The present invention relates to the installation of a wind turbine, e.g. an offshore wind turbine.

In a known method for installation of a wind turbine one or more cranes are employed to lift a nacelle including a generator and a hub driving the generator onto the top of a tower of a wind turbine. Commonly, the hub is provided with multiple blade mounting structures, e.g. three, each configured for securing thereto a rotor blade. In a later phase of the installation process, the rotor blades are fitted one by one to their respective blade mounting structure. Herein each rotor blade is lifted by a crane to a height allowing for securing of the blade root to a blade mounting structure.

Nowadays, the nacelle of a wind turbine often is a very bulky and heavy object. A weight of several hundred tonnes for a nacelle has become normal in the wind energy industry. The SG 14-222 DD wind turbine with a design capacity of 14 MW has a nacelle weight of some 500 tonnes. The Haliade-X 12 MW wind turbine has a nacelle weight of 675 tonnes.

In order to lift a heavy nacelle to the top of the wind turbine tower one or two tall and high capacity cranes are required. In this operation it is known to make use of a specific nacelle lifting tool that is suspended from the load connector of the one crane or from both cranes. The nacelle lifting tool in itself is a sizable object and may weigh tens of tonnes in order to handle the weight of the nacelle.

The nacelle is commonly provided with anchoring points which are configured to be connected to the nacelle lifting tool, commonly via slings. For example, three or four anchoring points are provided, e.g. three in a triangular configuration when seen from above. For example, one anchoring point is located rather forward on the hub on the centreline of the nacelle and two anchoring points are located more rearward on opposite sides of the nacelle.

In the prior art approach, once the nacelle has been lifted on top of the tower and has been secured to the top of the tower, the nacelle lifting tool is disconnected from the nacelle, e.g. by disconnecting the lifting slings from the anchoring points. Then the nacelle lifting tool is brought back down, e.g. to the ground or to a deck of a vessel when installing an offshore wind turbine, and is disconnected from the crane(s).

Then the process of installation of the rotor blades is performed, commonly using the same crane, or one of them, that has/have been used for installation of the nacelle on top of the tower.

The rotor blade has a blade body with a blade root, a blade tip, a length between the root and the tip, as well as a mass. The rotor blade is often made primarily of composite material.

In a common design of wind turbine rotor blades, the blade root is configured to be secured to a blade mounting structure of the hub of the wind turbine by means of one or more fasteners. In a well-known embodiment a series of bolts protrudes from the stern face of the hollow blade root, e.g. in the form of so-called T-bolts. The mounting structure of the hub is provided with a circular flange provided with a matching series of bolt holes, e.g. the flange being part of or integrated with a pitch bearing of the blade mounting structure. Once the bolts have been inserted through these bolt holes, nuts are fitted on the bolts to fasten the blade root to the hub.

The dimensions of the wind turbines have steadily increased over the years, mainly in view of economically efficient energy generation. As a result, wind turbines have very large rotor blades, e.g. over 75m, or even over 100m in length. For example, each blade of the Vestas 15 V236 wind turbine measures 115.5 meters in length. The Siemens Gamesa’s SG 14-222 DD direct drive wind turbine has rotor blades of 108 meters in length. This market development further increases demands on the installation of a rotor blade to a wind turbine, whether onshore or offshore. The blade root may have a diameter of more than 5 m. The mass of a single rotor blade may be well in excess of 50 tons.

For the installation of a rotor blade to the hub of the wind turbine, it is common to lift the blade by means of one crane using a blade lifting tool that is attached to the load connector of the crane. In a common approach, the crane is operated to lift the rotor blade whilst remaining in horizontal orientation to a height that is substantially level with a blade mounting structure, which is positioned in the so-called three o’clock or nine o’clock position. The crane is then operated to bring the rotor blade closer to the blade mounting structure of the hub, for example assisted by a taglines system of the crane in order to stabilize and align the rotor blade so that the bolts can be introduced into the bolt holes. It is noted as an aside that with the increasing dimensions and mass of the rotor blades, the so-called six o’clock installation has become rather problematic as it is difficult to hold the blade in a vertical position by means of a blade lifting tool.

Mating all the bolts on the blade root with the bolt holes of the mounting structure is difficult, and has become even more difficult in view of the developments discussed above. A major factor herein is the presence of undue relative motion between the blade mounting structure and the blade root. This factor and problems of mating the bolts and bolt holes is discussed, for example, in the article “Effects of Wind- Wave Misalignment on a Wind Turbine Blade Mating Process: “Impact Velocities, Blade Root Damages and Structural Safety Assessment”, Verma et al, 2019, Journal of Marine Science and Application, https://doi.org/10.1007/s11804-020-00141-7. In this article, it is described that the hub of an offshore wind turbine may be subject to sea state induced motions, e.g. the waves hitting the foundation, e.g. a monopile or otherwise, on which the tower is mounted.

The rotor blade that is lifted by means of a crane may obviously be subject to wind-induced motion as long as it is not fully secured to the hub. In practice, also crane induced motions may occur in the installation process of the rotor blade, e.g. vibrations of the crane boom.

The relative motion between the root end of the rotor blade and the blade mounting structure of the hub may be the source of an undesirable impact or collision between one of more bolts and the hub or other part of the nacelle. This could be a head-on impact or a sideways impact, or combination thereof. This impact may lead to damage, even hidden damage, in the blade root, e.g. (minimal) cracking of the laminated composite material, and/or damage to one or more of the bolts, etc. The same problem may arise if some of the bolts are initially replaced by longer guide rods, that protrude beyond the bolts and are to be introduced into the respective hole as a guide. For example, reference is made to EP2918969.

The above-mentioned article discusses that at sea the wind direction and the wave direction may be the same, yet they may also be different from one another. The latter is called windwave misalignment. As discussed, in both situations impact velocity of the blade root may be such that undue damage occurs on impact. The article shows graphs wherein periodic hub motion in the horizontal or XY-plane is depicted for different angles between waves and wind. The amplitude of the periodic hub motion may be about 1 meter due to waves hitting the foundation. At the same time, the blade suspended from the crane is subject to its own periodic motion, so that significant relative motion is present in the mating process. It is an object of the present invention to provide a more effective approach and associated equipment for the installation of a wind turbine, whether at sea or on land.

The invention provides a method according to claim 1 .

In the inventive method, use is made of an integrated device configured for nacelle lifting as well as for blade positioning, the integrated device having a nacelle lifting structure and a blade positioning assembly.

The method comprises connecting the integrated device to a nacelle and to the load connector of the crane. As discussed, in embodiments, two cranes can be employed for lifting the nacelle, yet the use of a single crane is preferred.

Connecting the integrated device to the nacelle can be done after the integrated device has first been connected to the load connector of the crane, e.g. the crane being used to bring the integrated device in position relative to the nacelle to allow its connection to the nacelle. In another approach, the integrated device is first connected to the nacelle, e.g. using another crane than the one used for actual lifting of the nacelle. This other crane can be significantly smaller in size and capacity than the crane(s) required for lifting the nacelle.

The nacelle is then lifted to the top of the tower, followed by fastening of the nacelle to the top of the tower.

After fastening the nacelle to the top of the tower, the load connector of the crane is disconnected from the integrated device which then remains connected to the nacelle. This in contrast to the prior art approach, wherein the dedicated nacelle lifting tool is disconnected from the nacelle and then removed by operation of the crane.

The integrated device is configured to have a stable position relative to the nacelle at least when disconnected from the load connector of the crane. The stable position is required in view of the use of the blade positioning assembly of the integrated device in the subsequent installation of the at least one rotor blade. The stable position may be provided in many different manners, e.g. the integrated device being rigidly connected to the nacelle, e.g. to the anchoring points of the nacelle. The stable position may also be provided by stabilizing members that function to stabilize the integrated device relative to the nacelle, e.g. stabilizing members being distinct from load transmitting connector members. For example, slings are use, as in the prior art, as load transmitting connector members, with additional stabilizer members serving the stabilize the integrated device. For example, one or more stabilizer members are operable between an inactive state and/or position and an active state and/or position. For example, the integrated device is provided with one or more operable stabilizers.

In embodiments, stabilization of the integrated device is obtained by one or more stabilizers engaging on the nacelle only. In another embodiment, the integrated device is configured to provide a stable position by engaging on the top end of the tower, e.g. in addition to engaging on the nacelle.

