WO2020043257A1

WO2020043257A1 - A crane system mountable on a section of an offshore wind turbine generator and a related method

Info

Publication number: WO2020043257A1
Application number: PCT/DK2019/050253
Authority: WO
Inventors: Jens Andersen Gad
Original assignee: Maersk Supply Service A/S
Priority date: 2018-08-31
Filing date: 2019-08-28
Publication date: 2020-03-05

Abstract

A crane system mountable on a section of an offshore wind turbine generator is disclosed. The crane system comprises a crane body having a base portion and a top portion, a coupling attachable to the section of the wind turbine generator, whereby, when the coupling is attached to said section, the coupling is arranged to receive the base portion of the crane body, wherein the base portion is pivotable in the coupling. The crane system comprises a hoisting system to hoist the top portion of the crane body so that the crane body pivots around the coupling and the top portion engages the wind turbine generator above the coupling. A method of installing a crane system on a section of an offshore wind turbine generator from a vessel is also disclosed.

Description

A crane system mountable on a section of an offshore wind turbine generator and a related method

Technical Field

The invention relates to a crane system mountable on a section of an offshore wind turbine generator and a related method of installing such crane system on an offshore wind turbine generator.

Background

In order to reduce the dependence on limited fossil fuel resources around the world, there has been an increasing demand for renewable energy generation. One such source of renewable energy that has become increasingly reliable is wind energy generation. Typically, electricity is generated from the wind with wind turbine generators (WTG) installed in locations with a reliable prevailing wind. Some wind turbine generators have been installed on land in windy areas such as on hilltops. Wind turbine generators installed on land are also known as“onshore” wind turbine generators. In recent times, the trend has been to install bigger and taller wind turbines. This increases the area that the blades of the wind turbine sweep through and increases the total potential energy production. In addition, by positioning the blades higher into the atmosphere, the wind blows more steadily, and the wind turbine blades are further from objects that may cause turbulent airflow. The feasibility of the construction of onshore wind turbine generators can be affected by the local population objecting to the noise and other environmental impact. Accordingly, larger wind turbine generators can be installed in coastal waters. Wind turbine generators installed in coastal waters, the sea or deep ocean are also known as“offshore” wind turbine generators. The complexity of installing offshore wind turbine generators is greatly increased with respect to installing onshore wind turbine generators. For example, the materials and structure of the offshore wind turbine generators must be transported to the installation site with a suitable vessel.

A method of offshore wind turbine generator installation is contemplated in WO2017/055598. This discloses installing separate parts of a wind turbine generator with a crane mounted to part of the tower. The crane is initially winched onto the tower from a barge. A problem with previous techniques however is the risk of damaging either the vessel, the crane or the wind turbine generator itself when installing the crane into place. Summary

It is an object of the invention to at least partly overcome one or more limitations of the prior art. In particular, it is an object to provide an improved crane system to be mounted on a section of an offshore wind turbine generator and a related method, in particular allowing for a facilitated installation of such crane system with a reduced risk of damaging the vessel, the crane or the wind turbine generator.

In a first aspect of the invention, this is achieved by a method of installing a crane system on a section of an offshore wind turbine generator from a vessel, the method comprising engaging a coupling mounted to the section of the wind turbine generator with a base portion of a crane body, and hoisting a top portion of the crane body so that the crane body pivots around the coupling and the top portion engages the wind turbine generator above the coupling.

In another aspect of the invention there is a method of installing a crane system on a section of an offshore wind turbine generator from a vessel, the method comprising: engaging a coupling mounted to the section of the offshore wind turbine generator with a base portion of a crane body wherein the coupling is arranged to support the weight of the crane system, hoisting a top portion of the crane body with a hoisting winch mounted on the top portion of the crane body so that the crane body pivots around the coupling and the top portion engages the offshore wind turbine generator above the coupling whilst being supported by the offshore wind turbine generator.

Optionally, the base portion of the crane body is lowered into the coupling. Optionally a support mounted on a top portion of the crane body is rotatable or slidable against the vessel so that the crane body is movable with respect to the vessel when the base portion of the crane is supported by the coupling.

Optionally, the method comprises attaching the coupling to the section of the wind turbine generator.

Optionally, the hoisting the top portion comprises connecting the top portion of the crane body with the wind turbine generator at a position above the coupling with a hoisting system, and pulling the crane body against the wind turbine generator with the hoisting system so that the top portion engages the wind turbine generator.

