RENEWABLE ENERGY MANAGEMENT-SOLAR BASEDLIGHTING SYSTEM WITH INVERTER AND CFL LAMP

LOAD

PROJECT THESIS

Submitted in partial fulfillment of the

Requirements for the award of the Degree of

BACHELOR OF TECHNOLOGY

IN

ELECTRONICS AND COMMUNICATION ENGINEERINGby

SYAMALAPALLI DIVYA BHANU 107R1A04A9

Under the esteemed guidance of

M.SRAVNTHI M.Tech

Assistant Professor

DEPARTMENT OF ELECTRONICS AND COMMUNICATION ENGINEERING

CMR TECHNICALCAMPUS

(AFFLIATED TO JNTU, HYDERABAD)

KANDLAKOYA (V), MEDCHAL, HYDERABAD - 501401

2013

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CMR TECHNICAL CAMPUS

(AFFLIATED TO JNTU, HYDERABAD)

ABSTRACT

Solar energy systems have emerged as a

viable source of renewable energy over the past two or three

decades, and are now widely used for a variety of industrial

and domestic applications. Such systems are based on a solar

collector, designed to collect the sun’s energy and to

convert it into either electrical power or thermal energy.

In this project Solar panel of 12V is used and a

rechargeable battery is provided to store the energy. The

back up time depends on the battery used and the circuit

design parameters. If CFL lamps are used, more back up time

can be achieved.

Emergency lamp with rechargeable battery

facility is an important project, which useful for house,

office and domestic purpose. This is much useful in rural

areas, as power cut problem is a common thing in villages.

These emergency lamps can provide sufficient light in

absence of electricity in the night time.

This consists of a colpitts oscillator, which

generates sinusoidal wave forms. These waveforms are

amplified and given to step up transformer. This step up2

transformer steps up the voltage to required level. This

also consists of battery charging unit. Auto cut off when

battery fully charged facility is also available.

There are two modes of operation, Economy mode and

bright mode. In economy mode, only one lamp will be glowing.

This gives us the long duration of back up. In bright mode

two lamps are ON. This gives more brightness, but less

duration of back up.

Chapter 1

INTRODUCTION

Renewable energy management is the sum of measures

planned and carried out to achieve the objective of using

the minimum possible energy while the comfort levels (in

offices or dwellings) and the production rates (in

factories) are maintained.

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It can be applied to a factory, to an office

building, to a sport center, to a dwelling, and to any kind

of building where energy use is required. To make an

efficient use of the energy and, as a consequence, to save

it, the actions are focused on:

Energy conservation

Energy recovery

Energy substitution

Energy is the driver of growth. International

studies on human development indicate that India needs much

larger per capita energy consumption to provide better

living conditions to its citizens. But such growth has to be

balanced and sustainable. Two important concepts here are

energy management and conservation.

Planning commission of India has estimated that

India has conservation potential at 23% of the total

commercial energy generated in the country. India's energy

requirement comes from five sectors; agriculture, industry,

transport, services and domestic, each having considerable

saving potential. For example, energy costs amount to 20

percent of the total production cost of steel in India which

is much higher than the international standards. Similarly

the energy intensity per unit of food grain production in

India is 3 - 4times higher than that in Japan. Sustainable

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growth also implies that our energy management and energy

conservation measures are eco-friendly and accompanied by

minimum pollution, in particular minimum carbon emission

Definition

Energy management is a process that not only manages

the energy production from different energy harvesting

Resources (solar, nuclear, fossil fuel) but also concerns

optimal utilization at the consumer devices. Another

comprehensive definition is “The judicious and effective use

of energy to maximize profits (minimize costs) and enhance

competitive positions”.

Objective

The objective of Energy Management is to achieve

and maintain optimum energy procurement and utilisation,

throughout the organization and:

To minimize energy costs / waste without affecting

production, comfort and quality. To minimize the

environmental effects.

One of such renewable energy is solar energy

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SOLAR POWER

Solar energy applies energy from the sun in the form

of solar radiation for heat or to generate

electricity. Solar powered electricity generation

either photovoltaic’s or heat engines (concentrated solar

power). A partial list of other solar applications includes

space heating and cooling through solar architecture, day

lighting, solar hot water, solar cooking, and high

temperature process heat for industrial purposes.

