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VSRD-MAP, Vol. 2 (5), 2012, 166-173

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1Dean Academic, Department of Mechanical Engineering, Lord Krishna College of Engineering, Ghaziabad, Uttar Pradesh, INDIA. 2Assistant Professor, Department of Civil Engineering, ACME College of Engineering, Ghaziabad, Uttar Pradesh, INDIA. *Correspondence : [email protected]

RRR EEE SSS EEE AAA RRR CCC HHH AAA RRR TTT III CCC LLL EEE

Distillation of Water by Solar Energy 1Anirudh Biswas* and 2Ruby

ABSTRACT

The purpose of this research is to design a water distillation system that can purify water from nearly any

source, a system that is relatively cheap, portable, and depends only on renewable solar energy. From the results

of project calculations a truthful estimate was made to prototype the most effective geometries of the distiller

and trough concentration system, one that will maximize evaporation/condensation and re capture waste heat to

minimize thermal losses. To achieve this goal, a system was designed incorporating a parabolic solar trough

coupled with a custom designed distillation device. The incoming solar radiation from the sun is focused and

concentrated onto a receiver pipe using a parabolic trough, heating the incoming impure water, at which point it

is sprayed into our custom designed distillation device where it evaporates and is re-condensed into pure potable

water. Future goals for this project include calculation refinement, material research/testing, and fabrication.

Keywords : Solar Collector, Distillation, Glass Basin, Flask.

1. INTRODUCTION

Solar distillation is a tried and true technology. The first known use of stills dates back to 1551 when it was used

by Arab alchemists. Other scientists and naturalists used stills over the coming centuries including Della Porta

(1589), Lavoisier (1862), and Mauchot (1869).The first "conventional" solar still plant was built in 1872 by the

Swedish engineer Charles Wilson in the mining community of Las Salinas in what is now northern Chile

(Region II). This still was a large basin-type still used for supplying fresh water using brackish feed water to a

nitrate mining community. The plant used wooden bays which had blackened bottoms using logwood dye and

alum. The total area of the distillation plant was 4,700 square meters. On a typical summer day this plant

produced 4.9 kg of distilled water per square meter of still surface, or more than 23,000 liters per day. This first

stills plant was in operation for 40years! Over the past century, literally hundreds of solar still plants and

thousands of individual stills have been built around the world. SolAqua stills have built upon years of still

Anirudh Biswas et al / VSRD International Journal of Mechanical, Auto. & Prod. Engg. Vol. 2 (5), 2012

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research and development, use NSF and FDA approved materials, and are the state of the art for commercial

solar still distillation.

The basic principles of solar water distillation are simple yet effective, as distillation replicates the way nature

makes rain. The sun's energy heats water to the point of evaporation. As the water evaporates, water vapor rises,

condensing on the glass surface for collection. This process removes impurities such as salts and heavy metals

as well as eliminates microbiological organisms. The end result is water cleaner than the purest rainwater.

2. LITERATURE REVIEW

Malik et. al. [5] developed a co-relation between rate of heat transfer coefficient between water and glass (hewg)

and rate of convective heat transfer coefficient from water to glass (hcwg), based upon Lewis relation. as:

Sampathkumar et. al. [6] carried out the detailed review of various designs of active solar stills and highlighted

on various parameters affecting the performance of these solar. They carried out thermal modeling for various

types of active single slope solar distillation system and highlighted on the scope for further areas of research.

Mario and Giovanni [7] designed simple solar still using tubes (Fig. 8) to desalinate the sea water. The

evaporation section comprises horizontal transparent thin-walled plastic / glass tubes of 0.10–0.25 m inner

diameter, half-filled with sea water which absorbs solar radiation. E. Delyannis, [8] carried out a historical

review on desalination techniques and renewable energy utilization with an emphasis on solar energy utilization

for desalination and concluded that what is a new development for us will be a history for next generation.

