Novel hybrid blade design and its impact on the overall and self-starting performance of a three-dimensional H-type Darrieus wind turbine

The present study proposes a novel hybrid blade design that is the combination of a conventional airfoil, namely the NACA0018, and its J-shaped profile to increase the torque generation at the start-up stage of the turbine while decreasing the potential efficiency loss at the high tip speed ratios. Therefore, a new 2D-based design methodology was proposed, and depending on this methodology, different hybrid blade configurations were determined for the investigation of the overall and self-starting performance of the H-type Darrieus vertical axis wind turbine. Due to the inherent shape of the proposed hybrid blade, a 3D CFD dynamic start-up model, which is based on the fluid–turbine​ interaction, was built and used to evaluate the performance of the different configurations of the hybrid blades. The results indicate that although the proposed design methodology is based on the 2D-CFD calculations, it enables a quicker prediction of the aerodynamic performance of the proposed hybrid blades compared to the 3D-based CFD simulations. Furthermore, the findings also clearly illustrate that the new proposed hybrid blade designs not only overcome the self-starting issue of the turbine but also provide a wider turbine operating range and an improvement in the turbine peak efficiency in contrast to the losses caused by J-shaped airfoils.