Effect of porous material and black coating on solar desalination for sustainable water harvesting: A thermo-exergo-economic and environmental analysis

Abstract

The aim of this research is to improve the amount of freshwater yield of a square base pyramidal solar still (SBPSS) using porous material with and without black coating for sustainable water harvesting. Seven separate cases, i.e., smooth basin (C-A1), an absorber plate with clay pots facing upward (C-A2), upward-downward (C-A3), downward (C-A4) and clay pots with black coating facing upward (C-A5), upward-downward (C-A6), downward (C-A7), were tested under the meteorological conditions of Andhra Pradesh (16.6834 degrees N, 80.3904 degrees E), India. To mitigate the impact of fluctuations in solar radiation, the tests were carried out specifically from 7:00 AM to 7:00 PM, focusing on days, especially, with clear sky. The influence of porous material and black coating on the performance of SBPSS is investigated from the viewpoints of thermo-exergo-economic parameters. By putting clay pots inside the basin, the freshwater yield increases up to 2.04 L/m2 for C-A4, while the yield enhances further by black coating (C-A7) to 2.38 L/m2. Findings revealed the overall daily thermal efficiencies for C-A7, C-A6, C-A4, C-A5, C-A3, C-A2, and C-A1 as 32.17%, 30.26%, 28.10%, 27.74%, 26.49%, 25.41%, and 17.00%, respectively. Additionally, the daily exergy values are 1.25%, 1.38%, 1.52%, 1.70%, 1.86%, 2.23%, and 2.78% for C-A1, C-A2, C-A3, C-A4, C-A5, C-A6, and C-A7. The optimal configuration was C-A7, exhibiting thermal and exergy efficiencies that surpassed C-A1 by 89.24% and 122.58%, respectively. Moreover, the daily productivity improved by 90.76%, accompanied by a cost reduction of 44.51%, and a reduction in payback period by 159 days. Among all, C-A5 achieves the highest CO2 mitigation at 7.06 tons/year, followed by C-A7 at 6.63 tons/year.