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EEEE 6203,6203,Renewable Energy TechnologyRenewable Energy Technology

UnitUnit II :II :

PHOTOVOLTAIC (PV)PHOTOVOLTAIC (PV)

SYSTEMSYSTEM

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Introduction :Introduction :

Solar Electricity is the electricity generatedSolar Electricity is the electricity generateddirectly from sunlight using solar or photovoltaicdirectly from sunlight using solar or photovoltaiccells.cells.

Photovoltaic refers an electric voltage causedPhotovoltaic refers an electric voltage caused

by lightby light TheThe pvpv power technology uses semiconductorspower technology uses semiconductors

cells (wafers), generally of several cmcells (wafers), generally of several cm22

Most solar cells are made of a form of silicon, aMost solar cells are made of a form of silicon, a

hard material either blue or red in appearance.hard material either blue or red in appearance. Individual solar cells can be compared toIndividual solar cells can be compared to

batteries used in torches & radios.batteries used in torches & radios.

Each silicon solar cell produces about 0.4 V toEach silicon solar cell produces about 0.4 V to

0.7 V0.7 V

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ContinuedContinued

Solar cells are connected together (inSolar cells are connected together (inseries) to produce a higher voltage.series) to produce a higher voltage.

Connecting solar cells together called asConnecting solar cells together called as

solar panels, solar cell modules,solar panels, solar cell modules, pvpvmodules etc.modules etc.

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Major Advantages of the PV powerMajor Advantages of the PV power

Short lead time to design, install & start up a newShort lead time to design, install & start up a newplant.plant.

Highly modular, hence the plant economy is notaHighly modular, hence the plant economy is notastrong function of size.strong function of size.

Power output matches very well with peak loadPower output matches very well with peak loaddemandsdemands

Static structure, no moving parts, hence no noise.Static structure, no moving parts, hence no noise.

High power capability per unit of weights.High power capability per unit of weights.

Longer life with little maintenance because of noLonger life with little maintenance because of nomoving parts.moving parts.

Highly mobile & portable because of light weight.Highly mobile & portable because of light weight.

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Principle:Principle:--

The physics of theThe physics of the pvpv cells is very similarcells is very similarto pto p--n junction diode.n junction diode.

When light is absorbed by the junction,When light is absorbed by the junction,the energy of the absorbed photons isthe energy of the absorbed photons istransferred to the electron system of thetransferred to the electron system of thematerial, resulting in the creation ofmaterial, resulting in the creation ofcharge careers that are separated at thecharge careers that are separated at the

junction.junction.

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How long willHow long will fossilefossile fuel last ??fuel last ??

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Continued.Continued.

Consider a hypothetical case where inConsider a hypothetical case where inearth contains a thin core filled entirelyearth contains a thin core filled entirelywith oil as shown in the previous slide. Itwith oil as shown in the previous slide. It

turns out that the volume of the oilturns out that the volume of the oilpresent ispresent is

1.0861.0861021m3((4/3)1021m3((4/3)(6378(6378103)3).103)3).

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ContinuedContinued

The energy density of fuel is in the range ofThe energy density of fuel is in the range of10000Wh/Lt.10000Wh/Lt.

The energy content in the fuel within the earth isThe energy content in the fuel within the earth is

obtained as 1.1obtained as 1.1

1025KWh. Assuming that growth rate is1025KWh. Assuming that growth rate ismaintained at 7% and the entire energy is suppliedmaintained at 7% and the entire energy is suppliedusing fossil fuels. The energy requirement at any time, tusing fossil fuels. The energy requirement at any time, tcan be calculated usingcan be calculated using 70701012e0.07t1012e0.07t KWhKWh

tt is obtained as 368 years. The fossil fuels will getis obtained as 368 years. The fossil fuels will getdepleted in about 368 years.depleted in about 368 years.

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ContinuedContinued If we consider the real situation, the earth is notIf we consider the real situation, the earth is not--

completely filled with oil as assumed and further thecompletely filled with oil as assumed and further theannual energy consumption rate is continually growing.annual energy consumption rate is continually growing.So the fuel may get exhausted in about 70So the fuel may get exhausted in about 70--100 years.100 years.

If the reserves of fuels decrease there will be a sharpIf the reserves of fuels decrease there will be a sharpincrease in the price of energy. This will lead to decreaseincrease in the price of energy. This will lead to decreasein energy consumption through fossil fuels. If alternativein energy consumption through fossil fuels. If alternative

sources are explored and utilized, then the fuel may besources are explored and utilized, then the fuel may beactually used for more number of years.actually used for more number of years.

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Energy DensitiesEnergy Densities

The alternative sources consideredThe alternative sources consideredhave energy density in the range ofhave energy density in the range of

10Wh/Lt where as fossil fuel energy10Wh/Lt where as fossil fuel energydensity is in the range ofdensity is in the range of10000Wh/Lt.10000Wh/Lt.

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Energy densities of fuelsEnergy densities of fuels

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What are the other alternative energyWhat are the other alternative energyoptionsoptions

Solar photovoltaicSolar photovoltaic

Solar thermalSolar thermal

WaveWave

TidalTidal

WindWind

GeothermalGeothermal BioBio

HybridHybrid

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Scope for alternative energiesScope for alternative energies

75% of energy comes from fossil fuels such as75% of energy comes from fossil fuels such ascrude oils, coal and natural gascrude oils, coal and natural gas

12% from bio fuels such as methane12% from bio fuels such as methane 9% from hydro based9% from hydro based

3% from nuclear3% from nuclear

1% from windmills and photovoltaic put1% from windmills and photovoltaic put

together hence scope to increasetogether hence scope to increase

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EndEndThank YouThank You