DK201500087A1

DK201500087A1 - Maintenance Member for a Wind Turbine and Method for using it

Info

Publication number: DK201500087A1
Application number: DKPA201500087A
Authority: DK
Inventors: Jan Gulløv Christensen
Original assignee: Gulløv Innovation Aps
Priority date: 2015-02-13
Filing date: 2015-02-13
Publication date: 2016-07-11
Also published as: WO2016128006A1; EP3256718A1; DK178578B1

Abstract

A wind turbine (2) comprising at least one rotor blade (8) is disclosed. The wind turbine (2) comprises at least one maintenance member (14) configured to be arranged in a first configuration in which the wind turbine (2) is in power generating mode and in a second configuration in which the wind turbine (2) is in maintenance mode.

Description

Maintenance Member for a Wind Turbine and Method for using it Field of invention

The present invention relates to a method for maintenance of wind turbine rotor blades. The present invention also relates to an apparatus for maintaining wind turbine rotor blades by bringing the rotor blades into close proximity to the remaining portion of the wind turbine (e.g. the tower).

Prior art

Conducting maintenance on rotor blades on wind turbines is only possible when the velocity of the wind is so low that the deformation of the blades is insignificant. Maintenance of rotor blades is performed by stopping the rotor blades and arranging the rotor blade that needs inspection vertically. The maintenance crew can use a lift from the tower to get access to the blade of relevance. However, this technique is impossible to use on offshore wind turbines due to the size of both the tower and the blades. On offshore wind turbines, the tip of the blade is approximately 20 meters from the tower. Consequently, it is impossible to use a lift to carry a maintenance crew over this distance to the blade. The reason for requiring this distance is to prevent the blade from colliding with the tower during power generation, when parts of the wind turbine, primarily the blades, are deflected up to maximum allowable wind speed.

At present, blades are normally maintained by hand, but this invention can also be used for semi- or full-automatic inspection and maintenance of blades.

In KR 101027743, a method for protecting a wind turbine at high wind velocities is described. The wind turbine is protected by rotating the nacelle so that the rotor blades point upwards. When the rotor blades point upwards, they are in a position which protects the wind turbine from overload by the wind. This position is not appropriate for the purpose of performing maintenance or service on the wind turbine due to the position of the blades.

In US 2012/0057979 Al, a wind power system comprising a vertical tower, a carriage and a wind turbine is described. The system includes a locking mechanism configured to lock the carriage in a working position at the top of the travel path, a maintenance position at the bottom of the travel path, and/or a storm position at a midpoint of the travel path.

In US 2010/0084864 Al, a device for monitoring a wind energy installation is described. The device comprises a tower and a rotor provided with rotor blades. The device is used for monitoring a possible collision of a rotor blade with the tower, and thus comprises at least one distance sensor arranged on the wind energy installation. Said sensor is used for measuring the non-contact by determining the distance between the rotor blades and a predetermined point on the wind energy installation.

Thus, there is a need for a method and an apparatus which allow for easy maintenance of rotor blades on wind turbines, especially on offshore wind turbines.

Summary of the invention

The object of the present invention can be achieved by a wind turbine with the features as defined in claim 1 and by a method as defined in claim 12. Preferred embodiments are defined in the dependent sub claims, explained in the following description and illustrated in the accompanying drawings.

The wind turbine according to the invention is a wind turbine comprising a tower, a nacelle, a rotor hub and at least one rotor blade. The wind turbine comprises at least one maintenance member configured to be arranged in a first configuration in which the wind turbine is in power generating mode and in a second configuration in which the wind turbine is in maintenance mode, and wherein the maintenance member is configured to bring a rotor blade in a configuration in which it extends basically parallel to the tower when the wind turbine is in maintenance mode, where the distance between the tip of the rotor blade and the tower is significantly shorter when the wind turbine is in maintenance mode than the distance between the tip of the rotor blade and the tower when the wind turbine is in power generating mode. Hereby, it is possible and easier to maintain rotor blades on wind turbines.

During maintenance, the rotor blades are prevented from colliding with the tower, and thereby damage to the rotor blades and the tower can be prevented. During maintenance mode, one may pitch a blade in order to reduce its distance to the remaining portion of the wind turbine (e.g. to the tower of the wind turbine).

When using prior art methods on offshore wind turbines, it is very challenging and in some cases impossible to use a lift to carry the maintenance crew from the tower to the rotor blades. By installing a maintenance member according to the invention, it is possible to bring the wind turbine into maintenance mode and carry out maintenance of the rotor blades. After maintenance of the rotor blades, the wind turbine can be brought into operational mode again. In operational mode, the wind turbine can generate energy, whereas it is impossible for the wind turbine to generate energy in maintenance mode as the blades are prevented from rotating by wind.

The wind turbine may comprise at least one maintenance member. The at least one maintenance member may be positioned in one of the following positions or in several of these positions: on at least one rotor blade; between the rotor blade and the hub; in the hub; between the hub and the nacelle; in the nacelle; between the nacelle and the tower or in the tower.

Activation of the maintenance member may be accomplished when the pitch axis and yaw axis are basically parallel. However, a non-zero angle may be provided between these two axes.

When the maintenance member is arranged in one or more of the specified positions, the wind turbine may be shifted between the operational mode and the maintenance mode by activation of the maintenance member.

The maintenance member is configured to change the orientation and/or position of the rotor blade(s), in such a manner that the distance between the tip of a blade and the tower is reduced.

When maintenance has been carried out, the maintenance member can be activated in order to bring the wind turbine back into operational mode again.

It may be beneficial that the wind turbine comprises a tower, a nacelle, a rotor, a hub and at least one rotor blade (E.g. two or three blades).

It may be an advantage that the maintenance member is configured to bring a rotor blade into a configuration in which it (or a major portion of it) extends basically parallel to the tower when the wind turbine is in maintenance mode. In this configuration where the wind turbine is in maintenance mode, the distance between the tip of the rotor blade and the tower is significantly shorter than the distance between the tip of the rotor blade and the tower when the wind turbine is in power generating mode.

Hereby, it is possible to use a lift to carry a maintenance crew from the tower to the blade due to the reduced distance between the tower and the blade.