Solar technologies are broadly characterized as either

passive solar or active solar depending on the way they

capture, convert and distribute solar energy. Active solar

techniques include the use of photovoltaic panels and solar

thermal collectors to harness the energy. Passive solar

techniques include orienting a building to the Sun,

selecting materials with favorable thermal mass or light

dispersing properties, and designing spaces that naturally

circulate air. Solar energy capture is also being linked to

research involving water splitting and carbon dioxide

reduction for the development of artificial

photosynthesis or solar fuels.

Solar energy is “the engine” beyond almost all

renewable energy sources. Secondary solar

energy powered resources such as wind energy, wave

power, hydroelectricity and biomass, account for most

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of the available renewable energy on earth. Geothermal

and tidal energy are not considered as secondary

products of solar energy because they exist even

without solar radiation. 

At nights and on very cloudy days solar energy is not

fully available and energy storage systems are very

important to save energy when it is available. Solar

energy can be stored in many forms, but most common are

conversion to thermal energy, storing electrical energy

in rechargeable batteries and pumped storage systems –

pumping water to higher elevation when solar energy is

available . 

Solar energy is renewable energy source because it

cannot be depleted like fossil fuels. Solar energy is

also very clean source of energy after installation

because there are no harmful emissions or pollution

caused by using solar panels or solar cells. 

There are three basic types of solar energy usage:

Solar panels – Direct conversion of solar energy into

heat. Mostly used for water heating.

Concentrating solar power – Focusing solar radiation

using arrays of mirrors to superheat some fluid.

Superheated fluid is then used to generate electricity.

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This is the main method used in today’s solar power

plants.

Solar cells – Conversion of solar energy directly into

the electrical energy

Chapter 2

DESCRIPTION OF BLOCK DIAGRAM2.1 SOLAR CELL DESCRIPTION

Figure 2.1: Solar cell

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A solar cell is a device that converts the energy

of sunlight directly into electricity by the photovoltaic

effect. Sometimes the term solar cell is reserved for

devices intended specifically to capture energy from

sunlight such as solar panels and solar cells, while the

term photovoltaic cell is used when the light source is

unspecified. Assemblies of cells are used to make so lar

panels, solar modules, or photovoltaic arrays. Photovoltaic

is the field of technology and research related to the

application of solar cells in producing electricity for

practical use. The energy generated this way is an example

of solar energy (also known as solar power).

The highly efficient solar cell was first developed by

Chapin, Fuller and Pearson in 1954 using a diffused silicon

p-n junction. In past four decades, remarkable progress has

been made. Megawatt solar power generating plants have now

been built.

Solar cells are often electrically connected and

encapsulated as a module. Photovoltaic modules often have a

sheet of glass on the front (sun up) side, allowing light to

pass while protecting the semiconductor wafers from the

elements (rain, hail, etc.). Solar cells are also usually

connected in series in modules, creating an additive

voltage.

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Connecting cells in parallel will yield a higher

current. Modules are then interconnected, in series or

parallel, or both, to create an array with the desired peak

DC voltage and current

The power output of a solar array is measured in watts

or kilowatts. In order to calculate the typical energy needs

of the application, a measurement in watt-hours, kilowatt-

hours or kilowatt-hours per day is often used. A common rule

of thumb is that average power is equal to 20% of peak

power, so that each peak kilowatt of solar array output

power corresponds to energy production of 4.8 kWh per day

(24 hours x 1 kW x 20% = 4.8 kWh).

2.1.1 WORKING:

To make practical use of the solar-generated energy,

the electricity is most often fed into the electricity grid

using inverters (grid-connected photovoltaic systems); in

stand-alone systems, batteries are used to store the energy

that is not needed immediately.

Solar cells can also be applied to other

electronics devices to make it self-power sustainable in the

sun. There are solar cell phone chargers, solar bike light

and solar camping lanterns that people can adopt for daily

use.

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Figure 2.2: Working of solar cell

When a photon hits a piece of silicon, one of three thingscan happen:

The photon can pass straight through the silicon

— this (generally) happens for lower energy photons, The

photon can reflect off the surface, the photon can be

absorbed by the silicon, if the photon energy is higher than

the silicon band gap value. This generates an electron-hole

pair and sometimes heat, depending on the band structure.

When a photon is absorbed, its energy is given to an

electron in the crystal lattice. Usually this electron is in

the valence band, and is tightly bound in covalent bonds

between neighboring atoms, and hence unable to move far. The

energy given to it by the photon "excites" it into the

conduction band, where it is free to move around within the

semiconductor. The covalent bond that the electron was

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previously a part of now has one fewer electron — this is

known as a hole. The presence of a missing covalent bond

allows the bonded electrons of neighboring atoms to move

into the "hole," leaving another hole behind, and in this

way a hole can move through the lattice. Thus, it can be

said that photons absorbed in the semiconductor create

mobile electron-hole pairs.

