Solar Desalination Tech Turns Sunlight to Fresh Water

Abstract

Solar desalination offers a sustainable solution for freshwater production with minimal carbon emissions by utilizing solar energy. However, the efficiency of solar-vapor generation is often limited due to its high energy demands, resulting in low water evaporation rates under natural sunlight. To overcome this challenge, La0.7Sr0.3MnO3, an oxide perovskite is introduced that acts as a highly efficient photothermal material. It effectively converts solar energy into heat by forming intra-band trap states, which facilitate non-radiative recombination of photoexcited electrons and holes, thereby enhancing heat release through thermalization. A key obstacle in solar desalination is salt accumulation, which can degrade material performance over time. To mitigate this, a novel device design is developed that enables one-directional fluid flow, establishing a salt gradient that pushes salt to the edges of the photothermal material, significantly reducing fouling and light shielding. By combining La0.7Sr0.3MnO3 with this innovative design, an impressive solar evaporation rate of 3.40 kg m⁻2 h⁻¹ under one sun is achieved, while ensuring strong antifouling capabilities in complex environments. This work demonstrates a breakthrough approach to enhancing the efficiency and durability of solar desalination through advanced material engineering and smart design.

A research team from UNIST has unveiled a novel solar desalination technology that efficiently harnesses sunlight to evaporate seawater and generate clean drinking water-completely independent of external electricity. Importantly, this advanced system addresses common issues, such as salt accumulation, which can impair performance over time, offering a promising solution for water-scarce regions worldwide.

Led by Professor Ji-Hyun Jang of the School of Energy and Chemical Engineering, the team introduced a device designed to prevent salt buildup on its surface, ensuring long-term durability and reliable operation-key considerations for deployment in developing countries facing water shortages.

The core of this solar evaporator features a distinctive inverse-L shaped paper structure. Thanks to its water-absorbing properties, similar to litmus paper, seawater naturally wicks upward along the paper column. When the water reaches the top, it encounters a heated photothermal material that rapidly converts it into vapor under sunlight. The material employed, La₀.₇Sr₀.₃MnO₃ (LSMO), a perovskite-based semiconductor, exhibits high thermal efficiency, enabling evaporation rates that are 8 to 10 times faster than conventional methods.

Owing to its unique inverse-L geometry, salt ions are driven toward the edges of the device, where they crystallize as solid deposits. This built-in salt rejection mechanism not only prevents fouling but also facilitates easy salt collection and reuse, keeping the photothermal surface clean and maintaining optimal performance over time.

The system achieves an impressive evaporation rate of 3.4 kilograms per square meter per hour (approximately 3.4 liters), vastly surpassing the typical 0.3-0.4 kg/m²/h observed under natural sunlight. Durability tests further demonstrated stable operation over two weeks in highly concentrated saline solutions with 20% salt content, exceeding the salinity of normal seawater.

Lead author Dr. Saurav Chaule explained, "The inverse-L-shaped evaporator offers a sustainable approach to freshwater production and has potential applications in eco-friendly resource recovery, such as salt harvesting."

Professor Jang emphasized, "By integrating innovative structural design with a perovskite-based photothermal material, we have developed a cost-effective, electricity-free device capable of producing 3.4 kilograms of freshwater per hour. This breakthrough provides a practical and scalable solution to the global water scarcity crisis."

This research has been selected as the back cover story of Advanced Energy Materials and published online on July 17, 2025. Supported by the ERC project at the Engineering Research Center for Microplastic through Bio/Chemical engineering Convergence Process and other funding sources, the study marks a significant step toward sustainable, low-cost desalination technology.

Journal Reference

Sourav Chaule, Doniyor Khudoyarov, Sungdo Kim, et al., "Inverse-L Shaped Evaporator Based on La1−xSrxMnO3 Perovskite with Efficient Salt Collection via Localized Salt Gradient," Adv. Energy Mater., (2025).