WO2013171257A1

WO2013171257A1 - A system and method for mounting devices to a wind turbine blade

Info

Publication number: WO2013171257A1
Application number: PCT/EP2013/060021
Authority: WO
Inventors: Dhinagaran Ramachandran; Rajkumar Rajamani
Original assignee: Lm Wp Patent Holding A/S
Priority date: 2012-05-16
Filing date: 2013-05-15
Publication date: 2013-11-21

Abstract

A system and method for mounting add-on devices to a wind turbine blade is described. The system uses at least one bracket which can be affixed to the root end of a blade, preferably by the mounting of the blade root end to a wind turbine hub. The bracket extends adjacent a portion of the surface of the blade, and the bracket provides a mounting point for any suitable add-on devices, e.g. aerodynamic devices such as spoilers, etc. Using the bracket as the mounting point for the add-on devices means that the devices do not have to be directly mounted to the blade surface, and can be relatively easily installed and removed without significant damage to the body of the blade. In a further embodiment, the bracket may extend adjacent the internal surface of the blade, and may provide a mounting point for any internal devices, e.g. a blade root bulkhead.

Description

A System and Method for Mounting Devices to a Wind Turbine Blade

Field of the Invention

The present invention relates to a system and method for mounting devices to a wind turbine blade, in particular to the root end of a wind turbine blade.

Background of the Invention

In wind turbine blade design, the need to tailor the individual aerodynamic performance of a blade regularly arises. An initial blade construction may need to be modified through the addition of various aerodynamic devices to points along the blade surface. This may include the use of e.g. aerodynamic slats, spoilers, vortex generators, stall fences, flow deflectors, gurney flaps, or acoustic devices such as wedges etc.

As wind turbine blades are generally formed from formed fibre-composite materials, the mounting of such aerodynamic add-on devices to the surface of a wind turbine blade usually requires riveting, bolting or gluing to the fibre-composite body of the blade, which may weaken the fibre-composite body. Such a mounting operation requires considerable care and attention during installation, so that the mounting of the devices to the blade does not damage the underlying blade body. Furthermore, this mounting method may require that the wind turbine blades are constructed with additional thickness of layers or reinforcement elements in the region of predicted mounting, to sufficiently carry any additional loads associated with mounted add-on devices. In a further aspect, in the case of a damaged add-on device which may need removal from the blade, and/or a device which is to replaced with an upgraded version of the device, such an operation to remove the add-on device from the wind turbine blade cannot be easily performed, and may result in further damage to the blade structure which must be repaired, and/or a further riveting, bolting or gluing operation on the blade body. It is an object of the invention to provide an alternative system and method for mounting add-on devices to a wind turbine blade, which eliminates the above problems.

Summary of the Invention

Accordingly, there is provided a system for attaching a device to a wind turbine blade, the system having at least one bracket comprising:

a mounting element provided at a first end of said bracket, the mounting element arranged to couple with a root end of a wind turbine blade to support said bracket relative to said wind turbine blade; and

a body extending from said first end of said bracket to a second end of said bracket, wherein said body is shaped to extend adjacent at least a section of the surface of a wind turbine blade when said bracket is coupled to a root end of the wind turbine blade, and wherein said body is arranged to support a device adjacent the surface of the wind turbine blade.

Preferably, at least a portion of the body of said bracket is shaped to extend adjacent at least a section of the external surface of a wind turbine blade, wherein the system is used to attach an aerodynamic device adjacent a section of the external surface of the wind turbine blade.

Preferably, said bracket comprises a C-shaped or an L-shaped bracket.

By providing a C- or L-shaped bracket, the mounting element of the bracket can be easily coupled to a root end of a blade, with the body portion of the bracket extending therefrom along either one or two adjacent surfaces of the blade, dependent on the shape of bracket selected.

Preferably, said bracket comprises a substantially planar body. As the body of the bracket is substantially planar, this provides for a bracket structure which can be provided adjacent the exterior surface of a blade without significantly affecting the aerodynamics of the blade, while furthermore providing a relatively light-weight bracket structure. Appropriate aerodynamic devices can be accordingly attached to and supported by the body of the bracket.

