# Is it possible to obtain a cold radiating material?

Global warming is awful, we all agree.

The problem is that there exists materials that warm up easily naturally or artificially. But, why isn't there cold materials? Cooling something requires energy (refrigerator).

I am going to present a fictional material and I hope you can tell me if it's possible or if not how could it be possible or do other similar things exist:

• this material would absorb a huge amount of heat
• if this can't occur naturally I wonder how we could make such a thing happen (use electricity?)
• and finally I wonder how we could evacuate the absorbed heat without warming the surroundings up again

Basically I just want something that can eliminate the heat and cool the surrounding effectively a place without consuming to much energy.

Maybe I am wrong with the idea of a heat absorbing material but then, can a "cold material" and how could it be (the solution can be completely different from what I thought).

• You already mentioned the refrigerator. Check out en.wikipedia.org/wiki/Thermoelectric_cooling . I don't know what you are asking - it sounds a bit like "how do I build a refrigerator that doesn't consume too much energy" - without a definition of what would be too much. But the problems with your question do not end there. You are way too vague. How cold do you want your stuff to get? What do you want to cool exactly? What temperature does it have now? What is an huge amount of heat? What do you mean by "radiating"? What is too much energy? What is "effectively" cooling? ... – Raditz_35 Jul 21 '17 at 12:49
• Any material that is colder than its environment surely "radiates" cold. – R.Joshi Jul 21 '17 at 13:02
• For heat evacuation, it doesn't work like that. Heat is nothing more than energy which is neither created nor destroyed. In the case of endothermic reactions, as explained elsewhere in this thread, the reaction requires energy to make the bonds and will chill its surroundings. Until you break that chemical bond, that energy is stored, no material disposal required. Cold is to Heat what Dark is to Light, i.e. a product of a lack of energy. You can no more make cold than you can turn on a "dark-bulb" that makes darkness. – hszmv Jul 21 '17 at 13:30
• Because cold doesn't exist. – Mazura Jul 21 '17 at 19:07
• @R.Joshi, Radiation is energy that travels in straight lines. "Cold" is a lack of energy. A cold object absorbs energy from warmer objects that it happens to touch, and it absorbs any radiated energy that happens to come its way. Everything around you is radiating energy. If you stand next to a wall of ice, and you happen to feel "coldness" in that direction it's probably mostly because you are feeling cold air that touched the ice wall, and maybe, on a really hot day, because you feel less radiated energy from the ice wall than you feel from everything else around you. – Solomon Slow Jul 21 '17 at 20:22

## 8 Answers

Dihydrogen monoxide seems to match almost all the criteria:

• Absorbs (a huge amount of) heat - it's specific heat capacity is about $4.2 J g^{-1} K^{-1}$ and the heat of fusion about $333 J g^{-1}$
• It can occur naturally, but our technological civilization is quite capable of producing it artificially (using electricity)
• If you need to evacuate the absorbed heat without warming the surroundings up again, the best and quite low tech solution is to arrange the exchange of "heated" blobs of the matter from high temperature regions with "cooled" blobs from low temperature regions. This is something that can very well occur even naturally.
• Keep in mind that Dihydrogen monoxide is a bloody dangerous material : it causes thousands of death each year from asphyxa. In gazeous state, it can cause severe burns, while in solid state there were records of several injuries and it even caused more than 1500 death on a particularly grim occasion. – Keelhaul Jul 21 '17 at 15:07
• As a universal solvent it's a major factor in erosion, and it is toxic. – Michael Jul 21 '17 at 16:22
• There are no known survivors of attempts to purify bodies of it either, though stories of those people not being truly dead even after burial are common. – user25818 Jul 21 '17 at 16:27
• @Keelhaul 1500 dead is nothing, in 1931 the largest recorded disaster from Dihydrogen monoxide release killed perhaps as many as about 4 million people. from a related series of events if you include both the immediate deaths and the resulting disease related deaths. – Gary Walker Jul 21 '17 at 17:45
• It's so dangerous that six years ago it took out a nuclear power plant. Wiped it out. Utterly destroyed 4 units, three uncontrolled meltdowns and destroyed a fourth unit even though it was unloaded, disassembled and totally inert. What chemical can do THAT??? – Harper - Reinstate Monica Jul 21 '17 at 21:50

I think you might be thinking about this slightly wrong.

