S-Rotors for Wind Turbines

The advantage of an S rotor is it doesn't waste time or energy reorienting itself in variable winds.

New Mexico winds (depending on location) are steadily above 30 knots, but may shift moment to moment by as much as 75 degrees. Very turbulent.

While I believe some big ones were built, the greatest advantage I saw was to the individual homeowner who needs something small and doesn't want a large tower out in his (perhaps non-existant) pasture.

I seem to remember Jay Leno helping with the promotion of one firm building them in California.

I also remember some attempted applications for ships, but don't know how that went.

That's a Savonius turbine and is one of the Vertical Axis Wind Turbine (VAWT) types.

If you are serious about wind energy, and do not live in the city, trust a Horizontal (HAWT) type of turbine. That one that Jay Leno has does nothing but spin and as I understand does not even have an alternator connected to it. (as most VAWTs you see in pictures) If they were better than HAWTs (propellor types), you would see lots of THOSE in the countryside, and not the typical multi-megaWatt HAWTs instead.

They (VAWT) just aren't as efficient as HAWTs and most people touting them say "they work near to the ground" when the fact is that there is MUCH less wind energy on the ground. There is no substitute for height where the non-turbulant wind is.

That being said, I think that the first VAWT company that even has a chance at succeeding is the Windspire by http://www.mariahpower.com/

boB K7IQ

I think he is actually talking about a derivative of the Darrieus turbine.

As you pointed out, these are not as efficient as horizontal axis turbines, I believe the max theoretical efficiency is 30%.

This arises because the blades can only generate for a portion of their travel, the actual proportion varying with the design, but just as a sailboat can only generate enough lift to sail to a certain angle into the wind, so these turbines have a portion of their travel in which they are providing drag, not lift.

They may not be self starting, this can be overcome by connecting the rotor to a savonius rotor (S shape in plan view, whereas the S shape darrieus unit is a helix).

There are then problems with feathering to prevent runaway in high winds. A horizontal axis unit either feathers the blades to produce negligible lift in these conditions, or use the windmill approach of turning it at 0 degrees to the wind to achieve the same effect.

They look good though.

i was watching t.v. and saw a guy from chicago that was using an s-rotor type of generator in the horizontal form, the unit was atop of a hi-rise an about 30 feet in length. thought it was kind of interesting. he said it made enough power to supply all the buildings needs, but did not say what the kw was, so as optimistic as i am, i remain skeptical on these.

From Chicago. That would probably be these guys:

http://www.aerotecture.com/

They've been around for at least 5 or 6 years now and have been becoming increasingly popular. Their turbines work horizontally mounted as well, so they can run them along rooflines, under bridges, etc. They are also completely silent running. We have a couple in our area, but I couldn't tell what the effeciency is or how much power they are actually generating. Just remember, they call Chicago the "windy city" for a reason. ;)

Oh, and it is not a simple S rotor / savonius. The S rotor is twisted into a helix to increase startup effeciency and it also incorporate that other darrieus / airfoil design.

Helixwind has a small unit that generates about 2.5 Kw in a light wind. I think if they used a quarter circle baffle on the wind capture side, they might increase their efficiency. Such a baffle would require positioning it with respect to the wind direction. The wind resistance side has about a 30 percent clear area for wind passage, due to the spiral design.

One possible way tp prevent "runaway" in high winds would be to be able to drop a canvas cover (like a large "Rubber" over the whole thing......with springs and some simple release mechanism you could make it automatic maybe.....