WO2014125460A1

WO2014125460A1 - Device and method for assembling a structure

Info

Publication number: WO2014125460A1
Application number: PCT/IB2014/059068
Authority: WO
Inventors: Etienne Clymans
Original assignee: High Wind N.V.
Priority date: 2013-02-18
Filing date: 2014-02-18
Publication date: 2014-08-21
Also published as: BE1021795B1

Abstract

The invention relates to a device for assembling a structure constructed from components, preferably at sea, in particular a wind turbine. The device comprises a hoisting means which is provided on a substrate and takes the form of a boom rotatable around a horizontal axis in a lifting plane, to which boom is connected an auxiliary hoisting means rotatable by means of rotation means around a second horizontal axis in the lifting plane, wherein the auxiliary hoisting means comprises at an outer end a pickup tool with which a component can be taken up. The invention likewise relates to a method for assembling a structure constructed from components, in particular a wind turbine, while making use of the invented device.

Description

Device and method for assembling a structure

The invention relates to a device for assembling a structure. The invention likewise relates to a method for assembling a structured The invention relates particularly to a device and method for assembling a wind turbine.

Although the invention will mainly be illustrated in the context of assembling a structure at sea, the device and method according to the invention are applicable on shore, as well as at sea.

The number of structures erected, maintained or repaired at sea is growing. A typical example is an offshore wind turbine comprising a gondola (or nacelle) which is placed on a mast and forms the housing for electromechanical equipment such as a power generator. The nacelle is provided with a hub on which a number of rotor blades are arranged. The rotor blades convert the kinetic energy of the wind into a rotating movement of the shaft of the nacelle, which is converted into electrical energy by the power generator.

During the placing of components of such large structures at sea the components are manipulated according to the prior art by a crane placed on a vessel, and placed on a support structure already available at sea for the structure. In the case of a wind turbine the support structure can for instance comprise a mast placed on a suitable foundation.

The lifting and placing of large, slender components, in particular wind turbine blades, at sea is hampered by wind load. Wind turbine blades attached to the crane can be exposed here to great and unexpected movements relative to the support structure or relative to already installed components. This makes assembly very much more difficult, or even impossible in the case of strong wind load. A wind turbine blade has to be attached by means of bolt connections to a hub, this requiring a precise positioning of the wind turbine blade relative to a hub already installed on a mast.

An object of the present invention is to provide a device with which (components of) large structures, in particular components of wind turbines, can be assembled and placed at sea in a manner less susceptible to wind. This object is achieved with a device having the characteristics according to claim 1. A device is provided according to the invention for assembling a structure constructed from components at sea preferably, in particular a wind turbine, which device comprises a hoisting means which is provided on a substrate, preferably a vessel, and takes the form of a boom rotatable around a horizontal axis in a lifting plane, to which boom is connected an auxiliary hoisting means rotatable by means of rotation means around a second horizontal axis in the lifting plane, wherein the auxiliary hoisting means comprises at an outer end a pickup tool with which a component can be taken up. Using the invented device components - which as for instance rotor blades are per se susceptible to wind - can be manipulated in a manner relatively unsusceptible to wind, whereby a large structure can be assembled, maintained or repaired at sea in more efficient and safer manner. Manipulation can moreover take place more accurately. The invented device therefore allows work to take place in practically all conditions, whereas the known device can only be deployed up to determined wind speeds. The assembly time of a structure at sea can hereby be significantly reduced.

An embodiment of the device according to the invention is characterized in that the boom extends over a boom length from a boom base to a boom top, and the connection of the auxiliary hoisting means to the boom is situated between the boom base and the boom top.

A further embodiment of the invention provides a device wherein the connection of the auxiliary hoisting means to the boom is located at between one third and two thirds of the boom length.

