A wind turbine blade and a method of making a wind turbine blade

Abstract

In a first aspect of the present invention there is provided a method of making a wind turbine blade. The method comprises providing a main blade part comprising a composite shell portion defining an airfoil profile. The composite shell portion extends longitudinally in a spanwise direction between an inboard end and a truncated outboard end which defines a shell end surface. The method further comprises providing a blade tip module defining a lightning receptor. The method further comprises providing a tip attachment member. Additionally, the method comprises applying a protective coating to the composite shell portion to form an outer skin covering the airfoil profile and the shell end surface, and attaching the blade tip module to the truncated outboard end of the composite shell portion via the tip attachment member, such that the blade tip module is separated from the composite shell portion by at least the outer skin covering the shell end surface.

Description

[0001] A wind turbine blade and a method of making a wind turbine blade

[0002] Technical field

[0003] The present invention relates generally to wind turbine blades and more particularly to a wind turbine blade comprising a blade tip module and a method for making such a wind turbine blade.

[0004] Background

[0005] Wind turbine blades typically include a composite shell and one or more lightning receptors that are configured to receive electricity at a defined location during a lightning strike and thereby protect the composite shell. An outboard tip of the wind turbine blade periodically defines the highest point on a wind turbine in use, and the blade may therefore be provided with a lightning receptor at the outboard tip to receive lightning effectively during a lightning strike.

[0006] However, the lightning receptor and composite shell are formed of different materials. As such, a protective outer skin applied to both the composite shell and the lightning receptor may experience better adhesion to the composite shell than to the lightning receptor. Further, the tip of the blade typically experiences the highest wind speeds in use. It follows that the protective coating at the tip of the blade may experience erosion and may separate from the lightning receptor.

[0007] Damage or wear that starts at the tip of the blade, for example at the lightning receptor, could propagate along the blade and cause damage to the outer skin covering the composite shell. Additional damage could occur at an interface between the lightning receptor and the composite shell following erosion or delamination of the outer skin at the lightning receptor, which could expose previously covered composite material at the interface. Again, damage at the interface could propagate inboard and cause further damage to the composite shell.

[0008] It is against this background that the present invention has been developed. Summary

[0009] In a first aspect of the present invention there is provided a method of making a wind turbine blade. The method comprises providing a main blade part comprising a composite shell portion defining an airfoil profile. The composite shell portion extends longitudinally in a spanwise direction between an inboard end and a truncated outboard end which defines a shell end surface. The method further comprises providing a blade tip module defining a lightning receptor. The method further comprises providing a tip attachment member. Additionally, the method comprises applying a protective coating to the composite shell portion to form an outer skin covering the airfoil profile and the shell end surface, and attaching the blade tip module to the truncated outboard end of the composite shell portion via the tip attachment member, such that the blade tip module is separated from the composite shell portion by at least the outer skin covering the shell end surface.

[0010] Accordingly, the blade tip module is attached to the truncated outboard end of the composite shell portion via the tip attachment member such that the blade tip module is separated from the composite shell portion by at least the protective coating applied to the shell end surface. The truncated outboard end of the composite shell portion, and in particular the shell end surface, is therefore protected by the outer skin, i.e. the protective coating applied to the composite shell, in use.

[0011] The composite shell portion may comprise a laminate structure comprising a plurality of layers of fibrous reinforcing material fixed in a resin matrix. Damage to the composite shell portion, for example due to erosion or impact damage, could cause layers of the composite shell portion to delaminate, thereby affecting the aerodynamic performance and structural integrity of the main blade part. Accordingly it is advantageous to protect as much of the composite shell portion with the outer skin as possible.

[0012] It will be appreciated that the shell end surface is the most outboard surface, i.e. defining the most outboard point, of the composite shell portion. Accordingly the shell end surface may experience some of the highest wind speeds when the blade is in use on an operational wind turbine. Protecting the shell end surface with the outer skin is therefore particularly advantageous because this can help to stop erosion or other failure mechanisms at the shell end surface that could cause delamination which could propagate further inboard along the composite shell portion in the spanwise direction.

