PV Tracking System - South Valley University Tracking System.pdf · PV Tracking System I Essam Ahmed Refaat Abdellah Sherkawy Basma Ahmed Aia Khalil Mustafa Mahmoud Mohammed Marwa

PV Tracking System Dual-Axis

B.SC Graduation Project 2014

PV Tracking System I

Essam

Refaat

Abdellah

Sherkawy

Basma

Ahmed

Aia

Khalil

Mustafa

Mahmoud

Ahmed

Mohammed

Marwa

Abd-ElHay

Omar

Mohammed

Amr

Ali

Mohammed

Abd-ElRady

Team Work

II

Acknowledgment

We would like to express our deepest appreciation

and gratitude to all those who provided us the

possibility to complete this project. A special

gratitude we give to our final year project managers,

Dr. Abd Elmo’men Mohamed

Dr. Shazly Abdu

whose contribution in stimulating suggestions and

encouragement helped us to coordinate our project

at this nice shape.

Furthermore we would also like to acknowledge with

much appreciation the crucial role of all the staff of

our college, qena Faculty of Engineering, who gave

the permission to use all required equipment and the

necessary materials to complete our project

Subscripted by Project Team Work

PV Tracking System III

to our DEAR

homeLAND EGYPT, our

dear parents,

specially our

precious mothers

and our families.

IV

Abstract

Chapter 1 The original idea for writing this project came after a number

of review papers were published in conference and the journals. The

purpose of this project is to give explanations the photovoltaic tracking

system mechanism and application of solar system processes.

This project can be used to design PV tracking system and inverter to

operate alone with battery banks in order to supply ac load in remote

area which the utility grid cannot reach for this load.The material

presented in this project covers a large variety of technologies for

conversion of solar energy to provide electricity.

In the introductory chapter, the project provides a review of energy-

related environmental problems and the state of climate. It also gives a

short historical introduction to solar energy, giving some details of the

early applications.

Chapter 2 gives overview of solar energy and photovoltaics.The

photovoltaic effect refers to photons of light exciting electrons in to a

higher state of energy. Allowing them to acts as charge carriers for an

electric current. Solar cells produce direct current electricity from

sunlight which can be used to power equipment or to recharge a battery

Chapter 3 present development of an automatic solar tracking system

whereby the system will caused solar panels will keep aligned with the

sunlight it order to maximize in harvesting solar power. The system

focuses on the controller design whereby it will caused the system is able

to tracks the maximum intensity of sunlight is hit.

Chapter 4 gives general review to the inverter and its types, how the

inverter works, the components of the inverter circuit, practical power

and control circuit for inverter, and how can we use for our project (PV

tracking system and inverter).

Chapter 5 gives the fundamental of batteries technology and charger

control strategies commonly used in stand-alone photovoltaic (PV)

system. Details are provided about the common types of flooded lead

acid, valve regulated lead acid (VRLA), including their design and

constructions. Daily operational profiles are presented for different

types of battery charger controllers, providing an in-depth look at how

these controllers regulate and limit battery overcharging in PV system.

Chapter 6 the results of our project

PV Tracking System V

TABLE OF CONTENTS

CHAPTER 1

INTRODUCTION

1.1 General introduction to nonrenewable & renewable energy technologies ............ 2

1.1.1 A non-renewable resource ....................................................................................... 2

1.1.2 Renewable energy .................................................................................................... 2

1.2 Power generation. ............................................................................................................ 3

1.3 Types of renewable energy ............................................................................................. 3

1.3.1 Solar photovoltaic cells (PV) ..................................................................................... 5

1.3.2 Thermal or solar renewable energy ......................................................................... 7

1.3.3 Hydropower ................................................................................................................ 8

1.3.4 Wind power ............................................................................................................... 10

1.3.5 Biomass ...................................................................................................................... 12

1.3.6 Geothermal energy ................................................................................................. 14

1.3.7 Ocean energy .......................................................................................................... 17

1.2 The Advantages and Disadvantages of Renewable Energy .................................... 19

CHAPTER 2

SOLAR ENERGY 2.1 Introduction ...................................................................................................................... 22

2.2 Solar Photovoltaic ........................................................................................................... 25

2.3 Photovoltaic Modeling ................................................................................................... 26

2.3.1 Series Resistance ................................................................................................... 27

2.3.2 Shunt Resistance ........................................................................................................ 27

2.3.3 Ideality Factor ............................................................................................................ 28

2.3.4 Characteristic equation ................................................................................................. 28

2.3.5 What is Maximum Power Point Tracking? ..................................................................... 29

2.3.6 Efficiency...................................................................................................................... 30

2.4 Effect of Solar Irradiance, Temperature on PV: ........................................................... 31

2.4.1 Effect of Solar Irradiance on PV .................................................................................... 31

VI

2.4.2 Effect of Temperature on PV ....................................................................................... 31

2.5 Components of PV system ............................................................................................. 32

2.6 Photovoltaic system types.............................................................................................. 35

2.6.1 Stand-alone systems ..................................................................................................... 35

2.6.2 Grid-connected systems ............................................................................................... 36

2.6.3 Hybrid systems ............................................................................................................ 36

2.7 Advantages and Disadvantages of Solar Energy ....................................................... 38

2.7.1Advantages of Solar Energy:- ......................................................................................... 38

2.7.2 Disadvantages of Solar Energy:- .................................................................................... 39

2.8 Applications of solar Energy .......................................................................................... 40

CHAPTER 3

TRACKING SYSTEM

3.1 Introduction ........................................................................................................................ 48

3.2 Basic Concept ................................................................................................................. 49

3.3 Tracking system and PV panel efficiency .................................................................... 51

3.4 Types of trackers .............................................................................................................. 52

3.4.1 Single axis trackers ................................................................................................... 52

3.4.1.1Horizontal single axis tracker (HSAT) ................................................................. 52

3.4.1.2 Vertical single axis tracker (VSAT) .................................................................... 54

3.4.1.3 Tilted single axis tracker (TSAT) ......................................................................... 54

3.4.1.4 Polar aligned single axis trackers (PASAT) ...................................................... 55

3.4.2 Dual axis trackers ...................................................................................................... 55

3.4.2.1 Tip–tilt dual axis tracker (TTDAT) ........................................................................... 55

3.4.2.2 Azimuth-altitude dual axis tracker (AADAT) ................................................... 57

3.5 Tracker type selection .................................................................................................... 57

3.6 Solar Tracking ................................................................................................................... 58

3.6.1 Tracking Mechanical System .................................................................................. 59

3.6.2 Tracking Control System .......................................................................................... 60

3.6.3 Controller ................................................................................................................... 62

3.6.4 Linear Actuator ......................................................................................................... 62

3.6.5 Methodology ............................................................................................................ 63

3.6.6 Arduino programe ................................................................................................... 65

3.7 Disadvantages................................................................................................................. 66

PV Tracking System VII

CHAPTER 4

SINGLE PHASE PULSE WIDTH

MODULATED INVERTERS

4.1 Introduction ...................................................................................................................... 68

4.2 Types of inverters ............................................................................................................. 69

4.2.1 Types of inverters according to input: ................................................................... 69

4.2.2 Types of inverter according to wave shape of ac output: ................................. 71

4.3 Principle of operation of single-phase inverter (VSI): .................................................. 73

4.4 Overview of Power Semiconductor switches used: .................................................... 75

4.5 Control strategy ............................................................................................................... 79

4.5.1 Analog Method: ....................................................................................................... 79

4.5.2 Digital Methods ........................................................................................................ 81

4.6 Simulation results of Digital Methods ............................................................................. 84

4.7 Inverter using lm555: ........................................................................................................ 86

4.8 Applications ..................................................................................................................... 86

CHAPTER 5

BATTERY AND CHARGER

CONTROLLER

5.1 Introduction ...................................................................................................................... 90

5.2 Storage in PV Systems ..................................................................................................... 90

5.3 Battery Design and Construction: ................................................................................. 91

5.4 Battery Types and Classifications .................................................................................. 93

5.4.1 Primary Batteries ....................................................................................................... 94

5.4.2 Secondary Batteries ................................................................................................. 94

5.5 Battery Charger ............................................................................................................... 97

5.5.1 Overcharge Protection ........................................................................................... 98

5.5.2 Over discharge Protection ...................................................................................... 99

5.6 Charge Controller Terminology and Definitions ........................................................ 100

5.7 Buck converter .............................................................................................................. 103

VIII

5.8 Boost Converter ............................................................................................................. 104

5.9 Buck-Boost converter .................................................................................................... 106

5.11 System Design .............................................................................................................. 107

CHAPTER 6

SIMULATION AND PRACTICAL

RESULTS

6.1 control circuit for tracking system ............................................................................... 110

6.1.1 Simulation ................................................................................................................ 110

6.1.2 Practical circuit (control circuit using DC drive L298) ........................................ 110

6.1.3 Control circuit using transistor and relays ............................................................ 111

Comment ............................................................................................................................. 111

6.1.4 PCB circuit ................................................................................................................... 111

6.2 Tracking system (practical) .......................................................................................... 112

6.2.1 Single axis PV TRACKING ....................................................................................... 112

6.2.2 Dual axis PV tracking ............................................................................................. 112

6.3 comparison between fixed and tracking solar panel .............................................. 113

6.3.1 Fixed solar panel..................................................................................................... 113

6.3.2 Single axis tracking solar panel ............................................................................. 116

6.3.3 Dual axis tracking solar panel ............................................................................... 119

6.3.4 Dual axis with cooling system ............................................................................... 122

6.4 power VS time for fixed and tracking system ............................................................ 125

Comments ........................................................................................................................ 126

6.5 inverter using LM555 .................................................................................................. 126

6.5.1 Simulation result ...................................................................................................... 126

6.5.2 PCB circuit ................................................................................................................... 127

6.5.3 Practical circuit and result ........................................................................................ 127

Conclusion………...………………………………………………………………………………..130

Appendix………...………………………………………………………………………………….132

References…..……………………………………………………………………………………...136

PV Tracking System IX

List of figures

Chapter 1

Fig (1.1) Total world energy consumption by source…………………………..……..…4

Fig (1.2) Photovoltaic sunshade 'SUDI' is an autonomous and mobile station that

replenishes energy for electric vehicles using solar energy………………….……...…7

Fig (1.3) the solar energy……………………...…………………………………….…….8

Fig (1.4) wind energy………………………………………………………………………12

Fig(1.5) Cogeneration station in Metz (France), using waste wood biomass from the

surrounding forests as renewable energy source………………………………….…...14

Fig (1.6) the Nesjavellir Geothermal Power Plan……………………………………….15

Fig.1.7Worldwide production of geothermal electricity…………………………………16

Fig (1.8) wave energy…………………………………………………………………...…18

Fig (1.9) Tidal energy…………………………………………………..……….………….18

Fig (1.10) ocean thermal energy……………………………………………………….…19

Chapter 2

Fig (2.1) nuclear fusion in sun……………………………………….……………………22

Fig (2.2) solar energy of the sun…………………………………….……………………23

Fig (2.3) Irradiated daily energy values over a 12 month period.……………………..24

Fig (2.4) Egypt has excellent Solar Resources…………………………………………25

Fig (2.5) Photovoltaic cell operation………………….................................................26

Fig (2.6) solar cell representation……………………….……………..…………………27

Fig. (2.7) the max power point tracking………………………………………….……….30

Fig (2.8a-2.8b) effect radiation of solar…………………………………………………..32

Fig (2.9a) effect of temperature on current & voltage of PV…………………………...32

X

Fig (2.9b) effect of temperature on power &voltage of PV…………………................33

Fig(2.10)Photovoltaic cells, modules, panels and arrays………………………………34

Fig (2.11) Components of PV system……………………………………………………35

Fig (2.12) Schematic representation of (a) a simple DC PV system to power a water

pump with no energy storage, (b) a complex PV system including batteries, power

conditioners, and both DC and AC

loads…………………………………………………………….…………………………..36

Fig (2.13) A grid-connected PV system…………………….…………………..……….37

Fig (2.14) a hybrid system. …………………………………………………………..…..37

Fig(2.15) PV Solar Cell………………………………………………………………..…..40

Fig(2.16) Solar Thermal………………………………………………………………...…41

Fig (2.17) Black metal absorber plate……………….……………………………..…….42

Fig (2.18) Solar …………………………………………………………….……..………..43

Fig (2.19) Solar Crop Dryers Stills……………….……………………………..………...44

Fig (2.20) Electrical generation………….………………………………….…………….45

Chapter 3

Fig (3.1) the effective collection area of a flat-panel solar collector varies with the

cosine of the misalignment of the panel with the Sun.………………………………...50

Fig (3.2) power vs Day Time curve …………………..………………………………….51

Fig (3.3) Horizontal single axis tracker in California …………………………………...53

Fig (3.4) linear horizontal axis tracker in South Korea …………………………………53

Fig (3.5) single axis trackers with roughly 20 degree tilted ……………………………54

Fig (3.6) Azimuth-altitude dual axis tracker – 2 axis solar tracker, Toledo, Spain ….56

Fig (3.7) Tracking system …………………………………………………………………58

Fig (3.8) Tracker …………………………………………………………………………...59

Fig (3.9) Tracking Control System………………………………………………………..60

Fig (3.10) LDR sensor …………………………………………………………………….61

Fig (3.11) Arduino unit …………………………………………………………………….62

Fig (3.12) DC geared motor……………………………………………………………….63

Fig (3.13) two light sensor are separated by divider……………………………………64

PV Tracking System XI

Fig (3.14) controlling circuit…………………………………………………...…………..64

Chapter 4

Fig (4.1) dc-ac converter ….………………………………………………………………68

Fig (4.2) sin and modified sin waves…………………………………………………….70

Fig (4.3) square wave of single-phase inverter…………………………………………72

Fig (4.4) single phase half bridge inverter……………………………………………....72

Fig (4.5) Output voltage of half wave bridge inverter…………………………………..73

Fig (4.6) single-phase full bridge inverter………………………………………………..74

Fig (4.7) thyristor and its VI characteristic……………………………………………….76

Fig (4.8) the characteristic and symbol of transistor……………….…………………...77

Fig (4.9) mosfet symbol……………………………………………………………………77

Fig (4.10) IGBT symbol…………………………………………………………………….78

Fig (4.11) Sine-Triangle Comparison…………………………………………………….80

Fig (4.12) Switching Pulses after comparison…………………………………………..81

Fig (4.13) multi-vibrator IC…………………………………………………………………82

Fig (4.14) LM555 IC………………………………………………………………………..83

Fig (4.15) states of multi-vibrator…………………………………………………………83

Fig (4.16) multi-vibrator simulation……………………………………………………….84

Fig (4.17) multi-vibrator simulation output………………………………….……………84

Fig (4.18) timer circuit……………………………………………………………….……..85

Fig (4.19) output of timer…………………………………………………………………..85

Chapter 5

Fig (5.1) battery design and construction………………………………………………..93

Fig (5.2) buck converter………………………………………………………………….103

Fig (5.3) Modes of operation of buck converter………………………………............104

Fig (5.4) Boost converter…………………………………………………………………105

Fig (5.5) modes of operation of boost converter………………………………...........105

Fig (5.6) Buck-Boost converter………………………………………………………….106

XII

Fig (5.7) Modes of operation of buck-boost converter………………………………..107

Fig (5.8) charge controller design……………………………………………………….108

Chapter 6

Fig (6.1) control circuit for tracking system…………………………………………….110

Fig (6.2) practical circuit (control circuit using DC drive L298) …………………..….110

Fig (6.3) control circuit using transistors and relays ……………………..…………...111

Fig (6.4) pcpcircuit ………………………………………………………………….……111

Fig (6.5) single axis pv tracking …………………………………………………………112

Fig. (6.6) Dual axis pvtracking ……………………………………………...................112

Fixed solar panel

Fig (6.7a) V-I curve at 11 am ……………………………………………………………113

Fig (6.7.b) V-P curve at 11 am………………………………………………….............113

Fig (6.8.a) V-I curve at 12 pm …………………………………...................................114

Fig (6.8.b) V-P curve at 12 pm ………………………………………………………….114

Fig (6.9.a) V-I curve at 1 pm ……………………………………………………………114

Fig (6.9.b) V-P curve at 1 pm …………………………………………………………...114

Fig (6.10.a) V-I curve at 2 pm………………………………………………..……….…115

Fig (6.10.b) V-P curve at 2 pm…………………………………...……………….……..115

Fig (6.11.a) V-I curve at 3 pm …………………………………………………………..115

Fig (6.11.b) V-P curve at 3 pm………………………………………………….……….115

Fig (6.12) T-P curve ……………………………………………….……………………..116

Single axis tracking solar panel

Fig (6.13.a) V-I curve at 11 am ………………………………………………………...116

Fig (6.13.b) V-P curve at 11 am…………………………………………………….…...116

PV Tracking System XIII

Fig (6.14.a) V-I curve at 12 pm …………………………………………………………117

Fig (6.14.b) V-P curve at 12 pm ………………………………………………………...117


Fig (6.15.b) V-P curve at 1 pm ………………………………………………………....117

Fig (6.16.a) V-I curve at 2 pm……………………………………………….………..…118

Fig (6.16.b) V-P curve at 2 pm………………………………..……………..…………..118

Fig (6.17.a) V-I curve at 3 pm ………………………………………………….……….118

Fig (6.17.b) V-P curve at 3 pm………………………………………….……………….118

Fig (6.18) T-P curve …………………………………………….………………………..119

Dual axis tracking solar panel

Fig (6.19.a) V-I curve at 11 am …………………………………………………………119

Fig (6.19.b) V-P curve at 11 am…………………………………………………………119


Fig (6.20.b) V-P curve at 12 pm ………………………………………………………...120



Fig (6.22.a) V-I curve at 2 pm……………………………………………………………121

Fig (6.22.b) V-P curve at 2 pm………………………………………………........…….121


Fig (6.23.b) V-P curve at 3 pm…………………………………………………………..121

Fig (6.24) T-P curve ……………………………………………………………………...122

Dual axis with cooling system

Fig (6.25.a) V-I curve at 11 am …………………..……………………………………..122

Fig (6.25.b) V-P curve at 11 am…………………………………………………………122

XIV


Fig (6.26.b) V-P curve at 12 pm ………………………………………………………..123



Fig (6.28.a) V-I curve at 2 pm…………………………………….…………………......124




Fig (6.30) T-P curve ……………………………………………………………………...125

Fig (6.31) T-P curve for fixed and tracking……………………………………………..126

Fig (6.32) simulation result for lm555 …………………………………………………..126

Fig (6.33) output of lm555 timer ………………………………………………………...127

Fig (6.34) pcb for inverter………………………………………………………………...127

Fig (6.35a-35b) practical circuit and result ……………………………………….……128

PV Tracking System XV

Chapter 1

Introduction

2

CHAPTER 1

INTRODUCTION 1.1 GENERAL INTRODUCTION TO NONRENEWABLE & RENEWABLE

ENERGY TECHNOLOGIES

1.1.1 A NON-RENEWABLE RESOURCE

A non – renewable resource (also known as a finite resource) is a resource that does not

renew itself at a sufficient rate for sustainable economic extraction in meaningful human time-

frames. An example is carbon-based, organically-derived fuel. The original organic material,

with the aid of heat and pressure, becomes a fuel such as oil or gas. Fossil fuels (such

as coal, petroleum, and natural gas), and certain aquifers are all non-renewable resources.

