Lightning protection system

Abstract

A method of manufacturing a lightning protection system for a wind turbine blade, the method comprising: providing a first metal layer; and constructing a metal reinforcing part directly onto the first metal layer using an additive manufacturing technique so as to create an electrical connection between the first metal layer and the metal reinforcing part, wherein a portion of the first metal layer extends laterally beyond the metal reinforcing part.

Description

[0001] LIGHTNING PROTECTION SYSTEM

[0002] FIELD OF THE INVENTION

[0003] The present invention relates to a method of manufacturing a lightning protection system for a wind turbine blade, a lightning protection system; a wind turbine blade, and a method of manufacturing a wind turbine blade.

[0004] BACKGROUND OF THE INVENTION

[0005] Wind turbines are susceptible to lightning strikes, and the blades of wind turbines are particularly susceptible to lightning strikes.

[0006] As a result, it is common for a wind turbine blade to include a lightning protection system that electrically couples the wind turbine blade to ground. This lightning protection system may include lightning receptors and conductors that are electrically connected from the blade, through the tower and nacelle, to ground. The lightning protection system may also include a surface protection layer (SPL), for instance a metal mesh or foil surface protection layer, incorporated into the blade shell at the outer surface of the blade and extending along at least a portion of the blade. This surface protection layer typically covers a significant portion of the blade surface and intercepts lightning strikes before reaching conductive components of the blade. The surface protection layer is typically connected to the lightning protection system at numerous points so as to ensure a good electrical connection from the surface protection layer.

[0007] WO2015 / 055215 describes a wind turbine blade having a blade shell with a lightning protection system comprising a metal layer at the outer surface of the blade shell, wherein the metal layer is reinforced at the location of an electrically conductive pin, which extends through the metal layer, by a reinforcing metal disc.

[0008] The reinforcing metal disc is typically a cast metal component, cast through the mesh or expanded metal foil metal layer. The metal layer may typically be Aluminium, and the reinforcing metal disc may comprise a metal alloy such as SnCu, which has a lower electrical conductivity, lower heat capacity and lower melting point than the Aluminium metal layer. This choice of alloy is suited to casting but the material properties of the cast disc are not ideal. The casting process also has inherent limitations on the design of the reinforcing metal disc part. The present invention seeks to address this issue.

[0009] SUMMARY OF INVENTION

[0010] A first aspect of the invention provides a method of manufacturing a lightning protection system for a wind turbine blade, the method comprising: providing a first metal layer; and constructing a metal reinforcing part directly onto the first metal layer using an additive manufacturing technique so as to create an electrical connection between the first metal layer and the metal reinforcing part, wherein a portion of the first metal layer extends laterally beyond the metal reinforcing part.

[0011] The metal layer may comprise a metal mesh or expanded metal foil. The metal layer may be manufactured from aluminium, brass, bronze or copper for example.

[0012] An additive manufacturing technique may be defined as a manufacturing technique comprising depositing and bonding layers of material to construct a three-dimensional component.

[0013] Manufacturing the metal reinforcing part using additive manufacturing techniques may allow greater design flexibility for the part, for example allowing the material to be made from different materials to those currently available. The additive manufactured part may comprise the same metal as the first metal layer to avoid galvanic interactions.

[0014] Additive manufacturing techniques may eliminate the need for any surface treatments or passivation of bonding surfaces and / or joints on or with the first metal layer during the manufacturing process.

[0015] The additive manufactured part may have higher electrical conductivity, heat capacity and melting point between the first metal layer and the metal reinforcing part than a conventional soldered joint between the metal reinforcing part and the metal layer. The metal reinforcing part may consequently be made thinner for a given performance requirement. With a thinner part a step with an adjacent fibre layer of a blade shell may be reduced. 3-D printing of metals is highly automated saving time and improving quality compared to a conventional metal part cast or soldered onto the metal layer. The metal reinforcing part could be formed on the metal layer as an assembly line process. For example, multiple metal reinforcing parts may be formed on a sheet of the first metal layer material, and then the sheet cut to form multiple pieces of first metal layer each having one or more of the metal reinforcing parts.

[0016] The metal reinforcing part may be in the form of a metal reinforcing disc.

[0017] The metal reinforcing part may include a pure metal (i.e. a non-alloy) metal material. The pure metal may have improved electrical conductivity than a metal alloy. In an example, the metal reinforcing part is formed from aluminium.

[0018] The additive manufacturing technique may comprise cold spray additive manufacture, direct energy deposition manufacture or friction stir additive manufacture.

[0019] Manufacturing the metal reinforcing part using cold spray additive manufacture, direct energy deposition manufacture or friction stir additive manufacture may improve the ease of manufacture compared to using a different additive manufacturing technique. For example, each of these additive manufacturing techniques does not require a fully sealed and / or shielded environment for metal deposition. Using one of the additive manufacturing techniques listed here may also allow manufacture of the metal reinforcing part to be made modular.

[0020] The method of manufacturing a lightning protection system according may further comprise constructing a plastic part coupled to the first metal layer and / or the metal reinforcing part using an additive manufacturing technique.

[0021] The plastic part may help with strain relief, thermal insulation, electrical insulation or sealant within the lightning protection system. A sealant may for example help to reduce the likelihood of liquid resin impingement and / or condensation affecting the porosity of the resin matrix during subsequent manufacture of a wind turbine blade. The plastic part may be additively manufactured using a different print head of the same machine used to additively manufacture the metal reinforcing part.

[0022] A second aspect of the invention provides a lightning protection system for a wind turbine blade, the lightning protection system producible according to the method of the first aspect of the invention. The lightning protection system comprises: a first metal layer; and a metal reinforcing part formed on the first metal layer so as to create an electrical connection with the first metal layer, wherein a portion of the first metal layer extends laterally beyond the metal reinforcing part.

[0023] The metal reinforcing part may extend from only one side of the first metal layer.

[0024] Providing the part as extending from a first side of the first metal layer only may improve ease of manufacture of the lightning protection system as there is no requirement for access to both sides of the metal layer. This arrangement may also improve ease of manufacture of a wind turbine blade by reducing the step in laminate layers laid over the reinforcing metal part.

[0025] The metal reinforcing part may comprise a first portion extending from a first side of the first metal layer and a second portion extending from a second side of the first metal layer opposite the first side.

[0026] The metal reinforcing part may extend through the first metal layer.

[0027] Providing a metal reinforcing part extending from both sides of the first metal layer may create a more structurally sound metal reinforcing part, which is less susceptible to separation from the first metal layer, especially if the first metal part has a large area and is rolled prior to incorporation in the wind turbine blade.

[0028] The metal reinforcing part may comprise a chamfer around at least a portion of an edge of the metal reinforcing part.