Once the nacelle has been installed at the top of the tower, the method is continued with the installation of at least one rotor blade, preferably all rotor blades, e.g. all three rotor blades. It is noted that the inventive method may, for example, also be applied for an approach known as the “bunny ears approach”, wherein the nacelle is already outfitted with two rotor blades prior to being lifted to the top of the tower so that only one rotor blade needs to be installed on the nacelle at the top of the tower.

For the installation of a rotor blade use is made of a blade lifting tool which retains the rotor blade and is suspended from a load connector of a crane. In embodiments, this crane has also been used for lifting the nacelle. As the rotor blade is a significantly lower weight than the nacelle, it is also possible to use another crane for the blade installation. For example, in an onshore situation, one or two high capacity cranes are used for installation of the nacelle. Then these one or two cranes are moved to a next wind turbine, e.g. of the same windfarm, and another, lower capacity crane, is brought in for installation of the rotor blades. This approach allows for optimal use of the high capacity crane(s) in the completion of a windfarm. For an offshore wind turbine in an offshore windfarm, it is a possible approach to use one vessel with one or two high capacity cranes for installation of the nacelle, possibly also of the tower ahead of the nacelle installation, and then use a second vessel with a crane for installation of the rotor blades. This second vessel can have a lower capacity crane, e.g. the entire vessel being smaller and/or lighter than the first vessel with the one or two high capacity cranes.

In an embodiment, for completion of a windfarm, multiple wind turbines are provided with a nacelle, wherein on each nacelle a respective integrated device is present. Then these wind turbines are provided with the at least one rotor blades, e.g. with all their blades. Installation of the nacelles can be done using one or two high capacity cranes, e.g. on board of a first vessel, and installation of the rotor blades using a lower capacity crane, e.g. onboard of a second vessel. This allows for optimal use of the first vessel, which may, for example, have a day rate that is higher than the second vessel.

An advantage of using the integrated device as discussed herein in combination with one or two first cranes for the installation of the nacelle and with a second crane for the installation of the at least one rotor blade, is that the second crane may be, and preferably is lighter, e.g. have a lighter boom and revolving superstructure on which the boom is pivotally mounted. A lighter design may allow for enhanced control of crane motions and/or accuracy compared to a heavy design required for lifting of the nacelle. This enhanced control may be of benefit when installing the blade, e.g. of alignment of the blade with the blade mounting structure and/or compensating for wind-induced blade motion, etc.

In the method, the crane is operated to lift the rotor blade to a height allowing for securing of the blade root to a respective blade mounting structure of the hub. In practical embodiments, the rotor blade is held horizontally throughout the lifting and securing of the rotor blade to the hub. This, for example, corresponds to the method of installing the blade in the so-called three o’clock or nine o’clock position. In another embodiment, as known in the art, the blade lifting tool is configured to controllably tilt the lifted blade into an inclined orientation, e.g. with the blade root upward or downward, e.g. at an angle of at most 30 degrees relative to horizontal.

In the inventive method, the rotor blade, e.g. the blade root, and/or the blade lifting tool is brought into engagement with the blade positioning assembly of the integrated device that is still present on the nacelle.

The blade positioning assembly is then used in positioning of the blade root relative to the blade mounting structure of the hub for the securing of the blade root to the blade mounting structure. The properly positioned blade root is then secured to the blade mounting structure, e.g. the bolts on the blade root being introduced through bolt holes and nuts being applied to secure the blade root to the hub.

In the inventive method, after installation of the at least one rotor blade of the wind turbine, the integrated device is disconnected from the nacelle and removed by means of a crane. Preferably, this is the same crane that has been used lifting the at least one rotor blade.

The inventive method is considered to provide increased efficiency in the installation of a wind turbine, whether on land or offshore. As the nacelle lifting structure needs to be strong and robust for its function in lifting of the (very) heavy nacelle, the lifting structure may in embodiments form the stable basis for the blade positioning assembly. Forces that may occur during the blade installation will, most likely, be of limited magnitude and can be readily absorbed by nacelle lifting structure.

In an embodiment, the nacelle lifting structure has a front connection that connects the nacelle lifting structure to the nacelle at the front nose end of the hub. Preferably, this front connection is primarily envisaged and/or configured for the purpose of stabilizing the structure relative to the nacelle and not, or merely in a limited manner, as a load transmitting connection for lifting of the nacelle. Preferably, this nacelle lifting structure has at least two connections to the nacelle at a more rearward location for lifting of the nacelle. Possibly, use is made of a temporary nacelle lift load transmitting connection to an anchoring point that is located within the nose of the hub, e.g. via a hatch in the nose located between adjacent blade mounting structures of the hub.

In an embodiment the integrated device, more in particular the nacelle lifting structure thereof, has a shank protruding upward and, at an upper end thereof, a shoulder. The one shank of the integrated device is configured to support the weight of the device as well as of the nacelle when being lifted by means of one or two high capacity cranes. Reference is made to W02020/055249 for possible embodiments and operation of this shank and load connector.

The blade position assembly of the integrated device may be embodied, for example, as disclosed in EP2538073.

For example, the blade positioning assembly is configured to center the blade root relative to the respective blade mounting structure.

In an embodiment, the blade positioning assembly comprises a stationary mounted blade engaging member, so stationary relative to the nacelle, e.g. a static guide, e.g. a roller, along which the blade is made to slide when mounting the blade root to the mounting structure.

In an embodiment, the blade positioning assembly comprises:

- a mobile blade engaging member, e.g. a blade coupler, e.g. a blade root coupler that is configured to couple to the exterior of the blade root,

- a motion mechanism supporting the blade engaging member, e.g. a motion arm, - a controllable actuator assembly comprising one or more actuators associated with the motion mechanism and a controller, the actuator assembly being configured to provide controlled motion of the motion mechanism in order to controllably move the blade engaging member.

For example, the centering of the blade root is done by means of the motion mechanism, e.g. providing for motion of the blade coupler in a plane that is perpendicular to the axis of the rotor blade to achieve a centering of the blade root.

For example, the motion mechanism is configured to provide at least controlled displacement of the mobile blade engaging member in direction of an axis along which the blade root is to be mounted to the blade mounting structure, e.g. perpendicular to a plane of a pitch bearing of said structure. For example, this embodiment is used to couple to the blade, e.g. the blade root, and then controllably move the blade root towards the blade mounting structure, e.g. introducing bolts protruding axially from the blade root into their respective bolt hole of the blade mounting structure.

In embodiments, the blade to be mounted to the respective blade mounting structure is held horizontally by the crane and blade lifting device during the mounting phase. This corresponds to the three o’clock or nine o’clock orientation. In another embodiment, e.g. as shown in figures 4 - 12, the blade can be held at an inclination, e.g. at an angle of about 30 degrees relative to the horizontal plane.

For example, the motion mechanism is operated to bring the mobile blade engaging member in a receiving position thereof so that the rotor blade lifted by the crane can be brought in engagement with the mobile blade engaging member.

In an embodiment, the blade coupler is configured as a blade root coupler that engages on, e.g. clamps about, the exterior of the blade root of the rotor blade. In another embodiment, the blade coupler is configured and operated to engage on another portion of the rotor blade, e.g. on the aerofoil portion thereof. In yet another embodiment, the blade coupler is configured and operated to couple with the blade lifting tool, e.g. an extender member of said blade lifting tool that extends towards the blade root.

The coupling of the blade coupler to the blade, e.g. the root, may be performed in a variety of manners, e.g. depending on the design of the blade coupler and/or of the blade/blade root. For example, the blade coupler may couple to the exterior of the blade or blade root by magnetically coupling, by vacuum coupling, etc.

Preferably, the blade coupler restrains the rotor blade at least in the longitudinal direction of the blade. Possibly, the blade coupler allows for (some) rotation of the blade about the longitudinal axis thereof, e.g. said rotation being caused by an appropriately design of the blade lifting tool, e.g. said rotation being performed in view of alignment of the bolts with the bolt holes. In another approach, such alignment is effected by rotation of the mounting structure, e.g. by means of the pitch adjustment mechanism thereof.

