Energy Free Cooling through Physics

greenhouse gases are the second most

important thing on earth making it

habitable the first being the

magnetosphere without these two we

wouldn't have the liquid water necessary

for the complex life we know

nowadays the amount of greenhouse gases

in the atmosphere is too much for the

life that currently lives here and

things are getting a bit hot

cooling things down requires a lot of

energy but there's a way to do this with

no energy input on our part

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the greenhouse effect is named as such

because of well greenhouses the air

temperature in an enclosed space

underneath a glass plane will always be

warmer than if it wasn't there we've all

experienced this when entering a car on

a hot sunny day so it feels intuitively

obvious but why does it happen

there are two ways heat transfers across

interfaces there is conduction the

physical Collision of molecules and

atoms transferring or absorbing kinetic

energy and there is radiation the

emittance and absorption of light

the majority of your personal

relationship with temperature is in the

form of radiation

so how does radiation influence

temperature

light is a property of oscillating

charges whenever charged particles

wiggle they produce light the inverse is

also possible and light can wiggle

charged particles

visible ultraviolet or what we call

shortwave radiation primarily Wiggles

the fast-moving electrons and the bonds

of molecules and atoms infrared

microwave or what we call Long wave

radiation Wiggles entire molecules

electrons exist as complex wave

functions that behave like particles

when two or more electrons are near each

other their waves interact or mix with

one another

this mixing is itself a new wave

function that oscillates and because it

is a mixing of charges there exists

regions of higher and lower densities

for that particle or charge

it's this oscillation that can be

influenced you must have this dance of

particles to absorb light

dancing electrons are called an electron

cloud you can mix multiple electrons

together to form electron clouds and

each electron cloud will have a specific

frequency to visualize this I've mixed

three out of frequency waves together

right now it looks like a jumbled mess

but if we zoom out we can see that it

starts to repeat therefore we can think

of this as our electron cloud

oscillating if we provide another wave

at the same frequency it will

fundamentally alter or oscillate the

electron cloud and the electromagnetic

field energy will be absorbed into the

electron field

what does this mean for the greenhouse

effect well light from our sun is

principally shortwave radiation the

electrons in glass or the gases in our

lower atmosphere aren't dancing in the

right manner to absorb this light the

shortwave radiation passes through and

is then subsequently absorbed by the

Earth warming it up since all molecules

atoms and particles are always dancing

the Earth itself is releasing light but

much weaker in the form of long wave or

infrared radiation

these wavelengths are now too low a

frequency to oscillate the electron

clouds however they can oscillate entire

molecules or ions

in most molecules there exists slight

variations in charges throughout them

some regions will be more negative or

positive than others

as our light wave passes through them

the oscillating electric field component

can oscillate these charge imbalances if

this vibration is a correct frequency

then our entire molecule becomes

vibrationally excited and the light

energy is absorbed into the kinetic

energy of this motion

I like to tell people to try to create a

wave in a water bottle you'll soon

realize you need to move it back and

forth a certain frequency for it to work

this is precisely what happens for

greenhouse gases except instead of a

waveforming our molecules become

vibrationally excited

this vibration or motion of the excited

molecule is heat it can then transfer

that heat to neighboring molecules via

conduction or it can simply radiate that

absorb light away in a random Direction

in our atmosphere the gases are too

spread out to transfer their heat by

conduction and thus will immediately

radiate the light away

this is the property of the greenhouse

effect

instead of Simply emitting the Earth's

heat away into space when our greenhouse

gases absorb that light there's roughly

a 50 chance it will be re-emitted back

to Earth and if it is emitted away it

could still be absorbed by another

molecule of that greenhouse gas which

then has another roughly 50 chance of

emitting that light back to Earth

that is the beauty and mechanism of the

greenhouse effect

an inverse Greenhouse allows infrared

light to pass right through thus no

potential to be returned to the Earth

additionally it blocks much of the

radiation from the Sun that was giving

the Earth its warmth in the first place

as a result the volume underneath an

inverse Greenhouse radiates away more

energy than it receives and cools down

so what kind of material will do this

infrared light is principally absorbed

by molecules with charge imbalances and

asymmetries simple polymers are kind of

the opposite of this they are simply

long chains of hydrocarbons not only are

there few charging balances to interact

with the light but even if they could

it's kind of hard to vibrate this large

