WO2010043647A2

WO2010043647A2 - Wind turbine blade

Info

Publication number: WO2010043647A2
Application number: PCT/EP2009/063402
Authority: WO
Inventors: Nicolas Dudley Barlow; Mark Hancock
Original assignee: Vestas Wind Systems A/S
Priority date: 2008-10-14
Filing date: 2009-10-14
Publication date: 2010-04-22
Also published as: WO2010043647A3; EP2347125A2

Abstract

The invention relates to a wind turbine blade comprising a blade body, a device for modifying the aerodynamic surface or shape of the blade and movably connected hereto, and operating mechanisms for controlling the position and/or movement of the device. The operating mechanism comprises a compressible pressure chamber arranged in relation to the blade body and the movable device such that the position and/or movement of the device relative to the blade body can be modified by changing the pressure in the pressure chamber thereby causing a change of its cross sectional diameter. The operating mechanisms may be connected to and driven by a pressure reservoir arranged within the wind turbine blade or for example constituted by parts of the blade spar.

Description

WIND TURBINE BLADE

Field of the invention

The present invention relates to the field of rotor blades for wind turbine installations. In particular, it relates to wind turbine blades comprising devices for modifying the aerodynamic surface or shape of the blade, and for operating mechanisms for controlling the position and/or movement of such devices.

Background

Most modern wind turbines are controlled and regulated continuously during operation with the purpose of ensuring optimal performance of the wind turbines in all operating conditions, such as at different wind speeds or subject to different demands from the power grid. Desirably, the wind turbine can also be regulated to account for fast local variations in the wind velocity - the so-called wind gusts. Also, as the loads on each of the blades vary due to e.g. the passing of the tower or the actual wind velocity varying with the distance to the ground (the wind profile), the ability to regulate each of the wind turbine blades individually advan- tageously enables the loads to be balanced, reducing the yaw and tilt of the rotor.

A well-known and effective method of regulating the loads on the rotor is by pitching the blades. However, with the increasingly longer blades on modern wind turbines (which at present can be of 60 m or longer) pitching becomes a relatively slow regulation method incapable of changing the blade positions fast enough to account for e.g. wind gusts or other rela- tively fast load variations.

Another way of regulating the blades is by changing their aerodynamic surfaces or shapes over parts or the entire length of the blade, thereby increasing or decreasing the blade lift or drag correspondingly. Different means of changing the airfoil shape are known such as different types of movable or adjustable flaps (e.g. trailing edge flaps, leading edge slats or Krueger flaps, Gurney flaps placed on the pressure side near the trailing edge, ailerons, or stall inducing flaps), vortex generators for controlling the boundary layer separation, adaptive elastic members incorporated in the blade surface, means for changing the surface roughness, adjustable openings or apertures, or movable tabs. Such different means are here and in the following referred to in common as aerodynamic devices or devices for modifying the aerodynamic surface or shape of the blade. One important advantage of the relatively small aerodynamic devices is a potentially faster response due to less inertia than if the whole blade is being pitched. One drawback with the known different systems of various aerodynamic devices of the above mentioned types is how they are actuated and controlled. In order to reach the devices potential in the regulation of wind turbines, the aerodynamic surface modifying devices need to be able to operate quickly and repeatedly. Therefore the power consumption could be consid- erable. In the known systems, the aerodynamic devices are powered directly from the hub via a power link. An electrical cable is however undesirable due to the inevitable implications in relation to lightning. Further, known systems may exhibit problems with their operational speed. Moreover, known systems may exhibit poor mechanical stability.

Description of the invention

It is therefore an object of embodiments of the present invention to overcome or at least reduce some or all of the above described disadvantages of the known wind turbine blades comprising devices for modifying its aerodynamic surface or shape. Moreover, it is an object of embodiments of the present invention to provide an alternative to known systems for changing the profile of a wind turbine blade. Moreover, it is an object of embodiments of the present invention to provide simple and reliable solution for changing the profile of a wind turbine blade. Additionally, it is an object of embodiments of the present invention to provide an inexpensive system for changing the profile of a wind turbine blade.

