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Renewables: Facts for Residents

The wind and the sun are the future for our energy supply. But how reliable are they? How will local people and nature be protected? We answer the most important questions surrounding wind and solar energy.

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Questions & Dates

All human interventions in nature have an environmental impact. This applies equally to new settlements and road traffic, as well as agriculture and forestry. Building a wind farm is also an environmental intervention. 

Before we build a wind farm, we therefore use detailed and independent expert reports to check whether birds live in the area, and if so, which species. This is taken into account in planning (1). 

  • For example, wind farms need to be located away from important breeding and roosting areas of bird species known to be sensitive to wind energy. Sensitive species include red kites, white-tailed eagles and cranes. 
  • In Brandenburg, for example, a protective radius of 3 km applies around the eyrie of a white-tailed eagle or a lesser spotted eagle. The flight route between the eyrie and the respective hunting grounds must also be kept clear. 

Birds and Other Animals Benefit from Compensatory Measures

When a wind farm is constructed, the environmental impact has to be compensated elsewhere. The compensatory measures have to be at least equivalent to the impact of the intervention. We might create mixed woodland, for example, or plant orchards, or renaturalise former industrial sites. 

For birds of prey, we can create new hunting grounds specifically to lure them away from wind farms. Such new habitats not only benefit the birds, but also many other animal and plant species as well as the soil.  

In Comparison: Wind Turbines Less Dangerous than Domestic Cats 

Despite our best efforts at protection, birds do die at wind turbines. But the number of bird casualties caused by wind energy is low compared to other sources of risk. 

It is estimated that 100,000,000 birds die every year in collisions with windows (2). 70,000,000 birds die every year on our roads (3). Birds of prey are particularly at risk because they look for small animals that have been run over by cars. Domestic cats catch up to 60,000,000 birds per year (4), and at least 1,500,000 birds collide with high voltage cables every year (5). Compared to this, a mere 100,000 animals die in collisions with wind turbines (6). 

Protecting our climate also protects nature  

The biggest threat to our indigenous fauna is in fact climate change. Renewable energies such as wind and solar energy can help to slow it down. This is why we are building wind farms.  

Sources:

(1)    Agency for Onshore Wind Energy (Fachagentur Windenergie an Land): “Mitigation measures during the planning and approval of wind farms“, September 2015 (in German): https://fachagentur-windenergie.de/fileadmin/files/Veroeffentlichungen/FA-Wind_Studie_Vermeidungsmassnahmen_10-2015.pdf

(2)     German Association for Nature Conservation (NABU), “The extinction of birds”, 2017 (in German): https://www.nabu.de/tiere-und-pflanzen/voegel/gefaehrdungen/24661.html

(3)    Lars Lachmann, “The extinction of birds: fact or fake?” In: Loccumer Protokolle, 63/2017 (in German): https://www.nabu.de/imperia/md/content/nabude/vogelschutz/loccumer_protokolle_63-17lachmann.pdf

(4)    Ibid.

(5)    Naturschutz aktuell – NABU-Pressedienst 2017: “NABU: 1.5 million birds die each year in collisions with power cables”:  https://shop.nabu.de/presse/pressemitteilungen/www.birdlife.org/www.nabu.de/themen/naturschutz/index.php?popup=true&show=19992&db=presseservice

(6)    German Association for Nature Conservation (NABU), “The extinction of birds”, 2017 (in German): https://www.nabu.de/tiere-und-pflanzen/voegel/gefaehrdungen/24661.html

Experience shows that ground-living animals quickly get used to wind turbines in their vicinity and return to their usual habitats shortly after construction. This means that wind turbines have no permanent effect on deer, hares or red fox (1). The same applies to farm animals such as sheep, cattle or horses.  

Wind farms in forests therefore do not interfere with hunting, and farmers can continue to use wind farm areas for grazing or keeping livestock. 
 

Sources:

(1)    German League for Nature and Environment (Dachverband der deutschen Natur- und Umweltschutzverbände (DNR) e.V.), 2012, “Wind energy compatible with nature and the environment (onshore)”, p. 258 (in German): https://www.lubw.baden-wuerttemberg.de/documents/10184/61110/Windkraft-Grundlagenanalyse-2012.pdf/656de075-a3d2-4387-aa30-7ec481c46c5c

(2)    ibid.

