3D numerical simulation of the Darrieus vertical axis wind turbine with J-type and straight blades under various operating conditions including self-starting mode

A comprehensive three-dimensional numerical analysis is applied in this study to evaluate the competence of the J-type blades in the vertical axis wind turbines under wide range of operating conditions including various wind speeds, tip speed ratios and wind turbulence intensities. It is found that the vortices which are encapsulated in the concave part of the J-type blades escape from the tips of the blades and become stronger than those originated from the straight blades. Such strong wakes behind the J-type blades are responsible for larger negative effects on generating the torque at high tip speed ratios. Neither of the wind speed, nor the wind turbulence intensity have significant effects on performance of the J-type blade turbines. Of particular interest is to discover the behavior of the J-type blade under self-starting conditions which is a major shortcoming with Darrieus turbines. The results show that replacing the straight blades with the J-type blades causes the generated torque to increase by 26.9% and 37.6% at the wind speeds of 10 m/s and 5 m/s, respectively. Better performance of the J-type blades under self-starting conditions, makes them a promising candidate, especially at low wind speed regions such as urban areas.