Method for lowering and / or lifting and method for servicing rotor blades of a wind turbine - Patents.com

Abstract

A method for lowering and / or lifting rotor blades (3) of a wind turbine (1) and varying a distance (6) between an end face (7) of a blade root (8) of the rotor blade (3) and a contact surface (64) of a blade bearing (9) of the rotor blade (3), comprising the steps of providing a plurality of actuators (27-34), in particular at least four actuators (27-34), each having a first part (48) and a second part (49), the second part (49) being movable relative to the first part (48) in a respective actuator movement direction (50, 55) by controlling the actuator (27-34), each first part (48) being coupled to a blade bearing (9) and each second part (49) being coupled to a rotor blade (3). ), whereby all actuator movement directions (50, 55) deviate from a vertical direction (14, 15) by less than 20°, less than 10°, or less than 5° when the rotor blades are in a given orientation (42); and while the rotor blades (3) are in the given orientation (42), controlling the actuators (27-34) to lower and / or raise the rotor blades (3), whereby a first group (35) of the actuators (27-34) each exerts a vertical upward force on a first circumferential section (40) of the blade root (8), and a second group (36) of the actuators (27-34) exerts a vertical downward force on a second circumferential section (41) of the blade root (8).

Description

[Technical Field]

[0001] The present invention relates to a method for lowering and / or lifting rotor blades of a wind turbine, in particular for servicing rotor blades. Additionally, the present invention relates to a method for servicing rotor blades of a wind turbine.

[0002] Background technology In wind turbines, rotor blades may require maintenance or replacement. An exemplary use case is the refurbishment of the blade root end faces of rotor blades. Such refurbishment may be necessary, for example, when lubricants get between the blade bearing contact surfaces, formed, for example, by the bearing's reinforcement plate, and the blade root end faces. Lubricants, such as grease, may cause increased wear and tear on the blade roots, especially if the blade roots are made of fiber-reinforced materials. Therefore, if such refurbishment is not carried out in time, it may be necessary to refurbish the blade root end faces or even replace the blades.

[0003] The blade root end face is typically in contact with the blade bearing contact surface and therefore cannot be accessed while the blade is mounted in the bearing. Thus, in the past, to perform maintenance on the blade root end face, it was necessary to remove the blade from the bearing and lower the blade completely to the ground. Such maintenance therefore requires a crane or jack-up vessel and causes extensive downtime for the wind turbine.

[0004] Removal and disengagement of rotor blades from blade bearings, as well as installation after blade maintenance, can be particularly challenging when conical rotors, such as those described in WO 2013 / 091635, are used. In such conical rotors, the blades are bent or angled forward from the blade root toward the windward direction, thus increasing their distance from the tower during operation. In this case, or generally when the blade's center of gravity cannot be placed directly below the center of the blade bearing while attached to the bearing, supporting the blade in the area of ​​the blade root during installation or removal is typically insufficient because the unavoidable horizontal offset of the center of gravity relative to the blade root causes strong torques on the rotor blade, resulting in rotor blade tilt that can damage wind turbine components. Therefore, additional support in the area of ​​the blade tip is typically required. Such additional support requires a crane or jack-up vessel.

[0005] It is therefore an object of the present invention to provide an improved technique for servicing rotor blades while the respective rotor blades are in a given orientation, or generally for lowering and / or lifting rotor blades, which in particular avoids or at least reduces the need to support the blades by external equipment, for example by a crane or jack-up vessel.

[0006] Summary of the Invention According to one aspect, the problem is a method for lowering and / or lifting rotor blades of a wind turbine and for varying the distance between the blade root end face of the rotor blade and the contact surface of the blade bearing of the rotor blade, in particular for the purpose of servicing the rotor blades, comprising the step of providing a plurality of actuators, in particular at least four actuators, each actuator having a first part, in particular a hydraulic cylinder, and a second part, in particular a piston, which second part is movable relative to the first part in a respective actuator movement direction by controlling the actuator, each first part being coupled to the blade bearing and / or to the hub, a second part of the problem is solved by a method including the steps of: coupling the actuators to the rotor blades so that all actuator movement directions deviate from vertical by less than 20°, less than 10°, or less than 5° when the rotor blades are in a given orientation; and controlling the actuators to lower and / or raise the rotor blades while the rotor blades are in the given orientation, so that a first group of actuators each exerts a vertically upward force on a first circumferential section of the blade root and a second group of actuators exerts a vertically downward force on a second circumferential section of the blade root.

[0007] In particular, the problem is solved by providing a method according to the independent claims.

[0008] By applying forces in two at least essentially opposite vertical directions to different circumferential sections of the blade root, a torque is exerted on the rotor blade about an imaginary axis extending across the blade root. This torque has been found to compensate for torque that can arise when the center of gravity of the blade is horizontally offset from the center of the region below the end face, for example, due to the use of rotor blades with a conical angle.

[0009] As an example, the use of rotor blades with their centers of gravity upwind from their respective blade bearings results in a tilting force toward the tower when the blades are pointing essentially vertically downward. This tilting force is typically absorbed by the contact surfaces of the blade bearings, which can support the end faces of the blade roots during normal operation of the wind turbine. When the blades are lowered, this support no longer acts, and the resulting torque exerts bending forces on components, such as bolts, used to guide the blade roots during movement.

[0010] To avoid damage to these components, additional support, e.g., by a crane or jack-up vessel, is typically required to compensate for the torque. By actively applying opposing forces to different circumferential sections of the blade root, the torque caused by the offset center of gravity of the rotor blade can be compensated for without additional external equipment. While this approach may result in additional stresses on the actuators and / or components, e.g., bolts used to connect each actuator to the rotor blade, this additional stress is typically compressive, e.g., in the longitudinal direction of the bolts, and is therefore easily handled by common components.

[0011] The blade root end faces can come into contact with the blade bearing contact surfaces during normal operation of the wind turbine. For most wind turbines and purposes, such as servicing the blade root end faces of rotor blades as described below, lowering the blades by 145 mm to 160 mm is sufficient. In an exemplary configuration used during development of this invention, a 150 mm lowering was robustly, safely, and repeatably possible at wind speeds averaged over 10-minute intervals of up to 8 m / s. Operation should be limited to wind speeds below a given threshold, which depends on the specific implementation.

[0012] The first and second circumferential sections of the blade root may be different from one another and in particular may not overlap.

[0013] Preferably, the first and second groups of actuators each include at least two actuators. However, it is also possible for the first and / or second groups to include only a single actuator. The actuators may be, for example, approximately equally spaced along the circumferential direction of the blade root. Preferably, both circumferential sections have approximately the same size. The first and / or second groups may include subgroups of actuators that are commonly controlled to reduce complexity. For example, a common pump may be used to apply essentially equal pressure to the hydraulic actuators in a given subgroup. In an exemplary embodiment, each group may include four actuators divided into two subgroups, each including two actuators. In particular, each subgroup may be assigned to a circumferential section spanning approximately 90°.

[0014] The actuator may preferably be specifically mounted for tasks requiring lifting and / or lowering of a rotor blade, for example for servicing, mounting, and / or removing one of the blades of the wind turbine. The actuator may later be detached and optionally removed from the wind turbine, for example for use on a different wind turbine at a later time. This allows the same actuator to be used on different wind turbines, thereby keeping the weight of the moving parts of the wind turbine low and saving resources. In this case, the step of mounting and / or removing the actuator may be considered an additional step in the described method.

[0015] Alternatively, the actuators can be permanently installed on the wind turbine, for example during construction of the wind turbine, and / or remain there after the current task has been performed. In general, the mounting and / or removal of the actuators can be performed outside the scope of the claimed methods.

