Modeling of Solar Photovoltaic Assisted Vapor Absorption Refrigeration System for Storing Different Vegetables

Transcription

1 Internatonal Journal of Engneerng Technology Scence and Research Modelng of Solar Photovoltac Asssted Vapor Absorpton Refrgeraton System for Storng Dfferent Vegetables Kamaljyot Talukdar Assstant Professor Department of Mechancal Engneerng, Bneswar Brahma Engneerng College,Kokrajhar, Assam Abstract:In ths paper,a detaled modelng of solar photovoltac asssted vapor absorpton refrgeraton system s done for storng vegetables safely lke carrots, potatoes and tomatoes n Kolkata cty located n Inda throughout the year.the mass of each vegetable s taken to be 5 tons.e. 5000kg and storage temperature for each vegetable s 15 o C. The analyss s done for month January and May due to the fact that January month has lowest solar radaton and May month has hghest solar radaton. Hence a combned photovoltac and vapor absorpton refrgeraton system whch works well n these two months can easly operate the combned system throughout the year. It s found that 17, 13, and 12 modules n parallel each havng 2 modules n seres of Central Electroncs Lmted Make PM 150 for vegetables carrots,potatoes and tomatoes respectvely can support the coolng requrement of vegetables present n godown. The power back up s provded usng battery bank of rated capacty of 239 Ah. 1.Introducton Use of solar energy s a very demandng technology. Solar radaton s obtaned on earth abundantly. If solar energy s used by dfferent technologes the energy crss can be mtgated. Many people have used solar technology n dfferent ways. Tsoutsos et al[1] studed the performance and economc evaluaton of a solar heatng and coolng system of a hosptal n Crete usng the transent smulaton program (TRNSYS).Rvera et al[2]presented a novel solar ntermttent refrgeraton system for ce producton developed n the Centro de Investgaco n en Energı a of the Unversdad Naconal Auto noma de Me xco. Pongtornkulpanch et al[3]desgned a solar-drven 10-ton LBr/H 2 O sngle-effect absorpton coolng system and nstalled at the School of Renewable Energy Technology (SERT), Phtsanulok, Thaland. Dorantes et al[4] presented a mathematcal smulaton for the dynamc thermal behavor of a solar ejector-compresson refrgeraton system wth a capacty producton of 100 kg of ce per day.guo and Sen[5] proposed a lumped method combned wth dynamc model for use n nvestgatng the performance and solar fracton of a solar-drven ejector refrgeraton system (SERS) usng R134a, for offce ar condtonng applcaton for buldngs n Shangha, Chna. Vdal et al[6] dealt wth the hourly smulaton of an ejector coolng cycle asssted by solar energy. The system was smulated usng the TRNSYS program and the typcal meteorologcal year (TMY) fle that contaned the weather data from Florano pols, Brazl.Helm et al[7]presented the system concept and the hydraulc scheme together wth an analyss of the energetc performance of the system followed by a report on the operaton of a frst plot nstallaton. Best and Ortega[8] presented a revew of solar coolng and refrgeraton technologes and a dscusson on the man reasons why these technologes were not presently economcally feasble was carred out and two nstallatons n Mexco were analysed. Enbe [9] dscussed photovoltac (PV) powered vapour compresson systems ; contnuous and ntermttent lqud or sold absorpton systems; and adsorpton systems.the author dscussed techncal and fnancal constrants whch lmt ther wdespread applcaton and strateges for overcomng them. In many applcatons excess energy generated s lost. Rechargeable battery technology can store excess energy generated to store excess energy and can be used durng energy defcent perod. Nar and Garmella[10] provded a modellng framework to be able to quantfy the assocated benefts of renewable resource ntegraton followed by an overvew of varous small-scale energy storage technologes.they presented a 168 Kamaljyot Talukdar