The movement or the movements bringing the wind turbine in maintenance mode are not necessarily comprised in only one or more maintenance members). The wind turbine can also be brought into maintenance mode by extended mobility in one or more of the movements, that are normally used in power generation mode, or a combination of these movements, without extended mobility, that are only used in maintenance mode.

The one or more maintenance member(s) may comprise one or more units which operate in the space between the main members of the power generating structure of the wind turbine without affecting the geometric positions of these main members. The maintenance members can be units moveably mounted on the tower, nacelle or hub. When in maintenance mode, they can bring persons and/or equipment closer to the blade than in power generation mode.

The movement or movements providing better access to maintenance of the blades can be movements that bring two or more blades closer to each other, in such a manner that it is possible for a lift to be simultaneously supported by two or more blades during maintenance of these blades.

It may be beneficial that the maintenance member comprises means for activa- tion (e.g. a driving mechanism) configured to change the configuration of the wind turbine between the power generating mode and the maintenance mode. The means for activation may comprise any suitable type of driving force. The means for activation may include members causing a linear motion. The means for activation may include members causing a non-linear motion. The means for activation may include members causing rotation of one or more elements. The means for activation may include members that use the gravitational force.

Hereby, the means for activation can be used to change the configuration of the maintenance member and thus the configuration of the wind turbine (including shifting between maintenance mode and power generating mode). Moreover, activation of the maintenance member is facilitated.

The means for activation may include members causing a linear motion by means of a cylinder and/or a membrane and/or magnetic forces (including use of permanent magnets and/or electromagnets) or a spring.

It is possible to apply a cylinder provided with a piston slidably mounted inside the cylinder. Movement of the piston may be achieved by changing the fluid volume inside the cylinder and/or by changing the temperature of the fluid in the cylinder (through a heating or cooling process).

It is possible to apply a reaction performed in the cylinder to create a pressure change that will move and hereby activate the piston. This chemical reaction may be a combustion reaction or any other suitable type of reaction.

It is possible to apply a membrane to generate and/or control a linear motion e.g. by applying a membrane mechanically connected to a piston. The membrane-piston system may be constructed in numerous ways. By way of example, the membrane-piston-system may comprise a cavity covered by a membrane, where the maintenance member according to the invention is configured to be activated by changing the volume of fluid in the cavity.

The volume of fluid may be changed by changing the temperature of the fluid or by carrying out a chemical reaction e.g. in the cavity or in an adjacent confined space.

In one embodiment, a linear motion or a non-linear motion may be generated by means of magnetic forces (including use of permanent magnets and/or electromagnets) or a spring. The spring may be attached to a piston, and the length of the spring may determine the degree of activation of the maintenance member. The maintenance member may be brought into operation mode when the spring is compressed, and the maintenance member may be brought into maintenance mode when the spring is released or vice versa.

It is possible to activate the maintenance member according to the invention in a manner that includes non-linear motion of one or more elements. This may be carried out by using a cylinder, a membrane, a spring, a pillow or magnetic forces.

It is possible to apply a pillow to activate or control a linear or non-linear motion. By changing the volume of the pillow e.g. by filling fluid into it or sucking fluid out of it, by changing the temperature of the fluid or by creating a chemical reaction or a combustion in the fluid, maintenance member may be activated.

It is possible to activate the maintenance member according to the invention in a manner that includes a rotational motion generated by means of an electric motor, a piston engine, a turbine, or the rotor of the wind turbine.

If a piston engine is used, the maintenance member may be activated by changing the volume of fluid in the cylinder of the piston e.g. by means of a pump, heating or cooling of the fluid or by means of a chemical reaction performed in a confined fluid.

It is possible to apply a turbine driven by a fluid flowing through the turbine. It would be possible to carry out a chemical reaction in the fluid. The chemical reaction may be a combustion process or any other suitable chemical reaction.

In one embodiment, the rotor of the wind turbine may also be used to activate the maintenance member. The rotor may indirectly or directly provide a driving force for activation of the maintenance member.

It is possible to use the gravitational force to activate the maintenance member e.g. by transferring potential energy into kinetic energy and hereby causing motion of the maintenance member (e.g. by means of a tilting movement).

The use of gravitational force to activate the maintenance member may be performed in numerous ways. For example, the maintenance member may be activated by transfer of potential energy so that an object having a mass is lowered.

The maintenance member may also be activated by other means, for example a jet engine, use of hand power, artificial muscle fibres, or a float in a tub with fluid.

All of the above-mentioned activation methods for activation of the maintenance member may have a driving mechanism. The driving mechanism may be either direct or indirect.

By an indirect driving mechanism is meant any driving mechanism which can apply pressure and/or which can apply a pulling force.

The driving mechanism can be any of the elements mentioned below or any combination of these.

The pulling force may be applied with either a chain or a belt. The pulling force may be constructed in such a manner that chains or belts are attached between two or more rotating components. The pulling force may be constructed in such a manner that chains or belts are attached between two or more translationally moving components. The pulling force may be constructed in such a manner that the chains or belts are attached between a combination of rotating and translationally moving components.

The pushing force may be applied by any suitable, moveable mechanism members which are pressed against each other. The pushing force may be achieved merely by applying normal forces or a combination of normal and frictional forces. These mechanisms may be: a rotating cam pressed against a path having an arbitrary geometry, a crankshaft pressed against a path with arbitrary geometry, two or more rotating members either concentric or non-concentric, two or more translational members moving on one or more pathways of arbitrary, geometry or it may be any combination of these mechanisms.

The driving mechanism may transfer forces in opposite directions. An example of such a driving mechanism may be a pivot joint with one or more axes. Other examples may be ball joints, rod ends, meshing engagement with a gear, meshing engagement with a rack gear, worm gears, spindle gears, crankshafts with a connecting rod, an eccentric member, or a forked engagement.

Construction of the maintenance member may be performed independently of "the activation of the maintenance member", "the driving mechanism", or "the position of the maintenance member on the wind turbine". The maintenance member may include swivel joints with one, two or three axes, or a ball joint, or a rod end.

The motion control member may apply its force or forces either directly or indirectly to the members of the driving mechanism or to the maintenance member. If the forces from the motion control member are applied indirectly, they may be applied by means of a mechanism with no other function.

