SYSTEMS FOR ALIGNING WIND TURBINE BLADES AND HUBS AND METHODS FOR MOUNTING WIND TURBINE BLADES
FIELD
[0001] The present disclosure relates to mounting of blades to a wind turbine hub, and more particularly to systems for aligning a wind turbine blade with a flange of a hub, and to methods for aligning wind turbine blades with mounting flanges of a hub using these systems.
BACKGROUND
[0002] Modern wind turbines are commonly used to supply electricity into the electrical grid. Wind turbines of this kind generally comprise a tower and a rotor arranged on the tower. The rotor, which typically comprises a hub and a plurality of blades, is set into rotation under the influence of the wind on the blades. Said rotation generates a torque that is normally transmitted through a rotor shaft to a generator, either directly ("directly driven" or "gearless") or through the use of a gearbox. This way, the generator produces electricity which can be supplied to the electrical grid.
[0003] The wind turbine hub may be rotatably coupled to a front of the nacelle. The wind turbine hub may be connected to a rotor shaft, and the rotor shaft may then be rotatably mounted in the nacelle using one or more rotor shaft bearings arranged in a frame inside the nacelle. The nacelle is a housing arranged on top of a wind turbine tower that contains and protects e.g. the gearbox (if present) and the generator and, depending on the wind turbine, further components such as a power converter, and auxiliary systems.
[0004] Wind turbine blades are generally coupled to the hub by a pitch bearing. A pitch bearing typically comprises an inner ring and an outer ring, and usually a plurality of rolling or roller elements between the inner and outer ring. A wind turbine blade may be attached either to the inner ring or to the outer ring, whereas the hub may be attached to the other of the inner and outer rings. The attachment may for example be performed with nuts and bolts.
[0005] The installation of wind turbine blades has become more and more of a challenging task due to the general tendency to increase the size and weight of modern wind turbine blades. Blades of modern wind turbines may be more than 70 or 80 meters long, or even more than 100 meters long. During installation, the wind turbine blades may be hoisted towards the rotor hub.
[0006] A known way of mounting a wind turbine includes the steps of transporting the different elements to the site of the wind turbine, assembling the tower sections and the tower, lifting the wind turbine nacelle with a large crane and mounting the nacelle on top of the tower. Then the wind turbine rotor hub can be lifted with the crane and mounted to a rotor shaft and/or the nacelle. Alternatively, the hub can be mounted to the nacelle and then the nacelle-hub assembly can be hoisted.
[0007] Afterwards, one or more blades are mounted to the wind turbine rotor hub. The rotor hub generally comprises a plurality of annular mounting flanges. Pitch bearings can be arranged with the mounting flanges. The blade can comprise a plurality of fasteners, such as bolts, or pins or studs at its blade root. During installation, these fasteners are to be fitted into openings in the mounting flange or pitch bearing on the hub.
[0008] It is also known to hoist a complete rotor assembly, i.e. the hub with the plurality of blades, and mount it to e.g. the nacelle. But in order to mount a complete rotor assembly, a large surface area is required, which is typically not available e.g. in the case of offshore wind turbines.
[0009] It is further known to mount blades individually. It is known to mount each of the plurality of blades substantially horizontally (e.g. -30° - +30° with respect to a horizontal plane) or substantially vertically.
[0010] Wind is inherently variable and winds from different directions, turbulent winds, and wind gusts can act on the wind turbine blade during hoisting and may provoke sudden movements and possibly oscillations of the blade during the hoisting operation. Fitting the blade to a hub may thus be complicated and time-consuming.
[0011] For offshore installations, the installation can be even more complicated. The vessel carrying a crane may move under wind and wave forces. Also, the wind turbine tower and the nacelle mounted on top of the tower can move under wind and wave forces.
[0012] Wind turbine farms may also be situated in remote sites, e.g. on hill-tops and typically in these places the lifting of the wind turbine blade may be subject to high winds.
