experimentation with solar energy nvis 6005 6005... · 2020. 3. 17. · nvis 6005 nvis technologies...

Experimentation with Solar Energy

Nvis 6005

Learning Material Ver 1.1

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Experimentation with Solar Energy Nvis 6005

Table of Contents 1. Introduction 4

2. Features 5

3. Technical Specifications 6

4. Safety Instructions 7

5. Theory 8

6. Experiments • Experiment 1 48

Study of the voltage and current of the solar cells

• Experiment 2 49 Study of the voltage and current of the solar cells in series and

parallel combinations

• Experiment 3 53 Study of both the current–voltage characteristic and the power curve

to find the maximum power point (MPP) and efficiency of a solar cell

• Experiment 4 56 To calculate the efficiency (η) of the solar cell

• Experiment 5 58 Study of the application of solar cells of charging Ni-Cd battery so

that the loads can be used even while the module is unexposed to light

• Experiment 6 59 Study of the application of solar cells of providing electrical energy

to the domestic appliances such as lamp, fan and radio

6. Sample Results 7. Glossary 61 8. Frequently Asked Questions 67 9. Warranty 68 10. List of Service Centers 69 11. List of Accessories 70 12. References 71

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Introduction Nvis 6005 Experimentation with Solar Energy is a versatile training system used in the laboratories. With this system students can understand the various characteristics and applications of solar energy. They will learn how solar cells are put together to generate the desired voltage and current and how solar energy can be utilized to operate different electrical and electronic appliances. This system is provided with a Experimentation with Solar Energy and Solar Panel. Solar Panel contains 6 cells each of 2V DC and 150mA DC rating. Experimentation with Solar Energy contains three sections: 1. Solar Input Section 2. Measurement Section 3. Application Section and are represented in such an easy way so that each section can be studied differently and so easily. The Solar Cell Input Section contains outputs of all 6 cells. Measurement Section contains Voltmeter, Ammeter and Potentiometer. Students can easily measure voltage and current of solar cells themselves using voltmeter and ammeter provided. Application section contains charging section and other appliances that can be operated using solar energy. Charging Section charges the battery directly by solar energy and provides supply to load through amplifier section. Domestic appliances like lamp, fan and FM radio are provided on board.

Experimentation with Solar Energy

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Features

• Complete training system to study the fundamentals of Photovoltaic System

• The system has two modes for study Characteristics & Application Modes

• On board voltmeter and ammeter are provided to measure the voltage and current respectively, during various modes of operation

• Charging the battery using solar energy

• Weather proof solar cells

• Portable and light weight

• User friendly manual is provided with theoretical and practical details

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Technical Specifications

Solar Panel : Consists of 6 solar cells

Maximum Voltage of each solar cell : 2V DC

Maximum Current of each solar cell : 150mA DC

Voltmeter : 0-10V DC

Ammeter : 0-500mA DC

Potentiometer : 5K

Rechargeable Ni-Cd Battery : 1.2V DC

Bulb : ~2V, ~250mA DC

Fan : ~2V, ~400mA DC

FM Band Radio : 12V DC

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Safety Instructions

Read the following safety instructions carefully before operating the instrument. To avoid any

personal injury or damage to the instrument or any product connected to the instrument.

Do not operate the instrument if suspect any damage to it.

The instrument should be serviced by qualified personnel only.

For your safety:

Use proper Mains cord : Use only the mains cord designed for this instrument. Ensure

that the mains cord is suitable for your country.

Ground the Instrument : This instrument is grounded through the protective earth

conductor of the mains cord. To avoid electric shock, the

grounding conductor must be connected to the earth ground.

Before making connections to the input terminals, ensure that

the instrument is properly grounded.

Use in proper Atmosphere : Please refer to operating conditions given in the manual.

1. Do not operate in wet / damp conditions.

2. Do not operate in an explosive atmosphere.

3. Keep the product dust free, clean and dry.

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Theory Energy is the capacity of a system to do work. That system may be a jet, carrying hundreds of passengers across the ocean. A baby’s body, growing bone cells. A kite, rising on the wind. Or a wave of light crossing a space. In moving or growing, each of these systems is doing work, and using energy. Every living organism does work, and needs energy from food or photosynthesis. Humans also create machines that do work for them, and that derive energy from fuels. Energy helps us do things. It gives us light. It warms our bodies and homes. It bakes cakes and keeps milk cold. It runs our TVs and our cars. It makes us grow and move and think. Energy is the power to change things. It is the ability to do work.

Energy is Light Light is a type of energy we use all the time. We use it so we can see. We get most of our light from the sun. Staying awake during the day saves money because sunlight is free. At night, we must make our own light. Usually, we use electricity to make light. Flashlights use electricity, too. This electricity comes from batteries.

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Energy is Heat We use energy to make heat. The food we eat keeps our bodies warm. Sometimes, when we run or work hard, we get really hot. In the winter, our jackets and blankets hold in our body heat.We use the energy stored in plants and other things to make heat. We burn wood and natural gas to cook food and warm our houses. Factories burn fuel to make the products they sell. Power plants burn coal and natural gas to make electricity.

Energy Makes Things Grow: All living things need energy to grow. Plants use light from the sun to grow. Plants change the energy from the sun into sugar and store it in their roots and leaves. Animals can’t change light energy into sugars. Animals, including people, eat plants and use the energy stored in them to grow. Animals can store the energy from plants in their bodies.

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Energy Makes Things Move It takes energy to make things move. Cars run on the energy stored in gasoline. Many toys run on the energy stored in batteries. Sail boats are pushed by the energy in the wind. After a long day, do you ever feel too tired to move? You’ve run out of energy. You need to eat some food to refuel.

Energy Runs Machines It takes energy to run our TVs, computers, and video games—energy in the form of electricity. We use electricity many times every day. It gives us light and heat, it makes things move, and it runs our toys and microwaves. Imagine what your life would be like without electricity.We make electricity by burning coal, oil, gas, and even trash. We make it from the energy that holds atoms together. We make it with energy from the sun, the wind, and falling water. Sometimes, we use heat from inside the Earth to make electricity.

Energy Doesn’t Disappear There is the same amount of energy today as there was when the world began. When we use energy,we don’t use it up; we change it into other forms ofenergy. When we burn wood, we change its energy into heat and light. When we drive a car, we change the energy in gasoline into heat and motion.There will always be the same amount of energy in the world, but more

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and more of it will be changed into heat. Most of that heat will go into the air. It will still be there, but it will be hard to use.

Some of the many forms that energy takes are

• Mechanical energy, which includes - Potential energy, stored in a system. - Kinetic energy, from the movement of matter.

• Radiant or solar energy, which comes from the light and warmth of the sun. • Thermal energy, associated with the heat of an object. • Chemical energy, stored in the chemical bonds of molecules. • Electrical energy, associated with the movement of electrons. • Electromagnetic energy, associated with light waves (including radio waves,

microwaves, x-rays, infrared waves). • Mass (or nuclear) energy, found in the nuclear structure of atoms.

All forms of energy are stored in different ways, in the energy sources that we use every day. These sources are divided into two groups -- renewable (an energy source that we can use over and over again) and nonrenewable (an energy source that we are using up and cannot recreate in a short period of time).

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Non-Renewable Energy Non-Renewable energy is energy which is taken from the sources that are available on the earth in limited quantity and will vanish fifty-sixty years from now. Non-renewable sources are not environmental friendly and can have serious affect on our health. They are called non-renewable because they cannot be re-generated within a short span of time. Non-renewable sources exist in the form of fossil fuels, natural gas, oil and coal. Renewable Energies Renewable energy is energy which is generated from natural sources i.e. sun, wind, rain, tides and can be generated again and again as and when required. They are available in plenty and by far most the cleanest sources of energy available on this planet. For eg: Energy that we receive from the sun can be used to generate electricity. Similarly, energy from wind, geothermal, biomass from plants, tides can be used this form of energy to another form. Solar power is another renewable energy source, where the energy from the sun is harnessed in order to produce energy. Because the sun is the sun, heat and energy found in sunlight is in limitless supply so long as the sun is shining, and thus is an excellent renewable energy source. Some areas of the world can not rely on solar power because their weather and climate are not conducive to its use if long periods of cloudiness are present. Overall however, solar power is a clean energy source that does not pollute the environment or contribute to global warming, and as such, it is a widely used source of renewable energy.

Courtesy by

http://www.technologystudent.com/energy1/solar1.htm Solar power is energy from the sun and without its presence all life on earth would end. Solar energy has been looked upon as a serious source of energy for many years because of the vast amounts of energy that are made freely available, if harnessed by modern technology. A simple example of the power of the sun can be seen by using a magnifying glass to focus the suns rays on a piece of paper. Before long the paper ignites into flames.

http://www.technologystudent.com/energy1/solar1.htm

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Courtesy by http://www.technologystudent.com/energy1/solar1.htm

This is one way of using the suns energy, but flames are dangerous and difficult to control. A much safer and practical way of harnessing the suns energy is to use the suns power to heat up water. A magnifying glass can be used to heat up a small amount of water. A short piece of copper tube is sealed at one end and filled with water. A magnifying glass is then used to warm up the pipe. Using more than one magnifying glass will increase the temperature more rapidly. After a relatively short time the temperature of the water increases. Continuing to heat the water will cause water vapour to appear at the top of the tube. In theory, with enough patience, several magnifying glasses and very strong sun light enough heat should be generated to boil the water, producing steam. This is one way of harnessing solar power. Modern solar panels are a combination of magnifying glasses and fluid filled pipes. The solar panel seen opposite has a glass front which is specially made to focus the power of the sun on pipes behind it. The pipes carry a special fluid that heats up rapidly. They are painted black to absorb the heat from the sun. The silver reflective surface behind the pipes reflects sun light back, further heating the pipes and the fluid they contain. The reflective surface also protects anything behind the solar panel (such as a roof).The heat produced in the pipes is then used to heat a tank of water. This saves using electricity or gas to heat up the water tank.

Courtesy by http://www.technologystudent.com/energy1/solar1.htm



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Tidal energy (Gravitational attraction of Sun, Earth and Moon) Tidal power plants use the energy provided by high and low tides. Water is stored during high tide and released during low tide, powering turbines in the process.

Tides are caused principally by the gravitational pull of the moon on the world’s oceans. The sun also plays a minor role, not through its radiant energy but in the form of its gravitational pull, which exerts small additional effect on tidal rhythms. And the rotation of the earth is also a factor in the production of tides. The rise and fall of the sea level can power electric-generating equipment. Tidal barrages, built across suitable estuaries, are designed to extract energy from the rise and fall of the tides, using turbines located in water passages in the barrages. The potential energy, due to the difference in water levels across the barrages, is converted into kinetic energy in the form of fast moving water passing through the turbines. This, in turn, is converted into rotational kinetic energy by the blades of the turbine, the spinning turbine then driving a generator to produce electricity.

Geothermal energy (Radioactivity and primordial heat in Earth’s Interior)

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Geothermal power plants use heat released from the interior through Earth’s crust. The heat can be used directly or converted to electricity. Geothermal energy is heat from within the Earth. Geothermal energy is generated in the Earth’s core, almost 4,000 miles beneath the Earth’s surface. The double-layered core is made up of very hot magma (melted rock) surrounding a solid iron center. Very high temperatures are continuously produced inside the Earth by the slow decay of radioactive particles.

