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PROJECT REPORT ON VERTICAL AXIS WIND TURBINE SUBMITTED TO STATE BOARD OF TECHNICAL EDUCATION AND TRAINING, HYDERABAD (In partial fulfilment of the requirement for the award of the Diploma) DIPLOMA IN ELECTRICAL AND ELECTRONICS ENGINEERING Under The Guidance of Submitted By
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Page 1: Vertical Axis Wind Turbine

PROJECT REPORTON

VERTICAL AXIS WIND TURBINE

SUBMITTED TOSTATE BOARD OF TECHNICAL EDUCATION AND TRAINING, HYDERABAD

(In partial fulfilment of the requirement for the award of the Diploma)

DIPLOMAIN

ELECTRICAL AND ELECTRONICS ENGINEERING

Under The Guidance of Submitted By

2ND SHIFT POLYTECHNICMADANAPALLE INSTITUTE OF TECHNOLOGY AND SCIENCE

MADANAPALLE-5173252011-2012

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STATE BOARD OF TECHNICAL EDUCATION AND TRAINING

HYDERABAD

MADANAPALLE INSTITUTE OF TECHNOLOGY AND SCIENCE

MADANAPALLE

DEPARTMENT OF ELECTRICAL AND ELECTRONICS ENGINEERING

CERTIFICATE

Certified that this is a bonafide record of the dissertation work entitled,

ROWTHU. HEMANTH KUMAR bearing PIN. No: 10276-EE-020 submitted to the faculty of

Electrical and Electronics Engineering, in partial fulfillment of the requirements for the

DIPLOMA with specialization in ELECTRICAL AND ELECTRONICS ENGINEERING

from MADANAPALLE INSTITUTE OF TECHNOLOGY AND SCIENCE,

MADANAPALLE.

Signature of the Guide, Signature of the Head of the Department

(Name & Designation) (Name & Designation)

2DIPLOMA IN ELECTRICAL ENGINEERING, MITS, MADANAPALLE

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ACKNOWLEDGEMENT

During my project work in the Madanapalle Institute of Technology and science

Madanapalle, several persons involved directly and indirectly with my work. With out their

support it would be not possible for me to finish my work. That is why I wish to dedicate this

section to recognize their support.

I would like to express my sincere thanks to my project guide Mr. B. Nanda Kumar

Lecturer in dept. of EEE, Madanapalle Institute of Technology and science Madanapalle, who

gave me an opportunity to work under his guidance and supervision. I received tremendous

motivation, encouragement and support from him during my studies and for the completion of

my work.

Also I would like to express my gratitude to Mr. B. Chandra Sekhar, Head of the

department of EEE, Madanapalle Institute of Technology and science Madanapalle, for his

support and valuable suggestions for the completion of my project.

I would like to express my profound thanks to Sri G.SADASIVA PRASAD, VICE

PRINCIPAL, MITS, Madanapalle andall the teaching faculty members and non teaching staff

of the department of Electrical Engineering. Also I wish to thank all my friends who gave their

valuable suggestions throughout the project.

We extend our special thanks to the principal DR. K. SREENIVASA REDDY, and the

management, who supported us in all aspects of the project.

At last, but the most important I would like to thank my family, for their unconditional

support, inspiration and love.

With gratitude

Mr. R. Hemanth Kumar

(10276-EE-020)

3DIPLOMA IN ELECTRICAL ENGINEERING, MITS, MADANAPALLE

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VERTICAL AXIS WIND

TURBINE

Final Report

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Chapter List

Abstract

Introduction

Background

Rotor Fabrication

Block Diagram and Parts

Conclusion

References

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Contents:

Chapters List Page

Abstract 1

1. Introduction 2

1.1. Project Background 2

1.2. Projecr Aims & Objectives 3

1.3. Project Management 3

1.3.1. Timeplan 3

1.4. Types VAWT’S

4

2. Background 5

2.1. Introduction 5

2.2. Energy

6

2.3. Wind Energy 7

2.3.1. Benefits of wind energy 9

2.3.2. Measuring of wind Energy 10

2.4. Wind turbine fundamentals 10

2.4.1. Power 10

2.4.2. Wind turbine Design Variation 12

2.5. Orientation of axis of rotation

13

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2.6. VAWT Development 17

2.6.1. Types of Rotors 17

2.6.2. The Flettur rotor 18

2.6.3. Savonious rotor 19

2.6.4. Helical rotor 20

2.7. Summary

22

3. Rotor Fabrication

3.1. Introduction

3.2. Rotor Design

3.3. Sizing of Rotor

3.4. Blade modification

3.5. Mounting rotor

3.6. Rotor Manufacture

3.6.1. Consideration

3.6.2. Selection Process

3.6.3. Final Blade

3.7. Summary

4. Block Diagram and Parts

5. Conclusion

6. References

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ABSTRACT

Rising sea levels and escalating pollution levels has generated worldwide interest and has

given rise to new wind turbines designs. Wind turbines mainly are of two types: vertical

axis(VAWT) and horizontal axis(HAWT). HAWT are the most common type of wind turbines

built across the world. VAWT is a type of wind turbine which have two or three blades and in

which the main rotor shaft runs vertically. They are however less frequently used as they are not

as effective as HAWT.

The main difference between the VAWT and HAWT is the position of blades. In HAWT,

blades are on the top, spinning in the air and are most commonly seen while in VAWT, generator

is mounted at the base of the tower and blades are wrapped around the shaft. The main advantage

of VAWT over HAWT is it's insensitivity to wind turbines and therefore can be mounted closer

to the ground making it effective for home and residential purpose.

Vertical-axis wind turbines (VAWTs) are a type of wind turbine where the main rotor

shaft is set vertically and the main components are located at the base of the turbine. Among the

advantages of this arrangement are that generators and gearboxes can be placed close to the

ground, which makes these components easier to service and repair, and that VAWTs do not

need to be pointed into the wind. Major drawbacks for the early designs (Savonius, Darrieus and

giromill) included the pulsatory torque that can be produced during each revolution and the huge

bending moments on the blades. Later designs solved the torque issue by using the helical twist

of the blades almost similar to Gorlov's water turbines.