Germany is home to 25 bat species (1), all of which are protected. Wind turbines are indeed a threat to bats. Even the sudden change in air pressure from the rotor blades can cause them serious injury.  

In the past years, we have learned a lot about bat behaviour. Much of this has come from bat observation carried out as part of wind farm construction. As a result, we can protect bats more effectively today. 

Bats predominantly fly in dry nights between July and September, when wind speeds are below 5.0 m/s and the air temperature is at least 10° Celsius.

In areas where we can expect bats to fly, we therefore turn off wind turbines during such weather conditions. As bats fly when wind speeds are low, yield losses are not significant. Today, bat-friendly operation is a condition for securing planning approval for a wind farm.  

Planners have to ensure that wind farms are sited at least 200 m away from regular flight corridors for bats. The same applies to bird migration routes and the hunting grounds of birds known or suspected to be at risk of collision.    

The nacelles of wind turbines contain systems that allow us to continuously monitor bat flight activities during operation. This allows us to check whether bats really only fly when expected and to adjust operating times accordingly. 

By the way: when we build a wind farm in a forest, we check every single tree for bat roosts before we clear the area. 

Sources:

(1) Wikipedia: https://de.wikipedia.org/wiki/Liste_von_Fledermausarten_in_Deutschland

Further Sources: 

Modern wind turbines generate "a moderate operating noise only, similar to a background murmur"(1). Most of the noise is caused by the rotor blades moving through the air, however the gearbox and generator also generate noise. 

We have to comply with strict limits to protect residents from noise pollution. The relevant legislation in Germany is set out in the Bundes-Immissionsschutzgesetz (Federal Emissions Protection Act) and in the Technische Anleitung zum Schutz gegen Lärm (Technical Guidelines on Noise Protection - TA Lärm). Wind turbines must comply with the same rules as other commercial turbines. The relevant calculations take account of their particular construction height. 

For example, noise emissions in "dedicated residential areas" must not exceed 50 dB(A) during the day and 35 dB(A) at night.(2) For comparison: 40 dB(A) corresponds to a quiet whisper (3) – outdoors rather than indoors. The noise emissions from a wind turbine with a hub height of 140 meters and a rotor diameter of 120 meters are lower than that already at a distance of 575 meters. A distance of 620 metres is sufficient for three wind turbines standing together (4). Generally speaking, the distance between wind turbines and the nearest residential area is even greater.

How do we ensure compliance with the noise threshold values?

Manufacturers use simulations and prototypes to analyse the acoustic properties of new wind turbines even during the development phase. The acoustic properties of new models are measured several times before they are launched on the market, so we have a very precise idea of the noise levels of a given wind turbine at the planning stage. Very wide tolerances are also applied to these levels.

We can predict at the planning stage how loud the wind turbines will be in the surrounding area based on the relevant sound power level data, because the propagation of sound follows fixed physical laws. 

  • The noise emission prognosis is part of the approval procedure: before a wind turbine is erected, residents can view the sound propagation map to see what maximum noise could be reached at their place of residence.
  • When calculating sound propagation, we begin with the worst-case scenario in which a turbine is at its loudest, which is when the wind blows just strong enough to drive the turbine at almost full power (approx. 10 m/s). At even greater wind speeds, the noise created by the wind and storm drowns out those generated by the wind turbine. Usually, however, the wind is less strong and the turbine much quieter.
  • Of course, wind turbines already in operation at the site in question are also considered as an acoustic preload, and we also take account of other technical installations or operations. The total noise pollution, which includes the preload and additional noise pollution, must not exceed the legally defined limits.
  • To ensure that the calculated sound levels are actually maintained following construction, we have to take measurements within a fixed period of time and at predefined emission points. 
  • All sound propagation calculations and emission value measurements are carried out by independent experts.

Less Noise through Technical Optimisation

Wind turbines have undergone rapid technical development in recent years. An important objective for the engineers was to make them quieter.

  • Rotor blade profiles, for example, have been optimised to generate less noise. 
  • Serrations can be attached to the blades to reduce the turbulence and thus the noise they generate. It is possible to reduce the noise generated by wind turbines by between two and four decibels (6) which corresponds to about half of the noise they emit.
  • Speed limitation is used to quieten the systems in "sound-optimised operating mode", which we use, for example, to ensure that a system is not too loud at night. Modern turbines no longer lose as much power as they once did in this thanks to technical improvements.
  • An amendment to the guideline for calculating the sound propagation of wind turbines as high-altitude sound sources from 2016 now enables even more accurate forecasts. 