Optionally, the method comprises suspending the crane body in a support structure above the vessel, and compensating for relative motion between the section of the wind turbine generator and the vessel such that the suspended crane body is stable relative to the section of the wind turbine generator when engaging the coupling.

Optionally, the method comprises building at least part of a tower of the wind turbine generator by placing at least a second segment on top of said section using the crane body.

Optionally, the method comprises hoisting the crane body to the second segment, and anchoring the crane body to the second segment for subsequent placement of least a third segment on top of said second segment using the crane body.

In another aspect of the invention, this is achieved by a crane system mountable on a section of an offshore wind turbine generator comprising a crane body having a base portion and a top portion, a coupling attachable to the section of the wind turbine generator, whereby, when the coupling is attached to said section, the coupling is arranged to receive the base portion of the crane body, wherein the base portion is pivotable in the coupling. The crane system comprises a hoisting system to hoist the top portion of the crane body so that the crane body pivots around the coupling and the top portion engages the wind turbine generator above the coupling.

In another aspect of the invention, there is provided a crane system mountable on a section of an offshore wind turbine generator comprising a crane body having a base portion and a top portion, a coupling attachable to the section of the offshore wind turbine generator, whereby, when the coupling is attached to said section, the coupling is arranged to receive the base portion of the crane body and support the weight of the crane system , wherein the base portion is pivotable in the coupling, ba hoisting system mounted on the top portion of the crane body and arranged to hoist the top portion of the crane body so that the crane body pivots around the coupling and the top portion engages the offshore wind turbine generator above the coupling whilst being supported by the offshore wind turbine generator.

Optionally, the system comprises a winch connector mountable to the wind turbine generator at a position above the coupling, wherein the hoisting system comprises a winch arranged at the top portion of the crane body and being mountable to the winch connector for winching of the top portion towards the winch connector.

Optionally the top portion comprises a support to be arranged against the vessel, wherein the support is rotatable or slidable against the vessel so that the crane body is movable with respect to the vessel while supported by the support.

Optionally the top portion comprises a support to be arranged against the vessel, wherein the support is rotatable or slidable against the vessel so that the crane body is movable with respect to the vessel while supported by the support and the base portion is engaged with the coupling.

Optionally, the system comprises a support structure to suspend the crane body above the vessel, at least one movable actuator coupled to the support structure and arranged to move the suspended crane body to compensate for relative motion between the section of the wind turbine generator and the vessel such that the suspended crane body is stable relative to the section of the wind turbine generator when engaging the coupling.

Optionally the crane body comprises anchors arranged to engage corresponding fastening elements of the wind turbine generator so that the crane body is anchored thereto.

Optionally the crane body is telescopic so that the top portion is movable with respect to the base portion, wherein a first anchor arranged at the top portion is movable with respect to a second anchor arranged at the base portion.

Optionally the crane body comprises a rail drive arranged to engage with a corresponding rail section of the wind turbine generator to move the crane body along the height of the wind turbine generator.

Further examples of the invention are defined in the dependent claims, wherein features for the first aspect may be implemented for the second aspect, and vice versa.

Engaging a coupling mounted to a section of the wind turbine generator with a base portion of a crane body and hoisting a top portion of the crane body so that the crane body pivots around the coupling until the top portion engages the wind turbine generator above the coupling, allows for mounting the crane body into place with a greater distance between the vessel and the wind turbine generator as well as reducing the risk of having the crane body swinging into the wind turbine generator in the transition from the vessel. Still other objectives, features, aspects and advantages of the invention will appear from the following detailed description as well as from the drawings.

Drawings

Embodiments of the invention will now be described, by way of example, with reference to the accompanying schematic drawings.

Fig. 1 is a schematic illustration, in a side view, of a crane system being mounted on a section of an offshore wind turbine generator from a vessel;

Fig. 2a is a schematic illustration of a base portion of a crane body being received in a coupling attached to a section of the wind turbine generator;

Fig. 2b is a schematic illustration of a top portion of the crane body being hoisted and pivoted around the coupling;

Fig. 2c is a schematic illustration of the top portion of the crane body engaging the wind turbine generator at a position above the coupling;

Fig. 3a is a schematic illustration of a crane system lifting segments to build a wind turbine generator tower;

Fig. 3b is a schematic illustration of a crane body being hoisted to tower segments of the wind turbine generator;

Fig. 4 is a schematic illustration of a crane body being moved along a rail section of the wind turbine generator;

Fig. 5 is a schematic illustration, in a side view, of a crane system being mounted on a section of an offshore wind turbine generator from a vessel;

Fig. 6 is a schematic illustration of a crane body being suspended in a support structure above the vessel;

Fig. 7a is a flowchart of a method of installing a crane system on a section of an offshore wind turbine generator from a vessel; and

Fig. 7b is another flowchart of a method of installing a crane system on a section of an offshore wind turbine generator from a vessel.