Motion control may be accomplished by controlling the flow of fluid between two or more chambers (e.g. having different volumes). These chambers may be shaped as cylinders with pistons connected to a tube, wherein the flow through the tube is controlled by a valve. Motion control may be accomplished by only regulating the flow out of the chambers. Typically, this could be accomplished by evacuating air from the chambers to the atmosphere.

The elements in the maintenance member may be used individually, or they may be combined. If the elements are combined, they may be combined in serial or parallel. For example, the elements may be a single rotary movement, serial-connected rotary movements, parallel-connected rotary movements, a combination of serial-connected and parallel-connected rotary movements, or a movement with telescopic elements.

The maintenance member may comprise curved rails or straight rails giving rise to movements along the curved rails or straight rails The movements may be provided by means of one or more parallel rails with the same geometry and orientation. As for movement on the curved rails, the movement may be a combination of a rotary and translational motion. The curved rails may have either a fixed geometry or a flexible (changeable) geometry. A combined rotational and translational motion may be performed on two or more nonparallel rails with different geometry and/or orientation. Both parallel and nonparallel rails may have a single rail system, a serial rail system or a telescopic rail system.

It is possible to have rails or a rail system with round cross section; however, the rails may have other geometries allowing the rails or rail system to lock the rotational movement using just one rail. It is possible to apply a rail guide arranged either externally or inside the rails. The rail guide may be constructed by applying contact with a wheel, contact bushings, or other suitable mechanical means.

It may be beneficial that the maintenance member comprises a motion control member configured to control or even stop the motion of the maintenance member.

The maintenance member according to the invention may comprise a motion control member. A motion control member may directly or indirectly prevent occurrence of uncontrollable or undesirable movements of the maintenance member. The motion control member may be constructed as one single motion control member part; however, it is also possible to apply several motion control member parts (they may be combined either in serial or parallel) constituting the motion control member.

The maintenance member may comprise a driving mechanism, activation means and movement stopping means.

The motion control member may apply any suitable type of motion control mechanism including elements stopped by means of frictional forces, brakes, mechanical engagements or magnetic forces.

The pushing force may be applied by any suitable moveable mechanism members which are pressed against each other. The pushing force may be achieved merely by applying normal forces or a combination of normal and frictional forces. It is possible to apply any suitable means to provide the required force.

The motion control member may function as a brake. The motion control member may be integrated in a driving mechanism which is self-locking or selfblocking, including a disc brake in a rotary engine, a drum brake in a rotary engine or a worm gear or a spindle gear.

Motion control may be accomplished by controlling the flow of fluid between two or more chambers with variable volumes. These chambers may be cylinders with pistons connected by a tube, where the flow through the tube is controlled by one or more valves. Motion control may be accomplished by controlling only the flow out of chambers. Typically, this could be high pressure air led directly to the atmosphere.

It may be beneficial that the maintenance member comprises a locking feature configured to maintain the maintenance member in a fixed configuration when the wind turbine is in power generating mode and/or in maintenance mode.

The maintenance member may comprise a locking feature capable of locking the maintenance member in at least two positions: in power generating mode and in maintenance mode. However, in some embodiments it may be desirable to lock the maintenance member in further positions.

The locking feature may include means for providing geometric locking, locking based on application of frictional forces between adjacent elements, locking using an attractive force or a combination of any of these locking features.

Geometric locking may be achieved by engagement of a locking feature within a receiving member. This may for example be a meshing engagement, or an engagement where a part of the locking feature is moved in engagement with a surface of one of the components in the maintenance member.

The locking feature may be provided as a separate element or may be integrated in the maintenance member, so that the locking movement is a secondary member of the maintenance member.

The locking member may be a rotably mounted locking member, a slidably mounted locking member or a combination of these locking members.

The locking member may be driven directly or indirectly by a spring, by gravitational force, by magnetic forces by hydraulic means, by pneumatic means, by spindle gears or other mechanical means.

It may be advantageous that the maintenance member comprises at least two segments movably mounted to each other.

The segments may be rotatably mounted to each other by means of a joint.

It may be beneficial that the maintenance member comprises one or more sensors configured to monitor the distance between the rotor blade and the tower of the wind turbine.

It may be an advantage if the maintenance member comprises sensors for measuring the distance between the rotor blade(s) and the tower of the wind turbine.

In one embodiment, the sensors for measuring the distance are capable of directly measuring the distance. By measuring the distance directly, it is possible to optimise the settings of the wind turbines in maintenance mode, and it is possible to let the blades come close to the tower of the wind turbine without danger of collision.

The sensors for monitoring the distance may be placed on several positions such as at the tower, at the blades, at the nacelle, at the hub, at the foundation, or somewhere within the close surroundings of the wind turbine.

It is possible to monitor the distance by using any technology applying ultrasound, laser, image recognition, wind noise, heating elements, heat sensors, inductive members or a combination of any of these methods.

Advantageously, the maintenance member comprises a control unit configured to receive signals from the one or more sensors and means for automatically controlling (activating and/or stopping) the activity of the maintenance member.

It may be beneficial that the control unit is configured to activate activation means in order to increase the distance between the rotor blade and the tower of the wind turbine when the one or more sensor(s) register a distance between the rotor blade and the tower of the wind turbine which is shorter than a predefined, low distance level.

Hereby, a safer and more reliable maintenance process can be carried out.

It may be beneficial that the maintenance member is configured to reduce the minimum distance from the tip of the rotor blades to the tower, in situations where the deflection of the rotor blades and other parts of the wind turbine is reduced because the wind speed is lower than the maximum operational wind speed.

In these situations, the sensors and the control unit can be used to directly monitor the minimum distance between the rotor blade and the tower, so that this minimum distance can be reduced without risking that the rotor blades collide with the tower.

It may be an advantage that the wind turbine is configured to be operated in a first power generating mode, in which the wind turbine generates power by the primary motion of the rotor blades relative to the rest of the structure of the wind turbine, wherein the wind turbine comprises secondary, geometric control movement means configured to optimise the relative, geometric position of the parts during power generation mode, wherein the geometric control movement means are configured to bring the parts of the wind turbine in a predefined position, and maintain them in this predefined position, wherein said position would not be allowable in power generation mode when operating up to maximum operational wind speed, without the risk of the parts colliding.

The objects of the invention may be achieved by a method as defined in claim 12.

