A team of Australian scientists has developed an ingenious system to harvest atmospheric water, considered by many to be the holy grail for the world’s critical shortage of drinking supplies.
About 1.2 billion people, or one-fifth of the world's population, live in areas of physical scarcity, according to the United Nations. Some 660 million people do not have ready access to a safe water supply.
Led by Professor Behdad Moghtaderi from University of Newcastle’s Institute for Energy and Resources, the Hydro Harvest Operation team have come with a system to tap the immense atmospheric reservoir and convert humidity into drinkable water.
The atmosphere hold a water volume on par with the combined reserves of surface and underground sources.
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Hydro Harvest is a finalist in the $1.75 million XPRIZE for water, a competition for new energy efficient technology to tackle the critical global shortage of drinking water.
XPRIZE teams are required to create a device that extracts a minimum of 2000 litres of water a day from the atmosphere.
The device must use 100 per cent renewable energy and cost no more than two cents per litre to run.
Previous attempts at atmospheric harvesting focused on create condensation with cool air, but the energy required to suck the heat away was too energy intensive to be useful to developing nations.
Hydro Harvest has turned the tables with a combination of new and old technology .
“Atmospheric water generators are usually based on refrigeration cycles that cool the air to below the dew point, the point at which condensation will form,” Prof Moghtaderi said.
Hydro Harvest system uses modular units with a sealable transparent perspex case that hold racks of silica gel balls.
The silica balls act as a desiccant, or material that draws water (little packets of the same silica balls are placed in shoes and other consumer goods, to keep them dry during storage and transport).
The process starts at night when the perspex case is swung open, so the silica balls are left “to do what they naturally do”, and absorb moisture from the cool air, Prof Moghtaderi explained.
They units are sealed up during the day, when solar energy heats up the air in the units.
Water in the balls evaporates in this hothouse, which can get to 80 degrees Celsius if the sun is strong enough.
And the hotter the air becomes, the more water it can hold.
“The temperature in the units increases so far above the ambient temperature it doesn’t matter if it’s summer or winter. We’re actually decoupling the units from the atmospheric conditions,” Prof Moghtaderi said.
In humid locations it may take just three to four hours for the balls to soak up their fill. In arid areas it may take all night.
Hydro Harvest is not just a reversal of previous systems.
Similar systems have been tried and abandoned in the past. They were set up to absorb water in the day and to use the cool night air to condense the moisture, but night-cooling at night was ineffective..
“We took that simple idea and turned it on its head,” Prof Moghtaderi said.
Hydro Harvest has developed a new heat exchange system to quickly and cheaply cool all that hot air trapped in the units.
“You need a novel and cost-effective heat exchange, and that is where we have our IP (intellectual property),” Prof Moghtaderi said.
Hydro Harvest’s system was designed to be as simple as possible, for use in developing countries.
To produce XPRIZE’s target volume of 2000L a day might take 50 or 100 units, depending on conditions, Prof Moghtaderi said.
The modular, environmentally friendly technology can work anywhere without being bound to climate, signifying the potential to transform the future of water generation around the world, said Hydro Harvest team member and Associate Professor Elham Doroodchi.
“There are no fancy materials, it’s purely looking at how air holds water and how that changes with temperature, and then how we can engineer a solution based on those known properties,” he said.
“Even if we don’t win, we will pursue the idea to ensure greater access to water for all.”
XPRIZE holds a range of competitions to solve “grand challenges”.
It kicked off with a successful competition in 1996 to send a passenger vehicle into space. It has also spurred solutions to oil spills, lunar landings and increased understanding of ocean acidification.
Current competitions include robotic space exploration, ocean exploration and adult literacy.