In an embodiment of the device the auxiliary hoisting means is connected to the boom for displacement in a longitudinal direction of the boom. The auxiliary hoisting means can hereby be displaced easily along the longitudinal axis of the boom, for instance away from the upper outer end of the boom, whereby the hoisting means can operate as a hoisting means as known in the prior art, for which purpose the hoisting means is provided with a hoisting cable with attaching means to which a component can be coupled and can be placed on a foundation available at sea. By placing the auxiliary hoisting means at a distance from the attaching means - for instance a hoisting tackle - there continues to be good accessibility from the deck of the vessel to components to be taken up by the hoisting means. Another embodiment has the feature that the rotation means comprise a lifting wire which runs between boom and auxiliary hoisting means and the variable free length of which determines the rotation position of the auxiliary hoisting means relative to the boom. The auxiliary hoisting means is rotated around the second horizontal axis in the lifting plane by tightening or, conversely, paying out the lifting wire. The second rotation axis generally coincides with the connection between boom and auxiliary hoisting means, although this is not essential. The use of one or more lifting wires makes the auxiliary hoisting means suitable for lifting and placing relatively heavy loads, such as for instance the rotor blades of a wind turbine. Provided in yet another embodiment is a device wherein the auxiliary hoisting means comprise mutually coupled levers which can be moved relative to each other. Such an embodiment of the auxiliary hoisting means generally comprises a main lever pivotally connected to the boom, a second lever or stick pivotally connected to an outer end of the main lever, and a pickup tool pivotally connected to another outer end of the stick. The pivoting movement of the main lever relative to the boom, of the stick relative to the main lever and of the pickup tool relative to the stick is realized in an embodiment by hydraulic cylinders which are incorporated in a hydraulic circuit and which are provided respectively between the boom and the main lever, between the main lever and the stick and between the stick and the pickup tool.

The number of degrees of freedom of the auxiliary hoisting means can be selected within broad limits, wherein a compromise must be sought between the flexibility and the loadability of the auxiliary hoisting means. A suitable auxiliary hoisting means with hydraulically movable levers can be rotated in the lifting plane around the second rotation axis, round the pivotable connection between main lever and stick and around the pivotable connection between stick and pickup tool. A component taken up in the pickup tool can hereby be rotated (turned upside down) through an angle of for instance 180 degrees in the lifting plane. A rotation option around a vertical axis preferably located in the lifting plane is also useful. This rotation option can for instance be provided by connecting the boom pivotally around a fixed outer end to a hoisting means platform which in turn is rotatable about a vertical rotation axis around a platform foundation. This degree of freedom makes it possible for the auxiliary hoisting means, and more specifically the pickup tool thereof, to reach over a large part of the vessel deck, and optionally even further than the vessel deck. A height adjustment is further obtained by connecting the auxiliary hoisting means to the boom for displacement in a longitudinal direction of the boom. Finally, it is possible in another embodiment of the device according to the invention to give the levers an extendable (telescopic) form. This is particularly advantageous when relatively great distances and heights have to be spanned by the auxiliary hoisting means, for instance in order to take up components from their storage location on the work deck of the vessel. Such an embodiment is also advantageous when a rotor blade has for instance to be mounted in vertical position on a nacelle already placed on the mast of a wind turbine. It is also advantageous to give the main lever a non-curved form. The central axis of the main lever then run substantially in a straight line.

It is advantageous to characterize the device according to the invention in that the length of the auxiliary hoisting means in furthest extended position lies between one quarter and three quarters of the boom length. The length of the auxiliary hoisting means in furthest extended position more preferably lies between one third and two thirds of the boom length. In an embodiment wherein the auxiliary hoisting means comprises mutually coupled levers which can be moved relative to each other, the furthest extended length corresponds to the length of the auxiliary hoisting means wherein the levers substantially lie mutually in line.

Another embodiment of the device is characterized in that the pickup tool is connected by means of a rigid connection to an attaching structure to which a component can be releasably attached. This embodiment has the advantage that the attaching structure can be selected subject to the component to be lifted.

It is further advantageous here to characterize an embodiment of the device in that the rigid connection and/or the attaching structure comprises means for displacing and/or rotating in three dimensions a component taken up in the pickup tool. This embodiment has the advantage that, once the component has been carried by the (auxiliary) hoisting means into the vicinity of the desired installation position, it can be displaced and rotated in precise manner about a rotation axis in order to carry the component accurately to the installation position. In the case of a wind turbine blade for instance this feature provides the option of mounting the blade on a hub, even when the blade mounting of the hub makes an angle other than zero with the horizontal. Precise displacements of the attaching structure enable a blade to be mounted without additional movements of the hoisting means.