In accordance with the invention this is obtained by a wind turbine blade comprising a blade body and one or more devices for modifying the aerodynamic surface or shape of the blade, where the device(s) is movably connected to the blade body and where the wind turbine blade further comprises one or more operating mechanisms for controlling the position and/or movement of the device. The operating mechanism comprises at least one first compressible pressure chamber arranged in a region next to one or more lever elements connected to the blade body or the device such that a change of pressure in the pressure cham- ber causes its cross sectional diameter to change so as to thereby move the lever element and thereby modify the position and/or movement of the device relative to said blade body.

Hereby is obtained an effective control and regulation mechanism allowing for a faster activation of the aerodynamic device and which can easily be arranged in conjunction with the device. The use of pressure as an activating medium is advantageous in that electrical wires in the blades (with the increased risk of damage due to lightning) can to a large extent be avoided. The described pressure chamber system is furthermore advantageous in being of low weight and of low manufacturing cost. Further still the operating system of the blade construction can be made compact and robust. In this context a 'compressible' chamber is understood to cover a chamber of a material such as an elastic thermoplastic capable of attaining a different cross sectional diameter or width depending on the pressure inside the chamber relative to the surrounding pressure and/or forces applied to it.

In an embodiment of the invention the wind turbine blade according to the above comprises at least two compressible pressure chambers and the pressure chambers are arranged on opposing sides of the lever element. Hereby is obtained that where a first pressure chamber may contribute to move the lever element and thereby the movable device in a first direction, a second pressure chamber on the opposite side of the lever element may act to move the lever element in the opposite direction. Hereby the regulation ability of the operating system is increased considerably compared to a single pressure chamber system and the position of the movable device can be controlled and regulated much more precisely independent on the winds acting on the blade as such. Further, the achievable regulation speed of the operating system can be increased by the use of several pressure chambers.

In an embodiment of the invention the wind turbine blade comprises at least one elastic element such as. a spring or other resilient element which is arranged on an opposing side of the lever element(s) compared to the pressure chamber(s) and/or arranged on the same side of the lever element(s) as the pressure chamber(s). The elastic element(s) hereby acts to dampen any vibrations in the blade/device system. An elastic element used together with a pressure chamber may further render the use of a further pressure chamber acting to push the lever element in the opposite direction as the first pressure chamber superfluous.

In a further embodiment of the invention the one or more pressure chambers are connected to one or more pressure reservoirs via at least one first valve system and for providing pres- surization and/or depressurization of said pressure chambers. By the use of a pressure reser- voir the use of electrical wires in the wind turbine blade can be minimized.

In a further embodiment of the invention the one or more pressure reservoirs is at least partly constituted by one or more sections of beam walls of the wind turbine blade and/or is at least partly placed within an internal spar of the wind turbine blade. This is advantageous due to the weight savings achieved hereby. Furthermore, such a construction of the pressure (or optionally a vacuum reservoir) for the operating system can be arranged in any position down the entire length of the wind turbine blade and can thus be arranged relatively close to any kind of aerodynamic device anywhere on the blade whether it is positioned in the root section of the blade, near the tip or anywhere in between. The use of the blade beams or internal spar furthermore makes it possible to make one or more pressure reservoirs of con- siderable sizes. According to another embodiment of the invention the pressure chamber(s) is connected to an outer surface of the wind turbine blade via at least one second valve system. Hereby, the pressure chamber may quickly and by simple means be depressurized to atmospheric pressure.

In an embodiment the at least one first and/or second valve system described above is connected to a control unit via a power link providing the valve system with control signals for the operating of said device. The aerodynamic surface of the wind turbine blade may hereby be regulated quickly and effectively and modified continuously according to signals from a central control unit placed for instance in the nacelle of the wind turbine. The control signals may be electrical or light or other electromagnetic wave for instance.

