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UNIVERSITY OF CAPE COAST

SCHOOL OF PHYSICAL SCIENCES

DEPARTMENT OF PHYSICS

CONSTRUCTION AND CHARACTERIZATION OF A

PROTOTYPE WIND TURBINE

BY

KWESI AANE KOOMSON

DISSERTATION SUBMITTED TO THE DEPARTMENT OF

PHYSICS OF THE SCHOOL OF PHYSICAL SCIENCES,

UNIVERSITY OF CAPE COAST IN PARTIAL FULFILLMENT

OF THE REQUIREMENT FOR THE AWARD OF BACHERLOR

OF SCIENCE DEGREE IN PHYSICS

JUNE 2014

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DECLARATION

Candidate’s Declaration

“I hereby declare that this dissertation is the result of my own original

research and that no part of it has been presented for another degree in

this university or elsewhere”.

Candidate‘s Signature: …………………..… Date: …….…………

Name: KWESI AANE KOOMSON

Supervisor’s Declaration

“I hereby declare that the preparation and presentation of the

dissertation were supervised in accordance with the guidelines on

supervision of dissertation laid down by the University of Cape Coast.”

Supervisor‘s Signature: …………………... Date: ………………

Name: MR. PATRICK K. MENSAH-AMOAH

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ABSTRACT

There is a growing need for alternate energy sources, to be

explored. A review of the potential of using wind as a supplementary

source of energy in Ghana has been carried out.

A portable prototype wind turbine has been designed and

constructed using simple, and cheap available materials. The built device

was able to generate electrical current and voltage of about 200

milliAmps and 0.20 Volts respectively thus, an average output power of

about 0.04 Watt was obtained.

Analyses made on the output from the device were consistent with

the laws of electromagnetic induction.

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ACKNOWLEDGEMENTS

My sincere gratitude goes to the Almighty Father in Heaven the source of

my life, for keeping me alive and giving me strength to make this

possible.

My wonderful supervisor, Mr. P. K. Mensah-Amoah, for his support,

encouragement and clear directions. His quick and detailed feedbacks and

corrections were much revered and were beyond my imagination.

Rebecca Saka Asuako I appreciate your motivation and kindness.

All staff of the Department, I owe you a Big Thank You!

Now to my siblings, Ekua, Kofi, Kwame and Efua, not forgetting Bro.

Maxwell and Castrol you are all invaluable to me.

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DEDICATION

I dedicate this work to Mr. John Kobena Koomson and Ms. Comfort

Mensah you have been my backbone!

Auntie Becky you are the inspiration!

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Table of Contents

DECLARATION ........................................................................................ ii

ABSTRACT .............................................................................................. iii

ACKNOWLEDGEMENT ......................................................................... iv

DEDICATION ............................................................................................. v

TABLE OF CONTENTS .......................................................................... vi

NOMENCLATURE .................................................................................... x

CHAPTER ONE .......................................................................................... 1

The Wind.................................................................................................. 1

History of Electricity ................................................................................ 2

Methods of Electricity Generation ........................................................... 2

Turbines ................................................................................................... 3

Sources of Electricity ............................................................................... 4

Wind Energy ............................................................................................ 4

Wind Turbine ........................................................................................... 6

Energy challenges in Ghana ..................................................................... 7

Statement of problem ............................................................................... 8

Aim of Study ............................................................................................ 8

Scope of Work ......................................................................................... 8

CHAPTER TWO ....................................................................................... 11

Overview ................................................................................................ 11

Wind Speed Variation ............................................................................ 11

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Power of the Wind ................................................................................. 12

Fundamental Equation of Wind Power .................................................. 12

Efficiency in Extracting Wind Power .................................................... 13

Betz Limit & Power Coefficient: ....................................................... 13

Turbine power output; ........................................................................ 14

Faraday‘s Law of Electromagnetic Induction and Lenz Law ................ 15

Wind Turbine Aerofoil........................................................................... 16

Torque, Lift and Drag ............................................................................ 17

Static Velocity and Static Torque: ......................................................... 21

Tip Speed Ratio ...................................................................................... 19

Number of blades ................................................................................... 22

Solidity of Wind Turbine ....................................................................... 23

The Generator, Gear Box and Gears ...................................................... 24

The Magnet and Conductor .................................................................... 25

Blade Element Momentum Theory ........................................................ 25

Blade Element Theory ........................................................................... 26

Savonius Wind Turbines ........................................................................ 27

Different Modification of Savonius Wind Turbine ................................ 29

Why Wind Energy ................................................................................. 30

Free Fuel (Cheap) ............................................................................... 30

Price stability and Fewer subsidy ....................................................... 31

Environmental friendly (very less pollution) ..................................... 31

Land conserved, Supports Agriculture ............................................... 32

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Wind Energy and Jobs ........................................................................ 32

Work Safety ........................................................................................ 29

Wind Energy Issues ............................................................................... 29

Infrasound ........................................................................................... 29

Visual Effects ..................................................................................... 34

Shadow Flicker Effects ...................................................................... 35

Electromagnetic Effects ..................................................................... 35

Wind Resource and Measurements in Ghana ..................................... 35

CHAPTER THREE ................................................................................... 41

Overview ................................................................................................ 41

Items and Materials Needed ................................................................... 41

Tools Needed ......................................................................................... 42

Construction ........................................................................................... 43

The Frame & Rotor Blades ................................................................ 43

The Generator ..................................................................................... 39

CHAPTER FOUR ..................................................................................... 50

Overview ................................................................................................ 50

Result and Analysis ................................................................................ 50

The variation of power with wind speed ............................................ 50

The variation of induced electromotive force, emf with

distance from coil to magnet .......................................................................... 52

Comparison of power generated with two-coil set to one-coil

set .................................................................................................................... 54

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Discussion .............................................................................................. 56

CHAPTER FIVE ....................................................................................... 60

Overview ................................................................................................ 60

Summary ................................................................................................ 60

Conclusion ............................................................................................. 61

Recommendation ................................................................................... 62

REFERENCES .......................................................................................... 63

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NOMENCLATURE

Abbreviations

Meaning

EMF:

Electromotive Force

HAWT: Horizontal Axis Wind Turbine

VAWT: Vertical Axis Wind Turbine

EC: The Energy Commission

NREL: National Renewable Energy Laboratory

SWERA: Solar and Wind Energy Resource Assessment

TSR: Tip Speed Ratio

BEM:

GMA:

Blade Element Momentum

Ghana Meteorological Agency

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CHAPTER ONE

INTRODUCTION

The Wind

The use of wind energy in various ways has been very useful to man since

antiquity, with some being sailing, grinding and pumping up water by use of

windmills. Latter ones included hot air balloon, paragliding, kite flying and then

the generation of electricity.

Wind is simply air in motion, which is bulk movement of air. Thus flow of

gases or air on a large scale on the surface of the earth. Winds are formed by the

uneven heating of the atmosphere by the sun‘s radiant energy in combination with

the irregular surface of the earth and the earth‘s rotation. The difference in

atmospheric pressure that exist as a result of the uneven heating by the sun, forces

air to move from the higher atmospheric pressure area to the lower, resulting in

winds of various speeds.

