Aerodynamic performance improvement of vertical axis wind turbines in a hybrid configuration

Because of wake losses and variations in wind speed, turbines often operate below their rated power, making efficiency improvements crucial for enhancing overall generation. This study introduces a novel design that integrates small turbines around a wind turbine tower to harness aerodynamic interactions and enhance overall system performance. A three-dimensional computational fluid dynamics based parametric study was conducted, considering four angular placements (0°, 30°, 60°, 90°), varying wind speeds (4, 6, 8, and 10 m/s), turbine height along the tower, and dual-turbine configurations. Performance was evaluated through power, torque, drag, and lift coefficients as well as flow field analysis. Results show that increasing wind speed enhances turbine performance, with the highest power coefficient (Cpower) of 0.5487 obtained at 90° under 8 m/s due to stronger local velocities and attached flow. Conversely, the 0° position yielded the lowest Cpower 0.07641 at 4 m/s because of tower-induced stagnation. Height variation along the tower, considering decreasing tower diameter and increasing wind speed, shows that the turbine at the upper elevation obtained the highest CPower of 0.4829 at D = 3.0 m, V = 10 m/s, while the lower section, benefiting from larger tower diameter, obtained CPower of 0.4055 at D = 6.0 m, V = 4 m/s. Dual-turbine analysis confirmed that configurations of T1: 45° and T2:90° obtained an improved total power coefficient (Cp-total), while closely spaced cases T1:30° and T2:90° were affected by a strong stagnation region. The total improvement efficiency analysis revealed that integration at 90° improved the horizontal axis wind turbine efficiency by 0.85%.