In a further example, the power link may be replaced and the control signals may be pressure control signals. This may be achieved by a pressure tube connecting the control unit to the first and/or second valve system. The pressure tube may comprise a gas of a lower molecular weight than 28.9 kg/kmol, such as Helium He, Ammonia NH₃, Hydrogen H₂, Hydroxyl OH, Methane CH₄, Natural Gas, Acetylene C₂H₂,, or Neon Ne. Dry air has a molecular weight of 28.96 kg/kmol (as determined e.g. in Chemical Rubber Company, 1983. CRC Handbook of Chemistry and Physics. Weast, Robert C, editor. 63rd edition. CRC Press, Inc. Boca Raton, Florida, USA) depending to some extent on the exact content of the different gasses in the mixture. Because the molecular weight of the gas according to the invention is lower than 28.9 kg/kmol and thereby lower than air, the speed of sound in the gas is correspondingly higher. Hereby is obtained a reduction in the delay of the control signals when sent from the control unit to the valve system as the pressure signals propagate with the speed of sound in the gas. The reduction in the signal delay is correspondingly larger, the longer the distance over which the signals are sent. The reduction of the time needed for transporting the signals is even more advantageous in view of the technological trend to increase the length of wind turbine blades, and as many aerodynamic devices are placed some distance from the blade root where the control signals are likely to terminate. The use of Helium may be further advantageous due to being light in combination with its non-corrosive, non-toxic, and non explosive properties while at the same time being relative easy to acquire. The use of pressure control signals avoids electrical conductors being placed in the wind turbine blades and therefore, the potential risk of damage from lightning is reduced.

In an embodiment of the invention according to any of the preceding, the lever element in itself constitutes a part of the device for modifying the aerodynamic surface or shape of the blade hereby yielding a more compact, simple and robust constructional design with fewer mechanical parts. This may for instance be achieved by arranging a pressure chamber directly or indirectly next to an interior surface of a trailing edge aileron, whereby the aileron will be moved and its position affected directly by a change of pressure in the pressure chamber.

In an embodiment of the invention the device for modifying the aerodynamic surface or shape of the blade comprises a movable trailing edge and/or an aileron.

In an embodiment of the invention the one or more pressure chambers are positioned essentially in a longitudinal direction extending from a root portion to a tip portion of the blade which is especially advantageous for controlling and regulating aerodynamic devices such as flaps and ailerons as these are conventionally arranged along the length of the wind turbine blade and are rotated or moved in the chordwise plane of the blade transverse to the longi- tudinal direction.

In an embodiment of the invention the device for modifying the aerodynamic surface or shape of the blade comprises a pressure skin and a suction skin, a first one of the pressure and suction skins being secured to or integral with the blade body, and a second one of the pressure and suction skins being slidably movable with respect to the blade body. Hereby may be obtained an essentially smooth surface of the blade during all or most of the regulation positions of the device.

Further, a part of the second one of the pressure and suction skins which is slidably movable with respect to the blade body may in another embodiment comprise a radial surface arranged such that it is ratable about a hinge. This construction allows for an essentially smooth and continuous surface of the blade over the connection between the blade body and the movable device irrespective of or during large portions of the device movement. Further, the construction may reduce the risk of dust, water etc entering any inner parts of the device or the blade.

In a further embodiment of the invention the device for modifying the aerodynamic surface or shape of the blade is at least partly divided into a number of sections by interstices or connecting portions having higher elasticity than said sections. By having the device for modifying the aerodynamic surface or shape of the blade divided into a number of sections is obtained that the ability of the device to bend and flex is considerable increased. As the devices are very often hinged or in other way fastened to the blade body along a considerable part of their length, the increased overall longitudinal bending flexibility of the device results in less resistance towards the activation and movement of the aerodynamic device. This in turn results in a lower forces and power consumption in the system and less friction and wear in the movable parts of the blade increasing the longevity of the device, any connection ele- merits to the blade body and the activation mechanisms. The construction of the aerodynamic device further results in the longitudinal bending modes of the blade and the device to decouple to a larger extent from the transverse bending modes. Furthermore, the modular nature of the construction allows a wider range and more efficient manufacturing methods for example thermoplastic moulding, and for easier maintenance where individual modules can be replaced or refurbished. Smaller modules may more readily be upgraded in a maintenance overhaul to later versions of the device. In connection to the operation mechanism according to the invention, this then provides for individual or continuous adjustment of the different sections of the aerodynamic device by arranging one or more pressure chambers for each section or a number of sections and being regulated independently of the other pressure reservoirs used. The pressure chambers may however optionally be connected to the same pressure or vacuum reservoir.

