沙漠研究 22-1, 163 -166 (2012 )"ICAL 1 / DT X"

Journal of Arid Land Studies－Refereed Paper－

Experimental Study on Built-in CDS and Its Comparative Analysis with SSSS
to Produce Irrigation Quality Water in Arid Regions
Rajan JAYAPRAKASH*1), Thirugnanasambantham ARUNKUMAR1), Birendra KUMAR2),
Sangeeta SINHA2) and Hiroaki MOCHIZUKI3)
Abstract: The objective of this work was to study the performance as well as comparisons between two solar still configurations:the single slope solar still (SSSS) with top cover cooling and the built-in concentrator distillation system (CDS) with top cover cooling.
The still basin bottom of the concentration coupled system is modified in the form of hemispherical shape. The main advantage wasthat the still with concentrator produced distillate yield in a shorter duration of time than was obtained for a single slope solar still for awhole day. The assembly of unit in the built-in concentrator distillation system is also small compared to single slope solar still.
The water temperature of the still in concentrator-coupled system was higher than the single slope solar still. The outcome of thestudy is that we can attain more evaporation rate by linking the solar concentrator in the solar stills. The built-in concentrator
distillation system and single slope solar still are well studied by flow the water over the top cover. The main parameters such as stills
productivity and efficiency are presented. On the basis of the results, built-in concentrator distillation system was found to be more
efficient than the single slope solar still.
Key Words: Concentrator, Distillate yield, Efficiency, Solar still

1. Introduction
Clean, safe and affordable water is one of the greatest
challenges in rural communities, living in arid and semi-arid
lands. Arid regions suffered more difficult problems to accessadequate drinking water. So water is the essential part to leadthe life in those particular remote areas. Desalination using
solar energy has been used to balance the crisis of fresh waterin those lands. Desalination of brackish water or sea water is
one of the ways to meet the water demand. The main
characteristic of this process is that they are friendly to theenvironment. Production of pure water using desalination
process driven by solar energy systems is a viable solution to
the water scarcity at remote areas.
Different studies attempting to improve still yield arereported, but generally enhancement of evaporation inside thestill and minimization of energy losses are the two main
approaches. The thermal efficiency of the unit in terms of
production per day per square meter can be increased byvarious passive or active methods. Evaporation rate can beincreased if the temperature difference between the basin andthe glass cover increases. This can be achieved by eitherincreasing the basin temperature or decreasing the covertemperature or both. Studies have been performed by thevariation of evaporative heat transfer coefficients in aconventional still and in an inverted absorber solar still (Sunejaand Tiwari, 1998; Abu-Arabi et al., 2002; Abu-Hijleh andMousa, 1997). A comparative study reported the effect of theAlgerian south-west desert climatic conditions on theperformance of a single basin solar still and a similar one
coupled to flat plate solar collector (Boukar and Harmim,2001).
Much research work has been done in theconcentrator technology (Broman and Broman, 1996), hightemperature cavity receivers (Hahm et al., 1999), hightemperature solar distillation system (Chaouchi et al., 2007;
Yadav and Yadav, 2004), non-focusing solar concentrators(Shaprio, 1971), 400 m2 big dish (Johnston, 1995), 20 m2 tiled
dish (Johnston, 1995) low cost dish solar concentrator (Palavrasand Bakos, 2006).
In this present study, we compared the built-in concentrator
distillation system with a single slope solar still. We usedwater flow over the top cover for cooling purposes in both thestills. The efficiency, water collection and feasibility of thesystem were compared.

2. Materials and Methods
2.1. Concentrated coupled single slope solar still
The built-in concentrator distillation system was* Corresponding Author: jprakash_jpr@rediffmail.com
Coimbatore, Tamilnadu, India
1) Department of Physics, SRMV College of Arts and Science
2) Centre for Renewable Energy and Environmental Research, Muzaffarpur, India

3) Faculty of Agriculture, Kagoshima University, JapanFig. 1. Schematic view of concentrator coupled solar still.

