Spar cap assembly

Abstract

This invention describes a spar cap assembly (1) comprising a spar cap (20) and a spar cap extension (10) attached to the spar cap (20), wherein the spar cap extension (10) includes: a channel (100) formed along an outer surface (10F) of the spar cap extension (10) and extending between the outer ends (10R, 10T) of the spar cap extension (10); and an optical fiber cable (30) of an optical sensing system (3) contained in the channel (100). The invention further describes a method for manufacturing such a spar cap assembly (1).

Description

[Technical Field]

[0001] [None] [Previous Technology]

[0002] Wind turbine rotor blades are typically equipped with various sensors to monitor the loads acting on the rotor blades and the structural health of the blades. The long rotor blades of multi-gigawatt wind turbines can withstand very high loads, and therefore are typically equipped with numerous sensors, such as fiber optic cables with Bragg grating sensors for measuring relevant parameters like strain. Such fiber optic cables (containing any number of sensors) can be fixed to the surface of any rotor blade assembly that will undergo deformation under load. Alternatively, to avoid damaging the fiber optic cables, they can be embedded in assemblies (e.g., rotor blade shells, spars caps, etc.). Spars caps are prefabricated composite materials, typically positioned along the main spars of the rotor blade during the lamination stage. Therefore, if the spars cap is to support the fiber optic cable, the fiber optic cable must be attached to or embedded within the spars cap before the lamination process.

[0003] In one method, fiber optic cables (containing any number of sensors) are embedded between carbon fiber reinforced polymer (CFRP) plates during the manufacture of the spar cap. This can be done manually or automatically. For example, customized equipment can be used to unroll the CFRP plates and multiple fiber optic cables from a reel and arrange them in the desired order. The spar cap stack is then positioned on a mold stage and bagged in preparation for the resin injection step. After the spar cap is injected and cured, the embedded fiber optic cables are fixed in position. Embedded fiber optic cables are considered advantageous for several reasons: improved robustness of the overall sensor assembly; simplified handling of the sensor assembly during rotor blade stacking; reduced rotor blade manufacturing cycle time; accurate positioning of the fiber optic cables relative to the rotor blades; and protection of the fiber optic cables from damage caused by mishandling or unintentional trampling during manufacturing.

[0004] However, known techniques for embedding fiber optic cables into spar caps also have many problems. Because the fiber optic cables need to be placed between thin CFRP sheets, which are prone to slipping before being bonded with resin, it is difficult to properly position the cables and ensure they remain in their intended positions during the injection and curing steps. In the aforementioned automated embedding technique (where the cable and carbon fiber sheet are unrolled from the reel), the possibility of fiber optic cable damage increases.

[0005] Furthermore, because the fiber optic cable has a certain thickness, its presence between the thin CFRP sheets can inhibit resin flow during injection and cause air gaps to remain after the curing step. In addition, any unintentional movement or slippage of the relatively rigid cable during the injection and curing steps can cause wrinkles in the thin CFRP sheets, which may also lead to air gaps, wrinkles, etc. Such defects will significantly reduce the structural integrity of the spar cap manufactured in this way.

[0006] Therefore, one object of the present invention is to overcome the above-mentioned problems.

[0007] This objective is achieved by the claimed spar cap assembly, the claimed method of manufacturing such a spar cap assembly, and the claimed method of manufacturing a wind turbine rotor blade including such a spar cap assembly. [Summary of the Invention]

[0008] In the following description, without limiting the invention in any way, it can be considered that the claimed spar cap assembly is cut to size for use in a wind turbine rotor blade that internally contains a spar. A wind turbine rotor blade spar typically includes a shear web, a spar cap on the pressure side of the rotor blade, and another spar cap on the suction side. The spar cap of a long wind turbine rotor blade can be integrally formed (from root to tip) or can be composed of multiple parts.

[0009] According to the present invention, a spar cap assembly includes a spar cap having a substantially rectangular cross-sectional shape and at least one spar cap extension portion adhered to one of the long sides of the spar cap. The spar cap assembly may include two such spar cap extension portions, one on each long side of the spar cap. The spar cap extension portion includes a groove or channel formed along an outer surface and extending between the root end and the tip end of the spar cap extension portion. The fiber optic cable of the optical sensing system is entirely contained within the channel. An example of the claimed spar cap assembly may be configured on the pressure surface and / or suction surface of a rotor blade spar.

