Eco-friendly coffee-based colloid for performance augmentation of solar stills

Recently, nanofluids have been extensively used in water desalination systems because of their superior photo-thermal properties and heat transfer characteristics. Most of inorganic nanoparticles such as metal, metal oxides and carbon have adverse environmental impacts due to the risk related to their production and disposal processes as well as the toxicity of some types of them. In addition, their high production cost is another issue that motivates researchers to find low cost and eco-friendly alternatives to inorganic nanoparticles. In this study, coffee-based colloid has been proposed as an organic, low cost, and eco-friendly alternative to conventional inorganic-based nanofluids to augment the fresh water productivity of solar stills (SS). The performance of the modified solar still (MSS) has been experimentally investigated and compared with another conventional solar still (CSS) under the same conditions. The daily freshwater productivity obtained from the MSS was 4865.73 ml/m² which was greater than that of CSS by 35.14 %. Energy and exergy efficiencies of MSS were improved by 35.34 % and 46.44 %, respectively, compared with that of CSS. Finally, the economic evaluation of the MSS is carried out via performing cost analysis. The cost of distilled water per liter produced by the modified solar still is 0.0136 $/l.