Design, Fabrication, and Experimental Validation of a Truncated Curved-Blade Rotor Based on Fibonacci Spiral Geometry for Vertical-Axis Wind Turbines

This study presents the design, fabrication, and experimental validation of a vertical-axis wind turbine (VAWT) rotor with truncated curved blades, whose geometry is rigorously based on the Fibonacci spiral and the aspect ratio defined by the golden ratio. The proposed configuration aims to enhance aerodynamic performance and energy conversion efficiency for small-scale wind energy applications, particularly in low to moderate wind speed regimes. The rotor was conceived as an alternative solution for decentralized generation systems and hybrid renewable energy configurations.

The aerodynamic behavior and operational performance of the proposed rotor were evaluated through a comprehensive experimental campaign that included controlled wind tunnel testing at laboratory scale and validation under real operating conditions. To systematically analyze the influence of design and operational parameters, a full factorial experimental design N=3KN = 3^KN=3K was implemented, considering two primary input factors (K = 2): the number of blades (NA = 2, 4, and 6) and the wind speed (Vv) at three levels, namely 6.4 m/s (low), 7.6 m/s (medium), and 8.8 m/s (high). The experimental setup was conducted in a wind tunnel with a controllable velocity range from 2.5 to 10 m/s, allowing precise regulation of the flow conditions.

The response variables analyzed included the available wind power (Pe), rotor mechanical power (Pr), tip-speed ratio (TSR), power coefficient (Cp), and rotational speed (rpm). Based on the experimental data, empirical mathematical models were developed to quantify the effect of the selected factors on power generation, aerodynamic efficiency, rotational dynamics, and TSR behavior. These models enabled a detailed assessment of performance trends and interactions between blade number and wind speed.

The experimental results reveal power coefficient values ranging from 0.55 to 0.57, indicating a high level of aerodynamic efficiency for a vertical-axis configuration. The available wind power varied between 0.588 and 1.586 kW, while the rotor mechanical power ranged from 0.344 to 0.887 kW. The TSR values were found between 0.64 and 0.85, and the rotational speeds varied from 155.6 to 288.62 rpm, depending on the operating conditions and blade configuration.

Overall, the obtained results demonstrate that the proposed Fibonacci-based rotor exhibits robust aerodynamic performance and stable operational behavior, positioning it as a viable and efficient alternative for mini wind energy systems and hybrid mini wind–solar generation schemes. The integration of Fibonacci spiral geometry and golden ratio proportions provides a promising design pathway for improving the performance of vertical-axis wind turbines in distributed renewable energy applications.