Blade icing can increase wind turbine sound levels as much as 5 decibels higher than quoted operating sound levels. Manufacturers may insist that their wind turbines don’t ice up. Right out of the crate, wind turbines blades with manufacturer-applied coatings might be resistant to icing. Give anything a year or two exposure to the elements, dust, bugs, hail, salt, and rime in Maine, and then see what happens.
Have wind facility permit applicants in Maine incorporated an icing noise factor of 3 to 5 dB in their noise predictions as a conservative design measure to ensure compliance with State regulations during winter months?
Background: “In cold climates, with sustained temperatures below 32○ F., atmospheric icing conditions are common. The northeast U. S. has the highest incidence of icing in North America. Due to their aerodynamic shape significant rime ice buildup can occur on turbine blades in cold weather and high humidity conditions. This effect is similar to the rime icing of airplane wings. The ice can build symmetrically and then be extremely difficult to detect. Even a low buildup of ice can disturb the aerodynamics of air passage over the blades and create higher noise emission due to increased turbulence. Generally blade noise is the predominant noise source and can be increased 3-5 dBA due to this rime ice, or other changes to the airfoil surface as due to insect accretion or dirt accumulation.” (Seifert, Henry, Technical Requirements for Rotor Blades Operating in Cold Climate, Deutsches Windenergie-Institut, 2003). – from Assessment of the Sound Level Study for the Mars Hill Wind Farm, Bolton, 2007.