Low-frequency noise on the line 

The government, parliament and all others were fooled by the country’s wind turbine giants and the Environmental Protection Agency, who worked in close cooperation to design the rules for the low-frequency noise limit of 20 decibels, and had them approved politically.

During the course of the proceedings, the EPA itself delivered the evidence that a world-leading noise researcher, Professor Henrik Møller at Aalborg University, was right, and that the EPA had been wrong about the problems of low-frequency wind turbine noise.

The central official of the EPA has retired. He was the link to the wind turbine industry, but not the only person responsible for what was happening. What remains now is a Danish EPA with a huge problem needing explanation. Henrik Møller is now fired.

With a red – i.e. urgent – briefing, the EPA warned the then Minister of the Environment, Karen Ellemann, on May 6, 2011, that » the new turbines from the industry do not comply with the EPA’s recommended low-frequency limit «. There was a very good reason for the briefing being marked red.

Because the Minister had earlier in a reply to parliament said the exactly opposite: » (…) when wind turbines comply with the usual noise limits, the low-frequency noise will not give problems, « she wrote while referring to a report which the private consulting company Delta had prepared for the EPA. The same was said over and over again by the EPA.

Both the EPA and the wind energy industry had taken great care to downplay the significance of low-frequency wind turbine noise, which in the population had given, and gives, rise to widespread concern. The situation was therefore delicate for the EPA.

If you dig yourself through the many acts below the surface, the preparation of the Danish wind turbine statutory order appears in a completely new light, with foul play in the process and other critical conditions that have not been exposed so far.

In the spring of 2011, the parties behind the parliament resolution on the national test center for offshore wind turbines in Thy had demanded a new low-frequency noise limit, and the EPA had started a review of the wind turbine statutory order.

At an initial meeting at Delta in Aarhus, all the participants were from the wind energy industry with the exception of the EPA representative. It was thus the wind turbine industry representatives who discussed and planned how to proceed. They found that it would be fine with a limit of 20 decibels, which is the limit for other industrial noise sources at night. Wind turbines run, as we all know, also during the night.

» But it depends on the overall objective that the new limit should not impose new restrictions on wind turbines. What is possible to establish today should also be possible after the summer; it’s a challenge, « says the minutes from the EPA.

Neither Professor Henrik Møller nor others from the country’s qualified and most independent institution for noise attended the meeting. There had been talks with them a few days before, but at that time no specific plans were on the table. There were fine intentions of good cooperation, but that never got off the ground. Henrik Møller and his colleagues heard nothing more on the matter before the rules had been designed.

If the critics were heard, it could end up with rules that would push wind turbines further away from neighbors. That this, for example, would create problems for the most economical turbine from Vestas, because it was not technically possible to reduce the noise, is documented in the personal letter, then CEO Ditlev Engel sent to the Minister of the Environment later in the process. The wind turbine industry had therefore a clear interest in seeing that the noise limit did not lead to tightened distance requirements.

From Siemens and Vestas the EPA received confidential noise data for a number of large industrial turbines and made confidential consequence analyzes. These showed that the low-frequency noise would often be more than 20 decibels. Now the EPA was left with a Gordian knot, since the Minister insisted that the limit should be 20 decibels.

After this, the EPA held a number of meetings with the Danish Wind Industry Association, Vestas and Siemens. So says the central official’s calendar. But there are apparently no minutes of what was discussed at these meetings. At least, the EPA has to date been unable to find any.

After these meetings, on 23 May 2011, the EPA issued a draft of a revised statutory order. In several stages, the sound insulation figures had been changed. Without further explanation they had now been increased again.

The sound insulation figures describe how well noise is transmitted to the interior of a house. The original numbers stem from measurements made in 1996, when quite simply a noise source was put up in the garden and the sound measured on the other side of the wall inside a number of houses. A high sound insulation figure means a good sound insulation and a low means poor sound insulation.

The use of sound insulation figures and the measurement method for low-frequency noise indoors have been key issues in the professional disagreement between Professor Henrik Møller and the EPA.

In addition to increasing the sound insulation figures, the EPA had introduced a prescribed uncertainty of 2 decibels – i.e. the low-frequency noise may exceed the noise limit by 2 decibels under inspection once the turbine has been set up. An inspection does not consist of a measurement at the neighbors, as one might think, but a measurement close to the turbine and then a calculation of the noise at the neighbor. In this way, the Gordian knot was cut.

At the same time, Aalborg University was underway with an update of a previous report, and the media had made inquiries. The EPA sent another urgent red briefing to the minister, bearing in handwriting » URGENT – political parties’ spokesmen to be informed today «. This means that the spokesmen had to approve the draft before the contents of the report from Aalborg University became known. The critical noise researchers should not be heard.

At that time, there had been a long-term professional disagreement on low-frequency wind turbine noise between researchers at Aalborg University and the EPA’s leading noise expert. Among other things, they had diverging opinions on the how the sound insulation for low-frequency wind turbine noise should be measured.

The EPA used a measurement method that should be applied carefully in order to be suitable. However, it was used incorrectly, said amongst others Henrik Møller. When used properly it may very well be suitable. But it is difficult to use in practice. And this was precisely where things went wrong.

In a so-called technical pre-hearing on the draft order, Professor Dorte Hammershøi from Aalborg University wondered about the interest to relax the rules as much as possible. » If the rules are not properly worked out, it may well be that you comply with them, but neighbors still cannot sleep at night, « she said, according to the report.

In 2008, Delta published a summary report for the Danish Energy Agency. Its professional quality is disputable. It is muddy and lacks consistency in tables and figures. However, it shows that the large turbines are unable to meet the noise limit of 20 decibels.

In 2010, Delta came to the opposite conclusion in a final report to the Danish Energy Agency. Now the noise from the large turbines had decreased to 20 decibels. The Minister has explained that other (higher) sound insulation figures had been used. That explains why the noise from the large turbines was lower. However, at the same time, the noise from small turbines had increased. This is not trustworthy. And the whole thing was just calculations. Not a single measurement of wind turbine noise indoors had been made.

Professor Henrik Møller and his staff were unable to get the numbers in the report to fit. They did further calculations and reached the conclusion that low-frequency noise from large wind turbines is a problem. And that is exactly the report the EPA would forestall politically.

The political parties got a noise limit of 20 decibels – and the wind energy industry got what they wanted. But essential preconditions had been changed behind closed doors.

The political process was guided with a steady hand by a central government official in close collaboration with the wind energy industry, so the mandatory noise limit will have no real impact – just as Delta later happened to reveal in a report to the Norwegian Ministry of the Environment – by mere eagerness to tell the Norwegians that are no problems with low-frequency wind turbine noise. The bottom line remains unchanged: Wind turbines make noise, and the low-frequency noise is a problem for the neighbors.

Also see:  The perfect political crime