[0010] One advantage of the spar cap assembly of the present invention is that it provides a cost-effective method for incorporating one or more fiber optic cables into a wind turbine rotor blade. This is because the spar cap can be a simple, off-the-shelf composite material that can be produced using known molding techniques without any expensive modifications. Alternatively, the fiber optic cables of the spar cap assembly of the present invention can be incorporated into an additional or supplementary portion that is cheaper than the spar cap and included together with the spar cap in the rotor blade stack. Since the supplementary portion is located next to or on the spar cap, it does not need to contribute to the structural strength of the spar. The spar cap itself should be understood as comprising a layer of resin-bonded reinforcing fiber material (e.g., carbon fiber reinforced material (CFRM)) and can have a simple shape, such as a rectangular cross-section along its length and a small variation in width. The thickness of the spar cap can be greatest in the mid-span region of the rotor blade and can gradually decrease towards the outer end (root and / or tip) of the rotor blade.

[0011] The method of manufacturing such a wing spar cap assembly according to the present invention includes the following steps: forming a wing spar cap extension having dimensions based on the dimensions of a wing spar cap; forming a channel along an outer surface of the wing spar cap extension; disposing an optical fiber cable of an optical sensing system in the channel; sealing the optical fiber cable in the channel; and attaching the wing spar cap extension to the wing spar cap.

[0012] One advantage of the method of the present invention is that any number of optical fiber cables can be easily integrated into a spar cap structure without affecting the manufacturing of the spar cap itself; that is, the spar cap is not compromised by defects such as air gaps or other discontinuities. Therefore, the spar cap of the assembly of the present invention is more robust than the conventional spar cap with embedded optical fiber cables.

[0013] The method of manufacturing a wind turbine rotor blade according to the present invention includes assembling a layer of reinforcing material in a mold to form a pressure area layer and a suction area layer of the rotor blade. During the lamination stage, an example of the spar cap assembly of the present invention is incorporated into one or both sides of the rotor blade, located on either side of the shear web. For example, one example of the spar cap assembly of the present invention may be placed on the pressure side of the shear web, while another example of the spar cap assembly of the present invention may be placed on the suction side of the shear web. The spar cap assembly of the present invention improves efficiency and reduces the cost of the rotor blade manufacturing process because the embedded fiber optic cables and the spar cap are incorporated into the lamination in a single process step. The fiber optic cables contained in the channels in the side extensions of the spar cap assembly can be connected to the optical sensing system of a wind turbine equipped with one or more such rotor blades. During the operation of the wind turbine, data collected by the optical sensors and transmitted via the embedded fiber optic cables can be evaluated to, for example, estimate the loads acting on the individual rotor blades.

[0014] Particularly advantageous embodiments and features of the invention are given in the dependent claims, as disclosed in the description below. Features from different claim categories may be combined as appropriate to provide other embodiments not described herein.

[0015] The spar cap extension should be understood as a component attached to the surface of the spar cap, thereby increasing the relevant dimensions of the spar cap. In the following text, the spar cap extension may be considered to be attached to the side of the spar cap, because the resulting shape of the spar cap assembly (which is no thicker than the spar cap, but wider) can be relatively easily incorporated into the pressure or suction surface of the rotor blade stack. While various other configurations are possible, for example, the spar cap extension may be attached to the top or bottom surface of the spar cap, the spar cap extension may be considered below as a "side extension," that is, a component bonded to the long side of the spar cap. In the following text, the terms "spar cap extension," "side extension," and simply "extension" should be understood as synonyms and can be used interchangeably.