Metal ores are other examples of non-renewable resources. The metals themselves are

present in vast amounts in the earth's crust, and are continually concentrated and replenished

over millions of years. However their extraction by humans only occurs where they are

concentrated by natural processes (such as heat, pressure, organic activity, weathering and

other processes) enough to become economically viable to extract. These processes

generally take from tens of thousands to millions of years. As such, localized deposits of

metal ores near the surface which can be extracted economically by humans are non-

renewable in human timeframes, but on a world scale, metal ores as a whole are

inexhaustible, because the amount vastly exceeds human demand, on all timeframes.

Though they are technically non-renewable, just like with rocks and sand, humans could

never deplete the world's supply. In this respect, metal ores are considered vastly greater in

supply to fossil fuels because metal ores are formed by crustal scale processes which make

up a much larger portion of the earth's near-surface environment than those that form fossil

fuels, which are limited to areas where carbon-based life forms flourish, die, and are quickly

buried. These fossil fuel-forming environments occurred extensively in the Carboniferous

Period.

1.1.2 RENEWABLE ENERGY

Renewable energy is generally defined as energy that comes from resources which are

naturally replenished on a human timescale such

as sunlight, wind, rain, tides, waves and geothermal heat. Renewable energy replaces

conventional fuels in four distinct areas: electricity generation, hot water/space heating, motor

fuels, and rural (off-grid) energy services.

PV Tracking System 3

About 16% of global final energy consumption presently comes from renewable resources,

with 10% of all energy from traditional biomass, mainly used for heating, and 3.4%

from hydroelectricity. New renewables (small hydro, modern biomass, wind, solar,

geothermal, and biofuels) account for another 3% and are growing rapidly. At the national

level, at least 30 nations around the world already have renewable energy contributing more

than 20% of energy supply. National renewable energy markets are projected to continue to

grow strongly in the coming decade and beyond. Wind power, for example, is growing at the

rate of 30% annually, with a worldwide installed capacity of 282,482 megawatts (MW) at the

end of 2012.

Renewable energy resources exist over wide geographical areas, in contrast to other energy

sources, which are concentrated in a limited number of countries. Rapid deployment of

renewable energy and energy efficiency is resulting in significant energy security, climate

change mitigation, and economic benefits. In international public opinion surveys there is

strong support for promoting renewable sources such as solar power and wind power.

While many renewable energy projects are large-scale, renewable technologies are also

suited to rural and remote areas and developing countries, where energy is often crucial

in human development. United Nations' Secretary-General Ban Ki-moon has said that

renewable energy has the ability to lift the poorest nations to new levels of prosperity.

1.2 POWER GENERATION .

Renewable energy provides 19% of electricity generation worldwide. As electricity demands

are increasing day by day causing unbalance in the present grid system which results in

various causes like load shedding, unbalance voltage and power quality etc. which ultimately

affects the consumers. Now to avoid all such situations the only option is to meet the demand

by increasing generation but, we are also lagging with the conventional sources so generating

more power is also not convenient by conventional ways. Therefore, recent researches are

interested in renewable energy system integrated with smart grid through advanced power

electronic converters.

Smart gird with renewable energy sources have been regarded as the most promising means

to solve the power quality, energy and environmental issues we face nowadays.

1.3 TYPES OF RENEWABLE ENERGY

Renewable energy is energy which comes from natural resources such as sunlight, wind,

rain, tides, and geothermal heat, which are renewable naturally replenished.

Chapter 1

Introduction

4

In 2008, about 19% of global final energy consumption came from renewable, with 13%

coming from traditional biomass, which is mainly used for heating, and 3.2% from

hydroelectricity. New renewable (small hydro, modern biomass, wind, solar, geothermal, and

bio-fuels) accounted for another 2.7% and are growing very rapidly. Wind power is growing at

the rate of 30% annually, with a worldwide installed capacity of 158 GW in 2009, and is widely

used in Europe, Asia, and United States. At the end of 2009, cumulative global photovoltaic

(PV) installations surpassed 21 GW and PV power stations are popular in Germany and

Spain.

Solar thermal power stations operate in the USA and Spain, and the largest of these is the

354 MW SEGS power plant in the Mojave Desert. The world's largest geothermal power

installation is The Geysers in California, with a rated capacity of 750 MW. Brazil has one of

the largest renewable energy programs in the world, involving production of ethanol fuel from

sugar cane, and ethanol now provides 18% of the country's automotive fuel. Ethanol fuel is

also widely available in the USA. While many renewable energy projects are large-scale,

renewable technologies are also suited to rural and remote areas, where energy is often

crucial in human development. Globally, an estimated 3 million households get power from

small solar PV systems. Micro-hydro systems configured into village-scale or county-scale

mini-grids serve many areas. More than 30 million rural households get lighting and cooking

from biogas made in household-scale digesters. Biomass cook stoves are used by 160 million

households.

Figure 1

Total world energy consumption by source


Renewable energy can be classified into

. Photovoltaic

.Thermal energy

.Hydro power generation energy

.Wind energy

.Biomass

.Geothermal energy

.Ocean and wave energy

1.3.1 SOLAR PHOTOVOLTAIC CELLS (PV)

convert sunlight into electricity and photovoltaic production has been increasing by an

average of more than 20% each year since 2002, making it a fast-growing energy

technology. While wind is often cited as the fastest growing energy source, photovoltaic since

2007 has been increasing at twice the rate of wind — an average of 63.6%/year, due to the

reduction in cost. At the end of 2011 the photovoltaic (PV) capacity world-wide was 67.4 GW,

a 69.8% annual increase.

Many solar photovoltaic power stations have been built, mainly in Europe. As of May 2012,

the largest photovoltaic (PV) power plants in the world are the Agua Caliente Solar

Project (USA, 247 MW), Charanka Solar Park (India, 214 MW), Golmud Solar Park (China,

200 MW), Perovo Solar Park (Ukraine, 100 MW), Sarnia Photovoltaic Power Plant (Canada,

97 MW), Brandenburg-Briest Solarpark (Germany, 91 MW), Solar park Finow

Tower (Germany, 84.7 MW), Montalto di Castro Photovoltaic Power Station (Italy, 84.2 MW),

and the Eggebek Solar Park (Germany, 83.6 MW).

There are also many large plants under construction. The Desert Sunlight Solar Farm is a 550

MW solar power plant under construction in Riverside County, California, that will use thin-film

solar photovoltaic modules made by First Solar. The Topaz Solar Farm is a 550 MW

photovoltaic power plant, being built in San Luis Obispo County, California. The Blythe Solar

Power Project is a 500 MW photovoltaic station under construction in Riverside County,

California. The California Valley Solar Ranch (CVSR) is a 250 MW solar photovoltaic power

plant, which is being built by Sun Power in the Carrizo Plain, northeast of California

Valley. The 230 MW Antelope Valley Solar Ranch is a First Solar photovoltaic project which is

under construction in the Antelope Valley area of the Western Mojave Desert, and due to be

completed in 2013.

Chapter 1

Introduction

6

Many of these plants are integrated with agriculture and some use tracking systems that

follow the sun's daily path across the sky to generate more electricity than fixed-mounted

systems. There are no fuel costs or emissions during operation of the power stations.

However, when it comes to renewable energy systems and PV, it is not just large systems

that matter. Building-integrated photovoltaic or "onsite" PV systems use existing land and

structures and generate power close to where it is consumed.

Benefits of a PV system to the householder

1- Solar PV systems generate electricity once the system has been purchased electricity is

generated from a free resource (the sun).

2- PV electricity is generated without emitting greenhouse gases.

3- PV panels or modules are silent, without any moving parts.

4- PV modules are generally unobtrusively mounted on an existing roof.

5- PV modules can be integrated into the building in the form of windows, walls, roof tiles or

pergolas.

6- PV electricity can supplement or provide all your electrical consumption.

7- PV electricity can be fed into the grid.

The drawbacks of photovoltaic systems

As a developing technology, PV systems have high initial costs and consequently their

economic value is evaluated over many years. Due to the diffuse nature of sunlight and the

current sunlight to electrical energy conversion efficiencies of photovoltaic devices, surface

area requirements for PV array installations are on the order of 8 to12 m2 per kilowatt of

installed peak DC-rated PV array capacity.


Fig.1.2 Photovoltaic sunshade 'SUDI' is an autonomous and mobile station that replenishes

energy for electric vehicles using solar energy.

1.3.2 THERMAL OR SOLAR RENEWABLE ENERGY

Concentrated solar power systems use mirrors or lenses to concentrate a large area of

sunlight, or solar thermal energy, onto a small area. Electrical power is produced when the

concentrated light is converted to heat which drives a heat engine (usually a steam turbine)

connected to an electrical power generator.

The collectors concentrate the sunlight, collect it as heat energy and store it. Then, the heat

energy is used generate steam that runs heat engines to produce electricity, which is

transferred to the grid. Heat engines have been around since antiquity; but, were only made

into useful devices during the industrial revolution. They continue to be developed today and

are very mature technologies.

In 2011 Egypt operates Korimate plant with capacity 140 MW.

Chapter 1

Introduction

8

Fig. 1.3 the solar energy

Table 1.1 Compare between the PV and thermal energy technologies

1.3.3 HYDROPOWER

Energy in water can be harnessed and used. Since water is about 800 times denser than air,

even a slow flowing stream of water, or moderate sea swell, can yield considerable amounts

of energy. There are many forms of water energy:

Hydroelectric energy is a term usually reserved for large-scale hydroelectric dams. The

largest of which is the Three Gorges Dam in China and a smaller example is the

Akosombo Dam in Ghana.

Micro hydro systems are hydroelectric power installations that typically produce up to

100 kW of power. They are often used in water rich areas as a remote-area power supply

(RAPS).

Run-of-the-river hydroelectricity systems derive kinetic energy from rivers and oceans

without the creation of a large reservoir.

Hydropower is produced in 150 countries, with the Asia-Pacific region generating 32 percent

of global hydropower in 2010. China is the largest hydroelectricity producer, with 721

terawatt-hours of production in 2010, representing around 17 percent of domestic electricity

use. There are now three hydroelectricity plants larger than 10 GW: the Three Gorges Dam in

China, Itapúa Dam across the Brazil/Paraguay border, and Guri Dam in Venezuela.


The basic principle of hydropower is that if water can be piped from a certain level to lower

level, then the resulting water pressure can be used to do work. If the water pressure is

allowed to move a mechanical component then that movement involves the conversion of the

potential energy of the water into mechanical energy. Hydro turbines convert water pressure

into mechanical shaft power, which can be used to drive an electricity generator, a grinding

mill or some other useful device.

The advantages of the hydroelectric power stations are evident:

It doesn’t need fuel because it uses a renewable energy, constantly replaced by the

nature for free.

It’s clean, because it contaminates neither the air nor the water.

The maintenance and operation costs are low.

The hydraulic turbine is simple, efficient and safe. It can be started up and stopped

quickly and requires very few attention.

Also it is necessary to indicate some disadvantages:

1. The costs per installed kilowatt are frequently very high.

2. It alters the normal course in the biological life (animal and vegetable) of the river.

3. The dam power stations have the problem of the water evaporation:

the zone where it is constructed, the relative humidity of the atmosphere increases as

a result of the evaporation of the water contained in the dam.

4. The location of the hydroelectric power station, determined by natural causes, can be

far from the center of consumption and this can demand the construction of an

electricity transmission system. Thus, it would increase the cost of the investment,

maintenance and loss of energy.

The hydro power generation in Egypt

Hydroelectric power plant in Egypt contribute with (11.2%) of total generation energy in Egypt,

and the following table showing the hydroelectric power plant in Egypt and its capacity.

Table.1.2 hydro power generation in Egypt

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Introduction

10

1.3.4 WIND POWER

Wind energy is one of the most promising alternative energy technologies of the future.

Throughout recent years, the amount of energy produced by wind-driven turbines has

increased exponentially due to significant breakthroughs in turbine technologies, making wind

power economically compatible with conventional of energy. Wind energy is a clean and

renewable source of power. The new windmills, also known as wind turbines, appeared in

Denmark as early as today, the wind-generated electricity is very close in cost to the power

from conventional utility generation in some locations. Wind is a form of solar energy and is

caused by the uneven heating of the atmosphere by the Sun, the irregularities of the Earth’s

surface, and rotation of the Earth. The amount and speed of wind depends on the Earth’s

terrain and other factors. The wind turbines use the kinetic energy of the wind and convert

that energy into mechanical energy, which in turn can be converted into electricity by means

of a generator.

These wind turbines generally have either two or three blades, called rotors, which are angled

at a pitch to maximize the rotation of the rotors. The horizontal-axis design slightly more

efficient and dependable than the vertical-axis windmill. Most of the windmill models that are

currently in production are thus horizontal-axis windmills.

Utility scale turbines can produce anywhere from 50 kilowatts to several megawatts of energy.

These large windmills are generally grouped together in a windy area in what is called a wind

farm. The proximity of the windmills in a wind farm makes it easier to feed the produced

electricity into the power grid.

Egypt contributes with (2%) from its total energy production, although the availability of wind

energy in Egypt, especially in Suez gulf region .in 2010 the ministry of electricity constructed

wind farm in Zafrana region having capacity 550 MW and there are project under construction

wind energy offers many advantages compared to fossil based power and even some other

types of alternative energy, which explains why it is the fastest growing energy source in the

world. The two main reasons are cleanliness and abundance. The fact that wind is a


renewable resource gives it a major advantage over oil and other non-renewable resources.

Considering that environmental pollution is being linked to several global problems that might

eventually threaten the existence or at the very least worsen human living conditions, the fact

that windmills do not produce any emissions whatsoever is another reason to increase the

use of wind turbines.

Increasing the percentage of wind power used by the United States would not be

unreasonable, seeing that the price of wind power is between 4 and 6 cents.

Even though wind energy has many environmental and supply advantages there are several

disadvantages that limit the usability of wind power. The main disadvantage to wind power is

that it is unreliable. Wind does not blow at a constant rate, and it does not always blow when

energy is needed. Furthermore, the windiest locations are often in remote locations, far away

from big cities where the electricity is needed. Just like with any other energy plant, people

oppose it because of aesthetic reasons. The rotor noise produced by the rotor blades is

another reason for opposition.

Airflows can be used to run wind turbines. Modern utility-scale wind turbines range from

around 600 kW to 5 MW of rated power, although turbines with rated output of 1.5–3 MW

have become the most common for commercial use; the power available from the wind is a

function of the cube of the wind speed, so as wind speed increases, power output increases

dramatically up to the maximum output for the particular turbine. Areas where winds are

stronger and more constant, such as offshore and high altitude sites, are preferred locations

for wind farms. Typical capacity factors are 20-40%, with values at the upper end of the range

in particularly favorable sites.

Globally, the long-term technical potential of wind energy is believed to be five times total

current global energy production, or 40 times current electricity demand, assuming all

practical barriers needed were overcome. This would require wind turbines to be installed

over large areas, particularly in areas of higher wind resources, such as offshore. As offshore

wind speeds average ~90% greater than that of land, so offshore resources can contribute

substantially more energy than land stationed turbines.

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Introduction

12

Fig.1.4 wind energy

1.3.5 BIOMASS

Biomass is biological material derived from living, or recently living organisms. It most often

refers to plants or plant-derived materials which are specifically called lignocelluloses

biomass. As an energy source, biomass can either be used directly via combustion to

produce heat, or indirectly after converting it to various forms of biofuel. Conversion of

biomass to biofuel can be achieved by different methods which are broadly classified

into: thermal, chemical, and biochemical methods.

Wood remains the largest biomass energy source today; examples include forest residues

(such as dead trees, branches and tree stumps), yard clippings, wood chips and

even municipal solid waste. In the second sense, biomass includes plant or animal matter that

can be converted into fibers or other industrial chemicals, including biofuels. Industrial

biomass can be grown from numerous types of plants,

including miscanthus, switchgrass, hemp, corn, poplar, willow, sorghum, sugarcane, bamboo,

and a variety of tree species, ranging from eucalyptus to oil palm (palm oil).

Plant energy is produced by crops specifically grown for use as fuel that offer high biomass

output per hectare with low input energy. Some examples of these plants are wheat, which


typically yield 7.5–8 tons of grain per hectare, and straw, which typically yield 3.5–5 tons per

hectare in the UK. The grain can be used for liquid transportation fuels while the straw can be

burned to produce heat or electricity. Plant biomass can also be degraded

from cellulose to glucose through a series of chemical treatments, and the resulting sugar can

then be used as a first generation biofuel.

Biomass can be converted to other usable forms of energy like methane gas or transportation

fuels like ethanol and biodiesel. Rotting garbage, and agricultural and human waste, all

release methane gas—also called "landfill gas" or "biogas." Crops, such as corn and sugar

cane, can be fermented to produce the transportation fuel, ethanol. Biodiesel, another

transportation fuel, can be produced from left-over food products like vegetable oils and

animal fats. Also, biomass to liquids (BTLs) and cellulosic ethanol are still under research.

