Placeholder Image

字幕列表 影片播放

  • Hey it's me Destin.

  • Welcome back to Smarter Every Day.

  • If you've ever watched Smarter Every Day you know that I spend a lot of time

  • off the grid.

  • Right now I'm in the Amazon rainforest and I don't really know what this thing is.

  • I think it's some kind of termite.. thing, on a tree.

  • I don't know.

  • Anyway, so one thing about being off the grid or in a developing nation

  • is light is always an issue.

  • Right now I'm using a headlamp.

  • I've done this all over the world.

  • I've done this in Africa, I've taken showers by headlamp,

  • it's an important thing.

  • But what if you live off the grid so far that you don't have access to batteries.

  • Today I want to talk about a new invention that I'm really stinking excited about,

  • it's sponsored by Shell.

  • It's a company called GravityLight.

  • Check this out.

  • I'm about to make light in the middle of the rainforest

  • alone, with nothing but gravity.

  • This is awesome.

  • I'm gonna have to put this head strap camera on because

  • I don't have enough hands, but check this out.

  • So there you go.

  • I'm in the middle of the rainforest powering a light with nothing but gravity

  • and that's a pretty big deal,

  • because humans have powered things with gravity for thousands of years

  • but we've never done personal source lighting.

  • So we're gonna figure out how this thing works

  • because that's obviously the next question,

  • how does it work.

  • Let's go to the UK where the offices are,

  • but let's make a pit stop on the way.

  • Harnessing the energy of gravity to power things is not a new idea at all.

  • In fact, here at Salisbury Cathedral in the UK

  • they've been using the power of gravity to power something for hundreds of years.

  • It's a clock, and we're about to go mess with it

  • and see if we can come up with any bright ideas.

  • The cathedral at Salisbury is over 750 years old.

  • It's home to beautiful choral music,

  • one of the original copies of the magna carta

  • and what's claimed to be the oldest working mechanical clock

  • in the entire world.

  • Clock expert Chris McKay agreed to walk me through the ancient technology

  • of powering something using gravity.

  • So it's ancient technology.

  • - It's very ancient technology.

  • Clocks generally work backwards.

  • Most machinery is you turning something fast

  • and making it slower.

  • With a clock you've got a, you know, slow,

  • faster,

  • and sort of fast as if it were.

  • The motive power is this thing here.

  • This is a weight,

  • and it's suspended by some pulleys

  • which go all the way up.

  • So the rope pulling on here tries to turn this wooden barrel.

  • And in fact it's turning it now.

  • But at a very slow rate,

  • and the rate is being governed by the escapement.

  • - There it goes.

  • [bell tolls]

  • [machinery sounds]

  • And it's stopped with a pawl and ratchet here.

  • The pawl and ratchet's very clunky isn't it.

  • It's really loud, so it's like you have this nice sound with the chimes

  • and then you have this [kunk kunk kunk kunk kunk].

  • OK so there's two takeaways to remember about clocks powered by gravity.

  • Number one. They take a slow moving object and speed up the movement with gears.

  • And number two, there's an escapement that regulates the release of potential energy.

  • Let's go to London.

  • Hey what's up man, I'm Destin.

  • - Pleased to meet you. Jim.

  • - Jim? This is Jim Reeves, co-inventor of GravityLight.

  • Jim told me that he had visited Kenya

  • where he had met people who had to use kerosene lamps at night

  • so their children could do their homework.

  • Children can get burned, the soot causes respiratory problems,

  • you've got to pay for the kerosene,

  • and think about it.

  • You're burning an open container of fuel inside your house.

  • It's a fire hazard.

  • Jim let me inside the secret lair where they developed GravityLight.

  • I wasn't really surprised when we took one apart and found

  • a DC generator on the inside.

  • OK so now what we're gonna do is we're gonna setup the GravityLight

  • prototype up here without a cover on it

  • and we're gonna look at how it actually works.

  • So I would expect that the side under tension is where it's gonna be moving slowest

  • and near the gear on the, or the belt on the motor with the generator,

  • they're the same thing by the way,

  • that's where it's gonna be driving fastest

  • so let's check it out.

  • So the weight on GravityLight moves very slow

  • and takes over 20 minutes to fall.

  • So how is this slow motion converted into something fast enough

  • to move that generator.

  • The clock in the church had really large metal teeth

  • capable of holding back that large weight.

  • But GravityLight is just made of plastic.

  • Wouldn't those teeth just break off under such a large load?

  • Jim taught me something interesting about how gears work.

  • If you have two gears touching on the outer diameter,

  • only one tooth is engaged at any time.

  • But if you have a gear running on the inner diameter

  • of another gear, multiple teeth are engaged at the same time

  • which has serious implications for the life of the gear.

  • So if a gear is mounted internally,

  • then you get multiple teeth touching,

  • therefore you transmit the force over multiple teeth

  • and so you decrease the contact stress..

  • - Exactly.

  • - Increasing the life of the gear.

  • - Precisely.

  • - I went to school for four years and you just taught me something.

  • Thank you so much.

  • Think about that.

  • One side of the mechanism is closest to the weight so the forces are larger.

  • Jim uses internal gearing here to distribute that load across more teeth.

  • The further through the drive train you go, the fewer the teeth you have to engage

  • because the torque gets lighter and lighter as the speed runs faster.

  • Eventually they're even light enough so that the generator can run with just a small rubber band,

  • which has the added bonus of being quiet at high speeds.

  • When you said the motor itself is at 1600 RPMs?

  • - That's right.

  • That's one of the reasons why we use a belt at the end,

  • because if you did that just with a spur gear it'd sound like a bag of nails.

  • - So the secret that you guys have uncovered to creating light with gravity

  • with these low powered LEDs is using ancient technology,

  • which is just falling weights,

  • but the way you've done it is distributed the load

  • on the teeth in a very particular way so that

  • these things last a long time and they don't break or wear out.

  • - Exactly.

  • - That's genius.

  • OK so we talked about the gearing,

  • but what about the escapement?

  • Why doesn't the weight just speed up until it hits the ground?

  • LEDs are way more efficient than traditional bulbs

  • but there's something else.

  • LEDs have a voltage limit.

  • Once the generator turns up to a certain speed and that voltage limit is reached,

  • the LED won't let it turn any faster.

  • It acts just like the escapement in a clock.

  • In fact, if you hang ten rocks on it, or gang 12 rocks on it,

  • it's always gonna fall at the same rate.

  • This is how GravityLight can run for so long.

  • - One of the advantages of GravityLight is there's no limit to that

  • reservoir of power as long as you're willing to go back over

  • and re-hoist the weight off the ground.

  • You can let that run all night for no cost.

  • - So there you go.

  • Jim and his team are using their technical talent to provide a safe

  • clean sustainable alternative to kerosene lamps.

  • I love this story.

  • I think it's because the solution was so obvious

  • but nobody connected the dots.

  • All we had to do was apply an ancient technology

  • to a technology that we have now,

  • and we can give light to 1.3 billion people that didn't have it before.

  • So kudos to Shell for funding GravityLight

  • to help try to make the world a brighter place.

  • I'm Destin,

  • you're getting Smarter Every Day.

  • Have a good one.

  • - So you plug the audio plug in the side of the product

  • and that interrupts the power to the LED

  • so you've got a really bright task light.