[0013] Frequently, difficulties can arise during the lifting operation due to oscillations. In order to perform the installation of the blade, manual aid is often required e.g. the blade is stabilized with ropes. This can lead to an increase of the risk for the operator.
[0014] Oscillations during hoisting operations may also lead to possible damage to the wind turbine blade or to other parts of the wind turbine. If for example a sudden movement occurs when a wind turbine blade is close to the hub, parts or components may be damaged e.g. the blade, a pitch bearing, or blade fasteners.
[0015] The present disclosure provides systems and methods to at least partially overcome some of the aforementioned drawbacks.
SUMMARY
[0016] In an aspect of the present disclosure, a device for aligning a wind turbine blade with a mounting area of a hub is provided. The device is configured for being mounted to the hub, and the device comprises one or more actuators, wherein the actuators are configured to contact an inside of the blade, and are further configured to pull the blade towards the hub.
[0017] According to this aspect, the time needed in order to align the blade and the hub may be drastically reduced while at the same time damage to elements in the blade and in the hub during the installation process e.g. due to an uncontrolled collision of the blade and hub which can provoked by oscillation of the blade may be prevented. The system may allow the blade to approach the hub and contact the hub in a controlled manner once hub and blade are aligned and may also allow the reduction of human intervention during the blade assembly. The overall process of installing the blade to the hub may be enhanced.
[0018] Throughout the present disclosure, aligning the blade with a mounting area of the hub may be regarded as positioning the blade in a position such that the central axis of the blade root end is substantially collinear with the central axis of the mounting area of the hub. Once both elements are aligned, they may be moved closer to each other and the blade may be mechanically joined to the mounting area e.g. via the pitch bearing.
[0019] In another aspect of the present disclosure, a method for mounting a wind turbine blade to a hub is provided. The method comprises mounting an alignment device for aligning the blade with the hub on the hub and hoisting the wind turbine blade with a crane and positioning the wind turbine blade in proximity of the hub. The method further comprises one or more actuators of the alignment device extending towards the blade for contacting an inside of the blade and pulling the actuators towards the hub to guide the blade to the hub.
[0020] In a further aspect of the present disclosure, an alignment device for aligning the blade with the hub is provided. The alignment device comprises a base configured to be mounted on the hub and a telescopic rod configured to longitudinally extend away from and retract to the hub. The alignment device further comprises a plurality of telescopic fingers mounted on the rod and configured to radially extend away from and retract to the telescopic rod. [0021] Additional objects, advantages and features of embodiments of the present disclosure will become apparent to those skilled in the art upon examination of the description, or may be learned by practice.
BRIEF DESCRIPTION OF THE DRAWINGS
[0022] Figure 1 schematically illustrates a perspective view of one example of a wind turbine;
[0023] Figure 2 illustrates an example of a hub and a nacelle of a wind turbine;
[0024] Figure 3 schematically illustrates a perspective view of an example of a wind turbine hub, a wind turbine blade and a system for aligning a wind turbine blade to a hub according to an example of the present disclosure;
[0025] Figure 4 schematically illustrates a perspective view of an example of a wind turbine hub, a wind turbine blade and a system for aligning a wind turbine blade to a hub according to another example of the present disclosure; and
[0026] Figure 5 shows a flowchart of an example of a method for aligning a blade of a wind turbine with respect to a hub.
DETAILED DESCRIPTION OF EXAMPLES
[0027] Reference now will be made in detail to embodiments of the disclosure, one or more examples of which are illustrated in the drawings. Each example is provided by way of explanation, not as a limitation. In fact, it will be apparent to those skilled in the art that various modifications and variations can be made in the present disclosure without departing from the scope or spirit of the teaching. For instance, features illustrated or described as part of one embodiment can be used with another embodiment to yield a still further embodiment. Thus, it is intended that the present disclosure covers such modifications and variations as come within the scope of the appended claims and their equivalents.
