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  • Thanks to Brilliant for supporting this episode of SciShow.

  • Go to Brilliant.org/SciShow to learn more.

  • [♪ INTRO]

  • Renewable energy sources like wind and solar are awesome,

  • but they have a downsidethey're intermittent.

  • That means, if we want to make our grids more sustainable,

  • we need to store some of the energy they produce for later.

  • Not everybody loves the idea of using electrochemical batteries

  • for this, though, because they're expensive, and they're not

  • all that great for the environmentwhich kind of defeats the purpose

  • of switching to renewables in the first place.

  • Luckily, there are other options, like mechanical batteries:

  • ones that store energy using the physical position

  • or motion of things rather than chemicals.

  • Many of these were initially designed ages ago,

  • but they're making a bit of a comeback.

  • And that's because, while we might be able to come up

  • with all sorts of completely new ways to store energy,

  • the ones that have worked for centuries can continue to be put

  • to good useespecially with some modern sprucing.

  • Let's start with one you're probably familiar with: compressed air.

  • Ever since the invention of the first air pump in 1650,

  • compressed air has been used to power things like railway brakes

  • and noisy pneumatic tools such as nail guns and jack hammers.

  • Turns out this idea can be scaled up a lot to be used

  • for energy storage.

  • First, a high-pressure compressor pumps air into a huge chamber,

  • like a salt cave or an abandoned mine.

  • Then, when we need the power back, the air is released to run

  • an electricity-generating turbine.

  • Thanks to their ginormous size, compressed-air batteries

  • offer the large-scale capacity needed by power plants

  • up to 321 megawatts at a time.

  • They're also pretty cheap, and can start pumping juice

  • in about twelve minutes, which is less than half of the response time

  • of conventional fossil-fuel turbines.

  • Plus, they can store the energy for over a year.

  • But there are some drawbacks.

  • Thanks to our friend thermodynamics, we know some of the energy

  • used to compress the air becomes heatwhich dissipates over time

  • into the chamber's walls.

  • And since the air also becomes cold when it's decompressed,

  • it needs to be reheated so that it doesn't damage the turbines

  • so energy is also lost on the way out, as well.

  • That means the ratio between the energy we put in and the energy

  • we can get outthe battery's round-trip efficiencyis lower

  • for compressed-air batteries than top-of-the-line chemical batteries.

  • Those have round-trip efficiencies around ninety percent.

  • But even modern compressed-air facilities, which reuse the heat

  • from the compression process to warm the outgoing air,

  • only reach sixty to seventy percent efficiency.

  • Engineers might be able to improve upon that, but for now,

  • we might want to turn to other retro battery technologies,

  • like rail energy storage.

  • That's basically a battery powered by gravity in the form

  • of a weighted train.

  • The process is simple: a locomotive pulls train cars

  • weighted with rock or cement up a slope.

  • More cars can be brought up to store additional energy as needed.

  • Then, when the cars roll downhill, the gravitational energy

  • is converted into electricity through regenerative braking,

  • a technology already used in some hybrid and electric cars.

  • We've used gravity to store energy since at least the fourteenth-century,

  • when mechanical turret clocks powered by suspended weights were invented.

  • And people have come up with several types of modern

  • gravity batteries, like ones which use cranes to raise

  • and suspend giant blocks.

  • But the only large-scale gravity battery in development

  • so far consists of this sort of train on a hill setup.

  • With a capacity of about fifty megawatts, rail batteries

  • offer less per-battery storage than compressed-air systems,

  • but they also have a bunch of advantages.

  • Like, you don't need a Batcave to house all that energy,

  • because rail storage can work anywhere with an incline

  • of at least five percent.

  • And they have decent round trip efficiency,

  • at about seventy-eight percent.

  • Plus, their startup time of five to ten seconds is an

  • order of magnitude better than what compressed-air storage can offer.

  • But that's slow compared to flywheel energy storage.

  • Flywheels are basically just wheels that take

  • considerable energy to put in motion.

  • Each rotates around a shaft, and because we know objects in motion

  • tend to stay that way, these spinning wheels can store

  • most of the effort put into moving them as kinetic energy.

  • Then, that energy can be siphoned off with deceleration

  • kind of like regenerative braking.

  • Flywheels are super old-school tech.

  • They have kept potter's wheels turning evenly since at least

  • the third millennium BCE.

  • And you have a flywheel to thank if you've ever ridden

  • in a non-electric car, because they smooth out the explosive bursts

  • of energy in internal-combustion engines.

  • But flywheels can also be used as batteries.

  • The first flywheel created specifically for energy storage

  • was developed in 1833 to power the first self-propelled torpedo.

  • They have some drawbacks, of course.

  • Like, they're less useful for large-scale power-plant storage,

  • since they can lose as much as twenty percent of their charge

  • per day to friction.

  • But modern flywheels use space-age materials like

  • carbon-fiber composites, and spin in a vacuum while

  • levitating on superconductive magnetic bearings.

  • This makes them lighter and smaller, limits the loss

  • of the stored energy from friction, and makes it possible

  • to increase their rotation speed and expand their storage capacity.

  • It also makes them super expensive to make, especially when

  • compared with compressed air or rail storage batteries.

  • Still, they're probably worth the investment,

  • since their round-trip efficiency can be as high as ninety percent.

  • And even though they're still slower than chemical batteries,

  • they have response times counted in hundreds of milliseconds.

  • Also, with all of that space-age technology, their relatively

  • small size makes it possible to use them in things like

  • uninterruptible power-supply systems in server farms, trains,

  • and hybrid race-cars.

  • These three ancient battery technologies show that

  • there really is truth to that age-old maxim:

  • if it ain't broke, don't fix it.

  • And one thing's for sureclean, cheap, and reliable energy storage

  • technologies like these are the way of the future

  • as retro as they may be.

  • Speaking of renewable energy: if you've ever found yourself wishing

  • you could learn more about themwell I have some good news!

  • With a premium subscription to Brilliant.org, you can take their

  • course on Solar Energy and learn all about the physics

  • of capturing sun power.

  • By the end of it, you'll be able to explain multi-junction cells

  • and doped semiconductors like a pro.

  • Plus, it's just one of the dozens of interactive,

  • expert-designed courses that Brilliant has to offer.

  • So if you love learning new things, you can head on over

  • to Brilliant.org/SciShow to learn more.

  • And, as a thank you for being a SciShow Viewer,

  • the first 200 people to sign up at that link will get 20% off

  • an annual Premium subscription.

  • [♪ OUTRO]

Thanks to Brilliant for supporting this episode of SciShow.

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B1 energy storage compressed air battery percent

The Surprisingly Retro Future of Batteries

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    林宜悉 posted on 2020/03/30
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