Environmental impact of wind power
Compared to the environmental impact of traditional energy sources, the environmental impact of (onshore) wind power is relatively minor, slightly higher than the environmental impact of hydro power on a life-cycle basis. Unlike electricity derived from fossil fuel and nuclear power plants, wind power consumes no fuel and, unlike fossil fuel power plants, emits no air pollution in operation.
There are reports of bird and bat mortality at wind turbines as there are around other artificial structures. The scale of the ecological impact may or may not be significant, depending on specific circumstances. Prevention and mitigation of wildlife fatalities, and protection of peat bogs, affect the siting and operation of wind turbines.
Net energy gain
Modern wind turbine systems have a net energy gain, in other words during their service life they produce significantly more energy than is used to build the system. Any practical large-scale energy source must produce more energy than is used in its construction. 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. According to a meta study, in which all existing studies from 1977 to 2007 were reviewed, the EROI for wind ranges from 5 to 35, with an average of around 18. EROI is strongly proportional to turbine size, and larger late-generation turbines are at the high end of this range, at or above 35. Since energy produced is several times energy consumed in construction, there is a net energy gain.
Carbon dioxide emissions and pollution
Wind power consumes no fuel and no water for continuing operation, and has no emissions directly related to electricity production. Wind turbines produce no carbon dioxide, carbon monoxide, sulfur dioxide, nitrogen dioxide, mercury, radioactive waste, particulates, or any other type of air pollution, unlike fossil fuel sources and nuclear power plant fuel production. Wind turbine manufacturer Vestas claims that initial energy "pay back" is within about 8.6 months of operation for a V80-2.0MW wind power plant under low wind conditions.
- CO2 emissions
A 2006 study of 3 installations in the US Midwest found the CO2 emissions of wind power ranged from 14 to 33 tonnes (15 to 36 short tons) per GWh of energy produced. Most of the CO2 emission came from producing the concrete for wind-turbine foundations.
A study by the Irish national grid stated that "Producing electricity from wind reduces the consumption of fossil fuels and therefore leads to emissions savings", and found reductions in CO2 emissions ranging from 0.33 to 0.59 tonnes (0.36 to 0.65 short ton) of CO2 per MWh.
The 2006 UK Energy Research Centre (UKERC) study focused on the intermittent nature of the output of some renewable energy sources, concluded that intermittency is not a major obstacle to the integration of renewable sources of electricity supply.
- Rare-earth mining pollution
The production of permanent magnets used in some wind turbines makes use of neodymium. Primarily exported by China, pollution concerns associated with the extraction of this rare-earth element have prompted government action in recent years, and international research attempts to refine the extraction process. Research is underway on turbine and generator designs which reduce the need for neodymium, or eliminate the use of rare-earth metals altogether. Additionally, the large wind turbine manufacturer Enercon GmbH chose very early not to use permanent magnets for its direct drive turbines, in order to avoid responsibility for the adverse environmental impact of rare earth mining.
Wind farms are often built on land that has already been impacted by land clearing. The vegetation clearing and ground disturbance required for wind farms is minimal compared with coal mines and coal-fired power stations. If wind farms are decommissioned, the landscape can be returned to its previous condition.
Farmers and graziers often lease land to companies building wind farms. In the U.S., farmers may receive annual lease payments of two thousand to five thousand dollars per turbine, and wind farms may also provide additional community payments "...to reward residents who have made no financial gains [directly] from wind energy development, but whose views of... [the] landscape now include a panorama of turbines".
The land can still be used for farming and cattle grazing. Livestock are unaffected by the presence of wind farms. International experience shows that livestock will "graze right up to the base of wind turbines and often use them as rubbing posts or for shade".
Wind-energy advocates contend that less than 1% of the land would be used for foundations and access roads, the other 99% could still be used for farming. A wind turbine needs about 200–400 m² for the foundation. A (small) 500-kW-turbine with an annual production of 1.4 GWh produces 11,7 MWh/m², which is comparable with coal-fired plants (about 15-20 MWh/m²), coal-mining not included. With increasing size of the wind turbine the relative size of the fundation decreases. Critics point out that on some locations in forests the clearing of trees around tower bases may be necessary for installation sites on mountain ridges, such as in the northeastern U.S. This usually takes the clearing of 5000 m² per wind turbine.