Another embodiment of the device applies an attaching structure which comprises a gripper for a mast section, a rotor blade or a nacelle of a wind turbine. In an

embodiment of the device according to the invention the attaching structure comprises a blade yoke. During hoisting of for instance a wind turbine blade the blade yoke gives the attaching means the desired width whereby tilting of the wind turbine blade is prevented.

A particularly advantageous embodiment of the invention provides a device, the attaching structure of which comprises a rotor blade spreader which can be oriented. The rotor blade spreader is an elongate structure with a longitudinal direction, a transverse direction and a vertical direction which in the present embodiment substantially corresponds to the lifting direction. The spreader is provided with means for rotating the spreader round a longitudinal axis and a transverse axis and for pivoting thereof round a vertical axis, for instance by means of a motor-driven pinion. In addition, the length of the spreader in the longitudinal direction is preferably

telescopically adjustable. It can thus be adjusted to the length of the engaging part of an elongate component, such as for instance a wind turbine blade. It is also advantageous for the spreader to be provided with a mechanism to enable displacement of the rotor blade in the longitudinal direction. The centre of gravity can hereby be made adjustable and the fastening bolts of a rotor blade can be pushed during assembly via a translation into the corresponding holes in the hub without additional displacement of the

(auxiliary) hoisting means. The spreader is further provided with engaging means in the form of for instance gripper arms, slings, clamping mechanisms and the like to enable securing of the component. The device according to the invention is particularly suitable for manipulating components such as a mast section, a rotor blade and/or a nacelle of a wind turbine, wherein the advantages of the invention are most clearly manifest in the manipulation of a rotor blade. The invented device enables assembly of offshore wind turbines up to wind speeds of 12m/s and more, where with the known device the mast and nacelle can be assembled up to wind speeds of lOm/s, a complete rotor (a hub on which three blades are mounted) up to 9m/s, a nacelle with hub and two pre-mounted blades (the so-called bunny ear method) up to about 9m/s and individual rotor blades up to 8m/s. The vessel can in principle be any vessel with sufficient load-bearing capacity for the device, but is preferably a jack-up offshore platform moored in the vicinity of the construction location, more particularly in the vicinity of the foundation for the structure present in the sea. A jack-up offshore platform generally comprises a work deck, which can bear a substantial load, and anchor piles which support the work deck. Each substantially vertically running anchor pile is movable in this direction from a high position during transport to a low position in the anchored situation, in which position - the piles support on the seabed. The height position of the work deck relative to the water level can be changed by displacing the work deck relative to the piles by means of (hydraulic) jacks. In the anchored position the work deck can be jacked up to a position above the water level. A space-saving device according to the invention is provided with an embodiment in which the vessel comprises a jack-up platform and the hoisting means is arranged around an anchor pile of the platform.

In order to enable the components to be brought within the working range of the hoisting means, and particularly within the working range of the pickup tool, an embodiment of the device is provided which comprises displacing means for displacing the components over the deck of the vessel into the working range of the auxiliary hoisting means. An advantageous embodiment has in this respect the feature that the displacing means comprise slide tracks or rails arranged on the deck. It is also possible to make the hoisting means displaceable.

The invention likewise relates to a method for assembling a large structure, preferably at sea, in particular a wind turbine, while making use of the device according to the invention. The method comprises of providing a device according to the invention on a substrate, preferably a vessel, taking up a component for placing using the pickup tool and placing the component on a foundation, preferably present in the sea, using the auxiliary hoisting means, wherein the component is brought into alignment with the foundation and components possibly already placed thereon by rotating at least the auxiliary hoisting means around the second horizontal axis relative to the boom.

The structure to be assembled at sea can in principle be any structure. The device and method according to the invention are suitable for assembling wind turbines at sea wherein the components comprise for instance mast parts and the gondola (or nacelle) with hub of the wind turbine, and in particular for placing the rotor blades of the wind turbine.