There is a great deal of research involving algal, or algae-derived, biomass due to the fact

that it’s a non-food resource and can be produced at rates 5 to 10 times those of other types

of land-based agriculture, such as corn and soy. Once harvested, it can be fermented to

produce biofuels such as ethanol, butanol, and methane, as well as biodiesel and hydrogen.

The biomass used for electricity generation varies by region. Forest by-products, such as

wood residues, are common in the United States. Agricultural waste is common

in Mauritius (sugar cane residue) and Southeast Asia (rice husks). Animal husbandry

residues, such as poultry litter, are common in the UK.

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Introduction

14

Fig.1.5 Cogeneration station in Metz (France), using waste wood biomass from the

surrounding forests as renewable energy source.

1.3.6 GEOTHERMAL ENERGY

Geothermal energy is from thermal energy generated and stored in the Earth. Thermal energy

is the energy that determines the temperature of matter. Earth's geothermal energy originates

from the original formation of the planet (20%) and from radioactive decay of minerals

(80%). The geothermal gradient, which is the difference in temperature between the core of

the planet and its surface, drives a continuous conduction of thermal energy in the form

of heat from the core to the surface. The `adjective geothermal originates from the Greek

roots geo, meaning earth, and thermos, meaning heat.

The heat that is used for geothermal energy can be from deep within the Earth, all the way

down to Earth’s core – 4,000 miles (6,400 km) down. At the core, temperatures may reach

over 9,000 °F (5,000 °C). Heat conducts from the core to surrounding rock. Extremely high

temperature and pressure cause some rock to melt, which is commonly known as magma.


Magma convicts upward since it is lighter than the solid rock. This magma then heats rock

and water in the crust, sometimes up to 700 °F (371 °C).

From hot springs, geothermal energy has been used for bathing since Paleolithic times and

for space heating since ancient Roman times, but it is now better known for electricity

generation.

Fig.1.6 the Nesjavellir Geothermal Power Plan

The different ways in which geothermal energy can be used:

Geothermal energy can be used for electricity production, for commercial, industrial, and

residential direct heating purposes, and for efficient home heating and cooling through

geothermal heat pumps.

Heating Uses

Geothermal heat is used directly, without involving a power plant or a heat pump, for a variety

of applications such as space heating and cooling, food preparation, hot spring bathing and

spas (balneology), agriculture, aquaculture, greenhouses, and industrial processes. Uses for

heating and bathing are traced back to ancient Roman times. Currently, geothermal is used

for direct heating purposes at sites across the

United States. U.S. installed capacity of direct use systems totals 470 MW or enough to heat

40,000 average-sized houses.

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Introduction

16

Geothermal Heat Pumps (GH)

Geothermal heat pumps take advantage of the Earth’s relatively constant temperature at

depths of about 10 ft. to 300 ft. GHPs can be used almost everywhere in the world, as they do

not share the requirements of fractured rock and water as are needed for an conventional

geothermal reservoir.

GHPs circulate water or other liquids through pipes buried in a continuous loop, either

horizontally or vertically, under a landscaped area, parking lot, or any number of areas around

the building. The Environmental Protection Agency considers them to be one of the most

efficient heating and cooling systems available.

Fig.1.7 Worldwide production of geothermal electricity

The International Geothermal Association (IGA) has reported that 10,715 megawatts (MW) of

geothermal power in 24 countries is online, which is expected to generate 67,246 GWh of

electricity in 2010. This represents a 20% increase in geothermal power online capacity since

2005. IGA projects this will grow to 18,500 MW by 2015, due to the large number of projects

presently under consideration, often in areas previously assumed to have little exploitable

resource. In 2010, the United States led the world in geothermal electricity production with


3,086 MW of installed capacity from 77 power plants; the largest group of geothermal power

plants in the world is located at The Geysers, a geothermal field in California

1.3.7 OCEAN ENERGY

Generating technologies for deriving electrical power from the ocean include wave energy,

tidal energy, and ocean thermal energy conversion.

Wave energy

Kinetic energy exists in the moving waves of the ocean. That energy can be used to power a

turbine. In this simple example, to the right, the wave rises into a chamber.

The rising water forces the air out of the chamber. The moving air spins a turbine which can

turn a generator. When the wave goes down, air flows through the turbine and back into the

chamber through doors that are normally closed. This is only one type of wave-energy

system. Others actually use the up and down motion of the wave to power a piston that

moves up and down inside a cylinder. That piston can also turn a generator. Most wave

energy systems are very small. But, they can be used to power a warning buoy or a small

light house.

Tidal Energy

Another form of ocean energy is called tidal energy. The rise and fall of the sea level can

power electric-generating equipment. The gearing of the equipment is tremendous to turn the

very slow motion of the tide into enough displacement to produce energy. Tidal energy

traditionally involves erecting a dam across the opening to a tidal basin.

The dam includes a sluice that is opened to allow the tide to flow into the basin; the sluice is

then closed, and as the sea level drops, traditional hydropower technologies can be used to

generate electricity from the elevated water in the basin. Some researchers are also trying to

extract energy directly from tidal flow streams. Some power plants are already operating

using this idea. The largest facility, the La'Rance station in France, generates 240 Megawatts

of power.

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Introduction

18

Fig.1.8 Wave energy

Fig.1.9 Tidal Energy

Ocean Thermal Energy


The final ocean energy idea uses temperature differences in the ocean. Power plants can be

built that use this difference in temperature to make energy. A difference of at least 38

degrees Fahrenheit is needed between the warmer surface water and the colder deep ocean

water. Ocean thermal energy conversion is limited to tropical regions, such as Japan, Hawaii,

and to a portion of the Atlantic coast.

Fig.1.10 Ocean Thermal Energy

1.2 THE ADVANTAGES AND DISADVANTAGES OF RENEWABLE ENERGY

Advantages

1. One major advantage with the use of renewable energy is that as it is renewable it is

therefore sustainable and so will never run out.

2. Renewable energy facilities generally require less maintenance than traditional generators.

Their fuel being derived from natural and available resources reduces the costs of operation.

3. Even more importantly, renewable energy produces little or no waste products such as

carbon dioxide or other chemical pollutants, so has minimal impact on the environment.

4. Renewable energy projects can also bring economic benefits to many regional areas, as

most projects are located away from large urban centers and suburbs of the capital cities.

These economic benefits may be from the increased use of local services as well as tourism.

Chapter 1

Introduction

20

Disadvantages

1. One disadvantage with renewable energy is that it is difficult to generate the quantities of

electricity that are as large as those produced by traditional fossil fuel generators. This may

mean that we need to reduce the amount of energy we use or simply build more energy

facilities. It also indicates that the best solution to our energy problems may be to have a

balance of many different power sources.

2. Another disadvantage of renewable energy sources is the reliability of supply.

Renewable energy often relies on the weather for its source of power. Hydro generators need

rain to fill dams to supply flowing water. Wind turbines need wind to turn the blades, and solar

collectors need clear skies and sunshine to collect heat and make electricity. When these

resources are unavailable so is the capacity to make energy from them. This can be

unpredictable and inconsistent.

3. The current cost of renewable energy technology is also far in excess of traditional fossil

fuel generation. This is because it is a new technology and as such has extremely large

capital cost.

Chapter 2

Solar Energy

22

CHAPTER 2

SOLAR ENERGY 2.1 INTRODUCTION

Solar energy comes from the sun. Every day the sun radiates

an enormous amount of energy. The sun radiates more energy

in one second than people have used since the beginning of

time. All this energy comes from within the sun itself. Like

other stars, the sun is a big gas ball made up mostly of

hydrogen and helium. The sun generates energy in its

core in a process called nuclear fusion. During nuclear

fusion, Fig (2.1) the sun’s extremely high pressure and hot temperature cause hydrogen

atoms to come apart and their nuclei to fuse or combine. Some matter is lost during nuclear

fusion. The lost matter is emitted into space as radiant energy. It takes millions of years for

the energy in the sun’s core to make its way to the solar surface, and then approximately

eight minutes to travel the 93 million miles to earth.

The solar energy travels to the earth at a speed of 186,000 miles per second, the speed of

light. Only a small portion of the energy radiated by the sun into space strikes the earth, one

part in two billion. Yet this amount of energy is enormous. Every day enough energy strikes

the United States to supply the nation’s energy needs for one and a half years! About 15

percent of the sun’s energy that hits the earth is reflected back into space. Another 30

percent is used to evaporate water, which, lifted into the atmosphere, produces rainfall.

Plants, the land, and the oceans also absorb solar energy. The rest could be used to supply

our needs.

Fig (2.1) nuclear fusion in sun


The Sun –An Overview

The Sun is the centre of our solar system and its energy drives nearly all systems on earth.

They include climate systems, ecosystems (plant & animal processes), hydrological systems,

wind systems, etc.). Solar energy is created at the core of the sun when hydrogen atoms are

fused to form helium by nuclear fusion. It is estimated that 700 million tons of hydrogen are

converted into 695 million tons of helium every second.

H++ H+ = He+++Energy.

The remaining mass of 5 million ton is converted into electromagnetic energy that radiates

from the sun’s radiation out into space. The rate at which energy is emitted from the sun’s

surface is estimated at 63,000,000W/m2. However the earth intercepts only a small fraction of

this enormous energy. When travelling through outer space, which is characterized by

vacuum, the solar radiation remains intact and is not modified or attenuated until it reaches

the top of the earth’s atmosphere.

Fig (2.2) solar energy of the sun

How Much Solar Energy?

The surface receives about 47% of the total solar energy that reaches the Earth, Fig (2.2)

only this amount is usable.

Chapter 2

Solar Energy

24

Irradiated energy

Solar radiation is an energy force radiated in all directions, equally, by the sun. Of that energy,

an output of 1.36kW/m2, called the solar constant, hits the outer earth’s atmosphere. This

solar radiation is reduced through reflection, dispersion and absorption in dust particles and

gas molecules. The portion of radiation which passes unimpeded through the atmosphere

and strikes the earth’s surface directly is known as direct radiation. That part of the solar

radiation which is reflected and/or absorbed by dust particles and gas molecules, irradiated

back and strikes the earth’s surface indirectly is known as diffused radiation. The sum total of

all direct and diffused solar radiation (Fig3.2) is called global radiation e.g. the global radiation

under optimum conditions (clear, cloudless sky at midday) amounts to a max. of 1000 W/m2.

With solar panels, as much as 75% of this global radiation can be utilized, depending on the

type of collector and the system size.

Fig 2.3 Irradiated daily energy values over a 12 month period

Solar Energy in Egypt.

The utilization of solar fuel in Egypt is very promising due to high availability and the good

advantage that is a clear energy and its utilization protects the environment. It has no

emissions like the conventional types of energies. Egypt is going to increase its solar farm by


the end of the year 2010, in a move that will further underline North Africa's emergence as

one of the world's most exciting solar energy markets.140MW solar plant was on track to

connect to the grid within the next six months of year 2010 and that would represent the

beginning of a major new strategy designed to ensure 20 per cent of the country's energy is

generated by renewable sources by 2020.

Fig (2.4) Egypt has excellent Solar Resources

2.2 SOLAR PHOTOVOLTAIC

The first conventional photovoltaic cells were produced in the late 1950s, and Throughout the

1960s were principally used to provide electrical power for earth orbiting satellites. In the

1970s, improvements in manufacturing, performance and quality of PV modules helped to

reduce costs and opened up a number of opportunities for powering remote terrestrial

applications, including battery charging for navigational aids, signals, telecommunications

equipment and other critical, low power needs. In the 1980s, photovoltaic became a popular

power source for consumer electronic devices, including calculators, watches, radios, lanterns

Chapter 2

Solar Energy

26

and other small battery charging applications. Following the energy crises of the 1970s,

significant efforts also began to develop PV power systems for residential and commercial

uses, both for stand-alone, remote power as well as for utility-connected applications.

How a PV cell work

A typical silicon PV cell is composed of a thin wafer consisting of an ultra-thin layer of

phosphorus-doped (N-type) silicon on top of a thicker layer of boron-doped (P- type) silicon.

An electrical field is created near the top surface of the cell where these two materials are in

contact, called the P-N junction.

When sunlight strikes the surface of a PV cell, this electrical field provides momentum and

direction to light-stimulated electrons, resulting in a flow of current when the solar cell is

connected to an electrical load Regardless of size shown in figure (2.5), a typical silicon PV

cell produces about 0.5-0.6 volt DC under open-circuit, no-load conditions.

The current (and power) output of a PV cell depends on its efficiency and size (surface area),

and is proportional to the intensity of sunlight striking the surface of the cell.

Fig (2.5) Photovoltaic cell operation

2.3 PHOTOVOLTAIC MODELING

The modeling of a PV generator, in which the current behave as in reality, represents a very

important goal. Indeed such a simulation facility would allow carrying out measurement and

tests. More cheaply and without constrains of the environmental conditions. Avoiding the use

of an actual PV array. For example, the optimal choice and design of the power converter

interfacing the PV generator to the utility or load and the study of all the problems related to


the power electronic control would be performed more rapidly and effectively. A solar cell is

usually represented by one diode model as shown in Fig (2.6).

Fig (2.6) solar cell representation

2.3.1 SERIES RESISTANCE

Series resistance in a solar cell has three causes: firstly, the movement of current through the

emitter and base of the solar cell; secondly, the contact resistance between the metal contact

and the silicon; and finally the resistance of the top and rear metal contacts. The main impact

of series resistance is to reduce the fill factor, although excessively high values may also

reduce the short-circuit current.

2.3.2 Shunt Resistance

Significant power losses caused by the presence of a shunt resistance, RSH, are typically due

to manufacturing defects, rather than poor solar cell design.

Low shunt resistance causes power losses in solar cells by providing an alternate current

path for the light-generated current. Such a diversion reduces the amount of current flowing

through the solar cell junction and reduces the voltage from the solar cell. The effect of a

shunt resistance is particularly severe at low light levels, since there will be less light-

generated current. The loss of this current to the shunt therefore has a larger impact. In

Chapter 2

Solar Energy

28

addition, at lower voltages where the effective resistance of the solar cell is high, the impact of

a resistance in parallel is large.

2.3.3 Ideality Factor

The ideality factor of a diode is a measure of how closely the diode follows the ideal diode

equation. The derivation of the simple diode equation uses certain assumption about the cell.

In practice, there are second order effects so that the diode does not follow the simple diode

equation and the ideality factor provides a way of describing them.

2.3.4 Characteristic equation

From the equivalent circuit. Applying, Kirchhoff's law, the current produced by the solar cell is

equal to that produced by the current source, minus that which follows through the diode,

minus which follows through the shunt resistor.

I= IPH – ID – ISH (2.1)

Where:

I: output current (A).

IPH: photo-generated current (A).

ID: diode current (A).

ISH: shunt current (A).

By the Shockley diode equation, the current diverted trough the diode is:

ID = IO (exp[q VPV/m kTC]-1) (2.2)

Where

q: Electron charge,

K: Poltizman constant, m: diode ideality factor

TC: absolute temperature of the cell, IP: reverse saturation current


2.3.5 What is Maximum Power Point Tracking?

It can be seen from characteristic, that there is a unique point on the characteristic at which

the photovoltaic power is maximum. This point is termed as the maximum power point (MPP)

the power corresponding to this point is termed as power at maximum power point (Pmpp) and

the voltage as voltage at maximum power point (Vmpp). Due to high cost of solar cell, it is must

be ensured that photovoltaic array operates at all time to provide maximum power output.

MPPT or Maximum Power Point Tracking is algorithm that included in charge controllers used

for extracting maximum available power from PV module under certain conditions. The

voltage at which PV module can produce maximum power is called ‘maximum power point’

(or peak power voltage). Maximum power varies with solar radiation, ambient temperature

and solar cell temperature. typical PV module produces power with maximum power voltage

of around 17 V when measured at a cell temperature of 25°C, it can drop to around 15 V on a

very hot day and it can also rise to 18 V on a very cold day. Also optimize output by following

the sun across the sky for maximum sunlight. These typically give you about a 15% increase

in winter and up to a 35% increase in summer.

How Maximum Power Point Tracking works

The major principle of MPPT is to extract the maximum available power from PV module by

making them operate at the most efficient voltage (maximum power point). That is to say:

MPPT checks output of PV module, compares it to battery voltage then fixes what is the best

power that PV module can produce to charge the battery and converts it to the best voltage to

get maximum current into battery. It can also supply power to a DC load, which is connected

directly to the battery.

Here is where the optimization or maximum power point tracking comes in. Assume your

battery is low, at 12 volts. A MPPT takes that 17.6 volts at 7.4 amps and converts it down, so

that what the battery gets is now 10.8 amps at 12 volts. Now you still have almost 130 watts,

and everyone is happy.

Ideally, for 100% power conversion you would get around 11.3 amps at 11.5 volts, but you

have to feed the battery a higher voltage to force the amps in. And this is a simplified

explanation - in actual fact the output of the MPPT charge controller might vary continually to

adjust for getting the maximum amps into the battery.

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30

Fig. (2.7) the max power point tracking.

If you look, you will see that it has a sharp peak at the upper right - that represents the

maximum power point. What an MPPT controller does is "look" for that exact point, and then

does the voltage/current conversion to change it to exactly what the battery needs. In real life,

that peak moves around continuously with changes in light conditions and weather. A MPPT

tracks the maximum power point, which is going to be different from the STC (Standard Test

Conditions) rating under almost all situations. Under very cold conditions a 120 watt panel is

actually capable of putting over 130+ watts because the power output goes up as panel

temperature goes down - but if you don't have some way of tracking that power point, you are

going to lose it.

On the other hand under very hot conditions, the power drops - you lose power as the

temperature goes up. That is why you get less gain in summer.

2.3.6 Efficiency

The efficiency is the most commonly used parameter to compare the performance of one

solar cell to another. Efficiency is defined as the ratio of energy output from the solar cell to

input energy from the sun.