[0016] As a preliminary step, the hub, rotor, or any other component carrying the blade bearings can be oriented to match a given orientation in which the rotor blades will be essentially vertical, or at least as nearly vertical as possible, while mounted in the bearings.

[0017] The term "given orientation" of a rotor blade may particularly refer to an orientation of the rotor blade in which lowering and / or maintenance of the rotor blade is performed, and may also be labeled a "maintenance orientation." In particular, the term "given orientation" may refer to an orientation of the rotor blade in which the axis of rotation of the rotor bearing is vertical or offset from the vertical by less than 20°, less than 10°, or less than 5°. Additionally or alternatively, the end face of the blade root may be essentially horizontal in the given orientation.

[0018] The lowering and / or lifting of the rotor blade, and therefore the movement direction of the actuator, may be essentially parallel to the axial direction of the blade bearing. The axial direction may coincide with the axis of rotation of the rotor blade as it rotates through the blade bearing. At a given orientation of the rotor blade, the axial direction of the blade bearing may be essentially vertical. Based on this axial direction, a local coordinate system may be defined that includes radial and circumferential directions relative to the blade bearing, and therefore the contact surface and end surface of the blade root.

[0019] Rotating the wind turbine rotor can shift and reorient the local coordinate system described above. In the global coordinate system, the vertical direction typically coincides with the main extension direction of the wind turbine tower. In the horizontal plane, the wind direction is particularly relevant, and a distinction can be made between upwind and downwind directions. During normal operation of a wind turbine, the hub, or generally the part of the rotor that carries the rotor blades, is oriented in the upwind direction. The upwind direction therefore corresponds to the forward direction, typically the direction facing outward from the nacelle and / or tower of the wind turbine. In other words, it is assumed that the rotor blades are positioned in the upwind direction from the tower, and that the tower position is in the downwind direction from the rotor blades.

[0020] When an orientation is given as essentially parallel or essentially orthogonal or essentially vertical or essentially horizontal, typically a tolerance of up to 20° or up to 10° is considered to satisfy these requirements if no other threshold is given.

[0021] Each actuator may be a hydraulic actuator. A first part of each actuator may be or include a hydraulic cylinder, and a second part may be or include a piston. Hydraulic actuators can provide large forces even when using fairly small hydraulic cylinders, allowing for precise positioning. Actuation of the pistons may be provided by a hydraulic pump, which may be located particularly remote from each actuator, for example, in the nacelle of the wind turbine.

[0022] In a preferred embodiment of the method, no cranes and / or jack-up vessels are used during the lowering, lifting, and / or servicing of the rotor blades. In particular, the method of the present invention does not use additional means to compensate for the torque caused by the position of the rotor blade's center of gravity during the lowering, lifting, and / or servicing of the blades. This torque can therefore be compensated exclusively by the above-mentioned application of an opposing normal force by the actuator.

[0023] In a given orientation of the rotor blades, the first portion of each actuator in the first group can be positioned vertically below at least a portion of the second portion of the respective actuator. As already mentioned above, the first group is configured to provide an upward force. Various actuators, particularly hydraulic actuators, particularly hydraulic actuators that use only pressure in a single chamber to move a piston and / or have only a single hydraulic connection to a pump or some other means for pressurization, can exert a greater force when moving a second portion, e.g., a piston, outward from the first portion and thus upward in the described arrangement.

[0024] Additionally or alternatively, the first portion of each actuator in the first group can have a first portion end surface that faces vertically downward in a given orientation of the rotor blade and is supported by a support plate that is supported by the blade bearing. As mentioned above, the actuators in the first group should primarily exert upward forces, and therefore support from below is advantageous.

[0025] In a given orientation of the rotor blades, the first portion of each actuator in the second group may, on the one hand, be arranged vertically above at least a portion of the second portion of the respective actuator, and / or may, on the other hand, have a first portion end face facing vertically upward and supported by a support plate, which may be mounted on a bearing.

[0026] Since the second group is configured to provide primarily downward forces, the arrangement of the parts of the respective actuators and / or the location of the support plates should advantageously be reversed compared to the first group.

[0027] Each second component of each actuator may be coupled to the rotor blade via at least one actuation bolt extending through a respective hole in the blade bearing, the actuation bolt being movable relative to the hole in a direction of movement of the respective actuator.

[0028] Each actuator of the first group may preferably comprise two actuating bolts, the first part of the actuator may be arranged between the two actuating bolts in the circumferential direction of the blade bearing, and the crossbar connecting the actuating bolts may form a stop for the second component, thus enabling the second component to press the actuating bolts upwards and thus exert an upward force on the blade root.

[0029] In each actuator of the second group, a second portion, for example a piston, can push a single actuation bolt downwards in a given orientation of the rotor blade.

[0030] Each actuation bolt may have a threaded end for attachment to a threaded hole in the end face of the blade root.

[0031] The rotor blades may be coupled to the blade bearings during normal operation of the wind turbine by a plurality of retention bolts, each retention bolt extending through a respective hole in the blade bearing. The step of providing the plurality of actuators may include: removing a sub-group of retaining bolts from their respective holes; passing each actuation bolt through at least some of the holes in the subgroup and connecting each actuation bolt to the rotor blade; It can further include:

[0032] In other words, some of the holes used for the blade root bolt connection to the bearing can be used to guide the actuation bolt. The retaining bolts can be shorter than the actuation bolts, for example, extending only a few centimeters from the holes to allow for the installation of nuts. By tightening the nuts, the end surfaces of the rotor blades are held firmly against the contact surfaces of the bearings. The actuation bolts must be long enough to extend through the holes after the blades are fully lowered.

[0033] The actuation bolts may occupy only a portion of the holes used for the retaining bolts. Most of the retaining bolts may remain installed until the actuator is operational and able to hold the rotor blades in place. The remaining retaining bolts may then be removed, allowing the blades to be lowered.

[0034] Some of the retaining bolts that are not replaced by the actuating bolts can be removed at an earlier step, for example, before the actuator is installed. For example, if the blade is nearly vertical or generally in a given orientation, some of the retaining bolts may be impossible to remove, or at least difficult to remove. These bolts can be removed before the blade is moved to the given orientation.

[0035] For example, some additional retaining bolts may be removed to make room for additional components to hold the first portion of each actuator in place, which removal may preferably be performed once a given orientation of the rotor blades is reached.

[0036] Reorienting the blades to a given orientation, for example, to approximately align the axial direction of the blade bearings with the vertical, can be achieved by rotating the rotor of the wind turbine. Optionally, the blades themselves can be rotated in their blade bearings to reach the given orientation. Actuators for rotating the rotor and / or blades in wind turbines are present in most wind turbines and are well known in the art.

[0037] After the blade has been lifted back into position, for example after servicing the blade, the steps described can be performed in reverse order to remove the actuator and reinstall the retaining bolt.

[0038] The step of providing the actuators may include the additional substep of inserting and securing respective expansion anchors into at least some of the holes in the subgroup not used for the actuation bolts, and a first portion of each of the actuators in the second group is coupled to the rotor bearing via at least one of the expansion anchors.

[0039] Since the actuators of the second group of actuators are configured to exert / apply a downward force on the blade root, it is necessary to prevent the first part of the actuators of the second group from moving upwards. An efficient way to achieve this is to fix each actuator to the bearing via an expansion anchor.

[0040] The expansion anchors can be formed, for example, by using bolts with expansion wedges fed through expansion sleeves. When the expansion wedges are pulled into the expansion sleeves, for example by tightening nuts on the sides of the bolts that extend beyond their respective holes, the sleeves expand and frictionally lock the expansion anchors inside the holes. While the rotor blades are still attached by at least some of the retaining bolts, it can be advantageous to check the sufficient frictional force of the expansion anchors by controlling the respective actuators to apply a force that matches or exceeds the maximum force required during the lowering and / or lifting of the blades.