Renewable energy technologies tap into natural cycles and systems, turning the ever- present energy around us into usable forms. The movement of wind and water, the heat and light of the sun, heat in the ground. The carbohydrates in plants all are natural energy sources that can supply our needs in a sustainable way because they are homegrown, renewable can also increase our energy security. Photovoltaic: Free electricity from sunlight Photo-voltaic (PV) comprises the technology to convert sunlight directly into electricity. The term “photo” means light and “voltaic,” means electricity. The word Photo-voltaic is a combination of the Greek word for Light and the name of the physicist Allesandro Volta. He identifies the direct conversion of sunlight into energy by means of solar cells. A photovoltaic (PV) cell, also known as “solar cell,” is a semiconductor device that generates electricity when light falls on it. Photovoltaic refer to the creation of voltage from light. Solar Photovoltaic System directly converts sunlight into useful electricity. This process is called photoelectric effect, discovered by Alexander Becquerel in 1839. The photoelectric effect describes the release of positive and negative charge carriers in a solid state when light strikes its surface. The energy generator in a PV system is the solar cell.

History of Photovoltaic Cells

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The development of solar cell technology begins with the 1839 research of French physicist Antoine-Cesar Becquerel. Becquerel observed the photovoltaic effect while experimenting with a solid electrode in an electrolyte solution when he saw a voltage develop when light fell upon the electrode.

First Solar Cell According to Encyclopedia Britannica the first genuine solar cell was built around 1883 by Charles Fritts, who used junctions formed by coating selenium (a semiconductor) with an extremely thin layer of gold.

Further Work on Solar Cells By 1927 another metal- D semiconductor-junction solar cell, in this case made of copper and the semiconductor copper oxide, had been demonstrated. By the 1930s both the selenium cell and the copper oxide cell were being employed in light-sensitive devices, such as photometers, for use in photography. Silicon Solar Cell These early solar cells, however, had energy conversion efficiencies of less than one percent. This problem was finally overcome with the development of silicon solar cell. In 1941, the American Russell Ohl invented a silicon solar cell.

Silicones are ideal for solar panel and photovoltaic (PV) applications. While solar cells themselves are made of silicon, silicones are used during module assembly and installation as encapsulants, coatings, potting agents, adhesives and sealants. The silicone advantage Silicones are renowned for their UV stability and moisture resistance

• Silicones are durable and solar radiation resistant • Silicones have excellent electrical insulating properties – excellent dielectric strength

and high volume resistivity • Silicones have low ionic impurities, low moisture absorption and a low dielectric

constant • Silicone encapsulants perform over a wide operating temperature range – from -40 to

150°C (-40 to 302°F) • Silicones are optically transparent over a wide spectrum • Silicones offer excellent adhesion to glass and photovoltaic cell substrates

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• Optical, mechanical and thermal properties can be varied to meet the requirements of specific photovoltaic applications

Efficient Solar Cells In 1954, three American researchers, Gerald Pearson, Calvin Fuller and Daryl Chapin, designed a silicon solar cell capable of six percent energy conversion efficiency with direct sunlight. The three inventors created an array of several strips of silicon (each about the size of a razorblade), placed them in sunlight, captured the free electrons and turned them into electrical current. They created the first solar panels. Bell Laboratories in New York announced the prototype manufacture of a new solar battery. Bell had funded the research. The first public service trial of the Bell Solar Battery began with a telephone carrier system (Americus, Georgia) on October 4 1955. By the late 1980s, silicon cells, as well as those made of gallium arsenide, with efficiencies of more than 20 percent had been fabricated. In 1989 a concentrator solar cell, a type of device in which sunlight is concentrated onto the cell surface by means of lenses, achieved an efficiency of 37 percent due to the increased intensity of the collected energy. In general, solar cells of widely varying efficiencies and cost are now available.

The Sun The sun is a hot sphere of gas whose internal temperatures reach over 20 million degrees kelvin due to nuclear fusion reactions at the sun's core which convert hydrogen to helium. The radiation from the inner core is not visible since it is strongly absorbed by a layer of hydrogen atoms closer to the sun's surface. Heat is transferred through this layer by convection. The surface of the sun, called the photosphere, is at a temperature of about 6000K and closely approximates a blackbody. The total power emitted from the sun is composed not of a single wavelength, but is composed of many wavelengths and therefore appears white or yellow to the human eye. These different wavelengths can be seen by passing light through a prism, or water droplets in the case of a rainbow. Different wavelengths show up as different colors, but not all the wavelengths can be seen since some are "invisible" to the human eye.

Properties of sun light Sunlight is a form of "electromagnetic radiation" and the visible light that we see is a small subset of the electromagnetic spectrum shown in the figure.

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Einstein, while examining the photoelectric effect (the release of electrons from certain metals and semiconductors when struck by light), distinguished the values of these quantum energy elements. For their work in this area Einstein won the Nobel Prize for physics in 1921, respectively and based on this work, light may be viewed as consisting of "packets" or particles of energy, called photons. There are several key characteristics of the incident solar energy which are critical in determining how the incident sunlight interacts with a photovoltaic converter. The important characteristics of the incident solar energy are:

• The spectral content of the incident light; • The radiant power density from the sun; • The angle at which the incident solar radiation strikes a photovoltaic module • The radiant energy from the sun throughout a year or day for a particular surface.

Energy of a photon A photon is characterized by either a wavelength, denoted by λ or equivalently energy, denoted by E. There is an inverse relationship between the energy of a photon (E) and the wavelength of the light (λ) given by the equation:

Where h is Planck's constant and c is the speed of light. The above inverse relationship means that light consisting of high energy photons (such as "blue" light) has a short wavelength. Light consisting of low energy photons (such as "red" light) has a long wavelength. When dealing with "particles" such as photons or electrons, a commonly used unit of energy is the electron-volt (eV) rather than the joule (J). An electron volt is the energy required to raise an electron through 1 volt, thus 1 eV = 1.602 x 10-19 J. By expressing the equation for photon energy in terms of eV and µm we arrive at a commonly used expression which relates the energy and wavelength of a photon, as shown in the following equation:

Absorption of light Photons incident on the surface of a semiconductor will be either reflected from the top surface, will be absorbed in the material or, failing either of the above two processes, will be transmitted

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through the material. For photovoltaic devices, reflection and transmission are typically considered loss mechanisms as photons which are not absorbed do not generate power. If the photon is absorbed it will raise an electron from the valence band to the conduction band. A key factor in determining if a photon is absorbed or transmitted is the energy of the photon. Photons falling onto a semiconductor material can be divided into three groups based on their energy compared to that of the semiconductor band gap: Eph < EG Photons with energy Eph less than the band gap energy EG interact only weakly with the semiconductor, passing through it as if it were transparent. Eph = EG has just enough energy to create an electron hole pair and is efficiently absorbed. Eph > EG Photons with energy much greater than the band gap are strongly absorbed

The absorption of photons creates both a majority and a minority carrier. In many photovoltaic applications, the numbers of light-generated carriers are of orders of magnitude less than the number of majority carriers already present in the solar cell due to doping. Consequently, the number of majority carriers in an illuminated semiconductor does not alter significantly. However, the opposite is true for the number of minority carriers. The number of photo-generated minority carriers outweighs the number of minority carriers existing in the solar cell in the dark, and therefore the number of minority carriers in an illuminated solar cell can be approximated by the number of light generated carriers.

The path of the photon After a photon makes its way through the cover glass it encounters the antireflective layer. The antireflective layer channels the photon into the lower layers of the solar cell. Once the photon passes the AR coating, it will either hit the silicon surface or the contact grid metallization. The metallization, being opaque, lowers the number of photons reaching the silicon surface. The contact grid must be large enough to collect electrons yet cover as little of the solar cell’s surface, allowing more photons to penetrate. Now, a photon causes the photovoltaic effect. As shown in the diagram below the region in the solar cell where the n-type and p- type Si layers meet is called the p-n-junction.

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Solar Cell Model So due to the p-n-junction, a built in electric field (about 0.6 to 0.7 volts) is always present across the (darkened) solar cell. When photons hit the solar cell, freed electrons (-) attempt to unite with holes on the p-type layer. The p-n-junction, a one-way road, only allows the electrons to move in one direction. If we provide an external conductive path, electrons will flow through this path to their original (p-type) side to unite with holes. The electron flow provides the current (I) and the cell's electric field causes a voltage (V). With both current and voltage, we have power (P), which is just the product of the two. Therefore, when an external load (such as an electric lamp) is connected between the front and back contacts, electricity flows in the cell, working for us along the way.

Reaction of Photons on Charge Carriers of n- and p-type

Semiconductor structure Semiconductors are made up of individual atoms bonded together in a regular, periodic structure to form an arrangement whereby each atom is surrounded by 8 electrons. An individual atom consists of a nucleus made up of a core of protons (positively charged particles) and neutrons (particles having no charge) surrounded by electrons. The number of electrons and protons is equal, such that the atom is overall electrically neutral. The electrons occupy certain energy levels, based on the number of electrons in the atom, which is different for each element in the periodic table. The structure of a semiconductor is shown in the figure below.

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Schematic representation of covalent bonds in a silicon crystal lattice

The bond structure of a semiconductor determines the material properties of a semiconductor. One key effect is to limit the energy levels which the electrons can occupy and how they move about the crystal lattice. The electrons surrounding each atom in a semiconductor are part of a covalent bond. A covalent bond consists of two atoms "sharing" a single electron, such that each atom is surrounded by 8 electrons. The electrons in the covalent bond are held in place by this bond and hence they are localized to region surrounding the atom. Since they cannot move or change their energy, electrons in a bond are not considered "free" and cannot participate in current flow, absorption or other physical processes of interest in solar cells. However, only at absolute zero are all electrons in a bonded arrangement. At elevated temperatures, the electron can gain enough energy to escape from its bond, and if this happens, the electron is free to move about the crystal lattice and participate in conduction. At room temperature, a semiconductor has enough free electrons to allow it to conduct current, while at or close to absolute zero a semiconductor behaves like an insulator.

The presence of the bond introduces two distinct energy states for the electrons. The lowest energy position for the electron is to be in its bound state. However, if the electron has enough thermal energy to break free of its bond, then it becomes free. The electron cannot attain energy values intermediate to these two levels; it is either at a low energy position in the bond, or it has gained enough energy to break free and therefore has a certain minimum energy. This minimum energy is called the "band gap" of a semiconductor. The number and energy of the free electrons is basic to the operation of electronic devices. The space left behind by the electrons allows a covalent bond to move from one electron to another, thus appearing to be a positive charge moving through the crystal lattice. This empty space is commonly called a "hole", and is similar to an electron, but with a positive charge. The most important parameters of a semiconductor material for solar cell operation are:

• The band gap; • The number of free carriers available for conduction; and • The "generation" & recombination of free carriers in response to light shining on the

material. Doping It is possible to shift the balance of electrons and holes in a silicon crystal lattice by "doping" it with other atoms. Atoms with one more valence electron than silicon are used to produce "n-type" semiconductor material, which adds electrons to the conduction band and hence increases the number of electrons. Atoms with one less valence electron result in "p-type" material. In p-

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type material, the number of electrons trapped in bonds is higher, thus effectively increasing the number of holes. In doped material, there is always more of one type of carrier than the other and the type of carrier with the higher concentration is called a "majority carrier", while the lower concentration carrier is called a "minority carrier."

Schematic of a silicon crystal lattice doped with

impurities to produce n-type and p-type semiconductor material The following table summarizes the properties of semiconductor types.

P-type (positive) N-type (negative) Dopant Group III (E.g. Boron) Group V (e.g. Phosphorous) Bonds Missing Electrons (Holes) Excess Electrons

Majority Carriers Holes Electrons Minority Carriers Electrons Holes

PN Junction Diode When a p-type semiconductor is joined to an n-type semiconductor, a p-n junction is created. While each side by itself is electrically neutral (there are as many electrons as there are protons) this is not the case for certain areas of the combined configuration. The concentration differences of holes and free electrons between n- and p- regions produce diffusion current: electrons flow from the n-side and fill holes on the p-side. This creates a region that is almost devoid of free charge carriers (i.e. free electrons or holes) and is therefore called the depletion zone. In the depletion zone there is a net positive charge on the n-side and a net negative charge on the p-side resulting in an electric field that opposes a further flow of electrons. The more electrons move from the n- to the p-side the stronger the opposing field will be and eventually an equilibrium will be reached in which no further electrons are able to move against the electric field. The potential difference of the equilibrium electr ic fie ld is called diffusion voltage. It cannot be used externally.

Diode Equation Ideal Diodes The diode equation gives an expression for the current through a diode as a function of voltage. The Ideal Diode Law, expressed as:

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Where,

I = the net current flowing through the diode; I0 = "dark saturation current", the diode leakage current density in the absence of light; V = applied voltage across the terminals of the diode; q = absolute value of electron charge; k = Boltzmann's constant; and T = absolute temperature (K). The "dark saturation current" (I0) is an extremely important parameter which differentiates one diode from another. I0 is a measure of the recombination in a device. A diode with a larger recombination will have a larger I0.

Note that: • I0 increases as T increases; and

• I0 decreases as material quality increases. At 300K, kT/q = 25.85 mV, the "thermal voltage".

Non-Ideal Diodes For actual diodes, the expression becomes:

Where: n = ideality factor, a number between 1 and 2 which typically increases as the current decreases. The diode equation is plotted on the interactive graph below. Change the saturation current and watch the changing of IV curve. Note that although you can simply vary the temperature and ideality factor the resulting IV curves are misleading. In the simulation it is implied that the input parameters are independent but they are not. In real devices, the saturation current is strongly dependent on the device temperature. Similarly, mechanisms that change the ideality factor also impact the saturation current. The diode law is illustrated for silicon on the following picture. Increasing the temperature makes the diode to "turn ON" at lower voltages.

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Working Model of solar cell:

The basic steps in the operation of a solar cell are:

• Generation of light-generated carriers;

• Collection of the light-generated carries to generate a current; • Generation of a large voltage across the solar cell; and

• Dissipation of power in the load and in parasitic resistances.

Working of solar cell The generation of current in a solar cell, known as the "light-generated current", involves two key processes. The first process is the absorption of incident photons to create electron-hole pairs. Electron-hole pairs will be generated in the solar cell provided that the incident photon has energy greater than that of the band gap. However, electrons (in the p-type material), and holes (in the n-type material) are meta-stable and will only exist, on average, for a length of time equal to the minority carrier lifetime before they recombine. If the carrier recombines, then the light-generated electron-hole pair is lost and no current or power can be generated.

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A second process, the collection of these carriers by the p-n junction, prevents this recombination by using a p-n junction to spatially separate the electron and the hole. The carriers are separated by the action of the electric field existing at the p-n junction. If the light-generated minority carrier reaches the p-n junction, it is swept across the junction by the electric field at the junction, where it is now a majority carrier. If the emitter and base of the solar cell are connected together (i.e., if the solar cell is short-circuited), the the light-generated carriers flow through the external circuit. The ideal flow at short circuit is shown in the figure below.

The absorption of a photon creates an electron-hole pair

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Ideally the minority carrier (in this case a hole) makes it across the junction & becomes a majority carrier

After passing through the load the electron meets up with a hole and completes the circuit

Characteristics of a Solar Cell The usable voltage from solar cells depends on the semiconductor material. In silicon it amounts to approximately 0.5 V. Terminal voltages is only weakly dependent on light radiation, while the current intensity increases with higher luminosity. A 100 cm² silicon cell, for example, reaches a maximum current intensity of approximately 2 A when radiated by 1000 W/m².

Without illumination, a solar cell has the same electrical characteristics as a large diode

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The greater the light intensity, the greater the amounts of shift

Since the cell is generating power the convention is to invert the current axis

Current-Voltage Characteristic of Silicon Solar Cell

The output (product of electricity & voltage) of a solar cell is temperature dependent. Higher cell temperatures lead to lower output and hence to lower efficiency. The level of efficiency indicates how much of the radiated quantity of light is converted into useable electrical energy.

Parameters to characterize solar cells 1. Short-circuit current (ISC), 2. Open-circuit voltage (VOC), 3. Fill factor (FF) 4. Efficiency

1. Short-circuit current

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The short-circuit current is the current through the solar cell when the voltage across the solar cell is zero (i.e., when the solar cell is short circuited).

I (at V=0) = ISC

ISC occurs at the beginning of the forward-bias sweep and is the maximum current value in the power quadrant. For an ideal cell, this maximum current value is the total current produced in the solar cell by photon excitation. Usually written as ISC, the short-circuit current is shown on the I-V curve below.

IV curve of a solar cell showing the short-circuit current

The short-circuit current is due to the generation and collection of light-generated carriers. For an ideal solar cell at most moderate resistive loss mechanisms, the short-circuit current and the light-generated current are identical. Therefore, the short-circuit current is the largest current which may be drawn from the solar cell. The short-circuit current depends on a number of factors which are described below:

• The area of the solar cell. To remove the dependence of the solar cell area, it is more common to list the short-circuit current density (Jsc in mA/cm2) rather than the short-circuit current;

• The number of photons (i.e., the power of the incident light source). Isc from a solar cell is directly dependant on the light intensity

• The spectrum of the incident light. For most solar cell measurement, the spectrum is standardized to the AM1.5 spectrum;

• The optical properties (absorption and reflection) of the solar cell

• The collection probability of the solar cell, which depends chiefly on the surface passivation and the minority carrier lifetime in the base.

2. Open-circuit voltage The open-circuit voltage, VOC, is the maximum voltage available from a solar cell, and this occurs at zero current. The open-circuit voltage corresponds to the amount of forward bias on the solar cell due to the bias of the solar cell junction with the light-generated current.

V (at I=0) = VOC The open-circuit voltage is shown on the I-V curve below.

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IV curve of a solar cell showing the open-circuit voltage.

3. Fill Factor (FF) The Fill Factor (FF) is essentially a measure of quality of the solar cell. It is calculated by comparing the maximum power to the theoretical power (PT) that would be output at both the open circuit voltage and short circuit current together. FF can also be interpreted graphically as the ratio of the rectangular areas depicted in Figure.

Getting the Fill Factor from the I-V Sweep

A larger fill factor is desirable, and corresponds to an I-V sweep that is more square-like. Typical fill factors range from 0.5 to 0.82. Fill factor is also often represented as a percentage. Efficiency (η) The efficiency is the most commonly used parameter to compare the performance of one solar cell to another. Efficiency is defined as the ratio of the electrical power output Pout, compared to the solar power input, Pin, into the PV cell. Pout can be taken to be PMAX since the solar cell can be operated up to its maximum power output to get the maximum efficiency. In addition to reflecting the performance of the solar cell itself, the efficiency depends on the spectrum and intensity of the incident sunlight and the temperature of the solar cell.

Pin is taken as the product of the irradiance of the incident light, measured in W/m2 or in suns (1000 W/m2), with the surface area of the solar cell [m2]. The maximum efficiency (ηMAX) found from a light test is not only an indication of the performance of the device under test, but, like all of the I-V parameters, can also be affected by ambient conditions such as temperature and the intensity and spectrum of the incident light.

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The efficiency of a solar cell is determined as the fraction of incident power which is converted to electricity and is defined as:

Where,

Voc is the open-circuit voltage; Isc is the short-circuit current; FF is the fill factor η is the efficiency.

Effect of temperature Like all other semiconductor devices, solar cells are sensitive to temperature. Increases in temperature reduce the band gap of a semiconductor, thereby effecting most of the semiconductor material parameters. The decrease in the band gap of a semiconductor with increasing temperature can be viewed as increasing the energy of the electrons in the material. Lower energy is therefore needed to break the bond. In the bond model of a semiconductor band gap, reduction in the bond energy also reduces the band gap. Therefore increasing the temperature reduces the band gap. In a solar cell, the parameter most affected by an increase in temperature is the open-circuit voltage. The impact of increasing temperature is shown in the figure below.

The effect of temperature on the IV characteristics of a solar cell

The open-circuit voltage decreases with temperature because of the temperature dependence of I0. The equation for I0 from one side of a p-n junction is given by;

Where:

q is the electronic charge

D is the diffusivity of the minority carrier given for silicon as a function of doping

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L is the diffusion length of the minority carrier;

ND is the doping; and

ni is the intrinsic carrier concentration given for silicon

In the above equation, many of the parameters have some temperature dependence, but the most significant effect is due to the intrinsic carrier concentration, ni. The intrinsic carrier concentration depends on the band gap energy (with lower band gaps giving a higher intrinsic carrier concentration), and on the energy which the carriers have (with higher temperatures giving higher intrinsic carrier concentrations).

Solar Cell Model

Basic structure of a silicon PV cell The thickness of solar cell is approximately 0.33 mm. The thickness of n-type semiconductor is approximately .002mm.

1. Cover Glass: The cover glass made of glass or other clear material such clear plastic, seals the cell from the external environment.

2. The Antireflective Coating (AR Coating): Through a combination of a favorable refractive index and thickness, this layer serves to guide light into the PV Cell. Without this layer, much of the light would bounce off the surface of the cell.

3. Contact Grid: The contact grid is made of a good conductor, such as a metal and it serves as a collector of electrons.

4. N-Type Silicon: N-type silicon is created by doping (contaminating) the Si with compounds that contain one more valance electrons than Si does, such as with either Phosphorus or Arsenic. Since only four electrons are required to bond with the four adjacent silicon atoms, the fifth valance electron is available for conduction.

5. P-Type Silicon: P-type silicon is created by doping with compounds containing one less valance electrons than Si does, such as with Boron. When silicon (four valance electrons) is doped with atoms that have one less valance electrons (three valance electrons), only three electrons are available for bonding with four adjacent silicon atoms, therefore an incomplete bond (hole) exists which can attract an electron from a nearby atom. Filling one hole creates another hole in a different Si atom. This movement of holes is available for conduction.

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6. Back Contact: The back contact, made out of a metal, covers the entire back surface and acts as a conductor.

Equivalent circuit of a solar cell An ideal and the simplest solar cell model consists of diode and current source connected parallel. Current source current is directly proportional to the solar radiation. Diode represents PN junction of a solar cell. Equation of ideal solar cell, which represents the ideal solar cell model, is:

Where

IPh - Photocurrent (A)

IS - Reverse saturation current (A) (approximately range 10-8/m2)

VD - Diode voltage (V)

VT - Thermal voltage (see equation below)

VT = 25.7 mV at 25°C

m - Diode ideality factor = 1...5 x VT (-) (m = 1 for ideal diode)

Thermal voltage, VT can be calculated with the following equation:

Where

k - Boltzmann constant = 1.38 x 10-23 J/K

T - Temperature (K)

q - Charge of electron = 1.6 x 10-19 C

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Ideal Solar Cell Model

In practice no solar cell is ideal, so a shunt resistance & a series resistance component are added to the model. The consequences of resistances are voltage drop & parasitic currents.