In an embodiment of the method according to the invention the auxiliary hoisting means is displaced in a longitudinal direction of the boom in order to take up or place the component for placing. Another embodiment comprises of rotating the auxiliary hoisting means with a lifting wire running between boom and auxiliary hoisting means, wherein the free length of the lifting wire is varied in order to determine the rotation position of the auxiliary hoisting means relative to the boom. A preferred embodiment of the method makes use of an auxiliary hoisting means comprising mutually coupled levers, wherein the levers are moved relative to each other during the manipulation of a component taken up with the auxiliary hoisting means. The levers are preferably driven here by hydraulic cylinders incorporated in a hydraulic circuit.

It is further advantageous in an embodiment of the method for the auxiliary hoisting means to be configured to carry exchangeable pickup tools. In an embodiment of the method a component taken up by the pickup tool is preferably displaced and/or rotated in three dimensions.

In another embodiment the component is attached to the pickup tool by means of an attaching structure comprising a blade yoke or blade spreader. A rotor blade is preferably engaged here in the vicinity of its centre of gravity, wherein for each engagement point the position of the engagement points does not lie further away from the centre of gravity than 20% of the overall blade length, and more preferably no further than 10% of the overall blade length.

The invention will now be elucidated in more detail with reference to the accompanying figures, without otherwise being limited thereto. In the figures:

Fig. 1 is a schematic side view of an embodiment of the device according to the invention in a first position;

Fig. 2 is a schematic side view of the device shown in figure 1 in a second position; Fig. 3 is a schematic side view of the device shown in figure 1 in yet another position; Fig. 4 is a schematic top view of the position of the device shown in figure 3;

Fig. 5 is a schematic side view of an embodiment of the auxiliary hoisting means according to the invention;

Fig. 6 is a schematic side view of a detail of the embodiment of the auxiliary hoisting means according to the invention shown in figure 5; and finally

Fig. 7 is a schematic front view of the embodiment of the auxiliary hoisting means according to the invention shown in figure 6.

Referring to figure 1, an embodiment of the device is shown specifically intended for assembly of a wind turbine 2 at sea, and particularly for placing wind turbine components such as a nacelle 21 or rotor blades 22 on an already available mast 23.

Mast 23 supports on a jacket 3, although any other foundation can be used. Driven piles (monopiles) with a so-called transition piece - a round transition structure located close to the waterline from monopile to mast mounting - can be applied in the case of for instance rather shallow water. Gravity-based foundations can also be applied in shallower water. In the case of deeper water or larger wind turbines so-called Tripods and Tripiles are also applied in addition to jackets.

The shown device 1 comprises a hoisting means 5, preferably a crane, which is placed on a jack-up platform 4 and a boom 50 of which is provided with a hoisting cable 52 on which an attaching means such as a hoisting tackle 53 is arranged and to which a component for lifting, such as a nacelle 21, can be releasably attached. Boom 50 and the (freely movable) hoisting cable 52 together form a lifting plane 54 (which corresponds for all figures except figures 4 and 7 to the plane of the figure). Boom 50 is connected at an outer end for pivoting around a horizontal shaft 55 in the lifting plane 54 to a hoisting means platform 56a, which is in turn rotatable round a platform foundation 56b around a rotation axis 57. Boom 6 can be luffed in, i.e. raised, and luffed out, i.e.

