GB2602060A

GB2602060A - Wind-turbine and method of operating a wind turbine

Info

Publication number: GB2602060A
Application number: GB2019955.0A
Authority: GB
Inventors: Long Nick
Original assignee: CROSS-FLOW ENERGY Co Ltd; CROSS FLOW ENERGY Co Ltd
Current assignee: CROSS-FLOW ENERGY Co Ltd; CROSS FLOW ENERGY Co Ltd
Priority date: 2020-12-17
Filing date: 2020-12-17
Publication date: 2022-06-22
Also published as: GB202019955D0

Abstract

A wind turbine with a rotor 3 mounted to a hub 4 for rotation about a rotor axis 10 perpendicular to a longitudinal axis of a support tower 2 where the hub is rotatable around the tower allowing passive yawing according to wind direction, and the hub is slidably mounted for movement along the long axis of the tower. The turbine may be a 3-blade HAWT (fig.9A) or a dual 3a/3b, cross-axis, scooped blade 9, shielded 17a/17b, wind turbine with multiple rotors 11a/11b that uses a flow splitter 46 to direct air away from the tower and onto the rotors. The wind turbine may be raised to predetermined locations at 1/2/5 metre spacings by an actuator according to wind speed readings from an anemometer or from other remote wind speed information received by a controller. The sliding or translation of the hub may be aided by rollers (30, fig.7) moving along a track. The tower may also bear communications equipment (fig.5). Also disclosed is a method of operating a wind turbine to vary a height of the rotor according to a wind speed variable, preferably comparing the variable to a maximum or minimum threshold beyond which an actuation occurs.

Description

WIND TURBINE AND METHOD OF OPERATING A WIND TURBINE

[0001] This invention relates to a wind turbine and a method of operating a wind turbine. BACKGROUND [0002] W02020021256 discloses a horizontal axis wind turbine with a rotor mounted to a support tower via a collar, where the collar includes a motor for active yawing of the rotor.

In high wind conditions the rotor can be rotated out of alignment with the wind to prevent the rotor from being damaged.

BRIEF SUMMARY OF THE DISCLOSURE

[0003] In accordance with the present disclosure there is provided a wind turbine comprising a support tower defining a longitudinal axis, a hub, and a rotor mounted to the hub for rotation about a rotor axis perpendicular to the longitudinal axis, wherein the hub is passively rotatable relative to the support tower about the longitudinal axis for passive yawing, and wherein the hub is slidably mounted to the support tower for movement of the hub along the support tower in the direction of the longitudinal axis.

[0004] In examples, when the support tower is mounted to the ground during use of the wind turbine the longitudinal axis is substantially vertical and the rotor axis is substantially horizontal. Accordingly, the wind turbine may be a horizontal axis wind turbine.

[0005] In examples, the wind turbine may further comprise an actuator arranged to slidably move the hub along the support tower in the direction of the longitudinal axis. In examples, the wind turbine may further comprise a controller configured to control the actuator to vary the position of the hub along the support tower according to a wind speed variable.

[0006] In some examples the controller is configured to determine the wind speed variable, for example using an anemometer. In other examples, the controller may be configured to control the actuator based on a control signal received from an external device, and wherein the external device is configured to determine the wind speed variable, for example using an anemometer.

[0007] In examples, the wind turbine may further comprise a communications unit in communication with the controller and an external device, and wherein the controller is configured to receive the wind speed variable and/or a control signal for controlling the actuator from the external device via the communications unit.

[0008] In various examples the wind speed variable comprises at least one of an instantaneous wind speed, an averaged wind speed based on a predetermined time period, and/or or a predicted wind speed. The instantaneous wind speed may be detected by an anemometer mounted on the wind turbine or nearby. The predetermined time period of the averaged wind speed may be between, for example, about 1 minute and about 5 hours, for example between about 30 minutes and about 2 hours. The predicted wind speed may be based on forecast data received from an external source, for example from a weather forecast agency.

[0009] In examples, the controller is configured to position the rotor in one of a plurality of predetermined positions along the support tower based on the wind speed variable. In examples, each predetermined position along the support tower is associated with a range of the wind speed variable, and the controller is configured to position the rotor at the predetermined position corresponding to the wind speed variable.

[0010] It will be appreciated that during use, when the support tower is mounted to the ground, the support tower and the longitudinal axis will be substantially vertical. Accordingly, movement of the rotor along the support tower in the direction of the longitudinal axis causes the height of the rotor above the ground to be varied. Therefore, during normal or low wind conditions the rotor can positioned at a maximum height permitted by the support tower to capture the maximum wind speed available. Also, in high wind conditions, when the wind speed is above a wind speed rating of the rotor or if a moment applied to the rotor and support tower by the wind is too high (and risks overturning the support tower), then the rotor can be lowered closer to the ground to reduce the wind speed incident on the rotor and maintain operation of the rotor and wind turbine. Furthermore, in very high wind conditions, for example during a storm, the rotor can be lowered to the ground surface and secured and/or covered to protect it and the wind turbine from damage.

[0011] Such control over the operating height of the rotor is particularly useful in locations where storms are prevalent that might otherwise damage the wind turbine.

[0012] In examples, the wind turbine may further comprise a yawing member attached to the rotor and arranged such that the rotor is passively yawed by oncoming wind to rotate the rotor into a windward orientation. The yawing member may comprise a vertical panel extending in a leeward direction from the rotor. Additionally or alternatively, the yawing member may comprise a vertical panel or surface of the rotor, for example the side panels described further hereinafter, that acts to rotate the rotor into a windward orientation in response to an oncoming wind flow.

[0013] Passive yawing of the rotor advantageously requires few components and control aspects compared to active yawing, while the capability to raise and lower the rotor along the support tower provides for reducing the wind speed incident on the rotor that might otherwise be controlled through active yawing. Accordingly, the combination of passive yawing and movement of the rotor along the support tower provides for controlling, in particular limiting, the wind speed incident on the rotor while the rotor is passively oriented in a windward direction.

[0014] In examples, the rotor may comprise a plurality of radially extending rotor blades.

The radially extending rotor blades may be fixed to an axle defining the rotor axis, or the radially extending rotor blades may be rotatably mounted to the axle for varying the angle of attack of the radially extending rotor blades (i.e., feathering the rotor blades), providing additional control over the rotational speed of the rotor in response to an oncoming wind flow.

