Small Wind Basics
What is a wind generator?
The proper name of a wind generator is actually “Wind Energy Converter” that being a device that converts the potential energy in the wind to another form of energy. This can either be mechanical or electrical.
How does the wind generator work?
When the wind blows, the rotor blade stops a percentage of the wind. That percentage is what is converted into energy. According to physics, the maximum amount of wind energy that can be converted is 59.3%. This is known as the Betz Limit.
I’ve seen lots of different looking designs, which is the best?
The most common designs include:
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Horizontal upwind: The generator shaft is positioned horizontally and the wind hits the blade before the tower. Examples: AIR and Whisper.
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Horizontal downwind: The generator shaft is positioned horizontally and the wind hits the tower first then the blade. Example: Skystream 3.7.
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Vertical Axis: The generator shaft is positioned vertically with the blades pointing up with the generator mounted on the ground or a short tower.
Experimentation has found that the horizontal axis upwind or down wind design to be the best design for overall efficiency and reliability.
There are two basic types of airfoils (blades) a lifting and drag type.
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The drag style airfoil is typically what you see with an old Dutch windmill or American water pumping windmill. The blades are generally a flat plat which the wind hits and causes to rotate. This type of design is great for very low wind areas and will develop a lot of torque to perform an operation. However, in medium to higher winds, their capabilities to produce energy are limited.
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The lifting style airfoil is what you see in most modern wind turbines and on airplanes. A properly designed airfoil is capable of converting significantly more power in medium and higher winds. A three-blade design has proven the most stable for this configuration.
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