Turbines are not generally installed in urban areas. Buildings interfere with wind, turbines must be sited a safe distance ("setback") from residences in case of failure, and the value of land is high. There are a few notable exceptions to this. The WindShare ExPlace wind turbine was erected in December 2002, on the grounds of Exhibition Place, in Toronto, Canada. It was the first wind turbine installed in a major North American urban city centre. Steel Winds also has a 20 MW urban project south of Buffalo, New York. Both of these projects are in urban locations, but benefit from being on uninhabited lake shore property.
In the UK there has also been concern about the damage caused to peat bogs, with one Scottish MEP campaigning for a moratorium on wind developments on peatlands saying that "Damaging the peat causes the release of more carbon dioxide than wind farms save".
Impact on wildlife
Environmental assessments are routinely carried out for wind farm proposals, and potential impacts on the local environment (e.g. plants, animals, soils) are evaluated. Turbine locations and operations are often modified as part of the approval process to avoid or minimise impacts on threatened species and their habitats. Any unavoidable impacts can be offset with conservation improvements of similar ecosystems which are unaffected by the proposal.
A research agenda from a coalition of researchers from universities, industry, and government, supported by the Atkinson Center for a Sustainable Future, suggests modeling the spatiotemporal patterns of migratory and residential wildlife with respect to geographic features and weather, to provide a basis for science-based decisions about where to site new wind projects. More specifically, it suggests:
- Use existing data on migratory and other movements of wildlife to develop predictive models of risk.
- Use new and emerging technologies, including radar, acoustics, and thermal imaging, to fill gaps in knowledge of wildlife movements.
- Identify specific species or sets of species most at risk in areas of high potential wind resoures.
Projects such as the Black Law Wind Farm have received wide recognition for its contribution to environmental objectives, including praise from the Royal Society for the Protection of Birds, who describe the scheme as both improving the landscape of a derelict opencast mining site and also benefiting a range of wildlife in the area, with an extensive habitat management projects covering over 14 square kilometres.
The meta-analysis on avian mortality by Benjamin K. Sovacool led him to suggest that there were a number of deficiencies in other researchers' methodologies. Among them, he stated were a focus on bird deaths, but not on the reductions in bird births: for example, mining activities for fossil fuels and pollution from fossil fuel plants have led to significant toxic deposits and acid rain that have damaged or poisoned many nesting and feeding grounds, leading to reductions in births. The large cumulated footprint of wind turbines, which reduces the area available to wildlife or agriculture, is also missing from all studies including Sovacool's. Many of the studies also made no mention of avian deaths per unit of electricity produced, which excluded meaningful comparisons between different energy sources. More importantly, it concluded, the most visible impacts of a technology, as measured by media exposure, are not necessarily the most flagrant ones.
The Sovacool study did a broad assessment of anthropogenic causes of avian mortality and brought together many studies on deaths due to wind energy, fossil fuel energy and nuclear energy. He arrived at a figure for bird deaths due to wind power of 0.269 fatalities per per gigawatt-hour (GWh), by which he extrapolated a total of 7193 US bird fatalities in 2006. He concluded that wind farms and nuclear power stations are responsible each for between 0.3 and 0.4 fatalities per gigawatt-hour (GWh) of electricity while fossil-fueled power stations are responsible for about 5.2 fatalities per GWh. Of the bird deaths Sovacool attributed to fossil-fuel power plants, 96 percent were due to the effects of climate change. While the study did not assess bat mortality due to various forms of energy, he considered it not unreasonable to assume a similar ratio of mortality. The Sovacool study has provoked controversy because of its treatment of data.