By providing at least one bracket which can be used to support an aerodynamic device at a wind turbine blade, the use and configuration of aerodynamic devices on a wind turbine blade can be separated from the manufacturing process of the blade itself. Furthermore, arranging aerodynamic devices using such brackets allows for the mounting of aerodynamic devices with little or no alteration or fixation to the blade along the length of the blade itself, thereby preserving the structural integrity of the blade body and not weakening the blade through gluing, welding or the machining of bolt holes or rivets on the blade body, which may be relatively brittle. In addition, the configuration of different aerodynamic devices on similar blades, e.g. the adjustment of different blade spoilers for wind turbines located in different positions in a wind farm having varying wind conditions, can be easily performed, and at a later stage of the installation process for a wind turbine blade, simultaneously facilitating ease of replacement or further adjustment if needed, without significantly impacting on the structural integrity of the wind turbine blade.

It will be understood that the aerodynamic devices may include any suitable elements used to modify the airflow and/or the aerodynamic characteristics of the wind turbine blade in the region of the bracket, e.g. slats, spoilers, vortex generators, stall fences, flow deflectors, gurney flaps, or acoustic devices such as wedges etc. It will further be understood that the system may be used to attach any device or system to a wind turbine blade.

In an additional or alternative embodiment, the body of said bracket may be shaped to extend adjacent at least a section of the internal surface of a wind turbine blade, wherein the system is used to attach a device adjacent a section of the internals surface of the wind turbine blade.

In such an embodiment, it will be understood that the bracket may be used to affix internal blade components, e.g. a blade bulkhead, a portion of a lightning down- conductor system, sensors system to monitor structural health, etc. Preferably, the body of said at least one bracket is arranged to extend from said first end to said second end in a direction substantially parallel to the longitudinal direction of a wind turbine blade from a root end towards a tip end of said blade. It will be understood however that the body of said at least one bracket may be shaped to extend in an alternative direction, e.g. due to the curvature of the wind turbine blade surface.

Preferably, the wind turbine blade is arranged for mounting to a wind turbine hub via a mounting connection between the wind turbine blade and the wind turbine hub, wherein the mounting element of said bracket is arranged to couple to at least a section of such a mounting connection.

This allows for the additional weight and loading of the bracket and any associated aerodynamic device to be transferred directly to the resilient mounting connection between the blade and the hub, preventing any significant loads being transferred to the wind turbine blade. As a result, the blade may be of a more light-weight or flexible construction than a similar blade having aerodynamic or other devices provided integrally with the blade structure.

The mounting connection may comprise any suitable blade mounting mechanism, e.g. root bushings provided at the root end of the wind turbine blade, bolts attaching the blade to the hub, root inserts or spars extending from the blade into a mount provided in the hub, etc. The mounting element may comprise any suitable mounting or connecting mechanism for attaching the bracket to the mounting connection, e.g. bolting, a press-fit or snap-fit connection, adhesive bonding, etc.

Additionally or alternatively, the mounting element may be arranged to 'clip- on' to the root end of the blade, e.g. by clamping or clasping onto a portion of the blade body at the root end. As the root ends of some wind turbine blades carry the weight of the full blade as well as any operational loading of the blade, the root ends may have a greater structural strength than other sections along the length of the blade. Accordingly, by arranging the bracket to couple to the blade root end, the loading associated with the brackets and aerodynamic devices or other is directly transferred to the considerably more resilient sections of the blade. In a preferred embodiment, there is provided a system for attaching a device, preferably an aerodynamic device, to a wind turbine blade, the system having at least one bracket comprising:

a lug provided at a first end of said bracket for coupling with a root bushing of a wind turbine blade to support said bracket on a wind turbine blade; and

a body extending from said first end of said bracket to a second end of said bracket, wherein said body is shaped to extend adjacent at least a section of the surface of a wind turbine blade when said bracket is coupled to a root bushing of the wind turbine blade, and wherein said body is arranged to support a device, preferably an aerodynamic device, adjacent the wind turbine blade.

In some wind turbine blade, threaded root bushings are either provided integrally with the blade at the root end of the blade during manufacture, or are inserted into the root end of a formed wind turbine blade, for the connection of the blade to the wind turbine hub using bolts. In such cases, a plurality of projecting cylindrical root bushings are arranged around the diameter of the root end of the blade, and accordingly provide a well-defined and easily accessible mounting point for the bracket. The lug of the bracket may comprise a through-going circular aperture adapted to fit about a root bushing. Alternatively, the lug may be configured as a substantially U-shaped projection configured to partly couple around the root bushing, to be secured in place during installation of the wind turbine blade on a hub.