A photon need only have greater energy than that of

the band gap in order to excite an electron from the valence

band into the conduction band. However, the solar frequency

spectrum approximates a black body spectrum at ~6000 K, and

as such, much of the solar radiation reaching the Earth is

composed of photons with energies greater than the band gap

of silicon. These higher energy photons will be absorbed by

the solar cell, but the difference in energy between these

photons and the silicon band gap is converted into heat (via

lattice vibrations — called phonons) rather than into usable

electrical energy.

2.2 AMPLIFIER

An amplifier is a device that changes and

increases, the amplitude of a signal. The relationship of

the input to the output of amplifier is expressed as a

function of the input frequency—is called the transfer

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function of the amplifier, and the magnitude of the transfer

function is termed the gain.

In popular use, an electronic amplifier, in which

the input "signal" is usually a voltage or a current.

In audio applications, amplifiers drive

the loudspeakers used in PA systems to make the human voice

louder or play recorded music. Amplifiers may be classified

according to the input (source) they are designed to amplify

(such as a guitar amplifier, to perform with an electric

guitar), the device they are intended to drive (such as

a headphone amplifier), the frequency range of the signals

(Audio, IF, RF, and VHF amplifiers, for example), whether

they invert the signal (inverting amplifiers and non-

inverting amplifiers), or the type of device used in the

amplification (valve or tube amplifiers, FET amplifiers,

etc.).

A related device that emphasizes conversion of

signals of one type to another (for example, a light signal

in photons to a DC signal in amperes) is a transducer,

a transformer, or a sensor. However, none of these

amplify power.

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Figure 2.3: Simple circuit to show the labels of a bipolar transistor

.

The essential usefulness of a transistor comes

from its ability to use a small signal applied between one

pair of its terminals to control a much larger signal at

another pair of terminals. This property is called gain. A

transistor can control its output in proportion to the input

signal; that is, it can act as an amplifier. Alternatively,

the transistor can be used to turn current on or off in a

circuit as an electrically controlled switch, where the

amount of current is determined by other circuit elements.

The two types of transistors have slight differences in

how they are used in a circuit. A bipolar transistor has

terminals labeled base, collector, and emitter. A small

current at the base terminal (that is, flowing from the base

to the emitter) can control or switch a much larger current

between the collector and emitter terminals. For a field-

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effect transistor, the terminals are labeled gate, source,

and drain, and a voltage at the gate can control a current

between source and drain.

The image to the right represents a typical bipolar

transistor in a circuit. Charge will flow between emitter

and collector terminals depending on the current in the

base. Since internally the base and emitter connections

behave like a semiconductor diode, a voltage drop develops

between base and emitter while the base current exists. The

amount of this voltage depends on the material the

transistor is made from, and is referred to as VBE.

2.3 TRANSFORMER

A transformer is a device that transfers electrical

energy from one circuit to another through inductively

coupled conductors—the transformer's coils. A varying

current in the first or primary winding creates a varying

magnetic flux in the transformer's core, and thus a varying

magnetic field through the secondary winding. This varying

magnetic field induces a varying electromotive force (EMF)

or "voltage" in the secondary winding. This effect is called

mutual induction.

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Figure2.4: Transformer Symbol

Transformer is a device that converts the one formenergy to another form of energy like a transducer.

Figure2.5: Transformer

2.3.1 Basic Principle

A transformer makes use of Faraday's law and the

ferromagnetic properties of an iron core to efficiently

raise or lower AC voltages. It of course cannot increase

power so that if the voltage is raised, the current is

proportionally lowered and vice versa.

Transformer refers to the static electromagnetic

setting which can transfer power from one circuit to another

one. In AC circuits, AC voltage, current and waveform can be

transformed with the help of Transformers. Each

transformation is usually to transfer from one circuit to

another one by the way of electromagnetism, but it has no

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direct relation with this circuit. It also can be

transformed through electromagnetism (electrical manner).

This electromagnetism is known as auto-

transformer. Transformer plays an important role in

electronic equipment. AC and DC voltage in Power supply

equipment are almost achieved by transformer’s

transformation and commutation. At the same time the

electrical parameters transformed by transformer are not one

but a few ones.Most of the isolation, matching and impedance

in the circuit carry out by transformer. Most of isolation,

matching and impedance in the circuit carry out by

transformer, two windings and AC power supply. The winding

is called the primary winding; another winding is connected

with load, and it is called secondary windings.

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Figurere2.6: Basic Principle

2.3.2 Transformer Working

A transformer consists of two coils (often called'windings') linked by an iron core, as shown in figurebelow. There is no electrical connection between the coils;instead they are linked by a magnetic field created in thecore.

Figure2.7: Basic Transformer

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Transformers are used to convert electricity from one

voltage to another with minimal loss of power. They only

work with AC (alternating current) because they require a

changing magnetic field to be created in their core.

Transformers can increase voltage (step-up) as well as

reduce voltage (step-down).

Alternating current flowing in the primary (input) coil

creates a continually changing magnetic field in the iron

core. This field also passes through the secondary (output)

coil and the changing strength of the magnetic field induces

an alternating voltage in the secondary coil. If the

secondary coil is connected to a load the induced voltage

will make an induced current flow. The correct term for the

induced voltage is 'induced electromotive force' which is

usually abbreviated to induced e.m.f.

The iron core is laminated to prevent 'eddy currents'

flowing in the core. These are currents produced by the

alternating magnetic field inducing a small voltage in the

core, just like that induced in the secondary coil. Eddy

currents waste power by needlessly heating up the core but

they are reduced to a negligible amount by laminating the

iron because this increases the electrical resistance of the

core without affecting its magnetic properties.

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Transformers have two great advantages over other methods of

changing voltage:

They provide total electrical isolation between the

input and output, so they can be safely used to reduce the

high voltage of the mains supply.

Almost no power is wasted in a transformer. They have a

high efficiency (power out / power in) of 95% or more.

2.3.3 Classification of Transformer

Step-Up Transformer

Step-Down Transformer

2.3.4 Step-Down Transformer

Step down transformers are designed to reduce

electrical voltage. Their primary voltage is greater than

their secondary voltage. This kind of transformer "steps

down" the voltage applied to it. For instance, a step down

transformer is needed to use a 110v product in a country

with a 220v supply.

Step down transformers convert electrical voltage from

one level or phase configuration usually down to a lower

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level. They can include features for electrical isolation,

power distribution, and control and instrumentation

applications. Step down transformers typically rely on the

principle of magnetic induction between coils to convert

voltage and/or current levels.

Step down transformers are made from two or more coils

of insulated wire wound around a core made of iron. When

voltage is applied to one coil (frequently called the

primary or input) it magnetizes the iron core, which induces

a voltage in the other coil, (frequently called the

secondary or output). The turn’s ratio of the two sets of

windings determines the amount of voltage transformation.

Figure 2.8: Step-DownTransformer

An example of this would be: 100 turns on the primary

and 50 turns on the secondary, a ratio of 2 to 1.

Step down transformers can be considered nothing more than a

voltage ratio device.

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With step down transformers the voltage ratio between

primary and secondary will mirror the "turn’s ratio" (except

for single phase smaller than 1 kva which have compensated

secondary). A practical application of this 2 to 1 turn’s

ratio would be a 480 to 240 voltage step down. Note that if

the input were 440 volts then the output would be 220 volts.

The ratio between input and output voltage will stay

constant. Transformers should not be operated at voltages

higher than the nameplate rating, but may be operated at

lower voltages than rated. Because of this it is possible to

do some non-standard applications using standard

transformers.

Single phase step down transformers 1 kva and larger

may also be reverse connected to step-down or step-up

voltages. (Note: single phase step up or step down

transformers sized less than 1 KVA should not be reverse

connected because the secondary windings have additional

turns to overcome a voltage drop when the load is applied.

If reverse connected, the output voltage will be less than

desired.)

2.3.5 Step-Up Transformer

A step up transformer has more turns of wire on the

secondary coil, which makes a larger induced voltage in the

secondary coil. It is called a step up transformer because

the voltage output is larger than the voltage input.

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Step-up transformer 110v 220v design is one whose

secondary voltage is greater than its primary voltage. This

kind of transformer "steps up" the voltage applied to it.

For instance, a step up transformer is needed to use a 220v

product in a country with a 110v supply.

A step up transformer 110v 220v converts alternating

current (AC) from one voltage to another voltage. It has no

moving parts and works on a magnetic induction principle; it

can be designed to "step-up" or "step-down" voltage. So a

step up transformer increases the voltage and a step down

transformer decreases the voltage.

The primary components for voltage transformation are

the step up transformer core and coil. The insulation is

placed between the turns of wire to prevent shorting to one

another or to ground. This is typically comprised of Mylar,

nomex, Kraft paper, varnish, or other materials. As a

transformer has no moving parts, it will typically have a

life expectancy between 20 and 25 years.

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Figure 2.9: Step-Up Transformer

Applications

Generally these Step-Up Transformers are used inindustrial applications only.

2.4 VOLTAGE REGULATOR

A voltage regulator is an electrical regulator

designed to automatically maintain a constant voltage level.

It may use an electromechanical mechanism, or passive or

active electronic components. Depending on the design, it

may be used to regulate one or more AC or DC voltages. There

are two types of regulator are they.

Positive Voltage Series (78xx) and

Negative Voltage Series (79xx)

78xx:

’78’ indicate the positive series and ‘xx’indicates the

voltage rating. Suppose 7805 produces the maximum

5V.’05’indicates the regulator output is 5V.

79xx:

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’78’ indicate the negative series and

‘xx’indicates the voltage rating. Suppose 7905 produces the

maximum -5V.’05’indicates the regulator output is -5V.

These regulators consists the three pins there are

Pin1: It is used for input pin.

Pin2: This is ground pin for regulator

Pin3: It is used for output pin. Through this pin we get the

output.

Figure 2.10: Regulator

2.5 INVERTER

Figure 2.11: Inverter

An inverter is an electrical device that

converts direct current (DC) to alternating current (AC);

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the converted AC can be at any required voltage and

frequency with the use of appropriate transformers,

switching, and control circuits.

Static inverters have no moving parts and are used in a

wide range of applications, from small switching power

supplies in computers, to large electric utility high-

voltage direct current applications that transport bulk

power. Inverters are commonly used to supply AC power from

DC sources such as solar panels or batteries.

The electrical inverter is a high-power electronic

oscillator. It is so named because early mechanical AC to DC

converters were made to work in reverse, and thus were

"inverted", to convert DC to AC.

2.5.1 Detailed operation

The simplified description above neglects several

practical factors, in particular the primary current

required to establish a magnetic field in the core, and the

contribution to the field due to current in the secondary

circuit.

Models of an ideal transformer typically assume a core

of negligible reluctance with two windings of

zero resistance. When a voltage is applied to the primary

winding, a small current flows, driving flux around

the magnetic circuit of the core. The current required to

create the flux is termed the magnetizing current; since the

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ideal core has been assumed to have near-zero reluctance,

the magnetizing current is negligible, although still

required to create the magnetic field.

The changing magnetic field induces an electromotive

force (EMF) across each winding. Since the ideal windings

have no impedance, they have no associated voltage drop, and

so the voltages VP and VS measured at the terminals of the

transformer, are equal to the corresponding EMFs. The

primary EMF, acting as it does in opposition to the primary

voltage, is sometimes termed the "back EMF". This is due

to Lenz's law which states that the induction of EMF would

always be such that it will oppose development of any such

change in magnetic field.

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2.6 RECHARGEABLE BATTERY

Figure 2.12: Rechargeable battery

A rechargeable battery or storage battery is a group of

one or more electrochemical cells. They are known as

secondary cells because their electrochemical reactions are

electrically reversible. Rechargeable batteries come in many

different shapes and sizes, ranging anything from a button

cell to megawatt systems connected to stabilize an

electrical distribution network. Several different

combinations of chemicals are commonly used, including:

lead-acid, nickel cadmium (NiCd), nickel metal hydride

(NiMH), lithium ion (Li-ion), and lithium ion polymer (Li-

ion polymer).

Rechargeable batteries have lower total cost of

use and environmental impact than disposable batteries. Some

rechargeable battery types are available in the same sizes

as disposable types. Rechargeable batteries have higher

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initial cost, but can be recharged very cheaply and used

many times.

Rechargeable batteries are used for automobile

starters, portable consumer devices, light vehicles (such as

motorized wheelchairs, golf carts, electric bicycles, and

electric forklifts), tools, and uninterruptible power

supplies. Emerging applications in hybrid electric vehicles

and electric vehicles are driving the technology to reduce

cost and weight and increase lifetime.

Normally, new rechargeable batteries have to be charged

before use; newer low self-discharge batteries hold their

charge for many months, and are supplied charged to about

70% of their rated capacity.

Grid energy storage applications use rechargeable

batteries for load leveling, where they store electric

energy for use during peak load periods, and for renewable

energy uses, such as storing power generated from

photovoltaic arrays during the day to be used at night. By

charging batteries during periods of low demand and

returning energy to the grid during periods of high

electrical demand, load-leveling helps eliminate the need

for expensive peaking power plants and helps amortize the

cost of generators over more hours of operation.

The US National Electrical Manufacturers

Association has estimated that U.S. demands for rechargeable

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batteries is growing twice as fast as demand for non

rechargeable.

2.6.1 CHARGING AND DISCHARGING

During charging, the positive active

material is oxidized, producing electrons, and the negative

material is reduced, consuming electrons. These electrons

constitute the current flow in the external circuit.

The electrolyte may serve as a simple buffer for ion flow

between the electrodes, as in lithium-ion and nickel-

cadmium cells, or it may be an active participant in

the electrochemical reaction, as in lead-acid cells.

Figure 2.13: Charging of a secondarycell battery.

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Figure 2.14: Battery charger

Figure 2.15: A solar-powered charger for rechargeable batteries

The energy used to charge

rechargeable batteries usually comes from a battery

charger using AC mains electricity. Chargers take from a few

minutes (rapid chargers) to several hours to charge a

battery. Most batteries are capable of being charged far

faster than simple battery chargers are capable of; there

are chargers that can charge consumer sizes of NiMH

batteries in 15 minutes. Fast charges must have multiple

ways of detecting full charge (voltage, temperature, etc.)

to stop charging before onset of harmful overcharging.

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Rechargeable multi-cell batteries are

susceptible to cell damage due to reverse charging if they

are fully discharged. Fully integrated battery chargers that

optimize the charging current are available.

Attempting to recharge non-rechargeable

batteries with unsuitable equipment may cause battery

explosion Flow batteries, used for specialized applications,

are recharged by replacing the electrolyte liquid.

Battery manufacturers' technical notes often

refer to VPC; this is volts per cell, and refers to the

individual secondary cells that make up the battery. For

example, to charge a 12 V battery (containing 6 cells of 2 V

each) at 2.3 VPC requires a voltage of 13.8 V across the

battery's terminals.

Non-rechargeable alkaline and zinc-carbon cells output

1.5V when new, but this voltage gradually drops with use.

Most NiMH AA and AAA batteries rate their cells at 1.2 V,

and can usually be used in equipment designed to use

alkaline batteries up to an end-point of 0.9 to 1.2V

2.6.2 Reverse charging

Subjecting a discharged cell to a current in the

direction which tends to discharge it further, rather than

charge it, is called reverse charging; this damages cells.

Reverse charging can occur under a number of circumstances,

the two most common being:

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When a battery or cell is connected to a charging

circuit the wrong way round.

When a battery made of several cells connected in

series is deeply discharged.

When one cell completely discharges ahead of the rest,

the live cells will apply a reverse current to the

discharged cell ("cell reversal"). This can happen even to a

"weak" cell that is not fully discharged. If the battery

drain current is high enough, the weak cell's internal

resistance can experience a reverse voltage that is greater

than the cell's remaining internal forward voltage. This

results in the reversal of the weak cell's polarity while

the current is flowing through the cells. This can

significantly shorten the life of the affected cell and

therefore of the battery. The higher the discharge rate of

the battery needs to be, the better matched the cells should

be, both in kind of cell and state of charge. In some

extreme cases, the reversed cell can begin to emit smoke or

catch fire.

In critical applications using Ni-Cad batteries,

such as in aircraft, each cell is individually discharged by

connecting a load clip across the terminals of each cell

thereby avoiding cell reversal, then charging the cells in

series

2.7 UNIDIRECTIONAL CURRENT CONTROLLER

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Diodes allow electricity to flow in only one

direction.  The arrow of the circuit symbol shows the

direction in which the current can flow.  Diodes are the

electrical version of a valve and early diodes were actually

called valves.

Figure 2.16: Diode Symbol

A diode is a device which only allows current to flow

through it in one direction.  In this direction, the diode

is said to be 'forward-biased' and the only effect on the

signal is that there will be a voltage loss of around 0.7V. 

In the opposite direction, the diode is said to be 'reverse-

biased' and no current will flow through it.

2.8 RECTIFIER

The purpose of a rectifier is to convert an AC waveform

into a DC waveform (OR) Rectifier converts AC current or

voltages into DC current or voltage.  There are two

different rectification circuits, known as 'half-wave' and

'full-wave' rectifiers.  Both use components called diodes

to convert AC into DC.

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2.8.1 The Half-wave Rectifier

The half-wave rectifier is the simplest type of

rectifier since it only uses one diode, as shown in figure.

Figure 2.17: Half Wave Rectifier

Figure 2.8.1 shows the AC input waveform to this

circuit and the resulting output.  As you can see, when the

AC input is positive, the diode is forward-biased and lets

the current through.  When the AC input is negative, the

diode is reverse-biased and the diode does not let any

current through, meaning the output is 0V.  Because there is

a 0.7V voltage loss across the diode, the peak output

voltage will be 0.7V less than Vs.

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Figure 2.18: Half-Wave Rectification

While the output of the half-wave rectifier is DC (it

is all positive), it would not be suitable as a power supply

for a circuit.  Firstly, the output voltage continually

varies between 0V and Vs-0.7V, and secondly, for half the

time there is no output at all. 

2.8.2 The Bridge Rectifier

The circuit in figure 3 addresses the second of these

problems since at no time is the output voltage 0V.  This

time four diodes are arranged so that both the positive and

negative parts of the AC waveform are converted to DC.  The

resulting waveform is shown in figure 4.

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Figure 2.19: Bridge Rectifier

Figure 2.20: Bridge Rectification

When the AC input is positive, diodes A and B are

forward-biased, while diodes C and D are reverse-biased. 

When the AC input is negative, the opposite is true - diodes

C and D are forward-biased, while diodes A and B are

reverse-biased.

While the full-wave rectifier is an improvement on the

half-wave rectifier, its output still isn't suitable as a

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power supply for most circuits since the output voltage

still varies between 0V and Vs-1.4V.  So, if you put 12V AC

in, you will 10.6V DC out.

2.9 POWER MOSFET

A Power MOSFET is a specific type of metal oxide

semiconductor field-effect transistor (MOSFET) designed to

handle significant power levels. Compared to the other power

semiconductor devices (IGBT,Thyristor...), its main

advantages are high commutation speed and good efficiency at

low voltages. It shares with the IGBT an isolated gate that

makes it easy to drive.

It was made possible by the evolution of CMOS

technology, developed for manufacturing Integrated circuits

in the late 1970s. The power MOSFET shares its operating

principle with its low-power counterpart, the lateral

MOSFET.

The power MOSFET is the most widely used low-voltage

(i.e. less than 200 V) switch. It can be found in most power

supplies, DC to DC converters, and low voltage motor

controllers.

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Figure 2.21: Power MOSFET

2.9.1 BASIC STRUCTURE

Power MOSFETs have a different structure than the

lateral MOSFET: as with all power devices, their structure

is vertical and not planar. In a planar structure, the

current and breakdown voltage ratings are both functions of

the channel dimensions (respectively width and length of the

channel), resulting in inefficient use of the "silicon

estate”. With a vertical structure, the voltage rating of

the transistor is a function of the doping and thickness of

the Nepitaxial layer (see cross section), while the current

rating is a function of the channel width. This makes

possible for the transistor to sustain both high blocking

voltage and high current within a compact piece of

silicon.Power MOSFET 2It is worth noting that power MOSFETs

with lateral structure exists. They are mainly used in high-

end audio amplifiers. Their advantage is a better behaviour

in the saturated region (corresponding to the linear region

of a bipolar transistor) than the vertical MOSFETs. Vertical

MOSFETs are designed for switching applications, so they are

only used in On or Off states.

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Figure 2.22: Basic Structure

2.10 LIGHT-EMITTING DIODE (LED):

The longer lead is the anode (+) and the shorter lead

is the cathode (&minus). In the schematic symbol for an LED

(bottom), the anode is on the left and the cathode is on the

right. Light emitting diodes are elements for light

signalization in electronics.

Figure 2.23: light emitting diode

2.10.1 Principle & Mechanism

The essential portion of the Light Emitting Diode is

the semiconductor chip. Semiconductors can be either40

intrinsic or extrinsic. Intrinsic semiconductors are those

in which the electrical behavior is based on the electronic

structure inherent to the pure material. When the electrical

characteristics are dictated by impurity atoms, the

semiconductor is said to be extrinsic. This chip is further

divided into two parts or regions which are separated by a

boundary called a junction. The p-region is dominated by

positive electric charges (holes) and the n-region is

dominated by negative electric charges (electrons). The

junction serves as a barrier to the flow of the electrons

between the p and the n-regions. This is somewhat similar to

the role of the band-gap because it determines howmuch

voltage is needed to be applied to the semiconductor chip

before the current can flow and the electrons pass the

junction into the p-region.

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Figure 2.24: working of LED

In general, to achieve higher momentum states (with

higher velocities), there must be an empty energy state into

which the electron may be excited. (In other words, to

achieve a net flow of electrons in one direction, some

electrons must change their wave vectors thereby increasing

their energy.) Band-gaps determine how much energy is needed

for the electron to jump from the valence band to the

conduction band. As an electron in the conduction band

recombines with a hole in the valence band, the electron

makes a transition to a lower-lying energy state and

releases energy in an amount equal to the band-gap energy.

This energy is released in photons. Normally the energy

heats the material. In a LED this energy goes into emitted

infrared or visible light.

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Figure 2.25: LED

They are manufactured in different shapes, colors and

sizes. For their low price, low consumption and simple use,

they have almost completely pushed aside other light

sources- bulbs at first place.

It is important to know that each diode will be

immediately destroyed unless its current is limited. This

means that a conductor must be connected in parallel to a

diode. In order to correctly determine value of this

conductor, it is necessary to know diode’s voltage drop in

forward direction, which depends on what material a diode is

made of and what colors it is. Values typical for the most

frequently used diodes are shown in table below: As seen,

there are three main types of LEDs. Standard ones get full

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brightness at current of 20mA. Low Current diodes get full

brightness at ten time’s lower current while Super Bright

diodes produce more intensive light than Standard ones.

Since the 8051 microcontrollers can provide only

low input current and since their pins are configured as

outputs when voltage level on them is equal to 0, direct

confectioning to LEDs is carried out as it is shown on

figure (Low current LED, cathode is connected to output

pin).

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Chapter 4

WORKING PROCEDURE:

The kit is provided with two sources i.e. one

renewable source through the solar panel and the other

non-renewable energy source through power connection

Now when the kit is connected to either of the sources

the rechargeable battery will start charging and the

charge is stored in the battery

When the kit is connected to the non renewable energy

source then firstly the voltage is decreased with the

help of step down transformer

After that the voltage passes through the bridge

rectifier where the AC is converted to pulsating DC and

the it passes through the capacitor filter where the

output is filtered and send to the regulator

Regulator then converts unregulated output to

regulated output

Now here we are provided with another ceramic filter

for proper filtering

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Then a LED(light emitting diode) is given to just find

whether the kit is working or not if the kit is proper

then the LED will glow otherwise not

Just before the LED a resistor is connected to protect

the LED from getting damaged

Now this output which is DC is send to the inverter

And if we are connecting the kit to a renewable source

of energy then the energy is stored into the battery

And here to prevent the kit from bidirectional current

flow a diode id connected in the way to inverter .this

diode acts as a unidirectional current controller

Now this power is given to the inverter

Inverter consists of power MOSFETS, Step up

transformer,RLC circuit

Power MOSFET amplify the power and here the DC is

converted to AC and then it is given to step up

transformer which increases the voltage and now the

output is given to RLC for smoothing f the output now

this output is a partial square wave.

Now the output is given to the load i.e. CFL lamp

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Chapter 5

ADVANTAGES OF THE PROJECT

Renewable and Non conventional Energy consumption

Works in Day and Night

Fit and Forget system

Low cost and reliable circuit

AC Charge provision

Durability

Convenience to operate

Low maintenance

Low power consumption

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Chapter 6

APPLICATIONS OF THE PROJECT

Office / Home

Hotels / Shops and house hold applications

Industries

Housekeeping Power

Solar power packs

Solar LED street lights have been in business in

introducing new lighting technology. Our primary focus is

to improve efficient energy use for all of humankind.

Solar garden illuminating

Solar lanterns

Solar LED garden lights

Solar light flashers

Solar LED lighting luminary

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49

Chapter

8

CONCLUSION

This project presents a solar based lighting system with

inverter and CFL lamp load.

Set up on the solar charging system, the battery used to

store the energy. The proposed solar inverter system can

convert the sun light into electrical energy and stores

in the rechargeable battery.

The result shows that higher generating power efficiency

is indeed achieved using the solar inverter system.

The proposed method is verified to be highly beneficial

for the solar power generation.

The recent success in solar lighting has created an

international focus on solar lighting technologies and

experts are looking at many applications that can take

advantages of all the benefits

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REFERENCE

Text Books:

[1] Working with Solar Energy by Cruise Leonardo

[2] Electrical Applications By Morris Hamington

Website:

[3] www.howstuffworks.com

[4] www.answers.com

[5] www.radiotronix.com

Magazines:

[6] Electronics for you

[7] Let us go Solar

[8] Electrikindia

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