CO2 emissions and pollutionWind power consumes no fuel for continuing operation, and has no emissions directly related to electricity production.
Wind power stations, however, consume resources in manufacturing and construction, as do most other power production facilities.
Wind power may also have an indirect effect on pollution at other production facilities, due to the need for reserve and regulation, and may affect the efficiency profile of plants used to balance demand and supply, particularly if those facilities use fossil fuel sources. Compared to other power sources, however, wind energy’s direct emissions are low, and the materials used in construction (concrete, steel, fiberglass, generation components) and transportation are straightforward.
Wind power’s ability to reduce pollution and greenhouse gas emissions will depend on the amount of wind energy produced, and hence scalability.
Wind power is a renewable resource, which means using it will not deplete the earth’s supply of fossil fuels. It also is a clean energy source, and operation does not produce carbon dioxide, sulfur dioxide, mercury, particulates, or any other type of air pollution, as do conventional fossil fuel power sources.
Electric power production is only part (about 39% in the USA) of a country’s energy use, so wind power’s ability to mitigate the negative effects of energy use as with any other clean source of electricity is limited (except with a potential transition to electric or hydrogen vehicles).
Wind power contributed less than 1% of the UK’s national electricity supply in 2004 and hence had negligible effects on CO2 emissions, which continued to rise in 2002 and 2003 (Department of Trade and Industry); the growth of installed wind capacity in the UK has been impressive (installed wind capacity doubled from 2002 to 2004, and again from end-2004 to mid-2006), but from low levels. Until wind energy achieves substantially greater scale worldwide, its ability to contribute will be limited.
Groups such as the UN’s Intergovernmental Panel on Climate Change state that the desired mitigation goals can be achieved at lower cost and to a greater degree by continued improvements in general efficiency in building, manufacturing, and transport than by wind power.
During manufacture of the wind turbine, steel, concrete, aluminum and other materials will have to be made and transported using energy-intensive processes, generally using fossil energy sources.
The energy return on investment (EROI) for wind energy is equal to the cumulative electricity generated divided by the cumulative primary energy required to build and maintain a turbine. The EROI for wind ranges from 5 to 35, with an average of around 18. This places wind energy in a favorable position relative to conventional power generation technologies in terms of EROI. Baseload coal-fired power generation has an EROI between 5 and 10:1. Nuclear power is probably no greater than 5:1, although there is considerable debate regarding how to calculate its EROI. The EROI for hydropower probably exceeds 10, but in most places in the world the most favorable sites have been developed.
Net energy gain for wind turbines has been estimated in one report to be between 17 and 39 (i.e. over its life-time a wind turbine produces 17-39 times as much energy as is needed for its manufacture, construction, operation and decommissioning). A similar Danish study determined the payback ratio to be 80, which means that a wind turbine system pays back the energy invested within approximately 3 months.This is to be compared with payback ratios of 11 for coal power plants and 16 for nuclear power plants, though such figures do not take into account the energy content of the fuel itself, which would lead to a negative energy gain.
The ecological and environmental costs of wind plants are paid by those using the power produced, with no long-term effects on climate or local environment left for future generations.
Because it uses energy already present in the atmosphere, and can displace fossil-fuel generated electricity (with its accompanying carbon dioxide emissions), wind power mitigates global warming. While wind turbines might impact the numbers of some bird species, conventionally fueled power plants could wipe out hundreds or even thousands of the world’s species through climate change, acid rain, and pollution.
Unlike fossil fuel or nuclear power stations, which circulate or evaporate large amounts of water for cooling, wind turbines do not need water to generate electricity.
Large-scale onshore and near-shore wind energy facilities (wind farms) can be controversial due to aesthetic reasons and impact on the local environment. Large-scale offshore wind farms are not visible from land and according to a comprehensive 8-year Danish Offshore Wind study on ‘Key Environmental Issues’ have no discernible effect on aquatic species and no effect on migratory bird patterns or mortality rates.
Modern wind farms make use of large towers with impressive blade spans, occupy large areas and may be considered unsightly at onshore and near-shore locations.
They usually do not, however, interfere significantly with other uses, such as farming.
The impact of onshore and near-shore wind farms on wildlife particularly migratory birds and bats is hotly debated, and studies with contradictory conclusions have been published.
Two preliminary conclusions for onshore and near-shore wind developments seem to be supported: first, the impact on wildlife is likely low compared to other forms of human and industrial activity; second, negative impacts on certain populations of sensitive species are possible, and efforts to mitigate these effects should be considered in the planning phase. Aesthetic issues are important for onshore and near-shore locations in that the ‘visible footprint’ may be extremely large compared to other sources of industrial power (which may be sited in industrially developed areas), and wind farms may be close to scenic or otherwise undeveloped areas. Offshore wind development locations remove the visual aesthetic issue by being at least 10 km from shore and in many cases much further away.
Clearing of wooded areas is often unnecessary, as the practice of farmers leasing their land out to companies building wind farms is common. In the U.S., farmers may receive annual lease payments of two thousand to five thousand dollars per turbine. The land can still be used for farming and cattle grazing. Less than 1% of the land would be used for foundations and access roads, the other 99% could still be used for farming.Turbines can be sited on unused land in techniques such as center pivot irrigation.
The clearing of trees around onshore and near-shore tower bases may be necessary to enable installation. This is an issue for potential sites on mountain ridges, such as in the northeastern U.S.
Wind turbines should ideally be placed about ten times their diameter apart in the direction of prevailing winds and five times their diameter apart in the perpendicular direction for minimal losses due to wind park effects. As a result, wind turbines require roughly 0.1 square kilometres of unobstructed land per megawatt of nameplate capacity. A 2 GW wind farm, which might produce as much energy each year as a 1 GW baseload power plant, might have turbines spread out over an area of approximately 200 square kilometres.
