Design And Development Of Miniature Electromagnetic Micro-Generator For Harvesting Energy From Vibration.
DESIGN AND DEVELOPMENT OF MINIATURE ELECTROMAGNETIC
MICRO-GENERATOR FOR HARVESTING ENERGY FROM VIBRATION
WONG SHI QUAN
UNIVERSITI TEKNIKAL MALAYSIA MELAKA
Design and Development of Miniature Electromagnetic Micro-Generator for
Harvesting Energy from Vibration
WONG SHI QUAN
This Report Is Submitted In Partial Fulfilment of Requirements for the Bachelor
Degree of Electronic Engineering (Telecommunication Electronics)
Fakulti Kejuruteraan Elektronik dan Kejuruteraan Komputer
Universiti Teknikal Malaysia Melaka
JUNE 2015
v
To my dearest parents and my beloved friends
vi
ACKNOWLEDGEMENT
First of all, I would like to express my gratitude to my parents who always
support and encourage me when completing my degree final year project.
Next, I would like to thank my project supervisor, Dr Kok Swee Leong who
guided me throughout the whole project. He had advised me and taught me various
things and knowledge in relevant field which aided me in completing this project.
With his motivation and encouragement, I gained my confidence and finished this
project.
Lastly, I would like to thank my friends who always standby me and willing
to help me during the research. Special thanks to my housemates, Lee Kian Loong
and Teh Wei Yang who gave me suggestion on my project and helped me in data
recording when I was desperate for a helping hand.
vii
ABSTRACT
Nowadays, green energy is widely use in our life and it becomes popular
since it is pollution free, energy conserve and cost saving. There are various types of
green energy which we can harvest from the environment such as the solar energy,
hydro energy, wind energy and vibration energy. One of the common energy we
found in our surrounding is vibration energy. Moving cars, refrigerator, washing
machine and industrial machine are the sources of the vibration energy. The vibration
energy can be harvested and converted into useful electrical energy which can use to
power up small electrical devices such as wireless sensor node.
In this project, a miniature electromagnetic micro-generator has been
designed and developed to harvest the free vibration energy from the vibration
source. The generator works purely based on electromagnetic theory which use the
magnetic induction to generate electricity.
The structure of the generator consists of a cantilever, Neodymium magnets,
magnetic wire coil and a rectifier circuit. The size of the generator is small with a
volume approximately 24cm3 which made it capable to be deployed in some
inaccessible place. Besides, the generator can be tuned to fit with the vibration source
by adjusting the length of the cantilever. It is capable to produce a maximum power
of 0.1Watt with a 2.1G vibration source at its resonant frequency of 49.1Hz.
viii
ABSTRAK
Pada masa kini, tenaga hijau diguna secara meluas dalam kehidupan kita dan
ia menjadi popular kerana ia tidak mencemarkan persekitaran, jimat cost dan dapat
dipulihkan. Terdapat pelbagai jenis tenaga hijau yang kita boleh dapat daripada alam
sekitar seperti tenaga suria, tenaga hidro, tenaga angin dan tenaga getaran. Salah satu
tenaga yang biasa kita dapati di sekitar kita adalah tenaga getaran. Kereta yang
berjalan, peti sejuk, mesin basuh dan mesin dalam industri merupakan sumber tenaga
getaran. Tenaga getaran dapat dikumpul dan ditransformakan kepada tenaga elektrik
yang berguna untuk meghidupkan alat-alat elektronik yang kecil seperti sensor tanpa
wayar.
Dalam projek ini, sebuah mesin penjana kecil elektromagnet telah direka dan
dicipta untuk menjana tenaga elektrik daripada sumber tenaga getaran dalam alam
sekitar. Mesin penjana itu berfungsi berdasarkan teori elektromagnetik yang
menggunakan induksi magnet untuk menjana tenaga elektrik.
Struktur mesin penjana terdiri daripada julur, magnet Neodymium, gegelung
wayar magnet dan litar penerus. Mesin penjana itu bersaiz kecil dengan isi padu
lebih kurang 24cm3, oleh itu ia dapat dipasang dan diguna dalam tempat atau ruang
yang kecil. Selain itu, ia dapat dilaraskan supaya muat dengan sumber getaran
dengan mengubah panjang julur ia. Ia mampu menghasilkan kuasa maksimum
ix
sebanyak 0.1Watt dengan sumber getaran 2.1G pada frekuensi salunan sebanyak
49.1Hz.
