Performance Study on Solar Still With Enhanced Condensation

Desalination 230 (2008) 51–61

Performance study on solar still with enhanced condensation

K. Vinoth Kumar*, R. Kasturi BaiDepartment of Bio-Energy, School of Energy, Environment and Natural Resources, Madurai Kamaraj University,

Madurai 625 021, Tamil Nadu, IndiaTel. +91 (452) 245-8471, ext. 366; email: [email protected]

Received 20 March 2007; Accepted 7 November 2007

Abstract

Water scarcity and pollution pose critical situation in all walks of life especially in the developing countries.Among the available purification technologies, solar desalination process proves to be a suitable solution forresolving this existing crisis. This renewable energy technology operates on a basic principle of which the solarradiation enters through the glass surface inside a closed chamber touching the black surface generating heat energy,which gets trapped inside. This gradually raises the temperature of the liquid resulting in evaporation process andfurther condensation, which is drained out for use. In this connection, a basin type solar still (0.5 m2) with improvedcondensation technique was designed and built, and a performance study was carried out with different samples suchas tap water, seawater and dairy industry effluent. The condensation occurs due to the temperature difference not onlyon the glass surface but also on the four sidewalls, which can be cooled by water circulation through tubes attachedon the wall surface for efficiency enhancement. The maximum daily production of the solar still was about1.4 L/m2.d, and its efficiency was about 30%. The condensate water quality was analysed and compared with waterquality standards, which was found to be comparable with rainwater and mineral water. Efficiency of the still wascalculated for all the samples and compared with each other. The reasons for the findings and their implications forthe design of the system are discussed. Some design features that would further enhance the thermal performanceof the still were also identified from this present investigation and highlighted.

Keywords: Solar still; Desalination; Enhanced condensation; Temperature

1. Introduction

Around 97% of the water in the world is in theoceans, approximately 2% of the water in the

*Corresponding author.

world is at present as ice stored in polar ice, anda mere 1% is fresh water available for the need ofplants, animals and human life. The over-exploitation of existing fresh water supplies isbecoming a problem in many parts of the world.In the USA, water shortages in many states have

0011-9164/08/$– See front matter © 2008 2008 Published by Elsevier B.V.doi:10.1016/j.desal.2007.11.015

K. Vinoth Kumar, R. Kasturi Bai / Desalination 230 (2008) 51–6152

resulted in long-term plans being prepared for anincrease in the use of desalination of seawater tosupplement the supply of drinking water [1].There are more than 15,000 desalination plants inmore than 120 countries. It has been estimatedthat there will be a 100% increase in the activeinstalled capacity of desalination plants duringthe period 2005–2015 [2].

The most common renewable energy sourcesare solar, wind, geothermal, and ocean. At pre-sent, uses of renewable energy sources for desali-nation are very limited. The world’s share of totalrenewable energy sources used for desalination isonly about 0.02% of the total energy used.Desalination powered by renewable energies canbe an ideal solution for some small communitieswhere an affordable fossil fuel supply fordesalination is not available [3].

Obtaining potable water through solar stills isone of the thermal applications harnessing thesolar energy, which is viable and economical. Inthe world’s population, at least 80% of thehabitations are in arid and semi-arid countries likeIndia and among them about 40% are sufferingfrom serious droughts. To resolve this existingcrisis, different methods of desalination tech-niques, have been adopted in several countries.Among these, solar distillation is a process wheresolar energy is used to distill freshwater fromsaline or brackish water for drinking purposesand other application. Solar distillation works onthe basic principle where the solar radiation fromthe sun gradually raises the temperature of thewater inside a closed environment at a tempera-ture higher than the ambient, resulting in theprocess of evaporation followed by condensationon the slanted glass surface and collected throughvents. Solar distillation of brackish water is apractical alternative which offers life to thoseregions where the lack of fresh water hindersdevelopment. It has been shown that the solardesalination remains the most favourable processfor the supplying of water to small communitiesin remote villages [4,5].

Desalination is used to produce potable waterfrom water sources containing dissolved salts,and is most often used when water sources aresalty; producing fresh water from seawater orbrackish water. The main application of conven-tional desalination techniques is the production offresh water on ships, islands, and in the coastalregions of some very arid Middle Eastern coun-tries. The water that is produced may be so purethat consumers do not like the lack of taste, andsmall quantities of salt water may then be added(this is called palatization) to improve the flavour.There are several methods of water desalination.The most appropriate method can be selected onthe basis of the TDS value of the raw water [6]. Areport [7] published by the World Bank in 1982,which indicates that, out of 2.4 billion peopleliving in the developing countries, less than500 million have access to potable water and thenumber of people who lack potable waterincreases by 70 million every year. Most of thevillages in many areas are isolated and theavailable source of potable water in these villagesis the rainwater stored in wells. Especially indesert areas, ground water is saline which isconsidered to be unsafe for drinking purposes. Onthe other hand, in addition to quantity of water,there are many places even in urban areas wherewater is polluted and has a high salt content. Ithas been estimated that around 500 millionpeople in the developing countries suffer fromwater-borne diseases.

A general equation is developed [8] to predictthe daily productivity of a single-sloped solarstill. The developed equation relates the depen-dent and independent variables which control thedaily productivity. This equation could be used topredict the daily productivity with a reasonableconfidence level (maximum error ±5%). Theexperiments were conducted [9] in Jordan usinga solar still with various cover tilt angles of 15,25, 35, 45 and 55°. An optimum tilt angle forwater production was found to be 35° during themonth of May. Salt was added to study the effect

K. Vinoth Kumar, R. Kasturi Bai / Desalination 230 (2008) 51–61 53

of the salinity of water on solar distillation. Dis-tilled water production decreased with salinity.The effect of water depth was also studied. Theresults show that water production decreased in asomewhat linear relationship with increasingwater depth in the still. The performance of asolar still with different size sponge cubes placedin the basin was studied experimentally. Theincrease in distillate production of the still rangedfrom 18%–273% compared to an identical stillwithout sponge cubes under the same conditions.The effects of sponge cube size, percent volumeof sponge, water depth, water salinity and the useof black coal and black steel cubes were alsoinvestigated. The study showed that the dailyproduction of such a still can be greatly enhancedusing sponge cubes [10].

Solar stills take advantage of direct solarenergy via the greenhouse effect. The process isas follows. A black-painted basin, sealed tightlywith a transparent cover, stores the saline water.Plastic black sheets can be used as well except ofblack paint. As the sun heats the water, the basinwater evaporates and vapor comes into contactwith the cool glass ceiling where it condenses toform pure water [11]. The water was drainedfrom the solar still for potable use. The maximumefficiency of solar stills was 35% of the energyentering the still effectively utilized to evaporatethe water [12]. This technology was optimizedwhen running at capacities of nearly 0.8 kg/d.Using heat recovery devices and hybrid systemsmay make solar stills more cost-competitive [13].Research has indicated that multiple-effect stillsincrease water production by 40–55% whenstacked in a vertical arrangement [4,12]. Solarstills require large amounts of land and can onlyhandle small quantities of water. They are not aviable option for most areas in the US [11].

A prototype solar still having a vertical flatabsorber of 0.817 m2 was designed, constructedand tested outdoors. It was constructed usinglocally available materials as well as local tech-nical assistance. The total area of the glass cover

is 0.8769 m2, and the absorbing surface consistsof a set of parallel black porous cloth wick platelocated in an enclosure. The still is formed by avertical absorbing surface, two transparent glasscovers and a vertical back wall made of gal-vanized iron, darkened with black colour inter-nally and covered externally with 5 cm of glasswool as insulator. Testing was performed on abatch basis with five modes of operation: (1) stilloperating alone for a 24-h period, (2) still con-nected to the collector for a 24-h period (all day),and (3) still connected to the collector duringdaylight hours 9 am to 5 pm only. These testswere performed with fresh tap water as feed inorder to avoid corrosive effects on the still andcollector material. The remaining two modeswere: (4) saline water feed, 35,000 ppm, with thestill operating alone for a 24-h period, and(5) saline water feed of the same salinity, with thestill connected to the collector for 24 h. The workhas led to the development of the vertical solarstill and to a technical improvement. In order toachieve the yield of the distilled, the still orien-tation should be the direction at which the highestaverage incident solar radiation is obtained [4].

Experimental investigation [14] of the solarstill collector system has shown that the produc-tivity of the system was substantially increased incomparison with that of the still alone. Mean-while, efficiency was reduced by a few percen-tage points. The results of testing are groupedinto five modes of operation. The first three arefor fresh tap water as feed and the last two are forsaline water feed, as follows:

1. The daily production of the still alone wasabout 2 L/m2.d, and its daily efficiency was about27%.

2. When the still was operated with the col-lector for 24 h, its production was increased by231% but efficiency was decreased by about2.5% compared to that of the still alone.