[0029] Providing a chamfer around the edge of the metal reinforcing part may help to reduce the step in laminate layers laid over the metal reinforcing part during lay up and manufacture of a wind turbine blade shell. The chamfer may also make the edge of the metal reinforcing part more flexible than the remainder of the metal reinforcing part, which may improve conformity when laid up in a mould for forming the wind turbine blade. The chamfer may be formed in the metal reinforcing part by the additive manufacturing technique, or the chamfer may be formed subsequent to forming the metal reinforcing part by the additive manufacturing technique. The metal reinforcing part may comprise a first portion and a second portion metallurgically bonded to the first portion. The first portion may be manufactured from a first metal and the second portion may be manufactured from a second metal. The first metal and the second metal may be different.

[0030] A metallurgic bond may be defined as a chemical bond between metals.

[0031] Providing a metal reinforcing part comprising multiple different materials may allow the characteristics of the part to be tailored to suit the requirements of a lightning protection system beyond that possible were a single material used. For example, the different metals may be tungsten or aluminium. Each metal may be a pure metal (i.e. a non alloy).

[0032] The first and second portions of the metal reinforcing part may both be formed by an additive manufacturing technique. Each portion of the metal reinforcing part may be formed by a different print head of a machine used in the additive manufacturing technique. Alternatively, each portion of the metal reinforcing part may be formed by a different machine used in one or more additive manufacturing techniques. Alternatively, only some portions of the metal reinforcing part may be formed by an additive manufacturing technique.

[0033] The first portion may encapsulate the second portion. The first portion and the first metal layer may be manufactured from the same metal.

[0034] Providing the first portion encapsulating the second portion may allow the second portion to be manufactured from a material that would not normally be suitable for exposure to the weather (in instances where the metal reinforcing part is exposed). Manufacturing both the first metal layer and the metal reinforcing part from the same material may improve the physical and electrical connection between the two. For example, the second portion may comprise tungsten, which has a relatively high heat capacity to soak up the energy in the event of a lightning strike to keep the temperature down, but relatively low electrical conductivity; and the first portion may comprise aluminium, which has relatively high electrical conductivity, but relatively low heat capacity.

[0035] The first metal may have a greater electrical conductivity than the second metal. Providing the first metal as having a greater electrical conductivity than the second metal may improve the electrical connection between the metal reinforcing part and the first metal layer, and may allow the second metal to be selected based on further different desirable characteristics.

[0036] The second metal may have a greater heat capacity than the first metal.

[0037] Providing a second metal having a greater heat capacity than the first metal may allow the overall heat capacity of the metal reinforcing part to be improved (which is good for lightning strike protection) whilst still maintaining, for example, a desirable electrical connection between the first metal layer and the metal reinforcing part.

[0038] The first metal may have a greater stiffness than the second metal.

[0039] Providing a first metal having a greater stiffness than the second metal may improve the strength of connection between the lightning protection system and adjacent components (such as for example a bolt) by increasing the compressive force which the metal reinforcing part can withstand without deforming. This may allow use of a stiff material near the centre of the metal reinforcing part which can receive a pin, and allows a flat interface. Further from the centre of the metal reinforcing part it is possible to transition the material to a softer material so that it conforms to the mould in which the blade shell is laid up.

[0040] Where the first portion encapsulates the second portion, the second portion may comprise a softer metal than the first portion such that when a pin is inserted through an aperture formed through the metal reinforcing part, the first portion may deform into the softer second portion under pressure (e.g. from tightening the pin) such that the outer first portion conforms to the shape of the pin and provides a robust electrical connection.

[0041] The first metal layer may include an array of apertures. Preferably, the first metal layer has an unapertured portion adjacent the metal reinforcing part and an apertured portion away from the metal reinforcing part. The apertured metal layer is lighter than an unapertured metal layer. Providing an unapertured portion adjacent the metal reinforcing part may improve manufacturability of the additive manufactured metal reinforcing part on the metal layer, e.g. metal powder does not fall through and a greater bonding area is made available.

[0042] The apertured portion may allow the first metal layer to conform to the shape of the wind turbine blade and will not experience fatigue failure during use of the blade.

[0043] The unapertured portion may have higher electrical conductivity than the apertured portion and so will experience a lower current density in the event of a lightning strike. This may achieve a better current spread across the first metal layer, which may make the lightning protection system more robust and so fewer metal reinforcing parts (e.g. connectors) can be provided within each blade.

[0044] The metal reinforcing part may be generally circular or oval or pear-shaped.

[0045] Manufacturing the metal reinforcing part using additive manufacturing techniques may allow the part to be designed in a non-traditional shape. This shape may be tailored to optimise the current distribution at the edge of the part and to minimise high temperature spots across the part.

[0046] The metal reinforcing part may alternatively be a strip. The strip may have an upper surface that is exposed on the outer surface of the wind turbine blade, e.g. to form a band around the circumference of the blade root. The band may provide electrical connection from the blade to a contact element of a lightning current transfer unit.

[0047] The metal reinforcing part may comprise a curved surface facing away from the first metal layer, preferably wherein the curved surface is a concave surface.

[0048] Providing a concave surface facing away from the first metal layer may improve the engagement between the metal reinforcing part and adjacent components such as for example a bolt or pin. The concave surface of the part may be designed to correspondingly engage with a convex underside of a bolt head. This may avoid the need for a separate washer to achieve the concavity, reducing parts count and assembly. The curved surface of the metal reinforcing part may be formed by an additive manufacturing technique, or the curved surface may be formed subsequent to forming the metal reinforcing part by an additive manufacturing technique.

[0049] The lightning protection system may further comprise a plastic part coupled to the first metal layer and / or the metal reinforcing part. The plastic part may be manufactured using an additive manufacturing technique.

[0050] The plastic part may help with strain relief, thermal insulation, electrical insulation or sealant within the lightning protection system.

[0051] The plastic part may comprise a chamfer around at least a portion of the edge of the plastic part and / or locating features for locating the lightning protection system relative to a mould.

[0052] Providing the plastic part with a chamfer may help to reduce the step in laminate layers laid over the plastic part during lay up and manufacture of a wind turbine blade shell. Locating features may help to position the lightning protection system relative to a mould and hence any laminate layers laid over the lightning protection system. The chamfer may be formed in the plastic part by the additive manufacturing technique, or the chamfer may be formed subsequent to forming the plastic part by the additive manufacturing technique.

[0053] A third aspect of the invention provides a wind turbine blade having a blade shell with a lightning protection system according to the second aspect of the invention, wherein the first metal layer is at an outer surface of the blade shell, and wherein the lightning protection system further comprises an electrically conductive pin extending through an aperture in the metal reinforcing part and through the first metal layer.

[0054] The electrically conductive pin may be used to electrically connect the first metal layer to one or more electrical components of the lightning protection system inside the blade shell, such as a down conductor cable or a tip array, or anti-icing system for example, to the first metal layer. The electrically conductive pin forms an intimate electrical connection to the first metal layer via the metal reinforcing part. This enables lightning current to be conducted via the first metal layer to ground through the electrically conductive pin. The aperture may be formed through the first metal layer for receiving the electrically conductive pin. The aperture in the first metal layer may be formed simultaneously with forming an aperture through the metal reinforcing part, during blade manufacture.

