1 Large Rotor Development: Sandia 100-meter Blade Research D. Todd Griffith, PhDSandia National LaboratoriesWIND TURBINE BLADE MANUFACTURE 201228 November, 2012Dusseldorf, GermanySandia Technical Report Number: SAND C
2 Wind Industry Trends & Challenges Costs (traditional)System ~ $3/lbBlades ~ $6/lbHigh-end Military ~ $1000/lbAerospace Industry ~ $100/lbSizeMWTowers: metersBlades: meters
3 Offshore Wind Energy: System Costs 4/1/2017Offshore Wind Energy: System CostsProjected costs for shallow water offshore siteCost of Energy (COE) reduction is key to realize offshore siting potentialLarger rotors on taller towersReduction in costs throughout system with better rotorResearch investments……Chart Reference: Musial, W. and Ram, B., Large-Scale Offshore Wind Power in the United States: Assessment of Opportunities and Barriers, National Renewable Energy Laboratory, September 2010.
4 Offshore Siting Analysis Offshore SandiaAddressing the challenge through research: Identifying and mitigating technology barriers and leveraging past experiencesOffshore Siting AnalysisSHM/PMfor O&M ProcessDOE/Sandia 34 meter VAWTSandia is supporting the development of an Offshore Wind Industry in the USMultiple projects in support of the DOE Offshore Wind program.Leveraging decades of land-based wind energy experience along with offshore-specific research thrustsThese projects provide technology development and assessment in research areas important for technology risk reduction, offshore siting, and reduction in offshore cost of energy.Project highlights: (1) Offshore siting analysis (better understanding of sediment mobility risk and offshore foundation impact), (2)Large Offshore Rotor Development (investigate technology barriers and cost reductions; Sandia 100-meter Blade Design), and (3) innovative rotor technology (vertical axis wind turbine (VAWT), there are advantages for VAWT offshore and we utilize decades of Sandia experience with VAWTs)Large Offshore Rotors
5 Large Rotor Project: Our Goals; Approach…. 4/1/2017Large Rotor Project: Our Goals; Approach….Identify challenges in design of future large bladesPerform detailed design (layup, design standards, analysis, etc.)Produce a baseline 100-meter blade; certification approachMake these models publicly availableTargeted follow-on studies for large bladesBlade weight reduction, advanced conceptsAeroelasticity; power performanceCost studies for large blades and large turbines
6 SNL Research Blade Designs: Late 1990’s to present Research GoalCX-100Strategic use of carbon fiberTX-100Bend-twist couplingBSDSFlatback/thick airfoils
7 Large Blade/Turbine Work Prior to this study 4/1/2017Large Blade/Turbine Work Prior to this studyStarting point needed…..Limited data is publicly available……no detailed layups in public domainHowever, a few “public studies” (Europe and US) provide some data for blades approximately 60 meters and turbines with rating of 5-6 MWDOWEC study : Blade beam properties and Airfoil definitions from maximum chord outboardNREL 5MW turbine: Used the DOWEC blade model; Turbine model (tower, drivetrain, etc.) and ControllerThese studies were useful for upscaling to 100-meter scale to develop the initial design models, although additional information and analysis was needed for this study
8 Initial Large Blade Trend Studies Blade Scaling and Design DriversWeight growth is one of the large blade challenges. Additional challenges are explored in the detailed design & analysis process.
