How we can turn the cold of outer space into a renewable resource
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0:02 - 0:04Every summer when I was growing up,
-
0:04 - 0:07I would fly from my home in Canada
to visit my grandparents, -
0:07 - 0:09who lived in Mumbai, India.
-
0:09 - 0:12Now, Canadian summers
are pretty mild at best -- -
0:12 - 0:16about 22 degrees Celsius
or 72 degrees Fahrenheit -
0:16 - 0:19is a typical summer's day,
and not too hot. -
0:19 - 0:22Mumbai, on the other hand,
is a hot and humid place -
0:22 - 0:26well into the 30s Celsius
or 90s Fahrenheit. -
0:26 - 0:28As soon as I'd reach it, I'd ask,
-
0:28 - 0:32"How could anyone live, work
or sleep in such weather?" -
0:34 - 0:37To make things worse, my grandparents
didn't have an air conditioner. -
0:38 - 0:41And while I tried my very, very best,
-
0:41 - 0:43I was never able
to persuade them to get one. -
0:44 - 0:47But this is changing, and fast.
-
0:48 - 0:52Cooling systems today
collectively account for 17 percent -
0:52 - 0:55of the electricity we use worldwide.
-
0:55 - 0:57This includes everything
from the air conditioners -
0:57 - 1:00I so desperately wanted
during my summer vacations, -
1:00 - 1:04to the refrigeration systems
that keep our food safe and cold for us -
1:04 - 1:05in our supermarkets,
-
1:05 - 1:09to the industrial scale systems
that keep our data centers operational. -
1:10 - 1:13Collectively, these systems
account for eight percent -
1:13 - 1:15of global greenhouse gas emissions.
-
1:16 - 1:17But what keeps me up at night
-
1:17 - 1:22is that our energy use for cooling
might grow sixfold by the year 2050, -
1:22 - 1:27primarily driven by increasing usage
in Asian and African countries. -
1:27 - 1:29I've seen this firsthand.
-
1:29 - 1:32Nearly every apartment
in and around my grandmother's place -
1:32 - 1:34now has an air conditioner.
-
1:34 - 1:37And that is, emphatically, a good thing
-
1:37 - 1:40for the health, well-being
and productivity -
1:40 - 1:43of people living in warmer climates.
-
1:44 - 1:48However, one of the most
alarming things about climate change -
1:48 - 1:50is that the warmer our planet gets,
-
1:50 - 1:53the more we're going to need
cooling systems -- -
1:53 - 1:57systems that are themselves large
emitters of greenhouse gas emissions. -
1:57 - 2:01This then has the potential
to cause a feedback loop, -
2:01 - 2:02where cooling systems alone
-
2:02 - 2:05could become one of our biggest sources
of greenhouse gases -
2:05 - 2:06later this century.
-
2:07 - 2:08In the worst case,
-
2:08 - 2:12we might need more than 10 trillion
kilowatt-hours of electricity every year, -
2:12 - 2:14just for cooling, by the year 2100.
-
2:15 - 2:18That's half our electricity supply today.
-
2:18 - 2:19Just for cooling.
-
2:21 - 2:25But this also point us
to an amazing opportunity. -
2:25 - 2:30A 10 or 20 percent improvement
in the efficiency of every cooling system -
2:30 - 2:34could actually have an enormous impact
on our greenhouse gas emissions, -
2:34 - 2:36both today and later this century.
-
2:38 - 2:42And it could help us avert
that worst-case feedback loop. -
2:43 - 2:47I'm a scientist who thinks a lot
about light and heat. -
2:47 - 2:50In particular, how new materials
allow us to alter the flow -
2:50 - 2:52of these basic elements of nature
-
2:52 - 2:55in ways we might have
once thought impossible. -
2:55 - 2:58So, while I always understood
the value of cooling -
2:58 - 3:00during my summer vacations,
-
3:00 - 3:02I actually wound up
working on this problem -
3:02 - 3:06because of an intellectual puzzle
that I came across about six years ago. -
3:07 - 3:13How were ancient peoples
able to make ice in desert climates? -
3:14 - 3:17This is a picture of an ice house,
-
3:17 - 3:20also called a Yakhchal,
located in the southwest of Iran. -
3:21 - 3:25There are ruins of dozens
of such structures throughout Iran, -
3:25 - 3:28with evidence of similar such buildings
throughout the rest of the Middle East -
3:28 - 3:30and all the way to China.
-
3:30 - 3:33The people who operated
this ice house many centuries ago, -
3:33 - 3:36would pour water
in the pool you see on the left -
3:36 - 3:39in the early evening hours,
as the sun set. -
3:39 - 3:41And then something amazing happened.