[0013] In addition to the advantages described above in relation to protecting the shell end surface by applying the protective coating to form the outer skin, the wind turbine blade resulting from method described herein has further benefits related to the blade tip module being separated from the composite shell portion. Separating the blade tip module from the composite shell portion, i.e. providing a break between these parts of the blade, advantageously means that damage or wear that starts at the tip of the blade cannot propagate along the blade and cause damage to the composite shell portion. Any such damage or wear at the blade tip module, such as erosion or paint peeling, is confined to the blade tip module and stopped from propagating to the composite shell portion by the break or separation between the blade tip module and the composite shell portion.

[0014] In some examples, the blade tip module may be attached to the truncated outboard end of the composite shell portion such that the blade tip module is spaced apart from the shell end surface of the composite shell portion by a spanwise gap of no more than 5 mm. In some preferred examples, the blade tip module may be attached to the truncated outboard end of the composite shell portion such that the blade tip module is spaced apart from the shell end surface of the composite shell portion by a spanwise gap of no more than 3 mm. Minimising the spanwise gap separating the blade tip module from the shell end surface of the composite shell portion may help to minimise noise and may improve the aerodynamic performance of the blade.

[0015] In some examples, the blade tip module may be attached to the truncated outboard end of the composite shell portion such that the blade tip module is spaced apart from the shell end surface of the composite shell portion by a spanwise gap of at least 1 mm. In some examples the blade tip module may be attached to the truncated outboard end of the composite shell portion such that a spanwise gap remains between the blade tip module and the outer skin covering the shell end surface. Providing a spanwise gap between the blade tip module and the composite shell portion may ensure that the composite shell portion is not damaged by geometric variations between the composite shell portion and the blade tip module resulting from different thermal expansion coefficients of the respective components.

[0016] In some examples, the protective coating may be applied to the composite shell portion before attaching the blade tip module to the truncated outboard end of the composite shell portion. For example, the method may comprise applying the protective coating by hand, for example using a paint roller. Performing the steps of the method in this order may advantageously facilitate unhindered access to the shell end surface such that the protective coating can be accurately applied to the shell end in a simple application process. This ensures that an effective outer skin is formed by the protective coating covering the airfoil profile and the shell end surface. Carboline Windmastic 8801 is a suitable protective coating that may be applied to the composite shell portion to form the outer skin.

[0017] In some examples, the method may further comprise applying a protective tip coating to the blade tip module before attaching the blade tip module to the truncated outboard end of the composite shell portion. It follows that in some examples the blade tip module may be prepared with the protective tip coating offline, in a separate process, and may be provided for attachment to the truncated outboard end of the composite shell portion in the present method already comprising a protective tip coating. This ensures that a high quality coating can be applied to the blade tip module to provide effective protection to all of the blade tip module.

[0018] In some preferred examples, the protective coating applied to the composite shell portion of the main blade part and the protective tip coating applied to the blade tip module may be different. Accordingly, preparing the blade tip module with the blade tip coating offline may facilitate the selection and use of optimised protective coatings specific to each of the blade tip module and the composite shell portion to provide optimal protection for each component.

[0019] In some examples, the method may comprise one or more blade tip module preparation steps before the protective tip coating is applied. For example, the method may include priming the blade tip module prior to application of the protective tip coating. For example, Carboline Windmastic Primer FC may be a suitable primer for priming the blade tip module. In some examples the one or more blade tip module preparation steps may include activation of the blade tip module, such as a chemical etching or mechanical abrasion process. In some examples a blade tip module preparation step may involve the use of one or more chemicals, such as a primer, that could degrade the composite shell portion. For example such a chemical could degrade an epoxy resin that binds laminate layers of fibre material together in the composite shell portion. Offline preparation of the blade tip module, in a separate process, may therefore be advantageous so that the blade tip module can be prepared in isolation without risking damage to the main blade part.

[0020] In some examples, the blade tip module may be formed of an electrically conductive material such that the entire blade tip module defines the lightning receptor. Such a configuration increases the electrically conductive surface area of the blade tip module, thereby improving the performance of the tip module as a lightning receptor. In some preferred examples, the blade tip module may comprise copper, and may for example be formed entirely of copper. It follows that in some examples the blade tip module may therefore be a cast copper component.

