Direct Optical Ice Sensing and Closed-Loop Controller Design for Active De-icing of Wind Turbines

134 Pages·2015·3.78 MB·English

University of Colorado, Boulder
CU Scholar
Aerospace Engineering Sciences Graduate Theses &
Aerospace Engineering Sciences
Dissertations
Spring 1-1-2015
Direct Optical Ice Sensing and Closed-Loop
Controller Design for Active De-icing of Wind
Turbines Using Distributed Heating
Shervin Shajiee
University of Colorado Boulder, [email protected]
Follow this and additional works at:https://scholar.colorado.edu/asen_gradetds
Part of theAeronautical Vehicles Commons, and theSystems Engineering and Multidisciplinary
Design Optimization Commons
Recommended Citation
Shajiee, Shervin, "Direct Optical Ice Sensing and Closed-Loop Controller Design for Active De-icing of Wind Turbines Using
Distributed Heating" (2015).Aerospace Engineering Sciences Graduate Theses & Dissertations. 124.
https://scholar.colorado.edu/asen_gradetds/124
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DirectOpticalIceSensingandClosed-LoopControllerDesignfor
ActiveDe-icingofWindTurbinesUsingDistributedHeating
by
ShervinShajiee
B.S.,AmirkabirUniversityofTechnology,2001
M.S.,SharifUniversityofTechnology,2004
M.S.,UniversityofMinnesota,2008
Athesissubmittedtothe
FacultyoftheGraduateSchoolofthe
UniversityofColoradoinpartialfulfillment
oftherequirementsforthedegreeof
DoctorofPhilosophy
DepartmentofAerospaceEngineeringSciences
2015
Thisthesisentitled:
DirectOpticalIceSensingandClosed-LoopControllerDesignforActiveDe-icingofWindTurbines
UsingDistributedHeating
writtenbyShervinShajiee
hasbeenapprovedfortheDepartmentofAerospaceEngineeringSciences
LucyY.Pao
RobertR.McLeod
Date
Thefinalcopyofthisthesishasbeenexaminedbythesignatories,andwefindthatboththecontentandthe
formmeetacceptablepresentationstandardsofscholarlyworkintheabovementioneddiscipline.
Shajiee,Shervin(Ph.D.,AerospaceEngineeringSciences)
DirectOpticalIceSensingandClosed-LoopControllerDesignforActiveDe-icingofWindTurbinesUsing
DistributedHeating
Thesisdirectedby LucyY.Pao
Iceaccumulationonwindturbinesoperatingincoldregionsreducespowergenerationbydegrading
aerodynamic efficiency and causes mass imbalance and fatigue loads on the blades. Due to blade rotation
andvariationofthepitchangle,differentlocationsonthebladeexperiencelargevariationsofReynoldsnum-
ber,Nusseltnumber,heatloss,andnon-uniformicedistribution. Hence,applyingdifferentamountsofheat
fluxindifferentbladelocationscanprovidemoreeffectivede-icingforthesametotalpowerconsumption.
