Structural Enhancements: The Way to lower LCOE
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2016 Wind Turbine Blade Workshop Structural Enhancements – The way to lower LCOE CTO and founder: Find Mølholt Jensen, PhD
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Transcript of Structural Enhancements: The Way to lower LCOE
2016 Wind Turbine Blade Workshop
Structural Enhancements –The way to lower LCOE
CTO and founder: Find Mølholt Jensen, PhD
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Outline
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1. Introduction and motivation
2. Breathing – D-String®
3. Twisting - X-Stiffener™
4. Buckling capacity - D-Stiffener
5. Financial impact of retrofit enhancements
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Weareexpertsinrootcauseanalysis ofblades andhavespecializedknowledgeonstructuralbladefailureandknowshowtoavoidfailuresonblades.
Bladena was founded in2011asaSpin-out fromRisøDTU.Thecompany isfounded on7groundbreakingpatentsallrelatedtostructural failures
Experts in blades –Structural related topics
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Worldwidepresence
BladenaispresentinEuropeandUSandhassalesrepresentativesinDenmark,France,Spain,CanadaandUS.
Global representation
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Motivation
Visibleoutside cracks
Mostoftenbladeshavesmallcrackswhichcanbefoundduringinspection.
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Motivation
Visibleandnotvisibleinside cracks
Mostoftenbladesareonlyinspectedfromtheoutsidebutcracksusuallyinitiatefromtheinside.Failuresinbond linescanusuallynotbeseenwithoutpreloadingthestructure.
Cracksaresometimesvisiblefromtheinsidewithoutpreloadingthestructure.
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Motivation – cracks within the structure
Debonding
Debondingofthecoreduetomanufacturingflawandbendingofthepanels.
core
laminateResin
debonding
Transversalcutinglasslayersthatleadtotransversalcrackinblades
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Bladena Products
Floor™
X-Stiffener™D-Stiffener™
D-String®
CapStiffener™
D-String®
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Root cause: Panel breathing
Deformations
Bladepaneldeformationsinducedbyedgewisegravityinduced loadsduringanyoperationofanywindturbinemakesthepanelsbreath.
Peeling
Thereisadirectconnection betweenthebreathingandthepeelingstressesintheadhesivebond lines:thehigherthemagnitudeofbreathing,thehigherthepeelingstresses.
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More aerodynamic profiles result in more breathing
FEM-modelshowing that itistheaerodynamicshape which results inout-of-planedeformation
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Transverse cracks on the trailing edge panels
Bending of the TE-panels causes transverse cracksAdvancedFEMsimulationshaveconfirmedthemeasurements.3DlongitudinalwavesarereducedwhentheD-Strings®areused.
Insideviewofthetrailingedge
FEMillustratingthepanelwaveswhentheD-Strings®arenotused.Withredcolour– highmagnitude
FEMillustratingthereductionofpanelwaveswhenD-Strings®areused.Withgreencolour– lowmagnitude
Transversecracksfoundduringinspection
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Effect of D-String®
Breathing deformations shownbefore andafter D-string installation
Peelingstressanalysisintrailingedge
WithouthD-Strings®installed
WithD-Strings®installed
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Field installations
FirstkitinstalledonaVestasV80turbineinTjæreborgEnge inJanuary2013,followedbyseveral installationsonGE,LM,Vestas,etc...blades
Almost4yearsofoperation
Almost4yearstheD-String®hasbeeninstalledonbladesinoperation.RecentinspectionsconfirmedthattherearenocracksintheTEmaxchordareaandtherearenosignsofbladedamagesrelatedtotheinstallationoftheD-String®
Platform orropeusedtoaccesstheblades
X-Stiffener™
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Root-Cause: Twisting
Backgroundonloadsonbladesinoperation
Loadsonwindturbinebladesduringoperationcanbesplitintwomaincomponents:• Edgewiseloads- dominatedbygravity.• Flapwise loads- dominatedbyaerodynamic
forces.
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Root-Cause: Twisting (also called cross-sectionalshear distortion)
Increased twisting
Asthenewflat-backprofilesaremoreandmoreused,thetwistingbecomeshigherduetothelackofsupportinthetrailingedge.
