VERTICAL AXIS CURRENT TURBINE USING ARM AND SELF-ADJUSTING
BLADE ANGLE FOR LOW SPEED CURRENT
FATEMEH BEHROUZI
UNIVERSITI TEKNOLOGI MALAYSIA
VERTICAL AXIS CURRENT TURBINE USING ARM AND SELF-ADJUSTING
BLADE ANGLE FOR LOW SPEED CURRENT
FATEMEH BEHROUZI
A thesis submitted in fulfilment of the
requirements for the award of the degree of
Doctor of Philosophy (Mechanical Engineering)
Faculty of Mechanical Engineering
Universiti Teknologi Malaysia
July 2017
iv
Alhamdulillah, Allah the Almighty above His statutes and all compassion and
wisdom given to me.
Dedicated to prophet Mohammad (S.A.W.)
And
My daughter Hediyeh for her toleration and sincere help during my study.
v
ACKNOWLEDGEMENT
Alhamdulillahirabbul'aalamiiin, praise is to Allah, the Lord of hosts. First of
all, thanks to ALLAH (S.W.T) for mercy, guidance and gave me full strength to
complete this research. I would like to take this opportunity to express my profound
appreciation to Prof. Dr. Adi Maimun bin Hj Abdul Malik, and Dr.Yasser Mohamed
Ahmed Abdel Razak my main supervisor and co-supervisor respectively for the
continued support in my Ph.D study and their motivations, encouragement, guidance
and constructive comments. Without their continued support and interest, this research
work would not have been the same as presented here.
Thanks to my beloved family, my husband Mehdi , my daughter Hediyeh, and
my parents whom I owe a very great debt for support, advice, encouragement and love
gave. My appreciation also extends to all lecturers especially Prof. Dr. Omar bin
Yaakob from mechanical engineering faculty who has given me a lot of valuable
knowledge along my study in this university.
I am also grateful to all technicians of Universiti Teknologi Malaysia- Marine
Technology Centre (UTM-MTC); Mr. Azlan, Mr. Ismail, Mr. Nazmi, Mr. Hazri, Mr.
Shahrizan, Mr. Haidi and Mr. Razief and Mr. Atef salem for the days worked
tirelessly together helping me to conduct the tests.
vi
ABSTRACT
Utilization of electrical energy is important for economic growth and
improvement of people's living, especially for rural and remote areas which have
access to the water but lack of electricity supply. It is known that global energy,
especially in developing countries such as Malaysia, is still heavily dependent on
fossil fuels, which are costly, cause environmental pollution and rapidly depleting.
Hydrokinetic energy, which is one of green and environmentally friendly energy
resources, is promising to replace fossil fuels for electricity generation. The objectives
of this research are firstly to investigate the effect of arm on torque coefficient of
turbine in low speed current, and secondly to determine the effect of self-adjusting
blades on power coefficient. Numerical and experimental research methodologies
have been applied to achieve the objectives. RANS equations have been applied in
CFD simulations using ANSYS-CFX commercial code. For validation of the
simulation results, towing tank experiments using fixed blades condition to obtain
suitable arm length have been carried out at the Marine Technology Centre (MTC)-
Universiti Teknologi Malaysia (UTM). Based on the results obtained by fixed blades
condition, a series of test using self-adjusting blades have been done in three
conditions of load at different current speeds to determine the performance of turbine.
The results show that the arm length and blades angle have a strong effect on the
performance of turbine, where there is 23% increase in terms of performance of self-
adjusting blades turbine compared to fixed blades turbine. This is because the
returning blade angle is in closed position which decreases the hydrodynamic
resistance. In addition, the advancing blade angle is in open condition to have the
maximum force acting. The combined effects result in the increase of torque by the
turbine. The maximum efficiency of the modified self-adjusting system was 16% at
tip speed ratio, λ=0.45. The developed turbine can be applied as a useful tool for
electricity generation in low speed currents. It could also be integrated with a wide
range of generators with different loads.