[0015] In other examples, the rotor may comprise a plurality of rotor blades extending substantially perpendicularly to the rotor axis. The plurality of rotor blades may be spaced from the rotor axis and distributed about a circumference of the rotor. The rotor may thereby define a substantially cylindrical volume within the rotor through an oncoming wind flow passes during use of the wind turbine.

[0016] In examples, rotor may comprise an axle and opposing side panels mounted to the axle for rotation about the rotor axis, and the plurality of rotor blades may extend between the opposing side panels. The opposing side panels may act as a yawing member to orientate the rotor in a windward direction, as described above.

[0017] In examples, each of the plurality of rotor blades is arcuate and comprises a concave trailing side and a convex leading side. During use, wind incident on the concave trailing sides generates more resistance than wind incident on the convex leading sides, causing rotation of the rotor in the direction of the concave leading sides. It will be understood that due to the rotational arrangement of the rotor about a horizontal rotor axis, at any time during use of the wind turning at least some of the convex leading sides are moving against the wind flow during a portion of the rotation of the rotor, while simultaneously at least some of the concave trailing sides are moved in the direction of the wind.

[0018] In examples, the rotor blades are arranged such that the concave trailing sides are directed windward at an upper rotational position of the rotor (i.e., when the rotor blades are furthest from the ground during rotation of the rotor), and the convex leading sides are directed windward at a lower rotational position of the rotor (i.e., when the rotor blades are closest to the ground during rotation of the rotor). However, it will be appreciated that the rotor may be configured to rotate in an opposite direction, such that the concave trailing sides are directed windward at a lower rotational position of the rotor, and the convex leading sides are directed windward at an upper rotational position of the rotor.

[0019] In examples, the wind turbine may further comprise a shield arranged on a windward side of the rotor to block the convex leading side of at least one of the rotor blades from an oncoming wind flow. In particular, the shield may be arranged to block the oncoming wind flow from at least some of the convex leading sides of rotor blades moving in a direction against the oncoming wind flow. Accordingly, the shield acts to reduce air resistance on rotor blades moving against the wind, increasing the efficiency of the rotor.

[0020] In examples, the shield may be shaped to substantially match a portion of the circumference of the rotor. In particular, the shield may be shaped as described in detail in W02011018651 or W02020021256, both of which are hereby fully incorporated by 10 reference.

[0021] In particular, the shield may comprise a shield member extending from a leading edge disposed on a windward side of the rotor to a trailing edge disposed towards the leeward side of the rotor. The leading edge may be disposed offset from the rotor axis in the longitudinal direction towards the rotor blades with their convex leading sides directed windward. The trailing edge may be disposed at a position having a larger offset from the rotor axis in the longitudinal direction towards the rotor blades with their convex leading sides directed windward.

[0022] In examples, the shield may further comprise a curved lip disposed in front of the leading edge of the shield member in a windward direction. The curved lip may be spaced from the leading edge of the shield member to define an opening therebetween.

[0023] In examples, the trailing edge may be curved in a direction away from the rotor.

[0024] In examples the shield is shaped to generate a negative relative pressure on the convex leading sides of at least some of the rotor blades, thereby improving the efficiency of the rotor.

[0025] In examples, the shield may further comprise side panels arranged substantially parallel to the longitudinal axis. The side panels may extend between the leading edge to the trailing edge of the shield and in a direction towards the rotor axis. The shield may therefore be arranged to at least partially surround the rotor, particularly on the side of the rotor where the convex leading sides of the rotor blades move in a direction opposite the wind direction during use. The side panels may act as a yawing member to orientate the rotor in a windward direction, as described above.

[0026] In examples, the shield is mounted to the hub, and the rotor is mounted to the shield on an axle supported by the side panels of the shield. Accordingly, the shield and rotor are mounted to the hub.

[0027] In examples, the wind turbine may comprise a first rotor having a plurality of rotor blades arranged on a first side of the support tower, and a second rotor having a plurality of rotor blades arranged on a second side of the support tower, and wherein the first rotor and the second rotor are arranged to rotate about the rotor axis.

[0028] The first and second rotors may be identical. The first and second rotors may be mounted to a common rotor axle, or mounted to separate but coaxial rotor axles. The rotor axle(s) may be offset from the support tower in a leeward direction.

[0029] In examples, the wind turbine may further comprise a flow splitter disposed between the first rotor and the second rotor and arranged to deflect oncoming wind flow away from the support tower and towards the first rotor and the second rotor.

[0030] In examples, the hub may comprise a sliding portion that is slidably attached to the support tower for movement in the longitudinal direction, and a rotatable portion to which the rotor is mounted, the rotatable portion being rotatably attached to the sliding portion for rotation about the longitudinal axis.

[0031] In examples, the sliding portion may comprise one or more rollers arranged to engage one or more corresponding tracks on the support tower for movement of the sliding portion along the support tower.

[0032] In examples, the wind turbine may further comprise a communications transceiver mounted to the support tower. In examples, the support tower may comprise an end portion extending beyond a maximum position of the rotor, and the communications transceiver may be mounted to the end portion of the support tower.

[0033] In one aspect, the present disclosure provides a wind turbine comprising a support tower defining a longitudinal axis, a first rotor and a second rotor, the first and second rotors being mounted to the hub for rotation about a rotor axis perpendicular to the longitudinal axis, and a flow splitter disposed between the first rotor and the second rotor and arranged to deflect oncoming wind flow away from the support tower and towards the first rotor and the second rotor.

[0034] In examples, the first and second rotors may be identical. The first and second rotors may be mounted to a common rotor axle, or mounted to separate but coaxial rotor axles. In examples, the rotor axle(s) may be offset from the support tower in a leeward direction. The first and second rotors may be passively yawed. The first and second rotors may be in fixed arrangement with each other. In examples, the first and second rotors may be rotatably mounted to the support tower for rotation about the longitudinal axis, and the first rotor and/or second rotor may comprise a yawing member arranged to yaw the first and second rotors about the longitudinal axis such that the first and second rotors are directed windward.

[0035] In examples, the wind turbine of this aspect may further include the shield described hereinbefore. In examples, the wind turbine of this aspect may comprise any of the other features of the wind turbine described hereinbefore.

[0036] In another aspect of the invention there is provided a method of operating a wind turbine, the wind turbine comprising: a support tower mounted to the ground and defining a substantially vertical axis, a rotor configured to be turned by wind for generating electrical energy, wherein the rotor is mounted to the support tower for movement of the rotor along the support tower in the direction of the substantially vertical axis, and an actuator configured to move the rotor along the support tower in the direction of the substantially vertical axis, wherein the method comprises controlling the actuator to move the rotor along the support tower to vary a height of the rotor according to a wind speed variable.