lowered, around pivot point 55 in known manner. The jack-up platform 4 is provided with anchor piles 40 which support a work deck 41. Anchor piles 40 are movable in vertical direction to the seabed, and the height position of work deck 41 relative to water level 10 can be changed by displacing work deck 41 relative to piles 40 by means of (hydraulic) jacks or a gear rack-pinion drive system. If desired, work deck 41 is provided with storage locations 42 for the components to be lifted and positioned, in particular for the rotor blades 22. In order to enable the method according to the invention to be performed the platform 4 is moored in the immediate vicinity of the jacket 3 available at sea, and in any case such that jacket 3 lies within reach of hoisting means 5 with boom 6 in luffed-out position. According to the invention an auxiliary hoisting means 6 is connected to boom 50. The connection between auxiliary hoisting means 6 and boom 50 is formed by a second horizontal shaft 61 which is for instance welded to boom 50 and around which the auxiliary hoisting means 6 can be rotated in lifting plane 54. In the embodiment shown in figures 1-3 this rotation is made possible by rotation means in the form of a lifting wire 62 running between boom 50 and auxiliary hoisting means 6. By varying the free length of lifting wire 62 the rotation position of auxiliary hoisting means 6 relative to boom 50 can be determined, i.e. the relative angle between boom 50 and auxiliary hoisting means 6. Auxiliary hoisting means 6 is connected to boom 50 for displacement in a longitudinal direction 501 of boom 50. This can take place for instance by embodying shaft 61 displaceably with boom 50 and by means of a displacing device (not shown) comprising in any case a tensioning cable and winch. A base of shaft 61 and boom 50 can for instance be provided for this purpose with first and second co- acting guide means in the form of a T-beam running in the longitudinal direction 501 of boom 50 and a pair of wheels connected to shaft 61, wherein the wheels of a pair of wheels are situated on either side of the flange and roll thereover. Both pressure forces and tensile forces can thus be absorbed. Depending on the wheel load, the wheels can optionally be replaced by double wheel bogies. It is of course possible to realize other methods of displaceability along boom 50. Auxiliary hoisting means 6 is shown in more detail in figure 5 and comprises mutually coupled levers (63, 64) which can be moved relative to each other. A main lever 63 is connected for pivoting around shaft 61 to boom 50 and at the other outer end likewise connected for pivoting around a shaft 65 to a stick 64. At the other outer end the stick 64 is finally connected for pivoting around a shaft 66 to a pickup tool 7 with which a component can be taken up. Levers (63, 64) and pickup tool 7 are driven by hydraulic cylinders (67, 68) which form part of a hydraulic circuit (not shown). With the embodiment of auxiliary hoisting means 6 shown in the figures a component such as wind turbine blade 22 taken up in pickup tool 7 can for instance be rotated (turned upside down) through an angle of 180 degrees in the lifting plane. This transition becomes apparent from comparison of the positions of auxiliary hoisting means 6 shown in figures 2 and 3. A further degree of freedom is provided by connecting boom 50 at an outer end for pivoting around the horizontal shaft 55 in lifting plane 54 to the hoisting means platform 56a, which is in turn rotatable round the platform foundation 56b about the vertical rotation axis 57, this transition being shown for instance by comparing the positions of boom 50 shown in figures 2 and 3. Figure 3 shows that auxiliary hoisting means 6, and more specifically pickup tool 7 thereof, can optionally reach even further than vessel deck 41. A further degree of freedom is the height adjustment achieved by connecting auxiliary hoisting means 6 to boom 50 for displacement in the longitudinal direction 501 of boom 50.

Although pickup tool 7 can have many embodiments, an embodiment particularly suitable for taking up and lifting a rotor blade 22 is shown in more detail in figures 6 and 7. Figure 6 shows here a side view and figure 7 a front view of pickup tool 7. Pickup tool 7 comprises an attaching structure in the form of rotor blade spreader 406 to which a rotor blade 22 can be releasably attached. Spreader 406 is connected by means of a rigid but pivoting connection to stick 64 of auxi liary hoisting means 6. The rigid connection comprises a T-shaped bridging construction 400 connected to web plates 401. Web plates 401 are connected with hinge connections 66 and 69 to respectively the stick 64 and piston cylinder 68. The rotor blade spreader construction 406 is connected for rotation around hinge 400a to bridging construction 400, the connection forming in this embodiment an actuator 402 to which spreader 406 is connectable or of which it forms part. Actuator 402 is rotatable around shaft 400a in a transverse direction 61 by means of hydraulic cylinders (403a, 403b). Actuator 402 and spreader 406 further comprise means for displacing and/or rotating parts of the attaching structure in three dimensions. A part 405 rotatable around a rotation shaft 400b running perpendicularly of shaft 400a can thus be rotated through action of hydraulic cylinder 404a and/or 404b. This will likewise rotate the telescopically extendable arms (406a, 406b) of rotor blade spreader 406. The length of spreader 406 is increased and adjusted if desired to the component for lifting by extending the arms (406a, 406b).

