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The Danish study did not determine the actual risk of debris being thrown from turbines.
An email from an Ohio Republican lawmaker to colleagues, activists and journalists notes a “rapidly increasing occurrence of wind turbine accidents around the world” and provides a three-year-old Danish study showing how far blade fragments and ice might be thrown from turbines.
While more incidents would be expected as the number of wind turbines has grown exponentially, the Danish report makes no determination of the risk that such events might actually happen. And a database maintained by British wind energy opponents shows no overall trend over the last decade for the types of accidents that the study says could cause those events.
“I distributed the study to those most likely to care about the wind setback issue,” said Rep. Bill Seitz, who is fighting an effort to roll back Ohio’s setback rules. Seitz sent his email to fellow lawmakers, media outlets and others on March 1 after receiving the study from Julie Johnson, an anti-wind activist.
Although Seitz’s email refers to a pending bill, he said he chose to send the report by email instead of formally introducing it into the legislative record because no additional hearings had yet been scheduled on Senate Bill 238. He added a concern that wind setbacks might also be addressed by the Ohio Senate in another pending bill to make the state’s renewable standards voluntary.
The study presents calculations based on assumed wind turbine speeds and energy outputs, without consideration of actual risks that those conditions would occur. Yet Seitz’s email went beyond what the report and the data in it say.
Seitz warned that blade fragments “can travel 700 meters to 2 kilometers.” That theoretical range applies only for an assumed “extreme” turbine speed of 150 meters per second, according to the report from researchers at the Technical University of Denmark.
The “normal” operating speed assumed by the researchers was less than half that rate. And the calculated distances for that assumed condition would all be below the range Seitz cited. The journal Wind Energy first published the report online on February 19, 2015.
Seitz’s email noted “the rapidly increasing occurrence of wind turbine accidents around the world.” But turbine accident statistics compiled by a British anti-wind group don’t show any clear trend for fires, ice throws or blade failures over the last ten years even as wind energy production has surged. Those are the types of accidents the Danish researchers, who cited the British group’s data, said could possibly lead to thrown material from a turbine.
Seitz’s email also referred to a sample of seven “safety distances” in one of the report’s figures, “the vast majority of which exceed current Ohio law.” Although that suggests Ohio law is very lax, the state’s current setbacks are among the strictest in the United States.
The sample table referenced by Seitz also deals only with the distance from a wind turbine to human structures, rather than the property line. For a property line setback, the prior 2014 requirement of 110 percent of the turbine height from the property line is more common, according to the American Wind Energy Association.
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What’s the real risk?
It does sound scary to have ice or parts flying hundreds of meters from a speeding wind turbine. However, the Danish study never determined the risk of such events actually happening.
“The throw distances presented by this study were obtained with respect to a set of initial parameters without taking into account their probabilities of occurrence,” Jens Nørkær Sørensen and his co-author Hamid Sarlak wrote.
“I expect the study to be used by planners of wind turbine installations and public authorities,” Sørensen said, but added that his team has done actual risk analyses for turbines “near highways, recreational areas, and close to important installations, such as power plants or bridges.”
A risk analysis for a wind turbine would consider the chances of someone or something being hit based on the actual location of a person or object, the likelihood of its presence at that point, and the probability that an accident would in fact happen, Sorensen explained. “The outcome is typically compared to some generalized probabilities, such as the probability of being hit by a lightning, to give a lay person a feeling of the risk,” he said.
The level of risk is not fixed in stone, either. “A way to reduce risks is simply to make [a] better blade design with respect to reducing fatigue,” Sørensen said. That would involve more reliable blade production, stronger materials, and a better knowledge of turbulence and other impacts from the wind.
Operators could also reduce problems through surveillance and operational controls, he noted. Wind turbines typically shut down in high winds and severe storms in order to prevent damage to the equipment.
Other recipients of Setiz’s March 1 email included wind energy opponents Kevon Martis, Tom Stacy and Jeremy Kitson, along with Sam Randazzo, whose firm represents anti-wind groups and Industrial Energy Users – Ohio. The Energy and Policy Institute has noted connections between Stacy and Martis and organizations that receive funding from fossil fuel interests. Emails received from the Checks and Balances Project show Seitz met with Johnson, Martis and Randazzo in October to discuss wind turbine setbacks.