WO2016079535A1

WO2016079535A1 - Method and apparatus for turbine blade repair

Info

Publication number: WO2016079535A1
Application number: PCT/GB2015/053545
Authority: WO
Inventors: Brian Forbes
Original assignee: Trac Engineering Limited
Priority date: 2014-11-20
Filing date: 2015-11-20
Publication date: 2016-05-26
Also published as: GB2532612A; GB201520481D0

Abstract

A method and system of repairing at least part of wind turbine blades. The method includes the steps of dividing or mapping at least the leading edge of a blade into one or more portions, removing at least part of a portion of the blade, and said at least part of said portion of the blade is replaced and/or substantially covered with one or more prefabricated portions and/or parts thereof.

Description

Method and Apparatus for Turbine Blade Repair

The present invention relates to the in situ repair of damaged wind turbine blades.

Although the following description refers to the repair of the leading edge and adjacent areas of a turbine blade, the skilled person will appreciate that the method and apparatus of the present invention could be used to replace other parts of the blade such as the trailing edge.

Power generation from wind and in particular the use of on-shore and offshore wind farms is increasingly being utilised as a cost effective method of generating renewable energy. At the present time, the UK has more offshore wind turbines (currently 1,075) than the rest of the world combined, and the offshore wind industry is rapidly expanding both here and on a global basis due to the significantly higher energy yield potential contrasted with onshore.

This greater energy yield comes at a price due to not only the greater technological demands of developing wind turbine generators (WTG) which are capable of being attached to the seabed, or the technological challenges of the next generation of floating turbines, but also the extremely high logistical cost of construction, which is compounded with inclement weather conditions.

Obviously, any operational down time of the WTG has a direct effect on the cost efficiency, annual energy production (AEP) cost and ROI, therefore any repairs required should be kept to a mijiimum along with the time taken to complete the same.

Turbine blades are the primary elements of WTGs. Most wind turbines start operating at a speed of 4-5 metres per second and reach maximum power at about 15 metres per second. Most modern turbine blades consist of an upper and lower composite shell with inner reinforcement, plus a circular foot section for mounting on the pitch-bearing (a pitch bearing is used by a pitch regulation device to maximise energy generation and protect the blades from being overpowered in excessive wind conditions).

Most modern turbine blades are manufactured in a highly specific process using composite material within the design constraints of achieving specified structural requirements. The manufacturing process of turbine blades typically involves bonding a suction side shell and a pressure side shell together at bond lines all along the trailing and leading edges, root and tip of the blade. The bond lines are generally formed by applying a suitable specification of bonding paste or compound along the bond line with a minimum designed bond width between the shell members to form a close fit. These bonding lines are a critical design constraint of the blades.

During their anticipated 20- to 25-year lifespan, they are exposed to dynamic loads and are also subject to frequent load fluctuations, the main sources of blade loading are: 1. Aerodynamic; 2. Gravitational; 3. Centrifugal; 4. Gyroscopic; and 5. Operational. Blades operate in demanding environmental conditions, which include extreme weather and surface "bombardment" with sand and dirt particles. A significant number of turbine blade field failures are bond line related, particularly leading edge failures, this may often be triggered by the erosion of the leading edge resulting in moisture intrusion. Separation of the bond line along the leading edge of an operational turbine blade can result in a catastrophic failure and damage to the wind turbine. The leading edges of blades are highly susceptible to erosion in the field conventional. Leading edge bond configurations are also highly susceptible to erosion in the field due to the conventional manufacturing practice of locating these bond lines in the centre of the leading edge, which results in costly and expensive field repairs; such repairs are costly and time consuming in remote onshore locations, however, in offshore locations the requisite time and costs are considerably greater. In addition to erosion, blade defects and damage can occur through impact (e.g. birds), ice, lightning, manufacturing related weaknesses or overstress due to turbulence or extreme wind forces, component related failure such as pitch regulation devices, UV, salt and insect build up.

The typical process of repairing a blade defect will involve the use of a ceramic (or other) abrasive grinder to remove sufficient composite material to reveal the unaffected composite structure beneath the defect, and to determine the extent and depth of the issue. Once the grinding process has been completed successive new layers of glass fibre matting impregnated with epoxy resin and hardener will then be added (through a variety of differing processes) allowed sufficient time to cure (again through a variety of differing processes according to preference, environment and technical demands) and the process repeated until surface coat preparation can be completed.

