DEVELOPMENT OF SMART PV TRAVEL PHONE CHARGER

NIK MOHD FARID BIN NIK IBRAHIM

UNIVERSITY MALAYSIA PAHANG

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ABSTRACT

Solar energy is a one of the alternative renewable energy resource. The energy

resource which directly produced by the sun can be converted to electricity by using

solar cell. The applications that using photovoltaic technology is a solar cell phone

travel phone charger. Solar cell phone charger can save energy compared to electric

socket cell phone charger besides not contributing to environmental pollution. The

weakness of this type of energy is it‟s depending on the existence or the brightness of

sunlight. The project aims to develop charging cell phone using Photovoltaic (PV)

otherwise to minimize electricity energy usage. The project also includes different

from conversional phone charger due to this travel phone charger have storage

battery to always be used when needed at certain times. In addition, this project using

the buck converter circuit to monitor the voltage level of the continuous at rated 5

Volt even of the input voltage from solar cell is constantly changing. If the voltage

from solar cell exceeds the permissible limits, its will be stabilized by using solar

charge controller (SCC) to maintain and the voltage can be set to normal state using

LM 2574 as step-down converter function. Thus the device will obtain a continuous

power and protected from the effects of under voltage and overvoltage.

Furthermore, this travel phone charger is also equipped PIC16F688 for the display

using LCD in order to reading of the storage battery can always be observed during

the running.

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ABSTRAK

Tenaga solar merupakan salah satu sumber tenaga alternatif yang boleh diperbaharui.

Sumber tenaga yang dihasilkan secara terus oleh sinaran cahaya matahari ini boleh

ditukar menjadi tenaga elektrik dengan menggunakan Photovoltaic (PV) yang juga

di kenali sebagai sel solar. Antaranya salah satu aplikasi yang meggunakan sistem ini

ialah pengecas bateri telefon mudah alih. Pengecas bateri solar ini boleh

menjimatkan tenaga berbanding pengecas soket elektrik yang sedia ada disamping

tidak menyumbang kepada pencemaran alam sekitar. Kelemahan sumber tenaga ini

adalah disebabkan kebergantungan kepada kehadiran atau kecerahan pada cahaya

matahari. Tujuan projek ini adalah untuk membangunkan pengecas bateri telefon

mudah alih dengan menggunakan Photovoltaic (PV) dalam hal lain untuk

mengurangkan kebergantungan kepada penggunaan tenaga elektrik. Projek ini juga

mempunyai kelainan daripada pengecas konvensional kerana pengecas telefon

mudah alih ini mempunyai bateri simpanan agar sentiasa dapat digunakan apabila

diperlukan pada waktu-waktu tertentu. Selain itu, projek ini menggunakan kaedah

iaitu litar penukar perendah untuk memerhati tahap voltan dari sel solar secara

berterusan pada kadar 5 Volt walaupun voltan masukan dari sel solar sentiasa

berubah. Jika voltan dari sel solar melebihi tahap yang dibenarkan, voltan tersebut

akan ditetapkan kepada keadaan normal menggunakan kawalan pengecas solar

(SCC) untuk kekalkan dan voltan akan di tetapkan kepada keadaan normal dengan

menggunakan LM2574 iaitu bertindak sebagai fungsi penukar perendah. Disebabkan

itu, alatan akan mendapat tenaga yang berterusan dan dilindungi dari kesan akibat

kekurangan voltan dan lebihan voltan. Disamping itu, pengecas mudah alih ini juga

dilengkapi PIC16F688 untuk paparan LCD supaya bacaan pada bateri simpanan

sentiasa dapat diperhatikan sepanjang proses berjalan.