[0021] In some examples, the tip attachment member may extend from the truncated end of the composite shell portion in the spanwise direction. For example, the tip attachment member may be part of the main blade part. In such an example the method may comprise attaching the blade tip module to the tip attachment member.

[0022] Alternatively, in some other examples, the tip attachment member may be formed integrally as part of the blade tip module. In such an example the method may comprise attaching the tip attachment member to the truncated end of the composite shell portion to thereby attach the blade tip module to the main blade part.

[0023] Further still, in some other examples the tip attachment member may be provided separately from either of the main blade part of the blade tip module. In such an example, the method may comprise attaching the tip attachment member to one of the blade tip module or the truncated outboard end of the composite shell portion, and subsequently attaching the other of the blade tip module or the truncated outboard end of the composite shell portion to the tip attachment member, such that the blade tip module is attached to the truncated outboard end of the composite shell portion via the tip attachment member. For example the tip attachment member may comprise one or more bolts that are arranged to extend from one of the blade tip module or the truncated outboard end of the composite shell portion in the spanwise direction. In such an example the method may comprise fastening the bolts into the other of the blade tip module or the truncated outboard end of the composite shell portion, for example via a nut or threaded bore associated with the same, to thereby attach the blade tip module to the truncated outboard end of the composite shell portion.

[0024] In some examples the tip attachment member may be formed of an electrically conductive material. Attaching the blade tip module to the tip attachment member may therefore comprise electrically connecting the blade tip module to the tip attachment member. Such a configuration of the tip attachment member may facilitate a fast and simple assembly process for both attaching and electrically connecting the blade tip module to the tip attachment member at the same time. In some examples the tip attachment member may be electrically coupled to a down conductor of the blade such that electricity from a lightning strike received by the lightning receptor of the blade tip module can be conducted safely to ground via the down conductor. Providing a defined path through the blade for electricity from a lightning strike helps to minimise the risk of such a lightning strike causing damage to the blade, in particular to the composite shell portion of the blade.

[0025] In some examples, the step of attaching the blade tip module to the tip attachment member may comprise removably fixing the blade tip module to the tip attachment member. For example, the tip attachment member and blade tip module and may be fastened together using bolts. Such a method may be particularly relevant to examples wherein the tip attachment member extends from one of the truncated outboard end of the composite shell portion or the tip attachment member. For example, bolts may extend through an outer surface of the blade tip module and into respective fastening bores in a tip attachment member extending from the truncated outboard end of the composite shell portion. Alternatively, the bolts may extend through an outer surface of the composite shell portion and into respective fastening bores in a tip attachment member extending from the blade tip module. Fastening the bolts may therefore releasably clamp the blade tip module to the tip attachment module. Removably fixing the blade tip module to the tip attachment member means that the blade tip module can be removed and replaced in a simple process if the blade tip module is damaged in use.

[0026] It will be appreciated that such disassembly for removal and replacement of the blade tip module is made particularly simple in examples where the outer skin covering the airfoil profile and shell end surface of the composite shell portion does not cover, and preferably does not extend onto, the blade tip module. A removably, i.e. releasably, fixed blade tip module may therefore be considered as an entirely separable add-on component in relation to the main blade part.

[0027] In some examples, providing the main blade part may comprise forming a first composite half shell portion and forming a second composite half shell portion. The method may comprise bonding the first and second composite half shell portions together to form the composite shell portion defining an airfoil profile. Forming each of the first and second composite half shell portions may comprise arranging a plurality of layers of fibrous reinforcing material in a lay-up in a mould, providing resin to the lay-up to infuse the fibrous reinforcing material, and curing the resin to integrate the layers and thereby form a half shell portion having a composite laminate structure.

[0028] In some examples, the method may further include a trimming process to form and prepare the shell end surface of the composite shell portion. Such a trimming process may be performed after the first and second composite half shell portions are bonded together to form the composite shell portion and before the protective coating is applied to the composite shell portion. Accordingly the protective coating may be applied to a finished shell end surface.

