1. Effect of phase change material on augmentation
of fresh water production of a triangular pyramid
solar still
Ravishankar S, M.E., (PhD)
Research Associate
Department of Mechanical Engineering
Hindustan Institute of Technology and
Science
Chennai
Hyacinth J Kennady
Professor
Department of Mechanical Engineering
Hindustan Institute of Technology and
Science
Chennai
P.K.Nagarajan
Professor
Department of Mechanical Engineering
S.A. Engineering College
Chennai.

2. Introduction
• A need of pure water is an important phenomenon in day-today life. Due to increase in population growth the need of
drinking water is shrinking.
• The possible ways of getting pure water is from rivers,
lakes, wells, rains etc. This kind of surface water must be
purified for human consumption.
• The purification of water involves the removal of un
dissolved substances, dissolved substances and harmful
microbes.
• The un dissolved substances are removed by sand filtration
and the microbes are killed through chlorination and by
boiling. Solar desalination does all the three function.

3. • People living in remote areas or islands, where fresh water
supply by means of transport is expensive, face the problem
of water shortage every day.
• Solar still presents some specific advantages for their use in
these areas due to its easier construction using locally
available materials, minimum operation and maintenance
requirements and friendliness to the environment.

4. Factors affecting the efficiency of
solar still
• The efficiency of the solar still depends upon the following
important parameters :1. Tilt angle of cover plate
2. Depth of water
3. Feed water flow rate
4. Cover plate temperature
5. Effect of stills
6. Convective heat transfer from cover plate and side walls
7. Design of structures and shapes
8. Solar tracking
9. Coating
10. External enhancement like heat pipe, coolers.

5. Literature review
Title
Author
Interference from the study
An experiment with a Cappelletti. G.M
plastic
solar
still,
Desalination, 142 (2002),
pp 221-227
Efficiency of still is 16 % due to
the low temperature in the lower
basin. By addition of asphalt
coating on the walls increases
productivity .
Life of the still is less since a
plastic material is used. A regular
maintenance is required
Effect of water depth on the G.N.Tiwari
performance of an inverted
absorber double basin solar
still, Energy
Conversion & Management
40 (1999) 1885–1897
The yield was 11.5 kgm-2day-1 and
keeps on decreasing when the
depth of water increased.
There is no significant increase in
the productivity if the number of
basin is more than three.

6. Title
Author
A Hybrid Solar Desalination Voropoulos.
and Water Heating System, Mathioulakis,
Desalination, 164 (2004), 2, Belessiotis, V
pp. 189-195
An experimental study on a
hemispherical solar still,
Desalination 286 (2012)
342–348
Interference from the study
K., Single basin integrated with heater.
E.,
Productivity of the still is 2.5 times
than the conventional solar still.
Arunkumar. T, R.
Jayaprakash , D.
Denkenberger,
Amimul Ahsan ,
M.S. Okundamiya ,
Sanjay
Kumar,
Hiroshi
Tanaka
,H.S. Aybar
Design and performance of a Basel I. Ismail
transportable hemispherical
solar still, Renewable Energy
34 (2009) 145–150
The average output of 3.5 l/m2/day
without cooling and 4.2 l/m2/day
with cooling of cover.
The temperature of the inlet water
can e increased by using PCM
storage tanks.
Typically produces 2.8 to 5.7 lm-2
day.

7. Title
Author
Interference from the study
Thermal performance of a El.Sebaii.A.A
triple basin solar still,
Desalination, 174 (2005), pp
23-37
Daily productivity equals 12.635
kgm-1day-1 with an average
intensity of 651 Wm-2.
The total daily productivity of the
system is maximum for the least
water masses in the lower and
middle basins without dry spots
over the base of the each effect
Performance of pyramid- Yazan Taamneh ,
shaped
solar
still: Madhar
M.
Experimental
study, Taamneh
Desalination 291 (2012) 6568
Daily yield was increased up to
25% compared to free convection
solar still.
For a concave wick type the
replacement of wick to be carried
out.
The effect of tilt angle on the
system performance has to be
studied. This may increase the
productivity.

