Abstract
Since millenaries humans have attempted to harness the wind energy through diverse means. Vertical axis wind turbines (VAWTs) were originally considered as very promising, before being superseded by the present, horizontal axis turbines. For various reasons, there is now a resurgence of interests for VAWTs, in particular Darrieus turbines. Using modern design tools and computational approaches, it should be possible to increase considerably the performance of traditional VAWTs, reaching a level almost comparable to that of horizontal axis turbines. Since VAWTs show many specific advantages (compact design, easier connection to gears/generator, easier blade control if needed, lower fatigue…), it is important to check quantitatively the efficiency of such turbines. This is the purpose of the present work, starting from the standard, straight Darrieus turbine (H-rotor). The aerodynamic investigation will be carried out for 20 different airfoils (Symmetric and Non-symmetric) by two-dimensional Computational Fluid Dynamics in order to maximize output torque coefficient and output power coefficient (efficiency). A considerable improvement of the H-rotor Darrieus turbine performance can be obtained in this manner.
▸ Darrieus turbine is a promising concept for small wind-energy systems, but suffers from a poor efficiency. ▸ 20 different symmetric and non-symmetric airfoils are investigated, after validating the unsteady numerical procedure. ▸ Absolute efficiency increase of the new design is 10.87% compared to the conventional design. ▸ Relative increase of the power coefficient by 26.83% corresponding to the S-1046 airfoil is obtained. ▸ Optimal configuration of Darrieus turbine involving S-1046 appears to be very promising for wind energy in urban areas.