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TABLE OF CONTENTS

CHAPTER TITLE PAGE

DECLARATION I

DEDICATION II

ACKNOWLEDGEMENT III

ABSTRACT IV

ABSTRAK V

TABLE OF CONTENTS VI

LIST OF TABLES X

LIST OF FIGURES XI

LIST OF SYMBOLS XIV

LIST OF APPENDICES XV

1 INTRODUCTION 1

1.1 Background 1

1.1.1 Advantages of Alternative Cell

Phone Charger Using Photovoltaic 2

1.2 Objective 2

1.3 Scope 2

1.4 System Description 3

1.5 Problem statement 5

1.6 Outline of Thesis 6

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2 LITERATURE REVIEW 8

2.1 Solar Energy 8

2.1.1 Advantages of Solar Energy 9

2.2 Photovoltaic (PV) Cell 10

2.2.1 Advantages of Photovoltaic Systems 14

2.3 DC-DC Converter 14

2.3.1 Buck Converter (Step-down) 14

2.3.2 Basic operation of Buck Converter 15

2.4 Battery charger using Electricity 16

2.5 Battery charger using Photovoltaic (PV) 17

2.6 Lithium-Ion Battery 18

2.7 Lead-Acid Battery 21

2.8 Integrated circuit (IC) LM2574 24

2.9 Solar charge controller 27

3 RESEARCH METHODOLOGY 30

3.1 Introduction 30

3.2 Hardware Development 30

3.3 Overall System Design using LM2574 32

3.4 Overall System Design using PIC

Microcontroller 33

3.5 Software Development 34

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4 RESULT AND DISCUSSION 40

4.1 Introduction 40

4.2 Result and Discussion 40

4.2.1 Software 41

4.2.1.1 Software using ISIS Proteus for

PIC16F688 41

4.2.1.2 Power supply circuit for PIC 42

4.2.2 Hardware 43

4.2.2.1 Hardware using Buck converter 43

4.2.2.2 Hardware using PIC based Digital

Voltmeter and LCD Displays 47

4.3 Data

4.3.1 Data for Photovoltaic Panel 52

4.3.2 Data for Battery Storage (Lead-Acid) 56

4.3.3 Data for Charging Voltage (Lead-Acid) 61

4.3.4 Data comparison type of Phone Charger 65

5 CONCLUSION AND RECOMMENDATIONS 66

5.1 Conclusions 66

5.2 Recommendations 67

REFERENCES 68

APPENDICES 70

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APPENDIX A (Gantt Chat PSM 1 and PSM 2) 71

APPENDIX B (Software using C Language Micro C Pro for PIC) 72

APPENDIX C (PIC16F688 Datasheet) 74

APPENDIX D (LM2574 Datasheet) 77

APPENDIX E (LM7805 Datasheet) 87

APPENDIX F (Lead Acid Battery Datasheet) 97

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LIST OF TABLES

TITLE NO. TITLE PAGE

Table 4.1 Pin out of LCD Display 50

Table 4.2 Data for Solar Panel

52

Table 4.3 Data for Solar Panel (12 hours)

54

Table 4.4 Data for Battery Storage (1 hours) 56

Table 4.5 Data for Battery Storage (12 hours) 59

Table 4.6 Data for Charging Voltage

61

Table 4.7 Data of comparison

65

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LIST OF FIGURES

FIGURE NO. TITLE PAGE

Figure 1.1 Global Block Diagram – Development of

Smart PV Travel Phone Charger 3

Figure 2.1 Ideal I-V curve for a PV cell 10

Figure 2.2 Typical current voltage I-V curve 11

Figure 2.3 PV cell, modules and array 12

Figure 2.4 Photovoltaic cell 13

Figure 2.5 A basic buck converter topology circuit 15

Figure 2.6 Equivalent circuit for switch closed 16

Figure 2.7 Equivalent circuit for switch opens 16

Figure 2.8 Charger battery by using electricity 17

Figure 2.9 Charger battery by using Photovoltaic (PV) 18

Figure 2.10 Li-ion battery 20

Figure 2.11 Lead-acid rechargeable battery 21

Figure 2.12 Discharge curves for one cell of each of the five

main types of rechargeable battery compared a

typical discharge rates 22

Figure 2.13 Block diagram and typical application 25

Figure 2.14 Typical performance characteristics 26

Figure 2.15 Solar charge controller 27

Figure 2.16 Insolation performance of a PV array 28

Figure 2.17 Temperature performance of PV array 28

Figure 2.18 Connections Solar Charge Controller with

Buck converter 29

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Figure 3.1 Process hardware development 31