For example, the blade coupler is first moved into a receiving position thereof and the coupled to the blade. In an embodiment, the motion mechanism is then operated to displace the blade root of the coupled blade to the blade mounting structure.

In embodiments, the blade root coupler is an openable gripper that is configured to grip about the blade root of the blade. For example, the gripper has a gripper base connected to the motion mechanism, e.g. arm, e.g. via a Z-axis swivel. For example, the gripper has one or more movable, e.g. pivotal, gripper jaws, e.g. one at each circumferential end of the gripper base.

In embodiments, the blade root coupler is an openable gripper that is configured to grip about the blade root, e.g. about a blade root having a diameter of at least 3 meters, e.g. of more than 4 meters.

The initial coupling of the blade to the blade coupler, e.g. to the blade root, is, preferably, done at a fairly large distance, e.g. a safety distance, from the blade mounting structure of the hub, so as to practically exclude the possibility of impact between the blade root and the mounting structure or other part of the nacelle, e.g. the outer hull of the nacelle and/or the generator.

In embodiments, the motion mechanism is configured to provide for controlled motion of the blade engaging member, e.g. the blade coupler, solely in two non-parallel horizontal directions, so in a horizontal plane.

In embodiments, the motion mechanism is or comprises an articulated motion arm having multiple interconnected arm segments including an inner arm segment that is connected to a frame component of the integrated device and an outer arm segment that carries the blade engaging member, e.g. blade coupler, possible also one or more intermediate arm segments between the inner and outer arm segments. In a practical embodiment, the arm segments are connected to one another via a Z-axis hinge. In an embodiment, the motion arm solely provides for motion in two non-parallel horizontal directions.

In a practical embodiments, all arm segments of the articulated motion arm are fixed length arm segments. In another embodiment, one or more of the arm segments are embodied as a telescopic arm segment.

In alternative embodiments the motion mechanism, e.g. the motion arm, is configured for motion in and/or rotation around the X-axis, Y-axis, and Z-axis such that motion with multiple, e.g. four, five, or six degrees of freedom is enabled for the blade engaging member, e.g. the blade coupler.

In an embodiment of the inventive method, the method comprises:

- operating the controllable actuator assembly to bring the blade coupler in a receiving position thereof,

- coupling the blade coupler in said receiving position thereof to the rotor blade, e.g. to the blade root of the rotor blade, which is lifted by the crane,

- with the blade coupler being coupled to the blade - operating the controllable actuator assembly so as to displace the blade root of the coupled blade into a pre-mounting position that is closer to the blade mounting structure than the receiving position,

- operating the controllable actuator assembly to perform a mounting motion wherein the blade root is moved from the pre-mounting position into the mounting position, and keeping the blade root in the mounting position during securing of the blade root, e.g. during fastening of the blade root to the mounting structure by one or more fasteners.

In an embodiment of the inventive method, the tower top is subject to sea state and/or wind induced tower top motion in at least one direction in a horizontal plane, e.g. as discussed in the mentioned scientific article. In an embodiment, the integrated device is configured and operated to perform a method which comprises:

- operating the controllable actuator assembly to bring and maintain the blade coupler in a motion compensated receiving position thereof, wherein the motion mechanism is operated to compensate for the tower top motion in at least one horizontal direction, e.g. in multiple horizontal directions, e.g. two orthogonal horizontal directions,

- coupling the blade coupler in the receiving position thereof to the rotor blade, e.g. to the blade root of the rotor blade, that is lifted by the crane, - with the blade coupler being coupled to the blade - operating the controllable actuator assembly so as to gradually bring, and then maintain, the coupled blade, e.g. the blade root , in a horizontal motion that is synchronized with tower top motion, and

- possibly simultaneously with said synchronization, operating the controllable motion arm actuator assembly to displace the blade root of the coupled blade into a pre-mounting position that is closer to the blade mounting structure than the receiving position,

- operating the controllable actuator assembly to perform a mounting motion wherein the blade root is moved from the pre-mounting position into a mounting position, and keeping the blade root in the mounting position during securing of the blade root, e.g. fastening of the blade root to the mounting structure by one or more fasteners.

In the motion compensated receiving position the blade coupler, e.g. blade root coupler, is substantially compensated for the tower top motion by appropriate operation of the controllable actuator assembly, e.g. the motion arm folding and stretching in embodiments, so that this coupler does not exhibit the tower top motion. The compensation may be such that the blade coupler is at a stationary or stabilized position in space. This greatly facilitates the act of engaging the suspended rotor blade, e.g. the exterior of the blade root, with the blade root coupler. This engaging act may involve operating the crane to move the rotor blade but may also entail controlled engagement motion of the blade coupler.

For example, the blade coupler is motion compensated at such a location that mere slew motion of the crane, e.g. without luffing motion of the crane boom, brings the blade root in position for the initial coupling. Hereby, any disturbance of the blade stability caused by luffing of the crane boom, which may be over 100 meters long in practical embodiments, is avoided.

Once the coupling is effected, the controllable actuator assembly is operated to gradually bring, and then maintain, the coupled blade in a horizontal motion that is synchronized with tower top motion.

In preferred embodiments, the motion mechanism, e.g. including or embodied as an arm, e.g. an articulated arm, is configured to exert selectively - under control of the actuator assembly - both a force pulling the blade, e.g. the root, towards the mounting structure as well as a force pushing against the blade, e.g. the root, away from the blade mounting structure. In embodiments, this allows for the mentioned synchronization with the nacelle. Use of the blade coupler and the associated motion mechanism allows for a controlled gradual approach of the blade root towards the blade mounting structure, e.g. including a pitch bearing, which is desired in view of the large mass of the rotor blade. For example, a rapid or even sudden approach would cause undue inertia-based forces, e.g. necessitating an unduly heavy motion mechanism and/or may cause excessive strain where the blade coupler engages the blade, e.g. the exterior of the blade root.

In some practical conditions, the tower top motion coincides mainly with a horizontally extending mounting axis defined by the blade mounting structure during blade installation. As the blade is then, preferably, lifted by the crane so that the longitudinal axis of the blade coincides with this axis, the motion mechanism may then, in embodiments, be operated so that synchronization takes place along this axis, so along the longitudinal axis of the blade suspended from the crane. As will be discussed below in more detail, the blade lifting tool and/or the crane may be configured and operated to let the blade follow this motion, so without being restrained by or unduly pulling on the crane, e.g. avoiding, or reducing vibrations of the boom due to the blade motion synchronization.

In some practical conditions, as discussed above, the tower top motion has a component that is perpendicular to the mounting axis or fully extends perpendicular to this axis. In these conditions, a blade root coupler will synchronize the blade root, yet the lengthy and heavy blade will likely not be following this synchronized motion. As will be explained herein, it is preferred for the blade root coupler to swivel about a Z-axis, or vertical axis, so as to avoid undue torsional load on the motion mechanism, e.g. motion arm, by the inertia of the massive rotor blade.

In embodiments, the method comprises, with the blade root gripper in its motion compensated receiving position, the opening of the gripper so that the coupling or engaging of the blade root comprises resting the blade root on a gripper base, e.g. by lowering the blade trough operation of the crane, and then closing the gripper about the blade root by actuation of the one or more movable, e.g. pivotal, gripper jaws. For example, one or more gripper jaws are hydraulically actuated.

In embodiments, during the act of engagement of the blade root, the motion mechanism is operated so that blade coupler is on the one hand compensated for tower top motion and on the other hand is caused to follow motion, e.g. sway, of the still not engaged blade root as the blade is suspended from the crane. It is noted that such motion of the blade, which effectively renders the engagement even more problematic, can also be (partly) countered by means associated with the crane and/or the blade lifting tool. For example, one or more taglines lines and associated winches can be employed to counter sway of the blade suspended from the crane. For example, the blade lifting tool may be equipped with means to counter sway, e.g. one or more gyroscopes, propellors that create air thrust, etc.

In embodiments, the synchronization of the coupled blade with the tower top motion is effected prior to displacing the coupled blade root into the pre-mounting position. For example, the articulated motion arm, whilst stabilizing the blade coupler in the receiving position, initially behaves like/is operated as a limp, flexible arm to compensate the tower top motion, and is then, e.g. gradually, stiffened, or made to behave stiffer, so that the blade gradually assumes the motion of the tower top and is no longer compensated for such motion. It will be appreciated that in view of the mass of the blade a gradual reduction of the compensating operation of the arm is preferred, so that the blade is gradually brought into the synchronised motion without undue stresses/load occurring in the process.

