A method for producing a rotor blade for a wind turbine

Abstract

A method for producing a rotor blade (5) of a wind turbine (1), the method comprising the steps of: a) providing (S1) at least two different components (9, 10, 11) of the rotor blade (5), b) placing (S2) an electric resistance element (22) between the components (9, 10, 11), c) placing (S3) a thermoplastic or weldable thermoset resin between the components (9, 10, 11), d) energizing (S4) the electric resistance element (22) such that the electric resistance element (22) applies heat (H) to the thermoplastic or weldable thermoset resin to melt or soften it, and (e) coupling (S5) the components (9, 10, 11) together with the aid of the melted or softened thermoplastic or weldable thermoset resin. Compared to known joining methods using thermoset resins such as epoxy resins, the method allows joining the components (9, 10, 11) of the rotor blade (5) in a shorter time. Once the resin is melted by the resistance welding process, the resin is added in the necessary quantity and form to compensate for the gaps between the components (9, 10, 11). The entire rotor blade (5) can be welded in a single operation using a mold (30) with a rotating and closing system.

Description

Technical Field

[0001] This invention relates to a method for producing rotor blades for wind turbines. Background Technology

[0002] Modern wind turbine rotor blades are constructed from fiber-reinforced plastics. Rotor blades typically consist of airfoils with rounded leading edges and sharp trailing edges. The rotor blades are connected to the wind turbine hub at their roots. Furthermore, the rotor blades are connected to the hub via pitch bearings that allow for pitch movement. Long rotor blades withstand high winds. This type of rotor blade can have lengths exceeding 60 meters.

[0003] The rotor blades are hollow composite structures designed to be as lightweight and rigid as possible to maximize the mechanical energy transferred from the wind to the generator of the wind turbine. The most commonly used materials for manufacturing hollow structures are composite materials, in which reinforcing fibers are embedded within a polymer matrix. To date, the polymers used have typically been thermosetting plastics, which, due to their molecular nature, cannot be reshaped or remelted once cured to their final shape and are not recyclable. Summary of the Invention

[0004] One object of the present invention is to provide an improved method for producing rotor blades for wind turbines.

[0005] Accordingly, a method for producing rotor blades for wind turbines is provided. The method includes the steps of: a) providing at least two different components of the rotor blades, b) placing a resistive element between the components, c) placing a thermoplastic or weldable thermosetting resin between the components, d) energizing the resistive element such that the resistive element applies heat to the thermoplastic or weldable thermosetting resin to melt or soften it, and e) joining the components together by means of the melted or softened thermoplastic or weldable thermosetting resin.

[0006] Because of the use of resistive elements and thermoplastic or weldable thermosetting resins, components can be joined together very quickly and without the need for curing epoxy resin. Rotor blades can be divided into components or sub-modules and can be assembled on-site. This improves the transportability of rotor blades, as components can be transported more easily than whole rotor blades.

[0007] This method can also be used to join pre-assembled sub-modules of rotor blades together. For example, a rotor blade can be divided into components or sub-modules along its longitudinal direction, which can be joined on-site using this method. In this context, "sub-module" or "component" means that a rotor blade comprises multiple sub-modules or components that together form the rotor blade. The terms "component" and "sub-module" are used interchangeably. Providing a component includes manufacturing the component.

[0008] In this context, "resistive element" means an electrically conductive element capable of generating heat by means of an electric current applied to it. A resistive element can be part of a heating device. A heating device includes the resistive element, a voltage source or energy source, and wires for connecting the voltage source to the resistive element. To "place" a resistive element between components means that the resistive element is arranged as an external part between components that must be connected together. Alternatively, a resistive element can also be part of one of the components.

[0009] Thermoplastic resins, or thermosetting resins, are plastic polymer materials that become flexible or moldable at a certain elevated temperature and solidify upon cooling. Thermosetting polymers, resins, or plastics, commonly referred to as thermosets, are polymers that irreversibly harden by curing from a soft solid or viscous liquid prepolymer or resin. In contrast, weldable thermosetting resins are materials that can be softened, at least by the application of heat, allowing them to be used to weld components together. Preferably, thermoplastic or weldable thermosetting resins can be placed as external parts between components. Alternatively, thermoplastic or weldable thermosetting resins can be part of one or more components.