[0028] Figure 1 is a perspective view of an example of a wind turbine 10. In the example, the wind turbine 10 is a horizontal-axis wind turbine. Alternatively, the wind turbine 10 may be a vertical-axis wind turbine. In the example, the wind turbine 10 includes a tower 15 that extends from a support system 14 on a ground 12, a nacelle 16 mounted on tower 15, and a rotor 18 that is coupled to nacelle 16. The rotor 18 includes a rotatable hub 20 and at least one rotor blade 22 coupled to and extending outward from the hub 20. In the example, the rotor 18 has three rotor blades 22. In an alternative embodiment, the rotor 18 includes more or less than three rotor blades 22. The tower 15 may be fabricated from tubular steel to define a cavity (not shown in figure 1) between a support system 14 and the nacelle 16. In an alternative embodiment, the tower 15 is any suitable type of a tower having any suitable height. According to an alternative, the tower can be a hybrid tower comprising a portion made of concrete and a tubular steel portion. Also, the tower can be a partial or full lattice tower.
[0029] The rotor blades 22 are spaced about the hub 20 to facilitate rotating the rotor 18 to enable kinetic energy to be transferred from the wind into usable mechanical energy, and subsequently, electrical energy. The rotor blades 22 are mated to the hub 20 by coupling a blade root portion 24 to the hub 20 at a plurality of load transfer regions 26. The load transfer regions 26 may have a hub load transfer region and a blade load transfer region (both not shown in figure 1). Loads induced to the rotor blades 22 are transferred to the hub 20 via the load transfer regions 26.
[0030] In examples, the rotor blades 22 may have a length ranging from about 15 meters (m) to about 90 m or more. Rotor blades 22 may have any suitable length that enables the wind turbine 10 to function as described herein. For example, non-limiting examples of blade lengths include 20 m or less, 37 m, 48.7 m, 50.2m, 52.2 m or a length that is greater than 91 m. As wind strikes the rotor blades 22 from a wind direction 28, the rotor 18 is rotated about a rotor axis 30. As the rotor blades 22 are rotated and subjected to centrifugal forces, the rotor blades 22 are also subjected to various forces and moments. As such, the rotor blades 22 may deflect and/or rotate from a neutral, or non-deflected, position to a deflected position.
[0031] Moreover, a pitch angle of the rotor blades 22, i.e., an angle that determines an orientation of the rotor blades 22 with respect to the wind direction, may be changed by a pitch system 32 to control the load and power generated by the wind turbine 10 by adjusting an angular position of at least one rotor blade 22 relative to wind vectors. Pitch axes 34 of rotor blades 22 are shown. During operation of the wind turbine 10, the pitch system 32 may particularly change a pitch angle of the rotor blades 22 such that the angle of attack of (portions of) the rotor blades are reduced, which facilitates reducing a rotational speed and/or facilitates a stall of the rotor 18.
[0032] In the example, a blade pitch of each rotor blade 22 is controlled individually by a wind turbine controller 36 or by a pitch control system 80. Alternatively, the blade pitch for all rotor blades 22 may be controlled simultaneously by said control systems.
[0033] Further, in the example, as the wind direction 28 changes, a nacelle 16 may be rotated about a yaw axis 38 to position the rotor blades 22 with respect to wind direction 28.
[0034] In the example, the wind turbine controller 36 is shown as being centralized within the nacelle 16, however, the wind turbine controller 36 may be a distributed system throughout the wind turbine 10, on the support system 14, within a wind farm, and/or at a remote-control center. The wind turbine controller 36 includes a processor 40 configured to perform the methods and/or steps described herein. Further, many of the other components described herein include a processor.
[0035] As used herein, the term “processor” is not limited to integrated circuits referred to in the art as a computer, but broadly refers to a controller, a microcontroller, a microcomputer, a programmable logic controller (PLC), an application specific, integrated circuit, and other programmable circuits, and these terms are used interchangeably herein. It should be understood that a processor and/or a control system can also include memory, input channels, and/or output channels.