Preferably, said at least one bracket is arranged to couple with a single root bushing of a wind turbine blade, but it will be understood that the bracket may comprise a plurality of lugs arranged to couple with a plurality of root bushings. This may provide for a more secure mounting of the bracket on a wind turbine.

Preferably, said at least one bracket is arranged to extend in a longitudinal direction adjacent at least a section of the surface of a wind turbine blade from a root end of the wind turbine blade towards a tip end of the wind turbine blade. In one aspect, the bracket extends from the root end of a wind turbine blade to the position of maximum chord along the length of the blade. In a first aspect, the bracket comprises at least a section of an aerodynamic or other devices provided on said body. This may be formed integrally with the bracket, or may be attached to the bracket prior to installation at a wind turbine blade. In a second aspect, said bracket is arranged to receive an attachment element for an aerodynamic or other device, such that said aerodynamic device or other is at least partly supported on said bracket. The bracket may comprise a connector or an aperture provided on the body of the bracket for coupling with an aerodynamic or other device through any suitable means, e.g. welding, riveting, fasteners, etc.

Preferably, the system comprises a plurality of brackets, wherein an aerodynamic or other device to be attached to the system is arranged to be supported by a plurality of brackets, e.g. a stall fence which extends substantially parallel to the chord line of a wind turbine blade.

In a further aspect, the system further comprises a cushioning element, wherein said cushioning element is arranged to be at least partly provided between the body of the bracket and an underlying adjacent surface of a wind turbine blade, to prevent damage to said surface of the wind turbine blade.

Said cushioning element is formed from any substantially resilient rubber, foam or plastics material.

In a first aspect, said cushioning element is provided as a sleeve, or cover, which is arranged to be positioned around the diameter of a portion of a wind turbine blade in the region of the root end of the blade, between the surface of the wind turbine blade and the body of said at least one bracket.

In an alternative aspect, said cushioning element is provided as a layer or coating applied to a first surface of the body of said at least one bracket, said first surface facing the surface of a wind turbine blade when said bracket is mounted at said blade.

Preferably, the system comprises a covering or tape, preferably PP tape, which is arranged to be applied to at least a portion of the body of said at least one bracket and to at least a section of the surface of the wind turbine blade, to provide a relatively smooth aerodynamic surface at said bracket, covering any bracket edges.

In a further enhancement, the system may comprise forming elements, preferably foam wedges, to be provided adjacent said at least a portion of the body of said at least one bracket, to provide for a smooth transition from the surface of the wind turbine blade to the bracket.

Preferably, the system further comprises at least one distal securing element, wherein said distal securing element is arranged to couple with said second end of said at least one bracket, to retain the body of said at least one bracket in a close alignment with the surface of the wind turbine blade.

Providing such a securing element ensures that the bracket will not be deflected away from the blade surface.

In one aspect, said distal securing element may be provided on the surface of a wind turbine blade, e.g. a lug for bolting said second end to the wind turbine blade. In a further alternative aspect, said distal securing element is provided as a ring element which is arranged to substantially extend around the diameter of a wind turbine blade, said second end of said at least one bracket adapted to couple with said ring element, to substantially secure said second end adjacent the surface of the wind turbine blade.

In one aspect, the distal securing element is provided as an open ring element having first and second free ring ends, the system further comprising a clamp element operable to couple with said first and second free ring ends, the clamp element arranged to be positioned at the trailing edge of the wind turbine blade to clamp said first and second free ring ends together to secure said distal securing element to a wind turbine blade.

In a further enhancement, the system comprises at least two brackets to be arranged at a root end of a wind turbine blade, wherein the system further comprises at least one inter-bracket support which extends between adjacent brackets at a wind turbine, to retain said adjacent brackets in a close alignment with the surface of the wind turbine blade. The support may comprise any suitable strut or bracing element, and may be integrally moulded between adjacent bracket elements, or may comprise connectors operable to couple the support with said brackets.

It will be understood that the system may be provided as a pre-formed arrangement of a plurality of brackets interconnected using a plurality of inter-bracket supports and/or at least one distal securing element, said pre-formed arrangement operable to be fitted to a root end of a wind turbine blade.

Preferably, the brackets extend in the root region of the wind turbine blade. Preferably, the brackets extend approximately up to the point of maximum chord of the wind turbine blade, preferably within approximately 10% of the longitudinal length of the wind turbine blade from the point of maximum chord of the wind turbine blade. There is further provided a wind turbine blade comprising the system for the attachment of an aerodynamic or other device as described above.

