vanDam_CWEC2010(1) - Research in Wind Turbine Rotor Design...

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Unformatted text preview: Research in Wind Turbine Rotor Design C.P. “Case” van Dam Mechanical & Aerospace Engineering University of California, Davis [email protected] California Wind Energy Collaborative Forum 10 May 2010 1 Acknowledgements Edward Mayda, Frontier Wind Jonathan Baker, Frontier Wind Kevin Standish, Siemens Windpower David Chao, Vestas Windpower Scott Larwood, University of the Pacific Dora Yen Nakafuji, HECO Mike Zuteck, MDZ Consulting Kevin Jackson, Dynamic Design Engineering, Inc. Wind Energy Technology Department, Sandia National Laboratories, Albuquerque National Wind Technology Center, NREL TPI Composites, Inc. K&C Wind Group UC Davis Et al Myra Blaylock Ray Chow Aubryn Cooperman Scott Johnson Henry Shiu 2 Outline Background Advanced Rotor Design Developments Blade System Design Study (BSDS) Rotor Sweep-Twist Adaptive Rotor (STAR) Ducted Rotor Active Aerodynamic Load Control (AALC) Rotor Circulation Control Rotor Concluding Remarks Source: vanMayda Source: Dam 3 Rotor Diameter (m) Evolution of U.S. Utility-Scale Wind Turbine Technology Source: NREL Year 4 Basic Rotor Performance (Momentum Theory) Disk area, Ad Power in wind, Pw = 1/2 ρ Vw3 Ad Wind speed, Vw Air density, ρ Maximum rotor power, P = 16/27 Pw Rotor efficiency, Cp = P / Pw Betz limit, max Cp = 16/27 = 59.3% 5 Efficiency of Various Rotor Designs Butterfield (2008) • Cp = Protor / (1/2 ρ Vw3 Ad) • Solidity = Blade Area / Ad • TSR = Tip Speed / Vw Cp • High power efficiency for rotors with low solidity and high TSR • Darrieus (VAWT) is less efficient than HAWT • Current three-bladed rotors achieve high efficiency Cp ⇒ 0.52 Tip Speed Ratio TSR = π D RPM / (60 Vw) 6 Critical Performance Challenges to Meet Goal of 20% Wind by 2030 Reduction in capital cost Recently, turbine cost have increased sharply Increase in turbine capacity factor Larger rotors for given rated power Reduced O&M cost Rapid growth has resulted in reliability issues Source: NREL 7 Increased Capacity Factor Larger rotors Advanced Drive Trains Advanced Tower Designs Increased energy capture Longer, lighter blades Load alleviation (passive, active) Taller towers Advanced Blades Higher wind speeds Innovative towers, erection methods Reduced losses Jack-up concept Telescoping concept Improved drivetrains, power electronics Wake losses 8 Utility Scale COE Reduction Potential Source: Thresher, NREL Technology Larger wind turbines (2-5 MW) Advanced rotors and controls Est. COE Reduction 0% ± 5% -15% ± 7% Flexible, more slender, higher tip speed, hybrid carbon-glass, active control, etc. Advanced drive train concepts -10% ± 7% Hybrid drive trains with low-speed PM generators, reduced cost PE, etc. New tower concepts -2% ± 5% Taller, modular, field assembled, load feedback control Improved availability and reduced losses -5% ± 3% Better controls, siting and improved availability Manufacturing improvements -7% ± 3% New manufacturing methods, volume production and learning effects Region and site tailored designs -5% ± 2% Tailoring of larger 100 MW wind plant turbine designs to unique sites 9 Sample Impact of Advanced Rotors on COE Baseline turbine Turbine with advanced rotor 2.0 MW with 90 m rotor Annual average wind speed at hub height = 6.5 m/s Capacity Factor = 0.327 COE = $0.085 /kWh 2.0 MW with 100 m rotor Annual average wind speed at hub height = 6.5 m/s Capacity Factor = 0.370 Increased cost for advanced blades (passive and/or active load control) COE = $0.077 - 0.080 /kWh Estimated improvement in COE = 6 - 9.5 % 10 Sweep-Twist Adaptive Rotor (STAR) 11 Sweep-Twist Adaptive Rotor (STAR) • 2004 DOE award to Blade Division of Knight & Carver to design, build, and demonstrate a rotor based on the sweep-twist concept • Rotor designed for testing on a Zond Z48 turbine with 750 kW rating • Goal to increase annual energy capture of baseline turbine by 5%10% without exceeding baseline rotor loads • To achieve this rotor radius was increased from 24 m to 27 m • Rotor test conducted in 2008 Source: van Dam • Program results published in SAND2009-8037 12 Sweep Twist Passive Load Control Concept 13 Structured Grid System Swept rotor Section shape in tip region Unswept blade Swept blade 14 Field Testing Source: K. Jackson Source: K. Jackson 15 Field Test Site Tehachapi Wind Resource Area Group 2 Z48 Group 1 Z48 STAR 54 STAR Blade Development • Final Review • 7 April 2009 Wind Protected Data 16 Power Comparison 17 Measured Power Curves 18 Energy Comparison 19 Flatwise Blade Root Moment Comparison STAR rotor loads compared to Z48 data collected at Lake Benton site STAR 54 Z48 20 Rank Ordered Blade Flatwise Load Maxima 21 Sweep Twist Adaptive Rotor Increased rotor energy capture through aeroelastically tailored blade design is feasible. STAR-54 captured 12% more energy over baseline Z48 turbines without increasing blade loads. Effectiveness of concept is demonstrated by fact that prototype STAR-54 is operating without any issues more than 2 years after installation and it remains the highest grossing “Z48” in Tehachapi. 