x
CONTENT
CHAPTER CONTENTS
I
PAGE
PROJECT TITLE
i
PROJECT STATUS CONFIRMATION FORM
ii
DECLARATION FORM
iii
DEDICATION
v
ACKNOWLEDGEMENT
vi
ABSTRACT
vii
CONTENTS
x
LIST OF TABLES
xiii
LIST OF FIGURES
xiv
INTRODUCTION
1.1
Project Overview
1
1.2
Motivation
2
1.3
Problem Statement
3
1.4
Objectives
3
1.5
Significant of project
4
1.6
Scope
4
1.7
Thesis outline
5
xi
II
LITERATURE REVIEW
2.1
Types of vibration energy harvester
2.1.1 Electromagnetic
based
vibration
6
energy 6
harvester
2.1.2 Magneto electric based vibration energy 12
harvester
III
IV
2.1.3 Piezoelectric Based vibration energy harvester
13
2.1.4 Hybrid energy harvester
17
2.2
Tuning Techniques
19
2.3
Rectifier circuit
23
2.3.1 Full wave bridge rectifier circuit
23
2.3.2 Voltage multiplier circuit
26
2.3.2.1 Voltage doubler circuit
27
2.3.2.2 DC Voltage Tripler Circuit
28
2.3.2.3 DC Voltage Quadrupler Circuit
28
RESEARCH METHODOLOGY
29
3.1
Design of electromagnetic generator
29
3.2
Choose of material
31
3.3
Building of electromagnetic generator
32
3.4
Experiment setting
35
3.5
Data collecting and processing
38
3.6
Rectifying circuit design
38
3.7
Prototyping
40
3.8
Flow Chart
41
RESULT
4.1
42
Factors that affect the resonant frequency of the 42
xii
cantilever
4.1.1 Effect of cantilever’s length
43
4.1.2 Effect of additional 2 extra magnets and mass 46
on the tip of the cantilever
V
4.1.3 Effect of the thickness of the cantilever
47
4.2
G-level measurement
49
4.3
Output analysis of electromagnetic generator
51
CONCLUSION AND RECOMMENDATIONS
54
5.1
Conclusion
54
5.2
Recommendations
55
REFERENCES
56
APPENDIX A
58
APPENDIX B
64
APPENDIX C
65
xiii
LIST OF TABLES
NO TITLE
2.1
PAGE
Young’s modulus of the materials aluminium, stainless steel and 21
copper
2.2
Summary of the result obtained from the parameters of each material
23
xiv
LIST OF FIGURES
NO
TITLE
PAGE
2.1
Vibration energy harvester designed by Gherca and Olaru
7
2.2
Layer structure of micro-electromagnetic vibration energy harvester
8
2.3
Fabricated energy harvester
10
2.4
Micro-fabricated silicon spiral spring
10
2.5
PDMS packaging substrate with multi-turned coil
11
2.6
Cross-sectional view of the micro-fabricated electromagnetic power
11
generator
2.7
Magneto electric energy harvester
12
2.8
Piezoelectric layers.
12
2.9
Structure of the meandering piezoelectric vibration energy harvester
14
2.10 Size of meandering piezoelectric vibration energy harvester
14
compared to a coin
2.11 Testing of electrode meandering energy harvester mounted
15
2.12 Schematic drawing of the piezoelectric cantilever
16
2.13 Cross-section drawing of the piezoelectric cantilever
16
2.14 Cross sectional view of magnets part
17
2.15 Testing of hybrid energy harvester
18
2.16 Structure of hybrid energy generator (HPVG)
19
2.17 Results of resonance frequency by varying the cantilever's length for
21
different materials.
2.18 Results of resonance frequency by varying the cantilever's thickness
22
for different materials
2.19 Results of resonance frequency by varying the cantilever's width for
different materials
22
xv
2.20 Full wave bridge rectifier
24
2.21 Rectifier in positive cycle
24
2.22 Rectifier in negative cycle
25
2.23 Function of smoothing capacitor
25
2.24 Basic multiplier circuit
26
2.25 Half wave voltage doubler
27
2.26 Voltage Tripler circuit
28
2.27 Voltage Quadrupler Circuit
28
3.1
Design of generator’s base
30
3.2
Design of cantilever
30
3.3
Design of electromagnetic generator
31
3.4
3D printed generator base
32
3.5
Cantilevers with different length
32
3.6
Magnetic wire coils
33
3.7
Neodymium magnets
34
3.8
Electromagnetic generator
34
3.9
Devices used in experiment
35
3.10 Setup of electromagnetic generator on electrical shaker
36
3.11 Acceleration sensor node by MicroStrain
37
3.12 Wireless data receiver
37
3.13 Deployment of acceleration sensor node on electric shaker
38
3.14 Normal full-wave bridge rectifier circuit
39
3.15 Voltage doubler circuit
39
3.16 Front view of the fabricated circuit
39
3.17 Back view of the fabricated circuit
39
3.18 3D view of electromagnetic genarator
40
3.19 Side view of electromagnetic generator
40
4.1
43
Graph of Induced voltage against frequency for 3.5cm cantilever
length
4.2
Graph of Induced voltage against frequency for 4cm cantilever length 43
4.3
Graph of Induced voltage against frequency for 4.5cm cantilever
44
length
4.4
Graph of Induced voltage against frequency for 5cm cantilever length 44
xvi
4.5
Comparison between different cantilever lengths
45
4.6
Graph of Induced voltage against frequency for cantilever’s tip with
46
additional 2 magnets
4.7
Difference in output for cantilever with and without additional
47
magnets
4.8
Graph of Induced voltage against frequency for cantilever with
47
0.35mm thickness.
