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The Impact of Active Aerodynamic Load Control on Wind Energy Capture at Low Wind Speed Sites

The Impact of Active Aerodynamic Load Control on Wind Energy Capture at Low Wind Speed Sites. Jose Zayas Manager, Wind Energy Technology Dept. Sandia National Laboratories www.sandia.gov/wind jrzayas@sandia.gov. Authors:.

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The Impact of Active Aerodynamic Load Control on Wind Energy Capture at Low Wind Speed Sites

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  1. The Impact of Active Aerodynamic Load Control on Wind Energy Capture at Low Wind Speed Sites Jose Zayas Manager, Wind Energy Technology Dept. Sandia National Laboratories www.sandia.gov/wind jrzayas@sandia.gov Authors: SNL: Dale Berg, David Wilson, Brian Resor, Jonathan Berg, and Joshua Paquette FexSys: Sridhar Kota, Gregory Ervin, and Dragan Maric Sandia is a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin Company,for the United States Department of Energy’s National Nuclear Security Administration under contract DE-AC04-94AL85000.

  2. Outline • Background & Motivation • External Conditions and Opportunity • Sandia’s SMART Research Approach • Grow the Rotor Technique • Morphing Technology (FlexSYS) • Results • Summary & Future Work

  3. Justification for Load Control Efforts • Increase in size results in decrease in COE • Leads to increase tower-top weight • Leads to increased gravity-induced stresses at blade root • Weight must be minimized • Technology innovation is needed • Need to minimize blade weight => reduce loads => load control (Passive or Active)

  4. Sandia Effort is Focused on Blades • Why are Blades a Key Research Opportunity? • 20% of turbine cost, but 100% of energy capture • Incremental improvements yield large system benefits • Source of loads for the entire turbine

  5. Turbines Experience Complex External Conditions • Large turbine size means loads vary along blade and change quickly (wind gusts) • Quickly changing loads cause fatigue damage • Active pitch control can only control “average” load on blade • Passive load control cannot respond to local load variations • Fatigue loads can drive the lifetime of all turbine components

  6. GOAL! Turbine Power Basics & Opportunity Wind Turbine Power Curve Power =½ρACpV∞3 Regions of the Power Curve Region I – not enough power to overcome friction Region II – Operate at maximum efficiency at all times Region III – Fixed power operation Wind Speed Distribution Goal: Develop advanced rotors which incorporate passive and/or active aerodynamics to address system loads, increase turbine efficiency, and energy capture.

  7. Future Design Needs • Advanced Control Strategies • Advanced Embedded Sensors • Structural Health Monitoring Sandia Strategy for Enabling Advanced Blades Enabling New Technology Develop small, light-weight control devices & systems to attenuate fatigue loads on turbine blades and increase turbine efficiency • Novel Concepts • Aeroacoustics Aerodynamics Controls Sensors • Also Need: • Structural analysis • Active aero device • Manufacturing (integration)

  8. Active Aerodynamic Blade Load Control is One Promising Option Consider Active Aerodynamic Load Control (AALC) Sensors distributed along blade sense local conditions current ongoing project (SNL-SBlade) Load control devices distributed along blade respond quickly alleviate local loads Control architecture and implementation • Apply devices near the blade tip (initial focus) • Maximum loads • Maximum control impact 1.5 MW Turbine Blade Model

  9. Previous AALC Work • Previous work (Risø & TU Delft) shows AALC has potential to significantly reduce blade loads • Approximately 50% • Successful AALC presents challenges • Integrate devices and sensors into blades • Maintain reliability • Minimize additional cost • Potential design and manufacturing impact • AALC may also increase energy capture Sandia effort is referred to as Structural and Mechanical Adaptive Rotor Technology (SMART)

  10. Grow the Rotor (GTR) Concept Estimate Cost of Energy: • Usual approach • Design new machine to withstand design loads (limit fatigue loads) • Determine component costs (subject to large errors) • Determine energy capture • Evaluate economics • Alternative approach • Examine existing machine • Determine reduction in fatigue loads due to active aero load control • Determine allowable increase in blade length • Determine additional rotor costs • Evaluate increase in energy capture • Evaluate economics

  11. FlexSys Morphing Trailing Edge Technology • Continuous deformation of upper & lower surfaces • Higher deflection without separation • Less drag for given deflection • No gap through which air can leak (noise) • Fast response (100 degrees/sec) 1990-era Zond Flap Technology FlexSys Demonstration Unit Comparison of Flap Geometries

  12. Fatigue Load Reduction Approach • Simulate turbine operation over operating wind-speed range • Evaluate fatigue damage at each wind speed • Rain-flow cycle counting • Linear damage accumulation • Combine with wind speed distribution to determine overall fatigue damage • Investigate baseline rotor, baseline with AALC (FlexSys Morphing Trailing Edge or FMTE) and 10% longer blades with AALC • Compare fatigue accumulation ratios • Normalize large fatigue calculation errors

  13. Effects of AALC on Turbine Components Turbine FAST/Aerodyn/Simulink Simulation Turbulent Wind Input Increase in Energy Capture Grow the Rotor Rain Flow Counting

  14. Blade Root Flap Moment for GTR is Comparable to Baseline Rotor

  15. Fatigue Damage Summary One-million Cycle Damage Equivalent Load (Baseline-AALC/Baseline Rotor) All results are % increase or decrease relative to baseline rotor FlexSys Morphing Trailing Edge. 20%c, +/-10° Configuration

  16. Fatigue Damage Summary One-million Cycle Damage Equivalent Load (10% GTR-AALC/Baseline Rotor) All results are % increase or decrease relative to baseline rotor FlexSys Morphing Trailing Edge. 20%c, +/-10° Configuration

  17. GTR Energy Capture is Increased for Comparable Blade Flap Fatigue Damage FMTE 20%c, +/-10° Configuration Blade Length Increase 10% Increase in energy capture is approximately 13% at 5.5 m/s, 12% at 6 m/s and 9% at 8 m/s 5.5 m/s Rayleigh Wind Speed Distribution

  18. Trailing Edge Demo

  19. Summary and Future Work • Use of AALC can achieve significant reductions in blade flap root fatigue damage • GTR concept results in significant additional energy capture at lower wind speed and provides a transition for the technology • Additional work remains • Control optimization (sensor/actuator optimization) • Analysis of impact on blade torsional compliance • Evaluate true “distributed” sensing & control

  20. Thank You! Jose Zayas Program Manager, Wind Energy Technology Dept. Sandia National Laboratories jrzayas@sandia.gov (505) 284-9446 www.sandia.gov/wind

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