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Renewable Energy Made by Mixing Salt and Fresh Water

September 9, 2009
full at source: Scientists have already designed several techniques in an attempt to harvest this energy, and have successfully generated power of about 1 kW for a fresh water flow of 1 liter per second. But these techniques are usually based on membranes through which the water flows, and problems such as high membrane cost and short lifetime are currently preventing the large-scale utilization of these techniques.

Now, Doriano Brogioli of the University of Milan Bicocca in Monza, Italy, has taken a different approach to extracting energy from salinity difference. As Brogioli explains in a recent issue of Physical Review Letters, the method is based on electric double-layer (EDL) capacitor technology.

clipped from www.physorg.com

Renewable Energy Made by Mixing Salt and Fresh Water

A computer simulation of two sponge-like structures that represent two electrodes, stacked one on top of the other. The colors represent the intensity of the electric field. In high salinity water (left), there is a low intensity electric field, while, after ion removal (right), the field intensity increases, thus increasing the potential difference. Image credit: Doriano Brogioli.

(PhysOrg.com) — When a river flows into the sea, the location is more than just a haven for water commerce. The mixing of fresh and salt water that occurs at an estuary also dissipates energy, as the different salinity waters combine into a state of less-ordered, uniform salinity. The mixing generates a significant 2.2 kJ of energy per liter of fresh water that flows into the sea.
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