Rolf Jarle Aaberg The mixing of freshwater and seawater where a river flows into the saltyoceanreleases large amounts of energy. Can this energy be exploited for commercial large scale power production? Rolf Jarle Aaberg, Statkraft SF, Norway describes a technique that could harness significant amounts of energy in this context. lf freshwater and saltwater is separated by a proper semi-permeable membrane the freshwater will spontaneously migrate through the membrane and dilute the salt-water due to the chemical potential difference. This phenomenon is known as osmosis. Provided the dissolved salt ions are completely retained by the membrane, the flux of water through the membrane generates a hydrostatic pressure which is known as the osmotic pressure. The salinity difference between ordinary freshwater and ocean water is enough to produce an equilibrium osmotic pressure of about 27 bars. Untapped RE source? The Norwegian state power company Statkraft SF, a company with a strong tradition in hydropower, believes that osmotic power can become a significant renewable energy source and has engaged in technology development aiming at cost-effective power production. Osmotic power technology under normal Fresh water o:: o:: w w � :; s: u:: MEMBRANE MODULES Fresh water bleed Power Flgure 1. Simplifıed process layout tor a typical osmotic power plant
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