Shunt Resistance (RSH) and Series Resistance (RS)

During operation, the efficiency of solar cells is reduced by the dissipation of power across internal resistances. These parasitic resistances can be modeled as a parallel shunt resistance (RSH) and series resistance (RS), as depicted in Figure .

For an ideal cell, RSH would be infinite and would not provide an alternate path for current to flow, while RS would be zero, resulting in no further voltage drop before the load.

Decreasing RSH and increasing Rs will decrease the fill factor (FF) and PMAX as shown in Figure . If RSH is decreased too much, VOC will drop, while increasing RS excessively can cause ISC to drop instead.

Effect of Diverging Rs & RSH from Ideality

It is possible to approximate the series and shunt resistances, RS and RSH, from the slopes of the I-V curve at VOC and ISC, respectively. The resistance at Voc, however, is at best proportional to the series resistance but it is larger than the series resistance. RSH is represented by the slope at ISC. Typically, the resistances at ISC and at VOC will be measured and noted, as shown in Figure.

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Obtaining Resistances from the I-V Curve

If incident light is prevented from exciting the solar cell, the I-V curve shown in figure can be obtained. This I-V curve is simply a reflection of the “No Light” curve from figure about the V-axis. The slope of the linear region of the curve in the third quadrant (reverse-bias) is a continuation of the linear region in the first quadrant, which is the same linear region used to calculate RSH in Figure. It follows that RSH can be derived from the I-V plot obtained with or without providing light excitation, even when power is sourced to the cell. It is important to note, however, that for real cells, these resistances are often a function of the light level, and can differ in value between the light and dark tests.

Real Solar cell model with serial and parallel resistance Rs and Rp

Schematic symbol of a solar cell:

Schematic Representation of a Solar Cell for use in Circuit Diagrams

Different Solar Cell Types One can distinguish three cell types according to the type of crystal: monocrystalline, polycrystalline and amorphous. The most common semiconductor material used in solar cells is silicon. A number of different degrees in lattice alignment are in use:

1. Monocrystalline Silicon (cell efficiency of approx. 14-17%) 2. Polycrystalline Silicon (cell efficiency of approx. 13-15%) 3. Amorphic Silicon (cell efficiency of approx. 5-7%)

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To produce a monocrystalline silicon cell, absolutely pure semi conducting material is necessary. Monocrystalline rods are extracted from melted silicon and then sawed into thin plates. This production process guarantees a relatively high level of efficiency.

Single-crystal silicon or monocrystalline silicon cell isn't the only material used in PV cells. Polycrystalline silicon is also used in an attempt to cut manufacturing costs, although resulting cells aren't as efficient as single crystal silicon. The production of polycrystalline cells is more cost-efficient. In this process, liquid silicon is poured into blocks that are subsequently sawed into plates. During solidification of the material, crystal structures of varying sizes are formed, at whose borders defects emerge. As a result of this crystal defect, the solar cell is less efficient. Amorphous silicon, which has no crystalline structure, is also used, again in an attempt to reduce production costs.

If a silicon film is deposited on glass or another substrate material, this is a so-called amorphous or thin layer cell. The layer thickness amounts to less than 1µm (thickness of a human hair: 50-100µm), so the production costs are lower due to the low material costs. However, the efficiency of amorphous cells is much lower than that of the other two cell types. Because of this, they are primarily used in low power equipment (watches, pocket calculators) or as facade elements.

Material Level of efficiency in % Lab (Research)

Level of efficiency in %Production (Commercial)

Monocrystalline Silicon approx. 24 14 to17 Polycrystalline Silicon approx. 18 13 to15

Amorphous Silicon approx. 13 5 to7

Over 95% of all the solar cells produced worldwide are composed of the semiconductor material Silicon (Si). As the second most abundant element in earth’s crust, silicon has the advantage, of being available in sufficient quantities, and additionally processing the material does not burden the environment. Other materials used include gallium arsenide, copper indium diselenide and cadmium telluride. Since different materials have different band gaps, they seem to be "tuned" to different wavelengths, or photons of different energies. One way efficiency has been improved is to use two or more layers of different materials with different band gaps. The higher band gap material is on the surface, absorbing high-energy photons while allowing lower-energy photons to be absorbed by the lower band gap material beneath. This technique can result in much higher efficiencies. Such cells, called multi-junction cells, can have more than one electric field.

From the Cell to the Panel In order to make the appropriate voltages and outputs available for different applications, single solar cells are interconnected to form larger units. Cells connected in series have a higher voltage, while those connected in parallel produce more electric current. The interconnected solar cells are usually embedded in transparent Ethyl-Vinyl-Acetate, fitted with an aluminum or stainless steel frame and covered with transparent glass on the front side.

The typical power ratings of such solar modules are between 10W peak and 100W peak. The characteristic data refer to the standard test conditions of 1000 W/m² solar radiation at a cell temperature of 25° Celsius. The manufacturer’s standard warranty of ten or more years is quite long and shows the high quality standards and life expectancy of today's products.

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Energy Losses in a Solar Cell There are various natural limits of efficiency as follows:

1. The different semiconductor materials or combinations are suited only for specific spectral ranges. Therefore a specific portion of the radiant energy cannot be used, because the light quanta (photons) do not have enough energy to "activate" the charge carriers. Visible light is only part of the electromagnetic spectrum. Electromagnetic radiation is not monochromatic. It is made up of a range of different wavelengths, and therefore energy levels. Light can be separated into different wavelengths, and we can see them in the form of a rainbow. Since the light that hits our cell has photons of a wide range of energies, it turns out that some of them won't have enough energy to form an electron-hole pair. They'll simply pass through the cell as if it were transparent. Still other photons have too much energy. Only a certain amount of energy, measured in electron volts (eV) and defined by our cell material (about 1.1 eV for crystalline silicon), is required to knock an electron loose. We call this the band gap energy of a material.

2. A certain amount of surplus photon energy is transformed into heat rather than into electrical energy. If a photon has more energy than the required amount, then the extra energy is lost (unless a photon has twice the required energy, and can create more than one electron-hole pair, but this effect is not significant). These two effects alone account for the loss of around 70 percent of the radiation energy incident on our cell. We can't choose a material with a really low band gap, use more of the photons. Because band gap also determines the strength (voltage) of our electric field, and if it's too low, then what we make up in extra current (by absorbing more photons), we lose by having a small voltage. Remember that power is voltage times current. The optimal band gap, balancing these two effects, is around 1.4 eV for a cell made from a single material.

3. There are optical losses, such as the shadowing of the cell surface through contact with the glass surface or reflection of incoming rays on the cell surface.

4. Electrons have to flow from one side of the cell to the other through an external circuit. We can cover the bottom with a metal, allowing for good conduction, but if we completely cover the top, then photons can't get through the opaque conductor and we lose all of our current (in some cells, transparent conductors are used on the top surface, but not in all). If we put contacts only at the sides of our cell, then the electrons have to travel an extremely long distance (for an electron) to reach the contacts. Remember, silicon is a semiconductor - it's not nearly as good as a metal for transporting current. Its internal resistance (called series resistance) is fairly high and high resistance means high losses. To minimize these losses, our cell is covered by a metallic contact grid that shortens the distance that electrons have to travel while covering only a small part of the cell surface. Even so, some photons are blocked by the grid, which can't be too small or else its own resistance will be too high.

5. Other loss mechanisms are electrical resistance losses in the semiconductor and the connecting cable. The disrupting influence of material contamination, surface effects and crystal defects, however are also significant.

Loss mechanisms such as photons with too little energy are not absorbed, surplus photon energy is transformed into heat cannot be further improved because of inherent physical limits imposed by the materials themselves. This leads to a theoretical maximum level of efficiency, i.e. approximately 24% for crystal silicon.

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New Directions Surface structuring to reduce reflection loss For example, construction of the cell surface in a pyramid structure, so that incoming light hits the surface several times. New material: for example, gallium arsenide (GaAs), cadmium telluride (CdTe) or copper indium selenide (CuInSe²).

Tandem or stacked cells In order to be able to use a wide spectrum of radiation, different semiconductor materials, which are suited for different spectral ranges, will be arranged one on top of the other.

Concentrator cells A higher light intensity will be focused on the solar cells by the use of mirror and lens systems. This system tracks the sun, always using direct radiation.

MIS Inversion Layer cells The inner electrical field is not produced by a p-n junction, but by the junction of a thin oxide layer to a semiconductor.

Gratzel cells Electrochemical liquid cells with titanium dioxide as electrolytes & dye to improve light absorption.

Applications of solar cells The electricity generated by the photoelectric effect can be either used directly or can be stored in batteries or can directly fed into an electric utility’s grid system. The energy stored in the battery (in the form of chemical energy) can be used to operate any electrical device. If the device operates on DC, then it can be directly connected to the output load. If the device operates on AC, then an inverter is required to convert DC into AC.

1. Rural Electrification The provision of electricity to rural areas derives important social and economic benefits to remote communities throughout the world. Power supply to remote houses or villages, electrification of the health care facilities, irrigation and water supply and treatment are just few examples of such applications.

The potential for PV powered rural applications is enormous. The UN estimates that two million villages within 20 of the equator have neither grid electricity nor easy access to fossil fuel. It is also estimated that 80% of all people worldwide do not have electricity, with a large number of these people living in climates ideally suited to PV applications.

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Even in Europe, several hundred thousand houses in permanent occupation (and yet more holiday homes) do not have access to grid electricity. The economics of PV systems compares favorably with the usual alternative forms of rural electricity supply, grid extension and diesel generators. The extension and subsequent maintenance of transmission lines over long distances of often a difficult terrain is expensive, particularly if the loads are relatively small. Regular fuel supply to diesel generators, on the other hand, often present problems in rural areas, in addition to the maintenance of the generating equipment.

2. Water Pumping More than 10,000 PV powered water pumps are known to be successfully operating throughout the world. Solar pumps are used principally for two applications: village water supply (including livestock watering) and irrigation. Since villages need a steady supply of water, provision has to be made for water storage for periods of low insulations. In contrast, crops have variable water requirements during the year which can often be met by supplying water directly to produce without the need for a storage tank.

Deep well Solar Pump 3. Lighting

In terms of the number of installations, lighting is presently the biggest application of photovoltaic, with tens of thousands of units installed worldwide. They are mainly used to

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provide lighting for domestic or community buildings, such as schools or health centers. PV is also being increasingly used for lighting streets and tunnels, and for security lighting. Solar power is used for many lighted highway signs, eliminating the need for diesel generators.

PV powered Traffic Light System 4. Domestic Supply

Stand-alone PV domestic supply systems are commonly encountered in developing countries and remote locations in industrialized countries. The size range varies from 50 Wp to 5 KWp (kilowatt-peak) depending on the existing standard of living. Typically larger systems are used in remote locations or island communities of developed countries where household appliances include refrigeration, washing machine, television and lighting. In developing regions large systems (5 KWp) are typically found for village supply while small systems (20-200 Wp) are used for lighting, radio and television in individual houses.

