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

Abstract

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 environmental 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/m2oC, 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.