“Shadow flicker” occurs when the blades of a large wind turbine pass between the sun and the observer, causing an on-again, off-again shadow to be cast by the blades. The flicker can be annoying when trying to read or watch television. If any effect is experienced, it is generally short-lived due to the moving path of the sun, incidence of cloud cover, and wind-driven angling of the turbine sideways to the sun.
For the CVEC projects, the shadow will be precisely calculated to determine whether a flickering will fall on a given location near the wind turbines, and for how many hours in a year it will do so (for example, 15 minutes a day for 20 days out of the year). Potential problems can be easily identified using these methods.
What are legitimate concerns about sound from a turbine?
There are two potential sources of sound: the turbine blades passing through the air as the hub rotates, and the gearbox and generator in the nacelle. Sound from the blades is minimized by careful attention to the design and manufacture of the blades, and control over the harmonics generated in the tower. Noise from the gearbox or generator is rarer in modern turbines, as the gearbox is contained within the nacelle and sound is controlled by insulation and isolation materials.
The predominant sound turbines produce is similar to a whooshing or swishing sound. The sound of the blowing wind is often louder. The best test is always to experience the sound from a turbine for yourself. You will find that it is perfectly possible to stand underneath a turbine and have a normal conversation, without raising your voice.
Distance from the wind turbine, height of the wind turbine relative to the surrounding topography, the quality of the sound (repetitive low frequency sound), wind conditions, and wind direction all affect how the wind turbine sound affects people.
Massachusetts law and the local town bylaws will not allow sound levels of 10 dB(A) over ambient sound at property lines. According to the Massachusetts Department of Energy, “Noise impacts are regulated by municipalities as well as the Massachusetts Department of Environmental Protection (MassDEP), and should not be a factor for wind projects sited an appropriate distance from residences.”1
Infrasound, sound at such low frequency that it can’t be picked up by the human ear, is the primary claim for those concerned about inaudible sound affects. At present there are well over 10,000 wind turbines installed and operating in North America, and tens of thousands of people who live and work in proximity to these wind turbines. Of these individuals, a very small number have claimed that their health has been impacted by wind turbines. Surveys of peer-reviewed scientific literature have consistently found no evidence linking wind turbines to human health concerns.2
1. Mass Executive Office of Energy and Environmental Affairs
2. Canada Wind Energy Association
Review papers included:
“Infrasound from Wind Turbines – Fact, Fiction or Deception?” by Geoff Leventhall
“Wind Turbine Facilities Noise Issues” by Dr. Ramani Ramakrishnan for the Ontario Ministry of the Environment
“Wind Turbine Acoustic Noise”, A White Paper by Dr. Anthony Rodgers at the University of Massachusetts at Amherst.
“Research into Aerodynamic Modulation of Wind Turbine Noise”, University of Salford, UK, July 2007
“Health impact of wind turbines” , prepared by the Municipality of Chatham-Kent Health & Family Services Public Health Unit
Energy, sustainable development and health, World Health Organisation, June 2004
What happens to the real estate value of homes located near wind turbines?
According to the National Association of Realtors, “Although research remains scant, wind farms appear to have a minimal or at most transitory impact on real estate. A three years study by the U.S. Department of Energy’s Lawrence Berkeley National Laboratory concludes ‘neither the view of wind energy facilities nor the distance of the home to those facilities was found to have any consistent, measurable, and significant effect on the selling prices of nearby homes. No matter how we looked at the data, the same result kept coming back – no evidence of widespread impacts.’
A study was released in May 2010 reflecting research done on real estate values. The study is entitled,
The study summarizes its research with, “Wind farm anticipation stigma is likely due to the impact associated with a fear of the unknown, a general uncertainty surrounding a proposed wind farm project regarding the aesthetic impacts on the landscape, the actual noise impacts from the wind turbines, and just how disruptive the wind farm will be. However, during the operational stage of the wind farm project, as surrounding property owners living close to the wind turbines acquired additional information on the aesthetic impacts on the landscape and actual noise impacts of the wind turbines to see if any of their concerns materialized, property values rebounded and soared higher in real terms than they were prior to wind farm approval.”
What about Birds & Bats?
Bird and bat populations in proximity to the turbine and any potential ramifications to them will be thoroughly investigated by CVEC engineers. Pointing to the link between global warming and the threat to birds and other wildlife, the Massachusetts Audubon Society and the National Audubon Society endorse wind energy development. It was also noted by the Audubon Societies that birds are over 10,000 times more likely to be killed by other human-related causes (e.g., by buildings, vehicles, pet cats, pesticides, etc.) than by a wind turbine.