Energy Lecture 10 SolarPower

8/17/2019 Energy Lecture 10 SolarPower

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07-Feb-2011 M Subramanian

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About Solar Energy

Solar energy is the most ancient source' and it is the rootmaterial for almost all fossil and renewable types.

Among the renewable energy sources' solar energy comes at thetop of the list due to its abundance' and more evenly distributionin nature than any other renewable energy types such as wind'geothermal' hydro' wave and tidal energies.

Appro/imately & 0 of the world1s desert area utili2ed by solarthermal power plants would be sufficient to generate the world1sentire electricity demand.




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*he Solar Spectrum

Solar intensity outside the atmosphere3 &.%# !45m6

+ncident solar intensity on the atmosphere3 &.$ !45m67 due toabsorption by water vapor' C86' etc.

9adiation reaches the Earth:s surface by direct radiation(focusable by mirrors) and diffuse radiation (unfocusable)

*he diffuse percentage is strongly dependent on how clear thes!y is' and a typical yearly average if about %$0.




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Solar intensity outside the atmosphere: 1.36 kW/m2

Incident solar intensity on the atmosphere: 1.0 kW/m2; due to absorption by water

vapor, CO2, etc.




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Direct and Diffuse 9adiation




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Solar Potential

Insolation for most part is from 150 to 300 W/m² or 3.5 to 7.0 kWh/m²/day.

World’s solar potential is about 100,000 TW. The small black dots show the area

of solar panels needed to generate all of the world's energy using 8% efficient

photovoltaics.




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Solar Map

of +ndia




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Solar Potential of +ndia

+ndia is endowed with vast solar energy potential. About 5,000trillion kWh per year energy (&;% 45m6) is incident over+ndia:s land area with most parts receiving . m

per day.

+n most parts of +ndia' clear sunny weather is e/perienced 6?$to %$$ days a year. *he annual global radiation varies from $$to 66$$ !4h5m6

+ndia is both densely populated and has high solar insolation'providing an ideal combination for solar power in +ndia.

+n solar energy sector' some large pro@ects have been proposed'and a %?'$$$ !m area of the *har Desert has been set aside forsolar power pro@ects' sufficient to generate ;$$ to 6'&$$gigawatts.




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Solar Energy Developments in 4orld

*he solar thermal power industry is growing rapidly with &.6 B4under construction as of April 6$$ and another &%. B4

announced globally through 6$&


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No. Sources / Systems Cumulative

Achievements (upto31.03.010!

A. Grid Interactive Power

& Solar Power &$.6 M4

"rom all rene#a$le sources 1%&1'. )W

B. Off-Grid Power

& Solar PF Power Plants 6.


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8pportunities for Solar Power in +ndia

Solar thermal power generation can play a significant importantrole in meeting the demand supply gap for electricity. *hreetypes of applications are possible3

&. 9ural electrification using solar dish collector technology3 byhybridi2ing them with biomass gasifier for hot air generation.

6. +ntegration of solar thermal power plants with e/istingindustries such as paper' dairy or sugar industry' which hascogeneration units.

%. +ntegration of solar thermal power generation unit withe/isting coal thermal power plants. Savings of upto 6


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National Solar Mission of +ndia *arget of 6$ B4 by the year 6$66 (i.e. by the end of &%th Iive

Jear Plan)

*he Mission anticipates achieving grid parity by 6$66 and paritywith coal=based thermal power by 6$%$.

*he !ey driver for promoting solar power would be through a9enewable Purchase 8bligation (9P8) mandated for powerutilities' with a specific solar component. *his will drive utilityscale power generation' whether solar PF or solar thermal




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National Solar Mission (contd.)

!e mission wo"ld #e res$onsi#le for%

Deployment of commercial solar technologies in the country

Establishing solar research facility

Encouraging private sector for manufacturing solar cells'e>uipments' etc.

Promoting collaborative research with international activities




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Progress of Solar in +ndia

Kangalore has the largest deployment of rooftop solar waterheaters in +ndia that will generate energy e>uivalent to 6$$ M4

everyday and will be the country1s first grid connected utilityscale pro@ect soon.

Kangalore is also the first city in the country to put in place an

incentive mechanism by providing a rebate' which has @ust beenincreased to 9s ?$' on monthly electricity bills for residents usingroof=top thermal systems which are now mandatory for all newstructures.

*ata Power has decided to set up ?$ M4 solar photovoltaicpower pro@ect at Mithapur in Bu@arat. *his proposed pro@ect willbe the largest single solar photovoltaic installation in the country




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Challenges and Constraints

*he investment cost stand=alone solar thermal power plants arein the range of 9s. 6$=66 Crore 5 M4' and that of solar pv based

power systems are in the range of 9s. %$=6? Crore 5 M4'compared to the investment cost of L 9s. # Crore 5 M4 for coalbased plants.

*he cost of production ranges from 9s &? to 9s %$ per unit

compared to around 9s ? to 9s per unit for conventionalthermal energy.

Per capita land availability is a scarce resource in +ndia. *heamount of land re>uired for utility=scale solar power plants

currently appro/imately & !m for every 6$"#$ megawatts (M4)generated could pose a strain on +ndia1s available landresource.




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9esearch Directions

+mproving the efficiency of solar pv cells

Iinding new materials

+mproving the battery life' energy storage systems

Application oriented research




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Converting Solar Energy

*here are three processes for converting solar energy

" heliochemical3 the photosynthesis process

" heliothermal3 heating of a secondary fluid (solar thermal)

" helioelectrical3 photovoltaics (solar cells)


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Solar Collection Systems *here are three general categories of solar=energy collection

systems3

" direct conversion of sun rays to electricity with solar cells(photovoltaics)'

" flat=plate systems producing low=temperature (&?$OI)

thermal energy for heating and cooling of buildings7 thethermal energy generated in the collector is usually removedby either air or an ethylene glycol=water solution' and

" concentrating solar collection systems that produce high=temperature thermal energy for the generation of electricity.