There is further provided a wind turbine comprising at least one blade as above. There is further provided a method of mounting aerodynamic devices to a wind turbine blade, the method comprising the steps of:

providing a wind turbine blade having a root end and a tip end, the wind turbine blade further having an airfoil profile having a leading edge and a trailing edge and a chord extending therebetween;

attaching at least one support bracket at the root end of said wind turbine, at least a portion of said support bracket extending from said root end towards said tip end; and attaching at least a section of an aerodynamic device to said at least a portion of said support bracket, such that said aerodynamic device is substantially carried on said support bracket and provided adjacent a surface of said wind turbine blade. This mounting method provides a relatively easy and adaptable method of accommodating aerodynamic devices on a wind turbine blade, without requiring the machining of the surface of the wind turbine blade.

Preferably, said wind turbine blade is arranged for mounting to a wind turbine hub via a mounting connection between said wind turbine blade and the wind turbine hub, wherein said at least one support bracket attached to said mounting connection.

Preferably, said method is performed using the attachment system as described above.

Description of the Invention

An embodiment of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which:

Fig. 1 shows a wind turbine;

Fig. 2 shows a schematic view of a wind turbine blade according to the invention;

Fig. 3 shows a schematic view of an airfoil profile of the blade of Fig. 2; Fig. 4 shows an enlarged view of the root portion of the blade of Fig. 2 having an attachment system according to an embodiment of the invention;

Fig. 5 shows an enlarged view of a blade having an attachment system according to a further embodiment of the invention being mounted to a wind turbine hub;

Fig. 6 is an illustration of an enlarged view of a blade having an attachment system according to a further embodiment of the invention;

Fig. 7 is a perspective view of a clamping ring for use in an embodiment of the attachment system of the invention;

Fig. 8 is a cross-sectional view in the longitudinal direction of an embodiment of a bracket of an attachment system of the invention when installed on a wind turbine; Fig. 9 is a perspective view of a further embodiment of a bracket of an attachment system of the invention;

Fig. 10 is a cross-sectional view in the transverse direction of a bracket of an attachment system of the invention; and

Fig. 11 is an enlarged view of the root portion of the blade of Fig. 2 having an attachment system according to a further embodiment of the invention.

Fig. 1 illustrates a conventional modern upwind wind turbine according to the so- called "Danish concept" with a tower 4, a nacelle 6 and a rotor with a substantially horizontal rotor shaft. The rotor includes a hub 8 and three blades 10 extending radially from the hub 8, each having a blade root 16 nearest the hub and a blade tip 14 furthest from the hub 8. The rotor has a radius denoted R.

Fig. 2 shows a schematic view of a first embodiment of a wind turbine blade 10 according to an embodiment of the invention. The wind turbine blade 10 has the shape of a conventional wind turbine blade and comprises a root region 30 closest to the hub, a profiled or an airfoil region 34 furthest away from the hub and a transition region 32 between the root region 30 and the airfoil region 34. The blade 10 comprises a leading edge 18 facing the direction of rotation of the blade 10, when the blade is mounted on the hub, and a trailing edge 20 facing the opposite direction of the leading edge 18.

The airfoil region 34 (also called the profiled region) has an ideal or almost ideal blade shape with respect to generating lift, whereas the root region 30 due to structural considerations has a substantially circular or elliptical cross-section, which for instance makes it easier and safer to mount the blade 10 to the hub. The diameter (or the chord) of the root region 30 is typically constant along the entire root area 30. The transition region 32 has a transitional profile 42 gradually changing from the circular or elliptical shape of the root region 30 to the airfoil profile 50 of the airfoil region 34. The chord length of the transition region 32 typically increases substantially linearly with increasing distance r from the hub. The airfoil region 34 has an airfoil profile 50 with a chord extending between the leading edge 18 and the trailing edge 20 of the blade 10. The width of the chord decreases with increasing distance r from the hub. It should be noted that the chords of different sections of the blade normally do not lie in a common plane, since the blade may be twisted and/or curved (i.e. pre-bent), thus providing the chord plane with a correspondingly twisted and/or curved course, this being most often the case in order to compensate for the local velocity of the blade being dependent on the radius from the hub.

