SE1551642A1 - Method for blade heating system repair and wind turbine rotor blade - Google Patents

Method for blade heating system repair and wind turbine rotor blade Download PDF

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Publication number
SE1551642A1
SE1551642A1 SE1551642A SE1551642A SE1551642A1 SE 1551642 A1 SE1551642 A1 SE 1551642A1 SE 1551642 A SE1551642 A SE 1551642A SE 1551642 A SE1551642 A SE 1551642A SE 1551642 A1 SE1551642 A1 SE 1551642A1
Authority
SE
Sweden
Prior art keywords
heating system
layer
perforated member
applying
wind turbine
Prior art date
Application number
SE1551642A
Other languages
Swedish (sv)
Other versions
SE539438C2 (en
Inventor
Nilsson Greger
Original Assignee
Nilsson Greger
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Nilsson Greger filed Critical Nilsson Greger
Priority to SE1551642A priority Critical patent/SE539438C2/en
Priority to FI20165961A priority patent/FI20165961A/en
Publication of SE1551642A1 publication Critical patent/SE1551642A1/en
Publication of SE539438C2 publication Critical patent/SE539438C2/en

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Classifications

    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F03—MACHINES OR ENGINES FOR LIQUIDS; WIND, SPRING, OR WEIGHT MOTORS; PRODUCING MECHANICAL POWER OR A REACTIVE PROPULSIVE THRUST, NOT OTHERWISE PROVIDED FOR
    • F03D—WIND MOTORS
    • F03D1/00—Wind motors with rotation axis substantially parallel to the air flow entering the rotor 
    • F03D1/06—Rotors
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F03—MACHINES OR ENGINES FOR LIQUIDS; WIND, SPRING, OR WEIGHT MOTORS; PRODUCING MECHANICAL POWER OR A REACTIVE PROPULSIVE THRUST, NOT OTHERWISE PROVIDED FOR
    • F03D—WIND MOTORS
    • F03D80/00—Details, components or accessories not provided for in groups F03D1/00 - F03D17/00
    • F03D80/50—Maintenance or repair
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F03—MACHINES OR ENGINES FOR LIQUIDS; WIND, SPRING, OR WEIGHT MOTORS; PRODUCING MECHANICAL POWER OR A REACTIVE PROPULSIVE THRUST, NOT OTHERWISE PROVIDED FOR
    • F03D—WIND MOTORS
    • F03D3/00—Wind motors with rotation axis substantially perpendicular to the air flow entering the rotor 
    • F03D3/06—Rotors
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F03—MACHINES OR ENGINES FOR LIQUIDS; WIND, SPRING, OR WEIGHT MOTORS; PRODUCING MECHANICAL POWER OR A REACTIVE PROPULSIVE THRUST, NOT OTHERWISE PROVIDED FOR
    • F03D—WIND MOTORS
    • F03D80/00—Details, components or accessories not provided for in groups F03D1/00 - F03D17/00
    • F03D80/50—Maintenance or repair
    • F03D80/502—Maintenance or repair of rotors or blades
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E10/00—Energy generation through renewable energy sources
    • Y02E10/70—Wind energy
    • Y02E10/72—Wind turbines with rotation axis in wind direction
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E10/00—Energy generation through renewable energy sources
    • Y02E10/70—Wind energy
    • Y02E10/74—Wind turbines with rotation axis perpendicular to the wind direction

Abstract

Abstract A method for repairing an electric heating system of a wind turbine rotor blade (1), which electricheating system comprises a heating system layer (7) of a material having a low conductivity andthrough which an electric current is directed. The method comprises freeing a defective region(11) of the heating system layer (7) of any exterior layers of material such that electricallyconducting parts of the heating system layer (7) are exposed and applying a perforated member(13) of an electrically conductive material onto the defective region of the heating system layer.The method further comprise bringing the perforated member (13) into electrical contact withelectrically conducting parts of the heating system layer (7), and applying a fixation layer (15)over the perforated member (13) in order to fixate the perforated member to the electricallyconducting parts of the heating system layer (7). A corresponding wind turbine rotor blade (1) is also described. (Pig. 3)