vii
ABSTRAK
Penggunaan tenaga elektrik adalah penting untuk perkembangan ekonomi dan
pembangunan taraf hidup, terutamanya di kawasan pedalaman dan terpencil yang
menerima bekalan air namun kekurangan saluran bekalan elektrik. Kita sedia maklum
bahawa tenaga global, khususnya di negara-negara membangun seperti Malaysia,
masih bergantung pada bahan api fosil, yang mana adalah mahal, penyebab
pencemaran alam sekitar dan semakin kehabisan. Tenaga hidrokinetik, yang mana
merupakan salah satu sumber tenaga hijau dan mesra alam, berpotensi menggantikan
bahan api fosil untuk penjanaan tenaga elektrik. Objektif kajian ini adalah pertama,
untuk mengkaji pengaruh lengan pada pekali tork turbin dalam arus halaju rendah, dan
kedua adalah untuk mengenalpasti kesan penggunaan bilah bolehubah pada pekali
kuasa. Kaedah berangka dan eksperiment telah gunakan untuk mencapai objektif
kajian. Persamaan RANS telah digunakan dalam simulasi CFD menggunakan kod
komersil ANSYS-CFX. Untuk pengesahan hasil keputusan simulasi, eksperimen
tangki tunda menggunakan situasi bilah tetap untuk mendapatkan panjang lengan yang
sesuai telah dijalankan di Pusat Teknologi Marin (MTC)- Universiti Teknologi
Malaysia. Berdasarkan keputusan daripada situasi bilah tetap, satu siri ujian
menggunakan bilah boleh laras-sendiri telah dijalankan dalam tiga situasi bebanan
pada halaju arus berlainan untuk mengenalpasti prestasi turbin. Keputusan
menunjukkan bahawa panjang lengan dan sudut bilah mempunyai pengaruh yang
besar pada prestasi turbin, di mana prestasi bilah bolehubah mempunyai peningkatan
sebanyak 23% berbanding bilah tetap turbin. Ini berikutan sudut bilah kembali adalah
dalam posisi tertutup, dan mengurangkan rintangan hidrodinamik. Tambahan pula,
sudut bilah maju adalah dalam posisi terbuka untuk tindakan tekanan maksimum.
Gabungan kesan-kesan ini telah meningkatkan tork turbin. Keberkesanan maksimum
oleh sistem bolehubah yang telah dimodifikasi ini adalah 16% pada nisbah halaju
hujung, λ=0.45. Turbin ini boleh diaplikasikan sebagai alat yang berguna untuk
penjanaan tenaga elektrik pada arus halaju rendah. Ia juga boleh diintegrasikan dengan
pelbagai jenis janakuasa dengan beban yang berbeza.
viii
TABLE OF CONTENTS
CHAPTER TITLE PAGE
DECLARATION iii
DEDICATION iv
AKNOWLEDGMENT v
ABSTRACT vi
ABSTRAK vii
TABLE OF CONTENTS viii
LIST OF TABLES xiv
LIST OF FIGURES xv
LIST OF ABBREVIATIONS xxii
LIST OF SYMBOLS xxiii
LIST OF GREEK SYMBOLS xxiv
LIST OF APPENDICES xxv
1 INTRODUCTION
1
1.1 Background 1
1.2 Problem Statement 4
1.3 Research Objectives 5
1.4 Research Scope 5
1.5 Organisation of Thesis 6
2 LITERATURE REVIEW 8
2.1 Introduction 8
2.2 The worldwide necessity for renewable energy 9
2.3 Hydropower capacity 12
ix
2.3.1 Hydropower energy extraction technique 13
2.4 Renewable energy potential and status in Malaysia 14
2.4.1 Electricity supply 15
2.4.2 Renewable energy potential 16
2.5 Hydrokinetic technology 17
2.5.1 Hydrokinetic devices 18
2.5.2 Energy extracted and turbine performance 20
2.5.3 Turbine size and selection 22
2.6 Development and progress of turbines 23
2.6.1 Performance increase of turbines in the world 24
2.6.2 Performance increase of turbines in Malaysia 34
2.6.3 Numerical and experimental procedure for
vertical axis turbine performance
investigation 39
2.7 Summary 42
3 METHODOLOGY
44
3.1 Introduction 44
3.2 Flowchart of research methodology 46
3.3 Strategy of research methodology 47
3.4 Computational methodology 49
3.4.1 General 49
3.4.2 CFD simulation 50
3.4.2.1 Pre-processing 51
3.4.2.2 Solver 51
3.4.2.3 Post-processing 52
3.4.3 Mathematical model 53
3.4.4 Turbulent models 53
3.4.4.1 Realizable kε turbulent model 53
3.4.4.2 kω SST turbulent model 55
3.4.5 Boundary layer at near-wall 57
x
3.4.5.1 Outer zone 57
3.4.5.2 inner zone 57
3.4.6 Boundary conditions 59
3.4.7 Meshing Model 60
3.4.8 Post-processing 62