Detailed Description

Embodiments of the invention will now be described more fully hereinafter with reference to the accompanying drawings, in which some, but not all, embodiments of the invention are shown. The invention may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein.

Fig. 1 is a schematic illustration of a crane system 200 being mountable on a section 301 , 304, of an offshore wind turbine generator (WTG) 300. For the purposes of clarity, the WTG 300 is not drawn to scale. The WTG 300 comprises a foundation 303 anchored to the seabed. It is conceivable however that in some examples the foundation can be floating. A transition piece section 304 is typically anchored to the foundation 303 as a first section of the WTG 300. The transition piece 304 projects out from the surface of the water. In one example the crane system 200 is initially mounted to a section 301 attached to the transition piece 304, as schematically shown in Fig. 1 . In another example, the crane system 200 is initially mounted directly to the transition piece section 304, as schematically shown in Fig. 5. The crane system 200 comprises a crane body 201 having a base portion 203 and a top portion 204 at opposite ends thereof. Various crane elements 215 may be attached to the crane body 201 , as exemplified in the schematic illustration Fig. 3a, but have been omitted in the other figures for a more clear presentation of the other features of the crane system 200.

The crane system 200 comprises a coupling 202 being attachable to the section 301 of the WTG. In one example the coupling 202 may be integrated with section 301 , e.g. by being molded onto the section 301 . In another example the coupling 202 may be attachable as a separate element to the section 301. In either case the coupling 202 is arranged to receive the base portion 203 of the crane body 201 when the coupling is fixed to the section 301. Fig. 2a is a schematic illustration of the base portion 203 engaging the coupling 203. The crane system 200 comprises a hoisting system 205 that may suspend the crane body 201 and transfer the crane body 201 from the vessel 400 towards the WTG 300 so that the base portion 203 can engage and interlock with the coupling 202. Fig. 2a shows one example of such hoisting system 205 but various other alternative hosting systems 205 are conceivable for lifting the base portion 203 of the crane body 201 into the coupling 202 from the vessel 400. The base portion 203 is pivotable in the coupling 202 once received therein. I.e. the crane body 201 may rotate as schematically shown in the example of Fig. 2b where the top portion 204 of the crane body 201 has been lifted from the vessel 400. The hoisting system 205 is thus arranged to hoist the top portion 204 of the crane body 201 so that the crane body 201 pivots around the coupling 202. The crane body 201 is pivoted so that the top portion 204 engages the WTG above the coupling 202, as schematically shown in Fig. 2c. The crane body 201 is thus fully deployed in a vertical configuration and may be subsequently utilized for lifting further segments 301’ of the WTG 300 onto the first section 301 as described further below with reference to Fig. 3a, or be utilized for various maintenance operations of the WTG 300.

Engaging a coupling 202 with a base portion 203 of a crane body 201 and hoisting a top portion 204 of the crane body 201 so that the crane body 201 pivots around the coupling 202 and having the top portion 204 engaging the WTG 300 above the coupling 202, allows for mounting the crane body 201 with a greater distance between the vessel 400 and the WTG 300. Previous solutions where a top portion of the crane is hoisted vertically to the WTG while a base portion is supported by a vessel necessitates a close proximity between the WTG and the vessel. It is undesirable for the vessel to be in immediate proximity of the foundation piece 303 for a protracted period of time because this increases the risk of collision of the vessel 400 with the foundation 303 and transition piece 304. The crane system 200 thus provides for reducing the risk of such collisions.

Furthermore, in the final stage of transferring the crane body from the vessel in previous solutions, there is a risk of having the crane body swinging into the WTG as the base portion is released from the support provided by the vessel while the top portion continues to be hoisted vertically. Pivoting the base portion 203 around the coupling 202 provides for a secure and controlled transfer of the crane body 201 onto the WTG 300. The crane system 200 thus avoids the risk of having the crane body 201 swinging into the WTG 300 when being transferred from the vessel 400.

