Sources of Wind Turbine Noise
Wind Turbine Aeroacoustic Issues Paul G. Migliore National Renewable Energy Laboratory California Wind Energy Consortium Forum University of California, Davis 17-18 December 2002
Operated for the U.S. Department of Energy by Midwest Research Institute • Battelle • Bechtel
Presentation Overview
Importance of Wind Turbine Noise Sources of Wind Turbine Noise Current State of the Art NREL Research Program Future Plans
Slide Number 2
National Wind Technology Center
Importance of Wind Turbine Noise – We are moving toward a sustainable energy future – EWEA estimates 12% of world’s energy may come from wind turbines by the year 2020 (1,260,000 MW) – This means wider deployment of wind turbines, at lower wind speed sites (close to people & transmission lines) – We need efficient turbines to exploit these sites – We need to minimize annoyance, which is a deterrent to deployment – Trade off: improve performance with minimum impact on noise or reduce noise to promote deployment (dB(A) ~ kWh ~ $$$)
Slide Number 3
National Wind Technology Center
The Earth Is Becoming Crowded!
Slide Number 4
National Wind Technology Center
Class 3 and Class 4 Wind Sites
Slide Number 5
Population Density
National Wind Technology Center
Design of wind turbines for low wind speed sites will have the effect of expanding the wind resource area More people will be impacted by turbine acoustic emissions
Slide Number 6
National Wind Technology Center
Presentation Overview Importance of Wind Turbine Noise Sources of Wind Turbine Noise – gearbox, generator, brakes, electronics, tower … – aeroacoustic (rotor blades)
Current State of the Art NREL Research Program Future Plans
Slide Number 7
National Wind Technology Center
Sources of Wind Turbine Noise – – – – – –
Slide Number 8
Laminar Boundary Layer Vortex- Shedding Noise Turbulent Boundary Layer Trailing Edge Noise Leading Edge Inflow Turbulence Noise Blunt Trailing Edge Noise Separation Noise Blade Tip Noise
National Wind Technology Center
Sources of Wind Turbine Noise – Laminar Boundary Layer Vortex- Shedding Noise – Turbulent Boundary Layer Trailing Edge Noise – – – –
Slide Number 9
Leading Edge Inflow Turbulence Noise Blunt Trailing Edge Noise Separation Noise Blade Tip Noise
National Wind Technology Center
Sources of Wind Turbine Noise – – – – – –
Slide Number 10
Laminar Boundary Layer Vortex- Shedding Noise Turbulent Boundary Layer Trailing Edge Noise Leading Edge Inflow Turbulence Noise Blunt Trailing Edge Noise Separation Noise Blade Tip Noise
National Wind Technology Center
Sources of Wind Turbine Noise – – – – – –
Slide Number 11
Laminar Boundary Layer Vortex- Shedding Noise Turbulent Boundary Layer Trailing Edge Noise Leading Edge Inflow Turbulence Noise Blunt Trailing Edge Noise Separation Noise Blade Tip Noise
National Wind Technology Center
Sources of Wind Turbine Noise – – – – –
Laminar Boundary Layer Vortex- Shedding Noise Turbulent Boundary Layer Trailing Edge Noise Leading Edge Inflow Turbulence Noise Blunt Trailing Edge Noise Separation Noise
– Blade Tip Noise
Slide Number 12
National Wind Technology Center
R. Stoker, The Boeing Company
Sources of Wind Turbine Noise – – – – – –
Laminar Boundary Layer Vortex- Shedding Noise Turbulent Boundary Layer Trailing Edge Noise Leading Edge Inflow Turbulence Noise Blunt Trailing Edge Noise Separation Noise Blade Tip Noise
Slide Number 13
National Wind Technology Center
Presentation Overview Importance of Wind Turbine Noise Sources of Wind Turbine Noise Current State of the Art NREL Research Program Future Plans
Slide Number 14
National Wind Technology Center
Sound Power Level – dB(A)
Acoustic Emission Trends with Turbine Size
J.J.D. van Dam, ECN
Rotor Diameter (m)
Slide Number 15
National Wind Technology Center
Trends in Noise Footprint with Time
Circular Area (m2)/kW
40 dB(A) Noise Footprint
J.J.D. van Dam, ECN
Calendar Year Time Scale Slide Number 16
National Wind Technology Center
Presentation Overview Importance of Wind Turbine Noise Sources of Wind Turbine Noise Current State of the Art NREL Research Program Future Plans
Slide Number 17
National Wind Technology Center
Aeroacoustic Field Tests at NREL
Slide Number 18
SWWP Whisper H40 AOC 15/50 Bergey Excel Bergey Excel (SH3052) Bergey XL.1 NPS 100 SWWP AIR-X SWWP Whisper H80
National Wind Technology Center
Bergey Excel 10 kW Turbine Improvements 85 80
sound pressure level (dB A)
75 70 65 60 55 50 Background 45
Old Blades - Turbine Loaded Old Blades - Unloaded
40
New Blades - Tubine Loaded New Blades - Unloaded
35 0
4
8
12
16
20
24
28
wind speed @ 10 m height (m/s)
Slide Number 19
National Wind Technology Center
Wind Tunnel Tests Conduct wind tunnel aeroacoustic tests to measure noise emissions of various airfoils and the sensitivity to inflow turbulence Conduct wind tunnel aerodynamic tests to obtain complementary performance data
Slide Number 20
National Wind Technology Center
Airfoils Tested SD 2030 – Southwest Windpower AIR-403 and AIR-X
FX 63-137 – Southwest Windpower Whisper H40/H80
S822 – Tangler/Somers (Re = 1,000,000)
S834 – Tangler/Somers (Re = 400,000)
SH 3055 – Bergey XL.10 (mod)
SG 6043 – Selig/Giguere (Low Re and High L/D) Slide Number 21
National Wind Technology Center
NLR Small Aeroacoustic Wind Tunnel Anechoic chamber absorbs noise below 250 Hz 16”x20” open jet (260 ft/sec) Acoustically lined end plates Inflow turbulence generators 48-microphone phased array acoustic antenna Netherlands National Aerospace Laboratory (NLR) Small Anechoic Wind Tunnel Slide Number 22
National Wind Technology Center
Source Plot Showing Strong Trailing Edge Imissions
Source Plot Showing Strong Leading Edge Imissions
Slide Number 23
National Wind Technology Center
Illustration of Undesirable Pure Tones
Pure Tones
Broadband Only, No Pure Tones
Slide Number 24
National Wind Technology Center
Illustration of Undesirable Pure Tones
Pure Tones
Broadband Only, No Pure Tones
Slide Number 25
National Wind Technology Center
Presentation Overview
Importance of Wind Turbine Noise Sources of Wind Turbine Noise Current State of the Art NREL Research Program Future Plans
Slide Number 26
National Wind Technology Center
Putting It All Together in a New Design Choose airfoil(s) – Aerodynamic performance – Aeroacoustic emissions
Optimize planform – Energy capture codes – Aeroacoustic design code
Avoid tower shadow problem (low-frequency impulsive noise) – CAA codes???
