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PRESENTATION ON WIND TURBINE AM

PRESENTATION ON WIND TURBINE AM. by Geoffrey Weller BSc CEng FIET. Introduction. ETSU-R-97 (ETSU) is failing to protect neighbours from Amplitude Modulation ETSU is used to assess noise in planning applications. Embedded into government policy

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PRESENTATION ON WIND TURBINE AM

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  1. PRESENTATIONON WIND TURBINE AM by Geoffrey Weller BSc CEng FIET

  2. Introduction • ETSU-R-97 (ETSU) is failing to protect neighbours from Amplitude Modulation • ETSU is used to assess noise in planning applications. Embedded into government policy • Additional protection for AM is needed because AM may exceed maximum level quoted in ETSU • I will summarise my Proof of Evidence, add recent events, amplify previous conclusions

  3. What is AM? • To demonstrate the character of AM, I would like to play two audio files.

  4. Source: Dick Bowdler FIOA Noise Consultant

  5. Source: Recordings of Nature website • There are actually two separate recordings in this file.

  6. Proof of Evidence • The DTI commissioned the 2006 Hayes McKenzie Partnership report: The Measurement of Low Frequency Noise at Three UK Wind Farms

  7. Recent and Forthcoming Papers • From 5th International Conference on Wind Turbine Noise Denver 28-30 August 2013 • Audible amplitude modulation - results of field measurements and investigations compared to psychoacoustical assessment and theoretical research • Mike Stigwood, Sarah Large and Duncan Stigwood, MAS Environmental Ltd, UK

  8. Renewable UK Annual Conference Birmingham 5-7 November 2013 • Only 3 papers will be presented on technical issues (Session B8), all of them devoted to AM noise of Onshore Wind Turbines • RenewableUK AM Research Project – Overview of Phase 1 Research Findings • Affective Response to Amplitude Modulated Wind Turbine Sound • Mechanisms and Causes of Amplitude Modulation (AM) and Other Amplitude Modulation (OAM) of Aeroacoustic Wind Turbine Noise

  9. ETSU-R-97 • ETSU explains level of AM assumed in noise limits: This modulation of blade noise may result in a variation of the overall A-weighted noise level by as much as 3dB(A) (peak to trough) when measured close to a wind turbine. As distance from the wind turbine/wind farm increases, this depth of modulation would be expected to decrease as atmospheric absorption attenuates the high frequency energy radiated by the blade. • The term ‘as much as’ indicates the maximum level of AM envisaged, and cannot be interpreted as a typical or indicative value. It is clear that lower levels were expected at increased distance, such as at a neighbouring property

  10. Statutory Nuisance • Without any national standards for AM, it is suggested that noise problems can use the Statutory Nuisance complaint procedure via the Local Authority • To this effect, a 127-page report detailing a complete Wind Farm Noise Statutory Nuisance Complaint Methodology has been produced for DEFRA

  11. AECOM Wind Farm Noise Complaint Methodology NANR 277 120 Appendix B: Wind Farm Complaint Investigation Flowcharts – Flow Chart 1: Overall Investigation

  12. Statutory Nuisance • Difficult, lengthy, risky and expensive process • Local Authority may not act, or may be delayed by appeals. ‘Best practicable means’ defence often available • Difficulty in proving noise nuisance –noise may last many nights, then disappear entirely for a while

  13. Controls to avoid Statutory Nuisance Claims • Foreseeable harm in allowing the level of AM to be uncontrolled • Precautionary approach needed • AM Planning Condition would be win-win for developer and neighbours

  14. Conditions • Den Brook planning conditions 20 and 21 regarding AM • 3 dB limit for AM, the maximum value for AM specified in ETSU. • ETSU has has no dose-response studies, so neither does the condition • Would not inhibit properly-designed windfarms

  15. Conditions • The Den Brook planning condition was reviewed by Moroney and Constable: The Den Brook condition is straightforward and that it is possible for this condition to be employed in a transparent and objective manner to demonstrate the existence of excess AM in wind turbine noise.

  16. Challenge to the Den Brook Conditions • RES challenged the Den Brook AM planning condition – their Dr Jeremy Bass reported background noise creates false positive indications of AM • The Moroney and Constable report showed how false positives could easily be avoided by correlating data with Blade Passing Frequency • MAS Environmental analysed the data used by Dr Bass, and showed false positives caused by common noise sources that would be recorded and disregarded - bird calls, aircraft and car alarms.

  17. Conclusions • Each of the five windfarms involved in this Conjoined Public Inquiry has more turbines than Den Brook, and these are all of similar height or taller than Den Brook. • Taller and more numerous turbines leads to an increased risk of AM. • AM is likely to be worse in areas of low background noise such as Mid Wales. • Precautionary approach needed • In the absence of nationally specified controls for AM the Den Brook AM test, or another test for AM agreed by the parties involved, should be a condition of development and operation.

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