Wind turbine blade

Abstract

Wind turbine blade having a substantially hollow blade body (11) comprising upper and lower half shells (12, 13) and first and second elongated webs (16, 17) each extending in a longitudinal direction of the blade (5) and arranged between and connected to the upper and lower half shells (12, 13), wherein each web (16, 17) comprises upper and lower flanges (19, 21) connecting the respective web (16, 17) to the respective half shell (12, 13), and wherein the first and second webs (16, 17) are supported relative to the respective half shell (12, 13) via a respective first and second reinforcement structure (27, 28) arranged between outer and inner layers (23, 26) of the upper and lower half shells (12, 13) and extending in the longitudinal direction of the blade (5), whereby the first and second reinforcement structures (27, 28) each comprise at least one stack (29, 30) consisting of a plurality of glass fibre layers (45, 46) impregnated with a resin (43), and at least one stiffening element (31) is arranged between the first and second reinforcement structures (27, 28), the stiffening element (31) extending parallel to the first and second reinforcement structures (27, 28) over at least a part of their length, the stiffening element (31) comprising at least one stack (32) consisting of a plurality of pultruded composite strips (47) comprising carbon fibres, wherein the strips (47) are fixed in the resin (43).

Description

Technical Field

[0001] The present invention relates to a wind turbine blade having a generally hollow blade body comprising an upper and a lower half-shell and first and second elongated webs, each extending along the longitudinal direction of the blade and disposed between and connected to the upper and lower half-shells, wherein each web includes upper and lower flanges connecting the respective web to the respective half-shell, and wherein the first and second webs are supported relative to the respective half-shells via respective first and second reinforcing structures disposed between an outer and an inner layer of the upper and lower half-shells and extending along the longitudinal direction of the blade. Background Technology

[0002] As is well known, wind turbine blades are part of a wind turbine used to generate electrical power. A wind turbine typically consists of three blades attached to a hub, which is connected to a generator housed in a nacelle. These blades interact with the passing wind, causing the hub to rotate, ultimately driving the generator.

[0003] Turbine blades typically comprise a hollow blade body with an upper half-shell and a lower half-shell, which are usually manufactured separately and attached to each other. First and second elongated webs are arranged within this hollow blade body, connecting and supporting the two half-shells while also transmitting loads acting on the respective shells due to aerodynamics and the circumferential motion of the blade during rotation. These loads include pressure and suction loads on the upper and lower half-shells, as well as compressive and tensile loads. For example, a wind turbine blade with this common configuration is disclosed in EP 2 791 500 B1.

[0004] To support the half-shell and to transfer the corresponding load, each elongated web extends longitudinally and is connected to the corresponding half-shell via flanges disposed on the respective web sides, the flanges being attached to the inner layers of the upper and lower half-shells by adhesive. To transfer the load or, consequently, to support the corresponding shell, each web is supported relative to the corresponding half-shell via corresponding first and second reinforcing structures. Such reinforcing structures are commonly referred to as spar caps. Like the corresponding webs and their flanges, these reinforcing structures or spar caps also extend longitudinally along the blade. As disclosed, for example, in EP 2 791 500 B1, these reinforcing structures are made from a stack comprising separate carbon fiber pultrusion strips arranged on top of each other and fixed in a resin matrix. During the manufacture of such pultrusion strips, carbon fibers are drawn through a supply of liquid resin, which is then heated and cured, ultimately forming the respective pultrusion strip. These pultruded carbon fiber strips exhibit excellent mechanical properties in bearing and distributing loads, and also absorb the high bending moments generated during blade rotation.

[0005] In known wind turbine blade designs, such as those disclosed in EP 2 791 500 B1, the blade includes first and second webs that extend almost entirely along the length of the blade and are arranged in the central body region, i.e., in the region where the upper and lower half-shells, viewed in a teardrop cross-section, are significantly apart. A third web may also be provided, arranged near the trailing edge of the blade. This third web extends only along a portion of the trailing edge, in which the trailing edge typically has a specific edge design and is subjected to specific loads, which are borne or distributed accordingly by this web.