[0055] The lightning protection system may comprise a reinforcing patch including the first metal layer and the metal reinforcing part, and the lightning protection system further comprises a second metal layer extending substantially over the outer surface of the blade shell. The first metal layer may have an area no more than 10% of an area of the second metal layer. A first portion of the second metal layer may surround the first metal layer at an outer surface of the blade shell, and a second portion of the second metal layer may overlap the first metal layer and is in intimate electrical contact with the second metal layer.

[0056] The first metal layer and the second metal layer are discrete and separate components when being laid up during manufacturing of the wind turbine blade. In this context ‘surrounds’ means that the first portion of the second metal layer encircles or fully surrounds the first metal layer. In this context the ‘area’ of the metal layers refers to the extent of the metal layer in the length and width dimensions perpendicular to the thickness dimension. The first metal layer and the second metal layer may each comprise a mesh or expanded metal foil.

[0057] Providing the first metal layer with the metal reinforcing part fixed as a separate component to the second metal layer may improve ease of manufacture of the wind turbine blade comprising the lightning protection system. The larger second metal layer may be handled easily as it does not contain the metal reinforcing part. In addition, the much smaller first metal layer may also be handled easily and positioned accurately despite containing the metal reinforcing part. Positional accuracy of the metal part in a mould for forming the blade shell is important. The metal layers may be fragile and so ease of handling is important to avoid handling damage so as to maintain good performance of the lightning strike protection system.

[0058] The second portion of the second metal layer may be located towards an inside of the blade with respect to the first metal layer.

[0059] In this way, the first metal layer may be laid up first in a mould for forming the blade shell, and the second metal layer may be laid on top of the first metal layer. By locating the second metal layer towards an inside of the blade with respect to the first metal layer, a portion of the second metal layer does not need to be removed to gain access to the metal reinforcing part from the outside of the blade.

[0060] The second portion of the second metal layer may overlap the metal reinforcing part.

[0061] The second portion of the second metal layer may be in intimate electrical contact with the metal reinforcing part. For example, the second portion of the second metal layer may extend over a surface of the metal reinforcing part so as to create a direct electrical connection with the metal reinforcing part, in addition to the indirect electrical connection with the metal reinforcing part via the electrical connection between the overlapping first and second metal layers.

[0062] The metal reinforcing part may in some cases not extend through the second metal layer.

[0063] The electrically conductive pin may extend through the second metal layer.

[0064] The wind turbine blade may further comprise an electrical component. The second metal layer may be electrically connected to the electrical component by the electrically conductive pin.

[0065] The electrical component may be a connector base for forming an electrical connection between the electrically conductive pin and one or more further electrical components of the lightning protection system. Alternatively, the electrical component may be a down conductor or tip array or other component of the lightning protection system, forming a direct electrical connection with the electrically conductive pin.

[0066] The electrically conductive pin may have a head. An underside of the head may face a surface of the metal reinforcing part. The underside of the head may have a shape conformal with the surface of the metal reinforcing part.

[0067] The wind turbine blade may further comprise a recess in which the head of the pin is located.

[0068] The recess may be provided in the metal reinforcing part. The recess may be provided in a portion of a forming element around the metal reinforcing part. The forming element may include a ramped section, e.g. a conical section, which deflects the first metal layer away from the outer surface of the blade towards the inside of the blade shell so as to enable the first metal layer to extend continuously over the recess.

[0069] The head of the pin may be substantially flush with the blade shell outer surface.

[0070] Providing a pin head that is substantially flush with the blade shell outer surface may reduce or negate the effect of the pin on aerodynamic performance of the wind turbine blade.

[0071] A fourth aspect of the invention provides a method of manufacturing a wind turbine blade shell with a lightning protection system, the method comprising: providing a mould surface; providing a lightning protection system having the first metal layer with the metal reinforcing part formed across a portion of the first metal layer formed using the method of the first aspect of the invention; arranging the lightning protection system on the mould surface; arranging one or more structural components on the lightning protection system; and consolidating the structural components and the lightning protection system under vacuum to form a blade shell.

[0072] The methods of manufacturing the lightning protection system and / or the wind turbine blade according to the first and / or fourth aspects may comprise steps for producing any of the features of the lightning protection system and / or the wind turbine blade according to the second and / or third aspects described above.

[0073] BRIEF DESCRIPTION OF THE DRAWINGS

[0074] Embodiments of the invention will now be described with reference to the accompanying drawings, in which:

[0075] Figure 1 shows a wind turbine;

[0076] Figure 2 shows a wind turbine blade; Figure 3 shows a planform view of a lightning protection system of a wind turbine blade including a metal layer in a blade shell of the blade;

[0077] Figure 4 shows a cross section view of a portion of a blade shell comprising a first example of a lightning protection system;

[0078] Figures 5A to 5C show a method of manufacturing a lightning protection system;

[0079] Figures 6A and 6B show a first example of a patch for a lightning protection system;

[0080] Figures 7A to 7D each show a second, third, fourth and fifth example of a patch for a lightning protection system;

[0081] Figure 8 shows a cross section view of a portion of a blade shell comprising a second example of a lightning protection system;

[0082] Figure 9 shows a cross section view of a portion of a blade shell comprising a third example of a lightning protection system;

[0083] Figures 10A to 10D each show a sixth, seventh, eighth and ninth example of a patch for a lightning protection system;

[0084] Figure 11 shows a cross section view of a portion of a blade shell comprising a fourth example of a lightning protection system; and

[0085] Figures 12A to 12F show a method of manufacturing a wind turbine blade comprising a lightning protection system comprising a patch according to any of the examples shown.

[0086] DETAILED DESCRIPTION OF EMBODIMENT(S)

[0087] In this specification, terms such as leading edge, trailing edge, pressure surface, suction surface, thickness, chord and planform are used. While these terms are well known and understood to a person skilled in the art, definitions are given below for the avoidance of doubt. The term leading edge is used to refer to an edge of the blade which will be at the front of the blade as the blade rotates in the normal rotation direction of the wind turbine rotor.

[0088] The term trailing edge is used to refer to an edge of a wind turbine blade which will be at the back of the blade as the blade rotates in the normal rotation direction of the wind turbine rotor.

[0089] The chord of a blade is the straight line distance from the leading edge to the trailing edge in a given cross section perpendicular to the blade spanwise direction. The term chordwise is used to refer to a direction from the leading edge to the trailing edge, or vice versa.

[0090] A pressure surface (or windward surface) of a wind turbine blade is a surface between the leading edge and the trailing edge, which, when the blade is in use, has a higher pressure than a suction surface of the blade.

[0091] A suction surface (or leeward surface) of a wind turbine blade is a surface between the leading edge and the trailing edge, which will have a lower pressure acting upon it than that of a pressure surface, when the blade is in use.

[0092] The thickness of a wind turbine blade is measured perpendicularly to the chord of the blade and is the greatest distance between the pressure surface and the suction surface in a given cross section perpendicular to the blade spanwise direction.