The consequences of the factors above are that any repairs, where and when it is logistically and financially feasible to identify defects and redress them, will be extremely expensive and often time consuming. OEMs face an exceptional set of challenges in:

1. Identifying all defects;

2. Securing all labour resources to ensure defects are repaired;

3. The scale of the degradation of their blades before End- of- Warranty (EoW);

4. The extreme costs involved in conventional repair methods due to the time and weather constraints, let alone a seasonal limitation on the months during which repairs may be successfully conducted; and

5. Competing with other OEMs for scarce labour resources.

In the worst case scenario where a blade is so badly damaged that it must be replaced, current information suggests that it isn't possible to hire a suitably equipped installation vessel to complete this process for several years due to high demand for and limited availability of these specialist vessels; in the event this were even possible there is a limit to the number of times an installation vessel may revisit the offshore WTG location due to the geo- technical problems which re-visitation creates on the seabed. The direct consequence of this factor is that there are limitations on the blade replacement option where WTG units are experiencing repeated failures. This means that in such scenarios the overarching priority of achieving ROI for this WTG is not possible and the entire cost of the WTG unit plus associated installation costs must be written off.

It is therefore an aim of the present invention to provide a method of repairing wind turbine blades that address the abovementioned problems.

It is a further aim of the present invention to provide an apparatus that addresses the abovementioned problems.

It is a yet further aim of the present invention to provide a turbine blade repair system that addresses the abovementioned problems.

In a first aspect of the invention there is provided a method of repairing at least part of wind turbine blades, said method including the steps of;

dividing or mapping at least the leading edge of a blade into one or more portions,

removing at least part of a portion of the blade, and wherein said at least part of said portion is replaced and/or substantially covered with one or more prefabricated portions and/ or parts thereof.

In one embodiment the prefabricated portions include one or more layers of fibreglass matting. Typically the fibreglass matting includes and you or any combination of uniaxial, biaxial and/or triaxial matting. Further typically the matting includes at least one resin and/ or hardener.

In one embodiment the resin and/ or hardener is cured to form a hard shell or hardened prefabricated portion. Typically the prefabricated portion is one or more substantially flexible portions comprising one or more layers of fibreglass matting.

In one embodiment the matting is cut or trimmed to fit as required. Typically the cutting and/or trimming is performed on site. Further typically the prefabricated portion is cured into position. Typically curing involves applying heat and/or pressure to the required area to bond and/or harden the same.

In one embodiment the prefabricated portion includes thermoplastic materials. In one embodiment the prefabricated portion is constructed substantially from and or more thermoplastics.

Typically the prefabricated portion includes one or more polymers or thermop olymer s .

In one embodiment the prefabricated portion comprises copolymers and/ or a polymer blend. Typically the polymer is an acrylate based polymer. Preferably the polymer includes acrylonitrile styrene acrylate and/or polycarbonate.

In one embodiment the prefabricated portion comprises a blend of acrylonitrile styrene acrylate and polycarbonate.

In one embodiment the prefabricated portions include graphene.

In one embodiment the prefabricated portions include one or more metals or metallic portions.

Typically the prefabricated section is bonded to the blade using one or more adhesives. Typically the adhesives include any one or any combination of paint on, spray on, catalyse, peel off, silicon, epoxy, VE resin, PU, PSA and/ or the like.

In one embodiment the prefabricated portion is impregnated with one or more adhesives, resins and/ or hardeners.

In one embodiment prefabricated portion includes a sheet of adhesive, resin and/ or hardener. Typically the portions of the blade include one or more blade sections. Further typically the prefabricated portions are prefabricated sections of a blade.

In one embodiment the damaged surface of the blade is removed as a first portion or section. Typically the prefabricated portion is a shell, matt or skin portion. Further typically the portions or sections removed are the outer layer or layers of the blade.

In one embodiment the portions removed are those immediately adjacent the damaged parts of the blade.

In one embodiment the portion is removed as a single continuous portion or strip.

