Street Light

INDEX S.NO TITLE PAGE NO 1 Introduction 1 2 solar Energy 4 3 P hotovoltaics 24 4 solar Cell 28 5 solar Road right smart 51 6 Comp championnt description 55 7 Working of Project 82 8 Conclusion 86 9 Images 91 10 Bibliography 93 INTRODUCTION INTRODUCTION solar zero, glad sparkle and waken from the sun, has been harnessed by humans since ancient times utilise a approveground of ever-evolving technologies.solar brawn technologies include solar soup uping, solar photovoltaics, solar caloric electricity and solar architecture, which tummy impinge on con lieurable contri saveions to solving some of the just about urgent vigor problems the manhood right away faces. solar super big businessman is the conversion of sun giddy into electricity, any directly training photovoltaic (PV), or indirectly victimization concentrated solar male monarch (CSP). Concentrated solar great power systems substance ab using up lenses or mirrors and tracking systems to snap a too large atomic number 18a of sunshine into a sensitive beam. Photovoltaics convert igniter into electric live using the photoelectric nitty-gritty. A Street idle, lamppost, street lamp, electric arc standard, or lamp standard is a raised inception of light on the edge of a road or walkway, which is turned on or lit at a certain time every night.Modern lamps whitethorn in like manner ready photosensitive photo kiosks to turn them on at nightf whole, off at dawn, or activate automatically in aristocratical weather. In older lighting this function would make been percourseed with the aid of a solar dial. It is not ridiculous for street lights to be on posts which impart wires strung between them much(prenominal) as on band poles or utility poles. New street lighting technologies, such(prenominal) as LED or k directlylight-emitting diodegeableness lights, emit a smock light that trys senior high levels of scotopic lumens al unkepting street lights with set ou t wattages and start photopic lumens to replace brisk street lights. Photovoltaic- provide LED lumin channeles atomic number 18 gaining wider acceptance.Preliminary stadium tests show that some LED luminaires ar vitality- efficacious and perform intimately in testing surroundingss. This project is a LED base solar Lights is an automatic street buoy up system using a LDR and 6V/5W solar panel. During day time, the internal rechargeable battery receives charging genuine from the affiliated solar panel. Here IC 555 is wired as a medium current inverting line driver, switched by an encapsulated light detector (LDR). When ambient light dims, the moves drive the white LEDs. When the ambient light level restores, circuit returns to its idle state and light(s) switched off by the circuit. Block Diagram SOLAR ENERGY SOLAR ENERGYsolar null, radiant light and heat from the sun, has been harnessed by humans since ancient times using a range of ever-evolving technologies. solar zip technologies include solar heating, solar photovoltaics, solar thermal electricity, solar architecture and dyed photosynthesis, which set up make considerable contributions to solving some of the approximately urgent energy problems the valet now faces. Solar technologies are broadly characterized as every peaceable solar or lively solar depending on the way they capture, convert and distribute solar energy. Active solar techniques include the physical exercise of photovoltaic panels and solar thermal aggregators to harness the energy. peaceable solar techniques include orienting a create to the Sun, selecting materials with favorable thermal mass or light dispersing properties, and designing spaces that naturally circulate air. In 2011, the International Energy way utter that the development of affordable, inexhaustible and clean solar energy technologies go out take over huge longer- marches benefits. It ordain increase countries energy security through relian ce on an indigenous, inexhaustible and mostly import-independent re tooth root, enhance sustainability, bowdlerize pollution, first gearer the embody of mitigating climate change, and keep fogey fuel prices lower than separatewise. These advantages are global.Hence the superfluous cost of the incentives for archaean deployment should be considered learning investments they must be wisely spent and need to be astray componentd. The Earth receives 174 petawatts (PW) of incoming solar shaft (insolation) at the upper atmosphere. Approximately 30% is reflected back to space while the rest is take up by clouds, oceans and land masses. The spectrum of solar light at the Earths jump is mostly spread across the visible and near-infrared ranges with a small part in the near- ultraviolet radiation. Earths land heighten, oceans and atmosphere absorb solar radiation, and this raises their temperature. Warm air containing evaporated urine from the oceans rises, create atmospheric circulation or convection.When the air reaches a high altitude, where the temperature is low, pissing vapor condenses into clouds, which rain onto the Earths climb, completing the piss system cycle. The latent heat of water compressing amplifies convection, producing atmospheric phenomena such as wind, cyclones and anti-cyclones. Sunlight absorbed by the oceans and land masses keeps the surface at an average out temperature of 14 C. By photosynthesis green industrial plants convert solar energy into chemical energy, which buzz offs food, wood and the biomass from which fossil fuels are come ind. The keep down solar energy absorbed by Earths atmosphere, oceans and land masses is approximately 3,850,000 exajoules (EJ) per year. In 2002, this was more energy in one hour than the domain apply in one year.Photosynthesis captures approximately 3,000 EJ per year in biomass. The technical potential available from biomass is from 100300 EJ/year. The amount of solar energy reach ing the surface of the planet is so vast that in one year it is about doubly as much as will ever be obtained from all of the Earths non-renewable resources of coal, inunct, natural gas, and mined uranium combined. Solar energy net be harnessed at different levels around the world, mostly depending on distance from the equator. pic Average insolation showing land knowledge domain (small sour dots) packd to replace the world primary energy supply with solar electricity. 18 TW is 568 Exajoule (EJ) per year. insolation for most people is from one hundred fifty to 300 W/m2 or 3. 5 to 7. 0 kWh/m2/day. Solar energy refers primarily to the use of solar radiation for unimaginative ends. However, all renewable energies, opposite than geothermal and tidal, derive their energy from the sun. Solar technologies are broadly characterized as either passive or active depending on the way they capture, convert and distribute sunlight. Active solar techniques use photovoltaic panels, pump s, and fans to convert sunlight into useful outputs. Passive solar techniques include selecting materials with favorable thermal properties, designing spaces that naturally circulate air, and referencing the position of a building to the Sun.Active solar technologies increase the supply of energy and are considered supply side technologies, while passive solar technologies nullify the need for alternate resources and are generally considered demand side technologies. APPLICATIONS OF SOLAR TECHNOLOGY Averageinsolationshowing land area (small black dots) required to replace the world primary energy supply with solar electricity. 18 TW is 568 Exajoule (EJ) per year. Insolation for most people is from 150 to 300 W/m2or 3. 5 to 7. 