Solar Based Mobile Charger.pdf

CHAPTER 1 INTRODUCTION Given the current energy crisis and increasing need for sustainable energy, we endeavored to create a cost-effective, small-scale electrical generator which could be used to power consumer electronics. Solar energy has proven its worth as an alternative energy source because it is low-impact and emission-free. It has been implemented with much success for power grids with hundreds of acres of enormous solar concentrators. In the small-scale, solar energy has been harvested through the use of photovoltaic (PV) panels and have been used to power anything from an iPod to a residential home. Although PV systems are considered part of the green energy revolution, materials utilized for its construction (like silicon) are extremely dangerous to the environment and much care must be taken to ensure that they are recycled properly. PV cells also only utilize the energy stored in specific wavelengths of light and therefore have an approximate efficiency between 14-19%. Sunlight, however, produces immense amounts of heat which only serves to heat up the surface of the solar cell. Although there are some PV cells that have reached efficiency levels over 40% (world record is 41.6%), they are enormously complex and expensive. Concentrated solar power (CSP) works differently because it focuses solar energy in its entirety rather than absorb it. Ultimately, our group will be designing and producing a SolarPowered Battery Charger

Figure :1 Solar Panel 1

The term "photovoltaic" comes from the Greek (photo) means "light", and "voltaic", means electric ,from the name of the Italian physicist “VOLTA "after whom a unit of electro-motive force, the volt is named. The sun is a star made up of hydrogen and helium gas and it radiates an enormous amount of energy every second . A photovoltaic cell is an electrical device that convert the energy of light directly into electricity by photovoltaic effect. Photovoltaics is the field of technology and research related to the practical application of photovoltaic cells in producing electricity from light, though it is often used specifically to refer to the generation of electricity from sunlight. Cells can be described as photovoltaic even when the light source is not necessarily sunlight (lamplight, artificial light, etc.). In such cases the cell is sometimes used as a photodetector (for example infrared detectors,detecting light or other electromagnetic radiation near the visible range, or measuring light intensity. The operation of a photovoltaic (PV) cell requires 3 basic attributes: The absorption of light, generating either electron-hole pairs or excitons. The separation of charge carriers of opposite types. The separate extraction of those carriers to an external circuit. In contrast, a solar thermal collector collects heat by absorbing sunlight, for the purpose of either direct heating or indirect electrical power generation. "Photoelectrolytic cell" (photoelectrochemical cell), on the other hand, refers either a type of photovoltaic cell (like that developed by A.E. Becquerel and modern dye-sensitized solar cells or a device that splits water directly into hydrogen and oxygen using only solar illumination. Photovoltaic power generation employs solar panels composed of a number of solar cells containing a photovoltaic material. Materials presently used for photovoltaics include monocrystalline silicon, polycrystalline silicon, amorphous silicon, cadmium telluride, andcopper indium gallium selenide/sulfide. Due to the increased demand for renewable energy sources, the manufacturing of solar cells and photovoltaic arrays has advanced considerably in recent years. Solar photovoltaics is a sustainable energy source. By the end of 2011, a total of 71.1 GW had been installed, sufficient to generate 85 TWh/year.And by end of 2012, the 100 GW installed capacity milestone was achieved. Solar photovoltaics is now, after hydro and wind power, the third most important renewable energy source in terms of globally installed capacity. More than 100 countries use solar PV. Installations may be ground-mounted (and sometimes integrated with farming and

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grazing) or built into the roof or walls of a building (either building-integrated photovoltaics or simply rooftop). Driven by advances in technology and increases in manufacturing scale and sophistication, the cost of photovoltaics has declined steadily since the first solar cells were manufactured, and the levelised cost of electricity (LCOE) from PV is competitive with conventional electricity sources in an expanding list of geographic regions. Net metering and financial incentives, such as preferential feed-in tariffs for solar-generated electricity, have supported solar PV installations in many countries.With current technology, photovoltaics recoup the energy needed to manufacture them in 3 to 4 years. Anticipated technology would reduce time needed to recoup the energy to 1 to 2 year. Solar energy is the energy produced directly by the sun and collected elsewhere, normally the Earth. The sun creates its energy through a thermonuclear process . The process creates heat and electromagnetic radiation. Only a very small fraction of the total radiation produced reaches the Earth. The radiation that does reaches the Earth is the indirect source of nearly every type of energy used today.

