Double-speed piezoelectric–electromagnetic hybrid energy harvester driven by cross-moving magnets

Abstract

Energy harvesters have gained popularity as green energy devices that transform mechanical energy from the environment into electricity. However, traditional piezoelectric energy harvesters are limited by narrowband response, and the output capability of electromagnetic energy harvesters is dependent on the rate of magnetic field changes on the coil, which is constrained by the device’s structure. To address these issues, this paper presents a hybrid energy harvester (HEH) that combines coils and arc magnets, forming an electromagnetic component (EMEH). Additionally, it incorporates a piezoelectric cantilever beam (PECB) as a piezoelectric component (PEH). Unlike traditional electromagnetic energy harvesters, this design utilizes two arc magnets to drive the rotating brackets, thereby achieving the opposite movement of the coil and magnet. This increases the relative velocity and consequently enhances the rate of magnetic field change on the coil. Simultaneously, it achieves frequency up-conversion by inducing vibration in the PECB through magnetic force. Under an external excitation of 5.5 Hz, the PEH achieves a maximum power of 0.362 mW at a load resistance of 330 kΩ, while the EMEH with 1200 turns of coil attains a maximum power of 8.74 mW at a load resistance of 110 Ω. The power density of the PEH reaches 94.96 μW cm−3. These results highlight the significant potential of the proposed energy harvester for powering low-power devices.