The new report KD 658 can be copied for free from my website:
www.kdwindturbines.nl at the menu KD-reports. The title of the 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".
This alternative rotor has a design tip speed ratio of 6.5 in stead of 8 for the original rotor and is used for 24 V battery charging in stead of 48 V battery charging. The starting torque coefficient is higher resulting in a lower starting wind speed. The Pel-V curve starts already at V = 2.2 m/s and is better at low wind speeds but worse at high wind speeds. The alternative rotor is therefore especially suitable for regions with low wind speeds.
In stead of the Gö 623 airfoil, the Gö 711 airfoil is used. This airfoil is flat over 97.5 % of the chord and it is therefore easy to provide the blades with this airfoil, also because the blades have a constant chord and a constant blade angle. A sketch of the rotor and the airfoil is added as attachment.
