Saturday, April 08, 2006

Affordable Clean Energy for Your Home

Wind Power Density

“Everyone knows” that to make more power from the wind, a wind turbine “needs” a bigger blade. The amount of energy that can be produced is directly related to the size of the swept area of the blade. It certainly is true of horizontal axis wind turbines (HAWTs). This means that a wind turbine with a 4-foot blade cannot produce as much power as one with a 10-foot blade at the same wind speed. The mathematical formula that reflects this is below:

Wpd=1/2 P*V3

The giant wind turbines that are seen in wind farms and on some coastlines internationally would seem to bear this out. Those awesome machines generate a lot of power, and they look like it too!

Our vertical axis wind turbine (VAWT), the MW 1100, is sized to fit on a roof without disturbing the neighbours. Yet it can generate 5 kilowatts or more of electricity at modest wind speeds.

Roof Power

So, how is it possible to make as much electricity as we do with only a 4-foot sweep? We use the roof of a house or other building to extend our reach and increase the volume of air reaching the sails of our VAWT. This gives us the effect of a larger surface area without actually having a larger vane. The great thing is that every house or other building also has a roof. The roof moves the wind, and that wind has a lot of energy.

The two major factors that determine how much energy is available are the vertical rise of the roof and the pitch, or angle, of the roof. The more rise there is, the more wind will hit it and be moved upward towards the VAWT. This is good. However, the steeper the roof is, the more wind energy will be lost in pressure against the roof and wind moving around the roof and the building as a whole. This is not so good.

A roof with a 10-foot vertical rise and a 30% angle will provide nearly a 200% increase in the amount of wind energy that is available to be turned into electricity. Compared to the same turbine just sitting on a pole, the roof effect increases the power yielded by operation of the wind turbine dramatically.

Installation of a Mag-Wind MW 1100 wind turbine on a peaked or hipped roof puts the VAWT at the top of an inclined area that causes concentration of the volume of air reaching the wind turbine.

The effect of the roof of a building such as a house is called Wind Power Density.
This gives us the ability to make a smaller turbine that costs less, and still produces a lot of power.
The Mag-Wind roof-top turbine obtains wind strength that is available to other types of turbines only if mounted on a tall tower.

Can our MW 1100 be mounted on a tower instead of a roof? Why yes, of course. But, considering the loss of potential wind power compared to putting it on a roof, why would anyone want to? Using a tower would only be helpful if trees or other objects that could not be removed were obstructing the wind from blowing on the wind turbine. —The most effective “tower” is a roof.


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