Experimental investigations on simple and modified concatenated stepped solar still units for the extraction of clean water: A comparative study

In this experimental research work, a parallel comparison of a modified concatenated stepped solar still (MCSSS) unit was done with a simple concatenated stepped solar still (SCSSS) unit for the extraction of clean water, considering thermo-enviro-economic aspects. Each stepped solar still in these experimental units had 0.25 m2 heat absorbing area. The MCSSS unit was equipped with internal reflectors, external reflector and glass cover cooling arrangement. The experimental units were feed with a pre-optimized tap water flow rate of 50 ml/min for the extraction of clean water. The comparison revealed that the MCSSS unit produced 3.43 L/day of distillate which was 18.72 % higher than that of SCSSS unit. In the MCSSS unit, the convective and evaporative heat transfer coefficients were found to be 15.29 % and 11.50 % higher, respectively. The energy and exergy efficiencies of MCSSS unit were 41.58 % and 14.52 % which were found to be respectively 19.93 % and 25.93 % higher than that of SCSSS unit. The MCSSS unit had lower energy payback time and earned higher carbon credits as compared to SCSSS unit. The economic payback period of MCSSS unit was evaluated to be lower than SCSSS unit by 1.297 months.