[0093] The term spanwise is used to refer to a direction from a root end of a wind turbine blade to a tip end of the blade, or vice versa. When a wind turbine blade is mounted on a wind turbine hub, the spanwise and radial directions will be substantially the same.

[0094] A view which is perpendicular to both of the spanwise and chordwise directions is known as a planform view. This view looks along the thickness dimension of the blade.

[0095] The term shear web is used to refer to a longitudinal, generally spanwise extending, reinforcing member of the blade that can transfer load from one of the windward and leeward sides of the blade to the other of the windward and leeward sides of the blade. Figure 1 shows a wind turbine 10 including a tower 12 mounted on a foundation and a nacelle 14 disposed at the apex of the tower 12. The wind turbine 10 depicted here is an onshore wind turbine such that the foundation is embedded in the ground, but the wind turbine 10 may be an offshore installation in which case the foundation would be provided by a suitable marine platform.

[0096] A rotor 16 is operatively coupled to a generator (potentially via a gearbox) (not shown) housed inside the nacelle 14. The rotor 16 includes a central hub 18 and a plurality of rotor blades 20, which project outwardly from the central hub 18. It will be noted that the wind turbine 10 is the common type of horizontal axis wind turbine (HAWT) such that the rotor 16 is mounted at the nacelle 12 to rotate about a substantially horizontal axis defined at the centre at the hub 18. While the example shown in Figure 1 has three blades, it will be realised by the skilled person that other numbers of blades are possible.

[0097] When wind blows against the wind turbine 10, the blades 20 generate a lift force which causes the rotor 16 to rotate, which in turn causes the generator within the nacelle 14 to generate electrical energy.

[0098] Figure 2 shows an example of one of the wind turbine blades 20 for use in such a wind turbine. The blade 20 has a root end 21 proximal to the hub 18 and a tip end 22 distal from the hub 18. The blade 20 includes a leading edge 23 and a trailing edge 24 that extend between the root end 21 and tip end 22. The blade 20 includes a suction surface 25 and a pressure surface 26. A thickness dimension of the blade extends between the suction surface 25 and the pressure surface 26.

[0099] The blade 20 has a cross section that may be substantially circular near the root end 21. The blade portion near the root must have sufficient structural strength to support the blade portion outboard of that section and to transfer loads into the hub 18. The blade 20 may transition from a circular profile to an aerofoil profile moving from the root end 21 of the blade towards a "shoulder" 28 of the blade, which is the widest part of the blade 20 where the blade 20 has its maximum chord. The blade 20 has an aerofoil profile of progressively decreasing thickness in an outboard portion of the blade, which extends from the shoulder 28 to the tip end 22. The wind turbine blade 20 may include an outer blade shell 29 defining a hollow interior space with a shear web extending internally between upper and lower parts of the blade shell 29.

[0100] As shown schematically in Figure 3, the blade 20 may include one or more lightning receptors 36, such as a tip array, and one or more lightning down conductor cables 38 which form part of a lightning protection system 30 for the wind turbine. The lightning receptors attract the lightning strike and the down conductor cables 38, which run through the hollow interior of the blade, conduct the energy of the lightning strike down the blade 20 via the nacelle 14 and tower 12 to a ground potential. In addition, the lightning protection system 30 may include a surface protection layer 40 at the outer surface of the blade. The surface protection layer 40 may be electrically connected at each end to the down conductor cables 38.

[0101] The surface protection layer is at the outer surface of the blade and this means that the surface protection layer may be just under the surface of the wind turbine blade, and may be covered by a gel coat, a paint later and / or a layer of fibre glass.

[0102] The majority of the outer surface of the blade 20 may be covered with the surface protection layer 40, or only a portion of the outer surface of the blade 20 may be covered with the surface protection layer 40. The surface protection layer 40 serves to shield conductive material in the blade from a lightning strike, and may act as either a lightning receptor, a down conductor, or both. The down conductor may extend substantially the full length of the blade. In some examples, such as where the majority of the outer surface of the blade 20 is covered with the surface protection layer 40, the down conductor cable 38 may connect to the surface protection layer 40 adjacent the tip end 22 of the blade and adjacent the root end 21 of the blade, with no down conductor cable 38 along the majority of the length of the blade covered with the surface protection layer 40. The surface protection layer 40 may extend from root to tip in which case there may be no need for a down conductor cable 38. The surface protection layer 40 may extend in sections along the length of the blade with down conductor cable sections between the surface protection layer 40 sections. The down conductor cable 38 may alternatively extend under the surface protection layer 40 (inside the blade) so that the down conductor cable 38 and surface protection layer 40 are electrically connected in parallel. At the root end 21 of the blade 20, the down conductor cable 38 may be electrically connected via an armature arrangement to a charge transfer route via the nacelle 14 or hub 18 and tower 12 to a ground potential. Such a lightning protection system 30 therefore allows lightning to be channelled from the blade to a ground potential safely, thereby minimising the risk of damage to the wind turbine 10.

[0103] The down conductor cable 38 and surface protection layer 40 may be connected by one or more connectors or receptors. The connectors may comprise an electrically conductive pin 60 that extends through the surface protection layer 40 and connects to the down conductor cable 38. Figure 3 shows five electrically conductive pins 60 connecting the down conductor cable 38 and the surface protection layer 40, although it will be understood that any suitable number of electrically conductive pin 60 may be used.

[0104] The surface protection layer 40 may extend up to the leading edge 23 of the wind turbine blade 20 and / or extend up to the trailing edge 24 of the wind turbine blade 20. Alternatively, the surface protection layer 40 may be spaced from the leading and / or trailing edge of the blade 20.

[0105] Figure 4 shows a section view of a portion of the wind turbine blade 20, in particular at the blade shell 29. It will be appreciated that the wind turbine blade shell 29 comprises a structural component 48 not discussed in detail here. The structural component 48 may for example include fibre layers, such as glass fibre layers, core materials such as foam, and similar, as will be appreciated by the person skilled in the art.

[0106] The surface protection layer 40 comprises a first metal layer 42 and forms part of the lightning protection system 30. The first metal layer 42 is sufficiently thin that it may be considered two dimensional. The first metal layer 42 is provided at an outer surface of the blade shell 29 as described previously with reference to Figure 3.

[0107] The lightning protection system 30 also comprises a metal reinforcing part 50 formed on and across a portion of the first metal layer 42. The metal reinforcing part 50 is fixed to the first metal layer 42 so as to create an electrical connection with the first metal layer 42. The metal reinforcing part 50 is smaller than the first metal layer 42, such that a portion of the first metal layer 42 extends laterally around the metal reinforcing part 50. The metal reinforcing part 50 is fixed to the first metal layer 42 so as to create an electrical connection with the second metal layer 42. As such, the metal reinforcing part 50 may be manufactured integral to the first metal layer 42 such that the metal reinforcing part 50 and the first metal layer 42 are not readily separable. The first metal layer 42 may be a mesh or expanded metal foil. The metal reinforcing part 50 may be solid. The metal reinforcing part 50 may be a generally planar, relatively thin, substantially two-dimensional part.

