Coupled aero-structural-electrical modeling and sensitivity analysis of a bladeless resonant wind turbine with hybrid energy harvesting

Abstract Bladeless resonant wind turbines are an alternative technology for small-scale wind energy harvesting because they convert vortex-induced structural oscillations into electrical power without rotating blades. However, their efficiency is strongly affected by the coupled interaction between wake dynamics, structural vibration and energy harvesting. This work presents a reduced-order aero-structural-electrical model for a bladeless resonant wind turbine with hybrid electromagnetic–piezoelectric energy harvesting. The wake dynamics are represented using a Van der Pol-type oscillator, while the structural subsystem is modeled as an equivalent mast-beam cantilever system governed by the first Euler–Bernoulli bending mode. An effective modal mass formulation is incorporated to account for the modal participation of the continuous mast-beam system. The electromagnetic harvester is coupled to the mechanical equation through the induced current and the corresponding electromagnetic reaction force. The piezoelectric contribution is represented through an equivalent damping term and an associated harvested-power expression, so that the energy extracted by the piezoelectric subsystem is also reflected in the mechanical response. The novelty of the proposed framework lies in the integration of nonlinear wake dynamics, effective-modal structural behavior, electromagnetic mechanical feedback, equivalent piezoelectric energy extraction, and energetic admissibility criteria within a single reduced-order model for regime-conditioned performance assessment. A parametric sensitivity analysis was performed to evaluate the influence of aerodynamic, structural and harvesting variables on the lock-in condition, vibration response, harvested power and overall conversion efficiency. Energetic acceptance criteria were applied to avoid non-physical results in which the harvested electrical power exceeded the available wind power or the mechanical power transferred to the structural coordinate. Within the prescribed parameter domain and energetic acceptance criteria, the maximum model-predicted accepted efficiencies were approximately 24.50% in pre-resonance, 43.62% in resonance, and 42.70% in post-resonance. These values represent reduced-order numerical predictions normalized by the configuration-specific projected wind-power input and should not be interpreted as experimentally validated efficiencies. The dominant variables changed with the operating regime: the Strouhal number, cylinder density and vortex saturation were most relevant in pre-resonance; the number of electromagnetic generators, load resistance, coupling factor, electromagnetic coefficient and cylinder stiffness dominated in resonance; and the number of electromagnetic generators, coupling factor, cylinder diameter, cylinder stiffness and equivalent piezoelectric damping were the most influential variables in post-resonance. These results show that the efficiency of bladeless resonant wind turbines cannot be assessed from isolated component models, since mast geometry, modal structural properties, wake parameters and harvesting coefficients modify both the available mechanical energy and the electromechanical damping. The proposed model provides a preliminary design tool for identifying dominant variables before experimental prototyping or high-fidelity numerical simulations.