An Experimentally Validated Lumped Circuit Model for Piezoelectric and Electrodynamic Hybrid Harvesters

Energy harvesters transform the ambient energy into usable electrical form that can be potentially used by sensors and other low-power devices. In this paper, modeling of a hybrid energy harvester that is composed of piezoelectric and electrodynamic mechanisms of energy conversion is presented and the predictions from the model are corroborated by experimental results from two hybrid harvesters designed and fabricated for the purpose. A method of representing a hybrid energy harvester using lumped circuit elements is proposed. The optimal electrical loads are then determined with relative ease from the equivalent circuit of the harvester. A magnetic circuit that provides maximum electromechanical coupling in the electrodynamic domain is designed. Moreover, a curved piezoelectric beam is analyzed for a compact arrangement of both domains in a single harvester. Two hybrid energy harvesters having the same electrodynamic domain, one with curved piezoelectric beam and the other with a straight piezoelectric beam, are fabricated and evaluated for their performance in comparison with that estimated from the proposed model. Experimental models generating 1.7 mW from 0.5 gn input acceleration have been realized with at least 50% of conversion efficiency.