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

2

Outline

2

1. Introduction and motivation

2. Breathing – D-String®

3. Twisting - X-Stiffener™

4. Buckling capacity - D-Stiffener

5. Financial impact of retrofit enhancements

3

Weareexpertsinrootcauseanalysis ofblades andhavespecializedknowledgeonstructuralbladefailureandknowshowtoavoidfailuresonblades.

Bladena was founded in2011asaSpin-out fromRisøDTU.Thecompany isfounded on7groundbreakingpatentsallrelatedtostructural failures

Experts in blades –Structural related topics

4

Worldwidepresence

BladenaispresentinEuropeandUSandhassalesrepresentativesinDenmark,France,Spain,CanadaandUS.

Global representation

5

Motivation

Visibleoutside cracks

Mostoftenbladeshavesmallcrackswhichcanbefoundduringinspection.

6

Motivation

Visibleandnotvisibleinside cracks

Mostoftenbladesareonlyinspectedfromtheoutsidebutcracksusuallyinitiatefromtheinside.Failuresinbond linescanusuallynotbeseenwithoutpreloadingthestructure.

Cracksaresometimesvisiblefromtheinsidewithoutpreloadingthestructure.

7

Motivation – cracks within the structure

Debonding

Debondingofthecoreduetomanufacturingflawandbendingofthepanels.

core

laminateResin

debonding

Transversalcutinglasslayersthatleadtotransversalcrackinblades

8

Bladena Products

Floor™

X-Stiffener™D-Stiffener™

D-String®

CapStiffener™

D-String®

10

Root cause: Panel breathing

Deformations

Bladepaneldeformationsinducedbyedgewisegravityinduced loadsduringanyoperationofanywindturbinemakesthepanelsbreath.

Peeling

Thereisadirectconnection betweenthebreathingandthepeelingstressesintheadhesivebond lines:thehigherthemagnitudeofbreathing,thehigherthepeelingstresses.

11

More aerodynamic profiles result in more breathing

FEM-modelshowing that itistheaerodynamicshape which results inout-of-planedeformation

12

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

13

Effect of D-String®

Breathing deformations shownbefore andafter D-string installation

Peelingstressanalysisintrailingedge

WithouthD-Strings®installed

WithD-Strings®installed

14

Field installations

FirstkitinstalledonaVestasV80turbineinTjæreborgEnge inJanuary2013,followedbyseveral installationsonGE,LM,Vestas,etc...blades

Almost4yearsofoperation

Almost4yearstheD-String®hasbeeninstalledonbladesinoperation.RecentinspectionsconfirmedthattherearenocracksintheTEmaxchordareaandtherearenosignsofbladedamagesrelatedtotheinstallationoftheD-String®

Platform orropeusedtoaccesstheblades

X-Stiffener™

16

Root-Cause: Twisting

Backgroundonloadsonbladesinoperation

Loadsonwindturbinebladesduringoperationcanbesplitintwomaincomponents:• Edgewiseloads- dominatedbygravity.• Flapwise loads- dominatedbyaerodynamic

forces.

17

Root-Cause: Twisting (also called cross-sectionalshear distortion)

Increased twisting

Asthenewflat-backprofilesaremoreandmoreused,thetwistingbecomeshigherduetothelackofsupportinthetrailingedge.

Hotspots

Deformed shape

Un-deformedshape

Cross-sectionalsheardeformationgeneratespeelingstressesintheadhesivebond lines.

Peelingstresses

Theeffectofthetwophenomenaistheapearanceofpeelingstressesintheadhesivebondlinesalongthebladesincertainhot spots.

18

Influence of X-Stiffener

Twistreduction

AfterinstallationoftheX-Stiffenerthetwistingreduces80-85%.Thishasadirectimpactonthepeelingstressesintheadhesivebond-lines,leadingtosignificantincreaseofthebladelifetime.

X-Stiffenerinstallation

X-Stiffener

19

Large scale testing: X-Stiffener enhancement

Testing

Loadsappliedinthetestcreatesthesametwistingofthebladeasseeninthefull-scaletestandfieldoperation. Differentloadingconfigurations

ThetestiscarriedoutatTechnicalUniversityofDenmark(DTU)

20

Large blades have more twisting

Sizeeffects…

Deformationsincreaseby250-300%whenbladeisscaledupwithafactorof2.Peelingstressesintheadhesivebondlinesfollowthisincrease.

D-Stiffener™

22

Root-Cause: Buckling of the TE-panels

Premisesforfailure

Thebendingofthebladeduetoaerodynamicforcesandreducedbucklingcapacityofthebladeinmidspanandmidspantowardsthetipcreatespremisesforfailure.

23

Root cause: vibrations

Design

Incaseofvibrations,suchasanearthquake,thebladeisloadedinamannerthatwasnotdesignedfor.AeroelasticandFEMsimulationsareusedintheRoot-CaseAnalysis.

Earthquakeforces FEMTransientResponseprovidesaccurateresults

Aero-elasticsimulationsprovidesageneralbladeresponse

Capacity

D-Stiffenerdoesnot removethevibrations,however itincreasesthebladecapacitytowithstandthem.

24

Technology

TheD-Stiffener™isasimpleyeteffectivetechnologydevelopedtoeliminatecracksinthetrailingedgemidspanareabyeliminatingbucklingastherootcause.

TheD-Stiffener™connectsthepressuresideandsuctionsidepanels,whichpreventsthe inwarddeformationofthepanels.

D-stiffener™

Anchoringelement

Stiffeningelement

25

D-Stiffener impact

Sketchshowing theposition ofD-Stiffenersintheblade

NoD-Stiffenersinstalled D-Stiffenersinstalled

DD-Stiffener

26

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

27

Design and Manufacturing Impact, OEM

Results

• Reducedmaterialconsumption,thinnerpanels

• Largermanufacturingtolerances

• Noneedfortrailingedgeoverlamination,lessworkinconfinedspace

• Lessriskforfailurs duringfullscaletestandinoperation

• Possibleoption forincreasedaerodynamicdesigns,increasedAEP

Contact

Ryan Hagelskjær Lauridsen / ryl@bladena.com

Find Mølholt Jensen / fmj@bladena.com

Dave Zanier / dz@bladena.com

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.