Performance analysis of step type solar still and comparison of the performance with evacuated tube collector coupled with single slope step type solar still

Abstract

This research project aims to address the growing need for freshwater in regions affected by water scarcity, particularly in coastal and desert areas. The focus is on evaluating the effectiveness of a solar-powered desalination system, which utilizes a single slope step type solar still and an Evacuated Tube Collector (ETC) to produce fresh drinkable water. Additionally, Computational Fluid Dynamics (CFD) analysis is conducted to gain insights into the natural convection of heat transfer within a glass tube, which creates a buoyant flow of saline water. The design consists of a solar evacuated tube, which heats up due to the exposure to sun rays and this heat is transferred to the impure/saline water (effluent). The water is then discharged to a single slope step type solar still which absorbs energy from sunlight and increases the evaporation rate in the solar still. Thus, the water evaporates and is then condensed by the inner surface of the glass roof hence purified water is collected. The CFD flow analysis of incompressible fluid under the effect of gravity in the transient condition is carried out for ETC in the ANSYS workbench. Also, fluid flow analysis of single slope step type solar still consisting of ten steps with a water depth of 3 cm in multiphase conditions using the VOF model is carried out to obtain the amount of distillate output per day in fair weather conditions in the location 13.2848⁰ N, 74.7486⁰ E in Katapady, Udupi. The amount of distillate collected as a result of CFD analysis was found to be 5.195 kg/day. The contours obtained from the steady state analysis for solar still showed the distribution of temperature, solar heat flux, and mass flow rate. The transient analysis of the ETC assisted well in obtaining the temperature in the ETC collector tank and the variation in solar radiation throughout the day. The contours of ETC showed the buoyant flow of water under natural convection, velocity distribution, density distribution and solar irradiation distribution on glass walls.