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Experimental investigation of design parameters of solar glass desiccant box type
system for water production from atmospheric air
Manoj Kumar and Avadhesh Yadav
Citation: Journal of Renewable and Sustainable Energy 7, 033122 (2015); doi: 10.1063/1.4922142
View online: http://dx.doi.org/10.1063/1.4922142
View Table of Contents: http://scitation.aip.org/content/aip/journal/jrse/7/3?ver=pdfcov
Published by the AIP Publishing
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Experimental investigation of design parameters of solar
glass desiccant box type system for water production
from atmospheric air
Manoj Kumar
a)
and Avadhesh Yadav
Department of Mechanical Engineering, National Institute of Technology, Kurukshetra,
Haryana 136119, India
(Received 5 September 2014; accepted 21 May 2015; published online 2 June 2015)
In this paper, experiments have been performed in order to determine the design
parameters, i.e., air gap height, inclination angle, effective thickness of glass, and
effective number of glazing for the water production from atmospheric air by using
silica gel as solid desiccant material. Experiments have been performed in the
Indian climatic condition at NIT Kurukshetra, India [29
58
0
(latitude) North and
76
53
0
(longitude) East]. A newly designed solar glass desi ccant box type system,
three in numbers, has been used. It is found that design parameters for the
maximum production of water from the atmospheric air are air gap height as
0.22 m, inclination in angle as 30
, effective thickness of glass as 3 mm, and
number of glazing as single.
V
C
2015 AIP Publishing LLC.
[http://dx.doi.org/10.1063/1.4922142]
INTRODUCTION
One of the major challenges in front of developed and developing countries is the supply
of drinkable water. Some of the countries have enough water resources, but their unequal distri-
bution in terms of geographical and seasonal spread combined with the adverse impact of cli-
mate change has raised the demand for fresh water. Also, the practice of efficient use of water
is not followed in the fields of agriculture, industry, and domestic activities. Currently, there
are many countries, which are facing water crisis. Many attempts have been made for the pro-
duction of fresh water from atmospheric air.
1
Conducted the experiments on the new composite
material, which has S-shaped isotherms, to obtain fresh water from the wet air. For the collec-
tion of 1 l of fresh water, the temperature required during nocturnal phase was 20
C, humidity
as 50%, and clear sky during diurnal phase per m
2
was stated.
2
Analytically studied the method
of fresh water production by using liquid desiccant for the typical summer climate of Saudi
Arabia. It was proposed that for a given set of operating conditions, it was possible to obtain
1.90 kg of water per m
2
of the unit.
3
Performed the experiment by developing the new selective
water sorbent (SWS). The test results demonstrated that fresh water of 3–5 tons can be pro-
duced by using 10 tons of dry SWS per day.
4
Theoretical analysis of adsorption and desorption
rate for the water production was done. It was found that by taking the strong solution concen-
tration, the value of cyclic efficiency can be increased more than 90%.
5
Used two host materi-
als, namely, mesoporous silica gel and alumina with the two composites SWS-1L and SWS-1A.
These were formed by impregnating two host matrices with CaCl
2
in order to study the kine-
matics of water vapor sorption. It was found that SWS-1L adsorbs more water than the other
materials.
6
Manufactured two samples of SWS-2C and SWS-2EG by using mesoporous syn-
thetic carbon subunit and macroporous expanded graphite impregnated with lithium bromide. It
was found that water sorption capacity of novel composite desiccant is 0.75 g per 1 g of dry
sorbent which is higher than that of the conventional silica gel or zeolite.
7
Performed
a)
Author to whom correspondence should be addressed. Electronic mail: manojkumar_nitk@yahoo.com. Tel.: þ91
8529037306.
1941-7012/2015/7(3)/033122/17/$30.00
V
C
2015 AIP Publishing LLC7, 033122-1
JOURNAL OF RENEWABLE AND SUSTAINABLE ENERGY 7, 033122 (2015)
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experiments on a desiccant collector system for the water production from the atmospheric air.
