Method of manufacturing a wind turbine blade comprising flexible glass films and related wind turbine blade

Abstract

The present disclosure relates to a method for manufacturing a wind turbine blade (22), The wind turbine blade (22) has a length in a longitudinal direction from a root end (217) to a tip end (215) and comprises a wind turbine blade shell (222), the wind turbine blade shell (222) having an aerodynamic profile with a pressure side (224) and a suction side (226). One or more flexible glass films (51, 61) are arranged in the wind turbine blade (22). The present disclosure also relates to a wind turbine blade (22) comprising one or more flexible glass films (51, 61).

Description

METHOD OF MANUFACTURING A WIND TURBINE BLADE COMPRISING FLEXIBLEGLASS FILMS AND RELATED WIND TURBINE BLADEFIELD

[0001] The present disclosure relates to wind turbine blades and, more particularly, to wind turbine blades comprising one or more flexible glass films. The present disclosure further relates to methods for manufacturing wind turbine blades comprising flexible glass films.BACKGROUND

[0002] Modern wind turbines are commonly used to supply electricity into the electrical grid. Wind turbines of this kind generally comprise a tower and a rotor arranged on the tower. The rotor, which typically comprises a hub and a plurality of blades, is set into rotation under the influence of the wind on the blades. Said rotation generates a torque that is normally transmitted through a rotor shaft to a generator, either directly (“directly driven”) or through the use of a gearbox. This way, the generator produces electricity which can be supplied to the electrical grid.

[0003] The wind turbine hub may be rotatably coupled to a front of the nacelle. The wind turbine hub may be connected to a rotor shaft, and the rotor shaft may then be rotatably mounted in the nacelle using one or more rotor shaft bearings arranged in a frame inside the nacelle. The nacelle is a housing arranged on top of a wind turbine tower that may contain and protect the gearbox (if present) and the generator (if not placed outside the nacelle) and, depending on the wind turbine, further components such as a power converter, and auxiliary systems.

[0004] Wind turbine blades extract kinetic energy from the wind and transform it into rotational kinetic energy. In order to extract more energy from the wind, the length of the blades has steadily increased in modern wind turbines. As a result, higher physical loads are introduced into the blade and related components. Thus, long blades need to remain structurally efficient to withstand all loads while remaining as light as possible to facilitate logistics and installation. Specifically, both extreme and fatigue loads need to be withstood while minimizing weight and cost of the blades.

[0005] Wind turbine blades generally comprise a shell body having an aerodynamic profile with a pressure side and a suction side. The geometry of the aerodynamic profile is optimized to maximize annual energy yield of the wind turbine for a specific wind speed distribution.

[0006] Different materials have been used for the manufacture of wind turbine blades. Said materials need to combine the necessary structural properties, e.g. high strength to weight ratio, with relatively low cost. Furthermore, materials used for the shell body need to have the ability to be formed into the airfoil shape required for an adequate aerodynamic performance. Fiber reinforced polymers, e.g. glass-fiber or carbon-fiber reinforced materials, have been typically used. Thus, blades shells are usually manufactured by arranging glass and / or carbon fiber plies in a mold. Resin is typically infused and subsequently cured to form laminates, which constitute the wind turbine blade shell. Alternatively, or in combination with the mentioned resin infusion process, pre-impregnated fibers, i.e. pre-preg composite materials, may also be employed for the manufacture of wind turbine blades.

[0007] The wind turbine blade shell is typically relatively lightweight and has structural properties that are insufficient to withstand all the bending moments and others loads acting on the wind turbine blade during operation. To improve the structural properties of the blade, e.g. stiffness and strength, the blade is generally reinforced with structural components, e.g. one or more spar caps at the suction and pressure side of the blade shell with a shear web connecting them. Spar caps are also typically manufactured with fiber reinforced materials. In particular, because of its structural properties, carbon fiber material is commonly employed for the spar caps. Furthermore, in some cases, spar caps are manufactured using pultruded planks.

[0008] The fibers arranged in the fiber reinforced composites making up the laminated blade shell and the structural reinforcement components are typically aligned according to a predefined direction. In some cases, all the fibers may be arranged in the same direction, i.e. unidirectional arrangement, whereas, in some other cases, the fibers may run in two perpendicular directions, i.e. bi-directional arrangement. In some further examples, triaxial arrangements may also be employed. The directionality of the fibers may pose some limitations on the structural properties of the wind turbine blade. In particular, certain directions may be defined to withstand some loads but this may result in a reduced strength in other directions.

[0009] Durability of wind turbine blades over the lifetime of the wind turbine is another critical aspect to consider while designing and manufacturing wind turbine blades. It is known that wind turbine blades, and particularly the leading edge area of the blades, may erode due to impact of e.g. rain droplets, hail or particles. In particular, the tip region of the blade may be especially susceptible to erosion effects due to its high linear speed. Furthermore, due to the alreadymentioned increasing length of the blades in modern wind turbines, the tip speed of the wind turbine blades also increases, which results in an aggravation of the erosion effects and to an increase in the rate of degradation of the wind turbine blade. Specifically, offshore wind turbine, which are typically subjected to less noise-related restrictions, may typically favor the use of even higher tip speeds, thus increasing the relevance of erosion effects.

[0010] Eroded blades exhibit an irregular surface, which can have a significant impact on the long term structural stability of the wind turbine blades and on the air flow around the blades, i.e. on the aerodynamic behavior of the wind turbine blade. Thus, roughened blades produce less lift and more drag for a given wind flow, which reduces the power produced by the wind turbine. Accordingly, blades with eroded leading edges may cause non-negligible reductions of annual energy production (AEP). These reductions may be exacerbated by the fact that the major contribution to rotor blade aerodynamic effectiveness comes from the blade tip region and part of midspan of the blade, which are the most sensitive regions to erosion due to the prevailing high speeds.

[0011] In order to withstand high tip speed velocities and to protect the leading edge from erosion, known solutions include the use of so-called leading edge protection (LEP) systems to coat and / or cover the leading edge of the wind turbine blade. Known ways to implement such LEP systems include the use of tapes or protective polymer based coatings, e.g. paints, which are applied on the region of leading edge of the wind turbine blade. In other cases, protective prefabricated shields are applied to the leading edge. In the latter case, polymer-based prefabricated shields have been commercially used to prevent erosion and metallic-based shields have been investigated.

[0012] Nevertheless, commonly proposed LEP systems exhibit certain drawbacks. In particular, tapes, polymer-based coatings and / or polymer / based shields exhibit only limited erosion resistance when subjected to the high kinetic energy of air particles or rain droplets, especially when considering the high blade tip speeds experienced by very long blades, such as those used in offshore wind turbines. Thus, wear and tear of polymer-based coatings or shields is observed. Furthermore, existing solutions to attach and bond said polymer-based solutions are not sufficiently durable either, which can result in separation of the LEP system from the leading edge. As a result, these solutions are not capable of providing efficient protection against erosion for the entire lifetime of the blade, e.g. for at least 20 years, which results in frequent inspection, repair and / or replacement operations. These maintenance operations are time consuming, difficult and, consequently, costly. This is especially the case for offshore wind turbines. Furthermore, a direct loss of energy production arises from the downtime associated to those repairment operations, which also impacts the annual energy production (AEP) of the wind turbine.

[0013] As far as metallic-based LEP systems are concerned, these also exhibit certain drawbacks. In particular, problems arise regarding lighting protection, i.e. protection of the wind turbine blade against lighting strikes. Thus, the structural integrity of the blade may become jeopardized by the use of metallic elements in the LEP system. Furthermore, as already described, wind turbine blades generally comprise a shell formed of composite materials, e.g. glass fiber composites. Achieving a sufficiently strong bond between a metallic LEP system and a composite material may be particularly difficult. The integrity of the metal to composite interface may degrade rapidly, causing the metallic LEP to separate from the outer surface of the wind turbine blade. Besides, metallic-based LEP systems may also suffer from corrosion problems, especially when applied in offshore environments, and they may add significant weight to the wind turbine blade.