8. Title
Author
Augmentation of saline V. Velmurugan , J.
streams in solar stills Mandlin , B. Stalin
integrating with a mini solar , K. Srithar
pond
Desalination
143–149
249
(2009)
Solar stills integrated with a Velmurugan
mini solar pond — analytical , K. Srithar
simulation and experimental
validation
Desalination
232–241
216
(2007)
Interference from the study
A mini solar pond was used to
store the solar thermal energy. The
heat energy stored by the mini
solar pond was used for preheating
saline water in fin type single basin
solar still and stepped solar still.
Experiments were carried out with
different salinity in the mini solar
pond. It was found that the
optimum value of salinity in solar
pond water was 80 g/kg.
Integration of a mini solar pond with a
solar still has been developed. Various
experiments for the yield of the
distilled water from ordinary still, still
with sponge, still integrated with a
pond, and still with sponge integrated
with mini solar pond are being carried
out. The average daily production of
distilled water has been found to be
increased considerably while the
sponged solar still is integrated with a
mini solar pond

9. Title
Author
Interference from the study
Single basin solar still with V. Velmurugan, M. he simple basin solar still was
fin
for
enhancing Gopalakrishnan, R. modified by using fins, sponges
productivity.
Raghu , K. Srithar and wicks for augmenting its
productivity. For the yield of the
Energy Conversion and
distilled
water,
various
Management 49 (2008)
experiments were conducted for
2602–2608
the
above
modifications.
Experimental results showed that
the average daily production was
higher when fins were used in the
still. The experimental analysis
agreed well with the theoretical.
The maximum deviation between
theoretical and experimental was
around 10%.
The productivity increased from
1.88 to 2.8 kg/m2
.

10. Title
Author
Interference from the study
Integrated performance
of stepped and single
basin solar stills with
mini solar pond
Desalination 249 (2009)
902–909
V. Velmurugan ,
S. Pandiarajan ,
P. Guruparan ,
L.Harihara
Subramanian ,
C.
David
Prabaharan
, K. Srithar
Two types of experiments are carried out. In the
first set of experiments, solar pond, stepped solar
still and single basin solar still are connected in
series to enhance the productivity of the solar
stills. For further augmentation of the
productivity, pebbles, baffle plates, fins and
sponges are used in both the solar stills. A
maximum productivity of 80% is obtained, when
fins and sponges are used in both the solar stills.
In the second set of experiments, a mini solar
pond, stepped solar still and wick type solar still
are connected in series. Pebbles, baffle plates,
fins and sponges are used in the stepped solar still
for further productivity
augmentation. The productivity during day and
night are calculated. It is found that maximum
productivity of 78% occurred, when fins and
sponges are used in the stepped solar still.
Pebbles store more thermal energy and releases
after the sun set. So, more night productivity is
obtained, when pebbles are used in the solar
stills. Industrial effluent is
used as feed. Theoretical analysis gives very good
agreement with the experimental results..

11. Title
Author
Interference from the study
Single basin double
slope solar still with
minimum basin depth
and energy
storing materials
Applied Energy 87
(2010) 514–523
K.Kalidasa
Murugavel,
S. Sivakumar,
J. Riaz Ahamed,
Kn.K.S.K.
Chockalingam,
K. Srithar
A single basin double slope still has been
fabricated and tested for different energy storing
materials like 1/4 in. quartzite rock, 1/4 in.
washed stones and mild steel scraps have been
used in the basin with layer of water equivalent to
0.5 cm depth. To improve the production further,
3/4 in. quartzite rock, 1 1/4 in. red brick pieces
and 1½ in. cement concrete pieces are used in the
basin with 0.75 mm depth of water. The still has
been theoretically modeled.
The transmittance and solar incidence variations
are considered. The total radiations on the sloped
covers are taken as input. The theoretical
performance of the still is compared with actual
still.
Out of different energy storing materials used,
3 /4 in. quartzite rock is the more effective which
yields higher production per day.

12. Title
Author
Desalination of effluent V. Velmurugan,
using fin type solar still C.K. Deenadayalan,
Energy 33 (2008) 1719– H. Vinod,
1727
K. Srithar
Interference from the study
The productivity of the single basin solar still is
augmented by integrating fins at the basin plate.
Effluent is used as a feed. To enhance the
productivity of solar still, it is modified with fin,
black rubber, sand, pebble and sponges.
Distillation of settled effluent has less
productivity than that of low salinity water. Also
it is found that productivity increased with
increase in solar intensity and decreased with
increase in wind velocity. Theoretical analysis
closely converges with experimental results.
From experimental results, it is observed that the
average evaporation rate in the conventional solar
still is 1.66 l per 8 h. The evaporation rate
increased by about 53% (2.54 l per 8 h) when fins
were integrated at the basin plate.