2 Internatonal Journal of Engneerng Technology Scence and Research smple, practcal and comprehensve assessment of battery energy storage technologes for small-scale renewable applcatons based on ther techncal mert and economc feasblty. Software such as Smulnk and HOMER provded the platforms for techncal and economc assessments of the battery technologes respectvely.ortz et al[11]demonstrated the feasblty of the desalnaton of bracksh water by means of an electrodalyss system powered drectly by photovoltac solar panels,and explaned theoretcally the nteracton between the photovoltac generator and the electrodalyss system durng the process.urbna et al[12]nvestgated the relablty of a rechargeable battery actng as the energy storage component n a photovoltac power supply system.they constructed a model that ncluded the solar resource, the photovoltac power supply system, the rechargeable battery and a load. The photovoltac system and the rechargeable battery were modelled determnstcally, and an artfcal neural network was ncorporated nto the model of the rechargeable battery to smulate damage that occured durng deep dscharge cycles. In the present study solar photovoltac modules asssted vapor absorpton refrgeraton system s used for storng dfferent vegetables.e. carrots, potatoes and tomatoes. Vegetables releases heat durng storng perod. So f ths heat s not rejected then vegetables may get spolt. So current generated by PV modules s gven to generator of vapor absorpton refrgeraton system (VARS) and the system contnues n operaton. 2.System Layout Fg.1 Schematc vew of combned photovoltac and VAR system when current produced by photovoltac modules s more than the current requred for generator. When solar radaton s avalable n plenty.e from 6:00hours to 18:00hours, solar modules generate current (I PV ).The excess current after meetng the requrement of vapor absorpton refrgeraton system(vars) generator( I G )goes to rechargeable battery(i PV I G ) for storng purpose. The current requrement for VARS generator (I G ) s dependent on heatng load and quantty of vegetables. 169 Kamaljyot Talukdar

3 Internatonal Journal of Engneerng Technology Scence and Research Fg.2 Schematc vew of combned photovoltac and VAR system when current produced by photovoltac modules s less than the current requred for generator. When solar radaton s not avalable n plenty.e. from 19:00hours to 5:00 hours, the current requrement (I G ) for VARS generator s obtaned from rechargeable battery whch stores the excess energy durng sunshne hours. 170 Kamaljyot Talukdar

4 Internatonal Journal of Engneerng Technology Scence and Research I G Q C Condenser T 1 VARS Generator Heat Exchanger Expanson valve Soluton pump Expanson valve Evaporator 4 Absorber Q E Vegetable godown Q A Fg.3 Schematc vew of vapor absorpton refrgeraton system. 171 Kamaljyot Talukdar

5 Internatonal Journal of Engneerng Technology Scence and Research Table 1. Operatng parameters of varous components n absorpton refrgeraton system Parameters Values Evaporator temperature 15 o C Absorber temperature 35 o C Heat exchanger effectveness 0.8 Generator temperature 80 o C Condenser temperature 35 0 C 3.Modelng of solar photovoltac modules The electrcal energy s generated by harnessng solar energy usng photovoltac modules. In the present work Central Electroncs Lmted Make PM-150 [13] solar photovoltac module has been used. The sngle cell termnal current s gven by[14]: PV (1) L D Where L s the lght current generated by a solar cell as a functon of solar radaton (G) and D s the dode current. The lght current generated from a photovoltac module at any gven ntensty of solar radaton and temperature s gven by [14]: L G scref sc T module Tmoduleref (2) G ref Where, G, G ref s the solar radaton at actual[15]and reference condton(1000 W/m 2 )[13] respectvely, scref -short crcut current at reference condton(a)[13], -manufacturer suppled temperature coeffcent of short crcut current(a/k)[13], condton(k)[13]. T mod ule and T mod uleref The module temperature s a functon of ambent temperature ( radaton(g) and gven by[14]: sc module temperature at actual and at reference T ambent ), wnd speed( v f ) and solar T ( K) (0.943T G v 4.3) (3) module ambent Where, T ambent s n 0 C[15], G n W/m 2 [15], v f wnd speed n m/s[16]. The dode current n equaton (1) s a functon of reverse saturaton current and gven by[14]: D q( V PV Rs ) exp sat 1 ktmodule f Where sat - reverse saturaton current(a), q -electron charge(1.6 x C), V -termnal voltage(v), R S -seres resstance, -shape factor, k -Boltzamann constant(1.38 x J/K). sat satref T T moduleref 3 q G 1 exp (5) ka Tmoduleref Tmodule module 1 where A-completon factor, G -materal bandgap(1.12ev for S),and (4) 172 Kamaljyot Talukdar

