Hybrid electromagnetic-piezoelectric transduction for a frequency up-converted energy harvester

This paper presents a novel low frequency vibration energy harvester with a contact based frequency upconversion and hybrid electromagnetic-piezoelectric transduction. The electromagnetic generator is proposed as the power source for wearable electronic devices, while an independent piezoelectric generator is used to provide power to an active rectification circuit for conditioning of the electromagnetic power output and thus increasing the efficiency of the harvester. A mathematical model of the proposed structure is developed and demonstrated by simulation study. Preliminary experimental results from a prototype structure give an average power output of 46.2μW and 3.6μW at an excitation frequency of 5Hz from the electromagnetic and piezoelectric transducers respectively - sufficient to drive ultra-low-power circuits such as a distributed monitoring sensor. Comparison between the model predictions and the experimental results show a good correlation at the datum point under investigation, with an average error of 8.6% for the two transducers.