NUMERICAL ANALYSIS AND EXPERIMENTAL TESTS OF A LOW WIND...

崑山科技大學

機械工程系

實務專題

NUMERICAL ANALYSIS AND EXPERIMENTAL TESTS OF A LOW

WIND SPEED VERTICAL AXIS WIND TURBINE

By

PATRICIA ARLEEN ESCOBAR WILLSON

葉若雅

SENIOR PROJECT FOR BACHELOR OF SCIENCE IN MECHANICAL ENGINEERING

TAINAN, TAIWAN

R.O.C.

MAY, 2010

Kun Shan University 2

Numerical Analysis and Experimental Tests of a Low Wind Speed Vertical Axis Wind Turbine May, 2010

ABSTRACT

In this work, a new type of Vertical Axis Wind Turbine, called Wollongong, is

developed by the application of a numerical analysis and later on by experimental

tests that aided to prove the theoretical results.

Firstly, the main problem was to find the best gear ratio that permits the Wollongong

Turbine to have the best efficiency. This could be performed by the numerical analysis

done to the gear system that is connected to the turbine’s blades and the wind vane.

This analysis leads the conclusion that the gear ratio equals to -1/2 was the most

appropriate for this configuration. The design and construction of the Wollongong

Turbine’s prototype was carried out based on this result. The scale model was build

applying the Rapid Prototyping process, which is a rapid way to construct any part.

The Savonius Turbine was acquired with the purpose of compare two different designs

of Impulse Type turbines. This prototype was already designed; however some

improvements were made, like the addition of bearings, which are essential for a

better rotation.

The results obtained from the experimental analysis of both turbines presented a

higher efficiency at the third fan speed. After the comparison between both turbines,

the Wollongong Turbine velocity values present a much higher average percentage

increase over the Savonius Turbine’s one, hence prove to have a better efficiency and

performance.



ACKNOWLEDGEMENT

At the end of this journey, first of all I want to thank God for being the One who gave

me the strength and wisdom during all these years.

Thanks to my Mom, for being my friend and my guide, for your unconditional love and

patience; I love you mommy. Thanks to my Dad, for encourage me to grow in my

professional career, for your love and support. To my beautiful sister, cousins,

nephews, nieces, grandmothers, my aunt, my uncle and my best friends who despite

the distance have always been there for me.

I would like to express my gratitude to my dear advisor Professor Song-Hao Wang, for

your advices, guidance and especially for your encouragement to be a better and

prepared engineer.

To my team “Wind Busters” for shared your abilities and knowledge with me. This

thesis would not have been possible without each of you.

To Taiwan ICDF, for giving me the great opportunity to come to Taiwan; I’m taking

from this country its sense of attention and respect to others.

For your support and help all these years, my sincere gratitude to the International

Office and the Mechanical Engineering personnel.

To Andres, thanks for being an angel in my path, my best friend, family and support

during these four years. Thank you for your love, it is one of the most valuable

treasures that I’m taking back home. You are an essential part of my life.

To Monse, thank you for your friendship which is one of the most important things

that I’ve got from this experience. Thanks for all the moments that we have shared

because I’ve learned so much from them; I’ll miss you sis!

To Cindy, xie xie for your wise advices, for taught me the value of the most little things

and for the entertaining Green Tea sessions, which relaxed me during these months.

You have been like my older sister, I’ll miss you too!



Thanks Karen for the hug, the smile and warmth that always you have for me; I thank

God for placed you in my way as the best roommate I could ever have had. Milton,

Ronny, Meme, Rey, Transporters and all KSU friends; thanks for being like a family in

this part of the world, definitely I’ll miss you all my life.



CONTENTS

Abstract 2

Acknowledgment 3

List of Figures 7

List of Tables 9

1 INTRODUCTION 10

1.1 Purpose of Study 10

1.2 Problem Statement 11

1.3 Overview of Methodology 12

1.3.1 Numerical Analysis 12

1.3.2 Experimental Set-up 12

2 BACKGROUND 13

2.1 Wind Power 13

2.2 Wind Turbines 15

2.2.1 Horizontal Axis Wind Turbine (HAWT) 16

2.2.2 Vertical Axis Wind Turbine (VAWT) 17

2.3 Savonius Turbine 18

2.4 Wollongong Wind Turbine 19

2.5 Numerical Analysis 21

2.6 Rapid Prototyping 21

3 NUMERICAL ANALYSIS 23

3.1 Gear Ratio 23

3.2 Numerical Analysis of Wollongong Turbine 24

4 EXPERIMENTAL TESTS 29

4.1 Savonius Wind Turbine 29

4.1.1 Optimization of Savonius Turbine 30

4.1.2 Assembly of Savonius Turbine 32

4.2 Wollongong Wind Turbine 32

4.2.1 CAD of Wollongong Turbine 33

4.2.2 Rapid Prototyping Process of Wollongong Turbine 37



4.2.3 Assembly of Wollongong Turbine 38

4.3 Other Experimental Equipments 40

4.3.1 3-phase Wind Turbine Kit 40

4.3.2 Home Ventilator and Tachometer Sensor 43

5 RESULTS AND DISCUSSIONS 44

5.1 Numerical Analysis Results 44

5.2 Experimental Tests Results 47

5.2.1 Savonius Turbine Results 47

5.2.2 Wollongong Turbine Results 51

5.2.3 Final Comparison 55

5.2.3.1 Power Calculation 56

CONCLUSIONS 57

FUTURE WORK 58

REFERENCES 59

APPENDIX 61



LIST OF FIGURES

Figure 1 – CO2 emissions by fuel from 1971 to 2007 (adapted from [20]) 14

Figure 2 – Internal description of HAWT’s rotor and a typical HAWT 16

Figure 3 – Original Design of Savonius Turbine, Darrieus Turbine and H-Rotor 17

Figure 4 – Turby, Wind-Sail and Windside 18

Figure 5 – Schematic views of the orientation of blades and rotor of the VAWT

(adapted from [25])

20

Figure 6 – Wollongong Turbine and Gear configuration 20

Figure 7 – Rapid Prototyping Machine used in experiments 22

Figure 8 – A particle located at P1 is displaced by an angle α or arc length s to

position P2

24

Figure 9 – Description of the arm and blades orientation 25

Figure 10 – Moment and Work at G= -1/2 28

Figure 11 – Wind Turbine Interface Circuit Board and StampPlot software 29

Figure 12 – Original Savonius Turbine, Original Threaded Shaft and New Shaft 30

Figure 13 – Support descriptions and New Support during RP process 31

Figure 14 – Original blade support, CAD design and new support 31

Figure 15 – Support with embedded bearing and Final Assembly 32

Figure 16 – Bottom view, right view and base in 3D 33

Figure 17 – Middle part CAD 34

Figure 18 – Upper part CAD 34

Figure 19 – Gears shaft support CAD 35

Figure 20 – Blade CAD 35

Figure 21 – Washer CAD 36

Figure 22 – Central gear pair and Blade gear pair 36

Figure 23 – Wind Vane CAD 37

Figure 24 – Wollongong Turbine set in the initial position 39

Figure 25 – Original Wind Vane design and Modified Wind Vane 39

Figure 26 – Final Assembly of Wollongong Turbine 39

Figure 27 – Stator and six powerful magnets 40

Figure 28 – Star Coil Arrangement and Resultant 3-phase AC output (adapted 41



from [24])

Figure 29 – Delta coil arrangement and resultant 3-phase AC output (adapted

from [24])

42

Figure 30 – Ordinary home ventilator 43

Figure 31 – Tachometer Sensor 43

Figure 32 – Moment and Work at G= ½ 44



Figure 35 – Savonius Turbine’s DELTA Screen Plot at Velocity 2 48

Figure 36 – Savonius Turbine’s DELTA Screen Plot at Velocity 3 49

Figure 37 – Savonius Turbine’s STAR Screen Plot at Velocity 1 50



Figure 40 – Wollongong Turbine’s DELTA Screen Plot at Velocity 1 52



Figure 43 – Wollongong Turbine’s STAR Screen Plot at Velocity 1 54



Figure 46 – Wind vane, central gear and upper part assembly 61

Figure 47 – Upper part, middle shaft and base assembly 61

Figure 48 – Middle gears and gear’s support assembly 62

Figure 49 – Small gear, big Gear and blade assembly 62



LIST OF TABLES Table 1 – Gear Ratio relationship 23

Table 2 – Materials of Savonius Turbine 30

Table 3 – Other parts of the Wollongong Turbine 38

Table 4 – Domestic Fan Velocities in rpm 47

Table 5 – Savonius Turbine Voltages on DELTA Configuration (millivolts, mV) 48

Table 6 – Savonius Turbine Voltages on STAR Configuration (millivolts, mV) 49

Table 7 – Wollongong Turbine Voltages on DELTA Configuration (millivolts, mV) 51

Table 8 – Wollongong Turbine Voltages on STAR Configuration (millivolts, mV) 53

Table 9 – Summary of Experimental Data Tests 55

Table 10 – Computed Power (Milliwatts, mW) 56



1. INTRODUCTION

1.1 Purpose of Study

In an economically and environmentally way, there are some issues to worry about in

regard to the future of energy production in the world. The most serious problem is

the dependence of oil, coal and gas in today’s society, since different estimations have

been presented on when the oil will start to deplete or become too expensive.

However, the most important concern falls into the large quantities of greenhouse

gases that have been emitted during all these past years, which is environmentally

unsustainable.

Due to the urgently warn about such pollution, has increased the desire of make a

better use of the freely available energy sources that surrounds us, where most of

scientists agreed that renewable energy sources are the best option [14]. The most

environmental friendly types of energy are wind power, solar power, wave power and

marine current power.

Nowadays energy that is generated from wind is becoming one of the most utilized

renewable energy sources. Wind power is an energy that presents largely potential

and has improved in the last decades growing at the rate of 30 percent annually, with

a worldwide installed capacity of 121,000 megawatts (MW) in 2008. [15].

Wind turbines are the systems used to generate electricity from the kinetic power of

the wind. At the present time are many kinds of wind turbines, which are divided in

Impulse Type Wind Turbines and Aerodynamic Type Wind Turbines.

This thesis deals with a Vertical Axis Wind Turbine (VAWT), called Wollongong that is

composed by a vertical main shaft, which had mounted on it a wind vane. This wind

vane holds a free bevel gear that controlled the pitching of the blades [14]. The main

objective of the numerical analysis, and the experimental test made during this

research, is to obtain the most suitable gear ratio between the main shaft and the

blades, since it will play an important role in the efficiency of the turbine. Also, to



compare its efficiency with a Savonius rotor, in order to prove the improvement in an

impulse type wind turbine.

1.2 Problem Statement

Global warming is increasingly becoming a crucial issue in the contemporary world,

which is why some nations, states, corporations and individuals are implementing

many responses.

Nowadays is known that there is enough wind globally to satisfy most of humanity's

energy requirements, and that is why every year the number of installed wind power

plants in the world increase. Actually the horizontal axis wind turbine (HAWT) is the

most common type of turbine that is installed around the world to the production of

megawatt levels. But on the other hand, VAWT’s do not play any role, because of its

lower efficiency, mostly caused by the high vibration, which is the most significant

operational problem [13]. However, there has been renewed interest in this device

because its simplicity.

Scientists have agreed that VAWT’s may be as efficient as current horizontal axis

systems, might be practical, simpler and significantly cheaper to build and maintain [2].

The principal advantages of VAWT’s, for instance, are the low level production of

noise and the independence of wind direction.

Because of the VAWT’s potential, a research about it started. VAWT’s, as mention

before, are divided in two types, impulse type and aerodynamic type. This work

studies an impulse type turbine that is based on a research made at the University of

Wollongong in Australia, which explain a new gear system design to control the blades

position while they are rotating, but there is no explanation about which gear ratio

was the more suitable to get the highest efficiency. A numerical analysis was made in

order to get the best gear ratio, and later on the experimental analysis was done to

compare the results with an original design of impulse type turbine, the Savonius.



1.3 Overview of Methodology

1.3.1 Numerical Analysis

This research presents a numerical analysis made to get the best efficiency of the

Wollongong wind turbine, which will be linked to the gear ratio of the system. First, a

derivation of an equation that described the orientation of the blades during its

rotation is needed. After the equation that represents the moment of the turbine was

obtained, with the aid of National Instruments LabVIEW the definite integration of the

equation was solved. This integration represents the Work done by the turbine.

Through the substitution of different gear ratios, finally the optimum one was got.

1.3.2 Experimental Set-up

Once the best gear ratio was obtained through numerical analysis, the experimental

analysis began. The first step was to buy another wind turbine that already was in the

market, for experimental purposes; the type is Savonius. This turbine came with

equipment that allows measuring the voltage at any wind velocity and by

mathematical calculations the power and current. Some improvements were done to

it for better performance.

Since the Wollongong Turbine data have to be compared to the Savonius one, the

swept area and size of both are similar. With the aid of CAD software, a model of the

Wollongong Turbine was developed. Almost all the components were designed,

including the gear system. These parts were printed out by Rapid Prototyping process.

The turbine was carefully assembled, since the gears system should be placed in a

specific initial position. The voltage and generated power of both turbines was

measured and compared.



2. BACKGROUND

2.1 Wind Power

The wind is the result of pressure differences in the atmosphere; the speed and the

direction of wind are determined by the ratio of the pressure differences and the

distance between the centers of high and low pressure. The wind speed increase as

the height increase. Closer to the ground this speed is reduced due to the resistance

the wind has met on its way.

Wind power is an energy that presents largely potential and has improved in the last

decades growing at the rate of 30 percent annually, with a worldwide installed

capacity of 121,000 megawatts (MW) in 2008 [15]. Like all renewable resources, wind

energy is a clean, emissions-free power generation technology and it is based on

capturing the energy from natural forces and has none of the polluting effects

associated with conventional fuels.

As shown in last year’s Intergovernmental Panel on Climate Change (IPCC) 4th

Assessment Report, the goal must be to ensure that global greenhouse gas emissions

peak, and begin to decline by 2020 at the latest [17]. This is the minimum necessary to

give to the next generation the chance to avoid the worst consequences of climate

change.

