Tall Tower Economics
Sitting towers and determining tower heights for small wind turbines (up 100 kW in capacity) is quite different than for commercial or utility-scale projects.

There are two things that can diminish the wind resource for a small wind turbine.

• Ground Drag - friction that occurs between the surface of the earth and air masses that flow over it. The more cluttered the landscape (with trees and buildings), the greater the ground drag will be in a given area. Ground drag reduces the wind’s speed, reducing its kinetic energy.

• Turbulence caused by the obstacles that clutter the earth. Trees and buildings cause the wind to tumble and swirl rather than flow smoothly. Turbulent winds also put undue stress and strain on the wind turbine and tower. Turbulence increases the maintenance on a wind generator, while it effectively reduces its life expectancy. Turbulence is the proverbial double whammy for small wind turbines!

How do you avoid ground drag and turbulence? Get up above it.

Not only does a tall tower get your wind system away from the ground drag and out of the turbulence zone, a taller tower will provide you greater wind speeds (wind speeds increase with height) and greater wind speeds gets you more power. Power equals energy. What does all this mean? 10% increase in wind speed = 33% increase in available power.

As with all things pertaining to wind energy there are many considerations to ponder. A taller tower will cost more money, but the expense may be justified by the increase in power, this would make a much nicer return on investment.

What are your local zoning ordinances? Can you erect a tall tower but not a taller tower? You can always increase your swept area and rotor diameter.

Improper Tower Height	Improper Tower Height

Simply stated, there are many considerations that should be taken when determining the right tower height to get optimum performance from a wind system and maximum return on your investment.

A short tower may work in an open field, but unless you can change the mathematics or physics of ground drag ( AKA alpha value) the wind system will not perform to its full potential.