|Wind turbines||0.02 – 0.57||0.269|
|Nuclear power plants||0.33||0.416|
|Oilfield oil waste & waste water pits||0.50 – 1||(n/a)|
|Nuisance bird control kills (airports, agriculture, etc...)||2||(n/a)|
|Communication towers (cellular, radio, microwave)||4 – 50||(n/a)|
|Large communications towers (over 180', N. America)||6.8||(n/a)|
|Fossil fuel powerplants||14||5.18|
|Cars & trucks||50 – 100||(n/a)|
|Building windows||97 – 976||(n/a)|
|Hunting||100 – 120||(n/a)|
|Transmission lines (conventional powerplants)||174 – 175||(n/a)|
|Domestic and feral cats||210 – 3,700||(n/a)|
Different sources have variously estimated that in the United States wind turbines kill between 20,000 and 573,000 birds per year, but either figure is minimal compared to bird deaths from other causes. Fossil-fueled power plants, which wind turbines replace, kill almost 20 times as many birds per gigawatt hour (GWh) of electricity. Bird deaths due to other human activities and cats total between 797 million and 5.29 billion per year in the U.S. (see Causes of avian mortality table). Additionally, while many studies concentrate on the analysis of bird deaths, few have been conducted on the reductions of bird births, which are the additional consequences of the various pollution sources that wind power mitigates.
Bird mortality at wind energy facilities can vary greatly depending on the facility's location, with some facilities reporting nearly zero bird fatalities, and others as high as four birds per turbine per year. An article in the journal Nature stated that each wind turbine in the U.S. kills an average of 0.03 birds per year, and recommends that more research needs to be done.
Environmental impact analysis conducted for proposed wind energy facilities in the U.S. have warned that some facilities sited in important bird areas could kill thousands of birds and bats per year, according to the U.S. Bureau of Land Management.
Wind facilities have attracted the most attention for impacts on iconic raptor species, including golden eagles. The Pine Tree Wind energy project near Tehachapi, California has one of the highest raptor mortality rates in the country; by 2012 at least eight golden eagles had been killed according to the U.S. Fish and Wildlife Service (USFWS). Biologists have noted that it is more important to avoid losses of large birds as they have lower breeding rates and can be more severely impacted by wind turbines in certain areas.
In 2009 a U.S. Fish and Wildlife Service scientist estimated that wind turbines kill 440,000 birds per year in the U.S., with future mortality expected to increase significantly as wind power generation expands by 2030 to levels about 12 times higher than 2009 levels. This estimate was disputed by several organizations, with the USFWS later pointing out that it was only an 'estimate' by one of many scientists and was not officially supported by the agency. By comparison approximately 80,000 birds are killed by aircraft in the U.S., and a 2013 report by scientists from the Smithsonian Conservation Biology Institute and the USFWS estimated that cats kill as many as 3.7 billion birds yearly in the same country. An earlier report by the American Bird Conservancy had estimated bird predation by U.S. cats at 500 million yearly.
Large numbers of bird deaths are also attributed to collisions with buildings. An estimated 1 to 9 million birds are killed every year by tall buildings in Toronto, Canada alone, according to the wildlife conservation organization Fatal Light Awareness Program. Other studies have stated that 57 million are killed by cars, and 97.5 million killed by collisions with plate glass in the United States alone. Promotional event lightbeams as well as ceilometers used at airport weather offices can be particularly deadly for birds, as birds become caught in their lightbeams and suffer exhaustion and collisions with other birds. In the worst recorded ceilometer lightbeam kill-off during one night in 1954, approximately 50,000 birds from 53 different species died at the Warner Robins Air Force Base in the United States.
In the United Kingdom, 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. In 2009 the RSPB warned that "numbers of several breeding birds of high conservation concern are reduced close to wind turbines" probably because "birds may use areas close to the turbines less often than would be expected, potentially reducing the wildlife carrying capacity of an area.
Concerns have been expressed that wind turbines at Smøla, Norway are having a deleterious effect on the population of White-tailed Eagles, Europe's largest bird of prey. They have been the subject of an extensive re-introduction programme in Scotland, which could be jeopardised by the expansion of wind turbines.
The Peñascal Wind Power Project in Texas is located in the middle of a major bird migration route, and the wind farm uses avian radar originally developed for NASA and the United States Air Force to detect birds as far as 4 miles (6.4 km) away. If the system determines that the birds are in danger of running into the rotating blades, the turbines shut down and are restarted when the birds have passed. A 2005 Danish study used surveillance radar to track migrating birds traveling around and through an offshore wind farm. Less than 1% of migrating birds passing through an offshore wind farm in Rønde, Denmark, got close enough to be at risk of collision, though the site was studied only during low-wind conditions. The study suggests that migrating birds may avoid large turbines, at least in the low-wind conditions the research was conducted in.