The method is a method for maintenance of at least one rotor blade of a wind turbine wherein the method comprises the steps of: - bringing the wind turbine in maintenance mode, in which a rotor blade is brought into a configuration in which it extends basically parallel to the tower, - bringing a rotor blade into a configuration in which the distance between the tip of the rotor blade and the tower is significantly shorter than the distance between the tip of the rotor blade and the tower when the wind turbine is in power generating mode.

It may be beneficial that the method comprises the step of receiving information from one or more sensors configured to monitor the distance between the rotor blade and the tower of the wind turbine and controlling (activating and/or stopping) the activity of the maintenance member on the basis of the received information.

It may be an advantage that the method comprises the step of increasing the distance between the rotor blade and the tower of the wind turbine when one or more sensors register a distance between the rotor blade and the tower of the wind turbine which is shorter than a predefined low distance level.

It may be advantageous that the method comprises the step of reducing the minimum distance from the tip of the rotor blades to the tower in situations where the deflection of the rotor blades and other parts of the wind turbine is reduced because the wind speed is lower than maximum operational wind speed.

Description of the Drawings

The invention will become more fully understood from the detailed description given herein below. The accompanying drawings are given by way of illustration only, and thus, they are not limitative of the present invention. In the accompanying drawings:

Fig. 1 a illustrates a schematic side view of a wind turbine according to the invention in which possible locations of the maintenance member are shown;

Fig. 1 b illustrates a schematic side view of a wind turbine according to the invention in which possible positions for monitoring the maintenance member are shown;

Fig. 2 illustrates schematic side views of a wind turbine according to the invention in which the maintenance member comprises two segments;

Fig. 3 illustrates schematic side views of a wind turbine according to the invention in which the maintenance member comprises four segments;

Fig. 4 illustrates schematic views of means for activating the maintenance member according to the invention;

Fig. 5 illustrates schematic side views of different activations of the maintenance member according to the invention by use of the gravitational force;

Fig. 6 illustrates schematic views of an indirect driving mechanism according to the invention;

Fig. 7a-e illustrate schematic side views of different constructions of the maintenance member according to the invention;

Fig. 7f-i illustrate schematic views of the mechanism in the maintenance member according to the invention;

Fig. 7j-l illustrate schematic top-views of different cross-sections of the rail system according to the invention;

Fig. 7m-n illustrate schematic top-views of a rail guide according to the invention;

Fig. 8 illustrates schematic views of different types of motion control according to the invention; and

Fig. 9 illustrates schematic views of a locking feature according to the invention.

Detailed description of the invention

Referring now in detail to the drawings for the purpose of illustrating preferred embodiments of the present invention, a wind turbine 2 of the present invention is illustrated in Fig. 1.

Fig. 1 a) illustrates a schematic side view of a wind turbine 2, in which possible mounting positions of the maintenance member 14, 14', 14", 14'", 14"", 14'"", 14""" are indicated. The wind turbine 2 comprises a tower 4 and a nacelle 6. A hub 12 is provided at the nacelle 6. The hub 12 and the nacelle 6 are connected to rotor blades 8, 8'.

The figure illustrates only some of the possible mounting positions of the maintenance members 14, 14', 14", 14'", 14"", 14'"", 14""". The mounting positions of the maintenance member 14, 14', 14", 14'", 14"", 14'"", 14""" may be either at the nacelle 14"", or at the hub 14", between the hub and the nacelle 14'", at the tower 14""", between the tower and the nacelle 14'"", at the rotor blade 14, or between the rotor blade and the hub 14'.

The maintenance member may not need to be arranged at one of the specified mounting positions. However, the maintenance member has to be arranged at least at one mounting positions, preferably at one of the illustrated mounting positions.

The maintenance members 14, 14', 14", 14'", 14"", 14'"", 14""" are configured to be arranged in a first configuration in which the wind turbine 2 is in power generating mode and in a second configuration in which the wind turbine 2 is in maintenance mode.

Fig. 1 b) illustrates a schematic side view of a wind turbine 2 according to the invention. The black boxes illustrate possible positions of sensors 42, 42', 42",42"',42"", 42""' for monitoring the distance between the rotor blade 8 and the remaining parts of the wind turbine 2, preferably between the rotor blade 8 and the tower 4.

By measuring the distance between the rotor blade 8 and the tower 4 directly, it is possible to optimise the settings of the wind turbine in maintenance mode. It is then possible to let the blades come close to the remaining parts (e.g. the tower 4) of the wind turbine 2 without danger of collision. The units (sensors) for monitoring the distance may be arranged on several mounting positions such as the bottom portion 42" of the tower 4, at the distal end 42'"" of the blades, at the lower portion 42'" of the nacelle 6, at the lower portion 42', 42"" of the hub, at the surface 42' of the foundation or the surroundings 42.

Fig. 2 illustrates schematic side views of a wind turbine 2 according to the invention. The wind turbine 2 comprises a tower 4 extending from a support surface 36. The support surface 36 may either be the ground, a foundation or a platform. At the distal end of the tower 4, a work platform 38 is arranged. A nacelle 6 is arranged at the top of the tower 4.

A maintenance member 14 and a wind orientation control (yaw control - not shown) are provided between the tower 4 and the nacelle 6. The wind orientation control controls the rotation of the nacelle 6 around the yaw axis 16. The yaw axis 16 is aligned with the centre axis of the tower 4, but may also advantageously extend parallel to the centre axis.

A rotor hub 12 is arranged at the nacelle 6. In the rotor hub 12, three rotor blades 8, 8', 8" are provided. The rotor blades 8, 8', 8" are mechanically coupled to a pitch mechanism (not shown). Each pitch mechanism includes blade bearing means and pitch actuating means allowing the blades 8, 8', 8" to pitch. The pitch mechanism rotates the rotor blades 8, 8', 8" about the pitch axis 20. In operation mode, the rotor hub 12 is turned to the area on one of the blades 8, 8', 8" to which access is wanted, is arranged in a position in which this area, by the movement caused by the maintenance member, may be moved to a position closer to the tower 4.

Fig. 2 a) illustrates a schematic view of a wind turbine 2 wherein the wind turbine 2 is in power generating mode.

