PROJECT REPORT ON SOLAR LIGHTING SYSTEM WITH 10W SOLAR PANEL
Submitted to the faculty of Electronics & Communication
engineering U.P. Technical University in the partial fulfillment
for the award of the degree ofBACHELOR OF TECHNOLY In Electronics
& Communication Engineering by Jyotsana Mourya Apoorva
MaheswariSana ZahidUnder the able guidance of ASTT.PRO. RAJAT
VARSHNEY FACULTY OF ELECTRONICS & INSTRUMENTATION ENGINEERING
INVERTIS INSTITUTE OF ENGINEERING AND TECHNOLOGY
CERTIFICATE
This is to certify that Miss Jyotsana Mourya, Apoorva Maheswari,
Sana Zahid have worked on their project SOLAR LIGHTING SYSTEM WITH
10W SOLAR PANEL for our college as a partial fulfillment of the
requirements for the degree of Bachelor Of Electronics &
Communication Engineering at Invertis Institute Of Engineering And
Technology, uttar Pradesh technical university,lucknow.
This is the report of work done by them under my guidance and
supervision.
Mr. Rajat Varshney Electronics & instrumentation Engineering
Bareilly. Date:Place: Bareilly
ACKNOWLEDGEMENT Coming up with an idea is not difficult to
everybody but giving it a start & taking to the completion is
different story altogether so here we are bound to be grateful to
the numerous people who made it possible for us to the idea we
considered it as our final year project.First we would like to
express my gratitude towards our project guide Mr. RAJAT SIR, head
of department Mr. TARUN DUBEY SIR and our group who provide the
expertise required making our idea red completion and help us at
every moment to complete the project. At last we acknowledge our
heartfelt gratitude to our parent without their support this
project would have been a dream.
Jyotsana MouryaApoorva Maheshwari Sana Zahid
ABSTRACTThe world can not continue to rely for long on fossil
fuels for its energy requirements. Fossil fuel reserves are
limited. In addition, when burnt, these add to global warming, air
pollution and acid rain. So solar photovoltaic are ideal for
providing independent electric power and lighting in isolated rural
areas that are far away from the power grid. These systems are
nonpolluting, do not deplete the resources and are cheap in long
run. The aim of this circuit is to demonstrate how we can utilize
solar light in rural areas, i.e. , how we can store the solar
energy and then use it for small scale lighting application.Solar
energy, radiant light and heat from the sun, has been harnessed by
humans since ancient times using a range of ever-evolving
technologies. Earth's land surface, oceans and atmosphere absorb
solar radiation, and this raises their temperature. Warm air
containing evaporated water from the oceans rises, causing
atmospheric circulation or convection. When the air reaches a high
altitude, where the temperature is low, water vapor condenses into
clouds, which rain onto the Earth's surface, completing the water
cycle. The latent heat of water condensation amplifies convection,
producing atmospheric phenomena such as wind, cyclones and
anti-cyclones. Sunlight absorbed by the oceans and land masses
keeps the surface at an average temperature of 14C. By
photosynthesis green plants convert solar energy into chemical
energy, which produces food, wood and the biomass from which fossil
fuels are derived.The total solar energy absorbed by Earth's
atmosphere, oceans and land masses is approximately
3,850,000exajoules (EJ) per year. In 2002, this was more energy in
one hour than the world used in one year. Photosynthesis captures
approximately 3,000EJ per year in biomass. The amount of solar
energy reaching the surface of the planet is so vast that in one
year it is about twice as much as will ever be obtained from all of
the Earth's non-renewable resources of coal, oil, natural gas, and
mined uranium combined. Solar cells are long lasting sources of
energy which can be used almost anywhere. They are particularly
useful where there is no national grid and also where there are no
people such as remote site water pumping or in space.
