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During coming years, India is going to witness a huge economical growth. This growth is

having a very deep impact in the energy needs. Probably the most important energy to

be available or this development is the electricity.

Manuel Millan Sanchez & Sanjay Gulati, tractebel enGineerinG

Integration in conventional coal

fred power plants: the easiest andlogical way or the development oConcentrated Solar Power in India

Nowadays the installed power gen-

erating capacity in India is around

160 GWe. From this amount al-

most 53% comes rom coal red plants

(85GW). Also, or 2031-2032, the Inte-

grated Energy Policy o India has oreseenan installed capacity o about 778 GWe

(386% increase!), mainly with ossil uels

and specically coal. It will be illogical to

think about India power sector uture, in

the short and mid term, without coal and

sub and supercritical coal red plants.

Though India has huge coal reserves,

the sustainability principle and environ-

mental and climate change policies should

press to give more eciency and renew-

able approach to this enormous amount o

power to be installed.On the other hand, the dispatchabil-

ity and availability o electrical energy is

a must, taking into account that uture

o the economic development will be de-

pendent on this production o electricity.

At this moment the contribution o

solar energy within the spectrum o power

production in India is negligible. Even, a-

ter the rst phase o Jawahar Lal Nehru

National Solar Mission (JNNSM) the con-

tribution will not be more than testimo-

nial. For that reason, it is essential to nda good solution to achieve the entire goal

at once: Whole power availability and dis-

patchability with the highest possible con-

tribution o renewable energy in the Indian

generation spectrum.

Other important actors to be consid-

ered are the ideal position o India within

the Sunbelt with part o the best areas

in the world in terms o Direct Normal Ir-

radiation (DNI) and huge acreages o land

to be used or solar power generationpurposes.

Around the world, there are already

several integrated plants in commercial

operation, combining the conventional

power generation rom ossil uels and the

solar power generation, which have been

built in dierent locations between 2007and 2011: Ain Beni Mathar (Morocco),

Hassi Rmel (Algeria), Kuraymat (Egypt),

Martin Energy Center (Florida-USA), Agua

Prieta (Mexico, under construction).

Joining all these ideas, it is possible,

and almost obvious, to think that integra-

tion should be the more logical and natu-

ral solution or the solar power generation

development in India. This article deals

with this option and how the integration

can emphasize the contribution o solar

energy integration in existing and newpower plants in India and it could be a ea-

sible way to enhance the solar generation

in the country and a very eective energy

eciency measure.

COALPOWER

2 APRIL11 energetica india

Figure 1. Integration types in Brayton, Rankine and Combined Cycles.

At this mOment the

COntributiOn Of sOLArenergy within the speCtrum

Of pOwer prOduCtiOn in

indiA is negLigibLe

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Solar-conventional integration

In the last ew years, several theoreticaland practical studies have been carried

out to dene dierent ways o integration

between conventional and solar power

production. These ways have been studied

both or standalone Rankine cycles (like

coal red plants) and or combined cycles.

In the Figure 1 is shown a general concep-

tual scheme o dierent kind o integra-

tion considering the several places where

the solar heat could be integrated into

the conventional cycle.

These kinds o integration can be clas-sied rom the point o view o easiness to

be tted in the power plant and they can

be divided in the ollowing types:

Hybridization: intrinsically inserted into

the process. These should come imple-

mented rom the original design be-

cause several equipment designs are

conditioned or them.

Externally add-on to the process. These

can be implemented in existing plants

because they do not aect main equip-

ments design.Both types are applicable in India gen-

eration range, depending on the phase

when the process is going to be imple-

mented. For existing plants, o course, the

externally add-ons are technically more

easily easible.

Regarding the solar technologies to

be used, almost all integration types could

be implemented with parabolic trough (oil

based or DSG), Fresnel technology or Cen-

tral Receiver System.

Making a brie comparison betweenintegrated plants and stand alone solar

plants it is easy to nd the ollowing ad-

vantages:

Much less investment because most o

the main equipments are included and

shared with the conventional plant:

steam turbine, cooling system, con-

denser system, electrical system, etc.

Dispatchability: The electrical power

is always available, during daylight itcomes, in part, rom the sun, but during

night time or transients the convention-

al part remains in operation, so there is

no discontinuity or lack o supply.

No need o storage: The storage is

conceived to provide dispatchability,

but in this case the conventional part

gives it.

Increasing power or uel saving: there

are two possibilities in the integration,

to design it or increasing the power, i

equipments allow it or or substitutingpart o uel consumption with solar en-

ergy contribution.

Better perormance or equipments in

long term: Due to the continuous oper-

ation o main equipments o the plant,

the daily starts and stops o the plant

get avoided, which otherwise are very

harmul or equipments.

Grid connection solved: When the inte-

gration is carried out within an existing

plant all problems related with grid con-

nection are already resolved. Competitive LEC: Besides the lower in-

vestment, the cost o maintenance is

also less because this cost is shared with

the whole plant one.