Although the power sector is not the only causer of the enormous greenhouse gas

emissions, it is the largest contributor of global carbon dioxide emissions, with a 40%

of total amount; and this number keeps increasing as it is shown in figure 1. In order

to make a major difference in power sector emissions, industries are focused in the

development of renewable energies. In practical terms for an optimum clean energy

future, wind will be an important part of a mix of renewable energy technologies,

playing a dominant role in some regions than in others.



Figure 1 - CO2 emissions by fuel from 1971 to 2007. [20]

North America was found to have the greatest wind power potential, although some

of the strongest winds were observed in Northern Europe, while the southern tip of

South America and the Australian island of Tasmania also recorded significant and

sustained strong winds. To be clear, however, there are extraordinarily large untapped

wind resources on all continents, and in most countries; and while this study included

some island observation points, it did not include offshore resources, which are

enormous [17]. In summary, wind power is a practically unlimited and clean free

power source, of which only a tiny fraction is currently being exploited.

For the utilization of this inexhaustible natural resource, the wind turbine generators

are the systems used to change wind energy into mechanical energy (such as wind mill

and moving weight) and to generate electricity.



2.2 Wind Turbines

Since very long time ago the wind has been used as an energy source; a good example

is sailing boats. The first windmills were used by the Persians approximately 900 AD.

These first windmills were VAWTs. During the Middle Ages horizontal axis windmills

were built in Europe and used for mechanical tasks such as pumping water or grinding

grain. These were the classical four bladed windmills that had a yawing system and

were mounted on a big structure. These windmills lost popularity after the industrial

revolution. At about the same time water pumping windmills became popular in the

United States, recognizable for their many blades and typically situated on a farm.

During the 20th century the horizontal axis wind turbines continued to evolve, which

resulted in bigger and more advanced turbines, leading to the modern HAWTs [19].

The amount of electricity that a turbine produces depends on its size and on the wind

speed. Most large wind turbines have the same basic parts: blades, a main shaft and a

gearbox. These parts work together to convert the wind’s kinetic energy into

mechanical energy that generates electricity. The process begins when the moving air

hit the turbine blades and makes them spin; these blades are connected to a low-

speed shaft. When the blades spin, the shaft turns. The low-speed shaft is connected

to a gearbox. Inside the gearbox, a large slow-moving gear turns a small gear quickly.

This gear turns another shaft at high speed, which is connected to a generator. As the

shaft turns the generator, it produces electricity. Then, the electric current is sent

through cables to a transformer that changes the voltage of the current before it is

sent out on transmission lines [21].

Wind turbines are stand-alone machines which are often installed and net-worked in a

place referred to as a Wind Farm or Wind Park. Wind farms can be located either

onshore or offshore [18]. Every year the number of installed wind power plants in the

world increases. The horizontal axis wind turbine is the most common type of turbine

but there exist other types like the vertical axis ones [12].

Wind turbines can be divided in two groups, impulse type wind turbine and

aerodynamic wind turbines. Impulse type wind turbines basically are VAWTs types



which cover the whole swept area and are designed to give a high resistance to the

wind that is coming in, in the direction of the rotation and as little as possible

resistance to wind blowing to the other side of the blade [4]. On the other hand,

aerodynamic wind turbines include the HAWT and VAWT, those have wing-shaped

blades that cover a small part of the swept area; the wind flow along these blades

generate a lift force perpendicular to the flow [4], same as airplanes wings do.

2.2.1 Horizontal Axis Wind Turbine (HAWT)

HAWT is the most common turbine configuration used today. It consists of a main

rotor shaft and an electrical generator at the top of a tower, and must be pointed into

the wind. Small HAWTs are pointed by a wind vane, while large turbines generally use

a wind sensor couples with a servo motor. Most of the HAWTs have a gearbox, which

turns the slow rotation of the blades into a quicker rotation, since it is more suitable

to drive an electrical generator [22].

Figure 2 - Internal description of HAWT’s rotor (left) and a typical HAWT (right)

Since a tower produces turbulence behind it, the turbine is usually pointed upwind of

it. HAWTs generally are composed of two or three blades, although some have more

blades. The turbine blades are made stiff to prevent the blades from being pushed

into the tower by high winds [22]. Additionally, the blades are placed at a considerable

distance in front of the tower and sometimes are tilted forward into the wind. Actually,

HAWTs are the most efficient type of turbine in terms of energy production.



2.2.2 Vertical Axis Wind Turbine (VAWT)

Vertical axis wind turbines have been developed in parallel with HAWTs, but with less

financial support and less interest. The engineer Sigurd Savonius invented the

Savonius turbine in 1922, which has a high starting torque [23]. Georges Darrieus

design a VAWT with straight or bent lifting blades in 1920’s also. But VAWTs came into

focus during 70’s and 80’s, when in Canada and United States were built many

prototypes of Darrieus rotors [11]. These installations proved that VAWTs are quite

efficient and reliable. An American company called FloWind commercialized the

Darrieus turbine in 80’s. During this decade more than 500 commercial VAWTs were

operating in California. The straight-bladed VAWT was also an invention included in

the original Darrieus patent. This turbine is usually referred as the straight-bladed

Darrieus turbine or the H-rotor, but has also have been called giro-mill [11]. These

original models of Darrieus turbine suffered from negative features such as violent

vibrations and high noise level, thereby significantly limiting its success [4]. The

different types are presented in figure 3.

Now it can be said that VAWTs fall into two major categories: Savonius and Darrieus.

Savonius turbine is VAWTs with blades covering the whole swept area and shaped to

offer a high resistance to the wind coming in. The Darrieus turbine has vertical blades

that rotate into and out of the wind. This type can capture more energy than drag

devices, using an aerodynamic lift.

Figure 3 - Original Design of Savonius Rotor (left), Darrieus Turbine (center) and H-

Rotor (right).



There are many advantages for vertical axis machines, such as the gearbox can be

placed on the ground, do not require a tower, low levels of noise, and they are always

facing the wind, which means that a mechanism to turn the blades into the wind is not

needed, as is do with a horizontal axis type. Also, VAWTs have more advantage than

HAWTs when there is a need to locate a turbine in high mountain areas, in regions

with extremely strong or gusty winds, or in urban areas [5].

Today development of VAWTs is most common in some small companies that produce

and promote small VAWTs usually design for urban areas and built-up environment.

Some companies that can be mention are Turby from Netherlands, Wind-Sail from

Russia, Windside from Finland, etc. See figure 4.

Figure 4 - Turby (left), Wind-Sail (center) and Windside (right)

2.3 Savonius Turbine

The Savonius rotor is an impulse type VAWT with a reasonable peak power and high

starting torque. It was invented in 1922 by the Finnish engineer Sigurd J. Savonius. In a

large scale, its use has been reduced because of the large surface area it employs [6].

Aerodynamically, the efficiency of Savonius turbine cannot compete with Darrieus

type, but Savonius turbines are simpler and cheaper to build. This is the main reason

of the renewed interest in this device.

