How Roof Effect Can Super-Charge Your Vertical Wind Turbine For The Home Project

Published: 26th September 2011
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When you are first looking into purchasing a vertical wind turbine for the home it is good to consider ALL the potential places on your property that it could be located. Studying the wind patterns at different points on a your roof is a very important part of that.

"Roof Effect" is a very important term for anyone who is thinking about mounting a windmill on their house. It turns out, there is one particular area of the roof that will give you the best return for your money.

In other words, the quality of the wind on your roof can have as much variability as the wind in any other area of your property. Where you install your windmill can a tremendous difference in how much power you convert.

This phenomenon of Roof Effect happens because wind collides with your roof and compresses. Aerodynamic pressure will increase the acceleration of the air flow. Then, the air travels along the contour of the roof in a faster boundary layer of 1 - 3 feet.

From the vantage point of the home wind turbine buyer, Roof Effect could increase the speed of your wind by 50-300% - depending on the shape, angle, and height of your roof.

Wind speed itself is the most powerful variable in the power equation for wind turbines. Since the velocity of the wind you have to deal with is cubed in the formula, a small change in wind speed can have an enormous impact on your power output.

So, placing your windmill at just the right spot on the roof can make the difference between an okay project and an outstanding project.

Here is what I mean by thatů

If your wind is blowing at 12 mph, then the impact of cubing its velocity is, 12 x 12 x 12 = 1,728

However, if your wind is blowing at 15 mph, then the impact of cubing its velocity is, 15 x 15 x 15 = 3,375!

Thus, it goes without saying that the best place to mount your turbine on your roof is on the ridgeline as high up as you can find. And, at the apex of the roof, the wind is strongest - because the wind is always stronger the higher up you go.

In studies by 2 major universities - Guelph University in Canada and Delft University in Holland - the Roof Effect has been shown to improve the performance of vertical wind turbines for the home.

In summary, Roof Effect is a powerful concept to recognize in deciding where to locate a windmill on your property. In order to maximize power production, the best place to put a wind turbine for the home is on the ridgeline as high up as possible.


Roger G. Brown has been an energy engineer for 20 years. Check out Roger's tips on how to save money AND get a Wind Tax Credit

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