-
3:41 - 3:44Even though the air temperature
might be above freezing, -
3:44 - 3:48say five degrees Celsius
or 41 degrees Fahrenheit, -
3:48 - 3:49the water would freeze.
-
3:51 - 3:55The ice generated would then be collected
in the early morning hours -
3:55 - 3:58and stored for use in the building
you see on the right, -
3:58 - 3:59all the way through the summer months.
-
4:00 - 4:03You've actually likely seen
something very similar at play -
4:03 - 4:06if you've ever noticed frost form
on the ground on a clear night, -
4:06 - 4:09even when the air temperature
is well above freezing. -
4:09 - 4:10But wait.
-
4:10 - 4:14How did the water freeze
if the air temperature is above freezing? -
4:14 - 4:16Evaporation could have played an effect,
-
4:16 - 4:20but that's not enough to actually
cause the water to become ice. -
4:20 - 4:22Something else must have cooled it down.
-
4:23 - 4:25Think about a pie
cooling on a window sill. -
4:26 - 4:29For it to be able to cool down,
its heat needs to flow somewhere cooler. -
4:29 - 4:31Namely, the air that surrounds it.
-
4:32 - 4:34As implausible as it may sound,
-
4:35 - 4:40for that pool of water, its heat
is actually flowing to the cold of space. -
4:42 - 4:44How is this possible?
-
4:44 - 4:48Well, that pool of water,
like most natural materials, -
4:48 - 4:50sends out its heat as light.
-
4:51 - 4:53This is a concept
known as thermal radiation. -
4:54 - 4:58In fact, we're all sending out our heat
as infrared light right now, -
4:58 - 5:00to each other and our surroundings.
-
5:01 - 5:03We can actually visualize this
with thermal cameras -
5:03 - 5:06and the images they produce,
like the ones I'm showing you right now. -
5:07 - 5:09So that pool of water
is sending out its heat -
5:09 - 5:11upward towards the atmosphere.
-
5:11 - 5:13The atmosphere and the molecules in it
-
5:13 - 5:16absorb some of that heat and send it back.
-
5:16 - 5:20That's actually the greenhouse effect
that's responsible for climate change. -
5:20 - 5:23But here's the critical thing
to understand. -
5:23 - 5:26Our atmosphere doesn't absorb
all of that heat. -
5:27 - 5:30If it did, we'd be
on a much warmer planet. -
5:30 - 5:31At certain wavelengths,
-
5:32 - 5:35in particular between
eight and 13 microns, -
5:35 - 5:39our atmosphere has what's known
as a transmission window. -
5:39 - 5:45This window allows some of the heat
that goes up as infrared light -
5:45 - 5:48to effectively escape,
carrying away that pool's heat. -
5:49 - 5:53And it can escape to a place
that is much, much colder. -
5:54 - 5:56The cold of this upper atmosphere
-
5:56 - 5:57and all the way out to outer space,
-
5:57 - 6:01which can be as cold
as minus 270 degrees Celsius, -
6:01 - 6:04or minus 454 degrees Fahrenheit.
-
6:05 - 6:09So that pool of water is able
to send out more heat to the sky -
6:09 - 6:10than the sky sends back to it.
-
6:10 - 6:12And because of that,
-
6:12 - 6:15the pool will cool down
below its surroundings' temperature. -
6:16 - 6:20This is an effect
known as night-sky cooling -
6:20 - 6:21or radiative cooling.
-
6:21 - 6:25And it's always been understood
by climate scientists and meteorologists -
6:25 - 6:27as a very important natural phenomenon.
-
6:29 - 6:30When I came across all of this,
-
6:30 - 6:33it was towards the end
of my PhD at Stanford. -
6:33 - 6:37And I was amazed by its apparent
simplicity as a cooling method, -
6:38 - 6:39yet really puzzled.
-
6:39 - 6:41Why aren't we making use of this?
-
6:43 - 6:46Now, scientists and engineers
had investigated this idea -
6:46 - 6:47in previous decades.
-
6:47 - 6:50But there turned out to be
at least one big problem. -
6:51 - 6:54It was called night-sky
cooling for a reason. -
6:54 - 6:55Why?
-
6:55 - 6:58Well, it's a little thing called the sun.
-
6:58 - 7:01So, for the surface
that's doing the cooling, -
7:01 - 7:03it needs to be able to face the sky.
