In WWII a device was provided for airmen whose planes went down at sea. It was a transparent balloon containing a black sponge which could be soaked in salt water. When the balloon was subsequently inflated and floated behind an inflated life saving raft, the sun would heat up the black sponge and evaporate the salt water which would condense on the inside skin of the balloon as freah water which would drip to the bottom of the balloon to be collected for drinking. This same system could be modified to become extruded plastic tubing with a black foam strip at the center that would be in contact with open sea water. The foam could continuously draw in the sea water which would continuously be evaporated by sunlight. When the sponge became impregnated with salt the sea water would redissolve it so that the salt would be returned to the sea. Sealed small floatation tubes on either side would keep the apparatus afloat so inflation would not be necessary and channels on either side of the upper condensation membrane would collect fresh water to be continuously drawn off. Parts of the extrusion could be vacuum coated with a reflecting surface to concentrate the sunlight on the black foam strip. The strip could form a matrix, perhaps acres in extent, floated off the seacoast of a country needing a supply of fresh water and it would be flexible enough to remain uninjured by storms or violent waves.
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Not sure the economics are favorable compared to a simple delasination plant. But have a look at "The Scientist Speculates: An Anthology of Partly-Baked Ideas" ed. I. J. Good. (Out of print, but available used.) This book has a long essay about how to evaporate sea water and direct it to farms.
A desalination plant requires an external form of energy and requires maintainance whereas my suggestion was to use abundant sunlight which is non-polluting. The tube system could be sold by the square foot in the form of interconnecting flexible mats so that it could grow by affordable increments.
The device in quesion simply increased the odds of survival by an individual in an emergency situation. To produce enough water for the good life would require a huge number of such devices, especially since the sun is not always abundant.