[0108] As shown in Figure 4, the lightning protection system 30 may further comprise an electrically conductive pin 60 extending through an aperture in the metal reinforcing part 50 and through the first metal layer 42. The aperture may be formed through the first metal layer 42 for receiving the electrically conductive pin 60. The aperture in the first metal layer 42 may be formed simultaneously with forming an aperture through the metal reinforcing part 50, optionally during blade manufacture.

[0109] The wind turbine blade 20 may further comprise an electrical component 32 electrically connected to the first metal layer 42 as shown in Figure 4. The electrical component 32 may be a connector base for forming an electrical connection between the electrically conductive pin 60 and one or more further electrical components of the lightning protection system 30. Alternatively, the electrical component may be a down conductor cable 38 or tip array 36 or other component of the lightning protection system 30, forming a direct electrical connection with the electrically conductive pin 60.

[0110] The electrical component 32 is electrically connected to the first metal layer 42 via the electrically conductive pin 60. In particular, an underside 62b of the electrically conductive pin 60 is in electrical contact with the metal reinforcing part 50.

[0111] The electrical component 32 may have a threaded aperture for receiving a threaded end of a shank 64 of the electrically conductive pin 60 for threadedly securing the electrically conductive pin 60 to the electrical component 32. The electrical component 32 may be fixed with respect to the inside of the blade shell 29.

[0112] Figures 5A to 5C illustrate a method of manufacturing the lightning protection system 30. Figure 5A shows the first metal layer 42 provided along with an additive manufacture machine 80. Figure 5B shows the additive manufacture machine 80 being used to additively manufacture the metal reinforcing part 50 on the first metal layer 42. That is to say that the metal reinforcing part 50 is constructed directly onto the first metal layer 42. As such, the first metal layer 42 may be considered the printing bed upon which the metal reinforcing part 50 is constructed. The metal reinforcing part 50 is therefore manufactured integral to the first metal layer 42 such that the metal reinforcing part 50 and the first metal layer 42 are not readily separable.

[0113] It will be appreciated that Figures 5A to 5C show a schematic representation of an additive manufacture machine 80 comprising a print head. Generally, the metal reinforcing part 50 may be constructed using any suitable additive manufacturing technique. Any suitable additive manufacturing technique is here defined as any additive manufacturing technique capable of constructing and fixing the metal reinforcing part 50 to the first metal layer 42 so as to create an electrical connection with the first metal layer 42. By way of non-limiting example, the additive manufacturing technique may comprise any of:

[0114] 1. Cold spray additive manufacture (CSAM) - where powder particles are accelerated in a high-velocity compressed gas stream to deform and bond together upon impact with the build surface;

[0115] 2. Direct energy deposition (DED) - where a focussed energy source (such as a plasma arc, a laser or an electron beam) is used to melt and bond material deposited by a nozzle; or

[0116] 3. Friction stir additive manufacture (FSAM) - where a rotating tool is passed over the workpiece and the heat generated due to friction between the tool and the workpiece plasticises deposited material to form a bond.

[0117] Constructing the metal reinforcing part 50 using an additive manufacturing technique may allow greater design flexibility for the part, for example allowing the material to be made from different materials to those currently available. The additive manufactured part may comprise the same metal as the first metal layer to avoid galvanic interactions. Additive manufacturing techniques may eliminate the need for any surface treatments or passivation of bonding surfaces and / or joints on or with the first metal layer during the manufacturing process. The additive manufactured part may have higher electrical conductivity, heat capacity and melting point between the first metal layer and the metal reinforcing part than a conventional soldered joint between the metal reinforcing part and the metal layer. The metal reinforcing part may consequently be made thinner for a given performance requirement. With a thinner part a step with an adjacent fibre layer of a blade shell may be reduced. 3-D printing of metals is highly automated saving time and improving quality compared to a conventional metal part cast or soldered onto the metal layer. The metal reinforcing part may include a pure metal (i.e. a non-alloy) metal material. The pure metal may have improved electrical conductivity than a metal alloy.

[0118] Constructing the metal reinforcing part 50 using an additive manufacturing technique may also enable non-standard shapes and / or profiles to be manufactured. Figure 5C shows a further step in the manufacture of the lightning protection system 30 where the additive manufacture machine 80 is used to construct a chamfer portion 52 about the edge of the metal reinforcing part 50. The chamfer portion 52 may help to reduce the step in laminate layers laid over the reinforcing metal part 50. The chamfer may also make the edge of the metal reinforcing part more flexible than the remainder of the metal reinforcing part, which may improve conformity when laid up in a mould for forming the wind turbine blade. Although shown as a distinct portion, it will be appreciated that the chamfer portion 52 may be a metal portion formed integral to the metal reinforcing part 50. As such the method step of constructing the chamfer portion 52 may be conducted concurrently with the method step of constructing the metal reinforcing part 50. The chamfer may be formed in the metal reinforcing part by the additive manufacturing technique, or the chamfer may be formed subsequent to forming the metal reinforcing part by the additive manufacturing technique.

[0119] A plastic part 55 (as shown most clearly in Figure 7B) may be coupled to the first metal layer 42 and / or the metal reinforcing part 50. The plastic part 55 may be constructed directly onto the first metal layer 42. In this case, the additive manufacturing technique may comprise a plurality of processes (e.g. additive manufacture using a separate printer head for each material) to construct the metal reinforcing part 50 and the plastic part 55. The plastic part 55 may provide the chamfer portion 52. The plastic part 55 may help with strain relief, thermal insulation, electrical insulation or sealant within the lightning protection system. The plastic part may be additively manufactured using a different print head of the same machine used to additively manufacture the metal reinforcing part 50.

[0120] The first metal layer 42 and the metal reinforcing part 50 may be provided as a patch 100 as shown in Figures 6A and 6B. The patch 100 may be incorporated into different lightning protection systems and / or different wind turbine blade designs. A common patch 100 comprising a metal reinforcing part 50 and a first metal layer 42 each having set dimensions may be manufactured and used in multiple locations in a wind turbine blade design and / or in multiple wind turbine blade designs. This may reduce the cost of manufacture and design of the blades.

[0121] Figures 6A and 6B show a first example of a patch 100. Here, the metal reinforcing part 50 extends from one side of the first metal layer 42 only as shown in Figure 6B. Arranging the metal reinforcing part 50 as such may improve ease of manufacture of the patch 100 and / or the metal reinforcing patch 50, particularly where the metal reinforcing patch is constructed using an additive manufacturing technique. Providing a metal reinforcing part 50 extending from a single side of the first metal layer 42 only may mean that access is required to just one side of the first metal layer 42, which may remove any need to flip or rotate the first metal layer 42 and / or patch 100 during manufacture. This arrangement of the patch 100 may also improve ease of manufacture of a wind turbine blade by reducing the step in laminate layers laid over the reinforcing metal part when manufacturing the blade shell 29.

