Enhancing Self-Starting Characteristics of Darrieus Wind Turbine: Effects of J-Blade on Performance of Double-Darrieus Turbine

Darrieus vertical-axis wind turbines (VAWTs) offer an attractive alternative to traditional horizontal-axis wind turbines (HAWTs). However, the poor self-starting performance of Darrieus wind turbines remains a significant limitation that needs improvement. The present study investigates design modifications to improve the self-starting performance of a Darrieus wind turbine. An unsteady Reynolds-Averaged Navier–Stokes (URANS) investigation was performed by utilising the SST k–ω turbulence model to evaluate the performance and flow physics of a double-Darrieus turbine incorporating a NACA 0021 aerofoil and 70%, 60% and 50% cut-ratio J-blade derived from the same aerofoil. A detailed investigation of changes in torque and pressure coefficients resulting from the design modifications was performed. The results indicate an improvement in the power coefficient at low tip speed ratios. An average power coefficient improvement of more than 100% was observed for a tip speed ratio of 1.5 with an inlet velocity of 9 m/s. The present findings suggest that the addition of a second rotor (J-blades) not only improves self-starting performance but also improves the performance of the base turbine at low tip speed ratios. Furthermore, geometric modification of the Darrieus turbine can provide a promising solution to its self-starting issue without the need for an external source of starting torque.