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CHAPTER 2 BACKGROUND LITERATURE SURVEY : The current market leader in efficient solar energy modules is Sun Power, whose solar panels have a conversion ratio of 19.3%, with Sanyo having the most efficient modules at 20.4%. However, a whole range of other companies (Holo Sun, Gamma Solar, Nano Horizons) are emerging which are also offering new innovations in photovoltaic modules, with a conversion ratio of around 18%. These new innovations include power generation on the front and back sides and increased outputs; however, most of these companies have not yet produced working systems from their design plans, and are mostly still actively improving the technology. 2.1 Hardware Components : 1. Solar panel 2. voltage Regulator 3. Resistors 4. Switch 5. Output jack 2.2 Solar Panel : A solar cell is a device that converts the energy of sunlight directly into electricity by the photovoltaic effect. Sometimes the term solar cell is reserved for devices intended specifically to capture energy from sunlight such as solar panels and solar cells, while the term photovoltaic cell is used when the light source is unspecified. Assemblies of cells are used to make solar panels, solar modules, and photovoltaic arrays. Photovoltaic is the field of technology and research related to the application of solar cells in producing electricity for practical use. An alternative charger circuit is also provided to charge the mobile by house hold general purpose 230V in the absence of the sun light. he solar panel can be used as a component of a larger photovoltaic system to generate and supplyelectricity in commercial and residential applications. Each module is rated by its dc output power under standard test conditions (STC), and typically ranges from 100 to 320 watts.

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2.3 History : The term "photovoltaic" comes from the Greek φῶς (phōs) meaning "light", and "voltaic", meaning electric, from the name of the Italian physicist Volta, after whom a unit of electro-motive force, the volt, is named. The term "photo-voltaic" has been in use in English since 1849. The photovoltaic effect was first recognized in 1839 by French physicist A. E. Becquerel. However, it was not until 1883 that the first solar cell was built, by Charles Fritts, who coated the semiconductor selenium with an extremely thin layer of gold to form the junctions. The device was only around 1% efficient. Subsequently Russian physicist Aleksandra Stoletov built the first solar cell based on the outer photoelectric effect (discovered by Heinrich Hertz earlier in 1887). Albert Einstein explained the photoelectric effect in 1905 for which he received the Nobel Prize in Physics in 1921. Russell Ohl patented the modern junction semiconductor solar cell in 1946, which was discovered while working on the series of advances that would lead to the transistor. The highly efficient solar cell was first developed by Chapin, Fuller and Pearson in 1954 using a diffused silicon p-n junction. In the past four decades, remarkable progress has been made, with Megawatt solar power generating plants having now been built. A solar panel (photovoltaic module or photovoltaic panel) is a packaged interconnected assembly of solar cell, also known as photovoltaic cell. The solar panel is used as a component in a larger photovoltaic system to offer electricity for commercial and residential applications. Because a single solar panel can only produce a limited amount of power, many installations contain several panels. This is known as a photovoltaic array. A photovoltaic installation typically includes an array of solar panels, an inverter, batteries and interconnection wiring. Solar cells are often electrically connected and encapsulated as a module. Photovoltaic modules often have a sheet of glass on the front (sun up) side, allowing light to pass while protecting the semiconductor wafers from the elements (rain, hail, etc.). Solar cells are also usually connected in series in modules, creating an additive voltage. Connecting cells in parallel will yield a higher current. Modules are then interconnected, in series or parallel, or both, to create an array with the desired peak DC voltage and current. 5

