Battery uses freshwater, salt water to produce power

Stanford researchers have come up with a rechargeable battery that takes advantage of the difference in salinity between salt water and freshwater to produce electricity and charge itself.

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Eric Mack
2 min read

The clean-energy geeks (definitely a term of endearment) at Stanford University have come up with a way to turn every river in the world into a power plant--no big ugly hydropower dams required.

Put simply, Yi Cui, associate professor of materials science and engineering at Stanford, and his research team want to put a newly developed rechargeable battery at the mouths of rivers; the batteries would take advantage of the difference in salinity between salt water and freshwater to produce electricity and charge themselves.

The cycle that generates electricity in Cui's new battery Yi Cui / Stanford

That's the simple explanation. For the explanation that includes a discussion of the relationship between voltage and the concentration of sodium and chlorine ions, check out the news from Stanford. That said, the basic concept behind the battery itself isn't too complex and is similar to other batteries--basically two electrodes immersed in water--but the Stanford team took advantage of nanotechnology, which is cool because...here, let's just let them explain it:

To enhance efficiency, the positive electrode of the battery is made from nanorods of manganese dioxide. That increases the surface area available for interaction with the sodium ions by roughly 100 times compared with other materials. The nanorods make it possible for the sodium ions to move in and out of the electrode with ease, speeding up the process.

The nanorods are also stronger than the fragile membranes that have been used to generate current in similar salinity projects.

Cui's team calculated that the batteries could create 13 percent of the world's current power consumption if deployed on every river. But there are plenty of obstacles to that ever becoming a reality, not the least of which is potential conflict with critical wildlife habitat.

"You would want to pick a site some distance away, miles away, from any critical habitat," Cui said in a release. "We don't need to disturb the whole system, we just need to route some of the river water through our system before it reaches the ocean. We are just borrowing and returning it."

Even if it doesn't solve the world's energy problems, the new technology can make a dent. Cui envisions that a power station at the mouth of a single river could generate enough energy for 100,000 homes.