Sources:

(1)    The Baden-Württemberg State Office for the Environment (Landesanstalt für Umwelt Baden-Württemberg), Immission Protection, Noise: https://www.lubw.baden-wuerttemberg.de/erneuerbare-energien/laerm

(2)    Sixth General Administrative Regulation on the German Federal Immission Control Act (Technical Guidelines on Noise Protection – Technische Anleitung zum Schutz gegen Lärm – TA Lärm), August 1998: https://www.verwaltungsvorschriften-im-internet.de/bsvwvbund_26081998_IG19980826.htm

(3)    Vgl.: Hörex, „Kleine Dezibel-Kunde“, https://www.hoerex.de/service/presseservice/trends-fakten/wie-laut-ist-das-denn.html

(4)    The Baden-Württemberg State Office for the Environment (Landesanstalt für Umwelt Baden-Württemberg), Immission Protection, Noise: https://www.lubw.baden-wuerttemberg.de/erneuerbare-energien/laerm 

(5)    Fachagentur Windenergie an Land, Schallimmissionen (Agency for Onshore Wind Energy, Sound Immissions): https://www.fachagentur-windenergie.de/themen/schallimmissionen/ 

https://www.windkraft-journal.de/2018/09/06/neue-technik-macht-windenergieanlagen-deutlich-leiser-2/126995
 

One of the issues raised most vociferously by public action groups in recent years concerns infrasound. 

The human ear is not able to process very low sounds below a frequency of approximately 20 Hertz (Hz), which is why this frequency range is referred to as infrasound, as it is below (lat. "infra") the so-called hearing threshold: one cannot hear infrasound by definition.

Infrasound also involves a spatially and temporally periodic fluctuation of air pressure the amplitude of which is oriented parallel to the direction of propagation. As with all forms of sound, infrasound can excite mechanical vibrations, which can be “felt” at extremely high sound levels. 

Wind turbine sound emissions cover a wide range of frequencies with components in both the audible and inaudible range and, in fact, they do emit a low amount of infrasound. However, provided that the legal requirements are complied with, the associated sound levels are orders of magnitude lower than the human perception threshold. 
The extent to which wind turbines emit infrasound has been thoroughly researched. Research by the Landesanstalt für Umwelt Baden-Württemberg (LUBW) have shown that even from a distance of 150 meters, a distance already exceeded by the hub height of contemporary wind turbines, the levels are well below the human perception threshold. At 700 metres, the acoustic technicians were no longer able to detect any difference in terms of whether a wind turbine was in operation or not, i.e., they were unable to distinguish the noise generated by the wind turbines from the natural infrasound generated by the wind.(1)

Various studies completed in 2020 again confirmed that wind turbine infrasound immissions are harmless. The German Federal Environmental Agency (Umweltbundesamt) published a laboratory study in September 2020 in which test persons were exposed to four different infrasound sources for 30 minutes each. The research team measured their heart rate, blood pressure, cortical activity and balance perception both during and after the acoustic irradiation and found no connection between "infrasonic sounds around or below the perception threshold and acute physical reactions". (2)

The VTT Technical Research Centre of Finland published a major study under the title "Infrasound Does Not Explain Symptoms Related to Wind Turbines". Noise immissions were measured in two residential buildings, each located 1.5 kilometres away from a wind farm comprising 17 turbines (3MW) over a period of 308 days.

Different sound recordings of the previously measured peak values in which the infrasound components were partially filtered out, were then played back to two comparison groups. Neither residents nor test persons with no previous exposure were able to recognise the recordings which included infrasound. And not just at the conscious level: stress indicators such as their respiratory and heart rates, pupil movements and the electrical conductivity of their skin also showed no reaction.(3)

However, the authors of the study assume a nocebo effect because local residents continue to complain about symptoms, such as insomnia or headaches, which they attribute to the infrasound from wind turbines: these symptoms can occur just through the mere belief that they are caused by wind turbines. 