0 kWh/m2/day. Solar energy refers primarily to the use ofsolar radiationfor practical ends. However, all renewable energies, other thangeothermalandtidal, derive their energy from the sun. Solar technologies are broadly characterized as either passive or activ e depending on the way they capture, convert and distribute sunlight.Active solar techniques use photovoltaic panels, pumps, and fans to convert sunlight into useful outputs. Passive solar techniques include selecting materials with favorable thermal properties, designing spaces that naturally circulate air, and referencing the position of a building to the Sun. Active solar technologies increase the supply of energy and are consideredsupply side technologies, while passive solar technologies keep down the need for alternate resources and are generally considered demand side technologies ARCHITECTURE AND urban PLANNING pic Darmstadt University of Technologyin Germanywon the 2007Solar Decathlonin Washington, D. C. with thispassive house intentional specifically for the humid and hot subtropical climate.Sunlight has influenced building design since the beginning of architectural history. Advanced solar architecture and urban planning regularitys were set-back employed by theGreeks andChinese, who oriented their buildings toward the south to provide light and warmth. The cat valium features ofpassive solararchitecture are orientation relative to the Sun, compact pro wad (a low surface area to volume ratio), selective blend (overhangs) andthermal mass. When these features are tailored to the local climate and environment they can go well-lit spaces that stay in a comfortable temperature range. Soc placeMegaron dwelling is a classic face of passive solar design.The most recent approaches to solar design use computer modeling ligature togethersolar lighting,heatingand airingsystems in an coordinatedsolar designpackage. Active solar equipment such as pumps, fans and switchable windows can complement passive design and improve system mathematical process. Urban heat islands (UHI) are metropolitan areas with higher(prenominal) temperatures than that of the surrounding environment. The higher temperatures are a result of increased dousing of the Solar light by urban materials such as asphalt and concrete, which commence loweralbedosand higherheat capacitiesthan those in the natural environment. A straightforward method of counteracting the UHI effect is to paint buildings and roads white and plant trees.Using these methods, a hypothetical imperturbable communities program inLos Angeleshas projected that urban temperatures could be reduce by approximately 3C at an estimated cost of US$1billion, giving estimated total annual benefits of US$530million from reduced air-conditioning costs and healthcare savings. 23 AGRICULTURE AND HORTICULTURE pic Greenhouseslike these in the Westland municipality of theNetherlands start vegetables, crops and flowers. Agricultureandhorticultureseek to optimize the capture of solar energy in order to optimize the productivity of plants. Techniques such as timed planting cycles, tailored row orientation, staggered heights between rows and the mixing of plant varieties can improve crop yields. 2425While sunlight is generally considered a plentiful resource, the exceptions highlight the greatness of solar energy to agriculture.During the compendious growing seasons of theLittle Ice Age, French andEnglish furthermostmers employed fruit walls to maximize the collection of solar energy. These walls acted as thermal masses and accelerated ripening by keeping plants warm. Early fruit walls were create perpendicular to the ground and facing south, but over time, sloping walls were actual to make unwrap use of sunlight. In 1699,Nicolas Fatio de Duillier heretofore suggested using atracking mechanismwhich could personal identification number to follow the Sun. 26Applications of solar energy in agriculture aside from growing crops include pumping water, drying crops, brooding chicks and drying volaille manure. 2728More recently the engine room has been embraced by vinters, who use the energy generated by solar panels to power grapeshot presses. 29Greenhousesconvert solar light to he at, enabling year-round production and the growth (in enclosed environments) of specialty crops and other plants not naturally suited to the local climate. Primitive greenhouses were first utilise during Roman times to producecucumbersyear-round for the Roman emperorTiberius. 30The first modern greenhouses were reinforced in Europe in the sixteenth century to keep exotic plants brought back from explorations abroad. 31Greenhouses remain an important part of horticulture today, and plastic transparent materials have as well been apply to similar effect inpolytunnelsandrow covers. TRANSPORT AND RECONNAISSANCE pic Australia hosts theWorld Solar Challengewhere solar cars like the Nuna3 race through a 3,021km (1,877mi) course from Darwin to Adelaide. cultivation of a solar powered car has been an engineering goal since the 1980s. TheWorld Solar Challengeis a biannual solar-powered car race, where teams from universities and enterprises repugn over 3,021 kilometres (1,877mi) across ce ntral Australia fromDarwintoAdelaide. In 1987, when it was founded, the winners average speed was 67 kilometres per hour (42mph) and by 2007 the winners average speed had better to 90. 87 kilometres per hour (56. 46mph). 32TheNorth American Solar Challengeand the aforethought(ip)South African Solar Challengeare comparable competitions that reflect an international interest in the engineering and development of solar powered vehicles. 3334Some vehicles use solar panels for adjutant power, such as for air conditioning, to keep the interior cool, thus reducing fuel consumption. 3536 In 1975, the first practical solar sauceboat was constructed in England. 37By 1995, passenger boats incorporating PV panels began appearing and are now utilise extensively. 38In 1996,Kenichi Horiemake the first solar powered crossing of the Pacific Ocean, and thesun21catamaran made the first solar powered crossing of the Atlantic Ocean in the winter of 20062007. 39There are plans to circumnavigate the glo be in 2010. 40 pic Helios UAVin solar powered flight. In 1974, the remote- considerledAstroFlight Sunriseplane made the first solar flight.On 29 April 1979, theSolar Risermade the first flight in a solar powered, fully controlled, man carrying short machine, reaching an altitude of 40 feet (12m). In 1980, theGossamer Penguinmade the first piloted flights powered solely by photovoltaics. This was promptly followed by theSolar Challengerwhich crossed the English Channel in July 1981. In 1990Eric Scott Raymondin 21 hops flew from California to North Carolina using solar power. 41Developments thus turned back to unmanned aerial vehicles (UAV) with thePathfinder(1997) and subsequent designs, culminating in theHelioswhich set the altitude inscribe for a non-rocket-propelled aircraft at 29,524 metres (96,864ft) in 2001. 42TheZephyr, unquestionable byBAE Systems, is the latest in a line of record-breaking solar aircraft, devising a 54-hour flight in 2007, and month-long flights are en visioned by 2010. 43 Asolar balloonis a black balloon that is worryed with ordinary air. As sunlight shines on the balloon, the air inside is heated and expands make an upwardbuoyancyforce, much like an artificially heatedhot air balloon. Some solar balloons are large enough for human flight, but usage is generally limited to the toy grocery store as the surface-area to payload-weight ratio is relatively high. 44 DAYLIGHTING pic Daylighting features such as thisoculusat the top of thePantheon, inRome, Italy have been in use since antiquity.The history of lighting is dominated by the use of natural light. The Romans recognized aright to lightas early as the6th centuryand English law echoed these judgments with the Prescription Act of 1832. 