22 Active Aerodynamic Load Control (AALC) 23 Active Load Control With wind turbines blades getting larger and heavier, can the rotor weight be reduced by adding active devices? Can active control be used to reduce fatigue loads? Can energy capture in low wind conditions be improved? Goal is to understand the implications and benefits of embedded active blade control, used to alleviate high frequency dynamics AALC review published in SAND2008-4809 24 Wind Turbine Load Control Techniques 25 Blade Load Control Techniques Techniques to control blade loads and rotor performance: Blade size (variable blade length) Incidence angle (variable pitch, variable twist) Airspeed (variable speed) Section aerodynamic characteristics ! In future consider the control of all of these simultaneously R { 2 2 $1 L = * &C L " Vwind + (2#nr ) 2 % r=0 } ' c)dr ( C L min + C L = C L , (, + - . , o ) + C L max • Focus is on small fast-acting systems that change sectional aerodynamic characteristics to alleviate load spikes due to gusts and to reduce blade tip deflections during high load conditions 26 Active Flow Control Triad Kral (1998) 27 Rotor Control Strategy Diagram 28 Microtab Concept Conceptualized in 1998 Tabs that deploy (near-)normal to flow direction Forward of the trailing edge Upper or lower surface Hinge-less device Small actuation forces htab ~ boundary layer thickness Trailing-edge flow condition is altered 29 Methodologies CFD Wind Tunnel Structural Dynamics Simulations Field Testing 30 Microtab Deployment 31 Microtab Deployment 32 Microflap Deployment Time Effect NACA 0012, α = 0˚, Re = 1.0×106, Ma = 0.25 33 Wind Tunnel System Evaluation 18-in. chord 33-in. span for 2D wind tunnel testing Tabs line both upper and lower surface Tabs Body Tail Maintains a 90% Solidity Ratio Unique airfoil design Detachable design: Main body & trailing-edge tail section Baseline modified airfoil Different actuation systems and designs (microtab, microflap, etc.) Modular design Span split into 6 bays Actuator system installation Structural ribs between tabs Contain air leakage in individual bay Source: Maglio Inc. & UC Davis 34 Effect of Tabs on Tip Displacement NREL CART (two-bladed upwind rotor, 600 kW), steady wind speed = 15 m/s Tip displacement as function of time. Tabs activated just before blade reaches tower (azimuth angle = 180 deg) and retracted after passing tower Tip displacement as function of azimuth angle Note: smaller blade tip displacement indicates larger tower clearance 35 Source: D. Lobitz, Sandia Active Aerodynamic Load Control Must be small and scalable Must have fast activation speed Activation forces and power must be low AALC system should be reliable and dependable Devices (sensors, actuators) should be durable and robust Blade manufacturing and maintenance should be considered when embedding AALC systems Driving factor is economics ⇒ successful system must reduce COE AALC systems are currently being field tested on wind turbines in Europe and USA Reports at http://www.sandia.gov/wind/TopicSelection.htm 36 Departing Thoughts Wind power is: Clean, renewable, emission-free A mature and reliable technology Economically viable Wind power can and will continue to play a significant role in the global energy portfolio at utility-, community- and building-scales Growth has brought new challenges, but also new opportunities Rotor RD&D is continuing to further reduce wind COE through: Reductions in blade loads and mass for given energy capture Improvements in rotor energy capture for given loads and mass Shiu 37 ...
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This note was uploaded on 11/13/2011 for the course AEE 495 taught by Professor O.uzol during the Spring '11 term at Middle East Technical University.

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