NL2016927A

NL2016927A - Hoisting system for installing a wind turbine

Info

Publication number: NL2016927A
Application number: NL2016927A
Authority: NL
Inventors: Lambertus Lagerweij Hendrik; Heinz Pubanz André; Van De Pol Aart; Waaijenberg Albèrt; Paul Corten Gustave
Original assignee: Lagerwey Wind B V
Priority date: 2016-06-09
Filing date: 2016-06-09
Publication date: 2017-12-18
Also published as: NL2016927B1

Abstract

A hoisting system for the installation of a wind turbine, wherein the wind turbine comprises a tower, the hoisting system comprising a column, a boom and a winch, wherein the column is arranged for creating a load bearing connection to a part of the tower of the wind turbine using one or more fixation points successively located along a longitudinal direction of the tower, and wherein the column is arranged to move the hoisting system essentially in vertical direction along said part of the tower when the load bearing connection is created.

Description

HOISTING SYSTEM FOR INSTALLING A WIND TURBINE Field of the invention

The present invention relates to a hoisting system for the installation of a wind turbine, to a wind turbine comprising measures to facilitate the use of said hoisting system, a segment of a wind turbine, a method for installing a wind turbine, a method for fixing a hoisting system to a wind turbine, a method for removing a hoisting system from a wind turbine and to a method for adapting an existing wind turbine.

Background of the invention

The costs of labor and maintenance increase only gradually with increasing turbine size, and therefore to minimize costs, wind turbines are getting bigger and bigger. With increasing size and height the installation costs of the turbines are not rising gradually but at least linearly with turbine size. The largest industrial cranes available are required to install the largest Sand based wind turbines. Those heavy modular crane units are expensive, often require strengthening of the roads and special transportation permits, in addition to these disadvantages said cranes need a lot of space which is not always available and when such a crane is needed for the next turbine in a wind farm it may occur that the crane cannot move thereto for example because the terrain is complex or the roads are too small. Then the crane has to be decommissioned, transported in parts and commissioned again which is an inefficient time consuming operation.

There is a need to be able to install a wind turbine more efficiently and in particular without the need of a large general purpose crane. WO2014/082176A1 discloses a rail that is attached to the tower and a lifting platform that can move up and down over said rail. This system has a drawback that the rail is required over the full length of the tower, which adds weight and increases the tower stiffness in one direction so that the tower eigen frequencies in that direction become higher than those in the perpendicular direction reducing the design freedom for modern variable rotor speed wind turbines where resonance between the tower eigen frequencies should be avoided in the full range of rotor frequencies and blade passage frequencies. Another drawback is that the lifting platform is attached to the rail over a vertical distance of about the length of one tower segment or less. This relatively short distance leads to large forces on the wind turbine tower when heavy parts like the nacelle are lifted. Furthermore, since the lifting platform moves over the entire rail length, the rail needs to be strong and heavy over the entire length and becomes expensive and economically inefficient.

Alternative lifting platforms are disclosed in US4311434, US6357549, US6614125 and US6522025, with similar disadvantages. US8069634 discloses a first crane, which can be a large industrial crane or a crane of a ginpole type, which is moveably attached to a partially constructed structural tower of a wind turbine. The first crane is applied to hoist and install a structural tower in several parts and, once the tower is completed, to lift a second lifting system, which is installed on top of the tower and serves to hoist the nacelle and the rotor. Besides to the disadvantage of requiring two lifting systems, the application is time consuming: the first crane is to hoist the second lifting system to the top and this second lifting system is to be installed and made operational. Then the first crane is to be positioned away to avoid interfering with the second lifting system. After that the nacelle and rotor can be hoisted and when this is finished all steps need to be repeated in reversed order, A further disadvantage is that the disclosed ginpole is not resistant to sideward wind loading: the tall crane has one or two slender beam I ike joints to the tower which cannot take the sideward wind load so that the entire crane could spin around the vertical axis. A further disadvantage of the disclosed ginpole moving system is that the system employs one or more standoff brackets for fixation of a jump rack slidably to the wind turbine tower. The ginpole is also connected siidabiy to the jump rack. Moving the ginpole is a stepwise procedure wherein each step consists of installing successive standoff brackets to wind turbine tower, shifting the jump rack so that it overlaps with the successive standoff brackets and subsequently sliding the ginpole over the jump rack. This cumbersome procedure. A similar ginpole solution with similar disadvantages is disclosed in DE-G9414643.8, which operation is time consuming and not cost-effective.

It should be noted that the erection of a wind turbine requires a period of calm weather and in particular low wind speeds. If the hoisting takes much time the probability of completing the job in the low wind period is reduced which further decreases efficiency. US2015/0048043A1 discloses another comparable iifting system, wherein, after completion of the tower, a crane is installed on the tower top to hoist the nacelle and rotor. This system has the disadvantages that it applies a winch at the tower bottom which acts as a counter weight, resulting in the downward forces on the tower top to be about double, and much long cables are required. Furthermore this system cannot lift tower segments, so that a large conventional crane is required.

An alternative method to install a wind turbine is by designing the nacelie of the wind turbine in such a way that is comprises a hoie which encloses a non-tapered tower as disclosed e.g. in US756216, DE2823525B1, DE2735298A1 and US6408575. Although the so-called Growian, a wind turbine of 100m in height, was made using this method, it turned out to be not efficient for large wind turbines: the iarge turbines require tapered towers to deal efficiently with the high bending moments. Therefore non-tapered towers have phased out for wind turbines with an axis height of above about 80 meters.

Known wind turbine towers are typically of the tapered structural type or of the tapered tubular type and sometimes the lower side of the tower is structurai and the upper side tubular. Structural towers are known to be transported in parts and assembled at the side. The appearance of tubular towers is generally better publicly accepted. Tubular towers protect the equipment inside the turbines such as the inverter, transformer and controller against the outdoor climate. Therefore, a solution for efficient installation of wind turbines is more relevant for tubular towers than for structural towers.

It should be noted that tubular towers are defined as towers of which horizontal cross sections are closed curves, which can be circular, polygonal, or of any other closed shape.

In DE19741988A1 and DE19647515A1 alternative lifting systems are disclosed, wherein the lifting systems can climb tubular towers by fixing itself by a system that surrounds the tower. Those systems easily damage the tower since large holding forces are needed to obtain sufficient friction on the tower wall to avoid the systems from gliding downward. Furthermore, these systems are most suitable for non-tapered towers which have phased out and these systems are not designed for carrying heavy parts of large modern wind turbines since the vertical length on which the bending moments are fed into the tower is less that the length of one tower segment or less than two tower top diameters which leads to unacceptable high forces on the tower wall.

Since wind speed increases with height, and the average hub height of wind turbines increases with the successive wind turbine generations, the hoisting is getting increasingly hindered by high wind speeds. In particular this is relevant to the hoisting of the entire rotor i.e. the hub and the blades in a single hoist: the large aerodynamicaily shaped blades are sensitive to gusts. The lifting devices of the above prior art are typically designed for single hoist lifting of the rotor and are not suitable for single blade hoisting and in particular not for the single blade hoisting in an about horizontal position.

