Friday, September 22, 2006

Irish wind energy planning guidelines

This is from section 5.6 of recent (June 2006) planning guidelines for wind energy from the Irish Department of the Environment, Heritage and Local Government.
In general, a lower fixed limit of 45dB(A)10 or a maximum increase of 5dB(A) above background noise at nearby noise sensitive locations is considered appropriate to provide protection to wind energy development neighbours. However, in very quiet areas, the use of a margin of 5dB(A) above background noise at nearby noise sensitive properties is not necessary to offer a reasonable degree of protection and may unduly restrict wind energy developments which should be recognised as having wider national and global benefits. Instead, in low noise environments where background noise is less than 30dB(A), it is recommended that the daytime level of the LA90, 10min of the wind energy development noise be limited to an absolute level within the range of 35-40dB(A).

Separate noise limits should apply for day-time and for night-time. During the night the protection of external amenity becomes less important and the emphasis should be on preventing sleep disturbance. A fixed limit of 43dB(A) will protect sleep inside properties during the night.

In general, noise is unlikely to be a significant problem where the distance from the nearest turbine to any noise sensitive property is more than 500 metres. Planning authorities may seek evidence that the type(s) of turbines proposed will use best current engineering practice in terms of noise creation and suppression.
Note they distinguish quieter rural areas from more suburban (I guess) areas. The allowable range for the noisier areas is from 45 dB to 5 dB above ambient. Obviously, this presumes an ambient level of at least 40 dB.

In quieter places (ambient less than 30 dB), they suggest an upper limit of 35-40 dB rather than a relative limit of 5 dB above ambient.

Their recommendation of 43 dB at night obviously applies to the noisier places, being meant as a lower maximum to allow sleep.

They also suggest that noise will not be a problem at a distance farther than 500 m, or just over 1,500 feet. (Note, however, the U.K. Noise Association's recommendation of a minimum distance of one mile from residences and the French Academy of Medicine's similar recommendation of 1.5 km.)

The 500 m limit is considered later (section 5.12) to also apply for shadow flicker, but they also state that flicker may still be a problem at a distance of 10 times the rotor diameter.

And here's an odd directive for maintaining "visual amenity": "Rotors should be kept rotating ..." (section 6.13) As many people have suggested, the generator acts as a motor if more electricity comes in than goes out, and that turbines are often seen turning with only a slight breeze. It has been suggested that it looks better to have them turning ...

Also in the same section: "Nacelles and towers should be kept clear of leakage from internal fluids." That suggests, of course, that leaks are common.

More (section 6.15): "Decommissioning should involve the removal of all of the aboveground elements of the wind energy development and making good of the site, with the possible exception of roads and tracks where some further use can be found for them and this is approved by the planning authority. Foundation pads can be covered with local soil and left for natural re-vegetation, although they should be re-sodded in highly exposed locations." A reminder that "restoration" of the site means leaving several tons of cement and steel right below the surface. That is the usual provision in the U.S. as well.

wind power, wind energy, wind farms, wind turbines, environment, environmentalism