A Review to Increase Productive Output of An Active Solar Distillation System

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1 A Revi to Increase Productive Output of An Active Solar Distillation System UMANG R SONI 1, Dr. P.K.BRAHMBHATT 2, HEMANT B PATEL 1P.d Student, Department of Mecanical Engineering, PAHER, Udaipur, Rajastan, Gayatrinagar society, vadali, dist: sabarkanta, Gujarat , India, , ID: soniur@gmail.com, 2 Associate Professor, Mecanical Engineering Department,Govt. Engg. College, Modasa , Gujarat India, ID: pragnesbrambatt@gmail.com, , 3 M.E.Termal Engg, Student at LJIET, Mecanical Engineering department, Amedabad, ID: emant.mec009@gmail.com Abstract Solar still is one of te best solutions to solve water problem in remote arid areas. One of te metods to increase te productivity is by decrease te volumetric eat capacity of te basin. Solar distillation is one of many processes tat can be used for water purification. Solar radiation can be te source of eat energy were brackis or sea water is evaporated and is ten condensed as pure water. So many works can be done on te active and passive solar still. From tis revi found tat if we make te still double basin and two stages te overall efficiency of te active solar still will increase. Keywords: solar still, solar collector, inverted absorber, PV/T collector. ***** I. INTRODUCTION Different types of treatment processes are available to supply clean drinking water, to rural and urban areas in large and small scales. But, for te peoples living in remote arid areas, no device is available at affordable cost, to supply potable water. Use of different types of renable energies for desalination as been compreensively revied by Kalogirou [1]. Solar still is one of te best desalination devices. Te still uses solar energy for converting available brackis or impure water into clean potable water. It is easy to fabricate and require no maintenance [2]. But te still is not popularly used because of its lower production. A number of works was carried out by researcers, to improve te production capacity of te still, by adopting different tecniques [3]. Solar energy is available in abundant in most of te rural areas and ence solar distillation is te best solution for rural areas and as many advantages of using freely available solar energy. It is a simple tecnology and more economical tan te oter available metods. A solar still operates similar to te natural ydrologic cycle of evaporation and condensation. Te basin of te solar still is filled wit impure water and te sun rays are passed troug te glass cover to eat te water in te basin and te water gets evaporated. As te water inside te solar still evaporates, it leaves all contaminates and microbes in te basin. Te purified water vapour condenses on te inner side of te glass, runs troug te lower side of te still and ten gets collected in a closed container [4]. Many solar distillation systems were developed over te years using te above principle for water purification in many parts of te world. Tis paper revis te tecnological developments of various active solar distillation systems developed by various researcers in detail. Te revi also extends to termal modeling of some active solar distillation systems, comparative studies of different active solar stills, scope for furter researc and recommendation. II. DESIGN OF SOLAR STILL Solar still is an airtigt basin, usually constructed out of concrete/cement, galvanized iron seet (GI) or fiber/glass reinforced plastic (FRP/GRP) wit a top cover of transparent material like glass, plastic etc. Inner surface of te solar still is blackened coating of absorber material to absorb solar radiation more effectively. Slope is provided for receive maximum solar radiation during te day period to te transparent glass cover wic ave negligible termal conductivity. [5] 843

2 Tis allows maximum solar radiation in te inner surface and distilled water collected at te end of glass cover and received by bucket. Temperature difference between evaporating water surface and condensing glass surfaces are increased by adding additional eat using solar collector, ot water tank, eat excanger arrangement outside te solar still wic is called active solar still as sown in Figure 1. III. IMPROVEMENT IN ACTIVE SOLAR DISTILLATION SYSTEM Our main focus is to improve te efficiency of active solar still. Te numerous parameters are affecting te performance of te still suc as material of te basin, wind velocity, water dept in te basin, solar radiation, ambient temperature, inclination angle and type of collector used. Te productivity of any type of solar still is determined Glass cover Figure 1. Active Solar Still [5] g g 1w w g w g g a g by temperature difference between inner surface of glass cover and surface of water. Sanjeev kumar et al. Present an Annual performance of an active solar still. Te following assumptions ave been made wile writing te energy balance for eac Component: Te eat capacity of te glass cover and te Insulation (bottom and sides of te still) is Negligible Te solar still is vapour-leakage proof Side area of te still is very small as compared to area of basin liner due to a small dept of Water in te basin. No stratification of water occurs in te basin of te solar still Absorptive of te glass cover is negligible By tis experiment tey can derive an analytical expression for water; glass cover temperature and yield ave been derived in terms of design and climatic parameters. α I t A T T A T T A.. (1) Water mass dtw Q U w 1 g Aw I t w Tg TW Ab mwcw 1 w Tw Tg Ag...(2) dt Basin liner αb 1 αg 1 αw AbI t w Tb Tw b Tb Ta A b... (3) And ourly yield per unit area can be evaluated from known values of water and glass temperatures, and it is given by, (Tw -T g ) 3600 m =... (4) L From tis experiment tey conclude tat for G.N. Tiwari at al. work wit te number of PV/T maximum annual yield, te optimum collector collectors connected in series as been integrated inclination for a fiat plate collector is 20 and wit te basin of solar still. Te optimization of for te still glass cover it is 15 [6]. number of collectors for different eat capacity of 844

