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"Horizontal" wind generators can reach speeds faster than the wind passing them, by setting the width and attack angle of the wings. Vertical wind generators can only move at the speed of the wind.
Horizontal wind generators must be directed to the wind. In turbulent winds (near urban roofs etc) there
is much energy lost, and this is a major drawback.
Enters the "Upward Wind Turbine". A simple winding ducts contraption which looks a bit like a large cockroach trap, captures wind from any direction, and sends it winding upward. At the top of the contraption there is a regular turbine that can reach the typical higher speeds of a horizontal generator. A cover which creates low pressure at the exit by a wing effect, could be added for better efficiency. This cover could be directed to allow wind out only in the direction of the wind by using a sail, or simply by shape (where the exit holes are always directed to towards the middle base).
The whole contraption could be set "upside down" so that the entrance is on top, and the exit on the bottom. For urban building roofs, usually with a fence around the roof - this would be great, since the fence would cause a low pressure area (no wind).
PLEASE NOTE that the windings are STATIC. Not like any of the Darius et al generators. And, if I understand correctly, not like the "vertical-hub Airscrew" idea here in this category.
Couldn't find the roach trap. So meanwhile
http://www.solarnav...vortex_cylinder.jpg here's an image that shows something of the idea, just with three openings on the side [pashute, Apr 13 2010]
[link]
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This could easily be made of lightweight but strong plastic material, and then attached to the roof for stability. |
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//Vertical wind generators can only move at the speed of the wind// |
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This is complete nonsense! The Darrieus rotor - a Vertical Axis Wind Turbine (VAWT) - is the Gold Standard for wind turbines moving faster than the wind (mostly because it utilizes the Bernoulli effect, unlike it's sister VAWT, the Savonius rotor, which is drag-based). |
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HAWTs - Horizontal Axis Wind Turbines - with either upwind or downwind impellers, are the notoriously slow wind turbine cousins of VAWTs as only their blade tips can exceed ambient wind velocity. |
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OK, so if its not the speed of rotors, obviously its the efficiency or perhaps cost, otherwise, why are all the giant wind farms (we have three in my country) regular two or three winged turbines. |
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Cost is a big chunk of it. Height above ground is a major factor in wind speed, and thus turbine electricity production. |
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Mounting a HAWT well above ground level is relatively inexpensive. Mounting a VAWT of the same scale the same height above ground is much more expensive and requires much more structure (which negates some of the advantages as the structure creates drag). |
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Also the propellor type turbines are much easier to adjust or even simply design for a wide range of windspeeds and conditions. |
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