[0036] Figure 2 is an enlarged sectional view of a portion of the wind turbine 10. In the example, the wind turbine 10 includes the nacelle 16 and the rotor 18 that is rotatably coupled to the nacelle 16. More specifically, the hub 20 of the rotor 18 is rotatably coupled to an electric generator 42 positioned within the nacelle 16 by the main shaft 44, a gearbox 46, a high-speed shaft 48, and a coupling 50. In the example, the main shaft 44 is disposed at least partially coaxial to a longitudinal axis (not shown) of the nacelle 16. A rotation of the main shaft 44 drives the gearbox 46 that subsequently drives the high-speed shaft 48 by translating the relatively slow rotational movement of the rotor 18 and of the main shaft 44 into a relatively fast rotational movement of the high-speed shaft 48. The latter is connected to the generator 42 for generating electrical energy with the help of a coupling 50. Furthermore, a transformer 90 and/or suitable electronics, switches, and/or inverters may be arranged in the nacelle 16 in order to transform electrical energy generated by the generator 42 having a voltage between 400V to 1000 V into electrical energy having medium voltage, e.g. 10 - 35 KV. Said electrical energy is conducted via power cables from the nacelle 16 into the tower 15.
[0037] The gearbox 46, generator 42 and transformer 90 may be supported by a main support structure frame of the nacelle 16, optionally embodied as a main frame 52. The gearbox 46 may include a gearbox housing that is connected to the main frame 52 by one or more torque arms 99. In the example, the nacelle 16 also includes a main forward support bearing 60 and a main aft support bearing 62. Furthermore, the generator 42 can be mounted to the main frame 52 by decoupling support means 54, in particular in order to prevent vibrations of the generator 42 to be introduced into the main frame 52 and thereby causing a noise emission source.
[0038] Optionally, the main frame 52 is configured to carry the entire load caused by the weight of the rotor 18 and components of the nacelle 16 and by the wind and rotational loads, and furthermore, to introduce these loads into the tower 15 of the wind turbine 10. The rotor shaft 44, generator 42, gearbox 46, high speed shaft 48, coupling 50, and any associated fastening, support, and/or securing device including, but not limited to, main frame 52, and forward support bearing 60 and aft support bearing 62, are sometimes referred to as a drive train 64.
[0039] In some examples, the wind turbine may be a direct drive wind turbine without gearbox 46. Generator 42 operate at the same rotational speed as the rotor 18 in direct drive wind turbines. They therefore generally have a much larger diameter than generators used in wind turbines having a gearbox 46 for providing a similar amount of power than a wind turbine with a gearbox.
[0040] The nacelle 16 may also include a yaw drive mechanism 56 that may be used to rotate the nacelle 16 and thereby also the rotor 18 about the yaw axis 38 to control the perspective of the rotor blades 22 with respect to the wind direction 28.
[0041] For positioning the nacelle 16 appropriately with respect to the wind direction 28, the nacelle 16 may also include at least one meteorological measurement system 58 which may include a wind vane and anemometer. The meteorological measurement system 58 can provide information to the wind turbine controller 36 that may include wind direction 28 and/or wind speed. In the example, the pitch system 32 is at least partially arranged as a pitch assembly 66 in the hub 20. The pitch assembly 66 includes one or more pitch drive systems 68 and at least one sensor 70. Each pitch drive system 68 is coupled to a respective rotor blade 22 (shown in figure 1) for modulating the pitch angle of a rotor blade 22 along the pitch axis 34. Only one of three pitch drive systems 68 is shown in figure 2.
[0042] In the example, the pitch assembly 66 includes at least one pitch bearing 72 coupled to hub 20 and to a respective rotor blade 22 (shown in figure 1) for rotating the respective rotor blade 22 about the pitch axis 34. The pitch drive system 68 includes a pitch drive motor 74, a pitch drive gearbox 76, and a pitch drive pinion 78. The pitch drive motor 74 is coupled to the pitch drive gearbox 76 such that the pitch drive motor 74 imparts mechanical force to the pitch drive gearbox 76. The pitch drive gearbox 76 is coupled to the pitch drive pinion 78 such that the pitch drive pinion 78 is rotated by the pitch drive gearbox 76. The pitch bearing 72 is coupled to pitch drive pinion 78 such that the rotation of the pitch drive pinion 78 causes a rotation of the pitch bearing 72.
