Equipotential Bonding of a Wind Turbine Rotor Blade

Abstract

A wind turbine rotor blade having a blade shell is provided. The blade shell has fiber laminae laid generally in the chordwise direction and spar caps in the spanwise direction. A lightning arrester extends over the spar caps, and the spar caps include a conductive material. An equipotential bonding member electrically bonds the lightning arrester to the spar caps. The equipotential bonding member extends between an outer edge of one fiber lamina stack and an inner edge of an adjacent fiber lamina stack, and these edges overlap to define an overlapping edge region.

Description

Field of the Invention

[0001] The present invention relates to wind turbine rotor blades, and in particular, to equipotential bonding within wind turbine rotor blades, and to methods of manufacturing wind turbine rotor blades. Background Art

[0002] Wind turbines convert the kinetic energy of the wind into electrical energy. A generator converts the wind energy captured by a rotor having one or more rotor blades into electrical energy that is typically supplied to an electrical grid. The generator and various components required for operating and optimizing the performance of the wind turbine are housed within a nacelle. A tower supports the loads provided by the nacelle and the rotor. In a horizontal axis wind turbine (HAWT), the rotor blades extend radially outward from a central hub that rotates about a generally horizontally aligned longitudinal axis. In operation, the blades are configured to interact with the passing air stream to generate lift that causes the rotor to rotate in a plane generally perpendicular to the direction of the wind.

[0003] Conventional rotor blades are made of a shell and a spar structure. The spar structure is used to transfer loads from the rotating blade to the hub of the wind turbine. Such loads include tensile and compressive loads oriented along the length of the blade due to the circumferential motion of the blade, and loads oriented along the thickness of the blade (i.e., from the windward side to the leeward side) due to the wind. The spar structure includes one or more shear webs extending between spar caps. The spar caps may be incorporated into the shell or may be attached to the shell.

[0004] The spar caps may include strips of pultruded fiber material. Pultrusion is a continuous process similar to extrusion, in which fibers are pulled through a source of liquid resin and then heated in an open chamber where the resin is cured. The resulting cured fiber material has a constant cross-section, but since the process is continuous, the material can be cut to any length once it is formed.

[0005] WO 2013 / 087078 describes a wind turbine blade having an extended reinforcement structure that includes a laminate of pultruded fiber composite strips. The pultruded fibers are carbon fibers and extend almost the entire length of the blade from the root to the tip.

[0006] In the past few years, the general trend in the wind turbine industry has been to make wind turbine blades longer. The longer the blades, the larger the rotor, and the more wind energy that can be captured, thus increasing the efficiency of an individual wind turbine.

[0007] Wind turbines are vulnerable to lightning strikes. Wind turbines typically include a lightning protection system that electrically connects the wind turbine components to ground. The blades and especially the blade tips are particularly vulnerable to lightning strikes. The blade may include a metal foil or a surface protection layer (SPL) bonded to a housing near the outer surface of the blade. The metal foil may cover only a portion or substantially all of the outer surface of the blade. Additionally or alternatively, the lightning protection system may include one or more discrete lightning arresters. The metal foil and / or the lightning arresters on the blade are both electrically connected to ground through the tower and the nacelle.

[0008] Although lightning strikes have a natural tendency to travel along the outer surface of a structure such as a rotor blade due to their high frequency, the presence of conductive fibres in the blade housing when a lightning strike occurs may cause an undesired discharge, which may lead to damage to the blade housing. This problem may be exacerbated in cases where the conductive fibres are continuous and extend along a substantial length of the rotor blade, especially for long blades. Summary of the Invention

[0009] There is provided a wind turbine rotor blade having a blade housing with a fibre pile laid generally in the chordwise direction and a spar cap generally in the spanwise direction. A lightning arrester extends over the spar cap, and the spar cap includes a conductive material. An equipotential bonding member electrically bonds the lightning arrester to the spar cap. The equipotential bonding member extends between an outer edge of one fibre pile laminate and an inner edge of an adjacent fibre pile laminate, these edges overlapping to define an overlapping edge region extending across the spar cap.

[0010] In particular, a first aspect of the present invention provides a wind turbine rotor blade having a root end and a tip end, the wind turbine rotor blade comprising: a wind turbine blade housing defining a suction side, a pressure side, a leading edge, and a trailing edge of the blade; at least one spar cap associated with the blade housing and including a conductive material; a lightning arrester; and an equipotential bonding member that electrically bonds the lightning arrester to the spar cap, wherein the blade housing includes a plurality of fibre pile laminates, each fibre pile laminate having an inner edge facing the root end of the blade, an outer edge facing the tip end of the blade, a front edge facing the leading edge of the blade, and a rear edge facing the trailing edge of the blade; wherein the equipotential bonding member extends between an outer edge of one laminate and an inner edge of an adjacent laminate, these edges overlapping to define an overlapping edge region extending across the spar cap.

[0011] The present invention can utilize the chordwise laying of the fibre pile laminates to provide a route for the equipotential bonding member from the lightning arrester to the spar cap.

[0012] The equipotential bonding component can have a first end that is attached to and in electrical contact with the lightning arrester, and a second end that is attached to and in electrical contact with the spar cap.

[0013] The spar cap can have an outer side and an inner side closest to the interior of the blade, and the equipotential bonding component can be attached to and in electrical contact with the outer side of the spar cap.

[0014] The equipotential bonding component can be a strip or a band, preferably including conductive wires or yarns woven into a fabric.

[0015] The equipotential bonding component can be attached to the lightning arrester and the spar cap, and the equipotential bonding component defines a path between the attachment point to the lightning arrester and the spar cap, and this path extends from the lightning arrester to the spar cap in a direction that is only away from the attachment point and does not return towards the attachment point.

[0016] The spar cap can include a stack of layers of conductive material, preferably a carbon fiber material, preferably a pultruded carbon fiber composite material.

[0017] The spar cap can have an abraded portion for exposing the conductive material, where the equipotential bonding component is attached to and in electrical contact with the spar cap.