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Solar-powered House 5. Health Care

Extensive vaccination programs are in progress throughout the developing world in the fight against common diseases. To be effective, these programs must provide immunization services to rural areas. All vaccines have to be kept within a strict temperature range throughout transportation and storage. The provision of refrigeration for this aim is known as the vaccine cold chain. Solar-powered refrigerator are able to keep perishable goods such as meat and dairy cool in hot climates, and are used to keep much needed vaccines at their appropriate temperature to avoid spoilage.

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Mobile Solar Vaccination Cooler Professional Applications For some time, photovoltaic modules have proved to be a good source of power for high-reliability remote industrial use in inaccessible locations or where the small amount of power required is more economically met from a stand-alone PV system than from mains electricity. Some of the most important applications of solar energy are nearly invisible. Telecommunications, oil companies, and highway safety equipment all rely on solar power for dependable, constant power, far from any power lines. Examples of these applications include: 1. Ocean Navigation Aids: Many lighthouses are now powered by solar cells

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PV-powered Navigation Aid 2. Telecommunication Systems

Radio transceivers on mountain tops or telephone boxes in the country can often be solar powered. Call Boxes: Roadside call box, are connected with a solar panel. California standardized on the use of solar power and cellular phones to eliminate the need for any buried cable connections to these phones. Given the sometimes literally life-saving nature of these call boxes, dependability is a must.

Telecommunications Installations: When you need a microwave repeater on a remote mountaintop, the last thing you want to do is run a power line up to it. The need for setting up solar panels for telecom tower operation is backed up by many valid reasons. Telecommunication sector runs completely on electricity and in number of villages across India, this facility is not available or conducive to expand it across remote areas. Due to this very reason, most of the times, electricity is pulled in from other sources like BTS (Base Transceiver Station)which provides battery back-up, but this also causes interruptions in the power supply resulting in shortening the battery life. This in turn increases the operational costs to run such services in rural areas. Not to forget about the additional costs that are incurred for maintaining this high-end backup systems and network costs all thanks to poor transportation facilities, problems in spare part supplies, and shortage of skilled labour. Another important factor that led to the thought of using the power of solar panel for telecom towers is the use of expensive diesel for running these towers. The consumption of diesel has been increased, that are needed for running engines and transmission equipment. This is again due to lack of reliable

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power in rural areas. All these factors contribute to additional costs. Increasing diesel costs are again a concern. Manufacturing, installation, running and even maintenance of telecom towers therefore prove very expensive.

Solar-powered Telecommunication Tower

3. Remote Monitoring and Control

Scientific research stations, seismic recording, weather stations, etc. Use very little power which, in combination with a dependable battery, is provided reliably by a small PV module. The main power source for an automatic weather station is usually one or more solar panels connected in parallel with a regulator and one or more rechargeable batteries. As a rule of thumb, solar output is at its optimum for only 5 hours each day. As such, mounting angle and position are vital. In the Northern Hemisphere the solar panel would be mounted facing south and vice versa for the Southern Hemisphere. The output from the solar panels may be supplemented by a wind turbine to provide power during periods of poor sunlight, or by direct connection to the local electrical grid

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Solar-powered Weather Station 4. Cathodic Protection

This is a method for shielding metal work from corrosion, for example, pipelines and other metal structures. A PV system is well suited to this application since a DC source of power is required in remote locations along the path of a pipeline.

Solar-powered Pipeline System

Given this growth, solar power will be a much larger part of our lives in future. Homes could incorporate solar power at the time that they are built, dramatically reducing both the cost of buying solar power and the cost of utility bills. New communications technology

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may make living in remote areas a practical reality given the availability of solar power. Mobile uses will undoubtedly increase. And industrial applications will continue to enjoy the versatility of solar power.

Electric Power Generation in Space The energy problem related to spacecraft can be split in two parts. The first major difficulty is of course to escape from the Earth. The second is to power the spacecraft once it is in space in the middle of nowhere, or better said in the middle of nothing.

The problem of leaving the Earth’s surface is usually solved by fuel-powered launchers like Ariane or by a manned Space Shuttle. The spacecraft is placed as payload in the launcher. Once it is in orbit around the Earth, the satellite or space probe is freed. A satellite will then go round the Earth in the chosen orbit while a space probe will be sent on its path in the solar system. In most cases, the spacecraft possesses its own engines and a small amount of fuel so that it can be maneuvered if necessary.

Once in space, the spacecraft (or the space station) must have access to a source of electricity in order to fulfill its mission. Even exchange of information between the spacecraft and the earth uses up energy. The mission would be pointless if the probe or the satellite could not send images or other forms of data back to Earth. Electricity will also be needed at one time or another to fire the engines, and to operate scientific instruments. In space the issue of providing spacecrafts or space stations with the necessary electricity to run the equipment on board is usually solved by means of solar panels. Solar panels convert the light coming from the sun into electricity. The energy available from the sun is always there but decreases as the probe travels further and further away from the sun. The amount of electricity produced is proportional to the surface of the solar panels. Often, the size of the panels is much greater than the size of the spacecraft itself. It is not possible to put the spacecraft and its deployed solar panels in a launcher like Ariane.

The panels can only deployed once the spacecraft has arrived in orbit and leaves the launcher. This of course can be a source of huge problems if the solar panels get stuck and refuse to deploy. In the case of a manned mission, the crew might be able to fix the problem. The panels of the space stations are actually mounted by the crew in space.

Most missions, however, are not manned and everything must be done automatically. It is therefore particularly important to devise a method of deploying solar panels that is safe and reliable. Photovoltaic solar generators have been and will remain the best choice for providing electrical power to satellites in an orbit around the Earth. Indeed, the use of solar cells on the U.S. satellite Vanguard I in 1958 demonstrated beyond doubt the first practical application of photovoltaic. Since then, the satellite power requirements have evolved from few Watts to several kiloWatts, with arrays approaching 100 kW being planned for a future space station.

A space solar array must be extremely reliable in the adverse conditions of space environment. Since it is very expensive to lift every kilogram of weight into the orbit, the space array should also have a high power-to-weight ratio.

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PV powered Satellite

Grid-connected Systems 1. PV Power Stations

Two types of grid-connected installations are usually distinguished, centralized PV power stations and distributed generation in units located directly at the customer's premises (PV in buildings). A PV power station feeds the generated power instantaneously into the utility distribution network (the 'grid') by means of one or more inverters and transformers. The first PV power station was built at Hysperia in southern California in 1982 with nominal power specification 1 MW, using crystalline silicon modules mounted on a 2 axis tracking system. PV power stations may be approaching economic viability in locations where they assist the local grid during periods of peak demand, and obviate the need to construct a new power station. This is known as peak shaving. It can also be cheaper to place small PV plants within the transmission system rather than to upgrade it ('embedded' generation).

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PV Power Station 2. PV in buildings

PV arrays mounted on roof tops or facades offer the possibility of large-scale power generation in decentralized medium-sized grid-connected units. Studies in Germany, Switzerland and the UK have shown that the roof and facade area technically suitable for PV installations is large enough to supply the country's electricity demand. The size envisaged for each decentralized residential PV system is typically 1- 5kW, with systems up to a hundred kW or so suitable for commercial and industrial buildings.

Building with Photovoltaic Façade Manufacturing companies of photovoltaic system have recently introduced "Sun slates" that can be fitted to existing roofs easily. Photograph of these are shown below:

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Solar Panel Installed on Existing Roofs The main advantages of these distributed systems over large PV plants are as follows: There is no cost in buying the land and preparing the site. The transmission losses are much lower because the load is on the same site as the supply. The value of the PV electricity is also higher because it is equal to the selling price of the grid electricity which has been replaced, rather that to the cost of generating it. However, it should also be noted that the price paid by utility companies for electricity exported from a decentralized source is a fraction of the utility sale price. The optimum economic benefit is therefore derived by consuming all PV produced electricity, with direct reduction of the energy imported from the utility. Thus grid connected PV systems are ideal for loads which vary in proportion to the irradiation. Typical loads are air-conditioning, refrigeration and pumping. Other significant loads can be timed to operate when PV power is likely to be available. Examples include washing machines and clothes dryers which can operate on timing clocks

Advantages of Photovoltaic Power: 1. Photovoltaic solar power is one of the most promising renewable energy sources in the

world. Compared to nonrenewable sources such as coal, gas, oil and nuclear, the advantages are clear: it's totally non-polluting, has no moving parts to break down, and does not require much maintenance. There are no fuel costs or fuel supply problems.

2. A very important characteristic of photovoltaic power generation is that it does not require a large scale installation to operate, as different from conventional power generation stations. Power generators can be installed in a distributed fashion, on each house or business or school, using area that is already developed, and allowing individual users to generate their own power, quietly and safely. The equipment can usually operate unattended. Rooftop power can be added as more homes or businesses are added to a community, thereby allowing power generation to keep in step with growing needs without having to overbuild generation capacity as is often the case with conventional large scale power systems.

3. When photovoltaic power is compared to other renewable energy sources such as wind power, water power and even solar thermal power, there are some obvious advantages. First, wind and water power rely on turbines to turn generators to produce electricity. Turbines and generators have moving parts that can break down, that require maintenance, and are noisy. Even solar thermal energy needs a turbine or other mechanical device to change the heat energy of the sun into mechanical energy for a generator to produce

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electric power. Photovoltaic power, by contrast, is generated directly from the sun. PV systems have no moving parts, require virtually no maintenance, and have cells that last for decades.

Hybrid solar lighting Artificial lighting accounts for the largest component of electricity use in commercial buildings. Hybrid solar lighting provides an exciting new means of reducing energy consumption while also delivering significant benefits associated with natural lighting in commercial buildings. The hybrid lighting technology was originally developed for fluorescent lighting applications but recently has been enhanced to work with incandescent accent-lighting sources, such as the parabolic aluminized reflector (PAR) lamps commonly used in retail spaces. Principles of Operation

The hybrid solar lighting system uses a roof-mounted solar collector to concentrate visible sunlight into a bundle of plastic optical fibers. The optical fibers penetrate the roof and distribute the sunlight to multiple “hybrid” luminaries within the building The hybrid luminaries blend the natural light with artificial light (of variable intensity) to maintain a constant level of room lighting. One collector powers about eight fluorescent hybrid light fixtures, which can illuminate about 1000 square feet. When sunlight is plentiful, the fiber optics in the luminaries provides all or most of the light needed in an area. During times of little or no sunlight, a sensor controls the intensity of the artificial lamps to maintain a desired illumination level. Unlike conventional electric lamps, the natural light produces little to no waste heat, having an efficacy of 200 lumens/Watt (l/W), and is cool to the touch. This is because the system’s solar collector removes the infrared (IR) light from the sunlight—the part of the spectrum that generates much of the heat in conventional bulbs. Because the optical fibers lose light as their length increases, it makes sense right now to use hybrid solar lighting in top-story or single-story spaces. The current optimal optical fiber length is 50 feet or less. The hybrid solar lighting technology can separate and use different portions of sunlight for various applications. Thus, visible light can be used directly for lighting applications while IR light can be used to produce electricity or generate heat for hot water or space heating. The optimal use of these wavelengths is the focus of continued studies and development efforts. The goal for future hybrid solar lighting systems is that they be

1. Multifunctional: Compatible with various electric lamps, light fixtures, hot water heaters, photovoltaics,etc., and usable for various applications

2. Reconfigurable: Easily modified asspace needs change

3. Seamlessly integrated: Connected to standard power sources to ensure that disruptions in service do not occur on cloudy days or at night

4. Architecturally compatible: Designed to eliminate architectural design hassles and maintenance

problems limiting the use of solar power.