In 2012, researchers reported that, based on their four-year radar tracking study of birds after construction of an offshore wind farm near Lincolnshire, that pink-footed geese migrating to the U.K. to overwinter altered their flight path to avoid the turbines.
At the Altamont Pass Wind Farm in California, a settlement between the Audubon Society, Californians for Renewable Energy and NextEra Energy Resources who operate some 5,000 turbines in the area requires the latter to replace nearly half of the smaller turbines with newer, more bird-friendly models by 2015 and provide $2.5 million for raptor habitat restoration. The proposed Chokecherry and Sierra Madre Wind project in Wyoming, however, is expected to kill nearly 5,400 birds each year, including over 150 raptors, according to a Bureau of Land Management environmental analysis.
Bats may be injured by direct impact with turbine blades, towers, or transmission lines. Recent research shows that bats may also be killed when suddenly passing through a low air pressure region surrounding the turbine blade tips.
In April 2009 the Bats and Wind Energy Cooperative released initial study results showing a 73% drop in bat fatalities when wind farm operations are stopped during low wind conditions, when bats are most active. Bats avoid radar transmitters, and placing microwave transmitters on wind turbine towers may reduce the number of bat collisions.
A 2013 study produced an estimate that wind turbines killed more than 600,000 bats in the U.S. the previous year, with the greatest mortality occurring in the Appalachian Mountains. Some earlier studies had produced estimates of between 33,000 and 888,000 bat deaths per year.
Weather and climate change
Wind farms may affect weather in their immediate vicinity. Spinning wind turbine rotors generate a lot of turbulence in their wakes like the wake of a boat. This turbulence increases vertical mixing of heat and water vapor that affects the meteorological conditions downwind. Overall, wind farms lead to a slight warming at night and a slight cooling during the day time. This effect can be reduced by using more efficient rotors or placing wind farms in regions with high natural turbulence. Warming at night could "benefit agriculture by decreasing frost damage and extending the growing season. Many farmers already do this with air circulators".
A number of studies have used climate models to study the effect of extremely large wind farms. One study reports simulations that show detectable changes in global climate for very high wind farm usage, on the order of 10% of the world's land area. Wind power has a negligible effect on global mean surface temperature, and it would deliver "enormous global benefits by reducing emissions of CO2 and air pollutants". Another peer-reviewed study suggested that using wind turbines to meet 10 percent of global energy demand in 2100 could actually have a warming effect, causing temperatures to rise by 1 °C (1.8 °F) in the regions on land where the wind farms are installed, including a smaller increase in areas beyond those regions. This is due to the effect of wind turbines on both horizontal and vertical atmospheric circulation. Whilst turbines installed in water would have a cooling effect, the net impact on global surface temperatures would be an increase of 0.15 °C (0.27 °F). Author Ron Prinn cautioned against interpreting the study "as an argument against wind power, urging that it be used to guide future research". "We’re not pessimistic about wind," he said. "We haven’t absolutely proven this effect, and we’d rather see that people do further research".
Impacts on people
Operation of any utility-scale energy conversion system presents safety hazards.
If a turbine's brake fails, the turbine can spin freely until it disintegrates or catches fire. This is rare and the odds of a major turbine fire or disintegration is in the order of 0.001% over the 20-25 year lifespan of a modern wind turbine. Some turbine nacelle fires cannot be extinguished because of their height, and are sometimes left to burn themselves out. In such cases they generate toxic fumes and can cause secondary fires below. However, newer wind turbines are built with automatic fire extinguishing systems similar to those provided for jet aircraft engines. The autonomous FIREX systems, which can be retrofitted to older wind turbines, automatically detect a fire, order the shut down of the turbine unit and immediately extinguish the fires completely.
