movement of the vessel by moving the motor device along the chain based on the heave movement signal received from the heave compensation system.

[0072] Further advantages, features and details are elucidated on the basis of preferred embodiments thereof, wherein reference is made to the accompanying drawings, wherein:

[0073] figure 1, a schematic illustration of a wind turbine provided with a wind turbine platform;

[0074] figure 2, a schematic illustration of a first stage of hoisting a load from a vessel to the wind turbine platform;

[0075] figure 3, a schematic illustration of a second stage of hoisting a load from a vessel to the wind turbine platform;figure 4, a schematic illustration of a third stage of hoisting a load from a vessel to the wind turbine platform;

[0076] figure 5, a schematic illustration of a fourth stage of hoisting a load from a vessel to the wind turbine platform;

[0077] figure 6, a schematic illustration of a fifth stage of hoisting a load from a vessel to the wind turbine platform;

[0078] figure 7, a first example of a heave compensation system of a hoisting assembly; figure 8, a second example of a heave compensation system of a hoisting assembly; figure 9, a third example of a heave compensation system of a hoisting assembly; figure 10, a fourth example of a heave compensation system of a hoisting assembly; figure 1 la, a first example of a motor device; and

[0079] figure 1 lb, a second example of a motor device.

[0080] Wind turbine 2 (figure 1) comprise mast 4. Attached to mast 4 is wind turbine platform 6. Furthermore, wind turbine crane 8 is provided on wind turbine platform 6. Wind turbine crane 8 is rotatable about crane axis 12, such that boom 14 of wind turbine crane 8 can be rotated around crane axis 12. In this way, hoisting end 16 of boom 14 can be positioned either above wind turbine platform 6 or above sea 10. Wind turbine 2 is positioned on the seabed of sea 10. Sea 10 has sea level L. Wind turbine platform 6 is in this illustrated embodiment positioned on height H with respect to sea level L. If cargo, equipment and / or personnel need to be transported onto wind turbine platform 6, the cargo, equipment and / or personnel needs to be hoisted upwards for at least part of total height H. No hoisting assembly is provided on wind turbine crane 8.

[0081] Hoisting end 16 (figure 2) is, compared to figure 1, rotated around crane axis 12 such that hoisting end 16 is provided above vessel 22. Vessel 22 is a maintenance vessel and is provided with cargo 24 which contains equipment and / or tools to perform maintenance on wind turbine 2. Operator 18 can transfer himself onto wind turbine platform 6 by means of ladder 5 provided on mast 4 of wind turbine 2. At hoisting end 16 chain 20 is attached. Chain 20 may have been attached to hoisting end 16 of boom 14 by operator 18.

[0082] Chain 20 extends from first chain end 20a to second chain end 20b. Chain 20 comprises a plurality of shackles which are connected to each other. First chain end 20a is attached to hoisting end 16 of wind turbine crane 8, and second chain end 20b is resting on deck 23 of vessel 22. Motor device 26 is located on vessel 22. Motor device 26 is configured to be operatively coupled to chain 20. Motor device 26 is further provided with a hook onto which cargo 24 can be attached.

[0083] Motor device 26 (figure 3) is attached to chain 20. Motor device 26 and chain 20 together form hoisting assembly 27. Motor device 26 is configured to move along chain 20. In this illustrated embodiment motor device 26 comprises a drive which drives a motor wheel. The motor wheel may be a toothed wheel, sprocket or chain wheel. The motor wheel grips onto the chain, andby rotation of the motor wheel when driven by the drive the motor device 26 can move itself along chain 20. Motor device 26 has moved itself slightly above deck 23 of vessel 22.

[0084] Hook 28 (figure 4) of motor device 26 is coupled to an eye that is provided on top of cargo 24. Drive of motor device 26 drives the motor wheel such that motor device 26 runs along chain 20 in an upward direction. In this way, cargo 24 is lifted from deck 23 of vessel 22. Motor wheel of motor drive 26 keeps rotating such that cargo 24 is hoisted towards wind turbine platform 24 (figure 5).

[0085] When motor device 26 (figure 6) has substantially reached hoisting end 16 of boom 14, in other words has reached first end 20a of chain 20, cargo 24 can be transported onto wind turbine platform 6. To transport cargo 24 onto wind turbine platform 6, boom 14 is rotated around crane axis 12. Motor device 26 can then move downwards along chain 20 to put cargo 24 on wind turbine platform 6. Operator 18 can then decouple hook 28 from cargo 24.

