'Stealth' wind turbines avoid aviation radar interference

The spinning blades of wind turbines have been known to scramble the radar waves needed to track airplanes. Two European companies have partnered to apply radar-absorbing materials to wind turbines in an attempt to fix the problem.

Danish outfit Vestas and U.K. defense tech contractor QinetiQ say they are building wind turbines whose blades are made with glass-reinforced epoxy and plastic foam, which produces a smaller radar signature during testing.

(SmartPlanet previously wrote about QinetiQ when it won a contract to power overseas U.S. Army bases with garbage.)

The technology could help wind farms avoid problems with their turbines deflecting short-wave radar -- so disruptive that, at times, the turbines can completely wipe an aircraft from a controller's screen.

Technology Review describes the problem:

Wind turbines can interfere with radar in several ways. The turbines can reflect the radar systems' microwave signals, creating a shadow that erases airplanes from radar operators' screens and clutters those screens with the turbines' signature. The signature is also always changing, as blades accelerate and decelerate with the wind, reaching speeds of well over 200 kilometers per hour. Aviation safety and military authorities insist that the potential for confusion and accidents is real.

But a Homeland Security study published last year (.pdf) found that the technology still hasn't made much of an impact in preventing disruption of long-wavelength L-band radars used by U.S. air traffic control officials. Vestas said it has demonstrated an L-band radar absorber.

Absorbing radar is not as easy as simply painting the wind turbine blades. A five-millimeter coating could add 1,200 kilograms to large turbine blades, notes Technology Review. Even if weight parity is achieved, there's still a cost premium to consider.

But for some wind farms whose operation has been blocked by the U.S. government over concern of disrupted radar waves -- a troubled 130-turbine wind farm in Cape Cod, for example -- the radar-absorbing technology might do the trick.

In the meantime, fingers are crossed that aging radar systems will soon be upgraded with new algorithms to handle the existence of wind farms on their screens.

This post was originally published on Smartplanet.com