Whether it’s to regulate the temperature
of food, medicine, or people, we’ll always need some form of cooling tech to survive. We tend to turn to air conditioning to solve
these problems, but that has us stuck in a positive feedback loop that isn’t at all
positive. Hot days are becoming hotter, and the demand
for cooling is surging. How do we break the cycle? A team of researchers from the Massachusetts
Institute of Technology have an idea: stack the same cooling techniques we’ve been using
for thousands of years by harnessing the power of aerogel. No power, no emissions…no problem? I’m Matt Ferrell … welcome to Undecided. Before we get into MIT’s aerogel proposal,
it’s important to discuss why curbing our AC addiction necessary. It’s because the way things are going, we
probably shouldn’t be keeping our cool about how we keep ourselves cool. According to the Clean Cooling Collaborative,
20% of the world’s electricity is spent powering air conditioning and electric fans,
and as temperatures intensify, usage is increasing. At this rate, the global number of AC units
is projected to triple by 2050. The International Energy Agency reports that
last year in particular saw cooling demand account for about 16% of all energy used in
buildings worldwide — about 2,000 TWh. The problem isn’t just a matter of energy
use, either. Air conditioning is a major contributor to
CO2 emissions. The indirect CO2 emissions from cooling buildings
more than doubled between 1990 and 2021 — to about 1 Gt.If that wasn’t bad enough, AC
also releases hydrofluorocarbon refrigerants (HFCs), which pollute the atmosphere even
more. And they’re thousands of times more potent
as a greenhouse gas than CO2. That said, air conditioning isn’t our only
option. People have been using natural methods of
staying comfortable indoors for thousands of years. We can see them in historic buildings all
over the world, from the “wind catcher” towers in the Middle East and North Africa
to the courtyards in China and Spain — and the “sleeping porches” in the American
South. These structures aren’t just for show. They’re examples of passive cooling: architectural
elements that control both the loss and gain of heat. So, managing a building’s temperature without
consuming electricity _or_ producing carbon emissions is nothing new. But when it comes to modern alternatives to
air conditioning, the passive cooling system presented by MIT researchers in September
is unique for its three-pronged approach. The design combines “insulated cooling with
evaporation and radiation” into one convenient package called ICER. It sounds a bit like a frozen drink maker,
but it’s more like a solar panel that uses the sun’s rays to produce cooling rather
than energy. Let’s break down what that all means. To start, it’s important to remember that
heat is our literal fair weather friend. It leaves when we need it in the winter, and
intrudes when we want to avoid it in the summer. The good news: even though we can’t change
the ways of an unreliable person, we can get around the way heat behaves with the power
of thermodynamics. Here’s how ICER does that. First, the “IC” is for insulated cooling. Generally speaking, insulation slows down
the flow of heat from warmer areas to colder ones. As for “E,” evaporative cooling is the
process of water lowering the temperature of a surface when it absorbs enough heat to
change from liquid to gas, which we experience whenever we sweat. Lastly, “R”: radiative cooling is the
loss of heat through thermal radiation, like when the Earth radiates heat out into space. This is what causes the chill we feel on cloudless
nights, and it’s also how the people of Iran and India managed to make ice long before
we could pop a tray into the freezer. In the context of reducing our reliance upon
air conditioning, there’s promising developments on the use of radiative sky cooling to effectively
shoot heat into space. I talked about how radiative cooling is being
implemented in a previous video. It 's pretty cool. The MIT researchers behind ICER, though, do
note that high-performance radiative cooling is typically limited to specific climate conditions. So now that we know the principles ICER operates on, how
does it work? You can think of it like an open-face sandwich. On the top is a layer of aerogel. Aerogel is basically what you get when you
put a gelatin mold into a dehydrator (assuming you like the taste of plastic). Normally, doing that would just reduce your
dessert to the powder you started with. The magic of aerogel is that it retains its
shape even after its initial gel form loses all its moisture. The result is a solid but extremely light
chunk of what NASA calls “one of the finest insulation materials available.” This is because aerogel is like a sponge,
but with pores too tiny for the human eye to see. They make up 95% of aerogel’s volume, giving
it a very low density.These pores are smaller than human hair; about the same size as air
molecules. Air has low thermal conductivity, meaning
that it’s difficult for heat to pass through it. So, as a result of all these factors, air
doesn’t have much space to flow freely through aerogel, making it very effective in thermal
insulation — effective enough to use while exploring the cold void of space. Speaking of space, infrared radiation passes