3.5 Experimental methodology 62
3.5.1 Towing tank 63
3.5.2 Main dimensions of Vertical Axis Current
Turbine 64
3.5.3 Turbine model fabrication 67
3.5.3.1 Blades and holders 68
3.5.3.2 Shaft 69
3.5.3.3 Arms and linkages 70
3.5.3.4 Bearings 72
3.5.4 Experimental setup and procedure 75
3.6 Summary 78
4 NUMERICAL PERFORMANCE CHARACTERISTICS
OF VERTICAL AXIS CURRENT TURBINE 79
4.1 Introduction 79
4.2 CFD study of the fixed blade turbine 79
4.2.1 Numerical model of turbine 81
4.2.2 Computational domain of fixed blades turbine 82
4.2.3 Model meshing 83
4.2.4 Boundary conditions and Details of the
numerical procedure 85
4.2.5 Mesh independency 86
4.2.6 Result and discussion 87
4.2.6.1 Turbine performance 88
4.2.6.2 CFD results of fixed blades turbine 93
4.3 CFD study of self-adjusting blades turbine 96
xi
4.3.1 Geometry and computational domain of self-
adjusting blades turbine 97
4.3.2 Model meshing 98
4.3.3 Boundary conditions and details of numerical
procedure 99
4.3.4 Mesh independency 101
4.3.5 Results and discussion 102
4.4 Summary 107
5 EXPERIMENTAL PERFORMANCE CHARACTERISTICS
OF VERTICAL AXIS CURRENT TURBINE AND CFD
VALIDATION 108
5.1 Introduction 108
5.2 The fixed blades turbine test 110
5.2.1 The fixed blades turbine test setup 112
5.2.2 The fixed blades turbine results and numerical
validation 118
5.2.2.1 Experimental results for different arm
length and discussion 118
5.3 The self-adjusting blades turbine test
124
5.3.1 The self-adjusting blades turbine model
preparation 125
5.3.2 The self-adjusting blades turbine test setup 129
5.3.3 The experimental results and numerical
validation 131
5.3.3.1 The self-adjusting blades turbine
results and discussion at dynamic
condition 131
5.3.3.2 The self-adjusting blades turbine test
results and discussion at static
condition 134
5.3.3.3 Torque variation in one revolution 138
xii
5.4 One blade test 139
5.4.1 One blade test preparation and setup 139
5.4.2 The experimental results and numerical
validation 143
5.4.2.1 The one blade test results and
discussion 143
5.5 Summary 144
6 NUMERICAL PARAMETRIC STUDY OF THE
PERFORMANCE CHARACTERISTICS OF SELF-
ADJUSTING BLADES TURBINE 145
6.1 Introduction 145
6.2 Effect of arm length to bucket diameter ratio (r/d) at
constant R on performance of self-adjusting blades
turbine 146
6.2.1 CFD study of self-adjusting blades turbine
using different arm length to bucket diameter
ratios (r/d) 146
6.2.2 Results and discussion 151
6.3 Effect of blades angle on performance of self-adjusting
blades turbine 154
6.3.1 CFD study on the self-adjusting blades turbine
using different blades angle 154
6.3.2 Results and discussion 159
6.4 Effect of different current speed on performance of
self-adjusting blades turbine 161
6.4.1 CFD study of self-adjusting blades turbine
using different current speed 162
6.4.2 Results and discussion 166
6.5 Comparative study 170
6.6 Hydraulic Transmission System (HTS) for low RPM
turbine 171
xiii
6.7 Summary 172
7 CONCLUSION AND FUTURE WORK 174
7.1 Conclusion 174
7.2 Recommendation for further work 175
REFERENCES 177
Appendices A-C 186-201
xiv
LIST OF TABLES
TABLE NO. TITLE PAGE
2.1 World renewable electricity generation and forecast (IEA,
2013) 12
2.2 Effect of separator and scoop on turbine performance (Batten
et al,2011) 27
2.3 Effect of Savonius stages on performance of turbine (Golecha
et al,2011a) 27
2.4 Deflector plate effect on Savonius turbine performance
(Golecha et al, 2011b and 2012) 30
2.5 Different configurations of blades and stators of vertical axis
marine current turbine 32
3.1 Turbine blade condition in different arm’s length 47
3.2 Main dimension of prototype 65
3.3 Model experiment dimension of turbine 67
4.1 Different arm length 80
4.2 Percentage differences of convergence summary for torque
coefficient of fixed blade turbine at certain tip speed ratio.