[0037] In various examples the wind speed variable comprises at least one of an instantaneous wind speed, an averaged wind speed based on a predetermined time period, and/or or a predicted wind speed. The instantaneous wind speed may be detected by an anemometer mounted on the wind turbine or nearby. The predetermined time period of the averaged wind speed may be between, for example, about 1 minute and about 5 hours, for example between about 30 minutes and about 2 hours. The predicted wind speed may be based on forecast data received from an external source, for example from a weather forecast agency.

[0038] In some examples the method includes determining the wind speed variable, for example detecting the wind speed using an anemometer. In other examples, the method may include receiving a control signal and/or the wind speed variable from an external device. In examples, the control signal is based on the wind speed variable. The external device may determine the wind speed variable, for example using an anemometer.

[0039] In examples, the method may comprise receiving the wind speed variable and/or a control signal for controlling the actuator from the external device via a communications unit, for example a wireless communications unit.

[0040] In examples, the method may comprise positioning the rotor at a maximum distance from the ground if the wind speed variable is less than a predetermined threshold.

[0041] In examples, the method may comprise positioning the rotor at a distance from the ground that is less than the maximum distance when the wind speed variable exceeds the predetermined threshold.

[0042] In examples, the method may comprise moving the rotor when the wind speed variable exceeds the predetermined threshold for a predetermined period of time, for example 1 minute, 5 minutes or 10 minutes.

[0043] In examples, the method may comprise positioning the rotor at a distance from the ground that is proportional to the wind speed variable. In examples, the method may comprise positioning the rotor at a distance from the ground that is proportional to the wind speed variable when the wind speed variable is between a first predetermined threshold and a second predetermined threshold. For example, the first predetermined threshold may be based on the maximum rated wind speed for operation of the rotor at the maximum distance from the ground, and the second predetermined threshold may be based on the maximum rated wind speed for any operation of the rotor. If the wind speed variable exceeds the second predetermined threshold then the method may include positioning the rotor at a minimum height such as ground level.

[0044] In examples, the method may include positioning the rotor in one of a plurality of predetermined positions along the support tower based on the wind speed variable. In examples, each predetermined position along the support tower is associated with a range of the wind speed variable, and the method includes positioning the rotor at the predetermined position corresponding to the wind speed variable.

[0045] Accordingly, the wind turbine can be operated with the rotor at the maximum height as default. In case of moderately higher winds that cause the wind speed variable to exceed the first threshold value the wind turbine can continue to be operated with the rotor at a reduced height. Further, in the case of very high winds (e.g., a storm) that cause the wind speed variable to exceed a second threshold the rotor can be grounded.

[0046] Advantageously, the method of operating the wind turbine means that the wind turbine can continue to operate even in wind speeds that would otherwise cause the wind turbine to have to stop operating due to exceeding the wind speed rating of the rotor or due to the overturning moment applied to the support tower. This is particularly important for a passively yawed rotor that typically has no other mechanism for reducing the wind speed incident on the rotor, and so in moderately high wind speeds the rotor has to be stopped, and in very high wind speeds the rotor may be damaged.

BRIEF DESCRIPTION OF THE DRAWINGS

[0047] Embodiments of the invention are further described hereinafter with reference to the accompanying drawings, in which: FIG. 1 shows a perspective view of a wind turbine, FIGS. 2A and 2B show front and rear perspective views of the rotor and the hub of the wind turbine of FIG. 1, FIG. 3 shows a top view of the rotor and the hub of the wind turbine of FIG. 1, FIG. 4 shows a perspective view of the rotor of the wind turbine of FIG. 1, FIG. 5 shows a rotor blade of the win turbine of FIG. 1, FIGS. 6A and 63 show the shield of the wind turbine of FIG. 1, FIGS. 7A and 73 show the hub of the wind turbine of FIG. 1, FIG. 8 shows the wind turbine of FIG. 1 with the rotor in a lowered position, FIGS. 9A and 93 show an alternative example wind turbine having radial rotor blades, FIG. 10 schematically illustrates a controller of the wind turbine of FIG. 1 or FIGS. 9A and 9B, and FIG. 11 illustrates a method of controlling a wind turbine.

DETAILED DESCRIPTION

[0048] The wind turbine 1 illustrated in FIG. 1 has a support tower 2, a rotor 3, and a hub 4. The support tower 2 is mounted to the ground 5 and extends in a vertical direction. The support tower has a longitudinal axis 6 that is substantially vertical when the support tower 2 is mounted to the ground 5.

[0049] The support tower 2 may be mounted to a base that is secured to the ground 5, for example a foundation. Alternatively, an end of the support tower may be pile driven into the ground 5.

[0050] As described further hereinafter, the rotor 3 comprises a horizontal axis type rotor having a plurality of rotor blades arranged to be turned by wind flow incident on the rotor.

[0051] The rotor 3 is mounted to the support tower 2 via the hub 4. The hub 4 permits passive rotation of the rotor 3 about the longitudinal axis 6 such that the rotor 3 is passively yawed. In particular, as described further hereinafter, the rotor 3 may include a yawing member arranged to be turned by the wind and orientated in a windward direction.

[0052] As described further hereinafter, the hub 4 is also slidably mounted to the support tower 2 for moving of the rotor 3 along the support tower 2 in the direction of the longitudinal axis 6. Such movement of the rotor 3 varies the height of the rotor 3 above the ground 5 during operation, as described further hereinafter.

[0053] Typically due to the surface friction effect the wind speed at or near the ground 5 will be less than the wind speed even a few metres spaced from the ground 5. This is commonly called the wind speed gradient. Accordingly, for a constant wind speed at the sit of the wind turbine 1, the wind speed incident on the rotor 3 can be varied by moving the rotor 3 up and down the support tower 2. As described further hereinafter, the rotor 3 may be raised and lowered according the wind speed to protect the rotor 3 and wind turbine 1 from damage by high winds while maintaining operation when possible. Movement of the rotor 3 up and down the support tower 2 also allows for less deep mounting of the support tower 2 to the ground 5, for example by a foundation, and may permit a smaller support tower 2, because in high winds the rotor 3 can be lowered to reduce the stress applied to the support tower 2 by the wind acting on the rotor 3. This reduces cost, materials and installation time of the wind turbine 1.

