The system, developed by Norway-based Ocas, uses a series of compact 3D radars mounted on turbine towers around the perimeter of a wind project to detect and track aircraft in the vicinity. When a plane or helicopter is on a dangerous heading towards the wind farm, the system activates the aviation strobe lights atop the turbines. If the aircraft does not take measures to avoid the turbines, a secondary audio warning is delivered to the pilot's cockpit radio.
The collision avoidance system was first installed last year in a pilot project at Enertrag's Nadrensee wind farm in northern Germany and is now operational at Enbridge's Talbot wind project in south-western Ontario. Ten radars are strategically located among Talbot's 43 Siemens 2.3MW turbines. Their cost makes the Ocas system "quite a bit more expensive" than traditional lighting solutions, says Melissa McCarthy, general manager of Ocas's Virginia-based US subsidiary.
Traditional turbine warning lights are constantly on and are often a source of community opposition to wind projects. Because the Ocas system only activates the lights when aircraft are detected, says McCarthy, it leaves the sky free from light pollution and lowers the overall visual impact of the wind farm. "The developers we're working with are finding it easier to get through the community-acceptance process and even the permitting process," she explains. "This is one area where they can actually put some mitigation strategies in place."
RES Canada, which developed the Talbot project, says it chose the Ocas technology because it would help minimise the visual impact on local communities. "We have been pleased with the results," says Andrew Fowler, chief operating officer of RES Canada. The company has no plans to use the system in other projects but says it would consider this option for sites close to populated areas.
In the US, says McCarthy, an increasing number of local permitting authorities are making the Ocas system mandatory. At the end of May, the Vermont public service board approved Green Mountain Power's 63MW Kingdom community wind project on the condition the company "take all reasonable steps" to get permission from the Federal Aviation Administration (FAA) to use Ocas technology.
So far, says McCarthy, it is the only system of its kind to be approved for use by both the FAA and Transport Canada. The technology has been commercially available since about 2007, she says, and was originally developed by two F16 pilots who lost several friends to wire-strike accidents and wanted a better way to mark the presence of transmission lines. Today, the company has more than 60 systems installed worldwide on power lines, bridges and other structures.