When the wind turbine 2 is in power generating mode, the maintenance member 14 is in a "closed position". In power generating mode, the wind turbine 2 can function in a normal mode and thereby generate energy. In power generating mode, the rotor blades 8, 8', 8" are prevented from colliding with the tower 4, even when the wind has a deformation impact on the rotor blades 8, 8', 8". Large rotor blade deformations may be observed when the wind turbine 2 is in power generating mode. In power generating mode, the rotor axis 18 extends parallel to the longitudinal axis of the maintenance member 14.

Fig. 2 b) illustrates a schematic side view of a wind turbine 2 wherein the wind turbine 2 is in maintenance mode. The wind turbine 2 is in maintenance mode when the maintenance member 14 is in an open position as illustrated in Fig. 2 b).

In maintenance mode, the wind turbine 2 cannot be operated like in power generating mode, and therefore no energy is generated. In maintenance mode, it is however possible to maintain the rotor blades 8, 8', 8".

When the wind turbine 2 is in maintenance mode, the maintenance member 14 rotates the nacelle 6 into a position in which the rotor axis 18 is angled relative to horizontal, and the horizontal distance d' between the tip of the rotor blade 24 and the tower 4 is decreased compared with the horizontal distance d in power generating mode.

Accordingly, in maintenance mode, it is possible to maintain the rotor blades 8, 8', 8". The maintenance crew can easily use a lift from the tower 4 to provide access to the tip of the rotor blades 24.

The maintenance member 14 comprises a first segment 32 attached to the top portion of the tower 4 and another segment 32' attached to the nacelle 6. The attachment of the segments 32, 32' may be established by means of any suitable fastening means 30 including screws, bolts or weldings. The segments 32, 32' may be constructed of plates made of metal or another suitable material.

The second segment 32' is rotatably mounted to the first segment 32 by means of a joint. The joint 28 may be a hinge joint configured to be maintained in two or more predefined positions.

The joint is configured to be brought into and maintained in a first position in which the two segments 32, 32' extend parallel to each other (when the wind turbine 2 is in power generating mode) and in a second position, in which the angle between the first segment 32 and the second segment 32' takes a predefined value, preferably within an angle range of 5-30° (when the wind turbine 2 is in maintenance mode, and the rotor blade 8 extends parallel to the tower 4).

The maintenance member 14 comprises means for being locked in these two positions to ensure that the wind turbine 2 will not unauthorized change between operation mode and maintenance mode.

When the wind turbine 2 has to be brought into maintenance mode, the rotation of the rotor blades 8, 8', 8" is stopped. Operating the nacelle 6 in maintenance mode requires that the rotation of the blades 8, 8', 8" is stopped. The nacelle 6 is brought into maintenance mode by rotating the segment 32' about the axis of the joint 28. The angle of rotation of the segment 32' is significantly less than 45°.

This method of conducting maintenance on the rotor blades 8, 8', 8" is beneficial and eliminates several of the disadvantages of the prior art methods. In power generating mode, the rotor hub 12 is turned to the area on one of the blades 8, 8', 8" where access is wanted, is positioned in such a position, that this area by the movement in the maintenance member may be moved to a position close to the tower 4.

When the tip of the rotor blade 8 is at its closest distance to the support surface 36, the wind turbine 2 can be brought into maintenance mode by activating the maintenance member 14. All rotor blades 8, 8', 8" can be maintained in turn if desired.

Fig. 3 illustrates schematic side views of a wind turbine 2 according to the invention. The wind turbine 2 comprises a tower 4 extending from a support surface (not shown). A work platform 38 is arranged at the lower portion of the tower 4. A nacelle 6 is provided at the proximal end of the tower 4. A maintenance member 14 and a wind orientation control (yaw control) are arranged between the tower 4 and the nacelle 6.

It may be advantageous that the maintenance member 14 is provided at the wind orientation control. Thereby, the wind orientation control can control the rotation of the nacelle 6 and the maintenance member 14 around the yaw axis 16.

It may be an advantage to arrange the maintenance member 14 and the nacelle 6 in such a manner that the maintenance member 14 and the nacelle 6 have the same orientation.

The yaw axis 16 extends along the centre axis of the tower 4. It is important to arrange the nacelle 6 is such a manner that the rotor blades 8, 8', 8" face the wind in order to maximise the energy generated.

A rotor hub 12 is arranged at the front of the nacelle 6. At the proximal end of the rotor blades 8, 8', 8", a blade pitch control may be provided. The blade pitch control may be configured to pitch the rotor blades 8, 8', 8" about their pitch axes 20.

The maintenance member 14 comprises four segments 32, 32', 32", 32'" and four joints 28, 28', 28", 28'". The four segments are mechanically connected by the joints 28, 28', 28", 28'" so that the four segments 32, 32', 32", 32'" form a quadrilateral, wherein the joints 28, 28', 28", 28'" are provided in each corner. The segments 32, 32" are provided in opposite positions, and the segments 32', 32'" are provided in opposite positions. The segments 32, 32', 32", 32'" support the nacelle 6 and their configuration determines the orientation of the nacelle 6.

In power generating mode, the wind turbine 2 generates energy. In power generating mode, the rotor blades 8, 8', 8" are prevented from colliding with the tower 4, even at high wind velocity.

Large rotor blade deformations may be observed when the wind turbine 2 is in power generating mode. In power generating mode, the maintenance member 14 ensures that the rotor hub 12 inclines slightly upwards. Hereby, there is a non-zero angle cp between horizontal and the rotor axis 18.

In maintenance mode, the rotor blades 8, 8', 8" are prevented from getting into contact with the tower 4. In maintenance mode, the maintenance member 14 brings the rotor hub 12 into an inclined position in which the rotor blade 8 extends basically parallel to the tower 4 (see Fig. 3 b).

Fig. 4 illustrates schematic views of activation means configured to activate a maintenance member according to the invention. The illustrations Fig. 4 a) to 4 g) show different ways of providing energy to the maintenance member. Fig. 4 a) to 4 c) illustrate different ways of activating the maintenance member by linear methods, whereas Fig. 4 d) to 4 g) illustrate different ways of activating the maintenance member by means of a non-linear method.

