i

DESIGN, SIMULATION AND IMPLEMENTATION OF A 1KVA ONLINE AC

SOLAR POWER SYSTEM

WRITTEN

BY

IKAFIA, UBONG SAM

09/EG/EE/524

ELECTRICAL/ELECTRONICS ENGINEERING

SUBMITTED

TO

THE DEPARTMENT OF ELECTRICAL/ELECTRONICS AND COMPUTER ENGINEERING

UNIVERSITY OF UYO

UYO.

IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE AWARD OF BACHELOR OF

ENGINEERING (B.ENG) IN ELECTRICAL/ELECTRONICS ENGINEERING.

MARCH, 2015.

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CERTIFICATION

I hereby certify that this is the original project report done by Ikafia, Ubong Sam of the

department of Electrical/Electronics and Computer Engineering under the supervision of Engr. Yeobong

Udoakah, Engr. Mfon Umoren and Dr. Simeon Ozuomba.

Ikafia, Ubong Sam ………………….. ………………

Student Signature Date

Engr. Yeobong Udoakah ………………….. ………………

Supervisor Signature Date

Engr. Mfon Umoren ………………….. ………………

Supervisor Signature Date

Engr. S. J Udofa ………………….. ………………

Head of Department Signature Date

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DEDICATION

I dedicate this project to my Awesome God who made this project a huge success despite the challenges

encountered.

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ACKNOWLEDGEMENT

All glory, thanks and adoration belongs to my Awesome God for making this project a huge

success. Special thanks go to my project supervisors; Engr. Yeobong, Engr. Umoren and Dr. Ozuomba

(project coordination) for their directive and correction to make this project a standard. I must sincerely

thank Mr. Iyakke Okon for directing us in this project.

I must not forget to appreciate my parents Mr./Mrs. Sam Ikafia and Sister (Miss Idongesit Ikafia and

Mbiatke Ikafia) for toiling day and night to ensure that my academic pursuit is successful. Also I thank

my sponsors; Delta Afrik Charitable Foundation and the Agbami Professional Scholarship Scheme and

Mr. Gregory Ikafia and Mr./Mrs. Owoidigheukem Jacob for their sponsorship.

My profound gratitude goes to my late minister Bro. Young Nwoacha, present minister Bro. Usen Ekpo

and members of the Church Of Christ, university of Uyo community for their prayers individually and

collectively.

Finally I thank my group members; Ekereobong Ette, Idorenyin Ekong, Uduak Justine, Daniel Nse and

Aniebiet Uko for their contributions and effort for the success of this project. To my friends, all I have to

say is thank you. I pray that my Awesome God to reward you all in Jesus name, Amen.

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TABLE OF CONTENT

Certification………………………………………………………………………………i

Dedication………………………………………………………………………………...ii

Acknowledgement………………………………………………………………………..iii

Table of content…………………………………………………………………………..iv

List of figures/tables……………………………………………………………………..vi

Abstract………………………………………………………………………………….viii

CHAPTER 1 - INTRODUCTION

1.1 Background of Study………………………………………………………………………1

1.2 Statement of Problem………………………………………………….…………………..1

1.3 Objectives of study………………………………………………………………………...2

1.4 Significance of study………………………………………………………………………2

1.5 Limitation of study………………………………………………………………………...3

1.6 Organization of Report.……………………………………………………………….…..4

CHAPTER 2 – LITERATURE REVIEW

2.1 Renewable energy…………………………………………………………………………5

2.2 Solar Power System……………………………………………………………………….5

2.3 Solar Power Technology…………………………………………………………………..6

2.4 Types of solar power system………………………………………………………………7

2.5 Components of Stand-alone system……………………………………………………….8

2.6 Advantages of solar power system……………………………………………………….13

CHAPTER 3 – DESIGN METHODOLOGY

3.1 Anticipated load forecast……………………………………..…………………………..14

3.2 Solar Module specification……………………………………………………………….15

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3.3 List of Equations………………………………………………………………………….16

3.4 Charging system and charging time………………………………………………………17

3.5 Control system……………………………………………………………………………18

3.6 Battery specification and analysis……………………………………………………….19

3.7 Inverter System……………………………………………………………………………20

3.7.1 Oscillator circuit design…………………………………………………………………...22

3.7.2 Pre-amplifier Design………………………………………………………………………23

3.7.3 The Power Drivers………………………………………………………………………...23

3.7.4 The Design of the Inverter………………………………………………………………...24

3.8 Transformer specification…………………………………………………………………26

3.8.1 Transformer design………………………………………………………………………..26

3.9 Inverter panel specification and design……………………………………………………28

CHAPTER 4 – CONTRUCTION OF THE SYSTEM

4.1 Implementation of system components……………………………………………………29

4.2 Testing……………………………………………………………………………………..31

4.3 Simulation…………………………………………………………………………………33

4.4 Installation…………………………………………………………………………………42

4.5 Evaluation…………………………………………………………………………………43

4.6 Troubleshooting…………………………………………………………………………...43

4.7 Maintenance……………………………………………………………………………….43

CHAPTER 5 – CONCLUSION AND RECOMMENDATION

5.1 Conclusion…………………………………………………………………………………44

5.2 Recommendation…………………………………………………………………………..44

References………………………………………………………………………………………….45

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Appendix…………………………………………………………………………………..48