[0043] Pitch drive system 68 is coupled to the wind turbine controller 36 for adjusting the pitch angle of a rotor blade 22 upon receipt of one or more signals from the wind turbine controller 36. In the example, the pitch drive motor 74 is any suitable motor driven by electrical power and/or a hydraulic system that enables pitch assembly 66 to function as described herein. Alternatively, the pitch assembly 66 may include any suitable structure, configuration, arrangement, and/or components such as, but not limited to, hydraulic cylinders, springs, and/or servomechanisms. In certain embodiments, the pitch drive motor 74 is driven by energy extracted from a rotational inertia of hub 20 and/or a stored energy source (not shown) that supplies energy to components of the wind turbine 10.
[0044] The pitch assembly 66 may also include one or more pitch control systems 80 for controlling the pitch drive system 68 according to control signals from the wind turbine controller 36, in case of specific prioritized situations and/or during rotor 18 overspeed. In the example, the pitch assembly 66 includes at least one pitch control system 80 communicatively coupled to a respective pitch drive system 68 for controlling pitch drive system 68 independently from the wind turbine controller 36. In the example, the pitch control system 80 is coupled to the pitch drive system 68 and to a sensor 70. During normal operation of the wind turbine 10, the wind turbine controller 36 may control the pitch drive system 68 to adjust a pitch angle of rotor blades 22.
[0045] According to an embodiment, a power generator 84, for example comprising a battery and electric capacitors, is arranged at or within the hub 20 and is coupled to the sensor 70, the pitch control system 80, and to the pitch drive system 68 to provide a source of power to these components. In the example, the power generator 84 provides a continuing source of power to the pitch assembly 66 during operation of the wind turbine 10. In an alternative embodiment, power generator 84 provides power to the pitch assembly 66 only during an electrical power loss event of the wind turbine 10. The electrical power loss event may include power grid loss or dip, malfunctioning of an electrical system of the wind turbine 10, and/or failure of the wind turbine controller 36. During the electrical power loss event, the power generator 84 operates to provide electrical power to the pitch assembly 66 such that pitch assembly 66 can operate during the electrical power loss event.
[0046] In the example, the pitch drive system 68, the sensor 70, the pitch control system 80, cables, and the power generator 84 are each positioned in a cavity 86 defined by an inner surface 88 of hub 20. In an alternative embodiment, said components are positioned with respect to an outer roof surface of hub 20 and may be coupled, directly or indirectly, to the outer roof surface.
[0047] Figure 3 schematically shows a perspective view of a hub 20 of a wind turbine and of a blade 22 of a wind turbine. The blade is substantially aligned with a mounting area of the hub before being attached to the hub 20. Figure 3 further shows an example of an alignment device 100 for aligning the blade 22 with a mounting area of the hub according to the present disclosure. [0048] The device 100 is configured for being mounted to the hub 20, wherein the device comprises one or more actuators 110, 120, 130, wherein the actuators 110, 120, 130 are configured for contacting an inside of the blade, and configured to pull the blade towards the hub.
[0049] More particularly, an alignment device 100 for aligning the blade with the hub, is provided, which comprises a base configured to be mounted on the hub 20, and a telescopic rod 103 configured to longitudinally extend away from and retract to the hub 20. The alignment device 100 further comprises a plurality of telescopic fingers 110, 120, 130 mounted on the telescopic rod 103 and configured to radially extend away from and retract to the telescopic rod 103.
[0050] In the example of figure 3, the telescopic fingers 110, 120, 130 are mounted at or near a distal end of the telescopic rod 103. More particularly in this example, a central part 105 is mounted at the distal end of the telescopic rod 103. The central part carries the telescopic fingers 110, 120, 130. In other examples, the telescopic fingers 110, 120, 130 may be directly attached to the telescopic arm e.g. to the second longitudinal portion 102 of the telescopic arm.