Fig. 7a is a flow chart of a method 100 of installing a crane system 200 on a section 301 of an offshore wind turbine generator (WTG) 300 from a vessel 400. The method 100 comprises engaging 101 a coupling 202 mounted to the section 301 of the WTG 300 with a base portion 203 of a crane body 201 . The method 100 further comprises hoisting 102 a top portion 204 of the crane body 201 so that the crane body 201 pivots around the coupling 202 and the top portion 204 engages the WTG 300 above the coupling 202. The method 100 thus provides for the advantageous benefits as described above for the crane system 200, and in particular for a facilitated and more secure installation of a crane system 200 on a WTG 300.

Fig. 7b is a further flow chart of a method 100 of installing a crane system 200 on a section 301 of a WTG 300 from a vessel 400. As described above, the coupling 202 may be integrated or attached to the section 301 of the WTG 300 in advance of installing the crane system 200. Alternatively, the method 100 may comprise attaching 1010 the coupling 202 to the aforementioned section 301 of the WTG 300 prior to engaging 101 and attaching the base portion 203 of a crane body 201 to the coupling 202.

The crane system 200 may comprise a winch connector 213 mountable to the WTG 300 at a position above the coupling 202, as shown in the example of Fig. 1. As with the coupling 202, it is also conceivable that the winch connector 213 may be integrated with the section 301 of the WTG 300. The hoisting system 205 may comprise a winch 214 arranged at the top portion 204 of the crane body 201 . The winch 214 is mountable to the winch connector 213 for winching of the top portion 204 towards the winch connector 213 as illustrated in Figs. 2b-c. The winch 214 may be part of a winch system to be subsequently utilized for lifting segments 30T of the WTG into place and thus already integrated with the crane body 201 or related crane elements 215. This provides for a robust and facilitated mounting of the crane system 200 onto the WTG 300.

Alternatively or additionally, a winch for hoisting the crane system 200 can be mounted on the section 301 of the WTG 300 or on the vessel 400.

With respect to the method 100, the hoisting 102 of the top portion 204 may thus comprise connecting 1021 the top portion 204 of the crane body 201 with the WTG 300 at a position above the coupling 202 with a hoisting system 205, e.g. with a winch 214, and pulling 1022 the crane body 201 against the WTG 300 with the hoisting system 205 so that the top portion 204 engages the WTG 300. It is also conceivable that hoisting 102 of the top portion 204 of the crane body 201 may comprise pushing the crane body 201 to the vertical position shown in Fig. 2c by actuators (not shown) mounted on the vessel 400. In either case the crane body 201 is pivoted around the coupling 20 to provide a secure mounting of the crane system 200 to the WTG 300 as described above. The hoisting system 205 may assume various configurations and be adapted depending on the type of WTG 300.

The top portion 204 may comprise a support 206 to be arranged against the vessel 400, as schematically illustrated in Fig. 1 . The support 206 may be rotatable or slidable against the vessel 400 so that the crane body 201 is movable with respect to the vessel 400 while supported by the support 206. The support 206 may thus compensate for any relative motion between the vessel 400 and the WTG and provide for a further facilitated, secure and stable anchoring of the base portion 203 in the coupling 202. The support 206 may comprise a roller or a surface of low friction arranged against the deck of the vessel 400 to facilitate the relative movement without risking damaging the WTG 300. The crane system 200 may comprise a support structure 207 arranged to suspend the crane body 201 above the vessel 400, as schematically illustrated in Fig. 6. At least one movable actuator 208 may be coupled to the support structure 207 and be arranged to move the suspended crane body 201 to compensate for a relative motion between the section 301 of the WTG 300 and the vessel 400 such that the suspended crane body 201 is stable relative to the section 301 of the WTG 300 when engaging the coupling 202. Mounting of the crane system 200 to the WTG 300 is thus further facilitated by compensating for any relative motion between the vessel 400 and the WTG 300 when the base portion 203 is to be anchored to the coupling 202. The positioning of the crane body 201 can be completed in less time and under more severe weather conditions. The support structure 207 may be coupled to a plurality of actuators 208 arranged to move the support structure 207 in three dimensions relative the vessel 400 based on real-time sensor feedback of the motion of the vessel 400.

Fig. 6 shows a schematic illustration of a sensor 217 connected to a motion compensation module 216 which controls the movable actuators 208 depending on the feedback from the sensor 217 so that the motion of the vessel 400 is compensated by a counter-motion of the support structure 207 to keep the suspended crane body 201 stable. Multiple sensors 217 may be arranged at various positions on the vessel 400 to detect any of the vessel’s rotating- or translational movements in three dimensions. In some examples, the sensors 217 for detecting the motion of the vessel 400 can be accelerometers, gyroscopes, cameras, or any other suitable sensors for detecting motion of the vessel 400. In some examples, the motion compensation module 216 calculates a deviation of the crane body 201 from a position relative the WTG 300 where the crane body 201 is to be transferred to. On detection of deviation from a stable crane position, the motion compensation module 216 then sends control instructions to the actuators 208 to move the crane body 201 back to the desired stable position. In this way, the motion compensation module 216 may control the actuators 208 to keep the crane body 201 fixed at a defined position, e.g. at a defined height, with respect to the WTG 300.

