Convert seawater into safe drinking water with solar device

 Solar device which produces 3.4 Litres/Hour without electricity by Korean scientists

Amid escalating global water scarcity, researchers at the Ulsan National Institute of Science & Technology have unveiled a ground breaking solar desalination technology which efficiently converts seawater into potable water using innovative materials and design, offering a sustainable solution without external electricity. Following are the some of the important points:-

Researchers at UNIST developed a solar desalination technology converting seawater into potable water.

The system achieves an evaporation rate of 3.4 litres/hour, surpassing typical solar desalination rates.

This breakthrough offers a sustainable and scalable solution to global water scarcity.

 The design addresses salt accumulation by directing it to the edges of the photothermal material.

   

                            

A compact new solar device from the Ulsan National Institute of Science and Technology (UNIST) turns seawater into safe drinking water, without any external power. The core trick is simple to state and hard to achieve. The system keeps the sun heated surface clean while moving salt to the edges, so evaporation does not stall. In an era where access to clean drinking water is becoming increasingly critical, researchers are making significant strides in solar desalination technology. A recent innovation showcases a promising advancement in this field. By harnessing the power of the sun, the new technology efficiently converts seawater into potable water without relying on external electricity sources. This cutting-edge approach not only promises to tackle the challenge of salt accumulation but also offers a sustainable solution with minimal carbon emissions. Using a novel material known as La0.7Sr0.3MnO3, this system exemplifies the potential of solar energy in addressing global water scarcity issues. The device channels sunlight into heat using La0.7Sr0.3MnO3, a black oxide that acts as a photothermal, converts light into heat and material. Heat forms right where water meets air, so energy is not wasted warming the whole tank.

The work was led by Sourav Chaule at UNIST. His research focuses on photothermal desalination and resource recovery. In controlled tests, plain water evaporated at about 0.12 pounds/square foot/hour, and a bare glass fibre membrane reached about 0.21 pounds/square foot/hour. The prototype kept steady performance for two weeks in feeds with 20% salt. The challenge of salt accumulation has long plagued solar desalination technologies, often leading to reduced efficiency and increased maintenance costs. The new device developed by the UNIST research team effectively addresses this issue through an innovative design. The system uses La0.7Sr0.3MnO3, a perovskite material, which converts solar energy into heat. This process is enhanced by forming intra-band trap states which facilitate the non-radiative recombination of photoexcited electrons and holes, boosting heat release. Water climbs through tiny channels in the membrane by capillary action, upward flow through small pores driven by surface tension. The design connects the water supply at one end, so flow goes in one direction and salt naturally concentrates at the far edge. The edge loading keeps the sunlit face clear, which boosts uptime and reliability. The team reports it delivered, maintaining strong antifouling capabilities in complex environments. .

Because salt crystallizes at the rim, it can be collected instead of returned to the source. The paper notes that the device enables Zero Liquid Discharge (ZLD) through effective salt collection. This breakthrough design incorporates one-directional fluid flow, creating a salt gradient which directs salt to the edges of the photothermal material. This strategic movement significantly reduces fouling and light shielding, common problems in conventional systems. As a result, the device achieves an impressive solar evaporation rate of 3.40 kg/m²/h (approximately 3.4 litres/hour) under standard sunlight conditions, while also ensuring strong antifouling capabilities in complex environments. The team screen-printed the material onto sturdy fibre membranes, then assembled several evaporators in a simple housing. This approach suggests manufacturing routes which do not depend on rare parts or tight tolerances. Outdoors in winter conditions, the setup produced about 5.33 pounds of evaporation/square foot over six hours, and captured roughly 2.46 pounds/square foot as liquid water. These values came from four small modules running side by side without external power. Tests with real seawater showed stable output and clean condensate. The authors explained that the condensed water was well below the World Health Organization (WHO) guidelines for safe drinking water.

The development marks a significant breakthrough in enhancing both the efficiency and durability of solar desalination systems. The evaporation rate achieved by the new technology vastly surpasses the typical rates observed under natural sunlight, which usually range from 0.3 to 0.4 kg/m²/h. Durability tests have shown that the system can operate stably for two weeks in highly concentrated saline solutions, containing 20% salt, which is higher than typical seawater salinity. La0.7Sr0.3MnO3 is a perovskite, a crystal family whose composition can be tuned, which absorbs across most of the solar spectrum. Strontium substitution narrows the electronic gap, which helps the material drink in sunlight. Inside the crystal, defect states favour non radiative recombination, electrons and holes meet and release heat instead of light, so absorbed energy turns into warmth. The warmth drives evaporation at the surface where it counts most. Infrared imaging showed the top surface warming from about 82 degrees Fahrenheit to about 117 degrees Fahrenheit in one hour, while the bulk water stayed near ambient. Keeping heat where vapour forms helps explain the high output and low heat loss.

Dr. Saurav Chaule, the lead author of the study, emphasized the potential applications of this innovation beyond freshwater production. The inverse-L-shaped evaporator design offers a sustainable approach not only for water desalination but also for eco-friendly resource recovery, such as salt harvesting. The use of La0.7Sr0.3MnO3 as an efficient photothermal material demonstrates the promising future of solar energy in addressing both water scarcity and sustainable resource management. A key challenge for any desalination system is bridging the gap between lab performance and daily use in real towns. The modular nature of this device means units can be added or removed, which allows operators to match output to local water needs. These modular blocks also make repairs easier, since a single faulty unit can be swapped without interrupting the entire setup. Field tests suggest that arrays of inverse L shaped evaporators can be organized into larger panels that run without skilled labour. Communities with strong sunlight but limited energy access could place these panels near shorelines or brackish wells and expand capacity over time.

The innovative design of this solar desalination device offers a practical and scalable solution to the global water scarcity crisis. By directing salt accumulation to the edges of the photothermal material, the system effectively prevents salt build-up on the surface. This approach, combined with the use of oxide perovskites, highlights the potential of next-generation solar desalination technologies in providing sustainable freshwater solutions. This approach could also help remote regions manage seasonal changes in demand by adding modules during dry months and storing extras when water is more plentiful. According to a global report, one in four people still lack safely managed drinking water. Affordable devices which run on sunlight can expand options where pipes, pumps and grids fall short. Lab reports often cite AM 1.5 G, a standard sunlight spectrum used for testing, as the reference for one sun condition. The standard gives a common yardstick for comparing devices across labs. Professor Ji-Hyun Jang, a key figure in the research, noted that the integration of innovative structural design with a perovskite-based photothermal material has led to the development of a cost-effective, electricity-free device. Capable of producing 3.4 kg of freshwater/hour, this breakthrough could be a game-changer in the fight against water scarcity. The researchers suggest that future developments could include robust evaporator systems made up of multiple inverse-L-shaped solar evaporators, forming a large-area single module to further enhance the efficiency and scalability of this technology.

This prototype points to practical upgrades, including better condensers to harvest more of the vapour it makes. Arrays of inverse L shaped evaporators could raise throughput while keeping maintenance low. The advancements in solar desalination technology demonstrate a promising future for sustainable water production. As the world grapples with the challenges of climate change and resource scarcity, innovations like these offer hope for a more resilient and sustainable future. The question remains: how quickly can such technologies be implemented on a global scale to effectively address the pressing issue of water scarcity around the world?