[0041] Respective sensors can be used to measure the relative positions of at least two of the actuators, particularly the first and second portions of at least one of each of the first and second groups, and the actuators can be controlled based on the measured relative positions. For example, wind speed and / or other external factors and / or variations in tolerances and / or actuator control can cause forces on the actuators to cause offsets in the relative movement between individual actuators or subgroups and / or groups of actuators. This can cause additional friction due to stresses in components, particularly actuation bolts, and / or tilting of the actuation bolts in their holes. This can be avoided by controlling the actual movement. Position sensors for essentially linear movement are well known. For example, ultrasonic distance sensors or magnetic movement sensors can be used. Preferably, a respective sensor is used for each individual actuator or for each commonly controlled subgroup of actuators.

[0042] Additionally, the present invention relates to a system for lowering and / or lifting rotor blades of a wind turbine and for varying the distance between the blade root end face of the rotor blade and the contact surface of the blade bearing of the rotor blade, in particular for the purpose of servicing the rotor blades, comprising: a plurality of actuators, in particular at least four actuators, each having a first part, in particular a hydraulic cylinder, and a second part, in particular a piston, the second part being movable relative to the first part in a respective actuator movement direction by controlling the actuator; a control unit configured to control the actuators to lower and / or raise the rotor blades while the rotor blades are in a given orientation, whereby a first group of actuators each exert a vertical upward force on a first circumferential section of the blade root and a second group of actuators each exert a vertical downward force on a second circumferential section of the blade root; Equipped with When the system is installed on the wind turbine, each first portion of each actuator is coupled to a blade bearing and / or hub, and each second portion is coupled to a rotor blade, so that all actuator movement directions deviate from vertical by less than 20°, or less than 10°, or less than 5° when the rotor blade is in a given orientation. Regarding the system.

[0043] The system may be configured to perform an embodiment of the inventive method described above when the system is installed inside a wind turbine. Additionally or alternatively, any of the features described above with respect to the inventive method may also be used in the inventive system with the above-mentioned advantages, and vice versa.

[0044] Additionally, a wind turbine is disclosed that comprises a plurality of actuators configured to perform the method of the invention, in particular for the purpose of servicing rotor blades, for lowering and / or raising rotor blades of the wind turbine and for varying the distance between the blade root end faces of the rotor blades and the contact surfaces of the blade bearings of the rotor blades. Further advantageous features of such a wind turbine that have already been described with respect to the method can be transferred to the disclosed wind turbine with given advantages and vice versa.

[0045] The present invention also relates to a wind turbine comprising at least one rotor blade having a blade root and a blade root end face, and a rotor bearing having a contact surface in contact with the end face during normal operation of the wind turbine, wherein the system according to the present invention as described above is part of the wind turbine and wherein a respective first part of each actuator is installed such that it is coupled to the blade bearing and / or the hub and a respective second part is coupled to the rotor blade, such that the direction of all actuator movement deviates from the vertical by less than 20°, or less than 10°, or less than 5° when the rotor blade is in a given orientation.

[0046] The wind turbine may be configured to carry out an embodiment of the inventive method as described above. Additionally or alternatively, any of the features described above with respect to the inventive method and / or system may be used in the inventive wind turbine with the advantages described above, and vice versa.

[0047] The present invention also provides a method for servicing a rotor blade of a wind turbine, comprising the steps of: lowering a rotor blade to expose a blade root end face of the rotor blade that contacts a contact surface of a blade bearing of the wind turbine during normal operation of the wind turbine, the blade being lowered using at least one actuator, the actuator having a first portion coupled to the blade bearing of the rotor blade and a second portion coupled to the rotor blade; priming the blade root end face while the rotor blade is coupled to the blade bearing via the actuator; using an actuator to lift the rotor blade so that the blade root end face contacts the contact surface; The present invention relates to a method, comprising:

[0048] Typically, rotor blades are rigidly attached to blade bearings, e.g., the inner or outer ring of the blade bearing, during normal operation of the wind turbine. Each other ring can be connected, for example, to the hub or to the rotor of the wind turbine in general. It may therefore be necessary to further loosen the connection of the blade to the bearing, for example, by removing the retaining bolts used for this connection. At least some of the retaining bolts or other connection means should typically remain until the actuator is operational. The connection is preferably restored after lifting of the rotor blade, for example, by reinstalling the retaining bolts.

[0049] The actuators can be permanently installed on the wind turbine, but preferably they are only installed when maintenance or generally lowering of the rotor blades is required. Possible approaches for installing the actuators have already been mentioned above.

[0050] Blade root end face preparation may include cleaning and / or milling and / or coating the end face.

[0051] In particular, cleaning can be performed to remove grease or other lubricants. For example, the lubricant used to lubricate the blade bearings can get into the bearings, more specifically between the outer support plate of the bearing and the blade root, because small gaps between these components can occur during operation. This can cause increased wear and tear on the section of the end face of the blade root that is covered by grease. Therefore, cleaning can be advantageous.

[0052] If the blade root is already damaged, the damaged area can be removed by milling, which is advantageously compensated for by the use of shim plates, as explained below.

[0053] Applying the coating, especially after cleaning and / or milling the surface, and preferably before installing the optional shim plate, can avoid or at least reduce future damage. It has been found that epoxy resin or another two-component adhesive, such as Araldite® 2022, can significantly reduce future damage to the blade root. The coating can be applied manually, especially by a mechanic, for example, using a spatula.

[0054] The rotor blades can be coupled to the blade bearings during normal operation of the wind turbine by a plurality of retaining bolts, each of which extends into a hole in the blade root end face, as described above. At least some of the retaining bolts can be removed, particularly before lowering the rotor blades, to leave at least some of the holes in the blade root end face open. The milling can be performed using a milling device having at least one protrusion, each of which can be inserted into a respective one of the open holes before milling to define the position of the milling device and thus the area of ​​the blade root end face where milling is performed.

[0055] As explained below, the precise definition of the milling area can be very relevant, especially when using shim plates to compensate for the milling. By using a single protrusion and aperture, the position of the milling device is well defined, but the orientation of the milling device remains flexible. The orientation can be defined, for example, by a guide means for the milling device that contacts the sidewall of the rotor blade. However, if a milling area with rotational symmetry about an arbitrary angle is used, such as when milling is performed using a rotating disk, a fixed orientation is not strictly required. Alternatively, two or more protrusions can be inserted into each aperture to robustly define the position and orientation of the milling device.

[0056] Damage to the blade root end face is typically due to lubricant entering the gap between the bearing and the end face, as described above. When the blade root is attached to the bearing using retaining bolts, lubricant typically cannot enter the area directly surrounding the retaining bolts, and therefore the area of ​​the end face near the respective holes, because this area is firmly pressed against the contact surface of the bearing by the respective retaining bolts. Therefore, it can be assumed that the area surrounding each hole will not be damaged, and this area can be used as a reference for the milling operation.

[0057] Therefore, it may be sufficient to mill the area to be milled up to a plane parallel to the area surrounding the hole and offset from this area by a given milling depth. This can be achieved, for example, by using the area surrounding the hole as a stop that contacts a reference surface of the milling device when a sufficient milling depth is reached. The reference surface can be, for example, a section of the disk used as a milling head positioned near the center of the disk. Preferably, an additional component, such as a guide bushing described below, can be mounted on the area surrounding the hole to further improve milling accuracy and / or act as a stop to protect the rotor blades.

[0058] Additionally or alternatively, sensors in the milling device may capture the relative position and / or orientation of the milling head with respect to at least one reference point located in the area surrounding the hole, particularly on the end face, in order to control the milling.