[0006] All webs comprise elongated web bodies with flanges disposed at the ends of the web bodies. Each web is supported by two reinforcing structures, namely spar caps, such that a total of six spar caps are arranged in two shells to support the three webs. If only the first and second webs are provided, four spar caps need to be integrated; if three webs are provided, six spar caps need to be integrated. The spar caps, made of carbon fiber strips, are prefabricated and arranged in the shell mold for their integration. Due to the need to integrate two or three webs and four or six spar caps, the total mass of this known turbine blade is high, but the mass of the spar caps themselves is reduced due to the use of carbon fiber pultruded stacks, which, on the other hand, need to be manufactured outside the shell and are expensive.

[0007] Therefore, there is a need for an improved wind turbine blade design that allows for proper load support and has a less complex and expensive design. Summary of the Invention

[0008] To address this issue, the wind turbine blades mentioned above are characterized in that each of the first and second reinforcing structures comprises at least one stack consisting of several glass fiber layers infused with resin, and at least one reinforcing element is arranged between the first and second reinforcing structures, the reinforcing element extending parallel to the first and second reinforcing structures over at least a portion of their length, the reinforcing element comprising at least one stack consisting of several pultruded composite strips comprising carbon fibers, wherein the strips are fixed in resin.

[0009] The wind turbine of the present invention is characterized by a specific layout or design of support structures integrated in the upper and lower half-shells for supporting the first and second webs, which are arranged in portions of two shells of a hollow body significantly spaced apart from each other. As in the prior art, both webs are supported by separate first and second reinforcing structures integrated between the outer and inner layers of the shell. Unlike known blade designs, these reinforcing structures are made solely of glass fiber laminates infused with resin and thus embedded in a resin matrix. Therefore, carbon fiber pultruded strips or corresponding pre-fabricated carbon strip laminates are not used to construct the corresponding reinforcing structures, which are expensive and difficult to repair, or consequently prevent the repair of adjacent areas, such as adhesive areas, if necessary. Instead, simple glass fiber laminate composite laminates are used, which can be easily constructed directly into the corresponding shells used for producing the half-shells by simply arranging the corresponding glass fiber layers for constructing the respective laminates together with other components required for producing the half-shells. Since the semi-shell, comprising several fiber layers infused with resin to construct the respective upper and lower shell layers, is ultimately infused with resin, the glass fiber stack is also infused with resin in this single infusion step. Therefore, the first and second reinforcing structures are infused simultaneously, and thus constructed while the remainder of the semi-shell is also infused and constructed.

[0010] Since these reinforcing structures, which are attached adjacent to the first and second webs to the inner layers of the respective shells, are made of glass fiber layers embedded in a resin matrix, another advantage of this arrangement is the simplification of the possibility of joint repair, where the webs or corresponding flanges are attached to the inner layers, because these glass fiber reinforcing structures can be drilled through from the outside of the blade and adhesive injected through the glass laminate, an action that is impossible when using carbon fiber pultruded reinforcing structures, as they cannot be drilled.

[0011] Therefore, the glass fiber-based reinforcement structures of the present invention exhibit several advantages. First, they are simple in design and easy to manufacture, and can be implemented in conjunction with the production of the corresponding housing. Second, since the first and second reinforcement structures do not include any carbon fiber strips, the mass of expensive carbon fiber-based reinforcement measures is greatly reduced. And third, it provides the possibility of repairing these areas, especially in the joint region, because the glass fiber-based reinforcement structures can be drilled.

[0012] The turbine blades of the present invention are characterized not only by the use of first and second glass fiber-based reinforcing structures, but also by the integration of a specific reinforcing element between the first and second reinforcing structures. Furthermore, this reinforcing element is also integrated between upper and lower layers in respective half-shells. At least one reinforcing element is provided, extending over at least a portion of the length of the first and second reinforcing structures. This reinforcing element comprises at least one stacked member consisting of a plurality of pultruded composite strips comprising carbon fibers. These strips are also embedded in resin, wherein the first and second glass fiber-based reinforcing structures are also embedded.

[0013] In summary, the present invention proposes a single reinforcing device comprising first and second reinforcing structures directly adjacent to the web, and a reinforcing device disposed between the two reinforcing structures, wherein the entire reinforcing device is injected or embedded in resin or a corresponding resin matrix. Therefore, this reinforcing device can be considered as a single spar cap supporting two webs.