The crane body 201 may be fixed to the support structure 207 by being held in a support structure connector 218, as schematically illustrated in Fig. 6. In some examples it is conceivable that the support structure 207 and connector 218 may hoist the crane body 201 from the vessel 400, via a pivoting motion around coupling 202, to the vertical mounted position illustrated in Fig. 2c without a separate hoisting system 205, although the latter being illustrated in the example of Fig. 6. Alternatively, the crane body 201 may be released from connector 218 after being secured to coupling 202, and then pulled into the vertical mounted position by the hoisting system 205.

The method 100 may thus comprise suspending 101 1 the crane body 201 in a support structure 207 above the vessel 400, and compensating 1012 for relative motion between the section 301 of the WTG 300 and the vessel 400 such that the suspended crane body 201 is stable relative to the section 301 of the WTG 300 when engaging the coupling 202.

The method 100 may comprise building at least part of a tower 302 of the WTG

300 by placing 103 at least a second segment 30T on top of the aforementioned section

301 using the crane body 201 , as schematically illustrated in Fig. 3a. Thus, when the crane system 200 has been transferred from the vessel 400 and mounted to the WTG 300 as described above, the crane body 201 and related crane elements 215 may hoist further segments 301’ of the tower 302 on top of each other.

The method 100 may comprise hoisting 104 the crane body 201 to the aforementioned second segment 30T, and anchoring 105 the crane body 201 to the second segment 30T for subsequent placement of least a third segment (not shown) on top of the second segment 30T using the crane body 201 . Fig. 3b is a schematic illustration of the crane body 201 being hoisted and mounted to the second segment 30T. The WTG tower 302 may thus be built by repeatedly moving the crane body 201 upwards as new segments 301 are mounted on top of each other. The crane system 200 may also be utilized for maintenance operations of the WTG.

The crane body 201 may comprise anchors 209, 209’, arranged to engage corresponding fastening elements 210, 210’, of the WTG 300 so that the crane body 201 can be anchored to the WTG 300. Fig. 3a shows an example where anchor 209’ is positioned at the level of the second segment 30T but below fastening element 210’ arranged on top of the second segment 30T. In Fig. 3b the crane body 201 has been hoisted further upward and the anchor 209’ has engaged the fastening element 210’. The base portion 203 has also been fixed to the WTG 300, via anchor 209 and fastening element 210.

The crane body 201 may be telescopic so that the top portion 204 is movable with respect to the base portion 203. Thus, a first anchor 209’ arranged at the top portion 204 may be movable with respect to a second anchor 209 arranged at the base portion 203. The first anchor 209’ may accordingly move upward with the top portion 204 and engage with a new segment of the WTG 300 and being attached thereto, while the base portion 203 is fixed in position via the second anchor 209 and a corresponding fastening element 210. The crane body 201 may be subsequently retracted, as the second anchor 209 is released, so that the top portion 204 pulls the base portion 203 upward along the tower 302 of the WTG 300. The procedure may then be repeated so that the crane system 200 may climb upwards on the WTG 300.

Alternatively, the crane body 201 may comprise a rail drive 21 1 arranged to engage with a corresponding rail section 212 of the WTG 300 to move the crane body 201 along the height of the WTG 300, as schematically illustrated in Fig. 4. The rail drive 21 1 may comprise a gear mechanism that interlocks with a corresponding structure of the rail section 212, such as gear teeth, so that the crane body 201 may be conveyed along the WTG 300.

In another embodiment, not shown in the embodiments, the bottom portion of 203 of the crane system 200 is initially connected to the coupling 202 with a cable. This means that the top portion 204 of the crane system 200 is connected by the cable of the first hoisting system 205 to the WTG 300 and the bottom portion 203 is also connected with a cable of a second hoisting system. A winch of the second hoisting system then retracts the cable and draws the bottom portion 203 towards the coupling 202 similar to the process described with reference to the first hoisting system 205. The winch 214 of the first hoisting system 205 can retract both the cables attach to the top portion 204 and the bottom portion 203 of the crane system 200 at the same time to bring the crane system 200 into contact with the WTG 300. This means that the bottom portion 203 does not have to be precisely located in the pivot point of the coupling 202. Accordingly, there can be less reliance on motion compensation of the vessel moving with respect to the WTG 300.

