Wind Turbune & Environmental Impact assessment

Noise

The unit used to describe the intensity of sound is the decibel (dB). Audible sounds range from 0 dB (“threshold of hearing”) to about 140 dB (“threshold of pain”). The normal audible frequency range is approximately 20 Hz to 20 kHz. The A-weighted scale, denoted as dB (A), approximates the range of human hearing by filtering out lower frequency noises, which are not as damaging as the higher frequencies. It is used in most noise ordinances and standards.
To provide a frame of reference, rustling leaves have a decibel level of 10 dB (A); suburban expressway at 90 meters, 60db (A); large truck pass by at 15 meters, 90dB (A); and aircraft takeoff, 120 dB (A). Also Table 9 provides a list of typical noise levels in the environment.

Wind turbine noise

In general wind turbines generate noise as every machine does. The noise from the wind turbine is divided into two major categories depending on the noise origin. These are:
1. Mechanical noise caused by the gearbox and the generator (tonal sound),
2. Aerodynamic noise caused by the interaction of the turbine blades with the wind

Modern wind turbines are machines producing little or no noise at all in comparison to their predecessors and to their rated power they produce. And this due to the fact that wind manufactures quickly realized that the noise problem needed to be dealt with and stared producing quieter machines. As a result the noise from the gearbox and the bladeswas reduced by careful attention to the design and manufacture of the components and also the noise for the generator minimized with good sound insulation within the turbine head.
On the other hand, wind farms are always located where the wind speed is higher than average, and the “background” noise of the wind tends to “mask” any sounds that might be produced by operating wind turbines.
Over and above that the VAWTs tend to generate less noise than the HAWTs mainly due to the fact that the blades do not create the whooshing noise that occurs with HAWTs when the blade pass close to the mast at each revolution. On the other hand due to the proximity of human activity, these applications could potentially result in noise complaints.

Aesthetics

The visual effect of wind turbines may be one of the most debated topics in the reviews of wind farm proposals. There is a wide variety of views on the aesthetics of wind turbines. The proposed site and its surrounding landscape, public attitudes, land use practices, and individual perspectives influence those views. When evaluating the visual impacts of wind energy projects, the essential question is not whether people will find them beautifully or not, but instead to what degree then may affect the important visual resources in the surrounding area. To some, the blades are an eyesore; to others, they’re a beautiful alternative to conventional power plants.
Since aesthetic judgments are subjective, responses from the public to a proposed wind farm can vary considerably.

In general, the visibility of a particular wind system will depend on many factors, including tower height, proximity to neighbors and roadways, local terrain, and tree coverage, public acceptance and knowledge of renewable energy technologies. What ever the surrounding environment is the developer should try to reduce the visual impact as
much s possible. The main visual aim of a wind farm layout should be to convey a sense of clarity.

Interference of a wind turbine with electromagnetic communication systems

Wind turbines in some areas can reflect electromagnetic waves (mainly due to the moving blades), which will be scattered and diffracted. This means that wind turbines may interfere with telecommunication links.

Wind Turbines and Birds

Wind energy’s ability to generate electricity without many of the environmental impacts associated with other energy sources (air pollution, water pollution, mercury emissions, and greenhouse gas emissions associated with global climate change) can significantly benefit birds, and many other plant and animal species.
However the populations of many bird species are experiencing long-term declines, due not only to the effects of energy use, but many other human activities. Especially in highways birds and bats sometimes die as a result of collisions with vehicles traveling the project roads.
On the other hand, the wind turbines per se are responsible only for a small portion of the total number of bird causalities caused by human builds.
However the place of the wind farm and wind speed generated from the passing cars it is possible to affect the mortality ratio. The variable speed turbine is a more serious threat as there is a correlation between the speed of rotation and the number of birds killed. Up to 80% of birds can fly through the rapidly rotating blades of variable speed turbines and remain unharmed (Winkelman 1992b). Birds have much more time to evade the blades of
a fixed speed turbine (www.windshare.ca/documents/EA_draftscreeningdoc.pdf).

Economic – Socioeconomic Impact of Wind Turbines

Several human activities have to be suspended within a wider area in order to mitigate the unwanted environmental interferences of the wind farm operation As with most business ventures, wind energy projects create jobs. In general, the employment opportunities associated with a wind power plant are in construction, operations and maintenance (O&M), and manufacturing. It should be noted that most wind energy jobs are in the manufacturing, construction and installation fields, with relatively few jobs in ongoing operations and maintenance.