New Battery Uses Seawater And Freshwater to Produce Electricity

Stanford University researchers have designed a rechargeable battery that uses the contrast in salinity between freshwater and seawater to produce an electric current, an innovation they say could potentially be used wherever a river meets the ocean. The battery contains two electrodes — one positive, one negative — immersed in a liquid that contains electrically charged sodium and chlorine ions. The battery is initially filled with freshwater and given a small electric current, and then drained and replaced with salty seawater. Because the seawater contains 60 to 100 times more ions than the freshwater, the voltage between the two electrodes increases, allowing users to gain more electricity than the amount used initially to charge the battery, according to a report published in the journal Nano Letters. Researchers say that if such batteries were deployed in all of the planet’s estuaries, the technology could produce about two terawatts of electricity a year — roughly 13 percent of current global consumption.