Vibrations energy harvesters based on trees, cantilever beams, flexible tubes and variation of parameters

Abstract

The aim of this thesis is to study vibrations energy harvesters based on trees, cantilever beams, flexible tubes and variable geometric and physical parameters. We first consider a design and testing of a device able of harvesting energy from trees vibrations. An experimental laboratory prototype constituted of a cantilever beam and an electromagnetic transducer is constructed. The vibration of the cantilever beam is generated by a rotative fan. We also investigate a pendulum electromechanical energy harvesting system (EHs) consisting of an electromechanical pendulum subjected to a wind excitation. The effects of a spring constant and of pendulum length have been analysed. For the both cases, the output voltage and power response of the system are analysed in terms of load resistance. A field investigation is carried out to find the amount of power that can be harvested with our device in our meteorological context. Because of the low-voltage amplitude of the vibration energy harvester (VEH), we propose a circuit to rectify and boost a low AC voltage to a high DC voltage. The circuitry uses Schottky diode and a voltage multiplier (octuplet) circuit for its optimum performance. This thesis aims also focus on an electrostatic vibration energy harvester (e-VEH) system with variable area, variable permittivity, and variable radius. Nonlinear oscillator equations are established for each case, and solved analytically and numerically. The power produced by each configuration of the harvester is presented in terms of resistive load, frequency and external excitation. A promising application is an increasing interest in the field of implantable biosensors. One of the application of this thesis considers the conversion of a pulsating fluid pressure in elastic tubes into electrical energy using a cylindrical electrostatic vibration energy harvester (e-VEH) attached to the tube. A special attention is paid on the case of blood flow in order to have energy that can be used to power artificial organs such as artificial pacemaker. It is found that the amount of power of the order of of Pmax = 0:47 mW can be obtained in the case of conversion of the pulsatile blood pressure into electrical energy for cylinder length of 30:0 mm and diameter of 25:0 mm.