The power output of a solar array is measured in watts or kilowatts. In order to calculate the typical energy needs of the application, a measurement in watt-hours, kilowatt-hours or kilowatt-hours per day is often used. A common rule of thumb is that average power is equal to 20% of peak power, so that each peak kilowatt of solar array output power corresponds to energy production of 4.8 kWh per day (24 hours x 1 kW x 20% = 4.8 kWh). To make practical use of the solar-generated energy, the electricity is most often fed into the electricity grid using inverters (grid-connected photovoltaic systems); in stand-alone systems, batteries are used to store the energy that is not needed immediately. Solar cells can also be applied to other electronics devices to make it self-power sustainable in the sun. There are solar cell phone chargers, solar bike light and solar camping lanterns that people can adopt for daily use. 2.4 Simple explanation : 1. Photons in sunlight hit the solar panel and are absorbed by semiconducting materials, such as silicon. 2. Electrons (negatively charged) are knocked loose from their atoms, allowing them to flow through the material to produce electricity. Due to the special composition of solar cells, the electrons are only allowed to move in a single direction. 3. An array of solar cells converts solar energy into a usable amount of direct current (DC) electricity. Photo generation of charge carriers : When a photon hits a piece of silicon, one of three things can happen: 1. the photon can pass straight through the silicon — this (generally) happens for lower energy photons, 2. the photon can reflect off the surface, 3. The photon can be absorbed by the silicon, if the photon energy is higher than the silicon band gap value. This generates an electron-hole pair and sometimes heat, depending on the band structure.

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When a photon is absorbed, its energy is given to an electron in the crystal lattice. Usually this electron is in the valence band, and is tightly bound in covalent bonds between neighboring atoms, and hence unable to move far. The energy given to it by the photon "excites" it into the conduction band, where it is free to move around within the semiconductor. The covalent bond that the electron was previously a part of now has one fewer electron — this is known as a hole. The presence of a missing covalent bond allows the bonded electrons of neighboring atoms to move into the "hole," leaving another hole behind, and in this way a hole can move through the lattice. Thus, it can be said that photons absorbed in the semiconductor create mobile electronhole pairs. A photon need only have greater energy than that of the band gap in order to excite an electron from the valence band into the conduction band. However, the solar frequency spectrum approximates a black body spectrum at ~6000 K, and as such, much of the solar radiation reaching the Earth is composed of photons with energies greater than the band gap of silicon. These higher energy photons will be absorbed by the solar cell, but the difference in energy between these photons and the silicon band gap is converted into heat (via lattice vibrations — called phonons) rather than into usable electrical energy. Charge carrier separation There are two main modes for charge carrier separation in a solar cell: 1. Drift of carriers, driven by an electrostatic field established across the device 2. Diffusion of carriers from zones of high carrier concentration to zones of low carrier concentration (following a gradient of electrochemical potential). In the p-n junction solar cells the dominant mode of charge is by diffusion. However, in thin films (such as amorphous silicon) the main mechanism to move the charge is the electric field and therefore the drift of carriers. The p-n junction Main articles : semiconductor and p-n junction The most commonly known solar cell is configured as a large-area p-n junction made from silicon. As a simplification, one can imagine bringing a layer of n-type silicon into direct contact 7

with a layer of p-type silicon. In practice, p-n junctions of silicon solar cells are not made in this way, but rather by diffusing an n-type dopant into one side of a p-type wafer (or vice versa). If a piece of p-type silicon is placed in intimate contact with a piece of n-type silicon, then a diffusion of electrons occurs from the region of high electron concentration (the n-type side of the junction) into the region of low electron concentration (p-type side of the junction). When the electrons diffuse across the p-n junction, they recombine with holes on the p-type side. The diffusion of carriers does not happen indefinitely, however, because charges build up on either side of the junction and create an electric field. The electric field creates a diode that promotes charge flow, known as drift current, that opposes and eventually balances out the diffusion of electron and holes. This region where electrons and holes have diffused across the junction is called the depletion region because it no longer contains any mobile charge carriers. It is also known as the space charge region. 2.5 Theory : Solar panels use light energy (photons) from the sun to generate electricity through the photovoltaic effect (this is the photo-electric effect). The structural (load carrying) member of a module can either be the top layer (superstrate) or the back layer (substrate). The majority of modules use wafer-based crystalline silicon cells or