4.9
Graph of difference in output for cantilever with different thickness
48
4.10 Response of vibration in time domain and frequency domain
50
4.11 Acceleration graph in frequency domain
50
4.12 AC output voltage during resonant frequency
51
4.13 Measuring DC output voltage
52
4.14 DC output voltage
52
4.15 Measuring DC output current
52
4.16 DC output current
52
1
CHAPTER 1
INTRODUCTION
1.1
Project Overview
Many research activities has been carried out in the area of micro-energy
harvesting which aimed to find an alternative solutions to batteries, which required
charging and replacement, as power supply of low power devices (Bouendeu et al.
2009). The main idea of micro-energy harvesting is to obtain free environment
energy and transform the energy into useful electrical energy which can be used to
power micro-electronic devices like wireless sensor nodes. Hence, energy harvesting
system is invented to replace the conventional chemical batteries that lead to costly
replacement fees in a huge wireless sensor network and cause chemical pollution
problems to the environment. The demand for energy harvesting system has been
growing rapidly due to the wide application of wireless sensor nodes and mobile
electronic devices (Yang et al. 2012).
Free environment energy can be found in the form of solar, thermal, chemical
or mechanical vibration. Inferior to solar energy, mechanical energy from the
ambient vibration source or known as vibration energy has been one of the major
power sources for energy harvesting system. Vibration energy is a green energy
which can be harvested from any moving mechanism of our surrounding including
biological and mechanical movement. There are various vibration sources in our
surrounding such as common household goods (refrigerator, washing machines and
2
air conditioners), industrial plant equipment, machines, moving vehicles such as
automobiles and structures such as buildings and bridges. The energy harvested can
be transform into useful electrical energy to power up small electronic devices such
as the sensor node. Wireless sensor node which is small in size, low power
consumption and its deployment in some inaccessible location has made the
vibration energy as an ideal and inexhaustible power source.
The vibration energy harvested is transform into electrical energy using
electromagnetic, electrostatic and piezoelectric transduction mechanisms. The
amount of energy generated by these approaches fundamentally depends upon the
quantity and form of the kinetic energy available in the application environment and
the efficiency of the generator as well as the power conversion electronics (Beeby et
al. 2007).
This project aimed to design and develop a miniature electromagnetic microgenerator for harvesting energy from ambient vibration source. The micro-generator
designed is small in size and works based on electromagnetic induction to transform
kinetic energy harvested from ambient vibration source into useful electrical energy.
Its basic structure consists of a cantilever, magnets, magnetic coils and an electrical
circuit. The power generated was measured tested to power up small electronics.
1.2
Motivation
Battery is a convenient power source for small electronic devices in our daily
life. However, the conventional use of chemical batteries in electronics such as
wireless sensor nodes in a large wireless network could be a problem for its user. The
batteries apply in the wireless sensor nodes network need to be replaced or recharged
from time to time to ensure a constant power supply. Hence, the user needs to spend
a costly replacement fees when the batteries of the sensors nodes are drained.
Besides, the replaced batteries will eventually become a chemical waste that causes
environment pollution.
3
The application of vibration energy harvester will serve as an alternative
power source which can eliminates the costly replacement fees of batteries in large
wireless sensor network and reduces the waste of chemical batteries.
1.3
Problem Statement
Conventional electromagnetic generator structure is big in size because it
consists of large magnets and large number of wire coils in order to produce
sufficient energy for the electrical device. Hence, it is inconvenient for the
electromagnetic generator to integrate with wireless sensor nodes which designed to
be deployed in a large scale of area and some inaccessible place for monitoring
purpose.
Besides, conventional electromagnetic generator produces a low output
voltage which is impossible to be rectified by the diodes. The output current must be
rectified into DC as electrical supply for electronic device. Hence, the output voltage
of the electromagnetic generator must be higher than 0.7V, which is the operating
voltage of a diode.
