Science & Technology, India (Commonwealth Union) – Water scarcity is a pressing global issue that affects millions of people worldwide. With an increasing demand for freshwater resources, alternative solutions are urgently needed. Solar desalination, a process that utilizes solar energy to convert seawater or brackish water into freshwater, offers a promising and sustainable approach to mitigate water scarcity. Solar desalination is the process of using solar energy to power the desalination of water. It involves harnessing the sun’s heat to evaporate water, separating it from impurities, and then condensing it to produce freshwater. There are various solar desalination technologies, including solar stills, solar-powered reverse osmosis, and solar multi-effect distillation.
The high temperature during summer, together with the higher chances of water scarcity that may emerge in the years ahead. This prompted researchers from the Indian Institute of Science (IISc) to create a novel thermal desalination system capable of functioning with the utilization of solar energy at an attempt to bring in more clean, potable water.
One of the most frequently used techniques for desalination are membrane-based reverse osmosis together with thermal desalination. The issue is that they both consume a lot of energy.
The new technique developed by the IISc researchers has a solar-powered desalination unit that has greater energy efficiency, more economical and portable, that is convenient for setting up in places with restricted access to non-stop electricity supplies, indicated Susmita Dash, who is Assistant Professor in the Department of Mechanical Engineering as well as corresponding author of the study published in Desalination.
The setup, formed by Dash along with her PhD student Nabajit Deka, consists of a reservoir of saline water, an evaporator, together with a condenser contained within an insulating chamber to prevent the loss of heat to the ambient air.
Their system functions with the application of solar thermal energy that evaporates a minute volume of water imbibed or “wicked” inside the evaporator, that contains a textured surface. The wicking of the liquid inside the evaporator makes use of the capillary effect of microscale textures. This effect permits the liquids to be transferred into narrow areas of a porous material, similar to water being absorbed by a sponge. Utilizing this technique, as opposed to heating the full liquid volume in the reservoir, will lead to a significant enhancement in the system’s energy efficiency, indicated Dash.
The condenser is frequently not taken into account in desalination studies, as indicated by the researchers, which is another key component for the solar desalination system. In blocking the production of the water film as condensation occurs, similar to the solar stills, Dash and Deka constructed a condenser that has alternating hydrophilic and superhydrophilic surfaces. The water droplets condensing on the hydrophilic patterns are drawn into the superhydrophilic area. The drawing of the condensed water to the superhydrophilic area makes it possible for the hydrophilic surface to end up free for a new batch of condensate, as indicated by Dash.
As the condensation occurs, certain levels of heat disappear into the environment. The researchers formed the system to take up this heat released as condensation occurs which is also trapped and used to warm up the imbibed saltwater for a different evaporator at the rear end of the condenser, this lowers the quantity of solar energy required, and elevates the efficiency of the system further. The researchers had a positive outcome when they joined multiple evaporator-condenser combinations in a series, that led to a multi-stage solar desalination process. This process when formed in a footprint area of 1 m2, is capable of forming 1 litre of potable water every 30 minutes. This is roughly double the amount formed by a traditional solar still having the same size.
The researchers are presently engaged in scaling up the system and enhancing its durability, and elevating the volume of drinking water formed, which can bring about domestic and commercial applications.