In addition to reflecting the performance of the solar cell itself, the efficiency depends on the

spectrum and intensity of the incident sunlight and the temperature of the solar cell.

Therefore, conditions under which efficiency is measured must be carefully controlled in order

to compare the performance of one device to another.

Efficiency can be computed from equations:-

2.3

2.4

2.4 EFFECT OF SOLAR IRRADIANCE, TEMPERATURE ON PV:

2.4.1 Effect of Solar Irradiance on PV

From Fig(2.8a-2.8b) change in irradiance (solar power) significantly affect the current and

power output of PV device but have a much small effect on voltage.

The fact that the voltage varies little with changing sunlight levels makes PV device well-

suited for battery charging applications.

2.4.2 Effect of Temperature on PV

From Fig (2.9a-2.9b) Increasing cell temperature results in a significant decrease in voltage,

however current output increases slightly, the net effect for most PV devices is decreasing

power output with increasing cell temperature.

Higher cell operating temperature reduces cell output efficiency and life time. Colder

operating environments results in higher operating voltage.

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32

Fig (2.8a-2.8b) effect of solar radiation.

Fig (2.9a) effect of temperature on current & voltage of PV.

2.5 COMPONENTS OF PV SYSTEM

Cells, modules, arrays

Photovoltaic cells are connected electrically in series and/or parallel circuits to produce higher

voltages, currents and power levels. Photovoltaic modules consist of PV cell circuits sealed in

an environmentally protective laminate, and are the fundamental building blocks of PV


systems. Photovoltaic panels include one or more PV modules assembled as a pre-wired,

field-installable unit. Photovoltaic array is the complete power generating unit, consisting of

any number of PV modules and panels.

Fig (2.9b) effect of temperature on power &voltage of PV.

The performance of PV modules and arrays are generally rated according to their maximum

DC power output (watts) under Standard Test Conditions (STC). Standard Test Conditions

are defined by a module (cell) operating temperature of 25o C (77o F), and incident solar

irradiance level of 1000 W/m2 and under Air Mass 1.5 spectral distribution. Since these

conditions are not always typical of how PV modules and arrays operate in the field, actual

performance is usually 85 to 90 percent of the STC rating.

Today’s photovoltaic modules are extremely safe and reliable products, with minimal failure

rates and projected service lifetimes of 20 to 30 years. Most major manufacturers offer

warranties of 20 or more years for maintaining a high percentage of initial rated power output.

When selecting PV modules, look for the product listing (UL), qualification testing and

warranty information in the module manufacturer’s specifications.

Related equipment

• Solar charge controller

Regulates the voltage and current coming from the PV panels going to battery and prevents

battery overcharging and prolongs the battery life.

Chapter 2

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34

Fig 2.10 Photovoltaic cells, modules, panels and arrays

• Inverter

Converts DC output of PV panels or wind turbine into a clean AC current for AC appliances or

fed back into grid line.

• Battery

Stores energy for supplying to electrical appliances when there is a demand.

• Load

Load is electrical appliances that connected to solar PV system such as lights, radio, TV,

computer, refrigerator, etc


Fig (2.11) Components of PV system

2.6 PHOTOVOLTAIC SYSTEM TYPES

PV systems can be very simple, just a PV module and load, as in the direct powering of a

water pump motor, or more complex, as in a system to power a house. While a water pump

may only need to operate when the sun shines, the house system will need to operate day

and night. It also may have to run both AC and DC loads, have reserve power and may

include a back-up generator. Depending on the system configuration, we can distinguish

three main types of PV systems: stand-alone, grid-connected, and hybrid. In either case,

basic PV system principles and elements remain the same. Systems are adapted to meet

particular energy requirements by varying the type and quantity of the basic elements. Ads as

systems are modular; they can always be expanded, as power demands increases.

2.6.1 Stand-alone systems

Stand-alone systems rely on PV power only. These systems can comprise only PV modules

and a load or can include batteries for energy storage. When using batteries charge

regulators are included, which switch off the PV modules when batteries are fully charged,

Chapter 2

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36

and switch off the load in case batteries become discharged below a limit. The batteries must

have enough capacity to store the energy produced during the day to be used at night and

during periods of poor weather. Figure (2.12) shows schematically examples of stand-alone

systems; (a) a simple DC PV system without a battery and (b) a large PV system with both

DC and AC loads.

Figure (2.12) Schematic representation of (a) a simple DC PV system to power a water pump

with no energy storage, (b) a complex PV system including batteries, power conditioners, and

both DC and AC loads.

2.6.2 Grid-connected systems

Grid-connected PV systems have become increasingly popular as building integrated

application. They are connected to the grid through inverters, and do not require batteries

because the grid can accept all of the electricity that a PV generator can supply. Alternatively

they are used as power stations. A grid-connected PV system is schematically presented in

Figure (2.13).

2.6.3 Hybrid systems

Hybrid systems consist of combination of PV modules and a complementary means of

electricity generation such as a diesel, gas or wind generator. Schematically is a hybrid

system shown in Figure (2.14), In order to optimize the operations of the two generators,

hybrid systems typically require more sophisticated controls than stand-alone PV systems For

example, in the case of PV/diesel systems, the diesel engine must be started when battery

reaches a given discharge level and stopped again when battery reaches an adequate state

of charge. The back-up generator can be used to recharge batteries only or to supply the load

as well.


Fig (2.13) A grid-connected PV system.

Fig (2.14) a hybrid system.

A common problem with hybrid PV/diesel generators is inadequate control of the diesel

generator. If the batteries are maintained at too high a state-of-charge by the diesel

generator, then energy, which could be produced by the PV generator is wasted. Conversely,

if the batteries are inadequately charged, then their operational life will be reduced. Such

Chapter 2

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problems must be expected if a PV generator is added to an existing diesel engine without

installing an automatic system for starting the engine and controlling its output.

2.7 ADVANTAGES AND DISADVANTAGES OF SOLAR ENERGY

2.7.1Advantages of Solar Energy:-

1) Solar energy makes use of a renewable natural resource that is readily available.

2) Solar power used by it creates no carbon dioxide or other toxic emissions.

3) Use of solar thermal power to heat water or generate electricity will help reduce the

Territory’s complete dependence on fossil fuels.

4) Solar water heaters are an established technology, readily available on the commercial

market, and simple enough to build, install and maintain by yourself.

5) The production of electricity by the photovoltaic process is quiet and produces no toxic

fumes.

6) PV cells generate direct-current electricity that can be stored in batteries and used in a

wide range of voltages depending on the configuration of the battery bank.

7) Although most electric appliances operate on alternating current, an increasing number of

appliances using direct current are now available. Where these are not practical, PV-

generated direct current can be changed into alternating current by use of devices called

inverters.

8) All chemical and radioactive polluting byproducts of the thermonuclear reactions remain

behind on the sun, while only pure radiant energy reaches the Earth.

9) Energy reaching the earth is incredible. By one calculation, 30 days of sunshine striking

the Earth have the energy equivalent of the total of all the planet’s fossil fuels, both used

and unused!


2.7.2 Disadvantages of Solar Energy:-

1) Solar thermal systems are not cost-effective in areas that have long periods of cloudy

weather or short daylight hours.

2) The arrays of collecting devices for large systems cover extensive land areas.

3) Photovoltaic-produced electricity is presently more expensive than power supplied by

utilities.

4) Batteries need periodic maintenance and replacement.

5) High voltage direct-current electricity can pose safety hazards to inadequately trained

home operators or utility personnel.

6) Sun does not shine consistently.

7) Solar energy is a diffuse source. To harness it, we must concentrate it into an

amount and form that we can use, such as heat and electricity.

8) Addressed by approaching the problem through:

9) Collection, 2) conversion, 3) storage

10) Efficiency is far less than the 77% of solar spectrum with usable wavelengths.

11) 43% of photon energy is used to warm the crystal.

12) Efficiency drops as temperature increases (from 24% at 0°C to 14% at 100°C.)

13) Light is reflected off the front face and internal electrical resistances are other factors.

14) Overall, the efficiency is about 10-14%.

15) Cost of electricity from coal-burning plants is anywhere b/w 8-20 cents/kWh, while

photovoltaic power generation is anywhere b/w $0.50-1/kWh.

16) Does not reflect the true costs of burning coal and its emissions to the nonpolluting

method of the latter.

Chapter 2

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17) Solar thermal systems only work with sunshine and do not operate at night or in

inclement weather. Storage of hot water for domestic or commercial use is simple,

using insulated tanks, but storage of fluids at the higher temperatures needed for

electrical generation, or storage of electricity itself, needs further technical

development.

2.8 APPLICATIONS OF SOLAR ENERGY

Photovoltaic

Photovoltaic are solar cells that produce electricity directly from sunlight. The solar cells are

made of thin layers of material, usually silicon. The layers, after treatment with special

compounds, have either too many or too few electrons. When light strikes a sandwich of the

different layers, electrons start flowing and electric current results see Fig (2.15).

Fig (2.15) PV Solar Cell


Photovoltaic are used throughout the nation and elsewhere to operate appliances, provide

lighting, and to power navigation and communication aids. Photovoltaic panels provide power

for equipment in space ships and satellites. PV cells supply power needed to operate many

kinds of consumer products such as calculators and watches. Photovoltaic systems provide

electricity to remote villages, residences, medical centers, and other isolated sites where the

cost of photovoltaic equipment is less than the expense of extending utility power lines or

using diesel-generated electricity.

Solar Thermal

Solar Thermal power is heat energy obtained by exposing a collecting device to the rays of

the sun. A solar thermal system makes use of the warmth absorbed by the collector to heat

water or another working fluid, or to make steam .Hot water is used in homes or commercial

buildings and for industrial processes Fig (2.17).

Fig (2.16) solar thermal

Steam is used for process heat or for operating a turbine generator to produce electricity or

industrial power. There are several basic kinds of solar thermal power systems including “flat

plate” solar water heaters; concentrating collectors, such as central tower receivers; and

parabolic trough and dish collectors. Flat plate solar water heaters – Water flows through

tubes that are attached to a black metal absorber plate see Fig (2.17). The plate is enclosed

in an insulated box with a transparent window to let in sunlight. The heated water is

transferred to a tank where it is available for home, commercial or institutional use. Central

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tower receivers – In order to produce steam and electricity with solar thermal energy, central

receivers have a field of tracking.

Mirrors called heliostats to focus sunlight onto a single receiver mounted on a tower. Water

or other heat transfer fluid in the tower is heated and used directly or converted into steam for

electricity. Parabolic dishes or troughs – curved panels which follow the direction of the sun’s

rays and focus the sunlight onto receivers. A liquid inside the pipes at the receivers’ focal

point absorbs the thermal energy. The thermal energy received can be converted to

electricity at each unit or transported to a central point for conversion to electricity.

Fig (2.17) Black metal absorber plate.

Solar Stills

Solar stills are systems designed to filter or purify water. The number of systems designed to

filter water have increased dramatically in recent years. As water supplies have increased in

salinity, have been contaminated, or have experienced periods of contamination, people have

lost trust in their drinking water supply. Water filtration systems can be as simple as a filter for


taste and odor to complex systems to remove impurities and toxins. Solar water distillation is

one of the simplest and most effective methods of purifying water. Solar water distillation

replicates the way nature purifies water. The sun's energy heats water to the point of

evaporation. As the water evaporates, purified water vapor rises, condensing on the glass

surface for collection.

This process removes impurities such as salts and heavy metals, as well as destroying

microbiological organisms. The end result is water cleaner than the purest rainwater.

Solar energy is allowed into the collector to heat the water. The water evaporates only to

condense on the underside of the glass Fig (2.18). When water evaporates, only the water

vapor rises, leaving contaminants behind. The gentle slope of the glass directs the

condensate to a collection trough, which in turn delivers the water to the collection bottle.

Fig (2.18) Solar Stills

Solar Crop Dryers

Using the sun to dry crops and grain is one of the oldest and most widely used applications of

solar energy. The simplest and least expensive technique is to allow crops to dry naturally in

the field, or to spread grain and fruit out in the sun after harvesting. The disadvantage of

these methods is that the crops and grain are subject to damage by birds, rodents, wind, and

rain, and contamination by windblown dust and dirt. More sophisticated solar dryers protect

grain and fruit, reduce losses, dry faster and more uniformly, and produce a better quality

Chapter 2

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product than open air methods. The basic components of a solar dryer are an enclosure or

shed, screened drying trays or racks, and a solar collector. In hot, arid climates the collector

may not even be necessary. The southern side of the enclosure itself can be glazed to allow

sunlight to dry the material. The collector can be as simple as a glazed box with a dark

colored interior to absorb the solar energy that heats air. The air heated in the solar collector

moves, either by natural convection or forced by a fan, up through the material being dried.

The size of the collector and rate of airflow depends on the amount of material being dried,

the moisture content of the material, the humidity in the air, and the average amount of solar

radiation available during the drying season.

There are a relatively small number of large solar crop dryers in the United States. This is

because the cost of the solar collector can be high, and drying rates are not as controllable as

they are with natural gas or propane powered dryers. Using the collector at other times of the

year, such as for heating farm buildings, may make a solar dryer more cost-effective. It is

possible to make small, very low cost dryers out of simple materials. These systems can be

useful for drying vegetables and fruit for home use see Fig (2.19).

Fig (2.19) Solar Crop Dryers

Electrical generation

PV has mainly been used to power small and medium-sized applications, from the calculated

power by a single solar cell to off-grid homes powered by a photovoltaic array. For large-

http://en.wikipedia.org/wiki/Photovoltaic_array


scale generation, CSP plants like SEGS have been the norm but recently multi-megawatt PV

plants are becoming common see in Fig (2.20).

Fig (2.20) Electrical generation

Charging Vehicle Batteries

PV systems may be used to directly charge vehicle batteries, or to provide a “trickle charge”

for maintaining a high battery state of charge on little-used vehicles, such as fire-fighting and

snow removal equipment and agricultural machines such as tractors or harvesters. Direct

charging is useful for boats and recreational vehicles. Solar stations may be dedicated to

charging electric vehicles.

Water Pumping and Control

PV is an ideal candidate for water pumping applications. Many water pumping needs, such

as livestock watering, are greatest during the sunniest hours of the day. These systems may

be either direct system, operating the pump only when the sunlight is sufficient, or they may

pump water to an elevated storage tower during sunny hours to provide available water at

any time. Either system avoids the use of batteries, resulting in a decrease in initial cost and

reducing maintenance needs. PV powered water pumping is used to provide water for

campgrounds, irrigation, remote village water supplies, and livestock watering.

http://en.wikipedia.org/wiki/SEGS

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Communications

Radio, television, and phone signals over long distances need to be amplified. Relay towers,

often called repeater stations, perform this function. The best sites for repeater stations are

usually at the highest possible elevation, where power lines are not commonly found and

transport of conventional generator fuels would be difficult and costly. In addition, as the use

of fiber optic cable spreads, photovoltaic repeater stations will be required. Coaxial cable can

carry power to amplify the signal carried, but fiber optic cable does not have this capability.

PV also is used on travelers’ information transmitters, portable computer systems, cellular

telephones, mobile radio systems, and emergency call boxes.

Solar Water Heater

There are two categories for solar water heaters: an electric or propane-powered backup

heater and a total solar hot water system that operates strictly on solar energy.

The backup heater kicks in when there is not enough solar energy to heat water to a pre-set

temperature, but it burns propane or expends grid electricity. In a solar hot water system, a

solar controller activates a solar-powered pump that brings water to a roof-mounted collector

that holds the water in sunlight until it heats; the heated water circulates to an insulated

holding tank for household use. If there is not sufficient sunlight to heat the water in the

collector, the solar controller sends it via gravity to a drain-back tank to ensure the water will

not freeze in the collector and damage it.

By using solar energy to heat your household water, you save money on your energy bill and

emit no greenhouse gasses.

Chapter 3

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CHAPTER 3

TRACKING SYSTEM

3.1 INTRODUCTION

The increasing demand for energy, the continuous reduction in existing sources of fossil fuels

and the growing concern regarding environment pollution, have pushed mankind to explore

new technologies for the production of electrical energy using clean, renewable sources, such

as solar energy, wind energy, etc.

Among the non-conventional, renewable energy sources, solar energy affords great potential

for conversion into electric power, able to ensure an important part of the electrical energy

needs of the planet.

The conversion of solar light into electrical energy represents one of the most promising and

challenging energetic technologies, in continuous development, being clean, silent and

reliable, with very low maintenance costs and minimal ecological impact. Solar energy is free,

practically inexhaustible, and involves no polluting residues or greenhouse gases emissions.

The conversion principle of solar light into electricity, called Photo-Voltaic or PV conversion, is

not very new, but the efficiency improvement of the PV conversion equipment is still one of

top priorities for many academic and/or industrial research groups all over the world.

Among the proposed solutions for improving the efficiency of PV conversion, we can mention

solar tracking, the optimization of solar cell configuration and geometry, new materials and

technologies, etc.

The global market for PV conversion equipment has shown an exponential increase over the

last years, showing a good tendency for the years to come.

Physically, a PV panel consists of a flat surface on which numerous p-n junctions are placed,

connected together through electrically conducting strips. The PV panel ensures the

conversion of light radiation into electricity and it is characterized by a strong dependence of

the output power on the incident light radiation.


As technology has evolved, the conversion efficiency of the PV panels has increased steadily,

but still it does not exceed 13% for the common ones. The PV panels exhibits a strongly non-

linear I-V (current - voltage) characteristic and a power output that is also non-linearly

dependent on the surface insolation.

In the case of solar light conversion into electricity, due to the continuous change in the

relative positions of the sun and the earth, the incident radiation on a fixed PV panel is

continuously changing, reaching a maximum point when the direction of solar radiation is

perpendicular to the panel surface. In this context, for maximal energy efficiency of a PV

panel, it is necessary to have it equipped with a solar tracking system.

The topic proposed in this paper refers to the design of a single axis solar tracker system that

automatically searches the optimum PV panel position with respect to the sun by means of a

DC motor controlled by an intelligent drive unit that receives input signals from a light intensity

sensor.

