Harvesting Energy from Estuaries? It Works in the Lab

By Paula Melton

Scientists have long known that when river water and seawater mix, as they do in river deltas and estuaries, the chemical reaction releases large amounts of waste energy. A recent breakthrough may enable the use of this reaction as a renewable energy source. Researchers at Stanford University, the University of Milan, and Penn State University created a device they call a “mixing entropy battery” that, when dunked alternately in seawater and river water, was able to store entropic energy created by the difference in salinity. According to an abstract on the website of the American Chemical Society ( www.pubs.acs.org), the battery achieved energy extraction efficiency of 74%. The researchers also claim that “the mixing entropy battery is simple to fabricate and could contribute significantly to renewable energy in the future”—up to 13% of global energy consumption, according to their estimates.