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SOLAR POWER INVERTER

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CHAPTER ONE
INTRODUCTION
1.1 BACKGROUND OF STUDY
We are like tenant farmers chopping down the fence around our house for fuel when we should be
using nature's inexhaustible sources of energy -- sun, wind and tide (Edison, 1931)
In 1931, not long before he died, the inventor told his friends Henry Ford and Harvey Firestone:
‘I’d put my money on the sun and solar energy. what a source of power! I hope we don't have to
wait until oil and coal run out before we tackle that.’
Solar power is a big idea, whose time has come. And, like the space program, solar is an idea that
can shape our nation in significant and positive ways. In the coming months, in the coming years,
we will face critical decisions on how to address climate change, reduce our dependence on foreign
energy, and boost our economic competitiveness. The beauty of solar power is that it offers an
elegant solution to all three of these challenges. Imagine what it would be like if every time that it
rained it rained oil, big black drops falling from the sky. Don't you think that we would find some
way to run around with a big bucket and collect all of that energy that was falling from the sky? I
know this sounds like an absurd picture, but the reality is that what we have outside today is
something very comparable to that. (Gifford, 2008)
Solar energy is quite simply the energy produced directly by the sun and collected elsewhere,
normally the Earth. The sun creates its energy through a thermonuclear process that converts about
650,000,000tons of hydrogen to helium every second. The process creates heat and
electromagnetic radiation. The heat remains in the sun and is instrumental in maintaining the
thermonuclear reaction. The electromagnetic radiation (including visible light, infra-red light, and
ultra-violet radiation) streams out into space in all directions. Only a very small fraction of the
total radiation produced reaches the Earth. The radiation that does reach the Earth is the indirect
source of nearly every type of energy used today. The exceptions are geothermal energy, and
nuclear fission and fusion. Even fossil fuels owe their origins to the sun; they were once living
plants and animals whose life was dependent upon the sun.
Solar power is a safe form of nuclear energy. We are using fusion reactions that are 93 million
miles away to make light that we then convert to electricity with photovoltaic modules (White,
2014).
Solar energy can be utilized to produce electric power by a solar inverter. A solar power inverter
is similar to a normal electric inverter but uses the energy of the sun
The need of running AC Loads on solar energy leads us to the design of Solar Power Inverter.
Since the majority of modern conveniences all run on 240 volts AC, the Power Inverter will be the
heart of the Solar Energy System. It not only converts the low voltage 12 volts DC to the 240 volts
AC that runs most appliances, but also can charge the batteries.
A solar inverter or PV (photovoltaic) inverter, is a type of electrical converter which converts the
variable direct current (DC) output of a photovoltaic (PV) solar panel into a utility frequency
alternating current (AC) that can be fed into a commercial electrical grid or used by a local, offgrid electrical network. It is a critical balance of system (BOS)–component in a photovoltaic
system, allowing the use of ordinary AC-powered equipment. Solar power inverters have special
functions adapted for use with photovoltaic arrays, including maximum power point tracking and
anti-islanding protect (Wikipedia, 2014)
The solar inverter is a critical component in a solar energy system. It performs the conversion of
the variable DC output of the Photovoltaic (PV) module(s) into a clean sinusoidal 50 or 60 Hz AC
current that is then applied directly to the commercial electrical grid or to a local, off-grid electrical
network
1.2 PROBLEM STATEMENT
1.3 AIM AND OBJECTIVES
1.3.1 AIM
The main aim of this project is to design and construct a 2KVA solar power inverter
1.3.2 OBJECTIVES
The objectives are;

Review of the project

Design of a 2KVA solar power inverter

Construction of a 2KVA solar power inverter

Test
1.4 SCOPE OF STUDY
Solar energy makes it possible to provide a clean reliable supply of alternative electricity free of
sags or surges which could be found in the line voltage frequency. This project design aims at
creating a 2KVA power source which can be utilized as a regular power source by individuals at
home or in the office
This project covers the design and construction of a 2KVA Solar Power inverter which involves a
solar panel, battery and an inverter.
.1.5 SIGNIFICANCE OF PROJECT
The major problem solved by this design is regularity of electricity supply at all times, as the
battery will be constantly charged during day periods without affecting the integrity of the battery
during night periods when it will be used as an alternate source if supply from the national grid
fails
The projects seek to improve solar power inverters and bring innovative features such as