In embodiments, the synchronization of the coupled blade with the tower top motion is effected at last in part simultaneously with displacing the coupled blade root into the premounting position.

In an embodiment, the rotor blade that is lifted by the crane and before being coupled to the blade coupler, is subject to motion in at least one direction in a horizontal plane, e.g. wind induced motion, e.g. a periodic motion. For example, wind or wind gusts may cause the blade to exhibit a periodic motion. In an embodiment, the integrated device is configured and operated to perform a method which comprises:

- with the blade coupler not yet being coupled to the blade - operating the controllable actuator assembly so as to gradually bring, and then maintain, the blade coupler, e.g. the blade root coupler, in a horizontal motion that is synchronized with blade motion in the at least one direction, e.g. in multiple horizontal directions, e.g. two orthogonal horizontal directions,

- coupling the motion synchronized blade coupler to the rotor blade, e.g. to the blade root of the rotor blade,

- operating the controllable actuator assembly to displace the blade root of the coupled blade into a pre-mounting position that is closer to the blade mounting structure,

- operating the controllable actuator assembly to perform a mounting motion wherein the blade root is moved from the pre-mounting position into a mounting position, and keeping the blade root in the mounting position during securing of the blade root, e.g. fastening of the blade root to the mounting structure by one or more fasteners. In this approach, the blade coupler is effectively made to follow the blade that is in (periodic) motion, e.g. the blade root, before actually coupling to the blade. Once the coupling is made, the motion mechanism, e.g. motion arm, is operated to move the blade root in a controlled process towards the blade mounting structure.

In embodiments, the method comprises a verification step that is performed with the blade root in the pre-mounting position and prior to initiating the mounting motion, which verification step comprises verification of the synchronization and/or of the alignment of the blade root with the blade mounting structure. As explained, the consequences of a collision between the blade root, in particular any bolts thereon, and the blade mounting structure or other part of the hub, and/or nacelle, can be drastic and irreversible. For example, a collision may damage the blade root, e.g. cracking of the laminated structure, such that installation of the blade is no longer possible, e.g. the blade needing to the shipped back to the factory for repairs. The verification step seeks to avoid this situation, e.g. by accurately measuring, e.g. using surveying equipment, the line-up of the blade with the axis along which the mounting motion is to be performed, and/or of the position of any bolts and/or temporary guides (e.g. to be later replaced by bolts) relative to the mounting structure, etc.

In embodiments, the crane used in the lifting of the rotor blade has a boom, and the crane is provided with a load connector active position control system that is configured and operated to actively control the position of the load connector in at least one horizontal direction, preferably in at least two non-parallel horizontal directions, relative to the boom. Examples of cranes having such capabilities are disclosed in WO2019156556, WO2018199743, and W02018106105. In embodiments, the method comprises operating the load connector active position control system of the crane in synchronicity with the blade coupler when coupled to the blade, e.g. as the blade root coupler moves in sync with the tower top motion, e.g. whilst the blade root is controllably advanced towards the pre-mounting position and/or to the mounting position. This approach effectively seeks to reduce or eliminate the effect that the suspension of the blade from the crane interferes with, and/or placed undue loads or stresses on, the motion arm. In embodiments, the load connector active position control system is configured and operated to cause the blade lifting tool to be moved in sync with the tower top motion, e.g. at least in one horizontal direction, possibly in two non-parallel directions in a horizontal plane.

In embodiments, the blade lifting tool comprises a frame that is attached to the load connector of the crane involved in the installation of the rotor blade, wherein the blade lifting tool comprises a blade holding assembly that is mobile mounted relative to the frame, e.g. at least mobile relative to the frame in one horizontal direction, e.g. along a length of the rotor blade held by the blade holding assembly, preferably two non-parallel horizontal direction, wherein the blade lifting tool comprises a controllable motion actuator device between frame and blade holding assembly. For example, the method comprises operating the controllable motion actuator device to move the blade holding assembly relative to the frame in synchronicity with the blade coupler, e.g. when coupled to the exterior of the blade root.

For example, the blade lifting tool comprises an active COG (centre of gravity) balancing system with a counterweight that is mobile mounted relative to frame and with a controlled motion actuator device between the frame and the counterweight, wherein the method comprises moving the counterweight relative to the frame in order to cause a common centre of gravity of the blade mass and the blade lifting tool to remain stable in a horizontal plane when the blade holding assembly and the blade held thereby are moved relative to the frame.

In embodiments, use is made of one or more sensors that measure the distance and/or position and/or angular orientation of the blade root relative to the mounting structure, e.g. said one or more sensors being linked to the controller of the controllable motion arm actuator assembly and/or to load connector active position control system and/or to the controllable motion actuator device that moves the blade holding assembly relative to the frame.

In embodiments, the method comprises the use of a control unit for control of the motion mechanism, e.g. said control unit being operated by a human operator that is present in or on the nacelle or on a platform or cabin on or in proximity of the nacelle.

In an embodiment, communication means are provided to cause communication between controller of the motion mechanism of the blade positioning assembly and the crane involved in lifting of the rotor blade, e.g. with the crane controller and/or with the crane driver. Alternatively or also there could be such communication with the blade lifting tool involved in lifting of the rotor blade. For example, the controller communicates, e.g. in two directions, with a load connector position control system for multi-axis, e.g. x-y-z axis, control of the position of the load connector of the crane lifting the rotor blade.

In an embodiment, the blade positioning assembly is provided with one or more force sensors configured to measure force exerted by the rotor blade on the assembly or components thereof. For example, force feedback is used for the control of operation of the crane and/or the blade lifting tool involved in lifting of the rotor blade. The force feedback can be automatically processed, and/or signalled to a crane drive, e.g. providing a warning signal when one or more forces become too high.

In embodiments, the blade positioning assembly may be provided with one or more sensors configured to provide signals, e.g. feedback signals, that are used for the control of operation of the crane and/or the blade lifting tool involved in lifting of the rotor blade.

In embodiments, after completion of fastening of the rotor blade to the hub of the wind turbine, the blade engaging member, e.g. blade coupler, is released from the blade, e.g. from the blade root, and the motion mechanism is then operated to move into a retracted configuration thereof, wherein a clearance is provided for the installed rotor blade during a rotation of the hub that is done so as to bring another one of the blade mounting structures into position for the installation of another rotor blade to the wind turbine.

In embodiments, the method comprises an emergency distancing routine, wherein the motion mechanism is operated to cause a rapid distancing of blade root away from nacelle, e.g. in case of a power and/or control signal anomaly, e.g. black-out, and/or in case of an anomaly in wind condition and/or sea state, e.g. wind gust, freak wave, etc.

The present invention also relates to an integrated device configured for nacelle lifting as well as for blade positioning, the integrated device having a nacelle lifting structure and a blade positioning assembly.

The integrated device may have one or more features as discussed herein.

The present invention also relates to the use of the integrated device in the installation of a wind turbine.

The present invention also a vessel loaded with multiple nacelles configured to each be installed on a respective offshore wind turbine tower, e.g. of an offshore wind farm, wherein each nacelle is pre-fitted with an integrated device configured for nacelle lifting as well as for blade positioning, the integrated device having a nacelle lifting structure and a blade positioning assembly. For example, this vessel is the vessel having the one or two cranes for lifting the nacelle or is a dedicated transport vessel, e.g. a barge.

