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Water from thin air

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The Earth’s atmosphere contains enormous amounts of water.  Being able to efficiently and economically extract some of it to provide drinking water would be extremely beneficial to the billions of people across the globe who face chronic water shortages.

There are existing technologies for atmospheric water harvesting – or AWH.  But there are downsides associated with size, cost, and efficiency.   A new device developed by mechanical engineering researchers at the University of Utah has the potential to provide a new drinking water source in arid places.

The device is a compact, rapid-cycling, fuel-fired AWH device.  It relies on adsorbent materials that draw water molecules out of non-humid air and then applies heat to release those molecules into liquid form.

Hygroscopic materials are those that have an affinity for water and soak it up at every opportunity.  Such materials are used, for example, in disposable diapers.  The Utah device makes use of metal organic frameworks, which have enormous amounts of surface area on the molecular scale.

The initial work on the Utah device targeted a small compact water generation unit for soldiers in the field.  Instead of lugging around a large canteen filled with water, the small unit can produce water on demand.  The prototype was able to produce 5 liters of water per day per kilogram of adsorbent material.  Within three days in the field, the system outperforms packing water.  The heat required to precipitate the liquid water was provided by a standard-issue Army camping stove.

Non-military needs are the ultimate application for the device.  The researchers have applied for a patent for what they hope will be a potential solution to a persistent global problem.

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Producing water out of thin air

Photo, posted August 9, 2012, courtesy of Enid Martindale via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio

Saving Water At Power Plants | Earth Wise

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Nearly 40% of all the water taken from lakes, rivers, and wells in the U.S. isn’t used for agriculture, drinking, or sanitation.  It is used to cool power plants that produce electricity by burning fossil fuels or with nuclear reactors.   Two-thirds of these power plants use evaporative cooling, which produces huge white plumes billowing from cooling towers.

A new company using technology developed at MIT has the goal of reducing the water needs of power plants and helping to alleviate water shortages in areas where power plants strain the capacity of local water systems.

The technology is relatively simple in principle but developing it to the point where it can be applied at full scale at industrial power plants was a greater challenge. 

The basic idea is to capture water droplets from both natural fog and from the plumes from power plant cooling towers.  The MIT researchers had to improve the efficiency of fog-harvesting systems, which previously captured only 1-3% of the water droplets that pass through them.  They found that water vapor collection could be made much more efficient by zapping the tiny droplets of water with an ion beam, giving them a slight electric charge, thereby making it easy to capture them with the metal mesh of the harvesting system.

The system can essentially eliminate cooling tower plumes and produce large quantities of high-purity water in the process, which has uses at many power plants.  The new company, called Infinite Cooling, has arranged to install their equipment on two operating commercial power plants later this year.  They expect the system to reduce the overall need for water by 20%.

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Vapor-collection technology saves water while clearing the air

Photo, posted March 5, 2019, courtesy of Sam LaRussa via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio.

Can We Tow Icebergs To Use Their Water? | Earth Wise

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At any given time, there are thousands of icebergs adrift in Antarctica that are hundreds or even thousands of feet across.  For at least fifty years, there has been speculation about whether such icebergs could be towed from the Antarctic to places experiencing freshwater shortages.  The feasibility of such a scheme is still the subject of studies that nowadays include sophisticated computer modeling.

Places like the Persian Gulf, Cape Town, South Africa, and Perth, Australia all experience water shortages and could benefit tremendously from having a large iceberg towed to their waters.

How big an iceberg would it take to quench the thirst of a city like Cape Town?  Computer models show that an iceberg 2,000 feet long and 650 feet thick could produce enough water to supply the city for more than a year.  However, with water temperatures in the 60s in the area, even such a large iceberg would melt away within weeks.  So, to get enough water for a year, it would require a much larger iceberg – one at least a couple of miles long.

Daunting problems include figuring out how many and what sort of ships would be required.  An alternative to such giant icebergs would be finding a way to insulate the icebergs so they don’t melt as quickly, thereby allowing much smaller and more towable icebergs to be harvested.

Beyond these issues, there are the ecological issues of the effects of huge amounts of very cold fresh water affecting local marine ecosystems. 

Despite a wide range of challenges, there is continued interest in the idea of using icebergs as a source of very pure fresh water.  In an increasingly thirsty world, it might someday actually happen.

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Can icebergs be towed to water-starved cities?

Photo, posted November 1, 2007, courtesy of M A Felton via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio.

WAMC Northeast Public Radio

WAMC/Northeast Public Radio is a regional public radio network serving parts of seven northeastern states (more...)