Table 2 Researches on designs of passive solar still
S. no. | Researchers | Still type and geometry | Parameters studied | Modification/methods/analysis | Results/achievements | Conclusions/remarks |
|---|---|---|---|---|---|---|
1. | Abderachid and Abdencer (2013) | Double slope symmetrical (DSS), and single slope double effect asymmetrical still (SSDAS), basin area—1 m2, condensing cover inclination—10°, 30°, and 45° (Fig. 10) | Effect of orientation, tilt angle, and water depth | Simulation study to compare the effect of DSS and SSDAS with different orientations and design parameters | Asymmetrical double effect solar still gives higher distillate output than symmetrical double slope still | South-North orientation of still, 10° tilt angle and 0.02 m water depth gives higher yield. However, these results are concluded only for one day data |
2. | Omara et al. (2013) | Stepped solar still (SS), basin area—1.16 m2, cover inclination—30° (Fig. 11) | Effect of internal reflectors | SS with internal reflectors | Increase of 75 and 57 % in productivity and 56 and 53 % in daily efficiency was observed in stepped solar still with and without internal reflectors, respectively | SS with and without internal reflectors shows better output than conventional stills. However, daily efficiency of SS with and without reflectors is not increased significantly (3 %) |
3. | Rajaseenivasan and Murugavel (2013) | Double slope single and double basin still, basin area—0.63 m2, cover inclination—30° | Water depth, and solar radiation | Theoretical and experimental validation of double slope single and double basin still | Maximum production of 4.75 l/m2/day (85 % higher) with double basin still | At lower water depth lower basin production is higher than upper basin Cost and maintenance for double basin still are concluded higher than single basin still |
4. | Arunkumar et al. (2013b) | Tubular solar still with rectangular basin, basin capacity—2 × 0.03 × 0.025 m | Condensing cover cooling with water and air, cost analysis | Compound parabolic concentrator concentric tubular solar still | Distillate output of 1.5 kg/m2 day and 2.5 kg/m2 day with a cost of approximately $0.018 and $0.015 per kg water was observed with air and water cooling, respectively | Water flow cooling gives more output than air flow cooling Cost estimation of solar still in their study not includes maintenance, labor and other service charges |
5. | Ziabri et al. (2013) | Cascade-type inclined solar still, basin area—1.16 m2, condensing cover inclination—20° | Weir dimensions | Weirs were constructed on each step of absorbing plate of inclined type of solar still | 6.7 l/m2/day distillate was collected with modified cascade solar still | Weir of appropriate size helps to improve the productivity of solar still. However, saline water flow rate can be optimized for better distillate output for the proposed still |
6. | Anubraj et al. (2013) | Inclined solar still, basin size—1 × 0.75 × 0.157 m condensing cover inclination—25°, 30°, 35° | Inclination angle (25°, 30°, 35°), wick materials (black cotton cloth, jute cloth, waste cotton pieces), energy storage and permeable materials (mild steel pieces, clay pot) | Modification in design of inclined solar still with rectangular grooves and ridges on absorber plate | 30° inclination angle facing south yield maximum of 3.77 l/day Increase of 12 % productivity was observed using black cotton cloth in basin liner | Energy storage and wicks improve the performance of a solar still at low cost. However, thickness of the wick materials needs to be optimized for future work |
7. | Ahsan et al. (2014) | Triangular solar still (TrSS), length, height, and width of TrSS—1, 0.44, and 0.5 m, respectively | Water depth, solar radiation intensity, and ambient temperature | TrSS fabricated with low, lightweight, and locally available materials | Correlation formulated between water depth (d w) and distillate output (P d) as: P d = 3.84 − 0.47 d w, for 1 ≤ d w ≥ 6 cm | Inverse relationship between daily productivity and water depth, and direct relationship with solar radiation. However, the suggested correlation has been formulated by collecting the data for 3 months only |
8. | Suneesh et al. (2014) | V-type solar still, basin area—1.5 m2 (Fig. 12) | Condensing cover cooling | Cotton gauge top cover cooling (CGTCC) with and without air flow | 4.3 l/m2 distillate with CGTCC and 4.6 l/m2 with air flow along with CGTCC | CGTCC without air flow is cost-effective modification. However, hot water supply inside the still with CGTCC may be taken as an objective for increased distillate output |
9. | Sathyamurthy et al. (2014) | Triangular pyramid solar still, basin area—1 m2 | Energy storage material | Paraffin wax in heat reservoir integrated with the still | 20 % (4.3 l/day) increase in distillate using phase change material (PCM) | Distillate output of solar still is improved using PCM, but it mainly depends on the specific heat capacity, latent heat of fusion, thermal conductivity and proper utilization of storage material |
10. | Arunkumar et al. (2012) | Hemispherical solar still, basin diameter—0.95 m (Fig. 13) | Cover cooling | Hemispherical top cover, water quality and cost analysis | 4.2 and 3.6 l/m2/day of distillate were observed with and without condensing cover cooling | Condensing cover cooling improves the performance of solar still, but there are some vapor losses from the flowing water |