Diffuser-Type Augmentation Impact on Dual Rotor Vertical Axis Wind Turbine Performance

Vertical Axis Wind Turbine (VAWT) is one of the wind energy harvesting devices. VAWTs are generally more cost-efficient than Horizontal Axis Wind Turbines (HAWTs) due to their simpler design, lower installation, and maintenance costs. Unlike HAWTs, VAWTs can operate in a wider range of wind conditions and do not require yaw mechanisms to adjust to wind direction, making them more adaptable and easier to deploy in various environments. Additionally, their compact design and minimal noise make them suitable for urban and residential areas, offering a viable option for decentralized energy production. However, VAWTs still face challenges regarding their high tip-speed ratio and self-starting capabilities, limiting their advantage over HAWTs. Overcoming these challenges is crucial for maximizing the potential of VAWTs, ensuring their widespread adoption in different wind energy applications, such as wind farms, buildings, and both onshore and offshore settings. To address VAWT self-starting and performance issues, various strategies have been explored. Optimizing airfoil design, using external starting devices like motors, and implementing blade pitch control can improve torque and efficiency. Passive control systems and magnetic or electrical devices also can help enhance self-starting. Additionally, wind flow control devices, as an auxiliary augmentation device, can boost aerodynamic performance. These approaches collectively improve VAWT reliability and efficiency in diverse environments. Recently. the Dual Rotor Vertical Axis Wind Turbine (DR-VAWT) approach has shown potential in addressing challenges related to performance and self-starting capabilities. Recent studies indicate improvements in overall performance and enhanced self-starting abilities. Furthermore, auxiliary devices offer additional potential for performance enhancement. In particular, diffuser-type augmentation has demonstrated positive effects, but only for single rotor vertical axis wind turbines. This study examines the impact of using a diffuser-type augmentation on Dual-Rotor Straight-Blade Vertical Axis Wind Turbines (DR-SBVAWT). Computational Fluid Dynamics (CFD) simulations are employed to model the combined rotors, examining the complex interactions between these dual rotors when using the diffuser device as an augmentation approach. The results demonstrated that the inclusion of a diffuser in the DR-SBVAWT configuration led to an increase in the moment compared to the dual-rotor system without a diffuser. These findings indicate that diffuser augmentation can enhance the performance of VAWTs, particularly in terms of generating higher moments. 3D simulations with experimental validation are recommended to capture more complex flow interactions to ensure the robustness of the current 2D computational model. Nonetheless, the results from this study provide a valuable proof of concept for further investigation into diffuser-enhanced dual-rotor VAWTs. This approach could potentially advance wind energy technology across different setups.