DK202370187A1

DK202370187A1 - A method for dismantling or installing a wind turbine blade of a wind turbine

Info

Publication number: DK202370187A1
Application number: DKPA202370187A
Authority: DK
Inventors: Botwright Adrian
Original assignee: Vestas Wind Sys As
Priority date: 2023-04-21
Filing date: 2023-04-21
Publication date: 2024-04-04

Abstract

A method for dismantling a wind turbine blade (2) of a wind turbine (4) is disclosed. A hoisting arrangement (11) with a main hoisting device (13) and an auxiliary hoisting device (14) is provided at an uptower position of the wind turbine (4). The wind turbine blade (2) to be dismantled is connected to the hoisting arrangement (11) in such a manner that the main hoisting device (13) is connected to the wind turbine blade (2) at a first position and the auxiliary hoisting device (14) is connected to the wind turbine blade (2) at a second position. The wind turbine blade (2) to be dismantled is disconnected from the wind turbine (4), and the main hoisting device (13) and the auxiliary hoisting device (14) are operated in a coordinated manner so as to lower the wind turbine blade (2) while changing an orientation of the wind turbine blade (2) towards a substantially horizontal orientation. A method for installing wind turbine blade (2) on the wind turbine (4) is also disclosed.

Description

1 DK 2023 70187 A1

A METHOD FOR DISMANTLING OR INSTALLING A WIND TURBINE BLADE OF A

WIND TURBINE

FIELD OF THE INVENTION

The present invention relates to a method for dismantling a wind turbine blade of a wind turbine, as well as to a method for installing a wind turbine blade of a wind turbine. The methods according to the invention applies an uptower hoisting arrangement for lowering or lifting the wind turbine blade from or to the installing position of the wind turbine blade at a hub of the wind turbine.

BACKGROUND OF THE INVENTION

When wind turbine blades of a wind turbine are to be installed, dismantled or replaced, it is necessary to apply appropriate hoisting equipment which is capable of handling the weight of the wind turbine blades as well as the size and shape of the wind turbine blades. To this end, a large external crane is often applied for lifting and/or lowering the wind turbine blades. The use of such large external cranes will normally introduce high costs, and scheduling of the installing, dismantling or replacing of the wind turbine blades may be limited by the availability of a suitable large external crane. This is in particular a challenge in the case that the wind turbine is an offshore wind turbine, in which case the large external crane needs to be transported to the site of the wind turbine by a sea vessel, possibly by a specialized sea vessel.

Furthermore, the wind turbine blades will normally be transported to or from the site of the wind turbine in a substantially horizontal orientation, i.e. with a longitudinal direction of the wind turbine blades arranged substantially horizontally. However, when the wind turbine blades are installed at their installing position on the hub of the wind turbine, they are oriented with their longitudinal direction in the rotor plane, which is normally slightly tilted with respect to a vertical direction. Accordingly, the orientation of a wind turbine blade needs to be changed during an installing or dismantling process. In order

, DK 2023 70187 A1 to handle this, additional equipment, e.g. including guide wires, may be applied.

This further complicates the process of installing, dismantling or replacing wind turbine blades, and adds to the costs thereof. Furthermore, it may be difficult to control the lifting or lowering process accurately, in particular in the case of windy or gusty wind conditions.

DESCRIPTION OF THE INVENTION

It is an object of embodiments of the invention to provide a method for dismantling or installing a wind turbine blade of a wind turbine, in which the costs involved can be reduced as compared to prior art methods, and using readily available equipment.

It is a further object of embodiments of the invention to provide a method for dismantling or installing a wind turbine blade of a wind turbine, in which the orientation of the wind turbine blade can be accurately controlled in an easy manner.

According to a first aspect, the invention provides a method for dismantling a wind turbine blade of a wind turbine, the method comprising the steps of: — providing a hoisting arrangement at an uptower position of the wind turbine, the hoisting arrangement comprising a main hoisting device and an auxiliary hoisting device, — connecting the wind turbine blade to be dismantled to the hoisting arrangement in such a manner that the main hoisting device is connected to the wind turbine blade at a first position and the auxiliary hoisting device is connected to the wind turbine blade at a second position, — disconnecting the wind turbine blade to be dismantled from the wind turbine, and — operating the main hoisting device and the auxiliary hoisting device of the hoisting arrangement in a coordinated manner so as to lower the wind

2 DK 2023 70187 A1 turbine blade while changing an orientation of the wind turbine blade towards a substantially horizontal orientation.