[0029] In some examples, the tip attachment member may be part of a pre-manufactured implant. Accordingly, the method may comprise bonding the pre-manufactured implant into one of the first or second composite half shell portions before the half shell portions are bonded together. In some examples, the method may additionally comprise bonding the premanufactured implant into the other of the first or second composite half shell portion when the half shell portions are bonded together to form the composite shell portion of the main blade part. Bonding the pre-manufactured implant into one of the first or second composite half shell portions may aid accurate and repeatable alignment and positioning of the tip attachment member.

[0030] In some examples, the pre-manufactured implant may comprise a non-conductive plug portion in which, or to which, the tip attachment member is secured. In some examples, the non-conductive plug portion may be formed of polyurethane. The plug portion of the pre-manufactured implant may be bonded to one of the first or second composite half shell portions. In some preferred examples, the tip attachment member may extend from the non-conductive plug portion. It will be appreciated that the pre-manufactured implant is bonded into one of the first or second composite half shell portions such that, when the half shell portions are bonded together to form the composite shell portion, the attachment member extends from the truncated outboard end of the composite shell portion, i.e. from the shell end surface, in the spanwise direction.

[0031] In another aspect of the present invention there is provided a wind turbine blade comprising a main blade part, a blade tip module defining a lightning receptor, and a tip attachment member. The main blade part comprises a composite shell portion defining an airfoil profile. The composite shell portion extends longitudinally in a spanwise direction between an inboard end and a truncated outboard end which defines a shell end surface. The main blade part comprises a protective coating applied to the composite shell portion to form an outer skin covering the airfoil profile and the shell end surface. The blade tip module is attached to the truncated outboard end of the composite shell portion via the tip attachment member, and the blade tip module is separated from the composite shell portion by at least the outer skin covering the shell end surface. In some preferred examples the composite shell portion may comprise a laminate structure comprising a plurality of layers of fibrous reinforcing material fixed in a resin matrix. For example, the composite shell portion may comprise layers of glass reinforcing fibre material, such as biaxial fibre reinforcing material, fixed in an epoxy resin matrix.

[0032] In some preferred examples the lightning receptor defined by the blade tip module may define the blade tip, i.e. the most outboard point of the wind turbine blade. Such a configuration may be advantageous for effectively receiving electricity from a lightning strike near to the blade tip, to avoid such a strike damaging the composite shell portion of the main blade part. In some preferred examples, the blade tip module may be formed of an electrically conductive material such that the entire blade tip module defines the lightning receptor. For example the blade tip module may comprise copper, and may for example be formed entirely of copper in some preferred examples. Again such a configuration may improve effectiveness of the lightning receptor.

[0033] In some examples, the tip attachment member may extend from the truncated end of the composite shell portion in the spanwise direction. In some examples, the blade tip module may be removably fixed to the tip attachment member by one or more bolts. As previously described with reference to examples of the method of making the wind turbine blade, such a configuration facilitates simple removal and replacement of the blade tip module if the blade tip module is damaged in use.

[0034] In some examples, the blade tip module may be spaced apart from the shell end surface of the composite shell portion by a spanwise gap of no more than 5 mm. In some preferred examples the blade tip module may be spaced apart from the shell end surface of the composite shell portion by a spanwise gap of no more than 3 mm. Minimising the spanwise gap separating the blade tip module from the shell end surface of the composite shell portion may help to minimise noise and may improve the aerodynamic performance of the blade. Accordingly, in some examples, the blade tip module may be butted up against, i.e. in contact with, the outer skin covering the shell end surface of the composite shell portion. Alternatively, in some other examples the blade tip module may be spaced apart from the shell end surface of the composite shell portion by a spanwise gap of at least 1 mm, such that there is a spanwise gap between the blade tip module and the outer skin covering the shell end surface. Such a configuration may facilitate easier and faster assembly of the blade tip module with the main blade part.

[0035] Brief description of the drawings Examples of the present invention will now be described by way of non-limiting example only, with reference to the accompanying figures, in which:

[0036] Figure 1 is a schematic perspective view of a portion of a wind turbine blade comprising a main blade part and a blade tip module;

[0037] Figure 2 is a schematic perspective view of the main blade part and the blade tip module in a step in an example of a method of making the wind turbine blade;

[0038] Figure 3 is a schematic cross-sectional view of a step in the method including applying a protective coating to a composite shell portion of the main blade part;

[0039] Figure 4 is a schematic cross-sectional view of the wind turbine blade showing the blade tip module attached to the main blade part;

[0040] Figure 5 is a schematic perspective view of a step in a method of making the composite shell portion of the main blade part from first and second composite half shell portions;

[0041] Figure 6 is a schematic cross-sectional view of the first and second composite half shell portions being arranged together and a pre-manufactured implant comprising a tip attachment member bonded into a composite half shell portion.