CONTENTS List of figure List of tables CHAPTER 1: Introduction
To The Solar Energy8 1.1: what is solar
energy?....................................................................................8
1.2: solar cell and its origins......10 1.3: construction and
working of solar cell...14 1.4: current developments.19 CHAPTER 2:
Solar Devices And Components.20 2.1: solar semiconductor
devices...21 2.1.1: solar detectors..23 2.1.2: solar storage
devices....27 2.2: solar cell materials..28 2.2.1: crystalline
silicon ....28 2.2.2: thin films..29
CHAPTER 3: Solar Lighting System.32 3.1: introduction..33 3.2:
components of the system...34 CHAPTER 4: Working Of Solar Lighting
System..47 4.1: circuit diagram ...48 4.2: working of
circuit...49
CHAPTER 5: Advantages And Disadvantages ...51 5.1: advantages
..52 5.2: disadvantages..54 5.3: limitations...55
CHAPTER 6:Applications.56
CHAPTER 7: Summary.64
BIBLIOGRAPHY
LIST OF FIGURES1. Radiation pattern of sun light falling on
earth..82. Spectrum of solar radiation...93. Solar
cell(polysilicon)..104. Amorphous solar cell...125. Crystalline
solar cell.136. Atomic structure of Si with doping..147. Schematic
diagram of power production by solar cell.158. Current and voltage
output of a single solar cell under varying light level.169. IV
characteristics of solar cell.1710. IV characteristics of solar
cell with max. power point1811. Solar power panel1912. Solar
cell..2113. Polycrystalline photovoltaic cell.2214. Photovoltaic
cell..2515. Si crystal solar cell...2916. Transformer..3517. Solar
panel3618. DPDT switch3719. ON/OFF switch....3720. Resistor.3821.
IC regulator...3922. 6V lead battery..4123. 12V relay...4324.
LED..4425. Diode4526. Capacitor...4627. Circuit diagram..4828.
Solar panel.5229. Solar home lighting system...5730. Solar home
power system.5831. Solar street light5932. Solar lanterns60List of
tables:1. Yearly solar flux and human consumption...62. Components
of system37
CHAPTER: 1INTRODUCTION TO SOLAR ENERGY
Introduction to the Solar Energy1.1: what is solar energy?Solar
energy, radiant light and heat from the sun, has been harnessed by
humans since ancient times using a range of ever-evolving
technologies.
Fig.1. radiation pattern of sun light falling on earthThe Earth
receives 174petawatts (PW) of incoming solar radiation (insulation)
at the upper atmosphere. Approximately 30% is reflected back to
space while the rest is absorbed by clouds, oceans and land masses.
The spectrum of solar light at the Earth's surface is mostly spread
across the visible and near-infrared ranges with a small part in
the near-ultraviolet.Earth's land surface, oceans and atmosphere
absorb solar radiation, and this raises their temperature. Warm air
containing evaporated water from the oceans rises, causing
atmospheric circulation or convection. When the air reaches a high
altitude, where the temperature is low, water vapor condenses into
clouds, which rain onto the Earth's surface, completing the water
cycle. The latent heat of water condensation amplifies convection,
producing atmospheric phenomena such as wind, cyclones and
anti-cyclones. Sunlight absorbed by the oceans and land masses
keeps the surface at an average temperature of 14C. By
photosynthesis green plants convert solar energy into chemical
energy, which produces food, wood and the biomass from which fossil
fuels are derived.The total solar energy absorbed by Earth's
atmosphere, oceans and land masses is approximately
3,850,000exajoules (EJ) per year. In 2002, this was more energy in
one hour than the world used in one year. Photosynthesis captures
approximately 3,000EJ per year in biomass. The amount of solar
energy reaching the surface of the planet is so vast that in one
year it is about twice as much as will ever be obtained from all of
the Earth's non-renewable resources of coal, oil, natural gas, and
mined uranium combined.Solar energy can be harnessed in different
levels around the world. Depending on a geographical location the
closer to the equator the more "potential" solar energy is
available.
