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American Wind Energy Association Logo
[Image: American Wind Energy Association]

The American Wind Energy Association (AWEA) is a "national trade association representing wind power project developers, equipment suppliers, services providers, parts manufacturers, utilities, researchers, and others involved in the wind industry."

The American Wind Energy Association's resource library is home to many types of resources relating to wind energy development, surrounding issues, and environmental impacts.

What are Greenhouse Gases?

The Greenhouse Effect [Image: NOAA Paleoclimatology]
The Greenhouse Effect
[Image: NOAA Paleoclimatology]

Gases in the Earth's atmosphere that trap heat are referred to as "greenhouse gases". Some of these greenhouse gases occur naturally in the atmosphere but are augmented by inputs from human activities. Others are unnatural compounds that are only created and emitted into the atmosphere from human activities. The principal greenhouse gases released into the atmosphere from human activities are carbon dioxide (CO2), methane (CH4), nitrous oxide (N2O), and fluorinated gases. The U.S. Environmental Protection Agency inventories greenhouse gas emissions and sinks and provides information about greenhouse gases and climate change.

Wind Energy

Wind energy is a "clean" and renewable energy source that can be harvested using turbines to create power or electricity. There are two primary types of wind turbines used for the production of electricity: horizontal-axis and vertical-axis turbines. These turbines can be found in many different applications, and in varying quantities, design, and scale, ranging from a single turbine used to power a private home or another structure with small electricity needs, to a large-scale installation where many large turbines are placed together (commonly referred to as a "wind farm").

Wind farms are becoming increasingly common, with a 30% increase in wind-generated electricity between 2006 and 2007 and a 51% increase between 2007 and 2008. Wind farms have the capacity to provide large quantities of power to regional conventional electrical grids. Wind resource potential varies with geography and topography, and wind farm development occurs both on land and off shore. Off shore wind farm development can be useful to supplement limited onshore site availability, however onshore wind farms have an additional benefit of providing tax revenue and economic gain to rural landowners and communities experiencing economic decline. The Bureau of Land Management manages 20.6 million acres of the lands that hold the potential to generate more than 800 megawatts of new power capacity from wind.

Advantages: clean, renewable, and cost effective
Wind energy is a clean and renewable resource, meaning it does not release greenhouse gases as a byproduct, has fewer environmental impacts than conventional energy resources, and is not being depleted over time. It can be developed in concert with other land use activities such as farming and ranching. It is also one of the lower priced renewable energy technologies currently available.

Disadvantages: transmission costs and wildlife effects
The widespread implementation of wind power has its own set of challenges, despite having many advantages. Large scale wind farm development has considerable up-front costs for turbine and transmission line installation. In addition, bird and bat collisions with wind turbines are an associated environmental impact that must be addressed in the continued development of this resource. (For more information on these topics, visit the Pollinators and Bird Conservation web pages). Finally, research indicates that global warming associated with climate change may affect prevailing wind currents and wind speeds, which may in turn alter regional wind energy siting potential and the production capacity of existing wind energy developments.

American Wind Energy Association
Breslow, P.B. and D.J. Sailor. 2002. Vulnerability of wind power resources to climate change in the continental United States. Renewable Energy 27(4):585-598.
Sailor, D.J., M. Smith, and M. Hart. 2008. Climate change implications for wind power resources in the Northwest United States. Renewable Energy 33(11):2393-2406.
U.S. Department of Energy: Wind and Water Power Program
U.S. Department of the Interior New Energy Frontier

Environmental Impacts of Wind Energy

Banner of wind turbines [Image courtesy of U.S. Department of Energy, Energy Efficiency and Renewable Energy]

The U.S. Environmental Protection Agency lists the following as environmental impacts of wind energy:

Air Emissions   Emissions associated with generating electricity from wind technology are negligible because no fuels are combusted.
Water Resource Use   Wind turbines in areas with little rainfall may require the use of a small amount of water. If rainfall is not sufficient to keep the turbine blades clean, water is used to clean dirt and insects off the blades so that turbine performance is not reduced.
Water Discharges   Wind turbines do not discharge any water while creating electricity.
Solid Waste Generation   Wind technologies do not produce any substantial amount of solid waste while creating electricity.

Land Resource Use   Wind turbines generally require the use of land, although they may also be sited offshore. Land around wind turbines can be used for other purposes, such as the grazing of cattle or farming.

When wind turbines are removed from land, there are no solid wastes or fuel residues left behind. However, large wind farms pose aesthetic concerns and wind turbines that are improperly installed or landscaped may create soil erosion problems. Wind farms can also have noise impacts, depending on the number of wind turbines on the farm. New blade designs are being used to reduce the amount of noise. Bird and bat mortality has been an issue at some wind farms. Improvements to wind turbine technologies and turbine siting have helped mitigate bird mortality. Research on impacts to bats is now underway.

Wind Energy Resources
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Bird and Bat Collisions

Bird near Big Horn Wind Farm, Wyoming. [Photo: NREL Image Library]
Bird near Big Horn Wind Farm, Wyoming.
[Photo: NREL Image Library]

Wind energy has many benefits as a clean, renewable energy source, but it is also associated with several environmental impacts. One of these impacts is bird and bat mortality from wind turbine collisions, especially a concern in areas with sensitive bird and bat species and high collision rates.

The total estimated annual avian collision mortality rate from wind turbines is low (0.01 - 0.02 %) when compared with fatality rates due to collisions with communication towers (1 - 2%) and with vehicles (15 - 30%) (Erickson et al., 2001 [PDF])]. However, these collisions are still a cause of concern, and recommended Wind Turbine Guidelines for assessing and minimizing impacts to wildlife, including collisions, are now available.

Bat collisions with wind turbines are also a potential negative environmental impact of wind energy, and can be high in some site specific locations.

Many birds and bats serve important ecological roles as pollinators. As wind energy development continues to grow, more research, monitoring, and planning will be needed to determine the best methods to reduce bird and bat mortality from wind turbine collisions.

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