During winter ice may form on turbine blades and subsequently be thrown off during operation. This is a potential safety hazard, and has led to localised shut-downs of turbines. Modern turbines can detect ice formation and excess vibration during operations, and are shut down automatically. Electronic controllers and safety sub-systems monitor many different aspects of the turbine, generator, tower, and environment to determine if the turbine is operating in a safe manner within prescribed limits. These systems can temporarily shut down the turbine due to high wind, ice, electrical load imbalance, vibration, and other problems. Recurring or significant problems cause a system lockout and notify an engineer for inspection and repair. In addition, most systems include multiple passive safety systems that stop operation even if the electronic controller fails.
Newer wind farms have larger, more widely spaced turbines, and have a less cluttered appearance than older installations. Wind farms are often built on land that has already been impacted by land clearing and they coexist easily with other land uses (e.g. grazing, crops). They have a smaller footprint than other forms of energy generation such as coal and gas plants. Wind farms may be close to scenic or otherwise undeveloped areas, and aesthetic issues are important for onshore and near-shore locations.
Aesthetic issues are subjective and some people find wind farms pleasant and optimistic, or symbols of energy independence and local prosperity. While some tourism officials predict wind farms will damage tourism, some wind farms have themselves become tourist attractions, with several having visitor centers at ground level or even observation decks atop turbine towers.
Residents near turbines may complain of "shadow flicker" on nearby residences caused by rotating turbine blades, when the sun passes behind the turbine. This can easily be avoided by locating the wind farm to avoid unacceptable shadow flicker, or by turning the turbine off for the time of the day when the sun is at the angle that causes flicker. If a turbine is poorly sited and adjacent to many homes, the duration of shadow flicker on a neighborhood can last hours.
The location of a wind farm is critical to its overall power-generation. Each turbine depends on “micro-sitting,” or the exact position of the turbine, because a difference of 30 m can sometimes double a turbine’s output. Coastal and areas of higher altitude are considered prime for wind farms, due to the constant wind speeds. Hills or ridges cause the wind to accelerate as it is forced over the higher altitude, increasing wind speed. A historical rule of thumb suggests that a site is not ideal for wind-farm usage unless it exhibits average wind speeds of 10 mph or higher. Both locations tend to be areas of high tourism and aesthetic pleasure, causing many local communities to protest the development of wind farms. Coastal regions, however, tend to be highly populated, thus requiring more energy. While small wind farms can connect to the local electricity distribution grid, locating large wind farms in rural areas increases the cost and complexity of transferring generated power to population centers. Both the proximity to densely populated areas and the necessary wind speeds make these locations ideal for wind farms.
In 2011, the British Acoustics Bulletin published the 10th independent review of the evidence on wind farms causing annoyance and ill health in people. And for the 10th time it has emphasised that "annoyance has far more to do with social and psychological factors in those complaining than any direct effect from sound or inaudible infrasound emanating from wind turbines". Two factors repeatedly came up. "The first is being able to see wind turbines, which increases annoyance particularly in those who dislike or fear them. The second factor is whether people derive income from hosting turbines, which miraculously appears to be a highly effective antidote to feelings of annoyance and symptoms".
A 2009 expert panel review, sponsored by the Canadian Wind Energy Association and American Wind Energy Association, delved into the possible adverse health effects of those living close to wind turbines. Their 85-page report concluded that wind turbines do not directly make people ill. The study did allow that some people could experience stress or irritation caused by the swishing sounds wind turbines produce. "A small minority of those exposed report annoyance and stress associated with noise perception..." [however] "Annoyance is not a disease." The study group pointed out that similar irritations are produced by local and highway vehicles, as well as from industrial operations and aircraft.
The 2009 study panel members included: Robert Dobie, a doctor and clinical professor at the University of Texas, Geoff Leventhall, a noise vibration and acoustics expert in the United Kingdom, Bo Sondergaard, with Danish Electronics Light and Acoustics, Michael Seilo, a professor of audiology at Western Washington University, and Robert McCunney, a biological engineering scientist at the Massachusetts Institute of Technology. McCunney contested statements that infrasounds from wind turbines could create vibrations causing ill health: "It doesn't really have much credence, at least based on the literature out there" he stated The academic and medical experts who conducted the study stated that they reached their conclusions independent of their sponsors. "We were not told to find anything," said panel expert David Colby, a public health officer in Chatham-Kent and a Professor of Medicine at the University of Western Ontario. "It was completely open ended."
