Today's larger wind plants, varying noise from different machine types, and the topography of some parts of Britain has led the working group behind the report to look for an alternative approach. Instead of set distances between turbines and property the group favours a more complex method of setting limits which relate to background noise. These limits should be set at the nearest properties, with separate limits for day and night.
Prepared by a working group of planners, developers and advisers -- set up two years ago to address shortcomings in existing advice on noise -- the report was expected a year ago. But as might have been expected from a group made up of representatives from both sides of the planning fence, it has taken far longer to reach a consensus. Meantime wind plant developers and authority planners have had to rely on the thin noise guidance contained in PPG22 -- the government's planning guidance note on renewable energy.
Mark Legerton from the government's Energy Technology Support Unit (ETSU) unveiled the group's preliminary recommendations at the British wind energy conference in July. It seems the new report will provide developers and planners with a clear, tight framework for assessing proposed wind projects. It will give the most detailed advice yet on how and where to set noise limits, what units of measurement to use and give specific limits.
Legerton revealed the group is calling for wind farm noise to be limited to 5 dB(A) above background sound for both day and night. It believes this gives neighbours a reasonable degree of protection both inside and outside their property. The group expects most wind farms to adopt this "margin above background" method of setting limits. However, it accepts that in very quiet rural areas this would be unduly restrictive. Here it proposes an "absolute lower limit" of 43 dB(A) for night-time, and for day a limit set within a range of 35 to 40 dB(A).
Where local residents have a stake in a wind project, and are therefore less likely to be concerned with noise, the group believes the limits could be relaxed. For very remote properties or single machines, the working group suggests a third and much simpler approach -- an absolute limit irrespective of background noise.