Availability of a low-cost power source

An ecofriendly backup power supply

Low maintenance cost
The use of solar power has many advantages. First, the energy from the sun is free and readily
accessible in most parts of the world. Moreover, the sun will keep shining until the world's end.
Also, silicon from which most photovoltaic cells are made is an abundant and nontoxic element
(the second most abundant material in the earth's crust).
Second, the whole energy conversion process is environmentally friendly. It produces no noise,
harmful emissions or polluting gases. The burning of natural resources for energy can create
smoke, cause acid rain and pollute water and air. Carbon dioxide, CO2, a leading greenhouse gas,
is also produced in the case of burning fuels. Solar power uses only the power of the sun as its
fuel. It creates no harmful by-product and contributes actively to the reduction of global warming.
1.6 ORGANISATION OF CHARTS
There are two chapters in all
Chapter 1 explains the background of the project, statement of problem, aims and objectives of the
project, significance of project and limitations
Chapter 2 talks of the literature review which entails the introduction to solar energy, solar cells,
how solar cells work, inverters, types of inverter and battery
1.7 LIMITATONS
The major limitation of this project is the dependence on a battery source to operate at night and
dc energy from solar panel to operate in the day. This means the possibility and duration of
operation is dependent on the availability of a DC source (battery or solar panel) to operate.
CHAPTER TWO
LITERATURE REVIEW
2.1 INTRODUCTION TO SOLAR ENERY
In today's climate of growing energy needs and increasing environmental concern, alternatives to
the use of non-renewable and polluting fossil fuels have to be investigated. One such alternative
is solar energy.
Solar energy is quite simply the energy produced directly by the sun and collected elsewhere,
normally the Earth. The sun creates its energy through a thermonuclear process that converts about
650,000,000 tons of hydrogen to helium every second. The process creates heat and electromagnetic radiation.
The heat remains in the sun and is instrumental in maintaining the thermonuclear reaction. The
electromagnetic radiation (including visible light, infra-red light, and ultra-violet radiation)
streams out into space in all directions.
Only a very small fraction of the total radiation produced reaches the Earth. The radiation that
does reach the Earth is the indirect source of nearly every type of energy used today. The
exceptions are geothermal energy, and nuclear fission and fusion. Even fossil fuels owe their
origins to the sun; they were once living plants and animals whose life was dependent upon the
sun.
Much of the world's required energy can be supplied directly by solar power. More still can be
provided indirectly
2.2 SOLAR PANELS
A solar panel is a device that collects and converts solar energy into electricity or heat. Solar
photovoltaic panels can be made so that the sun's energy excites the atoms in a silicon layer
between two protector panels. Electrons from these excited atoms form an electric current, which
can be used by external devices. Solar panels were in use over one hundred years ago for water
heating in homes. Solar panels can also be made with a specially shaped mirror that concentrates
light onto a tube of oil. The oil then heats up, and travels through a vat of water, instantly boiling
it. The steam is created and then it turns a turbine for power.
Some materials are able to absorb photons of light and release electron, this phenomenon is called
photoelectric effect. Photovoltaic cells convert sunlight directly into electrical energy without
using any mechanical or chemical mechanism.
Photovoltaic cell operation is based on the principal of semiconductor technology. When two
semiconductors, such as silicon and gallium arsenide, are put into contact with each other and
exposed to light, electricity will flow between them. This was first noted by Edmund Becquerel in
1839 (SEIA). Actual development of PV technology began in the 1950s and gained greater impetus
through the National Aeronautics and Space Administration (NASA) space program during the
1960s (NASA). Now researchers are trying to increase conversion efficiencies and mass
production strategies in order to cost down the producing of PV modules.
Solar energy offers several advantages over other energy sources