[0014] The present disclosure provides examples of methods for manufacturing wind turbine blades that at least partially overcome some of the drawbacks of existing wind turbine blades. Corresponding wind turbine blades are also provided by this disclosure.SUMMARY

[0015] In a first aspect, a method for manufacturing a wind turbine blade is provided. The wind turbine blade has a length in a longitudinal direction from a root end to a tip end and it comprises a wind turbine blade shell, the wind turbine blade shell having an aerodynamic profile with a pressure side and a suction side. One or more flexible glass films are arranged in the wind turbine blade.

[0016] According to this first aspect, a wind turbine blade incorporating flexible glass films is provided. Flexible glass films exhibit properties that are suitable for improving the performance of wind turbine blades. Specifically, flexible glass films exhibit electrical and mechanical properties that, as will be shown in more detail below, are adequate to enhance the structural and durability properties of wind turbine blades. In some examples, flexible glass may be based on borosilicate glass.

[0017] In an example, the wind turbine blade shell may define a leading edge and the method may comprise arranging a protective element covering at least a portion of the leading edge.The protective element may comprise at least one of the flexible glass film and it may extend along at least a portion of the length of the wind turbine blade.

[0018] According to this example, the mechanical flexibility and the hardness of glass films is used to protect the region of the leading edge of the wind turbine blade, thus providing a highly erosion resistant leading edge protection system. As mentioned above, erosion of the leading edge is an increasing concern for wind turbine blade manufacturers. This is especially the case as wind turbine blades become longer, which results in higher tip speeds that increase damage at the leading edge by, e.g. water droplets. Even if several leading edge protection (LEP) systems have been used in the past, these have exhibited certain limitations due to either their limited resistance to wear, their electrical behavior and / or the need for frequent maintenance. In particular, maintenance of leading edge protection systems can be especially cumbersome in some applications, such as offshore wind turbines.

[0019] By using flexible glass films, a LEP system can be provided that requires less maintenance and that provides extended life while enabling operation of the wind turbine at higher tip speeds, thus increasing power density. Indeed, by operating at higher tip speeds, higher rotational speeds may be enabled for the electrical generator rotor, thus increasing the generator power. Flexible glass films exhibit very high hardness values and they are highly resistant to erosion and wear as they can absorb kinetic energy from, e.g. rain drops, thus increasing the durability of the protection system.

[0020] Erosion protection provided by such glass films may be comparable to the one provided by certain LEP systems comprising metallic materials. Nevertheless, unlike metallic shields, a further advantage of glass films stems from its electrically insulating character. Indeed, the use of glass films may not interfere with the existing lighting protection system (LPS), thus avoiding unwanted effects during lighting strikes. Furthermore, flexible glass films are relatively lightweight, especially when compared with metallic-based LEP systems, so the overall weight of the blade may not increase significantly.

[0021] The flexibility of the glass films allows very small bending radius which permits adaptation of the glass film to the curved shape of the blade shell in the leading edge along the length of the blade. In other words, flexible glass films can bend to the radius of the blade leading edge. This flexibility provides different options for application of the glass films as will be detailed below in reference to different examples of the disclosure.

[0022] In another aspect of the disclosure, the wind turbine blade shell may comprise a plurality of fiber plies and at least one of the flexible glass films may be arranged together with the fiber plies.

[0023] According to this example, a further property of flexible glass films may be advantageously used to further improve the properties of wind turbine blades. In this case, the structural and mechanical properties of the glass film may be used to optimize the structural behavior of the blade so that it can withstand operating loads and provide desired mechanical characteristics for a given acceptable weight while maintaining manufacturability. Methods involving the use of fibers, e.g. glass fibers or carbon fibers, to obtain fiber reinforced polymers are very well-known. In said methods, fiber plies may be typically deposited in a mold and they may be infused with resin, which, upon curing, may result in a blade shell or a blade shell part. Different variants exist for such manufacturing methods which are well-known by those skilled in the art so no further details are deemed necessary.

[0024] Similarly, the spar cap or main laminate of the wind turbine blade may also be manufactured in a similar fashion. In such case, carbon fibers may be preferably used due to their mechanical properties. Alternatively, spar caps may also be manufactured using fiber pultruded with resin materials as known by those skilled in the art.

[0025] In any case, the arrangement of the fibers for the manufacture of blade shells and / or spar caps (or any other laminate in the wind turbine blade) is, at least partially, defined by the orientation of the fibers. Indeed, fibers may be arranged in a single direction, e.g. along the longitudinal axis of the wind turbine, in so-called unidirectional arrangements, or in bidirectional arrangements, in which fibers arranged at perpendicular orientations may be provided. Furthermore, arrangements including more directions, e.g. tri-axial arrangements, are also known. Nevertheless, in all those cases, the behavior and structural properties of the resulting laminates is, at least in part, dictated by the orientation of the fibers.

[0026] This is not the case with flexible glass films. Thus, flexible glass films exhibit isotropic mechanical and structural properties, i.e. they do not have a preferred orientation. Consequently, the combination of flexible glass films with fiber plies may allow an improved handling of the operational loads suffered by the wind turbine blade. To this end, the method according to this example comprises arranging some of such flexible glass films in an integrated manner with the currently existing laminates or panels.

[0027] The laminates may correspond to the blade shell of the wind turbine blade and / or to the spar-cap. Furthermore, the number and location of the flexible glass films may be optimized to account for the magnitude and orientation of the loads in different locations of the wind turbine blade. Indeed, a non-uniform distribution of flexible glass films may be provided, e.g. a larger number of glass films may be disposed in certain regions of the wind turbine blade.

[0028] In still another aspect of the disclosure, a wind turbine blade is provided. The wind turbine blade has a length in a longitudinal direction from a root end to a tip end and it comprises a wind turbine blade shell, the wind turbine blade shell having an aerodynamic profile with a pressure side and a suction side. The wind turbine blade comprises one or more flexible glass films.

[0029] According to this aspect, a wind turbine blade with improved structural and mechanical performance is obtained. Some of the advantages associated with the use of such glass films have been already described in reference to the method of manufacturing such a blade so they will not be repeated again.

[0030] In an exemplary wind turbine blade, a wind turbine blade shell may define a leading edge and the wind turbine blade may further comprise a protective element comprising a flexible glass film. The protective element may be configured for covering at least a portion of the leading edge and for extending along at least a portion of the length of the wind turbine blade, specifically for extending for at least a third of the length of the wind turbine blade.

[0031] According to this aspect, a blade with improved resistance against leading edge erosion may be provided. Reduced maintenance and / or operation at higher rotational speeds may be achieved, thus improving the overall behavior of the resulting wind turbine. Aspects of the example have been already addressed while discussing the associated method so we refer to previous paragraphs. Furthermore, details and advantages of the wind turbine blades according to this aspect will be detailed below in reference to specific examples.

[0032] In still a further example, a further wind turbine blade is provided. In this case, the wind turbine blade comprises a blade shell with fiber layers or plies . Flexible glass films are arranged under and / or above the fiber plies. In particular, the flexible glass films may be arranged to form the outermost layer of the shell.

[0033] As explained with reference to the associated method, a wind turbine blade with flexible glass films integrated in the laminate structures may exhibit increased structural performance.

