Performance of single slope solar stills: A comparative study of conventional and modified stills with nanofluid and reflectors

Abstract

Nature has naturally desalinated water for centuries through the process of solar heating, where oceanic water transforms into vapor and then returns to Earth as freshwater precipitation. Freshwater is vital for sustaining life, but growing populations, industrial expansion, and increased agricultural production have created a rising demand for it. Desalination has emerged as a potential solution to address water scarcity. Existing desalination technologies fall into two categories: single-phase processes like reverse osmosis and electro-dialysis, and phase-change processes such as distillation and solar stills. While single phase processes provide freshwater, some rely on non-renewable fossil fuels for energy, indirectly contributing to greenhouse gas emissions. Solar distillation, in contrast uses renewable energy from the sun, offers a promising and sustainable alternative for freshwater production. Solar stills employ shallow water basins within enclosed structures, as moisture collects on the interior surface of the glass cover, cooled by natural airflow. In this study, two 250 X 250 mm2 single slope solar stills were designed, one conventional and the other modified with nanofluids and reflectors. The experiment assessed their performance in Hyderabad’s typical climate, with a glass cover slope of 17.45°. Both stills operated with a 1 cm water depth (500 ml) to observe the water distillate output. Readings were recorded for two different nanofluid concentrations (considering 0.08% and 0.1% of Cerium Oxide nanoparticles by volume mixed with water) allowing for a comparison of their cumulative hourly yields and effectiveness in increasing freshwater output.