1
AN IMPROVED DESIGN OF PIEZOELECTRIC RAINDROP ENERGY HARVESTER
WONG CHIN HONG
UNIVERSITI SAINS MALAYSIA
2017
2
AN IMPROVED DESIGN OF PIEZOELECTRIC RAINDROP ENERGY HARVESTER
By
WONG CHIN HONG
Thesis submitted in fulfilment of the requirements for the degree of
Doctor of Philosophy
JANUARY 2017
ii
ACKNOWLEDGEMENTS
First, I would like to extend my greatest appreciation to my main supervisor, Dr. Zuraini Dahari of her professional guidance, encouragement, and constructive comments enlightened me in my research. I am also very thankful to my co- supervisor Prof. Dr. Othman Sidek of his advice and motivation. Without their support and concern, this thesis would not complete successfully. Second, I am grateful to Dr. Asrulnizam Abd. Manaf from School of Electrical and Electronic Engineering and Dr. Khairudin Mohamed from School of Mechanical Engineering of their suggestions regarding the required facilities, materials, and fabrication processes pertaining to this research.
I am also indebted to staffs and technicians from Nano-Optoelectronics Research and Technology Laboratory (NOR Lab), Nanofabrication and Functional Materials (NFM), as well as Dr Mohammad Hafizuddin, Ibtisam and Huwaida from Universiti Kebangsaan Malaysia (UKM), who are assisting me in supplying the relevant literatures and expertise. I would like to express thanks to the staffs from School of Electrical and Electronic Engineering, as a token of appreciation due to their valuable help. I would also like to acknowledge USM,’s Research Grant (1001/PELECT/814243) and MyBrain scholarship which made this research financially possible.
I am grateful to my parents and siblings of their endless love, care, and support during my study. Finally, I would like to extend my gratitude to my friends, Sew Sun, Jing Huey, Wei Hong, Belinda, Tow Leong, Swee Kheng, Wee Chuen, Lee Teng, Wei Zeng, Earn Tzeh, Yeong Chin, Hui Ting, Jing Rui, Boon Tatt, Kia, Liza, Mar Mar, Adrian and Nexus of their motivation and concern throughout my time in USM.
iii
TABLE OF CONTENTS
Page
ACKNOWLEDGEMENTS ii
TABLE OF CONTENTS iii
LIST OF TABLES viii
LIST OF FIGURES x
LIST OF ABBREVIATIONS xvi
LIST OF SYMBOL xviii
ABSTRAK xxiii
ABSTRACT xxv
CHAPTER ONE - INTRODUCTION 1
1.1 Background 1
1.2 Problem Statement and Motivations 4
1.3 Research Objective 7
1.4 Research Scope and Limitation 7
1.5 Summary of Contribution 9
1.6 Organisation of Thesis 10
CHAPTER TWO - LITERATURE REVIEW 11
2.1 Introduction 11
2.2 Raindrop Characteristics 11
2.2.1 Size of Raindrop 13
2.2.2 Velocity of Raindrop 14
2.2.3 Impact Types of Raindrop 14
2.3 Method to Predict Raindrop Size and Velocity 16 2.4 Review of Piezoelectric Raindrop Energy Harvesting 21
iv
2.5 Piezoelectric Overview 31
2.5.1 Piezoelectric Concept 31
2.5.2 Piezoelectric Material 36
2.6 Finite Element Modelling 37
2.7 Fabrication Process 41
2.7.1 PVDF Preparation and Forming 42
2.7.2 Electrode Deposition 45
2.7.3 Pattern Generation 45
2.7.4 Piezoelectric Film Poling Treatment 47
2.8 Summary 50
CHAPTER THREE - METHODOLOGY 52
3.1 Introduction 52
3.2 Design Flow and Methodology 52
3.3 Preliminary Experimental Investigation 54
3.3.1 Investigation of Raindrop Size and Fall Velocity 54
3.3.1(a) Photography Method 56
