Method for repairing a subsurface defect of a wind turbine rotor blade, wind turbine rotor blade and wind turbine

Abstract

The invention concerns a method for repairing a sub surface defect (144) of a wind turbine rotor blade (110), wherein - the wind turbine rotor blade (110) comprises a sh ear web (140) which connects two spar caps (136) to each other, and - the defect (144) is located in a joint (143) between the shear web (140) and one of the spar caps (136), the method comprising: - drilling a first pair of bore holes (150), wherein one bore hole (150) is arranged in the suction-side half she ll (132) and the other one is arranged in the pressure-side half shell (132), both bore holes (150) being arranged in the vicinity of the spar caps (136), - inserting a first reinforcing element (152) into the first pair of bore holes (150), and - fixedly connecting the half shells (132) by means of the first reinforcing element (152) such that a clamping force (F) acts on the two half shells (132) to at least partially bridge the defect (144). The invention also addresses a wind turbine rotor b lade (110) and a wind turbine (110).

Description

[0001] P2024,0023 WO N / PA 1185 WO April15,2025 -1 - Description Method forrepairing a subsurface defectofa wind turbinerotor blade, wind turbine rotor blade and wind turb ineThe invention relates to a method for repairing a s ubsurfacedefect of a wind turbine rotor blade. The invention alsorelates to a wind turbine rotor blade and wind turb ine withsuch a wind turbine rotorblade.Wind turbines with wind turbine rotor blades are wi dely knownfrom the state of the art and are used to convert w ind energyinto electrical energy. Wind turbine rotor blades a re usuallymanufactured in an aerodynamic shell design and com priseseveral components made of fiber reinforced laminat e, such asan aerodynamic shell. Typically, two half-shells ar e producedwhich are placed on top of each other after their r espectivemanufacture and bonded together to produce the roto r blade.The half-shells themselves may be segmented for man ufacturinga so-called split-blade orsegmented blade.Typically, the half-shell of the wind turbine rotor bladecomprises one or more spar caps, which are intercon nectedinside the rotorblade byone ormore (shear)webs running inthe longitudinal direction of the rotor blade. Thes e sparcaps and shear webs, in particular, absorb forces b etween thehalf-shells,especiallyduring operation,and thus stabilizethe aerodynamic shape of the rotor blade during ope ration.Under normal operating conditions, the wind turbine rotorblade is subjected to loads in the flapwise and edg ewisedirection as well as to torsional loads which are m ainlyaerodynamic and inertia loads. These loads cause de formations P2024,0023 WO N / PA 1185 WO April15,2025 -2 -in the half shells and at interfaces between the co mponentsof the wind turbine rotor blade, e.g. between a spa r cap anda shear web. Such deformations may induce peeling a nd shearstresseswhich lead to subsurface defects,e.g.in adhesive jointsofthe componentsofthe wind turbine rotor blade.Such deformations may reduce an overall strength of the windturbine rotor blade and / or compromise the aerodynam icefficiency of the blade since the designed construc tion ofthe blade profile is no longer maintained. But also due toother failures, the wind turbine blade may have sub surfacedefects, which negatively impact the lifetime and e fficiencyofthe blade.Such defects are often difficult or even impossible torepair,so itisnotuncommon fora rotorblade to have to bereplaced. However, there is typically a long period of timebetween a defect being detected and its repair or t hereplacementofthe whole wind turbine rotorblade.One task underlying the invention is to provide a c oncept torepaira subsurface defectofa wind turbine rotor blade reliablyand efficiently.This object is solved by the independent claim. Adv antageousembodimentsare given in the sub-claims. According to a firstaspecta method forrepairing a subsurface defectofa wind turbine rotorblade is disclosed.The wind turbine rotor blade comprises a pressure-s ide halfshell and a suction-side half shell, which are firm ly bondedto each other. Each half shell comprises a spar cap . The windturbine rotor blade comprises at least one shear we b whichconnects the two spar caps to each other. The defec t