Dimensionless optimization of piezoelectric vibration energy harvesters with different interface circuits

Abstract

Conversion of mechanical vibration energy into electric energy could provide reliable and efficient energy utilization. Both the harvested resonant power and the energy efficiency have been studied based on a single degree of freedom weak electromechanical coupling piezoelectric vibration energy harvester and normalized in a dimensionless form. Performance optimizations have been conducted for the energy harvester connected with different interface circuits in terms of normalized harvested resonant power and resonant energy harvesting efficiency to identify both qualitatively and quantitatively the best energy extraction and storage interface circuit. Both the dimensionless harvested resonant power and the resonant energy harvesting efficiency formulae have been normalized to contain only two normalized variables of resistance and force factor regardless of the size and excitation magnitude of the energy harvesters.

Coupling analysis of linear vibration energy harvesting systems

“…According to Guyomar et al [3], the force factor α and the blocking capacitance of the piezoelectric insert C 0 , are respectively defined as: where e 33 and ε S 33 are the piezoelectric constant and permittivity, respectively, and A, L are the piezoelectric insert surface area and thickness, respectively. According to the derivation in [21], the electrical load resistance and force factor are normalised into two dimensionless variables of R N and α N , which are given by:…”

“…Therefore, the dimensionless resistance R N defined in [20,21] reflects how close the harvesting circuit oscillation is to the resonance. Physical meaning of α N will be given in the sections below.…”

“…When s ¼ iU ω, consider a small damping, at the mechanical resonance, ωE(K/M) 0.5 , which represents a weak coupling, the dimensionless resonant mean harvested power can be derived [21] and is given by: …”

“…As a matter of fact, some of the piezoelectric vibration energy harvesters work more efficiently in the middle and high frequency than in the low frequency [21,26]. In the middle or high frequency, the established methods are not able to reliably predict the vibration energy harvesting performances of a series of vibration energy harvester systems of the same design.…”

“…The coupling loss factor has never been related to the electro-mechanical coupling factor k 2 e , although they are two different concepts. Wang et al [20,21] expressed dimensionless harvested power and energy harvesting efficiency as functions of only two dimensionless variables: dimensionless resistance R N and dimensionless force factor α N . However, they did not clearly indicate physical meanings of the dimensionless resistance R N and dimensionless force factor α N .…”