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Sunlight Helps Turn Salty Water Fresh

Posted by Soulskill on from the that's-very-kind-of-the-sunlight dept.

MTorrice writes "With energy-efficient desalination techniques, water-starved communities could produce fresh water from salty sources such as seawater and industrial wastewater. But common methods like reverse osmosis require pumping the water, which uses a substantial amount of energy. So some researchers have turned to forward osmosis, because in theory it should use less energy. Now a team has demonstrated a forward osmosis system that desalinates salty water with the help of sunlight. The method uses a pair of hydrogels to absorb and squeeze out freshwater."

4 of 58 comments (clear)

  1. Am I missing something? by Anonymous Coward · · Score: 5, Insightful

    How is this distinctly more efficient than simply using sunlight to warm water, which evaporates, and collecting the fresh water that condenses? Desalination plants work like this, except they tend to use energy from some other source to boil the incoming seawater.

    1. Re:Am I missing something? by OhANameWhatName · · Score: 4, Insightful

      How is this distinctly more efficient than simply using sunlight to warm water, which evaporates, and collecting the fresh water that condenses?

      It's patentable.

    2. Re:Am I missing something? by Anonymous Coward · · Score: 5, Insightful

      That is generally what I was wondering. And you don't have to actually boil the water, a proper dome will allow the water to evaporate, collect on the inner surface, and drip down sides for collection. Problem there is the large size you need for it to collect enough to be useful.

      I think you're not thinking big enough.

      Imagine a large sphere, maybe 8000+ miles across, illuminated by natural sunlight. You could put salt water on the outer surface of the sphere -- enough to cover 3/4 or so of the surface -- and it would naturally evaporate and condense above the surface of the sphere in certain regions and fall down in drops. A system of canals could be used to conveniently collect the water. All you would have to do is put devices that use water in those regions, and they'd have a steady supply of water. My calculations show that you could easily get 1000 kg per square meter per year in the right areas, without having to put in energy at all.

      Of course, there would also be parts of the sphere where almost no water would fall, but that problem is pretty easy to solve -- just don't put anything that needs water in those areas.

    3. Re:Am I missing something? by Anonymous Coward · · Score: 3, Insightful

      I wonder why people choose to live in such inhospitable places.

      At least in the US, it's because the people who live there don't realize that the area they have chosen to live cannot sustain them. They think of it as paradise, since they have "perfect weather year-round". It's up to Someone Else to worry about pumping fresh water over the Tehachapi Mountains, and about where that water is coming from.