DEVELOPMENT OF A VIBRATION BASED ELECTRET-CANTILEVER MICRO ENERGY HARVESTER

Abstract

The need to provide an efficient, small, and economical power supply to wireless sensor networks (WSNs), portable/wearable electronic devices, and implantable biosensors, in order to make life more comfortable are continuously leading to more energy harvesting technology research that offer the promise of power sources with very light weight, and longer operating time than existing batteries. Although, there are several existing methods of supplying power to these devices, increasing their power supply through long-lasting, smart and economical sources, is still much more desired. Previous studies on vibration energy harvesting show that the electromagnetic and the piezoelectric approaches have been in use, and the electrostatic approach with electret power generators have been mainly with vibrations in the horizontal plane. This research focuses on a vertical vibration-based electret-cantilever micro energy harvester. In this research, an electrostatic method of micro-power generation was set up whereby an electret was used as an electrostatic inducing generator; which was spin-coated on copper substrate of 20mm x 20mm fabricated out of a 1.5mm thick copper plate; and the fabrication of the upper electrode was carried out in the form of cantilevers (T-shape and A-shape) from materials of copper with embedded glass epoxy. Operation of the micro-power generator in non-contact mode (n.c.m); close to contact mode (c.c.m); and contact mode (c.m) with frequency, electret voltage and external load were investigated. It was observed that for the T-shaped cantilever generator, maximum power of 48nW with electret’s surface potential of 171V, was generated towards the contact point of both lower and upper electrodes at 100Hz. Also, higher power was generated from T-shaped cantilever generator than from A-shaped cantilever generator. With the A-shaped cantilever generators, higher power was generated with increased electret surface potential. Also higher output power was generated with decrease in frequency, but the power peaks at a certain frequency which is generator dependent. Maximum power is transferred to the external load when it is equal in value to the internal resistance of the generator