is P2024,0023 WO N / PA 1185 WO April15,2025 -3 -located in a joint between the shear web and one of the sparcaps.The method comprisesthe following steps: -drilling a firstpairofbore holesclose to the defect,wherein one bore hole is arranged in the suction-si de halfshell and the other one is arranged in the pressure -side halfshell, both bore holes being aligned with one anoth er andbeing arranged in the vicinityofthe sparcaps,- inserting a first reinforcing element into the fi rst pairofbore holes,and- fixedly connecting the half shells by means of th e firstreinforcing element such that a clamping force acts on thetwo half shells to at least partially bridge the de fect.The described method provides a solution to structu rallystrengthen the area around the defected joint betwe en thespar cap and the shear web by using a reinforcement element.The reinforcement element is configured to structur allybridge the defect for a transition period (typicall y severalmonths) until a repair of the defect takes place or the rotorblade is replaced. By means of the reinforcement el ement aclamping force is applied such, that a flow of forc e exertedon the rotor blade is guided through the reinforcem entelement to bridge the defect, i.e. no or only littl e forceruns through the defect. Thus, a load by-pass is es tablished.In other words, in the installed and / or operated st ate of thewind turbine, at least an essential portion of a lo ad whichwould act on the defect (and possibly would cause a defectgrowth) can be compensated by the reinforcement ele ment.Thus,the defected area isatleastfunctionalfor thetransition period and / or further degeneration is at leaststopped orreduced.During thistransition period, the rotor blade can continue to be used and the wind turbine can still be operated,atleastin partialload operation. P2024,0023 WO N / PA 1185 WO April15,2025 -4 - Forinstalling the reinforcementelement,the pair ofboreholes is drilled. Here, the bore holes are not dril led intothe sparcap and the shearweb,butclose to these components.The defect means a structural defect, in particular a poorquality of a bonding line (adhesive line) in the jo intbetween a shear web and a spar cap. Such defect whi ch is notrepaired could lead to a complete failure, e.g. bre ak of theblade.There are areas of the wind turbine rotor blade wit h no orlimited access to repair such bonding lines with ex tralamination or bonding paste injection. Especially i n suchregions the inventive method provides the above fun ctions andadvantages, since the weak adhesive joint is mechan icallyreinforced.According to an embodiment, the defect is located i n anoutboard region of the wind turbine rotor blade, wh ere theoutboard region accounts for 30 % of the total leng th of thewind turbine rotor blade starting from a rotor blad e tip. Insuch regions, a repair typically is not possible an ymore dueto limited space and access to the defected area. T he methodaccording to the invention is particularly advantag eous inthisoutboard region.According to an embodiment, the method comprises th e furthersteps:- drilling a second pair of bore holes, wherein one bore holeofthe second pairisarranged in the suction-side halfshell and the otherone isarranged in the pressure-side half P2024,0023 WO N / PA 1185 WO April15,2025 -5 -shell, both bore holes of the second pair being ali gned withone another and being arranged in the vicinity of t he sparcap,- inserting a second reinforcing element into the sec ond pairofbore holes,and- fixedly connecting the half shells by means of the secondreinforcing element such that a clamping force acts on thetwo half shells to at least partially bridge the de fect.The second reinforcing element and its installation areessentially the same as the first reinforcing eleme nt. Byproviding a second reinforcing element structurally bridgingthe defect is improved. In particular, the load-byp ass isestablished now via two reinforcing elements, whichcontributesto an improved structure.According to an embodiment, the first and / or secondreinforcing element is made from a non-conductive m aterial.Thus, problems arising from lightning strokes are e ffectivelyavoided.According to an embodiment, the first and / or secondreinforcing element is a string or a bolt, in parti cular ascrew bolt. Thus, an easy-to-install solution is pr ovided.According to an