Kabeel et. al. [9] in an attempt to find the most economical solar still made a cost analysis of 17 popular designs

of solar stills and concluded that the best average and best maximum daily productivity are for solar stills of

single slope and pyramid shaped, the highest average annual productivity was reported for Pyramid shaped solar

still as 1533L/m2 and lowest average annual productivity was estimated for modified still with sun tracking

system as 250 L/m2 . Velmurugan et. al. [10] developed a setup to distill the affluent water and introduced

additional surfaces in the basin in the form of fins, saw dust, black rubber, sand, pebble and sponges. They

found that with the additional surfaces the evaporation rate increased by 53% as compared with the conventional

single slope solar still. Kumar and Tiwari [11] estimated the internal heat transfer coefficients of a deep basin

hybrid (PV/T) active solar still ), based on outdoor experimental observation of hybrid (PV/T) solar still for

composite climate of New Delhi they evaluated the internal heat transfer coefficients by using thermal models

developed by various researchers and compared the result with experimental observations and made a

conclusion that, Kumar and Tiwari model (KTM) better validate the results than the others model. The average

annual values of convective heat transfer coefficient for the passive and hybrid (PV/T) active solar still were

observed as 0.78 and 2.41W/ m2- K, respectively at 0.05 m water depth. Ganeshan and Nirmalakhandan [12]

designed a solar still which maintained a vacuum in the evaporating chamber, exploiting the natural gravity law

and the barometric pressure head and developed a model. They demonstrated the correlation between the

predictions made by the theoretical model with the measured performance data and produced a yield of 7.5L/m2

–day of evaporation area using direct solar energy alone. With the addition of (PV/T) panel of 6m2 area they

system produced 12L/m2 –day of fresh water at an efficiency range of 65% to 90%. The average specific energy

feed was calculated as 2930 kJ/Kg of fresh water. Badran and Al-Tahaineh [13] modified a conventional passive

solar still by including a flat plate collector and reported a 36% increase in productivity El-Sebaii et. al. [14] in


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an attempt to improve the daily productivity of the single effect solar stills, integrated it with a SSP (shallow

solar pond) and reported that the annual average values of the daily productivity and efficiency of the still with

the SSP found to be higher than those obtained without the SSP by 52.36% and 43.80%, respectively. Shankar

and Kumar [15] studied the effects of design parameters, operational parameters and the climatic parameters on

the instantaneous energetic and exegetic efficiencies of a single slop passive solar still and observed that the

instantaneous energy efficiency increases from 0.4 to 10.7% with increase in the value from 0.014 to 0.115,

decreased by 21.8% and 36.7 % respectively with decrease in absorptive of basin liner from 0.9 to 0.6,

decreased by 0.47% and 0.75%, respectively with per degree increase in glass cover tilt and increased

marginally up to a wind velocity of 2m/s2 and after that these remained constant. Arjunan et. al. [16] reviewed

the solar status in India and concluded that India being a tropical country receives an average daily solar

radiation between 4 and 7 kWh per square meter in different parts of country with 250 to 300 clear sunny days

per year. Thus receiving about 5000 trillion kWh of solar radiation in an year. The solar distillation represents

the most attractive and simple technique, especially for small scale units. The conventional methods of

desalination not only using the high grade conventional energy are having negative impact on environment

Suleiman and Tarawneh [17], carried out the performance evaluation of double slope solar still by varying the

water depth, (0.5cm, 2cm, 3cm, and 4cm) with saline water TDS of 5000 ppm, under the same climatic

conditions at Mutah University and observed that the productivity is strongly dependent on the climatic, design

and operational conditions. The decreased water depth has a significant effect on the increased water

productivity, while the performance characteristics showed that the water productivity was closely related to the

incident solar radiation intensity. Medugu and Ndatuwong [18] designed and tested a solar still in Mubi, Nigeria

and carried out a theoretical analysis of the heat and mass transfer mechanisms inside this solar still. The

measured performance was then compared with results obtained by theoretical analysis. They observed that the

instantaneous efficiency increases with the increase of solar radiation and with the increase of feed water

temperature. The distillation efficiency of the still was in clear agreement with the theoretical analysis within the

range of 99.64%. Akash et. al. [19] studied the effect of absorbing materials on the performance of a double

slope single basin solar still in an attempt to enhance the productivity and observed that the productivity of

distilled water was enhanced by using absorbing black rubber mat increased by 38%, Using black ink it

increased by 45% and by using Black dye (being best absorbing material) the water productivity enhancement

by 60.

Arjunan et. al. [20] carried out experimental study in an attempt to store the excess solar radiation energy by

putting the blue stones in the hearth of the still and keeping the glass cover tilt at 10°, paralleled with a

conventional still and observed an increase in the productivity of the modified solar still by 5 % when using blue

metal stones as a storage medium and that the internal and external heat transfers influence the productivity of

the solar still. It was also observed that the maximum amount of heat loss occurring in the solar still is the

combined effect of radiation and convection heat transfer from glass to ambient.