From the description above follows that, although various embodiments of the invention have been described and shown, the invention is not restricted thereto, but may also be embodied in other ways within the scope of the subject-matter defined in the following claims.

Claims

1. A method (100) of installing a crane system (200) on a section (301 , 304) of an offshore wind turbine generator (300) from a vessel (400), the method comprising: engaging (101 ) a coupling (202) mounted to the section of the offshore wind turbine generator with a base portion (203) of a crane body (201 ) wherein the coupling is arranged to support the weight of the crane system,

hoisting (102) a top portion (204) of the crane body with a hoisting winch mounted on the top portion of the crane body so that the crane body pivots around the coupling and the top portion engages the offshore wind turbine generator above the coupling whilst being supported by the offshore wind turbine generator.

2. A method according to claim 1 wherein the base portion of the crane body is lowered into the coupling.

3. A method according to claims 1 or 2 wherein a support mounted on a top portion of the crane body is rotatable or slidable against the vessel so that the crane body is movable with respect to the vessel when the base portion of the crane is supported by the coupling.

4. A method according to claim 1 , comprising

attaching (1010) the coupling to the section of the wind turbine generator.

5. A method according to claims to 4, wherein hoisting the top portion comprises

connecting (1021 ) the top portion of the crane body with the wind turbine generator at a position above the coupling with a hoisting system (205),

pulling (1022) the crane body against the wind turbine generator with the hoisting system so that the top portion engages the wind turbine generator.

6. A method according to any of claims 1 - 5, comprising

suspending (101 1 ) the crane body in a support structure (207) above the vessel, compensating (1012) for relative motion between the section of the wind turbine generator and the vessel such that the suspended crane body is stable relative to the section of the wind turbine generator when engaging the coupling.

7. A method according to any of claims 1 - 6, comprising

building at least part of a tower (302) of the wind turbine generator by placing (103) at least a second segment (301’) on top of said section using the crane body.

8. A method according to claim 7, comprising

hoisting (104) the crane body to the second segment,

anchoring (105) the crane body to the second segment for subsequent placement of least a third segment on top of said second segment using the crane body.

9. A crane system (200) mountable on a section (301 , 304) of an offshore wind turbine generator (300) comprising

a crane body (201 ) having a base portion (203) and a top portion (204), a coupling (202) attachable to the section of the offshore wind turbine generator, whereby, when the coupling is attached to said section, the coupling is arranged to receive the base portion of the crane body and support the weight of the crane system , wherein the base portion is pivotable in the coupling,

a hoisting system (205) mounted on the top portion of the crane body and arranged to hoist the top portion of the crane body so that the crane body pivots around the coupling and the top portion engages the offshore wind turbine generator above the coupling whilst being supported by the offshore wind turbine generator.

10. A crane system according to claim 9, comprising a winch connector (213) mountable to the wind turbine generator at a position above the coupling,

wherein the hoisting system comprises a winch (214) arranged at the top portion of the crane body and being mountable to the winch connector for winching of the top portion towards the winch connector.

11. A crane system according to claim 9 or 10, wherein the top portion comprises a support (206) to be arranged against the vessel, wherein the support is rotatable or slidable against the vessel so that the crane body is movable with respect to the vessel while supported by the support and the base portion is engaged with the coupling.

12. A crane system according to any of claims 9 - 11 , comprising

a support structure (207) to suspend the crane body above the vessel, at least one movable actuator (208) coupled to the support structure and arranged to move the suspended crane body to compensate for relative motion between the section of the wind turbine generator and the vessel such that the suspended crane body is stable relative to the section of the wind turbine generator when engaging the coupling.

13. A crane system according to any of claims 9 - 12, wherein the crane body comprises anchors (209, 209’) arranged to engage corresponding fastening elements (210, 210’) of the wind turbine generator so that the crane body is anchored thereto.

14. A crane system according to claim 13, wherein the crane body is telescopic so that the top portion is movable with respect to the base portion,

wherein a first anchor (209’) arranged at the top portion is movable with respect to a second anchor (209) arranged at the base portion.

15. A crane system according to any of claims 9 - 14, wherein the crane body comprises a rail drive (211 ) arranged to engage with a corresponding rail section (212) of the wind turbine generator to move the crane body along the height of the wind turbine generator.