embodiment,the firstpairofbore holesandthe second pair of bore holes are arranged at oppos ite sidesof the shear web. This contributes to a particularl y goodforce flow distribution via the reinforcing element s and thusto a veryhomogenousbridging ofthe defect. According to an embodiment,a firstcoverplate is arranged on the surface ofthe pressure-side halfshelland a second P2024,0023 WO N / PA 1185 WO April15,2025 -6 -cover plate is arranged on the surface of the sucti on-sidehalf shell, the cover plates overlapping the respec tive sparcap in a top view of the half shell. In particular, in aviewing direction thatrunscentrallythrough both cover plates,the defectiscovered byboth ofthe cover plates.This contributes to a very good distribution of loa ds forbridging the defect.According to an embodiment, the first cover plate a nd thesecond coverplate are clamped onto the surface of therespective half shells by means of the first and se condreinforcement elements. The overlap of the cover pl ates atboth sides of the respective spar cap is dimensione d such,that the reinforcing elements run through bore hole s in thefirst and second cover plates. The bore holes in th e coverplates can be pre-drilled at pre-determined positio ns and thecover plates can be used as a template for the dril lingpositions on the rotor blade shells. This contribut es to theabove functionsand advantages.According to an embodiment, the first and / or second coverplate is glued to the surface of the respective hal f shell.This enables a fixed and predetermined position for the coverplates, in particular prior to installing the one o r morereinforcing elements. In this embodiment as well, t he overlapof the cover plates at both sides of the respective spar capisdimensioned such,thatthe reinforcing elements runthrough bore holes in the first and second cover pl ates. Thedrilling ofthe bore holesin the coverplatescan beexecuted in the same step as drilling the bore hole s in therotorblade shell. P2024,0023 WO N / PA 1185 WO April15,2025 -7 -According to an embodiment, the first and / or second coverplate has a chamfer at one or more edges of the cov er plate.This avoids stiffness peaks or load peeks in the tr ansitionregion between the cover plates and the surrounding shellstructure.According to an embodiment, the first and / or second coverplate is made of a composite material, in particula r glassfiber composite material. The material properties o f thecover plates are the same as the material propertie s of therotor blade shell. Additionally, the cover plates a re notprone to lightning strikes and thus there is no nee d toconnect them to the lightning protection system. Th iscontributesto the above functionsand advantages. According to a second aspect,a wind turbine rotor blade isdisclosed. The wind turbine rotor blade comprises a pressure-side half shell and a suction-side half shell, whic h arefirmly bonded to each other, each half shell integr allycomprising a spar cap. The wind turbine rotor blade comprisesatleastone shearweb which connectsthe two spar capsto each other.The wind turbine rotorblade comprises a defect,the defect being located in a joint between the she ar web andone of the spar caps. A first pair of bore holes is providedclose to the defect, wherein one bore hole of the f irst pairisarranged in the suction-side halfshelland the otheroneis arranged in the pressure-side half shell, both b ore holesare aligned with one another and are arranged in th e vicinityof the spar cap. A first reinforcing element is ins erted intothe first pair of bore holes and fixedly connects t he halfshellsin such a waythata clamping force actson the twohalf shells to at least partially bridge the defect . P2024,0023 WO N / PA 1185 WO April15,2025 -8 -The wind turbine rotor blade enables the above-ment ionedfunctions and advantages. The above-described embod imentswith respectto the firstaspectanalogouslyapply to the wind turbine rotorblade.According to a third aspect, a wind turbine is disc losed. Thewind turbine comprises a wind turbine rotor blade a ccordingto the second aspect.The wind turbine enables the above-mentioned functi ons andadvantages. The above-described embodiments with re spect tothe first and second aspect analogously apply to th e windturbine rotorblade.Further advantages, features and functions, which a reexplained in connection