Using of the kinetic energy of the wind has been so useful to man but

harnessing of it for electrical energy has been the most useful of all. The present

day wind turbine had its design and concepts from the old time windmill, which

can be traced to be in operation since the 7th

to 9th

century and became more

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useful for grinding and milling and also pumping of water until the discovery of

electricity generation.

History of Electricity

Electricity is the flow of electrons through a conductor, or the flow of

electric charges, and electricity generation is the process of generating electrical

power from other sources of primary energy. Between the 1820s and early 1830s

the British scientist Michael Faraday discovered the fundamental principles of

electricity generation. His basic method is still used today: electricity is generated

by the movement of a loop of wire, or disc of copper between the poles of a

magnet. When the permanent magnet is moved relative to the conductor, or when

the conductor is rather moved relative to the permanent magnet, an electromotive

force is created. This is the production of electricity by electromagnetic induction

which is the production of potential difference (voltage) across a conductor when

it is exposed to a varying magnetic field. If the conductor is connected through an

electrical load, current will flow, and thus electrical energy is generated,

converting the mechanical energy of motion to electrical energy. Electricity is

most often generated at a power station by electromechanical generators or

turbines, primarily driven by heat engines fueled by chemical combustion or

nuclear fission but also by other means such as the kinetic energy of flowing

water and wind.

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Methods of Electricity Generation

The use of turbines, thus electricity generation by the method of

electromagnetic induction turns out to be the power source for most of the world‘s

electricity generated! Although other methods of electricity generation exist such

as from photovoltaic (solar panels), electrochemistry (e.g. batteries) and very few

unpopular methods/processes like static electricity (e.g. triboelectric effect and

lightning), thermoelectric effect (e.g. Thermionic converters), piezoelectric effect

(e.g. piezoelectric generators) and nuclear transformation (e.g. betavoltaics), only

two methods that is the method of electromagnetic induction and that of

photovoltaic provides electrical energy for the worlds grid, thus for domestic and

industrial consumption. The other methods are still under research and most of

them produce electricity on a very small scale and are therefore used in the

laboratories as in thermocouples or for small household gadgets as in batteries.

Turbines

According to the CIA World Factbook 2009, out of the 20,261 TWh

(TeraWatts hour) per year 2008 electricity produced worldwide, only 12 TWh per

that same year constituting 0.06% was generated by photovoltaic, this show that

about 99% of the world‘s electrical energy comes from electromagnetic induction

which is mostly from turbines. A turbine is a rotary mechanical device that

extracts energy from fluid flow and converts it into useful work. Dealing with

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modern turbines it is accredited to two engineers, Sir Charles Parsons; a British

and Gustaf de Laval; a Swedish, who invented reaction turbine and impulse

turbine respectively in the late 1880s.

All turbines have at least a moving part called a rotor assembly which is a

shaft or drum with blades attached. With electrical turbine the moving fluid acts

on the blades so that they move and imparts rotation energy to the rotor, meaning

kinetic and potential energies from the fluid is converted to rotational energy

which will then be converted by the moving shaft to mechanical energy which

will finally be converted to electrical energy by the moving conductor and the

magnet. That is electricity by induction is finally produced from the energy in the

moving fluid.

Sources of Electricity

There are various sources of electricity production, these sources are

classified according to the resources or fuel used for the production. These are

nuclear, solar thermal, hydro, biomass, solar photovoltaic, thermal (burning of

fossil fuels like coal, oil, gas, etc.), geo thermal, wind and tides. These sources

can still be grouped into two namely renewable and non-renewable sources.

Renewable energy is generally energy that comes from resources which are

naturally replenished on a human timescale such as hydro, biomass, solar, geo

thermal, wind and tides. The renewable sources are ideal over the non-renewable

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because they do not produce any sort of waste or pollution to the environment and

it is much cheaper, as one does not need to buy fuel to generate the power, for

example wind or sunlight as compared to coal and oil.

Although non-renewable sources still forms the highest percentage in

world electricity generation about 80% (fossil fuels and nuclear) according to

OECD 2011-12 Factbook (2009 data), renewable sources enjoyed the highest

percentage growth from 2000 to 2010.

Wind Energy

Among the renewable resources also wind electric power appears to be the

cheapest and safest of them all and also efficient. It is the most environmental

friendly of all the electricity sources due to the fact that the land of wind farms

can still be used for any other thing including agriculture. In 2008 wind

contributed 1.1% of the world electricity generated and in 2012 wind power had a

30% growth rate with a worldwide installed capacity of 282,482 megawatts

(MW). Wind electrical energy is produced by wind turbine, which is a type of

turbine turned or rotated by the action of the wind.

All around the world countries are moving aggressively to increase their

wind generation capacity. This increase in installed generating capacity is

documented in the Global Wind Report Annual Market Update, with Europe and

Asia leading (GWEC, 2010, p.14).

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Fig.1.1: Global Cumulative Installed Wind Capacity 1996-2010 Information from

(GWEC, 2010, p.14)

Over the course of 2010 many countries, most notably China, have

dramatically increased their number of wind installations (GWEC, 2010, p.11).

Denmark has about 100% of their electrical energy from wind and they have not

being facing any electrical power challenges so far and over 83 countries around

the world are using wind power to supply the electricity grid.

Wind Turbine

The wind turbine is a mechanical device with a rotary part that converts

the wind‘s energy (potential and kinetic) to electrical energy. There are two

classifications of wind turbine; the airborne wind turbine and the grounded/tower

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wind turbine. An airborne wind turbine is a design concept for a wind turbine that

is supported in the air without a tower, thus benefiting from the higher velocity

and almost constant wind at high altitudes, while avoiding the expense of tower

construction, or the need for slip rings or yaw mechanism. There are two varieties

of the airborne wind turbine namely, the aerodynamic variety and the aerostat

variety. Currently airborne wind turbines are under research and there is no

airborne wind turbine in commercial use. The grounded/tower wind turbine is

directly or indirectly connected to the ground or suspended on water. There are

also two types, which are the horizontal axis wind turbine (HAWT) and vertical

axis wind turbine (VAWT). Following are the types.

Fig.1.2: Vertical Axis Wind Turbine Fig.1.3: Horizontal Axis Wind Turbine

(VAWT) (HAWT)

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There are also two types of the vertical axis wind turbines which are the

Darrieus and the Savonius, which are actually different with respect to the design

of the rotor/blades.

Energy challenges in Ghana

The economy of Ghana is growing, so is its population and energy

dependency. This pose challenges to the country with regard to its ability to

provide affordable and reliable electric power. Ghanaians are only able to access

less than 72% of electricity, which is a hindrance to sustainable development

(Essandoh, 2012). Currently, load shedding has been going on in various parts of

Ghana due to the energy crisis. There are even sometimes that the whole country

is cut out of electric supply. This erratic power supply is a big blow to the country

and as a result, hinders development and growth of the country, productivity and

economic activity have also declined for the past decade.