A VAWT tipped sideways, with the axis perpendicular to the wind streamlines, functions

similarly. A more general term that includes this option is "transverse axis wind turbine". For

example, the original Darrieus patent, includes both options. Drag-type VAWTs, such as the

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Savonius rotor, typically operate at lower tipspeed ratios than lift-based VAWTs such as

Darrieus rotors and cycloturbines. A unique, mixed Darrieus - Savonius VAWT type has

recently been developed and patented. The main benefits obtained are improved performance at

lower wind speeds and a lower r.p.m. regime at higher wind speeds resulting in a silent turbine

suitable for residential environments.

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Chapter 1: Introduction

1.1 Project Background

The fluid mechanics department in DIT Bolton Street were approached by a company called Brí

Toinne Teoranta with a design for a vertical axis wind turbine (VAWT). The company had

completed the preliminary design of the turbine but had not carried out any testing to determine

its performance. It was decided that the mechanical testing of this VAWT design would be

undertaken as an undergraduate final year project.

On accepting the project, videos of an early version of the turbine operating in a wind tunnel

were provided by the company to show the principle of operation of the turbine. These videos

were carefully analysed in order to gain an understanding of the challenges that were ahead for

the project. The company also provided the relevant CAD files for the unique turbine blades,

which would allow the blades to be manufactured in accordance with the company’s design.

The following dissertation was compiled to document the approach used in testing the Brí

Toinne Teoranta turbine design along with the testing methodologies which were devised for

analysing the turbines performance.

Figure 1 (Predicted Test Rig Design)

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1.2 Project Aims/Objectives

The aim of this project was to design and build a test rig for a vertical axis wind turbine (VAWT)

which can test the performance of the turbine. It was decided that by measuring the mechanical

power output and plotting dimensionless power curves, the performance of the turbine could be

assessed. A series of objectives were devised in order to successfully complete the project. The

main objectives of the project were as follows.

1. Carry out research into the area of wind energy and develop an understanding for the

fundamentals of wind power generation.

2. Manufacture the turbine blades designed by Brí Toinne Teoranta to a high standard.

3. Design a testing methodology to obtain performance curves for the turbine.

4. Design and fabricate a suitable test rig for the wind tunnel testing.

5. Carry out wind tunnel testing on the VAWT.

6. Analyse the results obtained from the wind tunnel testing.

7. Present the findings from testing in report form.

1.3 Project Management

Before any work was started for the project it was decided that the correct project management

procedures should be carried out in order to ensure the project was executed in a professional

manner. Both the direction and the time management for the project were carefully planned out

to avoid any time being wasted on areas which were not relevant to the project.

1.3.1 Time Plan

The time plan shown in Figure 2 below was devised in order to create deadlines within the

duration of the project itself. The project was divided up into five main sections which were

research, test rig design, turbine and rig manufacture, wind tunnel testing and analysis. These

sections were set out in a logical fashion, with specific deadlines for each section.

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Figure 2 (Project Time Plan)

1.4. Types of VAWT’S:

There are two types of Vertical Axis Wind Turbines.

1) Darrieus Wind Turbine:

Darrieus Wind Turbine are commonly known as an "Eggbeater" turbine. It was invented by

Georges Darrieus in 1931. A Darrieus is a high speed, low torque machine suitable for

generating alternating current (AC) electricity. Darrieus generally require manual push therefore

some external power source to start turning as the starting torque is very low. Darrieus has two

vertically oriented blades revolving around a vertical shaft.

2) Savonius Wind Turbine

A Savonius vertical-axis wind turbine is a slow rotating, high torque machine with two or

more scoops and are used in high-reliability low-efficiency power turbines. Most wind turbines

use lift generated by airfoil-shaped blades to drive a rotor, the Savonius uses drag and therefore

cannot rotate faster than the approaching wind speed.

Savonius vertical axis wind turbine needs to be manually started. The slow speed of Savonius

increases cost and produces less efficiency.

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Chapter 2: Background2.1 Introduction

The following chapter contains a literature review which was carried out in the areas of energy,

wind energy, wind turbine fundamentals and the development of vertical axis wind turbines.

Before any work could be done on designing the vertical axis wind turbine test rig, a good

understanding of the history of wind energy was obtained. In the following chapter, the history

and the development of the wind turbine is discussed, from its early conception in the form of the

windmill to the modern day electricity generating devices with which the world is now so

familiar.

The area of aerodynamics is explored in this chapter, pointing out the various characteristics of

aerofoils and the concepts behind aerofoil performance. This is a crucial area as the turbine being

tested in this project is a lift type device which has an aerofoil cross section.

The development of the VAWT was investigated, along with the various different rotor designs

which have been developed over the years. In this chapter the different rotor design are discussed

in order to gain an understanding of the performance expected from the unique VAWT rotor

design presented by Brí Toinne Teoranta.

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2.2 Energy

“The environmental implications of the continued global energy system’s dependence on fossil

fuels call for urgent action across the world”[1]

Most of the world’s energy currently comes from non-renewable sources as indicated in Figure 3

below. This graph from the BP statistical review of world energy 2011 gives a striking indication

as to the worlds dependence on fossil fuels like oil and coal, and taking into account the fact that

these resources will one day run out makes it a matter of urgency to pursue the development of

renewable energy technologies. It is vital that the world is able to reduce the amount energy

being produced from non-renewable sources.

Figure 3 (Graph showing energy consumption pattern (in million tonnes oil equivalent))

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2.3 Wind Energy

Wind energy is one of the clean, fastest and cost effective methods of producing electricity.

Horizontal axis wind turbine are very big compared to the power output and also are difficult to

install, due to this the vertical axis wind turbines are becoming popular. In our project we will be

designing a wind turbine which is capable of generating electricity at low wind speed say 5m/s.

The future scope in this technology is tremendous. For example: application of magnetic

levitation to increase the power production by reducing the friction.

Wind Energy has been used since several years to power homes, sail boats, pump water from

wells or heating and cooling homes and offices. Today with the ever increase in the demand for

fossil fuels and with the prices soaring all time high numerous resources have been invested in

the wind energy.

Wind energy has its own advantages and disadvantages. While on one side it is renewable source

of energy and cause less air and water pollution, on the other hand it also dirupts the ecological

balance as it poses threat to wildlife. Also, Wind energy can not be produced everywhere since

you need strength of wind to produce energy from it.