1.4
Objectives
The objective of this project is to design and develop a miniature
electromagnetic micro-generator which operates at its resonant frequency to function
with maximum efficiency. The size of the electromagnetic generator is aimed to
design in a 30- 130cm3 range to be integrated with the small electronic devices such
as wireless sensor node. Besides, the project aimed to determine the maximum power
generated by the micro-generator when it is tuned to work at its resonant frequency
resonant frequency. Lastly, a rectifier circuit is developed to rectify the output
voltage for the power of wireless sensor node.
4
1.5
Significant of project
The electromagnetic generator proposed in this project has a high
sustainability as it does not need to be replaced like conventional batteries. After the
electromagnetic generator is deployed, it can be left to work on its own as long as
there is any moving mechanism which served as the power source.
Besides, the miniature size of the electromagnetic generator made it possible
to be deployed in some inaccessible place for a long term application. This feature
makes the electromagnetic generator suitable to integrate with wireless sensor nodes
in a large wireless sensor network for surrounding condition monitoring purposes.
Last but not least, the electromagnetic generator may gain a high
marketability since it is a green technology which saves cost and energy. Free
vibrational kinetic energy can be harvested from the surrounding to be used for
powering small electronic devices instead of using chemical batteries which may
cause pollution and require scheduled replacement.
1.6
Scope
The electromagnetic micro-generator is work based on the oscillation of a
cantilever equipped with four Neodymium magnets from Bunting Magnetics Europe
Ltd work and a magnetic coil winded using magnetic wires from Magnetic Sensor
Systems Ltd. The working principle of the micro-generator is solely depended on
electromagnetic theory.
The physical volume of the micro-generator is approximately 24cm3. The
micro-generator has a vibrating frequencies range of 5Hz- 150Hz and a vibrating
level less than 50ms-2. It can only work efficiently with a limited bandwidth near the
resonant frequency of the vibration source apply and capable of generate an output
power of 0.1 to 5 milliWatts.
5
1.7
Thesis outline
Project Introduction provides a brief overview of this project that helps reader
to visualize and understand the aim of the project. Motivation and significant of this
project is discussed to explain the reason of why this project is proposed and its
advantages. Scope is then outlined to set the specifications and limitation of the
project proposed.
The Literature Review section presents some model of energy harvesters and
tuning methods used in previous researches. It shows the relation between this
project and those tasks done by other researchers.
Research Methodology part presents the overall process flow of this project
includes the design of the micro-generator proposed, construction of experimental
model, experiment test and optimising, as well as method of data collecting and
analysing.
Results and Discussion provides the reader with all the data obtained and
achievement of the research. The findings of this project are presented with the help
of tables, figures and graphs. This section also used to define the achievement of the
objectives set in the beginning of this research.
Lastly, the Conclusion and Recommendation section summarises the results
obtained after this research and recommends some direction for the future research of
energy harvesting system. Finally, it will discuss the knowledge obtained from this
research and contribution of this project to the university.
6
CHAPTER 2
LITERATURE REVIEW
This chapter presents some projects related to energy harvesting system done
by other researchers. It consists of various type of energy harvesting systems and
tuning techniques developed to harvest vibration energy from the surrounding.
Furthermore, literature review on rectifier circuit is also included in this section.
2.1
Types of vibration energy harvester
There are several types of energy harvester which harvest kinetic energy from
surrounding vibration mechanism to generate useful electrical energy for small
electronics use. The vibrational energy harvester can be differentiated into 3 main
categories which are electromagnetic, piezoelectric, the fusion of both categories
(hybrid) and magneto electric.
2.1.1
Electromagnetic based vibration energy harvester
Gherca and Olaru designed a vibration energy harvester that worked on
ambient vibration by the mean of electromagnetic induction (Ă & Olaru 2011). The
harvesting generator works at low frequencies which close to ambient vibration to
7
generate electrical energy. However, it can also be adapted to work at high values of
frequency.
Figure 2.1 shows the cross sectional area view of vibration energy harvester
designed based on the electromagnetic induction theory. The basic operating
principle of the system is a moving magnetic component inside a coil which capable
to generate electricity when the magnetic component sliding across the coil. The
mobile magnetic component is a rare earth permanent magnet, NdFeB, which is high
in energy density and good in sustainability. The housing that held the magnet in
place is winded with 2 windings of coil connected in phase opposition which use to
deliver the electricity generated when magnetic induction occurred. The magnetic
component is held “floating” by 2 fixed magnets with same pole oriented to the
mobile magnetic component, located at the top and lower covers respectively.
Figure 2.1: Vibration energy harvester designed by Gherca and Olaru. (Ă & Olaru
2011)
Ferro fluids are used as a lubricating agent attached to the permanent magnet.