Typically the turbine blades are substantially hollow. Further typically the blade is defined by a wall.

In one embodiment the prefabricated portions or sections thereof are thinner than the blade wall. Typically the removed portion does not penetrate the wall of the blade.

In one embodiment the one or more prefabricated portions or sections are of substantially the same or identical dimensions as the portions or sections removed from the blade. In this embodiment the prefabricated portions or sections do not have to be cut to length on site.

Alternatively, a damaged portion or section can be removed from the blade and prefabricated portion or section cut to fit on site.

In an alternative embedment one or more prefabricated portions or sections are added or adhered to the blade without substantially removing a portion of the blade. Typically the profile of the prefabricated portion is of substantially the same profile as the original profile of the leading edge of the blade. Once fitted the prefabricated shell, mat or skin portion or section will provide a new surface once adhered in position.

In one embodiment predetermined or pre-measured sections of a damaged blade can be removed and replaced with one or more pre-formed modular sections that correspond at least in size to the one or more sections removed on each particular model and make of blade.

In a preferred embodiment the prefabricated portions are one or more skin or shell portions. In one embodiment the prefabricated sections correspond in contour and form to the original blade portion. In one embodiment the original contour or form is restored without removing sections on each particular model and make of blade.

Typically the damaged parts of the blade fall or are located within one or more mapped portions or sections.

In one embodiment the portions or sections are removed by cutting and/ or grinding the same from the blade. Typically the cuts include a cut along or substantially parallel to a longitudinal axis of the blade; this cut may be complex due to the inherent requirement to scarf the surface to correspond to the scarfed feature of the prefabricated modular 'shell or skin' repair section which will subsequently be fitted to this area of the blade. Further typically the cuts include one or more cuts orthogonal to a longitudinal axis of the blade.

Preferably the portions or sections removed from the blade are sections of the leading edge. Typically only parts of the leading edge are removed leaving the remainder of the blade intact. In one embodiment only parts of the surface of the leading edge are removed leaving the remainder of the blade intact.

In one embodiment at least one portion or section of the leading edge is removed by cutting into the blade in a direction perpendicular or orthogonal to a longitudinal and/or horizontal plane of the blade. Typically the cut direction is likely to be effected using a scarfing technique. Further typically cutting in this manner removes a specific depth of composite material from the surface of the blade.

In one embodiment the cut in from the blade surface is to a depth of between 0.2-2.5mm.

Preferably the replacement shell or skin portions or sections are secured in place using one or more adhesives and/or resins. Typically the adhesives and/ or resins used correspond and/ or are identical to the adhesives and/ or resins used in the construction of the blade. Further, typically the resins are the same as those used when the upper and lower shells are bonded together.

Typically the bond line of the replaced portion or section runs substantially orthogonally and/ or at a right angle to the original OEM bond line of the blade.

In one embodiment the blade is divided up into one or more portions or sections using a software model of the 3D design of the blade.

In one embodiment the portions or sections are measured from the root of the blade in a direction towards the tip.

Preferably the composition and/or construction of the prefabricated sections is substantially the same or identical to the portions or sections removed from the blade. Typically the replacement shell or skin sections are substantially the same as or identical in any one or any combination of weight, profile, contour, lamination as the removed sections. Further typically the prefabricated sections conform to the manufacturing specification of the blade being repaired.

Typically prefabricated includes, any one or any combination of pre- manufactured, pre-moulded, pre-engineered, pre-cast, modular, manufactured or assembled before transport to the turbine site and/or the like.

In one embodiment the leading edge surface of the blade is scanned or mapped in three dimensions (3D). Typically the leading edge surface of the blade is scanned or mapped to generate CAD data. Further typically the data facilitates comparison between the leading edge blade surface geometry with a new blade incorporating the prefabricated portions. As such, a user can determine the extent to which the cutting patch and depth is required to be executed in order to substantially restore aerodynamic performance, once the new portion or module is installed, thus rejuvenating the surface geometry.

The results of this computer generated calculation dictates the precise machining process required for each and every leading edge to be repaired.