In an embodiment of the invention the interstices or connecting portions extend at least partly through a thickness of the device and from a trailing edge of said device and in an es- sentially chordwise direction, such that the overall longitudinal bending flexibility of the device is increased. Further is obtained, that the aerodynamic device may be assembled by the number of sections being premanufactured. The device can optionally be assembled during connection to or mounting on the wind turbine blade body.

In an embodiment of the invention, the pressure chamber(s) may comprise a pressure hose, or the pressure chamber(s) may comprise an inflatable bladder.

The invention finally relates to a wind turbine comprising at least one wind turbine blade according to any of the embodiments described in the preceding. Advantages hereof are as described above for the wind turbine blade.

Brief description of the drawings

In the following different embodiments of the invention will be described with reference to the drawings, wherein:

Fig. 1 shows a wind turbine blade according to prior art and comprising movable aerodynamic devices in the shape of a movable trailing edge and an aileron,

Figs. 2A, B, and C shows a wind turbine blade according to prior art in a cross sectional view with different types of movable aerodynamic devices, Figs. 3-4 show an embodiment of an active trailing edge being controlled and operated by pressure according to an embodiment of the invention, and as seen in two different positions.

Fig. 5 is a sketch of a wind turbine blade as subjected to edgewise gravity loads and comprising a movable trailing edge with a number of device segments according to the invention,

Fig. 6 shows a sketch of a wind turbine blade comprising an operating mechanism according to the invention,

Fig. 7 illustrates the connection of an operating mechanism according to the invention and connected to an inner pressure or vacuum chamber,

Figs. 8-9 show different embodiments according to the invention of operating mechanisms for controlling and moving a movable trailing edge and as seen in cross sectional views, and

Fig. 10 shows an embodiment of an aileron comprising an operating mechanism according to an embodiment the invention.

Detailed description of the drawings

Figure 1 shows a blade 100 for a wind turbine according to prior art and comprising some examples of so-called aerodynamic devices 101. When manipulated, the aerodynamic devices change or modify the aerodynamic surface or shape 105 of the wind turbine blade 100 thereby altering the lift and/or drag coefficients of the wind turbine blade during operation. In the examples illustrated in this figure, the aerodynamic shape of the wind turbine blade 100 can be changed and regulated by changing the position of the movable trailing edge flap 102 placed along a part of the length or longitudinal direction 106 of the blade, or by the activation of a number of ailerons 103 also placed near and along the trailing edge 104 of the wind turbine blade on its suction side.

The aerodynamic devices 101 may - as is the case with for instance the flaps or active trailing edges - be actuated or moved (rotated, translated, or combinations thereof) in a chord- wise plane 108 transverse to the length 106 of the blade. This is illustrated in the figures 2A, B, and C for different types of a slotted flap 109, an active trailing edge flap 102, and an aileron 103, respectively, which are all movably connected to the blade body 107. The chord- wise plane 108 here and throughout the description is used to describe a cross sectional plane transverse but not necessarily perpendicularly to the longitudinal direction 106 of the blade. In the figures 3 and 4 are shown an active trailing edge 101, 102 manipulated and controlled by an operating system according to an embodiment of the invention and in two different positions corresponding to its fully deactivated and fully activated state, respectively. Here, two pressure hoses 401, 402 are provided which run along the length of the aerodynamic device 101. The pressure hoses 401, 402 are arranged next to and in this embodiment on opposing sides or surfaces 406 of a lever element 404 connected to or a part of the movable trailing edge 102. The movable trailing edge 102 is movably connected to the blade body 107 and can be rotated in relation to the blade body around the hinge 405. In this embodiment the lever element 404 extends in a direction directly from the hinge 405 whereby the forces applied to the lever elements from the pressure hoses are optimally transferred to a rotational movement of the trailing edge around the hinge.

In the figures 3 and 4, pressure hoses 401, 402 are shown as the actuating means for moving the active trailing edge. The pressure hoses 401, 402 are pressure chambers that change shape and cross section. In another embodiment, for example, they could be a local chamber such as an inflatable bladder that does not extend along the length of the aerodynamic device 101. It is only necessary that the pressure chamber changes shape to impart movement to the lever element 404.