The Ferro fluids are a dispersion of magnetic particles (~10nm) in liquid base with
approximately of 1023 particles per cubic meter. The Ferro fluid possesses the
common properties of liquids as well as magnetic material.
MICRO-GENERATOR FOR HARVESTING ENERGY FROM VIBRATION
WONG SHI QUAN
UNIVERSITI TEKNIKAL MALAYSIA MELAKA
Design and Development of Miniature Electromagnetic Micro-Generator for
Harvesting Energy from Vibration
WONG SHI QUAN
This Report Is Submitted In Partial Fulfilment of Requirements for the Bachelor
Degree of Electronic Engineering (Telecommunication Electronics)
Fakulti Kejuruteraan Elektronik dan Kejuruteraan Komputer
Universiti Teknikal Malaysia Melaka
JUNE 2015
v
To my dearest parents and my beloved friends
vi
ACKNOWLEDGEMENT
First of all, I would like to express my gratitude to my parents who always
support and encourage me when completing my degree final year project.
Next, I would like to thank my project supervisor, Dr Kok Swee Leong who
guided me throughout the whole project. He had advised me and taught me various
things and knowledge in relevant field which aided me in completing this project.
With his motivation and encouragement, I gained my confidence and finished this
project.
Lastly, I would like to thank my friends who always standby me and willing
to help me during the research. Special thanks to my housemates, Lee Kian Loong
and Teh Wei Yang who gave me suggestion on my project and helped me in data
recording when I was desperate for a helping hand.
vii
ABSTRACT
Nowadays, green energy is widely use in our life and it becomes popular
since it is pollution free, energy conserve and cost saving. There are various types of
green energy which we can harvest from the environment such as the solar energy,
hydro energy, wind energy and vibration energy. One of the common energy we
found in our surrounding is vibration energy. Moving cars, refrigerator, washing
machine and industrial machine are the sources of the vibration energy. The vibration
energy can be harvested and converted into useful electrical energy which can use to
power up small electrical devices such as wireless sensor node.
In this project, a miniature electromagnetic micro-generator has been
designed and developed to harvest the free vibration energy from the vibration
source. The generator works purely based on electromagnetic theory which use the
magnetic induction to generate electricity.
The structure of the generator consists of a cantilever, Neodymium magnets,
magnetic wire coil and a rectifier circuit. The size of the generator is small with a
volume approximately 24cm3 which made it capable to be deployed in some
inaccessible place. Besides, the generator can be tuned to fit with the vibration source
by adjusting the length of the cantilever. It is capable to produce a maximum power
of 0.1Watt with a 2.1G vibration source at its resonant frequency of 49.1Hz.
viii
ABSTRAK
Pada masa kini, tenaga hijau diguna secara meluas dalam kehidupan kita dan
ia menjadi popular kerana ia tidak mencemarkan persekitaran, jimat cost dan dapat
dipulihkan. Terdapat pelbagai jenis tenaga hijau yang kita boleh dapat daripada alam
sekitar seperti tenaga suria, tenaga hidro, tenaga angin dan tenaga getaran. Salah satu
tenaga yang biasa kita dapati di sekitar kita adalah tenaga getaran. Kereta yang
berjalan, peti sejuk, mesin basuh dan mesin dalam industri merupakan sumber tenaga
getaran. Tenaga getaran dapat dikumpul dan ditransformakan kepada tenaga elektrik
yang berguna untuk meghidupkan alat-alat elektronik yang kecil seperti sensor tanpa
wayar.
Dalam projek ini, sebuah mesin penjana kecil elektromagnet telah direka dan
dicipta untuk menjana tenaga elektrik daripada sumber tenaga getaran dalam alam
sekitar. Mesin penjana itu berfungsi berdasarkan teori elektromagnetik yang
menggunakan induksi magnet untuk menjana tenaga elektrik.
Struktur mesin penjana terdiri daripada julur, magnet Neodymium, gegelung
wayar magnet dan litar penerus. Mesin penjana itu bersaiz kecil dengan isi padu
lebih kurang 24cm3, oleh itu ia dapat dipasang dan diguna dalam tempat atau ruang
yang kecil. Selain itu, ia dapat dilaraskan supaya muat dengan sumber getaran
dengan mengubah panjang julur ia. Ia mampu menghasilkan kuasa maksimum
ix
sebanyak 0.1Watt dengan sumber getaran 2.1G pada frekuensi salunan sebanyak
49.1Hz.