[0010] According to an embodiment, a resistive element is embedded in at least one of the components.

[0011] This means that the resistive element is part of at least one of the components. Alternatively, all components may have this type of resistive element. In this context, "embedded" may mean that the resistive element is placed on or under the surface of the component.

[0012] According to another embodiment, the resistive element has the form of a wire or a mesh.

[0013] Resistive elements can be made of metal. For example, a resistive element can be made of copper. Alternatively, a resistive element can be made of carbon fiber.

[0014] According to another embodiment, in step c), a thermoplastic or weldable thermosetting resin is placed between components in the form of resin strips.

[0015] Preferably, the resin strip is a continuous strip of a thermoplastic or weldable thermosetting resin. The resin strip can be made from pure resin. Alternatively, the resin strip can be fiber-reinforced but resin-rich.

[0016] According to another embodiment, the resin strip is wedge-shaped.

[0017] This allows for filling the gaps between components that must be joined. Specifically, resin strips are used to seal the gaps at the trailing edges of the rotor blades.

[0018] According to another embodiment, in step c), a thermoplastic or weldable thermosetting resin is placed between the components by forming a resin-rich surface layer on at least one of the components.

[0019] This means that a thermoplastic resin or a weldable thermosetting resin is a component of at least one part of the component. All components are capable of having that type of resin-rich surface layer. In this context, "resin-rich" means a fiber percentage of less than 90%, preferably less than 80%, more preferably less than 70%, more preferably less than 60%, more preferably less than 50%, more preferably less than 40%, more preferably less than 30%, more preferably less than 20%, and more preferably less than 10%.

[0020] According to another embodiment, after step e), the resistive element remains in the rotor blade.

[0021] This means that the resistive element is an integral part of the rotor blade. Therefore, the resistive element is not removed from the rotor blade after the connecting parts are assembled.

[0022] According to another embodiment, the resistive element includes resin-coated wires placed between components.

[0023] The conductor consists of a conductive core and a coating made of a thermoplastic or solderable thermosetting resin. The core can be made of metal or carbon fiber. When an electric current is applied to the core, the coating melts or softens to connect the components to each other.

[0024] According to another embodiment, during steps d) and e), external pressure is applied to the component.

[0025] External pressure presses the components together, causing the molten or softened thermoplastic or weldable thermosetting resin to join the components together.

[0026] According to another embodiment, external pressure is applied by means of a mold.

[0027] Specifically, external pressure is applied by means of a clamping system integrated into the mold.

[0028] Other possible embodiments or alternative solutions of the present invention also encompass combinations of features described above or below with respect to the embodiments (not explicitly mentioned herein). Those skilled in the art can also add single or individual aspects and features to the most basic form of the invention. Attached Figure Description

[0029] Further embodiments, features, and advantages of the invention will become apparent from the following description and dependent claims, taken in conjunction with the accompanying drawings, in which:

[0030] Figure 1 A perspective view of a wind turbine according to one embodiment is shown;

[0031] Figure 2 A perspective view of rotor blades according to one embodiment is shown;

[0032] Figure 3 It shows that according to Figure 2 An exploded view of the rotor blades;

[0033] Figure 4 It shows along Figure 2 A cross-sectional view of the wind turbine rotor blade at the intersection line IV-IV;

[0034] Figure 5 It shows that according to Figure 4 Detailed view V;

[0035] Figure 6 It was shown again according to Figure 4 Detailed view V;

[0036] Figure 7 It was shown again according to Figure 4 Detailed view V;

[0037] Figure 8 It shows that according to Figure 2 Exploded perspective detail of the rotor blades;

[0038] Figure 9 It shows that according to Figure 2 Another exploded perspective detail of the rotor blades;

[0039] Figure 10 A cross-sectional view of a resin-coated wire according to one embodiment is shown;

[0040] Figure 11 It shows that according to Figure 2 Another exploded perspective detail of the rotor blades;

[0041] Figure 12 It shows that according to Figure 2 Perspective detail of the rotor blades;

[0042] Figure 13 It shows that according to Figure 2 Another perspective detail of the rotor blades;

[0043] Figure 14 It shows that according to Figure 2 Another perspective detail of the rotor blades; and

[0044] Figure 15 It shows the production according to Figure 2 A block diagram of an embodiment of a method for rotor blades.