3.2 BASIC CONCEPT

The effective collection area of a flat-panel solar collector varies with the cosine of the

misalignment of the panel with the Sun.

Sunlight has two components, the "direct beam" that carries about 90% of the solar energy,

and the "diffuse sunlight" that carries the remainder - the diffuse portion is the blue sky on a

clear day and increases proportionately on cloudy days. As the majority of the energy is in the

direct beam, maximizing collection requires the sun to be visible to the panels as long as

possible.

The energy contributed by the direct beam drops off with the cosine of the angle between the

incoming light and the panel. In addition, the reflectance (averaged across all polarizations) is

approximately constant for angles of incidence up to around 50°, beyond which reflectance

degrades rapidly. For example trackers that have accuracies of ± 5° can deliver greater than

99.6% of the energy delivered by the direct beam plus 100% of the diffuse light. As a result,

high accuracy tracking is not typically used in non-concentrating PV applications.

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Fig 3.1

The sun travels through 360 degrees east to west per day, but from the perspective of any

fixed location the visible portion is 180 degrees during an average 1/2 day period (more in

spring and summer; less, in fall and winter). Local horizon effects reduce this somewhat,

making the effective motion about 150 degrees. A solar panel in a fixed orientation between

the dawn and sunset extremes will see a motion of 75 degrees to either side, and thus,

according to the table above, will lose 75% of the energy in the morning and evening.

Rotating the panels to the east and west can help recapture those losses. A tracker rotating in

the east-west direction is known as a single-axis tracker.

Direct power lost (%) due to misalignment (angle i )

i Lost = 1 - cos(i) I hours Lost

0° 0% 15° 1 3.4%

1° 0.015% 30° 2 13.4%

3° 0.14% 45° 3 30%

8° 1% 60° 4 >50%

23.4° 8.3% 75° 5 >75%


The sun also moves through 46 degrees north and south during a year. The same set of

panels set at the midpoint between the two local extremes will thus see the sun move 23

degrees on either side, causing losses of 8.3% A tracker that accounts for both the daily and

seasonal motions is known as a dual-axis tracker. Generally speaking, the losses due to

seasonal angle changes is complicated by changes in the length of the day, increasing

collection in the summer in northern or southern latitudes. This biases collection toward the

summer, so if the panels are tilted closer to the average summer angles, the total yearly

losses are reduced compared to a system tilted at the spring/fall solstice angle (which is the

same as the site's latitude).

There is considerable argument within the industry whether the small difference in yearly

collection between single and dual-axis trackers makes the added complexity of a two-axis

tracker worthwhile. A recent review of actual production statistics from southern Ontario

suggested the difference was about 4% in total, which was far less than the added costs of

the dual-axis systems. This compares unfavorably with the 24-32% improvement between a

fixed-array and single-axis tracker.

3.3 TRACKING SYSTEM AND PV PANEL EFFICIENCY

Fig.3-2 power vs Day Time curve

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52

Compared to a fixed panel, a mobile PV panel driven by a solar tracker is kept under the best

possible insolation for all positions of the Sun, as the light falls close to the geometric normal

incidence angle. Automatic solar tracking systems (using light intensity sensing) may boost

consistently the conversion efficiency of a PV panel, thus in this way deriving more energy

from the sun. Technical reports in the USA have shown solar tracking to be particularly

effective in summer, when the increases in output energy may reach over 50%, while in

autumn they may be higher than 20%, depending on the technology used Fig.3-2 . Solar

tracking systems are of several types and can be classified according to several criteria. A

first classification can be made depending on the number of rotation axes. Thus we can

distinguish solar tracking systems with a rotation axis, respectively with two rotation axes.

Since solar tracking implies moving parts and control systems that tend to be expensive,

single-axis tracking systems seem to be the best solution for small PV power plants. Single

axis trackers will usually have a manual elevation (axis tilt) adjustment on the second axis

which is adjusted at regular intervals throughout the year.

3.4 TYPES OF TRACKERS

3.4.1 SINGLE AXIS TRACKERS

Single axis trackers have one degree of freedom that acts as an axis of rotation. The axis of

rotation of single axis trackers is typically aligned along a true North meridian. It is possible to

align them in any cardinal direction with advanced tracking algorithms.

There are several common implementations of single axis trackers. These include horizontal

single axis trackers (HSAT), vertical single axis trackers (VSAT), tilted single axis trackers

(TSAT) and polar aligned single axis trackers (PSAT). The orientation of the module with

respect to the tracker axis is important when modeling performance.

3.4.1.1HORIZONTAL SINGLE AXIS TRACKER (HSAT)

The axis of rotation for horizontal single axis tracker is horizontal with respect to the ground.

The posts at either end of the axis of rotation of a horizontal single axis tracker can be shared

between trackers to lower the installation cost.


Field layouts with horizontal single axis trackers are very flexible. The simple geometry means

that keeping all of the axes of rotation parallel to one another is all that is required for

appropriately positioning the trackers with respect to one another.

Fig 3.3 Horizontal single axis tracker in California

Fig 3.4 Linear horizontal axis tracker in South Korea.

Appropriate spacing can maximize the ratio of energy production to cost, this being

dependent upon local terrain and shading conditions and the time-of-day value of the energy

produced. Backtracking is one means of computing the disposition of panels.

Horizontal trackers typically have the face of the module oriented parallel to the axis of

rotation. As a module tracks, it sweeps a cylinder that is rotationally symmetric around the

axis of rotation.

In single axis horizontal trackers, a long horizontal tube is supported on bearings mounted

upon pylons or frames. The axis of the tube is on a north-south line. Panels are mounted

upon the tube, and the tube will rotate on its axis to track the apparent motion of the sun

through the day.

http://en.wikipedia.org/wiki/File:RayTracker_Utility_Scale_Solar_Tracker_Installation.JPG

http://en.wikipedia.org/wiki/File:SeoulMarineSuncheon052.jpg

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3.4.1.2 VERTICAL SINGLE AXIS TRACKER (VSAT)

The axis of rotation for vertical single axis trackers is vertical with respect to the ground.

These trackers rotate from East to West over the course of the day. Such trackers are more

effective at high latitudes than are horizontal axis trackers.

Field layouts must consider shading to avoid unnecessary energy losses and to optimize land

utilization. Also optimization for dense packing is limited due to the nature of the shading over

the course of a year.

Vertical single axis trackers typically have the face of the module oriented at an angle with

respect to the axis of rotation. As a module tracks, it sweeps a cone that is rotationally

symmetric around the axis of rotation.

3.4.1.3 TILTED SINGLE AXIS TRACKER (TSAT)

All trackers with axes of rotation between horizontal and vertical are considered tilted single

axis trackers. Tracker tilt angles are often limited to reduce the wind profile and decrease the

elevated end height.

Fig 3.5 Single axis trackers with roughly 20 degree tilted

Field layouts must consider shading to avoid unnecessary losses and to optimize land

utilization.

With backtracking, they can be packed without shading perpendicular to their axis of rotation

at any density. However, the packing parallel to their axes of rotation is limited by the tilt angle

and the latitude.

http://en.wikipedia.org/wiki/File:Nellis_AFB_Solar_panels.jpg

http://en.wikipedia.org/wiki/File:Nellis_AFB_Solar_panels.jpg


Tilted single axis trackers typically have the face of the module oriented parallel to the axis of

rotation. As a module tracks, it sweeps a cylinder that is rotationally symmetric around the

axis of rotation.

3.4.1.4 POLAR ALIGNED SINGLE AXIS TRACKERS (PASAT)

This method is scientifically well known as the standard method of mounting a telescope

support structure. The tilted single axis is aligned to the polar star. It is therefore called a polar

aligned single axis tracker (PASAT). In this particular implementation of a tilted single axis

tracker, the tilt angle is equal to the site latitude. This aligns the tracker axis of rotation with

the earth’s axis of rotation.

3.4.2 DUAL AXIS TRACKERS

Dual axis trackers have two degrees of freedom that act as axes of rotation. These axes are

typically normal to one another. The axis that is fixed with respect to the ground can be

considered a primary axis. The axis that is referenced to the primary axis can be considered a

secondary axis.

There are several common implementations of dual axis trackers. They are classified by the

orientation of their primary axes with respect to the ground. Two common implementations

are tip-tilt dual axis trackers (TTDAT) and azimuth-altitude dual axis trackers (AADAT).

The orientation of the module with respect to the tracker axis is important when modeling

performance. Dual axis trackers typically have modules oriented parallel to the secondary

axis of rotation.

Dual axis trackers allow for optimum solar energy levels due to their ability to follow the sun

vertically and horizontally. No matter where the sun is in the sky, dual axis trackers are able to

angle themselves to be in direct contact with the sun.

3.4.2.1 TIP–TILT DUAL AXIS TRACKER (TTDAT)

A tip–tilt dual axis tracker is so-named because the panel array is mounted on the top of a

pole. Normally the east-west movement is driven by rotating the array around the top of the

pole. On top of the rotating bearing is a T- or H-shaped mechanism that provides vertical

rotation of the panels and provides the main mounting points for the array. The posts at either

Chapter 3

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end of the primary axis of rotation of a tip–tilt dual axis tracker can be shared between

trackers to lower installation costs.

Other such TTDAT trackers have a horizontal primary axis and a dependent orthogonal axis.

The vertical azimuthal axis is fixed. This allows for great flexibility of the payload connection to

the ground mounted equipment because there is no twisting of the cabling around the pole.

Field layouts with tip–tilt dual axis trackers are very flexible. The simple geometry means that

keeping the axes of rotation parallel to one another is all that is required for appropriately

positioning the trackers with respect to one another. Normally the trackers would have to be

positioned at fairly low density in order to avoid one tracker casting a shadow on others when

the sun is low in the sky. Tip-tilt trackers can make up for this by tilting closer to horizontal to

minimize up-sun shading and therefore maximize the total power being collected.

The axes of rotation of many tip–tilt dual axis trackers are typically aligned either along a true

north meridian or an east west line of latitude.

Given the unique capabilities of the Tip-Tilt configuration and the appropriated controller

totally automatic tracking is possible for use on portable platforms. The orientation of the

tracker is of no importance and can be placed as needed.

Fig 3.6 Azimuth-altitude dual axis tracker - 2 axis solar tracker, Toledo, Spain.

http://en.wikipedia.org/wiki/File:Seguidor2ejes.jpg

http://en.wikipedia.org/wiki/File:EuroDishSBP_front.jpg


Point focus parabolic dish with Stirling system. The horizontally rotating azimuth table mounts

the vertical frames on each side which hold the elevation trunnions for the dish and its integral

engine/generator mount.

3.4.2.2 AZIMUTH-ALTITUDE DUAL AXIS TRACKER (AADAT)

An azimuth–altitude dual axis tracker has its primary axis (the azimuth axis) vertical to the

ground. The secondary axis (often called elevation axis) is then typically normal to the primary

axis. They are similar to tip-tilt systems in operation, but they differ in the way the array is

rotated for daily tracking. Instead of rotating the array around the top of the pole, AADAT

systems can use a large ring mounted on the ground with the array mounted on a series of

rollers. The main advantage of this arrangement is the weight of the array is distributed over a

portion of the ring, as opposed to the single loading point of the pole in the TTDAT. This

allows AADAT to support much larger arrays. Unlike the TTDAT, however, the AADAT

system cannot be placed closer together than the diameter of the ring, which may reduce the

system density, especially considering inter-tracker shading.

3.5 TRACKER TYPE SELECTION

The selection of tracker type is dependent on many factors including installation size, electric

rates, government incentives, land constraints, latitude, and local weather.

Horizontal single axis trackers are typically used for large distributed generation projects and

utility scale projects. The combination of energy improvement and lower product cost and

lower installation complexity results in compelling economics in large deployments. In addition

the strong afternoon performance is particularly desirable for large grid-tied photovoltaic

systems so that production will match the peak demand time. Horizontal single axis trackers

also add a substantial amount of productivity during the spring and summer seasons when

the sun is high in the sky. The inherent robustness of their supporting structure and the

simplicity of the mechanism also result in high reliability which keeps maintenance costs low.

Since the panels are horizontal, they can be compactly placed on the axle tube without

danger of self-shading and are also readily accessible for cleaning.

Chapter 3

Tracking System

58

A vertical axis tracker pivots only about a vertical axle, with the panels either vertical, at a

fixed, adjustable, or tracked elevation angle. Such trackers with fixed or (seasonally)

adjustable angles are suitable for high latitudes, where the apparent solar path is not

especially high, but which leads to long days in summer, with the sun travelling through a long

arc.

Dual axis trackers are typically used in smaller residential installations and locations with very

high government feed in tariffs.

3.6 SOLAR TRACKING

Fig 3.7 Tracking system

A solar tracker is a device that orients a payload toward the sun Fig.3-7. Payloads can be

photovoltaic panels, reflectors, lenses or other optical devices. In flat-panel photovoltaic (PV)

applications, trackers are used to minimize the angle of incidence between the incoming

sunlight and a photovoltaic panel. This increases the amount of energy produced from a fixed

amount of installed power generating capacity. In standard photovoltaic applications, it is

estimated that trackers are used in at least 85% of commercial installations greater than 1MW

from 2009 to 2012. Sun trackers are a great way to get maximum performance of solar


panels. Positioning solar panels in a fixed location will do the job, but you will not reach

maximum efficiency.

A tracking system can increase the output of PV system by up to30% in the summer and 15%

in the winter over non–tracked systems and the following figure shows the difference between

the fixed mode and Tracking mode of Solar Panels.

3.6.1 TRACKING MECHANICAL SYSTEM

The solar panel will be fixed in a frame which is attached to the horizontal rotatable shaft by

means of two metals which take the C form. The rotatable shaft is connected with the

bearings that is mounted on a blate (using ball bearings in order to make the rotation smooth

and free.) on the vertical fixed shaft. The vertical shaft is mounted on steel base, the steel

base is free to move by using wheels at its four corners.

The motor used is a linear actuator(DC geared motor) which convert the rotational motion to

linear motion .When the motor is ON the stroke length of the linear actuator is increased

which make the horizontal rotatable shaft to rotate in one direction and that makes the solar

panel frame to rotate. When the polarity of the source which supply the motor is reversed the

horizontal rotatable shaft to rotate in the other direction and that makes the solar panel frame

to rotate. From the previous mentioned stages with their requirements, the tracking system for

the PV string has the following characteristics:

A mono-axis tracker with the motor source disposed outside the modules (i.e. the motor does

not act directly on a module), and transmitting the motion to the modules through a

mechanism. Does not act directly on a module), and transmitting the motion to the modules

through a mechanism.

Fig 3.8 tracker

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60

The Photoconductive Cell

A Photoconductive light sensor does not produce electricity but simply changes its physical

properties when subjected to light energy. The most common type of photoconductive device

is the Photo resistor which changes its electrical resistance in response to changes in the light

intensity. Photo resistors are Semiconductor devices that use light energy to control the flow

of electrons, and hence the current flowing through them. The commonly used

Photoconductive Cell is called the Light Dependent Resistor or LDR.

3.6.2 TRACKING CONTROL SYSTEM

Fig 3.9 Block diagram

The Light Dependent Resistor

As its name implies, the Light Dependent Resistor (LDR) Fig. 3-6 is made from a piece of

exposed semiconductor material such as cadmium sulphide that changes its electrical

resistance from several thousand Ohms in the dark to only a few hundred Ohms when light

falls upon it by creating hole-electron pairs in the material.


The net effect is an improvement in its conductivity with a decrease in resistance for an

increase in illumination. Also, photo resistive cells have a long response time requiring many

seconds to respond to a change in the light intensity.

Materials used as the semiconductor substrate include, lead sulphide (PbS), lead selenide

(PbSe), indium antimonide (InSb) which detect light in the infra-red range with the most

commonly used of all photo resistive light sensors being Cadmium Sulphide (Cds).

Cadmium sulphide is used in the manufacture of photoconductive cells because its spectral

response curve closely matches that of the human eye and can even be controlled using a

simple torch as a light source. Typically then, it has a peak sensitivity wavelength (λp) of

about 560nm to 600nm in the visible spectral range.

LDR or light dependent resistor has been chosen as the sensor because LDR is commonly

used in sun tracking system. This is because LDR is sensitive to the light.

The resistance of LDR will decreases with increasing incident light intensity.

Fig 3.10 LDR sensor

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62

3.6.3 CONTROLLER

For the controller, Arduino (In its simplest form, an Arduino is a tiny computer that you can

program to process inputs and outputs going to and from the chip.) had been chosen it has

multiple I/O ports for Sensors and motors. The Arduino is what is known as a Physical or

Embedded Computing platform, which means that it is an interactive system that through the

use of hardware and software can interact with its environment. This PIC programming will

give the pulse to the driver to move the motor. For the driver, bi-directional DC motor control

using relay has been used. The motor controller had been chosen because it can control the

motor to rotate clockwise and counterclockwise easily.

The Arduino can be used to develop stand-alone interactive objects or it can be connected to

a computer to retrieve or send data to the Arduino and then act on that data (e.g. Send

sensor data out to the internet).The Arduino can be connected to LEDs. Dot Matrix displays,

LED displays, switches, motors, temperature sensors, pressure sensors, distance sensors,

webcams, printers, GPS receivers. In the case of the Arduino the language is C.

Fig 3.11 Arduino Unit

3.6.4 LINEAR ACTUATOR

The linear actuator is DC geared motor that converts the rotational motion to linear motion

and low rpm. Relay driver has been used to control the direction of the DC geared motor.


Fig 3.12 linear actuator

In our project we use Super Jack linear actuator. Super Jack Heavy Duty series actuator is

low noise, high performance actuator for motorized satellite antenna system.

3.6.5 METHODOLOGY

The project is built using a balanced concept which is two signals from the different sensors

are compared. Light Dependent Resistor (LDR) as a light sensor has been used.

The two light sensor are separated by divider which will create shadow on one side of the

light sensor if the PV panel is not perpendicular to the sun.