3 water as been carried out on te basis of energy collector. However te daily and exergy efficiency and exergy. Expressions of inner glass, outer glass decreases linearly and nonlinearly wit increase of and water temperature ave been derived for te water mass. It as been observed tat te ybrid active solar system. For te numerical maximum yield occurs at N = 4 for 50 kg of water computations data of a summer day for Deli mass on te basis of exergy efficiency. Te climatic condition ave been used. It as been termal model as also been experimentally observed tat wit increase of te mass of water in validated. [7] te basin increases te optimum number of Figure 2. Scematic diagram of PV/T collectors connected in series [7] Vimal Dimri, Bikas Sarkar, Usa Sing, G.N. Tiwari evaluate inner and outer glass temperature and its effects on yield. Numerical computations ave been performed for a typical day in te mont of December, 2005, for te climatic condition of N Deli. Higer yield was observed for an active solar distillation system as compared to te passive mode due to iger operating temperature differences between water and inner glass cover. Te parametric study as also been performed to find out te effects of various parameters, namely tickness of condensing cover, collector absorbing surface, and wind velocity and water dept of te still. It is observed tat tere is significant effect on daily yield due to cange in te values of collector absorbing surface, wind velocity and water dept. For all te cases, te correlation of coefficients (r) between predicted and experimental values ave been verified and tey sowed fair agreement wit 0.90 < r < 0.99 and root mean square percent deviation 3.22% < e < 22.64%. Effect of condensing cover materials, namely copper and polyvinyl cloride (PVC), on daily yield ave also been investigated and compared. [8] Figure 3. Scematic vi of an active solar still coupled wit a flat plate [8] Rajes Tripati, G.N. Tiwari Presents te termal analysis of passive and active solar distillation system by using te concept of solar fraction inside te solar still wit te elp of AUTOCAD 845

4 2000 for given solar azimut and altitude angle different water depts in te basin (0.05, 0.1 and and latitude, longitude of te place. Experiments 0.15 m) for passive as well as active solar ave been conducted for 24 for N Deli distillation system. [9] during te monts of November and December for Figure 4. Potograp of te experimental set-up [9] Analytical expressions for water and glass cover temperatures and yield ave been derived in terms of design and climatic parameters. It is observed tat; (i) Te solar fraction plays a very important role at lower values of solar altitude angle (ii) Te internal convective eat transfer coefficient decreases wit te increase of water dept in te basin due to decrease in water temperature, (iii) Tere is a fair agreement between te experimental observation and teoretical prediction during daytime as compared to tat during te nigt. Hirosi Tanaka, Yasuito Nakatake and Masaito Tanaka work on some indoor experiment in vertical multi effect diffusion type solar still. Tey coupled a eat pipe solar collector wit solar still and lamps are used instead of solar radiation. Figure 5. Scematic diagram of vertical multiple-effect diffusion-type still coupled wit a eat- pipe solar Collector [10] 846