with the figures, are given in thefollowing exemplary embodiment of the invention. Id entical,similar or similarly acting elements are provided w ith thesame reference signsin the figures. In the figures: Figure 1 showsa schematicview ofa wind turbine, Figure 2 showsa schematicview ofa rotorblade, Figure 3 showsa schematicview ofa cross-section ofthe wind turbine rotorblade,Figure 4 shows a schematic cross-section of the win d turbinerotor blade according to an embodiment of the inven tion, P2024,0023 WO N / PA 1185 WO April15,2025 -9 - Figure 5 showsa schematicview ofthe rotorblade fromfigure 2 according to an embodiment of the inventio nFigure 6 shows a schematic cross-section of the win d turbinerotor blade according to an embodiment of the inven tion, andFigure 7 shows a schematic flow chart of a method f orrepairing a rotor blade shell according to an embod iment ofthe invention.Figure 1 shows a schematic view of a wind turbine 1 00, whichcomprises a tower 102. The tower 102 is fixed to th e groundby means of a foundation 104. A nacelle 106 is rota tablymounted at one end of the tower 102, opposite to th e ground.The nacelle 106, for example, comprises a generator which iscoupled to a rotor 108 via a rotor shaft (not shown ). Therotor 108 comprises one or more (wind turbine) roto r blades110,which are arranged on a rotorhub 112. During operation,the rotor108 issetin rotation byan airflow, for example wind. This rotational movement istransmitted to the generator via the rotor shaft an d, ifnecessary, a gearbox. The generator converts the me chanicalenergyofthe rotor108 into electricalenergy.Figure 2 shows an exemplary rotor blade 110. The ro tor blade110 has the shape of a conventional rotor blade and has arotor blade root area 114 facing the rotor hub 112. The rotorblade root area 114 typically has an essentially ci rcularcross-section. The rotor blade root area 114 is fol lowed by atransition area 116 and a profile area 118 of the r otor blade110.The rotorblade 110 hasa pressure side shell 122 and an opposite suction side shell124 extending along a P2024,0023 WO N / PA 1185 WO April15,2025 -10 -longitudinal direction 120 (also main extension dir ection).The rotorblade 110 isessentiallyhollow inside.In the rotor blade root area 114 a rotor blade root end 126with a flange connection 128 isprovided,bymeans ofwhichthe rotor blade 110 can be mechanically connected t o a pitchbearing oran extender.The rotorblade 110 can be a segmented rotorblade.Figure 3 shows a schematic cross-section profile 13 8 locatedin an outboard region 146(see figure 2) of the wind turbinerotor blade 110 running traverse to the longitudina ldirection 120.The rotorblade 110 hasa shell130 comprisingtwo half-shells, wherein a pressure side half-shell 122 and asuction side half-shell 124. The two half-shells 12 2, 124 arefirmly connected to each other along the longitudin al axis atopposite connecting surfaces located at the leading edge 134and trailing edge 135. Each half-shell 122, 124 has at leastone spar cap 136 embedded in the shell-structure. A spar cap136 can also be generally named “main laminate” and carriesmain loads during operation of the rotor blade 110. The rotorblade 110 furthercomprisesatleastone shearweb 140connecting the spar caps 136 within the rotor blade 110.In the shown embodiment,the rotorblade comprises one shearweb 140, which is adhesively bonded, e.g. via one o r morebonding lines, with its opposite ends 142 to the sp ar caps136. In such joint 143 between the shear web 140 an d a sparcap 136 a subsurface defect 144 can occur or be pre sent evenduring initial manufacturing. The defect 144 is, in thepresent example, a poor-quality bonding line betwee n theshearweb 140 and the sparcap 136. P2024,0023 WO N / PA 1185 WO April15,2025 -11 -As mentioned above, especially in areas where there is no oronly little access for service workers to repair su ch defect144, e.g. with extra lamination or bonding paste in jection.Such areas typically are located in an outboard reg ion 146 ofthe wind turbine rotor blade 11. Here, the outboard region146 accounts for 30 % of the total length of the wi nd turbinerotor blade 110 starting from a rotor blade tip 148 (seefigure 2). In the following,methodsforrepairing the defect 144 aredetailed, wherein the chemical union between the sp ar cap 136and the shear web 140 is reinforced by a