Modelagem de turbinas de vento verticais para regiões de vento de baixa velocidade: desempenho e optimização

Abstract

The urgent global transition to renewable energy sources, driven by growing concerns about climate change and the finite nature of fossil fuels, positions wind energy as a fundamental pillar. However, the application of traditional horizontal axis wind turbines (HAWTs) is often limited in regions characterized by low and variable wind speeds, common scenarios in urban and rural areas, especially in developing countries. In this context, vertical axis wind turbines (VAWTs), and particularly hybrid Savonius-Darrieus configurations, emerge as a highly promising alternative. These combine the self-starting capability in weak winds, inherent to the Savonius rotor, with the superior aerodynamic efficiency of the Darrieus rotor at higher speeds. This research aimed to develop a computational model to simulate the performance and optimize the design of vertical axis wind turbines intended to operate efficiently in regions with low wind speeds. The methodology employed an integrated, quantitative, exploratory, and computational approach. Advanced 3D modeling (Autodesk Fusion 360), detailed aerodynamic analysis through XII Computational Fluid Dynamics (CFD) with ANSYS Fluent, and optimization of aerodynamic profiles (Qblade, XFOIL, Xoptfoil), in addition to the use of Python for data processing, were utilized. The study focused on the analysis of specific aerodynamic profiles, such as NACA 63 415, and the simulation of the operation of various blade geometries and turbine configurations. Energy efficiency was evaluated as a function of variables such as angle of attack and number of blades. The results obtained demonstrated that the optimized NACA 63-415 airfoil showed significantly higher efficiency, resulting in higher lift coefficients (CL) and more efficient airflow behavior, with a notable improvement in the𝐶𝐿/𝐶𝐷 ratio. For the Darrieus turbine, the configuration with 4 blades and a Tip Speed Ratio (TSR) of approximately 2 revealed the best aerodynamic performance, optimizing power generation and stability. CFD simulations, confirmed by pressure and velocity contours, visually validated the expected behavior of the hybrid configuration: the Savonius rotor provides the initial torque required for self-starting in low wind speeds, while the Darrieus rotor assumes the main function of converting wind energy into useful power once in rotation. This study validates an innovative hybrid turbine model, specifically designed and optimized for low-intensity wind conditions, prevalent in regions such as Tete province, (Mozambique). The developed methodology and the ideas generated represent a significant contribution to the advancement of knowledge in wind energy and offer a solid technical basis for the development of turbine projects for supplying small rural and urban communities, especially where the average wind speed is not compatible with HAWTs. By promoting sustainable, low-cost, and accessible energy solutions, this work aims to boost energy inclusion and local socioeconomic development.