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SOLAR ENERGY

Solar cells convert sunlight directly into electricity. Solar cells are often used to

 power calculators and watches. They are ade of seiconducting aterials siilar 

to those used in coputer chips. !hen sunlight is a"sor"ed "y these aterials# the

solar energy $noc$s electrons loose fro their atos# allowing the electrons to

flow through the aterial to produce electricity. This process of converting light

%photons& to electricity %voltage& is called the photovoltaic %'(& effect.

Solar cells are typically co"ined into odules that hold a"out )* cells+ a nu"er 

of these odules are ounted in '( arrays that can easure up to several eters

on a side. These flat,plate '( arrays can "e ounted at a fi-ed angle facing south#

or they can "e ounted on a trac$ing device that follows the sun# allowing the to

capture the ost sunlight over the course of a day. Several connected '( arrays

can provide enough power for a household+ for large electric utility or industrialapplications# hundreds of arrays can "e interconnected to for a single# large '(

syste.

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Thin fil solar cells use layers of seiconductor aterials only a few icroeters

thic$. Thin fil technology has ade it possi"le for solar cells to now dou"le as

rooftop shingles# roof tiles# "uilding facades# or the glaing for s$ylights or atria.

The solar cell version of ites such as shingles offer the sae protection and

dura"ility as ordinary asphalt shingles.

Soe solar cells are designed to operate with concentrated sunlight. These cells are

 "uilt into concentrating collectors that use a lens to focus the sunlight onto the

cells. This approach has "oth advantages and disadvantages copared with flat, plate '( arrays. The ain idea is to use very little of the e-pensive seiconducting

'( aterial while collecting as uch sunlight as possi"le. /ut "ecause the lenses

ust "e pointed at the sun# the use of concentrating collectors is liited to the

sunniest parts of the country. Soe concentrating collectors are designed to "e

ounted on siple trac$ing devices# "ut ost re0uire sophisticated trac$ing

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devices# which further liit their use to electric utilities# industries# and large

 "uildings.

The perforance of a solar cell is easured in ters of its efficiency at turning

sunlight into electricity. Only sunlight of certain energies will wor$ efficiently to

create electricity# and uch of it is reflected or a"sor"ed "y the aterial that a$e

up the cell. /ecause of this# a typical coercial solar cell has an efficiency of 

123,a"out one,si-th of the sunlight stri$ing the cell generates electricity. Low

efficiencies ean that larger arrays are needed# and that eans higher cost.

4proving solar cell efficiencies while holding down the cost per cell is an

iportant goal of the '( industry# NREL researchers# and other 5.S. 6epartent

of Energy %6OE& la"oratories# and they have ade significant progress. The first

solar cells# "uilt in the 172*s# had efficiencies of less than )3.

4n A' the installed capacity is 897 :! as of Septe"er 8*12. 6uring the year 

8*1)# A'Trans;o has entered in to agreeents with 4''s to install <17

:!. NT'; also entered in to agreeent in the year 8*12 with A' Transco to

install 82* :! plant %first phase of the 1#***,:! ultra solar power pro=ect& in the

econoically "ac$ward Anantapur district.

Rural electrification 

Lac$ of electricity infrastructure is one of the ain hurdles in the developent of 

rural 4ndia. 4ndia>s grid syste is considera"ly under,developed# with a=or 

sections of its populace still surviving off,grid. As of 8**)# a"out ?*#*** of the

nation>s villages had not yet "ecoe electrified. Of these villages# 1?#*** could not

 "e electrified through an e-tension of the conventional grid. A target for 

electrifying 2#*** such villages was set for the Tenth National @ive Year 'lan

%8**88**9&. As of 8**)# ore than 8#9** villages and halets had "een

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electrified# ainly using solar photovoltaic systes. 6evelopents in cheap solar 

technology are considered as a potential alternative that allows an electricity

infrastructure consisting of a networ$ of local,grid clusters with distri"uted

electricity generation. 4t could allow "ypassing %or at least relieving& the need to

install e-pensive# lossy# long,distance# centralied power delivery systes and yet

 "ring cheap electricity to the asses.