[0045] In the figures, unless otherwise indicated, the same reference numerals indicate the same or functionally equivalent elements. Detailed Implementation

[0046] Figure 1 A wind turbine 1 according to one embodiment is shown.

[0047] The term "wind turbine" now refers to a device that converts the kinetic energy of wind into rotational energy, which can then be converted back into electrical energy.

[0048] The wind turbine 1 includes a rotor 2 connected to a generator (not shown), which is located inside a nacelle 3. The nacelle 3 is located at the upper end of the tower 4 of the wind turbine 1.

[0049] The rotor 2 comprises three rotor blades 5. The rotor blades 5 are connected to the hub 6 of the wind turbine 1. This type of rotor 2 can have a diameter ranging from, for example, 30 to 160 meters or even larger. The rotor blades 5 withstand high wind loads. At the same time, the rotor blades 5 need to be lightweight. For these reasons, the rotor blades 5 in modern wind turbines 1 are made of fiber-reinforced composite materials. Typically, glass fiber in the form of unidirectional fiber layups is used.

[0050] Figure 2 A rotor blade 5 according to one embodiment is shown.

[0051] The rotor blade 5 includes an aerodynamically designed portion 7, shaped for optimal wind energy utilization, and a blade root 8 for connecting the rotor blade 5 to the hub 6. The rotor blade 5 includes a longitudinal direction L. The longitudinal direction L originates from the blade root 8 along the direction of the aerodynamically designed portion 7. However, the longitudinal direction L can also be oriented in the opposite direction.

[0052] These rotor blades 5 are hollow composite structures designed to be as lightweight and rigid as possible to maximize the mechanical energy transferred from wind to the generator. The most commonly used materials for manufacturing hollow structures are composite materials, in which reinforcing fibers are embedded within a polymer matrix. To date, the polymers used have typically been thermosetting plastics, which, due to their molecular nature, cannot be reshaped, joined, or remelted once cured to their final shape, and are not recyclable. These materials are also difficult to drill and have poor load-bearing capacity for conventional fastening elements, and mechanical fastening methods are impractical given the massive size of current rotor blades exceeding 60 meters in length and the requirement for low weight. Thus, the size of the rotor blades conflicts with the requirement for low weight.

[0053] Figure 3 An exploded view of rotor blade 5 is shown.

[0054] To date, the options for joining, bonding, or welding the hollow structure of the rotor blades 5 have been limited to either forming the entire structure in a technically complex one-shot molding process that requires specialized tooling, or joining the sub-parts by means of adhesive bonding processes that also use thermosetting materials—most commonly the blade half-shells 9, 10.

[0055] The first half-shell 9 of the rotor blade 5 is manufactured and cured parallel to the second half-shell 10. The two half-shells 9 and 10, along with additional structural elements 11 or more, such as shear webs or spar caps, are then joined together using the adhesive. This adhesive, and the resulting bonded lines, is a material that is non-recyclable, adds weight, and introduces potential failure points into the structure of the rotor blade 5. More generally, the half-shells 9 and 10, and the structural elements 11, can be referred to as “components” of the rotor blade 5.

[0056] The bonding process involves the application of an adhesive paste for multi-component systems requiring mixing and metering equipment and pressurized pumps for dispensing. Physical bonding of the bonding surfaces is achieved through a mold-closing operation involving the rotor blades 5. The adhesive is cured at elevated temperatures and then cooled to allow demolding of the rotor blades 5 and further processing. The splice line of the rotor blades 5 in the bonding area must then be reinforced both internally and externally with additional glass fiber fabric reinforcement and resin to limit structural weaknesses caused by the bonding line.