Summary of the invention

The aim of the invention is to overcome the above mentioned disadvantages of existing solutions.

Hereto, according to an aspect of the invention a hoisting system is proposed for the installation of a wind turbine comprising a column, a boom and a winch wherein said column comprises measures to achieve a load bearing connection to the tower of the wind turbine and wherein said column comprises measures to move the hoisting system up and down along the tower. The tower comprises one or more fixation points and the column is arranged for creating the load bearing connection to a part of the tower using the one or more fixation points, and wherein the column is arranged to move the hoisting system essentially in vertical direction along said part of the tower when connected to the part of the tower.

Such a system can install successive tower segments while moving upwardly along the installed tower segments. After the tower is completed it can install the nacelle, generator, hub and the rotor blades.

Advantageously, the hoisting system of the present invention can be used instead of conventional large industrial cranes for installing wind turbines, enabling wind turbines to be built at lower costs and without requiring strengthening of roads and special transportation permits. Furthermore, the area of the building site of a wind turbine can be reduced from up to 3000m2 when using conventional cranes to about 200m2 when using the hoisting system of the present invention.

The column of the hoisting system typically comprises a rail which guides the hoisting system in essentially vertical direction along fixation points which are fixed to the tower. A beneficial maximum length of said rail is 60m, while a beneficial minimum length is 10m, preferably 20m , more preferably 34m. The relatively long rail allows the hoisting of heavy parts such as the lower tower segments or the nacelle without applying high sideward forces to the tower since force equals bending moment divided by arm.

The hoisting system is efficient since it allows simple and fast movement of the system up and down along the fixation points on the tower.

In an embodiment the hoisting system comprises a rail of which a section can be put in a first position wherein the rail section can be placed over a fixation point on the wind turbine tower and in a second position wherein it encloses the fixation point in such a way that the rail can only move up and down along the tower.

In an embodiment the column of the hoisting system comprises measures to move the hoisting system up and down along the tower. Such measures can comprise a climbing actuator and or a connection actuator which both can be of the type of a hydraulic cylinder or an electromechanical linear actuator. Those actuators can have a fixed part and a moving part. The fixed part of each actuator can be fixed at one end to the column possible in a hinged manner. In one embodiment according to the invention the other end of the fixed part of the climbing actuator is connected to the end of the moving part of the connection actuator so that the connection actuator can move the climbing actuator in a direction from nearby the column to further away from the column. The end of the moving part of the climbing actuator is the connection end, which comprises measures for connecting to a fixation point. A climbing system includes a climbing actuator which can move the hoisting system up and down and the connection end of the climbing actuators can be controlled by the connection actuator from a free position to a position wherein the connection end is connected to a fixation point.

In an embodiment a climbing system comprises a double set of climbing and connection actuators, which has the advantages of distributing the loads an therefore reducing the costs of the system and introducing redundancy so that the climbing system still can be operated when combination of climbing and connection actuator is failing. In case of such a failure the hoisting system at least still can be moved downward to the ground thanks to the redundancy.

In an embodiment the hoisting system comprises a first and a second climbing system, wherein the distance between the center of the connection of the first climbing actuator to the column and the center of the connection of the second climbing system to the column is about 5.7m and at least 1.8m in length direction of the column. The advantage of having two climbing systems is that each climbing actuators can have about half the length compared to a single climbing system which provides better stability and lower costs. The two climbing systems are repeatedly used to move the hoisting system in essentially vertical direction along the tower. For example first the first climbing system is fixed to a fixation point and pulls the hoisting upward over about 50% of the distance between fixation points, then the second climbing system connects to another fixation point, then the first climbing system disconnects and subsequently the second climbing system pulls the hoisting system further upwardly so that it can be fixed to the next fixation point. It will be clear that also three, four, five etc. climbing actuators can be used which each can move the hoisting over respectively about one third, one fourth, one fifth etc. of the distance between fixation points, which distance is usually between 6m and 26m, preferably between 10 and 18m, for example about 11.5m.

In an embodiment the hoisting system comprises a chain moving around over driven cogwheels which are fixed to the column. By fixing the chain to a fixation point it can move the hoisting system up and down. Another option to move the hoisting system is to fix a cable at one side to a fixation point and at another side to a winch which is mounted to the column.

In an embodiment the hoisting system comprises a coupling which can fix the hoisting system rigidly to a fixation point in such a manner that it can transfer vertical forces of the hoisting system to the fixation point in particular at least 30% of those vertical forces and more in particular at least 90% of those vertical forces. The height position of a coupling in the column is within the lower 65% of the length of the rail and preferably between 35% and 65% of the rail length.

In an embodiment the coupling between the column and the fixation point is such that during hoisting operation it allows for at least 0.25 degrees and preferably at least 0.5 degrees and more preferably at least 1 degrees for example 2 degrees rotational freedom about an imaginary horizontal axis between the parts joint by the coupling. This freedom avoids that large bending moments are exerted on the fixation points and therefore reduces costs. A beneficial embodiment of the hoisting system comprises a boom which reaches at least 15m from the rail and preferably at least 25m from the rail. According to one embodiment of the hoisting system the maximum length of the boom is 60m. A further beneficial hoisting system is that wherein the boom is fixed to the column via a yaw bearing and in particular wherein the rotation axis of said yaw bearing is inclined to the length direction of the rail by more than 0.5 degrees, preferably by more than 1 degree, more preferably by less than 5 degrees. In a further beneficial embodiment of the hoisting system the boom is fixed with a tilt hinge to the yaw bearing or the boom comprises a tilt hinge, wherein the tilt hinge can be adjusted over at least 20 degrees and preferably over less than 200 degrees. The tilt motion can be driven by a hydraulic or electro mechanic actuator.

In an embodiment the column is extended to more than 15m and preferably more than 25m above the rail and comprises a yaw bearing whereon an about horizontal boom is attached which comprises a hoisting point which can move along the boom.

In an embodiment the boom comprises a winch which drives the hoisting cable and in particular the boom comprises multiple winches which each have a separate hoisting cable leading to the hoisting point so that each winch carries part of the total load.

In an embodiment the hoisting system comprises a boom which is bended or inflected so that a line piece from the center of the tilt hinge to the hoisting point reaches a distance to the boom of at least 1.5m and preferably of at least 2.5m and more preferably of about 4m.

The hoisting system can be powered with an electric cable from the ground. In an embodiment the hoisting system comprises a power supply based on a chemical reaction such as a diesel generator, a fuel cell or a battery, wherein said power supply is installed in the hoisting system so that a long cable to the ground is avoided. This saves the costs and weight of the cable and avoids the problem of motion of the cables by the wind which reduces the weather window for hoisting operations and reduces the reliability of the system. In an embodiment the power supply is connected directly or indirectly via an electric motor to the hydraulic pump. In another embodiment the hoisting system comprises a second hydraulic pump, which e.g. can be driven by an electric cable from the ground as backup.