Bill of Engineering Measurement and Evaluation (BEME)………………………………53

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LIST OF FIGURES

Fig 2.1 Grid connected system……………………………………………………………8

Fig 2.2 Solar cell, Module and Array…………………………………………………….10

Fig 2.3 Deep cycle Battery……………………………………………………………….11

Fig 3.1 System block diagram……………………………………………………………14

Fig.3.2 Control Circuit…………………………………………………………………...19

Fig.3.3 Inverter block diagram…………………………………………………………...21

Fig. 3.4 Oscillator circuit……………………………………………………………....…22

Fig 3.5 Power driver circuit………………………………………………………………24

Fig. 3.6a. Duty Cycle…………………………………………………………………….26

Fig. 3.6b Output waveform..…………………………………………………………….26

Fig 3.5 Inverter casing Design…………………………………………………………..28

Fig 4.1 Oscillator circuit implementation……………………………………………..…29

Fig 4.2 Power Driver Circuit Implementation ………………………………………….30

Fig 4.3 Charging/Control circuit implementation ………………………………….…..30

Fig 4.3 Transformer……………………………………………………………………..31

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Fig 4.5 Power Driver simulation………………………………………………………..33

Fig. 4.6 Protues Simulation of control circuit……………………………………….….34

Fig 4.7 PVSYST System Design……………………………………………………….35

Fig 4.8 PVSYST simulation result………………………………………………………38

Fig.4.9 PVSYST simulation result………………………………………………………41

Fig 4.8 Complete Installation with team…..…………………………………………….41

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LIST OF TABLES

Tab.3.1 Load forecast…………………………………………………………………….14

Tab.3.2 Solar Module specification………………………………………………………15

Tab.3.3 Battery Specification……………………………………………………………20

Tab.3.4 Inverter Specification……………………………………………………………21

Tab.3.5 Transformer specification……………………………………………………….26

Tab 4.1 Testing and Results……………………………………………………..………31

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ABSTRACT

The increasing demand and meager supply of energy in Nigeria has been a great challenge to her development. The situation

is becoming very critical with the increasing population not balanced with sufficient energy development program. Solar

energy is abundant and offers significant potential climate change mitigation. There are a wide variety of solar technologies

of varying maturities that can contribute to a suite of energy services. This 1kVA (kilo Volt Ampere) Online AC Solar Power

System is designed as a solution to the Nation‟s energy challenges. The design, implementation and simulation of the system

were done in order to achieve the output of 1kVA. The solar array generates the DC (Direct Current) supply for the Inverter

and the battery. The battery saves the DC energy for operations at night and also on cloudy days. The inverters, being made

of various electronic components convert DC to AC (Alternating Current) for the household appliances. This stand-alone

system is able to provide a continuous renewable power supply to home appliances, thereby improving the Nation‟s energy

demand.

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CHAPTER 1

INTRODUCTION

1.1 BACKGROUND OF STUDY

The increasing demand and meager supply of energy in Nigeria has been a great

challenge to her development. The situation is becoming very critical with the increasing

population not balanced with sufficient energy development program. The incessant power

generation failure has grossly affected the economy of the nation and seriously slowing down

development in rural and sub-rural settlements with the present energy policy mainly beneficial

to urban dwellers. Globally, energy projections stipulate that between 2002 and 2025, global

need for energy needs may rise by 34%, with that of the developing nations doubling this

percentage (Ajayi et al, 2009).

Renewable energy which an energy source that is naturally replenished, making the

energy continuous provides a solution to this problem. Its sources include; sunlight (solar), wind,

biomass, hydro, tides, waves and geothermal heat (Stover, 2013). Solar energy technology

includes solar heating, solar photovoltaic, solar thermal electricity and solar architecture, which

can make a considerable contributions to solving some of the most urgent energy problems the

world now faces where about 1.7 billion people live without main access to electricity (IEA,

2014). This project is focused on power generation using solar photovoltaic systems which is one

of the major applications of solar energy.

1.2 STATEMENT OF PROBLEM

The epileptic nature of Nigerian power system aggravates the problems associated with of lack

of electricity. The government sectors, the industries and the educational sectors are all affected.

The national grid is not capable of supplying the demand load and some citizens living in remote

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areas are unable to access the grid. Everyone in the country is affected. The problem is very severe

that the technological development of the state is affected seriously. Public and

private businesses are crumbling due insufficient power supply.

The University of Uyo is not an exemption. The offices and lecture rooms become boring

to staff and students of the institution due to lack of power, the hostels have no power in the day

and the laboratories if not power with any source will not be functional for students‟ use.

These problems becomes enormous as the power in the nation is not sufficient and the university

generator cannot be ran 24-hours of the day due to its cost implication.

The solution to this problem is an alternative source of electricity, hence an Online AC Solar

Power System.

1.3 OBJECTIVE OF STUDY

At the end of this project, the following objectives would be achieved

I. Design and implementation of 1kVA solar power system.

II. Design and simulation of 1kVA online solar power system with Proteous

III. Design and simulation of 1kVA online solar power system using PVSYST.

IV. Evaluation of the whole system.

1.4 SIGNIFICANCE OF STUDY

Significances of the project are discussed below;

1. No greenhouse gases: The first and foremost significance is that, after energy production,

there is no emission of greenhouse gases unlike other sources of energy. This is the main

driving force behind all green energy technology. The Italy‟s Montalto di Castro solar park

is a good example of solar‟s contribution to curbing emissions as it avoids 20,000 tons per

year of carbon emissions compared to fossil fuel energy production (Hudson 2011). In

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addition to this, it also saves the ecosystem and livelihood by avoiding deforestation

associated with fossil fuel operation.

2. Ongoing free energy: Beyond initial installation and maintenance, solar energy is free. It

does not require ongoing raw materials like oil, gas and coal, and significantly low

operational labor than convectional power production. Solar modules produce a warranty

of 25-30years and have a life expectancy of 40years (Lombardo, 2014).

3. Going off the grid with solar: This is the stand-alone feature of solar power system as the

house has no connection to the grid. This is a major significance of solar power system to

people living in isolated and rural areas. Many city dwellers have decided to go off grid

with this alternative energy as a self-reliant lifestyle.

