Environmental Impacts of Wind

Wind energy offers many environmental benefits, from the use of renewable fuel to the absence of polluting emissions. Environmental concerns include impacts on local sites, scenery and wildlife. Modern wind technology has made great strides in addressing these concerns, and current impact studies for specific sites show significantly reduced impacts on wildlife when modern turbines are used.

Benefit: Renewable Energy Source

Clear skies behind the Lion Spring Farm 3.1 kW turbine in Dover, MA. Wind is a zero-emission energy technology.

Wind energy is a renewable resource, which means that it can't be exhausted like fossil fuels. It is also a domestic and local resource, reducing reliance on imported sources of fuel and reducing the risks of transporting these fuels. Because the wind is its only fuel, wind technology requires zero resource inputs - a significant contrast to both fossil fuels and some other clean energy sources like biomass and hydropower.

Benefit: Emissions and Waste

Because wind requires no physical resources for its fuel, it also produces zero emissions. In addition to displacing climate change and air quality emissions from fossil fuels, it eliminates other forms of pollution such as chemical and thermal discharges into water, and solid combustion and radioactive wastes.

These benefits make significant improvements to the environment. By displacing air quality emissions, wind can indirectly improve local human health. By displacing greenhouse gas emissions, it is one of the essential tools in combating climate change. Local environments also benefit by the displacement of fossil fuel plants that produce water and material wastes.

Benefit: Land Use

Wind is compatible with many different land uses, such as municipal land, landfills, and agricultural properties. In particular, wind is a growing option for farmers who can rent small areas of their property to wind developers. The revenues from wind can also be used by municipalities to protect open space and natural habitats.

Barrier: Siting

Both small and large wind installations offer major siting challenges. All sites must offer adequate wind resources, be close to end uses and the electric grid, and allow access for construction and maintenance purposes. Ideally, sites should be located in areas where environmental or aesthetic concerns can be mitigated or avoided. For multi-turbine installations, sites must be big enough to allow turbines to be spaced far enough apart to minimize performance losses. In Massachusetts, the high price of land and competing land uses present some significant siting obstacles. Regulatory conditions can further constrain siting options.

Solutions: Advanced technologies are being developed to expand wind's applicability, including turbines optimized for low-wind-speed operation and deepwater installations. Growing experience with land-based and offshore projects is providing guidance to mitigating or avoiding future environmental and aesthetic concerns. Siting criteria can help define the most appropriate locations for wind installations.

Barrier: Wildlife & Habitat

Wind energy projects do not emit pollutants that harm wildlife or contribute to climate change, which is already altering habitats worldwide. However, wind facilities can degrade and fragment wildlife habitat because towers and foundations, spinning blades, lighting systems, power lines, and access roads alter natural landscapes. This may lead to changes in animals' travel and migration pathways and to the physical displacement of individual animals. In addition, birds, bats, and insects that collide with spinning blades or stationary towers may be killed.

Solutions: Careful project siting and good design practices can reduce or eliminate these impacts. The best approach is to avoid locating projects in particularly sensitive habitats because the degree of risk posed by a site depends on both the types and numbers of animals that may be affected.

For proposed projects, environmental impact assessments are often conducted to inventory natural resources and examine how turbine installation and operation might change environmental conditions and species use patterns. Based on these studies, impact avoidance and mitigation strategies can be implemented. Common options include installing turbines in less sensitive locations and adjusting construction practices and schedules.

Barrier: Birds and Bats

Every energy facility can impact birds and bats, including wind installations. Birds and other flying creatures can die in collisions with turbine blades and support structures, as they do when they collide with smokestacks, power transmission and distribution equipment, and other structures.

Collisions with modern land-based wind turbines account for less than 1 out of every 10,000 bird deaths attributable to human causes. To put this number in perspective, wind turbines cause less than 0.01% of human-related bird fatalities, whereas predation by house cats accounts for about 10% and collisions with buildings and windows for more than 50%. According to the National Audubon Society, cats annually kill more than 100 million birds. Even if there is a massive expansion in wind capacity, the total number of birds killed by turbines and support structures will continue to be dwarfed by other human-related sources of bird mortality.

According to the best available data, wind power's adverse impacts on birds and bats occur at the individual rather than the population level, whereas positive effects-such as reductions in emissions of harmful pollutants and greenhouse gases-can be experienced at the population and species level.

Land-based wind power's reputation as a threat to birds arises largely from the singular experience at the Altamont Pass wind facility. Tens of thousands of raptors and other birds have been killed over the lifetime of this project, which is located inland of San Francisco Bay in an area habituated by raptors and rodent populations. The project incorporates a variety of experimental turbines, some of which were installed more than 20 years ago. Many are far smaller in scale and sping much faster than those commonly used today. They are also installed in tightly packed rows. These unusual conditions have caused the unfortunately high raptor mortality rates experienced at Altamont Pass.

More recent concerns about bats and wind turbines have arisen, again largely based on what appear to be site-specific problems. For example, at the Mountaineer Wind Energy Center, which includes 44 turbines installed on mountain ridges in West Virginia, hundreds of bat fatalities were documented over several months in 2003. Studies are under way to determine what may have caused these impacts, as well as elevated bat mortality levels at a nearby ridgetop facility in Pennyslvania.

