A billion people could access clean water through devices that use solar energy to condense water from the air. This is the conclusion of a team of American researchers led by Jackson Lord at X, The Moonshot Factory, which has developed a new tool to assess the global potential of water harvesting. His tool could soon help researchers design fully off-grid water sources that can be used by local communities in many parts of the developing world.
Lack of access to safely managed drinking water currently affects some 2.2 billion people worldwide. Solving this serious problem using existing technologies is a key part of the United Nations Sustainable Development Goals, which state that everyone should have access to five liters of clean drinking water every day.
This could be achieved in some regions by using Atmospheric Water Harvesters (AWH), which extract clean liquid water from humid air.
There are several types of AWH, and Lord and his colleagues focused on solar-powered continuous-mode AWH (SC-AWH). In this device, the heat of the sun draws warm, moist air through a heat exchanger, where it cools and releases water through condensation. Since the SC-AWH operates during the day, when relative humidity tends to be low, its efficiency is poor and it was unclear where in the world it could be used.
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Geospatial tool.
Now, Lord’s team has created a geospatial tool called “AWH-Geo” to assess the global potential for water harvesting.
Based on a Google Earth engine, the tool uses data from ERA5: a database containing a large number of historical climate observations dating back to 1979.
To assess the different results of atmospheric water uptake in different regions, AWH-Geo took into account the solar irradiance, relative humidity and average air temperature of each location. In addition, the tool took into account the annual variations of these parameters.
The team also looked at the global distribution of people without access to clean water, using data from the World Health Organization and UNICEF. Combining this with results from AWH-Geo, the researchers showed that collecting atmospheric water could realistically provide five liters of drinking water around one billion people in the world.
This is based on using a hypothetical SC-AWH with a catchment area of 1 m2. The team calculates that such a device could produce between 0.2 and 2.5 liters of water per kilowatt-hour of primary solar energy when operated between 30 and 90 percent relative humidity and an average temperature of the air of 20°.
Researchers are developing such a device and, with technological improvements, believe it could provide cost-effective, completely off-grid access to high-quality drinking water for many communities in the developing world.
Researchers will continue to use AWH-Geo to guide the development of new types of water harvesting devices, with the ultimate goal of moving closer to the UN goal of clean water.
More information: www.nature.com (English text).
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