EXPERIMENTAL STUDY ON THE INCREASE OF THE EFFICIENCY OF VERTICAL AXIS WIND TURBINES BY EQUIPPING THEM WITH WIND CONCENTRATORS

The vertical axis wind turbines, which are operating on the principle of aerodynamic drag, have relatively low efficiency of about 20 to 30%, but they have the great advantage that they can operate at full capacity and produce energy in areas with low wind potential or with turbulent winds. There are several ways one can improve the power coefficient of this type of wind turbine, such as establishing the ideal shape of the rotor blades or by choosing the optimal number of stages of the rotor. In this study, for the improvement of the power coefficient of the wind turbine, a concentrator (curtain) was used in order to cancel the negative moments that affect the rotational movement of the rotor and to increase the speed of the airflow at the entry into the rotor. By analyzing the behavior of the rotors without a concentrator and equipped with various types of wind concentrators one could determine the optimal configuration of the concentrator and the influence that it has on the operation of the wind turbines.