Cooling can be thought of as simply moving heat from one place to another. You take heat from one place and move it to a different one. If the first place is hotter than the second then 'cooling' happens all by itself as the temperatures equalise. If you want them to equalise faster or you want to move temperature from a hot place to a hotter place then that is when you have to use energy. All a refrigerator does is moves heat from the inside of the refrigerator to the outside (the pipes on the back are a radiator to get rid of the heat from inside).

So no, there exists no material that will 'just cool' all on it's own. That would be a violation of the laws of thermodynamics. You can have materials with a high heat capacity that you can dump heat into (Radovan Garabík's answer is a pretty good example of that!), but first they'll have to be cooled down, or start off cold. The bottom of the ocean is a good one for this: water is at it's densest around 4 degrees, so the bottom of the ocean is always around that temperature. You can pump heat into the ocean all day long, though it might have some unintended consequences. Eventually though your heatsinks will reach the same temperature as the thing you're trying to cool, and you'll have to spend more and more energy to move the heat from A to B.

But this brings us to endothermic reactions. If you have two materials which, when brought together, require energy in order to bond then they will suck heat out of the air nearby. Again though you run into a problem: These reactions will eventually stop, and you'll either need to use energy to break the chemicals apart again (thus releasing the heat) or introduce more of the chemicals you used in the first place. The exact whys and wherefores of how you can do this and what chemicals might be good is more chemistry than I'm comfortable professing to know, but it might help, especially if you have a way of shunting the result off world and bringing in more of the raw chemicals from somewhere else.

The third option is using the heat to extract usable energy, then shoving that energy somewhere else. Remember I said the ocean was a good heatsink? Well, it is. Turns out if you pump it up to ground level and equalise it's temperature with the surface water you can pull out usable energy, essentially using the entire ocean as a refrigerator, but in reverse. This actually works with wind as well, as winds are driven by temperature differentials. What you do with that energy is then up to you, but remember that if you use it on Earth all you're doing is (again) moving the heat around. Try firing lasers into space. If you're clever enough you might be able to balance the incoming and outgoing radiation and halt global warming. Or maybe just build a really good renewable power grid.

EDIT:

Heck, lets get crazy.

So, the problem is that you need somewhere to put the heat that isn't 'here'. So, first lets say that there are multiple universes, and that they're accessible. Second, lets say that we know some of these universes are much colder than ours, and some are warmer. Third, lets posit the existence of a specific crystalline matrix that will act as a 'bridge' to a universe colder than ours. Any crystals that can be convinced to grow into this 'Unobtanium matrix' will then act as a (potentially infinite) heatsink, into which we can pump heat with reckless abandon.

Which may piss off the frost giants on the other side...

• Don't forget Specific heat with water. Ever have your cold soda freeze despite swearing you thought it was liquid when you picked it up? This is a result of specific heat. Water doesn't just start changing phases when it reaches the magical temperatures. In fact, liquid water can exist well below freezing temperatures. This is because all phase changes require a specific heat, an energy addition, to change phase. Water is high, which helps cooling as it pulls in even more energy. In the case of your soda, that energery was you picking it up, which input energy into the liquid to freeze. – hszmv Jul 21 '17 at 13:35
• (Cont) This is also why sweating is cooling (the liquid evaporating pulls in heat energy from you, futher cooling your body) and why a watched pot never boils (the water needs time to heat to vapor AND an additional push to turn into vapor). A flash boil just means water is introduced to enough energy quick enough to reach boiling and specific heat. – hszmv Jul 21 '17 at 13:38
• @hsmv: I wan't considering phase changes at all in my answer, since the magnitude of energy put into an object doesn't change the fundamental nature of 'cooling is just moving heat', and if you want a heatsink that will operate well at over 100 degrees you do not want to be using anything that's going to get gaseous. – Joe Bloggs Jul 21 '17 at 13:43
• Fair... I was more bringing it up to show why water is a good heat sink. But yeah, ideally you want a substance that will still be solid/liquid at the level the heat your cooling is. – hszmv Jul 21 '17 at 13:59
• @hszmvI don't think you have your science right. Water needs to give up energy to freeze. I have never seen soda freeze like that, but if it was I would bet on the fact that ice needs space to expand, so the drop in pressure from opening the container is what freezes it. Or the motion removing the CO2 from the water and thus raising the freezing point – Andrey Jul 21 '17 at 18:28

