Effect of Solidity on Performance of Vertical Axis Wind Turbine Using Constant Chord Reynolds Number

Abstract

The demand for wind turbines has increased ever since fossil fuels showed signs of quick depletion. Among wind turbines, Vertical Axis Wind Turbine (VAWT) is compact, produces less noise, is omnidirectional, resilient to turbulent flow, and is easy to maintain. The power generated by a VAWT is a function of a non-dimensional geometric parameter known as solidity (s), which is a function of turbine diameter (D), blade chord (c) and the number of blades (n). The present work analyses the impact of solidity (0.12 and 0.18) as a complete non-dimensional parameter on wind turbine performance. Each parameter of solidity is varied, keeping any one of the parameters constant and numerically studied for its performance across a range of tip speed ratios (TSR). For each solidity, six different combinations of VAWT geometric parameters were analyzed. In all the cases, the chord Reynolds number is kept constant. CFD simulation was performed on the Darrieus H-type (NACA0018 airfoil) VAWT. Two dimensional (2D) computational domains are used to study the effect on the turbine’s performance as the solidity studied is less than 0.4. Unsteady Reynolds-Averaged Navier-strokes (URANS) equation is used to solve the CFD model using ANSYS Fluent 19.1 with 4-equation transition SST k-ω for turbulence modelling. The comprehensive study of the turbine performance keeping the turbine operation within a constant Re number range shows the Coefficient of Performance (Cp) overlaps for a given solidity.