Increasing energy efficiency of counter-rotating wind turbines by experimental modelling

Abstract

With the significant advance in exploiting wind energy, there has been a shift in research from the study of conventional systems to the study of counter-rotating systems due to additional energy input of the second rotor. The paper presents the results of the research on achieving an increase in the energy efficiency of counter-rotating wind power conversion systems. For this purpose, there have been designed different sizes of wind rotors, were 3D printed and tested in an open-circuit aerodynamic tunnel for different wind velocities and axial distances between rotors. The constructive design consisting of a smaller diameter front rotor and a larger rear rotor was chosen. The individual wind rotors were used to configure two experimental models of counter-rotating wind systems. The testing results analysis and interpretation enabled the establishing of the design and operating conditions that provide the highest power extracted from wind at 10 m/s velocity. A higher efficiency of the wind turbine system is achieved for a lower ratio between the front and rear turbines. In the case of the analysed experimental models, an increase in system efficiency of 49.14% is achieved for a 0.845 diameter ratio, and of 39.02% for 0.945 diameter ratio, respectively.