Science

Pumping water from the air with the help of the sun

Imagine a future where each house will have a device that will “pull” all the water needed by a household from the air even if the climate is too dry or even deserted. And this will be achieved only with the help of the energy from the sun. This future may not be so far away, thanks to an innovative solar collector that created researchers in the US. The appliance can “pump” several liters of water every day, even if the humidity does not exceed 20%.

The scientists at the MIT and California-Berkeley (Chemistry) universities, headed by Professor of Chemistry Omar Yagi, who published the publication in Science magazine, used a special material called the “metal-organic framework »(Metal-organic framework (MOF)).

With humidity of 20% to 30% in the environment, the device produces nearly three liters of water from the air over a period of 12 hours using a pound of MOF material. Tests that were made on the roofs of buildings have confirmed that the device is working in real conditions. Until today, water collectors could work either in high humidity conditions or with high electricity consumption.

“Our vision for the future is to have water outside a water supply network with a household appliance that will pump it out of the air to meet the needs of a household. It is something that, as our experiment shows, is feasible and we could call it personalized water, “Jagi said.

The American chemist invented metal-organic frames about 20 years ago by combining metals such as magnesium or aluminum with organic molecules in such a way as to create porous structures ideal for storing gases and liquids. Since then, more than 20,000 different MOF materials have been created internationally and some have already been tested by giant companies such as the German BASF for the storage and transport of chemicals such as methane or hydrogen.

In 2014, MIT and Berkeley researchers synthesized the first zirconium and adipic acid metal, called MOF-801, to chemically bind water vapor. They immediately proceeded to develop it in a normal system of collecting water from the atmosphere. The new device employs about one kilogram of MOF crystals, each of which is compressed between a solar energy collector and a water condensation pad.

As the air penetrates into the porous MOF material, the water molecules bind to its internal surface. Then the sunlight heats the material and leads the bounded water vapor to the condensation plate, where it is converted into liquid water, which is finally collected drop after drop into a separate chamber.

Technology has great room for improvement. Today the MOF material used can absorb only 20% of its weight in water, but using other materials the percentage could probably increase to 40% or more.
“To have running water constantly, it could design a system that absorbs moisture during the night and turns it into wet water during the day with sunlight,” Jagi said.

“Even if someone is cut off somewhere in the desert, they can survive thanks to this device. A person needs at least one bottle of water a day, which he can collect with this system in less than an hour, “he added. However, the metal zirconium used should be replaced because it costs $ 150 a kilo, so the water collection system is still expensive. Already researchers are testing the use of aluminum, which is 100 times cheaper.

Given that nearly two-thirds of the world’s population is experiencing greater or lesser water shortages in the year while the air around us has huge amounts of water in the form of water vapor (around 13 trillion liters worldwide, equivalent to 10% of all fresh water Of the Earth), the importance of new technology, which, if implemented on a massive scale, is perceived to bring about a revolution in the water sector.