-
7:03 - 7:04And during the middle of the day,
-
7:04 - 7:08when we might want
something cold the most, -
7:08 - 7:11unfortunately, that means
you're going to look up to the sun. -
7:11 - 7:12And the sun heats most materials up
-
7:12 - 7:15enough to completely counteract
this cooling effect. -
7:16 - 7:18My colleagues and I
spend a lot of our time -
7:18 - 7:21thinking about how
we can structure materials -
7:21 - 7:22at very small length scales
-
7:22 - 7:25such that they can do
new and useful things with light -- -
7:25 - 7:28length scales smaller
than the wavelength of light itself. -
7:28 - 7:30Using insights from this field,
-
7:30 - 7:33known as nanophotonics
or metamaterials research, -
7:33 - 7:37we realized that there might be a way
to make this possible during the day -
7:37 - 7:38for the first time.
-
7:38 - 7:41To do this, I designed
a multilayer optical material -
7:41 - 7:43shown here in a microscope image.
-
7:43 - 7:46It's more than 40 times thinner
than a typical human hair. -
7:46 - 7:49And it's able to do
two things simultaneously. -
7:49 - 7:51First, it sends its heat out
-
7:51 - 7:55precisely where our atmosphere
lets that heat out the best. -
7:55 - 7:57We targeted the window to space.
-
7:58 - 8:01The second thing it does
is it avoids getting heated up by the sun. -
8:01 - 8:03It's a very good mirror to sunlight.
-
8:04 - 8:07The first time I tested this
was on a rooftop in Stanford -
8:07 - 8:09that I'm showing you right here.
-
8:09 - 8:12I left the device out for a little while,
-
8:12 - 8:15and I walked up to it after a few minutes,
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8:15 - 8:18and within seconds, I knew it was working.
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8:18 - 8:19How?
-
8:19 - 8:20I touched it, and it felt cold.
-
8:21 - 8:26(Applause)
-
8:27 - 8:31Just to emphasize how weird
and counterintuitive this is: -
8:31 - 8:33this material and others like it
-
8:33 - 8:36will get colder when we take them
out of the shade, -
8:36 - 8:38even though the sun is shining on it.
-
8:38 - 8:41I'm showing you data here
from our very first experiment, -
8:41 - 8:43where that material stayed
more than five degrees Celsius, -
8:43 - 8:47or nine degrees Fahrenheit, colder
than the air temperature, -
8:47 - 8:50even though the sun
was shining directly on it. -
8:51 - 8:54The manufacturing method we used
to actually make this material -
8:54 - 8:57already exists at large volume scales.
-
8:57 - 8:58So I was really excited,
-
8:58 - 9:01because not only
do we make something cool, -
9:01 - 9:06but we might actually have the opportunity
to do something real and make it useful. -
9:07 - 9:09That brings me to the next big question.
-
9:09 - 9:12How do you actually
save energy with this idea? -
9:12 - 9:15Well, we believe the most direct way
to save energy with this technology -
9:15 - 9:17is as an efficiency boost
-
9:17 - 9:20for today's air-conditioning
and refrigeration systems. -
9:21 - 9:23To do this, we've built
fluid cooling panels, -
9:23 - 9:24like the ones shown right here.
-
9:24 - 9:27These panels have a similar shape
to solar water heaters, -
9:27 - 9:30except they do the opposite --
they cool the water, passively, -
9:30 - 9:32using our specialized material.
-
9:33 - 9:35These panels can then
be integrated with a component -
9:35 - 9:38almost every cooling system has,
called a condenser, -
9:38 - 9:41to improve the system's
underlying efficiency. -
9:41 - 9:43Our start-up, SkyCool Systems,
-
9:43 - 9:47has recently completed a field trial
in Davis, California, shown right here. -
9:48 - 9:49In that demonstration,
-
9:49 - 9:52we showed that we could actually
improve the efficiency -
9:52 - 9:55of that cooling system
as much as 12 percent in the field. -
9:55 - 9:57Over the next year or two,
-
9:57 - 10:01I'm super excited to see this go
to its first commercial-scale pilots -
10:01 - 10:04in both the air conditioning
and refrigeration space. -
10:04 - 10:08In the future, we might be able
to integrate these kinds of panels -
10:08 - 10:11with higher efficiency
building cooling systems -
10:11 - 10:14to reduce their energy
usage by two-thirds. -
10:14 - 10:18And eventually, we might actually
be able to build a cooling system -
10:18 - 10:20that requires no electricity input at all.
-
10:21 - 10:22As a first step towards that,
-
10:23 - 10:24my colleagues at Stanford and I
-
10:24 - 10:26have shown that you could
actually maintain -
10:26 - 10:31something more than 42 degrees Celsius
below the air temperature -
10:31 - 10:32with better engineering.