constructed. The basin is modified to hemispherical shape ismade up of copper of thickness 4 mm. The diameter of thehemi spherical base is 0.22 m, and this hemi spherical absorberwhich is attached at the bottom of the still.
The bottom and sides of the inner surface of the basin andthe outer surface are blackened and ¼ inch inlet pipe isprovided for water inlet. The top surface of the still is coveredby a cover of area 0.25 m × 0.25 m. The top cover is made upof transparent glass sheet of thickness 2 mm of transmittance
90%. Thermocouples were used to measure the temperatureinside the still. The top cover is placed over the grooves withuniform resting slope of 16°. A water collection segment isalso provided at the respective place. It has a length of 0.27 m
and a width of 0.025 m. This entire setup is mounted at focal of
the concentrator. The experimental setup is shown in Figure 1.
2.2. Single slope solar still (SSSS)
The water storage basin of the still is designed of area 0.50
m × 0.50 m. Bottom and sides of the inner surface of the still
are coated with black paint for absorbing maximum amount ofintensity of solar radiation. An inlet pipe of ½ inch is used for
pouring water into the still. An outer cover of the basin is
made up of wood. The gap between the basin and outer coveris filled with saw dust as insulation. The top cover of the stillis made by the glass of thickness 2 mm. The top cover isplaced over the grooves which are provided at all sides foruniform resting. A 16º slope is maintained for top glass cover.
Water Collection segment is placed at the desired position forcollecting the condensed water and with dimension 0.66 m x
0.038 m × 0.015 m. The schematic representation of device isshown in Figure 2.
The readings were recorded during clear sunny days
between 0900-1400 HRS. In the early morning basin is filledwith saline water and system is perfectly sealed.
Experimental data were collected at different time intervals.
The potable water output of the still is frequently measured.
The flow rate of the water is adjusted to the desired value

Fig. 2. Schematic view of single slope solar still.

during the top cover cooling process. Temperature of water,
air, inner cover and outer cover temperature are also recorded atregular intervals of fifteen minutes. Precision pyrheliometerand pyranometer are used for measuring the solar radiation
throughout the experiment.

3. Experimental Analysis
The hourly yield can be found as,me =q ew × 3600
L

(1)

Where qew is the evaporative heat transfer, L is the Latent heatof vaporization.
Instantaneous efficiency is given by,

ηi =

q ew
I

(2)

‘I’ refers the solar radiation.

4. Results and Discussion
The built-in concentrator distillation system (CDS) andsingle slope solar still (SSSS) were experimentally tested on
several sunny days in the campus of Sri Ramakrishna Mission
Vidyalaya College of Arts and Science, Coimbatore, India.
Data obtained included environmental condition (solarintensity radiation, ambient temperature and humidity), design
parameters (basin absorptivity and concentrator reflectivity),
and operational procedure (initial saline water temperature, airtemperature, inner cover and outer cover temperature) indicatedFig. 3. Variation of temperature with respect to time-Outer coverscooling.

that these decisively influence the still performance.
The variation of two different solar still temperatures ispresented in Figure 3. As shown from the illustration, thetemperatures have the same trend, as they increase in themorning hours and attain maximum values at around 2:00 p.m.,and decrease in the evening hours. This is obviously due tothe increasing solar incident radiation in the morning anddecrease in the afternoon. The maximum water temperature
measured was always between 1:00 p.m. and 2:00 p.m. was in
the range of 71-91°C for hemispherical basin solar still and34-64°C for the single slope solar still. But in the case ofconcentrator-coupled solar still the rise in temperature attains
maximum at higher sunshine hours and the distillate yield alsocollected to an optimum amount.
Similarly the airtemperature is achieved as 68-80°C for concentrator-coupledstill and 32-60°C for the single slope solar still.
Variations of efficiency of the stills are depicted in Figure 4.
The efficiency of the concentrator-coupled solar still with outer
cover cooling is in the range between 9%-42% and similarly
2%-32% for the single slope solar still with outer covercooling.
Figure 5 shows the variation in the hourly output of the
distillate yield with respect to time. It is clear from thegraphical representation that the built-in concentrator
distillation system (CDS) gives the higher yield as compared toconventional solar still. The maximum of total productivity
for the built-in concentrator distillation system with water flow
are 1.6 litres within four hours of time. But in the case of
single slope solar still the yield rate is 1.1 litres for a whole daycollection (i.e., eight hours). The top cover cooling ismaintained at constant flow rate for both the performance
study.

Fig. 4. Variations of efficiency with respect with to time with outer
cover cooling.

Fig. 5. Variation of hourly distillate yield with respect to time-Outercovers cooling.

The comparisons of both the studies reveals that expelledamount of distilled yield are obtained within a short period forthe concentrator-coupled solar still. When the efficiency andtemperature are considered, the built-in concentrator distillation
system is more helpful in the distillation process and the utility
would pave a new path for getting distillate water.

5. Conclusion
This work was carried out to evaluate the comparative
performance of two different solar still configurations; single
slope solar still (SSSS) and the built-in concentrator distillation
system with water flow over the cover. On the basis ofperformance results, the concentrator-coupled solar still wasfound to be more efficient than the conventional one. In thiscase, faster evaporation takes place from water surface andquick condensing occurred at the cover by cooling effect which
maintains larger temperature difference and improves
condensation.

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