Figure 3.2 Pin of LM2574 32

Figure 3.3 Block diagram when using LM2574 (Buck

converter) 32

Figure 3.4 Circuit using PIC microcontroller 33

Figure 3.5 Block diagram using PIC microcontroller 34

Figure 3.6 Project flow for PIC 35

Figure 3.7 PIC kit 2 Programmer Software 38

Figure 3.8 Import hex file with successfully 39

Figure 3.9 Position of PIC at USB Programmer 39

Figure 4.1 Simulation by ISIS Proteus for LCD display

(For 0V) 41

Figure 4.2 Simulation by ISIS Proteus for LCD display

(Increased until 6V) 42

Figure 4.3 Simulation by ISIS Proteus for Power supply

circuit 43

Figure 4.4 Buck converter complete design 43

Figure 4.5 Buck converter charging schematic design 44

Figure 4.6(a) Simulation circuit by using Target 3001 45

Figure 4.6(b) Verify of the output 5V using buck converter 45

Figure 4.6(c) Testing circuit for measure output 5V at USB 46

Figure 4.7 Digital Voltmeter hardware testing process 47

Figure 4.8 Testing process to verify value using Digital

Voltmeter and Multimeter 48

Figure 4.9 Pin out of LCD Display 49

Figure 4.10 LCD Contrast connection 51

Figure 4.11 LCD Contrast (Slow contrast) 51

Figure 4.12 LCD Contrast (High contrast) 51

Figure 4.13 Graf for Solar Panel (Voltage vs. Time) 52

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Figure 4.14 Graf for Solar Panel (Current vs. Time) 53

Figure 4.15 Graf for Solar Panel (Voltage vs. Time) for

12 hours 54

Figure 4.16 Solar Panel position side A 55

Figure 4.17 Solar Panel position side B 55

Figure 4.18 NPH Discharge Characteristic curves 57

Figure 4.19 Graf for Battery Storage (Lead-acid) for 1 hours 58

Figure 4.20 Graf for Battery Storage (Lead-acid) for

for 12 hours 59

Figure 4.21 Value of charging process for Battery Storage 60

Figure 4.22 Graf for charging voltage (Voltage vs. Time) 62

Figure 4.23 Testing of charging voltage process at

Battery Storage with 5.98V 63

Figure 4.24 Testing of charging voltage process at

Battery Storage with 5.99V 64

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LIST OF SYMBOLS

I Ampere

V Voltage

PV Photovoltaic

LED Light Emitting Diode

LM2574 Step-down converter

LM7805 Voltage regulator

DC Direct Current

AC Alternating Current

LIB Lithium-ion Battery

PIC Peripheral Interface Controller

IC Integrated Circuit

Frequency

I/O Input/output

VDD Supply Voltage

DVM Digital Volt Meter

SCC Solar charge controller

NPH Normal Pressure Hydrocephalus

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LIST OF APPENDICES

APPENDIX TITLE PAGE

A Gantt Chart PSM 1 and PSM 2 71

B Software using C Language

Micro C Pro for PIC 72

C PIC16F688 Datasheet 74

D LM2574 Datasheet 77

E LM7805 Datasheet 87

F Lead Acid Battery Datasheet 97

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CHAPTER 1

INTRODUCTION

1.1 Background

Due to the energy crisis, renewable energy sources have been deeply concerned

as possible solutions to remain resources on the earth. Among these energy sources,

solar energy, a free conversion, non-polluted and inexhaustible energy source, has

been use to generate electricity for decades.

The solar energy which directly produced by the sun and it can be converted to

electricity energy by using solar cell. For example, one of the applications that using

Photovoltaic (PV) technology is battery charger cell phone. Solar cell is a device that

converts the energy of sunlight directly into electricity by the photovoltaic effect.

The main focus of this project is to design the charger with environmentally friendly

materials and powered by alternative energy sources. The energy savings for battery

charger cell phone is important in order to make sure that energy resource can be

used for a long term.

This project consists of five elements which are Photovoltaic (PV) panel, solar

charge controller, buck converter circuit (DC-DC Converter) with rechargeable

battery (lead-acid type), PIC microcontroller and DC loads (lithium-ion battery). The

buck converter circuit is used to set the normal charging voltage level at 5 Volt. The

charge controller are used to stabilized the current and monitor the voltage or current

level at solar cell. The PIC microcontroller aims to measure the battery storage from

buck converter circuit.

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1.1.1 Advantages of alternative cell phone charger using Photovoltaic (PV)

When using a solar cell phone charger it able to store electricity for a few days.

There are several advantages when using the cell phone charger solar such as:

i. Plugging a charger to an electric socket can cause a shock to the wallet so

using photovoltaic to charge batteries can save money.

ii. Invest in a solar battery charger not have to pay any bills and neither to pay

maintenance costs.

iii. For the green consumer, rechargeable batteries are a great way to prevent

toxic chemicals like alkaline from finding their way into landfills, or just

reducing the cost of buying fresh, disposable batteries.

1.2 Objective

The objectives of this project are as follows:

i. To design a smart photovoltaic (PV) travel phone charger by using

PIC16F688.

ii. To develop a DC-DC converter with stabilized output 5 Volts.

iii. To simulate the circuit by using Target 3001 and Proteus simulation software.