Fig. 3 shows a schematic view of an airfoil profile 50 of a typical blade of a wind turbine depicted with the various parameters, which are typically used to define the geometrical shape of an airfoil. The airfoil profile 50 has a pressure side 52 and a suction side 54, which during use - i.e. during rotation of the rotor - normally face towards the windward (or upwind) side and the leeward (or downwind) side, respectively. The airfoil 50 has a chord 60 with a chord length c extending between a leading edge 56 and a trailing edge 58 of the blade. The airfoil 50 has a thickness t, which is defined as the distance between the pressure side 52 and the suction side 54. The thickness t of the airfoil varies along the chord 60. The deviation from a symmetrical profile is given by a camber line 62, which is a median line through the airfoil profile 50. The median line can be found by drawing inscribed circles from the leading edge 56 to the trailing edge 58. The median line follows the centres of these inscribed circles and the deviation or distance from the chord 60 is called the camber f. The asymmetry can also be defined by use of parameters called the upper camber and lower camber, which are defined as the distances from the chord 60 and the suction side 54 and pressure side 52, respectively.

Airfoil profiles are often characterised by the following parameters: the chord length c, the maximum camber f, the position df of the maximum camber f, the maximum airfoil thickness t, which is the largest diameter of the inscribed circles along the median camber line 62, the position dt of the maximum thickness t, and a nose radius (not shown). These parameters are typically defined as ratios to the chord length c. With reference to Fig. 4, an enlarged perspective view of the root region 30 of the blade 10 is illustrated, when employed with an attachment system according to the invention. The attachment system comprises a plurality of brackets 70 which are provided about the periphery of the circular or elliptical root section 30. The brackets 70 are arranged to couple with and be mounted to the root end 16 of the blade 10 (discussed in more detail below), and accordingly extend adjacent at least a portion of the blade external surface in the direction of the blade tip end 14.

The array of the plurality of brackets 70 at the root region 30 of the blade 10 provides a system or framework for the subsequent mounting of blade add-on devices to the blade 10, to influence the blade operation. The add-on devices may include, but are not limited to, aerodynamic devices which may improve the aerodynamic performance of the wind turbine blade 10 in the area of the root region 30 of the blade 10, e.g. spoilers, flaps, slats, flow deflectors, stall fences, vortex generators, etc.

By providing the array of brackets 70 as separate elements which can be relatively easily mounted to the root end 16 of a blade 10, the brackets 70 then providing a mounting point for subsequent add-on devices, this allows for the attachment of devices to a wind turbine blade, without requiring relatively complex bolting, riveting or gluing of the devices directly to the blade surface.

While the brackets 70 shown in Fig. 4 are of equal length and extend solely in the root region 30 of the blade, it will be understood that the plurality of brackets 70 may comprise any suitable array or arrangement of brackets of different lengths, widths, shapes, etc. For example, at least one of the brackets 70 may extend along the blade 10 in the region of the transition region 32 and/or the airfoil region 34 of the blade 10. Such a system may be used for the attachment of devices at different points along the length of the blade 10. With reference to Fig. 5, a sketch is provided of a root end 16 of a wind turbine blade 10, prior to mounting to a wind turbine hub 18. As in Fig. 4, the blade 10 comprises an attachment system according to the invention, the attachment system comprising a plurality of brackets 70 arranged about the circumference of the root region 30 of the blade 10. The brackets 70 project adjacent the surface of the blade 10, wherein a subset of the brackets 70a extend into the transition region 32 of the blade 10. The brackets 70,70a are arranged to couple with the root end 16 of the blade 10, so that the action of mounting the blade 10 to the wind turbine hub 8 acts to secure the brackets 70,70a in position with respect to the wind turbine blade 10. The brackets 70,70a are illustrated as supporting a pair of stall fences 71 adjacent the surface of the wind turbine blade 10.

With reference to Fig. 6, a sketch is provided of a root end 16 of a wind turbine blade 10 having an attachment system according to the invention, the attachment system comprising a plurality of brackets 70 arranged about the circumference of the root region 30 of the blade 10. The brackets 70 comprise a first end 72 arranged to couple with the root end 16 of the blade 10, and a distal second end 74. In fig. 6, the brackets 70 are illustrated supporting a leading edge slat 73. In order to retain the brackets 70 in position closely adjacent the surface of the wind turbine blade 10, the attachment system may further comprise a plurality of inter- bracket strips 76, said strips 76 extending between portions of adjacent brackets 70. The strips 76 are arranged to couple with the adjacent brackets 70, to bind adjacent brackets 70 together in a relatively fixed arrangement. As can be seen in Fig. 6, the strips 76 may be staggered or spaced at different locations along the length of the brackets between different adjacent bracket pairs, to provide a grid or lattice-like coupling of the entire attachment system on the blade 10.

