Energy harvesting properties of flexible piezoelectrets under wind-induced vibration

• A novel flexible flag-swing piezoelectret energy harvester (PEH) is proposed • The piezoelectret exhibits a high transverse piezoelectric coefficient of 0.235 V·m/N. • A peak power density of 118 μW/cm³ and Vpp of 9.6 V are achieved at 8 m/s. • FSI simulation reveals the vortex-induced vibration mechanism at the optimal performance point. • The operational limits and distinct failure modes of the flexible PEH are identified. Piezoelectrets, an innovative class of artificial electromechanical coupling materials, exhibit significant potential for applications in medical sensing and wearable devices. However, reports on the research of environmental energy harvesting based on the excellent piezoelectric-like effect of piezoelectret are relatively scarce. This study presents a novel flexible flag-swing piezoelectret energy harvester (PEH) developed through multi-layer polarization and pre-stretching techniques. The work couples experimental wind tunnel investigations with fluid-structure interaction (FSI) simulation to elucidate the energy conversion mechanism. For a 30 mm × 20 mm specimen, the PEH generated stable electrical output at wind speeds of 2–8 m/s, achieving a maximum peak-to-peak voltage (V_pp) of 9.6 V and an output power density of 118 µW/cm³. This performance demonstrates superior power density for a fully flexible harvester at low-to-moderate wind speeds. However, at wind speeds exceeding 10 m/s, the output voltage became unstable, resulting in erratic oscillations and reduced energy conversion efficiency. This work represents a theoretical innovation in the application of piezoelectrets for environmental energy harvesting and holds significant academic value.