1.3 Scope

There are two main elements considered in this project which are:

i. To understand theoretical aspect of photovoltaic panel, PIC and including

working principles, characteristics and specifications.

ii. To develop the travel phone charger using Photovoltaic (PV) systems.

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1.4 System Description

Figure 1.1: Global Block Diagram – Development of Smart PV Travel Phone

Charger

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The photovoltaic charger system consists of five subsystems, each with its own

function. These five subsystems are connected in accordance with the block diagram

presented in Figure 1.1.

The first subsystem (Solar Panel) consists of PV module as main element input

source in this project. This PV module has a rated power in 9.4 V and is formed by 3

photovoltaic cells connected in parallel (more technical specifications may be

consulted in detail). Due to not have suitable rated, these solar panel cells are used in

project.

The Solar Charge Controller (second subsystem) is used to increase the current

in 1 Ampere due to the solar panel cannot support current for charging process. If

current not enough, the charging process cannot charging with successfully.

Furthermore, it can be apply to backup support from overcharging for storage battery

in charging process occurs after diode zener at buck converter circuit.

The DC-DC Converter element (third subsystem) consists of one rechargeable

battery from lead-acid types and buck converter charging unit. It due to lead-acid

battery has high capacity storage from other battery in Photovoltaic systems [11].

The buck converters are used for step-down or stabilized voltage at 5 Volt (suitable

for phone charger charging).

The DC loads (fourth subsystem) consists of a rechargeable Lithium-ion (Li-

ion) battery from mobile phone. This battery has an output voltage of 3.7V and an

energy storage capacity of 550mAh/1000mAH (depends the type of capacity battery

are used for mobile phone from supplier)

The measurements (fifth subsystem) are used to measure capacity of the storage

battery at the buck converter and solar panel by using PIC16F688. If the full charge

battery capacity, the LCD act as display with 6V depends the type battery are used in

the project.

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1.5 Problem Statement

Nowadays, the portable equipments relying on the solar energy as a power

supply are widely used in the daily life [1]. With the increase of the energy demand

and the concern of environmental pollution around the world, photovoltaic (PV)

system is becoming more and more popular [1]

Due to the energy crisis, alternative energy sources have been deeply concerned

as possible solutions to remain resources on the earth [2]. Among these energy

sources, solar energy, a free conversion, non-polluted and exhaustible energy source,

has been used to generate electricity for decades [2].

The main purpose of establishing the working of mobile phones using solar

energy is to overcome the constraint of enormous emission of Carbon-di-Oxide in to

the atmosphere, hugely contributing to the depletion of ozone layer [3]. By using the

photovoltaic (PV) system, the system depends on sun energy as power supply which

is only available in limited period. It causes the limited energy supply. So, the system

must use the energy as minimum as possible but still can operate efficiently

A solar cell phone charger uses the energy of the sun to charge up mobile

phone. If someone are outdoors a lot, or do not have ready access to an electrical

outlet, getting a telephone charged can be principal hassle. With a solar cell phone

charger, we can easily use the energy of the sun to charge cell phone anytime and

anywhere. Using photovoltaic cells, a solar cell phone charger can rapidly turn the

power of the sun into electricity. This electricity can be used to recharge telephone

anywhere. A solar panel phone charger can be vital on a camping trip or an outdoor

adventure travel.

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1.6 Outline of Thesis

This Development of Smart PV Travel Phone Charger final thesis is consists of

five chapters including this chapter. The content of each chapter are outlined as

follows.

For Chapter 1(Introduction) it will be described about the introducing the

overview of the project including the background, objectives, problem statement and

scope of the project.

For Chapter 2 explained about the reviews on previous researches conducted

that is related to this project. Before starting the project, the background and

literature review about development of smart PV travel phone charger has been

studied in order to understand more about the operation and principle of charger

solar.

For Chapter 3 it includes the project methodology. This will explain how the

project was organized and the flow of the system designed. Before developing the

prototype, the simulation has been done to make sure that the circuit would be

working properly.

For Chapter 4 explained the result and discussion. The result will be analyzed

and discussed. This chapter shows the result achieved by doing this project. The

result are categorized into three parts includes the hardware, software and analysis of

the system.