Thus, according to the first aspect, the invention provides a method for dismantling a wind turbine blade of a wind turbine. In the present context the term ‘dismantling’ should be interpreted to mean that the wind turbine blade is removed from an installed position at a hub of the wind turbine, where it has been mounted while the wind turbine has been operating in a normal manner.

The wind turbine blade may, e.g., be dismantled as part of a general dismantling or decommissioning of the wind turbine. As an alternative, the wind turbine blade may be dismantled because it needs to be replaced by a new wind turbine blade, or because the wind turbine blade (or another part of the wind turbine) needs to undergo repair or maintenance which it is not possible to perform while the wind turbine blade is mounted on the wind turbine.

The wind turbine may be an onshore wind turbine, i.e. a wind turbine which is positioned on land. Alternatively, the wind turbine may be an offshore wind turbine, i.e. a wind turbine which is positioned offshore, such as at sea or on a lake. In this case the wind turbine may be mounted on a fixed foundation, i.e. a foundation which is fixedly attached to the seabed, or it may be mounted on a floating foundation which is merely anchored to the seabed via one or more suitable anchors, but which allows the position of the wind turbine to move within a limited area.

In the method according to the first aspect of the invention, a hoisting arrangement is initially provided at an uptower position of the wind turbine. In the present context, the term 'uptower position' should be interpreted to mean a position which is at or near an upper part of a tower of the wind turbine. The uptower position could, e.g., be a position inside or on top of a nacelle being mounted at the top of the tower.

The hoisting arrangement comprises a main hoisting device and an auxiliary hoisting device. The main hoisting device and the auxiliary hoisting device may advantageously be configured to be operated independently of each other.

Accordingly, operating the hoisting arrangement may include operating only the

, DK 2023 70187 A1 main hoisting device, operating only the auxiliary hoisting device, or operating the main hoisting device as well as the auxiliary hoisting device. This will be described in further detail below.

Next, the wind turbine blade to be dismantled is connected to the hoisting arrangement. This is done in such a manner that the main hoisting device is connected to the wind turbine blade at a first position and the auxiliary hoisting device is connected to the wind turbine blade at a second position. The first position and the second position are preferably spaced apart along the longitudinal direction of the wind turbine blade. Thus, operating the main hoisting device will cause manipulation of the wind turbine blade with a point of attack corresponding to the first position, while operating the auxiliary hoisting device will cause manipulation of the wind turbine blade with a point of attack corresponding to the second position. The first position of the wind turbine blade may, e.g., be at or near a centre of gravity of the wind turbine blade.

Next, the wind turbine blade to be dismantled is disconnected from the wind turbine. This may include releasing bolts or other suitable fastening means which interconnect the wind turbine blade and the hub, possibly via a pitch system.

Accordingly, the wind turbine blade is no longer carried by the hub of the wind turbine. Instead, it is carried solely by the hoisting arrangement.

Finally, the main hoisting device and the auxiliary hoisting device of the hoisting arrangement are operated in a coordinated manner so as to lower the wind turbine blade while changing an orientation of the wind turbine blade towards a substantially horizontal orientation.

Since the main hoisting device is connected to the wind turbine blade at the first position and the auxiliary hoisting device is connected to the wind turbine blade at the second position, the coordinated operation of the main hoisting device and the auxiliary hoisting device results in coordinated manipulation of the wind turbine blade with the first and second position, respectively, as points of attack.

Thus, by appropriately operating the main hoisting device and the auxiliary hoisting device, coordinated movement of the first and second positions of the wind turbine blade is obtained, and thereby the orientation of the wind turbine

DK 2023 70187 A1 blade can be appropriately manipulated. Accordingly, simply by appropriately operating the main hoisting device and the auxiliary hoisting device, the wind turbine blade can be lowered while the orientation of the wind turbine blade is simultaneously changed from the orientation which was required while the wind 5 turbine blade was mounted on the hub, towards a substantially horizontal orientation which is required for transporting the wind turbine blade away from the wind turbine. This is a very easy and accurate manner of ensuring this required change in orientation.

