Radar has difficulty distinguishing between airplanes, wind turbines, and stormy weather. Spinning blades reflect radar signals and create sensory interference and coverage shadows—a troublesome effect for air traffic controllers and military surveillance. Vestas, however, says recent developments will alleviate some worries and allow placing wind farms nearer to airports and military bases. The Danish company says it successfully tested a “stealth” rotor for its V90 model.
A Federal Aviation Administration permit for Oregon’s Shepherds Flat was delayed last summer when the Pentagon objected to its proximity to an Air Force base. Vestas estimates the radar issue is blocking plans for about 20 GW of wind power capacity worldwide.
Vestas says the rotor, made of radar absorbing materials, showed a 99% 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. However, the extra weight of a 5-mm coating on long, thin blades would hurt the performance. The recent blades’ structure features sheets of glass-reinforced epoxy and plastic foam. Costs were undisclosed although the company says it wouldn’t be significant. When they would be available is also unknown.
Another approach to modernizing radar is the UK’s National Air Traffic Service is looking into adjusting its Raytheon systems software with new algorithms. The upgrades may be able to discriminate between a turbine and say an aircraft flying over.