Giant Flow Batteries Could Power Your City in the Future

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Scientists are looking into sustainably powering
entire cities, and with liquid-based redox flow batteries, we’re one step closer to
making that happen. If we’re ever going to replace fossil fuels
with renewable sources like solar and wind power, then we’re going to need a way to
store energy for when it’s dark and not windy, or just for when the demand for power
exceeds the output. If you’re familiar with any sort of electronic
device, then there is one pretty obvious answer: batteries. Charge them up when demand is low but output
it high, then let the juice loose when that flips. But there are different battery types, and
all have their own strengths and weaknesses. This best battery for a job like this might
be one that uses flowing liquids, called a redox flow battery. A redox flow battery is sort of a hybrid between
a battery and a fuel cell. It consists of two tanks of an electrolyte
liquid, one positive and one negative. In between the tanks is a cell stack, where
the positive and negative solutions are pumped to but kept separated by a membrane. Inside the cell stack the ions in the negatively
charged solution give up an electron, a process called oxidation. Those electrons are picked up by an electrode
in the cell stack, and they travel through whatever needs to be powered before arriving
at another electrode on the other side of the membrane. There the ions in the positive solution pick
up the electrons, a process called reduction. This frees up positively charged hydrogen
ions, which travel back across the membrane and maintain the charge balance. When charging up, the entire process happens
in reverse. But hold up, why go through all this when
we have already lithium-ion batteries? You know, the ones in cell phones, laptops,
electric cars, and oh yeah, household battery packs designed for exactly this purpose? The problem is that while a big ol’ lithium-ion
battery might be suitable for your house, they don’t scale up well for something as
big as an entire city. Lithium isn’t an abundant material either,
so it’s not sustainable to use it for these huge applications. And anyone who’s had the same phone for
more that a couple years can tell you that lithium-ion batteries degrade and lose their
ability to hold a charge over time. On the other hand, flow cell batteries have
qualities that make them perfect for large-scale power storage, like scalability. Need to store more energy? Get bigger tanks that hold more solution,
that’s it. Worried about degradation? Some electrolyte solutions used in redox flow
batteries can last for about 5,000 charge cycles, five times longer than lithium-ion
batteries. What about price and sustainability? Ah, about that… The most popular metal used in redox flow
batteries is vanadium because it charges and discharges reliably for thousands of cycles. But the cost of vanadium is rising, and if
vanadium redox batteries go mainstream that price could skyrocket. Researchers have tried to replace vanadium
with organic molecules, but those tend to degrade and need replacement every few months,
or the solution they’re in has to be very acidic or basic, which can damage pumps or
be hazardous in case of a leak. But scientists are undeterred, and recently
researchers from USC announced organic water-based redox batteries that can last for about 15
years at one tenth the cost of a lithium-ion battery. So far the battery they’ve made is enough
for the basic electricity demands of a single house, but their goal is to one day have electricity
on tap for entire mega-cities. The technology is promising enough that China
is building a massive vanadium redox flow battery with a storage capacity of 800 Mega
Watt hours. That’s enough for thousands of homes. The battery is scheduled to come online by
2020. China has plenty of vanadium reserves so they’re
not too concerned about it’s cost, but if organic flow cell batteries become comparable,
those might not be too far behind. One day in the near future, they might play
a vital role in green energy grids around the world. If you liked this, subscribe! And then maybe watch this cool video about
how we can make batteries..out of DIAMONDS. And fun fact: While Vanadium may not be the
future of redox flow batteries, it is super cool. When vanadium gains electrons it changes color,
going from yellow, to blue, to green, and finally purple. thanks for watching and we’ll see you next
time on Seeker.

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