Health and Safety | Process | Sustainability/Other | Technical and Financial
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Health and Safety: The Health and Safety Report produced by the Health and Safety Subcommittee of CREB is now available online. See http://www.barringtonenergy.com/wind_energy_project/reports |
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What are the sound characteristics of a wind turbine?
Sound consists of a mixture of frequencies, with each frequency representing a particular pitch. Tonal sounds like a hum or a whine are concentrated at particular frequencies, while atonal sounds like the wind in the trees are spread over a wide range of frequencies, otherwise called broadband sound.Broadband sound is the primary component of the sound emitted by wind turbines and comes mostly from the interaction between wind and the rotating blades. Mechanical sounds can emanate from the nacelle at the rotor axis which houses the generator and gearing, but those sounds are generally minimized through engineering design. For more information on noise, see the Noise section of the health and safety report.
Does noise level from wind turbines change with wind speed? If so, how?
Wind turbines do emit more noise as wind speed increases, and thus noise measurements on wind turbines are taken when the turbine is rotating at its rated speed. At most, wind turbine noise rises about 3 decibels (dB) for each 2 mph increase in wind speed up to the rated speed. However, ground level noise from wind also increases about the same. Thus, wind turbine noise is not necessarily more audible in windier conditions. An exception can be during calm, clear nights when the air is still at ground level while wind at turbine height is sufficient to drive the turbine. For more information on sound, see the Noise section of the health and safety report.How would the pond affect sound propagation at Legion Way?
Most of the sound reaching a listener will travel in a straight line from a turbine. Some of it, however, will reflect off the ground or water. A listener across water may hear more sound than a listener at an equal distance across land that has trees or other obstructions. In the health and safety report, a sound model was used from the Renewable Energy Research Lab that assumes a hemispherical model for sound propagation. This model assumes a perfectly reflective medium at the ground. Therefore, the decibel levels projected for the turbine are conservative and hold for water as well as land. For more information, see the Noise section of the health and safety report.What sources of information were used to assess safety risks?
Many sources were consulted to assess risks of injury from construction or operation of a turbine. Worldwide injury statistics were obtained from the Caithness Wind Information Forum, whose records from 1975 through June 30, 2008 show that all but one of the documented injuries from wind turbines have been associated with accidents involving wind industry workers and not structural failure. A thorough analysis of worldwide wind turbine failures was conducted as part of a study of permitting setbacks in California. The authors of the study found an overall failure rate for all wind turbines which, when combined with the chance of a failed turbine part falling in a particular area, leads to an estimate of risk of injury at different distances from the turbine. These risks are comparable to those such as being hit by lightning. For more information, see the Structural Failure section of the health and safety report and the structural failure references.What happens if there is a hurricane?
The wind turbines under consideration are rated to survive sustained winds of 135 mph. Wind conditions like this have not occurred in Rhode Island in the 20th century. The highest wind occurred with the Great Hurricane of 1938, which had peak sustained winds of 121 mph. The last hurricane in RI was Hurricane Bob in 1991, which had peak sustained winds of 115 mph and peak sustained winds of 105 mph in RI.Large offshore projects on the east coast, such as Cape Wind and the RI offshore project, have also had to consider hurricanes in their analysis. Cape Wind is in the process of permitting, and manufacturing & construction will begin in 2010. The RI project is reviewing bids.
There are 1500 MW of installed turbines in Texas. There is a windfarm in Cuba. There is certainly data about how well turbines weather hurricanes. We welcome any information about this data (for example, data from hurricane Ike).