1.5 LIMITATION OF STUDY

The limitations of the study include;

The project is limited to 1kVA solar power. This is due to school‟s specifications

The project is designed to power some household appliances like fan, lighting and sound

system and television set (light load).

The exceptions to its application are Refrigerator (higher than 1kVA), Air conditioner,

Pressing Iron and other heavy loads.

It is a standalone system, not grid-tied.

This project is limited to Proteus and PVSYST software.

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1.6 ORGANIZATION OF REPORT

Chapter one covers the background of solar power system (i.e. the history, characteristics

and properties of solar power system), statement of problem, purpose of study, significance of

study, scope of study and limitation of study. Chapter two is dedication to the literature review of

solar power system. While chapter three explores the materials and method used in the design of

1kVA AC solar power system, chapter four brings to manifestation the implementation and

evaluation of 1kVA AC solar power system. Finally, chapter five carries the conclusion and

recommendation the project.

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CHAPTER 2

LITERATURE REVIEW

2.1 RENEWABLE ENERGY

The world relies predominantly on carbon-based energy sources such as oil, gas and coal to meet its

energy needs. Given that these resources are finite and a major cause of pollution, scientists and

engineers have sought for decades to develop alternative energy sources.

A research on renewable energy in Wale by Caitlin et al (2013) shows that renewable energy is a

general term used to describe any source of energy that occurs naturally and is not exhaustible, such as

solar energy, wind energy or wave energy. Energy from biological sources, such as wood burned as fuel,

can also be describe as renewable if the crop is managed sustainably. The research also shows that there

are several different technology types used to generate electricity from renewable source. In an article

written by the Stover (2013), the sources of renewable energy are; solar, wind, geothermal, hydro and

biomass.

2.2 SOLAR POWER SYSTEM: Solar energy is the main source of the earth‟s energy, which supplies

it with daylight, heat and radiation. Electricity produced from sunlight does not exhaust any of the

earth‟s natural resources and supplies the earth with unremitting energy. The sun is the primary source

of energy. According to Gupta (2013), solar energy reaching the earth in tropical zones is about 1kW/m2

giving approximately 5 to 10kW/m2 per day. In an experiment conducted by the U. S. Department of

energy (1995) to determine the amount and wavelength of light on solar cell, it was discovered that solar

cells also called Photovoltaic cells or PV cells, change sunlight directly into electricity. When sunlight

strikes the solar cell, electrons are knocked loose. They move toward the treated front surface. An

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electron imbalance is created between the front and the back. When the two surfaces are joined by a

connector, like a wire; a current of electricity travels between the negative and the positive sides.

2.3 SOLAR POWER TECHNOLOGY: Solar power technology includes; concentrating solar

technology and photovoltaic technology.

2.3.1. Concentrating Solar Technology: According to IRENA (2013), the concentrating solar power

(CSP) technology uses mirrors to concentrate sunlight onto a receiver, which collects and transfer solar

energy to heat transfer fluid that can be used to supply heat for end-use applications or to generate

electricity through convectional steam turbines. Also, IRENA (2013) adds that the large CSP plant can

be equipped with a heat storage system to allow for heat supply or generation of electricity at night or

when the sky is cloudy. In a report written by Sorin et al (2008), the concentrating solar technology is

divided into two general categories; the first is Concentrating Solar Thermal (CST), which includes

those concentrating the sun‟s energy on a thermal conductor and then using that heat to move an engine

or turbine. They usually the form of a large power plant and can concentrate using mirrors in a line or

around a point (Sorin et al, 2008). The research also shows that the other technology is the

Concentrating Photovoltaic (CPV), which concentrates the sun‟s energy directly onto high efficiency PV

material to directly create electricity. These technologies use both mirrors and lenses and can be

deployed in configurations that range from large systems to mid-sized systems, with some technologies

even able to be done at small modular scale similar to traditional PV modules (Sorin et al, 2008).

2.3.2. Photovoltaic technology: According to IRENA (2013), Photovoltaic (PV) solar cells directly

convert sunlight into electricity, using the photovoltaic effect. The process works even on cloudy or

rainy days, though with reduced production and conversion efficiency. The brief also indicated that the

PV cells are assembled into modules to build modular PV systems that are used to generate electricity in

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both gird-connected and off-grid applications, such as residential and commercial buildings, industrial

facilities, remote and rural areas and power plants (the utility PV system). In a research done by the

Yinghao (2011), the material presently used for photovoltaics include monocrystalline silicon,

polycrystalline silicon, amorphous silicon, cadmium telluride, and copper indium gallium

selenite/sulfide. The photovoltaic solar panel is the most commonly used solar technology to generate

electricity (Yinghao, 2011). In the review, he pointed that basic idea of photovoltaic is simple in that

electrons will emit from matter (metals and non-metallic solids, liquids or gases) as a result of their

absorption of energy from electromagnetic radiation of very short wavelength, such as visible or

ultraviolet light. Electrons emitted in this manner maybe referred to as “photoelectrons”.

2.4 TYPES OF SOLAR POWER SYSTEM: According to David et al (2012) solar PV system can be

classified based on the end-use application of the technology. They identified the two main types of

solar PV system to include; grid-connected (grid-tied) and stand-alone (or off-grid) solar PV system.

