Wind Turbine Types

There are two different types of wind turbines on the market today.

Horizontal axis, Tower-mounted Turbines

These are the units with which we are most familiar as they have been under development since the 1970’s. Shown here is the Skystream 3.7 which can be seen at Lickety Split in North Conway. It is one of the more recent and smaller units that is popular with homeowners. Generally it is recommended that the towers exceed the tree canopy height and that there be no trees or structures within 200 feet of the tower (free-standing, un-guyed pole, in this case).

The Skystream 3.7

Vertical Axis Turbines

These turbines are of more recent designs and are being rapidly developed. Here are the advantages of these units according to one manufacturer, TMA Global Wind Energy Systems.

• Most efficient vertical wind turbine in the world and compares with all prop styles

• The greater efficiency provides a higher capacity factor at like prevailing wind speeds

• Easier to operate and control in all aspects of operation and shut down procedures

• Operates in high or gusting wind and icing conditions when prop turbines shut down the net result is a longer period of effective power production

• Lower profile turbines that appear as buildings, creating less “visual pollution”

• No bird or bat kills resulting in better support from environmental groups and Government agencies

• Ease of maintenance and inspections at ground level on all major components as opposed to 250-300’ in the air at the nacelle or hub height

• Lower top speed ratio by almost 7 times compared to props reducing speed, vibration, fatigue, static, flex and other load stress profiles

• Reduced audible distortion (decibel rating) and audible resonance due to lower rotor speed and less cutting action of the turbine blades into the prevailing wind

• No magnetic field interference at the hub height from the generators therefore no interference with aircraft navigation or telecommunications

Interestingly, some manufactures are producing roof-mounted units, which of course would have much less visual impact than tower-mounted units.

Examples of roof-mounted wind turbines

An index to vertical axis turbine manufacturers can be found here.

Actually, there is a third type of wind turbine that has far greater curb appeal than either of the types described above. See if you can pick it out from the two shown in the photo below.

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Updated June 12, 2009