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Solar Photovoltaics

Solar photovoltaic (solar cell) is a direct conversion of the sun1selectromagnetic radiation to electricity' and is not limited byCarnot cycle efficiency considerations.

Photovoltaic (PF) cells employ a solid=state diode structure witha large area on a silicon wafer. *he surface layer is very thin andtransparent so that light can reach the @unction region of thesilicon sandwich. +n that region the photons are absorbed'releasing charges from their atomic bonds. *hese chargesmigrate to the terminals' raising the potential.

A single cell has an open circuit the voltage of appro/imately$.#=&.$ volts and a short circuit current of a few mA.

+n order to increase both current and voltage' the individual cellsare placed into (solar) arrays where cells may be connected inseries to raise the voltage and current output can be raised byparallel connection of cells.




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Photovoltaic 'tree' in Styria, Austria

•A more efficient conversion

(15%) of solar energy to electricalenergy is provided byphotovoltaic (PV) cells.




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Solar *hermal

Solar thermal is the use of a vapor power cycle that re>uires theconcentration of solar energy to reach high temperatures and

reasonable thermal efficiency.

Solar thermal energy concentration devices include parabolicmirrors and arrays of focused mirrors (heliostats)




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Solar *hermal Collectorsflat=plate collector


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Classification of Solar *hermal Systems based

on Iocus

large point focus3 power tower systems with heliostats. Moltensalts and li>uid metals are used as the wor!ing fluid that then

boils water for use in a 9an!ine cycle. Si2es of &$$ !4e to &$$M4e.

small point focus3 use parabolic hemispherical dishes to reflectlight to a focal point on each individual dish. *hese are forremote stand=alone systems (?=6? !4e)' and

line focus systems3 use parabolic shaped troughs' and havelower efficiency.




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Parabolic *rough Solar Collector



S l E B i S


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Solar Energy Benerating Systems

(SEBS) (SS! is the largest solarenergy generating facility in theworld.

+t consists of nine solar powerplants in California1s Mo@aveDesert' where insolation isamong the best available in the

nited States.

+nstalled capacity3 %?< M4

*he average gross solar outputfor all nine plants at SEBS isaround ;? M4 a capacityfactor of 6&0




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SEBS = +nstallations

*he facilities have a total of %#'%< mirrors and cover morethan &'#$$ acres (#.? !m6). Hined up' the parabolic mirrors

would e/tend over 66 miles (%;$ !m).

*he installation uses parabolic trough solar thermal technologyalong with natural gas to generate electricity. $0 of the

electricity is produced by the sunlight. Natural gas is only usedwhen the solar power is insufficient to meet the demand




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SEBS = Mirrors

*he parabolic mirrors are shaped li!e a half=pipe. *he sun shinesonto the panels made of glass' which are


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SEBS " Geat *ransfer

*he sun bounces off the mirrors and is directed to a central tubefilled with synthetic oil' which heats to over


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Dish=Stirling Systems

Dish"Stirling systems can beused to generate electricity inthe !ilowatts range.

A parabolic concave mirror (thedish) concentrates sunlight7 +nthe focus is a receiver which isheated up to #?$OC. *heabsorbed heat drives a Stirlingmotor' which converts the heat

into motive energy and drives agenerator to produce electricity.

*he system efficiency of Dish"Stirling systems can reach 6$0

or more. *he electricitygeneration costs of thesesystems are much higher thanthose for trough or tower powerplants.




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Aerial Photo of the Solar One 10 MWe Central Receiver Power Plant inDaggett, CA




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Efficiency of Solar *hermal Power Plants

Altogether' solar thermal trough power plants can reach annualefficiencies of about &?07 the steam=cycle efficiency of about

%?0 has the most significant influence. Central receiver systemssuch as solar thermal tower plants can reach highertemperatures and therefore achieve higher efficiencies.


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Solar Chimney


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Solar Chimney




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Solar Chimney

*he solar up2rat to#er is a proposed type of renewable=energy power plant. +t combines three old and proventechnologies3 the chimney effect' the greenhouse effect' and the

wind turbine.

Air is heated by sunshine and contained in a very largegreenhouse=li!e structure around the base of a tall chimney' and

the resulting convection causes air to rise up the updraft tower.*his airflow drives turbines' which produce electricity.

Geat can be stored inside the collector area greenhouse to be

used to warm the air later on. 4ater' with its relatively highspecific heat capacity' can be filled in tubes placed under thecollector increasing the energy storage as needed.



The First Pilot Plant


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A pilot solar chimney projectwas installed in

Spain to test the concept. This50kW capacity plant wassuccessfully operated between1982 to 1989.

The chimney had a height of195 m and a diameter of 10 mwith a collection area(greenhouse) of 46,000 m²(about 11 acres, or 244 mdiameter) obtaining amaximum power output of

about 50 kW.

Based on the test results, it was estimated that a 100 MW plant would requirea 1000 m tower and a greenhouse of 20 km2. Conversion efficiency of solar

energy to electrical energy is about 0.5 %.07-Feb-2011 M Subramanian



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Advantages of Solar Energy

*he advantages of solar energy include

" its nonpolluting nature7

" it is nondepletable'

" reliable' and

" free fuel.




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Disadvantages of Solar Energy

*he disadvantages of solar energy are

" the solar energy concentration is very dilute' so collectorswith large surface area are needed.

" +n addition' solar radiation is neither constant nor continuous

for terrestrial applications (i.e.' low capacity factor).

" *he solar energy received depends on latitude' season' time=of=day' and atmospheric conditions.



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Energy Lecture 10 SolarPower