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In coastal areas there the density between salt and sweat water can be used as energy source. Salt water wants to 'travel' to sweet water. It requires two types of membranes, namely one that is selectively permeable for positive ions and one that is selectively permeable for negative ions. It's called reversed electro dialysis or 'blue energy'. The technology is deferred from the haemodialysis technology that is used for treatment of kidney patients, but only setup reversed (not demanding power, but delivering it). Problems are finding the right performing membranes, for the right price (material and production) and the water pollution by the membranes. After solving these three problems each coastal area with a sweet water surplus will have it's own 'blue energy' plant. Water temperature, seawater salt percentage are beside the technology the main factors. Blue energy doesn't salinate sweet water environments, the processed water just go to the sea. Blue energy can also be made with the large near coastal sweet water reservoirs, but this water is too good to salinate it for energy use: it better can be explored for city use.

Author: Gijs Graafland

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