This method utilizes a membrane, permeable to water, to draw fresh water into the concentrated salt water, thus increasing the pressure in the salt water chamber. The resulting pressure can then be used to drive a turbine to produce electricity.
Estuaries are the locations where river water mixes with seawater. They are found along coastlines throughout the world, but what most people don’t realize is the significant potential to produce clean energy from these mixing water streams. The salinity gradient between the two streams of water contains a large amount of osmotic power, which can be thought of as the available energy (or chemical potential) from the differences in salt concentration between the fresh water and seawater. The enormous amounts of energy released where freshwater and seawater meet “can be utilized for the generation of power through osmosis”, which is “defined as the transport of water through a semi-permeable membrane.” 
The idea of obtaining energy from osmosis, or salinity gradient power, has been studied for decades, but in early 2009 two teams were racing to be the first to build a working prototype power plant making salinity gradient power…
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