Analysis of power output for piezoelectric energy harvesting systems

Abstract

Power harvesting refers to the practice of acquiring energy from the environment which would be otherwise wasted and converting it into usable electric energy. Much work has been done on studying the optimal AC power output, while little has considered the AC-DC output. This article investigates the optimal AC-DC power generation for a rectified piezoelectric device. In contrast with estimates based on various degrees of approximation in the recent literature, an analytic expression for the AC-DC power output is derived under steady-state operation. It shows that the harvested power depends on the input vibration characteristics (frequency and acceleration), the mass of the generator, the electrical load, the natural frequency, the mechanical damping ratio and the electromechanical coupling coefficient of the system. An effective power normalization scheme is provided to compare the relative performance and efficiency of devices. The theoretical predictions are validated and found to be in good agreement with both experimental observations and numerical simulations. Finally, several design guidelines are suggested for devices with large coupling coefficient and quality factor.

Efficiency of energy conversion for a piezoelectric power harvesting system

“…The consequence of pronounced shift in natural frequency from sc to oc leads to completely distinct optimization schemes for maximum power extraction. Shu and Lien [34] have studied the ac-dc power output for a rectified piezoelectricbased harvesting device. They have shown that the average harvested power has two identical peaks evaluated at two different electric loads at the respective operating points provided that k 2 e ζm 1 while it has only one peak otherwise.…”

Piezoelectric generator harvesting bike vibrations energy to supply portable devices

“…The vibrations energy harvesting principle using piezoelectric materials [4] is illustrated in figure 4. The conversion chain starts with a mechanical energy source: bike.…”

Piezoelectric MEMS Power Generators for Vibration Energy Harvesting

“…The measurement results are summarized in Table 3. The optimal load was found to be inversely proportional to the capacitance of the piezoelectric material [44,45]. For the same dimensions of the beam shape of the d31 and d33 mode devices, it was obvious that the capacitance of the d31 mode device was larger than the d33 mode device.…”