3. A slight increase in condensate production(about 2%) over that of the previous mode


occurred when the still was connected to thecollector during daylight hours only (8 am–5 pm).

4. In operating the system with 35,000 ofsaline water, an increase in production of 52%was noticed when the still was connected with thecollector over that of the still alone.

5. The most practical operating mode, regard-less of the salinity of the feed, is that of the stillconnected to the collector for 24 h.

Several types of solar stills exist, the simplestof which is the single-basin type. But the yield ofthis still is in the range of 2–4 L/d per m2 of stillarea, which is very limited. There are, however,several methods to augment this yield, whichgenerally fall into two categories: concentratorsand flat-plate collectors. This system, also calledthe “active” system, is probably appealing forcountries such as Jordan where flat-plate col-lectors are already being installed in increasingnumbers. All that is needed is to “add-on” a solarstill to an already existing collector and obtain anextra amount of distilled water at no extra cost tothe still. The reason why the efficiency decreasesis that the average temperature of the still andcollector combined is higher than that of the stillalone.

Because of a higher operating temperaturerange in the active solar distillation system due toadditional thermal energy available from thecollector, thermal energy loss increases. Hence,despite the higher yield, the efficiency of theactive solar distillation decreases. A study wascarried out with an active system of single-slope-type stills integrated with a flat-plate collectorunder the thermosyphon mode of operation. Itwas found that the maximum increase in the yieldwas up to 33% when the water in the still waspreheated in the collector. The performance of atriple-basin still integrated with a solar collector[15–17] was analyzed and found that the dailydistillate was more than double compared withthat of the still alone. Although it has been shownthat the overall efficiency of a passive solar stillis higher than that of an active one due to the

lower range of operating temperatures [18,19],the concept is still appealing in situations wherethe collectors are already available.

Recent works [20,21] indicate that research isstill active in the area, with more emphasis onmulti-effect desalination connected to solar col-lectors. Another recent work [22] reports that aproductivity of 25 L/m2.d was reached using sucha system. There are, however, recent works[23–25] that investigated similar systems thatwere integrated with storage tanks. It was foundthat coupling a solar still to a hot water tank gene-rally doubles the distilled water output within a24-h period [23]. A single-stage, basin-type solarstill and a conventional flat-plate collector wereconnected together in order to study the effect ofaugmentation on the still under local conditions.The still inlet was connected to a locally made,fin-tube collector such that its outlet was fed tothe still basin instead of the common storage tank.

Measurements of various temperatures, solarintensities and distilled water productions weretaken for several days at various operating con-ditions. Several modes of operation were studied:still connected to collector for a 24-h period; stillconnected only during sunlight hours from 8 amto 5 pm, and still operating alone for a 24-hperiod. These tests were performed using tapwater and saline water as a feed. It was found thatthe mass of distilled water production usingaugmentation was increased by 231% in the caseof tap water as a feed and by 52% in the case ofsalt water as a feed [14].

A number of solar distillation approaches havebeen recently reviewed [26], focusing on thoseinvolving humidification and dehumidification ofair. Indeed, solar distillation projects have beendemonstrated in several locations around theworld [27]. Seawater input with 35,000 ppm oftotally dissolved solids (TDS) was converted intopotable water with a TDS of 1–2 ppm. Yields upto 9 L/m2 day are obtained at 35°C ambient orapproximately 1000 W/m2 of insolation [28].Thus, this technology where solar energy is


available in abundance can be adopted for con-verting saline or brackish water into pure distilledwater. Numerous laboratory tests have indicatedwithout exception that when water-containingbacteria has been fed into the still, the resultingevaporated/condensed water contained nobacteria.

2. Methodology

The present study was carried out at MaduraiKamaraj University campus (9°54ON, 78°06OEand 100 masl), which is situated 15 km fromMadurai city, 450 km south of Chennai. Theclimate of values (average global solar radiationon a horizontal surface) of the order of 600 W/m2

throughout the year. Madurai is tropical with hot,dry summers and wet, mild winters. In summermonths (from mid-February to mid-June) theaverage daily temperature is around 34°C, whilethe average daily maximum day temperature ismore than 38°C. The insolation is strong withaverage daily values (average global solar radia-tion on a horizontal surface) of the order of600 W/m2 throughout the year [29].