[0016] In the following description, without limiting the invention in any way, it can be considered that the dimensions of the side extension are based on the dimensions of the spar cap; that is, the length and height of the side extension can be understood as corresponding to the length and height of the spar cap. The side extension of the spar cap assembly of the present invention can be a simple component with a rectangular cross-section and straight edges. Similarly, the thickness of the side extension can decrease with increasing distance from the spar cap, so that the laterally tapered extension can be easily embedded in the rotor blade stack. As mentioned above, the thickness of the spar cap can decrease towards the root and tip of the rotor blade. Because the side extension is attached to the long side of the spar cap, the thickness of the side extension can similarly decrease towards the root and tip of the rotor blade, so that the thickness of the side extension does not exceed the thickness of the spar cap.

[0017] The “outer surface” of the added portion should be understood as the surface that forms a channel for accommodating the optical fiber cable. Of course, at some point during the manufacturing of the rotor blade, this “outer surface” may be hidden.

[0018] In a preferred embodiment of the present invention, the spar cap extension comprises any of the following: balsa wood, polyethylene terephthalate, structural foam material, etc., because the extension itself does not need to contribute to the structural strength of the wind turbine rotor blade. The extension can be attached to the spar cap by any suitable means (e.g., through adhesive bonding, resin bonding, mechanical bonding, etc.). In a particularly preferred embodiment of the present invention, the extension is attached to the spar cap by co-bonding or co-injection.

[0019] The fiber optic cable of the optical sensing system must be connected in some way to the data acquisition unit or "reader," which consists of various photonic components (e.g., optical power sources and photodetectors). Subsequently, the free end (cable end) of the fiber optic cable can be connected to the data acquisition unit of the optical sensing system using a suitable fiber optic connector placed at the end of the cable.

[0020] In one possible method, channels may be formed in the spar cap extension such that the free end of the fiber optic cable extends beyond the end of the spar cap extension by a certain distance. However, any such additional free length of cable would complicate the lamination process when manufacturing rotor blades. Therefore, in a particularly preferred embodiment of the invention, a recess is formed near the outer end (e.g., the root end) of the spar cap extension, the size of which corresponds to the size of a junction box that can be installed into the recess. The fiber optic junction box may have any shape (e.g., rectangular or circular) and has a cover that can be opened to access the internal cavity. The side of the junction box is typically equipped with at least one cable entry device. In the method of the invention, such a cable entry device is used to secure the outer end of the embedded fiber optic cable to the junction box. In a preferred embodiment of the invention, the free end of the fiber optic cable is secured to the cable entry device of the junction box before the junction box and the fiber optic cable are installed into the respective recesses and channels of the spar cap extension.

[0021] The fiber optic cable can be embedded into the spar cap extension in various ways. For example, in the preparation step, the channel can be lined with at least one layer of reinforcing fiber material, and the fiber optic cable can be disposed in the lined channel. During the subsequent resin injection and curing of the spar cap assembly, the fiber optic cable becomes permanently bonded to the channel. Alternatively, the fiber optic cable can be first embedded in a composite material strip and / or a plastic shell, and such a strip or shell can be cut to size for installation in the channel or a lined channel. Furthermore, during the subsequent resin injection and curing of the spar cap assembly, the strip or shell can be permanently bonded to the channel.

[0022] The junction box can be embedded in the recess in a similar manner (e.g., by lining the recess with one or more layers of reinforcing fiber material), so that the junction box becomes permanently bonded to the recess during the subsequent resin injection and curing steps.

[0023] After the steps of arranging the fiber optic cable in the channel, positioning the required number of junction boxes in the appropriate recesses, and fixing the side extension portion along one side of the wing cap, the wing cap assembly of the present invention is completed by covering at least the outer surface of the side extension portion with at least one layer of reinforcing fiber material (RFM). Of course, if desired, this RFM layer can extend to the entire wing cap and its side extension portion. Subsequently, after placing the assembly on a suitable molding table, bagging it, and connecting the vacuum bag to the resin inlet and outlet, a resin injection and curing step is performed to obtain a wing cap assembly at least partially encased in the resin-injected reinforcing fiber material layer.

