Proposed Rule on Sound from Wind Generation Facilities VPIRG and - - PowerPoint PPT Presentation

Proposed Rule on Sound from Wind Generation Facilities

VPIRG and Bodwell EnviroAcoustics December 2, 2016

Background & Issues

• Lack of consistent protocol for pre-construction modeling and post-

construction operations testing

• Interior standard creates difficulty isolating wind turbine sound,

disruptive to project neighbors

• Turbine shutdowns/ambient noise are imprecise methods for gathering

sound data

• Complaint process is confusing and costly

VPIRG/BEA Proposal

• 1. Establish accurate and reliable methodologies
• Conservative modeling based on manufacturer’s sound level data
• Compliance measurements using test protocol designed to measure

conditions when wind turbine sound is most prominent

• 2. Establish metrics and limits
• Based on appropriate use of independent studies

Modeling

• Terrain-based acoustic model of the project
• Specify parameters including:
• Ground absorption including acoustically reflective surfaces
• Standard atmospheric conditions
• All turbines at full rated sound output
• No attenuation for trees and foliage
• Uncertainty based on turbine manufacturer warranty and model

uncertainty assumes “worst-case” sound levels

• Monitor locations with highest potential to

exceed limits (or proxy):

• Predominantly downwind (within 45°)
• Generally nearest residences to wind

turbines

• Similar elevations & line of sight
• Rigorous protocol conditions
• Notification and concurrence of DPS of times

and locations in advance.

Operations Test Protocol

Operations Test Protocol (cont.)

• Required Test Conditions
• Periods when wind turbine sound most

prominent

• Surface average wind speeds (10m) ≤6mph
• Upper winds sufficient to generate maximum

continuous rated sound power from nearest wind turbines

• Typically occurs during nighttime. Daytime

associated with atmospheric instability and high turbulence periods

10 m Wind Sensor

Protocol vs Variable Test Conditions

Ambient Adjustment Issues

• Site/wind conditions can change significantly between operating

and shutdown conditions

• Subtracting ambient sound levels introduces potential for

significant errors

• Results in extra expense and power loss
• Measurements under protocol conditions provide more

accurate/cleaner sound data for turbine operations

• Eliminates “sound data” confusion for quantifying turbine sound

levels and evaluating compliance

Limits & Method

• Need to be based on independent, factual community noise studies
• Those studies need to be applied correctly to support proper use of

sound metrics and time periods Proposed Limit: 45 dB(A) Leq 10 min exterior

• Supported by ANSI, ISO, EPA, and WHO standards and

recommended limits

Stetson II Analysis

• Highest measured sound level

applied to full year of turbine

• perations
• Illustrated that a limit of 45 dB(A)

Leq, based on conservative modeling, successfully met recommended limits:

• WHO: 40 Lnight,outside annual
• EPA: 45 Ldn

Setbacks

Setbacks do not correlate with sound levels

3000 ft 1500 ft

Conclusion

• Proposal based on proven sound modeling and testing resolves

major technical issues

• Enables appropriate limits and metrics based on independent

studies

• Consistent methodologies will benefit all stakeholders
• Meets Stated Goals: enforceability, predictability, reliability of data