While a conventional heavy crane requires several dozens of trucks, e.g. 50 trucks, for transportation, the hoisting system according to the invention can be transported by less than 5, e.g. just 2 standard trucks, which gives advantage in cost and space requirements at the site. A further advantage is that the hoisting system can be installed in several hours while the erection of a heavy crane takes several days.

An even further advantage is that the hoisting system can move up and down along the wind turbine tower relatively fast compared to the lifting systems found in the prior art.

According to a further aspect of the invention a wind turbine is proposed comprising a tower, a nacelle, a generator, a hub and at least a blade wherein the tower comprises fixation points for the fixation and guiding of a hoisting system and in particular of the hoisting system according to the invention.

In an embodiment the wind turbine comprises fixation points at a relative spacing of more than 10m and less than 30m.

In an embodiment the tower of the wind turbine comprises tubular overlapping segments which are bolted together on the overlap and wherein a fixation point is installed on the overlap so that less stiffening of the tower near the fixation points is required since the double layered overlapping parts have more stiffness by themselves.

In an embodiment a fixation point comprises a stiffening structure which is fixed to the tower and which extends from the center of the fixation point by at least 50 cm and preferably by at least 100 cm. Such a stiffening structure can be installed at the outer side or at the inner side or at both sides of the tower. In particular for the first or second tower segment of a segmented tower the stiffening structure may comprise a structural beam from the fixation point to the tower foundation or a structural beam in about horizontal direction to the tower wall at a position which is more than 10 degrees and preferably more than 30 degrees away from the fixation point when rotating around the tower axis along the tower wall.

In an embodiment the wind turbine the fixation points are aligned in the longitudinal direction of the tower with a maximum deviation. If there are N fixation points which are numbered 1 to N in upward direction for fixation point M for M = 1 to N-2, then the line between the centers of fixation points M and M+1 reaches a distance to the center of a successive fixation point of maximally 5 cm, in preferably of maximally 10 cm and more preferably of maximally 20 cm.

In an embodiment the wind turbine comprises a tower with a load carrying wall and in particular one wherein the wall is load carrying over a tower length a wind turbine according to the invention comprises a non-structural tower with a load carrying wall over its full length.

In an embodiment the wind turbine comprises a tower of which a horizontal cross section of the outer side is shaped circular or polygonal.

In an embodiment the wind turbine comprises a tubular tower which comprises vertical segments, which segments are made of bended or folded steel plates which extend over the vertical length of said segment.

In an embodiment the wind turbine comprises a tower which comprises multiple vertical segments of a length between 10m and 22m and preferably between 10m and 16m.

The tower can be of the tubular type and can be made of pre tensioned concrete or of wood or of steel. Alternatively, the tower can be a structural tower, or in other words a lattice tower made of steel or wood. The tower can be partly of the tubular and partly of the lattice type. The lower part of the tower can be a tripod with three tubular legs, a jacket or a floating structure, in particular in offshore sites.

In an embodiment the wind turbine comprises a tower which is tapered over at least 50% of the tower length and preferably over at least 80% of the tower length.

In an embodiment the hoisting system comprises a straight rail which can be guided over at least two fixation points during climbing and therefore the fixation points are typically aligned following a straight line in the longitudinal direction of the tower of the wind turbine. Due to spatial and dimensional tolerances in the fixation points in the rail, some curvature is allowed between the fixation points.

The rail of the hoisting system may not be straight has and can have a constant curvature instead. In such a case the hoisting system can climb towers with a constant curvature in the tower wall in vertical direction.

The rail of hoisting system can be connected to just one single fixation point in a part of the track. Then the hoisting system is typically also connected via the climbing system to a second fixation point. The advantage of such a hoisting system is that it can move along towers which change of taper level, e.g. from cylindrical to tapered.

In an embodiment the wind turbine comprises a tower of which the fixation points including the stiffening thereof cover together less than 10% and preferably less than 20% of the tower length in any side view of the tower.

In an embodiment the tower center is installed at a horizontal distance to the center of a dike of less than 100m, preferably less than 50m and more preferably less than 20m.

In an embodiment two hoisting systems are applied to the same wind turbine. The two hoisting systems can be installed below each other on the same track of fixation points or can be installed at different angles in a cylindrical coordinate system around the tower axis. The tower could comprise two tracks of fixation points at different angles from the bottom to the top or a single track at a first angle and just one or more fixation points at a second angle. In the latter case a first hoisting system can climb all the way up to the tower top along the single track of fixation points at said first angle and can install the second crane to the one or more fixation points at that second angle. The difference between said angles in said cylindrical coordinate system comprises at least 20 degrees, preferably at least 45 degrees and more preferably at least 60 degrees, for example 90 degrees.

Using two hoisting systems has several advantages. First the hoisting systems together can hoist heavier parts and therefore are suitable for the installation of larger wind turbines. Second the hoisting of parts by two cranes is less sensitive to the wind thus more stable so that the operational weather interval increases. Third the loads exerted by two hoisting systems to the tower are more distributed compared to the situation of a single heavier hoisting system. The distribution of loads reduces the costs of the hoisting systems and of the fixation points. Fourth the hoisting systems can be used more efficiently because the same system is used for installing mid size and large size wind turbines and when a wind farm is installed, each single hoisting system can be used to erect wind turbine towers while only for the hoisting of the nacelle, generator, hub and rotor the hoisting systems are applied together.

In an embodiment of the wind turbine comprises an offshore turbine, of which the part that passes the sea level can comprise a fixation point, e.g. wherein the transition piece comprises the fixation point for a hoisting system.

The term offshore turbine also refers to turbines installed in lakes or rivers.

In an embodiment an offshore turbine comprises a fixation point below the water line.

In an embodiment the hoisting system is pre-installed on a tower segment and said hoisting system and tower segment are in a single hoist installed on a lower already installed tower part.

In the embodiments concerning an offshore turbine the hoisting system can be used to complete the installation of the entire offshore wind turbine by lifting parts from a vessel and installing them. Said vessel does not need to be an expensive jack-up vessel and therefore reduces the installation costs much. Optionally the hoisting system remains on the turbine after commissioning to serve as maintenance tool or for the decommissioning of the turbine later.

In an embodiment the wind turbine has a axis height of more than 80m, preferably more than 130m and more preferably more than 180m, wherein the maximum axis height according to an embodiment is 500m.

In an embodiment the wind turbine has a design rpm, of which the ratio between the design rotor speed at 12m/s wind speed and at 6m/s wind speed is above 1.3, preferably above 1.5 and more preferably above 1.8, and less than 3. Such turbines with variable rotor speed have a range of excitation frequencies wherein the tower should not reveal resonance. In such cases, advantageously the attachment of fixation points hardly influences tower eigen frequencies and does not cause the tower to have different eigen frequencies for excitations in the plane of the tower axis and the fixation points compared to those in the plane perpendicular thereto and parallel to the tower axis.

According to an aspect of the invention a combination of a wind turbine according to the invention with a hoisting system according to the invention is proposed.

In an embodiment the rail of the hoisting system during hoisting work is fixed permanently in a rigid non-slidable manner to the column of the hoisting system while said rail is rigidly or slidably fixed to the fixation points on the tower of the wind turbine.