The invention will now be discussed with reference to the drawings. In the drawings: Fig. 1 shows schematically, in a view onto the front of the nacelle, the top of an offshore wind turbine with the inventive integrated device which is used in the installation of the rotor blades,

Fig. 2 shows schematically, in a view from above, the use of the inventive integrated device in the installation of a rotor blade,

Fig. 3 shows schematically , the installation of the rotor blade with the inventive integrated device as well as a blade lifting tool used in lifting of the rotor blade,

Fig. 4 shows schematically another embodiment of the inventive integrated device as well as a nacelle,

Fig. 5 shows the integrated device of figure 4 mounted on the nacelle,

Fig. 6 illustrates the connection between the integrated device and the nacelle of figure 5, Fig. 7 shows the nacelle having been lifted and secured onto the top of the tower of a wind turbine, with the integrated device remaining on the nacelle after having been disconnected from the crane(s),

Fig. 8 illustrates the operation of the blade positioning assembly of the integrated device of figures 4 - 7 in the installation of a rotor blade,

Fig. 9 illustrates the rotation of the hub after the rotor blade has been fastened to the respective blade mounting structure of the hub,

Fig. 10 illustrates the operation of the blade positioning assembly when installing the second rotor blade,

Fig. 11 illustrates the rotation of the hub after the second rotor blade has been fastened to the respective blade mounting structure of the hub,

Fig. 12 illustrates the operation of the blade positioning assembly when installing the third rotor blade,

Fig. 13 illustrates the removal of the integrated device from the nacelle once the installation of the rotor blades has been completed, and

Fig. 14 illustrates the top portion of the wind turbine once the installation thereof has been completed and the wind turbine is ready to generate electricity.

In figure 1 a top portion of a wind turbine is schematically shown. The wind turbine comprises:

- a foundation (not shown), e.g. fixed to the seabed, e.g. a monopile or a jacket, or a floating foundation,

- a tower 2 that is mounted on the foundation and has a tower top shown in figure 1 ,

- a nacelle 3 on the tower top. The nacelle 3 is provided with a horizontal axis hub 4 having multiple blade mounting structures 5a,b,c, here three, each configured for securing thereto a rotor blade 7, 8.

As is known in the art, the mounting structures 5a,b,c may each include a pitch bearing, allowing to adjust the pitch of the rotor blades by means of a pitch adjuster mechanism.

As is known in the art, the rotation of the hub 4 causes a generator of the nacelle 3 to generate electricity. The generator may be, for example, a direct drive type generator. In another embodiment, the drive train of the generator includes a gearbox.

With reference to figures 1 - 3 the inventive method will now be elucidated.

As discussed above, the nacelle 3 is bulky and heavy, and for lifting the nacelle 3 at least one high capacity crane (not shown) is used. This crane has a load connector 75, here a crane hook 75, suspended from winch driven cable(s) of the crane.

For installation of an offshore wind turbine at an offshore location, the crane will be mounted on a vessel, e.g. a jack-up vessel or a floating vessel e.g. a semi-submersible vessel.

Possibly, the nacelle 3 is transported to the site of the wind turbine on the same vessel. In another approach, the nacelle 3 is transported to the site on a distinct vessel, e.g. on a barge or other supply vessel.

In the inventive approach, for lifting of the nacelle 3 to the tower top, use is made of an integrated device 100 which is configured not only for nacelle lifting but also for blade positioning in the stage or phase of installation of the rotor blades to the hub of the nacelle.

The integrated device 100 has a nacelle lifting structure 110 and a blade positioning assembly 130.

The nacelle lifting structure 110 is configured to support the weight of the nacelle 3 as it is lifted by means of a crane.

The blade positioning assembly 130 serves to assist in and/or control the positioning of the blade relative to the blade mounting structure in the process of installation of the blade. For lifting the nacelle 3, the integrated device 100 is suspended from the load connector 75 of the crane, here by means of slings 80. Other connections to the load connector of the crane(s) are also possible, e.g. as shown in figure 4.

The method comprises connecting the integrated device 100 to the nacelle 3 and then lifting the nacelle 3 to the top of the tower 2 by means of the crane(s), followed by fastening of the nacelle 3 to the top of the tower. Various manners for connecting the device 100, in particular the structure 110 thereof, to the nacelle 3 are discussed herein.

After fastening the nacelle 3 to the top of the tower 2, the load connector 75 of the crane is disconnected from the integrated device 100, which device 100 then remains connected to the nacelle 3.

The integrated device 100 is configured to have a stable position relative to the nacelle 3 at least when disconnected from the load connector 75 of the crane.

For the installation of a rotor blade 7, 8 use is made, preferably, of a blade lifting tool 20 which retains the rotor blade 8 and is suspended from a load connector of a crane, e.g. the crane also having been used for lifting the nacelle but possible from another crane, e.g. a crane mounted on another, second vessel.

The crane is operated to lift the rotor blade 8 to a height allowing for securing of the blade root to a respective blade mounting structure 5c of the hub 4.

In the blade installation stage of the method, the rotor blade 8, e.g. the blade root 8a, is brought into engagement with the blade positioning assembly 130 of the integrated device 100 that is present on the nacelle 3.

The blade positioning assembly 130 is used in positioning of the blade root 8a with bolts 10 relative to the blade mounting structure 5c of the hub 4 for the securing of the blade root to the blade mounting structure 5c. The positioned blade root 8a is then secured to the blade mounting structure 5c, e.g. by sticking the bolts 10 through corresponding bolt holes in the structure 5c and then mounting nuts on the bolts 10.

After installation of all rotor blades 7, 8, here three, of the wind turbine, the integrated device 100 is disconnected from the nacelle 3 and is then removed by means of a crane, e.g. the crane also having been used for lifting the rotor blade. The integrated device 100 is configured to have a stable position relative to the nacelle at least when disconnected from the load connector of the crane that lifted the nacelle. The stable position is required in view of the use of the blade positioning assembly 130 of the integrated device 100 in the subsequent installation of rotor blades. The stable position may be provided in many different manners, e.g. the integrated device 100 being rigidly connected to the nacelle, e.g. to the anchoring points (also known as hard point) of the nacelle 3. For example, disconnectable rigid connectors 101 are provided between the device 100 and anchoring points of the nacelle. The rigid connectors may include, for example, tensile load resistant connector rods.

The stable position of the device 100 may also be provided by stabilizing members that function to stabilize the integrated device relative to the nacelle, e.g. stabilizing members 102 being distinct from load transmitting connector members 101. For example, slings are use, as in the prior art, as load transmitting connector members 101 , with additional stabilizer members serving the stabilize the integrated device. For example, one or more stabilizer members are operable between an inactive state and/or position and an active state and/or position. For example, the integrated device 100 is provided with one or more operable stabilizers.

In embodiments, stabilization of the integrated device 100 is obtained by one or more stabilizers engaging on the nacelle 3 only. In another embodiment, the integrated device is configured to provide a stable position by engaging on the top end of the tower, e.g. in addition to engaging on the nacelle. For example, reference is made to W02006/076920 wherein a nacelle lifting tool is provided with one or more mobile stabilizer arms that engage on the top end portion of the tower.

In the figures it is illustrated that the blade positioning assembly 130 is present at a lateral side of the nacelle 3. Other locations of the assembly 130 are also possible, e.g. generally above the nacelle 3, e.g. extending over the nose end of the hub provided with the mounting structures 5a,b,c.

In the figures it is illustrated that the integrated device 100 may comprise a counterweight 105 opposite from the blade positioning assembly 130.

In embodiments, the integrated device 100 has a front connection that connects to the nacelle 3 at the front nose end of the hub, e.g. an anchoring point at said location. For example, herein, the integrated device then has two more rearward connections to the nacelle.

In figure 1 it is illustrated that two of the three blades 6, 7 have already been installed to the hub 4. It is noted that at this stage, the load connector 75 has already been disconnected from the integrated device 100, e.g. allowing for the same crane to be used for lifting of the rotor blade to be installed, or allowing for the vessel with the nacelle lifting capacity crane to move away from this specific wind turbine and for a second vessel with a rotor blade lifting crane to be stationed near the specific wind turbine.

In the installation of the blades 6, 7, also as known in the art, use may be made of a vessel, which is provided with a crane having a load connector suspended from one or more winch driven cables of the crane, wherein a blade lifting tool 20 that is attached to the load connector is engaged with a rotor blade 8 in horizontal orientation. The figure 3 illustrates, as is preferred, that the centre of gravity (COG) of the blade 8 is located within the area where the tool 20 holds the blade 8.

Each rotor blade, like blade 8, has a blade body with a blade root 8a, a blade tip, a length, and a rotor blade weight.

The blade root 8a has an exterior and is configured to be secured in a mounting position of the blade root 8a to a blade mounting structure 5c of the hub of the offshore wind turbine by means of one or more fasteners, e.g. bolts 10 protruding from the root as is known in the art. For example, the structure 5c has bolt holes into which the bolts are to be introduced, after which nuts are secured on the bolts.

