One of the problems with wind farms is the effect of their turbine blades on air traffic control and defense radars. Wind turbine blades have extremely large radar signatures, especially when grouped in a farm, and their movement creates doppler effects. This generates massive amounts of radar “noise”, and a “shadow” region behind the wind turbines. “2D” radars that don’t use multiple vertical beams are especially prone; unfortunately, many air traffic control radars fit that profile.
Britain is especially interested in wind farm power, and this drawback posed a significant problem. They’re beginning to respond by buying new long-range radars from Lockheed Martin, for emplacement near wind farms. These moves follow a 2005 report [PDF] that concluded: