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As energy demands a round the world inc rea se, theneed for a renewab le energy sourc e that will notharm the environment has neve r been g rea ter. Someprojec tions ind ic a te that the g lob a l energy demand

will a lmost trip le by 2050.

Using photovolta ic (PV) cells is one way to meet theneed , c onverting sunlight d irec tly into elec tric ity withno moving pa rts and no ha rmful pollution.

Although more c onvent iona l sourc es of energy, suc has fossil fuels, are still sa tisfying the ma jority of theworld s energy demand , PV systems a re used in agrea t variety of app lic a tions.

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Sola r street lights c an d eliver tha t muc h-desiredoutc ome a nd offer an exc ep tiona l lighting p rog ramwhilst, at the same time, p roduc ing c onsiderab le

ec onomic and environmenta l savings.

Ca reful c onsidera tion has to be g iven, for example,to the kind of sola r panels to b e employed ; theba tteries; the lamps or LEDs - Light Emitt ing Diodes;

and the kind of elec tronic c irc uitry to be utilized inthe sola r c harger c ontroller and the bac k up system,need ed for days when the sun doesn t shine.

Sola r street lighting c an b e used not only on streets,

bouleva rds and highways but c an a lso p rovide c ost-effec tive, environmenta lly friend ly lighting for bothmilita ry and c ivilian sec urity insta lla tions; pa rk areas orpa rking spac es; a irports, doc ks and simila r a reas or,indeed, for whole c ommunities.

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Solar powered street lights are a very goodexamp le on wha t c an be d one with sola r energy.

A g rowing number of sola r street lighting p rojec tsare running in Afric a , Asia and the Midd le East.

The c onc ept is stra ight fo rward and we sha ll see

more c ountries migra ting this way.

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Powered fully by the sun

Automatic dusk to d awn opera tion

Sta nd -a lone system - no c ab ling , sub-sta tions orfeeder p illa rs required

Cha rge c ontroller/ regula tor p rotec ts ba tteriesaga inst to ta l d isc harge and over c harg ing

Ma intenanc e free ba tteries used for sa fe a ndeasy shipment

Fully assembled with o r without pole op tionavailable

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The working princ ip le o f sola r stree t lightis as fo llow :

The op tic a l effec t of sola r mo dulegene ra ting elec tric ity when the sunshining on the sola r module surfac e,

then the lead c a rried elec tric ity to thec ontroller. The sola r panel c onverts thesun's energy to dc elec tric ity.

Voltage is then regula ted to a spec ificvalue b y an elec tronic c irc uit to c hargethe batte ry. The sun light wearing off in

the night, the working vo ltage andpow er of sola r mo dule is fa lling a t thesame t ime. A solar c ontroller protec tsthe ba ttery from too low and overcharge.

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Fina lly the working volta ge will lower than the c ha rg ingelec tric ity vo lta ge w hic h has set b y controller. So thesola r ba tte ry stop c harg ing and sta rt d isc harg ing

electricity.

This p roc ess will not stop until the sola r module vo lta geb igger tha n the c ontro ller set vo lta ge. It is ac onsec utive c irc ling whic h is the working p rinc ip le oflight c ontrolling . When fully c ha rged , sola r lights usua llyc an work as many a s 15 hours, even if the sun isn tshining.

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Solar Panel Its ta sk is to c onvert the sun's

energy into elec tric ity.Different sizes and power

outp uts a re ava ilab le. Theyhave to be c arefully chosenfor the d esired app lic a tion.Sola r panels should be ab leto w ithhold and deliver inextreme wea ther c ond itions.Some are even designedunbrea kab le (vanda l p roo f),others will work well inoverc ast wea ther.

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Solar Controller

The basic c irc uitry on mostsola r powered street lightsc onsists essentia lly o f a nautomatic ba ttery charger

fed by the sola r panel anda lighting c ontrollerautomated for dusk todawn opera tion.

Automatic lighting c an betriggered by a photoc ell

or a timer.

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A good photovolta ic c ell c ontrollershould have the b a ttery charge a nd

d isc harge c ontrol, tempera ture c ontrol,maximum p ower trac king and over-c harge p rotec tion, over d isc hargeprotec tion, short c irc uit p rotec tion,

reverse pola rity protec tion and otherp rotec tion fea tures and automaticswitc hing and time ad justment func tion.

These will ensure reliab le opera tion o f thesystem with maximum output powereffic iently, und er d ifferent irrad ia tion andd ifferent tempera tures.

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Lamps The c ho ic e of lamps to use in sola r powered street lights is

d ic ta ted by the kind o f ap p lic a tion we're a fter:

1. LEDs (Light Emitting Diodes) a lso known a s SSL (solid -sta te light ing)ha ve a good c olor rend ition. LEDs c onsume a frac tion of theenergy of c omparab le lighting and have a very long life span.

2. CF (Compac t Fluoresc ent) lamp s p rod uce a white light and a reused in p lac es where c olor rend ering is desired .

3. HID (High Intensity Discharge) lamps, ma inly LPS and MH:a ) LPS (Low Pressure Sodium) lamp s genera te a monoc hromaticyellow -orange light a nd a re used when c olor rend ering is not anissue. They ha ve a lifespan of up to 18,000 hours.b ) MH (Metal Halide) lamp s p rod uce a c lea n white light and a reperfec t for app lic a tions where c olor rend ering is essential.

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ADVANTAGES

Outdoor sola r lights a reaffordable

Solar energy is free

Easy and quic k insta lla tion Virtua lly no c ost to opera te No road works or wiring required Safe a nd reliab le func tion

Minimum running c ost a ndmaintenance

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High c ost - The c ost of sola r stree t light will inc rease30%-60% for the ir sola r panel and ba tte ry, and we oftenput the sola r panel a t high p lac e, tha t mea ns put thesola r panel a t the highest p lac e of lamp pole. This willadd the c ost to the sola r street light.

The limit of c limate and geography - Solarstreet light c an not b e insta lled anywhere even there isgood sunshine, for example, under tree, b ehind house,or near b ig build ing .

Rated life of pa rts - We insta ll the ba ttery underground or lamp pole which takes wic ked cond itions toba ttery, and the tempera ture a nd humid ity of surround ingenvironment often chang ed , the freq uent rep lacementwhic h inc rea se the using c ost.

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