This biophysical impact assessment explores the environmental consequences of the then-emerging wind energy technology through field studies on a 100-kW turbine (two-bladed, horizontal-axis) located at the NASA Lewis Research Center's Plum Brook Station near Sandusky, Ohio.
The authors tested theoretical predictions from an earlier study (Rogers et al. 1976) that birds or other airborne fauna (e.g., insects) risk collision with rotating turbine blades. Field studies emphasized the microclimate effect of the operating turbine and the potential effect on night-migrating birds. The microclimate field studies indicated a negligible effect to the area immediately downwind of the turbine. Radar studies revealed that the number of nocturnal migrants during peak migration periods for songbirds in the area averaged 5,380 birds/mile of front/hour. During four migratory seasons of searching for dead birds, two birds were found dead near the meteorological tower and one bird was found dead near the turbine. Scavenging studies indicated that about 5 percent of carcasses were removed by predators before researchers could find them. The authors concluded that this wind turbine was not a high risk to airborne fauna, including the most vulnerable night-migrating songbirds. Behavioral studies indicated that the birds will avoid the turbine if they see it. The authors predicted that if blade tips reach higher than 500 ft (equivalent to the minimum altitude of most nocturnal migration) or if turbines are sited in locations where birds fly closer to the ground, birds could be at greater collision risk during inclement weather at night.