[0054] As shown in FIG. 1, the support tower 2 includes an extension 7 forming an end portion that extends above the rotor 3. In examples, a communications transceiver 8 may be mounted to the extension 7. The communications transceiver 8 may comprise a cellular communications transceiver and thus the support tower 2 may act as a cellular base station. Therefore, in examples the wind turbine 1 can be used as a telecommunications base station, where the rotor 3 provides electrical power for the communications transceiver 8. Further electrical energy sources may also be provided, for example one or more photovoltaic cells, generators, or connection to an electricity distribution network.

[0055] FIGS. 2A to 5 illustrate the rotor 3 and hub 4 in more detail. As shown, the rotor 3 includes a plurality of rotor blades 9 arranged to rotate about a rotor axis 10. The rotor axis 10 is perpendicular to the longitudinal axis 6 shown in FIG. 1, so the wind turbine 1 is a horizontal axis wind turbine.

[0056] In particular, as seen most clearly in FIGS. 3 and 4, the rotor 3 comprises a first rotor 3a and a second rotor 3b. The first and second rotors 3a, 3b are spaced apart and as shown in FIGS. 1, 2A and 23 are arranged on opposing sides of the support tower 2. Each of the first and second rotors 3a, 3b comprises a plurality of rotor blades 9 that extend parallel to the rotor axis 10. The first and second rotors 3a, 3b each comprise spaced side panels 11a, 11 b and the rotor blades 9 extend between the side panels 11a, 11b. The side panels 11a, 1lb are rotatably mounted to an axle 12 that defines the rotor axis 10.

[0057] In some examples, as shown, the first and second rotors 3a, 3b share a common axle 12. In other examples, the first and second rotors 3a, 3b are mounted on separate coaxial axles 12.

[0058] The first and second rotors 3a, 3b, including the side panels 11a, llb and the rotor blades 9, are rotatable about the rotor axis 10 on the or each axle 12.

[0059] As illustrated, the side panels 11a, llb are planar panels that define side walls of the first and second rotors 3a, 3b. In other examples, the side panels 11a, 11 b may comprise struts or a lattice framework rather than a panel.

[0060] As illustrated in FIG. 4, a generator 13 is mounted between the first and second rotors 3a, 3b. In particular, the generator 13 is mounted to the hub 4 and is rotatably connected to the axle 12 via a pulley 14 such that rotation of the first and second rotors 3a, 3b rotates the generator 13 and generates electrical energy. The electrical energy may be provided to the communications transceiver (8, see FIG. 1), and/or to a storage such as a battery, and/or to an electricity distribution network.

[0061] However, it will be appreciated that in some examples the generator 13 may be replaced by another work unit, for example a pump, or a pulley arrangement may be provided to transfer the rotational work generated by the rotor 3 away from the wind turbine 1.

[0062] As shown in FIG. 4, in each of the first and second rotors 3a, 3b the rotor blades 9 are spaced about the circumference of the rotor 3. In the illustrated example there are five rotor blades 9 in each of the first and second rotors 3a, 3b, but it will be appreciated that more or fewer rotor blades 9 may be provided, depending at least in part on the overall size of the rotor 3 and wind turbine 1.

[0063] Each of the first and second rotors 3a, 3b defines a substantially cylindrical volume 20 within the first and second rotors 3a, 3b, and oncoming wind flow passes through the volume 20 during use as described further hereinafter.

[0064] As shown in FIG. 5, each rotor blade 9 has an arcuate cross-section and includes a concave side 15 and a convex side 16. As shown in FIG. 4, the rotor blades 9 are arranged such that the concave sides 15 of each rotor blade 9 are directed in the same circumferential direction with respect to the rotor axis 10. During use, the concave sides 15 are concave trailing sides 15 and the convex sides 16 are convex leading sides 16. That is, as the rotor 9 rotates the rotor blades 9 move with the convex leading sides 16 ahead of the concave trailing sides 15.

[0065] During use, as will be described further hereinafter, the rotor 3 is directed windward and wind is incident on the concave trailing sides 15 of some of the rotor blades 9. Wind may also be incident on the convex leading sides 16 of some of the rotor blades 9. The concave trailing sides 15 will generate greater wind resistance than the convex leading sides 16 and so the rotor 3 will rotate in the direction of the convex leading sides 16.

[0066] In the arrangement illustrated in FIG. 4 the wind direction is indicated by arrow 21, and the rotational direction of the rotor 3 is indicated by arrow 22. That is, the rotor blades 9 disposed at the top of the rotor 3 (i.e., furthest from the ground) have their concave trailing sides 15 directed windward and so the rotor 3 rotates as indicated by arrow 22. During rotation, as the rotor blades 9 pass the lower part of the rotor 3 the convex leading sides 16 are directed windward. However, it will be appreciated that the rotor blades 9 could be arranged in the opposite direction for opposite rotation of the rotor 3.

[0067] As shown in FIGS. 2A, 2B, 3, 6A and 6B, the wind turbine 1 further includes a shield 17. The shield 17 is illustrated without the first and second rotors 3a, 3b in FIG. 6A for clarity, and FIG. 6B shows a side view with the shield 17 and rotor 3 visible.

[0068] As illustrated, the shield 17 has two parts -a first shield part 17a corresponding to the first rotor 3a and a second shield part 17b corresponding to the second rotor 3b. The first and second shield parts 17a, 17b are the same.

[0069] Each of the first and second shield parts 17a, 17b has a shield member 18 that acts as a wind blocking member. The shield member 18 is arranged to block an incoming wind flow from being incident on the convex leading sides 16 of the rotor blades 9 that are moving in a direction generally opposite to the wind direction, in this example at the bottom of the rotation of the rotor 3.

[0070] As shown in FIG. 6B, the shield member 18 has a leading edge 23 and a trailing edge 24. The leading edge 23 is disposed offset from the rotor axis 10 in the longitudinal direction (6, see FIG. 1) towards the rotor blades 9b with their convex leading sides directed windward. The trailing edge 24 is disposed at a position having a larger offset from the rotor axis 10 in the longitudinal direction (6, see FIG. 1) towards the rotor blades 9b with their convex leading sides directed windward. The shield member 18 is curved and at least partly shaped to match the circumference of the rotor 3.

[0071] Therefore, the shield member 18 is disposed on a windward side of the rotor blades 9b that are moving against the wind direction 21, while wind is allowed to meet the rotor blades 9a that are moving in the wind direction 21.