[0018] At least one of the layers of the spar cap can be chamfered at at least one of its ends such that the thickness of the layer tapers towards at least one end.

[0019] The layer of the spar cap closest to the lightning arrester can have a chamfered end and an abraded portion on the same side of the layer facing the lightning arrester.

[0020] The fiber laminate of the blade housing can include a glass fiber material.

[0021] The front edge of the fiber laminate of the blade housing can be at or adjacent to the leading edge of the blade, and the rear edge of the fiber laminate can be at or adjacent to the trailing edge of the blade.

[0022] Each fiber laminate of the blade housing can be provided as a preform.

[0023] The overlapping edges of adjacent fiber laminates can be formed by continuously terminating the individual layers in the laminate to form a step or a ramp.

[0024] The lightning arrester can be the metal foil of the lightning protection system.

[0025] The lightning arrester can be the outer surface of the blade.

[0026] The wind turbine rotor blade can further include a plurality of equipotential bonding components.

[0027] A plurality of equipotential bonding components can extend between the outer edge of one laminate and the inner edge of an adjacent laminate.

[0028] Multiple pairs of adjacent laminates can be spaced apart along the blade in the spanwise direction and can have at least one equipotential bonding component among the equipotential bonding components that extend between the outer edge of one laminate of the pair of adjacent laminates and the inner edge of the adjacent laminate.

[0029] The lightning arrester and the equipotential bonding component can be integrally formed.

[0030] Another aspect of the present invention provides a method of manufacturing a wind turbine rotor blade having a root end and a tip end, the method comprising the steps of: laying a shell of the wind turbine blade, the shell defining an inlet side, a pressure side, a leading edge, and a trailing edge of the blade, the shell including a plurality of fiber laminate stacks and a lightning arrester, each fiber laminate stack having an inner edge facing the root end of the blade, an outer edge facing the tip end of the blade, a front edge facing the leading edge of the blade, and a rear edge facing the trailing edge of the blade; laying a spar cap such that the lightning arrester extends above the spar cap, wherein the spar cap includes a conductive material; and providing an equipotential bonding component to electrically connect the lightning arrester to the spar cap, the equipotential bonding component extending between the outer edge of one laminate and the inner edge of an adjacent laminate, these edges overlapping to define an overlapping edge region extending across the spar cap.

[0031] Each fiber laminate stack of the blade shell can be laid as a preform in a mold, and the method can further include the steps of: resin-infusing the preform and curing it.

[0032] The equipotential bonding component can be attached to one of the fiber laminate stacks of the blade shell before being laid.

[0033] The lightning arrester and the equipotential bonding component can be integrally formed, and the lightning arrester and the equipotential bonding component can be attached to one of the fiber laminate stacks of the blade shell before being laid. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Embodiments of the present invention will now be described with reference to the drawings, wherein:

[0035] Figure 1 A wind turbine is shown;

[0036] Figure 2 A wind turbine blade is shown;

[0037] Figure 3 A schematic plan view of a wind turbine blade having lightning protection features is shown;

[0038] Figure 4a shows a Figure 3 cross-sectional view of a hollow blade taken along A-A in ; and Figure 4b shows a Figure 4a detail view of the outer shell, spar cap, and shear web at B in ;

[0039] Figure 5 shows a schematic diagram of the chordwise laying of the outer shell in the mold;

[0040] Figure 6 shows a schematic spanwise cross-section of the laminate of the outer shell, showing the overlapping edges of these laminates;

[0041] Figure 7 shows a schematic spanwise cross-section of a pair of adjacent laminates of the outer shell, wherein the equipotential bonding member extends from the surface protective layer to the spar cap through the overlapping edges of these laminates;

[0042] Figure 8 shows a first example, wherein the equipotential bonding member is laid between the laminates and directly contacts the surface protective layer at one end and directly contacts the spar cap at the other end;

[0043] Figure 9 shows a second example, wherein the equipotential bonding member is integrally formed with the corresponding part of the surface protective layer and laid together with the corresponding laminate of the outer shell;

[0044] Figure 10 shows a third example, wherein the equipotential bonding member is laid between the laminates and contacts the surface protective layer via a conductive pad;

[0045] Figure 11 shows a schematic spanwise cross-section of the conductive material layer of the spar cap, wherein there are inclined surfaces at each end and the lowermost layer is inverted;

[0046] Figure 12 shows another schematic spanwise cross-section of a pair of adjacent laminates of the outer shell, wherein the equipotential bonding member extends from the surface protective layer to the spar cap through the overlapping edges of these laminates;

[0047] Figure 13 shows a Figure 12 detail A of ; and

[0048] Figures 14 to 16 shows an alternative arrangement of the equipotential bonding member. Detailed Description

[0049] In this specification, terms such as leading edge, trailing edge, pressure side, suction side, thickness, chord, and platform are used. Although these terms are well known and understood by those skilled in the art, for the sake of clarity, definitions are given below.

[0050] The term leading edge is used to refer to the edge of the blade that will be at the front of the blade when the blade rotates in the normal rotational direction of the wind turbine rotor.

[0051] The term trailing edge is used to refer to the edge of the wind turbine blade that will be at the rear of the blade when the blade rotates in the normal rotational direction of the wind turbine rotor.

[0052] The chord of the blade is the straight-line distance from the leading edge to the trailing edge in a given cross-section perpendicular to the spanwise direction of the blade.

[0053] The pressure side (or windward side) of the wind turbine blade is the surface between the leading edge and the trailing edge, which has a higher pressure than the suction side of the blade during use.

[0054] The suction side (or leeward side) of the wind turbine blade is the surface between the leading edge and the trailing edge, and the pressure acting on this surface during use will be lower than the pressure on the pressure side.

[0055] The thickness of the wind turbine blade is measured perpendicular to the chord of the blade and is the maximum distance between the pressure side and the suction side in a given cross-section perpendicular to the spanwise direction of the blade.

[0056] The term spanwise direction is used to refer to the direction from the root end to the tip of the wind turbine blade, and vice versa. When the wind turbine blade is mounted on the wind turbine hub, the spanwise direction and the radial direction will be substantially the same.