Areas under onshore and near-shore windfarms can be used for farming, and are protected from further development.
Although there have been installations of wind turbines in urban areas (such as Toronto’s exhibition place), these are generally not used. Buildings may interfere with wind, and the value of land is likely too high if it would interfere with other uses to make urban installations viable. Installations near major cities on unused land, particularly offshore for cities ne
ar large bodies of water, may be of more interest. Despite these issues, Toronto’s demonstration project demonstrates that there are no major issues that would prevent such installations where practical, although non-urban locations are expected to predominate.
Offshore locations, such as that being developed on a large underwater plateau in eastern Lake Ontario by Trillium Power use no land per se and avoid known shipping channels. Some offshore locations are uniquely located close to ample transmission and high load centres however that is not the norm for most offshore locations. Most offshore locations are at considerable distances from load centres and may face transmission and line loss challenges.
Wind turbines located in agricultural areas may create concerns by operators of cropdusting aircraft. Operating rules may prohibit approach of aircraft within a stated distance of the turbine towers; turbine operators may agree to curtail operations of turbines during cropdusting operations.
Impact on wildlife
Onshore and near-shore studies show that the number of birds killed by wind turbines is negligible compared to the number that die as a result of other human activities such as traffic, hunting, power lines and high-rise buildings and especially the environmental impacts of using non-clean power sources. For example, in the UK, where there are several hundred turbines, about one bird is killed per turbine per year; 10 million per year are killed by cars alone.
In the United States, onshore and near-shore turbines kill 70,000 birds per year, compared to 57 million killed by cars and 97.5 million killed by collisions with plate glass. Another study suggests that migrating birds adapt to obstacles; those birds which don’t modify their route and continue to fly through a wind farm are capable of avoiding the large offshore windmills,at least in the low-wind non-twilight conditions studied. In the UK, the Royal Society for the Protection of Birds (RSPB) concluded that ‘The available evidence suggests that appropriately positioned wind farms do not pose a significant hazard for birds.’ It notes that climate change poses a much more significant threat to wildlife, and therefore supports wind farms and other forms of renewable energy.
Some onshore and near-shore windmills kill birds, especially birds of prey.More recent siting generally takes into account known bird flight patterns, but some paths of bird migration, particularly for birds that fly by night, are unknown although a 2006 Danish Offshore Wind study showed that radio tagged migrating birds travelled around offshore wind farms. A Danish survey in 2005 (Biology Letters 2005:336) showed that less than 1% of migrating birds passing an oshore wind farm in Rønde, Denmark, got close to collision, though the site was studied only during low-wind non-twilight conditions. A survey at Altamont Pass, California, conducted by a California Energy Commission in 2004 showed that onshore turbines killed between 1,766 and 4,721 birds annually (881 to 1,300 of which were birds of prey). Radar studies of proposed onshore and near-shore sites in the eastern U.S. have shown that migrating songbirds fly well within the reach of large modern turbine blades. In Australia, a proposed onshore/near-shore wind farm was canceled before production because of the possibility that a single endangered bird of prey was nesting in the area.
An onshore/near-shore wind farm in Norway’s Smøla islands is reported to have destroyed a colony of sea eagles, according to the British Royal Society for the Protection of Birds. The society said turbine blades killed nine of the birds in a 10 month period, including all three of the chicks that fledged that year. Norway is regarded as the most important place for white-tailed eagles.
The numbers of bats killed by existing onshore and near-shore facilities has troubled even industry personnel. A study in 2004 estimated that over 2200 bats were killed by 63 onshore turbines in just six weeks at two sites in the eastern U.S. This study suggests some onshore and near-shore sites may be particularly hazardous to local bat populations and more research is urgently needed. Migratory bat species appear to be particularly at risk, especially during key movement periods (spring and more importantly in fall). Lasiurines such as the hoary bat (Lasiurus cinereus), red bat (Lasiurus borealis), and the semi-migratory silver-haired bats (Lasionycteris noctivagans) appear to be most vulnerable at North American sites. Almost nothing is known about current populations of these species and the impact on bat numbers as a result of mortality at windpower locations. Offshore wind sites 10 km or more from shore do not interact with bat populations.
Recorded experience that onshore and near-shore wind turbines are noisy and visually intrusive creates resistance to the establishment of land-based wind farms in many places. Moving the turbines far offshore (10 km or more) mitigates the problem, but offshore wind farms may be more expensive and transmission to on-shore locations may present challenges in many but not all cases.
Some residents near onshore and near-shore windmills complain of ‘shadow flicker,’ which is the alternating pattern of sun and shade caused by a rotating windmill casting a shadow over residences. Efforts are made when siting onshore and near-shore turbines to avoid this problem.
Large onshore and near-shore wind towers require aircraft warning lights, which create light pollution at night, which bothers humans and can disrupt the local ecosystem. Complaints about these lights have caused the FAA to consider allowing a less than 1:1 ratio of lights per turbine in certain areas.
Wind power is nothing new.
Improvements in blade design and gearing have quietened modern turbines to the point where a normal conversation can be held underneath one.
In December 2006, a jury in Texas denied a suit for private nuisance against FPL Energy for noise pollution after the company demonstrated that noise readings were not excessive, with the highest reading reaching 44 decibels, which was characterized as approximately the same noise level as a wind of 10 miles per hour.
The suit was initially for visual intrusion, but that was disallowed, so it concentrated on noise, which with the large spreads involved, was bound to fail). Texas civil case law requires proof of personal injury in a suit against a neighbor’s activities (Klein v. Gehrung, 25 Tex. Supp. 232), so even if the plaintiffs had presented data showing more substantial noise, they would not have prevailed unless they could prove injury
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