ii

FINITE ELEMENT ANALYSIS OF HYBRID ENERGY HARVESTING OF

PIEZOELECTRIC AND ELECTROMAGNETIC

MUHAMMAD AMMAR FARIS BIN MUHAMMAD YAZID

This thesis is submitted as partial fulfilment of the requirements for the award of the Bachelor

of Engineering (Hons.) Mechatronics Engineering - (Dual Degree Programme with Karlsruhe

University of Applied Sciences, HsKA, Germany)

Faculty of Manufacturing Engineering

Universiti Malaysia Pahang (UMP)

MARCH 2016

vi

ABSTRACT

Harvesting energy from ambient vibrations is a highly sought after method because of the wide

range of available sources that produce vibration energy applicable from industrial machinery

to human motion application. This report studied the implementation of harvesting energy from

two technologies to form a hybrid energy harvester system. These two technologies involves are

relate to the piezoelectric harvesting energy as well as the electromagnetic harvesting energy. A

finite element model was developed by using the Ansys software with the harmonic analysis

solver to analyze and examine hybrid harvesting energy system. The variance dimension of

geometry on the bimorph piezoelectric cantilever beam is also being implemented in order to

study the performance of the beam relating to the difference perspective of dimension. The

proposed length of the cantilever beam was 16.5mm and 36.5mm with the width of 6.35mm,

12.7mm, and 19.05mm. Both power output generated from the magnet and the piezoelectric is

then combined to form one unit of energy. The result shows the system generate the maximum

power output of 14.85𝜇𝑊 from 100Hz, 4.905𝑚/𝑠2, and 0.6𝑐𝑚3 for resonance frequency,

acceleration, and the volume respectively from the selected sample of the energy harvester

design. The NPD result of 10.29 𝑘𝑔𝑠/𝑚3compared with other literature also can be used in

energy harvesting system for vibration application.

vii

ABSTRAK

Penuaian tenaga daripada getaran ambien merupakan kaedah yang sangat dicari-cari kerana

terdapatnya rangkaian yang luas untuk menghasilkan tenaga getaran. Ia juga boleh dihasilkan

dan digunapakai dalam pelbagai cabang aplikasi bermula daripada jentera-jentera atau mesin

yang terdapat di kawasan perindustrian sehinggalah pengunaan dalam sistem pergerakan tubuh

manusia. Laporan ini mengkaji pelaksanaan tenaga penuaian daripada dua teknologi untuk

menghasilkan satu sistem penuai tenaga hibrid. Implementasi kajian menggunakan kaedah

“model unsur terhingga” (FEA) telah dijalankan dengan menggunakan perisian Ansys sebagai

alat bantuan untuk membantu menyelesaikan analisa harmonik dalam kerangka sistem tenaga

penuaian hibrid. Kedua-dua teknologi yang digabungkan dalam sistem ini adalah berkaitan

dengan teknologi penuaian tenaga daripada piezoelektrik serta elektromagnet. Terdapat pelbagai

variasi dimensi geometri yang dicadangkan pada rasuk julur piezoelektrik bimorph mengikut

beberapa sampel. Perkara ini dilakukan untuk menguji prestasi sistem tenaga penuaian hibrid

mengikut pemboleh ubah dimensi. Kedua-dua pengeluaran kuasa yang dijana daripada magnet

dan piezoelektrik ini kemudiannya digabungkan untuk membentuk satu unit tenaga. Daripada

kajian yang telah dijalankan, sistem hibrid ini telah menghasilkan maksimum pengeluaran kuasa

sebanyak 14.85μW dari 100Hz, 4.905𝑚/𝑠2, dan 0.6𝑐𝑚3 frekuensi resonans, pecutan, dan

isipadu sampel yang terpilih daripada rekaan penuai tenaga. Hasil NPD menunjukkan sebanyak

10.29 𝑘𝑔𝑠/𝑚3 dapat diperoleh daripada sistem ini dan jumlah ini telah dibandingkan dengan

hasil daripada kajian-kajian yang dilakukan daripada penyelidik-penyelidik yang lain. Secara

tuntasnya, sistem penuaian tenaga hibrid ini boleh digunakan dalam sistem penuaian tenaga

khusus untuk aplikasi getaran.

