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Solar Salt Snake

A pipe that passively evaporates water
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I propose a giant pipe which snakes its way near an area that is too dry.

This pipe will be pumped partly full of seawater, and coated with solar plating where it is exposed to the sun, and otherwise coated with thermoelectric plating. Vents will be placed along the top of the pipe for water vapor to escape, the vents will be slanted downward to prevent rain from falling in.

The solar power powers the peltier-effect heaters, which transfer ambient heat into the pipe. The water in the pipe evaporates, some will condense on the outside of pipe which is cooled by the peltier effect.

The concentrated seawater which remains in the pipe can either be made into salt products, or returned to the sea. The peltier effect can be balanced against the pumping action to optimize the nature of the endstream result.

Madai, Nov 29 2004

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       <sigh>   

       At least you didn't fall into the dirt canal trap...so I withold the bone.   

       Such a pipe would cost at least USD2,000 per meter to construct. Each meter could produce say 10 cubic meters of fresh water per year (say the pipe was five meters wide and could evaporate @ 2 meters per annum). Applying an IRR of 6% to your capital cost and adding a similar cost for system maintenance makes that water cost the community (who paid for the pipe) about US2.4 cents per liter (that's about US$72,000 for an olympic pool full)   

       Water to my home (in Australia)costs US00.1 cent per liter, and farmers here pay about 1000 times less than that.
ConsulFlaminicus, Nov 30 2004
  

       Solar powered desalination is an active topic of research, and I guess it's a reasonable idea to combine your desalination and distribution network if possible. However neither the desalination process or the distribution process will be particularly efficient, as [Consul] points out. Much better to have an optimised desalination plant followed by an optimised piping network.
suctionpad, Nov 30 2004
  

       The price of solar and thermoelectric plating is high now, but with mass production the price should come down.   

       Meanwhile, this is not just about the ACTIVE effect, it is also about the passive effects. By running the snake through extremely dry areas, the snake adds humidity and slows evaporation and transpiration, even without the solar and thermal effects.   

       Finally, if there's nice cheap sources of water, great. This design is more intended for areas where it's either this water or no water, and also where the cooling will be appreciated.
Madai, Nov 30 2004
  

       So: convert solar energy into electricity at around 10% efficiency, then use that to create heat at about 5% efficiency. Spend quadzillions of dollars to do so, and quadzillions more to replace the horrificallly expensive salt-decayed components every two or three years.   

       5% of 10% is 0.5%.   

       I like the vented pipe, but just let it sit in the sun.
BunsenHoneydew, Mar 12 2008
  

       It would be much cheaper to have convex mirrors either side of the pipe and/or a linear fresnel lense above it. Efficiency could be increased further by having transparent strips in the pipe where the sunlight is focussed, heating the inside rather than the outside.
marklar, Mar 13 2008
  
      
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