Simplified Laws of Similarity for Wind Turbine Rotors

Laws of similarity or scaling laws for the character-istics of a wind turbine rotor are of importance to the designer even during the initial design phase of a new wind turbine con-cept, but are still more so when the designer wants to make ad-justments or modifications to a wind turbine, in order to improve the machine, optimize or adapt it to another wind climate than originally anticipated, or eventually redesign it by scaling up or down the rotor size. In the paper some esamples are shown to illustrate the principles, and equations for the laws of similarity are derived under simplified conditions such as neglecting the influence of the variation of the Reynolds Number. Some comments are presented on comparison of stall-and pitch-regulated wind turbines and on two speed operation. The optimization of a stall-regulated wind turbine to different wind climates by variation of the generator size is illustrated by examples.