(λ=0.2 and arm=270 mm). 88
5.1 Configurations of fixed blades turbine 110
5.2 Self-adjusting blades turbine test results to validate the CFD
results of forces and torque on blades at θ=0ᵒ 143
5.3 Fixed blades turbine test results to validate the CFD results of
forces and torque on blades at θ=0ᵒ 144
6.1 Configurations of buckets and arm in self-adjusting blades
turbine. 146
6.2 Different angles between two connected blades 154
xv
LIST OF FIGURES
FIGURE NO. TITLE PAGE
2.1 World electricity generation from various energy sources
(IEA, 2014) 9
2.2 The world electricity generation from 1971 to 2012 by fuel
(IEA, 2014) 10
2.3 Annual global energy demand record and future forecasts
(EIA, 2006) 11
2.4 World renewable electricity production and prediction (IEA,
2013) 11
2.5 Global renewable electricity production, by technology (IEA,
2013) 13
2.6 Map of Malaysia 14
2.7 Supply and consumption of electricity in Malaysia from
2010–2014 (Department of Statistics, Malaysia, 2015) 15
2.8 Power generation in Malaysia using different type of sources
for the years 2009-2013 (Department of Statistics, Malaysia,
2013) 16
2.9 Principle scheme of hydrokinetic turbines (Guney and
Kaygusuz, 2010) 18
2.10 Horizontal Axis Turbine (Khan et al., 2009) 19
2.11 Vertical Axis Turbine (Khan et al., 2009) 19
2.12 Comparison of CP–λ performance curves (Giudice and Rosa,
2009) 22
2.13 (a) Augmentation channel classification, (b) Channel shapes
(top and side view) (Khan et al., 2006) 25
2.14 New trapezoidal-bladed CFWT: (a) Turbine, (b) Top view of
blade, (c) Perspective view of blade (Zanette et al., 2010) 26
2.15 Different positions of deflector plate with respect to modified 28
xvi
Savonius turbine (Golecha et al., 2011a)
2.16 Comparison of power coefficient for modified Savonius
turbine with and without deflector plate (Golecha et al.,2011a) 29
2.17 Hybrid water current turbines based on a Savonius and
Darrieus turbines (Alam and Iqbal, 2010) 31
2.18 VACT configurations (a) 4-4 (b) 8-8 (c) 12-12 (Asim et al.
2013) 32
2.19 Variations in (a) torque and (b) power coefficient at various
TSR (Asim et al. 2013) 33
2.20 Two paddles and double stacking Savonius models (Yaakob
et al. 2008b) 35
2.21 Top view of Duct model showing a velocity distribution
(Aziz, 2010) 36
2.22 Comparison of a) performance coefficient and b) torque
coefficient between a conventional two-stage Savonius rotor
without deflector and with deflector (Ismail, 2015) 37
2.23 Performance characteristic of two cross flow turbine using
numerical and experimental methods (Aly, 2016) 38
2.24 Schematic of model experiment setting (Yaakob et al., 2013) 40
2.25 The setting of experimental test: (a) Schematic diagram of
Savonius rotor connected with mechanical torque
measurement arrangement (b) photograph, (1: pulley; 2:
nylon string; 3: weighing pan; 4: spring balance; 5: Savonius
rotor; 6: rotating shaft and 7: structure. (Mahmoud et al.,2013) 41
3.1 Computational domain of self-adjusting blades turbine model 45
3.2 Self-adjusting blades turbine model test 45
3.3 Research methodology flowchart 46
3.4 (a) The top view (b) Scheme of arm to bucket diameter ratio
(r/d) of turbine model. 48
3.5 Boundary conditions of turbine model 59
3.6 Three dimensional mesh elements of stationary computational
domain of turbine model 61
3.7 Mesh elements of rotational domain of fixed blades turbine 61
xvii
3.8 Mesh elements of self-adjusting blades turbine 62
3.9 Towing carriage 64
3.10 Scheme blades turbine 65
3.11 Four semi-circular bucket of turbine made by PVC 68
3.12 (a) The buckets with supporters, (b) Holders 69
3.13 (a) supporting structure (b) the model attached to supporting
structure from main shaft 70
3.14 Scheme operations of two blades of turbine 71
3.15 The arm and linkage of self-adjusting turbine 72
3.16 Different types of bearings 73
3.17 2-Bolts Flange bearings used in supporting structure 74
3.18 Shielded ball bearings used in holders 75
3.19 Experimental set up of turbine model test 76
4.1 Top views of turbine geometry with different arm lengths (a)
Arm length = 200mm, (b) Arm length = 270mm and (c) Arm
length = 340mm 82
4.2 Three - dimensional computational domains of fixed blades
turbine 83
4.3 Mesh structure of fixed blades turbine model 84
4.4 Boundary conditions given to fixed blades turbine models 86
4.5 Grid independency of numerical simulation for torque
coefficient of fixed blade turbine with different arm length at
certain tip speed ratio (λ=0.2). 87