Yearly Solar fluxes & Human Energy Consumption
Solar3,850,000 EJ
Wind2,250EJ
Biomass3,000EJ
Primary energy use (2005)487EJ
Electricity (2005)56.7EJ
Table.1.yearly solar fluxes & human energy consumption
Fig.2. spectrum of solar radiation1.2: solar cell and its
origins:-A solar cell (also called photovoltaic cell or
photoelectric cell) is a solid state electrical device that
converts the energy of light directly into electricity by the
photovoltaic effect.Assemblies of solar cells are used to make
solar modules which are used to capture energy from sunlight. When
multiple modules are assembled together (such as prior to
installation on a pole-mounted tracker system), the resulting
integrated group of modules all oriented in one plane is referred
to in the solar industry as a solar panel. The electrical energy
generated from solar modules, referred to as solar power, is an
example of solar energy.Photovoltaics is the field of technology
and research related to the practical application of photovoltaic
cells in producing electricity from light, though it is often used
specifically to refer to the generation of electricity from
sunlight.Cells are described as photovoltaic cells when the light
source is not necessarily sunlight (lamplight, artificial light,
etc.). These are used for detecting light or other electromagnetic
radiation near the visible range, for example infrared detectors,
or measurement of light intensity.The most common form of solar
cells are based on the photovoltaic (PV) effect in which light
falling on a two layer semi-conductor device produces a
photovoltage or potential difference between the layers. This
voltage is capable of driving a current through an external circuit
and thereby producing useful work.
Fig.3. solar cell (polysilicon)1.2.1: Origin of Solar
Cells:-Although practical solar cells have only been available
since the mid 1950s, scientific investigation of the photovoltaic
effect started in 1839, when the French scientist, Henri Becquerel
discovered that an electric current could be produced by shining a
light onto certain chemical solutions.The effect was first observed
in a solid material (in this case the metal selenium) in 1877. This
material was used for many years for light meters, which only
required very small amounts of power. A deeper understanding of the
scientific principles, provided by Einstein in 1905 and Schottky in
1930, was required before efficient solar cells could be made. A
silicon solar cell which converted 6% of sunlight falling onto it
into electricity was developed by Chapin, Pearson and Fuller in
1954, and this kind of cell was used in specialized applications
such as orbiting space satellites from 1958.Today's commercially
available silicon solar cells have efficiencies of about 18% of the
sunlight falling on to them into electricity, at a fraction of the
price of thirty years ago. There is now a variety of methods for
the practical production of silicon solar cells (amorphous, single
crystal, polycrystalline), as well as solar cells made from other
materials (copper indium dieseline, cadmium telluride, etc). The
term "photovoltaic" comes from the Greek meaning "light", and
"voltaic", from the name of the Italian physicist Volta, after whom
a unit of electro-motive force, the volt, is named. The term
"photo-voltaic" has been in use in English since 1849.The
photovoltaic effect was first recognized in 1839 by French
physicist A. E. Becquerel. However, it was not until 1883 that the
first photovoltaic cell was built, by Charles Fritts, who coated
the semiconductor selenium with an extremely thin layer of gold to
form the junctions. The device was only around 1% efficient. In
1888 Russian physicist Aleksandra Stoletov built the first
photoelectric cell based on the outer photoelectric effect
discovered by Heinrich Hertz earlier in 1887.Albert Einstein
explained the photoelectric effect in 1905 for which he received
the Nobel Prize in Physics in 1921. Russell Ohl patented the modern
junction semiconductor solar cell in 1946, which was discovered
while working on the series of advances that would lead to the
transistor.Solar cells are devices which convert solar energy
directly into electricity, either directly via the photovoltaic
effect, or indirectly by first converting the solar energy to heat
or chemical energy.Solar cells are usually made from silicon, the
same material used for transistors and integrated circuits. The
silicon is treated or "doped" so that when light strikes it
electrons are released, so generating an electric current. There
are three basic types of solar cell. Monocrystalline cells are cut
from a silicon ingot grown from a single large crystal of silicon
whilst polycrystalline cells are cut from an ingot made up of many
smaller crystals. The third type is the amorphous or thin-film
solar cell.
