A Dynamic Rotor Vertical Axis Wind Turbine with A Blade Transitioning Capability
This work presents an optimized design of a Dynamic Rotor Vertical Axis Wind Turbine (DR VAWT) that maximizes the operational Tip Speed Ratio (TSR) range and the average power coefficient (Cp) value while maintaining a low cut-in wind velocity. The DR VAWT is capable of mimicking a Savonius rotor during the startup phase, and transitioning into a Darrieus one with increasing rotor radius at higher TSRs. The design exploits the fact that with increasing rotor radius, the TSR value where peak power coefficient is attained increases. A 2.5D Improved Delayed Detached Eddy Simulation (IDDES) approach is adopted in order to optimize the dynamic rotor design, where results show that the generated blades trajectories can be readily replicated by simple mechanisms in reality. A thorough sensitivity analysis is conducted on the generated optimized blades trajectories, where results show that they are insensitive to values of Reynolds number. The performance of the DR VAWT turbine with its blades following different trajectories is contrasted with the optimized turbine, where the influence of the blade pitch angle is highlighted. Moreover, a cross comparison between the performance of the proposed design and that of the Hybrid Savonius-Darrieus one found in literature is carefully made. Finally, the effect of airfoil thickness on the performance of the optimized DR VAWT is thoroughly analyzed.