Wind energy schemes range from individual turbines to small clusters of turbines to large wind farms (comprising of several tens of turbines). They are unavoidably conspicuous, and it is therefore essential that projects are carefully sited and sensitively developed. The wind is a diffuse form of energy, in common with many renewable sources. A typical wind farm of 20 turbines might extend over an area of 1 square kilometer, but only 2 % of the land area would be taken out of use, the remainder can be used for other purposes, such as farming or as natural habitat. In this era of climate change, wind energy is the vanguard of clean energy technologies. It is the most viable energy option if we are to meet our future electricity needs without causing global warming and climate change. Wind energy can save the environment from the damage associated with conventional fossil fuel generation, such as coal and oil. Environmental pollution and the emission of CO2 (carbon dioxide) from the use of fossil fuels constitute a threat to health, the environment and sustainable economic growth. Other major pollutants from conventional electricity, which are avoided through wind power, include SO2, NOx, and PM10. The large scale use of renewable energy sources is essential if the necessary reductions in CO2 and other emissions from electricity generation are to be met and if sustainable development and sustainable growth are to be achieved. Wind turbines cause virtually no emissions during their operation and very little during their manufacture, installation, maintenance and removal. Because the fuel is free, wind generated kilowatts should be used as often as possible in the electricity system to replace intermediate power loads, from coal and gas. Whilst wind energy is a clean technology, it is not free of impacts on the environment. The main issues are:Visual impact: Attitudes towards wind turbines them will depend on aesthetic judgments on beauty and diversity, which are subjective and with general reactions towards the technology. Consultation with, and acceptance by, local communities is essential, especially in rural areas where a particularly high value is placed on landscape amenity. Visual impact can be minimized through careful design of a wind power plant. Using turbines of the same size and type and spacing them uniformly generally results in a wind plant that satisfies most aesthetic concerns. Computer simulation is helpful in evaluating visual impacts before construction begins. Sound emissions: Sound emission was an issue with some early wind turbine designs, but modern wind turbine designs have improved to the point where mechanical noise is insignificant, so the issue is now aerodynamic noise from the turning blades. Aerodynamic noise has been reduced by changing the thickness of the blades trailing edges and by making machines "upwind" rather than "downwind" so that the wind hits the rotor blades first, then the tower (on downwind designs where the wind hits the tower first, its "shadow" can cause a thumping noise each time a blade passes behind the tower). A small amount of noise is generated by the mechanical components of the turbine. At a distance of 300 meters from a 1 MW wind turbine, the expected sound level would be 45 decibels (dba). The noise from turbines is usually masked by other ambient sounds such as the movement of trees when the wind picks up, or near an industrial or urban area. Birds: Collisions with turbines have been an issue at some older wind farm sites due to result of poor sitting, out modeled turbines and tower technology. Proper sitting of turbines is important if adverse impacts are to be avoided. 99% of threats to birds are human related, from habitat loss to industrialization, over exploitation of natural resources, hunting, the pet trade, pollution, etc. No matter how extensively wind is developed in the future, bird deaths from wind energy are unlikely to ever reach as high as 1% of those from other human related sources such as hunters, house cats, buildings, and autos. Construction: The construction process usually takes no more than a few weeks depending on the size of the project. Once complete, apart from access roads, agricultural activity can resume right up to the turbine bases of an operational wind farm. Between 1-3% of a wind farm area is utilized by turbines, so up to 99% of the land is available for other uses. Shadow Flicker is occasionally raised as an issue by close neighbors of wind farm projects. A wind turbine's moving blades can cast a moving shadow on a nearby residence, depending on the time of the year (which determines how low the sun is in the sky) and time of day. It is possible to calculate very precisely whether a flickering shadow will in fact fall on a given location near a wind farm, and how many hours in a year it will do so. Therefore, it should be easy to determine whether this is a potential problem. Erosion which can be prevented through proper installation and landscaping techniques. Erosion can be a concern in certain habitats such as the desert, where a hard-packed soil surface must be disturbed to install wind turbines.
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