For Chapter 5 will be explained about the conclusion from this project. The

overall conclusions of this project that have been completed. The final chapter which

is chapter five elaborates the conclusion and recommendation of the project. The

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future works are recommendation and suggestions made for the project to improve in

near future

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CHAPTER 2

LITERATURE REVIEW

2.1 Solar Energy

Solar energy is the light and radiant heat from the sun that influences Earth's

climate, weather and sustains life. Solar power is sometimes used as a synonym for

solar energy or more specifically refer to electricity generated from solar radiation.

Solar energy technologies can provide electrical generation by heat engine or

photovoltaic means, space heating and cooling in active and passive solar buildings,

portable water via distillation and disinfection, day lighting, hot water, thermal

energy for cooking, and high temperature process heat for industrial purposes. Solar

energy refers primarily to the use of solar radiation for practical ends. All other

renewable energies other than geothermal derive their energy from energy received

from the sun.

Currently, our society‟s energy demands are fulfilled using conventional energy

sources such as water, coal, oil, natural gases or uranium [4]. The production of

energy using these conventional sources is a cause of concern of many

environmentalists [4]. The major problems can be quoted as follows:

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i. It causes atmospheric pollution, climate changes or nuclear waste and thus can

endanger our living condition on the earth.

ii. The extensive use of these limited conventional energy sources may result in

complete depletion of energy sources and hence, there is no guarantee of energy

supply for future.

The above mentioned problems can be solved by using renewable energy sources

such as sun and wind. The renewable energy sources use natural resources and do not

cause any pollution. Hence they are termed as green energy sources [5]. Moreover,

these renewable energy sources only use a small part of the flow that is why they

cannot damage natural surrounding and also do have the risk of being depleted. Sun

is considered as a potential source of renewable energy. Hence, the use of solar

energy for applications such as generation of electricity, running of automobiles, etc

is becoming popular. The generation of electricity using solar energy is done using

photovoltaic technology [6].

2.1.1 Advantages of Solar Energy

Solar technologies are broadly characterized as either passive or active

depending on the way they capture, convert and distribute sunlight. Active solar

techniques use photovoltaic panels, pumps, and fans to convert sunlight into useful

outputs. The advantages of solar energy are as following:

i. Solar energy is a renewable resource. Although it cannot be utilized at night

or on cloudy days, its availability may be generally relied upon day after day.

ii. Solar cells are long-lasting and require very little maintenance.

iii. Solar energy is non-polluting. Of all the advantages of solar energy over oil,

this is perhaps the most important. The burning of oil releases carbon dioxide

and other green house gases into the air. In addition to this, the process of

obtaining it may result in damaged ecosystems through dredging or spills.

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iv. Although solar panels and their accessories (solar lights, etc.) may be

expensive to buy at the onset, money is saved in the long run. This is because

energy from the sun is widely available and free.

v. Solar powered lights and other solar powered products are very easy to

install. This is because there are few wiring issues and little need to ever dig

supporting trenches.

2.2 Photovoltaic (PV) Cell

On the thesis the solar panel serves as power supply to the circuit. It receives

light from the sun and converts this to energy. The photovoltaic cell is a usual power

source where as most sources of electrical power are constant voltage sources, such

as a battery, a PV cell is a constant current source. The PV cell only displays this

constant current characteristic up to a limiting where the current collapses. For an

ideal PV module the voltage where the current collapses would be at the open circuit

voltage, Voc

Figure 2.1: Ideal I-V Curve for a PV cell

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Figure 2.2: Typical current-voltage I-V curve

The slight current drop between points M and A is a result of some of the

current passing through the internal resistance of the PV cell. Between points A and

S the load resistance increases forcing some of the current to flow through the diode

resulting in the fast drop in current to the load. This continues until point S where all

the current flows through the diode and the internal resistance.

Where the PV operates on this I-V curve is greatly determined by the

insulations, array voltage, cell temperature and the load connected to the array.

According to [14] by altering the amount of sun light that is available to the PV

module the current that the module can produce is also altered. The current and

power output of the used solar panel is approximately proportional to illumination

intensity (irradiance). At a given intensity, the module voltage is determined by the

characteristics of the load.

According to the conclusions achieved in [15] the effect of temperature on the

current of a PV cell is only small. By increasing the temperature a slightly higher

current is produced, however this increase in temperature has a negative effect on the

cell voltage. Increasing the temperature forces the diode in Figure 4 to conduct at a

lower voltage therefore reducing the PV voltage where the curve collapses and

greatly reducing the output power

Figure 2.2 shows the load lines for different load resistances. The slopes of

these load lines are given by 1/R. So, lower resistances result in steeper load lines