vawt design

[jonnyr48]

hi everybody. i would like to build a vawt capable of using most(or all) of the wind in a big storm, of which we have a lot - living in the windiest area of britain/europe.i have been looking for a very sturdy design that's fairly simple to make,and came across the following from a research group?(or dodgy investment company?)in spain - sorry can't get the picture to paste on here- see www.generadoreolicowm.com    please could some of you clever people tell me - a.is this design as super-efficient(over 40%!) as they claim?   b.if it's not much good, what design of vawt would be best given the above criteria?        

[kurt]

its a scam. rule of thumb, if there looking for investers its a scam.

[wooferhound]

About the easiest way that I know of

is to make a Savinous machine out of barrels

http://www.fieldlines.com/story/2005/6/25/18422/0421

[vawtman]

http://www.generadoreolicowm.com/ingles/index.htm

 I dont like it and think Woofs mention of barrels would be better and easier to build.

 When those shutters are closed there must be alot of drag.In other words must be very slow in my opinion.

[finnsawyer]

Take their design and put in a central cylinder half the size of the diameter and I bet you would be surprised by the result.  Plus with the large central cylinder you could build a much sturdier structure.

[vawtman]

If i were to rework the design i would have all the blades(shutters) fixed with airfoil shapes.Rotation would be set by the shape of the blades not the wind pushing it.Much faster rotation.

 Just a thought Fin.

[finnsawyer]

No problem with that.  The purpose of the large central cylinder is to speed up the air flow as seen by the vanes.  Of course, to design your airfoils you need to know what that speed up would be.  It might be best to use simple shutters at first just to get an idea what it would be.  If I'm right you should see an increase in rotational speed compared to the case with the small central shaft.  The cylinder could actually be quite large with just one set of shutters.  Keep in mind that you don't lose that incoming air.  You are channeling it and speeding it up, and the effect extends out to about one radius from the cylinder's surface.

[Nando]

The vertical venetian blinds will have a heavy maintenance requirement.

The design as the photo shows, I doubt that is not capable of 40 %, maybe in the 25 - 28 % or so .

The blades are rotated to reduce the drag that the blades present on the opposite side.

This scheme have being tried years ago, I saw one in South America about 20 Years ago.

Though all the blades had bearings up/down and even the push rods had them, as well, the maintenance, as I was informed was, quite continuous and demanding.

For high wind regimes it is best to use Torque Pitch controlled wind mills with twist blades.

How much power are you looking for ?.

Nando.

[alancorey]

Primitive, but cheap Savonius (from the 3rd world CD):

http://www.cd3wd.com/CD3WD_40/VITA/SAVROTOR/EN/SAVROTOR.HTM

Enhance as appropriate...

  Alan

[jonnyr48]

hi nando,thanks for your comments.i would ideally stick a really big old generator on the bottom - if its sitting on the ground weight doesn't matter(might even help hold it down!).i want to make this very sturdy to cope with the storms.is there info on this site on the torque pitch controlled windmills with twist blades? i tried to search it but it came up with nothing.cheers, jon .

[jonnyr48]

hi fin,thanks for your comments.it looks from nando's comments like the shutters aren't practical due to the maintenance.i like the idea of the large central cylinder making it stronger and faster,why isn't this being used by vawt manufacturers? would it create  turbulence? cheers, jon.

[finnsawyer]

I think a lot of what you see comes about because people just don't understand what is going on.  Although the speed up of air is something we encounter everyday, because air is transparent, we don't see the effects, and we're not very good at detecting pressure changes.  And if it didn't happen air would pile up when it encountered an obstacle.  So, that region of air flowing around an object is important, even though it's past the physical boundaries of the object.  Everyone knows that planes fly because of that effect, but that's about it.  A shame, really, because mathematical solutions exist for two simple cases; fluid flow around a sphere and around a cylinder.  And when you study them it can get quite interesting, particularly concerning power flow.