[0057] A view perpendicular to the spanwise direction and the chordwise direction is called the platform view. This view is along the thickness dimension of the blade.

[0058] The term spar cap is used to refer to a longitudinal, generally spanwise-extending reinforcement member of the blade. The spar cap can be embedded in the blade shell or can be attached to the blade shell. The spar caps on the windward and leeward sides of the blade can be connected by one or more shear webs extending through the internal hollow space of the blade. The blade can have more than one spar cap on each of the windward and leeward sides of the blade. The spar cap can form part of the longitudinal reinforcement spar or support member of the blade. In particular, the first spar cap and the second spar cap can form part of a load-bearing structure extending in the longitudinal direction and bearing the load of the blade bending in the flap direction.

[0059] The term shear web is used to refer to a longitudinal, generally spanwise extending reinforcement member of a blade, which can transfer loads from one of the windward and leeward sides of the blade to the other of the windward and leeward sides of the blade.

[0060] Figure 1 FIG. 4 shows a wind turbine 10 which includes a tower 12 mounted on a base and a nacelle 14 disposed at the top of the tower 12. The wind turbine 10 depicted herein is a land-based wind turbine such that the base is embedded in the ground, but the wind turbine 10 could be an offshore power generation installation, in which case the base would be provided by a suitable offshore platform.

[0061] The rotor 16 is operably coupled via a gearbox to a generator (not shown) housed within the nacelle 14. The rotor 16 includes a central hub 18 and a plurality of rotor blades 20 projecting outwardly from the central hub 18. It should be noted that the wind turbine 10 is of 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 center of the hub 18. Although Figure 1 the example shown has three blades, those skilled in the art will recognize that other numbers of blades are possible.

[0062] When the wind blows against the wind turbine 10, the blades 20 generate lift which causes the rotor 16 to rotate, which in turn causes the generator within the nacelle 14 to generate electrical energy.

[0063] Figure 2 FIG. 16 illustrates one of the wind turbine blades 20 for use in such a wind turbine. Each of the blades 20 has a root end 22 adjacent the hub 18 and a tip end 24 remote from the hub 18. A leading edge 26 and a trailing edge 28 extend between the root end 22 and the tip end 24, and each of the blades 20 has a respective aerodynamic high pressure side (i.e., pressure side) and an aerodynamic low pressure side (i.e., suction side) extending between the leading and trailing edges of the blade 20.

[0064] Each blade has a generally circular cross-section near the root end 22 since the blade near the root must have sufficient structural strength to support the blade outside of that section and transfer loads into the hub 18. The blade 20 transitions from a circular profile to an aerofoil profile which moves from the root end 28 of the blade towards the "shoulder" 30 of the blade, which is the widest part of the blade where the blade has its maximum chord. In the outer portion of the blade 20 extending from the shoulder 30 to the tip end 24, the blade 20 has an aerofoil profile with a gradually decreasing thickness.

[0065] AsFigure 3 Schematically shown, the blade 20 includes one or more lightning arresters and one or more lightning “down conductors”, which form part of the lightning protection system of the wind turbine. The lightning arrester attracts lightning strikes, and the down conductor conducts the energy of the lightning strike along the blade 20 through the nacelle 14 and the tower 12 to ground potential. The lightning arrester can take various forms, such as a surface metal foil 32 on the outer surface of the blade or a cable 38 passing through the interior of the hollow blade. The lightning arrester can include a metal foil 32 and / or discrete lightning arresters 34 mounted on the outer surface of the blade, or for example, a solid metal tip 36 or a metal-coated laminate (e.g., a copper cap) conforming to the blade shape closest to the tip 24 can be provided. The discrete lightning arresters 34 and the metal tip 36 can be electrically connected to the lightning arrester.

[0066] Most of the outer surface of the blade 20 can be covered with a metal foil 32. The metal foil 32 can act as a lightning arrester, a down conductor, or both. The down conductor can extend substantially the entire length of the blade. In the case where most of the outer surface of the blade 20 is covered with a metal foil 32, the cable 38 can be connected to the metal foil 32 adjacent to the tip 24 of the blade and adjacent to the root end 22 of the blade, and there is no cable 38 along most of the length of the blade covered with the metal foil 32. The metal foil 32 can extend from the root to the tip, in which case no cable 38 is required. The metal foil 32 can extend in sections along the length of the blade, and there are cable sections between the metal foil sections. Alternatively, the cable 38 can extend below the metal foil 32 (inside the blade) so that the cable 38 and the metal foil 32 are electrically connected in parallel. Alternatively, the blade can have a greater number of discrete lightning arresters on the blade surface, which are electrically connected via a down conductor cable extending substantially the entire length of the blade, rather than having a metal foil.

[0067] At the root end 22 of the blade 20, the down conductor 38 can be electrically connected to a charge transfer path via an armature arrangement, and the charge transfer path is connected to ground potential via the nacelle 14 or the hub 18 and the tower 12. Thus, such a lightning protection system allows lightning to be safely guided from the blade to ground potential, thereby minimizing the risk of damaging the wind turbine 10.

[0068] As Figure 4aAs shown, the wind turbine blade 20 includes a blade housing 40. The blade housing defines a suction side (including a suction surface), a pressure side (including a pressure surface), a leading edge, and a trailing edge. The blade housing also defines a hollow internal space 42, in which a shear web 44 extends inwardly between an upper portion and a lower portion of the blade housing 40. The blade housing 40 may include two half shells 40a, 40b, which are molded to form the blade 20 before being joined together (at the leading edge 26 and the trailing edge 28). It should be appreciated that the blade housing 40 need not be formed as two half shells that are subsequently joined together, but may be formed integrally with the shear web 42 in a "one-shot" single shell process.