[0014] Since carbon fibers are present only in the reinforcing elements, the total mass of the carbon pultruded material is reduced. Furthermore, considering the load or corresponding load distribution, the reinforcing device can be positioned optimally within the contour of the corresponding housing, as it exhibits enhanced mechanical properties; thus, the first and second reinforcing structures, directly connected via the resin matrix, also participate.

[0015] The reinforcing element preferably comprises layers of glass and / or carbon fiber arranged between each pair of strips, these layers being infused with resin. These intermediate glass or carbon fiber layers or fabrics allow resin infusion between adjacent pultruded strips, after which the pultruded strips are securely fixed to each other. Such reinforcing elements can be produced as prefabricated elements and inserted into a corresponding shell mold in which the shell is produced and embedded in the resin matrix when the shell is infused with resin. Alternatively, the reinforcing element can also be constructed directly in the corresponding shell mold, just like the reinforcing structure, simply by arranging the individual strips and intermediate fiber layers or fiber fabrics in the shell mold and providing resin infusion along with the overall shell infusion. This allows the reinforcing element to be constructed directly in the shell mold, and thus, the entire reinforcing device, including the reinforcing structure and the reinforcing element together, can be constructed in a single resin infusion step along with the overall infusion of the associated shell components.

[0016] Preferably, the glass and / or fiber layer sandwiched between two adjacent carbon pultruded strips is a biaxial layer. The biaxial fiber layer or fabric comprises fibers arranged at an angle of 0°, while other fibers are arranged at angles of, for example, ±45°. Such a biaxial layer is advantageous because it allows for the bearing of loads in different directions or correspondingly different types, such as flapwise or edgewise bending loads from the blades.

[0017] In another preferred embodiment of the invention, the first and second reinforcing structures and the reinforcing elements are mechanically connected via at least one glass or carbon fiber layer extending from the first reinforcing structure through the reinforcing element to the second reinforcing structure. The reinforcing structures and reinforcing elements are not only embedded in a common resin matrix but are also mechanically connected by at least one glass or carbon fiber layer extending through all these elements or corresponding portions of the reinforcing device. This common fiber layer serves to enhance the mechanical stability and stiffness of the arrangement structure and allows for even better load support and load distribution.

[0018] Preferably, at least one of the glass or carbon fiber layers of the reinforcing element extends into the two stacks of the first and second reinforcing structures. Thus, the mechanical connection is provided by at least one glass or carbon fiber layer sandwiched between two adjacent carbon pultruded strips and is therefore an integral part of the reinforcing element stack. This glass or carbon fiber layer extends laterally into the corresponding glass fiber stack, which then includes the extended reinforcing element layer as an integral layer of the stack. If the extended layer is a glass fiber layer, each reinforcing structure is an element comprising only glass fibers. If the extended fiber layer is a carbon fiber layer, the reinforcing element is almost entirely composed of glass fiber layers, with only one or a few carbon fiber layers sandwiched in between.

[0019] Even when only one layer extends through the two reinforcing structures and the reinforcing element, the through-reinforcing device achieves an improved mechanical layout. Preferably, all glass or carbon fiber layers of the reinforcing element extend into the two stacked members of the first and second reinforcing structures. Therefore, there are several mechanical connection planes connecting the reinforcing structures and the reinforcing elements, which further enhances the mechanical properties of the reinforcing device.

[0020] In the first inventive alternative, only one reinforcing element is provided, which extends over at least 70%, preferably at least 80%, and especially over the entire length of the first and second reinforcing structures. Thus, the two reinforcing structures are mechanically coupled by only one reinforcing element, which preferably extends over most of the length of the reinforcing structure, preferably over their entire length, such that the entire reinforcing device, which may also be called a hybrid reinforcing device or a hybrid spar cap, extends over almost the entire blade length in this particular arrangement.

[0021] In another alternative, two or more reinforcing elements can be provided, each extending only a portion of the length of the first and second reinforcing structures. In this embodiment, two or more separate and shorter reinforcing elements are provided, following each other longitudinally but spaced apart, such that gaps exist between the reinforcing elements when viewed in the longitudinal blade direction. These gaps can be filled, for example, with resin or a lightweight but rigid core element, made of, for example, wood or polymer, which is also embedded in the resin matrix of the entire reinforcing device. This embodiment allows for even greater reduction in the amount of carbon material used, and thus further reduces the overall cost.