Statement of problem

In view of the current energy crisis in Ghana and also persistence increase

in fuel prices and utility charges, it is necessary for the nation to consider

exploring the wind energy resource to diversify, sustain and save the energy

production crisis in Ghana, increase access to electricity and as well, improve the

reliability of power supply and make it more affordable, and then provide energy

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security for Ghana. Hence, the construction of the prototype wind turbine to meet

the energy demands.

Aim of Study

To design a wind turbine.

To construct a prototype of the design with simple, common and cheap

materials around.

To take current and voltage values at varied wind speeds with the

prototype and hence compute the power outage of the turbine.

Scope of Work

The study contains five chapters: the introduction thus chapter 1examines

the backgrounds, the wind, methods and sources of electricity. It also introduces

the subject of study in brief and then outlines the organization of the rest of the

research.

Chapter 2 (Literature Review) The purpose of this chapter which is to

present a review of current literature, arguments and mathematical theories related

to the wind turbine and linking existing studies to the current study. The

mathematics and physics of the rotor (blades), stator (coil windings and magnets

component) and all parts of the wind turbine are explained and related to the wind

energy and speed, and to the output. It also poses critics on the health and

environmental hazard of the wind turbine.

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Chapter 3 (Design and Construction) illustrates the research design and

ideas, process and methods for building the prototype and data collections. The

rationale behind the choice of each tool and the methods of analyzing the data is

elaborated. The objective of Chapter 3 is to illustrate the research design and

report the research and design processes of the study.

In chapter 4 (Analysis of Results), there is presentation and discussion of

the results by using different research instruments and methods. The results of the

quantitative and qualitative research conducted are presented and juxtaposed with

other literature available.

Chapter 5 is the conclusion of the study. In this, there is review of

significant findings and recommendations, especially to the Energy Commission

of Ghana, the Ghanaian community and to future researchers as to how wind

energy can be utilized into electrical energy, to curb the energy crisis in the

country.

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CHAPTER TWO

LITERATURE REVIEW

Overview

The principles and the actual theories and ground work that goes into the

making or manufacture and working of the wind turbine is what this chapter is

about. The working of the wind turbine to produce electricity involves a lot of

processes and choices as well, taking into consideration the blades, coil windings,

magnets and the choice of materials used etc. The mathematics and physics is

taking into play to explain all the concepts at hand. Also the positive and negative

impact of wind turbine is also discussed. The review will be started by first

talking about the wind.

Wind Speed Variation

Most of the power harness from the wind is as a result of its speed. The

instrument used to measure wind speed is called, Anemometer. However, the

nature of wind‘s speed is such that its direction, speed, and temperature vary. The

four main categories of wind variation are;

Variation with time; since winds are generated by difference in temperature of

air between two locations, it is subject to heat from sunshine and the temperature

of the surrounding in an area of the Earth. The variation can be momentary, daily,

and seasonal.

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Variation with height; the speed of the wind changes with height, normally at

higher heights the speed of the wind is greater. Thus the higher the height from

the surface of earth the higher the wind speed.

Variation with terrain; the speed of the wind is influence by all obstructions that

lies on its path, which tends to slow it down. Example trees, buildings, etc.

Variation with geography; the speed of the wind is affected by the climate at

region which is attributed to the geographical location (Hemani, 2012).

Power of the Wind

The amount of energy that can be captured from the wind is exponentially

proportional to the speed of the wind and it is known to be a function of the cube

of the wind speed. Thus power available from the wind varies as the cube of the

wind speed, so twice the wind speed means eight times the power. This is why

sites for wind turbine has to be selected carefully. (Hansen, 2008)

Fundamental Equation of Wind Power

Wind Power depends on:

• amount of air (volume)

• speed of air (velocity)

• mass of air (density)

flowing through the area of interest (flux)

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Kinetic Energy definition:

• KE = ½ * m * v2

Power is KE per unit time:

thus power in terms of rate of change of mass flow

• P = ⁄ *

* v

2

Fluid mechanics gives mass flow rate (density * volume flux):

thus rate of change of mass of the air flowing over a blade surface area A,

perpendicular to the direction of wind flow can be determined as;

•

= ρ* A * v

Therefore the power that can be harness in the wind can be theoretically

expressed as;

• P = ½ * ρ * A * v 3 i.e. if the turbine is perfectly efficient.

=> Wind Power Pw = (air density)*(rotor swept area A= πr2)*(cube of

velocity)

Efficiency in Extracting Wind Power

Betz Limit & Power Coefficient:

Since no machine is 100% efficient, a turbine cannot necessarily capture

all of the power in the wind passing over its blades. It can only absorb a portion of

it. There is a maximum value that no turbine in its best performance can exceed. It

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can be theoretically determined and is called the Betz limit. The value for Betz

limit is 16/27 = 0.59 or 59% efficiency.

Power Coefficient, CP, is the ratio of power extracted by the turbine, PT

to the total power contained in the wind resource, PW.

CP=PT / PW

=> Cp= PT/(½ρAV3)

Turbine power output;

is therefore the fraction of power harnessed by the turbine is;

PT = ½ * ρ * A * v3 * Cp taking Betz limit into consideration.

(Kalmikov and Dykes, 2011)

Fig.2.1: Turbine power out put

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Faraday’s Law of Electromagnetic Induction and Lenz Law

By defining magnetic flux as Φ = BAcosθ, where θ is the angle between B

and the direction perpendicular to the plane of the loop (along the axis of the

loop), Faraday's law states that the emf induced in a wire is proportional to the

rate of the flux through the loop. Mathematically as;

Ԑ =

a little modification of the law gives Lenz law, which states that the

direction of any induced current (or induced emf) will be such as to produce

effects which oppose the change that produces it.

Ԑ = -N

The N attributes to the number of turns of the conductor.

Substituting the magnetic flux relation into equation

Ԑ = -N

For a loop rotating periodically relative to a constant magnetic field, θ =

ωt, Where ω is the angular speed.

Ԑ = ωNBAsinωt

Then the maximum emf is,

εmax =ωNBA

(Serway & Beicher, 2000).

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The magnetic field B can be expressed in teams the permeability μ and the

distance of separation, d from Ampere‘s law (Kraus, 1992) as;

B(at 𝑑) =

The permeability of in this relation is an important characteristic of the

magnetic core material for the wire loop. The relative permeability μr is often

used to refer to the magnetic property of materials. Air has relative permeability

of 1.000 comparable to that of vacuum are paramagnetic material including

aluminium. Diamagnetic material, example copper, has relative permeability in

the order of 0.99990 to 0.99999, and ferromagnetic materials, example steel, Iron

(0.2) impurity, has an μr value in the order of 1,000 to 100,000 (Yong, 2008).

Wind Turbine Aerofoil

Modern HAWTs usually feature rotors that resemble aircraft propellers,

which operate on similar aerodynamic principles, i.e., the air flow over the airfoil

shaped blades creates a lifting force that turns the rotor. The nacelle of a HAWT

houses a gearbox and generator. HAWTS can be placed on towers to take

advantage of higher winds farther from the ground.

