http://www.urbangreenenergy.com/about_vawt.php

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About Vertical Axis Wind Turbines

Vertical axis wind turbines are different from traditional wind turbines in that their main axis is perpendicular to the ground. Their configuration makes them ideal for both rural and urban settings and offers the owner an opportunity to offset the rising cost of electricity and to preserve the environment.

There are many advantages of vertical axis wind turbines (VAWTs):

* VAWTs are not affected by the direction of the wind which is useful in areas where the wind changes direction frequently or quickly. Unlike traditional horizontal axis wind turbines no mechanism is needed to turn the wind turbine towards the wind meaning better performance in areas where a tall tower isn't feasible, obstacles are nearby, or the wind is more turbulent.
* VAWTs are better able to harvest turbulent air flow found around buildings and other obstacles; situations more common in areas where people live.
* VAWTs are ideal for both rural and urban applications including roof top installations. Depending on the roof's shape, wind flow over the roof may even be concentrated leading to an increased energy output.
* Simple to install and maintain
* Quiet operation
* Pleasant appearance