Piezoelectricity and Energy Harvester Modelling

Abstract

The direct piezoelectric effect is well-suited for harnessing environmental vibrations and to convert them into usable electrical energy. Coated on a cantilever beam, piezoelectric ceramics allows simple energy harvesting without additional mechanical structures. In addition, relatively small external excitations result in output voltages of several volts which do not require low-efficient startup mechanisms as known from thermoelectric generators. In order to give the reader a feeling about what is important for developing interface circuitry for piezoelectric energy harvesters, the basics of piezoelectricity and its usage in energy harevsting are presented in this chapter. After the physical conversion principle has been introduced roughly, its application in cantilever beam harvesters is explained. The last two sections are about the modeling of kinetic, vibration based energy harvesters in general and piezoelectric energy harvesters in particular. Electrical equivalent circuits of the energy harvesters are essential for the simulation of entire energy harvesting systems composed of the mechanical harvester structure and the electrical interface circuitry on one hand, and on the other hand to understand their behavior by means of analytical calculations.