In one embodiment one or more protective coatings and/or materials are applied to the prefabricated portions or sections thereof. Typically the protective materials are coatings and/or tapes. Further typically the protective coatings and or materials are applied during the manufacture of the prefabricated portion and/ or post manufacture.

In one embodiment the prefabricated portions or sections are installed on blades that are removed or dismounted from the turbine. Typically the prefabricated portions are installed on or otherwise attached to blades post manufacture of said blades. In one embodiment offshore wind turbine blades are removed and the prefabricated portions attached onshore.

In a second aspect of the invention there is provided one or more modular and/ or prefabricated sections of a wind turbine blade, wherein at least one section corresponds to at least one part of a leading edge of said turbine blade.

In one embodiment the modular and/or prefabricated sections are shell or skin portions. Typically these shell or skin portions correspond in shape to an outer layer or face of a wind turbine blade.

Preferably at least one edge or face of the prefabricated section is shaped to form a leading edge or face of a turbine blade. Typically the opposite edge or face opposing at least one edge is substantially parallel to the surface and corresponding to the curved contour of the leading edge. In one embodiment the opposing edge is scarfed at each end. Typically the portion is scarfed longitudinally.

Typically the modular and/or prefabricated sections can be aligned to form a complete leading edge of a turbine blade. Further, for certain makes and models of wind turbine blade the modular and/or prefabricated sections may be manufactured marginally or slightly over sized (1-2 mm) in order to be able to trim and/or sand down the joint lines to achieve a perfecdy smooth finish between the original blade material and the repaired section.

In a third aspect of the invention there is provided a system for on-site repair of turbine blades, said system including removing part of the leading edge of the blade and replacing the same with a pre-manufactured or pre- assembled section that corresponds at least in profile or shape to the part of the blade that is removed.

In a further aspect of the invention there is provided a method of manufacturing one or more wind turbine blade leading edge sections wherein the method includes moulding one or more components to form said leading edge.

In a further aspect of the invention there is provided a method of manufacturing one or more wind turbine blade leading edge sections wherein the method includes moulding one or more components to form said leading edge in a particularly thin shell or skin in order to cover said leading edge.

In a further aspect of the invention there is provided a method of manufacturing one or more wind turbine blade leading edge sections wherein the method includes the incorporation of new components into the leading edge sections in order to combat and reduce the operational wear and tear on the blades.

In a yet further aspect of the invention there is provided a method of repairing a wind turbine by removing a section of the blade and/ or tip and replacing the same with a corresponding pre-formed section of the blade and/ or pre-formed blade tip.

In a yet further aspect of the invention there is provided a system for removing blade material from at least the surface or deeper of a wind turbine blade wherein said removal is manual, semi-automated or automated.

Specific embodiments of the invention are now described with reference to the following figures, wherein:

Figure 1 shows a side view of a wind turbine generator; Figures 2a-2c show views of a wind turbine blade;

Figure 3 shows a schematic cross sectional diagram of a wind turbine leading edge; Figures 4a-4d show increasing amounts of damage to leading edges of wind turbine blades over time;

Figures 5a-5d show perspective and cross sectional views of blade repair in accordance with one embodiment of the invention;

Figures 6a-6c show perspective and cross sectional views of blade repair in accordance with one embodiment of the invention;

Figures 7 a-7c show perspective and cross sectional views of blade repair in accordance with one embodiment of the invention;

Figures 8a and 8b show cross sectional and perspective views of blade repair in accordance with one embodiment of the invention;

Figures 9-11 show perspective views of the joins between adjacent sections.

Wind turbine blade material is inherently vulnerable to erosion, but the sector of the blade which is particularly susceptible to this damage is the leading edge. Instead of repairing leading edge erosion numerous times during blade design life it's much more efficient to replace the leading edge material in this sector with a more durable material.

Our rapid, repeatable, in-situ repair solution is very cost effective and will introduce a machining process to surgically remove a thin layer from the damaged surface of the leading edge and replace that with a modular, prefabricated leading edge erosion shield. This high precision process will rejuvenate leading edge aerodynamics to recover valuable lost yield, onshore and offshore, and that's the only way owners/operators will maximise ROI on all assets, reduce the COE and achieve full blade design life.