[0072] As shown in FIG. 6B, the shield 17 has a curved lip 19 disposed in front of the leading edge 23 of the shield member 18 in a windward direction. The curved lip 19 is spaced from the leading edge 23 of the shield member 18 and an opening 25 is defined between. The curved lip 19 is shaped to guide wind flow through the opening 25 and along the shield member 18, which causes less wind flow turbulence than if the wind flow were allowed to directly flow against the shield member 18 close to the leading edge 23. Reducing turbulence in the vicinity of the leading edge 23 prevents disturbances to the wind flow moving through the rotor 3, particularly through the internal volume 20, thereby improving the efficiency of the rotor 3.

[0073] The trailing edge 24 of the shield 17 is curved in a direction away from the rotor 3 to direct air flowing over the shield member 18 away from the rotor blades 9. This arrangement creates a reduced pressure on the inside of the shield member 18 which helps reduce air resistance on the rotor blades 9b moving against the wind direction 21, thereby improving the efficiency of the rotor 3.

[0074] As shown in FIGS. 2B, 6A and 6B, the shield 17, in particular the first and second shield parts 17a, 17b, comprises opposing side panels 26a, 26b. The side panels 26a, 26b are arranged either side of the rotor 3, in particular either side of the first and second rotor portions 3a, 3b. The side panels 26a, 26b extend between the leading edge 23 and the trailing edge 24, and also to the curved lip 19 as shown in FIG. 6B. The side panels 26a, 26b extend from the shield member 18 towards the rotor axis 10 and thereby partially surround the rotor 3. In particular, the shield member 18 and side panels 26a, 26b at least partially surround the portion of the rotor 3 that is rotating against the wind direction 21 during use. The side panels 26a, 26b thereby act to further protect the rotor blades 9b moving against the wind direction 21 from incoming wind, thereby improving the efficiency of the rotor 3.

[0075] The side panels 26a, 26b also provide vertical surfaces that may act as a yawing member to rotate the rotor 3 about the longitudinal axis (6, see FIG. 1) into a windward orientation. In particular, the side panels 26a, 26b are substantially vertical planar during use, so when exposed to the wind flow would cause rotation of the rotor 3 and the hub 4 about the longitudinal axis (6, see FIG. 1), moving the rotor 3 into a windward orientation.

[0076] As shown in FIGS. 6A and 6B, the shield 17, in particular both shield parts 17a, 17b, are mounted to a mounting bar 27, which is attached to the hub 4. As shown in FIGS. 2A and 2B, the rotor axle(s) 12 is/are mounted to the side panels 26a, 26b of the shield 17.

Accordingly, in the illustrated examples the rotor 3 is mounted to the hub 4 via the shield 17. However, it will be appreciated that the rotor 3 and shield 17 may be mounted to the hub 4 in various ways.

[0077] As shown in FIGS. 2A, 2B, 3 and 6A, the wind turbine 1 also includes a flow splitter 46 disposed between the first rotor 3a and the second rotor 3b and arranged to deflect oncoming wind flow away from the support tower 2. The flow splitter 46 may direct the deflected wind flow towards the first rotor 3a and the second rotor 3b to increase fluid flow through the first and second rotors 3a, 3b, thereby improving operation of the wind turbine 1. As shown in FIG. 6A, the flow splitter 46 comprises inclined surfaces 47a, 47b that diverge from a windward point 48 to split the wind flow. The flow splitter 46 may be mounted to the shield 17.

[0078] In examples, the first and second rotors may be identical. The first and second rotors may be mounted to a common rotor axle, or mounted to separate but coaxial rotor axles. In examples, the rotor axle(s) may be offset from the support tower in a leeward direction. The first and second rotors may be passively yawed. The first and second rotors may be in fixed arrangement with each other. In examples, the first and second rotors may be rotatable mounted to the support tower for rotation about the longitudinal axis, and the first rotor and/or second rotor may comprise a yawing member arranged to yaw the first and second rotors about the longitudinal axis such that the first and second rotors are directed windward.

[0079] [0080] As shown in FIGS. 7A and 7B, the hub 4 includes a slidable portion 28 and a rotatable portion 29. The rotatable portion 29 is rotatably connected to the slidable portion 28, for example by a bearing, bushing, or roller arrangement. The rotatable portion 29 is mounted for rotation about the longitudinal axis (6, see FIG. 1).

[0081] The slidable portion 28 is slidably attached to the support tower 2. In particular, the slidable portion 28 has a plurality of rollers 30 arranged in pairs aligned in the longitudinal direction (6, see FIG. 1). The rollers 30 engage tracks 31 provided on the support tower 2, as shown in FIG. 7B. The rollers 30 and tracks 31 enable sliding of the hub 4 up and down the support tower 2. The rollers 30 and tracks 31 also prevent rotation of the slidable portion 28 of the hub 4 relative to the support tower 2 about the longitudinal axis (6, see FIG. 1).

[0082] As shown in FIG. 7B, the shield 17 (and by extension the rotor 3) is mounted to the rotatable portion 29, so can be rotated about the longitudinal axis (6, see FIG. 1) for yawing the rotor 3 [0083] The rotatable portion 29 is freely rotatable relative to the slidable portion 28 of the hub. In particular, there is no actuator, limiter or controller that limits or controls rotation of the rotatable portion 29 relative to the slidable portion 28. Accordingly, the rotor 3 is able to passively yaw and maintain a windward orientation.

[0084] As described above, the side panels 11a, 11 b of the rotors 3a, 3b and/or the side panels 26a, 26b of the shield 17 may act as yawing members that, when exposed to an incoming wind, act to rotate the hub 4 and rotor 3 into a windward orientation.

[0085] As shown in FIG. 8, an actuator 32 is provided to move the hub 4, shield 17 and rotor 3 up and down the support tower 2. In examples, the actuator 32 is a winch and a winch cable and pulley arrangement is provided within the support tower 2 to winch the hub 4 up and down the support tower 2. In particular, a pulley may be provided at an upper end of the support tower, and the winch cable may be attached to the hub 4, routed over the pulley and down the support tower 2 to the winch. Accordingly, winding or unwinding the winch cable from the winch 32 will raise and lower the hub 4, respectively.

[0086] FIG. 8 illustrates the rotor 3 in a grounded position, where the actuator 32 has moved the hub 4, together with the shield 17 and rotor 3, to the ground 5.

[0087] FIGS. 9A and 93 show an alternative wind turbine 1, in this example with a rotor 3 having radially extending rotor blades 33. In this example, the rotor blades 33 extend radially from a rotor shaft 34, which is mounted to the support tower 2 via a hub 35. The rotor blades 33 extend radially and are turned by the wind to rotate the rotor shaft 34. The hub 35 is mounted to the support tower 2 for rotation about the support tower for yawing, and is also slidably mounted to the support tower 2 for raising and lowering the position of the rotor 3 along the support tower 2.

