Comparative study of solar-powered water production from atmospheric air using different desiccant materials

Figures & data

Figure 1. Schematic diagram for Solar Glass Desiccant based System (SGDBS), Kumar and Yadav (2015).

Figure 2. Photograph of the experimental set-up (a) during adsorption process (b) during regeneration process.

Table 1. Properties of silica gel used as a desiccant material.

Product	Silica gel blue crystal
Size	3–5 mesh
Assay (as SiO2)	98.48%
Bulk density	0.585 g/ml
Specific heat	0.921 kJ/kg K
Loss on drying	1.2%
Friability	99.5%
Chloride (as NaCl)	0.002%
Cobalt (as CoCl2)	0.5%
Adsorption capacity @ 100% RH	35.82%

Table 2. Properties of activated alumina used as a desiccant material.

Product	Activated alumina ball
Size	3–5 mm
Pore volume	0.46 cc/gm
Surface area	370 m^2/gm
Bulk density	0.726 g/ml
Specific heat	1.0 kJ/kg K
Loss on attrition (% wt)	0.1
Crushing strength	175.95 N
Adsorption capacity %wt @ 100% RH	27.94%

Table 3. Properties of Molecular sieve 13 X used as a desiccant material.

Product	Molecular sieve 13 X
Shape and size	Beads 1.6 – 2.7
Pore diameter	10 Angstroms
Bulk density	0.674 g/ml
Specific heat	0.962 kJ/kg K
Loss on attrition (%wt)	0.1%
Crushing strength	45 N
Adsorption capacity for CO2 (%wt)	19.50%
Heat of adsorption	1100 kcal/kg of water adsorbed
Adsorption capacity %wt @ 100% RH	32%

Table 4. Levels and coded variables chosen for CCD.

Variables	−2 (α)	−1	0	+1	+2 (α)
Material temperature (°C)	58.15	46.3	70	93.7	81.85
Internal space temperature (°C)	48.82	41.4	56.25	71.1	63.67
Inner glass temperature(°C)	45.97	39.6	52.35	65.1	58.72
Outer glass temperature(°C)	47.35	41.4	53.3	65.2	59.25

Table 5. CCD values with experimental values of water production.

Run	Material temperature	Internal space temperature	Internal glass temperature	Outer glass temperature	Water production
1	46.3	41.4	39.6	41.4	0
2	48.8	44.6	41.2	43.3	0
3	54.6	45.9	43.5	43.8	0
4	62.9	50.5	49.8	50	10
5	70.3	53.9	54.4	53.7	20
6	75.9	57.5	55.8	56.9	30
7	80.1	60.6	58.8	59.2	45
8	85.3	65.5	63.2	65.2	65
9	87.4	68.1	63.7	64.5	80
10	88.5	68.9	63.5	62.3	110
11	90.9	70.5	64.5	62.8	130
12	92.1	70.9	64.9	63.4	140
13	93.6	71.1	65.1	64.3	150
14	93.7	70.7	65	62.2	160
15	91.5	69.3	63	59.5	160
16	85.1	64.7	59.1	56.3	160
17	77.9	62.1	56.9	55.8	160
18	46.3	41.4	39.6	41.4	0
19	48.8	44.6	41.2	43.3	0
20	54.6	45.9	43.5	43.8	0
21	62.9	50.5	49.8	50	10
22	70.3	53.9	54.4	53.7	20
23	75.9	57.5	55.8	56.9	30
24	80.1	60.6	58.8	59.2	45
25	85.3	65.5	63.2	65.2	65
26	87.4	68.1	63.7	64.5	80
27	88.5	68.9	63.5	62.3	110
28	90.9	70.5	64.5	62.8	130
29	92.1	70.9	64.9	63.4	140
30	93.6	71.1	65.1	64.3	150

Table 6. ANOVA for response surface quadratic model of water production.

Source	Sum of squares	df	Mean square	F value^a	Prob. > F (p-value)
Model	110629.554	14	7902.111	160.805	< 0.0001 *
A-Material temp.	2375.682	1	2375.682	48.344	< 0.0001*
B-Internal Space-temp.	3663.571	1	3663.571	74.552	< 0.0001*
C-Inner glass temp.	2869.437	1	2869.437	58.392	< 0.0001*
D-Outer glass temp.	2204.411	1	2204.411	44.859	< 0.0001*
AB	3421.459	1	3421.459	69.626	< 0.0001*
AC	39.110	1	39.110	0.796	0.3864
AD	0.167	1	0.167	0.003	0.9542
BC	2163.458	1	2163.458	44.026	< 0.0001*
BD	1198.884	1	1198.884	24.397	0.0002*
CD	378.772	1	378.772	7.708	0.0141*
A^2	1673.864	1	1673.864	34.063	< 0.0001*
B^2	2603.341	1	2603.341	52.977	< 0.0001*
C^2	1101.993	1	1101.993	22.425	0.0003*
D^2	6.323	1	6.323	0.129	0.7248
Residual	737.113	15	49.141
Lack of fit	737.113	2	368.557
Pure error	0.000	13	0.000
Cor total	111366.667	29