[0034] It is worth noting that flexible glass films may be manufactured as either monolayer or multilayer films. In the latter case, the flexible glass film, may comprise a plurality of layers bonded together by means of, e.g. an adhesive. The provision of multilayers may be preferred for the manufacturing process of the glass film itself and / or for providing specific characteristics to the glass film such as certain bending radius or resistance to UV radiation. Nevertheless, throughout this disclosure, both flexible glass films comprising a single layer and flexible glass films comprising multiple layers will be simply referred to as flexible glass films. In some examples, a plurality of said glass films, each of them comprising a monolayer or a multilayer internal arrangement, may be employed.BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Non-limiting examples of the present disclosure will be described in the following, with reference to the appended drawings, in which:Figure 1 illustrates a perspective view of a wind turbine according to one example;Figure 2 illustrates a detailed, internal view of a nacelle of a wind turbine according to one example;Figure 3 schematically illustrates a wind turbine blade assembly according to one example;Figure 4 schematically illustrates an internal structure of an example of a wind turbine blade;Figure 5 schematically illustrates an example of a protective element comprising a flat flexible glass film;Figure 6 schematically illustrates an example of a protective element comprising a pre-formed flexible glass film;Figure 7 schematically illustrates a cross-sectional view of an example of a wind turbine blade comprising a protective element;Figure 8A - 8C schematically illustrate an example of a method for manufacturing an exampleof a relatively stiff protective element and a cross-sectional view of a wind turbine comprising such protective element;Figure 9 schematically illustrates a leading edge region of a wind turbine blade comprising a sealant at the interface between a protective element and a blade shell surface according to an example;Figure 10 schematically illustrates an example of a protective element comprising tapered ends;Figure 11 schematically illustrates a step in a method for manufacturing a wind turbine blade shell comprising one or more flexible glass films according to an example.DETAILED DESCRIPTION OF EXAMPLES

[0036] Reference now will be made in detail to embodiments of the present disclosure, one or more examples of which are illustrated in the drawings. Each example is provided by way of explanation only, not as a limitation. In fact, it will be apparent to those skilled in the art that various modifications and variations can be made in the present disclosure. For instance, features illustrated or described as part of one embodiment can be used with another embodiment to yield a still further embodiment. Thus, it is intended that the present disclosure covers such modifications and variations as come within the scope of the appended claims and their equivalents.

[0037] Figure 1 is a perspective view of an example of a wind turbine 10. In the example, the wind turbine 10 is a horizontal-axis wind turbine. Alternatively, the wind turbine 10 may be a vertical-axis wind turbine. In the example, the wind turbine 10 includes a tower 15 that extends from a support system 14 on a ground 12, a nacelle 16 mounted on tower 15, and a rotor 18 that is coupled to nacelle 16. The rotor 18 includes a rotatable hub 20 and at least one rotor blade 22 coupled to and extending outward from the hub 20. In the example, the rotor 18 has three rotor blades 22. In an alternative embodiment, the rotor 18 includes more or less than three rotor blades 22. The tower 15 may be fabricated from tubular steel to define a cavity (not shown in figure 1) between a support system 14 and the nacelle 16. In an alternative embodiment, the tower 15 is any suitable type of a tower having any suitable height. According to an alternative, the tower can be a hybrid tower comprising a portion made of concrete and a tubular steel portion. Also, the tower can be a partial or full lattice tower.

[0038] The rotor blades 22 are spaced about the hub 20 to facilitate rotating the rotor 18 to enable kinetic energy to be transferred from the wind into usable mechanical energy, and subsequently, electrical energy. The rotor blades 22 are mated to the hub 20 by coupling a blade root portion 24 to the hub 20 at a plurality of load transfer regions 26. The load transfer regions 26 may have a hub load transfer region and a blade load transfer region (both not shown in figure 1). Loads induced to the rotor blades 22 are transferred to the hub 20 via the load transfer regions 26.

[0039] In examples, the rotor blades 22 may have a length ranging from about 15 meters (m) to about 90 m or more. Rotor blades 22 may have any suitable length that enables the wind turbine 10 to function as described herein. For example, non-limiting examples of blade lengths include 20 m or less, 37 m, 48.7 m, 50.2m, 52.2 m or a length that is greater than 91 m, or even greater than 100 m. As wind strikes the rotor blades 22 from a wind direction 28, the rotor 18 is rotated about a rotor axis 30. As the rotor blades 22 are rotated and subjected to centrifugal forces, the rotor blades 22 are also subjected to various forces and moments. As such, the rotor blades 22 may deflect and / or rotate from a neutral, or non-deflected, position to a deflected position.

[0040] Moreover, a pitch angle of the rotor blades 22, i.e., an angle that determines an orientation of the rotor blades 22 with respect to the wind direction, may be changed by a pitch system 32 to control the load and power generated by the wind turbine 10 by adjusting an angular position of at least one rotor blade 22 relative to wind vectors. Pitch axes 34 of rotor blades 22 are shown. During operation of the wind turbine 10, the pitch system 32 may particularly change a pitch angle of the rotor blades 22 such that the angle of attack of (portions of) the rotor blades are reduced, which facilitates reducing a rotational speed and / or facilitates a stall of the rotor 18.

[0041] In the example, a blade pitch of each rotor blade 22 is controlled individually by a wind turbine controller 36 or by a pitch control system 80. Alternatively, the blade pitch for all rotor blades 22 may be controlled simultaneously by said control systems.

[0042] Further, in the example, as the wind direction 28 changes, a yaw direction of the nacelle 16 may be rotated about a yaw axis 38 to position the rotor blades 22 with respect to wind direction 28.

[0043] In the example, the wind turbine controller 36 is shown as being centralized within the nacelle 16, however, the wind turbine controller 36 may be a distributed system throughoutthe wind turbine 10, on the support system 14, within a wind farm, and / or at a remote-control center. The wind turbine controller 36 includes a processor 40 configured to perform the methods and / or steps described herein. Further, many of the other components described herein include a processor.

[0044] As used herein, the term “processor” is not limited to integrated circuits referred to in the art as a computer, but broadly refers to a controller, a microcontroller, a microcomputer, a programmable logic controller (PLC), an application specific, integrated circuit, and other programmable circuits, and these terms are used interchangeably herein. It should be understood that a processor and / or a control system can also include memory, input channels, and / or output channels.

[0045] Figure 2 is an enlarged sectional view of a portion of the wind turbine 10. In the example, the wind turbine 10 includes the nacelle 16 and the rotor 18 that is rotatably coupled to the nacelle 16. More specifically, the hub 20 of the rotor 18 is rotatably coupled to an electric generator 42 positioned within the nacelle 16 by the main shaft 44, a gearbox 46, a high-speed shaft 48, and a coupling 50. In the example, the main shaft 44 is disposed at least partially coaxial to a longitudinal axis (not shown) of the nacelle 16. A rotation of the main shaft 44 drives the gearbox 46 that subsequently drives the high-speed shaft 48 by translating the relatively slow rotational movement of the rotor 18 and of the main shaft 44 into a relatively fast rotational movement of the high-speed shaft 48. The latter is connected to the generator 42 for generating electrical energy with the help of a coupling 50. Furthermore, a transformer 90 and / or suitable electronics, switches, and / or inverters may be arranged in the nacelle 16 in order to transform electrical energy generated by the generator 42 having a voltage of e.g. 400V to 1000 V into electrical energy having medium voltage (e.g. 10 - 35 KV). Offshore wind turbines may have for example generator voltages between 650 V and 3500 V, and transformer voltages may for instance be between 30 kV and 70 kV. Said electrical energy is conducted via power cables from the nacelle 16 into the tower 15.

[0046] The gearbox 46, generator 42 and transformer 90 may be supported by a main support structure frame of the nacelle 16, optionally embodied as a main frame 52. The gearbox 46 may include a gearbox housing that is connected to the main frame 52 by one or more torque arms 103. In the example, the nacelle 16 also includes a main forward support bearing 60 and a main aft support bearing 62. Furthermore, the generator 42 can be mounted to the main frame 52 by decoupling support means 54, in particular in order to prevent vibrations of the generator 42 to be introduced into the main frame 52 and thereby causing a noise emission source.

[0047] Optionally, the main frame 52 is configured to carry the entire load caused by the weight of the rotor 18 and components of the nacelle 16 and by the wind and rotational loads, and furthermore, to introduce these loads into the tower 15 of the wind turbine 10. The rotor shaft 44, generator 42, gearbox 46, high-speed shaft 48, coupling 50, and any associated fastening, support, and / or securing device including, but not limited to, main frame 52, and forward support bearing 60 and aft support bearing 62, are sometimes referred to as a drive train 64.