This large variation of required heat flux motivates using distributed resistive heating, with the capability
of locally adjusting thermal power as a function of location on the blade. The main contributions of this
researcharedevelopingtheexperimentalfeasibilityofdirecticesensingusinganopticalsensingtechnique
as well as development of a computational framework for implementation of closed-loop localized active
de-icing using distributed sensing. A script-base module was developed in a commercial finite-element
software (ANSYS) which provides the capability of (i) Closed-loop de-icing simulations for a distributed
network of sensors and actuators, (ii) investigating different closed-loop thermal control schemes and their
de-icing efficiency (iii) optimizing thermal actuation for a distributed resistive heating, and (iv) analyzing
differentfaultyscenariosforsensorsandthermalactuatorsunderknownfaultsinthenetwork. Differentsur-
rogatemodelswereusedtoenhancethecomputationalefficiencyofthisapproach. Theresultsshowedthat
optimalvalueofcontrolparametersinadistributednetworkofheatersdependsonconvectiveheattransfer
characteristics,layoutofheatersandtypeofclosed-loopcontrollerschemeusedforthermalactuation. Fur-
thermore, it was shown that closed-loop control provides much faster de-icing than the open-loop constant
heatfluxthermalactuation. Itwasobservedbothexperimentallyandnumericallythathighintensitypulsed
thermalactuationslightlyimprovesicemeltingbutrelativelyincreasestheamountofappliedthermalstress
tothebladestructure. Thisthesisincludes: (1)Aliteraturestudyondifferentmethodsoficedetectionand
iv
areviewonpassiveandactiveanti/de-icingtechniquesonwindturbines,(2)Developmentofanopticalice
sensingmethodfordirectdetectionoficeonthebladeincludingexperimentalresults,(3)Descriptionofan
aero/thermodynamicmodel,whichpredictshowmuchheatfluxisneededlocallyforde-icingundervariable
atmospheric conditions, (4) Experimental results showing the proof-of-concept of closed-loop de-icing us-
ingdistributedopticalicesensing,distributedtemperaturesensing,andresistiveheating,and(5)Numerical
modeling of ice melting on a blade for different distributed heater layouts and geometries in order to opti-
mizethermalactuationstrategy,improvede-icingefficiency,andfinally(6)Developmentofacomputational
frameworkforclosed-loopactivede-icingusingdistributedlocalizedheatingandsensing.
Dedication
ToMahnaz,Abdolhossein,Hooman,Jamshid,andIsabellefortheirloveandpatience
Acknowledgements
First, I would like to express my deepest gratitude to my advisor, Prof. Lucy Y. Pao for her excep-
tional guidance, patience, endless support as well as the freedom that she gave me during this research. I
truly express my extended appreciation for her invaluable guidance and continuous support in every single
moment over the past 5 years, her positive attitude and trust in my academic capabilities. She encouraged
my research and allowed me to grow as a research scientist. Her advice on both research as well as on
mycareerhavebeeninvaluable. Iwouldalsothankmyacademicco-advisor,ProfessorRobertR.McLeod
for his support during my research. His great feedback and comments have improved the quality of my
technicalwriting. Iamthankfulforhishelpinprovidingmewiththeexperimentalsetupforopticalsensing
duringthefirstthreeyearsofmyresearch.
I would like to express my special thanks to Patrick N. Wagner for his help in building an icing
chamber for my research. Also, I would like to thank Dr. Eric D. Moore for his guidance with the Optical
Frequency Domain Reflectometry (OFDR) software and for his help in the integration of the closed-loop
controllertotheopticalsensingsetup. IwouldliketothankDr. AliNajafifromANSYSInc. forassistingin
thecalculationsofthevolumeoficeresidueinANSYSandassistinginthedevelopmentofcomputational
modules in ANSYS for the closed-loop simulations of de-icing. Special thanks to ANSYS Inc. and Arin
RousefromANSYSforthekindsupportandprovidingthesoftwarelicenseduringmyresearch.
I appreciate the help of Dr. Patrick Moriarty from the U.S. National Renewable Energy Laboratory
(NREL) for providing a blade part for our test setup, and Kyle Kemble from the Colorado Space Grant
Consortium for using their cooling unit while developing the icing chamber for my research. I would like
to thank my committee members, Professor Kurt Maute, Dr. Patrick Moriarty, and Dr. Andrew Clifton for
vii
serving as my committee members and for their brilliant comments and feedback for my comprehensive
and final exam. I am very grateful to my colleagues including Dr. Eric Simley, Fiona Dunne, Jakob Aho,
Dr. Jason Laks, Dr. Hua Zhong, Dr. David Schlipf, Daniel Zalkind, and Arnold Braker for their valuable
comments during the progress of this research. I am thankful to Annie Brookover, graduate advisor in the
departmentofaerospaceengineeringsciences,forheradministrativesupportandadvice.