The capture area of a HAWT, the area over which the sweeping blades can

―capture‖ the wind, is given by

A= (D/2)2

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where D is the rotor diameter. However, this capture area must face

directly into the wind, to maximize power generation, so HAWTS require a

means for alignment (yawing mechanism) so that the entire nacelle can rotate into

the wind. On smaller wind turbines, a tail vane provides a ―passive‖ yaw control.

In large, grid-connected turbines, yaw control is active, with wind direction

sensors and motors that rotate the nacelle. (Boston University, 2009)

Torque, Lift and Drag

The efficiency of a wind turbine blade depends on the torque, drag and lift

produced by the blade. These factors are affected by the size and shape of the

blades, the number of blades, and the blade pitch.

Torque is a force that turns or rotates something. Torque is equal to the

force multiplied by distance. This means that the longer your blades are, the more

torque you can generate thus the easier the wind can turn the blades. On a wind

turbine, the long blades give the turbine a lot of leverage to provide power to the

generator. Wind turbine blades are optimized to generate a lot of torque and lift

with very little drag. (Kid Wind Project, 2008)

Airflow over any surface creates two types of aerodynamic forces— drag

forces, in the direction of the airflow, and lift forces, perpendicular to the airflow.

Either or both of these can be used to generate the forces needed to rotate the

blades of a wind turbine. (Boston University, 2009)

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Lift is the aerodynamic force that allows airplanes and helicopters to fly.

The same force applies to the blades of wind turbines as they rotate through the

air. Lift opposes the force of drag, helping a turbine blade pass efficiently through

air molecules. The main goal of a well-designed wind turbine blade is to generate

as much lift as possible while minimizing drag (Kidwind Project, 2008). More

energy can be extracted from wind using lift rather than drag, but this requires

specially shaped airfoil surfaces, like those used on airplane wings (Figure 2.2).

The airfoil shape is designed to create a differential pressure between the upper

and lower surfaces, leading to a net force in the direction perpendicular to the

wind direction.

Fig. 2.2: Lift-based wind turbine concept

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Rotors of this type must be carefully oriented (the orientation is referred to

as the rotor pitch), to maintain their ability to harness the power of the wind as

wind speed changes (Boston University, 2009). The amount of lift a blade or wing

can generate is determined by several factors—the shape of the blade, the speed

of the air passing around the blade, and the angle of the blade relative to the

apparent wind. Almost all HAWT make use of lift force for the rotation of their

blades.

Drag, or air resistance, is a force that is working against the blades, caus-

ing them to slow down. Drag is always important when an object moves rapidly

through the air or water. Airplanes, race cars, rockets, submarines, and wind

turbine blades are all designed to have as little drag as possible. Drag increases

with the area facing the wind—a large truck has a lot more drag than a

motorcyclist moving at the same speed. Wind turbine blades have to be

streamlined so they can efficiently pass through the air. Changing the angle of the

blades will change the area facing the apparent wind. This is why blade pitch

angles of 10-20 degrees tend to have much less drag than greater angles.

Drag also increases with wind speed. The faster an object moves through

the air, the more drag force it experiences. This is especially important for wind

turbine blades, since the blade tips are moving through the air much faster than

the base of the blade. The shape and angle of wind turbine blades changes along

the length of the blade to reduce drag at the blade tips.

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However in drag-based wind turbines, the force of the wind pushes against

a surface, like an open sail. In fact, the earliest wind turbines, dating back to

ancient Persia, used this approach. Some VAWT are drag based and therefore

make use of the drag force for the rotation rather than the lift, therefore drag is

rather increased and lift reduced. The Savonius rotor is a simple drag-based

windmill that works on drag. (Figure 2.3). It works because the drag of the open,

or concave, face of the cylinder is greater than the drag on the closed or convex

section (Boston University,2009).

Fig. 2.3: Drag-based wind turbine concept

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Static Velocity and Static Torque:

1. Start-up wind speed is the lowest wind speed at which the torque spins. It

depends on turbines design and construction.

2. Static torque is the torque of the wind applied about the centre of the rotor

when it is stationary. A high static torque indicates a low start-up wind

speed. (Weiss, 2010).

Tip Speed Ratio

The Tip Speed Ratio (TSR) is an extremely important factor in wind

turbine design. TSR refers to the ratio between the wind speed and the speed of

the tips of the wind turbine blades. Thus relationship between rotor blade velocity

and relative wind velocity, is the foremost design parameter around which all

other optimum rotor dimensions are calculated:

λ = Ωr⁄Vw

Vw = Windspeed

r = Radius

Ω = Rotational velocity (rad/s)

λ = Tip speed ratio

If your rotor spins too slowly, a lot of wind will pass through the gaps

between the blades rather than giving energy to your turbine. But if your blades

22

spin too quickly, they could create too much turbulent air or act as a solid wall

against the wind therefore a correct TSR should be considered when designing

wind turbine.

Aspects such as efficiency, torque, mechanical stress, aerodynamics and

noise should be considered in selecting the appropriate tip speed. The efficiency

of a turbine can be increased with higher tip speeds, although the increase is not

significant when considering some penalties such as increased noise, aerodynamic

and centrifugal stress. (Schubel and Crossley, 2012)

Number of blades

Efficiency of power extraction depends on the proper choice of the

number of blades. That is the limitation on the available power in the wind means

that the more blades there are, the less power each can extract. This is because

when the blades are close to each other, every blade will move in a turbulent air

cause by the preceding blade under fast rotation speed. Power extraction will be

minimized. It will also be less than the optimum if the blades are so far apart or

move so slowly that much of the air stream passes through the wind turbine

without interacting with the blade. Thus, the number of blades should depend on

TSR. To achieve optimum efficiency, the TSR is kept high by minimizing the

number of blades. Generally, only two or three blades are required (Tiwari et al,

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2010). A consequence of this is that each blade must also be narrower to maintain

aerodynamic efficiency. (WE Handbook)

Low tip speed ratios produce a rotor with a high ratio of solidity, which is

the ratio of blade area to the area of the swept rotor. It is useful to reduce the area

of solidity as it leads to a decrease in material usage and therefore production

costs (Schubel and Crossley, 2012). Meaning, less blades less material usage and

less cost.

Solidity of Wind Turbine

The solidity, σ of a wind turbine rotor is the ratio of the projected blade

area to the area of the wind intercepted. That is, BA ⁄2Aint. Where, B is the

number of blades, A is area swept by wind on a blade, Aint is the total area the

wind intercept with turbine blades. For a multiple blade water-pumping windmill,

it is typically around 0.7. For high-speed horizontal axis machines, it lies between

0.01 and 0.1; for the Darrieus rotor also it is of the same order. Solidity has a

direct relationship with the torque and speed. High-solidity rotors have high

torque and low speed, and are suitable for pumping water. Low-solidity rotors, on

the other hand, have high speed and low-torque, and are typically suited for

electrical power generation. (Tiwari, P, Swain, D, and Kumar, K. A,2010).