A thick corrugated layer of cloth was used as a bed and CaCl
2
as a desiccant material. It was
found that system produced 1.5 l/m
2
/day of fresh water.
8
Studied a nonconventional method of
water production from atmospheric air by using calcium chloride (CaCl
2
) as desiccant material.
It was observed that the system efficiency increased with the initial concentration and decreased
with the increase in regeneration air velocity and absorption temperature.
9
Experimentally
investigated the adsorption of water vapor on the horizontal surface of a sandy layer impreg-
nated with calcium chloride (CaCl
2
). It was found that rate of absorption decreased with
decrease in mixing ratio and mass transfer coefficient was highly affected by the desiccant con-
centration in the bed.
10
Studied the extraction of water from air by using patented technology
based on extraction of air humidity into water streams. For the production of water, low grade
energy of 100–150 kcal/l was required. As per this extraction of water from air (EWA) technology
adsorption/desorption ratio is 2:1 and it can be operated at ambient temperature range between 5
and 45
C and at relative humidity (RH) of 20%, whereas at RH 60%, system achieved maximum
capacity.
11
Experimental work was done on the glass pyramid shape with a multi shelf solar sys-
tem to extract water from the atmospheric air. Two beds made up of cloth and saw wood, sa tu-
ratedwith30%CaCl
2
solution, were used. It was found that 2.5 l/day/m
2
fresh water can be pro-
duced.
12
Experimentally investigated M CM-41 (Mobile Composite Material) for fresh water
generation from atmospheric air. It was found that 1.2 kg/day/m
2
of fresh water can be produced
by using the new composite material.
13
Performed the experiments on a sandy bed impregnated
with calcium chloride for recovery of water from atmospheric air. It was found that 1.0 l/m
2
of
water can be produced after regeneration of the liquid desiccant material.
Some of the researchers have developed composite material and they used adsorption and
regeneration properties of composite material in the applications like production of dry air or
desiccant cooling system. Few researche rs have done work in the production of water from
atmospheric air by using different desiccant materials, but none of them optimized the desig n
parameters, i.e., air gap height, inclination angle, the effective thickness of glass, and effective
number of glazing for the maximum production of water from atmospheric air by using silica
gel as solid desiccant material.
EXPERIMENTAL SETUP
The photograph of the experimental setup is shown in Figures 2(a) and 2(b). It consists of
solar glass desiccant box type system (SGDBS). This system consists of the following main
parts:
FIG. 1. Solar Glass Desiccant Box Type System.
033122-2 M. Kumar and A. Yadav J. Renewable Sustainable Energy 7, 033122 (2015)
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(1) Fiber Reinforced Plastic (FRP) container
(2) Glazing
(3) Wire mesh tray
(4) Water measuring cylinder
(5) Connecting pipe
(6) Desiccant material
(1) FRP container: Three containers of fiber reinforced plastic, FRP, have been used because of
its good strength and long life. The size of each SGDBS is 0.6 m 0.6 m 0.3 m as shown in
Figures 1 and 2(a) and 2( b). Two windows of size 0.3 m 0.3 m have been provided for the
process of adsorption during the night time. This is an advantage over the other setup designs
in which for the adsorption process, glass has to be removed and for regeneration, again glass
has to be fixed. A water collecting tray with slight slope has been provided on the front side
for the collection of drops coming along the glass after condensation.
(2) Glazing: A glass of 3 mm thickness is used for the purpose of glazing. This is also acting as a
condenser during the regeneration process. Glass allows the sun rays of shorter wavelength to
pass inside the SGDBS and traps the ray of longer wavelength which comes after heating the
solid desiccant material. It is used to create the greenhouse effect inside the SGDBS.
(3) Wire mesh tray: A wire mesh of steel wire is used inside the SGDBS for holding the solid des-
iccant material. The dimensions of the wire mesh are 3 mm 3 mm. Wire mesh is screwed on
the plastic frame.