[0057] Since the rotor blades 5 are manufactured using either wet coating or vacuum-assisted casting in a large mold, the resulting dimensional tolerances do not allow for tight positioning of all components. This results in gaps at the joint lines that need to be filled with adhesive, further reducing the mechanical properties of the joint and increasing its weight. Therefore, improving this process is desirable.

[0058] Figure 4 It shows that according to Figure 2 A cross-sectional view of the improved rotor blade 5 with the intersection line IV-IV in the figure.

[0059] The rotor blade 5 has an outer blade housing 12 comprising a first half-housing 9 and a second half-housing 10, which are connected to each other at the leading edge 13 of the rotor blade 5. The half-housings 9 and 10 are also connected to each other at the trailing edge 14 of the rotor blade 5. The outer blade housing 12 may comprise a composite fiber material, particularly a glass fiber layup. This fiber material is impregnated with a polymeric material, particularly a thermoplastic or weldable thermosetting resin. The first half-housing 9 constitutes the suction side of the rotor blade 5. The second half-housing 10 constitutes the pressure side of the rotor blade 5.

[0060] The first half-shell 9 includes an inner surface 15, and the second half-shell 10 includes an inner surface 16, the inner surfaces 15 and 16 being arranged opposite to and facing each other. The inner space 17 of the rotor blade 5 is defined by the inner surfaces 15 and 16. The structural element 11 is located inside the inner space 17 extending from the inner surface 15 of the first half-shell 9 to the inner surface 16 of the second half-shell 10.

[0061] Structural element 11 extends in the longitudinal direction L. Structural element 11 preferably comprises a fiber composite material, specifically a glass fiber layup. The structural element 11 can be a shear web, a spar cap, etc. In particular, structural element 11 is a shear web comprising two flanges 18, 19 attached to the inner surfaces 15, 16, and a web 20 connecting the flanges 18, 19 to each other.

[0062] Figure 5 It shows that according to Figure 4 The exploded detail view of rotor blade 5 in the detailed diagram V.

[0063] The flange 18 of structural element 11 has a surface 21 facing the inner surface 15 of the first half-shell 9 of rotor blade 5. Rotor blade 5 includes a resistive element 22. The resistive element 22 may be part of structural element 11 or part of the first half-shell 9. The resistive element 22 may be embedded in surface 21 or inner surface 15. Figure 5 As can be seen, the resistive element 22 is embedded in the surface 21 of the structural element 11. However, Figure 5 Only an exemplary embodiment of rotor blade 5 is shown.

[0064] The resistive element 22 comprises a conductive material, such as metal or carbon fiber. Copper can be used as the material. For example, the resistive element 22 comprises resin-coated wires or a resin-coated mesh. The resistive element 22 has connecting portions 23 and 24. A voltage source 25 is connected to the connecting portions 23 and 24 via wires 26 and 27. The resistive element 22, connecting portions 23 and 24, voltage source 25, and wires 26 and 27 form a heating device 28 for the rotor blades 5. Wires 26 and 27 are optional. The resistive element 22 can also be powered by induction.

[0065] The rotor blade 5 can include several heating devices 28. For example, each flange 18, 19 of the structural element 11 and the trailing edge 14 have that type of heating device 28. Moreover, the leading edge 13 can have a heating device 28.

[0066] In addition, a solid resin strip 29 is provided. This resin strip 29 can be a resin-rich fibrous material. The resin strip 29 can also be pure resin. The resin is a thermoplastic or weldable thermosetting resin. The resistive element 22 can be embedded in the resin strip 29, or it can be a separate material placed between the half-shells 9 and 10. Components of the rotor blade 5 can be heated by means of a voltage applied to the resistive element 22, which generates heat through the Joule effect. The resin strip 29 preferably has a normal gap thickness of approximately 6 ± 2 mm.

[0067] Figure 6 It was shown again according to Figure 4 Detailed image V.

[0068] To connect the structural element 11 and the first half-shell 9 to each other, mechanical pressure p is applied to the structural element 11 and the first half-shell 9 by means of a mold 30 or a vacuum bag. The pressure p is preferably applied by means of the mold clamping system of the mold 30, as is done in known adhesive bonding.