[0048] In some examples, the wind turbine may be a direct drive wind turbine without gearbox 46. Generator 42 operate at the same rotational speed as the rotor 18 in direct drive wind turbines. They therefore generally have a much larger diameter than generators used in wind turbines having a gearbox 46 for providing a similar amount of power than a wind turbine with a gearbox.

[0049] The nacelle 16 also may include a yaw drive mechanism 56 that may be used to rotate the nacelle 16 and thereby also the rotor 18 about the yaw axis 38 to control the perspective of the rotor blades 22 with respect to the wind direction 28.

[0050] For positioning the nacelle 16 appropriately with respect to the wind direction 28, the nacelle 16 may also include at least one meteorological measurement system 58 which may include a wind vane and anemometer. The meteorological measurement system 58 can provide information to the wind turbine controller 36 that may include wind direction 28 and / or wind speed. In the example, the pitch system 32 is at least partially arranged as a pitch assembly 66 in the hub 20. The pitch assembly 66 includes one or more pitch drive systems 68 and at least one sensor 70. Each pitch drive system 68 is coupled to a respective rotor blade 22 (shown in figure 1) for modulating the pitch angle of a rotor blade 22 along the pitch axis 34. Only one of three pitch drive systems 68 is shown in figure 2.

[0051] In the example, the pitch assembly 66 includes at least one pitch bearing 72 coupled to hub 20 and to a respective rotor blade 22 (shown in figure 1) for rotating the respective rotor blade 22 about the pitch axis 34. The pitch drive system 68 includes a pitch drive motor 74, a pitch drive gearbox 76, and a pitch drive pinion 78. The pitch drive motor 74 is coupled to the pitch drive gearbox 76 such that the pitch drive motor 74 imparts mechanical force to the pitch drive gearbox 76. The pitch drive gearbox 76 is coupled to the pitch drive pinion 78 such that the pitch drive pinion 78 is rotated by the pitch drive gearbox 76. The pitch bearing 72 is coupledto pitch drive pinion 78 such that the rotation of the pitch drive pinion 78 causes a rotation of the pitch bearing 72.

[0052] Pitch drive system 68 is coupled to the wind turbine controller 36 for adjusting the pitch angle of a rotor blade 22 upon receipt of one or more signals from the wind turbine controller 36. In the example, the pitch drive motor 74 is any suitable motor driven by electrical power and / or a hydraulic system that enables pitch assembly 66 to function as described herein. Alternatively, the pitch assembly 66 may include any suitable structure, configuration, arrangement, and / or components such as, but not limited to, hydraulic cylinders, springs, and / or servomechanisms. In certain embodiments, the pitch drive motor 74 is driven by energy extracted from a rotational inertia of hub 20 and / or a stored energy source (not shown) that supplies energy to components of the wind turbine 10.

[0053] The pitch assembly 66 may also include one or more pitch control systems 80 for controlling the pitch drive system 68 according to control signals from the wind turbine controller 36, in case of specific prioritized situations and / or during rotor 18 overspeed. In the example, the pitch assembly 66 includes at least one pitch control system 80 communicatively coupled to a respective pitch drive system 68 for controlling pitch drive system 68 independently from the wind turbine controller 36. In the example, the pitch control system 80 is coupled to the pitch drive system 68 and to a sensor 70. During normal operation of the wind turbine 10, the wind turbine controller 36 may control the pitch drive system 68 to adjust a pitch angle of rotor blades 22.

[0054] According to an embodiment, a power generator 84, for example comprising a battery and electric capacitors, is arranged at or within the hub 20 and is coupled to the sensor 70, the pitch control system 80, and to the pitch drive system 68 to provide a source of power to these components. In the example, the power generator 84 provides a continuing source of power to the pitch assembly 66 during operation of the wind turbine 10. In an alternative embodiment, power generator 84 provides power to the pitch assembly 66 only during an electrical power loss event of the wind turbine 10. The electrical power loss event may include power grid loss or dip, malfunctioning of an electrical system of the wind turbine 10, and / or failure of the wind turbine controller 36. During the electrical power loss event, the power generator 84 operates to provide electrical power to the pitch assembly 66 such that pitch assembly 66 can operate during the electrical power loss event.

[0055] In the example, the pitch drive system 68, the sensor 70, the pitch control system 80, cables, and the power generator 84 are each positioned in a cavity 86 defined by an inner surface 88 of hub 20. In an alternative embodiment, said components are positioned with respect to an outer surface of hub 20 and may be coupled, directly or indirectly, to the outer surface.

[0056] Figure 3 schematically illustrates a wind turbine blade 22 according to an example. The wind turbine blade 22 extends in a longitudinal direction between a root end 217 and a tip end 215. The wind turbine blade 22 comprises a shell 222 having an outer surface defining a pressure surface and a suction surface, a leading edge 218 and a trailing edge 220 and a loadbearing structure extending in the longitudinal direction.

[0057] Additionally, Figure 3 shows that the wind turbine blade 22 in this example may comprise a plurality of protective elements 41 covering at least a portion of the leading edge 218 of the wind turbine blade 22. More specifically, in this example, three protective elements 41 are shown which extend in a spanwise direction between a first lateral edge 411 and a second lateral edge 412. The protective elements 41 also define a first longitudinally extending edge 421 and a second longitudinally extending edge 422 (not visible in Figure 3; refer to Figure 7). The protective elements 41 may extend along at least a portion of the leading edge 218, such as along 20-50% of the spanwise extend of the leading edge 218 of the blade 22. Furthermore, as shown in Figure 3, the protective elements 41 may be arranged in an outermost part of the wind turbine blade 22, i.e. in a region of the wind turbine blade 22 that, in the longitudinal direction, is closer to the tip end 215 of the wind turbine blade 22. In some cases, the protective elements 41 may extend to the blade very tip end 215 whereas, in some other cases, the second lateral edge 412 of the protective elements 41 may lie e.g. some millimeters or centimeters away from the tip end 215.

[0058] Moreover, a leading edge laminate 228 is also schematically represented in Figure 3 (see also Figure 4). Such leading edge laminate 228 may also be present in a wind turbine blade 22 and it may comprise a fiber reinforced laminate comprising a plurality of fiber plies. The leading edge laminate 228 may extend along the length of the leading edge 218 to structurally reinforce the region. In some examples, the leading edge laminate 228 may extend along substantially the whole length of the blade 22. Although the leading edge laminate 228 may be arranged covering at least a portion of the leading edge 218, this element should not be confused with a LEP (Leading Edge Protection) system. Thus, the purpose of the leading edgelaminate 228 may be to structurally reinforce the blade 22 and not necessarily to prevent erosion of the blade shell 222 in the area of the leading edge 218.

[0059] Figure 4 is a schematic diagram illustrating a cross sectional view of an example of a wind turbine blade 22, e.g. a cross-sectional view of the airfoil region of the wind turbine blade 22. The wind turbine blade 22 comprises a leading edge 218, a trailing edge 220, a pressure side shell part 224, a suction side shell part 226, a first spar cap 274, and a second spar cap 276. The wind turbine blade 22 comprises a chord line 238 between the leading edge 218 and the trailing edge 220. The wind turbine blade 22 comprises one or more shear webs 242, such as a leading edge shear web and a trailing edge shear web. The shear webs 242 could alternatively be a spar box with spar sides, such as a trailing edge spar side and a leading edge spar side. The spar caps 274, 276, extending in a substantially spanwise direction within the blade 22, may comprise glass fibers, carbon fibers or a hybrid arrangement combining different fibers. The rest of the shell parts 224, 226 may comprise glass fibers. The spar caps 274, 276 may be part of, i.e. may be integrally formed, or they may be adhered to the respective blade shell parts. Furthermore, each shell part 224, 226 may comprise one or more additional spar caps. In some examples, the pressure shell part 224 and the suction shell part 226 may be manufactured separately in individual molds and subsequently bonded, e.g. glued. In other examples, the pressure shell part 224 and the suction shell part 226 may be manufactured together in a single mold. Furthermore, in the example shown in Figure 4, the blade 22 may further comprise a leading edge laminate 228 to structurally reinforce the leading edge 218 area of the blade 22.