FIG. 2. Photograph of the experimental setup (a) during adsorption process and (b) during regeneration process.
033122-3 M. Kumar and A. Yadav J. Renewable Sustainable Energy 7, 033122 (2015)
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(4) Connecting pipe: Connecting pipe is attached between water collecting tray and bottle. This
provides a path for the flow of condensed water droplets.
(5) Water measuring cylinder: A water measuring cylinder is used outside the SGDBS for the col-
lection of water. The water comes directly from the water collection tray through the connect-
ing pipe to the bottle. There is provision of measuring marks on the cylinder which indicates
the collected quantity of the water. The minimum quantity of water that can be measured is
5ml.
(6) Desiccant material: Silica gel is used as a solid desiccant material for the water production
from the atmospheric air. For this purpose, 1 kg of silica gel has been used. When the silica
gel is in the regenerated form, then it is indicated by the blue color and when it is in the
adsorbed form, then it is indicated by the pink color. This color indication is due to the cobalt
chloride. The rest of the properties of silica gel are in Table I as provided by Swambe
Chemicals Pvt., Ltd., India.
MEASURING DEVICES AND INSTRUMENTS
Different parameters were measured during the experiments as follows:
•
Temperature of material, inner side of glass, outer side of glass, and inside space temperature of
SGDBS
•
Ambient temperature
•
Solar radiation intensity
•
Weighing machine
Temperature of material, inner side of the glass, outer side of glass, and inside the SGDBS
were measured with the help of Resistance Temperature Detector PT100 thermocouples which
were connected with a digital temperature indicator that showed the temperature with a resolu-
tion of 0.1.
Dry and wet bulb temperatures of ambient air were measured using a sling Psychrometer.
The solar radiation intensity was measured during the day time with a Pyranometer-Model
CM11 of Kipp and Zonen, Holland.
Adsorption of moisture during the experiment was measured with the help of a digital
weighing machine having maximum capacity of 50 kg, minimum capaci ty of 1 g, and resolution
of 0.001 kg. Weighing machine with display meter, as shown in Figures 2(b) and 3, was the
maker of “THOMSON Electronic weighing scales.”
The experiment for the production of water was carried out in the month of July 2014.
Adsorption process started during the night time and regeneration, in the day time. The weight
evolution during adsorption process and data during regeneration process was manually moni-
tored at 30-min interval.
TABLE I. Properties of silica gel used as a desiccant material.
Product Silica gel blue crystal
Size 3–5 mesh
Assay (as SiO
2
) 98.48%
pH 5.8
Bulk density 0.585 g/ml
Loss on drying 1.2%
Friability 99.5%
Chloride (as NaCl) 0.002%
Cobalt (as CoCl
2
) 0.5%
Adsorption capacity at 100% RH 35.82%
033122-4 M. Kumar and A. Yadav J. Renewable Sustainable Energy 7, 033122 (2015)
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SYSTEM O PERATION
For the working of the experimental setup, the solid desiccant material, i.e., silica gel, is
placed on the wire mesh tray. For the adsorption process, the side windows of the SGDBS are
opened at 19:00 h in the evening. The adsorption process starts because the vapor pressure on
the surface of the desiccant material (adsorbent) is lower than the atmospheric air. This process
is continued up to late night till the equilibrium conditions, i.e., when the vapor pressure on the
adsorbent surface is same as that of atmospheric air, attained. In the morning at 6 o’clock, the
side windows are closed and setup is exposed to the sun rays for the regeneration process. As
the temperature of the desiccant material rises, the vapor pressure difference between the sur-
face of the desiccant material and the air of the inner space of the box increases. Therefore,
adsorbed moisture is transferred to the air of the inner space and increases the vapor pressure.
As the solar intensity increases, mass transfer of vapor from material to the air of inner space
increases and reaches to saturation condition. The water vapor condenses on the inner side of
the glass and after coalition forms the small drops. The small drops slide along the surface of
the glass and get collected in the water collection tray. Due to slope in water collection tray,
water goes to the water measuring container through a connecting pipe. The maximum regener-
ation temperature depends upon the available heat. The amount of collected water is measured
manually at 30-min interval.