In an embodiment the rail of the hoisting system is at least connected to two or three fixation point during hoisting work.

In an embodiment the highest fixation point where the hoisting system is fixed to the tower during the hoisting of tower parts corresponds to the overlapping part of the highest two installed tower segments.

According to an aspect of the invention a method is proposed for installing a wind turbine according to the invention, the method comprising building at least a part of a tower of the wind turbine by placing one or more tower segments using the hoisting system of the invention.

In an embodiment the lower one to three tower segments can be installed with a conventional method.

In an embodiment, subsequently the installation of the rail of the hoisting system to the fixation points of the one or more installed tower segments can be performed.

In an embodiment wherein the hoisting system is attached to the first two installed tower segments, the hoisting system hoists and installs the third segment without a fixation point installed and then installs the fixation point to the third segment. An advantage of this method is that when the third segment is lowered, the additional constraint is avoided and its fixation point should simultaneously fit into the rail of the hoisting system.

In an embodiment the hoisting of one to three higher tower segments in parts or in single hoists and the installation of said higher segments can be performed.

The repetition of unlocking, moving and relocking the hoisting system in a higher position and the hoisting and installation of one or two higher tower segments results in the tower being fully assembled.

In an embodiment the hoisting system can be unlocked, moved and relocked in the highest available position and the hoisting of the nacelle, generator, hub and the rotor blades can be performed in one or more combined hoists or in a single hoist.

In case of single blade hoisting the hoisting system can be used to turn the hub in a convenient position for installation a next blade by hoisting an installed blade to a lower or higher position.

According to an aspect of the invention the hoisting system an be unlocked and moved downwardly by repetitively locking and moving the hoisting system back to the tower bottom. At the bottom the hoisting system can be removed from the tower.

In the case that the hoisting system installs also (part of) the first tower segment, a temporal separate support can be required or the section of the first segment with a fixation point can be installed first by a conventional crane after which the hoisting system can be installed.

In an embodiment the horizontal distance between the hoisting point of the boom and the highest applied fixation point is less than the diameter of a hoisted tower segment.

Brief description of the drawings

The following drawings show exemplary embodiments of the invention:

Fig. 1: a wind turbine and a hoisting system;

Fig. 2: tower segments of a wind turbine;

Fig. 3: tower segments of a wind turbine;

Fig. 4: tower segments of a wind turbine;

Fig. 5: tower segments of a wind turbine;

Fig. 6: a wind turbine under construction and a hoisting system;

Fig. 7: a wind turbine under construction with two hoisting systems;

Fig. 8: installation of a hoisting system for an offshore wind turbine;

Fig. 9: installation of a hoisting system for an offshore wind turbine;

Fig. 10: a fixation point on a wind turbine tower;

Fig. 11: cross section of the fixation point in Fig. 10;

Fig. 12: a column of a hoisting system with three climbing systems;

Fig. 13: a column of a hoisting system with a single climbing system;

Fig. 14: a cross section of a fixation system;

Fig. 15: a cross section of a fixation and a climbing system; and Fig. 16: a wind turbine and a hoisting system.

The drawings are to be understood not to be drawn to scale.

Detailed description of the invention

Fig. 1 shows an exemplary combination 1 of a wind turbine and a hoisting system. The wind turbine comprises tower segments 2 which overlap in areas 8 and each have a fixation point 7, a nacelle 3, a generator 4, a hub 5 and several blades 6. The hoisting system comprises a column 10, a yawing platform 11 which carries via a tilt hinge 12 the boom 14. The boom can tilt by activation of the hydraulic cylinder 13. The hoisting cable 18 is lead via pulleys 16 and 17 to the winch 15. The hoisting system is fixed to a rail 9 which is, depending on its position, slidably attached to fixation points 7, 19 and 20, so that it can move up and down along the tower. Before hoisting is started any of the locking systems 21,22, 23, 24 locks the rail to a fixation point.

Advantageously, the hoisting system can be releasably fixed to one side of the tower without the need for a contra weight or means for creating a contra force at another side of the tower.

Fig. 2 shows the first three tower segments 30, 31 and 32 of an exemplary wind turbine. Segment 32 is elevated for illustrative reasons. Segment 30 comprises the fixation points 34 and 36 with respectively stiffening structures 33 and 35. Segments 31 and 32 comprise fixation points 39 and 40 with stiffening structures 38. Fixation points 36 and 40 comprise a hole 37 which is used for locking the hoisting system to the installed tower segments. The supporting beams 44 are fixed to stiffener 35 and to fixation means 45 which are fixed to the tower foundation 46. The dashed lines 41, 42 and 43 illustrate positions of the connection between the tower segments which e.g. can be bolted together. In this example the stiffeners 33, 35 and 38 are also bolted to the tower segments.

According to an installation method according to the invention a general purpose crane installs the first tower segment 30. Then the hoisting system is installed to the fixation points 34 and 36 of this first tower segment 30. The hoisting system uses locking system 22 to lock itself to hole 37 of fixation point 36. Then it hoists tower segment 31 on top of segment 30 and during this hoist the fixation point 39 is placed in the rail 9. The segments are bolted together and the hoisting system hoists segment 32 similarly on top of segment 31 and subsequently hoists the fourth segment. Then the hoisting system unlocks, moves upwardly and locks with locking system 23 to fixation point 37 of segment 32 so that it can hoist segment 5. This continues until the entire tower is installed. The hoisting system subsequently hoists and installs the nacelle, generator, hub and the blades, where several combined hoisting operations can be beneficial e.g. the nacelle and generator or the entire rotor comprising the hub and the blades or even the combination of the nacelle, the generator and the rotor in a single hoist.

Fig. 3 illustrates another embodiment of the first two tower segments 55 and 56 where segment 55 has two fixation points 34 and 62. Fixation point 62 is installed on stiffener 58 which is placed via plate 59 (shown by a dashed line) to the tower wall. Plate 59 has the same thickness as the wall of tower segment 56, so that this segment fits precisely between segment 57 and stiffener 58. The dashed lines 57 and 58 illustrate the positions for a bolted connections. In practice the bolts can be placed in multiple lines per connections which is not shown for illustrative reasons. Fixation point 62 is supported by beams 60 which are fixed to supports 61 on the inner side of the tower. The embodiment of Fig. 2 can also be combined with supporting beams on the inner side of the tower and that of Fig. 3 can be combined with supporting beams on the outside of the tower. In the embodiment of Fig. 3 the locking system 22 is optional.

Fig. 4 illustrates another embodiment of the first tower segments 70, 71 and 32 of a wind turbine. In this case segment 32 and the higher segments which are not shown have a standard length 78 which can be transported easily e.g. a length between 10m and 16m such as e.g. 12m. The tower segments overlap over a distance 76 which is e.g. 0.5m, so that the tower height increases 11.5m per standard segment. For the hoisting system it is beneficial when the fixation points always have the same vertical spacing 79, e.g. one fixation point per 11.5m. By increasing the length 75 of the first tower segment 70 it can comprise two fixation points at a spacing of 11.5m and still sufficient length is left for the overlap 76 with tower segment 71. This enables to attach the hoisting system to segment 70 and subsequently to hoist segment 71 and 32, without the need of the special structure with plates 58 and 59 in Fig. 3. A consequence is that segment 75 requires a longer transport length. Segment 71 has a shorter length 77 and does not carry a fixation point. Fixation point 74 has a stiffening structure 73 on the outer side of the tower and a stiffening structure 80 on the inner side of the tower.