mechanicalmeasurement, at least to structurally bridge the de fect 144until a final repair or replacement of the wind tur bine rotorblade 110 takesplace. In a firstembodimentofthe invention,in a first step S1,afirst pair of bore holes 150 is drilled close to th e defect140, wherein one bore hole 150 is arranged in the s uction-side halfshell124 and the otherbore hole 150 is arrangedin the pressure-side half shell 122, both bore hole s 150being aligned with one another and being arranged i n thevicinity of the spar caps 136. The bore holes 150 a re notdrilled into the spar caps 136 or into the shear we b 140.In a second step S2, a first reinforcing element 15 2 isinserted into the first pair of bore holes 150. The firstreinforcing element 152 is a screw bolt made of a n on-conductive material.In a third step S3, the half-shells 122, 124 are fi xedlyconnected together. In this regard it is noted that thereinforcing element 152, i.e. the bolt, is threaded and P2024,0023 WO N / PA 1185 WO April15,2025 -12 -comprises nuts for fixation. The bolt is fixed such that aclamping force F acts on the two half shells 122, 1 24. Inother words, a pressing force is exerted to push th e halfshells 122, 124 together. Thus, the defect 144 is a t leastpartiallybridged.Preferred, as is indicated in figure 4 by dotted li nes, asecond pair of bore holes 154 is drilled into the h alf shells122, 124 similar to the first pair of bore holes 15 0. Again,the bore holes 154 of the second pair being aligned with oneanother and being arranged in the vicinity of the s par cap136. The first pair of bore holes 150 and the secon d pair ofbore holes 154 are arranged at opposite sides of th e shearweb 136, with respect to a direction from the leadi ng edge134 to the trailing edge 135.A second reinforcing element 156 (dotted lines), wh ich isalso a screw bolt and made of a non-conductive mate rial, isinserted into the second pairofbore holes154.Likewise, in a subsequent step, both half shells 12 2, 124 arefixedly connected together, e.g. by the use of nuts . Thefixation is also made such to produce a pressing fo rce actingon the two half shells 122, 124 by the second reinf orcingelement 156. Thus, by both reinforcing elements 152 , 156contribute to the clamping force F acting on the ha lf shells122, 124. Thus, the defect 144 is partially bridged morehomogeneously.Optionally, shims or washers, preferably also non-c onductive,can be used to fix the first reinforcing element 15 2 and / orthe second reinforcing element 156 in order to opti mize theforce transmission into the halfshells122,124. P2024,0023 WO N / PA 1185 WO April15,2025 -13 -With regard to figure 5 another embodiment of the i nventionis shown. Figure 5 shows a rotor blade having a sub -surfacedefect 144 and a first cover plate 158 placed on th e surfaceofthe pressure side halfshell122.Figure 6 shows the embodiment of figure 5 in more d etail.Essentially, the above description with regard to f igure 4similarly applies. In difference to the above embod iment, afirst cover plate 158 is arranged on the surface 16 0 of thepressure-side half shell 122 and a second cover pla te 162 isarranged on the surface 164 of the suction-side hal f shell124. The cover plates 158, 162 overlap both spar ca ps 136,which spar caps 136 are connected via the shear web 140. Thecover plate 158 covers the defect 144 in a top view of one ofthe two half shells 122, 124, with the direction of viewrunning through both cover plates 158, 162. The cov er plates158, 162 are made of glass fiber composite material .The first cover plate 158 and the second cover plat e 162 areclamped onto the surface 160, 164 of the respective halfshells 132 by means of the first and second reinfor cementelements152,156.The cover plates 158, 162 are optionally glued to t herespective surfaces 160, 164 for better positioning .Further optionally, the cover plates 158, 162 can b echamfered atone more edgesthereof.As shown in figures 4 and 6, the wind turbine rotor blade 110comprisestwo sparcaps136 being connected byone shearweb140. In not shown embodiments, the wind turbine rot or blade P2024,0023 WO N / PA 1185 WO April15,2025 -14 -110 may comprises two further spar caps and a secon d shearweb.In such example,the two reinforcing elements 152 and156 are arranged such that the two shear webs are l ocated inbetween the two reinforcing elements152,156.