[0059] Each removed retaining bolt can in particular extend through a respective hole in the blade bearing, for example through the inner or outer ring of the blade bearing before being removed. The retaining bolts described can in particular be the same retaining bolts as described above. The holes in the end faces of the blade roots can be blind and / or threaded. As an alternative to threaded holes, a respective blade bushing with a screw thread can be installed further down the blade root.

[0060] A guide bushing can be inserted into each of the openings in the end face of the blade root. The guide bushing can include a hollow cylinder inserted into the opening and a flat, particularly ring-shaped, area extending radially outward from one end of the cylinder. The flat area of ​​the guide bushing can rest on an area of ​​the end face surrounding the opening. Respective protrusions of the milling device can be inserted into the hollow cylinder, and the protrusions can be inserted into each of the openings.

[0061] The use of bushings can be particularly advantageous when rotary protrusions, such as those of rotary disks used as milling heads, are used to protect the inner walls of the respective holes, especially if the holes are threaded. Additionally or alternatively, the bushings can provide a more precise stop and / or reference point for the milling operation.

[0062] The preparation of the blade root end face may include the attachment of at least one shim plate to the blade root end face, in particular in an area of ​​the end face from which end face material has been removed by milling in a substep prior to the step of preparing the blade root end face to replace the removed material.

[0063] The shim plate is preferably mechanically attached, for example, by at least one screw. Alternatively, the shim plate can be glued, for example, to the end face.

[0064] If the coating is applied as part of servicing the rotor blade, the shim plate is preferably installed after the substep of coating the end face. Preferably, the coating is dry, e.g., fully polymerized, before installation of the shim plate.

[0065] The shim plate preferably matches the shape of the end face, particularly the radius and width. The circumferential extension of the end face is preferably selected to match the milling area milled by the milling tool used. The thickness of the shim plate can be selected to match the milling depth. If different milling depths can be used, shim plates with multiple thicknesses can be provided and / or a stack of multiple shim plates can be installed to match the milling depth.

[0066] The method for servicing the rotor blade may include the additional step of installing a work platform inside the rotor blade before lowering the rotor blade, and / or the additional step of removing the work platform after lifting the rotor blade.

[0067] Rotor blades must be lightweight during wind turbine operation and therefore typically do not have adequate internal work platforms for maintenance personnel. Before the blade is lowered, the interior of the blade can be relatively easily accessed, for example, through holes in the blade bearing support plates, while the blade is essentially horizontal, e.g., at an angle of less than 30° or less than 15° relative to the horizontal. The installed work platform can also provide good access to the blade root end face even after the blade is lowered, particularly while the blade is in the given orientation described above and / or essentially vertical, e.g., at an angle of less than 30° or less than 15° relative to the vertical.

[0068] The working platform may be essentially parallel, for example, at an angle of less than 30° or less than 15° to the plane of rotation of the blade bearing and / or to the end surface of the blade root after installation and / or after the blade has been lowered.

[0069] The installed work platform may be inflatable or may include an inflatable component. The work platform may be moved to the blade during the step of installing the work platform and / or may be removed from the rotor blade during the step of removing the work platform with the work platform or inflatable component in a deflated state. The work platform or inflatable component may be inflated during the step of installing the work platform and / or deflated during the step of removing the work platform.

[0070] The use of inflatable work platforms or components allows for fitting of a largely assembled work platform through typical service openings in the bearing support plate, thus allowing for relatively quick installation and removal of the platform.

[0071] The expanded work platform may also have a certain amount of deformability so that it can be slightly deformed when pushed into position by a maintenance crew, for example. The work platform may be expanded while lying essentially flat on an essentially horizontal rotor blade, then tilted upward, and after expansion, pushed by a maintenance crew toward the tip of the rotor blade to conform to its final position.

[0072] For example, it may be sufficient to secure the work platform with a strap connected to the bearing, since the work platform can essentially be held in the desired position by friction caused by deformation of the expanded platform, and the strap only needs to support or partially support the weight of the maintenance personnel when the blade is essentially vertical.

[0073] A method for servicing a rotor blade includes: the additional step of disposing at least one spacer between the blade root end face and the blade bearing contact surface after lowering the blade and before servicing the blade root end face; The additional step of removing at least one spacer before lifting the rotor blade after end-face servicing is required. may include:

[0074] The use of spacers can stabilize the position of the blade relative to the bearing during maintenance and reduce the load on the actuation bolt, particularly as mentioned above. Each spacer can cover a small portion of the circumference of the blade root end face, e.g., less than 10%, and can have a fixed height corresponding to the desired distance between the end face and the contact surface during maintenance. Alternatively, a stack of thinner spacers can be used. Preferably, multiple spacers or stacks of spacers are distributed around the circumference of the end face.

[0075] One or more spacers may be clamped between the end face and the contact surface, for example, by first lowering the blade to create a wider gap than the spacer or stack of spacers being used, secondly inserting the spacer, and thirdly lifting the rotor blade slightly to clamp the spacer or stack of spacers.

[0076] To allow a robust positioning of the spacer, at least a portion of the spacer may have at least one recess, in particular two or more recesses, each for receiving a respective one of the above-mentioned actuation bolts.

[0077] The lowering and / or lifting of the rotor blades may be performed using the inventive method for lowering and / or lifting rotor blades of a wind turbine disclosed above.

[0078] The present invention also relates to a method for operating a wind turbine, in particular an offshore wind turbine, more in particular a floating offshore wind turbine, and / or for supplying electrical energy to a power grid, comprising the steps of: performing the steps of an embodiment or a combination of the method embodiments disclosed above for lowering and / or lifting rotor blades of a wind turbine and / or for servicing rotor blades of a wind turbine; generating power and / or electrical energy by a wind turbine; transmitting at least a portion of the power and / or electrical energy to a receiving facility, in particular the receiving facility is not located in international waters, is located on land, and / or is located within a 12-mile zone of each sovereign nation-state over which the respective country has jurisdiction; supplying at least a portion of the power and / or electrical energy to an electric utility grid, in particular a land-based electric utility grid; The present invention relates to a method, comprising:

[0079] It is to be understood that the features described above, such as the use of an actuating bolt and the use of a milling device, as well as those not yet described below, can be used not only in the respective combinations shown, but also in other combinations or alone without departing from the scope of the present invention. In particular, features of different aspects, embodiments and / or methods of the present invention can be combined with each other unless stated to the contrary.

[0080] The foregoing and other features and advantages of the present invention will become more apparent from the following detailed description read in conjunction with the accompanying drawings, in which like reference numerals refer to like elements and in which: [Brief explanation of the drawings]

[0081] [Figure 1] 1 is a schematic detailed view of a wind turbine illustrating an intermediate state in an embodiment of the inventive method for servicing rotor blades of a wind turbine after an embodiment of the inventive method for lowering and / or lifting rotor blades has been used to lower the rotor blades; [Figure 2] FIG. 2 is a schematic top view of one of the blade bearings shown in FIG. 1 showing the distribution of actuators used to raise and / or lower the rotor blades. [Figure 3] FIG. 1 discloses a flow chart of an embodiment of the inventive method for lowering rotor blades of a wind turbine. [Figure 4] 4 is a schematic diagram of an exemplary embodiment of an actuator for applying a vertical upward force, method according to FIG. 3. [Figure 5] 4 is a schematic diagram of an exemplary embodiment of an actuator for applying a vertical downward force in the method according to FIG. 3. [Figure 6] 1 discloses a flow chart of an embodiment of the inventive method for servicing rotor blades of a wind turbine. [Figure 7] 7 discloses a spacer that can be used in the method according to FIG. 6. [Figure 8]7 is a schematic diagram of milling the end face in the method according to FIG. 6; [Figure 9] 7 discloses the arrangement obtained after milling and application of shim plates in the method according to FIG. 6.

