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  • - Greg: The world is warm. - ( sighs )

  • Our cooling has officially been shut off.

  • - I'm so hot. - I'm making an off-grid fridge.

  • It's going to be complicated, possibly amazing...

  • - Moment of truth. - ...or a huge fail.

  • Snug as a button.

  • Mitchell: And I'm gonna cool our bunky with paint.

  • But this isn't your grandparents' white paint. It's high tech stuff.

  • Okay, we've got 53 degrees Celsius.

  • Where's Greg? He's better at the manual labor.

  • - Oh! - That's actually cool air.

  • Greg: Can we really cool our planet

  • with cheap and easy technologies?

  • - ( groans ) - ( stammers )

  • No!

  • Mitchell and Greg: This is "Shut It Off ASAP."

  • Mitchell: The world is warming, and that excess heat

  • is causing frequent wildfires, droughts, crop failures,

  • optimized conditions for disease vectors,

  • thermal-induced pollution-- the list goes on.

  • Unfortunately, we don't have a choice.

  • We need to keep ourselves cool. And that is a problem.

  • The cooling industry is responsible

  • for around 10% of carbon emissions,

  • which is around three times as much as shipping

  • and aviation combined.

  • So we have two universal, potentially sustainable

  • off-grid cooling experiments we want to try.

  • So there's been a trend in roofs in particular

  • to think about the color they actually are,

  • and to figure out how much light and heat they are actually absorbing.

  • So I decided I'm going to find the whitest paint I can

  • and paint the entire roof white

  • to see if we can get a big temperature drop inside

  • and ultimately cool ourselves down.

  • White paint has been used to cool buildings

  • for thousands of years across the Mediterranean,

  • the Middle East, and parts of Africa.

  • People have utilized white materials

  • to reflect the heat of the sun away from their homes.

  • These white structures, although picturesque

  • and quaint in the modern era, serve a practical purpose.

  • I actually spoke with the creator of the whitest paint ever,

  • which is able to reflect 98% of light,

  • including UV light, that we can't even see.

  • Professor, thank you so much

  • for taking the time to chat today

  • - about white paint in particular. - It's my pleasure.

  • We used a few different sort of innovations

  • that we came up with in seven years.

  • It's a long journey.

  • Sunlight has many different wavelengths.

  • We eventually found that using different particle sizes will help you.

  • Each particle size can scatter one wavelength.

  • If you use them all together,

  • they reflect all the wavelengths well.

  • So, do you think that there is

  • a long-term practical application

  • with cooling cities and potentially helping

  • against climate change and global warming?

  • We did an interesting analysis that you just need 1%

  • of the Earth's surface covered with white paint.

  • Then that is enough to cool the Earth down back by 1 degree,

  • and restore our climate hopefully.

  • That's wild. That's amazing.

  • Our ice caps naturally reflect incoming solar radiation,

  • which moderates our climate.

  • But as the Earth warms and they melt,

  • the effect is hugely reduced, which warms the Earth further.

  • Painting the top of buildings, roadways, and even cars

  • can make up for this and help fight climate change.

  • I'm gonna be focusing on cooling our food.

  • I'm gonna be making an off-grid fridge.

  • I'll be putting it underground, under the soil,

  • for some geothermal cooling aspects.

  • We're also going to be having some evaporative cooling aspects,

  • which will be part of this fridge

  • which is gonna be using Peltier modules,

  • which require electricity and fans,

  • which will be powered by solar panels

  • in order to create this underground fridge.

  • - I have so many questions. - They'll be answered in the video. Keep going.

  • - Okay. - Greg: Oh, there we go.

  • The complexity of my build means I need help

  • from Paul, our master builder.

  • I not only need his power tool skills,

  • but I also need his muscles.

  • My fridge has three parts.

  • There are the Peltier modules.

  • They need electricity, so we are powering them

  • using solar panels.

  • The Peltier models help to take heat away

  • from inside the cooler and disperse it.

  • Our evaporative cooling device

  • cools the outside of the Peltier modules

  • to maximize their efficiency.

  • And, lastly, for some geothermal cooling,

  • we're burying the cooling box and evaporative cooling device

  • in the ground to keep it colder

  • and its temperature stable.

  • More about that later.

  • Oh, God, I'm so deep in the hole.

  • Psych! Okay.

  • So, if you're wondering why I'm digging this hole,

  • it's 'cause I'm trying to teach you all

  • how to bury a body. I kid.

  • So we're digging this hole to put the cooler in,

  • and it's actually gonna help it keep cold,

  • because the Earth has so much more mass,

  • and so essentially it's a lot harder for the Earth to lose heat.

  • So we're just trying to take advantage

  • of those geological properties

  • in order to keep our cooler cool.

  • Mitchell: With the temperature above 35 degrees Celsius,

  • sleeping in the bunky has become unbearable.

  • It's way too hot, so I'm hoping that using a bit of science

  • will help me cool the place down.

  • It's time to paint. I've got my security harness.

  • We've got our scaffolding, and I've got, you know, my coverage and booties

  • to make sure I don't get any paint all over me.

  • The temperature right now-- I'm gonna check it--

  • is at 53 degrees Celsius, so more than halfway to boiling.

  • Okay, let's explore what makes white paint so special.

  • So, why is it that different colors

  • are better at reflecting light?

  • Whenever you look around you and see something colorful,

  • you're actually seeing the spectrum of visible light

  • that the object is not absorbing.