Fig. 5 illustrates another embodiment of the first tower segments. In this embodiment the first tower segment 85, which also could be an integrated part of the tower foundation 46, comprises the first fixation point 90 with stiffener 91 at a distance 94 from the foundation. The second segment 86 comprises a fixation point 92 with stiffener 93 and similar to Fig. 4 an internal stiffener 79. This embodiment has the advantage that the first, second and third segments can have equal or shorter lengths, respectively 88, 89 and 77, compared to the length 78 of the fourth segment 32, which can be the maximum transport length of all segments.

Fig. 6 shows an exemplary hoisting system and exemplary first tower segments in more detail compared to Fig. 1. The column of the hoisting system comprises a hydraulic cylinder 95 with piston 96 and an actuator in a state 97 so that it can pass a fixation point 99 and in a state 98 wherein it connects to fixation point 99. The hoisting system can move up after the actuator is in state 98 and is locked to fixation point 99 on tower segment 103 and the hydraulic cylinder 95 is actuated until the weight of the crane is carried by the hydraulic cylinder. Then the locking systems 21, 23 and 24 are unlocked, where it should be noted that although Fig. 6 illustrates three locking systems, any number of locking systems larger than zero is possible. Then the hydraulic cylinder 95 is further activated so that piston 96 is pulled into cylinder 95 so that the hoisting system moves upwardly. The upward movement continues until any locking system reaches a fixation point whereon it can be locked and the weight of the hoisting system can be transferred from the hydraulic cylinder 95 to the locking system.

It should be clear that also two cylinders are possible: each at one side of the column or even multiple cylinders e.g. cylinders which push the hoisting system upwardly instead of pulling it upwardly.

Fig. 6 also shows that due to the inflection of the boom, the boom reaches a distance 102 to the line segment 101 between the center of the tilt hinge and the hoisting point.

Fig. 6 further illustrates another tower segment 105 which still has to be hoisted. The segment comprises a fixation point 107 with edge 106 which serves to capture actuator 98. Fig. 7 shows an exemplary wind turbine tower under construction with two exemplary hoisting systems on opposite sides of the tower. In fig. 7 only the bottom tower segment 2 with overlapping part 8, fixation point 7 and additional fixation point 120 is shown with reference numbers for illustrative reasons. The higher tower segments are similar to the bottom tower segment. The hoisting system shown on the left hand side of the tower with rail 9, column 10, yaw bearing 11, tilt hinge 12, tilting actuator 13, boom 14 and hoisting cable 18 is similar to the second hoisting system shown on the right hand side. The hoisting systems together can advantageously be used for the hoisting of heavy parts such as e.g. the nacelle 122. Another advantage of two hoisting systems is that the hoisting of some parts, like the blade or the rotor, is less sensitive to wind gusts and more stable when using two cables, i.e. one cable from each hoisting system.

Most tower segments in the embodiment of Fig. 7 have two fixation points 7 and 120, i.e. one fixation point for each hoisting system. The two fixation points 7 and 120 may be positioned at any angle difference of at least 20 degrees in a cylindrical coordinate system around a tower center axis. In Fig. 7 the two fixation points 7 and 120 are located on opposite sides of the tower segment, i.e. at an angle difference of 180 degrees. In an alternative embodiment a first hoisting system is installed to the tower and climbs upwardly and subsequently installs a second hoisting system immediately at an elevated location suitable to hoist heavy parts. In the latter alternative embodiment the second hoisting system cannot climb or can only climb over a limited range so that not all tower segments need a second fixation point 120. The second hoisting system may be similar to the first hoisting system or may have a different layout. For example it may not comprise a climbing system or have a different boom.

Fig. 7 further illustrates two positions 123 and 124 where the boom 14 may have joints and position 125 where the column 10 may have a joint. At those joints the hoisting system may be folded or taken apart to facilitate transportation.

Fig. 8 shows an exemplary offshore wind turbine under construction. A vessel 130 with crane 131 uses a cable 132 to hoist a segment 135 of the tower of the offshore wind turbine. The segment 135 is for example a transition piece whereto an exemplary hoisting system with boom 136, rail 137, column 138 and fixation points 139 is attached. The hoisting system has, similar to the above exemplary embodiments, a tilt hinge 140 with actuator 141, but also may have a second tilt hinge 142 with a second tilt actuator 143 which are arranged so that the boom can fold to the column where the tip of the boom is connected at location 144 to the column to obtain a better structural stability. A relatively low cost vessel can be used to install the tower segment with the hoisting system in a single hoist on the foundation 133 of the offshore wind turbine.

In the example of Fig. 8 the foundation 133 is a monopile support structure which passes the sea level 134. Once the hoisting system is installed, it can pick up the subsequent tower segments and the other parts of the wind turbine from the same or another vessel and build the offshore wind turbine. The hoisting system can subsequently be removed or it stays on the turbine for maintenance work or for the replacement of parts of the wind turbine or for decommissioning of the turbine. An advantage of using the hoisting system on an offshore wind turbine is that the installation of parts of the turbine is cheaper than the conventional method wherein said parts are installed by a jack-up vessel. The hoisting system is even more convenient since it is attached to the tower under construction and therefore follows its movements.

Fig. 9 shows an alternative exemplary combination of an offshore wind turbine and a hoisting system. In this embodiment the hoisting system is hoisted with cable 157 from pontoon 150. Before the hoisting system is elevated, it may be placed on foot 151 which is arranged to stabilize the hoisting system for motion of the pontoon by waves. Foot 151 is e.g. placed on hydraulic cylinders 152 for stabilization and to lower the support completely below deck level, so that the other side of the hoisting system supported by wheel 156 can pass over it. While cable 157 hoists the system upwardly the cable 155 is released by winch 154 on support 153. This continues until the hoisting system is almost parallel to the tower. At a certain moment wheel 156 comes free from the deck and cable 155 is further released until wheel 156 reaches the wind turbine tower. After that the system is connected to the fixation points and performs the further completion of the offshore wind turbine by installing the remaining parts. Cable 157 can be pulled upwardly by a separate winch but also by the winch installed in the boom of the hoisting system, for example by guiding the hoisting cable from point 144 via the column 138 to the hook 158.

Fig. 10 shows an exemplary fixation point 160 in more detail. With protuberance 161 the fixation point can be installed with bolts 162 to the upper tower segment 169, so that this element can be hoisted together with the fixation points and installed on top of segment 168 where it is further fixed with bolts 163 in the overlap range 170. The element 164 is arranged to fit into the rail of the hoisting system and hole 165 serves for locking to the rail. Ribs 166 may be used to distribute the loads over a large part of the tower. Note also that only some of the bolts of the fixation points are drawn and those for the further connection of the upper and lower segments in the overlap zone 170 outside of the fixation point are not drawn. Element 167 is arranged to connect to the hoisting system and to carry the majority of the vertical loads during hoisting operations. It is installed close to the tower wall so that the vertical forces have a small arm and therefore exert a relatively small bending moment to the fixation point.