[0082] MODE FOR CARRYING OUT THE INVENTION 1 is a schematic detailed view of a wind turbine 1, i.e., a rotor 2, specifically a section of the hub in the given example. Two rotor blades 3, 4 are shown attached to either side of the rotor 2 to facilitate representation in a two-dimensional image. Obviously, the described method can be used for wind turbines with a greater or lesser number of rotor blades, in particular the common arrangement using three rotor blades spaced 120° apart around the axis of rotation 5 of the rotor 2. The rotor blades 3 are shown in a given orientation 42, with the axis of rotation 92 of the blade bearings 9 essentially coinciding vertically and the rotor blades 3 pointing downwards.

[0083] In Figure 1, the rotor blade 3 has been lowered using a method described below with particular reference to Figure 3 to increase the distance 6 between the end face 7 of the blade root 8 of the rotor blade 3 and the contact surface 64 of the blade bearing 9 of the rotor blade 3. During normal operation of the wind turbine, the end face 7 is tightly drawn against the contact surface 64 by the retaining bolts 11, as shown for the other rotor blade 4 and associated blade bearings 10 in Figure 1.

[0084] In this example, the blade bearings are formed by an outer ring 18 mounted on the rotor 2, an inner ring 17 mounted on the blade root 8 of each rotor blade 3, 4, and inner and outer support plates 19, 20. For servicing the rotor blades 3, and for other purposes, such as completely removing the rotor blades 3, it is advantageous to first lower the rotor blades 3 as shown in Figure 1.

[0085] In this example, lowering the rotor blade 3 allows a maintenance crew 24 to service the end face 7 without having to completely remove the rotor blade 3 from the wind turbine 1, which would require a crane or jack-up vessel. In this example, an inflatable work platform 25 is provided to support the maintenance crew 24. Servicing of wind turbines is described in more detail below with reference to Figures 6-9.

[0086] In the description, two separate coordinate systems are used: a global coordinate system can be defined by an upwind direction 12 pointing forward of the rotor 2 and away from the tower (not shown) and nacelle (not shown) of the wind turbine 1, an opposite downwind direction 13 pointing towards the tower and nacelle of the wind turbine 1, a crosswind direction 16, and an upward vertical direction 14 and a downward vertical direction 15. The upwind direction 12, the downwind direction, and the crosswind direction 16 are in a horizontal plane.

[0087] The local coordinate systems for the blade root 8 and its end face 7, and the inner ring 17 of the blade bearing 9 are also shown in FIG. 1, indicating the circumferential 21, radial 22, and axial 23 directions of the blade bearing 9.

[0088] A number of actuators 27-34 are used to lower the rotor blades 3 to the position shown in Figure 1. An exemplary distribution of these actuators 27-34 around the circumference of the blade bearing 9 is shown in Figure 2, which shows a schematic top view of the blade bearing 9 and therefore the inner support plate 19. For clarity, only simplified representations of two of the actuators 28, 33 are shown in Figure 1, and only the outlines of the actuators 27-34 are shown in Figure 2. Possible implementations of the actuators are described below with reference to Figures 4 and 5.

[0089] In the example shown in FIG. 1 , rotor blades 3, 4 are angled in the upwind direction 12 to increase the distance of their blade tips from the tower, making it difficult to lower rotor blade 3. Therefore, the center of gravity of each rotor blade 3, 4 is shifted forward, and thus to the left in FIG. 1 , relative to the center of its respective blade bearing, resulting in a torque 26 on rotor blade 3. This torque 26 is absorbed by contact surfaces 64 of blade bearings 9 during normal operation of wind turbine 1. When rotor blade 3 lowers, contact surfaces 64 can no longer absorb torque 26, and this torque results in bending forces on actuation bolts 37, 38 of actuators 27-34, potentially damaging these actuation bolts 37, 38 and further components of wind turbine 1.

[0090] To avoid this problem, a control unit 39 for the actuators 27-34, which is only shown schematically in FIG. 1 and which may be mounted, for example, on the outside of the rotor 2, controls the actuators 27-34 so that a first group 35 including the actuators 27-30 (FIG. 2) exerts a force in the upward vertical direction 14 on a first circumferential section 40 of the blade root 8, while a second group 36 including the actuators 31-34 (FIG. 2) exerts a vertically downward force on a second circumferential section 41 of the blade root 8. These opposing forces applied to different circumferential sections 40, 41 of the blade root 8 result in a torque on the blade root 8 directed in the opposite direction of torque 26, and thus, if the applied forces are appropriately selected, can partially or even completely compensate for torque 26. Therefore, bending forces on the actuation bolts 37, 38 can be avoided or at least significantly reduced.

[0091] Note that the circumferential sections 40, 41 are shown in Figure 2, and the blade roots 8 themselves are not visible as they are hidden behind the blade bearings 9. This representation was chosen to more clearly show the relationship between the affected circumferential sections 40, 41 and the groups 35, 36 of actuators 27-34.

[0092] The described control can be implemented during the lifting and lowering of the rotor blades 3, but also while the rotor blades 3 are held in place in the lowered position, without spacers installed to compensate for at least the torque 26. An example of a suitable spacer is given below with reference to FIG.

[0093] A possible approach for lowering the rotor blades 3 to reach the position shown in FIG. 1 will now be explained in more detail with further reference to the flow chart given in FIG.

[0094] In step S1, the rotor blades are oriented in a given orientation 42 by rotating the rotor 2 relative to the nacelle and / or tower (not shown) and / or by rotating the inner ring 17 of the rotor bearing 9 relative to the outer ring 18. In the given orientation 42, the rotor blades 3 are essentially oriented toward the downward vertical direction 15. Prior to this rotation, additional optional steps can be performed, particularly steps that are impossible or difficult to perform in the given orientation 42. One example is the removal of some retaining bolts 11, which may be inaccessible in the given orientation of the rotor blades. Another example is the installation of a work platform 25, which will be described in more detail later.

[0095] In step S2, a subgroup of retaining bolts 11 extending through each of the holes 43-46 of the blade bearing 9 marked in Figure 3, and therefore retaining bolts 11 in the area are actuators 27-34, are installed and removed from their respective holes 43-46, for example by unscrewing them from their respective threaded holes 47 in the end face 7 of the blade root 8 shown in Figure 1. Note that the same reference numerals are used for all holes 42-46 that perform the same function.

[0096] In step S3, the actuation bolts 37 of the actuators 27-30 of the first group 35 are inserted through the holes 43 and connected to the rotor blades 3, for example by threading them into respective threaded holes 47. In this example, two separate actuation bolts are used for each of the actuators 27-30. This is explained in more detail with further reference to Figure 4, which is a schematic diagram of an exemplary embodiment of an actuator 28 for applying a vertical upward force.

[0097] In step S4, the further components of the actuators 27-30 shown in Figure 4 are installed.

[0098] 4 has a first portion 48, formed in the example as a hydraulic cylinder, and a second portion 49, formed in the example as a piston. The second portion 49 is movable in an actuator movement direction 50 that essentially coincides with the upper vertical direction 14 when the rotor blade 3 is in a given position 42.

[0099] The first part 48 is connected to the blade bearing 9 in the region of the inner ring 17 via a support plate 51 that supports the lower end surface of the first part 48. Additionally or alternatively, the first part 48 is connected to the hub of the rotor 2. The second part 49 is connected to the rotor blade 3, i.e., to a crossbar 53 that is rigidly connected to the actuation bolt 37, which passes through the hole 43 in the blade bearing 9 and is rigidly connected to the blade root 8, as described above and shown in FIG. 1 . The hole 46 may remain open.