[0060] Figure 5 provides an example of a protective element 41 for a leading edge 218 of a wind turbine blade 22. In this example, the protective element 41 may comprise a substantially planar or flat flexible glass film 51 . Flexible glass films are thin films, with thicknesses as low as 50 .m, which allow them to be flexible while retaining glass properties. A method for arranging the protective element 41 may comprise attaching the flat flexible glass film 51 to an outer surface of the wind turbine blade shell 222 covering at least a portion of the leading edge 218 so that the flexible glass film 51 conforms to the shape of the wind turbine blade shell 222 at the leading edge 218. In other words, the flat flexible glass film 51 may be initially provided in a substantially planar or flat manner but, due to its flexibility, it may adapt to the shape of the wind turbine blade shall 222 for attachment to the outer surface of the wind turbine blade shell 222 in the area of the leading edge 218.

[0061] More specifically, the initially flat flexible glass film 51 may conform to the U-shaped curvature defined by the pressure side 224 and the suction side 226 of the blade shell 222 in the leading edge 218. Thus, the use of such a flat flexible glass film 51 may result in an effective protection of the leading edge 218 against erosion due to the hardness properties of the flat flexible glass film 51. Furthermore, the flat flexible glass film 51 may have a thickness in the range of 50 .m or higher, which may enable reduced bending radius, thus facilitating conforming to the shape of the leading edge 218 region.

[0062] In a variant of this example, a plurality of flat flexible glass films 51 may be provided instead of a single flat flexible glass film 51. In such case, the flat flexible glass films 51 may be pre-bonded, e.g. they may be adhered to each other. Subsequently, the provided pre-bonded flat flexible glass films 51 may be attached to the wind turbine blade shell 222 as a single unit in a single manufacturing step.

[0063] In an alternative variant, a first flat flexible glass film 51 may be attached to the outer surface of the wind turbine blade shell 222, and a subsequent flat flexible glass film 51 may be bonded to the already attached first flat flexible glass film 51 . The process may then be repeated for additional flat flexible glass films 51 in subsequent manufacturing steps.

[0064] In an example, the flat flexible glass film 51 may be provided in multiple pieces. The length of the provided pieces may range from 200 mm up to 3 or more meters. Specifically, the provided pieces may have a length of about 1 m. Thus, in different variants, either a single piece flat flexible glass film 51 may be arranged to protect at least a portion of the leading edge 218 or multiple pieces may be individually arranged in the longitudinal direction of the wind turbine blade 22 to cover at least a portion of the leading edge 218.

[0065] In another example of the disclosure, arranging a protective element 41 may comprise attaching a pre-formed component to an outer surface of the wind turbine blade shell 222 covering at least a portion of the leading edge 218, the pre-formed component comprising one or more of the flexible glass films 51 , 61. Thus, in this case, instead of an initially flat flexible glass film 51 , a component with a certain pre-existing curvature may be provided and attached to the wind turbine blade shell 222. More specifically, the protective component may be manufactured in such a manner that a curvature substantially matching the curvature of the blade shell 222 in the region of the leading edge 218 of the wind turbine blade 22 may be obtained. This may facilitate the attachment of the protective element to the blade shell 222 of the wind turbine blade 22.

[0066] Figure 6 shows an example of a system and a method for arranging a protective element 41 covering at least a portion of the leading edge 218 wherein the protective element 41 comprises a pre-formed component. In this example, the pre-formed component comprises a flexible pre-formed component comprising one or more pre-formed flexible glass films 61. In different variants of this example, the pre-formed glass film component may comprise either a single pre-formed flexible glass film 61 or a plurality of pre-formed flexible glass films 61. In the latter case, the multiple pre-formed flexible glass films 61 may be pre-bonded, i.e. they may be bonded to each other before attachment to the leading edge 218 in a similar manner as explained with reference to flat flexible glass films 51 .

[0067] The use of a pre-formed flexible glass film 61 may reduce stresses in the glass film during handling and bonding to the blade shell 222. More specifically, the pre-formed flexible glass films 61 may be pre-formed during their manufacturing process so as to facilitate later manipulation. Thus, the pre-formed flexible glass films 61 may be pre-formed with a U-shaped curvature. In any case, the pre-formed flexible glass films 61 may still retain flexibility to adapt and conform to the curvature of the leading edge 218. In other words, even if the pre-formed flexible glass films 61 may be provided with a certain curvature, they may remain flexible so that they conform to the curvature of the leading edge 218 during attachment in a similar manner as explained with reference to the initially flat flexible glass films 51 .

[0068] In an example, the pre-formed flexible glass film 61 may be provided in multiple pieces. The length of the provided pieces may range from 200 mm up to 3 or more meters. Specifically, the provided pieces may have a length of about 1 m. Each of the pieces may be pre-formed with a curvature so as to adapt to a specific section of the leading edge 218 along the length of the blade 22. Thus, in different variants, either a single piece pre-formed flexible glass film 61 may be arranged to protect at least a portion of the leading edge 218 or multiple pieces may be individually arranged in the longitudinal direction of the wind turbine blade 22 to cover at least a portion of the leading edge 218.

[0069] Figure 7 schematically illustrates a wind turbine blade shell 222 with a protective element 41 on the blade shell 222 covering at least a portion of the leading edge 218. Thus, in this example, the protective element 41 may either be a flat flexible glass film 51 , as shown in Figure 5, or a pre-formed flexible glass film 61 , as shown in Figure 6. The protective element 41 may be attached to the blade shell 222 in the region of the leading edge 218 and it may extend along a certain length along the leading edge 218 as schematically shown in Figure 3. Furthermore, the protective element 41 may only extend over a certain area of the leading edge218 region, so that a first longitudinally extending edge 421 and a second longitudinally extending edge 422 may be defined at the suction and pressure sides, respectively.

[0070] In cases comprising a flat flexible glass film 51 , attaching the flat flexible glass film 51 to the outer surface of the wind turbine blade shell 222 may comprise adhering the initially flat flexible glass film 51 with an adhesive 53, specifically comprising an adhesive in liquid state, a pressure sensitive adhesive or a hot melt adhesive.

[0071] During the attachment process, the flat flexible glass film 51 may be deformed to adapt to the curvature of the blade shell 222 in the region of the leading edge 218. In order to ensure a proper fixation, a tool may be used to keep the flexible glass film 51 in position, i.e. in close contact with the adhesive 53 on the surface of the blade shell 222. This may be particularly the case when using a liquid adhesive.

[0072] Similarly, as also shown in Figure 7, attaching the pre-formed component may comprise attaching the flexible pre-formed component, e.g. a pre-formed flexible glass film 61 , with an adhesive 53, specifically with an adhesive 53 comprising an adhesive in liquid state, a pressure sensitive adhesive or a hot melt adhesive.

[0073] In examples of the disclosure, different types of adhesive may be employed. Thus, adhesives in liquid state, e.g. comprising viscous material of two or three components, may be used. The adhesive may be applied in the outer surface of the blade shell 222 in the area of the leading edge 218, i.e. in the attachment region, and / or on the surface of the flexible glass film 51 , 61 to be adhered to the blade shell 222, i.e. the surface of the flexible glass film 51 , 61 facing the wind turbine blade 22 when attached. In other examples, a pressure sensitive adhesive (PSA) may be utilized. In this case, either single or double sided PSAs may be employed. In still further examples, adhesive tapes (either single or double sided), or self-adhering tapes (also single or double sided) may be used as adhesive 53.