a thin-film cell based on cadmium

telluride or silicon. Crystalline silicon, which is commonly used in the wafer form in photovoltaic (PV) modules, is derived from silicon, a commonly used semi-conductor. With a pencil, try this example to know the two types of energy. Put the pencil at the edge of the desk and push it off to the floor. The moving pencil uses kinetic energy Now, pick up the pencil and put it back on the desk. You used your own energy to lift and move the pencil. Moving it higher than the floor adds energy to it. As it rests on the desk, the pencil has potential energy. The higher it is, the further it could fall. That means the pencil has more potential energy.

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Fig 1 : Solar panel 6 volt,2 watt. In order to use the cells in practical applications, they must be : Connected electrically to one another and to the rest of the system Protected from mechanical damage during manufacture, transport, installation and use (in particular against hail impact, wind and snow loads). This is especially important for wafer-based silicon cells which are brittle. Protected from moisture, which corrodes metal contacts and interconnects, (and for thin-film cells the transparent conductive oxide layer) thus decreasing performance and lifetime. Most modules are usually rigid, but there are some flexible modules available, based on thin-film cells. Electrical connections are made in series to achieve a desired output voltage and/or in parallel to provide a desired amount of current source capability. Diodes are included to avoid overheating of cells in case of partial shading. Since cell heating reduces the operating efficiency it is desirable to minimize the heating. Very few modules incorporate any design features to decrease temperature; however installers try to provide good ventilation behind the module. New designs of module include concentrator modules in which the light is concentrated by an array of lenses or mirrors onto an array of small cells. This allows the use of cells with a very high-cost per unit area in a cost-competitive way.

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Depending on construction, the photovoltaic can cover a range of frequencies of light and can produce electricity from them, but sometimes cannot cover the entire solar spectrum (specifically, ultraviolet, infrared and

low or diffused

light). Hence

much of incident

sunlight energy is wasted when used for solar panels, although they can give far higher efficiencies if illuminated with monochromatic light. Another design concept is to split the light into different wavelength ranges and direct the beams onto different cells tuned to the appropriate wavelength ranges. This is projected to raise efficiency by 50%. Also, the use of infrared photovoltaic cells can increase the efficiencies, producing power at night. To make sure we have plenty of energy in the future, it's up to all of us to use energy wisely. We must all conserve energy and use it efficiently. It's also up to those who will create the new energy technologies of the future. All energy sources have an impact on the environment. Concerns about the greenhouse effect and global warming, air pollution, and energy security have led to increasing interest and more development in renewable energy sources such as solar, wind, geothermal, wave power and hydrogen.but we'll need to continue to use fossil fuels and nuclear energy until new, cleaner technologies can replace them. One of you who is reading this might be another Albert Einstein or Marie Curie and find a new source of energy. Until then, it's up to all of us. The future is ours, but we need energy to get there. Energy causes things to happen around us. Look out the window. During the day, the sun gives out light and heat energy. At night, street lamps use electrical energy to light our way. When a car drives by, it is being powered by gasoline, a type of stored energy.The food we eat contains energy. We use that energy to work and play.

