By setting up a sun-reflecting parabola (with for example recycled metal-old cans) and oriented towards the sea water and thus evaporating sea water. The water vapor would be desalted and may be cooled at ambient temperature (by placing an inclined cover next to the water vapor) and used to water fields and plantations.
Yes- in my birth country, Lebanon, we have what's called 'salterns' (Google it. You will find some case studies).
I am sorry Cherine, I did not find 'salterns' could you give me a link?
Salterns or salt-pans
Here are some links with some attached documents:
http://php.scripts.psu.edu/clubs/up/ases/papers/ASES2012_Diaz_Stewart_Brownson.pdf
http://orthodoxyouth.yolasite.com/deir-doukhoul-al-sayydeh-al-natour.php (find salt-pans here)
http://www.iopan.gda.pl/oceanologia/544madko.pdf
http://www.aquaticbiosystems.org/content/pdf/2046-9063-8-23.pdf
@Cherine, you did not understand what I meant, your links are about producing salt, I propose here to produce desalted water (with no salt). The process is the same except that you collect desalted water and not salt ( you may do both if you want)
How much distilled water are your trying to make on a good day? There are a number of solar water distillers (google "solar stills") and some are commercially available. It can be accomplished by using sunlight to increase the evaporation rate of a pan of water and condensing the water on a glass plate, you don't need the parabolic mirror. Incline the plate to let the water run into a trough which you collect. Please note that distillation will not necessarily remove any voitale organic compounds with lower boilng points than water.
As pointed by Larrabee... Solar stills
There are other reports on solar energy (ex: photo-voltaic) driven water purification and desalination.
http://www.adu-res.org/pdf/University_of_Wollongong.pdf
http://srp.iitm.ac.in/?q=node/16
@David, so why is it not used in countries lacking desalted water? indeed, it is not necessary a parabola. You say that 'distillation' will not remove compounds with lower boiling points than water, so is it really distillation? The desalted water could be used for fields and plantations.
@Sridhar: your links show only filtration and it needs photovoltaic covers, far too complicated
@Nathalie. This is always an issue with any distillation. When compounds have close boiling points there can be a significant partial pressure of compound A when you are distilling compound B. This is why water is sometimes triple distilled. Also some distillers would allow the condenced water to vent. The other approach is to pass the distilled water though a carbon filter to help remove the organics.
VOC's ares only a problem if there are organics like benzene present in the water (boiling point around 80C). In situations where they are missing it isn't a problem. I am working on a personal system for distilling water to eliminate a fine micron sized clay particles from an otherwise clean well. So this is an ideal solution.
I have tried to convince one facility to use solar distallation of the waste water from their kitchen to water their hay fields. This is a region with a lot of sunlight and low water resources. So far other issues have a larger priority.
I suspect the reluctance to use solar still is due to the large surface area required to produce a large volume of water in a short time. When land values are expensive and solar irradiation is highly seasonal or low it is probably more economical to use an electrical distillation process. For those of us who are interested in minizing fossel fuel useage, this is an unfortunate reality.
Good luck with your project!
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