[0100] As already explained in the general part of the description, the design of the actuator 28 is particularly suited to applying an upward force when the rotor blade 3 is in a given position 42. A sensor 54 can be used to monitor the actual movement of the actuator 53.

[0101] In step S5, the actuation bolts 38 of the actuators 31-34 of the second group 36 are inserted through the holes 44 and connected to the rotor blades 3, for example by screwing them into the respective threaded holes 47.

[0102] In step S6, further components of the actuators 31-34 are installed.

[0103] Figure 5 is a schematic diagram of an exemplary embodiment of actuator 33 for applying a vertical downward force. Because the force is applied in the opposite direction, the vertical orientation of first and second portions 49 and 50 is switched compared to Figure 4. First portion 48 is held between two support plates 58, 91 in this example, one of which is positioned above the top surface 56 of first portion 48 to support the first portion when a downward force is applied by actuator 33.

[0104] The support plate is attached to two extension bolts 57 which are held in place by respective expansion anchors 58. Each expansion anchor is formed by a bolt 59 having an expansion wedge 60 fed through an expansion sleeve 62. When the nut 61 is tightened, the expansion wedge 60 is pulled upward in FIG. 5, thereby pushing the expansion sleeve 62 apart and holding the expansion anchors 58 in place in their respective holes 45 by frictional forces.

[0105] As already explained in the general part of the description, the design of the actuator 33 is particularly suited to applying a downward force when the rotor blade 3 is in a given position 42. A sensor 54 can be used to monitor the actual movement of the actuator 53.

[0106] In step S7, the actuators are connected to the control unit 39 by connecting the hydraulic lines to the respective connectors 63.

[0107] In step S8, the actuators 27-34 are controlled to pull the end faces 7 of the blade roots 8 against the contact surfaces 64 of the blade bearings 9 and the remaining retaining bolts 11a that were removed. Thus, the rotor blades are held in place by the actuators 27-34.

[0108] In step S9, the actuators 27-34 are controlled to lower the rotor blade 3 to the position shown in Figure 1. In this example, this can be achieved by pushing fluid into the hydraulic cylinders of the actuators 31-34 and releasing fluid from the hydraulic cylinders 27-30. The pressure in each hydraulic cylinder corresponds to the pushing or pulling force exerted by the respective actuator 27-31. As already mentioned above, the two groups 35, 36 of actuators 27-34 exert forces in opposite directions to compensate for the torque 26 during the lowering of the rotor blade 3.

[0109] To reduce control complexity and the number of hydraulic pumps required, multiple actuators 27-32 in a given group may be attached to a common hydraulic pump, particularly by parallel connection. In this example, separate hydraulic connections and pumps (not shown) are used for four pairs of actuators: pair 27 and 28, pair 29 and 30, pair 31 and 32, and pair 33 and 34. Preferably, one of the actuators 27-34 in each pair of commonly controlled actuators 27-31 may have a sensor 54 to monitor the actual movement of that actuator 27-34 and use this data, for example, for a control feedback loop.

[0110] Lifting of the rotor blade 3, or generally any further modification of the distance 6 between the end face 7 of the blade root 8 and the contact surface 64 of the blade bearing 9, can then be performed by adding or removing fluid from the hydraulic cylinder, as described with reference to step S9.

[0111] Once the rotor blade 3 has been returned to its original position, steps S8-S2 may be performed essentially in reverse order to remove the actuators 27-34 and reinstall the retaining bolt 11.

[0112] It should be noted that the installation of the actuators 27-34 in steps S2-S8 is only necessary if the actuators are not present during normal operation of the wind turbine.

[0113] FIG. 6 discloses a flowchart of a method for servicing rotor blades 3 of a wind turbine 1. Generally, the method includes, in step S14, lowering the rotor blades 3 to expose end faces 7 of the blade roots 8; servicing the end faces 7 of the blade roots 8 while the rotor blades 3 are coupled to the blade bearings 9 via actuators 27-34 in steps S17-S20; and, in step S21, using the actuators 27-34 to lift the rotor blades and move the end faces 7 of the blade roots 8 into contact with the contact surfaces 64. While the use of all but one of the additional steps and servicing steps is optional, the inclusion of at least some of these steps or optional steps provides particularly advantageous embodiments. In this example, the use of multiple actuators 27-34 is assumed and advantageous, but alternative embodiments may use different approaches to lowering the rotor blades 3 to expose the end faces 7 and raising the rotor blades 3.

[0114] In the specific embodiment shown in FIG. 6 , the method starts with the wind turbine 1 in normal operating conditions, with no actuators 27-34 or maintenance platform 25 installed, and the rotor blades 3 attached to the blade bearings 9 via a number of retaining bolts 11.

[0115] In step S10, the rotor 2 of the wind turbine 1 is rotated to achieve a substantially horizontal orientation of the rotor blades 3. Specifically, the blade bearings 9 and / or at least the rotation axes 92 of the blade roots 8 may be oriented essentially parallel to the crosswind direction 16. In this orientation, a maintenance crew 24 can access the interior of the rotor blades through the blade bearings 9, and more specifically, through the maintenance openings 65 in the support plates 19, 20 shown in FIG. 2, and perform work therein without the need for complex support structures.

[0116] In step S11, the work platform 25 is moved into the interior space 66 of the rotor blade 3 while the work platform is retracted. Thus, the interior volume 67 shown in FIG. 1 is collapsed and the work platform is fairly compact and easily fits through a typical maintenance opening 65.

[0117] In step S12, the work platform is expanded and placed in the position shown in FIG. 1, for example, by pushing it toward the tip of the rotor blade 3. In this step, the rotor blade 3 is still oriented approximately horizontally, so the work platform forms a vertical wall. The work platform can be held in place by frictional forces. Preferably, the work platform is further secured to the blade bearing 9 by straps (not shown) or other means.

[0118] Once the maintenance personnel 24 leaves the interior space 66 and the area of ​​the rotor 2, the rotor can be rotated in step S13 to change the orientation of the rotor blades 3 to a given orientation 24, with the rotor blades 3 essentially extending vertically downward.

[0119] The rotor blade 3 can be lowered further to expose the end face 7 of the blade root 8. The lowering of the rotor blade 3 in step S14 can be achieved by performing steps S2 to S9 of the method described above with reference to FIG. 3. However, in alternative embodiments, a different method for lowering the blade by using at least one actuator can be used. For example, if the torque 26 is expected to be sufficiently small and / or if sufficiently robust actuation bolts 37, 38 are used, it is possible to use only the actuator exerting an upward force.

[0120] In step S15, a spacer is inserted between the end face 7 of the blade root 8 and the contact surface 64 of the blade bearing 9. To place the spacer, the mechanic 24 can re-enter the interior space 66 of the rotor blade 3, preferably while standing on the work platform 25.

[0121] An example of such a placement of a spacer 68 is shown in FIG. 7. To enable robust positioning of the spacer 68, the spacer 68 has a W-shape with two recesses 70, each of which receives one of the actuation bolts 37 described above. This shape allows the spacer to be inserted by moving it in the radial direction 22. The thickness of the spacer perpendicular to the image plane is selected to be equal to the distance 6 between the end face 7 and the contact surface 64 used during a later servicing step. To enable easy insertion of the spacer, the initial distance 6 after step S14 can be selected to be slightly greater than the thickness of the spacer. Instead of a single thick spacer, a stack of thinner spacers can be used.

[0122] As can be seen in Figure 7, a large portion of the end face 7 surrounding the plurality of apertures 69 remains accessible even after the installation of the spacer 68. Thus, it is typically possible to locate the spacer 68 to allow servicing of all relevant, e.g., damaged, areas of the end face 7 without changing the spacer position. However, if necessary, the spacer may be moved to reach all relevant areas and / or temporarily unused.