It consumes no conventional fossil fuels,

Creates no pollution

Is a widely available and reliable source of energy-

Has no associated storage or transportation difficulties

Is eminently reliable and practicable for wide scale power production
However, this technology can be limited because of the movement of the sun, especially in extreme
latitudes.
A variety of materials may be used in the manufacture of solar cells, each of which has different
cost efficiency. In fact, PV cells must be designed to convert different wave lengths of sunlight
that reaches the earth's surface into useful energy with high efficiency.
The materials used to make solar cells can be classified into three generations:

The first generation of PV technologies: crystalline silicon cells. Silicon is one of the most
abundant elements on the earth and it is very suitable for use in photovoltaic systems.
Depending on how silicon wafers are made, crystalline silicon cells are divided into two
general categories: mono-crystalline silicon and poly-crystalline silicon. Other crystalline
categories include gallium arsenide cells.

Second generation of PV technologies: Thin film solar cells. After more than 20 years of
research and development, thin film solar cells have started to spread. Compared to silicon
wafers, thin films reduced the cost of electricity quite significant. Three main types of thin
film solar cells, which have already been commercialized, are:
 Amorphous silicon (aSi/µc-Si)
 Cadmium telluride (Cd-Te)
 Copper–indium–selenide (CIS) and Copper- indium –gallium- selenide (CIGS)

