Original article:  Jennifer Chu | MIT News

The solar-powered system removes salt from water at a pace that closely follows changes in solar energy. As sunlight increases through the day, the system ramps up its desalting process and automatically adjusts to sunlight variations.

Works despite variations in sunlight

Because the system can quickly react to subtle changes in sunlight, it maximizes the utility of solar energy. In contrast to other solar-driven desalination designs, the MIT system requires no extra batteries for energy storage, nor a supplemental power supply.

The engineers tested a community-scale prototype on groundwater wells in New Mexico over six months, working in variable weather conditions and water types. The system harnessed on average over 94 % of the electrical energy generated from the system’s solar panels to produce up to 5,000 liters of water per day despite large swings in weather and available sunlight.

“Conventional desalination technologies require steady power and need battery storage to smooth out a variable power source like solar. By continually varying power consumption in sync with the sun, our technology directly and efficiently uses solar power to make water,” says Amos Winter, the Germeshausen Professor of Mechanical Engineering and director of the K. Lisa Yang Global Engineering and Research (GEAR) Center at MIT. “Being able to make drinking water with renewables, without requiring battery storage, is a massive grand challenge. And we’ve done it.”

Specially designed for desalination of brackish groundwater

The system is geared toward desalinating brackish groundwater — a salty source of water that is found in underground reservoirs and is more prevalent than fresh groundwater resources. The researchers see brackish groundwater as a huge untapped source of potential drinking water. They envision that the new renewable, battery-free system could provide much-needed drinking water at low costs.

“The majority of the population actually lives far enough from the coast, that seawater desalination could never reach them. They consequently rely heavily on groundwater, especially in remote, low-income regions. And unfortunately, this groundwater is becoming more and more saline due to climate change,” says Jonathan Bessette, MIT PhD student in mechanical engineering. “This technology could bring sustainable, affordable clean water to underreached places around the world.”

More information about the chosen desalination method, as well as and how the system can run without additional power supplies are available in the original article published on the MIT website.

Publication and support

The researchers report details of the new system in a paper published early October in Nature Water. Bessette, Winter, and staff engineer Shane Pratt are the co-authors of the study.

The research was supported in part by the National Science Foundation, the Julia Burke Foundation, and the MIT Morningside Academy of Design. The work was additionally supported in-kind by Veolia Water Technologies and Solutions and Xylem Goulds.