Yes, I have considered a shroud quite similar to what you show but I must admit I never considered the shaft into the building for generator protection and maintenance which I like.

The problem I first thought of with a shroud was losing the ability to use side gusts due to the shroud having to yaw into any side winds. Overall that may not be a big disadvantage if the shroud is light enough and on smooth bearings with a sizable tail fin.

I am anxiously awaiting the time when VAWTS mature to the point where they are in wide use. For my local winds they are really the only choice most of the year.

Please keep us posted as you develop this idea.

Cheers.

TomW

The Truth is the Truth, even if no one believes it; and a lie is a lie even if everyone believes it

Man I'm getting so proud to be a part of this group if only in a small way! I had so of the same thoughts regarding the VAWT, but not the thru the roof thing! I had tried to visualize a wind direction thing, but the posting above has it nailed!

I also feel these machines are about to become lot more popular.

One idea I've had is wrap the lower dsic with a band of soft steel, like a couch skirt, extending downward, and afix a mutitude of magents to this skirt, and also wind a series of huge coils so that even in very low wind this thing makes power. Am I just dreaming, or could this work like a macroturbine (as opposed to picoturbine)?

And No, TomW, I was refering to (over on your diary) the top and bottom plates as to stiffness and flatness. Would spokes of angle iron work, or do y'all think that would be too heavy?

Anyway, keep up the good work!

Power = .00119 x (V - u)^2 x u x A x C

where
V = the windspeed in ft/sec
u = the vane speed in ft/sec
A = the area of the vane in sq ft
C = drag coefficient of the vane

The drag co-efficient for a savinous is about 1 on the torque side and from .12 to .25 for the upwind side.  Basically you calculate the downwind side and the upwind side and find the difference.   If the vanes are offset, similar to the pico250 then you have to calculate the losses in driving vanes that arent doing anything.

With the savinous type as the vane speed increases the drag forces drop quickly but the power extracted still increases.  Maximum power occurs at a tip speed ratio (TSR) of about .33

Also, If you design the wings to be similar to an airfoil you can increase power as the wing passes center from the upwind side, basically extracting power from lift but only briefly.

The "cycloturbine" on my site is basically a modified drag/lift turbine which does much better than the savinous and the wings are quite simple to make as well as the basic frame structure.  The cam/tail assembly is quite simple and works well.  Not as efficient as the HAWT but much better than the standard savinous.

Lots of Fun!!!

From another discussion:

"For example the well-known (?) Jemmet engineering
manual '200 watt savonius wind generator'
gives a formula:
(1) P = 0,00087 x A x V x V x V
where P = power in watts
A = frontal area in sq ft
V = wind speed in mph

But Savonius rotors are quite simple to build.
So to make them powerful... just make them big enough.
I will maybe tomorrow post pictures of one really big one,
which looks quite... interesting and different.

I've as well been thinking about the layout, which was
suggested by Ed. Later I've learned that in Russia
they some time produced turbines with a similar layout,
but the turbine in horizontal position with a tail!

There are as well savonius type water turbines. They
work with water waves as well.

I think that a similar shape as with windside turbines
(see http://www.windside.com) is worth of trying to build.

I've seen here one home-made 'windside-type' turbine.
Its vanes are made of metal sheets.

Germans are using wood for vanes.