In late February 2009 the Minnesota Department of Health (MDH) received a request from the Office of Energy Security (OES) in the Minnesota Department of Commerce, for a “white paper” evaluating possible health effects associated with low frequency vibrations and sound arising from large wind energy conversion systems (LWECS). MDH agreed to evaluate health impacts from wind turbine noise and low frequency vibrations. In discussion with OES, MDH also proposed to examine experiences and policies of other states and countries. Below are the Introduction and Conclusions of the white paper released in May 2009. The full report can be accessed by clicking on the link at the bottom of this page.

This suit was filed against the Village of Libertyville (IL) and DPR Investments LLC shortly after a business-scale wind turbine was erected and became operational within 600 feet of residential properties. The Entegrity 50 kilowatt, 120-foot turbine is owned by DPR Investments doing business as Aldridge Electric Company. Complaints of noise, shadow flicker and blade flicker were heard right after the turbine started turning. On July 24, 2009, the Court issued a compromise ruling stating that the turbine was affecting neighboring residents and restricted the turbine hours of operation to weekdays from 9 a.m. to 3 p.m. (see: http://www.windaction.org/news/22373 )

Wind turbines are known to produce shadow flicker by interruption of sunlight by the turbine blades. Known parameters of the seizure provoking effect of flicker, i.e., contrast, frequency, mark-space ratio, retinal area stimulated and percentage of visual cortex involved were applied to wind turbine features. The proportion of patients affected by viewing wind turbines expressed as distance in multiples of the hub height of the turbine showed that seizure risk does not decrease significantly until the distance exceeds 100 times the hub height. Since risk does not diminish with viewing distance, flash frequency is therefore the critical factor and should be kept to a maximum of three per second, i.e., sixty revolutions per minute for a three-bladed turbine. On wind farms the shadows cast by one turbine on another should not be viewable by the public if the cumulative flash rate exceeds three per second. Turbine blades should not be reflective.