Description

A METHOD FOR REPAIRING AN ELECTRIC HEATING SYSTEM OF A WIND TURBINEROTOR BLADE AND A WIND TURBINE ROTOR BLADE WITH A REPAIR REGION Technical field of the inventionThe present invention relates to a method for repairing an electric heating system of a wind turbine rotor blade, and a wind turbine rotor blade having a repair region.
Background Rotor blades on wind turbines are exposed to the weather conditions all year around.They are exposed to heat, cold, hard winds, rain, hail, snow and sometimes also to lightning,which causes degradation of the material and mechanical wear. Moreover, they are alsoexposed to mechanical wear from e.g. collisions with birds or other objects that may occasionallybe carried by the wind. ln wintertime, the wind turbine blades are subject to ice crust formation, due to highhumidity, snow and low temperatures. ln order to maintain wind turbine efficiency and ensureproduction also during winter conditions, the blades are often provided with blade heat systems.Usually, the blade heat systems are based either on hot air circulation within the blade, or basedon heating the blade surfaces directly. ln the direct heat systems, the heat is generally generated by directing electric currentthrough carbon fibre mats with low conductivity, which are applied on the exposed areas of theblade. Such mats are usually made from carbon fibre composite material. The direct heatingmethod is the predominantly used method for glass fibre composite blades and is more energyeffective than circulating air, since direct heating can be limited to areas subjected to ice crustbuild-up. The heating mats are therefore primarily applied on or near the leading edge on theouter half of the blade. The heating mat is then covered by a protective glass fibre fabric layer.Unfortunately, this is also an area that is exposed to collisions and lightning strikes, which bothmay damage the direct heating systems. The exposure to lightning strikes is unfortunately alsoenhanced by the carbon fibre mats acting as unintentional lightning rods. Thus it happens thatthe protective glass fibre layer is damaged to such a degree that the underlying carbon fibre matis exposed and also subjected to damage.When the carbon fibre mats have been damaged, the damage will generate a hotspot as theelectric currents are rerouted around the damaged region. At these hotspots, laminatetemperatures may exceed the matrix/epoxy degradation temperature, which is potentiallydangerous since the operation of the heat system may aggravate the damage, eventually leading to catastrophic failure.
Summary of the invention lt is an object of the present invention to provide a method for repairing an electricheating system of a wind turbine rotor blade in a simple and efficient way, and in particular amethod that can be practically executed directly on the blade when mounted on the wind turbine,when the wind turbine is installed on its operation site.
Accordingly is defined a method for repairing an electric heating system of a windturbine rotor blade, which electric heating system comprises a heating system layer of a materialhaving a low conductivity and through which an electric current is directed, the methodcomprising - freeing a defective region of the heating system layer of any exterior layers of materialsuch that electrically conducting parts of the heating system layer are exposed, - applying a perforated member of an electrically conductive material over the defectiveregion of the heating system layer, - bringing the perforated member into electrical contact with electrically conducting partsof the heating system layer, and - applying a fixation layer over the perforated member in order to fixate the perforatedmember to the electrically conducting parts of the heating system layer.
By applying a perforated member of an electrically conductive material is obtained theadvantage that it will be possible to have more or less the entire perforated member in electricalcontact with electrically conducting parts of the electric heating system layer, i.e. both under theperforated member and at the edges of the perforated member. By applying the perforatedmember over the defective region is intended that it should cover the defective region. Further,the perforated member structure will make it possible to provide for good adhesion of theperforated member to the entire area of the heating system layer when the fixation layer isapplied over the perforated member. The perforations in the perforated member structure willallow for the fixation layer to penetrate into these openings and down to the heating system layerand thus fixate the perforated member over essentially the entire area of the heating systemlayer in the defective region. Thus it has been found that the electric heating system will have agood functionality after this repair. There is also the advantage that there is no need to have anyadhesive layer between the exposed electrically conducting parts of the heat system layer in thedefective region and the perforated member in order to ensure the required electric contact,since the combination of the perforations in the perforated member and the fixation layer will ensure the proper contact.
According to one feature, the method may comprise applying a vacuum bag such thatthe bag covers the perforated member and applying a vacuum pressure in said vacuum bag,prior to applying the fixation layer. When vacuum then is generated, the perforated member willbe pressed down against the heating system layer and against its exposed electricallyconductive parts, and there will be generated a contact pressure between the heating systemlayer and the underside of the perforated member.
