Analysis, Design and implementation of Energy Harvesting Systems for Wireless Sensor Nodes.

Ph.DDOCTOR OF PHILOSOPH

Piezoelectric energy harvesting from wind-induced flutter

Piezoelectric energy harvesting from fluid flow, to power Ultra Low Power (ULP) devices, has gained interest among researchers over the last decade. In this research, a "leaf and stalk" construct was investigated to harvest energy from wind-induced flutter. Fundamental Fluid Structure Interaction (FSI) studies were carried out to experimentally determine the dependence of physical properties of highly compliant cantilever beams on their flutter onset and flutter frequency. The results indicated that the theoretical 2D scaling laws could be extended to 3D environment. Also, for the first time, theoretical and experimental analyses were carried out to understand flutter characteristics of slender connected body systems consisting of revolute hinge, when placed at various positions along the beam. The analysis showed that as the hinge position was varied from the leading edge to the trailing edge of the beam, the system transitioned to higher modes of flutter, thereby reducing the amount of harvestable energy. Several leaf-stalk configurations were also experimentally tested to investigate the possibility of energy harvesting from coupled bending-torsional flutter. High-speed videos were used to identify and differentiate the flutter modes of the configurations to validate the power output results. The results indicated that asymmetrical configurations, when subjected to flutter, are more prone to chaotic flapping and fatigue, thereby reducing the overall power output and effective lifespan of these harvesters. Therefore, two symmetrical-type harvesters were placed in stream-wise, cross-stream and vertical directions to identify the proximity effects of these harvesters on their power output. It was found that when two harvesters were placed in stream-wise direction, at a particular separation distance, the downstream harvester provided 20-40% high power compared to the upstream harvester. The overall purpose of this work was to develop a scalable energy harvesting system for urban sustainability, mainly to power ULP devices like sensors and LED lights