[0022] In a preferred embodiment, the stack of the first and second reinforcing structures comprises biaxial and uniaxial glass fiber layers. As already mentioned, the biaxial fiber layer comprises fibers arranged at a 0° angle and other fibers arranged at, for example, ±45° angles. Alternatively, the uniaxial fiber layer comprises only parallel fibers that extend along the longitudinal blade direction, just like the 0° fibers of the biaxial layer. The biaxial layer allows for the resistance to loads in different directions or correspondingly different types, i.e., loads arising from blade flapping and flaring bending, while the uniaxial fibers or layers particularly enhance the stiffness against flapping bending. These different layer types can be arranged in an alternating manner, with a uniaxial layer followed by a biaxial layer, then another uniaxial layer, and so on. However, it is also possible to stack, for example, two or three uniaxial layers, followed by one or two biaxial layers, then three uniaxial layers, and so on. Thus, specific designs regarding the arrangement of the different layer types are possible.

[0023] Furthermore, preferably, the core elements are disposed adjacent to the first and second reinforcing structures between the outer and inner layers of the respective upper and lower half-shells. These core elements, used for further adjusting the mechanical properties of the blades in the region of the reinforcing device also close to the shell integration, are also sandwiched between the outer and inner layers of the respective upper and lower half-shells. These core elements may be made of, for example, foam, wood, or polymer, and this list is not exhaustive.

[0024] The present invention also relates to a wind turbine comprising a plurality of turbine blades as described above, preferably three turbine blades. Attached Figure Description

[0025] Other objects and features of the invention will become apparent from the following detailed description taken in conjunction with the accompanying drawings. However, the drawings are merely schematic diagrams designed for illustrative purposes only and do not limit the invention. The drawings show:

[0026] Figure 1 Schematic diagram of a wind turbine.

[0027] Figure 2 : Along Line II-II Figure 1 A cross-sectional view of the blade, and

[0028] Figure 3 : Figure 2 An enlarged view of section III. Detailed Implementation

[0029] Figure 1 A schematic diagram of a wind turbine 1 is shown, which includes a tower 2, a nacelle 3 mounted on top of the tower 2, and a rotor 4. The rotor 4 includes three wind turbine blades 5 attached to a hub, which is operatively coupled to a generator arranged in the nacelle 3. The generator is driven by the rotational energy of the rotor 4 to generate electrical power as known.

[0030] Each turbine blade 5 includes a root 7 for attaching the blade 5 to the hub 6 and a tip 8 at the other end. It also includes a leading edge 9 and a trailing edge 10.

[0031] This invention relates to the arrangement of wind turbine blades 5.

[0032] Figure 2 It shows along Figure 1The diagram shows a schematic cross-sectional view of a turbine blade 5 taken along line II-II. The blade 5 comprises a hollow body 11, which is made of an upper half-shell 12 and a lower half-shell 13, which are fixed to each other by adhesive 14 and enclose a hollow space 15. A first web 16 and a second web 17 are arranged in this space 15. The two webs 16 and 17 are arranged in regions of considerable distance between the upper half 12 and the lower half 13, where the blade has a large thickness. The two webs 16 and 17 extend almost parallel to each other and along almost the entire length of the blade 5, thus beginning adjacent to the root 7 and ending adjacent to the tip 8.

[0033] Both the first and second webs 16 and 17 are used to support the blade housings 12 and 13, and to bear and distribute the corresponding loads placed on the blade 5, which are caused by the aerodynamic conditions caused by the rotation of the rotor 4 and the mechanical conditions caused by the weight of the blade 5 itself.

[0034] The first web 16 includes a web body 18 and two flanges 19 integrally attached to the web body 18 at its ends. The same H-shaped design is also implemented in the second web 17, which includes a web body 20 and two end flanges 21 integrally attached to the web body 20.

[0035] Through these flanges 19, 21, the two webs 16, 17 are attached to the inner side 22 of the inner layer 23 by means of adhesives 24, 25, see also Figure 3 .like Figure 3 As shown, the inner layer 23 is part of the corresponding half-shells 12, 13. Figure 3 Only a portion of the upper half-shell 12 is shown, i.e. Figure 2 Section III. It should be noted that the same arrangement is also given at the lower half-shell 13. When the inner layer 23 forms the internal portion of the corresponding shells 12, 13, the outer layer 26 forms the external portion of the corresponding half-shells 12, 13. This design will be about Figure 3 To elaborate further.