4546In the 20th century artificiallightingbecame the main source of interior illumination but daylighting techniques and interbreeding solar lighting solutions are ways to reduce energy consumption. Daylightingsystems collect and distribute sun light to provide interior illumination. This passive applied science directly first bases energy use by replacing artificial lighting, and indirectly offsets non-solar energy use by reducing the need forair-conditioning. 47Although difficult to quantify, the use ofnatural lightingalso offers physiological and psychological benefits compared toartificial lighting. 47Daylighting design implies careful selection of window showcases, sizes and orientation exterior shading gubbinss may be considered as well. Deciduous trees at the east and west ends of buildings offer shade in the spend and do not block the sun in the winter. 48Individual features include sawtooth roofs,clerestory windows, light shelves,skylightsandlight tubes. They may be incorporated into existing organizes, but are most effective when integrated into asolar designpackage that sexual conquests for reckons such asglare, heat flux andtime-of-use.When daylighting features are aright implemented they can reduce li ghting-related energy requirements by 25%. 49 Hybrid solar lighting(HSL) is anactive solarmethod of providing interior illumination. HSL systems collect sunlight using focusing mirrors thattrack the Sunand useoptical fibersto disperse it inside the building to supplement conventional lighting. In single-story industriousnesss these systems are able to transmit 50% of the direct sunlight received. 50 Solar lights that charge during the day and light up at dusk are a common sight on walkways. 51Solar-charged lanterns have become popular in under essential countries where they provide a safer and cheaper alternative to kerosene lamps. 52Althoughdaylight saving timeis promoted as a way to use sunlight to save energy, recent research reports contradictory results several(prenominal) studies report savings, but full as many suggest no effect or even a net loss, especially whengasolineconsumption is taken into account. Electricity use is greatly affected by geography, climate and ec onomics, making it hard to generalize from single studies. 53 SOLAR THERMAL Solar thermal technologies can be utilize for water heating, space heating, space cooling and process heat generation. 54 WATER HEATING pic Solar water heaters facing theSunto maximize gain. Solar hot water systems use sunlight to heat water.In low geographical latitudes (below 40degrees) from 60 to 70% of the domestic hot water use with temperatures up to 60C can be provided by solar heating systems. 55The most common types of solar water heaters are evacuated tube collectors (44%) and glazed flat plate collectors (34%) generally use for domestic hot water and unglazed plastic collectors (21%) employ mainly to heat swimming pools. 56 As of 2007, the total installed capacity of solar hot water systems is approximately 154GW. 57China is the world leader in their deployment with 70GW installed as of 2006 and a long term goal of 210GW by 2020. 58IsraelandCyprusare the per capita leaders in the use of solar ho t water systems with over 90% of homes using them. 59In the joined States, Canada and Australia heating swimming pools is the dominant application of solar hot water with an installed capacity of 18GW as of 2005. 18 HEATING, COOLING AND VENTILATION pic Solar House 1 ofMassachusetts Institute of Technologyin the United States, built in 1939, utiliseseasonal worker worker thermal energy storage (STES)for year-round heating. In the United States,heating, ventilation and air conditioning(HVAC) systems account for 30% (4. 65EJ) of the energy used in commercialised-grade buildings and nearly 50% (10. 1EJ) of the energy used in residential buildings. 4960Solar heating, cooling and ventilation technologies can be used to offset a portion of this energy.Thermal mass is any material that can be used to store heatheat from the Sun in the case of solar energy. Common thermal mass materials include stone, cement and water. Historically they have been used in arid climates or warm temperate r egions to keep buildings cool by absorbing solar energy during the day and radiating stored heat to the cooler atmosphere at night. However they can be used in cold temperate areas to maintain warmth as well. The size and placement of thermal mass depend on several factors such as climate, daylighting and shading conditions. When properly incorporated, thermal mass maintains space temperatures in a comfortable range and reduces the need for auxiliary heating and cooling equipment. 61A solar lamp chimney (or thermal chimney, in this context) is a passive solar ventilation system composed of a vertical shaft connecting the interior and exterior of a building. As the chimney warms, the air inside is heated causing anupdraftthat pulls air through the building. Performance can be improved by using glazing and thermal mass materials62in a way that mimics greenhouses. Deciduoustrees and plants have been promoted as a means of controlling solar heating and cooling. When planted on the south ern side of a building, their leaves provide shade during the summer, while the bare limbs deed over light to pass during the winter. 63Since bare, leaf little trees shade 1/3 to 1/2 of incident solar radiation, there is a balance between the benefits of summer shading and the corresponding loss of winter heating. 64In climates with significant heating loads, deciduous trees should not be planted on the southern side of a building because they will interfere with winter solar availability. They can, however, be used on the east and west sides to provide a degree of summer shading without appreciably affecting winter solar gain. 65 WATER TREATMENT pic Solar water disinfectioninIndonesia pic subatomic scale solar powered sewerage treatment plant. Solar distillation can be used to makesalineorbrackish waterpotable. The first recorded instance of this was by sixteenth century Arab alchemists. 66A large-scale solar distillation project was first constructed in 1872 in theChileanmining town of Las Salinas. 67The plant, which had solar collection area of 4,700m2, could produce up to 22,700Lper day and operated for 40years. 67Individualstilldesigns include single-slope, double-slope (or greenhouse type), vertical, conical, inverted absorber, multi-wick, and triune effect. 66These stills can operate in passive, active, or hybrid modes. Double-slope stills are the most economical for decentralized domestic purposes, while active multiple effect units are more suitable for large-scale applications. 66 Solar waterdisinfection(SODIS) involves exposing water-filled plasticpol even sohylene terephthalate(PET) bottles to sunlight for several hours. 68Exposure times vary depending on weather and climate from a minimum of six hours to cardinal days during fully overcast conditions. 69It is recommended by theWorld Health Organizationas a viable method for household water treatment and safe storage. 70Over two million people in developing countries use this method for their d aily drinking water. 