Most wind farm plans include testing of emi. I would never put an wind farm in possible flight paths of an airport. The emi is design constraint of any power generation. Large remote wind turbines do not use metal blades because they require more maintenance and have more mass which translates to less efficient power generation. Most are fiber glass sometimes impregnated with wood or carbon fiber. More are being built with carbon fiber structural support and fiber glass as the main blade material, allowing for thiner lighter blades.
I need to make clear that I do not know the actual reason for the far offshore location of the google sponsered wind farm effort. What I am aware of is that a lot of decision are often made for indirect, but solid technical reasons.....and oftentimes purely political motivations. What I am pretty sure of is that either 2 or 3 of the 3 possibilities I gave are wrong.
actually you hit on part of the reason; interference with shipping traffic is part of it. when converging on one spot; a shipping port, the closer you get, the greater the congestion, so having it offshore at a distance insures minimal congestion the other is to eliminate the flack for multiple agencies and interests. "out of sight, out of mind" is the key operative here.