Slide Number 27
Southwest Windpower “Storm” 1.5 kW
National Wind Technology Center
Quasi-Empirical Noise Prediction Codes
Slide Number 28
National Wind Technology Center
Computational Aeroacoustics
D. Stead, NASA Langley Research Center
Builds on fundamental equations of motion with CFD input to CAA Attempts to capture flow physics Used extensively in airframe noise studies with considerable success Slide Number 29
National Wind Technology Center
Summary In the future, wind turbines are likely to be deployed closer to people. Wind turbine noise is an issue if it becomes a deterrent to deployment – there is a trade off between cost effectiveness ($$$) and noise. Many complex noise sources need to be considered. Lowest noise emission level for large turbines is ≅ 99 dB(A) [600 m2/kW for 40 dB(A) at receptor location]. NREL field tests, wind tunnel tests and computer code development to understand and mitigate noise emissions . Improvements expected for small and large wind turbines. Slide Number 30
National Wind Technology Center
Operated for the U.S. Department of Energy by Midwest Research Institute • Battelle • Bechtel
Presentation Overview
Importance of Wind Turbine Noise Sources of Wind Turbine Noise Current State of the Art NREL Research Program Future Plans
Slide Number 2
National Wind Technology Center
Importance of Wind Turbine Noise – We are moving toward a sustainable energy future – EWEA estimates 12% of world’s energy may come from wind turbines by the year 2020 (1,260,000 MW) – This means wider deployment of wind turbines, at lower wind speed sites (close to people & transmission lines) – We need efficient turbines to exploit these sites – We need to minimize annoyance, which is a deterrent to deployment – Trade off: improve performance with minimum impact on noise or reduce noise to promote deployment (dB(A) ~ kWh ~ $$$)
Slide Number 3
National Wind Technology Center
The Earth Is Becoming Crowded!
Slide Number 4
National Wind Technology Center
Class 3 and Class 4 Wind Sites
Slide Number 5
Population Density
National Wind Technology Center
Design of wind turbines for low wind speed sites will have the effect of expanding the wind resource area More people will be impacted by turbine acoustic emissions
Slide Number 6
National Wind Technology Center
Presentation Overview Importance of Wind Turbine Noise Sources of Wind Turbine Noise – gearbox, generator, brakes, electronics, tower … – aeroacoustic (rotor blades)
Current State of the Art NREL Research Program Future Plans
Slide Number 7
National Wind Technology Center
Sources of Wind Turbine Noise – – – – – –
Slide Number 8
Laminar Boundary Layer Vortex- Shedding Noise Turbulent Boundary Layer Trailing Edge Noise Leading Edge Inflow Turbulence Noise Blunt Trailing Edge Noise Separation Noise Blade Tip Noise
National Wind Technology Center
Sources of Wind Turbine Noise – Laminar Boundary Layer Vortex- Shedding Noise – Turbulent Boundary Layer Trailing Edge Noise – – – –
Slide Number 9
Leading Edge Inflow Turbulence Noise Blunt Trailing Edge Noise Separation Noise Blade Tip Noise
National Wind Technology Center
Sources of Wind Turbine Noise – – – – – –
Slide Number 10
Laminar Boundary Layer Vortex- Shedding Noise Turbulent Boundary Layer Trailing Edge Noise Leading Edge Inflow Turbulence Noise Blunt Trailing Edge Noise Separation Noise Blade Tip Noise
National Wind Technology Center
Sources of Wind Turbine Noise – – – – – –
Slide Number 11
Laminar Boundary Layer Vortex- Shedding Noise Turbulent Boundary Layer Trailing Edge Noise Leading Edge Inflow Turbulence Noise Blunt Trailing Edge Noise Separation Noise Blade Tip Noise
National Wind Technology Center
Sources of Wind Turbine Noise – – – – –
Laminar Boundary Layer Vortex- Shedding Noise Turbulent Boundary Layer Trailing Edge Noise Leading Edge Inflow Turbulence Noise Blunt Trailing Edge Noise Separation Noise
– Blade Tip Noise
Slide Number 12
National Wind Technology Center
R. Stoker, The Boeing Company
Sources of Wind Turbine Noise – – – – – –
Laminar Boundary Layer Vortex- Shedding Noise Turbulent Boundary Layer Trailing Edge Noise Leading Edge Inflow Turbulence Noise Blunt Trailing Edge Noise Separation Noise Blade Tip Noise
