Hello, Some desert areas, notably near the southern Mediterranean coast, are indeed below sea-level. Letting sea water flow towards them is a rather old idea which has various rationales: triggering economical development, producing hydroelectric renewable energy, etc. Increasing water evaporation for geoengineering purposes is a new one. I'd like to emphasize a fourth one: producing very large quantities of renewable energy thanks to salt gradients.
This is because these sub-sea-level areas have already been flooded, in geological times, so that salt has accumulated there (they're called evaporites - others are located in the Danakil desert, also below sea-level, in eastern Eritrea and Ethiopia). As the reverse of sea water desalination, letting very concentrated brine (which can be produced by salt dissolution into sea water) and usually concentrated sea water melt with each other can produce renewable energy. See: http://en.wikipedia.org/wiki/Blue_energy One technology (pressure retarded osmosis) is being developed by Norwegian society Statkraft: http://www.statkraft.com/Images/Statkraft%20Osmotic%20Power_tcm4-5362.pdf. It uses the same osmosis membranes that are currently used for water desalination, however, for price competitiveness, further cost reductions should come from scale economies. The other technology (reverse electro dialysis) is developed by Dutch Redstack: http://www.redstack.nl/RS-Pres01/RS-pres_bestanden/frame.htm Both are mainly developed in order to yield the salinity gradient between fresh water and sea water, but, as they also notice, the gradient between seawater and saturated brine is one order of magnitude greater, so that exploiting evaporites would be a huge quasi-renewable energy source. They are also interested in salt gradient conversion when the "sea water to Dead Sea" Project is to be realized. With Renaud de Richter, I am currently writing a book (in French) which will probably be named "20 energies renouvelables insolites" (20 unusual renewable energies). Salinity gradients will be the first of our 20 chapters. Best regards, Denis Bonnelle [email protected]<mailto:[email protected]> De : [email protected] [mailto:[email protected]] De la part de Ken Caldeira Envoyé : dimanche 7 juin 2009 22:27 À : geoengineering Cc : Johnnie Buttram Objet : [geo] Flooding below sea-level: Siphonics Natural Engineering (c) Folks, I ran across this pdf recommending the benefits of flooding sub sea-level desert areas. I believe the author of this document (cc'd) would enjoy your comments. Best, Ken ___________________________________________________ Ken Caldeira Carnegie Institution Dept of Global Ecology 260 Panama Street, Stanford, CA 94305 USA [email protected]<mailto:[email protected]>; [email protected]<mailto:[email protected]> http://dge.stanford.edu/DGE/CIWDGE/labs/caldeiralab +1 650 704 7212; fax: +1 650 462 5968 --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "geoengineering" group. To post to this group, send email to [email protected] To unsubscribe from this group, send email to [email protected] For more options, visit this group at http://groups.google.com/group/geoengineering?hl=en -~----------~----~----~----~------~----~------~--~---
