Piezoelectric Energy Harvesting from a Magnetically Coupled Vibrational Source

This article presents a new magnetically coupled method to efficiently transfer vibrational energy from a source to a piezoelectric energy harvester. This method enables energy harvesting from vibration sources to which direct physical contact is not feasible or not preferred. The proposed harvester uses the piezoelectric cantilever in combination with two permanent magnets; one attached to the free end of the cantilever while the other magnet is firmly attached to the vibrational source facing the magnet on the cantilever. These magnets are kept in repulsive mode. As the source oscillates, the attached magnet follows the movement of the source. Due to this, the magnet on the cantilever gets perturbed and follows the movement of the source, bending the cantilever cyclically and generating a voltage output. This proposed arrangement not only (a) helps to scavenge energy without directly fitting the piezoelectric element and associated wiring on the vibrating source but also (b) provides more flexibility to adjust the resonant frequency, by varying the air gap between the magnets, (c) gives higher bandwidth compared to the conventional piezoelectric harvesters, ensuring less effect due to small mismatch between the frequency of the source and resonant frequency of the harvester. This is automatically achieved due to the nonlinearity of the system, introduced by the magnets. Prototypes of the proposed harvester and an equivalent conventional harvester are developed and tested. Results proved the functionality of the proposed harvester and showed superior performance in terms of gain, bandwidth, and charging time of a storage capacitor.