x
CONTENT
CHAPTER CONTENTS
I
PAGE
PROJECT TITLE
i
PROJECT STATUS CONFIRMATION FORM
ii
DECLARATION FORM
iii
DEDICATION
v
ACKNOWLEDGEMENT
vi
ABSTRACT
vii
CONTENTS
x
LIST OF TABLES
xiii
LIST OF FIGURES
xiv
INTRODUCTION
1.1
Project Overview
1
1.2
Motivation
2
1.3
Problem Statement
3
1.4
Objectives
3
1.5
Significant of project
4
1.6
Scope
4
1.7
Thesis outline
5
xi
II
LITERATURE REVIEW
2.1
Types of vibration energy harvester
2.1.1 Electromagnetic
based
vibration
6
energy 6
harvester
2.1.2 Magneto electric based vibration energy 12
harvester
III
IV
2.1.3 Piezoelectric Based vibration energy harvester
13
2.1.4 Hybrid energy harvester
17
2.2
Tuning Techniques
19
2.3
Rectifier circuit
23
2.3.1 Full wave bridge rectifier circuit
23
2.3.2 Voltage multiplier circuit
26
2.3.2.1 Voltage doubler circuit
27
2.3.2.2 DC Voltage Tripler Circuit
28
2.3.2.3 DC Voltage Quadrupler Circuit
28
RESEARCH METHODOLOGY
29
3.1
Design of electromagnetic generator
29
3.2
Choose of material
31
3.3
Building of electromagnetic generator
32
3.4
Experiment setting
35
3.5
Data collecting and processing
38
3.6
Rectifying circuit design
38
3.7
Prototyping
40
3.8
Flow Chart
41
RESULT
4.1
42
Factors that affect the resonant frequency of the 42
xii
cantilever
4.1.1 Effect of cantilever’s length
43
4.1.2 Effect of additional 2 extra magnets and mass 46
on the tip of the cantilever
V
4.1.3 Effect of the thickness of the cantilever
47
4.2
G-level measurement
49
4.3
Output analysis of electromagnetic generator
51
CONCLUSION AND RECOMMENDATIONS
54
5.1
Conclusion
54
5.2
Recommendations
55
REFERENCES
56
APPENDIX A
58
APPENDIX B
64
APPENDIX C
65
xiii
LIST OF TABLES
NO TITLE
2.1
PAGE
Young’s modulus of the materials aluminium, stainless steel and 21
copper
2.2
Summary of the result obtained from the parameters of each material
23
xiv
LIST OF FIGURES
NO
TITLE
PAGE
2.1
Vibration energy harvester designed by Gherca and Olaru
7
2.2
Layer structure of micro-electromagnetic vibration energy harvester
8
2.3
Fabricated energy harvester
10
2.4
Micro-fabricated silicon spiral spring
10
2.5
PDMS packaging substrate with multi-turned coil
11
2.6
Cross-sectional view of the micro-fabricated electromagnetic power
11
generator
2.7
Magneto electric energy harvester
12
2.8
Piezoelectric layers.
12
2.9
Structure of the meandering piezoelectric vibration energy harvester
14
2.10 Size of meandering piezoelectric vibration energy harvester
14
compared to a coin
2.11 Testing of electrode meandering energy harvester mounted
15
2.12 Schematic drawing of the piezoelectric cantilever
16
2.13 Cross-section drawing of the piezoelectric cantilever
16
2.14 Cross sectional view of magnets part
17
2.15 Testing of hybrid energy harvester
18
2.16 Structure of hybrid energy generator (HPVG)
19
2.17 Results of resonance frequency by varying the cantilever's length for
21
different materials.
2.18 Results of resonance frequency by varying the cantilever's thickness
22
for different materials
2.19 Results of resonance frequency by varying the cantilever's width for
different materials
22
xv
2.20 Full wave bridge rectifier
24
2.21 Rectifier in positive cycle
24
2.22 Rectifier in negative cycle
25
2.23 Function of smoothing capacitor
25
2.24 Basic multiplier circuit
26
2.25 Half wave voltage doubler
27
2.26 Voltage Tripler circuit
28
2.27 Voltage Quadrupler Circuit
28
3.1
Design of generator’s base
30
3.2
Design of cantilever
30
3.3
Design of electromagnetic generator
31
3.4
3D printed generator base
32
3.5
Cantilevers with different length
32
3.6
Magnetic wire coils
33
3.7
Neodymium magnets
34
3.8
Electromagnetic generator
34
3.9
Devices used in experiment
35
3.10 Setup of electromagnetic generator on electrical shaker
36
3.11 Acceleration sensor node by MicroStrain
37
3.12 Wireless data receiver
37
3.13 Deployment of acceleration sensor node on electric shaker
38
3.14 Normal full-wave bridge rectifier circuit
39
3.15 Voltage doubler circuit
39
3.16 Front view of the fabricated circuit
39
3.17 Back view of the fabricated circuit
39
3.18 3D view of electromagnetic genarator
40
3.19 Side view of electromagnetic generator
40
4.1
43
Graph of Induced voltage against frequency for 3.5cm cantilever
length
4.2
Graph of Induced voltage against frequency for 4cm cantilever length 43
4.3
Graph of Induced voltage against frequency for 4.5cm cantilever
44
length
4.4
Graph of Induced voltage against frequency for 5cm cantilever length 44
xvi
4.5
Comparison between different cantilever lengths
45
4.6
Graph of Induced voltage against frequency for cantilever’s tip with
46
additional 2 magnets
4.7
Difference in output for cantilever with and without additional
47
magnets
4.8
Graph of Induced voltage against frequency for cantilever with
47
0.35mm thickness.
