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Wind expert quits thinktank 

Wind turbine noise expert Dick Bowdler has quit a government working party.

He says the Noise Working Group has become “redundant” in the light of the Government’s endorsement of a Salford University report that claims that rhythmic noises from wind turbines are negligible and unlikely to be a nuisance. The government says Salford’s report “eases concerns over wind turbine noise”.

Bowdler is an expert in wind turbine nuisance. He believes that official government ETSU guidelines are flawed and are unsuitable for modern larger turbines designed to the limits of the guidelines (Noise Bulletin May p4).

Despite his reservations, he has served on the Government’s noise working group aimed at establishing whether or not turbines are a nuisance, as is claimed by some residents and denied by Government and industry.

Experts agree that claims that turbines produce ‘infrasound’ are wrong – if residents are hearing beating it is aerodynamic modulation, the rapid fluctuation of normal frequency sound.

The Salford University report focuses on this aerodynamic modulation and whether it can produce significant disturbance. Councils were contacted to see how many complaints had been received on wind farms.

Salford found that 27 out of the 133 operational windfarms had received formal complaints about noise at some point in their history. Just four were found to be due to aerodynamic modulation.

The report concluded: “The low incidence of aerodynamic modulation and the low numbers of people adversely affected make it difficult to justify further research funding in preference to other more widespread noise issues.”

The Government took this further, saying: “Aerodynamic modulation is not an issue for the UK’s wind farm fleet.” It added that the report “cases concerns over wind turbine noise”. Energy Minister Malcolm Wicks said: “Where there are legitimate problems we will address them. But it is essential that we produce more wind power if we are to meet our climate change and security of supply aims.”

In his resignation letter to the working group, Dick Bowdler says: “Looking at the Government statement, it is clear that the views of the Noise Working Group (that research is needed into aerodynamic modulation to assist the sustainable design of wind farms in the future) have never been transmitted to government and so the statement is based on misleading information.”

Resignation hits wind findings

Resignation of a Government task force member underlines concerns that a report into wind turbine noise has missed the point

Acousticians arc not prone to grand gestures. So the high profile resignation of a wind turbine expert may prove a bit of a shock.

Dick Bowdler of consultant New Acoustics is an expert on wind turbines and has had long running concerns about nuisance from wind farms. He can be frequently found at public inquiries hired by protesters to look after their interests.

But while Bowdler was a critic of the ETSU guidance used to judge impact of wind turbines, he was also a key member of the DTI (now DBERR) noise working a thinktank which was reconvened last year to look at the phenomena of aerodynamic modulation (Noise Bulletin Aug/Sep 2006 p1). This is the drumming noise that some residents complain about, easily confused with infrasound. It is the rapid fluctuation of blade swish (itself at a normal frequency) and whatever the correct acoustical terminology, it sounds like a pile driver or drumming to normal people.

The working group was convened to take forward a Hayes McKenzie report which highlighted modulation as a problem and recommended further research (see box below). Salford University has now concluded that research and its new report has been released. The Government’s interpretation of that report has prompted Bowdler’s resignation.

The new report was set up specifically to take forward the prevalence of aerodynamic modulation on UK wind farm sites and to try to gain a better understanding of the likely causes, and to establish whether further research was required.

This brief was agreed by the noise working group which added that the study would identify up to ten potential sites which could be used to carry out objective noise measurements (including five where there had been complaints).

A survey of local authorities was carried out in two parts: a scoping survey aimed at identifying problem sites, and a detailed survey to establish whether aerodynamic modulation could have been a factor in causing complaints.

Salford’s results show that 27 of the 133 windfarm sites operational across the UK at the time of the survey had attracted noise complaints at some point. An estimated total of 239 formal complaints have been received about UK windfarm sites since 1991, 152 of which were from a single site.

The estimated total number of complainants is 81 over the same sixteen year period.

