Under the radar: Vestas' 'stealth' wind turbines

Can you distinguish between a wind turbine, a 747 and a thunderstorm? Radar systems can't always do so. Danish company Vestas hopes their turbine tech can help clear the air.
Written by Melissa Mahony, Contributor

The difference between airplanes, wind turbines, and stormy weather is fairly obvious. But on a radar screen, distinguishing between the three is not so simple. The spinning turbine blades can reflect radar signals and create sensory interference and coverage shadows—a troublesome scenario for air traffic controllers and military surveillance.

But Vestas hopes its latest turbine tech will alleviate some worries and allow emerging wind farms to get nearer to airports and military bases. A Federal Aviation Administration permit for Oregon's Shepherds Flat became delayed last summer when the Pentagon objected to its proximity to an Air Force base.

The Danish company announced Wednesday that it successfully tested a "stealth" rotor for its V90 model.

Vestas said the rotor, comprised of radar absorbing materials, showed a 99 percent reduction in reflected radar waves compared with standard turbines. For five years, the company and British defense contractor QinetiQ have been collaborating on turbine components that can dip under the radar. In 2009, they designed stealth turbine blades. Coatings of radar absorbing materials can work with turbine towers. The extra weight of even just a 5-millimeter coating on the long, thin blades, however, would hurt the performance. Instead, the blades' structure features sheets of glass-reinforced epoxy and plastic foam.

The cost mark-up for a radar-friendly turbine, the company tells Reuters, wouldn't be significant. Just how insignificant wasn't said. When they would hit the market is also unknown. In the meantime, Vestas estimates the radar issue is blocking plans for about 20 gigawatts of wind power capacity worldwide. Jon Arden tells Wind Directions, a publication of the European Wind Energy Association:

I think we will solve this problem with a range of different approaches. There's unlikely to be one magic bullet that does it all. The positive thing is that, after circling round the problem for many years, the industry has now got to the stage where it has a thorough understanding of the potential solutions.

At least one other approach is modernizing the radar. The UK's National Air Traffic Service is looking into adjusting its Raytheon systems software with new algorithms. Though still under testing, the upgrades could potentially discriminate between a turbine and say, the 747 flying over it.

On the flip side, planes can threaten turbines, too. Lockheed Martin plans to send its TPS-77 radar system (right) to British coastlines by the end of this year. Five offshore wind projects there have enlisted the technology to detect potential air attacks.

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Image: Vestas, Lockheed Martin, and US Air Force

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