The lever element 404 is provided so that it moves in response to the force imparted from pressure hoses 401, 404. Therefore, the lever element 404 must have a sufficient surface area on which the pressure hoses 401, 404 can act so that the force can be transferred to the lever element.

The pressure hoses are made of a compressible material such as for instance a thermoplast or elastomer which may be fibre reinforced allowing the hose to be compressed or squeezed thereby attaining a smaller cross sectional diameter or width 410 depending on the pressure inside the hose relative to the external pressure and forces applied to it. In the situation shown in figure 3, the first pressure hose 401 is depressurised (for instance by applying a vacuum to it or by venting it to atmospheric pressure), and the second pressure hose 402 has been pressurized whereby the first pressure hose 401 is compressed and squeezed to a certain extent resulting in the trailing edge flap 102 being held in its lowermost position. In figure 4, the first hose 401 is now pressurised and the second hose 402 is depressurised causing the lever element 404 between the two hoses to move which in turn causes the trailing edge flap 102 to move around the hinge 405.

The two hoses 401, 402 may run along parts of or the entire length of the trailing edge flap 102 whereby the entire trailing edge flap can be controlled uniformly by only a single control system. Alternatively, a number of pressure hoses may be connected in series or parallel to different parts or sections of the aerodynamic device whereby the trailing edge flap may be controlled faster. Several systems of pressure hoses may also be applied on different parts of the trailing edge flap to allow the flap movement to be gradually increased from one end to the other, or to allow different parts of the device to be controlled and moved independently and individually.

In the embodiment shown in figures 3 and 4, the compartment 408 comprising the two pressure hoses 401, 402 on each side of the lever element 405 is comprised in an intermediate attachment element 403 connecting the trailing edge to the blade body 107. This construction may be advantageous during assembly of the different blade parts allowing the trailing edge to be assembled with the attachment element prior to fastening to the main part of the blade. Alternatively the compartment 408 for the pressure hoses may be comprised directly in the main blade body.

For example, the pressure hoses 401, 402 may be provided in the main blade body at a chordwise distance away from the trailing edge flap 102. In such an embodiment, the pres- sure hoses 401, 402 may be located adjacent to the main structural spar of the blade 100. Therefore, in contrast to the embodiment shown in figures 3 and 4, the lever element 404 will extend from the trailing edge flap 102, in a chordwise direction, to a position inside the blade body adjacent to the main spar.

In another embodiment of the operating mechanism, the trailing edge flap 102 is connected to the blade body 107 by means of flexible connection joint around which the flap 102 rotates.

As illustrated in the figures 3 and 4, a radial surface 1200 with its center in the rotation hinge 405 may be provided to enable the flap 102 to move while maintaining the continuity of the blade surface when the flap is actuated. In another embodiment, the flap 102 may be a de- formable trailing edge and may be connected to the blade body 107 by means of a flexible and/or elastic connection at both the suction skin and the pressure skin, so that the radial surface 1200 and the hinge 405 are not required.

In figure 5 is shown a wind turbine blade 100 mounted to a hub 301. The gravity loads imposes large edgewise loads on the blade resulting in large compression and tension strains along the leading 303 and trailing 104 edges as illustrated by the arrows 302. The sign of the strains naturally reverse during the rotational cycle of the blade. Likewise, the longitudinal bending of the blade both in and out of operation due to the wind loads also result in large bending strains in the longitudinal direction 106 of the blade. Further, depending on the pre- sent load situation on the entire blade, the blade also flexes and twists to some extent down its length resulting in a varying complex three-dimensional stress and strain state.

However, the operation ability of the different devices 101 for modifying the aerodynamic surface or shape of the blade 100 has been found to be highly improved by dividing the de- vices 101 into a number of sections or segments 303 in the longitudinal direction 106 of the device. This is illustrated in the figure 5 for an active trailing edge flap 102 which may be controlled and moved by an operating mechanism according to the invention for instance as described for the embodiment illustrated in the previous or preceding figures. For clarity the specific movable connection of the flap and the actuation mechanism is not shown here. The aerodynamic device 101 which may for instance comprise a movable trailing edge, a flap, and/or an aileron, comprises a number of sections 303 divided by interstices or connecting portions 304. These have higher elasticity than the device sections 303 whereby the overall longitudinal bending flexibility of the device 101 is increased reducing the strains both from the edgewise and bending loads. In the embodiments of the device shown in figure 5, the interstices 304 are open gaps of a certain width allowing for the sections to deform relative to each other with no or little contact between the sections.