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64

Fig 3.13 schematic of sun position sensor

For the controlling circuit, microcontroller Arduino acts as a brain, Data received from the

sensors and processed by the microcontroller that controls the input base voltage of two

transistors (that acts as a switches) then control the coil of the relay to magnetize to change

the relay contacts.

Consequently, the movement of the Bi-directional DC-geared motor being controlled via relay.

Relay controls the rotation of the motor either to rotate clockwise or anticlockwise to ensure

solar panel is perpendicular towards the Sun, The PV panel that attached to the motor will be

reacted according to the direction of the motor.

Fig 3.14 schematic of control circuit


3.6.6 ARDUINO PROGRAME

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3.7 DISADVANTAGES

Trackers add cost and maintenance to the system - if they add 25% to the cost, and improve

the output by 25%, the same performance can be obtained by making the system 25% larger,

eliminating the additional maintenance.

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Single Phase Pulse Width Modulated Inverters

68

CHAPTER 4

SINGLE PHASE PULSE WIDTH

MODULATED INVERTERS

4.1 INTRODUCTION

The dc-ac converter, also known as the inverter as shown (fig4.1), converts dc power to ac

power at desired output voltage and frequency. The dc power input to the inverter is obtained

from an existing power supply network or from a rotating alternator through a rectifier or a

battery, fuel cell, photovoltaic array or magneto hydrodynamic generator. The filter capacitor

across the input terminals of the inverter provides a constant dc link voltage. The inverter

therefore is an adjustable-frequency voltage source. The configuration of ac to dc converter

and dc to ac inverter is called a dc-link converter.

Inverters can be broadly classified into two types, voltage source and current source

inverters. A voltage–fed inverter (VFI) or more generally a voltage–source inverter (VSI) is

one in which the dc source has small or negligible impedance. The voltage at the input

terminals is constant. A current–source inverter (CSI) is fed with adjustable current from the

dc source of high impedance that is from a constant dc source.

Fig (4.1)


A voltage source inverter employing thyristors as switches, some type of forced commutation

is required, while the VSIs made up of using GTOs, power transistors, power MOSFETs or

IGBTs, self-commutation with base or gate drive signals for their controlled turn-on and turn-

off. A standard single-phase voltage or current source inverter can be in the half-bridge or full-

bridge configuration. The single-phase units can be joined to have three-phase or multiphase

topologies. Some industrial applications of inverters are for adjustable-speed ac drives,

induction heating, standby aircraft power supplies, UPS (uninterruptible power supplies) for

computers, HVDC transmission lines, etc.

4.2 TYPES OF INVERTERS

a) The type of inverter according to Input:

1. Voltage source inverters.

2. Current source inverters.

b) The type of inverter according to the AC load:

1. Single-phase inverters.

2. Three -phase inverters.

c) The wave shape of inverter according to the AC output:

1. Sine wave.

2. Modified sine wave.

3. Square wave.

4.2.1 TYPES OF INVERTERS ACCORDING TO INPUT:

a) Voltage Source inverter

The inverter is called voltage source inverter (VSI), if the input dc is a voltage source.

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The VSI circuit has direct control over output ac voltage. Shape of voltage output waveforms

by an ideal VSI should be independent of load connected at the output.

The simplest dc voltage source may be a battery bank which may consist of several cells

connected in series-parallel combination. Solar photovoltaic cells can be another voltage

source. An ac voltage supply, after rectification into dc, will also qualify as a dc voltage

source. A voltage source is called stiff, if the source voltage magnitude does not depend on

load connected to it. All voltage source inverters assume stiff voltage supply at the input.

b) Current source Inverter (CSI)

Current source inverters, a DC source is connected to an inverter through a large series

inductor Ls .the inductor of Ls is sufficiently large that the direct current is constrained to be

almost constant.

The switch current output wave form will be roughly a square wave, since the current flow is

constrained to be nearly constant.

The line to line voltage will be approximately triangular. It is easy to limit over current in this

design but the output voltage can swing widely in response to changes in load.

The frequency of both current and voltage source inverters can be easily changed by

changing the firing pulses of the gates of the switches, so both inverters can be used to drive

ac motor at variable speeds.

Fig (4.2) sin and modified sin waves


4.2.2 TYPES OF INVERTER ACCORDING TO WAVE SHAPE OF AC OUTPUT:

Applications

a) Pure sine wave

Pure sine wave inverters produces a nearly perfect sine wave output (less than 3% total

harmonic distortion) that is essentially the same as utility-supplied grid power and are used to

operate sensitive electronic devices that require high quality waveform with little harmonic

distortion.

In addition, they have high surge capacity which means they are able to exceed their rated

wattage for a limited time. This enables power motors to start easily which can draw up to

seven times their rated wattage during startup. Virtually any electronic device will operate with

the output from a pure sine wave inverter.

Its design is more complex, and costs more per unit power, and thus it is compatible with all

AC electronic devices. This is the type used in grid-tie inverters.

b) Modified sine wave

Modified sine wave inverters (modified square wave or step wave) approximate a pure sine

waveform. Modified sine wave inverters are designed to satisfy the efficiency requirements of

the photovoltaic system while being less expensive than pure sine waveform inverters. These

inverters are capable of operating a wide variety of loads; electronic and household items

including but not limited to TV, VCR, and satellite receiver, computers, and printers.

The big advantage of the modified sine wave is that it has the same peak-to-RMS voltage

ratio as a true sine wave (RMS (2) = 1.414) while being as easy to generate as a square

wave. This has made MSW inverters very popular. They are compatible with most loads

except those unusually sensitive to the harmonic content. Costs are much cheaper than true

sine wave inverters.

Most AC motors will run on MSW inverters with an efficiency reduction of about

20% due to the harmonic content.

It's safe to say any electronic device that requires sensitive calibration can only be used with

pure sine wave inverters. For many electronic devices that don't require sensitive calibration,

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modified sine wave inverters are a more cost-effective option. Despite the drawbacks

associated with modified sine wave inverters, they are the most commonly used inverters on

the market.

c) Square wave

The earliest electronic inverters produced a square wave, which can be seen as a sine wave

sampled twice per cycle.

A square wave has a very high harmonic content and a peak-to-RMS voltage ratio of

1. Because electronic loads are usually sensitive to peak voltage while resistive loads such as

incandescent lamps respond to the RMS value, the square wave is suitable for non-sensitive

frequency loads such as resistive loads and lamps. (fig4.3)

Fig (4.3) square wave

Fig (4.4) single phase half bridge inverter.


4.3 PRINCIPLE OF OPERATION OF SINGLE-PHASE INVERTER (VSI):

One of the simplest inverter configurations is the single phase half bridge inverter shown in

(fig 4.4). The circuit consists of a pair of switches S11 and S12 connected in series across the

dc supply, and the load connected as shown.

The filter capacitor across the input terminals of the inverter provides a constant dc link

voltage. The switches S11 and S12 are controlled based on the control strategy.

Fig (4.5) Output voltage of half wave bridge inverter.

When S11 is on:

VO=VD/2.

When S12 is on:

VO=-VD/2.

The output voltage change its polarity at each switching instants resulting in an ac output

voltage that containing a very high harmonic content shown in figure (4.5).Harmonics can be

rejected by using filters.

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For single phase full wave bridge inverter: A single-phase full bridge inverter is as shown in

Figure (4.6), which consists of four switching devices, two of them on each leg. The full-bridge

inverter can produce an output power twice that of the half-bridge inverter with the same input

voltage.

When S11 and S22 is on:

VO=VD.

When S12 and S21 is on:

VO=-VD.

Fig (4.6) single-phase full bridge inverter.

Advantages of full bridge inverter over half bridge inverter:

1- Voltage gain is improved.

2- Increased load fundamental voltage.

3- Reduction in total current distortion.

4- Increased load power factor.


4.4 OVERVIEW OF POWER SEMICONDUCTOR SWITCHES USED:

To design the inverter there are number of different choices of switches. So now we have to

know what sort of switches to be used, and what control algorithm to use for switching them

on and off. The controllable switch category includes several device types including bipolar

junction transistors (BJTs), metal-oxide- semiconductor field effect transistors (MOSFETs),

thyristors, and insulated gate bipolar transistors (IGBTs).

Type of switches used:

Thyristors:

The main current flows from the anode (A) to the cathode (K).The symbol of thyristor and its

characteristic is shown in fig (4.7).

In its off-state, the thyristor can block a forward polarity voltage and not conduct.

The thyristor can be triggered into the on state by applying a pulse of positive gate current for

a short duration provided that the device is in its forward blocking state.

The forward voltage drop in the on state is only a few volts (typically 1-3 V depending on the

device blocking voltage rating).

Once the device begins to conduct, it is latched on and the gate current can be removed.

The thyristor cannot be turned off by the gate, and the thyristor conducts as a diode. Only

when the anode current tries to go negative, under the influence of the circuit in which the

thyristor is connected, does the thyristor turn off and the current go to zero.

Prosperities of thyristors as a switch:

Natural or line-commutated thyristors are available with rating up to 6000 V, 4500A.

Turn-off-time became very small (10 to 20 µs in 3000 V, 3600A).

Compared to transistors, thyristors have low on state conduction losses, and higher power

handling capability.

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On the other hand, transistors generally have superior switching performance in terms of

faster switching speed and lower switching losses.

Fig(4.7) thyristor and its VI characteristic

Bipolar Junction Transistors (BJTs):

The basic operation of a BJT as a switching device is:

The transistor is in the cutoff region because the base-emitter junction is not forward

biased. In this condition, there is ideally an open circuit between collector and emitter.

The transistor is in the saturation region because the base-emitter junction and the

base collector junction are forward- biased and the base current is made large

enough to cause the collector current to reach its saturation value. In this condition,

there is ideally a short circuit between collector and emitter, the transistor is on.

On-state voltage VCE (sat) of the power transistors is usually in the 1-2-V range, so

that the conduction power loss in the BJT is quite small.

Base current must be supplied continuously to keep them in the on state.

Disadvantages of BJT are that the bipolar transistor requires a high base current to

turn on, has relatively slow turn-off characteristics (known as current tail), and is liable

for thermal runaway due to a negative temperature co-efficient.


Used in power converters at frequency below 10 kHz

Power ratings up to 1200V, 400A.

Typical switching times are in the range of a few hundred nanoseconds to a

Few Microseconds.

It has a negative temperature coefficient of on-state resistance.

The characteristic and symbol of transistor is shown in figure (4.8).

Fig (4.8) the characteristic and symbol of transistor.

Power MOSFETs:

Operation:

This type has no physical channel, so it is in off state with zero gate-source voltage.

If we apply positive gate-source voltage, an induced voltage attracts electrons from P-type

subtract and accumulate them at the surface beneath the oxide layer. If this positive voltage is

equal or larger than the threshold voltage, sufficient numbers of electrons are accumulated to

form a virtual N-channel and the current flow from drain to source, Mosfet symbol is shown in

figure (4.9).

Fig (4.9) mosfet symbol

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78

Properties of mosfet as a switch:

Voltage controlled device and requires only small current input.

Its switching speed is very high.

It is relatively difficult to protect it under short circuit fault condition.

MOSFETs have a positive temperature coefficient, stopping thermal runaway.

The on-state-resistance has no theoretical limit, hence on-state losses can be far

lower. The MOSFET also has a body-drain diode, which is particularly useful in

dealing with limited freewheeling currents.

Used in high-speed power converters at frequency range of several tens of kHz.

Power ratings up to 1000V, 100A (relatively low power ratings).

IGBTs:

The IGBT is controlled by the gate voltage just like a MOSFET and it can be thought

of as a voltage controlled BJT, but with faster switching speeds.

Because it is controlled by voltage on the insulated gate, the IGBT has essentially no

input current and does not load the driving source.

When the gate voltage with respect to the emitter is less than a threshold voltage, the

device is turned off.

When the gate voltage with respect to the emitter is larger than a threshold voltage,

the device is turned on.

In general, the IGBT has the output switching and conduction characteristics of a

bipolar transistor but is voltage-controlled like a MOSFET.

This means it has the advantages of high-current handling capability of a bipolar with

the ease of control of a MOSFET. However, the IGBT still has the disadvantages of a

comparatively large current tail and nobody drain diode.

Used in power converters at frequency up to 20 kHz.

Power ratings up to 1700V, 2400A (high voltage high current).

Fig (4.10) IGBT symbol


All these advantages and the comparative elimination of the current tail soon mean that the

MOSFET became the device of choice for our project.

4.5 CONTROL STRATEGY

The power switches need to be driven by a suitable control circuit, allowing the controlled

commutation of the device from the “on” to the “off” state and vice versa.

Suitable drivers must be adopted, whose input is represented by the logic signals determining

the desired state of the switch and output is the power signal required to bring the switch into

that state. Now, we have to represent analog and digital methods of control that we find and

try to control the switches.

4.5.1 ANALOG METHOD:

The PWM is more general and often favored to shape the output voltage waveform.

The purpose of the PWM component of the controller is to generate pulses that trigger the

transistor switches of the inverter. The pulse-width modulated signal is created by comparing

a fundamental sine wave (vr) from a sine-wave generator with a carrier triangle wave (vc) from

a triangle wave generator as shown in (fig4.11a, 4.11b).

The variable width pulses from the PWM drives the gates of the switching transistors in the

inverter and controls the duration and frequency that these switches turn on and off. The

frequency of the fundamental sine wave of the PWM determines the frequency of the output

voltage of the inverter. The frequency of the carrier triangle wave of the PWM determines the

frequency of the transistor switches and the resulting number of square notches in the output

waveform of the inverter.

Vc is compared to Vr for each time period T, a square pulse operates the switch of the inverter

to output the fundamental waveform Vo1.

The pulse is high during the interval when the sine wave is greater than the triangle wave.

The square pulse waveform that is formed from the sine and triangle waves drive the gates of

the transistor switches in the inverter and control the duration and frequency that these

switches turn on and off as shown in fig (4.12).

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Fig (4.11a) Sine-Triangle Comparison

.

Fig (4.11b) Sine-Triangle Comparison


Fig (4.12) Switching Pulses after comparison.

4.5.2 DIGITAL METHODS

A- Multi a vibrator IC:

The multi-vibrator represented previously can be obtained by CD4047B shown in (fig 4.13),

which is capable of operating in either the monostable or astable mode. It requires an

external capacitor (between pins 1 and 3) and an external resistor (between pins 2 and 3) to

determine the output frequency in the astable mode.

Astable operation is enabled by a high level on the astable input or low level on the astable

input. The output frequency (at 50% duty cycle) at Q and Q outputs is determined by the

timing component, Typical output period or Pulse Width= ta(10, 11) = 4.40 RC

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82

Fig 4.13 multi-vibrator IC

b- 555 Timer

The 555 timer IC shown in (fig 4.14) is a very simple device to use. With very few extra

components it can be used as an ASTABLE timer. The 555 makes it easy to get accurate

time delays.

The ASTABLE circuit needs no trigger to start it. As soon as power is supplied the output will

begin to oscillate between 9 volts and 0 volts as shown in figure (4.15). The time the output

spends in each state depends on the values of R1, R2, and C.

The time the output is HIGH (9V) is called MARK and the time the output is LOW

(0V) is called SPACE. The time periods depend on the values of R1, R2 and C and can be

calculated using:-


MARK TIME=0.7*(R1+R2) *C

SPACE TIME=0.7*(R2*C)

FREQUENCY=1.44/ ((R1+2R2)*C)

Fig (4.14) LM555 IC

Fig (4.15) states of multi-vibrator

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4.6 SIMULATION RESULTS OF DIGITAL METHODS

A-multi-vibrator IC

Fig (4.16) multi-vibrator simulation

Fig (4.17) multi-vibrator simulation output


b- LM555 IC:

Fig (4.18) timer circuit

Fig (4.19) output of timer

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4.7 INVERTER USING LM555:

After trying all previous circuits and comparing their output wave shape, we

find that inverter using lm555 is the most suitable and effective one to be used

in our project.

4.8 APPLICATIONS

Uninterruptible power supplies

An uninterruptible power supply (UPS) uses batteries and an inverter to supply AC power

when main power is not available. When main power is restored, a rectifier supplies DC

power to recharge the batteries.

Induction heating

Inverters convert low frequency main AC power to higher frequency for use in induction

heating. To do this, AC power is first rectified to provide DC power. The inverter then changes

the DC power to high frequency AC power.

HVDC power transmission

With HVDC power transmission, AC power is rectified and high voltage DC power is

transmitted to another location. At the receiving location, an inverter in a static inverter plant

converts the power back to AC. The inverter must be synchronized with grid frequency and

phase and minimize harmonic generation.

Variable-frequency drives

A variable-frequency drive controls the operating speed of an AC motor by controlling the

frequency and voltage of the power supplied to the motor. An inverter provides the controlled

power. In most cases, the variable-frequency drive includes a rectifier so that DC power for

the inverter can be provided from main AC power.


Since an inverter is the key component, variable-frequency drives are sometimes called

inverter drives or just inverters.

VFDs that operate directly from an AC source without first converting it to DC are called

cycloconverters. They are now commonly used on large ships to drive the propulsion motors.

Air conditioning

An inverter air conditioner uses a variable-frequency drive to control the speed of the motor

and thus the compressor

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Chapter 5

Battery and Charger Controller

90

CHAPTER 5

BATTERY AND CHARGER

CONTROLLER

5.1 INTRODUCTION

In electricity, a battery is a device consisting of one or more electrochemical cells that convert

stored chemical energy into electrical energy. Since the invention of the first battery (or

"voltaic pile") in 1800 by Alessandro Volta and especially since the technically improved

Daniell cell in 1836, batteries have become a common power source for many household and

industrial applications. According to a 2005 estimate, the worldwide battery industry

generates US$48 billion in sales each year, with 6% annual growth.

There are two types of batteries primary batteries, this is a one-way process – the chemical

energy is converted to electrical energy, but the process is not reversible and electrical

energy cannot be converted to chemical energy. This means that a primary battery cannot be

recharged. For a secondary battery, the conversion process between electrical and chemical

energy is reversible, – chemical energy is converted to electrical energy, and electrical energy

can be converted to chemical energy, allowing the battery to be recharged. Batteries come in

many sizes, from miniature cells used to power hearing aids and wristwatches to battery

banks the size of rooms that provide standby power for telephone exchanges and computer

data centers and photovoltaic storing energy. For photovoltaic systems, batteries should be

rechargeable or secondary batteries.