ANALYSIS OF EXPERIMENTAL DATA
The adsorption rate of quantity of desiccant is the amount of water content absorbed by the
desiccant per unit time and is given by
14
G
A
¼ m
ws
dw
dt
: (1)
The equation of adsorption equilibrium isotherm for regular density silica gel is given by
15
RH
d
¼ 0:0078 – 0:05759 W þ 24:1655 W
2
– 124:78 W
3
þ 204:226 W
4
: (2)
RESULTS AND DISCUSSION
Case 1: Variation air gap height of SGDBS
In this case, the objective was to study the effective air gap height. For this purpose three
boxes have been taken and three air gap heights, i.e., 0.10 m, 0.16 m, and 0.22 m have been cre-
ated. In figures for this case, it is denoted as box-1 (0.10 m), box-2 (0.16 m), and box-3
(0.22 m).
(a) Adsorption rate of desiccant material
Adsorption rate of desiccant material at air gap height of 0.10 m, 0.16 m, and 0.22 m.
The experiment for the adsorption process was started at 19:00 h. The graph in Figure 4(a)
is for adsorption rate and ambient air temperature with time and Fig. 4(b) is plotted for adsorp-
tion rate and humidity ratio with time. At the initial stage, maximum adsorption rate is
FIG. 3. Photograph of displaymeter.
033122-5 M. Kumar and A. Yadav J. Renewable Sustainable Energy 7, 033122 (2015)
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0.049 kg/h for box-1 and 0.043 kg/h for box-2 and box 3 each. This is because at that time
pores were empty and with the progression of time, pores started to fill. This decreases the
adsorption rate. In box-1, adsorption rate is more instead of less space because the air from
box-1 was completely in touch with the material and was leaving the system after releasing its
moisture completely. In case of box-2, some of the air, without touching the material, was pass-
ing through the window which is the reason for less adsorption rate as compared to box-1. In
case of box-3, the adsorption rate was less as compared to box-1 and box-2, instead of having
more space after opening the side windows. This is because most of the air was leaving the
box without coming in contact with the material. Material adsorbed the moisture only from the
air which was coming in contact with it. All the three boxes saturated at 03:00 h.
(b) Temperature distribution of desiccant material
Variation in desiccant temperature and solar intensity with time at air gap height of 0.10 m,
0.16 m, and 0.22 m.
Figure 5 shows that at the starting of the experiment, the temperature of the desiccant ma-
terial in box 1 started to rise more as compared to the other boxes. This is because in box 1 the
material is closer to the glass and the volume is less. In box-2, the air gap height is 0.16 m and
volume inside is more as compared to box 1, so it takes more time to gain temperature. In box-
3, the air gap height is 0.22 m and volume inside the box is more as compared to box-1 and
box-2, so it takes more time to gain temperature. After 11:00 h, the material temperature in
box-3 started to rise more because the volume inside it started to accumulate more amount of
heat as compared to the other two boxes.
Figure 6 also shows that the maximum temperature of internal space occurs at the air gap
height of 0.22 m as that of Figure 5. This is because heat transfer to the surrounding is mini-
mum as compared to the other air gap height. The internal space temperature of box-3
FIG. 4. (a) Variation of adsorption rate and ambient air temperature with time for desiccant material on 03 July 2014 and
(b) variation of adsorption rate and humidity ratio with time for desiccant material.
033122-6 M. Kumar and A. Yadav J. Renewable Sustainable Energy 7, 033122 (2015)
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accumulated more heat because of having more volume than that of the other two boxes. The
maximum temperature inside box-1, box-2, and box-3 is 74.4
C, 78.8
C, and 79.1
C,
respectively.
