Design and evaluation of a piezoelectric-electromagnetic energy harvester with a lever structure

Abstract

This paper proposes a piezoelectric-electromagnetic energy harvester with a lever structure. The prototype combines electro-magnetic energy harvester (EMH) and piezoelectric energy harvester (PEH) organically, which improves the efficiency of energy harvesting. Combining Faraday’s law of electromagnetism with a spring-mass damped system, a physical model is developed and dynamic curves are predicted at different speeds. The output voltage and power of PEH and EMH are compared theoretically and experimentally, EMH performs better at lower loads and PEH is more dominant when the load resistance is high. Experiments have demonstrated that the coupling effect of EMH and PEH is relatively weak. Consequently, it is advisable to utilise the respective advantages of these two concepts by separating them. When the number of rotor contacts is 3, and the magnet diameter and number are 20 mm and 8 respectively, the prototype output is optimal. When the external load is 2KΩ, EMH reaches a maximum power of 5.06mW, whereas PEH output reaches a maximum of 1.04mW when the external load is 10KΩ. A series of experimental tests demonstrate that the prototype is capable of simultaneously providing power to two devices.