[0123] In step S16, the actuators 27-34 are controlled to slightly raise the rotor blade 3, thus clamping the spacer 68 between the end face 7 and the contact surface 64. Preferably, a low clamping force is used, as this clamping only serves to suppress accidental movement of the spacer 68 by wind or maintenance personnel 24.

[0124] In step S17, the end face 7 is cleaned by the mechanic 24, in particular to remove any grease or lubricant.

[0125] In step S18, milling of an area 71 of the end face 7 is performed to remove damaged material from the blade root 8, as shown schematically in Figure 8. The areas 72 immediately adjacent to the apertures 69 are assumed to be undamaged because the apertures 69 are used to attach the retaining bolts 11 during normal operation of the wind turbine 11 and therefore the areas 72 adjacent to these apertures 69 press firmly against the contact surfaces 64 of the blade bearings 9 and therefore cannot be covered by the lubricant of the blade bearings 9 during operation of the wind turbine 1. Therefore, the apertures 69 and the surrounding areas 71 can be used as a reference during milling.

[0126] In this example, milling is performed by using a milling device 73 having protrusions 74 which are inserted into each of the apertures 69 before milling in order to define the position of the milling device 73 and thus the area 71 of the end face 7 of the blade root 8 in which milling is performed. In this example, the protrusions 74 are protrusions of a disk 75 which carries the milling means 71 and which is rotated by a motor 77. In this case, the area to be milled 71 has rotational symmetry, so that a change in the orientation of the milling device 73 relative to the axis of rotation 78 of the disk does not change the milling area and therefore the use of additional guiding means to fix this orientation is not necessary.

[0127] For simplicity, the motor 77 is shown above the disk 75 in the example of FIG. 8, but it should be noted that it may be advantageous to use a motor that is offset orthogonal to the image plane of FIG. 8 and can therefore be located outside the gap between the end face 7 and the contact surface 64. Appropriate gearing can then be used to transfer the torque of the motor 77 to the disk 75. This can reduce the distance 6 between the end face 7 and the contact surface 64 required to perform the milling operation.

[0128] To protect the inner surface 79 and area 72 of the hole 69 from damage caused by the rotating disk 75 and its protrusions, a guide bushing 80 is inserted into the open hole 69 before milling. The guide bushing 80 comprises a hollow cylinder 81 inserted into the open hole 69 and a flat, in particular a ring-shaped, area 82 extending radially outward from one end of the cylinder 81. The flat area 82 of the guide bushing 80 rests on the area 72 of the end face 7 surrounding the hole 69. The protrusions 74 of the milling device 73 are then inserted into the hollow cylinder 81, and the motor 77 is started to begin drilling the hole.

[0129] In this example, the milling device is manually moved by the mechanic 24 toward the end face 7. The milling depth 85 is defined by the distance between the stop 84 formed by the flat area 82 of the guide bushing 80 and the reference surface 83 of the milling device. This allows for accurate milling to a given depth 85, even when the milling device 73 is manually moved to perform the milling.

[0130] In alternative embodiments, various features of the milling device 73 can be modified. Instead of a single protrusion 74, two or more protrusions of the milling device can be inserted into different openings 69. In this case, the protrusions can be part of the body of the milling device, which carries the movable milling means, e.g., a rotating disk. In this case, the protrusions do not rotate, so there is no need to use guide bushings. Alternatively or additionally, the milling means can be moved by an actuator of the milling device in the direction of the blade root 5, and the movement can be controlled by a sensor. This allows for automatic control of the milling depth, in which case the use of mechanical stops is optional.

[0131] After milling has been performed in all relevant areas, in step S19, a coating may be applied to the end face 7 of the blade root 8. By applying the coating, future damage to the end face 7 may be avoided or at least reduced. The coating may be an epoxy resin or another two-component adhesive, such as Araldite® 2022. The coating may be applied manually by the mechanic 24, for example, by using a spatula.

[0132] After the coating has completely dried and is preferably no longer tacky, a shim plate 86 is attached to the end face 7 in the milled area 71, step S20, as shown in Figure 9. Figure 9 illustrates the use of a single shim plate 86, which has a hole 87 for a protrusion 88 that surrounds the open hole 69 created by the area 72 where no milling was performed. The thickness 90 of the shim plate 86 corresponds to the milling depth 85. The shim plate 86 is mechanically attached to the blade root 8 using screws 89.

[0133] After servicing of the end faces 7 of the blade roots 8 is completed, the rotor blades can be reinstalled in the blade bearings 9 with the retaining bolts 11 in step 21. This step can include lifting the rotor blades to their original positions after removing the spacers 68 and after the maintenance personnel 24 leaves the interior space 66, attaching the rotor blades 3 to the bearings 9 with the retaining bolts 11 installed in all of the open holes 69, removing the actuators 27-34, and installing the retaining bolts 11 in the remaining holes 43-46.

[0134] Then, in step S22, the work platform 25 can be removed. This can be accomplished, for example, by first rotating the rotor 2 until the rotor blades are in a substantially horizontal orientation so that the maintenance personnel 24 can work in the interior space 66 without the need for a work platform. The work platform can then be retracted and removed by the maintenance personnel 24 through the work opening 65.

[0135] The wind turbine 1 is again in a more operational state and can resume its operation. Compared to complete removal of the rotor blades 3 for servicing the end faces 7 on the ground, less downtime is required and no crane or jack-up vessel is required when the described techniques are used.

[0136] While particular embodiments are disclosed herein, various changes and modifications can be made without departing from the scope of the invention. The present embodiments are to be considered in all respects as illustrative and not restrictive, and all changes which come within the meaning and range of equivalency of the appended claims are intended to be embraced.

[0137] It should be noted that embodiments of the present invention are described with reference to different subject matters. In particular, some embodiments are described with reference to apparatus-type claims, and other embodiments are described with reference to method-type claims. However, those skilled in the art will understand from the above and following description that, unless otherwise notified, in addition to any combination of features belonging to one type of subject matter, any combination between features relating to different subject matters, in particular between features of an apparatus-type claim and features of a method-type claim, is also considered to be disclosed together with this application.

Claims

1. 1. A method for lowering and / or lifting a rotor blade (3) of a wind turbine (1) and changing the distance (6) between an end face (7) of a blade root (8) of said rotor blade (3) and a contact surface (64) of a blade bearing (8) of said rotor blade (3), in particular for the purpose of servicing said rotor blade (3), comprising: Providing a plurality of actuators (27-34), in particular at least four actuators (27-34), each actuator (27-34) has a first part (48), in particular a hydraulic cylinder, and a second part (49), in particular a piston, said second part (49) being movable relative to said first part (48) in a respective actuator movement direction (50, 55) by controlling said actuator (27-34); each said first portion (48) being coupled to said blade bearing (9) and / or hub and each said second portion (49) being coupled to said rotor blade (3), such that all actuator movement directions (50, 55) deviate by less than 20°, or less than 10°, or less than 5° from a vertical direction (14, 15) when said rotor blade is in a given orientation (42); controlling the actuators (27-34) to lower and / or raise the rotor blades (3) while the rotor blades (3) are in the given orientation (42), thereby a first group (35) of said actuators (27-34) each exerting a vertical upward force on a first circumferential section (40) of said blade root (8); causing a second group (36) of said actuators (27-34) to exert a vertical downward force on a second circumferential section (41) of said blade root (8); A method comprising:

2. At the given orientation (42) of the rotor blade (3), the first portion (48) of each actuator (27-30) in the first group (35) on the other hand, vertically positioned below at least a portion of the second portion (49) of each of the actuators (27-30); and / or and / or on the other hand, a first partial end face (52) facing vertically downwards and supported by a support plate (51) supported by said blade bearing (9); At the given orientation (42) of the rotor blade (3), the first portion (48) of each actuator (31-34) in the second group (36) on the other hand, vertically positioned above at least a portion of the second portion (49) of each of the actuators (31-34); and / or On the other hand, it has a first partial end face (56) facing vertically upwards and supported by a support plate (91) attached to said blade bearing (9), The method of claim 1.