right through aerogel. That’s why ICER’s top layer can both insulates
and allow for radiative cooling. Hydrogel is the next layer of the ICER sandwich. As the name implies, it’s the wet sponge
to aerogel’s dry sponge: full of water instead of air. This water is the singular resource that ICER
consumes. As it evaporates over time, it rises past
the aerogel and out into the open, taking heat with it. When the hydrogel eventually dries out, recharging
the ICER is simple: All it needs is someone to “just add water.” The researchers estimate that the setup can
continue to function unattended for more than 10 days in most cases, or even over a month
on the U.S.’s west coast. In hot, arid regions like Las Vegas and Phoenix,
a single “charge cycle” can last about four days. Beneath the hydrogel lies ICER’s third and
final layer, which is its mirror-like base. It reflects sunlight back through the layers
above it, preventing the device’s materials from heating up. ICER’s aerogel is highly reflective, too,
providing even more resistance against the sun’s heat. So far, ICER has only been tested on a small,
10 cm-wide scale, on top of a MIT building’s roof. However, the results were significant. The researchers reported that even under poor
weather conditions, ICER’s capabilities represented a 300% improvement upon a radiative
cooler. This amounted to ICER reaching 9.3 C below
the ambient temperature under direct sunlight. Beyond its potential as a standalone cooling
system, ICER could also be used in retrofitting existing air conditioners to improve their
efficiency. Its inventors reference a 2017 Stanford University
study that used radiative cooling panels to lower the temperature of running water. Using a simulation, Stanford researchers estimated
that these panels could reduce the electricity consumption of an office building’s AC system
by 21%The MIT team predicts that ICER could save even more energy when integrated in a
similar way.This means that ICER might not necessarily need to replace an air conditioner,
allowing us to work with what we’ve got. Meaning this could be an additive solution
instead of a replacement. ICER could also make a big impact on the way
that we store food. One possible application is the preservation
of fruit and vegetable crops on off-grid farms, no energy necessary. The researchers calculated that cooling food
containers with ICER could extend the shelf life of produce by about 40% in humid areas
and over 200% in drier ones. Especially in regions where traditional cooling
systems are restricted by a lack of water or energy, ICER could theoretically prolong
the shelf life of food when it would otherwise spoil.It would be like having a cooler that
cools itself. But don’t throw your ice packs out just
yet. Manufacturing polyethylene aerogel, or PEA,
is unfortunately more complicated than sticking wobbly jelly into a drier. It’s a delicate operation that requires
slowly removing solvents without compromising the structure of the gel. This is accomplished through critical point
drying (CPD), which uses expensive special equipment. And as the researchers note, the CPD process
isn’t yet scalable. Long story short, producing the aerogel that
the ICER depends on is not cheap. But there’s still room for optimism. I mean … that’s what motivates me around
all of the videos I make. ICER’s aerogel component is the only one
that isn’t freely available right now, but that might change as aerogel becomes more
popular as a material for tech like supercapacitors and batteries.In the meantime, the MIT team
is seeking out a viable way to cut down on costs. This could look like using freeze drying rather
than CPD during production or swapping the PEA with a different kind of insulation altogether. In fact, we already know this is feasible. Researchers from Nanjing<!--naah]n-jing-->
Forestry University in China and the University of Applied Sciences and Arts in Germany have
also designed an aerogel-based passive cooler that blends radiative cooling and thermal
insulation. Like ICER, it reflects sunlight, releases
absorbed heat, and provides thermal insulation without any electricity.The difference is
that their aerogel is composed of cellulose nanocrystals and just so happens to be made
using freeze drying in a process that _can_ be scaled up. How does cellulose nanocrystal aerogel, or
CNC, compare with PEA? Well, hopefully all this talk about jelly
and sandwiches hasn’t gotten you too hungry, because here’s another food analogy. Marshmallows are a lot like aerogel: they’re
made of gelatin, and they’re full of air. When marshmallows are cooked in a microwave,
they inflate. PEA poofs up in a similar way as it’s made. In both cases, you end up with a big, fluffy
solid full of trapped air, but you can’t do much to change its shape. CNC is another story. It’s more like a soft serve ice cream cone,
which you carefully turn to form its iconic twisted look. When producing CNC, scientists have a similar
level of control over its structure as they direct the bonding of compounds that make
it up. Like other types of aerogel, CNC has low thermal
conductivity. However, gel-based networks of chemicals tend
to be brittle, and cellulose nanocrystals are more robust. The CNC created for this particular study