[0069] The heating device 28 is then powered by applying current to the resistive element 22. In this way, the resistive element 22 applies heat H to the resin strip 29. The resin of the resin strip 29 is then sufficiently softened, chemically activated, or melted to form a continuous joint, and then cooled, thereby solidifying again into a homogeneous laminate. Pressure p is still applied during the heating of the resin strip 29.

[0070] Figure 7 It was shown again according to Figure 4 Detailed image V.

[0071] After cooling, the rotor blade 5 is demolded. The welding process is complete. The joint between structural element 11 and the first half-shell 9 is a homogeneous and continuous laminate. Wires 26 and 27 are removed from the connecting parts 23 and 24, and the rotor blade 5 can be further processed.

[0072] Figure 8 An exploded perspective view of rotor blade 5 is shown.

[0073] Specifically, Figure 8 The trailing edge 14 of the rotor blade 5 is shown. As previously mentioned, a resin strip 29 is placed between the first half-shell 9 and the second half-shell 10. A resistive element 22 (which, as previously mentioned, is part of the heating device 28 (not shown)) is embedded in the second half-shell 10, specifically in the inner surface 16 of the second half-shell 10. The resistive element 22 is filled into the inner surface 16. Alternatively, the resistive element 22 can be disposed at or within the first half-shell 9. Both half-shells 9 and 10 can have the resistive element 22.

[0074] The resin strip 29 has the required shape to fill the designed gap in the trailing edge 14. The resin strip 29 may be wedge-shaped. This allows for a better fit to the designed gap in the trailing edge 14 as required. The resistive element 22 may be a mesh or a carbon layer.

[0075] Figure 9 Another exploded perspective detail of rotor blade 5 is shown.

[0076] In this configuration, the resistive element 22 comprises resin-coated wires 31 and 32. The resistive element 22 is positioned between the half-shells 9 and 10. The resistive element 22 also provides resin for connecting the half-shells 9 and 10.

[0077] Figure 10 This is a cross-sectional view of conductor 31.

[0078] The conductor 31 includes a conductive core 33. The core 33 can be a metal conductor or a carbon wire. The core 33 can be made of copper. The core 33 is coated with a thermoplastic or solderable thermosetting resin 34. The core 33 serves as a resistive element.

[0079] Figure 11 Another exploded perspective detail of rotor blade 5 is shown.

[0080] In this configuration, the resistive element 22 is in the form of carbon or a metal mesh. The resistive element 22 is placed between the half-shells 9 and 10. Thermoplastic resin is infused into the laminate of the half-shells 9 and 10, thereby forming resin-rich layers 35 and 36 on the surface. These layers 35 and 36 can be melted or softened by energizing the resistive element 22 to connect the half-shells 9 and 10 to each other.

[0081] Figure 12 A perspective detail view of rotor blade 5 is shown.

[0082] After the resistive element 22 (not shown) and the resin strip 29 are placed between the half-shells 9 and 10, pressure p is applied to the trailing edge 14 by means of the mold 30 (not shown). The edges of both half-shells 9 and 10 are in contact with the resin strip 29.

[0083] Figure 13 Another perspective detail of rotor blade 5 is shown.

[0084] While applying pressure p, the resistive element 22 (not shown) is energized by applying current to it. The resistive element 22 applies heat H to the resin strip 29. The resin strip 29 melts or gains sufficient molecular mobility and / or reactivity to polymerize with the laminates of the half-shells 9 and 10.

[0085] Figure 14 Another perspective detail of rotor blade 5 is shown.

[0086] The heat-affected zone of rotor blade 5 is cooled and the resin adheres to itself. The external pressure p is removed, and rotor blade 5 is demolded. The homogeneous and monomatrix composite remains as a result.

[0087] Once the resin is melted by the resistance welding process, resin is added in the necessary amount and form to compensate for gaps between components such as the half-shells 9 and 10 and structural element 11. The entire rotor blade 5 can be welded in a single operation using a mold 30 with a rotation and closure system. Pressure p is applied by means of the mold 30, a system integrated into the mold 30, and / or external tooling.