4.9
Graph of difference in output for cantilever with different thickness
48
4.10 Response of vibration in time domain and frequency domain
50
4.11 Acceleration graph in frequency domain
50
4.12 AC output voltage during resonant frequency
51
4.13 Measuring DC output voltage
52
4.14 DC output voltage
52
4.15 Measuring DC output current
52
4.16 DC output current
52
1
CHAPTER 1
INTRODUCTION
1.1
Project Overview
Many research activities has been carried out in the area of micro-energy
harvesting which aimed to find an alternative solutions to batteries, which required
charging and replacement, as power supply of low power devices (Bouendeu et al.
2009). The main idea of micro-energy harvesting is to obtain free environment
energy and transform the energy into useful electrical energy which can be used to
power micro-electronic devices like wireless sensor nodes. Hence, energy harvesting
system is invented to replace the conventional chemical batteries that lead to costly
replacement fees in a huge wireless sensor network and cause chemical pollution
problems to the environment. The demand for energy harvesting system has been
growing rapidly due to the wide application of wireless sensor nodes and mobile
electronic devices (Yang et al. 2012).
Free environment energy can be found in the form of solar, thermal, chemical
or mechanical vibration. Inferior to solar energy, mechanical energy from the
ambient vibration source or known as vibration energy has been one of the major
power sources for energy harvesting system. Vibration energy is a green energy
which can be harvested from any moving mechanism of our surrounding including
biological and mechanical movement. There are various vibration sources in our
surrounding such as common household goods (refrigerator, washing machines and
2
air conditioners), industrial plant equipment, machines, moving vehicles such as
automobiles and structures such as buildings and bridges. The energy harvested can
be transform into useful electrical energy to power up small electronic devices such
as the sensor node. Wireless sensor node which is small in size, low power
consumption and its deployment in some inaccessible location has made the
vibration energy as an ideal and inexhaustible power source.
The vibration energy harvested is transform into electrical energy using
electromagnetic, electrostatic and piezoelectric transduction mechanisms. The
amount of energy generated by these approaches fundamentally depends upon the
quantity and form of the kinetic energy available in the application environment and
the efficiency of the generator as well as the power conversion electronics (Beeby et
al. 2007).
This project aimed to design and develop a miniature electromagnetic microgenerator for harvesting energy from ambient vibration source. The micro-generator
designed is small in size and works based on electromagnetic induction to transform
kinetic energy harvested from ambient vibration source into useful electrical energy.
Its basic structure consists of a cantilever, magnets, magnetic coils and an electrical
circuit. The power generated was measured tested to power up small electronics.
1.2
Motivation
Battery is a convenient power source for small electronic devices in our daily
life. However, the conventional use of chemical batteries in electronics such as
wireless sensor nodes in a large wireless network could be a problem for its user. The
batteries apply in the wireless sensor nodes network need to be replaced or recharged
from time to time to ensure a constant power supply. Hence, the user needs to spend
a costly replacement fees when the batteries of the sensors nodes are drained.
Besides, the replaced batteries will eventually become a chemical waste that causes
environment pollution.
3
The application of vibration energy harvester will serve as an alternative
power source which can eliminates the costly replacement fees of batteries in large
wireless sensor network and reduces the waste of chemical batteries.
1.3
Problem Statement
Conventional electromagnetic generator structure is big in size because it
consists of large magnets and large number of wire coils in order to produce
sufficient energy for the electrical device. Hence, it is inconvenient for the
electromagnetic generator to integrate with wireless sensor nodes which designed to
be deployed in a large scale of area and some inaccessible place for monitoring
purpose.
Besides, conventional electromagnetic generator produces a low output
voltage which is impossible to be rectified by the diodes. The output current must be
rectified into DC as electrical supply for electronic device. Hence, the output voltage
of the electromagnetic generator must be higher than 0.7V, which is the operating
voltage of a diode.