5.2 STORAGE IN PV SYSTEMS

A fundamental characteristic of a photovoltaic system is that power is produced only while

sunlight is available. For systems in which the photovoltaic is the sole generation source, an

exact match between available sunlight and the load is limited to a few types of systems - for

example powering a cooling fan – and therefore storage is typically required. Even in hybrid or

grid-connected systems, where batteries are not inherently required, they may be beneficially


included for load matching or power conditioning. By far the most common type of storage is

chemical storage in the form of a battery.

However, in some cases other forms of storage can be used. For example, for small, short

term storage a flywheel or capacitor can be used for storage, or for specific, single-purpose

photovoltaic systems such as water pumping or refrigeration, the storage can be in the form

of water or ice.

In any photovoltaic system that includes batteries, the batteries have a major effect on the

system, impacting performance, cost, maintenance requirements, reliability, and design of the

photovoltaic system. The cost of the batteries in a stand-alone system is similar to the cost of

the photovoltaic modules. Because of large impact of batteries in a stand-alone photovoltaic

system, understanding the properties of batteries is critical in understanding the operation of

photovoltaic systems. The important battery parameters are the battery capacity and voltage

(and how these change and interact with other system parameters), battery maintenance

requirements, lifetime of the battery. These are controlled not only by the initial choice of the

battery but also by how it is used in the system, particularly how it is charged and discharged

and its temperature.

The primary functions of a storage battery in a PV system are to:

Energy Storage Capacity and Autonomy to store electrical energy when it is produced

by the PV array and to supply energy to electrical loads as needed or on demand.

Voltage and Current Stabilization to supply power to electrical loads at stable

voltages and currents, by suppressing or ' smoothing out' transients that may occur in

PV systems.

Supply Surge Currents to supply surge or high peak operating currents to electrical

loads or appliances.

5.3 BATTERY DESIGN AND CONSTRUCTION:

Materials and construction methods have evolved steadily, however, making modern batteries

far more powerful and reliable than their ancestors.

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Manufacturers have variations in the details of their battery construction, but some common

construction features can be described for most all batteries. Some important components of

battery construction are described below

. Terminals

Depending on the model, batteries come either with AMP Faston type terminals made of tin

plated brass, post type terminals of the same composition with threaded nut and bolt

hardware, or heavy duty flag terminals made of lead alloy.

A special epoxy is used as sealing material surrounding the terminals

. Relief valve

In case of excessive gas pressure build-up inside the battery, the relief valve will open and

relieve the pressure. The one-way valve not only ensures that no air gets into the battery

where the oxygen would react with the plates causing internal discharge, but also represents

an important safety device in the event of excessive overcharge.

Vent release pressure is between 2-6 psi; the seal ring material is neoprene rubber.

Plates (electrodes)

Power-Sonic utilizes the latest technology and equipment to cast grids from a lead-calcium

alloy free of antimony. The small amount of calcium and tin in the grid alloy imparts strength

to the plate and guarantees durability even in extensive cycle service. Lead dioxide paste is

added to the grid to form the electrically active material.

In the charged state, the negative plate paste is pure lead and that of the positive lead

dioxide. Both of these are in a porous or spongy form to optimize surface area and thereby

maximize capacity. The heavy duty lead calcium alloy grids provide an extra margin of

performance and life in both cyclic and float applications and give unparalleled recovery from

deep discharge.

Separators

Power-Sonic separators are made of non-woven glass fiber cloth with high heat and oxidation

resistance. The material further offers superior electrolyte absorption and retaining ability, as

well as excellent ion conductivity.


Case Sealing

Depending on the model the case sealing is ultrasonic, epoxy or heat seal.

Electrolyte

Immobilized dilute sulfuric acid: H2S04.

5.4 BATTERY TYPES AND CLASSIFICATIONS

Many types and classifications of batteries are manufactured today, each with specific design

and performance characteristics suited for particular applications. Each battery type or design

has its individual strengths and weaknesses. In PV systems, lead acid batteries are most

common due to their wide availability in many sizes, low cost and well understood

performance characteristics. In a few critical, low temperature applications nickel-cadmium

cells are used, but their high initial cost limits their use in most PV systems. There is no

“perfect battery” and it is the task of the PV system designer to decide which battery type is

most appropriate for each application.

Fig 5.1 battery design construction

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In general, electrical storage batteries can be divided into two major categories, primary and

secondary batteries.

5.4.1 PRIMARY BATTERIES

Primary batteries can store and deliver electrical energy, but cannot be recharged. Typical

carbon-zinc and lithium batteries commonly used in consumer electronic devices are primary

batteries. Primary batteries are not used in PV systems because they cannot be recharged.

5.4.2 SECONDARY BATTERIES

A secondary battery can store and deliver electrical energy, and can be recharged by passing

a current through it in an opposite direction to the discharge current. Common lead-acid

batteries used in automobiles and PV systems are secondary batteries.

Lead Acid Battery

Lead acid batteries, the oldest type of rechargeable batteries are still used today. Most people

today still use them quite significantly as a matter of fact, these are the batteries found in our

cars. The life expectancy of these batteries is not the greatest, but also not the worst. The

average lifespan of a car battery is about 5 to 8 years before the battery itself dies. There are

also other factors that can help to prolong the battery’s life as well. This can be seen through

the way in which lead acid batteries can be charged or recharged

There are several types of lead-acid batteries manufactured. The following sections describe

the types of lead-acid batteries commonly used in PV systems.

Lead-Antimony Batteries

Lead-antimony batteries are a type of lead-acid battery which use antimony (Sb) as the

primary alloying element with lead in the plate grids. The use of lead-antimony alloys in the

grids has both advantages and disadvantages.

Advantages include providing greater mechanical strength than pure lead grids, and excellent

deep discharge and high discharge rate performance. Lead-antimony grids also limit the

shedding of active material and have better lifetime than lead-calcium batteries when

operated at higher temperatures.


Disadvantages of lead-antimony batteries are a high self-discharge rate, and as the result of

necessary overcharge, require frequent water additions depending on the temperature and

amount of overcharge.

Lead-antimony batteries with thick plates and robust design are generally classified as motive

power or traction type batteries, are widely available and are typically used in electrically

operated vehicles where deep cycle long-life performance is required.

Lead-Calcium Batteries

Lead-calcium batteries are a type of lead-acid battery which uses calcium (Ca) as the primary

alloying element with lead in the plate grids. Like lead-antimony, the use of lead-calcium

alloys in the grids has both advantages and disadvantage.

Advantages include providing greater mechanical strength than pure lead grids, a low self-

discharge rate, and reduced gassing resulting in lower water loss and lower maintenance

requirements than for lead-antimony batteries.

Disadvantages of lead-calcium batteries include poor charge acceptance after deep

discharges and shortened battery life at higher operating temperatures and if discharged to

greater than 25% depth of discharge repeatedly.

Lead-Antimony/Lead-Calcium Hybrid

These are typically flooded batteries, with capacity ratings of over 200 ampere-hours.

A common design for this battery type uses lead-calcium tubular positive electrodes and

pasted lead-antimony negative plates. This design combines the advantages of both lead-

calcium and lead-antimony design, including good deep cycle performance, low water loss

and long life. Stratification and sulfation can also be a problem with these batteries, and must

be treated accordingly. These batteries are sometimes used in PV systems with larger

capacity and deep cycle requirements. A common hybrid battery using tubular plates is the

Exide Solar battery line manufactured in the United States.

Captive Electrolyte Lead-Acid Batteries

These which we use in our project to store the energy from PV system, because it suitable

type, easy to portable, robust, and have medium cost.

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Captive electrolyte batteries are another type of lead-acid battery, and as the name implies,

the electrolyte is immobilized in some manner and the battery is sealed under normal

operating conditions. Under excessive overcharge, the normally sealed vents open under gas

pressure. Often captive electrolyte batteries are referred to as valve regulated lead acid

(VRLA) batteries, noting the pressure regulating mechanisms on the cell vents. Electrolyte

cannot be replenished in these battery designs; therefore they are intolerant of excessive

overcharge.

Captive electrolyte lead-acid batteries are popular for PV applications because they are spill

proof and easily transported, and they require no water additions making them ideal for

remote applications were maintenance is infrequent or unavailable. It is essential that the

battery charge controller regulation set points are adjusted properly to prevent overcharging.

The charge regulation voltage should be limited to no more than 14.2 volts at 25o C for

nominal 12 volt batteries.

A benefit of captive or immobilized electrolyte designs is that they are less susceptible to

freezing compared to flooded batteries.

The two most common captive electrolyte batteries are the gelled electrolyte and absorbed

glass mat designs.

Table.4.1 Types of battery


Table.4.2 advantages and disadvantages of batteries type

5.5 BATTERY CHARGER

The primary function of a charge controller in a stand-alone PV system is to maintain the

battery at highest possible state of charge while protecting it from overcharge by the array

and from over discharge by the loads. Although some PV systems can be effectively

designed without the use of charge control, any system that has unpredictable loads, user

intervention, optimized or undersized battery storage (to minimize initial cost) typically

requires a battery charge controller. The algorithm or control strategy of a battery charge

controller determines the effectiveness of battery charging and PV array utilization, and

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ultimately the ability of the system to meet the load demands. Additional features such as

temperature compensation, alarms, meters, remote voltage sense leads and special

algorithms can enhance the ability of a charge controller to maintain the health and extend the

lifetime of a battery, as well as providing an indication of operational status to the system

caretaker.

Important functions of battery charge controllers and system controls are:

Prevent Battery Overcharge: to limit the energy supplied to the battery by the PV array when

the battery becomes fully charged.

Prevent Battery Over discharge: to disconnect the battery from electrical loads when the

battery reaches low state of charge.

Provide Load Control Functions: to automatically connect and disconnect an electrical load at

a specified time, for example operating a lighting load from sunset to sunrise.

5.5.1 OVERCHARGE PROTECTION

A photovoltaic system with battery storage is designed so that it will meet the system

electrical load requirements under reasonably determined worst-case conditions, usually for

the month of the year with the lowest isolation to load ratio. When the array is operating under

good-to-excellent weather conditions (typically during summer), energy generated by the

array often exceeds the electrical load demand. To prevent battery damage resulting from

overcharge, a charge controller is used to protect the battery. A charge controller should

prevent overcharge of a battery regardless of the system sizing/design and seasonal changes

in the load profile, operating temperatures and solar isolation.

Charge regulation is the primary function of a battery charge controller, and perhaps the

single most important issue related to battery performance and life. The purpose of a charge

controller is to supply power to the battery in a manner which fully recharges the battery

without overcharging. Without charge control, the current from the array will flow into a battery

proportional to the irradiance, whether the battery needs charging or not. If the battery is fully

charged, unregulated charging will cause the battery voltage to reach exceedingly high levels,

causing severe gassing, electrolyte loss, internal heating and accelerated grid corrosion. In


most cases if a battery is not protected from overcharge in PV system, premature failure of

the battery and loss of load are likely to occur.

Charge controllers prevent excessive battery overcharge by interrupting or limiting the current

flow from the array to the battery when the battery becomes fully charged.

Charge regulation is most often accomplished by limiting the battery voltage to a maximum

value, often referred to as the voltage regulation (VR) set point.

Sometimes, other methods such as integrating the ampere-hours into and out of the battery

are used.

Depending on the regulation method, the current may be limited while maintaining the

regulation voltage, or remain disconnected until the battery voltage drops to the array

reconnect voltage (ARV) set point. A further discussion of charge regulation strategies set

points is contained later in this chapter.

5.5.2 OVER DISCHARGE PROTECTION

During periods of below average isolation and/or during periods of excessive electrical load

usage, the energy produced by the PV array may not be sufficient enough to keep the battery

fully recharged. When a battery is deeply discharged, the reaction in the battery occurs close

to the grids, and weakens the bond between the active materials and the grids. When a

battery is excessively discharged repeatedly, loss of capacity and life will eventually occur. To

protect batteries from over discharge, most charge controllers include an optional feature to

disconnect the system loads once the battery reaches a low voltage or low state of charge

condition.

In some cases, the electrical loads in a PV system must have sufficiently high enough voltage

to operate. If batteries are too deeply discharged, the voltage falls below the operating range

of the loads, and the loads may operate improperly or not at all. This is another important

reason to limit battery over discharge in PV systems.

Over discharge protection in charge controllers is usually accomplished by open circuiting the

connection between the battery and electrical load when the battery reaches a pre-set or

adjustable low voltage load disconnect (LVD) set point. Most charge controllers also have an

indicator light or audible alarm to alert the system user/operator to the load disconnect

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condition. Once the battery is recharged to a certain level, the loads are again reconnected to

a battery.

Non-critical systems loads are generally always protected from over discharging the battery

by connection to the low voltage load disconnect circuitry of the charge controller. If the

battery voltage falls to a low but safe level, a relay can open and disconnect the load,

preventing further battery discharge. Critical loads can be connected directly to the battery, so

that they are not automatically disconnected by the charge controller.

However, the danger exists that these critical loads might over discharge the battery.

An alarm or other method of user feedback should be included to give information on the

battery status if critical loads are connected directly to the battery.

5.6 CHARGE CONTROLLER TERMINOLOGY AND DEFINITIONS

Charge regulation is the primary function of a battery charge controller, and perhaps the

single most important issue related to battery performance and life. The purpose of a charge

controller is to supply power to the battery in a manner to fully recharge the battery without

overcharging. Regulation or limiting the PV array current to a battery in a PV system may be

accomplished by several methods. The most popular method is battery voltage sensing,

however other methods such as amp hour integration are also employed.

Generally, voltage regulation is accomplished by limiting the PV array current at a predefined

charge regulation voltage. Depending on the regulation algorithm, the current may be limited

while maintaining the regulation voltage, or remain disconnected until the battery voltage

drops to the array reconnect set point.

While the specific regulation method or algorithm varies among charge controllers, all have

basic parameters and characteristics. Charge controller manufacturer's data generally

provides the limits of controller application such as PV and load currents, operating

temperatures, parasitic losses, set points, and set point hysteresis values. In some cases the

set points may be dependent upon the temperature of the battery and/or controller, and the

magnitude of the battery current. A discussion of basic charge controller terminology follows:


Charge Controller Set Points:

The battery voltage levels at which a charge controller performs control or switching functions

are called the controller set points. Four basic control set points are defined for most charge

controllers that have battery overcharge and over discharge protection features. The voltage

regulation (VR) and the array reconnect voltage (ARV) refer to the voltage set points at which

the array is connected and disconnected from the battery. The low voltage loads disconnect

(LVD) and load reconnect voltage (LRV) refers to the voltage set points at which the load is

disconnected from the battery to prevent over discharge. A detailed discussion of each

charge controller set point follows.

High Voltage Disconnect (HVD) Set Point

The high voltages disconnect (HVD) set point is one of the key specifications for charge

controllers. The voltage regulation set point is the maximum voltage that the charge controller

allows the battery to reach, limiting the overcharge of the battery.

Once the controller senses that the battery reaches the voltage regulation set point, the

controller will either discontinue battery charging or begin to regulate the amount of current

delivered to the battery.

Array Reconnect Voltage (ARV) Set Point

In interrupting (on-off) type controllers, once the module or array current is disconnected at

the voltage regulation set point, the battery voltage will begin to decrease. If the charge and

discharge rates are high, the battery voltage will decrease at a greater rate when the battery

voltage decreases to a predefined voltage, the module is again reconnected to the battery for

charging. The voltage at which the module is reconnected is defined as the array reconnects

voltage (ARV) set point.

Voltage Regulation Hysteresis (VRH)

The voltage differences between the high voltages disconnect set point and the array

reconnect voltage is often called the voltage regulation hysteresis (VRH). The VRH is a major

factor which determines the effectiveness of battery recharging for interrupting (on-off) type

controller. If the hysteresis is too big, the module current remains disconnected for long

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periods, effectively lowering the module energy utilization and making it very difficult to fully

recharge the battery. If the regulation hysteresis is too small, the module will cycle on and off

rapidly. Most interrupting (on-off) type controllers have hysteresis values between 0.4 and 1.4

volts for nominal 12 volts systems.

Low Voltage Load Disconnect (LVD) Set Point

Deep discharging the battery can make it susceptible to freezing and shorten its operating life.

If battery voltage drops too low, due to prolonged bad weather or certain non-essential loads

are connected the charge controller disconnected the load from the battery to prevent further

discharge. This can be done using a low voltage load disconnect (LVD) device is connected

between the battery and non-essential loads. The LVD is either a relay or a solid-state switch

that interrupts the current from the battery to the load.

Load Reconnect Voltage (LRV) Set Point

The battery voltage at which a controller allows the load to be reconnected to the battery is

called the load reconnect voltage (LRV). After the controller disconnects the load from the

battery at the LVD set point, the battery voltage rises to its open circuit voltage. When the PV

module connected for charging, the battery voltage rises even more. At some point, the

controller senses that the battery voltage and state of charge are high enough to reconnect

the load, called the load reconnect voltage set point. LRV should be 0.08 V/cell (or 0.5 V per

12 V) higher than the load disconnection voltage. Typically LVD set points used in small PV

systems are between 12.5 volts and 13.0 volts for most nominal 12 volt lead-acid battery. If

the LRV set point is selected too low, the load may be reconnected before the battery has

been charged.

Low Voltage Load Disconnect Hysteresis (LVLH)

The voltage difference between the low voltage disconnect set point and the load reconnect

voltage is called the low voltage disconnect hysteresis. If the low voltage disconnect

hysteresis is too small, the load may cycle on and off rapidly at low battery state-of-charge

(SOC), possibly damaging the load or controller, and extending the time it required to charge


the battery fully. If the low voltage disconnect hysteresis is too large the load may remain off

for extended periods until the array fully recharges the battery.

5.7 BUCK CONVERTER

A buck converter is a step-down DC to DC converter. Its design is similar to the step-up boost

converter, and like the boost converter it is a switched-mode power supply that uses two

switches (a transistor and a diode), an inductor and a capacitor.

