Agenda - Planning Commission - 08/06/2009

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Most people's reaction to turbines, even up close, is that they are much quieter than they expected. "Vermont turbine owner David Blittersdorf reports that the home next to his sold within one day for the full asking price. His new neighbors iater tOld,him that his 1 OkW turbine was a major factor in the quick sale. 'They said they wanted to live in a place where the community cared about the environment. They told me that they, too, wanted to instal! a small wind t.urbine someday, r says Blittersdorf. " - Permitting Small Wind Turbines: A Handbook: Learning from the California Experience. California Energy Commission, 2003. www.awea,orgj smallwindj documentsj permitting.pdf 4. Sound (can't): Planners and zoning committees should also keep in mind that: . Sound decreases significantly with distance from the source (including height - another good reason to allow tall towers). Doubling the distance from the turbine decreases the sound level by a factor of four. For example, sound level readings at 25ft. from the turbine hub drop by a factor of 4 at 50ft., and by a factor of 16 at 100ft. Noise intrusion across a property line from a turbine that is set back 100ft. or more is typically very limited. . Turbine manufacturers are keenly aware of the public demand for quieter machines and have invested in new materials and designs to minimize sound. As a result, today's turbines operate at near-ambient sound levels. . Only a few events or circumstances can cause a normal operating wind system to become audible, including utility blackouts (or a full battery bank for those models that incor[:lorate batteries). Both situations are temporary, and in many cases (but not all), easily remedied by the owner by manually shutting down the turbine. . Sound level test data for some turbines is available from the U.S. Department of Energy's (DOE) National Renewable Energy Laboratory (NREL).7 . Requiring certified noise tests for a residential wind system is unnecessary given the lower sound emissions of today's turbines and that sound data is readily available from manufacturers. Such tests are also beyond the' budget of any homeowner. . "Noise" is a subjective term. Whether a person generally favors wind turbines or not can determine how he Of she views a single, seemingly objective sound. . The single best way to understand the nature of a turbine's sound is to visit an installation site; All turbines are a marginally different so be sure to visit a location with a similar wind resource and the same model turbine as is in question. 7 . The National Renewable Energy Laboratory (NREL) has tested several residential-sized wind turbines for sound emission levels. NREL engineers noted a "marked progress toward quieter turbines" in recent years and concluded in one case that "the turbine noise could not be separated from the background noise," This is generally true of most of today's residential wind equipment over a great range of operating wind speeds. NREL engineers noted, however, that "the operating condition [of the wind turbine] has a strong influence on the noise characteristics." They found two scenarios where sound actually increased above normal operating conditions: when grid connection was lost (for grid- connected models) and when the batteries were full (for battery-charging models). The solution is simply for the owner to shut off the turbine in these situations to avoid excessive noise. See the NREL report, "Acoustic Tests of Small Wind Turbines," NRELjCP-500- 34662, by P. Migliore, J. van Dam, an.d A. Huskey at http://www. nrel.gov /docs/fy040sti/34662.pdf: Additional Resources: Alberts, Daniei J. ':Primer for Addressing Wind Turbine Noisen. Lawrence Technological University, 2005. http://home.n ethere.com/ dja 17 0 l/tech n ical_writi ng/ pa pers/ Addressin gWindTurbin eNoise. pdf