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In this research work, the productivity, energy, exergy, and economic and enviro-economic performance in crushed gravel sand heat storage and biomass evaporator-assisted solar still (CGS-BSS) have been investigated and compared the results with conventional solar still (CSS) under the similar climatic conditions of Coimbatore City during the year 2019. The heat accumulated in crushed gravel sand and biomass evaporator have been used to preheat the inlet saline water and air vapor before entering into the solar still. This results in enhanced air vapor mixture temperature and evaporative heat transfer rate of CGS-BSS significantly. The productivity, energy, and exergy efficiencies in CGS-BSS were improved by 34.6%, 34.4%, and 35%, respectively when compared to CSS. In economic analysis, the payback period (PBP) in both CGS-BSS and CSS was estimated to be about 4.7 months and 3.9 months, respectively. Furthermore, in enviro-economic analysis, the CO2 emission estimated in CGS-BSS and CSS was about 16.63 tons and 8.18 tons, respectively during its lifetime of 10 years.

In this paper, the performance of a single slope solar still has been improved using graphite plate fins and magnets (GPF-MSS) in the basin and compared with conventional solar still (CSS) under the same climate conditions. The experiments have been carried out at Coimbatore city in India during the summer months of 2019. The energy and exergy performances of solar stills have been assessed under the influence of solar irradiation, ambient temperature, and wind velocity. The economic and environmental benefits were evaluated for the period of 10 years. The quality of productivity collected was measured and compared with Bureau of Indian Standards (BIS). The results showed that the productivity, energy, and exergy efficiency of GPF-MSS were improved by 19.6%, 21.4%, and 18.1%, respectively, when compared to CSS. The exergy destruction in basin was reduced significantly in GPF-MSS due to sensible heat absorption by graphite plate fins and magnets when compared to CSS. The payback period of GPF-MSS and CSS was estimated as 3.4 and 3.6 months, respectively. The enviro-economic analysis revealed that the net CO2 emissions of GPF-MSS and CSS were estimated as 14.1 tons and 8.42 tons, respectively. The carbon credits earned for GPF-MSS and CSS were estimated as 338.4 USD and 202.1 USD, respectively. The quality of distillate obtained from both the solar stills has met the requirements of BIS.Graphical abstract.

In this research, the thermodynamic (energy and exergy) and economic assessments of heat pump-assisted solar still with paraffin wax was investigated under the climatic conditions of Coimbatore city in India during the year 2020. The observed experimental results in heat pump solar still (HPSS) was compared with conventional solar still (CSS) in the same climatic conditions. This model works on the principle of latent heat observed during condensation which was regenerated by heat pump to preheat the inlet basin saline water of solar still. The observed maximum productivity of HPSS was about 14.5 kg/m2, which was 83.7% higher than CSS. The energy and exergy efficiency improvement in HPSS were about 65% and 82.3%, respectively, higher than CSS. The observed maximum coefficient of performance (COP) of heat pump was about 2.61. The payback period (PBP) of CSS and HPSS was estimated to be about 4.1 months and 3.2 months, respectively. The results observed in HPSS have significantly improved the daily productivity than CSS.