Aerodynamic modulation was considered to be a factor in four of the sites, and a possible factor in another eight. Regarding the four sites, analysis of meteorological data suggests that the conditions for aerodynamic modulation would prevail between about 7% and 15% of the time. Aerodynamic modulation would not therefore be present most days, although it could occur for several days running over some periods.

Complaints have subsided for three out of these four sites, in one case as a result of remedial treatment in the form of a wind turbine control system. In the remaining case, which is a recent installation, investigations are ongoing.

Salford tried to assess the significance of the complaints by comparing the estimated yearly wind turbine complaints – 14 against industrial noise complaints – 7,522.

Researchers uncovered one confirmed case of turbines causing a statutory nuisance (as opposed to simple disturbance) over 14 years, against 1400 statutory nuisances for industrial noise in 2004/05.

From this comparison they conclude: “It is clear that complaints about noise from windfarms make up an extremely small proportion of the total noise complaints: complaints about industrial noise exceed those from windfarms by around three orders of magnitude, and complaints about noise in general exceed those from windfarms by between four and five orders of magnitude.”

It says that a possible interpretation of the lack of statutory nuisance cases might be that environmental health officers may not have the expertise or confidence in their experience to challenge an ETSU report and ire therefore more reluctant to declare a nuisance compared with less complex and better understood noise sources.

The report concludes: “The low incidence of aerodynamic modulation and the low numbers of people adversely affected make it difficult to justify further research funding in preference to other more widespread noise issues. On the other hand, since aerodynamic modulation cannot be fully predicted at present, and its causes are not fully understood, we consider that it might be prudent to carry out further research to improve understanding in this area.”

Former noise working group member Dick Bowdler told Noise Bulletin after his resignation: “I am a supporter of renewables. The irony is that if the original ETSU noise working group had been less influenced by developers then the developers would have had a much easier time now than they do.

“If the group had decided in 1996 that wind farms would be subject to the same standards as any other industrial noise then there would not be people like me supporting local authorities and objectors at public inquiries.

“Unfortunately I think that ETSU did serious harm to the cause for renewables. If wind firms were judged by BS4142, as I think they should be, about 10% of those that have received planning permission would have been refused and almost all those that had been objected to on the grounds of noise and subsequently been approved would have passed through the planning process much more easily.”

Editor’s comment

Even before it emerged that Bowdler had resigned in protest at the handling of the turbine noise issue, it was obvious that this report carried with it a ‘bad smell’.

“New report eases concerns over wind turbine noise” trumpets the Government press release, then saying aerodynamic modulation is “not an issue for the UK’s wind farm fleet”. This conclusion is not justified based on the report, and by halting further research work without transparently monitoring the wind farms subject to complaints will inflame, not ‘ease concern’ of objectors.

While the Government would justify trampling over facts in order to encourage worthy wind generation, some aspects of Salford University’s report contribute to the bad feeling. To conclude that wind turbine disturbance is not significant by comparing numbers of turbine complaints against more general UK-wide complaints should never have been done. The overall basket of noise complaints is made up from a myriad of ‘insignificant’ sources such as wind turbines. Together, they become significant and are certainly significant if faced with a new wind farm on your doorstep.

Only when the public can trust the Government and wind farm developers on noise issues will there be a chance that the public will accept them without a fight. This report could have gone some way to build that trust, but has done the opposite.

There are real fears that a similar steamroller approach will be taken to boost micro turbines. Underestimation of noise impacts and overestimation of benefits will lead to a future backlash against domestic generation that will be hard to manage.

Noise Bulletin, August/September 2007

This article is the work of the source indicated. Any opinions expressed in it are not necessarily those of National Wind Watch.

The copyright of this article resides with the author or publisher indicated. As part of its noncommercial educational effort to present the environmental, social, scientific, and economic issues of large-scale wind power development to a global audience seeking such information, National Wind Watch endeavors to observe “fair use” as provided for in section 107 of U.S. Copyright Law and similar “fair dealing” provisions of the copyright laws of other nations. Send requests to excerpt, general inquiries, and comments via e-mail.

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