Research On In-plane Multi-directional Piezoelectric Wind Energy Harvester

Wind energy harvesting from wind induced vibration has the advantages of stability,small size and low-cost.Wind energy harvesters are quite appropriate to serve as the power supply of wireless sensing nodes.However,most researches have only sought to improve the performance of wind energy harvesters which can only work under a single wind direction.Unfortunately,the direction and speed of the natural wind are featured with even higher uncertainty,conventional energy harvesters from wind induced vibration are not compatible with the natural wind.Meanwhile,conventional energy harvesters have not protective equipment and their electromechanical transduction components are exposed in environment directly.They are susceptible to harsh environmental conditions.Thus,it is necessary to develop a new kind of wind energy harvesters that can collect wind energy from different direction efficiently and provide protection for the inner electromechanical transducer simultaneously.This thesis reports a kind of piezoelectric multi-directional wind energy harvester with protective structure.By modifying the structure of traditional wind energy harvesters,that is,fixing the electromechanical transducer into the bluff body;the bluff body can not only capture wind energy,but also protect the inner electromechanical transducer from being eroded by rain,snow and sand.In order to collect wind energy from different direction,a transduction structure with three arc-shaped piezoelectric composite beams is proposed.This structure transforms the 1-DOF vibration of wind energy harvester into 3-DOF vibration and makes wind energy harvesters have the ability of converting the wind energy from different wind direction into electricity.The main content of this study contains:Considering the uncertainty of the natural wind and the destructiveness of meteorological environment,a cassette wind energy harvester with the structure of threecoupled arc-shaped piezoelectric composite beam is developed;According to the proposed wind energy harvester,a mechanic-electric coupling model is established.The stiffness properties of the inner flexible structure and the aerodynamic characteristics of different bluff bodies are stimulated by numerical software ANSYS and Fluent respectively and their pros and cons are also evaluated.In order to optimize the mass of piezoelectric wind/vibration energy harvester,an mass optimization model is built.With the help of Rayleigh damping model,the functional relationship between the mass of bluff body(mass block)and the damping coefficient is obtained.By introducing this relationship into the traditional onset wind speed prediction model of piezoelectric wind energy harvester and the voltage prediction model of piezoelectric vibration energy harvester,the higher prediction accuracies are achieved.A series of protypes are manufactured and tested,the experimental results show that the protype with pure cylinder bluff body possess great wind direction compatibility,but its output power is as low as 12.24μW.Protypes equipped by the bluff body with finshaped plate can only exhibit a relatively high electric output under certain wind direction.Among them,the protype has the bluff body with four fin-shaped plates exhibits the highest output power.At the same time,by decreasing the mass of the bluff body,the onset wind speed of the wind energy harvester can be reduced and the output voltage can be increased.A power management circuit and a wireless temperature/humidity sensing node are designed by taking the properties of the proposed wind energy harvester into account.Powered by the protype that equipped with the bluff body with four fin-shaped plates,the wireless temperature/humidity sensing node can operate normally.