According to one embodiment, the method may comprise applying a fixation layercomprising a thermosetting material. A thermosetting material, such as e.g. thermosettingpolymers, are fairly easy to apply and it will enter into the openings in the perforated memberand provide good adhesion of the perforated member to the underlying heat system layer, asdescribed above.
According to a variant, the method may comprise applying a fixation layer comprisingan ultra-violet radiation curable resin material. The use of an ultra-violet radiation curable resinmaterial, and to be able to use ultra-violet radiation to cure the fixation layer has the advantageof a relatively quick curing process. This will contribute advantageously to the possibility ofrepairing a damaged blade on the site of operation, without dismounting the blade.
Examples of suitable ultra-violet radiation curable resin materials are epoxy resin orpolyester resin.
The method may further comprise applying the fixation layer by vacuum infusion. This isan advantageous method for use with thermosetting material.
According to one feature, the method may comprise providing a perforated member ofan electrically conductive metal. This may for example be a perforated member of copper metalor aluminium metal, or alloys thereof. Another alternative is a steel member. Such perforatedmembers are easy to handle and economical.
The method may also comprise applying a cover layer over the fixation layer. Such acover layer will protect the repair region and may e.g. be made from a glass fibre reinforcedcomposite. Preferably it may be of the same type as the outermost layer of the blade.
Advantageously, the method may be performed on the rotor blade mounted on the windturbine, when the wind turbine is installed on an operation site.
According to another aspect of the invention is defined a wind turbine rotor bladeprovided with an electric heating system comprising a heating system layer of a material havinga low conductivity and through which an electric current is directed, said rotor blade having arepair region comprising a perforated member of an electrically conductive material applied ontoa region of the heating system layer, and a fixation layer applied over the perforated member in order to fixate the perforated member to electrically conducting parts of the heating system layer.
A wind turbine rotor blade having a repair region as defined will have good functionality in theelectric heating system, and will provide advantages corresponding to the advantages alreadydescribed above in connection with the method.
According to one embodiment, the fixation layer may comprise an ultraviolet radiationcured resin material.
According to on embodiment, the perforated member may be made of an electricallyconductive metal, such as copper metal or aluminium metal, or alloys thereof. The perforatedmember is preferably a fairly thin and/or flat member, of a sheet shape or similar, that will coverthe freed defective region after having been applied. The perforated member can for example bea net, or a perforated sheet or perforated film. lt is preferably flexible such that it will be able toadapt to the shape of the freed defective region when it is applied thereto.
Further features and advantages of the invention will also become apparent from the following detailed description of embodiments.
Brief description of the drawings The invention will now be described in more detail, with reference being made to theenclosed schematic drawings illustrating different aspects and embodiments of the invention,given as examples only, and in which: Fig. 1 is a schematic partial view of a damaged wind turbine blade in cross section, Fig. 2 is a schematic partial view of a defective region during repair, in cross section, Fig. 3 is a schematic partial view of the defective region after repair, in cross section, Fig. 4 is a schematic illustration of a repair region, and Fig. 5 is a diagram showing the main steps of an embodiment of the method accordingto the present invention.
Elements that are the same or represent corresponding or equivalent elements have been given the same reference numbers in the different figures.
Detailed description ln Fig. 1 is shown a cross section of a part of a damaged wind turbine blade 1. A windturbine blade is usually built up by a core section 3, usually made of balsa wood, a first innerprotective layer 5, an electric heating system layer 7 and a second outer protective layer 9. Theouter protective layer may in some cases be left out. The inner protective layer 5 is usually madeof a fibre reinforced composite material, e.g. glass fibre reinforced epoxy resin or polyester resin.The electric heating system layer 7 is made from a carbon fibre material having a low conductivity and through which an electric current is directed. The carbon fibre material may be a carbon fibre mat or fabric. The outer protective layer 9 is usually also made of a fibrereinforced composite material, e.g. glass fibre reinforced epoxy resin. ln the figure is alsoillustrated a defective region 11 of the blade 1. ln this defective region 11, the blade has beendamaged such that the outer protective layer 9 has been damaged and also the heating systemlayer 7 has been damaged. ln this illustration, the heating system layer is deformed anddamaged even though from the exterior there is no visible damage to the heating system layer,such as e.g. a recess that reaches all the way down to the heating system