Figure 7 shows that the inner glass temperature of box-1 is higher than that of the other
two boxes. This is because the desiccant material after gaining heat started to emit it very soon
as the air gap height is very less, i.e., 0.10 m. Whereas in case of box-2 the air gap height is
0.16 m so the inner glass temperature is low and in the case of box-3 the air gap height is
0.22 m so inner glass temperature is further low.
Figure 8 shows the same variation of temperature as that of Figure 7 but her e temperature
is measured for the outer surface of the glass. This is because the surface heating phenomena is
same for both cases. At 12:00 h, maximum temperature of box-1, box-2, and box-3 is 69.6
C,
67.4
C, and 68.6
C, respectively.
(c) Productivity of water by desiccant material
Productivity of water by desiccant material, i.e., silica gel at the air gap height of 0.10 m,
0.16 m, and 0.22 m.
Figure 9 shows that the rate of water production by box-1 is higher at initial, i.e., up to
11:00 h because inside box-1 the volume is less and the material got heated very fast as shown
in Figure 5. At the same time, the inner glass temperature is enough for the condensation while
the same condition is not for the other boxes. The water production rate decreases as the inner
glass temperature starts to increase. For box-2 result shows that at initial stage water productiv-
ity is lower as compared to box-1 because in this case inside temperature of the glass is not
FIG. 5. Variation in desiccant material temperature and solar intensity with time on 04 July 2014.
FIG. 6. Variation in internal space temperature and solar intensity with time on 04 July 2014.
033122-7 M. Kumar and A. Yadav J. Renewable Sustainable Energy 7, 033122 (2015)
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favorable for the condensation. But at later stages the productivity of the water decreases and
becomes almost equal. In case of box-3, the condition is favorable for the production of good
quantity of water. The maximum quantity of water produced by box-3 is 180 ml/kg/day where
as box-1 and box-2 produced 160 ml/kg/day of water.
Case 2: Variation in inclination angle to SGDBS
After finding the effective air gap height as 0.22 m for the production of maximum quantity
of water, the next case is to find out the effective angle. For this purpose, inside the three boxes
air gap height is adjus ted at 0.22 m and three angles are given to SGDBS as 10
,20
, and 30
.
In figures for this case it is denoted as box-1 (10
), box-2 (20
), and box-3 (30
).
(a) Adsorption rate of desiccant material
Adsorption rate of desiccant material at air gap height of 0.22 m and at an angle of inclina-
tion 10
,20
, and 30
.
The experiment for the adsorption process was started at 19:00 h. At an initial stage, maxi-
mum adsorption rate is 0.051 kg/h for box-2 and 0.049 kg/h for box-1 and box 3 each as shown
in Figures 10(a) and 10(b). The maximum humidity ratio is 0.02189 kg
water vapor
/kg dry
air.
(b) Temperature distribution of desiccant material
Variation in desiccant temperature and solar intensity with time at air gap height of 0.22 m
and at an angle of inclination 10
,20
, and 30
.
Figures 11 and 12 show that effect of inclination angle on the temperature of desiccant ma-
terial and internal space with solar intensity. The resu lt shows that at morning and evening time
FIG. 7. Variation in inner glass temperature and solar intensity with time on 04 July 2014.
FIG. 8. Variation in outer glass temperature and solar intensity with time on 04 July 2014.
033122-8 M. Kumar and A. Yadav J. Renewable Sustainable Energy 7, 033122 (2015)
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FIG. 10. (a) Variation of adsorption rate and ambient air temperature with time for desiccant material on 06 July 2014 and
(b) variation of adsorption rate and humidity ratio with time for desiccant material on 06 July 2014.
FIG. 9. Variation in water produced by three boxes and solar intensity with time on 04 July 2014.
FIG. 11. Variation in desiccant material temperature and solar intensity with time on 07 July 2014.
033122-9 M. Kumar and A. Yadav J. Renewable Sustainable Energy 7, 033122 (2015)
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for 10
inclination angle, the material has maximum temperature as compared to the other incli-
nations. Because of this condition, maximum solar radiations are absorbed, but at noon time
30
inclination angle has a maximum gain of solar heat. Maximum temperature attained by the
desiccant material inside box-1, box-2, and box-3 is 87.8
C, 82.3
C, and 87.1
C, respectively,
at 14:00 h. For the internal space temperature, the maximum temperature inside box-1, box-2,
and box-3 is 79.3
C, 75.9
C, and 78.3
C, respectively. Maximum solar intensity attained dur-
ing the experimental day is 827 W/m
2
.
Figures 13 and 14 show that the inner and outer glass temperatures of boxes. Figure shows
that up to noon, the 10
inclination in angle has more inner glass temperature as compared to
the other inclinations. After noon inner glass and outer glass temperatures of 30
inclination
raises more and in later stages it becomes more or less same to the other inclinations.
(c) Productivity of water by desiccant material
Productivity of water by desiccant material at air gap height of 0.22 m and at an angle of
inclination 10
,20
, and 30
.
Figure 15 shows that water production at 30
inclination gives maximum productivity. This
is because the inner glass temperature at an inclination of 30
is less as compared to other incli-
nations which is a favorable condition for condensation. The water produced by box-1, box-2,
and box-3 is 180 ml/kg/day, 190 ml/kg/day, and 200 ml/kg/day, respectively.
FIG. 12. Variation in internal space temperature and solar intensity with time on 07 July 2014.
FIG. 13. Variation in inner glass temperature and solar intensity with time on 07 July 2014.
033122-10 M. Kumar and A. Yadav J. Renewable Sustainable Energy 7, 033122 (2015)
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Case 3: Variation of thickness of glass of SGDBS
After finding the effective air gap height as 0.22 m and effective inclination angle as 30
for the production of maximum quantity of water, the next case is to find the effective thickness
of glass. For this purpose, three different thicknesses of glass as 3 mm, 5 mm, and 8 mm have
been taken for box-1, box-2, and box-3, respectively. In figures for this case it is denoted as
box-1 (3 mm), box-2 (5 mm), and box-3 (8 mm).
(a) Adsorption rate of desiccant material
The adsorption rate of desiccant materi al at air gap height of 0.22 m, at an angle of inclina-
tion 30
, and at different thicknesses of glass as 3 mm, 5 mm, and 8 mm.
The experiment for the adsorption process was started at 19:00 h. The maximum absorption
rate is 0.055 kg/h for box-2 and 0.049 kg/h for box-1 and box 3 each as shown in Figures 16(a)
and 16(b). The maximum humidity ratio is 0.02174 kg
water vapor
/kg dry
air.
(b) Temperature distribution of desiccant material
Variation in temperature of the desiccant material at an air gap height of 0.22 m, at an
angle of inclination 30
, and at different thicknesses of glass as 3 mm, 5 mm, and 8 mm.
Figure 17 shows that the desiccant material temperature of box wit h 8 mm thickness is
more as compared to the other thicknesses. Once the heat is accumulated in the box, there are
three ways to reject it to the surroundings. This is through conduction, convection, and radia-
tion. As per Fourier law, heat transfer through the conduction decreases if thickness increases.
FIG. 14. Variation in outer glass temperature and solar intensity with time on 07 July 2014.
FIG. 15. Variation in water produced by three boxes and solar intensity with time on 07 July 2014.
033122-11 M. Kumar and A. Yadav J. Renewable Sustainable Energy 7, 033122 (2015)
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It is found that the maximum temperature attained by the desiccant material inside box-1, box-
2, and box-3 is 90.7
C, 91.5
C, and 92.7
C, respectively, at 13:30 h. Maximum solar intensity
attained on experimental day is 664 W/m
2
.