[0002] P2024,0023 WO N / PA 1185 WO April15,2025 -15 - Reference signs 100 wind turbine 102 tower 104 foundation 106 nacelle 108 rotor 110 rotorblade 112 rotorhub 114 rotorblade rootregion 116 transition region 118 profile region 120 longitudinaldirection 122 pressure side shell 124 suction side shell 126 rotorblade rootend 128 flange connection 130 shell 132 half-shell 134 leading edge 135 trailing edge 136 sparcap 138 cross-section profile 140 shearweb 142 end 143 joint 144 defect 146 outboard region 148 rotorblade tip 150 firstpairofbore holes 152 firstreinforcing element 154 second pairofbore holes 156 second reinforcing element P2024,0023 WO N / PA 1185 WO April15,2025 -16 - 158 firstcoverplate 160 surface ofthe pressure-side halfshell 162 second coverplate 164 surface ofthe suction-side halfshell F clamping force S step

Claims

P2024,0023 WO N / PA 1185 WO April15,2025 -17 - Claims1. Method for repairing a subsurface defect (144) o f a windturbine rotorblade (110),wherein- the wind turbine rotor blade (110) comprises a pr essure-side half shell (132) and a suction-side half shell (132),which are firmly bonded to each other, each half sh ell (132)comprising a sparcap (136),- the wind turbine rotor blade (110) comprises at l east oneshear web (140) which connects the two spar caps (1 36) toeach other,and- the defect (144) is located in a joint (143) betw een theshear web (140) and one of the spar caps (136), the methodcomprising the following steps:- drilling a first pair of bore holes (150) close t o thedefect (144), wherein one bore hole (150) is arrang ed in thesuction-side halfshell(132)and the otherone is arrangedin the pressure-side half shell (132), both bore ho les (150)being aligned with one another and being arranged i n thevicinityofthe sparcaps(136), -inserting a firstreinforcing element(152)into the first pairofbore holes(150),and- fixedly connecting the half shells (132) by means of thefirst reinforcing element (152) such that a clampin g force(F) acts on the two half shells (132) to at least p artiallybridge the defect(144). 2.Method according to claim 1,wherein the defect islocatedin an outboard region (146) of the wind turbine rot or blade(110), where the outboard region (146) accounts for 30 % ofthe total length of the wind turbine rotor blade (1 10)starting from a rotorblade tip (148).P2024,0023 WO N / PA 1185 WO April15,2025 -18 -3. Method according to claim 1 or 2, comprising the furthersteps:- drilling a second pair of bore holes (154), where in onebore hole (154) of the second pair is arranged in t hesuction-side halfshell(132)and the otherone is arrangedin the pressure-side half shell (132), both bore ho les (154)of the second pair being aligned with one another a nd beingarranged in the vicinityofthe sparcap (136),- inserting a second reinforcing element (156) into t hesecond pairofbore holes(110),and- fixedly connecting the half shells (132) by means o f thesecond reinforcing element (156) such that a clampi ng force(F) acts on the two half shells to at least partial ly bridgethe defect(144).

4. Method according to claim 3, wherein the first a nd / orsecond reinforcing element(152,156)ismade from a non- conductive material.

5. Method according to claim 3 or 4, wherein the fi rst and / orsecond reinforcing element (152, 156) is a string o r a bolt,in particulara screw bolt.

6. Method according to claim 3 to 5, wherein the fi rst pairof bore holes (150) and the second pair of bore hol es (154)are arranged at opposite sides of the shear web (14 0).

7. Method according to claim 3 to 6, wherein a firs t coverplate (158) is arranged on the surface (160) of the pressure-side half shell (132) and a second cover plate (162 ) isarranged on the surface (164) of the suction-side h alf shell(132),the coverplates(158,162)overlapping the respectivespar cap (136) in a top view of the half shell (132 ).P2024,0023 WO N / PA 1185 WO April15,2025 -19 -8. Method according to claim 7, wherein the first c over plate(158)and the second coverplate (162)are clamped onto thesurface (160, 164) of the respective half shells (1 32) bymeans of the first and second reinforcement element s (152,156).

9. Method according to claim 7 or 8, wherein the fi rst and / orsecond cover plate (158, 162) is glued to the surfa ce (160,164)ofthe respective halfshell(132).

10. Method according to any one of claims 7 to 9, w herein thefirst and / or second cover plate (158, 162) has a ch amfer atone ormore edgesofthe coverplate (158,162).

11. Method according to any one of claims 6 to 8, w herein thefirstand / orsecond coverplate (158,162)ismade ofacomposite material, in particular glass fiber compo sitematerial. 12.Wind turbine rotorblade (110),wherein- the wind turbine rotor blade (110) comprises a pr essure-side half shell (132) and a suction-side half shell (132),which are firmly bonded to each other, each half sh ell (132)comprising a sparcap (136),- the wind turbine rotor blade (110) comprises at l east oneshear web (140) which connects the two spar caps (1 36) toeach other,- the wind turbine rotor blade (110) comprises a de fect asubsurface (144), the defect (144) being located in a joint(143) between the shear web (140) and one of the sp ar caps(136),P2024,0023 WO N / PA 1185 WO April15,2025 -20 -- a first pair of bore holes (150) is provided clos e to thedefect (144), wherein one bore hole (150) of the fi rst pairis arranged in the suction-side half shell (132) an d theother one is arranged in the pressure-side half she ll (132),both bore holes(150)are aligned with one another and are arranged in the vicinityofthe sparcap (136);- a first reinforcing element (152) is inserted int o thefirst pair of bore holes (150) and fixedly connects the halfshells (132) in such a way that a clamping force (F ) acts onthe two half shells (132) to at least partially bri dge thedefect(144).

13. Wind turbine (100), comprising a wind turbine r otor blade(110)according to claim 12.

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