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CHAPTER 3 VOLTAGE REGULATOR 3.1 IC7805 Voltage Regulator :

Figure 2 : Voltage Regulator The Digi lab board can use any power supply that creates a DC voltage between 6 and 12 volts. A 5V voltage regulator (7805) is used to ensure that no more than 5V is delivered to the Digi lab board regardless of the voltage present at the J12 connector (provided that voltage is less than 12VDC). The regulator functions by using a diode to clamp the output voltage at 5VDC regardless of the input voltage - excess voltage is converted to heat and dissipated through the body of the regulator. If a DC supply of greater than 12V is used, excessive heat will be generated, and the board may be damaged. If a DC supply of less than 5V is used, insufficient voltage will be present at the regulators output. If a power supply provides a voltage higher than 7 or 8 volts, the regulator must dissipate significant heat. The "fin" on the regulator body (the side that protrudes upward beyond the main body of the part) helps to dissipate excess heat more efficiently. If the board requires higher currents (due to the use of peripheral devices or larger breadboard circuits), then the regulator may need to dissipate more heat. In this case, the regulator can be secured to the circuit board by

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fastening it with a screw and nut (see below). By securing the regulator tightly to the circuit board, excess heat can be passed to the board and then radiated away. 3.2 Features : 1. Output current in excess of 0.5A 2. No external components 3. Internal thermal overload protection 4. Internal short circuit current-limiting 5. Output transistor safe-area compensation 6. Available in TO-220, TO-39, and TO-252 D-PAK packages 7. Output voltages of 5V, 12V, and 15V 3.3 DESCRIPTION:The 7805 is a VOLTAGE REGULATOR. It looks like a transistor but it is actually an integrated circuit with 3 legs. Turn it into a nice, smooth 5 volts DC.

You need to feed it at least 8 volts and no more than 30 volts to do this. It can handle around .5 to .75 amps, but it gets hot. Use a heat sink. Run off of 5 volts. It can take a higher, crappy DC voltage and Use it to power circuits than need to use or run off of 5 volts. The LM341 and LM78MXX series of three-terminal positive voltage regulators employ built-in current limiting, thermal shutdown, and safe-operating area protection which makes them virtually immune to damage from output overloads.

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With adequate heat sinking, they can deliver in excess of 0.5A output current. Typical applications would include local (on-card) regulators which can eliminate the noise and degraded performance associated with single-point regulation. The 7805 is a VOLTAGE REGULATOR. It looks like a transistor but it is actually an integrated circuit with 3 legs. Turn it into a nice, smooth 5 volts DC. You need to feed it at least 8 volts and no more than 30 volts to do this. It can handle around 5 to 75 amps, but it gets hot. Use a heat sink. Run off of 5 volts. It can take a higher, crappy DC voltage and Use it to power circuits than need to use or run off of 5 volts. The LM341 and LM78MXX series of three-terminal positive voltage regulators employ built-in current limiting, thermal shutdown, and safe-operating area protection which make them virtually immune to damage from output overloads. With adequate heat sinking, they can deliver in excess of 0.5A output current. Typical applications would include local (on-card) regulators which can eliminate the noise and degraded performance associated with single-point regulation. These regulators are rugged, provide over-current shut down, and will give a constant 6 volts output for currents from 0 to 1 amp. They are good for running low current 6-volt things like gauges. If your entire gauges draw a total of over about 0.75amps, it's a good idea to use more than one regulator with one or two gauges connected on each regulator, or use an output transistor to boost current. (Yeah, we’ll get to that in a minute) When using the 7806, it's a good idea to connect a small capacitor from the input pin to ground and another from the output pin to ground. The value of the capacitors is fairly non-critical and any value from 0.1uF to 10uF (that's micro-Farads) @ 25volts or more will work just fine. The capacitors help protect the regulator from electrical noise, and to stabilize the output under certain load conditions. My favorite caps for this are 1uF, 35v.