[0069] Figure 4b A detail view of the area where the shear web 44 meets the blade housing 40 is shown. The spar cap 46 may be incorporated into the housing 40 (as Figure 4b shown), or may be attached to the housing 40. The spar cap 46 is an extended reinforcement structure that extends substantially along the entire length of the blade 20 from the root end 22 to the tip end 24. The spar cap 46 includes a conductive material, such as carbon fiber. In particular, the spar cap 46 includes a conductive material layer 80 (as Figure 8 shown). For example, the spar cap may include pultruded fiber strips of a material such as pultruded carbon fiber composite material or other carbon fiber reinforced polymer material.

[0070] Returning to Figure 3 , the blade 20 may have more than one spar cap 46, which is incorporated into or attached to the upper and lower portions of the blade housing 40. In the example shown, the blade 20 has a main spar cap 46a and a rear spar cap 46b (also referred to as stringers), the main spar cap having a shear web 44 extending therebetween, and the rear spar cap may or may not have a shear web extending therebetween.

[0071] Each spar cap 46 may include a stack of conductive material layers. The shear web 44 may be adhesively bonded to the inner surface 48 of the spar cap 46. The outer surface 50 of the spar cap 46 may be placed adjacent to a lightning arrester in the outer surface of the blade housing 40. As Figure 4bAs shown, the lightning arrester can be in the form of a metal foil 32, which is separated from the outer surface 50 of the spar cap 46 by one or more layers 52 of an insulating material such as a glass fiber reinforced polymer. One or more further layers 52 of the glass fiber reinforced polymer can be provided on the outside of the metal foil 32. The layers 52 together form the outer skin of the blade housing 40. One or more further layers of the glass fiber reinforced polymer provide the inner skin 54 of the blade housing 40, and there is a core material 56 between the outer skin 52 and the inner skin 54. The core material can be a lightweight structural foam, but alternatively, other core materials such as wood (especially balsa wood) and honeycomb can be used to provide a lightweight core material. It should be appreciated that a substantially identical connection is made between the shear web 44 and the other side of the blade housing 40.

[0072] Now, the structure of the blade housing 40 (especially the outer skin) and its manufacturing method will be described in detail. As Figure 5 shown, a glass fiber reinforced fabric layer 52 is laid as a fiber laminate 70 in a mold 60. The fiber laminate 70 can include a plurality of fiber laminae that are stitched or otherwise attached together as a kit. The fiber laminate 70 can be pre-cut to fit the shape of the mold 60, such that the fiber laminate 70 easily conforms to the shape of the mold 60, and a number of laminae can be easily and quickly laid in the mold 60, preferably without any cutting or detailed forming of the laminae once in the mold 60. Alternatively, the laminae can be cut in the mold 60. The fiber laminate 70 can include dry fibers that are subsequently infused with resin, or alternatively, the fiber laminae can be wet or semi-dry fiber laminae that do not require or only partially require resin infusion before consolidation and curing within the mold 60. Alternatively, the fiber laminate 70 can be laid layer by layer in the mold 60. The fiber laminate 70 can be prepared outside the mold on a flat or near-flat surface such that the fiber laminate 70 assumes the form or shape it will have when placed in the mold 60. Alternatively, the fiber laminate 70 can be laid on a suitably formed surface outside the mold such that the fiber laminate 70 assumes the (near-final) form or shape outside the mold before being laid in the mold 60. Hereinafter, a fiber laminate laid on any surface outside the mold is referred to as a "preform".

[0073] In particular for the present invention, each fiber laminate 70 has an inner edge 71 facing the root end 22 of the blade, an outer edge 72 facing the tip end 24 of the blade, a front edge 73 facing the leading edge 26 of the blade, and a rear edge 74 facing the trailing edge 28 of the blade.

[0074] The fiber laminate stack 70 is arranged such that the outer edge 71 of one laminate in the stack 70 and the inner edge 72 of an adjacent laminate 70 overlap to define an overlap region 75 that extends across the spar cap. The overlap region 75 extends generally transversely across the location of the spar cap 46. This is commonly referred to as "chordwise laying" of the preform or fiber laminate stack 70. Each laminate in the fiber laminate stack 70 can extend across the entire chordwise width of the mold 60 such that the leading edge 73 of each fiber laminate stack 70 is at the leading edge 26 of the blade and the trailing edge 74 of each fiber laminate stack 70 is at the trailing edge 28 of the blade. Typically, the length of each fiber laminate stack 70 between the leading edge 73 and the trailing edge 74 is greater than the width of the laminate between the inner edge 71 and the outer edge 72. Note that this "chordwise laying" does not relate to the fiber direction of any of the plies that make up the fiber laminate stack 70, and any individual ply can have a fiber direction.

[0075] To avoid the risk of arcing between the conductive material of the spar cap 46 and the metal foil 32 or other lightning arresters, an equipotential bonding component 58 is used to bond the lightning arresters to the conductive material of the spar cap 46 in an equipotential manner, as Figure 7 shown. By electrically bonding the lightning arrester 32 to the spar cap 46, the spar cap 46 can be maintained at the same potential as the lightning arrester, such that in the event of a lightning strike, undesirable discharge or arcing between the lightning arrester 32 and the spar cap 46 can be avoided.

[0076] The overlapping edges of adjacent fiber laminate stacks 70 are formed by successively terminating the individual plies in the stack to form a step or ramp. Advantageously, this successive termination of each ply in the stack at the overlap region 75 forms a stepped path between the outer edge 72 of one laminate 70 and the inner edge 71 of an adjacent laminate 70, and the equipotential bonding component 58 extends through this path to electrically bond the metal foil 32 or other lightning arresters to the spar cap 46.

[0077] The equipotential bonding component 58 has: a first end 58a which is attached to the metal foil 32 at the attachment point 59 and is in electrical contact with the metal foil; and a second end 58b which is attached to the spar cap 46 and is in electrical contact with the spar cap. The spar cap 46 has an outer side 46a closest to the outer surface 29 of the blade 20 and an inner side 46b closest to the hollow interior 42 of the blade 20. The equipotential bonding component 58 can be attached to the outer side 46a of the spar cap 46 and is in electrical contact with the outer side of the spar cap. The stepped path followed by the equipotential bonding component 58 extends from the lightning arrester (metal foil 32) in a direction only away from the attachment point 59 with the lightning arrester and not returning towards the attachment point 59 to the spar cap 46. That is, the equipotential bonding component 58 itself does not fold back in a U-shape. This can prevent arcing from one part of the equipotential bonding component to another part of the equipotential bonding component.