5. Affordable

Advantages of Hybrid Solar Lighting

Electric lighting is the greatest consumer of electricity in commercial buildings and the generation of this electricity by conventional power plants is the building sector’s most

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significant cause of air pollution. Hybrid lighting can help conserve electricity in proportion to the amount of sunlight available. Hybrid solar lighting technology could benefit federal buildings, particularly in the Sunbelt where cooling is a significant source of energy use. Full-spectrum solar energy systems provide a new and realistic opportunity for wide-ranging energy, environmental, and economic benefits. Because hybrid solar lighting has no infrared component, it can be considered a high-efficiency light source. Other advantages of hybrid solar lighting are:

1. Roof penetrations are small and minimal, reducing the potential for leaks.

2. IR and UV energy in sunlight is separated from the visible light, rather than being

transmitted into buildings. Heating, ventilation, and air-conditioning (HVAC) loads are thus reduced by 5 to 10%, compared to buildings having conventional electric lighting systems.

3. Hybrid solar lighting systems are readily adaptable to commercial buildings with

multiple floors, relatively low ceiling heights, and interior walls, though currently fiber optic output is optimized on the top two floors. A single system can distribute enough sunlight to co-illuminate several rooms in a typical office building.

4. Large portions of valuable plenum space—the area between the roof and drop ceiling—

are not needed,so there is little competition with other building services, such as HVAC ducts, sprinkler systems, and electrical conduits.

5. Hybrid solar lighting can be used both for direct ambient lighting (as in skylights) and for indirect lighting, task lighting, and accent lighting.In retrofit applications, hybrid solar lighting is easily incorporated into existing building designs, and the optical fibers can be rerouted to different locations as lighting needs change. By intentionally misaligning the solar collector from the sun, occupants can even dim or curtail distributed sunlight.

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Experiment 1 Objective: Study of the voltage and current of the solar cells

Apparatus Required: 1. Experimentation with Solar Energy Nvis 6005 2. Solar Panel 3. DB15 connector 4. Patch cords

Procedure: 1. Take the Experimentation with Solar Energy Nvis 6005 along with Solar Panel. 2. Place the solar panel in the stand and adjust the panel at an angle of about 45º with the

ground. Direct the sunlight straight at the solar panel (angle of 90º). Note: If sunlight is not properly available then any source of light like lamp can be used.

3. With the DB15 connector connect the Experimentation with Solar Energy Nvis 6005 with the Solar Panel. Then wait for 1 minute to avoid errors due to temperature fluctuations.

4. Measure the voltage (V1) of S1 solar cell by connecting its output across voltmeter with the help of patch cords. Similarly, you can measure the voltages of other solar cells. Record the voltage of all cells (V1, V2, V3, V4, V5 and V6) respectively in the Observation Table.

5. Measure the current (I1) of S1 solar cell by connecting the ammeter across S1 solar cell with the help of patch cords. Similarly, you can measure the current of other solar cells. Record the current of all cells (I1, I2, I3, I4, I5 and I6) respectively in the Observation Table.

Observation Table:

S. No. Solar Cell DC Voltage (V)

DC Current (mA)

1. S1 2. S2 3. S3 4. S4 5. S5 6. S6

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Experiment 2 Objective: Study of the voltage and current of the solar cells in series & parallel combinations


Procedure: 1. Take the Experimentation with Solar Energy Nvis 6005 along with Solar Panel.

2. Place the Solar Panel in the stand and adjust the panel at an angle of about 45º with the ground. Direct the sunlight straight at the solar panel (angle of 90º).

Note: If sunlight is not properly available then any source of light like lamp can be used. 3. With the DB15 connector connect the Experimentation with Solar Energy Nvis 6005

with the Solar Panel. Then wait for 1 minute to avoid errors due to temperature fluctuations.

Series combination of cells: 4. With the patch cords, connect outputs of all cells one by one in series such that the

positive terminal of one connected to the negative terminal of the other as shown in figure.

5. Connect the positive and negative terminal of the series combination across the

voltmeter as shown in figure. Record the total voltage of the series combination in the Observation Table given below.

Voltmeter Connected to the Series Combination of Solar Cells

6. Now connect the positive and negative terminal of the series combination across the ammeter as shown in figure. Record the current of the series combination in the Observation Table given below.

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Ammeter Connected to the Series Combination of Solar Cells

Observation Table:

S. No. Solar Cell

Voltage (V)

Current (mA)

Voltage of the series combination

(V)

Current of the series combination

(mA)

1. S1 2. S2 3. S3 4. S4 5. S5 6. S6

Sum of the voltages of all solar cells =V Total=V1+V2+V3+V4+V5+V6 = ………V Total voltage of series combination =……….V

Hence it is clear that the total voltage of the series combination is equal to the sum of the voltage of all solar cells.

Total current in series combination =…………….mA Hence it is clear that the total current of the series combination is equal to the individual current of each solar cell.

Parallel combination of cells: 7. Take out all the cords from the trainer. 8. With the patch cords, connect all cells one by one in parallel such that the positive

terminal of one connected to the positive terminal of the other, and also the negative terminal of one connected to the negative terminal of the other as shown in figure.

9. Connect the positive and negative terminal of the parallel combination across the

voltmeter as shown in figure 48. Record the voltage of the parallel combination in the Observation Table given below.

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10. Now, connect the positive and negative terminal of the parallel combination across the ammeter as shown in figure. Record the total current of the parallel combination in the Observation Table given below.

Note: To measure current by on board ammeter, do not connect more than 3 solar cells in

parallel. For measuring total current of parallel combination of more than 3 solar cells, arrange a digital multimeter or analog ammeter of 1 Ampere rating in your laboratory.

Observation Table:

S. No. Solar Cell

Voltage (V)

Current (mA)

Voltage of the Parallel combination

Current of the parallel combination

1. S1

2. S2

3. S3

4. S4

5. S5

6. S6

Total voltage of parallel combination =………..V

Hence it is clear that the total voltage of the parallel combination is equal to the individual voltage of each solar cell.

Sum of the current of all solar cells = ITotal = I1+ I2 +I3 + I4 + I5 + I6 = ……………mA Total current of parallel combination =……….mA Hence it is clear that the total current of the parallel combination is equal to the sum of the current of all solar cells.

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Conclusion:

1. Solar cells in series boost voltage but the current remains the same.

2. Solar cells in parallel boost current rating but the voltage remains same.

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Experiment 3 Objective: Study of both the current–voltage characteristic and the power curve to find the maximum power point (MPP) and efficiency of a solar cell




3. With the DB15 connector connect the Experimentation with Solar Energy Nvis 6005 with Solar Panel. Then wait for 1 minute to avoid errors due to temperature fluctuations.

4. Set the potentiometer to maximum resistance i.e. at fully clockwise position and measure and record its resistance into the Observation Table.

5. Connect the solar cell as shown in the following circuit diagram.

Setup for determining characteristics of a solar cell

• Connect positive terminal of solar cell to P1 terminal of the potentiometer.

• Connect other end of potentiometer i.e. P2 to positive terminal of ammeter.

• Connect negative terminal of ammeter to negative terminal of solar cell.

• Now connect the positive terminal of voltmeter to P1 & negative terminal of voltmeter to P2.

6. Record the values of corresponding voltage & current into the Observation Table.

7. Now gradually move the potentiometer in anticlockwise direction so that the resistance of the potentiometer decreases. Now measure the resistances at successively smaller values and record the corresponding values of voltages and current into the Observation Table below.

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Note: Always to measure the resistance of potentiometer at any position, first remove the patch cords from P1 and P2 and measure resistance by multimeter. Reconnect these connections again for further measurements

Observation Table:

S. No. Resistance, R (Ω)

Voltage, V (Volts)

Current, I (mA)

Power calculated P = V. I (Watts)

1. 2. 3. 4. 5. 6. 7. 8. 9. 10.

8. Plot the I-V characteristics from the measurements recorded in the table, to show how the photoelectric current depends on the photoelectric voltage and to find maximum power point.

Expected I-V curve is as follows

From V-I characteristics you can easily find the maximum power point (MPP). Maximum power point (MPP) occurs where the product of voltage & current is greatest.

9. Plot the curve of power as a function of voltage from the measurements recorded in the table.

Expected Power-Voltage curve is as follows

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The maximum power point (MPP) is the maximum value of power in the above curve. The resistance, RMPP, at which the output power is at a maximum can be calculated using the following formula:

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Experiment 4 Objective: To calculate the efficiency (η) of solar cell


Theory: The efficiency of the solar cell is the ratio of produced electrical power (Pout) & the incident radiant power (Pin).

Efficiency of solar cell, η =

Where Pout is the electrical power (maximum power point)

Pin is calculated by multiplying approximated irradiance (“irradiance” means radiant power of the light incident per unit area) by the effective area of the solar cell on the panel.

This method used the fact that the practical value of the current (maximum photoelectric current measured) is proportional to the photons (radiation) striking the solar cell. This current is therefore proportional to the incident radiant power of the light. The open circuit voltage depends on the semiconductor material of which solar cell is made. It is not proportional to the incident radiant power and therefore cannot be used for this measurement.

Procedure: 1. Efficiency of solar cell,

η =

Where Pout (Output Electrical Power) = Maximum Power Point (MPP)

Pin (Incident radiant power) = Approximated Irradiance x Area of solar cell = (F x Ip) x A .....(eq.1) Here

A = Area of a solar cell (Length x Breadth) m2 Ip= Practical value of current (maximum photoelectric current measured) indicated on the

ammeter F = constant and is given by

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The maximum irradiance in summer is approx. 1000 W/m2. The maximum value of the current specified by the manufacturer is achieved at this value i.e. 150mA in the given solar cells. (The parameters of the solar cell/panel is related to the standard test conditions of 1000W/m2 and cell temperature of 25º C.)

2. Multiplying the practical value of current (Ip) indicated on the ammeter by the factor gives

an approximation of the radiant power per unit area (irradiance) striking the solar cell.

Approximation of the radiant power per unit area =……….

3. Now measure the area in m2 and put the values in the formula given in eq. 1. Pin = ………

Now, we can calculate the efficiency of solar cell with

η = Pout Pin

Where Pout or MPP =………….. (As calculated in the experiment 3) η =………..

The efficiencies of solar cells lie between 12 to 15 %. If efficiency is slightly less than determined value then it is due to measuring errors and inaccuracies in determining the incident radiant power. Furthermore, the efficiency of solar panel is less than that of their separate constituent cells. This is caused by losses that arise in matching solar cells that do not all have exactly the same properties. If the solar cells are connected in series to generate desired voltage, the maximum power point may not be same for all cells. Solar cell losses arise as not all photons striking the solar cell can be converted into charge carriers. Part of the light is reflected as soon as it hits the surface and the metal contacts cast shadows. Since the photon energy does not correspond to the energy gap, less than half of the incident energy is used. Recombination of charge carriers (atomic rebinding of electrons) and electrical losses caused by internal resistances (ohmic losses in the semiconductor) of the solar cell and its contacts also arise.

