Environmental and aesthetic impact
Compared to the environmental effects of traditional energy sources, the environmental effects of wind power upon greenhouse gases are minor; however, there are other adverse impacts of wind power including bird mortality. Wind power consumes no water, 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 of operation. While a wind farm may cover a large area of land, many land uses such as agriculture are compatible.
Danger to birds and bats has been a concern in many locations. Some[who?] dismiss the number of birds killed by wind turbines as negligible when compared to the number that die as a result of other human activities, and especially when considering the adverse environmental impacts of using non-clean power sources. Others strongly disagree about the placement of wind farms. New evidence suggests that the critically endangered California Condor is being killed at the Tehachapi Pass wind farm in Southern California. Bat species appear to be at risk during key movement periods. 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, but researchers are concerned if there are nearby bird colonies.
Aesthetics have also been an issue in some areas. In the USA, the Massachusetts Cape Wind project was delayed for years chiefly because of nearby residents’ aesthetic concerns. In the UK, repeated opinion surveys have shown that more than 70% of people either like, or do not mind, the visual impact. According to a town councillor in Ardrossan, Scotland, the overwhelming majority of locals believe that the Ardrossan Wind Farm has enhanced the area. They say the turbines are impressive looking and bring a calming effect to the town.
Effect on power grid
Utility-scale wind farms must have access to transmission lines to transport energy. The wind farm developer may be obligated to install extra equipment or control systems in the wind farm to meet the technical standards set by the operator of a transmission line. The company or person that develops the wind farm can then sell the power on the grid through the transmission lines and ultimately chooses whether to hold on to the rights or sell the farm or parts of it to big business like GE, for example.
Ground radar interference
Wind farms can interfere with ground radar systems used for defense, weather and air traffic control. The large, rapidly moving blades of the turbines can return signals to the radar that can be mistaken as an aircraft or weather pattern. Actual aircraft and weather patterns around wind farms can be accurately detected, as there is no fundamental physical constraint preventing that. But aging radar infrastructure is significantly challenged with the task. The US military is using wind turbines on some bases, including Barstow near the radar test facility.
Effects
The level of interference is a function of the signal processors used within the radar, the speed of the aircraft and the relative orientation of wind turbines/aircraft with respect to the radar. An aircraft flying above the wind farm’s turning blades could become impossible to detect because the blade tips can be moving at nearly aircraft velocity. Studies are currently being performed to determine the level of this interference and will be used in future site planning. Issues include masking (shadowing), clutter (noise), and signal alteration. Radar issues have stalled as much as 10,000 MW of projects in USA.
Some very long range radars are not affected by wind farms.
Mitigation
Permanent problem solving include Non-Initiation Window to hide the turbines while still tracking aircraft over the wind farm, and a similar method mitigates the false returns. England’s Newcastle Airport is using a short-term mitigation; to “blank” the turbines on the radar map with a software patch. Wind turbine blades using stealth technology are being developed to mitigate radar reflection problems for aviation. As well as stealth windfarms, the future development of infill radar systems could filter out the turbine interference.
In early 2011, the U.S. government awarded a program to build a radar/wind turbine analysis tool. This tool will allow developers to predict the impact of a wind farm on a radar system before construction, thus allowing rearrangement of the turbines or even the entire wind farm to avoid negative impacts on the radar system.
A mobile radar system, the Lockheed Martin TPS-77, has shown in recent tests that it can distinguish between aircraft and wind turbines, and more than 170 TPS-77 radars are in use around the world. In Britain, the Lockheed Martin TPS-77 will be delivered and installed in November 2011 at Trimingham in Norfolk, removing military objections to a series of offshore wind farms in the North Sea. A second TPS-77 is to be installed in the Scottish Borders, overcoming objections to a 48-turbine wind farm at Fallago.
Agriculture
The professor of atmospheric science Somnath Baidya Roy of the University of Illinois, in a study published in October 2010 in the scientific journal PNAS shows that in the immediate vicinity of wind farms, the climate is cooler during the day and slightly warmer during the night than the surrounding areas. According to Roy, the effect is due to the turbulence generated by the blades.
In another study conducted by Gene Takle and Julie Lundquist University of Colorado, presented at San Francisco conference of the American Geophysical Union Fall Meeting (December 13–18, 2010), the analysis carried out on corn and soybean crops in the central areas of the United States has noted that the microclimate generated by wind turbines improves crops as it prevents the spring and autumn frosts, and it reduces the action of pathogenic fungi that grow on the leaves. Even at the height of summer heat, the lowering of 2.5-3 degrees above the crops due to turbulence caused by the blades, can make a difference for the cultivation of maize.
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