[0088] As with the previous examples, the hub 35 is freely rotatably about the support tower 2 to provide passive yawing of the rotor 3 into a windward orientation. As illustrated, a yawing member 36 may be provided for maintaining a windward orientation of the rotor 20 3.

[0089] The hub 35, together with the rotor 3, are movable up and down the support tower 3 by an actuator, for example a winch similar to as previously described.

[0090] The rotor blades 33 may be rotatably mounted to the rotor shaft 34 for feathering.

[0091] Similarly to the previous examples, the position of the rotor 3 along the support tower 2 can be varied according to the wind speed. Lowering the height of the rotor 3 along the support tower 2, as shown in FIG. 9B, reduces the wind speed incident on the rotor 3 due to the surface friction effect that creates a wind speed gradient close to the ground. Accordingly, in winds that exceed the maximum wind speed rating of the rotor 3, the rotor 3 can be lowered while maintaining operation, and if the wind speed exceeds a predetermined threshold then the rotor 3 can be lowered to a minimum height position to protect it from the wind. At the minimum height position the rotor 3 may be covered, fixed, or otherwise protected.

[0092] The wind turbines 1 described above may be operated so that the position of the hub 4 and rotor 3 above the ground is based on the wind speed. During normal wind speeds the rotor 3 can be positioned at a maximum height from the ground 5 so that the rotor 3 is exposed to the maximum available wind speed and the most electrical energy is generated. In higher winds, where the rotor 3 cannot be operated at the maximum height because the wind speed at that height exceeds a threshold (e.g., based on the overturning moment of the support tower 2 or the wind speed rating of the rotor 3), the rotor 3 can be moved down the support tower 2 towards the ground 5 to reduce the wind speed incident on the rotor 3. In very high winds, for example during a storm, the rotor 3 can be moved to a minimum height, as shown in FIGS. 8 and 9B, in which the rotor 3 is as close to the ground 5 as possible and therefore protected against the higher winds and can be secured or covered.

[0093] Accordingly, the support tower 2 does not need to be designed to support the rotor 3 at the maximum height during high winds, so can be designed with a lower maximum overturning moment. This may permit smaller or shallower foundations or piles, reducing the cost of the wind turbine 1 and allowing installation in less stable ground. Additionally or alternatively, the support tower 2 can be thinner, (i.e., a smaller section) because it doesn't have to be rated to the overturning moment of the rotor at maximum height during the maximum expected winds.

[0094] In addition, the ability to move the rotor 3 up and down the support tower 2 is beneficial for installation and maintenance, as the rotor 3 can be installed at or lowered to close to ground level rather than operators having to be raised to the height of the rotor.

[0095] FIG. 10 illustrates a control system 37 for a wind turbine 1 as described above with reference to FIGS. 1 to 9B. In particular, FIG. 10 illustrates a control system 37 for a wind turbine 1 that has a substantially vertical support tower 2 and a passively yawed rotor 3 that is movable along the support tower 2 to vary the height of the rotor 3. As described above, varying the height of the rotor 3 changes the wind speed incident on the rotor 3 due to surface friction created by the ground. In particular, moving the rotor 3 closer to the ground 5 reduces the wind speed incident on the rotor 3.

[0096] As shown in FIG. 10, the control system 37 includes a controller 38 and an actuator 39 arranged to move the rotor 3 along the support tower 2, for example a winch as previously described. The controller 38 is configured to control the actuator 39 to move the rotor 3 along the support tower 2.

[0097] In examples, the control system 37 also includes an anemometer 40. The anemometer 40 may be arranged on the support tower (2, see FIGS. 1 and 9A) or nearby the wind turbine (1, see FIGS. 1 and 9A). The control system 37 may have more than one anemometer 40. For example, a plurality of anemometers 40 may be spaced along the support tower (2, see FIGS. 1 and 9A) at different heights, and/or nearby the wind turbine (1, see FIGS. 1 and 9A). In some examples, an anemometer 40 is mounted to the hub (4, see FIGS. 1 and 9A) and so measures wind speed incident on the rotor (3, see FIGS. 1 and 9A). Additionally or alternatively, an anemometer 40 may be mounted to the support tower (2, see FIGS. 1 and 9A), for example at or near the top of the support tower (2, see FIGS. 1 and 9A). In some examples, an anemometer 40 is mounted to the support tower (2, see FIGS. 1 and 9A) at the maximum height position of the hub (4, see FIGS. 1 and 9A). Accordingly, the or each anemometer 40 is arranged to measure an instantaneous wind speed at or near the wind turbine (1, see FIG. 1), in particular at or near the rotor (3, see FIGS. 1 and 9A).

[0098] The controller 38 is configured to receive wind speed information from the or each anemometer 40. The controller is configured to determine, in particular calculate, a wind speed variable based on the received wind speed information. In some examples the controller 38 calculates a wind speed variable based on the instantaneous wind speed measured by the or each anemometer 40. The wind speed variable may be based on the maximum wind speed detected by a plurality of anemometers 40. In some examples, the wind speed variable may be the wind speed information, i.e., the detected wind speed.

[0099] In other examples, the controller 38 calculates an average wind speed over a predetermined time period, for example between 5 minutes and 1 hour, for example about 10 minutes. In some examples, the controller 38 calculates a wind speed variable based on a combination of the instantaneous measure wind speed and an averaged wind speed, for example by applying a higher weight to the instantaneous wind speed when calculating an average.

[00100] In examples, the control system 37 additionally or alternatively includes a receiver 41. The controller 38 is configured to receive wind speed information, or a wind speed variable, via the receiver 41. For example, the controller 38 may be configured to receive measured or predicted wind speed information from an external device, for example a server. The controller 38 may be configured to control the actuator 39 based on a received wind speed variable or received wind speed information, or it may be configured to calculate a wind speed variable based on received wind speed information and to control the actuator 39 based on the calculated wind speed variable.

[00101] In some examples, a plurality of wind turbines are provided in a network. The plurality of wind turbines may be geographically close to each other. In such examples, a single control system 37 may be configured to control each of the wind turbines, in particular the actuator 39 of each wind turbine. In such examples, the control system 37 may comprise a plurality of anemometers 40, for example at least one anemometer 40 on or nearby each wind turbine. The controller 38 may receive wind speed information from the plurality of anemometers 40, calculate a wind speed variable, and control the actuator 39 accordingly. The controller 38 may calculate a wind speed variable for each wind turbine individually, or calculate a wind speed variable for groups of, or all of, the wind turbines.

