Between wind and solar power, we have access to an essentially unlimited supply of energy on Earth. We’ve made advances that make collecting renewables more efficient, but the sun isn’t always shining and the wind isn’t always blowing. That means we need batteries to store power for such times, and batteries have been slower to develop. Now, researchers from Stanford think they have created a viable water-based battery that could solve our energy woes with grid-scale capacity and a lifespan of more than a decade.
The battery is based on manganese-hydrogen technology, but the first incarnation is admittedly not very impressive. It’s about three inches tall and outputs a mere 20 milliwatts of power. That’s enough to power a small LED flashlight if you’re lucky. The team, led by materials science professor Yi Cui, says this is only the beginning. The same design should work the same when it’s scaled up to service a power grid.
This battery uses a reversible electron exchange reaction to store energy, and the key was an inexpensive industrial salt known as manganese sulfate. It’s used in fertilizers, paper, and other non-battery products. The manganese sulfate is dissolved in water, allowing it to interact with electrons as they flow into the battery. The electrons react with manganese sulfate to produce manganese dioxide on the electrodes. Excess electrons stick with hydrogen gas that bubbles up from the solution. That’s where the power is stored.
Getting power out of hydrogen gas is a well-established process, so that’s perfectly sound. The potential issue with this battery was making sure it could be recharged. The team did this by connecting the power supply again, this time using the power to restore the manganese dioxide to manganese sulfate salt. At that point, incoming electrons were again diverted into hydrogen gas for energy storage.
Cui calculates that the aqueous battery could be able to store 12 hours of power for a 100-watt light bulb for about a penny. He believes it will be possible to design a water battery that meets the Department of Energy’s recommendation that grid-scale batteries have a capacity of 20 kilowatt-hours or greater. The agency also suggests such batteries operate for at least 5,000 charge cycles. The Stanford team believes their battery will last twice as long, which means a decade of usable life. Cui plans to build larger versions of the battery to test this assertion.
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