Slide Number 13
National Wind Technology Center
Presentation Overview Importance of Wind Turbine Noise Sources of Wind Turbine Noise Current State of the Art NREL Research Program Future Plans
Slide Number 14
National Wind Technology Center
Sound Power Level – dB(A)
Acoustic Emission Trends with Turbine Size
J.J.D. van Dam, ECN
Rotor Diameter (m)
Slide Number 15
National Wind Technology Center
Trends in Noise Footprint with Time
Circular Area (m2)/kW
40 dB(A) Noise Footprint
J.J.D. van Dam, ECN
Calendar Year Time Scale Slide Number 16
National Wind Technology Center
Presentation Overview Importance of Wind Turbine Noise Sources of Wind Turbine Noise Current State of the Art NREL Research Program Future Plans
Slide Number 17
National Wind Technology Center
Aeroacoustic Field Tests at NREL
Slide Number 18
SWWP Whisper H40 AOC 15/50 Bergey Excel Bergey Excel (SH3052) Bergey XL.1 NPS 100 SWWP AIR-X SWWP Whisper H80
National Wind Technology Center
Bergey Excel 10 kW Turbine Improvements 85 80
sound pressure level (dB A)
75 70 65 60 55 50 Background 45
Old Blades - Turbine Loaded Old Blades - Unloaded
40
New Blades - Tubine Loaded New Blades - Unloaded
35 0
4
8
12
16
20
24
28
wind speed @ 10 m height (m/s)
Slide Number 19
National Wind Technology Center
Wind Tunnel Tests Conduct wind tunnel aeroacoustic tests to measure noise emissions of various airfoils and the sensitivity to inflow turbulence Conduct wind tunnel aerodynamic tests to obtain complementary performance data
Slide Number 20
National Wind Technology Center
Airfoils Tested SD 2030 – Southwest Windpower AIR-403 and AIR-X
FX 63-137 – Southwest Windpower Whisper H40/H80
S822 – Tangler/Somers (Re = 1,000,000)
S834 – Tangler/Somers (Re = 400,000)
SH 3055 – Bergey XL.10 (mod)
SG 6043 – Selig/Giguere (Low Re and High L/D) Slide Number 21
National Wind Technology Center
NLR Small Aeroacoustic Wind Tunnel Anechoic chamber absorbs noise below 250 Hz 16”x20” open jet (260 ft/sec) Acoustically lined end plates Inflow turbulence generators 48-microphone phased array acoustic antenna Netherlands National Aerospace Laboratory (NLR) Small Anechoic Wind Tunnel Slide Number 22
National Wind Technology Center
Source Plot Showing Strong Trailing Edge Imissions
Source Plot Showing Strong Leading Edge Imissions
Slide Number 23
National Wind Technology Center
Illustration of Undesirable Pure Tones
Pure Tones
Broadband Only, No Pure Tones
Slide Number 24
National Wind Technology Center
Illustration of Undesirable Pure Tones
Pure Tones
Broadband Only, No Pure Tones
Slide Number 25
National Wind Technology Center
Presentation Overview
Importance of Wind Turbine Noise Sources of Wind Turbine Noise Current State of the Art NREL Research Program Future Plans
Slide Number 26
National Wind Technology Center
Putting It All Together in a New Design Choose airfoil(s) – Aerodynamic performance – Aeroacoustic emissions
Optimize planform – Energy capture codes – Aeroacoustic design code
Avoid tower shadow problem (low-frequency impulsive noise) – CAA codes???
Slide Number 27
Southwest Windpower “Storm” 1.5 kW
National Wind Technology Center
Quasi-Empirical Noise Prediction Codes
Slide Number 28
National Wind Technology Center
Computational Aeroacoustics
D. Stead, NASA Langley Research Center
Builds on fundamental equations of motion with CFD input to CAA Attempts to capture flow physics Used extensively in airframe noise studies with considerable success Slide Number 29
National Wind Technology Center
Summary In the future, wind turbines are likely to be deployed closer to people. Wind turbine noise is an issue if it becomes a deterrent to deployment – there is a trade off between cost effectiveness ($$$) and noise. Many complex noise sources need to be considered. Lowest noise emission level for large turbines is ≅ 99 dB(A) [600 m2/kW for 40 dB(A) at receptor location]. NREL field tests, wind tunnel tests and computer code development to understand and mitigate noise emissions . Improvements expected for small and large wind turbines. Slide Number 30
National Wind Technology Center