[0086] After use motor device 26 can be uncoupled from chain 20, for example by moving motor device 26 downwards along chain 20 such that motor device 26 goes towards deck 23. Afterwards, first chain end 20a can be uncoupled from hoisting end 16 of boom 14. In this way, chain 20 and motor device 26 can be brought back to vessel 22. Vessel 22 can then sail towards a further wind turbine, for example wind turbine 3, and perform the same steps as disclosed in figures 1-6.

[0087] Vessel 122 may be subject to heave movements, for example because waves are present in sea 110. It is desired that these heave movements are compensated. If these heave movements are not compensated, cargo 124 can be damaged by deck 123 of vessel 122. For example, deck 123 may bump unto cargo 124, thereby damaging either cargo 124 or deck 123. Furthermore, it may be unsafe for personnel to work in the vicinity of cargo 124 during hoisting, as there are large relative movements between deck 123 and cargo 124.

[0088] One possible embodiment for achieving heave compensation with hoisting assembly 127 is illustrated in figure 7. Motion reference unit (MRU) 130 is provided on deck 123. Although MRU 130 in this illustrated embodiment is provided on deck 130, it is clear for the skilled person that any location on vessel 122 is possible. Any location of MRU 130 that comoves with vessel 122 is a suitable location, although it is preferred to locate MRU 130 in the vicinity of the location from where cargo 124 is hoisted from deck 123.

[0089] MRU 130 is configured to measure the relative motion of vessel 122, for example the heave movement of vessel 122 due to waves on sea 110. The relative motion of vessel 122 are sent from MRU 130 towards motor device 126. MRU 130 may generate a heave movement signal which indicates if and to which extend vessel 122 is subject to a heave movement. To this end motor device 126 comprises controller 132 that is configured to receive the heave movement signal from MRU 130. Based on the heave movement signal controller 132 controls the drive of motor device 126 such that the heave movement of vessel 122 is compensated. For example, if the heavemovement signal from MRU 130 indicates that vessel 122 moved 10 centimetres upwards, controller 132 controls drive of motor device 126 such that the motor wheel rotates in such a way that motor device 126, and thereby hook 128 and cargo 124, also move 10 centimetres upwards.

[0090] It is noted that although controller 132 in this illustrated embodiment is positioned on motor device 126, controller 132 may alternatively be positioned on vessel 122, for example on deck 123 of vessel 122. In that embodiment controller 132 may be operatively coupled, for example with a cable, to motor device 126.

[0091] Motion reference units may also be denoted as inertial measurement unit (IMU). The MRU may use one or more of accelerometers, gyroscopes, and / or magnetometers to measure the specific position, or change of position, of an object. The MRU may determine the relative position of an object to a reference location for example by measuring the acceleration and integrating the acceleration twice to acquire its position.

[0092] Figure 8 illustrates another embodiment with which hoisting assembly 227 can achieve heave compensation. Uever 234 is attached to motor device 226 with lever rotation axis 236. In this way, lever 234 is rotatably attached to motor device 226. In rest, lever 234 extends in direction D, which is substantially orthogonal to direction G in which chain 20 extends. Direction G is in general substantially parallel to the direction of the force of gravity. At end 235 of lever 234 rod 238 is attached. Rod 238 can be attached to vessel 222 in different ways, either directly or indirectly. One option, as illustrated in figure 8, is that operator 240 holds rod 238 with hand 242. In a different embodiment rod 238 may be attached to deck 223 of vessel 222. By attaching rod 238 to vessel 222, any heave movement of vessel 222 will result in a movement of rod 238. Rod 238 will act on lever 234, which then rotates around lever rotation axis 236. The rotation of lever 234 around lever rotation axis 236 generates a heave movement signal. The heave movement signal may be generated by measuring the rotational torque, the rotation force, or the rotational offset. Based on the heave movement signal, motor device 226 moves upwards or downwards along chain 220.

[0093] A further possible embodiment to provide heave compensation is illustrated in figure 9. As explained in relation to the other figures, motor device 326 effectively only runs on chain 320. Therefore, the length of chain 320 is not changed. As chain 320 is suspended from hoisting end 16 of boom 14 of wind turbine crane 8, chain 320 does not have a relative speed with respect to wind turbine 302. The relative position of chain 320 with respect to vessel 322 is therefore an excellent reference of the speed and position of vessel 322 with respect to wind turbine 2 or wind turbine platform 6.