4.6 Fixed blade turbine CFD results of torque with different arm
length 89
4.7 Fixed blade turbine CFD results of torque coefficient with
different arm length 89
4.8 Fixed blade turbine CFD results of power coefficient with
different arm length 90
4.9 Fixed blade turbine CFD results of maximum power output
versus arm length 92
4.10 Velocity vectors of fixed blade turbine 93
xviii
4.11 Velocity counters of fixed blade turbine with r=270 mm 94
4.12 Fixed blade turbine with r=340 mm; (a) velocity vector, and
(b) velocity stream line 95
4.13 The main axis and local axis in self-adjusting blades turbine 96
4.14 Geometry of self-adjusting blades using Solid Work 97
4.15 Computational domain of self-adjusting blades turbine 98
4.16 Mesh structure of self-adjusting blades turbine 99
4.17 Boundary conditions of self-adjusting blades turbine 100
4.18 Grid independency of numerical simulation for torque of self-
adjusting blades turbine at certain tip speed ratio (λ=0.2) 101
4.19 Self-adjusting blades turbine CFD results of torque coefficient
compared with fixed blades turbine 102
4.20 Self-adjusting blades turbine CFD results of power coefficient
compared with fixed blades turbine 104
4.21 Pressure counters of (a) fixed blades turbine and (b) self-
adjusting blades turbine at θ=90º 105
4.22 Self-adjusting blades turbine CFD results of static torque
coefficient 106
5.1 The turbine model, carriage and towing tank of UTM-MTC 109
5.2 Different configuration of fixed blades turbine: (a) arm
length=200mm (b) arm length=270mm (c) arm
length=340mm 112
5.3 The turbine model test attached to the towing carriage in
MTC-UTM 113
5.4 Experimental setting of turbine model at dynamic condition 114
5.5 Experimental setting of turbine model at dynamic condition 115
5.6 Experimental setting of turbine model at dynamic condition 116
5.7 Experimental setting of turbine model at static condition 117
5.8 Fixed blade turbine test results to validate the CFD results of
torque coefficient with 200 mm of arm length 118
5.9 Fixed blade turbine test results to validate the CFD results of
torque coefficient with 270 mm of arm length 119
xix
5.10 Fixed blade turbine test results to validate the CFD results of
torque coefficient with 340 mm of arm length 120
5.11 Fixed blade turbine test results to validate the CFD results of
power coefficient with 200 mm of arm length 121
5.12 Fixed blade turbine test results to validate the CFD results of
power coefficient with 270 mm of arm length 122
5.13 Fixed blade turbine test results to validate the CFD results of
power coefficient with 340 mm of arm length 122
5.14 Fixed blade turbine test results to validate the CFD results of
maximum power output versus arm length 123
5.15 Heating up the bearings to remove old grease 126
5.16 Washing process of bearings 127
5.17 Re-oiling of bearings 127
5.18 The self-adjusting blades turbine model test 129
5.19 The self-adjusting blades turbine test setup 130
5.20 Self-adjusting blades turbine test results to validate the CFD
results of torque coefficient 132
5.21 Self-adjusting blades turbine test results to validate the CFD
results of power coefficient 133
5.22 Details of torque calculation for self-adjusting blades turbine 135
5.23 Self-adjusting blades turbine test results to validate the CFD
results of static torque coefficient 137
5.24 Self-adjusting blades turbine test results to validate the CFD
results of dynamic torque coefficient at certain tip speed ratio
(λ=0.36) 138
5.25 The 6-component force measuring system 140
5.26 one blade test model 140
5.27 the experimental set up of the one blade test 141
5.28 The arrangement of main shaft on the blade: (a) the main
shaft attached on concave side, (b) the main shaft attached on
convex side 142
6.1 Pressure contours of self-adjusting blades turbine (a) self-
adjusting blades turbine with r/d=1.04 and (b) self-adjusting 148
xx
blades turbine with r/d=1.35
6.2 Velocity vectors of self-adjusting blades turbine (a) self-
adjusting blades turbine with r/d=1.04 and (b) self-adjusting
blades turbine with r/d=1.35 149
6.3 Velocity stream line of self-adjusting blades turbine (a) self-
adjusting blades turbine with r/d=1.04 and (b) self-adjusting
blades turbine with r/d=1.35 150
6.4 Self-adjusting blades turbine CFD results of torque coefficient
with different arm length to bucket diameter ratios (r/d). 151
6.5 Self-adjusting blades turbine CFD results of power coefficient
with different arm length to bucket diameter ratios (r/d) 152