Additionally or alternatively, the attachment system may further comprise a distal clamping ring 78, the clamping ring 78 arranged to couple with the distal second ends 74 of the brackets 70 in the attachment system, to retain the distal second ends 74 of the brackets 70 closely adjacent to the surface of the wind turbine blade 10.

The clamping ring 78 is illustrated in further detail in Fig. 7, wherein the clamping ring 78 comprises a relatively flexible band 80 which is arranged to be fitted about the wind turbine blade 10 at the location at which it is desired to clamp the distal second ends 74 of the brackets. Additionally or alternatively, the clamping ring 78 may be arranged to be fitted about the brackets 70 in the attachment system at a location between the first and second ends 72,74 of the brackets 70. The clamping ring 78 further comprises at least one clamping element 82, which is arranged to be located at the trailing edge of the wind turbine blade 10. It will be understood that the band 80 may be pre-formed from a resilient material to have a profile approximating the airfoil profile at the location it is desired to clamp the brackets 70, as shown in Fig. 7, or the band 80 may be formed from a ductile material which can be wrapped around at least a portion of the brackets 70 of the attachment system.

The band 80 may be provided as a single strip of material having a pair of free ends, which can be applied around the surface of a wind turbine blade 10, the clamping element 82 arranged to be secured to the free ends of the strip to hold the band 80 in position on a wind turbine blade 10. Alternatively, the clamping ring 78 may be provided as a single formed member comprising the band 80 and the clamping element 82, the member having a profile approximately corresponding to the airfoil profile of the wind turbine blade 10 at the location it is desired to secure the brackets 70 of the attachment system, the clamping ring 78 applied in that position by passage over the wind turbine blade 10 from the root end 16 of the blade 10.

Preferably, a wind turbine blade 10 comprises a plurality of blade root bushings 84 arranged around the root end 16 of the blade 10, the bushings 84 projecting from the root end 16 for subsequent coupling to a wind turbine hub 8 through, for example, bolting.

A cross-sectional view along the longitudinal direction of a single bracket 70 of an attachment system according to the invention is illustrated in Fig. 8. In Fig. 8, the bracket 70 is shown in use, mounted on a wind turbine blade 10 having blade root bushings 84 when coupled to a hub 8 of a wind turbine. A lug 86 is provided at the first end 72 of the bracket 70, wherein the lug 86 of a bracket 70 is arranged to couple with a blade root bushing 84 to secure the bracket 70 to the wind turbine blade 10. Once the blade 10 is subsequently mounted to a wind turbine hub 8, the bracket 70 is retained in position on the blade 10, the lug 86 of the first end 72 of the bracket 70 clasped between the root end 16 of the wind turbine blade 10 and the surface of the wind turbine hub 8.

It will be understood that the lug 86 may be provided as a flange having a through- going aperture, the aperture dimensioned to be fitted over a blade root bushing or a bolt projecting from the root end of a blade root, or the lug 86 may be provided as a pair of flange arms which are arranged to be positioned on opposed sides of a blade root bushing or a bolt projecting from the root end of a blade root. Add-on devices can be applied to the bracket 70 either before or after the mounting of the blade 10 to the wind turbine hub 8, and the associated securing of the bracket 70 in position on the wind turbine blade 10. This may be in the form of welding, bolting or riveting an add-on device to the surface of the bracket 70, but other arrangements may be used. For example, in the cross-sectional view of Fig. 8, the bracket 70 comprises first and second integrally formed stall fence projections 88. In such a configuration, it will be understood that a plurality of brackets 70 may be provided having stall fences 88 extending therebetween, forming a frame structure which can be applied to the root region 30 of a wind turbine blade. In Fig. 8, the attachment system further comprises a layer of protective or cushioning material 90 provided between the bracket 70 and the external surface of the wind turbine blade 10. The use of this protective layer 90 prevents any damage to the blade surface as a result of the mounting of the bracket 70 and any associated add-on devices to the blade 10, and further more prevents the blade surface from damage due to any operational loading of the brackets 70 and devices during turbine operation. Preferably, the protective layer is formed from a resilient deformable material, e.g. rubber, plastics, foam. In one aspect, the protective layer 90 is provided as a covering which is applied to the underside of the bracket 70. In Fig. 9, an enlarged isometric perspective view is provided of an alternative embodiment, wherein the protective layer is provided as a shielding sleeve or collar 92 which is wrapped around or fitted about at least a portion of the circumference of the root region 30 of a wind turbine blade 10. The protective sleeve 92 is applied prior to the attachment of the brackets 70 to the root bushings 84, which can then be applied about the root region 30 of the blade 10, with at least a portion of the body of the bracket 70 resting on the protective sleeve 92.