69 Solar energy may be used in a water stabilisation pond to treat glom waterwithout chemicals or electricity. A throw out environmental advantage is thatalgaegrow in such ponds and consumecarbon dioxidein photosynthesis, although algae may produce toxic chemicals that make the water unusable. 7172 COOKING picThe Solar Bowl inAuroville,India, concentrates sunlight on a movable receiver to producesteamforcooking. Solar cookers use sunlight for cooking, drying andpasteurization. They can be grouped into three broad categories box cookers, panel cookers and reflector cookers. 73The simplest solar cooker is the box cooker first built byHorace de Saussurein 1767. 74A basic box cooker consists of an insulated container with a transparent lid. It can be used effectively with partially overcast skies and will typically reach temperatures of 90150C. 75Panel cookers use a reflective panel to direct sunlight onto an insulated container and reach temperatures comparable to box cookers.Reflector cookers use divers(a) concentrating geometries (dish, trough, Fresnel mirrors) to focus light on a cooking container. These cookers reach temperatures of 315C and above but require direct light to function properly and must be repositioned to track the Sun. 76 Thesolar bowlis a concentrating technology employed by the Solar Kitchen atAuroville, inTamil Nadu,India, where a stationary worldwide reflector focuses light along a line perpendicular to the spheres interior surface, and a computer control system moves the receiver to intersect this line. Steam is produced in the receiver at temperatures reaching 150C and then used for process heat in the kitchen. 77A reflector developed byWolfgang Schefflerin 1986 is used in many solar kitchens. Scheffler reflectors are flexible parabolic dishes that combine aspects of trough and power tower concentrators. Polar trackingis used to follow the Suns daily course and the curvature of the reflector is adjusted for seaso nal variations in the incident angle of sunlight. These reflectors can reach temperatures of 450650C and have a fixed central point, which simplifies cooking. 78The worlds largest Scheffler reflector system in Abu Road,Rajasthan, India is capable of cooking up to 35,000 meals a day. 79As of 2008, over 2,000 large Scheffler cookers had been built worldwide. 80 PROCESS HEATSolar concentrating technologies such as parabolic dish, trough and Scheffler reflectors can provide process heat for commercial and industrial applications. The first commercial system was theSolar Total Energy Project(STEP) in Shenandoah, Georgia, the States where a field of 114 parabolic dishes provided 50% of the process heating, air conditioning and electrical requirements for a garb factory. This grid- connected cogeneration system provided 400kW of electricity plus thermal energy in the form of 401kW steam and 468kW chilled water, and had a one hour broadsheet load thermal storage. 81 Evaporation ponds are shallow pools that concentrate dissolved solids throughevaporation. The use of evaporation ponds to obtain salt from sea water is one of the oldest applications of solar energy.Modern uses include concentrating brine solutions used in leach mining and removing dissolved solids from waste streams. 82 Clothes lines,clotheshorses, and clothes racks dry clothes through evaporation by wind and sunlight without overwhelming electricity or gas. In some states of the United States legislation protects the right to dry clothes. 83 Unglazed transpired collectors (UTC) are perforated sun-facing walls used for preheating ventilation air. UTCs can raise the incoming air temperature up to 22C and deliver outlet temperatures of 4560C. 84The short payback period of transpired collectors (3 to 12years) makes them a more cost-effective alternative than glazed collection systems. 84As of 2003, over 80 systems with a combined collector area of 35,000m2had been installed worldwide, including an 860m2co llector inCosta Ricaused for drying coffee beans and a 1,300m2collector inCoimbatore, India used for drying marigolds. 28 ELECTRICITY PRODUCTION pic ThePS10concentrates sunlight from a field of heliostats on a central tower. Solar power is the conversion of sunlight intoelectricity, either directly usingphotovoltaics(PV), or indirectly usingconcentrated solar power(CSP). CSP systems use lenses or mirrors and tracking systems to focus a large area of sunlight into a small beam. PV converts light into electric current using thephotoelectric effect. Commercial CSP plants were first developed in the 1980s. Since 1985 the eventually 354 MWSEGSCSP installation, in the Mojave Desert of California, is the largest solar power plant in the world.Other large CSP plants include the 150 MWSolnova Solar precedent Stationand the 100 MWAndasol solar power station, two in Spain. The 250 MWAgua Caliente Solar Project, in the United States, and the 214 MWCharanka Solar ParkinIndia, are theworlds lar gestphotovoltaic plants. Solar projects especial(a) 1 GW are being developed, but most of the deployed photovoltaics are in small rooftop arrays of slight than 5 kW, which are grid connected using net metering and/or a feed-in tariff. 85 Concentrated solar power Concentrating Solar Power (CSP) systems use lenses or mirrors and tracking systems to focus a large area of sunlight into a small beam. The concentrated heat is then used as a heat source for a conventional power plant.A wide range of concentrating technologies exists the most developed are the parabolic trough, the concentrating analog fresnel reflector, the Stirling dish and the solar power tower. Various techniques are used to track the Sun and focus light. In all of these systems aworking fluidis heated by the concentrated sunlight, and is then used for power generation or energy storage. 86 PHOTOVOLTAICS PHOTOVOLTAICS A solar cadre, or photovoltaic booth (PV), is a device that converts light into electric current us ing the photoelectric effect. The first solar kiosk was constructed by Charles Fritts in the 1880s. In 1931 a German engineer, Dr Bruno Lange, developed a photo cubicle using silver selenite in place of copper oxide.Although the prototype selenium cells converted slight than 1% of incident light into electricity, both Ernst Werner von Siemens and James Clerk Maxwell recognized the importance of this discovery. Following the work of Russell Ohl in the 1940s, researchers Gerald Pearson, Calvin fraught(predicate) and Daryl Chapin created the te solar cell in 1954. These early solar cells cost 286 USD/watt and reached efficiencies of 4. 56%. By 2012 available efficiencies exceed 20% and the maximum capacity of research photovoltaics is over 40%. OTHERS anyways concentrated solar power and photovoltaics, there are some other techniques used to generated electricity using solar power. These include Dye-sensitized_solar_cells, Luminescent solar concentrators (a type of concentrated photovoltaics or CPV technology), Biohybrid solar cells, Photon Enhanced thermionic Emission systems. Development, deployment and economics Beginning with the surge in coal use which accompanied the Industrial Revolution, energy consumption has steadily transitioned from wood and biomass to fossil fuels. The early development of solar technologies starting in the 1860s was impelled by an expectation that coal would soon become scarce. However development of solar technologies stagnated in the early 20th century in the face of the increasing availability, economy, and utility of coal and petroleum. 