Bladed types need to be away from stuff like trees , buildings , and from the slopes of hills ,otherwise they wont work to their optimum efficiency.
This is essentially because of negative turbulence that structures or land masses like these interupt the gusts to some degree.
'NEGATIVE TURBULENCE'?
Isn't that like saying, "Ain't Not Got No More"?
ANY disruption (Turbulence) in the air flow is 'Negative' to production!
SO, just say 'Turbulence'!
VAWTS seem impervious to this because they essentially take the gust from whatever direction and if the blades are helical , draw the gust(no matter which direction it comes from) , upwards giving the blade a certain amount of lift also.(bit like them chimmneys that have screw - thread like veins on the outside of them - they keep them upright in high winds ! )
Blowing on the NON PRODUCING blades makes for resistance and drag that limit the output power of the Vertical Axis mills...
That and they really don't lend themselves well to being on tall towers that can get up into clean air flows...
With Horizontal Axis mills with blades, all the fan surface is producing torque to turn the generator,
AND,
The design lends it's self well to being on TALL TOWERS where the air flow is much cleaner and has less 'Turbulence'...
IMHO if your on a stealth bug out area , VAWTS will give you a less of a profile above the land, bladed ones need to be an apreciably lot higher in the air thus more susceptible to detection.
Not necessarily true...
The bladed windmill can be on a low mount, like a roof top, but it's MUCH less efficient than it would be on a taller tower, that's why you put them on tall towers!
Verticals are used on buildings because in most places, you MUST have 150% the heights of your mill to the property line...
So if the mill goes over, it won't get into the neighbors yards!
Jay Leno and the like use Verticals in the city for this reason... A tall tower would require buying stupid expensive LA land from the tower, to 1.5 Times the distance to the top of the rig in a radius out from that point!
The Verticals are not 'Towers' and not subject to the laws (Yet) and as long as they land on their own buildings, they are legal (for now).
They didn't use verticals because they are more efficient!
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Don't get me wrong, I think Verticals, Horizontal Drum, bladed towers, are ALL GOOD!
ANY Renewable Power you make is GOOD beyond belief!
And ANY GOOD you can do is much appreciated!
Just don't get roped into the advertising hype and believe that the verticals are more efficient than the bladed types!
If vertical 'Drum' types were more efficient, they would be in the huge fields of wind farms, not bladed types!