5 Size of tis still is very compact, and te tickness is less tan or equal to 10 cm, wen it is carried or in storage, furtermore, te proposed still was predicted to produce a greater amount of distilled water tan tat of a conventional multiple effect diffusion type solar still witout electricity. Figure 6. A Grap of Temp Time - solar radiation [10] Te predicted time variation of temperatures of te collector plate of te solar collector and te experimental results, and te experimental results of te experimental results of te overall production rates of te multiple-effect still were about 93% of wat was predicted. Tis indicates tat te eat pipe of te proposed still can transport termal energy well from te solar collector to te vertical multiple-effect diffusiontype still. Result as sown in fig.6. Time variations of te temperatures in te still and te distillate production rate on te second partition produced by varying te radiation from te eating lamps to imitate actual solar radiation are in good agreement wit te predictions. [10] Sangeeta Suneja, G.N. Tiwari works on transient analysis of a double basin solar still. Tey derived explicit expressions for te temperatures of various components of te inverted absorber double basin solar still and its efficiency. Figure 3. Scematic vi of an inverted absorber double basin solar still [11] Te effect of water dept in te lower basin on te performance of te system as been investigated compreensively. For enunciation of te analytical results, numerical calculations ave been made using meteorological parameters for a typical winter day in Deli. It as been observed tat te daily yield of an inverted absorber double basin solar still increases wit te increase of water dept in te lower basin for a given water mass in te upper basin. [11] IV. FUTURE SCOPE AND CONCLUSION From above revi conclude tat productivity of active solar still will increase wit increasing solar collector area. Tere is lots of work done to improve te solar still and tey generally used flat plate collector, inverted absorber. But if make tem double stage and wit te use of igly effective collector tey work as a one unit system and overall 847

6 efficiency of te system is increasing. So, te productive output of still almost doubled Te natural circulation mode (Termosipon Effect) is to be used in active solar still to avoid electricity consumption by pump in forced circulation mode. More researc may be carried out in active solar stills wit oter developed tecnologies like ETC, ETC wit eat pipes and multistage solar distillation. V. SYMBOLS A Area c w Specific eat of water in te solar still, j / kg C Convective eat transfer coefficient 1g from te basin liner to an ambient air troug bottom and side insulation, W/m2 C 1w Total eat transfer coefficient from te water surface to te glass cover, W/"# $ w Convective eat transfer coefficient from te basin liner to te water, W/m2 C Evaporative eat transfer coefficient from te water surface to te glass cover, W/m2 C I(t) Solar Radiation available at te plane of glass cover of te solar still, W/m2 m Instantaneous yield of still per unit area, kg/ m2 Q Rate of useful energy from collector, W U T a Ambient Temperature Subscripts g glass cover w water VI. REFERENCES [1] Kalogirou Soteris A. Seawater desalination using renable energy sources, Progress in Energy and Combustion Science 2005; 31:242e81 [2] Kalidasa Murugavel K, Cockalingam KnKSK, Sritar K, Progresses in improving te effectiveness of te single basin passive solar still, Desalination 2008; 220:677e86. [3] Kalidasa Murugavel K, Cockalingam KnKSK, Sritar K. Progresses in improving te effectiveness of te single basin passive solar still, Desalination 2008;220:677e86. [4] Tiwari GN, Tiwari AK, Solar distillation practice for water desalination systems. N Deli: Anamaya Publisers; [5] umang r soni, pragna r patel, tusar m patel. A revi to increase performance of an active solar distillation system, NTCMB147, (2012) [6] Kumar", GN Tlwarl, HN Sing, Annual performance of an active solar distillation system, Received 29 April 1999; accepted 22 May 1999 Desalination 127 (2000) [7] M.K. Gaur, G.N. Tiwari, Optimization of number of collectors for integrated PV/T ybrid active solar still, Centre for Energy Studies, Indian Institute of Tecnology, Hauz Kas, N Deli , India, Applied Energy 87 (2010) [8] Vimal Dimria, Bikas Sarkara, Usa Singb, GN Tiwaria, Effect of condensing cover material on yield of an active solar still: an experimental validation, Desalination 227 (2008) [9] Rajes Tripati, GN Tiwari, Termal modelling of passive and active solar stills for different depts of water by using te concept of solar fraction Solar Energy 80 (2006) [10] Tanaka, Yasuito Nakatake, Masaito Tanaka, Indoor experiments of te vertical multiple-effect diffusion-type solar still coupled wit a eat-pipe solar collector, Hirosi Desalination, 177 (2005) [11] Sangeeta Suneja, GN Tiwari, Effect of water dept on te performance of an inverted absorber double basin solar still, Energy Conversion & Management 40 (1999) 1885±