Fig. 4 a) illustrates a cylinder 44 in which a piston 46 is provided. A chamber 50 is confined between the cylinder 44 and the piston 46. The chamber 50 comprises a fluid. The cylinder 44 has two ends: a first end in which the piston 46 enters the cylinder 44 and a second end provided with an opening (fluid outlet) 48. The piston 46 is constructed in such a way that it is restricted to be moved in a linear manner causing a linear motion pattern of the cylinder 44. This means that the motion of the piston 46 back and forward within the cylinder 50 is linear.

The maintenance member according to the invention may be activated by means of the actuator illustrated in Fig. 4 a). Activation is accomplished by moving the piston 46. Changing the volume of fluid in the chamber 50 (e.g. filling or emptying the chamber 50) will cause the piston 46 to move along the longitudinal axis of the cylinder 44.

Fig. 4 b) illustrates a cavity upon which a membrane 52 is attached. A piston 46 is attached to the membrane 52. An opening (duct) 48 is provided in the cavity. The opening 48 is configured to increase or reduce the volume of fluid in the chamber 50 of the cavity. It is only possible for the piston 46 to move linearly due to restriction within the construction.

When the chamber 50 of the cavity is emptied, the membrane 52 is sucked partly into the chamber 50 of the cavity, whereas when the chamber 50 of the cavity is filled, the membrane 52 moves outwards. The motion of the membrane 52 causes motion of the piston 46. The movement of the piston 46 may be applied to activate the maintenance member according to the invention.

Fig. 4 c) illustrates a spring 54 attached to a stopper (a motion control member) 56. The stopper is provided within a channel that only allows linear motion of the stopper 56. The spring 54 can push and pull the stopper 56 dependent on the state of the spring (its length). Accordingly, the movement of the spring 54 may eventually be used to activate a maintenance member according to the invention.

Fig. 4 d) illustrates a cavity onto which a membrane 52 is attached in the same way as illustrated in Fig. 4 b). The difference between the piston 46 in Fig. 4 d) and 4 b) is that the piston 46 in Fig. 4 d) may move in a non-linear manner. The piston 46 in Fig. 4 d) may move in a three-dimensional fashion due to the fact that the piston 46 is free to be rotated as illustrated in Fig. 4 d). At the same time, the piston 46 can be moved due to the motion of the membrane 52.

Fig. 4 e) illustrates a cylinder 44 in which a piston 46 is slidably mounted. The piston 46 can be moved along the longitudinal axis of the cylinder 44, and at the same time it may be rotated like indicated by the arced arrow. Accordingly, the piston 46 in Fig. 4 e) may move in a three-dimensional fashion instead of just a one-dimensional fashion as in Fig. 4 a).

Fig. 4 f) illustrates a piston 46 attached to a spring 54. The motion of the spring can cause the piston 46 to be moved along a canal 58. As the canal 58 is curved, the motion of the piston 46 is a non-linear movement.

Fig. 4 g) illustrates a pillow 60 arranged between two segments 32, 32' which are rotatably attached to each other by means of a joint 28. The pillow 60 comprises a fluid, and the fluid may be either filled into the pillow 60 or sucked out of the pillow 60 through an opening 48.

When the pillow 60 is filled with fluid, the two segments 32, 32' are pushed away from each other. By varying the volume of fluid in the pillow, it is possible to control the configuration of the segments 32, 32' and hereby to activate the maintenance member according to the invention.

Fig. 5 illustrates a number of different ways of activating the maintenance member by the use of the gravitational force.

Both Fig. 5 a) and Fig. 5 b) illustrate embodiments that apply a mass 64 attached to a cord 66. The cord 66 is attached to a handle 70 (as shown in Fig. 5 b) through two pulleys 68, 68'. It is, however, not required to apply a pulley 68 as shown in Fig. 5 a). Further, it would be possible to apply only one pulley although not shown. The handle 70 may be attached to the wind turbine or the maintenance member through a joint 28.

Both Fig. 5 c) and Fig. 5 d) illustrate ways of how to activate a maintenance member by moving the centre of mass of an object 72 in such a manner that the potential energy of the system is minimised.

In Fig. 5 c), the object 72 is attached to the wind turbine or the maintenance member through a joint 28. The object is able to rotate about the axis of the joint 28. In Fig. 5 d), the object 72 comprises two wheels 74, 74' each rotatably attached to the object by means of a joint 28, 28'. The two sets of wheels 74, 74' are configured to be moved along the handle 70. The handle 70 is attached to a maintenance member according to the invention or a wind turbine through the joint 28".

Both Fig. 5 e) and f) illustrate a way of activating a maintenance member according to the invention. Activation is carried out by moving the centre of mass by rearranging counterweights. The counterweights may be a solid mechanical component (as shown in Fig. 5 e) or a fluid that is displaced (as shown in Fig. 5 f). A handle 70 is attached to the maintenance member or the wind turbine through a joint 28. Fig. 5 e) comprises a solid object 72 that is movably mounted to the handle 70. The object 72 comprises two rotatably mounted wheels 74, 74'. The position of the object 72 determines the orientation of the handle 70.

Fig. 5 f) illustrates an embodiment 78 comprising a fluid 76 housed within two separated chambers that are in fluid communication with each other through an intermediate pipe member comprising a pump member. The pump member is configured to generate a fluid flow from one chamber to the other chamber causing rotation of the handle 70.

Fig. 6 illustrates a number of different indirect driving mechanisms that may be used to activate a maintenance member according to the invention.

Fig. 6 a) illustrates a movable arm 80 rotatably mounted (via a joint 28) to a first segment 32 which is rotatably mounted (via a joint 28') to a second arced segment 32'. Rotation of the arm 80 causes rotation of the second segment 32' relative to the first segment 32.

Fig. 6 b) illustrates a pivot joint 82 with two axes. Fig 6 c) illustrates a ball joint 84. Fig. 6 d) illustrates a meshing engagement with a rack gear 86 in which a toothed wheel 117 is in engagement with a toothed rack 118.

Fig. 6 e) illustrates a concentric engagement 88 between two rotating concentric??? components 92, 92' configured to rotate about a centre axis 119.

Fig. 6 f) illustrates a forked engagement 90 comprising two concentric components 92, 92' brought into engagement and configured to rotate about a centre axis 119.