6.6 Self-adjusting blades turbine CFD results of maximum power
coefficient for different arm length to bucket diameter ratios
(r/d) 153
6.7 Scheme of blades angle (θ) 155
6.8 Pressure contour of self-adjusting blades turbine at θ=30º of
arm angle 156
6.9 Pressure contour of self-adjusting blades turbine at θ=30º of
arm angle 156
6.10 Velocity vector of self-adjusting blades turbine at θ=30º of
arm angle for blade angle (a) 95º and (b) 90º 157
6.11 Pressure contour of self-adjusting blades turbine at θ=30º of
arm angle for blade angle 85º 158
6.12 Velocity stream line of self-adjusting blades turbine at θ=30º
of arm angle for blade angle 85º 158
6.13 Self-adjusting blades turbine CFD results of torque coefficient
with different blade angles 159
6.14 Self-adjusting blades turbine CFD results of power coefficient
with different blade angles 160
6.15 Self-adjusting blades turbine CFD results of maximum power
coefficient 161
6.16 Pressure contour of self-adjusting blades turbine at θ=30º of
arm angle for current speeds (a) 0.64 m/s, (b) 0.32 m/s and (c) 163
xxi
0.17 m/s
6.17 Velocity vector of self-adjusting blades turbine at θ=30º of
arm angle for current speeds (a) 0.64 m/s, (b) 0.32 m/s and (c)
0.17 m/s 165
6.18 Self-adjusting blades turbine CFD results of torque coefficient
for different current speeds 166
6.19 Self-adjusting blades turbine CFD results of power coefficient
for different current speeds 167
6.20 Self-adjusting blades turbine CFD results of maximum power
coefficient 168
6.21 Self-adjusting blades turbine CFD results of torque 169
6.22 Self-adjusting blades turbine CFD results of power output 169
6.23 Comparison of Cp − λ performance curves 171
6.24 The scheme diagram of Hydraulic Transmission System 172
xxii
LIST OF ABBREVIATIONS
BEM - Boundary Element Method
BDA - Bidirectional diffuser augmented
B.C - Boundary conditions
CFD - Computational Fluids Dynamic
CICT - Centre for Information and Communication Technology
FDM - Finite Difference Method
FEM - Finite Element Method
FTT - Folding tidal turbine
FVM - Finite Volume Method
GHG - greenhouse gases
GW h Giga watt per hour
IEA - International Energy Agency
MFR - Multiple Frame of Reference
Mph - Miles per hour
MRF - Moving Reference Frame
MTC - Marine Technology Centre
PVC - Polyvinyl Chloride pipe
RNG - Re-Normalisation Group
RPM - Revolutions Per Minute
RANS - Reynolds Averaged Navier Stokes
SIMPLE - Semi-implicit method for pressure-linked equations
SREP - Small Renewable Energy Power Program
SMM - Sliding Mesh Motion
SST - Shear Stress Transport
TSR - Tip speed ratio
UTM - Universiti Teknologi Malaysia
VACT - Vertical axis Current Turbine
xxiii
LIST OF SYMBOLS
𝐴𝑠 - Swept area, (m2)
𝐴𝐵 - Bucket area, (m2)
𝐶𝑃 - power coefficient
𝐶𝑇 - Torque coefficient
𝐶𝑇𝑠 - Static torque coefficient
𝐷 - Turbine diameter, (m)
𝑑 - Bucket diameter, (m)
𝐹 - Force, (N)
𝐹𝐿 - Load cell force, (N)
𝐹𝑛 - Froude number
𝑔 - Gravity Acceleration, (m/s2)
𝐻 - Height of turbine, (m)
𝐿𝑝 - Prototype length, (m)
𝐿𝑚 - Model length, (m)
𝑃 - Power output, (Watt)
𝑃𝑚𝑎𝑥 - The total power available in the free stream flow, (Watt)
𝑅 - Radius of turbine, (m)
𝑟 - Arm length, (m)
𝑟𝑏 - Radius of bucket
𝑟1 - Radius of pulley, (m)
𝑟𝑤𝑖𝑟𝑒 - Radius of wire, (m)
𝑆 - Spring balance reading, (kg)
𝑇 - Torque (N.m)
𝑉0 - Current velocity, (m/s)
𝑌+ - wall distance
(x, y, z) - Cartesian coordinate system with its origin at the centre
of turbine
xxiv
LIST OF GREEK SYMBOLS
ω - Rotational speed
η - Efficiency
𝜂𝑡 - Total efficiency
𝜂𝑔 - Drive train efficiency
β - Overlap ratio
ρ - Density of water,(kg/m3)
λ - Tip speed ratio
ε - Dissipation energy
𝜏𝑤 - Shear stress
µ - Dynamic viscosity of water
γ - Scale factor
xxv
LIST OF APPENDICES
APPENDIX TITLE PAGE
A Procedure of fixed blades turbine model construction 186
B 6- component force measuring system 196
C publications 200
CHAPTER 1
INTRODUCTION
1.1 Background
The variety of energy in such country reflects the strength of the economic,
social, environmental and security development issues. It can be used as an sign for
income level, poverty, jobs and, access to social services, population growth, industrial
and agricultural production. On the other hand, the shortage of electrical energy causes
the economic crisis in many countries. Many people all over the world, especially in the
rural and poor areas have no access to electricity. According to one-third of the world’s
population does not have access to electricity, but does have access to flowing water
(Bertsch, 2012).
