Wind energy opponents often cite possible health effects from shadow flicker as a reason to oppose wind development. In 2009, the American Wind Energy Association and the Canadian Wind Energy Association established a multidisciplinary scientific advisory panel to review current literature on the perceived health effects of wind turbines. The panel reviewed current literature on the perceived health effects of the phenomenon known as shadow flicker, arriving at the following conclusions:
Shadow flicker occurs when the blades of a turbine pass in front of the sun to create a recurring shadow on an object. Computer models in wind development software can determine the days and times during the year that specific buildings in close proximity to turbines may experience shadow flicker. Mitigation measures can be taken based on this knowledge and may include setbacks or vegetative buffers. Issues with shadow flicker are less common in the U.S. than in Europe due to the lower latitudes and the higher sun angles in the United States.
The allegation is sometimes made that shadow flicker from wind turbines can cause epileptic seizures. This is not true—shadow flicker from wind turbines occurs much more slowly than the light “strobing” associated with seizures. The strobe rates generally necessary to cause seizures in people with photosensitive epilepsy are 5 to 30 flashes per second. Large wind turbine blades cannot rotate this quickly.
Epilepsy Foundation. Shedding Light on Photosensitivity, One of Epilepsy’s Most Complex Conditions
This site explores flicker and light-induced seizures.
Photo by Andreas Klinke Johannsen