[0024] Because the fiber optic cable is securely contained beneath a protective layer of reinforcing material, the complete spar cap assembly can be handled without special care. This hardened outer layer also covers the junction box. Therefore, in a subsequent stage, access to the interior of the junction box is made by cutting an appropriately sized opening through the hardened outer layer, allowing the junction box cover to be opened. The embedded fiber optic cable (as described above, secured to the junction box via a cable entry device) can be connected to the optical sensing system by any suitable means (e.g., via a splice connection). The step of connecting the embedded fiber optic cable to the optical sensing system can be completed before or after the resin injection of the rotor blade lamination. In the prior art, as described above, fiber optic cables are often damaged during the manufacturing stage due to accidental stepping and / or improper handling; the fiber optic cables are later damaged by impacts to the rotor blades. The method of the present invention cleverly overcomes these problems because the embedded fiber optic cable is protected from damage during the rotor blade manufacturing stage, and damage from rotor blade impacts is also avoided because the embedded fiber optic cable is much lower than the "skin" of the rotor blades.

[0025] In a particularly preferred embodiment of the invention, the fiber optic cable may include multiple sensors, such as Bragg gratings, Fabry-Perot interferometers, etc., at different locations along its length. In an exemplary embodiment, each long side of the spar cap has a spar cap extension, each extension containing an embedded fiber optic cable, and a plurality of spaced-apart Bragg gratings along the cable.

[0026] As an alternative to or in addition to sensors embedded in the fiber optic cable within the spar cap assembly, wind turbine rotor blades may include any number of sensors (located elsewhere on the rotor blade) that can be included in an optical sensing system. Additional sensors may be strain sensors, accelerometers, temperature sensors, etc., and load sensors are typically included within or on the rotor blade housing. Any of these sensors can be implemented as optical sensors, and it is known to use cables disposed inside the rotor blade to connect such optical sensors. Problems known in the art may arise from poor contact of the embedded load sensors due to irregularities in the rotor blade surface, contamination at the connection between the cable tip and the reader, etc. Therefore, in a preferred embodiment of the invention, the fiber optic cable of the spar cap assembly may include two or more separate segments to facilitate the placement of a branch junction box between these segments. Preferably, the branch junction box includes three cable entry devices and space for accommodating T-connections. In this way, these segments of the embedded fiber optic cable can be connected to form a "first straight line," and external fiber optic cables can also be connected. Embedded fiber optic cables can be "interrupted" by multiple such branch junction boxes, allowing a corresponding number of external fiber optic cables (leading to additional sensors) to be connected to the optical sensing system. As mentioned above, the branch junction boxes are initially concealed beneath a cured RFM protective layer, and an appropriately sized opening must be formed through that (typically translucent) cured outer layer to allow the junction box cover to be opened. Furthermore, the step of connecting external sensors between the segments of the embedded fiber optic cable can be completed before or after the resin injection for rotor blade lamination.

[0027] Other objects and features of the present invention will become more apparent from the following detailed description taken in conjunction with the accompanying drawings. However, it should be understood that the drawings are for illustrative purposes only and are not intended to limit the scope of the invention.

Implementation Method

[0030] Figure 1 shows a cross-section of a wind turbine rotor blade 2, illustrating how spars 20 and 21 are placed inside the rotor blade 2. The spars include a shear web 21 placed transversely to the chord plane, and spar caps 20 located at both ends of the shear web 21. The purpose of the spars 20 and 21 is to ensure that the rotor blade 2 can withstand high loads during wind turbine operation, and the spar caps 20 can be made of a robust material such as CFRP. As mentioned above, it is generally desirable to place sensors 2S at different locations within or on the rotor blade 2 to collect and evaluate valuable data throughout the service life of the rotor blade 2. The data collected by the sensors can provide information about the current loads acting on the rotor blade 2 and the structural health of the rotor blade 2. Because the spar caps 20 are typically prefabricated components, it is known that fiber optic cables can be embedded within the spar caps 20 to accommodate Bragg grating sensors or similar devices. However, as mentioned above, known solutions for manufacturing spar caps that embed fiber optic cables within CFRP layers are costly, and cavitation or other defects in the CFRP layers can weaken the spar cap 20, thereby shortening the lifespan of the rotor blades.