In the case that the first position of the wind turbine blade is at or near a centre of gravity of the wind turbine blade, the main weight of the wind turbine blade will be hanging from the main hoisting device, and operation of the auxiliary hoisting device will then cause rotation of the wind turbine blade essentially around the centre of gravity, requiring only little effort.

Furthermore, since the process of lowering the wind turbine blade while changing the orientation thereof is performed by means of the hoisting arrangement arranged at the uptower position of the wind turbine, a large external crane is not required, and therefore the costs involved with the dismantling of the wind turbine blade are reduced as compared to prior art methods. This further has the advantage that there are no relative movements between the wind turbine and the hoisting arrangement holding the wind turbine blade, and this makes it easier to avoid collisions between the wind turbine blade and the wind turbine during the process of lowering the wind turbine blade.

The step of connecting the wind turbine blade to be dismantled may comprise connecting the wind turbine blade to the hoisting arrangement via a blade holding tool.

According to this embodiment, the main hoisting device and the auxiliary hoisting device are not connected directly to the first and second positions, respectively, of the wind turbine blade. Instead, the main hoisting device is connected to a first position of a blade holding tool and the auxiliary hoisting device is connected to a second position of the blade holding tool, and the blade

DK 2023 70187 A1 holding tool is, in turn, connected to the wind turbine blade, in such a manner that a first point of attack is established between the main hoisting device and the wind turbine blade, at a position corresponding to the first position of the wind turbine blade, and a second point of attack is established between the 5 auxiliary hoisting device and the wind turbine blade, at a position corresponding to the second position of the wind turbine blade. Accordingly, the coordinated manipulation of the wind turbine blade described above is still possible, even though the main hoisting device and the auxiliary hoisting device are not directly connected to the wind turbine blade.

The method may further comprise the step of positioning a rotor of the wind turbine in a position which arranges the wind turbine blade to be dismantled along a substantially downwards pointing direction, prior to the step of connecting the wind turbine blade to be dismantled to the hoisting arrangement.

According to this embodiment, the rotor is arranged in a position in which one wind turbine blade points directly downwards, and the other two wind turbine blades point partly upwards, and symmetrically with respect to a substantially vertical axis of symmetry of the rotor. Such a position of the rotor is sometimes referred to as a ‘bunny ear’ configuration or a 'Y' configuration.

The wind turbine blade to be dismantled is the one which points downwards, substantially parallel to the tower, and thereby the wind turbine blade which is closest to the foot of the tower. However, this is also the position where the orientation of the wind turbine blade is furthest away from the horizontal position, and therefore the change in orientation described above is appropriate and required in this case.

The step of operating the main hoisting device and the auxiliary hoisting device of the hoisting arrangement in a coordinated manner may comprise operating the main hoisting device at a first hoisting speed and operating the auxiliary hoisting device at a second hoisting speed, where the second hoisting speed differs from the first hoisting speed.

DK 2023 70187 A1

As described above, operating the main hoisting device results in manipulation of the wind turbine blade with a point of attack corresponding to the first position, while operating the auxiliary hoisting device results in manipulation of the wind turbine blade with a point of attack corresponding to the second position. Accordingly, operating the main hoisting device and the auxiliary hoisting device at two different hoisting speeds results in the first position of the wind turbine blade and the second position of the wind turbine blade to be moved at two different speeds. This will cause a rotation of the wind turbine blade. Accordingly, by appropriately selecting the first hoisting speed and the second hoisting speed, in particular how the first hoisting speed and the second hoisting speed relate to each other, an appropriate and desired rotation of the wind turbine blade can be obtained, in particular a rotation which causes the orientation of the wind turbine blade to change from the installing orientation towards a substantially horizontal orientation.

For instance, in the case that the wind turbine blade to be dismantled is arranged in a downwards pointing direction, and the second position is closer to the tip of the wind turbine blade than the first position, then the first hoisting speed may be higher than the second hoisting speed. In this case the first position will be lowered faster than the second position, and this will result in the root end of the wind turbine blade being lowered faster than the tip end of the wind turbine blade. This in turn rotates the wind turbine blade towards a substantially horizontal orientation while it is lowered towards the base of the tower.

The main hoisting device and/or the auxiliary hoisting device may be (a) > winch(es). Winches are simple and lightweight hoisting devices, which are easy to handle an operate individually. They are therefore very appropriate for use in the present invention.