A rotor blade 22 can be suspended in two slings 303 attached to the spreader. The combination of displacement and rotation actuators provides the option of precisely placing a wind turbine blade in a random orientation relative to boom 50, and so also relative to jacket 3, and also to a nacelle 21 with hub 24 mounted on mast 23.

It will be apparent that power supply means (not shown) such as batteries, motors, pumps and the like are present for the purpose of operating the different components of the device, such as for instance the tugger winches and the hydraulic cylinders. It is also possible to place these provisions wholly or partially on hoisting means 5, wherein the hydraulic hoses, electrical and mechanical cables and the like required for the purpose of actuating the components are run along the boom to auxiliary hoisting means 6, wherein the required energy is carried for instance via so-called umbilical hoisting cables to auxiliary hoisting means 6. An umbilical hoisting cable comprises a steel cable, the core of which comprises not a strand but for instance an electrical power supply cable. Energy can in this way be carried easily to auxiliary hoisting means 6 via for instance slide rings in hoisting winch drums. Power supply to the diverse actuators on the rotor blade spreader is provided most easily by electrical or hydraulic

accumulators on the spreader itself. The operation of the diverse functions is performed most easily using radio remote control.

A suitable method for placing and attaching rotor blade 22 at sea to the hub 24 of a nacelle 21 of a wind turbine 2 comprises of providing a device according to the invention on a vessel 4, taking up the rotor blade 22 for placing using pickup tool 7 and placing rotor blade 22 on a jacket 3 present in the sea using the auxiliary hoisting means 6, wherein rotor blade 22 is brought into alignment with hub 24 of the already available nacelle 21 by rotating at least auxiliary hoisting means 6 around the second horizontal shaft 61 relative to boom 50. As shown in figure 1, boom 50 can also be used to place components such as a nacelle 21 in known manner on mast 23 of a wind turbine.

Auxiliary hoisting means 6 is preferably displaced for this purpose to the lower half of boom 50 so that in this position this auxiliary hoisting means 6 does not impede the nacelle 21 being taken up from work deck 41 with hoisting tackle 53 of boom 50. By luffing in boom 50 and rotating boom 50 around vertical axis 57 the taken-up nacelle 21 is brought into alignment with mast 23 and placed thereon in the position shown in figure 3.

The boom 50 is subsequently rotated back again so that in any case the auxiliary hoisting means 6 is carried within reach of platform work deck 41. Referring to figure 2, auxiliary hoisting means 6 is then rotated, by tightening lifting wire 62 relative to boom 50, into the shown position in which pickup tool 7 is carried into the immediate vicinity of a rotor blade 22 to be taken up. Rotor blade 22 is then carried in a substantially horizontal position into the immediate vicinity of nacelle 21, wherein auxiliary hoisting means 6 is displaced if desired along boom 50 in the longitudinal direction 501 of boom 50, boom 50 is rotated around axis 57 and levers (63, 64) of auxiliary hoisting means 6 are rotated relative to each other through the action of hydraulic cylinders (67, 68). In order to orient rotor blade 22 precisely relative to hub 24 of nacelle 21, the rotor blade 22 taken up by pickup tool 7 is displaced and/or rotated in three dimensions over relatively small distances by a rotation and/or displacement of pickup tool 7 or the spreader 406 connected thereto.

Once a good alignment has been obtained between rotor blade 22 and hub 24, rotor blade 22 is attached for instance by means of bolt connections to hub 24 of nacelle 21.

The above described operations are repeated as often as rotor blades 22 have to be placed. In the shown embodiment the total number of rotor blades to be coupled to nacelle 21 is three, so that a rotor comprises an assembly of a hub 24 and three rotor blades 22. Although it is not essential to hoist and place rotor blades 22 in a

substantially horizontal position, the device according to the invention is particularly suitable for doing so. In order to enable attachment of a new rotor blade 22 to a nacelle 21 already provided with a rotor blade 22, hub 24 of nacelle 21 can if desired be rotated around a longitudinal axis of hub 24. The invention is not limited to the embodiments shown in the figures, and many variants thereof are possible within the scope of protection of the appended claims.