2.4.1 Grid connected solar PV systems: According to Kumi et al (2013) in their work, the grid

connected system is a system connected to a large independent grid usually the public electricity grid

and feed power directly into the grid. DSG (2008) opines that these systems are usually employed in the

decentralized and decentralized grid connected PV applications. Decentralized applications include

rooftop PV generator, where the PV systems are mounted on rooftops and incorporated into the

building‟s integrated system (DSG, 2008). In a report written by Tom et al (1998), it was noted that the

grid connected system have demonstrated an advantage in the natural disasters by providing emergency

power capabilities when utility power is interrupted. Although the PV power is generally more

expensive than utility-provided power, the use of grid-connected systems is increasing. Kumi et al

(2013) in their study noted that a typical grid-connected system comprises the following components;

Solar PV Module: These convert sunlight into electricity.

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Inverter: This converts the DC generated by the solar PV modules to AC current for the utility

gird.

Main disconnector/isolator Switch.

Utility Grid.

Fig. 2.1 Grid connected system. (http://www.sunscapesolar.net/grid_tie_bu.htm)

2.4.2 Stand-Alone (Off-Grid) Solar PV System: According to Tan et al (2011) in his book, the stand

alone solar PV system is applicable for areas without power grid. Currently, such solar PV systems are

usually installed at isolated sites where the power grid is far away, such as rural areas or off-shore

islands (Tan et al, 2011). It can also be installed in the city where it is inconvenient or costly to tap from

the grid and where the power from the grid is insufficient and inconsistent. In a study done by Ahmed et

al (2013), it was noted that the load curve should be analyzed carefully and the PV system should be

sized and combined with the battery system in such a way to cover all the points of the load curve.

2.5 COMPONENTS OF A STANDALONE SOLAR PV SYSTEM

In a study done by Abu-Jasser (2010), the photovoltaic system is composed of a variety of equipment in

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addition to the photovoltaic array, a Balance-of-System is wired together to form the entire fully

functional system capable of supplying electricity and these components are:

PV Generator (Cell, Module, Array)

Battery

Inverter

Control

Balance

AC and DC Load

2.5.1 PV Generator (Cell, Module and Array): Hanson et al (2000) puts that a PV generator is the

whole assembly of solar cells, connections, protective supports etc.

2.5.1.1 Solar Cell: According to Hanson et al (2000), solar cell is made of materials (usually silicon),

which is treated to form an electric field, positive on one side (backside) and negative on the

other (toward the sun). When solar energy (photons) hits the solar cell, electrons are knocked

loose from the atoms in the semiconductor material, creating electron-hole pairs (Lorenzo,

1994). Abu-Jasser (2010) puts that an individual cell is usually quite small, typically producing 1

or 2 watts of power. To increase this output power, they are usually connected together to form a

larger unit called Module.

2.5.1.2 Solar Module: In a work done by Escudero-Pascual (2007), it was noted that; the solar module

or panel is composed of solar cells which collect solar radiation and transforming it into

electrical energy. He adds that most used module is the crystalline silicon, either monocrystalline

or polycrystalline while the less efficient is the amorphous silicon. IFC (2012) reveals that, in

general, good quality PV modules are expected to have a useful life of 25 to 30 years, although

their performance will steadily degrade over this period.

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2.5.1.3 Solar Array: Escudero-Pascual (2007) noted that the array is formed by a set of modules or

panels connected in series and/or parallel so as to provide the necessary energy for the load.

Also, he said that the electrical current supplied by an array of solar panels varies proportionally

to the solar radiation. As the solar energy changes in time due to the climatological conditions,

the hour of the day, etc. we must count with energy storage to supply energy when the sunlight is

lacking: the battery.

Fig.2.2 Solar cell, Module and Array (Lorida, 2007).

2.5.2 Battery: According to Sullivan (2010), the battery is an electrochemical storage device that

produces voltage and delivers electrical current. It is important to remember that a battery does

not store electricity, but rather it stores a series of chemicals, and through a chemical process

electricity is produced (Sullivan, 2010). Its storage capacity is measured in ampere hour (Ah).

Vutetakis (2001), sees a battery as a device that converts chemical energy directly to electrical

energy and consist of a number of voltaic cells; each voltaic cell consists of two half cells

connected in series by a conductive electrolyte containing anions and cations. He adds that one

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half-cell includes electrolyte and the electrode; the other half-cell includes electrolyte and the

electrode to which cations (positively-charged ions) migrate, i.e. the cathode or positive

electrode. Tan et al (2012) noted that an off-grid solar PV system needs deep cycle rechargeable

batteries such as lead-acid, nickel-cadmium or lithium batteries to store electricity for use under

conditions where there is little or no output from the solar PV system, such as during the night. It

is worthy of note that the deep cycle battery should not be discharged to a very low level in order

to prolong its lifespan and performance.

Fig.2.3. Deep cycle Batteries (Power sonic 2014).

2.5.3 Inverter: Vieri (2013) sees an inverter as a power electronics device which converts DC to AC,

allowing the DC power from these generators to be used with ordinary AC appliances. In a work

done by Doucet et al (2007), two methods of converting the DC to AC was presented; the first

being the conversion of the low voltage DC power to a high voltage DC source, and then the

high DC source is converted to AC waveform using pulse width modulation. The other method is

to first convert the low voltage DC power to AC, and then use a transformer to boost the voltage

to the desired value. He noted that the two different types of AC generated are the modified sine

wave and the pure sine wave. Doucet et al (2007) focusing on the Pulse Width Modulation

method opines that the Bubba Oscillator is a circuit that provides a filtered sine wave of any

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frequency the user desires based upon the configuration of resistors and capacitors in the circuit.

The H-Bridge converter is a switching configuration that consists of four switches which is built

from solid state transistors (Doucet et al, 2007). According to Lander (1993), the inverter is

recently made of two kinds of transistors; the Metal-On-Semiconductor Field-Effect Transistor

(MOSFET), which has a rapid switching action, and can be designed with a low resistance so

that it will pass high current efficiently, provided that the voltage is has to stand in the „OFF‟

state is low. The second is the Insulated Gate Bipolar Transistor (IGBT), which when designed

for a high „OFF‟-state voltages, outperforms the MOSFETs, although the MOSFET is still best at

lower voltages.

