Check out this new 'MVAWT': 'Magnetically-Levitated Axial Flux Alternator with Programmable Variable Coil Resistance, Vertical Axis Wind Turbine'
Large construction with many/large magnets and coils. And uses magnetic levitation rather than bearings.
Some proposed benefits"
+ roof mounted (no tower needed easing installation and neighbor problems)
+ 5mph cut-in speed
+ almost silent
+ variable resistance coils
+ increased efficiency due to no bearing friction
So looks like a huge axal flux VAWT. Some questions:
1. the magnetic bearings: how well would they actually work? while you eliminate the downward force friction, how does it stay cenetered to prevent friction from rubbing against the center pole?
2. the claims of 200% increased output due to 'roof effect' ??
3. the ouput claims seem overly optimistic?
Interesting!
Links:
http://www.enviro-energies.com/index.htm
(company page)
http://peswiki.com/index.php/Directory:Enviro_Energies
(PESWiki.com directory page - good info and vids)
http://www.treehugger.com/files/2007/01/magwind_vertica.php
(treehugger article)
http://www.jaylenosgarage.com/video/video_player.shtml?vid=913522&dst=nbc|widget|Jay%20Leno%27s%20Garage%20Video&__source=nbc|widget|Jay%20Leno%27s%20Garage%20Video
(short interview with Jay Leno)
So not ALL bearings are eliminated - just the load bearing ones.
There are still bearings on the vertical shaft to maintain alignment.
http://www.google.com/patents?id=luCfAAAAEBAJ&dq=7303369
Most the home-brew wind turbine builds use trailer hubs with heavy grease - lots of resistance.
Using electric motor grade bearings with oil reduces this.
'Magnetic bearings' might reduce this even further in this application and the way they are implemented are of interest.
How might horizontal (passive) magnetic bearings be developed/incorporated/developed?
And also the variable-resistance aspect.
A computer/logic circuit controlled coil array.
I think it's a great idea.
Rather than a fixed cut-in, you can produce at least SOME power in even very low-wind speeds, and then 'kick-in' additional coils as the wind speed increases for greater output.
Kind of like a star/delta switch, but more refined.
This is the first time I've seen this idea presented although it seems a basic idea.