Technische Universität München
Lehrstuhl für Leichtbau (LLB) Institute of Lightweight Structures
Smart Wind Turbine Rotor Blades
Luiz da Rocha-Schmidt, Felix Stroscher, Bin Wei, Horst Baier
03.07.2012
Technische Universität München
Lehrstuhl für Leichtbau (LLB) Institute of Lightweight Structures
Contents
• Motivation: Reduce peak (gust) loads on wind turbines
• Smart / Adaptive Wings: Aircraft, Helicopter
• Morphing Control Surfaces
• Gust Load Alleviation on Wind Turbines
• Conclusion
03.07.2012 2 Luiz da Rocha-Schmidt
Technische Universität München
Lehrstuhl für Leichtbau (LLB) Institute of Lightweight Structures
Motivation
• Wind Power is a well established, clean energy source
• Efficiency aim: build larger wind turbines
– Largest to date: Enercon E-126, d=126m, P=7,5MW
• Size limitation (among others):
– Structural loads due to gravity and wind
– Lifespan impact: instationary gust loads
03.07.2012 3 Luiz da Rocha-Schmidt
Technische Universität München
Lehrstuhl für Leichtbau (LLB) Institute of Lightweight Structures
Smart / Adaptive Structures
Sensor Controller Actuator
03.07.2012 4
• Sensor: observe a disturbance – e.g. wind, acceleration, strain sensor
• Controller: determine reaction to achieve desired result – e.g. feedback / feedforward controller
• Actuator: execute controller command – e.g. blade pitch axis rotation, control surface
Luiz da Rocha-Schmidt
Technische Universität München
Lehrstuhl für Leichtbau (LLB) Institute of Lightweight Structures
• Structural wing model
– Finite Element Method
• Aerodynamic Wing Model
– Doublet Lattice Method
• Coupled Aero-Elastic analysis
– time domain
Trailing edge devices for
flight- and load control
Dynamic Load Alleviation (aircraft)
03.07.2012 5 Luiz da Rocha-Schmidt
Technische Universität München
Lehrstuhl für Leichtbau (LLB) Institute of Lightweight Structures
Dynamic Load Alleviation (aircraft)
• Feedforward controller
– „Gust sniffer“ in front of the wing
– Control command on the flaps
• Structural response
– 30 % peak load reduction
03.07.2012 6 Luiz da Rocha-Schmidt
Technische Universität München
Lehrstuhl für Leichtbau (LLB) Institute of Lightweight Structures
Dynamic Load Alleviation / Noise Reduction (Helicopter Blade)
• „Smart“ Helicopter rotor blade
– Piezo-actuated Trailing edge
• +/- 6°deflection
– Reduced Blade loads
– Reduced Noise Level
03.07.2012 7 Luiz da Rocha-Schmidt
Technische Universität München
Lehrstuhl für Leichtbau (LLB) Institute of Lightweight Structures
Morphing Control Surfaces
• Plain flaps vs. Morphing Flaps
• Benefits:
– Reduced Drag, increased Lift
– More generated power with same structural loads
03.07.2012 8 Luiz da Rocha-Schmidt
Technische Universität München
Lehrstuhl für Leichtbau (LLB) Institute of Lightweight Structures
Airfoil morphing
9
S814 Airfoil S812 Airfoil S813 Airfoil
Sample reference rotor: AOC 15/50 – Layout and airfoils:
Adaptation using a generic elastoflexible airfoil
03.07.2012 Luiz da Rocha-Schmidt
See Poster by Institute of Aerodynamics and Fluid Mechanics!
Technische Universität München
Lehrstuhl für Leichtbau (LLB) Institute of Lightweight Structures
Transient Wind Loads (Video)
NREL 5 MW reference turbine
hub height: 90 m, rotor diameter: 126 m, mean wind speed: 12 m/s
03.07.2012 10 Luiz da Rocha-Schmidt
Technische Universität München
Lehrstuhl für Leichtbau (LLB) Institute of Lightweight Structures
Transient Wind Loads (Video)
NREL 5 MW reference turbine
hub height: 90 m, rotor diameter: 126 m, mean wind speed: 12 m/s
03.07.2012 11 Luiz da Rocha-Schmidt
Technische Universität München
Lehrstuhl für Leichtbau (LLB) Institute of Lightweight Structures
Effects of gust load alleviation on a wind turbine blade
• NREL 5 MW reference turbine, Lee et. al., KAIST, Daejeon, Korea
03.07.2012 12 Luiz da Rocha-Schmidt
Technische Universität München
Lehrstuhl für Leichtbau (LLB) Institute of Lightweight Structures
Challenges
• Reliability
– If the control system fails, the turbine can not be operated without the risk of damage
• Cost
– Additional hard- and software is needed
• Power Requirements
– Energy consumption of the controller and the actuators must be kept low
03.07.2012 13 Luiz da Rocha-Schmidt
Technische Universität München
Lehrstuhl für Leichtbau (LLB) Institute of Lightweight Structures
Conclusion
• Smart Rotor Blades are able to reduce peak loads
• Aerodynamically efficient control surfaces: Morphing Flaps
• Combined: Larger and more efficient wind turbines
03.07.2012 14 Luiz da Rocha-Schmidt
Technische Universität München
Lehrstuhl für Leichtbau (LLB) Institute of Lightweight Structures
Thank you – Questions?
03.07.2012 15 Luiz da Rocha-Schmidt
Technische Universität München
Lehrstuhl für Leichtbau (LLB) Institute of Lightweight Structures
BACKUP SLIDES
03.07.2012 16 Luiz da Rocha-Schmidt
Technische Universität München
Lehrstuhl für Leichtbau (LLB) Institute of Lightweight Structures
Passive Solution: Elastoflexible wing
17
Concept • Internal Support Structure
• Elastic membrane skin as aerodynamic surface
Reasoning • Large shape variations are possible with low effort
• passive flow control through load-dependent
membrane deflection
Source: TUM Institute of Aerodynamics and Fluid Mechanics & TUM Institute for Computational Mechanics
03.07.2012 Luiz da Rocha-Schmidt
Technische Universität München
Lehrstuhl für Leichtbau (LLB) Institute of Lightweight Structures
Feedforward adaptive filtering → Learning capabilities for specific input signal
→ Response on discrete gust triplet with adaptive filtering
→ Peak reduction increases with time, as filter parameters are adapted
→ ~ 50% Peak reduction
Dynamic Load Alleviation (aircraft)
03.07.2012 18 Luiz da Rocha-Schmidt
Technische Universität München
Lehrstuhl für Leichtbau (LLB) Institute of Lightweight Structures
19
Windenergieanlagen: morphing / adaptive rotors
Membrane wing – “Morphing“ (Airfoil adaptation; passive load control)
03.07.2012 Luiz da Rocha-Schmidt
Technische Universität München
Lehrstuhl für Leichtbau (LLB) Institute of Lightweight Structures
Dynamic Load Alleviation of wing-like structures in unsteady flow fields
→ Feedback controller
• Feedback of acceleration sensor
signal at the wingtip
• 2nd order transfer function for
damping of the 1st bending mode
• Control Command on Trailing Edge
Devices
→ Structural response:
• ~10% reduction of first peak in
bending moment, but very strong
reduction of following peaks
• Highly efficient damping of a steady
vibration
• Low efficiency of highly transient
response
03.07.2012 20 Luiz da Rocha-Schmidt
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