The interstices 304 or connecting portions may extend the whole way through the chordwise width 306 of the device or may alternatively extend only a certain portion such as e.g. 70- 90% through of the chordwise width 306 of the device from the device trailing edge 307 to- wards the blade body 107 and in the chordwise direction. Likewise, the interstices 304 or connecting portions may extend entirely or partly through the thickness of the device 101 (in and out of the paper).

The interstices 304 may be placed at even distances in the longitudinal direction 106 of the blade or may be advantageously unevenly spaced, for instance at smaller intervals in regions of larger deformations.

The two pressure hoses 401, 402 in the operation mechanism may as mentioned above run along parts of or the entire length of the trailing edge flap 102 and hereby control some or all of the sections of a sectioned trailing edge flap as sketched in figure 5. If the pressure hoses are connected to control each of the sections 303 of the aerodynamic device, all parts of the trailing edge flap may be controlled uniformly. Alternatively, several systems of pressure hoses may be applied on different parts or sections of the trailing edge flap allowing the flap movement to be gradually increased from one end to the other, or to allow different parts or sections of the device to be controlled and moved independently and individually. In figures 6 and 7 is shown how the operation mechanism comprising here a set of two pressure hoses 401, 402 may be pressurized by being coupled to a pressure reservoir 601 within the blade body 107. In this embodiment the pressure reservoir is conveniently placed in between the main beams or the spar 602 of the wind turbine blade 100 and is pressurized by a compressor 603 which may be placed in the root section of the blade or alternatively in the nacelle of the wind turbine. In one embodiment of the invention the spar 602 may in itself constitute a pressure reservoir for pressurizing the operating mechanism. The pressure reservoir is connected to the pressure hoses via a valve system 604 which based on control signals 609 from a controller 610 regulates the pressure in the different pressure hoses 401, 402 and hereby the position and movement of the aerodynamic device 101. One more detailed embodiment of a valve system 604 is shown in figure 7. For depressurizing the pressure hoses, this can be vented 611 by connection to for instance an outer surface of the blade or to some internal part of the blade of atmospheric pressure. In figure 6, the operating mechanism is illustrated for operating a movable trailing edge flap 102 which is segmented. However, the principles of the operating mechanism and its coupling to a pressure reservoir are the same for other aerodynamic devices for modifying the aerodynamic surface of the wind turbine blade such as ailerons, vortex generators etc. Sensors (not shown) such as strain gauges or pressure sensors may monitor the loads experienced by the wind turbine blade 100 and the output from these sensors are provided to the controller 610 which will determine how the pressure hoses 401, 402 should be regulated in response to the loads acting on the wind turbine blade.

The magnitude of the pressure and/or under pressure needed for controlling and regulating an aerodynamic device such as a movable trailing edge depend on different factors such as the dimensions (typically 15 -30% chord and 10-20% blade length) and weights of the de- vices to be moved and controlled, the regulation speed required, and the elastic properties of the pressure hoses. The regulation speed is typically of the order of 50-500 msec and the pressure required is typically 0.2-0.6 bar.

Instead of connection to a pressure reservoir, one or more of the pressure hoses could equally well be connected to a vacuum reservoir which similarly could be placed within or even in part constituted by the internal spar or main beams of the wind turbine blade.

Figure 8 illustrates an embodiment of the invention where the lever element 404 arranged in between the compressible pressure hoses 401, 402 is a part of the blade body 107, so that the pressure hoses are arranged within a compartment 408 comprised in the aerodynamic device 101 which in the illustrated example is a movable trailing edge 102. The operating mechanism according to the invention need not comprise exactly two compressible pressure hoses 401, 402, but can of course also function with one pressure hose alone where the reverse movement of the lever element up against the pressure hose may then optionally be regulated by the use of one or more elastic members such as springs. This is illustrated in figure 9, where a spring 901 is arranged opposite a pressure hose 401 on the other side of the lever element 404. The spring here acts to force the trailing edge back towards the pressure hose 401 if the pressure inside the pressure hose is lowered. The spring may naturally also be arranged next to the pressure hose connected to the lever element or on another side. Elastic members such as springs may also be used in combination with the previously illustrated embodiments of more than one pressure hoses.