2.5.4 Charge Controller: According to Abu-Jasser (2010), a voltage regulator or charge controller is

an essential part of nearly all power system that batteries, whether the power source is

photovoltaic, or utility grid. Its purpose is to keep your batteries properly fed and safe for the

long time. In a work done by RLH (2013), the charge controller continuously maintains the

correct charge level on a 12 or 24V lead acid type backup battery, and ensure a seamless power

transition to battery power when needed. As the input voltage from the solar array rises, the

charge controller regulates the charge to the batteries preventing any overcharging.

2.5.5 Balance: The balance-of-system as seen by Abu-Jasser (2010), are such protective devices that

keep the system components safe during their operation, blocking diodes that protects the

components from damage by back flow of electricity from battery at night and the by-pass

diodes connected across various cells to limit the power dissipated in shaded cells by providing a

low resistance path for the module current. Additional devices that are used to ensure proper

operation are monitoring, metering and disconnect devices.

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2.5.6 AC and DC Loads: These are appliances (such as lights and radios), and components such as

fridges, water pumps, washing machines and microwaves) which consumer the power generated

by the photovoltaic array (Abu-Jasser, 2010).

2.6 ADVANTAGES OF SOLAR POWER SYSTEM

Clean: Non-polluting harnessing sunlight into electricity and heat is the easiest and least harmful

option of our environment. No gases like CO2, SO2, and NO2 associated with global warming and

acid rain or carcinogens are released into the atmosphere when sunlight is converted into

electricity powering our everyday.

Renewable: Solar power system is one of the most abundant renewable sources of energy. On a

sunny day, a solar cell is bombarded with about one kilowatt of energy in a single hour of

sunlight (Gupta, 2013). The cloud may cover its brightness for a short but it always returns

burning bright and ample above us (Leone, 2011). Solar energy from the sun is expected to be

capable of supplying humanity energy for almost another 1billion years, at which point the

predicted increase in heat is expected to make the earth surface too hot for liquid water to exist

(Schroder et al, 2008). Energy from the sun is naturally replenished constantly making the

energy efficient.

Abundant: Solar energy is inexhaustible and free because it is highly diffused, released by the

sun and made available by the sun to everybody. For this reason, however, collecting it requires

a relatively large space and a large number of solar modules to harness useful amount of energy.

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CHAPTER 3

DESIGN METHODOLOGY

3.1 INTRODUCTION

The Stand-Alone Solar Power System is a renewable source of electricity for houses and homes.

It consist a variety of components connected together to form the whole system. The block

diagram is given below;

Fig 3.1 System block diagram

3.2 Anticipated Load Forecast for its application: This load forecast was done based on the

present load need in our compound. The result of the forecast is summarized in the table below.

Table 3.1 Load forecast.

Load Description Wattage (W) Number of points Total Wattage (W)

Lighting 11 15 165

Inductive load 80 1 80

TV set 60 1 60

Laptop charging 65 1 65

Solar Array Charging/Control system

Battery

Inverter System AC Load

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Refrigerator 100 1 100

Miscellaneous 30 30

Total 500

Table 3.2 Solar Module specification:

Solar module type Polycrystalline, STP100/12Rb

Number of modules 2

Rated Maximum Power (Pmax.) 100W

Current at Pmax. (Imp) 7.98A

Voltage at Pmax.(Vmp) 17.86V

Short-Circuit Current (Isc) 6.0A

Open-Circuit Voltage (Voc) 12.0V

Nominal Operating Cell Temperature (Tsoct) 50oC

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LIST OF EQUATIONS

Charging time

………..………………Eqn. 3.1

……………………………….Eqn. 3.3

……………………………Eqn. 3.4

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3.3.1 Solar Array Design: The individual solar cell creates relatively low voltage, typically

around 0.5V. The cells are connected in series together to form a module of the desired voltage.

The two modules used are connected in parallel to form an array to increase the ampere rating

but maintaining the output voltage of a single module.

The question in mind is “How long will it take for the array to charge the batter?” The time it

takes the array to charge the battery is dependent on the ampere rating of the panel and the solar

radiation of the day. Two modules connected in parallel gives , but still

17.86V. The choice of these solar modules is analyzed in the battery charging design.

3.4 Charging system: The charge controller operates in two main modes, viz:

Normal Operating condition, when the battery voltage fluctuates between maximum and

minimum voltage, and

Overcharge or over-discharge condition, which occur when the battery voltage reaches some

critical values.

To know if the amp rating is suitable; we know that a battery cannot be charged by a current

higher than 20% of its amp hour. So the 15.56A is suitable for charging.

3.4.1 Charging Time: The charging time is determined by;

Current capacity of the battery/Module amp rating=

…………………3.1

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Note that this is the time it will take to charge the battery from 0V to 13.5V. These hours of

sunlight may not be achievable in a day; the good news is that the battery control design will not

permit the battery voltage to drop below 10V.

If from

Therefore, from 10-13.5V will take of solar irradiation. This is very

achievable.

3.5 Control System: Since it is desirable not to allow the battery voltage to drop below 10V, the

control system sees 0-9.9V as low voltage and will turn ON the charging circuit to start charging

the battery.

Major components: The major components in the control circuit are PIC (Programmable

Interface Controller), Regulator, temperature sensor, buzzer, LCD display (LM04IL-16x4),

etc.

Power supply: The PIC does not require spike, so a DC voltage is used. It sees 0-2.8V as

low and 2.9-5V as High voltage. The 5V Regulator delivers 5V to the PIC provided that the

input voltage is above 5V.