[0074] In some examples, the surface of the blade shell 222, specifically in the area of the leading edge 218, may be coated and / or painted prior to the application of the adhesive 53 to attach the flexible glass films 51 , 61. In other examples, no such coating and / or paint may be present and the adhesive may be applied to a fiber reinforced composite.

[0075] Furthermore, in examples of the disclosure, different additional materials may be provided between the laminate of the blade shell 222 and the flexible glass films 51 , 61 when using any of the examples shown in Figures 5-7. Although not limited to that situation, this maybe particularly the case when arranging a protective elements 41 in wind turbine blades 22 already in the field. Thus, putty may be provided to rebuild eroded or damaged laminates of the blade shell 222 in the area of the leading edge 218. As indicated, this may be used when retrofitting or maintaining a wind turbine blade 22 in the field, and the putty may be used for structural or non-structural purposes. Furthermore, pore filler may also be used to obtain a smooth surface. Such pore filler may be applied either on a previously arranged putty or directly on the laminate of the blade shell 222. Liquid adhesive may also be used to rebuild the leading edge 218 of the blade shell 222.

[0076] Figures 8A-8C schematically depict a further example of a system and a method for manufacturing a protective element 41 for a leading edge 218 of a wind turbine 10. In this example, a pre-formed component is also provided by the method. In particular, in this case, the pre-formed component may comprise a pre-fabricated relatively stiff component 71 , the relatively stiff component 71 having a curvature substantially matching a curvature of the wind turbine blade shell 222 in the areas of the leading edge 218. The method may further comprise attaching the relatively stiff component 71 to an outer surface of the wind turbine blade shell 222 covering at least a portion of the leading edge 218. In this case, the pre-fabricated relatively stiff component 71 may be understood as an erosion shield.

[0077] In this example, the flexible glass films may be incorporated in a relatively stiff component, which may act as a mechanical shield to protect the leading edge 218 of the wind turbine blade 22. The pre-fabricated and relatively stiff component 71 may be attached to the leading edge 218 of the wind turbine blade 22 during production of the wind turbine blade 22. Alternatively, the relatively stiff component 71 may be attached to wind turbine blades 22 already installed in the field.

[0078] As shown in Figure 8A, the relatively stiff component 71 may comprise one or more flexible glass films 51 , 61 and fiber plies 101. Thus, either initially flat flexible glass films 51 or pre-formed flexible glass films 61 with a certain curvature may be employed. A mold 81 may be used to fabricate the relatively stiff component 71 by laying the flexible glass films 51 , 61 in the mold 81 together with the fiber plies 101 and by co-infusing the flexible glass films 51 , 61 and the fiber plies 101 with resin. Regarding the fiber plies 101 , either glass, carbon or a hybrid of glass and carbon fibers may be selected. Furthermore, resins of different chemistries like polyester, epoxy, polyurethane, vinylester, thermoplastic resins etc. may be utilized for the infusion process. After co-curing, the fiber plies 101 and the flexible glass films 51 , 61 may beconsolidated to form the relatively stiff component 71. In some examples, co-infusing and cocuring may comprise using vacuum.

[0079] In other examples, the relatively stiff component 71 may be manufactured by using pre-impregnated (pre-preg) fibers, which may be arranged in the mold 81 and cured to form a fiber reinforced composite, thus avoiding the need for a resin infusion process.

[0080] As shown in Figure 8A, the flexible glass films 51 , 61 may be first laid onto a molding surface defined by a cavity of the mold 81 , whereas fiber plies 101 may be subsequently arranged on top of the previously arranged flexible glass films 51 , 61. The molding surface of the mold 81 may be configured for forming an outer surface of the relatively stiff component 71 , the outer surface being shaped in a substantially complementary manner to the surface of the blade shell 222 in the leading edge 218 region. In this manner, the flexible glass films 51 , 61 may remain at one of the surfaces of the relatively stiff component 71 and, more specifically, on the surface that, as shown in Figure 8C, may be configured to face the exterior or the wind turbine blade 22. In a variant example, a plurality of flexible glass films 51 , 61 may be arranged in a laminate configuration with a first flexible glass film 51 , 61 forming an external surface of the relatively stiff component 71. The flexible glass films 51 , 61 may be bonded together and they may be integrated with a plurality of fiber plies 101.

[0081] The use of a relatively stiff component 71 may provide increased mechanical stability and enhanced protection against erosion. A mold 81 may be used with a shape that substantially matches the U-shaped curvature of the leading edge 218 of the wind turbine blade 22 at the location where the relatively stiff component 71 is to be positioned. In other words, the inner surface of the relatively stiff component 71 may be substantially complementary to the attachment surface of the rotor blade shell 222. Nevertheless, and even if the relatively stiff component 71 may be substantially stiff and robust, this may still remain slightly flexible such that it can be adjusted to the precise geometry of the leading edge 218. In this manner, tolerances of the manufacturing and assembly process may be improved.

[0082] After fabricating the pre-formed and relatively stiff component 71 , attachment to the blade shell 222 in the region of the leading edge 218 of the wind turbine blade 22 may be carried out. In particular, attaching the relatively stiff component 71 may comprise adhering the relatively stiff component 71 , e.g. with an adhesive 53, and / or fixing the relatively stiff component 71 with a mechanical interference by means of corresponding mechanical features in the relatively stiff component 71 and on the outer surface of the wind turbine blade shell 222. In cases comprisingattachment with an adhesive, a liquid adhesive may be employed. In cases comprising mechanical fixation, fastening means may be provided in the region of the leading edge 218 of the wind turbine blade shell 222 which may be configured to engage with corresponding connecting features in the relatively stiff component 71.

[0083] A further example of a method for manufacturing a wind turbine blade 22 with enhanced leading edge protection may be provided for wind turbine blades 22 comprising a leading edge laminate 228 (see Figures 3-4) to structurally reinforce the wind turbine blade shell 222 in the leading edge 218. Thus, a leading edge laminate 228 may be formed by laying fiber plies on an area covering at least a portion of the leading edge 218. Arranging a protective element 41 may then comprise providing at least one flexible glass film 51 , 61 in combination with the fiber plies and co-infusing the fiber plies and the flexible glass films with resin to obtain a fiber reinforced composite.

[0084] This method may be particularly applicable during blade manufacturing. Thus, providing a leading edge laminate 228 to reinforce that region of the wind turbine blade 22 is a common practice. In some examples, wind turbine blades 22 may be manufactured by fabricating two separate shells, i.e. a pressure side shell and a suction side shell, in respective molds. Subsequently, the two shells may be bonded at least along the trailing edge 220 and the leading edge 218 of the wind turbine blade 22 so as to form a blade shell 222. After gluing the two shells, a dedicated laminate may be provided in the region of the leading edge 218. In other examples, a single mold may be used to manufacture the complete blade shell 222 in a single step. In this case, the region corresponding to the leading edge 218 may also be reinforced by means of a dedicated laminate. In order to provide the leading edge laminate 228, a number of fiber plies or mats may be arranged on the wind turbine blade shell 222 along at least a portion of the leading edge 218 region, either extending for the whole length of the blade 22 or at selected longitudinal positions.

[0085] According to this example, one or more flexible glass films 51 , 61 may also be included while providing the leading edge laminate 228. In particular, the flexible glass films 51 , 61 may be added at the external surface of the leading edge laminate 228, so that they face the exterior of the wind turbine blade 22 during operation. Advantageously, the flexible glass films 51 , 61 may be co-infused with resin and co-cured with the fiber plies used for the leading edge laminate 228. This may facilitate the manufacturing process by integrating both the formation of the leading edge laminate 228 and the formation of the leading edge protection in a single manufacturing step. Furthermore, this method may also result in an enhanced mechanicalintegration of the leading edge protective system in the structure of the blade 22. In examples, consolidation of the flexible glass films 51 , 61 and the fiber plies may comprise or may not comprise using vacuum and / or pressure. Furthermore, in order to improve the performance of the arrangement, heat may be applied during the curing process of the materials. Alternatively, curing at ambient temperature may also be used.