[0051] The telescopic arm 103 may comprise two or more telescopic segments 101 , 102 wherein at least one of the segments can slide with respect to the other. In this particular example, the telescopic segment 101 may form a base of the telescopic arm. The telescopic segment 102 can slide and extend further out of the segment 101 or be retracted into segment 101. The telescopic arm may include e.g. a motor or hydraulic or pneumatic drive to slide telescopic segment 102 with respect to segment 101. The telescopic segments in this example are substantially tubular.
[0052] In some examples, in an extended position, the telescopic arm 103 may increase its length by 1 - 2 meters. In some examples, the extended device may have a length of 2 - 3 meters.
[0053] Similarly to the telescopic arm, the telescopic fingers may include a plurality of segments which can be moved or slide with respect to each other. In some examples, linear electric actuators may be used to drive the telescopic fingers. In other examples, the telescopic fingers may have a pneumatic drive or hydraulic drive.
[0054] In some examples, the plurality of telescopic fingers 110, 120, 130 may be driven with a joint drive which controls the plurality of fingers at the same time. In other examples, each of the telescopic fingers may have an independent drive e.g. they may be linear electric actuators. [0055] Although in this example the alignment device comprises three fingers, equidistantly arranged with respect to the central part, in other examples, two, diametrically opposed fingers, or four or more fingers may be used.
[0056] The device may be configured to be removably mounted to the hub. The alignment device may be temporarily installed for mounting of the wind turbine blades. After one of the blades has been mounted to the hub, the alignment device may be removed. The alignment device can be repositioned within the same hub for mounting of a subsequent blade, or it can be transported to another wind turbine.
[0057] In some examples, like the example of figure 3, the alignment device may be configured to be mounted on a mounting plate of a pitch system. Such a mounting plate may provide stiffness to the hub and carry e.g. a pitch drive. In general, the alignment device may be adapted to be mounted at an inside or inner part of the hub.
[0058] As schematically shown in figure 3, the wind turbine blade 22 may comprise one or more positioning features 200. In some examples, the positioning features 200 may be configured to be removably attached to an inner surface of the blade.
[0059] In some examples, the positioning features 200 may be mechanically and/or adhesively attached to the inner surface of the blade e.g. using glue. The positioning features 200 may be attached to the inner surface of the blade with detachable means, such that they may be removed from the blade once the blade has been installed in the hub, preventing the addition of unnecessary weight to the wind turbine blade.
[0060] In some examples, the positioning features 200 may comprise a plurality of mechanical reinforcements and may be configured to contact the second finger portion of the plurality of telescopic fingers 110, 120, 130. In further examples, the second finger portion may be configured to lock with the reinforcements, locking the blade position or orientation with respect to the alignment device. This may enhance the process of aligning the blade to the hub opening by preventing or hindering the aligned blade from moving to a different (non- aligned) position with respect the mounting area.
[0061] The example schematically illustrated in figure 3 may be operated as follows. In a method for mounting a wind turbine blade to a hub, the alignment device 100 for aligning the blade with the hub may be mounted on the hub.
[0062] The wind turbine blade 22 may be hoisted with a crane and the wind turbine blade may be placed in proximity of the hub. In particular, the blade may be positioned in proximity of the hub with the blade being arranged substantially horizontally. Hoisting with a crane may involve the use of two or more hoist lines, and depending on the implementation may further involve one or more cradles or slings to hold portions of the blade. Hoisting with the crane may further involve the use of one or more tag lines to control the movement of the wind turbine blade 22.
[0063] Once the blade is in proximity of the hub, e.g. within 2 meters of the hub, or within one meter of the hub, one or more actuators of the alignment device may extend towards the blade for contacting an inside of the blade and the actuators can then pull the blade towards the hub to guide the blade to the hub.
