Environmental impacts of wind power
Wind power is energy that does not produce emissions into air, water or soil. However, it has other environmental impacts, as does all energy production.
The noise of wind turbines comes from the aerodynamic noise of the blades and the individual parts of the electricity generation machinery, such as the gear box, generators and cooling systems. When defining the output level of noise of a wind turbine, the noise nuisance of the turbine is measured with the greatest possible production output. That is when the turbine is at its loudest.
The noise nuisance caused by wind power projects under plan is modelled with this maximum possible noise level. The assumption is that all turbines in a wind power project operate at their maximum production output at the same time. This model will obtain a maximum noise level which, however, occurs only up to 30% of the time in any one year.
Modelling is carried out in accordance with valid standards so that the wind speed at a height of 10 metres from the ground is assumed to be 8 m/s. In the modelling, a low-frequency noise and its travel into indoor spaces are taken into account.
The noise produced by wind power is about 40 dB at a distance of some 500–700 metres from the wind turbine. The noise level corresponds to that of a modern dishwasher. Normal household noises are in the region of 40–45 dB, and in offices the noise level rises to about 50–60 dB. In a moving car, the noise level is approximately 70 dB. Air heat pumps used in homes normally produce a noise of about 50–60 dB.
The noise emitted by wind turbines depends on the wind turbine and its properties. The output noise level of different wind turbines differ from one another. The output noise level is affected by the design of the wind turbines and, e.g. their aerodynamic properties, not the generator output.
According to a survey commissioned by the Finnish Wind Power Association in 2014, residents of municipalities with existing wind power found that traffic noise is the most disturbing source of noise. The residents were asked about their opinions on noise nuisance from wind turbines in a number of questions. Those who found the noise to be very or even somewhat disturbing were requested for more details about the situations and locations where the nuisance is experienced. Hardly anyone found the noise disturbing inside their homes and only a few found it to be disturbing in their gardens. Most people who found the noise disturbing could not specify the situation when the noise was a nuisance, and the majority of them, over 80%, did not find it disturbing even when standing next to the turbine.
As the sun shines behind the wind turbine, the rotor blade creates moving shadows as it rotates. The shadow is caused by the movement of the blades. This impact is called the shadow flicker. The effect can be noticed up to 1–2 km from the wind turbine. However, the flicker can only be noticed on the sunniest of days and only on certain hours of the day.
Impacts of wind power on the natural environment
Wind power may have impacts on birdlife and, with respect to the foundations of wind turbines and the connecting roads to be built in the area, on the rest of the natural environment, too.
One wind turbine with its foundations and erection areas requires a 0.5 hectare maintenance area free of trees. Wind turbines, their maintenance area and the roads within the wind farm take a total of some 3–4% of the wind farm area. It is possible to carry on farming and forestry work and to go berry picking and fishing in the wind farm area as before, and the roads built in the area can also be used.
Wind turbines do not pose any significant environmental risk to their immediate vicinity. In the winter, it is possible that ice and snow fall from the blades and tower of a wind turbine. However, the risk of this is very small.
The use of a wind turbine has no impact on the surrounding vegetation.
The impacts of wind turbines on birdlife mainly include the noise and the blade movement. In studies, the collision risk with birds is found to be small. With respect to the risk of collision, it has been discovered that birds get used to wind turbines and are able to avoid them almost without exception.
However, building of major wind farms along the main migration routes and close to resting places must be avoided.
Wind turbines may have similar impacts on bats as on birds. The design of wind turbines close to prime bat habitats must be avoided.
Impacts on wind power on the landscape
Wind turbines are major constructions that in clear weather can be visible to up to 10 km. The visibility of a wind turbine depends on the size of the turbine tower and its blades.
Impacts on the landscape are always investigated in the planning of a wind power project. The landscape is a constantly evolving entity. The landscape type is determined according to the landscape structure, scenery, land use and cultural and natural characteristics.
A change in the landscape may be rapid or progress in stages. Visual changes may also have an impact on people. Different groups of people experience changes in their environment in different ways.
The impact of turbines on valuable landscapes is investigated in the environmental impact assessment. The change of landscape does not result in a physical disadvantage to people, but it may have a negative effect especially immediately after the turbines have been erected, when the landscape is still new.