1.2.2: Types of Solar Cell:-1. Amorphous Solar Cells: Amorphous
technology is most often seen in small solar panels, such as those
in calculators or garden lamps, although amorphous panels are
increasingly used in larger applications. They are made by
depositing a thin film of silicon onto a sheet of another material
such as steel. The panel is formed as one piece and the individual
cells are not as visible as in other types. The efficiency of
amorphous solar panels is not as high as those made from individual
solar cells, although this has improved over recent years to the
point where they can be seen as a practical alternative to panels
made with crystalline cells. Their great advantage lies in their
relatively low cost per Watt of power generated. This can be
offset, however, by their lower power density; more panels are
needed for the same power output and therefore more space is taken
up.
Fig.4. amorphous solar cell2. Crystalline Solar
Cells:Crystalline solar cells are wired in series to produce solar
panels. As each cell produces a voltage of between 0.5 and 0.6
Volts, 36 cells are needed to produce an open-circuit voltage of
about 20 Volts. This is sufficient to charge a 12 Volt battery
under most conditions.Although the theoretical efficiency of
Monocrystalline cells is slightly higher than that of
polycrystalline cells, there is little practical difference in
performance. Crystalline cells generally have a longer lifetime
than the amorphous variety.
Fig.5. crystalline solar cell
1.3: Construction:-In solar cell production the silicon has
dopant atoms introduced to create a p-type and an n-type region and
thereby producing a p-n junction. This doping can be done by high
temperature diffusion, where the wafers are placed in a furnace
with the dopant introduced as a vapor. There are many other methods
of doping silicon. In the manufacture of some thin film devices the
introduction of dopants can occur during the deposition of the
films or layers.A silicon atom has 4 relatively weakly bound
(valence) electrons, which bond to adjacent atoms. Replacing a
silicon atom with an atom that has either 3 or 5 valence electrons
will therefore produce either a space with no electron (a hole) or
one spare electron that can move more freely than the others, this
is the basis of doping. P-type doping, the creation of excess
holes, is achieved by the incorporation into the silicon of atoms
with 3 valence electrons, most often boron and n-type doping, the
creation of extra electrons is achieved by incorporating an atom
with 5 valence electrons, most often phosphorus.
Fig.6. atomic structure of Si with dopingOnce a p-n junction is
created, electrical contacts are made to the front and the back of
the cell by evaporating or screen printing metal on to the wafer.
The rear of the wafer can be completely covered by metal, but the
front only has a grid pattern or thin lines of metal otherwise the
metal would block out the sun from the silicon and there would not
be any output from the incident photons of light.
1.3.1: Working of Solar Cell:-To understand the operation of a
PV cell, we need to consider both the nature of the material and
the nature of sunlight. Solar cells consist of two types of
material, often p-type silicon and n-type silicon. Light of certain
wavelengths is able to ionize the atoms in the silicon and the
internal field produced by the junction separates some of the
positive charges ("holes") from the negative charges (electrons)
within the photovoltaic device. The holes are swept into the
positive or p-layer and the electrons are swept into the negative
or n-layer. Although these opposite charges are attracted to each
other, most of them can only recombine by passing through an
external circuit outside the material because of the internal
potential energy barrier. Therefore if a circuit is made power can
be produced from the cells under illumination, since the free
electrons have to pass through the load to recombine with the
positive holes.
Fig.7.schematic diagram of power production by solar cell The
amount of power available from a PV device is determined by; The
type and area of the material; The intensity of the sunlight; and
The wavelength of the sunlight. Single crystal silicon solar cells,
for example cannot currently convert more than 25% of the solar
energy into electricity, because the radiation in the infrared
region of the electromagnetic spectrum does not have enough energy
to separate the positive and negative charges in the
material.Polycrystalline silicon solar cells have an efficiency of
less than 20% at this time and amorphous silicon cells, are
presently about 10% efficient, due to higher internal energy losses
than single crystal silicon.A typical single crystal silicon PV
cell of 100 cm2 will produce about 1.5 watts of power at 0.5 volts
DC and 3 amps under full summer sunlight (1000Wm-2). The power
output of the cell is almost directly proportional to the intensity
of the sunlight. (For example, if the intensity of the sunlight is
halved the power will also be halved).