9 SNL100-00 External Geometry 4/1/2017SNL External GeometryThe inboard airfoils of maximum chord were produced by interpolation.Otherwise, this baseline SNL designed uses a scaled-up chord distribution and outboard airfoil shapes from DOWEC; same twist as well
10 Design Loads and Safety Factors 4/1/2017Design Loads and Safety FactorsAcceptance of the design to blade design standards is a key element of the work; certification process using IEC and GL specifications; Class IB sitingWind ConditionDescriptionIEC DLC NumberDesign Situation(Normal or Abnormal)ETM (Vin < Vhub < Vout)Extreme Turbulence Model1.3Power Production (N)ECD (Vhub = Vr +/- 2 m/s)Extreme Coherent Gust with Direction Change1.4EWS (Vin < Vhub < Vout)Extreme Wind Shear1.5EOG (Vhub = Vr +/- 2 m/s)Extreme Operating Gust3.2Start up (N)EDC (Vhub = Vr +/- 2 m/s)Extreme WindDirection Change3.3EWM (50-year occurrence)Speed Model6.2Parked (A)EWM (1-year occurrence)6.3Parked (N)Safety factors for materials and loads included for buckling, strength, deflection, and fatigue analyses
11 SNL100-00: Design Constraints and Assumptions 4/1/2017SNL100-00: Design Constraints and AssumptionsAll-glass materialsno carbonTypical or traditional manufacturingPly-dropping, parasitic resin massTypical geometry and architectureNo flatbacksInitially two shear web design……….all these assumptions led to a baseline design that we’ve termed SNL100-00;Which is not formally optimized for weight, but is designed to work and reduce weight as much as possible despite the lack of inclusion of any blade innovations.
12 Initial SNL100-00 Design: Two Shear Web Architecture 4/1/2017Initial SNL Design: Two Shear Web ArchitectureLeading EdgePanelTrailing EdgeTwo shear webs not acceptable due to buckling failure and high weight
17 (1) Sandia Flutter Parameter Study Resor, Owens, and Griffith. “Aeroelastic Instability of Very Large Wind Turbine Blades.” Scientific Poster Paper; EWEA Annual Event, Copenhagen, Denmark, April 2012.Data shown are from classical flutter analyses:SNL CX-100; 9-meter experimental bladeWindPact meter 1.5MW concept bladeSNL 61.5-meter blade (preliminary design)SNL Baseline Blade
18 (2) High-fidelity CFD Analysis of SNL100-00 Fully coupled fluid/structure interaction model of Sandia’s 100m blade has been developed using AcuSolveAcuSolve CFD solution validated against existing toolsGood agreement with WT_Perf for all quantitiesSome curious results when comparing AcuSolve and WT_Perf to FASTModel extended to handle wind gusts and blade flutter simulationsCorson, D., Griffith, D.T, et al, “Investigating Aeroelastic Performance of Multi-MegaWatt Wind Turbine Rotors Using CFD,” AIAA Structures, Structural Dynamics and Materials Conference, Honolulu, HI, April , AIAA
19 (3.1) Sandia Blade Manufacturing Cost Model: Approach Components of the Model:Materials, Labor, Capital EquipmentInput the design characteristicsGeometry and BOM from blade design software (NuMAD)Materials cost based on weight or areaLabor scaled based on geometry associated with the subtaskCapital equipment scaled from typical on-shore bladesTwo principal questions:Trends in principal cost components for larger blades?Cost trade-offs for SNL100 meter design variants?
20 (3.2) Sandia Blade Manufacturing Cost Model: Total Cost Examples: labor scaling factor for subtasks based on component length, surface area, total ply length, bond line length, etc.Plans to document this soon, including SNL carbon blade studiesInitial feedback has been positive and constructiveMaterial costs become a much greater driver of overall manufacturing costsMaterials: 3rd power, Labor: 1.5, Equipment: 2.09, Overall: 2.7Weight reduction reduces the cost of both materials and labor
21 (3.3) Sandia Blade Manufacturing Cost Model: Labor Manufacturing operations related to blade surface area become a much larger driver of labor costs (skin lay-up and finishing operations like painting and sanding)