[0064] In the example of figure 3, the method may further comprise extending the telescopic arm 103 towards an inside of the wind turbine blade 22, and radially extend fingers 110, 120, 130 from the telescopic arm 103 towards an inner surface of the wind turbine blade. The fingers may touch an inside of the blade. As such the fingers can also act as sensors, and may incorporate sensors to determine the position of the blade with respect to the telescopic arm. I.e. if one of the fingers makes contact before the other fingers, this indicates that the blade is not centered around the telescopic arm, which is preferably positioned along the central axis of the mounting area of the hub and should substantially coincide with a longitudinal axis of the blade.
[0065] If the blade is substantially aligned with the hub 20, the telescopic arm 103 may be retracted to thereby exert a pulling force on the blade. At the same time, the crane and in general the hoisting system may be controlled to move the blade towards the hub whereby the fingers guide the blade and maintain the alignment of the blade with the hub.
[0066] In some examples, as the crane is operated, the method may also comprise temporarily retracting the fingers away from the blade and move the blade towards the hub using the crane. The fingers may then reengage with the blade again. By temporarily retracting the fingers, the operation of the crane may be facilitated.
[0067] In some examples, the contact of the one or more actuators (in this example, the fingers) with an inside of the blade comprises mechanically locking the actuators to an inner surface of the blade, e.g. with positioning features 200.
[0068] The blade and/or the hub may include alignment bushings and/or alignment pins which may establish contact before e.g. fasteners on the blade may contact with holes on a bearing ring. Once the blade makes contact with the hub (specifically the pitch bearing on the hub), fasteners such as studs may be used to connect the blade to the hub (specifically a ring of the pitch bearing).
[0069] In examples, the method may further comprise removing the device for aligning the blade with the hub from the hub. [0070] Figures 4a and 4b schematically illustrate a further example of a device 100 for aligning the blade 22 with a mounting area of the hub according to the present disclosure. In the example shown in figures 4a and 4b, the actuators are cables 415, which extend from a motor operated winding device 410, such as a winch. The cables may carry a hook or an eyelet 420 at an end of the cable.
[0071] When the blade 22 is in proximity of the hub 20, the hooks or eyelets 420 at the end of the cables may engage a catch or hook or some other retention system arranged at an inside of the wind turbine blade. Such retention systems may be equidistantly spaced around an inner circumference of the blade. In some examples, three or more winches 410 are equidistantly spaced inside the hub, and three or more corresponding retention systems may be provided in the blade.
[0072] In some examples, the plurality of winches may be mounted on a common base 300, and the base 300 may be attached at an inside of the hub 20, e.g. the mounting plate of the pitch system. Further, the retention systems or positioning features arranged at an inside of the blade may also be mounted on a common base 200, the base attached at an inside of the blade 22.
[0073] In some examples, the cables 415 may be coupled to the retention system prior to lifting the blade and hoisting it towards the hub i.e the cables may be attached to the retention system when the blade is still at ground level.
[0074] In other examples, the cables may be coupled to the retention systems as the blade is approaching the hub. In some examples, an operator may use a tool such as a pole to couple the various cables to the corresponding retention systems. In other examples, a tool may be used by an operator to aim at one retention system comprising an anchor attachment and subsequently throw or shoot one of the cables towards it, such that upon establishing contact, the cable couples to the retention system. Alternatively, this might be carried out automatically i.e. without human intervention.
[0075] In yet further examples, the blade may comprise a rail system which may be used to move the retention systems towards the root of the blade and thus towards the hub for easier coupling with the cables. Once the cables are coupled, the
[0076] Figures 4a and 4b show an example of three winches 410 mounted on a common base 300. Such a common base may be mounted to the hub. In other examples, the winches 410 may be individually attached to the hub e.g. a mounting plate of the pitch system.