[0078] The equipotential bonding component 58 can include: a strip or band containing a conductive material, or a conductive laminate incorporated into a laminate stack, or a cable or a series of cables or conductive wires. For example, the equipotential bonding component 58 can include a harness of conductive material (such as metal wire) woven into a fabric material (such as a fiberglass fabric). In an example, the conductive material of the equipotential bonding component 58 can be copper coated with tin. The material can be selected to avoid any galvanic reaction with the conductive material of the lightning arrester 32 or the spar cap 46. In an example, the equipotential bonding component can include a conductive layer as a conductive grid (such as a metal mesh or foil).

[0079] The metal foil 32 is typically a metal mesh or an expanded metal foil, or a woven or knitted or perforated mesh (such as made of aluminum or copper). The copper of the equipotential bonding component 58 coated with tin material avoids the galvanic reaction with the aluminum foil lightning arrester 32 or the carbon material of the spar cap 46.

[0080] The fiberglass material of the fiber laminate stack 70 between the spar cap 46 and the lightning arrester 32 mainly distributes mechanical loads, but the fiberglass also helps to avoid the current response between the carbon of the spar cap and the aluminum of the metal foil 32. Of course, it should be realized that the lightning arrester 32 can be formed of other suitable materials (such as copper), and the selection of the conductive material of the equipotential bonding component 58 can be selected according to other material selections.

[0081] Metal wires can be woven into a fabric material (especially a fiberglass fabric) so that the metal wires can be incorporated into the fiberglass fabric layers in the laminate 70 without using additional components, and resin can be poured during the manufacture of the blade housing 40 without voids.

[0082] The strip is kept as flat as possible by "stepping" the flat strip between the edges of adjacent fibrous lamina stacks 70.

[0083] The spar cap may be arranged to be connected isopotentially between the conductive material layers in the spar cap 46. The spar cap 46 may include a stack comprising a plurality of conductive material layers. The conductive material may include a pultruded fiber composite material, for example, carbon fiber reinforced polymer. The pultruded fibers may be oriented in the longitudinal direction of the spar cap 46, which longitudinal direction is aligned with the longitudinal or spanwise direction of the blade 20. By connecting adjacent conductive material layers 80 isopotentially, in the case of lightning striking the blade 20, undesired discharges or arcs from the spar cap 46 can be avoided.

[0084] The spar cap 46 may extend substantially over the entire length of the blade 20 and have a first end 82 closest to the root end 22 of the blade 20 and a second end 84 adjacent to the tip 24 of the blade. The spar cap 46 has a thickness that may vary along the length of the spar cap 46 in the stacking direction of the conductive material layers 80. At least one of the ends of the spar cap 46 may be tapered in the thickness direction.

[0085] In Figures 8 to 10 the example shown, both ends of the spar cap 46 are tapered. The tapers are formed by cutting the respective conductive material layers 80 in the conductive material layer 80 to different lengths. The taper at the first end 82 may be steeper than the taper at the second end 84. The shallower taper may be formed by sequentially terminating the layers 80 in a stepped manner. Each of the layers 80 may have the same thickness, but alternatively, the layers 80 may have different thicknesses. The varying thickness of the spar cap 46 along the length of the blade 20 increases from zero closest to the root end 22 and increases to a maximum through the shoulder 30 and then decreases towards the tip 24 of the blade 20. At least one of the conductive material layers 80 has a beveled end at each end of the layer. The bevels may assist in load transfer to and from the multiple layers 80 of the spar cap 46 to other materials of the blade 40.

[0086] Returning to Figure 3 , it can be seen that the metal foil 32 lightning arrester may extend substantially over the entire blade surface. A plurality of equipotential connection components 58 may be connected to the spar cap 46 at a plurality of positions along the blade length. In particular, a first equipotential connection component among the equipotential connection components 58 may be connected to the spar cap 46 at the end 84 of the spar cap 46, and a second equipotential connection component among the equipotential connection components 58 may connect the metal foil 32 to the first (root) end 82 of the spar cap 46. Further intermediate equipotential connection components 58 connect the metal foil 32 lightning arrester to the mid-span region of the spar cap 46, respectively.

[0087] In the case of the electrical connection provided by the equipotential bonding member 58 at both the root end and the tip end of the blade, there will be a voltage drop between the first end 82 and the second end 84 of the spar cap 46. Depending on the length of the blade 20, in particular depending on the length of the longest conductive material layer 80 in the spar cap 46, the value of the voltage drop between the first end 82 and the second end 84 of the spar cap 46 will change. If this voltage is lower than the threshold at which flashover may occur from the lightning arrester to one or more of the conductive material layers in the conductive material layer 80, it is sufficient to provide the equipotential bonding member 58 only at the ends 82, 84 of the spar cap 46. However, if the voltage drop between the ends 82, 84 of the spar cap 46 is higher than the said threshold, one or more further equipotential bonding members 58 may be required to electrically connect the metal foil 32 to an intermediate point between the first end 82 and the second end 84 of the spar cap 46.

[0088] Figure 8 A first example is illustrated, in which the equipotential bonding member 58 provides a direct attachment and electrical contact with the metal foil 32 at its first end, and provides a direct attachment and electrical contact with the outer surface 46a of the lowermost conductive material layer 80 of the spar cap 46. In this first example, the equipotential bonding member 58 may comprise a copper braid, and the metal foil 32 may comprise aluminum.