Cannot radiate cold. Can have a cool surface that absorbs radiation.

If you are consuming energy you are producing heat unless it is performing other work like lift a rock.

Yes you could cool a large object with high heat capacity but you would produce more heat cooling it then the object will absorb. If you could cool the object in space it would work.

A refrigerator in net produces heat but if you could get that heat out of the atmosphere than it would cool. A light beam (radiant energy) pointed at the atmosphere might work.

• Hmm — but, maybe an absence of heat can be radiated along a medium like the electron gap in a free-electron conductor … – can-ned_food Jul 21 '17 at 16:00
• @can-ned_food I only know of radiation as heat / light – paparazzo Jul 21 '17 at 16:04
• Laser cooling'll radiate cold. – Nat Jul 22 '17 at 4:37
• @Nat Not seein any evidence laser cooling will produce radiate cold. The nature of radiant energy is energy. – paparazzo Jul 24 '17 at 18:17
• @Paparazzi Energy can contribute to a loss of heat, e.g. snapping an instant ice pack. Laser cooling's similar; it's energy, it just causes the target to get colder. – Nat Jul 26 '17 at 3:46

While not "radiating cold" in the way you are thinking, there are developments of materials tuned to radiate in infrared frequencies which the Earth's atmosphere are transparent to, and placing these on a roof, would potentially allow you to radiate heat into the 3K background of Space, which is effectively an infinite heat sink for our purposes.

Stanford engineers have invented a material designed to help cool buildings. The material reflects incoming sunlight and sends heat from inside the structure directly into space as infrared radiation – represented by reddish rays. (Illustration: Nicolle R. Fuller, Sayo-Art LLC)

https://www.nextbigfuture.com/2014/12/breakthrough-in-passive-mirror-cooling.html

Abstract

Cooling is a significant end-use of energy globally and a major driver of peak electricity demand. Air conditioning, for example, accounts for nearly fifteen per cent of the primary energy used by buildings in the United States. A passive cooling strategy that cools without any electricity input could therefore have a significant impact on global energy consumption. To achieve cooling one needs to be able to reach and maintain a temperature below that of the ambient air. At night, passive cooling below ambient air temperature has been demonstrated using a technique known as radiative cooling, in which a device exposed to the sky is used to radiate heat to outer space through a transparency window in the atmosphere between 8 and 13 micrometres. Peak cooling demand, however, occurs during the daytime. Daytime radiative cooling to a temperature below ambient of a surface under direct sunlight has not been achieved because sky access during the day results in heating of the radiative cooler by the Sun. Here, we experimentally demonstrate radiative cooling to nearly 5 degrees Celsius below the ambient air temperature under direct sunlight. Using a thermal photonic approach we introduce an integrated photonic solar reflector and thermal emitter consisting of seven layers of HfO2 and SiO2 that reflects 97 per cent of incident sunlight while emitting strongly and selectively in the atmospheric transparency window. When exposed to direct sunlight exceeding 850 watts per square metre on a rooftop, the photonic radiative cooler cools to 4.9 degrees Celsius below ambient air temperature, and has a cooling power of 40.1 watts per square metre at ambient air temperature. These results demonstrate that a tailored, photonic approach can fundamentally enable new technological possibilities for energy efficiency. Further, the cold darkness of the Universe can be used as a renewable thermodynamic resource, even during the hottest hours of the day.