Solutions: Several advances in wind technology and application have reduced the risks posed to birds and other wildlife. Examples include the use of monopole towers rather than lattice-type or guyed structures, larger and slower-moving blades rather than small rapidly spinning ones, and widely spaced turbine arrays rather than dense ones.

Wind project siting and design can further reduce the potential for adverse impacts on birds and bats. The best approach is to avoid locating projects in areas used by rare or endangered species, where the dislocation or death of a few individuals could have population-level impacts.

For proposed projects, wildlife impact assessments are used to examine how turbine installation and operation might change habitat and species use patterns. Based on site-specific circumstances, avoidance and mitigation strategies can be implemented. For example, nesting seasons vary, certain types of lighting systems are less likely to attract wildlife, and specific bird behaviors and topographic features are known to increase the risks of collision. Technology installations that account for variables like these can help eliminate or reduce individual risk factors.

Continuing research and field experience also play an important role in reducing the risk of wind projects having a negative impact on wildlife. Many lines of inquiry focus on understanding and managing interactions between raptors, other species, and conventional land-based installations. Meanwhile, the growing worldwide base of installed wind capacity is providing new knowledge about the effects of ridgeline and offshore applications on birds, bats, and other wildlife.

Barrier: Noise Impacts

Current wind technology is generally very quiet, unlike some earlier turbine designs. Nonetheless, noise impacts may be experienced on properties located in close proximity to wind installations.

Today's turbines are engineered to reduce two sources of noise: (1) aerodynamic noise results from the interactions of flowing air and spinning blades, and (2) mchanical noise, the lesser of the two sources, arises from the gears and generators housed in the turbine's nacelle.

At wind speeds above about 9 miles per hour, background noise-created by blowing leaves and shrubs, waves, and other sources-begins to drown out the sound generated by modern turbines. At speeds above about 18 mph, background noise will, in most instances, completely obscure both aerodynamic and mechanical noise.

Solutions: The engineering advances that make wind energy less expensive, such as larger designs fitted with long, lightweight, strong blades, have greatly reduced aerodynamic noise. These and other advances have significantly reduced the noise problems experienced with earlier technologies.

Good siting and design practices can help further reduce or even eliminate adverse noise impacts. The most important impact mitigation tool is the setback requirement, which specifies a minimum separation distance between a turbine and nearby residences.

Barrier: Visual Impacts & Flicker

Commercial-scale wind turbines can be very visible. Some observers find turbines to be an aesthetically pleasing energy solution, while others find them visually obtrusive. Whether visibility impacts are perceived positively or negatively is a matter of subjective judgment.

A second visual impact may be experienced only by those located in close proximity to wind installations. Depending on the sun's position, turbine blades can cast flickering shadows that may be a nuisance for neighboring properties.

A third visual impact is indirect but definitely positive. Because the electricity produced by wind turbines frequently displaces generation from fossil power plants, wind power can reduce pollutant emissions. This can help alleviate air quality problems such as smog and haze that can reduce visibility and obscure scenic vistas.

Solutions: Visibility impacts are unavoidable.  The optimal approach is to avoid locating projects in highly visible locations, but in Massachusetts and many other areas, the best wind resources exist along ridgelines and hilltops and in coastal and nearshore regions.

Careful project siting and good design practices can help reduce or eliminate the adverse visual impacts associated with wind energy development.  Computer simulations and balloon and crane tests are commonly used to provide a realistic picture of how turbine installations might change views from specific locations. During project design, engineers can also plot very precisely whether and how often flickering shadows might fall on specific locations. Because the sun generally is not very low in U.S. skies, appropriate setbacks for noise are often sufficient to prevent nuisance flicker problems.

A variety of methods are used to alleviate adverse visual impacts. Options include deploying turbines in less visible locations and configurations, painting turbine components in low-contrast colors, installing low-intensity and nonintermittent lighting systems, and planting trees and other vegetation to screen views from residential and other settings.

Barrier: Blade Throw, Ice Throw, and Tower Failure

Modern wind turbines generally do not lose their blades, and modern towers do not collapse. Today's systems are engineered out of high-strength materials designed to withstand even the most severe weather conditions. The most serious potential concern with modern turbines is that ice accummulating on blades during the winter may be thrown by their spinning motion.

Solutions: Careful project siting and good design practices can eliminate the potential for adverse impacts from ice throw. The setbacks required to mitigate noise impacts are typically large enough to exclude the public from areas where ice throw might occur. In addition, modern machines are inherently resistant to ice throw problems because their control systems shut down when ice begins to accumulate on blades.

Barrier: Radar and Electromagnetic Interference

In general, residential-scale wind turbines do not create electromagnetic interference problems. Larger-scale units can cause line-of-sight interference with radio waves and TV signals (but not cable TV or radio signals). Larger-scale installations can also have echo effects on aircraft radar systems. Interference is generally limited to situations where turbine blades create a physical shadow, such as when aircraft are flying at a very low altitude.

Solutions: Careful project siting and good design practices can help avoid interference problems. Electromagnetic problems can be mitigated by installing improved antennas and by using relays to transmit radio and TV signals around wind projects. Technical studies of radar interference issues are necessary for wind projects proposed in areas near airports or military installations. For the limited circumstances under which radar interference might pose a problem, radar installations may be able to be modified.

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