layer. From theexterior the damage may e.g. only be observed as a superficial damage to the outer protectivelayer 9, but by using e.g. a heat sensitive camera, hot spots may be discovered that areindications that the heating system layer has been damaged. However, it may very well be thatthe damage is so bad that the recess goes all the way down through the outer protective layer 9and into the heating system layer 7. ln Fig. 5 is shown a diagram over the main steps of the method according to anembodiment of the present invention. The method for repairing an electric heating system of awind turbine rotor blade comprises- freeing a defective region of the heating system layer of any exterior layers of material suchthat electrically conducting parts of the heating system layer are exposed, - applying a perforated member of an electrically conductive material over the defective region ofthe heating system layer, - bringing the perforated member into electrical contact with electrically conducting parts of theheating system layer, and - applying a fixation layer over the perforated member in order to fixate the perforated member tothe electrically conducting parts of the heating system layer.
The first step in the method is to ensure that electrically conducting parts of the electricheating system are exposed to a sufficient degree and in a manner that will make it possible toperform the next steps of applying the perforated member and bringing the perforated memberinto contact with the electrically conducting parts of the heating system. lf there is an exteriorlayer, e.g. an outer protective layer of e.g. glass fibre reinforced epoxy, which to some extentcovers the defective region of the heating system layer, any such exterior layer has to beremoved in the defective region and possibly also in the close vicinity thereof. This may forexample be made by grinding, if the exterior layer is a glass fibre layer. When the heatingsystem comprises e.g. a carbon fibre mat, the electrically conducting carbon fibres have to beexposed. ln Fig. 2 is illustrated how the defective region 11 has been freed from an exterior layerin the form of the outer protective layer 9, and the heating system layer 7 with its electrically conducting parts has been exposed. ln order for the perforated member 13 to fit into the defective region 11, the perforated member may be cut to fit snugly into the defective region, orthe defective region is made to fit against the perforated member, e.g. when the defective regionis prepared by removing any exterior layer.
After this preparation of the defective region, a perforated member 13 of an electricallyconductive material is applied onto the defective region 11. This perforated member may forexample be made of suitable electrically conductive metal, such as copper or aluminium, oralloys thereof. The perforated member is preferably a fairly thin and/or flat member, of a sheetshape or similar, that will cover the freed defective region after having been applied. Theperforated member can for example be a net, or a perforated sheet or perforated film. lt ispreferably flexible such that it will be able to adapt to the shape of the freed defective regionwhen it is applied thereto.
The perforated member is then brought into electrical contact with the electricallyconducting parts of the electric heating system. This can be achieved, according to oneembodiment, by applying a vacuum bag over the perforated member and when vacuum isgenerated the perforated member will be pressed down against the heating system layer and itsexposed electrically conductive parts. ln the next step, a fixation layer 15 is applied over the perforated member 13 in order tofixate the perforated member to the electrically conducting parts of the heating system layer.According to one embodiment, the fixation layer 15 can comprise a thermosetting material. lnone embodiment, the fixation layer 15 comprises an ultraviolet radiation curable resin material,such as an epoxy resin or a polyester resin. The thermosetting material can be applied bymeans of vacuum infusion. After application of the thermosetting material, the next stepcomprises curing the thermosetting material, which can be made, for example, by usingultraviolet radiation.
Finally, a cover layer 17 may be applied over the fixation layer 15. Such a cover layer17 will serve to protect the repair region 21 and it will also have the function of filling up anyrecess in the outer protective layer 9 that may still remain after the repair having been made. ln Fig. 3 is shown a cross section of a part of a wind turbine rotor blade that has a repairregion 21 that has been repaired according to the method and Fig. 4 illustrates schematically aview from above of the repair region 21. ln Fig. 4 is also illustrated the original defective region11. Thus, the repair region 21 comprises a perforated member 13 of an electrically conductivematerial applied onto a region of the electric heating system 7 layer, and a fixation layer 15 isapplied over the perforated member 13 in order to fixate the perforated member to electricallyconducting parts of the heating system layer 7. The fixation layer is then covered by a cover layer 17, if required.
The method may advantageously be performed on a rotor blade when mounted on thewind turbine, when the wind turbine is installed on its operation site.
The invention shall not be considered limited to the illustrated embodiments, but can bemodified and altered in many ways, as realised by a person skilled in the art, without departing from the scope defined in the appended claims.