22 (4.1) Carbon Design Studies Conceptual carbon laminate introduced into Baseline SNL100-00 Blade Initial studies: replace uni-directional glass in either spar cap or trailing edge reinforcement with carbonSNL100-00: Baseline All-glass BladeCase Study #1: All carbon spar capCase Study #2: All carbon trailing edgeCase Study #3: All carbon spar cap with foamCase Study #4: Reduce spar width and replace with carbon; reduce TE reinforcement dimensions
23 Fatigue Lifetime (years) Lowest Buckling Frequency (4.2) Carbon Design Studies Design Scorecard Comparison: Performance and WeightSNL Baseline**Case Study #1CaseStudy #2Case Study #3Case Study #4All-glass baseline bladeCarbon Spar CapCarbon Trailing Edge ReinforcementCarbon Spar Cap plus FoamCarbon Spar width and TE reductionMax Deflection (m)11.910.312.012.7Fatigue Lifetime (years)1000N/A28172Governing locationfor fatigue lifetime15% spanedge-wiseflap-wise11% span flap-wiseLowest Buckling Frequency2.3650.6142.3322.3912.158Blade Mass (kg)114,19782,336108,89793,49478,699Span-wise CG (m)33.631.032.134.031.3
24 (4.3) Carbon Design Studies Design Scorecard Comparison: Bill of Materials SNL BaselineCase Study #4All-glass baseline bladeCarbon Spar width and TE reductionBlade Mass (kg)114,19778,699Span-wise CG (m)33.631.3E-LT-5500 Uni-axial Glass Fiber (kg)39,39413,894Saertex Double-bias Glass Fiber (kg)10,54610,623Foam (kg)15,06816,798Gelcoat (kg)927Total InfusedResin (kg)53,85732,234Newport 307 CarbonFiber Prepreg (kg)8,586
25 (4.4) Carbon Design Studies Observations: Comparison with SNL100-00 Baseline For Case Study #1, all carbon spar cap:buckling of the thinner spar capFor Case Study #2, all carbon trailing edge (reduced width):small decrease in blade weight; important for flutterFor Case Study #3, all carbon spar cap with foam:large weight reduction; flap-wise fatigue became driverFor Case Study #4, reduced carbon spar width and TE reductionfurther weight reduction, buckling satisfied, flap-wise fatigue driven, chord-wise CG forward = greater flutter marginWill finalize the updated design “SNL100-01” in near futureCost-performance tradeoffsUpdated 13.2 MW Turbine model with SNL bladesBoth blade and turbine to be publicly available
26 Large Blade Research Needs 4/1/2017Large Blade Research NeedsInnovations for weight and load reductionEvaluation of design code suitability for analysis of large-scale machinesLarge deflection behaviorSpatial variation of inflow across the rotorAnti-buckling and flutter mitigation strategiesAerodynamics and power optimization: aerodynamic twist, chord schedule, and tip speed ratioTransportation and manufacturing
27 Revisit SNL Research Blade Innovations…… Research GoalCX-100Strategic use of carbon fiberTX-100Bend-twist couplingBSDSFlatback/thick airfoils
28 4/1/2017Resources, Model FilesModel files on Project Website (both blade and turbine)SNL Blade: detailed layup (NuMAD), ANSYS inputSNL Land Turbine: FAST turbine, controller, IECWind, ModesReferences:Griffith, D.T., Ashwill, T.D., “The Sandia 100-meter All-glass BaselineWind Turbine Blade: SNL100-00,” Sandia National LaboratoriesTechnical Report, June 2011, SANDResor, B., Owens, B, Griffith, D.T., “Aeroelastic Instability of Very LargeWind Turbine Blades,” (Poster and Paper), EWEA Annual EventScientific Track, Copenhagen, Denmark, April 16-19, 2012.Griffith, D. T., Resor, B.R., “Challenges and Opportunities in LargeOffshore Rotor Development: Sandia 100-meter Blade Research,”AWEA WindPower 2012 (Scientific Track), Atlanta, GA, June 1, 2012.
30 Sandia Classical Flutter Capability SNL legacy capability (Lobitz, Wind Energy 2007) utilized MSC.Nastran and Fortran to set up and solve the classical flutter problem.Requires numerous manual iterations to find the flutter speedA new Matlab based tool has been developed in 2012Starting point: Emulate all assumptions of the legacy Lobitz toolContinued development and verification: automated iterations, higher fidelity modeling assumptionsFlutter Mode ShapeMatrixDescriptionM, C, KConventional matrices(with centrifugal stiffening)Ma(Ω), Ca(ω, Ω), Ka(ω, Ω)Aeroelastic matricesCC(Ω)CoriolisKcs(Ω)Centrifugal softeningKtcBend-twist coupling