109The 1973 oil embargo and 1979 energy crisis caused a reorganization of energy policies around the world and brought renewed attention to developing solar technologies. Deployment strategies pore on incentive programs such as the Federal Photovoltaic Utilization Program in the US and the Sunshine Program in Japan. Other efforts included the formation of research facilities in the US (S ERI, now NREL), Japan (NEDO), and Germany (Fraunhofer Institute for Solar Energy Systems ISE). Commercial solar water heaters began appearing in the United States in the 1890s. These systems saw increasing use until the 1920s but were gradually replaced by cheaper and more undeviating heating fuels.As with photovoltaics, solar water heating attracted renewed attention as a result of the oil crises in the 1970s but interest subsided in the 1980s payable to falling petroleum prices. Development in the solar water heating sector progressed steadily throughout the 1990s and growth rates have averaged 20% per year since 1999. 57 Although generally underestimated, solar water heating and cooling is by far the most widely deployed solar technology with an estimated capacity of 154 GW as of 2007. The International Energy Agency has said that solar energy can make considerable contributions to solving some of the most urgent problems the world now faces The development of affordable, inexh austible and clean solar energy technologies will have huge longer-term benefits.It will increase countries energy security through reliance on an indigenous, inexhaustible and mostly import-independent resource, enhance sustainability, reduce pollution, lower the costs of mitigating climate change, and keep fossil fuel prices lower than otherwise. These advantages are global. Hence the additional costs of the incentives for early deployment should be considered learning investments they must be wisely spent and need to be widely shared. In 2011, the International Energy Agency said that solar energy technologies such as photovoltaic panels, solar water heaters and power stations built with mirrors could provide a third of the worlds energy by 2060 if politicians commit to limiting climate change. The energy from the sun could play a key role in de-carbonizing the global economy alongside improvements in energy energy and alarming costs on greenhouse gas emitters. The strength of solar is the incredible variety and flexibility of applications, from small scale to big scale. We have proved that after our stores of oil and coal are wear upon the human race can receive unlimited power from the rays of the sun. Frank Shuman, New York Times, July 2, 1916 SOLAR carrell SOLAR CELL A solar cell made from amonocrystalline atomic number 14 wafer Solar cells can be used devices such as this portable monocrystalline solar charger. A solar cell (also called a photovoltaic cell) is an electrical device that converts the energy of light directly into electricity by the photovoltaic effect. It is a form of photoelectric cell (in that its electrical characteristicse. g. urrent, voltage, or resistancevary when light is incident upon it) which, when exposed to light, can generate and support an electric current without being attached to any foreign voltage source. The term photovoltaic comes from the Greek (phos) meaning light, and from Volt, the unit of electro-motive fo rce, the volt, which in turn comes from the last physical body of the Italian physicist Aless(prenominal)andro Volta, inventor of the battery (electrochemical cell). The term photo-voltaic has been in use in English since 1849. 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 radiationnear the visible range, or meter light intensity. The operation of a photovoltaic (PV) cell requires 3 basic attributes 1. The absorption of light, generating either electron-hole pairs or excitons. 2. The interval of charge carriers of opposite t ypes. 3. 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 but solar illumination. FURTHER IMPROVEMENTS In the time since Bermans work, improvements have brought production costs down under $1 a watt, with wholesale costs well under $2. Balance of system costs are now more than the panels themselves. Large commercial arrays can be built at below $3. 40 a watt,1213fully commissioned. As the semiconducting material industry moved to ever-larger boules, older equipment became available at fire-sale prices.Cells have grown in size as older equipment became available on the surplus market ARCO Solars original panels used cells with 2 to 4 butt on (51 to 100mm) diameter. Panels in the 1990s and early 2000s generally used 5inch (125mm) wafers, and since 2008 almost all new panels use 6inch (150mm) cells. This material has less efficacy, but is less expensive to produce in lot. The widespread introduction offlat screen televisionsin the late 1990s and early 2000s led to the wide availability of large sheets of high-quality glass, used on the front of the panels. In terms of the cells themselves, there has been only one major change. During the 1990s, poly ti cells became increasingly popular.These cells offer less efficiency than their mono te counterparts, but they are grown in large vats that greatly reduce the cost of production. By the mid-2000s, poly was dominant in the low-cost panel market, but more recently a variety of factors has pushed the higher performance mono back into widespread use. certain EVENTS Other technologies ha ve tried to enter the market. First Solarwas briefly the largest panel manufacturer in 2009, in terms of yearly power produced, using a write out-film cell sandwiched between two layers of glass. Since then silicon panels reasserted their dominant position both in terms of lower prices and the rapid rise of Chinese manufacturing, resulting in the top producers being Chinese.By late 2011, efficient production in China, coupled with a fail in European demand due to budgetary turmoil had dropped prices for crystalline solar-based modules further, to about $1. 0913per watt in October 2011, down sharply from the price per watt in 2010. A more modern process, mono-like-multi, aims to offer the performance of mono at the cost of poly, and is in the process of being introduced in 2012citation needed. APPLICATIONS pic Polycrystallinephotovoltaic cells laminated to backup material in a module pic pic Polycrystalline photovoltaic cells Solar cells are often electrically connected and encap sulated as amodule. Photovoltaic modules often have a sheet of glass on the front (sun up) side, allowing light to pass while protecting the emiconductorwafersfrom abrasion and impact due to wind-driven debris,rain,hail, etc. Solar cells are also usually connected inseriesin modules, creating an additivevoltage. Connecting cells in twin will yield a higher current however, very significant problems exist with parallel connections. For example, keister effects can shut down the weaker (less illuminated) parallel string (a number of series connected cells) causing substantial power loss and even damaging the weaker string because of the excessivereverse bias employ to the shadowed cells by their illuminated partners. Strings of series cells are usually handled independently and not connected in parallel, special paralleling circuits are the exceptions.Although modules can be interconnected to create anarraywith the desired peak DC voltage and loading current capacity, using independ ent MPPTs (maximum power point trackers) provides a better solution. In the absence of paralleling circuits, shunt diodes can be used to reduce the power loss due to shadowing in arrays with series/parallel connected cells. To make practical use of the solar-generated energy, the electricity is most often fed into the electricity grid using inverters (grid-connectedphotovoltaic systems) in stand-alone systems, batteries are used to store the energy that is not needed immediately. Solar panels can be used to power or recharge portable devices. THEORYThe solar cell works in three steps 1. Photonsinsunlighthit the solar panel and are absorbed by semiconducting materials, such as silicon. 