3.3.1(b) Image Processing 57
3.3.2 Investigation of Commercial PVDF Transducers 59 3.3.2(a) Piezoelectric Material Selection 60 3.3.2(b) Performance Comparison of Commercial PVDF
Transducers
61
3.3.2(c) Voltage Signal Processing 66
3.4 Finite Element Simulation of Basic Structure of PREH 67 3.4.1 Pre- and Post-Processing Simulation by Using COMSOL 68 3.4.1(a) Piezoelectric Material Properties Setup 69
3.4.1(b) 3D Layout and Mesh Setting 71
v
3.4.1(c) Post-Processing 73
3.5 Finite Element Simulation on Various Types of PVDF Structure Transducers
73
3.6 Fabrication of PREH 74
3.6.1 Microfabrication of Piezoelectric Transducer 75
3.6.1(a) PVDF Coating 76
3.6.1(b) Electrode Deposition 78
3.6.1(c) Poling Treatment 78
3.6.1(d) Piezoelectric Film Shaping 81
3.6.2 Mechanical Fabrication of Stand 81
3.7 Characterisation and Validation of Fabricated Piezoelectric Transducer
82
3.8 Experimental Investigation of Fabricated Transducer 83
3.9 Summary 84
CHAPTER FOUR - RESULTS AND DISCUSSIONS 85
4.1 Introduction 85
4.2 Experimental Results for the Size of Raindrop Prediction 85 4.3 Experimental Results of Commercial PVDF Basic Structure
Transducers
88
4.3.1 Experimental Results of Commercial PVDF Cantilever Structure Transducers
88
4.3.2 Experimental Results of Commercial PVDF Bridge Structure Transducers
92
4.3.3 Performance Comparison between Commercial PVDF Cantilever and Bridge Structure Transducers
97
4.3.4 Impedance Analysis on the 30 mm Bridge Structure Transducer
100
vi
4.4 Performance Analysis of Power Converter 104
4.4.1 Analysis of Open-Circuit Output Voltage from a Power Converter
104
4.4.2 Analysis of Closed-Circuit Output Voltage from a Power Converter
106
4.4.3 Analysis of Output Voltage by Applying Continuous Flow of Droplet
108
4.5 Finite Element Analysis of Piezoelectric Raindrop Energy Harvester
109
4.5.1 Finite Element Analysis of Bridge Structure 109 4.5.2 Finite Element Analysis of Various Shape of PREH 114 4.5.3 Finite Element Based Optimised Results of X-Shaped
Transducer
117
4.5.3(a) Width Optimisation of X-Shaped Transducer 118 4.5.3(b) Number of Spokes Optimisation for X-beam 121 4.5.3(c) Circular Pad Size Optimisation for Six-Spoke Wagon
Wheel Transducer
125
4.5.4 Overall Simulation Results 129
4.6 Fabrication Results of Optimised PREH 131
4.6.1 PVDF Thickness Analysis 132
4.6.2 Piezoelectric Film Poling Results 136
4.6.3 FESEM Analysis 138
4.6.4 XRD Analysis 139
4.6.5 FTIR Analysis 141
4.7 Experimental Results of Fabricated Six-Spoke Wagon Wheel Transducer
144
4.8 Summary 149
vii
CHAPTER FIVE - CONCLUSIONS AND RECOMMENDATIONS 152
5.1 Conclusion 152
5.2 Recommendations 154
REFERENCES 156
APPENDICES
LIST OF PUBLICATIONS
viii
LIST OF TABLES
Page
Table 1.1 Average annual precipitation from various countries in 2014 3 Table 2.1 Summary of methods to predict raindrop size and velocity 20 Table 2.2 Comparison of potential raindrop energy harvesters 28 Table 2.3 Properties of different piezoelectric materials 37 Table 2.4 FEM simulation on piezoelectric transducer from various
researchers
41
Table 2.5 Summary of PVDF formation 43
Table 2.6 Advantages and disadvantages of dry and wet etching 47 Table 3.1 PVDF properties from Piezotech S. A. S. (Hésingue,
France).