For example, if there is a need for a small amount of electricity, and solar panels are

not practical due to climate conditions or lots of trees, a homebuilt Savonius turbine

will work nicely. Hence, with the improvements in rotor performance characteristics,



it has the potential of generating considerable amount of power [7] and also it has

been proposed as an auxiliary starting device for the Darrieus turbine.

For this research, a Savonius rotor was bought. It was design and built by Learn Online,

Inc. The turbine consists of three blades, two simple blades’ supports, six magnets and

a threaded rod. This product came with a 3-phase Wind Turbine kit and a Wind

Turbine Interface circuit board.

2.4 Wollongong Wind Turbine

Wollongong is a turbine that originally was developed to get a small scale high torque

and self-starting VAWT for applications such as water pumping.

The development of the Wollongong Turbine was initiated when an Australian

inventor, called John Boothman, had the concept for a wind turbine and a working

model. Boothman approached to two professors of the University of Wollongong with

the idea, whom decided to expand and develop the concept. The working model had a

horizontal axis and a rotor with three blades with their axes held parallel to the main

rotor axis. The blades were simple flat plates, where the pitch of these was controlled

by means of a chain and sprocket arrangement so that the blades rotated about their

own longitudinal axes by only 180º for each full revolution of the main rotor. There is

a similar concept that had been mention by Golding (1976), but there is no evidence

of this device had been theoretically modeled in detail or built [25].

The rotor axis was brought to a vertical orientation with a wind vane mounted on a

control shaft to orientate the blades with changing wind direction. Boston G. devised a

system of bevel gears to replace the chains on the original working model that

controlled the pitching of the blades [25]. Thus, the configuration of the device was

transformed to a VAWT with wind vane for orientation of the blade pitch mechanism.

The motion of the blades is shown schematically in figure 5.



Figure 5 - Schematic views of the orientation of blades and rotor of the VAWT. [25]

Since the blades rotate a full 360º relative to the wind, the blade profile is symmetrical

about the mid-chord plane. Although this meant that a flat plate could be used, it was

decided that for structural and aerodynamic reasons to use a more aerodynamically

appropriate blade profile. The blade profile was the upstream half of a NACA 0010 –

65 sections reflected about the mid-chord [25].

Three blades are used, since is the quantity of blades that will not generate a large

amount of negative moment on the turbine. These blades were suspended between

the upper and lower support arms. The support arms are mounted on a main shaft,

which has a concentric shaft where the wind vane is mounted. The “control bevel gear”

is locked with the wind vane shaft to activate the blade pitch mechanism [14]. The

position of the blades is controlled by the bevel gear system that is connected to a

shorter shaft mounted on each turbine arm, which is also connected to a bevel gear

pair on the top part of each blade, see figure 6. By this arrangement, the blades angle

can be controlled at any moment of the whole turbine revolution.

Figure 6 - Wollongong Turbine (left) and Gear configuration (right)



2.5 Numerical Analysis

Numerical analysis is the area of mathematics and computer science that creates,

analyzes, and implements algorithms for solving numerically the problems of

continuous mathematics. Such problems originate generally from real-world

applications of algebra, geometry and calculus, and they involve variables which vary

continuously. During the past half-century, the growth in power and availability of

digital computers has led to an increasing use of realistic mathematical models in

science and engineering, and numerical analysis of increasing sophistication has been

needed to solve these more detailed mathematical models of the world [16].

Numerical analysis and mathematical modeling have become essential in many areas

of modern life. This is why sophisticated numerical analysis software is being

embedded in popular software packages, e.g. spreadsheet programs, allowing many

people to perform modeling even when they are unaware of the mathematics

involved in the process [16]. There are many popular numerical computing programs

such as MATLAB, S-PLUS, LabVIEW, and IDL as well as free and open source

alternatives. During the numerical analysis done in this project, LabVIEW was the

software used.

2.6 Rapid Prototyping

Rapid prototyping is defined as a special class of machine technology that quickly

produces models and prototype parts from 3-D computer-aided design (CAD)

database, using an additive approach to form the physical models [26].

RP has many benefits such as (1) reduce lead times to produce prototyped

components, (2) improved ability to visualize the part geometry due to its physical

existence, (3) earlier detection and reduction of design errors, (4) increased capability

to compute mass properties of components and assemblies. In addition to making

prototypes, RP techniques are now being used to produce tooling. Rapid tooling is

helping industries eliminate the costly and time consuming practice of machining



metal tools and dies [26]. The brand of the machine used during this experiment is

Dimension Elite and the software used is Catalyst, see figure 7.

Figure 7 – Rapid Prototyping Machine used in experiments.



3. NUMERICAL ANALYSIS

3.1 Gear Ratio

The gear ratio of the Wollongong Turbine’s bevel gear system plays an important role

in its efficiency, therefore is essential to find the most suitable ratio. The gear ratio is

the relationship between the numbers of teeth of two gears. In this system each arm

of the turbine is composed by two pairs of gears. The relationship of these gears is

expressed by the following equation,

G = NtG1

NtG2

* NtG3

NtG4 3.1

where NtGn is equal to the number of teeth of each gear in the turbine configuration.

The gear ratio functions as a multiplication, for example:

Table 1 - Gear Ratio relationship

Gear Pair 1 Gear Pair 2 Final Gear Ratio

1:1 1:1 1:1

1:2 1:1 1:2

1:2 1:2 1:4

1:2 1:3 1:6

2:1 3:2 6:2 = 3:1

Also the speed of the blades’ rotation can be controlled by this ratio [14].



3.2 Numerical Analysis of Wollongong Turbine

In this section, a numerical analysis of the turbine’s blades is labored. A single blade is

analyzed since all blades will have the same behavior during their complete rotation.

First, the following conditions were set:

a. A fix coordinate system is established based on the wind vane’s position; this

can be done because under normal conditions the wind vane will always be

parallel to the incoming wind direction. In this analysis the wind blows in the

+y direction.

b. Uniform wind velocity.

c. The lift force on blades is negligible.

d. Since it is a drag device, the force generated by the wind is proportional to the

blade’s projection on x.

The Angular Work done by the air force need to be considered, so the quantity of

energy that can be extracted from the air can be known.

By definition, the work done by a force is equal to the magnitude of the force times

the corresponding displacement. The angular work done by a force applied on a

rotating body is related to the angular displacement of the body.

Figure 8 - A particle located at P1 is displaced by an angle α or arc length s to

position P2.

Consider a body rotating about a fixed axis at O due to an applied force F. As

illustrated in figure 8, P1 and P2 represent the positions of a point in the body at times

t1 and t2, respectively. In the time interval between t1 and t2, the body rotates



through an arc of length s, the Force is projected in x and y axis, and the torque should

be applied at point O [28]. Thus, the Work done in that finite interval displacement is

W= M α dααf

α𝑖 3.2

Then to get a significant work, a large torque is needed.

Now, the turbine arm can be described as “r *(cos Ɵ) î + (sin Ɵ) ǰ+”, where r is the

length of the arm and “*(cos Ɵ) î + (sin Ɵ) ǰ+” describe its orientation.

Figure 9 – Description of the arm and blades orientation.