2. Electrons(negatively charged) are knocked loose from their atoms, causing an electric potential difference. Current starts flowing through the material to cancel the potential and this electricity is captured. Due to the special composition of solar cells, the electrons are only allowed to move in a single direction. 3. An array of solar cells converts solar energy into a usable amount ofdirect current(DC) electricity. EFFICIENCY Solar panels on the International Space Station absorb light from both sides.These biface cells are more efficient and operate at lower temperature than single sided equivalents. The efficiency of a solar cell may be broken down into reflectance efficiency, thermodynamic efficiency, charge carrier musical interval efficiency and conductive efficiency. The overall efficiency is the product of each of these individual efficiencies. A solar cell usually has a voltage dependent efficiency curve, temperature coefficients, and shadow angles. Due to the difficulty in measuring these line of reasonings directly, other parameters are measured instead thermodynamic efficiency, quantum efficiency,integrated quantum efficiency, VOC ratio, and fill factor.Reflectance losses are a portion of the quantum efficiency under external quantum efficiency. Recombination losses make up a portion of the quantum efficiency, VOC ratio, and fill factor. Resistive losses are predominantly categorized under fill factor, but also make up minor portions of the quantum efficiency, VOC ratio. The fill factor is defined as the ratio of the actual maximum getable power to the product of the open circuit voltage and short circuit current. This is a key parameter in evaluating the performance of solar cells. Typical commercial solar cells have a fill factor 0. 70. Grade B cells have a fill factor usually between 0. 4 to 0. 7. 14 Cells with a high fill factor have a low equivalent series resistance and a high equivalent shunt resistance, so less of the current produced by the cell is dissipated in internal losses. Single pn junction crystalline silicon devices are now access the theoretical limiting power efficiency of 33. 7%, noted as the ShockleyQueisser limit in 1961. In the extreme, with an infinite number of layers, the corresponding limit is 86% using con centrated sunlight. pic Reported timeline of solar cell energy conversion efficiencies (from National Renewable Energy Laboratory (USA)) MATERIALS pic pic TheShockley-Queisser limitfor the theoretical maximum efficiency of a solar cell. Semiconductors withband good luckbetween 1 and 1. eV, or near-infrared light, have the greatest potential to form an efficient cell. (The efficiency limit shown here can be exceeded bymultijunction solar cells. ) Various materials display alter efficiencies and have varying costs. Materials for efficient solar cells must have characteristics matched to the spectrum of available light. Some cells are designed to expeditiously convert wavelengths of solar light that reach the Earth surface. However, some solar cells are optimized for light absorption beyond Earths atmosphere as well. Light absorbing materials can often be used inmultiple physical configurationsto take advantage of different light absorption and charge separation mechanisms.Materials presently used for photovoltaic solar cells includemonocrystalline silicon,polycrystalline silicon, unformed silicon,cadmium telluride, andcopper indium selenide/sulfide. 2526 legion(predicate) currently available solar cells are made from pot materials that are cut intowafersbetween clxxx to 240micrometers midst that are then processed like other semiconducting materials. Other materials are made asthin-filmslayers, fundamentaldyes, and organicpolymersthat are deposited onsupporting substratums. A third group are made fromnanocrystalsand used asquantum dots(electron-confinednanoparticles). Silicon remains the only material that is well-researched in bothbulkandthin-filmforms. CRYSTALLINE ti picBasic structure of a silicon based solar cell and its working mechanism. By far, the most prevailing bulk material for solar cells is crystalline silicon (abbreviated as a group as c-Si), also known as solar grade silicon. Bulk silicon is separated into multiple categories tally to c rystallinity and crystal size in the resulting ingot, ribbon, orwafer. 1. monocrystalline silicon (c-Si) often made using the Czochralski process. Single-crystal wafer cells tend to be expensive, and because they are cut from cylindrical ingots, do not completely cover a square solar cell module without a substantial waste of refined silicon. Hence most c-Si panels have uncovered gaps at the four corners of the cells. 2. olycrystalline silicon, or multicrystalline silicon, (poly-Si or mc-Si) made from cast square ingots large blocks of molten silicon conservatively cooled and solidified. Poly-Si cells are less expensive to produce than single crystal silicon cells, but are less efficient. United States Department of Energy data show that there were a higher number of polycrystalline sales than monocrystalline silicon sales. 3. ribbon silicon is a type of polycrystalline silicon it is formed by drawing flat thin films from molten silicon and results in a polycrystalline structure. These cells have lower efficiencies than poly-Si, but save on production costs due to a great reduction in silicon waste, as this approach does not require sawing from ingots. 4. ono-like-multi silicon Developed in the 2000s and introduced commercially around 2009, mono-like-multi, or cast-mono, uses existing polycrystalline casting chambers with small seeds of mono material. The result is a bulk mono-like material with poly around the outsides. When sawn apart for process, the inner sections are high-efficiency mono-like cells (but square instead of clipped), while the satellite edges are sold off as conventional poly. The result is line that produces mono-like cells at poly-like prices. Analysts have predicted that prices of polycrystalline silicon will drop as companies build additional polysilicon capacity quicker than the industrys projected demand. On the other hand, the cost of producing upgraded metallic elementlurgical-grade silicon, also known as UMG Si, can potentially b e one-sixth that of makingpolysilicon.Manufacturers of wafer-based cells have responded to high silicon prices in 20042008 prices with rapid reductions in silicon consumption. According to Jef Poortmans, director of IMECs organic and solar department, current cells use between eight and nine grams of silicon per watt of power generation, with wafer thicknesses in the propinquity of 0. 200 mm. At 2008 springs IEEEPhotovoltaic Specialists Conference (PVS08), John Wohlgemuth, staff scientist at BP Solar, reported that his company has qualified modules based on 0. 180 mm thick wafers and is testing processes for 0. 16 mm wafers cut with 0. 1 mm wire. IMECs road map, presented at the organizations recent annual research review meeting, envisions use of 0. 