Hotspots
Deformed shape
Un-deformedshape
Cross-sectionalsheardeformationgeneratespeelingstressesintheadhesivebond lines.
Peelingstresses
Theeffectofthetwophenomenaistheapearanceofpeelingstressesintheadhesivebondlinesalongthebladesincertainhot spots.
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Influence of X-Stiffener
Twistreduction
AfterinstallationoftheX-Stiffenerthetwistingreduces80-85%.Thishasadirectimpactonthepeelingstressesintheadhesivebond-lines,leadingtosignificantincreaseofthebladelifetime.
X-Stiffenerinstallation
X-Stiffener
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Large scale testing: X-Stiffener enhancement
Testing
Loadsappliedinthetestcreatesthesametwistingofthebladeasseeninthefull-scaletestandfieldoperation. Differentloadingconfigurations
ThetestiscarriedoutatTechnicalUniversityofDenmark(DTU)
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Large blades have more twisting
Sizeeffects…
Deformationsincreaseby250-300%whenbladeisscaledupwithafactorof2.Peelingstressesintheadhesivebondlinesfollowthisincrease.
D-Stiffener™
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Root-Cause: Buckling of the TE-panels
Premisesforfailure
Thebendingofthebladeduetoaerodynamicforcesandreducedbucklingcapacityofthebladeinmidspanandmidspantowardsthetipcreatespremisesforfailure.
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Root cause: vibrations
Design
Incaseofvibrations,suchasanearthquake,thebladeisloadedinamannerthatwasnotdesignedfor.AeroelasticandFEMsimulationsareusedintheRoot-CaseAnalysis.
Earthquakeforces FEMTransientResponseprovidesaccurateresults
Aero-elasticsimulationsprovidesageneralbladeresponse
Capacity
D-Stiffenerdoesnot removethevibrations,however itincreasesthebladecapacitytowithstandthem.
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Technology
TheD-Stiffener™isasimpleyeteffectivetechnologydevelopedtoeliminatecracksinthetrailingedgemidspanareabyeliminatingbucklingastherootcause.
TheD-Stiffener™connectsthepressuresideandsuctionsidepanels,whichpreventsthe inwarddeformationofthepanels.
D-stiffener™
Anchoringelement
Stiffeningelement
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D-Stiffener impact
Sketchshowing theposition ofD-Stiffenersintheblade
NoD-Stiffenersinstalled D-Stiffenersinstalled
DD-Stiffener
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Financial and Operational Impact, WTO
Results
• Lessmaintenancetime=>reducedcostofenergy=>higherprofit
• E.g.D-String®:Thecostofone incidentrepairequalsthecostofaD-String® kitfor3blades(includingtheinstallation)
• Theriskofcracksincreaseswiththeageofthebladesduetothefatigueloading,bathtub curve
• Thetechnologiessecuresoperationofthebladeintheanticipatedlifetimeoftheturbinewithoutaddedmaintenancecost
• ROIlessthan2years
Owners risk
Warranty
Years ofoperation
Failu
rerate
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Design and Manufacturing Impact, OEM
Results
• Reducedmaterialconsumption,thinnerpanels
• Largermanufacturingtolerances
• Noneedfortrailingedgeoverlamination,lessworkinconfinedspace
• Lessriskforfailurs duringfullscaletestandinoperation
• Possibleoption forincreasedaerodynamicdesigns,increasedAEP
Contact
Ryan Hagelskjær Lauridsen / [email protected]
Find Mølholt Jensen / [email protected]
Dave Zanier / [email protected]
Universitetsparken 7DK-4000 RoskildeDenmarkwww.bladena.com
© 2016 Bladena. All rights reserved. Reproduction or distribution of this report in any form without prior written permission is strictly forbidden. Violation of the above restrictions will be subjects to legal action under the Danish Arbitration Act. The information herein is taken from sources considered reliable, but its accuracy and completeness are not warranted, nor are the opinions, analyses and forecasts on which they are based. Bladena cannot be held liable for any errors in this report, neither can Bladena be liable for any financial loss or damage caused by the use of the information presented in this report.
