Inspenet, October 14, 2023.
Engineers from MIT and China developed a completely passive device that is inspired by the ocean and is powered solely by solar energy . These details are found in an article published in the journal Joule where it is stated that this group of scientists has been working on an innovative desalination system for years and after facing various challenges in previous prototypes, they believe they have perfected the definitive version of the device. .
A promising device for desalination
The design of this device allows water to move in swirling patterns, similar to what occurs in the oceans, known as thermohaline circulation. This circulation, together with the influence of solar heat, induces the evaporation of water, separating it from the salt.
The resulting water vapor can be condensed and collected as pure, potable water. At the same time, the remaining salt continues to flow through the device instead of accumulating and causing system blockages. This mechanism offers greater water production and salt removal capacity compared to other solar desalination methods currently being investigated.
Drinking water at minimum cost?
The researchers maintain that if this system is scaled to a size similar to that of a small suitcase, it could generate between 4 and 6 liters of drinking water per hour and continue to operate for several years before requiring the replacement of some of its parts.
According to Lenan Zhang, a scientist at MIT’s Device Research Laboratory, ” for the first time, solar-generated water may be even more economical than tap water .”
The team of researchers imagines that a larger device could passively produce the necessary amount of drinking water to meet the daily demands of a small family. Additionally, it could be especially useful in isolated coastal communities, where access to seawater is convenient.
How does it work?
The new design focuses on a unique structure that resembles a thin box, which is covered with a dark material that efficiently captures solar energy . This box is divided into two sections: one upper and one lower. The flow of water runs through the upper part, where the roof has a layer that uses solar radiation to heat and evaporate the water.
The water vapor then moves to the bottom section of the box, where another layer converts it into drinking water, removing the salt as it cools. The scientists placed this tilted box inside a larger container and connected it by a tube that runs from the top of the box to the bottom of the container and floated it in salt water.
This way, water can naturally rise through the tube and enter the box. The tilt of the box, combined with solar energy, causes the water to flow in swirling patterns as it moves. These swirls facilitate the contact of water with the upper evaporation layer and prevent the accumulation of salt, avoiding blockages in the system.
The team made several prototypes with one, three and ten stages and evaluated their performance using water with different levels of salinity, including natural seawater and water seven times more saline.
According to the results obtained, the scientists calculated that if each stage were expanded to a surface area of 1 m 2 , they would have the capacity to generate up to 5 liters of drinking water per hour . Likewise, the system could desalinate water without accumulating salt for an extended period. Given its long life cycle and the fact that the system is completely passive, it does not require electricity to operate , leading the team to estimate that the total operating cost would be less than that of producing tap water in the United States. .
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