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The Generator, Gear Box and Gears

The generator converts the power from the rotating rotor shaft to electrical

power, which can be used on site, or be sent into the electrical grid (the system

that interconnects power plants, electrical distribution networks, and electrical

power users). Generators are used in all electrical power plants, including coal

and oil-fired plants. A generator can be thought of as an electric motor run in

reverse; in fact, many motors can also be used as generators. It contains the

magnets and the conductor (wire) that does the main work (induction).Typical

generators operate with a rotation speed of 1000 to 3600 revolutions per minute

(rpm). These speeds are far too fast for a wind turbine for several reasons,

including excessive stress and turbulence at high speeds and the fact that the tip

speed is limited by the speed of sound (340.3 m/s) due to both excessive drag and

noise caused by shock wave formation. The gear box solves the problem, by

converting the low speed rotation of the wind turbine rotor (typically less than

100 rpm) to the high rpm needed by the generator (Boston University, 2009). A

gear is a wheel with grooves (teeth) engraved on the outer circumference, such

that two such devices can interlock and convey motion from one to the other

while the gear box is a transmission containing the train of gears and to which a

gear lever is connected.

25

The Magnet and Conductor

This is the main component of the generator and hence the turbine. Since

the electricity is produced by the induction which is as a result of relative

movement of these two components. In fact in order to induce a high

electromotive force a magnet with high magnetic flux/density should be

considered and a higher number of turns for the conductor/wire. The wire most

preferably copper because of its high conductivity and resistance to rust is coated

or enameled. It is best that a lower gauge number (i.e. thicker wire) is used in

order to reduce the resistance and give way for higher emf and hence power,

from;

Resistivity, ρ =

Where R is resistance

A is cross sectional area

l is length

R =

so as A increases (i.e. thickness of wire) the lesser the resistance R

into V=IR, thus for a bigger voltage bigger current but smaller resistance as

from above. Therefore giving way for greater power output P=IV.

Blade Element Momentum Theory

The blade element momentum theory, BEM equates two methods of

examining how a wind turbine operates. That is:

26

1. By looking at the force generated,

2. By the effect of rotation of the turbine and wake system distribution

(i.e., torque) (Ingram, 2011).

Blade Element Theory

This theory is based on two assumptions:

1. There are no interactions between different blade elements.

2. The forces on the blade element solely Lift and drag.

If there are B number of blades, the area of turbine swept by wind A , the

relative velocity W, the flow angle ϕ, then for HAWT the trust T and torque τ

respectively are;

T=1/2BAρW2(CLsinϕ + CDcosϕ)

τ = ½ BRAρW2(CLsinϕ – CDcosϕ)

The effect of the drag force is clearly seen in the equations, an increase in

thrust force on the machine and a decrease in torque (and power output). For

VAWT the torque;

τ = ½ BRAρW2(CLcosϕ + CDsinϕ)

From the above equation, the effect of drag force rather increases the

torque as seen in equation (Igram, 2011). This is why Drag-Based turbine is

27

preferred for application that required direct mechanical work. Example, wind

turbine made for corn mill (Weiss, 2010). 27

Savonius Wind Turbines

Savonius turbines are one of the simplest and easy to construct turbines.

This is why it was chosen for this project. Aerodynamically, they are drag-base

type of vertical axis wind turbine consisting of two scoop or three scoops.

Because of the curvature, the scoops experience less drag when moving against

the wind than when moving with the wind. The differential drag causes the

Savonius turbine to spin. Because they are drag-type devices, Savonius turbines

extract much less of the wind's power than other similarly-sized lift-type turbines.

Much of the swept area of a Savonius rotor is near the ground, making the overall

energy extraction less effective due to lower wind speed at lower heights (Weiss,

2010).

28

Fig. 2.4: Top View of the Savonius VAWT (Kolachara, 2012).

As shown in figure , the blades rotate about the axis perpendicular to the

wind direction. The angle of attack of the blades varies constantly during the

rotation such that while one blade moves on downwind, the other rotates on the

upwind. When the turbine rotates the torque of one blade counters the

torque of the other giving a net torque. Therefore from BEM, the net

torque and power coefficient can be determined from the net drag force as;

𝐹d=𝐹dr−𝐹da

𝐹d =1/2 ρACdr(Vsinθ – ωR)2 – ½ ρACda(Vsinθ + ωR)

2

∫

= ∫ 𝐹𝑑

Rsinθdθ

Cp =

3

Cp= λ/3π[(Cdr (6λ2−3λ (𝜋−1) +4) – Cd (6λ

2+3 (𝜋 −1) +4)]

29

From this equation, Cp can be expressed as a function of the drag

coefficients and the tip speed ratio (Menet as cited in Kolachara, 2012).

Different Modification of Savonius Wind Turbine

The height of the shaft together with the blade is increase to increase the

capacity of wind capture. This is equivalent to increasing the length of the

cylindrical sections, if all the sections are aligned.

Alternatively a second set can be installed at 90° from the first half

cylinders. This adds to the uniformity of rotational torque on the shaft, since with

only two half cylinders the absorbed power pulsates (this is not uniform as the

rotor turns).

A gap is in the structure where the two half cylinders are joined. This

allows the air to pass through this gap from the segment capturing wind to the

segment opposing wind. The advantage is two-fold: wind is not trapped in the

capturing blade and has a more steady flow, and the opposing blade has an extra

force to help it push the air. This is the most efficient Savonius design because it

has the advantage of air being deflected twice, also the vanes act partly like an

airfoil when they are edge-on into the wind, creating a small lift effect and thus

enhancing efficiency

The other design arranges the two blades to be able to swing about an axis

at their outer edges. This arrangement can greatly decrease the resistance to the air

30

flow of the opposing blade. Both of these designs enhance the power coefficient,

and thus the capacity of a turbine for the same size, but introduce their own

complexities.

Another design for a Savonius rotor alteration is to twist each of the half

cylinders. This helps the captured power to be more uniform rather than pulsating

(Hemani, 2012).

Why Wind Energy

As discussed above in chapter one, there are several forms of generating

electricity so why should wind energy be preferred to the others? The following

discusses the reason for this venture.

Free Fuel (Cheap)

Unlike other forms of electrical generation where fuel has to be purchased

at high cost before converting to electricity, like; coal, crude oil, gas, nuclear etc

and shipped or transported to a processing plant, wind energy generates electricity

at the source of fuel, which is free. Wind is a native fuel that does not need to be

mined or transported, thus rolling out two important expensive costs out of long

term energy expenses. Making the final product thus electricity from wind less

expensive than the others. (windustry.org)

31

Price Stability and Fewer Subsidy

Since electricity from wind is rather cheaper than the other forms,

electricity is made available to the public at lower fee and since there no fuel

increase and transportation cost related to wind energy the electrical power will

remain forever stable. And also fewer subsidies are needed to support wind

energy compared to the subsidies to the other forms of energy. According to

Renewable Energy World magazine, conventional energy receives US$ 300

billion in subsidies per year, while renewable energy has received less than US$

20 billion of tax-payers‘ money in the last 30 years (windustry.org). In a country

like Ghana, where cost of fuel and transport keeps springing up every now and

then, causing increase in utility bills and hardship wind energy generation will be

the best option for us.