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Experiment 5 Objective: Study of the application of solar cells of charging the Ni-Cd battery so that the loads can be used even while the module is unexposed to light

Apparatus Required: 1. Experimentation with Solar Energy Nvis 6005 2. Solar Panel 3. DB15 connector 4. Rechargeable Ni-Cd Battery 5. Patch cords



3. With the DB15 connector connect the Experimentation with Solar Energy Nvis 6005 with Solar Panel Nvis 6005. Then wait for 1 minute to avoid errors due to temperature fluctuations.

4. Connect rechargeable Ni-Cd Battery in the holder provided in Charging Section.

Battery needs voltage of 1.5-2 V for standard charging at 80mA about 15 hours. Some batteries are provided with facility of quick charging at 210mA about 3-4 hrs. So connect the solar cells in series or parallel combination as per the required rating.

5. Now with the help of patch cords, connect the positive terminal of the solar cell to the positive terminal of diode and negative terminal of solar cell to negative terminal of battery Section.

6. Now connect the terminal T1 to positive terminal of battery. 7. Connect the voltmeter across battery terminals with patch cord. You can observe the

voltage variations. 8. Now to operate the load connects the positive terminal of battery to terminal T2 of

amplifier section and T3 to positive terminal of Load with patch cords. Now connect negative terminal of battery to negative terminal of Load with patch cord.

9. Observe that the group of LED glows. Here load is operating with the solar energy and battery is charging with the solar energy.

For direct operation of load with charged batteries i.e. when module is unexposed to light:

10. Remove the connections of the solar cells to Charging Section.

11. The charged nickel cadmium battery provides electricity to the load even the panel is unexposed to light and when battery will discharged then you can reconnect previous connections for charging the battery.

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Experiment 6 Objective: Study of the application of solar cells of providing electrical energy to the domestic appliances such as lamp, fan and radio Apparatus Required:

1. Experimentation with Solar Energy Nvis 6005 2. Solar Panel 3. DB15 connector 4. Domestic appliances such as lamp fan and radio

5. Patch cords Procedure for Lamp: 1. Take the Experimentation with Solar Energy Nvis 6005 along with Solar Panel.

2. Place the solar panel in the stand and adjust the panel at an angle of about 45º with the ground. Direct the sunlight straight at the solar panel (angle of 90º).

Note: If sunlight is not properly available then any source of light like lamp can be used.

3. With the DB15 connector connect the Experimentation with Solar Energy Nvis 6005 with Solar Panel Nvis 6005. Then wait for 1 minute to avoid errors due to temperature fluctuations.

4. Measure the voltage and current of the solar cells and connect the number of solar cells in parallel as per the desired voltage of around 2V and 250mA of current rating for lamp.

5. Now connect the positive and negative terminals of solar cell’s parallel combination across the lamp with patch cords. Observe that the lamp is glowing with solar energy.

6. Perform a comparative study between intensity of the lamp and recommended voltage/current rating.

7. If you insert any obstacle in between sunlight and solar panel you can see the effect of change of intensity of the lamp. If you insert a fully opaque obstacle then lamp will stop glowing and when you remove the obstacle lamp will again start glowing.

Procedure for Fan: 1. Repeat steps 1 to 3 from procedure for lamp.

2. Measure the voltage and current of the solar cells and connect the number of solar cells in parallel as per the desired voltage of around 2V and 400mA of current rating for fan.

3. Now connect the positive and negative terminals of solar cells’s parallel combination across the fan with patch cords. Observe that the fan is rotating with solar energy.

Note: Clockwise or anticlockwise rotation of fan depends on polarity of solar cell inserted across fan terminals.

4. Perform a comparative study between speed of fan and recommended voltage/current rating.

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5. If you insert any obstacle in between sunlight and solar panel you can see the change in speed of the fan. If you insert a fully opaque obstacle then fan will stop rotating and when you remove the obstacle fan will again start rotating.

Procedure for FM Receiver: 1. Repeat steps 1 to 3 from procedure for lamp.

2. Measure the voltage and current of the solar cells and connect the number of solar cells in series as per the desired voltage of around 10 to 12 V DC.

3. Set the Volume Control knob to full clockwise rotation for maximum volume and adjust the Frequency Selector knob to tune any FM Radio Station.

4. Now with the help of patch cords, connect the positive and negative terminals of solar cells series combination to the positive and negative terminals of FM Receiver respectively. Observe that the radio is working with solar energy.

5. Perform a comparative study between volume of FM Receiver and recommended voltage/ current rating.

6. If you insert any obstacle in between sunlight and solar panel you can see the change in volume of the FM Receiver. If you insert a fully opaque obstacle then FM Receiver will stop working and when you remove the obstacle, FM Receiver will again start working.

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Glossary 1. Absorber : In a photovoltaic device, the material that readily absorbs photons to

generate charge carriers (free electrons or holes).

2. Activated Shelf Life : The period of time, at a specified temperature, that a charged

battery can be stored before its capacity falls to an unusable level.

3. Activation Voltage(s) : The voltage(s) at which a charge controller will take action to

protect the batteries.

4. Adjustable Set Point : A feature allowing a user to adjust the voltage levels at which a charge controller will become active.

5. Alternating Current (AC) : A type of electrical current, the direction of which is

reversed atregular intervals or cycles. In the United States, the standard is 120 reversals or 60 cycles per second. Electricity transmission networks use AC because voltage can be controlled with relative ease.

6. Acceptor : A dopant material, such as boron, which has fewer outer shell electrons than

required in an otherwise balanced crystal structure, providing a hole that can accept a free electron.

7. Air Mass (sometimes called air mass ratio) : Equal to the cosine of the zenith angle or

that angle from directly overhead to a line intersecting the sun. The air mass is an indication of the length of the path solar radiation travels through the atmosphere. An air mass of 1.0 means the sun is directly overhead and the radiation travels through one atmosphere (thickness).

8. Ambient Temperature : The temperature of the surrounding area.

9. Amorphous Semiconductor : A non-crystalline semiconductor material that has no longrange order.

10. Amorphous Silicon : A thin-film, silicon photovoltaic cell having no crystalline

structure. Manufactured by depositing layers of doped silicon on a substrate

11. Amperage Interrupt Capability (AIC) : Direct current fuses should be rated with a

sufficient AIC to interrupt the highest possible current.

12. Ampere (amp) : A unit of electrical current or rate of flow of electrons. One volt across one ohm of resistance causes a current flow of one ampere.

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13. Ampere-Hour (Ah/AH): A measure of the flow of current (in amperes) over one hour; used to measure battery capacity.

14. Ampere Hour Meter: An instrument that monitors current over time. The indication is the product of current (in amperes) and time (in hours).

15. Angle of Incidence: The angle that a ray of sun makes with a line perpendicular to the

surface. For example, a surface that directly faces the sun has a solar angles of incidence of zero, but if the surface is parallel to the sun (for example, sunrise striking a horizontal rooftop), the angle of incidence is 90°.

16. Annual Solar Savings: The annual solar savings of a solar building is the energy

savings attributable to a solar feature relative to the energy requirements of a non-solar building.

17. Anode: The positive electrode in an electrochemical cell (battery). Also, the earth or

ground in a cathodic protection system. Also, the positive terminal of a diode.

18. Antireflection Coating: A thin coating of material applied to a solar cell surface that

reduces the light reflection and increases light transmission.

19. Array Current: The electrical current produced by a photovoltaic array when it is exposed to sunlight.

20. Array Operating Voltage: The voltage produced by a photovoltaic array when

exposed to sunlight and connected to a load.

21. Availability: The quality or condition of a photovoltaic system available to provide power to a load. Usually measured in hours per year. One minus availability equals downtime.

22. Azimuth Angle: The angle between true south and the point on the horizon directly

below the sun.

23. Balance of System: Represents all components and costs other than the photovoltaic modules/array. It includes design costs, land, site preparation, system installation, support structures, power conditioning, operation and maintenance costs, indirect storage, and related costs.

24. Band Gap: In a semiconductor, the energy difference between the highest valence band

and the lowest conduction band.

Band Gap Energy (Eg): The amount of energy (in electron volts) required to free an outer shell electron from its orbit about the nucleus to a free state, and thus promote it from the Valence to the conduction level

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25. Barrier Energy: The energy given up by an electron in penetrating the cell barrier; a measure of the electrostatic potential of the barrier.

26. Base Load: The average amount of electric power that a utility must supply in any

period.

27. Battery: Two or more electrochemical cells enclosed in a container and electrically inter connected in an appropriate series/parallel arrangement to provide the required operating voltage and current levels. Under common usage, the term battery also applies to a single cell if it constitutes the entire electrochemical storage system.

28. Battery Available Capacity: The total maximum charge, expressed in ampere-hours,

hat can be withdrawn from a cell or battery under a specific set of operating conditions including discharge rate, temperature, initial state of charge, age, and cut-off voltage.

29. Battery Capacity: The maximum total electrical charge, expressed in ampere-hours,

which a battery can deliver to a load under a specific set of conditions.

Battery Cell: The simplest operating unit in a storage battery. It consists of one or more positive electrodes or plates, an electrolyte that permits ionic conduction, one or more negative electrodes or plates, separators between plates of opposite polarity, and a container for all the above.

30. Battery Cycle Life: The number of cycles, to a specified depth of discharge, that a cell

or battery can undergo before failing to meet its specified capacity or efficiency performance criteria.

31. Battery Energy Capacity: The total energy available, expressed in watt-hours

(kilowatt-hours), which can be withdrawn from a fully charged cell or battery. The energy capacity of a given cell varies with temperature, rate, age, and cut-off voltage. This term is more common to system designers than it is to the battery industry where capacity usually refers to amperehours.

32. Battery Energy Storage: Energy storage using electrochemical batteries. The three

main applications for battery energy storage systems include spinning reserve at generating stations, load leveling at substations, and peak shaving on the customer side of the meter.

33. Battery Life: The period during which a cell or battery is capable of operating above a

specified capacity or efficiency performance level. Life may be measured in cycles and/or years, depending on the type of service for which the cell or battery is intended.

BIPV (Building-Integrated Photovoltaic): A term for the design and integration of Photovoltaic (PV) technology into the building envelope, typically replacing conventional building materials. This integration may be in vertical facades, replacing view glass, spandrel glass, or other facade material; into semitransparent skylight systems; into roofing systems, replacing traditional roofing materials; into shading "eyebrows" over windows; or other building envelope systems.

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34. Cadmium (Cd): A chemical element used in making certain types of solar cells and

batteries.

35. Cadmium Telluride (CdTe): A polycrystalline thin-film photovoltaic material.

36. Capacity Factor: The ratio of the average load on (or power output of) an electricity generating unit or system to the capacity rating of the unit or system over a specified period of time.

37. Captive Electrolyte Battery: A battery having an immobilized electrolyte (gelled or

absorbed in a material).

38. Cathode: The negative pole or electrode of an electrolytic cell, vacuum tube, etc., where electrons enter (current leaves) the system; the opposite of an anode.

39. Cathodic Protection: A method of preventing oxidation of the exposed metal in

structures by imposing a small electrical voltage between the structure and the ground.

40. Cell (battery): A single unit of an electrochemical device capable of producing direct voltage by converting chemical energy into electrical energy. A battery usually consists of several cells electrically connected together to produce higher voltages. (Sometimes the terms cell and battery are used interchangeably). Also see photovoltaic (PV) cell.

41. Cell Junction: The area of immediate contact between two layers (positive and negative) of a photovoltaic cell. The junction lies at the center of the cell barrier or depletion zone.