The third generation of PV technologies: In development. These technologies are still and still
being developed and tested. They include:
 Concentrated photovoltaic (CPV)
 Organic solar cells
 Dye-sensitized solar cell
 Polymer solar cells
 Liquid-crystal solar cells
Crystalline Silicon Cell Structure
(Four Peaks Technologies, 2011)
Layers of a Solar Cell
Dako Power, cc 2008
2.3 HISTORY OF SOLAR CELL
The history of solar cells started way back in 1876. William Grylls Adams along with a student of
his, Richard Day, discovered that when selenium was exposed to light, it produced electricity. An
electricity expert, Werner von Siemens, stated that the discovery was “scientifically of the most
far-reaching importance”. The selenium cells were not efficient, but it was proved that light,
without heat or moving parts, could be converted into electricity.
In 1953, Calvin Fuller, Gerald Pearson, and Daryl Chapin, discovered the silicon solar cell. This
cell actually produced enough electricity and was efficient enough to run small electrical devices.
The New York Times stated that this discovery was “the beginning of a new era, leading eventually
to the realization of harnessing the almost limitless energy of the sun for the uses of civilization.”
The year is 1956, and the first solar cells are available commercially. The cost however is far from
the reach of everyday people. At $300 for a 1-watt solar cell, the expense was far beyond anyone’s
means. 1956 started showing us the first solar cells used in toys and radios. These novelty items
were the first item to have solar cells available to consumers.
In the late 1950’s and early 1960’s satellites in the USA’s and Soviet’s space program were
powered by solar cells and in the late 1960’s solar power was basically the standard for powering
space bound satellites.
In the early 1970’s a way to lower to cost of solar cells was discovered. This brought the price
down from $100 per watt to around $20 per watt. This research was spearheaded by Exxon. Most
off-shore oil rigs used the solar cells to power the waning lights on the top of the rigs.
The period from the 1970’s to the 1990’s saw quite a change in the usage of solar cells. They began
showing up on railroad crossings, in remote places to power homes, Australia used solar cells in
their microwave towers to expand their telecommunication capabilities. Even desert regions saw
solar power bring water to the soil where line fed power was not an option!
Today we see solar cells in a wide variety of places. You may see solar powered cars. There is
even a solar powered aircraft that has flown higher than any other aircraft with the exception of
the Blackbird. With the cost of solar cells well within everyone’s budget, solar power has never
looked so tempting.
Recently new technology has given us screen printed solar cells, and a solar fabric that can be used
to side a house, even solar shingles that install on our roofs. International markets have opened up
and solar panel manufacturers are now playing a key role in the solar power industry.
2.4 HOW SOLAR PANELS WORK
The basic element of solar panels is pure silicon. When stripped of impurities, silicon makes an
ideal neutral platform for transmission of electrons. In silicon’s natural state, it carries four
electrons, but has room for eight. Therefore, silicon has room for four more electrons. If a silicon
atom comes in contact with another silicon atom, each receives the other atom's four electrons.
Eight electrons satisfy the atoms' needs, this creates a strong bond, but there is no positive or
negative charge. This material is used on the plates of solar panels. Combining silicon with other
elements that have a positive or negative charge can also create solar panels.
For example, phosphorus has five electrons to offer to other atoms. If silicon and phosphorus are
combined chemically, the results are a stable eight electrons with an additional free electron. The
silicon does not need the free electron, but it cannot leave because it is bonded to the other
phosphorous atom. Therefore, this silicon and phosphorus plate is considered to be negatively
charged.
A positive charge must also be created in order for electricity to flow. Combining silicon with an
element such as boron, which only has three electrons to offer, creates a positive charge. A silicon
and boron plate still have one spot available for another electron. Therefore, the plate has a positive
charge. The two plates are sandwiched together to make solar panels, with conductive wires
running between them.
Photons bombard the silicon/phosphorus atoms when the negative plates of solar cells are pointed
at the sun. Eventually, the 9th electron is knocked off the outer ring. Since the positive
silicon/boron plate draws it into the open spot on its own outer band, this electron does not remain
free for long. As the sun's photons break off more electrons, electricity is then generated. When all
of the conductive wires draw the free electrons away from the plates, there is enough electricity to
power low amperage motors or other electronics, although the electricity generated by one solar
cell is not very impressive by itself. When electrons are not used or lost to the air they are returned
to the negative plate and the entire process begins again
2.5 METHODS FOR USING SOLAR ENERGY
Photovoltaic systems are applicable for public consumption and agriculture. It can be connected
to the power grid or works as stand-alone systems (autonomous) with the fixed or mobile structure
in small or large scale from providing energy required for small calculators to large power plant.
Possibility to track the sun and maximizing electricity generation from the sun light during the day
are the key advantages of using mobile system however due to the high risk of failures in
mechanical systems, using this technology for small and sporadic scale are not recommended. This
technology has been used only in few PV power plants around the worlds.
2.5.1 GRID CONNECTED
In this method, electrical energy from photovoltaic systems is transferred directly to the national
power grid. Voltage and frequency of the electrical energy produced by the photovoltaic system
can be adjusted to meet the voltage, frequency and phase characteristic of the national power grid
using electrical equipment to convert direct current (DC) to alternating current (AC), such as
inverters connected to the network and etc.)
Centralize/decentralize form of grid connected PV system boosts energy power of distribution
network (injected voltage and current prevents voltage drop of power distribution network during
the day.)
By implementing grid connected PV system, each member of national power grid represents as a
small distributed generation (DG). In addition to providing enough supply of electrical energy
required by the consumer; a consumer surplus can be injected to distributed network grid
Grid-Connected Small Solar Electric Systems
(Encyclopedia of Science)
2.5.2 STAND-ALONE PV SYSTEM
A stand-alone system provides energy for telecommunications, residential house, nomadic tents
and rural cottages needs, in general areas lacking electricity network. These systems produce a
high proportion of the world’s off-grid power generation. In many countries without electricity
(especially developing countries) these systems can be used to provide electrical energy
requirements of villages, for example, Indonesia has been providing electricity for rural
households in this way, since 2007. (RENDEV, 2009)
The major benefits of these systems, particularly in deprived and rural areas are:

No need for fuel and problems to providing it, especially in hard to reach areas.