Today less than 5% of total world energy demands are met by wind energy and in the years to

come this figure is going to be much higher. This article covers the topic of "How Wind

Turbines Work" and basic understanding of the generation of electricity through out wind

turbines.

How Wind turbines Work?

Basically there are two types of wind Turbines: vertical axis wind turbine and horizontal axis

wind turbine. Both of them work in the exactly same way except the difference in their design.

The process of producing electricity is the same in both the turbines.

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Wind Turbines consists of a rotor or blades which converts the wind's energy into mechanical

energy (turbine). The energy that moves the wind ("kinetic energy") moves the blades.

They(blades) spin a shaft that leads from the hub of the rotor to a generator. The generator turns

that rotational energy into electricity which is then stored in batteries or transferred to home

power grids or utility companies for use in the usual way.

If you place an object like a rotor blade in the path of that wind, the wind will push on it,

transferring some of its own energy of motion to the blade. This is how a wind turbine captures

energy from the wind. At its essence, generating electricity from the wind is all about

transferring energy from one medium to another.

Just go through the video below and see how wind Turbines convert wind into electricity.

How wind Turbines work have to do with the size and shape of the rotors, the location of the

turbine, height of the blades. Two or three bladed turbines are most popular now days because of

more thrust and less wind resistance. wind Turbines can be made cheaper if more people opt for

it. Mass production in case of wind energy will bring down the material and installation cost,

which today is not possible for average consumer who needs cheap electricity.

Example:

Wind Energy in Ireland

Every year, wind energy is making a bigger contribution to the electricity supplied throughout

Ireland. At the end of June 2010 it was reported that there were 110 wind farms metered in

Ireland, bringing the total installed capacity for wind up to 1,379MW. The national target for the

year 2020 is to have 40% of our electricity coming from renewable sources, an estimated 5,500-

6,000 MW of wind generation is required to achieve this target. [3]

Looking at the data taken from the 2009 IEA Annual report for Ireland there is a promising

growth in wind power in Ireland. In Figure 4 below it is clear to see that there has been a

significant rise in the amount of wind sourced electricity being used in Ireland since the year

2000. This dramatic increase makes the national targets for renewable electricity look like they

are a realistic goal. [4]

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Figure 4: (Wind-sourced electricity in Ireland 2000-2009. Source: Eir Grid & SEAI EPSSU )

2.3.1 Benefits of Wind Energy

Wind energy is classed as a renewable source of energy and has certain benefits associated with

it when compared with other non-renewable processes used to produce power. A common theme

amongst renewable energies is that they can be described as “clean” energy sources. A “clean”

energy source does not produce any emissions like nitrogen oxide, sulphur dioxide, mercury and

carbon dioxide, which pollute the air. This means that not only can wind energy provide the

world with extra capacity for creating electricity; it can do so without producing any extra

emissions. When a country has got a well established system for producing electricity using wind

energy in place, it can then start to decrease the demand on electricity produced in power plants,

hence decreasing the amount of fossil fuels which will be consumed on a daily basis.

The development and progression of wind energy as a source of electricity has benefits on a

domestic level also. As the wind energy industry grows, there will be a diversification in the

market whereby the majority of the world’s electricity will no longer be coming from power

plants burning fossil fuels. This means that when there are dramatic increases in the price of oil

and other fossil fuels around the world, the cost of electricity for customers will not be as

dramatically affected. In an ideal situation, 100% of the energy supplied to a customer would be

from a wind energy source and electricity prices would not be affected at all by the cost of fossil

fuels. [5]

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2.3.2 Measuring wind energy

When choosing a source of energy which will be used to power a machine, it is crucial to be able

to measure exactly the amount of power the machine can produce using this energy source. It is

easy to calculate the performance and power input of a machine which will be powered by fossil

fuels, because of the set calorific value for the fuel. This set value guarantees a certain amount of

energy output from the machine, and when the machines efficiency is taken into account, the

performance of the machine can be calculated over any given period of time. Wind energy

however does not have this certainty of performance attached to it.

There are many factors which make harnessing the winds energy in a consistent and efficient

way, a very complicated process. Wind speed is one of these factors. The power input for a

turbine is calculated from knowing the wind speed. The faster the wind, the more power can be

extracted from it. The problem with this is that the wind speed is constantly fluctuating, so the

wind turbine does not have a constant power input, making calculations and efficiencies very

complicated. Another factor which affects the performance of a wind turbine substantially is its

placement. The placement of a wind turbine has to be exact in order to achieve the maximum

possible power output.[6]

2.4 Wind Turbine Fundamentals

A wind turbines main objective is to harness the power of the wind and convert it into some

useful form of energy. The modern day design of wind turbines did not come about by chance,

but was formed from constant upgrading and experimenting carried out over many years. There

are a few fundamental equations used to quantify the performance of a wind turbine.

2.4.1 Power

It is crucial to know the amount of power that can be gathered by a wind turbine, the equation for

this power is given by

P=12

C p ρA v3

Where Cp is the coefficient of power for the turbine, ρ is the density of the air which is flowing

through the turbine, A is the swept area of the turbine (the area which the blades or rotor sweeps

through), and v is the wind speed. 18

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The Cp for a wind turbine is the way in which the aerodynamic efficiency of the turbine is

quantified. Cp is a function of the tip speed ratio λ. This is the ratio of speed at the tip of the

turbine blade to wind speed and is given by

λ=ωRv

Where ω is the rotational frequency, R is the radius of the turbine and v is the wind speed. The

efficiency and performance of a wind turbine is usually displayed using power curves. Figure 5

below shows plots of power coefficient versus tip speed ratio for various different wind turbine

types. The theoretical maximum power coefficient is known as the Betz limit and is 0.59 for an

ideal wind turbine. This Betz efficiency is marked as the ideal efficiency of propeller-type

turbine in Figure 5 below. [7]

Figure 5 (Various Power Curves for wind turbines)

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2.4.2 Wind Turbine Design Variation

Wind turbines fall under the category of either a drag-type turbine or a lift-type turbine. Modern

day wind turbines mostly fall into the lift-type category, but it is worth knowing the principles of

both categories.