is also white and highly reflective.It doesn’t hurt that cellulose is the most abundant biopolymer
on earth, either. But did the cellulose aerogel perform as well? Turns out, the results published by the joint
research team in May are very similar to ICER’s. To refresh your memory, ICER’s cooling was
powerful enough to reach 9.3 C below the ambient temperature under direct sunlight.The CNC-based
cooler managed a drop of 9.2 C under direct sunlight and roughly 7.4 C in what the researchers
call “hot, moist, and fickle” weather. And using modeling, the researchers estimated
that their CNC cooler could reduce energy consumption in China-based buildings by about
35%. Aerogel is clearly a valuable resource in
the realm of thermal insulation. But how does it compare against existing insulating
materials in the real world? In a study published in September, a group
of researchers from universities in China and Australia put their own formula to the
test. Called anisotropic cooling aerogel, or ACA,
it’s produced with freeze drying like CNC. What makes ACA’s development different,
though, is that it’s inspired by 3D printing. The researchers built their aerogel panels
block by block the same way a 3D printer builds an object in layers. This provided them with enough precision to
keep the dimensions of the gel’s pores “aligned” and consistent in their dimensions. As for what “anisotropic” means and why
it matters, most materials are either isotropic or anisotropic. If something is isotropic, its properties
are even and identical throughout, regardless of the direction you measure it — nice and
predictable, like bulk glass and metals. Otherwise, a material is anisotropic, meaning
that its properties aren’t even or identical. Wood is a classic example. It’s stronger along its lines or “grain”
than against it.According to the researchers, anisotropic aerogels with highly aligned pores
act as better insulators than isotropic ones, so it’s worth finding ways to produce them. And the ACA did deliver. When the team placed the gel on a hot plate
heated to 90 C, its top surface eventually remained steady at a temperature of about
41 C. By comparison, two existing insulation products, EPS foam and silica aerogel, became
6 and 10 degrees C hotter than the ACA, respectively. In another series of tests, the researchers
measured the ACA’s thermal insulation capacity on a hot and humid day in Hong Kong. Under direct sunlight, the ACA panel maintained
a lower interior temperature than four other insulation materials: brick, glass, EPS foam,
and silica aerogel. The ACA also demonstrated passive cooling
with a drop of 6.1 C below ambient temperature. These experiments offer an exciting look into
aerogel’s capacity for passive cooling. Even so, it’ll be some time before mass
production of aerogel coolers is practical. In most cases, aerogel panels can be as much
as 10 times more expensive than traditional insulation materials, whether they’re composed
of silica or cellulose.Aside from cost, the majority of testing has only been done on
a lab scale. That’s not to say aerogel is lightyears
away from existing in our homes and workspaces. Its insulating properties are also useful
in another essential part of architecture: windows. Poorly insulated windows can be more wasteful
than you might think. According to MIT, each winter, windows across
the U.S. lose enough energy to power over 50 million homes. To address this problem, the U.S. government’s
Advanced Research Projects Agency-Energy (ARPA-E) began funding the production of materials
that improve the energy efficiency of windows in a program launched in 2016.The 14 teams
in the Single-Pane Highly Insulating Efficient Lucid Designs or SHIELD program are developing
products to apply to window panes and new window pane designs for retrofitting. Of these 14, four projects involve aerogel. And in 2019, MIT announced its success at
fabricating a transparent form of silica aerogel. The research team estimated that a double-pane
window with its air gap replaced by its aerogel panel would be 40% more insulating than traditional
ones. Aerogel-based insulation has already left
the lab. At this point, there’s a couple companies
that sell windows incorporating aerogel into their construction or aerogel-based glazing
that can be applied to windows and glass roofs. We’re long past wondering whether passive
cooling with aerogel is possible. The hurdle at hand is eliminating barriers
to widespread use. So are you still undecided? Do you think aerogel is going to make an impact
on cooling systems? And would you want to retrofit your AC with
one of these cooling panels? Jump into the comments and let me know. And be sure to check out my follow up podcast
Still TBD where we'll be discussing some of your feedback. If you liked this video, be sure to check
out one of these videos over here. And thanks to all of my patrons for your continued
support. You’re helping to make these videos possible. And thanks to all of you for watching. I’ll see you in the next one.
So, evaporative cooling with extra steps. I only skimmed around the video. Is there any explanation on how evaporative cooling on a country wide scale is a good idea? Is it more efficient to create water from power plants to use for evaporative cooling vs. run heat pumps?