42. Charge: The process of adding electrical energy to a battery.

43. Charge Carrier: A free and mobile conduction electron or hole in a semiconductor.

44. Charge Controller: A component of a photovoltaic system that controls the flow of

current to and from the battery to protect it from over-charge and over-discharge. The charge controller may also indicate the system operational status.

45. Charge Rate: The current applied to a cell or battery to restore its available capacity.

This rate is commonly normalized by a charge control device with respect to the rated capacity of the cell or battery.

46. Crystalline Silicon: A type of photovoltaic cell made from a slice of single-crystal silicon or polycrystalline silicon.

47. Diffuse Insolation: Sunlight received indirectly as a result of scattering due to clouds, fog,haze, dust, or other obstructions in the atmosphere. Opposite of direct insolation.

48. Diffuse Radiation: Radiation received from the sun after reflection and scattering by

the atmosphere and ground.

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49. Diffusion Furnace: Furnace used to make junctions in semiconductors by diffusing dopant atoms into the surface of the material.

50. Flat-Plate Photovoltaic (PV): A PV array or module that consists of no concentrating

elements. Flat-plate arrays and modules use direct and diffuse sunlight, but if the array is fixed in position, some portion of the direct sunlight is lost because of oblique sun-angles in relation to the array.

51. Full Sun: The amount of power density in sunlight received at the earth's surface at

noon on clear day (about 1,000 Watts/square meter).

52. Irradiance: The direct, diffuse, and reflected solar radiation that strikes a surface. Usually expressed in kilowatts per square meter. Irradiance multiplied by time equals insulations.

53. Photovoltaic (PV) Device: A solid-state electrical device that converts light directly

into direct current electricity of voltage-current characteristics that are a function of thecharacteristics of the light source and the materials in and design of the device. Solarphotovoltaic devices are made of various semiconductor materials including silicon, cadmium sulfide, cadmium telluride, and gallium arsenide, and in single crystalline, multicrystalline, or amorphous forms.

54. Photovoltaic (PV) Effect: The phenomenon that occurs when photons, the "particles"

in a beam of light, knock electrons loose from the atoms they strike. When this property of light is combined with the properties of semiconductors, electrons flow in one direction across a junction, setting up a voltage. With the addition of circuitry, current will flow and electric power will be available.

55. Photovoltaic (PV) Generator: The total of all PV strings of a PV power supply

system,which are electrically interconnected.

56. Photovoltaic (PV) Module: The smallest environmentally protected, essentially planar, assembly of solar cells and ancillary parts, such as interconnections, terminals, (and protective devices such as diodes) intended to generate direct current power under unconcentrated sunlight. The structural (load carrying) member of a module can either be the top layer (superstrate) or the back layer (substrate).

57. Photovoltaic (PV) Panel: Often used interchangeably with PV module (especially in

one module systems), but more accurately used to refer to a physically connected collection of modules (i.e., a laminate string of modules used to achieve a required voltage and current).

58. Photovoltaic (PV) System: A complete set of components for converting sunlight into

electricity by the photovoltaic process, including the array and balance of system components.

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59. Photovoltaic-Thermal (PV/T) System: A photovoltaic system that, in addition to converting sunlight into electricity, collects the residual heat energy and delivers both heat and electricity in usable form. Also called a total energy system.

60..Roof Mounted System : A solar system in which solar panels are mounted directly on the roof of a building or adjacent structure. The majority of solar systems are mounted on a roof.

61.Stand-Alone System: An autonomous or hybrid photovoltaic system not connected to a grid. May or may not have storage, but most stand-alone systems require batteries or some other form of storage.

62.Tilt Angle: The angle at which a photovoltaic array is set to face the sun relative to a horizontal position. The tilt angle can be set or adjusted to maximize seasonal or annual energy collection

63.Wafer: A thin sheet of semiconductor (photovoltaic material) made by cutting from a single crystal or ingot.

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Frequently Asked Questions Q1. What is solar energy?

Ans. Solar energy is the radiant energy produced by the Sun. It is both light and heat.

Q2. How do solar photovoltaic (PV) panels work?

Ans.Solar panels use layers of special materials called semi-conductors that create electricity when exposed to sufficient light. There are different types of solar panel construction. Some panels tend to perform better in high temperatures and low light situations, but take up around twice the space. Q3. What is alternative energy?

Ans. Alternative energy is any form of energy that does not come from fossil fuels. They are considered alternatives because they can be future replacements for the fossil fuels that now meet a considerable portion of our energy needs.

Q4. How do Photovoltaic Work?

Ans. Photovoltaic is the direct conversion of light into electricity at the atomic level. Some materials exhibit a property known as the photoelectric effect that causes them to absorb photons of light and release electrons. When these free electrons are captured, an electric current results that can be used as electricity.

Q5. What's the difference between solar photovoltaic and solar hot water systems?

Ans. While both types of solar systems capture energy from the sun, solar photovoltaic systems use photovoltaic panels to produce electricity. Solar hot water, or thermal, systems capture sunlight to heat water for domestic use, to heat a swimming pool, or for a radiant heating system.

Q6. What other factors are important to consider when installing a home solar energy system?

Ans. The location of your home and the local climate will play into where you place and how you install your solar electric or solar hot water system. Wind speeds, heavy snow loads, and salt water can all affect a solar array. Understanding how those inputs effect performance will determine the types of mounts or how the arrays are angled.

Q16. What components do you need to install a grid-tied solar electric system?

Ans. We will need a photovoltaic array to capture the sun's energy, an inverter to convert the direct current (DC) produced from the photovoltaic cells into alternating current (AC) used by our home, and a house utility meter – called a net meter – that can record both the electricity produced from your home's power system as well as any power you may use off the grid. These three system components are then connected through a series of wiring. The photovoltaic panels are secured to your roof with panel mounts or are installed on poles that can be adjusted for sun angle.

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Warranty

1) We guarantee the product against all manufacturing defects for 24 months from the date of sale by us or through our dealers. Consumables like dry cell etc. are not covered under warranty.

2) The guarantee will become void, if

a) The product is not operated as per the instruction given in the learning material. b) The agreed payment terms and other conditions of sale are not followed.

c) The customer resells the instrument to another party. d) Any attempt is made to service and modify the instrument.

3) The non-working of the product is to be communicated to us immediately giving full details of the complaints and defects noticed specifically mentioning the type, serial number of the product and date of purchase etc.

4) The repair work will be carried out, provided the product is dispatched securely packed and insured. The transportation charges shall be borne by the customer.

Note: Following items are not covered in the warranty:

• Voltmeter

• Ammeter

• Battery

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List of Service Center

Baroda Flat No. A/1, Mudra Complex,Behind Sudha Hotel, Ellora Park, Baroda-390023 (Gujarat) Tel: +91-0265-3089505 Fax : +91- 0265-3089506 email : [email protected]

Guwahati Avijit Roy Building, A.K. Dev Road, Fatashil Ambari, Near jalaram Mandir, Guwahati-25 Assam Mobile: 09435144068 email: [email protected]

Indore 94, Electronic Complex, Pardesipura, Indore-452-010 Tel: 91-731-2570301/02, 4211100, Fax: 91-731-2555643 E-mail: [email protected]

New Delhi First Floor, C-19, F.I.E., Patparganj Industrial Area, Delhi-110092 (INDIA) Ph:011-22157370, 22157371, Fax: +91-011-22157369 email: [email protected]

Bangalore 202/19, 4th Main Street, Ganganagar, Bangalore - 560032 Ph.: +91-080-41285011 T.Fax: +91-080-41285022 email: [email protected]

Kolkata AC-101, Prafullla Kanan, Near Kestopur Bus Stop, Krishnapur, Kolkata- 700059 (West Bengal) Tel: +91 33-65266800 Mob: 9433029888 email: [email protected]

Mumbai E Type, Bldg No. 5/1/3, Sector 1,Vashi, Navi Mumbai-400703 Ph: +91-022-27826616, 65266616 email: [email protected]

Jaipur Flat No. G-2, S-101, Bhagat Vatika North, Civil Lines, Jaipur - 302006 (Raj.) Mobile: 097998-10236 email: [email protected]

Lucknow First Floor, 279/54/20/A, Chuhar Singh Colony, Pan Dariba, Lucknow (U.P.) Mobile: 09918670737 email: [email protected]

Hyderabad Plot No. 24, Flat no. 203, Laxmi Residency, Chandragiri Housing Society, Trimulgherry Secunderabad- 500015. Ph:040-27740147,9247712763 email: [email protected]

Cochin/Kochi C/o Pragalbha Valsan, Poriyamadathil house, ABMS Lane, Asoka Road, Near Mathru-bhumi, Kaloor, Kochi - 682017 Ph: 0484-2409441 email: [email protected]

Chandigarh 201, 2nd floor KMB Hospitality Services, SCO 19, Near Kabir Petrol Pump, Ambala-Zirakpur Highway Zirakpur, Mohali - 140603Ph.: 0172-6530329 email: [email protected]

Pune 105/106, 1st floor, Ajinkyatara, Ganesh Mala, Sinhgad Road, Pune - 411030 Ph.: +91-020-24254244/55 Fax: +91-020-24254244 email: [email protected]

Chennai Flat C, 1st Floor, Old No. 49 New No. 64, Bajanai Koil Street, Sriram Nagar Extention, Pallipattu, Chennai-600113 Tel: 044-43514212, 43514213 email: [email protected]

Orissa Plot No-67 (1st Floor) Aerodrom Area,Vimpur mouza Near Vimpur Primary School Bhubaneswar- 751020 Mobile: 09238307873 email: [email protected]
















Nvis 6005


List of Accessories

1. Solar Panel .................................................................................................1 No.

2. Solar Panel Stand .......................................................................................1 No.

3. 15 Pin Cable (5 Meter) ..............................................................................1 No.

4. 12” Patch Cord (2 mm)...............................................................................15 Nos.

5. Rechargeable Battery .................................................................................1 No.

6. Fan Blade…................................................................................................1 No.

7. Learning Material CD..................................................................................1 No.

Nvis 6005


Reference 1.http://www.api.org/oil-and-natural-gas-overview/classroom-tools/classroom-curricula/what-is-energy.aspx 2.http://www.need.org/needpdf/infobook_activities/ElemInfo/IntroE.pdf 3.http://www.perkinelmer.com/Content/RelatedMaterials/Solar-Energy-Glossary-of-Terms.pdf 4. http://www.digitalconsummate.com/products/Solar-Panels-for-Telecommunication-Towers.html 5. http://www1.eere.energy.gov/femp/pdfs/tf_hybridsolar.pdf 6. http://www.universetoday.com/74599/what-is-alternative-energy/ 7. http://www.exergy.se/goran/hig/ses/06/tidal.pdf

http://www.api.org/oil-and-natural-gas-overview/classroom-tools/classroom

http://www.need.org/needpdf/infobook_activities/ElemInfo/IntroE.pdf

http://www.perkinelmer.com/Content/RelatedMaterials/Solar-Energy-Glossary-of

http://www.digitalconsummate.com/products/Solar-Panels-for-Telecommunication

http://www1.eere.energy.gov/femp/pdfs/tf_hybridsolar.pdf

http://www.universetoday.com/74599/what-is-alternative-energy/

http://www.exergy.se/goran/hig/ses/06/tidal.pdf

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