“…wind-energy projects create negative impacts on human health and well-being, the impacts are experienced mainly by people living near wind turbines who are affected by noise and shadow flicker.” [1]
According to the World Health Organization wind turbines have noise and visual burdens.[2]
Rotating wind turbine blades interrupt the sunlight producing unavoidable flicker bright enough to pass through closed eyelids, and moving shadows cast by the blades on windows can affect illumination inside buildings.[3] This effect is commonly known as shadow flicker.
People may be adversely affected from wind turbine shadow flicker both inside and outside of buildings.[4],[5]
Wind turbine shadow flicker has the potential to induce photosensitive epilepsy seizures however the risk is low with large modern models and if proper planning is adhered to. [6],[7] Planning should ensure the flash frequency does not exceed three per second, and the shadows cast by one turbine on another should not have a cumulative flash rate exceeding three per second. [8]
Shadow flicker has been reported to cause annoyance in many locations.[9],[10]
World Health Organization acknowledges annoyance is an adverse health effect.[11]
An American Wind Energy Association and Canadian Wind Energy Association sponsored report fails to discuss annoyance caused by wind turbine shadow flicker[12] however one of the authors of the report W. David Colby, M.D. describes the risks of annoyance and stress caused by wind turbines by stating
“We’re not denying that there are people annoyed and that maybe some of them are getting stressed out enough about being annoyed that they’re getting sick.”[13]
To mitigate risk to human health wind turbines should be sited to ensure people will not be adversely affected. For example in the northern hemisphere people located East-NE or WNW from the turbine must be protected from shadow flicker. [14]
Recommended shadow flicker setbacks for current wind turbine designs are 10 rotational diameters which would typically translate to approximately a kilometre. [15]
Greater setback distances may be required when wind turbines are sited on elevated ridges as the shadows can be cast over distances of several kilometres.
Wind turbine noise including low frequency noise may also contribute to the overall annoyance. [16]
A European study concludes
“Wind turbine noise is easily perceived and annoying even at low A-weighted SPLs….Wind turbines are furthermore prominent objects whose rotational movement attracts the eye. Multimodal sensory effects or negative aesthetic response could enhance the risk of annoyance. Adverse reactions could possibly lead to stress-related symptoms due to prolonged physiological arousal and hindrance to psychophysiological restoration.”[17]
Most jurisdictions do not have explicit regulations to protect people from the adverse health effects of shadow flicker.[18]
Further investigation into the effects of wind turbine stressors including shadow flicker is required to assist in the development authoritative guidelines designed mitigate potential adverse health effects. [19],[20],[21]
[1] National Research Council (NRC). Environmental Impacts of Wind-Energy Projects, 2007NRC, Washington, DC
[2] World Health Organization, Energy Sustainable Development And Health, June 2004
[3] Graham Harding, Wind Turbines, Flicker, And Photosensitive Epilepsy: Characterizing The Flashing That May Precipitate Seizures And Optimizing Guidelines To Prevent Them, 2008
[4] Minnesota Department of Health (MDH), Public Health Impacts of Wind Turbines, 2009
[5] Pedersen et al., 2008,Project WINDFARMperception Visual and acoustic impact of wind turbine farms on residents
[6] Smedley AR et al, Potential Of Wind Turbines To Elicit Seizures Under Various Meteorological Conditions., 2009
[7] Graham Harding, Wind Turbines, Flicker, And Photosensitive Epilepsy: Characterizing The Flashing That May Precipitate Seizures And Optimizing Guidelines To Prevent Them, 2008
[9] Minnesota Department of Health (MDH), Public Health Impacts of Wind Turbines, 2009
[10] National Research Council (NRC). Environmental Impacts of Wind-Energy Projects, 2007NRC, Washington, DC
[12] W. David Colby, M.D. et al., Wind Turbine Sound and Health Effects, An Expert Panel Review 2009, Prepared for American Wind Energy Association and Canadian Wind Energy Association
[13] W. David Colby, M.D., Sounding Board, 97.9 FM The Beach December 17, 2009
[14] Verkuijlen E, Westra CA. (1984) Shadow hindrance by wind turbines. Proceedings of the European wind Energy Conference. October 1984, Hamburg, Germany.
[15] Minnesota Department of Health (MDH), Public Health Impacts of Wind Turbines, 2009
[16] W. David Colby, M.D. et al., Wind Turbine Sound and Health Effects, An Expert Panel Review 2009, Prepared for American Wind Energy Association and Canadian Wind Energy Association
[17] Pedersen Eja, Human Response To Wind Turbine Noise: Perception, Annoyance And Moderating Factors , May 23, 2007
[18] National Research Council (NRC). 2007. Environmental Impacts of Wind-Energy Projects
NRC, Washington, DC.
[19] The Noise Association, Location, Location, Location An investigation into wind farms and noise, 2006
[20] Pedersen, E. and K. Persson Waye. Wind turbines—low level noise sources interfering with restoration? Environmental Research Letters. 3 (2008) 015002 (5pp)
[21] Minnesota Department of Health (MDH), Public Health Impacts of Wind Turbines, 2009