Temperature: The temperature of the MOSFETs will definitely increase when the system is

loaded. A heat sink made of Aluminum is screwed to the MOSFETs dissipate heat from the

30

MOSFETs. A temperature sensor is attached to the heat sink to monitor the temperature of

the MOSFETs. When the temperature on the heat sink is up to 350C, the two DC fans will

turn ON to blow the heat off. If the temperature is up to 400C, the big AC fan will be turn ON

too. The combination of these three fans will cool the system immediately. When this is

done, the fans will be shut down.

Battery Check: This unit will continually check the battery voltage, if lower than 10V, will

actuate the buzzer to sound an alarm and will activate pin 10 of SG3524 to shut down the

system in an event where the solar supply is not available. But if the solar supply is available,

it will activate the charging system to charge the battery. When the battery is fully charged

(up to 13.5V), the unit will cut off the solar supply.

31

Fig 3.2 Control Circuit

3.6 Battery Specification: The reliable battery for this project is the deep cycle battery which is

a lead-acid battery designed to be regularly deeply discharge using most of its capacity.

32

Table 3.3 Battery Specification.

Specification Rating

Battery type Deep cycle

Nominal rated Voltage 12V

Maximum Voltage 13.5V

Current Capacity 100AH

Manufacturer RITAR

3.6.1 Battery back-up time analysis: There will be no solar irradiation at night. Therefore, it is

incumbent on the battery as the only source of supply during this period. The durability of the

battery is dependent on the current capacity of the battery and the load.

Anticipated load = 500W

At full load, battery power capacity will be:

…………………………3.2

33

………………3.3

3.7 Inverter system: The inverter converts the direct current (DC) from battery or solar array to

Alternating Current (AC) for used by household appliances. This inverter works with the Online

technology which means that as the solar array is charging the battery, the inverter is also

inverting and supply the load.

The block diagram of the inverter system is given below;

Fig 3.3 Inverter block diagram.

Table 3.4 Inverter Specification.

Parameter Values

Inverter

Online Offline

Oscillator Pre-amplifier Power Driver Transformer Load

34

Output Power 1Kva

Operating Voltage (220-240)V AC

Operating Frequency (49-51)Hz

Battery Voltage 12V

Output Waveform Modified Sine wave

Power factor 0.8

3.7.1 Oscillator Circuit Design: An Oscillator generates alternate or pulsating signal when

triggered (i.e. the conversion of DC to AC). The types of Oscillator are RL, LC, RC and Crystal

Oscillator. The RC, LC and RL are analog circuits with slow time response due to the time it

takes to charge and discharge. In this project, a crystal Oscillator which is digital is used due to

its fast time response.

35

Fig 3.4 Oscillator circuit (www.cricuitstoday.com)

The SG3524 is an Integrated Circuit (IC) that has in its internal circuitry pulse width modulator,

oscillator, voltage reference, error amplifier, overload protection circuit and output drivers which

is the heart of the inverter circuit.

In the circuit above, resistor R2 and capacitor C1 sets the frequency of the ICs internal oscillator

while R1 is used to fine tune the oscillator frequency. From:

MOSFETs

MOSFETs

36

……………………………………………….3.4

The output of the IC gotten from pin14 and 11 is connected to the transistors Q2 and Q3. The

output is a pulsating signal that whose frequency can be set using the equation above.

Pin 13 and 12 are tied together at the transistors‟ collector terminals and then connected to the

8V regulator. With 6-8V at the base of the transistor Q3, the transistor will be turn ON. The two

resistors at the output of the transistors are called pull-down resistors which are used to clamp the

output down to the give the modified sine wave.

Pin 1-5 is for the Duty cycle. The duty cycle is the ratio of period when the signal stays high to

when the signal stays low.

…………………………………3.5

The duty cycle compares the voltage and send back to pin 1.

3.7.2 The Pre-amplifier Design: The Pulsating signal generated by SG3524 is not sufficient to

turn ON the MOSFETs, therefore the need of amplification. This is done by transistors to boast

the signal to a desired amount. In this project, two NPN transistors (BC337) are used. More

details of this transistor are show in the MSDS (Manufacturers Safety Data Sheet) in the

Appendix C.

3.7.3 The Power Drivers:

37

This is the part of the inverter that is responsible in carrying the load. The major

component of the power driver circuit is the Metal Oxide Semiconductor Field Effect Transistor

(MOSFET), model IRF3205. The two types of MOSFET include; the P-channel and the N-

channel. The N-channel is the used in this project. The MOSFET is a 3-terminal device that is

often likened to a Voltage Regulator. The terminals are; the Gate, Drain and Source. From the

Manufacturers Safety Data Sheet (MSDS), its wattage is 200W, also with maximum Drain

Source voltage, VDS of 55V and Maximum Gate Source voltage, VGS of 20V.

Fig 3.5 Power driver circuit.

3.7.4 The Design of Inverter:

The MOSFETs are connected in parallel to achieve the desired output power of 1kVA.

....................................................................................................3.6

P = Power in Watt,

Pf = Power factor (0.8).

38

. This indicates that the 1kVA is equivalent to 800W.

To determine the number of MOSFETs used;

We say;

Assuming the MOSFET rating is 150W, the number of MOSFETs will be 6. For

robustness we are using 10 MOSFETs totaling 20 MOSFETs, i.e. 10 MOSFETs to one

side of the Oscillator via the transistor collector terminal and the other 10 MOSFETs to

the other side. This design will give the tolerance level of over 700W for protection

against overloading.