[0086] In some examples, the arrangement of a protective element 41 covering at least a portion of the leading edge 218 of the wind turbine blade 22 may be integrated with the manufacturing of the wind turbine blade shell 222, thus resulting in a so-called “in-mold” operation. In these examples, the method may comprise arranging one or more flexible glass films 51 , 61 in a mold used for the manufacture of the wind turbine blade shell 222. Furthermore, fiber plies may be arranged in the mold used for the manufacture of the wind turbine blade shell 222. Subsequently, the fiber plies and the flexible glass films may be infused with resin, and the resin may be cured, so as to obtain a fiber reinforced composite.

[0087] Such co-infusion and co-curing process, which may include application of vacuum or not, may result in an embedded protective element 41 i.e. , in a protective element 41 that may be embedded in the blade shell 222. Accordingly, improved mechanical and structural integration of the protective element 41 may be achieved, thus increasing lifetime performance and reducing the frequency of maintenance operations and / or the risk of detachment or disengagement. As in previous examples, resin of different chemistries like polyester, epoxy, polyurethane, etc. may be selected to integrate the flexible glass films 51 , 61 directly on top of the laminate or laminates forming the wind turbine blade shell 222.

[0088] In examples comprising such “in-mold” process, the flexible glass films 51 , 61 may be laid up covering only portions of the mold surface corresponding to the region around the leading edge 218 and, more specifically, to those sections around the leading edge 218 for which a protective element 41 is intended. The flexible glass films 51 , 61 may be provided as a single piece or they may be cut into multiple pieces. Specifically, the length of the provided pieces may range from 200 mm up to 3 or more meters. More specifically, the provided pieces may have a length of about 1 m. Thus, in a variant of the disclosure, a single piece flexible glass film 51 , 61 may be laid up in the corresponding portion of the mold surface. In other variants, multiple pieces may be individually arranged on the mold surface at selected locations corresponding to different positions along the length of the wind turbine blade 22.

[0089] Figure 9 provides an example of a further aspect of the disclosure. Thus, a method of arranging a protective element 41 may be provided which may further comprise applying a sealant 55 at an edge of the protective element 41 so as to seal a joint between the protective element 41 and the wind turbine blade shell 222. Specifically, a sealant 55 may be applied at all edges of the protective element 41 so as to seal all the joints between the protective element 41 and the wind turbine blade shell 222. The application of such sealant 55 may be useful for any of the examples shown before with reference to Figures 5 - 8. Thus, all examples comprising attachment of a protective element 41 on an external surface of the blade shell 222 may benefit from usage of such a sealant 55. In some examples, the sealant 55 may be provided as an adhesive material which may be arranged at the corresponding edges, not only to seal the system, but also to further reinforce the mechanical fixation.

[0090] A number of further advantages may be associated to the use of a sealant 55. On the one hand, a sealant 55 may be helpful to prevent moisture ingress and, more generally, to prevent effects arising from environmental conditions. This may improve the attachment of the protective element 41 , thus reducing detachment risks and improving the operation and maintenance of the wind turbine 10. On the other hand, a sealant 55 may be provided to enable a smooth transition between the protective element 41 and the surface of the blade shell 222.

[0091] Figure 10 shows another example that may enable a smooth transition between the protective element 41 and the surface of the blade shell 222. In this example, which may also be combined with any of the examples shown with reference to Figures 5 - 9, the protective element 41 may be tapered or chamfered in a chordwise and / or lengthwise direction, thus allowing a smooth transition to the blade 22 surface along the longitudinally extending edges 421 , 422 and / or along the lateral edges 411 , 412 (see Figure 3). A smooth transition may be advantageous to improve the aerodynamic performance of the wind turbine blade 22. Furthermore, chamfered transitions may also avoid noise generation at the step between the protective elements 41 and the surface of the blade shell 222.

[0092] Described examples exhibit a symmetrical arrangement of the protective element 41. In some alternative examples, the protective element 41 may be arranged asymmetrically with respect to the leading edge 218, so that an extension of the protective element 41 extending from the leading edge 218 towards the suction side 226 may be larger than an extension of the protective element 41 extending from the leading edge 218 towards the pressure side 224. Thus, even if a reasonably smooth transition may be provided between the protective element 41 and the surface of the blade shell 222, some unwanted aerodynamic effects may arise from thepresence of even minor irregularities on the surface of the wind turbine blade 22. Thus, in order to better control the aerodynamic flow along the surface of the wind turbine blade 22, a precise design of the protective element 41 may provide for an efficient coverage of the relevant portion of the blade shell 222 in the region of the leading edge 218 while maintaining a substantially unaffected aerodynamic performance.

[0093] As indicated in Figure 3, an example of the disclosure may comprise a wind turbine blade 22 wherein the protective element 41 may comprise multiple parts distributed in the longitudinal direction of the wind turbine blade 22. Specifically, at least two of the multiple parts may have different properties and, more specifically, at least one part arranged closer to the tip end 215 of the wind turbine blade 22 may have a larger thickness than the other parts. Thus, by dividing the protective element 41 into multiple parts, an optimized protection may be provided with an optimum balance between leading edge protection, weight and cost. Specifically, some of the previously shown examples may be combined in a single wind turbine blade 22 by using different solutions at different locations. Furthermore, different flexible glass films 51 , 61 and / or a different number of such flexible glass films 51 , 61 may be provided at different locations. More specifically, thicker flexible glass films 51 , 61 and / or a larger number of flexible glass films 51 , 61 may be provided in those regions of the wind turbine blade 22 requiring increased protection against leading edge erosion.

[0094] Furthermore, in examples of the disclosure, the thickness of the protective elements 41 may also be optimized based on the environmental conditions, e.g. rainfall conditions, at the erection site for the wind turbine 10.

[0095] In order to better withstand environmental conditions and to reduce maintenance cost over lifetime of the wind turbine 10, the flexible glass films 51 , 61 may be provided with ultraviolet (UV) protection to prevent degradation.

[0096] Apart from a wind turbine blade 22, a protective element 41 for a wind turbine blade 22 is also provided by this disclosure. The wind turbine blade 22 has a length in a longitudinal direction from a root end to 217 a tip end 215 and it comprises a wind turbine blade shell 222, the wind turbine blade shell 222 having an aerodynamic profile with a pressure side 224 and a suction side 226 and defining a leading edge 218. The protective element 41 comprises a flexible glass film 51 , 61 and it is configured for covering at least a portion of the leading edge 218 of the wind turbine blade 22 and for extending along at least a portion of the length of the wind turbine blade 22.

[0097] Several examples comprising use of flexible glass films 51 , 61 for protecting the leading edge 218 of a wind turbine blade 22 have been provided. Nevertheless, further uses are also intended for such flexible glass films 51 , 61. Thus, flexible glass films 51 , 61 may be integrated in any of the laminates constituting a wind turbine blade 22, e.g. as part of the wind turbine blade shell 222 or as part of a spar cap 274, 276. Indeed, the mechanical properties of flexible glass films 51 , 61 are not directional, i.e. they are isotropic. This property may be used to complement or compensate for the directionality of commonly used fiber plies, whose properties are determined by the orientation of the fibers.

[0098] Thus, in an example of the disclosure, a wind turbine blade 22 is provided, wherein the wind turbine blade shell 222 comprises a fiber reinforced composite comprising a plurality of fiber plies. During the manufacturing process, the fiber plies may be infused with resin and subsequently cured. One or more flexible glass films 51 , 61 may be placed together with the fiber plies. Specifically, the flexible glass films 51 , 61 may be placed under or above the fiber plies. A composite component with optimized structural properties may be achieved after resin infusion and curing (with or without vacuum consolidation).

