NREL is a national laboratory of the U.S. Department of Energy Office of Energy Efficiency and Renewable Energy operated by the Alliance for Sustainable Energy, LLC Wind Turbine Spacing in Wind Farms and Sound BLM WEATS Workshop September 1, 2010 Patrick Moriarty, NREL
Wind Turbine Spacing in Wind Farms and Sound. BLM WEATS Workshop September 1, 2010 Patrick Moriarty, NREL. Why is noise an issue?. Objectionable noise is an impediment to deployment Complaints by residents threaten permitting - PowerPoint PPT Presentation
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NREL is a national laboratory of the U.S. Department of Energy Office of Energy Efficiency and Renewable Energy operated by the Alliance for Sustainable Energy, LLC
Wind Turbine Spacing in Wind Farms and Sound
BLM WEATS Workshop
September 1, 2010
Patrick Moriarty, NREL
National Renewable Energy Laboratory Innovation for Our Energy Future
Why is noise an issue?
Objectionable noise is an impediment to deployment– Complaints by residents threaten permitting– Projects must comply with established community noise
standards (40 – 45 dBA is typical)Noise reduced operation (NRO)
– Energy also lost
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Sound Pressure LevelMost common noise measurement (in Decibels – dB)
r = observer distanceDoubling distance = -3 dB in SPLDoubling intensity = +3 dB in SPLHuman ear detects around 3 dB change+10 dB = subjective doubling of perceived loudness
Sound Power Level
refref pp
IISPL 1010 log20log10
2
1r
I r
p 1
010log10WWLW
21010log (2 )WSPL L r
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A-weighting
dB vs. dB(A)Mimic behavior of human earCertain frequencies appear louder
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Noise and SPL
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Noise Trends for Large Wind Turbines
sound power level = 22 LOG(D) + 72
sound power level = 11 LOG (D) + 82
70
80
90
100
110
120
130
1 10 100 1000
Diameter [m]
soun
d po
wer
leve
l dB
[A]
80's90'sMulti MWSWT'sLog. (80's)Log. (90's)
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Types of wind turbine noise
Mechanical– Mostly tones– Gearbox– Generator– Tower resonance– Blade movement
Aerodynamic– Blades & tips
• Proportional to Vtip5
• Higher frequency and broadband
– Tower wake• Rotational (low
frequency)• 1-3 per rev
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Relative noise contributions
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Typical noise spectra
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Noise Regimes
3 different regimes
• Human perception
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Propagation
HumidityWind direction and speedWind ShearTurbulenceTerrain
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Noise Ordinances
Varies by place and use
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Background/Ambient Noise
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Human Response
Not as predictable as everything else
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Noise descriptions
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Low Frequency Noise and Infrasound
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