Hey! I've always wanted to build a wind turbine and I finally decided to just do it. I couldn't make the tower tall, and I didn't want it to spin too fast, so I built a rather large savonius wind turbine.
The rotor itself is made of two pieces, offset by 90 degress. Each of those pieces is 6 feet wide, 3 feet tall, and 2 feet deep. It resembles a giant flying coffee table, if you could imagine such a thing. The whole thing sits on a frame about 5 feet off the ground, and the top of the entire structure extends up 12 feet. It is constructed of wood, with cloth streched over the frame of the rotor. It uses about 90% used wood from a Habitat for Humanity ReStore, and cost about $150 to construct.
Here's a picture with me in front of it (warning, about 990kb):
http://winvistainfo.org/Documents/DSCF1763.jpg
Since then we've added flowers as decorations:
http://members.cox.net/nanee123/wind_turbine.jpg
Also, I have 2 videos of it in use, first in low winds, second video in faster winds of about 20mph I think:
http://www.youtube.com/watch?v=XMv2CEGXwqU
http://www.youtube.com/watch?v=M-aZWt6iFyc
Anyway, it's cool. It turns in winds almost too light to be felt. Not that there is much useable power in winds that light. We've also had people park their cars in the street to come talk to us. The neighbors all like it, but I'm not so sure the homeowners' association will. I'll be waiting a long time before adding a generator because of that.
So, the whole thing has a sweep area of about 3.3 square meters. I'm hoping for 500 watts at in a 30 mph wind. I was looking at buying 24 of those N42 2x1x0.5 inch rare earth magnets and some magnet wire to make an alternator. For a 3 phase alternator with 24 magnets, I'd need 18 coils, right? I have to keep in mind that this is a pretty low rpm machine, and hardly ever does more than 20-30 rpm except on a few wind days, or in a thunderstorm. I was also looking at using gearing. Of course that will make my efficiency even lower, but it might help with my very low rpms.
My question is - what gauge wire, and how many turns? I'm aiming for 12 volts in winds under 100 mph.
I'm sure by time I'm done, a solar pannel would have been cheaper and provide more power, but where is the fun in that?