1) Drag turbines

In a drag type device a force which acts in the same direction as the wind is blowing is exerted

on the blades or paddles of the turbine. This is the same principle by which sail boats operate, as

the wind exerts a force on the sails. In a turbine which works solely on the principle of drag, the

surface on which the wind is exerting a force cannot move faster than the speed of the wind. This

fact limits the tip speed ratio and hence the overall efficiency of these drag type turbines. Many

of the earlier vertical axis wind turbine designs used drag rotors, such as the bucket type wind

turbine shown in Figure 6.

Figure 6 (Drag-type rotor)

2) Lift turbines

In a lift type turbine like the ones shown in Figure 7 below the force generated by the wind acts

perpendicular to the direction that the wind is blowing. It should also be noted that in a lift type

turbine, the maximum speed of the blade is not limited to the speed at which the wind is blowing

as in drag type turbines. This means that lift type turbines can have much larger tip speed ratios

than their drag type counterparts. In order to fully understand exactly how lift type turbines

operate, an investigation must be done into the area of aerodynamics and aerofoil technology.

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Figure 7 (Left: Darreius type lift turbine, Right: Propeller type lift turbine)

2.5 Orientation of axis of rotation

The concept of the wind turbine has taken many different physical forms since it was first

introduced. Wind turbines can be divided up into two categories Horizontal axis wind turbines

(HAWTs) and vertical axis wind turbines (VAWTs).As things stand today, the HAWT

dominates as the most widely used type of wind turbine across the world. This does not mean

however that the concept of the VAWT should be discarded as a novel idea. There are various

advantages and disadvantages associated with both the HAWT and the VAWT, some of which

will now be discussed.

HAWTs and VAWTs have been developed almost in parallel, but there has been less interest and

investment in the development of VAWTs. This is one of the key reasons why the HAWT

dominates the wind power world today.

One of the main differences between the VAWT and the HAWT is the VAWTs ability to accept

wind which is blowing in any direction. This ability makes the VAWT very suited to areas where

there are changeable and gusting winds, such as the tops of large buildings. In the case of

HAWTs a yaw mechanism is required to point the propeller of the turbine into the wind and hold

it there. The time it takes the HAWT to point into the wind can be regarded as downtime in

which it is not producing as much electricity as it could be. The yawing mechanism also adds

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extra cost to the production of the wind turbine, as does the control system used to control the

yaw.

Because of the orientation of the axis of a VAWT, it is possible to place the power generating

equipment at ground level. This is a major advantage from the point of view of maintenance and

monitoring of the electricity generating equipment. Another advantage of having the power

generating equipment at ground level is that when selecting a generator, the criteria for selection

does not have to include minimizing the weight and physical size of the generator, and the sole

focus of the selection can be choosing the most efficient generator for the task.

The blades of a HAWT have to be self supporting because they are only attached to the turbine at

one end. It has been claimed that the HAWT has reached its maximum possible size, and that the

reversing gravity loads on the blades limits their progression. These reversing gravity loads

however, do not occur in VAWTs, which theoretically have no maximum possible size.

Guy wires can be used to support VAWTs which means that the main shaft of the turbine can be

of a smaller diameter. This is not the case with HAWTs, guy wires cannot be used on HAWTs

because they would interfere with the rotation of the propeller.

In a direct drive wind turbine the rotor or propeller is connected directly to the generator without

the drive going through a gearbox. The power generating equipment associated with direct drive

machinery is usually more bulky than the usual equipment used in a system with a gearbox. This

means that the nacelle (the area in a HAWT where the generating equipment is housed) will be

heavier and hence the turbine support mast will have to be larger. In a VAWT however this will

not be an issue as the power generating equipment can be located at ground level.

One of the problems Associated with VAWTs is the torque ripple which occurs in the rotors.

This torque ripple causes cyclic loading of the blades of the turbine which can lead to failure of

the blades. In HAWTs there is constant torque acting on all of the blades, so the issue of fatigue

due to cyclic loading does not arise.

A study was carried out comparing the power curves of three different turbines, a Darrieus type,

an H-type, and a standard HAWT. The power curves are shown in Figure 8 below. The power

curves were formed by plotting the coefficient of power (Cp) against the tip speed ratio (λ).

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The three turbines which are being compared in Figure 8 are a 100kw H-rotor VAWT, a 500kW

Darrieus VAWT (shown in Figure 9) and the HAWT data comes from the National Renewable

Energy Laboratory in the USA, and is said to represent the data associated with a typical HAWT.

The high values of Cp which can be seen for the HAWT show how much more developed the

HAWT is compared to the two VAWTs which are also plotted. It should be noted however that

the maximum value for coefficient of power for the Darreius type turbine is not very far off the

HAWT value, and considering how much more field testing and research has been carried out on

the HAWT, the performance gap between the two turbine concepts could easily be closed. [7]

Figure 8 (Power Curve Comparison)[7]

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Figure 9 (VAWTs used in comparison)[7]

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2.6 VAWT Development

2.6.1 Types of Rotors

The development and design of an efficient rotor is perhaps the most important step in making

VAWT’s more efficient as devices for gathering wind energy. The rotor of a VAWT must be

designed so that it can deal with pulsating torques and cyclic loading over the lifetime of the

wind turbine. Unlike the rotors used on HAWTs, VAWT rotors can differ greatly in both

appearance and in the fundamentals of aerodynamics which they use. It is necessary to have an

understanding of how the various rotor designs for VAWTs originated and the problems

associated with each design. In this section the background of the following rotors will be

discussed.

Flettner Rotor

Savonius Rotor

Darius Rotor

H-Type Rotor

Helical Rotor

Figure 10 (VAWT Rotor Designs)

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2.6.2 The Flettner Rotor

The history of the VAWT begins with a German engineer named Anton Flettner who came up

with the Flettner rotor. Although the Flettner rotor was never actually used as a VAWT rotor, it

inspired the design of the Savonius rotor which will be discussed later on. The Flettner rotor uses

the Magnus effect to turn wind energy into a lateral thrust in the direction which is perpendicular

to that of the wind.