Eighteen research reviews about wind turbines and health, published since 2003, all showed that there was very little evidence that wind turbines were harmful in any direct way. Simon Chapman, professor of public health at Sydney University, said that if wind farms did genuinely make people ill there would by now be a large body of medical literature that would preclude putting them near populated areas. But this is not the case. Sickness being attributed to wind turbines is more likely to be caused by people getting alarmed at the health warnings circulated by activists. Complaints of illness were far more prevalent in communities targeted by anti-wind groups. Chapman's report concludes "that illnesses being blamed on windfarms are more than likely caused by the psychological effect of suggestions that the turbines make people ill, rather than by the turbines themselves".
Nina Pierpont, a New York pediatrician and wife of an anti-wind energy activist, states that noise can be an important disadvantage of wind turbines, especially when building the wind turbines very close to urban environments. The controversy around Pierpont's work centers around her statements made in a self-published, non-peer-reviewed book that ultra-low frequency sounds affect human health, which are based on a very small sample of self-selected subjects with no control group for comparison. She asserts that wind turbines affect the mood of people and may cause physiological problems such as insomnia, headaches, tinnitus, vertigo and nausea. Simon Chapman has said that "wind turbine syndrome" is not recognised by any international disease classification system and does not appear in any title or abstract in the massive US National Library of Medicine's PubMed database. He says that the term appears to be spread by anti-wind farm activist groups. The 2009 expert panel review found that "wind turbine syndrome" symptoms are the same as those seen in the general population due to stresses of daily life, and include headaches, insomnia, anxiety, and dizziness.
A 2007 report by the U.S. National Research Council noted that noise produced by wind turbines is generally not a major concern for humans beyond a half-mile or so. Low-frequency vibration and its effects on humans are not well understood and sensitivity to such vibration resulting from wind-turbine noise is highly variable among humans. There are opposing views on this subject, and more research needs to be done on the effects of low-frequency noise on humans.
In a 2009 report about "Rural Wind Farms", a Standing Committee of the Parliament of New South Wales, Australia, recommended a minimum setback of two kilometres between wind turbines and neighbouring houses (which can be waived by the affected neighbour) as a precautionary approach. In July 2010, Australia's National Health and Medical Research Council reported that "there is no published scientific evidence to support adverse effects of wind turbines on health".
In Ontario, Canada, the Ministry of the Environment created noise guidelines to limit wind turbine noise levels 30 metres away from a dwelling or campsite to 40 dB(A). These regulations also set a minimum distance of 550 metres (1,800 ft) for a group of up to five relatively quiet [102 dB(A)] turbines within a 3-kilometre (1.9 mi) radius, rising to 1,500 metres (4,900 ft) for a group of 11 to 25 noisier (106-107 dB(A)) turbines. Larger facilities and noisier turbines would require a noise study.
A 2008 guest editorial in Environmental Health Perspectives published by the National Institute of Environmental Health Sciences, the U.S. National Institutes of Health, stated: "Even seemingly clean sources of energy can have implications on human health. Wind energy will undoubtedly create noise, which increases stress, which in turn increases the risk of cardiovascular disease and cancer."
Modern wind turbines produce significantly less noise than older designs. Turbine designers work to minimise noise, as noise reflects lost energy and output. Noise levels at nearby residences may be managed through the siting of turbines, the approvals process for wind farms, and operational management of the wind farm.
Many offshore wind farms are being built in UK waters. In January 2009, a comprehensive government environmental study of coastal waters in the United Kingdom concluded that there is scope for between 5,000 and 7,000 offshore wind turbines to be installed without an adverse impact on the marine environment. The study – which forms part of the Department of Energy and Climate Change's Offshore Energy Strategic Environmental Assessment – is based on more than a year's research. It included analysis of seabed geology, as well as surveys of sea birds and marine mammals.
- Environmental movement
- Environmental concerns with electricity generation
- Environmental effects of coal
- Environmental effects of nuclear power
- Environmental issues with energy
- Renewable energy debate
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