[0077] In the figures, a cable 415 extends from each of the winches and engages, via hooks or eyelets 420, one of the retention systems which are mounted on a common base 200 attached at an inside of the blade 22. Such a common base may be a bulkhead. The cable 415 may be configured to extend towards any of the retention systems which are spaced around the inner circumference of the blade.
[0078] In some examples, as shown in figure 4a, each of the cables 415 may engage a retention system which is substantially longitudinally aligned with the winch from which they extend i.e. winch and retention system have a same azimuthal position. In these examples, the cables 415 may extend substantially parallel to the central axis of the blade root end once the blade is aligned to the hub.
[0079] In other examples, as schematically represented in figure 4b, each of the cables 415 may engage a retention system located in an azimuthal position which is different from an azimuthal position of the winch e.g. a cable may engage the retention system which is diametrically opposite from the winch from which it extends once the blade and the hub are in an aligned position. For example, a cable from a winch at a twelve o’clock position extends towards a retention system at a six o’clock position, and a cable from a winch at a four o’clock position extends towards a retention system at a ten o’clock position. This position of the cables may facilitate the restriction of movement of the blade, enhancing its control during the mounting process.
[0080] Once the hooks or eyelets 420 engage the corresponding retention systems, the winches may be operated to pull the blade towards the hub. By coordinating the controls over the various winches, the approach of the blade towards the hub may be carried out in a controlled manner. Pulling one of the winches more than the others can help to reposition or reorient the blade as necessary. Maintaining tension on the cables of the winches can also reduce swinging and movements of the blade under the influence of e.g. the wind.
[0081] As described with reference to figure 3, once the blade is aligned with the hub and has approached the hub, suitable fasteners may be used for the mounting of the blade.
[0082] Figure 5 shows a flowchart of a method 500 for mounting a wind turbine blade to a hub. The method 500 comprises, at block 502, mounting one or more alignment devices to the hub. The alignment device may be e.g. according to the examples of figure 3 or 4a and 4b.
[0083] The method may further comprise, at block 504, hoisting the wind turbine blade with a crane and positioning the wind turbine blade in proximity of a mounting flange of the hub. In particular, the blade may be positioned in proximity of the hub with the blade in a substantially horizontal position. [0084] Accordingly, the blade may be arranged at a distance from the mounting flange of the hub of e.g. 0.5 - 2 m.
[0085] At block 506, one or more actuators of the alignment device (e.g. the cables or the fingers) may extend towards the blade for contacting an inside of the blade, and at block 508, the actuators may be pulled towards the hub to guide the blade to the hub. E.g. the telescopic arm may be retracted towards the hub in the example of figure 3. In the example of figures 4a and 4b, the winches may be operated to retract the cables and pull the cables toward the hub.
[0086] It is noted that extending the actuators towards an inside of the blade may occur before the blade is in proximity to the hub. E.g. while the blade is on the ground prior to being hoisted.
[0087] In coordination with the actuators pulling or retracting towards the hub, at block 510, the crane (and e.g. tag lines, hoist lines) may be controlled to guide the blade towards the hub.
[0088] Optionally, at block 512, the alignment device(s) may be removed from the hub. Other details already commented on with respect to figures 3 and 4 may equally be used in examples of the method 500.
[0089] The example of figure 5 should not be interpreted as requiring a specific order of the various method steps. E.g. it is possible for the mounting of the alignment device to occur simultaneously of after hoisting of the blade. Similarly, the control of the crane according to block 510 and pulling of the actuators at block 508 may occur simultaneously, or intermittently.
[0090] This written description uses examples to disclose the teaching, including the preferred embodiments, and also to enable any person skilled in the art to practice the teaching, including making and using any devices or systems and performing any incorporated methods. The patentable scope is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal languages of the claims. Aspects from the various embodiments described, as well as other known equivalents for each such aspects, can be mixed and matched by one of ordinary skill in the art to construct additional embodiments and techniques in accordance with principles of this application. If reference signs related to drawings are placed in parentheses in a claim, they are solely for attempting to increase the intelligibility of the claim, and shall not be construed as limiting the scope of the claim.