Environmental Friendly (very less pollution)

It is a fact that energy use in power plants accounts for 67% of Sulfur

Dioxide (SOB2B), the primary cause of acid rain. SOB2B causes acidification of

lakes and damages forests, crops, animals and other habitats. Then 25% of

Nitrous Oxide (NOx), which causes smog and respiratory ailments. Also 33% of

Hg (mercury), a persistent, bio-accumulative toxin which increases in

concentration as it moves up the food chain which is example from fish to birds,

causing serious deformities and nerve disorders.

32

Wind turbine one of the best choice that we have because it has no

harmful emissions such as Sulfur Dioxide (SOB2B), Nitrous Oxide (NOx), or

Mercury emissions. Also it does not have Greenhouse Gas Emissions. It also

don‘t need any cooling mechanism like cooling water that we always use at fuel

engines and nuclear reactors. There are water pollution that is always generated

by mining activities. After all there is no waste when using wind turbine.

Land conserved, Supports Agriculture

Wind power has the advantage of not being land intensive. Wind farms

generally require 0.08-0.13 km2/MW of generation capacity, (Andersen, 2008,

p.12) unlike mining of coal for power generation, where the land is damaged or

hydroelectric dam where a vast land has to be forfeited for water build-up and

retention. The land surrounding the wind turbines can remain as natural habitat or

agricultural land (Andersen, 2008, p.12). Many of the materials wind turbines are

made of can be recycled, and no decommissioning issues are associated with wind

turbines (Andersen, 2008, p.11). Wind turbines can therefore be installed amid

cropland without interfering with people, livestock or production.

Wind Energy and Jobs

The Conference Board of Canada has estimated, based on a 2000 MW

generating capacity, that the development and operation of offshore wind farms in

Ontario has the potential to create 3 900- 4 000 jobs during the construction

33

phase, from 2013-2026 (Conference Board of Canada, 2010). This development

would contribute between $4.8 and $5.5 billion to Ontario‘s economy for this

period (Conference Board of Canada, 2010).

The development of wind energy in Europe has created many new jobs. In

2007 in the European Union the wind energy sector directly employed 108 600

people, and indirectly employed over 150 000 (EWEA, 2008, p.13). It is expected

that by 2030 the number of people employed by the wind energy sector will have

risen to 375 000 (EWEA, 2008, p.11).

Work Safety

There are no risk factors like effect of heat and burns from boilers or

nuclear emission effects for the workers. Also no respiratory diseases and

infertility associated because of no harmful emission and excessive engine heat

respectively.

Wind Energy Issues

Above all these benefits wind energy is also noted for very few issues

which are as follows;

Infrasound

Concerns have been raised about human exposure to ―low frequency

sound‖ and ―infrasound‖ from wind turbines. There is no scientific evidence,

34

however, to indicate that low frequency sound generated from wind turbines

causes adverse health effects.

Low frequency sound and infrasound are everywhere in the environment.

They are emitted from natural sources (e.g. wind, rivers) and from artificial

sources including road traffic, aircraft, and ventilation systems. The most

common source of infrasound is vehicles which we are found of everywhere.

Under many conditions, low frequency sound below 40Hz from wind turbines

cannot be distinguished from environmental background noise from the wind

itself (Leventhall 2006, Colby et al 2009).

“The sound level from wind turbines at common residential setbacks is not

sufficient to cause hearing impairment or other direct health effects…” (King,

2010 p.2)

Visual Effects

Wind turbines are just normal structures to look at, just like trees, better

looking than boiler chimneys and open cast coal mine. Wind farms have relatively

little visual effect but however some people find it to be boring to look at. Drivers

also complain of them being disturbing. However manufacturers have than a lot to

this issue such as painting of turbine with neutral colours, arranging of turbine in

visually pleasing manner and also designing each turbine uniformly. Wind farms

are also situated far from road networks and residential areas.

35

Shadow Flicker Effects

Shadow flicker occurs when the blades of a turbine rotate in sunny

conditions, casting moving shadows on the ground that result in alternating

changes in light intensity appearing to flick on and off. Some people find these

shadows distasteful, about 3 per cent of people with epilepsy are photosensitive,

generally to flicker frequencies between 5-30Hz. Most industrial turbines rotate at

a speed below these flicker frequencies. This effect can however be prevented

with proper placement of wind turbines to avoid the particular setup necessary to

create this effect.

Electromagnetic Effects

Electromagnetic radiations are all around us, in fact they are ubiquitous

since every electronic gadget emits them and the earth also naturally emits them

around. To top up, wind turbines are 80 to 100 metres above the ground so any

emf produced will be far from any person around and the cables that carry the

power are underground thus no emf. However there are still some effects like

radio frequency and radar interference.

Wind Resource and Measurements in Ghana

Many studies have gone into Wind Energy assessment in Ghana by

renewable energy analysts and groups of researchers. Data has been compiled and

analysed by researching institutions such as Ghana Meteorological Agency

36

(GMA) and Energy Commission (EC). It has been observed that wind energy

generation are possible in some parts of the country, especially, along the coast, as

an alternate supplement to the hydro-electric power and for off-grid applications.

The monthly average wind speed for the identified potential sites along the coast,

ranges from 4.8 to 5.5 m/s. Across the country, Ghana is observed to have class 3

to class 6 wind resource, that is 6.4 m/s to 8.8 m/s wind speed. (energy

commission website)

37

Fig.2.5: Wind resource in Ghana

38

Table 2.1: Classes of wind resources in Ghana

Research also proves that, given a wind outage of 66 per cent over a whole

stretch of 1000km should guarantee 9000 MW of electrical energy at all times.

However if Ghana should install 9900 wind turbines across the country at the

potential sites we should produce 29,700 MW of energy! This is even far greater

than what Ghana currently receives from Akosombo and Takoradi Power stations

all together. (ghanaweb.com)

39

Table 2.2: Wind resource according to towns

40

This and many available facts and research proves Ghana has enough wind

resources and should therefore take steps in harnessing it to save our current

energy crisis.

41

CHAPTER THREE

DESIGN AND CONSTRUCTION

Overview

This is the chapter that talks about the design, process and methods for the

construction of the project. To make the savonius prototype turbine as potable as

possible while gunning on high efficiency, all the choices, processes and materials

used were taken into strict considerations. All the processes, materials and tools

applied to achieve the optimum design are what this chapter covers.

Items and Materials Needed

The following materials were used in the construction of the prototype

wind turbine;

Connecting hollow metal pipes and joints.