Claims (13)

Patent Claims
1. A method for repairing an electric heating system of a wind turbine rotor blade (1), whichelectric heating system comprises a heating system layer (7) of a material having a lowconductivity and through which an electric current is directed, the method comprising - freeing a defective region (1 1) of the heating system layer (7) of any exterior layers of materialsuch that electrically conducting parts of the heating system layer (7) are exposed, - applying a perforated member (13) of an electrically conductive material over the defectiveregion (11) of the heating system layer (7), - bringing the perforated member (13) into electrical contact with electrically conducting parts ofthe heating system layer (7), and - applying a fixation layer (15) over the perforated member (13) in order to fixate the perforated member to the electrically conducting parts of the heating system layer (7).
2. The method according to claim 1, comprising applying a vacuum bag such that the vacuumbag covers the perforated member (13) and applying a vacuum pressure in said vacuum bag, prior to applying the fixation layer (15).
3. The method according to any one of the preceding claims, comprising applying a fixation layer (15) comprising a thermosetting material.
4. The method according to any one of the preceding claims, comprising applying a fixation layer (15) comprising an ultra-violet radiation curable resin material.
5. The method according to any one of claims 3-4, comprising using ultra violet radiation to cure the fixation layer (15).
6. The method according to any one of the preceding claims, comprising applying the fixation layer (15) by vacuum infusion.
7. The method according to any one of the preceding claims, comprising providing a perforated member (13) of an electrically conductive metal.
8. The method according to claim 9, comprising providing a perforated member (13) of copper metal or aluminium metal, or alloys thereof.
9. The method according to any one of the preceding claims, comprising applying a cover layer (17) over the fixation layer (15).
10. The method according to any one of the preceding claims, wherein it is performed on the rotor blade mounted on the wind turbine, when the wind turbine is installed on an operation site.
11. A wind turbine rotor blade (1) provided with an electric heating system comprising a heatingsystem layer (7) of a material having a low conductivity and through which an electric current isdirected, said rotor blade having a repair region (21) comprising a perforated member (13) of anelectrically conductive material applied onto a region of the heating system layer (7), and afixation layer (15) applied over the perforated member (13) in order to fixate the perforated member to electrically conducting parts of the heating system layer (7).
12. The wind turbine rotor blade according to claim 11, wherein the fixation layer (15) comprises an ultraviolet radiation cured resin material.
13. The wind turbine rotor blade according to any one of claims 11-12, wherein the perforatedmember (13) is made of an electrically conductive metal, such as copper metal or aluminium metal, or alloys thereof.
SE1551642A 2015-12-14 2015-12-14 Method for blade heating system repair and wind turbine rotor blade SE539438C2 (en)

Priority Applications (2)

Application Number Priority Date Filing Date Title
SE1551642A SE539438C2 (en) 2015-12-14 2015-12-14 Method for blade heating system repair and wind turbine rotor blade
FI20165961A FI20165961A (en) 2015-12-14 2016-12-13 Method for Repairing a Wind Turbine Rotor Blade Electric Heating System and a Wind Turbine Rotor Blade with a Repair Area

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
SE1551642A SE539438C2 (en) 2015-12-14 2015-12-14 Method for blade heating system repair and wind turbine rotor blade

Publications (2)

Publication Number Publication Date
SE1551642A1 true SE1551642A1 (en) 2017-06-15
SE539438C2 SE539438C2 (en) 2017-09-19

Family

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Family Applications (1)

Application Number Title Priority Date Filing Date
SE1551642A SE539438C2 (en) 2015-12-14 2015-12-14 Method for blade heating system repair and wind turbine rotor blade

Country Status (2)

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FI (1) FI20165961A (en)
SE (1) SE539438C2 (en)

Also Published As

Publication number Publication date
SE539438C2 (en) 2017-09-19
FI20165961A (en) 2017-06-15

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