An additional condensation surface was pro-vided on the sidewalls of the still to enhance thedistillate yield and the efficiencies of still werestudied for samples like tap water, seawater anddairy effluent. To identify the initial quality andcharacteristic of the samples, pH, EC chloride,total hardness, and total dissolved solids wereanalyzed. The results from this initial analysiswere compared with that of the final distillatecollected from the still to identify the quality ofthe condensate retrieved from the solar desali-nation process.

2.1. Preliminary experiment

A preliminary experimental study was made tofind out the rate of evaporation of the samplesrelated to temperature, solar insolation and

Fig. 1. Preliminary experiment arrangement.

humidity in an open rectangular cement basin(0.5 m2) with black absorbing surface and moni-toring devices as shown in Fig. 1. The data willbe useful for the disposal of some liquid wastes.

The samples selected for the present inves-tigation were tap water, seawater and dairy efflu-ent. The samples were poured into it and testedwith and without surface temperature standardi-zation. Experimentation was carried out for allthe samples for five replication trials (two sets)each and averaged. Data regarding solar insola-tion, ambient temperature, temperatures of bot-tom surface, inner chamber, humidity etc., wererecorded on an hourly basis from 10 am to 5 pm.The experiment was conducted during the monthsof June–August 2003 when the ambient tempera-ture ranges from 33–36EC. This preliminaryexperiment was carried out to identify the rate ofthe evaporation of the working samples withrespect to the environmental conditions.

2.2. Performance experiment

In continuation of the preliminary experimen-tation, a basin type still (0.5 m2) was designedand fabricated (Fig. 2) with provision for watercirculation (Fig. 3.) to have condensation effecton all the side walls. The inner wall of still wasconstructed with mild steel sheet of dimension67×67 cm2 and was coated with mat black paint


Fig. 2. Performance experiment arrangement.

Fig. 3. Water circulation for wall condensation.

(absorptivity, 0.96; emissivity, 0.85) to absorb themaximum amount of sunlight for converting intoheat radiation. An aluminium tube of length72 cm and 0.5 cm diameter with three turns waswelded on the walls of iron surface for coolingchannel arrangement (Fig. 4). The outer structureof the still was cemented having dimensions 83×

Fig. 4. Cooling tubes with condensate water drain channelarrangement.

25 cm2 in the front side and 83×36 cm2 in thebackside. Glass cover poses the major role intransmitting the solar radiation into the still andacts as a trap for the humid air inside the basin(should have high transmitivity ratio). In such acontext, transmitivity ratio was identified for theglass cover (toughened). The glass cover wasslanted at an angle of 15º positioned on the top ina north–south direction (study area: 9°54ON,78°06OE and 100 masl), which was detachable foreasy maintenance and cleaning.

The insulation material provided was tightlypacked glass wool of thickness 3 cm around theiron walls and 4 cm thickness below the bottomfor heat loss reduction. The data was obtained fortwo cases.

1. Solar still working with condensation onthe sidewalls.

2. Solar still working without condensation onthe sidewalls.

The data for each of these two cases werenoted and compared for two different sampletemperatures (25ºC and 65ºC). The experimen-tation was carried out for all the samples underseven replication trials, which was averaged perday and represented graphically. Finally thechemical characteristics of the distillate were


analyzed and compared with the initial chemicalcharacteristics of the samples further comparedwith that of rainwater, mineral water and EPAstandards for potable drinking water.

3. Results and discussion

The initial characteristics of the sampleselected for the experimentation was analyzedand noted. From the preliminary experimentation,the rate of evaporation for different samples intwo different conditions was noted and tabulated(Table 1). This study was made as a step toidentify the initial quality of the sample and tocompare with that of the distillate collected after

experimentation. In all the samples the rate ofevaporation was found to be higher in withoutsurface cooling experiment compared againstwith surface cooling experimentation. This wasdue to the initial heat transfer in the liquid samplepoured for the experimentation from the pre-heated surface due to sun. From this study, it wasobserved that the rate of evaporation depends onthe various environmental parameters such asrelative humidity, solar insolation, temperature,wind speed etc. The rate of evaporation wasrecorded to be highest in without surface coolingexperiments for all the samples against other. Theaverage relative humidity recorded was 65-86%during the tenure of study.

Table 1Rate of evaporation for various samples

Sml.no.