The step of providing a hoisting arrangement may comprise lifting the hoisting arrangement to the uptower position and mounting the hoisting arrangement in or on a nacelle of the wind turbine.

2 DK 2023 70187 A1

According to this embodiment, the hoisting arrangement is not permanently arranged at the uptower position. Instead, the hoisting arrangement is mounted at the uptower position when dismantling of a wind turbine blade is required, and it may advantageously be removed again when the dismantling of the wind turbine blade (and possibly installing of a replacement wind turbine blade) has been completed. Thus, the hoisting arrangement need not have a size and shape which allows it to be accommodated inside the nacelle or the like.

The hoisting arrangement may, e.g., be lifted to the uptower position, in this case a position in or on the nacelle, by means of a smaller hoisting arrangement being permanently mounted in the nacelle, e.g. in the form of a nacelle crane or similar. The permanently mounted hoisting arrangement may not be capable of handling the wind turbine blade, but it may have sufficient lifting capacity to lift the larger hoisting arrangement to the uptower position. Thus, sufficient lifting capacity for handling the wind turbine blade to be dismantled can be provided without requiring a large external crane, and without requiring that such lifting capacity is permanently available in or on the nacelle.

In the case that the hoisting arrangement is mounted on the nacelle, rather than inside the nacelle, the hoisting arrangement may be partly supported by the root ends of the two wind turbine blades, which are not being dismantled.

As an alternative, the hoisting arrangement may be permanently mounted at the uptower position, e.g. in or on the nacelle.

According to a second aspect, the invention provides a method for installing a wind turbine blade on a wind turbine, the method comprising the steps of: — providing a hoisting arrangement at an uptower position of the wind turbine, the hoisting arrangement comprising a main hoisting device and an auxiliary hoisting device, — connecting the wind turbine blade to be installed to the hoisting arrangement in such a manner that the main hoisting device is connected

9 DK 2023 70187 A1 to the wind turbine blade at a first position and the auxiliary hoisting device is connected to the wind turbine blade at a second position, — operating the main hoisting device and the auxiliary hoisting device of the hoisting arrangement in a coordinated manner so as to lift the wind turbine blade towards an installing position of the wind turbine, while changing an orientation of the wind turbine blade from a substantially horizontal orientation towards an installing orientation, and — connecting the wind turbine blade to the wind turbine at the installing position.

The method according to the second aspect of the invention is essentially a reversed version of the method according to the invention, in the sense that a wind turbine blade is moved from a position at the foot of the tower to a position at the hub of the wind turbine where it is installed, rather than the wind turbine blade being detached from such a position and lowered towards the foot of the tower. The wind turbine blade being installed may, e.g., replace a wind turbine blade which has previously been dismantled from the wind turbine, e.g. by means of a method according to the first aspect of the invention. The remarks set forth above with reference to the first aspect of the invention are therefore equally applicable here. > In the method according to the second aspect of the invention, a hoisting arrangement is initially provided at an uptower position of the wind turbine, the hoisting arrangement comprising a main hoisting device and an auxiliary hoisting device. The hoisting arrangement is described in detail above with reference to the first aspect of the invention, and the remarks set forth in this regard are equally applicable here. In particular, the hoisting arrangement may be lifted to the uptower position and temporarily mounted there, e.g. in or on the nacelle, or it may be permanently mounted at the uptower position.

The main hoisting device and/or the auxiliary hoisting device may, e.g., be in the form of (a) winch(es), as described above.

10 DK 2023 70187 A1

Next, the wind turbine blade to be installed is connected to the hoisting arrangement in such a manner that the main hoisting device is connected to the wind turbine blade at a first position and the auxiliary hoisting device is connected to the wind turbine blade at a second position. As described above with reference to the first aspect of the invention, this allows for manipulating the wind turbine blade with a point of attack corresponding to the first position by appropriately operating the main hoisting device, and for manipulating the wind turbine blade with a point of attack corresponding to the second position by appropriately operating the auxiliary hoisting device. The main hoisting device and the auxiliary hoisting device may be connected directly to the wind turbine blade at the first and second positions, respectively, or they may be connected to the wind turbine blade via a blade holding tool. This has been described in detail above with reference to the first aspect of the invention.

