Modeling the performance of a micromachined piezoelectric energy harvester

Abstract

Piezoelectric energy microgenerators are devices that generate continuously electricity when they are subjected to varying mechanical strain due to e.g. ambient vibrations. This paper presents the mathematical analysis, modelling and validation of a miniaturized piezoelectric energy harvester based on ambient random vibrations. Aluminium nitride as piezoelectric material is arranged between two electrodes. The device design includes a silicon cantilever on which AlN film is deposited and which features a seismic mass at the end of the cantilever. EulerBernoulli energy approach and Hamilton's principle are applied for device modeling and analysis of the operation of the device at various acceleration values. The model shows good agreement with the experimental findings, thus giving confidence into model. Both mechanical and electrical characteristics are considered and compared with the experimental data, and good agreement is obtained. The developed analytical model can be applied for the design of piezoelectric microgenerators with enhanced performance. List of symbolsL Length of cantilever beam (m) B Width of cantilever beam (m) H Thickness of structural layer (m) T Thickness of piezoelectric layer (m) V Voltage across piezoelectric element (m) Z Coordinate parallel to beam thickness (m) X Coordinate parallel to beam length or axial coordinate (m) T k Kinetic energy (J) U Internal energy (J) W e Electrical work (J) W External work (J) q s Density of structural layer (kg m -3 ) q p Density of piezoelectric layer (kg m -3 ) U Displacement (M) S Applied strain (None) T Developed stress (Pa) EElectric field (V m -1 ) DElectric displacement (C m -2 ) dV s Differential volume of structural layer (m 3 ) dV p

Modeling, validation, and performance of low-frequency piezoelectric energy harvesters

“…A common problem, when a reduced-order model for piezoelectric energy harvesters is based on the Galerkin approximation, is the determination of the mode shapes and natural frequencies. The classical mode shapes of a fully covered piezoelectric cantilever beam is usually assumed for experiments where the piezoelectric material does not cover the whole substrate beam (Alamin et al, 2012; Hobeck and Inman, 2012; Masana and Daqaq, 2011; Song et al, 2009, 2010). In this work, we improve the prediction capability by deriving an analytical electromechanical model of a beam–mass energy harvester with a piezoelectric patch that does not cover the whole substrate beam.…”

A Low-Cost Nanostructured Multilayer Piezoelectric Energy Harvester for IoT Devices Using Three-Beam Lead-Free Architecture: A Complete Characterization

“…The beam dimensions are managed within a range of 12 to 17 mm in length, following a trapezoidal pattern. Piezoelectric energy harvesters have been demonstrated to achieve power levels in the range of 1-50 µW for typical ambient vibrations [26], or even over 100 µW with the caveat of using large accelerations and robust harvesters [23,27]. It is possible to improve the sensitivity of the energy harvesters in the frequency ranges available in the environment, usually up to 624 Hz [28].…”

High-efficiency MOSFET bridge rectifier for AlN MEMS cantilever vibration energy harvester

“…To measure this dependence, an AlN VEH was fabricated on a silicon-on-insulator (SOI) wafer with a 10µm-thick top Si layer and a 1-µm-thick buried oxide (BOX) layer using a standard semiconductor MEMS process. [6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22] The fabrication process flow is illustrated in Fig. 1.…”

“…A piezoelectric cantilever is preferable for this type of VEH. [6][7][8][9][10] A cantilever VEH generates alternating current (AC) power, and thus the use of a highefficiency rectifier circuit in combination with low-power electronics is highly important because the obtainable power is very small.…”