Time(s)

Avg.ambienttemp. (ºC)

Avg. watertemp.(ºC)

Avg.solar ins.(W/m2)

Avg.wind speed(m/s)

Avg. relativehumidity(%)

Rate ofevap. (%)

Conditions

1. 6300 36.5 41.75 969.7 1.8 74 80.40 Tap water(with cooling)

2. 6300 36 40.58 940.5 1.8 73 82.83 Tap water(with cooling)

3. 7500 34 40.93 668.8 1.4 73 97.86 Tap water(without cooling)

4. 8400 33.7 38.87 508.87 1.2 72 98.32 Tap water(without cooling)

5. 9600 35 41.35 915.58 2.1 74 55.62 Seawater(with cooling)

6. 9900 34.5 41.17 844.86 2.4 75 58.27 Sea water(with cooling)

7. 11400 34.0 40.25 583.3 1.2 71 90.96 Seawater(without cooling)

8. 12300 33.0 38.33 468.67 1.1 69 97.93 Seawater(without cooling)

9. 9900 35 39.17 538.3 1.8 73 41.03 Dairy effluent(with cooling)

10. 7400 34.9 38.28 934.9 2.4 75 69.88 Dairy effluent(with cooling)

11. 11200 35.01 41.56 594.99 1.2 70 82.74 Dairy effluent(without cooling)

12. 7400 35.32 42.57 909 1.1 74 91.91 Dairy effluent(without cooling)


Table 2Comparative analysis of samples

Parameters Initial char. of the sample Final char. of the sample Rainwater

Mineralwater

EPAstd.

Tapwater

Seawater Dairyeffluent

Tapwater

Seawater Dairyeffluent

pH 6.9 8.2 7.7 7.8 6.9 7.7 5.6 6.18 7–8.5EC (mSi/cm) 0.822 0.076 0.005 0.149 0.271 0.263 0.03 0.06 0.78Chloride (mg/l) 32.66 12666.4 211.2 17.04 42.06 8.52 5.68 14.2 200Total hardness (mg/l) 268 4480 540 44 53 52 16 5 200TDS (mg/l) 428.2 39350 1144 110.36 153 172.2 28.4 38.4 500

From the transmitivity test, it was found thatthe transmitivity ratio for the glass surface wasfound to be 80–88%. In the performance experi-mentation, the considerable rise in the efficiencywas noted for pre-heated sample (65ºC) comparedto that of the other. The highest efficiency of30.41% was reached in tap water for both sampletemperature conditions (25ºC and 65ºC). Thecharacteristics of the initial and final condensatewere noted and tabulated and were further com-pared with that of the rainwater, mineral waterand EPA standards for potable water (Table 2).The readings were noted and are representedgraphically (Figs. 5 and 6). The efficiencies werefound to be high with water circulation com-pared to that of without water circulation.

The maximum daily production of the solarstill was about 1.4 L/m2.d, and its efficiency wasabout 30% with corresponding average solarinsolation of 28 MJ/day. The final characteristicsof the condensate from the solar still for all thethree samples showed higher reduction in theirrespective values against the initial conditions.The final condensate values were noticed to beunder acceptable limits of EPA standards andfurther it was also compared with rain water andmineral water. A thermal model of a doublecondensing chamber solar still (DCS) has beenpresented. The thermal model is based on energybalance equations for the different components of

a double condensing chamber solar still (DCS),namely the water mass, the first and secondcondensing covers and the basin liner, includingthe reflecting mirror. Experiments were con-ducted for both the single-slope conventionalsolar still (CSS) and double-condensing chambersolar still (DCS) on an hourly basis for com-parison of their performance. The results havebeen compared with the experimental observa-tions. It was observed that there was a fair agree-ment between the theoretical and experimentalobservations [30].

The shallow water basin, 23° cover tilt angle,0.1 m insulation thickness and asphalt coating ofthe solar still were found to be the optimumdesign parameters that produced an averageannual solar still yield of 4.15 kg/m2 day. A costanalysis is performed to shed some light on thepotential of utilizing an array of simple solar stillsfor the production of drinking water in remoteareas [31]. The performance of a solar desali-nation plant (whether using thermal or photo-voltaic collectors) was influenced by the abilityof the glazing system to transmit solar radiationto the collector absorption surface. This abilitywas influenced by such factors as the intensity ofsolar radiation, the transmittance of the collectorglazing, the tilt angle of the absorbing surface, theoperating parameters of the plant, the propertiesof the materials of construction, etc. This plant


Fig. 5. Efficiencies of samples without circulation ofwater.

has a collector field area of 1864 m2 of absorbersurface and a multiple effect distillation unit forseawater desalination with a capacity of 120 m3/dof distilled water. The frequency of high-pressurewater jet cleaning on the performance of the plantwas also investigated. It was found that dustdeposition and its effect on plant performancedepend strongly on the season of the year and thefrequency of jet cleaning should be adjustedaccordingly [32].

