Compared to the environmental impact of traditional energy sources, the environmental impact of wind power is relatively minor. Wind power consumes no fuel, and emits no air pollution, unlike fossil fuel power sources. The energy consumed to manufacture and transport the materials used to build a wind power plant is equal to the new energy produced by the plant within a few months. While a wind farm may cover a large area of land, many land uses such as agriculture are compatible, with only small areas of turbine foundations and infrastructure made unavailable for use.

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.

There are anecdotal reports of negative effects from noise on people who live very close to wind turbines. Peer-reviewed research has generally not supported these statements.

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, sulfur dioxide, mercury, particulates, or any other type of air pollution, unlike fossil fuel power sources. Wind power plants consume resources in manufacturing and construction. During manufacture of the wind turbine, steel, concrete, aluminium and other materials will have to be made and transported using energy-intensive processes, generally using fossil energy sources. The wind turbine manufacturer Vestas states that initial carbon dioxide emissions “pay back” is within about 9 months of operation for off shore turbines.

A 2006 study found the CO2 emissions of wind power to range from 14 to 33 tonnes per GWh of energy produced. Most of the CO2 emission comes 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 of CO2 per MWh.

The UK Energy Research Centre (UKERC) study of intermittency also states that wind energy can displace fossil fuel-based generation, reducing both fuel use and carbon dioxide emissions.

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. However, Enercon did choose very early not to use permanent magnets for its direct drive turbines, in order to avoid responsibility in the bad environmental imprint of rare earth mining.

Net energy gain

The initial carbon dioxide emission from energy used in the installation is “paid back” within about 9 months of operation for off shore turbines. Any practical large-scale energy source must replace the energy 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. The EROI for wind ranges from 5 to 35, with an average of around 18, according to wind-energy advocates. 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.

Ecology

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, although the concrete foundations will be left in place and access tracks may also be retained.

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. Critics point out that the clearing of trees around tower bases may be necessary for installation sites on mountain ridges, such as in the northeastern U.S.

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. Toronto Hydro has built a lake shore demonstration project, and Steel Winds is 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”.

Offshore locations use no land and avoid shipping channels.

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. The first study to demonstrate impacts of wind farms on weather and climate used a regional climate model. Data from an operational wind farm in Palm Springs, California, confirmed the model results. Overall, wind farms lead to a warming at night and 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. Somnath Baidya Roy, the author of the study suggested that the 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 study published in Atmospheric Chemistry and Physics 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 one degree Celsius 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 degrees Celsius. 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”.

Hazardous waste

In 2011, a Minnesota wind-turbine blade manufacturing plant was fined $490,000 for air quality, hazardous waste, and stormwater violations.

Offshore

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.

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