[0122] In an alternative example (not shown), the metal reinforcing part 50 may extend from both sides of the first metal layer 42. This may be achieved by constructing a first portion of the metal reinforcing part 50 extending from a first side of the first metal layer 42 and a second portion of the metal reinforcing part 50 extending from a second side of the first metal layer 42 opposite the first side. The reinforcing metal part 50 may extend through the first metal layer 42. Providing a metal reinforcing part 50 extending from both sides of the first metal layer 42 may provide a stronger structural connection between the first metal layer 42 and the metal reinforcing part 50. This may create a more structurally sound metal reinforcing part, which is less susceptible to separation from the first metal layer, especially if the first metal part has a large area and is rolled prior to incorporation in the wind turbine blade.

[0123] Figures 7A to 7D show various examples of patches 100 comprising different metal reinforcing parts 50. It will be appreciated that although described in isolation, the features of each example of a metal reinforcing part 50 may be readily combined. It will also be appreciated that each patch 100 comprises a first metal layer 42 and a metal reinforcing part 50 formed on the first metal layer 42 as described previously. As such, details of the first metal layer 42 and its connection to the metal reinforcing part 50 will not be discussed again in detail. Figures 7A and 7B show examples of a metal reinforcing part 50 comprising a chamfer portion 52 extending around the edge of the metal reinforcing part 50 as described previously with reference to Figure 5C. It will be appreciated that the chamfer portion 52 may in some cases extend around only a portion of the edge of the metal reinforcing part 50. Figure 7A shows the chamfer portion 52 formed as an integral part of the metal reinforcing part 50, for example constructed from the same material (i.e. a metal) using the same manufacturing process, which may comprise an additive manufacturing technique as described previously.

[0124] Figure 7B shows the chamfer portion formed as a separate part coupled to the metal reinforcing part 50 and / or the first metal layer 42. The separate part may be manufactured from a different material to the metal reinforcing part 50, for example a plastic part 55. This may reduce the cost of the part and / or may allow the behaviour of the metal reinforcing part 50, in particular of the chamfer portion 52, to be tailored. By way of non-limiting example, the chamfer portion 52 may be manufactured from a plastic designed to deform to match the profile of a mould during subsequent assembly of the patch 100 into a blade shell 29. The chamfer portion 52 may further comprise one or more locating features 53 for locating the patch 100 relative to the blade shell 29 during manufacture of the blade shell 29.

[0125] In a further example (not shown) the chamfer portion 52 may taper towards the first metal layer 42. Where the metal reinforcing part 50 is manufactured using an additive manufacturing technique, this may be achieved using sacrificial support structures or any other suitable technique to achieve an overhang.

[0126] Figure 7C shows an example of a metal reinforcing part 50 comprising a first portion 54 and a second portion 56. The first portion 54 is manufactured from a first metal and the second portion 56 is manufactured from a second metal, the first metal being different to the second metal. The two portions are metallurgically bonded together, metallurgical bonding here defined as a chemical bond between atoms in each of the two metals. It will be appreciated that the metal reinforcing part 50 may comprise any number of a plurality of portions manufactured from different metals. Providing a metal reinforcing part 50 comprising multiple portions manufactured from different metals having different properties may allow the overall properties and / or behaviour of the metal reinforcing part 50 to be controlled or improved compared to a metal reinforcing part 50 comprising a single metal only. For example, the different metals may be tungsten or aluminium. Each metal may be a pure metal (i.e. a non alloy). The first and second portions of the metal reinforcing part may both be formed by an additive manufacturing technique. Each portion of the metal reinforcing part may be formed by a different print head of a machine used in the additive manufacturing technique. Alternatively, each portion of the metal reinforcing part may be formed by a different machine used in one or more additive manufacturing techniques. Alternatively only some portions of the metal reinforcing part may be formed by an additive manufacturing technique.

[0127] As shown in Figure 7C, the first portion 54 may encapsulate the second portion 56, such that the second portion 56 does not contact the first metal layer 42 and is not exposed to the environment. Providing the first portion encapsulating the second portion may allow the second portion to be manufactured from a material that would not normally be suitable for exposure to the elements. Here it may be preferable to manufacture the first portion 54 from the same metal as that used to manufacture the first metal layer 42. This may improve the electrical connection and / or the structural connection between the metal reinforcing part 50 and the first metal layer 42. Similarly, it may be preferable to manufacture the first portion 54 from a metal having a higher electrical conductivity than that of the metal used to manufacture the second portion 56, particularly where the first portion 54 encapsulates the second portion 56. This may again increase the likelihood of an effective electrical connection between the metal reinforcing part 50 and the first metal layer 42. Providing the (first) metal of the first portion 54 as having a greater electrical conductivity than the (second) metal of the second portion 56 may improve the electrical connection between the metal reinforcing part and the first metal layer, and may allow the metal of the second portion 56 to be selected based on further different desirable characteristics.

[0128] The second metal may be selected to achieve other preferable characteristics. For example, the second metal may have a greater heat capacity than the first metal. For example, the second portion may comprise tungsten or a metal matrix composite which has a high heat capacity to soak up the energy to keep the temperature down, but low electrical conductivity; and the first portion may comprise aluminium, which has high conductivity, but low heat capacity. This may increase the overall heat capacity of the metal reinforcing part 50 as a whole, whilst still maintaining an effective electrical connection between the metal reinforcing part 50 and the first metal layer 42. The first metal may have a greater stiffness than the second metal. This may increase the strength of connection that can be achieved between the metal reinforcing part 50 and the first metal layer 42 and / or the blade shell 29, for example by increasing the compressive force which the metal reinforcing part can withstand without deforming (for example when a pin 60 is passed through the metal reinforcing part and tightened to clamp the part to the turbine blade 20). This may allow to use a stiff material near the centre of the metal reinforcing part which can receive a pin, and allows a flat interface. Further from the centre of the metal reinforcing part it is possible to transition the material to a softer material so that it conforms to the mould in which the blade shell is laid up. Alternatively, where the first portion encapsulates the second portion, the first portion may comprise a softer metal than the second portion such that when a pin is inserted through an aperture formed through the metal reinforcing part, the first portion may deform into the softer second portion under pressure (e.g. from tightening the pin).

[0129] Figure 7D shows an example of a metal reinforcing part 50 comprising a curved surface 58 facing away from the first metal layer 42, preferably a concave surface as shown in Figure 7D. The curved surface 58 may be referred to as an outer surface 58 of the metal reinforcing part 50. More generally, the outer surface 58 may be shaped to engage with components adjacent the metal reinforcing part 50, such as the electrically conductive pin 60 described with reference to Figure 4. Where the pin 60 comprises a head 62 having an underside 62b facing the metal reinforcing part 50 as shown in Figure 8, the outer surface 58 of the metal reinforcing part 50 may be made conformal with the shape of the underside 62b. Where the underside 62b has a curved profile, the curved surface 58 of the metal reinforcing part 50 may avoid the need for a separate washer to achieve the concavity, reducing parts count and assembly. The curved surface of the metal reinforcing part may be formed by an additive manufacturing technique, or the curved surface may be formed subsequent to forming the metal reinforcing part by an additive manufacturing technique.