6 satref scref qv exp kt ocref moduleref Where Vocref -open crcut voltage at reference condton [13]. sat, sarref s taken from [14]. Shape factor ( ) whch s a measure of cell mperfecton s gven by[14]: N S Internatonal Journal of Engneerng Technology Scence and Research A NCS (7) Where A, NCS, N S s completon factor, number of cells connected n seres n a sngle module(specfed by manufacturer of the module) and number of modules connected n seres of the entre photovoltac array respectvely. N S Vsystem (8) V module Where Vsystem s the system voltage of the photovoltac array(consdered 48 V n present study) and ule s the voltage obtaned from sngle module. Current requrement on hourly bass( g ) s gven by: g V Where, system QG 1000 PF nverter QG -generator heat load on hourly bass, PF-power factor(0.85), nverter -nverter effcency(0.85) The desgn current requred from photovoltac array( spv ) s gven by: g, total DF spv (10) Peaksunshnehours Where I g,total s total current requrement n a day by generator of absorpton refrgeraton system n Ah, DF s de ratng factor of photovoltac module consdered to be 1.25[17], peak sunshne hours to be 7 hours[18]. No. of photovoltac modules n parallel(n p ) s gven by: spv N p (11) mpp Where mpp -current avalable from a sngle module under peak power condton. Net current from solar PV array s: array N (12) pv p (6) (9) V mod 3.Modelng of vapor absorpton refrgeraton system(vars) In the VARS, we consder a smple sngle effect H 2 O-LBr absorpton system consstng of a SHE(soluton heat exchanger). The Concentraton of the strong and weak soluton of the refrgerant as functons of operatng temperatures s known [19].Strong soluton concentraton s dependent on absorber and evaporator temperature, whle weak soluton concentraton s dependent on generator and condenser temperature. Thermodynamc propertes such as specfc enthalpy, entropy of the refrgerant (water) both n lqud and vapour state at varous pressures and temperature.e. at ponts 1,2,3, and 4 are determned from Internatonal Assocatons for the propertes of water and steam (IAPWS) formulaton 1997 [20]. Smlarly the thermodynamc propertes of H 2 O-LBr solutons at varous temperatures and concentraton.e at ponts 5,6,7,8,9 and 10 are calculated usng the correlatons proposed by Patek and Klomfar [21]. 173 Kamaljyot Talukdar

7 . Internatonal Journal of Engneerng Technology Scence and Research The mass flow rate of strong( m ss )along ponts 5,6,7and weak soluton( m ws )along ponts 8,9,10are calculated from the equatons from ref.[19]. The thermal load n the generator, absorber and condenser can be expressed as: Q m h m h m (13) Q Q G A C H2O 1 ws 8 ssh7 m (14) H2Oh4 mwsh10 mssh5 H2O h1 h2 m (15). QE mh O ( h4 h3 ) (16) 2 Where h -enthalpy at salent ponts, Q G -generator load, Q A -absorber load, Q c -condenser load.q E -evaporator load.. 4.Results and Dscusson A numercal code n C was developed for smulatng combned photovoltac and absorpton refrgeraton system for storng dfferent vegetables n godown. Table 2. Load requrements for storng dfferent vegetables. Commodtes Temperature( o C) Heat release n k J/ton-24hour TOR (for 5 tones of mass) Carrots [22] Potatoes [22] Tomatoes [22] In table 2 t s seen that vegetables are stored at 15 0 C. The heat release n k J/ton-24hour s obtaned from ref.[22]. The masses of each vegetables stored s 5 tones.e. 5000kg.Coolng load s gven n TOR.e. tons of refrgeraton Table3. Number of photovoltac modules requrement and cumulatve battery chargng and dschargng n dfferent months Commodtes No. of photovoltac modules n parallel No. of photovoltac modules n seres Battery charged(ah) for the month of January Battery dscharged(ah) for the month of January Battery charged(ah) for the month of May Battery dscharged(ah) for the month of May Carrots Potatoes Tomatoes Table 3 shows the number of photovoltac modules (n parallel and seres), battery chargng (Ah) and battery dschargng(ah) for the month of January and May. Here two months.e. January and May s taken because January month has lowest solar radaton and May month have hghest solar radaton. If a system works well n these two months t can work successfully throughout the year. Based on above mentoned results t s seen that rated battery capacty of Ah s suffcent to run the combned photovoltac and VAR system. 174 Kamaljyot Talukdar

