Making water from THIN AIR: Pioneering 'harvester' sucks moisture from dry areas using sunlight

The harvester uses a special metal-organic framework material
As ambient air diffuses through, water molecules attach to the interior surfaces
The prototype, under conditions of 20 to 30 per cent humidity, was able to pull 2.8 litres - from the air over a 12-hour period

Published: 19:00 BST, 13 April 2017 | Updated: 19:00 BST, 13 April 2017

A new technology could provide hope for drought stricken areas.

Scientists have created a pioneering solar panel rooftop 'harvester' capable of storing water from air.

The device uses only ambient sunlight to pull litres of water out of the air each day, and could provide water supplies to remote homes far from the water network.

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A pioneering new solar panel rooftop 'harvester' could make access to the valuable liquid a lot easier. The device uses only ambient sunlight to pull litres of water out of the air each day, and could provide water supplies to remote homes far from the water network

HOW DOES IT WORK?

The harvester consists of more than two pounds of dust-sized MOF crystals compressed between a solar absorber and a condenser plate, placed inside a chamber open to the air.

As ambient air diffuses through the porous MOF, water molecules preferentially attach to the interior surfaces.

X-ray diffraction studies have shown that the water vapour molecules often gather in groups of eight to form cubes.

Sunlight entering through a window heats up the MOF and drives the bound water toward the condenser, which is at the temperature of the outside air.

The vapour condenses as liquid water and drips into a collector.

The current MOF can absorb only 20 per cent of its weight in water, but other MOF materials could possibly absorb 40 per cent or more.

The material can also be tweaked to be more effective at higher or lower humidity levels.

Scientists at Massachusetts Institute of Technology built the harvester using a special material - a metal-organic framework (MOF) - produced at the University of California, Berkeley.

Professor Omar Yaghi, who led the study, said: 'This is a major breakthrough in the long-standing challenge of harvesting water from the air at low humidity.

'There is no other way to do that right now, except by using extra energy.

'Your electric dehumidifier at home "produces" very expensive water.'

The prototype, under conditions of 20 to 30 per cent humidity, was able to pull 2.8 litres - or nearly five pints from the air over a 12-hour period, using one kilo or 2.2 pounds of MOF.

Professor Yaghi added: 'One vision for the future is to have water off-grid, where you have a device at home running on ambient solar for delivering water that satisfies the needs of a household.

'To me, that will be made possible because of this experiment. I call it personalised water.'

Professor Yaghi invented metal-organic frameworks more than 20 years ago, combining metals like magnesium or aluminium with organic molecules in a tinker-toy arrangement to create rigid, porous structures ideal for storing gases and liquids.

Since then, more than 20,000 different MOFs have been created by researchers worldwide.

In 2014, Professor Yaghi and his UC Berkeley team synthesised a MOF - a combination of zirconium metal and adipic acid - that binds water vapour.

He then teamed up with MIT mechanical engineer Dr Evelyn Wang to turn the MOF into a water-collecting system.

The harvester consists of more than two pounds of dust-sized MOF crystals compressed between a solar absorber and a condenser plate, placed inside a chamber open to the air.

An artist's impression shows the device. The lines are organic linkers, and the intersections are multi-metallic units. The yellow balls represent the porous spaces that can fill up with water

As ambient air diffuses through the porous MOF, water molecules preferentially attach to the interior surfaces. X-ray diffraction studies have shown that the water vapour molecules often gather in groups of eight to form cubes.

Sunlight entering through a window heats up the MOF and drives the bound water toward the condenser, which is at the temperature of the outside air.

The vapour condenses as liquid water and drips into a collector.

'This work offers a new way to harvest water from air that does not require high relative humidity conditions and is much more energy efficient than other existing technologies,' Dr Wang said.

The current MOF can absorb only 20 per cent of its weight in water, but other MOF materials could possibly absorb 40 per cent or more.

The material can also be tweaked to be more effective at higher or lower humidity levels.

The researchers wanted to demonstrate that if you are cut off somewhere in the desert, you could survive because of this device

Professor Yaghi concluded: 'It's not just that we made a passive device that sits there collecting water; we have now laid both the experimental and theoretical foundations so that we can screen other MOFs, thousands of which could be made, to find even better materials.

'There is a lot of potential for scaling up the amount of water that is being harvested. It is just a matter of further engineering now.

'To have water running all the time, you could design a system that absorbs the humidity during the night and evolves it during the day.

'Or design the solar collector to allow for this at a much faster rate, where more air is pushed in.

'We wanted to demonstrate that if you are cut off somewhere in the desert, you could survive because of this device.

'A person needs about a Coke can of water per day. That is something one could collect in less than an hour with this system.'