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CHAPTER 4 BLOCK DIAGRAM 4.1 Resistors : In general, a resistor is used to create a known voltage-to-current ratio in an electric circuit. If the current in a circuit is known, then a resistor can be used to create a known potential difference proportional to that current. Conversely, if the potential difference between two points in a circuit is known, a resistor can be used to create a known current proportional to that difference. 1. Current-limiting. By placing a resistor in series with another component, such as a light-emitting diode the current through that component is reduced to a known safe value. 2. An attenuator is a network of two or more resistors (a voltage divider) used to reduce the voltage of a signal. 3. All resistors dissipate heat This is the principle behind electric heaters One of the common ways to reduce the voltage is by using a resistor. A resistor reduces voltage by an amount proportional to the value of the resistor (in Ohms) times the current flow through the resistor. The formula (Ohms law) is: V = I x R, where V is the voltage dropped across the resistor, I am the current through the resistor in amps and R is the value of the resistor in ohms. At the early stages of the project, it was thought that a mobile phone charging algorithm would have to be implemented. Early research indicated that mobile phone charging algorithm is employed on the phone itself and to charge a mobile phone it is just amatter of supplying the correct voltage to the charging input of the phone. It was decided that the best way to verify the operation of a mobile phone charger was to reverse engineer a commercial charger. For example : You have a 6 volt radio that draws 3 amps. You want run it on 12volts. Your 12 volt system actually is at about 13.8v with the motor running and you want the radio to get about 6.8 volts, which is roughly what the system voltage would be on a running 6 volt system. So...

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You've got 13.8v, but you want 6.8v on a device that draws 3 amps. 13.8v - 6.8v = 7v, so you need to drop 7 volts across the resistor at 3 amps.. Since V = I x R, it follows that R = V / I, and if we plug our numbers in we get R = 7 / 3, or R = 2.33 ohms to get 6.8 volts on a radio that draws 3 amps. 2.33 ohms is kind of an odd value, and you will probably have to use 2.5 ohms, which would give 6.3 volts instead. The power drop across the resistor causes it to heat up, so we need to make sure the resistor can handle the power load without burning out. That's what the wattage rating is all about. In our example, we dropped 7 volts across the resistor at 3 amps, and since W = V x I, our resistor will convert 21 watts of power into heat. That means our resistor must be rated for an *absolute minimum* of 21 watts. A larger wattage resistor will run cooler, and its good practice to use a resistor rated for at least 50% higher wattage than you expect to handle. For our radio example, I would use a 2.5-ohm, 40-watt resistor to do the job. 21 watts is quite a bit of heat... thinking about how much heat a 25-watt light bulb makes! Make sure that you mount voltage dropping resistors where they can't be a fire hazard, or bake any nearby plastic or rubber parts. 4.2 SWITCH: In electronics, a switch is an electrical component that can break an electrical circuit, interrupting the current or diverting it from one conductor to another. The most familiar form of switch is a manually operated electromechanical device with one or more sets of electrical contacts.A switch may be directly manipulated by a human as a control signal to a system, such as a computer keyboard button, or to control power flow in a circuit, such as a light switch. Automatically-operated switches can be used to control the motions of machines.

4.3 OUT PUT JACK: Output jack is used to collect the output of our circuit. .it give an output of 3.6 volts. output jack is connected to mobile for the purpose of charging it .

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CHAPTER 5 WORKING 5.1 CIRCUIT DIAGRAM :

CCIIIIRCUIT EXPLANATION Figure 3: Circuit Diagram CIRCUIT WORKING : The working of the circuit is simple. The output of the solar panel is fed via diode 1N5402 (D1), which acts as a polarity guard and protects the solar panel. An ammeter connected in series between diode D1and fuse to measure the current flowing during charging of the batteries. As in fig., we have used analogue multi meter in 500Ma range. Diode D2 ids used for protection against reverse polarity in case of wrong connection of the lead-acid battery. When you connect wrong polarity, the fuse will blow up. For charging a lead-acid battery, shift switch S1 to ‘on’ position and use connector ‘A’. After you connect the battery, charging starts from the solar panel via diode D1, multi meter and fuse. Note that pulsating DC is the best for charging lead-acid batteries. Mobile phones’ becoming the major source of business/personal communication, the mobile phone business is currently worth billion of dollars, and supports millions of phones. The need to