The rotor itself is a large cylinder which is revolved in order to create a difference in pressure on

both sides of the cylinder. This pressure difference between the two sides of the rotating cylinder

results in a lift force in the direction of the lower pressure.

The rotor that Flettner had designed was used on ships to propel the ship forward using wind

which was approaching the ship from its side; this process is illustrated in Figure 11. On these

ships, the rotation of Flettners rotors was powered by diesel engines. The reliability and speed

which became associated with the conventional propeller powered ships meant that the Flettner

rotor ceased to be used for the purposes of propelling ships. [9]

Figure 11 (Flettner rotors used on ships)

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2.6.3 Savonius Rotor

A Finish man by the name of Sigurd Savonius decided that it would be possible to use the wind

energy harnessed from offshore winds to turn the Flettner rotors which were used on ships,

removing the need for the diesel engines on these ships.

Savonius took the Cylindrical Flettner rotor and cut in into two semi-circles. The semi circles

were then offset from the centre of the rotor along the cutting plane, creating two semi circular

cups. The gap between the cups at the centre of the rotor meant that the air would flow into one

of the cups and pass through the gap, thus having a thrust effect on the rotor on the other side

also. When the Savonius rotor was tested against a Flettner rotor of comparable size, the

Savonius rotor produced a greater lateral thrust than the Flettner rotor. Despite this increased

lateral force, there was no real need for the rotor as a replacement for the Flettner rotor as it had

never taken off as a widely used method of propelling ships. [9]

Figure 12 (Savonius Rotor)[10]

The Savonius rotor uses drag as its driving force. It has been used as a rotor for water current

turbines to good effect. The Savonius rotor has various advantages associated with it, such as the

simplicity of its design and the ease with which it can be manufactured. This makes the Savonius

rotor an interesting, economical possibility for converting wind energy to electricity in under-

developed areas of the world.

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2.6.4 Helical Rotor

The helical rotor is a relatively new rotor design when compared with the others mentioned in

this report. The helical rotor was developed for use on a hydraulic turbine in the early nineties,

harnessing the different types of ocean currents to produce electricity. The Gorlov helical type

rotor shown in Figure 13, was developed in order to utilise all of the advantages of the Darreius

rotor, without any of the disadvantages.

The basic principle behind the helical rotor is that instead of straight blades which are used in

Darrieus rotors, the blades follow a spiral around the outer circumference of the rotor. This spiral

helps to get rid of the pulsating torque and the vibration problems which were associated with the

Darrieus rotor when it was tested in water.[11]

Figure 13 (Gorlov helical rotor)

A company form the UK called quietrevolution has developed a helical VAWT shown in Figure

14 called the Q5, which is designed to be used in urban areas where the turbine will be operating

close to the general public. The helical design eliminates vibration in the turbine, so it can be

attached onto buildings without causing any detectable shaking of the building. The company

also says that the helical design eliminates any noise from the turbine and provides it with a

robust structure. [12]

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Figure 14 (Helical VAWT from Quietrevolution)[12]

2.6.5 VAWT Case study

There have been a few reasonably successful attempts at creating large scale VAWTs in the past,

for example a VAWT called the Eole shown in Figure 15, which was built in 1986 by an

American company called FloWind. The Eole was a 96m tall Darrieus turbine which as the

largest VAWT ever built had a maximum power output of 3.8MW. During its five year lifetime

the Eole produced 12GWh of electricity, reaching power levels of around 2.7MW. Failure of the

bottom bearing in the Eole resulted in the turbine being shut down. The existence of this multi-

megawatt Darrieus type VAWT shows that it is realistic to believe that the VAWT could

someday be just as popular as the HAWT. [7]

Figure 15 (The Eole 3.8MW VAWT)29

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2.7 Summary

The research carried out in this chapter provided a good insight into the history of wind turbines

and some of the fundamental principles on which their operation depends. The areas investigated

also gave a good rounded insight into the position of wind energy in the world today.

The issue of global energy demands was investigated and it was clear that alternative energy

sources such as wind power generation will be crucial in meeting these demands in the future.

The sustainable and environmentally friendly nature of wind energy was also investigated and it

was clear from the information obtained that wind energy will play a leading role in reducing the

amount of fossil fuels being used worldwide.

The potential for wind power generation in Ireland was explored briefly in this chapter. Ireland’s

large Atlantic coastline gives it great potential to eventually source almost all of its power from

renewable sources like the wind. It is likely that in a strong economic climate, there will be huge

investment in developing offshore and onshore wind farms along the coast of Ireland.

The fundamentals of wind power generation were discussed in this chapter which involved the

differences between drag and lift turbines, the area of aerodynamics, the theory behind

calculating the power produced by a wind turbine and the differences between horizontal and

vertical axis turbines.

Particular attention was paid to the development of the vertical axis wind turbine along with the

different design concepts which have been devised in recent years. It was clear that the VAWT

had not seen the same commercial success as the HAWT but this could have been due to a lack

of investment into the development of the VAWT. The different VAWT rotor designs which

have been developed proved to be remarkably different in their appearance and operation. After

looking at the different rotor designs, it could be argued that the optimum VAWT rotor design

has not yet been discovered, thus making the testing of the rotor designed by Brí Toinne

Teoranta a relevant and worthwhile project.

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Advantages of Vertical Axis Wind Turbine:

1. The turbine generator and gearbox can be placed lower to the ground making

maintenance easier and lower the construction costs.

2. The main advantage of VAWT is it does not need to be pointed towards the wind to be

effective. In other words, they can be used on the sites with high variable wind direction.

3. Since VAWT are mounted closer to the ground they are more bird friendly and down not

destroy the wildlife.

4. VAWT quiet, efficient, economical and perfect for residential energy production,

especially in urban environments.

Despite these advantages VAWT's suffer from serious drawbacks. Let's have a look at some

of them:

1. As the VAWT are mounted closer to the ground, less wind speed is available to harness

which means less production of electricity.

2. VAWT are very difficult to erect on towers, which means they are installed on base, such

as ground or building.

3. Another disadvantage of VAWT is the inefficiency of dragging each blade back through

the wind.

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Chapter 3: Rotor Fabrication3.1 Introduction

In this chapter the fabrication of the VAWT rotor designed by Brí Toinne Teoranta is explained

in detail, documenting the various challenges which were involved with the fabrication of the

rotor.