[0089] Figure 9 A second example is illustrated, in which the equipotential bonding member 58 is integrally formed with the lightning arrester 32. In this example, the lightning arrester 32 includes a discrete portion of the metal foil that extends across the outer surface of the blade and then advances through between the inner edge 71 and the outer edge 72 of the adjacent fiber laminate stack 70. The discrete portion of the metal foil 32 may be bonded to the fiber laminate stack 70 such that the metal foil 32 is laid in the mold 60 together with the stack 70. Alternatively, the individual portions of the metal foil 32 and the integrated equipotential bonding member 58 may be laid in the mold next to the previously laid fiber laminate stack 70 and before laying the next adjacent fiber laminate stack 70. Again, the metal foil 32 may comprise aluminum, and thus a conductive pad 86 comprising, for example, a copper material may be provided between the end of the metal foil 32 and the outer surface 46a of the spar cap 46. The choice of the copper material in the pad 86 may be to avoid an electrical chain between the carbon material of the spar cap 46 and the aluminum foil lightning arrester 32. The pad 86 may comprise one or more of a variety of other conductive materials (such as tin, lead, carbon, etc.).

[0090] Figure 10 An example similar to Figure 8A third example, but in which the equipotential bonding member 58 includes a conductive carbon material, such as carbon fabric. A conductive pad 86 including, for example, a copper material may be disposed between the conductive carbon equipotential bonding member 58 and the aluminum metal foil 32 in order to interrupt the potential sequence.

[0091] Depending on the materials of the metal foil 32 and the equipotential bonding member 58, the material of the conductive pad 86 may be selected to avoid the electro-chain effect.

[0092] As described above, the ends of the conductive material layer 80 in the spar cap 46 may be chamfered to facilitate load transfer between the layer 80 of the spar cap 46 and the remainder of the blade housing 40. The pultruded carbon fiber composite material layer may be cut to a desired length, and then the ends 82, 84 of the layer 80 may be ground to achieve a desired chamfer profile before the layer 80 is stacked to form the spar cap 46.

[0093] To ensure good electrical contact between the equipotential bonding member 58 and the conductive material of the spar cap 46, the conductive material in the layer 80 may need to be exposed, i.e., such that it is not covered by the (insulating) resin. The same grinding process used to form the chamfers at the ends 82, 84 of the layer 80 may also be used to expose the conductive material to provide a suitable attachment surface for providing a good electrical connection between the conductive material of the spar cap 46 and the equipotential bonding member 58. Alternatively, the electrical connection between the conductive material of the spar cap 46 and the equipotential bonding member 58 may be sufficiently achieved by contact pressure without treating or otherwise exposing the conductive material in the layer 80.

[0094] Figure 11 An example is shown in which the respective ends 82, 84 of each of the plurality of conductive material layers 80 are chamfered. The lowermost layer 80 in the laminate also has a connection point 57 at which the equipotential bonding member 58 will be attached to and in electrical contact with the spar cap 46. The contact point 57 may include an abraded portion for exposing the conductive material.

[0095] Advantageously, the chamfers at the ends 82, 84 and the abraded portion at the contact portion 57 may both be provided on the same side of the layer 80. The contact point 57 may be provided on the lowermost layer 80 in the laminate on the lowermost (outer) side 46a of the spar cap 46 facing the arrester 32. In Figure 11 the example illustrated, each of the layers 80 may be subjected to a grinding process or other known process to form a chamfered end and an abraded portion at the contact point 57 on only one side of each of the layers 80.

[0096] It should be appreciated that Figure 11The lowermost layer 80 shown is inverted after the beveling process is completed so that the beveled ends 82, 84 of the lowermost layer 80 face in a direction opposite to the beveled ends of the upper layer 80 in the laminate forming the spar cap 46. Once the laying of the blade housing 40 is completed, consolidation will cause the beveled ends 82, 84 of the lowermost layer 80 in the laminate to deflect downward into the shape shown by the dashed line.

[0097] It should be appreciated that in this alternative, the lowermost layer 80 in the laminate can be subjected to a first process for forming beveled ends 82, 84 on the upper side of the layer 80 and a second process for forming an abraded portion at the contact point 57 on the lowermost side of the layer 80. Although this requires machining operations from two different sides of the layer 80, it is advantageous in terms of avoiding the need to invert the lowermost layer 80 of the laminate before laying other layers 80 to form the laminate of the layer 80 for the spar cap 46. As an alternative to the above-described grinding process for removing material to expose the conductive material of the layer 80, various other known processes can alternatively be used, such as etching, or laser or chemical activation.

[0098] Figure 12 and Figure 13 Further details are shown of how the equipotential bonding member 58 can be attached to the spar cap 46 and be in electrical contact with the spar cap. Figure 13 Shown is Figure 12 Detail C of, in which a plurality of equipotential bonding members 58 extending in the chordwise direction extend through the same overlapping region 75 between the outer edge 71 of one laminate in the laminate 70 and the inner edge 72 of the adjacent laminate 70. Each of the plurality of spanwise extending equipotential bonding members 58 at the overlapping region 75 can be in electrical contact with an equipotential bonding member 90 extending in the chordwise direction, which connects the corresponding ends 58b of the adjacent spanwise equipotential bonding members 58 at the overlapping region 75.

[0099] A first conductive pad 92 is provided between the innermost surface of the fiber laminate 70 and the end 58b of the spanwise extending equipotential bonding member 58. A second conductive contact pad 94 is provided between the equipotential bonding member 90 extending in the chordwise direction and the contact point 57 on the outermost surface 46a of the spar cap 46. The first contact pad 92 can include steel fleece. The second contact pad 94 can include carbon fleece. The equipotential bonding member 90 extending in the chordwise direction can have the same or similar structure and material as the spanwise extending equipotential bonding member 58.

[0100] The electrical connection between the conductive material of the spar cap 46 and the equipotential bonding component 58 can take various forms. For example, a contact pad can provide the electrical connection between the conductive material of the spar cap 46 and the equipotential bonding component 58. The contact pad can be a metallic interface, such as a nickel interface or strip.

[0101] Similarly, the electrical connection between the metal foil 32 or other lightning arrester and the equipotential bonding component 58 can take various forms. For example, a contact pad can provide the electrical connection between the metal foil 32 and the equipotential bonding component 58.