The step of connecting the wind turbine blade to be installed to the hoisting device may preferably be performed while the wind turbine blade is positioned at or near the foot of the tower. For instance, the wind turbine blade may be positioned in a cradle or a similar holding device, which could, e.g., be positioned on or form part of transport equipment, such as a truck or a seagoing vessel, such as a barge or a jack-up vessel.

Furthermore, when the wind turbine blade is connected to the hoisting arrangement, it may advantageously be oriented in a substantially horizontal orientation.

Next, the main hoisting device and the auxiliary hoisting device of the hoisting arrangement are operated in a coordinated manner so as to lift the wind turbine blade towards an installing position of the wind turbine, while changing an orientation of the wind turbine blade from a substantially horizontal orientation towards an installing orientation. This is similar to the coordinated operation of the main hoisting device and the auxiliary hoisting device described above with reference to the first aspect of the invention, and the remarks set forth in this regard are therefore equally applicable here. However, in this case, rather than lowering the wind turbine blade, the wind turbine blade is lifted from a position at or near the foot of the tower to an installing position of the wind turbine, e.g.

1 DK 2023 70187 A1 at the hub. Simultaneously, the orientation of the wind turbine blade is changed from the substantially horizontal orientation, which is appropriate during transport of the wind turbine blade to the site of the wind turbine, to an orientation which will allow the wind turbine blade to be mounted on the hub of the wind turbine. Thus, the movement of the wind turbine blade during this step may be regarded as a reversed version of the movement taking place when performing the method according to the first aspect of the invention, and which is described in detail above.

Finally, the wind turbine blade is connected to the wind turbine at the installing position. This may, e.g., include mounting the wind turbine blade on the hub of the wind turbine, possibly via a pitch system, e.g. by means of bolts or other suitable fastening means.

The method may further comprise the step of positioning a rotor of the wind turbine in a position which arranges the installing position of the wind turbine blade to be installed in a substantially downwards pointing direction, prior to the step of connecting the wind turbine blade to be installed to the hoisting arrangement.

According to this embodiment, the rotor is positioned in so-called ‘bunny ear’ configuration before the wind turbine blade to be installed in connected to the hoisting arrangement and subsequently lifted towards the installing position. The part of the hub where the wind turbine blade is supposed to be installed is thereby pointing in a substantially downwards direction, and in order to be able to mount the wind turbine blade on the hub, it must be oriented in an orientation which is substantially parallel to the tower, with the tip end pointing downwards and the root end pointing upwards.

ip DK 2023 70187 A1

This is similar to the situation described above with reference to the first aspect of the invention, except for the resulting movement of the wind turbine blade being reversed.

For instance, in the case that the installing orientation of the wind turbine blade is substantially parallel to the tower, and the second position of the wind turbine blade is closer to the tip of the wind turbine blade than the first position, then the first hoisting speed may be higher than the second hoisting speed. This will cause the first position to be lifted faster than the second position, and this will result in the root end of the wind turbine blade to be lifted faster than the tip end of the wind turbine blade. This in turn rotates the wind turbine blade from the substantially horizontal transporting orientation towards the installing orientation substantially parallel to the tower while the wind turbine blade is lifted towards the installing position.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be described in further detail with reference to the accompanying drawings in which

Figs. 1-3 illustrate mounting of a blade holding tool on a wind turbine blade to be dismantled as part of a method according to an embodiment of the invention,

Fig. 4 illustrates a hoisting arrangement for use in a method according to an embodiment of the invention,

Fig. 5 illustrates fitting of a blade tip bag on a wind turbine blade being dismantled or installed by means of a method according to an embodiment of the invention,

Figs. 6-13 illustrate a method for dismantling a wind turbine blade according to an embodiment of the invention, and

Fig. 14 shows the wind turbine illustrated in Figs. 6-13 from above.

13 DK 2023 70187 A1

DETAILED DESCRIPTION OF THE DRAWINGS

Figs. 1-3 illustrate mounting of a blade holding tool 1 on a wind turbine blade 2 to be dismantled as part of a method according to an embodiment of the invention. The wind turbine blade 2 is mounted on a hub 3 of a wind turbine 4, and the hub 3 has been arranged in a position in which the wind turbine blade 2 to be dismantled points in a substantially downwards directions, substantially parallel to a tower 5 of the wind turbine. This position is sometimes referred to as a ‘bunny ear’ configuration.