Fig. 6 g) illustrates a crankshaft with a connecting rod 94. The rod 120 is rotatably mounted to an object 72 by means of a joint 28". In the opposite end of the rod 120, an arm 80 is rotatably mounted to the rod 120 by means of a second joint 28'. The arm 80 is fastened to either a maintenance member or the wind turbine by means of a joint 28. The movement of the arm 80 causes the object 72 to move. The object 72 is movably arranged on a surface 106, and the object 72 comprises two wheels or rollers 74, 74'.

Fig. 6 h) illustrates an eccentric member 96 comprising a rod 120 rotatably attached to two arms 80, 80' at each end of the rod 120 by means of two joints 28', 28". The arms 80, 80' are rotatably attached to either a maintenance member or a wind turbine by means of a joint 28, 28'".

Fig. 7 a) to 7 e) illustrate different ways of constructing the actuation means of a maintenance member according to the invention.

Fig. 7 a) illustrates a schematic view of a maintenance member comprising two segments 32, 32' rotatably mounted to each other by means of a joint 28.

Fig. 7 b) illustrates a schematic view of a maintenance member comprising three segments 32, 32', 32" pairwise connected to each other by means of joints 28, 28'.

Fig. 7 c) illustrates a schematic view of a maintenance member according to the invention. The maintenance member comprises four segments 32, 32', 32", 32'" arranged in a quadrilateral configuration. Adjacent segments are rotatably mounted to each other by means of joints 28, 28', 28", 28'".

Fig. 7 d) illustrates a schematic view of a maintenance member according to the invention. The maintenance member comprises five segments 32, 32', 32", 32'", 32"". Four of the segments 32, 32', 32", 32'" constitute a configuration corresponding to the one illustrated in Fig. 7 c). However, a further segment 32"" is rotatably mounted to the segment 32'" by means of the joint 28".

Fig. 7 e) illustrates a maintenance member according to the invention. The maintenance member comprises two telescopic elements. The maintenance member comprises a rod 120 rotatably connected to two telescopic components 121, 121' by means of joints 28', 28".

Fig. 7 f) to Fig. 7 i) illustrate different schematic views of embodiments of a maintenance member according to the invention.

Fig. 7. f) illustrates a schematic view of a mechanism configured to activate a maintenance member according to the invention. The maintenance member comprises a plate member 72 having three wheels 74, 74', 74" and being movably arranged on two straight rails 98, 98'.

Fig. 7 g) illustrates a schematic view of a mechanism configured to activate a maintenance member according to the invention. The maintenance member comprises a rail system 100 comprising a first rail 98 connected to a second, additional rail 98' by means of a rail connection member 122.

Fig. 7 h) illustrates a schematic view of a mechanism configured to activate a maintenance member according to the invention. The maintenance member comprises a rail system 100 comprising two telescopic rod components 121, 121'.

Fig. 7 i) illustrates a schematic view of another mechanism configured to activate a maintenance member according to the invention. The maintenance member comprises a straight rail 98 arranged next to an arced rail 98'.

Fig. 7 j) to I) show different cross-sections of the rail system 100 according to the invention. In Fig. 7 j), the cross section is round. In Fig. 7 k), the cross section is square, while the cross section is triangular in Fig. 7 I).

Fig 7 m) and n) illustrate rail guides 102. In Fig. 7 m), the rail guide 102 is arranged inside a rail 98, whereas in Fig. 7 n), the rail guide 102 is arranged outside the rail 98.

Fig. 8 a) to b) illustrate different types of motion control members 104 according to the invention. In Fig. 8 a), the motion control member 104 works due to friction F) between two surfaces 106, 106' due to the normal force N. The friction F is given by the product of the normal force N and the coefficient of friction μ.

Fig. 8 b) illustrates a motion control mechanism according to the invention involving a motion control member 104. The motion control member 104 comprises means for controlling or limiting the amount of fluid flowing in or out of a chamber 50 within a cylinder 44. A piston 46 is slidably arranged within the cylinder 44. A vent 108 controls the flow of a fluid from the cylinder 44 and thereby moves the piston 46.

Fig. 8 c and d) illustrates a disk brake 110. The disk brake 110 is shown as a side view in Fig. 8 c), and from top view in Fig. 8 d).

Fig. 8 e) and f) illustrates a drum brake 112 according to the invention. The drum brake 112 is shown in a side view in Fig. 8 e), and from a top view in Fig. 8f).

Fig. 9 a) to Fig. e) illustrate locking features according to the invention. Fig. 9 a) illustrates how geometric locking means may be applied. The locking mechanism constitutes a locking feature 114 that may be applied to bring a first member in engagement with another member (e.g. a surface of one of the components in the maintenance member).

Fig. 9 b) illustrates a schematic view of a frictional locking feature 114 according to the invention. A maintenance member according to the invention may be brought into a locked position by means of a mechanism that applies friction between a locking feature 114 and a component to be locked.

Fig. 9 c) illustrates a locking feature 114 which applies an attractive force. A magnetic force is applied to bring the two surfaces 106, 106' together and to keep the surfaces 106, 106' in this configuration.

Fig. 9 d) illustrates a locking feature 114 comprising a member 72 of the mechanism which is intended to be locked or unlocked by engagement with the locking plate 116. The member 72 is adapted to conduct one type of movements being part of or being directly related to the movement of the maintenance member according to the invention. The member 72 is adapted to conduct another type of movements that will engage it with the locking plate 116. In Fig. 9 d), the locking plate 116 is fixed.

Fig. 9 e) illustrates a locking feature 114 comprising a member 72 of the mechanism which is intended to be locked or unlocked by engagement with the locking plate 116. The member 72 is adapted to conduct one type of movements being part of or being directly related to the movement of the maintenance member according to the invention. The member 72 is adapted to conduct another type of movements that will engage it with the locking plate 116. In Fig. 9 d), the locking plate 116 is fixed.

The features illustrated in Fig. 4, Fig. 5, Fig. 6, Fig. 7, Fig. 8 and Fig. 9 may be used in any suitable way in order to construct a maintenance member according to the invention. Any suitable combination of the features illustrated in these figures may be applied.

