Solar cellls


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Solar cellls

  1. 1. SOLAR CELLLS-THE FOUNDTION OF SOLAR ENERGY full reportABSTRACTA solar cell is asemiconductor device thatconverts solar energy intoelectricity by thephotovoltaic effect,representing thefundamental powerconversion unit of aphotovoltaic system ,worksunder the principle of a P-Njunction that absorbs light ,releases electrons and holes, creating a voltage in thecell , which is then appliedto load; beingenvironmentally aware, andwith the price of livingrising at an alarming rate,solar power, generatingenergy from the naturalresources of the sun, has inrecent times become quite aviable alternative to thenormal resources forgenerating electricity, witha great advantage that solarenergy is free; it needs nofuel and produces no wasteor pollution,environmentally friendly,so particularly useful insituations where electricalpower from the grid isunavailable such as inremote area power systems,Earth-orbiting satellites andspace probes, remoteradiotelephones and waterpumping applications,where its applicationsstands alone, and exploitwith their specialadvantages ,giving rebirthto the mankind.INTRODUCTIONSolar cells represent thefundamental powerconversion unit of a
  2. 2. photovoltaic system. Theyare made fromsemiconductors, and havemuch in common withother solid-state electronicdevices, such as diodes,transistors and integratedcircuits. For practicaloperation, solar cells areusually assembled intomodules.Many different solar cellsare now available on themarket, and yet more areunder development. Therange of solar cells spansdifferent materials anddifferent structures in thequest to extract maximumthe device while keepingthe cost to a minimum.Cheaper (but also lessefficient) types of siliconcells, made in the form ofamorphous thin films, areused to power a variety ofconsumer products. Wewere familiar with thesolar-powered watches andcalculators, but largeramorphous silicon solarmodules are also available.A particular class of high-efficiency solar cells fromsingle crystal silicon orcompound semiconductors(for example, galliumarsenide or indiumphosphide) are used inspecialized applications, forexample, to power satellitesor in systems which operateunder high-intensityconcentrated sunlight.WHAT IS A SOLARCELLA solar cell or photovoltaiccell is a semiconductordevice that converts solarenergy into electricity by
  3. 3. the photovoltaic effect..Photovoltaicâ„¢s is thefield of technology andresearch related to theapplication of solar cells asenergy. Sometimes the termsolar cell is reserved fordevices intendedspecifically to captureenergy from sunlight, whilethe term photovoltaic cell isused when the source isunspecified.SOLAR CELLWHAT IS THEPRINCIPLE OF A SOLARCELLIt is based on the ability ofa semiconductor to directlyconvert sunlight intoelectricity. Basically, asolar cell is a P-N junctionthat absorbs light, releaseselectrons and holes, reatinga voltage in the cell, whichis then applied to the load.HOW A SOLAR CELLDOES WORKSIn order to produce energyto work a load, e.g., light alight bulb, the solar cellneeds an outside source (theSun) to produce electricityto power it. When lightstrikes a photovoltaic(solar) cell, atoms arebombarded with photons,and produce electrons.When the atom loses theelectron, it leaves behind aËœholeâ„¢, which has anequal and opposite charge.Both the electron, with itsnegative charge, and thehole, with its positivecharge, begin are carrieddown the gradient. Aproportion of carriers whichcross this junction can beharvested by completing a
  4. 4. circuit from a grid on thecells surface to a collectoron the backplane. In thecell, the light "pumps"electrons out one side of thecell, through the circuit, andback to the other side,energizing any electricaldevices.In the conversion process,the incident energy of lightcreates mobile chargedparticles in thesemiconductor which arethen separated by thedevice structure andproduce electrical current.WHAT ARE THEADVANTAGES OFSOLAR -CELLSRecently, more people arebecoming environmentallyaware, and, with the priceof living rising at analarming rate, we are alllooking for ways to savesome money. So why nottry to save the environmentat the same time Solarpower, generating energyfrom the natural resourcesof the sun, has in recenttimes become quite a viablealternative to the normalresources for generatingelectricity.1. SOLAR ENERGY IS ARENEWABLERESOURCEYou will never run out ofsolar energy. Sure, the sunsets at night, and on thosedark and gloomy days itmay not always be visible,but you can be sure that itwill return. Oil, on the otherhand, is limited, and onceyou run out, it is goneforever. Although theamount of power the sun
  5. 5. can generate is limited tothe amount of sunlight youget, it is possible togenerate electricity even oncloudy days.2. SOLAR POWER ISNON-POLLUTINGUnlike oil, solar powerdoes not emit any sort oftoxic gases into theenvironment. It is acompletely environmentallyfriendly approach togenerating electricity.There is even work beingdone to make the recyclingof solar panels moreeffective.3. LIGHT FROM THESUN IS FREEAfter the initial costsinvolved in setting up thesolar panels and solar lightsetc, you will never have topay to run them.4. SOLAR POWER ISQUITE FLEXIBLEYou can have an array ofsolar panels on your roof togenerate power from yourhome. You can also havesmaller solar cells ongarden lights or anythingelse outside that only needsa small amount ofelectricity. Not having torun a wire can be a hugetime saver.5. SOLAR CELLSREQUIRE MINIMALMAINTENANCEOnce the solar cells are setup, they require very littlemaintenance, mainlybecause there are nomoving parts that have tobe maintained. Solar cellscan last a lifetime and isvery easy to install.6. SOLAR POWER IS
  6. 6. SILENTThe methods that are usedto find and extract oil arevery noisy. Even windpower can create a lot ofnoise. Solar power iscompletely silent.7. SOLAR ENERGY CANSAVE MONEY IN THELONG RUNSolar energy has manyadvantages, some of themnot as common as others.The main reason for thisperhaps is that the initialcost is quite high. However,you can save a significantamount of money usingsolar power, whichcompares favorably topaying an electricity bill atthe end of the month. Thereis a lot of work that hasbeen done to make solarpower more accessible tothe common man, withresearchers finding waysand means to make thisresource a commonpractice. Solar power isindeed an amazing, naturalenergy resource with somuch potential to be tappedinto. It is just a matter oftime before solar powerbecomes a global hit.WHAT ARE THEAPPLICATIONS OFSOLAR CELLAlong side a variety ofconsumer products -electronic watches,calculators, power forleisure equipment andtourism - there is anextensive range ofapplications where solarcells are already viewed asthe best option forelectricity supply. These
  7. 7. applications are usuallystand-alone, and exploit thefollowing advantages ofphotovoltaic electricity:¢ There are no fuel costsor fuel supply problems¢ The equipment canusually operate unattended¢ Solar cells are veryreliable and require littlemaintenanceTHE APPLICATIONSARE AS FOLLOWSRURALELECTRIFICATIONThe provision of electricityto rural areas derivesimportant social andeconomic benefits toremote communitiesthroughout the world.Power supply to remotehouses or villages,electrification of the healthcare facilities, irrigation andwater supply and treatmentare just few examples ofsuch applications.1. WATER PUMPING:Solar pumps are usedprincipally for twoapplications: village watersupply (including livestockwatering), and irrigation.Since villages need a steadysupply of water, provisionhas to be made for waterstorage for periods of lowinsolation. In contrast,crops have variable waterrequirements during theyear which can often bemet by supplying waterdirectly to produce withoutthe need for a storage tank.2. LIGHTENING: In termsof the number ofinstallations, lighting ispresently the biggestapplication of photo-