Fig.8. current & voltage output of a single solar cell under
varying light levels An important feature of PV cells is that the
voltage of the cell does not depend on its size, and remains fairly
constant with changing light intensity. However, the current in a
device is almost directly proportional to light intensity and size.
When people want to compare different sized cells, they record the
current density, or amps per square centimeter of cell area.
The power output of a solar cell can be increased quite
effectively by using a tracking mechanism to keep the PV device
directly facing the sun, or by concentrating the sunlight using
lenses or mirrors. However, there are limits to this process, due
to the complexity of the mechanisms, and the need to cool the
cells. The current output is relatively stable at thigher
temperatures, but the voltage is reduced, leading to a drop in
power as the cell temperature is increased. Solar cells are
essentially semiconductor junctions under illumination. Light
generates electron-hole pairs on both sides of the junction, in the
n-type emitter and in the p-type base. The generated electrons
(from the base) and holes (from the emitter) then diffuse to the
junction and are swept away by the electric field, thus producing
electric current across the device. Note how the electric currents
of the electrons and holes reinforce each other since these
particles carry opposite charges. The p-n junction therefore
separates the carriers with opposite charge, and transforms the
generation current between the bands into an electric current
across the p-n junction.
Fig.9. I V characteristics of solar cellIn solar cell
applications this characteristic is usually drawn inverted about
the voltage axis, as shown below. The cell generates no power in
short-circuit (when current Isc is produced) or open-circuit (when
cell generates voltage Voc). The cell delivers maximum power Pmax
when operating at a point on the characteristic where the product
IV is maximum. This is shown graphically below where the position
of the maximum power point represents the largest area of the
rectangle shown.
Fig.10. I V characteristics of a solar cell with the maximum
power point
The efficiency (n) of a solar cell is defined as the power Pmax
supplied by the cell at the maximum power point under standard test
conditions, divided by the power of the radiation incident upon it.
Most frequent conditions are: irradiance 100 mW/cm2 , standard
reference spectrum, and temperature 25 0 C. The use of this
standard irradiance value is particularly convenient since the cell
efficiency in percent is then numerically equal to the power output
from the cell in mW/cm2
1.4: Current Developments:-For most of the eighties and early
nineties the major markets for solar panels were remote area power
supplies and consumer products (watches, toys and calculators).
However in the mid nineties a major effort was launched to develop
building integrated solar panels for grid connected applications.
Rooftop PV is now driving the development of the market in Japan,
Europe and the USA. Japan currently has a program that aims to
build 70,000 solar homes, installing 400MW of PV by 2000 and
installing 4600MW by 2010. In Europe several countries are
supporting the construction of solar homes, with the European
parliament proposing a 1,000MW scheme. In the USA, President
Clinton announced a Solar Roofs Program, which aims to install
solar panels on one million roofs in America by 2010.In Australia
and the USA, the emergence of green power schemes, which permit
customers to choose renewable energy options, has added
considerable impetus to the growth of the industry. Grid connected
solar farms have been constructed in WA (Kalbarri)(see figure 12),
Singleton NSW (Hunter Valley) and SA (Wilpena Pound ), at many
sites in the USA and last year Greece announced a project to build
the worlds largest PV power station on Crete with a final capacity
of 50MW by 2003. Demonstration sites have also been established by
Australian electricity utilities including CitiPower Energy Park -
called Project Aurora, Energy Australia 's Home bush Park &
National Innovation Centre, and Great Southern Energy's Solar
Farm.
Fig.11. solar power plant
CHAPTER: 2SOLAR DEVICES AND COMPONENTS
Solar devices and componentsAsolar cell(also calledphotovoltaic
cellorphotoelectric cell) is asolid stateelectrical device that
converts the energy oflightdirectly intoelectricityby
thephotovoltaic effect.Assemblies of solar cells are used to
makesolar moduleswhich are used to capture energy from sunlight.