Figure 18 shows the variation of internal space temperature of three boxes with time,
atmospheric temperature, and solar intensity. The internal space temperature of box-1 accumu-
lated more heat because of the less thickness of the glass. This allows maximum sun rays to
pass through the glass with less reflection. In case of box-2 since the thickness is more, i.e.,
5 mm so reflection of sunrays is more so there is less accumulation of heat as compared to box-
1. In case of box-3, thickness is 8 mm so reflection is more so there is very less accumulation
of heat. The maximum temperature inside box-1, box-2, and box-3 is 80.2
C, 76.6
C, and
75.8
C, respectively.
FIG. 17. Variation in desiccant material temperature and solar intensity with time on 08 July 2014.
FIG. 16. (a) Variation of adsorption rate and ambient air temperature with time for desiccant material on 07 July 2014 and
(b) variation of adsorption rate and humidity ratio with time for desiccant material on 07 July 2014.
033122-12 M. Kumar and A. Yadav J. Renewable Sustainable Energy 7, 033122 (2015)
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Figures 19 and 20 show that the inner and outer glass temperatures of 8 mm thickness are
more. This is because the heat transfer to the atmosphere through the conduction is less for
more thickness as per the Fourier law. This is also discussed in Figure 17. Maximum tempera-
ture attained by inner glass of box-1, box-2, and box-3 is 69.0
C, 68.5
C, and 69.5
C, respec-
tively, at 13:30 h. The maximum temperature attained by the out er glass of box-1, box-2, and
box-3 is 78.4
C, 71.3
C, and 79.9
C, respectively.
FIG. 19. Variation in inner glass temperature and solar intensity with time on 08 July 2014.
FIG. 20. Variation in outer glass temperature and solar intensity with time on 08 July 2014.
FIG. 18. Variation in internal space temperature and solar intensity with time on 08 July 2014.
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(c) Productivity of water by desiccant material
Productivity of water by desiccant material at air gap height of 0.22 m, at an angle of incli-
nation 30
, and at different thicknesses of glass as 3 mm, 5 mm, and 8 mm.
Figure 21 shows that the water productivity of box-1 having glass thickness of 3 mm is
more because when thickness is less, the heat transfer to the surroundings is more. This reduces
the temperature of inner glass and increases the productivity of the water. The water produced
by box-1, box-2, and box-3 is 120 ml/kg/day, 110 ml/kg/day, and 80 ml/kg/day, respectively.
Case 4: Variation in number of glazing of SGDBS
After finding the effective air gap height as 0.22 m from glass, effective inclination angle
as 30
and effective thickness of glass as 3 mm, next step is to det ermine the effect of number
of glazing. Three cases have been considered as single glazing, double glazing and triple
FIG. 21. Variation in water produced by three boxes and solar intensity with time on 08 July 2014.
FIG. 22. (a) Variation of adsorption rate and ambient air temperature with time for desiccant material on 08 July 2014 and
(b) variation of adsorption rate and humidity ratio with time for desiccant material on 08 July 2014.
033122-14 M. Kumar and A. Yadav J. Renewable Sustainable Energy 7, 033122 (2015)
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glazing. In the figures it is denoted as box-1 (single), box-2 (double), and box-3 (triple). A gap
of 5 cm is kept between the two glasses.
(a) Adsorption rate of desiccant material
The adsorption rate of silica gel at the air gap height of 0.22 m, at an angle of inclination
30
, effective thickness of glass as 3 mm and with glazing as single, double and triple.
The experiment for the adsorption process was started at 19:00 h. The maximum adsorption
rate is 0.049 kg/h for box-2 and 0.047 kg/h for box-1 and box-3 each as shown in Figures 22(a)
and 22(b). The maximum humidity ratio is 0.02119 kg
water vapor
/kg
dry air.
From Figures 10(a) and 10(b), 16(a) and 16(b), and 22(a) and 22(b), it is found that the
adsorption rate doesn’t vary significantly by varying the inclination angle, thickness of glass
and number of glazing of glass. But it is affected by the height of desiccant material bed.
(b) Temperature distribution of desiccant material
Variation in desiccant material temperature at the air gap height of 0.22 m, at an angle of
inclination 30
, with thickness of glass as 3 mm and with glazing as single, double and triple.