  • Plants, for example, appear green

  • because they mostly absorb the blue and red spectrum

  • and not green light, which is then bounced

  • off the plant and hits your eye.

  • When something appears white, that actually means

  • that every color is bouncing back to your eye,

  • because, like a prism that splits white light into a rainbow,

  • white is actually all of the colors combined.

  • And it's the material or chemical makeup on an object

  • that defines how light will interact with it.

  • For example, our paint contains titanium dioxide in it,

  • which reflects around 80 to 90% of light,

  • ultimately making it appear white.

  • All right, first part is always the scariest.

  • Ooh-la-la!

  • Okay, that's very white. That's awesome.

  • This is easy.

  • Now I just have to be careful I don't step backwards and die.

  • Greg: The next step in my build

  • is the insulated box for the fridge,

  • and it's something I'm not looking forward to.

  • First, we have to glue this foam insulation,

  • before we build the exterior of our cooler,

  • but it is a separate AsapScience episode

  • about the physiology of why touching foam insulation

  • literally gives me the heebie-jeebies

  • and scream and salivate and freak out, so...

  • I think you should just do it. Or I'll do it!

  • I'm strong. Okay.

  • Aah! I hate it. I don't know, please.

  • Oh-kay. I know I seem insane, but I'm not kidding.

  • Oh, God, oh, God.

  • Ho! ( imitating squirting sound )

  • So skilled, so skilled.

  • You could do this at home with a normal cooler

  • that you just bought from a store,

  • but we've got Paul here.

  • Go deeper. Press, press, press.

  • ( imitates drill whirring ) Okay, good, good.

  • - Oh, God. - Oh.

  • - No. - Oh, my God.

  • I was like, "Oh, and I'm getting sued."

  • Where's Greg? He's better at the manual labor.

  • Mitch is literally watching paint dry, which is very practical,

  • but not nearly as complex as me trying to make an off-grid fridge.

  • But it shows you how cool it is

  • to just paint roofs white.

  • Like, we can all do that.

  • Whoo.

  • It's hot.

  • Greg: We are currently in an awful heat wave,

  • so we want to figure out how to cool

  • our bodies down right now.

  • If your core body temperature goes above 38.3 degrees Celsius,

  • you not only risk heat stroke,

  • but literally denaturing the proteins in your cells.

  • So the military has developed a couple techniques

  • to cool yourself down efficiently.

  • One in particular is called the Arm Emersion Cooling System.

  • Because your hands and feet have more surface area on them,

  • you want to focus on those.

  • If you can put your hands, up to your elbows,

  • in cold water, in particular, though,

  • 10 degrees Celsius is the optimum,

  • you can cool your core temperature down

  • by one degree Celsius.

  • - Does it feel good? - It's beautiful.

  • It's refreshing, it's great.

  • Okay, you may have heard that having a hot soup

  • on a hot day can cool you down, and this is true,

  • but only under specific circumstances.

  • This all has to do with sweating.

  • You see, the evaporation of water off of your body cools you down,

  • so eating something hot actually causes you to sweat.

  • But it's important that it's a dry day and it's not too humid,

  • and it's important that you also have some skin exposed,

  • and preferably, maybe, you're in the shade.

  • Also, there's receptors in your mouth,

  • the TRPV1 receptor,

  • which tells your brain, "Oh, my goodness, it's hot. Time to sweat."

  • And you can trigger those even with hot sauce.

  • So if you add that to your soup, even just to a cold soup,

  • you can trigger those receptors, cause your body to sweat,

  • and cool you down on a hot day.

  • Mm, warm soup. Refreshing.

  • Why does sweating have a cooling effect?

  • The answer is evaporative cooling--

  • turning a liquid such as sweat

  • from its liquid state into a gas requires energy.

  • This energy is taken from our body, or sweat, in the form of heat.

  • The resulting heat transfer leads to the desired cooling effect of sweating.

  • For sweating to ideally cool you down,

  • you need skin exposed to the air that isn't too humid,

  • you need to be hydrated,

  • and a shady, windy spot is ideal.

  • Wind increases the effect of evaporative cooling,

  • which you may have experienced

  • after leaving a swimming pool on a windy day.

  • You'll feel extra cool when wet in the wind.

  • This is because the wind increases the evaporation rate

  • of the liquid water from you skin's surface

  • and accelerates the amount that's being

  • converted to vapor, thus cooling your body.

  • ( thunder )

  • 'Tis absolutely raining. Cats and dogs, as they say.

  • I'm very happy that we moved away from the bunky to do this electrical circuitry.

  • So what we're about to do right now is create

  • a thermoelectric cooling effect.

  • We're essentially building a fridge,

  • but using a really interesting scientific principle.

  • First step is getting these components onto the box.

  • This is my favorite part, as someone who considers themselves fashionable.

  • It's the glasses. Okay.

  • I'm cutting holes for these things called Peltier modules,

  • which are made of semiconductors.

  • Snug as a button. Is that even a saying?

  • The heat sink is gonna be on this side of the Peltier module,

  • and the cooler side's gonna be over here.

  • So because this one's gonna get hot,

  • there's a fan here, but we're also gonna add

  • these 3-D printed fans on top,

  • and if you need to know what a Peltier module is, I'll explain it now.

  • It is wild, but it is true that if you run

  • an electrical current through a series

  • of specifically placed semiconductors,

  • you create a temperature difference.

  • Semiconductors are materials that aren't good conductors

  • of electricity, but they also aren't good insulators