1.4
Objectives
The objective of this project is to design and develop a miniature
electromagnetic micro-generator which operates at its resonant frequency to function
with maximum efficiency. The size of the electromagnetic generator is aimed to
design in a 30- 130cm3 range to be integrated with the small electronic devices such
as wireless sensor node. Besides, the project aimed to determine the maximum power
generated by the micro-generator when it is tuned to work at its resonant frequency
resonant frequency. Lastly, a rectifier circuit is developed to rectify the output
voltage for the power of wireless sensor node.
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1.5
Significant of project
The electromagnetic generator proposed in this project has a high
sustainability as it does not need to be replaced like conventional batteries. After the
electromagnetic generator is deployed, it can be left to work on its own as long as
there is any moving mechanism which served as the power source.
Besides, the miniature size of the electromagnetic generator made it possible
to be deployed in some inaccessible place for a long term application. This feature
makes the electromagnetic generator suitable to integrate with wireless sensor nodes
in a large wireless sensor network for surrounding condition monitoring purposes.
Last but not least, the electromagnetic generator may gain a high
marketability since it is a green technology which saves cost and energy. Free
vibrational kinetic energy can be harvested from the surrounding to be used for
powering small electronic devices instead of using chemical batteries which may
cause pollution and require scheduled replacement.
1.6
Scope
The electromagnetic micro-generator is work based on the oscillation of a
cantilever equipped with four Neodymium magnets from Bunting Magnetics Europe
Ltd work and a magnetic coil winded using magnetic wires from Magnetic Sensor
Systems Ltd. The working principle of the micro-generator is solely depended on
electromagnetic theory.
The physical volume of the micro-generator is approximately 24cm3. The
micro-generator has a vibrating frequencies range of 5Hz- 150Hz and a vibrating
level less than 50ms-2. It can only work efficiently with a limited bandwidth near the
resonant frequency of the vibration source apply and capable of generate an output
power of 0.1 to 5 milliWatts.
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1.7
Thesis outline
Project Introduction provides a brief overview of this project that helps reader
to visualize and understand the aim of the project. Motivation and significant of this
project is discussed to explain the reason of why this project is proposed and its
advantages. Scope is then outlined to set the specifications and limitation of the
project proposed.
The Literature Review section presents some model of energy harvesters and
tuning methods used in previous researches. It shows the relation between this
project and those tasks done by other researchers.
Research Methodology part presents the overall process flow of this project
includes the design of the micro-generator proposed, construction of experimental
model, experiment test and optimising, as well as method of data collecting and
analysing.
Results and Discussion provides the reader with all the data obtained and
achievement of the research. The findings of this project are presented with the help
of tables, figures and graphs. This section also used to define the achievement of the
objectives set in the beginning of this research.
Lastly, the Conclusion and Recommendation section summarises the results
obtained after this research and recommends some direction for the future research of
energy harvesting system. Finally, it will discuss the knowledge obtained from this
research and contribution of this project to the university.
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CHAPTER 2
LITERATURE REVIEW
This chapter presents some projects related to energy harvesting system done
by other researchers. It consists of various type of energy harvesting systems and
tuning techniques developed to harvest vibration energy from the surrounding.
Furthermore, literature review on rectifier circuit is also included in this section.
2.1
Types of vibration energy harvester
There are several types of energy harvester which harvest kinetic energy from
surrounding vibration mechanism to generate useful electrical energy for small
electronics use. The vibrational energy harvester can be differentiated into 3 main
categories which are electromagnetic, piezoelectric, the fusion of both categories
(hybrid) and magneto electric.
2.1.1
Electromagnetic based vibration energy harvester
Gherca and Olaru designed a vibration energy harvester that worked on
ambient vibration by the mean of electromagnetic induction (Ă & Olaru 2011). The
harvesting generator works at low frequencies which close to ambient vibration to
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generate electrical energy. However, it can also be adapted to work at high values of
frequency.
Figure 2.1 shows the cross sectional area view of vibration energy harvester
designed based on the electromagnetic induction theory. The basic operating
principle of the system is a moving magnetic component inside a coil which capable
to generate electricity when the magnetic component sliding across the coil. The
mobile magnetic component is a rare earth permanent magnet, NdFeB, which is high
in energy density and good in sustainability. The housing that held the magnet in
place is winded with 2 windings of coil connected in phase opposition which use to
deliver the electricity generated when magnetic induction occurred. The magnetic
component is held “floating” by 2 fixed magnets with same pole oriented to the
mobile magnetic component, located at the top and lower covers respectively.
Figure 2.1: Vibration energy harvester designed by Gherca and Olaru. (Ă & Olaru
2011)
Ferro fluids are used as a lubricating agent attached to the permanent magnet.
The Ferro fluids are a dispersion of magnetic particles (~10nm) in liquid base with
approximately of 1023 particles per cubic meter. The Ferro fluid possesses the
common properties of liquids as well as magnetic material.