Solar-powered desalination system requires no extra batteries

Introduction

MIT engineers have developed a new desalination system that operates in sync with solar energy, aligning with the Sustainable Development Goals (SDGs) of clean water and affordable and clean energy.

System Description

The solar-powered system efficiently removes salt from water by adjusting its desalting process according to changes in solar energy. As sunlight increases throughout the day, the system ramps up its desalination process, and it automatically adapts to sudden variations in sunlight, such as dialing down during cloudy periods or increasing output when the skies clear.

This system stands out from other solar-driven desalination designs as it does not require extra batteries for energy storage or a supplemental power supply from the grid. By quickly reacting to subtle changes in sunlight, it maximizes the utility of solar energy and produces large quantities of clean water despite variations in sunlight.

Testing and Results

MIT engineers tested a community-scale prototype of the system on groundwater wells in New Mexico over a six-month period, operating under variable weather conditions and water types. The system harnessed an average of over 94 percent of the electrical energy generated from the solar panels, producing up to 5,000 liters of water per day, even with large swings in weather and available sunlight.

Implications and Potential

The system is specifically designed for desalinating brackish groundwater, which is a more prevalent but salty source of water found in underground reservoirs. The researchers believe that brackish groundwater holds significant potential as a source of drinking water, especially in areas where fresh groundwater resources are scarce. The renewable, battery-free system has the potential to provide sustainable and affordable clean water, particularly for inland communities with limited access to seawater and grid power.

Research Details

The researchers published a paper detailing the new system in Nature Water. The study’s co-authors include Jonathan Bessette, Amos Winter, and Shane Pratt.

Previous Design and Improvements

The new system builds upon a previous design called “flexible batch electrodialysis.” The previous system used electrodialysis, which employs an electric field to draw out salt ions as water passes through ion-exchange membranes. The researchers developed a model-based control system that optimized the rate of water pumping and the voltage applied to the stack to maximize salt removal.

However, the previous system required additional batteries to compensate for fluctuations in solar power. To address this limitation, the researchers devised a simpler control strategy called “flow-commanded current control.” This strategy enables the system to adjust its desalination rate three to five times per second, closely matching consumed power with available solar power throughout the day.

Future Plans

The engineers plan to further test and scale up the system to provide low-cost, fully sun-driven drinking water to larger communities and municipalities. They aim to continue developing lower-cost and more sustainable desalination methods aligned with the SDGs.

Conclusion

The solar-powered desalination system developed by MIT engineers offers a promising solution for producing clean water using renewable energy. By maximizing the utility of solar energy and eliminating the need for additional batteries, the system has the potential to provide sustainable and affordable clean water to underreached areas around the world.

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