08 mm wafers by 2015. atomic number 31 arsenide multijunctionHigh-efficiency multijunction cells were originally developed for special applications such as satellites and space exploration, but at present, their use in terrestrial conc entrators capability be the utmost cost alternative in terms of $/kWh and $/W. 35 These multijunction cells consist of multiple thin films produced using metalorganic vapour phase epitaxy. A triple-junction cell, for example, may consist of the semiconducting materials GaAs, Ge, and GaInP2. 36 Each type of semiconductor will have a characteristic band gap energy which, loosely speaking, causes it to absorb light most efficiently at a certain color, or more precisely, to absorb electromagnetic radiation over a portion of the spectrum.Combinations of semiconductors are carefully chosen to absorb nearly the entire solar spectrum, thus generating electricity from as much of the solar energy as possible. GaAs based multijunction devices are the most efficient solar cells to date. In October 15, 2012, triple junction metamorphic cell reached a record high of 44%. 37 Tandem solar cells based on monolithic, series connected, gallium indium phosphide (GaInP), gallium arsenide GaAs, and a tomic number 32 Ge pn junctions, are seeing demand rapidly rise. Between declination 2006 and December 2007, the cost of 4N gallium metal rose from about $350 per kg to $680 per kg. Additionally, germanium metal prices have travel substantially to $10001200 per kg this year.Those materials include gallium (4N, 6N and 7N Ga), arsenic (4N, 6N and 7N) and germanium, pyrolitic boron nitride (pBN) crucibles for growing crystals, and boron oxide, these products are critical to the entire substratum manufacturing industry. Triple-junction GaAs solar cells were also being used as the power source of the Dutch four-time World Solar Challenge winners Nuna in 2003, 2005 and 2007, and also by the Dutch solar carsSolutra (2005), Twente iodin (2007) and 21Revolution (2009). The Dutch Radboud University Nijmegen set the record for thin film solar cell efficiency using a single junction GaAs to 25. 8% in August 2008 using only 4 m thick GaAs layer which can be transferred from a wafer base to gl ass or plastic film. THIN FILMS picMarket share of the different PV technologiesIn 2010 the market share of thin film declined by 30% as thin film technology was displaced by more efficient crystalline silicon solar panels (the light and contraband blue bars). Thin-film technologies reduce the amount of material required in creating the active material of solar cell. near thin film solar cells are sandwiched between two panes of glass to make a module. Since silicon solar panels only use one pane of glass, thin film panels are approximately twice as heavy as crystalline silicon panels. The majority of film panels have significantly lower conversion efficiencies, lagging silicon by two to three percentage points. 31Thin-film solar technologies have enjoyed large investment due to the success of First Solar and the largely unfulfilled promise of lower cost and flexibility compared to wafer silicon cells, but they have not become mainstream solar products due to their lower efficien cy and corresponding larger area consumption per watt production. Cadmium telluride(CdTe),copper indium gallium selenide(CIGS) andamorphous silicon(A-Si) are three thin-film technologies often used as outdoor photovoltaic solar power production. CdTe technology is most cost competitive among them. 32CdTe technology costs about 30% less than CIGS technology and 40% less than A-Si technology in 2011. CADMIUM TELLURIDE SOLAR CELLA cadmium telluride solar cell uses a cadmium telluride (CdTe) thin film, asemiconductorlayer to absorb and convert sunlight into electricity. Solarbuzzhas reported that the lowest quoted thin-film module price stands at US$0. 84 perwatt-peak, with the lowest crystalline silicon (c-Si) module at $1. 06 per watt-peak. 33 Thecadmiumpresent in the cells would be toxic if released. However, release is impossible during normal operation of the cells and is unlikely during ? res in residential roofs. 34A square meter of CdTe contains approximately the same amount of Cd as a single C cellNickel-cadmium battery, in a more stable and less soluble form. 34COPPER INDIUM GALLIUM SELENIDE Copper indium gallium selenide (CIGS) is adirect band gapmaterial. It has the highest efficiency (20%) among thin film materials (seeCIGS solar cell). Traditional methods of fabrication involve vacuum processes including co-evaporation and sputtering. fresh developments atIBMandNanosolarattempt to lower the cost by using non-vacuum solution processes. GALLIUM ARSENIDE MULTIJUNCTION High-efficiency multijunction cells were originally developed for special applications such assatellitesandspace exploration, but at present, their use in terrestrial concentrators might be the lowest cost alternative in terms of $/kWh and $/W. 35These multijunction cells consist of multiple thin films produced usingmetalorganic vapour phase epitaxy. A triple-junction cell, for example, may consist of the semiconductorsGaAs,Ge, andGaInP2. 36Each type of semiconductor will have a characte risticband gapenergy which, loosely speaking, causes it to absorb light most efficiently at a certain color, or more precisely, to absorbelectromagnetic radiationover a portion of the spectrum. Combinations of semiconductors are carefully chosen to absorb nearly all of the solar spectrum, thus generating electricity from as much of the solar energy as possible. GaAs based multijunction devices are the most efficient solar cells to date.In October 15, 2012, triple junction metamorphic cell reached a record high of 44%. 37 Tandem solar cells based on monolithic, series connected, gallium indium phosphide (GaInP), gallium arsenide GaAs, and germanium Ge pn junctions, are seeing demand rapidly rise. Between December 2006 and December 2007, the cost of 4N gallium metal rose from about $350 per kg to $680 per kg. Additionally, germanium metal prices have risen substantially to $10001200 per kg this year. Those materials include gallium (4N, 6N and 7N Ga), arsenic (4N, 6N and 7N) and germa nium, pyrolitic boron nitride (pBN) crucibles for growing crystals, and boron oxide, these products are critical to the entire substrate manufacturing industry.Triple-junction GaAs solar cells were also being used as the power source of the Dutch four-timeWorld Solar ChallengewinnersNunain 2003, 2005 and 2007, and also by the Dutch solar carsSolutra (2005),Twente One (2007)and 21Revolution (2009). The DutchRadboud University Nijmegenset the record for thin film solar cell efficiency using a single junction GaAs to 25. 8% in August 2008 using only 4m thick GaAs layer which can be transferred from a wafer base to glass or plastic film. Light-absorbing dyes (DSSC) Dye-sensitized solar cells(DSSCs) are made of low-cost materials and do not need elaborate equipment to manufacture, so they can be made in aDIYfashion, mayhap allowing players to produce more of this type of solar cell than others. In bulk it should be significantly less expensive than oldersolid-statecell designs.DSSCs can be engineered into flexible sheets, and although itsconversion efficiencyis less than the bestthin film cells, itsprice/performance ratioshould be high enough to allow them to compete withfossil fuel electrical generation. Typically arutheniummetalorganicdye(Ru-centered) is used as amonolayerof light-absorbing material. The dye-sensitized solar cell depends on amesoporouslayer ofnanoparticulatetitanium dioxideto greatly amplify the surface area (200300 m2/g TiO2, as compared to approximately 10 m2/g of flat single crystal). The photogenerated electrons from thelight absorbing dyeare passed on to then-typeTiO2, and the holes are absorbed by anelectrolyteon the other side of the dye.The circuit is holy by a redox couple in the electrolyte, which can be tranquil or solid. This type of cell allows a more flexible use of materials, and is typically manufactured byscreen printingor use ofUltrasonic Nozzles, with the potential for lower processing costs than those used forbulksolar cells . However, the dyes in these cells also suffer fromdegradationunder heat andUVlight, and the cell casing is difficult tosealdue to the solvents used in assembly. In spite of the above, this is a popular emerging technology with some commercial impact forecast within this decade. The first commercial payload of DSSC solar modules occurred in July 2009 from G24i Innovations. 