28 April 2011

Battery Harvests the Energy of Estuaries : Discovery News


Renewable energy exists in the most unusual places. For example, in coastal estuaries, where fresh water rivers meet up with saltwater seas, the difference in salinty can represent about a kilowatt of free energy for every liter of water.

Scientists in Standford University's Department of Materials Science and Engineering have developed a new battery that taps into that electrochemical energy. The team says their "mixing entropy battery" could potentially supply 13 percent of the world's energy needs.

The battery itself is quite simple, consisting of one positive and one negative electrode. The idea is to alternately flush river water and sea water through the battery. Both kinds of water contain charged particles called ions, but seawater contains 60 to 100 times more ions than freshwater. When freshwater and its ions are flushed out and replaced with seawater, the battery produces a charge. The scientists estimate that a power plant built near an estuary could potentially produce up to 100 megawatts.

The scientists state the mixing entropy battery's simple fabrication offers a practical solution and shows potential as a future source of renewable energy. The process for generating electrical energy can also be reversed to remove salt from sea water to produce drinking water. Currently the team is modifying the battery for commercial use.

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