I got a kick out of this build for a windmill. The author lives in an area where there is not much wind (so end result was it wasn’t worth the investment, except as a learning exerise) He did a great job documenting the project and highlighting areas that folks that build turbines do not cover, such as slip rings to keep the wires from tangling. And issues with using treadmill motors.
http://www.instructables.com/id/Seeing-Green-Energy-Stars-The-Wind-Turbin-Myth/