The present invention provides the manufacture and installation of modular leading edge component sections, which would be used to effect repairs to significant leading edge damage more rapidly and cost effectively than current procedures permit. The use of sections removes the need to repair each individual defect within the same area or section of the blade, by facilitating the removal of entire damaged leading edge sections which would then be replaced by modular leading edge component sections. In preference to the various typical conventional methods of repairing damage to the leading edges of wind turbine blades, which involves removing the damaged section then building up successive new layers of composite material before applying surface protection layers, the proposed method of using modular leading edge component sections would require the removal by a cutting process of a longitudinal section of the leading edge to a specified depth and length, subsequent to which the modular leading edge component section would be adhered to the prepared shell surface. This modular repair process would be considerably faster and require considerably less time to complete, which is a major limiting factor in determining access to wind turbines and in particular off shore wind turbines.

Optionally leading edge protection (LEP) coatings or tapes can be incorporated onto the blades. It's possible to apply LEP either during the manufacturing process (i.e. in mould/casting) and post manufacture in a controlled environment, which maximises operational durability; infield/situ.

Furthermore, there is the possibility of performing the modular installation in a factory post manufacture of new blades, or in alternative situations such as would occur if blades are required to be dismounted from the turbine and repaired in a temporary type structure on site onshore, or a warehouse, etc. or removed from an offshore wind turbine to be repaired onshore.

Figure 1 shows a conventional wind turbine generator 2 comprising a nacelle 4 mounted on a tower 6. The nacelle includes a hub 8 from which the blades 10 depend. The turbine can be situated on land (on-shore) or offshore, either by anchoring to the sea bed or positioning on floating platforms.

A plan view, perspective view and cross sectional view of a turbine blade 10 is shown in figures 2a-2c respectively. The root portion 12 of the blade is attached to the hub 8 and from the root 12 the rest of the blade extends in a substantially linear manner to the tip 14. The leading edge 16 meets the wind and is the part that typically sustains the majority of wear and/or damage the blade is subject to. The trailing edge 18 sustains relatively little damage compared to the leading edge.

The blade itself is usually formed from an upper shell 20 and a lower shell 22 attached together with adhesive to form an internal cavity 24. The internal blade spine or beam is formed one or more shear webs 26 and spar caps 28.

Figure 3 shows a cross sectional view along the longitudinal axis of the blade. The bond line 30 formed from the attachment of the upper 20 and lower 22 shells is located substantially centrally along the leading edge 16 of the blade. As discussed, it is this area that is damaged 32 the most from erosion, impact, etc. and considerable damage can be made if OEM bond line 30 is exposed and is open to the elements.

Figures 4a-4d show erosion of the leading edges 16 of turbine blades 10 from use of around one year in figure 4a, two years in figure 4b, around ten years in figure 4c to over ten years in figure 4d. The figures illustrate that is usually the outer layers of the blade that are stripped or eroded through use to expose the support material underneath.

Figure 5c and 5d shows a transverse cut line 34 which is made perpendicular or orthogonal to the OEM bond line 30, to remove at least part of the leading edge of the blade, and in particular the part that includes the damage. The cut can be made with a saw, chainsaw, grinder, angle grinder, circular saw and/or the like capable of cutting through the composite shell of the blade.

Figure 5c shows the cross sectional view once the damaged edge portion has been removed and one or more prefabricated modular sections 38 inserted into place. It can be seen that the OEM bond line 30 is covered, effectively by being capped and a new bond line runs orthogonal to the OEM bond line. Thus, in the event the modular section is damaged at the leading edge, the OEM bond line will not be exposed.

The modular repair sections 38, precisely resemble the original OEM specification and form so each modular section precisely mirrors the curvature of the leading edge of each blade along each damaged section to be replaced or repaired. These modular sections can be kept in stock and transported on site as required. It can be seen that usually in order to fit the modular sections, straight lines are required to be cut into the blade which significantly reduces the time an operator has to spend on repair and thus reduces the length of time the turbine is out of operation.

Figure 9 shows how the repair section 38 itself can be provided in a number of modules 38a-38c.