In a popular scientific and self-experiment, one staff member of the Bayreuth Center for Ecology and Environmental Research (BAYCEER) compared the extent of the infrasound pollution caused by a wind turbine with the everyday exposure level of a car trip and found that the infrasound energy to which we are exposed during a three-and-a-half hour car trip is similar to that which we would suffer if we were to live just 300 metres from a wind turbine for 27 years.(4) 

Whereas wind turbines are not relevant sources of infrasound, we are confronted with a multitude of infrasound emitters in our everyday lives, which, in addition to cars, include air conditioners, refrigerators, washing machines and pumps. However, even in these cases the levels are so low that they pose no threat. 

Sources:

(1)    Landesanstalt für Umwelt Baden-Württemberg (LUBS), „Tieffrequente Geräusche und Infraschall von Windkraftanlagen und anderen Quellen“, 2016, https://www.lubw.baden-wuerttemberg.de/-/bericht-tieffrequente-gerausche-und-infraschall-von-windkraftanlagen-und-anderen-quellen-veroffentlicht- 

(2)    Umweltbundesamt, “Lärmwirkungen von Infraschallimmissionen“, September 2020: Press release by the German Federal Environment Agency (Umweltbundesamt) about the infrasound study
(https://www.umweltbundesamt.de/presse/pressemitteilungen/infraschall-um-unter-der-wahrnehmungsschwelle). The full version can also be downloaded as a PDF at (https://www.umweltbundesamt.de/sites/default/files/medien/479/publikationen/texte_163-2020_laermwirkungen_von_infraschallimmissionen_0.pdf

(3)    The VTT Technical Research Centre of Finland, "Infrasound Does Not Explain Symptoms Related to Wind Turbines", 2020: VTT project website: (https://www.vttresearch.com/en/news-and-ideas/vtt-studied-health-effects-infrasound-wind-turbine-noise-multidisciplinary#-1),  download the complete study at 
(https://julkaisut.valtioneuvosto.fi/bitstream/handle/10024/162329/VNTEAS_2020_34.pdf?sequence=1&isAllowed=y / https://julkaisut.valtioneuvosto.fi/handle/10024/162329) and a summary of the results at Solariy (https://www.solarify.eu/2020/05/01/270-infraschall-von-windenergieanlagen/

(4)    The Bayreuth Center for Ecology and Environmental Research (BAYCEER), Infraschall im Auto” (Infrasound in Cars), October 2020, https://www.bayceer.uni-bayreuth.de/infraschall/de/forschung/gru/html.php?id_obj=157452

Citizens’ action groups opposed to wind turbines repeatedly accuse the German federal government of the “uncontrolled growth” of wind turbines and say that they are being built in an unplanned manner in unsuitable locations. That is actually incorrect.

The German Federal Building Code (BauGB) has granted “privileged permissibility” to wind turbines in outskirt areas since 1997 (1). German planning law defines “outskirt areas” as land located outside of municipal development plans and built-up areas. However, this does not mean that wind turbines could be erected just anywhere. 

The German federal states designate so-called priority areas for the construction of wind turbines, so care is already being taken at the regional planning level to ensure that wind turbines are only erected in areas where there are no conflicts with other land uses. 

  • As a matter of principle, it is prohibited to erect wind turbines in nature reserves and national parks.
  • Likewise, areas of particular cultural or historical importance are off limits for wind turbines.

Local authorities and municipalities also have the option of determining where wind turbines can be built in their development plans. Development plans are publicly accessible, and the public are able to participate in their preparation. 

Project developers planning to erect a wind turbine in a suitable area inform all “public interest groups” (the municipality, higher-level authorities, and associations). The impacts on residential development, the landscape, flora, and fauna are also examined and con-sidered during the approval process. 

Compliance with legal limits for noise emissions and shadow casting are an integral part of the assessment. The approval procedure is based on the German Federal Immission Control Act (Bundesimmissionsschutzgesetz), the Federal Nature Conservation Act (Bundesnaturschutzgesetz), the Environmental Impact Assessment Act (Umweltverträglichkeitsprüfung) and the Town and Country Planning Code (Baugesetzbuch). The approval process also includes a public hearing, in which local residents can voice their objections, followed by a subsequent discussion. 

It usually takes several years to clarify all issues and to prepare expert reports. Only then are we able to start construction. 

German Environment Agency (Umweltbundesamt), “Wind Energy”, 14th of August 2020: https://www.umweltbundesamt.de/themen/klima-energie/erneuerbare-energien/windenergie#mensch