In figure 10 is illustrated an embodiment where the operating mechanism according to the invention is controlling and regulating the position and movement of a trailing edge aileron 103. The principle of the operating mechanism is similar to illustrated above for a movable trailing edge.

While preferred embodiments of the invention have been described, it should be understood that the invention is not so limited and modifications may be made without departing from the invention. The scope of the invention is defined by the appended claims, and all devices that come within the meaning of the claims, either literally or by equivalence, are intended to be embraced therein.

Claims

1. A wind turbine blade comprising a blade body and one or more devices for modifying the aerodynamic surface or shape of the blade, said device(s) being movably connected to the blade body, the wind turbine blade further comprising one or more operating mechanisms for controlling the position and/or movement of said device; and where said operating mechanism comprises at least one first compressible pressure chamber arranged in a region next to one or more lever elements connected to said blade body or said device such that a change of pressure in said pressure chamber causes its cross sectional diameter to change so as to thereby move said lever element and thereby modify the position and/or movement of said device relative to said blade body.

2. A wind turbine blade according to claim 1 comprising at least two compressible pressure chambers; said pressure chambers being arranged on opposing sides of said lever element.

3. A wind turbine blade according to claim 1 or 2 comprising at least one elastic element arranged on an opposing side of said lever element(s) compared to said pressure chamber(s).

4. A wind turbine blade according to any of claims 1-3 comprising at least one elastic element arranged on the same side of said lever element(s) as said pressure chamber(s).

5. A wind turbine blade according to any of claims 1-4 where said pressure chamber(s) is connected to one or more pressure reservoirs via at least one first valve system and for providing pressurization and/or depressurization of said pressure chamber(s).

6. A wind turbine blade according to claim 5 where said one or more pressure reservoirs is at least partly constituted by one or more sections of beam walls of the wind turbine blade.

7. A wind turbine blade according to claim 5 or 6 where said one or more pressure reservoirs is at least partly placed within an internal spar of the wind turbine blade.

8. A wind turbine blade according to any of claims 1-7 where said pressure chamber(s) is connected to an outer surface of the wind turbine blade via at least one second valve system.

9. A wind turbine blade according to any of claims 5-8, where said at least one first and/or second valve system is connected to a control unit via a power link providing the valve system with control signals for said operating of said device.

10. A wind turbine blade according to any of the preceding claims, where said lever element in itself constitutes a part of said device for modifying the aerodynamic surface or shape of the blade.

11. A wind turbine blade according to any of the preceding claims, where said device for modifying the aerodynamic surface or shape of the blade comprises a movable trailing edge and/or an aileron.

12. A wind turbine blade according to any of the preceding claims, where said one or more pressure chambers are positioned essentially in a longitudinal direction extending from a root portion to a tip portion of said blade.

13. A wind turbine blade according to any of the preceding claims wherein said device for modifying the aerodynamic surface or shape of the blade comprises a pressure skin and a suction skin, a first one of the pressure and suction skins being secured to or integral with the blade body, and a second one of the pressure and suction skins being slidably movable with respect to the blade body.

14. A wind turbine blade according to claim 13, wherein a part of the second one of said pressure and suction skins being slidably movable with respect to the blade body comprises a radial surface arranged such that it is ratable about a hinge.

15. A wind turbine blade according to any of the preceding claims wherein said device for modifying the aerodynamic surface or shape of the blade is at least partly divided into a number of sections by interstices or connecting portions having higher elasticity than said sections.

16. A wind turbine blade according to claim 15 where said interstices or connecting portions extend at least partly through a thickness of the device and from a trailing edge of said device and in an essentially chordwise direction, such that the overall longitudinal bending flexi- bility of the device is increased.

17. A wind turbine blade according to any of the preceding claims, wherein said pressure chamber(s) comprise a pressure hose.

18. A wind turbine blade according to any of claims 1 to 16, wherein said pressure chambers) comprise an inflatable bladder.

19. A wind turbine comprising at least one wind turbine blade according to any of the claims 1-18.