61
Table 3.2 Experimental parameters of water droplet energy harvesting 62 Table 3.3 Parameters of water droplet generated from a syringe pump. 66 Table 3.4 Electrical and mechanical properties of PVDF 70 Table 4.1 Comparison between theoretical and MATLAB results of
droplet diameter released from 0.5 meter height
87
Table 4.2 Summary of the maximum voltage generated by 40 mm long cantilever transducers
91
Table 4.3 Summary of the maximum voltage generated by bridge transducers
97
Table 4.4 Summary of parameters that exhibit the largest output power for bridge transducer
103
Table 4.5 Summary of voltage and surface charge density for 1.5 and 2.0 mm width of X-shaped transducer
119
Table 4.6 Summary of voltage and surface charge density of four and six-spoke wagon wheel transducer
123
ix
Table 4.7 Summary of voltage and surface charge density of six-spoke wagon wheel transducer with an integrated 5 mm and 6 mm circular pad
127
Table 4.8 Summary of optimised structure 129
Table 4.9 Performance comparison between bridge and six-spoke wagon wheel structure
130
Table 4.10 Details of rain event 146
Table 4.11 Summary of the performance between commercial bridge structure transducer and fabricate six-spoke wagon structure transducer under actual rain fall.
148
x
LIST OF FIGURES
Page
Figure 1.1 Annual average precipitation in Penang from 2002 to 2011 4 Figure 2.1 Impact modes versus We and Oh (Guigon et al., 2008b). 15 Figure 2.2 Experimental setup for water droplet characterisation
(Salvador et al., 2009)
17
Figure 2.3 Schematic of the 2D-video disdrometer (Randeu et al., 2013)
17
Figure 2.4 PVDF water droplet energy harvester with bridge transducer (Guigon et al., 2008a)
21
Figure 2.5 Water drop energy harvesting with cantilever transducer (Vatansever et al., 2011)
23
Figure 2.6 PZT multimorph cantilever transducer (Al Ahmad and Jabbour, 2012)
24
Figure 2.7 Droplet energy harvesting experimental setup (Wong et al., 2014)
26
Figure 2.8 l was s orted two tr ang lar acr l cs ca s ng a incline from a side (Morrison and Decker, 2015)
27
Figure 2.9 “Log growth” stage and “ex onent al deca ” stage (Il as and Swingler, 2015)
27
Figure 2.10 Crystal structures of (a) non-piezoelectric and (b) piezoelectric effect (Ramadan et al., 2014)
31
Figure 2.11 The piezoelectric effect (1) before, (2) during, and (3) after poling of PVDF
32
Figure 2.12 Ill strat on o ‘33’ ode and ‘3 ’ ode o o erat on o piezoelectric material (Biswas et al., 2009)
34
Figure 2.13 Deflection of cantilever beam as force applied on the free end
38
xi
Figure 2.14 Deflection of bridge beam as force applied on the centre 38
Figure 2.15 Piezoelectric film fabrication 42
Figure 2.16 Piezoelectric polymer poling systems (a) corona poling and (b) electrode poling (Ramadan et al., 2014).
48
Figure 3.1 Overall process flow chart 53
Figure 3.2 Water droplet falling from a blunt needle 55 Figure 3.3 Flow chart to predict raindrop size and fall velocity 55 Figure 3.4 Experimental Setup for (a) actual and (b) block diagram
for capturing droplet image
56
Figure 3.5 Flow chart of imaging processing 57
Figure 3.6 Flow chart of comparison between commercial PVDF cantilever and bridge structure transducers
60
Figure 3.7 Experimental setup for (a) actual setup and (b) block diagram for vibration-based piezoelectric raindrop energy harvesting
63
Figure 3.8 Holder for the (a) bridge transducer and (b) cantilever transducer
64
Figure 3.9 (a) Circuit diagram and (b) circuitry of standard AC-DC converter (full-wave bridge rectifier) for water drop energy harvesting application
67
Figure 3.10 Experiment design for simulation phase 68 Figure 3.11 Impact pressure against water droplet diameter 69 Figure 3.12 Schematic diagram of (a) cantilever and (b) bridge
structure
71
Figure 3.13 PVDF sandwiched structure formed by two rectangular blocks
72
Figure 3.14 3D meshed model of cantilever and bridge structures. 72 Figure 3.15 Various beam design (a) S-shaped, (b) zigzag-shaped, (c)
H-shaped, and (d) X-shaped, structures for simulation.
74
xii
Figure 3.16 Flow chart of piezoelectric transducer fabrication 75
Figure 3.17 Piezoelectric fabrication process 76
Figure 3.18 M x ng the sol t on at C with hot plate and magnetic stirrer.
77
Figure 3.19 (a) The block diagram and (b) setup for corona poling 79
Figure 3.20 Mechanical fabrication process 81
Figure 4.1 Droplet fall along the vertical distance at different position.
86
Figure 4.2 Droplet diameter with respect to different sizes of blunt needle
87
Figure 4.3 Results of water droplets being released from heights of (a) 0.25 m and (b) 0.5 m hitting on the free end of the 4 mm wide and 25 µm thick PVDF cantilever transducer
89
Figure 4.4 Results of water droplets being released from (a) 0.25 m and (b) 0.5 m height hitting on the free end of 4 mm wide and 40 µm thick PVDF cantilever transducer
90
Figure 4.5 Maximum voltage generated from 40 mm long cantilever transducer recorded by an oscilloscope.
92
Figure 4.6 Results of the water droplets released from (a) 0.25 m and (b) 0.5 m and hitting the centre of 4 mm wide 25 µm thick PVDF bridge transducer
93
Figure 4.7 Results of water droplet released from (a) 0.25 m and (b) 0.5 m height falling on the centre of 4 mm wide 40 µm thick PVDF bridge transducer
94
Figure 4.8 Maximum voltage generated from 30 mm long bridge transducer recorded by an oscilloscope
95
Figure 4.9 Vibration frequency and natural frequency of (a) 25µm and (b) 40 µm thick bridge structure transducers with respect to various lengths
96
Figure 4.10 Peak voltage against kinetic energy for (a) cantilever and (b) bridge structure transducers
99
xiii
Figure 4.11 Output voltage and current against load 101
Figure 4.12 Output power against load 102
Figure 4.13 Output voltage waveform 102
Figure 4.14 Open-circuit AC-DC converter. 104
Figure 4.15 Open-circuit output voltage from multiple drop before (VAC) and after (VDC) rectified.
105
Figure 4.16 Open-circuit output voltage from single drop before (VAC) and after (VDC) rectified.
105
Figure 4.17 Closed-circuit AC-DC converter. 106
Figure 4.18 Closed-circuit output voltage from multiple drop before (VAC) and after (VDC) rectified.
107
Figure 4.19 Closed-circuit output voltage from single drop before (VAC) and after (VDC) rectified.
108
Figure 4.20 Output voltage generated from continuous flow of droplets.
109
Figure 4.21 Calculated results of (a) impact pressure and simulation results of (b) electrical potential, (c) surface charge density, and (d) total displacement against droplet.
110
Figure 4.22 Simulation results for (a) total displacement, (b) electrical potential and (c) surface charge density.
111
Figure 4.23 Experimental and simulation results or output voltage against bridge length
112
Figure 4.24 Simulation results of displacement against bridge length 113 Figure 4.25 Simulation results of electrical potential of (a) zigzag
bridge, (b) H-bridge, (c) S-bridge, and (d) X- beam
115
Figure 4.26 Output voltage and surface charge density of various transducers
116
Figure 4.27 Deflection of various transducers 116
Figure 4.28 Optimisation parameters 118
xiv
Figure 4.29 Voltage and surface charge density against width of X- shaped transducer
119
Figure 4.30 Deflection against X-beam width 120
Figure 4.31 Fundamental frequency against X-beam width 121 Figure 4.32 X-beam with (a) 4 spokes, (b) 6 spokes, (c) 8 spokes, and
(d) 10 spokes.
122
Figure 4.33 Voltage and surface charge density against number of spokes
123
Figure 4.34 Deflection against number of spokes 124
Figure 4.35 Fundamental frequency against number of spoke 125 Figure 4.36 Six-spoke beam with a circular pad in the middle 126 Figure 4.37 Voltage and surface charge density against centre pad
diameter
126
Figure 4.38 Deflection against centre pad diameter 128 Figure 4.39 Fundamental frequency against centre pad diameter 128 Figure 4.40 Physical dimension of optimised wagon wheel structure. 129
Figure 4.41 Dimension of stand in mm 130
Figure 4.42 Fabricated six-spoke wagon wheel transducer 132 Figure 4.43 ect o dr ed at C for (a) 15 minutes, (b) 20
minutes, and (c) 25 minutes
133
Figure 4.44 PVDF thickness against spin speed from 500 to 1000 rpm 134
Figure 4.45 Crack occurred on the PVDF film 135
Figure 4.46 PDVF thickness against spin speed from 100 to 400 rpm 136 Figure 4.47 Piezoelectric constant against poling voltage 137 Figure 4.48 FESEM micrograph of PVDF surface for (a) un-poled, and
poled at (b) 3.6 kV, (c) 4.8 kV, and (d) 6.0 kV
138
Figure 4.49 XRD pattern for un-pole and poled PVDF. 140
xv
Figure 4.50 FTIR spectra of (a) un-poled and poled at (b) 3600 V, (c) 4200 V, (d) 4800 V, (e) 5400 V and (f) 6000 V
142
Figure 4.51 β-phase content respect to different poling conditions 143 Figure 4.52 Open-circuit voltage waveform generated from fabricated
six-spoke wagon wheel transducer
144
Figure 4.53 Closed-circuit voltage waveform generated from fabricated six-s oke wagon wheel transd cer across a 33 kΩ res stor
145
Figure 4.54 Closed-circuit output voltage before (VAC) and after (VDC) rectified
146
Figure 4.55 Output voltage recorded for (a) commercial bridge structure and (b) fabricated wagon wheel structure from an actual rain event.
147
xvi
LIST OF ABBREVIATIONS
AC - Alternative Current
ACE - Acetone
AIN - Aluminium Nitride
CNC - Computer Numerical Control CVD - Chemical Vapour Deposition DBS - Dual Beam Spectropluviometer
DC - Direct Current
DMAc - N,N-Dimethylacetamide DMF - N,N-Dimethylformamide DMSO - Dimethyl Sulfoxide EHD - Electrohydrodynamic FEM - Finite Element Method
FESEM - Field Emission Scanning Electron Microscopy FTIR - Fourier Transform Infrared Spectrometer
ITO - Indium Tin Oxide
LPM - Laser Precipitation Monitor MEK - Methyl Ethyl Ketone NMP - N-Methyl-Pyrrolidene
PMMA/GO - Poly(Methyl Methacrylate)/Graphene Oxide
xvii
PREH - Piezoelectric Raindrop Energy Harvester PTFE - Polytetrafluoroethylene
PVD - Physical Vapour Deposition PVDF - Polyvinylidene Fluoride PZT - Zirconate Titanate TEP - Triethylphosphate THF - Tetrahydrofuran XRD - X-Ray Diffraction
xviii
LIST OF SYMBOL
- Vector of electrical field
- Electric charge density displacement - Vector of component mechanical stress A - Electrode area
Ad - Area of droplet in pixel Aα - α-phase absorbance bands Aβ - β-phase absorbance bands
Ag - Silver
Al - Aluminium
Au - Gold
BaTiO3 - Barium Titanate C - Capacitor CE - Elasticity
Cf - Friction coefficient Cpiezo - Piezoelectric capacitance
Cr - Chromium
c - Elastic constant
Ddrop - Droplet diameter
Dneedle - External diameter of the blunt needle
xix
d - Gauge between the electrodes plates dij - Piezoelectric strain coefficient EK - Kinetic energy
EU - Electrical energy Ecap - Energy stored
