In Germany where wind power is growing rapidly, some neighbors of wind farms are complaining of not just the noise of the turning blades, but of the flashing lights that are always on at night and during fog to warn low-flying planes to stay clear of the turbines. The red lights also reportedly attract birds, which can fatally collide with the blades.
The researchers at the Fraunhofer Institute for High Frequency Physics and Radar Techniques FHR have come up with a sensor technology called Parasol that will cause the lights to turn on only when low-flying aircraft are in the area, keeping the annoyance to a minimum, while also keeping aircraft safe.
The beacons use passive radar systems that don't emit a radar beam of their own. The sensors utilize local radio station frequencies to locate airplanes.The radio station transmitters send out signals that are reflected back by objects in the sky and then the system uses a mathematical algorithm to detect the distance, position and velocity of the aircraft. The sensors are located on the turbine's masts and a central CPU at the wind farm processes all the data.
“We are able to operate the system without a transmitter module of its own, and dependent on weather conditions. A transmitter license required for active radar systems is not required for this, so it can be operated cost-effectively,” says Heiner Kuschel, department head at FHR in Wachtberg. “The collision warning lights only switch on when an airplane is within a radius of four kilometers and flying below an altitude of about 2500 feet (700 meters). We use the passive radar sensors to essentially extend a protective umbrella over the wind farm like a parasol.”
The system has been tested at a wind farm in Germany and it's expected to go into operation elsewhere in 2015, hopefully removing some of the roadblocks that stand in the way of wind farm construction.