Reversed electrodialysis

Reverse electrodialysis (RED) is the salinity gradient energy retrieved from the difference in the salt concentration between seawater and river water.

[1] 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 process works through difference in ion concentration instead of an electric field, which has implications for the type of membrane needed.

[4][5] 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 Afsluitdijk in the Netherlands.