[0031] Figures 2 to 5 show various embodiments of the spar cap assembly 1 of the present invention, illustrating how the fiber optic cable 30 is embedded. These figures show the spar cap 20 in the form of a simple CFRP block 20, which has side spar cap extensions 10 on each long side. Each side extension 10 may be made of one or more suitable core materials (e.g., balsa wood, structural foam, polyethylene terephthalate, fiber-reinforced polymers, unreinforced polymers, ceramics, etc.). Here, the extension 10 is depicted as a simple rectangle, but it should be understood that other shapes are possible, such as a triangle that tapers with increasing distance from the spar cap.

[0032] A channel 100 of appropriate shape is formed in the side-added portion 10 to accommodate the fiber optic cable; recesses are formed at different locations to accommodate the required number of junction boxes.

[0033] In each case, the spar cap assembly 1 is manufactured by arranging the spar cap 20 and any additional portion 10 side-by-side. Fiberglass mats may be placed on one or more outer surfaces of the assembly as needed, and then the assembly is placed in a vacuum bag. In subsequent steps, each side additional portion is securely bonded to the spar cap using appropriate techniques (e.g., resin injection, co-curing (the side additional portion and the spar cap are held together by an adhesive film and cured simultaneously), co-bonding (the uncured or partially cured side additional portion is laid on the cured spar cap, or vice versa, and the two components are bonded by an adhesive)). In one method, when bonded to the spar cap, the spar cap additional portion is "empty": that is, its channels are empty, and the fiber optic cable and junction box are installed and sealed in a later stage. In another method, the fiber optic cable and junction box are installed and sealed in the channel of the wing spar cap extension before the wing spar cap extension is bonded to the wing spar cap, so that the preparation of the wing spar cap assembly of the present invention requires fewer process steps.

[0034] These figures also show the channels 100 formed in the outer surface 10F of each added portion 10 and the optical fiber cables 30 embedded in each channel 100. An enlarged view of the embedded optical fiber cables 30 is shown on the right side of each figure.

[0035] In Figure 2, the fiber optic cable 30 is placed in the channel 100, and the glass fiber layer 15 is placed above the upper surface 10F of the extension portion 10 to seal the cable 30 in the channel 100.

[0036] In Figure 3, a first fiberglass layer 13 is arranged to line the channel 100. Then, the fiber optic cable 30 is placed into the lined channel 100. Next, a second fiberglass layer 15 is placed on top of the extension 10 to cover the outer surface 10F and the channel 100 with the fiber optic cable 30. This figure shows that the side extension can be formed of balsa wood.

[0037] For the embodiment shown in FIG4, a composite strip 14 is manufactured in a preliminary step to embed the fiber optic cable 30 into the glass fiber sheath 15. In a subsequent step, the composite strip 14 (which is preferably flexible, at least as much as the spar cap) is placed in the channel 100, and then the glass fiber layer 15 is placed over the outer surface 10F to cover the channel 100 and the composite strip 14. This figure illustrates that the side extension can be formed from a suitable polymer.

[0038] In the embodiment shown in FIG5, the fiber optic cable 30 is encased in a plastic housing 16 in the initial step. The plastic housing 16 may have the same length as the channel 100, but its width and height may be smaller than the channel 100, such that the channel 100 can be lined with a first glass fiber layer 13 before the housing 16 and its embedded fiber optic cable 30 are placed into the channel 100. Then, a second glass fiber layer 15 is placed above the outer surface 10F of the side extension portion 10.

[0039] In each case, the resin injection and curing steps are then performed, and after curing is completed, the wing cap assembly 1 can be incorporated into the stacking process of the wind turbine rotor blade mold in a commonly used manner.

[0040] Figures 6 and 7 show another configuration of the spar cap assembly 1 of the present invention, namely, with the embedded fiber optic cable 30 connected to the acquisition device 33. For this purpose, a junction box 31 is embedded in the extension portion 10, for example, at the inner end 10R of the spar cap assembly 1. A cable entry device 310 on one side of the junction box 31 is connected to the fiber optic cable 30 (before or after the cable 30 is placed into the channel 100). In Figure 6, a short connection length 30C of fiber optic cable is stored in the junction box 31 and connected to the cable entry device 310. In subsequent steps, this connection length 30C may, for example, be overlapped to the fiber optic cable from the acquisition device.

