Camilty Wind Farm - Partnerships for Renewables

Camilty Wind Farm
Chart 8.25: Harburnhead - Cumulative scenario analysis
60
55
50
LA90,10min (dB)
45
40
35
30
25
20
Camilty plus Fauch Hill
Camilty plus Harburnhead
Operational limits (Quiet Daytime)
Operational limits (Night time)
4 5 6 7 8 9 10 11 12
Wind speed (m/s)
8.8.8 It can clearly be seen that the combination of Camilty wind farm with Fauch Hill wind farm
does not exceed the derived daytime limits at Harburnhead, however the combination of
Camilty wind farm with Harburnhead wind farm results in an exceedence.
8.8.9 It should be noted, however, that that the cumulative calculations assume that each NSR is
simultaneously downwind of all wind energy schemes considered. No correction has been
made for prevailing wind direction. This means that the model is likely to over predict and, as
such, should be regarded as a ‘worst case’ assessment.
8.8.10 It has become increasingly common for assessors to attempt to take account of the prevailing
wind direction in cumulative ES calculations, in order to limit overestimation of noise
immission levels.
8.8.11 In the Harburnhead ES, the cumulative assessment applies an adjustment derived from a
noise impact assessment undertaken by Dick Bowdler of New Acoustics in September 2007
(Clocaenog Forest, SSA wind farms).
8.8.12 In July 2012, the consultation paper “A good practice guide to the application of ETSU-R-97
for wind turbine noise assessment” was circulated for comment to the acoustics community.
Although this document has not yet been published formally and retains its consultation
status, it contains useful information in respect of assessing directivity, particularly with
regard to cumulative assessments.
8.8.13 The consultation paper suggests a method for undertaking an assessment, although it warns
that the methodology is not established and as such should be applied with care.
8.8.14 It suggests:
“Based on evidence from the Joule project in conjunction with advice in BS8233 and
ISO 9613-2, it seems reasonably conservative to assume that for a range of headings
from directly downwind (0°) up to 10 degrees from crosswind (80°), there may be little or
no reduction in noise levels; once in cross wind directions (90°) then the reduction may
be around 2dB(A) and when upwind the reduction would be around 10dB(A)”
March 2013 8-34 ES Chapter 8
Noise
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