[0036] Since the two webs 16, 17 are attached to the inner layer 23 of the shells 12, 13 by adhesives 24, 25, they need to be securely supported by the respective shells 12, 13. To achieve this support in each shell 12, 13, a first reinforcing structure 27 for supporting the first web 16 and a second reinforcing structure 28 for supporting the second web 17 are arranged or correspondingly integrated and sandwiched between the inner layer 23 and the outer layer 26. These reinforcing structures 27, 28 are made of corresponding stacks 29, 30, which are made of several layers of glass fiber fabric infused with resin. Figure 3 To elaborate further.

[0037] Between the two reinforcing structures 29 and 30 arranged in the two shells 12 and 13, a reinforcing element 31 is arranged, comprising a plurality of stacks of carbon fiber pultruded strips embedded in resin, preferably in a resin in which glass fiber stacks 29 and 30 are also embedded. Overall, the combination of the two reinforcing structures 27 and 28 and the reinforcing element 31 forms a single hybrid reinforcing device or hybrid spar cap, which is a very rigid element extending along the longitudinal direction of the blade and supporting the two webs 16 and 17, due to the embedding of the corresponding stacks 29 and 30 and the stack 32 including the carbon fiber pultruded strips.

[0038] As from Figure 2 As can be seen, the reinforcing element 31 is arranged in the blade region where higher loads occur. By inserting this carbon fiber-based reinforcing element in conjunction with the reinforcing structure, the blade shell is robustly strengthened, which supports the additional reinforcing web, enabling a very rigid blade region and design that can withstand and distribute the high loads generated during wind turbine operation.

[0039] The glass fiber-based reinforcement structures 27 and 28 primarily support the webs 16 and 17 and do not require fabrication from carbon fiber pultruded strip stacks. The reinforcing devices positioned between the reinforcement structures 27 and 28 provide corresponding reinforcement to the relevant blade regions and also provide further reinforcement to the reinforcement structures 27 and 28, as they are firmly attached to the reinforcing element 31 via a common resin matrix. Thus, the blade 5 of the present invention includes carbon fiber-based reinforcing elements arranged optimally in the profile of load occurrence, while the reinforcement structures 27 and 28, primarily supporting the webs 16 and 17, are made of glass fiber layers omitting the carbon fiber pultruded strips. Therefore, in the overall blade design, the amount of carbon pultruded material is reduced to what is necessary to provide the required mechanical properties, while the reinforcement structures 27 and 28 are made of common materials and constructed using a known procedure as described below.

[0040] Figure 3 Shown in cross section Figure 2An enlarged schematic diagram of section III is shown. It partially illustrates two webs 16, 17. Preferably, the two webs, having the same or similar arrangement, include cores 33, 34, made, for example, of balsa wood or foam, extending almost the entire length of the corresponding web bodies 18, 20. These cores are enclosed in glass fiber layers 35, 36 infused with resin 37, 38. The corresponding flanges 19, 21 are integral with the corresponding web bodies 18, 20. The flanges also include several glass fiber layers 39, 40, which are also injected or embedded in the resin 37, 38. Although only one of the corresponding glass fiber layers 35, 36 and 39, 40 is shown, several of these layers are configured to construct the corresponding large and mechanically rigid outer shell. In particular, the layers 39 and 40 that construct the central portion of the corresponding flanges 19, 21 also include biaxial and uniaxial glass fiber layers, which are injected or embedded in the corresponding resin 39, 40. In addition, the corresponding web bodies 18 and 20 may also include uniaxial and biaxial glass fiber layers, just as in the flanges 19 and 21, which may be stacked in any order.

[0041] like Figure 3 It is also shown that the corresponding flanges 19, 21 are securely attached to the inner surface 22 of the inner layer 23 by means of adhesive layers 24, 25. This provides a very robust joint, which is necessary because the corresponding load is transmitted through the joint.