[0099] The selected material for the fiber plies may depend on the part of the wind turbine blade 22. Thus, glass fibers may be selected for the blade shell 222 whereas carbon fibers may be preferred for the spar caps 274, 276. In all cases, the laminates may comprise a plurality of fiber plies or layers , e.g. between five and fifty layers may be utilized. Depending on the specific needs, one or more flexible glass films 51 , 61 may be arranged with said layers. Furthermore, flexible glass films 51 , 61 may be only arranged at selected longitudinal positions of the wind turbine blade shell 222. Specifically, flexible glass films 51 , 61 may be only arranged at certain portions along the longitudinal direction of the wind turbine blade 22.

[0100] Figure 11 schematically illustrates a step during manufacturing of a wind turbine blade shell 222 according to an example, in which a flexible glass film 51 , 61 may be integrated in the wind turbine blade shell 222. In this example, a mold 91 may be provided. The mold 91 may be used for the manufacturing of one of the blade shell halves, i.e. for a pressure side shell or a suction side shell. As shown in Figure 11 , one or more flexible glass films 51 , 61 may be laid on an internal surface of the mold 91. Subsequently, fiber plies 104 may be provided on top of the flexible glass films 51 , 61. As a result, the flexible glass films 51 , 61 may be disposed together with the fiber plies 104.

[0101] Even if this example shows a single flexible glass film 51 , 61 arranged with the fiber plies 104, more flexible glass films 51 , 61 may be provided. Furthermore, although not visible in Figure 11 , different materials and combinations may be used at different positions along the length of the mold 91. A resin infusion process may be carried out after providing the different layers as well-known by those skilled in the art. Subsequently, a curing step may be carried out to obtain a fiber reinforced composite to complete a blade shell. In another example (not shown in Figure 11), additional flexible glass films 51 , 61 may be arranged above the fiber plies 104 so that flexible glass films 51 , 61 may be provided both above and under the fiber plies 104.

[0102] Figure 11 shows an example wherein a mold 91 for a blade shell half may be provided. Nevertheless, in other examples of the disclosure, a mold intended for the manufacture of a complete blade shell in a single step may also be employed.

[0103] In still another example, several flexible glass films 51 , 61 may be stacked to form at least a part of a structural spar cap 274, 276 of the wind turbine blade 22.

[0104] This written description uses examples to disclose the present teaching, including the preferred examples, and also to enable any person skilled in the art to practice it, including making and using any devices or systems and performing any incorporated methods. The patentable scope is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal languages of the claims. Aspects from the various embodiments described, as well as other known equivalents for each such aspects, can be mixed and matched by one of ordinary skill in the art to construct additional embodiments and techniques in accordance with principles of this application. If reference signs related to drawings are placed in parentheses in a claim, they are solely for attempting to increase the intelligibility of the claim, and shall not be construed as limiting the scope of the claim.

Claims

CLAIMS1. A method for manufacturing a wind turbine blade (22), the wind turbine blade (22) having a length in a longitudinal direction from a root end (217) to a tip end (215) and comprising a wind turbine blade shell (222), the wind turbine blade shell (222) having an aerodynamic profile with a pressure side (224) and a suction side (226), wherein one or more flexible glass films (51 , 61) are arranged in the wind turbine blade (22).

2. The method of claim 1 , wherein the wind turbine blade shell (222) defines a leading edge (218), the method comprising arranging a protective element (41) covering at least a portion of the leading edge (218), the protective element (41) comprising at least one of the flexible glass films (51 , 61) and extending along at least a portion of the length of the wind turbine blade (22).

3. The method of claim 2, wherein arranging the protective element (41) comprises attaching a flat flexible glass film (51) to an outer surface of the wind turbine blade shell (222) covering at least a portion of the leading edge (218) so that the flexible glass film (51) conforms to the shape of the wind turbine blade shell (222) in the leading edge (218), specifically wherein attaching the flexible glass film (51) to the outer surface of the wind turbine blade shell (222) comprises adhering the flexible glass film (51) with an adhesive (53), more specifically comprising an adhesive (53) in liquid state, a pressure sensitive adhesive or a hot melt adhesive.

4. The method of claims 2 or 3, wherein arranging the protective element (41) comprises attaching a pre-formed component to an outer surface of the wind turbine blade shell (222) covering at least a portion of the leading edge (218), the pre-formed component comprising one or more of the flexible glass films (51 , 61).

5. The method of claim 4, wherein the pre-formed component comprises a flexible preformed component comprising one or more pre-formed flexible glass films (61), and further wherein attaching the pre-formed component comprises attaching the flexible pre-formed component with an adhesive (53), specifically with an adhesive (53) comprising an adhesive in liquid state, a pressure sensitive adhesive or a hot melt adhesive.

6. The method of claims 4 or 5, wherein the pre-formed component comprises a prefabricated relatively stiff component (71), the relatively stiff component (71) having a curvature substantially matching a curvature of the wind turbine blade shell (222) in the leading edge (218), and further wherein attaching the pre-formed component comprises attaching the relatively stiff component (71) to an outer surface of the wind turbine blade shell (222) covering at least a portion of the leading edge (218).

7. The method of claim 6, wherein the relatively stiff component (71) comprises one or more flexible glass films (51 , 61) and fiber plies (101), and further wherein a mold (81) is used to fabricate the relatively stiff component (71) by laying the flexible glass films (51 , 61) in the mold (81) together with the fiber plies (101) and by co-infusing the flexible glass films (51 , 61) and the fiber plies (101) with resin.

8. The method of any of claims 2 to 7, wherein the wind turbine blade (22) comprises a leading edge laminate (228) to structurally reinforce the wind turbine blade shell (222) at the leading edge (218), the leading edge laminate (228) being formed by laying fiber plies on an area covering at least a portion of the leading edge (218), and further wherein arranging the protective element (41) comprises providing at least one flexible glass film (51 , 61) in combination with the fiber plies and co-infusing the fiber plies and the flexible glass films (51 , 61) with resin.

9. The method of any of claims 2 to 8, wherein arranging the protective element (41) comprises: arranging one or more flexible glass films (51 , 61) in a mold used for the manufacture of the wind turbine blade shell (222), arranging fiber plies in the mold used for the manufacture of the wind turbine blade shell (222), infusing the fiber plies and the flexible glass films (51 , 61) with resin, and curing the resin.

10. The method of any previous claim, wherein the wind turbine blade shell (222) comprises a plurality of fiber plies and at least one of the flexible glass films (51 , 61) is placed under or above the fiber plies.

11. The method of claim 10, wherein the flexible glass films (51 , 61) are only arranged at selected longitudinal positions of the wind turbine blade shell (222) and, specifically, wherein the flexible glass films (51 , 61) are only arranged at certain portions along the longitudinal direction of the wind turbine blade (22).

12. A wind turbine blade (22) having a length in a longitudinal direction from a root end (217) to a tip end (215) and comprising a wind turbine blade shell (222), the wind turbine blade shell (222) having an aerodynamic profile with a pressure side (224) and a suction side (226), wherein the wind turbine blade (22) comprises one or more flexible glass films (51 , 61).

13. The wind turbine blade (22) of claim 12, wherein the wind turbine blade shell (222) defines a leading edge (218), the wind turbine blade (22) further comprising a protective element (41) comprising at least one of the flexible glass film (51 , 61), and further wherein the protective element (41) is configured for covering at least a portion of the leading edge (218) and for extending along at least a portion of the length of the wind turbine blade (22), specifically for extending for at least a third of the length of the wind turbine blade (22).

14. The wind turbine blade (22) of claim 13 wherein the protective element (41) comprises multiple parts distributed in the longitudinal direction of the wind turbine blade (22), specifically wherein at least two of the multiple parts have different properties and, more specifically, wherein at least one part arranged closer to the tip end (215) of the wind turbine blade (22) has a larger thickness than the other parts.

15. The wind turbine blade (22) of any of claims 12 to 14, wherein the blade shell (222) comprises fiber plies and wherein at least one of the flexible glass films (51 , 61) is arranged together with the fiber plies.

Images