Tuesday, November 1, 2005

Development of Obstruction Lighting Standards for Wind Turbine Farms

DOT/FAA/AR-TN05-50 Authors: James W. Patterson

Development of Obstruction Lighting Standards for Wind Turbine Farms

Wind turbines are being utilized in 32 of the 50 states in America, with predictions that turbines will at one time be constructed in all 50 states. The U.S. Department of Energy has mandated that renewable energy sources, such as wind turbines, will provide six percent of the nation’s electricity by the year 2020. With mandates such as this, it is almost certain that the country will see the rate of turbine construction greatly increase over the next several years.

Since these giant structures are considered obstructions, of the greatest concerns is how they will affect air navigation. Standing at heights of up to 442 feet, the turbines have now become obstructions, as they exceed the 200 foot height limit as defined by the Federal Aviation Administration (FAA) Federal Aviation Regulations (FARS). At heights above 200 feet, the FARS require that obstructions to air traffic be illuminated with the appropriate FAA approved flashing red, flashing white, or steady burning red light lighting as described in FAA Advisory Circular AC 70/7460-1K, titled Obstruction Lighting and Marking. The document includes some provisions for lighting or marking a single wind turbine, but does not provide any guidance for lighting a large group, or farm, of wind turbines.

Working jointly with the U.S. Department of Energy (DOE), the FAA conducted an evaluation to develop standards that would provide necessary guidance for air traffic to easily acquire, identify, and avoid the wind turbines, yet at the same time, minimize any impact to the surrounding community or to any nearby wildlife. Researchers visited eleven wind turbine sites to document how the lighting was installed, how it appeared from the air during both daytime and nighttime conditions, and how it was perceived from the surrounding community.

This report describes the research that was conducted to provide the foundation for the creation of new guidelines for lighting wind turbine farms as obstructions. It includes information on the site visits, various research activities, and the construction and evaluation of a test site in Lawton, Oklahoma that was used to validate the new suggested guidelines. Finally, it provides specific recommendations on how wind turbines should be illuminated.


Authors: James W. Patterson

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