From 8 to 23 May 2023, measurements were carried out in respect of abnormal noise (buzzing) from the wind turbines at N33. These measurements were carried out at homes in the vicinity of the wind farm as well as in one of the actual wind turbines. During the same period, local residents kept a complaints register. As a preliminary result, the measurements show that the noise nuisance mainly seems to occur during periods when curtailment is taking place (in order to maintain a balance within the energy network, the wind turbines keep turning but deliver little to no power). Siemens is going to make adjustments to the software for the wind turbines. The parties hope that this will reduce the noise nuisance.

Alderman Erik Drenth from the municipality of Midden-Groningen: "The results seem to indicate a cause but we want to know for sure that that is the case so that residents experience less nuisance from the wind farm." Alderman Henk Jan Schmaal from the muncipality of Veendam: "The results are the next step in the process of reducing the nuisance due to buzzing."

Aldermen Schmaal and Drenth: "Given the importance of our citizens and history, we want to know for sure that the adjustment of the software for the wind turbines will ensure that the buzzing nuisance is reduced. That is why we are once again inviting all parties to discuss how we can best continue to measure and monitor this."

Set-up of the investigation

The operators of the wind farm – RWE and Eurus Energy –, the Ministry of Economic Affairs and Climate Policy, the municipalities, manufacturer Siemens Gamesa, research bureau Arcadis and Jan van Muijlwijk (retired acoustics specialist from the municipality of Veendam) meet regularly to discuss the noise from the wind farm. Although the wind farm complies with Dutch noise standards and previous improvements have already resulted in reduced noise, the stakeholders wanted to investigate whether the perceived nuisance could be reduced even further.

The parties decided to carry out noise measurements at a home on the northern edge of Meeden and in the gondola of the wind turbine nearest to that home at the same time. In addition, the occupants of four homes in the immediate vicinity of the measurement location at the home were asked to keep a record of their perception of the noise from the wind turbine every half an hour during the measurement period by rating it on a scale of 1 (lowest intensity, normal background noise) to 7 (highest intensity). The noise measurements and the recording of perceptions by the occupants took place between the evening of Monday 8 May 2023 and the morning of Tuesday 23 May 2023.

Results of the investigation

Analysis of the measurements in relation to the feedback from local residents and the power output of the wind turbine shows that a range of tones (noise) can be heard and/or measured. The feedback from residents in the immediate vicinity of the measurement location has been crucial in order for us to be able to assess the audibility of and nuisance caused by the tones. All the parties would therefore like to thank the residents for their cooperation.

The investigation also shows:

• In the gondola of the wind turbine itself, tones occur in all weathers but many of those tones were not measured or heard at the home on the northern edge of Meeden. That is because of the way only some of the noise from the wind turbine is transmitted to the outside but also because ambient noise (such as traffic noise and the wind itself) masks the tones.
• No nuisance is experienced at nominal wind speed and power output (the maximum level of production of a wind turbine in optimum conditions according to the manufacturer).
• All four residents recorded nuisance on Saturday 13 May and 20 May.
• One resident experienced a high level of nuisance due to buzzing during the night.
• Nuisance was also reported during periods when no tones were measured in the wind turbine or at the home.
• Nuisance mainly occurs when the wind increases at low wind speed with wind from the north-east.
• In the majority of cases of nuisance, curtailment was also a factor. Curtailment means that the power output of the wind farm is sometimes reduced in order to maintain a balance within the energy network, for example (when supply is greater than demand). The wind turbines keep turning but deliver little to no power.

Adjustments

In July, Siemens-Gamesa will make adjustments to the software in the wind turbines in order to ensure that when curtailment occurs, the speed of the wind turbines will also be further reduced.

Joint consultation

The results of the investigation, the software adjustments and the possible consequences of these will be discussed during a joint consultation. The agreements made as a result of that consultation will then be made known.

Background

The initiative for an additional investigation arose from the meeting that took place between Stichting Platform Tegenwind N33 and Jesse Klaver and the operators in July 2022 in The Hague.

The additional investigation was carried out by the parties involved in the wind farm: the municipalities of Midden-Groningen, Veendam and Oldambt, the Ministry of Economic Affairs and Climate Policy, manufacturer Siemens Gamesa, research bureau Arcadis, acoustics specialist Jan van Muijlwijk and the operators of the wind farm, RWE and Eurus Energy.