viii

TABLE OF CONTENTS

Page

SUPERVISOR’S DECLARATION ii

STUDENT’S DECLARATION iii

ACKNOWLEDGEMENTS v

ABSTRACT vi

ABSTRAK vii

TABLE OF CONTENTS viii

LIST OF TABLES xi

LIST OF FIGURES xii

LIST OF SYMBOLS xv

CHAPTER 1 INTRODUCTION 1

1.1 Background of Project 1

1.2 Problem Statement 3

1.3 Objectives 3

1.4 Scope of Project 3

CHAPTER 2 LITERATURE REVIEW 4

2.1 Energy 4

2.1.1 Source of Energy 4

2.1.2 Electrical Energy 5

2.1.3 Faraday’s Law 6

2.1.4 Lenz’s Law 8

2.2 Fundamental of Energy Harvesting 9

2.3 Types of Energy Harvesting 10

2.3.1 Photonic 10

ix

2.3.2 Thermal 12

2.3.3 Vibration 13

2.4 Method To Generate Electricity 15

2.4.1 Electromagnetic 15

2.4.2 Piezoelectric 16

2.5 Previous Research 17

2.5.1 Energy Harvesting From Electromagnetic 17

2.5.2 Energy Harvesting From Piezoelectric 18

2.6 Summary 19

CHAPTER 3 METHODOLOGY 20

3.1 Introduction 20

3.2 Proposed Design 20

3.2.1 Design Geometry 21

3.2.2 Materials Properties 23

3.3 Procedure 24

3.4 Design Development And Analysis Tools 25

3.5 Modeling Design 26

3.5.1 Developing The Beam 26

3.6 Simulation Modeling 33

3.7 Calculation of Piezoelectric Power Output 39

3.8 Simulation of Electromagnetic 40

3.9 Calculation of Electromagnetic Power Output 41

3.10 Summary 42

CHAPTER 4 RESULT AND DISCUSSION 43

4.1 Introduction 43

4.2 Piezoelectric: Geometry Properties of the Beams 43

4.3 Piezoelectric: Stress Distribution of the Beam 45

4.4 Piezoelectric: Relationship between Deflection of the Beam and the

Natural Frequency of the System 46

x

4.6 Magnet: Voltage and Power Output 51

4.7 Total Power of the Hybrid Harvesting System 52

4.6 Comparison of Normalized Power Density 53

4.6 Summary 54

CHAPTER 5 CONCLUSION 55

5.1 Introduction 55

5.2 Conclusion 55

5.3 Recommendation for Future Work 56

REFERENCES 57

APPENDICES 60

xi

LIST OF TABLES

Table No. Title Page

3.1 Dimensions of the initial design. 22

3.2 List of dimension for each cantilever beam sample. 22

3.3 Mechanical and electrical properties used in the FEA. 24

3.4 Material property of magnet 41

4.1 Dimensions of the beam sample. 44

xii

LIST OF FIGURES

Figure No. Title Page

1.1 Typical implementation of microstructure device using the

piezoelectric inside the shoe as the power generator

2

1.2 CPU transistor counts for the year 1971-2008. 2

2.1 Two forms of energy, renewable energy and non-renewable energy. 5

2.2 Two kinds of electrical charge. The protons are said to be positive

(+). The electrons are said to be negative (-).

6

2.3 Electromagnetic Induction 7

2.4 Determination of the direction of induced current by the right-hand

rule

9

2.5 Generic sensor node architecture 10

2.6 The difference between Photovoltaic Cell, Module, and Array 11

2.7 The process known as the "Photovoltaic Effect" to produce the

electricity.

11

2.8 The configuration of the thermoelectric generator 13

2.9 Sources of generation of vibrational energy 14

2.10 Comparison of wavelength, frequency and energy for the

electromagnetic spectrum

16

2.11 (a) Normal condition of piezoelectric material, (b) energy

generation under tension, (c) energy generation under compression

17

3.1 Piezo-Electromagnetic design concept 21

3.2 Load and boundary conditions of the simulation setup. 21

3.3 Flowchart of the methodology 25

3.4 Standard plane direction selection use for 2D sketching. 27

3.5 2D sketching view of the rectangle on the front plane. 28

xiii

3.6 The yellow preview shows the extrusion of the rectangle. 29

3.7 The preview shows the complete solid geometry of the rectangle 29

3.8 The 3D document can be saves into different number of format. 30

3.9 The imported part in the assembly working environment. 31

3.10 The mate features used to joint two layers. 32

3.11 The complete assembly of the piezoelectric beam with the mass. 32

3.12 Harmonic response analysis was chosen from the analysis system

box.

34

3.13 Imported geometry in the Workbench ANSYS. 35

3.14 Defining the model properties using the Command (APDL) 36

3.15 Meshing the geometry 37

3.16 The fixed support area is selected at the free end of the cantilever

beam.

