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Environmental

Salty water may be useful as a power source

Prior posts have noted various potential alternative energy sources, from the nearly developed to the "still on the drawing board". One idea that may hold some promise was recently noted in a prestigious science journal. The key researcher likens his concept to the reverse of desalination, in which electricity is consumed to separate salt ions from seawater. In his method, the combination of fresh and salt water generates electricity when the ions diffuse through water.
 
In the first stage of the process, salt water is pumped into a container with two charged carbon electrodes. Salt ions (positively charged sodium and negatively charged chloride) are attracted to the surface of one of the two carbon electrodes, depending on the ions’ charge. Next, fresh water is pumped into the container, and the salt ions diffuse away from the surface of the electrodes and mix in the fresh water. Like pulling a rubber band taut, pulling the salt ions away from the charged electrodes creates increased energy in the system, the potential for work. The amount of energy generated is similar to that harnessed through existing techniques that use fresh and salt water to produce electricity, but at a fraction of the cost, the researcher alleges. For now, this is a benchtop device.
 
Detailed information about the process can be found at http://physicsbuzz.physicscentral.com/2009/07/electricity-from-salty-water.html. Other ocean related power sources are reviewed at http://memagazine.asme.org/Web/Harness_Seas.cfm.