As such, the prefabricated modular section 38 or plurality of sections 38a- 38d can conform to the original curved shape or profile of the outer shell or skin layers. Such an embodiment is shown in figures 5a-5d wherein a robotic arm removes a strip 42 of the outer layer of the blade leading edge. The removal is usually by cutting or grinding a channel thereby removing a substantially linear section of the leading edge. The edges of the strip 42 can include steps, lips and/or the like to improve the bonding between the channel and the repair section 38. In the examples given in figures 5 and 6 the edges of the channel are scarfed to form strong joints with a relatively small seam. In the example given in figure 5 around 2.5 mm of the leading edge outer layers are removed. In figure 6 around 0.2 mm is removed. In an embodiment shown in figures 7a-7c, the damaged portions are removed by machining or cutting away only the outer one or two layers of the blade material. The prefabricated strip 38 is overlaid and given the thinness of the repair, no joint formations are required. Figures 8a and 8b show an embodiment where no machining or cutting is performed and a precast or prefabricated section of 3-4 plys of thickness is applied over the damage.

Figures 9, 10 and 11 show examples of the different types of joints possible between adjacent prefabricated sections or modules 38a, 38b. Figures 9 and 11 show insertion and dovetail joints respectively. Figure 11 shows lap or splice joints.

One method of leading edge erosion (LEE) repair utilises fibreglass matting, whereby for each make and model of blade, there would comprise multiple layers of specified uniaxial, biaxial and/or triaxial fibreglass matting (or other such specification of matting— such as thermoplastic materials, or other materials which would be suitable for this purpose) which when bonded together using resin/hardener cure to form a hard shell. The hardness of the finished shell could vary according to need and preference.

Fibreglass matting is typically specified according to a number of different parameters, e.g_^ the weight per square meter (gsm), direction of fibres, flexibility, strength, combinations of materials, quality, etc.

This LEE repair solution we have developed uses such multiple layers as correspond, closely or exactly, to the leading edge design and manufacturing specification of each particular make and model of wind turbine blade. In certain circumstances it may be preferable to use other multiple layers which do not correspond or which are fundamentally different from the leading edge design and manufacturing specification. Within the necessary material performance parameters essential to the structural integrity of the blade leading edge, the selection of materials for each make and model may vary widely. In one embodiment the particular materials will not be pre-cured.

The combination of materials (typically, different matting specs and impregnated resins— e.g. Epoxy/VE resin system); for a given blade will then be bonded into the machined LE area using an adhesive which has been specified for compatibility with this material combination (e.g. Silicon, Epoxy, PU, or PSA). Adhesives are available in a number of specifications and forms/types— e.g. paint on, spray on, catalyse, peel off, etc.

In one embodiment an at least initially inert sheeted version of the specified adhesive, which may be catalysed with high heat and moderate pressure over a relatively short period of time. Therefore, for a given blade the requisite combination of matting, resin/epoxy and adhesive will be rolled together for convenient transportation to the repair site then unrolled, cut to fit as required, then cured into position.

An important aspect of this invention is the capability to scan in 3D the leading edge surface of the blade to generate CAD data, which then facilitates comparison between the LE blade surface geometry of a new blade to then determine the extent to which the cutting path and depth require to be executed in order to ultimately restore aerodynamic performance, once the new module is installed, by rejuvenating the surface geometry. The results of this computer generated calculation will uniquely dictate the precise machining process required for each and every LE to be repaired.

Claims

1. A method of repairing at least part of wind turbine blades, said method including the steps of;

removing at least part of a portion of the blade, and

wherein said at least part of said portion is replaced and/or substantially covered with one or more prefabricated portions and/ or parts thereof.

2. A method according to claim 1 wherein the prefabricated portions include one or more layers of fibreglass matting.

3. A method according to claim 2 wherein the fibreglass matting includes any one and/or any combination of uniaxial, biaxial and/ or triaxial matting.

4. A method according to claim 3 wherein the matting includes at least one resin and/or hardener.

5. A method according to claim 4 wherein the resin and/or hardener is cured to form a hard shell or hardened prefabricated portion.

6. A method according to claim 3 wherein the matting is cut or trimmed to fit as required.

7. A method according to claims 5 or 6 wherein the prefabricated portion is cured into position.

8. A method according to claim 7 wherein curing involves applying heat and/ or pressure, and/or time to permit the chemical reaction, to the required area to bond and/ or harden the same.

