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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
2
OVERVIEW OF PRESENTATION
Introduction and Objective of the work
Mathematical model of Absorption system
Modeling of solar photovoltaic modules
Results and Discussion
Conclusions
References
3
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
5
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.
6
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.
8
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
9
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)
10
MODELING OF SOLAR PHOTOVOLTAIC SYSTEM
iPV
iL
iD V
Rs
Fig. 4: Equivalent circuit diagram of a solar photovoltaic cell.
11
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
14Fig. 7: Variation of electrical energy supplied to and discharged from the battery for a
representative day in March
RESULTS AND DISCUSSION contd.
15Fig. 8: Variation of electrical energy supplied to and discharged from the battery for a
representative day in May
RESULTS AND DISCUSSION contd.
16Fig. 9: Variation of electrical energy supplied to and discharged from the battery for a
representative day in September
RESULTS AND DISCUSSION contd.
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
17
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).
19