MIT researchers claim to have created a revolutionary solar-powered desalination system powered directly from sunlight without any auxiliary external power or batteries.
The invention has 'adapted to sunlight optimistically and hopes to generate more water on sunny days and less on rainy days. With the new technology, cost is bound to be slashed dramatically with minimal compromises in efficiency and can, therefore, be seen as some sort of game changer for areas concerning themselves with water scarcity.
Solar Powered Desalination: Bringing Clean Water to Millions
Interesting Engineering reports that the new water-purification technology is a major technological leap with the solar-powered desalination system developed by the MIT team.
Unlike most other desalination methods, this system can use as much sun as possible in its creation and use of energy.
The speed at which this system desalination increases and decreases as the available sunlight increases and decreases throughout the day, thus not wasting any energy while it operates.
The other traditional desalination approaches, such as reverse osmosis (RO), are even too power-intensive and dependent on the grid. MIT's method, however, is purely solar-powered. Hence, the running cost of the system is far more economical as it does not operate as a secondary user of electricity provided elsewhere.
This thus saves it both in terms of energy and its environmental impact while desalting water.
Flexible Batch Electrodialysis: A Superior Alternative to Reverse Osmosis
Using "flexible batch electrodialysis," a technology that the researchers are developing and that transforms a previous design, Winter and his team—the former postdoc Wei He—have improved desalination.
"Compared to RO, electrodialysis membranes usually last about three times as long," Amos Winter, the director of the K. Lisa Yang Global Engineering and Research Center at MIT, told Interesting Engineering via email.
Unlike reverse osmosis, where high pressure pushes water through membranes, this method uses an electric field to remove salt ions. Flexibility to solar power: it will likely be an option in areas with uneven sunlight.
Reverse osmosis requires a stable source of power, which is a tad challenging when relying on the sun. The electrodialysis system is highly adaptable to varying solar power conditions because it instantaneously adjusts water flow and voltage.
Field testing of this technology has utilized 77 percent of the available solar power compared to the previous generations.
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Battery-Free Desalination: Response to Change of Sun Radiation Instantly
The most striking feature of MIT's system is undoubtedly its completely battery-free. Previous desalination systems required batteries to store excess energy and continue the flow through periods of depleted sunlight.
MIT's group, on the other hand, designed a "flow-commanded current control" strategy, which is sensitive to solar power, as it commands flow and electrical current by variations in solar power. It reacts almost immediately to changes in sunlight, meaning energy storage is not required.
In field tests on the Brackish Groundwater National Research Facility in New Mexico, it operated successfully under varied solar conditions. Generally, the system uses more than 94 percent of the solar panel's energy, confirming the system's effectiveness in utilizing solar power.
Cut Down on Battery Dependency and Energy Cost
Winter said the new control strategy reduced the system's battery capacity requirements by almost 100 percent. This is a breakthrough that not only cuts costs but simplifies the system's overall design to make it more viable and accessible for widespread use in water shortage-stricken areas.
The advantages of the technology include its benefits to regions where brackish groundwater exists. For sources with lower salt concentrations, such as brackish water, electrodialysis is much more energy-effective than reverse osmosis.
Winter says that for normal brackish water at a concentration of about 2,500 ppm, electrodialysis requires half the energy reverse osmosis uses.
The system is primarily intended for brackish desalination, but the group feels it would also be useful in certain situations for seawater desalination, though with much more modest energy savings.
More than half of the world's population lives over 100 kilometers from the shore, so desalination via seawater is not possible for them all. This would make the MIT system particularly worthwhile for regions with limited freshwater resources and high water stress, like India, North Africa, and the Middle East.
The study is published in Nature Water.
