New solar tech turns seawater into freshwater

September 19, 2025

A pioneering research team at UNIST has developed an innovative solar desalination system that transforms seawater into clean drinking water using only sunlight—completely eliminating the need for external electricity. This cutting-edge solution overcomes one of the biggest challenges in desalination: salt buildup, which often reduces efficiency over time. The breakthrough offers a sustainable pathway to address global water shortages, especially in regions facing extreme scarcity.

A durable, low-cost solution for water-stressed regions

The project, led by Professor Ji-Hyun Jang from the School of Energy and Chemical Engineering at UNIST, introduces a highly durable device engineered to prevent salt accumulation. By maintaining long-term stability and consistent performance, the system is particularly suited for deployment in developing countries struggling with limited access to safe water. The research findings were recently published in Advanced Energy Materials.

How the inverse-l solar evaporator works

At the heart of the device is a unique inverse-L-shaped paper structure designed to naturally absorb seawater—similar to litmus paper. Water travels upward through the paper column until it reaches a specially coated surface containing a perovskite-based semiconductor, La₀.₇Sr₀.₃MnO₃ (LSMO). Under direct sunlight, this photothermal material rapidly converts water into vapor with remarkable efficiency.

This advanced design achieves evaporation rates 8–10 times faster than traditional desalination methods, producing significantly more fresh water in less time.

Built-in salt rejection and resource recovery

Unlike conventional systems, this solar evaporator features an automatic salt-rejection mechanism. Its unique geometry directs salt ions toward the device’s edges, where they crystallize into solid deposits. This prevents fouling on the active surface, ensures uninterrupted performance, and allows for easy salt collection and reuse—making the system both eco-friendly and resource-efficient.

Record-breaking efficiency and stability

The solar desalination system delivers an outstanding evaporation rate of 3.40 kg m⁻² h⁻¹ (around 3.4 liters per hour). This is nearly 10 times higher than the natural evaporation rate of seawater under sunlight (0.3–0.4 kg m⁻² h⁻¹). Long-term tests further confirmed its durability in extreme saline conditions—even at 20% salt concentration, much higher than standard seawater levels, the device remained stable for over two weeks.

Towards a sustainable future in water and salt harvesting

According to Dr. Saurav Chaule, lead author of the study, “This inverse-L-shaped solar evaporator not only provides a sustainable method for clean water production but also opens opportunities for eco-friendly salt harvesting and resource recovery.”

Professor Jang added, “By combining innovative structural design with perovskite-based materials, we have developed a scalable, electricity-free desalination device capable of producing 3.4 liters of freshwater per hour. This breakthrough has the potential to transform global access to safe drinking water.”