The crane is operated to lift the blade lifting tool 20 and thereby the rotor blade 8, e.g. from a deck and/or a storage rack of the vessel, or from a barge, whilst remaining in horizontal orientation to a height that is substantially level with a blade mounting structure 5c of the offshore wind turbine.

The blade mounting structure 5c to which the blade 8 is installed, is oriented horizontally, so in the 3 o’clock or 9 o’clock position.

The figures illustrate that the integrated device 100 includes a blade positioning assembly 130, here more specifically an advanced blade motion synchronization and positioning assembly 130, which assembly 130 comprises: - a base frame 131 , that is integral with or fixated to a nacelle lifting frame structure 110 of the integrated device 100,

- a blade coupler, here a blade root coupler 132 that is configured to couple to the exterior of the blade root 8a,

- a motion mechanism, here a motion arm 140, between the base frame 131 and the blade coupler 132,

- a controllable actuator assembly comprising one or more actuators 150, 151 , 152 associated with the motion mechanism and a controller 160, the assembly being configured to provided controlled motion of the motion mechanism.

For example, in case the wind turbine is installed at sea, the tower top is subject to sea state and/or wind induced tower top motion in at least one direction in a horizontal plane, e.g. as discussed in detail in the documents referred to in the introduction.

The illustrated motion arm 140 is an articulated motion arm having multiple interconnected arm segments including an inner arm segment 141 that is connected to the base frame 131 and an outer arm segment 142 that carries the blade coupler 132.

The inner arm segment 141 is connected via a z-axis hinge 143 to the base frame 131.

In this embodiment, the base frame 131 has a vertically adjustable coupler member 131c, here guided on a vertical beam 131 d of the base frame, and an associated height adjustment actuator 131e allowing to set the height of the arm 140, and thereby the blade root coupler 132. The inner arm segment 141 is connected via vertical axis hinge 143 to this coupler member 131c.

The arm segments 141 , 142 are connected to one another via a Z-axis hinge 144.

The arm segments 141 , 142 are rigid arm segments having a fixed length, in this example.

For controlled (pivotal) motion of the arm segment 141 relative to the base frame an actuator 150 is provided.

For controlled (pivotal) motion of the arm segment 142 relative to the arm segment 141 an actuator 151 is provided. The blade root coupler 132 is carried on the outer arm segment 142 of the motion arm so as to be pivotal relative to the motion arm at least about a Z-axis swivel pivot 145, e.g. freely pivotal or provided with a damping arrangement, allowing for sway motion of rotor blade 8 suspended from the crane about the Z-axis swivel when coupled to the blade root coupler 132. As a result, the coupler 132 is movable in the horizontal plane, in two non-parallel directions, relative to the tower top.

It is illustrated that the blade root coupler 312 is an openable gripper that is configured to grip about the blade root 8a.

The gripper has a gripper base 132b that is connected to the motion arm, via the Z-axis swivel 145, and the gripper has one or more pivotal gripper jaws 132c, e.g. one at each circumferential end of the gripper base 132b.

It is illustrated, as an example, that the gripper base 132 not only is hinged about vertical swivel 145 but also about a horizontal swivel axis 146. To this end, the coupler 132 includes a subframe 132a between the arm, here segment 142 via swivel 145 and the base 132b. The subframe 132a swivels about the axis 145 and the base 132b swivels about the horizontal axis 146 relative to the subframe 312a. For example, an actuator 146a controls the swivel motion of the base 132a about the horizontal (swivel) axis 146. Similarly, an actuator 152 controls the swivel motion about the vertical axis 145.

In figure 1 the gripper 132 has been opened as the blade 8 has been properly installed already.

The gripper 132 can be opened so that the coupling of the blade root 8a comprises resting the blade root on the gripper base 132b, here also on one of the jaws 132c, and then closing the gripper by actuation of the one or more pivotal gripper jaws 132c.

The installation of the blade 8 to the hub 4 comprises:

- operating the controllable actuator assembly 150, 151 , 152, 160 to bring and maintain the blade coupler 132 in a motion compensated receiving position thereof, e.g. as in figure 2 or somewhat outwards thereof, wherein the motion arm 140 is operated to compensate for the tower top motion, - coupling the blade coupler 132 in said receiving position thereof to the rotor blade, here to the blade root 8a of the rotor blade, that is suspended from the crane, substantially level with a mounting structure 5c of the hub of the wind turbine,

- with the blade coupler 132 being coupled to the blade root 8a - operating the controllable actuator assembly 150, 151 , 152, 160 so as to gradually bring, and then maintain, the coupled blade, e.g. the blade root 8a, in a horizontal motion that is synchronized with tower top motion, and

- possibly simultaneously with said synchronization, operating the controllable actuator assembly 150, 151 , 512, 160 to displace the blade root 8a of the coupled blade into a premounting position (pm, see figure 2) that is closer to the mounting structure 5c than the receiving position,

- operating the controllable actuator assembly 150, 151 , 152 to perform a mounting motion wherein the blade root 8a is moved from the pre-mounting position pm into the mounting position (see figure 3), and keeping the blade root 8a in mounting position during fastening of the blade root to mounting structure 5c by one or more fasteners 10.

It is noted that figure 3 also shows the retracted position of the arm 140.

In an embodiment, the synchronization with the tower top motion is effected prior to displacing the blade root 8a of the coupled blade into the pre-mounting position by means of operation of the arm 140.

In an embodiment, the method comprises a verification step that is performed with the blade root 8a in the pre-mounting position pm and prior to initiating the mounting motion, here in axial direction of the blade 8 as defined by the extension of the bolts 10 and their introduction into bolt holes of the mounting structure 5c, which verification step comprises verification of the synchronization and/or alignment of the blade root with the mounting structure.

Verification may entail the use of one or more position detectors, e.g. contactless, e.g. from nacelle to blade root, e.g. a camera, a radar, infrared distance measuring, and/or satellite based position sensing, etc.

As is preferred, in an embodiment, the crane used in lifting of the rotor blade 8 has a boom, and the crane is provided with a load connector active position control system that is configured and operated to actively control the position of the load connector in at least one horizontal direction, preferably two non-parallel horizontal directions, relative to the boom, wherein the method comprises operating the load connector active position control system in synchronicity with the blade coupler 132, e.g. the blade root coupler when coupled to the exterior of the blade root 8a.

In embodiment, the blade lifting tool 20 comprises a frame 21 that is attached to the load connector of the crane, wherein the blade lifting tool comprises a blade holding assembly 22 that is mobile mounted relative to the frame, e.g. at least mobile relative to the frame in one horizontal direction, e.g. along a length of the rotor blade 8 held by the blade holding assembly, preferably two non-parallel horizontal direction, and wherein the blade lifting tool comprises a controllable motion actuator device 23 between frame and blade holding assembly. In an embodiment, the method comprises operating the controllable motion actuator device 23 to move the blade holding assembly 22 relative to the frame 21 in synchronicity with the blade coupler 132 when coupled to the blade 8 as discussed.

Preferably, use is made of one or more sensors that measure the distance and/or position and/or angular orientation of the blade root 8a relative to the mounting structure, e.g. said one or more sensors being linked to the controller 60 of the controllable motion mechanism actuator assembly and/or to load connector active position control system and/or to the controllable motion actuator device 23 that moves the blade holding assembly 22 relative to the frame 21 of the blade lifting tool 20.

For example, the method comprises the use of a control unit for control of the motion arm 140, e.g. said control unit being operated by a human operator present in the nacelle 3.

Figure 2 illustrates that after completion of fastening of the rotor blade 8 to the hub 4 of the offshore wind turbine, the blade coupler 132, e.g. blade root coupler, is released from the blade root 8a and the motion mechanism, here arm 140, is then operated to move into a retracted configuration wherein a clearance is provided for the installed rotor blade during a rotation of the hub that is done so as to bring another one of the mounting structures into position for the installation of another rotor blade to the offshore wind turbine.

