well I have been having fun trying different ideas of vawt contruction. and I found out a few things.
Bigger isn't always better lol. the last vawt I built had 3 large wings on it and it would start up in low winds but I could not get the rpm's I needed to charge up the 24 volt bank. a few things contributed to that.
1. The over all diameter of the wings in relationship to the magnet rotors
2. The wing design
3. the surrounding trees
4. the pulley system I tried to use to compensate things for rpm's
5. magnet rotors & coil design
results I found that worked against the project was, the over all diameter of the wing swept area required a very strong wind to get rpm's close to cut in speed. If I were to make the wings smaller in diameter from 36 inches deep to say 18 inches I would gain in rpms. also the number of wings would also help increase rpm's. problem I think that limits the rpm's is the other wings that are not being driven from the wind seem to slow the rpm's because they are fighting against the force to come around into the wind. so I think I will have to go with a different wing design.
the pulley system seemed like a good idea to get more rpm's out of the magnet rotors but in fact it acted like a brake. before I installed it, the wings would start up in very low winds and still required a strong wind to reach cut in speed. Now once I installed the pulley system the amount of wind required to get it moving was very high, around 17 to 20 plus mph. and the output ratio would not last very long because of the dirty winds.
the magnet rotors diameter was 12 inches with 12, 82 pound pull magnets on each one. The Stator had 9 coils with #14 magnet wire.
a way I have found to reach cut in speed in lower winds is to use more magnets on each rotor and increase the number of coils per phase from 3 to 5.
one other way I also found increases output is to increase the pound pull of the magnets. refer back to the pulse motor I built and attached a 3 phase to the drive shaft. the first set up used only 3 pound pull magnets. and produced 32 volts . the second set of magnet rotors built used 19 pound pull magnets and reached 50 volts. using the same stator I built a 3rd set of magnet rotors using 49 pound pull magnets and it reached over 100 volts.
So now I get to try all this information I have found and see what I can design. it should be a lot of fun. any ideas you guys want to throw into the mix would be fun to share.