Notes: SD – 7.01; Mean – 73.33; C.V. % 9.56; R² – 0.9934; Adj R² – 0.9872; Predicted R² – 0.8617; Predicted residual sum of squares (PRESS)-26536.52; Adeq. Precision – 34.938.

^a F-Test measures the significance of model.

* Significant.

Figure 3. Variation of water production with (a) material temperature, (b) internal space temperature and (c) inner glass temperature.

Figure 4. Influence of material temperature and internal space temperature for water production.

Table 7. Levels and coded variables chosen for CCD.

Variables	−2 (α)	−1	0	+1	+2 (α)
Material temperature (°C)	68.62	48.1	73.15	98.2	85.67
Internal space temperature (°C)	50.5	42.7	58.30	73.9	66.1
Inner glass temperature (°C)	45.67	39.4	51.95	64.5	58.22
Outer glass temperature (°C)	46.37	40.3	52.45	64.6	58.52

Table 8. CCD values with experimental values of water production.

Run	Material temperature	Internal space temperature	Internal glass temperature	Outer glass temperature	Water production
1	48.1	42.7	39.4	40.3	0
2	49.3	45.6	41	42.1	0
3	55.6	47.1	42.3	43.9	0
4	61.3	52.5	47.8	49.4	0
5	68.7	56	51.6	53.4	0
6	74.6	59.9	55.2	55.1	0
7	80.7	63.1	58.1	58.4	5
8	86.3	68.5	62.8	64.1	5
9	89.5	71.1	64	63.7	10
10	91.7	71.2	64.3	62	10
11	95.3	72.6	64.5	60.8	15
12	97.9	73	63.9	63.1	20
13	98.2	73.9	64.3	64.6	20
14	97.8	73.5	62.8	60.8	20
15	95.3	72.4	61.5	63.7	20
16	89.2	69.1	58.1	56.6	20
17	88.6	66.6	56.1	56.1	20
18	48.1	42.7	39.4	40.3	0
19	49.3	45.6	41	42.1	0
20	55.6	47.1	42.3	43.9	0
21	61.3	52.5	47.8	49.4	0
22	68.7	56	51.6	53.4	0
23	74.6	59.9	55.2	55.1	0
24	80.7	63.1	58.1	58.4	5
25	86.3	68.5	62.8	64.1	5
26	89.5	71.1	64	63.7	10
27	91.7	71.2	64.3	62	10
28	95.3	72.6	64.5	60.8	15
29	97.9	73	63.9	63.1	20
30	98.2	73.9	64.3	64.6	20

Table 9. ANOVA for response surface 2FI model of water production.

Source	Sum of squares	df	Mean square	F value^a	Prob. > F (p-value)
Model	2042.290	10	204.229	159.182	<0.0001*
A-Material temp.	9.124	1	9.124	7.112	0.0152*
B-Internal space temp.	21.452	1	21.452	16.720	0.0006*
C-Inner glass temp.	13.892	1	13.892	10.828	0.0038*
D-Outer glass temp.	0.203	1	0.203	0.158	0.6953
AB	0.761	1	0.761	0.593	0.4507
AC	0.147	1	0.147	0.115	0.7385
AD	0.145	1	0.145	0.113	0.7408
BC	0.043	1	0.043	0.034	0.8565
BD	0.167	1	0.167	0.131	0.7219
CD	0.699	1	0.699	0.544	0.4696
Residual	24.377	19	1.283
Lack of fit	24.377	6	4.063
Pure error	0.000	13	0.000
Cor total	2066.667	29
Residual	737.113	15	49.141
Lack of fit	737.113	2	368.557
Pure error	0.000	13	0.000
Cor total	111366.6667	29

Notes: SD – 1.13; Mean – 8.33; C.V. % 13.59; R² – 0.9882; Adj R² – 0.9820; Predicted R² – 0.9657; Predicted residual sum of squares (PRESS)-70.94; Adeq. Precision – 33.716.

^a F-Test measures the significance of the model.

* Significant.

Figure 5. Influence of material temperature and internal space temperature for water production.

Table 10. Levels and coded variables chosen for CCD.