[0102] Figures 14 to 16 Illustrated in detail Figure 12 and Figure 13 An example of the assembly 91 of the equipotential bonding component 58 shown. The equipotential bonding component assembly 91 can include a plurality (e.g., five) of equipotential bonding components 58 extending in the spanwise direction. The equipotential bonding component 58 can be formed as a strip or band of fiberglass fabric, where a tinned copper braid is woven into the fiberglass fabric or any other suitable material, as described above.

[0103] A transverse strip 96 of non-structural fibrous fabric can extend across the equipotential bonding component 58. The transverse strip 96 can be adjacent to but extend away from the end 58a and can serve to stabilize the assembly 91. For example, the transverse strip 96 can include a biaxial fiberglass fabric. A second conductive contact pad 94 can extend transversely at the end 58a of the equipotential bonding component 58 extending in the spanwise direction, thereby forming a contact surface of the assembly 91 with the surface 46a of the spar cap 46. The second conductive contact pad 94 can include, for example, carbon velvet. Alternatively, the transverse strip 96 can be omitted, and the plurality of equipotential bonding components 58 can be laid discretely through the gap between the laminates, i.e., the plurality of equipotential bonding components 58 are not transversely joined together before laying.

[0104] On the other side of the equipotential bonding component 58 opposite the second conductive contact point 94, a first conductive contact pad 92, which can include, for example, steel wool, extends across the set of equipotential bonding components 58. The first conductive pad 92 and the second conductive pad 94 can be fixed to the equipotential bonding component 58, for example, by a tag 98, which can include nylon or other suitable material. A transverse chordwise extending equipotential bonding component 90 extends between the first conductive contact pad 92 and the second conductive contact pad 94, as Figure 16 shown by the shaded dashed line in Figure 16 The equipotential bonding component 58 extending in the spanwise direction has an end 58b extending between the first contact pad 92 and the second contact pad 94, again, as

[0105] In another example, the equipotential bonding component 58 can be a sheet of conductive material (see Figure 3 ), rather than the assembly 91 of strips of the equipotential bonding component. The equipotential bonding component 58 formed as a sheet can have a width in the chordwise direction of the blade and a length in the spanwise direction of the blade. The width of the sheet can be greater than its length. The sheet can include a material similar to that of the strips of the equipotential bonding component described above. The electrical connection of the sheet to the conductive material of the spar cap 46 and / or to the metal foil 32 can be as described above.

[0106] During the manufacture of the blade 20, the blade shell 40 is laid as described above. In the case where the fiber laminate 70, for example made of a fiberglass material, is a dry fiber fabric, the laying undergoes a resin infusion, consolidation, and curing process to fully infuse the fabric with resin and then cure the resin to mechanically bond the structure of the blade shell 40 together. During this process, the fiber fabrics of the equipotential bonding components 58, 90 and / or the fluff of the first conductive contact pad 92 and / or the second conductive contact pad 94 (in the case where these are dry fiber fabric materials) will also be infused with resin, which is consolidated and cured in the same process.

[0107] Alternatively, the blade shell 40 can include a fiber laminate stack 70 of pre-impregnated material. In this case, the laying will not need to undergo a resin infusion process but will undergo a consolidation and curing process to mechanically bond the structure of the blade shell 40 together. During this process, the fiber fabrics of the equipotential bonding components 58, 90 and the materials of the first contact pad 92 and the second contact pad 94 (in the case where these also include pre-impregnated materials or dry fabric materials) can be consolidated and cured in the same process. In the case of dry fabrics, these fabrics can absorb resin from the surrounding material during the resin flow period and then become fully integrated into the blade laminate.

[0108] By either process, consolidation can ensure that the conductive material of the spar cap 46 is electrically connected to the equipotential bonding component 58, and curing mechanically bonds the spar cap 46, the equipotential bonding component 58, and the fiber laminate stack 70.

[0109] The wind turbine blade 20 is shown as a single complete blade, but in other examples, the blade can be a "split" or "segmented" blade, which includes a plurality of blade portions that are connected together to form a complete blade. For example, the wind turbine blade can include a first wind turbine blade portion and a second wind turbine blade portion, which can be connected at a joint to form a complete blade. It should be understood that the blade can have three or more blade portions with joints between adjacent blade portions.

[0110] The wind turbine rotor blade may also include a spar in the form of a trailing edge spar or a flaperon spar adjacent to the trailing edge of the blade. The spar may be incorporated into the blade shell 40. The spar may extend longitudinally along the length of the blade from the root to the tip, or along at least a portion of that length. The spar may be provided in each half of the blade shells 40a, 40b. Typically, the shear web does not extend between the spars. If there is a shear web, the shear web and the "spar" will form a flaperon spar structure, where the "spar" forms the spar cap. The spar or flaperon spar may include a conductive material, e.g., a carbon fiber material. The carbon fiber material may be unidirectional and aligned with the longitudinal direction of the blade. The carbon fiber material may include a pultruded type carbon fiber material similar to the aforementioned spar cap. In the case where the spar or spar cap of the flaperon spar includes a conductive material, the spar or spar cap may be electrically connected to a lightning arrester. The electrical connection may be provided similar to the aforementioned spar cap.

[0111] Although the invention has been described above with reference to one or more preferred embodiments, it should be appreciated that various changes or modifications can be made without departing from the scope of the invention as defined by the appended claims.

Claims

1. A wind turbine rotor blade (20) having a root end (22) and a tip end (24), the wind turbine rotor blade comprising: A wind turbine blade shell (40) defining an inlet side, a pressure side, a leading edge (26) and a trailing edge (28) of the wind turbine rotor blade; At least one spar cap (46) associated with the wind turbine blade shell and comprising a conductive material; A lightning arrester (32); And An equipotential bonding component (58) for electrically connecting the lightning arrester to the spar cap, Wherein the wind turbine blade shell comprises a plurality of fiber laminate stacks (70), each fiber laminate stack having an inner edge (71) facing the root end of the wind turbine rotor blade, an outer edge (72) facing the tip end of the wind turbine rotor blade, a front edge (73) facing the leading edge of the wind turbine rotor blade, and a rear edge (74) facing the trailing edge of the wind turbine rotor blade, Wherein the equipotential bonding component (58) extends between the outer edge of one fiber laminate stack and the inner edge of an adjacent fiber laminate stack, and the outer edge and the inner edge overlap to define an overlapping area (75) extending across the spar cap.

