Rotor design

The calculator on this page helps design a windmill rotor given some known characteristics.
The calculations are valid only under design conditions. In other words, these calculations produce a rotor with optimal power output at a certain wind speed and with a matched load.
Starting behaviour is not modelled.

More information and derivations of the used formulas can be found in the publication “Rotor design for horizontal axis windmills” (1977).
Available in pdf from:

For more details on windmill design and some worked-out examples we direct you to the website of Adriaan Kragten:
On this website you may find hundreds of reports written by dhr. Kragten on various windmill designs.
For beginners we recommend to read report KD 35 to understand the basic concepts of windmill design.

Note: this page is under construction. Future versions will help you find appropriate values for the input parameters and will have more helpful plots.

Variable Symbol Input
Rotor diameter (m) D
Hub diameter (m) Dh
Blade shape
Number of blades B
Design tip-speed ratio λd
Design airfoil lift coefficient Cl,d
Design airfoil angle of attack (deg) αd