[0130] It will be appreciated that generally, the lightning protection system 30, optionally the patch 100 may comprise a plastic part 55 coupled to the first metal layer 42 and / or the metal reinforcing part 50 and manufactured using an additive manufacturing technique. The plastic part 55 may take any form. By way of non-limiting example, the plastic part 55 may form a recess within the wind turbine blade 20 as shown in Figure 9. Alternatively, a recess may be provided in the metal reinforcing part 50, or in any other component of the wing turbine blade 20. This may allow the pin head 62 to be substantially flush with the outer blade shell surface such that the pin head 62 does not sit proud of the outer surface of the blade shell 29. The plastic part 55 may comprise locating features for locating the lightning protection system 30 relative to a mould.

[0131] Figures 10A to 10D show plan views of further examples of patches 100. In each case the first metal layer 42 is shown schematically as having a square profile, however it will be appreciated that more generally the first metal layer 42 may take any shape, such as for example a circle, an oval, or a rectangle.

[0132] Figure 10A shows a patch having a circular metal reinforcing part 50. This may provide a convenient shape for use with an electrically conductive pin 60 having a circular pin head 62.

[0133] Figure 10B shows a first metal layer 42 comprising an apertured portion 42a and an unapertured portion 42b. Generally, the first metal layer 42 may comprise apertures across its area to reduce the weight of and to improve the ease of handling the first metal layer 42. The apertured portion 42a may be formed as a mesh or as an expanded foil. Manufacturing a metal reinforcing part 50 directly onto an apertured surface may be challenging, particularly where additive manufacturing techniques (for example requiring fine power to be deposited onto the first metal layer 42) are used. As such, it is preferable to provide a first metal layer 42 comprising an unapertured portion 42b onto which the metal reinforcing part 50 may be constructed. It is further preferable to provide an apertured portion 42a away from the metal reinforcing part 50 to reduce the weight of the first metal layer 42 compared to an entirely unapertured first metal layer 42. Although shown as a rectangle spanning the entire length of the first metal layer 42, it will be appreciated that the unapertured portion 42b may take any shape, however is preferably at least as large as the metal reinforcing part 50. The apertured portion may allow the first metal layer to conform to the shape of the wind turbine blade and will not experience fatigue failure during use of the blade. The unapertured portion may have higher electrical conductivity and so have lower current density in the event of a lightning strike. The may achieve a better current spread across the first metal layer, which may make the lightning protection system more robust and so fewer metal reinforcing parts (e.g. connectors) can be provided within each blade. Figures 10C and 10D show examples of an oval and a pear shaped metal reinforcing part 50 respectively. These shapes may be more easily constructed using additive manufacturing techniques as described previously compared to casting components. The shape of the metal reinforcing part 50 may be designed so as to optimise the current distribution at the edge of the part and to minimise high temperature spots across the part. Providing asymmetric metal reinforcing parts 50 such as the pear shaped metal reinforcing part 50 shown in Figure 10D may in particular help to achieve this.

[0134] The metal reinforcing part may alternatively be a strip. The strip may have an upper surface that is exposed on the outer surface of the wind turbine blade, e.g. to form a band around the circumference of the blade root. The band may provide electrical connection from the blade to a contact element of a lightning current transfer unit.

[0135] Figure 11 shows a further example of a blade shell 29 comprising a lightning protection system 30, similar to that shown in Figure 4. Like parts are labelled using like reference numerals and will not be discussed again in detail.

[0136] The lightning protection system of Figure 11 comprises a patch 100 as described previously in relation to Figures 6 and 7, and further comprises a second metal layer 44. The second metal layer extends substantially over the outer surface of the blade shell 29 as described previously with reference to Figure 3. The second metal layer 44 may be referred to as the main surface protection layer.

[0137] The first metal layer 42 provides local reinforcement to the second metal layer 44 in the vicinity of the electrically conductive pin 60. As such, the area of the first metal layer 42 (at each electrically conductive pin 60 location) is no more than 10% of the area of the second metal layer 44. As shown in Figure 11 , the electrically conductive pin 60 extends through an aperture in the second metal layer 44. More generally, the second metal layer 44 may be electrically connected to the electrical component 32 described previously by the electrically conductive pin 60.

[0138] Since the area of the second metal layer 44 is greater than the area of the first metal layer 42, a first portion of the second metal layer 44 surrounds the first metal layer 42 at an outer surface of the blade shell 29. It will be appreciated that the first portion of the second metal layer 44 may alternatively be said to encircle or fully surround the second metal layer. A second portion of the second metal layer 44 overlaps the first metal layer 42 and is in intimate electrical contact with the first metal layer 42. The second portion of the second metal layer 44 may also overlap the metal reinforcing part 50. In the example shown, the metal reinforcing part 50 does not extend through the second metal layer 44. The second portion of the second metal layer 44 may be located towards an inside of the blade 20 with respect to the first metal layer 42, e.g. as illustrated in Figure 9. To allow any lightning current to be routed towards ground, the second portion of the second metal layer 44 is in intimate electrical contact with the first metal layer 42. This may be achieved by the second portion of the second metal layer 44 being in physical contact with the first metal layer 42.

[0139] The larger second metal layer 44 may be handled easily as it does not contain the metal reinforcing part 50. In addition, the much smaller patch may also be handled easily and positioned accurately within a mould for forming the blade shell 29 despite containing the metal reinforcing part 50. Forming the metal reinforcing part 50 across the smaller first metal layer 42 rather than across the larger second metal layer 44 makes handling of the metal layers easier.

[0140] Positional accuracy of the metal reinforcing part in a mould for forming the blade shell is important. The metal layers 42, 44 may be fragile and so ease of handling is important to avoid handling damage so as to maintain good performance of the lightning strike protection system. Blade moulds typically comprise a surface having double curvature. Laying metal sheet material onto a surface with double curvature can be difficult, particularly if multiple points of that metal sheet need to be in precise locations in the mould. This can lead to the metal sheet becoming wrinkled and / or stretched during lay-up. By providing a smaller first metal layer 42 having the metal reinforcing part 50 separate to the main second metal layer 44, the smaller first metal layer 42 and metal reinforcing part 50 can be precisely positioned with less chance of the first metal layer 42 becoming wrinkled and / or stretched. The larger second metal layer 44 may then be laid more easily to fit the double curvature of the mould without additional constraints of positioning a point, e.g. a metal part location. This may reduce the likelihood of wrinkling and / or stretching in the second metal layer 44.

[0141] In some cases, the second metal layer 44 may be in intimate electrical contact with the metal reinforcing part 50. In this case, the second portion of the second metal layer 44 may be in physical contact with the metal reinforcing part 50. A method of manufacturing the wind turbine blade 20 with the lightning protection system 30 will now be described with reference to Figures 12A to 12F. The lightning protection system 30 comprising the first metal layer 42 and the metal reinforcing part 50 are provided as a patch 100 as described previously.