2. The wind turbine rotor blade according to claim 1, wherein, The equipotential bonding component (58) has a first end (58a) attached to and in electrical contact with the lightning arrester (32), and a second end (58b) attached to and in electrical contact with the spar cap (46).

3. The wind turbine rotor blade according to claim 1, wherein, The spar cap (46) has an outer side (46a) and an inner side (46b) closest to the interior of the wind turbine rotor blade, and wherein the equipotential bonding component (58) is attached to and in electrical contact with the outer side of the spar cap.

4. The wind turbine rotor blade according to claim 1, wherein, The equipotential bonding component (58) is a strip or a band.

5. The wind turbine rotor blade according to claim 4, wherein, The equipotential bonding component (58) comprises a conductive wire or a conductive yarn woven into a fabric.

6. The wind turbine rotor blade according to claim 1, wherein, The equipotential bonding component (58) is attached to the lightning arrester (32) and the spar cap (46), and the equipotential bonding component defines a path between the attachment point (59) to the lightning arrester and the spar cap, the path extending from the lightning arrester to the spar cap in a direction only away from and not back towards the attachment point.

7. The wind turbine rotor blade according to claim 1, wherein, The spar cap (46) comprises a stack of a plurality of conductive material layers (80).

8. The wind turbine rotor blade according to claim 7, wherein, The conductive material is a carbon fiber material.

9. The wind turbine rotor blade according to claim 7, wherein, The conductive material is a pultruded carbon fiber composite material.

10. The wind turbine rotor blade according to claim 1, wherein, The spar cap (46) has an abraded portion for exposing the conductive material, at which the equipotential bonding component (58) is attached to and in electrical contact with the spar cap.

11. A wind turbine rotor blade according to any one of claims 7 to 9, wherein, At least one of the conductive material layers (80) of the spar cap is chamfered at at least one end (82, 84) of the at least one layer such that the thickness of the conductive material layer tapers towards the at least one end.

12. The wind turbine rotor blade according to claim 11, wherein, The conductive material layer of the spar cap (46) closest to the lightning arrester (32) has chamfered ends (82, 84) and an abraded portion on the same side of the conductive material layer facing the lightning arrester.

13. The wind turbine rotor blade according to claim 1, wherein, The fiber laminate of the wind turbine blade housing comprises a glass fiber material.

14. The wind turbine rotor blade according to claim 1, wherein, The front edge (72) of the fiber laminate (70) of the wind turbine blade housing is at or adjacent to the leading edge (26) of the wind turbine rotor blade, and the rear edge (74) of the fiber laminate is at or adjacent to the trailing edge (28) of the wind turbine rotor blade.

15. The wind turbine rotor blade according to claim 1, wherein, Each fiber laminate (70) of the wind turbine blade housing is provided as a preform.

16. The wind turbine rotor blade according to claim 1, wherein, The overlapping edges of adjacent fiber laminates (70) are formed by continuously terminating the individual layers in the fiber laminate to form a step or a ramp.

17. The wind turbine rotor blade according to claim 1, wherein, The lightning arrester (32) is a metal foil of a lightning protection system.

18. The wind turbine rotor blade according to claim 1, wherein, The lightning arrester (32) is at the outer surface of the wind turbine rotor blade.

19. The wind turbine rotor blade according to claim 1, wherein the wind turbine rotor blade further comprises a plurality of said equipotential bonding components (58).

20. The wind turbine rotor blade according to claim 19, wherein, A plurality of said equipotential bonding components (58) extend between the outer edge (72) of one fiber laminate and the inner edge (71) of the adjacent fiber laminate.

21. The wind turbine rotor blade according to claim 19 or 20, wherein, Pairs of adjacent fiber laminates (70) spaced apart along the wind turbine rotor blade in the spanwise direction have at least one said equipotential bonding component (58) extending between the outer edge (72) of one fiber laminate of the pair of adjacent fiber laminates and the inner edge (71) of the adjacent fiber laminate.

22. The wind turbine rotor blade according to claim 1, wherein, The lightning arrester (32) and the equipotential bonding component (58) are integrally formed.

23. A method of manufacturing a wind turbine rotor blade (20) having a root end (22) and a tip end (24), the method comprising the steps of: Laying a housing (40) of the wind turbine blade, the housing defining an inlet side, a pressure side, a leading edge (26) and a trailing edge (28) of the wind turbine rotor blade, the housing comprising a plurality of fiber laminates (70) and a lightning arrester (32), each fiber laminate having an inner edge (71) facing the root end of the wind turbine rotor blade, an outer edge (72) facing the tip end of the wind turbine rotor blade, a front edge (73) facing the leading edge of the wind turbine rotor blade and a rear edge (74) facing the trailing edge of the wind turbine rotor blade; Lay the spar cap (46) such that the lightning arrester extends above the spar cap, wherein the spar cap comprises a conductive material; and Provide an equipotential bonding member (58) to electrically bond the lightning arrester to the spar cap, the equipotential bonding member extending between an outer edge of one fiber laminate stack and an inner edge of an adjacent fiber laminate stack, the outer edge and the inner edge overlapping to define an overlap region (75) extending across the spar cap.

24. The method according to claim 23, wherein, Each fiber laminate stack of the housing is laid in a mold as a preform, and the method further comprises the steps of: infusing the preform with resin and curing it.

25. The method according to claim 23 or claim 24, wherein The equipotential bonding member is attached to one of the fiber laminate stacks of the housing of the outer shell before being laid.

26. The method according to claim 23 or claim 24, wherein The lightning arrester and the equipotential bonding member are integrally formed, and the lightning arrester and the equipotential bonding member are attached to one of the fiber laminate stacks of the housing of the outer shell before being laid.

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