India scenario

Some authors have developed very inter-esting articles about specic solar thermal

aided in coal red power plant. One inter-

esting article, written by K.S. Reddy et al

(2010), includes a very deep 4-E analysis o

power gains using solar energy into sub-

critical and supercritical coal red plants.

As main conclusion, an important uel

consumption reduction and CO2

emissions

reduction are achieved.

Far away o that objective, this paper

does not deal to demonstrate strictly the

power gain including solar add-on, whichis depending on the plant conguration

and the integration nature. Here, the solar

energy addition is considered as a whole,

taking into account an average peror-

mance, giving more importance to the DNI

value analysis in dierent Indian locations

and highlighting the signicance and links

between this DNI and coal red plant gen-

eration in the country.

Considering the whole spectrum o

Indian power generation rom coal red

plant, in Figure 2 is shown the geographicaldistribution o this electrical generation.

As it has been commented beore, the

solar resource in India is also very high in

great part o the country. Figure 3 depicts

the DNI map rom NREL showing the di-

erent DNI values within the Indian Terri-

tory.

Best DNI areas lie in Northern, West-

ern and Southern states. Western ones

enjoy a DNI close to 2400 kWh/m2 year,

which is an excellent value or solar plants

perormance.Joining o two geographical distribu-

tions has been elaborated graphically in

the Figure 4, rom where it is possible to

obtain some conclusions as under:

COALPOWER

3energetica india APRIL11

Figure 2. Electrical production from coal. Geographical distribution in India. Figure 3. DNI geographical distribution in India

ALmOst ALL integrAtiOntypes COuLd be impLemented

with pArAbOLiC trOugh

(OiL bAsed Or dsg), fresneL

teChnOLOgy Or CentrAL

reCeiver system

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COALPOWER

4 APRIL11 energetica india

Considering the 8 main states in pow-

er generation capacity rom coal, 7 o

them have excellent or very good DNI.

States with lowest DNI, & hence less ea-

sible or solar power plant, have insigni-

cant coal based power generation.

For more than 95% o power genera-

tion capacity locations, the solar plants

appear to be highly easible consideringthe DNI.

Gains with solar add-on in coal

fred power plant

Modelling a general solar eld and taking

into account the ollowing hypothesis:

Average perormance or a solar tech-

nology: Sun to steam

Nominal optical parameters in the solar

device

Average perormance or the Rankine

cycle: Steam to electricity The average coal LHV in India

it is possible to generate or dierent

DNI values, the amount o uel saved per

year vis-a-vis mirrors surace area. Figure 5

shows this graphic rom where it is easy to

conclude:

With a moderate solar eld size, it is

possible to obtain an important solar

power generation capacity.

The coal saving amount is linear with

the solar device surace area.

Above all, it is a matter o economicalbalance to determine the easibility or

installing such solar device, even with-

out a supporting eed-in tari or any

other incentive.

As an exercise, analysing a virtualscenario where existing coal red plant in

Northern and Western States were pro-

vided with a solar device, it is possible to

obtain around 500 MW rom Solar power

with the basis that 1% (as average) o

power source rom coal is substituted by

solar energy in all the plants.

Conclusions

Ater the refections realised in this article

we can obtain a wide range o conclu-

sions, both technical and economical.India has a very important conven-

tional power production rom dierent

sources, with special importance o coal

red plants. In coming 20 years the avail-

ability o power must increase seriously to

ace the industrial and social development

o the country.

Also India has globally a very high DNI,

and the areas with higher DNI match up

with high coal red production capacity.The integration o solar energy into

conventional power plant is a very good

option to reduce environmental eects, or

increasing the renewable and solar quota

in the energy market and or improving

the economical benet o the production

by saving tonnes o coal consumption.

The hybridation also has a lower

cost o investment than stand alone solar

plants, due to the sharing o main equip-

ments that are already considered within

the whole conventional power plant(steam turbine, cooling system, condenser

system, electrical system, etc...).

Thus, the cost o this solar energy is

much cheaper and could permit to devel-

op, at good price, new plants and, at same

time, to improve progressively the state

o the art, the technological knowledge

in order to decrease quickly the invest-

ment cost o solar plant aiming to become

competitive to the conventional ones in a

shorter span o time.

So, as general conclusion, the inte-gration o solar energy into conventional

power plants is a very good alternative or

developing solar power production in In-

dia.

Figure 5. Coal saving and power generatingcapacity with solar add-on..

Figure 4. DNI-Power generation in India.

in COming 20 yeArs the

AvAiLAbiLity Of pOwer

must inCreAse seriOusLy

tO fACe the industriAL And

sOCiAL deveLOpment Of the

COuntry

the hybridAtiOn hAs A LOwer

COst Of investment thAn

stAnd ALOne sOLAr pLAnts,

due tO the shAring OfmAin equipments thAt Are

ALreAdy COnsidered within

the whOLe COnventiOnAL

pOwer pLAnt