38

3.17 Frequency response output is selected to generate solution. 39

3.18 Magnetic model in Ansys Workbench. 41

3.19 Waveform amplifier drives current through the coil at resonance 42

4.1 The difference of volume amount between each sample of

cantilever beam.

44

4.2 The difference of total mass between each sample of cantilever

beam

45

4.3 The difference of von Mises stress between each sample of

cantilever beam.

46

4.4 Contour plot of von Mises stress profile from the Beam F sample. 46

4.5 The difference of deflection amount between each sample of

cantilever beam.

47

4.6 The resonance frequency range obtained for each sample of

cantilever beam.

48

xiv

4.7 The peak value of stress at a frequency response of the cantilever

beam E.

48

4.8 The voltage output generated from the piezoelectric bimorph beam

with the length of 16.5mm

49

4.9 The voltage output generated from the piezoelectric bimorph beam

with the length of 36.5mm.

50

4.10 The power output generated from the piezoelectric bimorph beam

with the length of 16.5mm.

50

4.11 The power output generated from the piezoelectric bimorph beam

with the length of 36.5mm.

51

4.12 Cross section geometry of the total magnetic flux density produced

from the electromagnetic analysis

52

4.13 Electrical potential produced from the electromagnetic analysis 52

xv

LIST OF SYMBOLS

𝐴𝑖𝑛 Input acceleration

b* Strain related to vertical displacement of the beam

c Speed of light

𝐶𝑝 Capacitance of the piezoelectric device

d Piezoelectric strain coefficient

D Electric displacement

E Electric field

f frequency

k Coupling coefficient

P Power

R Load resistance

𝑡𝑐 Thickness of the piezoelectric material

V Voltage

𝑌 Young’s Modulus

ωn Natural frequency of the system

ω Driving frequency

δ Mechanical strain

xvi

𝛷𝐵 Rate of change of magnetic flux

ζ Mechanical damping ratio

𝜀 Total induced EMF

ε Dielectric constant of the piezoelectric material

σ Mechanical stress

xvii

LIST OF ABBREVIATIONS

AC Alternate Current

CAD Computer Aided Drafting

CAE Computer Aided Engineering

DC Direct Current

EH Energy Harvester

EMF Electromagnetic Field

FE Finite Element

MEMS Micro-electromechanical Systems

NdFeB Neodymium Iron Boron

NPD Normalized Power Density

PE Piezoelectric-Electromagnetic

PV Photovoltaic

PZT Piezoelectric Material

VEH Vibrational energy harvesting

1

CHAPTER 1

INTRODUCTION

1.1 BACKGROUND OF PROJECT

The terms of harvesting energy can be referred as the process by which the energy

is derived from the ambient source, captured and being stored. Solar, wind, and thermal

energy are the common ambient energy sources used for energy harvesting. As the

sources of energy are becoming more scarce and expensive, the energy harvesting is

receiving more global interest and is currently a growing field.

In today’s world, energy harvesting plays a crucial role in supplying the energy to

various application such as small wireless autonomous devices. For example, the

Vibrational energy harvesting (VEH) with micro-electromechanical systems (MEMS)

generators based might be able to provide several amount of energy in microwatts of

electrical power. MEMS are micro-electromechanical systems comprising of computers

linked to tiny mechanical and other devices like sensors, valves, gears, and actuators,

embedded in semiconductor chips based on silicon as shown in Figure 1.1.

With the rapid development of microelectronic devices in military, medical, and

civil applications, a traditional bulky battery can no longer meet the needs of advanced

sensing technology due to its limited service life and difficulty in replacement. Hence,

much attention should be place for research and development in sustaining the power

requirement for autonomous wireless and portable devices. Energy harvesting has

2

becoming one of the best option for the implementation in order to fulfil the condition as

stated. Currently, the technological advancements have made the energy harvesting

become much more deployable since the devices introduced in commercial nowadays

were using the ultra-low power components. Figure 1.2 shows the number of transistors

per chip doubling every two years.

Figure 1.1: Typical implementation of microstructure device using the piezoelectric

inside the shoe as the power generator

Source: Ville Kaajakari (2010)

Figure 1.2: CPU transistor counts for the year 1971-2008.

Source: Wgsimon (2008)

3

1.2 PROBLEM STATEMENT

Vibration energy are generated from any perceivable activity and usually seen as

the noise. However, if the energy were scavenged at the certain level of resonance

frequency, it can produce the power output in which can be implemented to any useful

application especially in the milliwatt power levels application as such in the MEMS

technology. Several studies has been conducted by the scholars regarding on the energy

harvesting system by using the electromagnetic and piezoelectric transduction. These

research employ these two technologies to develop the hybrid harvesting energy systems

in order to capture the ambient source of energy from the vibration.

1.3 OBJECTIVES

This research is made to fulfill objectives:

i. Model hybrid energy harvesting system of piezoelectric and

electromagnetic using harmonic analysis in Ansys software.

ii. Analyze hybrid energy harvesting system with different width and length

of bimorph piezoelectric beam to produce power from the mechanical

strain

1.4 SCOPE OF PROJECT

To fulfill above, the scope of project study are:

i. Model hybrid harvesting energy using the piezoelectric and magnet material

ii. Bimorph piezoelectric cantilever beam is used with dimension as follows:

a. Width : 6.35mm, 12.7mm, 19.05mm

b. Length : 16.5mm, 36.5mm

iii. Simulation using the harmonic analysis in Ansys software to produce the

deflection of the beam and voltage output of the piezoelectric bimorph beam.

iv. The project required to be accomplished within the 6 month of period based

on the Gantt chart schedule proposed (Appendixes A).

4

CHAPTER 2

LITERATURE REVIEW

2.1 ENERGY

By definition, energy is the capacity of a physical system to perform work (Rouse,

2005). Energy exists in several forms such as heat, kinetic or mechanical energy, light,

potential energy, electrical, or other forms. According to the law of conservation of

energy, the total energy of a system remains constant, though energy may transform into

another form. The SI unit of energy is the joule (J) or newton-meter (N.m) in which it is

also the SI unit of work. In electrical circuits, energy is a measure of power expended

over time. In this sense, one joule (1 J) is equivalent to one watt (1 W) dissipated or

radiated for one second (1 s). A common unit of energy in electric utilities is the kilowatt-

hour (kWh), which is the equivalent of one kilowatt (kW) dissipated or expended for one

hour (1 h).

2.1.1 Source of Energy

Figure 2.1 shows the energy sources can be classified into two types,

nonrenewable energy and renewable energy. Nonrenewable resources, such as fossil fuels

and nuclear material, are removed from the earth and can be depleted. These resources

have been the most used type of energy in the modern era. Renewable resources, such as

wind, water, solar, and geothermal, come from sources that regenerate as fast as they are

consumed and are continuously available. Some, such as biofuel produced from food

crops and other plants, are replenished every growing season. In the early part of the

twenty-first century, renewable sources have become more popular as nonrenewable

5

sources have begun to be depleted. Though it is becoming a trend that more and more

people care about where the energy that we use comes from, we are not sufficiently

informed to have a well-founded opinion. People seem to be in favor of solar, wind and

hydroelectric power, but it is highly questionable how reliable our sources of information

are.

Figure 2.1: Two forms of energy, renewable energy and non-renewable energy.

Source: Types of Energy (2005)

2.1.2 Electrical Energy

Electrical energy results from the movement of an electrical charge, and is

commonly referred to as simply “electricity.” There are two types of electrical charge as

illustrated in Figure 2.2, called positive and negative. If two electrically charged objects

are brought close to one another, they will experience a force. If they have different

charges, they will attract one another. If the charges are the same either both positive or

negative, the force will act to push the objects away from one another. This repulsion or

attraction is known as the electromagnetic force, and it can be harnessed to create a flow

of electrical energy.

6

Figure 2.2: Two kinds of electrical charge. The protons are said to be positive (+). The

electrons are said to be negative (-).

Source: Luciano (2014)

Most electricity is generated by devices that convert rotational motion into

electrical energy, using the same principle as an electric motor, but in reverse. The

movement of coils of wire within a magnetic field produces an electric current.

Commonly, the heat which often generated by the burning of fossil fuels is used to

produce steam that powers a turbine to provide the rotational motion. In a nuclear power

plant, nuclear energy provides the heat. Hydroelectric power uses the movement of water

under gravity to drive the turbine. Electricity for small, low power devices is often

supplied by batteries. The energy produced from the chemical reaction inside the batteries

generate a relatively small electric current. They always generate a direct current, and

therefore have a negative and a positive terminal. Electrons flow from the negative to the

positive terminal when a circuit is completed.

