Wind Turbines: Clean, Renewable and Quiet?

Abstract

noise notes volume 9 number 1 In the United States, officials responsible for energy policy have been exhibiting renewed interest in wind energy as an alternate power source that is clean and renewable. Despite the new public enthusiasm for this option, wind turbine installations and wind farms must comply with U.S. Federal Environmental Protection Agency and Occupational Health and Safety guidelines and be approved by state and city regulators. Several recent news stories have indicated that turbine noise levels have become a factor in deciding whether to approve these installations— in part because they affect quality of life for nearby residents. Although wind is clean and renewable, wind turbine noise may impede extensive use of wind energy. The perception of wind turbine farms has both visual and acoustic criteria. Recent reports by Oerlemans and Schepers1 and Van den berg et al.2 confirm that “sound is one of the most annoying aspects of wind turbines.” Three recent examples highlight how important the problem has become, but I refrain from commenting on technical/legal merits of specific cases. The Bismark Tribune (North Dakota; July 9, 2009) reported that officials approved a wind farm despite noise complaints. State regulators approved the location of a wind farm in east central North Dakota despite noise complaints but recommended that operators move one of 80 turbines to an alternate site. Commissioners approved installation because it complied with U.S. Federal guidelines that turbine noise was not expected to exceed 50 dB outside the homes. To put this noise level in perspective other commonly encountered sounds are shown in Figure 1. In a second example, reported by KMBC-TV (Kansas City), a Missouri man is suing over wind turbine noise. His 20-acre farm is surrounded by 27 turbines (seven within ⁄2 mile of his house). He noted that on a bad day “it sounds like a helicopter or a train coming that never arrives.” A third example comes from Libertyville, IL (Chicago Sun Times; June 4, 2009) where residents protesting noise related to installation of a single wind turbine in a suburban setting close to residences obtained a temporary restraining order. These incidents clearly illustrate the need for noise reduction technologies and for metrics beyond Wind turbines: clean, renewable and quiet?