A further enhancement of the attachment system of the invention is illustrated in Fig. 10. A transverse cross-sectional view is shown of a single bracket 70 of the invention when mounted to a wind turbine blade 10. In order to mitigate against any negative aerodynamic effects from the mounting of the bracket 70 to the surface of the wind turbine blade 10, a covering layer 94 is provided over at least a portion of the bracket 70, extending to the adjacent blade surface. The use of the covering layer 94 provides a transition from the surface of the blade 10 to the bracket 70, thereby smoothing over any relatively sharp edges of the bracket 70, and providing a substantially clean aerodynamic surface for the wind turbine blade 10. It will be understood that the covering layer 94 may comprise any suitable smooth, flexible and/or erosion resistant material, e.g. a plastic sheeting material, PP tape, helicopter tape, etc.

Additionally or alternatively, the attachment system may comprise wedge members 96 provided adjacent at least a portion of the bracket 70, and extending in a longitudinal direction parallel to the bracket 70 between the first and second bracket ends 72,74. The wedge members 96 are shaped to provide a gradual transition from the surface of the wind turbine blade 10 to the body of the bracket 70, eliminating the stepped shape generated by the profile of a single bracket 70. The wedge members 96 may be adhesively applied to the bracket 70 and/or to the surface of the wind turbine blade. Additionally or alternatively, the wedge members 96 may be retained in place by applying a covering layer 94 extending over the bracket 70 and adjacent wedge members 96 to the blade surface. It will be understood that the wedge members 96 may comprise any suitable resilient, light-weight material, e.g. foam, polystyrene, plastics, etc.

With reference to Fig. 11, a further embodiment of the attachment system according to the invention is illustrated in an enlarged isometric perspective view of the root region 30 of a wind turbine blade 10. Similar to the view presented in Fig. 4, the attachment system comprises a plurality of brackets 170 having first and second ends 172,174, the brackets 170 are provided about the periphery of the root section 30. As above, the brackets 170 are arranged to couple with and be mounted to the root end 16 of the blade 10, and accordingly a section of the brackets 170 extend adjacent at least a portion of the external blade surface in the direction of the blade tip end 14.

In the embodiment of Fig. 11, the brackets 170 are further provided with an internal projecting member 198, which extends from the lug 186 provided at the second end 172 of the bracket 170, the projecting members 198 projecting parallel to the main body of the bracket 70. When the bracket 70 is mounted to the root end 16 of a wind turbine blade 10, with the main body of the bracket 170 extending adjacent the external blade surface, the internal projecting member 198 of the bracket 170 extends adjacent at least a section of the internal surface of the wind turbine blade 10.

The use of the internal projecting members 198 allows for the mounting of internal wind turbine blade components using the brackets 170, without requiring an attachment operation performed on the internal blade surface, e.g. welding, bolting or riveting. Such internal add-on components or devices may include, but are not limited to, a blade bulkhead, a portion of a lightning down-conductor system, internal lighting systems, a blade monitoring device, etc.

Alternatively, it will be understood that the attachment system may be configured such that internal mounting elements may be provided by reversing a subset of the brackets 70 shown in Fig. 4, such that a first plurality of the brackets 70 are arranged to extend adjacent the external blade surface and a second plurality of the brackets 70 are arranged to extend adjacent the internal blade surface. It will be understood that the features of any of the above-described embodiments are not intended to be exclusively limiting, and that the individual features of any particular embodiment may be implemented in the system of any of the other embodiments. The herein described embodiments present a system and method for the attachment of add-on devices for a wind turbine blade. The use of the brackets 70,170 of the attachment system provides for a relatively simple and adaptable mechanism for the attachment of external and internal add-on devices to a wind turbine blade, without significantly affecting the underlying surface of the wind turbine blade. Furthermore, the weight associated with the add-on devices and components is transferred directly to the wind turbine hub instead of to the wind turbine blade, resulting in lighter blades which can be easier to manufacture and transport. The invention is not limited to the embodiment described herein, and may be modified or adapted without departing from the scope of the present invention.

