Wind Shade Calculator
Do not operate the form until this page and its programme have loaded completely. If you are too fast, the programme will complain about missing data, and you will have to click reload.
You should have read about obstacles , roughness and porosity before using the calculator.
Turbine hub height m
Click in grey squares to insert or remove obstacles
Energy in per cent of undisturbed airflow
70 75 80 85 90 95 100
Select obstacle porosity:
0%= 30%= 50%= 70%=
? Distance between obstacle and turbine m
? Roughness length m
= roughness class
? Obstacle height m
? Obstacle width m
= % of sector width
? Porosity %

for m/s hub height wind speed

? Result: % wind speed decrease*
= % energy loss in this sector*
To print the results of the plotter programme you should make a screen dump

This calculator shows the shelter effect (wind shade) of blunt obstacles (buildings, trees) in any 30 degree sector near a wind turbine. You can change any number, except the results which are labelled with *. If the obstacle is too tall (more than half the hub height of your turbine) - or too close (less than five times the height of the obstacle) the programme will warn you that the results are uncertain, because the detailed geometry of the obstacle and the angle of the wind will have an important influence on the resulting effect.
Please note that you only have to consider the percentage of wind energy coming from this direction cf. the wind rose, because the obstacle obviously only affects your turbine's energy output when the wind is coming from this particular direction.
If you have a fast computer or some patience you may plot the wind speed or wind energy profile behind the obstacle. (If the plot window disappears, it is probably hidden behind another window).
© Copyright 1997-2003 Danish Wind Industry Association
Updated 9 June 2003
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