The unique rotor design is discussed briefly along with the key features of the blades, followed

by the size limitations which were faced and any additional design modifications which had to be

made to the blades before manufacture. The complex geometry of the turbine blades meant that

the manufacturing process used to make the blades needed careful consideration. The following

chapter also contains the details of how the rotor was mounted on a central shaft for operation.

3.2 Rotor Design

The vertical axis wind turbine (VAWT) rotor which was provided by Brí Toinne Teorannta is

shown in the figure below. The rotor is a hybrid design, incorporating elements of various

VAWT rotors such as the Darreius and helical rotors. The rotor consists of three helical blades

connected to a central shaft. The aerofoil cross section of the blades creates the lift force in the

rotor, causing the rotor to rotate. The helical design of the rotor should help to eliminate

pulsating torque in the rotor. This style of rotor is a relatively new design, and there has been

very little testing carried out on it in the past.

Figure 16 (Rotor Design)

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3.3 Sizing of rotor (scale)

Before any design modifications could be carried out on the rotor it was necessary to select an

approximate diameter for the VAWT rotor. Ideally the rotor should be as large as possible in

order to increase the accuracy of the testing and decrease the effect of any losses encountered.

There was however some constraints which placed a limit on the maximum diameter of the

turbine.

The first limiting factor was the physical size of the wind tunnel in D.I.T. Bolton Street. The

wind tunnel has a cross section of 500mm by 500mm as shown in Figure 17 below. Previous

testing was carried out with this wind tunnel on a turbine of diameter 568mm. The turbine was

too large for the wind tunnel and the blades were not experiencing the full free stream for a

complete revolution of the rotor, resulting in very low power output from the rotor. In order to

avoid this, it was decided that the rotor diameter should be kept well inside the cross section of

the wind tunnel. It was acknowledged that reducing the size of the rotor would also limit the

turbines power output, but because there was no other wind tunnel available it was considered to

be the best course of action.

Figure 17 (Wind tunnel dimensions)

The other factor which limited the size of the turbine was the capacity of the machines which

would be used to manufacture the blades. After looking at the possible manufacturing techniques

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which could be applied to the blades, it was concluded that the maximum rotor diameter was

limited to 200mm. The 200mm rotor would fit comfortably into the wind tunnel and there would

also be significant distance between the tip of the blades and the walls of the wind tunnel. This

gap was considered to be important as it helps to prevent blockage effects and should also

prevent issues with the boundary layers on the walls of the wind tunnel. Figure 18 below shows

the rotor placed in the cross section of the wind tunnel.

Figure 18 (Rotor size)

3.4 Blade Modifications

The SolidWorks file for the turbine blade was provided by the designer for use as part of the

project. The file was provided for the blade only and they did not include any components for

connecting the blades together to make the rotor.

The blade was scaled down from the original 300mm diameter to 194mm to enable its

manufacture as discussed above. The solid model of the scaled down blade had to be carefully

analysed, finding its centre of rotation and other key points so that the blades could be connected

together and mounted onto a central shaft.

Once the centre of rotation was determined, three blades were evenly spaced in a circle around

the centre as shown in Figure 19 below. This allowed for the design of a central hub to hold the

blades onto the central shaft. The blade provided by the designer had already got two holes in

each of the blade ends. During the scaling down of the blade these holes became too small to be

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used to fit the blades to the central shaft so it was necessary to replace these with 4.2mm holes

which would accommodate an M4 machine screw. The holes also had to be slightly re-located as

the new larger holes went too close to the edge of the blade which could potentially cause failure

of the blades. The re-located larger holes are also shown in Figure 19 below.

Figure 19 (Blades with modified holes)

3.5 Mounting Rotor

After the new holes were located in the blades, the blades had to somehow be connected to the

central shaft of the turbine. A component was designed to hold the blades in position and fix

them to the central shaft.

Firstly a central shaft diameter of 12mm was decided upon. The 12mm shaft was chosen in order

to prevent deflection and vibration occurring. The component shown in Figure 20 below was

designed using the modified holes in the blades as a template. An M5 grub screw was decided

upon as the preferred method of tightening the rotor to the shaft. The grub screw also enables the

rotor to be easily removed from the central shaft and to be moved up and down the shaft.

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Figure 20 (Hub design)

3.6 Rotor Manufacture

3.6.1 Considerations

The complex geometry of the rotor meant that the manufacture of the blades was a key area in

the success of the VAWT testing. Previous testing was carried out on blades which had

imperfections in the surface finish, and this affected the performance of the rotor. It was decided

that the blades must have the best possible surface finish and the most accurate replication of the

designed geometry possible.

Some key characteristics of the blade which needed to be focused on were the accuracy of the

trailing edge, the aerofoil profile, the overall surface roughness and the strength of the material

used. These features were used as the criteria for selection of the manufacturing process.

An investigation was carried out into different manufacturing processes which could be used to

manufacture the VAWT blades. Conventional machining techniques such as milling and turning

were ruled out due to the complex three dimensional curves which even on an automated

machine would have been difficult to achieve. It was decided to investigate the areas of rapid

prototyping and 3D printing as methods for the manufacture of the turbine blades.

3.6.2 Selection Process

Investigations were carried out into the suitability of three different rapid prototyping machines

for the manufacture of the VAWT blades. All three machines were located on the DIT Bolton

Street premises and were available for use. The machines available were the Rap-man 3D

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printer, Z-Corp 3D printer and the Dimension Fused Deposition Modeller. Both the Rap-man

and the Dimension machine use a plastic as their working material and the Z-Corp machine uses

a powder based material. In order to decide which machine would be used, a number of criteria

for selection were decided upon. The three machines were assessed by looking at parts

previously manufactured by each machine. The following criteria were marked on a scale of 0-5

in below.

Surface Finish

A smooth, uniform surface finish is vital to the performance of the VAWT blades. If the surface

of the blades is rough and uneven, the lift forces created by the aerofoil cross section will be

affected.

Geometry Replication

Accurate replication of the blade geometry is important so that the blade performs as the

designer intended. Accurate blade geometry also means that the current design of the blades is

being analysed correctly and design modifications can be implemented following the testing. It is

also necessary to manufacture three identical blades in order to ensure that the rotor is balanced.