Claims

1. Device for assembling a structure constructed from components, in particular a wind turbine, which device comprises a hoisting means which is provided on a substrate and takes the form of a boom rotatable around a horizontal axis in a lifting plane, to which boom is connected an auxiliary hoisting means rotatable by means of rotation means around a second horizontal axis in the lifting plane, wherein the auxiliary hoisting means comprises at an outer end a pickup tool with which a component can be taken up, the auxiliary hoisting means comprising mutually coupled levers which can be moved relative to each other.

2. Device as claimed in claim 1, characterized in that the boom extends over a boom length from a boom base to a boom top, and the connection of the auxiliary hoisting means to the boom is situated between the boom base and the boom top.

3. Device as claimed in claim 2, characterized in that the connection of the auxiliary hoisting means to the boom is located at between one third and two thirds of the boom length.

4. Device as claimed in any of the foregoing claims, characterized in that the auxiliary hoisting means is connected to the boom for displacement in a longitudinal direction of the boom.

5. Device as claimed in any of the foregoing claims, characterized in that the rotation means comprise a lifting wire which runs between boom and auxiliary hoisting means and the variable free length of which determines the rotation position of the auxiliary hoisting means relative to the boom.

6. Device as claimed in any of the foregoing claims, characterized in that the substrate comprises a vessel and the device is adapted for assembling a structure constructed from components at sea.

7. Device as claimed in claim 4, characterized in that the levers are driven by hydraulic cylinders incorporated in a hydraulic circuit.

8. Device as claimed in any of the foregoing claims, characterized in that the length of the auxiliary hoisting means in furthest extended position lies between one quarter and three quarters of the boom length.

9. Device as claimed in claim 8, characterized in that the length of the auxiliary hoisting means in furthest extended position lies between one third and two thirds of the boom length.

10. Device as claimed in any of the foregoing claims, characterized in that the pickup tool is connected by means of a rigid connection to an attaching structure to which a component can be releasably attached.

11. Device as claimed in claim 10, characterized in that the rigid connection and/or the attaching structure comprises means for displacing and/or rotating in three dimensions a component taken up in the pickup tool.

12. Device as claimed in claim 10 or 11, characterized in that the attaching structure comprises a gripper for a mast section, a rotor blade or a nacelle of a wind turbine.

13. Device as claimed in claim 12, characterized in that the attaching structure comprises a blade yoke or blade spreader.

14. Device as claimed in any of the foregoing claims, characterized in that the vessel comprises a jack-up platform.

15. Device as claimed in any of the foregoing claims, characterized in that it further comprises displacing means for displacing the components over the deck of the vessel into the working range of the auxiliary hoisting means.

16. Method for assembling a structure constructed from components, in particular a wind turbine, the method comprising of providing a device as claimed in any of the foregoing claims, taking up a component for placing using the pickup tool and placing the component on a foundation using the auxiliary hoisting means, wherein the component is brought into alignment with the foundation and components possibly already placed thereon by rotating at least the auxiliary hoisting means around the second horizontal axis relative to the boom, the auxiliary hoisting means comprising mutually coupled levers, that are moved relative to each other.

17. Method as claimed in claim 16, characterized in that the auxiliary hoisting means is displaced in a longitudinal direction of the boom in order to take up or place the component for placing.

18. Method as claimed in claim 16 or 17, characterized in that the auxiliary hoisting means is rotated with a lifting wire running between boom and auxiliary hoisting means, wherein the free length of the lifting wire is varied in order to determine the rotation position of the auxiliary hoisting means relative to the boom.

19. Method as claimed in any of the claims 16-18, characterized in that the substrate comprises a vessel, in particular a jack-up platform, and the components are placed on a foundation present in the sea.

20. Method as claimed in claim 19, characterized in that the levers are driven by hydraulic cylinders incorporated in a hydraulic circuit.

21. Method as claimed in any of the claims 16-20, characterized in that the component taken up by the pickup tool is displaced and/or rotated in three dimensions.

22. Method as claimed in any of the claims 16-21, characterized in that the component is attached to the pickup tool by means of an attach ing structure comprising a blade yoke or blade spreader.

23. Method as claimed in any of the claims 16-22, characterized in that the component for placing comprises a rotor blade of a wind turbine.