Fig 5.2 buck converter

Basic Operation of Buck Converter

Method 1: During ON state

When the switch is in ON state, diode become as reversed biased and the inductor will deliver

current and switch conducts inductor current. With the voltage (Vin -Vo) across the inductor,

the current rises linearly (current changes, ΔiL).

The current through the inductor increase, as the source voltage would be greater than the

output voltage and capacitor current may be in either direction depending on the inductor

current and load current. When the current in inductor increase, the energy stored also

increased. In this state, the inductor acquires energy. Capacitor will provides smooth out of

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inductor current changes into a stable voltage at output voltage and it’s big enough such that

V out doesn’t change significantly during one switching cycle.

As can see in Fig.5.3 when the switch is in OFF state, the diode is ON and the inductor will

maintains current to load. Because of inductive energy storage, IL will continue to flow. While

inductor releases current storage, it will flow to the load and provides voltage to the circuit.

The diode is forward biased. The current flow through the diode which is inductor voltage is

equal with negative output voltage.

Fig.5.3 Modes of operation of buck converter

5.8 BOOST CONVERTER

A boost converter (step-up converter) is a DC-to-DC power converter with an output voltage

greater than its input voltage. It is a class of switched-mode power supply (SMPS) containing

at least two semiconductor switches (a diode and a transistor) and at least one energy

storage element, a capacitor, inductor, or the two in combination.


Fig.5.4 Boost converter

Filters made of capacitors (sometimes in combination with inductors) are normally added to

the output of the converter to reduce output voltage ripple.

Operating principle

In a boost converter, the output voltage is always higher than the input voltage. A schematic

of a boost power stage is shown in Fig 5.5.

(a) When the switch is closed, current flows through the inductor in clockwise direction and

the inductor stores the energy. Polarity of the left side of the inductor is positive.

(b) When the switch is opened, current will be reduced as the impedance is higher.

Therefore, change or reduction in current will be opposed by the inductor. Thus the polarity

will be reversed (means left side of inductor will be negative now). As a result two sources will

be in series causing a higher voltage to charge the capacitor through the diode D.

Fig.5.5 modes of operation of boost converter

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If the switch is cycled fast enough, the inductor will not discharge fully in between charging

stages, and the load will always see a voltage greater than that of the input source alone

when the switch is opened. Also while the switch is opened, the capacitor in parallel with the

load is charged to this combined voltage. When the switch is then closed and the right hand

side is shorted out from the left hand side, the capacitor is therefore able to provide the

voltage and energy to the load. During this time, the blocking diode prevents the capacitor

from discharging through the switch. The switch must of course be opened again fast enough

to prevent the capacitor from discharging too much.

The two configurations of a boost converter, depending on the state of the switch S.

The basic principle of a Boost converter consists of 2 distinct states:

In the On-state, the switch S (see figure 1) is closed, resulting in an increase in the

inductor current;

In the Off-state, the switch is open and the only path offered to inductor current is

through the fly-back diode D, the capacitor C and the load R. These results in

transferring the energy accumulated during the On-state into the capacitor.

The input current is the same as the inductor current.

So it is not discontinuous as in the buck converter and the requirements on the input

filter are relaxed compared to a buck converter.

Fig.5.6 Buck-Boost converter

5.9 BUCK-BOOST CONVERTER

The buck–boost converter is a type of DC-to-DC converter that has an output voltage

magnitude that is either greater than or less than the input voltage magnitude.


Fig.5.7 Modes of operation of buck-boost converter

Principle of operations

The two operating states of a buck–boost converter: When the switch is turned-on, the input

voltage source supplies current to the inductor, and the capacitor supplies current to the

resistor (output load).When the switch is opened, the inductor supplies current to the load via

the diode D.

The basic principle of the buck–boost converter is fairly simple:

While in the On-state, the input voltage source is directly connected to the inductor (L). This

results in accumulating energy in L. In this stage, the capacitor supplies energy to the output

load.

While in the Off-state, the inductor is connected to the output load and capacitor, so energy is

transferred from L to C and R.

5.11 SYSTEM DESIGN

The photovoltaic (PV) charge controller was designed to protect the rechargeable battery. To

design this PV charge controller, it consists of seven parts where the first part is a buck

converter circuit, second part is a microcontroller circuit, third part is a driver circuit, four part

is rechargeable battery, five part is voltage sensor, six part is current sensor and seven part is

liquid crystal display, LCD.

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108

Fig.5.8 charge controller design

Chapter 6

Simulation and Practical Results

110

CHAPTER 6

SIMULATION AND PRACTICAL

RESULTS 6.1 CONTROL CIRCUIT FOR TRACKING SYSTEM

6.1.1 SIMULATION

Fig (6.1) control circuit for tracking system

6.1.2 PRACTICAL CIRCUIT (CONTROL CIRCUIT USING DC DRIVE L298)

Fig (6.2) practical circuit (control circuit using DC drive L298)


6.1.3 CONTROL CIRCUIT USING TRANSISTOR AND RELAYS

Fig (6.3) control circuit using transistors and relays

COMMENT

Control circuit using drive is more reliable and efficient therefore we use it in our

project.

6.1.4 PCB CIRCUIT

Fig (6.4) pcp circuit

Chapter 6


112

6.2 TRACKING SYSTEM (PRACTICAL)

6.2.1 SINGLE AXIS PV TRACKING

Fig (6.5) single axis pv tracking

6.2.2 DUAL AXIS PV TRACKING

Fig. (6.6) Dual axis PV tracking


6.3 COMPARISON BETWEEN FIXED AND TRACKING SOLAR PANEL

6.3.1 FIXED SOLAR PANEL

Fig (6.7a) V-I curve at 11 am Fig (6.7.b) V-P curve at 11 am

TIME VOLTAGE CURRENT POWER

12 P.M 0 7.4 0

26.1 6.5 179.65

28.24 4.7 132.728

31.74 0 0

Time Voltage Current power

11 a.m 0 7.8 0

26.8 6.7 179.56

28.9 4.7 135.83

32.32 0 0

0 5 10 15 20 25 30 350

20

40

60

80

100

120

140

160

180

VOLTAGE

PO

WE

R

0 5 10 15 20 25 30 350

1

2

3

4

5

6

7

8

volage

curr

ent

Chapter 6


114

Fig (6.8.a) V-I curve at 12 pm Fig (6.8.b) V-P curve at 12 pm


1 P.M 0 6.8 0

24.8 6.33 156.984

27.8 4.66 129.68

31.66 0 0


Time Voltage Current Power

2 p.m 0 8.08 0

19.5 5.8 104

26.85 4.57 122

30 0 O

0 5 10 15 20 25 30 350

1

2

3

4

5

6

7

8

VOLTAGE

CU

RR

EN

T

0 5 10 15 20 25 30 350

20

40

60

80

100

120

140

160

180

VOLTAGE

PO

WE

R

0 5 10 15 20 25 30 350

1

2

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6

7

voltage

curr

ent

0 5 10 15 20 25 30 350

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40

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80

100

120

140

160

voltage

pow

er




3 p.m 0 5.2 0

9.7 3.8 36.68

19.26 3.7 71.262

31.8 0 0


Time(hour) 11 a.m 12 p.m 1 p.m 2 p.m 3 p.m

Power(watt) 135.83 132.728 129.68 122 71.262

Average power=117.7 w

Efficiency=53%

0 5 10 15 20 25 30 350

1

2

3

4

5

6

7

8

9

voltage

curr

ent

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voltage

pow

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Chapter 6


116

Fig (6.12) T-P curve

6.3.2 SINGLE AXIS TRACKING SOLAR PANEL


11 a.m 0 8.1 0

27.1 6.9 186.69

29.3 5 146

33.5 0 0


11 11.5 12 12.5 13 13.5 14 14.5 1570

80

90

100

110

120

130

140

time(hour)

pow

er(w

att)

0 5 10 15 20 25 30 350

1

2

3

4

5

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8

9

voltage

curr

ent

0 5 10 15 20 25 30 350

20

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180

200

voltage

pow

er



12 p.m 0 7.7 0

26.4 6.8 179.52

28.9 5 144.5

32.2 0 0


Time Voltage current Power

1 p.m 0 7.1 0

25.1 6.7 168.17

28.3 4.9 138.67

32 0 0



2 P.M 0 8.28 0

19.8 6.1 120.78

27.1 4.8 130.08

30.2 0 0

0 5 10 15 20 25 30 350

1

2

3

4

5

6

7

8

voltage

curr

ent

0 5 10 15 20 25 30 350

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voltage

pow

er

0 5 10 15 20 25 30 350

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voltage

curr

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20

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voltage

pow

er

Chapter 6


118


Time voltage Current Power

3 p.m o 5.5 0

9.9 4.1 38.61

19.46 3.9 75.894

32 0 0


Average power=127.08 w

Efficiency=57%

0 5 10 15 20 25 30 350

5

10

15

20

25

30

voltage

curr

ent

0 5 10 15 20 25 30 350

20

40

60

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100

120

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voltage

pow

er

0 5 10 15 20 25 30 350

1

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curr

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voltage

pow

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Power(watt) 149.43 148.196 145.6 134.933 78.24



6.3.3 DUAL AXIS TRACKING SOLAR PANEL

Time voltage Current Power

11 a.m 0 8.2 0

27.2 7.1 139.12

29.3 5.1 149.43

32.72 0 0



12 p.m 0 7.8 0

26.5 6.9 182.85

28.74 5.1 143.7

32.1 0 0

11 11.5 12 12.5 13 13.5 14 14.5 1570

80

90

100

110

120

130

140

150

time(hour)

powe

r(wat

t)

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50

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voltage

pow

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voltage

curr

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Chapter 6


120


Time Voltage current Power

1 p.m 0 7.1 0

25.2 6.7 168.84

28 5.2 145.6

34 0 0


Time voltage current Power

2 p.m 0 8.28 0

19.9 6.2 123.38

27.15 4.97 134.9335

30.4 0 0

0 5 10 15 20 25 30 350

1

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3

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voltage

curr

ent

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curr

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voltage

pow

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3 p.m 0 5.6 0

10.1 4.2 42.42

19.56 4 78.24

32.2 0 0


0 5 10 15 20 25 30 350

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40

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voltage

pow

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curr

ent

0 5 10 15 20 25 30 350

10

20

30

40

50

60

70

80

voltage

pow

er

Chapter 6


122


Power(watt) 149.43 148.196 145.6 134.933 78.24

Average power=131.28w

Efficiency=59.67%


6.3.4 DUAL AXIS WITH COOLING SYSTEM

Time Voltage Current power

11 a.m 0 8.2 0

27.2 7.3 198.56

29.3 5.3 155.29

32.92 0 0


11 11.5 12 12.5 13 13.5 14 14.5 1570

80

90

100

110

120

130

140

150

time (hour)

pow

er(

watt

)

0 5 10 15 20 25 30 350

20

40

60

80

100

120

140

160

180

200

voltage

pow

er

0 5 10 15 20 25 30 350

1

2

3

4

5

6

7

8

9

voltage

curr

ent



12 p.m 0 7.9 0

26.7 7.1 189.57

28.84 5.4 155.536

32.3 0 0



1 p.m 0 7.4 0

25.4 6.99 177.546

28.5 5.2 148.2

32.46 0 0p



2 p.m 0 8.48 0

20.1 6.4 128.64

27.45 5.1 139.995

30.6 0 0

0 5 10 15 20 25 30 350

20

40

60

80

100

120

140

160

180

200

voltage

pow

er

0 5 10 15 20 25 30 350

1

2

3

4

5

6

7

8

voltage

curr

ent

0 5 10 15 20 25 30 350

20

40

60

80

100

120

140

160

180

voltage

pow

er

0 5 10 15 20 25 30 350

1

2

3

4

5

6

7

8

curr

ent

voltage

Chapter 6


124



3 p.m 0 5.8 0

10.3 4.4 45.32

19.86 4.1 81.426

32.4 0 0


Time 11 a.m 12 p.m 1 p.m 2 p.m 3 p.m

Power 155.29 152.12 148.2 138.17 81.426

Average power=135.04%

Efficiency=61%

0 5 10 15 20 25 30 350

1

2

3

4

5

6

7

8

9

voltage

curr

ent

0 5 10 15 20 25 30 350

20

40

60

80

100

120

140

voltage

pow

er

0 5 10 15 20 25 30 350

10

20

30

40

50

60

70

80

90

voltage

pow

er

0 5 10 15 20 25 30 350

1

2

3

4

5

6

voltage

curr

ent



6.4 POWER VS TIME FOR FIXED AND TRACKING SYSTEM

Time (hour) Fixed(watt) Single

axis(watt)

Dual axis(watt) Dual axis with

cooling

system (watt)

11 a.m 135.83 W 146.2 W 149.43 W 155.29 W

12 p.m 132.728 W 144.5 W 148.196 W 152.12 W

1 p.m 129.68 W 138.67 W 145.6 W 148.2 W

2 p.m 122 W 130.08 W 134.933 W 138.17 W

3 p.m 71.262 W 75.894 W 78.24 W 81.426 W

11 11.5 12 12.5 13 13.5 14 14.5 1580

90

100

110

120

130

140

150

160

time(hour)

pow

er(w

att)

Chapter 6


126

Fig (6.31) T-P curve for fixed and tracking

COMMENTS

From tables and calculations as compared to fixed PV

. By using single axis, power has increased by 6.7%.

. By using dual axis, power has increased by 10.6%

. By using dual axis and tracking, power has increased by 11.2%

6.5 INVERTER USING LM555

6.5.1 SIMULATION RESULT

11 11.5 12 12.5 13 13.5 14 14.5 1570

80

90

100

110

120

130

140

150

160

time (hour)

pow

er(w

att)

fixed

single axis

dual axis

with cooling


6.5.2 PCB CIRCUIT

6.5.3 PRACTICAL CIRCUIT AND RESULT

Chapter 6


128

130

CONCLUSION In this project work a sun tracker has been developed to increase the amount of power

generated by the solar panel by using two-axis tracking system.

The system was designed, as automatic system such that energy generated by solar

panel would be maximum.

The tracking mechanism is capable of tracking the sun automatically so that the

direction of beam propagation of solar radiation is perpendicular to the PV panel.

From the results of the performance test of designed system the following conclusion

can be drawn.

1. Mechanical set up characterizes the tracker and micro controller operated control

system. During its relatively short time of operation, it proved to be fairly precise and

reliable, even in adverse weather conditions.

2. The designed solar tracker automatically follows the sun path according to the

direction of beam propagation of solar radiation.

3. The excess output-power of the tracking solar panel with respect to fixed panel was

30-45% at average solar intensity of 1000% w/m2.

4. I.V characteristics also tested from PV cell outputs ,which approximately meet the

ideal characteristics curve.it was observed that at high temperature PV cell

performance becomes low.

5. The use of software outside the mechanical part makes the tracker flexible for future

development

6. Design simplicity, low cost and material availability will make the designed tracking

system more effective and competitive to other designed system.

7. The developed tracking mechanism can used efficiently to orient other concentrating

collectors such as parabolic dish collectors.


Considering all above aspects of this tracking system it can be concluded that, it is

flexible tracking system with low cost electromechanical set-up, low maintenance

requirements and ease of installation and operation.

Dual axis solar tracking system prototype model is successfully developed. The

designed system is focus on designing controller part and main concern is to design

appropriate circuits and circuits supposed to be able to control two DC-gear motor

rotation direction without considering motor speed.

The system is able to track and follow sun light intensity in order to collect maximum

solar power regardless of motor speed. The unique of developed system, motor speed

is not critical consideration because the DC -geared motors offers low output rated

speed and high output rated torque.


APPENDIX

Component used Number of component

PV module 220w 1

500w inverter 1

HEF4049BE inverting IC 1

LM555 timer 1

Aurdino UNO 1

Capactor (.1uf) 2

Capacitor (.01uf) 4

L298 drive 1

Voltage regulator L7815 2




N channel mosfet FQP20n06l 2

DC-Servo Motor 2

Solar charge controller 1

Lead acid battery 2


REFERENCES [1] Wikipedia, “Wind Power,” Wikimedia Foundation. 2007. Last Retrieved

March 30, 2007 from http://en.wikipedia.org/wiki/Wind_power

[2] Wind and Hydropower Technologies Program, “Advantages and

Disadvantages of Wind Energy,” U.S. Department of Energy. August 2005.

Last Retrieved March 31, 2007.

http://www1.eere.energy.gov/windandhydro/wind_ad.html

[3] T. Hammons, “Geothermal Power Generation Worldwide,” Power Tech

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[4] S. Sheth, M. Shahidehpour, “Geothermal Energy in Power Systems,” Power

Engineering Society General Meeting. Volume 2, Pg. 1972-1977. June 2004.

[5] Citizens and Scientists for Environmental Solutions, “How Hydroelectric

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renewable_energy_basics/how-hydroelectric-energy-works.html

[6] A. Darvill, “Hydro-electric power is generated from falling water,” Energy

Resources. December 2006. Last Retrieved March 19, 2007.

http://home.clara.net/darvill/altenerg/hydro.html

[7] T. Penick, B. Louk, “Photovoltaic Power Generation,” TEI

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PhotovoltaicPowerGeneration.pdf

[8] William David Lubitz, "Effect of Manual Tilt Adjustments on Incident

Irradiance on Fixed and Tracking Solar Panels", Applied Energy, Volume 88

(2011), pp. 1710-1719

[9] Ignacio Luque-Heredia et al., "The Sun Tracker in Concentrator

Photovoltaics" in Cristobal, A.B.,Martí, A.,and Luque, A. Next Generation

Photovoltaics, Springer Verlag, 2012

[10] B. Sc. Final Year Project “PV Tracking System and Inverter”, Egypt,

Qena, South Valley university, Faculty of Engineering 2013

Documents

PV Tracking System - South Valley University Tracking System.pdf · PV Tracking System I Essam Ahmed Refaat Abdellah Sherkawy Basma Ahmed Aia Khalil Mustafa Mahmoud Mohammed Marwa