Plywood about 50cmx30cm

2 Plastic small buckets (about 20cm diameter)

Long hollow rod/pipe

19 AWG enamel wire (about 1kg)

1 Big speaker magnet

Carton

Adhesive tape

Glue

42

LED

Flexible wire

Screws, bolts, nuts and washers

Fig.3.1: Materials Needed

Tools Needed

The following tools were also applied in the building of the project;

Measuring tape

Hacksaw blade

Screwdrivers

Ammeter/Voltmeter

Pipes Plywood

Carton

Magnets Screws, bolts & nuts

Enamel wire

43

Fig.3.2: Tools

Construction

The turbine was divided into two components; the frame and rotor blades

and the generator, and the steps that were undertaken in the construction of the

various components follow below.

The Frame & Rotor Blades

The hollow metal pipes were cut with the help of the hacksaw blade to the

required lengths; 35cm (12 pieces) and 60cm (4 pieces). With the help of the

connecting joints the pipes were connected together to form the frame/rack.

44

Fig.3.3: Turbine Frame

The two small buckets were both divided into two equal halves with the

hacksaw blade therefore becoming four equal halves. Two halves were then

screwed to a piece of plywood forming the ‗S‘ shape. This was repeated with the

other two halves on the other side of the plywood but perpendicular to the former.

45

Fig.3.4: The Rotor Assemble

A small hole was made at the center of the plywood with the blades.

The long hollow rod/pipe was then placed through the hole to serve as the axis.

Two bolts were fixed at the two hollow ends so that the bolts heads fixed into the

holes and the screw parts protruding outwards. Two pieces of plywood with small

holes punched at the centers were screwed one to the top and the other to the

bottom of the turbine frame/rack. The rotor assembly were placed in-between the

two plywood such that the bolts enter the holes, thus the rotor suspends between

the frame/rack.

46

Fig.3.5: Frame with rotor blades

The Generator

The Magnetic Component

The big speaker magnet was marked into four segments, and then cut into

four sections by a cutting machine with stone cutter blade on it. A piece of

plywood was cut into circular shape or disc of about 20cm diameter with the

hacksaw. Four sections were marked and cut out on the circular plywood to fit the

sizes of the four magnets respectively. The four magnets were then stacked into

these four holes, so that the magnets protrudes or shows on both sides of the disc.

47

A small hole was then made at the center of the plywood disc so that the hollow

rod of the rotor can be placed through it.

Fig.3.6: Magnetic component of stator

The Coil Component

A sheet of carton was folded into circular form of about 4cm and the

enamel wire was wound around it in a clockwise direction but first some surplus

of about 40cm was left behind and after the fourth coil winding. In all eight coil

windings was done thus two set, each set being four coils and each single coil

being around 120 windings/turns and in the same direction thus clockwise. The

windings was removed carefully and held in place by adhesive tape to prevent

unwinding. Each coil set thus four individual coils were arranged on a piece of

plywood to fit the arrangement of the magnets on the disc and tied to the plywood

with pieces of wires.

48

Fig.3.7: The Coil Component

A 4 cmx4 cm hole was cut out at the middle of one of the coil set so that

the hollow pipe of the rotor blade is passed through it before the disc with the

magnet is fixed onto it and supported with a washer and then placed onto the

second coil set, so that the disc with the magnet is in-between the two coil set, one

up and one below. Hence as the rotor blades rotate the plywood disc with the

magnet also rotates between the two coil set.

Fig.3.8: Generator Component

Coil

Coil

Magnet

49

White sheets were glued to the rotor component and the plywood disc to give it

aesthetic value.

Fig.3.9: Final Prototype Assembly

50

CHAPTER FOUR

RESULTS, ANALYSIS AND DISCUSSION

Overview

Presentation and discussion of the results acquired by different research

processes and methods, is what this chapter is about. The results of the

quantitative and qualitative research conducted are presented and juxtaposed with

the help of tables and graphs of the recorded values.

Result and Analysis

The result and analysis are presented in three parts, that is;

The variation of power with wind speed.

The variation of induced electromotive force, emf with distance from coil

to magnet.

Comparison of power generated with two coil set to one coil set.

The variation of power with wind speed

This measurement was taken to investigate the variation of wind speed to

the induced electromotive force (emf or voltage) and the current hence the power

that can be generated from the turbine since turbine power output, PT = ½ ρAv3

Cp, (v being the speed of wind).

51

The wind speed variation was achieved by using an electric fan (Bruder:

High Velocity fan) with three speed variations; speed 1(low), speed 2(medium)

and speed 3(high). The voltages and currents for these speeds were recorded with

a multimeter with uncertainty of ±0.01 in volts (V) and milliamps (mA)

respectively. The average voltages, V and currents, I for each speed was

computed from the statistical mean. The power, P in milliwatts (mW) was then

calculated thus P=IV. The results of the measurements is shown in table 4.1 and

the plotted result in figure 4.1

Table 4.1: Variation of Power (P/mW) with wind speed

Speed

Voltage V Mean

Voltage

V/V

Current I Mean

Current

I/mA

Power

P/mW V1/V V2/V V3/V I1/mA I2/mA I3/mA

1 0.036 0.028 0.032 0.032 0.812 0.778 0.791 0.794 0.025

2 0.060 0.073 0.069 0.067 0.869 1.037 0.985 0.964 0.065

3 0.111 0.124 0.126 0.120 1.195 1.314 1.289 1.266 0.152

52

Fig.4.1: The variation of power with wind speed

The variation of induced electromotive force, emf with distance from coil to

magnet

The readings here was taken to find the relation the induced electromotive

force, emf has with the distance from the wire loop to the magnet in order to

determine the best spacing distance that will yield an optimum emf. Since the emf

is a function of the magnetic field which varies with the separation distance,

d/mm. The induced emf was measured in volts scale (V) with a voltmeter with

uncertainty of ±0.01 and the separation distance with a millimetre (mm) scale

ruler. The average voltage, V for each distance measured was computed from the

0

0.2

0.4

0.6

0.8

1

1.2

1.4

0 1 2 3 4

Po

we

r/m

W

Speed

Voltage V/V

Current I/mA

Power P/mW

53

statistical mean. The result of the measurements is shown in table 4.2, and the

plotted result is shown in Figure 4.2

Table 4.2: Variation of voltages (V/V) with distance (d/mm) from coil to

magnet

Distance

d/mm

Voltage V Mean Voltage

V/V V1/V V2/V V3/V

10 0.093 0.103 0.089 0.095

20 0.057 0.062 0.053 0.057

30 0.021 0.027 0.025 0.024

40 0.010 0.015 0.009 0.011

54

Fig.4.2: The variation of induce electromotive force, emf with distance from coil

to magnet

Comparison of power generated with two-coil set to one-coil set

The measurement was taken to compare the efficiency of two-coil set to

one-coil set. A coil set for this project contains four wire loops/coils each of about

120 turns and a diameter of about 5cm. For the first case only a coil set was

placed below for the magnetic component to rotate over it while in the second

case, one-coil set was placed below and another above the magnetic component,

such that the magnet rotate in-between the two separate coil sets.