Fig. 11 shows cross section l-l of the fixation point in Fig. 10. From this side also stiffening plate 171 is visible.

Fig. 12 shows a combination of an exemplary wind turbine tower with a column of an exemplary hoisting system. The tower comprises segments 180, 181, 182, 183 of which the upper three have respectively fixation points 184, 185, 186 and hooks 187, 188, 189. Of the hoisting system only the column 190, the rail 191, a closed rail door 193, an opened rail door 194, fixation systems 192 and three hydraulic climbing systems are shown. For illustrative reasons the hoisting system is shown in a position wherein it can connect to the rail by moving the system towards the tower. The upper rail door 194 is open so that the fixation point 186 can move into the rail. The lower door 193 is shown in closed position for illustrative reasons, but will be open to connect to fixation point 186. When the fixation points 185 and 186 have entered the rail, the hoisting system can move downwardly so that also fixation point 184 enters the rail. Subsequently the doors 193 and 194 are closed and the system can be locked by one or more fixation systems 192.

In the exemplary embodiment of Fig. 6 the hoisting system included a climbing system with a hydraulic cylinder 95 with piston 96 and an actuator in states 97 and 98 for connecting to fixation point 99. The exemplary hoisting system of Fig. 12 includes an alternative climbing system that uses hooks next to the fixation points for climbing the tower.

In the embodiment of Fig. 12 the column is provided with three hydraulic climbing systems. The lower hydraulic climbing system comprises main cylinder 196 which is rotatably fixed with one end 195 to the column. The other end is guided through rail 198 by actuator 197. In Fig. 12 the piston 199 is fully extended and has a spherical end 200 which fits into any of the hooks, e.g. hook 188. When the column is unlocked from the fixation points and the lowest hydraulic climbing system is hooked on, it can pull the hoisting system upwardly over about one third of the distance between the successive fixation points. Then the mid hydraulic climbing system can extend its piston, connect it to hook 189 and pull the hoisting system further upwardly, after the lowest hydraulic climbing system is disconnected. The last step is performed by the highest hydraulic climbing system with hydraulic cylinder 202 which is connected at point 201 to the column and at the other end guided through rail 204 by control actuator 203. This highest hydraulic climbing system completes the stroke to the position where a fixation system can lock again to a fixation point. In Fig. 12 the parts of the mid hydraulic climbing system are not numbered but correspond to those of the highest hydraulic climbing system. A hoisting system with three climbing systems instead of one climbing system, wherein with each climb one third of the distance between successive fixation points is covered, has an advantage that shorter and therefore more stable and cheaper hydraulic cylinders can be used. The invention is not limited to three hydraulic climbing systems, and any number of climbing systems can be used in principle, including just one hydraulic climbing system.

Fig. 13 shows an alternative embodiment of a column 210 of the hoisting system. In this embodiment the length of the column extends over less than two times the distance between successive fixation points. An advantage of such a shorter system is that it is lighter and smaller, and therefore cheaper. Furthermore, since its rail can be slidably fixed by only a single fixation point during part of the climbing of the system, the system can move along towers of which the taper changes in longitudinal direction. In Fig. 13 the lowest tower segment 217 is cylindrical, while segments 182 and 183 are tapered.

In an embodiment of the hoisting system the column is arranged such that an operator has access to it. The column may have a door, one or more platforms and stairs inside so that an operator can carry out repairs and maintenance. From the inside of the column there may be inspection hatches, for example for the inspection of the fixation systems and/or climbing systems.

In an embodiment the hoisting system may have a single fixation system, for example the system of Fig. 12 only in the middle of the column and the system of Fig. 13 only at the upper end of the column.

In another embodiment of the hoisting system it may have no fixation system at all: For example the system of Fig. 12 may be executed without any of the fixation systems 192 and use the climbing systems for both climbing and fixation. The climbing systems are repeatedly activated so that always at least one climbing system connects the column to the tower. Advantages of such an embodiment are lower cost and more simplicity.

Figs. 6, 12 and 13 show climbing systems on one side of the column. Alternative embodiments may have climbing systems on both sides of the column.

The exemplary hoisting system of Fig. 13 includes a single climbing system with a relatively long cylinder 211 fixed in a hinged manner at end 212 and guided at the other end through rail 213 by controlling actuator 214. Piston 215 is locked into hook 189 with its spherical end 216. During climbing the column 210 is pulled up by the climbing system until the rail 191 is released from fixation point 184 after which the column is slidably fixed by fixation point 185 and further fixed via the piston of the climbing system to fixation point 186. In this part of the upward stroke the column can change slightly of tilt angle so that its rail is aligned to the successive fixation point.

Fig. 13 also shows an exemplary optional power system 218 which e.g. comprises a generator for electric and hydraulic power which are arranged such that the hoisting system can operate stand alone. The power system is fixed with joint 219 and the power and control lines between the column and the power system are led via joint 220. The hoisting system can comprise a backup hydraulic pump which can be driven by electric power fed via an electric cable from the ground.

Fig. 14 shows a cross section of an exemplary fixation system. On the left hand side part of two tower segments 168 and 169 are shown with a fixation point 230. On the right hand side part of the column 210 with the yaw platform 221 of a hoisting system are shown. Hydraulic cylinder 222 controls piston 223 with a hook 224 into the element 226 of the fixation point. The end 225 of the hook and element 226 together form a cylindrical hinge with the hinge axis approximately normal to the drawing plane and thus are arranged such that the column of the crane has some tilt freedom. The hook and thus also the column of the crane also has some rotational freedom of movement around the approximately horizontal axis of the piston 223. Those freedoms around the about horizontal axes avoid that large bending moments are exerted to the fixation point. During a fixation process, the column is lifted slightly first so that piston 223 can be extended. Then the column is lowered until hook 224 connects with element 226, and after that hydraulic cylinder 227 drives piston 228 in the hole 229 so that the column cannot move up or down anymore. The rail has a outside guiding strip 231 and an inside strip 232 with an mutual distance 233.

In an embodiment the thickness of plate 234 of the fixation point located is inside the rail is e.g. 15 cm, preferably 10 cm less and for example 5 cm less and at least 1 mm more than the mutual distance 233. An advantage of having a play of for example 5 cm is that the column has a tilt freedom of about 0.25 degree which allows the taper of the tower to change by about this amount over each section. Towers of changing taper have an structural advantage and can thus be installed with an hoisting system according to the invention.

The center of a fixation point may be defined by the center of plate 234.

The pistons 223 and 228 in Fig. 14 are directly driven by the hydraulic fluid. In an alternative embodiment any of those pistons may be guided pins which are driven by separate hydraulic cylinders. An advantage of such an embodiment is that the guided pins may be better suitable for sideward loading.

