Engineers at MIT have built a new solar-powered desalination system that produces large quantities of clean water, even under fluctuating sunlight, without relying on batteries. This cost-effective design offers an innovative approach to drinking water production compared to traditional solar-driven systems.
The system operates in sync with sunlight, adjusting the desalination process to match solar intensity. As the sun strengthens during the day, the system speeds up, and it responds quickly to sudden changes, such as cloud cover. This real-time adaptability ensures efficient solar energy use throughout the day.
Engineers tested a community-scale prototype for six months at a groundwater well in New Mexico. The system consistently utilized over 94% of the electricity generated by its solar panels and produced up to 5,000 liters of water per day, despite varying weather conditions.
“Traditional desalination relies on stable power and battery storage to smooth out fluctuations from renewable energy. Our system, by synchronizing directly with the sun, efficiently produces clean water without the need for batteries,” said Amos Winter, Professor of Mechanical Engineering at MIT and director of the K. Lisa Yang Center for Global Engineering.
Designed to desalinate brackish groundwater—a more common but underutilized water source than freshwater—the system aims to provide affordable drinking water to inland communities where access to seawater and grid power is limited.
“Most people live far from the coast, and seawater desalination is not an option for them. In remote, low-income regions, reliance on groundwater is increasing, and unfortunately, climate change is driving up groundwater salinity,” said MIT Ph.D. student Jonathan Bessette. “Our technology can bring sustainable and affordable clean water to remote communities worldwide.”
The research findings were published in the journal Nature Water, co-authored by Bessette, Winter, and senior engineer Shane Pratt.
System Innovations
The new design builds on earlier work by Winter’s team, including a desalination system that uses “flexible batch electrodialysis” to remove salt from water. Unlike reverse osmosis, which forces water through membranes under pressure, electrodialysis applies an electric field to extract salt ions as water flows through ion-exchange membranes.
While renewable energy integration poses challenges—especially for reverse osmosis, which requires stable power—the MIT team focused on electrodialysis for greater adaptability to fluctuating solar energy.
Their system uses model-based controls to optimize performance, adjusting pump speeds and voltages in real-time based on sensor readings. Field tests showed the system utilized 77% of available solar energy, a 91% improvement over traditional solar-powered electrodialysis designs.
However, Winter noted areas for further improvement: “During testing, clouds occasionally blocked sunlight, causing unexpected power drops. While the system compensated with battery backups, we aim to eliminate that dependency entirely.”
The team believes the system could offer a scalable solution for remote communities, providing clean water at a low cost without requiring batteries or additional grid power.
