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MODELING AND ANALYSIS OF A SOLAR MODELING AND ANALYSIS OF A SOLAR PHOTOVOLTAIC ASSISTED ABSORPTION PHOTOVOLTAIC ASSISTED ABSORPTION

REFRIGERATION SYSTEMREFRIGERATION SYSTEM

Presented by Dr. Aritra Ganguly

Assistant Professor

Department of Mechanical EngineeringBengal Engineering and Science University, Shibpur

Howrah, West Bengal-711103

Presented at

IVth

International Conference on Advances in Energy Research

Indian Institute of Technology Bombay

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OVERVIEW OF PRESENTATION

Introduction and Objective of the work

Mathematical model of Absorption system

Modeling of solar photovoltaic modules

Results and Discussion

Conclusions

References

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INTRODUCTION Air-conditioning has now become an integral part of modern life not only

from the view point of luxurious comfort, but also as a necessity in

places, where the weather condition is hostile.

Conventional VCR-based air-conditioning systems are most common in

domestic applications.

Large power consumption by the compressor, in view of present trend

towards energy conservation, is a matter of serious concern.

Harmful effects on the environment by the use of synthetic refrigerants

and lack of knowledge about the use of natural replacements are also

worrying factors.

Use of vapor absorption based system offers an attractive alternative to

technologists.

PROBLEMS OF VAPOUR COMPRESSION SYSTEM

• Large power consumption of compressor especially during start.

• Poor performance at part load condition.

• Necessity to superheat the refrigerant leaving the evaporator before entering compressor

• Harmful effects of synthetic refrigerant on environment.

Fig.1: Vapour Compression System

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ADVANTAGES OF VAR SYSTEM

Operated by low-grade thermal energy, instead of high-grade

electrical energy

Noise free operation & less maintenance requirement.

Absence of compressor — no problems with rotary component.

Can operate at reduced evaporator temperature and pressure.

The performance is marginally influenced under part load

condition.

The system can be built in very high capacities, even above

1000 TR.

The system can be used where the electricity is difficult to obtain

or is expensive.

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OBJECTIVE OF THE PRESENT WORK

Present work conceptualizes the use of solar photovoltaic

modules for powering a LiBr-H2O absorption system for a

cooling load of 0.5 TR.

A mathematical model has been developed for the LiBr-

H2O absorption refrigeration system as well as its power

system.

Performance analysis of the VAR as well as the power

system for representative days of various seasons of a

climatic cycle.

Computation of cumulative daylong electrical energy

supplied to and discharged from the battery.

SCHEMATIC REPRESENTATION OF PV POWERED VAR SYSTEM

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Fig.2: Schematic of PV POWERED VAR System

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MATHEMATICAL MODEL OF VAR SYSTEM

Condenser (TC )

QC

Generator (TG )

QG

Evaporator (TE )

QE

Absorber (TA )

QA

Heat Exchanger

1

2

3

4

5

6

7

10

8

9

Evaporator pressure (pE )

Condenser pressure (pC )

Refrigerant side

Mixture side

Fig.3: Schematic of VAR System

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MATHEMATICAL MODEL OF VAR SYSTEM

34 hhQm ER

wswsssss mXmX

wsRss mmm

781 hmhmhmQ sswsRG

56 hhmW RP

PGE WQQCOP

(1)

(2)

(3)

(4)

(5)

(6)

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MODELING OF SOLAR PHOTOVOLTAIC SYSTEM

iPV

iL

iD V

Rs

Fig. 4: Equivalent circuit diagram of a solar photovoltaic cell.

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Modeling of Solar Photovoltaic (PV) system Contd.

• The cell terminal current can be expressed as:

DLPV iii (7)

tref

trefuleulescscrefL I

ITTiii )](1[ modmod

(8)

(9)

1)

)(exp(

module

sPVsatD KT

RiVqii

(10)ule

systems V

VN

mod

The value of series resistance being very small, it has been neglected in the

present analysis (Paul et al. 2004).

RESULTS AND DISCUSSION

12Fig. 5: Hourly variation of mass flow rate of strong solution, weak solution, refrigerant and

generator heat load for the month of January.

RESULTS AND DISCUSSION contd.

13Fig. 6: Variation of electrical energy supplied to and discharged from the battery for a

representative day in January


representative day in March



representative day in May



representative day in September


Cumulative Daylong Electrical Energy Supplied to and Discharged from the Battery

January March May September

Energy to battery (Ah) 874 1246 1428 1246

Energy from

battery (Ah)138 139 231 141

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CONCLUSION

• A model for a solar photovoltaic powered LiBr-H2O absorption refrigeration system with battery back-up has been developed for a cooling load of 0.5 TR.

• The performance of the system has been analyzed for various seasons of a full climatic cycle considering weather data for the place as input.

• The study revealed that fifty two number of modules (CEL Make PM 150) each having two modules in series along with a battery bank of 1200 Ah ( 6 x 200 Ah) can power the system in a standalone manner.

• There is a considerable surplus of electrical energy in the battery throughout the year which can meet the requirement of energy deficit hours of the day satisfactorily. The surplus is found to be the maximum in May.

• The study thus reinforces the viability of a standalone LiBr-H2O absorption system which can meet its own energy needs through solar photovoltaic modules and also cater to the energy requirements of the surrounding community. 18

References Kim, D.S. and Ferreira, C.A.I. (2008) Solar refrigeration options – a state-of-the-art review, International Journal of

Refrigeration, 31, pp. 3–15. Pongtormkulpanicha, A., Thepa, S., Amornkitbamrung and Butcher, C. (2008) Experience with fully operational

solar driven 10 ton LiBr-H2O single effect absorption cooling system in Thailand, Renewable Energy, 33, pp. 943–949.

Enibe, S.O. (1997) Solar refrigeration for rural applications, Renewable Energy, 12, pp. 157-167. Chen, G. and Hihara, E. (1999) A new absorption refrigeration cycle using solar energy, Solar Energy, 66, pp. 479-

482. Patek, J. and Klomfar, J. (2006) A computationally effective formulation of the thermodynamic properties of LiBr–

H2O solutions from 273 to 500 K over full composition range, International Journal of Refrigeration, 29, pp. 566–578.

Wagner, W., Cooper, J.R., Dittmann, A., Kijima, J., Kretzschmar, H-J., Kruse, A., Mareš, R., Oguchi, K., Sato, H., Stöcker, I., Šifner, O., Takaishi, Y., Tanishita, I., Trübenbach, J. and Willkommen Th. (2000) The IAPWS industrial formulation 1997 for the thermodynamic properties of water and steam, Journal of Engineering Gas Turbine and Power, 122, pp. 150-182.

Chenni, R., Makhlouf, M., Kerbache, T., Bouzid, A. (2007) A detailed modeling method for photovoltaic cells, Energy, 32, pp. 1724-1730.

Tiwari, G.N. (2004) Solar energy-Fundamentals, design, modeling and applications, Narosa Publishing House, New Delhi, India.

Available online at www.celindia.co.in (accessed on 1.11.2011). Telecommunication Engineering Centre (TEC), New Delhi. Planning and maintenance guidelines for SPV (solar

photovoltaic) power supply. 2004; available online at http://www.tec.gov.in/guidelines.html (accessed on 27.05.2012).

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