Electricity is the fastest-growing final form of energy that International Energy
Agency (IEA) estimated a 53% increase in global energy consumption is foreseen by
2030 (International Energy Agency (IEA), 2014,). It is noteworthy that world energy,
especially in developing countries such as Malaysia (Chong and Lam, 2013) is still
heavily dependent on fossil fuels, which are costly, environmental pollutant and rapidly
being depleted. At current production rates, global proven reserves of crude oil and
natural gas are estimated to last for 41.8 and 60.3 years, respectively (Altan et al., 2008
and Kaltschmitt et al., 2007), so that the role of renewable energy as green and clean
2
energy to generate electricity, reduce the greenhouse gas emissions and decrease the
fuel prices (Bernad et al. 2008) is significant.
Malaysia is considering renewable energy to alleviate the high dependency on
fossil fuel. It is in the process of utilizing its available resources and discovering its
potential. It is considerable Malaysia has a significant amount of hydropower resources
as renewable energy, due to the geographical location of Malaysia, with the surrounding
South China Sea, equatorial climate, high rainfall rate of around 250 cm per year, long
coastlines such as the Straits of Malacca, many rivers and irrigation channels (Chong
and Lam, 2013). In addition, some remote areas in Malaysia beside the ocean but
without access to electricity are poised to exploit the great potential of ocean energy as
hydrokinetic energy to generate electricity, such as Sabah and Sarawak using
hydrokinetic devices.
Also, hydropower among the other renewables energy is the prime choice to
contribute to the world’s energy generation because it is continuously available, high
density, powerful, predictable and independent of random weather conditions, as
opposed to solar and wind options, and has less impact on environmental and human
activity (William and Jain, 2011; Junior, 2011; Paish, 2002; Frankel, 2002 and Yuen et
al. 2009).
There are different types of hydrokinetic turbine horizontal axis (axial-flow) and
vertical axis turbine where the turbine blades would turn the generator by capture the
energy of the water flow to produce electricity (Sornes, 2010; Frankel, 2004 and
Gorlov, 2004). There is no consensus yet on whether horizontal axis or vertical axis will
be the best option for using water current energy; however, the vertical axis turbine
appears to have advantages over the horizontal axis turbine in several aspects (Eriksson
et al., 2008).
Conventional current turbines which include Darrieus, Gorlov (helical), Davis,
Cyloidal and Kobold turbines are very much depending on current speed and water
3
depth. However, the average ocean current velocity in many locations in Malaysia is 1
m/s (Royal Malaysia navy, 2010 and Hassan et al., 2012), while the optimum current
speed for ideal turbine operation is at least 2 m/s (4 knots) (Hassan et al., 2012). Hence,
the use of conventional current turbines is no longer a feasible solution to employ them
for generating electricity in low current speed. As a result, modifications of turbine
system are needed to harness maximum power, especially for remote areas alongside
the ocean.
Despite attempts to develop renewable energy, up to now it has not been used to
its maximum potential in Malaysia because of restrictions on the head and current
speeds (Yogi, 2010 and Kamarulzaman, 2012) and it will be such a waste if these
natural sources of energy leave without any usage. It is essential for Malaysia to strike a
balance in terms of policies, and in the meantime continue the improvement and
development of kinetic energy devices towards a greater contribution of hydrokinetic
energy as renewable energy to ensure a secure and sustainable future.
Vertical axis current turbine to control energy of low speed currents is at the
early stage of development but have significant effect to generate electricity for future
supply of clean energy.
This research presents a new design of Vertical Axis Current Turbine (VACT)
applicable in low speed current which increase torque and decrease resistant of water
leading high output power and hence generate more electricity while is being
increasingly used to harness kinetic energy of water and convert it into other useful
forms of energy as a clean and renewable energy.
4
1.2 Problem statement
Nowadays, population growth, electrical demands, rising fuel prices, depleting
fossil resources, their environmentally harmful effects and economic problems, are
serious subjects to replace fossil resources with renewable energy to generate electricity
especially in developing countries.
Malaysia is a country that is surrounded by rivers, ocean and irrigation or rainy
channels have rich energy resources, but some of rural and remote areas where they are
located alongside ocean are very poor, with low living conditions and limited access to
media and information which grid extension way for electrification of them is
uneconomical hence hydrokinetic technology can generate a significant amount of
electric power. Another challenge is the characteristics of Malaysian currents. The
Malaysian ocean current velocity, averagely, is 1 m/s which are approximately half of
the speed for ideal turbine operation. These characteristics of the Malaysian current
impose some limitations on the energy that can be extracted, that some modifications
must be undertaken to allow hydrokinetic turbines to overcome this velocity limitation
so as to extract maximum power from the current and permit electrification of rural and
remote areas with access to running water but little electricity. There are very few and
limited studies that considered the problems associated with the low current speed in
Malaysia.