It has also been observed that the daily yieldof an inverted absorber double basin solar stillincreases with the increase of water depth in thelower basin for a given water mass in the upperbasin. It has been observed that, for a particularflow rate, the evaporative heat transfer coefficientdecreases as we increase the water depth in thebasin [33]. In an attempt to decrease the pre-heating time of the basin water of basin type solarstills, a single-slope single basin solar still withbaffle suspended absorber (SBSSBA) wasdesigned and built using locally available mater-ials. The effects of vent area and water depth ofthe upper and lower water columns on the dailyproductivity of the still were studied. Com-parisons of the performance of the SBSSBA andthe conventional unit, the single-slope singlebasin solar still (SBSS), have been carried out. Itwas found that the daily productivity of theSBSSBA is about 20% higher than that of theconventional still (SBSS) [34].

Fig. 6. Efficiencies of samples with circulation of water.

From the graphs, there is a clear picture that thecirculation of water on side wall tubes facilitatesbetter performance with enhanced efficiency. Thecondensation takes place not only on the glasssurface but also on the four side walls and thecondensate falls into the condensate collectionchannel draining to the vent. If samples has blackcolour by its nature, it would further facilitate thesolar still performance efficiently. So, the incor-poration of solar thermal energy devices with thesolar still makes to perform better. The pre-heating of the sample increases the productivityof the condensate enhancing the efficiency of thestill. Number of turns on the walls can beincreased for higher condensation and better per-formance. The aluminium tubes can be replacedby copper tubes for better performance. Usingblack rubber or black gravel materials within asingle-sloped solar still as a storage medium wasexamined to study experimentally the effect ofdifferent parameters such as rubber thickness andgravel size under the same operating conditionsfor four identical stills. The experimental resultsshowed that black rubber (10 mm thick) improvesthe productivity by 20% at the conditions of60 l/m2 brine volume and 15° glass cover angle.Also, using black gravel of 20–30 mm size im-proves the productivity by 19% at the conditionsof 20 l/m2 brine volume and 15° of glass coverangle [35]. There are problems such as growth ofalgae on the underside of the glass must be


controlled, and the unit must be effectively sealed[36]. Solar desalination technology reduces thesalts and pathogens in better rate when comparedto the initial quality of the sample.

Thus, it makes a great difference in people’shealth and environmental sanitation. For a givensolar energy input, the factor limiting the dis-tillate yield of solar still is inefficient conden-sation. The condensation rate can be increasedeither by lowering the wall temperature orincreasing the area of the surface for conden-sation. The retrieved distilled water, which is inpurest form pose a clean taste, odor free, elimi-nating hazardous chemicals and bacteria. It canbe used in laboratories, health centers, work-shops, batteries, cooking etc. In addition, it im-proves the taste and color of food and preservesthe natural flavor of beverages such as tea andcoffee etc., and is extremely important for use inbaby formulas and diet food.

4. Conclusions

The condensation occurs due to the tempera-ture difference not only on the glass surface butalso on the four sidewalls, which can be cooledby water circulation through tubes attached on thewall surface for efficiency enhancement. Themaximum daily production of the solar still wasabout 1.4 L/m2.d, and its efficiency was about30% with corresponding average solar insolationof 28 MJ/d. The condensate water quality wasanalysed and was found to be comparable withwater quality standards and against rainwater andmineral water. Increased cooling on the wallsurface was observed enhancing the condensationprocess. To comprise in a nutshell, conclusionscan be drawn that the utilization of solar energyin purifying water offers a good recommendationnot only on the environmental aspect but also onthe sanitation.

Acknowledgements

One of the authors, K. Vinoth Kumar, rendershis thanks to Er. V. Narasimhan (GARP-MKU)for his fruitful technical discussions, and Miss. J.Subha, for her consistent support in carrying outthis study.

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Performance Study on Solar Still With Enhanced Condensation

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