[00102] In examples, the controller 38 may communicate with the or each actuator 39 and the or each anemometer 40 by a wireless connection, for example via the receiver 40, which may be a transceiver.

[00103] The controller 38 may be configured to control the actuator 39 position based on the determined, calculated, or received wind speed variable. In examples, as described below, the controller 38 is configured to compare the wind speed variable to one or more predetermined values and control the actuator 39 based on if the wind speed variable is above or below a predetermined value. In examples, the controller 38 may be configured to control the actuator 39 proportionally to the determined, calculated, or received wind speed variable. In examples, the controller 38 may comprise a proportional and integrated (PI) controller, a proportional and derivative (PD) controller, or a proportional integral derivative (PID) controller.

[00104] In examples, the controller 38 may be configured to control the actuator 39 to position the rotor 3 in one of a plurality of predetermined positions based on the determined, calculated, or received wind speed variable. In particular, the rotor 3 may be moved to a predetermined position along the support tower 2 based on the wind speed, as set out in more detail below.

[00105] In examples, the controller 38 and optionally the actuator 39 may be powered by the rotor (3, see FIGS. 1 and 9A), in particular a generator (13, see FIG. 3) coupled to the rotor (3, see FIGS. 1 and 9A). In examples, a secondary power source, for example a photovoltaic panel or generator, is provided to power the controller 38 and actuator 39 when the power generated by the rotor 3 is not sufficient, for example if the wind speed is low.

[00106] FIG. 11 illustrates a method 42 of controlling a wind turbine, for example the wind turbines 1 described above with reference to FIGS. 1 to 9B. The method 42 may be performed by the control system 37 described with reference to FIG. 10, in particular the method 42 may be performed by the controller 28 of the control system 37.

[00107] The method 42 includes determining, calculating, or receive a wind speed variable 43. In examples, the method 42 includes determining or calculating the wind speed variable 43 based on an instantaneous wind speed, for example measured by one or more anemometers (40, see FIG. 10). The wind speed variable may be based on a maximum instantaneous wind speed where there is more than one anemometer. The wind speed variable may be the measured wind speed.

[00108] In other examples, the method 42 includes calculating the wind speed variable 43 based on an average wind speed over a predetermined time period, for example between about 1 minute and about 5 hours, or between about 5 minutes and about 2 hours, for example about 10 minutes. In some examples, the method 42 includes calculating the wind speed variable 43 based on a combination of an instantaneous measured wind speed and an averaged wind speed, for example by applying a higher weight to an instantaneous or recent wind speed measurement when calculating an average.

[00109] In other examples, the method 42 may include receiving, for example from an external device via a receiver (41, see FIG. 10), a wind speed variable or wind speed information used to calculate the wind speed variable 43. In some examples, the wind speed variable is based on a forecast. In other examples, the received wind speed variable or wind speed information is from a network of wind turbines and/or anemometers.

[00110] The method 42 further includes comparing the determined or received wind speed variable to one or more predetermined thresholds 44. Comparing the determined or received wind speed variable to one or more predetermined thresholds 44 may include a temporal factor, for example determining that the determined or received wind speed variable exceeds a predetermined threshold if the wind speed variable is greater or less than the predetermined threshold for a set period of time, for example 1 minute, 5 minutes, or 10 minutes.

[00111] In particular, the method 42 may include comparing the wind speed variable 43 to a first predetermined threshold. The first predetermined threshold is based on the maximum wind speed for operating the rotor at the maximum height. That is, the first predetermined threshold is based on one or both of: a maximum wind speed rating for the rotor, and/or a maximum overturning moment of the support tower. The first predetermined threshold is based on the lower of these factors. Accordingly, the first predetermined threshold corresponds to a wind speed at which the rotor should no longer be operated at the maximum height of the support tower, but may still be operated at a lower height.

[00112] In further examples, the method 42 includes comparing the wind speed variable 43 to a second predetermined threshold. The second predetermined threshold is greater than the first predetermined threshold. For example, the second predetermined threshold may correspond to a maximum wind speed rating for the rotor at any height. That is, the second predetermined threshold is a maximum operating wind speed of the wind turbine.

The second predetermined threshold may correspond to very high winds, for example a storm.

[00113] The method 42 also includes, based on the comparison of the wind speed variable and the first and/or second predetermined threshold, controlling the actuator (39, see FIG. 10) to vary the position of the rotor (3, see FIGS. 1 and 9A) along the support tower (2, see FIGS. 1 and 9A).

[00114] In particular, if the wind speed variable is less than the first predetermined threshold (i.e., if the wind speed does not preclude operating the rotor at the maximum height on the support tower) then the method includes controlling the actuator to position the rotor 3 at the maximum height on the support tower. Accordingly, when the wind speed permits that the rotor is operated at maximum height.

[00115] In examples, the method 42 may include controlling the actuator to vary the position of the rotor if the wind speed variable exceeds the predetermined threshold for a set time period, for example 1 minute, 5 minutes or 10 minutes.

[00116] Further, if the wind speed variable exceeds the first predetermined threshold then the method 42 includes controlling the actuator to move the rotor along the support tower, towards the ground, to lower the wind speed incident on the rotor.

[00117] Further, if the wind speed variable exceeds the second predetermined threshold (i.e., if the wind speed exceeds the maximum wind speed rating for the wind turbine), then the method 42 includes controlling the actuator to move the rotor to a minimum height position, i.e., as close to the ground as possible.

[00118] In examples, if the wind speed variable were between the first and second predetermined thresholds then the method 42 may include controlling the actuator to position the rotor between the minimum and maximum positions along the support tower. The position of the rotor may be proportional to the wind speed variable between the first and second predetermined thresholds.

[00119] In other examples, the method 42 may include controlling the actuator to position the rotor at one of a plurality of predetermined positions between the maximum and minimum heights along the support tower based on the wind speed variable. For example, if the wind speed variable is between the first and second predetermined thresholds then the method 42 may comprise positioning the rotor at one of a plurality of predetermined positions between the maximum and minimum heights along the support tower based on the wind speed variable. The plurality of predetermined positions along the support tower may be spaced apart by, for example, 1 metre, 2 metres, or 5 metres, and each of the plurality of predetermined positions is associated with a range of the wind speed variable. Accordingly, the method 42 may comprise moving the rotor to a particular predetermined position if the wind speed variable is within the range associated with that predetermined position. Predetermined positions towards the top of the support tower (i.e., further from the ground) are associated with lower wind speeds than predetermined positions towards the bottom of the support tower.