[0042] Figure 3 The enlarged view also shows two reinforcing structures 27, 28 and a reinforcing element 31. It is evident that both reinforcing structures 27, 28 and reinforcing element 31 are sandwiched between an inner layer 23 and an outer layer 26, which comprises several fiberglass layers 41, 42 injected or embedded in resin 43 that is injected throughout the respective housings 12, 13, and also embeds a core element 44, for example, made of foam or balsa wood, arranged adjacent to reinforcing structures 27, 28 in the respective housing regions. Needless to say, each layer 23, 26 may certainly include far more than just two fiberglass layers 41, 42, such as… Figure 3 As shown in the schematic diagram.

[0043] As mentioned, reinforcing structures 27 and 28 are sandwiched between the inner layer 23 and the outer layer 26. Each reinforcing structure 27 and 28 consists of a stack 29 and 30 comprising a number of glass fiber layers 45 and 46, some of which are in… Figure 3 As shown in the figure. These glass fiber layers 45, 46 include uniaxial and biaxial layers, and they can also be arranged in any order. These glass fiber layers 45, 46 are also injected or embedded in resin 43.

[0044] like Figure 3 As further shown, the reinforcing element 31 is arranged directly next to the reinforcing structures 27, 28. It includes a stack 32 comprising a plurality of carbon fiber pultruded strips 47. The widths of these strips 47 correspond to the gaps between the corresponding glass fiber stacks 29, 30 of the reinforcing structures 27, 28, such that the reinforcing structures 27, 28 are directly connected to the reinforcing element 31.

[0045] One or more glass fiber layers 48, preferably biaxial glass fiber layers or fabrics, are disposed between two adjacent strips 47 for infusing resin between them to secure them firmly. (See from...) Figure 3 Clearly, the glass fiber layer 48 of the reinforcing element 31 extends on both sides of the reinforcing element 31 and into the corresponding glass fiber laminates 29, 30 of the reinforcing structures 27, 28. This means that the extended glass fiber layer 48 also forms part of the corresponding glass fiber laminates 29, 30. Since the reinforcing element 31 is also injected or embedded in the integral resin 43, not only does the resin 43 provide a mechanical connection between the reinforcing structures 27, 28 and the reinforcing element 31, but the embedded glass fiber layer 48 also extends or stretches through the reinforcing element 31 and the two reinforcing structures 27, 28. Although Figure 3 Only one glass fiber layer 48 sandwiched between two strips 47 is shown, but obviously more such layers may exist, and of course more than three strips 47 may be provided. Preferably, all these glass fiber layers 48 sandwiched in the middle of the reinforcing element 31 extend into the corresponding glass fiber stacks 29, 30 of the reinforcing structures 27, 28, so that a number of connection planes can be achieved through these common glass fiber layers.

[0046] like Figure 3 As shown, the glass fiber-based reinforcement structures 27 and 28 are located in the direct extensions of the webs 16 and 17. This allows for repair work to be performed at the reinforcement structures 27 and 28, at the webs 16 and 17, and especially at the corresponding joints of the adhesives 24 and 25, if needed, because these glass fiber-based reinforcement structures 27 and 28 can be drilled. Holes or similar features may be drilled in these reinforcement structures, through which resin can be pressed or injected for repair purposes to repair the resin matrix of the reinforcement elements or adhesive joints, etc. This is possible because the reinforcement structures 27 and 28 in this embodiment consist only of glass fiber layers.

[0047] Even if carbon fiber layers 48 are used in the carbon fiber pultruded stack 32 and they extend in the corresponding glass fiber stacks 29, 30, they will not hinder the repair possibilities mentioned above, because these thin carbon fiber layers 48 can also be drilled, and only a few of these layers extend into the corresponding glass fiber stacks 29, 30.

[0048] The hybrid reinforcement device or hybrid spar cap, including reinforcing element 31 and reinforcing structures 27, 28, may consist of only one reinforcing element 31, which extends parallel to the reinforcing structures 27, 28 along almost the entire length of the blade 5. In addition to providing only one reinforcing element 31, two or more separate but shorter reinforcing elements 31 may be arranged one after another along the longitudinal direction of the blade 5, with a certain gap between them. This gap may be filled with a core element, such as a foam element, thereby allowing for a further reduction in the mass of carbon fiber used while providing sufficient stiffness because the several reinforcing elements 31 remain firmly embedded in the entire common matrix of resin 43 and are preferably also mechanically connected to the reinforcing structures 27, 28 by an extended glass fiber layer 48.