The Gates of the MOSFETs are connected to the 100kΩ and 10Ω resistor. 100kΩ resistor

is responsible for discharging the gate to drop the voltage instantaneously when the gate

is not triggered while the10Ω resistor is the limiting resistor to allow the input signal to

come into the MOSFETs.

The output voltage from the MOSFETs is given by the voltage divider rule.

………………………………………………………………………3.7

Where Vo is the MOSFET output voltage, R1 = Discharge Resistor (100kΩ), R2 =

Limiting Resistor (10Ω) and Vin is the input voltage from the pre-amplifier.

39

V0 = 7.9V. This voltage will definitely turn ON the MOSFETs since from the MSDS; it

requires 7V to turn it ON.

Note that the resistors are connected in parallel; therefore, the effective resistance will be

small.

………………………………………………………3.8

3.8 Transformer Specification:

Table 3.5 Transformer specification.

Specification Rating

Transformer Type Push-pull type transformer

Area of core 150.8cm2

Nominal input voltage 12V

Nominal Output voltage (220-230)V

Frequency 50Hz

3.8.1 Transformer Design:

40

At no load, the nominal voltage of the transformer is 12V, but at full load, the nominal voltage

will reduce to 10.5V. The design is such, at full load; the transformer should also give an output

voltage of 220V.

Duty cycle = 98% i.e. 2% for the Dead zone.

t

T

Fig 3.6a Duty Cycle

Duty cycle = t/T. With 10.5V, the output will look like;

Fig 3.6b Output wave form.

At low battery, we have: . The compensated at low battery.

where K is the Voltage constant.

Maximum flux, , from MSDS. We are using 1500guage with

reasons that if we use low gauge (1300), that will result in core wastage and if we use

2000gauge, the core will saturate.

41

Primary coil design;

……………………………………………………………………………3.9

Where = Number of turns in the secondary coil, f = frequency and = area of coil.

In total, we have (27turns for push and 27turns for the pull).

Secondary coil design:

. For the Push period, the transformer output will be 220V while for the Pull

period the output will be 0V.

Where

3.9 INVERTER PANEL SPECIFICATION AND DESIGN

42

Fig 3.7 Inverter Casing Specification.

CHAPTER 4

43

CONTRUCTION OF A 1kVA ONLINE AC SOLAR POWER SYSTEM

4.1 IMPLEMENTATION OF SYSTEM COMPONENTS

This 1kVA Solar Power system comprises the following components;

The Solar Modules

The Charging/Control Unit

The Inverter

Transformer.

4.1.1 INVERTER IMPLEMENTATION

The implementation process started with the Inverter. The inverter sections are the

Oscillator circuit, Pre-amplifier circuit and the Power Driver circuit.

Components for the Oscillator circuit were as specified in the circuit diagram and

implemented on the Vero board. The implemented Oscillator circuit is shown below:

Fig 4.1 Oscillator Circuit Implementation.

44

The next was to implement the power driver circuit. Components were also bought and

implemented on a bigger Vero board as showed below;

Fig. 4.2 Power Driver Circuit Implementation.

4.1.2 CHARGING/CONTROL CIRCUIT IMPLEMENTATION

The components where bought as specified in the circuit diagram and implemented

carefully on the Vero board. This is shown below;

45

Fig. 4.3 Charging/Control Circuit implementaion.

4.1.3 TRANSFORMER IMPLEMENTATION

The core of the transformer was gotten from a 1kVA Stabilizer transformer. The primary

coil of gauge 14 and secondary coil of gauge 16 were bought and wind on the former. The

diagram is shown below;

46

Fig. 4.4 Transformer.

4.2 TESTING

The testing was done at the completion of each section after a prior test of all the individual

components. The steps and result are shown on the table below;

Table 4.1 Testing and Results

TEST RESULT

On the Oscillator circuit, 12V was plugged at

Vcc.

The Regulator Output read 8.8V.

Testing pin8 and 16 of SG3524 The multimeter read 8V

Testing pin11 and 14 of SG 3524 The multimeter read 7V AC. This shows the

oscillator circuit is giving the desired output.

The MOSFET‟s Drain was tested The Multimeter read continuity.

47

The Drain and Source was tested The multimeter read 0.4567V, the voltage

drop across the diode, meaning that there are

in good condition.

12V was applied across the primary of the

transformer

Voltage measured across the secondary was

220V

In the Oscillator circuit, when Vcc of 12V is applied, the regulator will regulate it to 8.8V

which is sent to the SG3524. The SG3524 will invert 8V DC to 7V AC which is read across the

IC output pins (11 and 14). The pre-amplifier amplifiers the output voltage before supplying the

MOSFETs, testing the MOSFETs‟ drains shows continuity, indicating that the connection of the

MOSFETs is proper. The Drain Source voltage of the MOSFETs read 0.4567V showing the

MOSFETs are in good condition. The AC voltage is then fed to the primary coil of the

transformer, which is induced on the secondary coil and transformed to 220V, ready to be used.

4.3 SIMULATION OF THE SYSTEM

Multism 11.0, Proteus 8 and PVSYST were the softwares used in the simulation of this project.

Multism 11.0 was used to simulate the Power driver circuit. The circuit design and wave form

are shown below;

48

Fig 4.5 Power Drivers simulation.

49

Proteus 8 was used to simulate the control circuit; the result is showed below;

Fig. 4.6 Protues Simulation of control circuit.

50

PVSYST V5.06 was used to simulate the entire system. The first stage is input Project

destination parameters as shown;

Fig 4.7 PVSYST system design.

It is worthy of note that the PVSYST has global solar irradiation data for Port Harcourt and

Benin. Since Port Harcourt is closer to Uyo, it was chosen.

Load the porject and generate to have some result irradiation results and clearance index while

varying the irradiation unit;

51

The system design parameters were selected in the PVSYST and was simulated;

52

PVSYST simulation result.

The Meteorological data which are the global irradiation, the diffuse irration and the ambient

temperature of the system are shown to be 3.11kWh/m2.

day, 2.63 kWh/m2 and 24.7

oC

respectively. The values on the collector were; 3.17, 2.58, 0.02, 3.05 kWh/m2.day. Other

displayed values are for the system and the load.

53

Fig. 4.8 PVSYST simulation result.

54

The snapshot above shows the simulation parameters, PV array characteristics, Inverter

characteristics and the PV array loss factors. These PV array losses are due to poor ventilation,

underload or overload.

55

The main simulation result show the produced energy (531kWh/year), specific production of

758kWh/year and performance ratio (PR) of 52.1%

The normalized productions (per installed kWp), is the first chart bar chart showing the Lc:

Collection los (PV-array losses) of 1.59kWh/kWp/day, Ls: System loss(inveter…..) of 0.32

kWh/kWp/day and Yf: Produced useful energy (inverter output) of 2.o8 kWh/kWp/day. The

normalized energy reduced the month of April, May, June, July and August because in rainy

reason, there is no much solar irradiation.

The second chart is the Performance Ratio (PR) of 0.521 which the ratio of the produced useful

energy, Yf to the nominal yeild of the generator‟s direct current, Yr.

56

The snapshot above shows the loss diagram over the whole year.

57

58

Fig. 4.9 PVSYST simulation result.

4.4 INSTALLATION OF THE SYSTEM

Each segment of the system was connected to each other. The entire circuitry was installed in a

fabricated inverter casing. Fig 4.8 shows the complete installation.

Fig 4.10 Complete Installation with team.

59

At the inverter terminal, there are slots for solar array, Battery and output. These are where the

array is and battery are connected, and also the output is taken from it slot. The solar array was

placed on a stand at an angle.

4.5 EVALUATION

The entire system was evaluated by load the inverter with home appliances within the

load specification, the inverter conditions were monitored on the LCD screen. It was observed

that the system voltage decrease with increase in load. The temperature also increases with

increase in load.

4.6 TROBLESHOOTING:

Some troubleshooting techniques are shown below;

Low output voltage: Remove some load.

No AC output: Repairs should be done.

System not booting: Charge the battery.

4.7 MAINTENANCE

60

Over time, maintenance has been proven to improve the reliability of any system. The

maintenance to be done on this system is divide into;

Preventive maintenance: The preventive maintenance here is the routine inspection of

the system. The display on the LCD screen should be recorded for root cause analysis.

Corrective maintenance: Corrective maintenance should be done on the system when

there is no AC output. This maintenance should be done mainly by the manufacturer of

the system due to the fact that it will involve opening the inverter to troubleshoot.

CHAPTER 5

CONCLUSION AND RECOMMENDATION

5.1 CONCLUSION

The design, implementation, simulation and evaluation of 1kVA Online Solar Power system

were accomplished. At the end of this project, a constant power supply to home appliances with

no fluctuation, a renewable energy with no greenhouse effect, continuous power supply with

little running cost were achieved. The project also added to the improvement of the nation‟s

power supply system.

5.2 RECOMMENDATION

61

I strongly recommend that the system should not be loaded above 500W. This is because there is

no protection against overload. The user should be aware of his load needs and must not exceed

the maximum loading limit.

The installation process should be done by the manufacturer.

For further work, a sensor transformer with a relay should be used at the inverters output to trip

off the system in the case of overloading.

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65

APENDIX A

DIODE MANUFACTURER SAFETY DATA SHEET

66

APPENDIX B

SG3524 MANUFACTURER SAFETY DATA SHEET

67

68

APPENDIX C - TRANSISTOR

69

APPENDIX D – IRF3205 DATA SHEET

70

71

APPENDIX E

BILL OF ENGINEERING MEASUREMENT AND EVALUATION (BEME)

S/N COMPONENT QUANTITY UNIT PRICEN TOTAL

PRICEN

1 Transformer (220/12V) 2 200 400

2 Transformer (12/220V) 1 15000 15000

3 IN4002 Diode 5 10 250

4 Transistor (BC337 and

BC327)

3 20 60

5 10ΩResistor 22 10 220

6 47KΩ Resistor 1 10 10

7 1KΩ Resistor 6 10 60

8 Variable Resistor (2.2KΩ, 2 20 40

72

100KΩ)

9 4.7KΩ Resistor 2 10 20

10 10K Resistor 1 10 10

11 100K Resistor 24 10 240

12 47uF Capacitor 1 20 20

13 10uF Capacitor 2 20 40

14 104 Capacitor 3 50 150

15 220uF Capacitor 2 20 40

16 4700uF Capacitor 1 200 200

17 LED 2 10 20

18 SG3524 1 150 150

19 IC Socket 1 50 50

20 L7805 Regulator 1 100 100

21 MOSFETS (IRF3205) 20 150 3000

22 Heat sink 1 1500 1500

73

23 Nut and Bolt and washers 60 15 900

24 Multimeter 1 2500 2500

25 Screw set 6 600 6400

26 Soldering Iron 5 200 1000

27 Lead 1 1200 1200

28 Bread board 4 500 2000

29 Control circuit 1 12000 12000

30 Vero board 4 100 400

31 DC fan 2 300 600

32 AC fan 1 500 500

33 Circuit breaker 3 400 1200

34 Fabrication 1 10000 10000

35 Deep cycle battery 1 38000 38000

36 Solar panel 2 25000 50000

37 Installation wires 1 1500 1500

74

38 Fan Protectors 3 300 900

39 Installation accessories;

cable,

Lamb holder and Bulb.

1

1

1300

200

1300

200

TOTAL 130,280.00