[0142] A mould 70 for forming the blade shell 29 (or half shell) of a wind turbine blade is provided as shown in Figure 12A. The patch 100 is positioned over a mould surface 72 of the mould 70 as shown in Figure 12B. The mould surface 72 may comprise a marking 74 arranged to indicate a target position of the patch 100. The patch 100, e.g. the metal reinforcing part 50, may comprise an alignment feature (not shown) to help align the patch with the marking 74.

[0143] Once the patch 100 is positioned correctly, the second metal later 44 may be arranged in the mould over the patch as shown in Figure 12C. Then, one or more structural components 48 are arranged over the mould surface 72 and the patch 100 as shown in Figure 12D. The metal reinforcing part 50 may have chamfered edges facing the second metal layer 44 to avoid stress concentrations which may otherwise damage the second metal layer 44. The chamfered edges may also avoid stress concentrations in any surrounding blade material adjacent to the metal reinforcing part 50. As described previously, it will be appreciated that the structural components 48 may include fibre layers, core materials such as foam, and similar.

[0144] The structural components 48, the second metal layer 44 and the patch 100 are consolidated under vacuum to form a blade shell 29. This may involve covering the mould 70, containing the structural components 48, the second metal layer 44 and the patch 100, in a vacuum bag 75 and applying a vacuum pressure through a valve 76 as shown in Figure 12E. The structural components 48 may subsequently be cured, e.g. under heat and / or pressure. In some examples, the structural components 48 may comprise fibre layers (not shown) which may be dry fibre preforms, or similar, requiring the addition of resin to the mould 70. Once consolidated, a blade shell 29 is formed comprising a lightning protection system 30 as shown in Figure 12F.

[0145] In an alternative example, the first metal layer 42 (having the metal reinforcing part 50) is much larger and forms the main surface protection layer for the blade and there is no second metal layer. In this example, first metal layer 42 is positioned over the mould surface 72 of the mould 70. The mould surface 72 may comprise a marking 74 arranged to indicate a target position of the metal reinforcing part 50. The metal reinforcing part 50 may comprise an alignment feature to help align the metal reinforcing part with the marking 74.

[0146] Once the first metal layer 42 having the metal reinforcing part 50 is positioned correctly, one or more structural components 48 are arranged over the mould surface 72 and the first metal layer 42 having the metal reinforcing part 50. The structural components 48 may include fibre layers, core materials such as foam, and similar. The structural components 48 and the first metal layer 42 having the metal reinforcing part 50 are consolidated under vacuum, and may be subsequently be cured in the same way as described above.

[0147] The metal reinforcing part could be formed on the first metal layer as an assembly line process. For example, multiple metal reinforcing parts may be formed on a sheet of the first metal layer material, and then the sheet cut to form multiple pieces of first metal layer each having one or more of the metal reinforcing parts.

[0148] Although the invention has been described above with reference to one or more preferred embodiments, it will be appreciated that various changes or modifications may be made without departing from the scope of the invention as defined in the appended claims.

Claims

CLAIMS1. A method of manufacturing a lightning protection system for a wind turbine blade, the method comprising: providing a first metal layer; and constructing a metal reinforcing part directly onto the first metal layer using an additive manufacturing technique so as to create an electrical connection between the first metal layer and the metal reinforcing part, wherein a portion of the first metal layer extends laterally beyond the metal reinforcing part.

2. A method of manufacturing a lightning protection system according to claim 1 , wherein the additive manufacturing technique comprises cold spray additive manufacture, direct energy deposition manufacture or friction stir additive manufacture.

3. A method of manufacturing a lightning protection system according to claim 1 or 2, further comprising constructing a plastic part coupled to the first metal layer and / or the metal reinforcing part using an additive manufacturing technique.

4. A lightning protection system for a wind turbine blade, the lightning protection system producible according to the method of any of claims 1 to 3, the lightning protection system comprising: a first metal layer; and a metal reinforcing part formed on the first metal layer so as to create an electrical connection with the first metal layer, wherein a portion of the first metal layer extends laterally beyond the metal reinforcing part.

5. A lightning protection system according to claim 4, wherein the metal reinforcing part extends from only one side of the first metal layer.

6. A lightning protection system according to claim 4 or 5, wherein the metal reinforcing part comprises a chamfer around at least a portion of an edge of the metal reinforcing part.

7. A lightning protection system according to any of claims 4 to 6, wherein the metal reinforcing part comprises a first portion and a second portion metallurgicallybonded to the first portion, wherein the first portion is manufactured from a first metal and the second portion is manufactured from a second metal, and wherein the first metal and the second metal are different.

8. A lightning protection system according to claim 7, wherein the first portion encapsulates the second portion, and preferably wherein the first portion and the first metal layer are manufactured from the same metal.

9. A lightning protection system according to claim 7 or 8, wherein the first metal has a greater electrical conductivity than the second metal.

10. A lightning protection system according to any of claims 7 to 9, wherein the second metal has a greater heat capacity than the first metal.

11. A lightning protection system according to any of claims 7 to 10, wherein the first metal has a greater stiffness than the second metal.

12. A lightning protection system according to any of claims 4 to 11 , wherein the first metal layer includes an array of apertures, preferably wherein the first metal layer has an unapertured portion adjacent the metal reinforcing part and an apertured portion away from the metal reinforcing part.

13. A lightning protection system according to any of claims 4 to 12, wherein the metal reinforcing part is generally circular or oval or pear-shaped.

14. A lightning protection system according to any of claims 4 to 13, wherein the metal reinforcing part comprises a curved surface facing away from the first metal layer, preferably wherein the curved surface is a concave surface.

15. A lightning protection system according to any of claims 4 to 14, further comprising a plastic part coupled to the first metal layer and / or the metal reinforcing part and manufactured using an additive manufacturing technique.

16. A lightning protection system according to claim 15, wherein the plastic part comprises a chamfer around at least a portion of the edge of the plastic part and / or locating features for locating the lightning protection system relative to a mould.

17. A wind turbine blade having a blade shell with a lightning protection system according to any of claims 4 to 16, wherein the first metal layer is at an outer surface of the blade shell, and wherein the lightning protection system further comprises an electrically conductive pin extending through an aperture in the metal reinforcing part and through the first metal layer.

18. A wind turbine blade according to claim 17, wherein the lightning protection system comprises a reinforcing patch including the first metal layer and the metal reinforcing part, and the lightning protection system further comprises a second metal layer extending substantially over the outer surface of the blade shell, wherein the first metal layer has an area no more than 10% of an area of the second metal layer, and wherein a first portion of the second metal layer surrounds the first metal layer at an outer surface of the blade shell, and a second portion of the second metal layer overlaps the first metal layer and is in intimate electrical contact with the second metal layer.

19. A method of manufacturing a wind turbine blade with a lightning protection system, the method comprising: providing a mould surface; providing a lightning protection system having the first metal layer with the metal reinforcing part formed across a portion of the first metal layer formed using the method of any of claims 1 to 3; arranging the lightning protection system on the mould surface; arranging one or more structural components on the lightning protection system; consolidating the structural components and the lightning protection system under vacuum to form a blade shell.

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