Plans for the installation of wind farms the world over are being delayed or abandoned due to objections from the aviation community or air defense interests. The problem is that when it comes to low flying aircraft or wind turbines, conventional radar has a bit of an identity crisis - not being able to tell the difference. Recent tests in the U.K. of "stealth" turbine technology could provide a solution.

Radar technology tracks moving objects by looking for Doppler but if an aircraft flies low over a wind farm, even though only the moving parts on a turbine are its blades the radar is unable to easily distinguish one moving object from the other.

Technology consultants, QinetiQ (which was formed after the breakup of the UK Government's Defence Evaluation and Research Agency in 2001) and turbine manufacturer Vestas believe that the solution lies in hiding the turbines and blades from the radar using stealth technology.

In a project partly funded by the UK Government, radar absorbing materials were integrated in a turbine blade which was then fitted to an existing Vestas V90 turbine. Radar cross section measurements were then taken using a system developed by QinetiQ. The results showed a significant reduction in the radar signature of the turbine.

Integrating the stealth technology into towers and nacelles as well as blades could, according to the researchers, allow any small remaining radar presence to be factored out of air traffic and air defense systems and make wind farms invisible to radar.

"We believe that Stealth Turbine technology could be a genuine game-changer for the renewable energy industry by removing a major barrier to its development," said Mark Roberts, Strategic Business Director for Energy and Environment at QinetiQ.

Successful deployment would clear the way for the five gigawatts worth of potential wind generation sites in the UK that, according to the Department of Energy & Climate Change (DECC), have been blocked due to fears of radar interference.

In another approach to the problem, researchers from Raytheon will be spending the next 19 months working with the UK's main air navigation service to develop a system that can recognize the difference between turbines and low flying aircraft.