[0041] Before the final injection step illustrated in Figures 2-5 above, the cover 311 is placed on the junction box 31, and then the junction box is sealed with a suitable sealant or adhesive. Then, the final injection step is performed to complete the spar cap assembly 1.

[0042] After the rotor blades having one or more embedded layers 25 of such spar cap assembly 1 are cured, the fiber optic cable 30 can be connected to the acquisition device 33 or "interrogator" as shown in FIG. 7. For this purpose, the junction box 31 is exposed by forming appropriately sized holes in the cured fiberglass layers (e.g., by drilling or cutting), the cover 311 of the junction box is exposed, and then the cover 311 of the junction box can be opened to access the fiber optic cable of connection length 30C, which can then be connected to the acquisition device 33. For example, the connection length 30C can be attached to the external length 33C through a cable introduction device disposed in the cover 311 of the junction box, and then the box 31 can be closed again.

[0043] Figure 8 shows a schematic plan view of an embodiment of the spar cap assembly 1 of the present invention, showing two embedded fiber optic cables 30 next to the CFRP spar 20. Each fiber optic cable is equipped with several sensors 3S that can be read in a reflective manner, such as fiber Bragg gratings, Fabry-Perot interferometers, etc. This figure also shows the embedded junction box 31 at the inner end 10R of the spar cap assembly 1. After connecting the embedded fiber optic cables 30 to the acquisition device 33 as described above, the sensors 3S of each fiber optic cable 30 can be read in a reflective manner.

[0044] Figure 9 shows another detailed illustration of the embodiment of Figure 8, which is configured to allow transmissive reading of the sensor 3S, such as a long-period grating or a power-based sensor. For this purpose, each of the two fiber optic cables 30 terminates in an embedded junction box 31 located at the outer end 10T of the extension portion 10, and another fiber optic cable with a lateral length of 30T is connected between the two fiber optic cables as illustrated in Figure 7. After connecting the embedded fiber optic cable 30 to the acquisition device 33, the sensor 3S can be read transmissively.

[0045] Figure 10 shows another detailed illustration of the embodiment of Figure 8. Here, in addition to the junction box 31 at the outer ends 10R, 10T of the additional portion 10, several branch junction boxes 31B are embedded at different locations along the spar cap assembly 1. These branch junction boxes 31B allow various other sensors 2S (e.g., accelerometers, temperature sensors, strain sensors, etc.) configured in other locations in the rotor blade 2 (e.g., in the rotor blade housing, in the shear web, etc.) to be connected to the optical sensing system 3 via external cable portions 31C and embedded fiber optic cables 30. By providing cable entry devices and appropriate connection sections 31C on several sides of the branch junction boxes 31B, each additional sensor 2S can be read by the optical sensing system 3 as described above.

[0046] As shown in FIG9, by providing junction boxes at the outer end 10T of the wing spar cap assembly 1 and connecting these junction boxes through fiber optic cables with a lateral length of 10T, the embodiment of FIG10 can be applied to sensors that must be read in a transmission manner.

[0047] Figure 11 shows a perspective view of the conventional spar cap 7, in which fiber optic cables 71 are embedded between CFRP plates 70. As described in the introduction, the fiber optic cables 71 can be manually positioned between the CFRP layers 70, or a spar cap stack containing the fiber optic cables 71 can be formed using a special tool. This conventional spar cap 7 reliably protects the fiber optic cables 71 from damage. However, the performance of the spar cap 7 itself is worse than that of a "normal" spar cap (a solidified CFRP plate without any embedded elements) because the fiber optic cables 71 interrupt resin flow during the injection step, resulting in an air gap 7G that adversely affects the structural strength of the spar cap 7.

[0048] Although the present invention has been disclosed by way of preferred embodiments and variations thereof, it will be understood that various additional modifications and alterations may be made thereto without departing from the scope of the invention. For example, the spar cap described above is typically an integral assembly having a simple rectangular shape and a central axis disposed above the shear web, while the spar cap assembly of the present invention may include a side extension bonded to the side of the spar cap. However, in an alternative approach, it is preferable to provide two parallel spar caps, with a side extension "sandwiched" between them and bonded to the side of each spar cap.