[0094] To measure the relative position of chain 320 to vessel 322, chain measurement device 344 is arranged on deck 323 of vessel 322. Chain 320 is arranged through motor device 326 and is guided by guide 346 towards chain measurement device 344. Guide 346 extends in a directionperpendicular to the direction of the force of gravity. It is clear for the skilled person that other angles are also possible. Guide 346 is only configured to guide chain 320 towards chain measurement device 344 and away from cargo 324.

[0095] Chain measurement device 344 comprises a chain wheel that is operatively coupled to chain 320. The chain wheel may be biased with a constant low tensioning downwards, such that chain 320 is always straight or tight. In this way, the position of chain 320 relative to vessel 322 can be measured. For instance, if vessel 322 moves upwards to a wave present in sea 310, chain wheel of chain measurement device 344 will move up chain 320. If vessel 322 moves downwards, chain wheel of chain measurement device 344 will move down chain 320. Chain measurement device 344 is configured to measure how much length of chain 320 moves with respect to vessel 322. For example, chain measurement device 344 may measure the amount of rotation of the chain wheel and calculate the moved chain length based on the amount of rotation and the circumference of the chain wheel. In another embodiment, the moved chain length may be measured by a sensor that detects the number of shackles of chain 320 that pass the sensor.

[0096] Chain measurement device 344 generates a heave movement signal based on the determined moved chain length and sends this heave movement signal to controller 332 of motor device 326. Based on the heave movement signal, controller 332 then moves motor device 326 along chain 320 to compensate the heave movement of vessel 322.

[0097] In an alternative embodiment of figure 9 a power cable may be used in the same way as chain 320 to measure the heave movement of vessel 322. In this embodiment the chain wheel of the measurement device may be changed for a different wheel which effectively acts or grips onto the power cable.

[0098] An even further possible embodiment to provide heave compensation is illustrated in figure 10. In this embodiment power cable 448 is used to determine the heave movement of vessel 422. Power cable 448 is wound up around reel 450. Reel 450 is biased with a constant tensioning such that power cable 448 is always tight. In other words, reel 450 may be spring-loaded. Power cable 448 is guided towards reel 450 by guide 446. Reel 450 may measure the amount of power cable that is wound up by measuring the rotation of reel 450 in combination with the circumference of reel 450. Based on the wound up power cable, reel 450 may send a heave movement signal to controller 432 of motor device 426.

[0099] Based on the heave movement signal and the movement speed of motor device 426 itself, controller 432 may determine the heave movement of vessel 432. In this way, controller 432 can determine what part of the wounding up of power cable 448 is due to the heave movement of vessel 422 and what part is due to the movement of motor device 426 along chain 420. Based on the determined heave movement of vessel 422, controller 432 may provide instructions to the drive of motor device 426 to compensate the heave movement.Motor device 526 (figure 1 la) comprises housing 552. Hook 528 is attached at the lower end of housing 552 and is configured to receive a load. In housing 552 chain drive wheel 554 is attached. Chain drive wheel 554 is provided with sprockets 556 which are configured to grip into chain links 558 of chain 520. Chain drive wheel 554 is rotatable around rotation axis 560 in both clockwise as well as counterclockwise direction. Chain 520 is positioned around chain drive wheel 554 and subsequently positioned over chain guide 562. Chain guide 562 has in this illustrated embodiment a semicircular surface over which chain 520 can move.

[0100] Motor device 526 is able to move alongside chain 520 by rotating chain drive wheel 554. In this illustrated embodiment, when chain drive wheel 554 is rotated clockwise around rotation axis 560, motor device 526 moves downwards along chain 520. When chain drive wheel 554 is rotated counterclockwise around rotation axis 560, motor device 526 moves upwards along chain 520.

[0101] Motor device 626 (figure 1 lb) is in this illustrated embodiment similar to motor device 526, with the difference that motor device 626 is provided with chain bag 664. Chain bag 664 is positioned over chain guide 662 such that chain 620 is placed in inner space 666 of chain bag 664. In his way part of chain 620 can be stored inside chain bag 664 during operation, such that that chain 620 does not rest on the deck of the vessel. This has the advantage that damage to material on the deck and / or the chain is prevented.