When a blade is attached and aligned with the arm, which rotates around O, the blade

will keep the initial position during the total revolution of the arm; so the blade’s

initial angle has to be included in the orientation equation. Then the constant

orientation of the blade is described as,

rblade constant

|rblade constant| = *cos (Ɵ + Ɵi)+ î + *sin (Ɵ + Ɵi)+ ĵ 3.3

However, during the revolutions of the arm is not convenient to have the same

blade’s orientation, because when the blade is passing by the left side of our

coordinate system, it will produce a large torque in the opposite direction of the

turbine rotation.

Therefore a relation between the blade’s angle and the turbine arm angle was made.

This relation is done by the gear ratio (G), where G is the number of revolutions of the



blade for every revolution of the turbine arm. The sign of G indicates whether the

blade rotates in the same direction as the arm or in the opposite direction.

By adding G to the previous equation, the orientation of the blade is described as,

rblade

|rblade| = cos 1+G Ɵ+Ɵi i + sin 1+G Ɵ+Ɵi j 3.4

Knowing that in the coordinate system the wind is blowing to the +y direction, the

drag force generated by the wind will hit the blade which at the same time aids the

arm’s turbine to rotates. Then a relationship between the blade’s projection on X and

the force generated by the wind will exist. So the main objective is to find how the

blade’s projection in the x axis can be maximized.

Given that the wind force is proportional to the projection on x of the blade “(cos *(1 +

G) Ө + Өi+ î)”, and the projection on x of the arm is “r*cos Ө”, the moment generated

at O is,

M Ɵ = cos 1+G Ɵ + Ɵi × [r cos Ɵ ] 3.5

Note that “(cos *(1 + G) Ө + Өi+ î)” can be either positive or negative, because the

blade is designed in a symmetrical fashion.

The integration of the previous equation for given displacements will give us the

Angular Work; thereby a comparison for different gear ratios (G) and initial angles (Өi)

can be done.

The optimum way to compare the results is integrating from Ө= 0 to the “periodic

angle” for the gear ratio. The periodic angle (Өc) would be the angle when the blade

and arm return to their original position or an equivalent one.

For example, if G=1/2 the blade will need two arm’s revolutions to complete one

revolution. Therefore, at Ө= 0 and Ө= 2π, the blade would have equivalent positions,

then Өc= 2π.



The previous case is not the same for G=3/2, because at Ө= 2π the blade will not have

its equivalent angle, on the contrary it will have an angle of 2π/3. Hence, the periodic

angle is 6π.

The “periodic angle” or Өc is therefore given by,

2 π

|G| G =

m

n,n is odd, m|mЄ Z

Ɵ= π

G G =

m

n,n is even, m|mЄ Z 3.6

2π G|G Є Z

Once Өc have been determined, the work done by the wind is described by the

following equation:

W= M Ɵ dƟ= cos 1+G Ɵ + Ɵi *L cos Ɵ dƟƟc

0

Ɵc

0 3.7

The numerical analysis for different gear ratios was developed with the aid of

LabVIEW National Instruments, having as result that the G= -1/2 will give the

maximum initial torque; therefore, the blades rotate to the opposite direction of the

main shaft rotation. The figure 10 shows the Moment and Work at G= -1/2.

After these results, the initial positions of the blades can be set. The blade number

one will have a starting angle of 0˚ respect the horizontal line, since in that position

the swept area will have a larger contact with the incoming air.



Figure 10 – Moment and Work at G= -1/2



4. EXPERIMENTAL TESTS

4.1 Savonius Wind Turbine

For this research, a Savonius rotor designed and built by LearnOnLine, Inc was

acquired. The turbine came with an interface that helps to demonstrate the

capabilities of a wind turbine in model scale. The supplied materials for the data

recording are:

Wind Turbine Interface Circuit board

3-phase Wind Turbine kit

6 foot RS-232 to USB cable

StampPlot graphics software

Savonius turbine

Figure 11 – Wind Turbine Interface Circuit Board and StampPlot software

The materials supplied for the assembly of the Savonius Turbine are presented in table

2.



Table 2 – Materials of Savonius Turbine

Quantity Description

1 Stator (white disk with wires)

1 Rotor (black disk with magnets)

3 Rotor Blades (black)

2 Triangular Hub

1 6mm Threaded Shaft (20.3 cm long)

1 6mm Jam Nut (thin nut)

1 6mm Hex Nut (thick nut)

2 6mm Spacer Washers

1 6mm Split Lock Washer

1 6mm Acorn Nut

15 10.2x1 cm Pan Head Phillips Screw

4 Vinyl Self-Stick Feet

4.1.1 Optimization of Savonius Turbine

The performance of the rotor that was purchased, figure 12, was not very efficient, so

some improvements were implemented. These changes are listed below.

1. The original shaft of this product was a threaded shaft, which decreases the

rotation of the turbine. Therefore it was decided to change this shaft by a plain

one. The new shaft was heat treated and then machined in order to make the

threaded shape just at the bottom of it, so the nut could be tighten up.

Figure 12 – Original Savonius Turbine, Original Threaded Shaft and New Shaft



2. A new design of the blade’s support had to be created in order to include

bearings in each support, for a better rotation. These parts were modeled by

CAD and printed out with RP machine.

Figure 13 – Support descriptions and New Support during RP process

Figure 14 – Original blade support (left), CAD design (center) and new support

(right)



4.1.2 Assembly of Savonius Turbine

Once the supports and the new shaft were done, proceed to the assembly of the parts.

The blades were attached to both triangular hubs on the opposite ends of its. To

improve the spinning of the turbine, two bearings of 10 mm inner diameter and 20

mm external diameter were embedded to each of the blades’ support. The Savonius

Turbine spins in a counter-clockwise direction, since this makes the 3-phase kit

displays correctly when doing the experiments. The blades assembly was slip through

the new shaft and finally tightens up a nut at the bottom part of the stator.

Figure 15 – Support with embedded bearing and Final Assembly

4.2 Wollongong Wind Turbine

The necessary information for the construction of the Wollongong Turbine was

completed once the best gear ratio was obtained through numerical analysis. This real

turbine helped to record physical tests data that can sustain the theoretical

information. Since the Wollongong Turbine data would be compared to the Savonius,

the swept area and size of both needs to be similar. Most of the parts were designed

by CAD and some others were bought in a hardware store.



4.2.1 CAD of Wollongong Turbine

For the construction of Wollongong Turbine, all parts were designed by Autodesk

Inventor and then printed by RP. The shapes and dimensions of each designed part

are shown in the next figures.

1. The base of the turbine has at the bottom part 6 squared holes for placed the

magnets and a central hole to insert a bearing of 20 mm of diameter. In the

upper part it has another hole for the other bearing that holds the shaft. The

base includes three small holes for bearings that holds the lower part of the

turbine’s blades. All other details are described in figure 16.

Figure 16 – Bottom view, right view and base in 3D



2. The middle part is the principal shaft of the turbine. It is placed on the base

and it holds the top part which has mounted on it all the gear system. It has a

bottom diameter of 26 mm and an upper diameter of 13 mm.

