Piezoelectric energy harvesting from rail track vibration using frequency up-conversion mechanism

Piezoelectric energy harvesting has great powering potential in railway applications, but current piezoelectric literature for rail track vibration mainly focuses on a single piezoelectric element or piezoelectric cantilever, whose output power is usually at the level of μW. In this work, a piezo stack energy harvester using the frequency up-conversion method with attractive magnetic force is proposed and experimentally validated for harvesting energy from rail track vibration. It consists of two parts, an inertial mass system and a piezo stack system. The frequency up-conversion mechanism is realised by allowing the inertial mass to attach and detach the piezo stack transducer periodically with the help of the attractive magnetic force. The attractive magnetic force contributes to the collision between the two systems, especially when the excitation frequency is near the resonant frequency. A theoretical model of the proposed energy harvester considering the colliding motion and magnetic force is established. A prototype is fabricated and can generate a peak power of 96.69 mW and average power of 2.59 mW at an input acceleration of 1 g applied at 9 Hz with an optimum load impedance of 200 ω.