e - Piezoelectric coupling
Fimpact - Impact force
fbridge - Bridge resonance frequency fcantilever - Cantilever resonance frequency fnar - Natural frequency
g - Gravitational constant gij - Piezoelectric stress constant h - Droplet fall height
I - Moment of inertia k - Stiffness constant
kbridge - Stiffness constant of bridge kcantilever - Stiffness constant of cantilever kij - Electromechanical coupling constant kem - Electromechanical coupling coefficient
LAl_bottom - Al bottom layer
LAl_top - Al top layer
xx LPVDF - PVDF layer
l - Length
m - Mass of droplet mbeam - Mass of beam Oh - Ohnesorge number
P - Power
Pt - Platinum
Pimpact - Impact pressure
Pmax - Output power without loss Pout - Output power
Pout_eff - Output power with loss
Q - Charge
R - Resistance
S - Average volume deformation SE - Compliance
Tc - Curie temperature
timpact - Period of water droplet impact tvib - Vibration period
V - Voltage
VAC - Alternative current voltage VDC - Direct current voltage
xxi
VDC_AVE - Average DC voltage
VDC_SINGLE-DC - Voltage from single drop Vc - Poling voltage
Vg - Grid voltage
Voc - Open circuit voltage Vp - Peak voltage
v - Droplet Fall Velocity We - Weber number
w - Width
Y - Yo ng’s od l s ZnO - Zinc Oxide
γ - Water surface stress δ - Deflection
δbridge - Bridge deflection
δcantilever - Cantilever deflection
ε - Electrical permittivity coefficients ԑ0 - Electrical permittivity in vacuum ԑr - Relative permittivity of medium ϑ - Active volume
ρ - Density ρair - Density of air
xxii ρPVDF - PVDF density
ρwater - Water density, water density υ - o sson’s rat o
xxiii
PENAMBAHBAIKAN REKABENTUK PENUAI PIEZOELEKTRIK TENAGA TITISAN HUJAN
ABSTRAK
Penuaian tenaga titisan hujan memberikan sumber tenaga alternatif yang boleh digunakan semasa hujan. Walaupun penyelidikan yang ekstensif telah disiasat berkenaan penuaian tenaga titisan hujan mengunakan mekanisme piezoelektrik, penuai piezoelektrik tenaga titisan hujan (Piezoelectric Raindrop Energy Harvester (PREH)) yang bercekapan tinggi masih dalam penyelidikan. Kajian penyelidikan ini membentangkan rekabentuk dan pembangunan penambahbaikan rekabentuk baik PREH. Untuk mencapai rekabentuk yang lebih baik, beberapa langkah telah dilaksanakan. Ini termasuk siasatan ke atas profil titisan hujan untuk meramalkan tenaga kinetik dalam titisan hujan. Hasil kajian mendapati bahawa jumlah tenaga kinetik bergantung kepada saiz titisan dan halaju jatuh. Kedua, eksperimen telah dijalankan untuk membandingkan prestasi transduser PVDF komersial yang sering digunakan iaitu struktur jambatan dan julur yang tertakluk kepada titisan hujan simulasi. Keputusan eksperimen menunjukkan bahawa transduser berstruktur jambatan dengan dimensi 30 mm × 4 mm × 25 µm menjana voltan litar terbuka lebih tinggi daripada struktur julur, iaitu 4.22 V dan 0.41 V masing-masing. Langkah seterusnya adalah analisis kaedah unsur terhingga (FEM) melalui perisian COMSOL Multiphysics untuk menyiasat voltan litar terbuka, ketumpatan cas, pesongan transducer, dan frekuensi resonans. Berdasarkan struktur jambatan itu, pelbagai jenis struktur telah diubahsuai iaitu transduser berbentuk S, berbentuk zigzag, berbentuk H, dan berbentuk-X telah disiasat dengan lebih lanjut melalui simulasi FEM.
Berdasarkan keputusan simulasi, struktur optimum PREH adalah struktur enam jejari
