Three-dimensional Numerical Study of the Performance of a Small Combined Savonius-Darrieus Vertical Wind Turbine

Energy crisis and global warming have encouraged the use of renewable energy resources such as wind power. Among different types of wind turbines, vertical axis wind turbines can be easily installed in residential areas. In this study, a computational fluid dynamics analysis was performed to predict the performance characteristics of three configurations of small vertical axis wind turbines. For this purpose, an shear stress transport k-omega turbulent model and a rotating frame of reference were employed. Initially, a Savonius and a Darrieus wind turbine were simulated; the low power coefficient of the Savonius wind turbine and the poor performance of the Darrieus wind turbine in low tip speed ratios were the main disadvantages of these systems. Finally, a combined Savonius-Darrieus wind turbine was proposed to deal with these drawbacks. The power coefficient of this combined wind turbines was nearly as high as the Darrieus wind turbine (0.3), while the Savonius blades recover the low torque obtained at low tip speed ratios and help produce more consistent torque, making it suitable for residential applications.