Claims

1. A system for attaching a device to a wind turbine blade, the system having at least one bracket comprising:

2. The system of claim 1, wherein at least a portion of the body of said bracket is shaped to extend adjacent at least a section of the external surface of a wind turbine blade, wherein the system is used to attach an aerodynamic device adjacent a section of the external surface of the wind turbine blade.

3. The system of claim 1 or claim 2, wherein said bracket comprises a C-shaped or an L-shaped bracket.

4. The system of any one of claims 1-3, wherein said bracket comprises a substantially planar body.

5. The system of any one of claims 1-4, wherein at least a portion of the body of said bracket may be shaped to extend adjacent at least a section of the internal surface of a wind turbine blade, wherein the system is used to attach a device adjacent a section of the internals surface of the wind turbine blade.

6 The system of any one of claims 1-5, wherein the wind turbine blade is arranged for mounting to a wind turbine hub via a mounting connection between the wind turbine blade and the wind turbine hub, wherein the mounting element of said bracket is arranged to couple to at least a section of such a mounting connection.

7. The system of any one of claims 1-6, wherein said at least one bracket comprises: at least one lug provided at a first end of said bracket for coupling with at least one root bushing of a wind turbine blade to support said bracket on a wind turbine blade; and

a body extending from said first end of said bracket to a second end of said bracket, wherein said body is shaped to extend adjacent at least a section of the surface of a wind turbine blade when said bracket is coupled to a root bushing of the wind turbine blade, and wherein said body is arranged to support an aerodynamic device adjacent the wind turbine blade.

8. The system of any one of claims 1-7, wherein said bracket is arranged to receive an attachment element for an aerodynamic device, such that said aerodynamic device is at least partly supported on said bracket

9. The system of any one of claims 1-8, wherein the system further comprises a cushioning element arranged to be at least partly provided between the body of the bracket and an underlying adjacent surface of a wind turbine blade, to prevent damage to said underlying adjacent surface of the wind turbine blade.

10. The system of any one of claims 1-9, wherein the system further comprises a cover layer arranged to be applied to at least a portion of the body of said at least one bracket and to at least a portion of the surface of a wind turbine blade adjacent said bracket, said cover layer arranged to provide a transition surface between said portion of the body of said bracket and said portion of the surface of wind turbine blade.

11. The system of any one of claims 1-10, wherein the system further comprises forming elements, to be provided adjacent at least a portion of the body of said at least one bracket and adjacent at least a portion of the surface of a wind turbine blade adjacent said bracket, to provide a transition surface between said portion of the body of said bracket and said portion of the surface of the wind turbine blade.

12. The system of any one of claims 1-11, wherein the system further comprises at least one distal securing element, wherein said distal securing element is arranged to couple with said second end of said at least one bracket, to retain the body of said at least one bracket in a close alignment with the surface of the wind turbine blade.

13. The system of claim 12, wherein said distal securing element is provided as a ring element which is arranged to substantially extend around the diameter of a wind turbine blade, said second end of said at least one bracket adapted to couple with said ring element, to substantially secure said second end adjacent the surface of the wind turbine blade.

14. The system of any preceding claim, wherein the bracket is arranged to support at least one of the following devices: slats, spoilers, vortex generators, stall fences, flow deflectors, gurney flaps, acoustic wedges, a blade bulkhead, a portion of a lightning down-conductor system.

15. A wind turbine blade comprising a system as claimed in any one of claims 1-14 for attaching a device to the wind turbine blade.

16. A wind turbine comprising at least one wind turbine blade as claimed in claim 15.

17. A method for mounting aerodynamic devices to a wind turbine blade, the method comprising the steps of:

attaching at least one support bracket at the root end of said wind turbine, at least a portion of said support bracket extending from said root end towards said tip end; and

attaching at least a section of an aerodynamic device to said at least a portion of said support bracket, such that said aerodynamic device is substantially carried on said support bracket and provided adjacent a surface of said wind turbine blade.