- Even though it feels like
they're making us cooler refrigerators and air conditioners
are actually making our world warmer.
Not only do they use a huge amount of electricity,
but many older cooling methods also released tons
of molecules that are nearly indestructable
and shredding our ozone layer.
So how can we keep ourselves and our food cool.
Without accidentally warming up our world?
As humans, we've gone to sometimes crazy lengths
to keep cool in the summer heat.
Thousands of years ago,
inhabitants of ancient Persia built giant domes
that used evaporative cooling to make and store ice.
For thousands of years people
have dug deep pits underground just keep food from spoiling.
In the 1800s people shipped ice
across the United States and halfway around the globe
just to have a cool drink on a hot summer day.
And then in 1918,
the first self-contained home refrigeration unit
was unveiled forever changing kitchens.
Today, fridges and AC units are everywhere,
but you might wonder where all the extra heat goes,
that when you cool down at your home
and how a bunch of chemicals in your freezer
turn water into ice.
Well, let's start with your air conditioner.
Your air conditioner contains a chemical refrigerant.
What makes the refrigerant special
is that it can transition between a gas and a liquid
at a relatively low temperature.
The refrigerant is kept as a high pressure liquid
until it reaches an expansion valve.
Here, It's allowed to expand
in an area of lower pressure,
partially vaporizing and cooling down.
The refrigerant is now the coldest
it will be during the cycle
and moves into a series of evaporation coils.
Warm air from inside the house
is pulled into the air conditioner,
and then over these coils.
Heat from the warm air moves into the refrigerant.
This causes the refrigerant to change from a liquid to a gas
and also cools down the warm air.
The now cooled air is blown back into your home.
But now you have this hot gas refrigerant
that you need to cool down
and turn back into a liquid,
so the process can repeat.
A compressor pump compresses the refrigerant
into a high temperature, high pressure gas,
and then moves it into a condenser.
Another set of coils that is open to the outside air there.
There, the refrigerant releases its excess heat
into the outside air,
which has pushed away from your house
with a powerful fan.
This cools the refrigerant gas back down,
turning it back into a liquid.
And that's why if you stand
by the condenser coils of your air conditioner,
you'll get a face full of hot air.
The heat you're feeling is all the collected heat
from your house being released outside.
And now the cooled refrigerant moves back
to the original evaporation tubing,
repeating the cycle again
and keeping your home cool.
All of this works
because of the second law of thermodynamics,
which says that heat will spontaneously move from an area
of warm temperature to an area of cold temperature.
This is what causes the heat from the inside air
to flow into the refrigerant in the evaporation coils
and for the heat from the refrigerant
to flow into the outside air in the condenser.
Refrigerators work in a similar way.
If you take a peak behind your fridge,
you might even see a series of coils,
these are condenser coils,
shedding heat from your fridge into your kitchen,
but you can't just use any liquid as a refrigerant.
You need something with a low boiling point,
allowing it to transition from a liquid to a gas
in your refrigeration system.
It also has to be able to liquefy when compressed
and it needs to absorb lots of heat as it vaporizes,
a bunch of different chemicals
have been used for this over the years,
starting with Ether.
Yeah, that's the same molecule that old timey doctors used
to knock people out.
It was soon followed by ammonia,
methyl chloride, sulfur dioxide,
and a couple of other chemicals.
But these each had their own problems
from being fire hazards, to smelling like rotten eggs,
which is gross.
Ammonia by the way is actually even still used today.
But finally in the late 1920s,
chlorofluorocarbons were invented.
Now you may have heard of chlorofluorocarbons
or CFCs before.
As their name implies, they're composed of chlorine,
fluorine and carbon.
Their structures look like this.
With a central carbon or carbons surrounded
by fluorine and chlorine molecules.
They're amazing because they're stable odorless,
nontoxic and not to mention cheap to manufacture.
And because they have that
and all those valuable heat exchanging properties
we talked about earlier,
they became the GoTo refrigerants.
All of these benefits meant
that they started to turn up everywhere,
including in things like insulating foams and aerosol cans.
And by 1980,
the world was pretty seeing around
a million tons of CFCs each year.
(upbeat music)
Now, maybe right now you're thinking to yourself,
wait, aren't CFCs bad for the environment.
And yeah, you'd be right.
They're horrible for our atmosphere.
That's because one of the properties
that made CFCs so attractive as refrigerants,
their stability also means that they'll stick around
in the atmosphere for decades.
And over that time,
they're carried by winds up into our atmosphere,
including the stratosphere and the ozone layer.
This layer of our atmosphere
over 15 kilometers thick contains ozone.
A molecule composed of three oxygen atoms
rather than the typical O2 we need to breathe.
But that whole layer isn't packed with ozone molecules.
Instead they're spread out
so far out that if you squish them all down
to normal atmospheric pressure,
they would create a layer
that's only three to five millimeters thick.
The ozone molecules in our atmosphere,
protect the surface of our planet
from the sun's harmful UV radiation.
But that same radiation,
is also what creates the ozone in the first place.
The radiation breaks O2 molecules
into two single oxygen atoms.
These really want to react with other atoms,
so they float around until they can come into contact
and combine with oxygen molecules to make O3 or ozone.
(upbeat music)
Each year in late winter and early spring,
a whole forums in the ozone layer
over the Southern hemisphere.
That's right, the ozone hole
so many of us learned about in school, is seasonal.
- And there's also seasonal depletion of the ozone layer
seen across the globe with noticeable depletion
in the mid latitudes and the smallest effect
seen in the tropics.
Ideally the formation and destruction of O3 molecules
stays in equilibrium so that we don't have too much
or too little.
But the refrigerants ruined that balance.
In the 1970s, scientists discovered
that these processes were not in equilibrium
and that refrigerants like CFCs
were actually interfering with the normal ozone cycle.
(upbeat music)
When CFCs reached the ozone layer,
solar radiation can break them apart,
leaving lone chlorine atoms
floating around in the atmosphere.
These can break down ozone molecules,
leaving behind O2 and CLO or chlorine monoxide.
Now that would be bad enough,
but the oxygen atom in chlorine monoxide,
can go on to combine with a lone oxygen atom
in the atmosphere to become O2,
leaving behind chlorine again.
This means we once again have a chlorine atom
that can then react with a different O3 molecule,
starting the whole process over and over again.
In fact, one chlorine atom,
can destroy up to 100,000 ozone molecules.
And chlorine isn't the only thing,
that can break apart ozone molecules.
Bromine from halons and methyl bromide
found in things like fire extinguishers and pesticides,
also contributes to the Antarctic ozone hole
and bromine can even be 40 to 100 times
more destructive to ozone than chlorine.
For more info on those bromine reactions
and a fascinating cameo bipolar clouds in the stratosphere,
check out the link in the description.
So this is pretty bad.
Once we figured this out CFCs
were already abundant around the world
and in the atmosphere
and they weren't just used as refrigerants,
they were in aerosol propellant from a bug spray,
hairspray paint, asthma inhalers to more,
the list just goes on and on.
In 1985, scientists realized
that dramatic thinning of ozone
above Antarctica was suddenly appearing each spring.
When we looked back at their older measurements,
they found that the thinning began in about 1980.
And even though a number of nations agreed
to phase out CFCs in the late eighties,
the hole continued to expand
reaching its largest broadest point in 2000.
Thankfully it's starting to recover
as we continue to phase out CFCs,
but because these chemicals are so stable in the atmosphere,
scientists believe it'll be the year 2070
by the time it returns to the size it was in just 1980.
But CFCs are still being released into the atmosphere now.
Though the world stopped producing new refrigerators
at CFCs by 2010,
there are plenty of old refrigerators and insulating foams
still slowly leaking them into the atmosphere.
And even despite the global ban on CFCs,
some regions around the world apparently continue
to produce them raising emissions
to the atmosphere from 2013 through 2017.
Monitoring stations around the world,
we're able to show that some of the emission increase
is happening in Eastern China.
Evidence points to renewed production
being the cause of the increase.
So how do we solve the problem
of these chlorine atoms flying around and destroying ozone?
One way it would be to make refrigerants
without chlorine in them
or molecules that broke down
before they ever reached the stratosphere.
And that's what we've been doing for years now,
instead of using chloroflurocarbons,
modern refrigerants are often
either hydrofluorocarbons or hydrochloric fluorocarbons,
which are less damaging to the ozone.
They're a mouthful,
but these newer refrigerants either don't contain chlorine
or are much less efficient at breaking down ozone.
But these new refrigerants aren't perfect either.
HFCs still do deplete ozone
though by a smaller amount
and their production is already being phased out
around the world.
And HFCs are set to be phased down by 2047.
They can also be very strong greenhouse gases,
which are also real bad.
And there's another thing
that we haven't touched on at all yet.
The huge amount of energy
your refrigerator and AC use,
to power the compressor and multiple fans needed
to keep you and your food cool.
It's estimated that in the United States,
we use about 6% of all the energy,
our entire country produces
just to power our air conditioners.
6%, the entire state of Rhode Island,
uses less than 1% of total energy produced.
So what are our other options,
for keeping our food and ourselves cool?
We can start by using shorter lived gases
like hydrofluoric olefins,
and many car manufacturers have already started doing this.
But another possibility
is to use magnets, yeah, magnets.
Some materials are Magnetocaloric.
This means that they warm up,
when placed into a magnetic field
and then cool down when they're removed
from that magnetic field.
Now magnetic refrigerators,
aren't a new idea, early models date back to the 1930s.
And they've been used in some labs
to reach temperatures near absolute zero,
but that's like negative 459 degrees Fahrenheit,
which is way too cold to store your food.
And these models are expensive.
But now companies are working on new magnetic fridges
that are cheaper and work at temperatures
around 35 to 40 degrees Fahrenheit,
a nice brisk temperature to keep your lettuce crunchy,
but they're not quite ready to be rolled out
to every home yet.
And concerns still exist about their large weight
in their cooling range.
However, one estimate suggests that
if we converted all refrigerators to magnetic systems,
we could save up to $10 billion a year in electricity
because they're extremely efficient
and less energy means less CO2 released
from producing all that energy
as well as fewer ozone depleting gases.
But until then, maybe just turning up your AC a few degrees.
You might be a little bit warmer,
but hey, you can spend all that extra money you save
on mint chocolate chip.
Worth it for the planet and to the ice cream.
(upbeat music)