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### 57 ganguly

1. 1. MODELING AND ANALYSIS OF A SOLAR PHOTOVOLTAIC ASSISTED ABSORPTION REFRIGERATION SYSTEM Presented by Dr. Aritra Ganguly Assistant Professor Department of Mechanical Engineering Bengal Engineering and Science University, Shibpur Howrah, West Bengal-711103 IV th Presented at International Conference on Advances in Energy Research
2. 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 2
3. 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. 3
4. 4. PROBLEMS OF VAPOUR COMPRESSION SYSTEM • • Poor performance at part load condition. • Necessity to superheat the refrigerant leaving the evaporator before entering compressor • Fig.1: Vapour Compression System Large power consumption of compressor especially during start. Harmful effects of synthetic refrigerant on environment.
5. 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. 5
6. 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 6 supplied to and discharged from the battery.
7. 7. SCHEMATIC REPRESENTATION OF PV POWERED VAR SYSTEM 7 Fig.2: Schematic of PV POWERED VAR System
8. 8. MATHEMATICAL MODEL OF VAR SYSTEM QC QG 1 Condenser (TC ) Generator (TG ) 8 7 Condenser pressure (pC ) 2 Refrigerant side Mixture side Heat Exchanger 9 6 Evaporator pressure (pE ) 3 Evaporator (TE ) QE 5 4 10 Absorber (TA ) QA Fig.3: Schematic of VAR System 8
9. 9. MATHEMATICAL MODEL OF VAR SYSTEM  mR =QE (h4 −h3 ) (1)   X ss mss = X ws mws    mss = m R +mws    QG = mR h1 +mws h8 −mss h7  WP = mR ( h6 −h5 ) COP =QE (QG +WP ) (2) (3) (4) (5) (6) 9
10. 10. MODELING OF SOLAR PHOTOVOLTAIC SYSTEM iPV Rs iD V iL Fig. 4: Equivalent circuit diagram of a solar photovoltaic cell. 10
11. 11. Modeling of Solar Photovoltaic (PV) system Contd. • The cell terminal current can be expressed as: i PV =i L −i D i L = i scref [1 + ∆i sc (Tmod ule −Tmod ule ref iD (7)  It )] ×  I tref        q (V +i PV × Rs ) = i sat exp( ) −1 γKTmod ule   Ns = Vsystem Vmod ule (8) (9) (10) 11 The value of series resistance being very small, it has been neglected in the present analysis (Paul et al. 2004).
12. 12. RESULTS AND DISCUSSION Fig. 5: Hourly variation of mass flow rate of strong solution, weak solution, refrigerant and generator heat load for the month of January. 12
13. 13. RESULTS AND DISCUSSION contd. Fig. 6: Variation of electrical energy supplied to and discharged from the battery for a representative day in January 13
14. 14. RESULTS AND DISCUSSION contd. Fig. 7: Variation of electrical energy supplied to and discharged from the battery for a representative day in March 14
15. 15. RESULTS AND DISCUSSION contd. Fig. 8: Variation of electrical energy supplied to and discharged from the battery for a representative day in May 15
16. 16. RESULTS AND DISCUSSION contd. Fig. 9: Variation of electrical energy supplied to and discharged from the battery for a representative day in September 16
17. 17. Cumulative Daylong Electrical Energy Supplied to and Discharged from the Battery January Energy to battery (Ah) Energy from battery (Ah) March May September 874 1246 1428 1246 138 139 231 141 17
18. 18. CONCLUSION • • • • • A model for a solar photovoltaic powered LiBr-H 2O 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-H 2O absorption system which can meet its own energy needs through solar photovoltaic modules and also cater to the energy requirements of the 18 surrounding community.
19. 19. 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
20. 20. THANK YOU 20