Salinity Gradient Power

Salinity gradient power, also called osmotic power or blue energy, generates electricity from the difference in salt concentration between seawater and river water where the two meet, through one of two practical membrane based methods: pressure retarded osmosis, in which fresh water is drawn by osmosis through a membrane into pressurized seawater, and reverse electrodialysis, which uses a stack of membranes to generate a voltage directly from the salinity difference; both processes produce brackish water as their main byproduct. R.E. Pattle first pointed out the untapped power available where rivers meet the sea in 1954, and Sidney Loeb, inspired by watching the Jordan River flow into the Dead Sea, developed pressure retarded osmosis at Ben Gurion University in 1973 before inventing a reverse electrodialysis heat engine method in 1977. Both technologies have been confirmed under laboratory conditions and are being developed for commercial use, reverse electrodialysis in the Netherlands and pressure retarded osmosis in Norway, with newer, lower cost membranes, including one based on electrically modified polyethylene plastic, improving the technology commercial prospects after membrane cost had long been the main obstacle.