  8. 8. voltaic, with tens ofthousands of units installedworld-wide. They aremainly used to providelighting for domestic orcommunity buildings, suchas schools or health centers.PV is also beingincreasingly used forlighting streets and tunnels,and for security lighting.PROFESSIONALAPPLICATIONSFor some time, photovoltaicmodules have proved to bea good source of power forhigh-reliability remoteindustrial use ininaccessible locations, orwhere the small amount ofpower required is moreeconomically met from astand-alone PV system thanfrom mains electricity.Examples of theseapplications include:1. OCEAN NAVIGATIONAIDS: Many lighthousesand most buoys are nowpowered by solar cells.2.TELECOMMUNICATIONSYSTEMS: radiotransceivers on mountaintops or telephone boxes inthe country can often besolar powered.3. REMOTEMONITORING ANDCONTROL: scientificresearch stations, seismicrecording, weather stations,etc. use very little powerwhich, in combination witha dependable battery, isprovided reliably by a smallPV module.4. CATHODICPROTECTION: this is amethod for shielding
  9. 9. metalwork from corrosion,for example, pipelines andother metal structures. APV system is well suited tothis application since a DCsource of power is requiredin remote locations alongthe path of a pipeline.GRID CONNECTEDSYSTEMSTwo types of grid-connected installations areusually distinguished,centralized PV powerstations, and distributedgeneration in units locateddirectly at the customerspremises(PV in buildings).1. PV POWER Stations: APV power station feeds thegenerated powerinstantaneously into theutility distribution network(the grid) by means of oneor more inverters andtransformers. PV powerstations may beapproaching economicviability in locations wherethey assist the local gridduring periods of peakdemand, and obviate theneed to construct a newpower station. This isknown as peak shaving. Itcan also be cheaper to placesmall PV plants within thetransmission system ratherthan to upgrade it(embedded generation).2. PV In Buildings: PVarrays mounted on roof topsor facades offer thepossibility of large-scalepower generation indecentralized medium-sizedgrid-connected units.The main advantages ofthese distributed systemsover large PV plants are as
  10. 10. follows:¢ There are no costs inbuying the land andpreparing the site.¢ The transmission lossesare much lower because theload is on the same site asthe supply.¢ The value of the PVelectricity is also higherbecause it is equal to theselling price of the gridelectricity which has beenreplaced, rather that to thecost of generating it.ELECTRIC POWERGENERATION IN SPACEPhotovoltaic solargenerators have been andwill remain the best choicefor providing electricalpower to satellites in anorbit around the Earth.Indeed, the use of solarcells on the U.S. satelliteVanguard I in 1958demonstrated beyond doubtthe first practicalapplication ofphotovoltaics. Since then,the satellite powerrequirements have evolvedfrom few Watts to severalkilowatts, with arraysapproaching 100 kW beingplanned for a future spacestation.A space solar array must beextremely reliable in theadverse conditions of spaceenvironment. Since it isvery expensive to lift everykilogram of weight into theorbit, the space arrayshould also have a highpower-to-weight ratio.RESULTS1. We can havepollution“less world.2. Avoid the scarcity of
  11. 11. fossil fuels.3. Abundant electricity forall purposes.4. Supply power in deserts,oceans, and to remote areas.5. Supply of sufficientpower to earth orbitingsatellites and space probes.CONCLUSIONSolar cells are long lastingsources of energy whichcan be used almostanywhere particularlyuseful where there is nonational grid and alsowhere there are no peoplesuch as remote site waterpumping or in space,provide cost effectivesolutions to energyproblems in places wherethere is no mainselectricity. Moreover theyare totally silent and non-polluting. They have nomoving parts they requirelittle maintenance and havea long lifetime whencompared to otherrenewable sources they alsopossess many advantages;wind and water power relyon turbines which arenoisy, expensive and liableto breaking down. We areliving in a society wherethere is a tremendouspollution ,with the scarcityof fossil fuels and resources.To overcome thoseproblems we need tochange our life styles. Sincethe solar energy is abundantand is free of cost, we canutilize the solar power togive a rebirth to mankind.BIBLIOGRAPHY1.http://www.wikipedia.org2.
  12. 12. 3. Principles of electronicsby Sze Attached File(s) SOLAR CELLLS-THE FOUNDTION OF SOLAR ENERGY.doc (Size: 1.02 MB / Downloads: 351)Reference: