Aerodynamic performance of straight-bladed vertical axis wind turbines : a practical open source implementation

Abstract

This study presents a practical open source implementation that uses double-multiple streamtube model for the aerodynamic performance prediction of straight-bladed vertical axis wind turbines, particularly, the power coefficient (Cp) and tip speed ratio (λ) relationship. To improve the analytical capability of the proposed implementation, important aspects of performance such as dynamics stall and, fixed/variable pitch blade were added. In addition, a fast convergence method for finding the axial induction factor was adopted, giving simplicity to the implementation. Simulated Cp(λ) curves were compared with the experimental data (wind tunnel and field) reported in the literature. The mean absolute error of the simulated Cp(λ) curves, in terms of efficiency, was 0.06, with a mean maximum of 0.078 and a mean minimum of 0.047. The good agreement in combination with the low computing time, suggests that the proposed implementation provides a useful tool for predicting aerodynamic properties of the straight-bladed vertical axis wind turbines and, therefore, for its design. The implementation can be carried out successfully by using GNU-Octave