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provide a public charging service is essential. Many critics argued that a public mobile phone charging service is not a lucrative business because most users can charge their phones at home, in their office or in their cars. Coin Operated Mobile Phone Charger is a new business milestone because many are attending business conventions and forgetting their charger at home or in hotel rooms. Students and many that use the public transportation that don't know that their level of their battery is low are prospective customers for coin operated mobile phone charger service. Recommended locations include: Hotels, conference centers, exhibition halls, serviced offices, exchange halls, motels, leisure centers, health clubs, training centers, golf clubs, retail outlets, shopping malls, Internet cafes, universities, colleges, hall of residence, airports, train terminals, etc., so that the mobile phone users can reactivate a low or dead battery by simply plugging in and charging for one rupee. Here is a design based on ATMEL 89c51 a 40-pin micro controller that does the countdown timing for a period of 3 mints with LCD displays showing the actual time left. During the timing period a relay output is latched and a flashing led indicates timing in progress. The solar panels produce same direct current that we cannot be used in household appliances. The solar panel system will power the load whenever sun is shining strongly enough and the system will stop when it is not. In sunny weather solar panel supply so much electricity to the battery that it overcharges. When this happens, the acid and water mixture in the battery decomposes into hydrogen and oxygen. Reducing the acid level and eventually destroying the battery if not stopped. On the other hand if there is not much sun or we have been too ambitious for electricity, more will be drawn from the battery then the solar panel capable of replacing. This makes the battery go flat. The battery will no longer electricity supply until we will recharge. In simple system either overcharge or flatten the battery- both reduce the battery life. To solve this problem, we add a package of electronics known as charge controller. This controller prevents the solar panel from overcharging the battery during the sunny weather as well as protecting the battery from going flat; it can protect the battery in this way by automatically disconnecting the load from the battery. Systems as shown in above figure but including charge controller can work and have been used in many applications.

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5.2 Applications : 1. Relatively small size allows mobile use (ideal for camping and other recreation) 2. System requires no electrical start-up power 3. Solar concentrator can be used with any heat source 4. Higher efficiency than photovoltaic (PV) systems of the same scale 5. Ability to recharge AA batteries anytime and anywhere there is sunlight 6. Low maintenance, emission-free and environmentally-friendly power source 5.3 Features : 1. Versatile and effective solar concentrator (numerous available heat sources) 2. Charges (1) standard capacity AA Nickel-metal hydride cell (NiMH) in 4-8 hours 3. Outputs constant rate of charging current 4. Intelligent battery charging

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CHAPTER 6 CONCLUSIOAN & FUTURE SCOPE 1. To make sure we have plenty of energy in the future, it's up to all of us to use energy wisely. 2. We must all conserve energy and use it efficiently. It's also up to those who will create the new energy technologies of the future. 3. All energy sources have an impact on the environment. Concerns about the greenhouse effect and global warming, air pollution, and energy security have led to increasing interest and more development in renewable energy sources such as solar, wind, geothermal, wave power and hydrogen 4. In solar mobile charger ripples will not be there as we use DC power directly to charge the mobile. 5. Battery life is more as high voltages are not developed. 6. Versatility of Solar mobile charger is high. 7. Life of the battery will be high as we use solar mobile charger. 8. Adaptability is high.

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REFERENCES 1. Rhodes, Christopher J,Solar Energy : Principles and Possibilities. 2. Higgins, James M ,Solar Energy May Soon Power Our Homes, Offices Buildings, Automobiles, and iPods. 3. Childress, Vincent W ,Solar Power the Solution. 4. Marshall Cavendish ,Science and Technology. 5. Ozzie Zehner ,The Dirty Secrets of Clean Energy and the Future of Environmentalism. 6. David Elliott ,Technology for a Sustainable Future. 7. Mirel, Diana ,Solar Power Investments Can Offer Long-Term Savings in Energy Costs. 8. Frank N. Laird ,Technology Policy, and Institutional Values. 9. www.solarbuzz.com/going-solar. 10. www.solarserver.com/knowledge.

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