[0049] For clarity, it should be understood that the use of "a" or "an" throughout this application does not exclude a plurality, and "including" does not exclude other steps or elements. [Simplified Explanation of the Diagram]

[0028] Figure 1 shows a cross-section of a wind turbine rotor blade; Figures 2 to 10 show various embodiments of the wing spar cap assembly of the present invention; Figure 11 shows a conventional wing spar cap.

[0029] In these drawings, the same component symbols always refer to the same object. The objects in these drawings are not necessarily drawn to scale.

Claims

1. A wing spar cap assembly (1), comprising: One-winged cap (20); and a wing cap extension (10) attached to the wing cap (20), wherein the wing cap extension (10) includes: a channel (100) formed along an outer surface (10F) of the side extension (10) and extending between the outer ends (10R, 10T) of the wing cap extension (10); and an optical fiber cable (30) of an optical sensing system (3) contained in the channel (100).

2. The wing cap assembly as claimed in claim 1, wherein the additional portion (10) of the wing cap is attached to one side of the wing cap (20).

3. The wing cap assembly as claimed in claim 1 or 2, wherein the additional portion (10) of the wing cap is attached to the wing cap (20) by any one of an adhesive bonding, a resin bonding, a mechanical bonding and / or by any one of a co-curing step and a co-bonding step.

4. The wing cap assembly as claimed in claim 1 or 2, wherein the wing cap extension (10) includes a recess in a junction box (31, 31B) for receiving the optical sensing system (3).

5. The spar cap assembly of claim 1 or 2, wherein the fiber optic cable (30) comprises two or more segments, wherein the spar cap assembly (1) further comprises a branch junction box (32) disposed in a recess between consecutive segments of the fiber optic cable (30).

6. The spar cap assembly of request item 1 or 2, including a plurality of sensors (3S) configured along the fiber optic cable (30).

7. A method for manufacturing a spar cap assembly (1) as claimed in any one of claims 1 to 6, the method comprising: A wing spar cap extension portion (10) having dimensions (20L, 20H) based on the dimensions of a wing spar cap (20) is formed; a channel (100) is formed along an outer surface (10F) of the wing spar cap extension portion (10); an optical fiber cable (30) of an optical sensing system (3) is disposed in the channel (100); the optical fiber cable (30) is sealed in the channel (100); and the wing spar cap extension portion (10) is attached to the wing spar cap (20).

8. The method of claim 7, including a preparatory step of lining the channel (100) with at least one layer of reinforcing fiber material (13).

9. The method of claim 7 or 8 includes a preparation step of embedding the fiber optic cable (30) in a composite material strip (14) and / or a plastic housing (16), the composite material strip (14) and / or the plastic housing (16) being cut to size for installation in the channel (100).

10. The method of claim 7, comprising the steps of: providing a junction box (31, 31B) having a cable entry device (310) in one side wall; connecting the fiber optic cable (30) to the junction box (31) through the cable entry device (310); forming a recess in the spar cap extension portion (10); and disposing the junction box (31) in the recess.

11. The method of claim 7, comprising the steps of: covering at least the outer surface (10F) of the wing cap extension (10) with at least one glass fiber layer (15); and performing resin injection and curing to harden the glass fiber layer (15).

12. The method of claim 7 includes the step of forming an opening in the fiberglass layer (15) to expose a junction box (31).

13. A method of manufacturing a wind turbine rotor blade (2) comprising the steps of: assembling a plurality of reinforcing material layers to form a shell volume layer (25); and configuring a spar cap assembly (1) as claimed in any one of claims 1 to 6 in the shell volume layer (25).

14. The method of claim 13 includes the step of connecting an embedded fiber optic cable (30) to an optical sensing system (3) of the wind turbine rotor blade (2).

15. The method of claim 13 or 14, comprising the step of connecting a sensor (2S) located at another location in the rotor blade (2) to the optical sensing system (3) via a branch junction box (31B) between segments of an embedded fiber optic cable (30) in one of the wing cap assemblies (1).

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