Nature Power Marine Grade 400 Watt Wind Turbine (70500) - Manual (Page 7)

4. LOCATION SELECTION
To ensure good performance from the Wind Generator, it is important that
care is taken in the site of the machine. Buildings, trees and rocky outcrops
etc. disrupt the smooth flow of wind creating a “Wind Shear” with the wind
velocity nearer the ground being slower than that higher up. Turbulence is
also created by these obstructions. Turbulence is detrimental as the swirling
air causes the Wind Generator to yaw continually thus stressing the mechanical
parts and greatly increasing wear and tear.
Sharp edges
Create turbulence
Smooth, laminar airflow
2H
20H
Turbulent airflow
2H
H
Turbulent airflow created by obstructions (Ad. P. Gipe, 93)
Therefore, as a general rule the Wind Generator should be mounted twice
as high as any such obstructions. The power obtained from the wind is
proportional the cube of the wind speed, and the wind speed increases with
height from the ground. A 26% increase in wind speed from a higher tower
will yield a 100% increase in power from the wind generator. A little more
money spent on a higher tower will harvest the same power as 2 machines!
Preference should be given to the prevailing wind direction, but it should be
noted that tall features behind the Wind Generator can also slow down the
wind flow through the Wind Generator.
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