-
10:33 - 10:34Thank you.
-
10:34 - 10:38(Applause)
-
10:39 - 10:40So just imagine that --
-
10:40 - 10:44something that is below freezing
on a hot summer's day. -
10:46 - 10:50So, while I'm very excited
about all we can do for cooling, -
10:50 - 10:54and I think there's a lot yet to be done,
-
10:54 - 10:57as a scientist, I'm also drawn
to a more profound opportunity -
10:57 - 10:59that I believe this work highlights.
-
11:00 - 11:03We can use the cold darkness of space
-
11:03 - 11:05to improve the efficiency
-
11:05 - 11:08of every energy-related
process here on earth. -
11:09 - 11:13One such process
I'd like to highlight are solar cells. -
11:13 - 11:14They heat up under the sun
-
11:14 - 11:17and become less efficient
the hotter they are. -
11:17 - 11:21In 2015, we showed that
with deliberate kinds of microstructures -
11:21 - 11:23on top of a solar cell,
-
11:23 - 11:26we could take better advantage
of this cooling effect -
11:26 - 11:29to maintain a solar cell passively
at a lower temperature. -
11:30 - 11:32This allows the cell
to operate more efficiently. -
11:33 - 11:36We're probing these kinds
of opportunities further. -
11:36 - 11:39We're asking whether
we can use the cold of space -
11:39 - 11:41to help us with water conservation.
-
11:41 - 11:44Or perhaps with off-grid scenarios.
-
11:44 - 11:48Perhaps we could even directly
generate power with this cold. -
11:49 - 11:51There's a large temperature difference
between us here on earth -
11:51 - 11:53and the cold of space.
-
11:53 - 11:55That difference, at least conceptually,
-
11:55 - 11:58could be used to drive
something called a heat engine -
11:58 - 11:59to generate electricity.
-
12:00 - 12:04Could we then make a nighttime
power-generation device -
12:04 - 12:06that generates useful
amounts of electricity -
12:06 - 12:08when solar cells don't work?
-
12:08 - 12:10Could we generate light from darkness?
-
12:12 - 12:16Central to this ability
is being able to manage -
12:16 - 12:19the thermal radiation
that's all around us. -
12:19 - 12:22We're constantly bathed in infrared light;
-
12:23 - 12:25if we could bend it to our will,
-
12:25 - 12:28we could profoundly change
the flows of heat and energy -
12:28 - 12:31that permeate around us every single day.
-
12:31 - 12:35This ability, coupled
with the cold darkness of space, -
12:35 - 12:38points us to a future
where we, as a civilization, -
12:38 - 12:43might be able to more intelligently manage
our thermal energy footprint -
12:43 - 12:45at the very largest scales.
-
12:46 - 12:48As we confront climate change,
-
12:48 - 12:51I believe having
this ability in our toolkit -
12:51 - 12:53will prove to be essential.
-
12:53 - 12:57So, the next time
you're walking around outside, -
12:57 - 13:03yes, do marvel at how the sun
is essential to life on earth itself, -
13:03 - 13:08but don't forget that the rest of the sky
has something to offer us as well. -
13:09 - 13:10Thank you.
-
13:10 - 13:14(Applause)
- Title:
- How we can turn the cold of outer space into a renewable resource
- Speaker:
- Aaswath Raman
- Description:
-
What if we could use the cold darkness of outer space to cool buildings on earth? In this mind-blowing talk, physicist Aaswath Raman details the technology he's developing to harness "night-sky cooling" -- a natural phenomenon where infrared light escapes earth and heads to space, carrying heat along with it -- which could dramatically reduce the energy used by our cooling systems. Learn more about how this approach could lead us towards a future where we intelligently tap into the energy of the universe.
- Video Language:
- English
- Team:
- closed TED
- Project:
- TEDTalks
- Duration:
- 13:30
Brian Greene edited English subtitles for How we can turn the cold of outer space into a renewable resource | ||
Brian Greene edited English subtitles for How we can turn the cold of outer space into a renewable resource | ||
Brian Greene edited English subtitles for How we can turn the cold of outer space into a renewable resource | ||
Brian Greene edited English subtitles for How we can turn the cold of outer space into a renewable resource | ||
Brian Greene edited English subtitles for How we can turn the cold of outer space into a renewable resource | ||
Brian Greene approved English subtitles for How we can turn the cold of outer space into a renewable resource | ||
Brian Greene edited English subtitles for How we can turn the cold of outer space into a renewable resource | ||
Krystian Aparta accepted English subtitles for How we can turn the cold of outer space into a renewable resource |