论文总字数：23378字

University of Michigan–Dearborn

ME4671

Senior Design Report

——Turbulence Energy Harvester

Adviser: Oleg Zikanov

Honor Code: We have neither given nor received aid on this project.

Youyi Huang

Content

Abstract 3

1. Introduction 4

2. Work Plan 6

3. Theoretical Background 8

1. Turbulence 8

2. Piezoelectricity 9

4. Analysis and Sample Calculations 11

1. Pre-analysis for Material Selection 11

2. FEA Analysis 13

3. Circuit Diagram 14

5. Prototype Development 14

1. Plastic Sheet 15

2. Circuit 15

3. Fixture 16

6. Experiment and results 17

7. Ethical, Social, Environmental and Political Aspects of the Project 19

8. Safety 23

9. Cost Analysis 23

10. Conclusion 24

11. Bibliography 24

Abstract

To generate electric in narrow place though turbulence flow, we design the turbulence energy harvester with a piezoelectric disk as a core, which can generate electric proportional to its deformation. Besides, to transfer the kinetic energy of wind to potential energy of the disk, we use a plastic sheet to collect the wind energy. Calculations and FEA analysis have been done to define the material and the shape to maximize the bend of piezoelectric disk attached on it. “L” frames as well as a timber board make up the fixture, so that the whole structure can be stable in wind. Finally, the experiments in wind tunnel prove our design a success and show how the distances and angles from the structure and obstacle affect the charging ability.

Turbulence Energy Harvester

Fig. 1.1

1. Introduction

The use of wind power for electricity production has been growing rapidly around the world as a result of rapid development of windmill generator as well as the increasing demand for renewable energy. However, there has never been a windmill in a crowd city but only in suburb. As we know, any flow at high Reynolds number has velocity consisting of two parts, mean flow and fluctuations. Windmill generator, the most common facility to produce electric, is only suitable for steady flows where mean flow dominates, and that’s why the windmill generators are always built in open space. To take use of turbulence flows which commonly occur in big cities, a structure that can generate energy from the kinetic energy associated with fluctuations is built in our project which is called “Turbulence Energy Harvester”.

The goals of the design are definite: Theoretical research; Build the structure; Analyze its feasibility; Test different factors and find out their influence on the efficiency of our design. 

First, it comes to the problem that where turbulence concentrates and how the turbulence effects, so that we can find the way to gather the energy from it. Having wiped off the feasibility of using the fan, we shifted the way of thinking and try to utilize vibration instead to achieve our target.

How to gather electricity from the vibration? It is beyond what we learned before. To simplify the problem, we think it as a problem to transfer kinetic energy to electric energy. There are many methods to finish this transfer and we find a common feature of these methods is that all of them need a medium, for example, electromagnetic energy used in wind-mills and thermal energy used in heat-engine plant. Thus, the problem seems a little bit easier and we find piezoelectric.

Piezoelectric is the core part of our design, it’s a phenomenon that electric occurs in response to the stress in typical kind of materials. One of the properties of piezoelectric we pay most attention to is the more deflection it has the higher volts it has.

An ABS plastic sheet has been shaped to gather wind energy and the piezoelectric disk is attached to the part where stress concentrated on it. A circuit is designed to collect the piezoelectric disk generates. 

Besides, to lower the degree of freedom of plastic sheet vibration as well as make the whole structure much stable in face of wind. The flagpole-like fixture has been built by hand with “T” frames, screws and a timber board.

Finally, to improve our design, experiments in wind tunnels have been done to verify whether the position of the structure and wind speed have effects on the efficiency of our design. A cylinder is used to simulate the building after which the turbulence flow generates. The result comes out that the charging efficient is highest when the distance is about 10 cm from the cylinder and the cylinder angle is 15 degrees to the flow direction(the angle is relative, we can change the angle of structures in real life but not buildings to reach the highest rate of efficiency).

Testing our equipment in the Wind Tunnel Laboratory

Fig. 1.1

2. Work Plan