Figure 17 - Middle part CAD

3. The top part is the arms of the turbine. This part was designed with three holes

at the outermost side. In these holes the bearings with a diameter of 8mm are

embedded. Also has in each arm a squared hole with 1 mm of deep to place

the gears support. This part is shown in figure 18.

Figure 18 – Upper part CAD



4. Middle gears shaft’s support is placed in the middle of each turbine’s arm. Is

used to support the gears that transfer the movement of the wind vane in

order to set the blades’ initial position.

Figure 19 – Gears shaft support CAD

5. Blades: The Wollongong turbine has three blades, where each one is placed

from the outermost part of the turbine’s arm to the base of the turbine.

Details are display in figure 20.

Figure 20 – Blade CAD



6. Washers: Inside each bearing is necessary to place a washer to prevent the

free movement of the blades’ shaft and the wind vane’s shaft.

Figure 21 – Washer CAD

7. Gears system: This turbine has two gear pairs placed on each arm. The central

pair has a relation of 1:1, and it is locked to the wind vane shaft. This is done

because the rotation of the central gear will depends on the position of the

wind vane. This rotation is transfer to the middle gears, which in turn will give

the blade orientation by the pair placed on the top of it. This last will have a

relation between the teeth of 1:2.

Figure 22 – Central gear pair (left) and Blade gear pair (right)



8. A simple design for the wind vane was done. It was placed in the center of the

turbine and attached to the central gear.

Figure 23 – Wind Vane CAD

4.2.2 Rapid Prototyping Process of Wollongong Turbine

Once all the parts were designed, the RP process starts. This method has be chosen

because as its name says is a “rapid” way to construct a model. Contemporary

methods can take from several hours to several days, depending on the size and

complexity of the model. Additive systems for rapid prototyping can typically produce

models in a few hours, although it can vary depending on the size and number of

models being produced simultaneously.

The material used for the printing of this turbine was acrylonitrile butadiene styrene

(ABS), which has been used for functional and field tests; it has some characteristics as

heat resistance, flame resistance and weather-ability for outdoor use.

The RP machine used in this research comes with software called Catalyst. The CAD

files have to be saved in a STL format because it is the standard data interface

between CAD software and the RP machines. An STL file approximates the shape of a

part or assembly using triangular facets. Smaller facets produce a higher quality

surface. All the printed parts can be appreciated in the final assembly and appendix 1.



4.2.3 Assembly of Wollongong Turbine

Aside the parts done by RP, there are some components that need to be mention

since these were obtained in the market. The parts and their description are listed in

Table 3.

Table 3 – Other parts of the Wollongong Turbine

Parts Description

1. Hexagonal shape shafts (x7) Diameter = 2mm

2. Rounded shaft (x1) Diameter = 10 mm; Height = 8.3 cm

3. Bearing (x8) Inner Diam. = 3mm; Outer Diam. = 8mm

4. Bearing (x2) Inner Diam. = 10 mm; Outer Diam. = 16 mm

The hexagonal shape shafts were placed in different positions. Three of them were

placed at the top of each blade, where these hold the gears. Another three shafts

were inserted through the gear supports to hold the middle gears. And the other shaft

was attached to the wind vane and to the central gear. The hexagonal shape is mainly

because the gears cannot have free movement.

All the turbine’s parts were put together. The bigger bearings were inserted in the

respective holes of the base part. Through these bearings the rounded shaft was

slipped. Three of the small bearings were placed at the base part; these hold the

bottom part of each blade. In the top part, five small bearings were embedded in the

respective cavities.

The gears were carefully set, trying to put not much pressure between them in order

to prevent excessive friction and therefore have a proper rotation.

The most important part of the assembly is the position of the blades respect to the

wind vane position. The gears were put in a G= -1/2 and blades were placed in the

initial position shown in figure 24.



Figure 24 – Wollongong Turbine set in the initial position

The original design of the wind vane had to be improved because it did not have

enough torque to moves all the gear system. Using a plastic material, a bigger and

heavier wind vane was design and then attached to the original one, see figure 25. The

complete assembly of the Wollongong Turbine is displayed in figure 26.

Figure 25 – Original Wind Vane design (left) and Modified Wind Vane (right)

Figure 26 – Final Assembly of Wollongong Turbine



4.3 Other Experimental Equipments

4.3.1 3-phase Wind Turbine Kit

For the record of the experimental data, a 3-phase wind turbine system was used. It

came with the Savonius turbine that was bought. The 3-phase Wind Turbine is based

on much larger commercial wind turbines that has a similar operation. This system

uses six small powerful magnets that spin above three separate coils of wire. The

spinning magnets generate alternating current into the coils. Alternating current and

magnetism go parallel, since it was long ago discovered that by moving a magnet

across a coil of wire, an electrical current and voltage is generated. Today this simple

but important discovery is used to build highly efficient and powerful motors,

generators and alternators [24]. The system used in this experimental analysis can be

appreciated in figure 27.

Figure 27 – Stator (up) and six powerful magnets (down)



In this context the term “phase” has to do with a time displacement of electrical

energy that is directly based on the physical arrangement of coils of wire. In the stator

used, there are three sets of coils that are physically arranged 120 angular degrees

apart from one another. As the rotor turns, the magnets generate a separate voltage

in each of the three coils. The resultant voltages are from neutral (0 volts) positive to

negative and so on, because the magnets are alternately placed North-South followed

by South-North.

When the magnets pass over each coil in succession, the waveforms generated by

each coil will look like figure 28 (right). If is consider that one sine wave is 360 degrees

from start to finish, then the three sine waves generated by the three coils are spaced

120 degrees apart from one another. Because the three waveforms are phased 120

degrees apart, and the sine waves “alternate” from one phase to the next, this system

is called 3-phase AC [24].

Figure 28 - Star coil arrangement (left and center) and resultant 3-phase AC output

[24].

The coils can also be wired in another arrangement called “Delta”. The power output,

under no load, of this configuration is the same to the Star’s one. The major

difference lies in the fact that the Star arrangement generates more voltage while the

Delta generates more current for a given rotational speed of the magnets.



Figure 29 - Delta coil arrangement (left and center) and resultant 3-phase AC output

[24].

In commercial wind turbines both configurations are used because under load is when

the difference is notorious; turbines switched automatically between Star and Delta

based on the speed of the blades. When the wind turbine is just starting up, the coils

are configured as a Star, which allows the rotor to generate the same power at lower

rpm. However, when the turbine speed comes up, the extra voltage generated by the

Star arrangement is generally too high for the rated load, so the coils are

automatically switched to a Delta configuration to generate more current at a lower,

but standardized voltage. Another reason for starting a wind turbine with a Star

setting is because it allows the turbine to increase the speed faster. Therefore, both

Star and Delta coil arrangement have their individual applications in real-world power

producing systems.



4.3.2 Home Ventilator and Tachometer Sensor

Since one of the initial conditions for our research was that the wind flow should be

uniform, a domestic fan was used as wind simulator. This fan has a power of 90 W.

Figure 30 – Ordinary home ventilator

A tachometer (also called a revolution-counter or rev-counter) is an instrument that

measures the rotation speed of a shaft or disk, as in a motor or other machine. The

device usually displays the revolutions per minute (RPM) on a digital display. The

tachometer sensor used to record the rpm’s of the fan and the turbines is shown in

figure 30.

