Numerical investigation of solidity for cambered Darrieus VAWTs: Analysis of chord length

Abstract

Wind energy technology has seen steady growth in the energy market as a clean, renewable source of energy. This has brought attention to areas with moderate wind energy potentials. Darrieus type Vertical Axis Wind Turbines (VAWTs) allows capturing of this potential for energy production at a cost-effective scale. To improve the performance of these turbines their design needs to be modified. With better manufacturing methods currently available cambered blades are being investigated to improve the performance of these turbines. In particular, turbine solidity is investigated in this paper due to different chord lengths of the blades. The analysis is conducted following high fidelity CFD modeling in unsteady, turbulent regimes with a sliding/rotating mesh configuration to emphasize the role of rotor blades interaction. The study showed that low solidity turbines with cambered blades operate at low coefficients of performance (CP) over a large range of tip speed ratios (TSRs). High solidity turbines have much higher CP, but at smaller TSRs and short range of TSRs. Medium solidity turbines are faced with considerable interaction which compromises their operation at TSRs as low as 1.