Optimal parameters and power characteristics of piezoelectric energy harvesters with an RC circuit

Abstract

A piezoelectric based energy harvesting scheme is proposed here which places a capacitor before the load in the conditioning circuit. It is well known that the impedance between the load and source contributes heavily to the performance of the energy harvesting system. The additional capacitor provides flexibility in meeting the optimal impedance value and can be used to expand the bandwidth of the system. A theoretical model of the system is derived and the response of the system as a function of both resistance and capacitance is studied. The analysis shows that the energy harvesting performance is dominated by a bifurcation occurring as the electromechanical coupling increases above a certain value, below this point the addition of an additional capacitor does not increase the performance of the systems and above the maximum power can be achieved at all point between these two bifurcation frequencies.Additionally, it has been found that the optimal capacitance is independent of the optimal resistance. Therefore, the necessary capacitance can be chosen and then the resistance determined to provide optimal energy harvesting at the desired frequencies. For systems with low coupling the optimal added capacitance is negative (additional power to the circuit) indicating that a second capacitor should not be used for. For systems with high coupling the optimal capacitance becomes positive for a range of values inside the bifurcation frequencies and can be used to extend the bandwidth of the harvesting system. The analysis also demonstrates that the same maximum energy can be harvested at any frequency; however, outside the two bifurcation frequencies the capacitor must be negative.

Non-linear energy harvesting from coupled impacting beams

“…The load resistance of the system can be varied in order to maximize the power generated. Liao et al [34] analysed an RC circuit to determine the optimal system parameters to maximize the energy harvested.…”

Coupling analysis of linear vibration energy harvesting systems

“…From Eqs. (10) and (26) in Table 4, the formulae of the resonant energy harvesting efficiency are interchangeable from the zero coupling to a strong coupling when the resonant energy harvesting efficiency is divided or multiplied by (R N ) 2 . Comparing Eqs.…”

“…Electro-mechanical coupling factor k 2 e of the electromagnetic and piezoelectric vibration energy harvesters was defined in [1,2,[5][6][7][8][9][10][11]15,19,[22][23][24], which is a numerical measure of the conversion efficiency between electrical and vibration energy. Electro-mechanical coupling factor k 2 e of piezoelectric materials is equal to squared piezoelectric coefficient of the piezoelectric disk divided by the product of the free stress permittivity and short-circuited elastic rigidity of the piezoelectric disk or equal to the squared force factor divided by the product of the short-circuited stiffness and the capacitance of the piezoelectric disk.…”

Energy Harvesting Technologies: Thick-Film Piezoelectric Microgenerator

“…The vibration energy harvesting of piezoelectric materials is based on the concept of shunt damping to control mechanical vibration [29], however, rather than dissipating the energy through joule heating, the energy is used to power some electronic devices.…”