3. the respective second components (49) of the respective actuators (27-34) are coupled to the rotor blades (3) via at least one actuation bolt (37, 38) extending through respective holes (43, 44) in the blade bearings (9); the actuation bolts (37, 38) are movable relative to the holes (43, 44) in the movement directions (50, 55) of the respective actuators (27-34); 3. The method according to claim 1 or 2.

4. the rotor blades (3) are coupled to the blade bearings (9) by a plurality of retaining bolts (11) during normal operation of the wind turbine (1), each retaining bolt (11) extending through a respective hole (43-46) in the blade bearing (9); The step of providing the plurality of actuators (27-34) includes: the sub-step of removing a sub-group of said retaining bolts (11) from their respective holes (43-46); passing each actuation bolt (37, 38) through at least some of the holes (43-46) of the subgroup to connect each actuation bolt (37, 38) to the rotor blade; The method of claim 3, comprising:

5. the step of providing the actuators (27-34) includes the additional substep of inserting and securing respective expansion anchors (58) into at least some of the holes (43-46) of the subgroup not used for the actuation bolts (37, 38); the first portions (48) of each of the actuators (30-34) of the second group (36) are coupled to the rotor bearing (9) via at least one of the expansion anchors (58); The method of claim 4.

6. 6. The method according to claim 1, wherein a respective sensor (54) is used to measure the relative position of the first and second parts (48, 49) of at least two of the actuators (27-34), in particular of at least one respective actuator (27-34) of the first and second groups (35, 36), and the actuators (27-34) are controlled based on the measured relative positions.

7. 1. A system for lowering and / or lifting a rotor blade (3) of a wind turbine (1) and for varying the distance (6) between an end face (7) of a blade root (8) of said rotor blade (3) and a contact surface (64) of a blade bearing (8) of said rotor blade (3), in particular for the purpose of servicing said rotor blade (3), comprising: a plurality of actuators (27-34), in particular at least four actuators (27-34), each having a first part (48), in particular a hydraulic cylinder, and a second part (49), in particular a piston, the second part (49) being movable in a respective actuator movement direction (50, 55) relative to the first part (48) by controlling the actuators (27-34); a control unit (39) configured to control the actuators (27-34) to lower and / or raise the rotor blades (3) while the rotor blades (3) are in a given orientation (42), whereby a first group (35) of said actuators (27-34) each exerting a vertical upward force on a first circumferential section (40) of said blade root (8); A second group (36) of the actuators (27-34) exerts a vertical downward force on a second circumferential section (41) of the blade root (8). A control unit (39) and Equipped with when the system is installed on the wind turbine, the respective first parts (48) of each actuator (27-34) are coupled to the blade bearings (9) and / or hubs, and the respective second parts (49) are coupled to the rotor blades (3), so that all actuator movement directions (50, 55) deviate from the vertical direction (14, 15) by less than 20°, or less than 10°, or less than 5° when the rotor blades are in a given orientation (42); system.

8. 1. A wind turbine comprising: at least one rotor blade (3) having a blade root (8) and an end face (7) of the blade root (8); and a rotor bearing (9) having a contact surface (64) in contact with the end face (7) during normal operation of the wind turbine (1), wherein the system according to claim 7 of the wind turbine (1) is installed such that the respective first parts (48) of each actuator (27-34) are coupled to the blade bearing (9) and / or the hub, and the respective second parts (49) are coupled to the rotor blade (3), such that all actuator movement directions (50, 55) deviate from the vertical direction (14, 15) by less than 20°, less than 10°, or less than 5° when the rotor blade (3) is in the given orientation (42).

9. 1. A method for servicing a rotor blade of a wind turbine, comprising: lowering the rotor blades (3) to expose the end faces (7) of the blade roots (8) of the rotor blades (3) which are in contact with the contact surfaces (64) of the blade bearings (9) of the wind turbine (1) during normal operation of the wind turbine (1), the blade (3) is lowered using at least one actuator (27-34), the actuator (27-34) having a first portion (48) coupled to the blade bearing (9) and / or hub of the rotor blade (3) and a second portion (49) coupled to the rotor blade (3); - servicing the end faces (7) of the blade roots (8) while the rotor blades (3) are coupled to the blade bearings (9) via the actuators (27-34), in particular the servicing of the end faces (7) of the blade roots (8) comprising cleaning and / or milling and / or coating the end faces (7); using the actuators (27-34) to lift the rotor blades (3) and bring the end faces (7) of the blade roots (8) into contact with the contact surfaces (64); Including, In particular, the lowering and / or the lifting of the rotor blades (3) is performed using a method for lowering and / or lifting rotor blades (3) of a wind turbine (1) according to any one of claims 1 to 6. method.

10. the rotor blades (3) are coupled to the blade bearings (9) by a plurality of retaining bolts (11) during the normal operation of the wind turbine (11), each retaining bolt (11) extending into a hole (69) in the end face (7) of the blade root (8); at least some of the retaining bolts (11) are removed, in particular before the lowering of the rotor blades (3), leaving open at least some of the holes (69) in the end faces (7) of the blade roots (8); the milling is performed using a milling device (73) having at least one protrusion (74), each of which is inserted into each of the aperture holes (69) before the milling and defines the position of the milling device (73) and thus the area (71) of the end face (7) of the blade root (8) where the milling is performed; 10. The method of claim 9.

11. a guide bushing (80) is inserted into each of the openings (69) in the end face (7) of the blade root (8), the guide bushing (80) comprising a hollow cylinder (81) inserted into the openings (69) and a flat, in particular ring-shaped, area (82) extending radially outward from one end of the cylinder (81) resting on the area (72) of the end face (7) surrounding the hole (69), The respective protrusions (74) of the milling device (73) are inserted into the hollow cylinder (81), and the protrusions (74) are inserted into the respective opening holes (69). The method of claim 10.

12. said servicing of said end face (7) of said blade root (8) comprising attaching at least one shim plate (86) to said end face (7) of said blade root (8); the shim plate (86) is attached in particular to the area (71) of the end face (7) from which material has been removed by milling in a substep preceding the step of preparing the end face (7) of the blade root (8) to replace the removed material; 12. The method according to any one of claims 9 to 11.

13. 13. The method according to any one of claims 9 to 12, wherein the method comprises the additional step of installing a working platform (25) inside the rotor blade (3) before lowering the rotor blade (3) and / or the additional step of removing the working platform (25) after the lifting of the rotor blade (3).

14. The installed work platform (25) is inflatable or comprises an inflatable component; the working platform (25) is moved to the rotor blade (3) during the step of installing the working platform (25) and / or detached from the rotor blade (3) during the step of detaching the working platform (25) in a deflated state of the working platform (25) or the inflatable component; The work platform (25) or the inflatable component is inflated during the step of installing the work platform (25) and / or is deflated during the step of removing the work platform (25). The method of claim 13.

15. The method comprises: an additional step of placing at least one spacer (68) between the end face (7) of the blade root (8) and the contact surface (64) of the blade bearing (9) after lowering the rotor blade (3) and before servicing the end face (7) of the blade root (8); the additional step of removing said at least one spacer (68) after said servicing of said end face (7) and before lifting said rotor blade (3); 15. The method of any one of claims 9 to 14, comprising:

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