Also, it was noticed that the rotor designed for high wind speeds performs well also at sites of low mean speed. Existing rotors were used for the definition of the initial machines. In order to have comparable results all calculations were performed with the same parameters. Different design alternatives were considered. A summary of the tests is provided in Table 1 .
Columns correspond to different choices of design variables.
In the lower part of the table the gain of the energy production with respect to the performance of the initial machines is given in per cents. The dash indicates to insignificant gain whereas blank cells correspond to runs that were not performed. Columns 1-14 correspond to runs with the maximum power constrainted by the rated power of the initial machine. Column 15 is different. Instead of limiting the maximum power of the rotor, an upper limit for the maximum flapping moment at the root was set.