The voltages and currents for each speed were recorded for each case with

a multimeter with uncertainty of ±0.01 in volts (V) and milliamps (mA)

respectively. Hence the power, P in milliwatts (mW) for each case was also then

y = 3.7708x-1.515 R² = 0.916

0

0.02

0.04

0.06

0.08

0.1

0.12

0.14

0 10 20 30 40 50

Vo

ltag

es

V/V

Distance of separation, d/mm

Mean Voltage V/V

Power (Mean Voltage V/V)

55

calculated. The recorded values are shown in table 4.3 and the plotted values in

figure 4.3.

Table 4.3: The power generated with two-coil set and one-coil set

Speed

1 Coil set 2 Coil set

I/mA V/V P1/mW I/mA V/V

P2/mW

1 0.490 0.020 0.010 0.665 0.022 0.015

2 0.857 0.073 0.063 0.936 0.076 0.071

3 1.038 0.087 0.090 1.062 0.090 0.096

A coil set contains four individual wire loops/coils of about 120 turns each.

56

Fig.4.3: Comparison of power generated by one-coil set to two-coil set

Discussion

From the results collated and analyzed it can be observed that;

In the first part, wind speed plays a very vital role in the generation of

electricity using the wind turbine, since the energy source of which we are

converting to electricity is the wind. It was observed from the table 4.0 and the

graph, fig. 4.0 that both the voltage and current increased as the wind speed also

increased affirming the fact that voltage V is directly proportional to current I,

VαI

V=IR, where constant of proportionality R, is resistance.

Also from Power P=IV the power generated was calculated, and also

found to be increasing as wind speed increased as shown in the table 4.1 and the

0

0.02

0.04

0.06

0.08

0.1

0.12

1 2 3

Po

we

r/m

W

Speeds

P1/mW

P2/mW

57

graph Figure 4.1. This ascertains the fact that the power that can be harnessed by

a turbine PT is a function of the wind speed that is PT = ½ * ρ * A * v3 * Cp,

which was derived earlier in chapter two. It also confirms that power is directly

proportional to velocity from;

Power P=Fv where F is Force

v is Velocity

derived from P=

where W is work

t is time

But W=Fd

therefore P=F

but d/t=v

hence P=Fv where d is distance

so at a constant force, as velocity increases power also increases.

The results also agree with Faradays law, which states that the induced

electromotive force across a conductor is equal to the rate at which the magnetic

flux is cut by the conductor. In other words the frequency at which the conductor

makes with the magnet is equal to the induced electromotive force that will be

produced across the conductor.

E=

⁄

58

The bicycle dynamo effect is also supported here since the faster the

bicycle moves or travels the brighter the bulb/lamp shines which is similar to the

above case.

For the second part, it can be seen that from the table 4.2 and figure 4.2

thus the graph, the more close the magnet to the coil, (in other words the smaller

the distance) the higher the voltage thus the induced emf increases inversely as

the distance of separation between the magnet and the loop decreases;

Vα

so the smaller the distance of separation of the coil and the magnet, the

higher the voltage. The graph depicts an inverse graph with an R2 value of 0.916

which is good since it is around 1.0. This agrees with Ampere‘s rule for the

magnetic field, B at a point from a source field.

In the third part comparison was made between the power generated using

two coil set and one coil set. A coil set for this project contains four wire

loops/coils each of about 120 turns and a diameter of about 5cm. The comparison

showed that the two coil set produced greater power than the one coil set which

confirms to Lenz law which can be explained as the number of coil turns being

directly proportional to the induced electromotive force. However the difference

between the two individual power generated was not big enough this shows that

the two coil set is not so efficient. This agrees with the fact that for higher emf

there must be a greater magnetic field strength/magnetic flux density. Thus in

59

order to generate double or higher electromotive force hence greater power, the

concentration must be on providing more or stronger magnetic field/flux on the

conductor and not more conductor on a lesser magnetic flux. In order to generate

higher emf hence greater power, two magnetic sets one below, one on top with the

conductor with higher number of turns in-between the two magnet sets should

rather be used instead of two coil set to one magnetic set.

Finally, the lower readings recorded for the prototype wind turbine may be

due to low efficient construction and design. Another factor may come from the

irregular alignment of the magnets as a result of irregularities and unstable nature

of the wooden disc into which the magnets were stacked into thereby creating

longer and shorter coil and magnet spacing irregularly as it rotates. The less wire

turns/windings and lesser magnets used was also a key factor. The higher gauge

wire used was also noted as another agent. Also the fan was not able to blow a

much higher wind speed to create higher readings that will lead to greater power

generation. Lastly the long cord lengths used for the recording of values may also

be a factor.

60

CHAPTER FIVE

SUMMARY, CONCLUSIONS AND RECOMMENDATIONS

Overview

This chapter deals with the summary of the work and a general conclusion

based on the results gathered. There is also recommendation for further studies on

this project.

Summary

Generating electricity from sustainable energy resource using a

prototype wind turbine was studied. In this study, a pico-wind turbine was

designed and constructed to generate electricity from the wind energy. The

framework behind the generation of electricity was based mainly on the power in

the wind and how to harness it to electrical energy, the concept of Faraday‘s law

of electromagnetic induction and the principle in the design of Savonius VAWT.

Studies such as variation of power with wind speed, variation of induced

electromotive force, emf with distance from coil to magnet and Comparison of

power generated with two coil set to one coil set were done to determine the

parameters of Faradays law which can affect the magnitude of the power

generated.

61

Conclusion

A prototype wind turbine was designed and constructed at the end

of the project with simple, common and cheap materials around and it was able to

record higher values of about 200 mA and 0.20 V thus 0.04 W of power on a

normal afternoon at the third floor of the science building.

It was also realized at the end that wind speed greatly affects the voltages

and hence the power the turbine generates. So in order to produce greater power

output the turbine must be situated at high wind speed areas, which satisfies

Faradays law.

Observation was also made that the smaller the distance of

separation between the magnets and the coils, the better the induction hence

higher voltage and power which agrees with Ampere‘s rule for the magnetic field,

B at a point from a source field. Therefore to obtain optimum power output the

spacing between the magnet and the coil should be kept as small as possible.

The two coil set was found to be more efficient than the one coil set which

verifies the Lenz law. However to create more efficiency more magnets thus more

magnetic flux/field (two magnets set) must be incorporated to a coil set with more

turns/windings.

62

Recommendation

The following recommendations are offered for future work on the study:

1. Further study should be conducted on the prototype to improve the

efficiency of the turbine. Such as wider blades, lesser blades and less

friction.

2. A ferromagnetic material of very high relative permeability design with

little eddy current/effect should be used as the laminations/core material

for the wire loop instead of the air gap and also the space between the

magnet and wire loop should be reduced to increase the power output of

the turbine.

3. The gauge number of the winding wire used for the coil/loop should be

smaller than the 19 AWG used in this work in order to enhance the power

generated. Also more wire windings and magnets should be considered for

optimum power generation.

4. The use of gears or gear box should be incorporated into the design to

enhance its productivity.

5. The following circuit systems, such as a rectifying diode, rechargeable

battery and other available ones should be added to the design for the

storage and effective use of the energy generated.

63

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