Galloping Based Wind Energy Harvesting using Piezoelectric Materials

Abstract

The purpose of this thesis was to investigate the mechanics of galloping based energy harvesting systems and to create techniques which will allow for energy harvesting at minimal wind speeds, while still producing an acceptable power output for sensor nodes used in wireless sensor networks. In order to achieve this, three main objectives were set. The first objective was to develop an analytical model based on a non-linear approximation technique known as the harmonic balance method. The analytical model was then qualitatively validated by comparing it with a numerical simulation and also a previously validated simulation technique involving equivalent circuit modelling (ECM). Following this, the model was also validated through comparing with wind tunnel experiments with a prototype GPEH. The second objective was to use the validated analytical model to investigate the effects of the electromechanical coupling strength (ke 2) on a GPEH, particularly on the cut-in wind speed, output power and the electrical damping created. This was achieved by performing a parametric study on the desired output of a GEPH over a range of wind speeds and ke 2 values. Using this technique, it was found that increasing the ke 2 also increased all three of these variables, but then they would interact in different ways. The final objective was to investigate the feasibility of utilizing a synchronized switch harvesting on inductor (SSHI) interface circuit to regulate and enhance the power output of a GPEH. This was achieved by running ECM simulations for the two configurations of the SSHI interface (Parallel SSHI and Series SSHI) for both high and low wind speeds, and comparing the data with a simulation utilizing a standard circuit interface. Wind tunnel experiments were also performed to confirm the simulation data. From the experimental results, it was discovered that the series SSHI circuit was not acceptable as an interface for GPEH, as it produced a lower power output for every configuration of the experiments. The parallel SSHI also failed to surpass the standard interface circuit in lower wind speeds, but shows promise in higher wind speeds as it achieved a maximum of 102% increase in power output.