Variables	−2 (α)	−1	0	+1	+2 (α)
Material temperature (°C)	57.47	47.1	70	88.6	78.22
Internal space temperature (°C)	56.1	46.8	56.25	84	74.7
Inner glass temperature(°C)	52.35	45.7	52.35	72.3	65.65
Outer glass temperature(°C)	47.05	41.2	53.3	64.6	58.75

Table 11. CCD values with experimental values of water production.

Run	Material temperature	Internal space temperature	Internal glass temperature	Outer glass temperature	Water production
1	47.1	46.8	45.7	41.2	0
2	47.9	49	48.9	43.3	0
3	48.4	51.3	51.1	46	0
4	54.7	56.6	56.1	50.6	0
5	60.6	60.6	59.9	54.3	5
6	66.2	64.7	63.5	57	10
7	71.7	68.5	66.8	59.6	20
8	78.7	75.5	71.2	64.6	30
9	82.6	81.2	72.3	65.3	30
10	84.9	81.8	72.2	63.7	35
11	86.4	83.2	72.3	63	35
12	87.5	83.8	72.1	63.5	35
13	88.6	84	72.1	63.2	35
14	87.6	84	70.7	61.5	35
15	84.9	82	68.6	59.8	35
16	81.1	77.1	64.7	56.2	35
17	72.3	73.4	62.1	54.2	35
18	47.9	49	48.9	43.3	0
19	48.4	51.3	51.1	46	0
20	54.7	56.6	56.1	50.6	0
21	60.6	60.6	59.9	54.3	5
22	66.2	64.7	63.5	57	10
23	71.7	68.5	66.8	59.6	20
24	78.7	75.5	71.2	64.6	30
25	82.6	81.2	72.3	65.3	30
26	84.9	81.8	72.2	63.7	35
27	86.4	83.2	72.3	63	35
28	87.5	83.8	72.1	63.5	35
29	88.6	84	72.1	63.2	35
30	87.6	84	70.7	61.5	35

Table 12. ANOVA for response surface quadratic model of water production.

Source	Sum of squares	df	Mean square	F value^a	Prob. > F (p-value)
Model	6704.163	14	478.869	2152.345	<0.0001*
A-Material temp.	8.537	1	8.537	38.370	<0.0001*
B-Internal Space temp.	11.417	1	11.417	51.317	<0.0001*
C-Inner glass temp.	0.348	1	0.348	1.563	0.2303
D-Outer glass temp.	0.768	1	0.768	3.454	0.0828
AB	3.377	1	3.377	15.180	0.0014*
AC	4.675	1	4.675	21.013	0.0004*
AD	3.193	1	3.193	14.354	0.0018*
BC	6.824	1	6.824	30.669	<0.0001*
BD	5.055	1	5.055	22.721	0.0002*
CD	0.365	1	0.365	1.642	0.2195
A^2	6.897	1	6.897	31.001	<0.0001*
B^2	2.472	1	2.472	11.112	0.0045*
C^2	0.370	1	0.370	1.665	0.2165
D^2	0.318	1	0.318	1.428	0.2507
Residual	3.337	15	0.222
Lack of fit	3.337	2	1.669
Pure error	0.000	13	0.000
Cor total	6707.5	29

Notes: SD – 0.47; Mean – 21.50; C.V. % 2.19; R² – 0.9995; Adj R² – 0.9990; Predicted R² – 0.8851; Predicted residual sum of squares (PRESS)-5466.12; Adeq. Precision – 107.580.

^a F-Test measures the significance of model.

* Significant.

Table 13. Analysis report of water sample produced by the silica gel.

Parameter	Results
Colour	Colourless
Odour	Odourless
Turbity	No, Clear
pH	7.2
Electric conductivity (EC)	0.36 dS m^−1
Total hardness	230.4 ppm
Sodium	5.0 ppm
Potassium	2.5 ppm
Chloride	35.5 ppm
Calcium	12 ppm
Magnesium	4.8 ppm
Copper	Nil
Zinc	Nil
Iron	0.02 ppm
Manganese	Nil
Lead	Nil

Table 14. Cost analysis for SGDBS.

Materials	Cost in Indian Rs.
(a) SGDBS parts (For 0.36 m^2 collector area)
FRP structure	1200
Glass cover	250
Paint	80
Stand	500
Wire mesh tray	200
Water collecting bottle	100
Connecting pipe	20
Desiccant material (per kg)	150
Labor	500
Total cost	3000
(b) Salvage value
Salvage value of SGDBS	250

Kumar, Manoj, and Avadhesh Yadav. 2015. “Experimental Investigation of Design Parameters of Solar Glass Desiccant Box Type System for Water Production from Atmospheric Air.” Journal of Renewable Sustainable Energy 7: 033122.10.1063/1.4922142

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