Research Projects

As a result of climate change, scarcity of potable water is a major challenge before humanity. Seawater has potential to alleviate the deficit of freshwater once the salt is removed from it. Hence, desalination is essential. Membrane Desalination (MD) is a promising method, offering distillate production using low-grade thermal energy. In MD, externally heated seawater (feed) and ambient-temperature distillate water (permeate) flow through parallel channels in a counterflow arrangement, separated by a hydrophobic porous membrane. Temperature difference between two streams creates a vapor pressure gradient, which drives water vapor through the porous membrane while salt remain in the feed side. It is purely a thermally driven flow where use of solar heat makes it cost effective and environment-friendly. Despite its advantages, MD also faces challenges such as membrane fouling, relatively low energy efficiency, and the need to heat the entire bulk feed water limiting its overall performance. Photothermal Membrane Desalination (PMD) is a novel technology where nanoparticles are embedded at the top layer of porous hydrophobic membrane. These nanoparticles efficiently absorb sun-light and create localized heating in feed channel. Thus, losses due to bulk-heating is eliminated. Vapor generated in feed channel moves through the porous membrane and gets collected in permeate channel. So far, PMD systems have predominantly been tested in direct contact configurations, where deionized water is used in the permeate channel. However, conventional MD clearly demonstrates that employing a sweeping gas (SG) in the permeate channel—which carries the water vapor away to a separate condenser where it is condensed into distillate—can significantly enhance distillate flux. On top of that, such a separate condenser can be designed as a heat-recovery unit which can push the photothermal efficiency beyond the ceiling of unity. Integration of SG in PMD systems with heat recovery remains largely unexplored that presents a promising opportunity for performance improvement. The same is attempted here with a bioinspired heat-recovery unit where salt will also be taken as an output making it zero-discharge design. Following are the four major parts of the project. 1. Experimental Design and Testing A PMD system incorporating the SG configuration will be designed and experimentally evaluated under both a solar simulator—for controlled, repeatable conditions—and natural sunlight to assess real-world performance. 2. Development of a Nature-Inspired Multistage Evaporator In place of a conventional condenser, a novel multistage evaporator inspired by Deodar tree will be developed to reuse the latent heat released during condensation. In this design, water vapor coming-out from SG-PMD system condenses on the lower dome surface, releasing latent heat that is absorbed by a porous wick containing seawater positioned above. This triggers successive vapor generation, enabling a cascade of evaporation-condensation cycles across multiple stages. The design mimics the way snow accumulates along branch-edges of a Deodar tree. Similarly, salt will accumulate at the periphery of each dome, allowing for easy collection. This system not only enhances distillate flux but also facilitates salt extraction, utilizing high-salinity brine discharged from the SG-PMD system. 3. Numerical Modelling and Optimization A comprehensive numerical model will be developed to optimize the setup dimensions of both the SG-PMD system and the multistage evaporator, with the goal of maximizing distillate yield and salt recovery. 4. Prototype Fabrication Based on the optimized design parameters, a fully functional prototype of the integrated SG-PMD and multistage evaporator will be fabricated for potential field deployment.