The wind turbine 4 illustrated in Figs. 1-3 is an offshore wind turbine, i.e. it is positioned offshore, such as at sea or on a lake. However, it should be noted that the method according to the invention is also applicable to onshore wind turbines, i.e. wind turbines which are arranged on land.

The wind turbine 4 illustrated in Figs. 1-3 may be mounted on a fixed foundation which is fixedly connected to the seabed. As an alternative, the wind turbine 4 may be mounted on a floating foundation which is anchored to the seabed by means of one or more suitable anchors and one or more mooring lines or similar structures interconnecting the wind turbine 4 and the respective one or more anchors. In this case the position of the wind turbine 4 is allowed to shift or move within a limited area, determined by the position of the one or more anchors and the length of the one or more mooring lines.

In Fig. 1 the blade holding tool 1 is arranged on a cradle 6 which is adapted to hold a wind turbine blade 2 during transport to or from the site of the wind turbine 4. The cradle 6 is positioned on an outrigger 7 (visible in the insert), which is mounted on a jack-up vessel 8. As an alternative, the blade holding tool 1, possibly in the cradle 6, may have been positioned directly on the jack-up vessel 8, rather than on the outrigger 7. As another alternative, the blade holding tool 1 may have been positioned on another kind of seagoing vessel, such as a barge, which moves due to impact from waves, etc. As yet another alternative, in the case that the wind turbine 4 is mounted on a floating foundation, the blade holding tool 1, possibly in the cradle 6, may be moved from a seagoing vessel to a parking position on the floating foundation before

14 DK 2023 70187 A1 the installing process is initiated. The blade holding tool 1 may advantageously have been transported to the site of the wind turbine 4 by means of the jack-up vessel 8.

The cradle 6 is mounted on the outrigger 7 via a bolster swivel 9, allowing it to rotate relative to the outrigger 7. This allows the cradle 6 to be appropriately oriented for receiving a wind turbine blade 2. Furthermore, the cradle 6 can be moved sideways between the position on the outrigger 7, as illustrated in Fig. 1, and a position on the jack-up vessel 8. This is illustrated by arrows 10.

The blade holding tool 1 is connected to a hoisting arrangement 11 which is mounted at an uptower position of the wind turbine 4, more specifically on top of a nacelle 12 of the wind turbine 4. The hoisting arrangement 11 comprises a main hoisting device 13 and an auxiliary hoisting device 14, both in the form of a winch. The main hoisting device 13 and the auxiliary hoisting device 14 are connected to respective end parts of the blade holding tool 1.

In Fig. 2, the main hoisting device 13 and the auxiliary hoisting device 14 have each been operated in order to lift the blade holding tool 1 towards the wind turbine blade 2 to be dismantled. This has been done in such a manner that the end part of the blade holding tool 1 which is connected to the main hoisting device 13 has been moved a longer distance than the end part of the blade holding tool 1 which is connect to the auxiliary hoisting device 14. This has caused the blade holding tool 1 to rotate approximately 90%, as compared to the orientation illustrated in Fig. 1.

The insert of Fig. 2 shows a detail of a mounting arrangement 15 for the hoisting arrangement (11 - not shown in the insert) which is supported by the root ends of the two wind turbine blades which are not to be dismantled. A movable support cradle 16 allows the hoisting arrangement 11 to perform sideways movements relative to the nacelle 12.

In Fig. 3, the blade holding tool 1 has been connected to the wind turbine blade 2 to be dismantled. This establishes indirect connections between the main hoisting device 13 and a first position of the wind turbine blade 2, and between

DK 2023 70187 A1 the auxiliary hoisting device 14 and a second position of the wind turbine blade 2, the first position and the second position being spaced apart along a longitudinal direction of the wind turbine blade 2. This will allow the wind turbine blade 2 to be simultaneously lowered and rotated, by appropriately operating 5 the main hoisting device 13 and the auxiliary hoisting device 14 in a coordinated manner. This will be described in further detail below with reference to Figs. 6- 13.

It can further be seen from Fig. 3 that the auxiliary hoisting device 14 is mounted on the hoisting arrangement 11 in a manner which allows it to perform sideways movements. It should further be noted that the hoisting arrangement 11 may be allowed to perform swivel or rotating movements relative to the nacelle 12.