[00120] Accordingly, the method provides for controlling the position of the rotor along the support tower based on the wind speed variable, and in particular based on comparison of the wind speed variable to one or more predetermined thresholds. Moving the rotor along the support tower provides for changing the wind speed incident on the rotor due to lower wind speeds closer to the ground caused by surface friction. Accordingly, movement of the rotor along the support tower provides a mechanism to ensure that the rotor can be protected against excessively high wind speeds, and ensures that the rotor can be operated in a greater range of wind speeds, which would otherwise not be possible for a passively yawed rotor.

[00121] Throughout the description and claims of this specification, the words "comprise" and "contain" and variations of them mean "including but not limited to", and they are not intended to (and do not) exclude other components, integers or steps. Throughout the description and claims of this specification, the singular encompasses the plural unless the context otherwise requires. In particular, where the indefinite article is used, the specification is to be understood as contemplating plurality as well as singularity, unless the context requires otherwise.

[00122] Features, integers, characteristics or groups described in conjunction with a particular aspect, embodiment or example of the invention are to be understood to be applicable to any other aspect, embodiment or example described herein unless incompatible therewith. All of the features disclosed in this specification (including any accompanying claims, abstract and drawings), and/or all of the steps of any method or process so disclosed, may be combined in any combination, except combinations where at least some of such features and/or steps are mutually exclusive. The invention is not restricted to the details of any foregoing embodiments. The invention extends to any novel one, or any novel combination, of the features disclosed in this specification (including any accompanying claims, abstract and drawings), or to any novel one, or any novel combination, of the steps of any method or process so disclosed.

Claims

CLAIMSA wind turbine comprising: a support tower defining a longitudinal axis, a hub, and a rotor mounted to the hub for rotation about a rotor axis perpendicular to the longitudinal axis, wherein the hub is passively rotatable relative to the support tower about the longitudinal axis for passive yawing, and wherein the hub is slidably mounted to the support tower for movement of the hub along the support tower in the direction of the longitudinal axis.
2. The wind turbine of claim 1, further comprising an actuator arranged to slidably move the hub along the support tower in the direction of the longitudinal axis.
3. The wind turbine of claim 2, further comprising a controller configured to control the actuator to vary the position of the hub along the support tower according to a wind speed variable.
4. The wind turbine of claim 3, wherein the wind speed variable comprises at least one of: an instantaneous wind speed, an averaged wind speed based on a predetermined time period, and/or or a predicted wind speed.
5. The wind turbine of claim 3 or claim 4, further comprising a communications unit in communication with the controller and an external device, and wherein the controller is configured to receive the wind speed variable and/or a control signal for controlling the actuator from the external device via the communications unit.
6. The wind turbine of any preceding claim, further comprising a yawing member attached to the rotor and arranged such that the rotor is passively yawed by oncoming wind to rotate the rotor into a windward orientation.
7. The wind turbine of any preceding claim, wherein the rotor comprises a plurality of radially extending rotor blades.
8. The wind turbine of any of claims 1 to 6, wherein the rotor comprises a plurality of rotor blades extending substantially perpendicularly to the rotor axis.
9. The wind turbine of claim 8, wherein the plurality of rotor blades are spaced from the rotor axis and distributed about a circumference of the rotor.
10. The wind turbine of claim 9, wherein the rotor comprises an axle and opposing side panels mounted to the axle for rotation about the rotor axis, and wherein the plurality of rotor blades extend between the opposing side panels.
11. The wind turbine of claim 9 or claim 10, wherein each of the plurality of rotor blades is arcuate and comprises a concave trailing side and a convex leading side.
12. The wind turbine of claim 11, further comprising a shield arranged on a windward side of the rotor to block the convex leading side of at least one of the rotor blades from an oncoming wind flow.
13. The wind turbine of claim 12, wherein the shield is shaped to substantially match a portion of the circumference of the rotor.
14. The wind turbine of claim 12 or claim 13, wherein the shield further comprises side panels arranged substantially parallel to the longitudinal axis.
15. The wind turbine of any preceding claim, comprising a first rotor having a plurality of rotor blades arranged on a first side of the support tower, and a second rotor having a plurality of rotor blades arranged on a second side of the support tower, and wherein the first rotor and the second rotor are arranged to rotate about the rotor axis.
16. The wind turbine of claim 15, further comprising a flow splitter disposed between the first rotor and the second rotor and arranged to deflect oncoming wind flow away from the support tower and towards the first rotor portion and the second rotor portion.
17. The wind turbine of any preceding claim, wherein the hub comprises a sliding portion that is slidably attached to the support tower for movement in the longitudinal direction, and a rotatable portion to which the rotor is mounted, the rotatable portion being rotatably attached to the sliding portion for rotation about the longitudinal axis.
18. The wind turbine of claim 17, wherein the sliding portion comprises one or more rollers arranged to engage one or more corresponding tracks on the support tower for movement of the sliding portion along the support tower.
19. The wind turbine of any preceding claim, further comprising a communications transceiver mounted to the support tower.
20. The wind turbine of claim 19, wherein the support tower comprises an end portion extending beyond a maximum position of the rotor, and wherein the communications transceiver is mounted to the end portion of the support tower.
21. A method of operating a wind turbine, the wind turbine comprising.a support tower mounted to the ground and defining a substantially vertical axis, a rotor configured to be turned by wind for generating electrical energy, wherein the rotor is mounted to the support tower for movement of the rotor along the support tower in the direction of the substantially vertical axis, and an actuator configured to move the rotor along the support tower in the direction of the substantially vertical axis, wherein the method comprises controlling the actuator to move the rotor along the support tower to vary a height of the rotor according to a wind speed variable.
22. The method of claim 21, wherein the wind speed variable comprises at least one of: an instantaneous wind speed, an averaged wind speed based on a predetermined time period, and/or or a predicted wind speed.
23. The method of claim 22, further comprising receiving the wind speed variable and/or a control signal for controlling the actuator from an external device.
24. The method of any of claims 21 to 23, comprising positioning the rotor at a maximum distance from the ground if the wind speed variable is less than a predetermined 15 threshold.
25. The method of any of claims 21 to 24, comprising positioning the rotor at a distance from the ground that is less than the maximum distance when the wind speed variable exceeds the predetermined threshold.