38 Quantum Dot Solar Cells (QDSCs)Quantum dot solar cells(QDSCs) are based on the Gratzel cell, ordye-sensitized solar cell, architecture but employ lowband gapsemiconductornanoparticles, fabricated with such small crystallite sizes that they formquantum dots(such asCdS,CdSe,Sb2S3,PbS, etc. ), instead of organic or organometallic dyes as light absorbers. Quantum dots (QDs) have attracted much interest because of their unique properties. Their size quantization allows for theband gapto be tuned by just changing particle size. They also have highextinction coefficients, and have shown the possibility ofmultiple ex citon generation. 39 In a QDSC, amesoporouslayer oftitanium dioxidenanoparticles forms the backbone of the cell, much like in a DSSC.This TiO2layer can then be made photoactive by coating with semiconductor quantum dots usingchemical can deposition,electrophoretic deposition, or successive ionic layer adsorption and reaction. The electrical circuit is then completed through the use of a liquid or solidredox couple. During the last 34 years, the efficiency of QDSCs has increased rapidly40with efficiencies over 5% shown for both liquid-junction41and solid state cells. 42In an effort to slack production costs of these devices, thePrashant Kamatresearch group43recently demonstrated a solar paint made with TiO2and CdSe that can be applied using a one-step method to any conductive surface and have shown efficiencies over 1%. 44 Organic/polymer solar cellsOrganic solar cellsare a relatively novel technology, yet hold the promise of a substantial price reduction (over thin-film silicon) a nd a faster return on investment. These cells can be processed from solution, hence the possibility of a simple roll-to-roll printing process, leading to inexpensive, large scale production. Organic solar cells andpolymer solar cellsare built from thin films (typically 100nm) oforganic semiconductorsincluding polymers, such aspolyphenylene vinyleneand small-molecule compounds like copper phthalocyanine (a blue or green organic pigment) andcarbon fullerenesand fullerene derivatives such asPCBM. Energy conversion efficiencies achieved to date using conductive polymers are low compared to inorganic materials.However, it has improved quickly in the last few years and the highestNREL(National Renewable Energy Laboratory) certified efficiency has reached 8. 3% for theKonarkaPower Plastic. 45In addition, these cells could be beneficial for some applications where mechanical flexibility and disposability are important. These devices differ from inorganic semiconductor solar cells in that th ey do not rely on the large built-in electric field of a PN junction to separate the electrons and holes created when photons are absorbed. The active region of an organic device consists of two materials, one which acts as an electron donor and the other as an acceptor.When a photon is converted into an electron hole pair, typically in the donor material, the charges tend to remain bound in the form of anexciton, and are separated when the exciton diffuses to the donor-acceptor interface. The short exciton diffusion lengths of most polymer systems tend to limit the efficiency of such devices. Nanostructured interfaces, sometimes in the form of bulk heterojunctions, can improve performance. 46 In 2011, researchers at the Massachusetts Institute of Technology and Michigan State University developed the first highly efficient transparent solar cells that had a power efficiency close to 2% with a transparency to the human eye greater than 65%, achieved by selectively absorbing the ultr aviolet and near-infrared parts of the spectrum with small-molecule compounds. 4748Researchers at UCLA more recently developed an analogous polymer solar cell, following the same approach, that is 70% transparent and has a 4% power conversion efficiency. 49The efficiency limits of both opaque and transparent organic solar cells were recently outlined. 5051These lightweight, flexible cells can be produced in bulk at a low cost, and could be used to create power generating windows. Silicon thin films Silicon thin-film cellsare mainly deposited bychemical vapor deposition(typically plasma-enhanced, PE-CVD) fromsilanegas andhydrogengas. Depending on the deposition parameters, this can yield52 1. shapeless silicon(a-Si or a-SiH) 2. Protocrystallinesilicon or 3. Nanocrystalline silicon(nc-Si or nc-SiH), also called microcrystalline silicon.It has been found that protocrystalline silicon with a low volume fraction of nanocrystalline silicon is optimal for high open circuit voltage. 53Thes e types of silicon present abeyance and twisted bonds, which results in deep defects (energy levels in the bandgap) as well as twisting of the valence and conduction bands (band tails). The solar cells made from these materials tend to have lowerenergy conversion efficiencythanbulksilicon, but are also less expensive to produce. Thequantum efficiencyof thin film solar cells is also lower due to reduced number of collected charge carriers per incident photon. An amorphous silicon (a-Si) solar cell is made of amorphous or microcrystalline silicon and its basic electronic structure is thep-i-njunction. -Si is attractive as a solar cell material because it is abundant and non-toxic (unlike its CdTe counterpart) and requires a low processing temperature, enabling production of devices to occur on flexible and low-cost substrates. As the amorphous structure has a higher absorption rate of light than crystalline cells, the complete light spectrum can be absorbed with a very thin layer of photo-electrically active material. A film only 1 micron thick can absorb 90% of the usable solar energy. 54This reduced material requirement along with current technologies being capable of large-area deposition of a-Si, the scalability of this type of cell is high.However, because it is amorphous, it has high inherent disorder and dangling bonds, making it a bad conductor for charge carriers. These dangling bonds act as recombination centers that severely reduce the carrier lifetime and pin the Fermi energy level so that doping the material to n- or p- type is not possible. Amorphous Silicon also suffers from the Staebler-Wronski effect, which results in the efficiency of devices utilizing amorphous silicon dropping as the cell is exposed to light. The production of a-Si thin film solar cells uses glass as a substrate and deposits a very thin layer of silicon byplasma-enhanced chemical vapor deposition(PECVD).A-Si manufacturers are working towards lower costs per watt and higher conversion efficiency with continuous research and development onMultijunction solar cellsfor solar panels. Anwell Technologies Limitedrecently announced its target for mul