Fig. 4 illustrates a hoisting arrangement 11 for use in a method according to an embodiment of the invention. The hoisting arrangement 11 of Fig. 4 may, e.g., be the hoisting arrangement 11 applied in Figs. 1-3. Accordingly, the hoisting arrangement 11 comprises a main hoisting device 13 and an auxiliary hoisting device 14, each in the form of a winch, each mounted on a boom 17. The auxiliary hoisting device 14 is mounted on the boom 17 via a traveling beam 18 which allows the auxiliary hoisting device 14 to perform sideways movements relative to the boom 17.

Fig. 5 illustrates fitting of a blade tip bag 19 on a wind turbine blade 2 being dismantled or installed by means of a method according to an embodiment of the invention. The blade tip bag 19 is reached by an operator 20 in a mobile elevating work platform 21 mounted on a jack-up vessel 8.

Figs. 6-13 illustrate a method for dismantling a wind turbine blade 2 according to an embodiment of the invention. In Fig. 6, a blade holding tool 1 has been lifted to a position adjacent to the wind turbine blade 2 to be dismantled, by means of a hoisting arrangement 11, and essentially in the manner described above with reference to Figs. 1 and 2.

6 DK 2023 70187 A1

In Fig. 7, the blade holding tool 1 has been connected to the wind turbine blade 2 to be dismantled, essentially in the manner described above with reference to

Fig. 3. Accordingly, a connection has been established between the main hoisting device 13 and a first position on the wind turbine blade 2, and between the auxiliary hoisting device 14 and a second position on the wind turbine blade 2, respectively, via the blade holding tool 1.

Fig. 8 illustrates the situation of Fig. 7, and further shows a cradle 6 positioned adjacent to the wind turbine 4. The cradle 6 may be arranged on a seagoing vessel (not shown).

In Fig. 9 the wind turbine blade 2 to be dismantled has been disconnected from the hub 3 of the wind turbine 4 and lowered slightly. The lowering of the wind turbine blade 2 has been obtained by simultaneously operating the main hoisting device 13 and the auxiliary hoisting device 14 at essentially the same hoisting speed.

In Fig. 10 the wind turbine blade 2 has been lowered further. Furthermore, the wind turbine blade 2 has been rotated, thereby changing the orientation of the wind turbine blade 2 from the orientation required while the wind turbine blade 2 was mounted on the hub 3 towards a substantially horizontal orientation. This is obtained by simultaneously operating the main hoisting device 13 at a first hoisting speed and operating the auxiliary hoisting device 14 at a second hoisting speed, the first hoisting speed being higher than the second hoisting speed.

In order to avoid collisions between the wind turbine blade 2 and the nacelle 12 or the tower 5 of the wind turbine 4, the auxiliary hoisting device 14 may have been moved sideways, and/or the hoisting mechanism 11 may have been swivelled or rotated relative to the nacelle 12.

In Fig. 11 the movement of the wind turbine blade 2 described above with reference to Fig. 10 has been continued, so that the wind turbine blade 2 has been lowered further, and the orientation of the wind turbine blade 2 is closer to the substantially horizontal orientation.

DK 2023 70187 A1

In Fig. 12 the wind turbine blade 2 has been rotated and lowered even further, and is now oriented in the essentially horizontal orientation.

In Fig. 13 the horizontally oriented wind turbine blade 2 has been lowered further and is now positioned in the cradle 6. Subsequently, the blade holding 5 tool 1 will be disconnected from the wind turbine blade 2, and the wind turbine blade 2 will be transported away from the site of the wind turbine 4 by means of the seagoing vessel (not shown).

Fig. 14 shows the wind turbine 4 illustrated in Figs. 6-13 from above. The hoisting arrangement 11, connected to a wind turbine blade 2, is shown in two different positions. Hoisting arrangement 11a, comprising main hoisting device 13a and auxiliary hoisting device 14a, connected to wind turbine blade 2a, is in a position pointing in a directly forwards direction relative to the hub 3 of the wind turbine 4. This position is appropriate for connecting the hoisting arrangement 11a to a wind turbine blade 2a to be dismantled while it is connected to the hub 3 of the wind turbine.

