I'm experimenting with a generator that I can attach windmill blades. For now, I have a handle on it, so to speak. :) It uses a 12v printer motor I scrapped and a couple 4 x 608zz bearings I had laying around. I think they were rollerblade bearings. I ended up just using a clip to on hold the top of the motor mount.
The goal is to add a couple of small 6v solar panels and turning it into a more robust and efficient system that charges a lipo and can have a light and charge a cell phone or something.
It turns out to be surprisingly efficient. With the handle, it's pretty easy to generate 3-4 volts. I connected it to the electronics from an old solar e-cig charger that has solar panel inlets, a built in white LED flashlight, a lipo battery and charging circuit. It generates enough power to operate it, as you can see in the photos. It could be made even better with a larger main gear. I think it is currently 10:1. The main gear was reaching the max size of my printer.
Next I'm on to designing some light weight blades to spin it.