SOURCES – Stanford University, Nature, MIT Technology Review

So using radiative materials to eject heat energy through infrared "windows" in the atmosphere can be used to cool installations and buildings.

## Global Warming Doesn't Work Like That

The problem with global warming isn't that carbon dioxide or methane in the atmosphere "warms up easily" but rather that it absorbs too much of the infrared energy that Earth emits back to space. Therefore, we have as much solar energy coming in as always, but now not enough of Earth's infrared emissions are escaping to space before being reabsorbed. That excess of reabsorbed infrared is why we're accumulating heat.

To counteract the effect of greenhouse gasses like carbon dioxide you'd either have to either make the atmosphere reflect away more incoming solar energy, or have it emit more of the Earth's excess infrared. Neither of these involve the kind of cold-feeling heat-absorbing material you imagine.

## Heat Pump the Whole Earth

What you seem to be describing in your original post is a very brute-force way of dealing with the situation. Essentially, you're trying to invent a way to build a refrigerator that cools the Earth and dumps the excess heat into space. The problem is that not only would it be remarkably inefficient but it also means that the HeatIn>HeatOut problem of global warming is never truly solved; which means you're essentially creating a situation analogous to dumping buckets of water (heat) out of a sinking ship (hot Earth).

That's not to say it's impossible, but it is remarkably silly. You'd have to have Earth-surface-to-outer-atmosphere transport be so darn cheap that you can bring warm material from Earth up to the edge of space, for fancy space refrigerators to cool the material as cold as scientifically possible, and then transport it back to cool the Earth's surface. Essentially you'd have to have space travel be so cheap that you can ship Earth water to space to make into scifi-ice-cubes and ship them down to cool the oceans.

If space travel is that cheap, though, building a giant reflector (or a fleet of smaller reflectors) to reflect away a sufficient fraction of the sun's energy would be far simpler and would fix the HeatIn>HeatOut problem outright.

• Why does it mean the HeatIn>HeatOut problem is not solved? As I understand, increasing HeatOut enough would solve it? – Paŭlo Ebermann Jul 22 '17 at 8:59
• @Paŭlo Ebermann I mean that the rate of energy coming in from the sun is a larger quantity than the energy reradiated by the Earth. Which means that the space-ice-cube-delivery system has to be in constant operation to make up that difference or heat will continue to reaccumulate. – fenix d.Anconia Jul 22 '17 at 9:59
• @Paŭlo Ebermann You could say that the energy transferred via the space-ice-cube system is accounted for by the HeatOut term, but disguising the added active process under the same banners used by the passive system is messy. It would be clearer to say HeatIn=HeatOut+HeatDelivered. – fenix d.Anconia Jul 22 '17 at 10:10

Although you can't radiate cold (as it's the absence of heat), it can subjectively feel like a radiative effect in a heat-conductive medium (e.g. air). However, it doesn't follow an inverse square law like radiation.

There is a ficitonal precedent for your technology in science fiction; Alastair Reynold's Revelation Space series contains "Cryo-Arithmetic Engines", a fictional technology that locally violates the Second Law of Thermodynamics through quantum mechanics.

(A lot of the technology in his series is effectively handwavium, but done very well.)

If you're going to take a bit of artistic license with the laws of nature, you could postulate a hyper-efficient photosynthetic material which combines CO2 and H2O into formaldehyde and oxygen gas, using as its energy source infrared radiation (ie., heat).

The heat is absorbed and the CO2 is reduced. Be sure to collect the formaldehyde and use it as a feed stock for your organic chemicals industry.

Theoretical way to accomplish localized cooling as you desire. Is to create an energy drain. In this case a heat sink with an infinite capacity.

Several hypothetical ways that this might work.

The drain contains:

• a wormhole to another location in space where the energy is dumped

• a miniature black-hole that for some reason does not produce excessive radiation itself

• some type of energy to matter conversion technology that converts the heat energy into mass (gas, liquid etc.)

• another mini universe where the energy is dumped

• a portal to another universe to dump the energy

• a wormhole to the end of time (in a universe where the universe ends in total entropy)

• a pocket of space/time or a universe in which the time flows backward