Silver (Ag) based nanoparticles in paraffin wax as thermal energy storage for stepped solar still – An experimental approach

Abstract

Paraffin wax is used as a phase change material for thermal energy storage using silver (Ag) nanoparticles doped at different concentrations. The characteristics of Ag nanoparticles in terms of microstructural and thermal analysis are made to study the surface morphology of the nanoparticles. The weight composition of Ag nanoparticles in the paraffin wax is varied between 1 and 2%, and the comparison of thermal characteristics such as thermal conductivity (TC), Differential scanning calorimetry (DSC), and Thermogravimetric analysis (TGA) is made with respect to paraffin wax (PW) without nanoparticle. From the results of thermal conductivity, it is found that the relative improvement in thermal conductivity is found as 1.25 times using 2% of silver nanoparticle in paraffin wax as compared to the PW without NP’s. The DSC results revealed that the temperature of melting using 2% Ag NP’s 57.3 °C, as compared to PW without NP’s. Similarly, experiments are conducted on the stepped basin SS with Ag nanoparticle-based PW as thermal energy storage, and the thermal performance and palatable water generation are compared with SS using PW as thermal energy storage and without PW. The results indicated that with the use of nano-enhanced PW as heat energy storage in the basin of stepped SS, the water temperature, evaporation rate, and accumulated palatable water generation enhanced. The total palatable water generated from the SS using Ag nanoparticles in PW, PW without nano additive, and SS without PW is found as 7.98, 6.73, and 3.61 kg/m2, respectively. The relative improvement in the palatable water generation using Ag nanoparticle doped PW than pure paraffin wax which is due to the change in thermophysical properties, improved heat transport phenomenon, which improved the night time palatable water yield with higher retention of heat dissipated to the water through the basin. The economic analysis showed that the cost of producing potable water from the stepped SS by utilizing Ag-doped paraffin wax rose to 0.019 $ per litre, while the cost of producing potable water from the SS that used paraffin wax as thermal energy storage and SS without any thermal energy storage was determined to be 0.017 $ per litre and 0.018 $ per litre, respectively. However, the yearly palatable water generated from the SS employing the suggested modification is enhanced by about 18.42% and 120.72% in comparison to the SS with thermal energy storage and the SS without thermal energy storage, respectively. The results of the water quality investigation showed that the pH, TDS, thermal conductivity, and total hardness limitations of the consumable water generated by the thermal-based desalination system are within the limits of ISO 10500–2012 and WHO drinking water standards.