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Table 3 Studies on parameters affecting the performance of passive solar still

From: A comprehensive decade review and analysis on designs and performance parameters of passive solar still

S. no. Researchers Still type and geometry Parameters study Modification/methods/analysis Results/achievements Conclusions/remarks
1. Khalifa (2011) Single slope and double slope Cover tilt angle Relation between cover tilt angle and productivity, and between optimum tilt angle and latitude angle (a) Optimum cover tilt angle should be near to the latitude angle
(b) Productivity increases with increase in cover tilt angle throughout the year
In winter, higher cover tilt angle gives better results and opposite in summer season. However, similar type of results in regard of cover tilt angle has already been published in (Murugavel et al. 2008)
2. Tanaka (2011) Single slope still, glass cover inclination—20° Effect of inclination angle of the external reflector External bottom reflector to the front wall of solar still Optimum inclination angle of external reflector was found to be 40°, 55°, and 25° for spring, summer and winter seasons, respectively Effect of external reflector is greatest in summer season and minimum in winter. However, this work can also be carried out at different latitudes
3. Rajamanickam and Ragupathy (2012) Double slope solar still basin area—1 m2 Solar intensity, ambient temperature, wind speed, water depth, orientation Effect of water depth on internal heat and mass transfer and economic analysis Maximum distillate of 3.07 l/m2 at a water depth of 0.01 m and higher distillate was recorded in north south orientation Increase in water depth decreases output and evaporative heat transfer coefficients
4. Ahsan et al. (2012) Tubular solar still (TSS) Condensing cover material Polythene film as cover of TSS, rectangular trough, heat and mass transfer coefficients, cost analysis Fabrication cost and weight of new TSS were reduced to 92 and 61 %. Distillate output was found to be proportional to temperature difference inside the still Cost of water production highly reduced with the new design
5. Ansari et al. (2013) Single slope still, surface area—1 m2 Influence of PCM Numerical computation for three kinds of PCM of different melting point Productivity and efficiency of the system was greatly enhanced using PCM Melting point of PCM chosen is nearly to the maximum of basin water temperature for better distillate
Productivity of the still can also be checked for varying water depth in basin
6. Srivastava and Agrawal (2013) Single slope, basin area—0.5 m2, condensing cover inclination—24° Water depth, base and side insulation Blackened cotton cloth porous fin 7.5 kg/m2/day distillate collected in the month of May Still gives better performance at lower water depth and with insulation
7. Zoori et al. (2013) Weir type cascade solar still, evaporative area—0.45 m2, still inclination—30° Flow rate, water layer over absorber plate, solar intensity, ambient temperature Analyzed energy and exergy efficiency Maximum energy and exergy efficiency of 83.3 and 10.5 % were observed at 0.065 kg/min of brine flow rate Low brine flow rate and small water thickness over absorber plate improve the efficiency of the system
8. Bhardwaz et al. (2013) Single slope, basin area—0.27 × 0.27 m2 cover inclination—30° to 90° Cover inclination, material, contact angle Sponges, hot water bath, temperature controller Low contact angle, glass as condensing surface, high transmittance of solar radiation from surface produces higher yield Contact angle, cover material, reflection are considered as important parameters affecting water production
9. Rajaseenivasan et al. (2013) Double slope single (DSS) and double basin still (DBS), basin area—0.63 m2 cover inclination—30° Water depth, wick, porous, absorbing and storing material Additional upper basin with different wick, porous, energy absorbing and storing material at lower basin (a) 85 % higher distillate was collected in double basin still with maximum of 5.68 l/m2/day at lower water depth and using mild steel as energy storing material Providing a double basin, lower water depth in lower basin with different storing materials highly increases the distillate, but DBS is bulky and needs more cleaning and maintenance than DSS
10. Srivastava and Agrawal (2013) Single slope, basin area—0.52 m2, condensing cover Inclination—24° Effect of external reflectors, porous absorber, water depth Blackened jute cloth floated in basin water, external reflectors on side walls Distillate gain of 68 % with the modified still, and of 79 % over modified still with the use of twin reflectors Absorber and two-side reflectors significantly increase the productivity
However, impurities (high salt concentration) in basin water and ambient conditions (non-clear days) significantly affect the performance of the proposed still
11. Omara et al. (2014) Single slope and stepped solar still of basin area—1 and 1.16 m2, cover inclination—30° Effect of internal and external reflectors Internal and external (top and bottom) reflectors, cost analysis Internal and external reflector increases the productivity to 125 % than conventional solar still Use of reflectors greatly enhances the yield. However, the basin water depth has been maintained approximately constant throughout the working period which is difficult to maintain
12. El-Agouz (2014) Conventional and stepped solar still, absorber area—1 m2, cover angle—30° Storage tank, flow rate, cotton absorber Stepped solar still with layer of cotton cloth and continuous water circulation using storage tank Modified still shows 43 and 48 % increase in distillate for sea and salt water using black absorber, while 53 and 47 % using cotton absorber Maximum output is obtained at lower flow rate
13. Boodhan and Haraksingh (2015) Double slope cascade solar still, effective collector area—1.995 m2 glass cover inclination—10.5° Varying glass cover thickness and still orientations Double sided cascade-type solar still with varying cover thickness (3.18, 4.76, 6.35 mm) Glass cover thickness of 4.76 mm facing south resulted highest yield with average daily efficiency of 29.28 % Thickness of condensing cover should be selected which allows maximum solar radiation to enter the solar still and minimizing losses
14. El-Samadony and Kabeel (2014) Stepped solar still, basin area—1.16 m2 Cover cooling and film thickness, flow rate, wind speed, feed water temperature Theoretically performance evaluation of stepped solar still using water film cooling over the glass cover Optimum conditions: film thickness from 2.5 × 10−4 to 5.5 × 10−4 m, flow rate 4 × 10−5 to 8.5 × 10−5 m3/s, glass cover length from 2 to 2.8 m Performance of the stepped solar still increases with low water film cooling thickness and with high water film cooling volumetric flow rate over glass cover
15. Arjunan et al. (2014) Single slope single basin solar still, basin area—0.5 m2 cover inclination—10° Effect of different energy storage materials Cheap, simple, and easily available energy storage materials (blue metal stone, black granite gravels, pebbles, paraffin wax) effect on solar still performance Black granite gravel were observed more efficient storage medium and showed 9.69 % higher yield than conventional solar still Use of energy storage material is low cost improved modification, but the system becomes bulky with it