Finally, I would like to dedicate this thesis to my family: Abdolhossein, Mahnaz, Jamshid, Hooman
andIsabellefortheirpatience,love,devotion,encouragement,andsupport. Thisresearchisinthememory
ofmyfather,Abdolhossein,foralwaysteachingmetoworkhard.
ThisworkhasbeenpartiallysupportedbyCenterforResearchandEducationinWind(CREW)seed
grantduringthefirsttwoyearsofmystudy. Igreatlyappreciatetheirsupport.
Contents
Chapter
1 Introduction 1
1.1 Motivation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
1.1.1 TypesofAtmosphericIceaccumulation . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1.2 AerodynamicPowerDegradationDuetoIcing . . . . . . . . . . . . . . . . . . . . 5
1.2 SummaryofResearchGoals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
1.3 ThesisContributions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
1.4 ThesisOutline . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
2 IceSensingandThermalActuation: ExistingandProposedMethods 14
2.1 IceSensing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
2.1.1 BackgroundInformation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
2.1.2 ProposedDirectOpticalIceSensing . . . . . . . . . . . . . . . . . . . . . . . . . . 15
2.2 IceMitigation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
2.2.1 PassiveIcePrevention . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
2.2.2 ActiveThermalActuation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
2.2.3 ProposedDistributedThermalActuation . . . . . . . . . . . . . . . . . . . . . . . 20
3 BladeThermodynamics 23
3.1 CalculationofHeatFluxRequirementforDe-icing . . . . . . . . . . . . . . . . . . . . . . 23
3.2 VariationofConvectiveHeatFluxforDifferentWindTurbineOperatingConditions. . . . . 25
ix
3.3 TotalRequiredHeatFluxforDe-icing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
4 De-icingProfitabilityAnalysis 30
4.1 AerodynamicPowerLossDataforDifferentIceAccumulations . . . . . . . . . . . . . . . 31
4.2 ProfitabilityDerivations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
4.3 EstimatedEquipmentCostandPaybackTimefortheProposedActiveDistributedDe-icing . 34
5 ExperimentalSetupandClosed-LoopExperiments 36
5.1 ExperimentalSetupDescription . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36
5.2 ComputationalModelValidationwithExperiments . . . . . . . . . . . . . . . . . . . . . . 40
5.3 Closed-LoopDe-icingExperimentalResults . . . . . . . . . . . . . . . . . . . . . . . . . . 43
5.3.1 LowIntensityContinuousPIDController . . . . . . . . . . . . . . . . . . . . . . . 44
5.3.2 HighIntensityPulseAmplitudeModulation(PAM) . . . . . . . . . . . . . . . . . . 45
6 EvaluatingDifferentHeaterLayoutsforDe-icingUsingConstantHeatFlux 50
6.1 SimulationsofDifferentHeaterLayoutsforaSmall-ScaleBlade . . . . . . . . . . . . . . . 50
6.1.1 De-icingPerformanceMetricforHeaterLayoutEvaluation. . . . . . . . . . . . . . 52
6.1.2 De-icingPerformanceComparisonforDifferentHeaterLayouts . . . . . . . . . . . 53
6.2 SimulationsofDifferentHeaterLayoutsfora1.5MWBladeTipSegment . . . . . . . . . . 58
6.2.1 Non-UniformIceGeometryandBoundaryConditions . . . . . . . . . . . . . . . . 59
6.2.2 DistributedHeaterLayoutConfigurations . . . . . . . . . . . . . . . . . . . . . . . 62
6.2.3 De-IcingPerformanceMetricforHeaterLayoutEvaluation . . . . . . . . . . . . . 63
6.2.4 De-IcingPerformanceComparisonforDifferentHeaterLayouts . . . . . . . . . . . 64
6.2.5 SensitivityStudyofOtherBoundaryConditions . . . . . . . . . . . . . . . . . . . 67
7 ComputationalClosed-LoopControllerDesignforDe-icingUsingDistributedResistiveHeatersand
TemperatureSensors 75
7.1 ModelAssumptions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 76
7.2 Non-UniformIceGeometryandBoundaryConditions . . . . . . . . . . . . . . . . . . . . 77