Report KD 658 has been added to the menu KD-reports. The tittle of this report is: “Calculations executed for an alternative rotor of the VIRYA-4.2 windmill (lambda design = 6.5, Gö 711 airfoil) used for 24 V battery charging”. The advantage of the alternative VIRYA-4.2 rotor is that it has a higher starting torque coefficient than the original rotor which has a design tip speed ratio of 8. The starting wind speed is therefore lower. The Pel-V curve is better at low wind speeds but worse at high wind speeds. So the alternative rotor is especially meant for regions with low wind speeds.