Feasibility analysis of aerodynamic characteristics for vertical-axis turbines in offshore: A comprehensive analysis on scale and design of wind system

Abstract

With the continuously increasing installed capacity of offshore wind turbines, highly adaptable vertical axis wind turbines (VAWTs) are facing new opportunities. Large-scale offshore platforms need a megawatt installed capacity, at least 1∼2 MW, which requires the feasibility analysis of aerodynamic characteristics for large-scale VAWTs. Due to the unsteady aerodynamic phenomenon, i.e. the dynamic stall phenomenon, the power output of VAWTs is very sensitive to the variations of Reynolds number and reduced frequency, which are closely related to the scale of wind turbines. In order to explore the large-scale VAWTs for offshore platforms, three design methods are proposed: Increasing the Reynolds number; Decreasing reduced frequency; Forming an array. Their feasibility and economies are verified by a high-resolution numerical method, and the results show that increasing the Reynolds number could improve their power coefficients to 0.259 for a one-blade VAWT, while an excessive decrease of reduced frequency would lead to power losses. The form of installing one or more levels of VAWT arrays on a single platform is a better design scheme with averaged power coefficient of 0.326 and a blade weighing 2.7 tons per 10 MW, and for large offshore platforms, it could reach the lowest levelized cost of energy.