REVERSE ELECTRODIALYSIS (RED) is the salinity gradient energy retrieved from the difference in the salt concentration between seawater and river water . A method of utilizing the energy produced by this process by means of a heat engine was invented by Prof. Sidney Loeb in 1977 at the Ben-Gurion University of the Negev. --United States Patent US4171409
In reverse electrodialysis a salt solution and fresh water are let through a stack of alternating cation and anion exchange membranes. The chemical potential difference between salt and fresh water generates a voltage over each membrane and the total potential of the system is the sum of the potential differences over all membranes. It is important to remember that the process works through difference in ion concentration instead of an electric field, which has implications for the type of membrane needed.
In RED, as in a fuel cell , the cells are stacked. A module with a capacity of 250 kW has the size of a shipping container.
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In 2006 a 50 kW plant was located at a coastal test site in Harlingen
, the Netherlands, the focus being on prevention of biofouling of the
anode , cathode , and membranes and increasing the membrane
performance. In 2007 the Directorate for Public Works and Water
Management, Redstack, and ENECO signed a declaration of intent for
development of a pilot plant on the
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