13. Problem Identification
• Productivity of solar still is lower.
• Additional accessories added to increase the
productivity

14. Methodology
• Productivity increases by flowing water over the
glass.
• Use of any other heat source such as solar collectors,
electricity, and other conventional sources.
• Flat plate collector, storage tank, mini solar pond,
floating perforated plate and baffle suspended
absorber are used to increase the inlet temperature of
the water.
• The total daily productivity of the system is
maximum for the least water masses in the lower and
middle basins without dry spots over the base of the
each effect.

15. • The effect of tilt angle on the system
performance has to be studied. This may
increase the productivity.
• The yield of the still is directly proportional to
the plate collector area.

16. Experimental Investigation and
approach
• Experimental investigations are performed to
evaluate the performance of solar still under
outdoor climatic conditions of Chennai.
• It consists of a metallic container, which is
occupied by the saline water up to a certain level
and below the exit collecting area where the fresh
water flows to the collecting jars kept at three
corners of the solar still.
• The solar radiation is transmitted through a 2 mm
thick triangular glass cover with a transmissivity
of 0.88.

17. • The bottom plate is black coated which absorbs
the heat. with a allowable energy absorbed by the
water, a phase transformation takes place in water.
• The evaporated water rises and reaches the inner
surface of glass in inclined position.
• Vapor once again undergoes phase change from
vapor to liquid.
• The condensed water flows through the channel
made of ms sheet which connected to the outlet.
• The contaminated water which contains the
impurities is removed by desalination process.

18. Experimental setup

19. Experimental Parameters
• The parameters used in the experiment are
given in Table .
• The still temperature was recorded using Ktype thermocouples and digital temperature
indicators.
• The solar radiation intensity was recorded by a
precision pyranometer.

20. Parameter
Symbol
Value
Transmissivity of glass
τc
.88
Emissivity of glass
εc
.98
Density of water
ρ
995 kg/m3
Latent heat of vaporization
hfg
2376 kJ/kg
Latitude
φ
110 North

21. Results and Discussion

22. Hourly variation of distillate output
on different test days without PCM

23. Hourly variation of distillate output
on different test days with PCM

24. Variation of temperature difference
between glass and water temperature
with effect of PCM

25. Accumulated Yield without PCM

26. Accumulated Yield with PCM

27. Variation of solar efficiency and solar
radiation without heat storage

28. • It can be noted that the solar still efficiency
increases in the morning time till reaching
maximum value around midday and then
decreases at slower rate in the afternoon. It is
clear that the still efficiency profiles follow
similar trends as of those for solar radiation
and distillate yield.
• The maximum value of solar still efficiency
based
on
free
convection
reached
approximately 35.2%.

29. • The difference between the free convection
and conventional solar still fresh water
production was found to be 40%.
• The increase in the freshwater production is
due to the circulation of the air inside the solar
still and hence the evaporation rate that has
been increased by the wind velocity over the
glass surface

30. Conclusion
• A triangular pyramid solar still with built-in sensible
heat thermal energy storage system was fabricated to
improve the still productivity.
• Another still with the same characteristics without
LHTESS was also constructed for investigation of the
internal convective and evaporative heat transfer
coefficient.
• Solar still presents some specific advantages for their
use in these areas due to its easier construction using
locally available materials, minimum operation and
maintenance requirements and friendliness to the
environment for producing portable water.

31. • The effect of wind on the solar still shows there is a
decrease in productivity during the morning hours. The
daily efficiency was found to be 53% with LHTESS and
45% without LHTESS.
• Solar radiation on the test days reveals that the maximum
intensity occurred during the mid-day, and the productivity
shows that the solar radiation and production rate are
directly proportional.
• The temperature difference between water and glass varies
from 10-15.5oC during the off-shine period. Experimental
results concludes that with PCM the production of fresh
water improved to about 4.3 liters/day for a 24 hour
operation, its due to the higher specific heat capacity.

32. References
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34. Thank You