3. SOLAR STILL

Solar distillation has long been considered of making the impure water drinkable. The history goes back to as

early as 4th century B.C. Aristotle described a method to evaporate impure water and then condense it for


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potable use. Della Porta (1589), fig. 1, used wide earthed pots exposed to the intense heat of solar rays to

evaporate the water and collect the condensate into to P.I. Cooper, in his report on development and use of solar

stills, insists that Arabian alchemists were the earliest known peoples to use the solar distillation to produce the

potable water in the 16 solar stills was introduced for the first time in the Second World War when the large

scale solar stills were to support the US military.

A solar still is a simple way of distilling water, using the heat of the sun to drive evaporation from humid soil,

and ambient air to cool a condenser film. Two basic types of solar stills are box and pit stills. In a solar still,

impure water is contained outside the collector, where it is evaporated by sunlight shining through clear plastic.

The pure water vapour condenses on the cool inside plastic surface and drips down from the weighted low point,

where it is collected and removed. The box type is more sophisticated.

A solar still operates on the same principle as rainwater: evaporation and condensation. The water from the

oceans evaporates, only to cool, condense, and return to earth as rain. When the water evaporates, it removes

only pure water and leaves all contaminants behind. In this research solar still used for distillation of water,

purified waters are used in battery, chemistry lab, and other industrial use, so that some short of small scale

industries comes in the new world for the manufacturing of the distilled water and get employments’.

4. METHODOLOGY OF SOLAR DISTILLATION

The mechanism of solar distillation is as follows:

The sun energy in the form of short electromagnetic waves passes through the transparent/opaque

condensing cover (Glass/plastic/copper) and strikes at the blacked bottom surface of the still. This light

changes its wavelength to long wave of heat which is added to the water kept in the sallow basin bellow the

cover

As the water heats up it starts evaporating.

These warm vapors start rising upwards towards the inner surface of the cooler cover plate. There these get

condensed releasing their latent heat of condensation and forming a sheet of water on the under surface of

the transparent cover.

This condensed water than slips down the inner surface of the cover plate toward the distillate trough due to

gravity.

5. DESIGN

We need to reduce the working pressure inside the distiller to increase the rate of evaporation at lower

temperatures and hence increase efficiency. One more additional feature in the distiller that we are proposing is

that it would use the latent heat which is released during condensation to heat up the water at lower temperature.

This is achieved by using an innovative staged still design. The basic arrangement of the system can be

described as follows, before proceeding further we would like to mention a few assumptions that we made for

the Design :

The number is assumed to be the average size of a rural household. Data has also been confirmed with the

census data.


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The solar constant equals 1.3 kW/m2 but owing to losses incurred while passing through atmosphere we can

consider the solar irradiation to be 1kW/m2.

Specific heat of water = 4.2 kJ/kg

Latent heat of vaporization = Latent heat of condensation = 2260 kJ/kg

Manually operated Vacuum pump to reduce air pressure inside the distillation chamber operating conditions of

about 60oC to ensure low heat transfer losses.

At 60oC temperature the vapor pressure of water is 20 kPa.

A very low Conversion efficiency of around 20%.

Aperture Area = Energy required for distillation of 10 liters of water / Solar energy

= Available per m2 * Conversion efficiency

= (10 kg/day * 4.2kJ/kgoC * (60-30) oC)/ (1 kW/m2 * 3600 s/hour *6 hours/day)*(0.2)= 0.266 m2

So we need total area of 0.266m2 for the distillation of 30 liters of water daily.

6. DESIGN PARAMETER

There are a number of parameters which affect the performance of a solar still. These are broadly classified as

(1) Climatic parameters (2) Design parameters (3) Operating parameters,

[1] Climatic Parameters

Solar Radiation

Ambient Temperature

Wind Speed

Outside Humidity

Sky Conditions

[2] Design Parameters

Single slope or double slope

Glazing material

Water depth in Basin

Bottom insulation

Orientation of still

Inclination of glazing

Spacing between water and glazing

Type of solar still

[3] Operational Parameters

Water Depth

Preheating of Water

Coloring of Water

Salinity of Water

Stand

Solar still

Reflector


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Solar still

Stand

Inlet pipe

Outlet pipe

Distill water

Separator

Hanger

7. WORKING PROCESS

The systematic view of the working is as shown in the figure :

Impure water are put in the tank through the inlet pipe and solar still are hanged on the tripod stand in such a

way that solar still is on the focus point of the reflector , when sun light reflected through the reflector then

water on solar still vaporized and water vapor passing through the outlet pipe and condensate in the flask.