[0049] Although the invention has been described in detail with reference to preferred embodiments, the invention is not limited to the disclosed examples, and other variations can be derived by those skilled in the art from the disclosed examples without departing from the scope of the invention.

Claims

1. A wind turbine blade having a generally hollow blade body (11), the blade body (11) comprising upper and lower half-shells (12, 13) and first and second elongated webs (16, 17), each of the first and second elongated webs (16, 17) extending along the longitudinal direction of the blade (5) and disposed between and connected to the upper and lower half-shells (12, 13), wherein each web (16, 17) comprises a portion of the blade body (16, 17) that will support the blade body (16, 17). The corresponding webs (16, 17) are connected to the upper and lower flanges (19, 21) of the corresponding half-shells (12, 13), and wherein the first and second webs (16, 17) are supported relative to the corresponding half-shells (12, 13) via corresponding first and second reinforcing structures (27, 28), the reinforcing structures (27, 28) being arranged between the outer and inner layers (23, 26) of the upper and lower half-shells (12, 13) and extending along the longitudinal direction of the blade (5), characterized in that, The first and second reinforcing structures (27, 28) each include at least one stack (29, 30) consisting of a plurality of glass fiber layers (45, 46) infused with resin (43), and at least one reinforcing element (31) is disposed between the first and second reinforcing structures (27, 28), the reinforcing element (31) extending parallel to the first and second reinforcing structures (27, 28) for at least a portion of their length, the reinforcing element (31) including at least one stack (32) consisting of a plurality of pultruded composite strips (47) comprising carbon fibers, wherein the strips (47) are fixed in the resin (43).

2. The wind turbine blade according to claim 1, characterized in that, The reinforcing element (31) includes a glass and / or carbon fiber layer (48) disposed between each pair of strips (47), the layer (48) being infused with the resin (43).

3. The wind turbine blade according to claim 2, characterized in that, The glass and / or carbon fiber layer (48) is a biaxial layer.

4. The wind turbine blade according to any one of claims 1 to 3, characterized in that, The first and second reinforcing structures (27, 28) and the reinforcing element (31) are mechanically connected by at least one glass or carbon fiber layer (48) extending from the first reinforcing structure (27) through the reinforcing element (31) to the second reinforcing structure (28).

5. The wind turbine blade according to claim 2 or 3, characterized in that, At least one of the glass or carbon fiber layers (48) of the reinforcing element (31) extends into the two stacked parts (29, 30) of the first and second reinforcing structures (27, 28).

6. The wind turbine blade according to claim 5, characterized in that, All glass or carbon fiber layers (48) of the reinforcing element (31) extend into the two stacked parts (29, 30) of the first and second reinforcing structures (27, 28).

7. The wind turbine blade according to any one of claims 1 to 3, characterized in that, Only one reinforcing element (31) is provided, which extends over at least 70% of the length of the first and second reinforcing structures (27, 28).

8. The wind turbine blade according to any one of claims 1 to 3, characterized in that, Only one reinforcing element (31) is provided, which extends over at least 80% of the length of the first and second reinforcing structures (27, 28).

9. The wind turbine blade according to any one of claims 1 to 3, characterized in that, Only one reinforcing element (31) is provided, which extends over the entire length of the first and second reinforcing structures (27, 28).

10. The wind turbine blade according to any one of claims 1 to 3, characterized in that, Two or more reinforcing elements (31) are provided, each of which extends only a portion of the length of the first and second reinforcing structures (27, 28).

11. The wind turbine blade according to any one of claims 1 to 3, characterized in that, The stack (29, 30) of the first and second reinforcing structures (27, 28) includes biaxial and uniaxial glass fiber layers (45, 46).

12. The wind turbine blade according to any one of claims 1 to 3, characterized in that, The core element (44) is disposed adjacent to the first and second reinforcing structures (27, 28) between the outer and inner layers (23, 26) of the respective upper and lower half-shells (12, 13).

13. The wind turbine blade according to claim 12, characterized in that, The core element (44) is made of foam, wood or polymer.

14. A wind turbine comprising a plurality of wind turbine blades (5) according to any one of claims 1 to 13.

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