Rigidity

The blades of a VAWT are put under a considerable amount of mechanical stress during testing

at high wind speeds. It is vital that the blades are manufactured to be as rigid as possible in order

to prevent any bending and possible failure of the blades.

Compatibility (software)

In order to correctly produce the VAWT blades, the software for the rapid prototyping machine

should run smoothly without errors or complications. Incorrect use of the software could lead to

incorrectly produced parts and in turn wasted materials.

Capacity

The capacity of the rapid prototyping machine is one of the factors which determine the

maximum blade diameter which can be manufactured.

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Cost of Raw Material

Each rapid prototyping machine uses different materials to manufacture parts. The cost of this

raw material can vary greatly depending on the properties of the material.

Technical Support

Past experience and availability of technical support are vital to the successful manufacture of

the blades. Making decisions about orientating the blades during manufacture to produce

maximum strength and carrying out necessary modifications are made easier if there is a

technician available with a lot of past experience working with the rapid prototyping machines.

Rap-Man 3DZ-

CorpDimension

Surface Finish 2 3 3

Geometry Replication 3 2 5

Rigidity 3 1 4

Compatibility(software

)1 5 5

Capacity 5 5 5

Cost of Raw Material 3 4 1

Technical Support 1 5 5

Total: 18/35 25/35 28/35

Table 1 (Selecting manufacturing process)

3.6.3 Final Blade

The Standard Tessellation Language (STL) file for the blade was imported into a software

package called catalyst in order to prepare it to be sent to the Dimension machine. This file

contains the data required by the Dimension machine to manufacture the blades. The catalyst

programme calculates the required support material to be added to the model as shown in Figure

21. This support material is required so that the machine can print out parts of the blade which

are not sitting on the base of the machines build area. The orientation of the blade is essential to

minimizing the amount of support material required. Several orientations were investigated to

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see which used the smallest amount of support material. The catalyst software then calculated the

total build time for one blade to be 4 hours 51 minutes. The blades were manufactured and the

support material was carefully removed from the holes in the blade and the blade geometry.

Figure 21 (Catalyst Screenshot)

3.7 Summary

Before the investigation into the rotor manufacture began, the wind tunnel in DIT Bolton Street

was measured in order to determine the maximum size VAWT which could be tested accurately.

The wind tunnel had a cross section of 0.5m by 0.5m so the rotor diameter was immediately

limited to within these dimensions.

The next area which was investigated was the manufacturing methods available for the

manufacture of the blades in DIT Bolton Street. The 3D printing machines available were limited

to a maximum dimension of 200mm. This 200mm was then considered the maximum diameter

for the turbine blades. The CAD files for the turbine blades presented by Brí Toinne Teoranta

were carefully analysed and scaled down to the 200mm limit discussed above.

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A method for attaching the turbines blades to a central shaft had to be devised as there was no

attachment method specified with the blade design. Suitable hubs were designed to attach the

three turbine blades in an evenly spaced manner around the central shaft of the turbine. The

design of the turbine blades had to be modified slightly by adding a series of holes which would

allow the blades to be attached to the central hub.

Two different 3D printing based manufacturing processes were available for the manufacture of

the turbine blades. Prototypes were made using both of the 3D printing machines. The samples

made by each machine were inspected and by using specific selection criteria the appropriate

manufacturing method was selected.

The final blades shown in Figure 22 below were manufactured on a 3D printer using ABS plastic

as the material. The blades were of a reasonably high quality and were deemed appropriate for

use in the VAWT wind tunnel testing.

Figure 22 (Final Blades)

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Chapter 4: Block Diagram and Parts

Blcok Diagram:

Parts:

1. Rotor

2. Axle

3. Bearings

4. Metalsheet

5. 9V Motor

6. Clamp type Supporting

7. Guy Wire

8. Upper Hub

9. Lower Hub

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1) Rotor:

“The driven, rotating disk in a disk brake that is stopped when pressure is applied by

a stationary friction plate or by a caliper”.

2) Axle:

An axle is a central shaft for a rotating wheel or gear. On wheeled vehicles, the

axle may be fixed to the wheels, rotating with them, or fixed to its surroundings, with the

wheels rotating around the axle. In the former case, bearings or bushings are provided at

the mounting points where the axle is supported. In the latter case, a bearing or bushing

sits inside the hole in the wheel to allow the wheel or gear to rotate around the axle.

Sometimes, especially on bicycles, the latter type is referred to as a spindle.

On cars and trucks, several senses of the word "Tandem axle" co-occur in casual

usage, referring to the shaft itself, its housing, or simply any transverse pair of wheels.

The shaft itself rotates with the wheel, being either bolted or splined in fixed relation to it,

and is called an "axle" or "axle shaft". However, it is equally true that the housing around

it (typically a casting) is also called an "axle" (or "axle housing"). An even broader

(somewhat figurative) sense of the word refers to every transverse pair of wheels,

whether they are connected to each other or not. Thus even transverse pairs of wheels in

an independent suspension are usually called "an axle"

3) Bearings:42

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Bearings A Ball bearing is a type of rolling-element bearing that uses balls to maintain the

separation between the bearing races. The purpose of a ballock bearing is to reduce rotational

friction and support radial and axial loads. It achieves this by using at least two races to contain

the balls and transmit the loads through the balls. In most applications, one race is stationary and

the other is attached to the rotating assembly (e.g., a hub or shaft). As one of the bearing races

rotates it causes the balls to rotate as well. Because the balls are rolling they have a much lower

coefficient of friction than if two flat surfaces were sliding against each other.

4) Metal Sheet:

Metal Sheets

Metal sheets used for designing the blades. Sheet metal is simply metal formed into

thin and flat pieces. It is one of the fundamental forms used in metalworking, and can be cut and

bent into a variety of different shapes. Countless everyday objects are constructed of the

material. Thicknesses can vary significantly, although extremely thin thicknesses are considered

foil or leaf, and pieces thicker than 6 mm (0.25 in) are considered plate. Sheet metal is available

in flat pieces or as a coiled strip. The coils are formed by running a continuous sheet of metal

through a roll slitter.

