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Saltwater + Desert

Two things we have a lot of, and not currently many uses for. Put them together to get things we need and value
  (+2, -3)
(+2, -3)
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This was inspired by a diving trip to the lower Red Sea, where miles of flat desert ends at the shore of miles of flat sea. That's all there is!

The idea was to create a modular unit, looking a bit like a combination of a treadmill and a greenhouse.

Saltwater would be pumped up and deposited in a thin film onto the surface of the treadmill, which would be turning underneath a 'roof' made of solar panels. The electricity generated by the roof would be used to do 2 primary things. a) turn the treadmill b) refrigerate the underside of the roof

Any excess would then be tapped for distribution to grid etc.

The saltwater would rapidly evaporate, given that the ambient air temperature is very high and that the film of water is very thin. The moist air would condense on the underside of the solar panel roof, which would be angled downwards into collecting gutter tubes, and from there drained off into tanks - where it should be usable as drinking water, etc.

The treadmill surface will have a thin coating of salt, which will be scraped off as it goes back underneath the device on the return part of the cycle. The dislodged salt will fall with gravity into collecting bins which can be easily 'harvested'.

The output per unit might be small (maybe a few hundred millilitres or so of water per day, a few grams of salt, and a few watts of excess power) - but with the vast spaces available you could have lots of them, and they sound very simple and relatively cheap to manufacture.

So ... 'saltwater + desert = drinking water + electricity + salt'

Sounds neat to me!

kindachewy, Jul 10 2009

Link stolen from previous - small scale unit, works in Texas / Mexico http://www.txses.org/epsea/stills.html
This proves concept of the solar distillation, but doesn't do all the other things [kindachewy, Jul 10 2009]


       OOPS - just went ahead and posted this, forgetting to check for prior art first. Of which there is (obviously) lots. Apologies ...
kindachewy, Jul 10 2009

       However, the reason for posting was that several current ideas (Glass Steam Super Stacks, CO2 Scrubber New & Improved, Ocean Pump, etc) all seem to be heading in the same direction.   

       So - rather treat this as a reminder of all the great stuff that's gone before in this vein, and then consider:   

       - the economic value of these 3 usable outputs   

       - additionally, the direct cooling effect via evaporation   

       - additionally, the indirect cooling effect via escaping humidity, contributing to greater cloud cover   

       - additionally, the additional rainfall - some of which might fall onto the neighbouring deserts as air temperature falls with oncoming night, thus leading to greater fertility of affected land.   

       If we could build in some carbon sequestration effects it would be almost perfect.   

       However, that's REALLY easy, because all we have to do is to use (some of) the water produced to support highly intensive hydroponic agriculture - so we're up to 5 valuable outcomes (drinking water, electricity, salt, food and carbon sequestration)   

       The most intensive version could be to cultivate vast numbers of sheets of [danman]'s algae filter paper. Not sure if you could use the algal remains to make fertiliser, but - if so - that could put the cherry right on the top!   

       How big would this need to be to have any significant cooling/carbon effect??
kindachewy, Jul 10 2009

       [+] I love the idea of solar powered distillation, however it would be a very lenghthy process as thick water would increase evap. time.   

       We could also build solar plants (or algae filter plants if more efficient) elsewhere to subsidise electricity needed to heat the salt water.   

       //the additional rainfall - some of which might fall onto the neighbouring deserts as air temperature falls with oncoming night// Where is the extra rainfall coming from? Isn't it all collected? climate change?   

       The dead sea is being drained for its minerals and salt. This can a very dirty business and fragile habitats in places like the red sea would be badly affected.   

       If the correct amount of water was taken, however, it would be wonderful.
danman, Jul 10 2009

       Extra water from clouds in point above.   

       My version has open sides, which result in significant moisture lost into the atmosphere in order to allow this to happen, but will still manage to collect a reasonable amount of water, I believe.   

       Note that Mexican version (link, scavenged from earlier version idea) managed to make 20 gallons per day using a sheet of glass the size of a standard glass door panel, using an enclosed system   

       Seawater volumes: relatively low volumes would be taken per unit, because the film of water needs to be thin to evaporate effectively and the treadmill needs to turn slowly to give it time to do so.   

       Habitat impact: I'm envisaging vast 'far as the eye can see' fields of these units stretching across the desert, so yes ... it would stuff that habitat up quite badly, I suppose.
kindachewy, Jul 10 2009

       Not sure that's //required// [bigsleep] , although obviously it would help a lot. One thought was that the solar energy panels would be in the conveyor, allowing more sunlight to fall directly on it.   

       However, I reckon that a thin layer of salt water on a flat surface in ambient temperatures of 30 to 50 Celsius, particularly allowing air to pass freely over it, will be back to a dry surface again in pretty short order.
kindachewy, Jul 10 2009

       Don't think you even need solar powered refrigeration to cool the condensation surface. Pump some of your salt water up and let it run over the roof to cool it. Some will evaporate, which means yet more cooling, and moisture in the air. Bonus- it's preheated, ready for the evaporation chamber.
BunsenHoneydew, Jul 11 2009

       However, moving your treadles is a waste of energy, and thus of sunk dollars in solar panels. Just pump your payload - the water - and install a much smaller, cheaper setup
BunsenHoneydew, Jul 12 2009


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