molecule as a result most Plastics are

transparent to infrared light

so Plastics are a great starting place

but how can we make them reflect or

scatter shortwave light

researchers at MIT took advantage of a

principle of light called me scattering

whenever light encounters a sphere made

of dielectric material a fancy word for

insulators the waves passing through

interfere causing destruction and

scattering

when we think about light as a particle

or a photon these waves represent the

probability of deflection

although passing straight through is the

most probable outcome each Photon has a

certain likelihood of deflecting away

therefore if a material has thousands of

spheres then the likelihood of light

passing through every single one is very

low

this scattering effect is most prominent

when the sphere has a similar size as

the wavelength

so if this material had spheres with

sizes similar to the shortwave radiation

from the Sun then that light would be

most strongly reflected and that's

precisely what the researchers in this

paper did

big thanks to Arnie Leroy for answering

some of my questions on this and

discussing the research in his field

polyethylene the most basic of plastics

can be filled with nanopores to form an

arrow gel each pore acts like a sphere

and serves to scatter the incoming light

but that's not the main advantage of

using an arrow gel with many infrared

transparent Coatings although they do

facilitate the inverse greenhouse effect

simple conduction or what is referred to

as parasitic heat gain can permeate

through them into the material they are

supposed to insulate

Aero gel is extremely insulating thus

with its implementation you get the

benefits of its infrared transparency as

well as insulating against the

surrounding Heat

when this Aero gel coating is layered on

top of yet another infrared emitter

designed for cooling in certain

circumstances the surface underneath can

be over 10 degrees cooler than the

surrounding ambient temperature during

noon in the Atacama of Chile

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what's exciting about all of this

it's estimated that 15 percent of

electricity consumption and 10 percent

of greenhouse gas emissions are ascribed

to cooling systems these percentages and

gross values will certainly increase in

the coming years

as a greater percentage of humanity

shifts to electricity as their main

source of power the more we can reduce

that consumption the easier and Stabler

that transition will be finding methods

to passively cool structures and

buildings will be absolutely crucial

especially in regions where power supply

isn't very reliable turns out this is an

entire scientific field I wasn't even

aware of

by installing manufactured inverse

Greenhouse panels on the roof of a

building not only do you reflect

sunlight you can also run water

underneath carrying the ambient

temperature from inside the building

this heat can then be radiated away in

very hot environments the amount of

energy radiated away in a day is almost

double the amount of energy that would

be absorbed by traditional solar panels

this is because it's not reliant on the

light incidence angle and continues

working at night

there is also research in developing

infrared cooling Fabrics these two

papers were released in the last six

months and take two separate approaches

the first is a potentially convoluted

meta fabric which weaves

polytetrafluoroethylene or Teflon Nano

beads and nanofibers along with titanium

oxide nanoparticles into polyacetic

microfibers which essentially a bunch of

scatterers suspended in an infrared

transparent medium

the most impressive thing in this paper

to me was when used to cover a car the

covered car's interior was 30 degrees

cooler than the uncovered cars

personally I'm intrigued by the

possibility of its use in temporary

constructions and shelters imagine tents

and desert festivals or markets where

people can enter inside and actually

feel cooler than the surroundings

the second paper wanted to implement

this property into the ever fashionable

material silk this was achieved by

binding aluminum oxide to the silk

fibers with tetrabutal titanate

the main goal was to reduce Silk's very

strong ability to absorb ultraviolet

light

aluminum oxide particle diameter was

chosen to reflect the ultraviolet light

while still letting infrared light to

pass through

according to this paper the skin

temperature of someone wearing

nanoprocessed silk can be 10 degrees

cooler than when wearing cotton

kinda seems too good to be true but

those living in hot climates potentially

won't have to choose between looking

fresh or feeling fresh

I started this video with the ambition

to teach a bit about the way light

influences the world we live in and

ended up discovering a whole new field

of Material Sciences

that's probably one of my favorite

things about making these videos digging

deeper into a topic always uncovers

something equally or more interesting

and hopefully what I find will inspire

one of you to start your own research

into a field presented in one of these

videos

either way I want to thank you for

sticking around as the channel grows and

sharing my passion for the world around

us

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thank you

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