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 (