In a further embodiment of the hoisting system it may not have doors in the rail. For example the hoisting systems of Fig. 12 or Fig. 13 may be made without doors 193 and 194. They still can be installed on the rail aided by some play of the fixation points in the rail. In the case of Fig. 13 first fixation point 184 is slide in the rail by moving the hoisting system downwardly and subsequently by moving the system upwardly again, the rail slides over fixation point 185. The hoisting system in Fig. 12 may be installed in a similar manner.

Fig. 15 shows an exemplary wind turbine tower on the left hand side and an exemplary column of a hoisting system on the right hand side. For illustrative reasons the mid part of the column was not drawn. The column comprises a wagon 242 which comprises a hydraulic cylindre 245 with piston 246 which fits in the hole in plate 234 of the fixation point 230. A spindle 241 which is driven by a hydraulic motor 240 and is further positioned by bearing 244 slides through wagon 242 and drives it parallel to the rail through the back side of the rail. When wagon 242 is locked to a fixation point and hook 224 is unlocked, the hydraulic motor will move the hoisting system up and down by rotating the spindle. Advantages of climbing by a wagon connected to a spindle is that it saves the climbing system with the hydraulic cylindres, that locking to a fixation point with piston 246 is simpler than connecting to the hooks 187, 188, 189 and that the wagon is a relatively stable option.

Fig. 16 shows an exemplary wind turbine 250 with nacelle 252, hub 253 and blades 254 whereto a hoisting system 255 is attached. The wind turbine can be any one of the wind turbines of the above embodiments. The hoisting system can be any one of the hoisting systems of the above embodiments.

The above description focuses at the installation of wind turbines using a hoisting system. The invention is not limited to the installation of wind turbines and may additionally or alternatively be used for maintenance or decommissioning of wind turbines using the hoisting system.

The fixation point can be used for rigidly fixing or slidably fixing the hoisting system to the tower of the wind turbine and/or as support for the climbing system of which the latter is also a form of fixation and guiding of the hoisting system. Thus, where reference is made to a fixation point, it is to be understood that the fixation point can serve either or both as fixation and guiding of the hoisting system. Of course those functions can be split over multiple points for example wherein at least one point has a fixation function only or wherein at least one point has a guiding function only.

The hoisting system may be controlled via a computer that only allows for operation within the operational limits of the system. The system may be controlled by remote and fixed controllers, e.g. from the ground, in the crane and in the turbine under construction. A crane operator may be assisted by camera’s.

It is to be understood that in the present application, the term "comprising" does not exclude other elements or steps. Also, each of the terms "a" and "an" does not exclude a plurality. Any reference sign(s) in the claims shall not be construed as limiting the scope of the claims.

Claims

A hoisting system (255) for installing a wind turbine (250), the wind turbine comprising a tower, the hoisting system comprising a column (10, 138, 190, 210), a boom (14, 136) and a winch (15) ), wherein the column is arranged to create a bearing connection to a part of the tower using one or more attachment points (7, 19, 20, 34, 36, 49, 40, 62, 74, 90, 92, 99 , 107, 139, 160, 184, 185, 186, 230) which are located successively along a longitudinal direction of the tower, and wherein the column is arranged to move the hoisting system substantially in vertical direction along said part of the tower as the load-bearing connection has been created.

The hoisting system according to claim 1, wherein the bearing connection between the column and the attachment point is such that during hoisting operation it allows .25 degrees of freedom of rotation about an imaginary horizontal axis between parts connected by the bearing connection, preferably at least 0.5 degrees of freedom of rotation , more preferably at least 1 degree freedom of rotation.

The hoisting system according to claims 1 or 2, wherein the column is adapted to create a load-bearing connection further using a rail (9, 137, 191, 198, 204, 213) that makes it possible to guide the hoisting system along the bearing connection using the one or more attachment points.

The hoisting system according to claim 3, wherein the boom extends to a distance of the rail of at least 15 m and preferably at least 25 m.

The hoisting system of claim 4, wherein the boom is connected to the column via at least one of the following: a cross bearing, wherein preferably the angle between the axis of the cross bearing and the longitudinal direction of the rail is at least 0.5 degrees and more preferably is approximately 0.75 degrees; and a tilt hinge, preferably comprising a hydraulic cylinder or an electro-mechanical actuator for pivoting the boom relative to the column around the tilt hinge over a tilt angle change of at least 20 degrees.

6. The hoisting system according to any one of the preceding claims, wherein the boom comprises a cable winch for operating the hoisting cable.

The hoisting system according to any one of the preceding claims, wherein the boom is kinked or bent such that a distance of at least 1.5 m, preferably at least 2.5, is obtained between the boom and an imaginary line section from the hoisting point of boom to the center of a tilt hinge. m, and more preferably about 4 m.

The hoisting system according to any of claims 3-7, wherein the tower comprises the one or more fixing points and wherein the rail is connected to the column, wherein the rail preferably has a minimum length of 10 m, more preferably the rail has a minimum length of 20 m, and even more preferably the rail has a minimum length of 34 m.

The hoisting system according to any of claims 3-8, wherein a first section of the rail comprises provisions adapted to open the rail to place the rail at a mounting point, the provisions further being adapted to close the rail resulting in a slidable connection with the attachment point for allowing movement of the hoisting system relative to the tower substantially in a direction parallel to the rail.

The hoisting system according to any one of the preceding claims, wherein the column is adapted to move the hoisting system mainly in vertical direction along the tower, preferably using a continuous (circulating) chain or a climbing actuator or a wagon.

The hoisting system of claim 10, wherein the climbing actuator comprises a mounting actuator, wherein the mounting actuator is adapted to move one side of the climbing actuator in a direction to or from the column.

The hoisting system of claim 10 or 11, wherein the column comprises a first climbing system and a second climbing system, wherein each climbing system is arranged at one end to connect to a mounting point and is connected to the column at the other end, each climbing system is adapted to move the hoisting system along the tower in a substantially vertical orientation, wherein preferably the distance between the first climbing system and the second climbing system measured between their fixed ends is at least 1.8 m in the longitudinal direction of the column.

13. The hoisting system according to any one of the preceding claims, wherein the bearing connection comprises a bearing coupling for fixing the hoisting system to a mounting point, preferably such that during hoisting operation the bearing coupling transmits at least 90% of the vertical force to the tower via a single attachment point positioned in the upper 65% of the length of the rail, more preferably in the upper 35% of the length of the rail, for example in the upper 10% of the length of the rail.

The hoisting system according to any of the preceding claims, further comprising an energy supply based on a chemical reaction such as a diesel generator, a fuel cell or a battery.

15. The hoisting system according to any one of the preceding claims, adapted for hoisting and installation of the tower top segment and one or more of a gondola, a generator, a hub and blades, or parts thereof, of the wind turbine.

A wind turbine comprising a tower, a gondola, a generator, a hub and at least one blade, the tower comprising one or more mounting points that are sequentially located along a longitudinal direction of the tower for releasably mounting and guiding a hoisting system according to a of claims 1-15.