[0042] Figure 7 is a schematic perspective view of the first and second composite half shell portions bonded together to form the composite shell portion.

[0043] Detailed description

[0044] Figure 1 is a schematic perspective view of an outboard portion of a wind turbine blade 10. The blade 10 comprises a main blade part 12 which includes a composite shell portion 14 that defines an airfoil profile 16 configured for extracting energy from wind incident on the blade 10 in use. The composite shell portion 14 extends longitudinally in a spanwise direction (S) between an inboard end (not shown) and a truncated outboard end 18 which defines a shell end surface 20. In some examples the composite shell portion 14 may be formed of glass fibre reinforced plastic (GFRP).

[0045] As described in more detail later with reference to the cross-sectional view in Figure 3, the main blade part 12 comprises a protective coating 22 (shown in Figures 3 and 4) applied to the composite shell portion 14 to form an outer skin 24 (shown in Figure 3 and 4). Notably, the protective coating 22 forms an outer skin 24 covering both the airfoil profile 16 and the shell end surface 20 of the composite shell portion 14. Accordingly, the composite material of the main blade part 12 is protected by the outer skin 24 in use.

[0046] The wind turbine blade 10 additionally comprises a blade tip module 26 which defines a lightning receptor 28. As shown in Figure 2 and described later in more detail with reference to an example of a method of making the wind turbine blade 10, the blade tip module 26 is attached to the truncated end 18 of the composite shell portion 14 via a tip attachment member 30. As shown in Figure 2, in some examples such a tip attachment member 30 may extend from the truncated outboard end 18 of the composite shell portion 14 in the spanwise direction (S). The blade tip module 26 may be removably fixed to the tip attachment member 30 by one or more bolts 32. This is a simple and fast method for connecting the blade tip module 26 to the main blade part 12 via the tip attachment member 30 which also facilitates simple removal and replacement of the blade tip module 26 if it is damaged in use.

[0047] The blade tip module 26 is separated from the composite shell portion 14 by at least the outer skin 24 covering the shell end surface 20. The protective coating 22 is applied to the composite shell portion 14 to form a protective outer skin 24 covering both the airfoil profile 16 and the shell end surface 20. Accordingly the composite shell portion 14 is protected independently by the outer skin 24, and the outer skin 24 maintains a separation between the blade tip module 26 and the composite shell portion 14. In some examples, the blade tip module 26 is spaced apart from the shell end surface 20 of the composite shell portion 14 by a spanwise gap 34 of no more than 5 mm, and preferably no more than 3 mm. Maintaining a maximum separation of 5 mm, or preferably 3 mm, may help to minimise noise and improve the aerodynamic performance of the blade 10.

[0048] Examples of a method of making the wind turbine blade 10 will now be described with reference to the remaining figures.

[0049] Referring initially to Figure 2, the method includes providing a main blade part 12 comprising a composite shell portion 14 that defines an airfoil profile 16 as previously described. The method also includes providing a tip attachment member 30, which may extend from the truncated outboard end 18 of the composite shell portion 14 as shown in Figure 2. In such an example, the tip attachment member 30 preferably extends from the shell end surface 20 in the spanwise direction (S). In some examples the tip attachment member 30 may be part of a pre-manufactured implant 36 as described later in more detail with reference to Figure 6. Figure 2 also shows a blade tip module 26 which is provided in the method and which defines a lightning receptor 28. The blade tip module 26 is therefore configured to receive electricity in the event of a lightning strike at or near to a tip of the blade 10. It follows that the blade tip module 26 may be formed of an electrically conductive material such that the entire blade tip module 26 defines the lightning receptor 28.

