Experimental study of hemispherical solar still using sodium sulfate decahydrate and sodium carbonate decahydrate as energy storage materials: An enviro and economic analysis

The present study focuses on improving the performance of hemi spherical solar still (HSS) using hydrated salts – Sodium Sulfate Decahydrate (SSD), Sodium Carbonate Decahydrate (SCD) as energy storage materials and graphite plates. The performance of the modified solar still (MSS) is compared with the conventional solar still (CSS) in terms of clean water production, economics and environmental impact. The DSC curve shows a higher latent heat and broader melting-solidification range for SSD compared with SCD providing longer heat retention. The latent heat released by the salts in the MSS maintains a higher water temperature and vapor pressure than the CSS, creating a larger vapor pressure gradient that drives evaporation and results in 83.20 % increase in the evaporative heat transfer coefficient during 17.00–20.00 hrs. While the day time and night time distillate productivity of MSS-SSD is 15.20 % and 154.40 % respectively higher than CSS, the productivity of MSS-SCD is 12.80 % and 133.30 % higher when compared to CSS. The cost per liter for MSS-SSD is 19 % lower than CSS and it is 17 % cheaper for MSS-SCD. Enviro economic analysis shows that the net CO₂ emitted for CSS, MSS-SSD and MSS-SCD were estimated as 188.42, 313.54 and 311.16 kg respectively. The CO₂ mitigation potential is relatively higher for MSS-SSD and MSS-SCD which are mitigated 24 tons and 22.6 tons with over their life time compared with 16.8 tons from CSS. The carbon credit earned during the 5th year is $79.3 and an average value of $109.5 for the CSS and MSS respectively. The MSS accounts for an increase in carbon credit earning to 38 % in the 10th year and it is 39 % in 15th year when compared to CSS.