The wind turbine according to claim 16, wherein the tower comprises mounting points at a mutual distance of more than 10 m, preferably at a mutual distance of less than 30 m, more preferably at a mutual distance of less than 15 m.

The wind turbine according to claim 16 or 17, wherein the tower comprises a plurality of stacked segments, at least one fixing point being located on the overlap of two adjacent tower segments.

The wind turbine according to any of claims 16-18, wherein at least one mounting point is reinforced on the outside of the tower over a distance from the center of the mounting point to at least 50 cm away from the center of the mounting point, preferably to at least 100 cm away from the center of the attachment point.

The wind turbine according to any of claims 16-19, wherein the inside of the tower is reinforced at the point of attachment.

The wind turbine according to any of claims 16-20, wherein the centers of three consecutive fastening points are in a row in the longitudinal direction of the tower with a maximum deviation of 20 cm in a radial direction of the tower, preferably with a maximum deviation 10 cm in the radial direction of the tower, more preferably with a maximum deviation of 5 cm in the radial direction of the tower.

The wind turbine according to any of claims 16-21, wherein the tower comprises a load-bearing wall over 50% of the tower length, preferably over 80% of the tower length.

The wind turbine according to any of claims 16 to 22, wherein a section of the bearing wall in a direction perpendicular to the longitudinal direction of the tower is in the form of a circle or a polygon.

The wind turbine according to any of claims 16-23, wherein the tower is in the form of a tube and is composed of a plurality of vertical segments, each segment being composed of curved or set plates extending the length of a segment .

The wind turbine according to any of claims 18-24, wherein one or more of the segments has a length between 10 m and 16 m.

The wind turbine according to any of claims 16-25, wherein the tower is tapered over 50% of the tower length, preferably over 80% of the tower length.

The wind turbine according to any of claims 16 to 26, wherein the sum of the heights of all attachment points is less than 20% of the tower length, preferably less than 10% of the tower length.

The wind turbine according to any of claims 16-27, wherein the wind turbine is installed at a distance from the center of a dike of less than 100 m, preferably less than 50 m, more preferably less than 20 m.

The wind turbine according to any of claims 16-28, comprising one or more further mounting points (107) that are located successively along a vertical direction of the tower and at an angle difference of at least 20 degrees from the one or more mounting points in a cylindrical coordinates system around the tower, for releasably connecting a second hoisting system in accordance with the hoisting system of one of claims 1-15.

The wind turbine according to any of claims 16-29, wherein the wind turbine is an offshore wind turbine.

The wind turbine according to claim 30, comprising a structure that passes the sea level, the structure being a transition part comprising at least one or more attachment points for releasably connecting and guiding the hoisting system.

The wind turbine according to any of claims 16-31, wherein the wind turbine has an axle height and the axle height is more than 80 m, preferably more than 130 m, more preferably more than 180 m.

The wind turbine according to any of claims 16-32, wherein the wind turbine has a design speed, wherein the ratio between the design speed at 12 m / s wind speed and at 6 m / s is less than 3 and more than 1.3, preferably more than 1.5 and more preferably more than 1.8.

The wind turbine according to any of claims 16-33, wherein the hoisting system is releasably connected on the outside of substantially one side of the tower thereby forming a combination (1) of the wind turbine and the hoisting system.

The wind turbine of claim 34, wherein the hoisting system comprises a column and a rail, the column being attached to the rail and the rail adapted to guide the hoisting system along the tower, the rail being rigidly or slidably connected to at least one of the attachment points.

The wind turbine of claim 35, wherein the rail is slidably and / or rigidly connected to at least two attachment points.

The wind turbine according to claim 35 or 36, wherein a highest attachment point measured from the ground level used for releasably attaching the hoisting system to the tower for hoisting activities of tower parts during the erection of the wind turbine is located at the intersection of the two highest tower segments already installed.

The wind turbine according to any of claims 34-37, wherein the hoisting system is releasably connected to the tower without counterweight or measures for creating a counterforce approximately on the opposite side of the hoisting point with respect to the tilt hinge.

A tower segment, other than the tower top segment, of a wind turbine according to any of claims 16-38, wherein the segment comprises a mounting point for releasably mounting a hoisting system according to any of claims 1-15 if the segment is installed as part of the wind turbine.

A method for installing a wind turbine according to any of claims 16-39, the method comprising building up at least a part of the tower of the wind turbine by placing one or more tower segments using the hoisting system according to one of claims 1 -15.

The method of claim 40, further comprising building one or more lower tower segments that are close to the ground level using a conventional building method, not relating to the hoisting system.

The method of claim 40 or 41, comprising: hoisting one or more parts of consecutive tower segments using the hoisting system and installing the segments to form a part of the tower; and guiding the hoisting system upwards along the attachment points and rigidly and slidably connecting the rail to the one or more connection points of the successive tower segments.

The method of claim 42, further comprising, if the last segment is installed, the step of rigidly connecting the rail to at least one attachment point and hoisting and installing one or more of a gondola, a generator, a hub and blades, or parts thereof, of the wind turbine.

The method of claim 43, wherein, in the case of the blade lifting one by one, the method comprises the steps of rotating the hub by lifting the installed blade up or down using the hoisting system, to raise the make it possible to place the hub in a favorable position for hoisting and installing another blade.

The method according to any of claims 40-44, wherein during lifting of one of the four lowest tower segments as a whole, a horizontal distance between the lifting point of a boom of the hoisting system and the center of an upper attachment point between the hoisting system and the tower always less than the diameter of the tower segment.

The method of any one of claims 40-45, further comprising hoisting and installing a second hoisting system according to claim 29, wherein the hoisting and installing uses the hoisting system.

A method for releasably securing a hoisting system according to any of claims 1-15 to a wind turbine or a wind turbine under construction according to any one of claims 16-38, the hoisting system comprising a column and a rail, the column being attached to the rail, the wind turbine comprising a tower comprising two or more tower segments and one or more fixing points, the method comprising the step of rigidly fixing the rail to the fixing point or points.

The method of claim 47, wherein the wind turbine is an offshore wind turbine, the method further comprising hoisting the hoisting system while being attached to one or more tower segments of a vessel (130) on the foundation (133) of the wind turbine.

The method of claim 47, wherein the wind turbine is an offshore wind turbine, the method further comprising hoisting the hoisting system from a pontoon (150) to the mounting point or mounting points of an installed part of the wind turbine using a cable (157) ) connected to the installed part of the wind turbine.

A method for removing a hoisting system according to any of claims 1-15 from a wind turbine or a wind turbine under construction according to any of claims 16-38, the hoisting system comprising a column and a rail, the column being attached to the rail, the wind turbine comprising a tower comprising two or more segments and one or more attachment points, the method comprising the steps of releasing fixed connections from the rail to attachment points, moving the hoisting system down using sliding connections of the rail with attachment points , and disconnect the hoisting system from the wind turbine.

A method for adapting an existing wind turbine, comprising mounting one or more mounting points on a tower of the existing wind turbine to thereby releasably connect a hoisting system according to any of claims 1-15 to the one or more fixing points of the existing wind turbine.