Solar Distiller uses a trick capable of purifying salty sea water using only the sun's rays and increases the efficiency and production capacity of fresh water

Scientists create a solar still capable of purifying water obtained directly from the Red Sea, as well as brine produced by reverse osmosis installations, with salinity greater than 10%.

O solar still, who can purify 10 to 20 liters of water a day, was invented by professor Qiaoqiang Gan, who currently works at the King Abdullah University of Science and Technology in Saudi Arabia.

There was a problem at the time of creation, as there always seems to be with water desalination systems: over time, salt builds up on the absorbent material, reflecting sunlight and causing the system's effectiveness to decrease. After that, he switched gears and began to focus on hydrophobic surfaces and methods that use fluid convection to reduce the amount of mineral formation.

Now, the group has unveiled the first significant achievement resulting from using this new strategy: a solar distillation system capable of purifying water obtained directly from the Red Sea, as well as brine produced by reverse osmosis installations and containing more than 10% salt.

The technique is capable of producing twice as much fresh water as solar stills developed so far, and maintains its efficiency over time.

the new evaporator solar it is shaped like a cube only a few centimeters on a side and is made of plastic. Inside, it has numerous fiberglass membranes, which are very fine mesh materials that are often used for filtration.

The top surface of the cube has a light-absorbing layer composed of a horizontally aligned membrane covered in carbon nanotubes. This type of absorption is known as photothermal rather than photovoltaic. The solar absorber is kept separate from the salt water being introduced into the system by a series of vertically oriented membranes called “mass transfer bridges”.

The solar still has undergone a series of internal and external tests, and the results have shown that it is capable of meeting the daily water needs of two people, with an estimated raw material cost of US$50 per square meter.

These bridges have hydrophilic microchannels that draw salt water into the upper solar layer, where it is then distilled into steam, a process that takes place inside the bridges. When the level of salt accumulation exceeds a certain threshold, capillary action caused by concentration gradients causes the same microchannels to carry the brine back into the salt water.

In turn, the taller bridges allow conductive heat generated during salt backflow to travel to the solar still, which increases the amount of water that is evaporated. “Other evaporators can achieve good salt rejection, but with a short reflux process, there is a lot of thermal energy loss and this affects water generation rates,” said Kaijie Yang, who designed the new evaporator. “The new evaporator has a much more efficient heat transfer system, which reduces the amount of thermal energy lost.”

Developers claim that by connecting large numbers of cubes they can scale to a more extensive architecture. The new solar distillation device is being prepared for commercialization, as it has proved capable of long-term operation without the need for maintenance.