Consider extracting energy of current using vertical axis current turbines, it is
necessary to solve challenges associated with turbine configuration, enhancing the
efficiency and achieve high output power using the best design of turbines that can be
employed in low speed current.
According to above challenges, the research will develop a new vertical axis
current turbine using arm and self-adjusting blades which can decrease the resistance
force, produce high torque and output power, consequently generate more electricity as
a clean source that detail of it will be elucidated in the next chapters.
5
1.3 Research Objectives
The aim of this study is to develop new knowledge and find solution for
challenges about increasing performance of vertical axis current turbine and find the
suitable design that can operate in low current speed. The objectives of present research
are as follows:
i) To develop a vertical axis current turbine suitable for low speed currents.
ii) To evaluate the effect of arm and different (arm length (r)/blade diameter (d)) on
torque and performance characteristics of vertical axis current turbine.
iii) To study the resistance reduction and performance characteristics of vertical axis
current turbine due to the self-adjusting blades and different blades angle.
1.4 Research Scope
The aim of the project is to evaluate the performance of new vertical axis turbine
using arm and self-adjusting blades in low speed current. This project has been done
using numerical and experimental method to achieve the aim of research which each
one has several steps. The research scope is explained as follows:
i) The literature review was carried out about necessity of renewable energy,
Hydropower energy extraction technique, operation principle of turbines,
turbine performance, development and progress of turbines. This step made a
good guideline for present research work.
ii) The Computational Fluid Dynamics (CFD) method has been used for
numerical simulation and parametric study for investigation the torque and
power output, optimum angle and resistance reduction of blades, pressure and
6
velocity distribution on blade surface for different rotational blades angle,
different arm length for generate the torque.
iii) Experimental work has been conducted to validate the numerical simulation.
Characteristics of turbine performance - torque and power output - for fixed
and self-adjusting blades conditions have been measured to compare the
results with CFD simulation. The series of tests has been performed in
Universiti Teknologi Malaysia (UTM) - Marine Technology Centre (MTC).
1.5 Organization of thesis
This research composed of 7 chapters. The first chapter includes the
background, statement problem, research objectives, and research scope. The other
chapters (2-7) explain the literature review, research methodology, experimental works,
numerical simulation validation, parametric study, results and discussion. Also, it will
be mentioned in the conclusion and future work chapters that all of them are to be used
for paper publication in journals and presentation in conferences. A brief of each
chapter is mentioned in following:
Chapter 1 presents an introduction to the research study consist of the
background, statement problem, research objectives, and research scope.
Chapter 2 explains a comprehensive literature review of available scientific
information related to topic of this research. This chapter, the necessity for renewable
energy in the world and Malaysia, hydropower capacity, hydrokinetic technology, and
development and progress of turbines are reviewed.
In chapter 3, research methodology which composed of numerical and
experimental methods is described. Computational methodology includes the general
information about Computational Fluid Dynamics (CFD), turbulence models, solver,
7
model geometry and meshing, computational domains and boundary conditions. The
experimental methodology gives the background about towing tank of Marine
Technology Centre (MTC), Univerciti Teknologi Malaysia (UTM). Also, some
explanation about turbine model fabrication, experimental setup, torque measurement
and performance characteristic of turbine calculation are presented.
The numerical simulation of fixed blades turbine, and self-adjusting blades
turbine to show their characteristics in dynamic or static conditions are investigated in
chapter 4. The numerical works have been done using high performance computer in
centre for information and communication technology (CICT) - Universiti Teknologi
Malaysia (UTM).
In chapter 5, the experimental performance characteristics of fixed blades
turbine, Experimental performance characteristics of self-adjusting blades turbine in
static and dynamic conditions, experimental hydrodynamic characteristic of one blade
and CFD validation are investigated. The results of experimental test for fixed blades
turbine, self-adjusting blades turbine and one blade of self-adjusting blades turbine in
different condition are analyzed and compared with numerical simulation results. The
experimental results are validated the CFD simulations with good agreement.
Chapter 6 presents the parametric study using numerical simulation. This
chapter shows the performance characteristics of self-adjusting blades turbine affected
by different arm to blade diameter ratio (r/d) in fixed R, different blades angle and
different current velocity.
Finally, the important and valuable conclusions are described in chapter 7
included with results and discussion from present research. Moreover, some future
works for next research are recommended in this chapter.
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