VAWT Swept area

[farazmasroor]

For Horizontal Axis Wind turbines (HAWTS), there is a formula for calculating the expected power output. IT is:
efficiency * air density * swept area * windspeed ^3
For a HAWT, since it is sorta flat, the swept area is simply pi r^2 (r=radius).
However, for a VAWT (vertical AWT), the blades can be as high as they want.
How do you calculate the swept area in this case?

[rossw]

For Horizontal Axis Wind turbines (HAWTS), there is a formula for calculating the expected power output. IT is:
efficiency * air density * swept area * windspeed ^3
For a HAWT, since it is sorta flat, the swept area is simply pi r^2 (r=radius).
However, for a VAWT (vertical AWT), the blades can be as high as they want.
How do you calculate the swept area in this case?

If you look at a vawt from the side, the swept area will be the diameter of the rotor, times the height of the blades. It will describe a rectangle.
However most VAWT constructions I've seen have the blades only effectively working on the downwind side, so halve the area calculated above.
Then, consider that the effort isn't equal - the blades provide most power when they're at right angles to the wind, and progressively less (cosine?) of the angle as they come closer to the line of the wind. So take away some more And finally, when the blades are on the upwind side, they'll actually be providing drag and losing power, so take off a bit more again!

I guess I'm saying the calculation for "swept area" is probably straightforward, but determining the POWER you can get from the wind for a given "swept area" will be far more complex than with a hawt.

[farazmasroor]

Okay...
My blades are sorta like concentric circles... If you know what I mean.
Like they don't go all the way to the center.
Also, I will have a mechanism that blocks off one half of the turbine, so there is no part that's turning in the wrong way.
Well, there is, but there is no wind blowing on it, so it doesn't really matter.
So it's the diameter of the entire rotor (as if it were radial) times the height of the blade. There's no 3.14 in the calculation?
Yes, I'm using this to calculate power output. If there is a different formula, please tell me.

[electrondady1]

yes,
 among vawt enthusiasts it's generally accepted  width x height =swept area.

if your running a shroud that funnels air to the down wind side, or if it's simply a blocking shroud
i would say it's the whole devise.

http://www.vawts.net/index.spark?aBID=125317&p=1

this sort of thing comes up all the time at the vertical site


 

[KBwind]

It sounds like you have a drag VAWT which can only extract power from the downwind side of rotation. From there I would say your SA is the radius times height. Even if it were lift type the shroud would prevent it from extracting on thr upwind pass. Proper lift VAWTs make the majority of their power on the upwind side as the wind and tangnetial blade vectors are additive resulting in a higher Reynold's number and more lift.