[0088] The cycle time of the entire process will be an order of magnitude shorter than that of the standard coupling process, completing completely in a few seconds. There should be no additional materials added at any time, and the resulting rotor blades 5 will be as recyclable as the matrix material used, which, in the case of thermoplastic resins, may mean 100% recyclability of the resin.

[0089] Because no external paste material is needed for filling, and the resulting laminate will be a homogeneous structure, the gaps between the components of rotor blade 5 can be made smaller, thereby improving the mechanical properties of the joint.

[0090] The ability to form laminates with continuous microstructures in a very short cycle time could enable modular blade design, potentially eliminating the need for current full-size molds that completely disrupt current blade design and manufacturing processes. Cycle times could be reduced from approximately 30 hours per blade to well under 5 hours per blade. This also means that the current transportation challenges faced by large blades can be avoided through the field application of the aforementioned processes.

[0091] Figure 15 A block diagram of one embodiment of a method for producing rotor blade 5 is shown.

[0092] In step S1, at least two distinct components are provided, namely the half-shells 9 and 10 of the rotor blade 5 and / or structural element 11. In this context, "providing" may include manufacturing these components, for example, by means of a fibrous material coating process. Hereinafter, the half-shells 9 and 10, and the structural element 11, will be referred to as "components".

[0093] Step S2 of the method includes placing a resistive element 22 between components 9, 10, and 11. As previously mentioned, the resistive element 22 may be part of at least one of components 9, 10, and 11. In step S3, a thermoplastic or weldable thermosetting resin is placed between components 9, 10, and 11. This may be done in the form of a resin strip 29, as explained more previously.

[0094] In step S4, the resistive element 22 is energized, causing it to apply heat H to the thermoplastic or weldable thermosetting resin to melt or soften it. The resistive element 22 is energized using a heating device 28. Step S5 involves joining components 9, 10, and 11 together using the melted or softened thermoplastic or weldable thermosetting resin. In this way, the rotor blade 5 is formed. Furthermore, sub-modules of the rotor blade 5 can be formed in this manner. During steps S4 and S5, pressure p is applied to components 9, 10, and 11.

[0095] Although the invention has been described with reference to preferred embodiments, it will be apparent to those skilled in the art that modifications are possible in all embodiments.

Claims

1. A method for producing a rotor blade (5) of a wind turbine (1), the method comprising the following steps: a) providing (SI) at least two different components (9, 10, 11) of the rotor blade (5); b) placing (S2) an electric resistance element (22) between the components (9, 10, 11); c) placing (S3) a thermoplastic or weldable thermoset resin between the components (9, 10, 11); d) energizing (S4) the electric resistance element (22) such that it applies heat (H) to the thermoplastic or weldable thermoset resin to melt or soften it, and e) coupling (S5) the components (9, 10, 11) together with the aid of the melted or softened thermoplastic or weldable thermoset resin, wherein in step c) the thermoplastic or weldable thermoset resin is placed between the components (9, 10, 11) in the form of a resin strip (29), wherein the resin strip (29) is wedge-shaped, wherein in step c) the thermoplastic or weldable thermoset resin is placed between the components (9, 10, 11) by forming a resin-rich surface layer (35, 36) on at least one of the components (9, 10, 11), wherein the electric resistance element (22) comprises a resin-coated wire (31, 32) placed between the components (9, 10, 11).

2. The method of claim 1, wherein, The electric resistance element (22) is embedded in at least one of the components (9, 10, 11).

3. The method of claim 1 or 2, wherein, The electric resistance element (22) has the form of a wire or a mesh.

4. The method of claim 1 or 2, wherein, After step e) the electric resistance element (22) remains in the rotor blade (5).

5. The method of claim 1 or 2, wherein, During steps d) and e) an external pressure (p) is applied to the components (9, 10, 11).

6. The method of claim 5, wherein, The external pressure (p) is applied with the aid of a mold (30).

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