Figures 23 and 24 show that the box with the single glazing has higher material tempera-
ture and internal space temperature as compared to the boxes with double and triple glazing.
This is because single glazing allows sun rays to pass very easily where as double glazing act
as a hindrance to the sun rays and in triple glazing hindrance is more. Maximum temperature
attained by the desiccant material inside box-1 is 89.1
C at 14:00 h, box-2 is 84.6
C at 13:30
h, and in box-3 is 83.0
C at 13:00 h. Maximum solar intensity attained on experimental day is
848 W/m
2
.
FIG. 23. Variation in material temperature and solar intensity with time on 09 July 2014.
FIG. 24. Variation in internal space temperature and solar intensity with time on 09 July 2014.
033122-15 M. Kumar and A. Yadav J. Renewable Sustainable Energy 7, 033122 (2015)
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(c) Productivity of water by desiccant material
Productivity of water by desiccant material at air gap height of 0.22 m, at an angle of incli-
nation 30
, with thickness of glass as 3 mm, and with glazing as single, double, and triple.
Figure 25 shows that the maximum water production rate is by box-1 as 145 ml/kg/day.
This is because the adsorption rate, material temperature, and the internal space temperature of
box-1 is more as compared to box-2 and box-3. In case of box-2 water production is low as 65
ml/kg/day because there is less accumulation of heat due to double glazing. In case of box-3,
the water produced is just 40 ml/kg/day. After the experiment, it is found that most of the desic-
cant material has been regenerated in case of box-1, which is indicated by the blue color of the
silica gel, so the productivity is 145 ml/kg/day. In case of box-2 almost half of the desiccant
material regenerated, indicated by a blue color and half remained adsorbed, indicated by the
pink color of the desiccant material. In case of box-3 most of the desiccant material was pink
which means material couldn’t be regenerated, so the productivity is 40 ml/kg/day. It is also
found that triple glazing leads to less accumulation of heat, which further causes to the less
regeneration of desiccant material.
CONCLUSIONS
An integrated solar glass desiccant based system (SGDBS) has been used for the produc-
tion of water from atmospheric air. It is designed, fabricated, and experimentally tested. Silica
gel is used as desiccant material for the experiments.
The experimental results during the process of adsorption and regeneration have shown the
following important conclusions:
(1) Experimental results of SGDBS have shown that water can be produced from the atmospheric
air by keeping air gap height at 0.22 m, angle of inclination as 30
, thickness of the glass as
3 mm, and using single glazing.
(2) Result from the variation of the gap shows that water produced by the air gap height of 0.22 m
is 12.5% more than the air gap height of 0.10 m and 0.16 m.
(3) Result from the variation in inclination angle shows that water produced by the angle 30
is
11.11% more as compared to 10
angle and 5% more to 20
angle.
(4) Result from the variation of thickness of glass shows that water produced by the thickness
3 mm is 50% more as compared to 8 mm thickness and 9% more as compared to 5 mm
thickness.
(5) Result from the variation of effect of glazing shows that water produced by the single glazing is
3.6 times more as compared to triple glazing and 2.2 times more as compared to double glazing.
(6) The maximum amount of water produced during the experiments is 200 ml/kg/day.
FIG. 25. Variation in water produced by three boxes and solar intensity with time on 09 July 2014.
033122-16 M. Kumar and A. Yadav J. Renewable Sustainable Energy 7, 033122 (2015)
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RECOMMENDATIONS
During the experiments, it was observed that the experiments should be repeated at selected
days. It is further suggested that a theoretical model can be developed for the prediction of
water produced from the atmospheric air for covering a wide range of climatic conditions.
NOMENCLATURE
G
A
adsorption rate (kg/h)
m
ws
weight of desiccant on wet basis (kg)
RH
d
relative humidity
w moisture content in desiccant (kg
water vapor
/kg
desiccant
)
W water content of desiccant
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