8. ADVANTAGES

There are the following advantages & future scopes of this research :

If two stage or more stage of heating operation performed then rate of heat generation increase.

If it will be used as small scale industries then unemployment can minimize.

Small investment improves the working ability.

Residential Roof is sufficient to perform this operation as commercial sense.

Domestic & commercial like (chemistry lab) purpose distilled water can generate in house with small


172

investment.

Low maintenance cost in the operation.

9. FUTURE SCOPE

Distilled water is very useful water in industries house and technical College and any under graduate college in

workshop, Chemistry lab or for inverter battery. So this research will provide the facility in the village also

general people can setup small equipment on the roof of the building and get distill water continuous basis. This

research will provide the growth of the small scale industries in the village side in India. In the set up small

investment required in first time then very less lost will appear in maintenance also.

10. CONCLUSIONS

Clean water remains one of the most challenging international issues of today, and solar distillation offers

important and effective solutions in meeting potable water needs. Low cost solar stills offers immediate and

effective solutions in reliably providing safe distill water year after year. Single-basin solar stills are easy to

build, inexpensive and extremely effective in distilling water with a high total dissolved salt content and in

killing bacteria such as cholera and E. Coli. Single basin solar stills can use commonly available equipment,

based on proven solar still designs. Average water production is about 0.5 liters per square meter per sun hour.

Solar stills can bring immediate benefits to their users by alleviating chronic problems caused by water-borne

diseases. Solar stills offer the only realistic and cost-effective means to provide safe distill water for many

industrial and demotic use.

11. REFERENCES [1] K. Vinothkuumar and R. Kasturibai (2008). ‘Performance study on solar still with enhanced condensation’.

Desalination, 230, 51–61.

[2] G.N. Tiwari, H.N. Singh and Rajesh Tripathi, (2003), ‘Present status of solar distillation’, Solar Energy 75

pp. 367–373.

[3] C. Shen, Ya-Ling He, Ying-Wen Liu and Wen-Quan Tao, (2008), ‘Modeling and simulation of solar

radiation data processing with Simulink’, Journal of Simulation Modeling Practice and Theory, 2, pp. 721-

735.

[4] Horace McCracken and Joel Gordes, ‘Understanding solar stills’,1600 Wilson Boulevard, Suite 500

Arlington, Virginia 22209 USA

[5] M.A.S Malik, G.N. Tiwari, A. Kumar, and M.S. Sodha, (1982) ‘Solar Distillation’, Pregamon Press, Oxford

UK, pp.8–17.

[6] K. Sampathkumar, T.V. Arjunan, P. Pitchandi and P. Senthilkumar, (2010), ‘Active solar distillation—A

detailed review’, Renewable and Sustainable Energy Reviews Vol-14, pp. 1503–1526.

[7] Mario Reali and Giovanni Modica, (2008), “Solar stills made with tubes for sea water desalting,”

Desalination, 220, pp. 626–632

[8] E. Delyannis,(2003), ‘Historic background of desalination and renewable energies’, Solar Energy, 75,

PP.357–366


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[9] A.E. Kabeel, A.M. Hamed and S.A. El-Agouz, (2010), ‘Cost analysis of different solar still configurations,’

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[10] V. Velmurugan, C.K. Deendayalan, H. Vinod and K. Srithar, (2008), ‘Desalination of affluent using fin

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[13] O.O. Badran and H.A. Al-Tahaineh. (2005) ‘The effect of coupling a flat-plate collector on the solar still

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[14] A.A. Al-Sebaii, M.R.I. Ramadan, S. Aboul-Enein and N. Salem, (2008), ‘Thermal performance of a single

basin solar still integrated with a solar pond’, 49, pp. 2839-2848.

[15] Prem Shankar and Shiv Kumar, (2011), ‘Instantaneous Exergy Efficiency of a Passive Solar Still’,

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[16] T.V. Arjunan, H.S. Aybar and N. Nedunchezhian, (2009), ‘Status of solar desalination in India’, Renewable

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[17] M. Suleiman and K. Tarawneh, (2007), ‘Effect of Water Depth on the Performance Evaluation of Solar

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[18] D. W. Medugu and L. G. Ndatuwong, (2009), ‘Theoretical analysis of water distillation using solar Still’,

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[20] T.V. Arjunan, H. S. Aybar, N. Nedunchezhian and M. Sakthivel, (2009), ‘Effect of Blue Metal Stones on

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[21] G.N. Tiwari, A.K. Tiwari, (2007) ‘Solar distillation practice for water desalination systems’. Anamaya Pub.

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