9. A method according to claim 1 wherein the prefabricated portion includes thermoplastic materials.

10. A method according to claim 9 wherein the prefabricated portion is constructed substantially from one or more thermoplastics.

11. A method according to claim 10 wherein the prefabricated section is bonded to the blade using one or more adhesives.

12. A method according to claim 11 wherein the prefabricated portion is impregnated with one or more adhesives, resins and/ or hardeners.

13. A method according to claim 12 wherein the prefabricated portion includes a sheet of adhesive, resin and/ or hardener.

14. A method according to claim 1 wherein the damaged surface of the blade is removed as a first portion or section.

15. A method according to claim 14 wherein the prefabricated portion is a shell, matt or skin portion and the portions or sections removed are the outer layer or layers of the blade.

16. A method according to claim 14 wherein the prefabricated portions or sections thereof are thinner than the wall of the turbine blade.

17. A method according to claim 16 wherein the removed portion does not penetrate the wall of the blade.

18. A method according to claim 1 wherein the one or more prefabricated portions or sections thereof are of substantially the same or identical dimensions as the portions or sections removed from the blade.

19. A method according to claim 1 wherein one or more prefabricated portions or sections are added or adhered to the blade without substantially removing a portion of the blade.

20. A method according to claim 1 wherein the profile of the prefabricated portion is of substantially the same profile as the original profile of the leading edge of the blade.

21. A method according to claim 1 wherein the portions or sections are removed by any one or any combination of cutting, grinding, routing, sanding or otherwise abrading to remove the same from the blade.

22. A method according to claim 21 wherein the cuts include a cut along or substantially parallel to a longitudinal axis of the blade.

23. A method according to claim 21 wherein the cuts include one or more cuts transverse or orthogonal to a longitudinal axis of the blade.

24. A method according to claim 21 wherein the portions or sections removed from the blade are sections of the leading edge, leaving the remainder of the blade intact.

25. A method according to claim 21 wherein at least one portion or section of the leading edge is removed by cutting into the blade in a direction perpendicular or orthogonal to a longitudinal and/or horizontal plane of the blade.

26. A method according to claim 1 wherein the cut direction effected using a scarfing technique.

27. A method according to claim 1 wherein prefabricated portion is secured in place using one or more adhesives and/ or resins.

28. A method according to claim 27 wherein the adhesives and/or resins used correspond and/or are identical to the adhesives and/or resins used in the construction of the blade.

29. A method according to claim 28 wherein the resins are the same as those used when the upper and lower shells are bonded together.

30. A method according to claim 29 wherein the composition and/or construction of the prefabricated sections is substantially the same or identical to the portions or sections removed from the blade.

31. A method according to claim 27 wherein one or more of the adhesives and/or resins used do not correspond and/ or are different to the adhesives and/ or resins used in the construction of the blade

32. A method according to claim 1 wherein at least the leading edge surface of the blade is scanned or mapped in three dimensions (3D).

33. A method according to claim 32 wherein the leading edge surface of the blade is scanned or mapped generating any one or any combination of CAD data, aerodynamic data, and/or leading edge geometry in 3D.

34. A modular and/or prefabricated section of a wind turbine blade, wherein said at least one section corresponds to at least one part of a leading edge of said turbine blade, said correspondence achieved through 3D scanning or mapping of said blade.

35. A section of a turbine blade according to claim 34 wherein the modular and/ or prefabricated sections are shell or skin portions.

36. A section of a turbine blade according to claim 34 wherein the modular and/or prefabricated sections can be aligned to form a complete leading edge of a turbine blade.

37. A system for on-site repair of turbine blades, said system including removing part of the leading edge of the blade and replacing the same with a pre-manufactured or pre-assembled section that corresponds at least in profile or shape to the part of the blade that is removed.

38. A method of manufacturing one or more wind turbine blade leading edge sections wherein the method includes moulding one or more components to form said leading edge in a particularly thin shell or skin in order to cover at least part of said leading edge.

39. A system for removing blade material from at least the surface or deeper of a wind turbine blade according to any preceding claim, wherein said removal is manual, semi-automated or automated.