[0050] In some examples, the method may involve applying a protective tip coating to the blade tip module 26. The protective tip coating may be applied to the blade tip module 26 in isolation, i.e. before the tip module 26 is attached to the main blade part 12 via the tip attachment member 30. Accordingly, the protective tip coating and its application can be optimised for the blade tip module 26, to improve longevity of the coating and protection of the blade tip module 26 in use. Additionally, the method may include priming the blade tip module 26 prior to application of the protective tip coating. Again, preparation of the blade tip module 26 in isolation facilitates greater freedom for performing an optimal blade tip module preparation process.

[0051] With reference now to the cross-sectional view of the main blade part 12 in Figure 3, the method includes applying a protective coating 22 to the composite shell portion 14. The protective coating 22 forms an outer skin 24 covering the airfoil profile 16 and the shell end surface 20 of the composite shell portion 14. For example, the protective coating 22 may be applied by hand, and the method may therefore comprise applying the protective coating 22 using a hand paint roller (not shown), in some examples. Accordingly, in some preferred examples the protective coating 22 may be applied to the composite shell portion 14 before the blade tip module 26 is attached to the tip attachment member 30. Such a sequence of method steps may facilitate improved access to the shell end surface 20 for applying the protective coating 22.

[0052] As previously noted, the method includes attaching the blade tip module 26 to the truncated end 18 of the composite shell portion 14 via the tip attachment member 30. Figure 4 shows a schematic cross-sectional view of a portion of the blade 10 with the blade tip module 26 attached to the tip attachment member 30. The blade tip module 26 may be arranged and attached to the truncated outboard end 18 of the composite shell portion 14 via the tip attachment member 30 with a spanwise gap 34 of no more than 5 mm between the shell end surface 20 and the blade tip module 26, in some examples, to minimise noise and aerodynamic drag. As shown in Figure 4, in some examples the blade tip module 26 may be removably fixed to the tip attachment member 30. For example, the blade tip module 26 may be attached to the tip attachment member 30 by one or more bolts 32 extending through an outer surface of the blade tip module 26 into a respective bore 40 in the tip attachment member 30 to clamp the blade tip module 26 to the tip attachment member 30. In examples where both the tip attachment member 30 and blade tip module 26 are formed of an electrically conductive material, attaching the blade tip module 26 to the tip attachment member 30, for example by clamping with bolts 32, may form an electrical connection between the blade tip module 26 and the tip attachment member 30.

[0053] With reference now to Figures 5, 6 and 7, in some examples the main blade part 12 provided in the method may be formed of a first composite half shell portion 42a and a second composite half shell portion 42b. As shown in Figure 5, the composite half shell portions 42a, 42b may be formed in corresponding moulds 44a, 44b, for example in a vacuum assisted resin transfer moulding (VARTM) method. As such forming the composite half shell portions 42a, 42b may involve arranging a plurality of layers of fibre reinforcing material in each mould 44a, 44b, supplying resin, such as epoxy resin, to the fibre material in the mould 44a, 44b, and subsequently curing the resin to thereby form the half shell portions 42a, 42b.

[0054] As previously noted, in some examples the tip attachment member 30 may be part of a pre-manufactured implant 36. Accordingly the method may include bonding the premanufactured implant 36 into one of the first or second composite half shell portions 42a, 42b as shown in Figure 6. As shown, in some preferred examples the pre-manufactured implant 36 may be bonded into a composite half shell portion 42a, 42b before the half shell portions 42a, 42b are bonded together to form the composite shell portion 14. This simplifies assembly of the main blade part 12 and may help to ensure that the tip attachment member 30 is accurately aligned and positioned in the main blade part 12.

[0055] It follows that the method may include bonding the first and second composite half shell portions 42a, 42b together to form the composite shell portion, as shown in Figure 7. With the half shell portions 42a, 42b bonded together, the composite shell portion 14 defines an airfoil profile 16. In examples where a pre-manufactured implant 36 is bonded into one of the half shell portions 42a, 42b, it will be understood that the tip attachment member 30 extends from the shell end surface 20 of the composite shell portion 14 once the half shell portions 42a, 42b are bonded together, as shown in Figure 7. After forming the composite shell portion 14 of the main blade part 12, the protective coating 22 may be applied to form the outer skin 24, and the blade tip module 26 may be attached to the tip attachment member 30 as described previously with reference to Figures 2, 3 and 4.

