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The inaudible noise of wind turbines
Lars Ceranna, Gernot Hartmann, and Manfred Henger
Presented at the Infrasound WorkshopNovember 28 – December 02,
2005, Tahiti
Federal Institute for Geosciences and Natural Resources(BGR),
Section B3.11
Stilleweg 2, 30655 Hannover, Germany
Tahiti, Nov/Dec 2005 page 01
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Regional distribution of wind turbines in Germany
page 02
2605 WT1882 MW
3782 WT3563 MW
973 WT818 MW
1325 WT1442 MW
1197 WT1404 MW1955 WT
1589 MW
454 WT320 MW
329 WT322 MW
622 WT575 MW
596 WT542 MW
206 WT162 MW
34 WT28 MW 205 WT
182 MW8.05.95.816.6
NiedersachenNordrhein-WestfalenSachsen-AnhaltSchleswig-Holstein
4.54.1
Brandenburg Mecklenburg-Vorpommern
2.13.03.42.2
HessenRheinland-PfalzSachsenThürigen
0.60.31.1
Baden-WürtembergBayernSaarland
# w
ind
turb
ines
/ 10
0 km
2
source: Ender, 2003
Tahiti, Nov/Dec 2005
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Content
page 03Tahiti, Nov/Dec 2005
The Influence of Wind turbines on Infrasound recordings:
IGADE
Noise Measurements at a single Wind Turbine
Theoretical Estimation of the Sound Pressure Level
Conclusions
• Comparison with Measurements• Scenarios, large Wind Farms, 5
MW Wind Turbines
• The German Infrasound Station IGADE• Data Examples, routine
Analysis
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The German infrasound station IGADE
page 04Tahiti, Nov/Dec 2005
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Milestones of the establishment of IGADE
page 05
Site Inspection
30 April 2003
September 2004 - January 2005
September / October 2003
Installation of IGAH1
Extension to4 element array
April / May 2005
Growing number of Wind turbines close to the array
IGADE
Tahiti, Nov/Dec 2005
∆≈4 km, β≈220°
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The spectral fingerprint of wind turbines: IGAH1
page 06Tahiti, Nov/Dec 2005
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The spectral fingerprint of wind turbines: IGADE
page 07
14-Sep-2005 19:40 – 20:00 (UTC)07-May-2005 12:10 – 12:30
(UTC)
Tahiti, Nov/Dec 2005
3 blades, ∆f=1 Hz, 20 rpm 3 blades, ∆f=1.35 Hz, 27 rpm
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The fingerprint of wind turbines in the routine analysis
page 08
PMCC analysis
February – November 2005, [0.7 4.0] Hz
Tahiti, Nov/Dec 2005
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Content
page 09Tahiti, Nov/Dec 2005
The Influence of Wind turbines on Infrasound recordings:
IGADE
Noise Measurements at a single Wind Turbine
Theoretical Estimation of the Sound Pressure Level
Conclusions
• Comparison with Measurements• Scenarios, large Wind Farms, 5
MW Wind Turbines
• The German Infrasound Station IGADE• Data Examples, routine
Analysis
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A single wind turbine in northern Germany
page 10
VESTAS V47200 kWh=65 m, r=24 mrpm=[20 26]
Tahiti, Nov/Dec 2005
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Configuration of the Hufe field experiment
page 11Tahiti, Nov/Dec 2005
1 2 3 4: 07-Jul-2004 - 19-Jul-2004, HUF01, HUF02, HUF03, HUF041
5 6 7: 19-Jul-2004 - 29-Jul-2004, HUF01, HUF05, HUF06, HUF078 :
29-Jul-2004 - 05-Aug-2004, HUF08, HUF09, HUF10, HUF11
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Measuring along the track and in the wood
page 12
Huf08-Huf11
Huf07
Huf06
Huf05
Huf04
Huf03
Huf02
Huf01
Tahiti, Nov/Dec 2005
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Station Huf01
page 13Tahiti, Nov/Dec 2005
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Measured signals, Huf03, d=200 m
page 14
frequency domain
Tahiti, Nov/Dec 2005
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Measured signals, Huf03, d=200 m
page 14
time domain, 0.5 Hz high pass filtered
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Measured signals, Huf03, d=200 m
page 14
frequency domain
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Time-frequency analysis, Huf03, d=200 m
page 15Tahiti, Nov/Dec 2005
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Content
page 16Tahiti, Nov/Dec 2005
The Influence of Wind turbines on Infrasound recordings:
IGADE
Noise Measurements at a single Wind Turbine
Theoretical Estimation of the Sound Pressure Level
Conclusions
• Comparison with Measurements• Scenarios, large Wind Farms, 5
MW Wind Turbines
• The German Infrasound Station IGADE• Data Examples, routine
Analysis
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Theoretical SPL-estimation
page 17
( )∑
−−⋅= −
m
Qm
en
Tmenx
imnn aRk
mnBaRkJed
kP γγπ
πθ cos)sin(4
2 )2/(
Hubbard & Shepherd (1991, JASA)
Pn – RMS sound pressure of the n-th harmonicn – sound pressure
harmonic numberkn – nBω/cB – number of bladesω – rotor speedc0 –
sound speedRe – effective blade radius
d – distance from the rotorm – blade loading harmonic index
(m=…,-1,0,1,..)Jx – Bessel function of first kind and of order
x=nB-mγ – azimuth to listenerθ – altitude angle to listeneramQ –
complex Fourier coefficients of thrust forcesamT – complex Fourier
coefficients of torque forces
Tahiti, Nov/Dec 2005
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Comparison between measured and estimated SPL
page 18
SPL as a function of distance SPL as a function of azimuth
Tahiti, Nov/Dec 2005
account for surface effects (e.g. reflections) by adding 3 dB to
the estimated curves
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Estimating the SPL generated by wind turbines
page 19Tahiti, Nov/Dec 2005
Blade diameter
Tow
er h
eigh
tPower
Blade diameterTower height
Energy production per year
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Estimating the SPL generated by (a) large wind turbine(s)
page 20Tahiti, Nov/Dec 2005
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Estimating the SPL generated by (a) large wind turbine(s)
page 20
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Estimating the SPL generated by Wind Turbines/Farms at ~2 Hz
page 21
noise level
Tahiti, Nov/Dec 2005
single wind turbine 11-element wind farm
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Content
page 22Tahiti, Nov/Dec 2005
The Influence of Wind turbines on Infrasound recordings:
IGADE
Noise Measurements at a single Wind Turbine
Theoretical Estimation of the Sound Pressure Level
Conclusions
• Comparison with Measurements• Scenarios, large Wind Farms, 5
MW Wind Turbines
• The German Infrasound Station IGADE• Data Examples, routine
Analysis
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Conclusions
page 23Tahiti, Nov/Dec 2005
number of wind turbines and their size is constantly growing
wind turbines and wind farms generate strong infrasonic noise
which is characterized by their blade passing harmonics
(monochromatic signals)
generated noise of wind turbines can theoretically be estimated●
geometrical spreading ~ R-1● SPL ~ rpm4
recordings from field measurements near a single wind turbine
show that the theoretical model is also valid for frequencies below
a few Hz
minimum distance between an infrasound array and a wind farm can
be estimated to avoid reduction of the array’s detection capability
(e.g. 600MW wind turbine: d>15 km, 11-element wind farm: d>30
km)
