STAGGERED BIPLANE BLADE CONCEPT FOR ENHANCED AERODYNAMIC PERFORMANCE IN VERTICAL-AXIS WIND TURBINES

The accelerating global demand for clean electricity, combined with the progressive depletion of fossil fuel reserves, has placed renewable energy technologies at the forefront of engineering research. According to the International Energy Agency (IEA), wind power generated over 2,330 TWh in 2023-representing a 10% year-on-year increase-and global wind capacity is projected to nearly double to over 2,000 GW by 2030. Among wind energy converters, vertical-axis wind turbines (VAWTs) of the Darrieus type have attracted renewed interest owing to their omnidirectional operation, mechanical simplicity, and suitability for urban and offshore environments. Nevertheless, their aerodynamic efficiency remains a limiting factor compared to horizontal-axis machines. This study proposes a novel VAWT configuration based on the tandem biplane blade concept, combining geometric modifications aimed at improving aerodynamic performance. Two-dimensional steady-state Reynolds-Averaged Navier–Stokes (RANS) simulations were performed using the Spalart–Allmaras turbulence model in ANSYS Fluent, applied to a NACA 0018 airfoil at a chord Reynolds number of 4 Re 7.4 10 c   and a tip-speed ratio of 2  . Four blade arrangements were evaluated: a single-blade baseline, two blades without offset, two blades with a 0.5C upstream stagger, and two blades with a 0.5C downstream stagger. The results demonstrate that tandem-staggered configurations yield significant improvements in lift and tangential force coefficients relative to the single-blade reference, with the upstream-offset arrangement exhibiting the most favorable aerodynamic characteristics. These findings validate the biplane concept as a promising pathway for enhancing VAWT power output and operational stability.