Installing temperature and humidity sensors across the 18.6sq.km Black Law wind farm, a team led by the University of Leeds’ National Centre for Atmospheric Science director Stephen Mobbs found a slight warming at ground level that was localised within the site’s perimeter.
Last year, UK consulting clinical radiologist and geohydrologist Rachel Connor found that wind farms had contaminated water supplies in Scotland.
She made the revelations in a report as part of opposition to Community Windpower’s application to East Ayrshire Council for a 15m by 130m turbine windfarm at Sneddon Law within the boundary of the existing Whitelee Windfarm Extension.
Mobbs, who co-authored his own team’s findings published in the journal Environmental Research Letters, said the study helped clarify an understanding of the localised effect of wind farms that have until now been unknown and the subject of much speculation.
“For a long time there have been some concerns about what effects wind farms could have on the local climate and the land surface," Mobbs said.
“To be honest, it was mostly speculation with nothing very concrete. We set out to actually measure what was going on.
“We had a fantastic opportunity when [the operators] turned the wind farm off for several months for some major maintenance.
“What we were able to do, which had not been possible before, is to compare the effects with and without the turbines rotating.
“For the first time, we have been able to detect a climatic effect – there definitely is one.”
The Black Law wind farm has a generation capacity of 124 megawatts, with 54 turbines.
Mobbs’ team discovered that operational wind turbines raised air temperature by 0.18C, while absolute humidity also went up slightly during the night, and increased the variability in air, surface and soil temperature throughout the diurnal cycle.
The microclimatic influence of turbines on air temperature also decreased logarithmically with distance from the nearest turbine.
“These effects on ground-level microclimate, including soil temperature, have uncertain implications for biogeochemical processes and ecosystem carbon cycling, including soil carbon stocks,” Mobbs’ report said.
“Consequently, understanding needs to be improved to determine the overall carbon balance of wind energy.”
Wind turbines’ global installed electricity generating capacity soared from 48 megawatts to 370MW between 2004 to 2014 and the International Energy Agency believes it will increase more than any other renewable energy source by 2035, resulting in wind farms covering 293,333sq.km.
Mobbs’ report said that while the effects of this land use change on human populations and wildlife, including avian and bat communities, have received some consideration, there was a “paucity of data” on the effects of wind farms on soil and ground-level climates.
This “limits our ability to determine effects on biogeochemical processes that regulate plant-soil carbon cycling”, which in turn could have implications for the “true carbon balance” of the renewable energy technology.
“Wind farms have been postulated to affect climatic conditions from local to global scale through modification of the vertical distribution of energy and moisture within the atmosphere and exchange between the land surface and atmosphere,” the report said.
Previous studies have modelled the effects of turbines, measured air temperature differences upwind and downwind of turbines and used satellite data to examine temperature effects over a 10,000sq.km area of North America.
More recently, in addition to effects on heat fluxes, one row of turbines was reported to have increased carbon dioxide release from the land during the night and uptake during the day, potentially impacting soil carbon stocks.