[0056] The examples of the method described with reference to Figures 2 to 7 can be used to make a wind turbine blade 10 such as that shown in Figure 1. Accordingly, the method provides a wind turbine blade 10 having a blade tip module 26 that is separated from the composite shell portion 14 by the outer skin 24 which protects the shell end surface 20. This improves longevity of the composite shell portion 14 and may also facilitate simple assembly and replacement of the blade tip module 26.

[0057] The description provided herein serves to demonstrate a plurality of possible examples of the present invention. It will be appreciated that features described in relation to any of the examples above may be readily combined with any other features described with reference to other examples without departing from the scope of the invention as defined in the appended claims.

Claims

CLAIMS:

1. A method of making a wind turbine blade comprising: providing a main blade part comprising a composite shell portion defining an airfoil profile, the composite shell portion extending longitudinally in a spanwise direction between an inboard end and a truncated outboard end which defines a shell end surface; providing a blade tip module defining a lightning receptor; providing a tip attachment member; applying a protective coating to the composite shell portion to form an outer skin covering the airfoil profile and the shell end surface; and attaching the blade tip module to the truncated outboard end of the composite shell portion via the tip attachment member, such that the blade tip module is separated from the composite shell portion by at least the outer skin covering the shell end surface.

2. The method of claim 1, wherein the blade tip module is attached to the truncated outboard end of the composite shell portion such that the blade tip module is spaced apart from the shell end surface of the composite shell portion by a spanwise gap of no more than 5 mm, and preferably no more than 3 mm.

3. The method of any preceding claim, wherein the protective coating is applied to the composite shell portion before attaching the blade tip module to the truncated outboard end of the composite shell portion.

4. The method of any preceding claim, further comprising applying a protective tip coating to the blade tip module before attaching the blade tip module to the truncated outboard end of the composite shell portion.

5. The method of claim 4, further comprising priming the blade tip module prior to application of the protective tip coating.

6. The method of any preceding claim, wherein the blade tip module is formed of an electrically conductive material such that the entire blade tip module defines the lightning receptor.

7. The method of any preceding claim, wherein the tip attachment member extends from the truncated end of the composite shell portion in the spanwise direction, andwherein the method comprises attaching the blade tip module to the tip attachment member.

8. The method of claim 7, wherein the tip attachment member is formed of an electrically conductive material, and wherein attaching the blade tip module to the tip attachment member comprises electrically connecting the blade tip module to the tip attachment member.

9. The method of claim 7 or claim 8, wherein attaching the blade tip module to the tip attachment member comprises removably fixing the blade tip module to the tip attachment member.

10. The method of any preceding claim, wherein providing the main blade part comprises forming a first composite half shell portion, forming a second composite half shell portion; and bonding the first and second composite half shell portions together to form the composite shell portion defining an airfoil profile.

11. The method of claim 10, wherein the tip attachment member is part of a premanufactured implant, and wherein the method comprises bonding the pre-manufactured implant into one of the first or second composite half shell portions before the half shell portions are bonded together.

12. A wind turbine blade comprising a main blade part, a blade tip module defining a lightning receptor, and a tip attachment member, the main blade part comprising a composite shell portion defining an airfoil profile, the composite shell portion extending longitudinally in a spanwise direction between an inboard end and a truncated outboard end which defines a shell end surface, the main blade part comprising a protective coating applied to the composite shell portion to form an outer skin covering the airfoil profile and the shell end surface;; wherein the blade tip module is attached to the truncated outboard end of the composite shell portion via the tip attachment member; and wherein the blade tip module is separated from the composite shell portion by at least the outer skin covering the shell end surface.

13. The wind turbine blade of claim 12, wherein the tip attachment member extends from the truncated end of the composite shell portion in the spanwise direction.

14. The wind turbine blade of Claim 12 or claim 13, wherein the blade tip module is removably fixed to the tip attachment member by one or more bolts.

15. The wind turbine blade of any of claims 12 to 14, wherein the blade tip module is spaced apart from the shell end surface of the composite shell portion by a spanwise gap of no more than 5 mm, and preferably no more than 3 mm.

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