2.1.3 Faraday’s Law

In 1831, Michael Faraday discovered that, by varying magnetic field with time,

an electric field could be generated. Faraday law is one of the most basic and important

laws of electromagnetism. This law finds its application in most of the electrical

machines, industries and other field. The theory of Faraday’s law of electromagnetic

induction describe any change in the magnetic field of a coil of wire will cause an

7

electromagnetic force (EMF) to be induced in the coil. This EMF induced is called

induced EMF and if the conductor circuit is closed, the current will also circulate through

the circuit and this current is called induced current. Figure 2.3 illustrates the phenomenon

known as electromagnetic induction.

Figure 2.3: Electromagnetic Induction

Source: Liao (2004)

Method to change the magnetic field can be done by doing as follows:

1. Moving a magnet towards or away from the coil

2. Moving the coil into or out of the magnetic field

3. Changing the area of a coil placed in the magnetic field

4. Rotating the coil relative to the magnet

Faraday’s law of induction may be stated as follows:

The induced EMF ε in a coil is proportional to the negative of the rate of change

of magnetic flux 𝛷𝐵:

𝜀 =𝑑Φ𝐵

𝑑𝑡 (2.1)

8

For a coil that consists of N loops, the total induced EMF would be N times as

large:

𝜀 =𝑁𝑑Φ𝐵

𝑑𝑡 (2.2)

2.1.4 Lenz’s Law

Lenz's law is a common way of understanding how electromagnetic circuits obey

Newton's third law and the conservation of energy. Lenz's law is named after Heinrich

Lenz, and describe the law as if an induced current flows, its direction is always such that

it will oppose the change which produced it (Liao, 2004). Lenz's law is shown with the

negative sign in Faraday's law of induction which indicates that the induced voltage ℰ and

the change in magnetic flux 𝛷𝐵 have opposite signs as shown in the Eq. (2.3).

𝜀 =−𝑁𝑑Φ𝐵

𝑑𝑡 (2.3)

The minus sign in the equation is important as it means that the EMF creates a

current I and magnetic field B that oppose the change in flux 𝛷𝐵. The direction of induced

current can be determined by using the right-hand rule (Lenz Law of Electromagnetic

Induction, 2011). If the fingers of the right hand are placed around the wire so that the

thumb points in the direction of current flow, then the curling of fingers will show the

direction of the magnetic field produced by the wire as shown in Figure 2.4.

9

Figure 2.4: Determination of the direction of induced current by the right-hand rule

Source: Lenz Law of Electromagnetic (2011)

2.2 FUNDAMENTAL OF ENERGY HARVESTING

The term "energy harvesting" refers to the generation of energy from sources such

as ambient temperature, vibration or air flow. A typical energy harvesting system starts

with an energy collector or transducer device and depends on the type of energy one is

trying to convert. These are typically solar or photovoltaic cells for light energy,

piezoelectric for pressure, kinetic for movement, inductive for rotational or motion,

thermoelectric for heat or temperature differential, and electromagnetic. The energy

harvesting system is quiet significant as it has the potential to replace the batteries for

small, low power electronic devices. Figure 2.5 illustrate the key components of a simple

energy harvesting system to convert and store the ambient energy into electrical energy.

The stored electrical energy can then be used by various sensor nodes for applications

such as sensing, actuating, or sending wireless signals.

10

Ambient

Energy

Energy Harvesting

Device

Power

Management Energy Storage

Sensor Actuator Communication

Figure 2.5: Generic sensor node architecture

Source: Berder (2015)

2.3 TYPES OF ENERGY HARVESTING

It is important to note, that all energy sources are virtually unlimited and can be

harvest from various sources. The most common types of energy harvesting are photonic,

thermal, and vibrational.

2.3.1 Photonic

Common photonic harvesters rely on solar energy drawn with the use of

photovoltaics. Solar cell is the basic component for harvesting the sunlight using solar

photovoltaics and commonly made from semiconductors as shown in the Figure 2.6.

11

Figure 2.7 shows when a solar cell is exposed to sunlight, the photons (sunlight) strike

and ionize the semi-conductor material causing its outer electron to break free of the

atomic bonds. Due to the semiconductor’s structure, the electrons are force to move in

one direction, creating a flow of electrical current.

Figure 2.6: The difference between Photovoltaic Cell, Module, and Array

Source: Solar PV Cell Module Array (2014)

Figure 2.7: The process known as the "Photovoltaic Effect" to produce the electricity.

Source: Lambardo (2014)

According to Kwang (2014), solar cells are not 100% efficient because some

spectrums of the sunlight are being reflected, some are too weak to create electricity

(infrared spectrum) and some create heat energy instead of electricity (ultraviolet

spectrum) Susceptibility to pollutants such as dust that blocks light from the cells may

further impede their efficiency. The fragility of photovoltaic devices is still yet another

concern.