Osmotic power

"Blue energy" redirects here. For the NGO, see blueEnergy.
Part of a series on
Renewable energy

Osmotic power, salinity gradient power or blue energy is the energy available from the difference in the salt concentration between seawater and river water. Two practical methods for this are reverse electrodialysis (RED) and pressure retarded osmosis (PRO). Both processes rely on osmosis with membranes. The key waste product is brackish water. This byproduct is the result of natural forces that are being harnessed: the flow of fresh water into seas that are made up of salt water.

In 1954, Pattle[1] suggested that there was an untapped source of power when a river mixes with the sea, in terms of the lost osmotic pressure, however it was not until the mid ‘70s where a practical method of harnessing it using selectively permeable membranes by Loeb [2] was outlined.

The method of generating power by pressure retarded osmosis was invented by Prof. Sidney Loeb in 1973 at the Ben-Gurion University of the Negev, Beersheba, Israel.[3] The idea came to Prof. Loeb, in part, as he observed the Jordan River flowing into the Dead Sea. He wanted to harvest the energy of mixing of the two aqueous solutions (the Jordan River being one and the Dead Sea being the other) that was going to waste in this natural mixing process.[4] In 1977 Prof. Loeb invented a method of producing power by a reverse electrodialysis heat engine.[5]

The technologies have been confirmed in laboratory conditions. They are being developed into commercial use in the Netherlands (RED) and Norway (PRO). The cost of the membrane has been an obstacle. A new, lower cost membrane, based on an electrically modified polyethylene plastic, made it fit for potential commercial use.[6] Other methods have been proposed and are currently under development. Among them, a method based on electric double-layer capacitor technology[7] and a method based on vapor pressure difference.[8]

  1. ^ R.E. Pattle (2 October 1954). "Production of electric power by mixing fresh and salt water in the hydroelectric pile". Nature. 174 (4431): 660. Bibcode:1954Natur.174..660P. doi:10.1038/174660a0. S2CID 4144672.
  2. ^ S. Loeb (22 August 1975). "Osmotic power plants". Science. 189 (4203): 654–655. Bibcode:1975Sci...189..654L. doi:10.1126/science.189.4203.654. PMID 17838753.
  3. ^ ^ Israel Patent Application 42658 of July 3, 1973. (see also US 3906250  Erroneously shows Israel priority as 1974 instead of 1973 US 3906250 
  4. ^ ^ Weintraub, Bob. "Sidney Loeb," Bulletin of the Israel Chemical Society, Dec. 2001, issue 8, page 8-9. https://drive.google.com/file/d/1hpgY6dd0Qtb4M6xnNXhutP4pMxidq_jqG962VzWt_W7-hssGnSxSzjTY8RvW/edit
  5. ^ United States Patent US4171409
  6. ^ History of osmotic power (PDF) at archive.org
  7. ^ Brogioli, Doriano (2009-07-29). "Extracting Renewable Energy from a Salinity Difference Using a Capacitor". Physical Review Letters. 103 (5). American Physical Society (APS): 058501. Bibcode:2009PhRvL.103e8501B. doi:10.1103/physrevlett.103.058501. ISSN 0031-9007. PMID 19792539.
  8. ^ Olsson, M.; Wick, G. L.; Isaacs, J. D. (1979-10-26). "Salinity Gradient Power: Utilizing Vapor Pressure Differences". Science. 206 (4417). American Association for the Advancement of Science (AAAS): 452–454. Bibcode:1979Sci...206..452O. doi:10.1126/science.206.4417.452. ISSN 0036-8075. PMID 17809370. S2CID 45143260.