List of reference numerals 2 Wind turbine 4 Tower 6 Nacelle 8, 8', 8" Rotor blade 12 Rotor hub 14, 14', 14", 14'" Maintenance member 14"", 14'"", 14""" Maintenance member 16 Yaw axis 18 Rotor axis 20 Pitch axis 24 Tip 28, 28', 28", 28'" Joint 30 Fastening means 32, 32', 32", 32'", 32"" Segment 36 Support surface 38 Work platform 42, 42', 42", 42'" Sensor 42"", 42'"" Sensor 44 Cylinder 46 Piston 48 Opening 50 Chamber 52 Membrane 54 Spring 56 Motion control member 58 Canal 60 Pillow 64 Mass 66 Cord 68, 68' Pulley 70 Handle 72 Object (plate member) 74, 74' Wheel 76 Fluid 78 Construction 80, 80' Arm 82 Pivot joint 84 Ball joint 86 Meshing 88 Concentric engagement 90 Forked engagement 92, 92' Components 94 Crankshaft with connecting rod 96 Eccentric member 98, 98', 98" Rail 100 Rail system 102 Rail guide 104 Motion control member 106, 106' Surface 108 Vent 110 Disk brake 112 Drum brake 114 Locking feature 116 Plate 117 Toothed wheel 118 Toothed rack 119 Axis 120 Rod 121, 121' Telescopic components 122 Rail connection member d, d' Distance F(p) Friction μ Coefficient of friction a Angle N Normal force

Claims

A wind turbine (2) comprising at least one blade (8), wherein the wind turbine (2) comprises at least one maintenance unit (14) which is designed to be adjustable in a first configuration wherein the wind turbine (2) is in a power producing state and in another configuration, where the wind turbine (2) is in maintenance mode, characterized in that the maintenance unit (14) is designed to bring a blade (8) into a configuration where it extends substantially parallel to the tower (4), when the wind turbine (2) is in maintenance mode, where the distance (d ') between the tip (24) of the blade (8) and the tower (4) is substantially shorter when the wind turbine (2) is in maintenance mode than the distance (d) between the blade (8) ) tip (24) and tower (4) when the wind turbine (2) is in power producing state.

Wind turbine (2) according to claim 1, characterized in that the wind turbine (2) comprises a tower (4), a nacelle (6) and a rotor hub (12).

Wind turbine (2) according to one of claims 1-2, characterized in that the maintenance unit (14) comprises an actuating unit (eg a drive mechanism) which is designed to change the configuration of the wind turbine (2) between power producing mode and maintenance mode. .

Wind turbine (2) according to one of the preceding claims, characterized in that the maintenance unit (14) comprises a movement control unit (104) which is designed to control or even stop the movement of the maintenance unit (14).

Wind turbine (2) according to one of the preceding claims, characterized in that the maintenance unit (14) comprises a locking device (114) which is designed to hold the maintenance unit (14) in a fixed configuration when the wind turbine (2) is in place. power producing mode or in maintenance mode.

Wind turbine (2) according to one of the preceding claims, characterized in that the maintenance unit (14) comprises at least two segments (32, 32 ', 32 ") which are movably attached to each other.

Wind turbine (2) according to one of the preceding claims 2-7, characterized in that the wind turbine (2) comprises one or more sensors (42, 42 ', 42 ", 42'", 42 "", 42 '"" ), which is designed to monitor the distance (d, d ') between the wing (8) and the tower (4) of the wind turbine (2).

Wind turbine (2) according to claim 7, characterized in that the maintenance unit (14) comprises a control unit which is designed to receive signals from one or more sensors (42, 42 ', 42 ", 42'", 42 "" , 42 "") and means for automatically controlling (activating and / or stopping) the activity of the maintenance unit (14).

Wind turbine (2) according to claim 8, characterized in that the control unit is designed to actuate an actuating unit to increase the distance (d, d ') between the wing (8) and the tower (4) of the wind turbine (2) when one or more sensors (42, 42 ', 42 ", 42'", 42 "", 42 '"") record a distance (d, d') between the wing (8) and the tower (4) on the wind turbine (2) , which is shorter than a predetermined level for how short the distance must be.

Wind turbine (2) according to claim 8 or 9, characterized in that the maintenance unit (14) is designed to reduce the minimum distance (d) from the tip (24) of the wings to the tower (4) in cases where deflection of the wings (8) ) and other parts of the wind turbine (2) are reduced because the wind speed is lower than the maximum operating wind speed.

A wind turbine (2) according to one of the preceding claims, characterized in that the wind turbine (2) is designed to be operated in a first current producing state, in which the wind turbine (2) generates current via the primary movement of the wings (8) for the remainder of the wind turbine (2) construction, wherein the wind turbine (2) comprises secondary geometric control motion means designed to optimize the relative geometric position of the parts (blades and other portion of the wind turbine) in the current generating state in which the geometric control motion means are configured. to bring the parts of the wind turbine (2) into a predetermined position and hold them there where said position will not be allowed in the current generating state at up to maximum operating wind speed without the risk of the parts colliding.

Method for maintaining at least one blade (8, 8 ', 8 ") on a wind turbine (2), characterized in that the method comprises the following steps: - the wind turbine (2) is set in maintenance mode in which (a large part of) a wing (8) is brought into a configuration where it extends substantially parallel to the tower (4); - a wing (8) is brought into a configuration where the distance (d ') between the tip (24) of the wing (8) and the tower (4) is substantially shorter than the distance (d) between the tip (24) of the blade (8) and the tower (4) when the wind turbine (2) is in a power producing state.

Method according to claim 12, characterized in that the method comprises the step of receiving information from one or more sensors (42, 42 ', 42 ", 42'", 42 "", 42 '"") designed for monitoring the distance (d, d ') between the wing (8) and tower (4) on the wind turbine (2) and controlling (activating and / or stopping) the activity of the maintenance unit (14) on the basis of the information received.

Method according to claim 13, characterized in that the method comprises the step of increasing the distance (d, d ') between the wing (8) and the tower (4) of the wind turbine (2) when the one or more sensors (42, 42) ', 42 ", 42'", 42 "", 42 '"") record a distance (d, d') between the wing (8) and the tower (4) of the wind turbine (2) which is shorter than a predetermined level for how short the distance must be.

Method according to claim 13 or 14, characterized in that the method comprises the step of reducing the minimum distance (d) from the tip (24) of the wings to the tower (4) in cases where deflection of the wings (8) and other parts of the wind turbine (2) is reduced because the wind speed is lower than the maximum operating wind speed.