8 Internatonal Journal of Engneerng Technology Scence and Research 5. Concluson Based on the analyss t s found that 17, 13, and 12 modules n parallel each havng 2 modules n seres of Central Electroncs Lmted Make PM 150 for vegetables carrots,potatoes and tomatoes respectvely of 5000 kg mass each can support the coolng requrement of vegetables present n godown located n Kolkata, Inda.The power back up s provded usng battery bank of rated capacty of 239 Ah. The photovoltac module requrement and battery capacty requred wll change dependng on the temperature storage of vegetables and mass of vegetables. 6. References [1] T. Tsoutsos, E. Aloump, Z. Gkouskos, M. Karagorgas, Desgn of a solar absorpton coolng system n a Greek hosptal, Energy and Buldngs 42 (2010) [2] W. Rvera, G. Moreno-Quntanar, C.O. Rvera, R. Best, F. Martnez, Evaluaton of a solar ntermttent refrgeraton system, Solar Energy 85 (2011) [3] A. Pongtornkulpancha, S. Thepaa, M. Amornktbamrungb, C. Butcher, Experence wth fully operatonal solardrven 10-ton LBr/H 2 O, Renewable Energy 33 (2008) [4] R. Dorantes, C. A. Estradat, I. Platowsky, Mathematcal smulaton of a solar ejector-compresson refrgeraton system, Appled Thermal Engneerng 16 (8/9) (1996) [5] J. Guo, and H.G. Shen, Modelng solar-drven ejector refrgeraton system offerng ar condtonngfor offce buldngs, Energy and Buldngs 41 (2009) [6]H. Vdal, S. Colle, G. dos Santos Perera, Modellng and hourly smulaton of a solar ejector coolng system, Appled Thermal Engneerng 26 (2006) [7]M. Helm, C. Kel, S. Hebler, H. Mehlng, C. Schwegler,Solar heatng and coolng system wth absorpton chller and low temperature latent heat storage: Energetc performance and operatonal experence,internatonal journal of Refrgeraton 3 2 ( ) [8]R. Best and N. Ortega, Solar refrgeraton and coolng, Renewable Energy 16 (1999) [9]S.O.Enbe, Solar refrgeraton for rural applcatons, Renewable Energy 12(2) (1997) [10]N-K.C.Nar and N.Garmella, Battery energy storage systems: Assessment for small-scale renewable energy ntegraton, Energy and Buldngs 42 (2010) [11]J. M. Ortz, E. Expósto, F. Gallud, V. G.-García, V. Montel, A. Aldaz, Electrodalyss of bracksh water powered by photovoltac energy wthout batteres: drect connecton behavor,desalnaton 208 (2007) [12]A. Urbna, T.L. Paez, C. O Gorman, P. Barney, R. G. Jungst, D. Ingersoll, Relablty of rechargeable batteres n a photovoltac power supply system,journal of Power Sources 80 (1999) [13]Solar photovoltac modules pm ). [14]R.Chenn, M.Makhlouf, T.Kerbache, A.Bouzd,A detaled modelng method for photovoltac cells, Energy 32 (2007) [15]G.N.Twar, Solar energy-fundamentals,desgn, Modelng and Applcatons, Narosa Publshng House, New Delh, [16]Wnd speed n Kolkata,West Bengal ,Inda, (accessed ). [17] Telecommuncaton Engneerng Centre (TEC), New Delh, Plannng and mantenance gudelnes for SPV power, (accessed ). [18] S.K.Patra, P.P.Datta, Some nsghts nto solar photovoltacs-solar home lghtng system, NABARD Techncal Dgest 7, (accessed ). [19]F.L. Lansng, Computer modelng of a sngle stage Lthum Bromde/Water Absorpton refrgeraton unt, JPL Deep Space Network Progress Report 42-32, DSN Engneerng secton, [20]W. Wagner, J.R. Cooper, A. Dttmann, J. Kjma, H.J. Kretzschmar, A. Kruse, R. Mares, K. Oguch, H. Sato, I. Stocker, O. Sfner, Y. Takash, I. Tanshta, J. Trubenbach, and T. Wllkommen, The IAPWS Industral Formulaton 1997 for the thermodynamc propertes of water and steam, J of Engg. for Gas Turbne and Power 122 (2000) [21]J. Patek, and J. Klomfar, A computatonally effectve formulaton of thermodynamc propertes of LBr-H 2 O solutons from 273 to 500K over full composton range, Int. J. of Refrgeraton 29 (2006) [22]M.Prasad, Refrgeraton and Ar Condtonng, New Age Internatonal Publshers. 175 Kamaljyot Talukdar