5) Small DC Motor:

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9V DC Motor

In electricity generation, an electric generator is a device that converts mechanical

energy to electrical energy. A generator forces electric charge (usually carried by electrons)

to flow through an external electrical circuit. The source of mechanical energy may be a

reciprocating or turbine steam engine, water falling through a turbine or waterwheel, an

internal combustion engine, a wind turbine, a hand crank, compressed air, or any other source

of mechanical energy. The reverse conversion of electrical energy into mechanical energy is

done by an electric motor, and motors and generators have many similarities. Many motors

can be mechanically driven to generate electricity and frequently make acceptable generators.

6) Guy wire:

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Guywire

A guy-wire or guy-rope, also known as simply a guy, is a tensioned cable designed to

add stability to a free-standing structure. They are used commonly on ship masts, radio masts,

wind turbines, utility poles, and tents. One end of the cable is attached to the structure, and the

other is anchored to the ground at a distance from the structure's base. The tension in the

diagonal guy-wire, combined with the compressional strength of the structure, allows the

structure to withstand lateral loads such as wind or the weight of cantilevered structures. They

are often installed radially, at equal angles about the structure, in trios and quads. This allows the

tension of each guy-wire to offset the others. For example, antenna masts are often held up by

three guy-wires at 120° angles. Structures with lateral loads, such as electrical utility poles, may

require only a single guy-wire to offset the lateral pull of the electrical wires. Conductive guy

cables for radio antenna masts may disturb the radiation pattern of the antenna, so their electrical

characteristics must be included in the design.

7) Hub:

The rotor hub is a welded construction made of steel.  It houses the pitch mechanism and the

pitch bearing.  The hub connects to the rotor and blade assembly to the generator shaft.

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Chapter 5. Conclusion

5.1 Conclusion

The aim of this project was to carry out performance tests on an innovative vertical axis wind

turbine (VAWT) designed by Brí Toinne Teoranta. Overall the project was a great success and

all of the original objectives set out were achieved. The objectives set out at the start of the

project were as follows

1. Carry out research into the area of wind energy and develop an understanding for the

fundamentals of wind power generation.

2. Manufacture the turbine blades designed by Brí Toinne Teoranta to a high standard.

3. Design a testing methodology to obtain performance curves for the turbine.

4. Design and fabricate a suitable test rig for the wind tunnel testing.

5. Carry out wind tunnel testing on the VAWT.

6. Analyse the results obtained from the wind tunnel testing.

7. Present the findings from testing in report form.

Before work commenced on the project, a good understanding of the importance of sustainable

energy was obtained. It was clear from this research that in order to meet the global energy

demand, sustainable energy sources such as wind must be utilised. It was also clear that there

was a need to conduct more research into the area of vertical axis wind turbine technology.

Vertical axis wind turbines are more favourable than horizontal axis turbines in many

applications, making any research and development carried out in the area both relevant and

beneficial.

This project offered a good opportunity to gain experience in the area of turbine blade

manufacture. The 3D CAD files from the designer had to be interpreted and understood so that

the correct approach to manufacture could be taken. Several small design modifications had to be

made to the turbine blades designed by the manufacturer and components had to be designed to

mount the blades to the central shaft of the turbine. Experience was also gained in the area of

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prototyping components using different manufacturing techniques before deciding upon a final

solution.

The area of VAWT performance testing was investigated which provided several methodologies

for assessing a turbine’s performance. Several selection criteria were used to decide upon the

appropriate testing methodology for the test facility available. A more detailed investigation was

carried out into the selected testing methodology.

A VAWT test rig was designed which incorporated the selected testing apparatus. The test rig

design was optimised to ensure that it was both safe and easy to operate. The test rig was

designed to work specifically with the available wind tunnel test facility. Great experience was

gained in the area of fabrication as the test rig had to be completely fabricated and finished to a

high standard.

Wind tunnel testing of the VAWT was successfully carried out which yielded excellent results

using simple test procedures. The performance curves for the VAWT were successfully obtained

for several different wind speeds. The wind tunnel tests were carefully documented so that the

testing could be assessed correctly. An understanding of the challenges associated with wind

tunnel testing was gained along with valuable experience with troubleshooting any issues as

quickly as possible.

The results obtained from the VAWT wind tunnel testing were analysed in depth, presenting the

data in the form of dimensionless performance curves which allow for comparison between

different turbines. Excellent experience was gained in dealing with large amounts of data from

various wind tunnel tests and filing the recorded data correctly.

Overall this was a very successful project from start to finish. It provided the opportunity to gain

experience in a broad range of areas of the engineering profession. The project also made a

strong contribution to the wind turbine testing facilities present in DIT Bolton Street, providing

valuable experience to everyone involved with the project.

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Chapter 6. References

1. Jha, Ph.D., A.R. (2010). Wind turbine technology. Boca Raton, FL: CRC Press.

2. US Patent 1835018

3. Amina El Kasmi, Christian Masson, An extended k-epsilon model for turbulent flow

through horizontal-axis wind turbines, Journal of Wind Engineering and Industrial

Aerodynamics, Volume 96, Issue 1, January 2008, Pages 103-122, retrieved 2010-04-26

4. Sandra Eriksson, Hans Bernhoff, Mats Leijon, (June 2008), "Evaluation of different

turbine concepts for wind power", Renewable and Sustainable Energy Reviews 12 (5):

1419-1434, doi:10.1016/j.rser.2006.05.017., ISSN 1364-0321, retrieved 2010-04-26

5. Chiras, D. (2010). Wind power basics: a green energy guide. Gabriola Island, BC,

Canada: New Society Pub.

6. Fish hold the key to better wind farms

7. Steven Peace, Another Approach to Wind, retrieved 2010-04-26

8. Kathy Svitil, Wind-turbine placement produces tenfold power increase, researchers say,

retrieved 2012-07-31

9. Jha, Ph.D., A.R. (2010). Wind turbine technology. Boca Raton, FL: CRC Press.

10. Chiras, D. (2010). Wind power basics: a green energy guide. Gabriola Island, BC,

Canada: New Society Pub.

11. http://en.wikipedia.org/wiki/Vertical_axis_wind_turbine

12. http://www.sciencedaily.com/releases/2012/07/120730204607.htm

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