[0102] The present invention is by no means limited to the above described preferred embodiments thereof. The rights sought are defined by the following claims within the scope of which many modifications can be envisaged.

Claims

CLAIMS1. Hoisting assembly, comprising:a chain that is configured to be attached to a crane or outrigger of a wind turbine platform;a motor device that is operatively connected to the chain and is configured to move along the chain, wherein the motor device is provided with a hook that is configured to connect to a load on a vessel; anda heave compensation system that is operatively connected to the motor device, wherein the heave compensation system is configured to generate a heave movement signal based on the heave movement of the vessel and to transmit the heave movement signal to the motor device,wherein the motor device is configured to compensate the heave movement of the vessel by moving along the chain based on the heave movement signal received from the heave compensation system.

2. Hoisting assembly according to claim 1, wherein the heave compensation system is configured to be attached to the vessel.

3. Hoisting assembly according to claim 1 or 2, wherein the heave compensation system comprises a lever that is connected to the motor device with a rotation axis and is configured to be attached to the vessel such that the heave movement of the vessel causes a rotational movement of the lever around the rotation axis, and wherein the rotational movement generates the heave movement signal.

4. Hoisting assembly according to claim 3, wherein the heave compensation system further comprises a rod that is arranged between the lever and the vessel for attachment of the heave compensation system to the vessel.

5. Hoisting assembly according to claim 3 or 4, wherein the lever extends in a lever direction that is angled with respect to a chain direction in which the chain extends.

6. Hoisting assembly according to claim 1, wherein the heave compensation system further comprises a chain measurement device or cable measurement device, wherein the chain measurement device or cable measurement device is configured to generate a heavemovement signal based on movement of the chain or a power cable of the motor device with respect to the vessel.

7. Hoisting assembly according to claim 6. wherein the chain measurement device or cable measurement device comprises a spring-loaded or constant torque motor actuated chain wheel, wherein the chain or cable is positioned on the spring-loaded or constant torque motor actuated chain wheel.

8. Hoisting assembly according to claim 6, wherein the chain measurement device or cable measurement device comprises a reel, wherein the chain or power cable is attached to the reel and configure to wind be winded on the reel, and wherein the reel is biased to wind up the chain or power cable.

9. Hoisting assembly according to claim 6, wherein the chain measurement device comprises a sensor that measures the number of shackles of the chain that passes the sensor.

10. Hoisting assembly according to claim 1, wherein the heave compensation system comprises a motion reference unit (MRU) that is configured to be located on the vessel, wherein the MRU is configured to generate a heave movement signal based on the heave movement of the vessel and to transmit the heave movement signal to the motor device.

11. Hoisting assembly according to claim 1 or 2, wherein the heave compensation system comprises an extendable elongated element that extends between a first and a second end, the first end being attached to the vessel and the second end being attached to the fixed world, such as the wind turbine crane or chain, wherein the extension or contraction of the extendable elongated element is configured to generate the heave movement signal.

12. Hoisting assembly according to any one of the foregoing claims, wherein the motor device comprises a drive and a chain wheel, wherein the drive is configured to rotate the chain wheel to move the motor device along the chain.

13. Hoisting assembly according to any one of the foregoing claims, wherein the chain is configured to be detachable from the wind turbine crane or outrigger.

14. Hoisting assembly according to any one of the foregoing claims, wherein the motor device is detachable from the chain.

15. Hoisting system, comprising:a hoisting assembly according to any one of the foregoing claims; anda wind turbine crane or outrigger that is located on a wind turbine platform, wherein the chain of the hoisting assembly is attached to the wind turbine crane or outrigger.

16. Hoisting system according to claim 15, further comprising:a vessel,wherein the at least part of the heave compensation system is located on or attached to the vessel.

17. Method for hoisting a load to a wind turbine platform, comprising:providing a hoisting system according to claim 16;connecting the chain to the wind turbine crane or outrigger;connecting the motor device to the chain;connecting the load that is positioned on the vessel to the hook of the motor device; andmoving the motor device upwards along the chain towards the wind turbine platform.

18. Method according to claim 17, further comprising:generating, with the heave compensation system, the heave movement signal based on the heave movement of the vessel;transmitting the heave movement signal to the motor device; andcompensating the heave movement of the vessel by moving the motor device along the chain based on the heave movement signal received from the heave compensation system.

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