Hoisting arrangement 11b, comprising main hoisting device 13b and auxiliary hoisting device 14b, has been moved sideways as well as swivelled or rotated relative to the nacelle 12, as compared to the position of hoisting arrangement 11a. This positions the wind turbine blade 2b, which is now disconnected from the hub 3, next to the nacelle 12 and the tower 5 of the wind turbine 4. This allows the wind turbine blade 2b to be rotated towards an essentially horizontal orientation, as described above with reference to Figs. 6-13, without risking collisions between the wind turbine blade 2b and the nacelle 12 or the tower 5.

It should be noted that the steps described above with reference to Figs. 1-13 may be reversed, resulting in a method for installing a wind turbine blade 2 on the wind turbine 4.

Claims

8 DK 2023 70187 A1 CLAIMS

1. A method for dismantling a wind turbine blade (2) of a wind turbine (4), the method comprising the steps of: — providing a hoisting arrangement (11) at an uptower position of the wind turbine (4), the hoisting arrangement (11) comprising a main hoisting device (13) and an auxiliary hoisting device (14), — connecting the wind turbine blade (2) to be dismantled to the hoisting arrangement (11) in such a manner that the main hoisting device (13) is connected to the wind turbine blade (2) at a first position and the auxiliary hoisting device (14) is connected to the wind turbine blade (2) at a second position, — disconnecting the wind turbine blade (2) to be dismantled from the wind turbine (4), and — operating the main hoisting device (13) and the auxiliary hoisting device (14) of the hoisting arrangement (11) in a coordinated manner so as to lower the wind turbine blade (2) while changing an orientation of the wind turbine blade (2) towards a substantially horizontal orientation.

2. A method according to claim 1, wherein the step of connecting the wind turbine blade (2) to be dismantled comprises connecting the wind turbine blade (2) to the hoisting arrangement (11) via a blade holding tool (1).

3. A method according to claim 1 or 2, further comprising the step of positioning a rotor of the wind turbine (4) in a position which arranges the wind turbine blade (2) to be dismantled along a substantially downwards pointing direction, prior to the step of connecting the wind turbine blade (2) to be dismantled to the hoisting arrangement (11).

4. A method according to any of the preceding claims, wherein the step of operating the main hoisting device (13) and the auxiliary hoisting device (14) of

9 DK 2023 70187 A1 the hoisting arrangement (11) in a coordinated manner comprises operating the main hoisting device (13) at a first hoisting speed and operating the auxiliary hoisting device (14) at a second hoisting speed, where the second hoisting speed differs from the first hoisting speed.

5. A method according to any of the preceding claims, wherein the main hoisting device (13) and/or the auxiliary hoisting device (14) is/are (a) winch(es).

6. A method according to any of the preceding claims, wherein the step of providing a hoisting arrangement (11) comprises lifting the hoisting arrangement (11) to the uptower position and mounting the hoisting arrangement (11) in or on a nacelle (12) of the wind turbine (4).

7. A method for installing a wind turbine blade (2) on a wind turbine (4), the method comprising the steps of: — providing a hoisting arrangement (11) at an uptower position of the wind turbine (4), the hoisting arrangement (11) comprising a main hoisting device (13) and an auxiliary hoisting device (14), — connecting the wind turbine blade (2) to be installed to the hoisting arrangement (11) in such a manner that the main hoisting device (13) is connected to the wind turbine blade (2) at a first position and the auxiliary hoisting device (14) is connected to the wind turbine blade (2) at a second position, — operating the main hoisting device (13) and the auxiliary hoisting device (14) of the hoisting arrangement (11) in a coordinated manner so as to lift the wind turbine blade (2) towards an installing position of the wind turbine (4), while changing an orientation of the wind turbine blade (2) from a substantially horizontal orientation towards an installing orientation, and — connecting the wind turbine blade (2) to the wind turbine (4) at the installing position.

> DK 2023 70187 A1

8. A method according to claim 7, further comprising the step of positioning a rotor of the wind turbine (4) in a position which arranges the installing position of the wind turbine blade (2) to be installed in a substantially downwards pointing direction, prior to the step of connecting the wind turbine blade (2) to be installed to the hoisting arrangement (11).

9. A method according to claim 7 or 8, wherein the step of operating the main hoisting device (13) and the auxiliary hoisting device (14) of the hoisting arrangement (11) in a coordinated manner comprises operating the main hoisting device (13) at a first hoisting speed and operating the auxiliary hoisting device (14) at a second hoisting speed, where the second hoisting speed differs from the first hoisting speed.