Exploring Optimal Configurations for a Wind Farm with Clusters of Darrieus VAWT, Using CFD Methodology

Due to the alarming increase in greenhouse gases, switching to clean, renewable energy sources like wind energy has become imperative. As a result, the use of different wind turbines to generate electricity increased worldwide. Meanwhile, Darrieus vertical axis wind turbines (VAWTs) have gained considerable popularity due to their acceptable efficiency. Individual wind turbines are not efficient enough for widespread use and are only suitable for providing domestic energy; therefore, they should be placed in the form of turbine clusters in wind farms. The wind farm configuration and cluster placement have specific considerations, including the rotors' optimal installation distance and rotational direction. In the present study, the rotors installation distance in an array including a cluster of three Darrieus rotors is investigated, and the CFD and Kriging optimization results ensured that the best installation distance is equal to 1.5 times the diameter (1.5D). Also, the CFD results for the rotor's rotational direction at the installation distance of 1.5D showed that when the lower downstream rotor is counter-rotating the leading rotor and clockwise, the overall efficiency of the cluster increases by 67.1%. Additionally, two V-shaped and rhombic configurations are modeled, and the overall efficiency of each turbine in two different configurations is compared separately with the single turbine. In the optimum case, the overall efficiency of turbine A in the V-shaped configuration of three turbines and the rhombic configuration of 12 turbines improved by 54% and 36%, respectively, compared to the single turbine. The study of the streamlines showed that the main reason for improving the performance in the V-shaped configuration is the favorable velocity gradient around the blade, and the decrease in overall efficiency in the V-shaped and rhomboid configurations is wake flow intensity and trapping between the rotors which cause the stagnation zone.