Noise
One of the many misleading statements that Broadview and their ilk like to utter is that “modern turbines are much quieter” (the author heard an enterprising chap use these very words at the last Broadview Public Consultation Event). Like many of the things that developers say, it has an element of truth,
but only very slightt.
It is true that the gear boxes in modern turbines are quieter than in previous generations, but gear box noise was never a major issue unless you happened to be camping at the base of the turbine. The noise that will keep you awake at night (see
Bye Bye Sleep) has nothing to do with the gearboxes and only gets worse as turbine size increases. It is caused by the 10-20 tonne turbine blades moving through the air at
speeds around 170 mph. There are three sources of noise:
- The vortex generated at the tip of the rotor
- The compression of air as the rotor passes the column of the turbine
- The cumulative effects of multiple turbines whose individual noise interacts
One of the other statements that you hear from Broadview is that even though wind turbines aren’t noisy (?!), we’re safe because they have to comply with a noise abatement standard. What they fail to tell you is that the standard in question, ETSU R 97 has an interesting history and is widely discredited.
ETSU R 97 was established by a panel called the Noise Working Group (NWG) that was formed by the DTI’s Energy Technology Support Unit (ETSU). Many expert commentators have questioned the necessity to establish a new noise standard specifically for wind farms as there is a pre-existing standard called BS 4142 that despite a long history and a few amendments, has always proved effective and to date there are no known “wrong decisions” resulting from its methodologies. The desirability of a new standard for the NWG can be understood when you realise that ETSU R 97 permits wind turbines to generate MORE noise than BS 4142 would, and by examining the backgrounds of the individual members of the panel.
At the time ETSU R 97 was drafted, the NWG had fourteen members, as follows:
- Two from the DTI
- One solicitor
- One from the National Physical Laboratory
- Two Consultant Acoustician Companies
- Three officers from district councils
- Five wind farm developers
It can be seen that the largest represented body was the wind farm developers, but further examination highlights two additional facts. The two acoustic consultant companies in question work extensively for the wind industry and so have a vested interest in ensuring that as many wind farm applications proceed as possible, and further, that out of the fourteen, there are only two with real specialist knowledge of acoustics. It is hardly surprising that a leading acoustician, Mr. Dick Bowdler, wrote a paper entitled “
ETSU R 97 Why Its Wrong” and branded it laughable and deeply flawed.
Mr. Bowdler was appointed to the NWG after ETSU R 97 was adopted by the government as the standard to apply to wind farms. He eventually resigned in disgust after the DTI withheld crucial survey information from the NWG and withdrew authority for further investigation into amplitude modulation (the cumulative noise effect of turbines operating in close proximity to one another). He also points out that the DTI’s mandate is “prosperity for all by working to create the best environment for business success” and NOT “protection of the environment or citizens from nuisance or loss of amenity.
The only good thing about ETSU T 97 is that its authors stated that it should be reviewed after two years – this has never been permitted by the DTI. This is why a factory in Scotland that makes components for wind turbines is subject to more stringent noise regulations than the turbines it makes.
At a recent conference organised by the Institute of Acoustics (Bristol, January 2009) on wind turbine noise (interesting, don’t you think, that there is a necessity to hold a conference on this subject given that Broadview tell us they are not noisy?) MAS Environmental presented some research that indicates that at the moment, the experts really don’t know enough about the noise generated by wind turbines and that more work is needed.
They also showed that the current generation of turbines that are so large present additional problems and this has to do with a phenomenon called wind shear. Wind shear is a term used to describe the fact that the closer you are to the ground, the lower the wind speed is. At night, the difference between air speeds close to the ground and higher up is very marked. This is caused by the so-called nocturnal jet which is a stream of very fast moving air. In Britain, the nocturnal jet descends to heights as low as 50-70 m, meaning that turbines whose hubs are at 80 m are well inside this region of very fast moving air. Additionally, at night, air close to the ground is very still – this is relevant because it means that there is no sound caused by the wind to mask the turbine noise.
The overall effect of this is that at the time when it is most important for the turbines to be quiet, they are in fact generating more noise than ever and there is nothing to mask that noise. What makes this worse is that the electricity generated at night we don’t need as we’re all tucked up bed so it will be sold at a loss overseas as experienced by Denmark. Some 20% of electricity generated in Denmark comes from wind, but less than half of it is consumed by the Danish, the remainder being exported to Germany and Sweden. Not something we'll be able to do easily as the electrical connection between the UK and continental Europe is very low capacity.
And even if there was masking noise caused by the rustling of trees or traffic, the walls of your house will filter that out, but they will not be able to filter out the turbine noise as its frequency is too low.
The bottom line is this: turbines DO generate unpleasant noise that will keep you awake at night and affect your health. Do not be taken in by the forked tongue of Broadview and the government. They are working to an agenda that does not include your well being.