Performance evaluation of a concatenated stepped solar still system loaded with different masses of energy storage material

The influence of mass of paraffin wax as energy storage material (ESM) on solar distillation in a concatenated stepped solar still system (CS4) is investigated by considering its productivity, thermal, economic and environ-mental aspects. Experiments are carried out on CS4 loaded with 675 g, 1350 g, and 2700 g of paraffin wax as ESM, filled in 15, 30 and 60 numbers of copper tubes, respectively. CS4 containing 15, 30 and 60 numbers of copper tubes are symbolically represented as CS4-ESM15, CS4-ESM30 and CS4-ESM60, respectively. The amount of distillate obtained from CS4 is observed to increase with the mass of ESM, and CS4-ESM60 gives maximum distillate of 2486.1 g CS4-ESM60 is found to be thermally more efficient among the tested systems with maximum average values of convective and evaporative heat transfer coefficients as 4.17 and 34.16 W/m2?, respectively. Its overall energy efficiency is 86.57% which is respectively, 74.22% and 45.86% higher than those of CS4- ESM15 and CS4-ESM30. The overall exergy efficiency is also evaluated maximum for CS4-ESM60 as 3.53%. The carbon credits earned and CO2 mitigation by CS4-ESM60 are $132.4 and 8.83 tonnes, respectively that makes it ecologically friendlier. Also CS4-ESM60 is found economical with total productive cost of $101.21/year.