As discussed, the method may comprise an emergency distancing routine, e.g. programmed into controller 160, wherein the motion mechanism, here arm 140, is operated to cause a rapid distancing of blade root 8a away from nacelle 3, e.g. in case of a power and/or control signal anomaly and/or in case of an anomaly in wind condition and/or sea state. As discussed, when the blade 8 is suspended from a crane by means of the lifting tool 20, even when other measures are present to counter motion of the blade like taglines, etc, still some (residual) motion of the rotor blade may be present. For example, in horizontal plane oscillating sway of the rotor blade about Z-axis through load connector of the crane is often observed. Other motions are in vertical plane oscillations about a horizontal axis, usually at the point of suspension of the lifting tool 20 from the crane, in plane X-motion of the blade along length of rotor blade, and/or in plane Y-motion transverse to length of rotor blade. The motion is often a motion induced by wind, but due to the enormous mass of the blade as well as length of the crane boom required for the installation, crane motions (e.g. boom vibrations) are also a factor. This motion of the blade 8 may be the cause of undesirable loads/stress on the motion mechanism, here arm 140, the coupler 132, and/or the location where the coupler engages the blade 8, e.g. at the root. In this regard, the provision of a swivelling support of the coupler 132 relative to the mechanism, here arm 140, alleviates or reduces this issue.

As mentioned in the cited documentation, the wind direction may be the same as the wave direction, yet they may also differ and not-coincide, e.g. waves still being in a direction of earlier strong wind that has reduced in force and changed direction. The illustrated assembly 130 allows to effectively deal with such situations as well. As mentioned in the cited documentation, the periodic tower top motion may have a significant amplitude, e.g. more than 0.5 meter, even more than 1 meter. Given the accuracy needed to introduce the multitude of bolts 10 in their bolt holes, the use of the arm 140 is highly effective and at least enlarges the operational window for the blade installation over prior art approaches. As discussed, collision of the bolts 10 may cause damage to the bolts and/or to structure of blade root, e.g. of the composite material, e.g. in the form of internal cracks.

The bolts 10 may be T-bolts as is known in the art. Other fasteners may be used as well.

The advancing of the blade 8 by means of the motion mechanism, here the arm 140, in the installation process, may be accompanied by a corresponding operation of the crane, e.g. so that the point of suspension from the crane follows the motion governed by the arm. For example, the crane follows this motion primarily by slewing of the boom about a vertical slew axis, and/or by operation of a load connector position control system for x-y (possibly also-z) control of position of load connector that carries the blade lifting tool 20. The vessel on which the crane for lifting the rotor blades is mounted could be in a floating condition, but could also be a jack-up vessel so that the crane is not subject to hull motion. The crane may also be stabilized, e.g. mounted on a motion stabilized platform onboard a floating vessel.

In an embodiment, an optical (e.g. laser based) guidance system is provided that is used for control of the path of the blade coupler relative to mounting structure to which the blade is to be installed.

In an embodiment, the blade root coupler 132 frictionally couples to the exterior of the blade root, e.g. as the root is clamped by the gripper, e.g. by friction pads, e.g. pneumatic friction pads. Coupling to the blade, e.g. blade root, may also involve the use of vacuum, magnetic forces, etc.

In an embodiment, a load connector position control system of the crane is operated to bring and maintain the blade longitudinal axis in alignment with mounting axis, so with the direction of the bolts 10 when present, preferably when in stationary receiving position, and/or when moving to pre-mounting position, or when in mounting position.

In an embodiment, an angle sensing assembly is present to detect angle between the mounting axis and the longitudinal axis of blade, e.g. between blade root coupler and motion arm, e.g. the outer segment of the arm, in horizontal plane.

In the blade root coupler 132 there may be blade root engaging members that are resiliently mounted and/or associated with positioning devices, e.g. allowing to adjust to coupler 132 to transverse dimensions of the blade, e.g. to the diameter of the blade root.

After fastening blade root to mounting structure, the blade root coupler 132 is opened and disengaged from blade root 8a, involving moving the motion mechanism, here arm 140, to the retracted position thereof so that hub can be rotated to bring a further mounting structure in the horizontal position for installation of the next blade to the hub.

It is noted that the motion mechanism may also be embodied in different versions that the one shown in the figures. For example, the motion mechanism 140 may comprise a parallelogram mechanism that acts in a vertical plane and of a motion stage supported by the parallelogram mechanism, for example an X-Y-0 motion stage. For example, the parallelogram or four-bar-linkage mechanism is connected to the base frame via a vertical axis hinge and can be rotated or swivelled about this hinge by an actuator. The motion stage, e.g. an X-Y-0 stage, is mounted on the end of the parallelogram mechanism. The blade coupler 132 is mounted on the motion stage. In an embodiment, the motion mechanism can also function without the rotational component of the X-Y-0 stage and therefore be outfitted with an X-Y stage instead.

In an embodiment, use is made of a sensing assembly for sensing spatial motion of blade root 8a, e.g. inertia-based sensing assembly, e.g. only in horizontal plane, e.g. two nonparallel directions, e.g. length and transverse to length, rotation about Z-axis of load connector, rotation about Y-axis through load connector, all oscillations.

In an embodiment, a mass damper may be provided as part of the tower 2 (e.g. permanently installed or temporary installed). A mass damper may also be provided as part of the integrated device 100 as to (temporarily) reduce tower motion during blade installation.

For example, a gyroscopic stabilizer is provided in the device 100.

For example, a gyroscopic stabilizer is present in the blade lifting tool 20 and/or load connector of the crane, e.g. on a spreader from which the tool 20 is suspended.

In an embodiment, the blade coupler 132 comprises one or more slings, e.g. with one or more sling adjuster devices, configured to each be engaged with a circumferential portion of the blade, e.g. of the blade root 8a, e.g. the blade root being gradually tightened between multiple slings to couple the blade root.

In an embodiment, communication means are provided to cause communication between controller 160 of the mechanism 140 and the crane, e.g. the crane controller and/or the crane driver, and/or the blade lifting tool involved in lifting of the rotor blade. For example, the controller 160 communicates, e.g. in two directions, with a load connector position control system for multi-axis, e.g. x-y-z axis, control of the position of the load connector of the crane lifting the rotor blade.

In an embodiment, the blade positioning assembly 130 is provided with one or more force sensors configured to measure force exerted by the rotor blade on the assembly 130 or components thereof. For example, force feedback is used for the control of operation of the crane and/or the blade lifting tool involved in lifting of the rotor blade. The force feedback can be automatically processed, or signalled to a crane drive, e.g. providing a warning signal when one or more forces become too high. In general, the blade positioning assembly 130 may be provided with one or more sensors configured to provide signals, e.g. feedback signals, that are used for the control of operation of the crane and/or the blade lifting tool involved in lifting of the rotor blade.

In an embodiment, there is an automated operation of the crane lifting the rotor blade that is being installed in unison with the motion mechanism 140, e.g. when the root 8a is advanced from the receiving position to the pre-mounting position and/or when moving from premounting position to mounting position.

In an embodiment, there is an automated x-y control of crane lifting the rotor blade in order to align the longitudinal axis of the blade with the mounting axis, e.g. based on angle sensing by sensor(s) on the motion mechanism, e.g. on arm 140, or sensor(s) on an arm segment and/or a motion stage.

In an embodiment, as shown, there is a gimbal mounting of blade root coupler so as to allow for (limited) rotation of blade root, e.g. to avoid overloading the motion mechanism 140 due to blade motion.

In an embodiment, provision is made for a camera that is directed at the blade root 8a, e.g. at the protruding bolts 10, the image being displayed for a human operator, and/or used for an automated image processing, e.g. so as to avoid collision and/or to issue warning signal(s).

As discussed, one or more taglines of a tagline system of the crane may be used to orient and/stabilize lifting tool 20 and/or the blade 8, primarily in a horizontal plane.

In an embodiment, a so-called High Wind Boom Lock or other arrangement may be provided to stabilize the load connector relative to crane boom of the crane lifting the rotor blade.

In an embodiment, the integrated device 100 is provided with an integrated power supply, e.g. a battery, hydraulic power units(s), etc.

In an embodiment, the device 100 is provided with a fire extinguishing system.

In an embodiment, the device 100 is provided with an auxiliary crane, e.g. to allow lifting of (hand) tools that are to be used by personnel working on and in the nacelle during the installation process. Fig. 4 shows schematically another embodiment of the inventive integrated device 100’ as well as a nacelle 3’.

