TORNADO concept and realisation of a rotor for small VAWTs

The concept of a three-tier configuration for a vertical axis rotor was successfully developed into a experimental model. The rotor assembly is divided into three tiers with three straight blades in each tier. The three-tiers are shifted by an angle of 400 generating a full helical flow field inside the rotor. Thereby the new configuration has some different mechanism of torque generation as other Darrieus rotors. The three-tier configuration facilitates the operation by enabling the turbine to self-start at wind velocity as low as 2 m/s with good performance and a smoother driving torque. At the same time the design couples an esthetic appearance with low noise level.