Figure 31 – Tachometer Sensor



5. RESULTS AND DISCUSSIONS

5.1 Numerical Analysis Results

As mentioned on chapter 3, the numerical analysis gives the result that G= -1/2 was

the best gear ratio in order to get the higher efficiency of the Wollongong turbine.

However, during this analysis different ratios were input to see which one would give

the best results.

In figure 32 can be appreciated that all positive gear ratios generated the same

amount of positive and negative moment and work, so it canceled itself, which means

that the turbine cannot rotate.

Figure 32 – Moment and Work at G= ½



This leads to conclude that from the different gear configurations, only those negative

gave an appropriate results. However, only the ones that satisfy the following: G= -

[(1+2n) / (2+2n)] (n=1, 2, 3…), result in non-zero values for the net work generated

during a total revolution. As an example figure 33 and 34 present the Moment and

Work produced at G= -1/3 and at G= -3/4, respectively.

Figure 33 – Moment and Work at G=-1/3



Figure 34 – Moment and Work at G= -3/4



5.2 Experimental Tests Results

The results from the experimental tests shown in this section were performed with

the 3-phase Wind Turbine kit and StampPlot graphics software.

For this test a domestic fan was used as wind simulator, which has three different

velocities that were recorded by a tachometer sensor, see Table 4.

Table 4 – Domestic Fan Velocities in rpm

Fan Velocity RPM

1 3526.3

2 4141.9

3 4958.4

Each turbine was placed on the stator for measurements. The stator is connected to

the Wind Turbine Interface Circuit board which is plug in to the computer. The

interface provides the graph that shows the Volts vs. the time produced by the

generator. In order to have some load during the experiment, a 100 ohms resistor was

connected to the circuit. This resistance helped to calculate the generated power. Also

a capacitor of 320 µF was used to smoothes out the Rectified DC waveform.

Both turbines were subjected to the different speeds of the fan. For each speed, data

were taken for the two distinct stator’s configurations, STAR and DELTA. To compare

both turbines the STAR configuration was used, however DELTA results are also

present in this context.

5.2.1 Savonius Turbine Results

The voltages obtained from the Savonius Turbine test are shown below. First, the

results presented are from the DELTA configuration in table 5 and figures 35 and 36.

From the graphs can be observed that the velocity 1 did not throw any voltage higher

than zero. Since the rectified voltage is the most important factor, only velocity 3

produced a considerable output.



Table 5 – Savonius Turbine Voltages on DELTA Configuration (millivolts, mV)

Savonius VAWT

Voltage 1 (mV) Voltage 2 (mV) Voltage 3 (mV) Rectified Voltage (mV)

Vel. 1 (3526.3 rpm)

Lowest Highest Lowest Highest Lowest Highest Lowest Average Highest

0 0 0 0 0 0 0 0 0

Vel. 2 (4141.9 rpm)


0 400 0 400 0 400 0 17.5 35

Vel. 3 (4958.4 rpm)


0 590 0 500 0 540 0 60 120

Figure 35 – Savonius Turbine’s DELTA Screen Plot at Velocity 2



Figure 36 - Savonius Turbine’s DELTA Screen Plot at Velocity 3

Now, from Table 6 and figures 37, 38 and 39 can be observed the resulting voltages of

the Savonius Turbine on STAR configuration. The turbine present a performance

similar to the expected data showed in the User Manual. The Rectified Voltage for

velocity 1 did not throw any value larger than zero.

Table 6 – Savonius Turbine Voltages on STAR Configuration (millivolts, mV)

Savonius Turbine


Vel. 1 (3526.3 rpm)


0 510 0 480 0 480 0 0 0

Vel. 2 (4141.9 rpm)


0 750 0 700 0 750 130 140 150

Vel. 3 (4958.4 rpm)


0 900 0 890 0 900 230 265 300



Figure 37 – Savonius Turbine’s STAR Screen Plot at Velocity 1





5.2.2 Wollongong Turbine Results

The Wollongong Turbine Results for the two different configurations are presented in

this section. Noticeably, most of the values are higher than Savonius results.

Delta configuration’s results for Wollongong Turbine are display in Table 7 and figures

40, 41 and 42.

Table 7 - Wollongong Turbine Voltages on DELTA Configuration (millivolts, mV)

Wollongong Turbine


Vel. 1 (3526.3 rpm)


0 630 0 600 0 620 65 147.5 230

Vel. 2 (4141.9 rpm)


0 1100 0 1090 0 1120 250 445 640

Vel. 3 (4958.4 rpm)


0 1250 0 1230 0 1250 500 650 800



Figure 40 - Wollongong Turbine’s DELTA Screen Plot at Velocity 1

Figure 41 – Wollongong Turbine’s DELTA Screen Plot at Velocity 2



Figure 42 – Wollongong Turbine’s DELTA Screen Plot at Velocity 3

Next results display the highest values recorded for all three velocities. Evidently, this

indicates a better and admissible performance of the Wollongong Turbine. Table 8

and figures 43, 44 and 45 show all generated voltages on STAR configuration.

Table 8 - Wollongong Turbine Voltages on STAR Configuration (millivolts, mV)

Wollongong Turbine


Vel. 1 (3526.3 rpm)


0 1100 0 1050 0 1050 390 430 470

Vel. 2 (4141.9 rpm)


0 1620 0 1620 0 1620 880 940 1000

Vel. 3 (4958.4 rpm)


0 2100 0 2120 0 2125 1310 1365 1420



Figure 43 - Wollongong Turbine’s STAR Screen Plot at Velocity 1

Figure 44 – Wollongong Turbine’s STAR Screen Plot at Velocity 2



Figure 45 – Wollongong Turbine’s STAR Screen Plot at Velocity 3

5.2.3 Final Comparison

Once all necessary data was collected, a comparison between both turbines’

performance was done. With the aid of the tachometer sensor, the rpm of each rotor

was measured.

Table 9 presents a summary of the obtained data. Noticeably, the values for every

velocity presented by the Wollongong Turbine are significantly higher than the

Savonius Turbine.

Table 9 – Summary of Experimental Data Tests

Turbine Type

Velocity 1 Velocity 2 Velocity 3

RPM Rectified

Voltage (mV) RPM

Rectified Voltage (mV)

RPM Rectified

Voltage (mV)

Savonius 708.00 0 984.00 140.00 1092.20 270.00

Wollongong 1287.00 430.00 1473.00 940.00 2152.00 1365.00



5.2.3.1 Power Calculation

Knowing all the voltages that each turbine produced, the power (P) generated by

these can be computed. For these calculations the following equation was applied:

P= V2 / R

5.1

Where V is the voltage in Volts and R the resistance in Ohms (Ω).

The resistor used during the experiment was of 100 Ω and the averages of the

rectified voltages were considered. Table 10 displays the computed power for each

turbine at different velocities, resulting that Wollongong Turbine has higher values of

P than the Savonius Turbine.

Table 10 – Computed Power (Milliwatts, mW)

Power (mW)

Turbine Type Velocity 1 Velocity 2 Velocity 3

Savonius Turbine 0 0.196 0.729

Wollongong Turbine 1.849 8.836 18.632



CONCLUSIONS

In this project, a new type of Vertical Axis Wind Turbine is developed by the

application of a numerical analysis and later on by experimental tests that aided to

prove the theoretical results.

The numerical analysis done to the Wollongong Turbine’s gear system leads the

conclusion that the gear ratio equals to -1/2 was the most suitable for this

configuration. The design and construction of the Wollongong Turbine’s prototype

was carried out based on this result

The results obtained from the experimental tests of both turbines presented a better

performance at the third fan speed. The Savonius Turbine had a velocity of 1092.20

rpm, a rectified voltage of 270 mV and the power generated was 0.729 mW. On the

other hand, Wollongong Turbine presented a velocity of 2152 rpm, a rectified voltage

of 1365 mV and power generation of 18.632 mW.

After the comparison between both turbines, the Wollongong Turbine velocity values

present an average percentage increase of 76.13% over the Savonius Turbine’s one,

hence a better efficiency. This shows that the proposed configuration is feasible and

represents a new option for the Impulse Type turbines.



Future Work

This thesis presented a research and development of a new design of impulse vertical

axis wind turbines. However, the whole Wollongong Turbine was built by Rapid

Prototyping process, while the Savonius turbine’s blades were made from steel. The

results could not present the values for an exact comparison, since factors like weight

and density of turbines’ materials can affect.

Hence a further assembly of the Wollongong Turbine should be done by replacing all

parts made of plastic by steel or any equivalent metal material. Specially the gear

system, because actual plastic gears cause a lot of friction that prevents the optimum

rotation.

Another optimization suggested is that blades profile can be improved with an airfoil

design, in order to have a more aerodynamic rotation.

Also a real model can be constructed in order to compare the efficiency from two

different types of turbines by using the real wind. This project can be development

especially in urban areas where HAWT cannot play any role.



REFERENCES [1] Grinspan A. S., Kumar P. S., Saha U. K., Mahanta P., Rao D. V. R. and Bhanu G. V., (2001) “Design, Development and Testing of Savonius Wind Turbine Rotor with Twisted Blades”, Indian Institute of Technology, Guwahati-781 039, India, Proceedings of 28th National Conference on Fluid Mechanics and Fluid Power, pp. 428-431. [2] Sankar T. C., (2008) “The Case for Vertical Axis Wind Turbines”, Robert Morris University, Pittsburgh Pa, Technical Proceedings of the Clean Technology Conference and Trade Show, pp. 136 – 139 [3] Sargolzaei J., (2007) “Prediction of the power ratio and torque in wind turbine Savonius rotors using artificial neural networks”, WSEAS International Conference on Renewable Energy Sources, Arcachon, France, pp. 7-12. [4] Turby Co., “The wind turbine for the built-up environment”. [5] REFOCUS magazine (2003), “Feature – HAWT versus VAWT”, Elsevier Science, pp. 44-46. [6] Shankar, P.N., (1978), “Development of Vertical Axis Wind Turbines”, Rural Technology, IISc, Bangalore, pp. 145-162. [7] Vishwakarma, R., (2009) “Savonius Rotor Wind Turbine for Water Pumping-An Alternate Energy Source for Rural Sites”, Journal of Institution of Engineers, India, Vol.79, pp. 32-34. [8] Ferreira C., Gerard van Bussel, Gijs van Kuik, “2D CFD simulation of dynamic stall on a vertical axis wind turbine: verification and validation with PIV measurements”. [9] Hossain A., Iqbal A.K.M.P., Rahman A., Arifin M., Abdullah N. H., “Design and Construction of H-type Vertical Axis Wind Turbine”, Universiti Industri Selangor, Malaysia. [10] Vertical Wind Turbine Creative Offshore Challenge (2008), Aarhus University, Engineering College. *11+ Eriksson, S. (2008) “Direct Driven Generators for Vertical Axis Wind Turbines”.

Bachelor Thesis, Uppsala University.

[12] Eriksson S., Bernhoff H., and Leijon M., (2008) “Evaluation of Different Turbine

Concepts for Wind Power”, Renewable and Sustainable Energy Reviews, Vol. 12 , pp.

1419-1434.



[13] Tullis S., Fiedler A., McLaren K., and Ziada S., (2008) “Medium Solidity Vertical Axis

Wind Turbines for use in Urban Environments”, VII World Wind Energy Association

Conference, St. Lawrence College, Kingston, Ontario.

[14] Wang S., Machado M., Camacho A., Gómez M., Escobar P., (2009) “Numerical Analysis of Bevel Gear System in a Vertical Axis Wind Turbine”, Taiwan Wind Energy Conference, pp. 40-45. [15] “8th World Wind Energy Conference & Exhibition: Wind Power for Islands Offshore and Onshore” (2009) Jeju Island, South Korea. [16] Atkinson, K. (1989). An Introduction to Numerical Analysis. 2nd Edition. John Wiley & Sons Ltd. [17] Global Wind Energy Outlook 2008. GWEC.

[18] Andrawus, J.A. (2008), “Maintenance Optimization for Wind Turbines”. Ph.D, The Robert Gordon University. [19] Manwell, J.F., McGowan, J.G., and Rogers, A.L. (2002). Wind energy explained. 1st Edition. Amherst, USA: John Wiley and Sons Ltd. [20] Key World Energy Statistics (2009). International Energy Agency. [21] Exploring Wind Energy, Student Guide. NEED 2007. Virginia, USA. Available at http://www.need.org/needpdf/ExploringWindStudent.pdf [Accessed April 2010] [22] Energy Works – Engineering – Construction - Procurement http://solar-wind-nature-energy.com/win_turbines_hz.html [Accessed April 2010]. [23] Savonius, S.J. (1929). “Rotor Adapted to be driven by Wind or Flowing Water”. US Patent No. 1.697.574. [24] Wind Turbine Interface (2006) - A REEL Powertm (Renewable Energy Education Labtm) LearnOnLine, Inc. [25] Cooper P., and Kennedy O. “Development and Analysis of a Novel Vertical Axis Wind Turbine”. University of Wollongong, Australia. [26] Noorani, R. (2006) Rapid Prototyping. New Jersey: John Wiley and Sons, Inc. [28] Özkaya N., Nordin M. & Vzkaya N., (1999) “Fundamentals of Biomechanics:

Equilibrium, Motion, and Deformation”, Publishing by Springer.

http://www.amazon.com/exec/obidos/search-handle-url/ref=ntt_athr_dp_sr_2?%5Fencoding=UTF8&sort=relevancerank&search-type=ss&index=books&field-author=Margareta%20Nordin



APPENDIX 1

Rapid Prototyping Process of Wollongong Wind Turbine

Printed Parts

Figure 46 – Wind vane, central gear and upper part assembly

Figure 47 – Upper part, middle shaft and base assembly



Figure 48 – Middle gears and gear’s support assembly

Figure 49 – Small gear, big Gear and blade assembly

NUMERICAL ANALYSIS AND EXPERIMENTAL TESTS OF A LOW WIND...

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