Generally the device 100’ is composed of a nacelle lifting structure 110’ and a blade positioning assembly 130’.

The figure 4 illustrates that the integrated device 100’ is configured to be connected to load connector 75 as discussed in W02020/055249 to which reference is made.

The device 100’, more in particular the nacelle lifting structure 110’ thereof, has a shank 111 protruding upward and, at an upper end thereof, a shoulder 112. The one shank 111 of the device 100’ is configured to support the weight of the device 100’ as well as of the nacelle 3’ when being lifted by means of one or two high capacity cranes.

The load connector 75 comprises multiple cable sheaves through which the one or more winch driven cables are run so that the load connector 75 is suspended by the one or more winch driven cables in a multiple fall arrangement. The load connector 75 further comprises a female, open-centered body defining a shank receiving passage with a central vertical axis allowing introduction of the shoulder 112 of the device 100’ into the passage from below. Mobile tool retainers are provided, which are adapted to releasably engage under the shoulder 112 of the shank 111 so as to suspend the device 100’ underneath the load connector 75. These mobile tool retainers are distributed around the shank receiving passage, so as to each provide an operative and a non-operative position of the mobile tool retainer, the mobile tool retainers being adapted to - in a non-operative position - allow introduction of the shank 111 from below into the receiving passage and - in an operative position - engage below the shoulder 112 of the shank 111 that has been introduced into the passage so as to suspend the device 100’ from the load connector 75. In embodiments, preferably, a bearing supports the female, open-centered body in the load connector 75 so as to allow for swivelling of the female, open-centered body with the tool retainers, and thereby the device 100’ as well as the nacelle 3’ held thereby, about a vertical axis. In embodiments, preferably, a rotational drive is provided that is configured to selectively drive said swivelling of the female, open-centered body and of the mobile tool retainers mounted thereon, and thereby of the device 100’ as well as nacelle 3’, about a central vertical axis.

The nacelle 3’ is depicted in figure 4 with two opened hatches 3a that provide access to anchoring points 3b (see figure 6) located within the external housing of the nacelle 3’. The hub 4’ is shown without the blade mounting structures for reasons of clarity. The nacelle lifting structure 110’ is depicted with two rigid connector members 10T, here embodied as rods 10T that are configured to be secured to the two anchoring points 3b.

In the depicted example, the nacelle lifting structure 110’ is configured to extend over the nose end of the hub 4’ provided with the blade mounting structures. A bridge portion 104 5 of the structure 110’ extends over the nose end with the blade mounting structures.

The structure 110’ has a front connection 101” that connects to the nacelle 3’ at the front nose end of the hub 4’, e.g. an anchoring point 3c at said location. As shown, the integrated device 100’ has two more rearwardly located connections 10T to the nacelle 3’. The hub 4’ is rotatable whilst the device 100’ is in this position on the nacelle 3’.

In an embodiment, the front connection 101” that connects the nacelle lifting structure 110’ to the nacelle 3’ at the front nose end of the hub 4’ is primarily envisaged and/or configured for the purpose of stabilizing the structure 110’ relative to the nacelle 3’ and not, or merely in a limited manner, as a load transmitting connection for lifting of the nacelle 3’. For example, a load connector is temporarily arranged to engage on an anchoring point within the nose of the hub 4’ via a hatch 3d that is located between adjacent blade mounting structures, e.g. as shown in figure 4. Once the nacelle 3’ has been lifted and secured onto the tower top, this load connector is then removed, e.g. retracted out of the hub 4’, so that the hub 4’ can be rotated in the process of installation of the rotor blades. Possibly, this load connector associated with the nose of the hub 4’ is embodied as a sling, cable, chain or the like, which allows for easy disconnection, removal, and/or retraction.

Figure 5 shows that the integrated device 100’ has been mounted on the nacelle 3’. In the figure 6 the outer housing of the nacelle 3’ has been removed to better illustrate the connection between the connector members 10T of the integrated device 100’ and the anchoring points 3b of the nacelle 3’. It will be appreciated that the integrated device 100’, in particular the nacelle lifting structure 110’, is now held in a stable position on the nacelle 3’. This stability allows for the proper operation of the blade positioning assembly 130’ of the device 100’.

The nacelle 3’ is lifted to the top of a wind turbine tower 2 by means of one or two cranes. The figure shows that the nacelle 3’ has been lifted to the top of the tower 2 and has then been secured onto the top of the tower. The figure 7 also illustrates that the integrated device 100’ remains in stable position on the nacelle 3’ after having been disconnected from the crane(s). This allows for the use of the blade positioning assembly 130’ in the installation of the three rotor blades 6,7,8 to the hub 4’ of the nacelle 3’.

As discussed herein, the blade positioning assembly 130’ may have various designs and functionalities. The assembly 130’comprises a motion mechanism 140’ and an associated actuator assembly with controller.

As indicated in figure 8, the depicted blade positioning assembly 130’ is configured primarily to center or centralize the blade root of a rotor blade relative to the respective blade mounting structure of the hub. As shown, the blade coupler 132’ is primarily movable in a plane that extends perpendicular to the axis of the rotor blade, here in orthogonal directions, which allows for alignment of the blade root in this perpendicular plane with the blade mounting structure.

It is illustrated here, that the rotor blades 6, 7, and 8 are to be oriented at an angle of 30 degrees relative to horizontal with the blade root downward for the blade installation to the hub. For example, the blade lifting tool used in lifting of the rotor blade allows for lifting of the blade in horizontal orientation and then tilting of the blade to assume the inclined orientation that allows for the mounting to the hub.

In another embodiment, the assembly 130’ could also have a controlled motion in the direction of the axis of the rotor blade, e.g. to assist in controlled displacement of the blade root towards the blade mounting structure, e.g. in the process of insertion of bolts 10 into their respective bolt holes on the blade mounting structure. As known in the art, displacing the blade root towards the hub may, alternative to the use of the assembly 130’ or in combination therewith, also involve the use of a winch(es) and pull-in cable(s), the operation of the crane lifting the rotor blade, and/or operation of an appropriately designed blade lifting tool.

The blade positioning assembly 130’ can be configured to provide damping for the rotor blade that is to be connected to the blade mounting structure. For example, the assembly 130’ comprises resilient dampers or fenders for the blade, e.g. the blade root. For example, damping is achieved in one or more directions, e.g. in longitudinal direction of the rotor blade.

Damping of blade motion by means of the assembly 130’ can be achieved by means of the design of the motion mechanism and/or the operation/design of the related actuator assembly. For example, a hydraulic actuator assembly is present, wherein one or more hydraulic throttle components serve to obtain damping of blade motion once engaged by the blade coupler 132’.

Damping of blade motion by the assembly 130’ may be caused during a specific period, e.g. during an engagement period between the blade coupler and the rotor blade, with damping functionality then being terminated, e.g. to achieve position control of the coupled rotor blade by means of the blade positioning assembly 132’, e.g. in view of controlled motion of the blade root towards the blade mounting structure.

In figure 9 it is illustrated that the hub 4’ fitted with the first rotor blade 6 is rotated after the rotor blade 6 has been fastened to the respective blade mounting structure of the hub. Rotation of the hub may be effected in many different manners, e.g. using a specific drive of the nacelle 3’ or, possibly, a drive 106 present on the integrated device 100’, e.g. engaging the nose end of the hub. In other embodiments, the rotation is done by means of the crane that lifts the rotor blades.

Figure 10 illustrates the operation of the blade positioning assembly 130’ when installing the second rotor blade 7. Figure 11 illustrates the rotation of the hub 4’ after the second rotor blade 7 has been fastened to the respective blade mounting structure of the hub. Figure 12 illustrates the operation of the blade positioning assembly when installing the third rotor blade 8.

Now that all three rotor blades 6,7, and 8 have been secured to the hub 4’ the integrated device 100’ is no longer needed and is to be removed. The figure 13 illustrates the removal of the integrated device 100’ from the nacelle 3’ once the installation of the rotor blades has been completed. A load connector of the crane involved in the removal may be provided with the components discussed above to allow coupling with the shank 111 so that the device 100’ can be lifted. If desired, other connection arrangements between the crane and the device 100’ when being removed are possible as well.

The figure 14 illustrates the top section of the wind turbine once the installation thereof has been completed and the wind turbine is ready to generate electricity.