Effect Of Mechanical Input Energy On Piezoelectric Energy Harvesting

Piezoelectric energy harvesting technology is an alternative source for powering low power electronics. The ability of piezoelectric materials to convert ambient vibrational energy into usable electrical energy is seen as a promising battery-free solution to be used in inhospitable areas to self-power electronics for a longer time with little maintenance. The goal of this research is to maximise the mechanical input: elastic strain energy experienced by a lead zirconium titanate (PZT) bilayer piezoelectric buzzer by introducing four different boundary conditions during loading. Investigation of how mechanical input from each of these boundary condition influences the stored electrical output is carried out. The effect of three different static loads on each of the stored electrical output for four boundary conditions are studied. In order to accurately compare the data, the mechanical input (elastic strain energy) is calculated while the electrical output (stored energy) is measured experimentally. Given the brittle nature of ceramics, the maximum load bearing capacity for the PZT ceramic disc is determined by mechanical tests such as the ball-on-the-ring and uniaxial compression tests. This is to ensure that the experiments do not fracture the sample. Results show that, by inducing a bending mode in the buzzer, mechanical input values almost four orders of magnitude higher can be reached when compared to boundary conditions without bending modes. A similar result was found for the stored electrical energy with values for the bending mode of almost three orders of magnitude higher than when no bending is involved. The comparison between the calculated mechanical input and the measured electrical output shows good agreement in the boundary conditions involving bending. The energy conversion is highly efficient for the full range of applied loads for these boundary conditions. In the case of non-bending boundary conditions, the stored electrical energy is one order of magnitude high than predicted for the mechanical input and thus the model is in poor agreement with experiment