No need for constant repair and maintenance with proper lifetime.
2.6 INVERTERS
The inverter takes DC power from the charged battery bank and converts it to AC power for the
typical household lights and appliances. Once the number of watt-hours required for a day is
determined, the peak loads need to be ascertained to properly size the inverter. This is the number
of watts used based on all appliances and loads that will be running at one time. A water pump
and washing machine motor is an example of what may be the peak load requirements. A 1/2 HP
(horse power) pump and washing machine will use about 1875 (adjusted) watts per hour. If this
represents the total peak loads, an inverter that will be able to supply at least 1875 watts of
continuous power from the battery bank; say one in the 2000-watt range will be needed. It's a
good idea to start out the system with the size of inverter you plan to grow into, as upgrading to
newer, larger models is costly. (Pure Energies 2014)
2.7 TYPES OF INVERTERS
There are two basic types of inverters.
2.7.1 CENTRAL INVERTERS
Central inverters are well-tested and reliable systems that have been around for decades. These are
the most common types of inverters. With central inverters, every solar panel is wired in a “string”
to the inverter box. The conversion from DC to AC occurs at one central location, such as a garage.
Because the solar panels are wired in “series,” each panel’s power output depends on all of the
panels working. For example, In a string of Christmas tree lights. If one bulb goes out, the whole
string of lights go out until the bad bulb is replaced. So, if shade from a tree covers one panel, it
can seriously diminish the power produced by the whole solar system until the shade clears. This
is why an accurate shade analysis is so important.
2.7.2 MICRO INVERTERS
Micro inverters are relatively new to solar. Instead of converting the DC to AC power at a central
location, micro inverters are installed right under each solar panel. The main advantage to micro
inverters is the ability for each solar panel to transmit power into the house. In other words, each
panel produces its own solar power and keeps producing out solar watts regardless of what
happening to the panel beside it. The down side of micro inverters is that they can be more
expensive and take more labor cost to replace each inverter. Also, because they are so new, micro
inverter reliability is unproven outside of lab testing. (Pure Energies 2014)
2.8 HARDWARE REQUIREMENT FOR INVERTERS

Battery

PWM

Inverter

MOSFET

Photovoltaic cells/solar cells

Resistor

Capacitor
2.8.1 BATTERY
An electrical battery is a combination of one or more electrochemical cells, used to convert stored
chemical energy into electrical energy. The battery has become a common power source for many
household, robotics and industrial applications. Larger batteries provide standby power for
telephone exchanges or computer data centers.
2.8.2 PWM (Pulse Wave Modulation) INVERTER IC
The PWM Inverter is used to develop the PWM pulses based on a fixed frequency using a common
oscillator The IC SG3524 operates at a fixed frequency, the oscillation frequency is determined by
one timing resistor RT and one timing capacitor CT. The SG3524 contains an inbuilt 5V regulator
that supplies as a reference voltage, also providing the SG3524 internal regulator control circuitry.
Comparator provides a linear control of the output pulse width (duration) by the error amplifier.
The resultant PWM pulse from the comparator is passed to the corresponding output pass transistor
(Q1, Q2 refers block diagram) using the pulse steering flip flop, which is synchronously toggled
by the oscillator output.
2.8.3 MOSFET (IRF 510)
The metal–oxide–semiconductor field-effect transistor (MOSFET, MOS-FET, or MOS FET) is a
device used for amplifying or switching electronic signalsThe basic principle of the device a
voltage on the oxide-insulated gate electrode can induce a conducting channel between the two
other contacts called the source and drainIt is by far the most common transistor in both digital
and analog circuits, though the bipolar junction transistor was at one time much more common.
2.8.4 BC547 (NPN –Transistor)
The BC547 transistor is an NPN Epitaxial Silicon Transistor. It is used in general-purpose
switching and amplification BC847/BC547 series 45 V, 100 mA NPN general-purpose transistors.
The ratio of two currents (Ic/Ib) is called the DC Current Gain of the device and is given the symbol
of hfe or nowadays Beta, (β). The current gain from the emitter to the collector terminal, Ic/Ie, is
called Alpha, (α), and is a function of the transistor itself.
2.8.5 1N4148
The 1N4148 is a standard small signal silicon diode used in signal processing. The 1N4148 is
generally available in a DO-35 glass package and is very useful at high frequencies with a reverse
recovery time of no more than 4ns. This permits rectification and detection of radio frequency
signals very effectively, as long as their amplitude is above the forward conduction threshold of
silicon (around 0.7V) or the diode is biased.
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