Random Vibration Energy Harvesting by Piezoelectric Stack Charging the Battery

This paper highlights the electric energy harvesting system that consists of piezoelectric (PZT) stack transducer which is excited by random mechanical oscillating force and charges the Li-Ion battery. This battery is a power supply for LED lamp lighting. A very big electric capacitance of the multilayered PZT stack affects on the electric energy flow from PZT energy source to the electric sink. The reason for this influence is because the electric capacitance of the device, its mechanical losses and leakage increase along with the increased number of PZT layers. An electronic circuitry of the studied energy harvesting system provides the interfaces between the piezoelectric device and electric load. Such the circuits should match the input impedance of electric load (battery) and output impedance of voltage source (PZT stack). Basing on the experimental data and the finite element (FE) investigation we derive and tune the lumped model of multilayered PZT stack, which transforms the energy of low frequency mechanical excitation with random amplitudes and discretely distributed frequencies to the energy of electric current. In order to optimize an efficiency of harvester we find the number of PZT layers at constrained excitation parameters, stack's dimensions, and generated voltage required by the charging battery. The lumped model of the whole harvesting system has been built in SimElectronics / Simulink MATLAB© environment. It was also simulated to find the best harvesting system parameters.