When multiple modules are assembled together (such as prior to
installation on a pole-mounted tracker system), the resulting
integrated group of modules all oriented in one plane is referred
to in the solar industry as asolar panel. The electrical energy
generated from solar modules, referred to assolar power, is an
example ofsolar energy.Photovoltaicsis the field of technology and
research related to the practical application of photovoltaic cells
in producing electricity from light, though it is often used
specifically to refer to the generation of electricity from
sunlight.Cells are described asphotovoltaic cellswhen the light
source is not necessarily sunlight (lamplight, artificial light,
etc.). These are used for detecting light or otherelectromagnetic
radiation near the visible range, for exampleinfrared detectors, or
measurement of light intensity.
Fig.12. A single solar cellThe term "photovoltaic" comes from
theGreek (phs) meaning "light", and "voltaic", from the name of
theItalianphysicistVolta, after whom a unit of electro-motive
force, thevolt, is named. The term "photo-voltaic" has been in use
in English since 1849.Thephotovoltaic effectwas first recognized in
1839 by French physicistA. E. Becquerel. However, it was not until
1883 that the first photovoltaic cell was built, byCharles Fritts,
who coated thesemiconductorseleniumwith an extremely thin layer
ofgoldto form the junctions. The device was only around 1%
efficient. In 1888 Russian physicistAleksandr Stoletovbuilt the
first photoelectric cell based on the outerphotoelectric
effectdiscovered byHeinrich Hertzearlier in 1887.
Fig.13. polycrystalline photovoltaic cellTheory The solar cell
works in three steps:1. Photonsinsunlighthit the solar panel and
are absorbed by semiconducting materials, such as silicon.2.
Electrons(negatively charged) are knocked loose from their atoms,
causing an electric potential difference. Current starts flowing
through the material to cancel the potential and this electricity
is captured. Due to the special composition of solar cells, the
electrons are only allowed to move in a single direction.3. An
array of solar cells converts solar energy into a usable amount
ofdirect current(DC) electricity.4.
2.1.1. DetectorsAphotodiodeis a type ofphoto detectorcapable of
convertinglightinto eithercurrentorvoltage, depending upon the mode
of operation.The common, traditionalsolar cellused to generate
electricsolar poweris a large area photodiode.Photodiodes are
similar to regularsemiconductordiodesexcept that they may be either
exposed (to detectvacuum UVorX-rays) or packaged with a window
oroptical fiberconnection to allow light to reach the sensitive
part of the device. Many diodes designed for use specifically as a
photodiode use aPIN junctionrather than ap-n junction, to increase
the speed of response. A photodiode is designed to operate
inreverse bias.
Principle of operationA photodiode is ap-n junctionorPIN
structure. When aphotonof sufficient energy strikes the diode, it
excites an electron, thereby creating afree electron(and a
positively charged electronhole). This mechanism is also known as
the innerphotoelectric effect. If the absorption occurs in the
junction'sdepletion region, or one diffusion length away from it,
these carriers are swept from the junction by the built-in field of
the depletion region. Thus holes move toward theanode, and
electrons toward the cathode, and aphotocurrentis produced. This
photocurrent is the sum of both the dark current (without light)
and the light current, so the dark current must be minimized to
enhance the sensitivity of the device.Photovoltaic modeWhen used in
zerobiasorphotovoltaic mode, the flow of photocurrent out of the
device is restricted and a voltage builds up. This mode exploits
the photovoltaic effect, which is the basis forsolar cells a
traditional solar cell is just a large area
photodiode.Photoconductive modeIn this mode the diode is
oftenreverse biased(with the cathode positive), dramatically
reducing the response time at the expense of increased noise. This
increases the width of the depletion layer, which decreases the
junction'scapacitanceresulting in faster response times. The
reverse bias induces only a small amount of current (known as
saturation or back current) along its direction while the
photocurrent remains virtually the same. For a given spectral
distribution, the photocurrent is linearly proportional to
theluminance(and to theirradiance).Although this mode is faster,
the photoconductive mode tends to exhibit more electronic noise.The
leakage current of a good PIN diode is so low (